Auto-injector

Abstract

An auto-injector for administering a dose of a liquid medicament (M) comprises of a substantially cylindrical housing arranged to contain a pre-filled syringe with an injection needle, a plunger and a stopper for sealing a syringe barrel and a drive means releasably coupled to the plunger for advancing the syringe in the proximal direction (P) for needle insertion into an injection site and for displacing the dose of medicament (M) into the injection site. The drive means is arranged to be decoupled from the plunger for advancing a needle shroud to a safe position (PS) to surround the injection needle after the injection. According to the invention, the drive means bears against a thrust collar arranged to be releasably coupled to the plunger through a ramped engagement of a first tongue and a first recess so as to rotate the thrust collar on translation in proximal direction (P). At least one longitudinal gap (G 1 , G 2 ) is provided for guiding at a first and/or second protrusion of the thrust collar to prevent a rotation of the thrust collar. A circumferential gap (G 3 ) is arranged to allow the thrust collar to rotate out of engagement to the plunger on removal of the auto-injector from the injection site. An auto-injector includes a housing, a thrust member comprising a radial projection configured to engage a ramped surface within the housing when the thrust member is in a first rotational position and to disengage from the ramped surface when the thrust member is moved to a second rotational position, a drive spring disposed within the housing, and a needle shroud configured to (i) inhibit rotation of the thrust member when the needle shroud is in an extended positon and the thrust member is in the first rotational position, (ii) allow the thrust member to rotate from the first rotational position to the second rotational position when the needle shroud is in a retracted positon, and (iii) permit the thrust member, after the thrust member has been rotated to the second rotational position, to be moved axially by the drive spring.

The invention claimed is: 
     
       1. Auto-injector for administering a dose of a liquid medicament (M), comprising:
 a substantially cylindrical housing arranged to contain a pre-filled syringe with an injection needle, a plunger and a stopper for sealing a syringe barrel and   a driver releasably coupled to the plunger for advancing the syringe in the proximal direction (P) for needle insertion into an injection site and for displacing the dose of medicament (M) into the injection site,   wherein the driver is arranged to be decoupled from the plunger for advancing a needle shroud to a safe position (PS) to surround the injection needle after the injection,   wherein the driver bears against a thrust collar arranged to be releasably coupled to the plunger through a ramped engagement so as to rotate the thrust collar on translation in proximal direction (P), wherein guiding mechanism are provided for guiding the thrust collar during at least a part of its axial translation when inserting the needle and displacing the medicament (M) to prevent a rotation of the thrust collar, wherein the thrust collar is arranged to rotate out of engagement to the plunger on removal of the auto-injector from the injection site.   
     
     
       2. Auto-injector according to  claim 1 , wherein the ramped engagement between the thrust collar and the plunger comprises a first tongue and a first recess, wherein the guiding mechanism comprises at least one longitudinal gap (GI, G 2 ) for guiding a first or second protrusion of the thrust collar, wherein a circumferential gap (G 3 ) is arranged to allow the thrust collar to rotate out of engagement to the plunger on removal of the auto-injector from the injection site. 
     
     
       3. Auto-injector according to  claim 1 , wherein the thrust collar is releasably mounted to a coupling shroud rotationally fixed to the housing and firmly attached to the plunger, wherein the connection between the thrust collar and the coupling shroud is releasable by a relative rotation between the thrust collar and the coupling shroud. 
     
     
       4. Auto-injector according to  claim 1 , wherein the needle shroud is biased in a proximal direction (P) towards an advanced position (PA) and slidable from the advanced position (PA) in a distal direction (D) to a retracted position (PR) and from the retracted position (PR) in the proximal direction (P) beyond the advanced position (PA) to the safe position (PS), wherein sliding the needle shroud from the advanced position (PA) to the retracted position (PR) releases the driver. 
     
     
       5. Auto-injector according to  claim 4 , wherein at the needle shroud in the refracted position (PR) is arranged to prevent rotation of the thrust collar, thus preventing the release of the connection between the thrust collar and the coupling shroud. 
     
     
       6. Auto-injector according to  claim 5 , wherein the needle shroud comprises au-shaped indentation for receiving the second protrusion of the thrust collar to prevent the release of the connection between the thrust collar and the coupling shroud in the retracted position (PR), wherein the needle shroud is arranged to open the circumferential gap (G 3 ) on translation into the advanced position (PA) for allowing the thrust collar to rotate out of engagement to the plunger. 
     
     
       7. Auto-injector according to  claim 1 , wherein at the needle shroud is releasably mounted to the housing by a clip preventing travel in proximal direction (P) beyond the advanced position (PA), wherein the thrust collar is arranged to radially deflect the clip for releasing the needle shroud allowing it to be moved in the proximal direction (P) to the safe position (PS). 
     
     
       8. Auto-injector according to  claim 1 , wherein a syringe retainer is arranged for mounting the syringe within the housing, wherein a retaining element is attached to the syringe retainer, wherein the release element releasably couples the plunger to the syringe retainer. 
     
     
       9. Auto-injector according to  claim 8 , wherein the retaining element comprises at least one first catch that latches to a notch formed into the plunger to releasably couple the plunger to the syringe retainer.  
     
     
       10. Auto-injector according to  claim 8 , wherein the first catch is arranged to abut against an inner sleeve of the housing to prevent decoupling of the plunger and the syringe retainer, wherein an aperture is formed into the inner sleeve allowing for a radial outward deflection of the first catch to decouple the syringe retainer from the plunger when the syringe retainer is in a proximal position. 
     
     
       11. Auto-injector according to  claim 10 , wherein the coupling shroud comprises a flat first lateral wall that abuts against a corresponding flat second lateral wall of the inner sleeve to prevent a rotation of the coupling shroud relative to the housing. 
     
     
       12. Auto-injector according to  claim 1 , wherein a biasing mechanism biases the needle shroud in the proximal direction (P), wherein the biasing mechanism and the driver are fit into each other to optimally use available space within the housing. 
     
     
       13. Auto-injector according to  claim 1 , wherein the driver is arranged as a single compression spring. 
     
     
       14. Auto-injector according to  claim 13 , wherein the single compression spring is strained only translationally. 
     
     
       15. Auto-injector according to  claim 1 , wherein a rotating collar axially fixed to the housing engages the needle shroud in a manner that forces the rotating collar to rotate within the housing when the needle shroud is axially displaced from the advanced position (PA) into the safe position (PS). 
     
     
       16. Auto-injector according to  claim 1 , wherein the rotating collar comprises a pin that engages a track formed into the needle shroud, wherein the track comprises a straight first section for guiding the pin between the retracted position (PR) and the advanced position (PA) and a helical second section for guiding the pin between the advanced position (PA) and the safe position (PS). 
     
     
       17. An auto-injector for administering a dose of a liquid medicament, the auto-injector comprising:
 a housing configured to contain a syringe barrel of a syringe;   a thrust member comprising a radial projection, the radial projection configured to engage a ramped surface within the housing when the thrust member is in a first rotational position and to disengage from the ramped surface when the thrust member is moved to a second rotational position;   a drive spring disposed within the housing and configured to apply an axial force to the thrust member such that when the thrust member is in the first rotational position, the engagement between the radial projection and the ramped surface biases the thrust member from the first rotational position toward the second rotational position; and   a needle shroud configured to move from an extended position to a retracted position, the needle shroud configured to (i) inhibit rotation of the thrust member relative to the needle shroud when the needle shroud is in the extended positon and the thrust member is in the first rotational position, (ii) allow the thrust member to rotate from the first rotational position to the second rotational position when the needle shroud is in the retracted positon and (iii) permit the thrust member, after the thrust member has been rotated to the second rotational position, to be moved axially by the drive spring.   
     
     
       18. The auto-injector of claim 17, wherein the ramped surface is a surface of the housing. 
     
     
       19. The auto-injector of claim 18, wherein the radial projection of the thrust member has a ramp that engages the ramped surface within the housing when the thrust member is in the first rotational position. 
     
     
       20. The auto-injector of claim 17, wherein the thrust member further comprises a second radial projection. 
     
     
       21. The auto-injector of claim 20, wherein the radial projection and the second radial projection are circumferentially spaced apart from one another about the thrust member. 
     
     
       22. The auto-injector of claim 20, wherein the needle shroud has a longitudinal surface configured to engage the second radial projection to inhibit rotation of the thrust member relative to the needle shroud. 
     
     
       23. The auto-injector of claim 22, wherein the needle shroud defines a circumferential opening configured to allow the second radial projection to rotate relative to the needle shroud. 
     
     
       24. The auto-injector of claim 20, wherein the needle shroud defines a longitudinal opening arranged to allow the second radial projection to move axially within the longitudinal opening when the thrust member, after having been rotated to the second rotational position, is moved axially by the drive spring. 
     
     
       25. The auto-injector of claim 17, wherein the thrust member comprises a plunger configured to contact a stopper of the syringe and advance the stopper within a chamber of the syringe to administer the dose of the liquid medicament when the thrust member is moved axially by the drive spring and the syringe is disposed in the housing. 
     
     
       26. The auto-injector of claim 17, wherein the thrust member is coupled to the syringe when the syringe is disposed in the housing, and the thrust member is configured to advance the syringe axially within the housing when the thrust member is moved axially by the drive spring. 
     
     
       27. The auto-injector of claim 17, wherein the needle shroud has a surface configured to engage the radial projection to inhibit rotation of the thrust member relative to the needle shroud when the needle shroud is in the extended positon and the thrust member is in the first rotational position. 
     
     
       28. The auto-injector of claim 27, wherein the surface of the needle shroud that is configured to engage the radial projection of the thrust member is a longitudinal surface that is configured to circumferentially engage the radial projection. 
     
     
       29. The auto-injector of claim 17, wherein the needle shroud defines an opening arranged to receive the radial projection when the needle shroud is in the retracted positon to allow the thrust member to rotate from the first rotational position to the second rotational position, and the opening is arranged to permit the radial projection to move axially within the opening when the thrust member has been rotated to the second rotational position and is moved axially by the drive spring. 
     
     
       30. The auto-injector of claim 29, wherein the opening of the needle shroud includes a first portion and a second portion, at least part of the second portion being circumferentially offset from the first portion. 
     
     
       31. The auto-injector of claim 30, wherein the first portion of the opening is defined at least in part by a surface of the needle shroud that is configured to engage the radial projection of the thrust member such that the radial projection resides within the first portion of the opening when the thrust member is in the first rotational position. 
     
     
       32. The auto-injector of claim 31, wherein the opening of the needle shroud is arranged to permit the radial projection of the thrust member to move axially within the second portion of the opening when the thrust member has been rotated to the second rotational position and is moved axially by the drive spring. 
     
     
       33. The auto-injector of claim 29, wherein the opening of the needle shroud is at least partially defined by an axially extending arm of the needle shroud. 
     
     
       34. The auto-injector of claim 33, wherein the needle shroud further comprises a cylindrical end body from which the axially extending arm extends. 
     
     
       35. The auto-injector of claim 34, wherein the needle shroud further comprises a second axially extending arm that extends axially from the cylindrical end body. 
     
     
       36. The auto-injector of claim 17, wherein the needle shroud is configured to move from the retracted position to a safe position in which the needle shroud extends forward of the housing, and a portion of the housing is configured to engage the needle shroud to lock the needle shroud in the safe position. 
     
     
       37. The auto-injector of claim 17, wherein the drive spring directly contacts the thrust member. 
     
     
       38. The auto-injector of claim 17, further comprising a needle shroud spring that biases the needle shroud toward the extended position. 
     
     
       39. The auto-injector of claim 17, further comprising the syringe disposed in the housing. 
     
     
       40. The auto-injector of claim 39, wherein the syringe defines a chamber containing the liquid medicament, the syringe comprises a stopper slidably arranged within the chamber and an injection needle in fluid communication with the chamber, and the needle shroud is configured to surround at least a portion of the needle when the needle shroud is in the extended position. 
     
     
       41. The auto-injector of claim 17, further comprising a syringe retainer defining a chamber configured to receive the syringe, the housing being configured to contain both the syringe retainer and the syringe disposed in the chamber of the syringe retainer.