Auto-Injector

Abstract

An auto-injector for administering a dose of a liquid medicament (M) is presented having an elongate case, a carrier subassembly comprising a tubular carrier slidably arranged inside the case, where the carrier adapted to contain a syringe with a hollow injection needle. The injector also has, a drive spring and a plunger for forwarding load of the drive spring to a stopper of the syringe, wherein the syringe is lockable for joint axial translation with the carrier. A control spring is arranged around the carrier for translating the carrier in a proximal direction (P) for advancing the needle beyond a proximal end of the auto-injector, and a trigger button is used for releasing the control spring on actuation.

1 . Auto-injector ( 1 ) for administering a dose of a liquid medicament (M), comprising:
 an elongate case ( 12 ),   a carrier subassembly comprising a tubular carrier ( 7 ) slidably arranged inside the case ( 12 ), the carrier ( 7 ) adapted to contain a syringe ( 3 ) with a hollow injection needle ( 4 ), a drive spring ( 8 ) and a plunger ( 9 ) for forwarding load of the drive spring ( 8 ) to a stopper ( 6 ) of the syringe ( 3 ), wherein the syringe ( 3 ) is lockable for joint axial translation with the carrier ( 7 ),   a control spring ( 19 ) arranged around the carrier ( 7 ) for translating the carrier ( 7 ) in a proximal direction (P) for advancing the needle ( 4 ) beyond a proximal end of the auto-injector ( 1 ),   a trigger button ( 13 ) for releasing the control spring ( 19 ) on actuation,   
       wherein the drive spring ( 8 ) biases the plunger ( 9 ) in the proximal direction (P) against the carrier ( 7 ), wherein at least one resilient arm ( 15 ) is arranged on either the carrier ( 7 ) or the plunger ( 9 ) and in a ramped engagement to the other of the carrier ( 7 ) or the plunger ( 9 ) so as to disengage them under load of the drive spring ( 8 ), wherein a peg ( 14 ) is arranged to be coupled to the case ( 12 ) at least after actuation of the trigger button ( 13 ) so as to be positioned to support the resilient arm ( 15 ) preventing disengagement of the carrier ( 7 ) from the plunger ( 9 ) and thus release of the drive spring ( 8 ) when the carrier ( 7 ) is in a distal position, wherein the peg ( 14 ) is arranged to remain in position when the carrier ( 7 ) is translated for advancing the needle ( 4 ) so as to pull the resilient arm ( 15 ) away from the peg ( 14 ) thus allowing deflection of the resilient arm ( 15 ) due to the ramped engagement under load of the drive spring ( 8 ) for disengaging the plunger ( 9 ) from the carrier ( 7 ) and releasing the drive spring ( 8 ) for drug delivery when the carrier ( 7 ) has reached a predefined position during needle advance. 
     
     
         2 . Auto-injector ( 1 ) according to  claim 1 , characterized in that the trigger button ( 13 ) is arranged distally on the case ( 12 ), wherein the peg ( 14 ) protrudes from a distal end face of the trigger button ( 13 ) in the proximal direction (P), wherein the trigger button ( 13 ) abuts the case ( 12 ) after actuation so as to remain in position relative to the case ( 12 ) when the carrier ( 7 ) is translated for advancing the needle ( 4 ). 
     
     
         3 . Auto-injector ( 1 ) according to  claim 2 , characterized in that the distally arranged trigger button ( 13 ) is at least initially coupled to the carrier ( 7 ), wherein the case ( 12 ) is arranged to abut the trigger button ( 13 ) in an initial state preventing depression of the trigger button ( 13 ), wherein on translation of the case ( 12 ) into an advanced position relative to the carrier ( 7 ) the trigger button ( 13 ) remains coupled to the carrier ( 7 ) thus emerging from the case ( 12 ) so as to allow depression for starting an injection cycle. 
     
     
         4 . Auto-injector ( 1 ) according to  claim 2 , characterized in that the trigger button ( 13 ) is arranged distally, wherein the case ( 12 ) is arranged as a wrap-over sleeve trigger having a closed distal end face ( 12 . 10 ) covering the trigger button ( 13 ), wherein in an initial state a clearance ( 33 ) is provided between the distal end face ( 12 . 10 ) of the sleeve trigger ( 12 ) and the trigger button ( 13 ) allowing for some travel of the sleeve trigger ( 12 ) against the bias of the control spring ( 19 ) in the proximal direction (P) in a first phase before abutting the trigger button ( 13 ). 
     
     
         5 . Auto-injector ( 1 ) according to  claim 1 , characterized in that the peg ( 14 ) is attached to the case ( 12 ). 
     
     
         6 . Auto-injector ( 1 ) according to one of the previous claims, characterized in that the control spring ( 19 ) is released by activating a needle insertion control mechanism ( 24 ) for coupling a proximal end of the control spring ( 19 ) to either the carrier ( 7 ) or to a chassis ( 2 ), wherein the trigger button ( 13 ) is operatively connected to the needle insertion control mechanism ( 24 ), so that actuation of the trigger button ( 13 ) decouples the proximal end of the control spring ( 19 ) from the chassis ( 2 ) and couples the proximal end of the control spring ( 19 ) to the carrier ( 19 ). 
     
     
         7 . Auto-injector ( 1 ) according to  claim 6 , characterized in that the needle insertion control mechanism ( 24 ) is adapted to decouple the proximal end of the control spring ( 19 ) from the carrier ( 7 ) and to couple the proximal end of the control spring ( 19 ) to the chassis ( 2 ) for needle retraction depending on the relative axial position of the carrier ( 7 ) and the chassis ( 2 ). 
     
     
         8 . Auto-injector ( 1 ) according to  claim 6  or  7 , characterized in that the needle insertion control mechanism ( 24 ) comprises a first collar ( 20 ) biased by the control spring in a proximal direction (P), wherein at least one resilient beam ( 20 . 1 ) is proximally arranged on the first collar ( 20 ), wherein respective recesses are arranged in the carrier ( 7 ) and case ( 2 ), wherein a transversal extension of a head of the resilient beam ( 20 . 1 ) is wider than a gap between the carrier ( 7 ) and the chassis ( 2 ) causing the head of the resilient beam ( 20 . 1 ) to abut a distal face on the recess in the chassis ( 2 ) while being prevented from deflecting in an inward direction (I) by the carrier ( 7 ) or to abut a distal face on the recess in the carrier ( 7 ) while being prevented from deflecting in an outward direction ( 0 ) by the chassis ( 2 ) thereby forwarding load from the control spring ( 19 ) to the carrier ( 7 ) for needle insertion, wherein the resilient beam ( 20 . 1 ) is arranged to be switched between the chassis ( 2 ) and the carrier ( 7 ) by ramped engagement of the head to the distal faces under load of the control spring ( 19 ) depending on the relative longitudinal position between the chassis ( 2 ) and the carrier ( 7 ). 
     
     
         9 . Auto-injector ( 1 ) according to one of previous claims, characterized in that the trigger button ( 13 ) is operatively connected to a detent mechanism ( 18 ) that is arranged to provide a resistive force which has to be overcome to advance the carrier ( 7 ) in the proximal direction (P) for needle insertion. 
     
     
         10 . Auto-injector ( 1 ) according to  claim 9 , characterized in that the detent mechanism ( 18 ) is arranged to provide a resistive force resisting translation of the carrier ( 7 ) in the distal direction (D) relative to the chassis ( 2 ) for keeping the carrier ( 7 ) in a defined position in a transitional state with both ends of the control spring ( 19 ) decoupled from the carrier ( 7 ). 
     
     
         11 . Auto-injector ( 1 ) according to one of the  claims 8  to  10 , characterized in that the detent mechanism ( 18 ) comprises a resilient beam ( 2 . 1 ) on the chassis ( 2 ) and a rhomboid ramp member ( 7 . 1 ) on the carrier ( 7 ), the resilient beam ( 2 . 1 ) being essentially straight when relaxed and having a first beam head ( 2 . 2 ) arranged to interact in a ramped engagement with a proximal fourth ramp ( 7 . 2 ) or a distal fifth ramp ( 7 . 3 ) on the rhomboid ramp member ( 7 . 1 ) in such a manner that application of a translative force on the carrier ( 7 ) relative to the chassis ( 2 ) in the proximal direction (P) with the first beam head ( 2 . 2 ) engaged to the fourth ramp ( 7 . 2 ) deflects the resilient beam ( 2 . 1 ) in one transversal direction (O, I) when a predetermined value of the translative force, at least depending on the resilience of the resilient beam ( 2 . 1 ), is overcome so as to allow the first beam head ( 2 . 2 ) to travel along one transversal side of the rhomboid ramp member ( 7 . 1 ) on continued relative translation of the components ( 2 ,  7 ), wherein the resilient beam ( 2 . 1 ) is allowed to relax when the first beam head ( 2 . 2 ) has reached the fifth ramp ( 7 . 3 ) thereby engaging it in a manner that application of a translative force on the carrier ( 7 ) in the distal direction (D) deflects the resilient beam ( 2 . 1 ) in the other transversal direction (I, O) when a predetermined value of the translative force, at least depending on the resilience of the resilient beam ( 2 . 1 ), is overcome so as to allow the first beam head ( 2 . 2 ) to travel along the other transversal side of the rhomboid ramp member ( 7 . 1 ) on continued translation of the carrier ( 7 ). 
     
     
         12 . Auto-injector ( 1 ) according to one of the  claims 8  to  11 , characterized in that the case ( 12 ) is arranged to lock the detent mechanism ( 18 ) prior to being translated in the proximal direction (P) relative to the chassis ( 2 ), wherein the case ( 12 ) when translated into an advanced position in the proximal direction (P) is arranged to unlock the detent mechanism ( 18 ) rendering it operable. 
     
     
         13 . Auto-injector ( 1 ) according to one of the previous claims, characterized in that a syringe retraction control mechanism ( 25 ) is arranged for coupling a distal end of the control spring ( 19 ) to either the carrier ( 7 ) for needle retraction or to the case ( 12 ) otherwise. 
     
     
         14 . Auto-injector ( 1 ) according to  claim 13 , characterized in that the syringe retraction control mechanism ( 25 ) comprises a second collar ( 21 ) bearing against the distal end of the control spring ( 19 ) and having a resilient proximal beam ( 21 . 1 ) with a second beam head ( 21 . 2 ) having an inward boss ( 21 . 3 ), wherein the second beam head ( 21 . 2 ) is arranged to be in a ramped engagement with a second case detent ( 12 . 2 ) in the case ( 12 ) in a manner ramping the second beam head ( 21 . 1 ) in the inward direction (I) under load of the control spring ( 19 ) in the distal direction (D), wherein the inward boss ( 21 . 3 ) is arranged to inwardly abut the carrier ( 7 ) for preventing inward deflection of the second beam head ( 21 . 1 ) and keep the second collar ( 21 ) locked to the case ( 12 ), wherein a third recess ( 7 . 7 ) is arranged in the carrier ( 7 ) for allowing the inward boss ( 21 . 3 ) to be inwardly deflected on translation of the case ( 12 ) in the distal direction (D) relative to the carrier ( 7 ) on removal of the auto-injector ( 1 ) from the injection site. 
     
     
         15 . Auto-injector ( 1 ) according to one of the preceding claims, characterized in that a releasable noise component ( 28 ) is provided, capable of, upon release, generating an audible and/or tactile feedback, wherein the noise component ( 28 ) is arranged to be released when the plunger ( 9 ) reaches a position relative to the syringe ( 3 ) in which the stopper ( 4 ) is located in proximity of a proximal end of the syringe ( 3 ), and wherein the released noise component ( 28 ) impacts on a housing component ( 12 ,  13 ) indicating the end of the injection.