Single use syringe

摘要

A non-reusable hypodermic syringe is provided which comprises an elongated cylinder open at one end and substantially closed at the opposite other end. A hollow member is formed on the other end, which hollow end defines an internal duct communicating with the interior of the cylinder. The hollow member is configured and dimensioned to have a hypodermic needle affixed to it. The syringe plunger is comprised of a substantially rigid shaft and a resilient piston releasably attached to a first end of the shaft member. The piston fits into the interior of the cylinder in longitudinally sliding, frictional sealing engagement therewith. An engagement member is positioned on the piston member, and a retention member is positioned on the interior wall of the cylinder adjacent to, but spaced from the other end of the cylinder. The retention member projects into the interior of the cylinder so as to define a terminal end zone of the cylinder between the closed end and the retention member, and is configured and dimensioned to cooperate with the piston and the engagement member to allow insertion of the piston into the terminal end zone upon urging by the shaft in a first longitudinal direction toward the closed end and to blockingly engage the engagement member upon retraction of the shaft in a second opposite longitudinal direction so as to cause release of the piston from the shaft and retention of the piston within the terminal end zone upon continued retraction of the shaft.