Patent ID: 8590433

Claim:
A torque limiter comprising: a shaft member; a cylindrical member which faces the shaft member in a radial direction of the shaft member; a hydraulic expansion chamber for pressing a circumferential surface of one member of the shaft member and the cylindrical member against a circumferential surface of the other member of the shaft member and the cylindrical member, the hydraulic expansion member being provided in either the shaft member or the cylindrical member; one or more shear valves which communicate with the hydraulic expansion chamber at one end and project radially outwards of the outer circumferential surface of the one member at the other end; and a strip-shaped shear valve protection member which is disposed radially outwards of the shear valves and in the same axial position as the shear valves, which can be switched between a tightly attached state in which the strip-shaped shear valve protection member cannot move relatively to a cutting portion which connects to the other member by virtue of a frictional force generated between the cutting portion and itself by tightly attaching the cutting portion thereto in the radial direction and a tight attachment cancelled state in which the strip-shaped shear valve protection member can move in a circumferential direction relative to the cutting portion and which has one or more through holes which can expose the shear valves therefrom, wherein the shear valve protection member can be switched between a position where the shear valves are covered with the shear valve protection member and a position where the shear valves are exposed from the shear valve protection member through the through holes therein, and wherein the shear valve protection member comprises an annular member.