Patent ID: 7931617

Claim:
A safety syringe, comprising: a barrel, having a hollow passage disposed therein, and a barrel cover disposed at a distal portion of said barrel, said barrel cover having a chamber and a protruding end, said protruding end having a first perforation therein; a push rod, installed in said hollow passage of said barrel and having an accommodating cavity including a first pressing surface disposed therein, a first circular groove disposed at a periphery of a distal portion of said push rod, and a first cut surface with a first concave edge disposed on a surface of said distal portion of said push rod; a driving module, installed in said barrel cover and including a plunger, a piston pump, a first washer and a second washer, said plunger having a penetrating hole, said piston pump having a flange disposed at a first end thereof and a hollow penetrating hole therein, wherein said first washer couples an external edge of said plunger to said barrel cover and said second washer couples an internal edge of said penetrating hole of said plunger to said piston pump; a needle mount, installed in said piston pump of said driving module, and having a first rod portion, a second rod portion, a third rod portion, and a fourth rod portion extended from an end of said needle mount, and an external edge of said first rod portion being coupled with said flange of said piston pump, and a periphery of said second rod portion having a second circular groove, such that a third washer is pressed at said hollow penetrating hole of said piston pump, and the periphery of said third rod portion having a third circular groove, such that a fourth washer is pressed onto a second pressing surface of said protruding end of said barrel cover, and said fourth rod portion is disposed in said first perforation of said protruding end of said barrel cover, wherein depression of the push rod causes the push rod to come into contact with the driving module and needle mount such that the first cut surface is separated from the distal portion of the push rod and further depression of the push rod causes air pressure in the chamber to retract the needle mount into the accommodating cavity.