Patent Description:
Typically, an injection solution to be administered to a patient for medical treatment is stored within a syringe having a container for accommodating the injection solution and a plunger which is displaceable relative to the container in order to expel the injection solution from the container. In case the medical treatment plan for a patient provides for the administration of a dose of the injection solution which corresponds to the filling volume of the syringe or in case the dosage of the injection solution is of minor importance for the desired therapeutic effect, the injection solution may be administered to the patient directly from the syringe. However, in case the medical treatment plan for a patient requires the administration of a dose of the injection solution which differs from the filling volume of the syringe and/or in case an accurate dosage of the injection solution is necessary, the injection solution, prior to administration, may be transferred from the syringe to an injection device which finally is used to inject the desired dose of the injection solution into the patient.

<CIT> describes an injection device for injection of set doses of medicine from a cartridge. The injection device comprises a housing, a threaded piston rod which is linearly displaceable in the housing and a displaceable nut that moves relative to the housing and engages the thread of the piston rod so that the nut can screw along the thread of the piston rod. The displacement of the nut along the piston rod defines a quantity of medication to be injected by the injection device.

<CIT> describes a syringe for dispensing a fluid. The syringe includes a barrel, a plunger being adapted to move within the plunger and a rotational element adapted to rotate about a longitudinal axis of the syringe.

<CIT> describes a device for medicament delivery with syringe-like usability having a restraining mechanism.

<CIT> describes a syringe including a barrel with discharge end defining a discharge passage, a plunger being adapted to move axially within the barrel, wherein the plunger includes a control arm that includes a first and second releasable stop element.

<CIT> describes a fluid connector for selectively establishing fluid communication between a first medical container and a second medical container is provided.

The invention is directed at the object of providing an injection device which allows the accurate and reliable administration of a micro dose of an injection solution to a patient. Further, the invention is directed at the object of providing an injection solution transferring system for transferring an injection solution from a syringe to an injection device of this kind.

This object is addressed by an injection device as defined in claim <NUM> and an injection solution transferring system as defined in claim <NUM>.

An injection device comprises an injection solution receptacle. The injection solution receptacle and the protective outer barrel can be made from any suitable material, or combination of materials, including a plastic material or from glass. Suitable plastic material comprises for example cycloolefin polymer or cycloolefin copolymer. An example of a glass material may be borosilicate glass. Preferably, the glass material is tungsten-free. In one embodiment the injection solution receptacle may be uncoated. Uncoated means that the injection solution receptacle does not contain any other material other than the material of which the injection solution receptacle is made of. Alternatively, the injection solution receptacle may comprise an internal coating. Internal coating means a coating on the inner side of the injection solution receptacle which is in contact with the injection solution. Examples of such an internal coating comprise silicone coating or a fluorocarbon film made from a modified ethylene-tetrafluoroethylene copolymer. The injection solution receptacle may be silicone free, or substantially silicone free, or may comprise a low level of silicone as lubricant. Preferably, the injection solution receptacle is made of a sterile plastic material. Preferably, the injection solution receptacle is made of a sterile plastic material. Preferably, the injection solution receptacle does not comprise an internal coating. In one embodiment, the injection solution receptacle may meet USP789.

The injection solution receptacle may be designed in the form of an inner injection solution receptacle which is contained within a protective outer barrel. An injection solution receptacle designed in the form of an inner injection solution receptacle may be formed integral with the protective outer barrel. In the region of its proximal end, the protective outer barrel may be provided with a flange element which may serve to connect the protective outer barrel and the inner injection solution receptacle to a housing of the injection device. For example, the housing of the injection device may comprise a suitably shaped and dimensioned receptacle for receiving the flange element and hence fastening the protective outer barrel and the inner injection solution receptacle to the housing.

A distal end of the injection solution receptacle of the injection device may be provided with a male part of a Luer taper which is adapted to interact with a female part of a Luer taper. The female part of a Luer taper may, for example, be provided on a connecting port of an adapter element of a filling adapter which may be used to connect the injection device to a syringe containing an injection solution to be transferred from the syringe to the injection solution receptacle of the injection device. By means of the Luer taper, a fluid-tight connection can be established between the distal end of the injection solution receptacle of the injection device and the adapter element of the filling adapter in a simple manner. The outer barrel of the injection device, in the region of its distal end, may be provided with a Luer thread which is adapted to interact with a complementary Luer thread provided at the second connecting port of the adapter element of the filling adapter, in particular in the region of its outer circumference. As a result, also a reliable connection between the outer barrel of the injection device and the adapter element of the filling adapter can be effected.

The injection device further comprises a plunger. The plunger may be made of polycarbonate. At least a portion of the plunger is slidably received within the injection solution receptacle. The plunger is displaceable relative to the injection solution receptacle in a distal direction along a longitudinal axis of the plunger in order to expel an injection solution contained in the injection solution receptacle from the injection solution receptacle. At its proximal end which may protrude from the injection solution receptacle in a proximal direction, the plunger may carry an actuation button which may be depressed by a user in order to displace the plunger relative to the injection solution receptacle in the distal direction along the longitudinal axis of the plunger. At its distal end, the plunger may be provided with a tip element which may be attached to a plunger rod. A coupling between the plunger rod and the tip element may be effected, for example, by the interaction of a tip barb provided at a distal end of the plunger rod with a barb receptacle of the tip element. Further, the tip element may be provided with a sealing element which, for example, may be provided in the region of an outer circumferential surface of the tip element and which sealingly interacts with an inner circumferential surface of the injection solution receptacle.

The injection device further comprises a first plunger stop mechanism which is adapted to stop a displacement of the plunger relative to the injection solution receptacle in the distal direction at a first dosing position. Further, the injection device comprises a second plunger stop mechanism which is adapted to stop a displacement of the plunger relative to the injection solution receptacle from the first dosing position in the distal direction at a second dosing position. The first and the second dosing position of the plunger are selected in such a manner that the plunger, upon being displaced relative to the injection solution receptacle between the first and the second dosing position is adapted to expel a desired dose of the injection solution contained in the injection solution receptacle from the injection solution receptacle.

After filling the injection solution receptacle with the injection solution to be administered to a patient, a user of the injection device can expel excess injection solution from the injection solution receptacle by displacing the plunger relative to the injection solution receptacle in the distal direction until the plunger reaches the first dosing position. Upon reaching the first dosing position, the first plunger stop mechanism stops further displacement of the plunger in the distal direction. Consequently, the user is prevented from expelling too much injection solution from the injection solution receptacle. The residual injection solution contained in the injection solution receptacle can then be administered to a patient by further displacing the plunger in the distal direction until the plunger reaches the second dosing position. Upon reaching the second dosing position, the second plunger stop mechanism stops further displacement of the plunger in the distal direction and hence prevents that too much injection solution is administered to the patient.

The injection device allows the accurate and reliable administration of a micro dose of an injection solution to a patient. Further, the injection device can easily and comfortably be handled by a user. The injection device therefore is particularly suitable for treating a paediatric patient. In particular, the injection device may be designed in the form of an ophthalmic injection device for intraocular use.

In one embodiment, the injection device is filled with a dosage volume (i.e. the volume of injection solution intended for delivery to the patient) of between about <NUM>µl to about <NUM>µl, preferably between about <NUM>µl to about <NUM>µl, of an injection solution. In a preferred embodiment, the injection device is filled with a dosage volume of <NUM>µl, or <NUM>µl, or <NUM>µl, or <NUM>µl of an injection solution.

The injection device may be filled with any injection solution, for example an injectable medicament. In one embodiment, the injection device is filled with an injectable medicament comprising an active ingredient suitable for the treatment of an ocular disease. Examples of such ocular diseases include retinopathy of prematurity, geographic atrophy, glaucoma, choroidal neovascularisation, age-related macular degeneration (both wet and dry forms), macular edema secondary to retinal vein occlusion (RVO) including both branch RVO (bRVO) and central RVO (cRVO), choroidal neovascularisation secondary to pathologic myopia (PM), diabetic macular edema (DME), diabetic retinopathy, retinitis pigmentosa, Leber's congential aumaurosis, Bietti crystalline dystrophy, and proliferative retinopathy. In one embodiment, the medicament comprises a biologic active. The biologic active may be an antibody (or fragment thereof), a non-antibody protein, nucleic acids for gene therapy or cellular material for cell therapy. In one embodiment, the medicament comprises a VEGF antagonist. Suitable VEGF antagonists include ranibizumab (Lucentis™), bevacizumab (Avastin™), brolucizumab (also known as RTH258), aflibercept (Eylea™, also known as VEGF-Trap Eye), conbercept (KH902 from Chengdu Kanghong Biotechnologies Co. Ltd, described as FP3 in <CIT>) and the related glycoform KH906 or pazopanib (from GlaxoSmithKline).

In a preferred embodiment, the injection device is filled with <NUM> or <NUM> ranibizumab in <NUM>µl injection solution. In a most preferred embodiment, the injection device is filled with <NUM>µl of ranibizumab (<NUM>) and used for the treatment of retinopathy of prematurity.

In a preferred embodiment of the injection device, the first plunger stop mechanism comprises a dosing element which is attached to the plunger and which is adapted to abut against a first dosing surface provided on a housing element. Alternatively or additionally thereto, the second plunger stop mechanism may comprise a dosing element which is attached to the plunger and which is adapted to abut against a second dosing surface provided on a housing element.

Preferably, the dosing element of the first and/or the second plunger stop mechanism is formed integral with the plunger. For example, the dosing element may be designed in the form of a rib which may protrude from a surface of an actuation button of the plunger in the direction of the inner solution receptacle. Basically, it is conceivable that the injection device comprises a first dosing element associated to the first plunger stop mechanism and a second dosing element associated to the second plunger stop mechanism. Preferably, however, the injection device comprises only one dosing element which is attached to the plunger and which is associated to both the first and the second plunger stop mechanism. A single dosing element may be adapted, upon movement of the plunger in the distal direction, to first abut against the first dosing surface when the plunger reaches the first dosing position and then, upon further movement of the plunger from the first dosing position in the distal direction, against the second dosing surface when the plunger reaches the second dosing position.

The first and the second dosing surface are formed on a first housing element, i.e. on the same housing element of the injection device. The first and the second dosing surface preferably extend substantially parallel to each other, wherein the second dosing surface may be arranged parallel offset relative to the first dosing surface in the distal direction. A distance between the first and the second dosing surface in the distal direction may correspond to a desired travel distance of the plunger in the distal direction between the first and the second dosing position. Hence, by suitably arranging the first and the second dosing surface, the desired plunger displacement between the first and the second dosing position and hence the desired injection solution dose to be expelled from the injection solution receptacle upon displacing the plunger from the first to the second dosing position can be set. The first and the second dosing surface may extend substantially parallel to an abutting surface of the dosing element. For example, the first and the second dosing surface as well as the abutting surface of the dosing element may extend substantially perpendicular to the longitudinal axis of the plunger.

The first plunger stop mechanism may be designed in such a manner that it provides a resistance force that is adapted to stop the displacement of the plunger at the first dosing position, but that can be overcome, for example by increasing the actuation force acting on the plunger. In a particular preferred embodiment of the injection device, the first plunger stop mechanism, however, is adapted to provide a hard stop for the plunger, i.e. is adapted to prevent the plunger from being displaced relative to the injection solution receptacle from the first dosing position in the distal direction without damaging the first plunger stop mechanism. In particular in case the first plunger stop mechanism is designed as a hard stop for the plunger, the injection device preferably further comprises a plunger releasing mechanism which is adapted to deactivate the first plunger stop mechanism in order to release the plunger and to thus allow a displacement of the plunger relative to the injection solution receptacle from the first dosing position in the distal direction, i.e. in the direction of the second dosing position.

Also the second plunger stop mechanism may be designed in such a manner that it provides a resistance force that is adapted to stop the displacement of the plunger at the second dosing position, but that can be overcome, for example by increasing the actuation force acting on the plunger. In a particular preferred embodiment, the second plunger stop mechanism, however, is adapted to provide a hard stop for the plunger, i.e. is adapted to prevent the plunger from being displaced relative to the injection solution receptacle from the second dosing position in the distal direction without damaging the second plunger stop mechanism. The dose of the injection solution to be administered to a patient can then be set in a particularly accurate manner.

Preferably, the plunger releasing mechanism is adapted to allow a movement of at least one of the dosing element and the first dosing surface in order to disengage the dosing element from the first dosing surface. The movement of the dosing element and/or the first dosing surface may be manually induced by a user of the injection device. In a particular preferred embodiment of the injection device, it is sufficient for a user to move only the first dosing surface for disengaging the dosing element from the first dosing surface. As a result, it is not necessary for the user to induce a movement of the plunger for activating the plunger releasing mechanism. For example, only the housing element carrying the first dosing surface may be moved for activating the plunger releasing mechanism, whereas the plunger may remain in its position, which simplifies the use of the injection device.

The plunger releasing mechanism may be adapted to allow a rotational movement of at least one of the dosing element and the first dosing surface in order to disengage the dosing element from the first dosing surface. For example, the plunger releasing mechanism may be activatable by a manually induced rotation of the plunger and/or the first dosing surface. In particular, the plunger releasing mechanism may be adapted to allow a rotational movement of the housing element carrying the first dosing surface for activating the plunger releasing mechanism. The actuation of a rotational movement of the plunger and/or the first dosing surface and in particular of only the first dosing surface can easily be distinguished by a user from the pressing actuation of the plunger so as to move the plunger in the distal direction. As a result, the use of the injection device is further simplified.

In a preferred embodiment of the injection device, the first and the second dosing surface are arranged offset relative to each other, for example on different or the same housing element(s), in a circumferential direction of the plunger. The plunger releasing mechanism then may be adapted to displace the first and the second dosing surface in the circumferential direction of the plunger, in order to disengage the dosing element from the first dosing surface and to simultaneously align the second dosing surface with the dosing element, such that the dosing element abuts against the second dosing surface, when the plunger, upon being displaced relative to the injection solution receptacle from the first dosing position in the distal direction, reaches the second dosing position. Such a design of the plunger releasing mechanism allows a particularly simple and reliable handling of the injection device.

The first and the second dosing surface are formed on the first housing element which is rotatable relative to the plunger. In case the first and the second dosing surface are arranged offset relative to each other on the first housing element in a circumferential direction of the plunger, disengagement of the dosing element from the first dosing surface and simultaneous arrangement of the second dosing surface in a position wherein the second dosing surface is ready for engagement with the dosing element, when the plunger, upon being displaced from the first dosing position in the distal direction, reaches the second dosing position can easily be achieved by simply rotating the first housing element by a suitable rotation amount.

The second dosing surface may be defined by a bottom surface of a recess formed in the first dosing surface. Preferably, the recess is designed, i.e. shaped and dimensioned, so as to allow the dosing element to be received in the recess. When the plunger is arranged in its first dosing position and the dosing element abuts against the first dosing surface, the recess defined in the first dosing surface, via a rotational movement of the first housing element, can be brought into alignment with the dosing element. As a result, the dosing element is disengaged from the first dosing surface and the plunger can further be displaced in the distal direction until the dosing element is received in the recess and the abutting surface formed on the dosing element abuts against the second dosing surface defined by the bottom surface of the recess. A depth of the recess which defines the distance between the first and the second dosing surface in the distal direction may correspond to the desired travel distance of the plunger in the distal direction between the first and the second dosing position.

The first housing element which carries the first and the second dosing surface, in particular in the region of an outer surface, may be provided with a gripping structure. For example, the gripping structure may be designed in the form of a gripping rib array with individual gripping ribs extending, in dependence on the shape of the outer surface of the first housing element, substantially in a direction along the longitudinal axis of the plunger. The gripping structure simplifies the handling of the plunger releasing mechanism.

Preferably, the plunger releasing mechanism comprises a marker system which is adapted to indicate an activation of the plunger releasing mechanism. The marker system may, for example, comprise a first marker element which is provided on the first housing element which carries the first and the second dosing surface, for example in the region of an outer surface thereof. The marker system may further comprise a second marker element which is provided on a second housing element of the injection device, in particular in the region of an outer surface thereof. The first and the second marker element may be arranged on the first and the second housing element in such a position that they are positioned offset relative to each other, for example in a circumferential direction of the plunger, when the plunger releasing mechanism is not activated, but positioned in alignment with each other, when the plunger releasing mechanism is activated. The marker system provides a user with guidance information on how to activate the plunger release mechanism and hence simplifies the handling of the injection device.

The injection device preferably further comprises an activation mechanism which is adapted to prevent an activation of the plunger releasing mechanism unless the plunger is arranged at the first dosing position and which is adapted to allow an activation of the plunger releasing mechanism when the plunger is arranged at the first dosing position. The activation mechanism may be adapted to prevent a movement of the dosing element and/or the first dosing surface relative to each other unless the plunger is arranged at the first dosing position. In particular, the activation mechanism may be adapted to prevent a rotation of the first housing element carrying the first and the second dosing surface relative to the plunger carrying the dosing element unless the plunger is arranged at the first dosing position.

In a preferred embodiment of the injection device, the activation mechanism comprises a guiding channel which is provided on a circumferential surface of the plunger, which extends along the longitudinal axis of the plunger and which receives a guiding element provided on a housing element in such a manner that the guiding channel, upon displacement of the plunger relative to the injection solution receptacle, is displaced relative to the guiding element. An interaction between the guiding element and opposing side surfaces of the guiding channel may prevent a rotation of the plunger and the housing element relative to each other. When the activation mechanism comprises a guiding channel extending along the longitudinal axis of the plunger and a corresponding guiding element, the activation mechanism fulfills the double function to provide for a guided displacement of the plunger in the direction of its longitudinal axis on the one hand and to simultaneously prevent an unintentional deactivation of the first plunger stop mechanism when the plunger is not arranged at the first dosing position. The guiding element may be provided on the first housing element which carries the first dosing surface and preferably also the second dosing surface.

The activation mechanism may further comprise an activation channel which branches off from the guiding channel. For example, the activation channel may extend in a circumferential direction of the plunger substantially perpendicular to the guiding channel. The activation channel preferably is adapted to receive the guiding element when the plunger is arranged at the first dosing position and the first housing element which carries the guiding element and preferably also the first and the second dosing surface is rotated relative to the plunger. With such a design of the activation mechanism, the first dosing position of the plunger is defined by the position of the activation channel along the longitudinal axis of the plunger.

The second dosing surface may be defined by a bottom surface of a recess formed in the first dosing surface. Preferably, the recess is designed, i.e. shaped and dimensioned, so as to allow the dosing element to be received in the recess. When the plunger is arranged in its first dosing position and the dosing element abuts against the first dosing surface, the recess defined in the first dosing surface, via a rotational movement of the first housing element, can be brought into alignment with the dosing element. As a result, the dosing element is disengaged from the first dosing surface and the plunger can further be displaced in the distal direction until the dosing element is received in the recess and the abutting surface formed on the dosing element abuts against the second dosing surface defined by the bottom surface of the recess.

The plunger release mechanism may further comprise a locking arrangement which is adapted to lock the first dosing surface in its position relative to the dosing element after the first dosing surface has been moved relative to the dosing element in order to become disengaged from the dosing element. The locking arrangement thus allows the plunger release mechanism to be used only once for deactivating the first plunger stop mechanism. As a result, reuse of the injection device is reliably prevented.

The locking arrangement may comprise a resilient locking clip which is adapted to be resiliently urged out of a rest position by the interaction with a locking element when the first dosing surface is moved relative to the dosing element so as to become disengaged from the dosing element. For example, the resilient locking clip may be provided on the second housing element, whereas the locking element may be provided on the first housing element which carries the first dosing surface and optionally also the second dosing surface. The resilient locking clip then may be resiliently deformed when the first housing element is rotated relative to the second housing element. The locking clip preferably further is adapted to deform back into its rest position after completion of the movement of the first dosing surface and to interact with the locking element so as to lock the first dosing surface in its position relative to the dosing element. In particular, the locking clip may interact with the locking element so as to prevent a counter rotation of the first housing element relative to the second housing element and the plunger, after the first housing element has been rotated once in order to disengage the first dosing surface from the dosing element and to align the second dosing surface with the dosing element.

The injection device further comprise a limiting mechanism which is adapted to limit a movement of the dosing element and/or both the first dosing surface and the second dosing surface for disengaging the dosing element from the first dosing surface and for aligning the dosing element with the second dosing surface. The limiting mechanism prevents a user of the injection device from moving the dosing element and the first and the second dosing surface relative to each other in an excessive manner. Further, the limiting mechanism provides an haptic feedback to the user that the dosing element is properly disengaged from the first dosing surface and aligned with the second dosing surface, i.e. that the first plunger stop mechanism has been deactivated.

The limiting mechanism comprises a first limiting element which is provided on the first housing element carrying the first and the second dosing surface. Further, the limiting mechanism comprises a second limiting element which is provided on a second housing element. The second housing element may be adapted to remain stationary when the first housing element is moved, in particular rotated, for deactivating the first plunger stop mechanism. The first limiting element is adapted to abut against the second limiting element when the dosing element is disengaged from the first dosing surface and aligned with the second dosing surface.

In case the injection device comprises an above-described activation mechanism with an activation channel and a guiding element formed on the first housing element which also carries the first and the second dosing surface, the movement of the first dosing surface relative to the dosing element attached to the plunger may also be limited by an interaction between the guiding element and an end face of the activation channel which may act as an abutting surface for the guiding element when the first housing element, after being rotated relative to the plunger, has reached a position wherein the dosing element is disengaged from the first dosing surface and aligned with the second dosing surface.

The injection device may further comprise a first drag mechanism adapted to exert a retaining force which retains the plunger in its current position relative to the injection solution receptacle. The first drag mechanism thus prevents an unintentional displacement of the plunger relative to the injection solution receptacle - in other words, due to the presence of the first drag mechanism, active manual actuation, for example by the application of a pressing force, is necessary for displacing the plunger relative to the injection solution receptacle. The first drag mechanism may comprise a resilient drag element which may, for example, be provided on the second housing element. The resilient drag element may be adapted to exert a resilient retaining force on the plunger, i.e. the resilient drag element may be resiliently urged out of a rest position into a biasing position by an interaction with the plunger and, due to its resiliency, may apply a resilient reaction force on the plunger which retains the plunger in its current position. The resilient drag element may in particular interact with a drag rib which is provided on the outer circumferential surface of the plunger and which extends substantially parallel to the longitudinal axis of the plunger.

Alternatively or additionally thereto, the injection device may also comprise a second drag mechanism adapted to exert a retaining force which retains the first housing element in its current position, i.e. which retains the first housing element in its position relative to the second housing element. The second drag mechanism thus prevents an unintentional displacement of the first housing element relative to the second housing element and hence an unintentional deactivation of the first plunger stop mechanism. The second drag mechanism may comprise a friction element which is provided on the first limiting element of the limiting mechanism and which is adapted to interact with a retaining element of the second housing element.

The injection device may further comprise a plunger positioning mechanism which is adapted to prevent a displacement of the plunger relative to the injection solution receptacle from a proximal end position in a proximal direction. The plunger positioning mechanism may, for example, comprise a distal end face of the guiding channel which is provided in the circumferential surface of the plunger. An interaction between the distal end face of the guiding channel and the guiding element received therein then may define the proximal end position of the plunger.

The injection device may be pre-filled with a compound, via a pre-filled syringe (<NUM>), a vial, or other reservoir.

In one embodiment, the injection device (whether pre-filled or not) is sterilized and provided in a sealed package. In one embodiment, the injection device is pre-filled with a suitable injection solution and terminally sterilized. Such a terminal sterilization step may comprise known techniques such as ethylene oxide sterilization or hydrogen peroxide sterilization.

A preferred embodiment of the invention now will be described in greater detail with reference to the appended schematic drawings, wherein:.

<FIG> and <FIG> show an injection solution transferring system <NUM> which comprises an injection device <NUM> and a filling adapter <NUM>. The filling adapter <NUM> serves to connect a syringe <NUM> containing an injection solution to the injection device <NUM> for filling the injection device <NUM> with the injection solution from the syringe <NUM> as shown in <FIG> and as will be described further below. The syringe <NUM> is designed in the form of a pre-filled syringe <NUM> which contains an injection solution for intraocular use.

The filling adapter <NUM> comprises a hollow sleeve <NUM> which is shown in greater detail in <FIG>. The hollow sleeve <NUM> made of a coloured plastic material, for example Polycarbonate/Acrylnitril Butadien Styrol (PC-ABS) and is provided with an inner lumen which is dimensioned so as to allow the insertion of at least a distal portion of the syringe <NUM> at one end and of at least a distal portion of the injection device <NUM> at an opposing end. In the exemplary embodiment of a filling adapter <NUM> shown in the drawings, the hollow sleeve <NUM> has a substantially circular hollow cylindrical shape and the lumen extending therethrough has a substantially circular cross-sectional shape.

The filling adapter <NUM> further comprises an adapter element <NUM> which is accommodated within the hollow sleeve <NUM> and which comprises a first connecting port <NUM> and a second connecting port <NUM>. The adapter element <NUM> may, for example, be made of polycarbonate and is shown in greater detail in <FIG>. As shown in particular in <FIG>, the adapter element <NUM> is provided with two retention shoulders <NUM> which protrude from an outer circumferential surface of the adapter element <NUM> in opposing directions. Each retention shoulder <NUM> interacts with a pair of complementary crush ribs <NUM> protruding from an inner circumferential surface of the hollow sleeve <NUM> in order to fix the adapter element <NUM> in its position within the hollow sleeve <NUM>. The retention shoulders <NUM> and the complementary crush ribs <NUM> create an interference fit so as to reliably fix the adapter element <NUM> in its position within the hollow sleeve <NUM>.

The first connecting port <NUM> of the adapter element <NUM> is adapted to be connected to the syringe <NUM>, i.e. a distal end of the syringe <NUM>, when the filling adapter <NUM> is connected to the syringe <NUM> as shown in <FIG>. As becomes apparent in particular from <FIG>, the first connecting port <NUM> of the adapter element <NUM> forms a female Luer taper <NUM> which is adapted to interact with a male Luer taper provided at the distal end of the syringe <NUM> in order to establish a fluid-tight connection between the syringe <NUM> and the adapter element <NUM>. The second connecting port <NUM> of the adapter element <NUM> is adapted to be connected to the injection device <NUM>.

The adapter element <NUM> is provided with a through-opening <NUM> extending therethrough in a direction substantially parallel to a longitudinal axis L1 of the filling adapter <NUM>, see in particular <FIG>. A cannula <NUM> protrudes from the second connecting port <NUM> of the adapter element <NUM> and is arranged in fluid communication with the through-opening <NUM> extending through the adapter element <NUM>, see in particular <FIG>. The cannula <NUM> is made of stainless steel. The hollow sleeve <NUM> of the filling adapter <NUM>, however, extends beyond a distal tip of the cannula <NUM>. As a result, a user is protected from the cannula <NUM> during handling of the filling adapter <NUM>.

The adapter element <NUM> serves to establish a fluid connection between the syringe <NUM> and the injection device <NUM>, i.e. when the syringe <NUM> is connected to the first connecting port <NUM> of the adapter element <NUM> and the injection device <NUM> is connected to the second connecting port <NUM> of the adapter element <NUM> as shown in <FIG>, injection solution contained in the syringe <NUM> may be transferred into the injection device <NUM> by manually pushing a plunger <NUM> of the syringe <NUM> as shown in <FIG> so as to expel the injection solution from the distal end of the syringe <NUM> into the through-opening <NUM> provided in the adapter element <NUM> and further via the cannula <NUM> into an injection solution receptacle <NUM> of the injection device <NUM>.

As becomes apparent in particular from <FIG>, the hollow sleeve <NUM> of the filling adapter <NUM>, in the region of a first end which faces the syringe <NUM> when the syringe <NUM> is brought into engagement with the first connecting port <NUM> of the adapter element <NUM>, the hollow sleeve <NUM> comprises at least one resilient clip <NUM> which is adapted to engage with a collar <NUM> of the syringe <NUM> when the syringe <NUM> is brought into engagement with the first connecting port <NUM> of the adapter element <NUM>, see <FIG>. In the embodiment of a hollow sleeve <NUM> shown in the drawings, the hollow sleeve <NUM> is provided with two resilient clips <NUM>. Each resilient clip <NUM> comprises an arm <NUM> which extends in a recess <NUM> provided in the hollow sleeve <NUM> substantially parallel to the longitudinal axis L1 of the filling adapter <NUM> in the direction of the first end of the hollow sleeve <NUM>. A latching nose <NUM> protrudes from an inner surface of the arm <NUM> in the region of a free end of the arm <NUM>.

When the syringe <NUM> is brought into engagement with the first connecting port <NUM>, due to the interaction with the collar <NUM> of the syringe <NUM>, the resilient clip <NUM> is bent outwards. However, as soon as the syringe <NUM> has reached its final position with respect to the adapter element <NUM>, i.e. when the distal tip of the syringe <NUM> is connected to the first connecting port <NUM> of the adapter element <NUM> and the syringe <NUM> assumes the position relative to the hollow sleeve <NUM> which is shown in <FIG>, the resilient clip <NUM> resumes its original position substantially parallel to the longitudinal axis L1 of the filling adapter <NUM> such that the latching nose <NUM> comes into engagement with an end face of the collar <NUM> of the syringe <NUM>. As a result, the syringe <NUM> is firmly connected to the hollow sleeve <NUM>.

In the region of its first end, the hollow sleeve <NUM> at its outer circumferential surface is provided with two first gripping structures <NUM> each of which is designed in the form of a nub array. The first gripping structure simplifies the handling of the filling adapter <NUM> during connecting the syringe <NUM> to the filling adapter <NUM>. Further, the hollow sleeve <NUM>, in the region of its first end and the region of a second end which faces the injection device <NUM> when the injection device <NUM> is brought into engagement with the second connecting port <NUM> of the adapter element <NUM>, has an outer diameter which is larger than an outer diameter of the hollow sleeve <NUM> in an intermediate section arranged between the first and the second end. Such a design of the hollow sleeve <NUM> further simplifies the gripping and thus the handling of the filling adapter <NUM>.

As shown in in <FIG>, the injection solution receptacle <NUM> of the injection device <NUM> is designed in the form of an inner injection solution receptacle <NUM> which is contained within a protective outer barrel <NUM>. The inner injection solution receptacle <NUM> and the protective outer barrel <NUM> are formed integral with each other and are made of a sterile plastic material. In the region of its proximal end, the protective outer barrel <NUM> is provided with a flange element <NUM>. A distal end of the injection solution receptacle <NUM> is provided with a male Luer taper <NUM> which interacts with a female Luer taper <NUM> provided on the second connecting port <NUM> of the adapter element <NUM> of the filling adapter <NUM> when the filling adapter <NUM> is connected to the injection device <NUM> as shown in <FIG>. By means of the Luer tapers <NUM>, <NUM>, a fluid-tight connection can be established between the distal end of the injection solution receptacle <NUM> and the adapter element <NUM> of the filling adapter <NUM>.

As further becomes apparent from <FIG>, the outer barrel <NUM> of the injection device <NUM>, in the region of its distal end, is provided with a Luer thread <NUM>. The Luer thread <NUM> interacts with a complementary Luer thread <NUM> provided at an outer circumference of the second connecting port <NUM> of the adapter element <NUM>, see <FIG> and <FIG>, when the filling adapter <NUM> is connected to the injection device <NUM> as shown in <FIG>. As a result, also a reliable connection between the outer barrel <NUM> of the injection device <NUM> and the adapter element <NUM> of the filling adapter <NUM> can be effected.

In order to simplify the handling of the filling adapter <NUM> during bringing the injection device <NUM> into engagement with the second connecting port <NUM> of the adapter element <NUM>, the hollow sleeve <NUM>, in the region of a second end which faces the injection device <NUM> when the injection device <NUM> is brought into engagement with the second connecting port <NUM> of the adapter element <NUM>, at its outer circumferential surface is provided with a second gripping structure <NUM>. The second gripping structure <NUM> is designed in the form of two gripping rib arrays with individual gripping ribs extending substantially parallel to the longitudinal axis L1 of the filling adapter <NUM>.

Further, as shown in <FIG>, the hollow sleeve <NUM> is provided with longitudinal guiding ribs <NUM> which protrude from the inner circumferential surface of the hollow sleeve <NUM> and which extend substantially parallel to the longitudinal axis L1 of the filling adapter <NUM>. The guiding ribs <NUM> serve to guide the injection device <NUM> into engagement with the second connecting port <NUM>. The guiding function of the guiding ribs <NUM> prevents the cannula <NUM> from contacting the injection solution receptacle <NUM> of the injection device <NUM> upon connecting the filling adapter <NUM> to the injection device <NUM>. The hollow sleeve <NUM> and the longitudinal guiding ribs <NUM> are designed, i.e. shaped and dimensioned, in such a manner that a close sliding fit is generated between the guiding ribs <NUM> and an outer surface of the outer barrel <NUM> of the injection device <NUM>.

Turning back to <FIG>, the through-opening <NUM> extending through the adapter element <NUM> comprises an inlet section 26a which is arranged adjacent to the first connecting port <NUM>. In use of the filling adapter <NUM>, injection solution expelled from the syringe <NUM> thus enters the through-opening <NUM> via its inlet section 26a which has a flow cross-section which decreases in a direction of flow of the injection solution expelled from the syringe <NUM>. Further, the through-opening <NUM> comprises an intermediate section 26b which, in the direction of flow of the injection solution expelled from the syringe <NUM> during use of the filling adapter <NUM>, is arranged downstream of the inlet section 26a. The intermediate section 26b of the through-opening <NUM> has a substantially constant flow cross-section which substantially corresponds to the smallest flow cross-section of the inlet section 26a adjacent to the intermediate section 26b. Finally, the through-opening <NUM> comprises a receiving section 26c which, in the direction of flow of the injection solution expelled from the syringe <NUM> during use of the filling adapter <NUM>, is arranged downstream of the intermediate section 26b, i.e. adjacent to the second connecting port <NUM>. The receiving section 26c has a flow cross-section that is larger than the flow cross-section of the intermediate section 26b.

As further becomes apparent from <FIG>, the cannula <NUM> extends into at least a portion of the intermediate section 26b of the through-opening <NUM> so that the intermediate section 26b of the through-opening <NUM> or a portion thereof defines a cannula receiving bore of the adapter element <NUM> wherein a proximal end of the cannula <NUM> is fixed. The cannula <NUM> is received in the cannula receiving bore with a close slide fit. In addition, the cannula <NUM> is provided with bevelled ends. This design of the cannula <NUM> and the cannula receiving bore minimizes the generation of wear particles upon attaching the cannula <NUM> in the cannula receiving bore. The final bonding between the adapter element <NUM> and the cannula <NUM> is effected by means of a UV-cured glue. The cannula <NUM> extends from the intermediate section 26b of the through-opening <NUM>, through the receiving section 26c of the through-opening <NUM> and the second connecting port <NUM> so as to protrude from the second connecting port <NUM>. The receiving section 26c of the through-opening <NUM>, the second connecting port <NUM> and the hollow sleeve <NUM> of the filling adapter <NUM> define a concentric arrangement around the cannula <NUM>, see in particular <FIG>.

As shown in particular in <FIG>, the adapter element <NUM> is provided with two retention shoulders <NUM> which protrude from an outer circumferential surface of the adapter element <NUM> in opposing directions in the region of the inlet section 26a and the intermediate section 26b of the through-opening <NUM> extending through the adapter element <NUM>.

When the filling adapter <NUM> is connected to the injection device <NUM>, the cannula <NUM> extends into the injection solution receptacle <NUM> of the injection device <NUM>, i.e. a distal tip of the cannula <NUM> is arranged at a distance from the distal end of the injection solution receptacle <NUM> within the interior of the injection solution receptacle <NUM>, see in particular <FIG>. As a result, upon transferring injection solution from the syringe <NUM> to the injection device <NUM>, injection solution exiting the syringe <NUM>, via the cannula <NUM>, is supplied to the injection solution receptacle <NUM> of the injection device <NUM> not in the region of the distal end of the injection solution receptacle <NUM>, but at a position arranged at a distance from the distal end of the injection solution receptacle <NUM> within the interior of the injection solution receptacle <NUM>.

By simply holding the filling adapter <NUM> and the injection device <NUM> in an upright position with the longitudinal axis L1 of the filling adapter <NUM> and a longitudinal axis L2 of the injection device <NUM> being oriented substantially vertically and with the distal end of the injection device <NUM> facing downwards as shown in <FIG>, a gravity-driven flow of the injection solution from the distal tip of the cannula <NUM> downwards in a direction of the distal end of the injection solution receptacle <NUM> and further in the direction of the adapter element <NUM> can be induced. A part of the injection solution which is expelled from the distal tip of the cannula <NUM> and which in a gravity-driven manner flows back in the direction of the adapter element <NUM> is received in the receiving section 26c of the opening <NUM> provided in the adapter element <NUM>. Gas bubbles which are entrapped within the injection solution and hence transferred from the syringe <NUM> to the injection solution receptacle <NUM> together with the liquid phase of the injection solution are entrained with this gravity-driven flow and, due to the higher specific density of the liquid phase of the injection solution, are forced in the direction of the distal end of the injection solution receptacle <NUM> and further in the direction of the adapter element <NUM>.

Finally, the adapter element <NUM> is provided with a venting device <NUM> which is adapted to vent gas introduced from the syringe <NUM> into the injection device <NUM>, i.e. the injection solution receptacle <NUM> of the injection device <NUM>, via the through-opening <NUM> and the cannula <NUM> into the ambient. The venting device thus allows entrapped gas bubbles, in particular air bubbles, that are conveyed from the distal tip of the cannula <NUM> back to the adapter element <NUM> by the above described gravity-driven flow of the injection solution to be expelled into the ambient. The filling adapter <NUM> thus allows a gas free filling of the injection device <NUM> with the injection solution. As a result, manually expelling entrapped gas from the syringe <NUM> prior to connecting the syringe <NUM> to the filling adapter <NUM> can be dispensed with. Furthermore, an accurate and reliable preparation of a desired dose of the injection solution within the injection device <NUM> is made possible.

The venting device <NUM> comprises two radial bores <NUM> connecting the through-opening <NUM> extending through the adapter element <NUM> to the ambient. In particular, the radial bores <NUM> connect the receiving section 26c of the through-opening <NUM> to an outer circumferential surface of the adapter element <NUM> and hence to the ambient. In the embodiment of a filling adapter <NUM> shown in the drawings, the radial bores <NUM> of the venting device <NUM> extend coaxially from an outer circumferential surface of the adapter element <NUM> to the receiving section 26c of the through-opening <NUM> so as to connect the receiving section 26c of the through-opening <NUM> to the ambient. In order to ensure that gas bubbles entrapped in the injection solution can be vented to the ambient as desired without expelling a substantial amount of the liquid phase of the injection solution to the ambient, the flow cross-section, i.e. the diameter of the radial bores <NUM> is be selected in dependence on the physical properties, in particular the specific density, the viscosity and the surface tension of the injection solution to be transferred from the syringe <NUM> to the injection device <NUM>.

In order to ensure proper functioning of the venting device <NUM>, the retention shoulders <NUM> protrude from the outer circumferential surface of the adapter element <NUM> in the region of the inlet section 26a and the intermediate section 26b of the through-opening <NUM> extending through the adapter element <NUM>. Such a configuration ensures that, in the region of the receiving section 26c of the through-opening <NUM>, an air gap <NUM> is present between the outer circumferential surface of the adapter element <NUM> and the inner circumferential surface of the hollow sleeve <NUM> which allows an unhindered exit of gas from receiving section 26c via the radial bores <NUM> of the venting device <NUM>.

The injection device <NUM> of the injection solution transferring system <NUM> further comprises a plunger <NUM> which is depicted in greater detail in <FIG>. In the embodiment of an injection device <NUM> shown in the drawings, the plunger <NUM> is made of polycarbonate. At least a portion of the plunger <NUM> is slidably received within the injection solution receptacle <NUM> of the injection device <NUM>. The plunger <NUM> is displaceable relative to the injection solution receptacle <NUM> in a distal direction along a longitudinal axis of the plunger <NUM> in order to expel injection solution contained in the injection solution receptacle <NUM> of the injection device <NUM> from the injection solution receptacle <NUM>. At its proximal end which protrudes from the injection solution receptacle <NUM> in a proximal direction, the plunger <NUM> carries an actuation button <NUM> which may be depressed by a user in order to displace the plunger <NUM> relative to the injection solution receptacle <NUM> in the distal direction along the longitudinal axis of the plunger <NUM>.

At its distal end, the plunger <NUM> is provided with a tip element <NUM> which is attached to a plunger rod <NUM>, see <FIG>. A coupling between the plunger rod <NUM> and the tip element <NUM> is effected by the interaction of a tip barb <NUM> provided at a distal end of the plunger rod <NUM> with a barb receptacle <NUM> of the tip element <NUM>. Further, the tip element <NUM> is provided with a sealing element <NUM> which is provided in the region of an outer circumferential surface of the tip element <NUM> and which sealingly interacts with an inner circumferential surface of the injection solution receptacle <NUM>.

The plunger <NUM> of the injection device <NUM> can be arranged in a filling position as shown in <FIG>. When the plunger <NUM> is arranged in its filling position and the injection device <NUM> is engaged with the second connecting port <NUM> of the adapter element <NUM> of the filling adapter <NUM>, a distal tip of the plunger <NUM>, i.e. a distal end face of the tip element <NUM> provided at the distal tip of the plunger <NUM>, is disposed at a desired close distance D from the distal tip of the cannula <NUM> of the filling adapter <NUM>, see <FIG>. For example, the injection device <NUM> and the filling adapter <NUM> may be designed so as to set the distance D between the distal tip of the plunger <NUM> and the distal tip of the cannula <NUM> to approximately <NUM> +/-<NUM>. By arranging the distal tip of the plunger <NUM> and the distal tip of the cannula <NUM> at a close distance, the injection solution supplied to the injection solution receptacle <NUM> via the cannula <NUM> is reliably forced to flow in the direction of the venting device <NUM>. As a result, air-free filling of the injection solution receptacle <NUM> with the injection solution can be ensured.

Finally, the hollow sleeve <NUM> is provided with two observing windows <NUM> for observing the filling of the injection device <NUM> with the injection solution from the syringe <NUM>. The observing windows <NUM> allow an unhindered view of interior of the injection device <NUM> and the distal tip of the cannula <NUM>.

The plunger <NUM> is displaceably received in a housing <NUM> of the injection device <NUM> which comprises a first housing element <NUM> depicted in greater detail in <FIG> and a second housing element <NUM> depicted in greater detail in <FIG>. Both the first and the second housing element <NUM>, <NUM> are made of polycarbonate/acrylnitril butadien styrol, but have a different colour. The first housing element <NUM> is provided with a plunger through-hole <NUM> which receives the plunger rod <NUM> so that the plunger <NUM> is displaceable in a direction along its longitudinal axis relative to the first housing element <NUM>. Guiding elements <NUM> are provided on the first housing element <NUM> so as to protrude into the plunger through-hole <NUM>. When the plunger <NUM>, i.e. the plunger rod <NUM>, is received in the plunger through-hole <NUM> of the first housing element <NUM>, each guiding element <NUM> engages with a guiding channel <NUM> which provided in a circumferential surface of the plunger <NUM>, i.e. the plunger rod <NUM>, and which extends along the longitudinal axis of the plunger <NUM>, see in particular <FIG>.

For assembling the plunger <NUM> to the first housing element <NUM>, assembly channels <NUM> are provided in the outer circumferential surface of the plunger rod <NUM> which branch of from the guiding channels <NUM> in a distal region thereof and extend substantially perpendicular to the guiding channels <NUM> in a circumferential direction of the plunger rod <NUM>. Upon assembling the plunger <NUM> to the first housing element <NUM>, the guiding elements <NUM> are brought into engagement with the assembly channels <NUM>. Thereafter, the plunger <NUM> is rotated until the guiding elements <NUM> are received in the guiding channels <NUM> in a guiding manner, see <FIG>.

In order to simplify the handling of the injection solution transferring system <NUM>, the injection device <NUM> is delivered with the plunger <NUM> being arranged in its filling position which corresponds to a proximal end position of the plunger <NUM>. A plunger positioning mechanism <NUM> prevents that the plunger <NUM> can be moved further in a proximal direction relative to the injection solution receptacle <NUM> than into its proximal end position, i.e. its filling position. The plunger positioning mechanism <NUM>, however, allows a movement of the plunger <NUM> relative to the injection solution receptacle <NUM> from its filling position in a distal direction. Specifically, the plunger positioning mechanism <NUM> is defined by a distal end face <NUM> of the guiding channels <NUM> which are provided in the circumferential surface of the plunger rod <NUM> and the guiding elements <NUM> provided on the first housing element <NUM>. When the plunger <NUM> is arranged in its proximal end position which corresponds to its filling position, the guiding elements <NUM> abut against the distal end faces <NUM> of the guiding channels <NUM>. The interaction between the distal end faces <NUM> of the guiding channels <NUM> and the guiding elements <NUM> then prevents a further movement of the plunger <NUM> in the proximal direction and hence define the proximal end position, i.e. the filling position of the plunger <NUM>.

The second housing element <NUM> comprises two identical parts, see <FIG>, each of which comprises an interference pin <NUM> and an interference receptacle <NUM>. The two housing parts of the second housing element <NUM> are assembled by bringing the interference pins <NUM> into engagement with the respective interference receptacles <NUM> as shown in <FIG>. For aligning the parts of the second housing element <NUM> relative to each other upon assembly, alignment pins <NUM> are provided which, upon connecting the parts of the second housing element <NUM>, are received in respective alignment receptacles <NUM>. The injection solution receptacle <NUM> and the protective outer barrel <NUM> are connected to the second housing element <NUM> via the flange element <NUM> which extends from the outer barrel <NUM> at a proximal end thereof. Specifically, the flange elements <NUM> is received in a suitably shaped and dimensioned receptacle <NUM> of the second housing element <NUM>, see <FIG>.

As shown in particular in <FIG>, the second housing element <NUM> is provided with a plunger guide <NUM> which constrains the plunger rod <NUM> so that the plunger <NUM> is prevented from rotating relative to the second housing element <NUM>. A first drag mechanism <NUM> is adapted to exert a retaining force which retains the plunger <NUM> in its current position relative to second housing element <NUM>. The first drag mechanism <NUM> thus prevents an unintentional displacement of the plunger <NUM> relative to the injection solution receptacle <NUM> so that active manual actuation of the plunger <NUM>, for example by the application of a pressing force to the actuation button <NUM>, is necessary for displacing the plunger <NUM> relative to the injection solution receptacle <NUM>. The first drag mechanism <NUM> comprises a resilient drag element <NUM> which is provided on the second housing element <NUM>. The resilient drag element <NUM> exerts a resilient retaining force on the plunger <NUM>, i.e. the resilient drag element <NUM> is resiliently urged out of a rest position into a biasing position by an interaction with the plunger <NUM> and, due to its resiliency, applies a resilient reaction force on the plunger <NUM> which retains the plunger <NUM> in its current position. Specifically, the resilient drag element <NUM> interacts with a drag rib <NUM> which is provided on the outer circumferential surface of the plunger rod <NUM> and which extends substantially parallel to the longitudinal axis of the plunger <NUM>.

The injection device <NUM> further comprises a plunger locking mechanism <NUM> which interacts with the filling adapter <NUM>, i.e. the hollow sleeve <NUM> of the filling adapter <NUM>, so as to prevent the plunger <NUM> of the injection device <NUM> from being moved from its filling position relative to the injection solution receptacle <NUM> in a distal direction, i.e. in the direction of the distal tip of the cannula <NUM>, when the injection device <NUM> is connected to the filling adapter <NUM>. The plunger locking mechanism <NUM> serves to prevent an inadvertent contact between the plunger <NUM>, i.e. the distal tip of the plunger <NUM>, and the distal tip of the cannula <NUM>. The functioning of the plunger locking mechanism <NUM> now will be described in greater detail with reference to <FIG>.

Specifically, the plunger locking mechanism <NUM> comprises a lever element <NUM>, see <FIG>, which is displaceable within the second housing element <NUM> between an active position which is depicted in <FIG> and <FIG> and an inactive position depicted in <FIG>. When being arranged in its active position, the lever element <NUM> interacts with the plunger <NUM> and the hollow sleeve <NUM> of the filling adapter <NUM> so as to prevent the plunger <NUM> from being moved from its filling position in a distal direction when the injection device <NUM> is connected to the filling adapter <NUM>. To the contrary, when being arranged in its inactive position, the lever element <NUM> allows a movement of the plunger <NUM> from its filling position in a distal direction when the injection device <NUM> is not connected to the filling adapter <NUM>. The lever element <NUM> is mounted within the second housing element <NUM> so as to be rotatable between its active position and its inactive position. Specifically, the lever element <NUM> is provided with a hinge <NUM> which rotatably attaches the lever element <NUM> to a rotational axis <NUM> provided on the second housing element <NUM>.

The lever element <NUM> further comprises a pair of foot elements <NUM> which extend substantially parallel to each other and which are contacted by the filling adapter <NUM> when the injection device <NUM> is connected to the filling adapter <NUM>, in order to maintain the lever element <NUM> in its active position. In particular, as shown in <FIG>, the foot elements <NUM> face the filling adapter <NUM> and are contacted by a locking rim <NUM> of the hollow sleeve <NUM> which faces the injection device <NUM> when the injection device <NUM> is connected to the filling adapter <NUM>. Due to the interaction between the locking rim <NUM> of the hollow sleeve <NUM> and the foot elements <NUM>, the lever element <NUM> is pushed in a proximal direction substantially parallel to the longitudinal axis of the plunger <NUM> into contact with the plunger <NUM> and thus held in its active position shown in <FIG> and <FIG>.

The lever element <NUM> comprises a stop device <NUM> which comprises two tabs extending from a proximal end face of the lever element <NUM>. Further, a proximal portion of the plunger <NUM> extends further in a direction substantially perpendicular to the longitudinal axis of the plunger <NUM> than a distal portion of the plunger <NUM>. As a result, a shoulder which defines an abutment surface <NUM> is formed in a transition region between the distal portion and the proximal portion of the plunger <NUM>. Specifically, the abutment surface <NUM> is defined by an outer portion of a distal end face of the proximal plunger portion which protrudes from an outer circumferential surface of the distal plunger portion. When the lever element <NUM> is arranged in its active position as shown in <FIG>, the two tabs of the stop device <NUM> abut against the abutment surface <NUM> of the plunger <NUM>. As a result, the lever element <NUM> is held in its active position and, simultaneously, movement of the plunger <NUM> from its filling position in a distal direction is prevented.

The plunger locking mechanism <NUM> also comprises a retention device <NUM> which interacts with the foot elements <NUM> of the lever element <NUM>, in order to prevent that the foot elements <NUM> disengage from locking rim <NUM> of the filling adapter <NUM> when the lever element <NUM>, by the interaction between the locking rim <NUM> and the foot elements <NUM>, is maintained in its active position, see <FIG> and <FIG>. In particular, the retention device <NUM> prevents that the foot elements <NUM> slip around the locking rim <NUM> of the hollow sleeve <NUM> and hence disengages from the filling adapter <NUM> when the lever element <NUM> is pushed into engagement with the plunger <NUM>. The retention device is provided in the second housing element <NUM> and is designed in the form of a retention rib which prevents that the foot elements <NUM> of the lever element <NUM> deform away from the plunger <NUM> in a direction substantially perpendicular to the longitudinal axis of the plunger <NUM>.

After completion of the transfer of the injection solution from the syringe <NUM> to the injection solution receptacle <NUM> of the injection device <NUM> with the plunger <NUM> being arranged in its filling position as described above and as shown in <FIG>, the filling adapter <NUM> and the syringe <NUM> are detached from the injection device <NUM> by disengaging the male Luer taper <NUM> provided at the distal end of the injection solution receptacle <NUM> from the female Luer taper <NUM> provided on the second connecting port <NUM> of the adapter element <NUM> and by disengaging the Luer thread <NUM> provided at the distal end of the outer barrel <NUM> from the complementary Luer thread <NUM> provided at the second connecting port <NUM>, see <FIG>.

As soon as the filling adapter <NUM> is detached from the injection device <NUM>, the filling adapter <NUM>, i.e. the locking rim <NUM> of the hollow sleeve <NUM>, no longer contacts the foot elements <NUM> of the lever element <NUM>. Hence, when a pressing force is applied to the plunger <NUM> so as to displace the plunger <NUM> in a distal direction within the injection solution receptacle <NUM> of the injection device <NUM>, the lever element <NUM> is displaced into its inactive position shown in <FIG>. In particular, the lever element <NUM> is rotated around its rotational axis <NUM> from its active position into its inactive position and hence out of the way of the plunger <NUM>. As a result, the displacement of the plunger <NUM> is no longer hindered. Consequently, a needle (not shown in the drawings) can be attached to the injection device <NUM>, for example with the aid of the Luer thread <NUM> provided at the distal end of the outer barrel <NUM> and injection device <NUM> can be operated as will be described further below.

For administering an accurate dose, in particular an accurate micro dose of, for example, 10µl of the injection solution received within the injection solution receptacle <NUM> to a patient, in a first step, excess injection solution has to be expelled from the injection solution receptacle <NUM> by displacing the plunger <NUM> relative to the injection solution receptacle <NUM> in the distal direction as shown in <FIG>. Thereafter, the desired to dose of the injection solution has to be injected into the patient.

The injection device <NUM> therefore comprises a first plunger stop mechanism <NUM> which is adapted to stop a displacement of the plunger <NUM> relative to the injection solution receptacle <NUM> in the distal direction at a first dosing position P1, see <FIG>. Further, the injection device <NUM> comprises a second plunger stop mechanism <NUM> which is adapted to stop a displacement of the plunger <NUM> relative to the injection solution receptacle <NUM> from the first dosing position P1 in the distal direction at a second dosing position P2, see <FIG>. The first and the second dosing position P1, P2 of the plunger <NUM> are selected in such a manner that the plunger <NUM>, upon being displaced relative to the injection solution receptacle <NUM> between the first and the second dosing position P1, P2 is adapted to expel a desired dose of the injection solution contained in the injection solution receptacle <NUM> from the injection solution receptacle <NUM>.

Thus, during use of the injection device <NUM>, a user can expel excess injection solution from the injection solution receptacle <NUM> by displacing the plunger <NUM> relative to the injection solution receptacle <NUM> in the distal direction until the plunger <NUM> reaches the first dosing position P1. Upon reaching the first dosing position P1, the first plunger stop mechanism stops <NUM> further displacement of the plunger <NUM> in the distal direction. Consequently, the user is prevented from expelling too much injection solution from the injection solution receptacle. The residual injection solution contained in the injection solution receptacle can then be administered to a patient by further displacing the plunger <NUM> in the distal direction until the plunger <NUM> reaches the second dosing position P2. Upon reaching the second dosing position P2, the second plunger stop mechanism <NUM> stops further displacement of the plunger <NUM> in the distal direction and hence prevents that too much injection solution is administered to the patient.

As shown in particular in <FIG>, <FIG> and <FIG>, the first plunger stop mechanism <NUM> comprises a dosing element <NUM> which is attached to the plunger <NUM> and which is adapted to abut against a first dosing surface <NUM> provided on the first housing element <NUM>. The dosing element <NUM> also forms a part of the second plunger stop mechanism <NUM> and, as a part of the second plunger stop mechanism <NUM>, is adapted to abut against a second dosing surface <NUM> which is also provided on the first housing element <NUM>. The dosing element <NUM> is formed integral with the plunger <NUM> and is designed in the form of a rib protrudes from a lower surface of the activation button <NUM> in the direction of the inner solution receptacle <NUM>.

The first and the second dosing surface <NUM>, <NUM> extend substantially parallel to each other and parallel to an abutting surface <NUM> of the dosing element <NUM> substantially perpendicular to the longitudinal axis of the plunger <NUM>, wherein the second dosing surface <NUM> is arranged parallel offset relative to the first dosing surface <NUM> in the distal direction. A distance S between the first and the second dosing surface <NUM>, <NUM> in the distal direction corresponds to a desired travel distance of the plunger <NUM> in the distal direction between the first and the second dosing position P1, P2, see in particular <FIG>. Hence, the distance S between the first and the second dosing surface <NUM>, <NUM> in the distal direction sets the desired injection solution dose to be expelled from the injection solution receptacle <NUM> upon displacing the plunger <NUM> from the first to the second dosing position P1, P2.

Further, the first and the second dosing surface <NUM>, <NUM> are arranged offset relative to each other in a circumferential direction of the plunger <NUM>. Specifically, the second dosing surface <NUM> is defined by a bottom surface of a recess <NUM> formed in the first dosing surface <NUM> provided on the first housing element <NUM>.

When the plunger <NUM>, during use of the injection device <NUM>, is moved from its filling position shown in <FIG> in the distal direction, the abutting surface <NUM> of the dosing element <NUM> abuts against the first dosing surface <NUM> when the plunger <NUM> reaches the first dosing position P1 as depicted in <FIG>. The interaction of the dosing element <NUM> with the first dosing surface <NUM> prevents the plunger from being displaced further in the distal direction. Hence, the first plunger stop mechanism <NUM> provides a hard stop for the plunger <NUM> at the first dosing position P1. The injection device <NUM> therefore further comprises a plunger releasing mechanism <NUM> which is adapted to deactivate the first plunger stop mechanism <NUM> in order to release the plunger <NUM> and to thus allow a displacement of the plunger <NUM> relative to the injection solution receptacle <NUM> from the first dosing position P1 in the distal direction, i.e. in the direction of the second dosing position P2.

The plunger releasing mechanism <NUM> is adapted to allow a movement of the first dosing surface <NUM> relative to the dosing element <NUM>, i.e. relative to the plunger <NUM>, in order to disengage the dosing element <NUM> from the first dosing surface <NUM>. Specifically, the plunger releasing mechanism <NUM> is adapted to allow a rotational movement of the first dosing surface <NUM> relative to the dosing element <NUM>, i.e. relative to the plunger <NUM>, in order to disengage the dosing element <NUM> from the first dosing surface <NUM>. In order to effect the rotational movement of the first dosing surface <NUM> relative to the dosing element <NUM>, the first housing element <NUM> which carries the first and the second dosing surface <NUM>, <NUM> is designed so as to be manually rotatable relative to the second housing element <NUM>, see <FIG>. Since the plunger <NUM> is prevented from rotating relative to the second housing element <NUM> by means of the plunger guide <NUM>, a rotation of the first housing element <NUM> relative to the second housing element <NUM> inevitably results in a rotation of the first housing element <NUM> relative to the plunger <NUM>.

In order to be rotatable relative to the second housing element <NUM> in a guided manner, the first housing element <NUM> is provided with a retaining recess <NUM>, see <FIG>, <FIG> and <FIG>, which receives a retaining element <NUM> formed on the second housing element <NUM>, see <FIG>. Further, in order to simplify the handling of the plunger releasing mechanism <NUM>, the first housing element <NUM>, in the region of its outer surface, is provided with a gripping structure <NUM>. The gripping structure <NUM> is designed in the form of a gripping rib array with individual gripping ribs extending substantially in a direction along the longitudinal axis of the plunger <NUM>.

The rotation amount of the first housing element <NUM> relative to the second housing element <NUM> and hence relative to the plunger <NUM> is set such that the recess <NUM> formed in the first dosing surface <NUM> is brought into alignment with the dosing element <NUM> protruding from the activation button <NUM> of the plunger <NUM>. The plunger releasing mechanism <NUM> thus is adapted to displace the first and the second dosing surface <NUM>, <NUM> in the circumferential direction of the plunger <NUM>, in order to disengage the dosing element <NUM> from the first dosing surface <NUM> and to simultaneously align the second dosing surface <NUM> with the dosing element <NUM>.

In order to ensure that a user, upon activating the plunger releasing mechanism <NUM>, rotates the first housing element <NUM> relative to the second housing element <NUM> and the correct direction and by the correct rotation amount that is necessary to disengage the dosing element <NUM> from the first dosing surface <NUM> and to simultaneously align the second dosing surface <NUM> with the dosing element <NUM>, the plunger releasing mechanism <NUM> comprises a marker system <NUM> which is adapted to indicate an activation of the plunger releasing mechanism <NUM>. The marker system <NUM> comprises a first marker element <NUM> which is provided on an outer surface of the first housing element <NUM>. The marker system <NUM> further comprises a second marker element <NUM> which is provided on an outer surface of the second housing element <NUM>. The first and the second marker element <NUM>, <NUM> are arranged on the first and the second housing element <NUM>, <NUM> in such a position that they are positioned offset relative to each other a circumferential direction of the plunger <NUM>, when the plunger release mechanism <NUM> is not activated, but positioned in alignment with each other, when the plunger release mechanism <NUM> is activated, compare <FIG>.

The injection device <NUM> further comprises a limiting mechanism <NUM> which is adapted to limit the movement of the first and the second dosing surface <NUM>, <NUM> for disengaging the dosing element <NUM> from the first dosing surface <NUM> and for aligning the dosing element <NUM> with the second dosing surface <NUM>, see <FIG> and <FIG>. The limiting mechanism <NUM> comprises a first limiting element <NUM> which is provided on the first housing element <NUM> carrying the first and the second dosing surface <NUM>, <NUM>. Further, the limiting mechanism <NUM> comprises a second limiting element <NUM> which is provided on the second housing element <NUM> which remains stationary when the first housing element <NUM> is rotated in order to deactivate the first plunger stop mechanism <NUM>. The first limiting element <NUM> abuts against the second limiting element <NUM> when the dosing element <NUM>, due to the rotation of the first housing element <NUM> relative to plunger <NUM>, is disengaged from the first dosing surface <NUM> and aligned with the second dosing surface <NUM>. The limiting mechanism <NUM> prevents a user of the injection device <NUM> from excessively rotating the first housing element <NUM> relative to the second housing element <NUM>. Further, the limiting mechanism <NUM> provides an haptic feedback to the user that the first plunger stop mechanism <NUM> has been deactivated.

A second drag mechanism <NUM> serves to exert a retaining force which retains the first housing element <NUM> in its current position relative to the second housing element <NUM>. Due to the presence of the second drag mechanism <NUM>, active manual actuation is necessary for rotating the first housing element <NUM> relative to the second housing element <NUM>. The second drag mechanism <NUM> thus prevents an unintentional displacement of the first housing element <NUM> relative to the second housing element <NUM> and hence an unintentional activation of the plunger releasing mechanism <NUM>. The second drag mechanism <NUM> comprises a friction element <NUM> which is provided on the first limiting element <NUM> of the limiting mechanism <NUM> and which is adapted to frictionally interact with the retaining element <NUM> of the second housing element <NUM>.

The injection device <NUM> further comprises an activation mechanism <NUM> which is adapted to prevent an activation of the plunger releasing mechanism <NUM> unless the plunger <NUM> is arranged at the first dosing position P1 and which is adapted to allow an activation of the plunger releasing mechanism <NUM> when the plunger <NUM> is arranged at the first dosing position P1 see <FIG>, <FIG> and <FIG>. Specifically, the activation mechanism <NUM> prevents a rotation of the first housing element <NUM> relative to the plunger <NUM> and hence prevents a movement of the dosing element <NUM> and the first dosing surface <NUM> relative to each other unless the plunger <NUM> is arranged at the first dosing position P1.

The activation mechanism <NUM> comprises the guiding channel <NUM> which is provided on the circumferential surface of the plunger <NUM>, which extends along the longitudinal axis of the plunger <NUM> and which receives the guiding element <NUM> provided on the first housing element <NUM> in such a manner that the guiding channel <NUM>, upon displacement of the plunger <NUM> relative to the injection solution receptacle <NUM>, is displaced relative to the guiding element <NUM>. An interaction between the guiding element <NUM> and opposing side surfaces of the guiding channel <NUM> prevents a rotation of the plunger <NUM> and the first housing element <NUM> relative to each other. The activation mechanism <NUM> thus fulfills the double function to provide for a guided displacement of the plunger <NUM> in the direction of its longitudinal axis on the one hand and to simultaneously prevent an unintentional deactivation of the first plunger stop mechanism <NUM> when the plunger <NUM> is not arranged at the first dosing position.

The activation mechanism <NUM> further comprises an activation channel <NUM> which branches off from the guiding channel <NUM> and extends in a circumferential direction of the plunger <NUM> substantially perpendicular to the guiding channel <NUM>. The activation channel <NUM> receives the guiding element <NUM> when the plunger <NUM> is arranged at the first dosing position P1 and the first housing element <NUM> is rotated relative to the plunger <NUM>. Hence, the first dosing position P1 of the plunger <NUM> is defined by the position of the activation channel <NUM> along the longitudinal axis of the plunger <NUM>.

Finally, the plunger release mechanism <NUM> further comprises a locking arrangement <NUM> which locks the first dosing surface <NUM> in its position relative to the dosing element <NUM> after the first dosing surface <NUM> has been moved relative to the dosing element <NUM> in order to become disengaged from the dosing element <NUM>, see <FIG>, <FIG> and <FIG>. Specifically, the locking arrangement <NUM> comprises a resilient locking clip <NUM> which is provided on the second housing element <NUM> and which is resiliently urged out of a rest position by the interaction with a locking element <NUM> provided on the first housing element <NUM> when the first dosing surface <NUM> is moved relative to the dosing element <NUM> so as to become disengaged from the dosing element <NUM>, i.e. when the first housing element <NUM> is rotated relative to the second housing element <NUM>.

The locking clip <NUM> deforms back into its rest position after completion of the movement of the first dosing surface <NUM>, i.e. after completion of the rotation of the first housing element <NUM>, and interacts with the locking element <NUM> so as to lock the first housing element <NUM> relative to the second housing element <NUM> and the plunger <NUM>. In particular, the locking clip <NUM> interacts with the locking element <NUM> so as to prevent a counter rotation of the first housing element <NUM> relative to the second housing element <NUM> and the plunger <NUM>, after the first housing element <NUM> has been rotated once in order to disengage the first dosing surface <NUM> from the dosing element <NUM> and to align the second dosing surface <NUM> with the dosing element <NUM>. Consequently, the first dosing surface <NUM> is locked in its position relative to the dosing element <NUM>. The locking arrangement <NUM> allows the plunger release mechanism <NUM> to be used only once for deactivating the first plunger stop mechanism <NUM>. As a result, reuse of the injection device <NUM> is prevented.

Claim 1:
Injection device (<NUM>), comprising:
an injection solution receptacle (<NUM>);
a plunger (<NUM>) at least a portion of which is slidably received in the injection solution receptacle (<NUM>), wherein the plunger (<NUM>) is displaceable relative to the injection solution receptacle (<NUM>) in a distal direction in order to expel an injection solution contained in the injection solution receptacle (<NUM>) from the injection solution receptacle (<NUM>);
a dosing element (<NUM>) attached to the plunger;
a first housing element (<NUM>) that is rotatable relative to the plunger, the first housing element comprising:
a first dosing surface (<NUM>) that is adapted to abut against the dosing element to stop a displacement of the plunger (<NUM>) relative to the injection solution receptacle (<NUM>) in the distal direction at a first dosing position (P1); and
a second dosing surface (<NUM>) that is adapted to abut against the dosing element to stop a displacement of the plunger (<NUM>) relative to the injection solution receptacle (<NUM>) from the first dosing position (P1) in the distal direction at a second dosing position (P2), wherein the second dosing surface is offset from the first dosing surface in a circumferential direction relative to a longitudinal axis of the plunger; and
wherein the injection device further comprises a second housing element (<NUM>), wherein the first housing element is rotatable relative to the second housing element, and a limiting mechanism (<NUM>) comprising a first limiting element (<NUM>) attached to the first housing element and a second limiting element (<NUM>) that abuts the first limiting element when rotation of the first housing element relative to the plunger aligns the dosing element with the second dosing surface, wherein the second housing element (<NUM>) comprises the second limiting element.