US2874641A

US2874641A - Pump jack

Info

Publication number: US2874641A
Application number: US503736A
Authority: US
Inventors: Albanis P Mccandlish; William T Tallon
Original assignee: Recovery Oil & Gas Co Inc
Current assignee: Recovery Oil & Gas Co Inc
Priority date: 1955-04-25
Filing date: 1955-04-25
Publication date: 1959-02-24
Anticipated expiration: 1976-02-24

Description

A. P. MCCANDILISH ET AL 2,874,641

Feb. 24, 1959 PUMP JACK 6 Sheets-Sheet 1 Filed April 25. 1955 INVENTORS.

Feb. 24, 1959 A. P. M cANbusH ET AL 2,874,

PUMP JACK 6 ShgZcs-Sheet 2 5. 2 l i T P A d e l i F l Tu INVENTORS. EZ'ZZ'MZ l'mroeui's Feb. 24, 1959 A; P. M CANDLISH ET AL PUMP JACK 6 Sheets-Sheet 3 Filed April 25, 1955 PINIEN:ORS.. wjfizm .JMZW

Feb. 24, 1959 A. P. MOCANDLISH ETAL PUMP JACK 6 Sheets-Shet 4 Filed April 25, 1955 Y INVENTORS. MMZJ 1mm a ATTORNEYS Feb. 24, 1959 A. P. MOCANDLISH ET AL 2, 7

PUMP JACK Filed April 25, 1955 e Sheets-Sheet s IN V EN TORS.

AT TOHA/E Y5 Feb. 24, 1959 A. P. MGCANDLISH ET AL 2,

PUMP JACK Filed April 25, 1955 6 Sheets-Sheet 6 B2 m YE I 7??YZVTORS I M243 4% United S e Patent ghpas Co., Inc., Cincinnati, Ohio, a corporation of to Application April 25, 1955, Serial No. 503,736

8 Claims. (Cl. 103-46) This invention relates to pumping apparatus and is dirooted in particular to a hydraulically operated pump jack for oil wells.

One of the objectives of the invention is to provide a hydraulically operated pump jack of substantially simplified construction which may be manufactured and sold at a comparatively low cost,

' Another objective is to provide a pump jack which is considerably smaller in size than the pumping apparatus heretofore available.

I A further objective is to provide a pump jack which is adapted to be mounted directly upon the head of an oil well casing so that it is unnecessary to provide special platform installations for supporting and mounting it.

Another objective is to provide a hydraulically operated pump jack incorporating a novel heat exchanger which utilizes the production oil to cool the hydraulic fluid by means of which the pump jack is actuated.

An additional objective is to provide a pump jack which is fully automatic in operation and which includes simplified controls to vary the speed, acceleration and deceleration of the pumping stroke whereby the hammering" effect of a high pressure hydraulic system which occurs upon rapid reversal of flow is avoided.

Other objectives and advantages of the present invention will be readily apparent to those skilled in the art from the following detailed description of the drawings I in which:

view taken on Figure 6 is a fragmentary cross sectional view taken on the line 66 of Figure 4.

Figure 7 is an enlarged fragmentary view taken on the line 7-7 of Figure 4.

Figure 8 is a fragmentary cross sectional view taken on the line 8-8 in Figure 7.

Figure 9 is a diagrammatic side view of the unit showing it at the start ofa lift stroke.

Figure 10 is a view similar to Figure 9 showing the unit near the end of the lift stroke.

Figure 11 shows the unit at the start of a down stroke.

Figure 12 shows the unit near the end of the down stroke.

Figure 13 is a diagrammatic view illustrating the hy-,

draulic system of the unit.

The pump jack, which is designated generally by the numeral 10, is adapted to be installed as a unit on top of the head 11 of a well casing. The prime mover, in-

dicated generally at 12, for the pump jack is mounted upon 2,874,641 Patented Feb. 24, 1959 jack and a valve device 19 which is disposed between the heat exchanger and the power cylinder. These elements are aligned vertically on a common axis.

A base plate 20 is provided for mounting the pump jack on top of the head of the well. The base plate stands upon a plurality of heavy leveling screws 21 which are threaded down through tapped bores in the base plate and which rest upon an adapter ring 22 wihch is seated upon and which surrounds the top of the well head. The leveling screws are locked by nuts 23 which are tightened down onto the top of the base plate. It will be seen that by adjusting the respective screws, the base plate may be leveled with respect to the vertical axis of the well head. The base plate is slotted at one side to accommodate a tubular adapter fitting 24 which extends upwardly from the head 11 surrounding a polish rod 25 which is con nected, at its lower end, in the usual manner to the string of sucker rods which extend down to the bottom of the well. A conventional stufiing box 26 is provided at the top of the adapter tube to provide a seal for polish rod 25. The adapter fitting provides a means of clamping the pump jack in place. For this purpose a clamp block 27 is welded or otherwise secured to the base plate 20. The clamp block is made in two parts, one of which is adapted to be drawntoward the other by means such as screws 28 to tightly grip the adapter fitting. A similar clamp block 29 is provided adjacent to the upper end of the heat exchanger 18. The pump jack has a clevis 30 at its lower end which is engaged over the upper edge of a mount bracket 31. A pin 32 is engaged in the clevis and passes through an appropriate bore in the bracket, this pin being held in place by means such as cotter keys. The mount bracket may be formed as a part of the base plate or may be welded to it as shown. The pivot provided at the clevis structure provides a convenient means for installing the pump jack. The clevis may be engaged over the mount bracket and the pin 32 put in place while the pump jack is still laying in a substantially horizontal position. With the pin engaged, the pump assembly may be swung up into the vertical position shown in the drawings and then attached by means of

clamp blocks

27 and 29 to the adapter fitting 24. a

The sprocket assembly 17 comprises a heavy, rectangular post 33 having a bore 34 in the bottom thereof which fits over the upper end 35 of the piston 16. Post 33 mounts a cross shaft 36 which projects from the opposite sides thereof. A pair of sprocket wheels 37-38 are rotatably journalled upon the respective opposite ends of cross shaft 36. The two sprocket wheels are identical and each engages a chain 39 which passes over the top of the Wheel. One end of each chain is attached at one side of the pump jack to a tie bar 40, through an appropriate bracket. Bar 40 extends down along the pump jack to the bottom of the heat exchanger where it is anchored securely to mount bracket 31 by means such as a cross pin 41. The opposite ends of the respective chains 39 are secured to a yoke 42 by means such as pins 43-43. See Figure 2. The yoke has a vertical central bore in it through which the polish rod 25 projects. A spacer sleeve 44 surrounds the polish rod 25 above yoke 42. The sleeve extends upwardly beyond the two sprocket wheels and engages the underside of a clamp block 45 which is securely attached to the polish rod. A clamp block 46 similar to clamp 45 is secured to the polish rod below the yoke 42 and in spaced relationship therewith. Clamp 46 constitutes a safety device, which at the time of installation of the pump jack, rests upon top of the stuffing box .26 to carry the weight of the string of sucker rods. During the pumping operation the Weight of the string is carried by the upper one of the two clamps and by the spacer sleeve which is installed on the polish rod between upper clamp 45 and yoke 42.

It will be seen, therefore, that upward movement of the

sprocket wheels

37 and 38, which is the pumping movement of the jack, will result in a 2 to 1 ratio between the movement of the polish rod and the stroke of the piston 16 inasmuch as the opposite ends of chains 3? are anchored to the tie bar 40. It will be noted also that the clevis pin 32, by means of which the pump assembly is attached to mount bracket .31, .is directly below the central axis of cross shaft 36 and that the chains 39 at the one side of the sprocket wheels are in direct vertical alignment with the polish rod, whereas the chains at the opposite side of the sprocket wheels are in direct vertical alignment with the tie bar and the point at which it is anchored to mount bracket 31 by means of the cross pin 41. Thus the forces exerted in moving the sprocket head upwardly in a pumping stroke are all vertical in direction and are all borne by the base plate, so that little or no force is borne by fitting 24.

The valve block 19, being interposed between power cylinder and heat exchanger 18 provides a rigid mount for both of these members. The power cylinder comprises a cylindrical tube 47, respective upper and lower end blocks 48 and 49 and four tie rods indicated at 50. Upper end block 48 has an annular groove 51 in its underside which seats the upper rim of the cylinder 47. Lower end block 49 has a similar groove 52. The fit between the lower end of the cylinder and end block 49 must be such as to withstand the pressure of the hydraulic fluid which actuates the pump jack. Thus, appropriate packing may be used or the lower end of the cylinder may be brazed or welded into place in groove 52. A stufiing box 53 is mounted upon top of upper end block 48 and it includes an appropriate gland for the piston rod 35 which extends upwardly through the box and through end block 48. The upper ends of the respective tie rods 50 project through appropriate, aligned bores in the end block and in the stufling box, and are threaded to receive nuts 54 which are tightened down on top of the box. The lower ends of the rods 50 extend through aligned bores in end block 49, the valve block 19 and they respectively thread .into tapped bores which are provided in an end cap 55 which encloses the upper end of a barrel 56 which is part of the heat exchanger assembly 18. The tie rods thus hold the assembly together. In addition, their use simplifies the construction and assembly of the power cylinder inasmuch as the parts may be built up and assembled one on top of the other from the heat exchanger upwardly. The inside of the cylinder 47 is polished and it encloses a head 57 for piston 16 which has a plurality of piston rings 58 thereon to seal the head with respect to the inside of the cylinder. The piston head may be formed as an integral part of the piston rod or it may be made as a separate part and attached to the rod by known means.

The valve block 19 which is employed encloses a threeway pilot operated directional valve system of the sliding spool type. Essentially the pilot system is used to slide the spool from one side of the block to the other in order to alternately direct hydraulic pressure fluid to the power cylinder and to exhaust such hydraulic fluid. In referring to the valve, the side adjacent to the stufiing box 26 which is at the top of'the adapter fitting 24 will be designated the front. The valve is machined from a rectangular block of steel, and it has a substantially large cylindrical bore 60 which extends through it from one side to the other. The center of the cylindrical bore, in the middle of the block, is recessed to provide an enlarged annular chamber 61 which is concentric to the bore. Immediately to the left of chamber 61 there is an identical chamber 62 which will be referred to as the power chamber. Immediately to the right of chamber 61 there is another, identical chamber 63 which will be referred to as the exhaust chamber. During the operation of the pump jack the middle chamber 61 alternately is in communication with chamber 62 and with chamber 63.

Hydraulic fluid under pressure is admitted into the valve block through a bore 64 which extends into the block from the back thereof. The inner end of this bore, as shown in Figure 6, intersects power chamber 62 on the underside thereof. The outer end 65 of bore 64 is threaded in order to receive a standard coupling which is at the end of the conduit 13. The exhaust chamber 63 opens into a passageway 66 which extends downwardly through the block to its underside. The central chamber 61 has three passageways extending vertically upwardly from it. The passageways are each indicated by the numeral 67 and they are in communication through three, aligned bores (which pass through the lower end block of the cylinder assembly) with the inside of the power cylinder. The juncture between .lower end block 49 and the top of the valve block is sealed by means of an O ring 68 which resides in an annular groove 69, cut in the upper face of the block, surrounding the three passageways 67. v

Hydraulic fluid is alternately directed to and exhausted from the power cylinder by means of a sliding spool 70 which resides in cylindrical bore 60. The spool mcludes two

cylindrical heads

71 and 72 which are connected at a neck 73 which is of substantially smaller diameter than the heads of the spool. The spool has an axial bore 74 extending through it from one end to the other. A shaft 75 passes through the bore and extends beyond the two opposite sides of the valve block. 0 rings 76 and 77, which reside in the internal grooves in the spool adjacent to its opposite ends, seal the shaft with respect to the internal bore 74 through the spool. Both of the heads of the spool have oil retaining grooves in them according to conventional practice.

From Figure 4 it will be seen that .the overall length of the spool is substantially less than the length of the cylindrical bore 60 through the valve body and that the necked-in connector portion 73 of the spool will permit a flow of hydraulic fluid from the middle chamber 61 into the exhaust chamber 63 when the spool is at the right as shown in this figure. In this position of the spool, the hydraulic fluid is exhausted from the power cylinder through the passageways 67 and into the discharge passageway 66. When the spool is moved in the opposite direction, the exhaust chamber 63 is sealed from the middle chamber 61 and the pressure chamber 62 is in communication with chamber 61 and thus is open to the power cylinder through the passageways 67.

The spool is shifted from one position to the other by means of a pilot system which is controlled by the rotation of the shaft 75. A circular valve body 78 is secured to each one of the two sides of the valve block 19, being bolted thereto in each instance by four screws 79. The shaft 75 passes through both of the valve bodies 78 in closely fitting bores. The left end of shaft 75 has a collar 80 on it which is secured to the end of the shaft by a pin 81. The right end of the shaft has a substantially larger collar 82 on it which is secured to the shaft by a cross pin 83. The respective collars retain the shaft in place but permit it to be rotated. Rotation of the shaft is, however, limited to 45 by a detent 84, which comprises a pin having a head 85 and a stem 86. The stem of the pin is slidably seated in a bore 87 in collar 82, whereas the head 85 resides in an enlarged bore 88 which is coextensive with the bore 87. A helical coil spring 89 is seated within the larger bore surrounding circumferentially of shaft 75. One of these fingers, which is indicated at 90, is engageable by a trip dog 91 when the piston of the power cylinder reaches the upper end of its travel, for conditioning the pilot system, as will be explained, to exhaust the power cylinder. The other finger 92 is actuated by a trip dog 93 when the piston reaches the lower end of its travel in order to condition the pilot system for directing hydraulic pressure into the power cylinder. For this purpose, the shaft 75 has two cross bores in it. One, adjacent to the right end of the shaft, is within the circular valve body and is indicated at 94. The other cross bore, indicated at 95, resides within the circular valve body at the left side of the main valve block. The respective bores are offset at 45 with respect to one another in skew relationship. The bore 94 adjacent to the right end of the shaft, is moved into alignment with a passageway 96 which is diametrically disposed within the circular valve body, when the trip dog 91 engages finger 90 to rotate the shaft in a counterclockwise direction as viewed from the right end. This position is shown in Figure 4. One end of passageway 96 is in communication with the internal cylinder bore 60 of the valve block through a short connector passageway 97 which extends at right angles to passageway 96. The juncture of the relatively small circular valve body and the main valve block is sealed by means of a gasket 98, which gasket has an aperture in it to permit hydraulic fluid to pass through connector passageway 97 from the cylinder bore 60. The juncture of the two passageways 96 and 97 provides a convenient place for installing an adjustable throttle valve for controlling the flow of hydraulic fluid from one passageway to the other. The throttle valve may consist of two set screws 99 which are threaded into a continuation of passageway 96. The inner one of the two set screws provides the throttling action inasmuch as it can be threaded in or out in order to more or less block the juncture between the two passageways. maintaining the setting of the inner one. The two screws are accessible through an enlarged bore 100 which receives a removable plug 101 at its outer end.

The end of the passageway 96 opposite to the throttle valve is in communication with an exhaust passageway 102 by means of a short connector passageway 103, the gasket 98 having an appropriate opening in it at this point. The passageway 102 extends into the main valve block parallel with the axis of shaft 75 to a point near the middle of the block where it is connected by means of a vertical passageway 104 to a circular groove 105 which is cut into the underside of the valve block concentric with the vertical central axis -'of the body. The latter groove as will be seen from Figure 2 passes through or intersects main exhaustpassageway 66.

The pilot valve assembly at the opposite side of the block is substantially identical to the one just described, including a passageway 106 which extends diametrically through-the body of the circular valve body, two

short connector passageways

107 and 108 which are at the respective opposite ends of passageway 106, and a throttling device 109 which is identical to the one previously described. The parts arereversed, however,'so that in the present instance hydraulic fluid is exhausted from connector passageway 108 through a passageway 110 which extends from the left side of the main valve block to the middle of the block in front of bore 60 and The outer set screw provides a means of c na'ted 112 extends to the right.

munication with the annular groove through a vertical passageway 111. Rotation of the shaft in a clockwise direction as viewed from the right end thereof through 45 aligns cross bore 95 with the passageway 106 (at the left of shaft 75) and at the same time misaligns cross bore 94 with respect to the passageway 96 (at the right of shaft 75). It will beseen, therefore, that the ends of the cylinder bore 60 at the opposite ends of the spool 70 are alternately exhausted when the shaft is rotated from one position to the other.

Pressure is admitted into the pilot system through two passageways which extend from opposite sides of the main hydraulic pressure inlet bore 64. One passageway desig- The bore is parallel with shaft 75 and removed 45 from exhaust passageway 102 in a clockwise direction as viewed from the right. Passageway 112 is in communication with a passageway which extends diametrically through the valve body 78 at the right side through a short connector 113 which is similar to connector 103. The pressure passageway which extends diametrically through the small valve body is offset with respect to the exhaust passageway 96 by 45 and therefore is not shown in Figure 4. It will be understood, however, that the end of the pressure passageway through the small valve body is in communication with the internal bore 60 at the right end of the spool 70. The system for directing pressure to the left end of the spool is substantially the same as that at the right end, and in this case hydraulic fluid under pressure flows from inlet bore 64 through a passageway 114 which extends to the left parallel with shaft 75, being removed from exhaust passageway by 45 going in the clockwise direction as viewed from the left. Passageway 110 is in communication with a diametrically disposed pressure passageway 115 through a short connector 116. The relationship of the exhaust system relative to the pressure system at the left side of the valve is shown in Figure 5. As shown, the

pressure passageway 115 slants upwardly toward the back of the valve body, whereas the exhaust passageway extends across theshaft 75 substantially horizontally. In the position shown, the cross bore 95 is in alignment with the diametrically disposed pressure passageway 115 so that fluid under pressure may flow from the main inlet 64 through

passageways

114, 116, 115 and the cross bore 95 to a connector passageway 117 which opens into the in ternal bore 60 at the left end of the spool.

Starting with the valve in the condition shown in Figure 4 one cycle proceeds as follows. In the instance shown the shaft 75 has been rotated through 45 in the counterclockwise direction as viewed from the right, having been turned by the trip dog 91 in contacting finger 90. The right end of the bore 60 is open to exhaust through cross bore 94 and the respective passageways previously described. At the same time cross bore 95 at the left side is aligned with pressure passageway 115 and is in communication with inlet bore 64 through the passageways previously described so that hydraulic fluid underpressure may flow into the cylinder bore 60 at the left side of the spool. This moves the spool to the right (as shown) so that the pressure chamber 62 is blocked with respect to the central chamber 61. Under these circumstances, hydraulic fluid may flow from the power cylinder through the central chamber 61 and through exhaust chamber 63 down through exhaust passageway 66. The latter passageway opens into a heat exchanger tube 118 to be described in detail later. The How of fluid from passageway 66 into the heat exchanger tube is throttled by means of a needle valve 119 (Figure 8) which is threaded into the valve block from the right side, parallel to the spool and directly under it. The outer end of the needle valve has a cross slot 120 in it which is exposed to the outside of the valve block so that the needle may be adjusted by means of a screw driver. The needle valve projects through exhaust passageway 66 and is engageable at its parallel with shaft 75. .The latter passageway is in com- 75 inner endwitha conical seat 121 throughwhich fluid'flows from passageway 66 and through a connector bore 122 into "the heat exchanger tube 118. The needle valve 119 controls the rate of flow of fluid from the power cylinder at the time the piston is moving down to lower the string of sucker rods into the well and, therefore, constitutes an important adjustment which smooths out the action of the pump jack "in the exhaust part of the cycle.

When the piston reaches the lower end of its stroke the trip dog 93 is in position to engage the finger 92 for turning the shaft 95 through 45 in the clockwise direction as viewed from the right. This misaligns the cross bore 94 at the right with the exhaust passageway 96 and aligns it with the pressure passageway. Thus, hydraulic fluid may flow from the inlet 64 and through the passageways previously described into the right end of the internal bore 60 to shift the spool to the left. At the same time, cross bore 95, at the left of shaft 75 is aligned with'passageway 106 to connect the left end of spool 70 to the exhaust system previously described. With the spool shifted to the left the exhaust chamber '63 is blocked with respect to the center chamber 61, and the center chamber 61 is opened to the pressure chamber 52. Therefore, hydraulic fluid may flow from the inlet bore 64 through chamber-62 and chamber 61 into the vertical passageways 67 and thence into the power cylinder to raise the piston and therefore lift the string of sucker rods.

The two

trip dogs

91 and 93 are mounted upon a bar 123 which is rigidly secured at its upper'end to a bracket 124 by means such as bolts 125. The bracket is, in turn, bolted to the post 33 (which mounted the sprocket wheels and which is seated upon the upper end 35 of the piston rod). The bracket extends to the right from the back of post 33. Bar 123 depends vertically from the bracket down alongside of the power cylinder so that its lower end is to the right of the valve block 19 and is in back of the

fingers

90 and 92. The rod is T-shaped in cross section and is guided adjacent to its lower end in a dovetail slot defined by a pair of guide members 126 which are bolted to an arm 127. The arm is secured to the back of the valve block by means of screws 128 which pass through the arm and through a spacer block 129 and thread into a tapped bore provided at the back of the valve block. The two trip dogs are secured to bar 123 in vertical spaced relationship which defines the length of the stroke of the piston in cylinder 47. However, due to the 2 to 1 ratio obtained by the sprocket and chain apparatus, the spacing of the two trip dogs is just one half the length of the stroke of the polish rod. The two trip dogs are offset with re- :spect to one another so that the lower trip dog 91 is in vertical alignment with the finger 90 and the upper trip dog 93 is in vertical alignment with the finger 92. Hence, the trip dog 91, in engaging finger 90 at the top of the piston stroke, starts the exhaust part of the cycle; whereas the upper trip dog 93 in contacting finger 92 at the bottom of the piston stroke starts the pressure part of the pump cycle.

The valve block is seated directly upon top of the cap 55 of the heat exchanger barrel. The cap comprises a rectangular block of metal which has a vertical bore therein to accommodate the heat exchanger tube 118. In addition, the cap has a bore 130 through which production oil flows into the barrel around the heat exchanger tube. The bore 130 is connected by means of a coupling 131 to the inside of the adapter fitting 23. Thus, oil (or other liquids) raised by the pump into the adapter fitting flows through bore 130 and empties into the barrel of the heat exchanger. The production oil flows out of the lower end of the heat exchanger barrel through an outlet pipe 132. The heat exchanger tube is configurated into a double helical coil such that the tube extends downwardly through the center of the heat exchanger barrel and is then turned back upon itself and wound helically upwardly to a point adjacent to the upper end of the barrel where it is again reversed and wound in the opposite direction helically downwardly to terminate adjacent to the lower end of the heat exchanger barrel at a coupling 133 to which the exhaust conduit 14 is attached. The heat exchanger coil may be made in any shape so long as a large surface is exposed to the production oil flowing from the well. The coil shape described is shown in Figure 13. A bypass conduit 134 is provided to permit hydraulic fluid which leaks past the piston 'head to be returned to the exhaust system. The bypass opens into the upper end of cylinder 47 through a bore 135 in end block 48. The lower end of bypass conduit 134 is connected into the cap 55 at the top of the heat exchanger barrel and exhausts through a bore 136 into the upper end of the heat exchanger tube 118.

The hydraulic system is powered in the instance shown by an electrical motor 137. It will be obvious, however, that any source of power may be employed including diesel, gasoline or field gas engines. The motor is mounted upon or adjacent to a hydraulic fluid storage tank 138, and it drives a hydraulic pump 139. Hydraulic fluid enters the pump through an intake line 140 which depends into the storage tank and it flows from the pump through a conduit 141 to an adjustable pressure valve 142. The pressure valve, which is commercially available, may be adjusted to permit hydraulic fluid to pass it at anywhere from S0 to 2500 pounds pressure per square inch. The pressure employed is dependent, of course, upon the length of the string of sucker rods to be lifted in each pumping stroke. Assuming a setting of 1000 pounds per square inch, the hydraulic fluid flows at this pressure from valve 142 through a pipe 143 to a check valve 144 which is a one-way valve designed to prevent fluid from flowing back toward the pump 139. From the check valve the fluid under pressure flows through a pipe 145 to a T-fit 146. One side of the'T-fitting is connected as at 147 to the pressure conduit 13. The other leg of the T is connected by means of a pipe 148 to a hydraulic pressure accumulator device 149.

A hand operated throttle valve 150 is installed in the hydraulic fluid conduit between the T-fitting 146 and the valve block 19. This valve provides a convenient means for varying the speed of operation of the pump jack. Preferably the valve is of a type which may be closed so that it also provides a means of temporarily stopping the pump jack while the motor 137 is running.

The accumulator 149 inay be a conventional pneumatic type adapted to be charged with compressed air at an inlet valve 151. The accumulator permits the pump to be operated continuously and maintains hydraulic fluid pressure in the conduit 13 at a high level. Fluid under pressure thus builds up in the accumulator during the exhaust stroke of the pump jack so that a large volume of high pressure fluid is immediately available when the valve 19 is tripped at the start of a lifting stroke. The exhaust oil from the heat exchanger flows through conduit 14 and is connected into a return line 152 which leads from the adjustable pressure valve 142 into the hydraulic fluid storage tank.

Having described our invention we claim:

1. A hydraulically operated pump jack for an oil well having a casing at the head thereof and an adapter tube on the casing surrounding the polish rod of the string of rods depending into said well, said adapter tube providing an exit for production oil, said pump jack comprising a power cylinder, a valve block including a valve to control the flow of hydraulic fluid to and from said cylinder, a heat exchanger assembly, said cylinder, valve block and heat exchanger assembly being aligned vertically with the power cylinder above the valve block and with the heat exchanger assembly below the valve block, a piston within the power cylinder, a piston rod extending vertically upwardly from said power cylinder, a sprocket wheel assembly mounted upon the upper end of said piston, means to mount said pump jack directly upon said casing adjacent to said adapter tube, means 9 to clamp said pump jack to said adapter tube, themeans mounting said pump jack upon the casing including a pivot pin to carry the pumping load, a chain engaged over the sprocket wheel assembly and having one end thereof attached to the polish rod and having the opposite end thereof anchored to the means mounting the pump jack upon the casing, the point of attachment of the chain connector to the mounting means being at the side of the heat exchanger assembly opposite the adapter tube and being spaced from the pivot pin an amount equal to the spacing between said pin and the vertical axis of the polish rod, whereby upon introduction of fluid pressure intosaid cylinder the pumping load is balanced between the two vertical runs of the chain and the polish rod is lifted at a rate which is in the ratio of 2 to 1 with respect to the rate the cylinder is moved upwardly.

2. A hydraulically operated pump jack for an oil well having a casing at the head thereof and a polish rod extending upwardly from said casing, said pump jack including a power cylinder, means to mount said pump jack directly upon the casing at the head of the oil well at one side of said polish rod with the power cylinder thereof disposed vertically, a piston in said cylinder, a piston rod extending vertically upwardly from said cylinder, a sprocket wheel assembly mounted on the top of said piston rod, a chain engaged over the sprocket wheel of said assembly, one end of said chain extending vertically downwardly at one side of said pump jack, means anchoring the first end of said chain to a stationary part of the pump jack, thesecond end of said chain extending downwardly at the side of the pump jack opposite to the first end in vertical alignment with the oil well pump;

rod and being attached thereto, and the means mounting said pump jack upon the oil well casing including a horizontal pivot pin which is spaced equally between the vertical axis of the pump rod and the place the first end of the chain is anchored, whereby upon introduction of hydraulic fluid into the power cylinder of the pump jack to raise the oil well pump rod the resultant downward force is concentrated at the pivot pin.

3. A hydraulically operated pump jack for an oil well having a casing at the head thereof and a polish rod extending upwardly from said casing, said pump jack comprising a power cylinder, a valve block including a valve to control the flow of hydraulic fluid to and from said power cylinder, a heat exchanger barrel, said power cylinder, said valve block and said heat exchanger barrel being aligned vertically with the power cylinder being attached to the top of the valve block and with the heat exchanger barrel being attached to the bottom of said valve block, means to mount the pump jack directly upon the casing at one side or said polish rod, a piston slidably mounted within the power cylinder, a piston rod extending vertically upwardly from said power cylinder, a sprocket wheel assembly mounted upon the top of said piston rod, a chain engaged over the wheel of said sprocket wheel assembly and having one end thereof extending vertically downwardly parallel to the vertical axis of the pump jack and being anchored to the means mounting said pump jack on the casing at the side of the pump jack opposite to the polish rod, the second end of said chain extending vertically downwardly parallel to the vertical axis of said pump jack in alignment with the oil well pump rod and at the side of the pump jack opposite to the first end, and means attaching the second end to said oil well pump rod, whereby upon introduction of hydraulic fluid pressure into the-cylinder to move the piston upwardly the resulting forces are substantially vertical and borne by the oil well casing.

4. A hydraulically operated pump jack for an oil well having a casing at the head thereof and a polish rod extending upwardly from said casing, said pump jack comprising an elongated body including a power cylinder, the body of the pump jack being vertically disposed with 10 the power cylinder at the top thereof, means to mount the pump jack directly upon the casing at the head of the oil well at one side of said polish rod, a piston within the cylinder, a piston rod extending vertically upwardly from said cylinder, a sprocket wheel assembly mounted upon top of said piston rod, a chain engaged over the wheel of said sprocket wheel assembly and having one end thereof extending vertically downwardly parallel to the vertical axis of the pump jack and being anchored to the means mounting said pump jack on the casing, the second end of said chain extending vertically downwardly parallel to the vertical axis of said pump jack in alignment with the oil well pump rod and at the side of the pump jack opposite to the first end, and means attaching the second end of the chain to said oil well pump rod, whereby upon introduction of hydraulic fluid pressure into the cylinder to move the piston upwardly the resulting forces are substantially all vertical and borne by the oil well casing.

5. A hydraulically operated pump jack adapted to be mounted directly upon the. head of the casing at the top of an oil well said casing having an oil well pump rod extending upwardly therefrom, said pump jack comprising a power cylinder, a valve device, a heat exchanger assembly, said power cylinder, valve device and heat exchanger assembly being vertically aligned and disposed with the power cylinder on top of the valve device and with the heat exchanger assembly below said valve device, a piston vertical slidable mounted within said power cylinder, a piston rod extending upwardly from said piston, a sprocket wheel assembly mounted on top of said piston rod, a chain engaged over the sprocket wheel of the assembly, one end of said chain attached to the oil well pump rod, means anchoring the opposite end of said chain to a stationary part of the pump jack, whereby introduction of hydraulic fluid under pressure into said cylinder moves the piston upwardly at a ratio of 1 to 2 with respect to the movement of the oil well pump rod, a conduit connecting the head of the casing to said heat exchanger assembly, whereby production oil is discharged from the well through said heat exchanger assembly, and said heat exchanger assembly including a conduit which is in the hydraulic system serving the valve device, whereby the hydraulic fluid is cooled by the production oil flowing from the well.

6. A hydraulically operated pump jack for an oil well having a pump rod extending therefrom, said pump jack comprising a power cylinder, a valve device adapted to control the flow of hydraulic fluid to and from said power cylinder, a heat exchanger, means connecting the power cylinder to the oil well pump rod for discharging production. oil from the oil well, means conveying the production oil to the heat exchanger, whereby production oil flows directly from the oil well into the heat exchanger, means to discharge production oil from the heat exchanger, and said heat exchanger including a conduit which is in the exhaust portion of the hydraulic system serving the valve device so that all the exhausted operating fluid is forced to flow through said conduit, whereby the production of oil coming from the well cools the hydraulic fluid used to actuate the pump.

7. Ahydraulically operated pump jack for an oil well 7 having a casing at the head thereof and a polish rod extending upwardly from said casing, said pump jack comprising a power cylinder, a valve device adapted to control the flow of hydraulic fluid to and from said power cylinder, means connecting the power cylinder said heat exchanger barrel whereby production oil flows from the well directly into the heat exchanger barrel,

'means for discharging production oil from the barrel,

and a heat exchanger coil mounted within said barrel, said coil being in the hydraulic system which serves the valve device, whereby the production oil coming from the well cools the hydraulic fluid used to actuate the pump.

8. A hydraulically operated pump jack for an oil well having a casing at the head thereof and a polish rod extending upwardly from said casing, said jack adapted to be mounted directly upon the top of the casing at the head of an oil well, at one side of the polish rod and comprising a substantially elongated unitary body having a power cylinder at the top thereof and including means for connecting the power cylinder to the oil well pump rod, a clevis at the lower portion of said pump jack, and said pump jack adapted to be mounted upon a single, horizontal pivot pin which is at the bottom thereof, said pin effectively pivotally joining said clevis t0 the aforementioned well casing whereby in the installation of said pump jack the pivot pin may be engaged while the pump jack is laying on its side and References Cited in the file of this patent UNITED STATES PATENTS 1,619,475 Hubbard Mar. 1, 1927 2,033,210 Tennant et a1. Mar. 10, 1936 2,139,101 Spencer Dec. 6, 1938 2,572,748 Noll et al. Oct. 23, 1951 2,582,564 Schneck et al Jan. 15, 1952 2,651,914 Joy Sept. 15, 1953 2,726,512 Deitrickson Dec. 13, 1955 FOREIGN PATENTS 70.317 Norway Apr. 23, 1946