US2233227A - Hydropneumatic counterbalance - Google Patents

Description

Feb. 25, 1941. H w RAMEY TAL l 2,233,227

HYDROPNEUMAT I C CUNTERBALANCE Filgd Dec. 27, 1938 Patented Feb. 25, 1941 UNITED STATES PATENT ori-ics HYDROPNEUMATIC COUNTERBALANCE of West Virginia applicati@ December 27, 193s, 'serial No. 241,916

28 Claims.

This invention relates to counterbalances, and more particularly to hydropneumatic counterbalances for use with oil well pumping rigs.

` ing for several reasons. L, terbalancing force may be applied substantially As is well known, it has been the common practice for a number of years to counterbalance cil well pumping rigs to equalize the power demand during the pumping cycle. This usually has been done either by counter-weighting the walking beam or by counter-weighting the crank shaft from which the pitman is driven. Each -method possesses advantages over the other but the advantages of both methods are greatly onset by substantial disadvantages. Enr example, the use of heavy counterweights on the walking beam requires the use of a very heavy walking beam and the counter-weights can be adjusted only with great difficulty. In the case of a pitman failure, the weight oi' the walking beam obviously will move the walking beam downwardly and may result in wrecking the entire pumping rig and in causing injury to workmen unless the downward movement of the walking beam is stopped by a conventional headache post.

Rotary counterweights carried by the crank shafts have been largely used in recent years instead of beam weights because of certain advantages which they possess, but crank counterweights also involve substantial disadvantages. Such counterweights 4are not easily adjustable; they add substantially to the load on the crank and crankshaft; and they provide the counterweighting at a substantial distance from the ideal point, namely, adjacent the connection of the pump rods to the walking beam.

In order to overcome the numerous disadvantages oi the use of counterweights as counterbalancing means, it has been proposed in recent years to provide pneumatic counterbalancing means which operates to store energy on the down stroke of the pumping rods and to'expend energy on the up stroke. Such a mechanism is advantageous over conventional counterweight- For example, the counat the ideal point and lighter parts may be used through the elimination of heavy counterweights. Thus the use of heavy masses of reciprocating or rotating weights is eliminated and the pumping equipment may be made more portable and easier to install, and much less foundation is required for stability.v

Although advantageous over the use of counterweights, pneumatic counterbalancing also involves numerous disadvantages. Many wells (Ci. 'I4-589) are pumped night and day and itis essential that a counterbalance unit be made as trouble free as possible partly because of the fact that one pump attendant will frequently have in his charge a substantial number of pumping wells scattered over a considerable territory. Pneu-l maticl counterbalances provide too many possibilities of failure to render their use practicable thus resulting in a complete unbalancing oiy the pumping unit, and the same result may occur through the springing o! a leakin the packing of the compressor or in the packing oi' the counterbalance piston. There are numerous other disadvantages to pneumatic counterbalancing which need not be referred to in detail.

In the copending application of. Robert Griiiln De La Mater, Serial No. 157,189, med August 3, 1937, there is disclosed a hydropneumatic coun-- terbalance which is highly efficient, practicable and trouble proof since it overcomes the disadvantages of both the weight and pneumatic types of counter-balances. In the structure of the copending application referred to a vertical receiver is provided with a cylinder therein sealed at its upper end with respect to the receiver and open at its lower end for communication therewith. A plunger is reciprocable in the cylinder and the upper end of the plunger rod and the bottom of the receiver are respectively connected to the walking beam and to a stationary support whereby downward movement of the plunger will displace fluid from the lower end of the cylinder into .the receiver. A'

body of a suitable liquid such as oil is maintained in the bottom o! the receiver and the quantity of oil employed is such that its level never reaches the lower end o! the cylinder when the plunger reaches its upper limit of movement.

With such a construction. each downward movement of the plunger displaces oil from the cylinder thus causing the level in the oil in the receiver to rise and cause compression of the entrapped air or other compressible gas thereabove, thus storing energy to be expended upon each up stroke of the plunger. With such an apparatus, the entrapped air will remain indefinitely in the top of the receiver since it never reaches the plunger and accordingly cannot leak,

dusted. f It will be apparent that the pressure release ation of the apparatus, and any minor leakage of oil which may occur is compensated for by automatic means including a'reservoir, a small vmaximum pressure at which the valve 'valve referred te may be adjusted te determine I they mammum pressure in the receiver, thusv v providing a regulating means therefor and pre-YV` venting the accumulation of excess pressure incident to expansion caused by increased temperatures occurring during the day. Moreover.;l the valve maintains the desired maximum'pres-- sure in the receiver by supplying oil thereto to; compensate for any leakage, which may occur` as well-as any drops'in, pressure which occur incidentr to decreases in temperature. The system. also possesses Va degree ci' flexibility which 'l renders its use highly iulvantageousv over pneuy Vmatic counterbalances.; For example, by increasingor decreasing the amountgof oil in the receiver, pressure differences between minimum In the copending application of Harold W.

'Eames'. Serial No. 163,862, iiled September 14. 1987, there is disclosed a system. which is identical in principle to the system disclosed@ in the copending'application referred to above'. the dir-j ferences ylying in the provision in the counterments over the system in the earlier ledapplication. For example, in the application of :Harold W. Rainey a controllable by-pass is proj vided between'the receiver and the reservoir to permit the drainage of oil from the receiver and tov permit the manual controlling of maximum pressure in the receiver in the event of failure of the pressure release valve'. u The structure of the Ramey application also includes means for supplying oil to the upper end of the cylinder to increase the effective length of the plunger to provide a higher degree of compression of air above the plunger for initially charging the receiver when the apparatus isused with a short stroke pumping unit. The structure of the Rainey application also includesmeans for creating a partial vacuum above the plunger during the normal operation of the apparatus to increase difierential pressures between the iluids by compensating' for leakage ot oil and variations in temperature conditions, in most installations the variations in pressure due to temperature changes were not sulcient to noticeably ai'- fect thev operation of the apparatus. Moreover,

- the pressure release valve employed with the 'that'it eliminates the l uzr: l.. and maximum can be predetermined as desired. *by v piying en te the reeeiver. but instead er using s pressure'release valve to supply oil to the receiver in accordance with pressures therein, a

reservoir is employed and the apparatus is provided with means for returning to the reservoir all oil which may leak past the plunger. in the reservoir admits -oil to the pump to be tramierred to the receiver under pressure when the level of the oil in the reservoir is above a predetermined point, and the level of the oil in the rervoir rises only because oi the returning thereto of oil leaking past the counterbalance changes in temperature conditions which, for mesi;v installations,Y is unimportant. Therefore. the,y apparatus of the Rainey applica/tion Serial No.v 223.737,;is advantageous over the structures oi the'other pendingr applications referred to .in

an important object er: me present :avenues is ,'toprovide 'a' hydropneumatic counterbalance which embodies the l.advantages of `the structures voiv thecopending applications referred to but which is advantagecusthereover for the reason j that it eliminates the use of the pressure release. valve, as is true oi application Serial No. 223,737, www 0f the later led applis-M1011 0f 111mmand for the additional reason that it eununates the use of a separate reservoir and also the pump for supplying oil to the receiver. Y

More specifically, an important object of the invention is to provide a hydropneumatic coun-` f-terbalance the structure of which 'is confined to the c referred to wherein upward movedesired quantity of oil, will always operate with the same quantity of oil therein and pressures in -the receiver can vary only in accordance with use ofv the pressure release Y ment of the counterbalance plunger is utilized for I creating a. pressure effective for returning to the receiver oil which has leaked therefrom.

A further object is to provide means for utilizing the counterbalance plunger' and cylinder as a pump for returning to the cylinder oil which has leaked therefrom, wherein downward movement of the plunger creates a partial vacuum to draw some of the leaked oil into the cylinder and i wherein upward movement oi' the plunger returns der pressure, and for utilizing the same means for returning to the receiver any oil which leaked therefrom past the plunger.

A further object is 'to provide such anapparatus wherein the means for returning oil to the receiver may be utilized for increasing the amount oi' oil in the receiver .to increase the differential between minimum and maximum pres- Y may be readily returned to the receiver if it is desired to increase the amount of oil therein.

A further object is to provide an apparatus wherein pressure is created in the upper end of the cylinder during the up-stroke oi the plunger to return to the receiver oil which leaks past the plunger, and to control and utilize pressures in the upper end of the cylinder to improve the operation of the apparatus.

A further object is to provide such an apparatus wherein the pressures in the upper end of the plunger may be utilized in certain .installations and under certain operating conditions for controlling the inertia eilects of the pumping apparatus to greatly increase the degree of smoothness of operation oi the apparatus.

A further object is to provide an apparatus oi the character referred to wherein the tendency of the belt employed for driving the pltman crank shaft to chatter or vibrate excessively on the tight side of the belt may be eliminated by preventing excessive decreases in pressure diiterentials on opposite sides of the plunger due to the building up of back pressures above the plunger.

A further object is to provide means for bleeding air from the upper end of the cylinder to control back pressures therein.

A further object is to provide a bleeder pipe for the purpose just referred to wherein such pipe is connected to the means for returning leakage oil to the cylinder whereby any oil blowing out of the cylinder throuh the bleeder pipe may be returned to the cylinder to prevent the loss of such oil. l v o Other objects and advantages of the invention will become apparent during the course of the v'- following description.

f In the drawing we have shown two embodi- .4c

ments of the invention. In this showing:

Figure l is a side elevation of a standard well )rig showing the yinvention applied thereto,

-Figure 2 is a central vertical sectional view through the counterbalance, parts being broken away and partsbeing shown in elevation.,

Figure 3 is an enlarged detail sectional view of the upper end of the counterbalance cylinder showing the oil collecting means associated therewith,

Figure 4 is a fragmentary central vertical sec?` tional view taken at an angle to' Figure 2 showing pressure control means for the upper end of the counterbalance cylinder,l parts being shown is oscillated in the usual mannerby a pitman I3 driven by a crank I4 mounted on the usual crank shaft I5 and driven by any suitable prime mover (not shown). The well end of the beam is connected by the usual polished rod carrier I6 to conventional polished rods I1. The usual headache post need not be used in connection with the present apparatus for a reason which will become apparent. While the invention has been illustrated as being applied to a conventional pumping rig, it will become apparent that it can be used in connection with any type of analogous structure.

The present invention comprises s. self-conf tained counterbalance unit indicated as a whole by the numeral IB. This unit comprises a preis! erably cylindrical receiver Il having upper and lower heads. and 2I preferably welded to the body of the receiver. A supporting member 22 is preferably welded to the bottom head 2l and is pivotally connected asiat 22 to a suitable support 24 preferably mounted upon the usual base or foundation 25. While the receiver has been shown as an integral part of the counterbalance unit, it will become apparent that this arrange ment is preferred but not essential.

A cylinder 26 projects downwardly through an axial opening 21 formed in the upper head 28, the cylinder having an annular enlarged portion 28 at its upper end. ./The latter portion of the cylinder is provided with an outstanding annular flange 29 supported on a ring lII prei erably welded in position on the head 2l, the ilange I9 being secured in position by suitable bolts 3| passing through the ring 3l).

A bearing 32 is mounted in the upper end ci' the cylinder and is provided at itsA upper enel with a relatively heavy annular flange 33 over lying the upper enlarged end 28 of the cylinder and bolted thereto as at 34. The bearing l2 canI ries a suitable bushing 35 receiving a'verticaliy reciprocable plunger rod 38 to the lower end ci which is connected a plunger 31. Intermediate its ends, the bearing 32 is provided with an annular groove 3B forming a flange for a pur v,pose to be described, and the lower extremity of otally `connected to the walking beam as at ed to effect reciprocation oi the plunger upon cs` cillation of the walking beam.

Referring to Figure 3, it will be noted that a cap 4I is bolted as at 42 to the upper endoi' the bearing 32. Above the bushing 35 a compressi= bie packing ring 4l is arrangedv and this packing is compressible by a ring 44 engageable against the bottom of thecap 4I. An annular charmIz ber or space 45 is dened by the bearing 32.

`ring 44 and cap 4I, and communicates through small passages 46 with a conical recess or basin 41 formed in the ltop oi the capll and surrounding the plunger rod 36. The ilange I3 is provided with a radial passage 48 communicating at its inner end with the chamber 45 fora purpose to be described.

The casing contains a body 48 of non-corn-= pressible fluid, preferably oil, and plugs 5I) may y bearranged at dlfierent'levels in the wall o f the receiver to facilitate the initial :charging of the receiver with oil and to determine the level of the oil therein. The space above the oil is adapted to be charged with air or other compressible nuid and thev apparatus embodies means for pumping air into the top of the receiver. Refer ring to Figure 2 it will be noted that the ange 29 is provided with a passage 5I commenting with the chamber 38 adjacent the bottom there-- of. A piping connection 52 is connected between the outer end ofi the passage 5I and theV top of the receiver, and check valves 53 are arranged in the connection 52 and open outwardly with respect to the passage 5I. While two checir valves B3 have been shown, only one is necessary5 but two are preferably` used to insure .against leakage from the top of the receiver.

38, and the connection 54 communicates with such chamber adjacent the bottom thereof through a radial passage 56 formed in the ange 29. The lower end of the pipe connection 54 is preferably normally plugged as at 51, and near its lower end the piping connection 54 is provided with a manually operable cut off valve 58.`

In charging the receiver with air, it will be obvious that the plug 51 is removed and the valve 58 is opened, whereupon each downward movement of the plunger draws air into the cylinder through the connection 54 and discharges it to the receiver through the piping connection 52.

The latter piping connection is also utilized, dur

ing normal operation of the apparatus, for returning to the receiver oil which leaks past the plunger 31, and this forms one of the important features of the present invention.

It will be apparent that some slight leakage of oil past the plunger 31 will occur, and4 some of this oil will be employed in lubricating the plunger rod 36.

Slight amounts of oil will be scraped from the plunger rod by the cap 4I during downward movements of the plunger rod, and

this oil will be collected in the basin 41 and willflow downwardly into the chamber 45 (Figure 3).

Means are provided for automatically returning such oil to the receiver.

Referring to Figure 2 the numeral 59 designates an oil trap as a whole comprising a casing 60 closed by an upper head 6l and a pipe 62 is connected between this head and the radially outer end of the passage 48 to receive oil from the latter. A pipe 63 leads from the piping connection y54 to the Vinterior of the casing 60 and has its inner end turned upwardly and terminating in a valve seat 64 engageable by a valve 65 carried by the bottom of. a float 66. Whenever oil collects in the casing 60 to a sumcient extent to move the float 66 upwardly to open the val-ve 65, oil will be sucked into the pipe 63 when the plunger 31 moves downwardly and thehead 6 i ls vented to the atmosphere as at 61 to permit oil in .the casing 60 to flow into the pipe 63. When the valve 65 is'closed, it will be obvious that no air from the vent 61 may flow into the pipel 63.

In the copending applications of Robert Griiiin De La Mater Serial No. 157,189 Vand Harold W;

Ramey, Serial No'.- 163,862, referred to labove, the level of the oil in the receiver is maintained in accordance with pressure conditions therein, and

automatic means is provided for replenishing the oil in the receiver to maintain a fixed maximum pressure therein. Such means has associated therewith a pressure gage arranged in the piping connections associated with the automatic means referred to. No such means need be employed in the present construction but the receiver is preferably provided with a pressure gage 68 normally to cut oi from the receiver by a valve 69. -The receiver is also provided in the bottom thereof with a Valve 10 to permit the receiver to be Y drained, when desired.

In some installations and under some operat- 75 ing conditions it has been found that a greatly improved operation of the apparatus may be pro-l vided by controlling the quantity of ,air and the back pressures in the upper end of the cylinder 26, and means for this purpose is shown in Figure 4,. The upper end of the cylinder may be provided withl a passage 1I having a piping connection 12 leading to a passage 13 communicating Y with the chamber 45.- The piping connection 12 is provided with a check'valve 14 opening out-v wardly with respect to the passage 1 I and a man-' ually controllable valve 15 also is arranged in the connection 12. y

s will be explained, vthereceiver I9 contains a body of oil 49 to the proper depth according to operating conditions, andthe quantity of oil may be changed to adjust the apparatus for changes in working conditions. opening the valve 10 to release some of the oil from the receiver, or the amount of oil in the receiver may be increased by introducing oil into the bottom of the piping connection 54 if the valve 58 is opened. If desired, means may be provided, as shown in Figure 5 for maintaining I'his maybe done by oil in a position to be drawn into the lower end Y of the pipe 54. As shown, a pipe connectionr 16 leads from the bottom of the' receiver to the bottom of a small vcontainer 11, and a manually controllable valve 18 ,is arranged inthe pipe 16. Y

The lower end of the pipe connection 54`extends to a point adjacent the, bottom of the container 11.

The operation of the apparatus is as follows:

When the operation of the apparatusis to beV y started,`one of the plugs 50 may be removed and oil` or other non-compressible fiuid may be piped intothe receiver, the level of the oil depending upon the particular installation, and the plunger 31 being maintained in its lower position whileV This is accomplished by opening'the.

respect to the cylinder 26, andaccordingly the check valve closes immediately upon the beginningof each up stroke of the plunger. The check valves 53 open outwardly with respect to the upper end of the cylinder 26, and accordingly y they close upon each down stroke of the plunger while air is being drawn through the pipe 54 into the upper end of the cylinder.

It will be apparent that as pressure is accumulated in the top of the receiver,l each up stroke of the plunger must compress the air'in the upper end of the cylinder to a pressureabove the pressure in the receiverv before the check valves 53 will open. Therefore, the check valves 53 open slightly later-upon each up strokeV 0f the plunger. This is of no importance when the unit is being operated at its maximum stroking,

assess? the plug l1, hold an open `topped container of oil over the bottom of the pipe connection Il, and then open the valve ll.- This operation is performed, of course, before the charging operation commences and each down stroke of the plunger will draw oil into the upper end of the cylinder and the oil will lie above the plunger I1 to increase the eective length thereof. In other words, when the apparatus is used at a stroke shorter than the maximum, oil above the plunger will reduce the clearance space above, the plunger at the top of its stroke, thus permitting the plunger to compress air in the upper end of the cylinder to the extent necessary to charge the receiver to the desired pressure.

When the desired pressure in the receiver has been attained in the manner described, the system is ready for operation as a counterbalance. Upon each downward stroke .of the plunger 31. the oil or other non-compressible fluid will be displaced from the lower end o f the cylinder 20 into the receiver Il, thus raising the level of the oil. in the receiver against the pressure of the air or other compressible iiuid in the top of the receiver. Pressure in the receiver increases progressively upon thedownward stroke of the pump rods and reaches its maximum pressure when the pump rods reach their lowermost position.

It will be apparent that energy will be stored in the compressed fluid above the oil on each down stroke of the plunger, and this energy is expended on the up stroke of the pump rods to assume part of the load of the pumpmd and the oil being lifted from the well. Thus the` prime mover which drives the shaft Il is required to perform only aportion of the work lnecessary for moving the pump rods upwardly. The maximum upward force exterted by the counterbalance is preferably equal to the weight oi' the pump rods plus half the weight of the column of oil being lifted from the well, and at the beginning of the up stroke, therefore, the force exerted by the prime moveris the force necessary to elevate half the weight of the column of oil being lifted. 'I'he energy required for compressing the air in the receiver is theoretically equal to the energy expended by the compressed air in forcing the plunger upwardly during the up stroke of the pump rods. Thercfore, the force required to compress the fluid above the oil in the receiver on the down stroke of the pump rods is equal to the weight of the pump rods plus half the weight of the oil which is lifted on each up stroke of the pump rods. Accordingly the prime mover, when the plunger reaches the point of maximum compression of the air in the receiver, exerts a force equal to half the weight of the column of oil which is lifted from the well on each up stroke of the pump rods. It will be apparent therefore, that the prime mover is called upon to exert approximately the same force on the up and clown strokes of the plunger 31, thus rendering far more uniform the power demands which are made on'the prime mover throughout each cycle of operation.

It .will be apparent that variations in the pressures in the receiver at any given point in the movement of the plunger 31 will occur due to expansion and contraction incident to temperature changes and due to the relatively small leakage of oil which occurs Vpast the plunger 31.1, In the copending applications of Robert Griffin De La. Mater serial No. 157,189 and Harold W.

Ramley, Serial No. 163,862, leakage past theA plunger 'of the counterbalance was not directly taken into consideration in maintaining proper pressures in the receiver since in each casethe apparatus functioned automatically to maintain pressures regardless of the causes of variations in pressure. As previouslyvstated, such mecha v,

nisms required the use of the reservoir, apump for positively transferring .oil from the reservoir to the receiver, and a pressure release valve for determining the operativeness oi the pump for supplying oil to the receiver.

While each of the mechanisms referred highly emcient in operation, it was found that 'in most installations changes in pressure due to temperature changes were not sufficiently serious' to require that they be compensated for. Accordingly the apparatus disclosed in the copending application of Harold W. Ramey, Serial No. 223,737, referred to above, was developed. Such apparatus eliminates the use of a pressure release valve connected between the pump and the receiver, but employed a pump and a reservoir with means for transferring to the latter any oil which leaked past the plunger of the oounterbalance. As oil accumulated in the reservoir, its increased depth above a predetermined level'represented the exact amount of leakage of oil from the receiver, and a iioat in the reservoir would operate to supply to the pump the necessary ammmt of oil to exactly replenish the receiver with oil to replace the oil which had leaked past the plunger.

The present' construction is advantageous over the Rainey application Just referred to in that it periods of time and leakage past theplunger. During the therefore becomes a serious matter. normal operation of the present apparatus the valve Ul is maintained closed to prevent any air from being drawn into the top of the cylinder Il. ,Oil which leaks past theplungerwill accumulate thereomof course. and when this oil reaches the slightdepth necessary fomit to f beforcedupwardlyasfarasthepassagell- (Figure 2) at the upper limit -of the stroke of the plunger 81, thepressuregenerated by the up stroke of the plunger wm cause ou to be 1 pumpedthrough the passage il and through the or basin Il and iiows downwardly through the passages into the chamber 4B; llroxn this chamber the oil ilows by gravity through pipe l2 tothetrapllL` y The valve 65 is n'ormaiy `closed, thus rire--A venting thel of air into the pipe If any air were admitted into this `pipe itv would be drawn through the pipe connection ,M into the cylinder 'Ilupon eaclijdown stroke V'of the would force more 'airthrcughfthfpipe comicof tion 22 into vthe .top of thejreceiverto inc.

the pressure therein., When cil ecc'umuletesin the trap il to the depth necessary to support the iioat the vvalve Il will slightly open to permit di to tiow into the pipe 63, the valve '85 closing u soon as the cil level in the trap ceases to sup- 6 pont the oat Oil 'ilowins into the pipe B3 will be drawnthrough .the pipe M into-the top ci' the cylinder 2% and will -be returned to .the receiver, when the' plunger 311s at the top of its stroke, through the pipe connection 52. 1

lil Y From the Ioregonig it will be apparent that the present apparatus provides a selifcontained unit for ccunterbalancing a walking beam, it being unnecmary to employ an oil pump. a pressure `release valve, or an oil reservoir as e. sepa- .15 rate unit from the counterbalance. The exact amount yot oil leaking pastille plunger 31' willV always be compensatedriorby `the return of such oil Ito the receiver thus maintaining a constant amount of oil therein. Oi course, l'there will b`e 2o some slight diner-ences- -in -pressures due to changes in .temperature acontions. but in most installations, these diiigrences in pressures needl not be compensated for. It is necessary to compensate for leakage of oil past the plunger since auch leakage, over a long period of operation of the pumping apparatus, will be quite Sibihiial.

It will he apparent that .the greater -tleu'uantity of 'oililn the4 receiver the greater will be the differential beiween /minimum maximum so pressures at 'opposite ends of the stroke of, the

plunger Il. Conversely. a reduction in the quantity o! cil in the receiver will reduce the diierential between minimum and maximum presl aurea. The present apparatusv provides means as whereby the quantity o1' oil in the receiver readilymaybednnged to varythediierence bctwecn'minimum and maximum pressures in accordance with changes in operating conditions. Referring to 2 it will be apparent that if 40 it is. desired to reduce the diierential between minimum" and `maximum measures iftv vmerely is necessar'yto open the valve 1I and drain some of theoil from the receiver. This drainage of oil obviously will reduce the maximum pressurek 4s which againmay he increased merely by removthe plug lI'I and opening the valve 58 to charge vthev .top oi the receiver with more air until the'desired reading is secured on the gage In' this connection, attention is invited to '50 vthe tact that the use oi' the plug 51 is wholly unf'necessary, but its use is preferred since `it provideo a positive seal against the leakage of air intothe Pinelli! 'there should be any leakage paotthevalveil. y 55 It ist is desired to' increase the differential be` tween minimum and lmaximum pressures, the operator may remove the plug Il, hold a. con-` @einer of oil at l'the bottom o! the pipe il with the lower end of the pipe immersed in the oil,

` w and then open theY valve Il until 'the desired amount ci' oil has been drawn through the pipe Il. Oil willbe drawn through the pipe M into r the upper end of the cylinder 2| upon each down 65 stroke oi' the-plunger 31 and will be discharged upon the np stroke oi the plunger through the pipe connection I! into .the receiver. When the dired amount ci oil has been supplied to the receiver, the valve It may be closed. Accordingly 7o it will be apparent that the pipe connections l! and M and associated elements -form means tor charging the receiver with air; means torreturnlng to the receiver all ci the oil which leaks past the plunger 31; and means for increasing the wamountotoilinthereceiver-whenitisdesirede 2,233,227* l v v Y to increase the differential betweenminimum j maximumpressures. Y.

If desired, the arrangement shown inFgure 5V may be employed for reducing the'amount of oil in .the receiver or for increasing it. When itls desired to decrease the amount of oil inthe Kre-.5

Cil'

celver,` the valve 18 may be openedto lpermit oil; to flow from the receiver into the container TI,A

the valve 18 being closed after the' quantity'of oil in the receiver has been reduced .to .the desired i140 extent. vOil inthe container 11 provides a ready source of oil when it isdesired to increase the amount oi' cil ,in the receiver, it merely being necessary to` open the valve 58 whereupon oil will be drawnthrough the .pipe M to be pumped l5 into .the receiver as described in connection with the structure in Fig-ure 2. y

As is .true of the structures of 'the copendingVK applications referred to, the present invention adds nothing .to the weight of the walking beam, 20 and thus permits .the use oi' a muchllghter walking beam, and the counterbalance applies the counterbalancing force at a point close to the point where work is performed. vIt also will be apparent that downward movement o! the plung# 25 er is hunted. and accordingly the apparatus acts as a headache post to limit the downwardmovement ofthe adjacent end of the walking beam, thus eliminating the necessity ior using convene tional-headache posts.

Particular attention is .invited to the importance of the use of the bleed line 12 and its Ycontrol valve 15, this means being useful under cer` tain conditions, particularly during the normal operation oi the apparatus. It'has been found *35' that regardless of the type of oil used in the apparatus, the subjection of thefoil to substantial pressures causes the aerationlotthe oil, thus causing the oil to assume a ioa'my consistency when the pressure is released. -This characterf- 40 istie of the oil does not affect the functioning of the oil in the receiver to any noticeable exy tent for 'the Vreason that this oil is always main-f tained under sumci'ent pressureto prevent sulv stantial expansionof the oil under the inuence of -theair entrained therein. The aeration oi the oil must begiven serious consideration, however, in thefunctioning of the ccmpressionchamber.l that is, the space aboveV the plunger 31.

In .the'preferred practice of charging vthe re-` 50 ceiver, the walking beam is oscillated rbeiore being connected to the polished rods. the valve Il being opened and theplug 51 removed to admit air into the compressionchamber on each downstrokevof the plunger. Upon each up-stroke of 55 the plunger air VVis compressed and dischargedv over into the receiver to build up pressure therein. It will be apparentthat the clearance space above the plunger 31 determines the maximum pressure which canfbe built up in thecompression chamber and this pressure under any conditions obviously is suiiicient to discharge air over into ,the receiver when the. charging` operation is started. Itv is desired to reduce the clearance space above the plunger -when the latter is at the upper limit of its stroke. during the charg-l ing operation, for twol reasons. namely, in order to increase maximum pressures inthe compressionv chamber to reduce the time required for charging the receiver, and to insurevthe development kof suillclent pressure in the compression chamber to fully charge the receiver to its mlnimum pressure. Y

For this reason oil is introduced into the compression chamher in an amount suiliclent to 7.75 f

raise the level Aci the oil approximately to the level of the passages 5| and 56 when the plunger is at the upper limit of its stroke, in which case maximum pressures in the compression chamber can be developed upon each up-stroke ofI the plunger. As previously stated, each down-stroke of the plunger during the charging operation, draws air into the compression chamber, and it is this air which is compressed to be discharged over into the receiver.v Due to the characteristics of the oil as explained above, a certain amount of the air upon each up-stroke of the plunger will be entrained in the oil and when the plunger moves downwardly to create a partial vacuum and draw more air into the compressionchamber, the oil in such chamber-will expand. It is believed that the up-stroke of the plunger does not completely reduce the oil to its normal volume at the upper limit of the plunger stroke, and accordingly some little oil will pass over into the receiver during each reclprocatlon of the plunger.

Asa result, oil is gradually lost from the compression chamber by beingr pumpedA over into the receiver and while this action increases the quantity of oil in the receiver, the increase ls proportionately so small as to cause no noticeable diiference in the normal operation of theA Vand the minimum pressure 300 lb. per square inch. This minimum pressure may be easily and quickly built up in the receiver ii'y the clearance space in the compression chamber is maintained relatively small. Assuming that 3 quartsof oil are added to the compression chamber to reduce the clearance space therein to zero (except for the fixed clearance space Il) this quantity oi oil soon may be reduced one-half by the loss of oil due to the aeration and expansion ofthe oil and the pumping thereof to the receiver with the air. Under such conditions, the increase in the clearance space in the compression chamber will be such that air will not be compressed upon each up-stroke ofthe plunger to a pressure in excess of 300 lb. per square inch, which is necessary in order to fully charge the receiver` in the particular installation being considered.

Assuming that this condition occurs, the operator will close the valve 58 to prevent the admission of more air into the compression chamber, and `will open the bleeder valve 15. Upon each 11p-stroke of the plunger 31, therefore, some air will be discharged from the compression space through the pipe 12 until approximately atmospheric pressure will exist in the compression chamber at the top oi' the plunger stroke. The operator 'then may close the valve 15 (although this is not wholly necessary as will become apparent) and will open the valve 58 while holding a container oi' oil at the bottom of the pipe Il, whereupon down-stroke oi' the plunger will create a partial vacuum to vdraw oil into the compression chamber and thus reduce the clearance space therein to the point,

where the pressure blnlt up in the compression chamber will be sufficient to discharge air over into the receiver to establish the desired'minimum pressure therein. It 'will be obvious that in the form of the invention shown in Figure I oil may be maintained. in the receptacle il to supply the desired amount of oil underthe conditions just described. l

The foregoing charging operation is assumed to have been carriedout with the walking beam disconnected from the polished rod. It is not necessary that the charging operation to be completed to vestablish the desired minimum receiver pressure before connecting the walking beam to the polished rods. As soon as the counterbalance pressure reaches a-point where its reaction is approximately equal to the weight of the polished rods, which may be at about 275 1b. per square inch minimum, the unit may be shut down and the walking beam connected to the polished rods. With the valve 58 left open, the operation of the unit is continued until the minimum counterbalance pressure is built up, which pressure may be 300 lb. per square inch in the particular installation being considered. When Vsuch minimum counterbalance pressure has been established, the air intake valve 58 will be closed and the counterbalance will operate in its normal and intended manner. K

Assuming that normal operation of theapparatus is started with a relatively small clearance space lexisting in the compression chamber, it will be apparent that some air in most vcases will leak into the compression chamber. Such leakage occurs past the bearing audit also' will be apparent that some air may leak past the valve 58, particularly if this valve is carelessly closed. It is also possible that a lag` in the closing of the' float valve 65 may result in a'slight leakage of air into the pipe 63.- As-, suming that/such leakage occurs, and it actually does occur in many installations, there will be a l'gradual increase in the quantityof airpresent in the compression chamber.

At thebegmnmg of the normal operan r n`ef-v the apparatus and before the leakage of air into the compression chamber has progressed toj ak noticeable extent, it willbe apparent .that the minimum counterbalance action will be. provided when the plunger 31 is at the top' of its stroke and during most oi' the stroke of the plunger the pressure in the compression chamber will be at atmospheric or sub-atmospheric pressure;

'The fact that sub-atmospheric pressure exists,-

during a greater portion ci' the stroke of the` plunger obviously will tend to cause leakage of air into the compression chamber. As this leakage progresses, it will be apparentvthat pressures -in the compression chamber at'the upper limits of the plunger stroke will gradually increase, thus gradually decreasing differential pressures ail'ecting opposite ki'aces of the .plunger 31. De-

pending upon the amount of oil remaining in. Vthe compression chamber, the pressure therein.

as the leakage of air continues, will approach a maximum equal to the minimum receiver pressure and above such pressure' it will be obvious that air will be discharged over into the receiver.

assuming thatthis occurs, it has beenr found that the quantity of air pumped into the receiver, except in extreme cases, will be so slight as to cause no noticeable diii'erence thecounychamber, in Vwhich case no air will be pumped over into the receiver.

' Ii' this procedure is followed, it will be .apparent that substantial back pressure will exist in the compression chamber and this back pressure may be advantageous or disadvantageous depending upon the particular installation, and in any event, it can be properly controlled by the bleeder valve 16. It will be apparent that upon each down stroke of the plunger, pressure will be built up in the receiver and the increasing pressures will oier increasing resistance to the movement of the plunger, thus cushioning the movement of the walking beam to assist in deceleration thereof and tending to overcome the inertia of the parts when the walking beam reaches the limit oi its stroke. The compression of the air in the receiver during downward movement of the plunger stores energy 4which is expended duringthe up-stroke oi' the plunger to provide the desired counterbalancing action. If the clearance in the compression chamber is negligible, the energy stored in the receiver vwill exert a force tending to lift the plunger throughout its vupward stroke, substantially to the top limitl thereof, although the force exerted ywill progressively diminish as the pressure in the receiver approaches minimum.

However, if the compression chamber isfair locked, that is, if the quantity of air above the plunger is such that it will not be raised to a pressure sumcient to be discharged into the receiver'at the upper limit of the plunger stroke, it will be apparent that the eective counterbalancing action will be greatly reduced.. In other words, during therupward movement of the plunger the pressure in the receiver will be "progres'sively reduced as Apreviously described, lbut onthe otherhand, substantial back pressures will b e present in the compression chamber throughout the greater portionof the plunger stroke. For example, assuming that the minimum receiver pressure is 300 lb.per square inch, the compression chamber may contain so much air that the pressure therein will vary from 10 lb. below atmosphere for example, at the bottom of the plunger Astroke to a little less than 300 lb. per square inch at the top of the plunger stroke. Accordingly it will be apparent that throughout most of the up-stroke of the plunger super-atmospheric pressure will be present and it necessarily follows that differential pressures on oppositesid'es of the plunger will be very rapidly reducedas the plunger approaches its upper limit of movement. Y

This back, pressure is highly advantageous in some installationsl For example, if the unit is l operating at a speed faster than 10 strokes per minute, the back pressure not only may be permitted to remain in the compression chamber.

but will be quite advantageous in overcoming the inertiav of the parts. As pointed out, the building. up of pressure in the receiver on the down-stroke of the plunger tends to overcome the inertia of the parts at the lowermost limit of movement of the polished rods, and in a similar manner, the building up of pressure in the compression-chamber as thepolished rods appreach theirupperlimit of movement likewise advantageously provides a `deceleratine: eifect overcominginertia and improving the smooth.- ness of operation of the apparatus. y

At the top of the stroke of the reciprocating parts,I such parts tend to continueto move upwardly by inertia. Ordinarily, this throws. a shock load on the pitman assembly at the extreme end of the stroke, as the load on/ the pitman changes from tension to compression. Under high speeds, at the top of thek stroke,v the upward force due to inertia may be even greater than the weight of the parts themselves plus the reaction of the counterbalance and the resulting shock loadv may be materially reduced if lthe counterbalance reaction is reduced. The back pressure in the compression chamber, as previously stated, will act as a decelerant during the last half of the up-stroke, and after the cranks have crossed center and the beamV beginsr its downward travel the expanding air in the compression chamber will act as an accelerant. Therefore, during the last half of the up-stroke the beam will be decelerated and during the rst half of the down-stroke the beam will be accelerated, and accordingly it will be apparent that back pressure in the counterbalance materially assistsin stabilizing the action of the unit.

In other installations, however, for example,

in a unit operated at 10 strokes or less per minute, the inertia of the parts is not a serious question and the reaction provided by back pressure in the compression chamber against the receiver' pressures may be wholly disadvantageous. Un-

der such conditions, the operator may "crackv the valve l! in which case air will gradually es-` cape from the compression chamber until a pressure only slightly above that of the atmosphere will exist in the compression chamber at the top of each stroke of the plunger 37.l kDuring the ygreater portion of the downward travel of the plunger, therefore, sub-atmospheric pressure will exist in the compression chamber to increase the counterbalancing action,` pressures in the receiver under such conditions being effective throughout substantially thel entire' upward stroke of the plunger for assisting such movement. Any intermediate conditions maybe obtained by properly controlling the valve 15.' This valve may be adjusted so that the leakage therethrough approximates the leakage of air into the compression chamber, -in which case air pumped through the valve 15 upon each upward movement of the plunger will be approximately f proximately per cent. of the air drawn into the compression chamber will be discharged over into the receiver, with only approximately 5 per cent. o! the air escapingv through the valve 15.

Infinitely variableloadings are encountered in pumping oil from different wells and the loadings which will be lencountered on a well of given depth cannot be definitely forecast. The provision of a single type of counterbalance capable oi' taking care of variable conditions encountered therefore constitutes quite a serious problem. 'I'he present apparatus very effectively solves such problems because of its versatilitynot only with respect to. wells of diilerent depths but with respect to varying conditions in wells of the same depth. y I

In a great many installations it is wholly unnecessary to use the bleeder arrangement at all since the presence or back pressures in the compression chamber is advantageous. On the other hand there are many installations in which the use of the bleeder means renders the operation o! the unit materially smoother and more satisfactory. This fact, together with the fact that the counterbalance pressure dinerential may be varied between wide limits by varying 'the oil level in the receiver renders the present construction highly advantageous for use regardless of the depth of any particular well or the operatmechanism for the crank shalt l! during the latter part of the up-stroke, thereby causing the drive belts to chatter, or rather vibrate excessively on the tight side of the belts. Under such conditions, it is advisable to relieve the back pres. sure, and this obviously can bevv readily accomplished with the present apparatus by opening the bleed valve l5.

It will be apparent that some oil will flow out 'through the port 1|, and this is particularly true when the receiver is being charged with air in the manner previously described. As stated, if sunlcient oil is present above the plunger I1 to substantially reduce the clearance space at the upper limit of the plunger stroke. the oil will become aerated and will expand on the down stroke of the plunger. On each 11p-stroke of the plunger slight amounts oi' oilv will be blown through the port 1l due to the fact that the increasing pressures occurring during upward movement of the plunger 3 1 will not fully restore the oil toits normal volume. Oi course. some oil also will be blown through the lpassage 'll during the normal operation o. the apparatus, particularly ywhen it is being ,operated without substantial back pressure. It is highly desirable to prevent the loss of cil through .the passage 1I, and accordingly the pipe l2 is employed for conducting the escaping oil to the chamber 4I (Figure 3) the air blowing /through the pipe i2 escaping through the drain openings 4|. Any oil which escapes through such openings with the air will collect in the recess 4l and will subsequently drain back into the system in the manner previously described.

It isl to be understood that the forms of thel invention herewith shown and described are to be taken as preferred examples of the same and that various changes in the shape, size and arrangement/'of parts may be resorted to without departing trom the spirit of the invention or the scope of the subjoined claims.

. We claim:

1. A counterbalance 4for parts having uniform vsaid plunger in one direction, and means for utilizing reciprocating movement of said plunger tor supplying non-compressible iiuid directly to said receiver.

2. A counterbalance for parts having uniform relative movement, comprising a receiver, a vertical cylinder, a plunger reciprocable therein, said receiver being adapted to contain a non-compressible fluid extending into the lower end of said cylinder to be displaced therefrom upon downward movement or said plunger, and means for utilizing upward movement of said plunger tor supplying non-compressible fluid to said receiver. Y

3. A counterbalance comprising a receiver, a plunger reciprocabl'e therein, said receiver being adapted to contain a non-ccmpressible duid extending lnto one end of said cylinder to be displaced thereirom upon movement of said plunger in one direction, a source or non-compressible iluid, and means including now connections between said source and said receiver for utilizing reciprocation of said plunger for transferring non-compressible iiuid from said source to said receiver. A

4. A counterbalance for parts having uniform relative movement, comprising a receiver, a cylinder having one end communicating with said receiver, a plunger reciprocable in said cylinder. said receiver being adapted to contain a body of a non-compresslble uid at least" partially filling said receiver and extending into said end of said cylinder to be displaced therefrom bysaid plunger, said non-compressible fluid trapping a body ot a compresslble iluld in the top of said receiver, and means i'or utilizing variations in pressure in the other end oi' said cylinder incident to reclprocating movement of said plunger for supplying non-compressible fluid to said receiver.

5. A- counterbalance comprising a receiver, a

cylinder having one end communicating with said receiver, a plunger reciprocable in said-cylinder,

said receiver being adapted to contain a body of er; said non-compressible iiuid trapping a body of a compressible uid in the top of said-receiver, a source o i' non-compressible iiuid, means icr conducting auch4 fluid from said source to the -other end of said cylinder, and a. single means for conducting non-compressible fluid from said other end of said cylinder, said last named means .being connected directly to said receiver.

said receiver,` a plunger reciprocable in said cylindex', said receiver being adaptedV to contain'a said plunger, said non-compresslble nuid trapping abody of a compressible iiuid in the top of said receiver, a single means for conducting duid from the other end of said cylindensaid means being connected to said receiver, and means independent ofv said last named means for supplying non;

compressible mild to the last named end o! said cylinder.

1. A counterbalance comprising a receive ai cylinder having one end communicating with said receiver. a plunger reciprocable in said cylinder, said receiver being adapted to contain a body of a non-'compressible iluid at least partially nlling said receiver and extending intosaid endof said cylinder to be displaced therefrom by said plunger, said non-compressible iluid trapping a body of a compressi-ble uld in the top of said receiver, a connection for supplying non-l a cylinder having one end communicating with said receiver, a plunger reciprocable in said cylinder, said receiver being adapted to contain a body of a non-compressible fluid at least parrtially filling said receiver and extending into said end of said cylinder to be displaced therefrom by said plunger, said non-compressible uid trapping a body of a compressible fluid in the top of said receiver, a connection for supplying noncompressible fluid to the other end of said cylinder, a check valve in said connection opening inwardly with respect to said cylinder, a connection between the second named end of said cylinder and said receiver, said last named connection having a check valve therein opening outwardly with respect to said cylinder, and a manually operable valve normally closing said rst named connection to the atmosphere.

9. A counterbalance comprising a receiver, a cylinder having one end communicating with said receiver, a plunger reciprocable in said cyllnder, said receiver being adapted to contain a body ot a non-compressible fluid extending into said end of said cylinder to be displaced therefrom by said plunger, lan inlet connection communicating with the other end of said cylinder, a manually operable valve controlling communication between said inlet connection and the atmosphere, means for delivering non-compressible fluid to said inlet connection between said valve and the second named end of said cylinder, and an outlet connection communicating between the second named end of said cylinder and said receiver.

10. A counterbalance comprising a receiver, a cylinder having one end communicating with said receiver, a plunger reciprocable in said cylinder, said receiver being adapted to contain a body of a noncon.pressible iiuid extending into said end of said cylinder to be displaced there- Vfrom by said plunger, an inlet connection communicating with the other end of said cylinder, a manually operable valve controlling communication between said inlet connection and the atmosphere, a branch pipe leading to said connection and having a valve seat, a. container for non-compressible uid in which said valve seat is arranged, a iloat in said container, a valve carried by said oat and engageable with said seat, and an outlet connection communicating between the second named end oi' said cylinder and said receiver.

11. A counterbalance comprising a receiver, a substantially vertical cylinder having a. bearing -at its upper end and having its lower end communicatinswith said receiver, a plunger reciprocable in said cylinder and having a plunger rod mounted in said bearing, said receiver being adapted to contain a body of a non-compresslble fluid extending intothe bottom of said cylinder and trapping a body oi' a compressible fluid in the top of said receiver, means for collecting non-compressible fluid from said plunger rod above said bearing, means for delivering the collected duid to the upper end of said cylinder, and means for delivering non-compressible uid from the upper end of said cylinder to said receiver.

12. A counterbalance comprising a receiver, a substantially vertical cylinder having a bearing at its upper end and having its lower end communicating with said receiver, a plunger reciprocable in said cylinder and having a plunger rod mounted in said bearing, said receiver being adapted to contain a body of a non-compressible fluid extending into the bottom of said cylinder and. trapping a body of a compressible uld in the top of said receiver, an annular receptacle surrounding said plunger rod above said bearing for collecting non-compressible fluid from vsaid plunger rod, a pipe connection leading to the upper end of said cylinder and having a check Vvalve opening inwardly withrespect to said cylinder, said pipe connection being normally closed to the atmosphere, means for delivering noncompresslble fluid from said receptacle to said pipe connection, and a conduit connected between the upper end of said cylinder 'and said receiver and provided with a check valve opening outwardly with respect to said cylinder.-

13. A counterbalance comprising a receiver,.

a substantially vertical cylinder havingA a bearing at its upper end and having its lower end communicating with said receiver, a plunger reciprocable in said cylinder and having a plunger rod mounted in said bearing, said receiver being adapted to contain a body of a non-compresslble fluid extending into the bottom of said cylinder and trapping a body of a compressible' lng to the upper end of said cylinder and having a check valve opening inwardly with respect to said cylinder, a manually operable valve controlling communication between said pipe connection and the atmosphere, a container communicating with said pipe connection between the valves therein, means for delivering non-compressible iiuid from said receptacle to said container, a oat controlled valve mechanism ln said container, a conduit communicating between the upper end of said cylinder and said receiver, and a check valve in said conduit opening' outwardly with respect to said cylinder.

14. A counterbalance comprising a vertical receiver, a vertical cylinder projecting into said receiver from the upper end thereof and having its lower end open for communication with said receiver, a plunger reciprocable lnsaid cylinder, said receiver being adapted to contain a body of a non-compresslble iluid extending into the bottom of said cylinder to be displaced therefrom upon downward movement of said plunger, a conduit leading to the upper end of said cylinder and having a depending end provided with' a manual -valve controlling communication between said conduit and the atmosphere, said conduit having a check valve between said :manual valve and the upper end of said cylinder opening inwardly with respect to said cylinder, and means for utilizing pressure generated by upward movement of said plunger for transferring non-compressible iluld from the upper end of said cylinder to said receiver.

15. A counterbalancecomprising a vertical receiver, a vertical cylinder projecting into said receiver from the upper end thereof and having its lower end open for communication with said receiver, a plunger reciprocable in said cylinder, l

said receiver being adapted to contain a. body of a non-compressible huid extending into the bot- 'tom of said cylinder to be displaced therefrom upon downward movement of said plunger, a conduit leading into the upper 'end of said cylinder,

a check valve in said conduit opening inwardly with respect to said cylinder, a manually controllable'valve for controlling communication between said conduit and the atmosphere outwardly of said check valve, a conduit having one end arranged with respect to the upper end of said cylinder to receive non-compressible fluid there:

from and having its other end communicating with said receiver, and a check valve in said last named conduit opening outwardly with respect to said cylinder.

16. A counterbalance comprising a vertical receiver, a vertical cylinder projecting into said receiver from the upper end thereof and having its lower end open for communication with said receiver, aplunger reciprocable in said cylinder,

said receiver being adaptedto contain a'body non-compressible fluid into said first named oonduit between said valves, aA conduit having one end arranged with respect to the upper end of said cylinder 'to receive non-compressible uid therefrom and having its other vend communieating with said receiver, and a check valve in said last named conduit opening outwardly with respect to said cylinder. Y

1'7. A counterbalance comprising a vertical receiver, a vertical cylinder projecting into said receiver from the upper end thereof and having its lower end open for communication with said receiver, a plunger reciprocable in said cylinder, said receiver being adapted to contain a body of a non-compressible 'iluid extending. into the bottom of said cylinder to be displaced therefrom upon downward movement of saidY plunger, a conduit leading into the upper vend of said cylinder, a check valve in said conduit opening inwardly with respect to said cylinder, a manually controllable valve for controlling communi- I catiorrbetween said conduit and the atmosphere outwardly of said check valve, a container for non-compressible iluid having a pipe connection leading to said rst named conduit between said valves, a. float in said container controlling the admission of non-compressible fluid from said container to said pipe connection, a conduit having one end arranged with respect to the upper end of said cylinder to receive non-compressib-le iiuid therefrom and having its other' end communicating with said receiver, and a check valve in said last named conduit opening outwardly with respect to said cylinder.

18. A counterbalance comprising a substantially vertical receiver, a cylinder projecting into the upper end of said receiver and having its lower-end open for communication therewith, a bearing carried by the upper end of said cylinder, a plunger reciprocable in said cylinder and having a. plunger rod extending upwardly through said bearing, said receiver being adapted to contain a body of non-compressible iluid extending into the bottom ot said cylinder to be displacedv therefrom upon downward movement of said plunger, said non-compressible fluid being adapted to trap a body of a. compressible uid in the top of vsaid receiver, a conduit communieating between the top oi said cylinder and said receiver and having a check valve therein opening outwardly with respect to said cylinder, means for collecting non-compressible uid from said plunger rod above said bearing, and means for delivering non-compressible fluid from said last named means to the upper end of said cylinder,

19. A counterbalance comprising a substantially vertical receiver, a cylinder projecting into the upper end of said receiver and having its lower end open for communication therewith, a bearing carried by the upper end of said cylinder, a plunger reciprocable in said cylinder and having a plunger ro d extending upwardly through said bearing, saidreceiver being adapted to contain a body of non-compressible fluid extending into the bottom of said cylinder to be displaced therefrom upon downward movement of said plunger, said non-compressible iiuid being fluid from said last named means to said inlet conduit.

20.. A counterbalance comprising a substantially vertical receiver, a cylinder projecting into the upper'end of said receiver and having its lower end open for communication therewith, a bearing carried by the upper end oi said cylinder,

a plunger reciprocable in said cylinder and hav-A ing a. plunger rod extending upwardly through said bearing, said receiver beingadapted to contain a body oi non-compressible fluid extending into the bottom of said' cylinder to be displaced therefrom upon downward movement of said plunger, said non-compressible uid being adapted to trap a body of a compressible uid in the top of said receiver, a conduit communieating between the top of said cylinder and said receiver and having a check valve therein opening outwardly with respect to said cylinder, 'an inlet conduit leading into the upper end of said cylinder and provided with a check valve opening inwardly with respect to said cylinder, a con'- tainer into which the end of said inlet conduit projects, a drain conduit connected between the bottom of said receiver and said container and having a manually controllable valve therein, and a manually controllable .valve in said inlet conduit between said container and said check valve.

21. A counterbalance comprising a substantially vertical receiver, a cylinder projecting into the upper end of said receiver and f having its lower endopenor communication therewith, a bearing carried by the upper end of said cylinder, a plunger reciprocable in said cylinder and having a plunger lrod extending upwardly through said bearing, said receiver being adaptedto contain a body of non-compressore num extending into the bottom of said cylinder to be displaced therefrom upon downward movement oi' said plunger, said non-compressible viiuid being adapted to trap a body of a compressible iluid in the top of said receiver, a conduit communicating between .the top of said cylinder and said receiver and having a check valve therein opening outwardly with respect to said cylinder, an inlet conduit leading into the upper end of said cylinder and providedv with a check ,valve opening inwardly with respect to said cylinder, 'a container into which the endv oi said inlet conduit projects, a drain conduitj connected between the bottom oi said receiver and said container and having a manually controllable valve therein, a manually controllable valve in said inlet conduit between said container and said check valve, means iorcollecting non-compressible iluid from said'plunger rod, and iloat controlled means for delivering non-compressible duid from said last named `means to said inlet conduit between the valves therein.

22. A oounterbalance for parts having uniform" relative movement, comprising a receiver, a cylin-` der having one end communicating with said receiver.- a plunger reciprocablein said cylinder.

said plunger being movable in one direction to compress and store energy in :duid in said re-` ceiver, la head on the other end of said cylinder,

afi means for controlling maximum 'pressuresln the last named end of said cylinder. i

23. A counterbalance comprising a receiver, a

' cylinder having one end communicating with said receiver, a plunger reciprocable in said cylinder,

mid plunger being movable in one direction to` compress and store energy in uid in said Vicceiven'a head on the other end of said'cylinder,

means for supplying 'a non-compressible duid to.

the second named end of said cylinderv to reduce the clearance space therein, and means including e conduit ieading from the isst named end or asiel cylinder for controlling pressures therein;

24. A counterbalance comprising a receiver, a`

substantially vertical cylinder having itslower end communicating with said receiver, a plunger reciprocable lin said cylinder, said plunger being movable toward'the lower end thereof to compress and store energy in uid in said receiver, andv means connected to the upper end of said cylinder and operative independently oi pressures in seid receiver for governing diil'erential pressures above and below said plunger. n

25. A counterbalance comprising a receiver, a substantially vertical. cylinder having its'lower end communicating with said receiver, a plunger reclprocable in said cylinder, said plunger being movabletoward the lower end thereof to comi press and store energy in iluid in said receiver,

means for introducing'a non-comprensible'iuidk into the upper end of said cylinder` to reduce the clearance space therein, and means connected tol the upper end ofsaid cylinder and operative in dependently oi pressures in said receiver for reciprocating in said bearing vand connected to 10 said plunger, a conduit communicating at one end with the second named end of said cylinder and at its other end with the atmosphere, a check valve in said conduit opening outwardly with respect tosaid cylinder, and a manually con- V15V ltrollalile valve in said conduit between said check valve and the second named end oi said pipe.fsaid valve being adapted to be opened to relievepressure from the second named end o! said cylinder,l

27. A counterbalance comprising a receiver, a 20 cylinder having one end communicating with said receiver, a plunger reciprocable in said cylinder. said receiver being adapted to contain a body ofa nonncompressible duid at least partially illling said receiver and extending into said end of said, 2

,cylinder to be' displaced therefromv by said' plunger, lsaid non-comprensible iluid trapping aV body oi' acompressibleiluidin the top of said receiver. means connected for utilizing variations l in pressure in the other end of said cylinder in- 30 vcident to reciprocating movement oi' said plunger 1 for supplying non-compressibleiiuid to said ref ceiver, and manually controliablemeans for rc-` lieving maximum pressures in said other end of' said cylinder. Y 3'5, Y 28. A Vcounterlmlance comprising a receivena v substantially vertical cylinder having a bearing at its upper end andhaving its lower end com,-

municating with said rcceivena plunger recipro- Y r cable in said cylinder and having'ia plunger. rod ,wf l

mounted in'said bearing, said receiver beingY adapted to contain a body of a non-'compressible fluid extending info the bottom of said cylinder '3 and trapping a body ci a compressible duid in the top of said receiver, an'annular receptacle surrounding said plunger rod abovesaid bearing Y lor collecting non-compressible. fluid from said Vplunger rod. a pipe connection' leading to the upper end of said cylinder and having a check valve opening inwardly with respect to said cylinder, said pipe connection being normallyclcsed tof the atmosphere, means for delivering non-com- ,i pressible fluid from said receptacle to said pipe Y connection, a conduit connected between the' upper end of said cylinder and said receiver and provided with a check valve openingoutwardly i with respect to said cylinder, a pressure relieving pipe connected between the upper end oi said vcylinder and said annular receptacle, and a manually controllable valve in said pressure re-V llevlng pipe. e

HAROLD RAMEY.

EDGAR-FRENCH BPEIDEN.

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