Back to results
US 4,004,859 AGranted
Air tool with speed responsive shutoff
AssigneeCooper Industries, Inc.
InventorJohn A. Borries
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeCooper Industries, Inc.
InventorJohn A. Borries
Estimating the term…
A speed responsive shutoff for a pneumatic tool such as a nut runner is disclosed. The shutoff, effective to terminate air supply to the air motor under load, employs a centrifugally operated air valve having a flat valve head which is biased against a valve seat through which pressurized air travels en route to the motor. A small orifice in the valve head leads to an expansible chamber behind the head. In operation of the tool, when the throttle valve is open, initial air is supplied to the motor by a slight opening of the air valve due to a higher pressure in front of the valve head than behind it. The motor quickly reaches a predetermined speed level at which time the air valve is fully opened by centrifugal weights. Under loading approaching stall, the motor slows to a speed low enough to allow the air valve to move toward closure under the influence of a spring. Pressure builds up in front of the valve head but has sufficient time to pass through the orifice and pressurize the chamber behind the valve head, equalizing the two pressures and allowing the spring to fully close the air valve. Because the shutoff occurs before the stall condition is attained, stall jerking is substantially eliminated.
A speed responsive shutoff for a rotary air tool driven by an air motor operable by a throttle valve with an air passage therebetween, comprising:
A speed responsive shutoff control for a rotary fluid motor comprising, in combination, a fluid passage connecting a source of fluid under pressure with the motor, a throttle valve in the fluid passage, a shutoff valve in passage between the throttle valve and the motor, first means biasing the shutoff valve toward a closed position, said shutoff valve including second means for partially opening the shutoff valve on initial opening of the throttle valve to an extent and for a length of time sufficient to run the motor up to a predetermined minimum speed, a centrifugally operated device driven by the motor and operably positioned to fully open the shutoff valve as motor speed reaches said predetermined speed, and third means operable after the motor has reached said predetermined minimum speed for counteracting the force of said second means, whereby, after the motor has reached said predetermined speed to cause the centrifugally operated device to open the shutoff valve, a subsequent drop in motor speed to a low speed below said predetermined minimum speed will cause the shutoff valve to close under the influence of said biasing means, thereby shutting off the fluid supply to the motor.
A speed responsive shutoff for a rotary tool driven by a fluid motor and including a throttle valve controlling the supply of fluid through a fluid passage leading to the motor, comprising a shutoff valve biased toward a closed position, first means exposed to fluid pressure and effective to open the valve against the bias, second means responsive to motor speed effective to hold the valve open above a predetermined speed, and third means exposed to fluid pressure and effective to counteract said first means after a predetermined time period, whereby, after said predetermined time said third means has counteracted said first means and a drop in motor speed below the second predetermined speed has deactivated said second means, said valve will be biased to its closed position.
Dependencies are inferred from the claim text.