Impact Wrench: Centrifugal-Dog Clutch on a Reversible Air Motor

Louis Fosnot's impact wrench (Independent Pneumatic Tool, US 2,425,793, 1947). A reversible vane air motor turns a carrier that drags a heavy slotted hammer round with it. Centrifugal force throws two sliding dogs out of the hammer to strike the jaws of the anvil, which carries the socket; on each blow the hammer recoils, cam slots pull the dogs back in, and the motor, which never stops, spins the hammer up for the next blow. The blows land at the largest radius, so a small tool hits hard. The patent gives no sizes or materials beyond a light-metal case, and leaves the motor's ports to the trade; the motor is taken as a bought part. The picture: the patent's sheet 1.