Dispensing speed control mechanism and injection device

Abstract

The invention refers to a dispensing speed control mechanism for use in an injection device having a release button, which is displaceable to initiate dispensing of a set dose, a first component part, which is driven by a power reservoir during dose dispensing, and a second component part, which is stationary during dose dispensing. The speed control mechanism includes friction means for retarding the first component part during dose dispensing depending on the position of the release button. Further, the invention refers to a handheld injection device with such a speed control mechanism.

Claims

1. A dispensing speed control mechanism comprising: a user operable release button displaceable to initiate dispensing of a set dose; a first component part driven by a power reservoir to dispense the set dose during dose dispensing; a second component part stationary during the dose dispensing; and a friction mechanism configured to be engaged with an injection device to control a dispensing speed of a set dose from the injection device, wherein the friction mechanism is configured to generate friction on the first component part during the dose dispensing such that the friction mechanism retards the first component part depending on a position of the release button relative to the first component part, wherein the friction mechanism comprises a multi-plate clutch system configured to act between the first component part and the second component part to generate the friction, the multi-plate clutch system comprising a spring, at least one first clutch plate configured to be rotationally constrained to the first component part, and at least one second clutch plate configured to be rotationally constrained to the second component part, and wherein the spring is configured to expand when the first component part is displaced toward the second component part.

2. The dispensing speed control mechanism according to claim 1, wherein: the multi-plate clutch system comprises a cage configured to be rotationally constrained to the second component part and rotationally constrained to the at least one second clutch plate, and the spring is configured to bias the cage toward the first component part.

3. The dispensing speed control mechanism according to claim 1, wherein the friction causes a torque on the first component part that retards the first component part to reduce the dispensing speed, an amount of the torque depending on the position of the release button.

4. The dispensing speed control mechanism according to claim 1, wherein the release button is displaceable a first distance to initiate dispensing of the set dose, and displaceable a second distance during the dose dispensing to adjust a dispensing speed.

5. The dispensing speed control mechanism according to claim 1, wherein the release button is displaceable into a housing of the injection device to initiate the dispensing of the set dose, and then displaceable further into the housing of the injection device to decrease an amount of the friction on the first component part.

6. The dispensing speed control mechanism according to claim 1, wherein the friction mechanism is configured to generate an amount of friction depending on the position of the release button of the injection device relative to the first component part so as to retard the first component part and reduce the dispensing speed.

7. The dispensing speed control mechanism according to claim 1, wherein the release button comprises a dial grip operable to set the set dose.

8. The dispensing speed control mechanism according to claim 1, wherein the first component part comprises a portion of a drive member.

9. The dispensing speed control mechanism according to claim 1, wherein the second component part comprises a portion of a housing of the injection device.

10. The dispensing speed control mechanism according to claim 1, wherein the second component part comprises a portion of a dose setting mechanism of the injection device.

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 an exploded view of the components of an injection device in accordance with a first embodiment of the present invention;

(3) FIG. 2 shows a partial section view of the device of FIG. 1;

(4) FIG. 3 shows a sectional view of the device of FIG. 1 in the dose setting state;

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

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

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

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

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

(12) FIG. 9 shows an exploded view of components of an injection device in accordance with a second embodiment of the present invention;

(13) FIG. 10a shows a view of a detail of the device of FIG. 9 in the dose setting state;

(14) FIG. 10b shows a view of a detail of the device of FIG. 9 in the dose dispensing state;

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

(16) FIG. 12 shows an exploded view of the components of an injection device in accordance with a third embodiment of the present invention;

(17) FIG. 13 shows a view of the device of FIG. 12; and

(18) FIG. 14 shows a sectional view of the device of FIG. 12 in the dose setting state.

(19) FIGS. 1 and 2 show a drug delivery device in the form of an injection pen. The device has a distal end (left end in FIG. 2) and a proximal end (right end in FIG. 2). The component parts of the drug delivery device are shown in FIG. 1. The drug delivery device comprises a housing 10, a cartridge 20, a lead screw (piston rod) 30, a driver 40, a nut 50, a dial sleeve 60, a dial assembly 70, a number sleeve 80, a power reservoir (motor spring) 90, a clicker 100 and a spring 110. 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.

(20) The housing 10 or body comprises a main housing 11, a proximal housing 12 and a distal housing or cartridge holder 13. The main housing 11 is a generally tubular element with an oblong cross section with the lower side in FIG. 1 being widened compared with the upper side. A window 14 or aperture is provided in the main housing 11. The main housing 11, the proximal housing 12 and the cartridge holder 13 can be plugged or snapped together during assembly to close both open ends of the main housing 11. Further, the housing components may be glued or welded together to form a rigid and permanently attached housing unit. The cartridge holder 13 has a distal aperture in its upper region in FIG. 2, which may have an outer thread or the like for attachment of a needle arrangement. The proximal housing 12 has a proximal aperture in its lower region in FIG. 2. Further, the proximal housing 12 has on its inside near the proximal aperture a ring of teeth 15 (shown in more detail in the embodiment of FIG. 9) which forms part of a clutch with the driver 40. The cartridge holder 13 has on its lower side a splined pin 16 for guiding the clicker 100 and spring 110. The housing 10 provides location for the liquid medication cartridge 20, which is held in the upper part (as seen in FIG. 1) of the main housing 11 and the cartridge holder 13.

(21) The main housing has an inner wall with a threaded section 17 engaging piston rod 30. Further, there is a clicker arm 18 near the proximal end of main housing 11, which arm interacts with the driver 40 during dose dispensing.

(22) The cartridge 20 is a glass ampoule with a movable rubber bung 21 located in its proximal aperture.

(23) The lead screw 30 is an elongate member with an outer thread 31 which is rotationally constrained to the driver 40 via a splined interface. The interface comprises at least one longitudinal groove or track 32 and a corresponding protrusion or spline 44 of the driver 40. When rotated, the lead screw 30 is forced to move axially relative to the driver 40, through its threaded interface 17 with the housing 10. The distal end of the piston rod 30 is provided with a bearing 33, which may abut the cartridge bung 21.

(24) The driver 40 comprises a drive sleeve, which has for manufacturing reasons a drive sleeve lower part 41 and a drive sleeve upper part 42, and a drive tube 43. The drive sleeve lower part 41 and the drive sleeve upper part 42 are rigidly connected to form a unit when in use.

(25) The drive tube 43 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.

(26) On the inside of the drive tube 43, splines 44 are provided engaging corresponding grooves 32 of the piston rod 30. The drive tube 43 surrounds the piston rod 30 which is axially displaceable relative to the drive tube 43. As shown in FIGS. 1 to 4, the drive sleeve upper part 42 and the drive tube 43 each have at their proximal end a pinion 45, 46, which mesh such that rotation of the drive sleeve 41, 42, is transmitted to the drive tube 43. The drive sleeve 41, 42, is axially movable along the second axis II between a proximal position (during dose setting and correcting, see FIG. 3) in which pinion 45 further engages teeth 15 of the housing 10, and a distal (dose dispensing position, see FIG. 4) in which the pinion 45 is disengaged from the teeth 15. However, in both axial positions pinions 45, 46 remain in at least partial engagement.

(27) The drive sleeve 41, 42, has on its outer surface splines 47a, 47b for rotationally constraining the drive sleeve to the power reservoir 90. Further, splines 48 are provided on the inner surface of the drive sleeve 41, 42, for rotationally constraining the drive sleeve 41, 42, to nut 50.

(28) The nut 50 is part of a last dose limiter mechanism. The last dose nut 50 is located between the dial sleeve 60 and the drive sleeve 41, 42. It moves along a helical path relative to the dial sleeve 60, via a threaded interface 61, when relative rotation occurs between the dial sleeve 60 and drive sleeve during dialling, i.e. during dose setting or dose correcting. In the embodiments of FIGS. 1 to 11, the nut 50 is a half nut, i.e. a component extending approximately 180 around the second axis II of the device.

(29) The dial sleeve 60 is a tubular element arranged rotatably on the second axis II. A proximal section of the dial sleeve 60 is provided with a thread 61 guiding the nut 50. An adjacent distal section is provided with outer splines 62 for engagement with the number sleeve 80. Further, the dial sleeve 60 has a ring of inner teeth 63 at an intermediate stepped portion for releasably rotationally coupling the dial sleeve 60 to the dial assembly 70. Outer splines 64 are provided at the proximal end for engaging corresponding inner splines of the driver 40 during dose dispensing.

(30) The dial assembly 70 comprises dial grip 71 and a tubular element 72 which is rigidly attached to the dial grip 71. The dial grip 71 and the tubular element 72 are in the present embodiment separate components for manufacturing reasons but may as well be a single component. The dial assembly 70 is arranged on the second axis II and extends through the proximal aperture in the proximal housing part 12. At its distal end, the dial assembly is provided with a ring of detent teeth 73 on its distal face for interaction with clicker 100. Further, splines 74 are provided near the distal end of tubular element 72 engaging splines 63 in the dose setting position. The dial assembly 70 is axially movable along the second axis II between a proximal position (during dose setting and correcting, see FIG. 3) and a distal (dose dispensing position, see FIG. 4). The dial grip 71 abuts the drive sleeve 41, 42, such that axial movement of the dial grip 71 in the distal direction entrains the drive sleeve 41, 42, and axial movement of the drive sleeve 41, 42, in the proximal direction entrains the dial grip 71.

(31) The number sleeve 80 is a tubular element arranged on the second axis II. The outer surface of the number sleeve 80 is provided with a sequence of numbers arranged on a helical path. Further, the number sleeve has on its outer surface a thread 81 engaging a corresponding thread of the main housing 11. At its distal end, the number sleeve 80 is provided with an inwardly directed protrusion 82 for interaction with the clicker 100. Further, there are rotational hard stops on the number sleeve 80 and corresponding elements on the main housing 11 limiting the rotational movement of the number sleeve relative to the housing on its helical path defined by the threaded interface.

(32) The power reservoir comprises a reverse wound flat spiral spring 90, 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 90 is attached to a first spool 91, which is located on the first longitudinal axis I surrounding drive tube 43. A second end of the spring 90 is attached to a second spool 92, which is located on the second longitudinal axis II and is rotationally constrained to the drive sleeve 41, 42, by splines 47a, 47b and corresponding grooves 93 inside the second spool 92. Spring 90 is fully charged (tensioned) during assembly of the device by winding the spring on spool 92, whereas the spring tends to wind back on spool 91. The power reservoir is dimensioned such that spring 90 is able to drive the piston rod 30 from its retracted position shown in FIGS. 2 to 4 to a position, where the cartridge bung is pushed in its most distal direction. In other words, recharging of the spring 90 is not necessary for emptying cartridge 20.

(33) The clicker 100 is a tubular element positioned axially displaceable but rotationally constrained on splined pin 16 of the cartridge holder 13. As can be seen in FIGS. 8a to 8c, the clicker 100 has grooves 101 on its inner surface for engagement with the splined pin 16. Further, there are detent teeth 102 on the proximal end of clicker 100 mating with teeth 73 of the dial assembly 70. A finger 103, which interacts with protrusion 82 of the number sleeve, is provided near the detent teeth 102.

(34) Spring 110 is a compression spring located on splined pin 16 and inside clicker 100 urging clicker 100 in the proximal direction. Due to the contact between the clicker 100 and the dial assembly 70 and due to the contact between the dial assembly 70 and the drive sleeve 41, 42, the spring 110 pushes these components in the proximal direction as shown in FIG. 3, whereas a user may overcome the spring 110 force and push these components in the distal position shown in FIG. 4.

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

(36) Rotation of the dial grip 71 causes the number sleeve 80 to travel between the 0U and 120U stops in the housing 10. There is an axial detent toothed interface between the clicker 100 and tubular element of the dial assembly 70 (which are forced together by the spring 110) which generates the detented dose positions and user feedback. The drive sleeve 41, 42 is rotationally restrained during dialling via a splined interface to the housing 10.

(37) The key interfaces during dialling are: the dial sleeve 60 is splined to the dial grip 71, the number sleeve 80 is splined to the dial sleeve 60, the number sleeve 80 is threaded to the housing 10, the clicker 100 is splined to the cartridge holder 13 10, the drive sleeve 41, 42 is splined to the splined pin 16, the nut 50 is threaded to the dial sleeve 60, and the nut 50 is splined to the drive sleeve 41, 42.

(38) The zero and maximum dose stops are generated by abutments between the number sleeve 80 and housing 10. User input torque, applied to the dial grip 71, is reacted via the dial sleeve 60 and number sleeve 80 back to the housing 10 when the abutments are engaged.

(39) The nut 50 advances towards a rotational abutment at the proximal end of the dial sleeve 60 whilst there is relative rotation between the dial sleeve 60 and drive sleeve 41, 42. When the abutment is reached, dial torque is reacted through the dial grip 71, dial sleeve 60, nut 50 and drive sleeve 41, 42 back to the splined interface with the housing 10.

(40) To dispense a dose, the dial grip 71 is pressed by the user. It then disengages from the dial sleeve 60, and is rotationally constrained by the clicker 100 detent teeth engagement (between the tubular element 72 of the dial assembly 70 and the clicker 100). Axial force applied by the user is reacted by the spring 110, and by a direct abutment between the dial grip 71 and the housing 10. As the dial grip 71 is rotationally decoupled from the mechanism during dispensing, the user is unable to input abuse torques to the dispensing mechanism or adjust the dose.

(41) The drive sleeve 41, 42 is moved axially so that it first engages spline features 64 with the dial sleeve 60 then disengages from its splined interface 45, 15, with the housing 10. The spring 90 then causes the drive sleeve 41, 42 to rotate. Via the geared interface between the drive sleeve 41, 42 and the drive tube 43, the drive tube 43 is rotated which then drives the piston rod 30 through the housing 10 into the bung 21. The drive sleeve 41, 42 causes the number sleeve 80 to rotate back towards the 0U position, via the dial sleeve 60.

(42) The key interfaces during dispensing are: the drive sleeve 41, 42 is axially constrained to the dial grip 71 and displaced towards distal end of the device, the dial grip 71 disengages from the dial sleeve 60, the drive sleeve 41, 42 engages with splines on the dial sleeve 60, and the drive sleeve 41, 42 disengages from the housing 10.

(43) Dispensing of a dose continues until the number sleeve 80 reaches its 0U abutment with the housing 10, or the user releases the dial grip 71. When the 0U abutment engages, torque from the spring 90 is reacted via the dial sleeve 60 and number sleeve 80 into the housing 10. If the user releases the dial grip, the action of the spring 110 acts to re-engage the splined interface 15, 45, between the drive sleeve 41, 42 and housing 10.

(44) Feedback during dose setting is provided by an interaction between the tubular element of the dial assembly 70 and the clicker 100. The clicker 100 is splined to the cartridge holder 13 splined pin 16, and the spring 110 forces the clicker 100 into axial engagement with the tubular element of the dial assembly 70. Detent teeth 73, 102 provide an axial detent toothed interface between the components and the clicker 100 shuttles axially as the dial grip 71 is rotated, providing detented positions for the dial grip. This is shown in more detail in FIG. 5, where splines 74 of tubular element 72 are shown disengaged from the inner ring of splines 63 of the dial sleeve 60, i.e. the device is in its dose dispensing position. Further, teeth 73 and teeth 102 are shown.

(45) During dose dispense, tactile and audible feedback is created by the interaction of the drive tube 43 and the housing 10. As shown in FIG. 6, there is a compliant clicker arm 18 integrated into the main housing 11 which is displaced by rotation of the gear teeth 46 on the drive tube 43. The clicker arm 18 contacts the surface of the proximal housing 12 as the gear teeth 46 pass over the clicker arm 18, generating feedback for each dose unit dispensed.

(46) At the completion of the delivery of a dose, as the number sleeve 80 returns to its 0U position, additional audible feedback is created by the interaction of the number sleeve 80 and the clicker 100. As shown in FIGS. 8a to 8c, this interaction is dependent on the axial position of the clicker 100, and only occurs during dispense, when the clicker 100 is in its distal position, when the dial grip 71 is depressed by the user. By utilising the axial position of the dial grip to create this interaction, the end of dose feature does not need to be overhauled by the user during dialling of a dose (see FIG. 8c).

(47) In this embodiment, a radial finger 103 extends from the clicker 100, and a protrusion in the form of a ramped boss 82 is added to the inner surface of the number sleeve 80, such that the boss on the number sleeve 80 deflects the radial finger 103 as the number sleeve 80 rotates back from the 1U position (shown in FIG. 8a) to the 0U position (shown in FIG. 8b). As the number sleeve 80 returns to the 0U position, the radial finger 103 is released and springs back to its at rest state creating audible feedback to the user. As the clicker 100 is in direct contact with the dial assembly, tactile feedback will also be provided, as the dial grip will be being held in its depressed state by the user.

(48) It is possible to incorporate a mechanism that allows the user to control the speed of dispense by the degree of travel that they input to the dial grip 71. The second embodiment shows in FIGS. 9 to 10b a multi-plate clutch system 120 integrated into the device acting between the housing 10 and the drive sleeve 41, 42. This system comprises first clutch plates 121, which are splined to the upper drive sleeve 42, and second clutch plates 122 which are splined to a cage 123. The cage 123 has outer splines 124 engaging with corresponding grooves in the proximal housing 12 to rotationally constrain cage 123. A clutch spring 125 is interposed between the proximal housing 12 and the clutch plates 121, 122 within the cage 123.

(49) Multiple clutch plates increase the torque capacity of the clutch for a given clutch spring force. For the embodiment shown in FIG. 9, force applied to the clutch pack 121, 122 from the clutch spring 125 (FIG. 10a) reduces as the dial grip 71 is depressed, because the upper drive sleeve 42 is pushed by the dial grip 71 together with the cage 123 in the distal direction and away from the proximal housing 12 (FIG. 10b).

(50) In this embodiment, the overall dial grip 71 travel is increased to e.g. 5 mm, 2.5 mm for mechanism disengagement to commence dispense and 2.5 mm for user variable speed control. As the force applied by the clutch spring 125 reduces as the dial grip 71 is depressed, the frictional torque applied to the drive sleeve 41, 42 by the clutch pack 121, 122 also reduces, and the value of the frictional torque is dependent on the axial position of the dial grip 71. The torque available from the spring 90 must overcome the frictional torque of the clutch pack, which reduces the torque applied to the mechanism to dispense a dose. The speed of dispense therefore increases as the user continues to depress the dial grip 71 between the disengagement position and the full travel position. The force required to depress the dial grip 71 increases with its travel due to the combined actions of the spring 110 and clutch spring 125, with spring 110 increasing the resistance despite the weaker spring 125 reducing the resistance.

(51) The facility for removing the need for a user to prime the device when first used is also provided. This involves removing the variable distance (dependant on component and cartridge tolerances) between the cartridge bung 21 and the bearing 33 during manufacture such that the bearing 33 is in contact with, or applying a light load to, the bung 21 when assembled.

(52) This prime elimination is achieved using the following method: Rotation of the drive tube 43, independently from the drive sleeve 41, 42, advances the piston rod 30 for prime elimination. Therefore, prior to the proximal housing 12 being fitted, the drive tube 43 is displaced towards the proximal end of the device, so that it no longer engages with the drive sleeve 41, 42 gear teeth 45 (see FIG. 11). The drive tube 43 is then rotated to advance the piston rod 30 and hence its bearing 33 towards the cartridge bung 21. Contact with the bung 21 can either be sensed using measurement of the torque required to rotate the drive tube or by measurement of the axial position of the piston rod 30 relative to the thread 17 in the housing 10. The point at which the piston rod 30 moves to the opposite sides of its threaded engagement with the housing 10 indicates contact with the bung 21.

(53) A third, alternative embodiment is shown in FIGS. 12 to 14. Where appropriate, similar components are given the same reference numerals as in the first embodiment. The design and function of this device is in general very similar to that of the first embodiment. Further, this device is suitable for the speed control of the second embodiment and allows prime elimination as described above.

(54) The main changes with respect to the first embodiment relate to the drive sleeve 41, 42, the dial sleeve 60 and to the nut 50 of the last dose mechanism. Again, the drive sleeve comprises for manufacturing reasons two component parts 41, 42 which are snapped together to behave as a single component. However, the drive sleeve 41, 42 has a prolonged distal part 41 with a threaded section 49. On the other hand, dial sleeve 60 is shorter without the threaded section 61 of the first embodiment. The nut 50, which is a full nut in this embodiment, runs with its inner thread on this threaded section 49. Further, the nut 50 has a splined outer surface which is axially displaceably guided in grooves on the inner surface of dial sleeve 60.

(55) Again, as a user sets a dose, the dial sleeve 60 rotates together with the dial assembly 70, whereas the drive sleeve 41, 42 is coupled to the housing 10 via teeth 15, 45. Thus, nut 50 travels on the threaded section 49. During dose dispensing, the drive sleeve 41, 42, is decoupled from the housing and rotates together with the dial sleeve 60, such that the nut 50 maintains its relative position on the drive sleeve.