Autoinjector

1. An injection device comprising:

a case;

a syringe carrier slidably disposed within the case, the syringe carrier adapted to hold a syringe including a stopper;

a plunger slidably disposed within the syringe carrier, the plunger adapted to apply a force on the stopper;

a drive spring disposed within the plunger and adapted to bias the plunger relative to the syringe carrier;

a needle shroud slidably disposed within the case, the needle shroud telescopically arranged over the syringe carrier;

a detent mechanism adapted to couple the needle shroud to the syringe carrier, and adapted to couple the needle shroud to the case, wherein the detent mechanism comprises a resilient shroud beam on the needle shroud, the resilient shroud beam having a shroud boss configured to releasably engage a carrier opening in the syringe carrier;

a collar slidably arranged on the syringe carrier; and

a control spring applying a biasing force to the collar, wherein the collar comprises a resilient collar beam having a collar boss adapted to releasably engage a step on the syringe carrier, wherein the collar boss is prevented from deflecting radially by a narrow section in the case, wherein a wide section of the case is arranged distally from the narrow section such that upon axial movement of the syringe carrier and the collar in a distal direction, the collar boss deflects radially when the collar enters the wide section and disengages the collar from the syringe carrier under force from the control spring allowing the collar to advance further under the force of the control spring until it abuts the needle shroud.

2. The injection device according to claim 1 , wherein the case includes a proximal case boss configured to abut the shroud boss when the needle shroud is in a first extended position.

3. The injection device according to claim 1 , further comprising:

an engagement surface on the syringe carrier and an engagement surface on the plunger, the engagement surface of the syringe carrier configured to engage the engagement surface of the plunger to releasably couple the plunger to the syringe carrier.

4. The injection device according to claim 1 , further comprising a plunger release mechanism adapted to releasably couple the plunger to the syringe carrier, the plunger release mechanism comprising a resilient carrier beam on the syringe carrier having a carrier boss adapted to releasably engage a plunger opening in the plunger.

5. The injection device according to claim 1 , wherein the collar is configured to abut a carrier boss of the syringe carrier when the needle shroud is in a first extended position.

6. The injection device according to claim 5 , wherein the collar, the needle shroud, and the syringe carrier are configured to move proximally relative to the case when the needle shroud is moved from the first extended position to a first retracted position.

7. The injection device according to claim 6 , wherein a proximal end of the syringe carrier is configured to abut a proximal end of the case when the needle shroud is moved from the first extended position to the first retracted position to provide a feedback.

8. The injection device according to claim 6 , wherein the shroud boss of the needle shroud is configured to be proximal of a proximal case boss of the case when the needle shroud is in the first retracted position.

9. The injection device according to claim 8 , wherein the syringe carrier is configured to advance distally when the needle shroud is in a second retracted position proximal of the first retracted position, and the shroud boss disengages the carrier opening on the syringe carrier.

10. The injection device according to claim 9 , wherein the collar is configured to, when the shroud boss disengages the carrier opening to decouple the syringe carrier from the needle shroud,

push the syringe carrier distally until the syringe carrier abuts a front stop in the case, and

disengage the syringe carrier under the biasing force of the control spring and push the needle shroud into a second extended position relative to the case.

11. The injection device according to claim 10 , wherein, when the collar disengages the syringe carrier, the carrier boss disengages a plunger opening on the plunger to release the plunger.

12. The injection device according to claim 10 , wherein the shroud boss abuts a distal case boss when the needle shroud is in the second extended position.