Needle tip protector and indwelling needle assembly

An indwelling needle assembly comprising:

• an inner needle hub;
• an inner needle that extends out from a distal end of the inner needle hub;
• a hollow outer needle hub;
• a hollow outer needle that extends out from a distal end of the outer needle hub, the inner and outer needle hubs being assembled with each other by having the distal end of the inner needle hub inserted into a proximal end-side opening of the outer needle hub under a state where the inner needle is inserted into the outer needle;
• a needle tip protector including:
• a protector main body having an insertion passage where a needle is inserted, the protector main body being mounted against the needle by means of having the needle inserted into the insertion passage such that the protector main body being movable in an axial direction of the needle while extending along the same direction;
• at least one flexible plate attached to the protector main body extending toward the needle tip at a location orthogonally away from the needle inserted into the insertion passage of the protector main body in a way that allows its distal end to undergo flexural deformation in a direction of getting closer to the needle;
• a protection part laced at the distal end of the flexible late that protects the needle by being placed at a protective position to cover the needle tip when the flexible plate undergoes flexural deformation in the direction of having its distal end get closer to the needle in a state where the protector main body is moved toward the needle tip of the needle inserted into the insertion passage;
• an action ring that is externally fitted about the protector main body in a movable way in the axial direction of the needle and makes the protection part placed in the protective position by causing flexural deformation of the distal end of the flexible plate in the direction of having its distal end get closer to the needle through an advance movement toward a distal end side of the protector main body;
• and a slip-stop mechanism that prevents the action ring from slipping out of the protector main body in the axial direction of the needle, the needle tip protector being mounted to the inner needle;
• a hemostasis valve being arranged to fit in a distal end side of the outer needle hub so as to prevent a blood flow into the outer needle hub from flowing out of the proximal end-side opening through an inner hole of the outer needle in a state where the inner needle is retracted from the outer needle,
• a cylindrical containing part that extends in an axial direction of the inner needle is being provided on a distal end side of the inner needle hub at a distance from an outer periphery of the inner needle, whereas the protector main body mounted to the inner needle and the action ring externally fitted about the protector main body being arranged to fit in the cylindrical containing part;
• and
• a latching protrusion integrally formed with the action ring that extends out into the outer needle hub via a distal end-side opening of the cylindrical containing part,
• wherein the action ring is advanced relative to the protector main body as the inner needle and the protector main body move integrally when the inner needle is retracted from within the outer needle by having the latching protrusion latched to the outer needle hub, and the protection part is placed at the protective position by flexurally deforming the flexible plate.