Patent ID: 6953449

Claim:
A hypodermic syringe comprising: a barrel, said barrel having a hollow cylindrical body defining a longitudinally extended through hole, a first stop portion and a second stop portion formed in said longitudinally extended through hole near a rear end of said body of said barrel, and a receiving chamber defined between said first stop portion and said second stop portion; a constraint member shaped like a hollow conical cap having relatively greater rear side and a relatively smaller front side and mounted in said receiving chamber inside said barrel, said constraint member having an outer stop face stopped against said first stop portion of said barrel, and an inner stop face, a rear stop edge formed on the relatively greater rear side of said constraint member and stopped against said second stop portion of said barrel, a front stop edge formed on the relatively smaller front side of said constraint member, and at least one radial crevice; and a plunger, said plunger having an elongated stem inserted through said constraint member into the inside of said through hole of said barrel, a front stop flange extended around the periphery of said stem near a front end of said stem and movable with said plunger into said through hole of said barrel and to be stopped at said front stop edge of said constraint member upon a back stroke of said plunger relative to said barrel, and a thumb rest formed on a rear end of said stem.