HYPODERMIC SYRINGE WITH SELECTIVELY RETRACTABLE NEEDLE

摘要

A hypodermic syringe with a selectively retractable needle includes an elongate barrel defining a receiver and a hollow bore. The syringe has a plunger with an elongate cavity 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 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 of the plunger. A second portion and the first porti on are joined at an attachment to form a shoulder 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. Th e syringe includes an elongate sleeve sized to fit over the first portion of the plung er and extend from the shoulder. The plunger includes a stopper to a form fluid tight seal with the barrel. The sleeve has a cutting surface inside of the stopper. The syringe includes a hub with a proximal flange and a passageway 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.