Pneumatic screwdriver with torque responsive shut-off

In a pneumatically powered screwdriver, a motor housing, a clutch housing affixed to the motor housing, a valve movable to control flow of pneumatic fluid to the motor housing for operation of a rotary motor therein, a push rod for unseating of the valve to allow flow of pneumatic fluid to the motor, a valve spring which is biased to seat the valve to shut off flow of pneumatic fluid to the motor, a clutch member in the clutch housing and rotatably driven by the motor, a spindle in the clutch housing adapted for receipt of a tool bit shank, a plurality of balls arranged to convey rotary motion from the clutch member to the spindle, and a ball compression means urging the balls into engagement with the clutch member, a torque responsive shut-off means for the screwdriver comprising:

• movable means slidingly supported in the spindle and clutch member, compression means biasing said movable means into engagement with the push rod for unseating of the valve, a latch pin arranged in the clutch member, a spring biased for movement of the latch pin into the path of movement of one of said balls, and a lock pin arranged in the clutch member between the latch pin and the movable means for preventing sliding movement of said movable means, said lock pin responsive to movement of said latch pin caused by said one of said balls to release said movable means for sliding movement to enable said valve spring to overcome the bias of said compression means and seat said valve is seated.