Injection device

Abstract

The invention refers to an injection device comprising a housing (10), containing a cartridge (170) with an amount of liquid to be dispensed, a drive sleeve (41), which is rotationally constrained to the housing (10) during dose setting and spring driven rotatable relative to the housing (10) during dose dispensing, a dose dial member (60) for setting a dose to be dispensed, which is rotatable relative to the housing (10) during dose setting and during dose dispensing, and which is rotationally coupled to the drive sleeve (41) during dose dispensing. The device further comprises a last dose protection mechanism (41, 50, 60) for preventing the setting of a dose, which exceeds the amount of liquid left in the cartridge (170), with a limiter (50), which is interposed between the drive sleeve (41) and the dose dial member (60). Further, the device comprises two different display members (110, 120), each indicating the set dose.

Claims

1. An injection device comprising: a housing containing a cartridge with an amount of liquid to be dispensed; a drive sleeve which is rotationally constrained to the housing during dose setting and rotatable by a torsion spring relative to the housing during dose dispensing; a dose dial member to set a dose to be dispensed, which is rotatable relative to the housing during dose setting and during dose dispensing, and which is rotationally coupled to the drive sleeve during dose dispensing; a last dose protection mechanism to prevent the setting of a dose which exceeds the amount of liquid left in a cartridge, the last dose protection mechanism comprising a limiter, which is interposed between the drive sleeve and the dose dial member; and a display member to indicate the set dose, wherein during dose dispensing the drive sleeve is coupled to the torsion spring, which is strained during dose setting, wherein the cartridge is located on a first longitudinal axis (I), which is parallel to and spaced from the second longitudinal axis (II), on which the drive sleeve and the dose dial member are located.

2. The injection device according to claim 1, wherein the housing has a first aperture or window, wherein the display member comprises: a dose indicator which is positioned within the housing and rotatable relative to the housing during dose setting and during dose dispensing, and a gauge element which is interposed between the housing and the dose indicator, and which is axially guided within the housing and in threaded engagement with the dose indicator such that rotation of the dose indicator causes an axial displacement of the gauge element, the gauge element comprising a second aperture or window, wherein the second aperture or window is positioned with respect to the first aperture or window of the housing such that at least a part of the dose indicator is visible through the first and second apertures or windows.

3. The injection device according to claim 2, wherein the dose dial member is permanently rotationally constrained to the dose indicator.

4. The injection device according to claim 2, wherein the dose indicator is a number sleeve having a series of numbers or symbols arranged on a helical line on its outer surface, and wherein the gauge element has a distal part located on the distal side of the second aperture or window and a proximal part located on the proximal side of the second aperture or window, with the distal part and the proximal part having a different outer surface.

5. The injection device according to claim 1, wherein the last dose protection mechanism comprises a nut member as the limiter, which is rotationally constrained to the drive sleeve and in threaded engagement with the dose dial member.

6. The injection device according to claim 1, wherein the limiter comprises a rotational stop and the dose dial member comprises a corresponding counter stop, which abut if a dose is set, which exceeds the amount of liquid left in a cartridge.

7. The injection device according to claim 1, further comprising a piston rod coupled to the drive sleeve, which piston rod is rotationally constrained to the housing during dose setting and is allowed to rotate during dose dispensing.

8. The injection device according to claim 1, further comprising a ratchet clutch, which is arranged between the drive sleeve and the dose dial member, and which allows relative rotation of the drive sleeve and the dose dial member during dose setting and which rotationally constrains the drive sleeve to the dose dial member during dose dispensing.

9. The injection device according to claim 1, comprising a limiter mechanism defining a maximum settable dose and a minimum settable dose.

10. The injection device according to claim 1, wherein the two different display members are located on the second longitudinal axis (II).

11. The injection device according to claim 1, wherein the length of the device before and after dose setting is the same.

12. The injection device according to claim 1, further comprising at least one first clicker producing at least one of an audible or tactile first feedback during at least one of dose setting or dose dispensing and a second clicker producing at least one of an audible or tactile second feedback, distinct from the first feedback, during dose dispensing when a minimum dose position of the device is reached.

13. The injection device according to claim 1, wherein the cartridge contains a medicament.

Description

(1) Non-limiting, exemplary embodiments of the invention will now be described with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a perspective view of an injection device in accordance with a first embodiment of the present invention;

(3) FIG. 2 shows an exploded view of the components of the device of FIG. 1;

(4) FIG. 3 shows an enlarged view of a detail of the device of FIG. 1;

(5) FIG. 4 shows a sectional view of the device of FIG. 1 in the dose setting state;

(6) FIG. 5 shows an enlarged view of components of the device of FIG. 1;

(7) FIG. 6 shows an enlarged view of a detail of the device of FIG. 1;

(8) FIG. 7 shows a sectional view of the device of FIG. 1 in the dose dispensing state;

(9) FIG. 8a shows an enlarged view of a detail of the device of FIG. 1 in the dose setting state;

(10) FIG. 8b shows an enlarged view of a detail of the device of FIG. 1 in the dose dispensing state;

(11) FIG. 9a shows an enlarged view of a detail of the device of FIG. 1;

(12) FIG. 9b shows an enlarged view of a detail of the device of FIG. 1;

(13) FIG. 9c shows an enlarged view of a detail of the device of FIG. 1;

(14) FIG. 9d shows an enlarged view of a detail of the device of FIG. 1;

(15) FIG. 10 shows an exploded view of an injection device in accordance with a second embodiment of the present invention;

(16) FIG. 11 shows a sectional view of the device of FIG. 10 in the dose setting state; and

(17) FIG. 12 shows a sectional view of the device of FIG. 10 in the dose dispensing state.

(18) FIG. 1 shows a drug delivery device in the form of an injection pen. The device has a distal end (lower left end in FIG. 1) and a proximal end (upper right end in FIG. 1). The component parts of the drug delivery device are shown in FIG. 2. The drug delivery device comprises a housing 10, a cartridge holder 20, a lead screw (piston rod) 30, a driver 41, 42, a nut 50, a dial sleeve 60, a button 70, a dose selector 80, a torsion spring 90, a locking arm 100, a gauge element 110, a dose indicator (number sleeve) 120, a clutch plate 130, a clutch spring 140, a click activator 150, a drive spring retainer 160 and a cartridge 170. A needle arrangement (not shown) with a needle hub and a needle cover may be provided as additional components, which can be exchanged as explained above.

(19) The housing 10 or body is a generally tubular element with an elongate cross-section. In the embodiment shown in the figures, all components are located within the main housing 10 component, concentrically mounted about one of two, parallel axes I, II of the mechanism. A body cap 11 is snapped, press-fitted, and/or glued or welded onto the proximal end of main housing 10. Further, a lens 12 is inserted in an elongate aperture of main housing 10. The main housing 10 has a threaded inner wall 13 (web) for receiving piston rod 30. In addition, the housing 10 provides location for the liquid medicament cartridge 170 and cartridge holder 20, a housing cap (not shown), drive spring retainer 160, an interface to rotationally constrain the locking arm 100 and a feature on its external surface to axially retain the dial grip 80.

(20) The cartridge holder 20 is the distal part of the housing and may be snapped, press-fitted, and/or glued or welded onto the distal end of main housing 10. The cartridge holder 20 receives the cartridge 170 and has a distal opening for attachment of the needle and a window or aperture allowing a user to see the cartridge.

(21) The piston rod 30 has a bearing 31 on its distal end, which may be axially constrained to the piston rod 30 and acts on the bung within the liquid medicament cartridge 170. The piston rod 30 is a lead screw with an outer thread 32 for engagement with the threaded inner wall 13 and is rotationally constrained to the drive tube 42 via a splined interface 33. When rotated, the piston rod 30 is forced to move axially relative to the drive tube 42, through its threaded interface 13, 32 with the housing 10.

(22) In the exemplary embodiment, the driver 40 comprises two components, a drive sleeve 41 and a drive tube 42, which are located on the offset parallel axes I, II. The drive sleeve 41 extends from an interface (proximal face teeth 48) with the dial sleeve 60 (via the clutch plate 130) to a gear toothed engagement (pinions 43, 44) to the drive tube 42, and incorporates a spline toothed interface 45 with the locking arm 100. Further, drive sleeve 41 comprises splines 46 on its inner surface for engaging nut 50. The drive tube 42 is in gear toothed engagement to the drive sleeve 41 and is splined to the piston rod 30 via splines 47 on its inner surface. The drive tube 42 is fixed axially relative to both the housing 10 and drive sleeve 41.

(23) The last dose nut 50 is located between the dial sleeve 60 and the drive sleeve 41. It is rotationally constrained to the drive sleeve 41, via a splined interface. It moves along a helical path relative to the dial sleeve 60, via a threaded interface, when relative rotation occurs between the dial sleeve 60 and drive sleeve 41 (i.e., during dialing).

(24) The dial sleeve 60 is a dose dial member with a tubular form having an external thread 61 engaging the nut 50, a set of clutch spline teeth 62 at its proximal end for engagement with dose button 70 and splines 63 for engagement with clutch plate 130. Further splines 64 interact with corresponding grooves of the number sleeve 120.

(25) The dose button 70 is permanently splined to the dial grip 80 via outer teeth 72 and splined to the dial sleeve 60 when the dose button 70 is not pressed. This spline interface with the dial sleeve 60 is disconnected when the dose button 70 is pressed.

(26) The dial grip 80 is axially, but not rotationally constrained to the housing 10. It is rotationally constrained, via the splined interface, to the dose button.

(27) The drive spring 90 is attached at one end to the drive spring retainer 160 (which forms part of the housing with the main housing 10) and at the other end to the number sleeve 120. The drive spring 90 is a torsion spring pre-wound upon assembly, such that it applies a torque to the number sleeve 120 when the mechanism is at zero units dialed. The action of rotating the dial grip 80, to set a dose, rotates the number sleeve 120 relative to the housing 10, and further charges the drive spring 90.

(28) The locking arm 100 is rotationally fixed to the housing 10 but allowed to translate axially. When the dose button 70 is pressed, the locking arm 100 spline teeth 101 are disengaged from the drive sleeve 41 allowing the drive sleeve 41 to rotate.

(29) The gauge element 110 is constrained to prevent rotation, but allow axial translation relative to the housing 10 via a splined interface. It is also in threaded engagement to the number sleeve 120 such that rotation of the number sleeve 120 causes axial translation of the gauge element 110. A window 111 is provided in the gauge element with a distal part and a proximal part of the gauge element extending in the respective directions of the window. The outer surface of these parts has a different design, for example in the embodiment of FIG. 2 a triangle is printed on the distal part.

(30) The number sleeve 120 is rotationally constrained, via a splined interface, to the dial sleeve 60. Both components are constrained to the housing 10 to allow rotation, but not translation. The number sleeve 120 is marked with a sequence of numbers, which are visible through the gauge element 110 and a lens 12, located in a slot in the housing 10, to denote the dialed dose of medicament. A zero dose abutment feature 121 and a maximum dose abutment feature 122 are provided as rotational hard stops. Further, there is an end of dose clicker arm 123 at the distal end of number sleeve 120.

(31) The clutch plate 130 is splined to the dial sleeve 60. It is also coupled to the drive sleeve 41 via a ratchet interface (via teeth 131), which occurs on an axial abutment. The ratchet provides a detented position between the dial sleeve 60 and drive sleeve 41 corresponding to each dose unit, and engages different ramped tooth angles during clockwise and anti-clockwise relative rotation.

(32) The clutch spring 140 acts between the clutch plate 130 and the locking arm 100 to force the spline teeth into engagement with the drive sleeve 41 and to force the ratchet between the clutch plate 130 and the drive sleeve 41 together. The axial position of the locking arm 100, clutch plate 130 and dose button 70 are defined by the action of the clutch spring 140. In the at rest position, this ensures that the dose button 70 splines are engaged with the dial sleeve 60 and that the drive sleeve 41 spline teeth are engaged with the locking arm 100.

(33) The click activator 150 is axially constrained to the button cap 71 and moves the end of dose clicker arm outwards radially when the dose button 70 is depressed.

(34) The drive spring retainer 160 is held within housing 10 and receives the distal end of drive spring 90. In the embodiment of FIG. 2 the retainer is shown as a separate component part, however, the retainer may as well be an integral part of the housing 10.

(35) The removable cap (not shown) fits over the cartridge holder 20 and housing 10 components and is retained via clip features.

(36) In the following, the functioning of the disposable drug delivery device and its components will be explained in more detail.

(37) With the device in the At Rest condition, the zero dose abutment feature 121 of the number sleeve 120 is positioned against a corresponding zero dose abutment stop of the gauge element 110 (see FIG. 3) and the dose button 70 is not depressed. Dose marking 0 on the number sleeve 120 is visible through the window (lens 12) of the housing 10 and window 111 of gauge element 110. The drive spring 90, which has a number of pre-wound turns applied to it during assembly of the device, applies a torque to the number sleeve 120 and is prevented from rotating further by the zero dose abutment. It is also possible to back-wind the mechanism slightly due to an offset between the zero dose stop and the angular offset of the drive sleeve 41 spline teeth. This has the effect of preventing possible weeping of medicament when a dose is dialed and the zero dose abutment is disengaged.

(38) The user selects a variable dose of liquid medicament by rotating the dial grip 80 clockwise, which generates an identical rotation in the dial sleeve 60 and hence number sleeve 120. Rotation of the number sleeve 120 causes charging of the drive spring 90, increasing the energy stored within it. As the number sleeve 120 rotates, the gauge element 110 translates axially due to its threaded engagement thereby showing the value of the dialed dose. The gauge element 110 has flanges either side of the window area which may have visual differentiation to provide additional feedback as to the dialed/delivered dose value (shown in FIG. 5) and which obscure those numbers that would be visible in the body slot that do not correspond to the dialed dose display. The dial grip 80 has an increased diameter relative to the housing 10 which aids dialing. This is especially important for an auto-injector mechanism where the stored energy source is charged during dose setting.

(39) The drive sleeve 41 is prevented from rotating, due to the engagement of its splined teeth with the locking arm 100. Relative rotation must therefore occur between the clutch plate 130 and drive sleeve 41 via the dialing ratchet interface.

(40) The user torque required to rotate the dial grip 80 is a sum of the torque required to wind up the drive spring 90, and the torque required to overhaul the dialing ratchet feature. The clutch spring 140 is designed to provide an axial force to the ratchet feature and to bias the clutch plate 130 against the drive sleeve 41. This axial load acts to maintain the ratchet teeth engagement (teeth 48 and 131) of the clutch plate 130 and drive sleeve 41. The torque required to overhaul the ratchet is resultant from the axial load applied by the clutch spring 140, the clockwise ramp angle of the ratchet, the friction coefficient between the mating surfaces and the mean radius of the ratchet features.

(41) As the user rotates the dial grip 80 sufficiently to increment the mechanism by one unit, the dial sleeve 60 rotates relative to the drive sleeve 41 by one ratchet tooth. At this point the ratchet teeth 48, 131 re-engage into the next detented position. An audible click is generated by the ratchet re-engagement, and tactile feedback is given by the change in torque input required.

(42) Relative rotation of the dial sleeve 60 and the drive sleeve 41 also causes the last dose nut 50 to travel along its threaded path, towards its last dose abutment on the dial sleeve 60.

(43) With no user torque applied to the dial grip 80, the dial sleeve 60 is now prevented from rotating due to the action of the torque applied by the drive spring 90, solely by the ratchet engagement (teeth 48, 131) between the clutch plate 130 and the drive sleeve 41. The torque necessary to overhaul the ratchet in the anti-clockwise direction is resultant from the axial load applied by the clutch spring 140, the anti-clockwise ramp angle of the ratchet, the friction coefficient between the mating surfaces and the mean radius of the ratchet features. The torque necessary to overhaul the ratchet must be greater than the torque applied to the dial sleeve 60 (and hence clutch plate 130) by the drive spring 90. The ratchet ramp angle is therefore increased in the anti-clockwise direction to ensure this is the case whilst ensuring the dial-up torque is as low as possible.

(44) The user may now choose to increase the selected dose by continuing to rotate the dial grip 80 in the clockwise direction. The process of overhauling the ratchet interfaces between the dial sleeve 60 and drive sleeve 41 is repeated for each dose unit. Additional energy is stored within the drive spring 90 for each dose unit and audible and tactile feedback is provided for each unit dialed by the re-engagement of the ratchet teeth. The torque required to rotate the dial grip 80 increases as the torque required to wind up the drive spring 90 increases. The torque required to overhaul the ratchet in the anti-clockwise direction must therefore be greater than the torque applied to the dial sleeve 60 by the drive spring 90 when the maximum dose has been reached.

(45) If the user continues to increase the selected dose until the maximum dose limit is reached, the number sleeve 120 engages with its maximum dose abutment 122 on the gauge element 110, which prevents further rotation of the number sleeve 120, dial sleeve 60, clutch plate 130 and dial grip 80.

(46) Depending on how many units have already been delivered by the mechanism, during selection of a dose, the last dose nut 50 may contact its last dose abutment with the dial sleeve 60, which is shown in FIG. 7 as a landing on dial sleeve 60 between threads 61 and splines 63. The abutment prevents further relative rotation of the dial sleeve 60 and the drive sleeve 41, and therefore limits the dose size that can be selected. The position of the last dose nut 50 is determined by the total number of relative rotations between the dial sleeve 60 and drive sleeve 41, which have occurred each time the user sets a dose.

(47) With the mechanism in a state in which a dose has been selected, the user is able to deselect any number of units from this dose. Deselecting a dose is achieved by the user rotating the dial grip 80 anti-clockwise.

(48) The torque applied by the drive spring 90 on the mechanism is in the anti-clockwise direction, therefore the torque required from the user on the dial grip 80 to deselect a dose is that to overhaul the ratchet between the clutch plate 130 and drive sleeve 41 in the anti-clockwise direction less the drive spring 90 torque at that particular number sleeve 120 rotational position.

(49) When the ratchet is overhauled, anti-clockwise rotation occurs in the dial sleeve 60 (via the clutch plate 130), which returns the number sleeve 120 towards the zero dose position, and unwinds the drive spring 90. The relative rotation between the dial sleeve 60 and drive sleeve 41 causes the last dose nut 50 to return along its helical path, away from the last dose abutment on the dial sleeve 60.

(50) With the mechanism in a state in which a dose has been selected, the user is able to activate the mechanism to commence delivery of a dose. Delivery of a dose is initiated by the user depressing the dose button 70 on the top of the device.

(51) When the dose button 70 is depressed, its splined engagement with the dial sleeve 60 is disengaged, rotationally disconnecting the dose button 70 and hence dial grip 80 from the delivery mechanism so that the dial grip 80 does not rotate during dispense. The dose button 70 acts on the locking arm 100, which travels axially disconnecting the splined tooth engagement to the drive sleeve 41. The drive sleeve 41 can now rotate and is driven by the drive spring 90 via the number sleeve 120, dial sleeve 60 and clutch plate 130. Rotation of the drive sleeve 41 causes the drive tube 42 to rotate, which in turn causes the piston rod 30 to rotate due to their splined engagement. The piston rod 30 then advances due to its threaded engagement to the housing 10. The number sleeve 120 rotation also causes the gauge element 110 to traverse axially back to its zero position whereby the zero dose abutment stops the mechanism as shown in FIG. 3.

(52) Audible feedback during delivery is provided via a compliant cantilever dispense clicker arm 102 integrated into the locking arm 100, which interfaces axially with the spline teeth 45 of the drive sleeve 41. The spline teeth spacing corresponds to the drive sleeve 41 rotation required for a single dispense unit. During dispense, as the drive sleeve 41 rotates, the spline features 45 engage with the dispense clicker arm 102 to produce an audible click with each dose unit delivered.

(53) Delivery of a dose continues via the mechanical interactions described above while the user continues to depress the dose button 70. If the user releases the dose button 70, the clutch spring 140 returns the dose button 70 to its at rest position via the locking arm 100 and clutch plate 130, the drive sleeve 41 and hence drive tube 42 become rotationally constrained, and delivery of a dose is halted.

(54) During delivery of a dose, the drive sleeve 41 and dial sleeve 60 rotate together, so that no relative motion in the last dose nut 50 occurs. The last dose nut 50 therefore travels towards its abutment on the dial sleeve 60 during dialing only.

(55) Once the delivery of a dose is stopped by the number sleeve 120 returning to the zero dose abutment, the user may release the dose button 70, which will re-engage the locking arm 100 spline teeth 101 with teeth 45 of the drive sleeve 41. The mechanism is now returned to the at rest condition.

(56) It is possible to angle the spline teeth 45, 101 on either the drive sleeve 41 and/or the locking arm 100 so that when the dose button 70 is released the re-engagement of the spline teeth fractionally backwinds the drive sleeve 41 thereby removing the engagement of the number sleeve 120 to the gauge element 110 zero dose stop abutment. This removes the effect of clearances in the mechanism (for example due to tolerances) which could otherwise lead to slight advancement of the piston rod 30 and medicament dispense when the device is dialed for the subsequent dose (due to the number sleeve 120 zero dose stop no longer restraining the mechanism and instead the restraint returning to the splines between the drive sleeve 41 and gauge element 110).

(57) At the end of dose, additional audible feedback is provided in the form of a click (distinct from the dispense clicks) that informs the user that the dispense mechanism has returned to the zero position via the interaction of three components: number sleeve 120, gauge element 110 and click activator 150. The embodiment allows feedback to only be produced at the end of dose delivery (when the dose button 70 is depressed) and not when the device is being dialed into, or away from, the zero position.

(58) When the dose button 70 is not depressed (i.e. during dialing), the end of dose clicker arm 123 is sub-flush with the number sleeve 120 outer surface, and so is clear of the gauge element 110 as the device is dialed into, or away from, the zero position, hence no end of dose click can be produced. This is shown in FIG. 8a. When the dose button 70 is depressed (i.e. during dispense), the click activator 150 is moved axially so that it forces the end of dose clicker arm 123 radially outwards as shown in FIG. 8b.

(59) The function of the zero dose click is further shown in FIGS. 9a to 9d which depict the sequence of dispensing from 6 units set down to zero. Usually, the gauge element 110 would conceal the number sleeve 120 and its arm 123 at least partly. However, in FIGS. 9a to 9d the gauge element 110 is shown transparent. As the number sleeve 120 rotates towards the zero position during dispense, the deflected end of dose clicker arm 123 contacts the gauge element 110 at around six units (see FIG. 9a). This causes a preload to be generated in the clicker arm 123 in the radial direction (see FIG. 9b). The drive spring 90 is sufficiently strong to overcome the additional friction caused by the interference between gauge element 110 and the end of dose clicker arm 123 tip. This preload is maintained as the tip of the end of dose clicker arm 123 is in contact with the gauge element 110 up to a point just prior to zero unit position (see FIG. 9c). At this point the tip of the end of dose clicker arm 123 slides off a feature (not shown) formed locally at the trailing edge of the gauge element 110, producing an audible click (see FIG. 9d).

(60) As the dose button 70 needs to be released before the device can be dialed away from the zero unit position, the end of dose clicker arm 123 moves inwards radially as the click activator 150 moves rearwards with the dose button 70 and therefore it cannot interfere with the gauge element 110 during dialing. This ensures the end of dose click is only produced between one and zero units and only during dispense.

(61) Independent from the above detailed embodiment, the invention relates to a mechanism for use in a medical device that can be operated to deliver variable, user-selectable, doses of medicament from a cartridge, e.g. via a needle. The device is preferably disposable. It is delivered to the user in a fully assembled condition ready for first use.

(62) The mechanism provides separate user interfaces for setting and delivery of a dose. A dose is set by rotating a dial grip 80 located at the end of the housing 10. Delivery of a dose is initiated by pressing a dose button 70 on the end of the dial grip 80. Dose delivery will continue while the dose button 70 remains depressed, until the complete set dose has been delivered. The mechanism provides audible, visual and tactile feedback both on the setting and delivery of each dose.

(63) The mechanism contains a helical drive spring 90 to store energy, which is charged during setting of the dose, by the action of the user rotating the dial grip 80. The spring energy is stored until the mechanism is triggered for dispense at which point the energy stored is used to deliver the medicament from the cartridge to the user.

(64) Any dose size can be selected between zero and a pre-defined maximum, in increments to suit the medicament and user profile. The mechanism permits cancelling of a dose without any medicament being dispensed by rotation of the dial grip 80 in the opposing direction to when selecting a dose.

(65) FIGS. 10 to 12 show a second embodiment of the invention, which differs from the first embodiment amongst others in the design of the spring and in the way the dose is displayed.

(66) The device has a distal end (left end in FIG. 11) and a proximal end (right end in FIG. 11). The component parts of the drug delivery device are shown in FIG. 10. The drug delivery device comprises a housing 210, a cartridge 220, a lead screw (piston rod) 230, a driver 240, a nut 250, a dial sleeve 260, a dial assembly 270, a number sleeve 280, a power reservoir (motor spring) 290, a clicker 300 and a spring 310. A needle arrangement (not shown) with a needle hub and a needle cover may be provided as additional components, which can be exchanged as explained above.

(67) The housing 210 or body comprises a main housing 211, a proximal housing 212 and a distal housing or cartridge holder 213. The main housing 211 is a generally tubular element with an oblong cross section with the lower side in FIG. 11 being widened compared with the upper side. A window 214 or aperture is provided in the main housing 211. The main housing 211, the proximal housing 212 and the cartridge holder 213 can be plugged or snapped together during assembly to close both open ends of the main housing 211. Further, the housing components may be glued or welded together to form a rigid and permanently attached housing unit. The proximal housing 212 has a proximal aperture in its lower region in FIG. 10, and the cartridge holder 213 has a distal aperture in its upper region in FIG. 10, which may have an outer thread or the like for attachment of a needle arrangement. Further, the proximal housing 212 has on its inside near the proximal aperture a ring of teeth which forms part of a clutch with driver 240. The cartridge holder 213 has on its lower side a splined pin 216 for guiding clicker 300 and spring 310. The housing 210 provides location for the liquid medication cartridge 220, which is held in the upper part (as seen in FIG. 10) of the main housing 211 and the cartridge holder 213.

(68) The main housing has an inner wall with a threaded section 217 engaging piston rod 230. Further, there is a clicker arm 218 near the proximal end of main housing 211, which arm interacts with the driver 240 during dose dispensing.

(69) The cartridge 220 is a glass ampoule with a movable rubber bung 221 located in its proximal aperture.

(70) The lead screw 230 is an elongate member with an outer thread which is rotationally constrained to the driver 240 via a splined interface. The interface comprises at least one longitudinal groove or track and a corresponding protrusion or spline of the driver 240. When rotated, the lead screw 230 is forced to move axially relative to the driver 240, through its threaded interface 217 with the housing 210. The distal end of the piston rod 230 is provided with a bearing 233, which may abut the cartridge bung 221.

(71) The driver 240 comprises a drive sleeve, which has for manufacturing reasons a drive sleeve lower part 241 and a drive sleeve upper part 242, and a drive tube 243. The drive sleeve lower part 241 and the drive sleeve upper part 242 are rigidly connected to form a unit when in use. The drive tube 243 is arranged on a first longitudinal axis I and the drive sleeve is arranged on a second longitudinal axis II, which is parallel to and spaced from the first axis I.

(72) On the inside of the drive tube 243, splines 244 are provided engaging corresponding grooves of the piston rod 230. The drive tube 243 surrounds the piston rod 230 which is axially displaceable relative to the drive tube 243. As shown in FIGS. 11 and 12, the drive sleeve upper part 242 and the drive tube 243 each have at their proximal end a pinion 245, 246, which mesh such that rotation of the drive sleeve is transmitted to the drive tube. The drive sleeve is axially movable along the second axis II between a proximal position (during dose setting and correcting, see FIG. 11) in which pinion 245 further engages teeth 215 of the housing 210, and a distal (dose dispensing position, see FIG. 12) in which the pinion 245 is disengaged from the teeth 215. However, in both axial positions pinions 245, 246 remain into engagement.

(73) The drive sleeve has on its outer surface splines 247 for rotationally constraining the drive sleeve to the power reservoir 290. Further, splines are provided on the inner surface of the drive sleeve for rotationally constraining the drive sleeve to nut 250.

(74) The nut 250 is part of a last dose limiter mechanism. The last dose nut 250 is located between the dial sleeve 260 and the drive sleeve 241, 242. It moves along a helical path relative to the dial sleeve 260, via a threaded interface 261, when relative rotation occurs between the dial sleeve 260 and drive sleeve during dialing, i.e. during dose setting or dose correcting. In the embodiment of FIGS. 10 to 12, the nut 250 is a half nut, i.e. a component extending approximately 180 around the second axis II of the device.

(75) The dial sleeve 260 is a tubular element arranged rotatable on the second axis II. A proximal section of the dial sleeve 260 is provided with a thread 261 guiding the nut 250. An adjacent distal section is provided with outer splines 262 for engagement with the number sleeve 280. Further, the dial sleeve 260 has a ring of inner teeth at an intermediate stepped portion for releasably rotationally coupling the dial sleeve 260 to the dial assembly 270.

(76) The dial assembly 270 comprises dial grip 271 and a tubular element 272 which is rigidly attached to the dial grip 271. The dial grip 271 and the tubular element 272 are in the present embodiment separate components for manufacturing reasons but may also be a single component. The dial assembly 270 is arranged on the second axis II and extends through the proximal aperture in the proximal housing part 212. At its distal end, the dial assembly is provided with a ring of teeth on its distal face for interaction with clicker 300. Further, a pinion 274 is provided near the distal end of tubular element 272 engaging teeth of dial sleeve 260 in the dose setting position. The dial assembly 270 is axially movable along the second axis II between a proximal position (during dose setting and correcting, see FIG. 11) and a distal (dose dispensing position, see FIG. 12). The dial grip 271 abuts the drive sleeve such that axial movement of the dial grip in the distal direction entrains the drive sleeve and axial movement of the drive sleeve in the proximal direction entrains the dial grip.

(77) The number sleeve 280 is a tubular element arranged on the second axis II. The outer surface of the number sleeve 280 is provided with a sequence of numbers arranged on a helical path. Further, the number sleeve has on its outer surface a thread 281 engaging a corresponding thread of the main housing 211. At its distal end, the number sleeve 280 is provided with an inwardly directed protrusion for interaction with the dial sleeve 260. Further, there are rotational hard stops on the number sleeve 280 and corresponding elements on the main housing 211 limiting the rotational movement of the number sleeve relative to the housing on its helical path defined by the threaded interface.

(78) The power reservoir comprises a reverse wound flat spiral spring 290, that is a band-like spring, which has a spiral form in its unstressed condition and is wound counter to that unstressed spiral direction for tensioning the spring. A first end of the spring 290 is attached to a first spool 291, which is located on the first longitudinal axis I surrounding drive tube 243. A second end of the spring 290 is attached to a second spool 292, which is located on the second longitudinal axis II and is rotationally constrained to the drive sleeve by splines 247 and corresponding grooves inside the second spool 292. Spring 290 is fully charged (tensioned) during assembly of the device by winding the spring on spool 292, whereas the spring tends to wind back on spool 291. The power reservoir is dimensioned such that spring 290 is able to drive the piston rod 230 from its retracted position shown in FIGS. 11 and 12 to a position, where the cartridge bung is pushed in its most distal direction. In other words, recharging of the spring 290 is not necessary for emptying cartridge 220.

(79) The clicker 300 is a tubular element positioned axially displaceable but rotationally constrained on splined pin 216 of the cartridge holder 213. The clicker 300 has grooves on its inner surface for engagement with the splined pin 216. Further, there are clicker teeth 302 on the proximal end of clicker 300 mating with teeth of the dial assembly. A finger, which interacts with protrusion of the number sleeve, is provided near the teeth 302.

(80) Spring 310 is a compression spring located on splined pin 216 and inside clicker 300 urging clicker 300 in the proximal direction. Due to the contact between the clicker 300 and the dial assembly 270 and due to the contact between the dial assembly 270 and the drive sleeve, the spring pushes these components in the proximal direction as shown in FIG. 11, whereas a user may overcome the spring 310 force and push these components in the distal position shown in FIG. 12.

(81) During dose setting, the nut 250 advances towards a rotational abutment at the proximal end of the dial sleeve 260 whilst there is relative rotation between the dial sleeve 260 and drive sleeve 241, 242. When the abutment is reached, dial torque is reacted through the dial grip 271, dial sleeve 260, nut 250 and drive sleeve 241, 242 back to the splined interface with the housing 210. As the dial sleeve 260 and the drive sleeve 241, 242 both rotate during dose dispensing, the nut 250 maintains its position on the dial sleeve 260.

(82) Although not shown in the embodiment of FIGS. 10 to 12, a gauge element as described above may be included in this device in addition to the number sleeve 280.