US2247238A - Hydropneumatic pumping system - Google Patents

Description

June 24, 1941. D. Jol-NSTQN IIYDROPNEUMATIC -PUMPING SYSTEM 6 Sheets-Sheet l Filed April 17, 1939 III DOUGLA s Jan/sro HrroQA/EK D. JOHNSTON HYDROPNEUMATIC PUMPING SYSTEM' June 24, 1941.

Filed April 17, 1959 e sheets-sheet 2 June 24, E941. D. JOHNSTON HYDROPNEUMATIC PUMPING SYSTEM Filed Aprill', 1939 6 Sheets-Sheet 5 June 24, E941; D. JOHNSTON HYDROPNEMATIC PUMPING' SYSTEM Filed April 17, 1939 6 Sheets-Sheet .5

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D. .JOHNSTON HYDROPNEUMATIC PUMPING SYS TEM Filed April 17, 1939 6 Sheets-Sheet 6 Paienteei .lune Zi, ld-l :man

HYDRQFNEUMATIC PUMPENG SYSTEM Bougie-s Johnston, Shelbyville, Ill., assigner to Leslie R. Stallman, Gentry lL. Tallrnan, Emma S. 'liallman, Shelbyville, lll.

and elesse L. Tallinan,

all of l Claim.

'Ilie general object of this invention is to provide a novel hydro-pneumatic pumping system for use, more particularly in pumping oil from wells, which shall allord a smooth-working, high speed and highly eicient pumpmg unit, and which shall combine the economy and efciency cf the purely hydraulic system with the smoothness and quietness of the purely pneumatic system.

In the embodiment of the invention herein shown and described, I utilize as the main pump-- ing element the hydraulic motor described and ilustrated in Patent No. 2,128,948, granted to me August 23, 1938. The motor as illustrated in said patent was embodied in the form of a tramper for use in packing cotton, and hence the power stroke was downward. In the present, as the motor must exert a lifting action, the power stroke is upward; hence, in its embodiment in a pumping unit, the hydraulic motor of the patent referred to is reversed in position from that shown in the patent, or turned upside down. Otherwise, the motor is identical in construction and operation, so far as the hydraulic feature is concerned, with that shown in my patent.

An important feature of the present invention resides in the fact that I utilize air under pressure to co-operate with the pressure fluid, or oil, in such manner as to balance the reciprocating action of the motor in both directions.

It will be realized that in the case of a well from cne thousand to several thousand feet in depth, the weight of the pumping rod required is very great, and in the downward stroke would move the working cylinder of the motor downward with such rapidity and force as to produce a severe shock, and possible wreckage of the motor, if means were not provided for cushioning such downward movement.

On the other hand, most of the shock on a hydraulic pumping system occurs ai-,the extreme end of the downward travel, just as the hydraulic motor reverses and starts upward, lifting the weight of the pump rod and the iiuid; and there would be liability of a severe jerking action if the upward movement oi the cylinder were not also cushioned.

To provide for this cushioning action, I so arrange the admission to the motor of compressed air with the oil that at all times the air will be present in the System te balance the action oi the working cylinder and maintain the entire body of working iiuid under pressure.

It is a further feature of the invention to provide means, preferably in the form of a balancing tank, connected at one side with the discharge from the motor and at the other side with the suction side of the hydraulic pump whereby, on the downward stroke of the working cylinder of the hydraulic motor, the discharge from the motor is forced into the balancing tank by the weight of the pump rod. This acts to compress the air in said tank, which thus stores the energy made available by the weight of the pump rod when lowering the same. On the upward stroke of the working cylinder, this high pressure air forces the oil into the suction pipe of the hydraulic pump, thereby lessening the load of the pump and preventing loss of energy in the system, with the result that I secure very high efficiency in operation.

The disadvantages of a purely pneumatic system are high iirst cost of heavy, cumbersome equipment, and extremely poor efficiency due to heating losses in compression. On the other hand, the disadvantages oi a hydraulic system are that the fluid is non-compressible and therefore causes hammer and shock at medium and high speeds.

By combining the two systems in a single unit in accordance with the principle of my invention, I obtain all the advantages of both systems and eliminate the disadvantages of each. That is tosay, by using a hydraulic system in combination with a small and inexpensive air compressor, enough air is injected into the hydraulic system to absorb shocks and provide for smooth, quiet operation. The quantity of air injected into the system is so small that the compressor losses have a negligible eiect upon the efficiency of the system.

In pumping oil wells, it is necessary to change the length of the stroke of the pump rod in accordance with the height of the oil in the well, in order that the valve head on the lower end of the rod shall not engage and pound the oil in its downward stroke, which as known, produces very undesirable results. In pumping systems now employed, in which the pump rod is generally reciprocated by a walking-beam, this necessitates a laborious operation and expenditure of considerable time, owing to the weight and size of the equipment.

It is one of the principal objects of my inventic-n to provide simple means for changing the stroke of the working cylinder of the hydraulic motor, which comprises adjusting mechanism located on top of the unit capable of being readily turned in one direction or the other to determine the movement of the motor sleeve which controis the stroke of the cylinder, and which op` eration requires only a few minutes of time.

Other features of the invention, and various novel combinations of parts involved in my improved pumping system, will be set forth in the course of the description of the invention to follow.

In 4the accompanying drawings:

Figure 1 is a broken elevation View of the entire pumping system:

Figure 2 is a sectional plan view on the line 2 2 of Figure 1;

Figure 3 is a broken, elevational View on an enlarged scale, sectioned on the line 3-3 oi Figure 1;

Figure 4 is a vertical sectional view broken away, and greatly enlarged, of the stroke changing mechanism, the housing of which is mounted on, and extends a considerable distance above the top of the derrick, as shown in Figure l;

Figure 5 is an enlarged sectional plan view on the line 5-5 of Figure 1;

Figure 6 is a cross-section, fur-ther enlarged, on the line 6--6 of Figure 4, and viewed upwardly, as indicated by the arrows;

Figure 7 is a sectional plan View, further enlarged, on the line 'I-'I of Figure 4.

Figure 8 is a longitudinal sectional view on an enlarged scale taken on the line 8--8 of Figure 11 through the piston and sleeve, the latter being in its lowermost position, and showing a portion of the working cylinder and of `the hollow piston rod:

Figure 9 is a cross sectional view taken on the line 9--3 of Figure 8, and viewed in the direction of arrows;

Figure 10 is a view similar to Figure 8 but -taken on the line Ill- III of Figure 11 and viewed in the direction of the arrows;

Figure 11 is a cross sectional view taken on the line II-I I of Figure 10 and Viewed in the direction of the arrows;

Figure 12 is a central Vertical sectional view on the same scale as Figure 8, taken on the line IZ-IZ of Figure 9 and viewed in the direction of the arrows;

Figure 13 is a cross sectional view taken on the line I2-I2 of Figure 12 and Viewed in the direction of the arrows;

Figures 14, 15 and 16 are views corresponding respectively, lto Figures 8, l0 and l2, but showing in each view the sleeve in its uppermost position;

Figure 17 is a cross sectional view taken on the line I'I-I'I of Figure 14 and Viewed in the direction of the arrows; and

Figure 18 is a vertical sectional view on an enlarged scale taken on the line IB--I of Figure 3 and viewed in the direction of the arrows.

Referring now particularly to Figures 1, 3 and 5 of the drawings, the numeral I indicates a plat- 4form secured on the upper ends of uprights 2, the

lower ends of which are mounted on runners 3, these parts constituting a portable derrick of considerable height, and on which the hydraulic motor of the pumping system is mounted. The numeral 4 indicates the working cylinder of the hydraulic motor, on the lower end of which is screwed a flange 5 through openings in which extend lifting rods 6 having at their upper ends heads l by means of which they are sup-ported in thev flange 5. Below the ilange 5 there is secured on the lower end of the working cylinder a stuing ibex having a gland 9, which works over the stationary hollow piston rod IQ.. The

piston rod has secured on its lower end a circular plate II which is secured to and supported on an intermediate frame consisting of crossbars I2 connected at their ends to the uprights 2 and having secured between them I-beams I3. The numeral I4 indicates a pump rod, which is supported from and xedly associated with the lower end of the lifting rod S, in the following manner:

The numerals I5 indicate, respectively, two plates to each of which is welded on its inner side a jaw I6, which jaws are clamped about the upper end of the pumping rod by means of bolts I. The plates I5 are carried by a cross-pin I8, (Figure 3) which is supported in a saddle consisting of two beam-plates I9, between which are welded two plates 20 which are drilled for the lifting rods 6 to slide through. The lower ends of the lifting rods are screw threaded to receive nuts ZI, and between washers mounted on these nuts and the saddle plates 25, are interposed coil springs 22. I'hese springs afford a yieldable mounting for the pump rod support described and tend to eliminate the transmission of any shock or jerk to the pumping rod I4, which will sometimes cause fractures and breakage. However, while desirable, these springs are not essential.

The pump rod I4 works through a stuing box 23 mounted on the end of a short pipe section 24 which is, in eiect, a part of the stuihng box, and is connected to the upper end of a T coupling 25, in the lower end of which is screwed the upper end of the oil well production tube 26. Screwed into the side of the T coupling 25 is the production discharge pipe 2I, which conveys the pumped oil to a storage tank or pipe line. The numeral 28 indicates the casing, on which is mounted the usual casing head 29, on which is mounted, in turn, the support 30 for the tubing 26. Referring to the upper portion of Fig. 1, and rto Fig. 4, the cylinder 4 has welded on its upper end a flange 3| to the underside of which is welded the upper end of a guide key 32, which passes through a guide casting 33 (Fig. 2) and at its lower end is welded to a block 34, in turn welded to the lower end of cylinder 4. The purpose of the key 32 is to prevent the cylinder 4 from turning so that the lifting rods 6 will not rub against the I-beam supports.

Mounted on the upper end of the cylinder 4 of the hydraulic motor is the stroke changing device, which embodies a short pipe section 35 having welded on its lower end a flange 36 which is bolted at 3'I .to the flange 3l on the upper end of the cylinder 4. The upper end of the pipe 35 is connected to a reducing coupling 38 which at its upper end is connected to the lower end of a pipe 39 of considerable elevation. On the upper end of the pipe 39 is mounted a stuiiing 'box 4@ through which projects a rod 4I having mounted on its upper end a crank handle 42. By turning the crank handle the stroke adjuster, of whichvthe pipe 35, coupling 38 and pipe 39 form the housing, may be raised or lowered. This housing for the stroke adjuster also provides space for an air chamber constituting one element in the pneumatic means for cushioning the operation of the hydraulic motor.

A description in detail of the stroke adjuster will be deferred until after a .description of the hydraulic motor, as its purpose and operation may then be more clearly understood.

The pneumatic system comprises a prime mover, preferably in the form of a gasoline or electric motor 43, the shaft 44 of which is connected by coupling #l5 to the shaft i6 of a hydraulic pump M of any preferred construction. The shaft lili is provided with a pulley itl which by means of a belt i9 drives a pulley iii on the shaft of an air compressor 5i of any preferred 'o1' conventional type. Leading from the hydraulic pump is a discharge pipe 52 which is connected with an inlet 53 located near the lower end of hollow piston rod il?. As will be later described, a discharge pipe extends from the piston of the motor through the plate or flan-ge il, welded on the lower end of hollow piston rod lil and this pipe is connected by coupling 5 to a pipe 55 the other end of which communicates with a tank 56 toward the lower end thereof. This tank is of considerable height as compared with its diameter, and at its upper end is provided with an automatic spring-actuated release valve 5l'.

Near its lower end tank 56 communicates through a pipe 5i! with the suction side of the hydraulic pump fil. As will later appear, oil and air discharged from the hydraulic motor is discharged from the pipe fifi, into tank 556i, the air separating from the oil and passing to the upper portion of the tank, or into the air space indicated by 59, and the oil collects in the bottom. of the tank, or in the oil space indicated by Se. The air in space 59 is of course under pressure, and the valve 5l operates to permit the escape of excess air from the tank and thus maintains a balancing pressure of a certain deiinite, predetermined value.

This tank will be referred to hereafter as a balancing tank.

Leading from the air compressor 5i is a pipe 6! which., through a T-coupling @2 and a pipe section d3 connected thereto, communicates with an air cushion chamber Sli. The pipe 52 leading from the hydraulic pump is in two parts connected by a T-coupling d5, and a short pipe 65 is connected at opposite ends with this T-coupling 552. Chamber Eli always contains a relatively large amount of compressed air supplied from the air compressor.

In addition to the small quantity of cushioning air injected into the hydraulic uid line on the high pressure side 52 of the pump, of which compressed air, as stated, a relatively large volume is maintained in the cushioning chamber Sd,

the chamber 39, provided on top of the hydraulic motor also holds a large volume of air under pressure, and this chamber is kept filled by reason of the fact that in the hydraulic motor, as well as in the chamber (is, the air separates out of the oil to keep this chamber filled. At the beginning of the upward stroke, the air in chamber it@ is compressed by the driving uid and therefore acts as a further aid in providing a slow, smooth start. Even though the air compressor should, for any reason, be out of commission for several hours, the air chambers Se and iii would hold the air long enough to provide for a smooth operation of the motor.

From the foregoing it will be readily seen that the entire fluid system is kept under pressure, which is regulated by the relief valve 5'! in the top of the balancing tank. The pressure in this balancing tank. is maintained against the discharge line 55 from the hydraulic motor and this pressure is kept high enough to balance the weight of the pump .rod ifi in order, as stated, to prevent a sudden drop of the working cylinder of the hydraulic motor, causing slamming and possible breakage. Since the compressor is constantly feeding air into the system, the relief valve 5l is constantly discharging air therefrom, and thus maintains the air in tank 5b at the exact pressure required, regardless of the fact that the temperature changes affect the density of the air.

I will now describe the hydraulic motor and its operations, in order that the co-operation therewith of the pneumatic arrangement, and the manner of changing the stroke of the piston, to be later described, may be better understood.

At its upper end the hollow piston rod lil, previously referred to, is secured to, or formed integral with, the lower end of a stationary piston 5l. Slidably mounted on this piston is a sleeve ed having a closed upperL end 69. Piston rings 'lil are interposed at intervals between piston and sleeve 68. At its lower end the piston rod lil is welded, as indicated at il (Fig. 18) to the circular plate l i previously referred to.

The working cylinder i of the motor is mounted to slide up and down on the piston rod lli, and likewise has slidable and sealing Contact with the sleeve S8. To this end, piston rings il?. are interposed between the working cylinder and the sleeve. The upper end of the working cylinder has welded thereon at i3 (Fig. 4) the flange Si previously referred to. To prevent leakage between the working cylinder f3 and piston rod iii, there is provided on the lower end of the cylinder a packing gland 8 which is screwed on to the lower end of the cylinder and affords an interior shoulder 'E5 surrounding the cylinder l@ and slidably engaging the same. At its lower end the stuiiing box lli is closed in the usual manner by a gland 9 secured on it by bolts li, between which gland and the shoulder l5 is interposed pack.- ing l.

Oil under pressure is admitted into the hollow piston rod iii through the inlet 53 previously referred to, whence it passes upward through the inside of the piston rod. The oil discharges through a discharge pipe 'i9 (Figs. 3, l0, i2, 14, 15, 16 and 18), which extends upward through piston rod ib to the piston el, in the lower end of which it is screwed, as indicated at M. The lower portion of pipe 'i9 passes through the circular plate il (Fig, 18) welded to the lower end of the piston rod, and to prevent leakage of the high pressure oil at this point, a packing gland di is provided, the casing of which is welded on to the underside of plate lli. Slidably mounted on piston 5l below sleeve $8 is a ring 32 (Fig. 14). Screwed ush by shoulder 'l5 of the stuffing box 5 against the bottom of the working cylinder i is a sleeve 83. The sleeve SS acts as a valve to automatically change the flow of oil at each end of the stroke of the working cylinder so as to reverse its direction and keep it going continuously, as fully explained in my prior patent. In the upward movement of the cylinder, sleeve 83 will engage the ring 82, which will in turn engage the bottom of sleeve 58 to move the sleeve upward, the ring 82 merely acting as an auxiliary plunger, in connection with the sleeve 83, this arrangement being provided in order to prevent the necessity of having cylinder El move up so far that the packing it would be cut by the joint between piston rod it and piston 6l. In each upward movement of the cylinder, the sleeve 83 operates to push sleeve 68 up to its extreme uppermost pon sition.

At its extreme uppermost position sleeve t3 will have opened an outlet to the upper inside, or chamber, of the cylinder, which releases the pressure therein, allowing the high pressure oil being pumped into the lower chamber of the cylinder, located below piston lil, to lower said cylinder. As the cylinder reaches itsl lowermost position, the stroke changer, to be later described, will have engaged Sleeve 88 and shifted it back to its extreme lower-most position, in which position it will have closed the outlet to the upper chamber and opened a passage for the high pressure oil to be pumped into the upper chamber, to raise the cylinder. At the same time, this same passage will allow the oil in the lower chamber to also flow into the upper chamber. Hence, the cycle of operation is completed and the cylinder starts up on the next cycle, raising the lifting rods t. rThe arrangement of parts by means of which the foregoing operation of the cylinder is effected by the inlet of pressure oil to the piston, will now be described, referring to Figs. 8 to 18 inclusive of the drawings.

In its lower portion, the piston le is provided with a hollow portion, or chamber 85 (Figs. 8, l0 and l2), the wall of which is provided on` opposite sides with ports 85, 8l, and 88, 89 separated equal distances fr-om each other. The sleeve 68 in the portion thereof occupied by the piston rings 712 divides the cylinder into a lower chamber St and an upper chamber 9|, and the ports 8l, Si! communicate with the lower charnber 9e below the level of the bottom of sleeve 68 when the latter is in its lowermost position as shown by the figures referred to.

The sleeve 68 in its upper portion, that is in the part 63a thereof above the bearing portion containing the piston rings i2, is reduced in diameter to provide an annular space 92 between its wall and the wall of the cylinder li. Toward the upper end of this reduced portion the wall of the sleeve is provided with a port 93, which is located at such distance below the top 69 of the sleeve as to be moved beyond the upper end of the piston Eil when the sleeve is moved to its extreme upper position so as to open communication between the upper chamber Si, and a chamber Se provided between the top 69 of the sleeve :and the upper end of the piston till, when the top of the sleeve is moved upward, or away from the upper end of the piston (Figs. 14 to 16). The piston 8l, above the portion thereof containing the chamber 85 is is cored out to provide an outlet passage 85,

the outlet pipe 79, extending through the chamber 85 at a distance from its wall, being screwed into the piston 6l at the lower end of the outlet passage 95, in a manner to form a continuation of said passage (Figs. 8 and 14). At the top of the outlet passage 95, the wall of said passage and the body of the piston is cut through to provide an enlarged or circumferential port S (Figs. 8, 9, and l2) which, when the sleeve 68 is in its uppermost position (Figs. 14 to 16) registers with a circumferential series of portsI Si formed in the wall of the reduced portion 68a, of sleeve @8 at the bottom end thereof. When the ports 95 and 9'! are in register they establish communication from the upper chamber il! through the annular passage 92 to the outlet passagey 95.

To provide for the passage to the upper chamber Si of the cylinder of pressure oil passing through hollow piston rod i!) to the chamber 85 f the piston, the latter is provided with an inlet passage 98 extending longitudinally through the piston from the top of chamber 85 to near the top of the piston where a port 9G is provided leading from the top of inlet passage 98 to the outer of the cylinder sides of the piston (Figs. 10, 12, 15 and 16). When the sleeve is in its lowermost position as shown by Fig. 12, the port 99 of the piston is in register with the port 93 of the sleeve S8, previously referred to, which permits the pressure oil to pass directly from the chamber through passage 523, ports 98 and 93, and annular passage Q2 to the upper chamber Si of the cylinder.

In order to control the application of the pressure oil effective within the chamber 9@ oi the sleeve, to permit, or prevent, the movement of said sleeve in the upward or downward movement of the cylinder, so that said sleeve may function at the proper stage of said strokes to close or open the ports controlling the application of the pressure oil to the cylinder, the following construction is provided referring to Figs. 8 to 11 and Figs. 14, l5 and 17 of the drawings:

rThe piston i@ is longitudinally cored from its upper end to near its lower end to provide a cylindrical bore itil, (Figs. 9 and 17) in which is slidably mounted a plunger-valve, indicated generally by the numeral mi. This plungervalve comprises, preferably as an integral structure, a plunger-rod 582, having at its upper end a plunger-valve iii; above this valve a reduced portion ist, and at the upper end of the portion i3d a small head-valve 185. The valves H33 and IE5 divide the bore i8@ into a lower valve chamber E88 (Figs. le and 15) and an upper valve chamber i817 (Figs. 8 and 10). Between the valves i533 and |85 the reduced portion lili provides an annular intermediate valve chamber E68. The upper end of bore iill is :closed by a screw plug E85. A small longitudinal bore lill extending through valve m3, from end to end, thereof, serves to afford communication between the intermediate valve chamber i853 and the lower valve chamber iet for a purpose to be presently described. The piston @l is further provided with a cored hole lil (Figs. 11 and 16) extending from its upper side, from the lower end of which ports H2 (Figs. 10, 14 and 15), lead into the intermediate valve chamber leg whereby communication from sleeve chamber Sd through hole lil and ports H2 with the intermediate valve chamber le@ may be established. From the intermediate valve chamber w3 ports H3 (Figs. 8, 9 and 12) commun'cate with the outlet passage 95. Leading from the upper valve chamber Iii? are ports l ill, which extend through the wall of said chamber (Figs. 8 and 14) and which, when the sleeve 58 is in its lowermost position, as shown in Fig. 8, are in communication with ports H5, extending through the wall of the sleeve, whereby communication may be established between the annular space 92 and said ports with the upper valve chamber itl. When the plunger-valve it! has been raised, as hereinafter described, the ports lili and lili will be placed in communication with the intermediate valve chamber 88 and hence with ports lli, which movement of the plunger-valve occurs prior to the upward movement of sleeve @8, so that pressure oil from the upper cylinder chamber 9i may pass through the annular space 32, ports H5, lili, and H2, through bored hole lli to the sleeve chamber .ii-i, thus balancing the pressure on both sides of the sleeve. Hence, no resistance will be offered to the subsequent upward movement of said sleeve.

In order to maintain the plunger-valve ibi in its downward position prior to the time it is moved upward by Contact of sleeve 83 at the lower end of cylinder 4 with the slide-ring 82,

which in turn is adapted to engage plunger-rod |2, the small port H6 is provided, which permits high pressure oil from the inlet passage 93 to enter valve chamber lll, and thus exert downward pressure on the top of the plunger-Valve. (See Figs. and 15.)

The portion of the piston El below the bearing portion thereof provided with the piston rings 'lil is reduced in diameter and on this reduced portion is slidably mounted the ring 62, previously referred to. This ring is fluted on the outside to provide ports ll'i (Figs. 8 and 13) to allow free passage of oil on the upward strolre of the -cylinder from the lower chamber 99 to ports 85 and into the hollow portion, or chamber, 85 of piston (il. Mounted in a circular groove produced in the interior wall of sleeve 68 at its lower end is a stop ring H3 (Fig. 8) which also is adapted to slide upward upon the reduced portion of the piston. This reduced portion provides a. circular shoulder lid, which will serve to limit the upward movement of sleeve E58 when engaged by the stop ring l I8.

In order to cushion the sleeve 58 at the extreme limit of its upward movement, in case the cylinder should be operated without pumping oil, I provide a port |23, best shown in Figs. 12 and 13, which port is relatively wide at its lower end, and tapers to a mere slit at its upper end. This port is provided in the wall of the inlet passage 93 and hence oil may pass through said port to the annular space |2i surrounding the reduced portion of the piston and closed at its lower end by stop ring l i3. As the sleeve 68 is moved upward, the gradually decreasing area of port |26 oiers increasing resistance to the expulsion of oil through said port by stop ring H8, and causes the movement of the sleeve to be slowed down.

The operation of the motor will now be described, rst premising that Figs. 8, 10 and 12 and the sectional views, Figs. 9, 11 and 13, illustrate the position of parts when the cylinder "l, sleeve E8 and plunger-Valve are in their lowermost position; while Figs. 14, 15, 16 and 17 illustrate the position of parts when said elements are in their uppermost position.

Referring now to the i'lrst named iigures oi the drawings, with the ports in the position shown, oil under high pump pressure entering the inlet 53 passes up through the hollow piston rod l@ into piston chamber 85, through inlet passage 93, out of port QQ in piston, through registering port Q3 in sleeve 53, along annular passage B2 between cylinder and said sleeve, and into upper chamber Si of the cylinder. At the same time, oil, under the same pressure, is flowing out of the lower chamber 9i) of the cylinder through ports t6 and 88 into piston chamber 85 and in the same manner as described to the upper chamber QI of the cylinder. Since on the upward stroke the high pressure oil is exerting pressure in both the lower and upper chambers of the cylinder, the force in the upper chamber tending to push the cylinder up and the force in the lower chamber tending to push it down, it will be seen that the net force available for pumping will be equal to the difference between the areas which are filled with oil in the lower and upper chambers. In other words, the force pushing the cylinder up will be equal to the pump pressure times the net area it acts against. The area the pressure acts against upward is the area of the inside of the cylinder, while the area it acts against downward is equal to the same area diminished by the area of the plunger-rod l. Therefore, the net area upward is equal to the area of said piston-rod. It follows that the force the cylinder will exert is equal to the area of the piston-rod times the pressure developed by the pump.

On the upward stroke there `are no `outlets open. This feature of the invention reduces the quantity of oil needed to operate the motor. The amount of oil required to force the cylinder i up is equal to the area of the piston-rod multiplied by the length of the stroke.

The plunger-valve Nil is held in its lower position by high pressure oil passing through the small port H6 to valve chamber lili, from the inlet port 93. At the same time pressure oil passes from the upper chamber 9| of the cylinder through annular space 92 and ports H5, lill to said valve chamber. The intermediate valvechamber Hi8 is in communication with the cored hole il l in the piston through ports l2 and with the outlet 95, through ports H3. Chamber 9d in the upper end of sleeve B8, communicates through cored hole ill in the piston il), and ports H2 with the intermediate valve-chamber li. This communication exists always. In this position, there is no pressure in the upper chamber 94 of sleeve S8. The lower plunger chamber li has zero pressure, since it communicates through port l il) in valve lll with intermediate valve chamber EU8, which is in communication with outlet d5, through ports H3.

While pump pressure acts on the lower end of the plunger-rod |62 in piston cham-ber 95, since the area of this plunger-rod is less than that of valve |93, there will be a net force to hold valve |il3, in its lower position.

As the cylinder G moves upward under pressure of oil in its upper chamber 9i, the rst event occurs when sleeve 33 (Fig. 18) engages ring 82, which in turn engages plunger-rod HB2 to move plunger-valve |0| upward. To facilitate this operation I preferably secure a bar |22 (Figs. 8 and 14) to the lower end of the plunger-rod by means of a .bolt |23. This rod extends clear through the walls of the piston chamber into ring 82 to which it is secured (Fig. 13). The walls of 'chamber 85 are slotted to allow the bar |22 to move down and up, one of these slots .being shown in Fig. 14 and indicated by the numeral |24. Bar |22 will therefore be engaged at its opposite ends by ring B2 as the latter is moved upward yas will be apparent from the inspection of Fig. 13. As the plunger-valve moves up, the valve W3 will cover ports i3 before the ring 32 is moved up far enough to engage sleeve E8 and head valve |85 will first cover and then uncover ports llt to place them in communication with the intermediate valve-chamber i538 and ports H2. At this stage, i. e., with the plunger-valve raised to substantially the position shown in Fig. 14, but with sleeve 68 in the lowered position of Fig. 8, the h1gh pressure oil in upper chamber 9| is in communication with the sleeve chamber 94 by means of annular space 92, ports l5 land it, intermediate valve cha-mber lila, ports H2, and cored hole lli. Therefore, the pressure inside cham-bei' 9d is the same as outside and sleeve S3 will offer no resistance to being pushed up. The ring 82 now engages the lower end of sleeve 63 and pushes the sleeve up moving port 93 beyond Iport @il of inlet passage 93, thereby `closing port 9d and cutting off passage of pressure oil to the upper chamber 9| of the cylinder. The pressure on the upper end of sleeve 68 both inside and out, is now the same as the lower end, and the sleeve is therefore heating and Ionly a slight force is required to move it up, which is only the amount of for-ce required to overcome a small -frictional resistance. Also, except for the small force needed at first to hold up the plunger-valve, as explained later on, the same force is available for pumping as was available at the beginning of the upward stroke, namely, the oil pressure times the area of piston rod il?.

The oil is now flowing only into the lower chamber Q9, and no outlets are open. Therefore, this oil will move sleeve 68 up until port 93 in said sleeve opens chamber Qt, Fig. 14, which affords another means of allowing the oil in `chamber 9i of the cylinder and chamber Se of the sleeve Sii Ato communicate. In this movement of the sleeve, port H5 will be moved beyond port Hi, closing the latter (Figs. 8 and 1li). The

upward movement -of the sleeve t@ just described is permitted by the fact that the cylinder l moves upward simultaneously with the sleeve, ybut at a slower rate, since the cylinder area is larger than the area included in the sleeve annulus, and the cylinder moves up enough only to provide such additional volume as is displaced by the annular volume of the sleeve walls in its upward movement. Thus, as stated, the sleeve is oating, since on its lower end, chamber 85 and ports i Il;

inside lof its upper end, chamber gli; and outside its upper end chamber 9i, all pressures are the same, `and equal to the pump pressure, disregarding la slightly greater pressure in the lower piston chamber 35 due to the frictional resistance offered to movement by the sleeve. The l-atter is now free to move up because there is no uid pressure or mechanical -obstruction holding it down. At this point the sleeve is merely a floating connection between the iiuid in the lower and upperportions 90 and Qi, respectively, of the cyli.

inder. The oil 'pressure in the upper chamber is acting over the entire `area of the inside of the cylinder, while in the lower chamber the same pressure is acting only over the area of the inside of the cylinder, less the area of the piston rod. Therefore, as before, the net force exerted by the cylinder is equal to the pump pressure times the ldiierence between the area in the upper and lower chambers, which area is equal to the area of the Ipiston. rod. If, now, it be :assumed that the sleeve tjdoes not move upward at this point, then the oil being pumped into the lower chamber Se through hollow piston rod li), will immediately increase in pressure and act on the lower annular end of the sleeve, forcing Vthe sleeve up against the oil in the upper chamber 9i ofthe cylinder. This will cause the pressurein this chamber to rise equally (or nearly so) in amount to the rise of the pressure in thevlower chamber. However, the oil in the upper chamber 9i acts upward on the end of cylinder il on an area much larger then the annular area of chamber gil of the lower end of the cylinder. Therefore, the cylinder will have a greater increase in force upward and will travel upward, increasing the volume of the upper chamber 9i, allowing sleeve 68 to move upward. Finally, Iports S'lin sleeve 68 (Fig. 17 )are moved into register with port 95 in piston lil to relieve pressure in chamber Si by providing an outlet through annular passage 92, ports 9V and Bt and outlet passage 95.

At this stage, pressure both inside and outside of'sleeve 68, `including chamber 9| of the cylinder and chamber 9d of the sleeve, has been reduced to thatv in vtank 55, vand the sleeve has reached its uppermost position. The oil pressure in the lower cylinder chamber 9@ will hold sleeve 5S up in this position and force the cylinder to proceed downward, the oil in the upper chamber 9i being discharged.A

At this point, it may be-desirable to explain what holds the sleeve @S in its lowermost position for substantially the duration of the upward stroke of the cylinder, since in both lower charnber 90 and upper chamber el the pressures are equal and the friction of the cylinder tends to pull the sleeve up. This is best explained by assuming that sleeve 68 does rise, closing ports SS and e3, and cutting off the admission of oil into the upper chamber 9i. Now, as pressure oil is still being pumped, the immediate eiect will be a sudden rise of pressure in the lower chamber Sli. This rise in pressure in the lower chamber, when considered alone, will act against the area of sleeve t8, tending to push `it up further` However, this pressure also acts against the bottom area of the lower chamber 96. This will naturally tend to force the cylinder down. The effect of this will raise 'the pressure of the oil in the upper chamber 9i. Of course, it will not raise it nearly as high as the pressure in the lower chamber. Now, chamber 94 of the sleeve has a pressure in it equivalent to that in tank 5S, and as the area is equal to the area of the piston fi'i, the slight increase of oil pressure in the upper chamber @I acts over a large area, unopposed by pressure from the other side. Always to be con- `sidered is the fact that the oil in chamber Si acts against the area of the sleeve as well as that area equal to the piston area. The areas are so proportioned that the pressure increase in the upper chamber, (due to the increase of pressure in the lower chamber acting upon the bottom of the cylinder) tending to push the sleeve down against the entire area of the inside of the cylinder, of which area an amount of area equal to the piston area, has no pressure at all acting on the other side, pushes down on the sleeve with a greater force than the force in the lower chamber pushes up. The result is that the sleeve cannot rise, for as soon as it closes ports 93 and 99 slightly, a rise in pressure pushes it back.

I have heretofore referred to the small force needed at rst to hold the plunger-valve lill up 'as the cylinder approaches the limit of its upward movement. now be given.

As the completion of the upward stroke, the rst event occurs when the plunger-valve closes ports H3, thereby closing the outlet from the chamber gli. This requires a certain amount of force, which will have to be deducted from the force the cylinder will exert for pumping. However, assoon as ports H3 are closed and ports ll begin to open, no force will be required to push the plunger-valve for the remainder of the upward stroke. The reason for this is that as soon as ports H3 are closed and ports Elfi begin to open, the oil pressure in the intermediate valve chamber H38 will be the same as the pressure in the upper valve chamber lill, and through Vthe port I l0 in valve w3 the lower valve chamber ll will also have the same pressure. Since the pressure acting against the bottom of plunger-rod |02 is equal to the same pressure as in valve chambers lii and lill, all pressures will be the same and no force will be required to hold or push up the plunger-valve.

AsY soon as the cylinder starts downward the high-pressure oil communicating fromcored inlet An explanation or this will hole 93 through small port lit to upper valve chamber it? will force the plunger-valve back into its lowermost position, or that shown in Fig. 8.

Since ports I lll and i i are closed at this time, this high pressure oil cannot run out of chamber lill into the annular space @a to the upper chamber si and be wasted to the outlet. This is the reason ports iil and H5 need 'to be closed. Also, when the plunger-valve moves down it provides an additional outlet from upper chamber ill, through the annular space 92, port 93, chamw ber ist, the cored hole iii, ports H2, intermedi-- ate valve-chamber i, and ports H3 to the out let passage However, when the sleeve is shifted downward, ports Il@ and M5 will open before port llt in sleeve t3 closes communication with chamber which is connected to the outlet. Therefore, there will occur a momentary leakage of oil from inlet passage Q8 through port iid to chamber itl, through ports H and M5, annular space s2, port 93 to chamber se, out through the cored hole lll, ports H2, intermedie ate valve chamber lili? and ports M3 to outlet $5. This leakage will only be momentary as the sleeve @t is moving down rapidly at this stage. Also port its is so small that in the time available no appreciable amount of oil can flow through it.

With the plunger-valve in its lowermost position, as described, a means of escape of oil from sleeve chamber iid to outlet i295 is provided. through the cored hole il l, ports H2, intermediate valve chamber Hi8 and ports H3. As the cylinder nears its lowermost position, a circular plate M5 (Fig i) on the lower end of the stroke changer engages sleeve 68 and lowers it. This movement of the sleeve is permitted by reason of the fact that the bottom of the cylinder is of larger area than that of the sleeve, as is obvious from an inspection or the drawings. Accordingly, if the oil acts downward on a larger area oi' the cylinder than it acts upward on the sleeve, the cylin der will lower the sleeve, due allowance having been made for the weight of the cylinder. As the sleeve lowers, it will close outlet ports d@ and @l and port 53 in said sleeve, which allowed upper chamber @i another outlet through annular space d2 into sleeve chamber sii. The plunger-valve is still maintaining an outlet through this chamber, as explained above.

After the sleeve and cylinder have been lowered, in the manner just described, the parts will then be in the position as shown in Fig. 8 and the upward movement of the cylinder under the pressure of oil will be repeated in the manner which has been described.

While, as l have stated, the elements or my hydraulic motor are reversed in position as respects the position of the parts illustrated in my prior patent, the operation of the hydraulic motor is exactly the same in principle; and as the advantages of this particular construction of hydraulic motor are fully set forth in my said patent, I deem it unnecessary to repeat the same,

as said motor enters into the present invention only as an element in a combination embodying pneumatic means for balancing and cushioning the operation of the motor.

The stroke changer, which I have referred to in general terms during the course of the above description, will now be described in detail, referring particularly to Figure a.

The numeral 25 indicates an adjusting screw having welded on its lower end the circular plateI E previously referred to. This adjusting screw turns in a nut l2l' which is held down against the plate 36 by a coil spring 28 located within the pipe section 35 and held down by a tension nut l2@ which is screwed into the upper end of pipe 35. The purpose or" holding down the nut l2'l, with a spring is to provide a means to reduce shook when plate l25 on the adjusting screw engages the upper end or sleeve tu. The plate t@ and tension nut B29 are bored to permit the adjusting screw to slide through them. To prevent nut l2? from turning, it is provided with two slots itil (Fig. '7) which work over keys isi, which are welded inside the pipe 35 near the bottom thereof.

The shaft il on the upper end oi which a crank #i2 is secured has welded on its lower end a plate E32, which in turn is welded into the upper end oi a pipe section B33. Into the bottom of pipe there are welded inside two short keys i3d, (Fig. 6) which work in keyways ist milled in opposite sides or" adjusting screw E26.

This means of turning the screw is` provided in order to prevent leakage, such as would occur if the screw was extended through the sturing box mounted on the upper end of pipe 39, which may briefly be described as comprising a centrally apertured plug 35 welded in the top of pipe 3Q and through which the shaft lil extends, welded on the upper side of which plug is a stuing box I3?, inclosing packing ist, and a gland i3@ and closed by the cap lill, previously referred to.

The numeral Mii indicates a pin secured in the upper end of the adjusting screw to serve as a stop to prevent the adjusting screw from being screwed clear out of pipe ist, the engagement of the opposite ends of the pin with the top of tension nut H29, preventing this. The plate 355 Secured on top of cylinder i is provided with apertures lill and the nut i2? is provided with similar apertures iii?, the purpose of these apertures being to permit air forced into the cylinder Il with the pressure oil to pass, upward through said apertures into the stroke changer housing tents-tt, which thus forms a pressure chamber, the compressed air therein acting to cushion the upward stroke of the cylinder. That is to say, each time high pressure oil is admitted suddenly into the chamber Si of cylinder li, instead of having this chamber filled with a nonoompressable fluid, which would result in starting with a shock, the air in the upper part of said chamber, and the air in the stroke chamber housing, will compress like a spring under the pressure of the oil and provide resiliency, which will result in a slow, smooth, easy start. The operation of my improved hydro-pneumatic pumping system, will now be described.

Referring to Figs. 8, 10, 12 and 18, the sleeve t8 is shown in position for causing the upward stroke of the cylinder. Pressure oil is flowing in through inlet 5?, through the hollow piston rod l0, piston chamber 35, through inlet passage Q8 of the piston port 99 and sleeve port 93, which ports are in register. The oil iiowing as described, contains bubbles of air due to the fact that the air compressor 5l is continuously pumping a small supply of air through air compresser pipe Gl and air cushion pipe Si? into the pressure oil conduit 52. These air bubbles are compressible and provide the means of preventing cil hammer in the pipe lines. IThe air Ibubbles passing through the bottom of the cushioning chamber til, being lighter than oil, rise up in the chamber to keep it filled with air at all times. Any momentary resistance, such as when sleeve 53 shifts, reversing the direction of the movement of cylinder 4, which causes a sudden increase of pressure against the oil flowing in pipe 52, Will not cause hammer or shock, since the oil from pump fil will momentarily flow into chamber E@ and as stated above, the air bubbles in pipe 52 will compress. The above action will not only prevent any shock or hammer against the pump pipes, but it will at the same time provide for a smoother stopping and starting of the hydraulic motor.

After the cylinder il has started up or down, the higher pressures of the oil necessary to accelerate the machine from a stop to full speed having decreased, the air in the cushioning chamber d' will expand, driving out the oil pumped in under the higher pressure, hence the cushioning chamber 6d Will be ready again to receive a sudden supply of cil, due to suddenly increased pressure, caused by stopping and starting the cylinder at the end of the sroke.

The pressure conduit 52 does not contain a large volume of air, since the compressor 5i is very Small. Now if the conduit 52 were very long,

say several hundred feet, vand the hydraulic motor were operating at such a speed that the oil velocity in pipe 5l were high, then the air contained in pipe 52 would not be sumcient to cushion the hydraulic motor for smooth starting and stopping, since the momentum of the high velocity oil in the pipe 52 would be suiiciently great to build up an extremely high pressure, if a resistance were momentarily built up against the inlet to the hydraulic motor, such as is caused by suddenly stopping and starting. The air cushion t@ next to the pump, will be of diminishing benefit the longer the pipe 52 and the higher the velocity, since, as mentioned above, a long oil column moving at high speed cannot be stopped suddenly Without considern able shock. Therefore, it will be seen that it is necessary to provide an additional air cushion at, or preferably within, the hydraulic motor. The upper chamber 9i of the cylinder and the chamber of the stroke changer provided by the connected pipe sections and 3Q are utilized to provide such an additional air cushion.

As described above, the oil containing air bubbles is fiowinginto the upper chamber Sl of the cylinder. The air bubbles rise to the surface around and above the plate, or foot, IE5 of the Stroke changer which, of course, is of less diameter than the interior of the cylinder, keeping the Space H213 of the cylinder above the foot 25, and the stroke changer chamber iilled with air under pressure, this air passing through the apertures lill in the flange or plate 35 and the apertures M2 in nut |27, these apertures affords ing constant communication between the inside of the stroke changer and the 'space 53 of the cylinder.

The instant the oil begins iiowing out of port 33 of sleeve 68 through annular space S2 to the upper chamber 9|, either the cylinder must start with a certain shock or else there must be something to cushion the action of the cylinder. This result I attain by means of the air in the space litt which gives or compresses, affording a slow shockless acceleration. After the cylinder reaches a constant speed the pressure is reduced to normal operating pressure, and the air in space M3 and in the strokeV changer chamber expands to the original volume. When the cylinder reaches'the upper end of-the stroke, the shifter 75 sleeve 83 engages plunger ring 2 shifting plunger rod l t2, and the valve sleeve 68, moving the parts into position shown by Figures 14, l5 and 16. Here the pressure oil is owing into the lower chamber 9@ of the cylinder, beginning the downward stroke. The oil in the upper chamber 9| of the cylinder iiows out through annular space S2, the ports @l of sleeve 68 and 98 of the piston, as these ports are in register on the downward stroke. The air volume in the space E43 will gradually build up, driving the oil level M4 downwardly until the air begins to discharge through annular space 92, and ports 97 and 95 as mentioned above. At this level the air volume will be maintained constant. Turning the stroke .changer foot E25 up will decrease the air volume,

while turning it down will increase the air volume. However, this variation of air volume is not detrimental to the action of the machine, since turning the stroke changer down, increasing the air volume, shortens the stroke; and with a constant speed hydraulic pump Ll'l, this increases the number of strokes per minute in proportion to the amount the stroke is shortened. With a greater number of strokes per minute, a larger air volume is more desirable than with fewer strokes per minute, since the reversals and accelerations are more frequent. On the upward stroke, the hydraulic motor does not discharge any oil, the oil in the pipe i9 not being in motion. However, at the beginning of the downward stroke the oil in the upper chamber 9i of the cylinder begins to discharge through annular space $2, and ports 96 and 92'. In order to discharge oil, the oil in passage l must either be suddenly accelerated to a high velocity causing shock, or else something must give Again the air in the space H33 and in the stroke changer chamber compresses to allow the oil in passage 'i9 to be accelerated slowly and smoothly. Therefore, it will be seen that at the beginning of both the upward and downward strokes the air in the space U33 and in the stroke changer chamber serves to cushion the action of the machine.

The oil discharging from passage E9 through pipe 55 to tank 55 has to flow against the pressure in said tank, maintained at the desired Value by relief valve 5?. Since on the downward stroke the cylinder is supporting a very heavy load (the weight of the pump rod 5d) the hydraluic motor would drop with disastrous results were it not for the fact that by the pressure in tank 56 the oil discharging from the upper chamber 9i of the cylinder is held under a high enough pressure to insure that the force due to this pressure acting against the top of the cylinder will be sufficient to balance the weight of the cylinder. Therefore, the pump rod is air balanced, and no weights are required to balance the rod load, such as are necessary with the conventional walking-beam type of pump. Also, since the oil owing into the tank 55 on the downward stroke compresses the air to an even higher pressure in the space 59 of said tank, the energy available in lowering the pump rod is stored in compres- -sing this air, and is utilized to help raise the pump rod and the oil lifted on the upward stroke. The reason that the high pressure in the tank 58, helps raise the weight is that by increasing the pressure on the inlet to the pump, the pump differential (difference between suction and discharge pressures) is reduced, thereby putting a lighter load on the pump and making it easier to drive.

While I have described and preferred to employ in connection with the pneumatic system involved in this invention, the hydraulic motor forming the subject of my prior patent aforesaid, it will be understood that so far as the broad idea of my invention is concerned the hydro-pneumatic pumping system herein described and now to be claimed, is not limited to this particular type of hydraulic motor, or to the particular construction herein described of said motor, but that the pneumatic feature of the invention may be combined with other types of hydraulic motors, if any such there be, capable in operation of affording the cushioning action to the reciprocating element of the motor, and the other advantages which I have. herein set forth.

I claim:

A hydro-pneumatic pumping system for oil wells comprising a double-acting hydraulic motor having an inlet for pressure fluid and an outlet for the same, a reciprocable member for operating a pump rod adapted to be actuated by said pressure fluid, a hydraulic pump connected with said inlet for supplying pressure fluid to the motor, a balancing tank connected with said outlet having a space for oil in its lower portion and a space for air in its upper portion, said oil space being connected with the inlet to said hydraulic pump, an air compressor communicating with the connection between said pump and the inlet to said motorl and an air cushioning chamber interposed between said air compressor and said latter connection.

DOUGLAS JOHNSTON.

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