Disposable hypodermic syringe and needle combination having retractable, accident preventing sheath

Claim 1

A combination of a hypodermic needle and syringe of the type which is discardable after a single use, the combination comprising: a syringe barrel having a plunger mounted in the barrel; a hypodermic needle mounted to the barrel at an end of the barrel which is opposite to the end where the plunger enters the barrel; a sheath mounted to the barrel and extending therefrom in a first position to substantially cover the needle and thereby prevent the needle from accidental contact with a foreign object or person during transportation and storage of the combination, the sheath being made of a different plastic material than the barrel and the plunger and which melts at lower temperature than the plastic material of the barrel and plunger, below the temperature customarily used for sterilization by heat, whereby repeated use of the syringe through sterilization can be substantially avoided; means incorporated into the barrel and the sheath for permitting movement of the sheath upward on the barrel into a second position wherein the needle is at least partially exposed, for permitting downward movement of the sheath on the barrel into a third position wherein the needle is substantially covered by the sheath, and for substantially irreversibly locking the sheath to the barrel in the third position, whereby the needle is protected when the combination is discarded after normal use.