Medicament delivery device

1. An assembly for a medicament delivery device, the assembly comprising:

a housing;

a plunger rod slidably positioned within the housing, where the plunger rod comprises an open distal end and a hollow interior containing a proximal end portion of a resilient member biased against a closed proximal end of the plunger rod;

a flexible finger directly connected to the plunger rod to hold the plunger rod in a biased position relative to the housing;

an operation member rotatably positioned within the housing, where the operation member has a first position and a second position; and

an activation member slidably positioned within and rotatably restricted relative to the housing, where the activation member comprises a distal end operatively engaged with the operation member, where the distal end of the activation member is slidably engaged with the operation member when the operation member is in the first position, during rotation to the second position and when the operation member in the second position;

wherein a proximal movement of the housing relative to the activation member when the activation member is positioned at a medicament delivery site causes the distal end of the activation member to move axially and distally relative to the operation member causing the operation member to rotate relative to the housing and the activation member from the first position to the second position, and

wherein when the flexible finger flexes radially, the plunger rod moves axially in a proximal direction.

2. The assembly of claim 1 , wherein the operation member is rotatably positioned within a distal end of the housing.

3. The assembly of claim 1 , wherein the operation member comprises a co-acting pathway.

4. The assembly of claim 3 , where the distal end of the activation member has a co-acting protrusion slidably positioned in the co-acting pathway.

5. The assembly of claim 4 , wherein the co-acting pathway is non-linear.

6. The assembly of claim 3 , wherein the distal end of the activation member has a co-acting protrusion slidably positioned in the co-acting pathway such that the co-acting protrusion is guided by and follows the co-acting pathway when the operation member moves axially relative to the activation member.

7. The assembly of claim 1 , wherein the resilient member is in a pretensioned state when the operation member is in the first position, where the resilient member is pre-tensioned in an axial direction.

8. The assembly of claim 7 , wherein the resilient member is in a released state when the operation member is in the second position.

9. The assembly of claim 1 , wherein the distal end of the activation member has a protrusion that is slidably engaged with the operation member.

10. The assembly of claim 1 , wherein the distal end of the activation member comprises two distally extending arms, where each of the distally extending arms comprises a protrusion slidably engaged with the operation member.

11. The assembly of claim 10 , wherein the operation member further comprises two non-linear pathways, where the protrusions of the distally extending arms are slidably engaged with the two non-linear pathways.

12. The assembly of claim 1 , wherein the distal end of the activation member further comprises a lock to prevent proximal axial movement of the activation member when medicament delivery is complete and the activation member is removed from the medicament delivery site.

13. A method of initiating an injection of a medicament, the method comprising:

providing an assembly comprising:

an operation member;

a plunger rod slidably positioned relative to the operation member, where the plunger rod comprises an open distal end and a hollow interior containing a proximal end portion of a pretensioned first resilient member biased against a closed proximal end of the plunger rod;

a flexible finger directly connected to the plunger rod to hold the plunger rod in a biased position relative to the operation member; and

an activation member having a proximal end and a distal end and slidably arranged relative to the operation member;

pressing the proximal end of the activation member against an injection delivery site such that the activation member moves distally relative to the operation member;

slidably engaging the distal end of the activation member with the operation member to cause the operation member to rotate relative to the activation member;

radially flexing the flexible finger such that the flexible finger disengages from the plunger rod, and

releasing the pretensioned first resilient member such that the proximal end portion pushes the closed proximal end in a proximal direction to cause delivery of the medicament within the injection delivery site.

14. The method of claim 13 , further comprising moving a protrusion located on the distal end of the activation member along a non-linear pathway on the operation member.

15. The method of claim 13 , further comprising rotating the operation member to rotate from a first position to a second position.

16. The method of claim 15 , wherein the rotation of the operation member is counterclockwise when seen from a distal end of the assembly.

17. The method of claim 13 , further comprising locking the operation member in an extended position to prevent distal axial movement of the activation member when the activation member is removed from the injection delivery site.

18. The method of claim 13 , further comprising moving the activation member proximally by releasing an axially directed force in a second resilient member when the activation member is removed from the injection delivery site.