Patent ID: 7611489

Claim:
A safety syringe, comprising: a barrel which has a hollow passage inside and one end formed with annular grooves on an inner wall and an outer wall thereof opposing each other and coupled with a barrel cover which has a protruding end with a housing chamber formed therein; a push rod which is held in the hollow passage in a close contact and slidable manner and has a holding chamber with a bucking surface formed thereon and a distal end with an annular trough formed on the periphery and an indented rim and a cut surface formed at two end surfaces thereof; a driving module which is held in the barrel cover and includes an inner detent member, a piston seat and a piston rubber ring, the inner detent member having an aperture, an annular bulged element and an annular ring at one end, the piston seat being protrusive and having one end wedged in one end of the inner detent member, the piston rubber ring being adjacent to the inner detent member; and a needle mount which is coupled with the inner detent member and held in the piston rubber ring and has a first stem, a second stem and a third stem of different diameters at one end, the first stem being coupled with the annular bulged element of the inner detent member, the second stem having one end inserted in the piston rubber ring, the third stem being coupled with the protruding end of the barrel cover, whereby the push rod is movable forwards to push the inner detent member and the piston rubber ring of the driving module forwards to make a cut surface at one end of the push rod to hit one end of a first stem of the needle mount to be broken and separated so that continuous moving forward of the push rod causes instant release of air pressure inside to retract the needle mount in a holding chamber of the push rod to safely hold a needle after injection.