Security device for a syringe pre-filled with a liquid injection, in particular of a medicine

The invention relates to a safety assembly (E) for a syringe (S), comprising: a tubular sleeve (1) in which the syringe body (K) is intended to be housed axially displaceable, elastic return means (R), - Locking means (5) for immobilizing the body (K) relative to the sleeve (1), these locking means being releasable, a revolution cap (8), mounted to slide axially with respect to the sleeve (1), - inner lugs (10) for snapping the flange (CL) of the syringe body (K) on the cap (8), and - Two complementary shoulders (7, 11) forming abutments respectively provided on the cap (8) and the sleeve (1) to limit the stroke of the cap (8) after release of the locking means (5).