US2605612A - Hydraulic pumping jack - Google Patents

Description

Aug. 5, 1952 J, c, MASON 2,605,612

HYDRAULIC PUMPING JACK Filed Aug. 8, 1950 2 SHEETS-SHEET l 1N VEN TOR.

JOHN c, 44/150 g- 1952 J. c. MASON HYDRAULIC PUMPING JACK 2 Sl'IEETS-SHEET 2 Filed Aug. 8, 1950 I N V EN TOR. JOHN C. MAiU/V W i N P m r A Hydraulic Patented Aug. 5, 1952 fU I ED-15min PATENT/OFFICE I 2,605,612 I HYDRAULIC P'UMPING JACK I, Conley Mason, Greggton, Tex. I "-f Application August s, 1950, Serial No, 178,308 i This invention relates. to pumping jacksand is particularlyconcerned with long-stroke hydraulic pumping jacks of the general type employed to operate conventional plunger type bottom-hole pumps.

pumping jacks of the character above referred to have heretofore been characterized by theuse of pumpsiwith aconstant discharge, the discharge port of'which is alternately connected to a cylinder atone side of a reciprocating piston and teen air balance ac.- cumulator tank, and the intake of which is likewise alternately-connected:to said'cylinder at said side of the piston and the said air balance accumulator tank. This reversal of the order of the pump is automatically accomplished by means of a reversing valve mechanism. The piston is, of-course, connected to the polished rod of the-pump so that when the hydraulic pressure from the pump is exerted against the piston, the upstroke of the pump is eifected; The

of the hydraulic system, effects counterbalancing-ofthepump during such down stroke.

Consequently, when the pumping jack is in operation, a constant flow of fiuidunder' suflicient pressure is exerted against the piston to iefiect the up stroke of the pump, and at the top'of the up stroke, the' reversing' valve operates to reverse the order ofthe pump. Upon such reversal the fiuid under pressure at: the underside of the piston is pumped bythe pump back into the air balance tank, wherein the pressure is ad- "justed so as to effect counterbalancing. At the end of the down stroke, of course, the reversing the present invention to provide a hydraulic pumping jack having a relatively high efficiency and in which the necessity for reversing'valve systems is eliminated.= I It is' another object of the present invention to provide a-hydraullc' pumping jack having-a hydraulic system including a centrifugal pump and a' directly connected internal combustion engine', which are so associated with the hydraulic system that, by merely-adjusting' the throttle positions Of the latter; the system may be easily and quickly adjusted I x to suit different-pumping and counterweightediloads 11 2 Claims. (01.60-52) piston on the down stroke, through the medium- It is a further object of the stroke type in which the length of the stroke may be easily changed, and in which the reversal of direction of movement at the ends of the stroke is effected without the use of mechanically operated valve devices and in a cushioned manner so as to avoid unnecessary strains and shocks to the mechanism. v

One form which the invention may assume is exemplified in the following description and illustrated by way of example in the accompanying drawings, in which: Y

Fig. 1 is a schematic diagrammatic illustration of a pumping jack embodying the preferred form of the invention.

Fig. 2 is a fragmentary vertical sectional view illustrating the jack cylinder and piston of the present invention and disclosing certain details of construction.

Fig. 3 is a diagrammatic view of the pumping jack and its hydraulic system and controls therefor.

Fig. 4 is a view similar to Fig. 3 except the parts are shown in the position they assume when the prime mover is in a decelerated throttle position. I Y

Referring more particularly to the accompanying drawings, there is there disclosed a pumping apparatus embodyingv the preferred form of my invention. This apparatus includes an elongated jack cylinder In to be arranged vertically over the well to be pumped. For this purpose the cylinder is mounted on a rigid supporting .It is intended to frame II, preferably having skid rails I2 so that for the purposes of cleaning or repairs to the Well or the pump, the rig may be skidded to a nonobstructing position.

Reciprocably mounted in the cylinder 10 is a ;type bottom hole pumps having a long ,sstroke.

Inasmuch as such pumpsjform no part-of the present invention, one is not-idisclosed herein, it being sufficient .for. the presentpurposes to set forth that the polished rod 15. is connected irrthe usual manner-to the sucker-rod assembly .ofthe pump.

piston 14 for thepurpose ofjmo'vin'g'the piston upwardly in the cylinder. ID to. effect the upstroke of the pump. It'is further intended that, when this piston reaches the top'of the upstroke,

present invention toprovide a hydraulic pumping jack of the longprovide hydraulic xpressure within the'cylinder H] at the underside'of the of speed. On the upstroke, of course, sufficient pump pressure or hydraulic pressure is exerted beneath the piston Hi to effect a desired. rate of travel of the piston upwardly. As the"piston reaches approximately the end of it's-downstroke," its downward movement is arrested by increasing the hydraulic pressure at the underside or the 7 piston soasto reverse its direction of movement and recommencethe :ycle;-ju"stdescribed. y

In general, thehydraulie-system-for operating the piston IA is a closed'one cl'udes'a centrifugal pump -l 6 directly e ted to' a prime mover I! which inthisinstaneelis sliown as an internal combustion segues {Inthe hydraulic system there is also an air balance tank it, which is connected to the intake portbf the-centrifugal pump 18. The discharge portoifthe entrifugal pump it isconnected to the interiorfoif the bottom of the cylinder ifi' through the medium of a pipe line I 9. Thesy'st'em, therefore; is a' closed hydraulicsystem and sumeienepressu e is maintained in the air balance tank is which, together with other inherent features of the system, will properly counterbalance the wen loadon the piston M on the down stroke of-its'cycle. I

Along the length offthe eylinder are" two sets of spaced control orifices, that is t sayga set of upper control orifices or ports A a'n'd a se't of lower controlorifices or port's'B as'shown in Figure 1. The orificeshofthe group A are indicated in the drawings by the numeral-'ZU'KFigs. 3 and 4) and the orifices of tlielovver set*B"are indicated by the numeral2 I-' (Figs.-2 and-4) The orifices Of the st A" all communicate with a manifold 22 through individual manually-operated valves 23. The group of contr'olorific'es B is also connected with a control-manifold 25 for driving the same, is fitted with a throttle lever 28 having a toggle spring 29 fitted thereto, which spring tends to hold the throttle either in wide open accelerated position or completely closed decelerated position. By closed or decelerated position is meant a position wherein the engine ,will either merely idle or. perate at such a slow speed that the downward load on the piston will cause the piston'to'descend and reverse the fluid flow through the pump l6, although the pump continues to rotate in its nori mal direction. By open or accelerated posithrough manually bperatee 1 individual v'alvef 23.

It is one of thefunctions oft he control orifices 20 and 2| to regulate 'or adgiustthe length of the piston stroke. To-effect the maximum stroke,

the uppermost valve of the group K oftlie on fices 29 would be opento render the uppermost orifice 20 efiective'whilethe remainder'are closed to render the remainder ofthe orifices-20inch fective, and the lowermost valve of the-group B of the orifices 2| will be open to render the-lowermost orifice 2i effective, while the remainder are maintained closed and inefiective "bytheir associated valves. The manner in which the orifices 20 and 2| selectively'adjust or change the length of the pumping stroke will be clear from the further explanation herein :or the operation of the pumping jack.

The manifold 22 of the orifice group A is connected by a tubing 22a to'an engine speed control element 26, while the manifold 24 of thegroup B oi the orifices is connected by conduit '24s to an engine speed control element 21.. These control elements 26 and '21 and their "association with the hydraulic system are more? clearly disclosed in Figs. 3 and 4 of the drawings. Reference being had to these latter figures, 'it'will beseen tion. is. meant a throttle position driving the pump at such a speed that its output will be sufficient'to drive the piston through its upstroke ata desired rate of speed.

The throttle lever 28 is connected by a connection 3D to a throttle control lever 3|. This latter isconnected withlthe: piston rod 32 of the piston. 32a of the control :element "26. and also with the piston rod 23 for the piston 33a of the control element 2T. Each of these-control elements includes a cylinder in which its'associated piston is reciprocable. The: positions of the pistons 32a.and'33a; ia-i'eginfluenced by the fluid pressure 2 in the-cylinder in which is led to the cylinders through the 'mejdium of theiconduits 2 2a and. 24a connecting the. manifolds 2-2 and 24 to the ;-control elements52 6: and-2'1-. The piston 32a of control. element 28 is *solelyinfluenced :by the pressure .ofxthe: fluid entering the same, while the pistohjdaof the controlelem'ent 21 is spring-loaded :byfmeans of :a spring 34 which, to,a-predeterminedzidegree, opposes or modifies the influence-50f "the-fluid; pressure 3 on the piston; Aflost motionzdevice-ti-is-prqvided between the piston rod-33 of the control element 21 'andthe throttle control rlever 3-ljfor-the-purpose which willibe hereinafteridescribed; 77

However, it-ispthe .purposezof the. control elemen'ts'26 "and 2'! and their "connection'wit-h the interior 7 of :the cylinder. 1' 0:; and their-connection with the throttle of the; prime nr over or internal combustion engine 1'51; which'drives -;the centrifugal pump 1.6,) toj-so .:regulate; the iflp' t n :0 the prime mover, ll hand hence the-pump-I6 to effect the reciprocation;- of :the fpi st0nf4 "and its associated pumping mechanism, :1 That is: to say, when the piston is: at the bottom of its: stroke, as illustrated ,in -iFig;- -3 of the drawings, and assuming ;that the *lowgermost -controhorifice 2! is breather-cap Illa. Consequently, there beingatmospheric or; a relatively; lorr -pressure of that order against v the pistonfiQ-agofthe-control element 21, its spring 34will'overcome that pressure and urge 'the -pistonirod-3'3 and its-associated piston to theposfiion-shoWni in Fig. -3, moving the throttle --2 8 -to-accelerated or open position. At this accelerated 'orrb en rlihlOtflB position; the centrifugal pumpwill be-driven so as to pum'pfluid irom; the airmalance-tank i8 through the pipe linel9; into the cylinder 10 A at the underside of thezipiston-gi il; awhich pressure will be sufiicient:t jefi ctrt e: u tr ke f th u p. 1 t ra11y,=v the. perato nowing the :we load to be elevated can'adiust theopencraccelerated throttle position;ofgtheinternal combustion engine so that theputpu f:thqqentrifugal pump [6 will suit the requirement, thatis, the

. element 21.

requirement of effecting the upstroke of the pump at thespee d desired by theo'p'erator. f

; -'I'hus, by-merely adjustingthef position of the open or' accelerated throttle positio'n'to the pump loads and, therefore, as the present pumping jack I has the facilities herein set forth,.it can be easily accommodated to pumping "wells of different depths under-varying'well conditions.

Under the finfluenc'eof thepump pressure, the piston I4 will travel'upwardly from the position shown in Fig. 3 to a position shown Fig. 4, at which time it will have passed anduncove'red theupper control orifice 20 of theupper group A. Prior to the time that the piston M uncovered this port 20 to place it in communication with the interior ofthe cylinder ID at the underside of the piston I4, that control port 20 was in communication with the atmosphere. However, immediately that it is placed in communication with the underside of the piston l 4, it is then subjected to the pressure of the pump l6, which pump pressure will exert its force against the piston 32a of the control element 26 sufiiciently to overcome the forceof spring 34 and moving with it the piston rod 33 of the piston 33a of the control In so operating, it will also overcome the force of the toggle spring 29 and cause the throttle lever 28 to snap to the closed or decelerated throttle position. This will automatically cut down the delivery of the centrifugal pump to the underside of the piston [4 in the cylinder l0.-

Immediately that this is accomplished, the weight imposed upon the piston M by the well load through the polished rod l5 will cause the.

piston Hi to reverse its direction of travel and commenc its down stroke under the influence of that force. The downward movement of the piston l4 wil1 cause the fluid to flow in a reverse direction from the lower end of the cylinder ID through the pipe line I9 into the discharge port of the centrifugal pump and through'the c'entrifugal pump and its'intake port into the air balance tank l8 against the pressure which is maintained in the tank or accumulator [8. This pressure would be such as to effect a proper counterbalance of the load on the piston l4.

However, an additional control medium is pro vided in this respect by the setting of the closed or decelerated throttle position. That is to say,

value. Therefore, by regulating the decelerated or closed throttle position, the resistance at the centrifugal pump it, in addition to the back pressure in the air balance tank l8, may be utilized to counterbalance the Well load to' a desired degree.

What has been just described with respect to the lowermostand the uppermost of the orifices 20 and 21 takes place regardless of which of the orifices of the group A and group B are selected to determine the efiective length of the pump stroke. Naturally, by opening the uppermostof 1 theorifices 2'0 and the lowermost ofthe orifices 2|, the maximum length or pump stroke is 7 n' this in'stance, ins-vestiges at aecuuonm means of eus hioningthe end ofthe stroke of the piston when the maximumi s't'roke length is employed. This include'slthe plu'ng'ers' 40 land 40a on oppositeisides or the piston L-which are adapted to'enter orifices'lland 42 at'the upper and lower ends of the cylinders. Theplungers 40 and lfla are tapered so that as they enter and project through the orifices ll and 42 at the opposite end of the piston stroke, a dash -pot action will be created so as to cushion'the stopping of the pistonat the stroke end. Obviously, the piston will travel some distance past the selected effective orifices 20 and 2| at opposite ends of their tively short orv can befthe maximum permitted by the length of the cylinder l4. Consequently, the pumping jack here'shown will be adapted not only to varying pumping conditions, that is to say,'well depth, but it' can also be adapted to different types of pumps to accommodate different strokes thereof.

. In operation of the pumping jack, it is .constructed substantially as illustrated and described herein. Assuming that'the piston'is in its lowermost position-as illustrated in Fig. 3' of the drawings, the fact of atmospheric pressure in the control elements 26 and 2'! will cause thespring 34 to overcome the spring 29 and move the throttle to open or accelerated position; Of course, the throttle had been previously positioned with consideration to the well loada'swell as the pumpin speeds desired. As previously stated, the operator can compensate for these factors by the throttle setting. Immediately that the prime mover commences operation, the centrifugal pump I6, drawing its liquidfrom the air balance tank l8'-,--wil1 pump the same into the bottom of the cylinder in at the underside of the piston M, the pump output and pressure being sufficient to elevatethe piston 14] and eiiect the upstroke of e the pump at the desiredrate of speed.

: setting of the prime mover, the reason being that,

althoughv this pressure will be communicated to the control unit 21, ,thelost' motion device 35 preventsit from affecting the throttle position.

,Thepiston continues tomove upwardly until itpasses over'the selected control port 20, placing that port in communication with the cylinder It! at the undersideof the piston I4. At

that time pressure is immediatelytransmitted through the'selected effective'c'ontrol port 20 and its associated manifold to the, control element 26, moving the piston 32a therein to its opposite condition which, through the medium of its rod 32, moves the throttle control rod 3| to a point where-the throttle lever 28 is snapped to closed as? th Pe ee w l r re t d i of "have aeeaeia ahdhemmehceto descend'due to thegr'avitational pull of ,theload thereon. As the piston 14 desf endsjiti and gene "load carriedithereby will be, coun rjbalaiic'edfbyfthe resistance to the fluid pressur ih the ir aiahee tank 18.;-

As previouslyist'al'ied; 'the sp'eedof descent as well" s differel'lt' varying "well loads ma be compensated ffor not en y byf vajryingfthe pressure flowoflferedbythe centrifugal pump it and the in the air-balaheetan1 -l8,-"but also by setting the closed r 'de'eelerateii throttle position of'the 'pr h eiheverat pel t whereb the pum l6 will ofier' th'e addi 1 desired resistance to the reverse flow -of" fluid therethroil'g'h to the tank or "the drop in pressure "at the control e emental will cause the spring 34 to agaiii evereeme the spring on the'tlirettlelever 28 so as to move the throttle control lever 3 I a :suflieieht distance to throw the throttle lever 28 again to open or accelerated throttlepositionr By providing a toggle" spring "connection fbl" the thrbttle level 28; galloping or minor variations in engine speed will beavoided because the lthrdttle position at either open or closed position will remalnconstar'it.

Obviously, ltheioperation of thepum'pingjack is identical regardlessiof which ports, of thefis'ets of control ports A and B are selected to be effective. .If-Hthe .nlaximum stroke is desired, of

coursegtheuppermost; control port2lJ and the lowermost icontroliportr2 I- are rendered efiective by opening of the associated valve of the control ports 'A and Band closingtheremainden Thus,

by'mere selection ofiproper control-ports 20V and 2|, the lengthlofthestrokeof the piston may be determined, ;,Also, by simply changing the. setting ofthe'throttle position, the 'speedof the upstroke-as well as the. speed of the down stroke of the -pump may be maintained at a predetermined constant; h v

V obviously thereversalofthepiston I4 is ef- Y rec-ted; without; the necessity of providing reversing 'valves or any pthergmechanicallyoperated ech i m 5E0 3:25 0 11 t at. t m nation :of v the piston strokes will be effected without any sudden shock or strainbeing'placed on the system due to the fact that the reversal of pump. lfi fwlfi ich'is driver! a Small electric me-' li ui'el thet 1: jnseste' a lpredetermined.

"o he ineliorlliis elo'sedfopp' a and 'discha'rging'the liquid ck" into the closed hydraulic system. 'rthe p%impils. The discharge ire-m the pump 46 is connectedbyfaitubing 50 to 'thehydraulic is'ys't'e'mat "a; point adjacent the discharge of the 'centrifugalpump 16" as illustrated;

While I have shown th'epreferredform "of my invention; it to be "understood: that various The? made?iii-" ts;eenstrueiien. by

the spirit fof the hvehtieh asaehh a in the appended claims; n V I-Ia'ving thus described my invention; what I claim-and desire to obtain-by Letters Patent is:

1. 'A pump jack including a stationary elongat'edl vertically-positioned cylinder having a closed lower end; the upper end of the cylinder being in cornmunication'with the atmosphere, a piston 'reciprocahly mounted in the cylinder 'fo'r'connection at its lower end to a pump rod extending through'the lower end :of the cylinder. a hydraulic circuit for operating the piston including a centrifugal-pump having'its discharge connected'to the lower end of the cylinder beneath the pistfon and .its intake connected with a'n'ja'ccumulator' tankypressure responsive pump control means associated with the cylinder for automatically causing increase of the pump eutputjto' elevate the piston'at the'end of the down strokejthereofandto automatically decrease the pump output at theend of the upstroke thereof to enable the piston to lower under the influence ofthe .load thereonat the end of the upstroke.

2 'Apulnping jack'includin'g an elongated vertioallypositioned cylinderaa piston reciprocably mounted'therein and adapted to be connected at its lewerieha toa v um rod for operating the safn'e'fthe lower end of said cylinder being 'fiuirl tight, a hydraulic circuitfor operating the piston including a centrifugal pump having its discharge coiiiiectedito the lowerend of the cylinder at ajpoin't beneath the piston and having its intake connected with an accumulator tank, a prime'niover for driving the centrifugal pump, said prime mover having an acceleratedspeed position sufiicient to drive the pump at a speed producing an output sufficient to elevate. the piston and its load through its upstroke and'hav'ing a declerated speed position for driving the pump atia rate Where'the load on the pis'ton'will cause lowering of the same and reverse the'fiu'id 'floW through the.pump to the accumulator tank, and means automatically operable to move said prime mover to the a'ccelerated or decelerated position depending on" the position of the piston in the cylinder.

3'. A pumping'jack including an elongated'vertioally positioned cylinder having a closed lower end, the upper end thereof being in communication with the atmosphere, rapiston' reciprocably mounted in' ftl'l'e cylinderandjadapted to be connectedat itsilower endto a'pump rod extending through the'lower' end-of theic'ylinder for operat- "ingthe Ts'aln'e, a 'Closedhydraulic circuit for operating thiiii is'teh. including a centrifugal .pump

having its discharge connected to the lowernend er the 'e'yliheeh'heheath the piston and its intake s'p'eeaipesitieh sufiicient to operate the pump at 'aratepreclueih'g an output sufficie'nt to elevate the'jpis'ton'and' its connected load through its upstroke and having a decelerated speed position 's'b decre'a'singithe output of th'epump that the loadon the piston will cause the same to descend through its down stroke and reverse the fluid flow through the pump, and a prime mover control means associated with the prime mover and re- ,sp'onsive'to' changes in pressure in the cylinder at theend's of the piston'str'oke to effect a change i of the prime mover operation'from accelerated "position at the upper end of the'piston stroke to acceleratedposition and from decelerated posi tion at the lower end the piston stroke to accelerated position.

4. A pumping jack including an elongated vertically positioned cylinder, a piston reciprocably mounted therein and adapted to be connected at its lower end to a pump rod for operating the same, the lower end of the cylinder being closed but through which the pump rod extends, .the upper end of the cylinder being in. communication with the atmosphere, a closed hydraulicvcircult for operating the piston including a centrifuga1 pump having its discharge connected to the lower end of the cylinder beneath the piston and the intake connected with an air balance tank, said cylinder having a control port adjacent its upper end at a point below the piston when the piston is adjacent the end of its upper stroke, said cylinder having a lower control port adjacent its lower end at a point above the piston when the latter is adjacent the end of its down stroke, a prime mover for driving said pump, said prime mover having an accelerated speed position to drive the pump at an output capable of elevating the piston and its associated load.

through its upstroke and having a decelerated speed position reducing the output of the pump to a point where the load on the piston causes the same to lower through its 'down stroke, prime mover control means associated with the upper and lower control ports and responsive to pressure changes thereat to effect a change of the prime mover operation from accelerated position to decelerated position when the piston moves to place the upper port in communication with the cylinder below the piston and from decelerated position to acceleratedposition when the piston moves to place the lower port in communication with the cylinder at a point above the piston.

5. A pumping jack including an elongated vertically positioned cylinder, a piston reciprocably mounted therein and adapted to be connected at its lower end to a pump rod for operating the same, the lower end of the cylinder being fluid tight, a closed hydraulic circuit for operating the piston, said circuit including a centrifugal pump having its discharge connected to the cylinder at a point below the piston and having its intake connected with an accumulator, means for operating the pump at a speed to produce an output sufficient to elevate the piston and its load through its upstroke, means for operating the pump at a decelerated speed after the piston reaches the top of the upstroke whereby the load on the piston will cause the piston to lower and reverse the direction of flow of fluid through the pump whereby the pump will act to restrict said fluid flow and aid in counterbalancing said piston load.

6. A pumping jack includingan elongated vertically positioned cylinder, a piston reciprocably mounted therein and adapted to be connected at its lower end toa pumprod for operatingthe same, the lower end of the cylinder being fluid tight,-a closed hydraulic circuit for operating the piston, said circuit including a centrifugal pump having its discharge connected to the cylinder at a point below the piston and having its intake connected with an accumulator, means for operating the pump at a speed to produce an output sufiicient to elevate the piston and its load through its upstroke, means for operating the pump at a, decelerated speed after the piston reaches the top of the upstroke whereby the load on the piston will cause the piston to lower and reverse the d rect o o flow i .fillid through the pump whereby thepump will act to restrict said fluid flowandaid in counterbalancing said piston load, and means-for automatically effecting said speed change of the pump at the upper and lower ends of the piston stroke.

7. A pumping jack including a stationary elongated vertically positioned cylinder having a closed lower end, the upper end of the cylinder being in communication with the atmosphere, a piston reciprocably-mounted in the cylinder and connected at its lower end to a pump rod extending through the lower end of the cylinder, a hydraulic circuit for operating the piston including a centrifugal pumphaving its discharge connected to the lower end of the cylinder beneath the piston and its'intake connected with an air balance tank, pressure responsive pump control means for automatically causing increase of the pump output sufficiently to elevate the piston at the end of the downstroke thereof and to automatically decrease the pump output at the end of theupstroke thereof to enable the piston to lower under the influenceof vthe load thereon at the end of the upstroke, and means for returning excess liuid'alongthe-upper end of the .piston back into the hydrauliccircuit. r

8. A pumping jack including an elongated vertically positioned cylinder having a closed lower end, the upper end thereof being in communication with the atmosphere, a piston reciprocably mounted in'the cylinder and-adapted to be connected at its lowerend to apump'rod extending through the lower end of the cylinder for operating the same, a hydraulic circuit for operating the piston including a centrifugal pump having its discharge connected to the lower end of the cylinder beneath thepiston and its intake connected with a source of fluid, an internal combustion engine directly connected to the pump for driving the same, said engine having an accelerated throttle position for operating the pump at a speed producing an output sufiicient to elevate the piston and its connected load through its upstroke and having a decelerated throttle position driving the pump at a speed that the load on the piston will be suflicient to cause the same to descend through its down stroke and reverse the fluid fiowthrough the-pump, and a pressure responsive control means associated with the engine and responsive to changes in pressure at the ends of the piston stroke to effect a change of the engine operation from accelerated throttle position at the upper end of the piston stroke to decelerated throttle position and from decelerated throttleposition at the lower end of the piston stroketo accelerated throttle position.

9. A pumping jack including an elongated vertically positioned cylinder, -a piston reciprocably mounted therein and adapted to be connected at its lower end toa pump rod for operating the same, the lower end of the cylinder being closed but through which the pump rod extends, the upper. end'ofthecylinder being in communication with the atmosphere, a closed hydraulic circuit, foroperating the piston includingra centrifugal pump having its discharge connected to the lower end of the cylinder beneath the piston and the intake connected with an accumulator tank, said cylinder having a series of vertically spaced control ports capable of being selectively made effective, said ports being disposed i the upper portion of the cylinder, said cylinder having a series of vertically spaced lower control ports in its lower portion and capable of being selectively made efiective, a prime mover for driving said pump, said prime m over having an ac celerated speed position to drive-the pump at an output capable of elevating the piston and its associated load through'itsupstroke and having a decelerated speed position reducing the output of the pump to a point wheretheload on'thepiston would causethe same to-lower through the down stroke of the piston, prime mover control means associated with the selected effective upper and lower control ports, andresponsive to pressure changes thereat to eiiect a change of the prime mover operation from accelerated position to decelerated position when the-piston moves to place the selected upper port in communication with the cylinder belowthe piston and from decelermeans for driving the pump-,atan output suificient to elevatethe piston and its associated load through the upstroke of the piston and for driving the pump at a'decelerated speed after the piston reaches the top of the upstrokewhereby the load on the piston will cause the piston to 4 lower, reversing'the direction of fiowoffluid through the pump; whereby the pump will act-to restrict said fluid'fiow and aid in counterbalancing said pistonload.

11. A device of the character described comprising a variable speed motor having'a speed control lever'movable to high and low speed positions, a pressure responsive mechanism connected to said speed control lever whereby changes in pressure will cause said lever to move to a high or low speed position, whereby said motor will operate in ahigh or low speed, a centrifugal pump connected to and driven by said motor, said centrifugal pump having a fluid intake port and outlet port and being connected to a source of fluid at the intake port, a vertical cylinder being connected at itsbase to the outlet port of the centrifugal pump and'open to atmospheric pressure at its upper end, a piston slidably mounted in said cylinder and adapted to be constantly urged toward the base of said cylinder and to be moved upwardly as fluid is pumped intothe base of said cylinder, means secured to the'lower portion of said cylinder to transmit atmospheric pressure to the pressure responsive mechanism whereby said speed control lever is moved to the high speed position when the piston is below said means secured tothe lower portion of said cylinder thereby causing the output of the centrifugal pump to increase so as to force said piston upwardly in said cylinder, and means secured to the upper portion of said cylinder to transmit the internal pressure ofsaid cylinder to the pressure responsive. mechanism thereby moving said speed control. lever tov the low speed position when. the piston is above said means secured to the upper: portionof. the cylinder, thereby allowing the downward force of said piston to slowly'forc'e the fluid back through the centrifugalpump untilthe'pistonis once more below the means secured'to: the lower portion of said cylinder at which time' the output of the cen trifugal pump is again increased.

12; A device. of the character described comprising a variable speed motor having a speed control lever movable to highand low speed positions, at pressure responsive mechanism connected to said speed control lever whereby changes in pressure will cause said lever to move. to a high orv low speed position, whereby said motor will operate in ahigh or low speed, a centrifugal pump connected to and driven by said motor, said centriiugalxpump-h'avi-ng a fluid intake port and outlet port and zbeingconnectedv to a source of fluid at. theintakeport, a: vertical cylinder being connected at its base to the'outlet port oi the centrifugal pump-andopen to atmospheric pressure at its upper end, a piston slidablymounted in said cylinder andadapted to be constantly urged toward the base of said cylinder and to be moved upwardly asfluid is pumped into the base of said cylinder, said. pressure responsive means comprising means secured to the lower portion of said cylinder responsive'to high pressure in said cylinder to move from a firstposition to a second position and upon the release of pressure to move from said second position to said first position and: being operable during the latter movement to move said speed control lever from a low speed position to a high speed position, said pressure being released when said piston moves to a position below the'point of securement of the last named means to the cylinder, and means secured to the upper portion of said cylinder-responslve to high pressure in said cylinder to move from a first position to a,second position and operable during said movement to move said speed control lever from a high speed position to a low speed position, the last named means being subjected to high pressure'when said piston moves to a position above the point of securement of the last named means tothe cylinder..

JOHN CONLEY MASON.

REFERENCES CITED The following references are of record in the file of, this patent:

UNITED STATES PATENTS

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