BACK-END DEVICE FOR AN AUTO-INJECTOR AND AUTO-INJECTOR

摘要

According to the invention, a back-end device (1) of an auto - inj ector (A) adapted to be attached to a packaged syringe (2) comprises: - a plunger (1.3) 2) to translate an injection needle (2.5); - a drive means (1.7) capable of, upon release, driving the plunger in the proximal direction towards a proximal position; - a rotary sleeve (1.2) with a cam surface (1.2.1) adapted to be engaged by a plunger follower (1.3.1) formed to the plunger; - a torsion spring (1.8) arranged to exert a torque upon the rotary sleeve and - a release element (1.4) capable of, upon manual actuation, releasing the engagement of the plunger follower with the cam surface (1.2.1). Upon release of the engagement of the plunger follower with the cam surface, the rotary sleeve is arranged to rotate within the chassis (1.1). The cam surface re-engages the plunger follower after a time delay determined by a rotation speed of the rotary sleeve and is arranged to withdraw the plunger from the proximal position in a distal direction (D) by continued rotation of the rotary sleeve.