Patent ID: 8277422

Claim:
A vacuum-retractable safety syringe, the syringe comprising: a syringe body defining a distal portion, an intermediate portion, and a proximal portion; a proximal seal located in the proximal portion of the syringe body; a plunger assembly disposed within the syringe body, the plunger assembly comprising a shaft, a distal piston, and a proximal piston, the plunger assembly being traverseable between a retracted position and an engaged position; a needle coupled to a needle holder, the needle holder removeably engageable to the distal portion of the syringe body and engageable to the distal piston when the plunger assembly is traversed to the engaged position; a fluid chamber disposed within the syringe body, the fluid chamber located distally from the distal piston, the fluid chamber having a distal and proximal end, the proximal end of the fluid chamber being sealed, the fluid chamber in fluid communication with the needle through the distal end of the fluid chamber and configured to be reduced in volume as the plunger assembly is traversed towards the engaged position; a vacuum chamber disposed within the syringe body, the vacuum chamber located intermediate the proximal piston and the proximal seal, the vacuum chamber configured to provide a vacuum force on the proximal piston in a direction from the syringe body distal portion toward the syringe body proximal portion upon movement of the plunger assembly toward the syringe body distal portion responsive to the distal translation of the plunger assembly; and an intermediate chamber disposed within the syringe body, the intermediate chamber located intermediate the distal piston and the proximal piston, the intermediate chamber having an air-passage vent connecting a volume external to the syringe body to the intermediate chamber when the plunger assembly is traversed between the retracted position and the engaged position.