Dial-down mechanism for wind-up pen

Abstract

The present invention relates to a dial-down mechanism for an injection device comprising a torsion spring for assisting injection of a dose of medicament from the injection device, the dial-down mechanism comprising dial-up cam arranged to receive and engage with a dial-up key, wherein the dial-up cam and the dial-up key are adapted to, upon rotation of a dose setting member in a first direction, cooperate to strain the torsion spring of the injection device, and a dial-down cam arranged to receive and engage with a dial-down key, wherein the dial-down cam and the dial-down key are adapted to, upon rotation of the dose setting member in a second direction, cooperate to release the torsion spring of the injection device, the second rotation direction being opposite to the first rotation direction.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

FIG. 2 showsFIG. 2 shows FIGS. 2A and 2B show an exploded drawing of the radial embodiment of the dial-down mechanism according to the present invention. The main difference compared to the embodiment shown in FIG. 1 is that the embodiment of FIG. 2 FIGS. 2A and 2B applies different pick-up keys for dial-up (pick-up key 11) and dial-down (pick-up key 12). The dial-up key 11 engages with track 15 of the disc 14, whereas dial-down key 12 engages with track 16 of the disc 14. Tracks 15 and 16 are formed as through-going openings or indentations in a planar surface of the disc 14. The dial-up tracks 15 take the form of curved tracks whereas the dial-down tracks 16 are V-shaped. An obvious alternative to the V-shape is a rectangular shape. It should be noted that the general idea is that the dial-up tracks 15 should be capable of transferring a momentum to a torsion spring 18. In the same manner, the dial-down tracks 16 should be capable of releasing the dial-down keys (and thereby release energy) in case the disc 14 is rotated just a few degrees relative to the nut 10.

The dial-down keys 12 are integrated with the flexible arms 19. These arms are fabricated of a resilient material such as for example plastic. The flexible arms 19 with integrated dial-down keys 12 form an integral part of the ratchet 13. Thus, the ratchet including arms and dial-down keys may preferably be fabricated of the same material, such as of plastic. In order to bias the dial-down keys 12 against the teeth 20 of the nut 10 a torsion spring 18 is arranged coaxially with the ratchet 13. An opening 21 is provided in the center part of the nut 10. The side wall of this opening is provided with threads 22 which are adapted to engage with a threaded outer surface of a piston rod (not shown).

FIG. 3 shows another radial embodiment according to the present invention. In this embodiment, the movement of the arm 26 is controlled by a track 23 in the nut 27. The track 23 is engaged by the track/cam follower 24 which precisely guides the dial-down key 28 from one tooth to the neighboring tooth during dial-down. In contrast to FIG. 2 the opening 25 in the center of the nut 27 is provided with a track follower 29. This track follower is adapted to engage with a track in the outer surface of a piston rod (not shown).

FIG. 4 shows an injection device having a radial dial-down mechanism according to the present invention. Among other components the injection device shown in FIG. 4 shows a dose setting member 30, a piston rod 31 having a threaded outer surface and a drive track arranged in the axial direction of the piston rod, a nut 32, a torsion spring 35, a drive member 33, the threaded portion 34 of the housing, a lease mechanism 36, a toothing mechanism 37, and ratchet 38.

A dose is set by rotating the dose setting member 30 and the nut 32 whereby the torsion spring 35 is strained. The dose setting member 30 is prevented from returning to its initial position due the toothing mechanism 37 positioned between the nut 32 and the drive member 33. In case the user wants to reduce a preset dose, the dose setting member 30 is simply rotated in the opposite direction. The interaction between ratchet 38 and nut 32 during dial-down is described in connection with FIG. 2.

FIG. 5 shows FIGS. 5A and 5B show an injection device having an axial dial-down mechanism according to the present invention. Among other components the injection device shown in FIG. 5 5B comprising a dose setting member 40, an opening 41 defining dial-up and dial-down cam surfaces, a cam follower 42, a torsion spring 43, a ratchet 44, and a piston rod 45. The general idea behind the axial dial-down mechanism is to use the torsion spring 43 to both drive and rotate the piston rod 45 and to ensure that the upper and lower parts of the toothing 48 remain together.

When a dose is to be set, the cam follower 42 engages with cam surface 46. As a result the torsion spring 43 is strained because the ratchet 44 is prevented from reversing due to the toothing 48. During dial-up the ratchet 44 will move up and down along cam surface 46 as the upper and lower parts of the toothing 48 rotate relative to each other. In case of dial-down the cam surface 47 will lift and thereby release the upper part of the toothing from the lower part of the toothing thereby the ratchet 44 is allowed to rotate an angle corresponding to one tooth.

Claims

1. A dial-down mechanism for an injection device comprising a torsion spring (18) for assisting injection of a dose of medicament from the injection device, the dial-down mechanism comprising

dial-up cam (15) arranged to receive and engage with a dial-up key (11), wherein the dial-up cam (15) and the dial-up key (11) are adapted to, upon rotation of a dose setting member in a first direction, cooperate to strain the torsion spring (18) of the injection device, and

a dial-down cam (16) arranged to receive and engage with a dial-down key (12), wherein the dial-down cam (16) and the dial-down key (12) are adapted to, upon rotation of the dose setting member in a second direction, cooperate to release the torsion spring (18) of the injection device, the second rotation direction being opposite to the first rotation direction,

wherein the dial-up and dial-down cams form part of regions of the same track,

further comprising an arm wherein the dial-up and dial-down keys are both located on the same arm, said keys being adapted to engage and cooperate with dial-up and dial-down cams of the same track.

2. A dial-down mechanism according to claim 1, wherein the dial-up cam (15) forms part of a curved track.

3. A dial-down mechanism according to claim 2, wherein the curved dial-up cam (15) forms part of a circular, elliptical or parabolic track.

4. A dial-down mechanism according to claim 1 comprising a first and a second dial-up cam.

5. A dial-down mechanism according to claim 4 comprising a first and a second dial-up key, wherein the first dial-up key is adapted to engage and cooperate with the first dial-up cam, and wherein the second dial-up key is adapted to engage and cooperate with the second dial-up cam.

6. A dial-down mechanism according to claim 1, wherein the dial-down cam (16) forms part of a V-shaped track.

7. A dial-down mechanism according to claim 1 comprising a first and a second dial-down cam.

8. A dial-down mechanism according to claim 7 comprising a first and a second dial-down key, wherein the first dial-down key is adapted to engage and cooperate with the first dial-down cam, and wherein the second dial-down key is adapted to engage and cooperate with the second dial-down cam.

9. A medication delivery device comprising a dial-down mechanism according to claim 1.

10. A medication delivery device according to claim 9, wherein the medication delivery device is a handheld medication injection pen.

11. A method for using a wind up injection pen, the method comprising the steps of

rotating a first element in a first direction, the direction being a dial up direction;

causing a second element to be rotated in the same direction as the first element;

straining a torsional spring;

moving an arm that is in engagement with one edge to a neighboring edge, wherein when the arm is engaged with an edge it prevents the torsional spring from unwinding;

rotating the first element in a second direction opposite the first direction;

moving a pick-up key and radially lifting the arm out of engagement with an edge and when the arm is fully disengaged from an edge allowing the second rotatable element to rotate in the second direction and allowing the strain on the spring to be decreased.