Abstract: A retractable syringe includes a barrel, one end of which comprises a mounting collar. A needle carrier is releasably mounted within the collar, and releasably supports a needle cartridge. A hypodermic needle is mounted within the cartridge. A sheath attaches at one end to the cartridge, and at the other end to the collar. A plunger is telescoped into the barrel, and includes a relatively hard piston sealingly engaging the barrel. The piston includes a latch for engaging the carrier and releasing it from the collar. A pocket in the carrier has a support member in its center, and a pair of helical ribs for threadingly engaging a pair of tabs on the cartridge. The cartridge sealingly receives the support member. The collar has slots and inclined threads in its bore wall for engaging lugs on the carrier. The inclined threads have a friction bump near their blind ends. A retaining pin prevents relative rotation between the carrier and collar prior to desired retraction of the needle into the barrel.

Abstract: A retractable syringe includes a resilient barrel, one end of which comprises a mounting collar. A needle carrier is releasably mounted within the collar, and releasably supports a needle cartridge. A hypodermic needle is mounted within the cartridge. A sheath attaches at one end to the cartridge, and at the other end to the collar. A plunger is telescoped into the barrel, and includes a relatively hard piston sealingly engaging the barrel. The piston includes a latch for engaging the carrier and releasing it from the collar. A pocket in the carrier has a support member in its center, and a pair of helical ribs for threadingly engaging a pair of tabs on the cartridge. The cartridge sealingly receives the support member. The collar has slots and inclined threads in its bore wall for engaging lugs on the carrier. The inclined threads have a friction bump near their blind ends. A retaining pin prevents relative rotation between the carrier and collar prior to desired retraction of the needle into the barrel.

Abstract: A single use hypodermic needle syringe is constructed in a manner which provides for the automatic self destruction of the fluid passage during the initial use upon the first complete injection stroke. Because the fluid passage is destroyed upon the first initial use of the hypodermic needle syringe, the syringe is rendered useless and must be discarded. Because the syringe is discarded after one use, the spread of infectious diseases will be inhibited.

Abstract: A disposable safe hypodermic syringe. Includes a hollow barrel formed with a support collar at one end to enclose and releaseably latch a needle support member and a hypodermic needle carried by the support member. The barrel is formed at its distal second end to receive an injection piston carried by the plunger member. The plunger head and needle support member cooperate to form a latch for latching the support member to the plunger head, releasing the support member from the support collar, and withdrawing the plunger head, support member, and needle together to a protective position within the barrel. A latch carried by the injection piston and by the second end of the barrel finally latches the injection piston, plunger head, support member, and needle together to a contagion safe position. Two embodiments are disclosed.