Medicament delivery device

1. Medicament delivery device comprising

a distal housing part, and

a proximal housing part adapted to receive a medicament container comprising a movable stopper, wherein said housing parts are configured to be attached to each other;

a threaded plunger rod arranged within said medicament delivery device and being movable in a longitudinal direction of the device;

a drive nut configured to drive said threaded plunger rod towards a proximal end of the device; and

a spring is pre-tensioned and twisted arranged inside the threaded plunger rod and operably associated with said threaded plunger rod and configured to exert both a torsion force and a tension force on said threaded plunger rod for positioning the plunger rod in relation to the stopper and for avoiding drooling respectively.

2. Medicament delivery device of claim 1 , further comprising a drive force configured to drive said drive nut.

3. Medicament delivery device of claim 1 , further comprising

a guide member rotatably lockable but longitudinally slidably connected to said threaded plunger rod and configured to be switched by a lock and release mechanism between

a locked state in which the guide member is prevented to rotate when said housing parts are connected to each other and

a released state in which the guide member is allowed to rotate when said housing parts are disconnected.

4. Medicament delivery device according to claim 3 , wherein the torsion force acting on the threaded plunger rod when said guide member is in the released state, exceeds the tension force such that said threaded plunger rod is urged towards the proximal end of the device, and wherein the tension force acting on said threaded plunger rod when said guide member is in the locked state exceeds the torsion force such that the threaded plunger rod is urged towards a distal end of the device.

5. Medicament delivery device according to claim 1 , wherein said threaded plunger rod is configured to act on said stopper.

6. Medicament delivery device according to claim 1 , wherein the spring has a proximal end attached to a proximal fixation member and a distal end attached to a support member.

7. Medicament delivery device according to claim 1 , wherein said spring displays pulling and torsion properties.

8. Medicament delivery device according to claim 1 , wherein said spring comprises a tension spring.

9. Medicament delivery device according to claim 3 , wherein the device further comprises an actuation mechanism which is operably connected to said drive nut such that said drive nut is locked when said guide member is in the released state.

10. Medicament delivery device according to claim 9 , wherein said actuation mechanism further comprises

a manually operable actuation member, capable of, upon operation, releasing said drive nut and thus said drive means for driving said threaded plunger rod towards a proximal end of the device.

11. Medicament delivery device according to claim 6 , wherein a proximal part of said proximal fixation member is connected with a proximal end of the threaded plunger rod.

12. Medicament delivery device according to claim 6 , wherein said support member is connected to a drive force configured to drive a drive nut.

13. Medicament delivery device of claim 1 , further comprising a rotatable drive shaft and a torsion drive spring,

wherein rotation of the drive shaft causes said torsion drive spring to tension.

14. Medicament delivery device of claim 13 , wherein said torsion drive spring force acts on said threaded plunger rod in that actuation of the medicament delivery device causes the threaded plunger rod to move in a longitudinal direction on account of the tension of said torsion drive spring.

15. Medicament delivery device of claim 1 , wherein the device comprises a reusable auto-injector.