A Stop Mechanism For A Hypocycloid End-Of-Content Mechanism In An Injection Device

Abstract

The invention relates to a stop mechanism for a non-axial working End-of-Content mechanism which is geared by a hypocycloid gearing. The EoC mechanism comprises a stationary first element (10), an EoC element (30) and a rotational element (50) with a cam surface. The EoC element rotates around a center axis which is dislocated in relation to the center axis of the first element. The EoC element thus works as a hypocycloid element which rotates through a specific angle whenever a rotational element driven by a dose setting button is rotated one full revolution. The EoC element thus counts the number of set doses.

Claims

1. A non-axial working limiting mechanism for an injection device which prevents setting of a dose exceeding the injectable amount of liquid drug contained in the injection device, the limiting mechanism comprising; a stationary and non-rotatable first element having a first internal surface with a first internal diameter (D), a rotational element having a cam surface, an EoC element having a second external surface with a second external diameter (d) being smaller that the first internal diameter (D) and an internal surface rotationally abutting the cam surface and which EoC element is at least partly located inside the first internal surface of the first element, wherein; the stationary first element has a first centre axis (X), and the EoC element has a second centre axis (Y) being dislocated in relation to the first centre axis (X) such that the second external surface of the EoC element engages with the first internal surface of the first element, the stationary first element on the first internal surface carries a plurality of first teeth separated by first valleys, and the EoC element on the second external surface carries a plurality of second teeth separated by second valleys and wherein the first and second teeth engages with the second and first valleys, and the EoC element is provided with a first stopping surface and the rotational element is provided with a second stopping surface such that further rotation of the EoC element is prevented when the two surfaces abut in a predetermined stop position, and wherein means are provided moving the EoC element radially such that the first stopping surface and the second stopping surface abut when the EoC element enters into the predetermined stop position.

2. A non-axial working End-of-Content mechanism according to claim 1, wherein the means for moving the EoC element radially, comprises: a partly filled out volume of one valley in the plurality of first valleys or second valleys and at least one tooth of the EoC element or the stationary first element extending longer than the remaining teeth in the plurality of teeth in an axial direction, such that the extended tooth engages the filled out volume in the predetermined stop position.

3. A non-axial working End-of-Content mechanism according to claim 1, wherein the EoC element is ring shaped.

4. A non-axial working End-of-Content mechanism according to claim 1, wherein the EoC element rotate in a rotational direction opposite to the rotational direction of the rotational element.

5. A non-axial working End-of-Content mechanism according to claim 1, wherein the cam surface has an elliptic shape.

6. A non-axial working End-of-Content mechanism according to claim 1, wherein a part of the cam surface on the rotational element is formed as a flexible arm.

7. A non-axial working End-of-Content mechanism according to claim 2, wherein one or more of the teeth provided on the EoC element is prolonged.

8. A non-axial working End-of-Content mechanism according to claim 2, wherein at least one of the valleys of the stationary first element has a filled out volume.

9. An injection device for apportioning set doses of a liquid drug, comprising: a non-axial working limiting mechanism which prevents setting of a dose exceeding the injectable amount of liquid drug contained in the injection device according to claim 1, wherein the rotational element is coupled to a dose setting button to rotate with the dose setting button at least during dose setting, and the stationary first element is coupled to a housing forming the outer boundaries of the injection device.

10. An injection device according to claim 9, wherein a torsion spring is operational encompassed between the housing and the rotational element.

11. An injection device according to claim 9, wherein the dose setting button does not travel axially in relation to the housing during dose setting.

12. An injection device according to claim 9, wherein the dose setting button and the rotational element rotate around the same longitudinal extending centre axis (X) during dose setting.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The invention will be explained more fully below in connection with a preferred embodiment and with reference to the drawings in which:

[0058] FIG. 1 show an exploded view of the EoC mechanism.

[0059] FIG. 2 show a perspective view of the ratchet or rotational element.

[0060] FIG. 2a show a perspective view of the ratchet arm.

[0061] FIG. 3 show perspective view of the EoC or second element.

[0062] FIG. 4 show perspective view of the first element.

[0063] FIG. 5 show a cross section of the End-of-Content mechanism about to reach its predetermined locked position.

[0064] FIG. 6 show a cross section of the End-of-Content mechanism in its predetermined locked position.

[0065] FIG. 7 show the End-of-Content mechanism build into a torsion spring driven injection device.

[0066] 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

[0067] 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.

[0068] 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. In the figures, the rotational element 50 (the ratchet element) is provided at the proximal end as indicated in FIG. 1.

[0069] The hypocycloid End-of-Content mechanism basically comprises three elements shown in FIG. 1. [0070] A first element 10. [0071] A second element 30 also referred to in this text as the EoC element or EoC ring. [0072] A third element 50 also referred to as the rotational element.

[0073] The first element 10 has a first internal surface 11 having a first diameter (D). This first surface 11 is provided with a number of inwardly pointing first teeth 12 which are separated by a number of first valleys 13. Proximally these first teeth 12 has a different radial height as can also be seen in FIG. 4. This proximal part 14 of the teeth 12 engages the ratchet arms 51 of the rotational element 50 as will be explained later.

[0074] This first element 10 is stationary in relation to an outer frame of an injection device. The outer frame is usually the housing 63 of an injection device, and the first element 10 is either an integral part of the housing 63 or it is a separate part inrotatable secured to the housing 63 as disclosed in FIG. 7. In the disclosed example, the first element 10 is provided with protrusions 15 for securing the first element 10 to the housing 63 such that the first element can neither rotate nor move axially in relation to the housing 63.

[0075] The EoC element 30 has a second external surface 31 with a second external diameter (d). This second surface 31 is provided with a number of outwardly pointing second teeth 32 which are separated by a number of second valleys 33.

[0076] The second external diameter (d) of the external surface 31 is smaller than the internal first diameter (D) of the first element 10 and the EoC element 30 is thus able to rotate inside the first element 10.

[0077] Further, the EoC element 30 has an internal surface 34 which is guided on a cam surface 52 provided on the rotational element 50. The cam surface 52 is preferably elliptic and secures that the second teeth 32 of the EoC element 30 stays engaged with the first valleys 13 of the first element 10.

[0078] The stationary first internal surface 11 has a first centre line X as disclosed in FIG. 6, and the second external surface 31 has a second centre line Y. Due to the cam surface 52 of the rotational element 50, the second centre line Y is dislocated relatively to the centre line X as is known from a hypocycloid.

[0079] The rotational element 50 is coupled to a dose setting button 60 which is rotated by a user to set a desired dose to be injected. The rotational element 50 can be directly coupled to follow the rotation of the dose setting button 60, or it can be connected via a gearing such that the dose setting button 60 and the rotational element 50 rotate with different rotational velocities.

[0080] The rotational element 50 is provided with a radial ratchet arm 51 which engages the proximal part 14 of the teeth 12 of the first element 10. The lower part of the tip 54 of the ratchet arm 51 shown in details in FIG. 2a breaks against a flange on the teeth 12 such that the ratchet arm 51 is only allowed to rotate clock-wise in relation to the teeth 12 of the first element 10 and thus prevents rotation in the counter clock-wise direction. A mechanism for bending the ratchet arms 51 in a radial direction can easily be provided. When the ratchet arm 51 are moved radially to perform an inwardly pointing movement, the tip 54 of the arm 51 slip out of the engagement with the teeth 12 which allow the rotational element 50 to also rotate in the counter clock-wise direction. The ratchet arm 51 could e.g. be moved radially by activating the ratchet arm 51 itself, e.g. as disclosed in WO 2013/178372, or alternatively by activating an outward pointing part 56 of the ratchet arm 51 to move the ratchet arm 51 radially.

[0081] When the rotational element 50 is rotated in the clock-wise direction (A) by the dose setting button and the first element 10 is kept static, cam surface 52 upon which the EoC element 30 rotates forces the EoC element 30 to rotate counter clock-wise (indicated by the arrow “B”).

[0082] In the depicted embodiment, the first element 10 has a number of 24 valleys 13 equally distributed over the first internal diameter (D) and the EoC element 30 has a number of 23 teeth 32 equally distributed over the second external diameter (d).

[0083] The diameter ratio (D/d) and thereby the ratio of valleys 13, 33 and teeth 12, 32 are calculated such that the first tooth 32a on the EoC element 30 shifts to the next consecutive (anti clock-wise) valley 13 of the first element 10 whenever the rotational element 50 is rotated one full rotation (i.e. 360 degrees) clock-wise.

[0084] The hypocycloid gearing, which is further explained in WO 2014/117944 is thus configured such that the first tooth 32a is moved 15 degrees (360/24) counter clock-wise (B) whenever the rotational element 50 is rotated 360 degrees clock-wise (A). The EoC element 30 thus rotates 15 degrees in relation to the first element 10 for each full rotation of the rotational element 50.

[0085] A number of the teeth 32 on the EoC element 30 are prolonged in the axial direction of the injection device. The number of prolonged teeth 32a, b, c, d, e can be any number but in the depicted embodiment a total number of 5 of the teeth 32 are prolonged.

[0086] The working mode will be explained in relation to the engagement between the first tooth 32a of the EoC element 30 and the first valley 13a of the first element 10 as disclosed in FIG. 5 and FIG. 6. The prolonged teeth 32 following the first tooth 32a clock-wise are marked respectively 32b, 32c, 32d and 32e. In the same manner, the valleys 13 laying adjacent to the first valley 13a in the counter clock-wise direction is marked 13b, 13c, 13d and 13e respectively.

[0087] The total height of the EoC element 30 (in an axial direction) are approximately the same as the height of the prolonged teeth 32a-e which again has the same height as the distal part of the teeth 12 of the first element 10 such that the EoC element 30 rotate inside the distal part of the first element 10.

[0088] As previously explained, the ratchet arm 51 of the rotational element 50 engages the upper part 14 of the teeth 12 of the first element 10.

[0089] In order to interact with one of the prolonged teeth 32a-e, one specific valley 13a (dedicated as the first) of the first element 10 has a partly filled out volume 16 in the part able to come into contact with the prolonged part of one prolonged teeth 32a-e.

[0090] Whenever, the first prolonged tooth 32a engages the filled out volume 16 of the first valley 13a (arriving counter clock-wise (B)), the EoC element 30 is pushed out of its rotational engagement and jams. As a result the EoC ring 30 is unable to rotate any further as depicted in FIG. 6, thus the EoC ring 30 is only able to rotate less than 306 degrees.

[0091] Further, the EoC element 30 is provided with a first stop surface 35 which engages a second stop surface 55 on the rotational element 50. These two stopping surfaces 35, 55 are provided such that they engage each other when the EoC ring 30 jams as depicted in FIG. 6.

[0092] The part of the rotational element 50 clock-wise adjacent to the second stop surface 55 is made as a flexible arm 52 which can deflect when the two stopping surfaces 35, 55 engages.

[0093] In a new and fully filled injection device, the last (=the fifth) 32e of the prolonged teeth 32a-e is located in the second valley 13b counter clock-wise of the filled out valley 13a. This is, so to speak, the start position for a new and fresh injection device. In the depicted example this allows the first prolonged tooth 32a to move through a number of 18 free valleys 32 (23 free valleys minus 5 prolonged teeth=18) before it encounters the first valley 13a which has the filled volume 16. This therefore allows the rotational element 50 to rotate (18+1=) 19 full rotations before the EoC ring 30 jams. The nineteen's revolution is the very last full rotation stretching from the last of the free valleys until the tooth 32a encounters the partly filled out valley 13a.

[0094] If the injection device is a typical insulin injection device it would e.g. be filled with 3.0 ml of U100 insulin which would amount to a total of 300 I.U. Usually such injections devices have a dose dial of 24 I.U per full revolution. Thus the requirement before the 300 I.U is ejected is (300/24) 12.5 full revolutions of the rotational element 50. The EoC element 30 would then during manufacture of the injection device just need to be placed such that the first prolonged tooth 32a is in the correct starting valley 13 such that the first prolonged tooth 32a enters the filled out valley 13a when the rotational element 50 has been rotated 12.5 times.

[0095] The half rotation is best obtained by having a rotational distance of 180 degrees (i.e. half of a full rotation) between the first stop surface 35 and the second stop surface 55 in the start position. The rotational element 50 would then be allowed to move 12 full rotations before the first prolonged tooth 32a start to engage the filled out volume 16 of the first valley 13a and due to the 180 degrees angular different start position of the first stop surface 35 and the second stop surface 55 half a rotation will be added to the 12 full rotations thus allowing the rotational element 50 to rotate 12.5 times 360 degrees. The valley 13 in which the first tooth 32a should start is indicated 13m in FIG. 5.

[0096] It should thus be clear that if e.g. a U200 insulin is used, the 3.0 ml would contain 600 I.U and with 24 International Units per revolution, it would require the first tooth 32a to move through 24 free valleys 13 and into the partly filled-out twenty-fifth valley (=25 full rotations). It would thus require a different number of teeth 12, 32 and valleys 13, 33 which would still be within the invention as claimed in the appended claims.

[0097] During assembly of the drive mechanism for the injection device the first tooth 32a can be positioned in a different location than in the above examples. In some cases the torsion spring of the device is pre-tensioned during assembly meaning that the tooth 32a might be rotated counter clock-wise during assembly. In a different example, the drive mechanism could be tested after assembly but before assembling the entire injection device. In this case the tooth 32a might move clock-wise during assembly. However, this can easily be incorporated into the starting position of the tooth 32a. Once the injection device is finally assembled and delivered to the user, the tooth 32a has to be able to move the relevant amount of valleys 13 before reaching the filled out 16 valley 13a.

[0098] In order to allow the first stop surface 35 to properly engage with the second stop surface 55, a part of the cam surface 52 is provided on a flexible arm 53 which is allowed to flex as disclosed in FIG. 6, thus allowing the first surface 35 to abut the second surface 55.

[0099] FIG. 7 discloses the End-of-Content mechanism build into a torsion spring operated injection device. Proximally a dose setting button 60 is provided which engages the rotational element 50 such that the rotational element 50 rotate in the direction “A” whenever the dose setting button 60 is rotated to set a dose.

[0100] Internally the dose setting button 60 is provided with a protrusion like part which is able to bend the ratchet arm 51 radially when the dose setting button 60 is rotated in the opposite direction to lower a set dose.

[0101] The rotational element 50 is internally provide with a toothing 57 which couples the rotational element 50 to a ratchet element 61 which thereby rotate together with the rotational element 50. The ratchet element 61 could alternatively be moulded together with the rotational part 50 to form one unitary unit.

[0102] The ratchet element 61 is coupled to a not-shown drive element which is rotated together with the ratchet element 61 during dose setting. This is disclosed in details in WO 2014/001318 (see especially FIG. 20).

[0103] A torsion spring 62 is operational between a housing 63 and the drive element such that the torsion spring 62 is strained whenever the ratchet element 61 is rotated by the rotational element 50.

[0104] The torque build up in the torsion spring 62 during dose setting is held by the engagement between the ratchet arm 51 and the proximal part 14 of the teeth 12 of the first element 10 and can be released by moving the ratchet element 61 and the drive element out of engagement such that the torque of the torsion spring rotates the drive element.

[0105] The dose set is visualized to the user by a rotatable scale drum 64 provided between the drive element and the housing 63. This scale drum 64 is externally provided with a helical track which engages a similar track provided inside the housing 63 to move the scale drum 64 helically both during dose setting and during expelling of the set dose.

[0106] 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. It is especially stressed that the described hypocycloid geared EoC mechanism can easily be adjusted to accommodate any size of dosing from any initial content of liquid drug. It is further stressed that the disclosed positions of the EoC mechanism in the described embodiments could be different. The EoC mechanism could e.g. be provided in a different injection device and e.g. in a different position in the injection device itself.