Piston rod for a drug delivery device and drug delivery device comprising a piston rod

Abstract

A piston rod for a drug delivery device comprises a main body and an engagement means for engaging the piston rod with a part of the drug delivery device. The engagement means are retractable relatively the main body for enabling a disengagement of the engagement means from the part of the drug delivery device.

Claims

1. A piston rod for a drug delivery device, the piston rod comprising: a main body comprising a longitudinal axis and engagement means for engaging the piston rod with a part of the drug delivery device, wherein the engagement means are radially retractable relative to the longitudinal axis of the main body for enabling a disengagement of the engagement means from the part of the drug delivery device, wherein the main body comprises a plurality of openings in an outer surface of the main body, and wherein the engagement means comprise a plurality of threaded forms which are retractable through the plurality of openings.

2. The piston rod of claim 1, comprising a switching member configured such that an operation of the switching member causes at least one of an extension or retraction of the engagement means relative to the main body.

3. The piston rod of claim 2, configured such that an operation of the switching member comprises a rotational movement of the switching member.

4. The piston rod of claim 2, configured such that an operation of the switching member comprises a translational movement of the switching member.

5. The piston rod of claim 2, wherein the switching member is at least partially located inside the main body of the piston rod.

6. The piston rod of claim 2, wherein the switching member comprises at least one protrusion and wherein the piston rod is configured such that the engagement means is at least one of extended and retracted by an interaction of the engagement means with the protrusion.

7. The piston rod of claim 2, wherein the switching member comprises a cam shaft.

8. A drug delivery device comprising a piston rod of claim 1.

9. The drug delivery device of claim 8, comprising a main housing and a cartridge holder attachable to and detachable from the main housing.

10. The drug delivery device of claim 9, configured such that the piston rod is resettable to a start position when the cartridge holder is detached from the main housing.

11. The drug delivery device of claim 8, comprising a dose member for setting and/or dispensing a dose of a medication, wherein an operation of the dose member causes at least one of a retraction or extension of the engagement means.

12. The drug delivery device of claim 9, configured such that a detachment of the cartridge hold causes a retraction of the engagement means.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Further features, refinements and expediencies become apparent from the following description of the exemplary embodiments in connection with the figures.

(2) FIG. 1 schematically shows a side view of a drug delivery device.

(3) FIG. 2 schematically shows a sectional side view of a part of the drug delivery device of FIG. 1.

(4) FIG. 3A shows a perspective view of a first embodiment of a piston rod in an operational state.

(5) FIG. 3B shows a perspective sectional view of the piston rod of FIG. 3A.

(6) FIG. 3C shows an enlarged view of a part of the piston rod of FIG. 3B.

(7) FIG. 3D shows a perspective cross-sectional view of the piston rod of FIG. 3C.

(8) FIG. 4A shows a perspective sectional view of the first embodiment of the piston rod in a reset state.

(9) FIG. 4B shows a perspective cross-sectional view of the piston rod of FIG. 4A.

(10) FIG. 5 shows a side view of a switching member.

(11) FIG. 6 shows a schematic perspective cut-away view of a working principle of a second embodiment of a piston rod.

DETAILED DESCRIPTION

(12) Like elements, elements of the same kind and identically acting elements may be provided with the same reference numerals in the figures.

(13) FIG. 1 shows a perspective side view of a drug delivery device 1. The device 1 extends along a longitudinal axis 5. The device 1 comprises a main housing 2 and a cartridge holder 3 attached to the main housing. The cartridge holder 3 houses a cartridge comprising a medicament. Preferably, the medicament is a liquid medicament, for example insulin. Preferably, the drug delivery device 1 is a reusable device such that the cartridge can be exchanged. For this aim, the cartridge holder 3 may be detached from the main housing 2, an empty cartridge may be replaced by a full cartridge and the cartridge holder 3 may be re-attached to the main housing 2.

(14) The drug delivery device 1 comprises a dose member 8 for setting and dispensing a dose of a medication. In this context, the term setting a dose or dose setting operation may mean that the device 1 and, in particular, a drive mechanism of the device 1 is prepared for a subsequent dose dispense operation. In particular, the dose setting operation may be a step immediately preceding a dose dispense operation. As an example, the drug delivery device 1 may be a pull-push device such that the dose member 8 is pulled out of the housing 2 for setting a dose and is pushed towards the housing 2 for dispensing a dose. In a different embodiment, the device 1 may be a twist-push device such that for setting a dose, the dose member 8 is twisted and, thereby, may move helically outwards of the main housing 2. For dispensing the dose, the dose member 8 may be pushed towards the main housing 2.

(15) The drug delivery device 1 comprises a distal end 6 and a proximal end 7. The term distal end of the drug delivery device 1 or a component thereof may refer to that end of the device or the component which is closest to the dispensing end of the device 1. The term proximal end of the drug delivery device 1 or a component thereof may refer to that end of the device or the component which is furthest away from the dispensing end of the device. The arrows 27 and 28 are used to indicate the distal resp. the proximal direction, i.e. the direction towards the distal end 6 resp. towards the proximal end 7.

(16) The device 1 may be an injection device. A needle may be attached to the dispensing end of the device 1, i.e., at the distal end 6 of the device. In particular, the device 1 may be a pen-type injection device.

(17) The device 1 may be a fixed dose device, i.e., the device may be configured such that the size of each dose is predetermined by the configuration of the device. In particular, a user is not enabled to vary the size of a dose. Alternatively, the device 1 may be a variable dose device, i.e., the device is configured such that the user is enabled vary the size of a dose.

(18) FIG. 2 shows a sectional side view of a part of the drug delivery device of FIG. 1.

(19) The drug delivery device 1 comprises a piston rod 9. The piston rod 9 is configured for transferring a force to a piston 10, thereby displacing the piston 10 in the distal direction 27 with respect to a cartridge 4. The piston 10 is retained within the cartridge 4. The piston 10 may seal the medication within the cartridge 4. The piston 10 expediently seals the interior of the cartridge 4 proximally. Movement of the piston 10 with respect to the cartridge 4 in the distal direction 27 causes medication to be dispensed from the cartridge 4 through its outlet during operation of the device 1.

(20) The piston rod 9 comprises engagement means 12 for engaging the piston rod 9 with a part 11 of the device 1. In the shown embodiment, the part 11 of the device 1 is a nut member 13. The nut member 13 is fixed to the housing 2 such that relative movements between the nut member 13 and the housing 2 are prevented. Preferably, the nut member 13 is permanently fixed to the housing 2, in particular during dose set operations, dose dispense operations and during resetting operations of the device 1.

(21) The nut member 13 guides the piston rod 9 in a dose dispense operation of the device 1. The engagement means 12 of the piston rod 9 comprise thread forms 16 protruding from a main body 14 of the piston rod 9. The thread forms 16 are configured to engage with thread forms 29 of the nut member 13. In a dose dispense operation, the piston rod 9 moves in the distal direction 27 and, thereby, winds through the nut member 13.

(22) The movement of the piston rod 9 is caused by an operation of the dose member 8. In particular, the device 1 comprises a drive member 15 which transfers a force from the dose member 8 to the piston rod 9 and, thereby causes a movement of the piston rod 9. As an example, the drive member 15 may be coupled to the piston rod 9 such that a relative translational movement between the drive member 15 and the piston rod 9 is allowed and a relative rotational movement is prevented. Thereby, in a dose dispense operation, the drive member 15 may cause the piston rod 9 to rotate. Due to the threaded engagement of the piston rod 9 with the nut member 13, the piston rod 9 moves in the distal direction 27.

(23) In FIG. 2, the piston rod 9 is in a start position, i.e., in its most proximal position relative to the main housing 2. Accordingly, no medicament has been dispensed from the cartridge 4 yet. In a dose dispense operation of the device 1 the piston rod 9 is displaced from its start position in the distal direction 27. I particular, the piston rod 9 incrementally winds itself out of the housing 2 in a distal direction 27 each time a dose of medicament is dispensed.

(24) When the cartridge 4 is exchanged, the piston rod 9 may have to be moved back to its start position. Such a movement in the proximal direction 28 may be hampered by the engagement of the nut member 13 with the piston rod 9. In particular, when the piston rod 9 is engaged with the nut member 13, a movement of the piston rod 9 in a proximal direction 28 may not be possible at all or may require a large force. In order to facilitate a resetting of the piston rod 9 to a start position, the engagement means 12 may be configured to be retractable and, thereby, allow a disengagement from the nut member 13 during a reset operation.

(25) FIG. 3A to 4B show a first embodiment of a piston rod 9 comprising retractable engagement means 12. The piston rod 9 may be used in a device 1 as shown in FIGS. 1 and 2 or in a different drug delivery device.

(26) FIGS. 3A to 3D show the piston rod 9 in a state, wherein an engagement of engagement means 12 of the piston rod 9 with a part of a drug delivery device is enabled. This state may be denoted as operational state of the piston rod 9. In particular, the piston rod 9 may be in its operational state during a dose set and dose dispense operation of the device.

(27) FIGS. 4A to 4B show the piston rod 9 in a state, wherein the engagement means 12 are retracted such that a disengament from the part of the drug delivery device is enabled. This stated may be denoted as reset state of the piston rod 9. In particular, due to the retraction of the engagement means 12, a resetting of the piston rod 9 towards its start position may be facilitated.

(28) Now, turning to the operational state, FIG. 3A shows a perspective view of the piston rod 9. The piston rod 9 extends along a longitudinal axis 5, which may coincide with a longitudinal axis of a respective drug delivery device.

(29) The engagement means 12 of the piston rod 9 comprise a plurality of thread forms 16. The thread forms 16 are configured for a threaded engagement with a part of a drug delivery device 1, for example a nut member 13 as shown in FIG. 2. The piston rod 9 is configured as a lead screw, wherein the screw thread formed by the thread forms 16 is interrupted in an axial direction.

(30) The piston rod 9 comprises a main body 14. The main body 14 is shaped as a hollow rod comprising several openings 17 through which the thread forms 16 protrude.

(31) The piston rod 9 comprises a switching member 18 configured to switch the piston rod 9 from an operational state as shown in FIGS. 3A to 3D to a reset state as shown in FIGS. 4A and 4B and vice versa. Preferably, the switching member 18 is also configured to hold the piston rod 9 in one of the states.

(32) FIGS. 3B, 3C and 3D show sectional views of the piston rod 9 of FIG. 3A. In particular, FIG. 3B shows a perspective sectional view of the piston rod 9, wherein the section runs along the longitudinal axis 5 of the piston rod 9. FIG. 3C shows an enlarged view of a distal portion of the piston rod 9 of FIG. 3B. FIG. 3D shows a perspective cross-sectional view of the piston rod, wherein the cross-section runs along the line denoted by A-A in FIG. 3C.

(33) As can be seen in FIGS. 3B, 3C and 3D, the switching member 18 is configured as an internal shaft running inside the main body 14 and extending along the longitudinal axis 5 of the piston rod 9. The switching member 18 comprises a distal end portion 30 and a proximal end portion 31, wherein both end portions 30, 31 are at least partially embedded in the main body 14 such that the switching member 18 is fixed in radial directions relative to the longitudinal axis 5. Preferably, at least one of the end portions 30, 31 comprises means for maintaining the switching member 18 and, thereby, the piston rod 9 in its current state. As an example, the end portions 30, 31 may comprise notches engaging with the main body 14 such that a certain force is required for overcoming the engagement and rotating the switching member 18.

(34) The switching member 18 comprises a plurality of protrusions 21, 22, wherein the protrusions 21, 22 extend alternatingly in one radial direction of the switching member 18 and in an opposite radial direction of the switching member 18. The radial protrusions 21, 22 may function as cam lobes. Accordingly, the switching member 18 may function as a camshaft.

(35) In particular, the radial protrusions 21, 22 are configured to push the engagement means 12 out of the main body 14 when the switching member 18 is in the orientation shown in FIGS. 3B, 3C and 3D. In particular, here, each radial protrusion 21, 22, is located directly beneath an opening 17 of the main body 14. This orientation of the switching member 18 may be denoted a 12 o'clock orientation. When the switching member 18 is rotated around the longitudinal axis 5 by an angle of 180, the radial protrusions 21, 22 pull the engagement means 12 towards the main body 14 and, thereby, cause a refraction of the engagement means 12. This orientation of the switching member is shown in FIGS. 4A and 4B and may be denoted as 6 o'clock orientation.

(36) In the following, the working principle of the switching member 18 is described in more detail.

(37) Each thread form 16 of the engagement means 12 is located on a ring-shaped member 24, which is movable back and forth in a radial direction 25 relative to the main body 14. When the switching member 18 is rotated around the longitudinal axis 5 in a rotational direction 26 by an angle of 180, the protrusions 21, 22 urge the ring-shaped members 24 and, thereby, the engagement means 12 in the radial direction 25, such that the engagement means 12 are retracted towards the main body 14.

(38) FIG. 4A shows a perspective sectional view of the first embodiment of the piston rod 9 in its reset state. FIG. 4B shows a perspective cross-sectional view of the piston rod of FIG. 4A.

(39) The switching member 18 has been rotated to its 6 oclock position, such that the thread forms 16 are retracted towards the main body 14. The engagement means 12 may be fully retracted into the main body 14 such that they do not protrude to the outside, may be flush with an outer surface of the main body 14 or may be only partially retracted towards the main body 14 such that they protrude from the main body 14 to a minor extent. In all cases, the engagement means 12 are retracted such that a disengagement from a part of the drug delivery device 1, for example the nut member 13 as shown in FIG. 2 is enabled. In this state of the piston rod 9, a reset movement of the piston rod 9 is facilitated.

(40) In the following, a possible reset operation of a drug delivery device comprising the switching member as shown in FIGS. 3A to FIG. 4B is described in detail.

(41) When a cartridge holder 3 of a drug delivery device 1, for example as shown in FIG. 1, is detached from a main housing 2 to exchange a cartridge, the switching member 18 may be operated such that the engagement means 12 are retracted towards the main body 14 of the piston rod 9, thereby switching the piston rod 9 from an operational state into a reset state.

(42) An operation of the switching member 18 may be accomplished in different ways according to the specific design of the piston rod 9 or a respective drug delivery device 1. As an example, the switching member 18 may be coupled to a dose member 8 such that a rotation of the dose member 8 causes a rotation of the switching member 18. In particular, the proximal end of the switching member 18 which extends in axial direction from the main housing 14 as shown in FIG. 3A, for example, may be coupled to the dose member 8. In a further embodiment, the switching member 18 may be coupled to a cartridge holder 3 of the device 1 such that a detachment operation of the cartridge holder 3 causes a rotation of the switching member 18. In particular, the piston rod 9 may be switched to its reset state automatically when the cartridge holder 4 is detached.

(43) When switched to its reset state, the piston rod 9 may be moved back towards a proximal start position. As the piston rod 9 is disengaged from a part of the drug delivery device, the movement is unhindered by the part of the drug delivery device. Depending on the design of the device, the piston rod may be pushed back in the proximal direction or may be wound back in the proximal direction.

(44) When the piston rod 9 is in a proximal start position, it may be switched from its reset state to its operational state such that the engagement means 12 reengage with the part of the drug delivery device. Also here, the switching operation may be caused by a rotation of the dose member 8 or automatically by an attachment operation of the cartridge holder 4, as example.

(45) FIG. 5 shows a side view of a switching member 18, which may be used in a second embodiment of a piston rod 9.

(46) According to the second embodiment, engagement means 12 of the piston rod 9 are extended and retracted by a sliding movement of the switching member 18. Accordingly, the switching member 18 may function as a sliding camshaft. The sliding cam operation may be similar to a key in a lock barrel as shown in FIG. 6. The key 34 corresponds to the switching member 18 of the piston rod 9. Lock members 35 correspond to protrusions 21, 22 of the switching member 18.

(47) The switching member 18 comprises a number of protrusions 21, 22 extending in opposite radial directions. The respective piston rod 9 is configured such that when the switching member 18 is moved axially by half the length of the pitch 32 of the protrusions 21, 22 in an axial direction 33, the engagement means 12 of the piston rod 9 extend out of the main body 14 of the piston rod 9. When the switching member 18 is moved in the opposite direction, the engagement means 12 are urged back to the main body 14. The design of the engagement means 12 and the main body 14 of the piston rod 9 may be identical or similar to the design as shown in FIGS. 3A to 4B.