US2429011A - Pump - Google Patents

Description

Oct. 14, H. N. WYLE PUIIP Filed Aug. 2, 1944 4 SheetsSheet 1 Oct. 14, 1947' H.IN. WYLIE v 5 PUMP Filed Aug. 2, 1944 4 sheets-sheet s 44 v Q 0 J5 J5 J7 C) M Q E J /5 /8 O 42 5 /4 40 4/ A5 56 Z O 0 f7 J /9 r O f yefl/ ki i 12mm 21 Aw Hi)? H. N. WYLIE Oct. 14, 1947.

PUMP

Filed Aug. 2, 1944 4 Sheets-Sheet 4- Ja e/ 7 A MM W 1 Patented Oct. 14, 1947 Hamilton Neil Wylie, London,

England, assignor toAircraft Hydraulic Appliances Limited, London, England Application August 2,

In Great Britain 14 Claims. (Cl. 103-461) There is a known type of pump which comprises a cylinder assembly mounted to be driven for rotation on a valve shaft having lands to define an inlet leading to the cylinders and an outlet from them, the cylinders being directed radially or substantially radially, and pistons in the cylinders which are constrained to reciprocate therein by a track ring, usually of circular form. The track ring is movable between various positions in which it is eccentric with reference to the aXis of rotation of the cylinder assembly, or between concentric and eccentric positions, so that the stroke of the pistons, and consequently the rate of delivery of the pump for given running speeds, is variable. The track ring is loaded towards an eccentric position by controlling means in opposition to which fluid pressure produced in the cylinder assembly in operation of the pump against pressure actsto reduce eccentricity of the track ring, thereby reducingv the effective stroke of the pistons, and correspondingly the output.

In United States Patent 2,293,692 there was disclosed an extremely important improvement in such pumps of that general type above stated, the improvement residing in the feature that the track ring was urged towards its position of maximum eccentricity by resilient means (e. g., a spring), and the pump reaction, which is of course the total reaction of the pistons on the track ring, due to the internal pressure built-up in the pump when it is acting against pressure at the pump outlet-as fully explained in the aforesaid specification No. 2,293,692-was made effective to urge the track ring towards its position of minimum eccentricity in opposition to the resilient means. The arrangement was such that not the total reaction force but only a component of the total reaction force operated in opposition to the resilient means loading the track ring to its position of maximum eccentricity.

It is to the general type of pump first hereinbefore described, but modified in such a way that only a component of the total reaction force operates in opposition to the resilient means loading the track ring to its position of maximum eccentricity, that the present invention essentially relates, and for convenience in the following description such a pump is designated a pump of the type hereinbefore specified.

It has been found that when the track ring is mounted to be movable by rocking, the said critical pressure is effected by the viscosity of the fluid dealt with by the pump, and this has been found to be caused by the viscous drag between 1944, Serial No. 547,750

1 as described in the prior ferred that each piston August 10, 1943 the rotating cylinder assembly and the ring ap- I plying a rocking force to the track ring in opposition to the component of the total reaction force, which, in conjunction with the resilient means, determine the said critical pressure.

The objectof the present invention is to provide structural means supporting the track ring which oppose forces tending to rotate or rock the ring while giving it freedom to move to change its eccentricity.

In preferred embodiments of the invention, the pump rotor (that is to say the rotating cylinderand-piston assembly) rotating in the pump casing acts as an impeller to centrifuge working fluid delivered to the interior of the pump from an inlet relatively near the axis of rotation of the rotor to an outlet relatively remote from the axis, from which outlet of the centrifuge stage a branch communicates with the inlet to the cylinder assembly, through which working fluid is delivered to the cylinders at an initially boosted pressure.

United States specification 2,293,693; the centrifuge. stage being also utilised (as described therein, to discharge through an outlet branch) to circulate fluid through an external cooling circuit.

In regard to the bearing means which operate between the pistons and the track ring, it is preshall have a slipper-bearing surface rockably supported by or pivotally connected to the piston for slidable cooperation with the track ring to operate on the principle of Michell pad bearings.

It is to be appreciated that although the slipper bearings are preferred, other suitable bearings may be provided. Likewise it follows that, although in the preferred embodiments the pump operates with a centrifuge stage, there may be cases in which the centrifuge stage is unnecessary.

Referring to the drawings- Figure 1 is a side elevation of a pump according to the invention looking coaxially and showing the inlet and outlet ports;

Figure 2 is a section on ure 1; while Figure 3 is a section on the line III-I1I of Figure 2; and

Figure 4 is a sectional view illustrating a modification.

Referring now to the accompanying diagrammatic drawings, of which Figure 3 is possibly the most important from the point of view of illustrating the invention, the pump casing is represented by the reference numeral N. The track the line 11- of Figring is of circular form and is represented by the reference numeral l I. The valve shaft I2 is suit-l ably borne in the casing and embodies the-inlet or suction duct l3 and the outlet or pressure duct I4. The valve lands l5 and f6 serve to define .ports ll and IB. The rotor assembly is constitutcd by a central rotor body part, represented generally by the reference numeral IS, in which radial cylinders 20 are formed. The rotor body incorporates a hubportion 2| at one end, which is drivably connected with the splined drive coupling 22 suitably borne for rotation in the casing. A piston 23 operates in each cylinder 20 and mounts at its outer end the slipper-:bearing member 24, which conveniently can be pivotally connected to the piston by the wrist-pin 25. The bearing slippers 24 operate as Michell pad bearings, so that they virtually run on a fiim of oil interposed between the outer bearing surface of the slippers and the inner periphery of the track ring H. The stroke of the pistons 23 in the cyl inders 20 of course depends on the eccentricity of the track ring, so that when the track ring is disposed concentrically the pistons have no stroke; but when the track ring is eccentric in relation to the valve shaft, the cylinders as they pass the stationary port I I take in fluid as their volume increases, assuming clockwise rotation of the rotor; and as the volume is reduced again, due to the rotor eccentricity, the cylinders discharge the fluid they have taken in on the suction stroke into the port [8, from which it passes away to the outlet through the outlet or pressure duct M.

In regard to the-manner in which working fluid is delivered to and from the valve shaft, the inlet to the pump is seen at 26 in Figure 1. The inlet feeds into the interior of the pump within the track ring. In normal rotation the rotor centrifuges liquid through the slot 21 of the track ring into the centrifuge chamber 28, from which the duct 29 runs inward to duct 13 and inlet port I1 and into the cylinders, from which it is forced by the pistons 23 into the outlet port l8, and

thence into the high-pressure system. Any instantaneous excess pressure seeps past relief valve 3|, through holes 32A and 32B into the centrifuge outlet 32.

The centrifuge stage is preferably capable of delivering more fluid than is required to supply the cylinders, and the excess escapes through bore 13A and holes 32A and 32B and out through the centrifuge connection 32, and thus forms a cooling circuit.

The track ring I l is loaded to its fully-eccentric position, as shown in Figure 3, by the control force exerted by the spring 33 when the total reaction force (represented in Figure 3 by the arrow R) is not sufliciently large to reduce the stroke.

As so far described, the pump according to the present invention operates in the same manner as that described in the aforesaid United States specification No. 2293,692; but it will be appreciated that in certain cases, for instance when the pump is utilised to provide the source of pressure for a hydraulic system of an aircraft which may be called upon to operate under extremely low temperatures at high altitude, the oil or other fluid of the system may become very viscous. In that event the viscous drag as between the bearing surface of the slippers 24 and the track ring I I can resolve itself into a turning moment operating about the track ring centre, thereby tending to cause the track ring to hinge or rock, in the direction in which it is urged by the spring 33; and if that rocking or hinging tendency is not counteracted, it causes an increase in pumping pressure which may be excessive. The present invention is therefore directed essentially to the actual mounting of the track ring H.

It will be appreciated that since the total reaction force on the ring has only a small component parallel to the direction in which the ring moves, the means used for mounting the ring must be of a kind to move with very little friction.

A flattened portion 35 is provided on the track ring between which and a b-aring p.ate 36 roller bearings 31 operate. The rollers 31 are mounted in a cage 38, which moves in the same direction as the ring and through half the distance. The rollers are held against slipping between the flat surfaces by the load imposed by the pistons on the ring except when the pump is not generating pressure, and the ring then must be at maximum eccentricity. In this condition the cage 38 is located by the spring 39 pressing it against the pin 4|, which is fixed to the ring and moves in a slot 40 in the cage 38. The pin 42 projects into the slot 40 to assist in guiding and locating the cage 38. i

It will be appreciated that the drag moment could affect the eccentricity of the ring only if the track ring were permitted to rock about one of the rollers, and such rocking action is prevented by the rollers being spaced adequately apart. The reaction force R passes between the rollers close to the one remote from the spring 39, and the ring is therefore firmly held against this roller against the turning moment due to viscous drag which tends to lift it from the roller and rock it about the roller adjacent the spring 39.

The casing includes a pad or seating 34 opposite the rollers 3'! which prevents the ring from dropping out of place when the pump is not developing pressure.

In the pump shown in Figures 1 to 3, the spring 33 is of laminated leaf form, mounted inside the casing In, with one end located at 43 and the other end free to slide on the casing. The small rod 44 is interposed between the track ring H and a point of the spring 33 intermediate its ends. The spring 33 is considerably deflected when the ring is at maximum eccentricity, and the deflection, and hence the force it exerts, increases as the eccentricity decreases. The pressure characteristics depend among other things on the ratio between the deflection imposed on the spring at no eccentricity and that imposed at maximum eccentricity. Conveniently, the position of track ring maximum eccentricity is defined by the segment 45. When the reaction moment builds up at the critical pressure, a slight additional rise causes the ring it to move over in opposition to the spring 33 until delivery is reduced to zero. i I

For the spring 33 operating as the resilient means for loading the track ring to its maximum eccentricity position, any other suitable form of resilient control might be substituted. Thus, a spiral spring might be housed in the casing between the track ring and a suitable fixed abutment, which might be adjustable. Generally speaking, however, the leaf type of spring is preferable because it can be conveniently fitted into the casing. In all preferred constructions the spring 33 is of laminated form, the several laminae preferab y being stopped at graduated distances from the free end of the spring, as is usual on leaf springs to provide adequate flexibility; but all the laminae extend to the located 'sure at which the pump will end of the spring and are there clamped together in any suitable manner, thus giving an increase in damping effect. The use of a laminated spring of the construction described and clearly seen at 33 in Figure 3 provides for a marked damping effect on variation of deflection, which is advantageous in some cases. Moreover, such a spring provides a convenient means of initial adjustment of the rate of the spring because the rate can be increased as the spacer rod 44 is moved towards the fixed anchorage end 43. The actual force exerted ,by the spring 33 can be varied at choice on installation by selection of any one of several differently-dimensioned spacer rods 44.

Spacer rod 44 can be located in any convenient manner; for instance it may be engaged in lateralIy-spaced metal strips one at each side of the spring 33 and secured at the fixed anchorage 43 in any suitable manner.

The pump characteristics and the critical presangular setting of the be varied on installation is dependent upon the valve shaft, which can to direct the reaction force Generally speaking, the characteristics .will be determined on assembly of the pump; and having determ'ned the final setting of the valve shaft it is locked against rotation with respect to the casing by means of the dowel 41, seen in Figure 1. There may be cases, however, in'which provision is made for adjustment of the valve shaft l2.

Itris convenient to utilize the specially-formed segments 45 and 46 inside the casing I as the stop means for limiting the'range of movement of the track ring, but any other convenient stop means may be provided, and in certain cases such alternative stop means, provided for in stance by bolts extending through the casing I0, may be operable externally or adjust the limit positions of the track ring.

An alternative construction in which the track ring is supported on in Figure 4, in which the relevant parts similar to those shown in Figure .3 are designated by the same reference numbers.

The track ring II, which is acted on by the reaction force R, is supported by a tension link 50 pivoted to the block secured to the casing l0, and by a block 52 secured to the track ring I I, the track ring being also supported by a compression link 53 resting in a grooved block 54 secured to the casing l0, and awblock 55 secured to the track ring. Parts I l, 50 and 53 are shown in full lines in the position of maximum eccentricity and in broken lines in the position of no eccentricity. A bending strut- 56 abutting against block 51 secured block 58 secured to the track ring ll provides the resilient means forcing the track ring towards the position of maximum eccentricity, and a pad 34 is arranged to support the track ring when the pump is developing no pressure and prevents the block 55 from falling clear of link 53.

The arrangement is preferably such that the links are parallel when the track ring is in its mean position, and the links may be of equal length, in which case the track ring will be a straight The tension link may be shorter pression link. in which case the block 52 will be pulled down towards each end of the range more than the block 55 is permitted torise; hence the centre of the ring will be pulled down slightly line,

R appropriately.

pivoted links is illustrated to the casing I0 and than the com react in operation the casing to the path'of the centre of I towards each end of the range, thus doing work against the force R which acts upwards. is would give rise to forces urging the ring from maximum eccentricity towards the central or mean position, and also from minimum eccen tricity. The effect of this on the ring is the same as would result from making the strut 56 exert an increasedforce at small stroke and a decreased force at full stroke, and this in certain cases is a desirable effect. a

If thecornpression strut were shorter than the tension strut, the opposite efiect would result, and this might also be desired in certain cases.

If both links were tension links, the effect would be that due to a long compression link and short tension link, only more so, and if both links were struts, the effect would be that of a long tension link and a short compression link, but more so.

The arrangement can be used in conjunction with the leaf spring 33 illustrated in Figure 3 to compensate for the diminishing force exerted by the spring as the eccentricity increases, or in conjunction with the alternative spiral spring housed in the casing referred to on page 9, in which the spring acts between the track ring and a suitable fixed abutment, which may be a the hollow boss in the casing which contains the sprin What I claim is: v

1. In a pump including a track ring, a radial type piston and cylinder assemblyv mounted for rotation in said ring, and means mounting said ring for movement from a position of maximum eccentricity to a position of minimum eccentricity relative to the center of said assembly, the magnitude of the eccentricity of said ring determining the stroke of the pistons of said assembly; the reaction forces incident to operation of the pump tending to bias the ring to its position of minimum eccentricity; resilient means biasing said ring toward the position of maximum eccenits positions of eccentricity and thereby preventing modification of the load imposed on said resilient means by the reaction forces acting on the ring when the pump is in operation.

2. 'In a pump including a track ring, a radial type piston and cylinder assembly mounted for rotation in said ring, and means supporting said ring for movement from a position of maximum eccentricity to a position of minimum eccentricity relative to the center of said assembly, the magnitude of the eccentricity of said ring determining the stroke of the pistons of said assembly; the reaction forces incident to operation of the pump tending to bias the ring to its position of minimum eccentricity; resilient means biasing said ring toward the position of maximum eccentricity against the reaction forces acting on the ring when the pump is in operation, and means intermediate said ringand said ring supporting I type piston and cylinder assembly mounted for rotation in said ring, and means supporting said ring for movement from a position of maximum plug screwed into and said ring supporting I means for opposing rotation of the ring in all of path between said posieccentricity to a position of minimum eccentricity relative to the center of said assembly, the magnitude of the eccentricity of said ring determining the stroke of the pistons of said assembly, reaction forces incident to operation of the pump tending to bias the ring to its position of minimum eccentricity; resilient means biasing said ring toward the position of maximum eccentricity against the reaction forces acting on the ring when the pump is in operation, and axially rotatable bearing members situated on one side of the track ring between it and said supporting means, said bearing members lying on opposite sides of a line representing the reaction force which presses the ring onto them when the pump is developing pressure whereby, angular rocking movement of the track ring due to viscous drag between the piston and cylinder assembly and. the track ring is prevented.

4. A pump as claimed in claim 3 wherein a portion of the ring supporting means is provided with a fiat surface and a portion of the ring is also provided with a flat surface between which fiat surfaces the axially rotatable bearing members are interposed,

5. A pump as claimed in claim 3 wherein the track ring is provided with a flat surface and the ring supporting means is also provided with a flat surface, said axially rotatable bearing members being interposed between said flat surfaces and which further comprises a cage within which said axially rotatable bearing members are mounted, a projection extending from the fiat surface of said ring, and spring means urging the cage against said projection when said ring is in its position of maximum eccentricity.

6. In a pump including a track ring, a radial type piston and cylinder assembly mounted for rotating in said ring, and means supporting said ring for movement from a position of maximum eccentricity to a position of minimum eccentricity relative to the center of said assembly, the magnitude of the eccentricity of said ring determining the stroke of the piston of said assembly; the

reaction forces incident to operation of the pump tending to bias the ring to its position of minimum eccentricity; resilient means biasing said ring toward the position of maximum eccentricity against the reaction forces acting on the ring when the pump is in operation, and spaced link members extending between said ring and said ring supporting means, said link members bein constructed and arranged to oppose rotation of the ring while permitting the ring to move to change its eccentricity.

7. A pump as claimed in claim 6 wherein one of the link members is a tension link and the other member is a compression link and wherein the links are parallel with one another in the mean position of the track ring.

8. A pump as claimed in claim 6 wherein the link members are arranged on opposite sides of the track ring and on opposite sides of a line representing the reaction forces acting on the ring when the pump is in operation.

9. A pump as claimed in claim 6 wherein the link members are of equal length.

10. A pump as claimed in claim 6 wherein the link members are of unequal length.

11. A pump as claimed in claim 6 wherein both link members are tension links.

12. A pump as claimed in claim 6 wherein both link members are compression links.

13. A pump as claimed in claim 6 wherein one of the link members is a tension link and the other link member is a compression link and wherein the two links are of equal length.

14. A pump as claimed in claim 6 wherein the resilient means comprises a bending strut.

HAMILTON NEIL WYLIE.

REFERENCES CITED UNITED STATES PATENTS Name Date Wylie Aug. 18, 1942 Number

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