US20050131342A1 - Needleless hypodermic injection system, application device and medication cartridge therefor - Google Patents

Abstract

A needleless hypodermic injection system for injecting a liquid medication, which system comprises a disposable cartridge which contains a medication and which comprises a propellant and an igniter, and a reusable application device which comprises a pressure chamber for receiving the medication cartridge, actuation means including an ignition system and means for ensuring reliability and safety of the system. The reusable application device comprises: (a) a housing including a fist housing section and a second housing section which are adapted to be assembled together by a screwing operation, the first housing section comprising a front part having an injection outlet and a chamber adapted to receive a the cartridge contains the medication to be injected and also contains a propellant and an igniter, and (b) means for selectively activating said igniter of said cartridge when predetermined conditions are fulfilled.

Description

PRIORITY TO RELATED APPLICATIONS
• This application is a Continuation of Ser. No. 10/101,400, filed Mar. 19, 2002 which is pending. This application claims the benefit of U.S. Provisional Application Ser. No. 60/278,042, filed Mar. 22, 2001.
FIELD OF THE INVENTION
• The invention concerns a needleless hypodermic injection system for injecting a liquid medication.
• The invention also concerns a reusable application device which is a first part of such a system.
• The invention further concerns a disposable medication cartridge which is a second part of such a system.
BACKGROUND OF THE INVENTION
• Prior art systems and devices of the above mentioned kind have important disadvantages. They have a complex structure and are therefore not easy to assemble and to use, in particular for patients which have some handicaps or are not in full possession of their handling capabilities. Moreover they lack reliable means for preventing accidental release of injections and their negative consequences, e.g. loss of expensive medications and possible injures inflicted to the user.
• The main aim of the instant invention is therefore to provide a system an application device, and a medication cartridge of the above mentioned kind with which the above mentioned drawbacks can be eliminated or at least substantially reduced.
SUMMARY OF THE INVENTION
• According to a first aspect of the invention the above mentioned aim is attained with a needleless hypodermic injection system for injecting a liquid medication, which system comprises:
• • (a) a disposable cartridge which contains a medication and which includes a propellant and an igniter, and
  • (b) a reusable application device which comprises a pressure chamber for receiving said cartridge, and actuation means including an ignition system and means for ensuring reliability and safety of the system.
• According to a second aspect of the invention the above mentioned aim is attained with a reusable application device for a needleless hypodermic injection system for injecting a liquid medication contained in a cartridge inserted into said application device, said application device comprising
• • (a) a housing including a first section and a second section which are adapted to be connected with each other to form a housing assembly,
  • said first housing section comprising a chamber for receiving a cartridge containing a medication unit which contains a liquid medication,
  • said first housing section having a symmetry axis which extends along its length and a front part having an outer contact surface which is adapted to be applied on a skin surface, said contact surface having an opening through which liquid medication ejected from said cartridge can pass and be injected through said skin surface,
  • (b) ejection means for causing ejection of said liquid medication contained in said cartridge in order to perform an injection, a first part of said ejection means being contained in said cartridge and a second part of said ejection means being contained in said second housing section,
  • c) assembly detecting means which reach a first predetermined state when said first housing section is properly and completely assembled with said second housing section to form said housing assembly, said assembly detecting means being located within said housing assembly,
  • d) position detecting means which are located in part within said first housing section and in part in said second housing section, said position detecting means reaching a second predetermined state when the following conditions are simultaneously satisfied by the relative position of said housing assembly with respect to said skin surface,
  • d.2) said contact surface of said first section exerts a predetermined pressure on said skin surface, the distribution of said pressure over the area of said contact surface being substantially uniform, and
  • d.3) said symmetry axis of said first section is positioned substantially normal to said skin surface, and
  • e) actuator means for activating said ejection means, said actuator means being normally disabled and becoming operable only upon being enabled by a combination of predetermined effects provided by
  • said assembly detecting means after they reach said first predetermined state, and
  • said position detecting means when they reach said second predetermined state.
• According to a third aspect of the invention the above mentioned aim is attained with a reusable application device for a needleless hypodermic injection system for injecting a liquid medication contained in a cartridge inserted into said application device, said cartridge containing a propellant adapted to be ignited by application of electrical energy to two electrical contacts which are part of said cartridge, said application device comprising
• • a) a housing including a first section and a second section, each of these sections having a length axis and said first and second housing sections being adapted to be connected with each other to form a housing assembly, said housing assembly being so configured and dimensioned that it is adapted to be held by a user with one hand,
  • b) said first housing section comprising a chamber for receiving a cartridge containing a liquid medication, said first section having an outer contact surface which is adapted to be applied on a skin surface through which an injection is to be applied,
  • c) said second housing section containing electrical means for causing ignition of a propellant contained in a cartridge arranged in said chamber of said first housing section and actuator means for activating said electrical means, and
  • d) position detecting means for detecting whether said contact surface of said first section exerts a predetermined pressure on said skin surface and whether at the same time said length axis of said first section is positioned substantially normal to said skin surface, the distribution of said pressure over the area of said contact surface being substantially uniform, said means for detecting enabling said actuator means when the latter conditions are satisfied.
• According to a fourth aspect of the invention the above mentioned aim is attained with a reusable application device for a needleless hypodermic injection system for injecting a liquid medication, which application device comprises:
• • (a) a housing including a fist housing section and a second housing section which are adapted to be assembled together by a screwing operation,
  • said first housing section comprising a front part having an injection outlet and a chamber adapted to receive a cartridge containing a medication unit which contains the medication to be injected, a propellant, and an igniter, and
  • (b) means for selectively activating said igniter of said cartridge when predetermined conditions are fulfilled.
• According to a fifth aspect of the invention the above mentioned aim is attained with a medication cartridge for a needleless hypodermic injection system for injecting a liquid medication, said cartridge comprising a housing adapted to contain:
• • (a) a first chamber containing a medication unit configured and dimensioned to store a volume of liquid to be injected, said medication unit having a first region and a second region that are in liquid communication with each other, said first region being deformable and said second region having an injection outlet, and
  • (b) a second chamber containing a propellant,
  • said first chamber being divided by an elastic barrier in two zones, a first zone containing said medication unit and a second zone which is communication with said second chamber, so that upon ignition of the propellant in the second chamber gas generated thereby expands into said second zone of said first chamber, exerts pressure on and deforms said barrier which in turn transfers that pressure to and deforms said deformable first region of said medication unit and thereby causes ejection of said medication through said injection outlet, and
  • (c) means for mechanically setting the volume available within said cartridge for gas said expansion, so that said volume has a selected predetermined size.
• The main advantages attained with the invention are as follows:
• • Injections can only be performed when plurality of predetermined necessary conditions for a correct injection are satisfied. Therefore, the risk of accidentally released injections and their negative consequences, e.g. loss of expensive medications and possible injure of user, are substantially reduced.
  • A device and a system according to the invention are easy, safe and comfortable to use, so that they can be assembled and used by patients or other persons without any training or special instructions.
  • The manufacturing cost of a device and a system according to the invention is not higher than prior art devices for the same purpose.
BRIEF DESCRIPTION OF THE DRAWINGS
• The subject invention will now be described in terms of its preferred embodiments with reference to the accompanying drawings. These embodiments are set forth to aid the understanding of the invention, but are not to be construed as limiting.
• FIG. 1 shows a schematic cross sectional view of a basic structure of amedication cartridge11 used in a needleless injection system according to the invention.
• FIG. 2 shows a schematic cross sectional view of the basic structure of an application device according to the invention including a representation of amedication cartridge11 according toFIG. 1.
• FIG. 3 shows a schematic cross sectional view of the pressure chamber and locking means which are part of the application device according toFIG. 2 and which are adapted to enclose and contain amedication cartridge11 of the type shown byFIG. 1 during a high-pressure injection.
• FIG. 4 shows a schematic cross sectional view of a complete application device according to the invention without a medication cartridge inserted thereinto.
• FIG. 5 shows a side view of thenose section42 of an application device of the kind shown byFIG. 4.
• FIG. 6 shows a first perspective view of thenose section42 shown byFIG. 5.
• FIG. 7 shows a second perspective view of thenose section42 shown byFIG. 5.
• FIG. 8 shows a first exploded view of components of thenose section42 shown byFIGS. 5-7.
• FIG. 9 shows a second exploded view of components of thenose section42 shown byFIGS. 5-7.
• FIG. 10 shows a first schematic representation of the electrical ignition circuit of an application device of the kind shown byFIG. 4.
• FIG. 11 shows a second schematic representation of the electrical ignition circuit of an application device of the kind shown byFIG. 4.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
• According to the invention a reusable application device is used as part of a needleless hypodermic injection system for injecting a liquid medication contained in a cartridge inserted into said application device.
Medication Cartridge Assembly
• As shown byFIG. 1 amedication cartridge assembly11 according to the invention comprises components described hereinafter.
• Acartridge shell12 made e.g. of a plastic material contains among other components a sealed medication module which comprises a nozzle body13 and aflexible container wall14 that hermetically encloses a portion of the nozzle and forms areservoir15 for a liquid medication16 stored in the sealed medication module. This sealed module including liquid medication16 stored therein is manufactured under sterile conditions.
• A part of thecontainer wall14 forms a break-offprotective cap17 that covers ajet orifice18 of nozzle body13.Cap17 is removed by the user just prior to use.
• Anenvelope21 made e.g. of rubber surrounds theflexible container wall14 and serves as a protective barrier.Envelope21 protectsflexible wall14 from direct hot gas contact, and prevents hot gas from entering afluid channel22 within nozzle body13 andjet orifice18 of nozzle body13 even in the event of a break in theflexible container wall14.Envelope21 also forms a gas seal between thecartridge shell12 and the medication module containing the liquid medication16.
• Cartridge shell12 unifies the components contained therein and contains also gas generated withincartridge shell12 by a gas generator contained therein during actuation. The wall ofcartridge shell12 may be relatively thin since it transfers the gas pressure forces generated withincartridge shell12 to a surrounding high strength chamber that is part of a reusable actuation device described hereinafter.
• Injection energy is provided by a gas generator located in the rear part ofcartridge shell12. This gas generator is a subassembly consisting of a metalgas generator body23 which has apropellant containing chamber24 located between anoutlet orifice plate25 and a closure plug orclosure plate26. When the gas generator is actuated in order to provide the energy necessary for performing an injection of the liquid medication, a propellant contained inpropellant chamber24 is ignited by an electrically heated wire and produces hot gas that flows togas pressure chamber27 surroundingenvelope21,flexible container wall14 andmedication reservoir15 and anannular co-volume28 the size of which is defined by the axial position of aco-volume seal ring34.
• Heating wire adapted to be electrically heated is arranged withinpropellant chamber24. This heating wire is electrically connected withignition contacts31,32 arranged in closure plate. When the medication cartridge assembly is properly positioned within the reusable applicationdevice ignition contacts31,32 engage corresponding electrical contacts which are part of the application device described hereinafter. Electric power is deliverable to the heating wire35 (shown inFIG. 11) arranged withinpropellant chamber24 through the latter contacts andignition contacts31,32 engaged therewith.
• Cartridge shell12 further contains aninternal support33 which e.g. a structure made of a plastic material that snaps intocartridge shell12 and holds the above described sealed medication module and the gas generator in position. Whencartridge assembly11 is inserted into and properly positioned within an application device described hereinafter in order to perform an injection, a part of this application device pushes on the rear ofcartridge assembly11 and clamps theclosure plate26 of the gas generator,internal support33,envelope21 and the above described sealed medication module into the nose ofcartridge shell12.Cartridge assembly11 remains so clamped during actuation thereof by the application device for performing the injection. This clamping action oncartridge assembly11 assures that this assembly is hermetically sealed to prevent hot gas leakage aroundjet orifice18 of nozzle body13.
• When a cartridge assembly is actuated by the application device, pressure exerted by gas surrounding a part of the sealed medication module withincartridge shell12 is transmitted to liquid medication16 contained in the sealed medication module throughflexible container wall14. The pressure exerted in this way on the liquid medication causes a collapsing offlexible container wall14 and this drives the liquid medication throughjet orifice18 at high velocity. Peak pressure, up to 300 bar, occurs at the beginning of the injection and forces a jet of liquid medication to penetrate through a skin layer and thereby form a fluid delivery channel into the subcutaneous tissue. The pressure then drops to about 100 bar to complete the medication injection through the so formed fluid delivery channel.
• Ease of jet penetration varies between patients or between injection sites on the same patient. The initial peak injection pressure is therefore adjusted to control the jet penetration force to an appropriate value. This adjustment is effected by positioningco-volume seal ring34 at a suitable axial position with respect tocartridge shell12 in order to set the value of theannular co-volume28.
• Increasingco-volume28 increases the expansion volume of the gas generated and delivered by the gas generator and reduces the initial peak pressure to a lower value. Aco-volume setting ring48 that is part of the application device described hereinafter slides into the rear ofcartridge11 during loading ofcartridge11 into the application device, bringsco-volume seal ring34 into a selected position and holds this ring in this position.
• Acartridge assembly11 clamped into the actuation device described hereinafter is a hermetically sealed assembly, and retains as much as 100 bars pressure after actuation. The application device must therefore release the clamping force in a controlled way and allow that the gas pressure withincartridge11 forces closure plug26 of the gas generator out to break the seal with thegas generator body23 and vent the gas. This controlled pressure release makes it easy to open the application device after it is used to perform an injection and prevents that the amount of pressure remaining in the cartridge after an injection may cause an undesirable forceful opening of the application device that may cause an injury to a user of the device.
Structure of an Application Device According to the Invention
• The above described characteristics ofcartridge assembly11 define the basic functional requirements the application device has to satisfy. Additional requirements ensure safe and easy operation of the application device.
• The force a user has to apply for loading acartridge11 into an application device and the force a user has to apply for removing acartridge11 from the application device after use for performing an injection must be low enough to allow easy and sure operation of the application device by ill or elderly patients.
• Actuation of the application device must not be possible unless the device is fully closed and locked. Otherwise partial engagement of the locking mechanism might lead to failure and possible injury caused by the high pressure created during an injection operation.
• To ensure that actuation of the application device is not possible unless the device is fully closed and locked, operation of an application device according to the invention requires that the nose part of the application device is pressed uniformly and with a predetermined force against the skin surface to be injected before actuation of the application device is enabled. Main objectives of this security measure are to prevent accidental actuation resulting in ejection of a liquid jet that might cause eye injury and also to prevent wasted injections due to premature actuation of the application device before the nose part thereof is properly pressed against the skin surface at the injection site.
• The outer surface of the application device should not have any sharp edges or pinch points and the design of the application device has to satisfy ergonomic requirements.
• The shape of the application device has to be well adapted to the function it has to perform and therefore the procedures for loading and unloading acartridge11 into the application device and for actuating the application device should be so obviously and intuitively clear to the user that a minimum of user instruction is necessary to ensure proper use of the application device.
• Moreover, the application device and in particular the area around the cartridge nozzle that contacts the skin during the injection should be adapted to be easily cleaned.
• The injection system formed bycartridge11 and the application device described hereinafter should be fail-safe and resistant to tampering. Any faults in the device should result in failure of device actuation rather than in an unexpected or dangerous actuation. The design of the latter injection system should be such that it discourages a “clever” person from modifying or tricking the device so that it operates improperly.
• The application device described hereinafter meets the requirements outlined above.
• As shown byFIG. 2, anapplication device41 according to the invention comprises two sections: anose section42 which comprises apressure chamber49 defined by the interior of ashell43 and adapted for receiving acartridge assembly11, and abase section44 which comprises among other components abreech block45 and an electrical ignition system (not shown inFIG. 2).
• Nose section42 and abase section44 are assembled in two steps. In a first step acartridge11 is inserted intopressure chamber49 ofnose section42 and after thatnose section42 and thecartridge11 inserted thereinto are mechanically connected tobase section44. For this purpose,nose section42 andbase section44 are twisted with respect to each other ¼ turn to provide engagement of a set of locking lugs.
• In a secondstep nose section42 is twisted of about one turn with respect tobase section44 for tightening a screw mechanism that clampscartridge assembly11 with a required preload of e.g. 200 Newton. At thispoint application device41 is ready for performing an injection. For this purpose, the user removes break-offprotective cap17 fromcartridge11, pressesjet orifice18 of nozzle body13 against a skin surface at the injection site, and then presses an actuation switch to release an injection.
• Interlocks prevent actuation of the application device if it is not fully closed and if the skin contact surface of itsnose section42 is not uniformly pressed against the skin surface.
• A spent cartridge is removed by reversing the loading process. For this purpose,nose section42 is twisted of about one turn with respect tobase section44 to release the clamp screw mechanism and vent the residual cartridge gas pressure. The locking lugs are then disengaged by a further ¼ turn, andnose section42 andbase section44 are separated from each other so that the spent cartridge may be removed and discarded.
• Application device41 is a tightly integrated system that comprises the following subsystems:
• Pressure Chamber and Lock
• Pressure chamber49 and a lock which includes the above mentioned breech block are a set of mechanical components that enclose and contain acartridge assembly11 during a high-pressure injection.
• Housing
• A housing encloses and supports the other subsystems which form part of an application device according to the invention. This housing also forms the surfaces the user grips to administer injections and to open and close the application device for loading, respectively unloading of acartridge11.
• Electric Ignition System
• An electric ignition system includes a battery, an actuation switch, safety interlock switches and electrical connection leads. The electrical ignition system supplies electric current to theignition contacts31,32 ofcartridge11 and thereby to ignition wire35 (seeFIG. 11) to start an injection process when the user presses the actuation switch.
• Object Sensor
• An object sensor comprises a mechanical structure surroundingjet orifice18 of nozzle body13 ofcartridge11. This mechanical structure comprises a skin contact surface ofnose section42. Two diametrically opposite places of this skin contact surface must be pressed against the injection site in order to enableapplication device41 to actuate acartridge11 which has been loaded intoapplication device41.
• The following sections describe each of the above mentioned subsystems in detail.
• Pressure Chamber and Lock Mechanism
• FIG. 3 shows a general arrangement of apressure chamber49 and alock mechanism51.Pressure chamber49 is the interior of a generallycylindrical shell43 with a reduceddiameter opening46 at one end and afull diameter opening47 at the other end. Theshell43 ofpressure chamber49 is manufactured from high strength steel and dimensioned such that it will withstand about 900 bar internal pressure (that is three times a 300 bar maximum working pressure) without damage.
• Lock mechanism51 is part of a mechanical structure contained in and carried bybase section44. In order to load a new cartridge into the application device or to unload an spent cartridge from the application device,nose section42 andbase section44 are disassembled as described above in order to separate theshell43 ofpressure chamber49 fromlock mechanism51.
• Whencartridge11 is inserted intopressure chamber49 break-offprotective cap17 and the outer end of nozzle body13 extend through the reduced diameter opening46 of theshell43 ofpressure chamber49. Theshell43 ofpressure chamber49 has a clearance fit with respect tocartridge shell12. During an injection process the internal pressure withincartridge shell12 expands it elastically and its outer wall contacts the internal surface of theshell43 ofpressure chamber49, thereby transfers the pressure load to theshell43 ofpressure chamber49 during the injection process, and limits the mechanical stress oncartridge shell12. After an injection, the residual pressure in cartridge shell is released by venting (as described above) and cartridge shell elastically contracts. This restores the clearance fit ofcartridge shell12 with respect to theshell43 ofpressure chamber49 and this allows easy removal of a used cartridge. Nozzle body13 ofcartridge11 has sufficient strength to bridge the reduceddiameter opening46 and withstand the internal pressure incartridge11 during an injection process.
• Full diameter opening47 of theshell43 ofpressure chamber49 is closed whenshell43 is engaged withlock mechanism51.Lock mechanism51 has several functions. A first function oflock mechanism51 is that it locks to theshell43 ofpressure chamber49 and carries the axial pressure force (which is a function of the cartridge internal diameter and the gas pressure) which tends toseparate lock mechanism51 from theshell43 ofpressure chamber49. A second function oflock mechanism51 is that it carries the ignition contacts of the application device that engage theignition contacts31,32 ofcartridge11. A third function oflock mechanism51 is that it carries an interchangeable co-volume setting ring which serves for setting the axial position of theco-volume seal ring34 incartridge11. A fourth function oflock mechanism51 is that it comprises aclamp screw52 that allows the user to apply the necessary clamping force oncartridge11 prior to actuation thereof, and to release the residual pressure incartridge11 in a slow and controlled way after an injection process. A fifth function oflock mechanism51 is that it contains a mechanical interlock that assures that locking lugs are fully engaged beforeclamp screw52 can be turned to prepare and bring the system composed by the application device andcartridge11 to a state that allows actuation ofcartridge11 by the application device. Each of these functions is described in more detail in the following sections.
• A pair of male locking lugs53 on theshell43 ofpressure chamber49 engagefemale pockets54 in areceiver ring55 oflock mechanism51 to form a structural connection. The user makes this connection by inserting locking lugs53 intoreceiver ring55 with an axial motion, and then rotating theshell43 ofpressure chamber49 ¼ turn with respect toreceiver ring55 to engage lockinglugs53 with female pockets54. This type of connection is widely used in firearms and hose couplings because of its strength and reliability.
• After lockinglugs53 are fully engaged withfemale pockets54,clamp screw52 is turned to pushbreechblock45 intocartridge11.Clamp screw52, theshell43 ofpressure chamber49,receiver ring55 andbreechblock45 are all on a common axis, i.e. they are coaxially arranged. This screw action preloads the sealing ofcartridge11 with a force of about 200 Newtons, sets the axial position ofco-volume seal ring34 to a selected position, and pushes the ignition contacts of the application device against the ignition contacts ofcartridge11 so that electrical contact is established between these ignition contacts.
• After an injection process is terminated, a 100 bar residual pressure incartridge11 generates a force of about 1600 Newtons onclamp screw52. Under this mechanical load, the user turnsclamp screw52 to retractbreechblock45 and ventcartridge11. One of the ends ofclamp screw52 has right hand threads that engage matching threads inreceiver ring55, whereas the opposite end ofclamp screw52 has left hand threads that engage matching threads inbreechblock45. One or more pins inreceiver ring55 engage matching axial slots inbreechblock45, and prevent rotation ofbreechblock45 while allowing axial motion thereof. The provision ofclamp screw52 with the above mentioned different threads makes it possible to obtain an axial displacement ofbreechblock45 per revolution ofclamp screw52 that is twice as long as the axial displacement that would be obtained if clamp screw52 had only a single type of thread with the same thread pitch distance. A suitable choice of thread diameter and pitch favorably influences the amount of effort needed for disassembling, respectively assemblingapplication device41. This is discussed in more detail hereinafter.
• A pair of interlock levers56,57 consisting each of alatch portion69 and anarm portion68 are pivot mounted on apivot70 to thereceiver ring55. Interlock levers56,57 lie in a plane that includes the symmetry axis ofreceiver ring55, and the pivot axes are perpendicular to this plane and symmetrically placed on each side of the symmetry axis of the receiver ring. Interlock levers56,57 are spring biased by abias spring60 so that thelatch portions69 engage a pair of grooves (not shown) inclamp screw52, preventing screw rotation. When theshell43 ofpressure chamber49 is inserted intoreceiver ring55, thearm portions68 of interlock levers56,57 slip into a pair ofcam grooves58,59 in theshell43 ofpressure chamber49.Cam grooves58,59 are shaped to move thearm portions68 of interlock levers56,57 as theshell43 ofpressure chamber49 is rotated to engage lockinglugs53, so that thelatch portions69 are removed from the clamp screw grooves. The result is that rotation ofclamp screw52 is only possible when the locking lugs53 are fully engaged withpockets54.
• A second function of interlock levers56,57 is to prevent rotation oflugs53 and disengagement thereof frompockets54 once clamp screw52 is rotated from the starting position to clampcartridge11 and thereby the closure plug ofcartridge11 andpressure chamber49 by means ofbreechblock45. When clamp screw52 is rotated, thelatch portions69 of the interlock levers56,57 ride on the outside diameter ofclamp screw52, and can no longer enter the clamp screw grooves and rotate about pivots70. Thearm portions68 of interlock levers56,57 are therefore immovable, and bear against the sides of thecam grooves58,59 in theshell43 ofpressure chamber49 and block rotation of locking lugs53. This ensures that lugs53 remain fully engaged withpockets54 during actuation ofcartridge11 and can only be disengaged afterclamp screw52 is returned to the starting position. At this point thelatch portions69 of interlock levers56,57 can again drop into the clamp screw grooves, allowing thelatches69 of interlock levers56,57 to rotate about thepivots70.
• A third function of interlock levers56,57 is to preventshell43 ofpressure chamber49 from being inserted if clamp screw52 is not in the starting position. In this condition thelatch portions69 of the interlock levers56,57 ride on the outside diameter ofclamp screw52, displacing thearm portions68 of the levers so that they do not enter the cam grooves in theshell43 ofpressure chamber49. This blocks theshell43 ofpressure chamber49 from entering thereceiver ring55 far enough for the locking lugs53 to engagepockets54. The situation in which theshell43 ofpressure chamber49 is removed and theclamp screw52 is not in the starting condition is not normal, and indicates damage or tampering. Correction of this anomalous state requires device service or replacement.
• By careful selection of the design parameters ofclamp screw52, the required effort to assembly anddisassembly application device41 are approximately equal and this results in greatly improved ease of use.
• Frictional torque ofclamp screw52 varies in function of axial load, screw thread diameter, and friction coefficient. Load reaction torque varies in function of axial load and thread pitch. The reaction torque adds to the friction torque in the closing direction (when assembling application device41), and increases the user effort. Conversely, the reaction torque subtracts from the friction torque in the opening direction (when disassembling application device41) and assists the user. Since the axial force is about 200 Newtons in the closing direction and about 1600 Newtons in the opening direction, according to the invention the parameters ofclamp screw52 are selected to equalize the opening and closing torque. The following table summarizes the results of a typical design calculation.

  	Parameter	Value

  	Clamp screw diameter	8	mm
  	Screw thread friction coefficient	0.12
  	Peak closing force	200	N
  	Peak opening force	1600	N
  	Equalized opening and closing torque	20	N-cm
  	Screw pitch (Total of left and right	6	mm
  	hand clamp screw sections)

  
  Housing
• FIG. 4 shows a cross section ofapplication device41 including the housing components. As well as containing the functional components, the housing has important functions of its own. Thenose section42 of the housing is rigidly connected to theshell43 ofpressure chamber49, and serves as one handle through which the user applies opening and closing torque. Thebase section44 of the housing is rigidly connected to clampscrew52, and serves as the other handle. Thebase section44 of the housing rotates relative to thereceiver ring55 andbreechblock45. In combination, thenose section42 and thebase section44 of the housing also act as visual and tactile indicators, since they have oval profiles that line up when the device is fully closed. Closure ofapplication device41 is assisted by a spring-loaded pin anddetent61 that latch theapplication device41 in the closed position. Additional functions and features of the housing will become evident in the descriptions of other aspects ofapplication device41.
• FIGS.5 to9 show various views of thenose section42 and of some of its components.FIG. 5 shows a side view of thenose section42 of an application device of the kind shown byFIG. 4.FIG. 6 shows a first perspective view of thenose section42 shown byFIG. 5.FIG. 7 shows a second perspective view of thenose section42 shown byFIG. 5.FIG. 8 shows a first exploded view of components of thenose section42 shown byFIGS. 5-7.FIG. 9 shows a second exploded view of components of thenose section42 shown byFIGS. 5-7.
• Electric Ignition System
• FIGS. 10 and 11 show schematic representations of the electric ignition system ofapplication device41.
• In its simplest form, the electric ignition system ofapplication device41 consists of abattery62, anactuation switch63 controlled by the user, electrical contacts that engage electrical contacts ofcartridge11, and interconnection conductors. The user loads afresh cartridge11 intoapplication device41, closes and locks this device, removes break-offprotective cap17, pressesjet orifice18 against the skin at the injection site, and then pressespush button63 of the actuation switch. Current passing through an electrically heated wire in the gas generator ofcartridge11 lights the propellant and starts the injection. The invention uses this basic approach, and adds interlock mechanisms to reduce the chance of premature actuation that could cause a hazard or waste an injection cartridge.
• The physical configuration of the electric ignition system of this invention is illustrated inFIG. 4. Except as noted, the ignition components are attached to thebase section44 of the housing.Battery62 is permanently connected by soldering or a similar means, and will normally last the life ofapplication device41. Thepositive battery terminal64 is electrically connected to the input terminal of the normallyopen actuation microswitch71, and thenegative terminal65 is connected to the input terminal of the normallyopen interlock microswitch72. The output terminal of theactuation microswitch71 is connected to aconductive spring member73 that is biased into contact with the centralignition contact pin66. This contact connection is required since the centralignition contact pin66 rotates with thereceiver ring55, not with thebase section44 of the housing. The output terminal of theinterlock microswitch72 is connected to aconductive spring member67 that is biased into contact with the slidingconductive transfer pin74 in thereceiver ring55. Thetransfer pin74 forms a conductive path from theconductive spring member67 to theco-volume setting ring48 and then to thebreechblock45. Because thebase section44 of the housing and thereceiver ring55 have rotational and axial relative motion, contact takes place and ignition is possible only whenclamp screw52 is in the predetermined actuation position.
• The centralignition contact pin66 presses against the cartridgecenter ignition contact32. Thepin head75 is structurally connected to the slidingbreechblock45, but electrically isolated by an insulatingbushing76. The pin shaft passes through clearance holes in thebreechblock45 and clampscrew52, and is supported on center by an insulating sleeve bearing77 to maintain electrical isolation.
• The electrically conductive slidingbreechblock45 presses against theouter ignition contact31 ofcartridge11. As described above, current can only flow to thebreechblock45 when theclamp screw52 is in the actuation position and thetransfer pin74 makes contact with theconductive spring member67.
• When theinterlock microswitch72 is closed and theclamp screw52 is in the actuation position, theactuation microswitch71 is the only remaining barrier to current flow through the ignition contacts and the electricallyheated wire35 incartridge11. This results in the battery voltage appearing between the input and outlet terminals of theactuation microswitch71. This “ready to actuate” condition is visually indicated by aLED78 connected across the terminals. Actuation then takes place when the user closes theactuation microswitch71 by pressingpush button63.
• A mechanism consisting of apushbutton63,coil spring81,pin lever82 andflat spring83 is used to close theactuation microswitch71 when the user presses thepush button63. This arrangement allows thepushbutton63 to be positioned so that it is convenient for the user, while theactuation microswitch71 is positioned where housing space is available. Thepushbutton63 slides in asleeve84 in the housing, and is biased out by thecoil spring81. Thepin lever82 serves a dual purpose. First, it is pressed into thepushbutton63 and extends into openings in the sides of thesleeve84 to retain thepushbutton63 in the housing. Second, it acts as a lever that transfers the pushbutton motion to theflat spring83 that engages the actuationmicroswitch operating plunger85. Thepin lever82 pivots in a hole in the side of thesleeve84 nearest thenose section42 of the housing of theapplication device41, and swings through aslot86 in the opposite side. Theflat spring83 is anchored at one end, and passes over themicroswitch71 and extends to engage the end of thepin lever82. When thepin lever82 swings, it deflects theflat spring83 towards theactuation microswitch71 and pushes theactuation plunger85. Thesleeve84 in the housing is made of translucent plastic that is illuminated by the “ready to actuate”LED78.
• The schematic representation of the electrical ignition system shown byFIG. 10 illustrates the fact that in order that an injection can be performed withapplication device41 the following switches have to be closed: switches71,72, and switch formed bylock mechanism51, spring-loaded pin anddetent61 and electricalconductive transfer pin74. This latter switch is only then closed when theapplication device41 is completely assembled, that is when the components contained innose section42, inbase section44, and thecartridge11 are all in the proper position with respect to each other.
• The schematic representation of the electrical ignition system shown byFIG. 11 illustrates the state of this system when theapplication device41 is completely assembled and all necessary contacts for the ignition are established with exception ofswitches71 and72 which are still open. In this state LED78 received a current limited byresistor79. This current is well below the value necessary to cause ignition by electricallyheating ignition wire35, but is large enough to cause light emission byLED78 and thereby signalize thatapplication device41 would become ready for performing an injection if and when properly positioned on the injection site.
• When theapplication device41 reaches a proper position on the injection site, switch72 is closed by this positioning, and actuation ofpush button63 by the user can then cause closure ofswitch71. If this happens, the electrical ignition circuit is closed and a sufficiently large current is fed toignition wire35 to cause ignition of the propellant incartridge11.
• Object Sensor/Position Detector
• The object sensor or position detector requires thenose section42 of the housing of theapplication device41 to be pressed uniformly against the skin surface at the injection site before actuation is possible/allowed. The object sensor/position detector is illustrated inFIG. 4. Thenose section42 of the housing includes a flatannular surface91 which surrounds the end of theshell43 ofpressure chamber49 that protrudes from the housing and the injection nozzle. A pair of diametrically opposed sensor pins92,93 slide in holes in the housing, and their ends extend a short distance above the surface in the rest position. The interlock system according to the invention requires that both sensor pins92,93 are pushed flush with theannular surface91 to enable execution of an injection. Sensor pins92,93 support a concentric rigidmetal sensor ring94 that is free to pivot at the contact points with the sensor pins92,93. This defines the condition that two or more separate points must be pressed to push thesensor ring94 and bothpins92,93 flush with theannular surface91 and enable execution of an injection. If thesensor ring94 is pressed at any one point around its circumference it will tip, and at most one of the twosensor pins92,93 will be pushed flush with theannular surface91. The annular area, including thesensor ring94 and sensor pins92,93, is covered by aflexible rubber boot95. The inner edge of theboot95 is bonded to theshell43 of thepressure chamber49 at abond point105, and the outer edge ofboot95 fits in a groove in thenose section42 of the housing. Theboot95 forms a smooth, easily cleaned surface and protects the mechanism. It also retains thesensor ring94 and holds it in the proper spatial relationship with the sensor pins92,93 at the rest position.
• The sensor pins92,93 push arelay ring96 inside thenose section42 of the housing. Therelay ring96 in turn pushes atilt plate97. Thetilt plate97 contacts therelay ring96 with two diametrically opposed raised pivot points98 (98arespectively98b), and two diametrically opposed legs99 (99arespectively99b) extend towards thebase section44 of the housing. Thelegs99 are offset 90 degrees from the pivot points98, and lie in the same plane as the sensor pins92,93. Areturn spring101 formed from sheet spring material pushes thetilt plate97,relay ring96 and sensor pins92,93 towards thenose section42 of the housing so that thesensor ring94 is pushed out to the rest position. Acover plate102 on the surface of thenose section42 of the housing that abuts thebase section44 of the housing supports thereturn spring101 and shields the mechanism. Thetilt plate legs99 pass through holes in thecover plate102, with their ends flush with the outer surface in the rest position.
• When thenose section42 of the housing is attached to thebase section44 of the housing and theclamp screw52 is locked, one of the twotilt plate legs99 is aligned with theinterlock push pin103. This pin contacts theinterlock microswitch plunger104, and closes theinterlock microswitch72 when it is pushed by one of thetilt plate legs99. The other tilt plate leg contacts thebase section44 of the housing and forms a pivot point. If thesensor ring94 pushes both sensor pins fully, then therelay ring96 is pushed uniformly against the two tilt plate pivot points. This causes thetilt plate97 to rotate around the pivot point formed by the leg in contact with the housing so that the other leg extends, pushes theinterlock push pin103, and closes theinterlock microswitch72. In the event that only onesensor pin92 or93 is pushed, therelay ring96 tilts rather than moving uniformly. The two points on therelay ring96 that contact thetilt plate97 pivots move only half the full distance, with the result that thetilt plate leg99 moves only half the full distance and does not close theinterlock switch72.
• This above described object sensor/position detector has a number of useful features. First, it is electromechanical, and does not contain any electronic devices that are sensitive to and whose operation can be affected by spurious signals from electrostatic discharge or other sources of electromagnetic interference. Second, the electric ignition circuit is totally within thebase section44 of the housing, with no connections to theremovable nose section42 of the housing that could compromise reliability. Third, additional safety is provided by the fact that the device must be fully closed and locked to align thetilt plate leg99 with theinterlock push pin103. Fourth, the structure of the object sensor/position detector is symmetrical, so that thenose section42 of the housing may be connected to thebase section44 of the housing in either of two positions which are angularly spaced from each other of 180 degrees.
• List of Reference Numbers
• 11 medication cartridge/cartridge assembly
• 12 cartridge shell
• 13 nozzle body
• 14 flexible container wall
• 15 medication reservoir
• 16 liquid medication
• 17 break-off protective cap
• 18 jet orifice
• 19
• 20
• 21 envelope
• 22 fluid channel
• 23 gas generator body
• 24 propellant chamber
• 25 outlet orifice plate
• 26 closure plug/closure plate
• 27 gas pressure chamber
• 28 annular co-volume
• 29
• 30
• 31 ignition contact
• 32 ignition contact
• 33 internal support
• 34 co-volume seal ring
• 35 electrically heated wire/ignition wire
• 36
• 37
• 38
• 39
• 40
• 41 application device
• 42 nose section
• 43 shell of pressure chamber
• 44 base section
• 45 breech block
• 46 reduced diameter opening
• 47 full diameter opening
• 48 co-volume setting ring
• 40 pressure chamber
• 50
• 51 lock mechanism
• 52 clamp screw
• 53 male locking lugs
• 54 female pockets
• 55 receiver ring
• 56 interlock lever
• 57 interlock lever
• 58 cam groove
• 59 cam groove
• 60 bias spring
• 61 spring-loaded pin and detent
• 62 battery
• 63 push button/actuation button
• 64 positive terminal
• 65 negative terminal
• 66 central ignition contact pin
• 67 conductive spring member
• 68 arm portion
• 69 latch portion
• 70 pivot
• 71 actuation micro-switch
• 72 interlock micro-switch
• 73 electrical conductive spring member
• 74 electrical conductive transfer pin
• 75 pin head
• 76 insulating bushing
• 77 insulating sleeve bearing
• 78 Light Emitting Diode (LED)
• 79 electrical resistance
• 80
• 81 coil spring
• 82 pin lever
• 83 flat spring
• 84 sleeve
• 85 operating plunger/actuation plunger
• 86 slot
• 87
• 88
• 89
• 90
• 91 flat annular surface
• 92 sensor pin
• 93 sensor pin
• 94 metal sensor ring
• 95 flexible rubber boot
• 96 relay ring
• 97 tilt plate
• 98 pivot point (98a,98b)
• 99 leg (99a,99b)
• 100
• 101 return spring
• 102 cover plate
• 103 interlock push pin
• 104 interlock microswitch plunger
• 105 bond point
• Although a preferred embodiment of the invention has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.

Claims (17)

1. An application device for needleless hypodermic injection of a liquid medication said application device comprising

a) a housing having a length axis and an outer contact surface which is adapted to be applied on a skin surface through which an injection is to be applied;

b) said housing containing ejection means causing ejection of said liquid medication in order to perform an injection and actuator means for activating said ejection means; and

c) position detecting means for detecting whether said contact surface of said housing exerts a predetermined pressure on said skin surface and whether at the same time said length axis of said housing is positioned substantially normal to said skin surface, the distribution of said pressure over the area of said contact surface being substantially uniform, said means for detecting enabling said actuator means when the latter conditions are satisfied.

2. A device according toclaim 1, wherein the ejection means comprise a propellant and means for its ignition.

3. A device according toclaim 1, wherein said position detecting means exclusively comprise mechanical and electro-mechanical means, but no electronic means sensitive to electrical noise or other perturbating electrical signals.

4. A device according toclaim 1, wherein said position detecting means comprise a first switch adapted to be mechanically actuated by a movable part of said position detecting means to establish an electrical connection when said position detecting means senses application of the contact surface of the housing on said skin surface with a predetermined pressure applied on the skin surface.

5. A device according toclaim 1, wherein said housing is so configured and dimensioned that it is adapted to be held and used by a user with only one hand.

6. A device according toclaim 1, further comprising means providing a visual or audible indication to the user when said actuator means is enabled.

7. A device according toclaim 1, wherein the position detecting means comprise a purely mechanical object sensor, and a first switch adapted to be mechanically actuated by a movable part of the position detecting means to establish an electrical connection when said object sensor senses application of the contact surface of the housing on a body part.

8. A reusable application device for needleless hypodermic injection of a liquid medication said application device comprising

a) a housing having a length axis and an outer contact surface which is adapted to be applied on a skin surface through which an injection is to be applied wherein

the housing comprises a first section and a second section which are adapted to be connected with each other to form a housing assembly,

said first housing section comprising a chamber for receiving a cartridge containing a medication unit which contains a liquid medication,

said first housing section having a symmetry axis which extends along its length and a front part having the outer contact surface which is adapted to be applied on a skin surface, said contact surface having an opening through which liquid medication ejected from said cartridge can pass and be injected through said skin surface;

b) said housing containing ejection means causing ejection of said liquid medication in order to perform an injection and actuator means for activating said ejection means wherein

a first part of the ejection means is contained in said cartridge and a second part of said ejection means is contained in said second housing section;

c) assembly detecting means which reach a first predetermined state when said first housing section is properly and completely assembled with said second housing section to form said housing assembly, said assembly detecting means being located within said housing assembly;

d) position detecting means for detecting whether said contact surface of said housing exerts a predetermined pressure on said skin surface and whether at the same time said length axis of said housing is positioned substantially normal to said skin surface, the distribution of aid pressure overt the area of said contact surface being substantially uniform, said means for detecting enabling said actuator means when the latter conditions are satisfied wherein

the position detecting means are located in part within said first housing section and in part in said section housing section, said position detecting means reaching a second predetermined state when the following conditions are simultaneously satisfied by the relative position of said housing assembly with respect to said skin surface,

d.2) said contact surface of said first section exerts a predetermined pressure on said skin surface, the distribution of said pressure over the area of said contact surface being substantially uniform, and

d.3) said symmetry axis of said first section is positioned substantially normal to said skin surface; and

e) the actuator means are normally disabled and become operable only upon being enabled by a combination of predetermined effects provided by

said assembly detecting means after they reach said first predetermined state, and

said position detecting means when they reach said second predetermined state.

9. A device according toclaim 8, wherein said second housing section comprises means which are adapted to cooperate with a corresponding part of said first housing section for clamping with a predetermined preload and for hermetically closing a cartridge inserted into said cartridge receiving chamber.

10. A device according toclaim 8, wherein said first housing section and said second housing section are so shaped, dimensioned and configured that proper and complete assembly therefore is accurately defined and recognizable by visual and tactile inspection.

11. A device according toclaim 8, wherein said first housing section and said second housing section are adapted to be assembled together by assembling steps which include a screwing operation.

12. A device according toclaim 8, wherein injection is caused by an electrical circuit comprising

a battery,

a first switch

a second switch adapted to be actuated by a user,

interconnection conductors, and

two electrical terminals which correspond to

respective terminals of an igniter,

said electrical circuit being so configured that

electrical current can flow from the battery to the igniter only when the following conditions are met:

i) said cartridge is properly positioned within said chamber of said first housing section.

ii) said first and said second housing section are completely and properly assembled, whereby said two terminals of said electrical circuit contact said respective terminals of said igniter.

iii) said first switch is actuated by said object sensor and thereby establishes an electrical connection, and

iv) said second switch is actuated by a user.

13. A device according toclaim 8, wherein said assembly detecting means exclusively comprise mechanical means.

14. A needleless hypodermic injection system for injecting a liquid medication, which system comprises:

a) an application device according toclaim 1

i) a housing having a length axis and an outer contact surface which is adapted to be applied on a skin surface through which an injection is to be applied;

ii) said housing containing ejection means causing ejection of said liquid medication in order to perform an injection and actuator means for activating said ejection means; and

iii) position detecting means for detecting whether said contact surface of said housing exerts a predetermined pressure on said skin surface and whether at the same time said length axis of said housing is positioned substantially normal to said skin surface, the distribution of said pressure over the area of said contact surface being substantially uniform, said means for detecting enabling said actuator means when the latter conditions are satisfied; and

b) a disposable cartridge which contains a medication and which comprises a propellant and an igniter.

15. A medication cartridge for a needleless hypodermic injection system according toclaim 14 for injecting a liquid medication, said cartridge comprising a housing adapted to contain:

a) a first chamber containing a medication unit configured and dimensioned to store a volume of liquid to be injected, said medication unit having a first region and a second region that are in liquid communication with each other, said first region being deformable and said second region having an injection outlet,

b) a second chamber containing a propellant, said first chamber being divided by an elastic barrier in two zones, a first zone containing said medication unit and a second zone which is in communication with said second chamber, so that upon ignition of the propellant in the second chamber gas generated thereby expands into said second zone of said first chamber, exerts pressure on and deforms said barrier which in turn transfers that pressure to and deforms said deformable first region of said medication unit and thereby causes ejection of said medication through said injection outlet, and

c) means for mechanically setting the volume available within said cartridge for gas expansion, so that said volume has a selected predetermined size.

16. A medication cartridge according toclaim 15, further comprising an envelope which surrounds said elastic barrier and protects it from direct contact with hot gas generated by ignition of said propellant in said second chamber.

17. A medication cartridge according toclaim 16, wherein said envelope also forms a gas seal between said housing and said medication unit containing said liquid medication.

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