A SHIELD TRIGGER MECHANISM AND AN INJECTION DEVICE WITH A SHIELD TRIGGER MECHANISM

Abstract

The invention relates to a spring driven injection device for expelling doses a liquid drug. A housing structure secures a container containing a liquid drug to be injected via a spring driven dose engine. A needle shield is rotatably relatively to the housing structure between a locked position and an unlocked position. In the locked position the needle shield is prevented from axial movement and in the unlocked position axially movement is possible by applying an axial force onto the needle shield. Axial movement of the needle shield activates the spring driven dose engine to automatically eject the dose of the liquid drug from the container. The needle shield is rotational guided from the locked position to the unlocked position in a track arrangement which is further configured to prevent the needle shield in rotation from the locked position to the unlocked position during application of the axial force to the needle shield.

Claims

1. A shield trigger mechanism for triggering the ejection of a dose of a liquid drug from a spring driven injection device, comprising: a needle shield which is rotatably relatively to a housing structure between a locked position and an unlocked position, wherein the needle shield in the locked position is prevented from axial movement relatively to the housing structure, and wherein the needle shield in the unlocked position is axially movable relatively to the housing structure in response to an axial force (S) being applied to the needle shield to thereby activate the spring driven injection device to automatically eject the dose of the liquid drug, and which needle shield is rotational guided from the locked position to the unlocked position by a track arrangement, wherein the track arrangement is configured to prevent the needle shield in rotation from the locked position to the unlocked position during application of the axial force (S) to the needle shield by having a physical stop incorporated in the track arrangement.

2. The shield trigger mechanism according to claim 1, wherein the track arrangement comprises a helical track region

3. The shield trigger mechanism according to claim 2, wherein the helical track region is associated with the housing structure.

4. The shield trigger mechanism according to claim 2, wherein the needle shield is provided with a protrusion guided in the helical track region.

5. The shield trigger mechanism according to claim 2, wherein the helical track region terminates into an axial track.

6. The shield trigger mechanism according to claim 5, wherein the helical track region or the axial track are provided with a physical stop preferably preventing the protrusion on the needle shield in moving from the helical track region and into the axial track during application of the axial force (S) to the needle shield.

7. The shield trigger mechanism according to claim 6, wherein the needle shield is urged in the distal direction when the force (S) is removed from the needle shield whereby the protrusion is able to escape the physical stop.

8. The spring driven injection device for delivering doses of a liquid drug, comprising a housing structure having a container containing the liquid drug and a spring driven dose engine, a needle shield which is rotatably relatively to the housing structure between a locked position and an unlocked position, and wherein the needle shield when in the locked position is prevented from axial movement relatively to the housing structure, and wherein the needle shield in the unlocked position is axially movable relatively to the housing structure in response to an axial force being applied to the needle shield to thereby activate the spring driven dose engine to automatically eject the dose of the liquid drug from the container, and which needle shield is rotational guided from the locked position to the unlocked position in a track arrangement, wherein the track arrangement is configured to prevent the needle shield in rotation from the locked position to the unlocked position during application of the axial force (S) to the needle shield, by having a physical stop incorporated in the track arrangement.

9. The spring driven injection device according to claim 8, wherein the track arrangement comprises a helical track region.

10. The spring driven injection device according to claim 9, wherein the helical track region is associated with the housing structure.

11. The spring driven injection device according to claim 9 wherein the needle shield is provided with a protrusion guided in the helical track region.

12. The spring driven injection device according to claim 9, wherein the helical track region terminates into an axial track.

13. The spring driven injection device according to claim 12, wherein the helical track region or the axial track are provided with a physical stop preventing the protrusion on the needle shield in moving from the helical track region and into the axial track during application of the axial force (S) to the needle shield.

14. The spring driven injection device according to claim 13, wherein the needle shield is urged in the distal direction when the force (S) is removed from the needle shield whereby the protrusion is able to escape the physical stop.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The invention will be explained more fully below in connection with a preferred embodiment and with reference to the drawings in which:

[0061] FIG. 1 show a perspective view of the injection device with the protective cap attached.

[0062] FIG. 2 show a perspective view of the injection device with the protective cap removed.

[0063] FIG. 3 show an exploded view of the housing structure together with the cartridge.

[0064] FIG. 4 show a cross-sectional view of the protective cap.

[0065] FIG. 5 show a cross-sectional view of the needle shield.

[0066] FIG. 6A show a perspective view of the injection device with the base part of the housing structure visually removed and the protective cap attached.

[0067] FIG. 6B show a perspective view of the injection device with the base part of the housing structure visually removed and the protective cap removed.

[0068] FIG. 7A show the engagement between the needle shield and the transfer element in the stop position.

[0069] FIG. 7B show the engagement between the needle shield and the transfer element in the relaxed position.

[0070] FIG. 7C show the engagement between the needle shield and the transfer element in the injection position.

[0071] FIG. 8A show a schematic view of the movement without the stop functionality and with no force applied onto the needle shield.

[0072] FIG. 8B show a schematic view of the movement without the stop functionality and with a force applied onto the needle shield.

[0073] FIG. 8C show a schematic view of the movement with the stop functionality and with a force applied onto the needle shield

[0074] The figures are schematic and simplified for clarity, and they just show details, which are essential to the understanding of the invention, while other details are left out. Throughout, the same reference numerals are used for identical or corresponding parts.

DETAILED DESCRIPTION OF EMBODIMENT

[0075] When in the following terms as “upper” and “lower”, “right” and “left”, “horizontal” and “vertical”, “clockwise” and “counter clockwise” or similar relative expressions are used, these only refer to the appended figures and not 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.

[0076] In that context it may be convenient to define that the term “distal end” in the appended figures is meant to refer to the end of the injection device securing the needle cannula and pointing towards the user during injection, whereas the term “proximal end” is meant to refer to the opposite end usually carrying the dose dial button as depicted in FIG. 1. Distal and proximal is meant to be along an axial orientation extending along the longitudinal axis (X) of the injection device as also disclosed in FIG. 1.

[0077] FIG. 1 and FIG. 2 disclose the injection device with and without the protective cap 40 attached to the housing structure 1. The injection device comprises a housing structure 1 which can be made from any number of separate pieces connected together to form a full outer housing.

[0078] As disclosed in FIG. 3, the housing structure 1, in the present embodiment, comprises a base part 10, a cartridge holder part 20 and an initiator part 30 as also shown in PCT application PCT/EP2019/065451. These parts are preferably clicked together to form the housing structure 1.

[0079] The cartridge holder part 20 is in use covered by the movable needle shield 50 as also seen in FIG. 2. Internally the cartridge holder part 20 secures the cartridge 5 which contains the liquid drug to be injected. The base part 10 secures the dose engine which in the enclosed embodiment is a torsion spring driven dose engine as disclosed in WO 2019/002020.

[0080] When the housing structure 1 is assembled a helical track 60 emerges between the flanges of the cartridge holder part 20 and the initiator part 30 which helical track 60 locks around an outwardly pointing protrusion 52 on the needle shield 50 as will be explained. In the disclosed embodiment two such helical tracks 60 are provided. Each of the helical tracks 60 are functionally divided into two regions; a first track region 60A and a second track region 60B separated by a bridge 35 under which the outwardly pointing protrusions 52 are able to slide.

[0081] As there are two helical tracks 60 disclosed in this embodiment, the various other elements relating to these tracks 60 are preferably also provided in pairs. It is thus to be understood that even if described in singularity in the text, the various elements can be provided in plural.

[0082] The outwardly pointing protrusion 52 is provided on an axial extension 53 on the needle shield 50 as seen in FIG. 3 and in FIG. 5. The peripheral width of the outwardly pointing protrusion 52 is somewhat smaller than the peripheral width of this axial (and proximal) extension 53 of the needle shield 50. At one side the axial extension 53 is cut off in a sloped surface 54, the use of which will be explained later.

[0083] The protective cap 40 is mounted to cover the distal end of the housing structure 1 i.e. the cartridge holder part 20, while the opposite proximal end of the housing structure 1 i.e. the base part 10 is provided with a rotatable dose dial 2 which a user can rotate in a first rotational direction in order to set the size of the dose to be ejected. Since the injection device disclosed is an automatic spring operated injection device, the dose dial 2 is rotatable connected to the housing structure 1 such that the dose dial 2 do not move axially during dose setting but are allowed to rotate in relation to the housing structure 1.

[0084] The base part 10 is further provided with a window 11 through which the user can inspect the rotatable scale drum 70 carrying indicia 71 indicating the size of the dose being set. As further seen in FIG. 6A-B, the rotatable scale drum 70 is externally provided with a helical track 72 engaging a similar thread segment provided on the inner surface of the base part 10 such that the scale drum 70 moves helically when rotated relatively to the housing structure 1 as it is commonly known from injection devices.

[0085] As best seen in FIG. 2, the initiator part 30 is distally provided with a peripheral track 31 which has at least one axial opening 32.

[0086] The protective cap 40 which is disclosed in a cross-sectional view in FIG. 4 is proximally and on the inner surface provided with an inwardly pointing protrusion 41 which engages the peripheral track 31 such that the user is required to rotate the protective cap 40 before it can be axially removed from the housing structure 1 by pulling the inwardly pointing protrusion 41 through the axial opening 32. Typically, there would be two such axial openings 32 to accommodate two inwardly pointing protrusions 41 such that the user is required to rotate the protective cap 40 a little less than 180° before the protective cap 40 can be axially removed. Further, as shown in FIG. 2, the peripheral track 31 can be equipped with a parking position 33 separated from the peripheral track 31 by an axial rib.

[0087] During this mandatory rotation of the protective cap 40, a longitudinal rib 42 also provided on the inner surface of the protective cap 40 engage a similar rib 51 (see e.g. FIG. 2) provided on the needle shield 50 which is thus forced to follow the rotation of the protective cap 40. In the disclosed embodiment two longitudinal ribs 42 and two ribs 51 are provided.

[0088] The needle shield 50 which is disclosed in a cross-sectional view in FIG. 5 is proximally provided with a number of outwardly pointing protrusions 52 which engages the helical tracks 60 provided between the cartridge holder part 20 and the initiator part 30 in the housing structure 1. Consequently, when the user rotates the protective cap 40 to remove it, this rotation is transferred to a similar rotation of the needle shield 50. Since the helical tracks 60 in the disclosed embodiment are in fact helical, the needle shield 50 translates helically in the proximal direction during rotation.

[0089] Distally the needle shield 50 carries a cleaning unit 80 which is secured to the needle shield 50 such that the cleaning unit 80 both rotate and move axially together with the needle shield 50, thus the cleaning unit 80 also move helically when the needle shield 50 is rotated. The cleaning unit which is described in further details in PCT application PCT/EP2019/065451 has a cleaning chamber containing a liquid cleaning agent which is able to clean the distal tip of the needle cannula between injections. In one example, the cleaning agent can be based on the same preservatives as contained in the liquid drug inside the cartridge and in a preferred example; the cleaning agent is the identical same preservative containing liquid drug as present inside the cartridge 5.

[0090] When the injection device is delivered to the user, the outwardly pointing protrusion 52 is located in the start of the first track region 60A of the helical track 60 as shown in FIG. 6A.

[0091] During the rotation through the first track region 60A (approximately 90°) of the helical track 60 (indicated by the arrow “I” in FIG. 6A), both the needle shield 50 and the needle cannula moves axially such that a distal tip of the needle cannula is maintained inside the cleaning chamber of the cleaning unit 80 as explained in PCT application PCT/EP2019/065451. The movement of the outwardly pointing protrusion 52 through the first 90° inserts the proximal end of the needle cannula into the cartridge 5 and further moves the cartridge 5 a few millimetres in the proximal direction such that a quantum of the liquid drug in the cartridge 5 is forced into the cleaning chamber inside the cleaning unit which is thus filled with liquid drug from the cartridge 5. The preservative of the liquid drug thereafter works as the cleaning agent. The initial movement of the needle shield 50 and the needle cannula is referred to as the initiation of the injection device.

[0092] Once the needle shield 50 has been rotated approximately 90°, the axial extension 53 carrying the outwardly pointing protrusion 52 rotationally passes a one-way click-arm 24 provided on the cartridge holder part 20 and thus in the bottom of the helical track 60 as seen in FIG. 6A where after the needle shield 50 cannot be rotated back, i.e. when the axial extension 53 of the needle shield 50 has passed the one-way click-arm 24, the needle cannula has been irreversible inserted into the cartridge 5 and the cleaning chamber has been filled.

[0093] In the view shown in FIG. 6A, the first track region 60A of the helical track 60 is visible whereas in the second view in FIG. 6B, the injection device has been rotated to view the second track region 60B of the helical track 60. The cross-over from the first track region 60A of the helical track 60 wherein the injection device is being initiated and to the second track region 60B of the helical track 60 is also indicated by the one-way click arm 24 which in the view of FIG. 6B is hidden below the bridge 35 under which the outwardly pointing protrusion 52 passes once the initiation has been concluded.

[0094] As described in further details in WO 2019/002020, the driving force of the torsion spring in the dose engine is released when the user pushes the needle shield 50 against the skin. This axial movement of the needle shield 50 is transferred to an axial movement of a transfer element 90 which transfers the axial movement to the dose engine.

[0095] However, when the outwardly pointing protrusion 52 is located in the second track region 60 B it is not possible to move the needle shield 50 axially as the protrusion 52 when moved strictly axially (translational) would encounter and abut against the proximal side wall 61 of the second track region 60B. The user is thus required to rotate the needle shield 50 to an unlocked position (disclosed in FIG. 7C) wherein the outwardly pointing protrusion 52 is able to move axially in the proximal direction.

[0096] This is best seen in FIG. 7A-B-C which discloses the cartridge holder part 20 clicked together with the initiation part 30 and with the outwardly pointing protrusion 52 of the needle shield 50 located in the second track region 60B of the helical track 60. The figure also discloses the engagement with the transfer element 90.

[0097] In the unlocked position (FIG. 7C), the outwardly pointing protrusion 52 is located in an axial track 21 which connects to the second track region 60B of the helical track 60. The axial track 21 is physically provided in the cartridge holder part 20 as best seen in FIG. 3. Also, in the unlocked position, the outwardly pointing protrusion 52 abuts the transfer element 90 and is able to move the transfer element 90 strictly axially as disclosed in FIG. 7C.

[0098] If the user pushes the needle shield 50 against the skin before rotating the needle shield 50 and starts to rotate the needle shield 50 with the needle shield 50 pressed against the skin this will move the outwardly pointing protrusion 52 to abut and follow the proximal side wall 61 and when rotated into the injection position (represented by the axial track 21), the needle shield 50 will suddenly and uncontrolled move in the proximal direction when the outwardly pointing protrusion 52 reaches the axial track 21. This would simultaneously insert the needle cannula into the skin and release the dose engine. However, such sudden insertion and release has the ability to surprise the user who might then react by removing the needle shield 50 and the needle cannula from the skin.

[0099] In order to prevent that the user can rotate the outwardly pointing protrusion 52 into the injection position with the needle shield 50 pressed against the skin a physical stop 22 is preferably built into the proximal side wall 61 of the second track region 60B as e.g. disclosed in FIG. 7A-B-C.

[0100] In FIGS. 6B and 7A, which disclose the same situation, a force arising from the skin of the user pushes the needle shield 50 in the proximal direction. This force is indicated by the arrow “S” in both FIG. 6B and in FIG. 7A. This force also moves the outwardly pointing protrusion 52 against the proximal wall 61 of the second track region 60B of the helical track 60. However, if the user rotates the needle shield 50 anti-clockwise (seen from a distal position) and towards the unlocked position as indicated by the arrow “R” with the needle shield 50 pressed against the skin, the outwardly pointing protrusion 52 will rotationally engage with the physical stop 22 provided on the proximal wall 61 of the helical track 60 as disclosed in FIG. 7A. This abutment prevents the outwardly pointing protrusion 52 from moving into the axial track 21 and thus prevents a sudden injection in being performed.

[0101] As further disclosed in FIG. 7A, the sloped side 54 of the axial extension 53 pushes the transfer element 90 slightly in the proximal direction. The transfer element 90 is biased in the distal direction by a compression force delivered by a non-shown spring. The distal force applied by the spring is indicated by an arrow “F” in FIG. 7A-B-C. The distance that the axial extension 53 moves the transfer element 90 during rotation of the needle shield 50 is not sufficient to cause an injection to be performed.

[0102] Due to the physical stop 22, the user is not able to rotational (“R”) move the outwardly pointing protrusion 52 into the axial track 21 while simultaneously pushing the needle shield 50 against the skin (“S”).

[0103] In FIG. 7B, the user has removed the needle shield 50 from the skin and the axial force (“S”) arising from the skin is not present anymore. Therefore, the spring force “F” moves the transfer element 90 into the initial position which also moves the outwardly pointing protrusion 52 and the needle shield 50 in the distal direction. Since the needle shield 50 is moved in the distal direction, the axial extension 53 is also moved distally and no force is thus applied to the transfer element 90 in the proximal direction.

[0104] The proximal surface of the outwardly pointing protrusion 52 now (FIG. 7B) lies distally to the dotted line “L” and is thus free of the physical stop 22 incorporated in the track. A further rotation of the needle shield 50 and the outwardly pointing protrusion 52 is thus possible in this position.

[0105] The rotation of the needle shield 50 (from FIG. 7B to FIG. 7C) brings the outwardly pointing protrusion 52 into the position depicted in FIG. 7C. In this position, the outwardly pointing protrusion 52 rest on the distal side 62 of the helical track 60 and an injection can now be performed by pushing the needle shield 50 against the skin indicated by the arrow “S” in FIG. 7C which moves the outwardly pointing protrusion 52 further into the axial track 21 and henceforth moves the transfer element 90 in the proximal direction to thereby release the torque of the torsion spring and perform an injection.

[0106] The above is schematically disclosed in FIG. 8A-B-C.

[0107] FIG. 8A discloses the prior art way of operation. The user rotates the needle shield 50 e.g. by use of the protective cap 40. This rotation moves the outwardly pointing protrusion 52 along the distal side 62 of the track region 60B. When the end of the track region 60B is reached, the outwardly pointing protrusion 52 is delivered into the axial track 21 and an injection can be performed by pushing the needle shield 50 against the skin such that the outwardly pointing protrusion 52 moves axially through the axial track 21 in the proximal direction.

[0108] However, if the user applies a force (“S”) to the needle shield 52 and rotates the needle shield 52 simultaneously therewith the situation disclosed in FIG. 7B occurs.

[0109] The outwardly pointing protrusion 52 is pushed against the proximal side 61 of the track region 60B and once the outwardly pointing protrusion 52 is delivered into the axial track 21, the outwardly pointing protrusion 52 and the needle shield 50 will be forced rapidly in the proximal direction such that the needle cannula will penetrate the skin of the user and the dose will be injected almost simultaneously which can be very surprising to the user.

[0110] In order to avoid this, a physical stop 22 is built into the proximal side 61 of the track region 60B. This physical stop 22 will prevent the outwardly pointing protrusion 52 from entering into the axial track 21 as disclosed in FIG. 8C.

[0111] In order for the outwardly pointing protrusion 52 to pass the physical stop 22, the user needs to remove the needle shield 50 from the skin such that the compression force “F” of the spring via the transfer element 90 can move the needle shield 50 and the outwardly pointing protrusion 52 in the distal direction as indicated by the arrow “S′” in FIG. 8C.

[0112] Once the outwardly pointing protrusion 52 rests against the distal side 62 of the track region 60B, the user will be able to rotate the outwardly pointing protrusion 52 into the axial track 21 avoiding the physical stop 22 and thereafter to perform an injection by pushing the needle shield 50 against the skin.

[0113] Some preferred embodiments have been shown in the foregoing, but it should be stressed that the invention is not limited to these, but may be embodied in other ways within the subject matter defined in the following claims.