NEEDLE SYSTEM FOR DRUG INJECTION

the present invention provides a needle system comprising a needle assembly (1, 100, 200, 300) and a drug cartridge (30, 130, 230, 330), the needle assembly (1, 100, 200, 300) comprising a needle hub member (4.1, 104.1, 204.1, 304.1) in which an injection needle (15, 115, 215, 315) is fixedly mounted such that a front needle portion (15f, 115f, 215f, 315f) extends in a distal direction therefrom and a rear needle portion (15r, 115r, 215r, 315r) extends in a proximal direction therefrom, and a skirt member (4.2, 104.2, 204.2, 304.2) extending proximally from the needle hub member (4.1, 104.1, 204.1, 304.1) and defining a skirt cavity (4.9, 104.9, 204.9, 304.9) accommodating the rear needle portion (15r, 115r, 215r, 315r), the skirt cavity (4.9, 104.9, 204.9, 304.9) having a skirt cavity configuration, and the drug cartridge (30, 130, 230, 330) comprising a generally cylindrical body (31, 131, 231, 331) being sealed proximally by a slidable piston (239, 339) and having an outlet end portion defined by a neck (32, 132, 232, 332) and a head (33, 133, 233, 333), the head (33, 133, 233, 333) having a head configuration, wherein the skirt cavity configuration corresponds to the head configuration, providing for a tight fitting of the skirt member (4.2, 104.2, 204.2, 304.2) on the head (33, 133, 233, 333) which renders the rear needle portion (15r, 115r, 215r, 315r) a permanent resident of the outlet end portion.

FIELD OF THE INVENTION

The present invention relates to needle systems for use in drug injection procedures.

BACKGROUND OF THE INVENTION

Injection systems for self-administering of drugs comprising a pen injection device and an attachable needle unit have become increasingly popular due to generally simple and convenient handling patterns.

Predominantly, two types of pen injection devices are available, durable injection devices being capable of delivering one or more doses of drug from a prefilled drug cartridge which can be loaded into the device before use and replaced after exhaustion, and disposable injection devices being capable of delivering one or more doses of drug from a prefilled and non-exchangeable drug cartridge. Each of these types of pen injection devices are, or may in principle be, realised in various sub-types, such as e.g. single shot devices adapted to deliver only one dose of a predetermined, or selected, size from a drug cartridge, multi-shot devices capable of delivering a plurality of doses from a drug cartridge, manual devices, where the user provides the force needed for injection, automatic devices having a built-in energy source releasable to occasion the injection, fixed dose devices adapted to deliver doses of identical size, variable dose devices offering delivery of a plurality of doses of drug, each settable by the user from a range of possible dose sizes, etc.

As the labels suggest a durable injection device is intended for use over a considerable period of time during which multiple drug cartridges are exhausted and replaced, whereas a disposable injection device is intended for use until its dedicated drug cartridge is exhausted, after which the entire injection device is discarded.

Regardless of the type of pen injection device users of such injection systems are recommended to discard the needle unit after a single injection to minimise the risk of contamination. Hence, in the course of its lifetime a multi-use injection device is by default to be used with multiple needle units.

Needle units are typically wrapped and sealed individually to ensure sterility prior to use. In connection with a dose administration action the user must therefore unwrap the needle unit, mount it on the injection device to thereby establish fluid connection to the drug cartridge, perform the injection, dismount it from the injection device, re-wrap or otherwise encapsulate it to prevent needle stick injuries, and finally dispose of it, preferably in a dedicated sharps container.

The readying and subsequent removal of the needle unit is both the most complicated and the most time-consuming part of the injection procedure. With a traditional thread interface the mounting and dismounting of the needle unit even require users to perform a repetitive rotary hand movement which some find motorically difficult. In general, especially for young and elderly users the handling of the small items and foils can present a challenge and make the task of injection cumbersome.

WO 2015/117854 (Novo Nordisk A/S) discloses a combined cartridge and needle assembly for use in a re-usable injection device. The cartridge containing a liquid drug and the needle assembly are permanently attached to each other to form a single drug unit which is insertable in the injection device. The needle assembly comprises a housing, a telescopic needle shield and an axially movable needle hub which is moved axially to an injection position by a resilient element, once the combined cartridge and needle assembly is inserted in the injection device, upon rotation of the housing. The movement of the needle hub establishes fluid connection to the cartridge, creates a reservoir within the needle shield between two separable septa which are axially drawn apart, and generates a vacuum inside the reservoir which resultantly initiates a transfer thereto of a volume of the liquid drug from the cartridge. When the reservoir is thus filled, the injection device is ready to perform a first of a plurality of injections possible without change of the needle assembly, due to preservatives in the liquid drug cleaning the needle tip in the reservoir after each injection action, and when the cartridge is eventually empty, the drug unit can be replaced.

While this solution does ease the readying of the injection device and does reduce the number of user actions normally performed in connection with the needle handling, it still requires both an insertion of the drug unit into the injection device as well as a preparative rotation of the housing to cause the movement of the needle hub which leads to the establishment of fluid connection to the cartridge and the subsequent filling of the reservoir. Even though the filling of the reservoir is automatic and therefore does not require further actions from the user it prolongs the time necessary to ready an injection device with a new drug unit for injection. Furthermore, the solution entails a comparably complex needle assembly construction involving several movable parts, increasing the risk of malfunction.

SUMMARY OF THE INVENTION

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.

In particular, it is an object of the invention to provide a solution which reduces the number of handling steps associated with the use of a needle-based injection system.

It is a further object of the invention to provide a solution which enables a person to quickly and easily ready a needle-based injection system for use

It is a further object of the invention to provide such a solution which is simple, compact and cost-effective.

It is a further object of the invention to provide such a solution which is safe and reliable.

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.

In a first aspect the invention provides a needle system according to claim1.

Accordingly, a needle system is provided comprising a needle assembly and a drug cartridge. The needle assembly comprises a needle hub member in which an injection needle, extending along a reference axis, is fixedly mounted, e.g. by gluing. A front needle portion of the injection needle extends in a distal direction from the needle hub member, and a rear needle portion of the injection needle extends in a proximal direction from the needle hub member. The needle assembly further comprises a skirt member which extends proximally from the needle hub member and defines a skirt cavity accommodating the rear needle portion. The skirt cavity has a skirt cavity configuration, i.e. a certain size and shape.

The drug cartridge is a conventional type drug cartridge and comprises a generally cylindrical cartridge body and a slidable piston which define a chamber for holding a liquid substance. The cartridge body has an outlet end portion defined by a necked down section, or neck, and a head. The head has a head configuration which corresponds to the skirt cavity configuration.

This provides for a firm and stable attachment of the needle assembly to the drug cartridge by a tight fitting of the skirt member on the head, ensuring that the rear needle portion resides permanently in the outlet end portion in the sense that the rear needle portion is fluidly connected with the chamber at all times. Thereby, an assembled needle system can be inserted into an injection device and a force can be applied to the piston to expel a dose of the liquid substance immediately without any further preparatory user actions.

The tight fitting of the skirt member on the head additionally provides for a compact construction of the needle system and gives a solid sense of unitarity because there is no intermediate space to allow for wriggling. Thus, because the skirt cavity configuration corresponds to the head configuration, in the assembled needle system the skirt member and the head are firmly engaged such that no relative axial or tilting motion between the needle assembly and the drug cartridge is possible.

The needle assembly and the drug cartridge may be pre-assembled, e.g. by the manufacturer, and the needle system may thus be offered to the user in a pre-assembled state, e.g. in a sterile packaging which is easily removable to enable quick insertion into the injection device. The needle system may e.g. be designed to be front-loaded into a dedicated cartridge holder, or to be transversally clicked into a dedicated cartridge holder.

The skirt member and the needle hub member may be formed in one piece, whereby a particularly simple and cost-effective construction is obtained.

In some embodiments of the invention the head comprises a self-sealing septum sealing the outlet end portion, and an end cap for immobilising the self-sealing septum with respect to the generally cylindrical body. This allows for manufacturing of the needle assembly and the drug cartridge as separate entities.

In other embodiments of the invention the skirt member further comprises a pre-arranged self-sealing septum, and the rear needle portion transpierces a central portion of the self-sealing septum. The skirt cavity configuration thus corresponds to the head configuration of an open drug cartridge, and the outlet end portion will become sealed upon fitting of the skirt member on the head. Thereby, an end cap for immobilising the self-sealing septum is omitted, reducing the number of components needed for the needle system. It is noted that to provide an enhanced sealing effect the self-sealing septum may be slightly compressible, and in cases where the skirt cavity configuration corresponds to the head configuration of an open drug cartridge, this should be interpreted to include the skirt cavity configuration being slightly smaller than the head configuration to account for the compression of the self-sealing septum as the head enters the skirt cavity.

The skirt member may be configured to snap to the drug cartridge behind the head. In particular, the head may comprise a trailing rim and the skirt member may comprise a catch portion adapted to engage with the trailing rim. This will provide a very compact construction of the needle system.

The needle system may further comprise a removable plug member fitted tightly around a distal end of the front needle portion. Such a plug member will be able to serve a dual purpose of maintaining sterility of the section of the front needle portion that goes into the skin of the user and preventing leakage of the liquid substance from the drug cartridge through the injection needle. The removable plug member may be adapted to be slid along the distal end of the front needle portion.

While the above described needle system may be particularly suitable for use in a single shot type of injection device, where the drug cartridge is emptied and discarded after one injection action, it may be used in a multi-shot type of injection device capable of delivering a plurality of doses from the drug cartridge as well, if the distal end of the front needle portion is cleaned after each injection action. This could for example be accomplished by the removable plug member comprising a micro-bacterial growth inhibitor and the user remounting the removable plug member on the distal end of the front needle portion after each use of the injection device.

However, alternatively, the needle assembly may further comprise a, non-removable, plug member fitted tightly around a portion of the front needle portion, the plug member comprising a penetrable self-sealing front section and being displaceable, along a longitudinal axis of the injection needle, with respect to the needle hub between a forward plug position in which a distal end section of the front needle portion is housed within the plug member, proximally of the penetrable self-sealing front section, and a rearward plug position in which the distal end section is exposed. Since the plug member forms an integral part of the needle assembly the risk of the user losing it is eliminated. Consequently, the plug member is always available and positionable to prevent accidental needle stick injuries.

Also in this case the plug member may comprise a micro-bacterial growth inhibitor. In particular, the plug member may be made of a thermoplastic elastomer containing immobilised Zinc (Zi++) or immobilised silver (Ag++), as these ions are known to inhibit micro-bacterial growth. Since the plug member fits tightly around a portion of the front needle portion any micro-bacterial contaminants thereon will resultantly be neutralised. With the plug member in the forward plug position between use the distal end section is thereby kept in a biostatic environment between injections and the needle assembly is accordingly suitable for multiple use.

The plug member may further comprise a cylindrical plug body defining a solid plug portion with a cylindrical channel therein. In that case the cylindrical channel borders on the self-sealing front section and has a transversal channel dimension which is smaller than a transversal dimension of the injection needle.

The plug member may be axially displaceable with respect to the needle hub member by translation or by helical motion. In either case, the plug member may be biased towards the forward plug position, e.g. by a resilient element such as a spring.

Hence, the plug member may be displaced proximally from the forward plug position to the rearward plug position by the user placing the penetrable self-sealing front section on, and pressing the needle system against, the skin to insert the distal end section of the front needle portion and distally from the rearward plug position to the forward plug position by the resilient element upon removal of the injection needle from the skin.

In some embodiments of the invention the needle assembly further comprises means for displacing the plug member with respect to the needle hub member. For example, the needle assembly may further comprise a sleeve member rotatable relative to the needle hub member between a first angular position and a second angular position, and may be configured to cause a) a displacement of the plug member from the forward plug position to the rearward plug position in response to a rotation of the sleeve member from the first angular position to the second angular position and b) a displacement of the plug member from the rearward plug position to the forward plug position in response to a rotation of the sleeve member from the second angular position to the first angular position.

In a second aspect the invention provides a needle assembly for attachment to a drug cartridge comprising a generally cylindrical body being sealed proximally by a slidable piston and having an open outlet end portion defined by a neck and a head, the needle assembly comprising a needle hub member in which an injection needle is fixedly mounted such that a front needle portion extends in a distal direction therefrom and a rear needle portion extends in a proximal direction therefrom, a skirt member extending proximally from the needle hub member and defining a skirt cavity for reception of the head, and a self-sealing septum, wherein the rear needle portion extends into the skirt cavity through the self-sealing septum.

This allows for a combination of the needle assembly with the drug cartridge by insertion of the head into the skirt cavity, thereby producing a needle system for use with a drug injection device. The self-sealing septum may be arranged such that an insertion of the head into the skirt cavity seals the open outlet end portion around the rear needle portion. Specifically, the self-sealing septum may be arranged at a transversal wall connecting the needle hub member and the skirt member.

The needle assembly may further comprise means for retaining the head in the skirt cavity. In an exemplary embodiment thereof, the head has a head configuration, the skirt member comprises a radially inwardly protruding structure, such as e.g. a lip member, whereby a skirt cavity configuration is formed in the skirt member between the self-sealing septum and the radially inwardly protruding structure, and the skirt cavity configuration corresponds to the head configuration. Thereby, when the head is inserted into the skirt cavity the inwardly protruding structure holds the head firmly in place, providing a tight fitting of the needle assembly on the drug cartridge and sealing the open outlet end portion around the rear needle portion, which itself provides permanent fluid connection to the interior of the drug cartridge.

This allows for a simple and compact needle system which can be swiftly and easily inserted into an injection device, e.g. by sliding or snapping action, in a ready to use state, requiring no additional handling steps. Furthermore, the self-sealing septum can be affixed to the drug cartridge without the need for an additional end cap, reducing the number of components constituting the needle system. The needle assembly may further comprise a removable or non-removable plug member as described above.

The skirt cavity has a size and a shape, and the head has a size and a shape, and in the present context, the phrase “the skirt cavity configuration corresponds to the head configuration” means that the size and shape of the skirt cavity equals the size and shape of the head. However, for embodiments where the skirt member comprises a pre-arranged self-sealing septum the phrase also implicitly covers the skirt cavity configuration being slightly smaller than the head configuration such that the head compresses the self-sealing septum during entry into the skirt cavity to thereby increase the sealing capability of the self-sealing septum along a distal rim of the head.

In a third aspect the invention provides a method of manufacturing a needle system comprising a needle assembly and a drug cartridge, the method comprising i) providing a needle assembly comprising a needle hub member in which an injection needle is fixedly mounted such that a front needle portion extends in a distal direction therefrom and a rear needle portion extends in a proximal direction therefrom, a skirt member extending proximally from the needle hub member and defining a skirt cavity, and a self-sealing septum, wherein the rear needle portion extends into the skirt cavity through the self-sealing septum and the skirt member comprises a radially inwardly protruding structure such that a skirt cavity configuration is formed in the skirt member between the self-sealing septum and the radially inwardly protruding structure, ii) providing a drug cartridge comprising a generally cylindrical body being sealed proximally by a slidable piston and having an open outlet end portion defined by a neck and a head, wherein the head has a head configuration which corresponds to the skirt cavity configuration, and iii) mounting the skirt member on the head.

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.

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.

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.

In the figures like structures are mainly identified by like reference numerals.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

When/If 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.

FIG. 1is a longitudinal section view of a needle system according to a first exemplary embodiment of the invention, in the form of a needle assembly1and a drug cartridge30(of which only a distal portion is shown). The needle assembly1comprises a needle carrier4and an injection needle15. The injection needle15is fixated in a needle hub4.1, which forms a distal end portion of the needle carrier4, such that a front needle portion15fextends in a distal direction therefrom and a rear needle portion15rextends in a proximal direction therefrom. The front needle portion15fis provided with a sharpened front needle tip15tfor easy insertion through a skin barrier. A skirt4.2formed in one with the needle hub4.1has a circumferential interior lip4.7and is shaped provide a cavity4.9with a cavity configuration distally of the interior lip4.7. The rear needle portion15rextends into, and partly beyond, the cavity4.9.

The drug cartridge30comprises a generally cylindrical cartridge body31, with a neck32and a collar38at its distal most portion, defining an outlet end. The outlet end is sealed by a penetrable self-sealing septum36which is immobilised on the collar38by a ferrule34. The ferrule34is bent around, and thereby fastened behind, a proximal rim37of the collar38such that the collar38, the self-sealing septum36and the ferrule34together constitute a cartridge head33having a head configuration. The cartridge body31is proximally sealed by a slidable rubber piston (not shown), and the drug cartridge30thus comprises a confined chamber35which holds a liquid drug substance (not visible).

The cavity configuration corresponds to the head configuration, i.e. the cartridge head33has a size and a shape which exactly fits into the cavity4.9, such that when the skirt4.2is mounted on the cartridge head33the interior lip4.7snaps in behind the portion of the ferrule34which is bent around the proximal rim37. Thereby, a tight fitting of the needle assembly1on the drug cartridge30is obtained, which is both firm and stable, as no space for wriggling is present. Also, the rear needle portion15rpenetrates the self-sealing septum36and resides permanently in the chamber35. Hence, a fluid connection between the chamber35and the injection needle15is pre-established in the needle system which is consequently ready for injection upon insertion into a dedicated injection device (not shown).

The needle system is simple and made of few components which renders it inexpensive to produce. Furthermore, the needle assembly comprises no movable parts and the needle system is thus functionally very reliable.

A removable plug (not shown) can optionally be included to seal off the front needle portion15f. Such a plug could e.g. be made of an elastomeric material and structured to provide for easy removal by sliding motion along an exterior surface of the injection needle15.

FIG. 2is a longitudinal section view of a needle system according to a second exemplary embodiment of the invention, in the form of a needle assembly100and a drug cartridge130(of which only a distal portion is shown). The needle assembly100comprises a needle carrier104and an injection needle115. The injection needle115is fixated in a needle hub104.1, which forms a distal end portion of the needle carrier104, such that a front needle portion115fextends in a distal direction therefrom and a rear needle portion115rextends in a proximal direction therefrom. The front needle portion115fis provided with a sharpened front needle tip115tfor easy insertion through a skin barrier. A skirt104.2formed in one with the needle hub104.1has a circumferential interior lip104.7at a proximal end portion and a self-sealing septum136pre-arranged at a distal end portion. The skirt104.2thus defines a cavity104.9, between the self-sealing septum136and the interior lip104.7, which has a cavity configuration. The rear needle portion115rextends through the self-sealing septum136, into, and partly beyond, the cavity104.9.

The drug cartridge130comprises a generally cylindrical cartridge body131, with a neck132and a collar138at its distal most portion, defining an outlet end. The cartridge body131is proximally sealed by a slidable rubber piston (not shown), but in contrast to the first embodiment the outlet end is open and the drug cartridge130thus comprises an open chamber135which holds a liquid drug substance (not visible). In this case the collar138alone constitutes a cartridge head133having a head configuration.

The cavity configuration corresponds to the head configuration, i.e. the cartridge head133has a size and a shape which fits into the cavity104.9, such that when the skirt104.2is mounted on the cartridge head133the interior lip104.7snaps in behind the proximal rim137. Notably, in this case the fact that the cavity configuration corresponds to the head configuration actually comprises the cavity configuration being slightly smaller than the head configuration to account for any compressibility of the self-sealing septum136. Such compressibility will enhance the sealing of the drug cartridge130when the needle assembly100is mounted thereon, and the cartridge head133may therefore deform the self-sealing septum slightly upon entry into the cavity104.9.

A tight fitting of the needle assembly100on the drug cartridge130is thereby obtained, which is both firm and stable, as no space for wriggling is present. With this solution a ferrule for immobilising the self-sealing septum136can even be omitted, reducing the number of components of the needle system, because the skirt member104.2effectively takes over the function of the ferrule as the interior lip104.7snaps in behind the proximal rim137to maintain close contact between the cartridge head133and the self-sealing septum136.

Also, the rear needle portion115rresides permanently in the chamber135. Hence, a fluid connection between the chamber135and the injection needle115is pre-established in the needle system which is consequently ready for injection upon insertion into a dedicated injection device (not shown). The needle system is simple and made of few components which renders it inexpensive to produce. Furthermore, the needle assembly comprises no movable parts and the needle system is thus functionally very reliable.

A removable plug (not shown) can optionally be included to seal off the front needle portion115f. Such a plug could e.g. be made of an elastomeric material and structured to provide for easy removal by sliding motion along an exterior surface of the injection needle115.

FIG. 3is a perspective view of a needle assembly200for a needle system according to a third exemplary embodiment of the invention. The needle assembly200is shown in a pre-use state, sectioned by a 90° cut.

The needle assembly200comprises a needle carrier204and an injection needle215. The injection needle215is fixated in a needle hub204.1, which forms a distal portion of the needle carrier204, such that a front needle portion215fextends in a distal direction therefrom and a rear needle portion215rextends in a proximal direction therefrom. The front needle portion215fis provided with a sharpened front needle tip215tfor easy insertion through a skin barrier. A skirt204.2formed in one with the needle hub204.1has a circumferential interior lip204.7and is shaped provide a cavity204.9with a cavity configuration distally of the interior lip204.7. The rear needle portion215rextends into, and partly beyond, the cavity204.9.

At the junction between the needle hub204.1and the skirt204.2the needle carrier204is provided with a circumferential flange204.4which serves as a means for attachment of an outer track sleeve202. The outer track sleeve202is arranged concentrically about the needle hub204.1and has an interior rim202.8which is snapped behind the circumferential flange204.4. An inner track sleeve203is arranged within the outer track sleeve202and the two are both axially and rotationally interlocked, functioning as a single unit.

The needle assembly200further comprises a plug210fitted snugly around the front needle portion215f. The plug210is biostatic in that it is made of a thermoplastic elastomer containing immobilised Zinc (Zi++) for neutralising micro-bacterial contaminants and it has a self-sealing front section210.4and a pair of opposite plug arms210.5(only one is visible).

Extending distally from the junction between the needle hub204.1and the skirt204.2a pair of plug guides204.3(only one is visible) arranged opposite to one another form axial slots (not visible) in which the respective plug arms210.5are slidably received. The plug210is thus rotationally fixed but axially displaceable with respect to the needle carrier204.

A needle shield212is arranged about the plug210and is axially displaceable relative to the needle carrier204between a needle covering position, in which a distal end portion of the needle shield212extends beyond and thereby covers the front needle tip215t(as depicted inFIG. 3), and a needle exposing position in which the front needle tip215textends beyond the distal end portion of the needle shield212. The needle shield212, which is provided with a pair of diametrically opposite radial protrusions212.5(ref.FIGS. 7-9) is biased towards the needle covering position by a shield spring205.

FIG. 4is a longitudinal section view of the needle system, comprising the needle assembly200and a drug cartridge230, in a pre-assembled state. The drug cartridge230is identical to the drug cartridge30of the first embodiment of the present invention, i.e. it comprises a generally cylindrical cartridge body231, with a neck232and a collar238at its distal most portion, defining an outlet end. The outlet end is sealed by a penetrable self-sealing septum236which is immobilised on the collar238by a ferrule234. The ferrule234is bent around, and thereby fastened behind, a proximal rim237of the collar238such that the collar238, the self-sealing septum236and the ferrule234together constitute a cartridge head233having a head configuration. The cartridge body231is proximally sealed by a slidable rubber piston240, and the drug cartridge230thus comprises a confined chamber235which holds a liquid drug substance (not visible).

The cavity configuration corresponds to the head configuration, i.e. the cartridge head233has a size and a shape which exactly fits into the cavity204.9, such that when the skirt204.2is mounted on the cartridge head233the interior lip204.7snaps in behind the portion of the ferrule234which is bent around the proximal rim237. Thereby, a tight fitting of the needle assembly200on the drug cartridge230is obtained, which is both firm and stable, as no space for wriggling is present. Also, the rear needle portion215rpenetrates the self-sealing septum236and resides permanently in the chamber235. This is illustrated inFIG. 5which shows the needle system in an assembled state.

Hence, a fluid connection between the chamber235and the injection needle215is pre-established in the needle system which is consequently ready for injection upon insertion into a dedicated injection device250, as shown inFIG. 6. The injection device250comprises a housing251which accommodates a dose setting mechanism operable by rotation of a dose dial269and a dose expelling mechanism operable by depression of an injection button265. A scale drum259for indicating the size of a current set dose is viewable through a window in the housing251.

The injection system can be transversally snap fitted into a cartridge holder220(from the side opposite to the one visible in the figure) which is permanently attached to the housing251in axial extension thereof, and the injection device250can thereby by readied for use quickly and easily.

FIGS. 7-9show how the needle assembly200is operated during use of the injection device250. For the sake of clarity, the injection device250has been omitted from the figures but it is implicit that when the needle assembly is operated as described below the skirt204.2is mounted tightly on the cartridge head233and the rear needle portion215rresides in the chamber235. Also, the outer track sleeve202is depicted as a see-through component to allow presentation of interior track configurations (indicated with dotted lines) formed by interior geometries of the outer track sleeve202and an exterior shape of the inner track sleeve203.

InFIG. 7the needle assembly200is in a pre-use, or between-use, state where the needle shield212is maintained in the needle covering position by the shield spring205and the plug210covers the front needle tip215t. The injection needle215is thereby sealed off and no liquid can escape the chamber235. As mentioned, the outer track sleeve202and the inner track sleeve203together form interior track configurations. These serve to guide respective movements of the plug210and the needle sleeve212relative to the needle carrier204.

Specifically, the interior track configurations comprise a pair of diametrically opposite needle shield tracks291for sliding accommodation of the respective radial protrusions212.5, and a pair of diametrically opposite plug tracks (only one is visible) for sliding accommodation of the respective plug arms210.5. The needle shield tracks291extend axially along a longitudinal reference axis of the injection needle215, and each of the plug tracks comprise a circumferential track section293and a helical track section294. The circumferential track section293and the helical track section294are connected at a track narrowing formed by a bulb203.7. In the shown state of the needle assembly200the plug arms210.5rest in the respective circumferential track sections293and the radial protrusions212.5are positioned at respective distal ends of the needle shield tracks291. Both the plug210and the needle shield212are thereby axially locked with respect to the needle carrier204, safely covering the front needle tip215tand preventing accidental needle stick injuries.

In the following, with reference toFIGS. 8 and 9, only the movements of one plug arm210.5and one radial protrusion212.5are described, it being understood that the other plug arm210.5and the other radial protrusion212.5respectively undergo similar movements.

Firstly, the user grabs the needle carrier204with one hand and rotates the outer track sleeve202counter-clockwise (seen from a distal perspective) relative to the needle carrier204with the other hand, i.e. in the direction of the arrow shown inFIG. 8. By the user initially applying a relatively high torque the plug arm210.5elastically deforms as it passes the bulb203.7and enters the helical track section294. The relatively high torque needed to move the plug arm210.5out of the circumferential track section293is advantageous from a safety perspective as it reduces the risk of premature release of the plug210and the needle shield212, which could otherwise occur accidentally if e.g. the injection device250lying in a purse or bag were subjected to impact from neighbouring objects.

Continuing the rotation of the outer track sleeve202relative to the needle carrier204, now applying a lower torque, the user forces the plug arm210.5down the helical track section294, and thereby proximally in the axial slots formed by the plug guides204.3. The plug210is thus pulled proximally, eventually exposing the front needle portion215fwithin the needle shield212.

When the plug arm210.5reaches a proximal end of the helical track section294the user places the needle shield212on a skin surface and presses the needle carrier204towards the body. A proximally directed force from the skin is thereby applied to the needle shield212which consequently slides from the needle covering shield position to the needle exposing shield position as the radial protrusion212.5travels the axial needle shield track291against the force from the shield spring205. This is shown inFIG. 9. The front needle portion15fthus enters the skin and the user can perform an injection of a set dose of drug by operation of the injection button265.

Upon completion of the injection the user pulls the front needle portion215fout of the skin, whereby the shield spring205returns the needle shield212to the needle covering shield position, as the radial protrusion212.5return in the axial needle shield track291. Subsequently, the user rotates the outer track sleeve202clockwise relative to the needle carrier204to return the plug arm210.5along the helical track section294to the circumferential track section293. Again, a relatively high torque is needed for the plug arm210.5to pass the bulb203.7, but once the plug arm210.5is re-seated in the circumferential track section293the needle assembly200is safely locked, preventing any accidental needle stick injuries. This corresponds to the state shown inFIG. 7.

Since the plug210comprises a micro-bacterial growth inhibitor the needle system is suitable for multiple use, as the front needle portion215fhoused in the plug210is cleaned between injection actions. In particular, a needle system is thereby provided where the use time of the needle assembly200equals that of the drug cartridge230, such that the user only needs to change the needle assembly200when the drug cartridge230is exhausted. This markedly reduces the number of handling steps which the user must go through over time to prepare for injections with the injection device250.

FIGS. 10 and 11are longitudinal section views of a needle system according to a fourth exemplary embodiment of the invention, comprising a needle assembly300and a drug cartridge330, whereFIG. 10shows the needle system in a pre-assembled state andFIG. 11shows the needle system in an assembled state.

The needle assembly300is substantially identical to the needle assembly200described above in connection with the third embodiment of the invention, i.e. it comprises a needle carrier304with a needle hub304.1and a skirt304.2, the needle hub304.1carrying an injection needle315with a rear needle portion315r, and the skirt304.2being provided with an interior lip304.7, a front needle portion315f, and a front needle tip315t, an outer track sleeve302, an inner track sleeve303, a plug310with a self-sealing front section310.4and a pair of plug arms310.5, and a needle shield312which is biased distally by a shield spring305.

The only structural difference between the needle assembly300and the needle assembly200is the provision of a self-sealing septum336, pre-arranged within the skirt304.2just proximally of the needle hub304.1. The self-sealing septum336is permanently transpierced by the rear needle portion315rbut forms a sealing lip around a portion thereof. The skirt304.2thus defines a cavity304.9, between the self-sealing septum336and the interior lip304.7, which has a cavity configuration.

The drug cartridge330is identical to the drug cartridge130of the second embodiment of the present invention, i.e. it comprises a generally cylindrical cartridge body331, with a neck332and a collar338at its distal most portion, defining an outlet end. The cartridge body331is proximally sealed by a slidable rubber piston340, but in contrast to the former embodiment the outlet end is open and the drug cartridge330thus comprises an open chamber335which holds a liquid drug substance (not visible). In this case the collar338alone constitutes a cartridge head333having a head configuration.

The cavity configuration corresponds to the head configuration, i.e. the cartridge head333has a size and a shape which exactly fits into the cavity304.9, such that when the skirt304.2is mounted on the cartridge head333, as shown onFIG. 11, the interior lip304.7snaps in behind the proximal rim337. Notably, in this case the fact that the cavity configuration corresponds to the head configuration actually comprises the cavity configuration being slightly smaller than the head configuration to account for any compressibility of the self-sealing septum336. Such compressibility will enhance the sealing of the drug cartridge330when the needle assembly300is mounted thereon, and the cartridge head333may therefore deform the self-sealing septum slightly upon entry into the cavity304.9.

A tight fitting of the needle assembly300on the drug cartridge330is thereby obtained, which is both firm and stable, as no space for wriggling is present. With this solution a ferrule for immobilising the self-sealing septum336can be omitted, reducing the number of components of the needle system compared to that of the third embodiment of the invention, because the skirt member304.2effectively takes over the function of the ferrule as the interior lip304.7snaps in behind the proximal rim337to maintain close contact between the cartridge head333and the self-sealing septum336.

Also, the rear needle portion315rresides permanently in the chamber335. Hence, a fluid connection between the chamber335and the injection needle315is pre-established in the needle system which is consequently ready for injection upon insertion into a dedicated injection device, e.g. like the one shown inFIG. 6. In the assembled state of the needle system the needle assembly300is operated identically to the needle assembly200described above.