Drive Mechanism for an Injection Device

Abstract

The invention relates to an injection device for self-administration of doses of a liquid drug. The injection device carries a needle cannula (15) which is concealed by a telescopically movable shield (20). Further a stopping means (30) interconnects the shield with the helical rotatable scale sleeve (25) such that the shield can only be operated proximally when the scale sleeve is rotated away from its zero position. Once the scale sleeve returns to its zero position during expelling of the dose, the shield and the stopping means is allowed to slide distally and thus return to the locked position.

Claims

1. An injection device for self-administration of settable doses of a liquid drug comprising: a housing grippable by a user, a dose setting element by which the size of the dose is set, a needle cannula having a distal tip for penetrating the skin of the user during injection, a needle shield which is telescopically movable in a proximal direction from a first position to a second position and in a distal direction from the second position back to the first position by a resilient element, and wherein the needle shield in the first position is extended distally to cover at least the distal tip of the needle cannula and in the second position is retracted proximally to expose the distal tip of the needle cannula, and a rotatable scale sleeve indicating the size of the set dose which scale sleeve is helically guided relatively to the housing, the scale sleeve being helically moved away from an initial “zero” position during dose setting and helically returned to the same initial “zero” position during dose injection, wherein a stopping structure interconnects the needle shield and the scale sleeve, which stopping structure engages the scale sleeve when the scale sleeve is in the “zero” position such that the needle shield is prevented from being moved in the proximal direction from the first position and into the second position but is allowed to be moved in the distal direction from the second position and into the first position.

2. An injection device according to claim 1, wherein the needle shield and the stopping structure move together at least in the axially direction.

3. An injection device according to claim 2, wherein the needle shield carries the stopping structure.

4. An injection device according to claim 1, wherein the stopping structure comprises a proximally extending arm.

5. An injection device according to claim 1, wherein the stopping structure comprises a recession.

6. An injection device according to claim 5, wherein the recession 0 is provided on the axial extending arm,

7. An injection device according to claim 6, wherein the recession is provided in a peripheral side of the arm.

8. An injection device according to claim 6, wherein the recession is provided in a bottom surface of the arm.

9. An injection device according to claim 1, wherein the scale sleeve distally comprises a peripheral extension.

10. An injection device according to claim 5, wherein the peripheral extending protrusion engages the recession when the scale sleeve is in the “zero” position and the needle shield is the second position.

11. An injection device according to claim 10, wherein the engagement allows the needle shield and the stopping structure to slide axially from the second position and into the first position with the scale sleeve remaining in the zero position.

12. An injection device according to claim 1, wherein the stopping structure is formed flexible.

13. An injection device according to claim 1, wherein the stopping structure is rotationally mounted relatively to the housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The invention will be explained more fully below in connection with a preferred embodiment and with reference to the drawings in which:

[0048] FIG. 1 show a perspective view of the injection device with needle shield extending in the first position, and the scale drum in the “zero” position.

[0049] FIG. 2 show a perspective view of the injection device with the needle shield extending in the first position, and the scale drum dialled away from the “zero” position.

[0050] FIG. 3 show a perspective view of the injection device with the needle shield retracted to the second position, and the scale drum dialled away from the “zero” position.

[0051] FIG. 4 show a perspective view of the injection device with the needle shield retracted to the second position, and the scale drum returned to the “zero” position.

[0052] 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

[0053] 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 there relative dimensions are intended to serve illustrative purposes only.

[0054] 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 which usually carries the injection needle whereas the term “proximal end” is meant to refer to the opposite end pointing away from the injection needle and usually carrying the dose dial button.

[0055] Distal and proximal are meant to be along an axial orientation extending along the longitudinal axis of the disclosed injection device and is further indicated in FIG. 1,

[0056] FIGS. 1 to 4 discloses the injection device according to a first embodiment. The injection device comprises the following components: [0057] A housing 5. [0058] A dose dial element 10 [0059] A needle cannula 15. [0060] A needle shield 20 [0061] A scale sleeve 25

[0062] The housing 5 forms the outer shell carrying the cartridge containing the liquid drug and is usually held in the hand of the user when performing an injection.

[0063] The dose dial element 10 is provided proximally on the housing 5 and is usually rotational secured to the housing 5. The user rotates this dose dial element 10 in order to set the size of the dose to be injected. This rotation usually strains a not-shown torsion spring which again delivers the force needed to perform the injection. This is e.g. shown in EP 1,819,382.

[0064] The needle cannula 15 is preferably permanent secured to the injection device and has a sharp tip 16 which penetrates the skin of the user during injection.

[0065] The needle cannula 15 is hidden behind a needle shield 20 between injections. This needle shield 20 is usually urged in the distal direction by a resilient element positioned between the housing 5 and the needle shield 20.

[0066] The scale sleeve 25 has a helical groove or thread 26 which is engaged in a similar, male thread formed on the inside surface of the housing. However, the thread 26 of the scale sleeve 25 could alternatively be provided on the inside of the scale sleeve 25 and the thread of the housing 5 could be provided as an outwardly pointing thread on an internal tower forming part of the housing 5. In either case, the thread in the housing 5 needs only be a segment of a thread.

[0067] When a user wants to set a dose, the housing 5 is held in one hand and the dose dial element 10 is rotated using the other hand. This rotation is indicated with the arrow “A” in FIG. 2.

[0068] During dose setting, the scale drum 25 rotates and moves helical inside the housing 5. Usually indicia are provided on the scale drum 25 and preferably in a helical row such that when the scale drum 25 is rotated helically these indicia pass by a window 6 in the housing 5 one at the time thereby displaying the size of the set dose.

[0069] As disclosed in FIG. 1, when no dose is set, the scale sleeve 25 is in the “zero” position usually with the number “0” (or similar indicia) showing in the window 6.

[0070] In FIG. 2, during dose dialling, the scale sleeve 25 rotates away from the “zero” position and the indicia provided on the scale sleeve 25 rotate pass the window 6. When injecting as disclosed in FIG. 3, the scale sleeve 25 rotate back towards the “zero” position and the indicia pass by the window 6 in the opposition order. Once the injection is over as depicted in FIG. 4, the scale sleeve 25 has returned to its initiate “zero” position, and the number “0” (or similar indicia) is again shown in the window 6.

[0071] FIG. 1 depicts the injection device prior to dose setting with the scale drum 25 resting in the “zero” position and the number “0” (or similar indicia) therefore being displayed in the window 6.

[0072] The scale sleeve 25 is distally provided with a peripheral extending extension 27 e.g. in the form of a protrusion. This extension or protrusion 27 lies peripheral to the inside surface of the housing 5. Distally this peripheral extending extension 27 is provided with a distal side surface 28.

[0073] Further, a stopping means 30 is provided between the needle shield 20 and the scale sleeve 25. The stopping means 30 can in one embodiment be provided with an axial extending arm 31. The stopping means 30 can in one example be integral with the needle shield 20 or it can alternatively be a separate part inserted between the needle shield 20 and the scale sleeve 25.

[0074] The proximal extending arm 31, which extends from the stopping element 30 preferably has a recession 32 on the peripheral pointing towards the peripheral extending protrusion 27 of the scale sleeve 25. Most proximally this arm 31 has an end surface 33 which lies in the same peripheral plane as the scale sleeve 25.

[0075] As best seen in FIG. 1, when no dose has been set, i.e. when the scale sleeve 25 is positioned in the “zero” position, the needle shield 20 is prevented from telescoping in the proximal direction by the engagement between the arm 31 and the scale sleeve 25. The stopping means 30 distally engages the needle shield 20 (or the stopping means 30 is integral with the needle shield 20). Proximally the stopping means 30 preferably via the arm 31 engages the scale sleeve 25. The engagement with the scale sleeve 25 occurs as an abutment between the distal surface 28 of the extending extension 27 of the scale sleeve 25 and the proximal surface 33 of the arm 31.

[0076] When a user sets a dose as illustrated in FIG. 2, the dose dial element 10 is rotated (arrow “A”) which in turn also rotates the scale sleeve 25 to move helically away from the “zero” position. Once the scale sleeve 25 is rotated, the peripheral extending protrusion 27 is also rotated away from the engagement with the proximal end surface 33 of the arm 31. The arm 31 and thus the stopping means 30 are here after free to move proximally. Since the scale sleeve 25 rotates helically away the free space into which the arm 31 can move grows rapidly as the dose is being set.

[0077] At the start of the injection, the user presses the distal surface of the needle shield 20 against the skin “S” as indicated by the arrow “B” in FIG. 3. This presses the needle shield 20 and the stopping means 30 in the proximal direction. Since the scale sleeve 25 has been rotated proximally, sufficient space is available to move the stopping means 30 and the thus the arm 31 proximally.

[0078] The injection is thereafter done either manually by the user pressing an injection button or automatically by an electric motor or by a spring drive. When the injection is done automatically, the proximal movement of the needle shield 20 can be made to trigger the commencement of the injection.

[0079] As the injection is carried out and the liquid drug flow into the body of the user via the lumen of the needle cannula 15, the scale sleeve 25 graduately returns to the initiate “zero” position in a helical movement.

[0080] As indicated in FIG. 3, the needle cannula 15 is inserted into the skin (“S”) into the depth

[0081] “X”. When injecting a modern insulin product, this depth (“X”) is usually 3 to 8 mm. The needle shield 20 is thus retracted the same distance (“X”). As a result of this, the arm 31 of the stopping means 30 is also telescoped a distance “X” from the initiate position.

[0082] When the transfer of liquid drug has ended, the scale sleeve 25 has returned to the initiate “zero” position as disclosed in FIG. 4. In FIG. 4, the needle cannula 15 is still inserted into the skin (“S”) of the user. When the scale sleeve 25 returns to the “zero” position, the peripheral extending protrusion 27 will enter into the recession 32 in the arm 30. In FIG. 4 the recession 32 is disclosed as being positioned on the peripheral side of the arm 31 but the recession 32 could also be provided on the bottom surface of the arm 31 i.e. the part of the arm 31 pointing towards the centre line of the injection device. It could also be a combination of the two. The main point is that the arm 31 and the stopping means 30 must be able to slide distally into the first position with the scale sleeve 25 in the “zero” position. This could also be obtained by having flexibility build into the arm 31.

[0083] Further, the stopping means 30 could be allowed to rotate a few degrees during returning of the needle shield 20 e.g. against the force of a resilient element that would bring the stopping means 30 back to its initial rotational position once it has passed the peripheral extending extension 27 on the scale sleeve 25. The resilient element could e.g. be a torsion spring. In one example the spring urging the needle shield 20 in the distal direction could be a combined compression spring and torsion spring encompassed between the stopping means 30 and the housing 5. Such spring is explanatory disclosed in the FIGS. 1 to 4 with the reference “T”. This spring could simultaneously urge the stopping means 30 in a distal direction and torsional rotate the stopping means 30 into its rotational position, e.g. determined by a guiding arrangement 7 secured in the housing 5. In such case the needle shield 20 and the stopping means 30 are preferably made as independent parts such that the needle shield 20 which is in contact with skin (“S”) of the user during injection is only moved axially.

[0084] When the user removes the needle cannula 15 from the skin (“S”), the needle shield 20 slides into the locked position depicted in FIG. 1 and the needle shield 20 is thus prevented from being moved in the proximal direction.

[0085] 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.