US2545506A

US2545506A - Pump

Info

Publication number: US2545506A
Application number: US622918A
Authority: US
Inventors: Raymond A Walsh
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-10-17
Filing date: 1945-10-17
Publication date: 1951-03-20
Anticipated expiration: 1968-03-20

Description

R. A. WALSH March 20, 1951 PUMP 4 Sheets-Sheet 1 Filed Oct. 17, 1945 m ma m WW1 W VA T N T IJUM A we my} March 20, 1951 R, A. WALSH 2,545,506

PUMP

Filed Oct. 17, 1945 4 Sheets-Sheet 2 5 L IQ El ATTORNEY?! March 20, 1951 WALSH 2,545,506

PUMP

Filed Oct. 17, 1945 4 Sheets-Sheet 4 FRESH souQcE 0F JGI POWER ll 63 |4Q-- SLUSH PIT :FI El TO DRILL STEM |o| IGI d8 FRESH WATER SOURCE 20 I6 SOURCE OF %0 POWER /e5 FLL I 7 INVENTOR.

E aymundAWflah :Z Z Z S BY %.1/Mvzrm- ATTOPZVEYJ Patented Mar. 20, 1 951 UNliTEDi STATES PATENT O-FFl-C E1 PUMP v '5 lRaymondtA; 'Walsh, Davenporulowai Application October 17,1945, VSerialNb. 622,918

(Granted under theact of- March ,3,-- 1883,. as

22 Claims;

1 The; invention described :herein may be: manu-- factured and. used' byor;foritheuGovernment. for

amended April 30,1928; 3'70 0. G. 757) governmental purposes, ,without the; paymentto me of any royalty: thereon.

The presentinventionurelates generally to; the art Ofi fiuid' pumping-if More: particularly the invention-relates toua: novel type: of 1 hydraulic. pumping apparatus especiallyiadapted forrthe moving-Yer the creation ofgpressure within ax-liquid :which contains abrasive; materiaLof. such nature; as: to be ordinarily: harmful to those; portions off. the. pumping appa-- ratus withv whichvlit. comes; inzcontact;

Specifically: the. inventionv is disclosed: herein in' its 7 applicationto. apump of::.the=type; generally termedrafslush. pump or a'mudl.pump which is-adaptedato benemployed in the rotary. drilling; of oil:wells.. In theudrillingioftoil wellss. through. the various strata of earth. overlying relatively,v highs pressurev oil: fields such asare apt to: beencountered, for." example;.;ini the: Gulf Coast regions of the United States of America, itlis customary to employ; apparatus known, asna rotary drill rig; This: apparatuscomprises inadditionto the usual'derrick'and power equip: ment adjacent thesurfacerof the. well airOckbitor other suitable: cutting. tool i mounted on", the: lower'end of a-length of hollow tubingknown as the drill rod-:orgdrill stem which is: adapted to: be; rotated-.bypower equipment'at thesurface of the; well. As thecuttingatool cuts; its way into the surface ofithe earth'it'islusualto encounter-relatively high pressure areas: from time to time, thepressure of which generally increasesasthewell increases.- in depthrfor example; it iscommon in some fields to anticipatea'well pressurein an amountapproximatingone-half pound per square inchfor every foot .ofdepth .of the well. In rotary drilling-apparatus this well pressure is balanced F by theweight of a column-of chemicallyweighted liquid which is:continuously iorced' irom the-sure face by a slush pump down throughthe drill stem" to a point adjacent the cutting toolin the bottom of thewell andlthence upwardly; externally of-tthe drill stem but withinan outer length of: tubing generally referred to as the. casing. This drillingg fiuid in addition tocontrolling:the:pressure-- at the bottom of thewell serves :also tolwash the cuttings, sand, and lgritvproduced by the,cutting tool up through the well casing toaslush piton the surface adjacent the top. of the well wherethey may settle out of the drilling-fluid.

The present invention. as aforesaid. concerns:- itself in its specific aspects With a slush pump adapted to beemployed in the handling of abra-- from the annular chamber past the wiper to.

21 sive-containing drilling fluid: in well drilling: systems of the: type. just. described;

past has been the wearing action'of the abrasive fluid upon the working parts of the apparatus,

particularly the pump piston pac'kings. Thaincontaining fluids.

The invention i contemplates; broadly av slush:- pump having a conventional piston packing; therein and further including anauxiliary pump e ing device responsive: to the pressure of fluid within the drill stem of themain pump=cylinderfor delivering a nonabrasive fluid-toa point adjacent' the packing in such a manner thatthe main piston packing is always working" in a bath of 'nonabrasi-ve fluid' and hence is not'sub'ject to fluid' withirr the cylinder.

pump is'always higher ina certainpredetermined ratio than the pressure'of theabrasivefiuidwithin the drill stemor mainpump cylinder:

It is accordingly an important object of the present invention to' provide a slush pump for forcingdrilling fluid throughthe drillstem-of a rotary, well drilling apparatus whereini novel means are providedi'for protecting" the pump;

packing from thewearingacti'on of the abrasivecontainingfiuid within the pump cylinder.

Another object of the invention is to provide novel means in the'form ofa differentialipiston;

type pumpmounted within a slush pumppiston' and responsive to the delivery pressure of" the slush pump for circulating nonabrasive' fluid'atia y higher pressure around the' slush pump piston usual packing in such manner as to define an annular chamber into1which a nonabrasive fluid may be forced at alhigher pressure than that within the mainpump cylinder so thatacontinuous leakage ofnonabrasive fluid may take place In these: systems one 'of the most serious problems inzthew- 3 protect the packing from direct contact with the abrasive fluid within the pump cylinder.

A still further object of the invention resides in a novel method of packing expansible chamber type pumps.

Yet another object of the invention resides in the provision of a difierential piston pump having a valve actuating mechanism comprising a lostmotion device and a snap-action device for positively moving and resiliently retaining the valves in either open or closed position.

Another object of the invention is the provision of an auxiliary pumping source in fluid communication with an apertured pump piston of the type described and including a by-pass valve which may be adjustably and resiliently biased in one direction and which may be biased towards closed position by a device responsive to the delivery pressure of the main pump in such manner that the delivery pressure of the secondary pump is always somewhat higher in a predetermined ratio than the delivery pressure of the main pump.

' Other and further objects of the invention are: to provide a suitably apertured pump piston wherein an auxiliary pumping mechanism may be completely housed; to provide guiding means such as a plurality of axially inclined peripheral grooves on the Wiper element for restricted egress of the nonabrasive fluid to wash the cylinder walls ahead of the piston; to provide in a pump piston a differential piston pump having the motor piston thereof in fluid communication with the working face of the main piston and including a filtering device for protecting said opening; to provide a device for the admission of a secondary fluid to the interior of a pump piston through a conduit formed in the piston rod thereof; and to provide a pump of the type described having a source of secondary fluid integrally formed therewith.

The manner of attainment of the above and other objects of the invention as well as a more complete understanding thereof will become more clearly apparent by reference to the following detailed description taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention, wherein:

Fig. 1 is a longitudinal view in partial cross section of a slush pump embodying the invention, portions of the same being broken away and providing a foreshortened view;

Figs. 2 and 3 are cross sectional views to an enlarged scale of the differential piston pump forming a part of the invention and illustrating the motor piston and valve actuating mechanism in reversed positions, respectively;

Fig. 4 is a general view in front elevation of a complete slush pump assembly according to the invention including the prime mover and auxiliary fluid source;

Fig. 5 is a transverse cross sectional View taken along the line 55 of Fig. 2

Fig. 6 is a schematic view of a preferred form of hydraulic operating circuit of the pump illustrated in Fig. 1;

Fig. 7 is a schematic view similar to Fig. 6 but illustrating a. modified type of hydraulic operating circuit, and

Figure 8 is a fragmentary edge elevation of a portion of the wiper element.

Turning now to the drawings specifically and in detail, Fig. 4 illustrates an over-all assembly view of a horizontal piston, expansible chamber type slush pump of the general type commonly 4 employed in oil field operations and adapted to be used either singly or in various compounding arrangements for forcing drillin fluid down through the drill stem of a rotary drilling apparatus. The pump assembly is ordinarily mounted upon skids such as that designated generally by the reference numeral ID in Fig. 4. A prime mover ll suitably secured to the skid ID as by means of supporting leg l2 and bolts [3 is adapted to be operated in the present case by steam supplied from a source (not shown) to an inlet connection [4 and includes a steam exhaust connection I5. The pump end of the assembly consists of the pump cylinder it having an inlet connection I! and an outlet l8 and includes a piston designated by numeral 23 in Fig. 1 connected by means of a suitable piston rod I9 to the prime mover ll. Suitable supporting means 2| are provided on the pump cylinder l6 and are adapted to be secured to the skids H1 in any suitable manner as by means of the bolts 22.

As illustrated in Fig. 4, the pump end of the assembly also includes a reservoir 23 mounted on the pump cylinder It as by means of supporting members 24 and further includes a sleeve structure 25 mounted in an end wall 26 of the cylinder I6 and having a conduit 2! connected between said sleeve and the reservoir 23. A conventional stop valve 28 is provided in said conduit and is adapted to be operated by means of a handle 29. The piston rod [9 is also provided with an integral exhaust orifice comprising an adjustable choke valve 30. The operation and function of the choke valve 30, the sleeve 25, conduit 21, and reservoir 23 will be hereinafter more fully set forth. Aside from these elements the construction of the pump assembly thus far described is conventional including as it does the usual steam end and liquid end, the internal portions of which operate in conjunction with each other in a manner well understood in the art.

Turnin now particularly to Fig. 1, the pump piston 20 is seen to comprise a main body portion of substantially full cylinder width together with an extension of said main body portion of a reduced diameter generally designated by reference numeral 3|. The piston rod 59 includes an internal cap portion 32 adapted to be secured to the main body portion 20 of the piston as by means of a plurality of bolts 33 held in place by lock washers 34. Suitable inner and outer gasket packings 35 and 35, respectively, are provided between the opposed faces of the cap portion 32 and the piston main body portion 20 to provide a fluid-tight seal therebetween.

Both the main body portion 29 and the reduced diameter portion 3| of the piston are provided with coaxial cylindrical apertures, a larger diameter aperture 31 being provided in the body portion 20 and a smaller diameter aperture 38 being provided in the body extension 3!.

Suitable cylinder liners

39 and 40 of a wear resistant material are provided in the cylinders 3'! and 38 in a conventional manner. A differential piston pump designated generally by the reference numeral M is mounted within the

cylinders

31 and 38 and includes a large diameter portion 42 and a smaller diameter portion 43. Suitable packing means 44 and 45 are provided for the large diameter piston 42 and a similar packing 4B is provided for the smaller diameter piston 43. It will be understood that the

pistons

42 and 43 slidably fit in the

cylinders

31 and 38, respectively, engaging the Walls of the latter in a fluidtight manner and are mounted for joint reciprocation therein. The larger piston 42 constitutes a motor piston or prime mover for imparting motion to the smaller piston 43 which in turn operates as a pump. The details of operation of this portion of the mechanism will be more fully explained below particularly in connection with the description of the operation of the device.

The reduced diameter piston body portion 3| is provided with suitable apertures near its forward end which are connected to the small diameter cylinder 33 and which are adapted to receive a pair of valve assemblies 4'! and 58.

Each of these valve assemblies includes a cage,

portion 42 having a valve 58 mounted therein and adapted to seat against a seat portion 5|.

Suitable springs 52 are provided for urging the' valves 55 into closed position. It will be noted that the valve assemblies 47 and 48 are so mounted with respect to the cylinder 38 that the valve 41 opens inwardly towards the cylinder 38, whereas the valve 48 opens outwardly away from the cylinder 38 thus constituting inlet and exhaust valves, respectively, for the cylinder 38. The inlet valve 4'! is connected to a source of nonabrasive fluid by means of a conduit 53 in the piston body which in turn is connected to a conduit 54 in the piston rod having an inlet orifice 55. The method and apparatus for supplying nonabrasive fluid to the inlet valve 4! will be hereinafter more fully set forth.

Surrounding the reduced piston body portion 3| are a series of packing devices having the general shape of rings and including a backing ring or" felt or other suitable material designated by the reference numeral 55 which is adapted to abut the shoulder 5'! formed at the juncture of the cut away portion 3| and the mainbody portion 28. Seated against the backing piece 56 is a main packing member 58 which may be made of rubber or other suitable packing material and which, as disclosed herein, is provided with an outwardly tapering sealing lip 59 adapted to firmly engage the inner wall of the cylinder I5 in sealing contact therewith. Holding the main packing member 53 in position is a spacer element 88 having a generally angular shape. A wiper element iii of general ring shape, provided with axially inclined peripheral grooves 5i and having a pair of backing plates 62 and 63 on opposite sides thereof, is adapted to be next slid over the reduced portion 5! into abutting engagement with the inner portion of the angular member 88. All of the ring portions thus far described are securely held in place by means of a locking ring 84 which is secured in threaded engagement with the reduced body portion 3!.

The construction of the main packing element 58, the angular spacer 60, and the wiper element BI is such as to provide an annular chamber 55 surrounding the reduced body portion 3!. A suitably cut away portion-68 is provided in the spacer 68 adjacent the exhaust valve 48 which in turn is held in place by an apertured locking member 67 to provide for free discharge of fluid from the cylinder 38 through the valve 48 and into the annular chamber 55. On the other hand the inlet valve 41 is adapted to be secured in place by means of a locking member 58 threadedly engaged with the body portion 3| which is solid and in fluid-tight engagment'with said bod portion, fluid being supplied to the inlet valve 41 through the conduit 53. It will be noted from Fig. 1 that the main pump cylinder inlet and outlet connections I1 and i8 are provided with inlet and outlet valves 69 and I8, re-

spectively. Each of these valves is similar to.

the smaller inlet and outlet valves 4! and 48, re-

spectively, previously described, and includes a.

housing ii, a valve seat 12, a valve 13, and a spring is, urging the valve onto its seat. The valve housings "H in this case are provided with suitable gaskets and flanges 15 adapted to be secured to the apertured bosses it on the cylinder It as by means of bolts 11. I noted that the right-hand end of the cylinder 16 is suitably closed by a gasket and an end wall 18 secured to a flange or ring portion 79 formed on the end of thecylinder l5 by means of a pm rality of bolts 80.

Referring now to the left-hand portion of Fig. 1, which it will be noted is considerably foreshortened by virtue of the broken away portions so that the relative positions of all the parts are not in true perspective, the left-hand end wall 2'5 of the cylinder I5 is secured to. a flange 8| formed on the end of the cylinder l6 by means of a plurality of bolts 82. An aperture or vent 83 is provided in the cylinder It at its-left-hand end for permitting free inlet and discharge of air into the space within the cylinder at the lefthand end of the piston as the latter is reciprocated during pumping operations and also to provide for discharge of any leakage fiuid which would otherwise be trapped in this space. The end Wall 25 is also formed with an inner apertured flange portion 84-. An elongated cylindrical sleeve 85 is provided approximately mid. way between its ends with a radially outwardly extending flange portion 36 adapted to be secured to the flange 84 by means oia plurality of bolts 8?. The sleeve 85 is preferably constructed with an outside diameter approximately equal to the internal diameter of the aperture formed in the end wall 25 so that although there is nothing critical in this relationship a snug fit of the parts is provided. The sleeve 85 is provided with an internal diameter appreciably larger than the external diameter of the piston rod which passes coaxially therethrough as a result of which an annular chamber 88 is provided between the piston rod and the inner walls of the sleeve. The

sleeve 85 is also providedwith annular internal flanges 85 adacent each of its ends and includes suitable packing elements 98 adapted to be compressed between the annular fianges 89 and a threaded gland member 9|. The sleeve member 85is provided adjacent its top portion with an apertured stud 92 constituting a fluid cou pling between the conduit 2'! andthe annular chamber 88. The length of the sleeve 85 is so chosen and proportioned with regard to the reciprocatory length of travel, of the piston 28 and rod [9 that the orifice 55 connected to the conduit 54 within the rod will alwaysbe in open communication with the annular chamber 88 during and within the limits of the'reciprocation of the pump piston 28. The sleeve 85 thus constitutes a device for the admission of fluid from the reservoir 23 throughthe valve 28, conduit 21, annular chamber 88, orifice 55, conduit 54, and conduit 53 to the inlet valve. .311 for the differential piston pump cylinder 38.

Referring now again to Fig. 1 and more particularly to Figs. 2 and 3, which disclose the dif: ferential pump mechanism in detail, the latter will be seen to consist of the larger diameter motor .piston 42 reciprocably mounted in the cylinder 3? and the smaller diameter pump pis- It will likewise be- 7. ton 43 reciprocably mounted in the smaller diameter cylinder 38. The smaller diameter piston 43 is provided with a main packing piece 46 similar to but much smaller than the main packing member 58 of the main pump piston 20. The packing 46 is adapted to be secured over a projecting boss 93 formed as an extension on the end of the smaller piston 43 and to be held in place against a backing member 94 by means of a locking ring 95 threadedly secured over the end of the boss 93. The boss 93 is also internally threaded to receive a threaded stud 96 formed on the end of a -tube 91 which projects from the boss 93 and which is in fluid engagement with a conduit 98 formed in the interior of the iston 43. Referring to Fig. 1 the tube 9? is shown as extending through a packing member 99 and gland I into the inside of a screen or strainer device H'II mounted on the end of the reduced piston portion 3| of the main pump piston as by means of a securing ring I02, and bolts IE3 and Iilt. The construction is such that the tube 91 reciprocates through the packing 99-I9fl in fluid-tight relationship therewith as the differential piston pump is operated, the open end of the tube 9? at all times being within the confines of the strainer screen NH and thus being subject at all times to theworking pressure within the main pump cylinder.

Referring back to Fig. 2, the large diameter portion 42 of the difierential piston pump is preferably formed integrally with the smaller diameter portion 43 and is provided with similar packings 44 and 45 held in place by locking rings I and I06 against resilient backing members I0! and I08, respectively. Two sets of packings are provided on the larger diameter piston 62 for the reason that the latter is double-acting and is required to be sealed against fluid pres sure admitted alternately against its opposite faces. The larger piston 42 is also provided with a boss I09 which is internally threaded to receive a coupling stud H0 formed on the end of a tube III which projects from the boss I99. A packing similar to the packing 99-400 and consisting of a packing element H2 and securing ring H3 is mounted in an aperture formed in the face of the piston rod cap portion s2 and is adapted to seal around the tube I I I in fluid-tight relationship therewith. The tube III is con nected at its inner end to a conduit us formed in the boss I69 and extending into the inner portion of the larger diameter piston 42, and as shown in Figs. 1 and 3, the tube III is open at its outer end and reciprocates within a conduit H5 formed axially of the piston rod I9 and terminating at its outer end at the adjustable choke valve 30.

The piston 42 is provided centrally thereof with a pair of apertures I I6 and l I! in communication with the conduits B8 and H t, respectively. Mounted within the aperture H6 is a valve H8 having two oppositely seating heads I I9 and I29 adapted to alternately seat against the valve seat inserts I2I or I22 which are threadedly secured into opposite sides of the aperture I IS. The valve I I8 is also provided with an elongated valve stem I23 extending at opposite sides of the aperture H6 which is adjustably secured to a pair of contacting rings I25 and I25, respectively. The contacting rings I 24 and I25 are mounted for limited reciprocation with respect to a pair of actuating cages I26 and IE1, respectively, each of which is provided with one or more compression springs I28 adapted to urge the contacting rings i 24 and I25 inwardly towards the aperture I IE or conversely to urge the actuating cages outwardly. The contacting ring I24 is provided with one or more spring-pressed detents I29 (two or" which are shown in the drawings) adapted to seat in one of two annular grooves formed on the outer periphery of the piston 43. The valve portions H9 and I29 are adapted to alternately seat outwardly and thus constitute inlet valves for the admission of pressure fluid from the conduit 98 and aperture I I6 to one side or the other of the piston 52 while simultaneously preventing the admission of pressure fluid to the opposite face of the piston 42. The aperture II'I contains a valve E36 mounted therein having two sealing faces I3I and I32 adapted to alternately seat against valve seat inserts IE3 or 13d. The valve I38 is likewise provided with elongated stem portions I35 and H6 extending from its opposite ends and adapted to be adjustably secured in the contacting rings I24 and I25, respectively. It will be noted that the valve I39 seats inwardly towards the working faces of the piston 42 and thus constitutes an exhaust valve for the discharge of working fluid alternately from one side or the other of the piston 42 whichever is not at the moment connected to receive pressure fluid. The discharge of spent fiuid takes place through the appropriate valve seat insert I33 or E34, the aperture Ill, the conduit HQ, the tube III, the conduit H5 in the main piston rod and finally the adjustable choke valve 39. The structure which been just described constitutes a set of inlet and exhaust valves for the piston 42 and in addition comprises a lost-motion mechanism together with a snap-acting device for positively moving resiliently holding the valves in one of two positions depending upon the position of the piston 32.

The snap-acting device for resiliently maintaining the differential piston pumping valves in one of two positions for admitting fluid to one side or the other of the piston 42 is illustrated to an enlarged scale in Fig. 5. As shown in this figure, the spring-pressed detent I29 is seento consist of a cage member I31 having a ball I36 partially projecting from its open end and a spring l39 pressed between the inside of the cage and the ball.

As previously mentioned, Fig. 6 is a schematic or diagrammatic view of the hydraulic operating circuit for ing a part of the present invention. Actually the representation of Fig. 6 is substantially identical, from the hydraulic standpoint, to that previously described and illustrated in Figs. 1 through 5, although in this case the structural details of the working parts of the mechanism have been substantially altered, the device being shown as broken down into its various separate components which are physically separated in space. The device as previously described and illustrated in Figs. '1 through 5 is of course a preferred embodiment of the invention, both hydraulically and mechanically, although it is contemplated that mechanism such as that illus trated in Fig. 6 could be arranged for satisfactory operation if desired.

Referring now specifically to Fig. 6 certain reference numerals have been applied to some of the parts to indicate similar structure to that previously set forth. The reference numeral II indicates a suitable source of power which may be any type of prime mover but is preferably an expansible chamber steam engine of the type illustrated generally in Fig. 4. This power source is connected through a connectingrod I9 to the piston 25 which operates in the cylinder designated by reference numeral I6. Inlet and outlet valves 69 and 'I!) are provided in the end of the cylinder I6 for controlling the admission and ex haust, respectively, of the working fluid thereto. The inlet valve 69 is connected by means of a conduit I! to a primarysource of abrasive fluid herein indicated schematically as a slush pit and designated by the reference numeral I40. The outlet or exhaust valve I3 is connected to a conduit I8 which as heretofore indicated is adapted to be attached through conventional hydraulic fittings to the drill stem of a rotary well drilling apparatus. The piston rod I9 and piston 24 is provided with a conduit I4I having an external connection on the periphery of the rod I9 designated by reference numeral I42 and opening internally of the piston 23 to the annular chamber 55 formed between the working face of the piston 23 and a wiper element 5| previously described. A flexible conduit I43 is connected to the inlet fitting I42 for supplying nonabrasive fluid thereto as the rod and piston reciprocate within the cylinder under the mechanical actuation of the power source I I.

The differential piston mechanism constituting an auxiliary pumping device for maintaining a supply of nonabrasive fluid adjacent the working face of the main pump piston 20 is illustrated in Fig. 6 as comprising the larger diameter cylinder 3'! having the piston 42 reciprocably mounted therein and a smaller diameter cylinder 38 having the piston 43 similarly mounted therein. Inlet and outlet valves are provided at the lefthand end of the smaller cylinder 38 for'the admission and discharge of nonabrasive fluid to the cylinder 38. The nonabrasive fluid is indicated herein as fresh water supplied from a suitable source such as the reservoir 23 through a conventional stop valve 28 and the conduit I44 to the inlet valve of the auxiliary pump cylinder 38. nected through a conduit condui member I43. It will thus be clear that as the piston 43 is reciprocated in the cylinder 38 fresh water from the source 23 will be drawn through the valve 28, conduit I44, and the inlet valve into the cylinder 38 and be discharged through the exhaust valve, the conduit I45, the

conduit I43, the fitting I42 and the conduit I4I formed in the 'main connecting rod I9 to the annular space 55 adjacent the working face of the main pump piston 24.

Reciprocation of the piston 43 within the cylinder 3-3 is effected by means of the larger diameter piston 42 operating within the cylinder 31,

The outlet valve of the cylinder 38 is con- I45 to the flexible the parts 3? and 42 constituting in effect a double-acting expansible chamber motor for driving the piston 43. Pressure fluid for operating the motor piston 42 is obtained from a conduit I46 leading from the exhaust conduit I8 of the main pump cylinder I6. A filter IIlI is provided in the conduit I45 to prevent abrasive particles of appreciable size from reaching the valving and reciprocating parts of the differential piston motor. Admission of pressure fluid to opposite sides of the piston 42 is controlled by means of a balanced piston or barrel type valve designated generally by reference numeral. I41. Pressure fluid supplied through the conduit I46 to the valve I4? intermediate its sealing portions is adapted to be supplied alternately to one of two conduits, I48 of I43, which are connected to opposite ends of the cylinder 31. That end of the to one of two exhaust conduits I55 or ISI.

cylinder 31 which is not connected through its conduit I48 or I43 to the pressure conduit I45 is adapted to be connected through the valve I 41 The exhaust conduits I50 and I5I are interconnected adjacent their ends and are provided with a fluid discharge line through an adjustable choke valve 33. Actuation of the valve I4? is effected by means of a rod I52 connected to the piston 42 and a rod I53 connected to the valve I41, the rods I52 and H53 being interconnected by a lost-motion device such as'a slot and pin connection designated by the reference numeral I54.

As illustrated in Fig. 6 the piston 42 has just moved to its extreme right-hand position, the rod I52 with its associated pin having contacted the right-hand end of the slot I54 and having moved the valve I41 to its extreme right-hand position by means of the rod I53. Pressure fluid from the conduit I46 is thus being admitted through the central valve body to the conduit I49 and thence to the right-hand portion of the cylinder 31 and is starting to move the piston 42 and consequently the piston 43 to the left. During movement of the piston 43 to the left fresh water which had previously been drawn into the cylinder 38 through the conduit I44 will be forced out through the conduits I45, I43, and I4I to the annular space adjacent the Working face of the main 'pump piston 23. As soon as the piston 42 moves to its extreme left-hand position the slot and pin connection I54 will be operative throughthe rods I52 and I53 to shift the valve I4? to the left, thus closing off the port leading to conduit I49 and opening the port leading to conduit I48 for admission of pressure fluid thereto through the central portion of the valve from the conduit I46. As soon as the limit of movement of piston 42 to the left has been reached the valve I41 will also have been moved suffi-' function of the adjustable choke valve 33 will now be apparent. Since the piston 43 moving in the cylinder 38 is illustrated as single-acting there will be relatively little resistance to move- I ment in the right-hand direction thereof during the intake stroke or while clear fluid is being drawn from the conduit I44 into the cylinder 38. In view of the relatively high pressure being admitted through the conduits I43 and I48 to the left-hand end of the cylinder 3i at'that time there would be a tendency for the piston 42- to snap back very quickly to the right unless suitable meanswere provided for throttling the discharge of fluid within the cylinder 3? on the right-hand side of the piston 42 as it is discharged. The adjustable choke valve 35 is in- I tended to accomplish this function and to prevent a too rapid actuation of the dilferential piston pump on its intake stroke.

In the operation of the schematic circuit illustrated in 'Fig. 6, it will be noted that the pressure face of the piston 42 which is subject to the'p'ressure fluid supplied through conduits I43 and I48 of Fig. 6.

ll principles this total force must be substantially equal to the total force produced by the piston 63 within the cylinder 38, and since further the area of the working face of the piston 43 is appreciably less than that of the piston 42 in square inches, it follows by a simple equation that the unit pressure in pounds :per square inch within the cylinder 38 will be proportionately greater than the unit pressure in pounds per square inch within the cylinder 31. This proportion, subject of course to the usual and calculable differences occasioned by both mechanical and hydraulic friction, will remain substantially constant regardless of the pressure applied to the piston 62 and will be determined solely by the ratio or proportion of the cross sectional areas of the piston 42 and the piston 43. It thus follows that since the working face of the piston 42 is subject to the pressure in the conduit I66, or in effect the delivery pressure within the main pump cylinder I6, that the pressure within the cylinder 38 during the pumping stroke of the piston 63 will always be higher than the pressure within the conduit I66 or the cylinder IS in this same predetermined ratio. The result of this hydraulic arrangement is that the pressure fluid delivered through the conduits I45, I43, and I4! to the annular space 65 will always be somewhat greater than the pressure within the cylinder I6 so that a slight amount of the nonabrasive fluid supplied by the differential piston pump will be permitted to escape past the wiper BI in such manner as to wash the cylinder wall in advance of the main piston 26 to prevent contact of the main piston and its packing members with the abrasive fluid within the cylinder I6. It is contemplated that the pressure diiferential existing between the cylinder I6 and the annular space 65 will be so adjusted by means of the design proportions of the

differential pump pistons

42 and 43 that the leakage of clear fluid past the wiper 6| will in no case be excessive or in such amount as to dilute to any substantial extent the primary working fluid supplied to the cylinder I6.

Referring now specifically to Fig. 7 there is illustrated diagrammatically a modified type of hydraulic operating circuit designed to effect a similar action to thatjust described in connection with the circuit illustrated in Fig. 6. In this case, however, the differential pump mechanism has been omitted and in its place an auxiliary pump, which may be of any well-known type, has been substituted together with a by-pass or relief valve designed to control the delivery pressure of this auxiliary pump. The only requirement of the modified system is that the auxiliary pump be inherently capable of delivering the nonabrasive fluid at a pressure in excess of any operating pressure liable to be encountered or built up by the main pump. It will thus be possible through proper actuation of the by-pass valve to control the output pressure of the auxiliary pump in such manner that at all times it will be proportionately higher than the delivery pressure of the main pump.

In Fig. 7, the prime mover is again designated by the reference numeral I i and is similar to that The slush pit is also designated by reference numeral I46 and the details of the main pump are in all respects similar to those described in connection with Fig. 6 and include a piston rod I9, main piston 2!], cylinder I6, inlet and exhaust conduits I1 and I8 connected to inlet and exhaust valves 66 and I6, respectively, an

annular space 65 formed between the working face of the piston 26 and a Wiper 6|, and a conduit I4! in the piston rod and piston'connected by means of a fitting I42 to a flexible conduit I43. The auxiliary pump is designated by the reference numeral I and is suitably connected in any known manner preferably to a separate motor or other prime mover designated by reference numeral I56. The auxiliary pump I55 receives fluid through an inlet conduit I51 from a suitable source 23 and has its discharge side connected through a discharge conduit [58 to a bY-pass valve generally designated by reference numeral I59. The by-pass or relief valve I59 is provided with an external pressure-tight housing which contains the working parts of the valve and includes a return line I66 leading back to the source 23 and a discharge conduit I6! connected to the flexible conduit I63 leading to the annular space in the main pump piston. A valve I62 is mounted on a valve stem I63 which is slidably mounted in suitable brackets within the valve body. The valve I62 is adapted to seat against a valve seat I6 for variably restricting the flow of fluid through the by-pass conduit I66 in order to control the eflective flow through the discharge conduit I6l. A rocker arm I65 is pivotally mounted within the valve housing and is connected to the valve stem I63 for longitudinal movement therewith. A spring I66 mounted between the opposite end of the rocker arm I65 and an adjusting mechanism I6? is adapted to initially bias the valve 562 with respect to the valve seat I6 3. The upper end of'the valve stem I63 is directly connected to the free end of a Sylphon bellows I68 which has its other end suitably anchored within the valve housing. The inside of the bellows I66 is connected by means of a conduit I46 to the discharge line I8 of the main pump. A suitable strainer or filter mechanism HII is likewise provided in the conduit I46 as in the circuit illustrated in Fig. 6.

In the operation of the hydraulic circuit illustrated in Fig. '7 it will be noted that the bellows I66 is responsive to pressure within the conduits I46 and I6 or, in other words, to the delivery pressure from the main pump cylinder I6. As th pressure within conduit I46 increases it tends to expand the bellows I68 in such manner as to force the valve stem I63 and valve I62 downwardly against the valve seat I64 to restrict the flow of fluid through the by-pass conduit I66. more fluid will thus be available for delivery through the conduits I6I, I43, and I6! to the annular space 65 adjacent the working face of the main pump piston. As pressure within the valve housing I59 increases, it tends to collapse the bellows I66, or in other words to move the valve stem I63 upwardly to lift the valve I62 from its seat I65. This tendency to move the valve up wardly is of course resisted by the pressure within the bellows I66 received through the conduit I46 and hence by suitably adjusting the spring I66 by means of the adjusting mechanism I61 it is possible to provide a biased pressure balance which will tend to maintain within the conduit I6I a delivery pressure which is at all times somewhat in excess of the pressure within the conduit I46. As previously indicated, this effect is obtained by controlling the permissible amount of fluid to be by-passed through the by-pass conduit I66 and hence to retain the excess pressure within the condit IBI it is only necessary for the pump I55 be inherently capable at all times of delivering fluid at such a pressure. This object is not particularly diflicult of attainment since the volume of fluid to.be deliveredby the 13 auxiliary pump I55 will at all times be relatively small in comparison with th volume of fluid to be delivered by the main pump I620. Obviously, various other types of suitable pressure-responsive by-pass valves or pressure-responsive pumping devices may be provided, the specific details illustrated inFig. 7 being purely diagrammatic for purposes of explanation and such other devices being per se well-known in the hydraulic art.

The operation of the device constituting a preferred embodiment of the invention as illustrated in Figs. 1, 2, and 3 is substantially identical in its functional aspects to the operation of the schematic circuit illustrated in Fig. 6. Referring to Fig. 1 it will be noted that the entire differential piston mechanism is mounted within the main pump piston itself. The filter IOI is likewise mounted on the face of the main pump piston where its motion with respect to the abrasive fluid serves to prevent clogging or obturation of the screens and the admission and discharge of pressure fluid for operation of the piston 42 is effected through the packed tubes 91 and I I I which reciprocate with the differential piston structure. The adjustable choke valve 30 as illustrated in Fig. 1 is so located on the piston rod is as to be at all times freely open exteriorly of the pump and may of course be provided with any suit able means for leading away the exhaust fluid vent contact of the main piston packing 58 with the abrasive fluid being pumped, a nonabrasive fluid such as clear water from the reservoir 23 is supplied through the conduit 2'1, sleeve 85,

conduits

54, 53, and the inlet valve 41 to the auxiliary piston pump chamber 38 whence it is discharged through the exhaust valve 48 to the annular space 65. Since as previously explained the discharge pressure of the differential piston pump, or in other words the pressure created within the chamber 38, is always in excess of the pressure within the main cylinder I8 by reason of the design proportions of the differential piston pump working face areas, the annular space 85 will be maintained full of fresh water which is permitted to leak past the Wiper mechanism BI. Preferably the wiper is provided with a series of tangential grooves Or apertures which are axially inclined and which serve to direct the leakage or discharge of clear fluid from the annular space 65 so that it produces a scouring or washing action against the cylinder walls in advance of the piston. The amount of this leakage is at all times accurately controlled by the designof the differential piston pump to the end that relatively little dilution of the drilling fluid within the main pump cylinder will take place.

The operation of the differential piston pump per se is most clearly illustrated in Figs. 2 and 3 of the drawings wherein pump is shown in two opposite positions. As illustrated in Fig. 2, the differential piston 42-43 has just completed a movement to the left and the valve mechanism has been actuated in such manner as to admit pressure fluid to the left-hand face of the piston 42 to initiate movement thereof in a righthand direction. As shown in this figure, the valves I I8 and I30 are in their extreme righthand position wherein the valve H9 is seated against the valve seat I2I and the valve I32 is seated against the valve seat I34. Pressure fluid supplied from the working face of the main pump piston through the tube 91 and the conduit 98 is thus admitted past the valve I20 and the valve seat I22 into the cylinder 3! on the left-hand side of the piston 42 to force the same to the right within the cylinder 31. Since the valves I32 and H9 are closed, no pressure fluid can be admitted to the right-hand face of the piston 42 nor can any of the pressure fluid on the left-hand face of the piston 42 escape through the exhaust conduit I I4 and tube II I. The fluid trapped Within the cylinder 31 on the right-hand face of the piston 42 is, however, free to escape past the valve I3I, valve seat I33, and aperture II'I into the conduit H4 and tube III. This exhaust fluid is eventually discharged as shown in Fig. 1 through the conduit II5 and the adjustable choke 38.

As the differential piston moves to the right, the valves I I8 and I30 are retained in the position which they occupy in Fig. 2 by the engagement of the spring-pressed detent I29 with its associated right-hand groove. As the piston 42 approaches the limit of its right-hand travel during which time a pumping stroke of the piston 43 has taken place within the cylinder 38, the valve actuating cage I28 abuts against the righthand Wall of the cylinder 31 and is gradually compressed against contacting ring I 24 against the action of the compression springs I28. As the motion of the piston 42 towards the right is continued the actuating member I26 eventually comes up solid against the contacting ring I24 or at least sufficiently to disengage the detent I29 from the right-hand groove at which time the springs I28 operate to snap the contact ring I24 to the left so that the detent I29 will then be seated in its associated left-hand groove. At this time the valve parts will be in the positions indicated in Fig. 3 wherein it will be noted that the contacting ring I24 through its connection with the valve stem extensions I23 and I35 has moved the valves H8 and I30 into their extreme left-hand positions so that the valve I20 is now seated against the valve seat I22, the valve II9 is lifted from its seat I2 I, the valve I3I is seated against its valve seat I33, and the valve I32 is lifted from its associated seat I34. This positioning of the parts now provides for the admission of pressure fluid through the conduit 98 and the aperture I I6 past the valve H9 and seat I2I into the right-hand portion of the cylinder 31 to initiate movement of the piston 42 in a left-hand direction. The position of the exhaust valve I30 is likewise such that the pressure fluid now being admitted to the right-hand side of the piston 42 cannot escape through the closed valve I3II33 whereas the spent fluid on the left-hand side of the piston 42 is now free to escape through the exhaust valve I32I34 into the conduit H4 andtube III. The differential piston is thus condi tioned for a return movement to the left during which time the piston 43 performs an intake stroke drawing clear fluid into the pumping chamber 38. I

As previously mentioned violent action or a snapping back of the differential piston in the left-ehand v,directiomdue,to the ,lack of; resistance during; the intakestroke of the piston 43 is prevented by theadjustable choke valve 39' which throttles the fluid being discharged from the left-hand side of the cylinder 31. When the differential piston reaches the left-hand limit of its movement the actuating cage I21 contacts the leftehand end of the cylinder 31 and throughits associatedcontact ring E25, springs H28, and valve stem.,extensions l3fi acts to, unseat thespringpressed detent I29 from its associated left-hand groove and to positively move the same rapidly into seating engagement with its right-hand groove whereupon the valves I I8 and BB" will againbe positioned-as illustrated in Fig. 2 for initiating movement of the piston 52in a righthand direction. The operation of the diflerential piston 42-43 is thus seen to be cyclic in nature wherein the piston 42 operates as a motor under the action of pressure fluid delivered through the conduit 97-58 from the working face of the mainpump piston 28 to reciprocate the piston 43 as a pump within its cylinder'38. It will also be apparent from aconsideration of Figs. 2 and 3 that the relative cross sectional areas of the

pistons

42 and 43 are substantially different as a result' of which the unit pressure in pounds per square inch Within the cylinder-33 will always be maintained at a predetermined higher proportionate pressure than the unit pressure in pounds persquare inch of the working fluid operating against the piston 42 within the cylinder 31. The relative cross sectional areas of these piston faces asgexplainedaboveare so chosen that the design will provide fora predetermined slight amount of leakage of 'nonabrasive fluid past the wiper El where itis ultimately mixed with the abrasive or primary working fluid within the main pump cylinder.

Throughout the specification refeernce has been made to oil wellsand rotary drilling apparatus as well as to fluid pumps. It will be obvious to one skilled in the artthat the principles of the invention may be equally adapted to doubleacting pumps as well as to single-acting pumps of the type disclosed. Likewise the invention will find many other uses and is not limited in its applicability to oil wells or to rotary drilling apparatus but maybe used with other types of drilling apparatus or in the drilling of other types of wells. Similarly, although the nonabrasive fluid has been referred to as clear water, it-will be apparent that various other types of primary and secondary fluids may be substituted for the specific examples disclosed.

It will be further apparent that by the practice of the invention as set forth herein it is possible to protect'the packings and cylinder walls of "abrasive fluid pumps for indefinite periods of timeand that in the event replacement of parts becomes necessary, such parts as the wiper device-or-the relatively small sized differential piston portions :which strain contactwith theabrasive fluid will .be much less expensive to replace.

Numerous other modifications and alterations of the structure'which has been disclosed herein for purposes of illustration will be apparent to one skilled in the. art and it is obvious that the same'may be made without departing from the spirit and scope of the invention as defined in the following claims.

Iclaim:

1. A slush pump for forcing drilling fluid through the drill stem of a rotary well drilling apparatus, comprising a prime mover, a main pump cylinder, a main pump: piston having a piston rod'secured'thereto, means; operatively connecting said prime mover to said rod forreciprocatin the latter, valve. means inthe pressure end of said cylinder for the admission and discharge of drilling fluid thereto, said piston comprisin an apertured central body portion and a. wiper portion defining a substantially closed annular space therebetween, said wiper portion having a plurality of axially inclined peripheral groove providing restricted fluid egress from said annular space, a secondary differential piston type pump mounted Withinthe apertures in said main piston central body portion including, at least two pistons of different diameters, the larger diameter piston constituting a power source for actuating the smaller diameter piston, inlet and outlet valves associated with the aperturecontaining saidrsmaller diameter piston for controlling the admission and discharge of washing fluid thereto, said larger di'! ameter piston including valve means for controlling the admission and discharge of pressure fluid on opposite side thereof, a reservoir mounted on said main pump cylinder adapted to contain washing fluid, conduit means interconnecting said rservoir and said inlet valve, and second conduit means adapted to provide for the-inlet and discharge of pressure fluid to said largerdiameter differential piston valve means, thepressure inlet of said'second conduit means being in fluid communication with the pressure side of said main pump piston whereby the washing fluid within said annular space is maintained at a predetermined substantially constantly proportionate higher pressure than that of the drilling fluid within said main pump cylinder.

2. A slush pump for forcing drilling fluid through the drill stem of a rotary well drilling apparatus, comprising a prime mover, a main pump cylinder, a main pump piston having a piston rod secured thereto, means operatively connecting said prime mover to said rod for reciprocating the latter, valve means in the pressure end of said cylinder for the admission and discharge of drillin fluid thereto, said piston comprising an apertured body portion, first means forming an annular space therein and second means providing restricted fluid egress from said annular space, a secondary differential piston type pump mounted within the apertures in said main piston body portion includin at least two pistons of different diameters, the larger diameter piston constituting a power source for actuating the smaller diameter piston, inlet and outlet valves associated with the aperture containing said smaller diameter piston for controlling the admission and discharge of washing fluid thereto, said larger diameter piston including valve means forcontrolling the admission and discharge of pressure fluid on opposite sides thereof, a reservoir mounted on said main pump cylinder adapted to contain washing fluid, conduit means interconnectin said reservoir and said inlet valve, and second conduit means adapted to provide for the inlet and discharge of pressure fluid to said larger diameter diiler ential piston valve means, the pressure inlet of said second conduit means being in fluid'communication with the pressure side of said main pump piston whereby the washing fluid within said annular space is maintained at a predetermined substantially constantly proportionate higher pressure than that of the drillin fluid within said main pump cylinder.

3. A slush pump for forcing drilling fluid through the drill stem of a rotary well drilling apparatus, comprising a main pump cylinder, a main pump piston having a piston rod secured thereto, valve means in the pressure end of said cylinder for the admission and discharge of drilling fluid thereto, said piston comprising an apertured central body portion and a wiper portion defining a substantially closed annular space therebetween, said wiper portion having a plurality of axially inclined peripheral grooves providing restricted fluid egress from said annular space, a secondary differential piston type pump mounted within the apertures in said main piston charge of pressure fluid on opposite sides thereof,

a reservoir mounted on said main pump cylinder adapted to contain washing fluid, conduit means interconnecting said reservoir and said inlet valve, and second conduit means adapted to fluid to said larger diameter differential piston valve means, the pressure inlet of said second conduit means being in fluid communication with the pressure side of said main pump piston space is maintained at a predetermined substantially constantly proportionate higher pressure than that of the drilling fluid within said main pump cylinder.

provide for the inlet and discharge of pressure 4. A pump comprising a prime mover, a main pump cylinder, a main pump piston having a piston rod secured thereto, means operatively connecting said prime mover to said rod for reciprocating the latter, valve means in the pressure end of said cylinder for the admission and discharge of drilling'fluid thereto, said'piston comprising an apertured central body portion and a wiper portion defining a substantially closed annular space therebetween, said wiper portion having a plurality of axially inclined peripheral grooves providing restricted fluid egress from said annular space, a secondary differential piston type pump mounted within the apertures in said main piston central body ferent diameters, the larger diameter piston constituting a power source for actuating the smaller diameter piston, inlet and outlet valves associated with the aperture containing said smaller diaportion including at least two pistons of difmeter piston for controlling the admission and discharge of washing fluid thereto, said larger diameter piston including valve means for controlling the admission and discharge of pressure fluid on opposite sides thereof, a reservoir mounted on said main pump cylinder adapted to.

contain washing fluid, conduit means interconnecting said reservoir and said inlet valve, and second conduit means adapted to provide for the inlet and discharge of pressure fluid to said larger diameter differential piston valve means, the pressure inlet of said second conduit means being in fluid communication with the pressure side of said main pump piston whereby the washing fluid within said annular space is maintained at 35- whereby the washing fluid within said annular a predetermined substantially constantly prop'ortionate higher pressure than that of the fluid Within said main pump cylinder.

5. A pump of the expansible chamber type comprising a main cylinder, inlet and outlet valves for controlling admission and exhaust of primary working fluid to said main cylinder, and a main piston, said main piston comprising a main body portion having a plurality of apertures of differentdiameterstherein and a rod portion having a conduit therein, a secondary differential piston type pump mounted in the apertures in said main body portion and including at least two pistons of diflerent diameters, the larger diameter piston constituting a power source for actuating the smaller diameter piston, a first tube projecing from said smaller diameter piston in fluid-tight relationship therewith and with its associatd aperture and constituting a fluid connection between the larger diameter piston and the pressure face of said main piston, a strainer mounted on the pressure face of said main piston and enclosing the open end of said first tube, a

second tube projecting from said larger diameter piston into the conduit in said rod portion in fluid-tight relationship therewith and with its associated aperture and constituting a fluid connection between the larger diameter piston and said conduit, inlet and outlet valves associated with the aperture containing said smaller diameter piston, a source of washing fluid, means connecting said source to said lastmentioned inlet valve, and means operatively associated with said last mentioned outlet valve for providing restricted egress of washing fluid to the pressure face of said main piston, the entire assembly being constructed and arranged whereby in operation the washing fluid will be constantly delivered to the pressure face of said main piston at a proportionately higher pressure than that of said primary working fluid.

6. A pump of the expansible chamber type comprising a main cylinder, inlet and outlet valves for controlling admission and exhaust of primary working fluid to said main cylinder, and a main piston, said main piston comprising a main .body portion having a plurality of apertures of different diameters therein and a rod portion having a conduit therein, a secondary differential piston type pump mounted in the apertures in said main body portion and including at least two pistons of different diameters, the larger diameter piston constituting a power source for actuating the smaller diameter piston, a first tube projecting from said smaller diameter piston in fluid-tight relationship therewithv and with its associated aperture and constituting a fluid connection between the larger diameter piston and the pressure face of said main piston, a second tube projecting from said larger diameter piston into the conduit in said rod portion in fluid-tight relationship therewith and with its associated aperture and constituting a fluid connection between the larger diameter piston and said conduit, inlet and outlet valves associated with the aperture containing said smaller diameter piston, a source of washing fluid, means connecting said source to said last mentioned inlet valve, and means operatively associated with said last mentioned outlet valve for providing restricted egress of washing fluid to the pressure face of said main piston, the entire assembly being constructed and arranged whereby in operation the washing fluid will be constantly delivered to the pressure face of said main piston at a 19 proportionately higher pressure than that of said primary working fluid.

7. A pump of the 'expansible chamber type comprising a main cylinder, inlet and outlet valves for controlling admission and exhaust of *primary working fluid to said main cylinder, and a main piston, said main piston comprising a main body portion having a plurality of apertures of diiierent diameters therein and a rod portion having a conduit therein, a secondary difierential piston type pump mounted in the apertures in said main body portion and including at least two pistons of different diameters, the larger diameter piston constituting a power source for actuating the smaller diameter piston, means constituting a fluid connection between "the larger diameter piston and the pressure face jof said main piston, means constituting 'a fluid "connection between the larger diameter piston and said conduit, inlet and outlet valves associated with the aperture containing said smaller diameter piston, a source of washing fluid, means connecting said source to said lastmentioned inlet valve, and means operatively associated withsaid last mentioned outlet valve for providing restricted egress of washing fluid to the pressureface'of said main piston, the entire assembly being constructed and arranged whereby in operation the washing fluid will be constantly delivered to the'pressure face or said main piston at aproportionately higher pressure than that of said primary working fluid.

8. A pump of the expansible chamber type comprising a main cylinder, inlet and outlet valvesfor controlling admission and exhaust of primary working fluid to said main cylinder, and a main -piston,said main piston comprising a main 'bodyportion having a plurality of apertures at different diameters therein and a rod portion, a secondary "difierential -piston type pump-mounted'i-n the apertures in said main body portion andincluding at least twopistons of different diameters, the larger diameter-piston constituting a power source for actuating the smaller diameter -piston, inletand outlet valves associated with the aperture containing said "smaller diameter piston,a source of washing fluid, means connecting-said source to said last mentioned inlet valve, and means operatively asso- "ciated with said lastmentiohed outlet 'valve for providing egress of washing fluid to the pressure face of said main piston, the entire assembly "being constructed and arranged whereby' i'n' operf'ation the washing fluid will beconstantly delivered to the pressure faceof said main piston ata proportionately higher p'ressure than that of'said primary working fluid.

'9. In a pump of the expansible chamber type, a main piston having a plurality of apertures of different diameters therein, a secondary difierential piston type pump mounted in said ap'ertures and including at least two pistons of 'difierent diameters, the larger diameter piston constituting a power source for actuating the-smaller I diameter piston, a source of washing fluid, valved means for admiting such fluid'to the smaller diameter aperture, valved means for providing egress of washing fluid from said smaller diameter aperture to the pressure face of said main "piston, and means for subjectingsaid larger diameter piston to such operating pressures thatpr'essures developed by said smaller diameter piston "will exceed pressures in the expans'ible pum chamber whereby in opera ion the washingfluid will be constantly delivered to the pressure face 20 of said main piston at a proportionately higher pressure than that of said primary working fluid.

10. In combination with a pump of the expansible chamber type comprising a main' pump cylinder and a main piston therein, a source "of washing fluid, means for providing egress of washing fluid around the outer peripher of said main piston, and a secondary differential piston type pum- 'including at least two pistons having different working face pressure areas, the larger piston constituting a-power'source for actua ing the smaller piston, said secondary pump being interconnected between said source and said ress means and said larger =pistonbeing respon "sive to the working pressure within said -main pump cylinder, the relative areas of said ;mai-n piston, saidlarger pistonand said'smaller piston being such that pressures developed by said smaller piston will exceed pressures developed-by said main piston whereby-in operation thewashing fluid will beconstantly delivered to the pressure face ofsaidmain-piston at a pressurewhich issubstantiallyalwayshigher in a predetermined uniform proportion than the pre'ssurewithin said main pump cylinder.

11. In combination with a 'pump of the expansible'chamber type comprising a mainrpuinp cylinder and a main piston therein,-a-source'-of washing fluid, means for providing egress of Washing fluid around the circumferential *periphery of :said .main piston, and means comprisinga piston responsive'to the deliverypressur'e'of said main pump piston-hydraulically interposed between said source and said egress means and constructedandiarranged whereby in operation the washing fluid will be constantly delivered to said main piston'at a 4 pressure which is "higher in a predetermined substantiall uniform proportion than the delivery pressure of said main pump piston.

'12. In a pump ada-p'edto createpressureinan abrasive-containing fluid and comprising a main pump piston fand cylinder, 'p'acking means providing a movable seal bet'weensaid piston and cylinder, and means comprising a piston carried bysaid-pum'pand responsive tdthe pressure of said abrasive-containing "fluid for deliveringa secondary, nonabrasiveflu'id' adjacent said packingat a proportionately higher pr'essure than that of said abrasive-containing -fluid whereby to substandally prevent contact of said packing with said *abrasive containing fluid.

-13. Ina 'pu'mp 'adaptedto'create pressurein a pri'rnary flui'd and comprising a main pump piston and cylinderfl packing means providing a movable "seal between said piston "and cylinder, and means comprising 'a pistoncarrie'd by said pump and responsive to 'the pressure of said primary fluid for delivering a s'econdary fluid adjacent "said packing at a proportionately higher pressure than that of said primary fluid whereby to substantially prevent contact -of said packing with said primary fluid.

14.'Apparatus for 'moving an abrasive-contaming fluid comprising, a pressure enerating "device including a portion in contact with said fluid, packing means" for said-portion; and means comprising a piston carried -b said"deviceand '-:responsive do the pressure 'of sa id fluid for cl'eliver'ing a secondary 'n'onab-rasive fluid adjacent "said "packing at a proportionately higher pressure *thanthat of said abrasive containing fiuid "whereby to subrsta'ritially 'prevent-contact of said packing with"said abrasive containing fluid.

15. Apparatus for moving a primary fluid comprising, a pressure generating" device including .a,-portion in contact with said primary fluid,

packing means for said portion, and means comprising a piston carried by said device and responsive to the pressure of said primary fluid for delivering a secondary fluid adjacent said packing at a. proportionately higher pressure than that of said primary fluid whereby to substantially prevent contact of said packing with said primary fluid.

16. A slush pump for supplying drilling fluid to the drill stem of a rotary well drilling apparatus comprising a prime mover, a main pump cylinder, a main pump piston having a piston rod secured thereto, said piston including a packing and means forming an annular chamber adjacent to said packing and said rod including a conduit connected to said chamber at one end and having its other end open exteriorly of said cylinder, means operatively connecting said prime mover to said piston rod for reciprocating the latter, valve means in the pressure end of said cylinder for the admission and discharge of drilling fluid thereto, an auxiliary prime mover, an auxiliary pump adapted to be driven by said auxiliary prime mover and capable, relative to said main pump, of delivering a smaller volume of fluid at a higher pressure, a source of washing fluid connected to the inlet of said auxiliary pump, conduit means connecting the outlet of said auxiliary pump to the open end of said first mentioned conduit and including by-pass valve means therein having a return line to said source, resilient means for adjustably biasing said by-pass valve, and means responsive to the delivery pressure of said main pump for biasing said by-pass valve towards closed position whereby to maintain the pressure of washing fluid delivered to said chamber at a proportionately higher pressure than the delivery pressure of said main pump.

17. A slush pump for supplying drilling fluid to the drill stem of a rotary well drilling apparatus comprising, a main pump cylinder, a main pump piston having a piston rod secured thereto, said piston including a packing and means forming an annular chamber adjacent to said packing and said rod including a conduit connected to said chamber at one end and having its other end open, an auxiliary pump capable, relative to said main pump, of delivering a smaller volume of fluid at a higher pressure, a source of washing fluid connected to the inlet of said auxiliary pump, conduit means connecting the outlet of said auxiliary pump to the open end of said first mentioned conduit and including by-pass valve means therein having a return line to said source, re-

silient means for adjustably biasing said by-pass valve, and means responsive to the delivery pressure of said main pump for biasing said by-pass valve towards closed position whereby to maintain the pressure of washing fluid delivered to said chamber at a proportionately higher pressure than the delivery pressure of said main pump.

18. A pump of the expansible chamber type comprising a main cylinder, inlet and outlet valves for controlling admission and exhaust of primary working fluid to said main cylinder, and a main piston having a piston rod secured thereto, said piston including a packing and means forming an annular chamber adjacent to said packing and said rod including a conduit connected to said chamber at one end and having its other end open exteriorly of said cylinder, an auxiliary prime mover, an auxiliary pump adapted to be driven by said auxiliary prime mover and capable, relative to' said r'nainpump, 'of delivering a smaller volume of fluid at a higher pressure, a source of washing fluid connected to-the inlet of said auxiliary pump, conduit means connecting the outlet of said auxiliary pump to the open end of said first mentioned conduit and including by-pass valve means therein having a return line to said source, resilient means for adjustably biasing said by-pass valve, and. means responsive to the delivery pressure of said main pump for biasing said by-pass valve towards closed position whereby to maintain the pressure of washing fluid delivered to said chamber at a proportionately higher pressure than the delivery pressure of said main pump.

19. A pump of the expansible chamber type comprising a main piston including packing means and means forming an annular chamber adjacent to said packing means, conduit means connected to said chamber at one end and having its other end open, an auxiliary pumpcapable, relative to said main pump, of delivering a smaller volume of fluid at a higher pressure, a source of washing fluid connected to the inlet of said auxiliary pump, conduit means connecting the outlet of said auxiliary pump to the open end of said first mentioned conduit and including by-pass valve means therein having a return line to said source, resilient means for adjustably biasing said by-pass valve, and means responsive to the delivery pressure of said main pump for biasing said by-pass valve towards closed position whereby to maintain the pressure of washing fluid delivered to said chamber at a proportionately higher pressure than the delivery pressure of said main pump.

20. In a pump of the expansible chamber type, a piston, packing means for said piston, means forming an annular chamber adjacent to said packing means, first conduit means connected to said chamber at one end and having its other end open, auxiliary pressure generating means capable, relative to said pump, of delivering a smaller volume of fluid at a higher pressure, second conduit means connecting the outlet of said auxiliary pressure generating means to the open end of said first mentioned conduit and including by-pass valve means therein, first means for biasing said by-pass valve, and second means responsive to the delivery pressure of said pump for biasing said by-pass valve towards closed position whereby to maintain the pressure of fluid delivered to said chamber at a proportionately higher pressure than the delivery pressure of said pump.

21. In a pump of the expansible chamber type, a piston, packing means for said piston, means forming a chamber adjacent to said packing means, first conduit means adapted to be connected to said chamber at one end, auxiliary pressure generating means capable, relative to said pump, of delivering fluid to said chamber at a higher pressure, second conduit means adapted to connect the outlet of said auxiliary pressure generating means to the other end of said first mentioned conduit and including bypass valve means therein, and means responsive to the delivery pressure of said pump for biasing said by-pass valve towards closed position whereby to maintain the pressure of fluid delivered to said chamber at a proportionately higher pressure than the delivery pressure of said pump.

22. In a pump of the expansible chambr type, a piston, packing means for said piston, means forming a chamber adjacent; to, said packing means, auxiliary pressure generating means capable, relative to said pump, of delivering fluid to. said chamber at a higher pressure, by-pass valve means operatively associated. with said auxiliary pressure generating means, and means responsive vtoizhe delivery pressure of said pump for biasing said lay-pass valve towards closed position whereby to maintain the pressure of fluid delivered to said chamber at a proportionately higher pressure than the, delivery pressure of said pump.

RAYMOND A. WALSH.

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

UNITED STATES PATENTS Number Name Date 547,538 Cofiey Oct. 8, 1895 1,529,918 Richards. Mar. 17,1925 1,550,933, Trippleiaorn Aug. 25, 1925 1,647,425 Wise Nov. 1,1927 1,774,967 Ellis Sept. 2, 1930 1,792,641) Leonard .Feb. 17, 193i 1,818,;87 Bailey Aug; 11, 1931 2,367,185 Cary Jan. 16, 1%5