Auto-injector

Abstract

According to the invention, 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 filled with the medicament (M), a needle shroud slibably arranged with respect to the housing and adapted to rest on the skin of a patient receiving an injection, a releasable drive means arranged within the housing that is capable of, upon release, translating the needle shroud in a proximal direction (P) towards a safe position (PS) and a rotating collar rotatably arranged within the housing. The needle shroud in the safe position (PS) surrounds the injection needle after the injection has been carried out. The rotating collar engages the needle shroud in a manner that forces the rotating collar to rotate within the housing when the needle shroud is translated in the proximal direction (P).

Claims

1. An auto-injector comprising: an outer sleeve; a needle sleeve slidable relative to the outer sleeve between (i) a first position in which a proximal end of the needle sleeve extends beyond a proximal end of the outer sleeve by a first distance and (ii) a second position in which the proximal end of the needle sleeve extends beyond the proximal end of the outer sleeve by a second distance that is less than the first distance, the needle sleeve comprising two distally projecting arms, the auto-injector configured such that distal movement of the needle sleeve relative to the outer sleeve from the first position to the second position causes a pin to move along a ramped surface which rotates an annular rotating collar about a longitudinal axis of the outer sleeve; a needle sleeve spring having a proximal end that is in engagement with a surface of the needle sleeve to apply a proximally-directed biasing force to the surface of the needle sleeve and bias the needle sleeve in the first position; a syringe containing a medicament and having a proximal end with an injection needle; a syringe retainer retaining the syringe via an engagement between an outer proximal surface of the syringe and an inner proximal surface of the syringe retainer, an outer proximal surface of the syringe retainer engaging an inward protrusion of the auto-injector to limit proximal movement of the syringe retainer relative to the outer sleeve, the syringe retainer and the syringe being sized such that (i) a distal end of the syringe extends distally beyond a distal end of the syringe retainer while the outer proximal surface of the syringe is engaged with the inner proximal surface of the syringe retainer and (ii) a distal flange of the syringe is distally spaced apart from the distal end of the syringe retainer while the outer proximal surface of the syringe is engaged with the inner proximal surface of the syringe retainer; and a member comprising a resilient part that is releasably coupled to a plunger rod such that when the resilient part is in a first position the resilient part is prevented from deflecting out of a coupled relationship with the plunger rod by an engagement between the resilient part and a blocking surface of the auto-injector which limits proximal movement of the plunger rod relative to the outer sleeve while a surface of the plunger rod is subject to a proximally-directed force of a compression drive spring that is disposed within a recess of the member, the recess extending distally from a proximal surface of the member, and when the resilient part is in a second position the resilient part has deflected out of the coupled relationship with the plunger rod by a relative movement between the member and the blocking surface which causes proximal movement of the plunger rod relative to the outer sleeve while the surface of the plunger rod is subject to the proximally-directed force of the compression drive spring, the resilient part comprising an angled protrusion, wherein the auto-injector is configured such that a proximal movement of the outer sleeve relative to the needle sleeve causes the needle sleeve to move from the first position to the second position which causes (i) the pin to move along the ramped surface to rotate the annular rotating collar about the longitudinal axis of the auto-injector, (ii) the resilient part to move from the first position to the second position which causes proximal movement of the plunger rod relative to the member and the outer sleeve, and (iii) a proximal end of the plunger rod to displace a stopper of the syringe in a proximal direction to dispense the medicament from the injection needle of the syringe.

2. The auto-injector of claim 1, wherein an outer surface of the outer sleeve is configured to be held by a user in order to use the auto-injector to dispense the medicament.

3. The auto-injector of claim 2, wherein the auto-injector is configured such that a single, uninterrupted proximal movement of the outer sleeve relative to the needle sleeve is sufficient to cause the needle sleeve to move from the first position to the second position and dispense the medicament from the syringe.

4. The auto-injector of claim 2, wherein the outer surface of the outer sleeve is configured to be held by the user in order to position the auto-injector such that the proximal end of the needle sleeve engages an injection site of the user.

5. The auto-injector of claim 4, wherein the outer surface of the outer sleeve is configured to be held by the user in order to move the outer sleeve relative to the injection site to cause the needle sleeve to move from the first position to the second position.

6. The auto-injector of claim 1, wherein the auto-injector is configured to automatically dispense the medicament when the outer sleeve proximally moves relative to the needle sleeve by a predetermined distance.

7. The auto-injector of claim 6, wherein the predetermined distance corresponds to a distance in which the blocking surface of the auto-injector moves relative to the member to release the engagement between the blocking surface and the resilient part of the member such that the resilient part is allowed to deflect from the first position to the second position.

8. The auto-injector of claim 1, wherein the ramped surface defines a guiding track for the pin.

9. The auto-injector of claim 1, wherein the resilient part is a resilient arm that extends in a proximal direction on a sleeve portion of the member and the angled protrusion is located on a proximal end of the resilient arm.

10. An auto-injector comprising: an outer sleeve; a needle sleeve slidable relative to the outer sleeve between (i) a first position in which a proximal end of the needle sleeve extends beyond a proximal end of the outer sleeve by a first distance and (ii) a second position in which the proximal end of the needle sleeve extends beyond the proximal end of the outer sleeve by a second distance that is less than the first distance, the needle sleeve comprising two distally projecting arms, the auto-injector configured such that distal movement of the needle sleeve relative to the outer sleeve from the first position to the second position causes a pin to move along a ramped surface which rotates an annular rotating collar about a longitudinal axis of the outer sleeve; a needle sleeve spring having a proximal end that is in engagement with a surface of the needle sleeve to apply a proximally-directed biasing force to the surface of the needle sleeve and bias the needle sleeve in the first position; a syringe retainer configured to retain a syringe containing a medicament and having a proximal end with an injection needle via an engagement between an outer proximal surface of the syringe and an inner proximal surface of the syringe retainer, an outer proximal surface of the syringe retainer engaging an inward protrusion of the auto-injector to limit proximal movement of the syringe retainer relative to the outer sleeve, the syringe retainer and the syringe being sized such that (i) a distal end of the syringe extends distally beyond a distal end of the syringe retainer while the outer proximal surface of the syringe is engaged with the inner proximal surface of the syringe retainer and (ii) a distal flange of the syringe is distally spaced apart from the distal end of the syringe retainer while the outer proximal surface of the syringe is engaged with the inner proximal surface of the syringe retainer; and a member comprising a resilient part that is releasably coupled to a plunger rod such that when the resilient part is in a first position the resilient part is prevented from deflecting out of a coupled relationship with the plunger rod by an engagement between the resilient part and a blocking surface of the auto-injector which limits proximal movement of the plunger rod relative to the outer sleeve, wherein the auto-injector is configured such that a proximal movement of the outer sleeve relative to the needle sleeve causes the needle sleeve to move from the first position to the second position which causes (i) the pin to move along the ramped surface to rotate the annular rotating collar about the longitudinal axis of the auto-injector, and (ii) a proximal end of the plunger rod to displace a stopper of the syringe in a proximal direction to dispense the medicament from the injection needle of the syringe.

11. The auto-injector of claim 10, wherein the outer sleeve is substantially cylindrical.

12. The auto-injector of claim 10, wherein an outer surface of the outer sleeve is configured to be held by a user in order to use the auto-injector to dispense the medicament.

13. The auto-injector of claim 12, wherein the auto-injector is configured such that a single, uninterrupted proximal movement of the outer sleeve relative to the needle sleeve is sufficient to cause the needle sleeve to move from the first position to the second position and dispense the medicament from the syringe.

14. The auto-injector of claim 12, wherein the outer surface of the outer sleeve is configured to be held by the user in order to position the auto-injector such that the proximal end of the needle sleeve engages an injection site of the user.

15. The auto-injector of claim 14, wherein the outer surface of the outer sleeve is configured to be held by the user in order to move the outer sleeve relative to the injection site to cause the needle sleeve to move from the first position to the second position.

16. The auto-injector of claim 10, wherein the auto-injector is configured to automatically dispense the medicament when the outer sleeve proximally moves relative to the needle sleeve by a predetermined distance.

17. The auto-injector of claim 16, wherein the predetermined distance corresponds to a distance in which the blocking surface of the auto-injector moves relative to the member of the auto-injector to release an engagement between the blocking surface and the resilient part of the member such that the resilient part is allowed to deflect from the first position to a second position in which the resilient part has deflected out of the coupled relationship with the plunger rod.

18. The auto-injector of claim 17, wherein the blocking surface is substantially cylindrical.

19. A method comprising: engaging a proximal end of a syringe with an inwardly angled protrusion of a syringe retainer to limit proximal movement of the syringe relative to the syringe retainer, the syringe containing a medicament, the inwardly angled protrusion being located at a proximal end of the syringe retainer, the syringe retainer and the syringe being sized such that when the syringe is engaged with the inwardly angled protrusion of the syringe retainer, a distal end of the syringe extends distally beyond a distal end of the syringe retainer and a distal flange of the syringe is distally spaced apart from a distal end of the syringe retainer, engaging an outward protrusion extending outward from an outer surface of the syringe retainer with an inward protrusion of an auto-injector to limit proximal movement of the syringe retainer relative to a member of the auto-injector, the member comprising a flexible arm that is releasably coupled to a plunger rod such that when the flexible arm is in a first position the flexible arm is prevented from deflecting out of a coupled relationship with the plunger rod by an engagement between the flexible arm and a blocking surface of the auto-injector which limits proximal movement of the plunger rod relative to an outer sleeve; and proximally sliding the outer sleeve relative to a needle sleeve thereby causing (i) a pin of the auto-injector to move along a ramped surface of the auto-injector to rotate an annular rotating collar of the auto-injector about a longitudinal axis of the outer sleeve and (ii) the flexible arm of the member to deflect to release the plunger rod such that the plunger rod moves relative to the member, relative to the outer sleeve, and relative to the needle sleeve under a proximally-directed force of a compression drive spring to dispense the medicament from the syringe.

20. The method of claim 19, wherein proximally sliding the outer sleeve relative to the needle sleeve causes the needle sleeve to move from (i) a first position in which a proximal end of the needle sleeve extends beyond a proximal end of the auto-injector by a first distance to (ii) a second position in which the proximal end of the needle sleeve extends beyond the proximal end of the auto-injector by a second distance that is less than the first distance.

21. The method of claim 20, comprising disposing the needle sleeve within the auto-injector such that an additional inward protrusion of the auto-injector is disposed within an opening of at least one of two distally projecting arms of the needle sleeve, a surface of the opening configured to engage the additional inward protrusion to limit further proximal movement of the needle sleeve within the auto-injector beyond the first position of the needle sleeve.

22. The method of claim 19, comprising attaching the member to a distal end of the auto-injector.

23. The method of claim 19, comprising disposing the compression drive spring in a recess of the member and engaging a proximal end of the compression drive spring to a surface of the plunger rod to apply the proximally-directed force to the plunger rod.

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 an auto-injector according to a first embodiment of the invention with a hinged release element before an injection,

(3) FIG. 2 is an expanded sectional view of the auto-injector according to the first embodiment, wherein the release element is blocked to prevent an inadvertent release of a drive means,

(4) FIG. 3 is an expanded sectional view of the hinged release element that is actuated to release the drive means,

(5) FIGS. 4A and 4B are two different sectional views of the auto-injector according to the first embodiment after a drug has been delivered,

(6) FIG. 5 is an isometric view of a needle shroud,

(7) FIGS. 6A and 6B are two different sectional views of the auto-injector according to the first embodiment after an injection has been performed,

(8) FIGS. 7A and 7B are two different sectional views of an auto-injector according to a second embodiment of the invention,

(9) FIG. 8 is a sectional view of a distal end section of the auto-injector according to the second embodiment of the invention,

(10) FIGS. 9A and 9B are two different sectional views of an auto-injector according to a third embodiment of the invention,

(11) FIG. 10 is a sectional view of a distal end section of the auto-injector according to the third embodiment of the invention.

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

DETAILED DESCRIPTION

(13) FIGS. 1A and 1B show two sectional views of an essentially cylindrical auto-injector 1 according to a first embodiment of the invention, wherein the sectional plane shown in FIG. 1A is oriented perpendicularly to the one shown in FIG. 1B. The auto-injector 1 comprises a housing 2, a proximal needle shroud 3, a syringe retainer 4 adapted to mount and move translatably with a pre-filled syringe 5 within the housing 2, a coupling shroud 6 slidably arranged within the housing 2 and a release element 7 hinged to a lateral side of the substantially cylindrical housing 2 of the auto-injector 1.

(14) A single drive means 8 is arranged between the distal end of the housing 2 and the coupling shroud 6 to bias the coupling shroud 6 in a proximal direction P towards the skin of a patient receiving an injection.

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

(16) The coupling shroud 6 is releasably coupled to a plunger 9 that is connected to a stopper 10 fluid-tightly sealing a distal end of a syringe barrel 11 containing a dose of a medicament M. 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) Before the injection, the coupling shroud 6 abuts against a distal end of the release element 7 to releasably retain the coupling shroud 6 in a first position I, wherein the coupling shroud 7 is located at a distal end of the housing 2. The drive means 8 is compressed, so that the coupling shroud 6 is strongly biased in the proximal direction P.

(18) The plunger 9 extends from the syringe barrel 11 in a distal direction D and comprises a shoulder 9.1 of increased diameter. The coupling shroud 6 comprises an inwardly protruding coupling catch 6.1 that bears against the shoulder 9.1 so that the plunger 9 and the coupling shroud 6 may be jointly moved in the proximal direction P by the action of the relaxing drive means 8.

(19) The proximal end of the needle shroud 3 is designed to be pushed against the skin surface 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 within 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 the distal direction D. A biasing means 13 bears against the needle shroud 3 and the housing 2 to bias the needle shroud 3 towards the advanced position PA.

(20) An annular rotating collar 14 engages an outer surface of the needle shroud 3. The rotating collar 14 rotates around an axis of the substantially cylindrical auto-injector 1 when the needle shroud 3 is longitudinally displaced in the proximal and/or the distal direction P, D. The rotating collar 14 acts as a damping means that creates friction to slow down the movement of the needle shroud 3 and to reduce the pressure exerted onto the skin of the patient receiving the injection.

(21) The release element 7 hinged to the housing 2 works like a see-saw: a proximal section may be pushed radially inwards, whereby the release element 7 pivots about a hinge 15, so that the distal section of the release element 7 moves radially outwards and the coupling shroud 6 is disengaged to release the drive means 8.

(22) The auto-injector 1 comprises safety means S that prevent an early release of the drive means 8. The safety means S ensure that the needle shroud 3 is pushed against the skin of the person receiving the injection before the drive means 8 may be released.

(23) According to the first embodiment of the invention, the safety means S comprise a blocking element 16 slidably arranged with the housing 2. When the needle shroud 3 is positioned in the advanced position PA, the blocking element 16 is positioned to prevent a pivoting movement of the release element 7 and thus a release of the coupling shroud 6. A radially outwards protruding blocking projection 16.1 of the blocking element 16 is located opposite to an inward protrusion 7.1 formed to the release element 7. If the proximal section of the release element 7 is pushed inwards, the inward protrusion 7.1 abuts against the blocking projection 16.1 to limit the pivoting movement of the release element 7, so that a release of the coupling shroud 6 and the drive means 8 is prevented.

(24) FIG. 2 shows a proximal section of the auto-injector 1 in a sectional view with the blocking element 16 positioned to prevent an inadvertent actuation of the hinged release element 7 to release the drive means 8.

(25) A distal end of the needle shroud 3 is clipped to the housing 2 and retained between two inwardly protruding retaining protrusions 2.1 formed into an inner surface of the housing 2. The two retaining protrusions 2.1 are longitudinally displaced from each other to limit the range of axial displacement of the needle shroud 3 with respect to the housing 2. A boss 3.1 formed into an outer surface of the needle shroud 3 bears against an inner surface of the blocking element 16, so that the blocking element 16 may move with the needle shroud 3 in the proximal direction P to deblock the release element 7.

(26) The blocking projection 16.1 comprises a central indention that forces a user of the auto-injector 1 to perform a sequence of actions necessary to inject the dose of the medicament M in the proper order. If the release element 7 is pushed inwards before the needle shroud 3 is moved proximally from the advanced position PA towards a retracted position PR (see FIG. 3) by pushing the needle shroud 3 towards the skin of the patient, the inward projection 7.1 is retained in the central indentation of the blocking projection 16.1, so that both the longitudinal displacement of the needle shroud 3 and the pivoting movement of the release element 7 is blocked.

(27) A proper sequence of actions for injecting the dose of the medicament M is described in the following. First, the user pushes the needle shroud 3 against the skin to move the needle shroud 3 distally to the retracted position PR illustrated in FIG. 3. The blocking element 16 jointly moves with the needle shroud 3 in the distal direction D, so that the release element 7 may be manually actuated to pivot about the hinge 15, whereby the drive means 8 are released.

(28) Upon release of the drive means 8, the coupling shroud 6 is urged in the proximal direction P. The single and fully compressed drive means 8 drives the coupling shroud 6 and the plunger 9 coupled thereto in the proximal direction P. The coupling shroud 6 first pushes the syringe retainer 4 by means of plunger 9, stopper 10 and the friction between stopper 10 and syringe 11 proximally to insert the injection needle 12 into the skin of the patient and a first clip connection 2.2 formed into a lateral side of the housing 2 latches to an outward protrusion 4.1 of the syringe retainer 4, as illustrated in more detail in FIG. 4B.

(29) The syringe retainer 4 and the pre-filled syringe 5 mounted thereto is now locked to the housing 2. The coupling shroud 6 is moved further in the proximal direction P by the action of the relaxing drive means 8, whereby the plunger 9 is depressed into the syringe barrel 11 to expel the dose of the medicament M contained therein through the injection needle 12.

(30) FIGS. 4A and 4B show two sectional views of the auto-injector 1 according to the first embodiment of the invention with the plunger 9 fully depressed within the syringe barrel 11. The dose of the medicament M has been delivered beneath the skin of the patient. The coupling shroud 6 is located in an intermediate second position II. The drive means 8 is not yet completely discharged and biases the coupling shroud 6 in the proximal direction P. The shoulder 9.1 engages a ramp of the coupling catch 6.1 to deflect the coupling catch 6.1 in a radial outward direction. An aperture 2.3 is formed into the housing 2 to allow for a radial outward deflection of the coupling catch 6.1, so that the coupling catch 6.1 overcomes the shoulder 9.1 decoupling the coupling shroud 6 from the plunger 9.

(31) In a possible embodiment of the invention, the aperture 2.3 defining the second position II is located at a longitudinal position along the housing 2 that allows for a full depression of the plunger 9 completely emptying the syringe barrel 11 before the plunger 9 is decoupled from the coupling shroud 6.

(32) Alternatively, the aperture 2.3 defining the second position II may be located at a longitudinal position along the housing 2 that allows for an adjustment space accounting for manufacturing tolerances. The adjustment space is dimensioned as to allow for a reliable decoupling of the plunger 9 from the coupling shroud 6 even if the parts constituting the auto-injector 1 comprise mismatch in mould or are slightly misaligned. In this alternative embodiment, the dose of the medicament M may or may not be completely expelled before the plunger 9 is decoupled from the coupling shroud 6.

(33) The retaining protrusions 2.1 are elastically supported and may be deflected radially outwards to release the needle shroud 3. The coupling shroud 6 engages a ramp of the retaining protrusions 2.1 and splays the retaining protrusions 2.1 outwards, whereby the needle shroud 3 is released and allowed to move proximally from the retracted position PR towards an extended safe position PS.

(34) The drive means 8 is still partially loaded when the coupling shroud 6 is located in the second position II. In a possible embodiment of the invention the biasing force of the drive means 8 exerted on the coupling shroud 6 in the second position II is about 10 N.

(35) The coupling shroud 6 bears against a distal end of the needle shroud 3, so that the needle shroud 3 may be moved to the safe position PS by the action of the further relaxing drive means 8. As the biasing force exerted onto the needle shroud 3 by the drive means 8 may be relatively large and could even bruise the patient, the rotating collar 14 is arranged within the housing 2 to partially absorb the excess energy of the drive means 8 and slow down the proximal movement of the needle shroud 3 by generating friction.

(36) FIG. 5 shows an isometric view of the needle shroud 3. A helical recess 3.2 is formed into a tubular proximal section 3.3 of the needle shroud 3. The proximal section 3.3 of the needle shroud 3 is inserted into the annular rotating collar 14, wherein a pin 14.1 formed to an inner surface of the rotating collar 14 protrudes into the helical recess 3.2 as shown in FIG. 6A. The linear translatory movement of needle shroud 3 towards the safe position PS thus causes the rotating collar 14 to rotate within the housing 2 around the axis of the auto-injector 1.

(37) FIGS. 6A and 6B show two different sectional views of the auto-injector 1 according to the first embodiment of the invention after the injection has been performed. The needle shroud 3 is permanently locked to the safe position PS by a second clip connection 2.4 formed into the housing 2. The needle shroud 3 surrounds the injection needle 12 and extends a suitable distance proximally beyond the needle tip to avoid accidental needle stick injuries after the auto-injector 1 has been used.

(38) FIGS. 7A and 7B show two different sectional views of an auto-injector 1 according to a second embodiment of the invention before the injection. The sectional plane shown in FIG. 7A is oriented perpendicularly to the sectional plane shown in FIG. 7B.

(39) The needle shroud 3 of the auto-injector 1 according to the second embodiment substantially extends over the axial length of the housing 2. Before the injection, the needle shroud 3 is mounted to the housing 2 by the retaining protrusions 2.1 that protrude into orifices formed into a lateral side of the needle shroud 3. The orifices comprise a longitudinal length that allows the needle shroud 3 to be slid from the advanced position PA to the retracted position PR.

(40) A retaining catch 2.5 is formed to an inner surface of the housing 2 and protrudes through an opening formed into the needle shroud 3 to releasably mount the syringe retainer 4 retaining the pre-filled syringe 5. The retaining catch 2.5 comprises a bevelled ramp and is deflectable in a radial outward direction. The retaining catch 2.5 latches to the outward protrusion 4.1 formed to the outer surface of the syringe retainer 4 when the needle shroud 3 is in the advanced position PA

(41) The needle shroud 3 abuts against the bevelled ramp of the retaining catch 2.5 when the needle shroud 3 is moved from the advanced position PA in the distal direction D, whereby the retaining catch 2.5 is deflected in a radial outward direction and disengages the outward protrusion 4.1, so that the syringe retainer 4 may be moved in the proximal direction P.

(42) The release element 7, shown in more detail in FIG. 8, is arranged as a push button and mounted to a distal end of the housing 2. The release element 7 may be pushed in the proximal direction P to release the drive means 8 when the needle shroud 3 is in the retracted position PR, whereas the release element 7 and thus the release of the drive means 8 is blocked when the needle shroud 7 is in the advanced position PA.

(43) According to the second embodiment of the invention, the safety means S that prevent the early release of the drive means 8 comprises clips 2.6 that may deflect in a radial outward direction and a bushing 17 locking the plunger 9 before use of the auto-injector 1.

(44) Before the auto-injector 1 is used, the clips 2.6 formed to the housing 8 latch to the release element 7. (See FIG. 7B) The clips 2.6 block the movement of the release element 7 in the proximal direction P, so that a manual actuation of the release element 7 is prevented as long as the needle shroud 3 is in the advanced position PA. A distal movement of the release element 7 is blocked by a first detent 2.7 engaging an inner surface of the release element 7.

(45) The clip 2.6 comprises a ramp that the needle shroud 3 engages when pushed distally from the advanced position PA to the refracted position PR, whereby the clip 2.6 is deflected radially outwards to disengage the needle shroud 3. The release element 7 may be pushed in the proximal direction P when the needle shroud 3 is in the retracted position PR.

(46) The plunger 9 comprises a distal end 9.2 of increased diameter that is retained in the bushing 17 firmly attached to a distal end of the housing 2. The bushing 17 comprises an inner surface corresponding to the distal end 9.2 of the plunger 9 that engages the distal end 9.2 in a locked position L to lock the plunger 9 and the coupling shroud 6 coupled thereto to the housing 2 before use of the auto-injector 1. The bushing 17 abuts radially against an annular inner collar 7.2 of the release element 7 in the locked position L shown in FIGS. 7A and 7B. A radial outward deflection of the bushing 17 releasing the plunger 9 is thus prevented.

(47) FIG. 8 shows a sectional view of a distal end section of the auto-injector 1 according to the second embodiment of the invention. The needle shroud 3 is located in the retracted position PR and the release element 7 is pushed in the proximal direction P, so that the bushing 17 disengages the annular inner collar 7.2 of the release element 7. The bushing 17 is positioned in an unlocked position U and may deflect outwardly to release the plunger 9.

(48) Furthermore, the bushing 17 acts as a counter bearing for the drive means 8 bearing against the bushing 17 in the distal direction D.

(49) FIGS. 9A and 9B show two different sectional views of an auto-injector 1 according to a third embodiment of the invention, wherein the release element 7 is arranged as an outer sleeve extending over a substantial length of the auto-injector 1.

(50) According to the third embodiment of the invention, the safety means S that prevent the early release of the drive means 8 comprise clips 2.6, second and third detents 2.8, 7.3, a locking catch 6.2 formed to the coupling shroud 6 and the bushing 17 that comprises an inner sleeve 17.1 receiving a lug 7.4, wherein the locking catch 6.2 latches to a collar 17.2 of the inner sleeve 17.1.

(51) The release element 7 of the third embodiment is gripped by a user to perform the injection. When the needle shroud 3 is in the advanced position PA, the proximal displacement of the release element 7 is blocked by the clips 2.6 in a similar manner as in the second embodiment described herein above.

(52) Additionally, the release element is releasably retained in position before the injection by the second and the third detents 2.8, 7.3 respectively formed to an outer surface of the housing 2 and to an inner surface of the release element 7, wherein the second and third detents 2.8, 7.3 comprise correspondingly shaped ramps facing each other.

(53) The bushing 17 of the third embodiment comprises the inner sleeve 17.1 that receives the lug 7.4 formed to an inner surface of the release element 7. A proximal end of the lug 7.4 snugly fits in the central aperture of the inner sleeve 17.1, so that an inward deflection of the inner sleeve 17.1 is prevented.

(54) The inner sleeve 17.1 comprises a collar 17.2. An inwardly protruding locking catch 6.2 of the coupling shroud 6 latches to the collar 17.2 before use of the auto-injector 1 to releasably retain the coupling shroud 6 in the first position I.

(55) FIG. 10 shows a sectional view of a distal end section of the auto-injector 1 according to the third embodiment of the invention. The release element 7 is actuated and moved in the proximal direction P. The proximal end of the lug 7.4 disengages the inner sleeve 17.1 of the bushing 17, so that the inner sleeve 17.1 may bend radially inwards, whereby the locking catch 6.2 disengages the collar 17.2 and releases the coupling shroud 8 and the drive means 8.