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 (G1, G2) 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 (G3) 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..]. .Iadd.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..Iaddend.

Claims

.[.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, G2) for guiding a first or second protrusion of the thrust collar, wherein a circumferential gap (G3) 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 (G3) 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)..].

.Iadd.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..Iaddend.

.Iadd.18. The auto-injector of claim 17, wherein the ramped surface is a surface of the housing..Iaddend.

.Iadd.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..Iaddend.

.Iadd.20. The auto-injector of claim 17, wherein the thrust member further comprises a second radial projection..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

.Iadd.34. The auto-injector of claim 33, wherein the needle shroud further comprises a cylindrical end body from which the axially extending arm extends..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

.Iadd.37. The auto-injector of claim 17, wherein the drive spring directly contacts the thrust member..Iaddend.

.Iadd.38. The auto-injector of claim 17, further comprising a needle shroud spring that biases the needle shroud toward the extended position..Iaddend.

.Iadd.39. The auto-injector of claim 17, further comprising the syringe disposed in the housing..Iaddend.

.Iadd.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..Iaddend.

.Iadd.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..Iaddend.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIGS. 1A and 1B show two different sectional views of the auto-injector before an injection;

(3) FIG. 2 shows in a perspective view a thrust collar connected to a coupling shroud by a thread connection;

(4) FIG. 3 shows an interior mechanism of the auto-injector in a perspective view before an injection;

(5) FIG. 4 shows details of the auto-injector that illustrate the release of a drive means in a perspective view;

(6) FIG. 5 shows the interior mechanism of the auto-injector in a perspective view after an injection stroke;

(7) FIG. 6 shows the interior mechanism of the auto-injector in a perspective view, wherein the decoupling of the thrust collar and the coupling shroud is illustrated;

(8) FIG. 7 shows details of the auto-injector that illustrate the release of a needle shroud;

(9) FIG. 8 shows details of the auto-injector that illustrate the locking of the needle shroud in a safe position;

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

DETAILED DESCRIPTION

(11) FIGS. 1A and 1B show two sectional views of an essentially cylindrical auto-injector 1, wherein the sectional planes shown are oriented perpendicularly with respect to each other. The auto-injector 1 comprises a housing 2, a proximal needle shroud 3, a syringe retainer 4 adapted to mount a pre-filled syringe 5 within the housing 2, a coupling shroud 6 slidably arranged within the housing 2 and a thrust collar 7 releasably connected to the coupling shroud 6 by a connection that is released by rotating the thrust collar 7 relative to the coupling shroud 6.

(12) The releasable connection between the thrust collar 7 and the coupling shroud 6 is released by a rotation about a relative small angle around the axis of the substantially cylindrical auto-injector 1, like, for example, a quarter twist. The thrust collar 7 and the coupling shroud 6 may be connected by a bayonet kind of coupling or, alternatively, a thread connection with a corresponding lead that allows for a release by a relative small twist.

(13) A drive means 8 is arranged between the distal end of the housing 2 and the thrust collar 7. The drive means 8 biases the thrust collar 7 in a proximal direction P towards the skin of a patient receiving an injection. The thrust collar 7 carries a threaded connection to the coupling shroud 6 with a steep pitch angle, and the coupling shroud 6 is restrained against rotation relative to the housing 2, so that the thrust collar 7 is additionally biased to rotate around the axis of the auto-injector 1.

(14) According to one possible embodiment of the invention, the drive means 8 is arranged as a single, conventional compression spring.

(15) The coupling shroud 6 is firmly attached to a plunger 9 arranged to push on a stopper 10 fluid-tightly sealing a distal end of a syringe barrel 11 containing a dose of a medicament M. A plunger collar 9.2 of the plunger 9 protrudes into a locking recess 6.1 formed into the distal end of the coupling shroud 6 to attach the plunger 9 to the coupling shroud 6.

(16) An inner cavity of the syringe barrel 11 is in fluid communication with an injection needle 12, so that the dose of the medicament M may be expelled through the injection needle 12 by displacing the stopper 10 in the proximal direction P.

(17) The needle shroud 3 is designed to be pushed against the skin of the patient during the injection. Edges of the needle shroud 3 may thus be smoothed to avoid injuries. The needle shroud 3 is slidably arranged with the housing 2 of the auto-injector 1, so that the needle shroud 3 may be pushed from an advanced position PA shown in FIGS. 1A and 1B in a distal direction D. A biasing means 13 bears against the needle shroud 3 and the distal end of the housing 2 to bias the needle shroud 3 towards the advanced position PA.

(18) The biasing means 13 and the drive means 8 are fitted into each other to optimally use available space within the housing 2.

(19) In a possible embodiment of the invention, the biasing means 13 is arranged as a compression spring having a diameter that differs from the diameter of the compression spring of the drive means 8 in a manner that allows the drive means 8 and the biasing means 13 to expand independently from each other without interfering.

(20) A retaining element 14 is attached to a distal end of the syringe retainer 4 that releasably couples the plunger 9 to the syringe retainer 4, so that the syringe retainer 4 may jointly move with the plunger 9 in the proximal direction P to expose the injection needle 12. The retaining element 14 comprises at least one and preferably two or more first catches 14.1 arranged equi-spaced around retaining element 14, wherein each first catch 14.1 latches to a respective notch 9.1 formed into the plunger 9. The first catch 14.1 abuts against an inner sleeve 2.2 of the housing 2 in the radial outward direction, so that a deflection of the first catch 14.1 and hence a decoupling of the plunger 9 and the syringe retainer 4 is prevented.

(21) The plunger 9 is coupled to the retaining element 14 and the syringe retainer 4 until the syringe retainer 4 mounting the pre-filled syringe 5 is moved proximally to expose the injection needle 12. A longitudinal aperture 2.3 is formed into the inner sleeve 2.2 of the housing 2 that allows for a radial outward deflection of the first catch 14.1 when the syringe retainer 4 is in a proximal position and the injection needle 12 is exposed. The plunger 9 is released from the retaining element 14 in the proximal position and may move proximally to displace the stopper 10, whereby the dose of medication M is expelled through the injection needle 12.

(22) A ring-shaped rotating collar 15 is circumferentially arranged around a tubular proximal section of the needle shroud 3. A pin 15.1 is formed to an inner surface of the rotating collar 15 that engages a track 3.1 formed into an outer surface of the needle shroud 3. The track 3.1 comprises a straight first section 3.1.1 and a helical second section 3.1.2 that can best be seen in FIG. 5. The first section 3.1.1 of the track 3.1 extends essentially parallel to the axis of the auto-injector 1, whereas the second section 3.1.2 of the track 3.1 is angled with respect to the first section 3.1.1. As the needle shroud 3 is axially displaced with respect to the housing 2, the pin 15.1 travels along the track 3.1, so that the rotating collar 15 is forced to rotate around to the needle shroud 3. The friction generated by the rotation slows down the proximal movement of the needle shroud 3 and reduces pressure exerted upon the skin surface of the patient by the needle shroud 3.

(23) FIG. 2 shows the coupling shroud 6 with the thrust collar 7 connected thereto in a perspective view. The connection between the thrust collar 7 and the coupling shroud 6 is releasable upon rotation. A helical first recess 6.2 is formed into an outer surface of the coupling shroud 6. A first tongue 7.1 that is correspondingly shaped to the first recess 6.2 is formed to an inner surface of the thrust collar 7. The first tongue 7.1 engages the first recess 6.2 to releaseably connect the coupling shroud 6 and the thrust collar 7 in a thread type connection.

(24) The coupling shroud 6 is slidably arranged within the housing 2 and comprises a flat first lateral wall 6.3 that abuts a corresponding flat second lateral wall 2.4 of the inner sleeve 2.2 to prevent a rotation of the coupling shroud 6 relative to the housing 2.

(25) The essentially ring-shaped thrust collar 7 comprises an outer surface with a plurality of first and second protrusions 7.2, 7.3 formed thereto. The first and second protrusions 7.2, 7.3 are circumferentially displaced from each other and protrude radially outwards. The first protrusions 7.2 have a quadrangular shape, whereas the second protrusion 7.3 comprises a triangular shape.

(26) FIG. 3 shows the auto-injector 1 in a perspective view before an injection is performed. For illustrative purposes, the outer shell 2.1 of the housing 2 is not shown. FIG. 3 illustrates an interior mechanism of the auto-injector 1 that is hidden from view by the outer case 2.2 during normal use. The needle shroud 3 is positioned in the advanced position PA.

(27) The quadrangular first protrusion 7.2 comprises a first ramp 7.2.1 that abuts against a corresponding second ramp 2.5 formed to the housing 2. Furthermore, the first protrusion 7.2 abuts against the needle shroud 3 in a circumferential direction. Before the injection, the biased thrust collar 7 is retained in a first position I by the first protrusion 7.2 abutting against the needle shroud 3 and the second ramp 2.5 of the housing 2.

(28) The injection is initiated by pressing the needle shroud 3 against the skin of the patient receiving the injection, whereby the needle shield 3 is displaced from the advanced position PA in the distal direction D to a retracted position PR. As shown in detail in FIG. 4, the distal movement of the needle shroud 3 to the retracted position PR makes way for a circumferential displacement of first protrusion 7.2. The thrust collar 7 rotates around the axis of the auto-injector 1 by a small angle, insufficient to release thrust collar 7 from coupling shroud 6. The first protrusion 7.2 is guided by the first and second ramps 7.2.1, 2.5 into a longitudinal first gap G1 between the needle shroud 3 and the housing 2. The thrust collar 7 blocking the drive means 8 is now released. The fully compressed drive means 8 drives the thrust collar 7 and the coupling shroud 6 connected thereto in the proximal direction P, whereby the first protrusion 7.2 travels along the first gap G1 in the proximal direction P. At the same time the second protrusion 7.3 travels proximally along a longitudinal second gap G2 that is arranged between the housing 2 and the needle shroud 3 in a similar manner as the first gap G1. As the first Gap G1 is arranged to limit a circumferential displacement of the first protrusion 7.2, a further rotation of the thrust collar 7 is prevented until an injection stroke delivering the dose medication M is completed.

(29) The thrust collar 7 is connected to the coupling shroud 6 that is attached to the plunger 9. The plunger 9 in turn is coupled to syringe retainer 4 via the retaining element 14. Thus, the coupling shroud 6 driven by the drive means 8 first translates the syringe retainer 4 holding the pre-filled syringe 5 in the proximal direction P until the syringe retainer 4 bears against a bearing surface 2.6 formed to the housing 2 as best seen in FIG. 1A. The bearing surface 2.6 defines an injection depth of the injection needle. The injection needle 12 now protrudes from the needle shroud 3 in the proximal direction P and penetrates the skin surface of the patient at the desired injection depth.

(30) The deflectable first catches 14.1 that couple the plunger 9 to the syringe retainer 4 are now located adjacent to the longitudinal apertures 2.3 formed into the inner sleeve 2.2 of the housing 2. The first catches 14.1 deflect in the radial outward direction due to their ramped engagement with the notches 9.1 and disengage from the notches 9.1 to decouple the plunger 9 from the syringe retainer 4.

(31) The drive means 8 further relaxes and drives the coupling shroud 6, the thrust collar 7 and the plunger 9 in the proximal direction P. The plunger 9 pushes the stopper 10 proximally to expel the dose of medication M contained in the syringe barrel 11 through the injection needle 12.

(32) When the stopper 10 reaches a proximal end of the syringe barrel 11, the injection stroke is completed and the dose of medication M is completely expelled. At the same time, the thrust collar 7 reaches a proximal second position II shown in FIG. 5.

(33) FIG. 5 shows the auto-injector 1 in a perspective view after the injection stroke is completed. Similar to FIGS. 3 and 4, the outer shell 2.1 is not shown to illustrate the interior mechanism of auto-injector 1.

(34) The needle shroud 3 is still pressed against the injection site to retain the needle shroud 3 in the retracted position PR. At the same time, the thrust collar 7 is located in the second position II. The triangular second protrusion 7.3 of the thrust collar 7 is retained in a u-shaped indentation 3.2 formed to the needle shroud 3. The u-shaped indentation 3.2 constitutes a proximal end of the second gap G2 and comprises a circumferential width that corresponds to the second protrusion 7.3. The u-shaped indentation 3.2 abuts against the second protrusion 7.3 in the circumferential direction, so that a rotation of the thrust collar 7 and thus a decoupling of the thrust collar 7 and the coupling shroud 6 are prevented until the needle shield 3 leaves the retracted position PR.

(35) The auto-injector 1 is removed from the injection site. The biasing means 13 relaxes to return the needle shroud 3 to the advanced position PA. As a consequence, the needle shroud 3 moves proximally with respect to the housing 2 and the thrust collar 7 connected to the coupling shroud 6.

(36) FIG. 6 shows the interior mechanism of the auto-injector 1 in a perspective view after the auto-injector 1 has been removed from the injection site. The proximal movement of the needle shroud 3 opens a circumferential gap G3 between the housing 2 and the needle shroud 3. The triangular second protrusion 7.3 travels through the circumferential gap G3 in the circumferential direction, whereby the thrust collar 7 slightly rotates around the axis of the auto-injector 1 due to the ramped engagement of the first tongue 7.1 with the first recess 6.2. The drive means 8 bears against the thrust collar 7 and pushes a third ramp 7.3.1 on the second protrusion 7.3 against a corresponding fourth ramp 3.3 on the needle shroud 3 when the thrust collar 7 is located in an intermediate third position III. The thrust collar 7 tries to rotate due to its threaded connection with the coupling shroud 6.1 relative to the housing 2 and relative to the coupling shroud 6. If a bayonet connection was used instead of the thread the third and fourth ramp 7.3.1, 3.3 would cause the thrust collar 7 to further rotate. This final rotation of the thrust collar 7 suffices to decouple the coupling shroud 6 and the thrust collar 7. The decoupled thrust collar 7 is then driven further in the proximal direction P by the drive means 8 until an inner surface of the thrust collar 7 engages a fifth ramp 2.7 of a clip 2.8 connecting the housing 2 with the needle shroud 3 that is shown in more detail in FIG. 7.

(37) FIG. 7 shows the release of the substantially t-shaped clip 2.8 that mounts the needle shroud 3 to the housing 2. The t-shaped clip 2.8 is retained in a second recess 3.4 formed in the needle shroud 3. The second recess 3.4 comprises axial dimensions that allow for a sliding movement of the needle shroud 3 relative to the housing 2 between the advanced position PA and the retracted position PR while the clip 2.8 is retained in the second recess 3.4.

(38) The clip 2.8 is deflectable in the radial inward direction to release the needle shroud 3. As shown in FIG. 7, the thrust collar 7 slides over the fifth ramp 2.7 to bend the clip 2.8 radially inwards after the thrust collar 7 and coupling shroud 6 have been decoupled. The t-shaped clip 2.8 is deflected inwards and disengages from the second recess 3.4, so that the needle shroud 3 may be proximally advanced towards a safe position PS. The drive means 8 further relaxes and pushes the decoupled thrust collar 7 further in the proximal direction P. The thrust collar 7 bears against the needle shroud 3 to advance the needle shroud 3 towards the safe position PS shown in more detail in FIG. 8.

(39) When the needle shield 3 moves proximally from the advanced position PA to the safe position PS, the pin 15.1 of the rotating collar 15 travels along the second section 3.1.2 of the track 3.1 formed into the needle shroud 3. As the second section 3.1.2 is oriented at an angle with respect to the axis of the auto-injector, the translatory movement of the needle shroud 3 causes the rotating collar 15 to rotate around the axis, whereby friction is generated. The generated friction slows down and damps the proximal movement of the needle shroud 3.

(40) FIG. 8 shows a perspective view of the interior mechanism of the auto-injector 1, wherein the needle shroud 3 is locked in the safe position PS. In the safe position PS, the needle shroud 3 protrudes proximally from the housing 2 of the auto-injector 1 and permanently surrounds and protrudes proximally beyond the tip of the injection needle 12 after an injection to prevent accidental needle stick injuries.

(41) As the thrust collar 7 and the needle shroud 3 have travelled proximally beyond the clip 2.8, the clip 2.8 deflects outwards to return to its prior position. The needle shroud 3 abuts against the t-shaped clip 2.8 in the distal direction D, so that a distal movement of the needle shroud 3 in the safe position PS relative to the housing 2 is prevented. Thus, the needle shroud 3 is permanently locked in the safe position PS and a re-exposure of the injection needle 12 is prevented. The thrust collar 7 travelled over the fifth ramp 2.7 and is located in a maximum proximal fourth position IV, wherein the thrust collar 7 abuts the needle shroud 3.