Patent ID: 8636705

Claim:
An injection needle assembly comprising: a needle possessing a proximal end portion and a sharp distal end portion to puncture skin, the needle comprising a through hole extending along a longitudinal extent of the needle and opening to the sharp distal end portion and to the proximal end portion of the needle; a first member possessing a through hole extending between proximal and distal ends of the first member, the through hole of the first member being open at the proximal end of the first member and being open at the distal end of the first member; the needle being positioned in the through hole in the first member and being fixed in place in the through hole in the first member such that the sharp distal end of the needle projects distally beyond a distal end face of a distal end portion of the first member so the sharp distal end portion is exposed to puncture the skin and such that the proximal end of the needle projects proximally beyond a proximal end face of a proximal end portion of the first member so the proximal end of the needle is exposed; a second member possessing a through hole so the second member possesses an inner surface, the through hole of the second member extending between proximal and distal ends of the second member, the through hole in the second member being open at the proximal end of the second member and being open at the distal end of the second member, a proximal end portion of the through hole in the second member being configured to receive a discharge part of a syringe; the proximal end portion of the first member being positioned inside the second member so that an outer peripheral surface of the proximal end portion of the first member faces the inner surface of the second member; and an elastic member disposed inside the second member, the elastic member possessing an outer peripheral surface in liquid-tight contact with the inner surface of the second member, the elastic member also comprising an insertion hole extending throughout a longitudinal extent of the elastic member so that the elastic member possesses an inner surface, a portion of the inner surface of the elastic member being in liquid-tight contact with an outer peripheral surface of the needle; wherein the elastic member includes an abutting end face at an axial end of the elastic member that is adapted to abut against the discharge part of the syringe, the elastic member including a needle side valve element part adjacent the abutting end face of the elastic member, the portion of the inner surface of the elastic member that is in liquid-tight contact with the outer peripheral surface of the needle being the inner surface of the needle side valve element part, the needle side valve element possessing an outer surface with a tapering outer diameter so that pressure applied to the tapering outer diameter by liquid medicine discharged from the discharged part of the syringe presses the inner surface of the needle side valve element part toward the outer peripheral surface of the needle.