US3094842A

US3094842A - Hydraulic pumping system

Info

Publication number: US3094842A
Application number: US104605A
Authority: US
Inventors: Rufus B Johnston
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-04-21
Filing date: 1961-04-21
Publication date: 1963-06-25
Anticipated expiration: 1980-06-25

Description

June 25, 1963 R. B. JOHNSTON 3,094,842

HYDRAULIC PUMPING SYSTEM Filed April 21, 1961 5 Sheets-Sheet 1 m 7- v r/i' I I W34 22 I J0 fl 24a 3/ /2 N L/ L 1 -/4 1% Q 1 38 /J 25 e I 2/ ll 37 /6 250' I o {I 36 P L P /7 i 63 20 Z6 Z9 28 /l K '7 2.4% J2 A? 34 2.90 /9 o QR I z 2567\ V I 35 E /7 33 P P a 35 /74 23 INV EN TOR.

/5 23a M m ATTORNEYS June 25, 1963 R. B. JOHNSTON 3,094,842

HYDRAULIC PUMPING SYSTEM Filed April 21, 1961 3 Sheets-Sheet 2 :4 22 i l f /3 22A I J 14 15/ 39 A 35 a v 1 P f J 6 0/921 da/znJzari /5 INVENTOR.

ATTORNEY? June 25, 1963 3,094,842

R. B. JOHNSTON HYDRAULIQPUMPING SYSTEM fiufz/J 49. (/0/7/74" fafl IN VEN TOR.

States Unite This invention relates to reciprocable hydraulic pumping systems of the balanced type. More particularly, it relates to improvements in systems of this type wherein the pistons of a pair of motor cylinders are reciprocated by a single power unit and the weight of the rod for one piston is counterbalanced by the weight of the rod for the other piston.

Systems of this type are particularly well suited to the pumping of deep wells or other applications where the rod weight comprises a major factor in the power required to reciprocate the pistons. With the rod weight counterbalanced, the power unit need only lift the weight of the well fluid being pumped, as well as extra loads due to friction and other relatively minor factors which may be ignored; In such systems, the lower sides of the pistons are fluidly connected by a balance line, and the power unit is alternately connected to the upper side of first one and then the other piston so as to reciprocate them in opposite directions within the cylinders. If desired, each rod may be connected to thedown-the-hole pump of a well so that both wells are pumped by the single power unit. On the other hand, the system contemplates that one piston may be counterbalanced by some means other than well fluid.

Previous systems of this type have employed unduly complicated mechanisms for operating a reversing valve in shifting the power fluid from the upper side of one piston to the upper side of the other. Apparently, the presence of power fluid above the pistons has precluded others from attempting to accomplish this shifting of the reversing valve with the ordinary check valve-controlled lines.

Some in this field have used a closed system wherein the power fluid from above one piston discharges into the pump suction. This requires the use of high rate-d pumps, and may even put conventional pumps out of the usable range. Others have suggested a single system for supplying power to the motor pistons as well as for replacing hydraulic fluid lost from the system during its operation. In such an arrangement, the single pump must raise the pressure of the power fluid to above that in the balance line, which is impractical in view of the volume of power fluid required. Also, such systems ordinarily have complex arrangements for dumping an excess of such replenished fluid to maintain the motor pistons properly synchronized.

An object of this invention is to provide a system of the type described in which the shifting of the reversing valve is accomplished with the more conventional and simplified shifting lines.

Another object is to provide a system of this type having a pump with a non-pressurized or atmospheric suction as well as a separate pump for replenishing lost fluid.

A further object is to provide such a system having a simplified arrangement for dumping excess fluid, and, more particularly, one which requires no additional valves.

Still another object is to provide such a system which is easy to start, and especially one which does not require preparation, such as the opening and closing of valves, prior to starting.

Yet another object is to provide a simplified reversing valve and attendant parts for such a system, and more atent O 3,094,842 Patented June 25, 1963 particularly a spool valve for this purpose having conventional outwardly urged sealing rings thereabout.

-In the drawings, wherein like reference characters are used throughout to designate like parts:

FIG. 1 is a diagrammatic illustration of a system constructed in accordance with one embodiment of the invention, and at a stage of its operation wherein the piston in the leftmost or control cylinder is being raised and the piston in the rightmost or slave cylinder lowered;

FIG. 2 is a similar view of the system at a subsequent stage of its operation, and particularly wherein the control piston has reached the upper limit of its reciprocation and the slave piston its lower limit, and during shifting of the reversing valve to a position for reversing the direction of reciprocation of the two pistons;

FIG. 3 is another view similar to FIGS. 1 and 2, but wherein the reversing valve has shifted to cause the control piston to start its downward movement and the slave piston to start its upward movement;

FIG. 4 is a further view similar to FIGS. 1 to 3, but wherein the control piston has reached its lower limit of reciprocation and the slave piston its upper limit, and further wherein the reversing valve has started to shift back to the position of FIG. 1 in order to again reverse the reciprocation of the pistons;

FIG. 5 is still another view similar to FIGS. 1 to 4, but showing the system during the initial stage of the starting of same;

FIG. 6 is a still further view similar to FIG. 5, but showing the system during a subsequent stage of the starting of same, and particularly wherein excess hydraulic fluid is being dumped from the slave cylinder so as to bring the two pistons into proper phase; and

FIG. 7 is an enlarged detail view, partly in section, of the reversing valve and pilot valve therefor shown in each of FIGS. l to 6.

With reference now to the details of the above-described drawings, the system, which is indicated in its entirety by reference character It includes a first cylinder 11 having a piston 12 reciprocable therein and a second cylinder 13 having a piston :14 therein. The cylinder 11 and piston 12 are conventionally termed the control cylinder and piston since the movement of the latter controls shifting of the reversing valve, while the cylinder 13 and piston 14 are normally called the slave cylinder and piston since they act responsive to the others.

A rod 15 is connected to control piston 12 and a rod 16 to slave piston 14, each rod extending through the lower endof its respective cylinder for connection to a load bearing element. As previously indicated, each of such elements may comprise a piston disposed within the cylinder of a down-the-hole pump for raising well fluid therefrom. On the other hand, one of the

rods

15 and 16 may be connected to a counterbalancing element such as a piston disposed within an air cylinder or the like for loading same. In either case, and as will be described hereinafter, the pistons 12' and 14 reciprocate in opposite directions so that the load-bearing element suspended from one is moving downwardly while the other is moving upwardly.

There is a pump 1'] connecting on its suction side with a non-pressurized or atmospheric reservoir 17a of hydraulic fluid and on its discharge side with an inlet 18 to a reversing valve 19. There is a piston 22 shiftable between positions within the reversing valve for delivering pumped power fluid from the inlet to one of the

conduits

20 or 21 connecting such valve with the upper sides of control piston 12 and slave piston 14, respectively. Power fluid from the upper side of the other cylinder piston is at the same time exhausted through outlet 23 from the valve back to the reservoir 17a. Thus, for example,

with the reversing valve piston 22 disposed in the position of FIG. 1, the pumped fluid is directed through conduit 21 to the upper side of slave piston 14 to urge the same downwardly, while hydraulic fluid on the upper side of control piston 12 is returned through conduit 20 to the hydraulic fluid reservoir 17a as such control piston moves upwardly.

More particularly, the lower sides of the

slave pistons

12 and 14 are fluidly connected to one another by a balance line 23a connecting with the lower ends of cylinders 11 and 13. In this manner, and as will be understood from the description to follow, the rod weight upon the piston being raised (control piston 12 in FIG. 1) is counterbalanced by the weight of the rod upon the other piston (slave piston 14 in FIG. 1). Although a perfect balance assumes equal rod weights, among other things, the counterbalancing eflect will be at least partial under any circumstances, thereby resulting in a net power 1 consumption about the same as would occur in the case of equal loadings. That is, even though the power pump 17 will work harder in one-half of the cycle, it will have a correspondingly lighter load during the other half. The shortcoming of this latter arrangement is, of course, that the rated capacity of the power pump will have to be large enough to handle the high side of the cycle.

I have used the terms upper and lower in designating the opposite sides of the

pistons

12 and 14 as this is their normal orientation when the system is used in raising and lowering load bearing elements. Thus, the upper side of each such piston is the side opposite that from which the rod extends, while the lower side thereof is the side from which such rod extends.

In analyzing the forces in the system, it Will be appreciated that the fluid in the balance line 23a and beneath the

pistons

12 and 14 will be at a pressure due to the combined weight of the well fluid or other loading element and the rod on the piston which is being raised. Inasmuch as the rod weight of the piston being raised is counterbalanced, the pressure of the power fluid from pump 17 will be only that necessary to lower the other piston in order to raise the well fluid. The system will also contain fluid communicating with the reservoir 17a and thus at substantially atmospheric pressure, or less than either the pump pressure or the balance line pressure. In the operation of the system, the fluid beneath

pistons

12 and 14 is therefore always at a higher pressure than that above the pistons, the difference depending on Whether the upper side of the particular piston is being subjected to power fluid or is in communication with atmospheric pressure.

Thus, with reference to FIG. 1, power fluid from the pump 17 acting upon the upper end of slave piston 14 is opposed by fluid at substantially atmospheric pressure acting upon the upper side of control piston 12, so that the slave piston moves downwardly as the control piston moves upwardly, the output of the pump 17 being only that necessary to overcome the weight of the fluid being raised by the rod 15. When, however, the

pistons

12 and 14 reach their limits of reciprocation, as shown in FIG. 2, the reversing valve piston shifts, as shown in FIG. 3, so that power fluid from pump 17 is directed to the upper side of the control piston 12 and the upper side of slave piston 14 discharges to the reservoir 17a, whereby the pistons are caused to reverse their reciprocation. When the pistons reach their opposite limits of reciprocation, as shown in FIG. 4, the valve piston 22 is again shifted back to the position of FIG. 11 so as to again direct hydraulic fluid from the pump 17 to the upper end of the slave piston, while discharging fluid from the upper end of the control piston back to the reservoir 17a, this shifting resulting in a further reversal of reciprocation of the cylinder pistons.

In accordance with this invention, I accomplish this automatic shifting of the reversing valve piston 22 by means of conventional valve-controlled

shifting lines

24 and 25 connecting with the control cylinder 11 at spacedapart levels therein with a pilot valve 26 for the reversing valve. I have found this to be possible by taking advantage of the fact that the pressure of the balance line fluid is ordinarily sufliciently greater than that of the pumped power fluid to permit it to be used as a control fluid in actuating both the pilot and reversing valves. More particularly, I have found this necessary pressure diflerential to occur in systems of this type when employed in the pumping of wells or in other applications where the rod weight is an important factor.

Thus, I apply the balance line fluid to one end of the reversing valve piston and to one end of a piston 29 reciprocable in the pilot valve to shift each of them to one position, and then use the valve-controlled

lines

24 and 25 to alternately admit such fluid to and exhaust it from the other ends of the pistons in order to shift them to and from the first-mentioned position. With reference 'now to the details of this means for reversing the piston 22, there is a line 27 common to the shifting

lines

24 and 25 which connects with the body 28 of pilot valve 26 on one side of the piston 29 reciprocable therein. The opposite end of pilot valve piston 29 is connected with an end of reversing valve piston 22 by means of a conduit 30 extending between the pilot valve body 28 and the body 31 of reversing valve 19. A further conduit 32 connects the body of pilot valve 26 with the reversing valve body 31 on the opposite side of reversing valve piston 22.

As is apparent from the drawings, the left-hand ends 22b and 29b of the

pistons

22 and 29, respectively, are

These smaller ends of the pistons are fluidly connected with balance line pressure through a conduit 33 connecting the balance line 24 with the left-hand end of reversing valve body 31. Since the smaller ends of

pistons

22 and 29 are thus at all times subjected to balance line pressure, the

pistons

22 and 29 will be maintained in their rightmost positions, as shown in FIG. 1, as long as their opposite larger ends are subjected to a considerably lesser pressure, as is the case of the power fluid as well as the pressure within the reservoir 17a.

However, when the control piston 12 moves upwardly to the position of FIG. 2, fluid beneath such piston passes through

conduits

24 and 27 to the larger end 29a of pilot valve piston 29 so as to shift it to the left. This shifting connects balance line fluid with the conduit 32 and thus with the larger end 22a of the reversing valve piston, which in turn causes the latter to shift to the left and thereby direct power fluid from the pump 17 to the upper end of the control piston 12 While permitting fluid i on the upper end of the slave piston 14 to return to the 1 reservoir 17a, as shown in FIG. 3. i

This passage of balance line fluid into the pilot valve 26 is controlled by means of an upwardly seating check valve 24a in shifting line 24 as well as an upwardly seating check valve 25a in shifting line 25. That is, the movement of control piston 12 above the shifting line 24 will open valve 24a While the valve 25a remains seated. When, however, the control piston 12 moves downwardly past the connection of shifting line 24 with the control cylinder, as shown in FIG. 3, the balance line fluid will move the check valve 24a upwardly into isieafied position against the lesser pressure of the power Valve 24a will remain seated so as to maintain the balance line fluid upon the right-hand end 29a of pilot valve piston 29 until such time that the control piston 12 moves below the connection of shifting line 25 with the control cylinder, as shown in FIG. 4. At this time, the balance line fluid will unseat the valve member 25a and thus be vented into the control cylinder 11 for exhaustion to the reservoir. When the pressure of the fluid within the pilot valve body 28 on the right-hand end of the piston 29 drops below balance line pressure, the

balance line pressure on the left end of the piston will quicklycause it to shift to the right. This, in turn, will also cause the reversingvalve piston 22 to move to the right by'Vir-tue of the fact that balance line fluid on the right-hand end 22a of piston 22 is connected through conduits32 with the reservoir 17a.

For this latter purpose, there is another conduit 34 which connects intermediate portions of the pilot and reversing valve bodies for communication at all times with the outlet or return line 23 to-the hydraulic fluid reservoir 17a. In the right-hand position of the pilot valve piston 29, the conduit 34 is connected to the conduit 32 so that the pressure of the fluid on the righthand end of reversing valve piston 22 may be vented to atmosphere, as above described. On the other hand, andasdescribed above, the shifting of the pilot valve piston to-the left, as shown in FIG. 2, will connect the conduit 32 with balance line fluid on the left end 29b of such piston.

During operation, there will be some leakage of hydraulic fluid from different parts of the system. In accordance with another novel aspect of the present invention, this fluid is replenished or replaced by means of a separate pump 35 having its suction side connected to the reservoir 17a, similarly to the pump 17, and its discharge side' connected with a conduit 36. This last conduit is, in turn, connected to the conduit 33 between balance line 23a and the reversing valve body 31 adjacent the smaller end 22b of piston 22. This pump 35 operates continuously so as to replenish fluid as needed, and in response to out of phase movement of the

pistons

12 and 14. Its provision separate from and in addition to pump 17 is a considerable improvement over most prior systems wherein a single power unit provides the power. fluid as well as replenishing lost fluid, because it avoids the necessity of employing the high capacity, relatively low' pressure pump 17 at the higher pressure required' in pumping against balance line pressure. That is, the pump 35 may be a low capacity, high pressure pump suitable for this purpose.

Inevitably, the fluid replenished by' pump 35 will be in excess of that lost, so that some means must be provided for dumping the excess fluid in order to keep the reciprocation of

pistons

12 and 14 in phase. This is accomplished, in accordance with another novel aspect of my invention, by means of a line 39' connecting slave cylinder 13 at a level just above the upper limit of reciprocation of slave piston 14' with conduit 21. Thus, when excess hydraulic fluid. is put into the system, the slave piston 14 will move above its upper limit of reciprocation, as shown in FIG. 6, to exhaust balance line fluid onits lower side through conduit 39 into conduit 21 andTthus t-hrough return 23 to the reservoir 17a.. As will be appreciated, this-requires only the dump line 39, apart from any'valving in addition to that necessarily provided in the reversingv valve 19 for alternately delivering power fluidto the upper sides of

pistons

12 and 14. Infact, if desired, the. dump line may be connected directly to the reservoir, although the arrangement shown reduces piping to a minimum.

There is a. choke 40 disposed in the conduit 32. Adjustment of this choke permits the operator toregulate the speed with which the reversing valve piston 22 is shifted, thereby avoiding shocks in the system at the limits of reciprocation of the control and slave pistons.

Operation When the system is first started, both

pistons

12 and 14 will ordinarily be resting on thebottom of their respective cylinders. Both pumps 17 and 35 are then started, particularly in the event they are driven by the same" prime mover. The pump 35- will immediately build up pressure in the balance line 23a so as to shift both the pilot valve and reversing valve pistons to the right, or the position shown in FIG. 1. This pressure from the pump 35 will also move the control piston 12 upwardly, while the slave 6 piston 1'4 is held down on the bottom of its cylinder 13 by virtue of the fact that power. fluid is acting upon its upper side and the upper end of the control piston is exhausting to atmosphere. As the control piston moves upwardly, fluid from pump 17 is by-passed into the reservoir 17a through relief valve 37.

When the control piston 12 is raised above the connection of shifting. line 24 with its cylinder, the pilot valve piston as well as the reversing valve piston will be shifted to-the left, for reasons previously described. This shift ing of the reversing valve, and thus the direction of power fluid to the upper side of the control piston 12 and exhaustion of such fluid from the upper side of the slave piston, will move the former downwardly and raise the slave piston from the bottom of slave cylinder 13. Obviously, since the slave piston was originally positioned beneath its normal lower limit of reciprocation, additional fluid must be pumped into the system through the pump 35 before the slave piston will be raised to its upper limit of reciprocation. I have found, however, that this additional fluid will be put into the system upon a relatively small number of reciprocations of the two pistons. In other words, the slave piston will quickly rise to a position in which'it rises slightly above the intersection of dump line 39 with slave cylinder 13, so that the control and slave pistons are brought into phase with one another.

As an alternative to the starting procedure above described, the operator may first close the cushioning choke 40 while the two

pistons

12 and 14 are disposed in the lower ends of their cylinders. As in the other procedure, this will shift the pistons in both valves to the right and also raise control piston 12. However, since the choke 40 is closed, the reversing valve piston 22 cannot shift to the left upon shifting of the pilot valve piston 29', and the control piston will continue upwardly into engagement with the top of cylinder 11.

As the control piston 12 is held against the upper end of its cylinder, hydraulic fluid pumped by the pump 35 will by-pass through relief valve 38 in the conduit 36 into reservoir 17a. The choke 40 is then opened so that the reversing valve piston is also shifted to the left to permit the normal downstroke of the control piston 12 and upstroke of slave piston 14. Since excess fluid was introduced into the system by the pump 35 in moving the control piston to the top of its cylinder, the slave piston will move above dump line 39 before control piston 12 reaches its lower limit and stay in such position and dump excess fluid from its lower side until the control piston reaches its lower limit to cause further shifting of the pilot and reversing valves.

In order to deactivate the system for any reason, the operator need only shut down the

pumps

17 and 35 ahd then open the relief valve 38. This will drain hydraulic fluid from beneath the control and slavesystems to permit them to rest on the bottom of their cylinders and relieve all pressure from the system.

With reference now to the details of the valves shown in FIG. 7, the body 31 of the reversing valve 19 has a smooth bore 41 in which the piston 22 is sealably slidable between the alternate positions of FIG. 1 and FIG. 3. As shown in FIG. 7, this piston is disposed in its rightmost position wherein it connects the inlet 18 which leads from the outlet of the pump 17 with an opening 42 in thevalve body connectable to conduit 21 leading to the upper end of slave cylinder 14, while at the same time connecting the return line 23 with a secondopening 43. therein connectable with conduit 2G leading to the upper end of the control piston 12. As also shown in FIG. 7, the piston 29 of pilot valve 19 is also in its rightmost position. to connect theconduit 32' with conduit 34 connecting through the reversing valve with the return line 23 soas to subject the right-hand end 22a of reversing valve piston 22 to the exhaustpressure.

At the same time, balance line pressure is admitted through conduit 33 connecting with port 43 in the lefthand end of reversing valve body 31 so as to subject the smaller, left-hand end 22b of the reversing valve piston to balance line pressure. This same pressure is also admitted to the smaller, left-hand end 29]; of the pilot valve piston 29 through

passageways

44 and 45 in the reversing valve and pilot valve bodies, respectively, connecting with the passageway 30 therebetween. The conduit 27 from the shifting

lines

24 and 25 of the control cylinder connects with the inlet 46 in the right-hand end of the pilot valve body for admitting the exhaust or atmospheric pres sure to the larger, right-hand end 29a of pilot valve piston 29.

The reversing valve piston 22 has annular recesses formed along its length intermediate a left-hand enlargement 47, intermediate enlargements 48 and 49, and righthand enlargement 50 thereon. The left-hand enlargement 47 is sealably slidable within a reduced section 51 of the reversing valve body bore so as to define the smaller pressure responsive area on the end 22b of the piston. On the other hand, the right-hand enlargement 50 on the piston 22 is sealably slidable within an enlarged portion 52 of such bore so as to define the larger pressure responsive area on the end 22a of the piston. Each of the intermediate' enlargements 48 and 49 is also sealably slidable within the enlarged section 52 of the bore, and the leftmost 48 of these intermediate enlargements is engageable with a reduced shoulder 53 in the bore to locate the piston 22 in the left-hand position of FIG. 3.

There is a passageway formed centrally of the piston 22 comprising an opening 54 extending axially thereof and connecting with lateral ports 55 and 55a therein. As can be seen from FIG. 7, when the piston 22 is shifted to the right-most position, the annular enlargements 48 and 4-9 are disposed on opposite sides of the connection of inlet 18 and opening 42. On the other hand, the recessed portion of the piston 22 intermediate these enlargements is imperforate to form an annular passageway between the valve body and the piston which, as

previously described, directs pumped fluid from the inlet 18 through the reversing valve into the opening 42 connecting with conduit 21, which in turn leads to the upper end of slave piston 14. At the same time, the piston enlargements 47 and 4 8 are disposed on opposite sides of the connection of return line 23 and opening 43 with the valve body. Furthermore, the recessed portion of the piston 22 intermediate these enlargements is also imper-forate to define another annular passageway through which the upper end of control piston 12 is exhausted to the reservoir 17a into which the return 23 discharges. It will also be noted that the conduit 34 connects with ports 56 and 57 in the pilot and reversing valve bodies, respectively, to connect the conduit 32 with this same annular passageway within the reversing valve so that, again as previously mentioned, the fluid on the right-hand end 22a of the piston 22 is also exhausted to atmosphere.

When the piston 22 shifts to the left-hand position shown in FIG. 3, the enlargements 49 and 50 on the spool type piston are disposed on opposite sides of the opening 42 from the valve body so as to connect such opening with the port 55a in the piston and the longitudinal opening 54 through the piston and its other lateral port 55. The intermediate enlargement 48 on the piston has moved to a position intermediate opening 43 and return line 23. Since the port 55 is to the left of this enlargement 48, the opening 42 is thereby connected with the return line 23 so that fluid on the upper end of slave piston 14 and conducted through conduit 21 is exhausted to the atmosphere. At the same time, the inlet 18 is connected with opening 43 by virtue of the disposal of enlargement 48 to the left of opening 43 and the disposal of enlargement bore 58 in which the piston 29 is slidable. This piston outwardly urged rings 64a.- This has been made possible by the machining of annular pressure equalizing has a reduced section 59 slidable within a reduced end 58 of the bore to define the smaller pressure responsive area of the left end 29b of the piston. An enlarged section 60 of the piston is sealably slidable within an en-. larged portion 61 in the pilot valve body to define the larger pressure responsive area on the end 29a of the piston 29. The left end of the enlarged section 60 is engageable with a shoulder 62 intermediate the two sections of the bore to locate the piston 29 in its left-hand position of FIG. 3.

There is a passageway 63 extending longitudinally and laterally through the piston 29 to connect its left-hand end 29b with an intermediate portion of its enlargement 60'. With the piston 29 in the right-hand position of FIG. 7, the enlargements 59 and 60 are disposed on opposite sides of the connection of conduit 32 with the valve body as well as port 56 connecting the conduit 34 therewith. Thus, as previously described, the conduit 32 is connected to port 56 through the annular passageway between the valve body and piston to exhaust the larger end of piston 22 to the return line 23 to the reservoir. At the same time, the lateral connection of passageway 63 is disposed between spaced-apart sealing portions on the enlargement 60 so as to seal off such passageway and thereby prevent the escape of balance line fluid from the left-hand end 2% of the pilot valve piston. As previously described and as shown in FIG. 1, the right-hand end 29a of such piston is, at this time, exhausting through inlet 27 so that the piston 29 is maintained in its right-hand position.

However, upon movement of the control piston 12 to its upper limited position, whereby balance line fluid is admitted through inlet 27 to the right-hand end 29a of the pilot valve piston, the latter is caused to move to the left. In the leftmost position of the piston 29, the enlargements 59 and 60 are disposed on opposite sides of the port 56 so as to isolate conduit 34 from conduit 32. At the same time, the spaced-apart sealing portions of the enlargement 60 are disposed on opposite sides of the connection of conduit 32 with the pilot valve body so as to connect the passageway 63 with such conduit. This, of course, permits the balance line fluid on the left-hand end 2912 of the piston 29 to flow through conduit 32 and against the right-hand end 22a of the reversing valve piston 22, thereby shifting it to the left in the manner previously described.

The sealing portions on the enlargements 59 and 60 of piston 29 are provided by outwardly urged rings 64 of conventional construction. In the case of the enlargement 60, the rings 64 are arranged in spaced-apart pairs to define an annular recess 65 connecting with the lateral porize the pressure about the piston and thus prevent it from binding in the bore of the valve body. In order to provide a satisfactory seal between such a piston and the bore of the valve body, it has also been conventional to grind or hone the latter. This expensive procedure has been followed, despite the fact that the use of outwardly urged sealing rings would be cheaper and would operate Withless leakage and in more extreme temperature conditions, because such rings would expand and hang up in the undercut annular grooves.

However, in accordance with another novel aspect of my invention, the valve 19 is of such construction that the sealing portions on the enlargements 47 to 50 of the piston 22 may also comprise the conventional type of recesses on the outside, rather than the inside, of the valve body, as shown in FIG. 7 at 66 and 67

opposite openings

42 and 43 in the valve body. Moreparticularreference to other features and subcombin-ations.

ly, these openings to the bore of the valve body are connected with the annular recesses 66 and 67 by means of ports 68 and 69 formed through webs 70 and 71, respectively, having inner surfaces which form a smooth continuation of the bore of the valve body. Obviously, therefore, the sealing rings 64:: will slide freely over the ports 68 and 69 during shifting of the piston 22. Preferably, the webs 70 and 71 are formed by machining the recesses 66 and 67 to a depthcorresponding to the outer surfaces of the webs. As shown, certain of the circular ports 68 and 69 may be provided with longitudinal extensions on each side.

The outer sides of the annular recesses are closed by means of annular sleeves 73 and 74 welded or otherwise secured to the exterior of the valve body. Thus, as can be :seen trom FIG. 7, the provision of a separate body for the reversing valve, as well as the cylindrical construction of the right-hand end of the reversing valve body, enable the sleeves 73 and 74 to be merely moved over and then secured in place about the recesses.

From the foregoing it will beseen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the appara-tus.

It will be understood that certain features and subcombinations are of utility and may be employed without This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. An hydraulic pumping system, comprising a pair of cylinders each having a piston reciprocable therein, a rod extending from each piston through the cylinder for connection to a load to he raised, a balance line fluidly connecting the cylinders to one another below the pistons, means shiftable between positions for alternately delivering hydraulic fluid to the upper end of one piston while exhausting it from the upper end of the other piston so as v to reciprocate the pistons in opposite directions, a first line connecting with the one cylinder below the upper limit of reciprocation of the piston therein and having a check valve movable to an open position when said piston reaches said upper limit to admit balance line fluid to said shiftable means, and a second line connecting with the one cyinder above the lower limit of reciprocation of the piston therein and having a check valve movable to an open position when said piston reaches said lower limit to exhaust balance line fluid from said shiftable means.

2. An hydraulic pumping system, comprising a pair of cylinders each having a piston reciprocable therein, a rod extending from each piston for connection to a load to be raised, a reversing valve having a piston reciprocable therein between alternate positions for admitting hydraulic fluid to the upper end of one cylinder piston while exhausting it from the upper end of the other cylinder piston, whereby the cylinder pistons reciprocate in opposite directions, a balance line fluidly connecting the lower ends of the cylinder pistons to one another and the one end of the valve piston which is smaller than the other, and means for shifting the valve piston between said alternate positions including valve-controlled lines for connecting the larger end of the valve piston with the fluid communicating with alternate sides of the piston in one cylinder as said cylinder piston reciprocates therein.

3. An hydraulic pumping system of the character defined in claim 2., wherein said lines are connected to the one cylinder at spaced-apart levels for admitting balance line fluid to the larger end of said valve piston, when said one cylinder piston reaches its upper limit of reciproca- 10 tion, and exhausting said fluid therefrom when said one cylinder piston reaches its lower limit of reciprocation;

4. An hydraulic pumping system, comprising a pair of cylinders each having a piston reciprocable therein, a rod extending from each piston and through the cylin der for connection to a load-bearing element, a reversing valve including a piston shiftable between a first position for admitting hydraulic fluid to one cylinder on the upper side of the piston therein while exhausting hydraulic fluid from the other cylinder on the upper side of the piston therein, and a second position for admitting hydraulic fluid to the other cylinder on said upper side-ofits piston while exhausting hydraulic fluid firom the one cylinder on said. upper side of its piston, a balance line fluidly connecting the cylinders on the lower sides of their pistons, and means including valve-controlled lines connecting with said one cylinder for shifting said reversing valve piston from said first to said second position, when the piston in said one cylinder reaches a limited position in one direction of its reciprocation, and then shifting said reversing valve piston from said second to said first position, when said cylinder piston. reaches a limited position in the other direction of its reciprocation.

5. An hydraulic pumping system of. the character defined in claim 4, wherein said last-mentioned means includes a fluid connection between the balance line and one end of the reversing valve piston, and a pilot valve for admitting balance line fluid to the other end of. said reversing valve piston when said cylinder piston reaches its limited position in one direction and exhausting said fluid from said other end of the. reversing valve piston when the cylinder piston reaches its limited position in the other direction.

6. An hydraulic pumping system, comprisinga pair of cylinders each having a piston reciprocable therein between limited positions, a rod extending from each piston and through the cylinder for connection to a load-bearing element, a reversing valve, a pump, means for delivering hydraulic fluid from the pump to the reversing valve and for returning it from said reversing valve to said pump, conduits connecting the reversing valve with said cylinders on the upper sides of the pistons therein, a piston reciprocable within the reversing valve between positions for alternately connecting the pump inlet to one conduit while connecting the other conduit with the pump return, a balance line fluidly connecting the cylinders on the lower sides of the pistons to one another and the reversing valve on an end of the piston therein which is smaller than the other end, and means including valve-controlled lines connecting with one cylinder for admitting balance line fluid to the other end of the reversing valve piston, when the piston in said cylinder reaches one limited position, and exhausting hydraulic fluid from said other end of the reversing valve piston, when said cylinder piston reaches its other limited position.

7. An hydraulic pumping system of the character defined in claim 6, wherein one line has a check valve therein adapted to open when said cylinder piston reaches one limited position, and another line has a check valve therein adapted to open when said cylinder reaches said other limited position.

8. An hydraulic pumping system of the character defined in claim 6, wherein said last-mentioned means includes a pilot valve having a piston reciprocable therein, said pilot valve piston having a larger end connected with said valve-controlled lines and a smaller end fluidly connected to the balance line, and means responsive to reciprocation of the pilot valve piston for alternately admitting balance line fluid to the larger end of the reversing valve piston and exhausting balance line fluid from said larger end of the reversing valve piston.

9. An hydraulic pumping system of the character defined in claim -6, including means for controlling the rate of admission and exhaustion of fluid to and from the larger end of the reversing valve piston.

1 1 I 10. -An hydraulic pumping system of the character defined in claim 6, including means for replenishing balance line fluid and for dumping excess balance line fluid from between the sides of the cylinder pistons from whiclrthe rods extend.

11. An hydraulic pumping system of the character defined in claim 10, wherein said replenishing means includes another pump, and including a common source of hydraulic fluid for both pumps.

12. An hydraulic pumping system of the character defined in claim 10, wherein said dumping means includes a line connecting with the other cylinder at a level above the one limit of reciprocation of the piston therein for returning said fluid to said pump.

13. An hydraulic pumping system, comprising a pair of cylinders each having a piston reciprocable therein between limited positions, a rod extending from each piston through the cylinder for raising a load connected thereto, a balance line fluidly connecting the cylinders to one another on the lower sides of the pistons, means for delivering hydraulic fluid to the balance line and alternately to the upper end of one piston while exhausting it vfrom the upper end of the other piston so as to reciprocate them in opposite directions, and a line connecting with one of said cylinders above the upper limit of reciprocation of the piston therein for dumping fluid from a of said bores between first and second positions, one end inlet to the pilot valve bore on the larger end of its piston, a port connecting with the reversing valve bore on the smaller end of the piston therein, an inlet to and outlet from the reversing valve bore, first and second openings in the reversing valve bore, passageways in the reversing valve connecting the inlet to the reversing valve bore with the first opening and the outlet therefrom to the second opening, in the first position of said piston, and connecting said inlet with the second opening and said outlet with the first opening in its second position, a first conduit connecting the pilot valve bore with the larger end of the reversing valve bore, and passageways in the pilot valve connecting the first conduit-with the second conduit in a first position of the pilot valve piston and connecting its smaller end with the first conduit in a second position thereof. Q

16. Valve apparatus of the character defined in claim 15, wherein said reversing valve piston has outwardly urged sealing rings thereabout and annular recesses intermediate the rings to form part of the passageways therein, and said reversing valve bore has an annular recess at each of said openings therein and connecting with said bore through ported webs forming a smooth continuation of the bore.

17. Valve apparatus of the character defined in claim 16, wherein said body means comprises separate reversing valve and pilot valve bodies, and there are sleeves 'slidably received over an end of the reversing valve body and secured over the annular recesses thereabout.

References Cited in the file of this patent UNITED STATES PATENTS 2,024,252 Romaine et a1. Dec. 17, 1935 2,355,669 Moser Aug. 15, 1944 2,575,241 White Nov. 13, 1951 Witt Janv 4, 1955

Claims

1. AN HYDRAULIC PUMPING SYSTEM, COMPRISING A PAIR OF CYLINDERS EACH HAVING A PISTON RECIPROCABLE THEREIN, A ROD EXTENDING FROM EACH PISTON THROUGH THE CYLINDER FOR CONNECTION TO A LOAD TO BE RAISED, A BALANCE LINE FLUIDLY CONNECTING THE CYLINDERS TO ONE ANOTHER BELOW THE PISTONS, MEANS SHIFTABLE BETWEEN POSITIONS FOR ALTERNATELY DELIVERING HYDRAULIC FLUID TO THE UPPER END OF ONE PISTON WHILE EXHAUSTING IT FROM THE UPPER END OF THE OTHER PISTON SO AS TO RECIPROCATE THE PISTONS IN OPPOSITE DIRECTIONS, A FIRST LINE CONNECTING WITH THE ONE CYLINDER BELOW THE UPPER