Needle holder positioning structure for safety hypodermic syringe, comprises barrel, needle holder, and locating ring

摘要

New needle holder positioning structure comprises: (A) a barrel (1) having a fluid chamber; (B) a needle holder (2) mounted in the barrel; and (C) locating ring (3) mounted inside the barrel and coupled to the needle holder. New needle holder positioning structure comprises: (a) a barrel (1); (b) needle holder (2); and (c) locating ring (3). The barrel comprises a fluid chamber. The fluid chamber has a front small inner diameter section, a rear big inner diameter section, a shoulder connected between the front small inner diameter section and the rear big inner diameter section, and an inside flange disposed in the rear big inner diameter section adjacent to the shoulder. The needle holder mounted in the barrel comprises a tubular center base and a sleeve coaxially formed integral with the periphery of the tubular center base. The tubular center base has a retaining portion near a rear side of the base. The sleeve has a front engagement section press-fitted into the inside of the front small inner diameter section of the fluid chamber of the barrel and a springy rear expansion section. The rear expansion section has a front side edge corresponding to a back side of the shoulder of the barrel and a rear side edge stopped at a front side of the inside flange of the barrel. The rear expansion section defines with the periphery of the tubular center base a backwardly extended annular coupling chamber. The locating ring is mounted inside the barrel and coupled to the needle holder. The locating ring has an outside wall disposed in contact with an inside wall of the rear big inner diameter section of the fluid chamber of the barrel for enabling the locating ring to be moved axially in the barrel. An inside wall is disposed in contact with the periphery of the tubular center base of the needle holder for enabling the locating ring to be moved axially relative to the needle holder. The outside wall of the locating ring has a front section forming a neck adapted for engaging into the rear expansion section of the sleeve of the needle holder. The neck has an outer diameter not less than the inner diameter of the expansion section of the sleeve so as to expand the rear expansion section of the sleeve for enabling the rear side edge of the rear expansion section stopped at the front side of the inside flange, a first retaining portion integral with a front part of the inside, wall of the locating ring are adapted for engaging the retaining portion of the tubular center base of the needle holder, and a second retaining portion formed integral with a rear part of the inside wall of the locating ring.