Drug Delivery Device

Abstract

The disclosure is generally directed to a drug delivery device for selecting and dispensing a number of user variable doses of a medicament. The device comprises a housing having a proximal end and an opposite distal end, a dose setting member rotatable relative to the housing during dose setting and during dose dispensing, and an axially compressible torsion spring which is rotationally and axially constrained with a first end to the housing. The device further comprises a spring collar, which is rotationally constrained to the dose setting member and axially displaceable thereto between a proximal dose setting position and a distal dose dispensing position. The torsion spring is rotationally constrained with a second, opposite end to the dose setting member via the spring collar, and the torsion spring biases the spring collar into its dose setting position.

Claims

1-15. (canceled)

16. A drug delivery device for selecting and dispensing a number of user variable doses of a medicament, the device comprising: a housing having a proximal end and an opposite distal end, a dose setting member rotatable relative to the housing during dose setting and during dose dispensing, an axially compressible torsion spring having a first end that is rotationally and axially constrained with respect to the housing; and a spring collar which is rotationally constrained with respect to the dose setting member and axially displaceable relative to the dose setting member between a proximal dose setting position and a distal dose dispensing position, wherein the torsion spring has a second end, opposite the first end, that is rotationally constrained with respect to the spring collar, and the torsion spring biases the spring collar into its dose setting position.

17. The drug delivery device according to claim 16, wherein the device further comprises a driver which is axially displaceable relative to the housing between a proximal dose setting position and a distal dose dispensing position, and the torsion spring biases the driver into its dose setting position via the spring collar.

18. The drug delivery device according to claim 17, wherein the spring collar has a first axial contact surface and the driver has a second axial contact surface abutting the first axial contact surface.

19. The drug delivery device according to claim 18, wherein the driver comprises a radial flange with its distal face being the second axial contact surface, and the spring collar comprises a proximal end face being the first axial contact surface.

20. The drug delivery device according to claim 17, wherein the dose setting member is coupled to the driver via at least one clutch such that during one of dose setting or dose dispensing, relative rotation between the dose setting member and the driver is allowed, while during the other of dose setting or dose dispensing relative rotation between the dose setting member and the driver is prevented.

21. The drug delivery device according to claim 20, wherein the at least one clutch comprises a ring of teeth on a proximal face of the driver and corresponding teeth on a distal face of a separate clutch plate which is rotationally constrained to the dose setting member, and the torsion spring axially biases the driver towards the clutch plate.

22. The drug delivery device according to claim 17, wherein the driver, in the dose setting position, is rotationally constrained with respect to the housing and, in the dose dispensing position, is rotatable relative to the housing.

23. The drug delivery device according to claim 17, further comprising a button located at the proximal end of the housing and coupled to the driver such that an axial movement of the button in a distal direction displaces the driver and the spring collar against the axial bias of the torsion spring, and such that an axial movement of the driver and the spring collar in a proximal direction displaces the button.

24. The drug delivery device according to claim 16, wherein the spring collar has a third axial contact surface and the dose setting member has a fourth axial contact surface abutting the third axial contact surface.

25. The drug delivery device according to claim 24, wherein the spring collar comprises a proximal face being the third axial contact surface, and the dose setting member has an internal flange with a distal face being the fourth axial contact surface.

26. The drug delivery device according to claim 16, wherein the dose setting member is axially constrained with respect to the housing.

27. The drug delivery device according to claim 16, wherein the dose setting member comprises at least one axially extending spline engaging at least one corresponding spline of the spring collar to allow relative axial movement between the dose setting member and the spring collar while preventing relative rotation between the dose setting member and the spring collar.

28. The drug delivery device according to claim 16, wherein the torsion spring is a drive spring configured to drive the dose setting member or the driver during dose dispensing.

29. The drug delivery device according to claim 28, wherein during dose setting, energy is stored in the torsion spring and during dose dispensing, energy is released from the torsion spring.

30. The drug delivery device according to claim 16, further comprising a cartridge containing a medicament.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0084] FIG. 1 shows a top view of the drug delivery device in the minimum dose position;

[0085] FIG. 2 shows an exploded view of the components of a known device similar to that of FIG. 1;

[0086] FIG. 3 shows a sectional view of the device of FIG. 2;

[0087] FIG. 4 shows a spring collar of the drug delivery device;

[0088] FIG. 5 shows an interface between the dose setting member and the spring collar of FIG. 4;

[0089] FIG. 6a shows an enlarged sectional view of a detail of the device of FIG. 1 in the dose setting mode; and

[0090] FIG. 6b shows an enlarged sectional view of a detail of the device of FIG. 1 in the dose dispensing mode.

DETAILED DESCRIPTION

[0091] FIG. 1 shows a drug delivery device in the form of an injection pen. The device has a distal end (left end in FIG. 1) and a proximal end (right end in FIG. 1). The component parts of the drug delivery device are shown in FIG. 2. The drug delivery device comprises a body or housing 10, a cartridge holder 20, a lead screw (piston rod) 30, a drive sleeve 40, a nut 50, a dose indicator (number sleeve) 60, a trigger element in the form of a button 70, a dial grip or dose selector 80, a torsion spring 90, a cartridge 100, a gauge element 110, a clutch plate 120, a clutch spring (not present in the embodiments) and a bearing 140. 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. All components are located concentrically about a common principal axis I of the mechanism, which is shown in FIG. 3. As can be seen in FIGS. 4, 6a and 6b, the device further comprises a spring collar 130 interposed between the dose setting member 60 and the spring 90. The annular spring collar has outer splines 131 or the like, a proximal end face 132 and means for engaging the drive spring 90.

[0092] The housing 10 or body is a generally tubular element having a proximal end with an enlarged diameter. The housing 10 provides location for the liquid medication cartridge 100 and cartridge holder 20, windows 11a, 11b for viewing the dose number on the number sleeve 60 and the gauge element 110, and a feature on its external surface, e.g. a circumferential groove, to axially retain the dose selector 80. A flange-like or cylindrical inner wall comprises an inner thread engaging the piston rod 30. The housing 10 further has at least one internal, axially orientated slot or the like for axially guiding the gauge element 110. In the embodiment shown in the Figures, the distal end is provided with an axially extending strip partly overlapping cartridge holder 20. The Figures depict the housing 10 as a single housing component. However, the housing 10 could comprise two or more housing components which may be permanently attached to each other during assembly of the device.

[0093] The cartridge holder 20 is located at the distal side of housing 10 and permanently attached thereto. The cartridge holder may be a transparent or translucent component which is tubular to receive cartridge 100. The distal end of cartridge holder 20 may be provided with means for attaching a needle arrangement. A removable cap (not shown) may be provided to fit over the cartridge holder 20 and may be retained via clip features on the housing 10.

[0094] The piston rod 30 is rotationally constrained to the drive sleeve 40 via a splined interface. When rotated, the piston rod 30 is forced to move axially relative to the drive sleeve 40, through its threaded interface with the inner wall of housing 10. The lead screw 30 is an elongate member with an outer thread (FIG. 3) engaging the corresponding thread of the inner wall of housing 10. The leadscrew thread may have a large lead-in, for example a wedge shape form, at its distal end to engage a corresponding housing thread form on the first rotation. The interface comprises at least one longitudinal groove or track and a corresponding protrusion or spline of the driver 40. At its distal end, the lead screw 30 is provided with an interface for clip attachment of the bearing 140.

[0095] The drive sleeve 40 is a hollow member surrounding the lead screw 30 and arranged within number sleeve 60. It extends from an interface with the clutch plate 120 to an interface with the housing 10. The drive sleeve 40 is axially movable relative to the housing 10, the piston rod 30 and the number sleeve 60 in the distal direction against the axial bias of drive spring 90 and in the opposite proximal direction under the axial bias of drive spring 90.

[0096] A splined tooth interface with the housing 10 prevents rotation of the drive sleeve 40 during dose setting. This interface comprises for example a ring of radially extending outer teeth at the distal end of drive sleeve 40 and corresponding radially extending inner teeth of the housing component 10. When the button 70 is pressed, these drive sleeve 40 to housing 10 spline teeth are disengaged allowing the drive sleeve 40 to rotate relative to housing 10.

[0097] A further splined tooth interface with the number sleeve 60 is not engaged during dialling, but engages when the button 70 is pressed, preventing relative rotation between the drive sleeve 40 and number sleeve 60 during dispense. This interface may comprise inwardly directed splines on a flange on the inner surface of the number sleeve 60 and a ring of radially extending outer splines of drive sleeve 40. The corresponding splines are located on the number sleeve 60 and the drive sleeve 40, respectively, such that axial movement of the drive sleeve 40 relative to the (axially fixed) number sleeve 60 engages or disengages the splines to rotationally couple or decouple the drive sleeve 40 and the number sleeve 60. Preferably, the splines are arranged such that they are decoupled when teeth of drive sleeve 40 and inner teeth of housing component 10 mesh and engage when teeth and inner teeth disengage.

[0098] A further interface of the drive sleeve 40 comprises a ring of ratchet teeth located at the proximal end face of drive sleeve 40 and a ring of corresponding ratchet teeth of clutch plate 120.

[0099] The driver 40 has a threaded section providing a helical track for the nut 50. In addition, a last dose abutment or stop is provided which may be the end of the thread track or preferably a rotational hard stop for interaction with a corresponding last dose stop of nut 50, thus limiting movement of the nut 50 on the driver thread. At least one longitudinal spline engages a corresponding track of the lead screw 30. Further, the drive sleeve is provided with a ramp interacting with a clicker arm when the drive sleeve 40 is in its distal position during dose dispensing, i.e. when button 70 is depressed.

[0100] The driver 40 comprises a flange 41 extending radially outwards (FIGS. 6a, 6b). The distal face of this flange 41 is designed to abut the proximal end face 132 of spring collar 130 under the bias of spring 90.

[0101] The last dose nut 50 is located between the number sleeve 60 and the drive sleeve 40. It is rotationally constrained to the number sleeve 60, via a splined interface. It moves along a helical path relative to the drive sleeve 40, via a threaded interface, when relative rotation occurs between the number sleeve 60 and drive sleeve 40 which is during dialling only. As an alternative, the nut 50 may be splined to the driver 40 and threaded to the number sleeve 60. A last dose stop is provided engaging a stop of drive sleeve 40 when a dose is set corresponding to the remaining dispensable amount of medicament in the cartridge 100.

[0102] The dose setting member or number sleeve 60 is a tubular element as shown in FIGS. 2 and 3. The number sleeve 60 is rotated during dose setting (via dose selector 80) and dose correction and during dose dispensing by torsion spring 90. Together with gauge element 110 the number sleeve 60 defines a zero position (at rest) and a maximum dose position. Thus, the number sleeve 60 may be seen as a dose setting member.

[0103] For manufacturing reasons the number sleeve 60 of the embodiment shown in the Figures comprises a number sleeve lower 60a which is rigidly fixed to a number sleeve upper 60b during assembly to form the number sleeve 60. Number sleeve lower 60a and number sleeve upper 60b are separate components only to simplify number sleeve 60 mould tooling and assembly. As an alternative, the number sleeve 60 may be a unitary component. The number sleeve 60 is constrained to the housing 10 by features towards the distal end to allow rotation but not translation. The number sleeve lower 60a is marked with a sequence of numbers, which are visible through the gauge element 110 and the openings 11a, 11b in the housing 10, to denote the dialled dose of medicament.

[0104] Further, the number sleeve lower 60a has a portion with an outer thread engaging the gauge element 110. End stops are provided at the opposite ends of this thread to limit relative movement with respect to the gauge element 110.

[0105] An inner surface of the number sleeve lower 60a is provided with a step or internal flange 61 defining an axial abutment surface. This portion receives the spring collar 130 which has outer splines 131 engaging internal splines 62 of the number sleeve lower 60a such that the spring collar 130 is permanently rotationally constrained to the number sleeve lower 60a. In the embodiment depicted in FIGS. 4 and 5, the number sleeve is provided with protrusions 62 guided in recesses 131 of the spring collar. However, other splined interfaces between number sleeve 60 and spring collar 130 are possible. The proximal end face 132 of the spring collar is designed to contact the axial abutment surface of the number sleeve lower 60a defined by the step or flange 61, thus limiting axial movement of the spring collar 130 in the proximal direction. As an alternative (or in addition) the length of the spline grooves of the number sleeve lower 60a may limit the axial movement of the spring collar 130 in the proximal direction. As an alternative, flange 41 of the drive sleeve 40 contacts proximal end face 132 of the spring collar 130. This pushes proximal end face 132 out of contact with flange 61 and biases the drive sleeve 40 in the proximal direction.

[0106] The dose selector 80 is axially constrained to the housing 10. It is rotationally constrained, via the splined interface, to the button 70. This splined interface which includes grooves interacting with spline features formed by the annular skirt of button 70 remains engaged irrespective of the dose button 70 axial positions. The dose selector 80 or dose dial grip is a sleeve-like component with a serrated outer skirt.

[0107] The torsion spring 90 is attached at its distal end to the housing 10 and at the other end to the spring collar 130. The torsion spring 90 is located inside the number sleeve 60 and surrounds a distal portion of the drive sleeve 40. The torsion spring 90 may be pre-wound upon assembly, such that it applies a torque to the number sleeve 60 when the mechanism is at zero units dialled. The action of rotating the dose selector 80, to set a dose, rotates the number sleeve 60 relative to the housing 10, and charges the torsion spring 90 further.

[0108] The torsion spring 90 is formed from a helical wire with at least two different pitches. Both ends are formed from closed coils, i.e. the pitch equals the wire diameter and each coil contacts the adjacent coil. The central portion has open coils, i.e. the coils do not contact each other. This allows the spring 90 to exert an axial force in addition to a torque.

[0109] The cartridge 100 is received in cartridge holder 20 (FIG. 3). The cartridge 100 may be a glass ampoule having a moveable rubber bung 101 at its proximal end. The distal end of cartridge 100 is provided with a pierceable rubber seal which is held in place by a crimped annular metal band. In the embodiment depicted in the Figures, the cartridge 100 is a standard 1.5 ml cartridge. The device is designed to be disposable in that the cartridge 100 cannot be replaced by the user or health care professional. However, a reusable variant of the device could be provided by making the cartridge holder 20 removable and allowing backwinding of the lead screw 30 and the resetting of nut 50.

[0110] The gauge element 110 is constrained to prevent rotation but allow translation relative to the housing 10 via a splined interface. The gauge element 110 has a helical feature on its inner surface which engages with the helical thread cut in the number sleeve 60 such that rotation of the number sleeve 60 causes axial translation of the gauge element 110. This helical feature on the gauge element 110 also creates stop abutments against the end of the helical cut in the number sleeve 60 to limit the minimum and maximum dose that can be set.

[0111] The gauge element 110 has a generally plate or band like component having a central aperture or window and two flanges extending on either side of the aperture. The flanges are preferably not transparent and thus shield or cover the number sleeve 60, whereas the aperture or window allows viewing a portion of the number sleeve lower 60a. Further, gauge element 110 has a cam and a recess interacting with the clicker arm of the number sleeve 60 at the end of dose dispensing.

[0112] The clutch plate 120 is a ring-like component. The clutch plate 120 is splined to the number sleeve 60. It is also coupled to the drive sleeve 40 via a ratchet interface. The ratchet provides a detented position between the number sleeve 60 and drive sleeve 40 corresponding to each dose unit, and engages different ramped tooth angles during clockwise and anti-clockwise relative rotation. A clicker arm is provided on the clutch plate 120 for interaction with ratchet features of the button 70.

[0113] The drive spring 90 acts as a torsion spring and as a compression spring. The axial position of the drive sleeve 40, clutch plate 120 and button 70 is defined by the action of the drive spring 90, which applies a force on the drive sleeve 40 (via spring collar 130) in the proximal direction. This spring force is reacted via the drive sleeve 40, clutch plate 120, and button 70, and when at rest it is further reacted through the dose selector 80 to the housing 10. The spring force ensures that the ratchet interface between driver and clutch plate is always engaged. In the at rest position, it also ensures that the button splines are engaged with the number sleeve splines, and the drive sleeve teeth are engaged with teeth of the housing 10. In addition, the force of the drive spring 90 is sufficient to push button 70 back in the proximal direction after dose dispensing.

[0114] The spring collar 130 is shown in FIG. 4 in detail. In addition to its splines 131 and the proximal contact face 132 it comprises anchor features 133 for retaining the proximal hook end of spring 90. The spring is thereby axially and rotationally constrained to spring collar 130. In other words, the spring collar 130 is a ring with a guide surface that guides the end of spring 90 during assembly and an anchor point to locate the hook end form of the spring 90.

[0115] The bearing 140 is axially constrained to the piston rod 30 and acts on the bung 101 within the liquid medicament cartridge. It is axially clipped to the lead screw 30, but free to rotate.

[0116] With the device in the at rest condition as shown in FIG. 6a, the number sleeve 60 is positioned against its zero dose abutment with the gauge element 110 and the button 70 is not depressed. Dose marking 0 on the number sleeve 60 is visible through the windows of the housing 10 and gauge element 110, respectively. The torsion 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 60 and is prevented from rotating by the zero dose abutment. Further, the spring 90 applies an axial force on the spring collar 130, the drive sleeve 40 (via abutment faces 41, 132), the clutch plate 120 and the button 70 biasing these component parts in the proximal direction (right hand side in FIG. 6a). This force is reacted through the dial grip 80 to the housing 10. As an alternative, it may be reacted by the spring collar 130 abutting with its face 132 the flange 61 of the lower part 60a of number sleeve 60.

[0117] The user selects a variable dose of liquid medicament by rotating the dose selector 80 clockwise, which generates an identical rotation in the number sleeve 60. Rotation of the number sleeve 60 causes charging of the torsion spring 90, increasing the energy stored within it. As the number sleeve 60 rotates, the gauge element 110 translates axially due to its threaded engagement thereby showing the value of the dialled dose. The gauge element 110 has flanges either side of its window area which cover the numbers printed on the number sleeve 60 adjacent to the dialled dose to ensure only the set dose number is made visible to the user.

[0118] A specific feature of some embodiments is the inclusion of a visual feedback feature in addition to the discrete dose number display typical on devices of this type. The distal end (flange) of the gauge element 110 creates a sliding scale through the small window 11a in the housing 10. As an alternative, the sliding scale could be formed using a separate component engaged with the number sleeve 60 on a different helical track.

[0119] As a dose is set by the user, the gauge element 110 translates axially, the distance moved proportional to the magnitude of the dose set. This feature gives clear feedback to the user regarding the approximate size of the dose set. The dispense speed of an auto-injector mechanism may be higher than for a manual injector device, so it may not be possible to read the numerical dose display during dispense. The gauge feature provides feedback to the user during dispense regarding dispense progress without the need to read the dose number itself. For example, the gauge display may be formed by an opaque element on the gauge element 110 revealing a contrasting coloured component underneath. Alternatively, the revealable element may be printed with coarse dose numbers or other indices to provide more precise resolution. In addition, the gauge display simulates a syringe action during dose set and dispense.

[0120] The openings 11a, 11b in the housing 10 allow the user to view the gauge feature and number display. To reduce dust ingress and prevent the user from touching moving parts, these openings 11a, 11b are covered by translucent windows. These windows may be separate components, but in this embodiment they are incorporated into the housing 10 using twin-shot moulding technology.

[0121] The mechanism utilises a dose selector 80 with an increased diameter relative to the housing 10 which aids dialling although this is not a requirement of the mechanism. This feature is particularly useful (but not essential) for an auto-injector mechanism where a power supply is charged during dose setting and the torque required to turn the dose selector 80 may be higher than for a non-auto injector device.

[0122] The drive sleeve 40 is prevented from rotating as the dose is set and the number sleeve 60 rotated, due to the engagement of its splined teeth with teeth of the housing 10. Relative rotation must therefore occur between the clutch plate 120 and drive sleeve 40 via the ratchet interface.

[0123] The user torque required to rotate the dose selector 80 is a sum of the torque required to wind up the torsion spring 90, and the torque required to overhaul the ratchet interface. The torsion spring 90 is designed to provide an axial force to the ratchet interface and to bias the clutch plate 120 onto the drive sleeve 40. As the user rotates the dose selector 80 sufficiently to increment the mechanism by one increment, the number sleeve 60 rotates relative to the drive sleeve 40 by one ratchet tooth. At this point the ratchet teeth 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.

[0124] Relative rotation of the number sleeve 60 and the drive sleeve 40 is allowed as splines are disengaged during dose setting. This relative rotation also causes the last dose nut 50 to travel along its threaded path, towards its last dose abutment on the drive sleeve 40. With no user torque applied to the dose selector 80, the number sleeve 60 is now prevented from rotating back under the torque applied by the torsion spring 90, solely by the ratchet interface between the clutch plate 120 and the drive sleeve 40. The user may now choose to increase the selected dose by continuing to rotate the dose selector 80 in the clockwise direction. If the user continues to increase the selected dose until the maximum dose limit is reached, the number sleeve 60 engages with its maximum dose abutment on the maximum dose abutment of gauge element 110. This prevents further rotation of the number sleeve 60, clutch plate 120 and dose selector 80.

[0125] Depending on how many increments have already been delivered by the mechanism, during selection of a dose, the last dose nut 50 may contact its last dose abutment with stop face of the drive sleeve 40. The abutment prevents further relative rotation between the number sleeve 60 and the drive sleeve 40, and therefore limits the dose that can be selected. The position of the last dose nut 50 is determined by the total number of relative rotations between the number sleeve 60 and drive sleeve 40, which have occurred each time the user sets a dose.

[0126] With the mechanism in a state in which a dose has been selected, the user is able to deselect any number of increments from this dose. Deselecting a dose is achieved by the user rotating the dose selector 80 anti-clockwise. The torque applied to the dose selector 80 by the user is sufficient, when combined with the torque applied by the torsion spring 90, to overhaul the ratchet interface between the clutch plate 120 and drive sleeve 40 in the anti-clockwise direction. When the ratchet is overhauled, anti-clockwise rotation occurs in the number sleeve 60 (via the clutch plate 120), which returns the number sleeve 60 towards the zero dose position, and unwinds the torsion spring 90. The relative rotation between the number sleeve 60 and drive sleeve 40 causes the last dose nut 50 to return along its helical path, away from the last dose abutment.

[0127] 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 button 70 axially in the distal direction. When the button 70 is depressed, splines between the button 70 and number sleeve 60 are disengaged, rotationally disconnecting the button 70 and dose selector 80 from the delivery mechanism, i.e. from number sleeve 60, gauge element 110 and torsion spring 90. Splines on the button 70 engage with splines on the housing 10, preventing rotation of the button 70 (and hence the dose selector 80) during dispense. As the button 70 is stationary during dispense, it can be used in the dispense clicker mechanism. A stop feature in the housing 10 limits axial travel of the button 70 and reacts any axial abuse loads applied by the user, reducing the risk of damaging internal components.

[0128] The clutch plate 120 and drive sleeve 40 travel axially with the button 70. This engages the splined tooth interface between the drive sleeve 40 and number sleeve 60 preventing relative rotation between the drive sleeve 40 and number sleeve 60 during dispense. The splined tooth interface between the drive sleeve 40 and the housing 10 disengages, so the drive sleeve 40 can now rotate and is driven by the torsion spring 90 via the number sleeve 60, and clutch plate 120. Further, the distal movement of drive sleeve 40 compresses the spring 90 as the spring collar 130 is moved distally together with the drive sleeve 40 (via abutment faces 41, 132). Compression of spring 90 is possible due to the open coils in the middle portion of the spring 90.

[0129] Rotation of the drive sleeve 40 causes the piston rod 30 to rotate due to their splined engagement, and the piston rod 30 then advances due to its threaded engagement to the housing 10. The number sleeve 60 rotation also causes the gauge element 110 to traverse axially back to its zero position whereby the zero dose abutment stops the mechanism.

[0130] Delivery of a dose continues via the mechanical interactions described above while the user continues to depress the button 70. If the user releases the button 70, the torsion spring 90 returns the drive sleeve 40 to its at rest position (together with the spring collar 130, the clutch plate 120 and button 70), engaging the splines between the drive sleeve 40 and housing 10, preventing further rotation and stopping dose delivery.

[0131] During delivery of a dose, the drive sleeve 40 and number sleeve 60 rotate together, so that no relative motion in the last dose nut 50 occurs. The last dose nut 50 therefore travels axially relative to the drive sleeve 40 during dialling only.

[0132] At the end of dose dispensing, additional audible feedback is provided in the form of a click, distinct from the clicks provided during dispense, to inform the user that the device has returned to its zero position via the interaction of the clicker arm on the number sleeve 60 with the ramp on the drive sleeve 40 and the cam and the recess on the gauge element 110. This embodiment allows feedback to only be created at the end of dose delivery and not created if the device is dialled back to, or away from, the zero position.

TABLE-US-00001 Reference Numerals: 10 housing 11a opening (window) 11b opening (window) 20 cartridge holder 30 lead screw (piston rod) 40 driver (axially movable drive sleeve) 41 flange 50 nut 60 dose indicator (number sleeve) 60a number sleeve lower 60b number sleeve upper 61 flange 62 spline 70 button 80 dose selector 90 torsion spring 100 cartridge 101 bung 110 gauge element 120 clutch plate 130 spring collar 131 spline 132 proximal contact face 133 anchor feature 140 bearing I longitudinal axis