Torsion Spring for an Injection Device and an Injection Device Comprising Such Torsion Spring

Abstract

The present invention relates to a helically coiled torsion spring for a torsion spring based automatic injection device, coiled in a longitudinal direction (X) and having a number of consecutive windings located between a distal winding having a distal end and a proximal winding having a proximal end. Each winding further has an outwardly pointing surface. At least one end of the torsion spring is abruptly cut to form a flat end surface with no bends and at least a number of the consecutive windings are coiled with a gap between the consecutive windings such that that the torsion spring apply an axial force when the distal end and the proximal end are moved axially against each other. The invention further relates to a torsion spring based automatic injection device for expelling settable doses of a liquid drug utilizing such torsion spring to urge the abruptly cut ends into proper engagement.

Claims

1. A helically coiled torsion spring in a torsion spring based automatic injection device, coiled in a longitudinal direction and comprising: a number of consecutive windings wherein a distal winding has a distal end and a proximal winding has a proximal end, and each winding further having an outwardly pointing surface, wherein one or both of the distal end and the proximal end are cut to form a predominantly straight and non-bended end surface, and wherein a number of the consecutive windings in a first region are coiled with no gap between the consecutive windings to form a closed coil form and a number of the consecutive windings in a second region are coiled with a gap between the consecutive windings to form an open coil form such that that the torsion spring apply an axial force when the distal end and the proximal end are moved axially against each other.

2. A torsion spring based automatic injection device for expelling settable doses of a liquid drug comprising: a housing assembly and a dose setting assembly being relatively rotatable, a torsion spring according to claim 1 encompassed between the housing assembly and the dose setting assembly such that the torsion spring is strained upon rotation of the dose setting assembly relatively to the housing assembly, and wherein the torsion spring is helically coiled having a longitudinal direction and a number of consecutive windings wherein a distal winding has a distal end and a proximal winding has a proximal end, the distal end and/or the proximal end are cut to form a straight and non-bended end surface, each winding further having an outwardly pointing surface, wherein a number of the consecutive windings in a first region are coiled with no gap between the consecutive windings to form a closed coil form and a number of the consecutive windings in a second region are coiled with a gap between the consecutive windings to form an open coil form such that that the torsion spring applies an axial force when the distal end and the proximal end are moved axially against each other, and wherein at least one of the housing assembly or the dose setting assembly is at least partly made from a polymeric material and comprises a spring receiving arrangement comprising a first surface substantially parallel with the longitudinal direction of the helical torsion spring for abutting the distal end surface or the proximal end surface of the helical torsion spring and which spring receiving arrangement further comprises a second surface substantially parallel with the longitudinal direction of the helical torsion spring for supporting the outwardly pointing surface of the at least distal winding or the at least proximal winding, and wherein when the dose setting assembly are rotated relatively to the housing assembly to strain the torsion spring, the first surface of the spring receiving arrangement is pressed against the cut, straight and non-bended end surface of the torsion spring to strain the torsion spring thereby forcing the outwardly pointing surface of the at least distal winding and/or the at least proximal winding to press against the second surface.

3. A torsion spring based automatic injection device according to claim 2, wherein the dose setting assembly comprises a polymeric dose setting member in which the spring receiving arrangement is integrally formed.

4. A torsion spring based automatic injection device according to claim 2, wherein the housing assembly comprises a polymeric housing member in which the spring receiving arrangement is integrally formed.

5. A torsion spring based automatic injection device according to claim 2, wherein the spring receiving arrangement comprises a cut-out.

6. A torsion spring based automatic injection device according to claim 5, wherein the first surface is part of the cut-out.

7. A torsion spring based automatic injection device according to claim 5, wherein the cut-out comprises a distally located guiding surface extending substantially perpendicular to the longitudinal direction of the helical coiled torsion spring.

8. A torsion spring based automatic injection device according to claim 2, wherein the second surface comprises a step-wise configuration.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The invention will be explained more fully below in connection with a preferred embodiment and with reference to the drawings in which:

[0045] FIG. 1A show a cross sectional view of the torsion spring arrangement.

[0046] FIG. 1B show a cut-over perspective view of the torsion spring arrangement of FIG. 1A.

[0047] FIG. 2A-B show cross sectional views (180 degrees displaced) of the torsion spring attachment with the housing member.

[0048] FIG. 2C show a cut-over perspective view of the torsion spring attachment with the housing member.

[0049] FIG. 3A-B show cross sectional views (180 degrees displaced) of the housing member.

[0050] FIG. 3C show a cut-over exploded view of the housing member.

[0051] FIG. 4A-B show cross sectional views (180 degrees displaced) of the alternative torsion spring attachment with the housing member.

[0052] FIG. 4C show a cut-over perspective view of the torsion spring attachment with the housing member.

[0053] FIG. 5A-B show cross sectional views (180 degrees displaced) of the alternative housing member.

[0054] FIG. 5C show a cut-over exploded view of the alternative housing member.

[0055] FIG. 6 show a different embodiment of the torsion spring.

[0056] FIG. 7 show an enlarged cross sectional view of the embodiment depicted in FIG. 6.

[0057] 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

[0058] 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.

[0059] 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. The directions are indicated with arrows in FIGS. 1A and 1n FIG. 6.

[0060] FIG. 1A-B discloses a part of a torsion spring driven injection device according to a first embodiment of the invention. The torsion spring 1 is at its distal end 2 attached to a dose setting member 10 being a part of the dose setting assembly and at its proximal end 3 connected to a housing member 20 being part of the housing assembly.

[0061] The dose setting member 10 is further connected to a not-shown dose setting button via a toothed interface 11 such that the dose setting member 10 can be rotated when the user dials a dose. The housing member 20 is via locking protrusions 21 rotational locked to the not-shown housing but could alternatively be moulded integrally with the housing.

[0062] In WO 2014/001318 by Novo Nordisk A/S, which is incorporated by reference, the housing member (referred to as the spring base in FIG. 20) is numbered “180” and the dose setting member (referred to as the drive tube) is numbered “170”. The dose setting member“170” is connected to a distally located dose setting button (numbered “1004) via a ratchet element “185”. A scale drum “160” is slidable connected to dose setting member “170”. In the present invention a scale drum carrying indicia can be axially slidable connected to the dose setting member 10 which again is part of the dose setting assembly.

[0063] Whenever the user dials a dose by rotating the dose setting button, the dose setting member 10 rotates with it thereby straining the torsion spring 1 encompassed between the dose setting member 10 and the housing member 20.

[0064] The connection between the housing member 20 and the torsion spring 1 is further disclosed in the FIGS. 2A-C, 3A-C and 4A-C.

[0065] The torsion spring 1 is helical coiled and has a distal winding 4 ending in a distal end 2 and a proximal winding 5 ending in a proximal end 3. Both these ends 2, 3 are abruptly cut to form flat end surfaces 7, 8 which are best seen at the distal end 2 in FIGS. 2B and 2C.

[0066] Further, as disclosed in FIG. 2C, each winding of the torsion spring 1 has an outer surface 6. Since the torsion spring 1 is coiled from a circular wire, the outer surface 6 runs in parallel with the longitudinal direction (X) of the helical spring 1 which is also the longitudinal direction of the injection device.

[0067] The spring receiving arrangement of the housing member 20 is further shown in the FIGS. 3A to 5C. A similar spring receiving arrangement can be provided in the dose setting member 10 as indicated in FIG. 1A-1B.

[0068] The arrangement has a cut-out 22 having a first surface 23 which is parallel to the longitudinal axis X of the torsion spring 1 such that the abruptly cut proximal surface 8 of the torsion spring 1 abuts this first surface 23 when the user strains the torsion spring 1.

[0069] Distally, the housing member 20 is provided with a second surface 24 also being in parallel with the longitudinal direction X of the torsion spring 1.

[0070] When the torsion spring 1 is strained by rotating the dose setting member 10 relatively to the housing member 20, the proximal flat end surface 8 abuts the first surface 23 and further rotation of the dose setting member 10 causes the outer diameter of the torsion spring 1 to be increased.

[0071] Since the torsion spring 1 has both flat end surfaces 7, 8 encompassed between two similar first surfaces 23 (the other surface is the not-shown first surface of the dose setting member 10) provided in the same permanent axial distance, the diameter of the torsion spring 1 will increase as the two surfaces 23 rotate relatively to each other building up torque in the torsion spring 1.

[0072] This increase of the outer diameter of the torsion spring 1 causes the outer surface 6 of at least the proximal winding 5 to abut the second surface 24 of the housing member 20.

[0073] The friction occurring between the outer surface 6 of the torsion spring 1 and the second surface 24 means that the torque build up in the torsion spring 1 during straining is distributed to the housing member 20 over a large area whereby stressing of the first surface 23 is minimized.

[0074] The second surface 24 has in one embodiment a stepwise configuration as best seen in FIG. 1A wherein each step is configured to abut the outer surface 6 of consecutively windings.

[0075] Each step of the second surface 24 can alternatively tilt inwardly towards the centreline X with a small angle which would provide a better grip on each consecutive winding.

[0076] FIG. 4A-C and FIG. 5A-C discloses an alternative embodiment wherein the second surface 24 is parallel to the longitudinal extension (X) of the helical torsion spring (1) without any steps.

[0077] Also, as best seen in FIG. 5B and FIG. 5C, the cut-out 22 is provided with a distally located guiding surface 25 for guiding the abruptly cut flat surfaces 7, 8 of the torsion spring 1 into abutment with the first surface 23.

[0078] Further, as indicated in FIG. 1A-1B, the dose setting member 10 can be formed in the same way such that the torsion spring 1 is fixated in the same manner both in its distal end 2 and in its proximal end 3.

[0079] FIGS. 6 and 7 discloses a different embodiment in which the torsion spring 100 is also encompassed between a housing assembly and a dose setting assembly.

[0080] The dose setting assembly comprises a dose setting member 110 being connected to a not-shown dose setting button via the toothed interface 111 as in the previous embodiment.

[0081] The housing assembly comprises a housing member 120 connected the housing assembly via a number of protrusions 121.

[0082] This torsion spring 100 is also at a distal end 102 provided with a distal winding 104 having an abruptly cut end surface 107 and the proximal end 103 has a proximal winding 105 with an abruptly cut end surface 108.

[0083] The distally abruptly cut end surface 107 abuts the dose setting member 110 and the proximally located abruptly cut end surface 108 abuts the housing member 112 such that the torsion spring 100 is strained when the dose setting member 110 is rotated relatively to the dose setting member 120 during dose setting.

[0084] The housing member 120 is, as in the first embodiment, provided with a second surface 124 which is parallel with the longitudinal direction X of the torsion spring 100. This is e.g. disclosed in FIG. 7 which depicts an enlarged view of the proximal end.

[0085] The outwardly pointing surface 106 of at least the proximal winding 105 at the proximal end 103 is thus forced against this second surface 124 whenever the dose setting member 110 is rotated to set a dose.

[0086] A similar design is preferably but not necessarily provided at the distal end 102 of the torsion spring 100.

[0087] Further, the torsion spring 100 of the second embodiment is provided with a zone or region Y in which the coils of the torsion spring 100 is coiled with a gap 109 between consecutive windings.

[0088] Due to the gap 109, the torsion spring 100 applies an axial force when compressed such that the abruptly cut surface 107 (when viewing the proximal end as in FIG. 7) during assembly is in a position in which the guiding surface 125 can properly grip the proximal end 103 of the torsion spring 100 and guide the abruptly cut surface 108 into abutment with the first surface 123 (23 in the embodiment in FIG. 5C).

[0089] The axial force urges the distal end 102 and the proximal end 103 away from each other and into proper engagement with their respective guiding surfaces (125 for the proximal end 103 in FIG. 7). In this position, the first surfaces (123 for the proximal end 103) pushes properly on the abruptly cut end 108 (107 for the distal end).

[0090] 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.