HK1158998B - Medication delivery device and method for operating a medication delivery device - Google Patents

Description

Drug delivery device and method of operating a drug delivery device

Technical Field

The present invention relates to a drug delivery device for administering a dose of a drug, such as insulin or heparin. The drug delivery device may be a pen injector for administering a preset dose of a drug. In particular, the device may be a device where a user may trigger the drug delivery device.

Background

Such drug delivery devices may function when a person, such as a patient, who has not received formal medical training needs to administer an accurate, pre-set dose of a drug. In particular, such devices function when the drug is administered regularly or irregularly over a short or long period of time.

Document WO 02/05876a2 discloses a liquid drug delivery device for delivering a desired dose, the device comprising an engine (engine).

Document US 4,601,212 discloses a precision micropipette device comprising a spring for returning a plunger shaft assembly (plunger shaft assembly) to a preferred rest position after each use.

Disclosure of Invention

It is an object of the present invention to provide a drug delivery device and a method of handling the drug delivery device which enable a simple and accurate use of the drug delivery device. In particular, it is an object to reduce drug leakage from the drug delivery device after each dose delivery.

This object is achieved by the features of the independent claims. Advantageous embodiments are given in the dependent claims.

According to a first aspect, a drug delivery device comprises: a housing having a proximal end and a distal end, a cartridge for holding a medicament and having an outlet, a movable piston held within the cartridge, a drive member movable in a proximal direction relative to the housing for setting a dose of the medicament to be delivered and in a distal direction relative to the housing for delivering the dose, and a piston rod adapted to drive the piston in the distal direction relative to the housing for delivering the dose. The drive member is releasably coupled to the piston rod. The drug delivery device further comprises a resilient member arranged to move the drive member in a proximal direction relative to the housing after dose delivery and thereby reduce the pressure of the piston rod on the piston.

This has the advantage that a simple and accurate use of the drug delivery device is made possible. The user may administer several pre-set doses of the drug. For example, after drug delivery, the force acting on the drive member in the distal direction for drug delivery purposes has been removed from the drive member, moving the drive member in the proximal direction relative to the housing due to the resilient member mechanically interacting with the drive member. The drive member is movable in an axial direction relative to the housing and/or rotatable relative to the housing. The proximal movement of the drive member may occur before the setting of the next dose. The piston rod may at least partly follow the movement of the drive member in the proximal direction. In particular, the drive member may be moved in the proximal direction relative to the housing by the resilient member, wherein the piston rod may be moved indirectly by the resilient member by a movement of the drive member transmitted to the piston rod in the proximal direction relative to the housing. Thus, the piston rod is movable in a proximal direction relative to the piston. Thereby, the distance between the piston rod and the piston can be increased. In this way, space is provided that allows the deformed piston, in particular the elastically deformed piston, to relax in the proximal direction after each dose delivery.

Accordingly, the pressure exerted by the piston rod on the piston may be reduced or removed from the piston after the piston rod is moved proximally. Thus, the deformed piston may relax in the proximal direction after dose delivery. The uncontrolled piston relaxation in the distal direction, which may lead to undesired dispensing of the medicament from the cartridge, may thereby be reduced. Furthermore, the increased distance between the piston rod and the piston before setting a subsequent dose may reduce the risk of undesired dispensing of medicament out of the cartridge due to vibrations, due to e.g. an interruption of the mechanical connection between the piston and the piston rod.

In general, dose accuracy may be improved by moving the piston rod in the proximal direction after dose delivery. Preferably, the piston rod is moved in the proximal direction after dose delivery only if it is necessary to allow relaxation of the piston in the proximal direction.

The piston may comprise a deformable material, preferably elastically deformable, such as a compressible material. For example, the piston comprises rubber. In dose delivery, the piston may be deformed due to the force transmitted from the piston rod to the piston for dose delivery purposes. For example, the piston may be compressed. The deformation of the piston may result in a change in volume of the piston, or the volume of the piston may remain unchanged during and/or after the deformation.

After the force in the distal direction is removed from the piston, the deformed piston tends to return to its previous shape, i.e., the undeformed shape. Thereby, the piston may exert a pressure on the medicament in the distal direction, which may result in an undesired dispensing (weeping) of medicament from the cartridge after the medicament delivery should have been completed. The weeping may be significantly reduced if the piston rod is moved in the proximal direction after dose delivery. For example, drugs such as heparin may cause visible bruising (bruising) when in contact with the surface of the human body. By reducing or preventing the exudation of the drug delivery device, the risk of visible bruising at the surface of the user may be reduced or eliminated.

The piston rod may be withdrawn from the piston by mechanical energy, which may be stored in the resilient member during drug delivery. No electrical energy is required to achieve this.

In an advantageous embodiment, the resilient member is arranged to move the drive member and thereby the piston rod in a proximal direction relative to the housing after dose delivery to move the piston rod away from the piston for a distance. It is preferred that the distance is in the range of (about) 0.1 to 2.0mm, in particular in the range of (about) 0.1 to 2.0 mm. Such a distance is particularly advantageous for providing sufficient space for the piston to relax in the proximal direction, especially if the piston comprises rubber.

In another preferred embodiment, the drive member is releasably coupled to the piston rod such that the piston rod follows movement of the drive member in the distal direction relative to the housing for delivering a dose and does not follow movement of the drive member in the proximal direction relative to the housing for setting a dose. It is of course advantageous to couple the piston rod with the drive member such that the piston rod follows the proximal movement of the drive member relative to the housing due to the mechanical interaction of the drive member with the resilient member after dose delivery, in particular before the next dose setting.

This has the advantage that a simple and accurate use of the drug delivery device by a user is made possible, for example in order to administer several predetermined doses of a drug with high dose accuracy. Thus, persons not having formal medical training, such as patients, may repeatedly administer accurate and pre-set doses of medication.

In another advantageous embodiment, the drive member comprises a first rack (rack) and a piston rod coupled to the first rack via a pinion, wherein the pinion is engaged with the second rack and the second rack is connected to the housing. The first rack of the drive member is advantageously movable relative to the housing. Preferably, the first rack is axially movable between a first end and a second end position.

In another preferred embodiment, the drive member comprises a first support element and a piston rod coupled to the first support element via a lever, wherein the lever engages the second support element and connects the second support element to the housing.

In a further advantageous embodiment, the second toothed rack or the second support element is formed integrally with the housing or is fixed in order to prevent a rotational and/or axial movement thereof relative to the housing.

In this way, an advantageous coupling for the piston rod movement (actuation) can be provided.

In another advantageous embodiment, the recoverable element is formed integrally with the housing, or as a separate element, for example integrally with an insert of the housing.

In this way an accurate and secure coupling of the recoverable element to the housing can be provided. Furthermore, the elastic member and the housing are conveniently manufactured. Preferably, the insert of the housing is fixed to the housing. The insert may comprise a resilient member. For example, the resilient member is integrally formed with an insert of the housing, wherein the insert of the housing comprises the second rack in addition to the resilient member. Preferably, the resilient member and the piston are different.

In another advantageous embodiment, the resilient member is arranged to mechanically interact with the drive member at a distal side of the drive member, in particular in dose delivery.

Thus, the resilient member may interact with the drive member to move the drive member in a proximal direction relative to the housing after dose delivery in a simple manner.

In another advantageous embodiment, the resilient member and the drive member are arranged to generate a force on the return member in the distal direction during dose delivery to bias the resilient member (bias) such that the biased resilient member moves the drive member in the proximal direction relative to the housing after dose delivery and after removal of the force in the distal direction.

Thus, after the dose has been delivered, the resilient member is adapted to move the drive member in a proximal direction with respect to the housing. The elastic member is, for example, a spring such as a circular spring (circular spring), a leaf spring (leaf spring), or a coil spring. Preferably, the resilient member is deformed during distal movement of the drive member during dose delivery, e.g. towards the end of dose delivery, to store mechanical energy for moving the drive member in the proximal direction.

According to a second aspect, a method for handling a drug delivery device according to the first aspect of the invention is provided. After setting a dose of medicament by moving the drive member in a proximal direction and after moving the drive member in a distal direction for delivering the dose by applying a force on the drive member in a distal direction which causes the piston rod to move in the distal direction with respect to the housing and the resilient member to be biased, the method comprises the steps of waiting a preset time period and then removing the force in the distal direction from the drive member, while moving the drive member in the proximal direction with respect to the housing by a mechanical interaction between the biased resilient member and the drive member which causes a movement of the piston rod in the proximal direction with respect to the housing.

This has the advantage of providing a simple and accurate method of handling a drug delivery device. For example, a user may administer a number of preset doses of a drug. After dose delivery, after removing the distal force acting on the drive member, e.g. when the user removes a finger from the dose button, the drive member is moved in a proximal direction relative to the housing by interaction with the biased resilient member, in particular before the next dose setting, preferably after dose delivery. The piston rod may at least partly follow the movement of the drive member in the proximal direction. The piston rod is thus movable relative to the piston and thereby reduces the pressure of the piston rod acting on the piston and possibly increases the distance between the piston rod and the piston. Accordingly, the piston may relax primarily in the proximal direction.

The distal force acting on the drive member is conveniently removed before the next dose setting of the medicament, preferably after dose delivery, which causes the piston rod to be moved in the proximal direction with respect to the housing by the mechanical interaction between the resilient member and the drive member. After moving the drive member distally and into abutment with one end of said resilient member during dose delivery, and preferably biasing the resilient member upon further distal movement, the biased resilient member may exert a proximal force on the drive member, i.e. a force acting on the drive member in a proximal direction. In dose delivery, the distal force acting on the drive member, such as exerted by a user, is conveniently greater than the proximal force exerted on the drive member by the resilient member. Thus, if the distal force acting on the drive member is removed after dose delivery, the (relaxed) resilient member may move the drive member in a proximal direction relative to the housing. It should be noted that the method as described above may be performed without interaction of the drug with the human body.

In an advantageous embodiment, the piston is elastically deformed in the movement of the piston rod in the distal direction, and the piston starts to resume its undeformed shape by relaxing in the distal direction for a preset period of time, and thereby expelling additional medicament from the cartridge. Preferably, after moving the piston rod in the proximal direction with respect to the housing, the piston continues to resume its undeformed shape by (mainly) relaxing in the proximal direction.

By waiting a preset period of time, the deformed piston is given a time to relax in the distal direction before the pressure of the piston rod on the piston is removed. This relaxation in the distal direction causes additional medicament to be expelled from the cartridge. It is therefore preferred that the amount of drug expelled within the preset interval is a fraction of the dose. After the end of the distally directed movement of the drive member for dose delivery purposes, the deformed piston tends to return to its previous shape more quickly and immediately. Thereafter, the slack is slowed. It is therefore suggested to wait a preset period of time after the distally directed movement of the drive member and the piston for dose delivery purposes and to consider the amount of drug expelled as part of the (preset) dose. The accuracy of the dose can be increased in this way.

After partial relaxation of the piston in the distal direction, and thus partial removal of the distal force acting on the drive member, the piston may relax (substantially) in the proximal direction.

In an advantageous embodiment, the predetermined period of time is greater than or equal to 5 seconds and less than or equal to 15 seconds, for example 10 seconds.

In another preferred embodiment, the restriction member restricts the movement of the drive member relative to the housing in the proximal direction due to the action of the resilient element. The limiting member may for this purpose be arranged to mechanically interact with the drive member.

In this way, an uncontrolled proximal movement of the drive member after dose delivery is avoided. A pawl (content) as a limiting member may limit the movement of the drive member in the proximal direction, e.g. caused by the interaction of the drive member with the resilient member. When a subsequent dose of medicament to be delivered is set, the drive member may be moved in a proximal direction relative to the housing, wherein a proximal force exerted by a user on the drive member may easily overcome the resistance provided by the restriction member. In contrast thereto, movement of the drive member in the proximal direction caused by interaction of the drive member with the resilient member preferably does not overcome the resistance provided by the restriction member.

In another advantageous embodiment, the distance by which the drive member is moved in the proximal direction relative to the housing after dose delivery is smaller than the distance by which the drive member is movable in the proximal direction for setting a (subsequent) dose of medicament to be delivered, caused by the resilient member.

The term "drug delivery device" may refer to a single-dose or multi-dose or pre-set dose or predefined, disposable or reusable device designed to dispense a user selectable or predefined dose of a drug, such as 7 predefined doses. The drug may include insulin, growth hormone, low molecular weight heparin, and/or analogs and/or derivatives thereof, and the like. The device may have any shape, such as compact or pen-shaped. Further, the device may include a needle or may be needle-free. In particular, the term "drug delivery device" may refer to a disposable needle-type pen-type device providing a plurality of predefined doses, having mechanical and manual dose delivery and dose setting mechanisms, which is designed to be suitable for persons who have not received formal medical training, such as patients. Preferably, the drug delivery device is of the syringe type.

The term "housing" may refer to any outer housing ("main housing", "body", "housing") or inner housing ("insert", "inner body") having a unidirectional axial connection to prevent proximal movement of particular components. The housing may be designed to enable safe, accurate and comfortable handling of the drug delivery device or any of its mechanisms. Typically, it is designed to house, fix, guide and/or engage any internal member (e.g. sleeve, piston rod) of the drug delivery device by limiting exposure to contaminants such as liquid, dust, dirt. In general, the housing may be a unitary or multi-piece member having a tubular shape or a non-tubular shape. Preferably, the outer housing is provided with a plurality of maximum dose stops adapted to abut axial stops (axial stops) provided on the drive component.

The term "mesh" may particularly refer to an interlocking of two or more members of a drug delivery device, such as a spline (spline), a thread or a milled teeth connection, preferably an interlocking of milled teeth of the members.

The term "drive member" may refer to any member adapted to run through or in the housing, which is designed to transmit axial movement through or in the drug delivery device, preferably from a drive means (actuation means) to the piston rod. In a preferred embodiment, the drive member is also releasably coupled to the piston rod. The drive part may have an integrated or multi-part construction.

The term "releasably coupled" may preferably mean that the components of two instant devices are engaged together, preferably in dispensing, in order to transmit force or motion in only one direction. Preferably, the drive member is releasably coupled to the piston rod such that the piston rod follows movement of the drive member in the distal direction relative to the housing for delivering a dose and does not follow movement of the drive member in the proximal direction relative to the housing for setting a dose. The piston rod is conveniently coupled with the drive member such that the piston rod follows a proximally directed movement of the drive member relative to the housing, which movement is caused by a mechanical interaction of the drive member with the resilient member after dose delivery, in particular before the next dose setting.

The term "piston rod" may refer to a member adapted to run through or in the housing, which is designed to transmit axial movement through or in the drug delivery device, preferably from the drive member to the piston, to expel/dispense the injectable product. The piston rod may be flexible or rigid. It may be a simple rod, lead-screw (lead-screw), rack and pinion system, turbine system, or the like. The term "piston rod" may also refer to a member having an annular or non-annular cross-section. It may be made of any suitable material known to those skilled in the art and may have a unitary or multi-part construction. Preferably, the piston rod comprises a series of one or more sets of longitudinally spaced ribs and/or recesses.

The term "pinion" may refer to a toothed wheel used in conjunction with a rack, preferably a rack for transmitting force and/or motion. Preferably, the term "pinion" refers to a pinion mounted within the carrier.

The term "lever" may refer to any rod-like member that pivots about a fulcrum to transmit force and/or motion. In a preferred embodiment, the fulcrum is located on the housing and the load is applied by the drive member. In yet another preferred embodiment, the term "lever" may refer to any rod-like member that is pivoted substantially proximally relative to the piston rod during dose setting and substantially distally relative to the piston rod during dose delivery. For example, a lever assembly may refer to any component that includes a lever and a carrier for transmitting force and/or motion.

The term "rack" may refer to any member having a linear array of ribs and/or notches and/or teeth. In a preferred embodiment, one rack is located within the housing or while the other rack is located within the drive component. In another preferred embodiment, one and/or both, more preferably one rack, on the housing or on the drive member is flexible and/or pivotable and/or movable in one or more axial directions, more preferably in one axial direction.

The "distal end" of the device or a component of the device may refer to the end closest to the dispensing end of the device.

The "proximal end" of a device or a component of a device may refer to the end furthest from the dispensing end of the device.

Drawings

Exemplary embodiments are explained below with the aid of schematic figures.

Fig. 1 shows a cross-sectional view of an exemplary embodiment of a drug delivery device in a first, full sleeve (cartridge full) position.

Fig. 1A shows another cross-sectional view of the drug delivery device in the first position, i.e. the full cartridge position.

Fig. 2 shows a cross-sectional view of the drug delivery device in the second position, i.e. the first dose setting position.

Fig. 3 shows a cross-sectional view of the drug delivery device in a third, final dose dispensing position.

Fig. 4 shows a partial three-dimensional view of a drug delivery device.

Fig. 5 shows a cross-sectional view of another exemplary embodiment of a drug delivery device.

Fig. 6A and 6B show cross-sectional views of schematic views of a drug delivery device.

Elements of identical design and function shown in different figures are denoted by the same reference numerals.

Detailed Description

Fig. 1 shows a cross-sectional view of a drug delivery device 1 in a first, full cartridge position.

The drug delivery device 1 comprises a cartridge housing 2 and a cartridge 3. The cartridge 3 is held within the cartridge housing 2. The sleeve has an outlet 3'. The device 1 comprises a main (outer) housing 4 having a proximal end P and a distal end, which is closest to a dispensing end D of the drug delivery device 1. The proximal end of the cartridge housing 2 and the distal end of the main housing 4 are secured together by any suitable means known to those skilled in the art. In the illustrated embodiment, the cartridge housing 2 is secured within the distal end of the main housing 4.

A cartridge 3 is arranged within the cartridge housing 2, from which cartridge 3 a plurality of doses of medicament M may be dispensed. Retaining the piston 5 within the proximal end of the barrel 3. A removable cap 6 is releasably retained over the distal end of the cartridge housing 2. The removable cap 6 may optionally be provided with one or more windows facing the sleeve 6' from which the position of the piston 5 within the sleeve 3 is visible.

In the shown embodiment the distal end of the cartridge housing 2 is provided with a distal threaded region 7 designed for attachment of a suitable needle assembly to enable dispensing of the medicament from the cartridge 3. In the embodiment shown, the main housing part 3 is provided with an insert, i.e. an inner housing 8. The inner housing 8 is fixed against rotational and axial movement relative to the main housing 4. The inner housing 8 is provided with a second toothed rack 9, which extends along the main axis of the inner housing 8. Alternatively, the second rack 9 and the main housing 4 may be integrally formed. Alternatively, the inner case 8 and the main case 9 may be integrally formed. Further, the inner housing 8 is provided with a plurality of guide tabs 32 (see fig. 4) and a pawl device 34 (see fig. 1A and 4). The jaw means 34 may be an integral part of the inner housing 8 or may be a separate component.

The piston rod 10, which extends through the main housing 4, has a first set of recesses 11' (see fig. 1A) which extend longitudinally along the outer surface of the piston rod 10. In particular, the piston rod 10 is designed and arranged to be fixed against rotational movement relative to the main housing 4. A second set of recesses 11 extends longitudinally along the inner surface of the piston rod 10. The first set of recesses 11' of the piston rod 10 extends through and engages pawl means 34 provided on the inner housing 8, e.g. on or connected to the second gear rack 9, to prevent movement of the piston rod 10 in the proximal direction relative to the housing in setting of a dose. The bearing surface 12 at the distal end of the piston rod is arranged to abut the proximal end face of the piston 5. In the embodiment shown, the longitudinal spacing of the first and second sets of notches 11 is substantially equal.

Comprising a carrier 14 and a pinion 15, and a pinion device (pinion gear)13 freely rotatable in the carrier 14 is located in a groove in the piston rod 10. The pawl arms 16 (fig. 1A) on the carrier 15 are releasably engaged with the second set of recesses 11 of the piston rod 10. The pawl arms 16 of the carrier 14 are designed to transmit a force to the piston rod 10 in a distal direction during dispensing and to allow a relative movement between the pinion means 13 and the piston rod 10 in a proximal direction during dose setting. The teeth of the pinion 15 and the teeth of the second rack 9 of the inner housing 8 are permanently meshed.

The drive member 17 extends alongside the piston rod 10 and releasably couples it to the piston rod 10. The drive member 17 includes a rack portion 18 and a trigger portion 19. The rack portion 18 and the trigger portion 19 are secured together to prevent rotational and axial movement therebetween. Alternatively, the drive means 17 may be an integrated member comprising an integrated rack portion 18 and trigger portion 19.

The rack portion 18 is provided with a first rack 20 extending along a main axis of the rack portion 18. The teeth of the first rack 20 of the rack portion 18 and the teeth of the pinion 15 are permanently meshed.

The drive member 17 has a plurality of guide grooves (not shown) in which guide pieces 32 of the inner housing 8 are disposed (see fig. 4). These guide slots define the extent of the axial movement allowable of the drive member 17 relative to the housing 4. In the illustrated embodiment, the guide slots also prevent rotational movement of the drive member 17 relative to the main housing 4.

The drug delivery device 1 further comprises a resilient member 21. The resilient member 21 is arranged to move the drive member 17, preferably the drive member 17 and the piston rod 10 together, in a proximal direction with respect to the main housing 4 after dose delivery and thereby reduce or even eliminate the pressure of the piston rod 10 on the piston 5. The resilient member 21 is arranged to mechanically interact with the drive member 17 at the distal side of the drive member 17. In this exemplary embodiment, the elastic member 21 and the inner case 8 are integrally formed. Alternatively, the elastic member 21 and the main housing 4 may be integrally formed. In another embodiment, the resilient member may also be a separate element from the housing and the inner housing. The elastic member 21 is, for example, a spring such as a circular spring, a leaf spring, or a coil spring.

The trigger portion 19 of the drive member 17 has a plurality of gripping surfaces 22 and a dispensing surface 24. In order to increase the intuitiveness of the operation of the device 1 and the visual feedback indicating the dose setting, a window facing the drive member 4' may optionally be provided on the main housing 4 from which a graphical status indication provided on the drive member 17 is visible.

Hereinafter, the operation of the drug delivery device 1 will be described.

To set a dose, the user grips the gripping surface 22 of the drive member 17. The user then pulls the drive member 17 in a proximal direction away from the main housing 4 and thus moves the rack portion 18 in a proximal direction. The proximal movement of the rack portion 18 causes the pinion 15 to rotate and move proximally due to the meshing of the teeth of the pinion 15 of the gear arrangement 13 with the teeth of the first rack 20 of the rack portion 18 and the teeth of the second rack 9 of the inner housing 8, thereby moving the pinion 13 in a proximal direction.

The piston rod 10 is prevented from moving proximally in dose setting by the interaction between the jaw means 34 of the inner housing 8 and the first set of recesses 11' on the piston rod 10. As the drive member 17 is moved in a proximal direction relative to the piston rod 10, the claw arms 16 of the carrier 14 are resiliently inwardly displaced (displaced inwardly) by interaction with the second set of recesses 11 of the piston rod 10.

The proximal movement of the drive member 17 is limited to the guide groove of the rack portion 18. At the end of the movement of the drive member 17, the pawl arm 16 of the carrier 14 engages the next successive recess of the second set of recesses 11 of the piston rod 10, as shown in fig. 2. The action of the pawl arms 16 of the carrier 14 positively engaging the second set of recesses 11 of the piston rod 10 produces an audible and tactile feedback to the user to indicate that a dose has been set.

When a dose has been set, the user may then dispense the dose by pressing the dispensing surface 24 of the trigger portion 19 of the drive member 17. By this action, the drive member 17 and the rack portion 18 are moved axially in the distal direction relative to the housing 4. As a result of the teeth of the pinion 15 of the pinion means 13 meshing with the teeth of the first rack 20 of the rack portion 18 and the teeth of the second rack 9 of the inner housing 8, the pinion 15 of the pinion means 13 is caused to rotate and move in a distal direction and thereby move the pinion means 13 longitudinally in a distal direction. As the claw arms 16 of the carrier 14 of the pinion device 13 engage the second set of recesses 11 of the piston rod 10, the piston rod 10 is caused to move longitudinally in the distal direction relative to the inner housing 8.

Distal axial movement of the piston rod 10 causes the bearing surface 12 of the piston rod 10 to bear against the piston 5 in the sleeve 3 and to deform and move the piston 5 distally and thereby cause dispensing of a dose of medicament through an attached needle (not expressly shown).

The distal movement of the drive member 17 is limited to a guide groove (not explicitly shown) of the rack portion 18. An audible and tactile feedback indicating that a dose has been dispensed is provided by the interaction of the jaw means 34 of the inner housing 8 with the first set of recesses 11' of the piston rod 10. Furthermore, visual feedback on the dose dispensing may optionally be shown by a patterned status indicator provided on the drive member 17, which is visible through an optional window in the main housing 4 facing the drive member 4'.

Other doses may be delivered as needed up to a preset maximum dose amount. Fig. 3 shows the drug delivery device 1 of the present invention in a state in which a maximum number of doses therein have been delivered. In this state, the proximal end face 26 of the carrier 14 abuts the inner distal end face 28 of the piston rod 10 to prevent further axial movement of the pinion device 13 and, hence, the drive member 17 in the proximal direction.

After the end of the distal movement of the drive member 17 for dose delivery purposes, the resilient member 21 has been biased. For example, the distal face of the drive member may have moved into abutment with the resilient member 21, and the drive member 17 may have continued to move in the distal direction with the resilient member 21 and thereby bias the resilient member 21. After the user removes the force acting on the drive member 17 in the distal direction, the biased resilient member 21 moves the drive member 17 and the piston rod 10 in the proximal direction relative to the main housing 4. Thus, the pressure of the piston rod 10 on the piston 5 is reduced as the piston rod is withdrawn from the piston. In this way, space for the piston to relax in the proximal direction may be provided. In this way, a slack of the piston rod 5 in the distal direction can be reduced or avoided. Accordingly, undesired leakage of the device may be reduced.

Preferably, the piston rod 10 is moved a distance away from the piston 5 and/or the drive member 17 is moved a distance in the range of (about) 0.1 to 2.0mm, in particular in the range of (about) 0.1 to 0.5mm in the proximal direction relative to the main housing 4 by moving the drive member 17 in the proximal direction after dose delivery by the resilient member 21. The distance the drive member 17 moves need not be the same as the distance the piston rod 10 moves, i.e. with mechanical advantage the piston rod 10 is coupled with the drive member 17.

A limiting member, such as one or more detents (see fig. 4, 6A, 6B), may limit movement of the drive member 17 relative to the main housing 4 in the proximal direction, which movement is caused by the resilient member 21. The restricting member 30 may be provided or fixed to the housing. When setting the next dose of medicament M to be delivered, the drive member 17 may be moved in a proximal direction with respect to the housing 4, wherein a proximal force applied by a user of the medicament delivery device 1 may easily overcome the resistance provided by the restriction member 30 against proximal movement of the drive member 17. Uncontrolled proximal movement of the drive member 17 by the resilient member 21 may be avoided by the restriction member 30.

After the distally directed movement of the drive member 17 for dose delivery purposes is ended and the resilient element is biased, it is preferred that the user of the drug delivery device 1 waits a preset time period during which the user holds the drive member 17 in the distal position and only thereafter the force acting on the drive member in the distal direction is removed. This is particularly advantageous if the piston 5 is elastically deformed, e.g. compressed, during dose delivery due to the pressure exerted on the piston 5 by the piston rod 10. The amount of piston 5 relaxation is typically highest immediately at the end of the distally directed movement of the piston rod 10 for dose delivery purposes. The pressurized piston often relaxes exponentially. It is therefore advantageous to allow the piston 5 to relax first in the distal direction. The amount of drug expelled in the relaxation in the distal direction may be part of the dose. Therefore, if the medicament is injected into the body by the user, it is advisable to leave the needle of the device in the body for a preset period of time. After the preset period of time has elapsed, the distal force is removed from the drive member 17 and, due to the biased resilient member 21, the drive member 17 and the piston rod 10 are moved in the proximal direction and thereby the piston 5 is allowed to complete the relaxation, mainly in the proximal direction.

The preset time period may be greater than or equal to 5 seconds and less than or equal to 15 seconds, for example, 10 seconds. Since the amount by which the piston is pressed may depend on the applied force, waiting a preset time after the end of the distally directed movement of the drive member has the advantage that the accuracy of the dose is increased, since the initial relaxation of the piston after the distally directed movement of the drive member stops facilitates the dose delivery. After dose delivery, due to the interaction of the drive member 17 and the resilient member 21, the distance the drive member 17 is moved in the proximal direction with respect to the main housing 4 is conveniently smaller than the distance the drive member 17 is moved proximally for the purpose of setting a dose of the drug M to be delivered.

In the illustrated embodiment, the drug delivery device 1 is a fixed dose pen. Alternatively, the drug delivery device 1 may be a pen for delivering a variable dose, preferably a user set dose.

Fig. 4 shows a partial three-dimensional view of the drug delivery device 1.

The resilient member 21 of the drug delivery device 1 is arranged to move the drive member 17 (see fig. 1) in a proximal direction relative to the main housing 4 after dose delivery. The resilient member 21 is arranged to mechanically interact with the drive member 17 at its distal side. In this exemplary embodiment, the elastic member 21 and the inner case 8 are integrally formed. The proximal end face of the inner housing 8 comprising the second rack 9 comprises a resilient member 21. The resilient member abuts the trigger portion 19 of the drive member 17 towards the end of dose delivery and bends said resilient member in the distal direction as the drive member continues to move in the distal direction and thereby biases the resilient member. The elastic member 21 is designed as a flexible region, for example, a U-shaped region, of the inner housing 8. When the user removes the distal force from the trigger part 19, the resilient member 21 relaxes in the proximal direction and moves the drive member 17 in the proximal direction. The drive member 17 may be moved proximally until the drive member 17 engages a limiting member 30, such as one or more detents.

Movement of the drive member 17 in the proximal direction moves the piston rod 10 in the proximal direction and away from the piston rod 5, coupling the piston rod to the drive member via the carrier 14 and the pinion 15.

Fig. 5 shows a cross-sectional view of another exemplary embodiment of a drug delivery device 1. The shown drug delivery device 1 comprises another actuator of the piston rod 10.

The inner housing 8 is provided with a fulcrum 36 for attachment of a lever 38. Alternatively, the inner housing 8 and the main housing 4 may be integrally formed. The lever 38 includes one or more protrusions (lug) 40. The lever 38 is located in a groove in the main housing 4. The protrusions 40 of the lever 38 are releasably coupled with the first set of recesses 11 of the piston rod 10. The first set of recesses 11 is designed to allow a force transmission of the piston rod 10 in the distal direction during drug delivery and to allow a relative movement between the lever 38 and the piston rod 10 in the proximal direction during dose setting. The drive member 17 comprises a first support element 42 and couples the piston rod 10 to the first support element 42 via the lever 42, wherein the lever 38 is engaged with a second support element 44 connected to the housing 4. The second support element 44 is attached to the fulcrum 36 of the inner housing 8 to allow pivotal movement between the lever 38 and the inner housing 8.

The drive member 17 includes a slot 46 and an activation portion 19, wherein the slot 46 and the activation portion 19 are secured to one another to prevent rotational and/or axial movement therebetween. Alternatively, the drive member 17 may be an integral component including the integrated slot 46 and the trigger portion 19. The first support element 42 is located within a slot 46 of the drive member 17. The slot 46 of the drive member 17 is designed to allow lateral movement, rather than longitudinal movement, of the first support element 42 relative to the drive member 17.

The rest of the design and mechanism of the drug delivery device 1 corresponds to the above described embodiment of the drug delivery device 1.

Fig. 6A and 6B show cross-sectional views of simplified schematic views of parts of the drug delivery device 1 to further illustrate the mode of operation of the drug delivery device 1.

To set a dose of medicament to be delivered, the drive member 17 is moved in a proximal direction relative to the housing 4. During delivery of a dose of medicament, the drive member 17 is moved in a distal direction relative to the housing 4 by a first distal force F1 (see fig. 6A) applied by the user to the drive member 17. The piston 5 may be compressed during drug delivery (not explicitly shown) due to the drug in the sleeve and the force F1 acting on the piston 5 from the opposite side of the piston. Furthermore, the resilient member 21, e.g. a spring, and the drive member 17 are arranged such that the first force F1 also acts on the resilient member 21 during dose delivery. In this way, the resilient member 21 is biased such that after dose delivery and after removing the first force F1 from the drive member 17 in the distal direction, the biased resilient member 21 exerts a second force F2 on the drive member 17 and moves the drive member 17 in the proximal direction relative to the housing 4. Accordingly, the drive member is moved a distance Z relative to the housing 4. In this way, the pressure of the piston rod 10 on the piston 5 (not explicitly shown) may be reduced and the relaxation of the piston 5 in the proximal direction is facilitated. For example, the distance Z may be in the range of about 0.1 to 2.0mm, preferably in the range of 0.1 to 2.0 mm.

Thus, the piston 5 may relax substantially in the proximal direction after the dose delivery is completed and after the first force F1 is removed, the second force resulting in a movement of the piston rod 10 away from the piston 5.

Preferably, the resilient element is biased during a distally directed movement of the drive member 17, such as deformation and/or compression, in particular towards the end of the movement of the drive member for dose delivery purposes.

A device similar to the one described above is described in document WO 2008/058666 a1, the disclosure of which is expressly incorporated in the present invention by reference.

Reference numerals

1 drug delivery device

2 Sleeve housing

3 sleeve

3' (sleeve) outlet

4 (Main) casing

Window with 4' facing the drive member

5 piston

6 removable cover

6' Sleeve-faced Window

7 threaded zone

8 inner shell (insert)

9 second tooth part

10 piston rod

11, 11' (piston rod) recess

12 bearing surface

13 pinion gear device

14 load carrier

15 pinion

16 claw arm

17 drive member

18 rack part (of the drive member)

19 trigger part

20 (of the rack part) first rack

21 elastic member

22 gripping surface

24 dispensing surface

26 proximal face of carrier

28 distal end face of piston rod

30 limiting member

32 guide piece

34 claw device

36 fulcrum of lever

38 lever

40 (lever) projection

42 first support element

44 second support element

46 (of the drive member)

D distribution terminal

F1 first force

F2 second force

M drug

P near end

Distance Z

Claims (10)

1. A drug delivery device (1) comprising:

a housing (4) comprising a proximal end (P) and a distal end (D),

-a cartridge (3) for holding a medicament (M), the cartridge (3) having an outlet (2),

-a movable piston (5) which is held within the sleeve (3),

-a drive member (17) movable in a proximal direction with respect to the housing (4) for setting a dose of a drug (M) to be delivered and in a distal direction with respect to the housing (4) for delivering the dose, and

-a piston rod (10) adapted to drive the piston (5) in a distal direction relative to the sleeve (3) to deliver the dose,

releasably coupling the drive member (17) to the piston rod (10)

It is characterized in that

The drug delivery device (1) further comprises a resilient member (21), the resilient member (21) being arranged to move the drive member (17) in a proximal direction relative to the housing (4) after dose delivery and thereby reduce the pressure of the piston rod (10) on the piston (5).

2. The drug delivery device (1) according to claim 1,

it is characterized in that

The resilient means (21) is arranged to move the drive means (17) and thus the piston rod (10) in a proximal direction relative to the housing (4) after dose delivery to move the piston rod (10) away from the piston (5) a distance in the range of 0.1 to 2.0 mm.

3. The drug delivery device (1) according to claim 1,

it is characterized in that

Releasably coupling the drive member (17) to the piston rod (10) such that the piston rod (10) follows movement of the drive member (17) in a distal direction relative to the housing (4) for delivering a dose and does not follow movement of the drive member (17) in a proximal direction relative to the housing (4) for setting a dose.

4. The drug delivery device (1) according to claim 1,

it is characterized in that

The drive means (17) comprises a first rack (20) and couples the piston rod (10) to the first rack (20) via a pinion (15), wherein the pinion (15) engages a second rack (9) and connects the second rack (9) to the housing (4).

5. The drug delivery device (1) according to claim 1,

it is characterized in that

The drive member (17) comprises a first support element (42) and couples the piston rod (10) to the first support element (42) via a lever (38), wherein the lever (38) engages a second support element (44) and connects the second support element (44) to the housing (4).

6. The drug delivery device (1) according to claim 4,

it is characterized in that

-forming the second rack (9) integrally with the housing (4), or-fixing the second rack (9) against rotational and/or axial movement relative to the housing (4).

7. The drug delivery device (1) according to claim 5,

-forming the second support element (44) integrally with the housing (4), or fixing the second support element (44) against rotational and/or axial movement relative to the housing (4).

8. The drug delivery device (1) according to any of claims 1 to 5,

it is characterized in that

-forming the elastic member (21) integrally with the housing (4) or integrally with an insert (8) of the housing (4).

9. The drug delivery device (1) according to any of claims 1 to 5,

it is characterized in that

-arranging the resilient member (21) to mechanically interact with the drive member (17) at a distal end of the drive member (17).

10. The drug delivery device according to any one of claims 1 to 5,

it is characterized in that

The resilient member (21) and the drive member (17) are arranged such that a force in the distal direction is exerted on the resilient member (21) during drug delivery to bias the resilient member (21) in such a way that after drug delivery and after removal of the force in the distal direction, the biased resilient member (21) drives the drive member (17) in the proximal direction relative to the housing (4).