Abstract: A molded plastic unit in the form of a frame surrounds a rotatably mounted ratchet wheel. Oppositely directed ratched engaging arms extend from inner walls of the frame each at an angle approximately equal to the slope of the top of a ratchet wheel tooth. The frame, when moved reciprocally, engages the ratchet wheel via one of the ratchet engaging arms imparting on the ratchet wheel a portion of one revolution of motion during the first half of the reciprocation. In a similar manner, a like portion of one revolution is imparted on the ratchet wheel in the same direction by the other ratchet engaging arm on the return half of the reciprocation. One of the ratchet engaging arms urges against the top of one of the ratchet wheel teeth to hold the ratchet wheel immovable between reciprocations. In the first and second embodiments, a cam is mounted with the ratchet wheel on a shaft for coaxial rotation.