WO2009095701A1

WO2009095701A1 - Automatic injection device with hidden trigger

Info

Publication number: WO2009095701A1
Application number: PCT/GB2009/000299
Authority: WO
Inventors: Barry Peter Liversidge
Original assignee: Barry Peter Liversidge
Priority date: 2008-02-01
Filing date: 2009-02-02
Publication date: 2009-08-06
Also published as: GB0801874D0

Abstract

An injection device has an elongate housing (10) containing a pre-filled syringe (13) having a needle (14) and a tubular shield (17) for protecting that needle until the device is to be used. On pressing the forward end of the (shield 17) against the skin of a patient, the shield moves rearwardly into the housing (10) and causes an operating button (40) to emerge either from the rearward end (12) of the housing (10) or into a window (52) through the housing wall. Depression of the operating button (40) releases the energy of a power unit (30) located within the housing to drive the syringe piston (29) forwardly and so effect an injection.

Description

AUTOMATIC INJECTION DEVICE WITH HIDDEN TRIGGER

This invention relates to an injection device for the administration of medicaments from a pre-filled syringe. In particular, but not exclusively, this invention relates to an injection device known as an "auto-injector" where a user may press the device on to an injection site and then simply operate a control in order for the device then to perform an injection, on a fully automatic basis.

Throughout this specification, reference is made to the relative terms "forward" and "rearward": "forward" and "forwardly" refer to the end of the device which is presented to a body when an injection is to be performed (that is, the tip end of the needle) and the direction towards that end; and the terms "rearward" and "rearwardly" refer to the other end of the device (that is, the end of the device nearer a syringe with which the device may be used) and the direction towards that other end.

There is a requirement for an injection device which is very easy to use and which can reliably deliver a set dose of a medicament, in order that the device may be used for self-injection or by other unskilled personnel, to deliver a medicament to a patient. For example, a patient susceptible to anaphylactic shock will normally carry an auto-injector device pre-charged with adrenalin to allow an emergency injection of that drug in the event that the patient is suffering from anaphylactic shock. Speed is of the essence and it may be necessary for a completely unskilled person to use the injection device to administer that injection. A similar situation where an emergency injection may have to be performed by an unskilled person is on a battlefield, where an antidote to a chemical agent may have to be administered very quickly and under extremely difficult conditions.

For the above purposes, auto-injector devices have been developed which may be used merely by pressing the device on the skin of a patient and then working some kind of control to perform the injection. Other devices are known which operate automatically when pressed against a surface, following release of a safety catch or shield for the needle. It is a common problem with an auto-injector that it is used the wrong way round and so with the operator pressing the wrong end of the device against the skin of a patient and then pressing the needle end of the device, in the hope of effecting the injection. This results in the injection being performed on the operator, rather than the patient. The consequence is that the patient may not be saved as these devices are intended for one-time operation only and the user of the device has wasted the injection on himself. It is a principal aim of the present invention to provide an injection device which addresses the above issues and seeks to prevent inadvertent operation even should an attempt be made to use the device the wrong way round and so present the wrong end of the injection device to the patient.

According to this invention, there is provided an injection device comprising an elongate housing containing a pre-filled syringe having a needle and a piston for expelling medicament out of the needle, a tubular shield for protecting the needle and movable rearwardly into the housing, a power unit for driving the piston, and a release control for the power unit which release control is initially at least partially concealed within the housing and emerges from the housing on rearward movement of the shield, to become exposed so as to be operable to release the energy of the power unit.

The injection device of this invention is configured to make it essentially impossible for the device to be operated until such time as the shield has been pressed on to a required injection site, so exposing the release control for operation, to allow release of the stored energy within the power unit. In the event that a user holds the housing the wrong way round and then presses on the end of the shield in an attempt to obtain some functionality, the device will not operate since the release control cannot be operated to release the energy of the power unit with the same hand as is grasping the housing and is pressing the end of the shield.

A preferred form of the device has the release control disposed at the rear end of the housing, such that the release control emerges axially out of the housing when the shield moves rearwardly with respect to the housing, on being pressed into engagement with the required injection site. In this case, pressing the wrong (rearward) end of the device on to the skin of a patient will prevent the release control emerging from the housing, and so the device still cannot be operated. Further, to reduce the likelihood of inadvertent operation even when the shield has been pushed into the housing, the release control may be arranged for operation to release the stored energy of the power unit by being moved transversely of the length of the housing.

According to a second aspect of this invention, there is provided an injection device comprising an elongate housing containing a pre-filled syringe having a needle and a piston for expelling medicament out of the needle, a power unit for driving the piston of the syringe, and a release control for the power unit which release control is operable transversely of the length of the housing to release the energy of the power unit. As with the first form of this invention, the injection device of this second aspect may have a tubular shield for protecting the needle which shield is slidably mounted within the housing for rearward movement thereinto so as to expose the needle.

Advantageously, the release control is connected to a plunger for driving the piston by a frangible connection, the release control serving to hold the plunger against the action of the stored energy of the power unit until the release control has been broken away from the plunger.

In a preferred injection device of this invention which has a shield slidable with respect to the housing, the shield may have an initial position and a final position where the shield projects from the housing and an intermediate position where the shield is pressed back into the housing. Preferably, the syringe is mounted in a carrier which is slidable within the shield, the carrier being configured for supporting a conventional syringe though that syringe may have a modified plunger in order for co-operation with the power unit. In such an arrangement, following operation of the release member to release the stored energy of the power unit, initially the syringe is driven forwardly with respect to the shield to project the needle beyond the end of the shield and then the syringe piston is driven forwardly with respect to the syringe body, to expel medicament out of the needle. This action is possible in view of the hydraulic resistance to movement of the piston with respect to the syringe, in expelling medicament out of the syringe body, through the needle.

The injection device may have means for locking the shield in its final position, following the completion of an injection procedure and so when the shield is protecting a used needle. This locking means may comprise a rearwardly projecting lock member on the shield which is arranged to engage behind an abutment on the housing when the shield is in its protecting position. A wedging member may be associated with the syringe such that forward movement of the syringe with respect to the shield deforms the lock member outwardly, thereby allowing the lock member to move to its locking position on subsequent forward movement of the shield with respect to the syringe.

The housing of the injection device may be modified to include a guard which partially encloses the release control when projecting from the housing. Only limited access to the release control may then be gained, so reducing the likelihood of operation of the release control other than when the forward end of the device has been pressed on to the required injection site, so moving the shield fully rearwardly.

In any of the embodiments of this invention, the syringe within the injection device may be pre-fitted with a needle, or it may be necessary to ready the device for use, by fitting a needle thereto when an injection is to be performed.

By way of example only, one specific embodiment of injection device of this invention will now be described in detail, reference being made to the accompanying drawings in which:-

Figure 1 is an axial sectional view through the embodiment of injection device, in an initial setting;

Figure 2 is an axial sectional view through the device of Figure 1 , but with a needle stripped, ready for use; Figure 2A is a partly cut away isometric view of the device, in the setting of Figure 2;

Figure 3 is an axial sectional view through the device of Figure 1 but in a second setting, at the commencement of use;

Figure 3A is a partly cut away isometric view of the device, in the setting of Figure 3;

Figure 4 is an axial sectional view through the device of Figure 1 , but with a release control broken away;

Figure 4A is a partly cut away isometric view of the device, in the setting of Figure 4; Figure 5 is an axial sectional view through the device of Figure 1 , but at the completion of an injection procedure;

Figure 5A is a partly cut away isometric view of the device, in the setting of Figure 5;

Figure 6 is an isometric view on the end region of a modified form of the device of Figure 1 , in an initial setting;

Figure 7 is similar to Figure 6, with the release control broken away;

Figure 8A to 8E are isometric drawings showing the sequence of operation of the injection device of Figures 1 to 7; Figures 9A and 9B show a second embodiment of this invention where an operating button emerges axially into a window in the housing;

Figures 10A and 10B show a third embodiment of this invention where an operating button emerges by rotation into a window in the housing; Figure 11A shows a fourth embodiment where the operating button emerges through a window, for operation transversely of the housing;

Figure 11 B is a detail view on an enlarged scale of the encircled part of the fourth embodiment;

Figure 12A shows a fifth embodiment where the operating button emerges through an opening at the end of the housing; and

Figures 12B and 12C are detail views on an enlarged scale of the encircled part of the fifth embodiment, respectively with the operating button in its inoperable condition and subsequently for operation axially or transversely of the housing. There is shown in the drawings a single-use injection device intended primarily for self-injection or for the administration of an injection by persons other than skilled medical personnel. The device is thus configured to ensure safety in operation as well as subsequent to the performance of an injection. Moreover, the device is arranged to ensure that the full dose of a required drug is delivered, in the course of the injection process. The device uses a compact and reliable power unit which has been pre-charged with energy to allow the performance of the injection under the force derived from the power unit and which has been configured to ensure that the energy is released only when an operator positively requires that to occur. The device comprises a cylindrical housing 10 having moulded plastics front and rear parts 11 and 12 snap-fitted together so as to be essentially inseparable once conjoined as shown. Contained within the housing is a conventional single-use syringe body 13 having a needle 14 secured to the front end of the syringe body and an outwardly projecting lip 15 at the rear end of the body. The syringe is located within a tubular carrier 16 slidably mounted within a tubular shield 17, itself slidably mounted within the front part 11 of the housing 10. A needle cover 18 is fitted to the forward end of the shield 17 and has a sheath 19 located therewithin, which sheath fits on to the needle hub 20 at the forward end of the syringe body 13 and also receives the sharp tip of the needle 14.

At its forward end, the shield 17 is tubular as best seen in Figure 2A. Opposed windows 21 are formed through the tubular part of the shield 17, which windows align with corresponding openings 41 (Figures 8A to 8E) in the front part 11 of the housing 10, when the housing and shield have the relative positions of Figures 1, 2 and 8A. Rearwardly of the window 21, the shield has an upstanding annular rib 22 from which a pair of opposed fingers 23 project rearwardly. Forwardly of the rib 22, there is a plurality of vanes 24, imparting stability on the rib. The rear end of the carrier 16 has a flange 25 formed with a pair of opposed slots, the fingers 23 locating one in each slot, respectively. The carrier may thus slide within the shield 17 but not rotate relative thereto. At the forward end of the carrier 16 there is an in-turned lip 26 against which the forward end of the syringe body 13 engages, to define a limiting forward position of the syringe with respect to the carrier. The syringe and carrier may thus move as a unit within the shield 17, as will be described in further detail below. A wedging washer 27, having a generally conical forward face, is slidably mounted on the carrier 16 adjacent the flange 25 and is engageable with ramp surfaces formed on the fingers 23, on forward movement of the carrier with respect to the shield 17.

The syringe body 13 is furnished with a plunger 28 having a piston 29 fitted to the forward end thereof, for dispensing a liquid medicament contained within the syringe body out of the needle 14. The piston 29 and forward end of the plunger 28 are essentially conventional but the rearward end portion of the plunger forms part of a power unit 30 contained within the housing 10, for delivering medicament from the syringe through the needle 14, when the needle has penetrated a required injection site.

As best seen in Figures 1 to 3, the power unit 30 has a tubular first component 31 the forward end of which is located between the rearward ends of the fingers 23 of the shield 17, forward movement of that first component with respect to the shield 17 being limited by inwardly-directed projections 32 formed on the fingers. The rearward end portion of the plunger 28 defines a second component 33 for the power unit and has an annular abutment 34 which is slidable within the first component 31. A helical compression spring 35 is disposed around the second component 33 and acts between the annular abutment 34 thereof and in-turned lip 36 at the rearward end of the first component 31.

Towards the end of the second component 33, there is formed a neck 37 defining a weakened zone, that neck interconnecting the plunger 28 to a release control 38. Adjacent the neck 37, the release control has a generally part-spherical form 39 and projecting from that form is an operating button 40 having a part-conical profile, the button flaring outwardly towards its free end.

The rearward end of the housing rear part 12 has an end wall 42 with a central aperture, through which the operating button 40 projects to a small extent, when the device is in its initial setting, as shown in Figures 1 and 2. A shield spring 43 acts between that end wall 42 and the projections 32 formed on the fingers, the spring surrounding the first component 31 of the power unit 30 and extending within the space between the fingers 23. Figures 1 and 8A show the injection device in its storage setting, with the power unit 30 pre-charged for delivering a medicament from a pre-filled syringe located within the device. In this setting, it is possible to view the medicament in the syringe, through the openings 41 in the housing 10 and the aligned windows 21 in shield 17. The first stage of the procedure to use the injection device is to strip the sheath 19 from the needle 14 by pulling the needle cover 18 away from the forward end of the shield 17 and housing 10 (Figure 8B). The needle is then ready for use as shown in Figure 2 but still lies wholly within the shield 17 and so is still protected. Further, the shield 17 prevents sight of the needle and this facilitates the performance of a self-injection even by those suffering from needle-phobia (aprilophobia). In this initial setting of Figures 1 , 2 and 8B, a small part of the operating button 40 projects beyond the end wall 42 of the housing 10. The shield spring 43 urges the shield 17 forwardly, but the inter-engagement of that operating button with the end wall 42 prevents the shield 17 being moved forward under the action of the spring 43. Further, the interengagement of the part spherical form 39 of the release member 38 with the lip 36 at the rearward end of the first component 31 prevents the plunger 28 being driven forwardly with respect to the syringe under the action of spring 35, contained within the power unit. An injection is performed by grasping the housing 10 like a dagger and pressing the forward end of the shield 17 against the skin at the required injection site. This moves the housing forwardly towards the skin and so the projecting part of the shield 17 moves rearwardly into the housing until the first component 31 abuts the end wall 42 as shown in Figure 3. In turn this causes the button 40 to emerge from the end wall 42 of the rear part 12, so bringing the part spherical form 39 into the opening in the end wall 42, as shown in

Figure 8C. While still grasping the housing 10, lateral pressure may be applied to the button 40, for example by the thumb of a user, so breaking neck 37 and freeing the release control 38 from the remainder of the plunger. With the release member 38 broken away from the plunger, spring 35 acting on the annular abutment 34 drives the plunger 28 forwardly with respect to the first component 31 of the power unit. The hydraulic resistance of the medicament being expelled through the needle results in a considerable force being needed on the piston 29 to dispense the medicament. The result of driving the plunger forwardly therefore has the initial effect of driving the syringe body 13 and carrier 16 forwardly within the shield 17 until the limiting forward position is reached, defined by interengagement of the flange 25 of the carrier with the rib 22 of the shield 17. As shown in Figures 4 and 8D, this causes the needle 14 to project beyond the forward end of the shield 17 and so into the tissues beneath the skin of the patient, before the plunger 28 and piston 29 is driven forwardly with respect to the syringe body 13, to expel the medicament through the needle and into those tissues.

Once medicament delivery has been completed, the housing 10 is moved away from the injection site, so allowing shield 17 to move forwardly under the action of spring 43, thereby shielding once more the sharp tip of the needle (Figure 8E). By virtue of the interengagement between the wedging washer 27 and the fingers 23, that washer 27 is also moved forwardly with the shield 17, sliding on the carrier 16. The rear ends of the fingers 23 spring outwardly to engage behind an abutment surface 44 formed at the forward end of the rear part 12 of the housing, disposed within the front part thereof, to lock the shield against subsequent movement rearwardly with respect to the housing.

The injection device includes a further safety feature in that should the user place a thumb or finger over the operating button 40 on grasping the housing and before the forward end of the shield has been pressed on to the injection site, the shield cannot move rearwardly by virtue of the axial pressure on the operating button 40. It will thus be seen that the power unit cannot be released to dispense the medicament until the forward end of the shield 17 has been pressed on to the required injection site, since until then the operating button 40 cannot be manipulated to break the neck 37. The same will apply equally should the user hold the housing 10 the wrong way round and so present the operating button 40 to the injection site, and then attempt to press the forward end of the shield 17 to perform the injection. Again, no injection will occur since the button 40 cannot be moved laterally to allow the neck 37 to be broken.

Referring now to Figures 6 and 7, there is shown a modification to the rear part 12 of the housing 10 of the injection device, so as to reduce yet further the likelihood of inadvertent breaking of the neck 37, for example in either of the circumstances outlined immediately above. As shown in these Figures, a part-cylindrical guard 46 is carried by the rear part, so as to project rearwardly from the end wall 42. Even when the operating button 40 projects to its fullest extent from that end wall (as shown in Figure 7) the end of the button does not project beyond the guard 46. Consequently access to the button to effect breaking of the neck 37 can be gained only through the cut away part 47 of the guard 46, for example by way of the thumb of a user's hand grasping the housing 10.

Figures 9A and 9B show a second embodiment which operates on a broadly similar manner to that described above with reference to Figures 8A to 8E, except that the operating button 50 does not emerge axially from the rearward end of the housing 51. Rather, the housing is provided with a window 52 in the side wall at the rear end thereof and the operating button 50 moves axially rearwardly to emerge into that window when the shield 53 at the forward end of the housing is pressed into engagement with the skin of a patient, as has been described above with reference to the first embodiment. Pressing the operating button 50 through the window causes operation of the device, as described previously.

Figures 10A and 10B show a third embodiment similar to the second embodiment described with reference to Figures 9A and 9B, but in this third embodiment the operating button 50 emerges into the window 52 by rotation, rather than axial movement. The rotation is caused by a suitable camming mechanism within the housing, operated upon movement of the shield 53 into the housing. As shown in the second and third embodiments, the operating button may carry wording to indicate how the device should be operated. Instead of such wording, or perhaps in addition to that wording, the operating button may be coloured to show where pressure should be applied. In the case of the third embodiment, a panel (not shown) may lie circumferentially closely adjacent but not connected to the operating button, that panel also being coloured but with a different colour from that of the operating button. For example, the panel may be coloured green and the operating button red, such that when the shield is pressed against the skin of a patient, the red operating button comes into view showing that the device is then ready to operate.

Figure 11A shows a fourth embodiment where the operating button 55 emerges transversely through a window 56 in the housing 51 , as the shield 53 is pressed against a patient. Once emerged, as shown in Figure 11 B, transverse pressure on the operating button causes operation of the device, as a whole, again as described with reference to the first embodiment.

Figures 12A to 12C show a fifth embodiment where there is provided a window 58 in the generally spherical end portion 59 of the housing and the operating button 60 has a grooved outer surface 61 which emerges generally axially through that window 58. In this embodiment, operation of the device is possible by axial pressure or transverse pressure on the operating button 60, or by pressure on that button at an angle lying between the axial and transverse directions. In this embodiment, the grooved outer surface of the button may be coloured green and the side faces of the button red, such that the setting of the device ready to operate becomes apparent from the red becoming visible and the area for pressure is marked by the green colour.

Claims

1. An injection device comprising an elongate housing containing a pre- filled syringe having a needle and a piston for expelling medicament out of the needle, a tubular shield for protecting the needle and movable rearwardly into the housing, a power unit for driving the piston, and a release control for the power unit which release control is initially at least partially concealed within the housing and emerges from the housing on rearward movement of the shield, to become exposed so as to be operable to release the energy of the power unit.

2. An injection device as claimed in claim 1 , wherein the release control is disposed at the rear end of the housing and emerges axially from the housing when the shield moves rearwardly.

3. An injection device as claimed in claim 1 or claim 2, wherein the release control, when emerged from the housing, is operable transversely of the length of the housing to release the energy of the power unit.

4. An injection device as claimed in claim 1, wherein the release control emerges from behind a guard so as to become operable by pressure applied thereto.

5. An injection device as claimed in claim 4, wherein the release control is operable when emerged from behind the guard by pressure applied axially, transversely or a combination of axial and transverse pressure applied thereto.

6. An injection device as claimed in claim 5, wherein the guard comprises a part of the housing.

7. An injection device comprising an elongate housing containing a pre- filled syringe having a needle and a piston for expelling medicament out of the needle, a power unit for driving the piston of the syringe, and a release control for the power unit which release control is operable transversely of the length of the housing to release the energy of the power unit.

8. An injection device as claimed in claim 7, wherein a tubular shield for protecting the needle is slidably mounted within the housing for rearward movement thereinto.

9. An injection device as claimed in any one of claims 1 to 6 or claim 8, wherein the syringe is mounted for axial sliding movement within the shield.

10. An injection device as claimed in claim 9, wherein the syringe is mounted in a carrier slidably mounted within the shield, whereby a conventional syringe is employed within the injection device.

11. An injection device as claimed in claim 10, wherein following the operation of the release control, the power unit initially drives the syringe forwardly with respect to the shield to project the needle beyond the end of the shield and then drives the piston forwardly with respect to the syringe to expel medicament.

12. An injection device as claimed in any of claims 9 to 11 , wherein resilient means is provided to drive the shield forwardly with respect to the syringe to a protecting position following performance of a procedure, thereby once more to protect the needle.

13. An injection device as claimed in claim 12, wherein lock means is arranged to lock the shield in its protecting position, following performance of an injection procedure.

14. An injection device as claimed in claim 13, wherein the shield has a rearwardly projecting lock member and there is a wedging member associated with the syringe which wedging member thrusts the lock member outwardly on movement of the syringe forwardly with respect to the shield, thereby to allow the lock member subsequently to engage behind an abutment provided on the housing.

15. An injection device as claimed in any of the preceding claims, wherein the release control is connected to a plunger for the piston by a frangible connection, the release control holding the plunger against movement under the action of the power unit until the release control has. been broken away from the plunger.

16. An injection device as claimed in any of the preceding claims, wherein the power unit includes a pre-charged spring held in its charged state until released by the release control.

17. An injection device as claimed in any of the preceding claims, wherein a guard is provided for the release control when emerged from the housing, limiting access to the release control for the manipulation thereof.