Drive mechanism of a drug delivery device

Abstract

A drive mechanism of a drug delivery device for setting and dispensing of a dose of a medicament includes a housing, a piston rod, a dose indicating member with a dose size information thereon, and a drive wheel. The piston rod engages with a piston of a cartridge for displacing the piston in a distal direction. The dose indicating member is connected to a spring element and is rotatable in a dose incrementing direction against the action of the spring element for setting a dose. The drive wheel is operably engaged with the piston rod for displacing the piston rod in the distal direction for dose dispensing. The dose indicating member is engageable with the drive wheel during dose dispensing to transfer a force to the drive wheel when driven by the relaxing spring element in a dose decrementing direction.

Claims

1. A drive mechanism of a drug delivery device for setting and dispensing of a dose of a medicament, the drive mechanism comprising: a housing; a piston rod to operably engage with a piston of a cartridge for displacing the piston in a distal direction; a dose indicating member with dose size indicating numbers or symbols thereon, wherein the dose indicating member is connected to a spring element and is rotatable in a dose incrementing direction against an action of the spring element for setting of the dose, and wherein the dose indicating member is rotatable in a dose decrementing direction under an action of the spring element for dispensing of the dose, the dose decrementing direction being opposite to the dose incrementing direction; and a drive wheel operably engaged with the piston rod for displacing the piston rod in the distal direction for dose dispensing, wherein the dose indicating member is engageable with the drive wheel during dose dispensing to transfer a driving force to the drive wheel when driven by the relaxing spring element in a dose decrementing direction.

2. The drive mechanism according to claim 1, wherein the dose indicating member comprises a flat-shaped dose indicating disc.

3. The drive mechanism according to claim 1, wherein the spring element comprises a spiral spring having a first end section connected to the housing and having a second end section connected to the dose indicating member.

4. The drive mechanism according to claim 1, further comprising a ring-shaped dose setting member rotatably supported by the housing and being selectively engageable with the dose indicating member for setting of the dose.

5. The drive mechanism according to claim 4, wherein the ring-shaped dose setting member comprises a circumferential side wall portion extending into the housing.

6. The drive mechanism according to claim 5, wherein a last dose limiting member radially sandwiched between the side wall portion and the housing is threadedly engaged with the side wall portion and rotatably locked to the housing.

7. The drive mechanism according to claim 1, further comprising a dose dispensing member rotatably fixed to the housing and being depressible in an axial direction against an action of a dispensing spring element.

8. The drive mechanism according to claim 7, wherein the dose indicating member axially abuts with the dose dispensing member.

9. The drive mechanism according to claim 7, wherein the dose dispensing member comprises a through opening serving as a dose indicating window through which a portion of the dose size indicating numbers of symbols of the dose indicating member is visibly displayed.

10. The drive mechanism according to claim 7, wherein a dose dispensing member is radially enclosed by a dose setting member.

11. The drive mechanism according to claim 1, wherein the dose indicating member comprises a spiraled groove to engage with a single dose limiting member.

12. The drive mechanism according to claim 11, wherein the single dose limiting member is radially displaceable relative to a dose dispensing member along the spiraled groove and is rotatably fixed to the dose dispensing member.

13. The drive mechanism according to claim 12, wherein the dose dispensing member comprises a radially outwardly extending appendix engaged with a notch of the single dose limiting member.

14. The drive mechanism according to claim 1, wherein the dose indicating member comprises a centrally located toothed through opening engaged with at least one resilient ratchet element in a dose setting configuration.

15. A drug delivery device for setting and dispensing of a dose of a medicament, the drug delivery device comprises: a drive mechanism comprising: a housing; a piston rod to operably engage with a piston of a cartridge for displacing the piston in a distal direction; a dose indicating member with dose size indicating numbers or symbols thereon, wherein the dose indicating member is connected to a spring element and is rotatable in a dose incrementing direction against an action of the spring element for setting of the dose, and wherein the dose indicating member is rotatable in a dose decrementing direction under an action of the spring element for dispensing of the dose, the dose decrementing direction being opposite to the dose incrementing direction; and a drive wheel operably engaged with the piston rod for displacing the piston rod in the distal direction for dose dispensing, wherein the dose indicating member is engageable with the drive wheel during dose dispensing to transfer a driving force to the drive wheel when the dose indicating member is driven by the relaxing spring element in the dose decrementing direction; and the cartridge containing the medicament and being arranged in the housing of the drive mechanism.

16. The drug delivery device according to claim 15, wherein the dose indicating member comprises a flat shaped dose indicating disc.

17. The drug delivery device according to claim 15, wherein the spring element comprises a spiral spring having a first end section connected to the housing and having a second end section connected to the dose indicating member.

18. The drug delivery device according to claim 15, further comprising a ring-shaped dose setting member rotatably supported by the housing and being selectively engageable with the dose indicating member for setting of the dose.

19. The drug delivery device according to claim 18, wherein the ring-shaped dose setting member comprises a circumferential side wall portion extending into the housing.

20. The drug delivery device according to claim 19, wherein a last dose limiting member radially sandwiched between the side wall portion and the housing is threadedly engaged with the side wall portion and rotatably locked to the housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, a non-limiting embodiment of the invention will be described in detail, by making reference to the drawings, in which:

(2) FIG. 1 shows the outer appearance of the drug delivery device,

(3) FIG. 2 is a longitudinal cross-section through the drug delivery device,

(4) FIG. 3 illustrates a top view of the drive mechanism without dose setting and dose dispensing member,

(5) FIG. 4 is an enlarged view of the central portion of the dose indicating member according to FIG. 3,

(6) FIG. 5 shows a transverse cross-section through the drive mechanism,

(7) FIG. 6 shows the dose indicating member together with a locking member inside the housing in cross-section,

(8) FIG. 7 is illustrative of the last dose limiting member located on the outer circumference of the dose setting member,

(9) FIG. 8 is a perspective exploded view of the drug delivery device,

(10) FIG. 9 shows a maximum dose configuration at the end of a dose setting procedure,

(11) FIG. 10 corresponds to the illustration according to FIG. 9 without dose setting member and without dose dispensing member,

(12) FIG. 11 shows another longitudinal cross-section through the drive mechanism,

(13) FIG. 12 shows a cross-section according to FIG. 11 from another perspective,

(14) FIG. 13 shows a partial but isolated view of the spiral spring,

(15) FIG. 14 shows another longitudinal cross-section through the drive mechanism,

(16) FIG. 16 shows a ratchet mechanism on the basis of a support member,

(17) FIG. 17 shows the interaction of the dose indicating member with the ratchet mechanism in a perspective view,

(18) FIG. 18 shows the mutual interaction of the single dose limiting member, the dose dispensing member and the dose indicating member,

(19) FIG. 19 is illustrative of a zero-dose stop,

(20) FIG. 20 shows a maximum dose stop provided on the dose indicating member,

(21) FIG. 21 is illustrative of the last dose limiting member radially sandwiched between the housing and the dose setting member,

(22) FIG. 22 shows another view of the dose limiting member according to FIG. 21,

(23) FIG. 23 shows an isolated perspective view of the dose setting member,

(24) FIG. 23a shows an enlarged view of a radial stop and

(25) FIG. 23b shows an enlarged view of another radial stop provided on the outer circumference of the dose setting member,

(26) FIG. 24 shows a portion of the drive mechanism in cross-section during dose setting,

(27) FIG. 25 shows the cross-section according to FIG. 24 during dose dispensing,

(28) FIG. 26 is illustrative of another perspective cut view of the drive mechanism,

(29) FIG. 27 shows the mutual interaction of the ratchet member with the dose indicating member during dose setting and

(30) FIG. 28 is indicative of the interaction between the ratchet element and the dose indicating member in dose dispensing mode,

(31) FIG. 29 shows another cross-section of the drive mechanism,

(32) FIG. 30 is illustrative of the single dose limiting member in a zero-dose configuration,

(33) FIG. 31 shows the single dose limiting member prior to audibly reach a zero-dose configuration, and

(34) FIG. 32 shows the drug delivery device as seen from the bottom in a final stage of assembly without a lower housing component.

DETAILED DESCRIPTION

(35) As illustrated in particular in FIGS. 1, 8 and 32 the drug delivery device 10 comprises at least in sections an elongated, substantially cylindrically-shaped housing 20. In distal direction 1, which faces towards the area of treatment during an injection procedure, the housing 20 comprises a cartridge holder section 21a, 22a as shown in FIG. 8 which is adapted to receive a cartridge 12, typically featuring a vitreous barrel and being filled with a medicament to be dispensed.

(36) The cartridge 12 as illustrated in cross-section in FIG. 2 comprises a piston 14, by way of which the inner volume of the cartridge 12 is sealed in distal direction 2. The distal end of the cartridge 12 is typically provided with a pierceable seal, such like a septum, which is typically fastened and fixed to a neck portion of the cartridge 12 by way of a crimped cap. As shown in FIG. 2, a needle assembly 16 featuring a double tipped needle 17 is releasably attachable to the cartridge holder portion 21a, 22a of the housing 20. The needle assembly 16 typically comprises a threaded needle hub to be screwed on a correspondingly-shaped screwed socket provided on the distal end of the cartridge holder section 21a, 22a.

(37) The needle assembly 16 is further provided with a removable needle cap 18. Moreover, the cartridge holder section 21a, 22a as shown in FIG. 8 is to be covered by a cylindrically-shaped and releasable protective cap 23.

(38) The housing as shown in FIG. 8 comprises a lower housing component 21, which is illustrated to the top in FIG. 8 and an upper housing portion 22. Lower and upper housing components 21, 22 are adapted to either positively or frictionally engage upon final assembly of the drug delivery device 10. The cartridge holder portion 21a is integrally formed with the lower housing component 21 and the cartridge holder portion 22a is correspondingly integrally formed with the upper housing component 22.

(39) Alternatively, it is also conceivable, that the cartridge holder portion is provided as a separate cylindrical sleeve releasably attachable to the housing 20. The drug delivery device 10 may be designed as a reusable device allowing to replace an empty cartridge 12 by a new one. Alternatively, the device 10 is provided and designed as a disposable device, which is intended to be discarded in its entirety once the content of the medicament provided in the cartridge 12 has been dispensed.

(40) The proximal end of the housing 20 comprises a somewhat disc-like and hence circular shape. In particular, the upper housing component 22 comprises an annular or cylindrical-like sidewall 24 featuring a through opening 25 towards the top. As indicated in FIGS. 1, 9 and 10 the upward facing portion of the upper housing component 22 accommodates a ring-shaped dose setting member 30 and a dose dispensing member 70 located therein.

(41) The dose setting member 30 as illustrated for instance in FIG. 23 comprises an annular-shaped sidewall 34 to be arranged in a radially overlapping configuration with the annular sidewall portion 24 of the upper housing component 22. Additionally, the dose setting member 30 comprises a radially inwardly extending flange, on which axially, hence upwardly extending gripping portions 31 are provided. The gripping portions 31 allow for an intuitive gripping and handling of the dose setting member 30 for rotating the same, e.g. in a clockwise, hence dose incrementing direction 5 as illustrated in FIG. 10.

(42) The gripping portions 31 comprise a radially inwardly located arc shaped portion terminated by radially outwardly extending radial sections 32. In particular by the radial sections 32, a user may induce a dose setting torque to the dose setting member 30.

(43) The dose setting member 30 comprises a central through opening 33 which is completely filled by the dose dispensing member 70 serving as a depressible dose button. The dose button 70 comprises a through opening 72 serving as a dose indicating window, through which dose size indicating digits of a dose indicating mechanism are visibly displayed.

(44) The disc-shaped proximal end of the housing 20 allows for a comparatively flat and compact design. The radially outwardly extending bulged portions of the housing 20 further support an ergonomical handling of the drug delivery device 10 and may fit in a palm of a user's hand.

(45) The drive mechanism 3 as shown in the various FIGS. 1-32 comprises a piston rod 120 featuring a widened pressure piece 122 at its distal end to engage with a proximal end face of the piston 14 of the cartridge 12. The piston rod 120 further comprises a toothed profile and may feature a respective rack portion 124 to engage with a pinion 131 of a drive wheel 130 rotatably supported in the housing 20 as illustrated for instance in FIG. 26.

(46) Additionally, the drive mechanism 3 comprises a spring element 100 in form of a planar shaped spiral spring. Said spring element 100 is to be strained and biased during a dose setting procedure, thereby storing mechanical energy in the drive mechanism 3. Upon activating a dose dispensing procedure, the spring 100 will release its mechanical energy and will be coupled with the drive wheel 130 in such a way that the piston rod 120 is displaced in distal direction 1.

(47) The drive mechanism 3 is almost completely located in the disc-shaped proximal section of the housing 20. Here, reference to axial direction 4 refers to the geometry of the disc-like shape of the proximal portion of the housing 20. The axial direction 4 is therefore specified by the axis of rotation of e.g. the dose setting member 30 or the dose indicating member 40.

(48) In the following, setting of a dose is described.

(49) For setting of a dose, a user may take the drug delivery device 10 and may hold the lower housing component 21 in one hand while dialing the dose setting member 30 in a dose incrementing direction 5 with e.g. thumb and index finger of the other hand. As illustrated in FIG. 24, the dose setting member 30 comprises a radially outwardly extending rim 36 engaging with a correspondingly shaped groove 26 of the upper housing component 22. In this way, the dose setting member 30 is axially fixed relative to the housing 20.

(50) Near its radially outwardly located sidewall portion 34, the dose setting member 30 comprises a crown wheel portion 37 to engage with a correspondingly shaped crown wheel portion 41 of the dose indicating member 40 located underneath. The dose indicating member 40 comprises a disc featuring a central through opening 43 with a toothed structure 44. As shown in FIGS. 4 and 16, the dose indicating member 40 is rotatably supported on an axially extending shaft portion 111 of a support member 110 separately illustrated in FIG. 15.

(51) The support member 110 is fixedly attached to the housing 20 of the drive mechanism 3 by way of its radially outwardly extending fixing arms 118 provided with radially outwardly extending latch elements 119. Said latch elements 119 engage with radially inwardly extending fixing elements 93 of a frame 90 as shown in FIG. 32. The frame 90 is fixedly attached to the housing 20. It may be sandwiched or squeezed between upper and lower housing components 22, 21.

(52) At an upper end, the shaft portion 111 of the support member 110 comprises two radially resiliently deformable ratchet elements 112. Said ratchet elements 112 are arc-shaped and feature a radially outwardly extending tooth 113 to mate with the toothed structure 44 of the dose indicating member's 40 through opening 43. Apart from producing a click sound upon rotating in dose incrementing direction 5 or dose decrementing direction 6 the radially outwardly biased ratchet elements 112 serve to rotatably lock the dose indicating member 40 and to secure the dose indicating member 40 against self-actuated spring driven rotation.

(53) The dose indicating member 40 comprises a disc-like shape and features a series of dose indicating digits 48 on its upward facing side face as indicated in FIGS. 3 and 10. The dose dispensing member 70 acting as a downwardly depressible dose button is rotatably fixed to the housing 20 via the support member 110. As for instance illustrated in FIGS. 15 and 27, the dose dispensing member 70 comprises an axially extending centrally located shaft 71 featuring radially outwardly extending protrusions 77 to engage with correspondingly-shaped grooves 115 located on a hollow inside facing sidewall portion of the shaft portion 111 of the support member 110. In this way, the dose dispensing member 70 can be displaced in axial direction 4 but remains rotatably locked and fixed to the support member 110 and hence to the housing 20.

(54) Correspondingly, the shaft portion 110 comprises radially inwardly extending and axially extending protrusions 114 to mate with correspondingly-shaped recesses (not illustrated) of the shaft 71 of the dose dispensing member 70.

(55) A rotation of the dose setting member 30 therefore equally transfers to the dose indicating member 40 located underneath, thereby indicating consecutive numbers 48 in the dose indicating window 72 in an incrementing manner during a dose incrementing rotation 5 and in a decrementing manner when dialed in the opposite, dose decrementing direction 6.

(56) The dose dispensing member 70 comprises a downward pointing axially extending shaft 73 serving as a bearing for a gear wheel 60 as illustrated in FIG. 5. The gear wheel 60 comprises a toothed rim 61 meshing with a corresponding geared rim located on a radial inside facing geared portion 51 of a dose indicating ring 50. As indicated in FIG. 3, said dose indicating ring 50 provides a dose indicating information 52 in form another scale of digits, e.g. 0-12, representing tens or steps of ten, e.g. 10, 20, 30, 40, . . . , 120 in the dose indicating window 72. As illustrated in FIG. 3, the dose indicating member 40 comprises three consecutive scales from 0-9.

(57) Accordingly, the dose indicating member 40 comprises three radially inwardly extending tapered portions 45 to mate with a respective tappet 62 of the gear wheel 60 located axially offset from the toothed rim 61 of the gear wheel 60. The tapered portions 45 are equidistantly arranged along the circumference of the dose indicating member 40. The mutual engagement between the tappet portion 45 and the tappet 62 is only active when the digit 9 of the dose indicating disc is followed by a 0 in the dose indicating window 72. Then, the rotation of the dose indicating member 40 is transferred to a respective rotation of the gear wheel 60, thereby rotating the dose indicating ring 50 one digit further.

(58) By means of the mutually engaged dose indicating member 40 and the dose indicating ring 50, a rather large scale of variable dose sizes can be displayed in the dose indicating window 72 in steps of single units.

(59) The dose indicating member 40 is furthermore directly interconnected with the spiral spring 100 as illustrated in detail in FIGS. 11-13. The spiral spring 100 comprises an upward pointing end section 102 at its radial outer circumference which is engaged with a correspondingly-shaped fastening structure provided on the lower face of the dose indicating member 40. A radially inwardly located opposite end section 101 points downwardly and is connected with the frame 90.

(60) Since the frame 90 is fixedly attached in the housing 20 and since the dose indicating member 40 is permanently engaged with the spiral spring 100, a dose incrementing rotation 5 of the dose setting member 30 leads to a respective straining of the spiral spring 100. The dose indicating member 40 is hindered from rotating in a dose decrementing direction 6 by the engagement with the ratchet mechanism provided by the two diametrically oppositely located ratchet elements 112 of the support member 110. In this way, mechanical energy transferred to the spiral spring 100 during setting of a dose can be stored in the drive mechanism 3.

(61) The drive mechanism is further provided with a single dose limiting mechanism implemented by means of a single dose limiting member 170 as shown in detail in FIGS. 18, 30 and 31. The upward facing portion of the dose indicating member 40 comprises a spiral-shaped groove 42 radially extending between the dose size indicating information 48 and the radially outwardly located crown wheel portion 41. In an initial zero-dose configuration, the single dose limiting member 170 is in circumferential and/or radial abutment with a radially extending stop 46 or stop face at the end of the spiral groove 42.

(62) Additionally and as indicated in FIG. 18, the dose dispensing member 70 comprises a radially outwardly extending appendix 76 positively engaging with a notch 171 on the upward facing portion of the single dose limiting member 170. Since the dose dispensing member 70 is rotatably fixed to the housing 20, the single dose limiting member 170 is equally rotatably fixed relative to the housing 20.

(63) When the dose indicating member 40 is subject to rotation, the single dose limiting member 170 is guided in the spiral groove 42 and may therefore experience a radially directed displacement relative to the housing 20, hence relative to the dose dispensing member 70. Radially adjacent to the dose indicating digits 48, the spiral groove 42 ends and provides a radial stop 47. When the single dose limiting member 170 engages with said stop 47, it serves to block a further dose incrementing rotation of the dose indicating member 40. This configuration typically corresponds to a maximum dose size of e.g. 120 IU of insulin, as for instance indicated in FIGS. 10, 30 and 31.

(64) During a dose dispensing, which will be explained later on, the dose indicating member 40 is subject to a counter-directed dose decrementing rotation 6. Accordingly, the single dose limiting member 170 will travel along the spiral groove 42 in the opposite direction and will be displaced radially outwardly until a leading stop face 172 of the single dose limiting member 170 radially and/or circumferentially abuts with a respective radial stop 46 at the opposite end of the spiral groove 42.

(65) Typically and as illustrated in FIGS. 30, 31 the single dose limiting member 170 comprises a radially resiliently deformable clicking member 173, e.g. located near at least one of its circumferential stop faces 172 or elsewhere in the single dose limiting member 170. The clicking element 173 is adapted to audibly engage with a correspondingly-shaped radially extending clicking member 49 provided near the zero-dose stop 46 and/or near the maximum dose stop 47 of the spiral groove 42. In this way, an audible click sound can be generated prior to the single dose limiting member 170 reaching its zero-dose configuration or its maximum dose configuration, e.g. at the end of a dose dispensing or dose setting procedure.

(66) In this way, an audible feedback can be generated indicating to the user or patient, that a dose dispensing or dose setting procedure is just terminating.

(67) Additionally and as illustrated in more detail in FIGS. 23-25 there is also provided a last dose limiting member 180 featuring an arc-shaped geometry and being disposed radially between the sidewall portion 24 of the upper housing component 22 at the outer threaded portion 35 of the annular sidewall 34 of the dose setting member 30. The last dose limiting member 180 comprises an inner thread 184 to mate with the outer thread 35 of the dose setting member 30. Moreover and as illustrated in FIGS. 7, 21 and 22, the last dose limiting member 180 comprises a radially outwardly extending protrusion 183 to be axially guided in a correspondingly-shaped radially outwardly extending recess or groove 27 of the inside facing sidewall portion 24 of the upper housing component 22.

(68) In this way, the last dose limiting member 180 is axially splined to the housing 20. The last dose limiting member 180 is only allowed to move in axial direction 4 relative to the housing. It is hindered from rotating with the dose setting member 30 during dose incrementing or dose decrementing. As a consequence, the last dose limiting member as illustrated in an initial configuration in FIGS. 24 and 25 will start to travel in an axial downward direction when the dose setting member 30 is rotated in a dose incrementing direction 5. Accordingly, when the dose setting member 30 is rotated in a dose decrementing direction, the last dose limiting member 180 is subject to an upwardly directed axial displacement, e.g. during dose correction.

(69) In FIGS. 7, 21 and 22, the last dose limiting member 180 is illustrated in both of its end configurations. At an upper end of the outer threaded portion 35 of the dose setting member 30 there is provided a radially outwardly extending radial stop 39a whereas another correspondingly shaped radially outwardly extending stop 39b is provided at an axial opposite end portion of the outer thread 35. The radial stop 39a is adapted to abut with a respective stop face 181 of the last dose limiting member 180.

(70) This stop configuration corresponds to a zero-dose configuration prior to a first setting and dispensing of a dose. As the drug delivery device 10 and the drive mechanism 3 is used repeatedly for individually setting and dispensing of a dose, the last dose limiting member 180 consecutively travels downwardly in axial direction until its opposite stop face 182 engages with the last dose stop 93b. When reaching this stop configuration, the dose setting member 30 is immediately blocked from being rotated further in dose incrementing direction 5. In this way it can be effectively prevented, that a dose exceeding the residual filling level or exceeding the amount of medicament left in the cartridge 12 can be set and subsequently dispensed in an inaccurate way.

(71) Since the last dose limiting member 180 is sandwiched between and is engaged with both, the housing 20 and the dose setting member, an immediate and precise blocking feedback can be provided to a user when the last dose configuration has been reached.

(72) In the following, dispensing of a dose is described.

(73) For dispensing of a dose, the user simply depresses the dose dispensing member 70 in axial direction 4 as indicated in FIG. 5. Since the disc-shaped dose button or dose dispensing member 70 comprises an axially extending annular rim 74 in axial abutment with the dose indicating member 40, the downward directed axial displacement of the dose dispensing member 70 is equally transferred to the dose indicating member 40.

(74) In this way, the crown wheel 41 of the dose indicating member 40 disengages from the correspondingly shaped crown wheel portion 37 of the dose setting member 30. As further illustrated in FIG. 5, there is provided a ring-shaped locking member 80 axially sandwiched between the frame 90 and the dose indicating member 40. Said locking member 80 further comprises at least one axially extending and axially resiliently deformable integrated dispensing spring element 84. In this way, the combined depression of the dose dispensing member 70 and the dose indicating member 40 occurs against the action of the dispensing spring element 84.

(75) Moreover, the locking member 80 as illustrated in cross-section in FIG. 6 comprises an axially extending slot 82 to receive a correspondingly-shaped axially extending locking pin 28 of the housing 20. By means of the locking pin 28 the locking member 80 is rotatably fixed to the housing 20. Additionally, the locking member 80 comprises a radially toothed structure 81 along its outer circumference. The toothed structure 81 is disengaged from a radially inwardly extending and correspondingly-shaped toothed structure or protrusion 38 extending radially inwardly from the sidewall 34 of the dose setting member 30.

(76) As illustrated in FIG. 24, when the toothed structure 81 and the protrusions 38 are not yet engaged, the dose setting member 30 can be freely rotated. However, depression of the dose dispensing member 70 and the dose indicating member 40 together with the locking member 80 axially displaces the toothed structure 81 in an overlapping and engaging configuration with the protrusions 38 of the dose setting member 30. In this way, the dose setting member 30 can be rotatably locked during dose dispensing.

(77) Since the locking member 80 is rotatably fixed to the housing 20, the mutual engagement of locking member 80 and dose setting member 30 effectively blocks a further rotation of the dose setting member 30 while the drive mechanism 3 is in dose dispensing mode. In this way, it can be effectively prevented, that the dose setting member 30 and hence the last dose limiting member 180 is manipulated during dose dispensing.

(78) Additionally and as illustrated in FIG. 6 and FIG. 29, the locking member 80 comprises axially extending clicking elements 83 that reach into a slot of the lower housing component 21. In said slot there are provided radially inwardly extending protrusions 29 engaging with the radially resiliently deformable clicking elements 83 of the locking member 80. When pressing down the locking member 80 at the beginning of a dispensing procedure, the mutual engagement of the clicking elements 83 with the radial protrusions 29 serve to generate an audible feedback to the user that the dose dispensing procedure begins. Accordingly, when releasing the dose dispensing member, typically at the end of a dispensing procedure, the clicking elements repeatedly engage with the protrusions 29 thereby audibly indicating that the device is switched into dose setting mode.

(79) The downwardly or inwardly directed axial displacement of the dose indicating member 40 equally transfers to the toothed structure 44 of its central though opening 43. As a consequence and as it is apparent from a comparison of FIGS. 27 and 28, the ratchet elements 112 release the toothed structure 44 thereby allowing that the dose indicating member 40 starts to rotate in a dose decrementing direction 6 under the action of the relaxing spiral spring element 100.

(80) The torque exerted by the spring 100 to the dose indicating member 40 is transferred to a gear wheel 140 featuring a crown wheel portion 141 on its side face facing towards the lower face of the dose indicating member 40. In order to transfer a respective driving torque to the gear wheel 140, the dose indicating member 40 comprises a correspondingly-shaped crown wheel 41a at its lower surface. Typically, the teeth of the mutually engaging crown wheels 41a, 141 are such, that a torque transmission between the spring driven dose indicating member 40 and the gear wheel 140 is already established before the toothed structure 44 of the dose indicating member 40 disengages from the ratchet elements 112 of the support member 110. In this way a substantially slipless clutch for switching between the dose setting mode and the dose dispensing mode can be effectively provided.

(81) The gear wheel 140 is rotatably supported by the shaft portion 111 of the support member 110. As becomes apparent from FIG. 26, the gear wheel 140 comprises an outer geared rim 142 engaged with a correspondingly-shaped upper toothed rim 151 of another gear wheel 150. As illustrated in FIG. 12, gear wheel 150 is rotatably supported by an axially extending shaft portion 91 of the frame 90. The gear wheel 150 further comprises a lower toothed rim 152 axially offset from the upper toothed rim 151.

(82) The lower toothed rim 152 meshes and mates with an upper toothed rim 161 of another gear wheel 160. Said gear wheel 160 is rotatably supported by the shaft 111 of the support member 110. It is arranged coaxial to the gear wheel 140. As further illustrated in FIG. 12, the gear wheel 160 also comprises a lower toothed rim 162 that meshes with an outer toothed rim 134 of a drive wheel 130. As illustrated in FIG. 12, said drive wheel 130 is rotatably supported in the shaft portion 91 of the frame 90. For this purpose, the drive wheel 130 comprises axially extending and radially resiliently deformable shaft elements 133 to positively engage with a correspondingly-shaped recessed structure at the inside facing portion of the shaft portion 91.

(83) Axially offset from its toothed rim 134, the drive wheel 130 comprises a pinion 131 or sprocket operably engaged with the rack portion 124 of the piston rod 120. The gearing set up by the various gear wheels 140, 150, 160 and the drive wheel 130 provides a required transmission gear in order to provide a required transmission ratio between the rotation of the dose indicating member 40 and a respective distally directed translational displacement of the piston rod 120.

(84) As further illustrated in FIG. 26, the drive wheel 130 comprises a pin 132 axially extending from the pinion 131. Said pin 132 is located and supported by a correspondingly shaped receptacle or bearing of the lower housing component 21. In this way, the drive wheel 130 is radially constrained on both sides of the piston rod 120. In this way, mechanical play or backlash that may otherwise arise from a loose fitting of the drive wheel 130 can be reduced to a minimum.

(85) If a user prematurely releases the dose dispensing member 70 before the end of a dispensing procedure has been reached, the locking member 80, the dose indicating member 40 and the dose dispensing member 70 will return into their initial position under the effect of the dispensing spring element 84. In the course of such an upwardly directed axial displacement, the interlocking engagement of the dose indicating member 40 and the ratchet elements 112 will be immediately re-established even before a torque transmitting mutual engagement between the gear wheel 140 and the dose indicating member 40 is abrogated.

(86) Distally directed displacement of the dose dispensing member 70 under the action of the dispensing spring element 84 is delimited by means of at least one radially extending axial stop 75 provided at the outer circumference of the dose dispensing member 70. Said stop 75 will engage with a radially inwardly located rim of the dose setting member 30. In this way, the dose dispensing member 70 can be axially secured in the upward direction.

(87) As illustrated in the cross-section according to FIG. 5, the piston rod 120 extends through a passageway 117 extending in distal direction through a base portion 116 of the support member 110. The support member 110 can be fastened to the bottom of the lower housing component 21 by means of axially upwardly extending latching elements 21b engaging with the base portion 116 of the support member 110.

(88) The through opening 43 of the dose indicating member 40 comprises a click sound generating structure 44a axially adjacent to the toothed structure 44. When in dispensing mode as illustrated in FIG. 28, the ratchet elements 112 may audibly engage with said click sound generating structure 44a, thereby audibly indicating to a user, that a dose dispensing procedure is in progress. This audible feedback can be provided in addition to the inherent visual feedback of the dose indicating window 72 during a dose dispensing procedure.

(89) In FIG. 32 the final step of assembly of the drug delivery device 10 is illustrated. Here, all functional components of the drive mechanism except the lower housing component 21 are assembled to the frame 90 and/or to the upper housing component 22. Moreover also the cartridge 12 is appropriately arranged in the respective cartridge holder portion 22a. Since the device is initially in dose setting mode, the piston rod 120 can be displaced in distal direction 1 until its pressure piece 122 abuts with the piston 14 of the cartridge 12. During this final step of assembly, the drive wheel 30 may be set in a rotative movement. Since the gearing provided by the various gear wheels 130, 140, 150, 160 is operably disconnected from the dose indicating member 40 and the various dose limiting members 170, 180, this initial manipulation of the drive mechanism 3 is substantially effect less on the dose indicating mechanism.

(90) Distally directed displacement of the piston rod 120 may also be induced by a manual rotation of the drive wheel 130. Naturally, the upper housing component 21 further comprises a guiding structure 22b to translationally guide the piston rod 120 in distal direction 1. Furthermore, the gear wheels 140, 160 are arranged inside and extend through a central through opening 92 of the frame 90. Hence, the drive mechanism 3 extends above and below the frame 90.

LIST OF REFERENCE NUMERALS

(91) 1 distal direction 2 proximal direction 3 drive mechanism 4 axial direction 5 dose incrementing direction 6 dose decrementing direction 10 drug delivery device 12 cartridge 14 piston 16 needle assembly 17 needle 18 needle cap 20 housing 21 lower housing component 21a cartridge holder portion 21b latching element 22 upper housing component 22a cartridge holder portion 22b guiding structure 23 protective cap 24 sidewall 25 through opening 26 groove 27 recess 28 pin 29 protrusion 30 dose setting member 31 gripping portion 32 radial section 33 through opening 34 sidewall 35 outer thread 36 rim 37 crown wheel 38 protrusion 39a radial stop 39b radial stop 40 dose indicating member 41 crown wheel 41a crown wheel 42 groove 43 through opening 44 toothed structure 44a sound generating structure 45 tappet portion 46 radial stop 47 radial stop 48 dose indicating information 49 clicking member 50 dose indicating ring 51 geared portion 52 dose indicating information 60 gear wheel 61 toothed rim 62 tappet 63 bearing 70 dose dispensing member 71 shaft 72 dose indicating window 73 shaft 74 rim 75 axial stop 76 appendix 77 protrusion 80 locking member 81 toothed structure 82 slot 83 clicking element 84 dispensing spring element 90 frame 91 shaft portion 92 through opening 93 fixing element 100 spring element 101 end section 102 end section 110 support member 111 shaft portion 112 ratchet element 113 tooth 114 protrusion 115 groove 116 base portion 117 passageway 118 fixing arm 119 latch element 120 piston rod 122 pressure piece 124 rack portion 130 drive wheel 131 pinion 132 pin 133 shaft element 134 toothed rim 140 gear wheel 141 crown wheel 142 geared rim 150 gear wheel 151 upper toothed rim 152 lower toothed rim 160 gear wheel 161 upper toothed rim 162 lower toothed rim 170 single dose limiting member 171 notch 172 stop face 173 clicking element 180 last dose limiting member 181 stop face 182 stop face 183 protrusion 184 inner thread