Patent ID: 6578824
Filing Date: 2003-06-17
Classification: B66D,Y10S

Abstract:
An overload-preventing device for a winch, including:a drive shaft that transmits a rotating force to a load sheave; a pressure-receiving member that is fixed at said drive shaft; a pressing drive member that is screwed with said drive shaft so as to advance the retreat, and presses and rotates said pressure receiving member via a reverse rotation preventing wheel that is fitted to the outside of said pressure receiving member and via a pair of friction members that are disposed at both sides thereof; a truncated cone member, the diameter of which is reduced toward the side of said pressure-receiving member, that is not permitted to rotate with respect to said pressing drive member but is movable in the axial direction; and a rotation drive member, having an inner circumferential surface following the outer circumferential surface of said truncated cone member, which is outwardly fitted so that it is brought into frictional contact with the outer circumferential surface of said truncated cone member and the tip end side face in the axial direction of said pressing drive member; in which said truncated cone member is pressed toward said pressing drive member by a truncated cone pressing member; wherein an accommodation hole for accommodating a movable piece is formed in said rotation drive member so as to open in the contact surface with said pressing drive member; said movable piece is retained so as to come out of and sink in the axial direction in said accommodation hole but not to move in the circumferential direction of said rotation drive member; said movable piece is pressed to the side of said pressing drive member by said movable piece pressing member; an engagement groove having a depth in which a part of said movable piece has infiltrated is formed on the same radius as that of said accommodation hole on the contact surface of said pressing drive member; said engagement groove has a length by which said movable piece can move in the circumferential direction; an end portion at a winding-up side of said engagement groove is formed so that it becomes shallow toward the winding-up side to become consecutive on the contact surface; and an end portion at an unwinding side of said engagement groove is formed on the fitting plane on which said movable piece cannot move in the unwinding direction.