Housing for an Injection Device

Abstract

The present invention relates in one aspect to a housing for an injection device, comprising: a body (30) to accommodate a drive mechanism (5) to operably engage with a piston (52) of a cartridge (50) filled with a liquid injectable medicament (53), a cartridge holder (20) having a cartridge receiving space (25) to accommodate the cartridge (50), wherein the cartridge holder (20) and the body (30) comprise an elongated shape and extend along an axial longitudinal direction (1, 2), wherein the cartridge holder (20) has an insert section (21) at a proximal end (23), wherein the body (30) has a receptacle (31) at a distal end (33) to receive the insert section (21) of the cartridge holder (20), wherein the body (30) comprises a first latch element (34) on an inside (32) of a sidewall (32) of the receptacle (31), wherein the cartridge holder (20) comprises a first through recess (24) in a sidewall (22) of the insert section (21) which through recess (24) is configured to receive the first latch element (34), wherein the through recess (24) comprises a narrowed neck receiving portion (24a) extending axially into a widened latch receiving portion (24b), wherein a first lateral width (w1) of the neck receiving portion (24a) is smaller than a second lateral width (w2) of the latch receiving portion (24b).

Claims

1. A housing for an injection device, the housing comprising: a body (30) to accommodate a drive mechanism (5) to operably engage with a piston (52) of a cartridge (50) filled with a liquid injectable medicament (53), a cartridge holder (20) having a cartridge receiving space (25) to accommodate the cartridge (50), wherein the cartridge holder (20) and the body (30) comprise an elongated shape and extend along an axial longitudinal direction (1, 2), wherein the cartridge holder (20) has an insert section (21) at a proximal end (23), wherein the body (30) has a receptacle (31) at a distal end (33) to receive the insert section (21) of the cartridge holder (20), wherein the body (30) comprises a first latch element (34) on an inside (35) of a sidewall (32) of the receptacle (31), wherein the cartridge holder (20) comprises a first through recess (24) in a sidewall (22) of the insert section (21) which through recess (24) is configured to receive the first latch element (34), wherein the through recess (24) comprises a narrowed neck receiving portion (24a) extending axially into a widened latch receiving portion (24b), wherein a first width (w1) of the neck receiving portion (24a) is smaller than a second width (w2) of the latch receiving portion (24b).

2. The housing according to claim 1, wherein the first through recess (24) adjoins the proximal end (23) of the cartridge holder (20) and wherein the through recess (24) is open towards the proximal end (23).

3. The housing according to claim 1 or 2, wherein the neck receiving portion (24a) adjoins the proximal end (23) and wherein the neck receiving portion (24a) is located axially between the latch receiving portion (24b) and the proximal end (23).

4. The housing according to any of the preceding claims, wherein the first latch element (34) comprises a narrowed neck portion (34a) extending axially into a widened latch portion (34b).

5. The housing according to claim 4, wherein the latch portion (34b) comprises a maximal width (w3) that is larger than the first width (w1).

6. The housing according to claim 5, wherein the latch portion (34b) of the first latch element (34) is wedge-shaped with an increasing width in proximal direction (2).

7. The housing according to claim 5 or 6, wherein the latch portion (34b) comprises a minimal width (w4) at a distal end and further comprises the maximal width (w3) at a proximal end.

8. The housing according to any one of the preceding claims, wherein the receptacle (31) comprises a first protrusion (134) which extends inwardly from the sidewall (32) of the receptacle (31) at a first distance (t1) from the first latch element (34).

9. The housing according to claim 8, wherein the insert section (21) comprises a first slit (124) adjoining the proximal end (23) and extending in distal direction (1) from the proximal end (23) at the first distance (t1) from the first through recess (24) and wherein the first slit (124) is configured to receive the first protrusion (134).

10. The housing according to claim 9, wherein a first sidewall section (122) of the insert section (21), which is confined by the first through recesses (24) and the first slit (124), is flexible in a tangential direction from an initial unbiased state towards a biased state when the latch element (34) axially enters into the first through recess (24).

11. The housing according to claim 10, wherein a transverse size (S1) of the first protrusion (134) is substantially equal to a transverse size (S2) of the first slit (124) when the first sidewall section (122) is in the unbiased state.

12. The housing according to claim 10 or 11, wherein the first protrusion (134) comprises a lateral abutment face (135) to abut with a lateral abutment face (125) of the first sidewall section (122) of the insert section (21).

13. The housing according to any one of the preceding claims 8 to 12, wherein the first protrusion (134) comprises a ramp section (136) with a beveled surface (138) extending inwardly from the inside (35) of the sidewall (32) of the receptacle (31).

14. The housing according to claims 12 and 13, wherein the ramp section (136) is located at or near a proximal end of the receptacle (31) and wherein the lateral abutment face (135) of the first protrusion (134) adjoins the ramp section (136).

15. An injection device for administering an injectable medicament into biological tissue, the device comprising: a housing according to any one of the preceding claims, a drive mechanism (5) assembled inside the body (30), and a cartridge (50) assembled inside the cartridge holder (20).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0073] In the following, a non-limiting embodiment of the invention is described in detail by making reference to the drawings, in which:

[0074] FIG. 1 shows a perspective and partially cut view of the distal end of a body of a housing of an injection device,

[0075] FIG. 2 shows a perspective view of a cartridge holder to be connected to the body according to FIG. 1,

[0076] FIG. 3 is an enlarged perspective view of the insert section of the cartridge holder,

[0077] FIG. 4 is an enlarged and partially cut view of the cartridge holder and of the body at the beginning of an insertion of the cartridge holder's insert section into the receptacle of the body,

[0078] FIG. 5 is a view according to FIG. 4 but with cartridge holder and body in a final assembly configuration,

[0079] FIG. 6 is a view according to FIGS. 4 and 5 with the assembly of body and cartridge holder rotated by 90 degrees with respect to the longitudinal axis,

[0080] FIG. 7 is an enlarged and partial view of a slit in the sidewall of the insert section of the cartridge holder in an initial unbiased state,

[0081] FIG. 8 is the same view as FIG. 7 but with the sidewall section of the cartridge holder in a biased state in which the first slit is narrowed due to a tangentially directed deflection of the sidewall section,

[0082] FIG. 9 is a partially cut and perspective view during insertion of the insert section of the cartridge holder into the receptacle prior to or at the beginning of a tangential deflection of a sidewall section of the cartridge holder's insert section,

[0083] FIG. 10 is the same view as FIG. 9 but with cartridge holder and body during a tangential deflection and deformation of a sidewall section of the insert section of the cartridge holder prior to reach a final state of assembly,

[0084] FIG. 11 is a perspective view according to FIGS. 9 and 10 when the cartridge holder and the body have reached the final assembly configuration,

[0085] FIG. 12 is an exploded view of an exemplary injection device equipped with a housing in accordance to FIGS. 1-11 and

[0086] FIG. 13 is a longitudinal cross-section through the injection device according to FIG. 12.

DETAILED DESCRIPTION

[0087] The injection device 10 as shown in FIGS. 12 and 13 is configured as a pen-type injector. It comprises an elongated housing 11 extending in a longitudinal or axial direction. Towards a distal direction 1 the injection device 10 comprises a distal housing component denoted as cartridge holder 20. In the opposite longitudinal direction the housing 11 comprises a second housing component denoted as body 30. Both housing components, namely cartridge holder 20 and body 30 are of tubular and elongated shape. The cartridge holder 20 is configured to accommodate a cartridge 50 comprising a tubular-shaped barrel 51 filled with a liquid medicament 53. At a distal end the cartridge 50 comprises a pierceable seal 54 typically inform of a pierceable septum of an elastomeric material.

[0088] At the opposite proximal end the cartridge 50 is sealed by a piston 52 slidably arranged inside the barrel 51 of the cartridge 50. For dispensing of a dose of the liquid medicament 53 the cartridge holder 20 comprises a threaded socket 19 at its distal end to receive a correspondingly threaded needle assembly with a double-tipped injection needle. A proximal tipped end of the injection needle of the needle assembly, which is presently not illustrated, is configured to pierce the distal seal 54 of the cartridge 50 thereby gaining access to the interior of the cartridge 50. The distal end of the injection needle is then configured to puncture biological tissue to deliver the medicament into biological tissue. For medicament delivery the piston 52 is to be displaced in distal direction 1 under the action of a distally advancing piston rod 110 of a drive mechanism 5 of the injection device 10. The drive mechanism 5 is accommodated and fixed in the body 30 of the injection device 10. There is further provided a protective cap 40 covering the distal portion of the cartridge holder 20 when assembled and attached thereto.

[0089] The cartridge holder 20 and the body 30 are to be interconnected by means of a positive connection as it is explicitly shown in FIG. 4. As illustrated in FIGS. 1 and 2 the cartridge holder 20 comprises a proximal end 23 to interconnect non-releasable with a distal end 33 of the body 30. The cartridge holder 20 and the body 30 are interconnectable in an interleaved or nested way. In the presently illustrated embodiment the proximal connecting end of the cartridge holder 20 comprises an insert section 21 axially confined in distal direction 1 by a radially outwardly extending annular ridge or flange section 27. The distal connecting end of the body 30 comprises a receptacle 31 to axially receive the insert section 21 of the cartridge holder 20. The outer diameter of the insert section 21 exactly matches with the inner diameter of the receptacle 31 so that the insert section 21 can be inserted into the receptacle 31 by means of a sliding motion in proximal direction 2 relative to the body 30.

[0090] From the combination of the FIGS. 2-4 it is immediately apparent, that the insert section 21 of the cartridge holder 20 is located at a proximal end 23 of the cartridge holder 20 and that the receptacle 31 is located at a distal end 33 of the body 30. Once mutually assembled the insert section 21 of the cartridge holder 20 is fully or entirely located inside the receptacle 31 of the body 30.

[0091] The annular flange section 27 radially outwardly protruding from the sidewall 22 of the insert section 21 comprises an abutment face 28 facing in proximal direction 2. When assembled with the body 30 the abutment face 28 is in axial abutment with a distal end face 38 of the sidewall 32 of the body 30. Additionally and as it is apparent from FIG. 4 the proximal end 23 of the cartridge holder 20 may optionally also axially abut with a web 36 extending across the inner diameter of the tubular-shaped body 30. The web 36 comprises a central through opening 37 that may be threaded. The threaded through opening 37 may be threadedly engaged with the piston rod 110, in particular with a distal thread 112 of the piston rod 110 of the drive mechanism 5 as illustrated in FIGS. 12 and 13. The web 36 may comprise a closed surface and confines the receptacle 31 of the body 30 in proximal direction.

[0092] As further illustrated in FIG. 2 the cartridge holder 20 comprises a cartridge receiving space 25 in its interior that is typically completely occupied by the cartridge 50. Near a distal end or in an intermediate section the sidewall 22 of the cartridge holder 20 further comprises at least one transparent window 26 or a respective through recess in order to provide visual inspection of the cartridge 50 located therein. There is further shown a radially outwardly extending protrusion 29 in close proximity to the flange section 27. The protrusion 29 which is located distally from the flange section 27 and which is hence visible from outside when the injection device 10 is configured to engage with a correspondingly-shaped protrusion or snap feature on the inside of the sidewall of the protective cap 40. In this way a snap-fit or positive engagement of cartridge holder 20 and protective cap 40 can be provided.

[0093] As it is apparent from FIGS. 1 and 2 as well as from FIGS. 4 and 5 there is provided at least a first through recess 24 in the sidewall 22 of the insert section 21 of the cartridge holder 20. The first through recess comprises a neck receiving portion 24a having a first width w1. The neck receiving portion 24a axially extends into a laterally or tangentially widened latch receiving portion 24b of the first through recess 24. The latch receiving portion 24b comprises a second width w2 that is larger than the first width w1.

[0094] As further shown in FIGS. 2 and 3 the first through recess 24 adjoins the proximal end 23 of the cartridge holder 20. The first through recess 24 is hence open towards the proximal direction 2. It is configured to receive a latch element 34 protruding radially inwardly from the inside 35 of the sidewall 32 of the receptacle 31.

[0095] The radial extension or radial protrusion of the first latch element 34 substantially matches with the thickness of the sidewall 22 of the insert section 21 of the cartridge holder 20. So when fully assembled as illustrated in FIG. 5 the first latch element 34 entirely occupying the first through recess 24 forms a somewhat even and closed inner surface with the inside of the sidewall 22 of the insert section 21.

[0096] The latch element 34 comprises a latch portion 34b and an adjoining neck portion 34a. The neck portion 34a extends in axial distal direction into the latch portion 34b. As illustrated in FIGS. 1, 4 and 5 the latch portion 34b is wedge-shaped and comprises an increasing tangential width in proximal direction 2. Hence, the latch portion 34b comprises a minimal width w4 at a distal end as shown in FIG. 4. Near a proximal end and close or in direct vicinity to the neck portion 34a the latch portion 34b comprises a maximal width w3 in tangential direction. The maximal width w3 matches with the second width w2 of the latch receiving portion 24b of the first through recess 24.

[0097] As it is exemplary illustrated in FIG. 4, the minimal width w4 at the distal end of the latch element 34b is smaller than the first width w1 of the neck receiving portion 24a of the first through recess 24. So for inserting the first latch element 34 into the first through recess 24 along the axial longitudinal direction, and in particular in distal direction 1 the distal end of the wedge-shaped first latch element 34 will easily enter the narrowed neck receiving portion 24a of the first through recess 24. Upon a further distally directed displacement of the body 30 relative to the cartridge holder 20 the side faces 34c and 34d of the latch element 34 will engage with correspondingly-shaped side faces 24c of the insert section that laterally or tangentially confine the neck receiving portion 24a.

[0098] Since the latch portion 34b continuously and smoothly widens in tangential direction towards the proximal direction and since the latch portion 34b is urged further into the neck receiving portion 24a the side faces 34c, 34d of the latch portion 34b will start to abut and to engage with the side faces 24c, 24d of the insert section 21. Consequently and as the maximal width w3 of the latch portion 34b is larger than the first width w1 and since the first latch element 34, in particular its latch portion 34b is substantially inelastic the insertion of the latch portion 34b into the first through recess 24 leads to a temporary deformation of the insert section 21 of the cartridge holder 20. Consequently, the neck receiving portion 24a of the first through recess 24 will be subject to a widening in tangential or lateral direction.

[0099] As a consequence a first sidewall section 122 of the insert section 21 that tangentially confines the first through recess 24 will be subject to a lateral or tangential deformation so as to give way for the widened latch portion 34 of the first latch element. When reaching a final assembly configuration in which the latch element 34 is completely received inside the first through recess 24 abutment faces 34e and 34f at the proximal end of the latch portion 34b will engage with correspondingly-shaped abutment faces 24e and 24f that are located at the proximal end of the latch receiving portion 24b of the first through recess 24. The abutment faces 34e and 34f face in proximal direction 2 and extend in tangential direction inwardly from the proximal end of the latch portion 34b. Via the abutment faces 34e and 34f the latch portion 34b extends into the tangentially narrowed neck portion 34a.

[0100] The correspondingly-shaped abutment faces 24e and 24f of the first through recess 24 face in distal direction 1 so as to axially abut with the abutment faces 34e and 34f. Once a final assembly configuration has been reached as shown in FIG. 5, the abutment faces 24e and 34e as well as the abutment faces 24f and 34f are in axial abutment so as to prevent a sliding movement of the cartridge holder 20 in distal direction relative to the body 30. In this way an axial interlock of cartridge holder 20 and body 30 is obtained. The mutual engagement of the first through recess 24 with the first latch element 34 provides an axial interlock that inhibits a separation of cartridge holder 20 and body 30 in axial direction. The engagement of the end face 38 with the abutment 28 of the annular flange section 27 as well as an eventual axial abutment of the proximal end 23 of the cartridge holder 20 with the web 36 extending across the inner cross-section of the body 30 prevent a further insertion of the insert section 20 into the body 30. This abutment therefore provides a kind of an axial interlock that prevents a further movement of the cartridge holder 20 in proximal direction relative to the body 30.

[0101] Since the first through recess 24 is open towards the proximal direction 2 the positive engagement of the first through recess 24 with the first latch element 34 can be obtained without any radial deformation of the insert section 21 of the cartridge holder. In this way the cartridge 50 already assembled inside the cartridge holder 20 prior to the final assembly step of interconnecting body 30 and cartridge holder 20 will not be subject to mechanical load acting in radial direction. In this way mechanical stress eventually applied to the cartridge during the final step of assembly of body 30 and cartridge holder 20 can be effectively reduced. A likelihood of cartridge breakage can be also reduced which enhances production quality and patient safety.

[0102] From FIG. 2 as well as from FIG. 6 it is immediately apparent that the cartridge holder comprises not only the first through recess 24 but also a second through recess 224. In the present embodiment the second through recess 224 is located diametrically opposite to the first through recess 24. Correspondingly also the body 30 comprises not only a first latch element 34 but also a second latch element which is not shown explicitly in the Figures but which is identically shaped and configured as the first latch element 34. The second latch element is also located opposite to the first latch element 34. By having two pairs of through recesses and latch elements, a twofold positive interconnection of body 30 and cartridge holder 20 can be provided thus improving the stability and durability of the positive interconnection of body 30 and cartridge holder 20.

[0103] In addition to the mutual engagement of at least the first through recess 24 with the first latch element 34 the insert section 21 of the cartridge holder 20 further comprises a first slit 124 that adjoins the proximal end 23 and which extends in distal direction 1 from the proximal end 23. The first slit 124 is located at a first tangential or lateral distance t1 from the first through recess 24 as illustrated in FIG. 2. Correspondingly to the first slit 124 also the receptacle 31 comprises a first protrusion 134 that is axially elongated and which extends inwardly from the inside 35 of the sidewall 32 of the receptacle 31. The first protrusion 134 is located at the first tangential or lateral distance t1 from the first latch element 34.

[0104] A transverse size S1 of the first protrusion 134 is substantially equal to a transverse size S2 of the second through recess 124 when the first sidewall section 122 is in an unbiased state. At least an axial section of the first protrusion, typically a proximal end section of the first protrusion 134 comprises a transverse size S1, hence an expansion in tangential direction that is substantially identical to the transverse size S2 of the first slit 124. Upon final assembly of body 30 and cartridge holder 20 not only the first latch element 34 engages with the first through recess 24 but also the first protrusion 134 axially enters the first slit 124. The first slit 124 and the first protrusion 134 may engage simultaneously with the engagement of the first latch element 34 and the first through recess 24. The engagement of the first protrusion 134 with the first slit 124 provides an additional axial and longitudinal guiding for the insert section 21 sliding into the receptacle 31 in proximal direction 2 relative to the body 30.

[0105] Apart from that and when reaching a final assembly configuration as shown in FIGS. 6 and 11 a lateral abutment face 125 of a first sidewall section 122 of the insert section 21 that confines the first slit 124 is in tight tangential or circumferential engagement with a lateral abutment face 135 of the first protrusion 134. As shown in FIG. 11 and when a final assembly configuration has been reached the sidewall section 122 located laterally or tangentially between the first slit 124 and the first through recess 24 is tangentially sandwiched between the first latch element 34 and the first protrusion 134. Hence, when fully assembled the first sidewall section 122 of the insert section 21 of the cartridge holder 20 entirely occupies a free space 39 laterally or tangentially between the first latch element 34 and the first protrusion 134. The lateral abutment of abutment faces 125 and 135 actually prevent a deformation of the first sidewall section 122 towards the tangential or lateral direction.

[0106] This serves to prevent a release or disengagement of the first latch element 34 and the first through recess 24. Once the positive interconnection of body 30 and housing 20 is attained it cannot be abrogated without destroying at least one of the housing component's cartridge holder 20 or body 30.

[0107] Since the geometric shape, especially the tangential width of the first sidewall section 122 exactly matches with the free space 39 between the first latch element 34 and the first protrusion 134 it would be quite difficult to arrive at the final assembly configuration as shown in FIG. 11 since the first sidewall section 122 is subject to a tangentially directed elastic deformation during the process of assembly as described above. In FIGS. 7 and 8 the degree of tangential deformation of the first sidewall section 122 is apparent. In FIG. 7 the initial unbiased state is illustrated that corresponds to the geometry of the insert section 21 according to FIG. 4. In FIG. 8 a biased state of the first sidewall section 122 is shown that substantially corresponds to the configuration of FIG. 10, in which a final assembly configuration has been almost reached.

[0108] Since the neck receiving portion 24a of the first through recess 24 is subject to a tangential widening, the first sidewall section 122 is subject to a respective tangential deformation at the expense of the tangential width of the first slit 124. From a comparison of FIGS. 7 and 8 it is immediately apparent that the first slit 124 in FIG. 8 is narrower in tangential or circumferential direction compared to the first slit 124 with the first sidewall section 122 being in the unbiased initial state.

[0109] Since the tangential width of the first slit 124 exactly matches with the tangential width of the first protrusion 134 the first protrusion 134 will be unable to completely enter the first slit 124 as long as the first sidewall section 122 is subject to an elastic deformation. For enabling and facilitating the process of assembly, i.e. the sliding motion of the insert section 21 into the receptacle 31, the first protrusion 134 comprises a ramp section 136 as best seen in FIG. 1. Typically, the longitudinally extending first protrusion 134 comprises two ramp sections 136 near its proximal end, hence near or adjoining the web 36. The at least one ramp section 136 comprises a beveled surface 138 facing in distal direction 1. The beveled surface 138 extends from the inside 35 of the sidewall 32 of the receptacle radially inwardly as seen in proximal direction 2.

[0110] Hence, as seen from the distal end towards the proximal end of the first protrusion the ramp section 136 comprises a gradually and continuously increasing extension radially inwardly from the inside 35 of the sidewall 32. The distal end of the ramp section 136 is integrally formed with the inside 35 of the sidewall 32. The distal end of the ramp section 136 is flush with the inside 35 of the sidewall 32. As the insert section 21 of the cartridge holder 20 is pushed into the receptacle 31 as shown in the sequence of FIGS. 9-11 a proximal and lateral edge 126 of the first sidewall section 122 engages with the ramp section 136 of the first protrusion 134. In this way the proximal and lateral edge 126 of the first sidewall section 122 is subject to a small but distinct radially inwardly directed deformation and deflection. Prior to reach a final state of assembly the lateral edge 126 of the first sidewall section 122 radially overlaps with at least the ramp section 136 of the first protrusion 134. This radial overlap persists during the process of assembly and as long as the first sidewall section is subject to a tangential deflection from its initial unbiased state.

[0111] Due to the radial deformation of the edge 126 the first sidewall section 122 is allowed to flex and to deform in tangential or lateral direction towards the first protrusion 134 and to radially overlap at least in sections with the first protrusion 134. When the final assembly configuration has been reached as shown in FIG. 11 the first sidewall section 122 returns into its unbiased state thereby increasing the lateral or tangential size of the first slit 124 to the initial size. Consequently and due to the mutually matching geometries of the first sidewall section 122 and the free space 39 between the first latch element 34 and the first protrusion 134 the first sidewall section, in particular the proximal and lateral edge 126 thereof is free to relax radially outwardly so as to enter and to occupy the free space 39.

[0112] As it is shown in FIGS. 1 and 11 the ramp portion 136 with its beveled surface 138 is located at a proximal end of the receptacle 31. It is hence operable to deflect only a limited proximal and lateral edge 126 of the insert section 21 of the cartridge holder 20. Positioning of the ramp section 136 towards a proximal end of the interface of insert section 21 and receptacle 31 is beneficial to reduce any radially inwardly directed mechanical load that may otherwise be present to the cartridge 50. If the radially inwardly directed deflection of the proximal and lateral edge 126 of the first sidewall section 122 should be of such a magnitude that the inside of the first sidewall section 122 gets in mechanical contact with the barrel 51 of the cartridge 50 the mechanical load will be present to a proximal end of the cartridge, which is stabilized by the piston 54 as well as by an enamel edge of the vitreous body 51 of the cartridge.

[0113] In the present embodiment there are provided two protrusions, 134 and 334, that are provided on opposite, e.g. geometrically opposite portions on the inside 35 of the sidewall 32 of the receptacle 31. Likewise and corresponding to the position and shape of the first protrusion 134 and the second protrusion 334 there are provided a first slit 124 to receive the first protrusion 134 as well as a second slit 324 to receive the second protrusion 334.

[0114] In the illustrated embodiment the first and the second protrusions 134 and 334 are located diametrically opposite. Correspondingly, also the first slit 124 and the second slit 324 are located diametrically opposite on the insert section 21. Logically, there is not only a first sidewall section 122 as described above, but there exists altogether four sidewall sections 122, 222, 322 and 422 that are simultaneously subject to a tangential deformation as the first and second latch elements 34 engage with correspondingly-shaped first and second through recesses 24, 224. In this context it is further to be mentioned, that the present concept of establishing a snap-fit connection of cartridge holder 20 and body 30 is not limited to only two pairs of through recesses and latch elements or two pairs of slits and protrusions but may be expanded to an arbitrary number of mutually positively engaging structures.

[0115] In the following the general functionality and features of the drive mechanism 5 is described. The drive mechanism 5 is only exemplary for one of a plurality of differently configured drive mechanisms that are generally implementable in a disposable pen-injector. The drive mechanism as described above is explained in more detail e.g. in WO2004/078239A1, WO 2004/078240A1 or WO 2004/078241A1 the entirety of which being incorporated herein by reference. The interface and interconnection of housing components, such like the cartridge holder 20 and the body 30 as explained above can be generally implemented with a large variety of different drive mechanisms 5 and injection devices.

[0116] The drive mechanism 5 comprises numerous mechanically interacting components. A flange like web 36 or support of the body 30 comprises a threaded axial through opening 37 threadedly engaged with a distal thread 112 of the piston rod 110. The distal end of the piston rod 110 comprises a bearing 115 on which a pressure foot 116 is free to rotate with the longitudinal axis of the piston rod 110 as an axis of rotation. The pressure foot 116 is configured to axially abut against the proximally facing thrust receiving surface of the piston 52 of the cartridge 50. During a dispensing action the piston rod 110 rotates relative to the body 30 thereby experiencing a distally directed advancing motion relative to the body 30 and hence relative to the barrel 51 of the cartridge 50. As a consequence, the piston 52 of the cartridge 50 is displaced in distal direction by a well-defined distance due to the threaded engagement of the piston rod 110 with the body 30.

[0117] The piston rod 110 is further provided with a second thread 114 at its proximal end. The distal thread 112 and the proximal thread 114 are oppositely handed.

[0118] There is further provided a drive sleeve 100 having a hollow interior to receive the piston rod 110. The drive sleeve 100 comprises an inner thread threadedly engaged with the proximal thread 114 of the piston rod 110. Moreover, the drive sleeve 100 comprises an outer threaded section 105 at its distal end. The threaded section is axially confined between a distal flange portion 102 and another flange portion 104 located at a predefined axial distance from the distal flange portion 102. Between the two flange portions 102, 104 there is provided a last dose limiting member 106 in form of a semi-circular nut having an internal thread matching the threaded section 105 of the drive sleeve 100.

[0119] The last dose limiting member 106 further comprises a radial recess or protrusion at its outer circumference to engage with a complementary-shaped recess or protrusion at an inside of the sidewall 32 of the body 30. In this way the last dose limiting member 106 is splined to the body 30. A rotation of the drive sleeve 100 in a dose incrementing or clockwise direction during consecutive dose setting procedures leads to an accumulative axial displacement of the last dose limiting member 106 relative to the drive sleeve 100. There is further provided an annular spring 96 that is in axial abutment with a proximally facing surface of the flange portion 104. Moreover, there is provided a tubular-shaped clutch member 90. At a first end the clutch member 90 is provided with a series of circumferentially directed saw teeth. Towards a second opposite end of the clutch member 90 there is located a radially inwardly directed flange.

[0120] Furthermore, there is provided a dose dial or dose indicating sleeve 80. The dose indicating sleeve 80 is provided outside of the spring 96 and the clutch member 90 and is located radially inward of the body 30. A helical groove 81 is provided about an outer surface of the dose indicating sleeve 80. The body 30 is provided with a window 44 through which a part of the outer surface of the dose indicating sleeve 80 can be seen. The body 30 is further provided with a helical rib at an inside sidewall portion of an insert piece 70, which helical rib is to be seated in the helical groove 81 of the dose indicating sleeve 80. The tubular shaped insert piece 70 is inserted into the proximal end of the body 30. It is rotationally and axially fixed to the body 30. There are provided first and second stops on the body 30 to limit a dose setting procedure during which the dose indicating sleeve 80 is rotated in a helical motion relative to the body 30.

[0121] A dose dial grip 66 is disposed about an outer surface of the proximal end of the dose indicating sleeve 80. An outer diameter of the dose dial 66 typically corresponds to the outer diameter of the body 30. The dose dial 66 is secured to the dose indicating sleeve 80 to prevent relative movement there between. The dose dial 66 is provided with a central opening.

[0122] Furthermore, a dose button 60 of generally T-shape is provided at a proximal end of the injection device 10. A stem 62 of the dose button 60 extends through the opening in the dose dial 66 through an inner diameter of extensions of the drive sleeve 100 and into a receiving recess at the proximal end of the piston rod 110. The stem 62 is retained for limited axial movement in the drive sleeve 100 and against rotation with respect thereto. A head 64 of the dose button 60 is generally circular. A skirt extends from a periphery of the head 64 and is further adapted to be seated in a proximally accessible annular recess of the dose dial 66.

[0123] To dial a dose a user rotates the dose dial 66. With the spring 96 also acting as a clicker and the clutch member 90 engaged, the drive sleeve 100 the spring or clicker 96, the clutch member 90 and the dose indicating sleeve 80 rotate with the dose dial 66. Audible and tactile feedback of the dose being dialed is provided by the spring 96 and by the clutch member 90. Torque is transmitted through saw teeth between the spring 96 and the clutch member 90. The helical groove 81 on the dose indicating sleeve 80 and a helical groove in the drive sleeve 100 have the same lead. This allows the dose indicating sleeve 80 to extend from the body 30 and the drive sleeve 100 to climb the piston rod 110 at the same rate. At a limit of travel a radial stop on the dose indicating sleeve 80 engages either with a first stop or a second stop provided on the body 30 to prevent further movement. Rotation of the piston rod 110 is prevented due to the opposing directions of the overall and driven threads on the piston rod 110.

[0124] The last dose limiting member 106 keyed to the body 30 is advanced along the threaded section 105 by the rotation of the drive sleeve 100. When a final dose dispensed position is reached, a radial stop formed on a surface of the last dose limiting member 106 abuts a radial stop on the flange portion 104 of the drive sleeve 100, preventing both, the last dose limiting member 106 and the drive sleeve 100 from rotating further.

[0125] Should a user inadvertently dial beyond the desired dosage, the pen-injector 10 allows the dosage to be dialed down without dispense of the medicament from the cartridge 50. For this the dose dial 66 is simply counter-rotated. This causes the system to act in reverse. A flexible arm of the spring or clicker 96 then acts as a ratchet preventing the spring 96 from rotating. The torque transmitted through the clutch member 90 causes the saw teeth to ride over one another to create the clicks corresponding to dialed dose reduction. Typically, the saw teeth are so disposed that a circumferential extent of each saw tooth corresponds to a unit dose.

[0126] When the desired dose has been dialed the user may simply dispense the set dose by depressing the dose button 60. This displaces the clutch member 90 axially with respect to the dose indicating sleeve 80 causing dog teeth thereof to disengage. However, the clutch member 90 remains keyed in rotation to the drive sleeve 100. The dose indicating sleeve 80 and the dose dial 66 are now free to rotate in accordance with the helical groove 81.

[0127] The axial movement deforms the flexible arm of the spring 96 to ensure the saw teeth cannot be overhauled during dispense. This prevents the drive sleeve 100 from rotating with respect to the body 30 though it is still free to move axially with respect thereto. The deformation is subsequently used to urge the spring 96 and the clutch member 90 back along the drive sleeve 100 to restore the connection between the clutch member 90 and the dose indicating sleeve 80 when the distally directed dispensing pressure is removed from the dose button 60.

[0128] The longitudinal axial movement of the drive sleeve 100 causes the piston rod 110 to rotate through the through opening 133 of the support 132 of the body 30, thereby to advance the piston 52 in the cartridge 50. Once the dialed dose has been dispensed, the dose indicating sleeve 80 is prevented from further rotation by contact of a plurality of members extending from the dose dial 66 with a corresponding plurality of stops. A zero dose position is finally determined by the abutment of one of axially extending edges of members of the dose indicating sleeve 80 with a corresponding stop of the body 30.

REFERENCE NUMBERS

[0129] 1 distal direction [0130] 2 proximal direction [0131] 5 drive mechanism [0132] 10 injection device [0133] 11 housing [0134] 19 threaded socket [0135] 20 cartridge holder [0136] 21 insert section [0137] 22 sidewall [0138] 23 proximal end [0139] 24 through recess [0140] 24a neck receiving portion [0141] 24b latch receiving portion [0142] 24c side face [0143] 24d side face [0144] 24e abutment face [0145] 24f abutment face [0146] 25 cartridge receiving space [0147] 26 windows [0148] 27 flange section [0149] 28 abutment face [0150] 29 protrusion [0151] 30 body [0152] 31 receptacle [0153] 32 sidewall [0154] 33 distal end [0155] 34 latch element [0156] 34a neck portion [0157] 34b latch portion [0158] 34c side face [0159] 34d side face [0160] 34e abutment face [0161] 34f abutment face [0162] 35 inside [0163] 36 web [0164] 37 through opening [0165] 38 end face [0166] 39 free space [0167] 40 cap [0168] 44 window [0169] 50 cartridge [0170] 51 barrel [0171] 52 piston [0172] 53 medicament [0173] 54 seal [0174] 60 dose button [0175] 62 stem [0176] 64 head [0177] 66 dose dial [0178] 70 insert piece [0179] 80 dose indicating sleeve [0180] 81 helical groove [0181] 90 clutch member [0182] 96 spring [0183] 100 drive sleeve [0184] 102 distal flange portion [0185] 104 flange portion [0186] 105 threaded section [0187] 106 last dose limiting member [0188] 110 piston rod [0189] 112 distal thread [0190] 114 proximal thread [0191] 115 bearing [0192] 116 pressure foot [0193] 122 sidewall section [0194] 124 slit [0195] 125 abutment face [0196] 126 edge [0197] 134 protrusion [0198] 135 abutment face [0199] 136 ramp section [0200] 138 beveled surface [0201] 222 sidewall section [0202] 224 through recess [0203] 322 sidewall section [0204] 324 slit [0205] 334 protrusion [0206] 422 sidewall section