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.

Description

FIELD OF THE INVENTION

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

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.

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. Upon loss of prime, the air-driven pump,attached to an open and pressurized air entry connection, continues to cycle and it thereby pumps air instead of fluid. 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.

It is accordingly desirable to provide a means to protect pumps of this kind,so that they do not continue to cycle whenever a lodd of prime exists, thereby preventing seal damage during such conditions. It is also desirable to create an indication of the unprimed pump condition,alerting the user so that prompt action can be taken to restore prime and remedy the problem.

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,the device available as ARO STOP® Pump Saver Control Valve of the Ingersoll-Rand Company, described in that company's one page product service brochure designated 23644-400, has been found to lack various requirements. 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.

The reference to “fluid” herein is taken to mean both self-leveling liquids such as oil and non-self-leveling but pumpable materials such as greases.

SUMMARY OF THE INVENTION

The present invention provides a novel automatic speed control device for air operated pumps that functions to automatically stop operation of the air-operated pumps whenever loss of prime occurs. The control device utilizes the fluid output pressure of the pump as a feedback element to provide the necessary control.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates schematically the location of the speed control device of the invention in a typical pump and reservoir system.

FIG. 2 is a side view of the speed control device of the invention shown in a continuous pumping mode.

FIG. 3 is a view similar to that of FIG. 2 with the speed control device of the invention shown in the interrupt pump-off mode.

FIG. 4 is a perspective view of the speed control device of the invention in the interrupt or pump-off mode and with the body of the control device section cut away to reveal the device interior.

DETAILED DESCRIPTION OF THE INVENTION

While the invention is described primarily with the application of an automatic shut off valve for use with a reciprocating piston air pump, it will be apparent to those skilled in the art that the invention is applicable for use also in conjunction with rotary air operated pumps.

Reference to FIG. 1 of the drawing shows the placement of the over speed control device of the invention when installed for use in conjunction with a pumping system. The speed control device of the invention 109 is mounted between the incoming compressed air supply line 106 (air line 106 being a pressure hose,tube or other suitable conduit for compressed air) and the supply air line 104 to the pump air motor 101 a conventional limit that comprises an air-operated fluid piston pump 102 and motor 101. The fluid pump 102 is connected to a pump outlet path 105 which comprises a fluid line or lines having a branch 112 connected to the fluid input port 11 (see also FIG. 2) of the over speed device 109 and another branch 110 attached to a fluid flow network,functioning thereby through a fluid resistance load 107, and then outward for useful dispensing of the pumped fluid. The fluid resistance load consists of piping, hose reels, dispense control handles and other conventional components which conduct and control the movement of fluid to one more disensing points.

Reference to FIG. 3 shows details of the over speed control device of the invention while in the continuous pumping mode. As illustrated in FIG. 3, compressed air is supplied to the air inlet port 8 of the over speed conrtol device; the air immediately enters an air pressure chamber 9,and then proceeds to an adjacent air exhaust outlet chamber 10. From there, the air passes to an output port 7 which is connected, directly or by a hose or enclosed passage, to the inlet port of the air motor 101 (see FIG. 1) of an air-operated piston pump (101 and 102). A valve spool 13 located inside the body 1 of the device, is shaped so that, in the valve spool position shown in FIG.3,air passes freely from the air pressure chamber 9 to the air exhaust chamber 10. Thw free passage of the compressed air connected through a series of conduits, ports and chambers is continuous from the compressed air supply to the air motor of the pump and is unrestricted in the condition of the speed control device shown in FIG. 3. In such condition,the air motor is being energized by compressed air to provide continuous pumping.

Referring again to FIG. 3, a fluid pressure chamber 2 contiguous to the fluid input port II is provided,exposed to one end of the spool 13 such that any positive pressure which might exist in the fluid pressure chamber 2 exerts an axial thrust on the spool 13. Also,adjacent to and aligned with the air chambers 9, 10, and opposite the position of the fluid pressure chamber 2,a spring body chamber 3 is provided,containing a coil compression spring 12. The spool 13 and the spring body chamber 3 are shaped so as to create shoulders which contact, contain and contract the ends of the spring 12 and substantially compress it during the condition shown in FIG. 3. The spring 12 thereby exerts an axial force on the spool 13 in opposition to the axial force on the spool 13 exerted by the fluid pressure which occurs via chamber 2.

Reference is now made to FIG. 2 which shows details of the over speed control device of the invention while in the interrupted, or pump off, mode. As shown in FIG. 2, the valve spool 13 is shifted to a spring compressing position. The shape of the spool is such that, in the position shown in FIG. 2 compressed air is interrupted and cannot pass from air pressure chamber 9 to the adjacent air exhaust chamber 10 due to the sealed closure of the passage. Accordingly, in the spool position of FIG. 2, air provided for operation of the air motor 101 is interrupted and the pump cannot be energized and therefore becomes inoperable.

In the operable and inoperable stages of the over speed control valve shown in FIGS. 3 and 2 respectivly,the size and force of the spring, as well as the size and force of the spool-end area exposed to pressure in the fluid body chamber, are selected to obtain the following conditions:

Condition 1: If pressure in the fluid pressure chamber 2 is greater than any pressure which would occur there when the pump displaces air only (unprimed),then the axial force on the spool (13) due to fluid pressure exceeds the axial forces on the spool 12 due to the spring (12) and also due to internal friction of parts. In this condition (pump operable),the spool will shift to the arrangement of FIG. 3 and will be maintained in that position.

Condition 2: If pressure in the fluid pressure chamber 2 is less than or equal to any pressure which would occur there when the pump displaces air only (unprimed), then the axial force in the spool 13 due to fluid pressure is less than the axial forces on the spool 13 due to the spring 12 and also due to internal friction of parts. In this condition,the spool will shift to the arrangement of FIG. 2 (pump inoperable) and will be maintained in that position.

Due to the capability of the speed control device 109 to provide conditions 1 and 2, the pump will be energized and will operate continuously whenever it is in a primed condition as in condition 1. It will cease operation promptly whenever a primed pump condition is lost as in condition 2. The device therefore functions to stop all operation of the pump in the presence of an unprimed condition,thereby preventing pump and seal damage.

When the pump does not operate on command when a dispense valve is opened, the service operator will be alerted to the pump's unprimed condition, so this will prompt a remedying of the condition, avoiding pump damage that would otherwise occur.

In order to provide a means of initially operating the pump to obtain a first condition of prime a suitable mechanism such as a pull handle 6 is provided, (shown in FIGS. 2 and 3), to manually displace the spool to an air-open condition and cycle the pump until the line is filled with fluid and pressurized. Thereafter, the pump will maintain this operable condition due to its primed condition and sufficient pressure existing in the fluid body chamber 2.

While the invention has been described with reference to the preferred embodiments, it will become apparent to those skilled in the art that many modifications and variations to details can be derived from the description provided. Accordingly the invention is intended to include all such variations and modifications encompassed within the appended claims.

Claims

1. An over speed control device for fluid pumps comprising: a) A longitudinal assembly;b) An air inlet chamber contained in said assembly;c) An air inlet port to said chamber;d) An air pressure chamber aligned and on the opposite side of said air inlet chamber;e) An air exhaust chamber aligned and on the opposite and aligned with said inlet air chamber;f) An air outlet port from said air exhaust chamber provided for connecting to an inlet part of a pump air motor;g) A valve spool in said assembly positioned contigenous to said air exhaust chamber; andh) A compression coil spring arranged to exert axial pressure on said valve spool;

2. The over speed control device of claim 1 provided with associated mechanism to obtain an initial condition of pump prime.

3. The device of claim 2 wherein the associated mechanism compromise a handle that when pulled manually functions to dispense the valve spool to an air open condition.

4. The speed control device of claim 1 in functional combination with a responding piston air pump.

5. The speed control device of claim 1 in functional combination with a rotary air operated pump.

6. The overspeed control device of claim 1 wherein a continually-compressed gas in the spring body chamber is used in place of a mechanical spring.

7. A method for automatically shutting down ait operated fluid dispensing pumps upon loss of pump prime comprising spring-means to permit an open passage for the dispensing of fluid from the pump so long as fluid prime exists, said spring-means being extended to stop the pumped air supply and shut off the fluid passage upon loss of prime due to air leakage or fluid supply depletion and fluid pressure means fuctioning to compress sain spring-means and enable air supply and dispensing of fluid when fluid prime is restored.