Patent ID: 8650726

Claim:
A buckle device having a buckle main body configured to releasably receive a tongue plate connected to webbing, the buckle main body comprising: a frame member; a slide button provided slidably on one side of the frame member; a base member fixedly provided on the frame member so as to be positioned above the slide button; a latch member provided in the base member, movably in a direction perpendicular to the frame member, the latch member configured to be engaged with the tongue plate when the tongue plate is inserted, and to be disengaged with the tongue plate by slidingly moving the slide button; a stopper member provided at an end face portion of the base member facing the slide button, rotatably in a direction toward the frame member, the stopper member configured to stop movement of the slide button when the stopper member is rotated toward the frame member; and an urging member configured to urge the stopper member to rotate in a direction away from the frame member, wherein the stopper member comprises: an inertial mass body which is provided at the end face portion of the base member so that an end portion of the inertial mass body is rotatable toward the frame member and gravity center of the inertial mass body is eccentric toward the frame member from a rotation axial core; and a lever member which is provided at the end face portion of the base member so that an end portion of the lever member is rotatable toward the frame member, the lever member being able to get in contact from a side of the frame member with the end portion of the inertia mass body, wherein the end portion of the inertial mass body and the end portion of the lever member are pivotally urged in a direction away from the frame member by the urging member, wherein the slide button comprises an abutment portion which faces the end portion of the lever member, and wherein, when the buckle main body with the tongue plate inserted therein experiences abrupt acceleration in a direction to tighten the webbing, disengagement of the latch member and the tongue plate is prevented by stopping movement of the slide button in such a manner that an inertial force acting on the inertial mass body subsequently causes the end portion of the inertial mass body, which has been rotated to the frame member, to get in contact with the lever member and causes the end portion of the lever member to rotate to the frame member against an urging force of the urging member so that the end portion of the lever member gets in contact with the abutment portion of the slide button slidingly moved by an inertial force acting on the slide button and stops the movement of the slide button preventing disengagement of the latch member and the tongue plate.