Patent ID: 7789855

Claim:
An improved barrel type plunger for use with a needle-retractable safety syringe, the plunger comprising: a barrel comprising a front portion which is fitted over a sealing rubber pad; a needle retracted trigger; and a supporting member; wherein: a slotted hole is disposed at a wall of the front portion of said barrel; a bearing piece is disposed in said slotted hole; one end of said bearing piece is connected to a front side wall of said slotted hole; said bearing piece is deflected laterally towards an interior of said barrel such that said bearing piece is resettable in order to support said needle retracted trigger; said needle retracted trigger is disposed at a front end of a cavity of said barrel and is supported on said bearing piece which has been deflected laterally; said supporting member is disposed in said barrel, a front end of said supporting member supporting said bearing piece which has been deflected laterally, and a rear end of said supporting member comprises a base for sealing the opening at a rear end of said barrel; said barrel and said supporting member each comprising a snap-in structure respectively, which are releasably engaged cooperatively with one another; and said supporting member translates backwards under the action of a needle retraction force so that said bearing piece is returned to a position wherein said needle retracted trigger and said needle are retracted backwards to the interior of said barrel.