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

Louis P. Fosnot (Independent Pneumatic Tool Co.) · Public domain (expired patent)

작성자

Martin

23. 10월 2026

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.

고급

2 days

안내

Fit valve, trigger and nipple in the cast case

Use the motor case and side handle cast in one piece of light metal. Fit the spring-closed throttle valve (4) in the handle's air passage (3), the trigger block (5) to open it, and the hose nipple (6) at the passage's end.

이 단계의 재료:

공구 모터 케이스1 개

스로틀 밸브1 개

공구 방아쇠1 개

호스용 나사 니플1 개

필요한 도구:

멍키스패너

Mount the vane motor

Clamp the vane motor's cylinder (13), fixed against turning, between its end plates (14) in the case. The plates carry ball bearings (15) for the rotor's shaft ends (16); the rotor (9) sits off-centre with sliding blades (10) in its slots (11).

이 단계의 재료:

베인식 에어 모터1 개

볼 베어링2 개

필요한 도구:

아버 프레스

Fit the reversing valve

Fit the turning reversing valve (22) in the case between the rotor and the throttle valve, with its handle (23) outside: one way the motor screws up right-hand threads, the other way it undoes them.

이 단계의 재료:

전환 밸브1 개

필요한 도구:

멍키스패너

Pin the dogs into the hammer

Slide one rectangular dog (47) into each end of the hammer's cross-slot (46). Press a pin (48) through the bore (49) of each dog so its ends stick out into the hammer's radial slots (50), letting the dog slide in and out but not fall out. Ours: arbor press.

이 단계의 재료:

임팩트 클러치 해머1 개

임팩트 도그2 개

강철 핀2 개

필요한 도구:

아버 프레스

Build the carrier round the hammer

Put the hammer on the carrier shaft (38) through its centre openings (54). Fit the lower plate (37) on the shaft's hexagon (39). The pin ends now ride in the curved cam slots (53) of both plates.

이 단계의 재료:

클러치 캐리어1 개

필요한 도구:

아버 프레스

Set the carrier in the anvil

Lower the carrier into the anvil cup (27): a thrust plate (43) between the lower plate and the anvil's end wall (30), the shaft's lower end (41) in a roller bearing (42) inside the hollow spindle (26). The dogs face the anvil's jaws (32) through its side openings (31).

이 단계의 재료:

임팩트 클러치 앤빌1 개

스러스트 플레이트1 개

원통 롤러 베어링1 개

필요한 도구:

아버 프레스

Couple to the motor and bolt on the housing

Engage the rotor's shaft end in the upper plate's socket (44). Bolt the clutch housing (24) to the motor case; its bushing (25) carries the anvil spindle. Ours: wrench for the bolts.

이 단계의 재료:

클러치 하우징1 개

금속 부싱1 개

필요한 도구:

멍키스패너

Fit the socket and run it

Put a socket (28) of the nut's size on the spindle. Ours: connect an air hose from a compressor. Run the nut down; once it is tight the dogs strike the jaws in rapid blows. On each blow the hammer recoils and the cams draw the dogs in until the carrier spins it up again.

이 단계의 재료: