Abstract: An anti-roll device including a gear fixed on a drive shaft and a gear fixed on a driven shaft, a pinion engaged on a rod, a number of gradually narrowing notches formed in the pinion, a roller and a spring disposed in each of the notches, the rollers being biased to move toward the narrower ends of the notches, the pinion being engaged with either of the gears, the rollers being caused to be wedged between the narrower ends of the notches and the rod when the pinion rotates in one direction, thereby locking the gear and the rod together, rotation of the pinion in an opposite direction is prevented.

Abstract: A power wrench includes a socket which is rotatably retained in a head portion of the wrench by a retainer. A yoke is actuated to swing by a driving axle. A number of grooves are formed in the yoke and in the retainer, each groove gradually changes from narrow to wide and receives a roller and a spring. The rollers slidably contact the socket. When the yoke rotates in one direction, the socket is actuated to rotate. When the yoke rotates in a reverse direction, the rollers in the retainer are caused to hold the socket and prevent the socket from backlash.

Abstract: A power wrench includes a socket which is rotatably retained in a head portion of the wrench by a retainer. A yoke is actuated to rotate reciprocally by a driving axle. A number of recesses are formed in the middle portion and the upper portion of the socket, each recess in the middle portion of the socket receives a roller, and each recess in the upper portion of the socket receives a ball. When the yoke rotates in one direction, the socket is actuated to rotate by the rollers. When the yoke rotates in a reverse direction, the balls are caused to hold the socket and prevent the socket from backlash.