Patent ID: 7147621

Claim:
A single use syringe that has: a syringe body which has an open rear end, and a front end formed with an opening, a needle assembly which comprises a needle which has an outer end and an inner end, and a needle holder which is attached to the inner end of the needle, the needle holder having a body portion which has an inner end and an outer end, the inner end of the body portion extending into the syringe body and having a tapered face, the outer end extending into the opening in the front end of the syringe body, the body portion having a circumferential portion which initially diverges and then converges from the inner end to the outer end, the needle holder being releasably attached adjacent the front end of the syringe body, a plunger moveable along the syringe body, the plunger having a plunger body and a plunger head, the plunger head being formed with a concave portion which is adapted to extend about at least a portion of the inner end of the body portion of the needle holder when the plunger head is pushed against the inner portion, the plunger having sealing means extending in front of the plunger head to seal the plunger against the inside wall of the syringe body, the sealing means being attached to the plunger via a hinge portion, the sealing means pushing against the front of the syringe body when the plunger is pushed fully forwardly and causing the opening in the front end of the syringe body to enlarge thereby releasing the needle holder, the forward part of the plunger adapted for compressive engagement with the converging portion on the needle holder to provide a propelling force to shoot the needle holder back into the plunger body.