Mechanical device for transmitting power

The present invention relates to a mechanical device for transmitting power, and particularly to such a power-transmission device with a shear pin which is designed to fail at a predetermined force in order to protect automotive accessories such as a compressor of an automotive air conditioning system. A device includes a power-transmission pulley rotatably mounted on an automotive accessory housing, a drive plate fixedly connected to a rotating shaft of the accessory, and shear pins which connect the pulley and the drive plate. The shear pins each have a notched portion and a flanged portion which is offset from the notched portion and which is sandwiched between the pulley and the drive plate. The diameter of shear-pin insertion holes formed in the drive plate is larger than the shear pins which are fixedly connected to the pulley. The shear pins are fixedly connected to the drive plate.