US Patent 8182380 Power transmission device

A power transmission device is capable of switching the rotation direction of a drive shaft between positive rotation and negative rotation as power is transmitted to the drive shaft from a drive source via the power transmission device. To cause positive rotation of the drive shaft, only the positive rotation belt is tensed by the belt switching means, and rotation from the positive rotation drive pulley is transmitted to the drive shaft via the positive rotation shaft. To cause negative rotation of the drive shaft, only the negative rotation belt is tensed by the belt switching means, and rotation from the negative rotation drive pulley is transmitted to the drive shaft via the negative rotation shaft.