A HYPOCYCLOID END-OF-CONTENT MECHANISM

Abstract

The invention relates to a torsion spring driven injection device for delivering individually set doses of a liquid drug wherein a torsion spring is strained by rotation of a rotatable dose setting element and released by axial movement of a clutch which couples the dose setting element with the drive tube and the drive tube with a piston rod guide driving the piston rod. When straining the torsion spring the clutch is decoupled from a piston rod guide such that the piston rod guide is able to rotate independently and coupled to the dose setting element. During dose expelling the clutch is moved into engagement with the piston rod guide and out of engagement with the dose setting element such that the piston rod guide rotates with the clutch under influence of the torsion spring. The invention further relates to a non-axial movable End-of-Content mechanism preventing the user from setting a dose larger than the content of the injectable liquid drug remaining in the cartridge of the injection device.

Claims

1. A torsion spring driven injection device for delivering individually set doses of a liquid drug, comprising: a housing, a rotatable dose setting element which is axially fixated in the housing, a piston rod having an outer surface with an outer thread which extend helically in a longitudinal direction and which outer surface further is provided with a longitudinal extending engagement surface such that the outer surface of the piston rod has a non-circular shape, a nut member having an inner thread mating the outer thread of the piston rod, a piston rod guide engaging the longitudinal extending engagement surface of the non-circular cross section of the piston rod such that the piston rod is moved axially when the piston rod guide and the nut member are rotated relatively to each other, and wherein either the nut member or the piston rod guide is non-rotational engaged in the housing, a drive tube axially fixated in the housing and engaging an axially movable dose release clutch, a torsion spring which is strained by rotation of the rotatable dose setting element, and which torsion spring is encompassed between the housing and the drive tube, such that a torque is build up in the torsion spring during rotation of the drive tube relatively to the housing during dose setting and which torque is released to rotate the drive tube during ejection, wherein the release clutch is axially movable in relation to the drive tube between a first position and a second position; wherein the release clutch is decoupled from the piston rod guide such that the piston rod guide is able to rotate independently of the release clutch and the release clutch is coupled with the rotatable dose setting element to rotate simultaneously with the rotatable dose setting element in order to set a dose, wherein the release clutch is decoupled from the rotatable dose setting element such that the release clutch is able to rotate independently of the rotatable dose setting element under influence of the torsion spring, and the release clutch is coupled with the piston rod guide such that the piston rod guide rotates simultaneously with the release clutch in order to drive the piston rod, and wherein the release clutch is rotational locked to the drive tube such that the release clutch and the drive tube rotates in unison but can move axially in relation to each other, wherein the release clutch and the drive tube rotate together in a first rotational direction by rotation of the dose setting element when the release clutch is in the first position thereby straining the torsion spring to build up torque, and the release clutch and the drive tube rotate together in a second opposite rotational direction by the torsion spring when the release clutch is in the second position thereby releasing the torque of the torsion spring.

2. The torsion spring driven injection device according to claim 1 wherein, the nut member is non-rotational engaged in the housing.

3. The torsion spring driven injection device according to claim 1, wherein, the housing comprises a spring base to which the torsion spring is attached.

4. The torsion spring driven injection device according to claim 1, wherein a compression spring is provided between the drive tube and the release clutch urging the drive tube and the release clutch in opposite axial directions.

5. The torsion spring driven injection device according to claim 1, wherein the ratchet element is provided with an annular bearing flange rotatably carrying a rotatable disc-shaped End-of-Content (EoC) element.

6. The torsion spring driven injection device according to claim 5, wherein the annular bearing flange is eccentric.

7. The torsion spring driven injection device according to claim 5, wherein the disc-shaped EoC element is provided with one or more axially extending protrusions.

8. The torsion spring driven injection device according to claim 5, wherein the housing is provided with a peripheral track guiding at least one of the protrusions provided on the disc-shaped EoC element.

9. The torsion spring driven injection device according to claim 5, wherein an additional ring-shaped EoC gear element is provided.

10. The non-axial working End-of-Content mechanism for the torsion spring driven injection device according to claim 5, wherein: the rotatable dose setting element is rotatable around a first axis (X), and the disc-shaped EoC element is rotatable around a second axis (Y) which second axis is dislocated in relation to the first axis (X), wherein arresting structure is provided for stopping the rotation of the cycloid disc in a predetermined position.

11. The non-axial working End-of-Content mechanism according to claim 10, wherein the arresting structure comprises an axially extending protrusion provided on the disc-shaped EoC element and a stopping valley provided in a guiding track in the housing.

12. The non-axial working End-of-Content mechanism for the torsion spring driven injection device according to claim 5, wherein: the rotatable dose setting element is rotatable around a first axis (X), and the disc-shaped EoC element has a first protrusion guided in a first track and a second protrusion guided in a second track, wherein the second track is provided with at least one curled part introducing at least one oscillating radial movement to the disc-shaped EoC element for each full rotation of the dose setting element, and arresting structure for stopping the rotation of the disc-shaped EoC element in a predetermined position.

13. The non-axial working End-of-Content mechanism according to claim 12, wherein the first track is provided in the housing, and the second track is provided in the dose setting element.

14. The non-axial working End-of-Content mechanism for the torsion spring driven injection device according to claim 5, wherein: the rotatable dose setting element is rotatable around a first axis (X), and the ring-shaped EoC gear element is rotatable around a second axis (Y) which second axis is dislocated in relation to the first axis (X), whereby rotation of the ring-shaped EoC gear element is transformed to a rotation of the disc-shaped EoC element, wherein arresting structure is provided for stopping the rotation of the disc-shaped EoC element in a predetermined position.

15. The non-axial working End-of-Content mechanism according to claim 14, wherein the arresting structure comprises an axially extending protrusion provided on the disc-shaped EoC element and a stopping position provided in a guiding track in the housing.

16. The torsion spring driven injection device according to claim 5, wherein the spring base is provided with a peripheral track guiding at least one of the protrusions provided on the disc-shaped EoC element.

17. The non-axial working End-of-Content mechanism according to claim 10, wherein the arresting means structure comprises an axially extending protrusion provided on the disc-shaped EoC element and a stopping valley provided in a guiding track in the in the spring base.

18. The non-axial working End-of-Content mechanism according to claim 12, wherein the first track is provided in the spring base, and the second track is provided in the dose setting element.

19. The non-axial working End-of-Content mechanism according to claim 14, wherein the arresting structure comprises an axially extending protrusion provided on the disc-shaped EoC element and a stopping position provided in a guiding track in the spring base.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0085] The invention will be explained more fully below in connection with a preferred embodiment and with reference to the drawings in which:

[0086] FIG. 1 show an exploded view of the injection device according to a first embodiment of the invention.

[0087] FIG. 2 show a cross sectional view of the spring engine of FIG. 1.

[0088] FIG. 3 show a side view of the ratchet element of FIGS. 1 and 2

[0089] FIG. 4 show an exploded view of the End-of-Content system of the injection device disclosed in FIG. 1.

[0090] FIG. 5 show a top view of the spring base of FIG. 4 viewed from a proximal position.

[0091] FIG. 6 show a perspective view of the cycloid disc-shaped EoC element disclosed in FIG. 4.

[0092] FIG. 7 show an exploded view of the injection device according to a second embodiment of the invention.

[0093] FIG. 8 show an exploded view of the End-of-Content system of the second embodiment shown in FIG. 7.

[0094] FIG. 9 show a side view of the ratchet element of FIG. 8.

[0095] FIG. 10 show a top view of the spring base of FIG. 8 viewed from a proximal position.

[0096] FIG. 11 show a view of the proximal end of the ratchet element of FIG. 8 as viewed from a distal position.

[0097] FIG. 12 show perspective view of the disc-shaped EoC element disclosed in FIG. 6.

[0098] FIG. 13 show an exploded view of the injection device according to a third embodiment of the invention.

[0099] FIG. 14 show an exploded view of the End-of-Content system of the third embodiment shown in FIG. 13.

[0100] FIG. 15 show a top view of the spring base of FIG. 14 viewed from a proximal position.

[0101] FIG. 16a-b show views of the disc-shaped EoC element disclosed in FIG. 14.

[0102] FIG. 17a-b show views of the cycloid gearing element of the FIG. 14.

[0103] 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

[0104] 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.

[0105] 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. Distal and proximal is meant to be along an axial orientation of the injection device along a virtual centre line marked X in FIG. 1.

The Torsion Spring Engine

[0106] FIG. 1 and FIG. 2 disclose the torsion spring engine for a torsion spring driven medical injection device according a first embodiment of the invention. Such torsion spring driven medical injection device is usually an oblong pre-filled injection pen provided with an injection needle at the distal end.

[0107] By torsion spring engine is here meant the mechanism which secures the torsion spring and allows the torsion spring to be both strained and released. The mechanism also secures that the torque is held in the torsion spring once a dose is set and that the torque is releasable during dose injection.

[0108] The torsion spring engine is a separate unit which is secured in a housing 10 to thereby form an injection device. The torsion spring engine is proximally closed by a spring base 20. The torsion spring engine drives a piston rod 75 which is engaged by a nut member 30. Distally to the nut member 30, the housing 10 usually carries a not-shown cartridge-holder which secures a cartridge containing the liquid drug to be injected by forward movement of the piston rod 75. The cartridge-holder can either be permanently secured to the housing 10 in which case the injection device is a so-called pre-filled injection device or the cartridge holder can be removable secured to the housing 10 allowing a user to change the cartridge thus making the injection device durable.

[0109] The torsion spring engine disclosed in FIG. 1 henceforth comprises: [0110] The spring base 20, (either being separate or a part of the housing structure). [0111] The ratchet element 40 (also referred to as the dose setting element). [0112] The clutch 60. [0113] The drive tube 50. [0114] The torsion spring S1. [0115] The compression spring S2

[0116] The spring engine comprising at least these elements has the ability to strain the torsion spring S1 by rotation of the dose dial 15 and to release the torque applied to the torsion spring S1 by axial movement of the clutch 60 as will be explained in details in the following.

[0117] Both the spring base 20 and the nut member 30 are inrotatable secured to the housing 10 such that these three parts 10, 20, 30 together form one constructional element. In an alternative, the spring base 20 and the nut member 30 could each or both be moulded as integral parts of the housing 10. Further, the housing 10 could be a part of structure and is generally meant to be the outer shell surrounding the mechanism of the torsion spring driven injection device.

[0118] The dose setting arrangement comprises the dose dial 15, the ratchet element 40, the drive tube 50 and the clutch 60 as these elements rotate together during dose setting as will be explained. The dose dial 15 is coupled to the ratchet element 40 such that the ratchet element 40 rotates together with the dose dial 15 during dose setting and during dose adjustment.

[0119] To drive the injection a torsion spring S1 is at its distal end secured to the drive tube 50 and at its proximal end to the spring base 20.

[0120] The drive tube 50 is on the outer surface provided with a number of outwardly pointing flanges 52 as seen in FIG. 1 which slides in tracks 65 provided on the inner surface of the clutch 60 as depicted in FIG. 2. Further, teeth 51 also provided on the outer surface of the drive tube 50 slides in longitudinal openings 61 provided in the clutch 60. The clutch 60 is thus able to slide proximally in relation to the drive tube 50 a distance indicated by the arrow C in FIG. 2. However, in all situations are the clutch 60 and the drive tube 50 rotational bound to rotate together in unison.

[0121] A compression spring S2 is provided between the drive tube 50 and the clutch 60 urging the clutch 60 in the distal direction and urging the drive tube 50 in the proximal direction. As seen in FIG. 2, the compression spring S2 abuts the clutch 60 on a shelve provided internally in the clutch 60.

[0122] The inner surface of the clutch 60 is distally provided with a plurality of inwardly pointing teeth 62 which engages similar outwardly pointing teeth 71 provided on a piston rod guide 70.

[0123] The inwardly pointing teeth 62 on the inside of the clutch 60 however only engages the outwardly pointing teeth 71 on the piston rod guide 70 when the clutch 60 is moved to its proximal position against the bias of the compression spring S2 as will be explained.

[0124] The piston rod guide 70 is further provided with a non-circular inner surface 72 for engaging a piston rod 75 which on the outer surface is provided with a helical thread 76 which engages a similar internal thread 31 provided in the nut member 30.

[0125] The piston rod 75 is further formed with a non-circular cross section 77 which in the disclosed embodiment is formed as a number of longitudinal flat recesses. However, the non-circular cross section 77 can be made in many different ways e.g. as a longitudinal track. The purpose of the non-circular cross section 77 is to engage with the non-circular inner surface 72 of the piston rod guide 70 such that rotation of the piston rod guide 70 is directly transformed to a rotation of the piston rod 75.

[0126] Whenever the piston rod 75 rotates it is moved both rotational and axially (i.e. helically) due to the engagement between the outer thread 76 on the piston rod 75 and the internal thread 31 in the nut member 30.

[0127] In a different and not-shown embodiment the internal thread 31 can be provided in the piston rod guide 70 and the non-circular inner surface 72 can be provided in the nut member 20. In such embodiment, the piston rod 75 would move axially forward without any rotation when the piston rod guide 70 is rotated relatively to the nut member 20.

[0128] In order to visually inspect the size of the individual dose being set by rotating the dose dial 15, a scale drum 35 is provided. This scale drum 35 is on the outer surface provided with indicia 36 which are visible through a window 11 in the housing 10. The outer surface is further provided with a helical thread 37 which engage a similar thread or thread segment provided on the inside surface of the housing 10 such that the scale drum 35 moves helically in relation to the housing 10 when rotated.

[0129] On the inner surface the scale drum 25 is provided with a longitudinal track 38 which engages a similar protrusion 63 provided on the outer surface of the clutch 60 such that the scale drum 35 is able to rotate together with the clutch 60 but is axial slidable in relation to the clutch 60. A second protrusion also engaging the track 38 on the scale drum 35 can as depicted in FIG. 2 be provided distally on the clutch 60 to balance the movement of the scale drum 35.

[0130] The clutch 60 is further provided with an internal toothing 64 on the inside which internal toothing 64 engages outwardly pointing teeth 41 provided on the ratchet element 40 such that the clutch 60 follows rotation of the ratchet element 40 when the clutch 60 is in its proximal position.

[0131] The ratchet element 40 is rotated by the dose dial 15 via a set of transfer arms 44 provided on the ratchet element 40 and engaged by the dose dial 15 to transfer rotation to the ratchet element 40. The ratchet element 40 is further provided with a radial tooth 42 which engages a toothed ring 21 (see e.g. FIG. 4) provided proximally in the spring base 20 such that the ratchet element 40 can only be rotated in one direction in relation to the spring base 40. The allowed direction that the ratchet element 40 can be rotated by the dose dial 15 is the one that sets and increases the dose size.

[0132] However, the dose dial 15 is further provided with means for moving the radial tooth 42 out of its engagement with the toothed ring 21 of the spring base 40 which allows the dose dial 15 to be rotated in the opposite direction to decrease a set dose size.

[0133] The dial down rotation of the ratchet element 40 is primarily done by the torque stored in the torsion spring S1 which is released when the radial tooth 42 is moved radially towards the centre line X. If the user does not continue rotating the dose dial 15 in the dose lowering direction, the radial tooth 42 will be caught in the previous valley of the toothed ring 21 such that the set dose is lowered with one single increment.

[0134] When setting a dose to be ejected, the user rotates the dose dial 15 which in unison rotates the ratchet element 40 due to the engagement with the transfer arms 44. Since the ratchet element 40 engages the clutch 60 via the outwardly pointing teeth 41 engaging the toothing 64, the clutch 40 follows the rotation of the ratchet element 40 and thus of the dose dial 15. The scale drum 35 follows the rotation of the clutch 60 and moves helically due to its engagement with the housing 10 thus allowing the user to visually see the size of the dose being set.

[0135] The clutch 60 further rotational engages the drive tube 50 which is therefore also rotated. This rotation strains the torsion spring S1 which is encompassed between the drive tube 50 and the spring base 20. The torque so build in the torsion spring S1 is secured by the releasable one-way engagement between the radial teeth 42 of the ratchet element 40 and the toothed ring 21 of the spring base 20.

[0136] The toothed ring 21 is formed such that it prevents relative rotation of the radial teeth 42 in the not dose setting direction. However, as mentioned, the radial teeth 42 can be forced radially out of its engagement with the toothed ring 21 allowing the torsion spring S1 to counter rotate the ratchet element 40 via its engagement with the clutch 60 to lower a set dose when the dose dial 15 is rotated in the not dose setting direction.

[0137] When not injecting e.g. during dose setting, the clutch 40 is urged to its distal position by the compression spring S2. In this position the teeth 62 are disengaged from the external teeth 71 on the piston rod guide 70 as seen in FIG. 2. The piston rod guide 70 is thus free to rotate when the clutch 60 is in its distal position.

[0138] When the torsion spring engine herein described is used in a prefilled injection device the piston rod 75 would abut a plunger (e.g. via a piston rod foot) provided inside the cartridge containing the liquid drug to be injected. The fact that the piston rod guide 70 is freely rotatable between injections allows the piston rod 75 to move axially should the liquid drug in the cartridge move the plunger as a consequence of a temperature change.

[0139] The torque applied to the torsion spring S1 during rotation of the dose dial 15, the ratchet element 40, the drive tube 50 and the clutch 60 is thus held by the engagement between the internal toothing 64 on the clutch 40 and the outwardly pointing teeth 41 on the ratchet element 40 and between the radial tooth 42 on the ratchet element 40 and the toothed ring 21 of the spring base 20.

[0140] In order to eject the set dose, the clutch 60 is moved in the proximal direction as indicated by the arrow C in FIG. 2. Once the internal toothing 64 on the clutch 60 is disengaged from the outwardly pointing teeth 41 on the ratchet element 40 nothing holds the clutch 60 and the torsion spring S1 will rotate the drive tube 50 and the clutch 60 in unison. The ratchet element 40 which no longer is coupled to the clutch 60 will remain in its rotational position. At the same time as the clutch 60 is moved proximally, the inwardly pointing teeth 62 on the clutch 60 engages the external teeth 71 on the piston rod guide 70 which therefore rotates together with clutch 60 and the drive tube 50 during ejection.

[0141] The clutch 60 is preferably moved in the proximal direction by a needle shield abutting the skin of the user during injection, however, the housing could alternatively be provided with a slidable button which could be operated by the user to push the clutch 60 in the proximal direction.

[0142] Rotation of the piston rod guide 70 is directly transformed to a rotation of the piston rod 75 which thereby is screwed forward in the internal thread 31 of the nut member 30 such that the plunger inside the attached cartridge is moved in the distal direction to press out liquid drug from the cartridge.

The End-of-Content Mechanism, Example 1

[0143] In order to keep track of the number of set an ejected doses an End-of-Content system is disclosed in a first embodiment in the FIGS. 1 to 6, which EoC system comprises the ratchet element 40, the spring base 20 and a cycloid disc-shaped EoC element 80 as disclosed in FIG. 4.

[0144] The ratchet element 40 which is disclosed in details in FIG. 3 is rotated during dose setting around the centre axis X of the injection device as indicated in FIG. 4. However, the ratchet element 40 is provided with an annular bearing flange 43 which is formed eccentric such that the axis Y of the annular bearing flange 43 is offset a small distance from the centre axis X as seen in FIG. 3.

[0145] The cycloid disc-shaped EoC element 80 has, as best seen in FIG. 4 and in FIG. 6, a circular centre opening 81 defining an inner periphery 82 and an outer periphery 83. The inner periphery 82 rolls on the annular flange 43 of the ratchet element 40 during dose setting and the outer periphery rolls 83 on the toothed ring 21 of the spring base 20 and can be formed with one or more external teeth engaging the toothed ring 21.

[0146] The relationship between the diameter of the outer periphery 83 on the cycloid disc-shaped EoC element 80 and the inner diameter of the toothed ring 21 together with the small distance between the centre axis X of the ratchet element 40 and the centre line Y of the annular flange 43 and thus the cycloid disc-shaped EoC element 80 is such that the cycloid disc-shaped element 80 is rotated only a short distance for each full rotation of the annular flange 43 on the ratchet element 40. The rotational direction of the cycloid disc-shaped EoC element 80 is opposite the rotational direction of the ratchet element 40.

[0147] This hypocycloid working principle of this End-of-Content system is explained in details in WO 2014/117944 which is hereby incorporated by reference.

[0148] As can be best seen in FIG. 4 and in FIG. 6, the cycloid disc-shaped EoC element 80 is on its distal surface provided with an axially extending protrusion 84. This axially extending protrusion 84 engages a track 22 provided in the spring base 20. The track 22 is preferably formed with a number of valleys 25. In the depicted example in FIG. 4 and FIG. 5, the track 22 consists of 14 such valleys 25. A start valley 23 rotationally followed by 12 ordinary valleys 25 and at the end a stop valley 24.

[0149] The axially extending protrusion 84 can as disclosed in FIG. 6 also form an external teeth engaging the toothed ring 21.

[0150] When delivering the injection device to the user, the axially extending protrusion 84 is located in the start valley 23 thus leaving 12 valleys 25 free to travel before entering the stop valley 24. Further the diameter relation between the outer periphery 83 of the cycloid ring 80 and the inner diameter of the toothed ring 21 of the spring base 20 is selected such that the axially extending protrusion 84 moves through one valley 25 for each full rotation of the ratchet element 40. The axially extending protrusion 84 is thus able to move through the remaining 12 valleys 23 before coming to the stop valley 24 of the track 22. When the axially extending protrusion 84 is located in the stop valley 24 it is not possible to rotate the Cycloid disc-shaped EoC element 80 further which also prevents the ratchet element 40 from rotating further.

[0151] Since the ratchet element 40 follows the rotational movement of the dose dial 15, this design allows the dose dial 15 to rotate 12 full rotations before the axially extending protrusion 84 enters the stop valley 24 and thus abuts the end wall of the track 22. Once this happen the cycloid disc-shaped EoC element 80 is prevented from further rotation. This also means that neither the ratchet element 40 nor the dose dial 15 can rotate further in the dose setting direction. However, it is still possible to rotate the dose dial 15 in the opposite direction which moves the axially extending protrusion 84 in the opposite direction and thus lowers the size of the set dose.

[0152] If the herein disclosed EoC system is used for a torsion spring driven injection device for injecting insulin such injection devices often carries 300 I.U. of insulin in the cartridge and has a dose setting of 24 I.U. for each full revolution of the dose dial 15. The result being that once the user has rotated the dose dial 15 a number of 12 full revolutions then (1224) 288 I.U. has been set and ejected. In order to stop further rotation once exactly 300 I.U. has been set and ejected, the distance from the last ordinary valley 25 to the stop valley 24 needs to be equal to only half rotation of the dose dial 15. The Disc-shaped EoC element-shaped EoC element is thus able to perform 12.5 rotations thus allowing (12.524) 300 I.U. to be ejected. However, any number of valleys 25 can be selected depending on how many rotations should be allowed before the cycloid disc-shaped EoC element 80 comes to its stop position.

The End-of-Content Mechanism, Example 2

[0153] FIG. 7 to FIG. 12 disclose a second embodiment wherein the same constructional elements are numbered using the same reference numbers however with a 1 in front, the piston rod is henceforth numbered 175 in this embodiment.

[0154] The spring engine herein disclosed operates in the same way as the spring engine of the first embodiment; however, the EoC system is different as will be explained.

[0155] The EoC system primarily consist of three parts as disclosed in FIG. 8. These parts are; the ratchet element 140 (FIG. 9), the disc-shaped EoC element 180 (FIG. 12) and the spring base 120.

[0156] FIG. 12 discloses the cycloid disc-shaped EoC element 180 of the second embodiment in details. On the distal surface an axially extending first protrusion 184 is present as in the first embodiment. On the proximal surface a second protrusion 185 is provided which also extend axially. Further, the centre opening 181 has an oval shape such that the disc-shaped EoC element 180 is able to oscillate in a radial direction.

[0157] The first protrusion 184 is guided in a first track 122 provided in the spring base 120 as seen in FIG. 8 whereas the second protrusion 185 is guided in a second track 145 provided in the ratchet element 140. The spring base 120 is, as in the first embodiment, an operational part of the housing 110 either physically or by engagement. Internally the spring base 120 is provided with a toothed ring 121 supporting the outer periphery 183 of the disc-shaped EoC element 180 and a first track 122 as disclosed in FIG. 8.

[0158] The first track 122 is provided with a start valley 123, a stop valley 124 and a predetermined number of ordinary valleys 125 whereas the second track 145 is primarily a circular track but with a curled part 146 as best seen in FIG. 11.

[0159] The ratchet element 140 is, as in the first embodiment, provide with an annular flange 143 supporting the disc-shaped EoC element 180 as best seen in FIG. 9. However, in this embodiment, the annular flange 143 is circular allowing the opening 181 of the Disc-shaped EoC element-shaped EoC element 180 to rotate there upon.

[0160] As in the first embodiment, the rotational force is transmitted from the dose dial (not shown in this embodiment) to the ratchet element 140 via the transfer arms 144 and the radial tooth 142 engages the toothed ring 121 of the spring base 120.

[0161] In use, the user rotates the dose dial, which is not depicted in FIG. 7. This rotation is transformed to a rotation of the ratchet element 140 as in the first embodiment. At this moment, the first protrusion 184 is located in the start valley 123 and the second protrusion 185 is located in the circular part of the track 145. As long as the second protrusion 185 is located in the circular part of the second track 145, the disc-shaped EoC element 180 is not rotated when the ratchet element 140 is rotated.

[0162] At some point during the rotation of the ratchet element 140, the second protrusion 185 enters the curled part 146 of the second track 145. This will force the Disc-shaped EoC element-shaped EoC element 180 to oscillate in the radial direction such that the second protrusion 185 is moved toward the centre line X as best seen in FIG. 8. As the first protrusion 184 moves out of the curled track 146, the second protrusion 185 is moved away from the centre line X and thus into the first ordinary valley 125.

[0163] This pattern of movement will continue as the user sets subsequently doses and the second protrusion 185 will move one ordinary valley 125 for each full rotation of the ratchet element 140. The disc-shaped EoC element 180 will thus move in the same rotational direction as the ratchet element 140 and after a predetermined number of rotations of the ratchet element 140 and henceforth of the dose dial, the first protrusion 185 will enter the stop valley 124 of the first track 122 and prevent both the Disc-shaped EoC element-shaped EoC element 180 and the ratchet element 140 from further rotation.

The End-of-Content Mechanism, Example 3

[0164] In the third embodiment disclosed in FIGS. 13 to 17b, the spring engine operates as in both the previous two embodiments. The housing 210 distally carries a nut member 230 and proximally a spring base 220. The torsion spring S1 is encompassed between the housing 210 and the drive tube 250. The release clutch 260 is coupled to the drive tube 250 and axially movable in relation to the drive tube 250. Between injections the release clutch 260 is urged in the distal direction by the compression spring S2 such that the release clutch 260 in this first position is decoupled from the piston rod guide 270 allowing the piston rod guide 270 to rotate independently of the release clutch 260. At the same time the release clutch 260 is coupled with the rotatable dose setting element 240 to rotate simultaneously with the rotatable dose setting element 240 in order to set a dose.

[0165] In the second position the release clutch 260 is decoupled from the rotatable dose setting element 240 such that the release clutch 260 is able to rotate independently of the rotatable dose setting element 240 under influence of the torsion spring S1. Further, in this second position the release clutch 260 is coupled with the piston rod guide 270 such that the piston rod guide 270 rotates simultaneously with the release clutch 260 in order to drive the piston rod 275 forward.

[0166] The EoC system is disclosed in FIG. 14 and comprises the ratchet element 240, the spring base 220 and the disc-shaped EoC element 280. In addition an extra cycloid ring-shaped EoC gear element 290 is used in this embodiment.

[0167] This cycloid EoC gear element 290 has a centre opening 291 which rolls on the annual flange 243 of the ratchet element 240. The annular flange 243 on the ratchet element 240 is in this embodiment eccentric as in the first embodiment thereby introducing a hypocycloid rotational movement to the cycloid ring-shaped EoC gear element 290 during rotation of the ratchet element 240. This is similar to the first embodiment and the cycloid EoC gear element 290 thus rotates in the opposite rotational in relation to the ratchet element 240.

[0168] Whenever the user rotates the ratchet element 240 one full revolution by rotating the dose dial 215, the cycloid ring-shaped EoC gear element 290 rotates a smaller angular distance in the opposite rotational direction.

[0169] As can be seen from the FIG. 17, the cycloid ring-shaped EoC gear element 290 has a circular opening 291 and a proximal toothed periphery 292 and a distal toothed periphery 293. The proximal toothed periphery 292 rolls on the toothed ring 221 of the spring base 220 in a hypocycloid movement whereas the distal toothed periphery 293 is coupled to the disc-shaped EoC element 280.

[0170] Rotation of the cycloid EoC gear element 290 thus introduces a rotation of the disc-shaped EoC element 280 in the opposite rotational direction of the cycloid EoC gear element 290. The result being that whenever the ratchet element 240 is rotated e.g. in a clockwise direction, the cycloid ring-shaped EoC gear element 290 rotate a smaller angle in the anti-clockwise direction which again forces the disc-shaped EoC element 280 to rotate an even smaller angle in the clockwise direction thus following the rotational direction of the ratchet element 240.

[0171] When delivering the torsion spring driven injection to the user the axially extending protrusion 284 of the disc-shaped EoC element 280 is located in the start position 223 of the track 222 formed in the spring base 220. Every time the ratchet element 240 is rotated one full rotation in one rotational direction, the axially extending protrusion 284 is moved a smaller angle in the same rotational direction in the track 222. The angular movement of 284 is determined by the gearing ratio and after a predetermined number of rotations of the ratchet element 240 the axially extending protrusion 284 comes to the end position 224 in the track 222 where the axially extending protrusion 284 abut the end of the track 222 and thereby prevents further dose setting.

[0172] 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.