Patent ID: 6979314

Claim:
A safety syringe comprising: a hollow barrel having a proximal open end; and a distal open end; a plunger slidably mounted inside the hollow barrel and having a distal end; a proximal end; a neck formed integrally and extending from the proximal end of the plunger, and having a distal end, a proximal end and a longitudinal axis; a first positive limit attached to the proximal end of the neck; a protrusion extended from the first positive limit and along the longitudinal axis of the neck, and having a distal end and a proximal end; and a second positive limit attached to the proximal end of the protrusion; a plug mounted around the neck on the plunger; a cylindrical connector rotatively mounted around the protrusion of the plunger, and having a side-wall; a longitudinal axis; a through hole formed along the longitudinal axis of the connector; and a groove formed in the side-wall and parallel to the longitudinal axis of the connector, and communicating with the through hole of the connector; a needle hub mounted in the proximal open end of the hollow barrel and having a connecting tube having a distal end; a proximal end; and a connecting chamber formed in the distal end of the connecting tube and having a proximal open end, a distal end and an inner surface, wherein the connecting chamber has a radius larger than that of the connector; and a needle attached to the proximal end of the connecting tube and having a central passage; and an engaging device formed between the connector and the connecting chamber of the needle hub and connected the connector and the connecting chamber of the needle hub together when the connector is inserted in to the connecting chamber, and comprising multiple limit stubs; multiple curved limit channels each corresponding to one of the limit stubs and having a first inclined side wall; and multiple notches each communicating with one of the curved limit channels and having a second inclined side wall formed opposite to the first inclined side wall on a corresponding one of the curved limit channels, and the first inclined side wall formed near the corresponding notch, wherein each notch is larger than the corresponding limit stub and each limit stub wedges against the second inclined side wall of the corresponding notch when the connector is inserted into the connecting chamber.