Patent ID: 8684105

Claim:
A power tool comprising a torque transmission device that transmits torque and interrupts torque transmission between a first rotating member and a second rotating member which are coaxially arranged to be opposed to each other, the torque transmission device comprising: a projection formed on one of opposed surfaces of the first and second rotating members and protruding in a direction of a rotational axis, a recess for receiving the projection, which is formed in the other of the opposed surfaces and recessed in the direction of the rotational axis, a pair of projection-side engagement surfaces formed on side surfaces of the projection in a direction of torque transmission, the projection-side engagement surfaces being oriented such that a gap defined therebetween asymptotically decreases toward a radially outer end in a radially extending direction, and a pair of recess-side engagement surfaces formed on side surfaces of the recess in the direction of torque transmission, the recess-side engagement surfaces being oriented such that a gap defined therebetween asymptotically decreases toward a radially outer end in the radially extending direction, torque is transmitted when the projection-side and recess-side engagement surfaces are engaged with each other by relative movement of the first and second rotating members toward each other, while the torque transmission is interrupted when the projection-side and recess-side engagement surfaces are disengaged from each other by relative movement of the first and second rotating members away from each other, wherein the projection-side and recess-side engagement surfaces are inclined at a predetermined angle with respect to normals of the first and second rotating members.