US2708912A

US2708912A - Hydraulic pump jack

Info

Publication number: US2708912A
Application number: US296867A
Authority: US
Inventors: Earl M Vanalstyne
Original assignee: LORIN A LOCKARD
Current assignee: LORIN A LOCKARD
Priority date: 1952-07-02
Filing date: 1952-07-02
Publication date: 1955-05-24
Anticipated expiration: 1972-05-24

Description

May 24, v1955 E. M. vANALs'rYNE YHYDRAULIC PUMP JACK 3 Sheets-Sheet 1 Filed July 2, 1952 May 24, 1955 E. M. vANALsTYNE HYDRAULIC PUMP JACK -3 Sheets-Shea?l 2 Filed July 2, 1952 Q LLM/UMA AT TORNE V May 24, 1955 E. M. vANALsTYNE 2,708,912

HYDRAULIC PUMP JACK Filed July 2, 1952 I5 Sheets-Sheet 5 fA M M/V 5 7)//1/.5

INVEN TOR.

.BY l M1/M TTORNE) United States Patent O HYDRAULIC PUMP JACK Earl M. Vanalstyne, Anaheim, Calif., assignor of onehalf to Lorin A. Lockard, Garden Grove, Calif.

Application July 2, 1952, Serial No. 296,867 11 Claims. (Cl. 121-150) My invention relates to the ield of pumping equipment, and more particularly to a hydraulic pump jack, and is a continuation-in-part of my application, Serial No. 135,225 entitled Oil Well Pumping Unit, iiled December 27, 1949, now abandoned.

in the pumping of an oil well the pump is normally situated near the bottom of the hole, and is actuated by the vertical reciprocating movement of the sucker rod which extends downwardly to the pump from the ground surface. A vertical reciprocating movement may be imparted to the sucker rod by numerous mechanical devices which, however, have the common disadvantage that they place a considerable mechanical stress on the sucker rod as its direction or" movement is reversed. Due to the length of the sucker rod and the elasticity of t'he metallic material from which it is normally fabricated, the rod tends to act as a rubber band as it reciprocates vertically. Thus, as the rod is moved upwardly on one stroke it tends to be elongated, and as this process s taking place its direction is reversed and compressive forces are exerted thereon. Obviously, under such conditions severe mechanical stresses are set up in the rod, which stresses ultimately result in progressive failure of the metal forming the r'od, and the breaking or rupturing of the rod.

The primary purpose in devising my present invention is to provide a hydraulic pump jack that minimizes the mechanical shock to which the sucker rod is subjected as its direction of movement is reversed.

The major object of my invention is to provide a hydraulic pump jack that reduces the stress peaks to which a sucker rod is subjected as its movement is accelerated and decelerated in a pumping operation.

Another object of my invention is to furnish a hydraulic pump jack that has an extremely simple mechanical structure, permits the frequency of the stroke of the sucker rod to be varied by a simple manual operation, and requires a relatively small amount of main-- tenance attention after the device is installed on a well.

Further objects of my invention are to provide a hydraulic pump jack that ceases to reciprocate the sucker rod after a bre-ak or rupture has occurred in the rod, that is compact in appearance and occupies a minimum of floor space that can be fabricated from standard commercially available materials, and which may be sold at a price that is competitive with that of existing pumping equipment of a like capacity. v

Yet another object of my invention is to furnish a h dranlic pump jack having a valve device forming a cornponent part thereof that permits the time interval at each end f the stroke to be lengthened or shortened before the direction of movement of the sucker rod is reversed. i

An additional object of my invention is to provide a hydraulic pump jack having a novel scavenging arrangement whereby there is eliminated the need of a separate scavenging pump. This is an important feature inasmuch as the separate scavenger pumps of existing hydraulic t; ICC

pumping jacks have proved to be a source of considerable trouble and expense.

These and other objects and advantages of my invention will become apparent from the following description of two preferred forms thereof, and from the drawing illustrating these forms wherein:

Figure l is a vertical crosss-ectional view of a hydraulic pump jack embodying my invention, with Huid being admitted 'to the cylinder, and the upstroke of the piston and polished rod partially completed;

Figure 2 is a vertical cross-sectional view of said jack, with the piston at the top of the stroke;

Figure 3 is a vertical cross-sectional view of said jack, with the piston at the bottom of the stroke.

Figure 4 is a side elevational view of a moditied from of hydraulic pump jack embodying my invention; and

Figure 5 lis a vertical cross-sectional View of a detail of construction of the jack shown in Figure 4.

Referring now to the drawings for the general arrangement of the hydraulic pump jack embodying my invention, it will be seen that it comprises broadly a vertical elongated cylinder C shown mounted on a tripod T, the latter having its legs resting on the floor of the oil well derrick. A piston P is slidably movable within hte confines of the cylinder C, and is aixed to the upper end of a polished rod R in a conventional manner. The polished rod R extends downwardly through the cylinder C, and has its lower end connected to a sticker rod (not shown), with the sucker rod continuing downwardly to a conventional reciprocating pump (not shown) suitably located in the oil well from which production is to be taken.

Referring now to Figures l, 2 and 3, the cylinder C is preferably fabricated in two portions; an upper portion it) and a lower portion 1l.. The upper cylinder portion 10 has a totally enclosed dome i2 formed on the upper end thereof, with the dome 12 being odset from the longitudinal axis of the cylinder portion 1?. The upper end of the cylinder portion 10 extends upwardly into the dome 12 to form a baille 13, the purpose of which will hereinafter become apparent. An annular flange 14 is shown formed on the lower end of the cylinder portion 10, and this flange engages a complementary flange 15 formed on the upper end of the lower cylinder portion 11. The

anges

14 and 15 are removably affixed to one another, as by bolts 14a.

The lower end of the lower cylinder portion 1l is provided with a closure 17, which closure includes a stuffing box 18 of conventional design through which the polished rod R may reciprocate. The tripod T includes a rigid member 19 which extends outwardly from the closure 17, and from which a number of legs 2l) extend downwardly to the derrick oor 21 or other suitable supporting surface.

Hydraulic fluid may be admitted into the confines of the cylinder C by means of a supply conduit 22 which extends through the Wall of the cylinder portion lll. Hydraulic fluid may be discharged from the cylinder C by means of a discharge conduit 23, which conduit is in communication with the interior of the shell portion il, and is shown vertically spaced above the conduit 22.

A cylindrical valve sleeve 25 is shown coaxially positioned within the contines of the cylinder portion 1i, which sleeve is formed with one or more ports 26. These ports are in horizontal alignment with the outlet of the supply conduit 22 when the lower edge of the sleeve 25 is resting on the upper surface of the closure 17.

lt will be noted in the drawing that an annular collar 27 is shown formed on the outer surface of the sleeve 25, with another annular collar 28 shown formed on the interior surface thereof; both collars preferably being in the same horizontal plane. The

collars

27 and 28 each have a lower horizontal annular surface 27a and 28a, respectively,` the purpose of which will hereinafter be explained. The vertical surface of the collar 28 is in slidable contact with the exterior surface of a vertically positioned cylindrical guide 30 disposed within the lower confines of the cylinder portion 11, this guide having its lower end aflxed to the upper surface of the closure 17. A longitudinally extending counterbore 31 is shown formed in the lower part of the cylinder portion 11. This counterbore 31 defines at its upper end a body shoulder 32 with respect to and coaxial with a longitudinally extending bore 33 of slightly larger diameter. zontal ports 34 are shown formed in the valve sleeve 25 below the

collars

27 and 28. A number of circumferentially spaced rectangular slots 25a are shown formed around the lower edge of the sleeve 25, each slot providing a horizontal area 25h.

An elongated U-shaped conduit 35 extends longitudinally along one side of the cylinder C. with one leg 36 of the conduit extending through the wall of the upper cylinder portion lt! in substantially the same horizontal plane as the bottom 37 of the dome 12. The other leg 38 of the conduit 35 extends through the wall of the lower cylinder portion 11 and is in alignment with the port 32 when the sleeve 25 is in its lower position, as shown in Figures l and 3. A branch conduit 39 having a check valve 40 incorporated therein extends from the conduit 35 to pass through the wall of the cylinder portion 1t) at an appreciable distance above the flange 14. A check valve 41 is shown positioned in the conduit 35 above the branch conduit 39, and a throttle or speed valve 42 is shown disposed in the conduit 35 below the branch conduit 39.

A completely enclosed reservoir 44 is shown disposed adjacent the lower left side of the cylinder C. This reservoir 44 may be of relatively small capacity. An air vent pipe 45 is shown extending upwardly from this reservoir.

A conduit 46 is in fluid communication with the cylinder i portion 10 above the level of the conduit leg 36, which conduit extends downwardly to the reservoir 44 terminating a short distance under the top 47 thereof. A conduit 48 serves as a vent line and extends from a bore formed in the wall of the cylinder portion 11 slightly below the body shoulder 32 of the reservoir 44, extending through the top 47 of the reservoir to terminate a short distance above the bottom 49. A cylindrical hydraulic accumulator 51 may be provided, which accumulator is shown connected by a conduit 52 to the bottom 37 of the dome 12. A check valve 53 permitting downward flow of fluid is shown incorporated in the conduit 52 for reasons which will hereinafter be explained.

The piston P, for reasons that will hereinafter be explained, is preferably not' formed as a single unit, but includes an annular head 55 and a cylindrical skirt 56. The head 55 has an annular flange 57 of somewhat smaller diameter extending downwardly therefrom, and forms a body shoulder' 5S with thc upper portion of the head 55. The skirt 56 is formed as a cylindrical shell that slidably engages the exterior surface of the flange 57. Suitable fluid sealing such as rings may be positioned on the exterior surface of the skirt in a conventional manner. The interior surface of the cylindrical shells 10 and 11 should be given a highly polished surface whereby the skirt 56 may be easily slidable therein.

The operation of my invention is extremely simple. Hydraulic fluid is supplied to the device through the conduit 22. This conduit 22 is connected to a pressure tank (not shown) having an air cushion formed therein, which tank is supplied with hydraulic fluid from a conventional pump (not shown). As hydraulic fluid is forced through the conduit 22 with the valve sleeve 25 in the position shown in Figure 1, the fluid passes through the bore 26 into the confines of the cylinder C. The piston P is thereby F caused to move upwardly at a velocity dependent upon the rate of flow of the hydraulic fluid entering the cylinder C through the conduit 22. As the piston P moves upwardly, the polished rod R is likewise moved upwardly, as well as the sucker rod attached to the polished rod. Thus, the

One or more horipump situated at the bottom of the well is actuated to take a pumping stroke.

The piston P continues upwardly under the influence of the hydraulic fluid being admitted to the cylinder C until the piston P has assumed the position shown in Figure 2. Hydraulic fluid is then admitted into the upper end of the conduit 35 and flows downwardly therein past the check valve 41 into the annular space 61 formed between the interior surface of the counterbore 31 and the exterior surface of the cylindrical guide 30. The hydraulic fluid in the space 61 may pass through the port 34 and slots 25a so as to exert upward pressure on the horizontal surfaces 25b, 27a and 28a. Since the area provided by the surfaces 25h, 27a and 28a is greater than the annular horizontal surface 62 formed on the upper end of the sleeve 25, the sleeve 25 is caused to move upwardly into the position shown in Figure 2 under the influence of hydraulic fluid admitted to the space 61. As the valve sleeve 25 is moved to its upper position, the port 26 is brought into horizontal alignment with the discharge conduit 23.

The weight supported by the sucker rod S and polished rod R causes the piston P to immediately start to descend whereby hydraulic fluid will be discharged through the conduit 23; the port 26 having been brought into alignment therewith. As the piston P starts to descend on its down stroke, upwardly directed hydraulic pressure is maintained on the sleeve surfaces 27a, 28a, and the lower end surface of the sleeve, since the check valve 41 positively restrains any upward flow of hydraulic fluid in the conduit 35. The check valve 41 at all times, however, permits flow of hydraulic fluid from the conduit 35 into the cylinder C. Thus, after the piston P has moved downwardly to the position shown in Figure 3, there is no longer appreciable hydraulic pressure above the piston P, and a portion of the hydraulic fluid in the conduit 35 below the check valve 41 will flow through the check valve 40 into the confines of the cylinder C. As such flow of hydraulic fluid takes place the pressure on the sleeve surfaces 25b, 27a and 28a is reduced to substantially the pressure existing above the piston P in the cylinder C. Hence, the valve sleeve 25 will move downwardly under the influence of the hydraulic pressure exerted on the upper horizontal end 62 thereof to the position shown in Figure 3.

It should be noted that as the piston P is moved upwardly by hydraulic fluid being admitted to the cylinder C, the air situated above the piston in the cylinder is compressed and escapes therefrom by flowing downwardly through the conduit 46 to the reservoir 44. The air escapes from the reservoir 44 by passing outwardly therefrom through the vent 45. It will be apparent from the drawing that any hydraulic fluid remaining above the piston P may also flow downwardly from the conduit 46 to the reservoir 44. However, the internal diameter of the conduit 46 is relatively small in comparison to the internal diameter of the conduit 52, and the major portion of any hydraulic fluid disposed above the piston P will be displaced over the baille 13 into the dome portion 63. The fluid displaced into the dome portion 63 may flow downwardly therefrom through the conduit 52 to the accumulator tank 51. The conduit 52 serves as a scavenger line to return hydraulic fluid that may have reached a position above the piston P in the cylinder C to the hydraulic system. The check valve 53 permits only downward flow of hydraulic fluid in the conduit 52. The scavenged fluid may be transferred from the tank 51 to the aforementioned pressure tank (not shown), as by means of a conventional scavenger pump (not shown).

As the piston P starts its downward stroke in the cylinder C a vacuum tends to be formed therein, which vacuum is relieved by air flowing upwardly from the reservoir 44 through the conduit 46 to equalize the air pressure above the piston P with that of the atmosphere. If hydraulic fluid should accumulate in the reservoir 44 to the extent that the lower end of the conduit 46 is under the surface in has been raised to a predetermined point.

The conduit 48 serves substantially the same function for the annular space above the

collars

27 and 28, and the interior surface of the counterbore 31 and valve sleeve 25, as conduit 46 does for the space in the cylinder C above the piston P; that is, it serves to transfer fluid from said space to the reservoir 44.

It will be apparent that should the piston P be formed in one piece, and the polished rod R or the sucker rod S aixed thereto break, that the piston could be caused to move upwardly in the cylinder C with suliicient velocity as to do considerable damage to the upper portion thereof. To eliminate this danger the piston P is formed of two component parts, the head 5S, and the skirt 56.

In moving the piston P upwardly, the hydraulic uid exerts upward pressure on the surface of the lower annular edge of the flange 58 as well as on the bottom surface of the head 55. The combined areas of these two surfaces are considerably greater than the surface area of the lower annular edge of the skirt 56, with the result that upon the breakage of the polished rod R or the sucker rod the upward force exerted upon the head 55 by the hydraulic uid in the cylinder C is considerably greater than the upward force exerted upon the skirt 56. This force differential permits the head 55and skirt 56 to separate whereby hydraulic uid is allowed to flow upwardly to the top of the cylinder C and escape through the

conduits

46 and 52. After the piston P has separated into its two component parts, the skirt 56 drops downwardly to contact the upper edge of the sleeve 25 and cause the sleeve to move to the closed position shown in Figure 2. With the sleeve 25 in the closed position, hydraulic uid is prevented from entering the cylinder C, and there is no possibility of the polished rod R and the sucker rod S afxed thereto reciprocating after a break has occurred in either of these rods.

In the operation of my device the time interval at the top of the stroke before the piston P starts downwardly may be controlled by the throttle or speed valve 42. vWith the valve 42 adjusted so as to restrict the flow of hydraulic iluid in the conduit 35, a greater time interval is required to raise the valve sleeve 25 Ato the position shown in Figure 2', at which position fluid can escape from the cylinder C through the conduit 23, and the piston P allowed to start its downward stroke. Likewise the time interval at the bottom of the stroke may be controlled by regulating the quantity of hydraulic lluid admitted into the cylinder C through the conduit 22.

Referring now to Figures 4 and 5, there is shown a modied form of pump jack embodying the present invention. In its general arrangement this embodiment is seen to comprise a vertical elongated cylinder C' mounted on a tripod T; the latter having its legs resting upon a base B. A piston P' is slidably movable within the confines of the cylinder C', and is aixed to the upper end of a polished rod R in a conventional manner. The base B also mounts a two-stage pressure tank and a conventional centrifugal pump 72.

It will be apparent that the general arrangement of the modified embodiment of the invention is similar to that of the embodiment disclosed in Figures l, 2 and 3. The major point of the departure of this embodiment is the incorporation of novel means for disposing of the hydraulic fluid remaining in the cylinder above the piston after the latter has undergone a pressure stroke. As set forth hereinbefore, with the arrangement of Figures l,

d 2 and 3 a separate scavenger pump must be utilized to return spent hydraulic fluid from the scavenge fluid tank 51 to the pressure tank (not shown) whereby such Huid may be recirculated. The embodiment of Figures 4 and 5 completely eliminates the need for such a scavenger pump.

Referring again to Figures 4 and 5, the cylinder C' is preferably fabricated in three portions; an upper portion 74, an intermediate portion 76, and a lower portion 78. The upper cylinder portion 74 includes a totally enclosed dome Stb formed on its upper end. The three cylinder portions may be interconnected by means of complementary sets of

anges

82 and 84, which flanges may be secured together by conventional fastening means, such as bolt and nut combinations 85. The lower end of the lower cylinder portion 78 is provided with a stuffing box S6 of conventional design through which the polished rod R may reciprocate.

Hydraulic fluid may be admitted into the cylinder C through a supply conduit 88 which interconnects the intermediate portions 76 of the cylinder and the high pressure section 90 of the pressure tank 70. Hydraulic fluid may be discharged from the cylinder by means of a discharge conduit 92 which interconnects the intermediate portion of the cylinder with the low stage section 94 of the pressure tank 7 0.

A cylindrical valve sleeve 96 is shown coaxially positioned within the lower and intermediate portions of the cylinder, which sleeve cooperates with the supply and discharge conduits S8 and 92 respectively, in a similar fashion to that of the valve sleeve 25 described previously in connection with the embodiment shown in Figures l, 2 and 3. It should be particularly noted, however, that the valve sleeve 96 additionally serves as a means for pumping scavenged fluid from the cylinder to within the low pressure section 44 of the pressure tank 70, in the manner to be hereinafter described.

An elongated U-shaped conduit 98 extends longitudinally along one side of the cylinder C with one leg 98 extending through the wall of the upper cylinder portion 74; another leg 102 extending through the wall of the intermediate cylinder portion 76; and the bottom leg 104 extending through the wall of the lower cylinder portion 7S. The conduit 98 includes a check valve 106 and its leg 102 includes a check valve 108. The U-shaped conduit 9S and the three legs cooperate with the piston P and valve sleeve 96 in a similar fashion as does the U-shaped conduit 35 described hereinbefore in connection with the embodiment shown in Figures l, 2 and 3. To this end the conduit 98 may incorporate a throttle or speed valve for the purpose of regulating the time interval occurring at the top of the stroke before the piston P starts downwardly.

A reservoir 112 is shown positioned adjacent the lower end of the upper cylinder portion 74. This reservoir corresponds generally to the reservoir 44 described in connection with the embodiment shown in Figures l, 2 and 3. The upper end of reservoir 112 is connected to the dome 80 by a conduit 114. The upper end of this reservoir is also connected with the extreme upper end of the cylinder C by a second conduit 116. This reservoir is vented as by a vent pipe 113. The conduit 114 serves to conduct spent hydraulic fluid from the dome 30 to the reservoir 112, which iiuid is forced into the dome 80 by the piston P during its upward stroke. The conduit 116 serves to conduct spent hydraulic uid and/ or air trapped above the piston P which cannot be handled by the conduit 114. The lower end of the reservoir 112 is in communication with the low pressure section 94 of the pressure tank 70 by a conduit 120 and a cross tting 122. A check valve 124 is interposed in the conduit 120 and a second check valve 126 is disposed in the cross fitting 122.

Referring now particularly to Figure 5, it` will be noted that the lower cylinder portion 78 includes an enlarged counterbore 124. This counterbore slidably receives a colla1 127 formed on the valve sleeve 96. It should be particularly noted that the surface area of the upper side of the collar 127 is greater than the surface area of the upper side of this collar. The inner periphery of the valve sleeve 96 below the collar 127 has sliding engagement with an annular projection 12S formed upon the upper end of a vertically fitting cylindrical guide 130. An annular projection 132 formed at the lower end of the valve sleeve 96 has a sliding engagement with the inner periphery of the lower cylinder portion 78. A length of small diameter tubing 134 connects the annular space between the guide 13G and the inner periphery of the valve sleeve 96 with the cross fitting 122. It will be noted that the bottom leg of the U-shaped conduit 98 is in communication with the lower end of the counterbore 124. The upper end of this counterbore is in communication with the cross fitting 122 and hence the low pressure section 94 of the pressure tank 70.

The operation of this modified form of this invention is substantially similar to that described in conjunction with the embodiment shown in Figures l, 2 and 3. Thus, hydraulic fluid is conducted into the cylinder through the supply conduit 8S; the valve sleeve 96 being in its lower position as shown in Figure 5. The entry of this hydraulic fluid causes the piston P' to move upwardly within the cylinder, and when the piston has reached the upper limit of its stroke, hydraulic fluid will flow down the U-shaped conduit 98 and through its bottom leg 104 into the counterbore 124. This fluid exerts upward pressure on the underside of the collar 127 so as to cause the valve sleeve 96 to rise. As the valve sleeve is moved into its upper position, its port 136 is brought into horizontal alignment with the discharge conduit 92 whereby the weight supported by the polished rod R will cause the piston l to descend. As the piston descends, the hydraulic fluid disposed thereunder will be discharged through the discharge conduit 92 into the low pressure section 94 of the pressure tank 70.

It should be particularly noted that as the piston P rises during its next stroke any spent hydraulic fluid forced by the piston into the reservoir 112 may enter the counterbore 124 by means of the conduit 120 and its cross fitting 122; the valve sleeve 96 and its collar 126 being disposed at their lower position shown in Figure 5. Hence', when the valve sleeve is again urged upwardly the spent hydraulic fluid disposed in the counterbore 124 will be pumped therefrom to the cross fitting 122, and thence into the pressure section 94 of the pressure tank 70. Accordingly, it is not necessary to supply a scavenger pump for the purpose of forcing spent hydraulic fluid into the pressure tank.

The valve sleeve collar 127 cooperates with the counterbore 124 not only as a pump for returning scavenged fluid to the pressure tank, but also as an air pump. In this regard, it is essential that some means be provided to force air into the low pressure section 94 of the pressure tank. Such air is necessary to replace that lost from the fluid entering the cylinder from the high pressure section 9i) as its pressure is lowered at the end of the pressure stroke of the piston. Since the air pumped by the valve sleeve collar 127 into the low pressure section 94 may create an air cap within this section, it is desirable to incorporate a pressure relief valve 138 at the upper portion thereof. A similar pressure relief valve 140 may be mounted at the upper end of the high pressure section of the pressure tank in order to take care of the air cap created therein.

The fact that the valve sleeve collar 127 and the counterbore 124 will act as an air pump is insured by the fact that the upper surface area of the collar is greater than the surface area on the underside thereof whereby the annular space swept by the collar on its upward stroke will be greater than the annular space swept by the collar on its downward stroke. This is important since the major portion of the scavenged fluid will be that which enters below the collar through the conduit 98 and is thereafter returned through this conduit above thc piston P; the latter being in its lowermost position within the cylinder.

The danger of a vacuum lock developing between the projection 132 of the valve sleeve and the lower ends of the cylinder portion 78 is eliminated by the provision of the tubing 134.

Although I have hereinabove described what is presently believed to be the preferred apparatus embodying the present invention, it will be apparent to those skilled in the art that various changes and modifications may be made thereto without departing from the spirit of the invention or the scope of the appended claims.

I claim:

l. A hydraulic pump jack that includes: a vertical cylinder; a piston vertically slidably mounted in said cylinder; a rod extending coaxially downwardly from said piston through the lower portion of said cylinder; a sleeve valve longitudinally movable in the lower portion of said cylinder, with said sleeve being capable of occupying either an upper or lower position, and said sleeve having a port formed therein that permits hydraulic fluid to be introduced into said cylinder when said sleeve is in said lower position and discharged from said cylinder when said sleeve is in said upper position, with said introduction and discharge of said fluid causing said piston to complete an upstroke and downstroke; conduit means in communication with said hydraulic lluid in said cylinder, with said conduit means permitting flow of said fluid to actuate said valve from one position to the other after completion of a stroke by said piston; and a valve in said conduit to control the flow of said fluid therein whereby the time interval between the completion of a stroke by said piston and the start of a stroke by said piston in the other direction can be regulated.

2. A hydraulic pump jack that includes: a vertical cylinder; a piston vertically slidably movable in said cylinder; a rod extending coaxially downwardly from said piston through the lower portion of said cylinder; a hydraulically operated sleeve valve coaxially movably mounted in the lower portion of said cylinder, with said sleeve when in the lower position permitting fluid to be introduced into said cylinder to cause said piston to complete an upstroke, and said sleeve when in the upper position permitting said fluid to be discharged from said cylinder to cause said piston to complete a downstroke; a conduit permitting hydraulic fluid in said cylinder to move said sleeve from said lower to said upper position after said piston has completed an upstroke; and a valve in said conduit to control the flow of hydraulic fluid therein whereby the time interval between the completion of a stroke by said piston and the start of a stroke by said piston in the other direction can be regulated.

3. A hydraulic pump jack that includes: a vertical cylinder; a piston vertically slidably movable in said cylinder; a rod extending coaxially downwardly from said piston through the lower portion of said cylinder; a hydraulically operated sleeve valve coaxially movably mounted in the lower portion of said cylinder, with said sleeve when in the lower position permitting fluid to be introduced into said cylinder to cause said piston to complete an upstroke, and said sleeve when in the upper position permitting said fluid to be discharged from said cylinder to cause said piston to complete a downstroke; a conduit permitting hydraulic fluid in said cylinder to move said sleeve from said lower to said upper position after said piston has completed an upstroke; a valve in said conduit to control the flow of hydraulic fluid therein whereby the time interval between the completion of a stroke by said piston and the start of a stroke by said piston in the other direction can be regulated; a reservoir; and a plurality of conduits in communication with the upper portion of said cylinder, with one of said con- 9 duits serving as an air vent for said cylinder, and another of said conduits serving to have hydraulic iluid that may have by-passed said piston discharged therein on the upstroke of said piston, with said fluid being conducted by said conduit back to the reservoir from which said hydraulic fluid actuating said piston is stored.

4. A hydraulic pump jack that includes: a vertical cylinder; a piston vertically slidably movable in said cylinder; a rod extending coaxially downwardly from said piston through the lower portion of said cylinder; a dome formed in the upper portion of said cylinder; a baffle formed in said dome; a hydraulically operated sleeve valve coaxially movably mounted in the lower portion of said cylinder, with said sleeve when in the lower position permitting uid to be introduced into said cylinder to cause said piston to complete an upstroke and said sleeve when in the upper position permitting said liuid to be discharged from said cylinder to complete a downstroke; a conduit extending from the upper portion of said piston to the bottom thereof,'with said conduit permitting a portion of said lluid used in raising said piston to ow therethrough to raise said sleeve to the upper position; a valve in said conduit to control the ilow of hydraulic Huid therein whereby the time interval between the completion of va stroke by said piston and the start of a stroke by said piston in the other direction can be regulated; a reservoir; conduit means leading from said cylinder to said reservoir and said conduit means venting said cylinder and permitting hydraulic fluid ow to and from said reservoir; and a discharge conduit leading from the lower portion of said dome, with said conduit conducting hydraulic fluid discharged over said baffle on the upstroke of said piston to a container whereby said iluid is returned to the hydraulic iiuid used in actuating said piston.

5. A hydraulic pump jack, comprising: a vertical cylinder; a piston vertically slidably movable in said cylinder; a rod extending coaxially downwardly from said piston through the lower portion of said cylinder; a hydraulically actuated sleeve valve coaxially movably mounted in the lower portion of said cylinder for movement between a first and a second position, said sleeve valve when in its first position permitting uid to be introduced into said cylinder to thereby cause said piston to undergo a stroke, and said sleeve valve when in its second position permitting said iluid to be discharged from said cylinder whereby said piston may return to its original position; and conduit means permitting iluid in said cylinder to move said sleeve valve from its rst to its second position after said piston has undergone a stroke.

6. A hydraulic pump jack, comprising: a vertical cylinder; a piston vertically slidably movable in said cylinder; a rod extending coaxially downwardly from said piston through the lower portion of said cylinder; a hydraulically actuated sleeve valve coaxially movably mounted in the lower portion of said cylinder for movement between a first and a second position, said sleeve valve when in its first position permitting uid to be introduced into said cylinder to thereby cause said piston to undergo a stroke, and said sleeve valve when in its sec-l ond position permitting said fluid to be discharged from said cylinder whereby said piston may return to its original position; a radially extending surface formed on said sleeve valve; a port formed in said cylinder below the highest point reached by said piston during its stroke; a second port formed in said cylinder below the underside of said radially extending surface; and conduit means interconnecting said ports permitting uid in said cylinder to move said sleeve valve from its rst to its second position after said piston has undergone a stroke.

7. A hydraulic pump jack, comprising: a vertical cylinder; a piston vertically slidably movable in said cylinder; a rod extending coaxially downwardly from said piston through the lower portion of said cylinder; a hydraulically actuated sleeve valve coaxially movably mounted in the lower portion of said cylinder for movement between a first and a second position, said sleeve valve when in its irst position permitting uid to be introduced into said cylinder to thereby cause said piston to undergo a stroke, and said sleeve valve when in its second position per mitting said fluid to be discharged from said cylinder whereby said piston may return to its original position; a radially extending projection formed on said sleeve valve; an enclosed compartment in said cylinder wherein said projection is reciprocated upon movement of said sleeve valve between its first and second positions whereby said projection and compartment may cooperate to serve as pumping means; and conduit means permitting uid in said cylinder to move said sleeve valve from its lirst to its second position after said piston has undergone a stroke.

8. A hydraulic pump jack, comprising: a cylinder; a piston slidably movable in said cylinder; a hydraulically actuated sleeve valve movably mounted in said cylinder for movement between a first and a second portion, said sleeve valve when in its rst position permiting fluid to be introduced into said cylinder to thereby cause said piston to undergo a stroke, and said sleeve valve when in its second position permitting said fluid to be discharged from said cylinder whereby said piston may return to its original position; a radially extending collar formed on said sleeve valve; a counterbore in said cylinder wherein said collar is reciprocated upon movement of said sleeve valve between its first and second positions whereby said collar and counterbore may cooperate to serve as pumping means; a port formed in said cylinder below the highest point reached by said piston during its stroke; a second port formed in said cylinder below the underside of said radially extending surface; and conduit means interconnecting said ports permitting fluid in said cylinder to move said sleeve valve from its irst to its second position after said piston has undergone a stroke.

9. A hydraulic pump jack, comprising: a cylinder; a piston slidably movable in said cylinder; a hydraulically actuated sleeve valve movably mounted in said cylinder for movement between a rst andv a second portion, said sleeve valve when in its first position permitting fluid to be introduced into said cylinder to thereby cause said piston to undergo a stroke, and said sleeve valve when in its second position permitting said fluid to be discharged from said cylinder whereby said piston may return to its original position; a radially extending collar formed on said sleeve valve; a counterbore in said cylinder wherein said collar is reciprocated upon movement of said sleeve valve between its rst and second positions whereby said collar and counterbore may cooperate to serve as pumping means, said sleeve valve being proportioned whereby the radially extending surface of the upper side of said collar Vis greater than the radially extending surface of the underside of said collar; a port formed in the upper portion of said cylinder below the highest point reached by said piston during its stroke; a second part formed in said cylinder in the lower portion of said counterbore; and conduit means interconnecting said ports permitting uid in said cylinder to move said sleeve valve from its first to its second position after said piston has undergone a stroke.

10. A hydraulic pump jack, comprising: a cylinder; a piston slidably movable in said cylinder; a hydraulically actuated sleeve valve movably mounted in said cylinder for movement between a rst and a second portion, said sleeve valve when in its first position permitting fluid to be introduced into said cylinder to thereby cause said piston to undergo a stroke, and said sleeve valve when in its second position permitting said iluid to be discharged from said cylinder whereby said piston may return to its original position; a radially extending projection formed on said sleeve valve; an enclosed compartment in said cylinder wherein said projection is reciprocated upon movement of said sleeve valve between its first and second positions whereby said projection and compartment may cooperate to serve as pumping means; a tank from which uid for moving said piston is withn drawn, said compartment being in communication with the upper end of said cylinder and with said tank and conduit means permitting fluid in said cylinder to move said sleeve valve from its first to its second position after said piston has undergone a stroke and uid entering said compartment from the upper end of said cylinder to be pumped into said tank.

1l. A hydraulic pump jack, comprising: a cylinder; a piston slidably movable in said cylinder; a hydraulically actuated sleeve valve movably mounted in said cylinder for movement between a first and a second portion, said sleeve valve when in its first position permitting Huid to be introduced into said cylinder to thereby cause said piston to undergo a stroke, and said sleeve valve when in its second position permitting said iiuid to be discharged from said cylinder whereby said piston may return to its original position; a radially extending collar formed on said sleeve valve; a counterbore in said cylinder wherein said collar is reciprocated upon movement of said sleeve valve between its first and second positions whereby said collar and counterbore may cooperate to serve as pumping means; piping means connecting said counterbore with the upper portion of said cylinder whereby any uid which may have by-passed said piston may flow downwardly into said counterbore; a check valve in said piping means preventing upward movement of by-passed uid from said counterbore into said cylinder; a tank from which fluid for moving said piston is withdrawn, said counterbore being in communication with the upper end of said cylinder and with said tank; a second check valve interposed between said tank and said counterbore permitting fluid to travel only from said counterbore into said tank; a port formed in the upper portion of said cylinder below the highest point reached by said piston during its stroke; a second port formed in said cylinder in the lower portion of said counterbore; and conduit means interconnecting said ports permitting fluid in said cylinder to move said sleeve valve from its first to its second position after said piston has undergone a stroke and uid entering said counterbore from the upper portion of said cylinder to be pumped into said tank.

References Cited in the tile of this patent UNITED STATES PATENTS 539,339 Breitenstein May 14, 1896 1,811,737 Van Bezel June 23, 1931 1,813,930 James July 14, 1931 2,185,448 Suter Jan. 2, 1940 2,195,208 Cornelius Mar. 26, 1940 2,481,623 Rued Sept. 13, 1949 2,527,915 Cherry et al Oct. 31, 1950