Auto-Injector

Abstract

An auto-injector for administering a dose of a liquid medicament (M) is present having a tubular chassis telescopable in a tubular case, a carrier subassembly comprising a tubular carrier slidably arranged relative to the chassis inside the case, where the carrier is 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 insertion of the needle through the chassis into an injection site.

1 . Auto-injector ( 1 ) for administering a dose of a liquid medicament (M), comprising:
 a tubular chassis ( 2 ) telescopable in a tubular case ( 12 ),   a carrier subassembly comprising a tubular carrier ( 7 ) slidably arranged relative to the chassis ( 2 ) 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 insertion of the needle ( 4 ) through the chassis ( 2 ) into an injection site,   wherein the control spring ( 19 ) is arranged to bias the case ( 12 ) against the chassis ( 2 ) in a distal direction (D) so as to extend the chassis ( 2 ) out of a proximal end (P) of the case ( 12 ), wherein an insertion depth of the needle ( 4 ) is defined by the carrier ( 7 ) abutting the chassis ( 2 ) in a predefined position, wherein the case ( 12 ) is arranged to release or allow release of the control spring ( 19 ) for needle insertion on translation of the case ( 12 ) in the proximal direction (P) relative to the chassis ( 2 ) against the bias into an advanced position.   
     
     
         2 . Auto-injector ( 1 ) according to  claim 1 , characterized in that the carrier ( 7 ) is arranged to be translated in the distal direction (D) for retracting the needle ( 4 ) when the case ( 12 ) is moved in the distal direction (D) relative to the chassis ( 2 ) by a predefined distance. 
     
     
         3 . Auto-injector ( 1 ) according to one of the  claim 1  or  2 , characterized in that a trigger button ( 13 ) is arranged distally or laterally in or on the case ( 12 ), wherein a needle insertion control mechanism ( 24 ) is arranged for coupling a proximal end of the control spring ( 19 ) to either the carrier ( 7 ) for advancing it for needle insertion or to the chassis ( 2 ) for needle retraction depending on the relative axial position of the carrier ( 7 ) and the chassis ( 2 ), wherein a plunger release mechanism ( 27 ) is arranged for releasing the plunger ( 9 ) for injection when the carrier ( 7 ) has at least almost reached an injection depth during needle insertion, wherein a detent mechanism ( 18 ) is arranged for coupling the chassis ( 2 ) to the carrier ( 7 ) for joint axial translation relative to the case ( 12 ), wherein the detent mechanism ( 18 ) is arranged to decouple the chassis ( 2 ) from the carrier ( 7 ) upon actuation of the trigger button ( 13 ) thus allowing the carrier ( 7 ) to move relative to the chassis ( 2 ) so as to cause the needle insertion control mechanism ( 24 ) to switch the proximal end of the control spring ( 19 ) to the carrier ( 7 ) for needle insertion, wherein 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. 
     
     
         4 . Auto-injector ( 1 ) according to  claim 3 , 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 ). 
     
     
         5 . Auto-injector ( 1 ) according to one of the  claim 3  or  4 , characterized in that the plunger release mechanism ( 27 ) comprises at least one resilient arm ( 15 ) on the carrier ( 7 ) arranged to be in a ramped engagement to the plunger ( 9 ) so as to disengage them under load of the drive spring ( 8 ), wherein a peg ( 14 ) protrudes from a distal end face of the trigger button ( 13 ) in the proximal direction (P) in a manner 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 trigger button ( 13 ) is arranged to remain in position relative to the case ( 12 ) 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 advancement. 
     
     
         6 . Auto-injector ( 1 ) according to one of the  claims 3  to  5 , characterized in that the detent mechanism ( 18 ) 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. 
     
     
         7 . Auto-injector ( 1 ) according to one of the  claims 3  to  6 , 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 ). 
     
     
         8 . Auto-injector ( 1 ) according to one of the  claim 6  or  7 , 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 ). 
     
     
         9 . Auto-injector ( 1 ) according to one of the  claims 3  to  8 , 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 ) when the chassis ( 2 ) is being pressed against an injection site, 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. 
     
     
         10 . Auto-injector ( 1 ) according to one of the  claims 3  to  9 , 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 the initial state preventing depression of the trigger button ( 13 ), wherein on translation of the case ( 12 ) into the advanced position when the chassis ( 2 ) is being pressed against the injection site 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. 
     
     
         11 . Auto-injector ( 1 ) according to one of the  claims 3  to  10 , 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. 
     
     
         12 . Auto-injector ( 1 ) according to one of the  claims 3  to  11 , 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 ). 
     
     
         13 . Auto-injector ( 1 ) according to one of the  claims 3  to  12 , characterized in that a releasable noise component ( 28 ) is provided, capable of, upon release, generating an audible and/or tactile feedback to a user, 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 one component of the auto-injector ( 1 ) indicating the end of the injection. 
     
     
         14 . Auto-injector ( 1 ) according to  claim 13 , characterized in that the component of the auto-injector ( 1 ) comprises at least part of the chassis ( 2 ), the case ( 12 ), the trigger button ( 13 ), the carrier ( 7 ), the plunger ( 9 ) and/or the sleeve trigger ( 12 ). 
     
     
         15 . Auto-injector ( 1 ) according to one of the  claims 4  to  14 , characterized in that a visual use indicator is provided, comprising at least one indicator window ( 32 ) in the case ( 12 ), wherein a part of the chassis ( 2 ) is arranged to be located behind the indicator window ( 32 ) when the case ( 12 ) is in its distal position biased by the control spring ( 19 ), wherein a tab ( 20 . 4 ) on the first collar ( 20 ) is located outwardly from the part of the chassis ( 2 ) after the collar ( 20 ) has been translated in the proximal direction (P) during needle insertion, wherein the tab ( 20 . 4 ) and the part of the chassis ( 2 ) exhibit a visually distinctive feature.