HYPODERMIC SYRINGE WITH SELECTIVELY RETRACTABLE NEEDLE

摘要

A syringe has a retractable needle and a barrel having an open proximal end and an open distal end defining a receiver with an inward shoulder. The barrel h as a hollow bore, an elongate plunger with a proximal end and a distal open end with a cavity therewithin. A stopper occludes the open end of the cavity. The syringe has an elongate hub with a proximal flange. The hub is within and sized for slidable movemen t within the receiver at the distal end of the barrel with the flange defining a dist al end of a chamber. There is a sleeve sized to fit with a clearance about the hub disposed between the shoulder and the flange when the hub is in the receiver, the sleeve havi ng a sharpened proximal end disposed against the flange. The needle has a pointed distal en d and a proximal end connected to the passageway of the hub with the pointed end of the needle extending outwardly. There is a spring disposed about the hub compressed to provide a bias between the receiver and the flange so that when a force greater than required to expel fluid from the chamber is applied, the plunger causes the cutting surface to cut through the flange and stopper and expose the cavity to allow the spring to urge the hub into the cavity in the plunger and retract the needle to a position within t he syringe.