Patent attributes
Pre-filled injection ampoules for administering a readily-available dose of fluid medication, are provided with a retractable needle. The needle is held in a projecting configuration from a barrel against a rearward bias exerted on the needle by a spring located within a spring housing. A piston is positioned within the barrel for expelling the fluid medication therefrom. The piston is configured to release the needle after completion of an injection stroke and to receive the needle in an internal cavity. In alternative embodiments, a retractable-needle injection device includes a housing for receiving a pre-filled medication cartridge of the type having a slidable piston positioned therein. A stationary plunger is located within the housing for maintaining the piston at a fixed location as the cartridge is urged into the housing to administer an injection. After the end of an injection stroke, the cartridge is further urged into the housing to release a effectuate retraction.
