Autoinjector

1. An autoinjector comprising:

a case including a rib;

a needle shroud telescopically coupled to the case and movable between a first extended position, a retracted position and a locked second extended position;

a carrier slidably arranged in the case and adapted to hold a medicament container, the carrier movable from a first axial position to a second axial position relative to the case;

a collar rotatably and slidably disposed in the case, the collar coupled to the needle shroud and the carrier;

a trigger button operably coupled to the carrier; and

a control spring biasing the collar in a distal direction relative to the case,

wherein the carrier abuts the rib in the first axial position and the needle shroud is configured to move to the first extended position and disengage the rib when the needle shroud is moved to the retracted position and the trigger button is pressed to advance the carrier to the second axial position,

wherein the collar includes a shroud boss adapted to engage a shroud slot in the needle shroud and a carrier boss adapted to engage a carrier slot in the carrier, and

wherein the collar couples a force of the control spring to either the carrier or the needle shroud based on axial and rotational positions of the needle shroud and the carrier relative to the collar.

2. The autoinjector according to claim 1 , further comprising:

a plunger slidably coupled to the carrier; and

a drive spring biasing the plunger relative to the carrier.

3. The autoinjector according to claim 2 , wherein the carrier includes a compliant beam having a boss adapted to engage an opening in the plunger when the carrier is in the first axial position.

4. The autoinjector according to claim 3 , wherein the boss is adapted to engage the case when the carrier is in the second axial position.

5. The autoinjector according to claim 1 , wherein the collar is configured to be in a first angular position relative to the case when the needle shroud is in the first extended position and the carrier is in the first axial position.

6. The autoinjector according to claim 5 , wherein the collar is configured to rotate to a second angular position relative to the case and to translate proximally relative to the case when the needle shroud moves from the first extended position to the retracted position.

7. The autoinjector according to claim 6 , wherein the collar is configured to translate distally relative to the case when the needle shroud is in the retracted position and the carrier moves from the first axial position to the second axial position.

8. The autoinjector according to claim 7 , further comprising a plunger slidably coupled to the carrier; and a drive spring biasing the plunger relative to the carrier,

wherein a boss of the carrier is configured to disengage an opening in the plunger and abut the case when the carrier is in the second axial position, and

wherein the plunger is configured to translate axially relative to the carrier under the force of the drive spring to advance the carrier from the second axial position to a third axial position relative to the case.

9. The autoinjector according to claim 8 , wherein the collar is configured to rotate to a third angular position relative to the case and to translate with the needle shroud distally relative to the case when the carrier is in the third axial position.

10. The autoinjector according to claim 9 , wherein the collar is configured to rotate to a fourth angular position relative to the case when the needle shroud is in the locked second extended position.

11. The autoinjector according to claim 10 , wherein the carrier boss is adapted to abut a surface in the carrier slot when the collar is in the fourth angular position and the needle shroud is in the locked second extended position.

12. The autoinjector according to claim 11 , wherein the engagement of the carrier boss and the carrier slot and the engagement of the carrier to the case substantially fixes the collar in an axial position relative to the case.

13. The autoinjector according to claim 1 , wherein the carrier includes a compliant beam adapted to engage the rib when the carrier is in the first and second axial positions.

14. The autoinjector according to claim 13 , wherein the needle shroud includes a ramp adapted to engage and deflect the compliant beam as the needle shroud translates from the first extended position to the retracted position.