Figures 20A-B show the unlocking of the plunger rod by the user pushing the injector skin sensor detector into the auto injector 1000 after cap removal in close-up views of figure 19D.

Figures 21A-D show the interaction of the plunger rod, the cassette activation part, and the

20 plunger rod support part.

Figures 22A-C show the cassette detector and cassette interaction for locking the cassette in the auto injector.

25 Figure 23 shows an exploded view of an example of a cassette extending along a longitudinal direction L.

Figures 24A-E show the locking of the cassette in the auto injector.

30 Figure 25A show the plurality of longitudinal positions which the skin sensor may move into relative to the syringe holder, and figure 25B shows the rotational positions which the index ring may be rotated between.

RECTIFIED SHEET (RULE 91) ISA/EP Figures 27A-I show a second example of the syringe holder, the skin sensor, and the index ring, and the injector release member in different skin sensor longitudinal positions and index ring rotational positions as the injector release member moves longitudinally in the index ring track.

Figures 28A-B show a third example of the syringe holder, the skin sensor, and the index ring.

Figure 28C shows the cassette housing in a third example of figures 28A-B.

Figures 29A-G show the syringe holder, the skin sensor, and the index ring of figures 28A-B, and the injector release member in different skin sensor longitudinal positions and index ring rotational positions as the injector release member moves longitudinally in the index ring track.

Figures 29H-I show a cut-through of the cassette housing and the skin sensor of figures 29A- G showing the skin sensor in non-locked position (figure 29H) and the final position LP3 (figure 29I).

Figures 30A-D show the removal of the cassette cap from the cassette.

Figures 31A-G show perspective views of parts of a cassette and the auto injector during a process of unlocking of the cassette cap, removal of the cap, medicament delivery and during resetting of the auto injector after medicament delivery

Figures 32A-D show a damper included in the auto injector.

Figures 33A-B show an exploded view of another example of an auto injector extending along a longitudinal direction L (figures 33A), and in a cut-through view (figure 33B).

Figures 34-40 show selected parts in the auto injector of figures 33A-B in close-up views.

Figures 41 A-D show selected parts of the auto injector of figures 33A-B during activation of the second auto injector.

Figures 42A-H show cut-throughs of the auto injector of figures 33A-B during a process of receiving a cassette, unlocking of the cassette, whereby the plunger rod can be unlocked, during medicament delivery, after end medicament delivery, and after reloading of the auto injector.

Figure 421 shows a cut-through of the auto injector of figures 33A-B during an early lift before medicament delivery has been finalized.

Figures 43A-D show cut-throughs close-ups of the auto injector of figures 33A-B during unlocking of the plunger rod allowing for medicament delivery.

Figures 44A-B show a cut-throughs of the auto injector of figures 33A-B when receiving an unused cassette (figure 44A) and when receiving an already used cassette (figure 44B).

Figures 45A-B show a linear damper inside the plunger rod cavity in close-ups.

Figures 46A-B show an exploded view of a third example of an auto injector extending along a longitudinal direction L (figures 46A), and in a cut-through view (figure 46B).

Figures 47-55 show selected parts in the auto injector of figures 46A-B in close-up views.

Figures 56A-C show selected parts of the auto injector of figures 46A-B during activation of the third auto injector.

Figures 57A-B show an exploded view of a fourth example of an auto injector extending along a longitudinal direction L (figures 57A), and in a cut-through view (figure 57B).

Figures 58A-61 show selected parts in the auto injector of figures 57A-B in close-up views.

Figure 62 show an exploded view of a fifth example of an auto injector extending along a longitudinal direction L.

Figure 63 shows a selected part in the auto injector of figure 62 in close-up view.

Description of examples

Exemplary examples will now be described more fully hereinafter with reference to the accompanying drawings. In this regard, the present examples may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the examples are merely described below, by referring to the figures, to explain aspects. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. Expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

In the drawings, thicknesses of a plurality of layers and areas are illustrated in an enlarged manner for clarity and ease of description thereof. When a layer, area, element, or plate is referred to as being “on” another layer, area, element, or plate, it may be directly on the other layer, area, element, or plate, or intervening layers, areas, elements, or plates may be present therebetween. Conversely, when a layer, area, element, or plate is referred to as being “directly on” another layer, area, element, or plate, there are no intervening layers, areas, elements, or plates therebetween. Further when a layer, area, element, or plate is referred to as being “below” another layer, area, element, or plate, it may be directly below the other layer, area, element, or plate, or intervening layers, areas, elements, or plates may be present therebetween. Conversely, when a layer, area, element, or plate is referred to as being “directly below” another layer, area, element, or plate, there are no intervening layers, areas, elements, or plates therebetween.

The spatially relative terms “lower” or “bottom” and “upper” or “top”, "below", "beneath", "less", "above", and the like, may be used herein for ease of description to describe the relationship between one element or component and another element or component as illustrated in the drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientation depicted in the drawings. For example, in the case where a device illustrated in the drawings is turned over, elements described as being on the “lower” side of other elements, or "below" or "beneath" another element would then be oriented on “upper” sides of the other elements, or "above" another element. Accordingly, the illustrative term "below" or “beneath” may include both the “lower” and “upper” orientation positions, depending on the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented ’’above” the other elements. The exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below, and thus the spatially relative terms may be interpreted differently depending on the orientations described.

Throughout the specification, when an element is referred to as being “connected” to another element, the element is “directly connected” to the other element, or “electrically connected” to the other element with one or more intervening elements interposed therebetween. The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “At least one” is not to be construed as limiting “a” or “an.” It will be further understood that the terms “comprises," "comprising," "includes" and/or "including," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It will be understood that, although the terms “first,” “second,” “third,” and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, “a first element” discussed below could be termed “a second element” or “a third element,” and “a second element” and “a third element” may be termed likewise without departing from the teachings herein.

"About" or "approximately" as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" may mean within one or more standard deviations, or within ± 30%, 20%, 10%, 5% of the stated value.

Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this invention pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined in the present specification.

Exemplary examples are described herein with reference to cross track section illustrations that are schematic illustrations of idealized examples, wherein like reference numerals refer to like elements throughout the specification. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, examples described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims. Some of the parts which are not associated with the description may not be provided in order to specifically describe exemplary examples of the present disclosure.

Figure 1A show an exploded view of an example of an auto injector 1000 extending along a longitudinal direction L. The auto injector 1000 is extending from a proximal end 1002 to a distal end 1004 and comprises a number of different parts as shown in close-up views in figures 2-16. The different parts in the auto injector 1000 includes a plunger rod 1020 with a plunger rod resetting part 1026, a drive spring 1040, a drive spring guide 1050, a cassette receiver 1100, a resetting sleeve 1200, a plunger rod support part 1300, a chassis sleeve 1400, a cassette activation part 1500, a pullback part 1600, an injector skin sensor detector 1700, an injector skin sensor detector spring 1710, a cassette detector 1800, a cassette detector spring 1810, a proximal injector housing 2100, and a distal injector housing 2200. The auto injector 1000 may possibly comprise a rotational damper 1900 as shown in figures 32A- D. Figure 1 B shows the assembled auto injector 1000. During loading and preparation of a cassette 100 (an example of a cassette 100 is shown in figure 23) for medicament delivery, and during medicament delivery, there is no rotational movement between the different parts in the auto injector 1000. Instead, the different parts in the auto injector 1000 move relative to each along the longitudinal direction L and some part flex and/or tilt relative to other parts as described in the following. After medicament delivery and removal of the cassette 100, the auto injector 1000 is reloaded by rotation of the resetting sleeve 1200 and the distal injector housing 2200 relative to the other parts of the auto injector 1000. This retracts the plunger rod 1020 to its initial distal position and reloads the drive spring 1040 as described in the following.

Figures 2A-B show a closeup of the resetting sleeve 1200 as seen from both the proximal end 1202 in figure 2A and the distal end 1204 in figure 2B. The resetting sleeve 1200 has a tubular form. The resetting sleeve 1200 comprises a resetting thread 1206 extending in a helical manner on an inner surface 1205 of the resetting sleeve 1200. The plunger rod resetting part 1026 engages with the resetting thread 1206 such that a rotation of the resetting sleeve 1200 moves the plunger rod 1020 along the longitudinal direction L (see details in figures 4A-B).

On the outer surface 1208 of the resetting sleeve 1200 is a number of outer housing channels 1209. The outer housing channels 1209 are configured for containing inner resetting sleeve locking parts 2209 on the distal injector housing 2200 (see figure 3). The interaction between the outer housing channels 1209 and the inner resetting sleeve locking parts 2209 rotationally locks the two parts together. The resetting sleeve 1200 and distal injector housing 2200 shown in figures 2-3 have four sets of outer housing channels 1209 and the inner resetting sleeve locking parts 2209. Few or more could also be imagined. The locking of the resetting sleeve 1200 and distal injector housing 2200 is shown in figures 17B-C.

At the proximal end 1202 of the resetting sleeve 1200 are two chassis sleeve interacting hook 1210 configured for engaging with resetting sleeve interacting tabs 1410 on the chassis sleeve 1400 (see figure 9B). During reloading of the auto injector 1000, the resetting sleeve 1200 is rotated in a first rotational direction DR1 relative to the chassis sleeve 1400. This brings the chassis sleeve interacting hooks 1210 in contact with the resetting sleeve interacting tabs 1410 on the chassis sleeve 1400. The contact, when rotating in the first rotational direction DR1 , is between sloping surfaces 1211 , 141 1 on both the chassis sleeve interacting hooks 1210 and the resetting sleeve interacting tabs 1410. The chassis sleeve interacting hooks 1210 can flex radially outwardly. Thus, when the sloping surfaces 1211 , 1411 coming into contact with each other when rotating the resetting sleeve 1200 in the first rotational direction DR1 , the chassis sleeve interacting hooks 1210 flex radially outwardly allowing the resetting sleeve 1200 to continue its rotation. However, if rotating in a direction opposite the first rotational direction DR1 , steep surfaces 1212, 1412 on both the chassis sleeve interacting hooks 1210 and the resetting sleeve interacting tabs 1410 come into contact with each other. This prevents further relative rotation between the two parts.

Figure 3 shows a closeup of the distal injector housing 2200. The distal injector housing 2200 is positioned outside the resetting sleeve 1200 at the distal end 1004 of the auto injector 1000. The distal injector housing 2200 is extending from a proximal end 2202 to a distal end 2204. The distal injector housing 2200 has a cylindrical shape. In the shown example, the injector housing has a non-circular elliptic cylindrical shape. Alternative shapes, such as round, squared, triangular cylindrical shapes, or similar could also be imagined. On an inner surface 2205 of the distal injector housing 2200 is found the number of inner resetting sleeve locking parts 2209 for rotationally locking the resetting sleeve 1200 and the distal injector housing 2200. On an outer surface 2208 of the distal injector housing 2200 are user grip lines 2206, which makes it easier for the user to hold and operate the auto injector 1000.

The distal injector housing 2200 comprises a distal injector housing plate 2212 at the distal end 2204. On the distal injector housing plate 2212 of the distal injector housing 2200 is a rotational stop surface 2210. When the plunger rod resetting part 1026 comes in contact with the rotational stop surface 2210 further relative rotation of the plunger rod 1020 and the resetting sleeve 1200, rotationally locked to the distal injector housing 2200, is prevented. The plunger rod resetting part 1026 comes in contact with the rotational stop surface 2210 after the plunger rod resetting part 1026 has moved along the resetting thread 1206. This is shown in figures 17B-C.

Normally, there will be two sets of resetting thread 1206 and rotational stop surface 2210 on the inner surface 1205 of the resetting sleeve 1200 and the distal injector housing plate 2212 of the distal injector housing 2210. When two sets of resetting thread 1206 and rotational stop surface 2210 are used, the relative rotation between the plunger rod resetting part 1026 and the resetting thread 1206 will normally be approximately 180 degrees. If only one set of resetting thread 1206 and rotational stop surface 2210 is used, the relative rotation between the plunger rod resetting part 1026 and the resetting thread 1206 may be larger, such as up to 360 degrees. Multiple rotational rounds could also be imagined.

On the distal injector housing plate 2212 there are also plunger rod support part alignment tabs 2214, which rotationally and axially aligns the distal injector housing 2200 and the plunger rod support part 1300.

Figures 4A-B show the plunger rod 1020 as seen from two different directions. The plunger rod extends from a proximal end 1022 to a distal end 1024. At the distal end 1024 is found the two plunger rod resetting parts 1026, which each travels along one of the two resetting threads 1206 inside the resetting sleeve 1200 when the two parts rotate relatively. The plunger rod resetting parts 1026 are two pin parts positioned opposite another. Other configurations could also be imagined.

The plunger rod 1020 has a plunger rod cavity 1030 (see figure 1 B and figures 19A-I). Thus, the plunger rod 1020 is hollow. Inside the plunger rod cavity 1030 is found the drive spring 1040.

The plunger rod 1020 comprises a number of outer protrusions. The number of outer protrusions includes a pullback part stop part 1021 on the outside surface 1031 of the plunger rod 1020. A distally directed surface 1023 on the pullback part stop part 1021 engages a plunger rod engagement surface 1608 on the pullback part 1600 when the user resets the auto injector 1000 after medicament delivery by rotation of the resetting sleeve 1200 thereby moving the plunger rod 1020 and the pullback part 1600 distally.

The number of outer protrusions also includes a number of plunger rod tabs 1027 located on the outside surface 1031 of the plunger rod 1020. The plunger rod tabs 1027 have a sloping distal surface 1028 and a steep proximal surface 1029. The steep proximal surface 1029 on the most proximally positioned plunger rod tab 1027a engages a plunger rod release tab 1310 on the plunger rod support part 1300 when the auto injector 1000 is in an initial position ready for receiving the cassette 100. This ensures that the plunger rod 1020 and the plunger rod spring 1040 are not allowed to move proximally for medicament delivery before the user initiates medicament delivery. The initiation of medicament delivery - and thereby release of the plunger rod 1020 and the drive spring 1040 allowing the drive spring 1040 to expands ! decompress thereby pushing the plunger rod 1020 in the proximal direction - is done by the user pressing the cassette 100 against the injection site. This presses the injector skin sensor detector 1700 distally bringing a distal release end surface 1709 on the injector skin sensor detector 1700 into contact with the plunger rod release tab 1310. The distal release end surface 1709 pushes the plunger rod release tab 1310 radially outwardly whereby contact with the plunger rod tab 1027a is no longer present. The release of the plunger rod 1020 by the injector skin sensor detector 1700 is shown in details in figures 20A-B.

The remaining plunger rod tabs 1027b ensures that if stopping mid medicament delivery, the plunger rod 1020 does not continue its movement to the most proximal position for full medicament delivery. Early lift of the cassette 100 from the injection site will result in the injector skin sensor detector 1700 being pushed in the proximally due to the spring force of the injector skin sensor detector spring 1710. When the injector skin sensor detector 1700 moves proximally, the distal release end surface 1709 no longer keeps the plunger rod release tab 1310 flexes radially outwardly. This allows the plunger rod release tab 1310 to stop the movement of the plunger rod 1020, by coming into contact with one of the other plunger rod tabs 1027b. See also figures 19H-I.

The number of outer protrusions further includes a longitudinally extending bar 1033 located on the outside surface 1031 of the plunger rod 1020. The longitudinally extending bar 1033 prevents distal movement of the cassette activation part 1500 after positioning a cassette 100 in the auto injector 1000 as described in further details in figures 21A-D.

Figure 5 shows a closeup view of the drive spring 1040. The drive spring 1040 extends from a proximal end 1042 to a distal end 1044. The drive spring 1040 is adapted for moving the plunger rod 1020 in a proximal direction during medicament delivery. When the drive spring 1040 is in a compressed state, it is confined inside the plunger rod cavity 1030 (see figure 1 B and figures 19A-I). When the compressed drive spring 1020 relaxes, it pushes the plunger rod 1020 in the proximal direction resulting in the distal end 1044 of the drive spring 1044 extending outside the plunger rod 1020 at the distal end 1024 of the plunger rod 1020. Inside the plunger rod cavity 1030, the proximal end 1042 of the drive spring 1040 abuts a spring proximal end surface 1032 (see figure 1 B). The distal end 1044 of the drive spring 1040 abuts a spring distal end surface 1056 located at a distal end 1054 of the drive spring guide 1050 (see figure 1 B and figure 6). The drive spring guide 1050 is shown in a closeup view in Figure 6. The drive spring guide 1050 extends from a proximal end 1052 to the distal end 1054. The drive spring guide 1050 comprises a spring guide rod 1058 extending from the proximal end 1052 of the drive spring guide 1050 to the spring distal end surface 1056. The drive spring 1040 is positioned around the spring guide rod 1058 (see figure 1 B).

Figures 7A-B show the plunger rod support part 1300 from two different directions. The plunger rod support part 1300 extends from a proximal end 1302 (view from proximal end in figure 7A) to a distal end 1304 (view from distal end in figure 7B). The plunger rod support part 1300 is positioned between the plunger rod 1020 and a tubular chassis part 1401 of the chassis sleeve 1400.

At the distal end 1304 of the plunger rod support part 1300 is support part end plate 1303. The distal end 1054 of the drive spring guide 1050 is secured in a spring guide connecting opening 1301 in the support part end plate 1303. From the support part end plate 1303, a first proximally extending arm 1305 and a second proximally extending arm 1308 are extending.

On the first proximally extending arm 1305 is plunger rod support bar 1306 and a cassette activation part stop protrusion 1307. The plunger rod support bar 1306 supports and guides the plunger rod 1020 by its abutment with the longitudinally extending bar 1033 on the plunger rod 1020.

Together with the longitudinally extending bar 1033 on the plunger rod 1020 and a distal end protrusion 1510 on the cassette activation part 1500, the cassette activation part stop protrusion 1307 prevents distal movement of the cassette activation part 1500 after positioning a cassette 100 in the auto injector 1000. This is described in further details in figures 21A-D.

On the second proximally extending arm 1308, there is a flexible side arm 1309, which is able to flex radially outwardly. The flexible side arm 1309 comprises the plunger rod release tab 1310 which abuts the steep proximal surface 1029 on the most proximally positioned plunger rod tab 1027a on the plunger rod 1020 prior to activation of the auto injector 1000. When the injector skin sensor detector 1700 is pushed distally by the skin sensor 400 in the cassette 100 (see figures 19A-G), the distal release end surface 1709 of the injector skin sensor detector 1700 abuts the plunger rod release tab 1310 and causes the flexible side arm 1309 to flex radially outwardly. When the flexible side arm 1309 flexes radially outwardly, the plunger rod release tab 1310 no longer abuts the steep proximal surface 1029 on the most proximally positioned plunger rod tab 1027a on the plunger rod 1020. This allows the compressed drive spring 1040 to relax thereby forcing the plunger rod 1020 in the proximal direction for medicament delivery.

At the proximal end 1302 of the plunger rod support part 1300 is a proximal protruding part 131 1. The proximal protruding part 1311 and a support part lock tab 1511 on the cassette activation part 1500 interact for locking the plunger rod support part 1300 in position prior to mounting of the cassette 100 in the auto injector 1000. The support part lock tab 1511 is positioned against the distal end of the proximal protruding part 1311 on the plunger rod support part 1300. The proximal protruding part 1311 is positioned on a proximal flexible part 1312 of the first proximally extending arm 1305. When a release surface 1806 on the cassette detector 1800 is pushed against the proximal protruding part 1311 , the proximal flexible part 1312 flexes radially, thereby releasing the cassette activation part 1500. This allows for locking of the cassette 100 in the auto injector 1000 by proximal movement of the cassette activation part 1500. See further specification for the situation where the user tries to insert a used cassette in the auto injector 1000 in connection with figure 14.

Figures 8A-B shows the pullback part 1600 from two different directions. The pullback part 1600 is extending from a proximal end 1602 to a distal end 1604. The pullback part 1600 extends along the longitudinal direction L with a step type bend 1605 along the direction with a part extending in the radial direction. The pullback part 1600 has cassette activation part tab surfaces 1606 adapted for holding pullback interacting tabs 1506 on the cassette activation part 1500 (see figures 10A-C and figures 19A-H). The pullback part 1600 is tillable relative to the cassette activation part 1500 around connecting points constituting a cassette activation part tab surface 1606 and a pullback interacting tab 1506.

The pullback part 1600 comprises the plunger rod engagement surface 1608 at the distal end 1604 of the pullback part 1600. The plunger rod engagement surface 1608 comes in contact with the pullback part stop part 1021 on the plunger rod 1020 when the plunger rod 1020 moves distally upon resetting of the auto injector 1000. This moves the pullback part 1600 and the cassette activation part 1500 distally (see further description of the movement of the pullback part 1600 and the cassette activation part 1500 in connection with figures 10A-C). The pullback part 1600 further comprises a cassette interacting tab 1601. The cassette interacting tab 1601 (and the pullback part 1600) is movable in the longitudinal direction L between a proximal cassette locking position PP and a distal cassette release position PD (see figures 19A-B). Prior to receiving a cassette 100 in the reusable auto injector 1000, the cassette interacting tab 1601 is in the distal cassette release position PD.

The cassette interacting tab 1601 is shown as being positioned on the pullback part 1600, but could also be integrated into the cassette activation part 1500 instead.

The pullback part 1600 and/or the cassette activation part 1500 may comprise a second cassette interacting tab 161 1 (see figures 32A-D) for structural stability.

The cassette interacting tab 1601 is movable in the radial direction by the user pressing the cassette interacting tab 1601 downwards. This is due to the interaction with a flexible pullback arm 1507 on the pullback part 1500 (see figures 10A-C and figures 19A-H) and the tilting connecting point constituting the cassette activation part tab surfaces 1606 and the pullback interacting tabs 1506. When the user presses the cassette interacting tab 1601 downwards, the cassette activation part 1600 and the pullback part 1500 can be moved in the proximal direction. Doing so moves injector release members 1508 on the pullback part 1500 into the cassette 100 for activation of the cassette 100 as described in connection with figures 19A-H, figures 26A-I, and figures 27A-I.

Figures 9A-B show the chassis sleeve 1400. The chassis sleeve 1400 extends from a proximal end 1402 to a distal end 1404. Figure 9A shows the chassis sleeve 1400 from the proximal end 1402 and figure 9B shows the chassis sleeve 1400 from the distal end 1404.

The chassis sleeve 1400 comprises a tubular chassis part 1401 . The tubular chassis part 1401 is positioned between the plunger rod 1020 and the resetting sleeve 1200.

The tubular chassis part 1401 comprises a longitudinally extending channel 1403. Normally, as shown in figures 9A-B, two longitudinally extending channels 1403 positioned opposite one another on the tubular chassis part 1401 are present in the tubular chassis part 1401. The plunger rod resetting part 1026 travels in the longitudinal direction inside the longitudinally extending channel 1403. On the inside of the tubular chassis part 1401 , a plunger rod support part coupling surface 1408 is also found. The proximally extending arms 1305, 1308 on the plunger rod support part 1300 are extending inside the plunger rod support part coupling surface 1408.

The chassis sleeve 1400 comprises a chassis sleeve plate 1407. Extending in the proximal direction from the chassis sleeve plate 1407 is a distal skin sensor spring support rod 1405. The distal skin sensor spring support rod 1405 supports a distal end 1714 of the injector skin sensor detector spring 1710. The injector skin sensor detector spring 1710 can move in the longitudinal direction relative to the chassis sleeve 1400. The injector skin sensor detector spring 1710 can thereby extend at least partly into the tubular chassis part 1401 when in a distal position.

Extending in the proximal direction from the chassis sleeve plate 1407 is also a distal cassette detector spring support rod 1406. The distal cassette detector spring support rod 1406 supports a distal end 1814 of the cassette detector spring 1810 (see figures 22A-C). The cassette detector 1800 can move in the longitudinal direction relative to the chassis sleeve 1400.

Extending proximally from the chassis sleeve plate 1407 are coupling surfaces 1409. The outside 1413 of the coupling surfaces 1409 extend inside chassis sleeve channels 2108 on the proximal injector housing 2100 (see figure 16). The inside 1414 of the coupling surfaces 1409 contains the outer coupling surfaces 1108 on the cassette receiver 1100 (see figures 15A-B).

The chassis sleeve 1400 further comprises a number of resetting sleeve interacting tabs 1410 on a proximal outside end of the tubular chassis part 1401. The resetting sleeve interacting tabs 1410 has on one side a sloping surface 1411 and on the other side a steep surface 1412. As described in connection with figure 2, during reloading of the auto injector 1000, the resetting sleeve 1200 is rotated in a first rotational direction DR1 relative to the chassis sleeve 1400. This brings the chassis sleeve interacting hooks 1210 in contact with the resetting sleeve interacting tabs 1410. The contact, when rotating in the first rotational direction DR1 , is between the sloping surfaces 1211 , 141 1 on the chassis sleeve interacting hooks 1210 and the resetting sleeve interacting tabs 1410. When the sloping surfaces 1211 , 1411 coming into contact with each other, the chassis sleeve interacting hooks 1210 flex radially outwardly allowing the resetting sleeve 1200 to continue its rotation. However, if rotating in a direction opposite the first rotational direction DR1 , the steep surfaces 1212, 1412 on the chassis sleeve interacting hooks 1210 and the resetting sleeve interacting tabs 1410 come into contact with each other. This prevents further relative rotation between the two parts.

Figures 10A-C show the cassette activation part 1500 seen from three different directions. The cassette activation part 1500 extends from a proximal end 1502 to a distal end 1504. The cassette activation part 1500 comprises injector release members 1508 extending proximally. The cassette activation part 1500 are movable into the cassette 100 for activation of the cassette 100 as described in connection with figures 19A-H, figures 26A-I, and figures 27A-I. Each injector release members 1508 comprises a track-guide protrusion 1509 at the proximal end of the cassette activation part 1500. The cassette activation part 1500 also comprises the flexible pullback arm 1507 interacting with the pullback part 1600 when the user presses the cassette interacting tab 1601 radially inwards (see figures 8A-B and figure 19A).

The pullback part 1600 is tillable relative to the cassette activation part 1500 around connecting points constituting a cassette activation part tab surface 1606 and a pullback interacting tab 1506. The pullback part 1600 is locked to the cassette activation part 1500 at the connecting points constituting a cassette activation part tab surface 1606 and a pullback interacting tab 1506 such that the two parts 1500, 1600 move together in the longitudinal direction L.

The cassette activation part 1500 also comprises a distal end protrusion 1510, which together with the longitudinally extending bar 1033 on the plunger rod 1020 and the cassette activation part stop protrusion 1307 on the plunger rod support part 1300 prevents distal movement of the cassette activation part 1500 after positioning a cassette 100 in the auto injector 1000 as described in further details in figures 21A-D and plunger rod 1020 movement in the proximal direction for medicament delivery.

The cassette activation part 1500 further comprises the support part lock tab 1511. The support part lock tab 1511 locks the plunger rod support part 1300 in position prior to mounting of the cassette 100 in the auto injector 1000. The support part lock tab 1511 is positioned against the distal end of the proximal protruding part 1311 on the plunger rod support part 1300.

The cassette activation part 1500 further comprises a guiding tab 1512 that slides inside a chassis sleeve 1103 in the cassette receiver. Figure 12 shows the injector skin sensor detector 1700 and figure 11 the injector skin sensor detector spring 1710. The injector skin sensor detector 1700 extends from a proximal end 1702 to a distal end 1704. The injector skin sensor detector spring 1710 extends from a proximal end 1712 to a distal end 1714. The injector skin sensor detector 1700 comprises a proximal skin sensor spring support rod 1705. The proximal end 1712 of the injector skin sensor detector spring 1710 is positioned around the proximal skin sensor spring support rod 1705. The injector skin sensor detector spring 1710 is thereby positioned between the proximal skin sensor spring support rod 1705 on the distal skin sensor spring support rod 1405 and the distal injector skin sensor detector support rod 1405 on the chassis sleeve 1400.

Extending proximally from the proximal skin sensor spring support rod 1705 is an injector skin sensor detector pin 1703, which is configured for entering the cassette 100 and interacting with the cassette skin sensor 400 as described in connection with figures 26A-I, figures 27A-I and figures 29A-G.

The injector skin sensor detector 1700 comprises a plate part 1706 with a plate part channel 1707 allowing the plunger rod tabs 1027 on the plunger rod 1020 to pass by during medicament delivery and reloading of the auto injector 1000.

Figure 14 shows the cassette detector 1800 and figure 13 shows the cassette detector spring 1810. The cassette detector 1800 extends from a proximal end 1802 to a distal end 1804. The cassette detector spring 1810 extends from a proximal end 1812 to a distal end 1814. At the distal end 1804 of the cassette detector 1800 is a proximal cassette detector spring support rod 1805. The proximal end 1812 of the cassette detector spring 1810 is positioned around the proximal cassette detector spring support rod 1805. The cassette detector spring 1810 is thereby positioned between the proximal cassette detector spring support rod 1805 on the cassette detector 1800 and the distal injector cassette detector spring support rod 1406 on the chassis sleeve 1400 (see figures 22A-C).

Extending proximally is a cassette detector pin 1803, which is configured for entering into and interacting with the cassette 100. The cassette detector 1800 further comprises the release surface 1806, which unlocks the cassette activation part. When the cassette 100 is inserted in the auto injector 1000, the release surface 1806 on the cassette detector 1800 is in contact with the proximal protruding part 1311 on the plunger rod support part 1300 (see figure 22A). The cassette detector 1800 detects that a cassette 100 is positioned in the auto injector 1000 when the cassette detector pin 1803 comes in contact with a proximal end 422 of a skin sensor 400 in the cassette 100. This contact result in the cassette detector 1800 being pushed distally. Thereby, the release surface 1806 is pushed against the proximal protruding part 131 1 on the plunger rod support part 1300. The proximal flexible part 1312 flexes radially inwardly as a consequence thereof, thereby releasing the cassette activation part 1500 from the plunger rod support part 1300 (see figure 22C). This allows for locking of the cassette 100 in the auto injector 1000 by further proximal movement of the cassette activation part 1500 (see figures 26A-I and figures 27A-I).

If a used cassette is inserted into the auto injector 1000, the cassette detector pin 1803 is not pushed distally by the proximal end 422 of the skin sensor 400 since the skin sensor is locked in a position being so proximal compared to the skin sensor position in a new cassette that pushing the cassette detector pin 1803 distally is impossible. The cassette activation part 1500 is therefore not released from the plunger rod support part 1300, and the used cassette is not locked in the auto injector 1000 (see figure 22B).

Figures 15A-C show the cassette receiver 1100. The cassette receiver 1100 extends from a proximal end 1102 to a distal end 1104. The cassette receiver 1100 comprises a tubular part 1101 at its proximal end 1102. The cassette 100 is inserted inside the tubular part 1 101 of the cassette receiver 1100 when received in the auto injector 1000. Inside the tubular part 1101 are cassette locking parts 1109 for securing the cassette 100 inside the auto injector 1000 as described in figures 24A-E.

Distally of the tubular part 1 101 is a cassette receiver end plate 1110 against which the cassette 100 is positioned. Extending in the distal direction of the cassette receiver end plate 1110 is a first spring support surface 1105 inside which the injector skin sensor detector spring 1710 is positioned. The injector skin detector pin 1703 and the proximal skin sensor spring support rod 1705 are further normally positioned inside the first spring support surface 1105. Also extending in the distal direction of the cassette receiver end plate 1110 is a second spring support surface 1106 inside which the cassette detector spring 1810 is positioned. The majority of the cassette detector 1800 is further normally positioned inside the second spring support surface 1106.

The cassette receiver 1100 is positioned inside the proximal injector housing 2100 (see figure 1 B, and figure 16). Between the cassette receiver 1100 and the proximal injector housing 2100 is the chassis sleeve 1400. The proximal injector housing 2100 and the cassette receiver 1100 are rotationally fixed by mutual interaction with the chassis sleeve 1400. The outer coupling surfaces 1108 extends inside 1414 the coupling surfaces 1409 on the chassis sleeve 1400, and the outside 1413 of the coupling surfaces 1409 extends inside the chassis sleeve channels 2108 of the proximal injector housing 2100.

The cassette receiver 1100 comprises an activation part channel 1107 through which the cassette interacting tab 1601 extends.

The cassette receiver end plate 1110 has a number of openings including a plunger rod opening 1120 through which the plunger 1020 can extend for medicament delivery. The injector skin sensor detector pin 1703 can extend into the cassette 100 through an injector skin sensor detector opening 1115 in the cassette receiver end plate 1110. The cassette detector pin 1803 can extend into the cassette 100 through a cassette detector opening 1116 in the cassette receiver end plate 1 110. The injector release members 1508 can extend into the cassette 100 through injector release member openings 1118 in the cassette receiver end plate 1110.

Figure 16 shows the proximal injector housing 2100. The proximal injector housing 2100 extends from a proximal end 2102 to a distal end 2104. At the proximal end 2102, the proximal injector housing 2100 comprises a first tubular part 2101 with a cassette view opening 2106 through which the cassette 100 can be seen. At the distal end 2104, the proximal injector housing 2100 comprises a second tubular part 2109. The second tubular part 2109 comprises a second activation part channel 2107 through which the cassette interacting tab 1601 extends. Inside the second tubular part 2109 is chassis sleeve channels 2108 in which the outside 1413 of the coupling surfaces 1409 on the chassis sleeve 1400 are found. In the shown example, the first tubular part 2102 and the second tubular part 2109 have non-circular cylindrical shapes. Alternative shapes, such as round, elliptical, squared, triangular cylindrical shapes, or similar could also be imagined

Figure 17A shows the plunger rod 1020 and the resetting sleeve 1200 during a resetting of the auto injector 1000 by rotation of the resetting sleeve 1200, where the plunger rod resetting part 1026 travels along the resetting thread 1206 in the resetting sleeve 1200.

In figures 17B-C, the distal injector housing 2200 is shown together with the plunger rod 1020 and the resetting sleeve 1200 in a view from the proximal direction. After end resetting in figure 17C, the plunger rod resetting part 1026 abuts the rotational stop surface 2210 on the distal injector housing plate 2212 of the distal injector housing 2200. This prevents further rotational movement of the resetting sleeve relative 1200 relative to the plunger rod 1020 since the resetting sleeve 1200 is rotationally locked to the distal injector housing 2200. The plunger rod resetting part 1026 comes in contact with the rotational stop surface 2210 after the plunger rod resetting part 1026 has moved along the resetting thread 1206.

Figures 18A-E show the resetting of the auto injector 1000 by rotation of the resetting sleeve 1200. The resetting sleeve 1200 is shown in a view partly showing the inside the auto injector 1000 during resetting. The movement of the plunger rod resetting part 1026 when rotating the distal injector housing 2200, and also the resetting sleeve 1200 rotationally locked thereto, forces the plunger rod 1020 to move distally due to the interaction of the plunger rod resetting part 1026 with the resetting thread 1206. In figure 18D, the plunger rod resetting part 1026 abuts the rotational stop surface 2210 inside the distal injector housing 2200 thereby preventing further rotational movement of the resetting sleeve 1200 and the distal injector housing 2200 relative to the plunger rod 1020.

Figures 19A-G show cut-throughs of the auto injector 1000 during a process of receiving a cassette, unlocking of the cassette, whereby the plunger rod can be unlocked, during medicament delivery and during resetting of the auto injector after medicament delivery. The cassette has been omitted in figures 19A-G for a clearer view of the injector parts.

Figure 19A shows auto injector 1000 in the configuration prior to receiving the cassette. In figure 19B, a cassette has been received in the auto injector 1000 and the cassette interacting tab 1601 has been pressed radially inwardly and in the proximal direction, whereby the injector release members 1508 have been moved proximally. This locks the cassette in the auto injector 1000. Along with the injector release member 1508, the injector skin sensor detector pin 1703 also moves proximally. The injector skin sensor detector pin 1703 thereby comes into contact with a skin sensor 400 in the cassette 100. In the locked position shown in figure 19B, a cap 700 on the cassette (see figures 30A-D) can be removed. This unlocks the skin sensor 400 allowing it to move proximally (see figures 26A-I, figures 27A-I and figures 29A- G).

The removal of the cap 700 and the proximal movement of the skin sensor 400 in the cassette 100 allows the injector skin sensor detector pin 1703 to move further proximally into the cassette 100 as shown in figure 19C. The auto injector and cassette system is now ready for medicament delivery.

In figure 19D, the user has pressed the cassette against the injection site, which pushes the skin sensor 400 to a distal position also pushing the injector skin sensor detector pin 1703 into the auto injector 1000. Pushing the injector skin sensor detector 1700 into the auto injector 1000 unlocks the plunger rod 1020 (see details in figures 20A-B). The plunger rod spring 1040 therefore pushes the plunger rod 1020 in the proximal direction medicament delivery as shown in figure 19E.

In figure 19F, the user has removed the cassette from the injection site after end medicament delivery, which allows injector skin sensor detector 1700 to push the skin sensor 400 to a locked proximal position (see figures 25A-B, figures 26A-I, figures 27A-I and figures 29A-G). The cassette can now be removed from the auto injector 1000.

In figure 19G, the user has reloaded the auto injector 1000, which has retracted the cassette activation part 1500, the pullback part 1600 and the plunger rod 1020 and reloaded the plunger rod spring 1040.

Figures 19H-I show the auto injector of figures 19A-G in a situation, where the user has interrupted the medicament delivery and removed the cassette and auto injector system from the injection site prior to completing the medicament delivery. The two views are cut-through of the auto injector 1000 at two different angles. If the user has interrupted the medicament delivery mid-delivery, the skin sensor 400 in the cassette 100 is pushed forward to a locked position by the injector skin sensor detector 1700 of the auto injector 1000 due to the injector skin sensor spring 1710 pushing the injector skin sensor detector 1700 in the proximal direction as shown in figure 19H. The proximal movement of the injector skin sensor detector 1700, secures the plunger rod 1020 in an intermediate position. When the injector skin sensor detector 1700 moves proximally, the distal release end surface 1709 no longer keeps the plunger rod release tab 1310 flexes radially outwardly. This allows the plunger rod release tab 1310 to stop the movement of the plunger rod 1020, by coming into contact with one of the plunger rod tabs 1027b. This ensures that if stopping mid-delivery, the plunger rod 1020 does not continue its proximal movement to the most proximal position for full medicament delivery. The remaining medicament is thereby kept in the now locked cassette. The cassette can be removed from the auto injector 1000 during resetting of the auto injector 1000.

Alternatively, the cassette interacting tab may be moved from the proximal cassette locking position PD to the distal cassette release position PP prior to resetting the auto injector. This may seem more natural for the user wanting to remove and discharge of the cassette before resetting the auto injector. The movement of the cassette interacting tab from the proximal cassette locking position PD to the distal cassette release position PP may be user controlled by movement of e.g. the cassette interacting tab. Figure 20A-B show the unlocking of the plunger rod 1020 by the user pushing the injector skin sensor detector 1700 into the auto injector 1000 after cap removal. Figure 20A-B are close-up views of the area M marked with the dotted square in figure 19D. When the injector skin sensor detector 1700 is pushed distally, the distal release end surface 1709 on the injector skin sensor detector 1700 abuts the plunger rod release tab 1310 and causes the flexible side arm 1309 to flex radially outwardly. When the flexible side arm 1309 flexes radially outwardly, the plunger rod release tab 1310 no longer abuts the plunger rod tabs 1027a on the plunger rod 1020. This allows the compressed drive spring 1040 to relax thereby forcing the plunger rod 1020 in the proximal direction for medicament delivery. The movements are indicated with the arrows. Figure 19E shows the movement the plunger rod 1020 in the proximal direction medicament delivery after release of the plunger rod 1020.

Figures 21A-D show the interaction of the longitudinally extending bar 1033 on the plunger rod 1020, the distal end protrusion 1510 on the cassette activation part 1500, and the cassette activation part stop protrusion 1307 on the plunger rod support part 1300. This interaction ensures that the cassette activation part 1500 cannot move distally during medicament delivery. In figure 21 A is shown the auto injector 1000 prior to a cassette 100 being inserted in the auto injector 1000. The cassette activation part 1500 is still in the distal cassette release position PD. The distal end protrusion 1510 is positioned between the plunger rod support bar 1306 and the cassette activation part stop protrusion 1307 in the initial position prior to positioning a cassette 100 in the auto injector 1000. In figure 21 B, the cassette activation part 1500 has been moved to the proximal cassette locking position PP locking the cassette 100 in the auto injector 1000. The injector release members 1508 now extend into the cassette 100 (not shown in the figures). In this position, the distal end protrusion 1510 on the cassette activation part 1500 is allowed to flex radially inwardly and move to a position proximally of the cassette activation part stop protrusion 1307 on the first proximally extending arm 1305. In figure 21 C, the plunger rod 1020 has been releases and now moves proximately for medicament delivery. This moves the longitudinally extending bar 1033 on the plunger rod 1020 to a proximal position in contact with the distal end protrusion 1510 preventing the distal end protrusion 1510 from flexing inwardly. The distal end protrusion 1510 is thereby prevented from moving distally by the longitudinally extending bar 1033 and the cassette activation part stop protrusion 1307. In figure 21 D, medicament delivery has finalized and the plunger rod 1020 is in the most proximal position. The distal end protrusion 1510 is still prevented from moving distally until auto injector 1000 has been reloaded and the plunger rod 1020 retracted distally. Figures 22A-C show the cassette detector 1800 and cassette 100 interaction for locking the cassette 100 in the auto injector 1000. When the cassette 100 is inserted in the auto injector 1000, the release surface 1806 on the cassette detector 1800 is in contact with the proximal protruding part 1311 on the plunger rod support part 1300. The cassette detector pin 1803 extends proximately through the end plate 1110 in the cassette receiver 1100 as shown in figure 22A.

The cassette detector 1800 detects that a cassette 100 is positioned in the auto injector 1000 when the cassette detector pin 1803 comes in contact with a proximal end 422 of a skin sensor 400 in the cassette 100. This contact result in the cassette detector 1800 being pushed distally as shown in figure 22C. Thereby, the release surface 1806 is pushed against the proximal protruding part 1311 on the plunger rod support part 1300. The proximal flexible part 1312 flexes radially inwardly as a consequence thereof, thereby releasing the cassette activation part 1500 from the plunger rod support part 1300. This allows for locking of the cassette 100 in the auto injector 1000 by further proximal movement of the cassette activation part 1500.

If a used cassette is inserted into the auto injector 1000, the cassette detector pin 1803 is not pushed distally by the proximal end 422 of the skin sensor 400 (see figure 23), since the skin sensor is locked in a position being so proximal compared to the skin sensor position in a new cassette that pushing the cassette detector pin 1803 distally is impossible as shown in figure 22B. The cassette activation part 1500 is therefore not released from the plunger rod support part 1300, and the used cassette is not locked in the auto injector 1000.

Figure 23 shows an exploded view of a cassette 100 extending along a longitudinal direction L, and a syringe 200 for being mounted in the cassette 100. The cassette comprises a syringe holder 300, a skin sensor 400, an index ring 500, a cassette housing 600, a cap 700, and possibly a cassette housing cover 800. The cassette housing cover 800 may be formed as an integral part of the cassette housing 700.

The syringe 200 extends from a proximal end 202 to a distal end 204. At the distal end 202 of the syringe 200 is a flange 220, which assists in securing the syringe 200 inside the cassette 100. The medicament is contained inside a syringe compartment 206, which is in fluid connection with a syringe outlet 208 (see figures 30A-D). Inside the syringe compartment 206 is a stopper 210 (see figure 28B), which pushes medicament out of the syringe outlet 208 when moving in the proximal direction. Normally, the stopper 210 is pushed in the proximal direction by means of a plunger rod 1020 included in the auto injector 1000 into which the cassette 100 with the syringe 200 is mounted. The syringe outlet 208 may be a hollow needle attached to the syringe compartment 206 as shown in figures 30A-D. The needle 208 may be detachable to the syringe compartment by means or e.g. threaded connection or a Luer lock, or be an integral part of the syringe. The syringe compartment 206 has a shoulder 218 at its proximal connecting to the syringe outlet 208. Positioned around the syringe shoulder 218 is a needle shield 212, e.g. a rigid needle shield. The needle shield 212 may be constructed from two parts; an inner part and an outer part. The needle shield 212 protects the needle prior to use.

The syringe holder 300 is extending from a proximal end 302 to a distal end 304 and is has openings 306, 315 at both of these ends 302, 304. The syringe 200 is mounted in the syringe holder 300 through the opening 315 at the distal end 304 of the syringe holder 300. When mounted in the syringe holder 300, the syringe compartment 206 is contained in a syringe holder tubular part 310 having a syringe holder tubular part inspection opening 312 through which the syringe 200 can be inspected. At the distal end 304 of the syringe holder 300 is a distal tubular ring part 314 having a larger outer diameter than that of the syringe holder tubular part 310. At the most distal end, there is a hinged syringe holder lid 330 with a lid opening 332 having a diameter, which allows passage of the plunger rod 1020 included in the auto injector 1000 there through. The syringe holder lid 330 is closed during assembly when a syringe 200 has been inserted into the cassette 100. The shown syringe lid 330 is just one example of a way to close the syringe holder 300 and secure the syringe 200 inside the syringe holder 300. A number of different ways to secure the syringe 200 inside the syringe holder 300 may also be imagined. For example, the syringe holder lid 330 may be substituted with flexible arms, which flex inwardly to secure the syringe 200 after mounting of the same in the syringe holder 300. The proximal opening 306 in the syringe holder 300 has a diameter, which allows the needle shield 212 to pass there through, but which prevents the syringe compartment 206 to pass there through.

The cassette housing 600 extends from a proximal end 602 to a distal end 604 and has an opening 606 at the distal end 602 through which the index ring 500, the skin sensor 400, and the syringe holder 300 is mounted. When the cassette 100 is assembled, the cassette housing 600 at least partly if not fully encloses the syringe holder 300, the syringe 200 when positioned in the syringe holder 300, the skin sensor 400, and the index ring 500. The syringe holder 300 will normally be longitudinally and rotationally locked to the cassette housing 600. The cassette housing 600 has an inspection opening 610 on at least one surface side allowing the user to inspect the syringe compartment 206 containing the medicament when the syringe 200 is mounted inside the cassette 100. The cassette 100 may be symmetrically constructed such that it may be mounted in an auto injector in different orientations. At the distal end of the cassette housing, cassette securing tabs 612 are positioned. The locking mechanism for locking the cassette 100 in the auto injector 1000 is shown and described in figures 24A-E.

The cassette cap 700 is removably attached to the cassette housing 600 at the proximal end 602 of the cassette housing 600. The cassette cap 700 comprises an inner cassette cap part 714 with second distally extending part 710 in the form of a tubular cap part, which is configured for griping the needle shield 212 by means of e.g. a gripping portion 712. When removing the cassette cap 700, the needle shield 212 is also removed allowing for medicament delivery. Enclosing the inner cassette cap part 714 is an outer cassette cap part 716, which the user can hold when removing the cassette cap 700. The inner and the outer cassette cap parts 714, 716 may also be formed as one integral item. On the inner cassette cap part 714 is also found a cap locking part 706 with a cassette cap locking protrusion 708. The cap locking part 706 with the cassette cap locking protrusion 708 ensures that the cassette cap 700 is firmly secured to the cassette housing 600 before enabling the cassette 100 for cassette cap removal.

Positioned around the syringe holder 300 is a skin sensor 400, which extends from a proximal end 402 to a distal end 404. At the proximal end 402 of the skin sensor 400 is a proximal skin contact surface 405, which rest against the skin of the patient during medicament delivery. At the proximal end 402 is also a proximal recess 406 in which the cassette cap locking protrusion 708 of the cassette cap 700 is secured prior to assembling the cassette 100 in the auto injector 1000 and initiation release of the cassette cap 700. The proximal recess 406 is adjacent to a protruding tab 408 connected by a proximal protruding ramp 410 as more clearly seen in figures 30A-D.

The skin sensor 400 has a tubular skin sensor part 420 from where cassette skin sensor pins 422 extends in the distal direction. The tubular skin sensor part 420 has an inspection opening 426 for inspection of the syringe 200. The skin sensor 400 is normally symmetrically with a cassette skin sensor pin 422 on both sides of the skin sensor 400 and inspection openings 426 on both sides as well.

The skin sensor 400 is rotationally locked relative to the syringe holder 300. The skin sensor 400 is movable relative to the syringe holder 300 in the longitudinal direction L. The skin sensor 400 may move relative to the syringe holder 300 between a plurality of longitudinal positions including at least a proximal longitudinal position LP and a distal longitudinal position LD. As seen in figure 25A, three proximal positions LP are present apart from the distal position LD. The three proximal positions LP include an initial locked position LP1 , an intermediate position LP2, and a final locked position LP3. The proximal positions LP are all positions, where the skin sensor 400 covers the syringe outlet 206 when a syringe 200 is mounted in the cassette 100, whereas the syringe outlet 206 is exposed when the skin sensor 400 is in the distal longitudinal position LD. The proximal positions LP1 , LP2, LP3 may be positions in which the skin sensor 400 is locked relative to the syringe holder 300 in at least one longitudinal direction. Thus, in a locked position, proximal and/or distal movement of the skin sensor 400 relative to the syringe holder 300 is prevented. Whether the position is a locked position or not is determined by the rotational position of the index ring 500, as the skin sensor 400 and the index ring 500 are coupled such the rotation of the index ring 500 locks and/or releases the skin sensor 400 for longitudinal movement in either the proximal and/or the distal direction.

The skin sensor 400 also has a first locking recess 412 and a second locking recess 414 for interacting and coupling with the index ring 500. Between the two locking recesses 412, 414 is a first locking tab 413 and distally of the second locking recess 414 is a second locking tab 415. The second locking tab 415 is longer than the first locking tab 413. The distally directed surface of the second locking tab 415 is referred to as the first distal surface 416. The skin sensor 400 also comprises a proximally directed surface referred to as the first proximal surface 418. The first proximal surface 418 is proximally of the first locking recess 412.

The index ring 500 extends from a proximal end 502 to a distal end 504. The index ring 500 is positioned around the syringe holder 300 and is longitudinally locked to the syringe holder 300. The index ring 500 is rotationally movable relative to the skin sensor 400 ! the syringe holder 300 between a plurality of rotational positions including at least a first rotational position R1 in which the skin sensor 400 is prevented from moving distally, and a second rotational position R2 in which the skin sensor 400 is moveable between the distal longitudinal position LD and the proximal longitudinal position LP. The rotational positions are illustrated in figure 25B, and as seen in the figure, the two rotational positions; the cap-release rotational position and the delivery rotational position both fall under the definition of a second rotational position R2 in which the skin sensor 400 is moveable between the distal longitudinal position LD and the proximal longitudinal position LP (see also the positions in figures 26B-E)

The index ring 500 has two first longitudinally extending part 506 positioned opposite each other on the index ring 500. A tubular index ring part 520 on the index ring 500 is extending around the syringe holder 300. The index ring 500 comprises a first radially extending part 522, which may be part of the first radially extending part 522 as shown most clearly in figures 26A-I. The first radially extending part 522 has a first surface area 528 extending between a first proximal surface 524 and a first distal surface 526 (see e.g. figure 26H). The first surface area 528 comprises a track 530 extending from a first corner 532 of the surface area 528 to a second corner 534 of the surface area 528 as shown in figure 26A. The surface area 528 on the first radially extending part 522 need not cover the entire surface of the first radially extending part 522, but can instead be a smaller area, which is defined by the by the two corners 532, 534 between which the track 530 extends.

The track 530 extends from the first corner 532 in an angled direction towards the second corner 534, wherein the angled directions is between 20 and 70 degrees, such as between 30 and 60 degrees, such as between 35 and 55 degrees, such as between 40 and 50 degrees, such as approximately 45 degrees relative to the longitudinal direction of the cassette. In the track 530m shown most clearly in figures 26A-I, the track 530 comprises a first track section 536, a second track section 538 and a third track section 540. The first track section 536 extends from the first corner 532 in a first angled direction towards a first middle point 542, the second track section 538 extends from the first middle point 542 to a second middle point 544 along the longitudinal direction of the cassette in a second angle direction, and the third track section 540 extends from the second middle point 544 in a third angled direction towards the second corner 534, as shown most clearly in figure 26I.

The first and/or third angled directions are normally sloping directions, with an angle between 20 and 70 degrees, such as between 30 and 60 degrees, such as between 35 and 55 degrees, such as between 40 and 50 degrees, such as approximately 45 degrees relative to the longitudinal direction of the cassette. The second track section 538 is normally a plateau track section with a second angled directions between -20 and 20 degrees, such as between -10 and 10 degrees, such as approximately 0 degrees relative to the longitudinal direction of the cassette.

On the first longitudinally extending part 506 of the index ring 500 is a second radially extending part 512. The second radially extending part 512 forms a locking tab 507, which is configured for fitting into the two locking recesses 412, 414 on the skin sensor 400. The locking tab 507 has a second proximal surface 514 and a second distal surface 516 of the second radially extending part 512.

The position of the locking tab 507 and thereby the rotational position of the index ring 500 relative to the skin sensor 400 is controlled by one or more injector release members 1508 in the auto injector 1000 when the cassette 100 is secured in the auto injector 1000. More specifically, the index ring 500 is configured for rotating from the first rotational position R1 to a second rotational position R2 when the cassette 100 is inserted in the auto injector 1000 and a track-guide protrusion 1509 comprised in the auto injector travels proximally inside the track 530. When the track-guide protrusion 1509 travels distally again, the index ring 500 rotates back form the second rotational position R2 to the first rotational position R1. Thus, by retrieving the injector release member 1508 with the track-guide protrusion 1509 into the auto injector again, the index ring is rotated back to its initial position.

As seen in figure 25B and figures 26B-E, the two rotational positions; the cap-release rotational position and the delivery rotational position both fall under the definition of a second rotational position R2 in which the skin sensor 400 is moveable between the distal longitudinal position LD and the proximal longitudinal position LP. Thus, the second rotational position R2 need not be a position from where the index ring 500 cannot rotate further. The second rotational position may also be an intermediate position in which the skin sensor 400 is unlocked, but in which the skin sensor 400 is still prevented from moving to the most proximal position and/or the most distal position possible.

When assembling the cassette 100 and the auto injector 1000, the cassette 100 is first loaded into the auto injector 1000. Upon loading of the cassette 100 in the auto injector 1000, cassette securing tabs 612 at the distal end 604 of the cassette housing 600 snap behind corresponding cassette locking parts 1109. By forward movement of the injector release member 1508, the cassette securing tabs 612 are prevented from deflecting and moving past the cassette locking parts 1109 thereby locking the cassette 100 to the auto injector 1000. As the cassette 100 is now firmly locked inside the auto injector 1000. When the injector release member 1508 moves distally again, the cassette 100 is unlocked. The locking process is shown in figures 24A-E, where figures 24A-C show the cassette being inserted into the injector 1000 and engaging into a snap fit connection. Figures 24D-E show the movement of the injector release member 1508 into the cassette 100 thereby locking the cassette 100 to the injector 1000. Thus, the injector comprises one or more cassette locking parts 1109 configured for engaging in a snap-fit connection with corresponding one or more cassette securing tabs 612 on the cassette 100 when the cassette is inserted into the injector, and wherein proximal movement of the injector release member 1508 prevents a disengagement of the snap-fit connection thereby securing the cassette 100 inside the auto injector 1000. The locking mechanism shown in figures 24A- E could alternatively be substituted with the similar locking turned 90 degrees.

As described in connection with figures 10A-C, the auto injector 1000 comprises injector release members 1508 each comprising a track-guide protrusion 1509. The injector release member 1508 travels inside the index ring track 530 thereby rotating the index ring 500, when the auto injector is activated after a cassette 100 is mounted in the auto injector 1000.

As described in connection with figure 11 and figure 12, the auto injector 1000 further comprises an injector skin sensor detector pin 1703 and an injector skin sensor detector spring 1710, which pushes the injector skin sensor detector pin 1703 proximally. When the cassette 100 is mounted in the auto injector 1000, the injector skin sensor detector pin 1703 will push the skin sensor 400 proximally when the skin sensor 400 is free to move proximally, and the user is not pressing the skin sensor in the distal direction simultaneously. Normally, the injector skin sensor detector pin 1703 will be abutting one of the cassette skin sensor pins 422 in the skin sensor 400.

As described in connection with figure 13 and figure 14, inside the auto injector 1000 is a cassette detector 1800 and a cassette detector spring 1810, which detects when a cassette 100 has been mounted in the auto injector 1000 by making contact with the other cassette skin sensor pin 422 in the skin sensor 400.

Figures 26A-I show the syringe holder 300, the skin sensor 400, the index ring 500, and the injector release member 1508 in the injector in the different skin sensor longitudinal positions and index ring rotational positions as the injector release member 1508 moves longitudinally in the index ring track 530.

Figure 26A shows the initial locked position in which the cassette 100 is in prior to use. The locking tab 507 on the index ring 500 is secured in the first locking recess 412 on the skin sensor 400, which prevents longitudinal movement of the skin sensor 400 relative to the syringe holder 300. The skin sensor 400 is in the initial locked position LP1 and the index ring 500 is in the first rotational position R1. The first rotational position may also be seen as a locking rotational position, since this rotational position always locks the skin sensor 400 longitudinal in one of the proximal longitudinal positions.

Figure 26B shows the cap-release position in which the cassette cap 700 can be removed from the cassette 100 (see description of figures 30A-D for further details). Between figure 26A and figure 26B, the auto injector track-guide protrusion 1509 on the injector release member 1508 has moved into the index ring track 530 through the injector release member opening 322 and into and along the first track section 536 and is in the second plateau track section 538 in figure 26B. This has rotated the index ring 500 into the cap-release rotational position Rcr in which the locking tab 507 is released from the first locking recess 412 in the distal direction allowing the skin sensor to move proximally until the locking tab 507 abuts the second locking tab 415, which is longer than the first locking tab 413 securing the locking tab 507 inside the first locking recess 412 in figure 26A. figure 26B shows the position of the skin sensor 400 after release, but before the skin sensor 400 is moved from the initial locked position LP1 to the ready-to-remove-cap position LP2.

In figure 26C, the skin sensor 400 has moved proximately to the intermediate position LP2, where the cassette cap 700 can be removed. The index ring 500 is still in the cap-release rotational position Rcr, and the locking tab 507 abuts the second locking tab 415, which ensures that the skin sensor 400 is prevented from moving further in the proximal direction during cassette cap removal. The skin sensor 400 can however be moved in the distal direction by a user. This is shown in figure 26D, where the skin sensor is pushed into the distal longitudinal position LD where the needle 208 is no longer covered by the skin sensor 400 but instead inserted into an injector site. A second proximal surface 514 on the second radially extending part 512 / locking tab 507 abuts a second distal surface 424 on the skin sensor 400 therefore preventing further distal movement of the skin sensor 400.

When the skin sensor 400 is pushed into the distal longitudinal position LD as shown in figure 26D, the auto injector track-guide protrusion 1509 is ready to moved further proximally in the index ring track 530. When moving along the third track section 540, the index ring 500 is rotated to the delivery rotational position Rd as shown in figure 26E. When the auto injector track-guide protrusion 1509 reaches this position inside the index ring track 530, the injector release member 1508 is decoupled from the plunger rod 1020. The plunger rod 1020 is thereby enabled for further proximal movement for medicament delivery while the injector release member 1508 remains in the position as shown in figure 26A.

After medicament delivery, the user removed the skin sensor 400 from the skin and the injector skin sensor detector pin 1703 and injector skin sensor detector spring 1710 ensures that the skin sensor 400 is pushed first into the intermediate position LP2 as shown in figure 26F and finally into the final position LP3 as shown in figure 26G. When the skin sensor 400 is the final position LP3 as shown in figure 26G, the plunger rod 1020 can be moved distally by resetting of the auto injector 1000. The plunger rod 1020 and the injector release member 1508 moves together distally, which forces the index ring 500 to rotate from the delivery rotational position Rd into the first rotational position R1 again. When the index ring 500 is in the first rotational position R1 once more, the skin sensor 400 is locked longitudinally, this time in the final position LP3 as shown in figure 26H. The locking tab 507 now abuts a first distal surface 416 on the second locking tab 415. Figure 26I shows the locked position, which the auto injector forces the cassette into if a user having removed the cassette cap when the cassette was in a configuration as shown in figure 26C, but for some reason have been prevented from continuing the medicament delivery process by inserting the needle into the injections site by pushing the skin sensor 400 distally. If this happens, the auto injector may be programmed to after a pre-determined time period move the injector release member 1508 distally, whereby the index ring 500 rotates into the first rotational position R1 thereby locking the skin sensor in the intermediate position LP2, where the locking tab 507 is secured in the second locking recess 414 on the skin sensor 400. The cassette 100 will be seen as being a used cassette if the user tries to mount it again the auto injector 1000, since the injection needle 208 may have been contaminated after removal of the needle shield 212 when removing the cassette cap 700.

Figures 27A-I show a second example of the syringe holder 300, the skin sensor 400, the index ring 500, and the injector release member 1508 in the different skin sensor longitudinal positions and index ring rotational positions as the injector release member 1508 moves longitudinally in the index ring track 530. The positions which are shown are the same in the a-i figures for the examples shown in figure 26 and figure 27, i.e. figure 27A shows the initial locked position in which the cassette 100 is in prior to use; figure 27B shows the cap-release position; figure 27C shows the skin sensor in the intermediate position LP2, where the cassette cap 700 can be removed; figure 27D shows the position, where the skin sensor is pushed into the distal longitudinal position LD, but the index ring not completely rotated for delivery; figure 27E shows the delivery position; figure 27F shows an intermediate position after delivery; figure 27G shows the final position LP3 before locking; and figure 27H shows the locked final position, figure 27I shows the locked position, which the auto injector forces the cassette into if a user having removed the cassette cap when the cassette was in a configuration as shown in figure 27C, but for some reason have been prevented from continuing the medicament delivery process by inserting the needle into the injections site by pushing the skin sensor 400 distally.

The differences between figures 26A-I and figures 27A-I are the design and form of the skin sensor 400 and the index ring 500. In figures 27A-I, the index ring 500 has a second longitudinally extending part 518 such that the longitudinal extending parts 516, 518 and the radially extending parts 512, 522 form a rectangle. Inside the rectangle on the first longitudinally extending part 506 is a first recess 508 and a second recess 510. These recesses are configured for containing a protruding tab 408 on the skin sensor 400. In the initial locked position LP1 as shown in figure 27A, the protruding tab 408 is contained inside the first recess 508. When the skin sensor 400 is in the intermediate position LP2, the protruding tab 408 is either in the second recess 510 if the index ring is rotated to the first rotational position as shown in figure 27I, or above the second recess 510, but supported in the proximal direction by the second distal surface 516 of the second radially extending part 512 thereby preventing further proximal movement during cap removal as shown in figure 27C. When the delivery of medicament occurs, the index ring 500 is rotated such that the protruding tab 408 is aligned with an opening 513 in the second radially extending part 512 such that when the skin sensor 400 is removed from the injection site, the protruding tab 408 is allowed to pass through the opening 513 in the second radially extending part 512 to the most proximal position, i.e. the final position LP3. This alignment is shown in figures 27E-G. When the index ring 500 is rotated back to the first rotational position R1 , the protruding tab 408 is abutting the second proximal surface 514 of the second radially extending part 512 preventing the exposure of the needle 208 after medicament delivery as shown in figure 27H.

Figures 28A-C and figures 29A-I show a third example of the cassette, where figures 28A-B show the syringe holder 300, the skin sensor 400, the index ring 500, figure 28C shows the cassette housing 600, figures 29A-G show the syringe holder 300, the skin sensor 400, the index ring 500, and the injector release member 1508 in the different skin sensor longitudinal positions and index ring rotational positions as the injector release member 1508 moves longitudinally in the index ring track 530, and figures 29H-I show a cut-through of the cassette housing 600 and the skin sensor 400 showing the skin sensor 400 in non-locked position (figure 29H) and the final position LP3 (figure 29I).

The differences between figures 26A-I, figures 27A-I, figures 28A-C, and figures 29A-I, are the design and form of the skin sensor 400 and the index ring 500, the shape of the injector release member 1508 in the injector 1000, and the locking of the skin sensor 400 in the final locked position LP3. In the third example, the track 530 is positioned on the first longitudinally extending part 506, which is attached to the tubular index part 520 on its outside. The track 530 is an open track. On an inner surface of the longitudinally extending part 506 are a first recess 508', a second recess 510' and an index ring ramp 509 extending distally from the first recess 508'. The skin sensor 400 has a protruding tab 408, which is confined in the first recess 508' prior to us as shown in figure 29A. After the index ring 500 is rotated to the cap-release rotational position Rcr position as shown in figure 29B, the skin sensor 400 moves to the capremoval position shown in figure 29C. The cassette cap 700 and the needle shield 212 can be removed as shown in figure 29C. In the position shown in figure 29C, the protruding tab 408 rest against the second distal surface 516 of the second radially extending part 512. During distal movement of the skin sensor 400 by the user for insertion of the needle at the injection site, the index ring 500 is rotated to the delivery rotational position Rd as shown in figure 29D. Thus, in the third example shown in figures 28A-B and figures 29A-G, the injector release member 1508 is not the item rotating the index ring from the cap-release rotational position Rcr to the delivery rotational position Rd, but instead the protruding tab 408 coming in contact with the index ring ramp 509 thereby forcing the index ring 500 to rotate. During medicament delivery as shown in figure 29E, the injector release member 1508 moves further into the cassette 100. After end medicament delivery, the skin sensor 400 moves to the final position LP3 due to the spring force from the injector skin sensor spring system 1700, 1710 in the injector 1000. This is shown in figure 29F. In the position shown in figure 29G, the skin sensor 400 is in final locked position. In the final locked position LP3, the skin-sensor 400 is pushed proximally by a spring system as described in the previous examples of the cassette and auto injector and locked into a locking position in the cassette housing 600. The locking is obtained by a cassette housing locking protrusion 428 on the skin sensor 400 fitting into a skin sensor locking opening 614 in the cassette housing 600 as shown in figure 29I. In the position shown in figure 29H, the skin sensor 400 is in non-locked position. The skin sensor locking opening 614 in the cassette housing 600 is visible most clearly in figure 28C.

In figure 28A, an alternative securing of the syringe 200 inside the syringe holder 300 is also shown, where two flexible syringe securing tabs 320 moves from an open to a closed position securing the syringe 200 inside the syringe holder 300.

Figures 30A-D show the removal of the cassette cap 700 from the cassette 100. The cassette cap 700 has locking cap parts 706 extending distally from a proximal end 702 of the cassette cap 700. Prior to use, a cassette cap locking protrusion 708 on each of the one or more locking cap parts 706 is secured inside the cassette housing 600 by a cap holding part 608, which is extending radially inwardly at the proximal end 602 of the cassette housing 600. At the proximal end 402 of the skin sensor 400, the skin sensor 400 has a ramp 410 and a recess 406 positioned distally of the ramp 410. The ramp 410 normally forms a protruding tab 408. An inwardly extending part 709 of the cassette cap locking protrusion on each of the locking parts 706 are secured between the recess 406 of the skin sensor 400 and a cap holding part 608, and is further abutting the proximal protruding ramp part 410 preventing proximal movement of the cassette cap 600 prior to use as shown in figure 30A. This locks the cassette cap 700 to the cassette 100 and prevents that the cassette cap 700 is removed from the cassette 100 before the cassette 100 is assembled inside the auto injector 1000.

The cap locking parts 706 and/or the cassette cap locking protrusion 708 on each of the one or more cap locking part 706 are flexible. Upon proximal movement of the skin sensor 400 from the initial locked position LP1 to the intermediate position LP2, the cap locking parts 706 and/or the cassette cap locking protrusion 708 on the locking part 706 first flex slightly radially inwards in the recess 406 of the skin sensor 400 thereby enabling the cassette cap locking protrusion locking protrusions 708 to move proximally pass the cap holding part 608. When the skin sensor 400 is moved from the initial locked position LP1 to the intermediate position LP2, the distal locking ends 708 thereby move outside the cassette housing 600 as shown in figure 30B. Since the locking parts 706 and/or the cassette cap locking protrusion 708 on the locking part 706 are configured to flex, they now flex radially outwardly and slide up the ramp 410 as the user removes the cassette cap 700 from the cassette 100. This is shown in figure 30C. The cassette cap 700 with the needle shield 212 inside may be positioned on the skin sensor 400 after use to provide an additional security preventing access to the used needle. This is shown in figure 30D. The cassette cap 700 is not non-removably connected to the cassette 100 again, but it will stay in position unless pulled off again by a user.

Figures 31A-G show perspective views of parts of a cassette 100 and the auto injector 1000 during a process of unlocking of the cassette cap 700, removal of the cap 700, medicament delivery and during resetting of the auto injector 1000 after medicament delivery. In figure 31 A, the cassette and auto injector are shown just after assembly but prior to locking of the cassette in the auto injector. In figure 31 B, the injector release members 1508 have moved into the cassette 100 by user movement of the cassette interacting tab 1601. This locks the cassette 100 in the auto injector 1000 as described in figures 24A-E. The injector release members 1508 movement also rotates the index ring 500 whereby the cap 700 can be removed as shown in figure 31 C. Removal of the cap 700 allows the injector skin sensor detector spring 1710 to push the injector skin sensor detector 1700 proximally whereby the skin sensor 400 is also pushed forward in a proximal position as shown in figure 31 C. In figure 31 D, the user has pressed the proximal end 402 of the skin sensor 400 against the injection site. The needle 208 can be seen in figure 31 D. Full medicament delivery is shown in figure 31 E, and in figure 31 F, the cassette has been removed from the injection site whereby the injector skin sensor detector 1700 pushes the skin sensor 400 to the final locked proximal position. In figure 31G, the auto injector 1000 has been reset and the injector release members 1508, the cassette interacting tab 1601 , and the injector skin sensor detector 1700 are once again in a distal position whereby the auto injector 1000 is ready for use again with a new cassette.

Figures 32A-D show a rotational damper 1900, which may be included in the auto injector 1000. The rotational damper 1900 comprises a damper sleeve 1902 positioned between the chassis sleeve 1400 and the resetting sleeve 1200. In figures 32A-D, only the chassis sleeve 1400 can be seen through a damper channel 1904 in the damper sleeve 1902. The damper channel 1904 extends helically around the damper sleeve 1902. The damper sleeve 1902 is rotatable relative to the chassis sleeve 1400.

The plunger rod resetting part 1026 extends through the damper channel 1904 and into the resetting thread 1206 (not shown here) in the resetting sleeve 1200.

The rotational damper 1900 further comprises a damper end surface 1906. In the shown example, the damper end surface 1906 is a damper plate. Other configurations could also be used.

Movement of the plunger rod 1020 in the proximal direction rotates the damper sleeve 1902 due to the plunger rod resetting part 1026 extending through the damper channel 1904. This can be seen by comparing figures 32A-C showing the rotational damper prior to injection (figure 32A), during injection (figure 32B), and after injection (figure 32C). The damper end surface 1906 is not moving during injection and the damper sleeve 1902 and the damper end surface 1906 thereby rotates relatively during injection. This reduces, i.e. dampens, a speed of the plunger rod 1020 during injection when moving in the proximal direction.

During reloading, the damper end surface 1906 rotates with the damper sleeve 1902 as shown in figure 32D. The damper sleeve 1902 is non-rotatable relative to the resetting sleeve 1200 during distal movement of the plunger rod 1020, i.e. during reloading. The rotational damper 1900 have two damper channels 1904. Each of these damper channels 1904 may have a pitch in the first rotation direction being identical to a pitch of the resetting thread 1206 in the resetting sleeve 1200 in the first rotation direction R1 . This ensures that rotation of the damper sleeve 1902 relative to the resetting sleeve 1200 is prevented. Normally a gearwheel (not shown) will connect with the damper sleeve 1904 to control the movement of the damper sleeve 1904.

The example shown in figures 32A-D has a second cassette interacting tab 1611 in addition to the first mentioned cassette interacting tab 1601 for activation of the auto injector 1000. The additional second cassette interacting tab 1611 may provide an improved structural stability.

Figure 33A show an exploded view of an example of another auto injector 1000a extending along the longitudinal direction L. The auto injector 1000a is very similar to the first shown auto injector 1000 and like parts are marked with the same reference numbers. The auto injector 1000a is extending from a proximal end 1002 to a distal end 1004 and comprises different parts, some of which are shown in close-up views in figures 34-40. Parts not shown separately are similar both in function and design as the parts shown and described in connection with the auto injector 1000 shown in figures 1-32.

Both the auto injector 1000 of figures 1A-B and the auto injector 1000a of figures 33A-B may comprise a distal housing cap 2216 attached to a distal end 2204 of the distal injector housing 2200 as shown in figure 33A. The additional distal housing cap 2216 is included to provide an easier assembly of the auto injector.

Figure 33B shows the assembled auto injector 1000a of figure 33A. During loading and preparation of a cassette 100 (an example of a cassette 100 is shown in figure 23) for medicament delivery, and during medicament delivery, there is no rotational movement between the different parts in the auto injector 1000a. Instead, the different parts in the auto injector 1000a move relative to each along the longitudinal direction L and some parts flex and/or tilt relative to other parts as described in the following. After medicament delivery and removal of the auto injector and cassette system from the injection site, the auto injector 1000a may be reloaded by rotation of the resetting sleeve 1200 and the distal injector housing 2200 relative to the other parts of the auto injector 1000a in a similar manner as described previously for the auto injector 1000 of figures 1A-B. This retracts the plunger rod 1020a to its initial distal position and reloads the drive spring 1040 as described in the following.

Figure 34 shows the plunger rod 1020a of the auto injector 1000a of figures 33A-B. The plunger rod 1020a extends from a proximal end 1022 to a distal end 1024. At the distal end 1024 is found the two plunger rod resetting parts 1026, which each travels along one of the two resetting threads 1206 inside the resetting sleeve 1200 when the two parts rotate relatively as described for the auto injector 1000 of figures 1A-B.

The plunger rod 1020a comprises a distal tubular part 1034 and a proximal tubular part 1035. The two tubular parts 1034, 1035 have different diameters. The average circumference of the distal tubular part 1034 is larger than the average circumference of the proximal tubular part 1035. The plunger rod cavity 1030a inside the plunger rod 1020a still contains the drive spring 1040 as is best seen in figures 42A-H and 45A-B. Compared to the plunger rod cavity 1030 as described for the auto injector 1000 of figures 1A-B, the plunger rod cavity 1030a in the second example of the auto injector does not extend to the proximal end 1022 of the plunger rod 1020a. The plunger rod cavity 1030a mainly extends through the distal tubular part 1034. The plunger rod 1020a of figure 34 may also be used in the auto injector 1000 of figures 1A- B. The plunger rod 1020a as shown in figure 34 comprises a plurality of plunger rod openings 1036. The plunger rod openings 1036 are found on an outer surface of the proximal tubular part 1035. The number of plunger rod openings 1036 includes a first plunger rod opening 1036A. Before insertion of a cassette 100 in the auto injector 1000a, a plunger rod release hook 1356 on a plunger rod release element 1350 (see figures 37A-B) is secured in the first plunger rod opening 1036A (see figures 42A-C). This prevents proximal movement of the plunger rod 1020a. Thus, it is ensured that the plunger rod 1020a and the plunger rod spring 1040 (see figures 33A-B) are not allowed to move proximally for medicament delivery before the user initiates medicament delivery. The initiation of medicament delivery - and thereby release of the plunger rod 1020a and the drive spring 1040 allowing the drive spring 1040 to expands ! decompress thereby pushing the plunger rod 1020a in the proximal direction - is done by the user pressing the cassette 100 (see figures 26-27) against the injection site. This pushes the plunger rod release hook 1356 out of the first plunger rod opening 1036A as shown in figures 43A-D allowing the plunger rod 1020a to move proximally for medicament delivery.

If the user stops mid medicament delivery, e.g. performing an early lift of the auto injector system from the patient's skin, the plunger rod 1020a does not continue its movement to the most proximal position for full medicament delivery. Instead, the plunger rod 1020a is stopped by the plunger rod release hook 1356 entering into one of the other plunger rod openings 1036B, as shown figure 43.

The drive spring guide 1050a is shown in a closeup view in figures 35A-B. The drive spring guide 1050a extends from a proximal end 1052 to the distal end 1054. The drive spring guide 1050a comprises a spring guide rod 1058 extending from the proximal end 1052 of the drive spring guide 1050a to the spring distal end surface 1056. The drive spring 1040 is positioned around the spring guide rod 1058 (see figure 33B). The spring guide rod 1058 comprises spring guide tracks 1060 for supporting the drive spring 1040.

Depending on the medicament to be delivered and its viscosity, different requirements to the spring force may be required. Some types of medicaments may be uncomfortable to receive if delivered too fast. Also, if there is a distance between proximal end 1022 of the plunger rod 1020a and the stopper 210 inside the syringe compartment 206 after mounting of the cassette 100 in the auto injector 1000a, the user may experience the impact when the plunger rod 1020a comes in contact with the stopper 210 during medicament delivery as an uncomfortable event. Some users may wrongly assume that something is wrong and remove the injector system from the skin too early, i.e. prior to medicament delivery has been finalized. This scenario may equally well occur for the auto injector 1000 of figures 1A-B. Dampening of the drive spring 1040 is therefore sometimes needed, e.g. to improve user experience. To overcome such problem, a rotational damper 1900 as shown and described in connection with figures 32A-D can be implemented. As an alternative, or in combination, a linear damper may be implemented.

The plunger rod 1020a comprises a cassette activation lock element 1038. The cassette activation lock element 1038 is found at a proximal end 1046 of the distal tubular plunger rod part 1035. Prior to a cassette 100 being received in the auto injector 1000a, the cassette activation lock element 1038 is secured by the one or more plunger rod lock elements 1518 on the cassette activation part 1500a as shown in figures 41A-B.

Figure 36 shows the plunger rod support part 1300a from two different directions. The plunger rod support part 1300a does not have the flexible side arm 1309 as shown for the plunger rod support part 1300a of the auto injector 1000 shown in figures 1A-B since the direct lock and release of the plunger rod 1020a has been relocated to plunger rod release element 1350 as shown in figures 37A-B.

Figures 37A-B show the plunger rod release element 1350 from two different directions. The plunger rod release element 1350 extends from a proximal end 1352 to a distal end 1354. The plunger rod release element 1350 comprises a plunger rod release hook 1356, which is seen most clearly in figure 37A. Prior to insertion of a cassette 100 in the auto injector 1000a, the plunger rod release hook 1356 is secured in the first plunger rod opening 1036A (see figures 42A-C). This prevents proximal movement of the plunger rod 1020a.

The plunger rod release element 1350 shown in figures 37A-B comprises chassis sleeve interacting rods 1360 as seen most clearly in figure 37B. The chassis sleeve interacting rods 1360 are positioned at the distal end 1354 of the plunger rod release element 1350. The plunger rod release element 1350 is tiltable, i.e. able to rotate slightly, around the chassis sleeve interacting rods 1360. The tilting moves the plunger rod release hook 1356 radially outwardly as the proximal end 1352 of the plunger rod release element 1350 moves radially outwardly.

A push back spring 1370 acting on a push back surface 1362 of the plunger rod release element 1350 exert a force on plunger rod release element 1350 radially inwardly securing the plunger rod release hook 1356 in the first plunger rod opening 1036A (see figure 34) prior to use. The push back spring 1370 is positioned between the plunger rod release element 1350 and the injector skin sensor detector 1700a (see figure 40). The plunger rod release element 1350 of figures 37A-B comprises two push protrusions 1358 positioned on opposite sides of the plunger rod release element 1350. The push protrusions 1358 each abuts a sloping surface 1720 on the injector skin sensor detector 1700a (see figure 43B and figure 43D). When the injector skin sensor detector 1700 moves distally relative to the plunger rod release element 1350, the sloping surface 1720 on the injector skin sensor detector 1700a forces the push protrusions 1358 radially outwardly. This pushes the plunger rod release hook 1356 out of the first plunger rod opening 1036A. The plunger rod 1020a is now released. After release of the plunger rod 1020a, the plunger rod 1020a moves proximally for medicament delivery (see figures 42A-H).

As shown in figure 42I, if the user removes the auto injector and cassette system from the injection site mid medicament delivery, the injector skin sensor detector 1700a is pushed proximally by the injector skin sensor detector spring 1710 (similar as described for the injector skin sensor detector 1700 shown in the auto injector 1000 of figures 1A-B). The sloping surface 1720 thereby no longer abuts the push protrusions 1358. Since the plunger rod 1020a has not moved all the way to its most proximal position at the end of medicament delivery, the proximal tubular part 1035 of the plunger rod 1020a is close to the plunger rod release hook 1356. The push back spring 1370 acting on a push back surface 1362 of the plunger rod release element 1350 exerts a force on plunger rod release element 1350 radially inwardly. This pushes the plunger rod release element 1350 radially inwardly.

The additional plunger rod openings 1036B found on the plunger rod 1020a distally of the first plunger rod opening 1036A facilitates that the plunger rod release hook 1358 may be secured in these openings when the user removes the auto injector and cassette system from the skin before medicament delivery has been finalized. This ensures that the medicament delivery does not continue after the user has removed the injector during an early lift. The early lift and the subsequent securing of the plunger rod release hook 1356 in the additional plunger rod openings 1036B is shown in figure 43.

When the user removes the auto injector and cassette system from the skin after end medicament delivery, the injector skin sensor detector 1700a is still pushed proximally by the injector skin sensor detector spring 1710. The push back spring 1370 still acts on a push back surface 1362 of the plunger rod release element 1350 exerting a force on plunger rod release element 1350 radially inwardly. However, the plunger rod release element 1350 is not pushed (much) radially inwardly, since the plunger rod release hook 1356 now abuts the thicker distal tubular part 1034 of the plunger rod 1020a and not the thinner proximal tubular part 1035. Further proximal movement of the plunger rod 1020a is prevented by the proximal end 1046 of the distal tubular part 1034 abutting the end plate in the cassette receiver 1 110.

The cassette activation part 1500a is shown in figures 38A-B. In the auto injector 1000a of figures 33A-B, the cassette interacting tab 1601 is coupled to the cassette activation part 1500a instead of the pullback part 1600 as the latter is not included in the auto injector 1000a of figures 33A-B. The cassette interacting tab 1601 may be positioned in a cassette interacting tab interface 1522 as shown in figure 38B and figures 41C-D. Alternatively, the cassette interacting tab 1601 is a part of the cassette activation part 1500a as shown in figure 38A.

The cassette activation part 1500a shown in figures 38A-B comprises two plunger rod lock arms 1516 extending distally. At the distal end 1504 of the cassette activation part 1500a (and thereby also the distal end of the plunger rod lock arms 1516), plunger rod lock elements 1518 are positioned. The cassette activation lock element 1038 on the plunger rod 1020a is secured in the plunger rod lock elements 1518 prior to the auto injector 1000a receiving a cassette 100 as most clearly seen in figure 41A. This prevents relative longitudinal movement of the cassette activation part 1500a and the plunger rod 1020a prior to the auto injector 1000a receiving a cassette 100.

The cassette activation part 1500a further comprises a plunger rod interaction arm 1524 extending from distally. When the plunger rod 1020a moves proximally for medicament delivery, the distal tubular part 1035 of the plunger rod 1020a secures the plunger rod interaction arm 1524 between the distal tubular part 1035 and the chassis sleeve 1400.

The release of the cassette activation lock element 1038 on the plunger rod 1020a from the plunger rod lock elements 1518 is controlled by a unlock sledge element 1750 as shown in figures 39A-B.

The unlock sledge element 1750 as shown in figures 39A-B extends from a proximal end 1752 to a distal end 1754. The unlock sledge element 1750 is further configured for moving between a proximal position USP and a distal position USD as shown in figures 41A-D. In the proximal position, longitudinal movement of the cassette activation part 1500a is normally prevented. In the distal position, longitudinal movement of the cassette activation part 1500a into the cassette 100 is normally permitted. The unlock sledge element 1750 comprises an unlock sledge release tab 1758. When the unlock sledge element 1750 moves distally relative to the cassette activation part 1500a, the unlock sledge release tab 1758 pushes the two plunger rod lock elements 1518 away from each other. The cassette activation lock element 1038 on the plunger rod 1020a is thereby released from the plunger rod lock elements 1518 as shown in figure 41 B and figure 41 D. This allows relative longitudinal movement of the cassette activation part 1500a and the plunger rod 1020a. The one or more plunger rod lock elements 1518 flex outwardly when the unlock sledge release tab 1558 moves distally, whereby the grab on the plunger rod 1020a is released. However, other solutions for releasing the plunger rod 1020a from the cassette activation part 1500a could also be imagined.

The unlock sledge element 1750 and the injector skin sensor detector 1700a as shown in figures 41A-D are longitudinal locked. The unlock sledge element 1750 comprises an injector skin sensor detector lock tab 1756 fixing the unlock sledge element 1750 in a sledge receiving channel 1716 in the injector skin sensor detector 1700a. Alternatively, the unlock sledge element 1750 may be part of the injector skin sensor detector 1700a. Splitting the unlock sledge element 1750 and the injector skin sensor detector 1700a into two parts may be done to facilitate easy assembly of the auto injector parts.

When an unused cassette 100 is received in the auto injector 1000a, the injector skin sensor detector pin 1703 on the injector skin sensor detector 1700a is pushed distally. This moves the unlock sledge element 1750 distally thereby releasing the two plunger rod lock elements 1518 hold on the cassette activation lock element 1038 on the plunger rod 1020a.

When the cassette activation part 1500a is no longer locked to the plunger rod 1020a, the cassette activation part 1500a is allowed to move proximally such that the one or more injector release members 1508 into the cassette 100. The cassette activation part 1500a can thereby be moved proximally by the user for locking the cassette 100 in the auto injector 1000a. Movement of the one or more injector release members 1508 into the cassette 100 locks the cassette 100 in the auto injector 1000a as shown in figures 24A-E. The skin sensor 400 is also allowed to move proximally by the index ring 500 interaction with the injector release members 1508 as described previously.

In the example shown in the figures, the cassette activation part 1500a is moved proximally by the user. The user moves the cassette activation part 1500a proximally by pushing the cassette interacting tab 1601 proximally. The unlock sledge element 1750 is configured for moving distally when an unused cassette 100 is received in the auto injector 1000a thereby moving the injector skin sensor detector 1700a distally. However, if an already used cassette is received in the auto injector 1000a, the injector skin sensor detector 1700 is not moved distally as the injector skin sensor detector pin 1703 is not pushed distally by the skin sensor 400 in the cassette 100 being in a too proximal position when the cassette is a used cassette. The unlock sledge is thereby also not moved distally, and the cassette activation part 1500 is thus not unlocked. This ensures that the auto injector 1000a cannot be activated if a used cassette is inserted into the auto injector 1000a instead of an unused cassette. This is illustrated in figures 44A-B.

Figures 41A-B show the interaction of the unlock sledge element 1750, the cassette activation part 1500a, the plunger rod 1020a, and the injector skin sensor detector 1700a before (figure 41 A) and after (figure 41 B) distal movement of the unlock sledge element 1750 and the injector skin sensor detector 1700a relative to the cassette activation part 1500a and the plunger rod 1020a. The distal movement of the unlock sledge element 1750 and the injector skin sensor detector 1700a unlocks the cassette activation part 1500a from the plunger rod 1020a. Figure 41 C and figure 41 D show the cassette activation part 1500a and the unlock sledge element 1750 at the same parts positions as in figure 41C and figure 41 D, respectively. The dotted circles (1 ) highlight the unlock sledge release tab 1758 movement, and the dotted circles (2) highlight the plunger rod lock element 1518 movement to release the cassette activation lock element 1038 on the plunger rod 1020a.

Figures 42A-H show cut-throughs of the auto injector 1000a of figures 33A-B during a process of receiving a cassette, unlocking of the cassette, whereby the plunger rod can be unlocked, during medicament delivery and after resetting of the auto injector after medicament delivery. The cassette has been omitted in figures 42A-H for a clearer view of the injector parts.

Figure 42A shows auto injector 1000a in the configuration prior to receiving the cassette. The injector skin sensor detector pin 1703 are in a proximal position extending proximally from the end plate in the cassette receiver 1110.

In figure 42B, a cassette has been received in the auto injector 1000a. When the cassette is received in the auto injector 1000a, the injector skin sensor detector pin 1703 comes into contact with a skin sensor 400 in the cassette 100 and are pushed distally by the skin sensor 400. This moves the unlock sledge element 1750 distally thereby unlocking the cassette activation part 1500a as shown in figures 41A-B. In figure 42C, the user has subsequently moved the cassette activation part 1500a proximally by pushing the cassette interacting tab 1601 proximally. Moving the cassette activation part 1500a proximally as shown in figure 42C, locks the cassette in the auto injector 1000a. The cap 700 on the cassette (see figures 30A-D) can now be removed. At this point, the skin sensor 400 is unlocked allowing it to move proximally (see figures 26A-I, figures 27A-I and figures 29A-G).

Due to the injector skin sensor detector spring 1710 acting on the injector skin sensor detector 1700a, the injector skin sensor detector 1700a, and the unlock sledge element 1750 moves proximally when the skin sensor 400 is moved proximally as shown in figure 42D. The auto injector 1000a, and cassette system is now ready for medicament delivery.

In figure 42E, the user has pressed the cassette against the injection site, which pushes the skin sensor 400 to a distal position also pushing the injector skin sensor detector pin 1703 and thereby the injector skin sensor detector 1700a, into the auto injector 1000a. Pushing the injector skin sensor detector 1700a into the auto injector 1000a unlocks the plunger rod 1020 (see figures 43A-D).

In figure 42F, the plunger rod spring 1040 has pushed the plunger rod 1020a in the proximal direction medicament delivery. Figure 42F shows the auto injector 1000a after full medicament delivery.

In figure 42G, the user has removed the cassette and auto injector system from the injection site after end medicament delivery, which allows injector skin sensor detector spring 1720 to push the injector skin sensor detector 1700a proximally, which in turn pushes the skin sensor 400 in the cassette to a locked proximal position (see figures 25A-B, figures 26A-I, figures 27A-I and figures 29A-G). The auto injector 1000a is now ready for resetting by rotation of the distal injector housing 2200 coupled to the resetting sleeve 1200 relative to the proximal injector housing 2100 as shown in figures 18A-E. The cassette can subsequently be removed from the auto injector 1000a.

Alternatively, the injector release member 1508 and the cassette interacting tab 1601 may be moved from the proximal cassette locking position PD to the distal cassette release position PP prior to resetting the auto injector. This may seem more natural for the user wanting to remove and discharge of the cassette before resetting the auto injector. The movement of the cassette interacting tab from the proximal cassette locking position PD to the distal cassette release position PP may be user controlled by movement of e.g. the cassette interacting tab. The reset auto injector 1000a as shown figure 42H, brings the auto injector 1000a back to the configuration identical to the one shown in figure 42A, i.e. where the auto injector 1000a is ready for receiving a new unused cassette. During resetting of the auto injector 1000a by rotation of the resetting sleeve 1200 in the first rotational direction DR1 , the plunger rod 1020a is moved in the distal direction as described previously in connection with e.g. figures 18A-D. As the plunger rod 1020a moves distally, the cassette activation lock element 1038 on the plunger rod 1020a comes into contact with the one or more plunger rod lock elements 1518 on the cassette activation part 1500a and is positioned inside a lock element enclosure 1520 formed by the plunger rod lock elements 1518 as shown in figure 41A. Further distal movement of the plunger rod 1020a pulls the cassette activation part 1500a, the injector skin sensor detector 1700a, and the unlock sledge element 1750 along distally. This resets the cassette activation part 1500a, the injector skin sensor detector 1700a, and the unlock sledge element 1750 to the original positions.

Figure 42I shows the auto injector 1000a in a situation, where the user has interrupted the medicament delivery and removed the cassette and auto injector system from the injection site prior to completing the medicament delivery. If the user has interrupted the medicament delivery mid-delivery, the skin sensor 400 in the cassette 100 is pushed forward to a locked position by the injector skin sensor detector 1700a of the auto injector 1000a due to the injector skin sensor spring 1710 pushing the injector skin sensor detector 1700a. The proximal movement of the injector skin sensor detector 1700a, secures the plunger rod 1020a in an intermediate position by the plunger rod release hook 1356 movement into one of the other plunger rod openings 1036B.

In figures 43A-D, release of the plunger rod 1020a for medicament delivery is shown in a close-up. Figures 43A-B are two different close-up views of figure 42D, where the cassette is locked in the auto injector 1000a but the user is yet to push the skin sensor 400 against the injection site. As seen in figure 43B, the sloping surface 1720 of the injector skin sensor detector 1700a is not in contact with the push protrusion 1358 on the plunger rod release element 1350. The plunger rod release hook 1356 secured in the first plunger rod opening 1036A prevents proximal plunger rod 1020a movement as shown in figure 43A.

Figures 43C-D are two different close-up views of figure 42E, where the user has pushed the skin sensor 400 against the injection site. As seen in figure 43D, the sloping surface 1720 of the injector skin sensor detector 1700a has pushed the push protrusion 1358 radially outwardly as the injector skin sensor detector 1700a is pushed distally. The plunger rod release hook 1356 is no longer secured in the first plunger rod opening 1036A as shown in figure 43C and the plunger rod 1020a is therefore ready for proximal medicament delivery movement.

Figure 44A and figure 44B show the difference between the auto injector 1000a when an unused cassette and a used cassette is received in the auto injector 1000a, respectively.

As shown in figures 45A-B, the reusable auto injector 1000a may comprise a linear damper. The linear damper comprises an O-ring 1010 extending around a first part 1062 of the drive spring guide 1050a extending inside the plunger rod cavity 1030a. The O-ring 1010 is in contact with an inner surface 1037 of the plunger rod cavity 1030a. Frictional force between the O-ring 1010 and the plunger rod cavity 1030a upon proximal movement of the plunger rod 1030a introduces a linear dampening effect.

The plunger rod 1020a may also comprise an inner plunger rod tube extending into the plunger rod cavity 1030a. At least a part of the drive spring 1040 may be positioned around the inner plunger rod tube, and at least a part of the spring guide 1050a may be extending through the inner plunger rod tube. The O-ring 1010 may exert an additional linear damper effect by being movable into the inner plunger rod tube when the drive spring 1040 pushes the plunger rod 1020a proximally.

Figure 46A show an exploded view of an example of another auto injector 1000b, also referred to as a third example of the auto injector 1000b, extending along the longitudinal direction L. The auto injector 1000b is very similar to the first shown auto injector 1000 and the second shown auto injector 1000a. Like parts are therefore marked with the same reference numbers. The auto injector 1000b is extending from a proximal end 1002 to a distal end 1004 and comprises different parts, some of which are shown in close-up views in figures 47-55. Parts not shown separately are similar both in function and design as the parts shown and described in connection with the auto injector 1000 shown in figures 1-32, and/or the auto injector 1000a shown in figures 33-46.

Compared to the auto injectors 1000, 1000a of figures 1A-B and figures 33A-B, the auto injector 1000b of figures 46A-B comprises a user button 2020 and a converter 2000. Rotation of the user button 2020 and a converter 2000 locks a cassette 100 (an example of a cassette 100 is shown in figure 23) in the auto injector 1000b as described in connection with figures 56A-C. Apart from the user button 2020 and the converter 2000 rotation, during loading and preparation of the cassette 100 for medicament delivery, and during medicament delivery, there is no rotational movement between the other parts in the auto injector 1000b. Instead, the other parts in the auto injector 1000b move relative to each along the longitudinal direction L and some parts flex and/or tilt relative to other parts as described also for the auto injector shown in figures 33A-B. After medicament delivery and removal of the auto injector and cassette system from the injection site, the auto injector 1000b may be reloaded by rotation of the resetting sleeve 1200b and the distal injector housing 2200b relative to the other parts of the auto injector 1000b in a similar manner as described previously for the auto injector 1000 of figures 1A-B, and the auto injector 1000a of figures 33A-B. This retracts the plunger rod 1020b to its initial distal position and reloads the drive spring 1040 as described previously for the auto injector 1000a of figures 33A-B.

Figure 47 shows the plunger rod 1020b of the auto injector 1000b of figures 46A-B. Compared to the plunger rod 1020a shown in figure 34, the plunger rod 1020b in figure 47, the cassette activation lock element 1038 on the distal tubular part 1034 is not present. The remaining parts have similar functions as described previously for the plunger rod 1020a shown in figure 34.

Prior to a cassette 100 being received in the auto injector 1000b, the plunger rod 1020b is secured by the plunger rod release element 1350 as shown for the previously described second example of the auto injector 1000a.

Figures 48A-B show the injector skin sensor detector 1700b from two different directions. Compared to the previously shown and described injector skin sensor detectors 1700, 1700a, the injector skin sensor detector 1700b in figures 48A-B has a converter blocking surface 1718. The converted blocking surface 1718 prevents rotation of the converter 2000 until an unused cassette 100 is positioned in the auto injector 1000b. This is shown and described in more detail in figures 56A-C.

Figures 49A-B show the chassis sleeve 1400b from two different directions. Compared to the chassis sleeve 1400 of figures 9A-B, the chassis sleeve 1400b of figures 49A-B has an activation part plate channel 1416. The activation part plate channel 1416 is a channel in which an activation part plate 1530 on the cassette activation part 1500b may extend. The two interfaces 1416, 1530 do normally not prevent movement of one compared to the other. Instead, the activation part plate 1530 can move inside the activation part plate channel 1416 in the longitudinal direction.

The activation part plate 1530 is clearly seen in figures 50A-B showing the cassette activation part 1500b from two different directions. The activation part plate 1530 has an activation part plate thread 1532. A resetting sleeve pin 1214 on the resetting sleeve 1200b can come in contact with and travel inside the activation part plate thread 1532 when the resetting sleeve 1200b is rotated. Thus, when the resetting sleeve 1200b is rotated for resetting of the auto injector 1000b, the cassette activation part 1500b is pulled from a proximal (forward) position and distally (backward) to the initial position due to the resetting sleeve pin 1214 traveling inside the activation part plate thread 1532 forcing the activation part 1500b to move distally. Thus, the reloading of the auto injector 1000b by rotation of the resetting sleeve 1200b also retracts the cassette activation part 1500b. This unlocks the cassette 100, since the injector release members 1508 no longer lock the cassette 100 in the auto injector 1000b. The cassette activation part 1500b comprises a quaternary converter pin receiving channel 1534 for containing a quaternary converter pin 2004 of the converter 2000 (see figures 56A-C).

Figures 51A-B show the resetting sleeve 1200b with the resetting sleeve pin 1214 from two different directions. The resetting sleeve pin 1214 is not positioned inside the activation part plate thread 1532 in the initial and the final position. Instead, the resetting sleeve pin 1214 enters into the activation part plate thread 1532 during rotation of the resetting sleeve 1200b and exits the activation part plate thread 1532 before a full resetting rotation of the resetting sleeve 1200b is completed. The remaining parts of the resetting sleeve 1200b have already been described in connection with the first shown resetting sleeve 1200.

Figures 52A-B show the cassette receiver 1100b from two different directions. Compared to the first shown cassette receiver 1100, the cassette receiver 1100b shown in figures 52A-B comprises a cassette receiver channel 1124 through which the cassette activation part 1500b can travel. The cassette receiver 1100b also comprises an interface 1126 to the plunger rod release element 1350. On an outer surface of the cassette receiver 1100b is interfaces to interact with the converter 2000. Inside a tertiary converter pin receiving opening 1 133, a tertiary converter pin 2003 on the converter 2000 can be positioned. The tertiary converter pin receiving opening 1133 constitutes the axis around which the converter 2000 rotates. A converter pin channel 1134 provides a channel for movement of a quaternary converter pin 2004 of the converter 2000. When the converted is rotated around the axis defined by the tertiary converter pin 2003 and the tertiary converter pin receiving opening 1 133, the quaternary converter pin 2004 travels inside the converter pin channel 1134. This is shown and described in more details in connection with figures 56A-C. The remaining parts of the cassette receiver 1100b have already been described in connection with the first shown cassette receiver 1100.

Figures 53A-B show the converter 2000 from two different directions. The converter 2000 comprises a number of converter pins 2001 , 2002, 2003, 2004. The converter pins 2001 , 2002, 2003, 2004 extends from either a primary converter plate surface 2010 or a secondary converter plate surface 2012 of a converter plate 2008. The primary converter plate surface 2010 is opposite the secondary converter plate surface 2012. The converter pins 2001 , 2002, 2003, 2004 include a primary converter pin 2001 , a secondary converter pin 2002, a tertiary converter pin 2003, and a quaternary converter pin 2004. The primary converter pin 2001 and the secondary converter pin 2002 extends from the primary converter plate surface 2010. The tertiary converter pin 2003 and the quaternary converter pin 2004 extend from the secondary converter plate surface 2012. The primary converter pin 2001 and the tertiary converter pin 2003 may also be seen as a throughgoing pin extending through the converter plate 2008. The converter 2000 also comprises a skin sensor detector pin interaction surface 2018. The skin sensor detector pin interaction surface 2018 abuts against the converted blocking surface 1718 on the injector skin sensor detector 1700b until an unused cassette 100 is positioned in the auto injector 1000b. By positioning an unused cassette 100 in the auto injector 1000b, the injector skin sensor detector 1700b is pushed distally as previously described. The skin sensor detector pin interaction surface 2018 no longer abuts the converted blocking surface 1718, and rotation of the converter 2000 is possible. This is shown and described in more detail in figures 56A-C.

Figures 54A-B show the user button 2020 from two different directions. The user button 2020 comprises a user button plate 2022 with a primary user button plate surface 2024 and a secondary user button plate surface 2026. The primary user button plate surface 2024 is opposite the secondary user button plate surface 2026. The user button 2020 comprises a user button tab 2028. The user uses the user button tab 2028 a knob for rotating the user button 2020. The user button tab 2028 extend from the primary user button plate surface 2024. The user button 2020 comprises a primary converter pin receiving opening 2031 and a secondary converter pin receiving opening 2032. The converter pin receiving openings 2031 , 2032 are on the secondary user button plate surface 2026. The primary converter pin 2001 of the converter 2000 is positioned inside the primary converter pin receiving opening 2031 of the user button 2020. Similarly, the secondary converter pin 2002 of the converter 2000 is positioned inside the secondary converter pin receiving opening 2032 of the user button 2020. The user button 2020 and the converter 2000 are thereby coupled such that they do not move relative to each other. Instead of the user button 2020 and the converter 2000 being two separate parts, one combined part could also be imagined.

The proximal injector housing 2100b as shown in figure 55 comprises a user button receiving opening 2021 in which the user button 2020 is positioned. The user button 2020 is allowed to rotate inside the user button receiving opening 2021 . Figures 56A-C show the resetting sleeve 1200b, the cassette activation part 1500b, the injector skin sensor detector 1700b, and the converter 2000 during activation of the auto injector 1000b of figures 46A-B. In figure 56A, an unused cassette 100 has not yet been positioned in the auto injector 1000b and the skin sensor detector pin interaction surface 2018 therefore abuts the converted blocking surface 1718 on the injector skin sensor detector 1700b. This prevents rotation of the converter 2000.

In figure 56B, an unused cassette 100 (not shown in the figures) has been positioned in the auto injector 1000b, and the injector skin sensor detector pin 1703 has been pushed distally. The skin sensor detector pin interaction surface 2018 therefore no longer abut the converted blocking surface 1718 on the injector skin sensor detector 1700b. This allows for rotation of the converter 2000 by the user rotating the user button 2020.

In figure 56C, the converter 2000 has been rotated around the axis defined by the tertiary converter pin 2003 inside the tertiary converter pin receiving opening 1133. This is illustrated with the arrow in the figure. The rotation of the converter 2000 moves the injector skin sensor detector 1700b proximally due to the position of the quaternary converter pin 2004 inside the quaternary converter pin receiving channel 1534. Thus, when the converter 2000 rotates, the injector skin sensor detector 1700b moves proximally along the longitudinal direction. This locks the cassette 100 inside the auto injector 1000b in a similar manner as described in figures 24A-E. Since the resetting sleeve pin 1214 is not positioned inside the activation part plate thread 1532 until the resetting sleeve 1200b is rotated, the resetting sleeve 1200b is not affected by the rotation of the converter 2000, which locks the cassette 100 in the auto injector 1000b. When the resetting sleeve 1200b is rotated for reloading of the auto injector 1000b, the cassette activation part 1500b is moved distally. The converter 2000 is thereby rotated back to its original position due to the quaternary converter pin 2004 being positioned inside the quaternary converter pin receiving channel 1534 of the cassette activation part 1500b.

Figure 57A show an exploded view of an example of another auto injector 1000c, also referred to as a fourth example of the auto injector 1000c, extending along the longitudinal direction L. The auto injector 1000c is very similar to the previously shown auto injectors 1000, 1000a, 1000b. Like parts are therefore marked with the same reference numbers. The auto injector 1000c is extending from a proximal end 1002 to a distal end 1004 and comprises different parts, some of which are shown in close-up views in figures 58A-61. Parts not shown separately are similar both in function and design as the parts shown and described in connection with the previously shown auto injectors 1000, 1000a, 1000b of figures 1-56. Compared to the auto injector 1000b of figures 46A-B, the auto injector 1000c of figures 57A- B comprises an alternative user button 2020c, an alternative cassette receiver 1100c, an alternative proximal injector housing 2100c, and a cover part 2050. Compared to the auto injector shown in figures 46A-B, sideways movement of the user button 2020c translates to a rotation of the converter 2000, which in turn locks a cassette 100 (an example of a cassette 100 is shown in figure 23) in the auto injector 1000c as described previously. Apart from the rotation of the converter 2000 during loading and preparation of the cassette 100 for medicament delivery, and during medicament delivery, there is no rotational movement between the other parts in the auto injector 1000c. Instead, the other parts in the auto injector 1000b move relative to each along the longitudinal direction L or an axis perpendicular thereto, and some parts flex and/or tilt relative to other parts as described also for the auto injectors 1000a, 1000b shown in figures 33A-B and 46A-B. After medicament delivery and removal of the auto injector and cassette system from the injection site, the auto injector 1000c may be reloaded by rotation of the resetting sleeve 1200b and the distal injector housing 2200b relative to the other parts of the auto injector 1000c in a similar manner as described previously for the auto injector 1000 of figures 1A-B, and the auto injector 1000a of figures 33A-B. This retracts the plunger rod 1020b to its initial distal position and reloads the drive spring 1040 as described previously.

Figures 58A-B show the cassette receiver 1 100c from two different directions. Compared to the cassette receiver 1100b shown in figures 52A-B, the cassette receiver 1100c shown in figures 58A-B comprises a cover part plate tab receiving opening 1128 for receiving a cover part plate tab 2058 on the cover part 2050.

Figure 59A-B show the cover part 2050 from two different directions. The cover plate 2050 comprises primary cover part plate surface 2054 and a secondary cover part plate surface 2056 opposite the primary cover part plate surface 2054. The cover plate 2050 further comprises a cover part plate tab 2058 which is positioned inside a cover part plate tab receiving opening 1128 on the cassette receiver 1100c. The cover plate 2050 is able to rotate around an axis defined by the cover part plate tab 2058. The rotation is defined by the sideway movement of the user button 2020c. The cover plate 2050 is positioned such that it is visible at least partly inside the user button receiving opening 2110 of the proximal injector housing 2100c. The cover plate 2050 comprises a curving cover part surface 2060 in which the user button 2020c is able to come in contact with the converter 2000. Figure 60A-B show the user button 2020c from two different directions. The user button 2020c has a squared shape instead of the round shape of the user button 2020 shown and described in figures 54A-B. The user button 2020c comprises two primary user button protrusion 2040 together forming a user button channel 2042 in which the secondary converter pin 2002 travels. Sideways movement of the user button 2020c thereby rotates the converter 2000 as described previously. In addition to the two primary user button protrusion 2040, two secondary user button protrusions 2044 are present on the secondary user button plate surface 2026. The secondary user button plate surface 2026 follows the curving cover part surface 2060 on the cover part 2050. The movement of the user button 2020c from one side to the other in a direction perpendicular to the longitudinal direction, causes the cover part 2050 to rotate around the cover part plate tab 2058. Movement of the user button 2020c back to its original position, rotates the cover part 2050 to its original position. The cover part 2050 is visible inside the user button receiving opening 2110 of the proximal injector housing 2100c.

Figure 61 shows the proximal injector housing 2100c with the user button receiving opening 2110 under which the cover part 2050 is visible.

Figure 62 show an exploded view of an example of another auto injector 1000d, also referred to as a fifth example of the auto injector 1000d extending along the longitudinal direction L. The auto injector 1000d is very similar to the previously shown auto injectors 1000, 1000a, 1000b, 1000c. Like parts are therefore marked with the same reference numbers. The auto injector 1000d is extending from a proximal end 1002 to a distal end 1004 and comprises an alternative proximal injector housing 2100d with no opening for a user button, and an alternative resetting sleeve 1200d shown in more details in figure 63. Parts not shown separately are similar both in function and design as the parts shown and described in connection with one or more of the previously shown auto injectors 1000, 1000a, 1000b, 1000c of figures 1-61.

Compared to the auto injector 1000b of figures 46A-B and the auto injector 1000c of figures 57A-B, the auto injector 1000d of figure 62 comprises no user button. Instead, the converter 2000 is rotated by a rotation of the resetting sleeve 1200d. The rotation of the converter 2000 is a consequence of the interface between the quaternary converter pin receiving channel 1534 of the cassette activation part 1500b and the quaternary converter pin 2004 of the converter 2000 as described previously. Thus, the converter 2000 rotates when the cassette activation part 1500b moves proximally to lock the cassette 100 in the auto injector 1000d. The converter rotation locking the cassette 100 in the auto injector 1000d is normally in an opposite rotational direction, such as a second rotational direction compared to the rotational direction for resetting of the auto injector 1000d, such as a first rotational direction.

As shown in figure 63, the resetting sleeve 1200d comprises a number of sleeve pins 1214, 1215, 1216. The resetting sleeve 1200d comprises one resetting sleeve pin 1214, which can travel inside activation part plate thread 1532 of the cassette activation part 1500. When the resetting sleeve 1200d is rotated in a rotational direction opposite the resetting direction, the resetting sleeve pin 1214 enters into the activation part plate thread 1532 of the cassette activation part 1500 thereby moving the cassette activation part 1500 proximally for locking an unused cassette 100 in the auto injector 1000d. Further rotational movement of the resetting sleeve 1200d is prevented by a first blocking pin 1215 abutting the activation part plate 1530. When the resetting sleeve 1200d is rotated in the resetting rotational direction, further rotational movement than that required for the resetting is prevented by a second blocking pin 1216 abutting the activation part plate 1530. Thus, the resetting sleeve 1200d is configured for rotating forth and back depending on whether one is locking cassette in the auto injector 1000d or resetting the auto injector and unlocking the cassette after medicament delivery. The rotational movement is normally a 180 degrees movement is a first or a second rotational direction depending on whether one is locking or resetting the device.

The remaining functionality of the auto injector 1000d is as described for the previous auto injectors 1000, 1000a, 1000b, 1000c.

The invention is further described in the following items.

1. A reusable auto injector (1000, 1000a, 1000b, 1000c, 1000d) for administration of medicament, the auto injector being configured for receiving a cassette (100) comprising a syringe (200) containing the medicament; wherein the auto injector is extending from a proximal end (1002) to a distal end (1004) along a longitudinal axis (L); wherein the cassette (100) is configured for being removable received in the auto injector in a longitudinal direction along the longitudinal axis (L); wherein the auto injector comprises: a cassette receiver (1100, 1100b, 1100c) configured for receiving the cassette (100); a plunger rod (1020, 1020a, 1020b) configured for proximal movement of a stopper (210) inside the syringe (200) for medicament delivery; a plunger rod resetting part (1026) connected to and protruding radially from the plunger rod (1020, 1020a, 1020b); a drive spring (1040) adapted for moving the plunger rod (1020, 1020a, 1020b) in a proximal direction; and a resetting sleeve (1200, 1200b, 1200d) rotatable relative to the cassette receiver (1100, 1 100b, 1100c) in a first rotational direction (DR1 ), the resetting sleeve (1200, 1200b, 1200d) comprising a resetting thread (1206) located on an inner surface (1205) of the resetting sleeve (1200, 1200b, 1200d), wherein the plunger rod resetting part (1026) engages with the resetting thread (1206) such that a rotation of the resetting sleeve (1200, 1200b, 1200d) in a first rotational direction (DR1 ) moves the plunger rod (1020, 1020a, 1020b) in a distal direction for resetting the plunger rod (1020, 1020a, 1020b).

2. The reusable auto injector according to item 1 , wherein the cassette receiver (1 100, 1100b, 1 100c) is configured for receiving the cassette (100) releasably in the cassette receiver (1100, 1100b, 1 100c).

3. The reusable auto injector according to any preceding item, wherein rotation of the resetting sleeve (1200, 1200b, 1200d) in the first rotational direction (DR1 ) moves the plunger rod (1020, 1020a, 1020b) in a distal direction for resetting the plunger rod (1020, 1020a, 1020b) relative to the cassette receiver (1100, 1100b, 1100c).

4. The reusable auto injector according to any preceding item, wherein the plunger rod (1020, 1020a, 1020b) is configured for proximal movement between a retracted plunger rod position and an extended plunger rod position, wherein the resetting sleeve (1200, 1200b, 1200d) is configured for moving the plunger rod from the extended plunger rod position to the retracted plunger rod position by rotation of the resetting sleeve (1200, 1200b, 1200d) in the first rotational direction (DR1 ) a predefined amount of degrees relative to the cassette receiver (1100, 1100b, 1 100c).

5. The reusable auto injector according to item 4, wherein the predefined amount of degrees is between 150 degrees and 210 degrees, such as between 160 degrees and 200 degrees, such as between 170 degrees and 190 degrees, such as 180 degrees. 6. The reusable auto injector according to item 4 or 5, wherein the predefined amount of degrees is between 150 degrees and 360 degrees, such as between 160 degrees and 340 degrees, such as between 170 degrees and 320 degrees, such as between 175 degrees and 300 degrees, such as between 175 degrees and 280 degrees, such as between 175 degrees and 260 degrees, such as between 175 degrees and 240 degrees, such as between 175 degrees and 220 degrees, such as between 175 degrees and 200 degrees, such as between 175 degrees and 190 degrees, such as between 175 degrees and 185 degrees.

7. The reusable auto injector according to any preceding claim, wherein the plunger rod (1020, 1020a, 1020b) is non-rotatable relative to the cassette receiver (1100, 1100b, 1100c).

8. The reusable auto injector according to any preceding item, wherein the plunger rod resetting part (1026) extends from a distal end (1024) of the plunger rod (1020, 1020a, 1020b).

9. The reusable auto injector according to any preceding item, wherein the plunger rod resetting part (1026) comprises two pin parts positioned opposite another.

10. The reusable auto injector according to item 9, wherein the resetting thread (1206) comprises two helical threads positioned opposite each other inside the resetting sleeve (1200, 1200b, 1200d), each of the two helical threads interfacing with each of the two oppositely positioned pin parts extending from a distal end (1024) of the plunger rod (1020, 1020a, 1020b).

11. The reusable auto injector according to any preceding item, wherein the reusable auto injector further comprises a distal injector housing (2200, 2200b) surrounding the resetting sleeve (1200, 1200b, 1200d), the distal injector housing (2200, 2200b) being rotatable relative to the cassette receiver (1100, 1100b, 1100c).

12. The reusable auto injector according to item 11 , wherein the distal injector housing (2200, 2200b) is rotationally locked to the resetting sleeve (1200, 1200b, 1200d).

13. The reusable auto injector according to any of the items 11-12, wherein the distal injector housing (2200, 2200b) comprises at least one rotational stop surface (2210) protruding from a distal injector housing plate (2212) of the distal injector housing (2200, 2200b), wherein the at least one rotational stop surface (2210):

• prevents further rotation of the resetting sleeve (1200, 1200b, 1200d) than a predefined amount of degrees relative to the cassette receiver (1100, 1100b, 1100c), and/or

• abuts the plunger rod resetting part (1026) when the resetting sleeve has been rotated the predefined amount of degrees relative to the cassette receiver, whereby further rotation of the resetting sleeve (1200, 1200b, 1200d) relative to the cassette receiver (1 100, 1100b, 1100c) is prevented.

14. The reusable auto injector according to any of the items 11-13, wherein the reusable auto injector further comprises a distal housing cap (2216) attached to a distal end (2204) of the distal injector housing (2200, 2200b).

15. The reusable auto injector according to any preceding item, wherein the rotation of the resetting sleeve (1200, 1200b, 1200d) in the first rotational direction (DR1 ) compresses the drive spring (1040).

16. The reusable auto injector according to any preceding item, wherein the plunger rod (1020, 1020a, 1020b) comprises a plunger rod cavity (1030, 1030a) extending into the plunger rod (1020, 1020a, 1020b) and wherein the drive spring (1040) is positioned at least partly inside the plunger rod cavity (1030, 1030a).

17. The reusable auto injector according to item 16, wherein the reusable auto injector comprises a spring guide (1050, 1050a) around which at least a distal end (1044) of the drive spring (1040) extends, wherein the drive spring (1040) is biased between a proximal end surface (1032) inside the plunger rod cavity (1030, 1030a) and a distal end surface (1056) of the spring guide (1050, 1050a).

18. The reusable auto injector according to item 17, wherein the spring guide (1050, 1050a) extends into the plunger rod (1020, 1020a, 1020b) opening.

19. The reusable auto injector according to any preceding item, wherein the reusable auto injector further comprises a first damper assembly configured for dampening at least part of the proximal movement of the drive spring (1040) during medicament delivery. 20. The reusable auto injector according to item 19, wherein during medicament delivery, the plunger rod (1020, 1020a, 1020b) is configured for moving a total plunger rod movement length, the total plunger rod movement length being from an initial distal plunger rod position to a proximal delivery plunger rod position, wherein the first damper assembly is configured for dampening a first part of the total plunger rod movement length or the entire total plunger rod movement length.

21. The reusable auto injector according to item 20, wherein the first damper assembly is configured for dampening only a first part of the total plunger rod movement length, wherein the first part of total plunger rod movement length is less than 25%, such as less than 20%, such as less than 15% of the total plunger rod movement length.

22. The reusable auto injector according to any of the items 19-21 , wherein the plunger rod (1020, 1020a, 1020b) is configured for moving between: o an initial distal plunger rod position where the plunger rod (1020, 1020a, 1020b) is not in contact with the stopper (210) inside the cassette (100); o a stopper contact position, wherein the plunger rod is in contact with the stopper (210) inside the cassette (100); and o a proximal delivery plunger rod position, where the stopper (210) inside the syringe (200) has been moved proximally for medicament delivery, wherein the first damper assembly dampers the movement of the plunger rod (1020, 1020a, 1020b) only from the initial distal plunger rod position to the stopper contact position.

23. The reusable auto injector according to any of items 19-22 depending on any of the items 16-18, wherein the first damper assembly comprises an O-ring (1010) extending around a first part (1062) of the spring guide (1050a) extending inside the plunger rod cavity (1030a), wherein the O-ring (1010) is in contact with an inner surface of the plunger rod cavity (1030a), and wherein movement between the O-ring (1010) and the plunger rod cavity (1030a) upon proximal movement of the plunger rod (1030a) introduces a dampening effect.

24. The reusable auto injector according to item 23, wherein movement between the O-ring (1010) and the plunger rod cavity (1030a) is a frictional force introducing a linear dampening effect. 25. The reusable auto injector according to any of the items 23-24, wherein the plunger rod (1020a) comprises an inner plunger rod tube (1039) extending into the plunger rod cavity (1030a), wherein at least part of the drive spring (1040) is positioned around the inner plunger rod tube (1039), and at least a part of the spring guide (1050a) is extending through the inner plunger rod tube (1039), wherein the O-ring (1010) is movable into the inner plunger rod tube (1039) when the drive spring (1040) pushes the plunger rod (1020a) proximally.

26. The reusable auto injector according to any of items 16-25, wherein the spring guide (1050a) comprises a spring guide rod (1058) comprising spring guide tracks (1060) for supporting the drive spring (1040).

27. The reusable auto injector according to any preceding item, wherein the reusable auto injector further comprises a chassis sleeve (1400, 1400b) positioned between the plunger rod (1020, 1020a, 1020b) and the resetting sleeve (1200, 1200b, 1200d), the chassis sleeve (1400, 1400b) comprising a longitudinally extending channel (1403) through which the plunger rod resetting part (1026) extends, the chassis sleeve (1400, 1400b) being non-rotatable relative to the cassette receiver (1100, 1100b, 1100c), wherein the channel (1403) is configured for preventing the plunger rod (1020, 1020a, 1020b) from rotating when the resetting sleeve (1200, 1200b, 1200d) is rotated in the first rotational direction (DR1 ).

28. The reusable auto injector according to any preceding item, wherein the reusable auto injector further comprises a cassette interacting tab (1601 ).

29. The reusable auto injector according to item 28, wherein the cassette interacting tab (1601 ) is movable in the longitudinal direction (L) between a proximal cassette locking position (PP) and a distal cassette release position (PD), wherein prior to receiving a cassette (100) in the reusable auto injector, the cassette interacting tab (1601 ) is in the distal cassette release position (PD).

30. The reusable auto injector according to item 29, wherein when the cassette (100) is received in the reusable auto injector, user induced movement of the cassette interacting tab (1601 ) from the distal cassette release position (PD) to the proximal cassette locking position (PP) locks the cassette (100) in the reusable auto injector . 31. The reusable auto injector according to any of the items 29-30, wherein the reusable auto injector is configured for moving the cassette interacting tab (1601 ) from the proximal cassette locking position (PP) to the distal cassette release position (PD) when resetting the reusable auto injector by rotation of the distal injector housing (2200, 2200b) or the resetting sleeve (1200, 1200b, 1200d) in the first rotational direction (DR1 ), whereby the cassette (100) is unlocked and removeable from the reusable auto injector .

32. The reusable auto injector according to any of the items 29-31 , wherein the cassette interacting tab (1601 ) is accessible for a user through a channel (1107) in the cassette receiver (1100, 1100b, 1100c) in which the cassette interacting tab (1601 ) is movable along the longitudinal direction (L).

33. The reusable auto injector according to any preceding item, wherein the reusable auto injector further comprises a pullback part (1600).

34. The reusable auto injector according to item 33, wherein the pullback part (1600) comprises the cassette interacting tab (1601 ).

35. The reusable auto injector according to any preceding item, wherein the reusable auto injector further comprises a cassette activation part (1500, 1500a, 1500b) configured for moving in the longitudinal direction (L) relative to the cassette receiver (1100, 1100b, 1100c).

36. The reusable auto injector according to item 35 depending on item 33, wherein the cassette activation part (1500a) comprises the cassette interacting tab (1601 ).

37. The reusable auto injector according to any of the items 35-36, wherein the cassette activation part (1500, 1500a, 1500b) comprises one or more injector release members (1508).

38. The reusable auto injector according to item 37, wherein the one or more injector release members (1508) are configured for locking the cassette (100) in the auto injector by proximal movement of the one or more injector release members (1508) into the cassette (100). 39. The reusable auto injector according to any of the items 37-38, wherein the one or more injector release members (1508) are configured for releasing a skin sensor (400) in the cassette (100) after securing the cassette (100) in the auto injector, wherein the skin sensor (400) is released by proximal movement of the one or more injector release members (1508) into the cassette (100).

40. The reusable auto injector according to any of the items 35-39 depending on items 33 or 34, wherein the pullback part (1600) comprises at least one cassette activation part tab surface (1606), wherein the cassette activation part (1500) comprises at least one pullback interacting tab (1506), and wherein the at least one cassette activation part tab surface (1606) on the pullback part (1600) engages the at least one pullback interacting tab (1506) on the cassette activation part (1500) such that the cassette activation part (1500) can be moved in relation to the pullback part (1600).

41. The reusable auto injector according to item 40, wherein the cassette activation part (1500) and the pullback part (1600) are configured for moving together in the longitudinal direction.

42. The reusable auto injector according to item 40 or 41 , wherein the cassette activation part (1500) can be tilted in relation to the pullback part (1600).

43. The reusable auto injector according to any of the items 35-42, wherein the cassette activation part (1500) can be tilted in relation to the pullback part (1600) around an interaction point constituting the at least one cassette activation part tab surface (1606) on the pullback part (1600) and the at least one pullback interacting tab (1506) on the cassette activation part (1506).

44. The reusable auto injector according to any preceding item further comprising a converter (2000).

45. The reusable auto injector according to item 44, wherein the converter (2000) comprises one or more converter pins selected from the group of:

• a primary converter pin (2001 );

• a secondary converter pin (2002);

• a tertiary converter pin (2003); and

• a quaternary converter pin (2004). 46. The reusable auto injector according to any of the item 45, wherein the converter (2000) comprises a tertiary converter pin (2003) and the cassette receiver (1100c, 1100d) comprises a tertiary converter pin receiving opening (1133) in which the tertiary converter pin (2003) is positioned.

47. The reusable auto injector according to item 46, wherein the converter (2000) is rotatable in a first rotational direction around the tertiary converter pin (2003).

48. The reusable auto injector according to any of the items 45-47 depending on any of the items 36-43 depending on item 35, wherein the converter (2000) comprises a quaternary converter pin (2004) and the cassette activation part (1500b) comprises a quaternary converter pin receiving channel (1534) in which the quaternary converter pin (2004) is movable.

49. The reusable auto injector according to item 48, wherein rotation of the converter (2000) around the tertiary converter pin (2003) in the first rotational direction moves the quaternary converter pin (2004) proximally, whereby the cassette activation part (1500b) is moved proximally along the longitudinal direction.

50. The reusable auto injector according to any preceding item further comprising a user button (2020, 2020c).

51. The reusable auto injector according to item 50 depending on any of the items 45-49, wherein the converter (2000) comprises a primary converter pin (2001 ) and the user button (2020) comprises a primary converter pin receiving opening (2031 ) in which the primary converter pin (2001 ) is positioned.

52. The reusable auto injector according to any of the items 50-51 depending on any of the items 45-49, wherein the converter (2000) comprises a secondary converter pin (2002) and the user button (2020) comprises a secondary converter pin receiving opening (2032) in which the secondary converter pin (2002) is positioned.

53. The reusable auto injector according to any of the items 50-52 depending on any of the items 45-49, wherein the converter (2000) and the user button (2020, 2020c) are rotationally locked to each other. 54. The reusable auto injector according to any of the items 50-53 depending on any of the items 45-49, wherein the user button (2020) is configured for rotating in the first rotational direction whereby the converter (2000) rotates in the first rotational direction.

55. The reusable auto injector according to item 50 depending on any of the items 45-49, wherein the converter (2000) comprises a secondary converter pin (2002) and the user button (2020c) comprises a user button channel (2042) in which the secondary converter pin (2002) is configured to travel.

56. The reusable auto injector according to item 55, wherein the user button (2020c) is configured for moving sideways whereby the converter (2000) rotates in the first rotational direction.

57. The reusable auto injector according to any preceding item further comprising a proximal injector housing (2100, 2100b, 2100c, 21 OOd).

58. The reusable auto injector according to item 57 depending on any of the items 50-56, wherein the proximal injector housing (2100c, 21 OOd) comprises a user button receiving opening (2110) configured for receiving the user button (2020, 2020c).

59. The reusable auto injector according to any of the items 44-58, wherein the converter (2000) comprises a converter plate (2008) with a primary converter plate surface (2010) and a secondary converter plate surface (2012).

60. The reusable auto injector according to item 35 or any of the items 36-59 depending on item 35, wherein the cassette activation part (1500b) comprises an activation part plate (1530) with an activation part plate thread (1532), and wherein the resetting sleeve (1200b, 1200d) comprises at least one resetting sleeve pin (1214) configured for traveling inside the activation part plate thread (1532).

61. The reusable auto injector according to item 60, wherein during rotation of the resetting sleeve (1200d) in the first rotational direction (DR1 ) for resetting the auto injector, the at least one resetting sleeve pin (1214) travels inside the activation part plate thread (1532) thereby moving the cassette activation part (1500b) from an extended to a retracted position. 62. The reusable auto injector according to any preceding item, wherein the resetting sleeve (1200d) is configured for rotating relative to the cassette receiver (1100b) in a second rotational direction (DR2) opposite the first rotational direction (DR1 ).

63. The reusable auto injector according to any of the items 60-62, wherein the at least one resetting sleeve pin (1214) is configured for traveling inside the activation part plate thread (1532) when rotating the resetting sleeve (1200d) in the second rotational direction (DR2), whereby the cassette activation part (1500b) is moved proximally to the extended position.

64. The reusable auto injector according to item 63, wherein the resetting sleeve (1200d) comprises a first blocking pin (1215) configured for stopping the rotation of the resetting sleeve ( 1200d) in the second rotational direction (DR2) when abutting the activation part plate (1530) thereby limiting the rotation of the resetting sleeve (1200d) in the second rotational direction (DR2) to a predefined angle.

65. The reusable auto injector according to any of the item 63 or 64, wherein the resetting sleeve (1200d) comprises a second blocking pin (1216) configured for stopping the rotation of the resetting sleeve (1200d) in the first rotational direction (DR1 ) when abutting the activation part plate (1530) thereby limiting the rotation of the resetting sleeve (1200d) in the first rotational direction (DR1 ) to a predefined angle.

66. The reusable auto injector according to any preceding item, wherein the auto injector comprises a plunger rod support part (1300, 1300a).

67. The reusable auto injector according to item 66, wherein the plunger rod support part (1300, 1300a) comprises a spring guide connecting opening (1301 ) for supporting a distal end (1054) of the spring guide (1050, 1050a).

68. The reusable auto injector according to item 66 or 67, wherein the plunger rod (1020, 1020a, 1020b) comprises at least one plunger rod tab (1027) located on an outside surface (1031 ) of the plunger rod (1020, 1020a, 1020b), and wherein the plunger rod support part (1300, 1300a) comprising a plunger rod release tab (1310), wherein the plunger rod release tab (1310) abuts the at least one plunger rod tab (1027) when the auto injector is in an initial position ready for receiving the cassette (100). 69. The reusable auto injector according to any preceding item, wherein the auto injector comprises an injector skin sensor detector (1700, 1700a, 1700b) configured for moving proximally into the cassette (100) and for moving distally again by a user pressing the cassette (100) against an injection site.

70. The reusable auto injector according to item 69 depending on item 44 or on any of the items 45-68 depending on item 44, wherein the injector skin sensor detector (1700b) comprises a converter blocking surface (1718), and wherein the converter (2000) comprises a skin sensor detector pin interaction surface (2018), wherein the injector skin sensor detector (1700b) is configured for being moved from an initial extended position to a distal position, wherein when in the initial extended position, the converter blocking surface (1718) abuts the skin sensor detector pin interaction surface (2018) thereby preventing rotation of the converter (2000), and wherein when in the distal position, the converter blocking surface (1718) no longer abuts the skin sensor detector pin interaction surface (2018) thereby allowing rotation of the converter (2000).

71. The reusable auto injector according to any of the items 35-69, wherein the reusable auto injector comprises an unlock sledge element (1750) configured for moving between : a proximal position (USP), wherein longitudinal movement of the cassette activation part (1500a) is prevented; and a distal position (USD), wherein longitudinal movement of the cassette activation part (1500a) into the cassette (100) is permitted.

72. The reusable auto injector according to any of the items 35-69 and 71 , wherein the cassette activation part (1500, 1500a) comprises one or more plunger rod lock elements (1518), and the plunger rod (1020a) comprises a cassette activation lock element (1038), and wherein prior to a cassette (100) being received in the auto injector, the cassette activation lock element (1038) is secured by the one or more plunger rod lock elements (1518) preventing relative longitudinal movement of the cassette activation part (1500a) and the plunger rod (1020a).

73. The reusable auto injector according to item 72 depending on item 71 , wherein the unlock sledge element (1750) comprises an unlock sledge release tab (1758), wherein distal movement of the unlock sledge element (1750) relative to the cassette activation part (1500a) moves the unlock sledge release tab (1758) towards the one or more plunger rod lock elements (1518) whereby the cassette activation lock element (1038) is released from the one or more plunger rod lock elements (1518) thereby allowing relative longitudinal movement of the cassette activation part (1500a) and the plunger rod (1020a).

74. The reusable auto injector according to item 73, wherein the cassette activation part (1500a) is configured for being moved proximally thereby moving the one or more injector release members (1508) into the cassette (100).

75. The reusable auto injector according to any of the items 71-74 depending on item 69, wherein the unlock sledge element (1750) and the injector skin sensor detector (1700a) are longitudinal locked.

76. The reusable auto injector according to item 69 or any of the items 71-75 depending on item 69, wherein the plunger rod (1020a) and the drive spring (1040), being in a compressed state, are configured for being unlocked when the injector skin sensor detector (1700, 1700a, 1700b) is moved in the distal direction, thereby allowing the compressed drive spring (1040) to push the plunger rod (1020a) in the proximal direction for medicament delivery as the drive spring (1040) expands.

77. The reusable auto injector according to item 69 depending on any of the items 67-68 or any of the items 71-76 depending on item 69 depending on any of the items 67-68, wherein the injector skin sensor detector (1700, 1700a) comprises a distal release end surface (1709) configured for pushing the plunger rod release tab (1310) radially outwardly when the user is pressing the cassette (100) against an injection site, whereby the plunger rod release tab (1310) no longer abuts the at least one plunger rod tab (1027) thereby allowing the drive spring (1040) to move the plunger rod (1020a) proximally for medicament delivery.

78. The reusable auto injector according to any of the items 69-77, wherein the reusable auto injector further comprises an injector skin sensor detector spring (1710) configured for pushing the injector skin sensor detector (1700, 1700a) proximally after removal of the cassette (100) received in the auto injector from the injection site.

79. The reusable auto injector according to any preceding item, wherein the plunger rod (1020a, 1020b) comprises at least a first plunger rod opening (1036A). 80. The reusable auto injector according to any preceding item, wherein the auto injector comprises a plunger rod release element (1350) with a plunger rod release hook (1356).

81. The reusable auto injector according to item 80 depending on item 79, wherein the plunger rod release hook (1356) is secured in the first plunger rod opening (1036A) thereby preventing proximal movement of the plunger rod (1020a) when the auto injector is in an initial position ready for receiving the cassette (100).

82. The reusable auto injector according to item 81 , wherein the plunger rod release element (1350) comprises:

• a chassis sleeve interacting rod (1360) around which the plunger rod release element (1350) is tiltable moving the plunger rod release hook (1356) radially outwardly; and

• a push protrusion (1358) abutting a sloping surface (1720) on the injector skin sensor detector (1700a, 1700b); wherein distal movement of the injector skin sensor detector (1700a, 1700b) relative to the plunger rod release element (1350) pushes the plunger rod release hook (1356) radially outwardly by relative movement of the sloping surface (1720) against the push protrusion (1358) whereby the plunger rod release hook (1356) is released from the first plunger rod opening (1036A) releasing the plunger rod (1020a) for proximal movement.

83. The reusable auto injector according to any of the items 80-82, wherein the auto injector comprises a push back spring (1370), wherein the push back spring (1370) is positioned between the plunger rod release element (1350) and the injector skin sensor detector (1700a, 1700b) exerting a pressure on the plunger rod release hook (1356) radially inwardly.

84. The reusable auto injector according to any preceding item, wherein the auto injector comprises a cassette detector (1800).

85. The reusable auto injector according to item 84 depending on any of the items 67-83, wherein the cassette detector (1800) comprises a release surface (1806), wherein the plunger rod support part (1300, 1300a) comprises a proximal flexible part (1312) with a proximal protruding part (1311 ), and wherein the cassette activation part (1500, 1500a, 1500b) comprises a support part lock tab (151 1 ) abutting the proximal protruding part (131 1 ) prior to inserting a cassette (100) in the auto injector, wherein when the release surface (1806) is pushed against the proximal protruding part (131 1 ), the proximal flexible part (1312) flexes radially, thereby releasing the cassette activation part (1500, 1500a, 1500b), thereby enabling locking of the cassette (100) in the auto injector by proximal movement of the cassette activation part (1500, 1500a, 1500b).

86. The reusable auto injector according to any of the items 67-85, wherein the cassette activation part (1500, 1500a, 1500b) further comprises a distal end protrusion (1510), wherein the plunger rod support part (1300, 1300a) comprises a cassette activation part stop protrusion (1307), wherein the plunger rod (1020, 1020a, 1020b) comprises a longitudinally extending bar (1033), wherein the cassette activation part stop protrusion (1307) prevents distal movement of the cassette activation part (1500, 1500a, 1500b) after positioning a cassette (100) in the auto injector by the distal end protrusion (1510) being positioned between the cassette activation part stop protrusion (1307) and the longitudinally extending bar (1033).

87. The reusable auto injector according to any of the items 33-86, wherein the pullback part (1600) further comprises a second cassette interacting tab (161 1 ) moving with the cassette interacting tab (1601 ) in the longitudinal direction, the second cassette interacting tab (161 1 ) being radially non-movable.

88. The reusable auto injector according to any preceding item, wherein the reusable auto injector further comprises a rotational damper (1900) comprising:

• a damper sleeve (1902) positioned between the chassis sleeve (1400, 1400b) and the resetting sleeve (1200, 1200b, 1200d), the damper sleeve (1902) comprising one or more damper channels (1904); and

• a damper end surface (1906); wherein the plunger rod resetting part (1026) extends through the one or more damper channels (1904) and into the resetting thread (1206) in the resetting sleeve (1200, 1200b, 1200d); wherein the damper sleeve (1902) is rotatable relative to the chassis sleeve (1400, 1400b); and wherein movement of the plunger rod (1020, 1020a, 1020b) in the proximal direction rotates the damper sleeve (1902) due to the plunger rod resetting part (1026) extending through the one or more damper channels (1904) in the damper sleeve (1902); and wherein the damper sleeve (1902) and the damper end surface (1906) rotates relatively during injection, such that a speed of the plunger rod (1020, 1020a, 1020b) during injection in the proximal direction is reduced.

89. The reusable auto injector according to item 88, wherein the damper sleeve (1902) is rotatable relative to the resetting sleeve (1200, 1200b, 1200d) during proximal movement of the plunger rod (1020, 1020a, 1020b).

90. The reusable auto injector according to any of the items 88-89, wherein the damper sleeve (1902) is non-rotatable relative to the resetting sleeve (1200, 1200b, 1200d) during distal movement of the plunger rod (1020, 1020a, 1020b).

91. The reusable auto injector according to any of the items 88-90, wherein the one or more damper channels (1904) in the damper sleeve (1902) each has a pitch in the first rotation direction being identical to a pitch of the resetting thread (1206) in the resetting sleeve (1200, 1200b, 1200d) in the first rotation direction (R1 ), whereby rotation of the damper sleeve (1902) relative to the resetting sleeve (1200, 1200b, 1200d) is prevented.

92. The reusable auto injector according to any of the items 88-91 depending on any of the items 11-87, wherein the damper end surface (1906) is positioned inside distal injector housing (2200, 2200b) and connected to the distal injector housing (2200, 2200b).

93. The reusable auto injector according to any of the items 88-92 depending on any of the items 1 1-87, wherein the damper end surface (1906) and the distal injector housing (2200, 2200b) are rotationally locked.

94. The reusable auto injector according to any of the items 37-93, wherein the reusable auto injector is configured for receiving a cassette (100) comprising:

• a syringe holder (300) for receiving the syringe (200) containing the medicament;

• a skin sensor (400) movable in the longitudinally direction relative to the syringe holder (300) between two or more longitudinal positions including at least a first locked position prior to securing the cassette (100) in the auto injector and an unlocked position after securing the cassette (100) in the auto injector ; wherein the cassette activation part (1500, 1500a, 1500b) comprises the one or more injector release members (1508) configured for releasing the skin sensor (400) in the cassette (100) after securing the cassette (100) in the auto injector, wherein the skin sensor (400) is released by proximal movement of the one or more injector release members (1508) into the cassette (100).

95. The reusable auto injector according to any preceding item, wherein the reusable auto injector is configured for receiving a cassette (100) comprising a cap (700) positioned at the proximal end of the cassette (100), and wherein the injector skin sensor detector (1700, 1700a, 1700b) is configured for moving proximally into the cassette (100) after removal of the cap (700).

96. The reusable auto injector according to item 95 depending on item 94, wherein after removal of the cap (700), the skin sensor (400) is configured for moving in the distal direction by a user pressing the skin sensor (400) towards the injector site, wherein the injector skin sensor detector (1700, 1700a, 1700b) is configured for moving in the distal direction when the skin sensor (400) is pressed towards the injector site.

97. The reusable auto injector according to item 96 depending on any of the items 78-95, wherein when the injector skin sensor detector spring (1710) pushes the injector skin sensor detector (1700, 1700a, 1700b) proximally after removal of the cassette (100) received in the auto injector from the injection site, the skin sensor (400) of the cassette (100) is configured for being moved into a final locked position (LP3).

98. The reusable auto injector according to any of the items 33-97, wherein the pullback part (1600) further comprises a plunger rod engagement surface (1608) configured for coming into contact with and abutting a distal end (1024) of the plunger rod (1020, 1020a, 1020b) during medicament delivery whereby the pullback part (1600) moves proximally with the plunger rod (1020, 1020a, 1020b) during at least a last part of the medicament delivery.

99. A reusable auto injector (1000, 1000a, 1000b, 1000c, 1000d) for administration of medicament, the auto injector comprising:

• a cassette receiver (1100, 1 100b, 1100c) configured for receiving a removable cassette (100) containing the medicament;

• a plunger rod (1020, 1020a, 1020b) configured for movement of a stopper (210) inside the cassette (100) in a first longitudinal direction for medicament delivery;

• a plunger rod resetting part (1026) connected to and protruding radially from the plunger rod (1020, 1020a, 1020b); • a drive spring (1040) adapted for moving the plunger rod (1020, 1020a, 1020b) in the first longitudinal direction; and a resetting sleeve (1200, 1200b, 1200d) rotatable relative to the cassette receiver (1 100, 1100b, 1100c) in a first rotational direction (DR1 ), the resetting sleeve (1200, 1200b, 1200d) comprising a resetting thread (1206), wherein the plunger rod resetting part (1026) engages with the resetting thread (1206) such that a rotation of the resetting sleeve (1200, 1200b, 1200d) in a first rotational direction (DR1 ) moves the plunger rod (1020, 1020a, 1020b) in a second longitudinal direction opposite the first longitudinal direction for resetting the plunger rod (1020, 1020a, 1020b).

100. A reusable auto injector (1000, 1000a, 1000b, 1000c, 1000d) for administration of medicament, the auto injector being configured for receiving a cassette (100) comprising a syringe (200) containing the medicament, wherein the auto injector is extending from a proximal end (1002) to a distal end (1004) along a longitudinal axis (L), the auto injector comprising:

• a plunger rod (1020, 1020a, 1020b) configured for proximal movement of a stopper (210) inside the syringe (200) for medicament delivery, the plunger rod (1020, 1020a, 1020b) being configured for moving a total plunger rod movement length, the total plunger rod movement length being from an initial distal plunger rod position to a proximal delivery plunger rod position;

• a drive spring (1040) adapted for moving the plunger rod (1020, 1020a, 1020b) in a proximal direction; and

• a first damper assembly configured for dampening at least part of the proximal movement of the drive spring (1040) during medicament delivery, wherein the first damper assembly is configured for dampening a first part of the total plunger rod movement length or the entire total plunger rod movement length.

101 . The reusable auto injector according to item 100, wherein the first damper assembly is configured for dampening only a first part of the total plunger rod movement length, wherein the first part of total plunger rod movement length is less than 25%, such as less than 20%, such as less than 15% of the total plunger rod movement length.

102. The reusable auto injector according to any of the items 100-101 , wherein the plunger rod (1020, 1020a, 1020b) is configured for moving between: o an initial distal plunger rod position where the plunger rod (1020, 1020a, 1020b) is not in contact with the stopper (210) inside the cassette (100); o a stopper contact position, wherein the plunger rod is in contact with the stopper (210) inside the cassette (100); and o a proximal delivery plunger rod position, where the stopper (210) inside the syringe (200) has been moved proximally for medicament delivery, wherein the first damper assembly dampers the movement of the plunger rod (1020, 1020a, 1020b) only from the initial distal plunger rod position to the stopper contact position.

103. The reusable auto injector according to any of items 100-102, wherein the reusable auto injector comprises a spring guide (1050, 1050a) around which at least a distal end (1044) of the drive spring (1040) extends, wherein the drive spring (1040) is biased between a proximal end surface (1032) inside the plunger rod cavity (1030, 1030a) and a distal end surface (1056) of the spring guide (1050, 1050a), and wherein the first damper assembly comprises an O-ring (1010) extending around a first part (1062) of the spring guide (1050a) extending inside the plunger rod cavity (1030a), wherein the O-ring (1010) is in contact with an inner surface of the plunger rod cavity (1030a), and wherein movement between the O-ring (1010) and the plunger rod cavity (1030a) upon proximal movement of the plunger rod (1030a) introduces a dampening effect.

104. The reusable auto injector according to item 103, wherein movement between the O- ring (1010) and the plunger rod cavity (1030a) is a frictional force introducing a linear dampening effect.

105. The reusable auto injector according to any of the items 103-104, wherein the plunger rod (1020a) comprises an inner plunger rod tube (1039) extending into the plunger rod cavity (1030a), wherein at least part of the drive spring (1040) is positioned around the inner plunger rod tube (1039), and at least a part of the spring guide (1050a) is extending through the inner plunger rod tube (1039), wherein the O-ring (1010) is movable into the inner plunger rod tube (1039) when the drive spring (1040) pushes the plunger rod (1020a) proximally.

106. A system comprising a reusable auto injector according to any of the preceding items and a cassette (100), the cassette (100) comprising:

• a skin sensor (400) longitudinally movable relative to the syringe holder (300) between two or more longitudinal positions including at least a first locked position prior to securing the cassette (100) in the auto injector and an unlocked position; wherein one or more injector release members (1508) in the reusable auto injector is configured for releasing the skin sensor (400) in the cassette (100) after securing the cassette (100) in the auto injector, wherein the skin sensor (400) is released by proximal movement of the one or more injector release members (1508) into the cassette (100).

107. The system according to item 106, wherein the skin sensor (400) is movable in the longitudinally direction relative to the syringe holder (300) between two or more longitudinal positions selected from: o a distal position (LD); o a final locked position (LP3); o an initial locked position (LP1 ) between the final locked position (LP3) and the distal position (LD); and o an intermediate position (LP2) between the initial locked position (LP1 ) and the final locked position (LP3).

108. The system according to item 107, wherein when the skin sensor (400) is in the distal longitudinal position (LD), the syringe outlet (204) is exposed, and wherein the skin sensor (400) covers the syringe outlet (208) when the skin sensor (400) is in either of:

• the initial locked position (LP1 ); or

• the intermediate position (LP2); or

• the final locked position (LP3).

109. The system according to item 107 or 108, wherein the skin sensor (400) is in the initial locked position (LP1 ) prior to securing the cassette (100) in the reusable auto injector and movable to the intermediate position (LP2) after release of the skin sensor (400) by the one or more injector release members (1508).

110. The system according to any of the items 106-109, wherein the cassette (100) further comprises an index ring (500) rotatable relative to the skin sensor (400) between two or more rotational positions selected from: o a first rotational position (R1 ); o a delivery rotational position (Rd) in which the skin sensor (400) is moveable between the distal position (LD) and the final locked position (LP3); o a cap-release rotational position (Rcr) positioned between the first rotational position (R1 ) and the delivery rotational position (Rd), wherein the one or more injector release members (1508) are configured for rotating the index ring (500) between the two or more rotational positions when the one or more injector release members (1508) moves proximally and comes into contact with the index ring (500).

111. The system according to any of the items 106-110, wherein the cassette (100) further comprises a syringe (200) received in the syringe holder (300), the syringe (200) comprising: o a syringe medicament compartment (206); o an outlet (204) at the proximal end (202) of a syringe medicament compartment; and o a stopper (210) positioned inside the syringe compartment, wherein the stopper is movable from a distal end (204) of the syringe compartment towards the proximal end of the syringe compartment for emptying the medicament in the syringe compartment through the outlet.

112. The system according to any of the items 106-111 , wherein the index ring is configured for moving from the cap-release rotational position (Rcr) to the delivery rotational position (Rd) preparing the reusable auto injector for medicament delivery when the skin sensor (400) is in the distal longitudinal position (LD).

113. The system according to any of the items 106-112, wherein the index ring (500) comprises a track (530) extending in a sloping direction, and wherein the one or more injector release members (1508) is configured for traveling inside the track (530), and wherein the index ring (500) is rotated when the injector release member (1508) travels proximally inside the track (530).

114. The system according to item 113, wherein each of the one or more injector release members (1508) comprises a track-guide protrusion (1509), and wherein the trackguide protrusion (1509) is configured for traveling inside the track (530).

115. The system according to any of the items 106-114, wherein the auto injector comprises one or more cassette locking parts (1109) configured for engaging in a snap-fit connection with corresponding one or more cassette securing tabs (612) on the cassette (100) when the cassette (100) is inserted into the auto injector, and wherein proximal movement of the injector release member (1508) prevents a disengagement of the snap-fit connection thereby securing the cassette (100) inside the auto injector . 116. The system according to item 115, wherein the one or more injector release members (1508) are adapted for moving to the initial position after delivery of medicament, whereby the cassette (100) is unlocked from the auto injector for removal of the cassette (100) after medicament delivery.

117. The system according to any of the items 1 15-116, wherein the auto injector comprises an injector skin sensor detector (1700, 1700a, 1700b) and a skin sensor spring (1710) adapted for pushing the injector skin sensor detector (1700, 1700a, 1700b) against a cassette skin sensor pin (422) upon proximal movement of the injector release member (1508) after release of the skin sensor (400) from the initial locked position.

118. The system according to item 1 17, wherein the skin sensor spring (1710) is adapted for pushing the cassette skin sensor (400) in a proximal direction to the proximal longitudinal position (LP2) when the index ring (500) is in the cap-release rotational position (Rcr).

119. The system according to any of the items 1 17-118, wherein the skin sensor spring (1710) is adapted for pushing the cassette skin sensor (400) in a proximal direction to the proximal longitudinal position (LP3) when the index ring (500) is in the delivery rotational position (Rd).

120. The system according to any of the items 117-119, wherein after medicament delivery and removal of the reusable auto injector from the delivery site, the skin sensor spring (1710) is configured for keeping the skin sensor (400) in the final longitudinal position (LP3) during distal movement of the injector release member (1508) whereby the index ring (500) is rotated from the delivery rotational position (Rd) to the first rotational position (R1 ).

121. The system according to any of the items 1 17-120, wherein the index ring (500) is in the first rotational position (R1 ) prior to use and wherein when the index ring (500) is moved from the first rotational position (R1 ) to the cap-release rotational position (Rcr) by proximal movement of the one or more injector release members (1508), the skin sensor spring reusable auto injector (1026) is adapted for pushing the skin sensor (400) to the intermediate position (LP2).

122. The system according to any of the items 106-121 , wherein the cassette further comprises a cassette housing (600) comprising a cap holding part (608) at a proximal end (602) of the cassette housing (600), and a removable cassette cap (700) comprising one or more locking cap parts (706) extending distally from a proximal end (702) of the cassette cap, wherein prior to use, a cassette cap locking protrusion (708) on each of the one or more locking cap parts (706) is secured inside the cassette housing (600), wherein upon proximal movement of the skin sensor from the initial locked position (LP1 ) to the intermediate position (LP2), the distal locking ends (708) moves outside the cassette housing (600).

References

100 cassette

102 proximal end of the cassette

104 distal end of the cassette

200 syringe

202 proximal end of the syringe ! proximal end of the syringe compartment

204 distal end of the syringe ! distal end of the syringe compartment

206 syringe compartment

208 hollow needle ! syringe outlet

210 stopper

212 needle shield / RNS

214 inner part of the needle shield

216 outer part of the needle shield

218 syringe flange

220 syringe shoulder

250 syringe sleeve

252 proximal end of the syringe sleeve

254 distal end of the syringe sleeve

256 syringe sleeve inward protruding support surface

258 C-shaped longitudinal mounting opening

260 distal syringe sleeve support surface

300 syringe holder

302 proximal end of the syringe holder

304 distal end of the syringe holder

306 proximal opening in the syringe holder

308 syringe support surface

310 syringe holder tubular part

312 syringe holder tubular part inspection opening

314 distal tubular ring part

315 opening in the distal end of the syringe holder

316 proximal index ring support surface

318 syringe holder lid locking opening

320 syringe securing flexible tab at the distal end of the syringe holder

322 injection injector release member opening

330 syringe holder lid

332 syringe holder lid opening

334 lid locking tab 336 C-shaped lid part

337 opening in the C-shaped lid part

338 support lid part

340 inner surface on the C-shaped lid part

342 C-shaped lid part channel

344 bridge portion

400 skin sensor

402 proximal end of the skin sensor

404 distal end of the skin sensor

405 proximal skin contact surface of the skin sensor

406 proximal recess

408 protruding tab

410 proximal protruding ramp

412 first locking recess on the skin sensor

413 first locking tab

414 second locking recess on the skin sensor

415 second locking tab

416 first distal surface

418 first proximal surface

420 tubular skin sensor part

422 cassette skin sensor pin

424 second distal surface

426 inspection opening in the skin sensor

428 cassette housing locking protrusion

500 index ring

502 proximal end of the index ring

504 distal end of the index ring

506 first longitudinally extending part

507 locking tab

508, 508' first recess on the index ring

509 index ring ramp

510, 510' second recess on the index ring

512 second radially extending part

513 opening in the second radially extending part

514 second proximal surface of the second radially extending part

516, 516' second distal surface of the second radially extending part

518 second longitudinally extending part 520 tubular index ring part

522 first radially extending part

524 first proximal surface of the first radially extending part

526 first distal surface of the first radially extending part

528 first surface area of the first radially extending part

530 track in the first radially extending part

532 first corner of the first radially extending part

534 second corner of the first radially extending part

536 first section of the track

538 second section of the track

540 third section of the track

542 first middle point of the track

544 second middle point of the track

600 cassette housing

602 proximal end of the cassette housing

604 distal end of the cassette housing

606 opening at the distal end of the cassette housing

608 cap holding part

610 inspection opening

612 cassette securing tabs

614 skin sensor locking opening

700 cassette cap

702 proximal end of the cassette cap

704 distal end of the cassette cap

706 cap locking part

708 cassette cap track-guide protrusion / cassette cap locking protrusion

709 inwardly extending part of the cassette cap locking protrusion

710 second distally extending part / tubular cap part

712 gripping portion

714 inner cassette cap part

716 outer cassette cap part

800 cassette housing cover

1000 auto injector

1000a auto injector

1000b auto injector

1000c auto injector

1000d auto injector 1002 proximal end of the auto injector

1004 distal end of the auto injector

1010 O-ring

1020 plunger rod

1020a plunger rod

1020b plunger rod

1021 pullback part stop part

1022 proximal end of the plunger rod

1023 distally directed surface on the pullback part stop part

1024 distal end of the plunger rod

1025 proximally directed surface on the pullback part stop part

1026 plunger rod resetting part

1027 outer plunger rod tabs

1028 sloping distal surface on outer plunger rod tabs

1029 steep proximal surface on outer plunger rod tabs

1030 plunger rod cavity

1030a plunger rod cavity

1031 outer surface of the plunger rod

1032 spring proximal end surface inside the plunger rod cavity

1033 longitudinally extending bar

1034 distal tubular part

1035 proximal tubular part

1036 plunger rod opening

1036A first plunger rod opening

1036B second plunger rod opening

1037 inner surface of the plunger rod cavity

1038 cassette activation lock element

1040 drive spring

1042 proximal end of the drive spring

1044 distal end of the drive spring

1046 proximal end of the distal tubular plunger rod part

1050 drive spring guide

1050a drive spring guide

1052 proximal end of the spring guide

1054 distal end of the spring guide

1056 spring distal end surface of the spring guide

1058 spring guide rod 1060 spring guide track

1062 first part of the drive spring guide

1100 cassette receiver

1100b cassette receiver

1100c cassette receiver

1101 tubular part of the cassette receiver

1102 proximal end of the cassette receiver

1103 chassis sleeve channel

1104 distal end of the cassette receiver

1105 first spring support surface for the injector skin sensor detector spring

1106 second spring support surface for the cassette detector spring

1107 activation part channel for the cassette activation part

1108 outer coupling surface

1109 cassette locking part

1110 end plate in the cassette receiver

1115 injector skin sensor detector opening

1116 cassette detector opening

1118 injector release member opening

1120 plunger rod opening

1122 cassette receiver tab

1124 cassette receiver channel

1126 interface to plunger rod release element

1128 cover part plate tab receiving opening

1133 tertiary converter pin receiving opening

1134 converter pin channel

1200 resetting sleeve

1200b resetting sleeve

1200d resetting sleeve

1202 proximal end of the resetting sleeve

1204 distal end of the resetting sleeve

1205 inner surface of the resetting sleeve

1206 resetting thread

1208 outer surface of the resetting sleeve

1209 outer housing channel

1210 chassis sleeve interacting hook

1211 sloping surface on the chassis sleeve interacting hook

1212 steep surface on the chassis sleeve interacting hook 1214 resetting sleeve pin

1215 first blocking pin

1216 second blocking pin

1300 plunger rod support part

1300a plunger rod support part

1301 spring guide connecting opening

1302 proximal end of the plunger rod support part

1303 support part end plate of the plunger rod support part

1304 distal end of the plunger rod support part

1305 first proximally extending arm

1306 plunger rod support bar on the first proximally extending arm

1307 cassette activation part stop protrusion on the first proximally extending arm

1308 second proximally extending arm

1309 flexible side arm

1310 plunger rod release tab

1311 proximal protruding part

1312 proximal flexible part of the first proximally extending arm

1350 plunger rod release element

1352 proximal end of the plunger rod release element

1354 distal end of the plunger rod release element

1356 plunger rod release hook

1358 push protrusion

1360 chassis sleeve interacting rod

1362 push back surface

1370 push back spring

1400 chassis sleeve

1400b chassis sleeve

1401 tubular chassis part

1402 proximal end of the chassis sleeve

1403 longitudinally extending channel in the tubular chassis part

1404 distal end of the chassis sleeve

1405 distal skin sensor spring support rod

1406 distal cassette detector spring support rod

1407 chassis sleeve plate

1408 plunger rod support part coupling surface

1409 coupling surface

1410 resetting sleeve interacting tab 1411 sloping surface on the resetting sleeve interacting tab

1412 steep surface on the resetting sleeve interacting tab

1413 outside of the coupling surface

1414 inside of the coupling surface

1416 activation part plate channel

1500 cassette activation part

1500a cassette activation part

1500b cassette activation part

1502 proximal end of the cassette activation part

1504 distal end of the cassette activation part

1506 pullback interacting tab

1507 flexible pullback arm

1508 injector release member

1509 track-guide protrusion

1510 distal end protrusion

1511 support part lock tab

1512 guiding tab

1516 plunger rod lock arm

1518 plunger rod lock element

1520 lock element enclosure

1522 cassette interacting tab interface

1524 plunger rod interaction arm

1530 activation part plate

1532 activation part plate thread

1534 quaternary converter pin receiving channel

1600 pullback part

1601 cassette interacting tab

1602 proximal end of the pullback part

1604 distal end of the pullback part

1605 step type bend on the pullback part

1606 cassette activation part tab surface

1608 plunger rod engagement surface

1611 second cassette interacting tab

1700 injector skin sensor detector

1700a injector skin sensor detector

1700b injector skin sensor detector

1702 proximal end of the injector skin sensor detector 1703 injector skin sensor detector pin

1704 distal end of the injector skin sensor detector

1705 proximal skin sensor spring support rod

1706 plate part on the injector skin sensor detector

1707 plate part channel for the plunger rod

1709 distal release end surface

1710 injector skin sensor detector spring

1712 proximal end of the injector skin sensor detector spring

1714 distal end of the injector skin sensor detector spring

1716 sledge receiving channel

1718 converter blocking surface

1720 sloping surface of the injector skin sensor detector

1750 unlock sledge element

1752 proximal end of the unlock sledge element

1754 distal end of the unlock sledge element

1756 injector skin sensor detector lock tab

1758 unlock sledge release tab

1800 cassette detector

1802 proximal end of the cassette detector

1803 cassette detector pin

1804 distal end of the cassette detector

1805 proximal cassette detector spring support rod

1806 release surface

1810 cassette detector spring

1812 proximal end of the cassette detector spring

1814 distal end of the cassette detector spring

1900 rotational damper

1902 damper sleeve

1904 damper channel

1906 damper end surface

2000 converter

2001 primary converter pin

2002 secondary converter pin

2003 tertiary converter pin

2004 quaternary converter pin

2008 converter plate

2010 primary converter plate surface 2012 secondary converter plate surface

2018 skin sensor detector pin interaction surface

2020 user button

2020c user button

2022 user button plate

2024 primary user button plate surface

2026 secondary user button plate surface

2028 user button tab

2031 primary converter pin receiving opening

2032 secondary converter pin receiving opening

2040 primary user button protrusion

2042 user button channel

2044 secondary user button protrusion

2050 cover part

2052 cover part plate

2054 primary cover part plate surface

2056 secondary cover part plate surface

2058 cover part plate tab

2060 curving cover part surface

2100 proximal injector housing

2100b proximal injector housing

2100c proximal injector housing

2100d proximal injector housing

2101 first tubular part of the proximal injector housing

2102 proximal end of the proximal injector housing

2104 distal end of the proximal injector housing

2106 cassette view opening

2107 second activation part channel for the cassette activation part

2108 chassis sleeve channel for the coupling surface on the chassis sleeve

2109 second tubular part of the proximal injector housing

2110 user button receiving opening

2200 distal injector housing

2200b distal injector housing

2202 proximal end of the distal injector housing

2204 distal end of the distal injector housing

2205 inner surface of the distal injector housing

2206 user gripping lines 2208 outer surface of the distal injector housing

2209 inner resetting sleeve locking part

2210 rotational stop surface

2212 distal injector housing plate

2214 plunger rod support part alignment tabs

2216 distal injector housing cap

PP proximal cassette locking position

PD distal cassette release position

LD distal position of the syringe holder

LP1 initial locked proximal position of the syringe holder

LP2 intermediate proximal position of the syringe holder

LP3 final locked proximal position of the syringe holder

R1 first rotational position of the index ring

R2 second rotational position of the index ring

R3 third rotational position of the index ring

Rd delivery rotational position of the index ring

Rcr cap-release rotational position of the index ring

DR1 first rotational direction

USP proximal unlock sledge element position

USD distal unlock sledge element position

Claims

1. A reusable auto injector (1000, 1000a, 1000b, 1000c, 1000d) for administration of medicament, the auto injector being configured for receiving a cassette (100) comprising a syringe (200) containing the medicament; wherein the auto injector is extending from a proximal end (1002) to a distal end (1004) along a longitudinal axis (L); wherein the cassette (100) is configured for being removable received in the auto injector in a longitudinal direction along the longitudinal axis (L); wherein the auto injector comprises:

• a cassette receiver (1100, 1100b, 1100c) configured for receiving the cassette (100);

• a plunger rod (1020, 1020a, 1020b) configured for proximal movement of a stopper (210) inside the syringe (200) for medicament delivery;

• a plunger rod resetting part (1026) connected to and protruding radially from the plunger rod (1020, 1020a, 1020b);

• a resetting sleeve (1200, 1200b, 1200d) rotatable relative to the cassette receiver (1100, 1100b, 1100c) in a first rotational direction (DR1), the resetting sleeve (1200, 1200b, 1200d) comprising a resetting thread (1206) located on an inner surface (1205) of the resetting sleeve (1200, 1200b, 1200d), wherein the plunger rod resetting part (1026) engages with the resetting thread (1206) such that a rotation of the resetting sleeve (1200, 1200b, 1200d) in a first rotational direction (DR1 ) moves the plunger rod (1020, 1020a, 1020b) in a distal direction for resetting the plunger rod (1020, 1020a, 1020b).

2. The reusable auto injector according to claim 1 , wherein the cassette receiver (1100, 1100b, 1100c) is configured for receiving the cassette (100) releasably in the cassette receiver (1100, 1100b, 1100c).

3. The reusable auto injector according to any preceding claim, wherein rotation of the resetting sleeve (1200, 1200b, 1200d) in the first rotational direction (DR1) moves the plunger rod (1020, 1020a, 1020b) in a distal direction for resetting the plunger rod (1020, 1020a, 1020b) relative to the cassette receiver (1100, 1 100b, 1100c).

4. The reusable auto injector according to any preceding claim, wherein the plunger rod (1020, 1020a, 1020b) is configured for proximal movement between a retracted plunger rod position and an extended plunger rod position, wherein the resetting sleeve (1200, 1200b, 1200d) is configured for moving the plunger rod from the extended plunger rod position to the retracted plunger rod position by rotation of the resetting sleeve (1200, 1200b, 1200d) in the first rotational direction (DR1 ) a predefined amount of degrees relative to the cassette receiver (1100, 1100b, 1100c).

5. The reusable auto injector according to claim 4, wherein the predefined amount of degrees relative to the cassette receiver is between 150 degrees and 210 degrees, such as between 160 degrees and 200 degrees, such as between 170 degrees and 190 degrees, such as 180 degrees.

6. The reusable auto injector according to any preceding claim, wherein the plunger rod resetting part (1026) comprises two pin parts positioned opposite another, wherein the resetting thread (1206) comprises two helical threads positioned opposite each other inside the resetting sleeve (1200, 1200b, 1200d), each of the two helical threads interfacing with each of the two oppositely positioned pin parts extending from a distal end (1024) of the plunger rod (1020, 1020a, 1020b).

7. The reusable auto injector according to any preceding claim, wherein the reusable auto injector further comprises a distal injector housing (2200, 2200b) surrounding the resetting sleeve (1200, 1200b, 1200d), the distal injector housing (2200, 2200b) being rotatable relative to the cassette receiver (1100, 1 100b, 1 100c), wherein the distal injector housing (2200, 2200b) is rotationally locked to the resetting sleeve (1200, 1200b, 1200d).

8. The reusable auto injector according to claim 7, wherein the distal injector housing (2200, 2200b) comprises at least one rotational stop surface (2210) protruding from a distal injector housing plate (2212) of the distal injector housing (2200, 2200b), the at least one rotational stop surface (2210) preventing further rotation of the resetting sleeve (1200, 1200b, 1200d) than the predefined amount of degrees relative to the cassette receiver (1100, 1100b, 1100c), wherein the rotational stop surface (2210) preferably abuts the plunger rod resetting part (1026) when the resetting sleeve has been rotated the predefined amount of degrees relative to the cassette receiver, whereby further rotation of the resetting sleeve (1200, 1200b, 1200d) relative to the cassette receiver (1100, 1100b, 1100c) is prevented.

9. The reusable auto injector according to any preceding claim, wherein the rotation of the resetting sleeve (1200, 1200b, 1200d) in the first rotational direction (DR1 ) compresses the drive spring (1040), wherein the plunger rod (1020, 1020a, 1020b) comprises a plunger rod cavity (1030, 1030a) extending into the plunger rod (1020, 1020a, 1020b) and wherein the drive spring (1040) is positioned at least partly inside the plunger rod cavity (1030, 1030a).

10. The reusable auto injector according to any preceding claim, wherein the reusable auto injector further comprises a first damper assembly configured for dampening at least part of the proximal movement of the drive spring (1040) during medicament delivery.

11. The reusable auto injector according to claim 10, wherein during medicament delivery, the plunger rod (1020, 1020a, 1020b) is configured for moving a total plunger rod movement length, the total plunger rod movement length being from an initial distal plunger rod position to a proximal delivery plunger rod position, wherein the first damper assembly is configured for dampening a first part of the total plunger rod movement length or the entire total plunger rod movement length.

12. The reusable auto injector according to claim 11 , wherein the first damper assembly is configured for dampening only the first part of the total plunger rod movement length, wherein the first part of total plunger rod movement length is less than 25%, such as less than 20%, such as less than 15% of the total plunger rod movement length.

13. The reusable auto injector according to any of the claims 9-12, wherein the reusable auto injector comprises a spring guide (1050, 1050a) around which at least a distal end (1044) of the drive spring (1040) extends, and wherein the first damper assembly comprises an O-ring (1010) extending around a first part of the spring guide (1050, 1050a) extending inside the plunger rod cavity (1030, 1030a), wherein the O-ring (1010) is in contact with an inner surface of the plunger rod cavity (1030, 1030a), and wherein contact between the O-ring (1010) and the plunger rod cavity (1030, 1030a) upon proximal movement of the plunger rod (1030, 1030a) introduces a dampening effect.

14. The reusable auto injector according to any preceding claim, wherein the reusable auto injector further comprises a chassis sleeve (1400, 1400b) positioned between the plunger rod (1020, 1020a, 1020b) and the resetting sleeve (1200, 1200b, 1200d), the chassis sleeve (1400, 1400b) comprising a longitudinally extending channel (1403) through which the plunger rod resetting part (1026) extends, the chassis sleeve (1400, 1400b) being non-rotatable relative to the cassette receiver (1100, 1100b, 1100c), wherein the channel (1403) is configured for preventing the plunger rod (1020, 1020a, 1020b) from rotating when the resetting sleeve (1200, 1200b, 1200d) is rotated in the first rotational direction (DR1 ).

15. The reusable auto injector according to any preceding claim, wherein the reusable auto injector further comprises a cassette interacting tab (1601 ) movable in the longitudinal direction (L) between a proximal cassette locking position (PP) and a distal cassette release position (PD), wherein prior to receiving a cassette (100) in the reusable auto injector, the cassette interacting tab (1601 ) is in the distal cassette release position (PD), wherein when the cassette (100) is received in the reusable auto injector, user induced movement of the cassette interacting tab (1601 ) from the distal cassette release position (PD) to the proximal cassette locking position (PP) locks the cassette (100) in the reusable auto injector .

16. The reusable auto injector according to any preceding claim, wherein the reusable auto injector further comprises a cassette activation part (1500, 1500a, 1500b) configured for moving in the longitudinal direction (L) relative to the cassette receiver (1100, 1100b, 1100c), wherein the cassette activation part (1500, 1500a, 1500b) comprises one or more injector release members (1508) configured for:

• releasing a skin sensor (400) in the cassette (100) after securing the cassette (100) in the auto injector, wherein the skin sensor (400) is released by proximal movement of the one or more injector release members (1508) into the cassette (100), and/or

• locking the cassette (100) in the auto injector by proximal movement of the one or more injector release members (1508) into the cassette (100).

17. The reusable auto injector according to claim 16, wherein the reusable auto injector further comprises a pullback part (1600) comprising at least one cassette activation part tab surface (1606), and wherein the cassette activation part (1500, 1500a, 1500b) comprises at least one pullback interacting tab (1506), and wherein the at least one cassette activation part tab surface (1606) on the pullback part (1600) engages the at least one pullback interacting tab (1506) on the cassette activation part (1500, 1500a, 1500b) such that the cassette activation part (1500, 1500a, 1500b) can be moved in relation to the pullback part (1600).

18. The reusable auto injector according to claim 17, wherein the cassette activation part (1500, 1500a, 1500b) and the pullback part (1600) are configured for moving together in the longitudinal direction, and wherein the cassette activation part (1500, 1500a, 1500b) can be tilted in relation to the pullback part (1600), wherein the cassette activation part (1500, 1500a, 1500b) can be tilted in relation to the pullback part (1600) around an interaction point constituting the at least one cassette activation part tab surface (1606) on the pullback part (1600) and the at least one pullback interacting tab (1506) on the cassette activation part (1506).

19. The reusable auto injector according to any preceding claim further comprising a converter (2000). wherein the converter (2000) comprises one or more converter pins selected from the group of:

• a primary converter pin (2001);

• a secondary converter pin (2002);

• a tertiary converter pin (2003); and

• a quaternary converter pin (2004).

20. The reusable auto injector according to claim 19, wherein the converter (2000) comprises the tertiary converter pin (2003) and the cassette receiver (1100c, 1100d) comprises a tertiary converter pin receiving opening (1133) in which the tertiary converter pin (2003) is positioned, and wherein the converter (2000) is rotatable in a first rotational direction around the tertiary converter pin (2003).

21. The reusable auto injector according to claim 20, wherein the converter (2000) comprises the quaternary converter pin (2004) and the cassette activation part (1500b) comprises a quaternary converter pin receiving channel (1534) in which the quaternary converter pin (2004) is movable, wherein rotation of the converter (2000) around the tertiary converter pin (2003) in the first rotational direction moves the quaternary converter pin (2004) proximally, whereby the cassette activation part (1500b) is moved proximally along the longitudinal direction.

22. The reusable auto injector according to any preceding claim further comprising a user button (2020, 2020c).

23. The reusable auto injector according to claim 22 depending on any of the claims 19-21 , wherein the converter (2000) comprises the primary converter pin (2001 ) and the secondary converter pin (2002), and wherein the user button (2020) comprises a primary converter pin receiving opening (2031 ) in which the primary converter pin (2001 ) is positioned, and a secondary converter pin receiving opening (2032) in which the secondary converter pin (2002) is positioned.

24. The reusable auto injector according to claim 23, wherein the user button (2020) is configured for rotating in the first rotational direction whereby the converter (2000) rotates in the first rotational direction.

25. The reusable auto injector according to claim 22 depending on any of the claims 19-21 , wherein the converter (2000) comprises the secondary converter pin (2002) and the user button (2020c) comprises a user button channel (2042) in which the secondary converter pin (2002) is configured to travel, wherein the user button (2020c) is configured for moving sideways whereby the converter (2000) rotates in the first rotational direction.

26. The reusable auto injector according to claim 16 or any of the claims 17-25 depending on claim 16, wherein the cassette activation part (1500b) comprises an activation part plate (1530) with an activation part plate thread (1532), and wherein the resetting sleeve (1200b, 1200d) comprises at least one resetting sleeve pin (1214) configured for traveling inside the activation part plate thread (1532), wherein during rotation of the resetting sleeve (1200d) in the first rotational direction (DR1 ) for resetting the auto injector, the at least one resetting sleeve pin (1214) travels inside the activation part plate thread (1532) thereby moving the cassette activation part (1500b) from an extended to a retracted position.

27. The reusable auto injector according to claim 26, wherein the resetting sleeve (1200d) is configured for rotating relative to the cassette receiver (1100b) in a second rotational direction (DR2) opposite the first rotational direction (DR1 ), wherein the at least one resetting sleeve pin (1214) is configured for traveling inside the activation part plate thread (1532) when rotating the resetting sleeve (1200d) in the second rotational direction (DR2), whereby the cassette activation part (1500b) is moved proximally to the extended position.

28. The reusable auto injector according to claim 27, wherein the resetting sleeve (1200d) comprises a first blocking pin (1215) and/or a second blocking pin (1216), wherein first blocking pin (1215) is configured for stopping the rotation of the resetting sleeve (1200d) in the second rotational direction (DR2) when abutting the activation part plate (1530) thereby limiting the rotation of the resetting sleeve (1200d) in the second rotational direction (DR2) to a predefined angle, and wherein the second blocking pin (1216) configured for stopping the rotation of the resetting sleeve (1200d) in the first rotational direction (DR1 ) when abutting the activation part plate (1530) thereby limiting the rotation of the resetting sleeve (1200d) in the first rotational direction (DR1 ) to a predefined angle.

29. The reusable auto injector according to any preceding claim, wherein the auto injector comprises an injector skin sensor detector (1700, 1700a, 1700b) configured for moving proximally into the cassette (100) and for moving distally again by a user pressing the cassette (100) against an injection site.

30. The reusable auto injector according to claim 29 depending on claim 19 or any of the claims 20-28 depending on claim 19, wherein the injector skin sensor detector (1700b) comprises a converter blocking surface (1718), and wherein the converter (2000) comprises a skin sensor detector pin interaction surface (2018), wherein the injector skin sensor detector (1700b) is configured for being moved from an initial extended position to a distal position, wherein when in the initial extended position, the converter blocking surface (1718) abuts the skin sensor detector pin interaction surface (2018) thereby preventing rotation of the converter (2000), and wherein when in the distal position, the converter blocking surface (1718) no longer abuts the skin sensor detector pin interaction surface (2018) thereby allowing rotation of the converter (2000).

31. The reusable auto injector according to claim 29, wherein the plunger rod (1020, 1020a, 1020b) and the drive spring (1040), being in a compressed state, are configured for being unlocked when the injector skin sensor detector (1700, 1700a, 1700b) is moved in the distal direction, thereby allowing the compressed drive spring (1040) to push the plunger rod (1020, 1020a, 1020b) in the proximal direction for medicament delivery as the drive spring (1040) expands.

32. The reusable auto injector (1000) according to claim 29 or 31 , wherein the plunger rod (1020) comprises at least one plunger rod tab (1027) located on an outside surface (1031 ) of the plunger rod (1020), and wherein the auto injector (1000) comprises a plunger rod support part (1300) comprising a plunger rod release tab (1310), wherein the plunger rod release tab (1310) abuts the at least one plunger rod tab (1027) when the auto injector (1000) is in an initial position ready for receiving the cassette (100), and wherein the injector skin sensor detector (1700) comprises a distal release end surface (1709) configured for pushing the plunger rod release tab (1310) radially outwardly when the user is pressing the cassette (100) against an injection site, whereby the plunger rod release tab (1310) no longer abuts the at least one plunger rod tab (1027) thereby allowing the drive spring (1040) to move the plunger rod (1020) proximally for medicament delivery.

33. The reusable auto injector (1000) according to any of the claims 18-32, wherein the auto injector (1000) comprises a cassette detector (1800) with a release surface (1806), wherein the auto injector (1000) comprises a plunger rod support part (1300) comprising a proximal flexible part (1312) with a proximal protruding part (1311 ), and wherein the cassette activation part (1500) comprises a support part lock tab (1511 ) abutting the proximal protruding part (131 1 ) prior to inserting a cassette (100) in the auto injector (1000), wherein when the release surface (1806) is pushed against the proximal protruding part (131 1 ), the proximal flexible part (1312) flexes radially, thereby releasing the cassette activation part (1500), thereby enabling locking of the cassette (100) in the auto injector (1000) by proximal movement of the cassette activation part (1500).

34. The reusable auto injector (1000) according to any of the claims 18-33, wherein the cassette activation part (1500) further comprises a distal end protrusion (1510), wherein the plunger rod support part (1300) comprises a cassette activation part stop protrusion (1307), wherein the plunger rod (1020) comprises a longitudinally extending bar (1033), wherein the cassette activation part stop protrusion (1307) prevents distal movement of the cassette activation part (1500) after positioning a cassette (100) in the auto injector (1000) by the distal end protrusion (1510) being positioned between the cassette activation part stop protrusion (1307) and the longitudinally extending bar (1033).

35. The reusable auto injector (1000a) according to any of the claims 16-31 , wherein the cassette activation part (1500a) comprises one or more plunger rod lock elements (1518), and the plunger rod (1020a) comprises a cassette activation lock element (1038), and wherein prior to a cassette (100) being received in the auto injector, the cassette activation lock element (1038) is secured by the one or more plunger rod lock elements (1518) preventing relative longitudinal movement of the cassette activation part (1500a) and the plunger rod (1020a).

36. The reusable auto injector (1000a) according to any of the claims 16-31 and 35, wherein the reusable auto injector (1000a) comprises an unlock sledge element (1750) configured for moving between:

• a proximal position (USP), wherein longitudinal movement of the cassette activation part (1500a) is prevented; and

• a distal position (USD), wherein longitudinal movement of the cassette activation part (1500a) into the cassette (100) is permitted.

37. The reusable auto injector (1000a) according to claim 36 depending on claim 35, wherein the unlock sledge element (1750) comprises an unlock sledge release tab (1758), wherein distal movement of the unlock sledge element (1750) relative to the cassette activation part (1500a) moves the unlock sledge release tab (1758) towards the one or more plunger rod lock elements (1518) whereby the cassette activation lock element (1038) is released from the one or more plunger rod lock elements (1518) thereby allowing relative longitudinal movement of the cassette activation part (1500a) and the plunger rod (1020a).

38. The reusable auto injector according to any preceding claim, wherein the plunger rod (1020, 1020a, 1020b) comprises at least a first plunger rod opening (1036A), and wherein the auto injector comprises a plunger rod release element (1350) with a plunger rod release hook (1356) secured in the first plunger rod opening (1036A) thereby preventing proximal movement of the plunger rod (1020a) when the auto injector is in an initial position ready for receiving the cassette (100).

39. The reusable auto injector according to claim 38, wherein the plunger rod release element (1350) comprises:

• a push protrusion (1358) abutting a sloping surface (1720) on the injector skin sensor detector (1700, 1700a, 1700b); wherein distal movement of the injector skin sensor detector (1700, 1700a, 1700b) relative to the plunger rod release element (1350) pushes the plunger rod release hook (1356) radially outwardly by relative movement of the sloping surface (1720) against the push protrusion (1358) whereby the plunger rod release hook (1356) is released from the first plunger rod opening (1036A) releasing the plunger rod (1020a) for proximal movement.

40. The reusable auto injector according to any preceding claim, wherein the reusable auto injector further comprises a rotational damper (1900) comprising: