Syringe with self-retracting needle

Claim 1

A syringe with a self-retracting needle, comprising a body (1) carrying at one end a means (5) for supporting an injection needle (6), a plunger (13) which is movable within said body, a protective sheath (14) within which said body (1) can slide, a spring (17) disposed between said sheath (14) and said body (1), a means for catching said sheath (14) on the body (1) comprising first and second shoulders (21, 23) on the outer wall of said body (1) and at least a first flexible toe (19) borne by said sheath (14) so as to cooperate in abutment with said first shoulder (21) for defining a first blocking position of said body (1) in relation to said sheath (14) in a first direction, said spring (17) being compressed and said needle (6) protruding from said sheath in this first position, and with said second shoulder (23) for defining a second blocking position in the same direction, said spring (17) being at least partially released and said needle (6) being withdrawn inside said sheath (14) in this second position, the transition from said first position to said second position being made by cooperation of said plunger (13) with said first flexible toe (19) for freeing said toe (19) of said first shoulder (21) at the end of stroke of said plunger (13), thereby causing said body (1) to retract into said sheath (14) under the effect of said spring (17) until it blocks in said second position, characterized in that it comprises at least a second flexible toe (20, 20', 33) and a third shoulder (24), respectively in the opposite direction to said first flexible toe (19) and two first shoulders (21, 23), respectively positioned on said sheath (14) and wall of said body (1) for blocking said body (1) in said sheath (14) when it is in said second blocking position, in the opposite direction to said first direction.