Patent ID: 7806858

Claim:
A retractable safety syringe for preventing accidental needle pricking and needle reuse, the syringe comprising: a syringe body defining a distal portion and a proximal portion; a plunger disposed within the syringe body and extending through the proximal portion of the syringe body, the plunger being traverseable between a retracted position and an engaged position; a needle removeably engageable to the distal portion of the syringe body and engageable to the plunger when the plunger is traversed to the engaged position; a variable fluid chamber inside the syringe body, the variable fluid chamber located distally from the plunger, the variable fluid chamber having a distal and proximal end, the proximal end of the variable fluid chamber being sealed, the variable fluid chamber in fluid communication with the needle through the distal end of the variable fluid chamber and configured to be reduced in volume as the plunger is traversed toward the engaged position, and further configured so that a fluid medication contained in the variable fluid chamber is expelled from the variable fluid chamber through the needle when the plunger is traversed toward the engaged position; a shell attached to the plunger and disposed external to the syringe body, the shell and the syringe body defining a sealed external vacuum compartment wherein the external vacuum compartment is increased in volume as the plunger is traversed toward the engaged position creating a first retraction force; and wherein when the plunger engages the needle at the engaged position, the first retraction force of the external vacuum compartment traverses the needle into the syringe body.