US2914037A - Hydraulic pumping system - Google Patents

Description

NOV. 24, JOHNS-[QM HYDRAULIC PUMPING SYSTEM Filed Sept. 23, 1957 3 Sheets-Sheet 1 INVENTOR.

' ATTORA/EVJ v fo Nov. 24, 1959 Filed Sept. 23, 1957 R. B. JOHNSTON 2,914,037

HYDRAULIC PUMPING SYSTEM 3 Sheets-Sheet 2 6 43 54 I 44 l 2? 54 b 4 22 4A 54 1 I j/ a 42 I 33 Z5" J6 7 7 v 34 24 46 L- 3 i j; /7 f" I v 38 J3 J5 36 y 56 v 48 49 47 j j 32 v 44 l 2! 4/ 1 ZZ /l g L 33 53 r J 59 Rufus B. dab/7a fan 49 INVENTOR. 52

53 a BY 50 Nov. 24, 1959 Filed Sept. 23, 1957 R. B. JOHNSTON HYDRAULIC PUMPING SYSTEM 3 Sheets-Sheet 3 .5 4/;9/7/7 6 fan INVENTOR.

. v g I /l ATTORNEY? t v 2,914,031w HYDRAULIC PUMPINGSYSTEM r Rufus B; Johnston, Dallas, Tex., assignor to Wilson Supply Company,'Houston, Tex., a corporation of Texas Application September 23, 1957, Serial N assess Claims. (Cl. 121- 150) This invention relates generally to an hydraulic pumping system and, more particularly, to improvements in' a single-actingand essentially automatic hydraulic motor of: the general type "shown in mygcopending application,

Serial No. 577,435, filedApril 10, 1956, and entitled' Hydraulic Pumping System. f i As pointed out in my earlier application; motors of this general type customarilyinclude a pilot valve control so connected to the motor'cylinder as to automatically and .positively'shitt a reversing valve between positions foradmittingand exhausting hydraulic :fluid to and from the working side-of the motor pistonin response to movement of -the motor piston into'the li-mits of its return and working strokes, re'spectively,-- In accordance with my earlier invention, th'e'ineed for sucha pilot valve control was obviated'by the pro'visionof a reversing valve in which the valvemember was seatable and unseatable in response to reciprocation of apiston having fluid iconnections with/ the 1 motor cylinder. These connections were so arranged; that thevalve piston was movablein'opposite directions to unseat and-permit seating; of the valve member in response to movement of the motorpis- 2,914,037 7 Patented Nov. 24, 1959 2 an open position are provided for exhausting said hy- 'draulic fluidfrom said one side of the piston to permit itsinovement in an opposite direction to a second ex- 'tremefpositionl More particularly, this valve comprises a bo dy h aving a passageway therein connecting with the c'ondu'ittmd-ari outlet from the body, and a valve mem berseatable upon a valve seat disposed across the passageway intermediate its connection with the conduit and outlet so that said valve member closes the passageway when seated. e

This system also includes pressureresponsive means movable upon the admission of hydraulic fluid thereto. in

one direction to unseat the valve member and conduit meansconnecting the motor cylinder at spaced apart levels-therein with the pressure responsive means. Valve meansfinthe conduit means are automatically operable in the first-extreme position of the piston to admit said hydraulic -fluid from said cylinder on said one side of thepistonand through one of said connections to the pressure responsive means and, in the second extreme position of the piston, to exhaust said hydraulic fluid from said pressure responsive means and through said othenconnection into the cylinder on said other side ofthe' piston. Means to be described more fully hereinatter: are provided for urging the pressure responsive means in anopposite direction so that the valve member. may seat upon the exhaustion of hydraulic fluid from said pressure responsive means. 7

Thisvalv ef means is'operable during movement of the'piston bet-ween said extreme positions to prevent communicationthrough saidconduit means between said pressure'responsive meansand'said one side of the piston. As previously mentioned, it is the initial stage of ton into thelimits-of its Working and return strokes, re-

spectivelyy 1 t "Intermediate theseilimits of motor piston imovement, however, the fluid connections were operableto prevent communication between the valve piston and working side ofthe, motorwpiston. In orderv to prevent the system from 1 getting on dead .center, 'lthe: valve piston lwas provided with aspringepressed actuator or plunger formaintaining the. valvemember unseate'd during the initialstage of return movement? of the; piston. The ValVe"L0f my earlier invention also't'included. a spring forretracting the piston to insure seatingof the valve member during the initial stage of working movementlof the piston. Although this motor enjoyed: considerable commercial success, I did encounter -some difficulty with breakagetof the aforementioned actuator spring, particularly since it was of considerable length and relatively small diameter.

An object of. this .invention ,is to provide a "single .Anotherobject s to provide-a r'evers1ng.,va l ve for a' motor of the general type above-described having means for retracting the valve piston with' a greater force than being'more compact."

These and other objects are accomplished fby a system the spring of my earlier invention while, at the s'ametime,

which, similar to thel system'of my earlier invention, in- I cludes a motor cylinder, having apiston reciprocable therein and a co'nduit connected to the cylinder for ading it ina working directionto a first extreme position. The opposite side of the motoi piston -is continuously this movement of the piston from the first toward the second extreme position whichis' critical. The system of my present invention includes additional rneans automatically operable to admit hydraulic fluid from the cylinder on said one side of the piston to said pressure responsive means during "at least the critical stage. of motor-piston movement when communication through said conduit meansbetween said cylinder on said one side of the piston and said pressure responsive means is prevented. p

This additional automatically operable means comprises additional conduit means for communicating the pressure responsive means with the'motor cylinder at a level nearer the second extreme position of the motor piston than saidone connection, and a second valve member adapted to open said additional conduitmeans in respons to movement of the pressure responsive means in'a" direction to open the first valve member: and to close such communication in response to movement of thepressure responsive member in the opposite direction. Thus, as 'the motorpiston moves into its first extreme position and starts back on its return stroke, the force upon thje pressure responsive means due to the hydraulic fluid admitted through the additional conduit means will move" said pressure responsive means to a position'to maintain'the reversing valve member unseated. On the other ha'nd,as the motor piston moves into its second extreme position and starts back on its working stroke; 'the closing of the second valve member will prevent the application of such a force to the pressure responsive means and thereby avoid premature opening of the reversing'valve member.

The second-valve member as wellas the pressure responsive means are contained within the body of the reversing valve. For this purpose, the body also includes a cylinder ofiset from the passageway connecting the convented and means includinga reversingvalve movableto duit for admitting hydraulic fluid to the cylinder and an outlet from the body. Ports are provided in the cylinder for connection with the conduit means and additional con,

acre-e7- duit means, and a valve seat for the second valve member I is disposed intermediate the cylinder and the port which is connectable to the additional conduit means. The pressure responsive means of the valve comprises a piston reciprocably mounted in the cylinder and extending. between said valve members to provide a force transmitting connection operable to unseat the first valve member when the piston is urged in one direction by the admission of hydraulic fluid to said cylinder and to seat the second valve member when the piston moves in the opposite direction upon the exhaustion of hydraulic fluid from said cylinder.

In accordance with another novel aspect of the present invention, the piston of thereversing valve-may be provided witha surface forming a part .of a pressure chamber Within the cylinder and so arranged as to urge the piston in a direction to permit seating of the first valve member upon the admission of pressure fluid to the chamber and l the exhaustion of hydraulic fluid from the opposite side of the piston. More particularly, this chamber is con.- nected with the passageway in the valve body sotthat' the piston is retracted by the force of hydraulic fluid acting reversing valve of the general character defined which may 1 i be easily. and quickly-adjustedin such a manner: as to im sure the substantially simultaneous seating ofboth valve members.

For this, purpose,.means are provided for changipgtlie effective length of the. forcetransmitting.connectionbetween the, valve members. This may be accomplished either by adjusting the position of at least one of saidseats with respect to the other seat or by adjusting the length 'of the piston. In av preferred form, the passageway and cylinder in thevalve body are substantially axially aligned;

and'one of the valve seats is formedon an axially'movable bushing to permit the aforementioned adjustment The valve member seatable on the other seat may be releasably located in seatedposition by means of an axially-movable stem so as to facilitate the aforementionedadjustment.

Itis. desirable to gradually decelerate movement of. the motor piston toward the end of its return-stroke so as to reduceshockloads on the system. When the motor is used to reciprocate. a sucker rod for a down-the-wellpump, debris will oftenaccumulate below the valves of the pump, and it is necessaryto bump bottom With-1116 pump in order to shake this debris loose.

A further object of thisinvention is to provide a system. which is adjustable in a manner. to perform botlrof these functions. i p

This latter object is accomplished by means of a-system of the general type describedwhich includes anadjustable choke in the conduit means intermediate the. pressure responsive means and the other connection of saidlconduit means into the motor cylinder. Thus, thischoke controls the rate at which hydraulic fluid is exhausted from-the pressure responsive means so that, if it is desired to bumpbottom, the choke is closed down to substantially restrict exhaust through the conduit means. On the other hand, the choke may be adjusted to cushion thereturn movement. of the motor piston to any desired degree.

Other objects, advantages and features ofthis invention. will be apparent to one skilledin. the art upona considera= tion of the writtenspecification, attached claims and the annexed drawings.

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

Figure .1 is a schematic sectional view of the motorof the hydraulic system of this invention during an intermediate portion of the working stroke of the motor piston;

Figure 2 is a view similar to Figure l but with the motor piston at one extreme position or limit of its working stroke;

Figure 3 is another similar view of the motor during an intermediate portion of the return stroke of the motor piston;

Figure 4 is a view similar to Figure 3, butin which the motor piston has descended still further in its return stroke;

FigureS is a further similar view with the motor piston at its other extreme position or limit of its return stroke;

Figure 6 is an enlarged sectional view of one embodiment of the reversing valve of the motor of Figures 1-5, with both valve members in seated position;

Figure 7 is a cross-sectional view of the valve of .Figure 6, taken substantially along. broken line 77 thereof;

Figure 8 is an enlarged sectional view of another embodiment of a reversing valve suitable for the purposes of the present invention, with both. valve members in .unseated position; and V I Figure 9 is across-sectional view of the valve of Figure 8, taken substantially along broken-line 9-9;

Referringfirst to the schematic views of Figures 1-5, the motor of the present invention includes'a motor cylinder20 which is closed atits upper end 21, a piston 22 reciprocable in'the motor cylinder, and a rod 23 on the piston extending. through the lower end 24 of the cylinder. Inaccordance with a preferred usage of the motor,,the rod may be'a' polish rod for connection with a down the-well pump,- in a manner well known in the art. The piston is moved in a working or upwardly direction by means of hydrauliofluid supplied to the workingor lower side 25 thereofthrougha conduit 26 connected to the lower end of the cylinder 20. The conduit 26 maybe connected-with a suitable reservoir .(not shown) of hydraulic fluid under: pressure.- The lower end of the cylinder is provided with a reduced diameter portion having an upwardly facing shoulder 27 which" prevents movement of the piston 22 over the connection of conduit 26 with the interior of the cylinder. The opposite or'upper end 28 ofthemotor piston 22 is-continuously' vented by means of a conduit 30 connectingtheupper'endof' the cylinder-with any suitable source; at a pressure" substantially: less than-that of the hydraulic fluid and-similanto that' towhichsuch fluid is exhaustedlfrom the working side 25 of the motorpiston, in amannerto' be described hereinafter. s I

A reversing valve 31 includes a body 32 havinga passageway 33 therein connecting with theconduit 26 and an outlet 34' therefrom. valve member 35 is seatable upon a valve seat 36 disposed across the passageway 33 intermediateits connection with conduit 26and outlet 34 so as to close thepassageway. When the valve meniber 35 is seated, as shownin Figures 1 and 5, hydraulic fluid'conducted through conduit 26 will be admitted to the cylinder on the lower side 25 of the piston 22 so as to move the piston in 'a working. direction; However, when the valvemember isunseated, in a manner to he described below, the hydraulic-fluid on the lower'side ofthemotor piston will be exhausted from the cylinder and through the conduit 26 and passageway 33"into' the outlet 34; As previously mentioned, it is contemplated by the'present invention that conduit 30 ando'utletf34 will connect at their outer ends (not shown) with sources having the same, or at least substantially the same pressure. For example, in a continuous pumping system of this type,- each of; the conduit 30 and outlet 34: may connectwith theupper end of a-hydraulic-fluid reservoir (such-as that-connecting-with conduit 26) which may beat an atmospheric pressure. In such a case, conduit- 30 may. connect with the portion of the passageway 33 in the valve body,32 beneath seat 36, the outlet 34, as showninFig fi, q

The valve 31 is also providedwith pressure responsive means in a form of acylinder,37; in the body 32 thereof and a piston 38 in the. cylinder which-is movable upon the admission of hydraulic. fluid to the lower side 39 thereof in a direction to unseat the valve member 35. Each of a pair of conduits 40 and 41 is connected to the motor cylinder at one of two spaced apart levels and both conduits have a common connectionthrough a conduit 42 with the valve cylinder beneath the valve piston 38. Disposed within conduit 40 is a check valve 43 automatically operable, upon movement of the piston to the extreme position o f Figure}, to admitrhydraulic fluid from the cylinder beneath'themotor piston v22 to the valve cylinder 37 beneath the valve piston This check. valve 43: may comprise any suitable construct do pos seated due to the exhaustion of hydraulic fluid fronrbe .tion, such as is shown schematicallyin Figures 1-5, which erable, upon movement of the motor system to the. limit of its return stroke (Figure 5 to exhaust the hydraulic fluid from beneath the valve piston 38 through conduits 42 and 41 into the motor cylinder 201m the side 28 of the motor piston. More particularly, the check valve 44 is of suitable construction which is urgedto a'closed position by means of fluid pressure inthe" end of conduit 41 connecting with the motor cylinder. i

The valve member 35 comprises a ball and the piston 38 is provided with an actuator 45 which extends through an opening 46 connecting passageway 33 and cylinder 37 of the body so that when the piston is moved upwardly by the admission of hydraulicfluid to the valve cylinder beneath piston 38, the upper end of the actuator forces the ball otiofits'seat. A coil spring is dis posed about the. actuator between the cylinder and the piston 38 to urge the latter in'a downward direction. Thus, upon the exhaustion of hydraulic fluid from be.-

neath the piston 38, the valvepiston will be retractedso as to permit the valve member 35Lt'o se'at. In a mad her to be described more fully hereinafter, the coilspring 47 may be replaced by other Suitable means, such as fluid pressure, for urging the valve'piston in a direction to permit seating the valve member 35.

'Obviously, the'valve is so designed that, in the Fig. 4 position of the motor, the combined force on the valve member 35 and in the spring 47 will be suificient-v to retract the valve piston, while," in the Fig. 2 position thereof, the force due to hydraulic fluid acting upon the side 39 0f the piston'will 'be suflicient to overcome the force in the spi'ingand on'the valve member so as to move the piston upwardly.

It will be understood that as themotor piston 22 begins to move downwardly from its extremeposition of Fig. 2, it ,will cover the connection of conduit 40 with the cylinder and thereby prevent communication through the conduit 42 between said cylinder beneath the motor piston and the valve cylinder. 37 beneath the valve piston 38. If it were not. for the novel apparatus of this invention, and this return movement of the motor piston were so fast that the valvemember 35 was barely lifted from its seat, this shutting oif of hydraulic fluid fromthebottom of piston 38 might cause the valve mem ber 35 to seat prematurely and the system toget on dead center wherein the motor piston would reciprocate inshort, incomplete strokes. V

This novel apparatus comprises a conduit 48 connecting the valve cylinder 37 beneath the piston 38 with the conduit 41 intermediate the check valve 44 and. the connection of said conduit 41 with the motor cylinder 20,

and a valve member 49 seatable upon the connection of conduit 48 with the cylinder 37 to open said conduit in response to movement of the piston 38 in an upward direction to unseat the valve member 35 and to close neath the valve piston 38, will not be prematurely unseated by means of hydraulic fluidflowingintothe cyl inder 37 through conduit 48 because the. conduit 48.11215 been closed by the valve member 49 The valve member 49 also comprises a-ball, the upper end of which is engaged by the lower side39 of the valve piston 38 as the latter movesidownwardly toper: mit seating of the valve member 35. Obviously,- however, both valve members may take other forms. For example, the valve member 49 may be integral with the piston 38. Also, if desired, both valve members may be of a sleeve type cooperable; with ports in the valve body.

,As previously mentioned, it is important that .both valve members 35 and 49 are seated substantially SiIDlli', taneously. That is, if, upon movement of the motorpiston into the Fig. 5 position, the valve member 49 does not seat substantially simultaneously with the valve mem: ber 35, the motor piston may' rise above the connection of conduit 41 with themotor cylinder prior to seating of the valve member 49. I As aresult, thevalve piston 38' may be raised and thevalveninember 35 unseated prematurely. I i

Theoretically, inorderfor the valve and 49 to seat simultaneously, the piston 38 and actuator must provide a forceetransmitting connection equal in length to the distance between theseated positions of the valve. members. Thisadjustment of the valve parts may be made, either upon the installation of the system or after Wear upon the parts, by means which, in the reversing valve 31 of Figs. 6 and 7, comprises a bushing 50 threadedly received in the lower end of the valve body for movement axially of the cylinder 37 and passageway 33 and having the seat for valve member 49 formed thereon. Thebushing 50 is provided with a threaded socket 51 for receiving the conduitk48, anda passagewaySZ therethrough connecting the socket and cylinder 37-1t0 form a continuation of the 'conduit48.- Thus,"thebush ing maybe moved inwardly or-outwardly, as desired,j't6 bring the piston 38 andits actuator 45 into engagement at its opposite ends with the seated valve members 35 and 49. An O-ring 53.surrounds'the bushing to sealwith the remainder'of the body, and a nut 53a on an outer threaded portion of the bushing permits it to belocked in adjusted position. Y t 3 t i The motor piston descends at a rate which is deter mined by the rate of flow past the unseated valve meme ber 35. This rate of flow is, in turn, controlled by means of a stem 54 threadedlyreceived in the opposite end of the valve body. for extension axially of the passageway 33. This stern may be adjusted soas to determine the extent of movement of the valve member 35 off ofits'se'at 36, and thus the rate of flow past such seat. This adjustable stem 54 also aids anoperator intfeeling the movement of actuator 45 into "engagement with'valve'inember 35 during manipulation of bushing 50. Obviously, after the adjustment has been made,.the stem may be retracted into a position limiting unseating movement of valve member 3'5 to a desired amount. .The stem is sealed with respect to the remainder of the body by an O-ring 54a and may be locked in either valvelmember locking or limiting position by means of a nut 54b. a

The valve seat 36 is also formed qnaseparatehushs between an annularshoulder-60 at the upper end of cyl- Y ind'er 37 andan annular surface on the top of piston 38 surroundingactuator 45. An enlarged diameter portion of'thepiston' isprovided'with seal rings 61 thereabout for sealably sliding within an'enlarged diameter portion of thecylinder 37. An annular shoulder 62 at the top of this last-mentioned'cylinder portion provides a stop to upw'ard'movement of'the piston 38.

The embodiment of reversing valve shown in Figs. 8 and 9 is, in many respects, similar to that above-described in connection with Figs. 6 and 7. Thus, as shown inFiguresS' and'9', this valve 63'comprises a valve body 64" having a passageway 65' therein provided with ports for connection with the conduit 26. A valve seat 66 is disposed'across the passageway intermediate its intersection with conduit 26 and an outlet 34 therefrom so that a ball valve member 67 is seatable thereon to close the passageway. Also, the valvebody is provided with a cylinder 68 therein substantially axially aligned with the passageway 65, and ports'in the cylinder for connection with conduits 42 and 48 below the lower side 69 of a piston 70- reciprocable within the cylinder.

As in the case of the previously described embodiment, the-valve body 64 has an opening 71 therethrough'conmeeting its passageway and cylinder, and the piston 70' has-an actuator 72 extending through said opening for engagement at its upper end with the ball valve member 67. .Thus, upon the admission of hydraulic fluid'to the valve cylinder 68'beneath the piston 70, the piston and actuator 72 will be moved upwardly so as to unseat the valvemember67. On the other hand, upon the exhaustion of hydraulic fluid from beneath the piston 78, the piston will move downwardly to permit seating of the valvemember 67.

As distinguished from* the previously described embodim'ent, however, the piston 70 of the valve 63 is urged downwardly by pressure responsive means which is capable of providing a larger retracting force and which takes" up lessspace'than the coil spring 47 of said other embodiment; Thus, the body 64 of the valve is provided-withone or more ports 73' therethrou'gh (shown rotated in Fig. 8); for connecting the passageway 65 above seat 66 with: an: annular chamber in the cylinder 68-formed on; opposite sides between the actuator 72 of the piston and the valve cylinder and sealed below by seal rings 75 about anenlarged diameter of the piston 70 and above by av seal ring- 74 carried by the body in the opening 71 forsealing about the actuator 72. It-w-illbe understood-that thepressure of the hydraulic fluid in the passageway 65 above the seat 66 will urge the piston 70 downwardly.

Although this-pressureresponsive retracting means may bepreferred over the; coil spring. of the Figs. 6 and 7 embodiment forthel reasons previously noted, there are some auxiliary advantages of a coil spring which may make it desirable to use same in conjunction with the pressure responsiveuretracting means. For example, a

coil spring arranged as shown in Fig. 6 will compensate The-seal rings 75- on the-piston are spaced apart and the piston and its actuator 72' are ported at 76 to connect the portionof the passageway 65 intermediate seat 66' and seal ring=74 with an annular space about the piston between the rings Inasmuch as the fluid in this portion of the passageway is substantially atmospheric, or less than system pressure, it prevents leakage from the annular chamber'above the topmost ring into the cylinder beneath the piston 70.

As in i thecase of the previously' described embodiment, the bottom'69of the piston 70 is engageable with a valve member 77 so' as to move it into seated position upon the seat formed at the intersection of conduit 48- with the cylinder 68. In this embodiment of the invention, the scatter valve member 77 is formed upon the removable lowerend 78 of the body, and the adjustment for insuring substantially simultaneously seating of the valve member 66 and 67 comprises an axially adjustable stem 79 on the lower end 69 of the piston. As in the caseof the adjustable bushing 50 of the valve embodiment ofFigs. 6 and 7, this valve also includes an adjustable stem 80' for limiting the extent to which the valve member'67 maybe unseated and thus control ling the rate of flow'past the seat 66.

Referring again to Figs. 1-5, the adjustable choke 81 is shown disposed within conduit 41 intermediate the connection of said conduit with motor cylinder 20 and the" conduit 48. As previously described, this choke is adjustable to cushion the descent of the motor piston to a desired extent. At' the same time, it cushions the rise of the piston in a manner obvious from the drawings. If the. adjustable choke 81 is also to be used in bumping; bottom, the down-the-well pump is so supported from the rod'as to be spaced just a few inches above the bottom of the well. Thus, the pump will be caused to bump bottom, for the purposes above-described, upon closing down of the choke.

Reviewing now the overall operation of the system, particularly with respect to the reversing valve 31, it will be understood that'with the pump for the hydraulic fluid shut off, the locating stem 54 may be moved inwardly to seat the valve member 35 on its seat and the bushing 50' moved inwardly to force the upper end of the actuator 45 against the bottom side of the valve member 35. The locating stem may then be retracted to permit a desired amount of travel for the valve mem-, ber 35.

At this, time, both the motor piston and valve piston are in the lowered positions of Fig. 5 and the valve members 35 and'49 are seated. As the pump is started, hydraulic fluid is admitted to the cylinder 20 beneath the motor piston to move it upwardly past the connection of conduit 41 with the motor cylinder. However, the check valve 44 is effective to prevent hydraulic fluid beneath the motor piston from admission to the lower side 39 of the valve piston through the conduit 42. Since the area across seat 36 is greater than that across the seat for valve member 49, it is obvious that the force due to system fluid acting upon valve member 35 plus the force of spring 47 is greater than the force due to such fluid acting upon valve member 49 so that the valve piston remains in its lower position to maintain the valve member 49 seated despite the fact that bydraulic fluid is conducted through the conduit 48 be.- neath the piston to the lower side of the valve member 49.

When, however, the motor piston moves upwardly past the connection of conduit 40 with the motor cylinder (Fig. 2),. the check valve 43, is effective to permit hydraulic fluid to, be admitted through conduit 42 to the lower side of the valve piston 38. Since the force due to system fluid acting upon the surface 39 of piston 38 is greater than. that due to the spring 47 and the fluid at reduced pressure on the opposite surface of the pis ten, the valve piston is raised so as to unseat the valve piston permits the valve member 49. to unseat due tov the a influence of hydraulic fluid acting ,upon,,its lower side. Thus, even though the motor piston, might drop uickly past the connection of conduit40 withthe motor cylinf der, the force upon the lower side of the'piston due to the. admission of hydraulic, fluid through the conduit 48 will insure suflicient travelof the valve member 35 in an unseating direction so as to prevent the system from getting on dead center.

To explain further, as soon as the motorv piston 22 moves above theintersectio'n of conduit 40 with the motor cylinder, the system ,fiuid will be admitted to the pressure responsive surface 39 of piston 38 of the reversing valve so asto unseat ball valve member 35. As the ball valve member is unseated, system fluid will be vented from beneath the motor piston through the outlet 34. If the upwardly directed force upon the pistonv of the reversingvalve is not suflicient to fully unscatthe ball 35, there may be a pressure drop across therestriction between; the ball and its seat which, together, with venting of system'fiuid through the, outlet 34,,v may be suflicient to draw the ball back downonto its seat. \On the other hand, even if the ball valve member 35 is not prematurely seated, if it isnot fully unseated, the motor piston will not move downwardly at the intended speed. It is to avoid these shortcomings that motors of this type have heretofore included a pilot valve control of the type previously described.

This last mentioned force is effective during the travel of the motor piston downwardly to a position in which it covers the connection of conduit 41 with the motor cylinder. As the motor piston drops further past this last'mentioned connection, the check valve 44 is effective to permit hydraulic fluid to be exhausted from beneath the valve piston through the conduit 42; :As a result, intermediate the positions Figures 4 and-5,"the valve piston will be lowered to permitseating of the valve member 35. Thus, hydraulic fluid con ducted through conduit 26 will again be directed to the working side of the motor piston so that it is again urged in an upwardly or working direction. This exhaustion of hydraulic fluid from beneath the valve piston and the resulting downward movement of such piston also causes the valve member 49 to be seated. In this way, even though the motor piston might start back upwardly at a fast rate, the valve member 49 will be seated prior to the uncovering of the connection of conduit 41 with the motor piston upon upward movement of the motor piston.

From the foregoing it will be seen 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 apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. 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. In an hydraulic pumping system, a motor compris ing a cylinder and a piston reciprocable therein, means for admitting hydraulic fluid to one side of the piston for moving it in a working direction to a first extreme position, means for continuously venting the other side of the piston, means including a reversing valve movable t9 an open position for exhausting said hydraulic fluid 10 from said ,one'piston side to permit its movement in an oppositedirectionto a second extreme position, pressure responsive means movable, upon the admission of hydraulicfluid thereto, in a direction to open the valve and, upon the exhaustion of hydraulic fluid therefrom, in a direction to permit closing of the valve, conduit means connecting the cylinder at spaced apart levels therein with the pressure responsive means, valve means in said conduit means automatically operable, in the first extreme position of the piston, to admit said hydraulic fluid from said cylinder on said one side of the piston and through Oneof said connections to the pressure responsive means and, in the second extreme position of the piston, to exhaust said hydraulic fluid from said pressure responsive means and through said other connection into the cylinder on said other side of the piston, said valve means being operable during movement of the piston between its first and its second extreme positions to prevent communication through said conduit means between said pressure responsive means and said one side of. the piston, and means automatically operable to admit hydraulic fluid from the cylinder on said one side of the piston to said pressure responsive means during said prevention of communication uponmovementof thev piston from its first toward its second extreme position.

2; A motor of the character defined in claim 1, wherein said. automatically operable means comprises additional conduit means for communicating said pressure responsive means with the cylinder at a level nearer the sec- Olld extreme position of the motor piston than said one connection, and a valve member for opening. the addisonar conduit means in response to movement of the pressure responsive means in a direction to open the valve and for closing said additional conduit means in response to movement of the pressure responsive meansin a direction topermit closing of the valve.

"" 3. A motor of the character defined in claim 2, wherein said additional conduit means is connected to said first-mentioned conduit means intermediate said valve means and said other connection.

4'. A motor of the character defined in claim 3, including an adjustable choke 'in said first-mentioned conduit means'intermediate the connection of said additional conduit means therewith and said other connection.

5. In an hydraulic pumping system, a motor cylinder and a piston reciprocable therein, a conduit for admitting hydraulic fluid to one side of the piston for moving it in a working direction to a first extreme position, means for continuously venting the other side of the piston, a

valve body having a passageway therein connecting with the conduit and an outlet therefrom, a valve seat across the passageway intermediate its connection with the conduit and the outlet, a valve member seatable upon the seat to close the passageway, pressure responsive means movable, upon the admission of hydraulic fluid thereto, to unseat said valve member and thereby permit hydraulic fluid on said one side of the piston to be exhausted through said outlet and, upon the exhaustion of hydraulic fluid therefrom, to permit seating of the valve member, means automatically responsive to movement of the piston into said first extreme position to admit said hydraulic fluid from the cylinder on said one side of the piston to said pressure responsive means and, responsive to movement of the piston from said first toward said second extreme position, to prevent communication between the cylinder on said one side of the piston and said pressure responsive means, and means automatically operable during the prevention of communication between said cylinder on said one side of the piston and pressure responsive means to admit hydraulic fluid from the cylinder on said one side of the piston to said pressure responsive means.

6. In an hydraulic pumping system, a motor comprising a motor cylinder and a piston reciprocable therein, a conduit for admitting hydraulic fluid to one side of the piston for moving it in a working direction to-a-first extremeposition, means for continuously ventingthe other side of the piston, a valve body-having a passageway therein connecting with the conduit'and an" outlet therefrom, a valve seat across the passage:- way intermediate itsconnection with the conduit and the outlet, a valve member seatable upon the first seat toclose the passageway, means including a pis'ton-h'aving' oppositely disposed pressure responsivesurfaces and' movable in one direction to unseat said-valve member,- and thereby permit hydraulic fluid on said one side of thepiston tobe exhausted through said outlet, andin an opposite direction to permit said valve member; to seat, means automatically operable, in the first. extreme position of the motor piston, to. admit hydraulic fluid from said cylinder on said one side of the piston to. one surface of said second mentiOned piston. for'moving itin said one direction and, in the second'extreme posi-- tion ofthe motor piston, to exhaust hydraulic fluid'from said one surface of said second-mentioned piston into the-cylinder on said other side of the piston to permit said second-mentioned. piston to move in said other direction, the opposite surface ofsaid second-mentioned piston. forming part of a chamber sealed off fromthe passageway intermediate the seat and outlet,.and means for conducting hydraulic fluid from the cylinderbeneath the motor piston to the chamber during. theexhaustion of. hydraulic fluid from said second-mentioned pistonto. move it in said opposite direction. v

7. A motor of the character defined in. claim. 6., wherein said conducting means includes a. conduit connecting the chamber with the passageway of. the valve bodyintermediate the seat and its connectionsaidfirst: mentioned conduit.

8. In an hydraulic pumping system, a motor cylinder and a piston reciprocable therein, meansfor. admitting hydraulic fluid to one side of the piston. for moving it ina working direction to a first extreme. position,.means for continuously venting the other side of the. piston; means including a reversing valve movable to an open position for exhausting said hydraulic. fluid. from said one piston side to permit its movement in an opposite direction to a second extreme position, pressure-:responsive meansmovahle; upon the admission of: hydraulic fluid thereto, toopen the valve and, upon the exhaus tionofhydraulic fluid'therefrom, to permit the valve to' close; conduit means having two connections wit'll the cylinder at spaced apart levels therein with the pressure responsive means, valve means'in said conduit means automatically operable in the first extreme posi:' tion of the piston, to admit said hydraulic fluid from said cylinder on said one side-of the piston and through one of said'connections to the pressure responsive means and, inthe second" extreme position of the piston, to exhaust said hydraulic fluid from said pressure I'CSPOII': sive-meansand through the other of said connections into thecylinder on said other side of the piston, and an adjustable choke in the conduit means intermediate said pressure responsive means and said other connec+ tion into the cylinder.

9. In anhydraulic pumping system of the character defined in claim 5, whereinsaid automatically operable means comprises conduit means for communicating said pressure'responsive means-with the cylinder, anda-valve member for openingthe conduit means substantially simultaneously with openingof the valve and for closing said conduit means substantially simultaneously with closing of the valve.

10; Inarr hydraulic pumping system of the character defined in claim 9, including means for choking said conduit-means.

References-.Gited in the file of this patent UNITED STATES PATENTS 2,048,550 Helenberg: July 21, 1936 2,377,115 Van Der. Werif May 29,1945 2,404,796. Grant et al. July 30, 1946 2,669,972 Crossv Feb. 23, 195.4 2,708,912 Vanalstyne May 24, 1955 2,726,642 Zintyet al. Dec. 13, 1955 2,853,057 McAuley Sept. 23, 1958 FOREIGN PATENTS 992,937 1 France Oct. 6, 1944

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