Resettable Drug Delivery Device

Abstract

The present disclosure is generally directed to a resettable drug delivery device for selecting and dispensing a number of user variable doses of a medicament. The drug delivery device comprises a housing, a cartridge holder, releasably attached to the distal end of the housing, a piston rod, engaging a housing insert and a drive member, a dose setting member, guided within the housing to allow rotation of the dose setting member during dose setting and dose dispensing, and a clutch for rotationally coupling the drive member and the dose setting member. The housing insert is rotationally constrained to the housing and is axially movable together with the drive member relative to the housing between a dose setting and dispensing position, and a resetting position. In the dose resetting position. the drive member is rotationally de-coupled from the housing.

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 distal end and a proximal end, a cartridge holder releasably attached to the distal end of the housing, a piston rod engaging a housing insert and a drive member, a dose setting member guided within the housing to allow rotation of the dose setting member during dose setting and dose dispensing, and a clutch for rotationally coupling the drive member and the dose setting member, wherein the housing insert is rotationally constrained to the housing and is axially movable together with the drive member relative to the housing between a dose setting and dispensing position, and a resetting position, and the drive member is rotationally de-coupled from the housing in the resetting position.

17. The drug delivery device according to claim 16, further comprising at least one spring biasing the housing insert and the drive member into the resetting position.

18. The drug delivery device according to claim 16, wherein the housing insert and the drive member are coupled such that the housing insert entrains the drive member in an axial movement of the housing insert into the dose setting and dispensing position and that the drive member entrains the housing insert in an axial movement of the drive member into the resetting position.

19. The drug delivery device according to claim 16, wherein the housing insert and the cartridge holder are coupled such that the cartridge holder entrains the housing insert in an axial movement of the cartridge holder upon attachment of the cartridge holder to the housing.

20. The drug delivery device according to claim 16, wherein the housing insert comprises an inner thread engaging an outer thread of the piston rod.

21. The drug delivery device according to claim 16, further comprising a last dose mechanism with a nut which is in threaded engagement with one of the drive member and the dose setting member and rotationally constrained, but axially movable, relative to the other of the drive member and the dose setting member

22. The drug delivery device according to claim 16, further comprising a locking element which is rotationally constrained to the housing and is axially movable relative to the housing between a dose setting position, in which the drive member is rotationally constrained to the housing, and a dose dispensing position, in which the drive member is rotationally de-coupled from the housing.

23. The drug delivery device according to claim 22 further comprising at least one spring biasing the housing insert and the drive member into the resetting position and biasing the locking element into the dose setting position.

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

25. The drug delivery device according to claim 16, further comprising a drive spring interposed between the housing and the dose setting member.

26. The drug delivery device according to claim 16, further comprising a gauge element radially interposed between the housing and the dose setting member, wherein the gauge element is axially movable relative to the housing and is in threaded engagement with the dose setting member.

27. The drug delivery device according to claim 26, wherein the housing comprises at least one aperture, the gauge element comprises at least one aperture, and an outer surface of the dose setting member comprises markings, wherein at least one of the markings is visible through the aperture of the gauge element and the aperture of the housing during dose setting and dose dispensing.

28. The drug delivery device according to claim 26, wherein the gauge element comprises a minimum dose rotational stop and a maximum dose rotational stop, and the dose setting member comprises a minimum dose rotational counter stop and a maximum dose rotational counter stop.

29. The drug delivery device according to claim 16, wherein the clutch comprises clutch teeth on the drive member and a clutch member rotationally constrained to the dose setting member with corresponding clutch teeth, wherein the clutch member is axially movable together with the drive member relative to the housing into a resetting position in which the clutch member is rotationally de-coupled from the dose setting member.

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

31. A method of resetting a drug delivery device comprising: unscrewing a cartridge holder from an outer housing of the drug delivery device and removing a used cartridge from the cartridge holder. inserting a new cartridge into the cartridge holder and reattaching the cartridge holder containing the new cartridge to the outer housing of the drug delivery device, thereby pushing a piston rod further into the outer housing, and; rotating the cartridge holder, after the cartridge holder contacts a housing insert, wherein a spline to couple a drive sleeve with a locking element and a spline to couple a clutch plate with a number sleeve, are reengaged.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0101] Non-limiting, exemplary embodiments will now be described with reference to the accompanying drawings, in which:

[0102] FIG. 1a shows a top view of the drug delivery device in the minimum dose position;

[0103] FIG. 1b shows a top view of the drug delivery device of FIG. 1a with a dose of 96 units dialed;

[0104] FIG. 2 shows an exploded view of the components of the device of FIG. 1a;

[0105] FIG. 3 shows a sectional view of the device of FIG. 1a in the dose setting mode;

[0106] FIGS. 4a, b show in sectional views details of the device of FIG. 1a in the dose setting mode;

[0107] FIGS. 5a, b show in sectional views details of the device of FIG. 1a in the dose dispensing mode;

[0108] FIGS. 6a, b show in sectional views details of the device of FIG. 1a in the resetting mode; and

[0109] FIGS. 7a-c show in sectional views the sequence of resetting the device of FIG. 1a.

DETAILED DESCRIPTION OF THE DRAWINGS

[0110] FIG. 1a shows a drug delivery device in the form of an injection pen. The device has a distal end (left end in FIG. 1a) and a proximal end (right end in FIG. 1a). 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 setting member which is a dose indicator (number sleeve) 60, a button 70, a dial grip or dose selector 80, a torsion spring 90, a locking element 100, a gauge element 110, a clutch element 120, a clutch spring 130, a bearing 140, a housing insert 150 and a cap 160. 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.

[0111] The housing 10 or body is a generally tubular element. The housing 10 provides location for a liquid medication cartridge and cartridge holder 20, windows 11a, 11b for viewing the dose number on the dose indicator 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. The housing 10 further has at least one internal, axially orientated slot or the like for axially guiding the gauge element 110. Further, housing insert 150 is axially guided within housing 10 such that relative rotation is prevented, while, preferably limited, axial relative movement is allowed. In addition, locking element 100 is axially guided in housing 10 such that relative rotation is prevented while axial relative movement is allowed.

[0112] The cartridge holder 20 contains the replaceable cartridge and acts to limit the axial travel of the housing insert 150 in the distal direction. When the cartridge holder 20 is removed, the trigger spring 130 forces the housing insert 150, drive sleeve 40 and clutch plate 120 axially in a distal direction, disengaging the spline teeth 41, 101 between the locking element 100 and the drive sleeve 40 and the spline teeth between the clutch plate 120 and the number sleeve 60, allowing the device to be reset. A bias spring (not shown) may be provided to act between the housing 10 and the cartridge to bias the cartridge in a distal direction. The removable cap 160 is provided to fit over the cartridge holder 20 and may be retained via clip features on the housing 10.

[0113] The piston rod 30 is an elongate lead screw element with an outer thread 31 and at least one axially extending spline or rib. The piston rod 30 is rotationally constrained to the drive sleeve 40 via this splined interface. When rotated, the piston rod 30 is forced to move axially relative to the housing 10, through its threaded interface 31, 151 with the housing insert 150. The bearing 140 is attached to the distal end the piston rod 30, e.g. by a snap connection.

[0114] The drive sleeve 40 is a tubular member surrounding the piston rod 30 and being at least in parts received within the dose setting member 60. The drive sleeve 40 extends from the interface 42, 121 with the number sleeve 60 (via the clutch plate 120) down to a splined tooth interface 41, 101 with the locking element 100. This provides a rotational constraint to the drive sleeve 40 during dose setting. When the button 70 is pressed, the locking element 100 is moved axially in a distal direction such that these spline teeth 41, 101 are disengaged, allowing the drive sleeve 40 to rotate under the action of the drive spring 90, dispensing the set dose.

[0115] 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, i.e. during dialing and resetting only.

[0116] The dose setting member 60 is a tubular number sleeve which is constrained, via a clip at its distal end, to the housing 10 to allow rotation but not axial translation in all conditions. The number sleeve 60 is marked with a sequence of numbers, which are visible through opening 111 in the gauge element 110 and the slot-like window 11b in the housing 10, to denote the dialed dose of medicament. In the embodiment shown in the Figures, the dose setting member 60 comprises a lower part 60a and an upper part 60b which are fixed to each other during assembly. The lower part 60a is provided with the numbers and with the thread engaging the gauge element 110. The upper part 60b comprises a splined interface 61, 122 with the clutch plate 120.

[0117] The button 70 is splined to the upper part 60b of number sleeve 60 when in the dialing condition. This spline interface is disconnected when the button 70 is pressed to trigger a dispense. When depressed, the button 70 is rotationally constrained to the housing 10 via a splined engagement. The dose selector 80 is radially constrained to the housing 10 and rotationally constrained to the button 70. Further, the button 70 comprises a compliant clicker arm interacting with ratchet features on the upper part 60b during dose dispensing.

[0118] The dial grip 80 is radially constrained to the housing 10 and rotationally constrained to the button 70.

[0119] The drive spring 90 is attached at one end to the locking element 100 and at the other end to the number sleeve 60. The drive spring 90 is pre-wound upon assembly, such that it applies a torque to the number sleeve 60 when the mechanism is at zero units dialed. 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 drive spring 90.

[0120] The locking element 100 mainly has the form of an arm or a half-shell and is rotationally splined to the housing 10 and axially constrained to the button 70 in all conditions. It is axially movable relative to the housing 10 between a proximal dose setting position (locking the drive sleeve 40 to the housing) and a distal dose dispensing position (allowing rotation of the drive sleeve 40). The locking element 100 has teeth 101 engaging corresponding teeth 41 of the drive sleeve when in its dose setting position.

[0121] 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 helical features on its inner surface which engage with the helical thread cut in the dose setting member 60 such that rotation of the dose setting member 60 causes axial translation of the gauge element 110. These helical features on the gauge element 110 also create stop abutments against the end of the helical cut in the dose setting member 60 to limit the minimum and maximum dose that can be set. An opening or window 111 allows viewing a portion of the dose setting member 60 through the gauge element 110.

[0122] The clutch plate 120 is splined to the upper part 60b of number sleeve 60 via interface 61, 122 when in the dialing and dispensing conditions. On entry to the reset condition the clutch plate 120 moves axially in a distal direction, disconnecting this spline interface 61, 122 with the upper part 60b of number sleeve 60. The clutch plate 120 is also coupled to the drive sleeve 40 via a ratchet interface 42, 121, which occurs on an axial abutment. The ratchet provides a detented position between the number sleeve 60 and drive sleeve 40 corresponding to each dose increment, and engages different ramped tooth angles during clockwise and anti-clockwise relative rotation.

[0123] The clutch or trigger spring 130 is axially interposed between the clutch 120 and the button 70. In the at rest position, the trigger spring 130 applies a biasing force on the button 70 in the proximal direction to ensure that the button 70 splines are engaged with the upper part 60b of number sleeve 60.

[0124] The bearing 140 is axially constrained to the piston rod 30 and acts on the bung within the liquid medicament cartridge.

[0125] The housing insert 150 is rotationally splined to the housing 10 and biased in a distal direction against the cartridge holder 20 by the trigger spring 130. The axial positions of the drive sleeve 40 and clutch plate 120 are also defined by the action of the trigger spring 130, which applies a biasing force in the distal direction to ensure the drive sleeve 40 splines are engaged with the locking element 100 and the ratchet 42, 121 between the drive sleeve 40 and clutch plate 120 is engaged. The maximum travel in the distal direction of these components is defined by a stop face between the housing insert 150 and the cartridge holder 20.

[0126] With the device in the at rest condition or dose setting mode as shown in FIGS. 1a, 3, 4a and 4b, 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 11b and 111 of the housing 10 and 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 60 and is prevented from rotating 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 40 spline teeth. This has the effect of preventing possible weepage when a dose is dialed and the zero dose abutment is disengaged.

[0127] 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 drive 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 dialed dose. The gauge element 110 has flanges either side of the window area which cover the numbers printed on the number sleeve 60 adjacent to the dialed dose to ensure only the set dose number is made visible to the user.

[0128] One specific element of this type of mechanism is inclusion of a visual feedback feature in addition to the discrete dose number display typical on devices of this type. The distal end 112 of the gauge element 110 creates a sliding scale (although this could be formed using a separate component engaged with the number sleeve 60 on a different helical track if desired) through the small window 11a in the housing 10. 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. Comparing FIGS. 1a and 1b shows how the distal end 112 of the gauge element 110 moves proximally during dose setting. 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 element 110 feature provides feedback to the user during dispense regarding dispense progress without the need to read the dose number itself.

[0129] The gauge element 110 display may be formed by an opaque sliding element revealing a contrasting colored component underneath. Alternatively, the concealed component may be printed with coarse dose numbers or other indices to provide more precise resolution. In addition, the gauge element 110 display simulates a syringe action during dose set and dispense.

[0130] The drive sleeve 40 is prevented from rotating as the dose is set due to the engagement of its splined teeth 41 with teeth 101 of the locking element 100, and the clutch plate 120 is rotated due to the engagement of its splined teeth 61, 122 with the number sleeve 60. Relative rotation must therefore occur between the clutch plate 120 and drive sleeve 40 via the ratchet interface 42, 121.

[0131] The user torque required to rotate the dose selector 80 is a sum of the torque required to wind up the drive spring 90, and the torque required to overhaul the ratchet feature 42, 121. The trigger spring 130 is designed to provide an axial force to the ratchet feature and to bias the clutch plate 120 onto the drive sleeve 40. This axial load acts to maintain the ratchet teeth engagement of the clutch plate 120 and drive sleeve 40. The torque required to overhaul the ratchet 42, 121 in the dose set direction is a function of the axial load applied by the trigger spring 130, the clockwise ramp angle of the ratchet 42, 121, the friction coefficient between the mating surfaces and the mean radius of the ratchet features 42, 121.

[0132] As the user rotates the dose selector 80 sufficiently to increment the mechanism by 1 increment, the clutch plate 120 rotates relative to the drive sleeve 40 by 1 ratchet tooth. At this point the ratchet teeth 42, 121 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. Relative rotation of the number sleeve 60 and the drive sleeve 40 causes the last dose nut 50 to travel along its threaded path, towards its last dose abutment on the drive sleeve 40.

[0133] With no user torque applied to the dose selector 80, the number sleeve 60 is now prevented from rotating back due to the torque applied by the drive spring 90, solely by the ratchet engagement 42, 121 between the clutch plate 120 and the drive sleeve 40. The torque necessary to overhaul the ratchet in the anti-clockwise direction is a function of the axial load applied by the trigger spring 130, the anti-clockwise ramp angle of the ratchet 42, 121, 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 number sleeve 60 (and hence clutch plate 120) 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.

[0134] The user may now choose to increase the selected dose by continuing to rotate the dose selector 80 in the clockwise direction. The process of overhauling the ratchet interfaces 42, 121 between the clutch plate 120 and drive sleeve 40 is repeated for each dose increment. Additional energy is stored within the drive spring 90 for each dose increment and audible and tactile feedback is provided for each increment dialed by the re-engagement of the ratchet teeth 42, 121. The torque required to rotate the dose selector 80 increases as the torque required to wind up the drive spring 90 increases. The torque required to overhaul the ratchet 42, 121 in the anti-clockwise direction must therefore be greater than the torque applied to the number sleeve 60 by the drive spring 90 when the maximum dose has been reached.

[0135] 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 gauge element 110. This prevents further rotation of the number sleeve 60, clutch plate 120 and dose selector 80.

[0136] 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 the drive sleeve 40 as shown in FIG. 7a. 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.

[0137] 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 drive spring 90, to overhaul the ratchet 42, 121 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 drive 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.

[0138] 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 as shown in FIGS. 5a and 5b.

[0139] 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. Splines on the button 70 also engage with splines on the housing 10 (such that the dose selector 80 and button 70 do not rotate during dispense). The button 70 force acts on the locking element 100 which travels axially and disconnects the splined engagement 41, 101 with the drive sleeve 40, allowing rotation of the drive sleeve 40. The force on the ratchet 42, 121 between clutch plate 120 and drive sleeve 40 is increased by compression of the trigger spring 130, causing these components to spin together rather than overhaul the ratchet 42, 121, driven by the drive spring 90 via the number sleeve 60. 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 31, 151 to the housing insert 150. 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.

[0140] Tactile feedback during dose dispense is provided via a compliant cantilever clicker arm integrated into the button 70. This interfaces radially with ratchet features on the clutch plate 120. During dispense, as the clutch plate 120 rotates and the button 70 is rotationally coupled to the housing 10, the ratchet features engage with the clicker arm to produce an audible click with each dose increment delivered.

[0141] 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 trigger spring 130 returns the button 70 to its at rest position, the drive sleeve 40 becomes rotationally constrained and delivery of a dose is halted.

[0142] 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 on the drive sleeve 40 during dialing (and reset) only.

[0143] Once the delivery of a dose is stopped by the number sleeve 60 returning to the zero dose abutment with the gauge element 110, the user may release the button 70, which will re-engage spline teeth 41 of the drive sleeve 40 with teeth 101 of the locking element 100. The mechanism is now returned to the at rest condition.

[0144] The mechanism may incorporate a bias spring (not shown in the embodiment) which acts on the rear face of the cartridge. This aids dose accuracy as it ensures the cartridge is always biased distally, removing the effect of the tolerance on the cartridge length and the possibility of the cartridge moving proximally when a needle is fitted to the device.

[0145] It is possible to angle the spline teeth 41, 101 on either the drive sleeve 40 or locking element 100 so that when the button 70 is released the re-engagement of the spline teeth 41, 101 fractionally backwinds the drive sleeve 40 thereby removing the engagement of the number sleeve 60 to the gauge element 110 zero dose stop abutment. This compensates for 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 60 zero dose stop no longer restraining the mechanism and instead the restraint returning to the splines between the drive sleeve 40 and housing 10).

[0146] To reset the mechanism, the user first unscrews the cartridge holder 20, which allows the trigger spring 130 to move the housing insert 150, drive sleeve 40 and clutch plate 120 axially in a distal direction. This axial travel is sufficient to disconnect the splines 41, 101 between the locking element 100 and the drive sleeve 40 and the splines 61, 122 between the clutch plate 120 and the number sleeve 60. It also removes some compression from the trigger spring 130.

[0147] The user can then fit a new cartridge into the cartridge holder 20, and the bearing 140 and piston rod 30 can be pushed back into the mechanism. As the piston rod 30 is returned into the mechanism, a rotation in the piston rod 30 is generated due to the thread interface 31, 151 with housing insert 150. This piston rod 30 rotation causes the drive sleeve 40 to rotate due to their spline interface, which acts to backwind the last dose nut 50 towards its start position.

[0148] Towards the end of reset, the cartridge holder 20 contacts the housing insert 150 and at this point the bearing 140, piston rod 30 and last dose nut 50 have reached a fully reset position. Rotation of the cartridge holder 20 acts to move the housing insert 150 and drive sleeve 40 in a proximal direction, reengaging splines 41, 101 between the drive sleeve 40 and locking element 100, and splines 61, 122 between clutch plate 120 and number sleeve 60.

TABLE-US-00001 Reference Numerals:  10 outer housing  11a opening (window)  11b opening (window)  20 cartridge holder  30 piston rod (lead screw)  31 outer thread  40 drive sleeve  41 teeth  42 ratchet teeth  50 nut  60 dose setting element  61 spline  70 button  80 dose selector  90 torsion spring 100 locking element 101 teeth 110 gauge element 111 opening 112 distal end 120 clutch 121 ratchet teeth 122 spline 130 trigger spring 140 bearing 150 housing insert 151 thread 160 cap I longitudinal axis