Patent ID: 7004929

Claim:
A medical device comprising: a hollow barrel having a forward end; a cartridge disposed within the barrel containing a medication; a needle having a sharpened forward end and operable between an extended position, in which the sharpened forward end projects from the forward end of the barrel, and a retracted position, in which the sharpened forward end is enclosed within the barrel; a plunger slidably disposed in the cartridge and operable to expel the medication from the cartridge; a biasing element that biases the needle towards the retracted position; and a needle retainer releasably engaging the barrel to maintain the needle in the projecting position against the force of the biasing element, wherein axial pressure on the plunger displaces the plunger forwardly to expel medication from the cartridge and release the needle retainer from engagement with the barrel, after which the needle is automatically propelled from the extended position to the retracted position by releasing pressure on the plunger.