Patent ID: 7351224

Claim:
A syringe comprising a hollow body with first and second open ends and an inside wall of varying inside diameter extending between the first and second open ends, a needle retraction mechanism insertable into the body through the second open end, a plunger having a forwardly extending plunger head insertable into the body through the second open end behind the needle retraction mechanism, and a needle extending forwardly of the first open end, wherein: the body comprises a nose adjacent to the first open end, a barrel adjacent to the second open end, and a transition zone connecting the barrel and nose; the needle retraction mechanism comprises an elongated needle holder, a compressed retraction spring, and a retainer member; the elongated needle holder further comprises a needle holding portion secured in fixed relation to the needle, a reduced diameter portion at one end of the needle holding portion, the reduced diameter portion extending forwardly through the first open end; a head at another end of the needle holding portion opposite the reduced diameter portion; a fluid path extending longitudinally through the needle holder in fluid communication with the needle and with a variable fluid chamber inside the body between the needle holder and the plunger; the needle holding portion is grounded inside the nose adjacent to the first open end by a barrier limiting forward motion of the elongated needle holder inside a front portion of the nose prior to or during retraction; the compressed retraction spring is positioned prior to retraction in an annulus disposed between the needle holding portion and the inside wall of the hollow body; the plunger head is aligned to separate the retainer member from the head of the needle holding portion and release the compressed retraction spring during retraction; and the plunger comprises a retraction cavity into which part of the retraction mechanism is received during retraction so that the needle no longer extends forwardly of the first open end.