US20100069846A1 - Injection device - Google Patents

Abstract

An injection device comprising an outer housing inside which is located a medicament-holding barrel with a needle at one end thereof, at least part of the needle being moveable in and out of the outer housing, a plunger moveable within the barrel, an inner housing intermediate the outer housing and the barrel and plunger and an energy source in communication with said inner housing. The inner housing is moveable by the energy source between a first position in which the plunger and barrel are movable axially so as to move at least part of said needle out of the outer housing; a second position in which the plunger is movable axially into said barrel so as to expel medicament through the needle; and a third position in which the plunger and barrel are able to retract in order to retract the needle into the outer housing.

Description

CROSS REFERENCE TO RELATED APPLICATION
• This application is a continuation of U.S. patent application Ser. No. 10/597,379, filed Jul. 21, 2006, which is a national stage application under 35 U.S.C. 371 of PCT Application No. PCT/GB2005/000223 having an international filing date of Jan. 24, 2005, which designated the United States, which PCT application claimed the benefit of United Kingdom Application Serial No. 0401469.2, filed Jan. 23, 2004; Canada Application Serial No. 2,455,937, filed Jan. 27, 2004; and U.S. patent application Ser. No. 10/767,860, filed Jan. 28, 2004, the entire disclosures of which are hereby incorporated herein by reference.
• This invention relates to the field of injection devices for the administration of liquid medication, for example, insulin or growth hormone.
• One type of injection device is known as a mini-needle or micro-needle device. These devices comprise a pressurised (“forced”) injection system and have a needle which is shorter than that of conventional needle systems. The needle is normally hidden which is advantageous both for avoiding needle stick injuries and for minimising trauma to needle-phobic patients. The needle is hidden both before and after the injection is delivered, appearing only for the duration of the injection. Mini needle devices can typically deliver a larger volume of medication than needle-free devices and can deliver faster than conventional needle systems.
• One such known device is described in WO00/09186 (Medi-Ject Corporation) for “Needle assisted jet injector” and this document gives a useful summary of prior art devices.
• The device of WO 00/09186 includes a needle which is, in one embodiment, retractably located within an injector nozzle assembly. Upon activation of a force generating source, a portion of the needle extends past the nozzle assembly and penetrates the outer layer of skin to deliver medicament via jet injection to a deeper region. After activation, the needle retracts back into the nozzle assembly. The retractable needle is housed within the nozzle and is pushed forward so that it emerges in order to deliver an injection by the liquid medicament itself, when the medicament is itself pushed forward by the plunger.
• Although the present invention may relate to mini-needle or jet injection devices, the invention is equally applicable to other types of injection device, for example those for deep-penetrating muscular injection as well as those which are for shallower, subcutaneous, injection.
• According to a first aspect of the present invention there is provided an injection device comprising an outer housing inside which is located
• • a barrel for holding a volume of a medicament;
  • a needle at one end of the barrel, the needle and barrel being such that at least part of the needle is axially moveable in and out of said outer housing but is biased to be normally wholly inside said housing;
  • a plunger, axially moveable within the barrel;
  • an inner housing intermediate the outer housing and the barrel and plunger; and
  • an energy source in communication with said inner housing,
    wherein the inner housing is moveable by the energy source between three positions, namely
  • a first position in which the inner housing is in communication with both the plunger and the barrel such that, in use, the plunger and barrel are movable axially so as to move at least part of said needle out of the outer housing;
  • a second position in which the inner housing is in communication with the plunger but not the barrel such that, in use, said plunger is movable axially into said barrel so as to expel medicament through the needle; and
  • a third position in which the inner housing is in communication with neither the plunger nor the barrel such that, in use, the plunger and barrel are able to retract in order to retract the needle into the outer housing.
• The injection device according to the present invention provides a simple and cost-effective means of delivering medicament through a retractable needle. If desired, the device is able to deliver medicament to a depth beyond the length of the needle because of the propulsive force provided by the energy source. As mentioned above, the injection device is equally suitable for needle-assisted jet injection (delivering medicament to a depth beyond the length of the needle), conventional injection (to the depth of the needle penetration), or even to a user-adjustable needle penetration depth.
• The device requires that the needle (and hence also the barrel to which it is normally fixed) is moved axially so that the needle can appear beyond the end of the nozzle for the duration of the injection, after which the needle retracts automatically, out of sight of the user. The device also requires that the plunger is moved axially (into the barrel) so that medicament is ejected. The overall complexity of the injection device is significantly reduced by both of these requirements being effected by one component, namely the inner housing.
• Preferably, said inner housing includes one or more radially flexible tags, each preferably located at the end of a resiliently flexible leg.
• Preferably, one or more of said tags are situated at the rear end of the inner housing and are moveable radially into and out of communication with the plunger. In one embodiment, the tags are biased radially inwardly into communication with the plunger, preferably by communication with the outer housing. Alternatively, the tags are stored in their relaxed condition, before an injection is initiated.
• Each rear tag may be moveable out of communication with the plunger when aligned with a corresponding recess in the outer housing. Preferably, each rear tag is substantially T-shaped. One leg of the T-shape enables the rear tag to hook over the plunger and, effectively, pull the plunger forward (in the first and second positions mentioned above). The other leg of the T-shape enables the rear tag to move radially outwardly to catch in a recess in the housing (in the third position mentioned above).
• Preferably, one or more of said tags are situated at the forward end of the inner housing and are moveable radially into and out of communication with the barrel. In one embodiment, the forward tags are biased radially inwardly into communication with the barrel, preferably by communication with the outer housing. Alternatively, the forward tags are stored in their relaxed condition, before initiating an injection.
• Each forward tag may be moveable out of communication with the barrel when aligned with a corresponding recess in the outer housing. Preferably, each rear tag is substantially L-shaped.
• In a preferred embodiment, said energy source is a compressed gas. Alternatively, said energy source is a spring.
• Preferably, the injection device further includes means for allowing the inner housing to move axially only forward with respect to the outer housing. Ideally, said means is an arrangement of serrations, barbs, ratchet teeth or the like intermediate the housings.
• Preferably, the injection device further comprises guide means for guiding, in use, the relative axial movement of the inner and outer housings, the guide means preferably comprising one or more protrusions on said inner housing which, in use, cooperate with corresponding recesses on an interior surface of said outer housing.
• Preferably, said needle is biased to be normally wholly inside said housing by means of a spring intermediate the barrel and the outer housing.
• In one embodiment, the needle is removable from the device, this being of benefit in applications where the device is reusable (for example if a multiple-use cartridge of medicament is utilised).
• In a further embodiment, said needle, barrel and plunger are removable from said device. It is intended that the device of the present invention could be constructed around a standard needle, barrel and plunger of known type.
• Preferably, the injection device further includes a removable needle cover which protects the needle during storage and before use. Advantageously, said needle cover includes means for pulling a protective rubber sheath or the like from said needle when said needle cover is removed from the device. Said pulling means may include a floating rivet intermediate the needle cover and the protective rubber sheath or the like, whereby twisting forces applied to said needle cover are substantially prevented from being transmitted to said rubber sheath or the like.
• Preferably, the presence of said needle cover on said device serves as a safety lock, substantially preventing relative forward movement of said outer housing.
• In a preferred form, the injection device further comprises a viewing window in said barrel aligned with a viewing window in said outer housing such that said medicament can be viewed by a user prior to an injection taking place. Preferably, in use during an injection, said inner housing moves intermediate said viewing window in the outer housing and said barrel so as to obscure the window in the barrel from the user's view.
• Preferably, the injection device includes means for emitting an audible and/or physical indication to a user that the injection is complete.
• According to a second aspect of the invention there is provided an injection device comprising an outer housing inside which is located
• • a barrel for holding a volume of a medicament;
  • a needle at one end of the barrel, the needle and barrel being such that at least part of the needle is axially moveable in and out of said outer housing but is biased to be normally wholly inside said housing;
  • a plunger, axially moveable within the barrel;
  • an inner housing intermediate the outer housing and the barrel and plunger; and
  • an energy source in communication with said inner housing,
  • wherein the inner housing is moveable by the energy source between two positions, namely
  • a first position in which the inner housing is in communication with the plunger but not the barrel such that, in use, said plunger is movable axially into said barrel so as to expel medicament through the needle; and
  • a second position in which the inner housing is in communication with neither the plunger nor the barrel such that, in use, the plunger and barrel are able to retract in order to retract the needle into the outer housing.
• According to a third aspect of the invention there is provided an injection device comprising an outer housing adapted to receive:
• • a barrel for holding a volume of a medicament;
  • a needle at one end of the barrel, the needle and barrel being such that at least part of the needle is axially moveable in and out of said outer housing but is biased to be normally wholly inside said housing; and
  • a plunger, axially moveable within the barrel,
  • characterised in that the injection device further comprises:
• an inner housing intermediate the outer housing and the barrel and plunger; and
• • an energy source in communication with said inner housing,
  • wherein the inner housing is moveable by the energy source between three positions, namely
  • a first position in which the inner housing is in communication with both the plunger and the barrel such that, in use, the plunger and barrel are movable axially so as to move at least part of said needle out of the outer housing;
  • a second position in which the inner housing is in communication with the plunger but not the barrel such that, in use, said plunger is movable axially into said barrel so as to expel medicament through the needle; and
  • a third position in which the inner housing is in communication with neither the plunger nor the barrel such that, in use, the plunger and barrel are able to retract in order to retract the needle into the outer housing.
• Preferred embodiments of the present invention will now be more particularly described, by way of example only, with reference to the accompanying drawings wherein:
• FIG. 1 is a perspective view, partly in section, showing the injection device, in the condition in which it is supplied to a user, apart from the needle cover;
• FIG. 2, drawn to a larger scale, shows detail of part of the device shown inFIG. 1;
• FIG. 3 is a perspective view, partly in section, showing the injection device, during an injection;
• FIG. 4, drawn to a larger scale, shows detail of part of the device shown inFIG. 3;
• FIG. 5 is a perspective view, partly in section, showing the injection device, with the plunger fully depressed into the barrel;
• FIG. 6, drawn to a larger scale, shows detail of part of the device shown inFIG. 5;
• FIG. 7 is a perspective view, partly in section, showing the injection device, after use and safe to dispose of;
• FIG. 8, drawn to a larger scale, shows detail of part of the device shown inFIG. 7;
• FIG. 9 is a perspective view of the device, including the needle cover;
• FIG. 10 is perspective view, partly in section, showing detail of the needle cover;
• FIG. 11 is perspective view, partly in section, showing detail of the needle cover part way through being removed from the injection device;
• FIG. 12 is a schematic view showing the relationship betweentags7A andram4, in one embodiment of the invention;
• FIG. 13 is a perspective view of the inner housing (also referred to as the “plunger housing”);
• FIG. 14 is a side view of the inner housing ofFIG. 13;
• FIG. 15 is a perspective view, partly in section, showing an alternative embodiment of the injection device, in the condition in which it is supplied to a user;
• FIG. 16, drawn to a larger scale, shows detail of the rear end of the device shown inFIG. 15;
• FIG. 17 shows detail of the interaction between thespring housing41 and the rear of theouter housing30;
• FIG. 18 is a perspective view, partly in section, showing the injection device with the needle cover removed, immediately prior to initiating an injection;
• FIG. 19 is a perspective view, partly in section and drawn to a larger scale, showing the front part of the device immediately before initiating an injection;
• FIG. 20 is a perspective view, partly in section, showing the front part of the device at the start of an injection;
• FIG. 21 is a perspective view showing the device in the same condition asFIG. 20, i.e. at the start of an injection with the needle emerging from the end of the device and the plunger beginning to travel down the barrel;
• FIG. 22 is a perspective view, partly in section, showing the injection device with the plunger fully depressed into the barrel;
• FIG. 23 is a perspective view, partly in section, showing the injection device after use and with the needle retracted into the device;
• FIG. 24 is a perspective view of the assembled device, including the needle cover;
• FIG. 25 is a schematic view of part of the front end of the device, showing the helical protrusion on the nozzle.
• FIG. 26 is perspective view, partly in section, showing detail of the needle cover; and
• FIG. 27 is perspective view, partly in section, showing detail of the needle cover after removal from the device.
• Throughout the following description, reference to a “forward” direction means the direction which is towards the patient when the injection device is in use. The “forward” end of the injection device is the end nearest the patient's skin when the device is in use. Similarly, reference to a “rearward” direction means the direction which is away from the patient and the “rearward” end of the device is the end furthest from the patient's skin when the injection device is in use.
• FIG. 1 is a perspective view, partly in section, showing the injection device, in the condition in which it is supplied to a user, apart from the needle cover (which is described below after describing the main operation of the device).
• The principal components of the device will now be described with reference toFIGS. 1 and 2. Anenergy source1 is provided at the rear of the device which, in this embodiment, is a gas cylinder similar to the type used in a conventional aerosol can or the like i.e. having a valve through which gas can be released at will and in a controlled manner. In an alternative embodiment of the invention, a spring is used as the energy source in place of a gas cylinder and this embodiment is described later with reference toFIG. 13 et seq.
• The valve2 of the gas cylinder opens into achamber3, which inFIG. 1 is of relatively small volume. The front wall of thechamber3 is defined by aram4 which has an annular seal5 at the rear thereof in order to make thechamber3 gas-tight. The rear wall of thechamber3 is defined by the back face of a generallycylindrical chamber housing6.
• The forward part of theram4 abuts or alternatively is integrally-formed with aninner housing7 which closely surrounds a plunger8 (and can therefore be referred to as the “plunger housing”). The rear of the plunger housing includes four orthogonally placedtags7A, which each have a “hammer head” or T-shape and whose tendency to spring radially outwardly is restricted by the diameter of thechamber housing6. If theram4 is integrally formed with theplunger housing7 as illustrated inFIGS. 13 and 14, thetags7A are positioned at the end of flexible legs cut into the housing, so that thetags7A can move radially, with respect to theram4 and remainder ofhousing7.
• The hammer head of eachtag7A hooks over theenlarged head8A of theplunger8, so that thetags7A are in contact with theplunger head8A, as shown best inFIG. 2.
• Theplunger8 is the plunger of a syringe arrangement comprising abarrel9 in which a predefined volume of liquid medicament is supplied and aneedle10 through which the medicament can be delivered to the patient. Anozzle11 at the front end of the injection device normally conceals theneedle10 from the user's view. Aspring12, positioned between the outer housing and thebarrel9 biases the needle to be normally wholly within thenozzle11.
• At the front end of theplunger housing7, there are further orthogonally placedtags7B, which each have a generally L shape and whose tendency to spring radially outwardly is restricted by the diameter of thechamber housing6. Thetags7B each abut the flange at the rear ofbarrel9.
• Other means of interaction between the inner housing and the plunger may be envisaged, instead oftags7A, for example tags that are not T-shaped, or means that push the plunger rather than pulling as in the described embodiment.
• There are four main stages in the operation of the device.Stage1 is the condition shown inFIGS. 1 and 2, i.e. the device as supplied to a user, and as described above. The medicament is already present in thebarrel9 and theneedle10 is concealed from view within thenozzle11. Theplunger8 is fully withdrawn from the barrel9 (because of the liquid medicament contained within the barrel) and the head of theplunger8A abuts thetags7A. The rear of the remainder ofhousing7 abuts theram4. Thechamber3 is of minimal volume.
• Stage2 of operation is the injection stage illustrated inFIGS. 3 and 4. With the injection device held against the patient's skin at the injection site, downward force is applied to the device in the direction indicated by the arrow F inFIG. 2. This force causes the valve of thegas cylinder1 to open, releasing gas into thechamber3. As thechamber3 fills with gas, theram4 is urged forward, consequently urgingtags7A against theplunger8. As thetags7A, and hence theplunger housing7, are urged forward, the cooperation of thetags7B against thebarrel9 means that the barrel is also urged forward, against the bias of a spring12 (shown inFIG. 3). As thebarrel9 moves forward, so does theneedle10 which is attached thereto and so the needle protrudes out of thenozzle11 sufficiently to enable an injection to be delivered. Therefore, initially, theram4 causes theplunger housing7, theplunger8, thebarrel9 and theneedle10 to move forwards.
• Shortly after theplunger housing7 starts to move forward, thetags7B reach a lip in thechamber housing6. Thetags7B spring radially outwardly over this lip, as shown inFIGS. 3 and 4. Once thetags7B have sprung outwardly in this way, they are no longer in abutment with thebarrel9. This means that the barrel9 (and hence needle10) is no longer urged forwards because the forwardly-movingplunger housing7, includingtags7B, are free to continue moving forward without contacting thebarrel9.
• Therefore, once the device has reached the condition illustrated inFIGS. 3 and 4, continued forward movement of theram4 andplunger housing7 causes theplunger8 to be urged forward into thebarrel9. This expels the liquid medicament from thebarrel9, through theneedle10 to deliver an injection. It is the cooperation of thetags7A with theenlarged head8A of the plunger which transmits the forward force from theram4/housing7 to theplunger8.
• The third stage in the operation of the device is illustrated inFIGS. 5 and 6. When theplunger8 is depressed into thebarrel9, the desired dose of medicament is delivered into the patient. At this point, thetags7A reach recesses13 cut into theplunger housing6 whereupon they are able to spring radially outwardly into those recesses (as illustrated inFIGS. 5 and 6). An audible click may be emitted which indicates to the user that the injection is complete. In addition, the user may “feel” that the injection is complete as a result of thetags7A locating inrecesses13.
• The outward movement of thetags7A means that the “hammer head” shape is no longer in contact with theenlarged head8A of theplunger8 and therefore theplunger8 is no longer driven forward by theram4 andtags7A. Theplunger housing7 may continue further forward until an end stop is reached.
• The final stage in the operation of the device is illustrated inFIGS. 7 and 8. With thetags7A located withinrecesses13, neither theplunger8 nor the barrel is impeded by any part of theplunger housing7. Therefore thespring12, which had been compressed by the forward motion of thebarrel9, urges thebarrel9 and hence theplunger8 backwards until theram4 prevents further backward movement thereof. The backward movement is sufficient to cause theneedle10 to retract into thenozzle11 so that it is no longer visible to the user and safe from the risk of causing a needle-stick injury. The used injection device can then be safely disposed of.
• Blow-back is prevented by the provision ofserrations14 which guide the relative movement of the chamber housing and the outermost housing. These serrations only permit relative movement in one direction, i.e. thechamber housing6 moving forward with respect to the outermost housing.
• FIG. 9 is a perspective view of the injection device which, in this Figure, includes aneedle cover15. The needle cover is shown in further detail inFIGS. 10 and 11 and is used to protect the needle end of the injection device during transit, storage and before use to deliver an injection. Theneedle cover15 has the further advantage of preventing accidental or unintended activation of the device, as it is not possible to fire the device with theneedle cover15 in place.
• Regulations require that the needle (which is in direct communication with the medicament in the barrel) is sealed from the outside environment before use. This is achieved by providing protection in the form of arubber moulding16 which covers the end of the needle, therubber moulding16 being surrounded by anylon sheath17. The rubber moulding and nylon sheath (the “needle protection”) are fixed with respect to one another by a friction fit between one ormore protrusions16A on the rubber moulding and a corresponding one ormore recesses17A in the nylon sheath.
• The configuration of the needle protection depends upon the type of needle/barrel/plunger (“syringe assembly”) employed in the injection device. It is envisaged that the injection device of the present invention could be assembled around a standard syringe assembly of known type (the selection thereof depending upon the required dose range, the type of medicament to be administered etc, for example). Different syringe assemblies may be supplied with slightly differing needle protection.
• The nylon sheath and rubber moulding are firmly fixed on theneedle10 and it is difficult, if not impossible, for a patient to pull them from the needle using his/her fingers alone because of their position inside thenozzle11. Therefore anouter needle cover15 is provided which not only improves the aesthetic appearance of the injection device, before use, but also serves the function of facilitating the removal of the nylon sheath and rubber moulding.
• Theneedle cover15 is releasably retained on the front end of the injection device by the fit ofannular protrusions18 on part of the device housing withgrooves19 on the interior of the needle cover. Theprotrusions18 andcorresponding grooves19 preferably extend around two equally opposed 60° portions of the circumference of thenozzle11.
• Thegrooves19 are located on one or more (preferably equally spaced)flexible legs20 which are flexible compared to the rest of theneedle cover15, about point P shown inFIG. 9. Forward of eachgroove19 is provided an inwardly projectingtab21 on eachflexible leg20. Eachtab21 abuts the rear of thenylon sheath17.
• Turning now toFIG. 11, when it is desired to remove theneedle cover15 from the device, the user grips the needle cover, preferably in a region having texture or other grip-improvingmeans22, and pulls in the direction indicated by the arrow inFIG. 11. The flexibility of thelegs20 permits the needle cover to ride over theprotrusions18, disengaging them from thegrooves19. The flexibility of thelegs20 is minimal enough not to cause thetabs21 to become disengaged from the rear of thenylon sheath17.
• Therefore, as theneedle cover15 is pulled in the direction indicated by the arrow, thetabs21 are urged against the rear of thenylon sheath17 and sufficient force can be applied thereby to disengage theneedle10 from therubber moulding16. In this way, theentire moulding16,nylon sheath17 and needle cover15 can be removed from the injection device and discarded, so that the injection device is then ready to use.
• Other types ofneedle cover15 may be envisaged, suited to the particular type of syringe assembly used in the device, for example that described below with reference toFIG. 25 et seq.
• FIGS. 13 and 14 show more detail of an embodiment of theinner housing7 in which theram4 is integral with thehousing7.
• The inner housing is injection moulded as a single piece having four orthogonally placed tags at each end thereof. Eachtag7A,7B is at the end of a resiliently flexible leg, cut out of the material of thehousing7, so that each leg (and its respective tag) is able to flex radially with respect to the remainder of thehousing7.
• The rear part of theinner housing7 constitutes the equivalent of theram4 described above. The ram is provided with an annular groove orrecess4A, into which theball bearings42 locate.
• Theinner housing7 may also be provided with one or more guide means which, in the illustrated embodiment, take the form ofelongate protrusions7C. Theseprotrusions7C cooperate with corresponding recesses on the interior surface of theouter housing30 so that, in use, relative axial movement of the inner and outer housings is guided.
• A spring-powered embodiment of the injection device is described below with reference toFIG. 15 et seq.
• In this embodiment, there is a generally cylindricalouter housing30 extending all the way from the rear of the device to theneedle cover15. Thegas cylinder1 and valve2 are replaced by a spring-powered energy source. Referring particularly toFIG. 16, aspring40 is provided under compression at the rear of the device, intermediate the rear of aspring housing41 and theram4. Thespring40 is retained in its compressed condition by means of one ormore ball bearings42 sitting inannular recess4A on theram4, theball bearings42 being wedged against theouter housing30 and located in apertures41C at the front of thespring housing41. Thespring housing41 interacts with the back of theouter housing30 by means of an arrangement illustrated inFIG. 17.
• Thespring housing41 is provided withelongate slots41B and generally circular apertures41C. The corresponding part of the outer housing is provided withelongate protrusions30B on the interior surface thereof, which fit into theslots41B as illustrated inFIG. 17. The ball bearings42 (not shown inFIG. 17) fit through the circular apertures41C.
• InFIG. 15 it can be seen that the front end of theouter housing30 is in close relation, or abutting, theneedle cover15. This substantially prevents any forward movement of theouter housing30 in relation to thespring housing41 and other components.
• InFIG. 18, the needle cover has been removed and it is now possible to place the device against the user's leg (or other injection site) ready to initiate an injection.FIG. 19 shows the front part of the device at this stage, in more detail.
• Referring now toFIGS. 19 and 20, the front part of the device is shown in more detail. At the front of theouter housing30, there are provided twoannular grooves30A and30A′ on the interior surface thereof. Aspacer part50 is fixed with respect to thenozzle11 and other components internal of theouter housing30. Thespacer part50 is provided with an exteriorannular protrusion51 which initially locates in theforwardmost groove30A.
• The leading edge offorwardmost groove30A is generally blunt so that location ofprotrusion51 therein (as illustrated inFIG. 19) inhibits the user from pulling theouter housing30 rearwardly off thespring housing41 et al, which might dangerously expose the internal components of the device. It is difficult for a user to apply sufficient rearward force to cause theprotrusion51 to ride over the blunt leading edge.
• The trailing edge of theforwardmost groove30A and both edges of thegroove30A′ are curved or tapered.
• To initiate an injection, the user grasps theouter housing30 and effects forward movement of theouter housing30 in relation to thespring housing41. As shown inFIG. 20, the forward movement causes theprotrusion51 to disengage from theforwardmost groove30A and, as theouter housing30 moves forward with respect to thespacer50, theprotrusion51 engages in therearmost groove30A′.
• Referring now toFIGS. 18 and 21, the relationship between theram4,ball bearings42 andspring housing41 is described in more detail. In the first position, shown inFIG. 18, theball bearings42 sit in theannular groove4A in theram4 and are wedged in place in the apertures41C at the front of thespring housing41.
• FIG. 21 shows the device in the same condition as inFIG. 20 i.e. wherein forward movement of the outer housing in relation to the spring housing has caused theprotrusion51 to be engaged in therearmost groove30A′.
• In this position, thespring housing41 has moved closer to the rear of theouter housing30. This relative axial movement is sufficient to cause the apertures41C to retreat back past an undercutarea30A″ inside theouter housing30. Theball bearings42 are now free to move radially out of the apertures41C and into said undercutarea30A″, out of engagement with theram4. Theram4 is now free to travel forwards in the direction indicated by the arrow inFIG. 21, under the power of thespring40.
• The forward-movingram4 causes theinner housing7 to deliver the injection as previously described. This is illustrated inFIG. 21 (Stage2 as previously described) andFIG. 22 (Stage3 as previously described).
• FIG. 23 shows the position in which the injection has been fully delivered and the needle caused to retract back inside the nozzle (final stage as previously described).
• In an alternative embodiment (not illustrated), theball bearings42 are replaced by a living joint, moveable into undercutarea30A″ and out of engagement with theram4.
• In another embodiment (not illustrated), theprotrusion51 andgrooves30A,30A′ are replaced or supplemented by a ratchet arrangement described hereafter. A spring housing is provided which has a substantially square cross-section. A portion of the inside of theouter housing30 is correspondingly shaped with a square cross-section so that the spring housing and outer housing closely fit together but relative axial movement between them is possible. Relative rotational movement between them is substantially prevented by the square cross-section. At least one surface of the square cross-section spring housing is provided with a plurality of barbs, protrusions, ratchet teeth or the like which cooperate with an inwardly-depending protrusion or tag on the inside of the outer housing.
• The ratchet arrangement performs the same function asprotrusion51 andgrooves30A,30A′ i.e. to control forward movement of theouter housing30 in relation to thespring housing41. The ratchet arrangement may provide further advantages, for example:
• • Improved strength;
  • Rotational alignment between spring housing and outer housing;
  • Improved resistance to rearward force generated by the user pushing the device hard into the injection site;
  • Improved resistance to the user pulling the outer housing rearwardly off the device, the ratchet teeth permitting forward movement of the outer housing only;
  • Improved defining of the relative axial position of the outer housing and internal components of the device.
• Alternative embodiments are envisaged in which, instead of a square cross-section, the spring housing has at least one flat surface on which the barbs, protrusions, ratchet teeth or the like are disposed; the remainder of the spring housing may be of any cross-sectional shape so long as the inside of the outer housing is correspondingly shaped.
• Other modifications to the injection device are illustrated inFIG. 13 et seq which are equally applicable to the gas-powered embodiment described earlier.
• Thebarrel9 may be provided with a transparent window9awhich, in use, is aligned with awindow32 in the outer housing (seeFIG. 24) so that the liquid medicament is visible. During the injection (i.e. during firing of the injection device), theplunger housing7 becomes visible as it moves forwardly intermediate thebarrel9 and outer housing. As theplunger housing7 moves forwardly, it progressively obscures the window9athus giving a visual indication to the user of the progress of the injection. The window9amay be completely obscured by theplunger housing7 when the injection is complete. Theplunger housing7 may be brightly coloured e.g. red to increase its visibility through thewindow30.
• It is observed that plastics of the type which may be used to form theplunger housing7 will, over time, tend to gain a memory of the position in which they are stored. It is essential for operation of the device that thetags7A spring properly into and out of engagement with theenlarged head8A of the plunger. Therefore, as visible inFIG. 18, atapered surface31 is provided on the interior of theouter housing30. This enables thetags7A to be stored in their “relaxed” position, i.e. sprung radially-outwardly to abut theouter housing30, as illustrated inFIG. 18.
• When an injection is initiated as shown inFIG. 21, the forward movement of theouter housing30 in relation to theplunger housing7 causes thetags7A to ride up the taperedsurface31 and into engagement with theenlarged head8A of the plunger.
• When theplunger housing7 has moved forward sufficiently fortags7A to reachrecesses13, thetags7A will have an increased tendency to spring outwardly into the position in which they had been previously stored, ensuring efficient operation of the device.
• FIGS. 26 and 27 show an alternative embodiment of theneedle cover15. Like parts are given the same reference numerals as inFIG. 11. In theFIG. 26 embodiment, theneedle cover15 is releasably retained on the front end of the injection device by the fit ofprotrusions11A on the exterior of thenozzle11 with corresponding recesses on the interior of theneedle cover15.
• Theprotrusions11A may take the form of a single helical protrusion as illustrated inFIG. 25, or alternatively several discrete protrusions may be used.
• At the front end of theneedle cover15 is a floatingrivet35 which has rearwardly directedbarbed fingers36 which pass through an aperture in the front end of thesheath17.
• Theprotrusions11A thebarbed fingers36 and the interaction of the nozzle with theneedle cover15 atsurface15A mean that thenozzle11 and associated components are prevented from moving axially with respect to thehousing30 in the situation illustrated inFIG. 26. This means that the device cannot be inadvertently fired whilst theneedle cover15 is still in place.
• When it is desired to remove theneedle cover15 from the device, the user grips the needle cover and pulls in the direction indicated by the arrow inFIG. 26, using a twisting motion to cause the needle cover to ride along the nozzle guided by thehelical protrusion11A.
• The floatingrivet35 allows theneedle cover15 to be twisted in order for it to move alonghelical protrusion11A, but thesheath17 does not twist and is simply pulling axially off the needle. This means there is no risk of damage to theneedle10 caused by twisting forces.
• As theneedle cover15 is pulled in the direction indicated by the arrow, thebarbed fingers36 pull thesheath17 with sufficient force to disengage theneedle10 from therubber moulding16. In this way, theentire moulding16,nylon sheath17 and needle cover15 can be removed from the injection device and discarded, so that the injection device is then ready to use. Removal of theneedle cover15 has the second function of allowing the nozzle etc to be free to move axially with respect to thehousing30, which enables the device to be fired as described above.
• When the end of theprotrusion11A is reached, theneedle cover15 is disengaged from thenozzle11 as illustrated inFIG. 27.
• A further embodiment of the present invention is envisaged wherein the needle is exposed upon removal of theneedle cover15. Such an embodiment may be suitable for users where needle-phobia is not a concern and where the complexity (and hence cost) of the device can be reduced by eliminating the need for the first stage (i.e. the forward movement of the needle out of the nozzle11). Theoptional needle cover15 may be omitted from such an embodiment. As mentioned above, it is possible that the injection device of the present invention may be supplied separately from and then assembled around a standard syringe assembly (needle/barrel/plunger) of known type.
• In a further development, it is envisaged that it would be readily possible to adapt the device of the present invention to be operable with a standard cartridge or vial of medicament (containing a volume of medicament from which several doses of user-defined volume can be provided) instead of a syringe assembly. In such case the needle could be removable and replaceable so that the device could be reused until the medicament cartridge is empty.

Claims (20)

1. An injection device comprising an outer housing inside which is located

a barrel for holding a volume of a medicament;

a needle at one end of the barrel, the needle and barrel being such that at least part of the needle is axially moveable in and out of said outer housing but is biased to be normally wholly inside said housing;

a plunger, axially moveable within the barrel;

an inner housing intermediate the outer housing and the barrel and plunger; and

an energy source in communication with said inner housing,

Characterized in that the inner housing is moveable by the energy source between three positions, namely

a first position in which the inner housing has one or more readially flexible tags which are in communication with the barrel such that, in use, the plunger and the barrel are movable axially so as to move at least part of said needle out of the outer housing;

a second position in which the inner housing has one or more radially flexible tags which are in communication with the plunger but not the barrel such that, in use, said plunger is movable axially into said barrel so as to expel medicament through the needle; and

a third position in which said one or more radially flexible tags on the inner housing are in communication with neither the plunger nor the barrel such that, in use, the plunger and barrel are able to retract in order to retract the needle into the outer housing.

2. An injection device as claimed inclaim 1 further comprising a spring housing intermediate the outer housing and the inner housing.

3. An injection device as claimed inclaim 1 wherein one or more of said tags is located at the end of a resiliently flexible leg.

4. An injection device as claimed inclaim 1, wherein one or more of said tags are situated at the rear end of the inner housing and are moveable radially into and out of communication with the plunger.

5. An injection device as claimed inclaim 2, wherein said tags are biased radially inwardly into communication with said plunger, preferably by communication with said spring housing.

6. An injection device as claimed inclaim 1, wherein said tags are stored in their relaxed condition, before initiating an injection.

7. An injection device as claimed inclaim 2, wherein each rear tag is moveable out of communication with the plunger when aligned with a corresponding recess in the spring housing.

8. An injection device as claimed inclaim 1, wherein each rear tag is substantially T-shaped.

9. An injection device as claimed inclaim 1, wherein one or more of said tags are situated at the forward end of the inner housing and are moveable radially into and out of communication with the barrel, wherein said forward tags are biased radially inwardly into communication with said barrel, preferably by communication with said spring housing, wherein said forward tags are stored in their relaxed condition, before initiating an injection, wherein each forward tag is moveable out of communication with the barrel when aligned with a corresponding recess in the outer housing, and wherein each forward tag is substantially L-shaped.

10. An injection device as claimed inclaim 1, further including means for allowing the inner housing to move axially only forward with respect to the outer housing, wherein said means is an arrangement of serrations, barbs, ratchet teeth or the like intermediate the housings.

11. An injection device as claimed inclaim 1, further comprising guide means for guiding, in use, the relative axial movement of the spring and outer housings, the guide means preferably comprising one or more protrusions on said spring housing which, in use, cooperate with corresponding recesses on an interior surface of said outer housing.

12. An injection device as claimed inclaim 1, wherein said needle is biased to be normally wholly inside said housing by means of a spring intermediate the barrel and the outer and/or spring housing.

13. An injection device as claimed inclaim 1, further including a removable needle cover which protects the needle during storage before use, wherein said needle cover includes means for pulling a protective rubber sheath or the like from said needle when said needle cover is removed from the device, and wherein said pulling means includes a floating rivet intermediate the needle cover and the protective rubber sheath or the like, whereby twisting forces applied to said needle cover are substantially prevented from being transmitted to said rubber sheath or the like.

14. An injection device as claimed inclaim 13, wherein the presence of said needle cover on said device serves as a safety lock, substantially preventing relative forward movement of said outer housing.

15. An injection device as claimed inclaim 1, further comprising a viewing window in said barrel aligned with a viewing window in said outer housing such that said medicament can be viewed by a user prior to an injection taking place.

16. An injection device as claimed inclaim 15 wherein, in use during an injection, said inner housing moves intermediate said viewing window in the outer housing and said barrel so as to obscure the window in the barrel from the user's view.

17. An injection device as claimed inclaim 1, further comprising means for emitting an audible and/or physical indication to a user that the injection is complete.

18. An injection device comprising an outer housing inside which is located

a barrel for holding a volume of a medicament;

a needle at one end of the barrel, the needle and barrel being such that at least part of the needle is axially moveable in and out of said outer housing but is biased to be normally wholly inside said housing;

a plunger, axially moveable within the barrel;

an inner housing intermediate the outer housing and the barrel and plunger; and

an energy source in communication with said inner housing,

characterized in that the inner housing is moveable by the energy source between two positions, namely

a first position in which the inner housing has one or more radially flexible tags which are in communication with the plunger but not the barrel such that, in use, said plunger is movable axially into said barrel so as to expel medicament through the needle; and

a second position in which said one or more radially flexible tags on the inner housing are in communication with neither the plunger nor the barrel such that, in use, the plunger and barrel are able to retract in order to retract the needle into the outer housing.

19. An injection device comprising an outer housing adapted to receive:

a barrel for holding a volume of a medicament;

a needle at one end of the barrel, the needle and barrel being such that at least part of the needle is axially moveable in and out of said outer housing but is biased to be normally wholly inside said housing; and

a plunger, axially moveable within the barrel,

wherein the injection device further comprises:

an inner housing intermediate the outer housing and the barrel and plunger; and

an energy source in communication with said inner housing,

characterized in that the inner housing is moveable by the energy source between three positions, namely

a first position in which the inner housing has one or more radially flexible tags in communication the barrel such that, in use, the plunger and barrel are movable axially so as to move at least part of said needle out of the outer housing;

a second position in which the inner housing has one or more radially flexible tags in communication with the plunger but not the barrel such that, in use, said plunger is movable axially into said barrel so as to expel medicament through the needle; and

a third position in which the said radially flexible tags on the inner housing are in communication with neither the plunger nor the barrel such that, in use, the plunger and barrel are able to retract in order to retract the needle into the outer housing.

20. An injection device as claimed inclaim 19 further comprising a spring housing intermediate the outer housing and the spring housing.

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