Patent ID: 7909701

Claim:
A power transmission apparatus comprising: a pulley mounted rotatably on a casing of a rotary device having a rotary shaft; a hub coupled to the pulley by fitting between depressions and protrusions to transmit the torque with the pulley; a power shutoff member for shutting off the transmission of an excessive torque between the rotary shaft and the hub; and an engaging device for causing the hub to engage the pulley to prevent the hub from coming off from the pulley after activation of the power shutoff member; wherein the engaging device includes a first stepped portion formed in radial direction on the outer periphery of the hub and a second stepped portion formed in the radial direction on the inner peripheral wall of a rim portion of the pulley to engage the first stepped portion in axial direction, wherein the hub includes an elastic member having at least one protrusion adapted to be fitted in at least one depression of the pulley to transmit the torque with the pulley, and wherein the first stepped portion is formed on the elastic member.