US2293693A

US2293693A - Radial pump

Info

Publication number: US2293693A
Application number: US299348A
Authority: US
Inventors: Wylie Hamilton Neil; Groves Walter Robert
Original assignee: AIRCRAFT HYDRAULIC APPLIANCES
Current assignee: AIRCRAFT HYDRAULIC APPLIANCES; AIRCRAFT HYDRAULIC APPLIANCES Ltd
Priority date: 1938-12-21
Filing date: 1939-10-13
Publication date: 1942-08-18
Anticipated expiration: 1959-08-18
Also published as: NL66843C

Description

RADIAL PUMP 3 Sheets-Sheet l Filed Oct. 13, 1939 4 MMG fnA Zw. e www W fHawpw/W a /MA J Aug., 38, 194?.- H.'N. WYLIE ET AL RADIAL PUMP Filed oct. 13, 1939 s sheets-sheet 2 u-g- 18, 1942. H. N. WYLIE ET Ag. 2,293,693

RADIAL PUMP FiledOcL 13, 1959 3 Shees-Sheet 3' [fr ve/yfars Hamilton N. Wylie Walter Grove Patented Aug. 18, 1942 RADIAL PUMP Hamilton Neu Wylie, London, ana walter Robert Groves,'lsleworth, England, assignors to Aircraft Hydraulic Appliances Limited, London,

England Application October 1.3, 1939, Serial No. 299,348 In Great Britain December 21, 1938 2z claims.

This invention relates to radial pumps, and

is concerned with that kind of Dump in which a cylinder assembly with the cylinders radially or substantially' radially directed and having cooperating pistons, rotates in an enclosure relatively to a track ring which by virtue of eccentricity causes the relative reciprocation between the pistons and cylinders. The invention, whilst applicable broadlyA to such pumps whether of variable or fixed stroke, is more fully applicable to the variable kind, in which the eccentricity of the track ring is variable. Where' such pumps are required for heavy duties, by way of high speeds, high pressures, or high'powe'r output, it becomes especially desirable tov provide adequate cooling and lubrication. The problem .of adequate cooling may be especially important in a variable-delivery pump since at low delivery rate, usually corresponding to high pressure, the throughput of the cylinder assembly may be inadequate to take away (by convection) sufficient of the generated heat to avoid undue rise of temperature. It isalso desirable, especially if high speed occurs and the iuid pumped is a liquid of substantial viscosity, to feed the cylinders under positive pressure. It is also frequently desirable to make pumps of the stated kind small, compact, and light, for a given output. Moreover it is necessary to provide bearing arrangements between the reciprocating parts and the track ring which will withstand heavy load and high speed and which will accommodate themselves to the changing angular positions between such parts in the course of running; and which Will be of small mass so that they exert relatively small centrifugal forces on the ring. The design of arrangements is facilitated if these parts of the pump, used to pump a liquid of lubricating nature, are kept flooded by a ow of the liquid. l

The invention further relates to variable delivery pumps in which a cylinder assembly including a, rotatable cylinder block and pistons caused to reciprocate with respect to the cylinders of the block as the assembly is rotated is associated with means for varying the effective stroke and thereby the delivery flow from the cylinder and pistonv assembly, said'cylinder assembly itself serving as an impeller to centrifuge liquid outwardly from inlet means near the axis of rotation and center of casing enclosing the assembly to outlet means -spaced from the said axis and connected to the intake of the rotating cylinder assembly.

'I'he invention seeks to satisfy some or all of 55 these requirements in a practical and efficient way.

The invention further seeks to provide a method of pumping of liquids, in which whilst the merits of pumps of the radial kind above specified are retained, will ensure adequate cooling and lubrication even if the radial pump be subject to heavy, continuous, and maybe fluctuating loads: and by which two separate deliveries at different pressures, may be obtained.

According to. thisinvention a radial pump of the kind stated is combined with a centrifugal impeller which' is rotatable with the radial pump, and which is so connected or combined .therewith for fluid-flow that the output of the impeller is wholly or partly fed into the cylinders of the radial pump, the centrifugal fluid immersing the cylinder assembly in its passage. Preferably the cylinder assembly of the radial pump, comprising cylinders, pistons and rotating bearing arrangements, constitutes the impeller; the invention therefore further comprises a radial pump of the kind stated, in which the cylinder assembly and an enclosure in which it rotates are adapted and arranged to act as a centrifugal pump, the operation or function of the assembly as impeller being independent of its function as a reciprocating pump. According to a further aspect of the invention, the cylinder assembly of a radial pump of the kind stated comprises a cylinder block and pistons of which the radially outer ends are tted with slippers pivotally supported by the pistons and adapted to slide around an inwardly directed circular track or tracks of a track ring, the assembly and track or tracks being within an enclosure of which the internal space is approximately circular, and this enclosure has an inlet nearer its axis and an outlet or diffuser passage nearer its periphery which passage is connected to the inlet side of the radial stage of the pump and especially if the radial pump be variable, is also connected to the source from which the pump as a whole is supplied, in such a manner that, the enclosure being supplied by the source, the cylinder assembly acts as a centrifugal impeller, and some or all of the relatively low pressure output impelled thereby is led to the cylinders (whence it is expelled at relatively high pressure) whilst surplus low-pressure output (if any) is fed back to the source. The working parts of the pump are thus kept flooded, and assuming the pump is Working with lubricating liquid, not only cooled but freely lubricated. 'I'he centrifugal impelling may take place within a space bounded by the track-ring and the latter be adapted to confine the fluid for this purpose.

The invention also embraces certain constructional details, notably in connection with the slippers, which are deemed to be especially suitable for employment in a pump having the broader features above stated, and more epecially when the radial stage is variable. Such subordinate features will be described in greater detail by way of example, and delined in the claims.

The accompanying drawings illustrate an example of the present invention.

Figure 1 is a partly sectional elevation in the axial direction;

Figure 2 is a partly sectional elevation at right angles to Figure 1;

Figure 3 is a detail view in plan, showing a slipper arrangement;

Figure 4 is a partly sectional end elevation of the slipper arrangement;

Figure 5 illustrates, by way of partly sectional and perspective detail view, sectioned through the track ring, a modication related to the form of this ring;

Figure 6 is a sectional view of an alternative construction of slipper, across the running direction;

Figure '1 is a sectional view of the construction of Figure 6 at right angles;

Figure 8 is a sectional view showing, in simplified manner, the rocking support of a slipper; and

Figure 9 illustrates schematically an alternative rocking support.

In Figures 1-4 there is shown a stationary enclosure in the form of a casing I the internal space of which is of roughly circular form. 'I'he internal peripheral wall of the casing supports a block 2 one end of which forms an abutment at 2A for a spring and the other end of which presents a knife-edge at 2B upon which is located and can rock pivotally, a stepped or notched abutment 3A of the circular track ring 3. The ring 3 is of channel section presenting two tracks 3B, 3C, inwardly. Clearance within the casing I permits the track ring to swing or rock about the axis dened by the edge 2B. Between a peripheral abutment 3D on the outside of the ring 3 and the abutment 2A, is a laminated, compression strut spring I, which being bowed and tending to straighten urges the ring 3 to a position of maximum eccentricity. Within the ring 3 is the cylinder assembly; this comprises a block of radial cylinders 5, each having a piston 6, each piston being furnished with a slipper arrangement described later. The cylinder block has a central, axially bored, boss 5A, by which the cylinder assembly is rotatably borne on a stationary spindle 1 which being appropriately bored and ported, constitutes a valve element. The spindle 1 is iixed in the casing I, substantially coaxially with the interior space thereof. The

axis of rotation of the cylinder assembly is consequently the axis of the spindle 1, and it is with relation to this axis that the track ring 3 is variably eccentric. 'I'he boss 5A is axially continued to be connected for drive to a driving shaft 8 which is ba1l-borne in the wall of the casing I and rotates in a gland. A union is provided in casing I such as that indicated at IA, for the supply of liquid to be pumped.

The internal peripheral wall of the casing I, at IB, IC, forms abutments for the ring 3, limiting the swing of the ring, The wall between IB and IC is arcuate upon the axis dened by the sure stage.

edge 2B, so that the ring 3 is guided by the casing wall. The casing I, at ID, has an outlet formed through it which is preferably a radial channel somewhat divergent in the direction of rotation of the pump. This outlet or diffuser passage communicates with the inlet duct 1A of the spindle valve 1, by a duct IE formed in the casing I. A branch from the duct IE, shown at IF. communicates back to the source of liquid through either a lightly spring-loaded valve or a constricted resistance passage, and returns to the source such liquid as cannot be accommodated by the radial cylinders. A relief by-pass with a high-pressure valve 9, permits the output c of the pump to return to source if excessive delivery pressure should arise.

The spindle 1, as well as having the outlet duct 1A, has the deliveryduct 1B, bored axially in it, and this communicates by a union III to the supplied system. The ducts 1A, 1B, open into grooves 1C, 1D, respectively; these grooves open to ports 5B of the cylinders 5, as the cylinder assembly rotates. The grooves 1C, 1D, are separated by lands 1E, 1F of the spindle 1, which lands define the inlet and pressure phases or sides of the pump. The spindle 1 may be angularly settable in the enclosure to adjust the phase deilnition with precision, and in this way the piston-reaction on the ring I may be set in direction and its moment about the axis at 2B determined.

The disposition of the pistons and slippers can be seen especially by reference to Figures 3 and 4. The outer ends of the pistons 6 are transversely slotted, the oor of the slot at 6A, being convexly arced on an axis parallel with the axis of the track ring and which is. for preference, between the floor 6A and the inner end, or head,

of the piston. The slippers are formed like an H, each comprising a pair of spaced pads II, interconnected by a bridge I2 of which the ilat underside rocks on the iloor 3A and which bridge is located in the slot of the piston. On the underside of the pads II are lugs IIA which are transversely bored to receive a slightly nexible wire IIB which passes through a perforation 3B in the piston within the iloor 6A and is strained by the lugs I IA to press the slipper to the piston, alfording a certain slight resilient resistance to the rocking of the slipper. The outer or bear,- ing surfaces of the pads II are ilnished to an arc exactly corresponding to the circular form of the track 3B, 3C, against which they bear outwardly and slide. In the running direction (shown by arrows), the pads` are somewhat longer ahead of the bridge I2 than behind it. 'Ihe recognised principle of Micheli pad bearings is thus introduced. 'The skirts of the cylinders 5 are cut away as required to clear the pads and the bridge.

The. whole cylinder assembly in rotating in the casing I, acts as a centrifugal impeller and as such, forms a iirst-stage low-pressure pump. Its output being in part fed to the cylinders, charges them under low-pressure. The pistons and cylinders then co-act as a second high pres- Swinging of the ring 3 against the spring 4 varies the stroke, and therefore the delivery rate, of the second stage by varying the eccentricity. This variability is controlled by the ilnal output pressure. The dimensions and design are such that, within the operative speed range, there is always a greater throughput in the first stage than the second (the surplus returning to source). When the final delivery is reduced by the effect of rising delivery pressure, for a given speed, the throughput in the first stage `is not quantitatively substantially altered. Hence the workingI parts continue to be flooded, lubricated, and cooled, by a large vthroughput despite the decreased final delivery, and conditions which may give rise to considerable heat generation.

It will be apparent that the cylinder assembly may be rendered more effective as an impeller by the provision of vanes, webs, or the like to increase its eil'lcacy as an impeller.

Referring now to Figure 5, a modification is here shown in which the centrifugal action takes place within an enclosure formed by the track ring. To avoid unnecessary description the cylinder assembly will be assumed to be as before. The outer casing i supports the track ring 59 through a pin between partly-cylindrical bearing surfaces. The pin 5| which is prevented from rotation by a, lug at 5|A, is transversely bored by apassage-way 52, and this registers with a first-stage outlet passage 52A in the casing I and with a diuser passage 52B through the periphery of the ring 59. A divergent diffuser channel 52C conducts outflow through these passages. The sides of the track ring 50 are extended inwardly by lateral annular walls 53 with central openings 53A large enough to clear the rotating parts and spindle of. the pump, allowing for variation of eccentricity-of the ring 50 and to admit uid from the source.

The cylinder assembly (5, 6, etc.) is virtually enclosed within the track ring and its walls, and in rotating therein, produces awhirl of liquid, and a centrifugal radial pressure gradient, the liquid emerging via the

passages

52, 52A, 52B, to which flow the channel 52C conduces. In this one across to the other is a bridge part 64 which i rests against the inside of the peripheral wall 90 on each side of the opening 6|. 'I'he plates 93 and part 64 are held together by dowelpins 65, locked by wires 66 which traverse the bridge part 69. The dowel pins 65 are preferably a free clearance flt in the bridge part 94 and are for retaining rather than to act as substantially loaded parts. A springy wire 6l extends through the piston l5 (as before) and its ends lie in the notches of the lugs 63A, the Wire 91 preferably being slightly strained in assembly. The bridge part 59 bears on the piston 6 rockably on a line contact bearing, in the manner of Figure 8 or 9. It will be noted that the slipper extends fur ther in the forward direction than in the rearward direction referred to the running direction indicated by the arrow.

In Figure 8 a bridge part 80 of a slipper (which in this case is constructed as in Figures 6 and '7) is resiliently attached to the piston 8| by a case it is obviously less desirable that the casy ing should be of approximately circular form.

A potential advantage of the modification' is that the centrifugal pressure of liquid is exerted only on the inside of the track ring: also that the cylinder assembly, being enabled to sweep its enclosure more closely, may be more effective as an impeller.

It will be obvious that the output from `the first or low pressure centrifugal stage may be utilised as a low pressure source for any purpose requiring such a source, and the pump can therefore be regarded in effect as having twoy parallelv outputs, respectively at low and 'high pressure. The great advantage gained by having the working parts of the high pressure stage immersed by the throughput of the first stage independently of the resistance to high pressure delivery, is still obtained, though the lesser advantage of charging the cylinders positively, may y be absent.

In Figures 6 and 7 an alternative construction of slipper is illustrated, whichA may be advantageous in production, and which is again well adapted to use in a relatively high-loaded pump in which the cylinder assembly is immersed and causes whirl of liquid. This form of slipper can be made by cutting and machining from a circular ring of channel section material, with its channel inwards, and -with a periphery which is of the same radius as that of the tracks. From such a ring is cut an arcuate piece of suitable length, and the peripheral wall thereof has 'an opening 6| made in it. Inside the two side walls 62 are tted two plates 63 with notched inwardly projecting lugs 63A formed thereon.

Within the plates 63 again and extending from 75 wire 82. The outer end of the piston 8| is formed with an extending lug 8|A atthe rearward side of the bridge part 80, and with an endwise bearing surface which presents an arcuate sectional ridge at 8|B upon which .the flat underside of the bridge part can rock on a line contact. The ridge formation at v8|B may be arcuate or may be sharply edged. Thebearing surface of the piston meets the foot of the lug 8|A at an obtuse anglejat 83,sf1o locatedv that the edge of the part` 80 (which is 'a'. right angle) may in an extreme angularv position'of' the slipper relative to the piston,liefin', .and belocated f Y by, the angle vat83. f

being wholly dislodged; and't the slipperv against friction and liquid resist-l ance, especially during the suction"'stroke.`

l In lFigure 9 is shown aschematic slipper 90 with a knife-edge at 9|, formed von a bridge part. The edge 9| is engaged in an 'obtuse angled recess .(also identified at foot of aillug 92 and endwise surface '93,'01 a piston 94.A Side plates of the slipper indicated at 95, enable the slipper to-,beresiliently attached to the piston 94 by a wire 96. A slipper such as that indicated in Figure 9 may be machined from a solid sectioned circular ring of suitable material. It will be obvious that the required rocking of the slipper relative to the edge at 9|, on a line contact bearing.

In` each case the openings (such as 3|) or other formation and the cylinders are continued so as to clear each other.

What we claim is:

1. A radial pump of the kind stated comprising a cylinder block having a plurality of radially extending cylinders rotatably mounted on pintle, pistons slidably engaging said cylinders and having their outer ends fitted with slippers pivotally supported by the pistons, a track ring surrounding the cylinder and piston assembly having an inwardlyv directed circular track or tracks against which said slippers slide, a casing enclosing said assembly and track and cooperating therewith to form the side walls of van enclosure in which said assembly rotates and provides Vthe vanes for a centrifugal pump, a fluid inlet for said enclosure adjacent a side wall of said impeller cylinder assembly and an outlet passage adjacent its periphery, which outlet passage is connected for inlet to said pistons of said assempiston 94, takes place on the axis dened by the Should", he wire* 82, fail OI` break, the lug Us. may-.drive 9|) formed by the 1 my. said assembly thereby operating in 'said cssf ing as a centrifugal impeller and piston pump.

` 2. A pump of the kind specified, comprising an enclosure, a cylinder assembly rotatable'therein, means whereby .said assembly is kept immersed in liquid in said enclosure and whereby the liquidis permitted to be centrifugally impelled from said enclos'uieiby rotation of vsaid assembly, a

' l 2,293,693 y y portion-of the. liquidtlow from' said casing to the interior of the cylinders of said assembly track ring presenting atrack or tracks within said enclosure, slipper bearing means comprised in said assembly and operative between parts of said assemblypand said rack or tracks, line contact bearing means supporting said slipper means rockably in said assembly about axes parallel with that ofrotation of said assembly, and means comprising knife-edge bearing means between said casing and said track ring to support the track ring rockably for change of eccentricity.

3. A pump of the kind specified, comprising an enclosure, a cylinder assembly rotatable therein, means whereby said assembly is kept immersed in liquid in said enclosure and whereby the liquid is permitted to be centrifugally impelled from said enclosure by rotation of said assembly, a track ring presenting a track or tracks within said enclosure, slipper bearing means comprised in said assembly and operative between parts of said assembly and said track or tracks, and line-contact bearing means supporting said slipper means rockably in said assembly about axes parallel with that of rotation of said asi sembly.

4. A pump according to claim 3, in which each one of said slipper means is. supported rockably by a piston of said assembly.

5. A pump according to claim 3, in which each one of said slipper means is supported by a piston of said assembly by bearing means including an arcuate surface adapted to roll on a second surface.

6. A pump according to claim 3, in which each one of said slipper means is supported by a piston of said assembly by bearing means including a knife-edge bearing formation.

7. A pump according to claim 3, in which each one of said slipper means is attached to a piston of said assembly by means permitting relative rocking against resilient resistance.

8. A pump according to claim 3, in which each one of said slipper means is attached to a piston of said assembly by a resilient wire passing through the piston and located in the slipper.

9. A radial pump of the kind stated, comprising a plurality of radially positioned cylinder and piston assemblies rotatable in an enclosure within a casing, said cylinder assemblies as a whole being operative as the vanes of a centrifugal impeller in said enclosure, an inlet for supplying fluid to said enclosure to be centrifuged by said cylinder assembly, and an outlet passage for said enclosure through which centrifuged fluid is discharged into said casing, and means to conduct said centrifuged fluid to the inlet side of said assembly acting as a reciprocating pump to supply the same with fluid.

10. A variable delivery pump comprising a piston and cylinder assembly, a casing within which said assembly is rotatable, a track ring cooperating with said assembly, said track ring and said cylinder assembly cooperating with said casing to provide a plurality of chambers, means to direct fluid into said chambers, means for directing iluid centrifuged within said chambers by rotation of said cylinder assembly to within the body of said casing, and means to direct a and direct the balance of said centrifuged iluid to a supply source. i.

11. A variable delivery pump comprising means to deliver a volume of fluid under low pressure to a high pressure delivery means'which is greater than the delivery means can handle, said high pressure delivery means withdrawing a portion of said fluid and discharging same at high pressure, the balance of the low pressure uid beingy assembly rotating within said track ring to operate as a centrifugal pump, means for supplying fluid within said track ring and means for educting fluid under centrifugal pressure to the pistons of the cylinder assembly, means to control the rate of fluid delivery from the cylinder assembly and means to permit continuous flow of fluid through the pump casing by the centrifugal pumping action of the cylinder assembly when no fluid is being delivered by the piston pump, whereby the pump is cooled.

13. A radial pump comprising means to deliver liquid under low pressure, means to withdraw said liquid and discharge same at high pressure, and means to permit the low pressure liquid to flow through the pump casing and discharge therefrom at low pressure to cool the pump when the high pressure pump is operating but not delivering liquid.

14. A variable delivery pump comprising a casing, a cylinder assembly rotatable therein, rotation of said assembly providing a centrifugal pump to place liquid in said casing under low pressure for delivery to the cylinders of said assembly, and means to permit the whole of said low pressure liquid which is forced through the pump casing due to the centrifugal pumping action of the cylinder assembly to continue flow through the pump without passing through said assembly when the same is rotating but not delivering high pressure liquid, whereby thev pump is cooled.

15. A radial pump comprising acasing, a cyl` inder assembly rotatable therein, rotation of said assembly providing a centrifugal pump to place fluid in said casing under low pressure, means for conducting said low pressure fluid to the cylinders of -said assembly, a by-pass in said continuing flow through said by-pass when the pumpA is rotating but not delivering, whereby the pump is cooled.

16. In a variable delivery pump including a casing, a cylinder assembly in said casing and rotatable with respect thereto, uid inlet means for said cylinder assembly, outlet means leading out through the casing from said cylinder assembly, piston means reciprocable within said Aof said cylinder assembly; said cylinder -assembly itself thereby operating to centrifuge the working uid from the inlet means of the casing and through the outlet means in communication with the inlet to said cylinder assembly.

17. The variable delivery pump comprising a` casing, a cylinder assembly rotatable within said casing, a track ring cooperating with said cylinder assembly, means for varying the eccentricity between said cylinder assembly and said track ring -to control the output of said cylinder assembly, wall means cooperating with said track ring to form a pumping chamber within which said cylinder assembly rotates and provides the vanes of a centrifugal pump, inlet means for said pumping chamber, outlet means positioned near the periphery of said pumping chamber for directing uid from said pumping chamber into said casing, an inlet for said cylinder assembly, and means connecting said casing with said inlet.

18. A variable delivery pump comprising a casing, a cylinder assembly rotatable within said casing, a track ring cooperating with said cylinder assembly, the eccentricity between said track ring and said cylinder assembly being variable to control the output of said assembly, said casing and said track ring cooperating to form a pumping chamber within which said cylinder assembly providesthe vanes for a centrifugal pump, inlet means near the center of rotation of said cylinder assembly, outlet means positioned near the periphery of said cylinder assembly, said outlet means communicating with a second chamber provided in the interior of said casing, an inlet for said cylinder.` assembly, and means connecting said second chamber with said inlet.

19. A variable delivery pump comprising a casing, a cylinder assembly rotatable within said casing, a track ring cooperating with said cylinder assembly, the eccentricity between said track ring and said cylinder assembly being variable to control the output of said assembly, wall means cooperating with said track ring for providing a pumping chamber in said casingr within which said cylinder assembly provides the vanes of a centrifugal pump, inlet means near the center of rotation of said cylinderassembly` outlet means positioned near the periphery of said cylinder assembly, said outlet means communicating with a second chamber provided in the interior of said casing, an inlet for sind cylinder assembly, means connecting said second chamber with said inlet, and means in said last mentioned means for by-passing the fluid pumped by the centrifugal action of said cylinder assembly when said cylinder assembly is not delivering high pressure fluid.

20. A variable delivery pump comprising a casing, a cylinderassembly rotatable within said case, Ia track ring cooperating with said cylinder assembly, the eccentricity between said track ring and said cylinder assembly being variable to control the output of said assembly, wall means cooperating with said track ring for providing a pumping chamber in said casing within which said cylinder assembly provides the vanes of a centrifugal pump, inlet means near thecenter of rotation of said cylinder assembly, outlet means positioned near the periphery of said cylinder assembly, said outlet means communioatingwith a second chamber provided in the interior of said casing, an inlet for said cylinder assembly, means connecting said second chamber with said inlet, and means in said last mentioned means for by-passing the fluid pumped by the centrifugaly action of n"said cylinder assembly when said cylinder assembly is in substantially no stroke position.

21. A variable delivery pump comprising a casing, a cylinder assembly rotatable ywithin said casing, a track ring cooperating with said cylinder assembly, the eccentricity between said track ring and said cylinder assembly being variable to control the output of said assembly, said casing and said track ring cooperating to form a pumping chamber within which said cylinder assembly provides the vanes for a centrifugal pump, inlet means near the center of rotation of said cylinder assembly, outlet means positioned near the periphery of said cylinder assembly, said outlet means communicating with a second chamber provided in the interior of said casing, an inlet for said cylinder assembly, means connecting said second chamber with said inlet, said cylinder assembly being capable of pumping a greater volume than can be handled by said cylinder assembly acting as a piston pump, and means in said last means for by-passing excess fluidcentrifugally pumped by said cylinder assembly, said by-pass providing means for bypassing the entire quantity of fluid centrifugally pumped by said cylinder assembly when said assembly is not delivering fluid by means of the piston pumps thereof.

22. A variable delivery pump comprising a casing, a cylinder assembly rotatable within said casing, a track ring cooperating with said cylinder assembly, the eccentricity between said track ring and said cylinder assembly being variable to control the output of said assembly, said casing and said track ring cooperating to form a pumping chamber within which said cylinder assembly provides the vanes for a cenly pumped by said cylinder assembly, said last means including a resistor for restricting the now of fluid by-passed therethrough to establish positive pressure in the means connecting said second chamber with the inlet of said piston assembly,

HAMILTON NEIL WYLIE. WALTER ROBERT GROVES.