US2582564A - Hydraulic pumping jack for in-the-well pumps - Google Patents

Description

Jan' 15, 1952 F. w. scHNEcK r-:TAL 2,582,564

HYDRAULIC PUMPING JACK FOR IN-THE-WELL PUMPS Filed Nov. 1,. 195o 2 SHEETS-SHEET 1 IIIIIII I I Ill yF. W. Schneck R. M. /Vlc Nei/l wwf/f7 ATTORNEY Jan. 15, 1952 F, w SCHNECK rA| 2,582,564

HYDRAULIC PUMPING JACK FOR IN-THE-WELL PUMPS FiledlNov. 1, 1956 2 SHEETS- Smm 2 ffff INVENToRs F. W. Schneck R. IVI. McNeill.

BY /f ATTORNEY Patentesi Jan. 15, 1952 HYDRAULIC PUMPING JACK' FOR lN-THE-WELL PUMPS Frederick W. Schneck, Northridge, and Robert M. McNeill, North Hollywood, Calif., assignors to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application November 1, 1950, Serial No. 193,381

Claims.

This invention relates to hydraulic Dumping Jacks for reciprocating the suckerl rods ,of -pumps in deep wells such as oil wells.

An object of the invention is toprovide a hy- .v

`lraulic pumping jack that is reliable and eflicient and is largely automatic in operation Another object is to provide a practicable and simple system for producing a pausel or dwell of controllable duration Ain the movement of the sucker rod at each end of the stroke.

Another object is to provide automatic safety means for stopping the pumping action in response to the development of abnormal conditions in the apparatus that would make continued operation undesirable.

Another object is to provide n 'effective and reliable system for replenishing hydraulic iluid lost by leakage from the hydraulic circuit.

Another object is to provide automatic interruption of the pumping action in the event of insufficient or excess hydraulic fluid for proper operation and automatic resumption of the pumping action as soon as the fluid supply has been restoredto the proper value.

Another object is to provide, in a hydraulic pumping jack incorporating a counterbalance system utilizing compressed gas to balance the power consumption during the up and down strokes of the pump, an automatic control for varying the counter balance gas pressure as necessary to maintain substantially equal power consumption on the up and down strokes of the pump.

Other more specic objects and features of the invention will appear from the description to follow.

Briefly, a system in accordance with the present invention comprises a hydraulic ram connected to the pump sucker-rodsf'forlifting and lowering them, a counterbalance 'containing a supply of hydraulic fluid under'a substantially constant pressure, a constantly drivenpump, and a main valve for alternatelyvconnecting the input for the pump to the counter balance and the output of the pump to the rainv 'to move the ram through its upstroke,Y andvconne'ct the input of the pump to the ram and the'jvout'put to the counter balance on the downstrokeLf-The main valve is a servo valve actuated by hydraulic pressure under the control of a pilot'. valve that is mechanically tripped .or reversedfat the upper and lower ends of the stroke ofthe ram. The hydraulic actuating mechanism ofthe main valve consists of a pair of motor pistons which are mechanically separate from the valve, so that each is capable of moving the valve in one direction but the valve is capable of moving away from the piston at a more rapid rate. Furthermore, the valve is provided with a centering spring, and pressure fluid is supplied to the pilot valve through a restricted passage, but an exhaust line of vunrestricted dimensions returns exhaust fluid from the pilot valve to the reservoir. The result is that when the pilot valve is reversed, pressure uid is supplied at a slow rate, because of the restriction, to the piston at one end of the main valve, tending to move the latter through its stroke. However the centering spring moves the main valve into neutral position faster than the pressure iiuidsupplied through the restricted passage can move it. The result is that the main valve is quickly moved into neutral position by its centering spring `and holds in neutral yposition until the motor piston being slowly 'moved by the pressure fluid flowing through the restricted passage catches up with the main valve and moves it on into its other extreme position.

The result is that the main valve moves quickly into neutral position to stop the ram, pauses in neutral position, causing a corresponding pause or dwell in the movement of the ram, and then moves into its other extreme. position to start' the ram moving in the other direction. This pause or dwell can be varied in length by varying the restriction in the pressure fluid supply to the pilot valve.

There is a constant leakage of hydraulic iluid from the system including the ram, the main valve, and the counter balance, and to compensate for this leakage fluid must be introduced lby a replenish system. In accordance with the present invention, the counter balance comprises' a cylinder having hydraulic fluid in one end portion and compressed air or gas in the other portion, the two being separated by a free piston in the cylinder. the proper amount of fluid the free piston reciprocates between certain predetermined limits in the counterbalance cylinder. If the amount of fluid fails below a desired value the free piston moves'farther in one direction and contacts and slightly shifts a replenish valve which admits additional iluid from a separate replenish pump. To increase 4the'e fiectiveness vof the replenish valve it is provided lwith afhydraulic damping system which permits it tog'returnifrom open to closed position relatively slowly instead of following the free vpiston -as'the latter moves on its return stroke. y ijf.

Normally only small amounts of replenish fluid are required from time to time, and the total quantity of iluid in the system does not drop So long as the system contains 3 below a. value to permit 'full stroke operation ofthe ram. However it is conceivable that as a result of some abnormal condition the quantity of fluid in the system might drop below that necessary to permit the ram to make its full stroke. In such event the free piston in the counterbalance cylinder will move the replenish valve beyond its normal position, and, in accordance with the invention, there is provided an auxiliary, hydraulically actuated valve between the pilot valve .and the main valve which returns the main val've to neutral in the event the free piston in the counter balance is moved beyond its normal limit. However, continued operation of the replenish pump should normally restore the quantity of uid, thereby moving the free piston away from the replenish valve and permitting it to move back into normal position, which inturn releases the auxiliary valve and permits the ram to resume its operation. The

pumping action is therefore automatically interrupted 'only as long as there is insufficient fluid,

' ,and when the normal amount of fluid has been restoredoperation is automatically resumed.

The air-pressure in the counterbalance cylinder is supposed to balance the weight of the `sucker rod and half the weight of the column of ing the 'downstroke It/is possible however for the load on an oil well pump to vary during the course of operation. Such variation may for example be produced by a variation in the amount of gas in the oil being pumped. To maintain equal load on' the prime mover during the up and down strokes of the ram, the air pressure in the counterbalance should be correspondingly varied. In accordance with the present invention the air pressure in the counterbalance is automatically controlled in response to the load on the pump. This is accomplished by providing an auxiliary cylinder having a free piston therein and connected at one end to the ram line and at the other end to the counterbalance line. This auxiliary cylinder can be relatively small so that it shunts relatively little uid from the pump, and the connection at one or both ends of the cylinders can contain restricted passages which permit only small rates of flow into opposite ends of the cylinder. As long as the counterbalance air pressure is at the proper value to perfectly balance the load on the ram, the time of the upthis is that more fluid will be admitted to onel end of the auxiliary cylinder than to the other, which will gradually move the average position of the free piston toward one end of the auxiliary cylinder. Appreciable drift of the free piston beyond its normal stroke limit causes it to open a valve to admit air under pressure to the counterbalance chamber and raise the mean air pressure to a value such as to balance the increased load on the ram. When this'balance has been restored. the free piston will again move between I2 includes a main valve cylinder I8 containing` `counterbalance cylinders.

d its normal stroke limits. On the other hand, if the load on the ram should lighten. the free piston would gradually drift in the opposite 'direction and after appreciable movement-beyond its usual stroke limit in this direction it contacts and opens a valve that releases some air from the counterbalance chamber. In this way, an approximately perfect balance between the counterbalance pressure and the pump load is automatically maintained.

A full understanding of the invention may be hadfrom the following description read in connection with the drawing, in which:

-tion of which is connected by a supply line I4 to the main valve assembly I2, and a, main pump I5 driven by a prime mover 53 and having an inlet line I6 and an outlet line I1 connected to the main valve assembly I2. During normal operation the valve assembly vI2 functions to alternately connect the inlet line `II to. the ram line II while connecting the outlet line I1 to the counterbalance or supply line I4, and vice versa, to raise and lower a piston Illa in the ram I0 which piston is connected by a piston rod Illd to the polish rod of a pump (not shown).

Main valve and operation thereof Referring to Fig. 2, the main valve assembly a shiftable valve element or piston I9 reciprocable therein. The valve piston I9 has three lands Isa, I9b and I9c which cooperate with ports in the valve cylinder I8 to control the iiow of uid between the pump and the ram and Thus cylinder ports I8a and IBe are connected to the pump inlet line I6. Cylinder port I8b is connected to the supply line I4. Cylinder port I8c is connected to the pump outlet line I1, and cylinder port Id is connected to the ram line II.

The valve piston I9 is shown in extreme left position, in which the supply line I4` is connected to the pump inlet line I6 and the ram line II is connected to the pump outlet line I'I, so that fluid is pumped from the counterbalance cylinder into the ram to elevate the ram piston.

When the main valve piston I9 is in mid (neutral) position, the land Ib thereon is positioned between the cylinder ports I8c and I8d. This connects the cylinder port I8a directly to the cylinder port I8Ic, permitting fluid to ow freely from the pump outlet line I1 into the pump inlet line I6. However, the port I8d is completely blocked by the piston lands IQb'and I9c so that the same time. the pump inlet line I6 is connected by the ports |8e and I 3d to the ram line so that uid is pumped from the ram to the counterbalance cylinder to lower the ram piston.

Centering springs 22 and 23, respectively, are provided atvopposite ends of the valve piston I9 for moving it into its central neutral position whenever it is not held in one or the other end position by hydraulic motor means next to be described. 'I'his motor means comprises a motor piston 24 ina small motor cylinder 25 extending from the left end of the valve cylinder I8, and a motor piston 26 in a small motor cylinder 21 extending from the right end of the valve cylinder y I8. 'I'he opposite ends of the valve cylinder I8 are vented to the reservoir by exhaust lilies 29 and 29, respectively. Hence there is never any pressure fluid in the ends of the cylinder I8 to act upon the piston I9. The outer end of the motor cylinder 25 is connected by a passage 39 and by a port 3Ia in an auxiliary valve cylinder 3| to a port 34h in a pilot cylinder 34 of a pilot valve consisting of the cylinder 34 and a piston 35. The outer end of the motor cylinder 21 is connected by a passage 36 and a port 3Id in the auxiliary Valve cylinder 3| to a port 34d in the pilot valve cylinder 34. The pilot valve port 34e is normally connected by the auxiliary valve cylinder ports 3Ic and 3|b toa line 38 connected through a throttling valve 39 (Fig. 1)' to the supply line |.4 extending to the counterbalance cylinder, so that pressure fluid is supplied from the counterbalance cylinder to the port 34c. The other two ports, 34a and 34e of the pilot valve, are connected by an exhaust line 4I to the reservoir. In Figs. 1 and 2 the pilot valve piston 35 is in leftmost position, in which it applies pressure fluid from the line 38 to the right motor cylinder 21l of the main valve and connects the exhaust line 4I to the left motor cylinder 25, to hold the main valve in -leftmcst position as shown.

Referring to Fig. 1, when the ram piston Illa approaches its uppermost position an actuator |b on the upper end of the piston contacts a control lever 42 connected to a pulley 43 having a crank pin 43a thereon which is connected by a connecting rod 44 to the pilot valve piston 35, so that final upward movement of the piston rocks the lever 42 and the connecting rod 44 to shift the pilot valve piston 35 into its rightmost position. Referring back to Fig. 2, this movement of the pilot valve connects the pressure line 39 through ports 34e and 34h to the left motor cylinder 25, and connects the exhaust line 4| through ports 34e and 34d to the right motor cylinder 21. The lines 35 and 4I offer a path of low resistance for the flow of uid from the motor cylinder 21 back to the reservoir, so that the centering spring 22 can quickly restore the main valve piston I9 into neutral position, in which the ram line is blocked, and the pump lines I6 and I1 are shortcircuited. Therefore, the ram piston I0a is held at the upper end of its stroke. During this initial movement of/the main valve piston I9 by the centering spi/ing 22 back into neutral position, the valve piston I9 runs away from the motor piston 24, which is moving only slowly because of the throttling effect of the 'throttle valve 39 (Fig. l) in the pressure supply line 38. Eventually, the motor piston 24 catches'up with the valve piston I9 and carries the latter from neutral position into extreme rightmost position, in which the pump outlet line I1 is yconnected to the counterbalance or supply line I4 and the pump inlet I6 is connected to the ram line Il,

to reverse the movement of the ramv piston and start it on its downward stroke. l

Referring back to Fig. l, as the ram piston |0a approaches its lowermost position, a lower actuator |0c thereon contacts a lever 46 connected to a pulley 41 which is coupled by a belt 48 to the pulley 43, and final movement of the piston IIIa into lowermost position rocks the lever 43, the pulleys 41 and 43. and the connecting rod 44, to shift the pilot valve piston 35 back into its leftmost position in which the original connections as shown in Fig. 2 are restored. Hence, the left motor cylinder 25 is now connected to exhaust, the right centering spring 23 is effective to quickly move the main piston I9 back into neutral position, again blocking the ram line I I, and causing the ram piston to pause or dwell in its lower end position until the pressure fluid supplied through the metering or throttling valve 39 to the right motor cylinder 21 causes the motor piston 26 to overtake the valve piston I9 and carry it into extreme left position as shownI in Fig. 2 thereb completing a cycle of operation.

The provision of the centering springs 22 and 23.in combination with the low resistance passage from one of the motor cylinders 25 to exhaust while providing throttled flow of pressure fluid to the other motor cylinder provides a simple and effective way of producing a pause or dwell at each end of the stroke of the ram piston and the extent of the dwell can be adjusted by regulating the throttling valve 39.

Replemsh systm It will be observed from the foregoing description that the main pump I5 simply circulates fluid back and forth between the lower end of the counterbalance cylinder I3 and the lower end of the rain III. In such systems, it is usually impractical to prevent a constant slight leakage of fluid which would eventually result in depletion of the fluid supply. Hence it is necessary in a practical system to provide for the frequent replenishment of small quantities of fluid to the system to compensate for that lost by leakage. In the present system, referring to Fig. 1, fluid is supplied from the reservoir '50 through an intake pipe 5I .to a replenish pump 52 which may be constantly driven by the same prime mover 53 that drives the main pump I5. A substantially constant flow of fluid is delivered by the replenish pump 52 through a line 54 and a fan motor 55 to a line 56, which is connected through a manually controlled valve 51 and a check valve 58 and a line 59 to the main supply line I4, which is permanently connected to the lower end of the accumulator'cylinder I3. Normally, fluid is freely bypassed from the line 56 to the reservoir through a line 6I, a relief valve 62, and a return line 63. f

The fan motor 55 drives a fan 55a which is used to supply cooling air for the equipment and is of no importance in connection with the rest of the hydraulic circuit. The motor 55 is bypassed by a throttlevalve 55h which is used to regulate the speed of the motor 55. v

The replenish pump 52 delivers a substantially constant flow of fiuid through the fanmotor 55 and the bypass valve 55b and thence (normally) through the pipe 6| and the normally open relief valve 62 and return line 63 back to the reservoir 50. As long as-the relief valve 62 is open, no pressure is developed in the line 56 and hence no flow can occur through the check valve 58 aaaces.- y

7 o tlli replenish pipe 69 leading to the supply ine The valve 62 is of the pilot type which remains )pen in response to free ow through a pipe 65 eading therefrom, but closes in response to stop- )age of free ow through the pipe 66. When :onditions are such as to require replenishment, '.he pipe 65 is closed. causing the valve 62 to close ind build up suilicient pressure in the line 56 to nass fluid through the check valve 56 into the supply line I4.

' Referring to the schematic illustration of the 'elief valve 62 shown in Fig. 3, pressure iiuid 'rom the pipe 6I is applied to a cylinder 62a :ontaining a piston 62h that is urged to the right )y a spring 62e. The piston 62h is provided with a' bleed hole 62d therein which permits a ilow flow of uid from the cylinder 62a past the lJiston 62h and to the pipe 6I. If the other end if pipe 6I is closed, pressure builds up in the .eft end of the cylinder 62a so that the pressures )n the two ends `of the piston 62h are balanced and the piston is held in its rightmost position is shown in Fig. 3 by the spring 62e. In this `:osition a poppet 62e on the'right end of the `aiston 62h closes a seat 62j leading to the pipe i3. so that no fluid can ow into the pipe 63. However if the other end of pipe 6I is open, so that the small flow of fluid through the bleed hole 62d cannot build up pressure inthe left end of the cylinder 62a, then the pressure acting on the right end ofithe piston 62h is sulcient to over- :ome the force of the spring 62c and move the oiston 62D to the left thereby carrying the poppet 52e clear of the seat 62! and permitting free ow if uid from the pipe 6I through the valve tov ahe pipe 63. f

In addition to opening in response to free ow f uid through the pipe 6I, the valve 62 will )pen in response to a predetermined excess pres- :ure in the line 6| even though the pipe 6I is dosed. Thus the left end of the cylinder 62a s connected by a passage 62g to a ball relief valveV eat closed by a ball valve 62h actuated by a .pring 62j. Pressure in excess of the predeternined value lifts the ball valve 62h o its seat, )ermitting flow of fluid from the left end of the :ylinder 62a so that a pressure is developed igainst the right end of the piston to open the vJoppet 62e and permit free discharge of fluid from the pipe 6I through the pipe 63 back to the reservoir. The pilot valve 62h. is provided purely -or safety reasons to prevent the pressure from rising to an excessive value in the event of an abnormal condition. Normally it remains closed. Referring back to Fig. 1, the pipe 65 connects to a port 61 in a valve cylinder 66 formed in the lower end of the counterbalance cylinder I3 and containing a valve piston 69 which is normally held in an upper limit position by a spring 16. In this position, longitudinal grooves 69a in the valve piston 69 connect the port 61 to a port 1I next below the port 61 and to a port 12 next below the port 1I. The port 1I 1s connected to the return pipe 63 leading back to the reservoir. 'Ihe port 12 is connected by a pipe 14 to a chamber in the main valve assembly I2, the purpose of which will be described later.

The operation of the replenish system is as follows: It will be observed that as long as the valve piston 69 is in its uppermost position as shown in Fig. 1, the pipe 65 is connected by the port 61, the groove 69a, and the port 1I to the return pipe 63 so that no pressure is developed Det .62e (Fig. 3) in the valve 62 remains open to'freely bypass uid from the pipe 6I to the return lpipe 63 so that .insuicient pressure is built vup in the pipe 56 to exceed the pressure in the main supply line Il. Therefore the check valve 66 remains closed and there is no replenishment of the iluid supply.

Now let it be assumed that as a result of a leakage of fluid from the system, the total quantity of fluid in the ram I6, the ram line II, the supply line Il. and the counterbalance cylinder I3 diminishes until eventually during the nal movement of the ram piston Illa on an upstroke the liquid level in the lower part of the counterbalance cylinder I3 becomes so low that a free piston I3a separating the liquid from the gas contacts the upper end of the piston 69 and depresses it. A very slight depression of the piston 69 carries the grooves 69a out of registration with the port 61, isolating the latter and permitting pressure to build up in -the pipe 65. `'I'his closes the relief valve 62 causing the pressure `to build up in the pipe 56 to a value exceeding the pressure in the supply line I4 so that uid flows fromthe pipe 56, through the valve 51 and the check valve 56 and the pipe 69 into the supply line I4.

The piston 69 will be depressed a slight amount on each downward stroke of the free piston I3a until the quantity of uid in the system has been restored to its normal value causing the free piston I3a to no longer contact the replenish valve piston 69.

It is desirable in practice to cause the valve piston 69 to remain in depressed position longer than it would normally be held, down by the free piston I3a. To produce this result, the lower end of the valve cylinder 69 is connected to a chamber 11 which is connected by a check valve 18 with the lower end of the ounterbalance cylinder I3. During downward movement of the` valve piston 69, the fluid displaced by the entry of the piston into the chamber 11 is freely displaced therefrom past the check valve 18 into the counterbalance cylinder I3. However when the free pistonl 13a moves upward again, and the valve piston 69 tends to follow it, rapid return of the valve piston is prevented by the pressure of the uid in the counterbalance cylinder, a com pensating pressure in the chamber 11 being built up only lslowly by ow of fluid through a bleed passage 19 in the check valve poppet 19. 'I'he spring 10 is not stiff enough to draw a vacuum in the chamber 11. As a result of the delayed return of the valve piston 69 by the check valve 13 only a few depressions of the valve piston 69 by the free piston l3a are normally necessary to s'o restore the quantity of fluid in the system as to prevent further contact of the free piston I3a with the valve piston 69.

Conceivably, during a period of inactivity, a relatively large amount of fluid might leak out of the system, so that when the unit is rst started'up there is insuflicient fluid contained within the countenbalance cylinder I3 and the ram I0 to produce a full upstroke of the ram piston 10a without fully depressing the free piston I3a in the counterbalance. This could cause cavitation of the main pump I5 due to a lack of uid on the input side thereof. Apparatus is therefore provided for centering the main valve in the event the free piston I3a drops materially below the normal upper position of the valve piston 69. The mechanism for automatiin the pipe 65. Under these conditions, the pop- 16 cally centering the main valve is controlled by means of the -port 12 in the valve cylinder 88. During a. normal replenish operation, the upper ends of the vertical grooves 89a in the valve piston 89 never drop below the port 1I', so that the port 12 is always connected to the return line 63 and no pressure can be built up in the port 12 and the pipe 14. However, if the fluid supply in the system should drop so low that the free piston I3a in the counterbalance cylinder could approach its lower limit position. thereby preventing all further delivery of iluid to the supply line I4, the valve piston 69 will be depressed to such an extent that the grooves 69atherein connect the port 12 with the chamber 11, which in turn is always connected by the bleed passage 19 with the counterbalance cylinder. This sup'- plies pressure fluid to the pipe 14 leading to the main valve assembly I2. l y

Referring now to Fig. 2, the piston 32 ofv the auxiliary valve' is exposed at its leit end to the pressure of uid in a chamber 82 to which the pipe 14 is connected. A rise in pressure in the' pipe 14l and the chamber 82 moves the piston 32 to the right to the limit of its travel, compressing a spring 83 in a mechanical link which connects the piston 32 with aneccentric 84 that is manually rotated through 180 to start and stop the apparatus. Movement of the valve piston 32 to the right causes a land 32a thereon to completely block the pressure fluid supply port 3Ib thereby preventing the admission of pressure fluid to either of the main valve operating motors 24 and 21. Another land 32h on the piston uncovers port 3Id thereby interconnecting ports 3|a and 3|d which are connected by the passages 30 and 36 respectively to the motor cylinders 25 and 21. One or the other of the centering springs 22 or 23 thereupon immediately restores the main valve piston I9 to neutral position, in which the ram line Il is blocked and the pump inlet pipe I1 is connected to the pump inlet line I8.

It will be seen, therefore, that if the apparatus is startedv with insufllcient Huid in the system the following sequence of operation takes place: The ram piston Ia starts its upstroke and due to the insui'licient supply of fluid in the system the free piston I3a in the counterbalance drops into its lowermost position before the ram-piston has completed its upstroke. The resultant large depression of the valve piston 69 by the free piston I3a closes the relief valve 62 as previously described so that the replenish pump develops full pressure in the line 56 to deliver iiuid through the check valve 58 tothe supply line i4, l

thereby beginning to restore the vfluid supply.

pipe 14 shifts the main valve into neutral position as previously described, thereby short-circuiting the main pump I5 and blocking the ram line I I to hold the ram piston |0a in whatever position it had been lifted to at the time the free piston I3a in the counterbalance reached its lowermost position. The action ofthe replenish pump gradually increases the amount of fluid `in the counterbalance cylinder I3, liftingy the free piston I3a therein and permitting rise of the` valve piston 69. This rise will, after a period of time, carry the grooves 69a in the piston 09 clear of the chamber 11 but the pressure previously built up in the line 14 will be maintained until further rise of the groovesv 89a connects the port 12 to the return port 1|. This releases the pressure in the pipe 14 permitting the auxiliary valve piston 32 (Fig. 2) to be restoredby the spring 83 and'permitting the pilot valve to again take control and shift the main valve into position to cause the main pump |5 to again deliver fluid from the supply'line I4 to the ram line II. The ram piston I0a will thereupon be again lifted, until the free piston I3a in the counterbalance cylinder again depresses the valve piston 69 to repeat the cycle ofoperations. The overall result is thatthe ram piston I0a is lifted by small incrementsduring the replenish of iluid to'the system, until the ram piston reaches the upper end of its stroke and trips the lever 42 causing the reversal of the main valve and the commencement of the downstroke. The next succeeding upstroke will ordinarily be completed in normal fashion except in the event of a very abnormal condition producing insuillcient leakage of iluid from the system during one cycle ofloperation to cause the free piston I3a to fully depress the valve piston 69 on the next succeeding downstroke.

Conceivably, through some accident, the systeni could be overlled with fluid, in which event, during the upstroke of the free piston ,I3a it would rise beyond its usual limit position, and such abnormal rise is utilized to release some fluid from the system. Thus excessive upward movement of the free piston I3a will cause it to contact and elevate a valve piston reciprocable in a valve cylinder 9|, the latter containing two ports 9Ia and 9|b which are normally blocked from each other by a land 90a onl the piston 90. The port 9|a is connected to the return pipe 63 and the port 9|b is connected to the pilot pipe 94 of a relief valve 95 connected to the pump outlet pipe I1. The construction of the valve 95 may be identical with the valve 02, as shown in Fig. 3. The valve 95 is normally closed, but will open either to abnormal pressure in the pump outlet line I1 or to release of pressure from the pilot line 94. Pressure will be maintained in the pilot line 94 as long as the port 9Ib is blocked by the piston land 90a.

However if there is excess uid in the system,

causing the free piston I3a to lift the valve piston 90 andinterconnect the port 9| a tothe port SIb', pressure is immediately relieved in the pilot line 94, causing the valve 95 to open and discharge uid from the system until vthe free piston I3a is` lowered sufficiently to permit the valve piston 90 to restore it to its normal position, again blocking "the port 9 Ib.

l Counterbalance'air pressure regulator As was described in the introduction, the air pressureabove the free piston I3a should be such as `to produce equal loading ofthe main pump I5 during the up and down strokes of the ram; It is also. desirable that the air pressure above the free piston I 3a vary as little as .possible during each stroke. To this end the air chamber of the counterbalance cylinder I3 is connected by a pipe 91 to an air tank 98 which is preferably of large volume compared to the volurne of the counterbalance cylinder I3. The air pressure in the tank98 is controlled by an exhaust valve |00 connected thereto by a pipe I0| and by a supply valve |02 ,which is adapted to connect the pipe |0| to a pipe |04 leading to an air compressor I 05 which may be connected to and driven by the same prime mover 53 that drives the main pump I5 and the replenish pump 52. Both of the valves |00 and |02 are normally closed, but the valve |00 is opened to relieve the auoauee air pressure in the event it is too high, and the valve |02 is opened toadmit more air from the compressor |05 in case the pressure is too'low. These valves and |02 are actuated by pilot valves |01 and |08, respectively, in opposite ends of a cylinder |09 containingV a free piston IIO. The left end of the cylinder |09 is connected by a pipe 81 to the ram'line II, and the right end of the cylinder |09 is vconnected by the pipe 30 to the supply line I4. It will be observed therefore that during the upstroke of the ram I0 the pressure developed by the main pump I is applied to move the free piston I|0 to the right. and that during the downstroke of the ram the pressure developed by the pump is applied to move the free piston IIO to the left. It is desirable that the cylinder |09 be of small dimensions so as not to bypass any more fluid from the main pump than is necessary. To permit this, ow into and out of the right end of the cylinder is restricted by a bleeder passage I I2 in the right end of the cylinder.

As long as the air pressure in the tank 93 and in the upper end of the counterbalance cylinder I3 is at its optimum value, the pressure differential developed by the main pump I5 will be the same on both the up and down strokes ofthe ram, and the time of the upstroke will equal the time of the downstroke. While this condition is maintained, the free piston |I0 in the cylinder |09 will move back and forth through a fixed distance between end limits that are well spaced from the ends of the cylinder |09. However if the mean air/pressure in the counterbalance cylinder is insuillcient to balance'the load on the ram, the pressure differential applied across the free piston I I0 during the upstroke of the ram will be greater and will be of longer duration than the pressure differential applied in the opposite direction during the downstroke of the ram. The result will be that the free piston ||0 will work toward the right end of the cylinder 09 and will contact and trip the valve I 08 thereby permitting some of the pressure fluid in the right end of the cylinder |09 to flow through a pipe I I 3 into a cylinder I5 in the valve |02 where it will'develop a pressure to move a piston I I3 and open a poppet valve |I1 to admit air from the compressor |05 through the pipe |04 and through the pipe IOI to the air tank 93. The pressure fluid in cylinder I5 will leak out through a bleed passage ||3 to the return line 83, so that the valve ||1 will automatically close shortly after the free piston I I0 has moved away from the valve |08. However, on successive movements of the free piston I0 into its right end position, the valve |08 will be opened to again open the valve ||1, until the air pressure in the tank 98 and in the counterbalance cylinder I 3 has been restored into proper balance with the load on the ram I0a, whereupon the free piston IIO- will again ride clear of the valve |08'. Should the condition be reversed and the air pressure be too high for the ram load, the pressure conditions in the cylinder |09 will be reversed, with the result that the free piston 0 will contact the valve |01 in the left end of the cylinder thereby admitting pressure fluid through a pipe into a cylinder |26 in the valve I 00. causing a piston |21 therein to move and open the bleeder valve |00 to relieve air pressure from the tank 98 through the pipe I0I.4 To relieve the pressure in the cylinder |26 after the valve |01 has closed, the cylinder |26 is connected by a bleed passage |28 to the return pipe 03.

Miscellaneous features The manual valve 01 previously referred to contains a piston 01a which is normally biased by a spring 01h to connect the line 5B to the check valve 08 for replenishing the fluid supply in the counterbalance cylinder I3 under the control of the relief valve 62 as previously described. However, by manipulating a lever 51e the valve 'piston 01a can be shifted and held against the force of the spring 51h, to connect the pipe 68 to a pipe |40 leading to the lower end of the ram I0. This. is used when it is desired to lift the ram under manual control, as when testing or making adjustments.

A normally'closed valve I4| connects the pipe |40 to the return pipe 83,`and by opening this valve uld can be released from the lower end of the ram to controllably move the ram piston |0a downwardly. l

Although for the purpose of explaining the invention, a particular embodiment thereof has been shown and described, obvious modifications will occur to a person skilled in the art, and we do not desire to be limited to the exactdetails shown and described.

We claim:

l. In a hydraulic pumping jack for reciprocating the sucker rod of an in-the-well pump: a hydraulic ram adapted to be mechanically connected to the sucker rod for lifting it in response to delivery of pressure fluid to the ram and lowering itin response to release of pressure fluid from the ram; a pump having inlet and outlet ports; a fluid supply line; a ram line for fluid flow to and from said ram; a main valve for controlling fluid flow between said lines and said pump and containing a shiftable valve element movable between first and second end positions through a neutral position, said valve having ports and passages controlled by said shiftable element for connecting the pump inlet port to said supply line and the pump outlet port to said ram line in said first position, blocking said ram line in said neutral position, and connecting said pump inlet port to said ram line and said pump outlet port to said supply line in said second position; restoring means constantly urging said valve element toward neutral position; hydraulic motor means having first and second ports for shifting said valve element into its two respective end positions; a source of pressure fluid; a pilot valve operable between two positions for connecting said first motor port tosaid pressure fluid source and the said second motor port to exhaust in one position and viceversa in the other positions: means restricting the rate of flow of said pressure fluid to said pilot valve to a value such that the speed at which said motor means tends to shift said valve element is less than the speed at which the element is shifted into neutral position by said restoring means; and over-running drive means mechanically coupling said motor means to said valve element whereby during movement of said motor means by pressure fluid applied thereto the motor means is capable of driving said valve element in one direction but the valve element ismovable in the'same direction into neutral position by said restoring means at a faster rate than said motor means drives it.

2. A hydraulic pumping jack according to claim 1 in which said shiftable valve element comprises a slide valve, said restoring means comprises a slide valve centering spring, and s ald motor means comprises a stationary cylinder aligned with said slide valve and a piston in said cylinder adapted to abut against said slide valve and drive it inonedirection.

3. In a hydraulic pumping jack for reciprocating the sucker rod of an in-the-well pump: a hydraulic ram adapted to be mechanically connected to the sucker rod for lifting it in response to delivery of pressure uid to the ram and lowering it in response to release of pressure uid from the ram; a pump having inlet and outlet ports; a uid supply line; aram line for fluid iiow to and from said ram; a main valve for controlling iiuid flow betweensaid lines and said pump and containing a shiftable valve element movable between rst and second positions through a neutral position said valve having ports and passages controlled by said valve element for connecting the pump inlet port to said supply linel and the pump outlet port to said ram line in said first position. blocking said ram line in saidneutral position, kand connecting said pump inlet port to said ram line and said pump outlet port to said supply line in said second position; restoring means constantly urging said valve element toward neutral position; said main valve including hydraulic motor means having iirstgand second ports for shifting said valve element into its two respectiveend positions; a source of pressure fluid; a pilot valve operable between two positions for connecting said first motor port to said pressure uid source and said second motor port to exhaust in one position. and vice versa in the other position: an auxiliary valve interposed in the fluid lines leading to said pilot valve and having an on position in which it completes connections from said pressure source and said motor means to said pilot valve and an off position in which it blocks ilow of pressure iluid to and connects said motor means to exhaust: and means for manually actuating said auxiliary valve between on and off positions.

4. A hydraulic jack according to claim 3 including a counterbalance means connected to said uid supply line for supplying pressure iluid thereto; auxiliary Ahydraulic motor means responsive to pressure fluid for moving said auxiliary valve from on position into olf position; and means responsive to depletion of the pressure uid in said counterbalance means below a predetermined limit for applying pressure fluid to said auxiliary hydraulic motor.

5. A hydraulic pumping jack according to claim 4 including a yieldable spring link coupling said auxiliary valve to said manual actuating means whereby said auxiliary motor can override said manual actuating means to shift said auxiliary valve into "off position while the manual actuating means is in on position.

- 6. In a hydraulic pumping jack for reciprocating the sucker rod of an in-the-well pump: a hydraulic ram adapted to be mechanically-'connected to the sucker rod for lifting it in response to delivery of pressure fluid to the ram and lowering it in response to release of pressure fluid from the ram: a pump having inlet and outlet ports; a counterbalance cylinder having a piston therein defining with one end of said cylinder an expansibie and contractable counterbalance chamber and means urging said piston to maintain pressure in said chamber; a ram line 'for fluid ow to and from said ram; a main valve for alternately connecting said pump to deliver fluid from said chamber to said ram and from said ram to said chamber, to reciprocate the 14 l sucker rod; a source oi' replenish fluid under pressure; a replenish valve and actuating means therefor projecting into said one end of said cylinder adapted to be contacted and moved by said piston in response toh movement of the piston toward said one end past a predetermined limit position, for moving said replenish control valve out of normal position; and means for delivering fluid from said replenish fluid source to said chamber in response to said movement of said replenish valve out of normal position.

7. A hydraulic pumping jack according to claim 6 including means for returning said replenish valve to normal position at a predetermined slow speed following movement of said piston away from said actuating means. y

8. A pumping jack according to claim 'I in which said replenish valve and actuating means comprises a valve cylinder in said one end of said counterbalancev cylinder, a valve piston sealing in said valve cylinder and extending therefrom into said Ycounterbalance cylinder, a spring urging said valve vpiston into normal position, a passage connecting the outer end of said valve cylinder to said counterbalance cylinder. check valve means permitting free flow through said passage from said valve cylinder to said counterbalance cylinder, and means permitting restricted flow through said passage from said counterbalance cylinder to said valve cylinder.

9. A pumping jack according to claim 6 including pressure-actuated means for moving said main valve into neutral position, land means responsivev to movement of said replenish valve away from neutral positionr beyond the position for delivering fluid from said replenish uid source to said chamber for delivering pressure fluid to said pressure-actuated means to actuate the latter and move said main valve into neutral position.

10. A pumping jack according to claim`6 in which: said source of replenish fluid comprises a continuously running replenish pump and duct means including a check valve connecting the output of said replenish-pump to said counterbalance chamber; a pressure Vrelief valve connecting said replenish pump-output to exhaustl and having a pilot port. said relief valve `opening in response to unimpeded iiow from said pilot port to unload said pump and closing in response to stoppage of flow from said pilot port; said replenish valve having a first port connected to said pilot port, a second port connected to exhaust, and means for interconnecting said first and second ports in said normal position of said replenish valve and breaking connection between said rst and second ports in response to movementl of said replenish valve out of normal position.

11. A pumping jack according to claim 10 in which said replenish valve comprises a valve cyly inder and a valve piston reciprocable therein Aby excess travel of said counter balance piston away from a normal position to the extent of said excess travel, said valve cylinder having progressively longitudinally spaced rst, second, third, and fourth ports and said valve piston having a recess interconnecting said first, second and third ports in normal position, interconnecting said second and third ports when slightly displaced from normal position, and interconnecting said third and fourth ports in response to further displacement from normal position; pressureactuated means for moving said main valve into neutral position connected to said third port 'and a source of pressure fluid connected to said fourth ing the sucker rod oi' an in-the-well pump: a hydraulic ram. adapted to be mechanically connected to the sucker rod for lifting it in response to delivery of pressure fluid to the ram and lowering it in response to release of pressure fluid from the ram; a pump having inlet and outlet ports; a counter balance cylinder having a piston therein defining with one end of said cylinder an expansible and contractable counter balance chamber and means urging said piston to maintain pressure in said chamber; a ram line for fluid flow to and fromy said ram; a main valve for alternately connecting said pump to deliver fluid from said chamber to said ram and from said ram to said chamber, to reciprocate the sucker rod; and means contacted by said counter balance piston in response to movement thereof a predetermined distance from said one end of said counter balance cylinder for connecting said pump toA exhaust in response to said contact.

13. In a hydraulic pumping jack for reciprocating the sucker rod of an in-the-well pump; a hydraulic ram adapted to be mechanically connected to the sucker rod for lifting it in response to delivery of pressure fluid to the ram and lowering it in response to release of pressure uid from the ram; a counterbalance chamber containing iluid and gas unedr pressure; valve and conduit means for alternately connecting said pump to deliver fluid from said ram to said counterbalance chamber and vice versa. to reciprocate said ram through a predetermined stroke; a source of replenish gas for said counterbalance chamber; a container having a movable barrier therein dividing it into two variable volume compartments, and means defining two restrictive passages connecting said compartments to said ram andv said counterbalance 4chamber respectively, the flow impedances of said restricted passages having a predetermined ratio to each other and being of such sizes relative to the size of said containerfand the mean pressure developed by said pumpthat the normal stroke of said barrier is less than the free path of travel thereof; a first normally closed valve for connecting said source of replenish gas to said counterbalance chamber; a second normally closed valve for exhausting gas from said counterbalance chamber; first actuating means operable -by said barrier in response to ,overtravel thereof into the compartment connected to said counterbalance chamber for opening said nrst valve; and second actuating means operabieby said barrier in response to overtravel thereof into the compartment connected to said ram for opening said second valve.

14. A pumping jack according to claim 13 including a bypass passage in shunt to eachvof said restricted passages and a check valve in each bypass passage permitting free flow therethrough into the associated compartment while preventing reverse flow.

15; In a hydraulic pumping jack for reciprocating the -sucker rod of an in-the-well pump: a hydraulic ram adapted to be mechanically connected to the sucker rod for lifting it in response to delivery of pressure fluid to the ram and lowering itin response to release of pressure fluid from the ram; a counterbalance chamber containing fluid and ,gas under pressure; valve and conduit means for alternately connecting said pump to deliver fluid from said ram to said counter-balance chamber and vice versa, to reciprocate said ram through a predetermined stroke; a container having a movable barrier therein dividing it into two variable volume compartments, and means dening two restricted passages connecting said two compartments to said ram and to said counterbalance chamber respectively, the now lmpedances of said restricted passages having a predetermined ratio to each other and being of such sizes relative to the size of said container and the mean pressure developed by said pump that the normal stroke of said barrier is less than the free path of travel thereof; a normally closed valve for varying the quantity of gas in said counterbalance chamber, and actuating means operable by said barrier in responsevto overtravel thereof into one of said compartments for opening said normally closed valve.

FREDERICK W. SCHNECK. ROBERT M. McNEILL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,596,145` Black Aug. 17, 1926 2,299,686- Ernst Oct. 20, 1942 2,299,692 Goehring Oct. 20, 1942 2,555,427 Trautman June 5, 1951

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