US2939397A - Fluid operated multiplex pump - Google Patents

Description

June 7, 1960 c. J. COBERLY 2,939,397

FLUID OPERATED MULTIPLEX PUMP Filed Dec. 10, 1956 4 Sheets-Sheet 1 BY HIS HTTOPNK$. HnRR/S, Klan-g, Fos'rse 8; HH RRIS June 7, 19 60 c. J. COBERLY 2,939,397

FLUID OPERATED MULTIPLEX PUMP Filed Dec. 10, 1956 4 Sheets-Sheet 2 f? 2 I420. 33 [U0 lJda I32 //v VENTOR. CLARENCE -J. COBERLY BY H/S HTTORNEYJ. HARRIS, Mac 4, FOSTER & Haekls C. J. COBERLY FLUID OPERATED MULTIPLEX PUMP jun 7, 1960 Filed Dec. 10, 1956 4 Sheets-Sheet 3 lNVENTOQ. 25o CLARENCE. d. COBERLY BY H/S ATTORNEYS. Heme/s, K/acH, Fos'ru? & HARE/5 Clarence I. Coherly,- saniManno; "a ssighdr rs Kobe, Inc., 'H untingt6nPark, -Calif., a corporation of j Filed Dec-10,195t5,,Ser.No.627,29$ f Claims. 01. 103-5 means, whereby the pump piston means pumps fluid from the well upwardly through a production tubing to the surface. Theoperating fluid foractuating the pump, whichfis usuallyclean crude oil, is conveyed downwardly. thereto at a relatively high pressure through. a supply tubing set in the well. The spent operating fluid discharged by the pump at a lower pressure is either mixed with the productionfluid and returned tothe surface through the production tubing, or is returned to the S111? face through a separate, return tubing set in the well.

The engine and pump piston-means of a fluid operated pump of the foregoingcharacter. are incorporated in a pump unit and the engine valve means thereof is incorporated in a valve. unit which may be'combined .with. the structureof the pump unit, or which may best sepa-.

rate structure, ,as disclosed in'my copending. application;

V In the first instance, the pump iand valve units are installed in and Serial No. 598,785,;fi1 6d July 19, 1956;

removed, from thewell in unison, while in the second the pump and valve units maybe installed in and re-' moved from the Well independently of each other. The present invention is applicable to either case; Y

. Fluid operated pumps are also of either the; free type or the -set type; i a pumpof the former type; being movable betweenvits operatingposition in the .well and the surfacethrough one of the tubings of, the tubing system associated therewith so that removal of the tubing system displacement is'usually not'double that-of a correspondsited a s aFmtAE-OT to"intr. oducc hydraulic shock, this being particularly true when' thei pump -is.run at high speed. Hydraulic shock, ofcourse, is. responsible for many of the repairs;required by fluid operated pumps, particularlythose utilized in deep wells. i x

@Double acting-1 pumps have aconsiderable' advantage over {the single acting. type'in that both strokes are'working stroke'sJThus, a'double acting pump gets the benefit of the full piston speed,'instead of one-half of the piston speed as in a single acting pump. However, the

ing single acting pump since the engine and pump piston means must be smaller for the reasons previously outlined. Double acting pumps do permit more uniform flows of the operating and pumped fluids and thus are less likely to produce hydraulic shock than a single acting pump. Howeventhe piston means of double acting pumps must stop at each end of their-stroke, which results in momentary interruptions of the flows of the operatingand pumpedfluids and'tends to produce some hydraulic shock. Also, all single acting and double acting pumps are subject to the'tendency to race when the pump cylinder does not completely fill with solid fluid. In prior fluid operated pumps, it'is necessary to provide some form ofgoverningmeans to prevent such racing, which'makes for-complexity. While various features of theiinvention may be embodied in either a single acting pump or a double acting pump, the invention is preferably applied to a pump ofthe single acting type since the: basic objects ofi the invention maybe achieved with this type and themore complex structure ofthe double acting type is thus avoided.

With the foregoing" as background, a primary object of the inventionis, as hereinbefore suggested, to provide a fluidoperated bottom hole pump having a much higher 1 pumping capacity than pumpsheretofore available and having substantially no tendency to introduce hydraulic shock into the system, the latter effect in particular being achieved by producing substantially continuous flow of both the operating and pumped fluids.

More particularly, a'-' basic object ofthe invention is} to provide a fluid operated pump whichmay' convenient-ly be termed a multiplex" pump and which includes two or more fluid operated pump,unitshavingparallel-1 connected enginerne'ans and series connected pump means, thisj'multiplex pump including control means for operating suchpump unitsin timed relation, with pre-.

determinedphaserelations therebetween, in such a man ner that at least one of'the pump units is on its working stroke at all ti'rnes. Another object in this connection 3 is to provide a multiplex pump comprising twoor more in order to removev the pumpis unnecessary. With a pump of the setttype, on the other hand, removal of at least part of the. tubing system is necessary to permitremoval ofthe pump sincethe, pump is attached to one of thetubings Again. the presentinvention is applicable to pumpsof either. of these types. 4 I

Fluid operated oilwell pumps may beef-either the singleacting or double acting type, the former being the more common since it is simpler and since it permits the use of larger engine and pump pistons or piston means, the pistons of a double acting pump necessarily being smaller than those of a single acting one because of the additional passages required for the .operating .fluid and thepumped fluid. Any single acting pump has the limitation thatonly one stroke is the working stroke fluid operated pumpunits wherein only one of the pump units is on its return stroke at any instant, the remaining pump unit or units being on its or'their working stroke orfstrokes.

\ A further object of the invention is to provide a fluid operated multiplex 'pump in which the control'means overlaps the working strokes of the pump units in such aiway'that the pumping load is progressively shifted from one pump unit to another as each pump unit approachw the end of its workingstroke. In other words, a'further object of the invention is to provide a multiplex pump having control means for initiatingthe working stroke of the engine and pump. piston means of .the'next pump unit in the"s eries as the engine and pump piston i means of the preceding pump unit therein approach the end of their working stroke.

With the foregoing construction, a pumping capacity very much higher than anything heretofore attainable n under-comparable conditions is achieved through the use, of two or more fluid operated pump units, which is an' fluid through the tubing system with which themultip'lexv pump is associatedare substantially constant to minimize hydraulic shock, which is anotherimportant feature'of the invention. Further, since the pump-means of the pump units are connected in series, and since the pump ing load is divided among the pump ,means of" two or more pump units in any embodiment which includes three or more pump units, either the operating fluid pressure, or the areas of the engine means of the; pump units on which the operating fluid acts, may be reduced, which is still another important feature. I

Another object of the invention is to provide. a multi plex pump wherein the control means for maintaining the proper phasing between or among the pump units is also fluid operated and is actuated by the pump units as the piston means thereof approach the ends of their working strokes. Thus, as the piston means of one pump unit approach the, end of their pumping stroke, they actuate the control means to cause the latter to initiate the working stroke of the next pump unit in the series. An object in connection with one embodiment of the invention is to provide a multiplex pump wherein the control means includes a number of valve units corresponding to the number of pump units and wherein the valve units control the respective pump units. A related object is to provide such a control means wherein each pump unit in turn either directly or indirectly acne ates the valve unit corresponding thereto, and also actuates the valve unit corresponding to another of the pump units. Thus, the operations of the various pump and valve units are interrelated so, as to achieve the proper phasing of the pump units.

Another object is to provide a control means which includes a single valve unit controlling all of the pump units and controlled thereby in turn to achieve the-desired phasing of the pump units. More particularly, an object is to provide a control means comprising a single valve unit which includes a rotary valve and fluid op.--

erated means actuable by the various pumpunits for rotating the valve from one of its operating positions. to the next as the piston means of each pump unit approachthe end of its working stroke. 7

Anotherobjectot importance is toprovide a multiplex pump having two or morepump units provided with pump piston means and working valves relatedv in sucha manner in structureand operation that. no standing valve or. valves are required. This result is achieved by so phasing the operation of the pump units that at least one of the pump piston means is on its working stroke at all times so that the corresponding working valve is closed, thereby obviating any necessity .for one or more standing valves.

Another important object of the invention is to provide a multiplex pumpwherein the pump units are axially aligned and wherein the pumped fluid flows throughaxial;

passages in, the engineand pump piston means of the pump units seriatim, thereby minimizing flow resistance,

closed, whereby no standing valve or valves. are required,

A further object of; the invention :isjto provide a multi! plex fluid operated pump including two or more-fluid: operated pump units which are independent, but inter related in operation, and which have some or all of the features hereinbefore outlined, each pump unithaving its,

own fluid operated engine means and itsv own pump means.

Another object is to provide a fluid operated multiplex pump wherein the engine and pump piston means of each pump unit move through their return stroke at a speed such that they are ready for their working stroke before the engine and pump piston means of another of the pump units reach the end of their working stroke. In the case ofa triplex pump embodying the invention, this means a return stroke speed at least twice the workingstrokespeed, and anotherobjectof the invention isto provide such a, triplex pump. V V

rrhe rore oxng objeet's, -advantages, features and results of the present invention, together with various other objects, advantages, features and resultsthereof which are presented in the original claims of this application,

or which will be apparent to those skilled in the fluid operated pump art in the light of this disclosure, may be attained with the exemplary embodiments of the invention described in detail hereinafter and illustrated in the accompanying drawings, in which: v

Fig. l is a diagrammatic view illustrating a fluid operated duplex pump which embodies the invention;

Fig. 2 is a diagrammatic view of a fluid operated triplex pump embodying the invention;

Fig. 3 is a diagrammatic view which illustrates another embodiment of a fluid operated triplex pump of the invention;

.Fig. 4 is a view similar to Fig. 3, but illustrating various components in different operating positions;

Figs. 5, 6 and 7 are enlarged, fragmentary sectional views respectively takenalong the arrowed lines 5-5, 6-6 and 7-7 of Fig. 3; and

Fig. 8 is an exploded perspective view illustrating fragmentarily a pump-unit control means of the invention inc'orporated in the triplex pump of Fig. -3 of the drawings.

is 'aduplex pump 10 of the invention which includes two vices- 12a and 12b respectively including fluid-operated pump units 14a and14b. As will become apparent, each of these pump units has its own fluid operated engine means and'its "own pump means, the two" engine-means being connected in parallel and the two pump means in series. The two pump units 14a and14b are controlled by a' control means 16 which includes independent but interrelated engine valve units 16a and 16b, these valve units forming parts of the pumping devices 12a and 12b, respectively,- and controlling thepump units 14a and' 14b, respectively;"

The foregoing components of the pump ltl are actuated by-iopera ting fluid underpressure delivered to the pump through a supply tubing 18. In the particular construction illustrated, the spent operating fluid is returned to the surface through a return tubing 20. A production bythe pump units'14a'and 14b to the surface.

- The pump units 14a and 14b are similar to those disclosed in my aforementioned copending application Serial No. 598,785 and include combined engine and pump pistons or piston means 24a and 24b, respectively. The pistons 24a and 2412 respectively include plungers 26a and 26b reciprocable in cylinders 28a and 28b, and

include rods 30a and 30b connecting the plungers 26a bores 36:: and 36b in fluid-tight, sliding engagement with the wallstthereof The-pistons 24a and 24b are provided therethr'ough with axial pas'sages-38a and 38b for fluid being pumped from an .inlet 40 into the production tubing 22, the-passagesSSa and 38b being connected in series and reverse flow therethrough being prevented by working valves 42a and 421?, respectively. .Aswilhbeapparenhas long as, the working stroke of each. piston 24a and: 241:, the:

amass? which therdesiredphasing of the working strokes ofthe pistons24a and 24b is,maintained willj be'considered hereinafter,

As hereinbefore suggested; during the working 1 stroke of each piston 24a and 24b, the corresponding one of the working valves 42a and 42b is seatedsdthat the pumped fluid is displaced upwardly'throughtheproduc tion tubing 22; During the return strokepf each'piston 24a and 24b, which is the downward stroke thereof, the corresponding one ofthe working-valves 42a and 42b is open to permit bypassing of pumped fluid from below such piston through the corresponding one of the passages 38a and 38b into the corresponding one of the cylinders 28a and 28b thereabove. t

The working stroke of the piston 24a is affected by applying the operating fluid pressure'in the supply tubing 18 to the lower surface of the plunger 26a and the spent operating fluid pressure or exhaustpressure in thereturn tubing 20 to the upper surface of the plunger 32! whereupon the piston 24a moves upwardly to displace pumped fluid upwardly through'the production tubing 22 and to draw pumpedfluid upwardly through the axial passage 38b through the piston 24b. The working stroke of the piston 24b iseffected in the same way and, piston moves' upwar dly through its working stroke, it displaces pumped fluid upwardly throughthe axialpassage 38a .in the piston 24a and draws fluid upwardly through the inlet 40. The return stroke of the piston 24a is produced by applying the operatingfluid pressure to both the lower surface of the plunger 2611,.and the'upper surface of the plunger 32a, the area of the latter surface slightly exceeding that of the former so that the piston 24;; moves downwardly through its return stroke when equal pressures are applied to such surfaces. Since, in order to effect the return stroke of the piston 24a, it is only necessary to overcome mechanical friction between the plungers 26a and 32a and the cylinders 28a "and 34a, and fluid friction resulting from the flow ofpumped fluid throughthe axial passage 38a past the working valve 42a) the area of the upper surface of the plunger 32a needs be only slightly greater than the area of the lower surface of the plunger 26a. This may be accomplished by making the diameter of the cylinder 34a a few' thousandths of an inch greater-thanf the diameter of the cylinder 28a. The returnstroke of the piston 24b is effected in exactly the same 'way so that a detailed description is unnecessary.

Considering the manner in which the operating fluid and exhaust pressures are applied to the pistons 24a and 24b to accomplish the foregoing, the operating fluid pressure is constantlya'pplied to the lower surfaces of the plungers 26a and 26b through a main passage 44 and branch passages 46a and 46b, the main passage communicating with the supply tubinglS and the branch passages communicating with the cylinders 28a and 28b. Communicating with the cylinders 34a and 34b to apply either operating fluid pressure or exhaust pressure to'the' upper surfaces of the plungers 32a and 32b are passages 48a and 48b, these passages being controlled by the valve units 16a and 1612, respectively. When the exhaust pressure is applied to the upper surfaces of the plungers 32a and 32b to produce the working strokes of the pistons 24a and 2417, the valve units'16a and 16b connect the passages 48a and 48b to the return tubing 20 through passagesSOa and 50b, respectively. Conversely, when the operating fluid pressure-is'applied to these areas to producethe return strokes of'the-pis'tons 24a and 24b,

this beingaccomplishedjby thecontrol means the valves 16a and 16b 'connectthe passages 48a and 48b to branch passages 52a and 5212, respectively, these branch passages communicating with the main passage 44 from the supply tubing 18. n v

Considering the control means' lfi in more detail, the valve units 16a and 1' 6b"r espectively include diiferential area engine valves 56a "and 56b respectively having plungers 58a and 58b connected to plungers 60a and 60b by rods 62a and 62b, these plungers and rods-being slidable in suitable" bores or cylinders in fluid-tight engagement with the walls thereof; as will be apparent from Fig.

i 1 of the drawings. [Thebores for. the plungers'58a .and

58b 3are identified by the reference characters 64a and 64b,

the bores for the plungers 60a and 56b are identifiedby the reference characters 66a and 66b, and the bores for the rods 62a and 6% are identified by the reference characters 68a and 68b.

The operating fluid pressure is constantly applied to the upper ends of the valves 56a and 56b through branch passages 70a and 70b leading from the main passage 44 to the upper ends of the bores 64a and 64b. The passages 52a and 52b communicate with the lower ends of the bores 64a and 64b so as to constantly apply the operating fluid pressure to the annulanareas at the lower ends of the plungers 58a and 58b. The annular areas at the upper ends of the plungers 60a and 60b are constantly exposed to the exhaust pressure through branch passages 72a and 72b communicating with the passages 56a and 50b, leading from the return tubing 20, the passages 50a and 5% also communicating with the bores 6.4a and 64b intermediate the ends thereof. ,7 With the foregoing pressures constantly applied to theupper ends of the plungers 58a and 58b, the annular areas at the lower ends of these pl-ungersand the annular areas at the upper ends of the plungers 60a and 60b, the valves 56a and 56b will move upwardly when the operating fluid pressure is applied to the lower ends of the plungers 60a and 60b and will move downwardly when the exhaust pressure is'applied'thereto. When the lower ends of the valves 56a and 56b are exposed, to exhaust pressure in the bores 66a and 66b, the net downward force applied to each valve is equal to the product of the cross sectional area of the corraponding one of the rods 62a and 62b and the difference between the operating fluid and spent operating fluid pressures. When the lower ends of the plungers 68a and 60b are exposed to operating fluid pressure in the bores 66a and 66b,'the net upward force on each of the valves 56a and 56b is equal to the product of the difference between the operating fluid and exhaust pressuresand the differ-. ence between the cross sectional area of the correspond-. ing'one of the rods 62a and 62b and the cross sectional area of the corresponding plungers, assuming that both plungers of each valve have the same cross sectional area. I r 7 Considering the manner in which either the operating fluid pressure or the exhaust pressure is applied to the lower ends of the valves 56a and 56b, passagesv 74a and 74b respectively communicate with the lower ends of the bores 66band66a and'thus communicate with the lower ends of the plungers 66b and 60a. 'The passages 74a and 74b communicate with passages 76a and 76b leading-tothe bores 36a and 36b in which the rods 30a, and 3050f the pump-unit pistons 24a and 24b are disposed, these passages being referred to hereinafter as control passages. The passages 76a and 76b are adapted to be connected to passages 78a and .7812 by control ports 80a and 80b in the rods 30a and 30b as the pistons'24a and 24b approach the ends of their working strokes, butbeforethese pistons reach the ends of their working strokes. The, passages 78a and 78b, which are also control passages, cornmuni? cate with the bores 64a and 64b and constantly register with annular channels "82a and 82b in the plungersjSSq and 58b. The channels 82a and 82b also constantly com-j municate with the passages 50a and 50b leading .to the re}; turn tubing 20 so that the spent operating fluid pressure 61; and 86b.

is constantly present in these channels. When the valves 56a and 56b. are in their lower positions, the channels 82:: and -82b.also communicate with the passages 48a and 43b leading to the pump-unit cylinders 34a: and 34b. However, when the valves 56a and 56b are in their upper positions, the channe1sf82a and 82b also communicate with passages 84a and'84b' leading from thebores 64a and "63417 ,to-the passages 74a and 745 through restrictors The foregoinginterconnections between-thepumpand valve units 1421', 1411,16 1 and 16b interrelate the operations' of theseuni'ts in such a way that the flow of pumped fiuid through. the production tubing 22 and the flows of operating fluid under pressure and spent operating fluid through the supply and return tubings 18 and 20 are substantially constant to minimize hydraulic shock. This interrelationwill become apparent from the following description of the operationof the duplex pump 10.

Operation of pump It is thought that the operation of the duplex pump 10 may be understood more readily if it is kept in mind that, insofar as the operation of the pump units 14a and "14b is concerned, the valves 56a and 56b control the working and return strokes of the pistons 214a and 24b, these pistons moving upwardly through their working strokes when the valves are in their lower positions and moving downwardly through their return strokes when the valves are in their upper positions. As regards upward movement of the valves 56a and 56b, the valve 56b controls the valve 56a and the valve 56a controls the valve 56b. With'respect to downward movement of the valves 56a and 56b, the piston 24a controls the valve 56b and the piston 24b controls the valve 56a. With the foregoing in mind, the operation of the duplex pump 10 will now be considered in detail. a

It will be assumed that the pistons 24a and 24b. and the valves 56a and 56b are in the positions shown in Fig. l of the drawings. This being the case, the piston 24a is moving upwardly through its working stroke, as indicated by the arrow 88a, and the piston 24b is moving downwardly through its return stroke, as indicated by the arrow 88b, or has just reached the end of its return stroke. The working stroke of the piston 24a resultsfrorn the application of exhaust pressure to the upper surface of the plunger 32a through the passage 48a, the annular channel 821: in the valve 56a, and the passage Stia. The return stroke of'the piston 24b results from the application of the operating fluid pressure to the upper surface of the plunger32b through the passage 48b, the lower end of the bore 541;, the passage 5% and the passage '44. During" the working stroke of thepiston 24a, the working valve 42a is closed so that pumped fluid is displaced upwardly through the production tubing 22. At the same time, the workingvalve 42b is open as the piston Mb negotiates its return stroke so that pumped fluid flows from the inlet 46 through the piston 24b into the region between the two pistons.

As the piston 24a approaches the end of its working stroke, ,but before it reaches the end of such stroke, the control port 80a bridges the control passages 76:: and 78a. Whenthis occurs, the lower end of the valve 56b is exposed to the exhaust pressure through the passage 74a, the control passage 76a, the control port 800, the control passage 7811, the annular channel 82a in the valve 56a, and the passage 50a. Consequently, the valve 56b moves downwardly into its lower position, with two results.

First, it disconnects the upper surface of the plunger 32b of the piston 24b from the supply tubing 18 and connects it to the return tubing 20 through the passage 48b, the annular channel 82b in the valve 56b, and the passage 50b. Consequently, the working stroke of the piston 24b is initiated to displace pumped fluid upwardly, the working stroke of this piston being initiated before the working stroke of the piston 24a is m na 0 that the pumping load is gradually shifted from the piston 24a to the piston 24b to avoid hydraulic shock, which is an'important feature of the invention.

, The second thing that happens when the valve 56b movesdownwardly'into its lower postiion is that it ape pliesifthe ,operat ingfluid pressure tothe'lower end of the va1ve, 5,;6 'a tinoughlthe passage 44, the passage 70b, the bore fi iliabov the valve 56b, the passage 84b, the restrictor sobfand'the'passage 74b, the passage 76b being closed by mean 3%. under. such conditions] This application; of the operatingfluid pressure to the lower end of the valve;56a through the restrictor 86b produces upward movement of thevalve 56a toward its upper position at a rate controlled by the restrictor 86b, which rate is such as to delay termination of the working stroke of the piston 24a until the piston 24b attains full speed on its work ing stroke. When the valve 56a reaches its upper position, it disconnects the upper surface of the plunger 32a of'the piston 24a from the return tubing 20 and connects it to the supply tubing 18 through the passage 44, the passage 52a, the bore 64a below the plunger 58a of the valve and the passage 48a. Consequently, the return stroke of the piston 24a is initiated. The piston 24a moves downwardly at a substantially uniform rate which is relatively high due to the fact that only mechanical friction and fluid friction through the axial passage 38a past the working valve 42a must be overcome. Consequently, the piston 24a reaches the end of its return stroke before the piston 24b completes its working stroke, and remains in its lower position until the piston 24b approaches the end of its working stroke. The desired speed of the piston 24a during its return stroke is readily achieved by making the area of the upper surface of the plunger 32a sufliciently largersthanthe area of the lower surface of the plunger 26a.

The valve 56b is held in its lower position during the working stroke of the piston 24b in the following manner. When the valve 56a is in its upper position, as hereinbefore described, the passage 84a communicates with the return tubing 20 through theannular channel 820 in the valve 56a and the passage 50a.. Consequently, the exhaust pressure in the return tubing 20 is applied to the lower end of the valve 56b through the passage 50a, the annular. channel 82:1 in the valve 56a, the passage 84a,

the restrictor 86a and the passage 74a, the passage 760.

being closed by the rod 30a. Thus, a hydraulic locking means for maintaining the valve 56b in its lower position throughout the working stroke of the piston 24b is provided.

Summarizing the foregoing, as the piston 24a ap-. proaches the end of its working stroke, it moves the valve 56b downwardly to start the working stroke of the piston 24b before the piston 24a completes its working stroke. The valve 56b moves the valve 56a upwardly to initiate the return stroke of the piston 24a. In a simithe valve 56b upwardly to, initiate the return stroke of the piston 24b.

Considering how the foregoing is accomplished, as the piston 24b approaches the end of its working stroke, but before it completes such stroke, the control port 80b bridges the control passages 76b and 78b to apply exhaust pressure to the lower end of the valve 56a through the passage 50b, the annular channel 82b in the valve 56b, the control passage 78b, the control port 8%, the control passage 76b, and the passage 74b. Consequently, the valve 56;; moves downwardly, the flow resistance offered by the restrictor 86b being sufliciently high that, even though it is open to the operating fluid pressure in the supply tubing 18 through the passage 44, the passage 70b,

1 the :bore 64b above the valve 56b, and the passago84b under such conditions, it does not appreciably increase; the pressure applied to the lower end of the valve 56a above the exhaust pressure. When the valve 56a moves downwardly into its lower position in the foregoing manner, two eventstake place. First, the upper surface of'the plunger 32a of the piston 24a is disconnected from the supply tubing 18 and is connected to the return tubing ZO-through the passage 50a,- the annularchannel 82a in the valve 56a, and the' passage 48a. Thus, the working strokerof thepiston 24a is initiated, this taking place before the completion of the working stroke'of the pisto'n'24bso' that again the pumping load is gradually transferredfrom the piston 24b -to the piston 24a to preventhydraulic shock. The second thingithat occurs in response to downward movement of the valve 56a to its lower position is that it connects the lower end of the valve 56b to the supply tubing 18 through the passage 44, the passage- 70a, the bore 64a above theplunger 58a, the passage 84a, the restrictor 86a, and the passage 74a. Consequently, the valve 56b is moved upwardly into its upper position'to disconnect the upper surface of the plunger 32b of the piston 14b from the return tubing 20 and to connect it to the supply tubing 18 through the passage 44, the passage 52b, the bore 64b below the plunger 58b, and the passage 48b. 1 This produces the downward or return stroke of the piston 24b,- the latter moving downwardly at a sufliciently high speed that it reaches the end of its return stroke beforethe piston 24a reaches the end of-its working stroke, as hereinbefore discussed in connection with the piston 24a. The desired, relatively high return speed for-the piston 24b is achieved by making" the area of the upper-surface'ofthe plunger 32b sutfi ciently larger than the area of the lower surface of the plunger 26b. 1 Y i As previously described, the valve 56b is locked in its lower position when the valve 56a is in its upper position by applying theexhaust pressure to the lower-end of the valve through the passage 50a, the annular channel 82a, the passage 84a, the restrictor 86a and the passage 74a. The valve 56a is locked in its lower position when the valve 56b is in its upper position by applying exhaust pressure to the lower end of the valve 56a through the-passage 50b, the annular channel 82b, the passage 84b, the restrictor 86b and the passage 74b; The valve 56b is locked in its upper position when the valve 56a is in its lower position by applying the operating fluid pressure to the lower end of the valve 56b through the passage 44, the passage 7012, the upper end of the bore 64a, the passage 84a, the restrictor 86a andthe passage 74a. The

valve 56a is locked in its upper position when the valve 56b is in its lower position by applying the operating fluid pressure to the lower end of the valve 56a through the passage 44, the passage 70b, the upper end of the bore 64b, the passage 84b, the restrictor 86b, and the passage 74b. 1 v I -'From the foregoing description of the operation of the pump 10, it will be apparent that as each of the pistons 24a and 24b approaches the end of the working stroke, it initiates the working stroke of the other to eifect a gradual transfer of the pumping load from one piston to 'the other. Subsequently, the first piston completes its working strokeand thereafter executes its return stroke before the second piston reaches the end of its working stroke. Thus,.the second of the pump units 14a and 14b always starts up before the first completes its working stroke, the resulting gradual transfer of the pumping load resulting in continuous flow of the pumped fluid so that no hydraulic shock in the production tubing 22 results. Also, since the engine portions or means of both pump units 14a and 14b are connected in parallel and thus are alwaysreceiving operating fluid under pressure and discharging spent operating fluid, the flows of operating'fluid under pressure and of spent operating fluid are substantially 114b, the corresponding components thereof will be desigcontinuous so that no hydraulic shock results in either the supply tubing 18 or the return tubing 20. v

The amount by which each of the pump units 14:: and 14b'leads the other with respect to initiation of theworlo' ing stroke of its piston z4 z or 24b dependsuponf the'j IOCatiOHSfOft-he' control ports a and 80b inthe rods 30a: and 30b. 7 These ports are so located as to permit the sco'ndpiston to attainnorrnal fullspeedbefore thefirst piston' completes its working jstroke. "'l heyamount of overlap of the working strokes of the two pistons 24a" and 24b is "also controlled-partly by the restrictors 86a and-86b since these restrictors control the rates of upward movement ofthe valvesf56a-and 56b and thus control the times at which the working strokes of the pistons 24a and24b arecompleted'and the return strokes thereof initiated. Thus, the phasing of the working strokes of the two pistons 24a and 24b is determined by boththe locations of the control ports 80a and 80b and the flow re-' sistances of the restrictors 86a and 86b. I

Since the pumping portions or pump means of the two pump units 14a and 14b are connected in series to produce a substantially continuous flow of pumped fluid, it will be apparent that the pumping capacity is greatly increased for. the same over-all pump diameter, which is an important'feature. Conversely, the over-all pump diameter may be greatly reduced to provide the same pump capacity as conventional pumps of larger diameter.- This is sometimes of great economic advantage, as the use of a pump of a smaller over-all diameter permits the use of a smaller tubing forjthe pump and thus permits the use ofa smaller well casing and a smaller well bore, thereby reducing drilling costs, casing cos'ts and tubing costs. The net'result is a very substantial saving'in' capital costs.

Triplex pump' 110 i The triplex pump of the invention which is illustratedin Fig. 2 of the drawings is designated'generally by the numeral 110 and includes three pumping devices 112a, 1121: and 1120, respectively, including axially aligned pump units 114a, 114k and 1140: having pump portions, or means connected in series andengine portions or means connected in parallel, as will become apparent. The pump units 114a, 1141 and 1140 are regulated by a control means 116 which, in the embodiment presently under consideration, comprises axially aligned valve .units 116a, 1161: and 1160, respectively, controlling the pump units 114a, 114b and 114C, the valve units being spaced from and located alongside the pump units. The triplex pump 110 is supplied with operating fluid under pressure through a supply tubing 118 and, in the particular construction illustrated, which is a closed system, the spent operating fluid isreturned to the surface through a return tubing 120. The fluid discharged by the pump units.114a, 114b and 1140 is pumped to thesurface through a production tubing 122. v j The pump units 114a, 114b and 114c'are all identicalf and are substantially identical to the pump 1421' and- 141) of the duplex pump 10, dififering' therefrom solely in substituting two"control ports, which willvbe described hereinafter, for the single control ports 80a and 80b of thejpump units 14a and 14b. Consequently, those components of the pump units 114a and 11 4b which are identical to corresponding components of the pump units 14aand 14b will, be designated by reference characters differing from the reference characters utilized in connection with the pump units 14a and 14b by the addition of the number thereto. Also, since the pump unit 1140 is identical to the pump units 114a and".

nated by reference characters differing from the reference characters associated with the pump units 114a and 1145 by the substitution of the sufl'ix c for the the suffix bi The inlet corresponding to thcinlet4Q" 11 of the duplex pump 10 will be designated by the reference character 140, a 1

AS in the case of the pistons 24a and 24b of the pump units 140 and 14b, the lower surfaces of the plungers 126a, 126b and 1260 of the pistons 124a, =124band 1240 are constantly exposed to the operating fluidpressure in the supply; tubing, 118 through a mair'i'passa'ge 144 and branch passages 146a, 1461) and 51460. The upper surfaces of the plungers 132a, 1321: aridI1320 are alternately exposed to the operating fluid pressure'in the supply tubing 118 and the spent operating fluid pressure or exhaust pressure in the return tubing 120 through passages:150a, 15012 and 1500 controlled by the valve units 116a, 1161) and 1160. The valve units 116a, 116k and 116 respectively include engine valves 152a, 1521:. and 1520 which are movable between upper and lower positions, these valves ,connecting'the passages 150a, 15% and 1500 to passages 154a, 154b and 1540 leading to the return tubing 120 when in their upper positions, and connecting the passages 150a, 150b and 1500 to branch passages 156a, 156b and 1560 of a main passage 158 leading to the supply tubing 118 when in their lower positions. Thus, the valves 152a, 15% and 1520 are in their upper positions to produce the upward or working strokes of the pistons 124a, 124b and 1240 and are in their lower positions to produce the downward or return strokes of the pistons. Thus, the relation of valve position to piston stroke in the pump 110 is the reverse of that in the pump 10.

The valves 152a 152b and 1520 are similar in construction and operation to those disclosed in my aforementioned copending application Serial No. 598,785 so that an extremely detailed description thereof herein will n ot be necessary. i

The valves 152a, 15% and 1520 are differential area valves each having a three-speed action during its upward movement, at which time it is controlling the acceleration of the corresponding piston 124a, 124b, or 1240 at the beginning of its upward or working stroke, and each having a two-speed action during its downward movement, atwhich time it controls the initiation of the downward or return stroke of the corresponding piston. The valves 152a, 152b and 1520 include relatively smaller plungers 1600, 16% and 1600 and relatively larger plungers 162a, 162b and 1620, the smaller plungers being reciprocable in bores 164a, 164b and 1640, and the larger plungers being reciprocable in bores 166a, 166b and 1660 and being connected to the smaller plungers by reduced-diameter rods or stems 168a, 1681: and 1680. When the valves 152a, 152b and 1520 are in their upper positions, the passages 150a, 15012 and 1500 are connected to the passages 154a, 154b and 1540 through'the annular spaces around the rods 1680, 168b and 1680 to produce the working strokes of the pistons 124a, 1241; and 1240. When the valves are in their lower positions, the passages 150a, 1501; and 1500 are connected to the passages 156a, 156b and 1560 through the bores 164a, 1641) and 1640 above the plungers 160a, 16% and 1600 to produce the return strokes of the pistons 1241a, 124b and 1240.

The plungers 162a, 162b and 1620 of the valves 152a, 1521; and 1520 are provided adjacent the upper ends thereof with external annular channels 170a, 17% and 1700, respectively. These channels communicate with branch passages 172a, 172b and 1720 of the main pas sage 158 when the valves 152a, 15 2b and 1520 are in their-upper positions and as they move upwardly from their lower positions to their upper positions, the main passage 158 leading to the supply tubing 118, as hereinbefore described, and thus supplying operating fluid under pressure to the channels 170a, 1701) and 1700 under the conditions specified. The lower ends of' the channels 1700, 17% and 1700 communicate with external helical' speed control grooves or threads 174a, 1741 and 1740.

grooves 176a, -176b and 1760 which, in turn, communicate with axial passages 178a, 178b and 1780 in the plungers 162a, 16% and 1620 through radial ports 180a, 18012 and 1800 therein. These axial passages extend to the lower ends of the valves 152a, 15% and 1520. When' the valves 1520, 152b and 1520 are in their lower positions, the annulargrooves 1760, 176b and 1760 communicate with branch passages 182a, -182b and 1820 of. control passages 184a, 1841; and 1840 which extend from the pump-unit bores 136a, 1361) and 1360 to the lower ends of the valve-unit bores 164a, 16% and 1640. As will be apparent, the branch and control passages just mentioned always communicate with the return tubing through'the annular spaces around the valve rods 168a, 1681) and 1680 and the passages 154a, 154b and 1540 so that the exhaust pressure is always present in these passages.

The plunger 162a, 162b and 1620 of the valves 152a, 1521) and 1520 are provided below the grooves 176a, 176b and 1760 with external annular grooves 186a, 1861) and 1860 which communicate with the axial passages 178a, 178b and 1780 through radial ports 188a, 188b and 1880, and which register with branch passages 190a, 1901: and 1900 of the main passage 158 in intermediate positions of the valves 1520, 15% and 1520, the main passage 158, as hereinbefore stated, communicating with the supply tubing 118 so that it always contains operating fluid under pressure.

Below the annular grooves 1860, 186b and 1860 the plungers 162a, 16% and 1620 are provided with relatively wide, external annular channels 1920, 19212 and 1920 whichcommunicate with the axial passages 178a, 1781: and 1780 through radial ports 194a 7194b and 1940, and which register with control passages 1960, 196b and 1960 when the valves 1520, 15% and '1520 are in their lower positions and when they are in intermediate positions. The control passage 196a leads to the bore 136b of the pump unit 114b to provide for control of the valve 1520 by the piston 12411. Similarly, the control passage.

of the pump unit 1140, which means that the piston. Thus; the.

124a exercises control over the valve 1520. uppermost pump unit 114a exercises control over the lowermost 'valve unit 1160 while the intermediate and.

lowermost pump units 1141) and 1140 exercise control over the uppermost and intermediate valve units 116a and 11'6b to provide the desired timed relation or phasing between the pump units, as will be discussed in more detail hereinafter.

Additional control passages 198a, 19811 and 1980 extend from the bores 136a, 136b and 1360 of the pump units 114a, 114b and 1140 to the lower ends ofthe major bores 166a, 166b and 1660 of the respective valve units 116a, 1161; and 1160. As will be described in detail here inafter, the control passages 198a, 1981) and 1980 permit the pump units 114a, 1140 and 1140 to exercise control over the respective valve units 116a, 1161; and 1160. Thus, control over the valve units 1160, 116 b and 1160 is exercised not only by pump units other than the'pump units 114a, 114b and 1140 which the respective valve units 116a, 11611 and 1160 control, but also by the pump units 114a, 1 14b and 1140 which the respective valve units 1160, 116b and 1160 control.

The rods a, 13% and 1300 of the pistons 1240, 124b and 1240 are provided with control ports 200a, 2001) and 2000, respectively, and control ports 202a, 2021) and 2020, respectively. As the pistons 124a, 124b and 1240 approach the ends of their working strokes, but before they complete their working strokes, the control ports 200a, 20% and 2000 connect the control passages 1960, 196a and 196b, respectively, to the cylinders 128a, 1281; and 1280, respectively. These cylinders always contain operating fluid under-pressure because 01.. their conneci3 tions to the supply tubing .118 through the branch pas sages 146a, 14Gb and 1460, respectively, and the main passage 144. At the-same time as or shortly after the control ports 200a, 2001) and 2090 accomplish the foregoing, but again before the pistons 124a, 12 4b and 124c reach the ends of their working strokes, the control port 202a bridges the control passages 184a and 198a, the control port 20% bridges the control passages 184b and 19%, and the control port '202c bridges the control passages 1840 and 1980'. As will become apparent, the control ports 200a, 290i; and Ztittcthus cause the pump units 114a, 1|14b and 114c to exercise control over certain of the valve units 116a, 11'6b and 1160 other than the valve units by which the respective pump units are controlled, while the control ports 202a, 2022b and, 2620 cause the pump units 114a, 11 1b and 114a to exercise control over the respective valve units 116a, 1165 and 116s by which they are controlled.

Operation pump 110 For convenience in considering the operation of the triplex pump 110, the detailed operation of the valves 152a, 152k and 152c will be considered first. Thereafter, the over-all operation of the pump 110, including the interrelations between the pump units 114a, 1141: and 1140 and the valve units 1161:, 11Gb and 116s, will be considered. Since the valves 152a, 152k and 1520 are identical, they all operate in exactly the same way and only the operation of the valve 152a willbe discussed in detail. I

As will be apparent, the upper end of the valve 152a is always exposed tothe operating fluid pressure in the supply tubing 118 through themain passage 158 and the branch passage 156a. Similarly, the annular areas at the lower end of. the plunger'160a and the upper end of the plunger 162a are always exposed to the exhaust pressure in the return tubing 120 through the passage 154a. Thus, the operating fluid pressure constantly acts downwardly on the area of the plunger 160a and the exhaust pressure constantly acts downwardly on the difierence between the areas of the plungers 160a and 162a. Therefore, when the exhaust pressure is applied to the lower end of the valve 152a, this valve moves'downwardly, the downward force producing this movement being the product of the area of the plunger 160a and the ditterence between the operating fluid and exhaust pressures. Conversely, the valve 152a moves upwardly when the lower end thereof is exposed to the operating fluid pressure, the net upward force being the result of theapplication of the difference between the operating fluid and exhaust pressures to the ditference between theareas ofthe plungers 162a and 160a.

Considering first upward movement of the valve member 152a from its lower position, such movement'is initiated by the application of the operating fluid pressure to the lower end thereof through the controlpassage 196a, the annular channel 192a, the radial port 194a and the axial passage 178a. All of these passages ofier relatively little restriction to operating fluid flow so that the valve 152a moves upwardly, at a relatively high first speed. Eventually, the annular channel 192a moves upwardly out of register with the control passage 196a, which marks theend of upward movement of the valve 152a at its first speed. At this point, the channel 170a registers with the branch passage 172a of the'main passage 158 leading to the supply tubing 118, whereupon the pressure of the operating fluid in the supply tubing is applied to the lower end of the valve 152a through the main passage 158, the branch passage 172a, the channel 170a, the helical groove or thread 174a, the annular groove 176a, the-radial port 180a and the axial passage 178a. Under these condition, the valve 152a continues its upward movement at a relatively slow second speed, determined by the flowcapacity of the helical thread 174a. As the valve152a moves upwardly at its relatively slow second Preferably, the radial port 180a, determining the relatively slow second downwardspeed of the valve 152a I speed, the plunger 160a begins to uncover the passage a to connect the cylinder 134a above the plunger 132a to the return tubing 120 through the annular space around the rod 168a and the passage 154a. This connection of thecylinder 134a above the plunger 132a to the return tubing ,120 is thus initiated slowly so as to initiate the working stroke of the piston 124a slowly to avoid hydraulic-shock andto prevent racing of the piston 124a in the event that it is not acting on solid fluid.

After the plunger a has begun to uncover the passage 15tia to initiate the working stroke of the piston 124a in the foregoing manner, the annular groove 186a registers with the branch passage'190a leading to the supply tubing 118 through the main passage 158, whereupon operating fluid under pressure from the supply tubing may flow. through the main passage 158, the branch pas-.

sage 19021, the annular groove 186a, the radial port 188a and the axial passage 178a to the lower end of the valve,

speed attainable with the helical thread 174a alone. Thus,

the relatively high third speed of the valve 152a is approximately four times the relatively slow second speed thereof. The relatively high third speed of the valve 152a permits the establishment of full communication between the return tubing 120 and cylinder 134aabove the plunger 132:: at a relatively high' rate, after initial communication has been established slowly in the manner hereinbefore described, to permit the piston 124a to achieve its normal working-stroke speed as quickly as possible, such slow establishment of initial communication preventing hydraulic shock as the piston 124a starts its working stroke.

As the valve 152a approaches its upper position, the

annular groove 186a moves upwardly out of register with the passage 190a so that the final upward movement of the valve is again controlledlby the'helical thread 174a. Consequently, this helical thread also acts to lock the valve-152a in its upper position since, under the condition existing at this stage, the lower end of the valve 152a is exposed to the operating fluid pressure in the supply tubing 118 through the passage 158, the passage 17241, the annular channel a, the helical thread 174a, the annular groove 176a, the radial port a and the axial passage 178a. a

Considering now the downward movement of the valve- 152a, as soon as the exhaust pressure is applied to the lower end of this valve through the passage 198a, the valve starts downwardly at a relatively high first speed. The passage 198a communicates with the bore 166a somewhat above the lower end thereof so that the plunger 162a the .the valve 152a eventually covers the passage 198a, thev plunger 1620 beginning to cover the passage 193a when the plunger 160a begins to uncover the passage 150a. Thereafter, the-valve 152a moves downwardly at a relatively slow second speed to establish communication between the supply tubing 118 and the cylinder 134a draulic shock. The relatively slow second downward speed of the valve 152a is produced by the radial port 180a, the lower end of the valve 152a being connected tothe return tubing 120 by way of the passage 154a,. the

annular space around the rod 168a, a portion of the control passage 184a, the branch passage 182a; the annular groove 176a, the port 180a, and the axial passage 178a.

is approximately the same size as the radial port 188a controlling the third upward speed of the valve. Once the valve 152a reaches its lower position, the lowerlend thereof continues to be exposed to the exhaust pressure in the return tubing 120 through the passage 154a, the annular space around the rod 168a, a portion of the control passage 184a, the branch passage 182a, the annular groove 176a, the radial port 180a and the axial passage 178a. Thus, the port 186a acts as a hydraulic lock for the valve 152a when it is in its lower position.

As hereinbeforestated, the valves 152i) and 1520 operate in exactlythe same way asthe valve 152a in moving from their lower positions to their upper positions and from their upper positions to their lower positions. Consequently, no description of the operation of the valves 1521: and 1520 is necessary.

Consider now the over-all operation of the triplex pump 110, the valves 152a and 1520 are shown in their upper positions and the valve 152!) is shown in its lower position so that the pistons 124a and 1240 are on their working strokes, as indicated by the arrows 204aand 2204c, and the piston 1241) is on its return stroke, as indicated by the arrow 204b, or has reached the end of its return stroke. The piston 1246 is leading the piston 124a by approximately 120', the piston 124:; is leading the piston 12% by approximately 120, and the piston 124b is leading the piston 1240 by approximately 120, considering the working and return strokes of one of the pistons as constituting a 360 operating cycle. This timing or phasing of the movements of the pistons 12411, 12%

and 1240 is achieved in a manner that will become apparent in the light of the description which follows.

Considering the piston 1240, it will be noted that it is approaching'the end of its working stroke and that the control port is about to connect the cylinder 1230 to. the control passage 196b. When this occurs, operating fluid under pressure flows from the supply tubing'118 through the main passage 144, the branch passage 146e, the cylinder 1280, the control port 2000, the control passage 196b, the annular channel 192b in the valve 152b, the radial port 19% in this valve,'and the axial passage 17% therein into the bore 166b below the valve 152b. The operating fluid pressure is thus applied to the lower end of the valve 152k to move it upwardly in the manner hereinbefore described, whereupon the valve 152!) disconnects the upper surface of the plunger 132b from the supply tubing 118 and connects it to the return tubing 12%, through the passage'150b, the annular space around the rod 168b and the passage 154b, to initiate the working stroke of the piston 124b. Thus, the piston 124-0, as it approaches the end of its working stroke, moves the valve 15% from its lower position to its upper position to initiate the working stroke of the r piston 124b, thereby effecting a gradual pumping load transfer fromthe piston 1240 to the piston 124b. Thus, the piston 1240 exercises control over a valve, viz., the valve 152b, other than the valve, viz., the valve 1520, by which the piston 1240 itself is controlled.

The piston 1240 also exercises control over the valve, viz., the valve 1520, by which it is controlled. More specifically, at about the time the control port 2000 connects the control passage 19622 to the cylinder 1280,

"or immediately thereafter, the control port 2020 bridges the control passage 1840 and 1980. When this occurs, the exhaust pressure is communicated to the lower end of the valve 1520 through the passage 1540, the annular the passage 158, the passage 1560, the bore 1640 above the. valve plunger-.1660, and the passage 1500. Consequently, the return stroke of the piston 1240'is initiated,

this occurring after initiation of the working stroke of the piston 12 3b to insure the hereinbefore-described pumping load transfer from the piston 1240 to the piston 12%.

Similarly, when the piston 124a has substantially reached the end of its working stroke, the control port Ziitla acts through the control passage 1960 to move the valve 1520 upwardly to initiate the working stroke of the piston 1240, and the control port 202a acts through the control passage 198a to move the valve 152a downwardly into its lower position to initiate the return stroke of the piston 124a. Thus, a' gradual pumping load transfer from the piston 12441 to the piston 1240 occurs. Again in a similar manner, as the piston 12% approaches the end of its working stroke, the control port 20Gb acts through the control passage 196a to move the valve 152a upwardly to initiate the working stroke of the piston 124a, and the control port 20212 acts through the control passage 1923b to cause the valve 15% to move downwardly to initiate the return stroke of the piston 124b, thereby gradually transferring the pumping load from the piston 12411 to the piston 124a. The operating cycle is completed when, as hereinbefore described in detail, the piston 1240 moves the valve 152b upwardly to initiate the working stroke of the piston 12% and moves the valve 152c downwardly to initiate its own return stroke. The piston 124a controls the valves 1520 and 1520 and the piston 124b controls the valves 152a and 15% in exactly the same manner as the piston 1240 controls the valves 152b and 1520 so that a detailed description is unnecessary.

As will be apparent from the foregoing, the phasing or timing of the working and return strokes of the pistons 124a, 1241) and 1240 is such that two of these pistons are on their working strokes at all times, since the pumping load carried by each of the pistons as it approaches the end of its working stroke is transferred to a piston which has completed its return stroke.

As two of the pistons 124a, 12% and 1240 move upwardly through their working strokes in phased relation, with one leading the other by approximately the third piston is moved downwardly through its return stroke, or has completed its return stroke and is standing at the lower end of its travel waiting for the next piston in the series to approach the end of its working stroke. In order to achieve this, it will be apparent that the speed of each piston during its return stroke must be at least twice its speed during its working stroke. This is accomplished readily by making the area of the upper surface of each plunger 132a, 13% and 1320 sufficiently larger than the area of the lower surface of the corresponding one of the plungers 126a, 1261: and 1260. Since only mechanical friction and fluid friction through the Considering some of the advantages of the triplex pump 110, since the pumping load is always transferred from the piston 124a, 124b or 1240 which is nearing the end of its working stroke to the piston which is standing at the lower end of its travel before the first piston mentioned reaches the end of its working stroke, there is substantially no tendency to induce hydraulic shock in the pumped fluids Also, since the engine portions or means of the pumpunits 114a, 114b and 1146 are connected in pnraliel, the [lows of operating fluid under pressure from the supply tubing 118 andof'spent' operating fiuid to the return tubing 120 are substantially constant to avoid inducing hydraulic shock in either the operating fluid column or the spent operating fluid column.

Since the pumping load is always carried by two of the pistonslZ-ta', 24b and 1240, and since these pistons 17 are preferably identical, it will be apparent that the pumping load is always divided equally between two of the pistons. Consequently, the operating fluid pressure required for a given pumping capacity is only half that which would required if only one of the pistons were on its working stroke at any instant. Conversely, if the same operating fluid pressure is used, the engine areas,

i.e., the areas of the upper surfaces of the plungers 1320, 132b and 1320 and the areas of the lower surfaces of the plungers 1260, 1215b and 1260 may be reduced by a factor of two for the same pumping capacity.

Reducing the operating fluid pressure by a factor of two has the advantage of reducing the strength requirements of the entire structure of the pumping system, while reducing the engine areas by a factor of two with the same operating fluid pressure has the advantage of a reduction in pump size without any reduction in pumping capacity. Such a reduction in pump size is, as hereinbefore pointed out, occasionally of great economic advantage, since it permits the use of a smaller pump tubing, a smaller well casing and a smaller well bore, thereby reducing tubing, casing and drilling costs.

On the other hand, if maximum operating fluid pressure and maximum pump size are utilized with the triplex pump 110 of the invention, very large increases in pumping capacity, as compared to conventional pumps, may be realized. For example, a triplex pump 110 of the invention operating at the samepressure as and of the same over-all diameter as a comparable prior art pump will have a pumping capacity of nearly five the pumping capacity of the prior 'art pump.

The triplex pump 110 also has the advantages hereinbefore ascribed to the duplex pump 10. For example,

the axially aligned flow passages 138a, 13% and 1380 making a standingvalve or valves'unnecessary. The

straight axial flow through the pistons 124a, 124b 1240 and the absence of standing valves contribute materially to the increased capacity of the pump '110 by minimizing resistance to flow of the pumped fluid. a

While the invention has thus far been considered as applied to duplex and triplex pumping, it will be apparent to those skilled in the art thaty'the invention may very readily be extended-to quadruplex pumping, quintuplex operation, and so forth. This may be accomplished very readily by inserting additional pumping devices, similar to the pumping devices 1121:, 11% and 1120, between any two of the pumping devices 112a, 11% and 1120. For example, the triplex pump 110 may be converted to a quadruplex pump by inserting a pumping device similar to the pumping devicm 112a, 1121; and 1120 between the pumping devices 112a and1-12b, this additional pumping device being related to the pumping device 112b in the same manner as the pumping device 112a is related to the pumping device 112b, and being related to the pumping device 112a in the same manner as the pumping device 112b is related to the pumping device 112a. A quintuplex pump may be produced by inserting two such pumping devices in the manner indicated. In any such multiplex pump, all but one of the pistons would be on their working strokes at all times. Thus, assuming a multiplex pump having n pumping devices, the pumping load is always carried by 11-1 pistons. Therefore, either the operating fluid pressure, or the engine areas, may be reduced by a factor of nl, or, alternatively, by maintaining the operating fluid pressure and the engine areas at maximum values, the pumping capacity may be correspondingly increased. As will be apparent, by increasing the value of n, the operating fluid pressure, or the engine Triplex pump 210 I Referring now to Figs. 3 to 8 of the drawings, and particularly to Figs. 3 and 4 thereof for the time being, illustrated therein is another triplex pump of the invention which is designated generally by the numeral 210 and which includes pumping devices 212a, 2212b and 2120. These pumping devices include pump units 214a, 214b and 2140 the operation of which is regulated by a control means 216 which consists of a single v'alve unit common to the three pump units.

The pump 210 is supplied with operating fluid under pressure through a supply tubing 218 and spent operating fluid is returned to the surface through a return tubing 220. Pumped fluid enters the pump 210 through an inlet 240 and is conveyed to the surface through a production tubing 222.

The pump units 214a, 214b and 2140 are substantially identical to the pump units 114a, 114b and 1140, the only difference being that control ports to be described are substituted for the control ports 200a, 200b, 2000, 202a, 232k and 2020. Consequently, components of the pump units 214a, 21412 and 2140 which are identical to corresponding components of the pump units 114a, 114b and 1140 are identified by reference characters higher by than the reference characters associated with the pump units 114a, 114k and 1140. Thus, detailed descriptions of the pump units 214a, 2141) and 2140 will be unnecessary. 1

As in the previous embodiments, the lower surfaces of the plungers 226a, 2261; and 2260 are constantly exposed to the operating fluid pressure through a main passage 244- and branch passages 246a, 246b and 2460. The upper surfaces of the plungers 232a, 232b and 2320 are alternately exposed to the exhaust pressure in the return tubing 220 and the operating fluid pressure in the supply tubing 218 through passages 248a, 248b and 2480 controlled by the valve unit 216, exposure of the upper surfaces of the plungers 2320,2321) and 2320 to the exhaust pressure resulting in the working strokes of the pistons 224a, 224b and 2240, and exposure of these surfaces to the operating fluid pressure resulting in the re turn strokes of the pistons.

Considering the valve unit 216 in more detail, it is located alongside the pump units 214a, 214b and 2140 and includes a tubular rotary valve 250 rotatable about an axis parallel to the axis of the pump units. The

valve250 is rotatable in axially aligned bores 2520, 252b and 2520 with which the passages 2480, 248b and 2480 communicate respectively, the valve being in fluidtight engagement with the walls of such bores. j

The valve 250 is provided with an axial passage 254 therethrough which communicates at its upper end with the supply tubing 218 so that operating fluid under'pressure is always present in such passage. The valve 250 is provided with radial pressure ports 256a, 2561) and 2560, as shQWn inligsVS, 6' and 7, respectively, which are adapted to register with the passages 243a, 248i; and 2480, respectively, to produce the return strokes of the pistons 224a, 224-12 and 2240, respectively, by communicating the operating fluid pressure to the upper surfaces of the plungers 2320, 23% and 2320, respectively. The

ports 256a, 256b and 2560 are spaced apart circumferentially of the valve 250 by so that, as the valve is rotated through three operating positions in sequence by actuating means 260 to be described, the pistons 224a, 224b and 2240 are caused to execute their return strokes in sequence with phase angles of 120 between the return strokes. p v

The valve 250' is surrounded by an annular space262 which is divided into two axially spaced parts at the bore 252b, these axially spaced parts being connected by a passage 264. The annular space 262 communicates with the return tubing 220 through a passage 266. Thus, spent operating fluid atthe exhaust pressure in the return tubing 220 is always present in both parts of the annular space 262.

The valve 250 is provided therein with external exhaust recesses or ports 268a, 268k and 2680 which communicate with the annular space 262 and which are adapted to communicate with the passages 248a, 248b and 2480, respectively, as the valve 250 is rotated by the actuating means 260, thereby applying the exhaust pres- Sure to the upper surfaces of the plungers 232a, 2321) and 2320 to effect the working strokes of the pistons 224a, 224k and 2240. The ports 268a, 2681) and 2680 are spaced apart circumferentially by angles of 120 so that, they produce the working strokes of the pistons 224a, 2241 and 2240 in sequence with phase angles of 120 between such working strokes. The ports 268a, 2681) and 2680 are located diametrically opposite the ports 256a, 2561; and 2560, respectively, and have angular extents in excess of 120, as best shown in Figs. 5, 6 and 7. Consequently, whenever one of the ports 256a, 256b and 2560 is in register with the corresponding one of the passages 2484, 248b and 2480 to produce the return stroke of the corresponding one of the pistons 2240, 22417 and 224-0, two of the exhaust ports 268a, 2681) and 2680 are in register with the corresponding pair of the passages 2480, 248b and 2480 to produce the working strokes of the cor: responding pair of the pistons 224a, 224i; and 2240. Thus, two of the pistons are on their working strokes at all times, while the third is on its return stroke, or is standing at the lower end of its travel. The necessary high return speeds for the pistons 224a, 224b and 2240 are attained in the same manner as hereinbefore described in connection with the triplex pump 110. The leading edges of the exhaust ports 2680, 268b and 268 are so positioned circumferentially relative to the pressure ports 256a, 256k and 2560 that, as the valve 250 rotates from one of its three positions to the next, one of the exhaust ports 2680, 268b and 2680 registers with the corresponding one of the passages 248a, 248b and 2480 before one of the pressure ports 256a, 2561) and 256 registerswith the corresponding one of the passages 2480, 248b and 2480. This starts one of the pistons 224a, 2241; and 2240 on its working stroke before another of the pistons is startedon its return stroke, thereby providing a gradual load transfer to minimize hydraulic shock.

Considering the actuating means 260, it includes a piston 270 reciprocable axially of the rotary valve 250 in a cylinder 272, the piston having a stem 274 which makes a sliding fit in the lower end of the passage 254 through the valve. The piston 270 and its stem 274 are provided with an axial passage 2'76 therethrough which communicates at its upper end with the passage 254 and at its lower end with the cylinder 272, there being a restrictor 278 between the ends of the passage 276. The cylinder 272 below the piston 270 communicates with a main passage 280 having branch passages 2820, 282i: and 2820 respectively communicating with the bores 236a, 236b and 2360 of the pump units 2140, 214b and 2140. The passages 282a, 2821: and 2820 are adapted to be connected to the cylinders 234a, 234b and 2340, respectively, by control ports 284a, 284k and 2840, respectively, in the rods 230a, 2301) and 2300, respectively, of the pistons 224a, 2241; and 2240, respectively. These control ports regulate the pressure applied to the lower end of the piston 270,- in a manner which will be described hereinafter. The upper end of the stem 274 is always exposed to the operating fluid pressure in the passage 254, and an area of the upper surface of the piston 270 equal to the difference between the cross sectional area of the piston and the external cross sectional area of the stem 274 is constantly exposed to the exhaust pressure through a passage 286 in the valve 250, the passage 286 communieating with the annular space 262 through the exhaust port 2680-, Thus, 'as will be discussed'i'n more detail hereinafter, the. piston 270. is a differential area device, which is caused to. move upwardly when the operating fluid pressure is applied to the lower end thereof through the-passage 276, and which is caused to move downwardly when the exhaust pressure is applied to the lower end of the piston through the passage 280, the downward movement of the piston under such conditions being the result of the constant application of operating fluid pressure to the upper end of the stem 274.

As best shown in Fig. 8, the piston, 270 is. provided with an upwardly extending annular flange or skirt 283 provided externally with helical ribs or splines 290 and internally with straight ribs or splines 292. The valve 250 is provided with straight external splines 294 which key the valve to the piston 270 for simultaneous rotation while permitting reciprocation of the piston relative to the valve. The external helical splines 290 on the skirt 288 engage internal helical splines 296 on a ratchet member 298 having three teeth 300 spaced apart and engageable by a spring biased pawl 302 carried by the body, 304, of the valve unit 216. The teeth 300 are so oriented that the pawl 302 permits counterclockwise rotation of the ratchet member 298 as viewed from above, but prevents clockwise rotation thereof. Thus, when the piston 270 moves upwardly, the helical splines 290 and 296 try to rotate the ratchet member 298, but this is prevented by the pawl 302. Therefore, as the piston 270 moves upwardly, it rotates in the counterclockwise direction and causes the valve 250 to rotate with it due to the action of the straight splines 292 and 294.

A second ratchet member 306 is carried by the upper end of the valve 250 and is provided with teeth 308 engageable bya spring biased pawl 310 carried by the valve body 304. The ratchet teeth 308 are also spaced 120 apart and are so oriented that the pawl 310 permits counterclockwise rotation of the valve 250, but prevents clockwise'rotation thereof. Therefore, when the piston 270 moves upwardly, it causes the valve 250 to rotate counterclockwise through an angle of 120", but when the piston 270 moves downwardly, the valve 250 is held against rotation and the ratchet member 298 rotates counterclockwise instead. As may be concluded from the foregoingQthe angles of the helical splines 290 and 296 and the stroke of the piston 270 are so related that one stroke of the piston produces 120 of rotation of the valve 250.

1 c Operation ofpumpZlO Asv shown in Fig. 3 of the drawings, the piston 224a is adjacent the upper end of its travel and is moving downwardly through its return stroke, as designated by the arrow 312a, the return stroke resulting from the fact that thevalve 250 is in a position to connect the pressure port 256a to the passage 248a to apply operating fluid pressure tothe upper surface of the plunger 232a. At the same time, the pistons 22% and 2240 are moving upwardly. through their working strokes, as indicated by the munication with the passage 2480 in the preceding valve position. As previously explained, the exhaust ports 2680, 268b and 2680 register with the corresponding passages 248a, 248b and 2480 for two angular positions. of the valve 250 spaced 120 apart due to the fact that these exhaust ports are more than 120 in angular extent.

Under the foregoing conditions, after the piston 224a has reached the end of its return stroke and as the piston 224B reaches the end of its working stroke, the control port 2840 of the piston 2124c connects the cylinder 234a to the passage 282a. Since exhaust pressure is present in the cylinder 234c under these conditions, the exhaust pressure is applied to the lower end of the piston 270 through the passage 282c and the passage 280. When this occurs, the piston 270 moves downwardly, Fig. 4, rapidly at a rate determined by the sizes of the passages connecting the cylinder 272 to the return tubing 220 and the difference between the operating fluid and exhaust pressures. As the piston 270 moves downwardly, it rotates the ratchet member 298 through an angle of 120 and the pawl 302 engages the next ratchet tooth 300 carried by this ratchet member. As this occurs, the piston 2241: continues to move upwardly through its working stroke to cause the control port 2840 to cut off communication between the cylinder 2.340 and the passage 282c. Consequently, the cylinder 272 below the piston 270 is cut off from its source of exhaust pressure and, when this occurs, the pressure in the cylinder 7.72 below the piston 27 builds up to the operating fluid pressure as operating fluid flows through the restrictor 278, this restrictor being sufficiently small to prevent any pressure buildup during the preceding application of exhaust pressure to the lower end of the piston. The operating fluid pressure now applied to the lower end of the piston 270 through the restrictor 278 causes the piston 274) to move upwardly again and, since the ratchet member 298 is now prevented from rotating by the pawl 302, the valve 250 rotates in the counterclockwise direction, having previously been prevented from rotating in the clockwise direction during downward movement of the piston 270 by the pawl 310 and ratchet member 306.

As previously explained, the foregoing downward and upward movement of the piston 270 rotates the valve 250 through an angle of 120 in the counterclockwise direction to bring the exhaust port 268a into register with the passage 248a and to bring the pressure port 2561) into register with the passage 2481). The initiates the working stroke of the piston 224a, and initiates the return stroke of the piston 224b, the piston 22.40 meanwhile continuing on its working stroke. Thus, .two of the pistons are always on their working strokes, while the third is on its return stroke, or is standing at the lower end of its travel.

When the control ports 284a and 284b connect the cylinders 234a and 234b to the passages 282a and 282b, the valve 250 is rotated through angles of 120 in the same manner as hereinbefore described in connection with bridging of the cylinder 234a and the passage 2.82s by the control port 2840. Thus, whenever one of the control ports 284a, 2841) and 2840 bridges the corresponding one of the cylinders 234a, 234b and 2340 and the corresponding of the passages 282a, 2821: and 2820, the actuating means 260 is energized to advance the valve 250 through 120 to start one of the pistons 224a, 22 8b and 2240 on its working stroke and to start another thereof on its return stroke.

It will be noted that when the pistons 224a, 22% and 2240 move downwardly, the control ports 284a, 284b and 2340 respectively bridge the cylinder 234a and the passage 282a, the cylinder 23 th and the passage 282b, and the cylinder 234s and the passage 2820. However, when the pistons are moving downwardly, the cylinders 234a, 2341) and 2340 are open to the supply tubing 218 for the reasons hereinbefore described so that they con tain fluid at the operating fluid pressure. Since the operating fluid pressure is normally applied to the lower end of the piston 27% through the restrictor 278 to hold it in its upper position, such application of operating fluid pressure by the control ports 284a, 1284b and 284a during the return strokes of the pistons 224a, 224b and 224c has no efiect. Thus, the control ports cause rotation of the valve 250 during the working strokes of the pistons only. I

While it is thought that the operation of the triplex pump 210 will be clear from the foregoing, Fig. 4 of the drawings shows more clearly the action of one of the control ports, viz., the control port 284b, in'moving the piston 270 downwardly. In Fig. 4, the pistons 224a and 224b are moving upwardly, as indicated by the arrows 314a and 314b, while the piston 224c is moving downwardly through its return stroke, as indicated by the arrow 314c. The piston 22411 is in a position to cause the control port 2841) to bridge the cylinder 23412 and the passage 282b, whereby to apply exhaust pressure to the lower end of the piston 270 through the passage 280 to produce movement of the piston downwardly into its lower position, as shown. As soon as the piston 224b moves upwardly to cut oil communication between the cylinder 23% and the control port 284b, the piston 270 will move upwardly due to pressure built up therebeneath through the restrictor 278.

The triplex pump 210 has all of the advantages of the triplex pump 110 so that a detailed discussion thereof is unnecessary, it being suflicient to point out that the pump 210 may readily be converted to a duplex pump, or to a quadruplex or quintuplex pump, or the like. For example, the triplex pump 210 may be converted to a quadruplex pump readily by adding another pump unit identical to the pump units 214a, 2141: and 214a and by modifying the structure ot the actuating means 260 and the porting of the valve 250 to provide for four operating positions of the valve spaced apart angularly by 90. Conversion to duplex pumping, quintuplex pumping, or the like, may be effected in similar fashion.

Another important feature of the invention common to the embodiments hereinbefore disclosed is that such embodiments may be assembled from parts presently available, such as the parts disclosed in my aforementioned copending application Serial No. 598,785, irrespective of Whether the resulting pump is a duplex pump, a triplex pump, a quadruplex pump, a quintuplex pump, or the like. This interchangeability tends to lower costs appreciably since a few basic components may be utilized for a wide variety of pumps.

Although various exemplary embodiments of the present invention have been disclosed herein for purposes of illustration, it will be understood that numerous changes, modifications and substitutions may be incorporated in such embodiments without departing from the spirit of the invention as defined by the following claims.

I claim:

1. In a fluid operated multiplex well pump, the combination of: at least two axially aligned fluid operated pump units connected in tandem and each adapted to sustain a pumping load; and control means located alongside and spaced from said pump units and operable by said pump units for applying the pumping load to said pump units seriatim, said control means including means for removing the pumping load from each of said pump units after the pumping load has been applied to another of said pump units.

2. In a fluid operated multiplex well pump, the combination of: two or more axially aligned fluid operated pump units connected in tandem and each having a fluid operated engine means and a pump means connected to and actuable by said engine means; and fluid operated control means actuable by said pump units for operating said engine means of said pump units in timed relation, said control means including axially aligned fluid operated valve units corresponding in number to the number of said pump units and respectively controlling said engine means of said pump units, said axially aligned valve units being connected in tandem and being lo- ,H. 23 cated alongside and spaced from said axially aligned pumpv units.

3. Ina. fluid operated multiplex well pump, the combination of: two or more axially aligned fluid operated pump units connected in tandem and each having a fluid operated engine means and a pump means connected to and actuable by said engine means; and fluid operated control means actuable by said pump units for operating said engine means of said pump units in timed relation, said control means including a single, rotary, fluid operated valve unit controlling said engine means of all of said pump units and located alongside and spaced from said axially aligned pump units.

4. In a fluid operated. multiplex pump, the combination of: two or more fluid operated pump units each having a fluid operated engine means and a pump means connected to and actuable by said engine means; and fluid operated control means actuable by said pump units for operating said engine means of said pump units in timed relation, said control means including a single valve unit controlling said engine means of all of said pump units, said valve unit including a rotary valve and. including fluid operated means actuable by said pump units for" rotating said valve.

5. In a fluid operated multiplex pump, the combination, of: two or more fluid operated pump units each having a double acting fluid operated engine means and a single acting pump means connected to and. actuable by said engine means; fluid operated control means actuable by said pump units for operating said engine means of said pump units in timed relation; means connecting said engine means of said pump units in parallel; and means connecting said pump means of said pump units in series.

6. In a fluid operated multiplex well pump, the combination of: at least two axially aligned fluid operated pump units connected in tandem and each having piston means movable through working and return strokes, each of said piston means having therethrough an axial passage, said axial passages being connected in series; a single working valve in each of said passages; and fluid operated control means connected in fluid communication with said pump units and controlled by said piston means thereof for initiating the working stroke of one of said piston means as another of said piston means approaches the end of its working stroke.

7. In a fluid operated multiplex pump, the combination of: at least two fluid operated pump units each having working and return strokes; and valve units equal in number to the number of pump units and respectively controlling said pump units, each of said pump units having means for operating a valve unit other than the valve unit by which it is controlled, and each of said valve units having means for operating another of said valve units.

8. In a fluid operated multiplex pump, the combination of: at least two fluid operated pump units each having piston means movable throughworking and return strokes and each having a passage therethrough for pumped fluid, said pass-ages being in series; working valves in said passages, respectively, and preventing flow therethrough in one direction; and fluid operated control means connected in fluid communication with said pump units and controlled by said piston means thereof for maint-aining at least one of said piston means on its working stroke at all times.

9. In a fluid operated multiplex well pump, the combination of: at least two axially aligned fluid operated pump units connected in tandem and each having piston means movable throughworking and return strokes, each ofi-said piston means having an axial passage therethrough for pumped fluid, said passages being in series; working valves carried by said piston means, respectively, and. preventing flow through said passages, respectively, in one direction; and fluid operated control means connected in fluid communication with said pumpunits and controlled by said piston means thereof for maintaining at least one of said piston means on its working stroke at all times.

10. In a fluid operated multiplex well pump, the combination of: at least two axially aligned fluid operated pump units connected in tandem and each having piston means movable through working and return strokes, each of said piston means having an axial passage therethrough for pumped fluid, said passages being in series; working valves carried by said piston means, respectively, and preventing flow through said passages, respectively, in one direction; and fluid operated control means located alongside and spaced from said pump units and actuable by said piston means of said pump units for maintaining at least one of said piston means on its working stroke at all times.

11. In a fluid operated multiplex well pump, the combination of: at least two axially aligned fluid operated pump units connected in tandem and each including fluid operated double acting engine means and single acting pump means connected to and operable by said engine means; means connecting said engine means of said pump units in parallel; and means connecting said pump means of said pump units in series.

12. In a fluii operated triplex well pump, the combination of: three axially aligned fluid operated pump units connected in tandem and each including fluid operated double acting engine means and single acting pump means connected to and operable by said engine means; means connecting said engine means of said pump units in parallel; means connecting said pump means of said pump units in series; and fluid operated control means actuable by said pump units for operating said engine means of said pump units in timed, overlapping relation.

13. In a fluid operated triplex well pump, the combination of: three axially aligned fluid operated pump units connected in tandem and each including fluid operated engine means and pump means connected to and operable by said engine means; means connecting said engine means of said pump units in parallel; means connecting said pump means of said pump units in series; and fluid operated control means actuable by said pump units for operating said engine means of said pump units in timed, overlapping relation, said control means including a single valve unit located alongside and spaced from said pump units and controlling said engine means of all of said pump units.

14. In a fluid operated multiplex pump, the combination of: at least two fluid operated pump units each having working and return strokes; and valve units equal in number to the number of pump units and respectively controlling said pump units, each of said valve units including a reciprocable valve, each of said pump units having means for moving the valve of the valve unit by which it is controlled in one direction and for moving the valve of a valve unit other than the valve unit by which it is controlled in the opposite direction.

15. In a fluid operated multiplex pump, the combination of: at least two fluid operated pump units each having working and return strokes; and valve units equal in number to the number of pump units and respectively controlling said pump units, each of said valve units including a reciprocable valve, each of said pump units having means for moving in one direction the valve of a valve unit other than the valve unit by which it is controlled, and each of said valve units having means for ,moving in the opposite direction the valve of another of said valve units.

(References on following page);

UNITED STATES PATENTS Massey Aug. 12, 1890 Holliday Oct. 4, 1910 5 Grant Nov. 15, 1932 Mayer Aug. 27, 1940 Vickers Feb. 24, 1942 26 Archer May 12, 1942 Buchanan June 8, 1948 Hjarpe Dec. 25, 1951 Kent et a1 Dec. 1, 1953 Knox Jan. 28, 1958 FOREIGN PATENTS Gen-many July 21, 195-2 UNITED STATES PATENT UFFICE QE TIFICATE OF 'CORECTION Patent Nor 2339 397 June 7 1960 Clarence J Coberly It is hereby certified that error aopears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 73, after "each". insert --r such "5 column '1, line 51 for "bore 54b" read bore 64b --3 column 14L lines 43 and 44, for "condition" read conditions column 15, line 14 for "Consider" read Consideringv 3 oolumn l7 line 5 after "would" insert be column 21,,

line 39, for "The" read This --5 line .53 before "of the passages" insert one Signed and sealed this 8th day of November 1960.

(SEAL) Affififiii KARL H4. AXLINE ROBERT C. WATSON Attesting Oficer Commissioner of Patents

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