Blood collecting syringe with retractable needle

A blood taking syringe comprising:

• A syringe housing having a first chamber adapted to accept a removable blood-collecting vacuum vial and a second chamber adapted to hold a releasably mounted needle assembly under tension with an outwardly extending protrusion on the syringe housing at the intersection of the first and second chambers of the syringe housing, with said protrusion having an inwardly open slot extending entirely around the periphery of the syringe housing;
• A needle assembly, including a cylindrically shaped needle retainer, having first and second ends, with a double-ended hypodermic needle extending through the center thereof, with said needle and needle retainer being axially aligned with the central axis of the syringe housing;
• A compressable spring, normally held in a compressed mode, seated in the second chamber of the syringe housing for applying pressure to the needle retainer along the central axis of the syringe housing;
• A needle assembly restraining means for applying a restraining force to the needle retainer to counter the force of the compressed spring and for maintaining said needle assembly in a state of equilibrium, wherein the needle assembly restraining means consists of an annular ring, with the center hole being sufficiently large to allow the needle assembly to pass unobstructively therethrough, upon releasing the restraining force, with the centerline axis of the ring normally being off-set from the central axis of the syringe housing and needle assembly while in a restraining mode, during which one edge of the annular ring intrudes into the slot in the protrusion of the syringe housing to hold the needle assembly in a state of equilibrium;
• Manually responsive pressure means for disengaging the needle assembly restraining means to allow the compressed spring to force the needle assembly into the first chamber of the syringe housing.
• Safety cap means for stopping the retracting needle assembly and for sealing the open end of the first syringe chamber prior to release of the needle restraining means.