Safety hypodermic syringe

Claim 1

In combination with a standard syringe whose fluid chamber has a piston slidable therein and is provided at its front end with a projecting nozzle and a cylindrical, internally-threaded socket concentric therewith; a safety hypodermic needle and shield assembly adapted to prevent accidental stick by the point of the needle after the needle has been injected into a patient and then withdrawn, said assembly comprising: a hub provided with a hollow base and an apex thereabove to support the needle, said base being threadably receivable in the socket of the syringe whereby the nozzle is then received in the hollow base to communicate with the needle to conduct fluid from the chamber into the needle or to conduct fluid from the needle into the chamber; B a pedestal integral with the hub to support a spring; C a compressible helical spring surrounding the needle, the lower end of the spring being anchored on the pedestal; D a shield supported at the upper end of the spring whose normal length is such as to place the shield just above the point of the needle, said shield having a center opening therein to permit the needle to pass therethrough; E a releasable latching mechanism supported on the pedestal which in a retracted mode of the assembly when the spring is compressed to retract the shield is adapted to hold the shield at its retracted position at which the needle is exposed for use, and in an extended mode of the assembly when the mechanism is released causes the shield to assume its place above the point to prevent accidental stick; and F a removable overcap which in the retracted mode of the assembly protectively covers the needle and surrounds the releasable latching mechanism to prevent accidental release thereof, thereby ensuring that the assembly is maintained in its retracted mode during shipment and storage.