US2972952A - Combination main burner and after burner fuel pump - Google Patents

Description

Feb. 28, 1961 J. F. MURRAY 2,972,952

COMBINATION MAIN BURNER AND AFTER BURNER FUEL PUMP Filed May 18, 1955 3 Sheets-Sheet 1 IN VEN TOR.

JOHN F. MURRAY Feb. 28, 1961 J. F. MURRAY 2,972,952

COMBINATION MAIN BURNER AND AFTER BURNER FUEL PUMP Filed May 18, 1955 3 Sheets-Sheet 2 JOHN F. MURRAY ATTORNEYS Feb. 28, 1961 J. F. MURRAY 2,972,952

COMBINATION MAIN BURNER AND AFTER BURNER FUEL PUMP Filed May 18, 1955 3 Sheets-Sheet 3 R ii -8 00 J Q 1 Q 1 a 1 q 0% an O 0 c 9 0 CO /I\ 3\$ a "I B 8 R W 2 a --R U a: 3 8 N N p N m 9 N INVENTOR.

JOHN F. MURRAY ATTORNEYS United States Fatent COMBINATION MAIN BURNER AND AFTER BURNER FUEL PUMP John F. Murray, Macedonia, Ohio, assignor to Thompson Ramo Wooldridge Inc., a corporation of Ohio Filed May 18, 1955, Ser. No. 509,313

10 Claims. (Cl. 103-4) This invention relates generally to pumps and more particularly relates to a combination pump of the type utilized in an aircraft fuel system wherein three separate pumping units are provided, two of the pumping units comprising an after burner pump and a main burner pump discharging to separate points of utilization and the third pump unit constituting a supplemental pump discharging fluid to a transfer device having means formed to parallel selectively the discharge of the third pump with the discharge of the first and second pump units, respectively.

Briefly described, the present invention relates to a pressure-loaded multiple gear pump. A pump casing or housing is provided with a plurality of pumping cavities housing a corresponding plurality of rotary fluid-displacement means. For example, three sets of intersecting bores are provided in the exemplary construction herein described and three separate sets of rotary gears move fluid from an inlet on one side of each respective pumping cavity to an outlet on the other side of each respective pumping cavity. The pump further includes a volute pumping chamber in which is rotated a centrifugal impeller so that fluid at the inlet of the pump may be initially pressurized and supplied to the respective inlets of the gear pumping units, thereby reducing inlet losses.

According to the present invention, the pump incorporates a flow transferring means in the casing of the pump for selectively paralleling pairs of outlets. For example, the three outlets of the gear pumping units comprise threelongitudinally spaced openings selectively controlled by a valve having opposed spaced apart piston control portions each respectively adapted to close one of the end openings of the outlet. Whenever one of the end openings is closed, the other end opening will be in parallel with the middle opening. Thus, one of the pumping units advantageously supplies fuel to the main burners of -a jet engine and the other pumping unit supplies fuel to the after burners of the jet engine, the third pumping unit having its discharge selectively directed in parallel with either the main burner pumping unit or the after burner pumping unit.

The transfer valve embodies a spring which operates as a control spring to bias the valve in one direction, thereby biasing the valve in one direction.

The transfer valve is further provided with a motive surface subjected to fluid at pressures generated by the main burner pumping unit. The force thus generated is applied to the valve in a direction opposite the thrust imparted to the valve by the control spring. Accordingly, when the pump is idle the valve will be biased by the coil spring in one direction to parallel the main burner pumping unit and the supplemental pumping unit. Upon operation of the pump, the pressure acting against the motive surface of the valve will build up to a predetermined value, whereupon the valve will be moved aginst the bias of the spring and the supplemental pump will be placed in parallel with the after burner pumping unit.

If for any reason such as mechanical failure, jamming 2,972,952 Patented Feb. 28, 196i ice or other interferences with pump operation the main burner pumping unit should fail to maintain a predetermined value of pressure against the motive surface, the coil spring will again move the valve so that the discharge of the supplemental pumping unit will be directed to the point of utilization normally served by the main burner pumping unit.

It is an object of the present invention, therefore, to provide a combination main burner and after burner fuel pump having flow-transferring means which are pressure-responsive.

Another object of the present invention is to provide a combination multiple pump unit having flow transfer means which will insure a supply of fluid to separate points of utilization.

Yet another object of the present invention is to provide a transfer valve for a multiple pump which will selectively parallel different pairs of pumping unit outlets in response to variations in a pressure condition.

Many other objects, advantages and additional features of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.

On the drawings:

Figure 1 is an end elevational view of a pump provided in accordance with the principles of the present invention;

Figure 2 is a cross-sectional view taken substantially on line I'III of Figure 1;

Figure 3 is an enlarged fragmentary cross-sectional view illustrating additional details of construction of the flow-transferring means provided in accordance with the principles of the present invention; and

Figure 4 is a diagrammatic plumbing diagram illustrating the paths of fluid flow in connection with a pump provided in accordance with the principles of the present invention.

As shown on the drawings:

The pump of the present invention is indicated generally by the reference numeral 10 and comprises a casing or housing 11 which constitutes a plurality of connected housing parts identified on Figure 2 from left to right by the reference numerals 12, 13, 14, 15 and 16.

The housing part indicated at 15 has a mounting pad 17 from which projects a plurality of threaded studs 18 by means of which the pump may be connected to a con duit for supplying fluid to the pump inlet formed in the housing part 15 and indicated by the reference numeral 19. There is further provided in the housing part 15 a volute pumping chamber 20 in which is rotated a centrifugal impeller 21.

The housing parts 12, 13, 14 and 15 together form three longitudinally spaced pumping cavities for three separate gear pumping units indicated generally by the reference characters A, B and C, respectively.

Before proceeding with the further description of the structural details of the pump 10, reference can be advantageously made to the plumbing diagram of Figure 4 wherein is illustrated the environment in which the pump 10 finds particular utility.

First of all, there is indicated at 22a fuel cell from which fluid is supplied to the inlet 19, initial pressurization of the fluid being effected by the centrifugal impeller 21 in the volute pumping chamber 20. The centrifugal pumping unit discharges through a strainer indicated diagrammatically at 23 to a common inlet supplying each of the gear pumping units A, B and C.

The pumping unit A discharges to a main burner control indicated at 24 and the fuel is supplied to the main burners 26 of an aircraft propulsion engine utilizing jet burners. A by-pass 27 from the main burner control 24 takes excess fuel not required at the burners 26 to a point interstage of the pump 10, namely, a point between the centrifugal impeller 21 and the gear pumping units A, B and C.

Fluid from the gear pumping unit C is supplied to an after burner control 28 which controls the supply of fuel to the burners 29 of the after burner portion of the jet engine. A by-pass 30 carries excess fuel not required by the after burners 29 from the after burner control 28 to a point interstage of the pump 10, namely, a point intermediate the centrifugal impeller 21 and the gear pumping units A, B and C.

The third gear pumping unit B discharges to a flowt'ransferring means indicated generally by the reference numeral 31, the flow-transferring means operable to selectively parallel the discharge of the third pumping unit B with the discharge of the first and second gear pumping units A and C, respectively.

As will be explained in greater detail hereinafter, it will be noted that the flow-transferring means 31 has one end thereof vented as at 32 to discharge pressure from the pumping unit A and the opposite end is vented as at 33 to interstage pressure corresponding to the pressure on the inlet side of the gear pumping units A, B and C.

Each of the gear pumping units A, B and C are substantially identical with respect to structural features, and, accordingly, common reference numerals will be used wherever possible.

Each gear pumping unit comprises a driven gear 34 meshing at an area'of intermesh 36 with a driver gear 37.

Extending axially outwardly from the hub portion of each respective driver and driven gear is a first shaft extension 38 and a second shaft extension 39. Each shaft extension 38 is journaled by a stationary bushing member 40 received in 'a corresponding housing bore and having a flange '41providing a sealing face for engaging and sealing against the adjoining side face of the gear.

Each gear shaft extension 39 is journaled in the casing by a movable pressure-loaded bushing 42 having a flange 43 providing a front face 44 for engaging and sealing against an adjoining gear side face and a rear face 46 which together with means including the housing 11 forms a pressure control chamber 47 communicating with pump-generated discharge pressure to pressure load the movable bushing 42'into'sealingrelationship against the side face of the gear.

The housing part 12 is closed by a cover member 48 assembled in firm assembly to the housing part 12 by a plurality of fasteners 49. A shaft driving member 50 has a splined portion 51 adapted to be connected to a prime mover on the outside of the pump and extends inwardly into thehousing part 12 for connection to the gear pumping units A, B and C. The driving member 50 has acollar portion 52 splined to a quill shaft 53 which extends through hollow portions of the driver gears 37 of the gear pumping units A and B. The quill shaft 53 is in turn splined tothe driver gear of the gear pumping unit C and also to a second quill shaft member 54 which extends through the gear pumping unit C and has attached thereto at one end a gear 56 forming part of a gear train 57 driving the centrifugal impeller 21. Thus, the gears of the gear pumping units A, B and C are rotated at a speed corresponding'to arated efficiency speed for intermeshing gears and the centrifugal impeller 21 is rotated at a much higher speed corresponding to the speed for greatest rated efficiency of centrifugal impellers. The cover member 16 is fastened to the housing part by a plurality of fasteners indicated at 58, thereby enclosing the gear train 57 and closing the end of the pump housing 11. p

The shaft extensions and the hubs of the driver gears 37 are hollow and 'thes'haft extensions38*and-39" as 4 well as the hub portions of the driven gears 34 are also hollow, thereby providing through passages the length of the pump housing 11. Thus, all of the internal cavities such as the cavity 59 in the pump housing 11, which are separated from the actual outlet portions of the pump can be communicated with a source of low pressure such as the pump inlet to facilitate the use of low pressure seals for minimization of leakage and other sealing problems.

Moreover, this arrangernnt affords another advantageous structural and functional feature, according to the principles of the present invention, which permits the flooding and lubrication of a thrust bearing associated with the driving means just described. In reference to this arrangement, it should be noted on Figure 2 that the driving member 50 has a radially outwardly extending annular flange 60 characterized by the provision on one face thereof of a chamfered bearing face 61 engaging a ring of bearing material 62 seated in an annular recess 63 formed in the cover member 48. A coil spring 64 .is located in a recess jointly provided by the driving member 50 and the quill shaft 53 so that one end of the coil spring 64 is bottomed against the driving member 50 and the opposite end is bottomed against the quill shaft 53, thereby maintaining a continuous biasing force between the two parts.

The driving member 50 is provided with an axially extending annular lip 66 and the cover member 48 is provided with an additional recess 67 in which is mounted a sealing assembly 68, the sealing assembly 68 engaging against the lip 66 and effecting an adequate seal between the cover member 48 and the driving member 50. Since the sealing assembly 68 is located outside of the thrust bearing formed by the flange 60 and the bearing ring 61, the thrust bearing can be flooded with the fluid contained within the cavity 59 to insure adequate lubrication and cooling even though the pump is operated at high speeds.

Referring now specifically to Figure 3 in conjunction with Figure 2, it will be noted that each of the pump units A, B and C has a separate outlet portion indicated by the reference numerals 70, 71 and 72, such outlet portions being provided by cored areas or recesses within the housing part 13. It should be particularly noted that these outlet portions 70-, 71 and 72 are in longitudinally spaced relation and are arranged to lie adjacent to and in communication with a tubular bore 73, the outlet portions 70, 71 and 72 constituting annular recesses located radially outwardly of the bore 73.

The flow transfer means 31 is received within the bore 73 and comprises a tubular sleeve 74 abutting at one end against the housing part 14 as at 76 and sealed within the housing part 13 to separate the outlet portions 70, 71 and 72 by a plurality of sealing rings 77.

The tubular sleeve member 74 is particularly characterized by the provision of a central bore 78 communicating in fluid flow relation with the outlet'portion 71 by a plurality of openings 79.

At opposite ends of the sleeve member 74, there is formed a counterbore 80 and 81, respectively, a chamfered shoulder 82 separating the center bore 78 from the counter-bore 80 and a chamfered shoulder 83 separating the center bore 78 from the counterbore 81.

The counterbore 80 has flow communication with the outlet portion 72 by means of a plurality of openings 84 formed in the walls of the counterbore 80 outwardly of the shoulder 82. Likewise, the counterbore81 communicates with the outlet portion 70 by means of a plurality of openings 86 formed in the bore walls of the counterbore 81 outwardly of the shoulder 83.

By virtue of the arrangement thus far described, it will be appreciated that the outlet openings 79, 84 and 86 can be selectively paired by closing either of the'end openings 84 and 86.

'To effect that end, the presentinvention contemplates tl1e provision" of "21 control mechanism-utilizing a valve member indicated generally at 87 and having oppositely disposed longitudinally spaced control portions consisting of a first piston 88 and a second piston 89 spaced apart from one another by a shaft member 90.

The piston 88 comprises a head portion chamfered at its peripheral edge to provide a seating surface 91 engaging the shoulder 83 and a piston skirt 92 extending axially away from the head portion of the piston 88 and engaging the bore Walls of the counterbore 81. When the piston 88 is seated against the shoulder 83, the outlet portion 70 is isolated from the outlet portion 71.

In like manner, the piston 89 has a chamfered peripheral edge forming a seating portion 93 adapted to seat and engage the shoulder 82, the piston 89 further including an axially extending skirt 94 which slidably en'- gages the bore walls of the counterbore 80. When the piston 89 is seated against the shoulder 82, the outlet portion 72 is isolated from the outlet portion 71.

The shaft member 90 has longitudinally spaced shoulders 96 and 97 abutting against the head portions of the pistons 88 and 89 and separated from one another by a spacing dimension greater than the spacing dimension between the outlet openings 84 and 86 so that positioning of the valve 87 with either of the seating portions 91 or 93 engaged against a corresponding shoulder 82 or 83 will pair the outlet opening 79 with one of the outlet openings 84 or 86.

A sealing ring 98 is located between the shaft member 90 and each respective piston 88 and 89 and the pistons are retained in assembly with the shaft member 90 against the corresponding shoulders 96 and 97 by appropriate fastening means indicated at 99.

The housing part 14 has a recess 100 disposed longitudinally adjacent the bore 73 in the housing part 13 to bottom one end of a coil spring 101, the other end of the coil spring 101 being bottomed against the head portion of the piston 89. Thus, a continuous biasing force is exerted against the valve 87 tending to seat the valve seat 93 against the shoulder 82 and paralleing the discharge of the pumping unit B with the discharge of the pumping unit A Whenever the pump 10 is at rest.

In order to facilitate automatic pressure-responsive operation of the valve 87, however, motive means are provided in accordance with the principles of the present invention for effecting automatic operation of the flowtransferring device. First of all there is provided a cylinder member 102 which is received in the bore 73 and sealed therein by a sealing ring 103. The cylinder member 102 has a bore 104 which communicates as at 105 with the pump discharge of the gear pumping unit A, thereby communicating pump-generated fluid pressure to the bore 104 of the cylinder member 102.

Slidably reciprocable within the bore 104 is a piston member 106 attached as at 107 to one end of the valve 87. The piston has formed on one end thereof a motive surface 108 which is subjected to the fluid pressures in the bore 104, thereby to impose a thrust force against the valve 87 tending to move the valve 87 in longitudinal direction against the continuous biasing force exerted by the coil spring 101.

After the pump 10 is started, pump-generated pressure will be communicated to the bore 104 whereupon the build-up of pressure will eventually supply sufficient force to the valve 87 to overcome the continuous biasing force exerted by the coil spring 101. When this occurs, the valve 87 will move to the right as shown in Figure 3 and the piston 88 will close off the outlet opening 86 and parallel the discharge of the gear pumping unit B with the discharge of the gear pumping unit C.

To insure full response of the valve 87 to the pressure forces acting in the cylinder chamber 104, the spaces behind the pistons 88 and 89 are vented to a zone of low pressure previously indicated in connection with an explanation of the plumbing diagram of Figure 4 as the interstage pressure ahead of the gear pumping units 'A, B

and C. Thus, the cavities 110 in the housing part 14 are vented to interstage pressure and the shaft 90 has a passage 111 extending therethrough to vent this low pressure to the area behind the piston 88.

With the arrangement thus described, it will be appreciated that the pumping unit A can be effectively utilized as a main burner pump, while the pumping unit C can be utilized as an after burner pump. Moreover, the third gear pumping unit or pumping unit B functions as a supplemental pump which can be selectively paralleled in response to changes in a pressure condition. Thus, for starting, pumps A and B are in parallel because the valve 87 is normally biased in one direction by the control spring. When a predetermined value of discharge pressure is obtained, the valve moves and pumps B and C are paralleled.

This arrangement has an added safety feature since it insures delivery of fluid to separated points of utilization. For example, if the pump 10 is in full operation and pumps B and C are in parallel discharging to the after burner control 28 and the pump A is discharging to the main burner control 24, then failure of the pump A because of binding or seizure or some other cause of reduction in discharge pressure will reduce the pressure acting on the motive surface 108 of the piston 106 whereupon the valve 87 will be shifted and the discharge from the pump B will be directed to the point of utilization previously served by the pump A. In this manner, the pump B operates as a standby main burner fuel pump.

Although various minor structural modifications might be suggested by those versed in the art, it should be understood and I wish to embody Within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

1. In combination, first and second pumps each discharging to separated points of utilization, a third pump having a flow-transferring means receiving the discharge thereof, said flow-transferring means comprising a sleeve having three longitudinally spaced openings, the end openings communicating separately with the separated points of utilization, the intermediate opening receiving the discharge of the third pump, a valve reciprocably slidable in said tubular sleeve between spaced portions in said sleeve and having longitudinally spaced portions for selectively closing off either of said end openings, thereby to selectively parallel the discharge of the third pump with the discharge of said first and second pumps upon movement of said valve to either of said spaced positions through the intermediate opening and the other of said end openings.

2. In combination, first and second pumps each discharging to separated points of utilization, a third pump having a flow-transferring means receiving the discharge thereof, said flow-transferring means comprising a sleeve having three longitudinally spaced openings, the end openings communicating separately with the separated points of utilization, the intermediate opening receiving the discharge of the third pump, a valve reciprocably slidable in said tubular sleeve between spaced portions in said sleeve and having longitudinally spaced portions for selectively closing 01f either of said end openings, thereby to selectively parallel the discharge of the third pump with the discharge of said first and second pumps upon movement of said valve to either of said spaced positions through the intermediate opening and the other of said end openings, said valve having means providing a motive surface, and means for communicating fluid at pressures generated by said first pump to said motive surface for moving said valve to one of said positions.

3. In combination, first and second pumps each discharging to separated points of utilization, a third pump having a flow-transferring means receiving the discharge thereof, said flow-transferring means comprising a sleeve having three longitudinally spaced openings, the end openings communicating separately with the separated points of utilization, the intermediate opening receiving the discharge of the third pump, a valve reciprocably slidable in said tubular sleeve between spaced portions in said sleeve and having longitudinally spaced portions for selectively closing ofl? either of said end openings, thereby to selectively parallel the discharge of the third pump with the discharge of said first and second pumps upon movement of said valve to either of said spaced positions through the intermediate opening and the other of said end openings, said valve having means providing a motive surface, and means for communicating fluid at pressures generated by said first pump to said motive surface for moving said valve to one of said positions, and a continuous biasing means between said valve and said sleeve normally biasing said valve to the other of said positions wheneverthe pressure on said motive surface is below a predetermined amount.

4. A pump comprising, acasing having three pumping cavities formed therein,'each having an inlet and an outlet, rotary fluid displacement means in each of said cavities for moving fluid from a corresponding inlet to a corresponding outlet, and flow-transferring means in said casing selectively paralleling pairs of said outlets for directing discharge of said pump to two separate points of utilization, said outlets comprising three longitudinally spaced openings, said flow-transferring means comprising a valve member having opposed spaced apart outletcontrolling portions each respectively adapted to close one of the end openings of said outlets, thereby paralleling the middle opening and the other end opening, and a spring between said housing and said valve biasing said valve to move one of said controlling portions toward closing relation with a corresponding end opening.

5. A pump comprising, a casing having three pumping cavities formed therein, each having an inlet and an outa valve member having opposed spaced apart outletcontrolling portions each respectively adapted to close one of the end openings of said outlets, thereby paralleling the middle opening and the other end opening, and a spring between said housing and said valve biasing said valve to move one of said control-ling portions toward closing relation with a corresponding end opening, and motive means for moving said valve in an opposite direction against the bias of said spring to parallel the middle opening with an opposite end opening.

6. A pump comprising, a casing having three pumping cavities formed therein, each having an inlet and an outlet, rotary fluid displacement means in each of said cavities for moving fluid from a corresponding inlet to a corresponding outlet, and flow-transferring means in said casing selectively paralleling pairs of said outlets for directing discharge of said pump to two separate points of utilization, said outlets comprising three longitudinally spaced openings, said flow-transferring means comprising a valve member having opposed spaced apart outlet-controlling portions each respectively adapted to close one of the end openings of said outlets, thereby paralleling the middle opening and the other end opening, and a spring between said housing and said valve biasing said valve to move one of said controlling portions toward closing relation with a corresponding end opening, and motive means for moving said valve in an opposite direction against the bias of said spring to parallel the middle opening with an opposite end opening, said motive means comprising a piston connected to said valve and movable on the axis of said valve to impart a longitudinal thrust thereto.

7. A pump comprising, a casing having three pumping cavities formed therein, each having an inlet and an outlet, rotary fluid displacement means in each of said cavities for moving fluid from a corresponding inlet to a corresponding outlet, and flow-transferring means in said casing selectively paralleling pairs of said outlets for directing discharge of said pump to two separate points of utilization, said outlets comprising three longitudinally spaced openings, said flow-transferring means comprising a valve member having opposed spaced apart outletcontrolling portions each respectively adapted to close one of the end openings of said outlets, thereby paralleling the middle opening and the other end opening, and a spring between said housing and said valve biasing said valve to move one of said controlling portions toward closing relation with a corresponding end opening, motive means for moving said valve in an opposite direction against the bias of said spring to parallel the middle opening with an opposite end opening, said motive means comprising a piston connected -to said valve and movable on the axis of said valve to impart a longitudinal thrust thereto, a rotary shaft connected to said rotary fluid displacement means and projecting out of said casing for connection to a source of power, a flange on said shaft adjoining one wall of said casing on the inside of said casing, a thrust bearing ring carried by said casing engaging said flange and together with said flange forming a thrust bearing, and a sealing assembly between said casing and saidshaft and being located in said casing outside of said flange, said casing having recess portions adjacent said flange vented to the inlet of the pump to flood said thrust bearing with pumping medium for cool-ing and lubricating the thrust bearing.

8. In combination, first and second pumps each discharging to separate points of utilization, a third pump having a flow transferring means receiving the discharge thereof, each of said pumps having a common pump casing formed with separate pumping cavities and said casing having formed therein a tubular bore for said flow transferring means communicating with said pumping cavities, said flow-transferring means further comprising a sleeve insaid tubular bore having three longitudinally spaced openings, the end openings communicating separately with the separated points of utilization, the intermediate opening receiving the discharge of the third pump, a valve reciprocably slidable in said tubular sleeve between spaced portions in said sleeve and having longitudinally spaced portions for selectively closing off either of said end openings, thereby to selectively parallel the discharge of the third pump with the discharge of said first and second pumps upon movement of said valve to either of said spaced positions through the intermediate opening and the other of said end openings.

9. In combination, first and second pumps each discharging to separated points of utilization, a third pump having a flow transferring means receiving the discharge thereof, said flow transferring means comprising a sleeve having three longitudinally spaced openings, the end openings communicating separately with the separated points of utilization, the intermediate opening receiving the discharge of the third pump, a valve reciprocably slidable in said tubular sleeve between spaced portions in said sleeve and having longitudinally spaced portions for selectively closing ofl either of said end openings, thereby to selectively parallel the discharge of the third pump with the discharge of said first and second pumps upon movement of said valve to either of said spaced positions through the intermediate opening and the other end openings, said valve having motive surfaces thereon responsive to pump-generated pressures and operating to automatically position said valve in said sleeve, thereby to parallel thefirst and third pump up to a predetermined value :ofpressure for discharge to one of the separated points of utilization and operating to parallel the second and third pumps above said predetermined value of pressure to discharge to the other of said separated points of utilization.

10. In combination, first and second pumps each discharging to separated points of utilization, a third pump having a flow transferring means receiving the discharge thereof, said flow transferring means comprising a sleeve having three longitudinally spaced openings, the end openings communicating separately with the separated points of utilization, the intermediate opening receiving the discharge of the third pump, a valve reciprocably slidable in said tubular sleeve between spaced portions in said sleeve and having longitudinally spaced portions for selectively closing ofi either of said end openings, thereby to selectively parallel the discharge of the third pump with the discharge of the first and second pumps upon movement of said valve to either of said spaced positions through the intermediate opening in the other of said end openings, said valve having pressure-respon- 10 sive actuating elements for switching the discharge from one of said pumps to the discharge of another of said pumps whenever the discharge pressure of said other of said pumps falls below a predetermined value, thereby to insure flow of fluid to the separated points of utilization.

References Cited in the file of this patent UNITED STATES PATENTS 2,452,253 McGill Oct. 26, 1948 2,490,115 Clarke Dec. 6, 1949 2,506,611 Neal et a1. May 9, 1950 2,554,047 Moon May 22, 1951 2,617,361 Neal Nov. 11, 1952 2,620,733 Overbeke Dec. 9, 1952 2,640,423 Boyer June 2, 1953 I 2,665,637 Lauck Jan. 12, 1954 2,699,724 Murray et a1. Jan. 18, 1955 2,780,172 Coar Feb. 5, 1957 2,823,615 Haberland Feb. 18, 1958

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