This invention relates to a method of pumping a fluid from a well and also to an apparatus for carrying out a pumping action.

Many designs of pumps have been developed for raising water from bored wells, including those having manually operating mechanism or for use with animal power, electric motors, gasoline engines and wind driven means. There has developed a need for a pump system which can lift water from very deep wells, particularly in third world countries. Most known devices, which are of a sufficiently simple design to be able to be maintained without skilled workmanship, do not have deep well capabilities.

Also, numerous types of pump jacks have been developed for use in oil wells for raising oil to the surface usually from considerable depths. The most common pump jack used in the oil fields is one having a walking beam pivotally mounted for pivotally swinging back and forth in a vertical plane on the top of a framework frequently referred to as a Samson post. One end of the walking beam is connected to the polished rod which transfers the up and down reciprocating movement to the pumping string in the well. The oscillating movement of the walking beam is achieved by driving the walking beam by a pitman connected at one end to the end of walking beam opposite to the end connected to the polished rod. The other end of the pitman is connected to a rotating crank which is the output of a gear reducer. An electric motor or an engine is normally used to drive the gear reducer. Usually the input or drive to the gear reducer is at a constant speed which results in the output motion delivered to the walking beam being sinusoidal which is not a particularly efficient arrangement and results in relatively high input load peaks for the prime mover which is not cost effective. Not only is the cost of input power more expen¬ sive with such peak loading, but the motor or engine, as well as the gear reducer must be heavy duty relative to the average load being experienced. Furthermore, the forces

produced in a conventional walking beam pump jack requires a heavy support structure and a substantial foundation for the supporting framework.

It is an object of the present invention to provide a method of pumping fluid from a well bore which allows for the use of a novel apparatus in a simple and economical design.

According to one aspect of the present invention there is provided a method for use with a well equipped with a pumping rod which operates on a pumping cycle having a load lifting stroke and downward return stroke. The method includes the step of mounting a walking beam on a fulcrum with one end of the walking beam mounted over the well and connected to the pumping rod, the walking beam and fulcrum being shiftable relative to each other in the longitudinal direction of the walking beam, the walking beam having a balanced end disposed on the opposite side of the fulcrum as a well. The method further includes the steps of shifting the walking beam in a first direction relative to the fulcrum toward the balanced end and past the loaded balance condition to cause the balancing end to swing downwardly from a raised to a lower position and thereby effect the lifting stroke of the pumping rod, and then shifting the walking beam in a second direction relative to the fulcrum past an unloaded balanced condition to cause the pumping rod to move downward¬ ly through the return stroke and effect the raising of the balancing end from the lower position to the raised position. The above steps of shifting the walking beam relative to the fulcrum in opposite directions are repeated to cause the pump rod to repeat the pumping cycle.

According to another aspect of the invention, there is provided an apparatus for pumping a fluid from a well equipped with a pumping rod extending down into the well and having a pumping cycle consisting of an upward load lift stroke and a return gravity stroke. The apparatus includes an elevated fulcrum means and a walking beam means supported on the fulcrum means and having a lifting end disposed above

the well and a weighted balancing end disposed on the opposite side of the fulcrum as the lifting end. Connecting means is provided between the lifting end of the walking beam and an upper end of the pumping rod. Means is provided to mount the walking beam on the fulcrum means for permitting longitudinal shifting of a walking beam relative to the fulcrum means in a first direction past a loaded balanced condition and in a second direction relative to the fulcrum means past an unloaded balanced condition. Thus, the balancing end swings downwardly from a raised to a lower position on completion of the shifting in the first direction to thereby effect the load lift stroke of the pumping rod, and the pumping rod moves through the return gravity stroke on completion of the shifting in the second direction.

In a specific embodiment of the invention, the relative shifting between the walking beam means and the fulcrum is achieved by shifting the fulcrum relative to its stationary support means.

In the accompanying drawings, which illustrate a number of embodiments of the invention, as examples:

Figures la and lb depict two different relative posi¬ tions of the walking beam relative to the fulcrum for the purpose of illustrating the operating principle of the present invention;

Figure 2 is a side view of one embodiment of the apparatus of the present invention;

Figure 3 is a view from the well head end of the apparatus of Figure 2;

Figure 4 is a cross-sectional view as seen from 4—4 of Figure 2;

Figure 5 is a schematic of a hydraulic actuating mechanism for accomplishing the relative shifting between the walking beam and the supporting fulcrum;

Figures 6a and 6b are similar to Figures la and lb but illustrates a pulley and cable arrangement for providing operating advantages during the longitudinal shifting of the walking beam;

Figure 7 is a view showing an apparatus in which the fulcrum is shifted relative to the top of the supporting structure and wherein there is no relative shifting of the walking beam relative to the support structure;

Figures 8a and 8b, which appear on the same sheet as Figures la and lb, depict two different positions of the walking beam relative to the fulcrum in an embodiment, such as that shown in Figure 7 in which the fulcrum is shifted;

Figure 9 is a side view of yet another alternative embodiment of the present invention;

Figure 10 is a cross section view of the embodiment of Figure 9 as seen along the line 10—10 of Figure 9; and

Figure 11 is a graph indicating the input energy in relation to the energy utilized by the pumping rod for the arrangement depicted in Figures 7a and 7b.

The broad operating principle of one embodiment of the invention is illustrated in Figures la and lb which shows a walking beam in a simplified form at 10 mounted for pivotable movement on a fulcrum F. The fulcrum F would normally be supported above the ground on a small tower or post which is not shown. Means is provided, as will be described in more detail below, with reference to other figures of drawings, which permit the walking beam to be shifted longitudinally relative to the fulcrum. It will also become apparent that the reference to the shifting of the walking beam relative to the fulcrum also is meant to refer to the arrangement where the beam does not actually shift but the fulcrum moves so as to support the walking beam at a different location along its length.

In Figure la, the walking beam is shown at a position with end 11, which is the end connected to the pumping rod of the well, hereinafter referred to as the lifting end of the walking beam, in a lowered position. The position of the walking beam shown in Figure la depicts a position where the pumping rod or sucker rod in the well is at the end of its downward or return stroke and the beam has been shifted to initiate the raising of the sucker rod. In this position a

counter weighted end 12 of the walking beam is in its raised position. As can be seen, the fulcrum F pivotally supports the walking beam 10 intermediate the lifting end 11 and the weighted end 12 and means is provided (not shown) for shifting the walking beam in a longitudinal direction relative to the fulcrum F in opposite directions as indicated by the arrow d. of Figure la and the arrow d ₂ of Figure lb. When the sucker rod is in its lower most position, the weight W, at the lifting end 11 of the walking beam 10 includes the weight of the sucker rod and the head of liquid being lifted on the up or lifting stroke in the pumping cycle. If, as an example, the pumping string or sucker rod is 136 Kg and the head is 68 Kg, the total weight ₁ would be 204 Kg. In this example, the total length of the walking beam 10 may be 1.5 m, and the counter weight W may be 136 Kg. It can be seen that as the walking beam 10 is shifted in the direction d. , relative to fulcrum F, a balanced condition, hereinafter referred to as a loaded balance condition, is reached when a, equals about .6 m and b, equals .9 m, because the counterclockwise turning force to the left of fulcrum F, would equal 204 Kg x .6 m = 122 Kg-m, which is the clockwise turning moment provided to the left of the fulcrum F. by the counter weight force W , i.e., 136 Kg x .9 m = 122 Kg-m. Thus, as the shifting of the walking beam in the direction d. passes the loaded balanced condition, the turning moment provided by the force W is greater than the turning force required to lift the weight W.. The head of fluid is thus lifted so as to discharge a quantity of the fluid, such as water or oil, to the ground surface.

As the lifting stroke is completed, shifting of the walking beam 10 in the opposite direction, as shown by arrow d ₂ in Figure lb can be carried out. The weight of the counter weight Wc is constant and when the beam starts to shift in the direction d, the effective weight of the column of fluid in the well reduces to zero as the one-way valve in the pump piston (not shown) opens. When the walking beam has been shifted to a position where a, = b- = 0.76 m, the turning force on opposite sides of the fulcrum F are equal

and opposite, this representing an unloaded balanced condi¬ tion. Further shifting of the walking beam from the position shown in Figure lb in the direction of the arrow d- results in the turning force applied by weight ₂ being greater than the turning force applied by the counterweight W -__ . The pumping rod is therefore allowed to sink to its lowermost stroke, i.e. it completes its downward return stroke thereby finishing one complete pumping cycle. The head of fluid is thus in position to be lifted and the above-described operations are repeated.

There is illustrated in Figure 2 a hydraulic drive means for shifting the walking beam 10 relative to the fulcrum F. The walking beam is mounted at the top of a support means which may be a framework or Samson post 13 mounted on a foundation 14 at the surface 15 of the ground. The lifting end of the walking beam is positioned approximately over a well head 16 which is shown projecting above the ground surface 15. The well head may be provided with the usual packing gland means (not shown) through which projects a polished rod 17. The polished rod 17 is pulled up by .the walking beam and is pulled down by the weight of the sucker or pumping string or rod (not shown) connected to the lower end of the polished rod. The fluid brought to the surface may be conducted away from the well head by a pipe or other means (not shown).

The weighted end 12 of the walking beam 10 is disposed on the opposite side of the fulcrum F as the well head and the walking beam is mounted to oscillate about fulcrum F in a vertical plane. The walking beam is mounted for longitudinal shifting relative to the fulcrum F within a fulcrum carriage 18 in the embodiment of Figure 2, 3 and 4. At the top of the Samson post there is provided a pair of upwardly extending side lugs 20 between which extends a horizontal shaft 21 forming the fulcrum F. The fulcrum carriage 18 includes a main body portion 22 having downwardly extending flanges 23 through which the shaft 21 passes, the shaft is fitted in aligned openings in lugs 20 and in aligned openings in

flanges 23 to allow relative turning of the shaft relative to the lugs 20 and/or flanges 23, so that the carriage can rock on Samson post 13 about the axis of the shaft 21 which thus provides the fulcrum F. The walking beam 10 through at least its intermediate portion may have an I-beam cross section.

The fulcrum carriage 18 has a bottom wall 24, opposite side walls 25,25 and a top wall 26 forming the main body portion 22. The flanges 23 are affixed to the bottom wall 24 and project downwardly therefrom. The bottom wall, which is spaced below a bottom flange 27 of the walking beam 10, is joined at its outer edges to side walls 25,25. The top wall 26 is located immediately above and is parallel to the upper flange 28 of the walking beam. A pair of shafts 30,30 extend across the main body portion 22 between side walls 25,25, and a pair of rollers 31,31 are journalled on the shafts so as to be mounted immediately above the bottom wall 24. The bottom flange 27 of the walking beam 10 rests on the rollers 31,31. On each side of the walking beam 10 a pair of vertical shafts 32,32 extend between bottom wall 24 and top wall 26. Rollers 33 are journalled on shafts 32 and engage the sides of web 34 of the walking beam. Thus the longitudinal movement of the walking beam 10 within the fulcrum carriage is closely guided.

A pair of downwardly depending transverse flanges 35 are affixed to opposite ends of bottom wall 24 of the fulcrum carriage 18, each flange 35 having lugs 36. At a distance from each end of fulcrum carriage 17 the walking beam 10 is provided with a downwardly depending lug 37. A pair of hydraulic cylinders 38a, 38b are connected between the lugs 36 and 37 at opposite ends of the fulcrum so that as cylinder 38a contracts and cylinder 38b expands, the walking beam is moved longitudinally towards the lifting end, and alterna¬ tively when cylinder 38a expands and cylinder 38b contracts, the walking beam shifts longitudinally through the fulcrum carriage toward the weighted end.

Mounted over the well head is a support structure 40

carrying a pair of pulleys 41. The pulleys 41 are ^' journalled on horizontal transverse shafts 42 positioned to guide a cable means 43 in direction to align exactly with the polished rod 17. The weight at the weighted end of the walking beam may be affixed directly to the beam, or as shown the weight W may be suspended by cable means 44 affixed at an upper end to the walking beam. The weight W may be made up of a plurality of individual removable plates to allow for the adjustment of the magnitude of the weight W depending on the conditions being experienced for each individual well. As shown the cable means passes through a pair of pulleys 45 mounted on a support structure 46 positioned below the weighted end 12 of the walking beam 10.

In Figure 2, the beam is shown by dotted lines 10 in a position corresponding to that of Figure la and by dotted lines 10" in a position corresponding to that of Figure lb. Because the fulcrum F is stationary in the embodiment of Figure 2, it can be seen that the lifting end of the walking beam shifts from a position which is inside of a vertical line projecting from the well head to a position outside of the imaginary vertical line projecting from the well head as the polished rod is pulled upwardly through its lifting stroke. Due to the presence of the pulley 41,41 between which the cable means 43 is pulled the lift force on the polished rod is directly upward. Similarly when the polished rod is permitted to move to its lowered position during the return stroke the cable is pulled around the outer pulley 41 and applies no side force to the polished rod. A similar action is experienced by the cable means 44 of the weight W .

Figure 3 illustrates a cable connection 43 between the end 11 of the walking beam 10 and the upper end of the polished rod 17 which avoids binding of the sucker rod in the packing gland to any side forces. It can be seen that instead of a single cable 43 being used, a pair of cables 43, 43, which are equally spaced on either side of the lon¬ gitudinal axis of the polished rod, are used. A yoke 48, which is horizontal and extends perpendicular to the plane in

which the walking beam oscillates, is secured to the top end of the polished rod 17 by a nut 49 threaded onto the polished rod. The cables 43,43 are fixed to opposite ends of the yoke 48 and are connected at their upper ends to a cross member 47 extending from opposite sides of the lifting end of the walking beam. In this arrangement, it is necessary, of course, to provide two pairs of guide pulleys 41,41 one pair for each of cables 43.

In the embodiment of the invention which provides, for actual longitudinal shifting of the walking beam relative to a fulcrum which is stationary relative to its surroundings, various drive means can be used to apply shifting forces to the walking beam. Such drive means include mechanical devices such as rack and pinion, lever mechanisms, worm and gear combinations, etc., all of which can be designed to derive the input energy from a manual operated device, such as a hand turned crank, or from other prime movers, such as an electric motor or a gasoline engine. The input energy may be converted into a hydraulic force producing system such as that shown in Figure 5. The system illustrated schematically in Figure 5 can be used to activate the hydraulic cylinders 38a, 38b shown in Figure 2, or as another example, the cylinders 38a and 38b could be used to shift a pinion carriage which will be described in more detail in connection with the embodiment of Figure 9.

The system shown in Figure 5 includes a reservoir enclosure or tank 50 from which an oil or hydraulic fluid is drawn through an input conduit 52 by a pump 51. A motor or a hand driven gear mechanism is provided (not shown) and is connected by a shaft or other drive means to the pump 51 so as to produce a quantity of pressurized fluid through an outlet to a supply line or conduit 53. The pump 51 may be of a type other than a rotary pump as shown in drawing, such as a piston and cylinder pump which can be actuated by an oscillating hand lever and would be practical for use with a deep water well. On the other hand a more elaborate pump, such as variable displacement pump may be desirable in an oil

well installation. Depending on the nature of the pump, and particularly if it is one of a positive displacement type, the supply conduit 53 may be connected to a pressure relief valve 64 via a conduit 63 so as to permit fluid to return directly to tank 50 by way of conduit 65.

The actuation of cylinders 38a and 38b is controlled by a directional control valve 54 having an inlet connected to supply conduit 53 and an outlet connected to a return conduit 57. When the control valve 54 is in the position indicated by the arrow in Figure 5, the pressurized fluid from conduit

53 is directed through a port of the valve 54 to a conduit 55 which branches into a pair of conduits 55a and 55b, the former being connected to the inner end of cylinder 38a and the latter being connected to the outer end of cylinder 38b. Another conduit 56 also connected to a port of the control valve 54 branches into conduits 56a and 56b which are respec¬ tively connected to the outer end of cylinder 38a and the inner end of cylinder 56b. It can be seen, therefore that as pressurized fluid is provided from pump 51, through conduit 53 to control valve 54 and then to conduit 55, the ^" pres¬ surized fluid enters the inner end of cylinder 38a to cause the piston to retract and enters the outer end of cylinder 38b to cause the piston of this cylinder to extend. At the same time the outer end of cylinder 38a and the inner end of cylinder 38b are connected through conduit 56, control valve

54 and conduit 57 to the reservoirs so that as cylinder 38a contracts and cylinder 38b expands, the fluid in the opposite ends of these cylinders is forced back to the reservoir. With this particular stage of the actuation of the cylinders, the walking beam 10, as shown in Figure 2 is shifted to the left, i.e. the position shown as 10 . Thus the pump rod of the well pump proceeds to move through its downward return stroke.

When the control valve 54 is moved to its alternative position, conduit 56 is connected to the pressurized fluid of conduit 53, and conduit 55 is connected to return conduit 57. Thus cylinder 38a expands and cylinder 38b contracts to shift

the walking beam 10 to the right as shown in Figure 2, i.e. as shown at 10 . This action would occur after the comple¬ tion of the return stroke of the well pump piston and once the shifting results in the walking beam being shifted towards its counter balance end a distance sufficient to pass the loaded balanced condition, the balanced end of the walking beam starts to travel to its lowered position to thereby effect the lift stroke of the well pump.

The timing of the shifting of the control valve 54 between its two opposite positions is shown as being con¬ trolled by a unit 62 in a circuit 61 which could be an electrical circuit or a hydraulic circuit. The unit 61 could be a solenoid or a hydraulic actuator depending on whether an electrical or hydraulic current is used. The flow of electricity or fluid in the circuit 61 is controlled by limit switches 60a and 60b which are positioned to be separately actuated by movement of walking beam 10 or some moving part thereof. Thus, the control valve is shifted from one position to another when the walking beam reaches a predeter- mined position and engages switch 60a, and then the control valve is subsequently shifted back to its first position when the walking beam reaches a second predetermined position detected by limit switch 60b. In a simpler mechanical form, it is possible to utilize a rod or lever connected to the walking beam and adapted to push and pull the control valve between its two positions. The control valve 54 may have, a neutral position which it occupies between the two opposite activation stages of the cylinders 38a and 38b, so that pressurized fluid is simply directed from supply conduit 53 to return conduit 57.

The timing may also be controlled with a throttling device 69 which controls the rate of flow in conduits 53 and 57. Separate throttling devices may be used in each of conduits 55 and 56. Such devices can be used to achieve other cycling characteristics in the pumping cycle by way of presetting the rate at which the cylinders are expanded and contracted. For example, to obtain a particular pump cycle

profile the walking beam may be shifting one direction slower than in the other to provide a dwell before the lifting stroke.

In the structure of the invention as depicted in Figure 6a and 6b guide pulleys 64 and 65 over which cables 43 and 44 pass are located in a manner which allows a small amount of power for shifting the walking beam 10 relative to the fulcrum F. This may be advantageous in a pump installation for a deep water well which is operated manually. The arrangement has the disadvantage, however, that a shorter pumping stroke is provided in relation to the amount the walking beam is shifted longitudinally. Like the pulleys 41 of the embodiment shown in Figure 2, the pulley 64 is used to direct the position of the cable 43 between the pulley and the polished rod 17 in a vertical direction coaxial with the polished rod 17. The walking beam 10 shown in the position A-C is at the end of the return stroke of the pump rod, and as the walking beam is shifted to the position shown at B-D, the lifting end of the walking beam travels in the arc AB and the balancing end travels in an arc CD. The pulley 64 is positioned so that the arc AB has a centre about the point of contact of the cable 43 with the rim of the pulley 64, which point only moves slightly during the shifting of the walking beam. The same relation exists between the arc CD and the point of contact of the cable 44 with the pulley 65. In Figure 6b, the motion involved in the shifting of the beam after the lifting stroke of the pump has been completed is depicted. The walking beam 10 is shifted from the position indicated as G-E to the position indicated as H-F, and during this shifting, the radius of the arc G-H is on a centre of the approximate initial contact point of the cable 43 with the rim of the pulley 64, and the centre of the radius of the arc EF is approximately at the initial point of contact of the cable 44 with the rim of the pulley 65. Thus as there is only a small change in the length of the cable between the ends of the walking beam and their respective guide pulleys, little change in the position of the height of the polished

rod 17 and the counter weight is brought about in relation to the amount of longitudinal shifting of the walking beam.

In Figure 7 there is shown an embodiment of the inven¬ tion in which the fulcrum F, is movable relative to its support which is shown as Samson post 13. Mounted on top of the Samson post 13 are horizontal rails 70 which extend in the same direction as the longitudinal axis of the walking beam 10. A carriage 71 is mounted for sliding movement in a back and forth direction as indicated by the double headed arrow 72. The reciprocating movement of carriage 71 can be achieved by utilizing a piston and cylinder type motor (not shown) or by a hydraulic system using a pair of hydraulic cylinders 38a and 38b as shown in Figure 5. Alternatively a rack and pinion or worm and gear device could be used. The pinion or the worm could be driven by way of simple hand crank in an installation where other power is not available, or a hand lever could be used for pushing the carriage back and forth.

The carriage 71 includes a pair of widely spaced side walls 73 between which extends a transverse horizontal top wall 74. The top wall 74 is adapted to be in sliding contact with the top of the walking beam 10 as the carriage 71 moves longitudinally relative to the walking beam. A pair of uprights 75 are connected to the Samson post and are joined by a pair of horizontal members 76 which extend along either side of the walking beam 10. The walking beam has a pair of slots 77 in either side which receive inwardly projecting heads 80 affixed to the member 76. The engagement of the heads 80 in the slots 77 prevents longitudinal movement of the walking beam relative to the Samson post 13.

The carriage 71 further includes a pair of spaced upright lugs 81 which support a transverse horizontal shaft 82. A pinion 83 is rotatably mounted on shaft 83 which forms fulcrum F and engages a longitudinally extending rack 84 formed on or affixed to the bottom surface of the walking beam 10. As the carriage moves back and forth relative to

the walking beam, the pinion meshes with the teeth of the rack, and the fulcrum F, which is the axis of the shaft 82, thus shifts relative to the Samson post and along the length of the walking beam which does not shift longitudinally relative to the Samson post 13. An obvious alternative to the above-described structure would be that of mounting the rack on the carriage 71, and supporting the walking beam on a pinion rotatably mounted on a transverse shaft affixed to the walking beam.

It can be seen than an embodiment of the type shown in Figure 7, wherein the fulcrum is the part which actually shifts, has advantages over that shown in Figure 2, wherein it is actually the walking beam which shifts. The structure of the embodiment of Figure 7 can be simple in nature and additional guide means are not required for the cable as the motion of the walking beam is conventional. The lifting or load end of the walking beam can be provided with the usual horses head to provide the vertical suspension of the cable between the walking beam and the polished rod. The mechanism which forms the present invention, i.e. the parts which accomplish the longitudinal shifting of the walking beam relative to the fulcrum, can be provided separate from the walking beam and support structure of the fulcrum, so as to be used with existing structures. It can be seen that the parts required for the embodiment could be provided in a small kit form for use in a deep well situated in remote areas, and the Samson post and walking beam could be con¬ structed from timbers or other locally available materials.

Referring to Figures 8a and 8b, the amount of work and the timing of the energy input can be readily visualized. When the pump rod has reached the bottom of its stroke, the fulcrum is still at the position identified as F. in Figure 8a. As it is shifted to position F ₂ , through a distance d- the balancing weight is raised a distance M representing an energy input at this stage of W x M. During the lift stroke the balancing end of the walking beam swings downward to the lowermost position shown in Figure 8b. The fulcrum is

then shifted to the right as indicated by the arrow d _f from the position F ₂ to the position F., and this raises the balancing weight a height N representing an energy input of W x N. Under the effect of the turning force provided by the pump rod W, the walking beam swings to the lower position shown in Figure 8a. The fulcrum is then shifted as indicated at d _f in Figure 8a to start a repeat of the pumping cycle.

In an example, of the embodiment just described, using a walking beam having a length of 122 cm and an oscillation of 40°, a lifting stroke S equal to 42 cm is obtained by shifting the fulcrum a distance d _f equal to 13 cm. The distance of lift M or N of Wc„ at both ends of the stroke is 7 cm, i.e. N = M = 7 cm. Preferably the beam is balanced so that the pump rod weight W, is two-thirds (2/3) times the weight of the balancing end W and the fluid head is one- third (1/3) times the weight of the balancing weight so that the weight of the pumping rod W, plus the weight of the fluid head, i.e. W ₂ is equal to W .

Referring now to Figures 9 and 10, there is shown a structure wherein the fulcrum is shifted relative to the walking beam 10", the Samson post 13 providing the support structure for the walking beam. The fulcrum includes a fulcrum carriage structure 18" which is mounted within a housing shown as an enclosure 90 by dashed lines. The fulcrum carriage 18" has upper and lower fulcrum members 103 and 104 which co-operate with upper and lower track means 91 and 97 to allow shifting of the fulcrum carriage relative to the walking beam 10" and the Samson post 13. The fulcrum carriage may be shifted with a hydraulic power means similar to that shown in Figures 2 and 5, or other mechanical means which, for example, may be actuated by a manual operated crank or lever.

Affixed to the top of the Samson post 13 and within the enclosure 90 is the lower stationary track means 97 having a pair of parallel slide surfaces 101 which are disposed below the upper surface of a track member 100, the

slide surfaces 101 extending in the same direction as the walking beam 10".

The walking beam 10" has an intermediate section which is split to thus provide a pair of side members 94, 94 straddling the fulcrum structure so as to be disposed on opposite sides of the enclosure 90. The walking beam 10" and/or the side members, which are joined by a metal top plate 95, may be formed by wood beams, for example, for the sake of light weight and economy. The plate 95 is connected at its midpoint to the upper surface of a track member 92 of the upper track means 91 by a short post member 106. The lower surface of the track member 92 has a pair of parallel slide surfaces 93 which extend along opposite edges of the track member and are recessed relative to its lower surface.

The upper and lower fulcrum members 103 and 104 are joined by a fulcrum pin 102 so as to allow relative pivoting of the two fulcrum members about an axis which extends transverse to the longitudinal axis of the walking beam 10". upper fulcrum member 103 has a plate member 105 which is provided with side recesses or channels 106,106 receiving slide shoes 107,107. The shoes 107,107 may be made of a wear material such as oil impregnated bronze and are preferably detachably connected to the plate member 105 by screws (not shown) so that they can be replaced when they become worn. The slide shoes are parallel and spaced to engage the slide surfaces 93,93 of the upper track means 91.

The structure of the lower fulcrum member 104 is similar to that of the upper fulcrum member, having a plate 108 provided with side recesses or channels 109 in which there are secured slide shoes 110,110. The slide shoes of the lower fulcrum member are spaced for longitudinal sliding on parallel slide surfaces 101 in track member 100.

It can be seen that the fulcrum carriage can be shifted first in one direction and then the opposite relative to the walking beam 10" and the support port 13 which do not shift

relative to each other in the longitudinal direction of the walking beam. Thus the fulcrum provided by transverse pin 102 is displaced relative to the walking beam which results in relative imbalances to thereby cause the walking beam to tilt first in one direction and then the other resulting in a pumping action.

The sliding shoes 107,107 and 110,110 may be of identi¬ cal structure, and as indicated above may provide the wearing element of the sliding structure. The surface 93,93 and 101,101 are preferably polished to reduce fulcrum loss and wear. The enclosure 90 is preferably a casing capable of containing a lubrication bath and is provided with a resilient seal means at the location where the port 106, which continually tilts from one side to the other, extending through the top of the casing.

It is apparent that the sliding shoes 107,107 and 110, 110 could be affixed to the members 92 and 100 of the upper and lower track means, with the plates 105 and 108 being provided with the slide surfaces against which the shoes slide.

The Energy Path Diagram of Figure 9 illustrates the potential of the present invention to act as an efficient pump actuator. The graph is prepared with an assumed positive displacement pump rod weight equal to twice the water weight, i.e. the weight of the column to be lifted by the pump is one half of the weight of the rod. During the first stage of the pump cycle, the pump rod remains station¬ ary as either the fulcrum or the walking beam is moved. This movement continues until the moment about the fulcrum by the counterweight is slightly greater than that of the pump rod and water column. This process requires an input of energy caused by the lifting of the counterweight as described above. The cumulative energy input (work) is shown by the line indicated as X. The line indicated as Y shows that no work is being performed by the pump during this stage.

Stage two consists of the balancing weight W. falling while the pump rod goes through its full stroke. Since no energy is input into the system, the X energy path remains constant. The energy path of the pump, however, indicates that the pump is having a great amount of energy input. The peak of the curve is equal to the work of raising both the water column and the rod weight through the pump stroke. Obviously, if no counterweight existed the energy path X would have followed the same line.

When the pump reaches the top of its stroke, the pump rod is again made to stay stationary as the fulcrum or walking beam is moved (stage three). This movement is continued in the opposite direction to stage one until the moment created by the weight of the rod is slightly greater than that of the counterweight. Again, lifting of the counterweight requires an input of energy.

The final stage of the pump cycle occurs when the pump rod falls while the counterweight rises to its initial position. No input of energy into the system is required for this to occur because of the unequal moments around the fulcrum. Nevertheless, the pump energy path reflects the lost potential energy as the pump rod is returned to its original position.

At the end of the cycle the two energy paths converge. The point at which this occurs on the graph represents the amount of work required to lift one unit of water through one unit of head (using a specific weight of water also equal to one) . The use of the present invention thus resulted in only having to input to the system this single unit of work which was split evenly between stages one and three. If the invention was not used, three times the amount of work would have been required during the pump's up stroke. After that, the extra effort would have been lost unless another method was developed to capture the potential energy of the pump rod as it returns to the bottom of its cycle. This is an advantage to the invention, its input energy requirements

exactly equal (in a frictionless system) the equivalent hydraulic energy delivered at the pump end. Further, its input energy requirements are split between two stages of the pump cycle.

The advantages of the invention allows one to design a hand operated energy input system which could drive a positive displacement pump operating at substantial depths. In a hand operated system, it is important that the slope of the energy path (equivalent to work load) be held as constant as possible (such that the operator does not "stall" while proceeding through the cycle). For motor driven systems, this slope should be made constant through all stages of the pump cycle to avoid cyclic loads on the motor.

While a number of alternative embodiments have been

I illustrated additional embodiments which are within the spirit of the invention as defined in the appending claims will be obvious to those skilled in the art.