Drug delivery device with a dose counting mechanism

Abstract

The present invention provides a drug delivery device having a dose counting mechanism and a content termination indicator.

Description

Field of the Invention

[0001] The present invention generally relates to drug delivery devices, and more particularly to fixed-dose delivery devices having a remaining dose indicating device. Background Art

[0002] For self-administration of drugs by humans, it has become customary to use kits that include a drug-filled vial, a syringe with a needle, and an alcohol swab. In some disease areas and in some countries, such kits are increasingly being replaced by pen injection devices. Pen injection devices are particularly convenient because they allow the user to perform dose injections from a pre-filled drug reservoir without having to first manually transfer a specific dose from one reservoir (vial) to another reservoir (syringe).

[0003] There are mainly two types of pen injection devices available, one being a durable injection device that is capable of delivering one or more drug doses from a pre-filled drug cartridge that can be loaded into the device before use and replaced after depletion, and the other being a disposable injection device that is capable of delivering one or more drug doses from a pre-filled non-replaceable drug cartridge. Each of these types of pen injection devices is implemented in various subtypes or can in principle be implemented in various subtypes, such as a single-dose injection device adapted to deliver only one dose from a drug cartridge, a multi-dose injection device capable of delivering multiple doses from a drug cartridge, a manual device in which the user provides the force required for injection, an automatic device having a releasable built-in energy source to effect injection, a fixed-dose device adapted to deliver a predetermined drug dose, a variable-dose device that provides delivery of different drug doses that can be set by the user, and the like.

[0004] As the name implies, a durable injection device is intended to be used over a relatively long period during which multiple drug cartridges are exhausted and replaced, while a disposable injection device is intended to be used until its dedicated drug cartridge is exhausted, after which the entire injection device is discarded.

[0005] Multi-dose injection devices can be of the fixed-dose type or the variable-dose type, and the drug expulsion mechanism in these devices can be mechanical, i.e., where the movement of the piston rod is mechanically controlled, such as in a manual device or a spring-driven device, or can be electromechanical, i.e., where the movement of the piston rod is electronically controlled, such as in a motor-driven device.

[0006] Multi-dose injection devices ideally should be provided with a content termination indication to prevent potential dangerous situations in which the user performs a dose expulsion action but does not receive the full expected dose because the expected dose exceeds the dose remaining in the drug reservoir. Such content termination indications tend to increase the complexity and cost of the device construction.

[0007] WO 01 / 19434 (Novo Nordisk A / S) discloses examples of such a content termination indicating mechanism for use in different types of injection devices, where the content termination indication is obtained by a relative rotational movement between components of the respective device. However, these solutions are not attractive for all types of multi-dose injection devices. Summary of the Invention

[0008] The object of the present invention is to eliminate or reduce at least one drawback of the prior art or to provide a useful alternative to prior art solutions.

[0009] In particular, an object of the present invention is to provide a multi-dose drug delivery device having a simple and cost-effective content termination indicating device.

[0010] Another object of the present invention is to provide a simple and reliable counting mechanism for recording the number of doses dispensed by a fixed-dose type multi-dose delivery device and / or the number of doses still available for injection.

[0011] In the disclosure of the present invention, aspects and embodiments will be described which will solve one or more of the above objects and / or will solve objects that are apparent from the following text.

[0012] A drug delivery device embodying the principles of the present invention is configured to perform a predetermined number of dose dispensing actions and includes a housing that houses a dose dispensing mechanism, an activation device configured to undergo a predetermined movement relative to the housing during each dose dispensing action to permit the dispensing of a dose, the predetermined movement including a displacement from a first position to a second position and back to the first position, and a counting device operatively coupled to the activation device and configured to change state in response to the activation device undergoing the predetermined movement.

[0013] Thereby, a simple way of recording the number of doses dispensed by the drug delivery device is provided, since the counting device changes state if and only if the activation device is displaced in association with a dose dispensing action. If, for example, the counting device includes an electronic transducer, the transducer can be operatively coupled to an electronic display configured to visually represent a usage-related state of the drug delivery device, such as the cumulative number of dose dispensing actions performed.

[0014] In a mechanical form, the counting device can be configured, for example, to move relative to the housing in a forward counting direction in response to a displacement of the activation device from a first position to a second position, and to remain stationary in response to a displacement of the activation device from the second position to the first position. Such a movement pattern can be achieved by a combination of a first one-way ratchet mechanism acting between the activation device and the counting device and a second one-way ratchet mechanism acting between the counting device and the housing or a component fixed relative to the housing, wherein the first one-way ratchet mechanism prevents movement of the activation device relative to the counting device in the forward counting direction, and the second one-way ratchet mechanism prevents movement of the counting device relative to the housing in a direction opposite to the forward counting direction.

[0015] The drug delivery device may further comprise a contents termination indicating device, which is operatively coupled to the counting device and the activation device and is configured to become activated in response to the counting device having changed state a plurality of times corresponding to a predetermined number of dose expulsion actions.

[0016] Activation of the contents termination indicating device provides a signal to the user that a predetermined number of dose expulsion actions have been performed, indicating that the drug delivery device should be discarded. The signal can be electronic, such as an indication on an electronic display, or mechanical.

[0017] The contents termination indicating device may comprise a locking device, which is operatively coupled to the counting device and the activation device and is configured to prevent displacement of the activation device from the first position to the second position in response to the counting device having changed state a plurality of times corresponding to a predetermined number of dose expulsion actions.

[0018] Since displacement of the activation device from the first position to the second position is a prerequisite for initiating a dose expulsion action, once the counting device has changed state the said plurality of times and the locking device is effective, a dose expulsion action cannot be initiated. Thus ensuring that any attempt to perform a further dose expulsion action with the drug delivery device after a predetermined number of dose expulsion actions have been performed is unsuccessful.

[0019] The drug delivery device can be monitored, controlled or driven, for example, electronically, or it can be a purely mechanical device without any electronic components.

[0020] In one aspect of the present invention, there is provided a drug delivery device according to claim 1.

[0021] Therefore, a drug delivery device for performing a predetermined number of dose expulsion actions is provided. The drug delivery device may be, for example, a drug injection device, a drug infusion device, a drug inhalation device, etc., and includes a housing extending along an axis and accommodating a dose expulsion mechanism, and an activation device in the form of a reciprocating element, the reciprocating element being operatively coupled to the dose expulsion mechanism and configured to undergo a predetermined movement relative to the housing during each dose expulsion action to expel a dose. The predetermined movement includes a displacement from a first position to a second position in a first axial direction, and subsequently a displacement from the second position to the first position in a second axial direction opposite to the first axial direction. The drug delivery device further includes a counting device in the form of a counting element, the counting element being movable relative to the housing in the first axial direction, a first one-way ratchet mechanism that prevents movement of the reciprocating element relative to the counting element in the first axial direction while allowing movement in the second axial direction, and a second one-way ratchet mechanism that allows movement of the counting element relative to the housing in the first axial direction while preventing movement in the second axial direction.

[0022] Therefore, in each dose expulsion action, the counting element is driven in the first axial direction by the reciprocating element during the displacement of the reciprocating element from the first position to the second position, and is partially passed by the reciprocating element during the subsequent displacement of the reciprocating element from the second position back to the first position. Thus, when a dose expulsion action is performed, the counting element moves incrementally slowly in the first axial direction, that is, in each dose expulsion action, the counting element undergoes an incremental displacement relative to the housing, and the number of such incremental displacements corresponds to the number of dose expulsion actions.

[0023] Therefore, the position of the counting element relative to the housing indicates the number of dose expulsion actions currently performed by the drug delivery device, and thus the number of available dose expulsion actions can be derived as the predetermined number of dose expulsion actions minus the number of dose expulsion actions currently performed. In the case where the drug delivery device further includes an electronic device for monitoring one or more activities on or by the drug delivery device, such an electronic device may include means for recording dose expulsion actions and counting the number of dose expulsion actions currently performed and the number of potentially available dose expulsion actions. The electronic device may further include a display for presenting at least some of this information. In the case where the drug delivery device is a purely mechanical device, the housing may include a window allowing visual inspection of the position of the counting element. A scale may additionally be arranged to provide a reading of, for example, the number of incremental displacements of the counting element.

[0024] The drug delivery device may further comprise a base member axially and rotationally fixed relative to the housing. The first one-way ratchet mechanism may comprise first axial teeth on one of the reciprocating element and the counting element and a pawl member on the other of the reciprocating element and the counting element, and the second one-way ratchet mechanism may comprise second axial teeth on one of the counting element and the base member and a pawl member on the other of the counting element and the base member.

[0025] The counting element may be configured to undergo movement in the first axial direction relative to the housing in multiple steps corresponding to a predetermined number of dose ejection actions from a pre-use position taken prior to a first dose ejection action to a contents termination position. Upon reaching the contents termination position, the counting element may engage axially with the base member and be blocked from further movement in the first axial direction relative to the housing. This will mechanically prevent further movement of the reciprocating element from the first position to the second position, thereby preventing initiation of further dose ejection actions and signaling to the user that a new drug delivery device is required.

[0026] The drug delivery device may further comprise a drug reservoir holder disposed in an axially extending portion of the housing, and the dose ejection mechanism may comprise an activation structure operable from a distal portion of the drug reservoir holder to displace the reciprocating element in the first axial direction against a biasing force. It will thus be possible to activate the dose ejection mechanism from the distal end of the drug delivery device.

[0027] The drug reservoir holder may comprise receiving means for receiving a needle module at a distal portion and provide an operative coupling of an axially movable part of the needle module with the activation structure. The needle module may comprise a needle base accommodating a needle interface which carries a front needle insertable into the skin and has means for establishing a fluid connection with one or more drug reservoirs. The needle base may be adapted to be attached to the drug reservoir holder in its axial extension, and the axially movable part of the needle module may comprise a needle guard axially movable relative to the needle base between a first guard position in which the front needle is covered and a second guard position in which the front needle is exposed to the environment.

[0028] The needle guard may be configured to displace the reciprocating element in the first axial direction in response to the exposure of the front needle insertable into the skin (i.e., when moving from the first guard position to the second guard position). This provides a needle guard-triggered dose ejection mechanism and thus a simple mode of use in which the user only needs to place the needle guard against the skin and press the drug delivery device towards the skin to perform a dose ejection action.

[0029] The drug delivery device may further include a dose preparation structure configured to prepare a dose to be delivered from the drug delivery device in response to distal movement of a loading member relative to the housing, and a protective cap for the drug reservoir holder, the protective cap being operatively coupled to the dose preparation structure when covering the drug reservoir holder and configured to cause the loading member to move distally relative to the housing in response to removal from the cartridge holder. Thus, the drug delivery device incorporates an automatic dose preparation action, whereby simply removing the protective cap from the drug reservoir holder prepares the drug delivery device to dispense a drug dose. The user can perform the dose dispensing action without further preparation steps.

[0030] The dose dispensing mechanism may be powered by a torsion spring member, and the dose preparation structure may include a spring tensioning mechanism for tensioning the torsion spring member. Thus, the dose preparation structure may be configured to convert the distal movement of the loading member relative to the housing into rotation of the spring tensioning member relative to the housing. The spring tensioning mechanism may include a retaining structure for holding the torsion spring member in a tensioned state in which the torsion spring member stores sufficient energy to cause a dose to be dispensed from the drug delivery device when the dose dispensing mechanism is activated.

[0031] The counting element may be configured to engage in a rotationally interlocking engagement with the spring tensioning member in response to reaching the end-of-content position. Thus, distal movement of the loading member relative to the housing will be blocked because rotation of the spring tensioning member relative to the housing is blocked. Thus, depending on the specific engagement interface between the protective cap and the loading member, the protective cap will stick to the drug reservoir holder or be more difficult to remove therefrom, providing the user with a clear signal that no doses are available in the drug delivery device.

[0032] As used herein, the terms "distal" and "proximal" denote positions at or along the drug delivery device, where "distal" refers to the drug outlet end and "proximal" refers to the end opposite the drug outlet end.

[0033] In this specification, reference to an aspect or an embodiment (e.g., "an aspect", "a first aspect", "an embodiment", "an exemplary embodiment", etc.) means that a particular feature, structure, or characteristic described with respect to the corresponding aspect or embodiment is included in at least one aspect or embodiment of the invention, or is inherent to that at least one aspect or embodiment, but is not necessarily included in all aspects or embodiments of the invention / is inherent to all aspects or embodiments of the invention. However, it is emphasized that any combination of the various features, structures, and / or characteristics described with respect to the invention is covered by the invention, unless explicitly described herein or clearly contradicted by the context.

[0034] Unless otherwise stated, the use of any and all examples or exemplary language (e.g., "such as") in this document is intended solely to illustrate the invention and not to limit the scope of the invention. Additionally, no language or wording in this specification should be construed as indicating that any non-claimed element is essential for the practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Hereinafter, the invention will be further described with reference to the drawings, in which

[0036] Figure 1 the working principle of a dose counting mechanism according to an exemplary embodiment of the invention is shown,

[0037] Figure 2 a longitudinal cross-sectional view of an exemplary drug delivery device employing a dose counting mechanism in two different states is shown,

[0038] Figure 3 two different longitudinal cross-sectional views of the proximal portion of a drug delivery device in an initial pre-use state are shown,

[0039] Figure 4 a cross-sectional view similar to that Figure 3 when initiating the delivery of the first dose from the drug delivery device is shown,

[0040] Figure 5 a cross-sectional view similar to that Figure 3 when delivering the first dose and removing the drug delivery device from the skin is shown,

[0041] Figure 6 a cross-sectional view similar to that Figure 3 when delivering the last dose provided by the drug delivery device is shown,

[0042] Figure 7 is a perspective top view of the position where the contents of the components of the dose counting mechanism in the drug delivery device terminate, and

[0043] Figure 8 is a perspective view of the drug delivery device.

[0044] In the drawings, similar structures are mainly identified by similar reference numerals. DETAILED DESCRIPTION

[0045] When relative terms such as "upward" and "downward" and "left" and "right" are used hereinafter, these refer to the drawings and not necessarily to actual usage. The drawings shown are schematic representations, and for this reason, the construction of different structures and their relative dimensions are intended solely for illustrative purposes.

[0046] Figure 1a-d show the principle of a dose counting mechanism for a drug delivery device according to an embodiment of the present invention in side views of three interacting components that are in different states from start to end during use.

[0047] The first component 1 extends along a longitudinal axis and includes a first tooth row that axially extends from a distal tooth 1.1 to a proximal tooth 1.5. This particular tooth row has a second tooth 1.2, a third tooth 1.3, and a fourth tooth 1.4 disposed between the distal tooth 1.1 and the proximal tooth 1.5, i.e., it consists of a total of five teeth.

[0048] The second component 2 is disposed outside the first component 1 and includes a pair of radially opposed arms 2.1, each arm 2.1 being radially deflectable, extending to the right and terminating in a hook 2.2. The second component 2 also includes a radially deflectable leg 2.3 that extends to the left. The leg 2.3 terminates in a foot 2.4, which in Figure 1 a rests on the distal tooth 1.1. This constitutes the initial state of the dose counting mechanism. In the case of a drug delivery device, since the distal tooth 1.1 is dedicated to initially holding the second component 2, the number of remaining teeth in the first tooth row that the foot 2.4 can move to is four, and thus the total number of doses provided to the user is four. This will be further described in detail below.

[0049] The five teeth in the first tooth row are uniformly shaped, each tooth having a straight transverse right side and an inclined left side, and the foot 2.4 has a corresponding straight transverse left side and an inclined right side. Thereby, the first tooth row and the leg 2.3 together constitute a first one-way ratchet mechanism that allows the second component 2 to move to the right relative to the first component 1, but restricts the second component 2 from moving to the left relative to the first component 1.

[0050] The third component 3 is disposed outside the first component 1 and includes two parallel second tooth rows, each tooth row axially extending from a distal tooth 3.1 to a proximal tooth 3.5. For each second tooth row, a second tooth 3.2, a third tooth 3.3, and a fourth tooth 3.4 are disposed between the distal tooth 3.1 and the proximal tooth 3.5, similar to the first tooth row on the first component 1. The two hooks 2.2 are adapted to interact with the two second tooth rows simultaneously. However, the interaction between only one of the hooks 2.2 and one of the second tooth rows will be described below.

[0051] The five teeth in the second tooth row are uniformly shaped, each tooth having a straight transverse right side and an inclined left side, and the hook 2.2 has a corresponding straight transverse left side and an inclined right side. Thereby, the second tooth row and the arm 2.1 together constitute a second one-way ratchet mechanism that allows the third component 3 to move to the left relative to the second component 2, but restricts the third component 3 from moving to the right relative to the second component 2.

[0052] In the initial state of the dose counting mechanism, as Figure 1 As shown in Figure a, hook 2.2 engages distal tooth 3.1. The third component 3 is configured to perform a reciprocating motion relative to the first component 1. During one dose delivery action, the third component 3 moves back and forth once. This means that each time a dose of medication is expelled, the third component 3 moves from a starting position to an intermediate position relative to the first component 1 and returns to the starting position. Figure 1 ac shows the relative motions involved during such a dose expulsion, where Figure 1 The third component 3 in b has moved rightward from the starting position to the middle position, and Figure 1 The third component in c has moved from the middle position to the left back to the starting position.

[0053] During movement of the third component 3 from the starting position to the intermediate position, the distal tooth 3.1 of the second tooth row applies force to the hook 2.2, thereby causing the second component 2 to follow to the right. Consequently, the foot 2.4 slides along the inclined left side of the second tooth 1.2 of the first tooth row and passes over it. During the subsequent movement of the third component 3 back from the intermediate position to the starting position, the foot 2.4 abuts against the lateral right side of the second tooth 1.2 of the first tooth row, thereby preventing the second component 2 from moving leftward relative to the first component 1. This causes the second tooth 3.2 of the second tooth row to slide along the inclined right side of the hook 2.2 and pass over it.

[0054] After the first dose expulsion action, the second component 2 is thus incrementally displaced along the first component 1 by a distance corresponding to the distance between the right lateral side of the distal tooth 1.1 in the first tooth row and the right lateral side of the second tooth 1.2 in the first tooth row. It is worth noting that the second component 2 has been incrementally displaced along the third component 3 by the same distance.

[0055] The foot 2.4 now rests on the second tooth 1.2 in the first tooth row and the hook 2.2 engages with the second tooth 3.2 in the second tooth row ( Figure 1 c) The next dose delivery action will be to pass the foot 2.4 through the third tooth 1.3 in the first tooth row and the hook 2.2 through the third tooth 3.3 in the second tooth row in a similar manner to that described above.

[0056] After the second dose expelling action, the foot 2.4 thus rests on the right lateral side of the third tooth 1.3 in the first tooth row, and the hook 2.2 engages the right lateral side of the third tooth 3.3 in the second tooth row. This movement pattern continues until the last dose is expelled, at which point the foot 2.4 rests on the right lateral side of the proximal tooth 1.5 of the first tooth row, and the hook 2.2 engages the right lateral side of the proximal tooth 3.5 of the second tooth row. In this example, this corresponds to four doses that can be expelled from the drug delivery device.

[0057] Figure 2 Figure a is a longitudinal cross-sectional view of a fixed-dose injection device 10 incorporating a dose-counting mechanism of the above type. The injection device 10 includes a housing 11 extending along a longitudinal axis and a cartridge holder 30 in its axial extension. The cartridge holder 30 houses a first cartridge 35 holding a first substance (see Figure 2 b) and a second cartridge (not visible) holding a second substance.

[0058] A needle module 40 is attached at the distal end of the cartridge holder 30. It includes a needle base 41 engaging with a collar portion of the cartridge holder 30, and a needle interface 42 holding a front needle 43 and two rear needles (not visible). The front needle 43 is fluidly connected to each rear needle in a manifold configuration, and each rear needle has a fluid passage to one of the two cartridges in the cartridge holder 30. Thus, the injection device 10 is capable of delivering two substances to a single delivery site.

[0059] The needle module 40 further includes a needle guard 45 axially movable relative to the needle base 41 and having a distal opening 46 for the tip portion 43t of the front needle 43 to pass through. An activator arm 44 axially fixed relative to the needle guard 45 extends into the cartridge holder 30 and is Figure 2 ready to interact with an axially movable front activator 12 in Figure a. In the initial state of the needle module 40 on the injection device 10, the front needle 43 is safely housed in the needle guard 45.

[0060] The housing 11 having a longitudinally side wall 18 with an elliptical cross-section and proximally closed by an end wall 19 houses a dose-setting mechanism and an injection mechanism, which will be described below. Each of the two cartridges includes a cartridge wall, a distally penetrable self-sealing diaphragm, and a proximal piston, which is slidable along the cartridge wall by a piston rod (a first piston rod 53, respectively a second piston rod 54, see Figure 3 a) relative to the distal forward movement of the housing 11. The movement of the piston rods 53, 54 is powered by a drive spring 5, which is a torsion spring having a spring proximal end rotatably fixed to a spring base 15 and a spring distal end rotatably fixed to a spring clutch 17 at a spring interface 17i. The spring base 15 is fixed to the housing 11 via a spring base collar 15c.

[0061] The spring clutch 17 is of a hollow construction and is rotatably arranged relative to the housing 11 and has a non-self-locking thread 17t provided on its distal outer surface. The non-self-locking thread 17t axially extends approximately half of the total length of the spring clutch 17 from the thread distal end towards the thread proximal end and is configured to interact with a loader nut 20n forming part of a loader 20. The loader 20 further includes an elongate loader leg 20l having a snap interface 20s to a protective cap 60 of the cartridge holder 30 (reference Figure 8 ). The loader 20 is axially movable relative to the housing 11 but not rotatable, so the threaded connection between the loader nut 20n and the non-self-locking thread 17t ensures that axial movement of the loader 20 causes rotation of the spring clutch 17 and vice versa.

[0062] The protective cap 60 is configured to engage with the snap interface 20s of the loader leg 20l and axially pull the loader 20 in the distal direction when removed from the cartridge holder 30. Such a cap removal action correspondingly rotates the spring clutch 17, thereby causing angular deformation of the drive spring 5. When the loader nut 20n reaches the thread distal end of the non-self-locking thread 17t during axial movement of the loader 20, the geometry (not visible) in the cartridge holder 30 allows the loader leg 20l to flex radially inwards, causing the protective cap 60 to disengage.

[0063] The post-activator 13 extends longitudinally through the spring clutch 17, which is axially fixed relative to the housing 11, and the post-activator 13 is adapted to move axially in a reciprocating manner during use of the injection device 10. The post-activator 13 has a distal end contacting the tilt arm 7 and a proximal end abutting a reset member 14. The reset member 14 is biased in the distal direction by a reset spring 6. At the proximal end, the post-activator 13 is provided with a pair of diametrically opposed ratchet teeth 13p, each ratchet tooth 13p being configured to interact with a spring base collar 15c in a ratchet interface that restricts counterclockwise rotation (seen from the proximal end) of the post-activator 13 relative to the housing 11. The post-activator 13 and the spring clutch 17 are rotationally interlocked by mating splines on an outer surface portion of the post-activator 13 and correspondingly an inner surface portion of the spring clutch 17.

[0064] The contents stop ring 16 is arranged externally of the spring base 15 and is configured to move axially stepwise along the spring base, as will be further described below. The contents stop ring 16 includes a pair of diametrically opposed axially extending locking arms 16l, the purpose of which will become apparent from the following text.

[0065] In Figure 2In a, the loader nut 20n is located at the threaded distal end of the non-self-locking thread 17t, which corresponds to the above situation, where during the axial disassembly from the cartridge holder 30, the protective cap 60 axially pulls the loader 20 relative to the housing 11, thereby rotating the spring clutch 17 to tension the drive spring 5. The spring clutch 17 rotatably fixed to the rear activator 13 is locked in this angular position by ratchet engagement between the spring base collar 15c and the pawl 13p. Rotational energy is thus stored in the drive spring 5, and the injection device is ready to deliver the corresponding predetermined doses of the substances in the two cartridges. Thus, in practice, the dose setting action is performed by removing the protective cap 60 from the cartridge holder 30. In an alternative embodiment of the present invention, the protective cap 60 is not configured to engage with the loader 20, and the user manually tensions the drive spring 5 by pulling the loader leg 20l in an independent action.

[0066] Figure 2 b shows the injection device 10 in a state where the needle shield 45 is placed against the user's skin and the housing 11 is pressed towards the skin, such that the needle shield 45 moves proximally relative to the needle base 41, thereby causing the tip portion 43t to protrude through the opening 46. The movement of the needle shield 45 further pushes the adjacent portion 44a of the activator arm 44 proximally relative to the cartridge holder 30, thereby activating the front activator 12, and the proximal finger 12f of the front activator 12 activates the tilt arm 7, which pivots about the fulcrum 8 and causes a proximal displacement of the rear activator 13, the proximal displacement being equal to 1 / 3 of the proximal displacement of the front activator 12.

[0067] By the proximal movement of the rear activator 13, the reset member 14 is pressed towards the end wall 19 against the bias of the reset spring 6, and the pawl 13p is lifted out of engagement with the spring base collar 15c, thereby releasing the tensioned drive spring 5. Since the proximal end of the spring is fixed relative to the housing 11, the release of the stored rotational energy causes the distal end of the spring and thus the spring clutch 17 and the rear activator 13 to rotate about the longitudinal axis. As will be explained below, this rotation delivers the predetermined doses of the two substances from the injection device 10.

[0068] When the user subsequently retracts the tip portion 43t from the skin, the return spring 6 causes the entire system including the return member 14, the rear activator 13, and the front activator 12 to return via the inclined arm 7, the activator arm 44, and the needle shield 45 distal to the housing 11, whereby the tip portion 43t is again located within the needle shield 45. Each time the dose expulsion operation is completed with the injection device 10, the above components undergo the corresponding movements described. However, it should be noted that in an alternative embodiment of the present invention, the automatic return of the components achieved by means of the return spring 6 can be replaced by a manual reset mechanism, where for example a button in the end wall 19 allows the user to manually press the components backward after retracting the tip portion 43t from the skin.

[0069] Figure 3 The proximal portion of the injection device 10 is shown in two different longitudinal sectional views, where Figure 3 a particularly shows the arrangement of the first piston rod 53 and the second piston rod 54 on either side of the rear activator 13, and the engagement between the return member 14 and the content termination ring 16. The first piston rod 53 is threadedly engaged with the first nut member 51, and the second piston rod 54 with a different pitch from the first piston rod 53 is threadedly engaged with the second nut member 52. Figure 3 b particularly shows the engagement between the spring base 15 and the content termination ring 16.

[0070] In principle, the spring base 15 corresponds to Figure 1 the first component 1 in Figure 3 the content termination ring 16 corresponds to the second component 2, and the return member 14 corresponds to the third component 3. Thus, the interaction between these three components during the dose expulsion operation provides the dose counting mechanism of the injection device 10. The content termination ring 16 has a proximal arm with a hook 16h that initially engages with the farthest tooth 14.1 in the axial return member teeth 14t, as shown in Figure 3 a, and a distal foot 16f that initially rests on the farthest tooth 15.1 in the axial spring base teeth 15t, as shown in Figure 3 b. The axial position of the return member 14 in Figure 2 corresponds to the axial position in a, which in combination with the axial position of the content termination ring 16 relative to the housing 11 means that the injection device 10 is in a state where the initial first dose has not yet started to be expelled.

[0071] Figures 4 - 6 The injection device 10 in various subsequent states is shown by similar sectional views of the proximal portion. Figure 4 The injection device 10 is shown in a state similar to Figure 2 b, where the tip portion 43t extends through the opening 46 and triggers the injection mechanism. In particular, fromFigure 3 As can be seen, the rear activator 13 has been displaced proximally, thus disengaging the pawl 13p from the spring base collar 15c. By this proximal displacement, the splined section 13s of the rear activator 13 slides into splined engagement with the central clutch 58. The central clutch 58 is rotatably coupled to the first piston rod driver 55 and the second piston rod driver 56 via respective blunt gear interfaces.

[0072] The first piston rod driver 55 is rotationally locked to the first piston rod 53, and the second piston rod driver 56 is rotationally locked to the second piston rod 54. Thus, when the rear activator 13 rotates due to the pawl 13p disengaging from the spring base collar 15c to release the drive spring 5, the central clutch 58 is forced to rotate with the rear activator 13. This then causes rotation of both the first piston rod driver 55 and the second piston rod driver 56, whereby the first piston rod 53 advances helically in the distal direction through the first nut member 51, and the second piston rod 54 advances helically in the distal direction through the second nut member 52.

[0073] The advancement of the first piston rod 53 causes axial advancement of the piston in the first cartridge 35, thereby causing a first predetermined dose of the first substance to be expelled through the front needle 43. Similarly, the advancement of the second piston rod 54 causes axial advancement of the piston in the second cartridge and thereby causes a second predetermined dose of the second substance to be expelled through the front needle 43. The magnitude of the first predetermined dose is determined by the total angular displacement of the spring clutch 17 during relaxation of the drive spring 5 and the pitch of the first piston rod 53, and the magnitude of the second predetermined dose is determined by the total angular displacement of the spring clutch 17 during relaxation of the drive spring 5 and the pitch of the second piston rod 54. The total angular displacement of the spring clutch 17 during relaxation of the drive spring 5 is the angular displacement exhibited by the spring clutch 17 when the loader nut 20n travels the non-self-locking thread 17t from the thread distal end to the thread proximal end.

[0074] Furthermore, by the proximal displacement of the rear activator 13, the reset member 14 has been pushed towards the end wall 19, thereby causing the contents stop ring 16 to be actuated due to the engagement between the hook 16h and the furthest tooth 14.1. During the displacement of the contents stop ring 16, the feet 16f have passed through the second tooth 15.2 in the axial spring base teeth 15t in a manner similar to that described above in Figure 1 b, as shown in Figure 4 b.

[0075] Figure 5Fig. 0 shows the injection device 10 in a state where, after the retraction of the tip portion 43t from the user's skin, the reset member 14 and the rear activator 13 have returned to their initial axial positions in the housing 11 by the return spring 6. The distal movement of the reset member 14 causes the hook 16h to pass through the second tooth 14.2 in the axial reset member teeth 14t, while the foot 16f abuts against the second tooth 15.2 in the axial spring base teeth 15t. The first dose discharge action of the injection device 10 thus causes an incremental proximal displacement of the contents stop ring 16 along the spring base 15 from the most distal tooth 15.1 to the second tooth 15.2 and relative to the reset member 14 from the most distal tooth 14.1 to the second tooth 14.2.

[0076] In each dose discharge action, the contents stop ring 16 undergoes such an incremental displacement relative to the spring base 15 and the reset member 14, so that the number of doses discharged from the injection device 10 and / or the number of doses yet to be discharged can be determined using the current respective positions of the foot 16f and the hook 16h. For example, the spring base teeth 15t and / or the reset member teeth 14t can be made visible through a window (not shown) in the housing 11.

[0077] The contents stop ring 16 creeps slowly upward along the spring base 15 from one tooth to the next until the foot 16f rests on the most proximal tooth 15.5 in the axial spring base teeth 15t and the hook 16h engages with the most proximal tooth 14.5 in the axial reset member teeth 14t. In Figure 6 which is shown, where Figure 6 a shows the position of the hook 16h, and Figure 6 b shows the position of the foot 16f after the retraction of the front needle 43 from the skin after the fourth dose discharge action of the injection device 10.

[0078] As can be seen from Figure 6 b, in this state of the injection device 10, the contents stop ring 16 is prevented from moving further proximally relative to the spring base 15 by the stop surface 15s on the spring base collar 15c. Since the engagement between the most proximal tooth 14.5 and the hook 16 prevents the proximal displacement of the reset member 14 relative to the housing 11, any attempt to lift the rear activator 13 by the proximal displacement of the front activator 12 is unsuccessful. Therefore, the needle shield 45 of the new (or same) needle module 40 attached to the cartridge holder 30 cannot be depressed to expose the tip portion 43t, which would provide a contents termination signal indicating to the user that there are no more doses available in the injection device 10.

[0079] As described above, when the dose expelling action is completed, the loader nut 20n is positioned at the proximal end of the non-self-locking thread 17t. The protective cap 60 is adapted to be mounted on the cartridge holder 30 between dose expelling actions to protect the two cartridges. During mounting onto the cartridge holder 30, the protective cap 60 re-engages with the loader leg 20l such that when the protective cap 60 is subsequently removed from the cartridge holder 30 in preparation for the next dose expelling action, the loader nut 20n will be forced to travel the non-self-locking thread 17t to the distal end, thereby tensioning the drive spring 5 by the resulting rotation of the spring clutch 17.

[0080] An additional contents termination indication is provided in the injection device 10 which has signaled to the user the need for a new device when the protective cap 60 is removed. Figure 7 is a perspective top view of selected components in the housing 11 showing their respective relative positions after the last possible dose expulsion. The view shows the lateral collar bottom 15b of the spring base collar 15c and a pair of internal arcs with different thicknesses 15a which form a support for the pawl 13p, the support of the pawl restricting the counterclockwise rotation of the post-activator 13 relative to the spring base 15. The pawl 13p forms part of the activator head 13h which is a radially enlarged end portion of the post-activator 13.

[0081] The contents termination ring 16 includes a pair of proximally extending locking arms 16l which, during incremental movement of the foot 16f to the most proximal tooth 15.5 in the axial spring base teeth 15t, each pass through a dedicated hole in the collar bottom 15b and into a recess 13r in the periphery of the activator head 13h. This also effectively restricts the clockwise rotation of the post-activator 13 relative to the spring base 15 and thus the spring clutch 17 will be rotationally locked relative to the housing 11. Since the spring clutch 17 cannot rotate, the loader nut 20n will not be able to travel the non-self-locking thread 17t, which means that the loader leg 20l will be axially locked relative to the housing 11. Thus, when the user attempts to remove the protective cap 60, the loader 20 will provide resistance to the axial removal movement.

[0082] Depending on the exact construction of the snap interface 20s, the protective cap 60 will be adhered to the cartridge holder 30 or a part of the cap / loader interface will flex to allow the protective cap 60 to disengage from the loader leg 20l when the axial separation force between the protective cap 60 and the housing 11 is large enough. In any case, the user will experience significantly greater resistance to removing the protective cap 60 than before.

[0083] Thus, if the user is one who normally replaces the needle module 40 after each dose ejection (as is recommended), he (she) can dispense with the installation of a new needle module, because the disassembly hindrance of the protective cap 60 provides a signal of the end state of the contents of the injection device 10, such that it will not be necessary to check whether the needle guard is blocked.

[0084] Figure 8 Is a perspective view of the drug delivery device 10 in a state in which the protective cap 60 is removed from the cartridge holder 30. Protrusions 31 are provided on both sides of the cartridge holder 30 for receiving and releasably holding the needle module 40, and the aperture 32 provides a passage for the activator arm 44 into the interior of the cartridge holder 30 to operably connect with the aforementioned front activator 12.

Claims

1. A drug delivery device for performing a predetermined number of dose expelling actions, the drug delivery device comprising: a housing extending along the axis and housing the dose expelling mechanism, a reciprocating element operatively coupled to the dose expelling mechanism and configured to undergo a predetermined movement relative to the housing during each dose expelling action to allow expelling a dose, the predetermined movement comprising a displacement in a first axial direction from a first position to a second position and subsequently from the second position to the first position in a second axial direction, a counter element, said counter element being movable relative to said housing in said first axial direction, a first one-way ratchet mechanism configured to prevent movement of the reciprocating element relative to the counter element in the first axial direction and to allow movement in the second axial direction, and - a second one-way ratchet mechanism configured to allow movement of the counter element relative to the housing in the first axial direction and to prevent movement in the second axial direction.

2. The drug delivery device of claim 1 , further comprising a base member axially and rotationally fixed relative to the housing, wherein the first one-way ratchet mechanism comprises first axial teeth on one of the reciprocating element and the counting element and a pawl member on the other of the reciprocating element and the counting element, and the second one-way ratchet mechanism comprises second axial teeth on one of the counting element and the base member and a pawl member on the other of the counting element and the base member.

3. A drug delivery device according to claim 2, wherein the counter element is configured to undergo movement in the first axial direction relative to the housing from a pre-use position to a content end position in a plurality of steps corresponding to a predetermined number of dose expulsion actions, and in response to reaching the content end position, enter into axial interlocking engagement with the base member, thereby being prevented from further movement in the first axial direction relative to the housing.

4. The drug delivery device of claim 3 , further comprising a drug reservoir holder arranged in the axial extension of the housing, wherein the dose expelling mechanism comprises an activation structure operable from a distal end portion of the drug reservoir holder to displace the reciprocating element in the first axial direction against the biasing force.

5. A drug delivery device according to claim 4, wherein the drug reservoir holder comprises a receiving means configured to receive a needle module at the distal end portion and provide an operative coupling of the axially movable portion of the needle module with the activation structure.

6. A drug delivery device according to claim 5, wherein the axially movable portion of the needle module is a needle shield adapted to selectively cover and expose a front needle insertable into the skin, and wherein the needle shield of the received needle module is configured to shift the reciprocating element in the first axial direction in response to exposure of the front needle insertable into the skin.

7. The drug delivery device according to any one of claims 4-6, further comprising a dose preparation structure configured to prepare a dose to be delivered from the drug delivery device in response to distal movement of a loading member relative to the housing, and a protective cap for the drug reservoir holder, the protective cap being operatively coupled to the dose preparation structure when covering the drug reservoir holder and configured to move the loading member distally relative to the housing in response to being removed from the drug reservoir holder.

8. A drug delivery device according to claim 7, wherein the dose expelling mechanism is powered by a torsion spring member, wherein the dose preparation structure includes a spring tensioning mechanism for tensioning the torsion spring member and is configured to convert distal movement of the loading member relative to the housing into rotation of the spring tensioning member relative to the housing, and wherein the counter element is rotationally fixed relative to the housing and is configured to enter into rotational interlocking engagement with the spring tensioning member in response to reaching the end-of-content position, thereby preventing distal movement of the loading member relative to the housing.

9. A drug delivery device according to claim 1 or 2, further comprising a drug reservoir holder arranged in an axial extension of the housing, wherein the dose expelling mechanism comprises an activation structure operable from a distal end portion of the drug reservoir holder to displace the reciprocating element in the first axial direction against the biasing force.

10. The drug delivery device of claim 9, wherein the drug reservoir holder comprises a receiving arrangement configured to receive a needle module at the distal end portion and provide an operative coupling of the axially movable portion of the needle module with the activation structure.

Images