Medical syringe made of plastic and intended for a single use, re-use being made impossible by disconnection of the head and the shaft of the plunger at the start of injection

摘要

Medical syringe made of plastic and intended for a single use, re-use being made impossible. The shaft (1) of square cross-section is introduced almost to the bottom of a sleeve (2), likewise of square cross-section and integral with the head of the plunger, in such a way that wide notches which are formed in the two pieces facing each other, one towards the bottom, the other towards the top, can come into line and form a cylindrical space occupied by a wedge (3). By virtue of the shape of the notches, the suction movement is possible (wedge carried by a concavity of the notch of the shaft) while the start of the push movement expels the wedge held between the inclined parts of the notches. The injection can be carried out once, but the slightest attempt at a second suction movement is ineffective because the shaft leaves the sleeve/plunger head assembly. IMAGE