US Patent 7393281 Power transmission device

In the power transmission device having a torque limiting function for shutting off the transmission of an excessively high torque between the pulley 1 and the rotary shaft 5, the hub 2 and the rotary shaft 5 are connected to each other by means of screw engagement between the female screw portion 2d, which is formed on the inner circumferential face of the hub 2, and the male screw portion 5d which is formed on the outer circumferential face of the forward end portion 5a of the rotary shaft 5, and the seal means 4 for sealing between the hub and the rotary shaft is provided adjacent to the front face or the front and rear faces of the screw engaging portion. The torque limiting function may be provided on the rotary shaft side or the hub side.