Injection device with suspended front

Abstract

The present invention provides a drug delivery device (1, 101, 201) comprising a skin interface (3, 103, 203) extending along a reference axis, being adapted to hold a liquid drug and comprising a distal drug outlet end portion (22, 122, 222), a proximal end portion (23, 123, 223), and a proximally facing surface (3s, 103s, 203s), the proximally facing surface (3s, 103s, 203s) being axially fixed with respect to the distal drug outlet end portion (22, 122, 222), a handle (2, 102, 202) being axially displaceable with respect to the skin interface (3, 103, 203) between a first extreme position and a second extreme position, where displacement from the first extreme position to the second extreme position involves a maximum distal movement of the handle (2, 102, 202) relative to the skin interface (3, 103, 203), an activatable dose expelling mechanism (50, 59; 150, 159; 250, 260) adapted to be activated upon movement of the handle (2, 102, 202) to a predetermined position distally of the first extreme position, and energy means (19, 119, 219) arranged to act between the skin interface (3, 103, 203) and the handle (2, 102, 202) and adapted to apply a distally directed force to the proximally facing surface (3s, 103s, 203s) when the handle (2, 102, 202) is positioned distally of the first extreme position.

Description

[0001] INJECTION DEVICE WITH SUSPENDED FRONT

[0002] FIELD OF THE INVENTION

[0003] The present invention relates generally to drug delivery devices and more specifically to medical injection devices having a short or no injection needle.

[0004] BACKGROUND OF THE INVENTION

[0005] Needle-free injection and injection with a needle are two different methods for delivering a medication or vaccine into the body. The primary difference between the two methods is the way whereby the skin is penetrated.

[0006] Injection with a needle involves piercing the skin with a sharpened needle tip and injecting the medication or vaccine into the underlying tissue or muscle. This method has been used for many decades and is the most common type of injection. However, needle-based injections can cause pain, discomfort, and anxiety for some people, and there is a risk of infection or injury if the needle is not used correctly. Just the mere sight of the needle may prepare some mentally for an experience of pain which ends up increasing their actual sensation of pain. To avoid this, injection devices with a retractable and extendable needle shield which prevent the user from seeing the needle have been developed, and while such feature may have some positive effect, a sensation of pain is still likely because the needle is configured to penetrate the epidermis and enter a compartment with plenty of free nerve endings.

[0007] Needle-free injection, on the other hand, delivers medication or vaccine into the body without the use of a needle. Instead, it uses an initial high-pressure jet of liquid to penetrate the skin and a subsequent lower-pressure deposition of the medication or vaccine in the underlying tissue or muscle. If performed properly, this method is less invasive, reducing the risk of infections. Furthermore, it offers an attractive alternative to people who suffer from needlephobia, or who simply do not like the thought of inserting a needle through the skin. However, to perform the method properly requires pressing an end portion of the injection device against the skin surface with a certain minimum force over a period of time sufficient to allow the penetration of the skin and the expelling of the full dose of drug. A slight reduction in the contact pressure between the injection device and the skin may result in the liquid jet not being able to penetrate the skin, consequently producing a so-called wet-shot, where the drug is sprayed onto the skin surface instead. If the user accidentally moves the injection device during an injection, this may result in a partial wet-shot and / or lacerations to the skin. In any case, the user will not receive the intended dose of drug, and the therapeutic effect thereof will accordingly be lost or markedly reduced.

[0008] As a sort of compromise between these two modes of drug delivery, solutions employing a very short and thus barely visible needle in combination with a high-pressure injection system have been suggested. Examples of such solutions are presented e.g. in US 6,231 ,540 (Novo Nordisk A / S) and US 7,744,582 (Antares Pharma, Inc.).

[0009] The short needle is adapted to penetrate one or more layers of the epidermis without going in deep enough to reach the free nerve endings in the dermis. The penetration of the short needle into the epidermis allows for the use of a reduced pressure, compared to needle-free injection, to deposit the drug at the desired depth, because the liquid does not have to overcome the strong mechanical barrier formed by the stratum corneum. Consequently, it advantageously reduces the accompanying recoil from the impulsive force that creates the high-pressure liquid jet.

[0010] Nevertheless, there is still a significant risk of performing a wet-shot with a short needle on the injection device, as it can be difficult to maintain a sufficient contact pressure on the skin over the course of the high-pressure dose initiation and the subsequent dose expelling. In addition, in the absence of a sufficient contact pressure there is a risk of more severe skin lacerations in view of the potential slippage of the short needle across the skin surface.

[0011] SUMMARY OF THE INVENTION

[0012] It is an object of the invention to eliminate or reduce at least one drawback of the prior art, or to provide a useful alternative to prior art solutions.

[0013] In particular, it is an object of the invention to provide a device for drug delivery via a short needle, or without a needle, having a reduced risk of wet-shots and / or skin lacerations.

[0014] It is a further object of the invention to provide a device which offers reduced pain and discomfort during an injection compared to conventional needle-based and needle-free injection devices.

[0015] It is an even further object of the invention to provide a non-bulky and simple-to-use drug delivery device, which can be handled also by people with low dexterity. In the disclosure of the present invention, aspects and embodiments will be described which will address one or more of the above objects and / or which will address objects apparent from the following text.

[0016] In one aspect the invention provides a drug delivery device according to claim 1.

[0017] Hence, a drug delivery device is provided which comprises a handle unit and a skin interface unit. The skin interface unit extends along a, longitudinal, reference axis and is adapted to hold a liquid drug. It comprises a distal drug outlet end portion, a proximal end portion, and a proximally facing surface, the proximally facing surface being axially fixed with respect to the distal drug outlet end portion. The handle unit is axially displaceable with respect to the skin interface unit between a first extreme position and a second extreme position. A displacement from the first extreme position to the second extreme position involves a maximum distal movement of the handle unit relative to the skin interface unit. Thus, the first extreme position is a proximal extreme position, and the second extreme position is a distal extreme position.

[0018] The drug delivery device further comprises an activatable, e.g. releasable, dose expelling mechanism for expelling a dose of a held liquid drug, the activatable dose expelling mechanism being adapted to be activated, e.g. released, upon movement of the handle unit to a predetermined position distally of said first extreme position, and energy means arranged to act between the skin interface unit and the handle unit. The energy means is adapted to apply a distally directed force to the proximally facing surface when the handle unit is positioned distally of the first extreme position. This means that at least at some point between the first extreme position and the second extreme position of the handle unit the energy means applies a distally directed force to the proximally facing surface.

[0019] The effect thereof is that during a dose administration procedure when the distal drug outlet end portion is held against a skin surface and the handle unit is moved away from the first extreme position, a proper contact pressure will be established in the device / skin interface, due to the distally directed force which is applied to the proximally facing surface by the energy means and the axially rigid connection between the proximally facing surface and the distal drug outlet end portion, reducing the risk of the skin interface unit losing contact with the skin or moving laterally across the skin surface. Consequently, the risks of performing a wet-shot and potentially experiencing related skin lacerations are reduced.

[0020] The proximally facing surface may form part of the proximal end portion or may be separate therefrom. The energy means may for example comprise a mechanical entity, such as a compression spring, or a pneumatic entity, such as a compressed gas cylinder. At least in case the energy means comprises a compression spring the distally directed force to the proximally facing surface will be applied as soon as the handle unit leaves the first extreme position, and it will increase as long as the handle unit moves towards the second extreme position, further stabilising the position of the distal drug outlet end portion relative to the skin surface.

[0021] The activatable dose expelling mechanism may be adapted to be activated manually when the handle unit reaches the predetermined position. For example, an operation of a dose release button to activate the dose expelling mechanism may be enabled, or may have an effect, in response to the handle unit reaching the predetermined position.

[0022] Alternatively, the activatable dose expelling mechanism may be adapted to be activated automatically in response to the handle unit reaching the predetermined position. This provides a very simple and easy-to-use drug delivery device which requires minimum hand dexterity.

[0023] The predetermined position may be selected by the manufacturer as a position of the handle unit wherein a particular minimum force is applied to the skin interface unit which results in a certain contact pressure in the interface between the distal drug outlet end portion and the skin surface. Alternatively, or additionally, the predetermined position may be selected based on a desire for a particular way of handling the drug delivery device.

[0024] In exemplary embodiments of the invention the first extreme position and the second extreme position are separated axially by a distance of at least 5mm and at most 100mm. Thereby, the travel of the handle unit relative to the skin interface unit is sufficiently large for the energy means to have the desired effect, and the drug delivery device retains an attractive size profile.

[0025] The handle unit may be configured to slide relative to the skin interface unit by application of a force of at least 2N and at most 20N. In particular, the handle unit may form a sheath and may be configured to slide concentrically over the skin interface unit. This provides a particularly slim and easy-to-handle drug delivery device.

[0026] The skin interface unit may comprise means for receiving a drug reservoir holding a liquid drug and may allow for exchange of an exhausted drug reservoir, whereby the drug delivery device may be used to deliver drug from multiple drug reservoirs. Alternatively, the skin interface unit may comprise a pre-mounted, non-exchangeable drug reservoir, in which case the drug delivery device must be discarded following an emptying of the non-exchangeable drug reservoir.

[0027] In particular, the skin interface unit may comprise a variable volume reservoir which defines a drug chamber for the liquid drug, and the variable volume reservoir may comprise a movable wall adapted to be urged distally upon activation of the activatable dose expelling mechanism.

[0028] Furthermore, an outlet member may be arranged at the distal drug outlet end portion for conveying the liquid drug out of the drug chamber.

[0029] The variable volume reservoir may be a drug cartridge comprising a cylindrical cartridge wall, and the movable wall may be a sealing piston being axially slidable along the cylindrical cartridge wall.

[0030] The outlet member may comprise a needle member or, alternatively, a nozzle member. In particular, the outlet member may comprise a distally extending injection needle protruding at least 0.5mm and at most 2.5mm from a distal end surface of the distal drug outlet end portion. Such a short injection needle will be able to penetrate the outermost layer of the skin and allow for deposition of the drug at a lower pressure than what would have been required with a nozzle member.

[0031] The dose expelling mechanism may be adapted to expel the liquid drug at a pressure of at least 2 bar and at most 20 bar. The dose expelling mechanism may alternatively be adapted to expel the liquid drug at a pressure of at least 2 bar and at most 10 bar. However, in some embodiments, e.g. without an injection needle, the pressure may be higher than 20 bar.

[0032] In an alternative arrangement, where the outlet member is not fixed with respect to the distal drug outlet end portion, the drug delivery device may further comprise a penetrable selfsealing septum sealing the distal drug outlet end, and the outlet member may comprise a needle hub and a distally extending injection needle and may be displaceable in the drug chamber between a proximal pre-use position in which the injection needle is accommodated in a sealed space between the needle hub and the penetrable self-sealing septum and a distal in-use position in which the distally extending injection needle transpierces the penetrable self-sealing septum and protrudes at least 0.5mm and at most 2.5mm from a distal end surface of the distal drug outlet end portion. Accordingly, in a pre-use state of the drug delivery device the injection needle is safely accommodated within the boundaries of the skin interface unit and does accordingly not pose a risk to inattentive users. The outlet member may be displaced from the proximal pre-use position to the distal in-use position by the pressure increase in the drug chamber resulting from the activation of the dose expelling mechanism.

[0033] In exemplary embodiments of the invention the drug delivery device further comprises a needle hub bias member biasing the outlet member towards the proximal pre-use position. Such needle hub bias member may comprise a compression spring, or other resilient means for returning the outlet member from the distal in-use position to the proximal pre-use position near the end of the dose expelling.

[0034] The needle hub may comprise a manifold carrying the injection needle and at least a second distally extending injection needle fluidly connected to the drug chamber, where the at least a second distally extending injection needle protrudes at least 0.5mm and at most 2.5mm from the distal end surface of the distal drug outlet end portion in the distal in-use position of the outlet member.

[0035] The cylindrical cartridge wall may comprise a radially inwardly protruding geometry defining a distal end stop for the sealing piston which prevents the sealing piston from further distal movement relative to the cylindrical cartridge wall, and the radially inwardly protruding geometry, the sealing piston, and the needle hub may be configured to allow the outlet member to move back to the proximal pre-use position, when the sealing piston is positioned at the distal end stop. The movement of the outlet member back to the proximal pre-use position following a completed dose administration will retract the injection needle, or the injection needles, into the sealed space between the needle hub and the self-sealing septum, whereby subsequent needle stick injuries are prevented from happening. Furthermore, any remaining volume of the liquid drug will be contained within the skin interface unit behind the self-sealing septum, whereby the drug delivery device will not exhibit dripping.

[0036] The activatable dose expelling mechanism may comprise a piston rod and a compressed injection spring. The piston rod may comprise a distal piston rod end portion adapted to interface with the axially slidable piston, and a proximal piston rod end portion being releasably anchored to the proximal end portion of the skin interface unit, and the compressed injection spring may be arranged to act between the distal piston rod end portion and the proximal end portion of the skin interface unit. This provides for a very simple and compact dose expelling mechanism, which renders the drug delivery device cost-effective and attractively small.

[0037] In exemplary embodiments of the invention, the proximal end portion of the skin interface unit comprises a radially extending wall having a through-going central bore, and the proximal piston rod end portion comprises axial prong members extending through the through-going bore, where each axial prong member is radially inwardly deflectable and comprises a proximal hook portion which engages with a proximal surface portion of the radially extending wall.

[0038] The activatable dose expelling mechanism may alternatively comprise a piston rod and a motor unit configured to drive the piston rod distally relative to the cylindrical cartridge wall. The piston rod may comprise a threaded shaft engaging with the motor unit, and a distal piston rod end portion adapted to interface with the axially slidable piston.

[0039] The handle unit may comprise an activation structure configured to activate the activatable dose expelling mechanism in response to the handle unit reaching the predetermined position, which may e.g. be the second extreme position. In the second extreme position of the handle unit the skin interface unit is likely to exhibit a maximum force from the energy means, which may result in an optimum contact pressure between the distal drug outlet portion and the skin, and thereby a maximum likelihood of avoiding a wet-shot.

[0040] In exemplary embodiments of the invention, the handle unit comprises an activation structure which is configured to deflect the above-mentioned axial prong members radially inwardly by interaction with the proximal hook portions to thereby disengage the piston rod from the radially extending wall in response to the handle unit reaching the second extreme position.

[0041] In other exemplary embodiments of the invention, the handle unit comprises an activation structure which is configured to activate the motor unit in response to the handle unit reaching the predetermined position. This activation structure may further be configured to deactivate the motor unit in response to the handle unit moving from the predetermined position towards the first extreme position. The dose expelling will thereby automatically be interrupted if the desired contact pressure in the device / skin interface is not maintained.

[0042] The handle unit may alternatively comprise an activation structure configured to allow manual activation of the activatable dose expelling mechanism in response to the handle unit reaching the predetermined position. For the avoidance of any doubt, in the present context the term “injection device” designates an apparatus suitable for injecting fluid media into the body of a subject, e.g. with the aid of an attachable needle device, and the term “drug” designates a medium which is used in the treatment, prevention or diagnosis of a condition, i.e. including a medium having a therapeutic or metabolic effect in the body. Further, the terms "distal" and "proximal" denote positions at, or directions along, a drug delivery device, a drug reservoir, or a needle unit, where "distal" refers to the drug outlet end and "proximal" refers to the end opposite the drug outlet end.

[0043] In the present specification, reference to a certain aspect or a certain embodiment (e.g. "an aspect", "a first aspect", "one embodiment", "an exemplary embodiment", or the like) signifies that a particular feature, structure, or characteristic described in connection with the respective aspect or embodiment is included in, or inherent of, at least that one aspect or embodiment of the invention, but not necessarily in / of all aspects or embodiments of the invention. It is emphasized, however, that any combination of the various features, structures and / or characteristics described in relation to the invention is encompassed by the invention unless expressly stated herein or clearly contradicted by context.

[0044] The use of any and all examples, or exemplary language (e.g., such as, etc.), in the text is intended to merely illuminate the invention and does not pose a limitation on the scope of the same, unless otherwise claimed. Further, no language or wording in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0045] BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In the following the invention will be further described with references to the drawings, wherein

[0047] Fig. 1 is an exploded view of an injection device according to an exemplary embodiment of the invention,

[0048] Fig. 2 is a longitudinal section view of the injection device of Fig. 1 in a pre-use state,

[0049] Fig. 3 shows the injection device in abutment with a skin surface prior to an injection,

[0050] Fig. 4 shows the injection device in an initial phase of an injection action,

[0051] Figs. 5-8 show, sequentially, the release of the dose delivery mechanism, Figs. 9-13 are close-up views of a distal end portion of the injection device, showing the needle unit in different states during an injection procedure,

[0052] Fig. 14 is a longitudinal section view of the injection device during an injection,

[0053] Fig. 15 is an exploded view of an injection device according to another exemplary embodiment of the invention,

[0054] Fig. 16 is a longitudinal section view of the injection device of Fig. 15 in a pre-use state,

[0055] Fig. 17 is a longitudinal section view of the injection device in a plane perpendicular to the one in Fig. 16,

[0056] Figs. 18-22 show the injection device, or part of the injection device, in various situations during use,

[0057] Figs. 23-26 are perspective, partly sectioned, views of a proximal portion of the injection device, showing a manual dose release mechanism in operation,

[0058] Fig. 27 is an exploded view of an injection device according to yet another exemplary embodiment of the invention,

[0059] Fig. 28 is a perspective view of a skin interface unit, with some parts being indicated as transparent,

[0060] Fig. 29 is a perspective view of the injection device of Fig. 27, partly sectioned and with some parts being indicated as transparent,

[0061] Fig. 30 is a longitudinal section view of the injection device of Fig. 27 in a pre-use state,

[0062] Figs. 31-35 show the injection device in various situations during use, and

[0063] Fig. 36 show the injection device after completion of a dose delivery action.

[0064] In the figures like structures are mainly identified by like reference numerals. DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0065] When / lf relative expressions, such as "upper" and "lower", "left" and "right", "horizontal" and "vertical", "clockwise" and "counter-clockwise", etc., are used in the following, these refer to the appended figures and not necessarily to an actual situation of use. The shown figures are schematic representations for which reason the configuration of the different structures as well as their relative dimensions are intended to serve illustrative purposes only.

[0066] Fig. 1 is an exploded view of an injection device 1 according to a first exemplary embodiment of the invention. The injection device 1 comprises a handle housing 10 having a cylindrical housing portion 11 and an end wall portion 12. Two axial guide tracks 16 (only one is visible) are arranged, diametrically opposite one another, along an interior surface of the cylindrical housing portion 11. The injection device 1 further comprises a handle spring 19, a reservoir holder 20 accommodating a drug reservoir 30, and a dose expelling mechanism in the form of a piston rod 50 biased by an injection spring 59. The piston rod 50 comprises a piston rod foot 52 from which two radially deflectable prongs 51 extend proximally, each prong 51 having a proximal end shaped as a hook 53.

[0067] The reservoir holder 20 has a distal skin interface 22 for abutment against a skin surface and a proximal end wall 23, separated along a longitudinal axis by a pair of legs 21. The proximal end wall 23 is provided with a through-going bore 24, and the distal skin interface 22 is provided with an outlet opening 25. Each leg 21 has an elongate outward protrusion 26 at its proximal end which is configured for sliding engagement with one of the axial guide tracks 16 to prevent relative rotation between the handle housing 10 and the reservoir holder 20.

[0068] The drug reservoir 30 comprises a cylindrical reservoir wall 31 with an open proximal end, and a distal reservoir end wall 32 with an outlet orifice 39 which is sealed by a penetrable selfsealing septum 38. A piston 33 comprising a main body with a distally protruding piston bulb 35 is arranged in sealing contact with the cylindrical reservoir wall 31. The cylindrical reservoir wall 31 , the distal reservoir end wall 32 with the self-sealing septum 38, and the piston 33 together define a sealed chamber which houses a needle unit 40 comprising a needle hub 41 holding a short hollow needle 45 and having a circumferential recess 42 for a sealing ring 43, and a return spring 49.

[0069] Fig. 2 is a longitudinal section view of the injection device 1 in a pre-use storage state, before exposure to any injection action. Generally, the injection device 1 comprises a handle unit 2 comprising the handle housing 10, and a skin interface unit 3 comprising the reservoir holder 20 and the drug reservoir 30. The cylindrical housing portion 11 defines an interior in which the handle spring 19 is arranged, one spring end being seated in a longitudinal spring seat 13 in the end wall portion 12, and the other spring end abutting the proximal end wall 23. The proximal end wall 12 further has a conical interior wall section 14 defining a keyhole 15, the purpose of which will be clear from the below description of the dose release mechanism.

[0070] The drug reservoir 30 is arranged distally in the reservoir holder 20, the distal reservoir end wall 32 neighbouring the distal skin interface 22, and the piston rod 50 is arranged proximally in the reservoir holder 20, the prongs 51 extending through the through-going bore 24 and the hooks 53 engaging a proximal surface portion of the proximal end wall 23. The injection spring 59 is in a pre-tensioned state, one end resting against a distal surface portion of the proximal end wall 23 and the other end resting against a proximal surface portion of the piston rod foot 52, and is retained in that state due to the engagement between the hooks 53 and the proximal end wall 23.

[0071] Inside the cylindrical reservoir wall 31 the needle unit 40 is in a pre-use position displaced a short distance from the distal skin interface 22 by the return spring 49. The short hollow needle 45 is thereby accommodated in a sealed needle chamber 37 and does not yet protrude through the self-sealing septum 38. A drug chamber 36 holding a liquid drug is formed between the piston 33 and the needle hub 41. An initial axial clearance between the piston 33 and the piston rod foot 52 ensures that the liquid drug is not prematurely pressurised.

[0072] In the depicted pre-use storage state of the injection device 1 , the handle unit 2 and the skin interface unit 3 are in an extended relative position in which the elongate outward protrusions 26 are situated at respective track ends 17 of the axial guide tracks 16. The handle unit 2 and the skin interface unit 3 are biased towards this extended relative position by the handle spring 19, and the track ends 17 prevent the reservoir holder 20 from dislodging from the handle housing 10.

[0073] In the following a use of the injection device 1 will be described with reference to Figs. 3-14.

[0074] In Fig. 3 the injection device 1 has been placed against a skin surface S and is ready for execution of a dose administration. The user grips the handle housing 10 and moves it distally over the reservoir holder 20 against the force from the handle spring 19 which is being increasingly compressed. This is illustrated in Fig. 4. Since the handle spring 19 acts between the end wall portion 12 and the proximal end wall 23, the distal motion of the handle housing 10 relative to the reservoir holder 20 results in a distal force being applied to the reservoir holder 20 which urges the distal skin interface 22 against the skin surface S, establishing a stabilising contact pressure P in the interface between the injection device 1 and the skin.

[0075] As the handle housing 10 is moved further down over the reservoir holder 20 the handle spring 19 is even further compressed, and the resulting distal force to the reservoir holder 20 increases proportionally, strengthening the contact with the skin surface S. In the relative position of the handle housing 10 and the reservoir holder 20 shown in Fig. 5 much of the handle spring 19 is compressed into the longitudinal spring seat 13, and the hooks 53 approach the keyhole 15.

[0076] In Fig. 6 the conical interior wall section 14 initiates an interaction with inclined surfaces of the hooks 53 as the handle unit 2 and the skin interface unit 3 approach a compacted relative position, causing a radially inward deflection of the prongs 51 , and in Fig. 7 the handle spring 19 is fully compressed and the handle unit 2 and the skin interface unit 3 has reached the compacted relative position in which the end wall portion 12 abuts the proximal end wall 23, preventing further distal motion of the handle housing 10 relative to the reservoir holder 20. At this point the prongs 51 exhibit maximum deflection, leading to the hooks 53 becoming disengaged from the proximal end wall 23 and urged through the through-going bore 24 by the now released injection spring 59, as the piston rod foot 52 is firstly being brought into contact with the piston 33.

[0077] In Fig. 8 the injection spring 59 has further expanded and caused the piston rod 50 to initiate a distal displacement of the piston 33 relative to the cylindrical reservoir wall 31 , which consequently pressurises the drug chamber 36.

[0078] Figs. 9-13 are close-up views of what happens in the drug reservoir 30 in the course of a dose administration. For the sake of clarity, the skin into which the drug is injected has been omitted from the views. Fig. 9 shows a distal portion of the injection device 1 just before the abovedescribed release of the injection spring 59. In this state, where the short hollow needle 45 resides in the needle chamber 37, the needle hub 41 is positioned in sealing contact with a thickened portion 311 of the cylindrical reservoir wall 31 , the sealing being provided by the sealing ring 43 in the circumferential recess 42. As the piston rod foot 52 impacts the piston 33 and propels the piston 33 forward due to the expanding injection spring 59, the resulting sudden pressure increase in the drug chamber 36 firstly causes a displacement of the needle hub 41 along the thickened portion 311 against the force of the return spring 49, whereby the short hollow needle 45 penetrates the self-sealing septum 38 and enters a distance of 1mm into the skin as the needle chamber 37 collapses, and secondly causes the liquid drug to escape the drug chamber 36 through the short hollow needle 45. Fig. 10 shows a state of the injection device 1 during injection, where the piston 33 has been advanced to such a degree that a leading edge 34 thereof is close to a ledge 311 formed by the thickened portion 311.

[0079] In Fig. 11 the leading edge 34 has reached the ledge 311, and the piston 33 is prevented from further distal motion relative to the cylindrical reservoir wall 31. As can be seen, the drug chamber 36 is not completely emptied of the liquid drug, but as the pressure therein eventually drops the return spring 49 expands and brings the needle unit 40 back to its original pre-use position. The return motion of the needle unit 40, which is made possible by a cup-shaped rear end 44 of the needle hub 41 conforming to the piston bulb 35, is shown in Figs 12 and 13.

[0080] During the return motion of the needle unit 40 the short hollow needle 45 is retracted from the skin and brought back into the re-established needle chamber 37. The remaining drug from the now collapsed drug chamber 36 will accordingly be expelled into the needle chamber 37 and will thus not cause dripping because of the sealing action of the self-sealing septum 38. In addition, since the short hollow needle 45 is now contained within the needle chamber 37, the injection device 1 does not present a risk of needle stick injuries following a completion of the drug injection procedure.

[0081] To avoid a wet-shot and potential skin lacerations it is important to maintain the same position of the distal skin interface 22 on the skin surface S during the entire injection, i.e. both when the injection spring 59 is released and a recoil may be experienced, and afterwards as the liquid drug is expelled from the drug reservoir 30. The injection procedure normally takes several seconds, and it can be difficult to know if a sufficient contact pressure is maintained during this period. An advantage with the present invention, which is illustrated in Fig. 14, is that even if the user relaxes a little and eases the downward force on the handle housing 10 at some point during the expelling of the liquid drug, the force from the compressed handle spring 19 on the proximal end wall 23 will ensure that the skin interface unit 3 upholds a proper contact pressure on the skin. This minimises the risk of the distal skin interface 22 losing contact with the skin or undergoing lateral displacements along the skin surface S, and hence minimises the risk of both a wet-shot and any related skin lacerations.

[0082] Fig. 15 is an exploded view of an injection device 101 according to a second exemplary embodiment of the invention, which in build and general functionality is similar to the previously described embodiment, but which in contrast thereto has a manually releasable dose expelling mechanism.

[0083] The injection device 101 comprises a handle housing 110 having a cylindrical housing portion 111 with a radially inwardly depressible activation button 118, and an end wall portion 112. Two axial guide tracks 116 (only one is visible) are arranged, diametrically opposite one another, along an interior surface of the cylindrical housing portion 111. The injection device 101 further comprises a handle spring 119, a reservoir holder 120 accommodating a drug reservoir 130, and a dose expelling mechanism in the form of a piston rod 150 biased by an injection spring 159. The piston rod 150 comprises a piston rod foot 152 from which a shaft 151 extends proximally. The shaft 151 has a proximal end which is shaped as a hook 153.

[0084] The reservoir holder 120 has a distal skin interface 122 for abutment against a skin surface and a proximal end portion 123, separated along a longitudinal axis by a pair of legs 121 . The proximal end portion 123 consists of a thickened transversal end wall having a slot 127 for slidable reception of an insert 128 and is provided with an axially through-going bore 124. The insert 128 itself has a through-going T-shaped bore 129, and the distal skin interface 122 is provided with an outlet opening 125. Each leg 121 has an elongate outward protrusion 126 at its proximal end which is configured for sliding engagement with one of the axial guide tracks 116 to prevent relative rotation between the handle housing 110 and the reservoir holder 120.

[0085] The drug reservoir 130 comprises a cylindrical reservoir wall 131 with an open proximal end, and a distal reservoir end wall 132 with an outlet orifice 139 which is sealed by a penetrable self-sealing septum 138. A piston 133 comprising a main body with a distally protruding piston bulb 135 is arranged in sealing contact with the cylindrical reservoir wall 131. The cylindrical reservoir wall 131 , the distal reservoir end wall 132 with the self-sealing septum 138, and the piston 133 together define a sealed chamber which houses a needle unit 140 comprising a needle hub 141 holding a short hollow needle 145 and having a circumferential recess 142 for a sealing ring 143, and a return spring 149.

[0086] Fig. 16 is a longitudinal section view of the injection device 101 in a pre-use storage state, before exposure to any injection action. Generally, the injection device 101 comprises a handle unit 102 comprising the handle housing 110, and a skin interface unit 103 comprising the reservoir holder 120 and the drug reservoir 130. The cylindrical housing portion 111 defines an interior in which the handle spring 119 is arranged, one spring end being seated in a longitudinal spring seat 113 in the end wall portion 112, and the other spring end abutting a proximal surface 103s (see Fig. 18) of the proximal end portion 123.

[0087] The drug reservoir 130 is arranged distally in the reservoir holder 120, the distal reservoir end wall 132 neighbouring the distal skin interface 122, and the piston rod 150 is arranged proximally in the reservoir holder 120, the shaft 151 extending partially through the through- going bore 124 and the T-shaped bore 129, and the hook 153 engaging a proximal surface portion of the insert 128. The injection spring 159 is in a pre-tensioned state, one end resting against a distal surface portion of the proximal end portion 123 and the other end resting against a proximal surface portion of the piston rod foot 152, and is retained in that state due to the engagement between the hook 153 and the insert 128.

[0088] Inside the cylindrical reservoir wall 131 the needle unit 140 is in a pre-use position displaced a short distance from the distal skin interface 122 by the return spring 149. The short hollow needle 145 is thereby accommodated in a sealed needle chamber 137 and does not yet protrude through the self-sealing septum 138. A drug chamber 136 holding a liquid drug is formed between the piston 133 and the needle hub 141 . An initial axial clearance between the piston 133 and the piston rod foot 152 ensures that the liquid drug is not prematurely pressurised.

[0089] In the depicted pre-use storage state of the injection device 101 , the handle unit 102 and the skin interface unit 103 are in an extended relative position in which the elongate outward protrusions 126 are situated at respective track ends 117 of the axial guide tracks 116. The handle unit 102 and the skin interface unit 103 are biased towards this extended relative position by the handle spring 119, and the track ends 117 prevent the reservoir holder 120 from dislodging from the handle housing 110.

[0090] In the following a use of the injection device 101 will be described with reference to Figs. 17- 26.

[0091] Fig. 17 is a longitudinal section view of the injection device 101 in a plane perpendicular to the one in Fig. 16. From this view, it can be seen that the activation button 118 has a thickened proximal portion with an inner contact surface 118c. The inner contact surface 118c is adapted for interaction with the insert 128, as explained in the below. The figure shows the injection device 101 in a ready-to-use state, in principle with the distal skin interface 122 placed against a skin surface, but the skin surface has been omitted for the sake of clarity.

[0092] As illustrated in Fig. 18, the user now grips the handle housing 110 and moves it distally over the reservoir holder 120 against the force from the handle spring 119 which is being increasingly compressed. Since the handle spring 119 acts between the end wall portion 112 and the proximal end wall 123, the distal motion of the handle housing 110 relative to the reservoir holder 120 results in a distal force being applied to the reservoir holder 120 which urges the distal skin interface 122 against the skin surface, establishing a stabilising contact pressure in the interface between the injection device 101 and the skin.

[0093] It is noted that if the user at this point depresses the activation button 118 radially inwardly nothing will happen because no part of the inner contact surface 118c is able to touch the insert 128.

[0094] As the handle housing 110 is moved further down over the reservoir holder 120 the handle spring 119 is even further compressed, and the resulting distal force to the reservoir holder 120 increases proportionally, strengthening the contact with the skin surface. In the relative position of the handle housing 110 and the reservoir holder 120 shown in Fig. 19 the handle spring 119 is fully compressed and a maximum contact pressure in the interface between the injection device 101 and the skin is established. If the user now depresses the activation button 118 radially inwardly the inner contact surface 118c will abut the insert 128 and cause a radial displacement thereof. This is illustrated in Fig. 20.

[0095] In the area of the T-shaped bore 129 the insert 128 is provided with a ramp 128r. This ramp 128r approaches the hook 153 as the insert 128 continues to move radially inwardly. When the ramp 128r reaches the hook 153, the distally directed force from the pre-tensioned injection spring 159 will urge the hook 153 down the ramp 128r and eventually past a ramp edge 128e. Consequently, from the moment the ramp 128r reaches the hook 153 and the injection spring 159 is allowed to expand, a dose will be expelled from the drug reservoir 130 regardless of whether the user decides to release the activation button 118 or keep it depressed.

[0096] The expansion of the injection spring 159 will initially force the piston rod foot 152 into contact with the piston 133, as shown in Fig. 21 , and the piston rod foot 152 will subsequently force the piston 133 distally relative to the reservoir wall 131 , resultantly pressurising the drug chamber 136. Fig. 22 depicts the situation where the expanding injection spring 159 urges the shaft 151 through the T-shaped bore 129 and a leading edge 134 of the piston 133 towards a ledge 1311 formed by a thickened portion 131t of the reservoir wall 131. From this point on, the dose expelling occurs exactly as described above in connection with the first exemplary embodiment of the invention.

[0097] Figs. 23-26 are perspective, partly sectioned, views of a proximal portion of the injection device 101 , detailing the manual dose release mechanism. As can be seen, the handle spring 119 is fully compressed providing a maximum force to the proximal surface 103s. In Fig. 23, the activation button 118 is not yet depressed and the hook 153 rests stably on the insert 128, retaining the injection spring 159 in the pre-tensioned state. When the user depresses the activation button 118, the inner contact surface 118c moves the insert 128 sideways, and the hook 153 resultantly slides towards the ramp 128r, as depicted in Fig. 24.

[0098] Once the hook 153 reaches the ramp 128r the injection spring 159 will start to expand and will force the piston rod 150 downwards. This will cause the hook 153 to travel the ramp 128r, as indicated on Fig. 25, and as it does so, the insert 128 is forced further sideways, by the force from the hook 153. This establishes a clearance 199 between the inner contact surface 118c and the insert 128 that prevents jamming of the dose release mechanism.

[0099] Eventually, the hook 153 passes the ramp edge 128e, whereby the motion of the insert 128 stops and the piston rod 150 is completely free to move through the T-shaped bore 129. The injection spring 159 will force the piston rod 150 further downwards, whereby the piston 133 will be displaced relative to the reservoir wall 131 and the drug will be expelled in a manner as described above.

[0100] Notably, due to the axial extent of the inner contact surface 118c there is not just one single position of the handle housing 110 in which the activation button 118 can be depressed to activate the dose release mechanism. This means that the user does not need to fully compress the handle spring 119 to be able to perform an injection. The button 118 is designed to allow the manual dose release at any point between when the handle housing is moved approximately halfway down over the reservoir holder 120 and when the handle spring 119 is fully compressed.

[0101] Fig. 27 is an exploded view of an injection device 201 according to a third exemplary embodiment of the invention. The injection device 201 generally comprises a handle unit 202 and a skin interface unit 203. The handle unit 202 comprises a handle housing 210 which has a cylindrical housing portion 211 and an end wall portion 212. Two axial guide tracks 216 (only one is visible) are arranged, diametrically opposite one another, along an interior surface of the cylindrical housing portion 211. In Fig. 27 the handle housing 210 is shown longitudinally cross-sectioned to reveal a spring seat 213 in the end wall portion 212 as well as an inner diameter of the cylindrical housing portion 211 that varies along the longitudinal axis from a first inner diameter at a regular inner wall portion 211 i to a smaller second inner diameter at a thickened inner wall portion 211t via a ramp portion 211 r that smoothly connects the regular inner wall portion 211 i and the thickened inner wall portion 211t. A small metallic plate 218 is fixed to the thickened inner wall portion 211t.

[0102] The skin interface unit 203 comprises a reservoir holder 220 accommodating a drug reservoir 230, and a motor unit 260. The injection device 201 further comprises a handle spring 219 and a dose expelling mechanism in the form of a piston rod 250 advanceable by the motor unit 260. The piston rod 250 comprises a piston rod foot 252 and a threaded shaft 251 with a longitudinal track 254.

[0103] The reservoir holder 220 has a distal skin interface 222 for abutment against a skin surface and a proximal end portion 223, separated along the longitudinal axis by a pair of legs 221. The proximal end portion 223 is provided with a through-going bore 224, and the distal skin interface 222 is provided with an outlet opening 225. Each leg 221 has an elongate outward protrusion 226 at its proximal end which is configured for sliding engagement with one of the axial guide tracks 216 to prevent relative rotation between the handle housing 210 and the reservoir holder 220.

[0104] The drug reservoir 230 comprises a cylindrical reservoir wall 231 with an open proximal end, and a distal reservoir end wall 232 with an outlet orifice 239 which is sealed by a penetrable self-sealing septum 238. A piston 233 comprising a main body with a distally protruding piston bulb 235 is arranged in sealing contact with the cylindrical reservoir wall 231. The cylindrical reservoir wall 231 , the distal reservoir end wall 232 with the self-sealing septum 238, and the piston 233 together define a sealed chamber which houses a needle unit 240 comprising a needle hub 241 holding a short hollow needle 245 and having a circumferential recess 242 for a sealing ring 243, and a return spring 249. Hence, the drug reservoir 230 is similar in design and function to the previously described drug reservoirs.

[0105] The motor unit 260 comprises a motor unit housing 261 accommodating an electromotor 275 with a drive wheel 276 and having receptacles 269 for respective button cell batteries 270. The motor unit housing 261 has a proximal housing end 263 and a distal housing end comprising four legs 262 with a longitudinal space 266 between each pair for reception of, and fixation to, the proximal end portion 223 of the reservoir holder 220. The motor unit 260 further comprises a printed circuit board (PCB) 267, and a pair of deflectable metallic sliders 268 on one side of the motor unit housing 261. An actuator gear 265 with a toothed outer rim and a threaded central hole is adapted for toothed engagement with the drive wheel 276 and for threaded connection with the threaded shaft 251 of the piston rod 250.

[0106] Fig. 28 is a perspective view of the skin interface unit 203, where some parts are indicated by dotted lines as transparent for the sake of clarity. The proximal housing end 263 has a generally flat proximal surface 203s which serves as a base for the handle spring 219. The skin interface unit 203 is shown in an assembled state before final assembly of the injection device 201. In this state, a drug chamber 236 formed between the piston 233 and the needle hub 241 holds a volume of a liquid drug.

[0107] Fig. 29 is a perspective view of the injection device 201 after final assembly, partly sectioned and with some parts being indicated as transparent, again for the sake of clarity. The figure shows the connection between the drive wheel 276, which is fitted on a drive shaft 274, and the actuator gear 265, respectively between the actuator gear 265 and the piston rod 250. The longitudinal track 254 is slidably engaged with a radially inwardly directed axially extending protrusion (not visible) in the through-going bore 224, ensuring a splined connection between the threaded shaft 251 and the proximal end portion 223 that prevents rotation of the piston rod 250 relative to the reservoir holder 220. The figure also shows the arrangement of the metallic plate 218 on the thickened innerwall portion 2111 that, notably, is circumferentially aligned with the metallic sliders 268.

[0108] Fig. 30 is a longitudinal section view of the injection device 201 in a pre-use state. It is seen that the cylindrical housing portion 211 defines an interior in which the handle spring 219 is arranged, one spring end being seated in the spring seat 213 in the end wall portion 212, and the other spring end abutting the proximal surface 203s of the proximal housing end 263. The drug reservoir 230 is arranged distally in the reservoir holder 220, the distal reservoir end wall 232 neighbouring the distal skin interface 222, and the piston rod 250 is arranged proximally in the reservoir holder 220, the threaded shaft 251 extending through the through-going bore 224 (best seen in Fig. 28). Inside the cylindrical reservoir wall 231 the needle unit 240 is in a pre-use position displaced a short distance from the distal skin interface 222 by the return spring 249. The short hollow needle 245 is thereby accommodated in a sealed needle chamber 237 and does not yet protrude through the self-sealing septum 238. In the depicted pre-use state of the injection device 201 , the handle unit 202 and the skin interface unit 203 are in an extended relative position in which the elongate outward protrusions 226 are situated at respective track ends (not visible) of the axial guide tracks 216. The handle unit 202 and the skin interface unit 203 are biased towards this extended relative position by the handle spring 219 and said track ends prevent the reservoir holder 220 from dislodging from the handle housing 210. Inside the cylindrical housing portion 211 the metallic sliders 268 are positioned distally of the ramp portion 211 r and are thus in a non-deflected and electrically unconnected state.

[0109] In the following a use of the injection device 201 will be described with reference to Figs. SI- 36. During an injection the distal skin interface 222 is placed against a skin surface. The skin surface is, however, omitted from the figures for the sake of clarity.

[0110] As illustrated in Fig. 31 , the user grips the handle housing 210 and moves it distally over the reservoir holder 220 against the force from the handle spring 219 which is being increasingly compressed. Since the handle spring 219 acts between the end wall portion 212 and the proximal housing end 263, the distal motion of the handle housing 210 relative to the reservoir holder 220 results in a distal force being applied to the skin interface unit 203 which urges the distal skin interface 222 against the skin surface, establishing a stabilising contact pressure in the interface between the injection device 201 and the skin.

[0111] At some point during the distal motion of the handle housing 210 the metallic sliders 268 reach the ramp portion 211 r and are radially compressed. The user thereby experiences an increased resistance to the action, which in essence is haptic feedback that informs of an impending dose initiation, in case of continued distal motion of the handle housing 210.

[0112] Continued distal motion of the handle housing 210 further compresses the handle spring 219 and increases the contact pressure in the interface between the injection device 201 and the skin. The metallic sliders 268 slide along the thickened inner wall portion 211t until they enter the area of the metallic plate 218 at which point an electrical connection is established that activates the electromotor 275.

[0113] The activation of the electromotor 275 causes rotation of the drive shaft 274 and the drive wheel 276 which in turn causes rotation of the actuator gear 265, due to the toothed engagement between the drive wheel 276 and the actuator gear 265. The threaded engagement between the actuator gear 265 and the threaded shaft 251 in combination with the splined connection of the longitudinal track 254 to the proximal end portion 223 results in a distal linear displacement of the piston rod 250, initially bringing the piston rod foot 252 in contact with the piston 233, as shown in Fig. 32.

[0114] Within the limits of an expellable or pre-programmed dose, as long as the metallic sliders 268 are electrically connected via the metallic plate 218 the electromotor 275 will rotate the actuator gear 265 and the piston rod 250 will undergo distal displacement relative to the reservoir holder 220. The piston rod foot 252 will accordingly urge the piston 233 distally relative to the cylindrical reservoir wall 231 , thereby pressurising the drug chamber 236.

[0115] The pressure increase in the drug chamber 236 firstly causes a displacement of the needle hub 241 along a thickened portion 231t of the cylindrical reservoir wall 231 against the force of the return spring 249, in a manner as described in connection with the first exemplary embodiment of the invention, whereby the short hollow needle 245 penetrates the self-sealing septum 238 and enters a distance of 2.5mm into the skin as the needle chamber 237 collapses, and secondly causes the liquid drug to escape the drug chamber 236 through the short hollow needle 245. This is indicated in Fig. 33.

[0116] The injection may in principle continue until the piston 233 has been advanced to such a degree that a leading edge 234 thereof abuts a ledge 2311 formed by the thickened portion 2311. However, in contrast to the two previous exemplary embodiments of the invention, in this case, if the user relaxes the grip of the handle housing 210 and the handle spring 219 consequently forces the handle housing 210 proximally relative to the skin interface unit 203 such that the metallic sliders 268 leave the area of the metallic plate 218, as shown in Fig. 34, the electromotor 275 will instantly become deactivated and the distal displacement of the piston 233 will stop. It is thus possible to pause the injection if so desired for some reason.

[0117] As the pressure in the drug chamber 236 eventually drops the return spring 249 expands and brings the needle unit 240 back to its original pre-use position in which the short hollow needle 245 is hidden behind the self-sealing septum 238. The user can thereby safely move the skin interface unit 203 to a different skin site without risking a needle injury.

[0118] Regardless of whether the user moves the interface unit 203 to a different skin site or not, the injection may be continued simply by again pressing the handle housing 210 down over the reservoir holder 220 to obtain a recommended contact pressure between the injection device 201 and the skin, correlating with the metallic sliders 268 taking up a position within the area of the metallic plate 218. Such action will re-activate the electromotor 275 and accordingly repressurise the drug chamber 236, firstly causing a displacement of the needle unit 240 that makes the short hollow needle 245 re-penetrate the self-sealing septum 238, and subsequently causing further ejection of the liquid drug from the drug chamber 236. This is illustrated in Fig. 35.

[0119] Fig. 36 shows the injection device 201 in a post-use state after removal from the skin. In this state the handle housing 210 has been forced back to its original pre-use position by the handle spring 219 and the needle hub 241 has been forced to return to its original pre-use position within the drug reservoir 230 by the return spring 249. A volume of the liquid drug remains in the drug chamber 236, and the injection device 201 is thus an example of a multiuse device, where the user may decide on a specific volume to deliver, or where the PCB 267 e.g. comprises a memory and a processor with one or more pre-programmed or calculated target encoder values for displacing the piston rod 250 one or more predefined distances to cause the injection device 201 to expel one or more doses of one or more predetermined dose sizes. Hence, the electromotor 275 may be designed to run for as long as the metallic sliders 268 are in contact with the metallic plate 218, until the leading edge 234 of the piston 233 reaches the ledge 2311, or until a dose of the one or more predetermined dose sizes has been expelled.

Claims

CLAIMS1. A drug delivery device (1 , 101 , 201) comprising:- a skin interface unit (3, 103, 203) extending along a reference axis, being adapted to hold a liquid drug and comprising a distal drug outlet end portion (22, 122, 222), a proximal end portion (23, 123, 263), and a proximally facing surface (3s, 103s, 203s), the proximally facing surface (3s, 103s, 203s) being axially fixed with respect to the distal drug outlet end portion (22, 122, 222),- a handle unit (2, 102, 202) being axially displaceable with respect to the skin interface unit (3, 103, 203) between a first extreme position and a second extreme position, where displacement from the first extreme position to the second extreme position involves a maximum distal movement of the handle unit (2, 102, 202) relative to the skin interface unit (3, 103, 203),- an activatable dose expelling mechanism (50, 59; 150, 159; 250, 260) adapted to be activated upon movement of the handle unit (2, 102, 202) to a predetermined position distally of the first extreme position, and- energy means (19, 119, 219) arranged to act between the skin interface unit (3, 103, 203) and the handle unit (2, 102, 202) and adapted to apply a distally directed force to the proximally facing surface (3s, 103s, 203s) when the handle unit (2, 102, 202) is positioned distally of the first extreme position.

2. A drug delivery device according to claim 1 , wherein the distally directed force to the skin interface unit (3, 103, 203) increases as the handle unit (2, 102, 202) moves towards the second extreme position.

3. A drug delivery device according to claim 1 or 2, wherein the activatable dose expelling mechanism (50, 59; 150, 159; 250, 260) is adapted to be activated automatically in response to the handle unit (2, 102, 202) reaching the predetermined position.

4. A drug delivery device according to any of the preceding claims, wherein the handle unit (2, 102, 202) forms a sheath and is configured to slide concentrically over the skin interface unit (3, 103, 203).

5. A drug delivery device according to any of the preceding claims, wherein the skin interface unit (3, 103, 203) comprises a variable volume reservoir (30, 130, 230) which defines a drug chamber (36, 136, 236) for the liquid drug, the variable volume reservoir (30, 130, 230) comprising a movable wall (33, 133, 233) adapted to be urged distally upon activation of the activatable dose expelling mechanism (50, 59; 150, 159; 250, 260), and an outlet member (40, 140, 240) arranged at the distal drug outlet end portion (22, 122, 222) for conveying the liquid drug out of the drug chamber (36, 136, 236).

6. A drug delivery device according to claim 5, wherein the variable volume reservoir (30, 130, 230) is a drug cartridge comprising a cylindrical cartridge wall (31 , 131 , 231), and the movable wall (33, 133, 233) is a sealing piston being axially slidable along the cylindrical cartridge wall (31 , 131 , 231).

7. A drug delivery device according to claim 5 or 6, wherein the outlet member (40, 140, 240) comprises a distally extending injection needle (45, 145, 245) protruding at least 0.5mm and at most 2.5mm from a distal end surface of the distal drug outlet end portion (22, 122, 222).

8. A drug delivery device according to claim 6, further comprising a penetrable self-sealing septum (38, 138, 238) sealing the distal drug outlet end portion, wherein the outlet member (40, 140, 240) comprises a needle hub (41 , 141 , 241) and a distally extending injection needle (45, 145, 245) and is displaceable in the drug chamber (36, 136, 236) between a proximal pre-use position in which the injection needle (45, 145, 245) is accommodated in a sealed space (37, 137, 237) between the needle hub (41 , 141 , 241) and the penetrable self-sealing septum (38, 138, 238) and a distal in-use position in which the distally extending injection needle (45, 145, 245) transpierces the penetrable self-sealing septum (38, 138, 238) and protrudes at least 0.5mm and at most 2.5mm from a distal end surface of the distal drug outlet end portion (22, 122, 222).

9. A drug delivery device according to claim 8, further comprising a needle hub bias member (49, 149, 249) biasing the outlet member (40, 140, 240) towards the proximal pre-use position.

10. A drug delivery device according to claim 8 or 9, wherein the needle hub (41 , 141 , 241) comprises a manifold carrying the injection needle (45, 145, 245) and at least a second distally extending injection needle fluidly connected to the drug chamber (36, 136, 236), the at least a second distally extending injection needle protruding at least 0.5mm and at most 2.5mmfrom the distal end surface of the distal drug outlet end portion (22, 122, 222) in the distal in- use position of the outlet member (40, 140, 240).11 . A drug delivery device according to any of claims 8 - 10, wherein the cylindrical cartridge wall (31 , 131 , 231) comprises a radially inwardly protruding geometry (311, 1311, 2311) defining a distal end stop for the sealing piston (33, 133, 233) which prevents the sealing piston (33, 133, 233) from further distal movement relative to the cylindrical cartridge wall (31 , 131 , 231), and wherein the radially inwardly protruding geometry (311, 1311, 2311), the sealing piston (33, 133, 233), and the needle hub (41 , 141 , 241) are configured to allow the outlet member (40, 140, 240) to move back to the proximal pre-use position, when the sealing piston (33, 133, 233) is positioned at the distal end stop.

12. A drug delivery device according to any of the preceding claims, wherein the dose expelling mechanism is adapted to expel the liquid drug at a pressure of at least 2 bar and at most 20 bar.

13. A drug delivery device according to any of claims 6 or 8 - 12, wherein the activatable dose expelling mechanism (50, 59; 150, 159) comprises a piston rod (50, 150) and a compressed injection spring (59, 159), wherein the piston rod (50, 150) comprises a distal piston rod end portion (52, 152) adapted to interface with the sealing piston (33, 133), and a proximal piston rod end portion (53, 153) being releasably anchored to the proximal end portion (23, 123) of the skin interface unit (3, 103), and wherein the compressed injection spring (59, 159) is arranged to act between the distal piston rod end portion (52, 152) and the proximal end portion (23, 123) of the skin interface unit (3, 103).

14. A drug delivery device according to claim 13, wherein the proximal end portion (23) of the skin interface unit (3) comprises a radially extending wall having a through-going central bore (24), and wherein the proximal piston rod end portion (53) comprises axial prong members (51) extending through the through-going bore (24), each axial prong member (51) being radiallyinwardly deflectable and comprising a proximal hook portion engaging with a proximal surface portion of the radially extending wall.

15. A drug delivery device according to claim 14, wherein the handle unit (2) comprises an activation structure (14) configured to deflect the axial prong members (51) radially inwardly by interaction with the proximal hook portions (53) to thereby disengage the piston rod (50) from the radially extending wall in response to the handle unit (2) reaching the second extreme position.

Images