Pump loss-of prime automatic shut off valve

Abstract

A pump shutoff device is provided wherein compressed air supplied to the air inlet port of the over speed control device enters an air pressure chamber, and then proceeds to an adjacent air exhaust chamber. From there, the air passes to an outport which is connected,directly to the inlet port of the air motor of an air-operated piston pump spool located inside the body of the device, is shaped such that the valve spool functions to allow passage of air freely from the air pressure chamber to the air exhaust chamber. Compressed air is connected through a series of unrestricted conduits,ports and chambers continuous from the compressed air supply to the air motor of a pump. The air motor is energized by compressed air to provide continuous pumping.Positive pressure existing in the fluid pressure chamber exerts an axial thrust on the spool. Adjacent to the air chambers and opposite the position of the fluid pressure chamber is a coil compression spring. The spool and the spring are shaped so as the spring is compressed it exerts an axial force on the spool in opposition to the axial force on the spool exerted by the fluid pressure chamber

Description

FIELD OF THE INVENTION[0001]The present invention relates to a loss-of-prime automatic shunt off valve for use with air operated pumps of the kind used primarily for oil and grease dispensing equipment in facilities that service motor vehicles, such as quick lube service centers, automobile dealership service departments, truck fleet garages and the like.BACKGROUND OF THE INVENTION[0002]When pumps such as compressed-air-driven piston pumps are in operation,they generate a (pumped) fluid pressure at the pump output port. This pressure effect is due to the fact that the pump is pushing fluid from the pump. This pressure is maintained so long as; 1) the pump, is energized with compressed air; 2) the pump is attached to the output load;and 3) the pump is primed so as to continuously induct fluid from the supply reservoir.[0003]If an air leak occurs in the incoming suction line from the reservoir to the pump, or if the pump reservoir level is allowed to deplete and run dry during pump op...

AI Technical Summary

Benefits of technology

[0007]The present invention provides a novel automatic speed control device for air operated pumps that functions to automatically stop operation of the air-opera

Problems solved by technology

If an air leak occurs in the incoming suction line from the reservoir to the pump, or if the pump reservoir level is allowed to deplete and run dry during pump operation, then a loss of prime occurs within the pump.

Because air (instead of fluid) is moving against an attached load in pumps of this kind,a much lower pressure is produced at the pump outport port and the pump responds by accelerating and then cycles at a very rapid and often damaging cycle frequency.Additionally, during loss of prime,piston seals in the fluid pumping chamber of the pump are purged clean of the pumped fluid and are damaged because the fluid also typically serves to lubricate those seals.

Specifically,friction heat is generated and the seals which are no longer submerged,and the pump itself, are subjected to damage particularly when allowed to run for a sustained period in an unprimed dry condition.

Rapid pump cycling plus dry seal contact leads to unacceptable levels of seal heating and therefore to rapid seal failure from wear or deformation.

While prior attempts have been made to alleviate the damage resulting from original damage that occurs to pumps and seals whenfluid in the reservoir is depleted or functionally inadequate,at the present time no known practical and adequate solution has been identified.

For example,devices of this kind fail to shut off pump operation is and when the pump suddenly draws in compressed air at a more rapid rate.

In practice, when a typical pump loses prime,the increased cycle frequency and therefore the increased rate of flow of compressed air into the pump often is insufficient in magnitude to trigger this kind of shut off means.

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