Abstract: A pneumatic screwdriver or nutsetter includes a manually actuated electrical switch and a solenoid operated motive air shutoff valve which includes a spring biased reset element for moving the shutoff valve closure element from a valve closed position to a valve open position prior to introduction of compressed air to the tool motor. The reset element is retracted away from the closure element by pressurized air upon startup of a tool operating cycle. The closure element is released upon deenergization of the solenoid at a predetermined signal to close the shutoff valve. In an alternate embodiment the switch is replaced by a pneumatic valve and the reset element is pressure air biased to move the shutoff element from the shutoff valve closed position to the open position.

Abstract: A pneumatic screwdriver or nutsetter includes a manually actuated electrical switch and a solenoid operated motive air shutoff valve which includes a spring biased reset element for moving the shutoff valve closure element from a valve closed position to a valve open position prior to introduction of compressed air to the tool motor. The reset element is retracted away from the closure element by pressure air on startup of a tool operating cycle. The closure element is released upon deenergization of the solenoid at a predetermined signal to close the shutoff valve. In an alternate embodiment the switch is replaced by a pneumatic valve and the reset element is pressure air biased to move the shutoff element from the shutoff valve closed position to the open position.

Abstract: An artificial hinge pin having a self-cutting threaded portion is inserted into a prepared bone with reduced reaction moment by a hand-held power tool which imposes a rotary oscillating movement on the pin during the insertion process. The tool has an output shaft driven by an overriding ratchet type coupling providing repeated impacts to the output shaft. A plurality of elastic rods connected to the output shaft are arranged coaxially around the shaft and are anchored to a rotary brake disk. Braking force on the disk is controlled by an adjustable compression spring. The eigenfrequency of the elastic system comprising the rods and output shaft may be adjusted to the impact frequency of the ratchet coupling.