US2269787A

US2269787A - Counterbalancing apparatus

Info

Publication number: US2269787A
Authority: US
Inventors: Walter E Saxe
Original assignee: Individual
Current assignee: Individual
Priority date: 1940-04-09
Filing date: 1940-04-09
Publication date: 1942-01-13
Anticipated expiration: 1959-01-13

Description

Jan. 13, 1942. w, SAXE 2,269,787

GOUNTERBALANCING APPARATUS Filed April 9, 1940 3 Sheets-Sheet 1 by M4 RR/s, K/ECl-l, Fa; TE HARR 1.5

v FOR 7715 FIRM A rrowsxs Jan. 13, 1942. w. E. sAxE 2,269,787

COUNTERBALANCING APPARATUS Filed April 9, 1940 3 Sheets-Sheet 3 //v VENTOK/ WALTER E.\5AX

d3 Y //A RAP/5, mac/1, F05 TER & HARR/J ATTORNEYS Patented Jan. 13, 1942 UNITED STATES PATENT o-FFicE couu'rannaifa l z ii mans-ms I Walter a. sue, Alhambra, can. Application Ap l 9, 1940, Serial No.

n (or so -1s) My invention relates to apparatus for counterbalancing the load on a prime mover, such as the load imposed by a reciprocating member, and is directed specifically to means for automatically varying the counterbalancing force to follow.

changes in the magnitude of the load.

Since my invention is applicable with exceptional advantages to the problem of automaticalLv counterbalancing pumping apparatus for oil wells, I elect to direct my disclosure to an embodiment of the apparatus for oil well pumping.

Those skilled in the art, however, will find suflicient guidance herein for embodying the invention in other apparatus for other purposes.

In oil well pumping apparatus it is customary to employ a prime mover for rotating a shaft and to translate the-rotary movement of such shaft to the reciprocating movement of a pump plunger through a crank arm, a pitman, and a walking-beam. When the crank arm, in its rotation, is nearly vertical, the component of its movement parallel to the direction of travel of the walking-beam and the pump plunger is relatively small, and therefore the load on the prime mover when the crank is in this position is also relatively small. On the other hand, when the crank arm is near either of its horizontal posi tions, it has a relatively large component of its movement parallel to the direction of travel of the walking-beam and the pump plunger, and the load on the prime mover is then most influenced by the load on the walking-beam. If no counterbalance is employed, it is evident that on the upstroke of the string of sucker rods, when the crank arm is horizontal, the prime mover is subjected to its greatest load, being required at that time-to lift with greatest velocity the walking-beam, the string of sucker rods, and all of the liquid being elevated in the well tubing; while on the downstroke, the walking-beam and string of sucker rods fall by gravity, subjecting the prime mover to little or no load.

As disclosed in my Patent No. 2,122,871, issued July 5, 1938, effective counterbalancing in an oil well pumping apparatus may be achieved by compressing air on the downward stroke of the walking-beam to store energy and releasing such energy to assist the prime mover on the upward stroke. By proper adjustment of such apparatus, I am able to equalize the burden on the prime mover during the downward stroke with the burden on the prime mover during the upward stroke for increased efficiency and longer life of the pumping apparatus.

I have found, however, that in the case of many wells, the load during the upstroke of the sucker rod does not remain constant but may f vary gradually and, over a period of hours-may be considerably altered. This change may come about through operation of various factors. The.

fraction of water contained in the oil may change, resulting in a heavier or lighter column I of liquid to be raised;-or change in the fraction of gas contained in the oil may change the weight.

of the column of liquid. Moreover, in those wells situated adjacent the ocean, the well pressure and the load on the sucker rod are found to change with the tide. In such installations, it is desirable to vary the counterbalancing force as the load on the sucker rod varies, to make the burdens on the prime mover equal during th upward and downward strokes of the sucker rod.

- To do ordinarily requires close attendance to the apparatus, a requirement to be avoided.

In my copending application, Serial No. 228,536, filed September 6, 1938, now Patent No. 2,196,816, entitled Method and apparatus for automatically counterbalancing pumping apparatus on oil wells," I disclose and generically claim a method and apparatus for varying a counterbalancing force in such apparatus as may be required for equalization under conditions of changing load. The underlying concept is that of comparing the upstroke stage with the downstroke stage of the pumping cycle with respect to force exerted or work done, or some factor that is correlated with 'force or work and causing any significant differences between the two stages with respect to the selected factor or factors to be brought into effect in a cumulative manner to change the magnitude of the counterbalancing force until equalization is restored at a new level of values. If the emphasis is on force as a factor, the apparatus may be designed to equalize the maximum operative forces of the two stages respectively; whereas by bringing into effect time as a factor along with force, the equalization may be between work performed on the upstroke and work performed on the downstroke regardless of relative magnitudes of force involved. In both cases it may be said that the end sought is equalization of loads on the prime mover.

The present disclosure illustrates the fact that automatic counterbalancing may be achieved by integrating some factor related directly to the prime mover, including such factors as pressure, temperature, amperage, fuel or other energy input, by-product, etc. Such factors are to be distinguished from driving torque, driving pressure, and other forms of applied force that may be identified in the mechanism for transmitting energy from the prime mover to the load.

An object of the present invention is' to base the required automatic operation on one of the factors related directly to a prime mover, the particular prime mover chosen for illustration being an internal combustion engine, and the particular factor selected being the intake pressure of the engine. The manner in which I make the counterbalancing force responsive to the pressure in the intake manifold of an engine will clearly indicate how in other forms of my invention counterbalancing control may be based on other factors relating to an internal combustion engine, or on factors associated with a steam engine, an electric motor, or other form of prime mover.

Other objects and advantages of my invention will be apparent from consideration of the following detailed description and the accompanying drawings.

In the drawings:

Fig. 1 is a side elevation of the preferred form of my automatic counterbalancing apparatus, a portion of the apparatus being broken away for clarity;

Fig. 2 is a plan view on an enlarged scale of a portion of the apparatus shown in Fig. i;

Fig. 3 is a side elevation of the mechanism shown in Fig. 2. the view being partly in section;

Fig. 4 is a fragmentary section taken as indicated by the line 4-4 of Fig. 2;

Fig. 5 is a section taken as indicated by the line 5-5 of Fig. 4;

Fig. 6 is an enlarged sectional detail of Fig. 3;

Fig. 7 is an enlarged section of a valve emplayed in the preferred form of my apparatus; and

Fig. 8 is a similar view of a second valve employed in the apparatus.

The drawings illustrat my invention as applied to the pumping apparatus for an oil well 20. The well 20 has a casing 2i and a pump tubing 22 in the lower end of which a pump plunger 23 is reciprocated by a string of sucker rods 24. The

sucker rods 24 extend upwardly through the pump tubing to above the surface of the earth and are attached by suitable means, such as a cable 25, to the working end of a walking-beam 26, the other end of the walking-beam being mounted upon a pivot 21 carried by a fulcrum frame 23. This assembly is arranged in such manner that rocking of the walking-beam results in reciprocation of the pump plunger 23 through a pumping cycle comprising an upwardly directed pumping stroke and a downwardly directed return stroke. The fulcrum frame 23 and the remainder of the pumping and counterbalancing apparatus are preferably mounted on an under frame 28.

In the form of pumping apparatus illustrated in the drawings, a prime mover 30 in the form of an internal combustion engine drives a relatively large sprocket 3| through a chain 32, the sprocket being mounted on and keyed to a countershaft 33. A small sprocket (not shown) that is also keyed to the countershaft 33 drives a second large sprocket 33 through a chain 38, and the large sprocket 35 in turn drives a crank arm 31 on a second countershaft 38. Attached to the crank arm 31 and operatively connected with the walking-beam 23 is a pitman 40, the described apparatus being adapted to raise and lower the walking-beam once for every revolution of the crank arm 31.

As in my issued patent, first ahove nmtioned, I preferably counterbalance the pumpim apparatus by counterbalancing means that incltliea a cylinder 4i secured at its lower end to a horning 42 with which it freely communicates. Reciprocable within the cylinder 4i is a piston 43 having a connecting rod 43 pivotally connected thereto. As a protective cover for the cylinder 4| the connecting rod 45, by preference, carria a hood 43. The housing 42 normally communicates with a compression and expansion chamber 41 having a normally closed release valve 43 and the chamber 4! in turn normally communicata with a relatively large additional chamber 33 through a pipe II and valve 52. The valve 32 and a valve 53 between the cylinder 4| and the chamber 41 are ordinarily Open unless the walking-beam is to be disconnected from the sucker rod, or the various units of the apparatus are to be isolated for some other reason.

Normally a liquid 55, preferably 011, fills the housing 42 and extends upward to present a surface in contact with the piston 43 in the cylinder 4| and a second surface in contact with a gas within the chamber 41, the gas being, by preference, compressed air and filling the remaining space in the chamber 41 and the whole of the space in the chamber 50. The

chambers

41 and 50, the housing 42, and the cylinder 4| thus constitute a chamber that contains gas and liquid and is closed by the movable piston 43.

In normal operation, as the walking-beam is moved down, the piston 43 forces liquid out of the cylinder 4i and housing 42 into the chamber 41, compressing the gas in the

chambers

41 and 50 and requiring the prime mover to exert a torque on the downward stroke of the walkingbeam, which torque is determined by the dimensions of the gas space, the stroke of the piston. and the initial pressure of the gas in the compression space. The use of a relatively large chamber 50 to provide a relatively large compression space results in a relatively small change in gas volume upon movement of the piston 43, and therefore results in a relatively small change in gas pressure throughout the cycle of movement of the piston. On the upward stroke the gas in the

chambers

41 and 50 acts upon the piston 43 to help raise the walking-beam, at the same time expanding to its original volume. The present form of my invention is adapted to automatically seek equality of work required by the prime mover to raise the walking-beam on its upstroke with work required of the prime mover on the downstroke of the walking-beam. It is contemplated that whenever work performed by the prime mover on the upstroke of the walking-beam exceeds the work performed by the prime mover on the downstroke of the walking-beam, gas will be added to the counterbalancing system to raise the counterbalancing pressure and that, on the other hand, when greater work is expended on the downstroke of the walking-beam than on the upstroke, gas will be released from the counterbalancing system automatically.

The means for lowering the counterbalancing pressure may be simply a valve controlled release pipe connected at any suitable point to the counterbalancing apparatus, for example, a valve controlled release pipe 56 connected to the pipe II and controlled by automatic means to be described hereinafter.

For raising the gas pressure in the counterbalancing system when required, I may provide a high pressure reservoir I! in which a reserve air at the required pressure, any suitable pump means may be employed. The drawings show a reciprocating air pump 50 that is continuously driven through the medium of a belt 60 from a sheave 6! on the countershaft 33. In my preferred arrangement the pump has a compression ratio corresponding to the required pressure in the reservoir 51 and is in continuous communication with the reservoir through a pipe 62 so that the pump delivers air into the reservoir whenever the reservoir pressure tends to drop 'but at other times the air in the air pump is merely expanded and contracted without dis placement into the reservoir S'|.- The reservoir 51 may be provided with a safety valve 63 and pressure gauge 65 and connects with a high pressure pipe 66 through which air may be transmitted to the counterbalancing apparatus when required, the high pressure pipe leading, for example, to the chamber 50 and being controlled by an automatic valve described below.

Although various types of controllable arrangements may be employed to govern flow through the two pipes 56 and 06, I contemplate the employment of a well-known type of pressure regulating valve. Such a valve involves the application of amechanical force exerted by a spring or weight in opposition to the pressure of the fluid controlled by the valve, the critical pressure at which the valve operates to release fluid varying with the magnitude of the applied force. In my preferred arrangement I rely upon a weight rather than spring means to oppose the fluid pressure, and I prefer an arrangement in which the operation of the two required valves is varied by movement of a single weight towards and away from a fulcrum axis. Thus, as best shown in Fig. 2, I provide a pressure regulating valve 10 for the release pipe 56 and a second pressure regulating valve II for the high pressure pipe 66 and I provide a single weight 12 common to the two valves, which weight is movable towards and away from a fulcrum axis .r-x.

The pressure regulating valve III has a control lever 13 that is fulcrumed-in a bracket 15 on the valve and continuously presses down on a plunger 16 that in turn presses against a diaphragm with-. in the valve in opposition to fluid pressure from the counterbalancing system, the principle of the valve operation being well known in the art. When this pressure regulating valve is open it releases counterbalancing gas to the atmosphere through a short discharge pipe 11. As shown in Fig. 7 the valve I includes a housing 200 that is spanned by a diaphragm 21, the diaphragm forming with the housing a valve chambar 202. The above mentioned plunger 16 is operatively connected to the diaphragm 20!, and mounted on the lower side of the diaphragm is a valve member 203 in the valve chamber 202. Normally the valve member 203 is retained in a valve seat 204 to cut off the discharge pipe 11. The previously mentioned release pipe 50 for lowering the counterbalancing pressure of the system is in communication with the valve chamber 202 to permit the counterbalancing pressure to be exerted against the diaphragm 20l in opposition to pressure from the plunger 16. Whenever the gas pressure in the valve chamber 202 predominates over whatever downward force is transmitted through the plunger IS, the diaphragm is moved upward to unseat the valve member 203 and thereby permit gas to be released from the counterbalancing system through the pipe 11. i

It is apparent that the magnitude 'of the downward force exerted through the plunger 10 determines the critical pressure in the counterbalancing system at which the valve I0 automati- In like manner the pressure regu-,

cally opens. lating valve II has a control lever 18 in a vertical plane parallel to the vertical plane of the control lever 13, the control lever 18 being fulcrumed in a bracket 00 to press downward against a plunger 8|. The valve 1i may be constructed as shown in Fig. 8. In this construction a housing 205 is spanned by a diaphragm 206 that defines with the housing a valve chamber'20l. A hollow portion 200 extends inwardly from the housing 205 into the valve chamber 201 and is formed with a valve passage 209 that communicates with the high pressure reservoir 51 through the right-hand pipe 06. Mounted on the diaphragm 206 to move therewith is a valve member 2i0 which is normally positioned in a valve seat 2| I closing oil the valve passage 20!, the arrangement being such that gas pressure in the valve chamber 201 against the diaphragm 206 tends to maintain the valve member 2! in closed position. The left-hand pipe 66 communicates directly with the valve chamber 201 so that unseating of the valve member 2i0 permits flow through the pipe line 66 to the counterbalancing system. It is apparent that whenever the gas pressure in the valve chamber 201 derived from the counterbalancing system drops sufficiently to permit the plunger 8i to flex the diaphragm downward, high pressure gas is introduced into the counterbalancing system and the critical pressure in the counterbalancing system at which gas will be introduced is determined by the force transmitted to the plunger 8| from the control lever 18.

The weight 12 is provided with four flanged supporting wheels 02, two of which on each side of the weight rest upon one of the control levers I3 and 18. By virtue of the described arrangement, movement of the weight "towards the fulcrum axis x:c lowers the pressure point of the counterbalancing system at which the valve 10 opens to release compressed air from the counterbalancing system and also lowers the pressure point at which the valve 1| opens to feed high pressure air into the system. Preferably, a relatively small pressure differential is maintained between the two valves, say, a differential of two pounds per square inch, so that the valve 10 always opens at a higher pressure in the counterbalancing system than the valve 1|. At the end of each of the control arms or levers 13 and I8, I provide what I call a tare" weight 83 that may be employed not only to provide the required pressure differential between the two valves, but also to compensate for any minor irregularities in the system.

The present embodiment of my invention is based on the conception of measuring the intake pressure of the engine 30 over the period of the upstroke of the walking-beam 26, measuring the intake pressure of the engine over the period of the downstroke of the walking-beam, accumulating the differential of these measurements over successive pumping cycles and shifting the weight 12 in accordance with, or in response to the accumulated differential, the movement of the art that various arrangements may be made to vary the position of the weight I2 in response to the intake pressure or other characteristic or factor of the engine in various practices and embodiments of my invention. The principal parts of the arrangement relied upon for control in the present disclosures are: an upstroke vacuum chamber II; a downstroke vacuum chamber 85;

a valve operating means generally designated 81;

an upstroke bellows 88; a downstroke bellows 9n; and a yoke or frame 8| that controls the previously mentioned weight I2 in response to the two bellows 88 and 88.

The function of the upstroke vacuum chamber II is to house a body of air at a pressure representing the intake pressure of the engine 38 intecrated over the period of the upstroke of the walking-beam, and the function of the downstroke vacuum chamber 88 is to represent the intake pressure on the downstroke of the walkingbeam in the same manner.

chambers

85 and 88, together with an intermediate valve chamber 82, are provided by a housing. generally designated 88, that is integral with and is supported by a standard 85 mounted on the under frame 29 of the apparatus. The valve chamber 92, which is sealed off from the atmosphere, is in continuous communication with an intake manifold 95 of the engine 38 through a suitable pipe 81. The valve chamber 82 has

ports

88 and 88 communicating with the vacuum chambers II and 88 respectively, and, as best shown in Fig. 6, encloses a valve assembly, generally designated I88, for controlling the two ports.

The valve assembly IIIII includes a valve stem III siidingly mounted in a pair of stationary supports I82, the valve stem having a valve member III on one end to control the port 88 and having a valve member I88 on the other end to control the port 88. The central portion of the valve stem III has an enlargement IIII between a pair of opposed helical springs I88 and I 88, and the enlargement is circumferentially grooved for engagement by a forked rocker arm II I. When the forked arm swings in one direction to shift the valve stem III longitudinally against the resistance of the spring I88, the valve member I closes the port 88, and when the valve stem IOI is moved in the opposite direction by the rocker arm in opposition to the spring I08, the alve member I closes the port 98.

The forked rocker arm III is keyed to a shaft III that extends outward through the wall of the valve chamber 82, the shaft being journaled in the chamber wall in an airtight manner. As best shown in Figs. 4 and 5 a friction disc Iii is keyed to the shaft III outside of the valve chamber 92 and a complementary friction disc III is rotatabiy and slidingly mounted on the shaft for cooperation with the first friction disc. suitable facing III preferably being provided on at least one of the discs. To urge the friction disc III against the friction disc iii a suitable helical spring I28 may be mounted on the shaft in compression between the disc I I I and a circular plate III that is secured to the end of the shaft by a. suitable cap screw I22. While the construction of the valve assembly IIIII is such that it will limit the oscillation of the rocker arm I I I and thereby limit oscillation of the shaft 5, I prefer to rely upon other limiting means to avoid excessive pressure against the valve springs I88 and I08. The limiting means may include, for example, a radial arm I28 on the friction disc iii, a flange The two vacuum is adjustable in length,

.arm I28. 0n downward movement the radial arm is stopped by the flange I25 and on upward movement the arm is stopped by a pair of nuts I28 onthe bolt I26, the range of movement permitted being suilicient to permit the rocker arm II I to alternately close the ports of the two vacuum chambers and 88. a

It is contemplated that the friction disc III will be oscillated in synchronism with the upand-down strokes of the walking-beam 28 in such manner that at the initiation of each of the strokes, the rocker arm I II will move to open one of the vacuum chamber ports and simultaneously close the other port. The desired synchronism and extent of oscillation on the part of the friction disc I I! may be obtained by operatively connecting the friction disc with any of various moving parts of the pumping apparatus, but I prefer simplyto operate the friction disc directly from the walkingbeam 26. In the particular construction shown in Figs. 1, 4, and 5, the friction disc II! has a radial arm I38 that is operatively connected to the walking-beam 26 by a connecting rod I3I. Preferably, the connecting rod I8I being fabricated in two sections that are oppositely threaded into an interconnecting adjustment sleeve I32.

The yoke or frame 8i is of rectangular construction and movably surrounds the standard 85 below the two vacuum chambers. The previously mentioned metal bellows 88 that cooperates with the upstroke vacuum chamber 85 is confined between one face of the standard 88 and the corresponding end of the surrounding frame 9i, and the bellows is in communication with the vacuum chamber 85 through a fluid passage I33 formed in the standard. Preferably, a suitable valve I85 is provided to restrict flow through the fluid passage I33 to whatever extent may be desired. The second metal bellows that cooperates with the downstroke vacuum chamber 86 is in like manner mounted on the opposite face of the standard 85 between the standard and the corresponding end of the frame 8|, and the second metal bellows communicates with the vacuum chamber 88 through a second fluid passage I86 having a valve I31. The fluid occupying the two vacuum chambers and the two bellows may be air, but for the sake of a desirable dashpot action I prefer to fill each of the two bellows and partially fill each of the corresponding vacuum chambers with bodies I38 of suitable liquid, such as light oil. The dashpot action arising from the inertia and viscosity of the oil may be controlled by adjustment of the valves I35 and I31. Itis apparent that the relative longitudinal dimensions of the two bellows will determine the position of the frame 9i and that movements of the frame may be readily transmitted to the weight I2 by suitable means such as a rod I48. Since the weight I2 should be permitted to cant from side to side as well as to rise and fall, the rod I may be pivotally connected to a bracket Ill on the end of the and pipe 91.

is shifted to open the port 96 to place the upstroke vacuum chamber 65 in communication with the intake manifold 96 of' the engine through the .valve chamber 92 and the pipe 91. Upon initiation of the subsequent downstroke of the walking-beam, the valve mechanism I99 shifts in the opposite direction to close the port 99 and open the port 99 to place the downstroke vacuum chamber 86 in communication with the engine intake through the valve chamber 92 Since the upstroke vacuum chamber 85 is in communication with the engine intake substantially continuously throughout the upstroke of the walking-beam, the pressure in the vacuum chamber 85 tends to follow the intake pressure of the engine during the upstroke of the walking-beam. In like manner the pressure in the vacuum chamber 96 tends to follow the intake pressure of the engine during the downstroke of the walking-beam. So long as the pressure in the vacuum chamber 85 is substantially equal to the pressure in the vacuum chamber 66, there is substantially no tendency for oil to flow in either direction through either of the fluid passages I33 and I36. If the prevailing pressure in one of the vacuum chambers drops below the prevailing pressure in the other vacuum chamber, oil will tend to flowfupward into the vacuum chamber having a relatively low pressure. For example, if the pressure in the upstroke vacuum chamber 85 drops relative to oil pressure in the chamber 86, oil will tend to flow into the chamber 85 from the metal bellows 68, and by virtue of the rectangular frame 9| interconnecting the two metal bellows, the second metal bellows 90 will tend to expand and -thereby cause oil to flow downward from the second vacuum chamber 96. In other words, the two bodies of oil I38, although isolated from each other, tend to act as one body, oil flowing out of one vacuum chamber and simultaneously flowing into the other vacuum chamber at the same rate. Whenever the vacuum chamber pressures become unbalanced, the automatic control mechanism tends to shift the weight I2 to an equilibrium position at which there is pressure equalization between the two

vacuum chambers

85 and 86.

Since the time factor is brought into effect by arranging for each of the vacuum chambers to be in continuous communication with the engine intake throughout the period of the pump stroke represented by the vacuum chamber, it is ap parent that average pressures rather than maximum or minimum pressures are balanced between the two vacuum chambers and therefore the mechanism tends to equalize the work performed by the engine on the two strokes.

For improved operation, various refinements may be incorporated in the described arrangement. For example, a choke chamber I45 may be interposed in the high pressure pipe 66 between the chamber 59 and the pressure regulating valve II to dampen surges of pressure I transmitted to the pipe 66 from the counterbalancing body of gas. In a typical situation, for example, the gas pressure in the counterbalancing system will vary from 146 to 154 pounds in the operating cycle of the apparatus. If the choke chamber is provided with suitably restricted ports, the pressure transmitted to the pressure regulating valve II will remain rather close to the average pressure of 150 pounds throughout the operating-cycle of the mechanism. Such a choke chamber, then, avoids unnecessary operation of the two pressure regulating valves I9 and 'II and also permits a relatively low pressure diiferential between the two valves.

A further refinement may be the provision of a check valve I46 for each of the

vacuum chamber ports

96 and 99 to control the communication of each of the vacuum chambers with the valve chamber 92. Each of the check valves I46 may be of familiar construction in which, as best shown in Fig. 6, a spring I41 continuously urges a valve member I46 into closed position, the valve member being disposed to open in response to preponderance of pressure within the vacuum chamber over the pressure in the valve chamber 92. When such check valves are used, each of the vacuum chambers remain sealed regardless of action of the valve assembly IIIII so long as pressure in the vacuum chamber is below the pressure in th valve chamber 92. Under such an arrangement, some anomalous action on the part of the internal combustion engine preventing development'of the usual vacuum on one of the pump strokes will not cause corresponding anomalous action on the part of the automatic control mechanism, because in such event the corresponding check valve will remain closed to maintain the degree of vacuum in the correspending vacuum chamber that truly represents the load on the engine. Some means, however, is desirable to permit air to enter each vacuum chamber because otherwise the pressure in a vacuum chamber would not drop to reflect a drop in the actual load on the engine. A simple bleeder port of relatively small cross section for each of the two vacuum chambers would suffice, but I prefer instead to provide an equalizing by-pass I59 having a small adjustment valve I5I so that whenever there is a difference in pressure between the two vacuum chambers, air flows at a relatively slow rate from the chamber of relatively high pressure to the chamber of relatively low pressure. By using one by-pass common to the two vacuum chambers instead of individual bleeder ports for the chambers, I avoid any problem of providing equal rates of leakage from the chambers under equal pressure differentials It will be readily appreciated that the rate 0t equalizing flow through the by-pass I50 must be relatively low to make the control mechanism suffciently sensitive to changes in pressure in the intake manifold of the engine. The addition of the two check valves I46 and the bypass serves to reduce the tendency of the control mechanism to hunt.

In my previously mentioned copending application the mechanism for automatically varying the counterbalance pressure is responsive to the energy output of the prime mover or to the energy transmitted through some operative connecting means between the prime mover and the well pump. In my present arrangement, however, the automatic means is responsive to a factor that varies with the energy input of the prime mover. More specifically, the present embodiment of the invention responds to a factor associated with the fuel consumption of the engine. Other factors associated with the fuel consumption that might be relied upon for automatic control could be found in carburetion or in the exhausting of fuel from the engine. If the prime mover were an electric motor, a corresponding factor associated with the energy input would be the amperage of the energizing current.

The preferred form of my invntion disclosed in speciflc detail herein for the purpose or illustration and to teach the principles involved will suggest to those skilled in the art various changes, modifications, and substitutions under my inventive concept. I reserve the right to all such changes, modifications, and substitutions that come within the scope of my appended claims.

I claim as my invention:

1. In an apparatus in which a prime mover has a characteristic associated with and varying with the prime mover input and in which the prime mover reciprocates a loaded member through a power stroke and a return stroke, the combination therewith of: adjustable counterbalancing means adapted to derive energy from said prime mover on said return stroke and to deliver said energy to said member on the subsequent power stroke thereby to substantially equalize the loads on the prime mover on the two strokes; and means responsive to said characteristic to vary the adjustment of said counterbalan'cing means to increase or decrease the magnitude of said derived energy as the load on said member is increased or decreased.

2. In an apparatus in which a prime mover reciprocates a loaded member through a power stroke and a return stroke. and in which means involved in the fuel consumption of the prime mover varies when the load on the prime mover varies, the combination therewith of: adjustable counterbalancing means adapted to derive en-- ergy from said prime mover on said return stroke and to deliver said energy to said member on the subsequent power stroke thereby to substantially equalize the loads on the prime mover on the two strokes: and means responsive to said variable means to change the adjustment of said counterbalancing means to increase or decrease the magnitude of said derived energy as the load on said member is increased or decreased.

3. In an apparatus having a prime mover for reciprocating a loaded member through a power stroke and a return stroke, and including a course for fluid flow through said prime mover involving the consumption of fuel by the prime mover. the combination therewith of adjustable counterbalancing means adapted to derive energy from said prime mover on said return stroke and to deliver said energy to said member on the subsequent power stroke thereby to sulwtantially esualize the loads on the prime mover on the two strokes; and means responsive to pressure at a point in said fluid course to vary the adjustment of said counterbalancing means to increase or decrease the magnitude of said derived energy as the load on said member is increased or decreased.

4. A combination as set forth in claim 3 in which said prime mover is an internal combustion engine and said point in said fluid course is at thelengine intake.

5. In an apparatus in which a prime mover reciprocates a loaded member through a power stroke and a return stroke, and in which some mean responds to the load imposed on the prime mover, the combination therewith of: a fluidpressure system for applying a counterbalancing force to a moving part of said apparatus for substantial equalization of loads on said prime mover during said strokes; regulating means for said system responsive to an applied regulating force, said regulating means being adapted to admit fluid into the system to increase said counterbalancing force when said applied force is increased and to release fluid from the system to decrease the counterbalancing force when said applied force is reduced; weight means to apply 5 the regulating force to said regulating means,

load-responsive, means during the power strokes and adapted to urge said weight means inthe direction to increas said applied regulating force; and a, second fluid-pressure means responsive to said load-responsive means during the return strokes to urge said weight means in the direction to decrease said applied regulating force.

6. In an apparatus having a prime mover for reciprocating a loaded member through a power stroke and a return stroke and including a fluid course for fluid flow through said prime mover involving the consumption of fuel by the prime mover, the combination therewith bf: adjustable means to apply a counterbalancing force to a moving part of said apparatus .to substantially equalize the loads on said prime mover on said strokes; a first means adapted to urge adjustment of said adjustable means in the direction of increased counterbalancing force; and a second 3 means adapted to urge adjustment 0! said adjustable means in the direction of decreased counterbalaneing force, one of said urging means being responsive to pressure in said fluid course during the power strokes of the apparatus and the other or said urging means being responsive to pressure in said fluid course during the return strokes of the apparatus.

7. A combination as set forth in claim 6 in which each of said urging means applies fluid 0 pressure to urge adjustment of said adjustable means and applies the fluid pressure throughout both strokes of the apparatus.

8. In an apparatus having a prime mover for reciprocating a loaded member through a power stroke and a return stroke and including a fluid course for fluid flow through said prime mover involving the consumption 01. fuel by the prime mover, the combination therewith of: adjustable means to apply a counterbalancing force to a moving part of said apparatus to substantially equalize the loads on said prime mover on said strokes; a first fluid-pressure means adapted to urge adjustment of said adjustable means in the direction of increased counterbalancing force; a

second fluid-pressure means adapted to urge adjustment of said adjustable means in the direction of decreased counterbalancing force; and means responsive to a moving part of the apparatus adapted to place one of said urging means in communication with said fluid course on one of said strokes and to place the other of said urging means in communication with said fluid course during the other of said strokes.

9. In an apparatus having a prime mover lot reciprocating a loaded member through a power stroke and a return stroke and including a fluid course for fluid flow through said prime mover involving the consumption of fuel by the prime mover, the combination therewith of: a fluid- 7 pressur system for applying a counterbalancing force to a moving part of said apparatus for substantial equalization of loads on said prime mover during said strokes; regulating means for said system responsive to an applied regulating force,

said regulating means being adapted to admit fluid into the system to increase said counterbalancing force when said applied regulating force is increased and to release fluid from the system to reduce the counterbalancing force when said applied regulating force is reduced; means to apply the regulating force to said regulating means to govern the magnitude of said counterbalancing force, said force-applying means being adjustable in one direction to increase the applied regulating force and adjustable in the opposite direction to decrease the applied regulating force; a first means responsive to fluid pressure in said fluid course to urge adjustment of said force-applying means in the direction of increased applied force; a second means responsive to fluid pressure in said fluid course to urge adjustment of said force-applying means in the direction of decreased applied force; and means responsive to a moving part of the apparatus to place said first and second fluid-pressure responsive means alternately in communication with said fluid course on alternate strokes of the apparatus.

10. In an apparatus having a prime mover for reciprocating a loaded member through a power stroke and a return stroke and including a fluid course for fluid flow through said prime mover involving the consumption of fuel by the prime mover, the combination therewith of: adjustable means to apply a counterbalancing force to a moving part of said apparatus to substantially equalize the loads on said prime mover on said strokes; a fluid-pressure chamber representing the power stroke of the apparatus; means to place said chamber in communication with said fluid course during the power stroke of the apparatus and to cut off the chamber from the fluid course during the return stroke of the apparatus; a second fluid-pressure chamber representing the return stroke of the apparatus; means to place said second chamber in communication with said fluid course during the return stroke of the apparatus and to cut ofl. the second chamber from the fluid course during the power stroke of the apparatus; a flrst means responsive to fluid pressure in one of said chambers to urge adjustment of said adjustable means in the direction of increased counterbalancing force; and a second means responsive to fluid pressure in the other 01 said chambers to urge adjustment of said adjustable means in the direction of decreased counterbalancing force.

11. In an apparatus having a prime mover for reciprocating a loaded member through a power stroke and a return stroke and including a fluid course tor fluid flow through said prime mover involving the consumption of fuel by theprime mover, the combination therewith of: adjustable means to apply a counterbalancing force to a moving part of said apparatus to substantially equalize the loads on said prime mover on said strokes; a fluid-pressure chamber representing the power stroke of the apparatus, said chamber having a relatively small bleeder port; means to place said chamber in communication with said fluid course during the power stroke of the apparatus and to cut oil the chamber from the fluid course during the return stroke of the apparatus; a second fluid-pressure chamber representing the return stroke of the apparatus, said second chamber having a relatively small bleeder port; means to place said second chamber in communication with said fluid course during the return stroke 0! the apparatus and to cut of! the second chamber from the fluid course during the power stroke of the apparatus; a first means responsive to fluid pressure in one of said chambers to urge adjustment of said adjustable means in the direction of increased counterbalancing force; and a second means responsive to fluid pressure in the other of said chambers to urge adjustment of said adjustable means in the direction of decreased counterbalancing force.

12. In an apparatus in which a prime mover reciprocates a loaded member through a power stroke and a return stroke, and in which some i means responds to the load imposed on the prime mover, the combination therewith of: a fluidpressure system for applying a counterbalancing force to a moving part of said apparatus for substantial equalization of loads on said prime mover during said strokes; a first regulating means for said system responsive to an applied regulating force and adapted to release fluid from the system when said applied regulating force is decreased; a second regulating means for said systern responsive to an applied regulating force and adapted to admit fluid to the system when said applied regulating force is increased; a-flrst weight means adapted to apply regulating force to said first regulating means; a second weight means adapted to apply lesser force to said second regulating means, both of said weight means being adjustable to vary said applied regulating forces; and means responsive to said load-responsive means to vary the adjustments of said two weight means simultaneously to automatically increase the counterbalancing force when the load on said member increases and vice versa.

WALTER E. SAXE.