INJECTOR DEVICE WITH MECHANISM FOR PREVENTING ACCIDENTAL ACTIVATION

There is provided an injector device comprising a housing (26), a drug container (10) positioned in the housing; a drug delivery mechanism associated with the drug container, the drug delivery mechanism comprising a stored energy source; an activation member (18) coupled to the housing, the activation member configured to contact the injection site in use and movable relative to the housing to an activation position to activate the drug delivery mechanism; and a removable cap (134) coupled to the activation member and to the housing, wherein in a first position a first portion of the housing engages the activation member to prevent the activation member from moving into the activation position, and wherein a portion of the cap engages the housing to retain the first portion of the housing in the first position such that the activation member is prevented from moving into the activation position until the cap is uncoupled from the activation member.

FIELD OF THE INVENTION

The present invention relates to injector devices, such as autoinjectors, that have an automatic mechanism that is triggered by pressing the device against the injection site. In particular the invention relates to mechanisms for preventing accidental triggering of the automatic mechanism prior to intended use.

BACKGROUND TO THE INVENTION

Prefilled injector devices allowing for self administration of drugs are becoming increasingly prevalent, as self administration has clear benefits in terms of cost to health care providers and well as improving patient convenience.

One type of prefilled injector device is an autoinjector, which includes an automatic delivery mechanism which, once activated, provides for automatic delivery of the drug. In autoinjectors, the delivery mechanism includes a stored energy source which, when released, drives the drug delivery mechanism and may also drive needle insertion.

Activation of the delivery mechanism can be achieved in a number of ways depending on the design of the device. However, there are clear benefits in terms of usability if the delivery mechanism is activated simply by pressing a front end of the device against the injection site. This removes the need to press any additional buttons or otherwise manipulate the device, which can be problematic for users suffering from disorders such as arthritis. Alternatively if the autoinjector includes an activation button or similar mechanism then an additional interlock unlatched by pressure on the front end of the device from the injection site can reduce the risk of accidental premature activation. The front end of the device is typically covered by a removable cap in order to keep the front end of the device that contacts the injection site clean prior to use. However, it is important to ensure that the delivery mechanism is not activated before the intended use of the device. Even though the front end of the device may be spring biased into an extended position, injector devices may be subject to high impact and vibration during transport and may be dropped during transport or by the end user prior to intended use. If the delivery mechanism is triggered, by vibration or impact forces before intended use, then the drug in the device is wasted and, with disposable, single use devices, the device itself is wasted. In addition, there is a potential needle stick injury risk if the device is activated before intended use. Another problem is that the user may be relying on a particular device to deliver the drug, not knowing that the device has already been activated. This is not good in any circumstances, but is dangerous when the drug is required in an emergency situation.

It is an object of the present invention to address the problem of unintended activation of automatic delivery mechanisms in injector devices.

SUMMARY OF THE INVENTION

The invention is defined in the appended claims to which reference should be made.

In one aspect there is provided an injector device comprising: a housing; a drug container positioned in the housing; a drug delivery mechanism associated with the drug container, the drug delivery mechanism comprising a stored energy source; an activation member coupled to the housing, the activation member configured to contact the injection site in use and movable relative to the housing to an activation position to activate the drug delivery mechanism; and a removable cap coupled to the activation member such that the activation member is prevented from moving into the activation position until the cap is uncoupled from the activation member.

Using a removable cap to prevent relative movement between the activation member and the housing means that the delivery mechanism can only be operated after the cap has been removed from the device. A cap is typically secured to the device to maintain the portion of the device that contacts the injection site clean prior to use. As an alternative, or in addition, the cap may function to remove a needle shield which keeps the needle sterile prior to use and which may also seal the end of the needle to prevent premature loss of drug. The cap is secured to the device or is retained by secondary packaging in such a way that it will not easily come away from the device during transport and handling.

The cap may be coupled to the housing. The cap may abut or engage the housing to prevent the cap and activation member together moving relative to the housing. As an alternative, or in addition, the cap may be coupled to the drug container to prevent the cap and activation member moving together relative to the housing. The cap may be coupled to a needle shield that covers a needle coupled to the drug container.

The activation member may move telescopically with respect to the housing. The activation member may comprise a generally cylindrical member and may have a substantially closed front end except for an aperture allowing for passage of a needle therethrough. The front end then provides a front surface for contacting an injection site. A rear end of the activation member may engage with one or more parts of the delivery mechanism or with a locking arrangement for the delivery mechanism.

In some embodiments, in a first position, a portion of the cap, or an intermediate component coupled to the cap, may engage the activation member to prevent the activation member from moving into the activation position, and a portion of the housing may engage the cap to retain the cap in the first position.

The cap may be coupled to an exterior surface of the activation member. For example, the cap may be coupled to the activation member by a helical threaded engagement. The cap may also (or alternatively) be coupled to the housing by a helical threaded engagement. The helical threads on the activation member and on the housing may have the same helix angle.

The cap may engage a lug, recess or aperture on the activation member to prevent the activation member from moving into the activation position. The cap may comprise a flexible arm that engages with the lug, recess or aperture on the activation member. For example, the cap may be pushed onto the activation member in a longitudinal direction and may comprise flexible arms that flex in a direction non-parallel with the longitudinal direction to engage with the lug recess or aperture on the activation member. The flexible arm may be retained in engagement with the lug, recess or aperture on the activation member by a portion of the housing. When the cap is moved away from the housing in a longitudinal direction, the portion of the housing is removed from engagement with the flexible arm, allowing the flexible arm to be released from engagement with the lug, recess or aperture in the activation member.

The housing may comprise a cam surface to assist in decoupling of the cap from the activation member as the cap is removed from the housing. For example, the cap may include a lug that engages a lug or recess in the activation member and a cam surface on the housing may be provided adjacent to the lug or recess to urge the cap out of engagement with the lug or recess on the activation member as it is removed from the housing.

Alternatively, or in addition, in some embodiments, the cap may be coupled to an interior surface of the activation member. The cap may be directly coupled to an interior surface of the activation member or may be coupled to the interior surface of the activation member by one or more intermediate components. For example, the intermediate component may be a removable needle shield provided to maintain a needle in a sterile condition. Alternatively, the intermediate component may be an additional element coupled to a removable needle shield, the removable needle shield being coupled to the cap and to the drug container.

The intermediate component may comprise a resilient element that is deformed by the cap to engage the activation member to thereby prevent the activation member from moving into the activation position. Movement of the cap relative to the activation member may then release the resilient element from engagement with activation member allowing the activation member to move to the activation position. For example, the removable needle shield may comprise a resilient element that is deformed by the cap when the cap is fully engaged with the housing to engage a rear facing surface of the activation member if the activation member moves towards the activation position. Initial movement of the cap away from the housing releases the resilient element to allow it to return to a configuration in which it can pass through an aperture in a front surface of the activation member.

Alternatively, the intermediate component may have a flexible arm that engages the activation member in an unstressed state, configured such that movement of the cap away from the housing deforms the flexible arm to decouple the flexible arm from the activation member.

The cap may be coupled to the activation member by engagement of a thread on the cap with a thread on an internal surface of the activation member or on an intermediate element positioned inside the activation member and between the cap and the activation member. The engagement of the threads on the activation member and the cap may require less than a full turn of rotation to move from a fully engaged position to a fully disengaged position. Alternatively they may require more than one full rotation to move from a fully engaged position to a fully disengaged position.

The activation member may comprise a skin contact surface configured to contact the injection site in use, the skin contact surface including at least one aperture, and the cap may comprise an engagement element configured to be received in the at least one aperture such that relative rotation between the cap and the activation member causes the engagement element to engage the activation member to prevent the activation member from moving into the activation position. This arrangement is similar to a bayonet type fitting as an initial relative rotation is required to disengage the cap from the activation member but thereafter they can be separated by a translational movement.

In another embodiment, in a first position a first portion of the housing engages the activation member to prevent the activation member from moving into the activation position, and a portion of the cap engages the housing to retain the first portion of the housing in the first position. The first portion of the housing may be flexible (and may be resilient) and the cap may engage the housing to prevent the first portion of the housing moving out of a first position engaging the activation member, and may deflect the first portion of the housing into the first position, wherein on removal of the cap, the first portion of housing is able to move out of the first position to allow the activation member to move to the activation position. In the first position the first portion of the housing may engage a slot or recess in the activation member. The activation member may include a cam surface configured to allow the activation member to move past the first portion of the housing after the cap has been removed from the housing.

It should be clear that features of the invention described in relation to one aspect may be applied to other aspects of the invention, and that features described in different embodiments of the invention may be used in combination with one another.

DETAILED DESCRIPTION

FIG. 1is a perspective, cross-sectional view of an autoinjector configured to be activated by pressing an activation member18against an injection site. The autoinjector shown inFIG. 1comprises a primary drug container10housing a drug12. A plunger16is positioned within the drug container10. In use, the plunger16is driven through the drug container to expel the drug12through a needle14, which is fixed to the front end of the drug container10.

The autoinjector has a housing24,26, which houses the drug container10as well as a drive mechanism20. The activation member18is mounted to the front end of the housing24,26. As shown inFIG. 1the housing24,26comprises two parts, an outer housing26and an inner housing portion24that is fixed to the outer housing26. However, it should be clear that these may be formed as a single component.

The drive mechanism20as shown inFIG. 1comprises two springs held in a compressed condition prior to use. A first, outer spring is used to drive the drug container10forward through the housing to a needle insertion position, in which the front end of the needle extends beyond the activation member18. A second spring is used to drive a drive rod21, which engages the plunger16, to drive the plunger through the drug container10to expel the drug through the needle14. The drug container is retained against the force of the drive mechanism20by latching arms22, which engage the front end of the drug container10against the force of the springs in the drive mechanism.

As shown inFIG. 2, when the activation member18is pressed against the injection site it moves backwards into the housing26and a window28in the activation member18is moved back to a position adjacent to the front end of retaining arms22. In this position, the arms22are able to flex outwardly into the windows28allowing the drug container to move forward through the housing to a needle insertion position. The drug container10then moves forward through the housing until it is stopped by engagement with the housing24, after which the plunger16is driven through the drug container10to expel the drug. The operation of the drive assembly20will not be described in detail in this specification, as any suitable drive assembly may be used, incorporating one more springs, or any suitable type of stored energy. A detailed description of a drive assembly of the type shown inFIGS. 1 and 2can be found in WO2012/073035, the contents of which are incorporated herein by reference.

Although not shown inFIGS. 1 and 2, a needle shield element may be provided to cover the needle in order to maintain the needle14in a sterile condition prior to use. A cap is also typically provided over the front end of the housing to maintain the activation member, and in particular the surface29of the activation member18that contacts the injection site, clean prior to use. The cap may also assist in the removal of the needle shield element by the user prior to the injection process.

However, with a cap over the front end of the housing26, it is still possible for the activation member18to move to an activation position, i.e. the position where the latching arms22can move into windows28in the activation member, unless some means is provided for preventing the activation member from moving to its activation position. A biasing spring is typically provided between the activation member and the housing24to bias the activation member away from the housing24(item39, as shown inFIG. 5) but this spring cannot be relied on to prevent activation of the device in all conditions.

FIG. 3is a perspective view of an autoinjector of the type shown inFIGS. 1 and 2incorporating a mechanism for preventing the activation member18from moving to the activation position until a cap34(shown inFIGS. 4 and 5) is at least partially removed from the housing. In the embodiment shown inFIG. 3, thread elements30are formed on an outer surface of the activation member and corresponding thread elements32are formed on an outer surface of the housing26. These thread elements30,32are configured to engage corresponding internal grooves36,38on cap34, as shown inFIGS. 4 and 5. The thread elements30have the same helix angle as thread elements32.FIG. 4is a perspective view of the cap34, showing the internal grooves36that engage the threads30on the activation member, and the internal grooves38that engage the threads32on the housing26. In the embodiment shown inFIGS. 3,4and5, the thread elements comprise four, discontinuous thread elements, circumferentially spaced around the activation member18and housing26. However, it should be clear that a single, continuous thread may be used, or any other number of thread elements.

FIG. 5is a cross-section through the front end of the autoinjector ofFIG. 3with the cap34ofFIG. 4engaged and an associated needle shield40. The cap34is screwed onto the front end of the autoinjector and helical grooves36engage with the threads30on the activation member18, and helical grooves38engage with the threads32on the housing. The cap34can be screwed onto the activation member18and housing26during device assembly. The cap34is then effectively braced between the activation member18and the housing26and so prevents movement of the activation member18relative to the housing26thereby preventing activation of the device prior to cap removal. A biasing spring39is also shown inFIG. 5, which ensures that the activation member is biased into an extended position before and after use. However, the biasing spring39alone is not sufficient to prevent accidental activation of the device.

FIGS. 6,7,8and9illustrate a second embodiment in accordance with the invention, in which the cap engages with protrusions64on the activation member18, and with the housing26, to prevent movement of the activation member to the activation position.FIG. 6is a perspective view of the front end of an autoinjector in accordance with this second embodiment. The cap34comprises flexible arms60which, when assembled to the autoinjector, extend into and are retained in a receiving recess62in the housing26.FIG. 7illustrates the embodiment ofFIG. 6with a portion of the housing26removed for clarity. It can be seen inFIG. 7that the flexible arms60include enlarged head portions68which prevent the activation member, and specifically projection64, from moving beyond them. The flexible arms60can flex to allow the enlarged head portions68to move past the projection64but are prevented from flexing when engaged with portion66of the housing26. If the activation member18is moved backwards prior to use, lugs64will come into engagement with enlarged head portions68of the flexible arms60and are prevented from moving further back into the housing26. This prevents inadvertent activation of the device.

Removal of the cap34from the housing26is illustrated inFIGS. 8 and 9. As the cap is pulled off the autoinjector, in a first stage the enlarged head portions68are moved to a position where they are free of the portion66of the housing. This is shown inFIG. 8. Further pulling of the cap results in inward deflection of the legs60, as shown inFIG. 9, allowing the enlarged head portions to move past the lugs64, thereby releasing the cap34. Once the cap34has been removed, the activation member18is free to move backward to an activation position, allowing the autoinjector to be operated. The cap34and flexible arms60can be formed by injection moulding using any suitable material, such as polypropylene.

FIG. 10is a perspective, cross-sectional view of a third embodiment of the invention.FIG. 10shows the front end of an autoinjector of the type shown inFIG. 1, with a cap34and needle shield40. In the embodiment ofFIG. 10, the cap34includes flexible portions70which extend into an aperture formed in the activation member18, and thereby prevent inward movement of the activation member to the activation position.

FIG. 11shows the embodiment ofFIG. 10with the cap and needle shield removed. The housing26includes an enlarged portion72which defines a passageway through which the flexible portions70on the cap can pass and flex inwardly to engage a window in the activation member18. To remove the cap34, the cap is simply pulled off in a direction parallel to the axis of the needle14. The cap may include a plurality of spaced apart flexible portions70, spaced around the circumference of the cap or may include a single flexible portion. The cap and flexible portions can be formed by injection moulding using any suitable material, such as polypropylene.

FIG. 12is a perspective view of the front end of an autoinjector in accordance with a fourth embodiment of the invention. In the embodiment ofFIG. 12, the outer housing26includes a window portion82, into which a flexible portion of the cap34is received. The flexible portion of the cap in the window portion82engages a protrusion80on the activation member18to prevent movement of the activation member18into an activation position.FIGS. 13 and 14are cross-sectional views of the embodiment ofFIG. 12, illustrating the engagement of the cap34with the window82. In order to facilitate removal of the cap, the housing includes cam surfaces84formed adjacent the window82that engage with the corresponding cam surfaces86on the interior surface of the cap. As the cap is pulled away from the housing, cam surfaces84engage with cam surface86and slide past one another, thereby urging the flexible portion of the cap88out of engagement with aperture82and past protrusion80formed on the activation member.

FIG. 15is a cross-section through a front end of an autoinjector in accordance with a fifth embodiment of the invention. In the embodiment ofFIG. 15the activation member18is prevented from moving to the activation position by an intermediate component100, coupled to the cap34. The intermediate component is positioned substantially within an interior of the activation member18. Movement of the activation member towards the activation position results in the front face of the activation member18abutting the intermediate component100, which is itself constrained from movement by abutment with interior housing24and by latching element110.

FIG. 16is a perspective view of the intermediate component100. As shown inFIG. 16, the intermediate component comprises a ring structure102, from which four resilient, U-shaped legs104extend. The intermediate component100may be formed from any suitable resilient material, such as spring steel or a moulded plastic such as polypropylene, and may have a different number of legs.

FIG. 17is a perspective cross sectional view of the intermediate component100engaged with cap34. The intermediate component100is pushed over and retained by latching element110formed inside the cap. The cap also includes resilient gripping arms112, which are configured to grip needle shield40during cap removal, thereby removing the needle shield, and a retaining ring114that fits within the space formed underneath the U-shaped legs104. As can be seen inFIG. 15, the retaining ring114prevents the legs104from radially compressing so that they cannot pass through the aperture formed in the front face29of the activation member18.

However, as the cap34is pulled away from the housing26the retaining ring114moves out of the space defined by U-shaped legs104. This is shown inFIG. 18. As the cap34is further pulled away from the housing, the ring102abuts the latching element110and the legs104are then pulled down to engage the activation member18. Angled surfaces on the activation member18and the ends of arms104engage one another such that movement of the intermediate component away from the housing causes the arms104to be radially compressed by the activation member, allowing the intermediate component to move through the aperture in the activation member18. This is illustrated inFIG. 19.FIG. 20shows the cap34and needle shield40fully removed from the activation member18. The activation member18is then free to move into the activation position.

FIG. 21is a perspective view of an alternative design for an intermediate component of the type shown inFIG. 16. In the embodiment ofFIG. 21, in addition to resilient U-shaped legs122of the type described with reference toFIG. 16, the intermediate component120incorporates gripping arms126to grip the needle shield40extending from ring124.

The operation of the embodiment ofFIG. 21is similar to that shown inFIGS. 16 to 20.FIG. 22shows the cap and intermediate component120assembled to the activation member18and housing26. The intermediate component is coupled to the cap by latching members110. The legs122on the intermediate component prevent the activation member from moving back into the housing26to the activation position. The legs122are prevented from radially compressing to allow the activation member to move past the legs by retaining ring114. Gripping arms126grip the needle shield40.

FIG. 23shows the cap moved away from the housing to a position in which the legs122are clear of the retaining ring114. The legs122have been radially compressed by the activation member18in the same manner as described with reference toFIG. 19, allowing the intermediate component120to pass through the aperture in the front face of the activation member18. At the same time, gripping arms126have engaged the needle shield40and pulled it away from the drug container10. As with the embodiment ofFIGS. 16 to 20, the first part of the motion of the cap34away from the housing26allows the intermediate component110to move clear of the retaining ring114and in a second part of the motion of the cap34away from the housing26the intermediate component120is able to deform allowing it to move clear of the activation member18.

FIGS. 24 to 27show a further alternative design for an intermediate component of the type, shown inFIG. 21.FIG. 24is a partial perspective cross-sectional view of the front end of an autoinjector of the type shown inFIG. 1. The intermediate component130again provides both the function of locking the activation member18and gripping the needle shield40. However, in the embodiment ofFIGS. 24 to 27, the intermediate component130is deformed to allow it to pass through an aperture in the activation member by tensioning the intermediate component130between the needle shield40and the cap34as the cap is being removed from the housing. The intermediate component130is more clearly illustrated inFIG. 25, which is a cross-sectional view of the cap and intermediate component. The intermediate component130comprises four circumferentially spaced arms131on a ring structure136. The intermediate component is retained on the cap by retaining latches110. At the end of each arm remote from the ring structure is a gripping hook134for engaging the needle shield and a pair of locking fingers132. The arms131include an elbow133so that they have a lower portion between the ring structure and the elbow, and an upper portion between the elbow and the gripping hook134. The locking fingers132are attached to the upper portion and extend parallel to the upper portion so that their distal end cannot pass through the aperture in the front end of the activation member. Movement of the intermediate component130is limited by the latch element110. The activation member18is therefore prevented from moving to the activation position by the locking fingers132.

When the cap is pulled away from the housing, the gripping hooks134engage the needle shield40. The needle shield40is sealed to the drug container10and so before the needle shield comes away from the drug container the intermediate component130is placed under tension by the movement of the cap34away from the housing26. This tension causes the arms131to straighten at the elbow, which causes each locking finger132to move to a position parallel to the lower portion of the corresponding arm131. This is shown inFIG. 26. In this tensioned state the locking fingers132can move through the aperture in the front face29of the activation member18and the intermediate component130and needle shield40can be completely removed from the rest of the device. This is shown inFIG. 27.

The embodiments ofFIGS. 15 to 27include an intermediate component between the cap34and the needle shield40. It should be clear that it is possible to use the same type of mechanism to deform elements that engage an interior of an activation member, in which the deforming element are an integral part of the needle shield.

FIG. 28is a perspective view of the front end of an activation member for use in an autoinjector in accordance with an eighth embodiment of the invention. In the embodiment ofFIG. 28, a cap34(as shown inFIG. 29) is coupled to the activation member18by a screw thread engagement. The cap includes a thread144formed on an interior of the cap for engagement with a groove140formed on an interior surface of the activation member18. The activation member is, as in the previous embodiments, a generally cylindrical shaped element with a front surface29configured to contact the injection site and has an aperture formed in the front surface, through which the needle passes. In the embodiment ofFIG. 28a bore of the aperture in the front face of the activation member has a helical groove140formed in it.FIG. 29is a perspective cross sectional view of a cap34for engagement with the activation member18shown inFIG. 28. The cap34has a plurality of latching members142formed on an interior of the cap, for engagement with a needle shield40, as shown inFIG. 30. A threaded shaft144is formed around the base of the latching members142.

FIG. 30shows the cap ofFIG. 29engaged with the activation member ofFIG. 28. The cap34is screwed on the activation member18by engaging the threaded shaft144with the groove140and clips over and also engages the needle shield40. The cap34then is effectively braced between the activation member18and the housing26and so prevents the activation member from moving to the activation position. To remove the cap34, it is unscrewed from the activation member18using a twisting motion. As the cap is unscrewed from the activation member18it pulls the needle shield40from around the needle14. Once the threaded shaft144is clear of the groove140the activation member18is free to move to the activation position.

FIG. 31is a perspective view of the front end of an activation member18in accordance with an alternative embodiment, similar to that shown inFIG. 28. In the embodiment ofFIG. 31, instead of a single helical groove formed in the activation member18, a plurality of separate grooves150are formed in the activation member. Each groove150engages with a corresponding bead or thread in the cap34.FIG. 32is a cross sectional perspective view of a cap34for engagement with the activation member18shown inFIG. 31. It is essentially the same as the cap34shown inFIG. 29except for the design of the thread shaft154. In the embodiments shown inFIGS. 31 and 32, the cap34can be disengaged and engaged with the activation member18by only a quarter turn between the two.FIG. 33is a cross sectional view showing the cap ofFIG. 32engaged with the activation member ofFIG. 31.

The embodiments ofFIGS. 28 to 33are based on a threaded engagement between the activation member and the cap. The embodiment shown inFIGS. 34 to 38uses a bayonet type engagement between the activation member18and the cap34.FIG. 34is a perspective view of the front end of an activation member in which the aperture161in the front face29of the activation member18has four lugs160projecting into it. These lugs160engage with corresponding slots formed on the interior of a cap34. A cross sectional perspective view of the cap for engagement with the activation member shown inFIG. 34is shown inFIG. 35. Between the latches162formed in the cap34to engage the needle shield40there are four slots164corresponding to the four lugs160formed on the activation member. At the bottom of the slots164is an undercut with a recess166in which each lug160sits in order to prevent the activation member18moving to the activation position.FIG. 36is a perspective cross sectional view of the cap ofFIG. 35engaged with the activation member ofFIG. 34. The lugs160can be seen engaged in recess166so that, whilst the cap is abutting the housing26, the activation element18cannot move rearwardly into the housing26to the activation position. The latches162are shown clearly engaging the removable needle shield40.

In order to remove the cap and allow the autoinjector to be activated, the cap34is first rotated relative to the activation member18to move the lug160out of the recess166to a position at the bottom of the slots164. This position is shown inFIG. 37. The cap34can then be pulled with a longitudinal translational movement away from the housing26to remove the cap34and the needle shield40, so that the device is ready for use.FIG. 38shows the cap34during removal, as the needle shield40is pulled off the drug container. In this position the activation member is free to move back into the activation position.

FIG. 39illustrates a twelfth embodiment of the invention.FIG. 39is a perspective view of an autoinjector of the type shown inFIG. 1with a cap134placed over the activation element.FIG. 40is a cross section of the autoinjector shown inFIG. 39. The housing26of the autoinjector includes a pair of flexible fingers174that extend into corresponding recesses176formed in the activation member. The flexible fingers174are retained in the recesses176by walls172of the cap134and thereby prevent rearward movement of the activation member18to the activation position. This is more clearly shown inFIG. 42. Once the cap134is removed from the housing26, the flexible fingers174can deflect out of the recesses176to allow the activation member to move to the activation position.

FIG. 41is a perspective view of the cap34shown inFIGS. 39 and 40. The cap includes radially enlarged pockets170the walls172of which engage the flexible fingers174and retain them inside the recesses176formed in the activation member.FIG. 42is a perspective cross sectional view of the activation member18and illustrates the recess176formed on the outer surface of the activation member18. A front end of the recess176includes an angled or chamfered surface178over which a front end of the flexible finger174travels as the activation member18moves rearwardly to the activation position. This is illustrated inFIG. 43which shows the flexible finger174riding on the surface178to deflect out of the cavity176.FIG. 44shows the activation element18moved to the activation position, with the flexible fingers174positioned on the outside of the activation member, clear of the recesses176.

Although multiple separate embodiments have been described in the specification, it should be clear that features of one or more of the embodiments could be combined with the features of one or more of the other embodiments. For example, the cap may be fixed to the housing by a helical thread engagement while being engaged to the activation member by an intermediate component of the type shown inFIG. 16,21or25. It is also possible to include in a single implementation more than one mechanism to lock the activation member against moving to the activation position.

Although the embodiments have all been described in relation to in particular autoinjector design, it should be clear that the invention is applicable to any drug delivery device which is activated by pressing an activation element against a surface.