Patent ID: 7297135

Claim:
A hollow needle applicator for administering a fluid from a cartridge which has a fixed needle, said applicator comprising an applicator body in which the cartridge is mounted; a piston assembly located within the cartridge and slidable therein to discharge the fluid contents of the cartridge via the needle; a force applying actuator mounted into the body and having at least one force transmitting part which provides a coupling with the piston assembly effective to displace the piston assembly within the cartridge to discharge contents of the cartridge; and a provision for automatic needle retraction after cartridge contents discharge comprising spring means arranged within a forward portion of the applicator body to act between the applicator and the cartridge to which the needle is fixed; wherein the piston assembly comprises a deformable piston, a piston rod which transmits force to the piston from the actuator, and a triggering means which is movable by the piston, when deformed into the end of the cartridge, to release the coupling between the force transmitting part or parts of the actuator and the piston assembly and bring about needle retraction; and wherein the piston rod is hollow and has driven extension parts which co-operate with the force transmitting part or parts of the actuator and are deflectable away from each other upon release from said force transmitting part or parts and the triggering means comprises a rod which is slidable within the hollow piston rod to deflect said extension parts.