Auto-Injector

Abstract

An auto-injector comprising an elongate housing containing a syringe. The housing having an orifice intended to be applied against an injection site. The syringe is slidably arranged with respect to the housing. A spring pushing the needle from a covered position into an advanced position, operating the syringe and covering the needle. An activator arranged to lock the spring prior to manual operation and capable of, upon manual operation, releasing the spring means for injection. A first gear arrangement and a second gear arrangement arranged fro converting torque from a first end and a second end of the torsion spring into a translative force. The first end groundable in the housing while the second end acts on a plunger through the second gear arrangement for advancing the needle and supplying the dose.

1 . Auto-injector ( 1 ) for administering a dose of a liquid medicament (M), comprising:
 an elongate housing ( 2 ) arranged to contain a syringe ( 7 ) with a hollow needle ( 19 ) and a stopper ( 10 ) for sealing the syringe ( 7 ) and displacing the medicament (M), the elongate housing ( 2 ) having a distal end (D) and a proximal end (P) with an orifice intended to be applied against an injection site, wherein the syringe ( 7 ) is slidably arranged with respect to the housing ( 2 ),   spring means ( 14 ) capable of, upon activation, pushing the needle ( 9 ) from a covered position inside the housing ( 2 ) into an advanced position through the orifice and past the proximal end (P), operating the syringe ( 7 ) to supply the dose of medicament (M), and covering the needle ( 19 ) on removal of the auto-injector ( 1 ) from the injection site,   activating means ( 4 ,  20 ,  24 ) arranged to lock the spring means ( 14 ) in a pressurized state prior to manual operation and capable of, upon manual operation, releasing the spring means ( 14 ) for injection,   
       characterized in that the spring means ( 14 ) is a single torsion spring ( 14 ). 
     
     
         2 . Auto-injector ( 1 ) according to  claim 1 , characterized in that a first gear arrangement ( 13 ,  13 . 1 ,  9 ) and a second gear arrangement ( 15 ,  11 . 1 ,  11 ) are arranged for respectively converting torque from a first end ( 14 . 1 ) and a second end ( 14 . 2 ) of the torsion spring ( 14 ) into a translative force, wherein the first end ( 14 . 1 ) is arranged to be groundable in the housing ( 2 ) while the second end ( 14 . 2 ) is configured to act on a plunger ( 11 ) through the second gear arrangement ( 15 ,  11 . 1 ,  11 ) for advancing the needle ( 19 ) and supplying the dose, wherein the activating means ( 4 ,  20 ,  24 ) is arranged to block or release the second gear arrangement ( 15 ,  11 . 1 ,  11 ) and wherein the first end ( 14 . 1 ) is releasable from the ground in the housing ( 2 ) for causing a translation through the first gear arrangement ( 13 ,  13 . 1 ,  9 ) resulting in the needle ( 19 ) getting covered. 
     
     
         3 . Auto-injector ( 1 ) according to  claim 2 , characterized in that a needle shroud ( 3 ) is arranged in the housing ( 2 ) surrounding the syringe ( 7 ) and translatable in longitudinal direction, wherein the needle shroud ( 3 ) is coupled to the first gear arrangement ( 13 ,  13 . 1 ,  9 ) in a manner to be translated in proximal direction (P) over the advanced needle ( 19 ) on release of the first end ( 14 . 1 ) from the ground in the housing ( 2 ). 
     
     
         4 . Auto-injector ( 1 ) according to  claim 3 , characterized in that the torque required to advance the needle shroud ( 3 ) is configured to be less than the torque required to advance the plunger ( 11 ) and the stopper ( 10 ). 
     
     
         5 . Auto-injector ( 1 ) according to one of the  claims 2  to  4 , characterized in that the first gear arrangement ( 13 ,  13 . 1 ,  9 ) and the second gear arrangement ( 15 ,  11 . 1 ,  11 ) respectively comprise a first gear member ( 13 ,  15 ) coupled to the respective end ( 14 . 1 ,  14 . 2 ) of the torsion spring ( 14 ), wherein the first gear member ( 13 ,  15 ) is engaged through a respective screw thread ( 13 . 1 ,  11 . 1 ) to a respective second gear member ( 9 ,  11 ) arranged to translate on rotation of the first gear member ( 13 ,  15 ). 
     
     
         6 . Auto-injector ( 1 ) according to  claim 5 , characterized in that the needle shroud ( 3 ) is arranged to be in an initial position protruding from the proximal end (P) of the housing ( 2 ) in an initial state interlocked to the activating means ( 4 ,  20 ,  24 ) for preventing manual operation, wherein the needle shroud ( 3 ) is arranged to be translated in distal direction (D) into the housing ( 2 ) into a distal position against the load of a shroud spring ( 12 ) when pushed against the injection site, wherein the needle shroud ( 3 ) is rotationally fixed to the housing ( 2 ) and to the second gear member ( 9 ) of the first gear arrangement ( 13 ,  13 . 1 ,  9 ), wherein in the distal position the needle shroud ( 3 ) is arranged to rotationally fix the first gear member ( 13 ) to the second gear member ( 9 ) of the first gear arrangement ( 13 ,  13 . 1 ,  9 ) and to allow operation of the activating means ( 4 ,  20 ,  24 ). 
     
     
         7 . Auto-injector ( 1 ) according to  claim 6 , characterized in that the activating means ( 4 ,  20 ,  24 ) is arranged to be in a splined engagement with the first gear member ( 13 ) of the first gear arrangement ( 13 ,  13 . 1 ,  9 ) in the initial state so as to rotationally fix it to the housing ( 2 ), wherein the activating means ( 4 ,  20 ,  24 ) is arranged to remove this splined engagement on manual operation. 
     
     
         8 . Auto-injector ( 1 ) according to one of the  claims 2  to  7 , characterized in that a clip arrangement is provided comprising at least one resilient chassis clip ( 16 ) attached to the housing ( 2 ), the chassis clip ( 16 ) engageable proximally behind a shoulder ( 11 . 2 ) in the plunger ( 11 ) in a manner to prevent translation of the plunger ( 11 ) in proximal direction (P), wherein the shoulder ( 11 . 2 ) is arranged to flex the chassis clip ( 16 ) outwards due to ramped engagement when a force in proximal direction (P) is applied to the plunger ( 11 ), wherein the activation means ( 4 ,  20 ,  24 ) comprises an end trigger button ( 4 ) arranged at the distal end (D) translatable between a distal position and a proximal position, wherein at least one trigger beam ( 4 . 1 ) is arranged on the trigger button ( 4 ) in a manner to outwardly support the chassis clip ( 16 ) to prevent it from being outwardly deflected when the end trigger button ( 4 ) is in the distal position, wherein the trigger beam ( 4 . 1 ) is arranged to be repositioned on translation of the end trigger button ( 4 ) into the proximal position in a manner to allow outward deflection of the chassis clip ( 16 ). 
     
     
         9 . Auto-injector ( 1 ) according to  claim 8 , characterized in that at least one flexible first beam element ( 2 . 2 ) is arranged on the housing ( 2 ), the flexible first beam element ( 2 . 2 ) arranged to obstruct the path of the end trigger button ( 4 ) so as to prevent its depression, wherein a second beam element ( 3 . 1 ) is arranged on the needle shroud ( 3 ) in a manner to deflect the flexible first beam element ( 2 . 2 ) out of the path of the end trigger button ( 4 ) on depression of the needle shroud ( 3 ). 
     
     
         10 . Auto-injector ( 1 ) according to  claim 8 , characterized in that a third rib ( 2 . 6 ) is arranged in the housing ( 2 ) in a manner to obstruct the path of a resilient part of the end trigger button ( 4 ) so as to prevent its depression, wherein a lateral trigger button ( 20 ) is laterally arranged on the housing ( 2 ) arranged to inwardly deflect the resilient part of the end trigger button ( 20 ) in a manner to bypass the third rib ( 2 . 6 ) thus allowing depression of the end trigger button ( 4 ), wherein the needle shroud ( 3 ) is arranged to inwardly support the resilient part of the end trigger button ( 4 ) when in the initial position so as to prevent deflection, wherein the inward support of the resilient part of the end trigger button ( 4 ) is arranged to be removed on translation of the needle shroud ( 3 ) into the distal position, wherein the end trigger button ( 4 ) is biased in proximal direction against the housing ( 2 ) by a trigger spring ( 23 ). 
     
     
         11 . Auto-injector ( 1 ) according to  claim 8 , characterized in that a wrap over sleeve trigger ( 24 ) is arranged over the distal end (D), the sleeve trigger ( 24 ) translatable in longitudinal direction between a distal position and a proximal position, the sleeve trigger ( 24 ) having at least one locking feature ( 24 . 1 ) engageable with a respective mating part ( 3 . 6 ) on the needle shroud ( 3 ) in the initial position so as to prevent depression of the sleeve trigger ( 24 ) from the distal position into the proximal position, wherein the mating part ( 3 . 6 ) is arranged to be inwardly withdrawn by a cam feature on translation of the needle shroud ( 3 ) into the distal position so as to allow the sleeve trigger ( 24 ) to be depressed, wherein the end trigger button ( 4 ) exhibits at least one latch feature ( 4 . 5 ) arranged to abut against a respective stop ( 2 . 7 ) in the housing ( 2 ) so as to prevent depression of the end trigger button ( 4 ), wherein at least one latch actuation boss ( 24 . 2 ) on the sleeve trigger ( 24 ) is arranged to inwardly deflect the latch feature ( 4 . 5 ) disengaging it from the stop ( 2 . 7 ), wherein the end trigger button ( 4 ) is biased in proximal direction against the housing ( 2 ) by a trigger spring ( 23 ). 
     
     
         12 . Auto-injector ( 1 ) according to  claim 11 , characterized in that the trigger spring ( 23 ) and the shroud spring ( 12 ) are specified to balance each other's load. 
     
     
         13 . Auto-injector ( 1 ) according to one of the  claims 5  to  12 , characterized in that the screw thread ( 13 . 1 ) ends with a pitch of zero on its proximal end allowing remaining torque in the torsion spring ( 14 ) to be released when the second gear member ( 9 ) reaches the zero pitch. 
     
     
         14 . Method for operating an auto-injector ( 1 ) comprising an elongate housing ( 2 ), a syringe ( 7 ) with a hollow needle ( 19 ) and a stopper ( 10 ), a torsion spring ( 14 ), activating means ( 4 ,  20 ,  24 ) for locking and releasing the torsion spring ( 14 ), a first gear arrangement ( 13 ,  13 . 1 ,  9 ) and a second gear arrangement ( 15 ,  11 . 1 ,  11 ) arranged for respectively converting torque from a first end ( 14 . 1 ) and a second end ( 14 . 2 ) of the torsion spring ( 14 ) into a translative force, a plunger ( 11 ) for transmitting motion from the second gear arrangement ( 15 ,  11 . 1 ,  11 ) to the stopper ( 10 ) and/or the syringe ( 7 ), the method comprising the steps of:
 grounding the first end ( 14 . 1 ) in the housing ( 2 ) and blocking the second gear arrangement ( 15 ,  11 . 1 ,  11 ) in an initial state prior to manual operation of the activating means ( 4 ,  20 ,  24 ),   releasing the second gear arrangement ( 15 ,  11 . 1 ,  11 ) on manual operation of the activating means ( 4 ,  20 ,  24 ) so as to translate the plunger ( 11 ) in proximal direction (P) for advancing the needle ( 19 ) and supplying a dose of medicament from the syringe ( 7 ) under torque from the second end ( 14 . 2 ),   releasing the first end ( 14 . 1 ) from the ground in the housing ( 2 ) for causing a translation through the first gear arrangement ( 13 ,  13 . 1 ,  9 ) under torque from the first end ( 14 . 1 ) resulting in the needle ( 19 ) getting covered.   
     
     
         15 . Method according to  claim 14 , characterized in that the first gear arrangement ( 13 ,  13 . 1 ,  9 ) translates a needle shroud ( 3 ) in proximal direction (P) over the advanced needle ( 19 ) on release of the first end ( 14 . 1 ) from the ground in the housing ( 2 ), wherein the needle shroud ( 3 ) is held in an initial position protruding from the proximal end (P) of the housing ( 2 ) in the initial state, wherein the needle shroud ( 3 ) is interlocked to the activating means ( 4 ,  20 ,  24 ) for preventing manual operation in the initial state, wherein the needle shroud ( 3 ) is translated in distal direction (D) into the housing ( 2 ) into a distal position against the load of a shroud spring ( 12 ) when pushed against the injection site, wherein the needle shroud ( 3 ) is rotationally fixed to the housing ( 2 ) and to a second gear member ( 9 ) of the first gear arrangement ( 13 ,  13 . 1 ,  9 ), wherein in the distal position the needle shroud ( 3 ) rotationally fixes a first gear member ( 13 ) to the second gear member ( 9 ) of the first gear arrangement ( 13 ,  13 . 1 ,  9 ) and releases the interlock so as to allow operation of the activating means ( 4 ,  20 ,  24 ).