Patent ID: 7972300

Claim:
A retractable safety syringe, the syringe comprising: a syringe body defining a proximal portion, a distal portion, and a longitudinal axis, the syringe body having a first generally circular cavity defining a first inner surface and a second generally circular cavity defining a second inner surface, the second generally circular cavity disposed closer to the distal portion compared to the first generally circular cavity, the second generally circular cavity being larger than the first generally circular cavity; a needle removeably engageable to the body distal portion; a piston disposed within the body and bi-directionally traversable between the proximal and distal portions before completion of an injection stroke, the piston configured to engage the needle so that the needle is removed from the body distal portion upon completion of the injection stroke; a shaft disposed within the body and extending through the proximal portion of the body, traversal of the shaft through the body configured to traverse the piston between the proximal and distal portions; a variable vacuum compartment disposed within the syringe body, the variable vacuum compartment configured to provide a gradually increasing vacuum force on the shaft in a direction from the syringe body distal portion toward the syringe body proximal portion upon movement of the piston toward the syringe body distal portion; a braking member having a plurality of elongate bases and a plurality of lobes, a lengthwise direction of the plurality of elongate lobes and elongate bases defining a longitudinal axis, the longitudinal axis of the elongate lobes and elongate bases generally parallel to the longitudinal axis of the syringe body, the braking member further including a living hinge; and a ram attached to the shaft for axially driving the braking member from the first cavity into the second cavity upon completion of the injection stroke; wherein the braking member is initially disposed within the first generally circular cavity so the plurality of bases are biased toward and frictionally engaged to the first inner surface and the plurality of lobes are biased toward and frictionally engaged to the shaft so that a braking force sufficient to hold a position of the piston during bi-directional traversal of the piston before completion of the injection stroke is provided, the braking member being slideably traverseable into the second generally circular cavity by the ram wherein the plurality of elongate bases are disengaged from the first and second inner surfaces and the plurality of elongate lobes are disengaged from the shaft so that the braking force is eliminated and withdrawal of the needle into the syringe body from the distal portion of the syringe body upon completion of the injection stroke is allowed.