This invention relates generally to control devices and more particularly to a pneumatic fluid flow limiting device for preventing overrun of a pneumatic fluid driven device such as a power tool or pump, for example, piston pumps suffer damage and use excessive air when they are run dry (the pumped fluid is no longer available at the inlet). If permitted to continue for an extended period of time, the packings will overheat and subsequently leak after inlet (suction) supply is restored.
Prior art control devices are known which will shut off the air supply to the pump when the air requirement exceeds its setpoint. The difficulty with the known prior art is that it must be adjusted to accommodate varying conditions and requires adjustment when the air pressure changes. Another difficulty is that it must be manually reset after being tripped in the overrun position.
Other devices which could be used would include air logic circuits which are both costly and may require an electrical interface. One of the benefits of using air operated pumps is that they can be used in applications without using electricity for pump operation and/or control.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.