US3491538A - Air balanced oil well pumping system - Google Patents

Description

Jan. 27, 1970 R. G. PEARSON AIR BALANCED OIL WELL PUMPING SYSTEM 2 Sheets-Sheet 1 Filed March 4. 1968 W w.. w. .w am@ T5 m@ Jan. 27, 1970 R. G. PEARsoN AIR BALANCED OIL WELL PUMPING SYSTEM 2 Sheets-Sheet 2 Filed March 4. 1968 l Z'N vE/y roza j@ 055er @u PEQESoN BY mw/ T-roe/Ev.

United States Patent O 3,491,538 AIR BALANCED OIL WELL PUMPING SYSTEM Robert G. Pearson, Long Beach, Calif., assignor to Driltrol, Long Beach, Calif., a corporation of California Filed Mar. 4, 1968, Ser. No. 710,126 Int. Cl. F1511 15/18; F04b 17/00 U.S. Cl. 60--52 16 Claims ABSTRACT OF THE DISCLOSURE In the production of certain oil wells which do not have sufficient formation pressure to effect flowing of the well fluids to the earths surface, it is the practice to employ artificial fluid lift. One common lift comprises a reciprocating pump adapted to be installed in the well and operable by a string of reciprocable sucker rods which extend to the earths surface, the sucker rod string being caused to reciprocate by power means such as a walking beam, or, as in the case of the present invention, by a pump jack operable by hydraulic fluid pressure.

Various pump jack operating and control systems have been proposed heretofore, including the use of air or other gas, such as nitrogen or the like, herein generically referred to as air, under pressure to apply a force to the hydraulically operable pumping jack, whereby to at least partially balance the dead Weight of the sucker rod string and desirably a portion of the weight of the hydrostatlc column of well uid in the well production pipe. Such systems, obviously, reduce the required hydraulic pressure applicable to the pump jack periodically to effect lifting of the sucker rod string.

Ordinarily, such systems are periodically or constantly supplied with air under pressure from an outside source, so as to maintain a desired balancing force on the system, and more particularly, on the pump jack.

An object of the present invention is to provide a well pumping system of the air pressure loaded, hydraulically operated pump Ajack type which is relatively simple to build, and, therefore, inexpensive, but which, at the same time, is durable, and therefore has long life expectancy.

Another object of the invention is to provide an air pressure loaded, hydraulically operated pump jack operating system that requires the application of small additional horsepower to a pump to effect flow of the hydraullc fluid and lifting of the sucker rod string.

Yet another object is to provide an air pressurized, hydraulically operated pumping jack system, in which air is continuously supplied to the hydraulic fluid reservoir from the hydraulic system itself during operation of the system, thereby eliminating the need for the application of air pressure to the system, either periodically orucontinuously from an outside source. More specifically, in accordance with this objective, a low-speed compressor is employed to return hydraulic fluid from a system drain to the pressurized reservoir, such drain fluid inherently having air entrained therein, whereby to maintain the reservoir under the desired working or sucker rod counterbalancing pressure.

3,491,538 Patented Jan. 27, 1970 rice Still another object of the invention is to provide an air pressure loaded, hydraulically actuated, pump jack operating system wherein a control valve is moved between first and second positions to cause flow of hydraulic fluid to the pump jack and exhaust of hydraulic fluid from the pump jack, the control valve being controlled by a pilot valve which is responsive to fluid pressure when the pump jack reaches the end of its upstroke to cause shifting of the control valve to its second position, initiating, thereby, the downstroke of the pump jack.

A further object of the invention is to provide an air pressure loaded, hydraulically actuated, pump jack system in which a pump is employed to supplement the hydraulic pressure and cause flow to effect upstroke of the pump jack, wherein pressure regulator means are provided to prevent the application of an inlet pressure on the pump in excess of the pump outlet pressure, when the pump jack commences its downstroke.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

FIGURE 1 is a View diagra'mmatically illustrating an air pressure loaded, hydraulically operated, pump jack system in accordance with the invention, the system being conditioned for upstroke of the pump jack; and

FIG. 2 is a view similar to FIG. 1, but showing the system conditioned for downstroke of the pump jack.

In the system herein illustrated, it is desired that a pump jack P, comprising a fluid pressure operated actuator having a cylinder 1 and a piston 2 with rod 3, be operated to effect reciprocation of a string of sucker rods (not shown) which extend downwardly into an oil well. Within the well, the sucker rod string would be connected to the plunger of a reciprocating pump (not shown) t0 cause the ow of well uids upwardly through the well pipe 4 and into a flow line A5, from which the well iiuid Will ow to a suitable reservoir or tank, as is well known.

At its upper end, the sucker rod string would be con- I nected to a reciprocable polish rod 6 which extends through the usual stuffing box 7, and this polish rod is connected by a coupling 8 to the lower end of the piston rod 3. In order that the rod 6 may be reciprocated, the cylinder 1 has a conduit 10 for the admission and exhaust of hydraulic fluid under pressure below the piston 2, upon operation of the air-hydraulic system hereinafter to be described. At the upper end of the cylinder 1 is an outlet conduit 20, and at the lower end of the cylinder 1 is an outlet conduit 30. Outlet conduits 20 and 30 may be respectively provided with check valves 21 and 31, and each of these outlet conduits leads to a drain tank 40'. These conduits 20 and 30 carry leakage to the drain tank 40 and prevent vacuum interference with the operation of the pump jack in coniunction with check valves 21, 31.

As viewed in FIG. 1, the pump jack P is shown as upstroking, pressure fluid being supplied through conduit 10 below the piston 2. In order to effect such upstroking of the pump jack P, the force derived from the pressure uid supplied through the conduit 10 must overcome the weight of the entire string of sucker rods, plus the weight of the column of uid in the well pipe 4, and obviously must overcome friction. Thus, the necessary force may be substantial, as, for example, when the pump operated by the pump jack is located several thousands of feet down in the earth. As will hereinafter be more fully described, the hydraulic fluid is pressurized to effect upstroke of the pump jack P by air pressure in a supply tank 50 and by supplemental pressure derived from a pump 60. As previously indicated, the system may be pressurized by air so as to provide an upward force on the pump jack piston 2 equal to the weight of the entire sticker rod string, plus a desired portion of the weight of the column of well uid to be lifted.

Referring to the supply tank 50, it is preferably provided with a filler valve 51, a shut-off Valve 52 adapted to allow filling of the tank to the desired level, a working pop valve 53 and associated pressure gauge 54, and a safety pop valve 55. A return conduit 56 is provided, and at the lower end of the tank-is an outlet conduit 57 leading to a normally .open solenoid valve 58 which provides means for causing a ball valve 59 in an outlet conduit 61 to remain open during operation of the system. This outlet conduit 61 will supply Huid fromthe tank 50, in a manner hereinafter to be described, to the pump 60 and to the pump jack inlet when the valve 59 is open.

In order to .open the valve 59, it is provided with an operator lever 62 connected to the rod 63 of a 'differential area operated actuator cylinder 64. Conduit 57 is connected to the lower portion of the tank 50 and has a branch 57a leading to one side of the piston of actuator cylinder 64, line 57 leading to the other side of the actuator piston through the solenoid valve 58 when it is in one position. However, when the solenoid of valve 58 is energized, as seen in FIGS. l and 2, the valve 58 closes olf conduit 57 and the larger end area of the actuator piston is exhausted to the drain tank 40 through a conduit 65. Therefore, the pressure of uid in the supply tank 50, acting on the smaller effective area of the piston of the actuator cylinder 64, will cause the rod 63 to open the valve 59. Thus, energization of the solenoid valve 58 conditions the system for operation.

Hydraulic fluid flowing from the tank 50 through conduit 61 follows three courses: rst, via a branch conduit 61a to the inlet 66 of a pilot valve means PV; secon-d, via a branch conduit 61b to a port 67 .of a control valve means CV; and a third, via a branch conduit 61e to the conduit 10 which leads into the pump jack cylinder 1.

In the illustrative embodiment, the pilot valve means PV is a hydraulically controlled, spring biased four-way valve which is adapted to be shifted between a first position shown in FIG. 1 and a second position shown in FIG. 2, whereby to cause shifting of the control valve means CV between a first position shown in FIG. 1 and a second position shown in FIG. 2. More specifically, the pilot valve PV includes an outlet 70 communicating with a conduit 71, which leads to an end port 72 of the control valve CV, and the pilot valve PV further includes a spool 73 spring loaded to the above-mentioned first position so that ports 66 and 70 are in communication, whereby pressure uid flows from the pilot valve PV to the end port 72 of the control valve CV. This control valve CV has a spool 74 which is forced by pressure entering port 72 to the above-mentioned rst position, so that the control valve port 67 is in communication with a control valve port 75 leading to an inlet conduit 76 connected to the inlet side of the aforementioned pump 60.

When the pilot Valve spool 73is in the first position of FIG. l, port 70a thereof is in communication with an exhaust port 7.0b which leads through an exhaust conduit 7 0c to a junction with the aforementioned conduit 65 leading to the drain tank 40. An end port 72a of the control valve CV communicates through a conduit 72b vwith the pilot valve port 70a, whereby to exhaust this end ofthe control valve CV, so that the control valve spool 74 is held in its first position by the pressure of fiuid at port 72 at the other end of the spool 74.

The discharge side of the pump 60 is connected by a discharge conduit 77 to the center inlet port 78 of the control valve CV, which, when the spool 74 is in the first position of FIG. 1, communicates with a discharge port 79 of the valve CV. A conduit 80a leads from the valve port 79 to the abovementioned conduit 10 through a pump inlet pressure regulator valve REG, hereinafter to be described.

Thus, when the spool 73 ,of pilot valve PV and the spol 74 of control valve CVare in ytheir rst positions, pressurized fluidis suppliedto the pump jack cylinder 1 via conduit 10 to cause the piston 2 to upstroke, lifting the polish rod 6 and attached string of pump sucker rods.

Various auxiliary valves and other equipment may be employed in the system as thus far described. For example, a metering valve VM'may be installed in the inlet conduit 61aleading to the center port 66 of the p ilot valve PV, A filter F may be installe-d in the system, as, for example, in the conduit 61C. A relief valve VR may be installed in the pump discharge conduit 77, such'relief valve having a conduit 77a leading back to the supply tank 50. The pump 60 ymay be driven by an electric motor M and an electric circuit 60a to the motor M may include a low pressure shut-offl switch PS in pressure communication with the pump inlet conduit 76. A fluid level switch LS may also be in the circuit 60a to the motor M and in pressure communication with the drain tank 40 to shut off the motor if the fluid level in the drain tank rises above a predetermined level, for example, due to excessive leakage in the system.

The downstroke phase of operation .of the pump jack will be described in relation to second positions of the spool 73 of the pilot valve PV and the spool 74 of the control valve CV. A conduit leads from the upper end of pump jack cylinder 1 at a location at which, when the piston 2 is at any position below its uppermost position, the conduit 80 communicates with the aforementioned conduit 20 which leads to the drain tank `40. This conduit 80 also communicates with an end port 81 of pilot valve PVso that the adjacent end of pilot valve spool 73 is exposed to atmosphere, thereby enabling the pilot valve spool 73 to assume and remain in its first position under the inuence of the valve spring 73a, thereby causing the spool 74 of control valve CV toassume and remain in its rst position under the influence of uid pressure at port 72, as previously described.

However, when the pump jack piston 2 reaches its uppermost position, it will he seen in FIG. 2 that the conduit 80 will be in communication with the pressure uid inlet conduit 10, but the conduit 20 will be shut off by piston 2. Thus, pressure fluid will ow through the pump jack cylinder 1 to conduit 80 and to the end port 81 of pilot valve PV, causing a force fwhich will move the valve spool 73 to the right or the second position shown in FIG. 2. At this time, port 72 of the control valve CV will communicate through conduit 71 with pilot valve port 70, thereby exhausting the right hand end of the control valve CV to the drain tank through conduit 70C. In addition, the pilot valve inlet port 66 communicates with port 70a, so that pressure uid from the supply tank 50 flowing through conduit 61a will flow through the pilot valve PV to the end port 72a of control valve CV, whereby to forc the spool 74 to'its second position (FIG. 2).

At this second position of spool 74 of the control valve CV, its port 78 and port 67 communicate so Athat the discharge side of the pump 60, namely, the conduit 77, is connected back to the supply tank 50; while the inlet side of the pump 60, namely, conduit 76, is connected to the conduit 10 through the regulator valve REG.

This regulator valve, as previously indicated, serves to prevent the application of an inlet pressure on the pump 60 which exceeds the discharge pressure. In this Iconnection, it will be understood that when the pump jack' piston first commences its downstroke, following movement of the pilot and control'valve spools 73 and 74to their respective second positions, and the pump jack cylinder 1 below the piston 2 communicates with the pump inlet conduit 76, the pump inlet pressure is a function of the entire weight of the sucker rod string, plus the weight of the column of fluid in the well pipe 4, and the effective cross-sectional area of the piston 2, forcing fluid into the pump inlet conduit 76 as the entire Weight moves downwardly. On the other hand, the discharge pressure of the pump60 is, as previously indicated, a'function of the pressure of the air in the supply tank 50, which will be selected so as to balance the Weight of the sucker rod string and a portion, say one-half, ofthe weight of the Well fiuid column, Under these circumstances, the inlet pressure lat pump 60 may exceed the ldischarge pressure an amount resulting from one-half the weight of the well fluid column acting to force the piston 2l downwardly. This condition, as will be understood in the art, is a momentary condition, since the reciprocating'pump plunger in the well vhas a travelling valve which closes on the upstroke of the plunger and opens responsive to downstroke of the plunger. Thus, when the just-mentioned travelling valve opens, the weight of the well fluid columnwill be supported by the Well pump standing valve, and the inlet pressure on the pump K60 will be reduced.

In' any event, the regulator Valve REG reacts tothe ypresence of an inlet pressure greater than outlet pressure at pump 60 to adjust the pressure atthe pump inlet. Accordingly, while regulator means may be employed either inthe pump inlet conduit 76`or in the pump discharge conduit,'the valve REG, in the illustrative embodiment', is shown as being interposed between thecontrol valve CV and the pump discharge conduit 77. This valve REGincludes a spool 90, an end ofthe valve having a port 91 which is connected by a branch conduit 91a to the pump discharge conduit 77, so that pump discharge pressure is always applied to oneend of the spool 90. The otherend ofthe valve REG has a .port 92 which is connected by a conduit 92a to the control valve port,79 which receives pump discharge during -upstroke of the pump jack. Thus,

.during upstroke of ,the pumprjack, the discharge presfsure.- from the pump 60 is also applied to the regulator valve.spool90 through port. 92, as Well as port 91, and

the spool 90 is balanced., the pump discharge flow passing through vthe full open center ports 90C and 90d of the regulator valve RFGf, However, when the spool 74, of control valve CV is in its second position, the conduit 92a will be conducting fluid to port 79 from the pump jack vcylinder 1, and port 70 communicates with the inlet conduit 76 to pump 60. Thus, the lcomparatively high pressure, at the regulator valve port 92 will shift the regulator valve spool 90 tothe right, as seen in FIG. 2, to reduce the iiow throughY the regulator valve` and thereby reduce the pressurey at the inlet to pump 60 during the initial downward travel vof thevk pump jack piston, until 1 y the well pump *travelling valve opens to reduce the weight aifectin g the inlet pressure at' pump 50.

f The downstroke ofthe pump jack will continue yuntil lthe piston 2 passes a branch conduit 80e adjacent the lower end of the'fcylinder 1, at which time the pressure in lconduit 80 holding the pilot valve spool 73 in its second position will be vented through a check valve 80h in branch conductory 80e into the cylinder 1 above piston 2, a checkl valve 80C being provided in the conduit 80 to y prevent such venting when the piston 2 is above the branch means comprises a compressor 100 connected by an intake conduit 101 to the drain tank 40 and having the aforementioned return conduit 56 leading to the supply tank 50 from the discharge side of the compressor. Preferably, the compressor 100 is of the'rnultiple piston type driven by the motor M through a speed reducer at such a speed as to constantly scavenge the drain fluid from the drain tank, along with air entrained in the fluid, and replenish the supply tank with compressed air and with the scavenged fluid. Preferably, the compressor should operate at a speed which is more than adequate to scavenge the drain fluid, thus the pumping chambers of the compressor will fill partially with drain fiuid and partially with air from the atmosphere. The speed of compressor 100 should also be such that tank 50 is supplied with air in greater volume than is required to maintain the desired balance pressure, excess air being relieved through the working pop valve 53, or, in the event of failure of the valve 53, through safety pop valve 55.

The operation of the system as a Whole is believed to be clear from the foregoing, without further elaboration, and while specific details and arrangements of conduits and valve, as well as other components, have been herein shown and described, changes and alterations may be made without departing from the spirit of the invention.

I claim:

1. In a system for operating a pump jack having a cylinder and a piston reciprocable in said cylinder for reciprocating a string of well pump sucker rods: a supply tank for hydraulic pump jack operating fluid, said tank having means enabling pressurizing the same with air, a drain tank, means including iiuid operated control means lfor conducting said fluid to said pump jack cylinder from said supply tank and for returning said fluid from said pump jack cylinder cyclically, means for exhausting said control means to said drain tank, and a compressor connected to said drain tank and to said supply tank for returning iuid and compressed air from said drain tank to said supply tank to maintain the air pressure in said supply tank.

2. A system as defined in claim 1; wherein said means for conducting said fluid includes a pump, control valve means interposed between the pump inlet and the pump discharge and movable between a irst position at which said pump discharge is connected to said cylinder and said pump inlet is connected to said supply tank and a second position at which said pump discharge is connected to said supply tank and said pump inlet is connected to said cylinder, and means for moving said control valve means between said positions. 3. In a system for operating a pump jack having a cylinder and a piston reciprocable in said cylinder for reciprocating a stringof well pump sucker rods; a supply tank for hydraulic pump jack operating fluid, said tank having means enabling pressurizing the same with air, a drain tank, means including fluid operated control means for conducting said -fluid to said pump jack cylinder from said supply tank and for returning said iiuid from said pump jack cylinder cyclically, means for exhausting said control means to said drain tank, and compressor means for returning fluid and compressed air from said drain tank to said supply tank to maintain the air pressure in said supply tank, said means for conducting said uid including a pump, control valve means interposedbetween the pump inlet and the pump discharge and movable between a first position at which said pump discharge is connected to said cylinder andsaid vpump inlet is connected to said supply tank and a second position at which said pump discharge is connected to said supply tank and said pump inlet is connected to said cylinder, and means for moving said control Valve means between said positions, said .moving means including pressure regulator means for preventing a pressure at said pump inlet greater than pressure at said pump discharge when said valve means is in said second position.

4. A system as defined in claim 1; wherein said means for conducting said fluid includes a pump, control valve means interposed between the pump inlet and the pump discharge and movable between a first position at which said pump discharge is connected to said cylinder and said pump inlet is connected to said supply tank and a second position at which said pump discharge is connected to said supply tank and said pump iniet is connected to said cylinder, and means for moving. said control valve means between said positions including pilot valve means connected to said cylinder and to said control valve means and responsive to movement of said pump jack piston to the end of its movements in opposite directions to cause movement of said control valve means to said first and second positions.

5. A system as defined in claim l; wherein said means for conducting said fluid includes a pump, control valve means interposed between the pump inlet and the pump discharge and movable between a first position at which said pump discharge is connected to said cylinder and said pump inlet is connected to said supply tank and a second position at which said pump discharge is connected to said supply tank and said pump inlet is connected to said cylinder, means for moving said control valve means between said positions, a source of power for said pump, and drive means connected to said source of power for operating said compressor means.

6. Ina system for operating a purnp jack having a cylinder and a piston reciprocable in said cylinder for reciprocating a string of well pump sucker rods: a supply' tank for hydraulic pump jack operating fluid, said tank having means enabling pressurizing the same with air, a drain tank, means including uid operated control means for conducting said iiuid to said pump jack cylinder from said supply' tank and for returning said fluid from said pump jack cylinder cyclically, means for exhausting said control means to said drain tank, and compressor means for returning fluid and compressed air from said drain tank to said supply tank to maintain the air pressure in said supply tank, said means for conducting said fluid including a pump, control valve means interposed between the pump inlet and the pump discharge and movable between a first position at which said pump discharge is connected to said cylinder and said pump inlet is connected to said supply tank and a second position at which said pump discharge is connected to said supply tank and said pump inlet is connected to said cylinder, means for moving said control valve means between said positions, a source of power for said pump, drive means connected to said source of power for operating said compressor means, said compressor means comprising a multiple piston compressor, and said drive means including speed reducer means for driving said compressor at low speed relative to said pump.

In an oil well pumping system for connection to a string of reciprocable pump sucker rods: a pump jack having a vertically disposed cylinder, a piston and rod reciprocable in said cylinder and connectible to said string of pump rods, an inlet and outlet conduit below said piston, means for cyclically supplying pressure fluid to said cylinder and exhausting said fluid from said cylinder through said conduit to effect upstroking and downstroking of said piston and rod, said means including a fluid supply tank having air therein for applying a load balancing force to said fluid during upstroking of said piston and r'od, pump means having an inlet and a discharge, valve means movable between a first position connecting said pump means discharge to said conduit and said pump means inlet to said supply tank and a second position connecting said conduit to said pump means inlet and said pump means discharge to said supply tank, means for moving said valve means to said first position when said piston and said rod reach the end of said downstroke and for moving said valve means to said second position when said piston and rod reach the end of said upstroke, and pressure regulator means for preventing the application of pressure at said pump means inlet in excess of the pressure at said pump means discharge when said valve means is in said second position.

8. A pumping system as defined in claim 7; wherein said pressure regulator means includes a pres-sure operated regulator valve interposed between said pump means inlet and said pump means discharge. ,i

9. A pumping system as defined in claim 7; wherein said pressure regulator means includes a pressure operated regulator valve interposed between said pump means inlet and said pump means discharge, said regulator valve having a spool, a conduit connecting said regulator valve to said pump means discharge to subject one end of said spool to the 4pressure at said pump means discharge, another conduit connecting said regulator valve to said valve means to subject the other end of said spool to fluid pressure, and said valve means including means for admitting the pressure of fluid from Said pump means discharge to said another conduit when said valve means is in said first position and for admitting the pressure of fluid from said pump means inlet to said another conduit when said valve means is in said second position.

10. A pumping system as defined in claim 7; `Jvherein the means for moving said valve means to said first and second positions includes pilot valve means movable to a first position for causing said first-mentioned valve means to move to said first position, said pilot valve means being movable to a second position to cause said first-mentioned valve means to move to said second position, and means for moving said pilot valve means to said first and second positions when said piston and rod reach the end of their downstroke and upstroke.

11. A pumping system as defined in claim 7; wherein the means for moving said valve means to said first and second positions includes pilot valve means including a spool movable to a first position for causing said firstmentioned valve means to move to said first position, said pilot valve means spool being movable to a second position to cause said first-mentioned valve means to move to said second position, and means for moving said pilot valve means spool to said first and second positions when said piston and rod reach the end of their downstroke and upstroke including conduit means connecting said pump jack cylinder to said pilot valve means to cause movement of said spool to said first and second positions when said piston and rod reach the end of their downstroke and upstroke.

12. In a well pumping system for connection to a string of reciprocable pump rods: a pump jack having a vertically disposed cylinder, a piston and rod reciprocable in said cylinder and connectible to said string of pump rods, a supply tank for air pressurized fluid, conduit means leading from said tank to said cylinder beneath said piston, pump means in said conduit means, control valve means in said conduit means for alternately reversing the flow between said tank and said cylinder upon reversal of said control valve means, pilot valve means in said conduit means for reversing said control valve means, said pilot valve means having fluid pressure responsive means for operating the same upon movement of said piston to an upper position and to a 1iower position, a pilot conduit leading to said pilot valve means and communicating with said cylinder below said piston when said piston reaches its upper position and above said piston when said piston reaches its lower position to conduct uid pressure to said fluid pressure responsive means, a drain tank, an exhaust conduit leading from said pilot valve means to said drain tank, a compressor connected to said drain tank, and a conduit leading from said compressor to said supply tank for conducting compressed air and fluid from said drain tank to said supply tank.

13. A well pumping system as defined in claim 12; wherein said control valve means is fluid pressure operated, and including pilot conduit means connecting said control valve means to said pilot valve means, said pilot valve means having means for exhausting said pilot conduit means to said drain through said exhaust conduit upon reversal of said control valve means.

14. A well pumping system as defined in claim 12; wherein pressure regulator means are provided for preventing the application of an inlet pressure on said pump means in excess of the discharge pressure of said pump means when said control valve means reverses at the end of the upward movement of said piston.

15. A Well pumping system as dened in claim 12; wherein said supply tank is provided with pop valve means for limiting air pressure in said supply tank in response to operation of said compressor.

16. A well pumping system as defined in claim 12; wherein shut-olf valve means are provided in said conduit means leading from said supply tank to said cylinder, said shut-Off valve means including an actuator cylinder, an actuator piston in said actuator cylinder having a rod projecting from said actuator cylinder and connected to said shut-off valve means to open and close the same upon shifting of said actuator piston, conduit means leading from said supply tank to said actuator cylinder at oppo- References Cited UNITED STATES PATENTS 2,470,252 5/ 1949 Kyle. 2,481,623 9/ 1949 Rued. 2,489,412 11/1949 Harvey. 2,665,551 1/ 1954 Chenault. 2,729,942 1/1956 Billings et al. 2,780,063 2/1957 Bacchi.

EDGAR W. GEOGHEGAN, Primary Examiner U.S. Cl. X.R. 103-45

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