US Patent 7147621 Single use syringe

A single use syringe uses a “pinching” action between a specially designed plunger and a specially designed needle holder to shoot the needle back into the syringe body upon completion of the piston stroke. The needle is not biased by a helical spring and the syringe remains in an unbiased condition until the plunger is pushed against the needle holder that creates the pinching action to shoot the needle back into the syringe body.