Hypodermic syringe with selectively retractable needle

摘要

A hypodermic syringe (10) with a selectively retractable needle (56) includes an elongate barrel (12) defining a receiver (18) and a hollow bore (20). The syringe has a plunger (22) with an elongate cavity (34) open to the proximal end. The plunger is sized to fit within the bore of the barrel for a slidable movement to define a chamber (36) for receiving and expelling fluids. The inside diameter of the cavity in the plunger is sufficient to accept telescopically at least a part of a first portion (26) of the plunger. A second portion (32) and the first portion are joined at an attachment (38) to form a shoulder (40) extending outwardly from the first portion, with the plunger being telescopically collapsible by movement of the second portion into the cavity by of sufficient distal force to frangibly disrupt the attachment. The syringe includes an elongate sleeve (42) sized to fit over the first portion of the plunger and extend from the shoulder. The plunger includes a stopper (44) to a form fluid tight seal with the barrel. The sleeve has a cutting surface (46) inside of the stopper. The syringe includes a hub (50) with a proximal flange (52) and a passageway (54) within the receiver. The syringe has a needle with a pointed distal end mounted in the passageway of the hub extending distally outwardly. When sufficient distal force is applied to collapse the plunger, the cutting surface of the sleeve cuts through the stopper and through the flange of the hub and releases it from the receiver to retract the needle.