Patent ID: 12220563

Corresponding parts are marked with the same reference symbols in all figures.

DETAILED DESCRIPTION

A ramped engagement in the terminology of this specification is an engagement between two components with at least one of them having a ramp for engaging the other component in such a manner that one of the components is flexed aside when the components are axially pushed against each other provided this component is not prevented from flexing aside.

FIGS.1A and1Bshow two longitudinal sections of an auto-injector1in different section planes, the different section planes approximately 90° rotated to each other, wherein the auto-injector1is in an initial state prior to starting an injection. The auto-injector1comprises a chassis2. In the following the chassis2is generally considered as being fixed in position so motion of other components is described relative to the chassis2. A syringe3, e.g. a Hypak syringe, with a hollow injection needle4is arranged in a proximal part of the auto-injector1. When the auto-injector1or the syringe3is assembled a protective needle sheath5is attached to the needle4. A stopper6is arranged for sealing the syringe3distally and for displacing a liquid medicament M through the hollow needle4. The syringe3is held in a tubular carrier7and supported at its proximal end therein. The carrier7is slidably arranged in the chassis2.

A drive spring8in the shape of a compression spring is arranged in a distal part of the carrier7. A plunger9serves for forwarding the force of the drive spring8to the stopper6.

The drive spring8is loaded between a distal carrier end face10of the carrier7and a thrust face11arranged distally on the plunger9.

The carrier7is a key element housing the syringe3, the drive spring8and the plunger9, which are the components required to eject the medicament M from the syringe3. These components can therefore be referred to as a drive sub-assembly.

The chassis2and the carrier7are arranged within a tubular case12. A trigger button13is arranged at a distal end of the case12. In a plunger release mechanism27a peg14protrudes from a distal end face of the trigger button13in the proximal direction P between two resilient arms15originating from the distal carrier end face10thus preventing them from flexing towards each other in an initial state A illustrated inFIG.15A. InFIG.15Aonly one of the resilient arms15is shown to illustrate the principle. Outwardly the resilient arms15are caught in respective first recesses16in a distal plunger sleeve17attached distally to the thrust face11and arranged inside the drive spring8. The engagement of the resilient arms15in the first recesses16, forming a releasable form-locking connection between the plunger9and the carrier7, prevents axial translation of the plunger9relative to the carrier7. The resilient arms15are ramped in a manner to flex them inwards on relative motion between the plunger9and the carrier7under load of the drive spring8, which is prevented by the peg14in the initial state A.

The carrier7is locked to the chassis2for preventing relative translation by a detent mechanism18illustrated in more detail inFIGS.11A to11D.

The trigger button13is initially engaged to the case12by a button release mechanism26and cannot be depressed. The button release mechanism26is illustrated in detail inFIGS.16A to16C. Referring now toFIG.16Athe button release mechanism26comprises a resilient proximal beam13.1on the trigger button13, the proximal beam13.1having an outward first ramp13.2and an inward second ramp13.3. In an initial state A illustrated inFIG.16Athe outward first ramp13.2is engaged in a ramped first case detent12.1preventing the trigger button13from moving out of the distal end D. The trigger button13proximally abuts both the case12and the carrier7hence being prevented from being depressed in the proximal direction P.

Referring again toFIGS.1A and1Ba control spring19in the shape of another compression spring is arranged around the carrier7and acts between a proximal first collar20and a distal second collar21. The control spring19is used to move the carrier7and hence the drive sub-assembly in the proximal direction P for needle insertion or in the distal direction D for needle retraction.

In the state as delivered as shown inFIGS.1aand1ba cap22is attached to the proximal end of the case12and the protective needle sheath5is still in place over the needle4and the needle hub. An inner sleeve22.1of the cap22is arranged inside the chassis2and over the protective needle sheath5. In the inner sleeve22.1a barb23is attached. The barb23is engaged to the protective needle sheath5for joint axial translation.

A sequence of operation of the auto-injector1is as follows:

A user pulls the cap22from the proximal end of the case12. The barb23joins the protective needle sheath5to the cap22. Hence, the protective needle sheath5is also removed on removal of the cap22.FIGS.2A and2Bshow the auto-injector1with the cap22and needle sheath5removed. The carrier7and syringe3are prevented from moving in the proximal direction P by the detent mechanism18being in a state A as inFIG.11A. Referring now toFIG.11A, the detent mechanism18comprises a resilient beam2.1on the chassis2with an inwardly protruding first beam head2.2. The first beam head2.2has a proximal third ramp2.3. The detent mechanism18further comprises a rhomboid ramp member7.1on the carrier7having a proximal fourth ramp7.2and a distal fifth ramp7.3. In state A a rounded off distal side of the first beam head2.2abuts the ramp member7.1in the distal direction D resisting movement of the carrier7in the proximal direction P relative to the chassis2. A rib on the case12is provided for preventing outward deflection of the resilient beam2.1thereby also preventing motion of the carrier7relative to the chassis2.

Referring again toFIGS.2A and2Bthe user grabs the case12and places the chassis2protruding from the case12at the proximal end P against an injection site, e.g. a patient's skin. As the auto-injector1is pressed against the injection site the case12translates in the proximal direction P relative to the chassis2into an advanced position as illustrated inFIGS.3A and3B. The second collar21is locked to the case12and is moved with the case12relative to the chassis2and relative to nearly all other components of the auto-injector1thus slightly compressing the control spring19against the first collar20which is prevented from moving in the proximal direction P by the chassis2due to a needle insertion control mechanism24being in a state A illustrated in detail inFIG.12A. Referring now toFIG.12A, a resilient member in the shape of an arrowhead20.1is proximally arranged on the first collar20. The first collar20with the arrowhead20.1is being forced in the proximal direction P under load of the compressed control spring19. An outward sixth ramp20.2on the arrowhead20.1interacts with a second distal seventh ramp2.4on the chassis2ramping the arrowhead20.1in an inward direction I which is prevented by the arrowhead20.1inwardly abutting the carrier7. Hence, the first collar20cannot translate in the proximal direction P.

Referring again toFIGS.3A and3Bthe second collar21is locked to the case due to a syringe retraction control mechanism25being in a state A illustrated in detail inFIG.13A. Referring now toFIG.13A, the syringe retraction control mechanism25comprises a resilient proximal beam21.1on the second collar21, the proximal beam21.1having a second beam head21.2having an inward boss21.3and a distal outward eighth ramp21.4. The distal outward eighth ramp21.4is engaged in a ramped second case detent12.2in a manner ramping the second beam head21.1in the inward direction I with the second collar21under load of the control spring19in the distal direction D which is prevented by the inward boss21.3inwardly abutting the carrier7.

Referring again toFIGS.3A and3B, if the user was to move the case12away from the injection site, the control spring19expands returning the auto-injector1to the initial condition after removal of the cap22as illustrated inFIGS.2A and2B.

In the state as inFIGS.3A and3Bthe carrier7continues to be prevented from moving in the proximal direction P by the detent mechanism18, however with the case12in its advanced position the detent mechanism18is unlocked as the rib on the case12has also moved and no longer prevents outward deflection of the resilient beam2.1. Movement of the case12relative to the carrier7, which is locked to the chassis2by the detent mechanism18, causes the button release mechanism26to switch to a state B illustrated inFIG.16B. The trigger button13cannot translate with the case12in the proximal direction P as it is abutted against the carrier7. The ramp on the first case detent12.1interacts with the outward first ramp13.2on the proximal beam13.1on the trigger button13deflecting the proximal beam13.1in the inward direction I thus engaging the inward second ramp13.3on the proximal beam13.1in a ramped carrier detent7.4arranged in the carrier7. As the case12is translated further in the proximal direction P it supports the proximal beam13.1outwardly thus locking the trigger button13to the carrier7. The trigger button13now protrudes from the distal end D of the chassis12and is ready to be pressed.

In the state as inFIGS.3A and3Bthe user depresses the trigger button13in the proximal direction P. As the trigger button13abuts against the carrier7the carrier7is pushing in the proximal direction P against the chassis2, the carrier7and the chassis2interacting in the detent mechanism18. The force exerted by the user pressing the trigger button13is resolved through the chassis2onto the injection site, not between the trigger button13and the case12. The detent mechanism18provides a resistive force when the user pushes the trigger button13. Once the user applies a force which exceeds a pre-determined value the detent mechanism18releases, initiating the injection cycle. Referring now toFIG.11Bshowing the detent mechanism18in a state B, the resilient beam2.1on the chassis2begins to bow under load from the rhomboid ramp member7.1on the carrier7, storing elastic energy. Despite the proximal fourth ramp7.2on the ramp member7.1friction between the contacting faces of the first beam head2.2and the proximal fourth ramp7.2prevents movement of the first beam head2.2in the outward direction O until the straightening force in the resiliently deformed beam2.1is sufficiently large to overcome it. At this point the resilient beam2.1is deflected in the outward direction O moving out of the way of the carrier7thus allowing the carrier7to translate in the proximal direction P. When the carrier7travels sufficiently far in the proximal direction P the rhomboid ramp member7.1on the carrier7passes under the first beam head2.2thus allowing it to relax and move back in the inward direction I distally behind the rhomboid ramp member7.1in a state C illustrated inFIG.11Cat the same time constraining translation of the carrier7in the distal direction D relative to the chassis2.

Once the carrier7slides far enough in the proximal direction P relative to the first collar20the needle insertion control mechanism24is switched to a state B as illustrated inFIG.12B. InFIG.12Bthe carrier7has been translated in the proximal direction P in such a manner that the arrowhead20.1on the first collar20is no longer inwardly supported. This may be achieved by a second recess7.5in the carrier7. The arrowhead20.1is now deflected in the inward direction I into the second recess7.5under load of the control spring19arriving at a state C as illustrated inFIG.12C. The first collar20is now decoupled from the chassis2. Instead, the arrowhead20.1couples the first collar20to the carrier7by an inward ninth ramp20.3engaging a distal tenth ramp7.6on the carrier7at the proximal end of the second recess7.5. Hence, the control spring19continues moving the carrier7in the proximal direction P from this point. Whilst the user advances the needle4by a proportion of its travel, the control spring19takes over insertion before the needle4protrudes from the proximal end P. Therefore the user experience is that of pressing a button, rather than manually inserting a needle.

The detent mechanism18relies on the user applying a force rather than a displacement. Once the force applied exceeds the force required to switch the detent the user will push the trigger button13fully, ensuring that the first collar20will always switch. If the user fails to pass the detent, the trigger button13returns to its unused state ready for use as illustrated inFIGS.3A and3B. This feature avoids the auto-injector1arriving in an undefined state.

FIGS.4A and4Bshow the auto-injector1with the trigger button13depressed sufficiently for the control spring19to couple on to the carrier7and continue moving the carrier7forwards, but not yet abutting the case12.

The carrier7coupled to the first collar20is translated in the proximal direction P driven by the control spring19. As the syringe3is arranged for joint axial translation with the carrier3the syringe3and needle4are also translated resulting in the needle4protruding from the proximal end P and being inserted into the injection site. The trigger button13returns to its initial position relative to the case12and latches back to the case12from the carrier7as in state A inFIG.16A. The carrier7translates further in the proximal direction P preventing inward deflection of the proximal beam13.1so the outward first ramp13.2cannot disengage from the first case detent12.1.

Immediately prior to the needle4reaching full insertion depth as illustrated inFIGS.5A and5Bthe peg14on the trigger button13is completely pulled out from between the resilient arms15on the carrier7. Hence, the plunger release mechanism27arrives in a state B shown inFIG.15Bwith the resilient arms15no longer inwardly supported by the peg14. Due to the ramped engagement of the resilient arms15in the first recess16they are deflected in the inward direction I under load of the drive spring8arriving in a state B illustrated inFIG.15C. The engagement between the resilient arms15on the carrier7and the first recess16in the distal plunger sleeve17of the plunger9together form a releasable form-locking connection between the plunger9and the carrier7. Hence, the plunger9is released from the carrier7and driven in the proximal direction P by the drive spring8, ready to inject the medicament M. The force to pull the peg14out from between the resilient arms15is provided by the control spring19while the force required to deflect the resilient arms15out of engagement to the plunger9is provided by the drive spring8.

While the plunger9moves and closes a gap to the stopper6the movement of the carrier7in the proximal direction P is completed by the control spring19pushing the first collar20. As the carrier7moves with respect to the chassis2during needle insertion the needle insertion mechanism24arrives in a state D illustrated inFIG.12D. The arrowhead20.1has moved with the carrier7and is still kept inwardly deflected by the chassis2thus preventing the first collar20from disengaging the carrier7. The arrowhead20.1must be able to deflect in the outward direction O to allow retraction which will be discussed below. In order to allow outward deflection the arrowhead20.1travels proximally beyond the part of the chassis2shown inFIGS.12A to12Fnext to an aperture2.5in the chassis2. However, as long as the case12is being kept pressed against the injection site and not allowed to return in the distal direction D beyond a predefined distance under load of the control spring19the arrowhead20.1will be kept from deflecting in the outward direction O by a first rib12.3on the case12(not illustrated inFIGS.12Ato F, seeFIGS.5A to8A) during about the second half of its motion for needle insertion.

The needle4is now fully inserted into the injection site as illustrated inFIGS.6A and6B. The time between the trigger button13pressed and the needle4being fully inserted is very short, however several mechanical operations take place in this time. The needle insertion depth is defined by the carrier7relative to the chassis2not relative to the case12, so if the user flinches or fails to hold the auto-injector I hard against the skin, only the case12will move in the distal direction D while the injection depth remains constant.

As soon as the plunger9has closed the gap to the stopper6under force of the drive spring8the stopper6is pushed in the proximal direction P within the syringe3displacing the medicament M through the needle4into the injection site.

Immediately prior to the end of injection with the stopper6having almost bottomed out in the syringe3as illustrated inFIGS.7A and7Ba noise component28is released. The stack up of tolerances, most notably due to the syringe3requires that the noise must always be released prior to the end of injection. Otherwise, with certain combinations of parts, the noise would not always release. The noise component28comprises an elongate portion28.1arranged within the distal plunger sleeve17and a distal end plate28.2arranged between the carrier end face10and an end face of the trigger button13. Two second resilient arms30originate from the distal carrier end face10and extend in the proximal direction P. A noise spring29is arranged to bias the noise component28in the distal direction D relative to the carrier7by proximally bearing against a rib on the second resilient arms30and distally against the noise component28(not illustrated).

Note: the noise component28is not illustrated inFIGS.16A, B and C for clarity since it does not affect the function of the button release mechanism26. A noise release mechanism31for releasing the noise component28is schematically illustrated inFIGS.14A,14B and14C. Referring now toFIG.14A, the noise release mechanism31comprises the second resilient arms30. A ramped inward boss30.1is arranged on each second resilient arm30which is engaged to a respective outward eleventh ramp28.3on the elongate portion28.1of the noise component28in such a manner that the second resilient arm30is deflected in the outward direction O under load of the noise spring29. In an initial state A of the noise release mechanism31the second resilient arms30are prevented from being outwardly deflected by outward support of the distal plunger sleeve17thus preventing translation of the noise component28relative to the carrier7. The noise release mechanism31remains in state A until immediately prior to the end of injection with the stopper6having almost bottomed out in the syringe3as illustrated inFIGS.7A and7B. At this point the plunger9has been translated in the proximal direction P relative to the carrier7to such an extent that the second resilient arms30are no longer supported by the distal plunger sleeve17. The noise release mechanism31has thus arrived in a state B illustrated inFIG.14B. Due to the ramped engagement between the ramped inward boss30.1and the outward eleventh ramp28.3the second resilient arm30is outwardly deflected under load of the noise spring29thus disengaging the noise component28from the carrier7and allowing the noise component28to move in the distal direction D driven by the noise spring29in a state C illustrated inFIG.14C. Hence, the noise component28is accelerated in the distal direction D and the distal end plate28.2impacts on the inside of the trigger button13producing audible and tactile feedback to the user that the injection is about finished.

FIGS.8A and8Bshow the auto-injector1with the stopper6having entirely bottomed out in the syringe3.

As mentioned above the user is able to let the case12move by a few millimetres in the distal direction D under the force of the control spring19without affecting the position of the needle4as long as that motion is below a predefined distance. If the user wishes to end the injection, at any time, they must allow the case12to move in the distal direction D beyond that distance.FIGS.9A and9Bshow the auto-injector1lifted from the injection site with the case12moved all the way in the distal direction D so that the chassis2protrudes from the proximal end of the case12. As the case12is moved the first collar20releases the carrier7and then the second collar21releases from the case12and pulls the carrier7in the distal direction D. The sequencing of this switching is critical as retraction will fail if both collars20,21are attached to the carrier7at the same time. This is overcome by separating the switching of the collars20,21by a significant displacement of the case12.

The switching of the first collar20is illustrated inFIGS.12Eand F. InFIG.12Ethe case12has been allowed to move in the distal direction D under load of the control spring19during removal of the auto-injector1from the injection site. The first rib12.3(not illustrated, secFIG.9A) is removed from outwardly behind the arrowhead20.1. The first collar20is still being pushed in the proximal direction P by the control spring19. Due to the engagement of the inward ninth ramp20.3on the arrowhead20.1with the distal tenth ramp7.6on the carrier7the arrowhead20.1is deflected in the outward direction O into the aperture2.5of the chassis2(illustrated inFIGS.12A to12F), the needle insertion control mechanism24arriving in a state E as illustrated inFIG.12E, decoupling the first collar20from the carrier7and latching it to the chassis2.

As the case12is moving further in the distal direction D on removal from the injection site the syringe retraction control mechanism25switches from its state A (cf.FIG.13A) into a state B illustrated inFIG.13B. The case12and the second collar21locked to the case12move together in the distal direction D while the carrier7is held in place by the detent mechanism18in its state C as described above (cf.FIG.11C). Due to this motion the inward boss21.3on the second beam head21.2of the proximal beam21.1on the second collar21no longer inwardly abuts the carrier7. Instead the inward boss21.3is deflected in the inward direction I into a third recess7.7in the carrier7due to the ramped engagement of the second beam head21.1to the ramped second case detent12.2under load of the control spring19. The syringe retraction control mechanism25thus arrives in a state C as illustrated inFIG.13Cwith the second collar21decoupled from the case12and coupled to the carrier7. The detent mechanism18applies a small retarding force to the movement of the carrier7before the syringe retraction control mechanism25switches to state C as there is a small sliding force, applied by the second collar21, pulling the carrier7in the distal direction D on translation of the case12in the distal direction D when the needle insertion control mechanism24has already been switched into state E. If the carrier7moves too far in the distal direction D before the second collar21switches, the case12runs out of travel before the inward boss21.3can deflect into the third recess7.7preventing retraction.

Starting from the position C of the detent mechanism18(cf.FIG.11C) the carrier7and hence the rhomboid ramp member7.1are translated in the distal direction D under load of the control spring19. Hence, the distal fifth ramp7.3of the rhomboid ramp member7.1engages the proximal third ramp2.3on the first beam head2.2of the resilient beam2.1in a manner deflecting the resilient beam2.1in the inward direction I. This applies the small retarding force to the movement of the carrier7required for ensuring the switching of the second collar21to the carrier7. The resilient beam2.1and the rhomboid ramp member7.1are offset sideways to allow the resilient beam2.1to pass without contacting the rhomboid ramp member7.1as soon as the first beam head2.2is entirely inwardly from the ramp member7.1in a state D illustrated inFIG.11D.

The control spring19is grounded at its proximal end in the case by the first collar20being abutted against the chassis2. The distal end of the control spring19moves the second collar21in the distal direction D taking with it the carrier7and hence the syringe3with the needle4overcoming the detent mechanism18as illustrated inFIG.11D. Note that the needle4is retracted out of the skin by the auto-injector1as soon as the user allows the case12to translate sufficiently far as opposed to auto-injectors with needle shields which require the user to remove the auto-injector from the injection site thereby themselves pulling the needle out of the skin for allowing the needle shield to advance.

As the movement allowed of the noise component28is limited relative to the carrier7it is no longer in contact with the trigger button13which has moved in the distal direction D with the case12on removal from the injection site. When the retraction begins the noise spring29does not provide any retarding force. Once the noise component28hits the trigger button13again on retraction of the carrier7the noise spring29must be recompressed, reducing the force driving the final part of retraction. In order to ensure a reliable retraction despite this reducing force the control spring19must be appropriately dimensioned.

The retraction ends when the distal collar21meets a first back stop12.4on the case12as inFIGS.10A and10B. The arrowhead20.1on the first collar20is inwardly supported by the carrier7in a state F illustrated inFIG.12Fand thus prevented from deflecting in the inward direction I. The outward sixth ramp20.2of the arrowhead20.1is engaged behind the first rib12.3on the case12preventing the case12from being pushed in the proximal direction P again. A clearance may be provided between the arrowhead20.1and the first rib12.3to allow for tolerances.

The detent mechanism18returns to state A as inFIG.11Alocking the carrier7in position relative to the chassis2as it did initially, however it cannot be unlocked now as the case12cannot move relative to the chassis2.

A tab20.4on the first collar20is now visible through an indicator window32in the case12—indicating the auto-injector1has been used.

FIG.17is an isometric view of an alternative embodiment of the plunger release mechanism27. The plunger release mechanism27prevents movement of the plunger9in the proximal direction P relative to the carrier7until the carrier7is moved in the proximal direction P for needle insertion. As opposed to the plunger release mechanism27ofFIG.15, where relative movement of the carrier7and trigger button13are used to trigger the release of the plunger9, the alternative embodiment ofFIG.17releases the plunger9by movement of the carrier7relative to the second collar21.FIG.17illustrates the plunger release mechanism27prior to plunger release. The second collar21is shown transparent to improve clarity. The plunger9is being pushed in the proximal direction P by the drive spring8. In order for the plunger9to advance, it must rotate around a twelfth ramp7.8on the carrier7. A ramp member9.1on the plunger9is arranged to engage this twelfth ramp7.8. Rotation of the ramp member9.1is blocked by an inward longitudinal rib21.5on the second collar21splined in a longitudinal aperture7.9in the carrier7. The case12and the second collar21remain in the same position, i.e. coupled to each other for joint axial translation. Accordingly, the case12and the second collar21, coupled to the case12for joint axial translation, together form a releasable form-locking connection between the plunger9and the case12. On depression of the trigger button13the carrier13and the plunger9being part of the drive sub-assembly are moved in the proximal direction P, first by the user pressing the trigger button13and then by the control spring19taking over via the first collar20as described above. Once the carrier7moves sufficiently far in the proximal direction P relative to the second collar21the ramp member9.1on the collar9comes clear of the longitudinal rib21.5on the second collar21and can rotate past the proximal end of the longitudinal rib21.5due to its ramped engagement to the twelfth ramp7.8under load of the drive spring8. Hence, the drive spring8advances the plunger9in the proximal direction P for injecting the medicament M. Accordingly, the releasable form-locking connection between the plunger9and the case12can be released when the ramp9.1of the plunger9clears the rib21.5on the second collar21.

FIG.18is a longitudinal section of an alternative embodiment of the button release mechanism26. Other than the button release mechanism26ofFIG.16which gives the appearance of a revealing trigger button13on skin contact by switching the ground of the trigger button13between the carrier7and the case12, the button release mechanism26ofFIG.18starts with the trigger button13locked but protruding from the distal end of the case12. Once the carrier7has moved in the distal direction D on skin contact of the chassis2, it is possible to depress the trigger button13and activate the auto-injector1. This ensures a sequenced operation.

In the embodiment ofFIG.18the trigger button13has two proximal beams13.1, each of them having a ramped outward boss13.4. In the initial state shown inFIG.18the ramped outward bosses13.4are engaged in respective fourth recesses12.5in the case12. Disengaging the ramped outward bosses13.4from the fourth recesses12.5is prevented by the carrier7inwardly supporting the proximal beams13.1in a manner to keep the proximal beams13.1from deflecting inwardly. Inward protrusions13.5on the proximal beams13.1abut against a second rib7.10on the carrier7in a manner preventing the carrier7from moving further in the proximal direction P in the initial state. Once the carrier7has moved in the distal direction D on skin contact of the chassis2a first window7.11in the carrier7is moved behind the inward protrusion13.5so as to allow the proximal beams13.1to be inwardly deflected due to their ramped engagement in the fourth recesses12.5on depression of the trigger button13. The proximal beams13.1are now outwardly supported by the case12and remain engaged to the carrier7even on retraction of the needle4. The trigger button13does therefore not return to its initial position, indicating that the auto-injector1has been used.

The button release mechanism26illustrated inFIG.18may preferably be combined with the plunger release mechanism27illustrated inFIG.17.

FIGS.19A and19Bshow two longitudinal sections of an alternative embodiment of the detent mechanism18. The detent mechanism18ofFIGS.11A to11D, which may be referred to as a “race track” mechanism because of the first beam head2.2travelling around the rhomboid ramp member7.1has multiple functions which control the movement of the carrier7relative to the chassis2. The alternative detent mechanism18ofFIGS.19A and19Buses three clips7.12,7.13,2.6to produce the same effect.

The first clip7.12is arranged as an outwardly biased resilient beam on the carrier7extending from the carrier7in the proximal direction P. the first clip7.12is arranged to prevent the carrier7from being moved in the proximal direction P prior to the chassis2being depressed or rather the case12being translated on skin contact. The first clip7.12is composed of two sections side by side. A first section7.14prevents movement of the carrier7in the proximal direction P by abutting the chassis2in a recess. A second section7.15is arranged as an outwardly protruding clip head arranged to be ramped inwards by a ramp feature12.6on the chassis12for releasing the first clip7.12thereby unlocking the carrier7from the chassis2when the case12is being translated in the proximal direction P on skin contact. A longitudinal slot2.7in the chassis2is arranged for allowing the second section7.15to slide in the proximal direction P once the lock has been released. A slight friction force between the first clip7.12and the chassis2provides the retarding force required to ensure retraction.

The second clip7.13is arranged as a resilient beam on the carrier7extending in the distal direction D having an outwardly protruding third beam head7.16with a proximal ramp. The third beam head7.16serves as a back stop against a third rib2.9on the chassis2for preventing the carrier7moving in the distal direction D from its initial position. The carrier7and chassis2are assembled with the second clip7.13in this position prior to inserting the syringe3into the carrier7which is facilitated by the proximal ramp on the third beam head7.16. The syringe3locks the clip in place by preventing inward deflection thus creating a fixed stop.

The third clip2.6is a resilient beam on the chassis2extending in the distal direction D. A ramped fourth beam head2.8on the third clip2.6is arranged to inwardly engage in a fifth recess7.17in the carrier7. Once the first clip7.12is unlocked, the user can load the third clip2.6by pressing the carrier7in the proximal direction P on depression of the trigger button13. The third clip2.6is loaded in compression, i.e. it will bend outwards and release suddenly due to its ramped engagement to the carrier7providing the detent functionality similar to that illustrated inFIG.11B.

FIG.20is a longitudinal section of a third embodiment of the detent mechanism18which is a variation on the embodiment ofFIGS.19A and19B. In this embodiment the detent function of the third clip2.6has been added into the first clip7.12. The lock between the case12and the carrier7is released in the same way, but the detent is provided by deflecting the first clip7.12inwards a second level which is achieved by the chassis2not having a slot2.7for the second section7.15. Instead the second section7.15, once ramped inwards by the ramp feature12.6on the case12has to be further ramped inwards inside the chassis2on axial load between the chassis2and the carrier7, suddenly releasing their engagement.

FIG.21is a longitudinal section of an alternative embodiment of the noise release mechanism31. As opposed to the noise release mechanism31ofFIG.14where the noise spring29acts between the carrier7and the noise component28, in the embodiment illustrated inFIG.21the noise spring29acts between the case12and the noise component28. During needle insertion the noise spring29is compressed as the noise component28moves with the carrier7relative to the case12. When the noise component28is released by the plunger9shortly before the end of dose, the noise component28moves in the distal direction D and impacts the trigger button13. Other than inFIG.14the noise spring29is not being recompressed during needle retraction since it is grounded in the case12not in the carrier7.

FIGS.22A and22Bshow longitudinal sections of an alternative embodiment of the needle insertion control mechanism24which is also arranged to perform the detent function of the detent mechanism18on needle retraction and needle insertion.FIG.23shows a corresponding isometric view. A fourth clip20.5on the first collar20is arranged as a resilient beam with a beam head having an inward proximal thirteenth ramp20.6for engaging a fourth rib7.18on the carrier7and outwardly supported by the case12so as to keep the first collar20engaged to the carrier7prior to use, during needle insertion and during injection. When the user lifts the case12away from the injection site at the end of injection, a sixth recess12.7in the case12is moved outwardly behind the fourth clip20.5allowing the fourth clip20.5to release when the carrier7is pulled in the distal direction D by the second collar21. Since the fourth clip20.5has to be ramped outwards a small force is required to release the fourth clip20.5, providing the retraction detent.

A fifth clip2.10on the chassis2abuts a block20.7on the first collar20prior to use preventing the first collar20and hence the carrier7engaged to the first collar20from moving in the proximal direction P. In order to release, the fifth clip2.10must be deflected outwards and over the block20.7. Outward deflection of the fifth clip2.10is initially prevented by the case12. Once the case12has moved on skin contact a second window12.8in the case12appears outwardly from the fifth clip2.10allowing outward deflection. The fifth clip2.10is then deflected by a fourteenth ramp7.19on the carrier7when the carrier7is pushed in the proximal direction P on button depression as the fourth clip20.5does allow translation of the carrier7in the proximal direction P relative to the first collar20but not the other way round. The detent for needle insertion is provided by having to deflect the fifth clip2.10when it is loaded by the control spring19.

FIGS.24A and24Bshow longitudinal sections of a third embodiment of the needle insertion control mechanism24, also arranged to perform the functions of the detent mechanism18.FIG.25is an isometric view of the needle insertion control mechanism24ofFIG.24. The embodiment is similar to that illustrated inFIGS.22A,22B and23. The difference is that the fifth clip2.10is arranged on the first collar20and the block20.7is arranged on the chassis2, i.e. their position has been switched, so there are two clips2.10and20.5on the first collar20.

The fourth clip20.5is identical to that inFIG.22B. It keeps the first collar20connected to the carrier7until the needle retraction is triggered, ensuring full injection depth is reached and maintained until the retraction cycle is initiated by removing the auto-injector1from the skin.

The fifth clip2.10provides the detent for needle insertion and releases the first collar20from the chassis2, initiating needle insertion. The fifth clip2.10prevents the first collar20and hence the carrier7engaged to the first collar20from moving in the proximal direction P prior to use by abutting the block20.7on the chassis2. In order to release, the fifth clip2.10must be deflected outwards and over the block20.7. Outward deflection of the fifth clip2.10is initially prevented by the case12. Once the case12has moved on skin contact the second window12.8in the case12appears outwardly from the fifth clip2.10allowing outward deflection. The fifth clip2.10is then deflected by the fourteenth ramp7.19on the carrier7when the carrier7is pushed in the proximal direction P on button depression as the fourth clip20.5does allow translation of the carrier7in the proximal direction P relative to the first collar20but not the other way round. The detent for needle insertion is provided by having to deflect the fifth clip2.10when it is loaded by the control spring19.

FIGS.26A and26Bshow a longitudinal section of a third embodiment of the noise release mechanism31. This embodiment works without the need for a dedicated noise spring. The plunger9comprises a proximally ramped rib9.2arranged to splay two seventh clips7.21on the carrier7immediately prior to the end of dose. When the proximally ramped rib9.2has travelled past the seventh clips7.21they snap back and impact the plunger9generating a sound. The tubular shape of the carrier7helps to transmit the sound.FIG.26Ashows the noise release mechanism31before release.FIG.26Bshows the noise release mechanism31after release. Proximal faces of the seventh clips7.21on the carrier7are axially offset to facilitate assembly by lifting the seventh clips7.21over the distal side of the proximally ramped rib9.2one by one.

FIGS.27A and27Bshow longitudinal sections of another embodiment of the auto-injector1in different section planes, the different section planes approximately 90° rotated to each other, wherein the auto-injector1is in an initial state prior to starting an injection. The auto-injector1is essentially identical to the one described inFIGS.1to16. However, other than the auto-injector ofFIGS.1to16the auto-injector1of this embodiment has a wrap-over sleeve trigger instead of a trigger button.

The wrap-over sleeve trigger12is the same component as the case12which has a closed distal end face12.10other than the one inFIGS.1to16. An internal trigger button13is arranged at the distal end inside the sleeve trigger12. Other than inFIGS.1to16the trigger button13is not visible nor does it protrude from the case12in any state. In the initial state a clearance33is provided between the distal end face12.10of the sleeve trigger12and the internal trigger button13allowing for some travel of the sleeve trigger12without interfering with the trigger button13.

As the auto-injector1does not differ from the auto-injector ofFIGS.1to16in other respects it is essentially operated in the same way with the following exceptions:

As the chassis2is placed against the injection site the sleeve trigger12translates in the proximal direction P relative to the chassis2into the advanced position in a first phase of sleeve travel removing the clearance33between the distal end face12.10of the sleeve trigger12and the internal trigger button13. As in the embodiment ofFIGS.1to16this motion unlocks the detent mechanism18and the trigger button13. As the user continues to depress the sleeve trigger12in a second phase of sleeve travel thereby further advancing it in the proximal direction P the distal end face12.10hits the internal trigger button13thereby depressing it until the first collar20is released from the chassis2and the control spring force is coupled on to the carrier7. The carrier7then advances until the internal trigger button13stops on another rib in the case12and the plunger release mechanism27is released (note the peg14is shorter in this embodiment.

From a user perspective, the detent mechanism18is arranged to provide a resistive force when the user reaches the second phase of sleeve travel. Internally, there is no difference to the embodiment ofFIGS.1to16at this point.

Needle insertion is triggered by the user fully advancing the sleeve trigger12in the second phase of sleeve travel thereby fully depressing the internal trigger button13and overcoming the detent mechanism as in the embodiment ofFIGS.1to16.

As the control spring19takes over on button depression fully advancing the carrier7for needle insertion the internal trigger button13bottoms out on an internal fifth rib12.11in the sleeve trigger12and the internal trigger button13switches back to being locked to the sleeve trigger12as inFIG.16C.

The embodiment ofFIGS.27A and27Bmay also be combined with the alternative features illustrated inFIGS.17to26.

It goes without saying that in all ramped engagements between two components described in the above embodiments there may be just one ramp on one or the other component or there may be ramps on both components without significantly influencing the effect of the ramped engagement.