US2638848A - Hydraulic pump and motor - Google Patents

Description

May 19, 1953 E. H. JOHNSON HYDRAULIC PUMP AND MOTOR Filed Feb. 15, 1951 s Sheets-Sheei 1 Inventor Attorney May 19, 1953 Filed Feb. 15, 1951 E. H. JOHNSON HYDRAULIC PUMP AND MOTOR 3 Sheets- Sheet 2 y 9, 1953 E. H. JOHNSON 2,638,848

HYDRAULIC PUMP AND MOTOR Filed Feb. l5, 1951 3 Sheets-Sheet 5 Reser 1/0) I Pump Inventor Attorney Patented May 19, 1953 UNITED STATES PATENT OFFICE HYDRAULIC PUMP AND MOTOR Edward Harry Johnson, Coventry, England, as-

signor to The Keelavite Company Limited, Coventry, England, a company of Great Britain Application February 15, 1951, Serial No. 211,118 In Great Britain February 16, 1950 13 Claims. (01. 103-42) hydraulic fluid through the working clearances referred to and, in some cases, of reducing the unbalanced thrusts acting on parts of the mechanism of the pump or motor.

One example of such a pump or motor is described in the specification of United States Patent No. 2,483,705. X

The invention is particularly but not exclusively applicable to hydraulic motors of thelkind usually called sensitive motors, that is to. say motors which are required to rotate at aspeed closely related to their consumption of hydraulic fluid (i. e. the rate at which hydraulic'fiuid is permitted to pass through them) and to maintain an exact relationship between speed andffluid consumption down to very low speeds, such motors being used, for example, for training and elevating guns and for similar purposes.

It will be seen that with pumps or m'otors'of the kind referred to as described in United States patent specification No. 2,483,705 having a pressure control valve which maintains the hydraulic pressure within the casing at a value between the inlet and outlet pressures of the pump or motor and preferably midway between these pressures, there will be a greater flow of fluid into the casing than out of the casing through the working clearances during part of each revolution of the motor and a greater fiow of fluid out of the casing than into it through the working clearances during another part of each revolution of the motor, according to the proportions of the working clears ances which, at different points in the rotation of the motor, are subject respectively to the'pressures on the high and low pressure sides of the motor, there being alternate flow into and out of the casingthrough the pressure control valve. In other words, the fact that the'pressure control valve maintains a constant pressure within the casing means that the rate of flow of fluid from the working chamber through the parts of the working clearances subject to high pressure varies with the variations in the length of such part or parts ,of the working clearances occurring during each revolution of the pump or motor.

the motor.

Moreover, similar changes in the rate of flow through the working clearances with variations in the lengths of the parts of the Working clearances subject respectively to high pressure and low pressure would occur in other types of hydraulic pumps or motors of the kind referred to having a pressure control valve maintaining a pressure in the casing between the pressureson the high and low pressure sides of the pump or motor.

At high motor speeds when the quantity tr fluidflowing through the motor is high the variations in the rate of escape of fluidthrough the part or parts of the working clearances subject to the pressure in the high pressure part or parts of the working chamber or chambers have little effect since the maximum rate of escape is'only a very small proportion of the total flow through When, however, the rate of flow through the motor is small it will be seen. that the variations in the rate of escape vof fluid through the part or parts of the working clear; ances subject to the pressure in the high pres: sure part or parts of the working chamber or chambers will have an appreciable efiect and in fact that, if the rate of flow through the motor is reduced to a point at which it approximately equals the rate of escape of fluid through the part or. parts of the working clearances subject to high pressure at the rotational position of maximum escape the motor will come to a stop.

at this position.

' The object of the present invention is to overcome this difiicultyand to provide a pump or motor in which the speed of rotation will be closely allied to the rate of fluid flow through the pump or motor over the whole working range.

including especially the low speed and flow range.

To this end a hydraulic pump or motor of the kind referred to according to the present inven-' tion, instead of having a pressure control valve such as is employed in the form of pump or motor "described in the specification of United States Patent No. 2,433,705, has a closed casing which flow of fluid into the casing from the high pressure side of the pump or motor and out of the casing to the low pressure side would be greater than the normal steady load working pressure for which the pump or motor is intended, but preferably less than the maximum pressure which the pump ormmotor and...,the, apparatuswith whichdit is to beiusedbis desig-ned.-.towithstand-so thattthe valves will act together as safety valves preventing the occurrence of dangerous hydraulic loads on the pump or motor or its associated apparatus.

Moreover, it will generally be preferredttorpro vide non-return valves constructed and arranged so that they will open under peak pressure conditions in the apparatus withnwhichtthe.purppor motor is associated and in fact at a pressure appreciably below the peak pressuraw-hich would occur during working of the apparatuswerethe non-return valves not provided so that .awperiodic opening of the valves and consequent flow of fluid through thecasing will becausedautomatica'11y..at; intervals, during operation; of,the apparatus.

"'Whenlas willjoften be'the cas e,lthe,pump or motor is intended to operate. ,in' either direction and/onto act alternatively, as, a, pump or motor, "the ,nlon-return. valves. are preferably duplicated so asito provide a pair of non-return valves arranged to function. in the *de'sire'd manner irrespect'ive of the direction of operation of the pumpor motor or of whether it, is at. the ,moment serving the purposeof a;,pump .or, vmotor. Thus in "such. an "arrangement" there would be provided two pressureoperated non-return valves disposed respectively between .the' interior of. the

casing andthe-inietandoutiet portsof the pump pressures-required'to cause opening of anon-return"valve*permittingifiow' of fluid from one of the-po'rts intoifthe teasing and open ng ofthe asso'ciatedynon-return valvepermittingi fiow of fluid-out of the" casing to the'other port" exceeds the-difference "between the pressures" in the two portvduring-thenormal steady load working ooriditions'with the pump or motorg'operatingiin the appropriate direction.

It will' be understood in" this connection that the-pressure-difierence required to'cause'ithe two appropriate non-return-v'alvesto open, when one port -is" at the-higher pressure-may be the same 'as or different from 'that'required to cause opening'of the other" two 'non return values when -the other port is; at the 1 higher pressure.

The; invention may be applied to; pumpsand motors' ofthe kind referred to' of various kinds but'one 'arrangcmentaccording to the invention applied to a rotary pump orwmotor of."the vsocalledrotary abutmendtype. is shown by Way of ejX'am'ple'inthe accompanying'drawings; in which "Figure' 1 isia sectional side. elevationgofthe pump .or' motor,

fiEigure'Z is. a cross sectional view {of the pump ormotor in the;planexindicatedby the line2 2 n'F 'e *Figureii is a sectional plan'on angehlarged scale, showing the. arrangement of; non-return valves provided in .itheypump or motor shown in 'Eigures 1 and 2,and

Figure 4 is a diagrammatic illustration of a hydraulic system incorporating a pump or motor according to the invention.

In the construction of pump or motor shown in Figures 1, 2 and 3, the pump or motor is of known general type comprising a fluid-tight caslihgaAuvithincwhich are. mounted. the v parts of it'hefpumpcor motor enclosing thezsworleing chamber. These parts comprise an outer part or .,housing B having formed therein two intersecting cylindrical bores B 13 constituting respecitivelytitheaouter circumferential wall C of an annular.,working chamber C and the principal part ?.'.D =of"the* circumferential wall of a rotary abut- ..ment.-.'chamber. jSecured to one end of the housing part B is an inner part E which forms ffi eofuthe working chamber C the in-ner circumferential Wall C of the working cham-beciand the smaller part D of the circumferential wall of the abutment chamber. Securedyto thepther end of .the housing part B is, an end'rplatefF which closes; the adjacent ,end or ,the abutment chamberD,'D -.an'd has anyaperture thereinzcoaxialwith. and of the samefdiameter as .the outergcircumferential wall Ooffithe working :"chamber; while a ring F coaxial with andgof. the same: externalzdiameter as the inner circumferential walr C .of the working ..chamber is also secured to the housingiB so thatthere isan annular slot between thejparts F and'F .of ithe same" cross sectional dimensions as the .working chamber.

TCarried' in hearings Gand' G in: the partsjjfE and? is a rotor assembly comprisin aJSha'itFH to which is keyed a r0tor"I-I compri1sing a. disclike ,portionili f from which extends a; cylindrical flange-like part'frl which liesiwithinand makes a close sealing. fit with the inner andyoutertcircuniferential walls vofthe; annular slot between "the parts F and? g and itself carries',two' blades H which extend across the working chamber and makea sealingffit with its'inner .and outer circumferentialwallsi'C, C anclthe. end wallf'c The 'shaftf'I-I extends ithroughaflnid-tight gland ffi in the casing A.

Mounted Withinthe abutment chamber is a rotary zabutment J having tWO'blade-receiVing recesses J thereinfthis abutment being mount- ,ed on a sh'aftJ supported in' bearings 1 37 in thegpartIE;andifdriven,"soas to rotate at; the same speed asbutinithe QPposite directiorrgfrom the rotort'Hi;.through gearingK.

"Inlet: and outlet ports" L, Mopening' into the working. Chamber. respectively on the two sides of the abutment'J communicate respectively with inlet. and; Qut1et ,passases; L and M Assmniu thejdevice. ,togbeyin operation has a ,,pump, as the rotor, and abutment rotatethejiiuidis,drawnirom onaof' the passagesiL 011M by the .blades and deliveredthrough thero'ther and;.'the abutment, while"maintaining,a, seal at all ,times acrcssfthe working chamber .between the, inlet .and outl p rtscomes into position ,fonone of its blade receiving recesses J to receive, a, blade andflpfirmit such; blade to pass the abutment at,the.appropriate times.

"Pressure; balancin recesses and pas a e are ShQWn associated With "the ,.abutment' blllix i fl theseand; the general functioningjof devices of the kind shown arelmown they willnotbe further;;describcd.

'j -M0unte'd onthe housing part B is a va1v :,.hous ingN containing .two parallelbores one of? which c0mprises...a,centra1 s ction 0, of, relativel small diam t penin byway of. con calyal eseatines O into end portions 0 ,0 of relatively large diameter while the other, P, is of approximately thesame diameterthroughout its length apart from such small differences in diameter as will be apparent fromFigure 3 of the drawings. The ends of the bores 0, 0 -O and P are closed by screwthreaded caps Q.

Communicating with the central part 0 of the bore 10, O 0 is one end of a passage R the other end of which communicates with the interior of the casing A at its highest point as shown in Figure 1. Similarly communicating with the central portion of the bore P is one end of a passage S the other end of which communicates with the interior of the casing A at a point displaced from its highest point. One pair of adjacent ends of the two bores O, 0 O and P communicate with a common passage T opening into the passage L while the other pair of adjacent ends of such bores communicate with a passage U opening into the passage M Associated with each of the valve seatings O and O is a ball valve V, V normally maintained in contact with its seating by a spring V acting through a thrust member V Mounted in the :"bore P on opposite sides of the passage S are two valve seating members W, W making fluid-tight joints with the surface of the bore, ,these valve seating members being provided with bores W W terminating in valve seatings at their adjacent ends in contact with which ball valves W, W are normally maintained by a spring W acting through thrust members W".

It will thus be seen that ifthe pressure in the passage L or the passage M rises sufficiently relatively to the pressure in the casing A the valve W or W as the case may be will be lifted by pressuretra nsmitted through the passage T or U so that fluid will flow into the casing A through the passage 8. Also if the pressure in the casing A rises sufliciently relatively to that in one or other of the passages L of fluid into the casing A, one or other of the valves V or V will open, that is to say whichever of these valves leads to the passage T or U for the time being, at lower pressure.

In practice the casing A is filled with working fluid and it will be seen that, assuming that there is no air space in the casing A, the pressure in one or other of the passages L or M must rise sufficiently to cause opening of the appropriatevalve W or W and of the associated valve V or V before the valves in question will open to permit simultaneous flow of fluid to the casing A through one of ,the valves W or W and from the casing through the appropriate one of the valves V or V It will moreover be apparent that the opening of the two appropriate valves and the corresponding flow of fluid into the casing A through the passage S and out of the casing through the passage R will take place whenever the pressure in either of the passages L or M exceeds that in the other by an appropriate amount.

The pressure difference required to cause opening of the valves W and V may or may not be the same as that required to cause opening of the valves W and V Usually, however, the arrangement and setting of the springs V V and W will be such that approximately the same pressure difference causes the appropriate two valves to open, whether the higher pressure is in the passage L1 or in the passage M Preferably, moreover the spring W is of such effective strength relative to that of the springs W and V that approximately the same pressure difference or M due to such delivery is required across each of the'four valves to open it. Thus whenever a pair of valves opens the pressure within the casing A is approximately half Way between the pressures in the passages L and M The dimensions of the parts and the forces exerted by the springs are preferably so determined in relation to the characteristics of the hydraulic apparatus with which the pump or motor is to be used that while during normal steady load operation the valves remain closed, the appropriate pair of valves will open each time peak working conditions are experienced so that each time such peak working conditions occur, fluid Will be causedto flow into the casing through the passage 8 and out of it through the passage R. In this way not only does the valve apparatus act as a safety valve to prevent the apparatus being subjected to excessive hydraulic loads but should there be any tendency for air to collect in the highest part of the casing A it will beejected through the passage R. Thus the casing tends to be maintained completely filled with liquid. In this way, as explained earlier, leakage and variations in such leakage through the working clearances between the parts constituting the working chamber tend to be reduced.

One particularly useful application of the invention is to a sensitive pump or motor constituting part of a hydraulic power transmission system for moving intermittently heavy apparatus, for example a gun or gun turret wherein there may be heavy peak loads when starting and stopping the apparatus with periods of normal steady load between them.

One such hydraulic system is shown diagrammatically in Figure 4, in which the system comprisesa hydraulic fluid reservoir X from which a suction passage X leads to the inlet passage M of a hydraulic pump having an outer casing A and constructed as shown in Figures 1, 2 and 3. The outlet passage L of this pump leads through a pressure line X to the inlet port of a control valve Y of the known rotary type having a rotary distributing valvemember Y controlled by suitable mechanism diagrammatically shown at Y The valve Y has on the one hand two alternativepressure outlet passages Y Y leading re--v spectively t the inlet and outlet passages M and L of a hydraulic motor having a casing A andalso constructed as shown in Figures 1, 2 and 3, and on the other hand two relief passages Y leading to the reservoir. Since the valve Y will be of well known form and in itself constitutes no part of the present invention it will not be further described or shown.

The hydraulic motor is connected by suitable transmission mechanism to a load indicated at Z having a considerable inertia such for example as a gun or gun turret.

In operation the pump delivers hydraulic fluid continuously from the reservoirX to the control valve Y which in its central or neutral position closes both the passages Y and Y and opens the passage X to the passages Y so that the pump merely circulates fluid freely.

When the valve member Y is moved in one direction or the other from such central positionit progressively closes communication between the passage X and the passages Y while opening one or other of the passages Y or Y to the pressure line X and the other of these two passages to one of the relief passages Y Thus the motor is caused to rotate in one direction or the other according to the direction in which, the

memberfi rhas sheen moved. from: its :central position.

*izSincetLtha zload' Zv has; substantial;inertiaathe suddemmovementa ofz. .the;.memb;er cause peak pressures to be built up in the appropriate one ef :the passages=Y 3.01 Y .beioresithe; inertia ofnthe loadsisnovercome: ands'undensuch-condi tionsitthe 'appropriate: pair of non return valves Wiaxand'iVL or'nW :and-ilFWould ,open: to :limit' the hydraulic load. isimila rly ifizithe control member Y 1. -is..sudden.ly moved: torstoprimovementooi the load'zj Z-.'the momentum lot .the. load may :build up awpeakapressure in; the a appropriates one of the passages Y or" Y awhichl-isiz then closed by" the valve-,2 anclizthe:other':appropriate-main ofmonreturn valves :in the motordwillwopen. *rMoreover, each: time this occurs; any: air in the casing of the pump'will bezegieotedthrouglr the passage R. 5 :Thet non-retumn 1 valves :would sh'OWBVETbEECOIlstruct'ediand arranged so athatizunder normal steadya-rload conditions; thatiis ito= say zwheir tthe loadiizuisz sbfiillg moved: at: other than approximately max imumracceleraition and .is znotrhaving approximately :inaximum 'deceleration z'imposed upon'rit the:-non.+return valves wilrremainuclosed.

nIt Willi the; appreciated :that; ;.a1-though: :for convenience thespump hasbeen;describediasaofcthe kindishownziniFsigures 1 2.a-nd 3xit=neednot necessarilyhbes provided with :nonereturn valve -;.apparatu sacoordin'g 'jto the: :invention.

vmhatl In claimaasz any? invention. 2 and Z desire" :to securezbyi LattersPatent; is:

'11 rotary -.hydraulicamachinecomprising =relatii'elyamovingiparts 'enclosing aworlsing chamber with working clearances between? the relatively I moving pants and inlet and outlet passages communicatingitwith the working chamber; a substantial-ly *=lflii-id-*-tight casing enclosing I the said relatively moving parts and' vvith which'communicate the ends -0fthe Working I clearances remote from the worhingchamber, vsaid casing 'being 'arranged to befilled-with Working fluid, and valveapparatusincluding in combination a'pressure-operated nonreturn valve arranged to-perlet passages to the-interior'of theca'sing and-a second: -pressure=-operated non-return valve arranged to permit flow of fluid from the casing to the other-of the said-inlet and outlet passages.

2.-A rotary hydraulic machine comprising relatively-moving parts enclosing a workingchamber with working clearances between the relatively moving pairtsand inletand outlet passages communicating with the working "chamber," a -sub-- stantiaily fiuidj-tight casing f enclosing said relatively moving parts and :Withwhich communi catelthe ends of-ithe said working clearances remote from the working chambensaid casing being arranged to be filled with working fluid, two pressure operated non-return admission valves arranged to permit'zflow of fluid into the casing respectively from" the iinlet and "outlet passages, and-two pressure operate'doutletvalves arranged torupermit 'tflow of'fluid from the casing respectively-to: the inlet and outlet passages.

3. A rotarytzhydrau'lic machine'as claimed in claim '1 in which each of the non-return valves is constructed and arranged to open on the-"occurrence of approximately the same-predetermined'pressure difference across "it whereby beth' valveswopen'on the occurrence of twice that pressure difierence between the pressures respectivelyin the inlet andoutlet passages.

14. A.rrotary hydraulic machine as claimed in claim-11in which-each or the non-return admis- 8 sion/valveszcontrolling:theiflovw ofiifluid iirom" one ofirthasaidrinlet and;.outletzpassagesztoathenasing .gis constructed: and; arranged: tor.open1at-.substantially-the:same.::pressure idifferenceracrossz fit asxcauseszlthe opening: of the; associated hon -returnzotrtletv'valve controllingrthe flow. 10f ifluicl-rto the other of said passages. e

350A: hydraulic system sin'cluding ati dea'stnone hydraulic'machine.asclaimed in claim i in whi'ch the nonreturn: valves! are: constructed to open: at a' pressu-re :whiichds greaterithan the pressure dinposedlthereon whenzthe system isioperating zunder steady load conditions-what less than the pressure imposed. thereon when the: system is :operating underpeak load conditions.

6 Aghydraulicisysjtem .as claimed in claim 5 'in which each of the non return valves -is constructed and arranged: to;-open. at sub'stantially the:sameapressure-ldifference.across' it 'as thatwrequired to .1 cause the: o'ther non return valve -"-to open.

'"7.;-.Axhydraulic system including at least one hydraulimmachine as claimed in claim" 2"i1'1'Whl0h tha-two non-return*valves which are arranged to open to permit fiowof fluid-through thecasing eachi direction are constructed to open at a pressure which:;is=:greater than the pressure imposedr on tithem when the system is operating under-steady? :load conditions but less than -that imposed .Onthem. when; the system -iSf operating underzpeak .ioad conditions.

- 8. Aahydraulicssystemi as claimed in claim" Tin which each .of f the non1-return..--valves *is con-- structeds andrarranged :to open at substantially the; seiner-pressure across; rite as that require'd' to cause each of s the Mother non-return valves-to open.

c9.. .A rotary;hydrau1icmachine comprising rela tivelyrrotatingixparts enclosing between them an annuiarxworking.chamber; one-0t saidparts-being stationary and including the outer--circumferentiahvvall-oi the working chamber through which pass inlet: and outlet passages at oircumierentially spaced points while the other. of said parts rotates and :constitutes :one :end wall of I the Working chamber and carrieswat leasttwo-spaced blades extending. acrossrrtheiworking chamber, a rotary abutment extending across the working chamber between the. :inlet and outlet passages and-maka "substantially fiuid-tight*seal-with the :inner andzouter walls-of the .working chamber andhaving blade receiving recessesthereintvhich during itS'fIDtatiOn.(701118"111130 position to receive the bladestandrpermit them to pass the abutmenta substantially fluid tight casing enclosing the relatively -rotatable 'partsand the rotary abutmentz and into-'which-open the ends of the Workingxclearances'between these parts remote from the working "chamber; and valve apparatus including a pressure operated-non-return valve arranged to permit flow of"fiuid"from one of the said inlet and outlet passages to the interior of the casing and 'a second pressure operated nonreturn 'valve arranged to-permitflow 'ofgfiuid from the casing! to the other of' said inlet and outlet ports.

10. A rotary hydraulic machine; as claimed in claim' 9 in which each of 'thepressureoperated non-returnvalves-is-arranged to'open on the occurrence of'substantially the same pressure difference across it.

11. A rotary hydraulic machine as claimed in claim 9 in which four' pressure operated; nonreturn valves are "provided; two: of ,said valves 9 casing respectively from the inlet and outlet passages while the other two are arranged to permit flow of fluid out of the casing respectively to the inlet and outlet passages.

12. A hydraulic system including at least one hydraulic machine as claimed in claim 9 in which the two non-return valves are constructed and arranged to open at a pressure which is greater l0 ing conditions due to leakage through the working clearances of the hydraulic machine at the rotational positions of the parts thereof in which the greatest length of working clearance is subject to pressure from within the working chamber.

EDWARD HARRY JOHNSON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 589,462 Bibus Sept. 7, 1897 1,064,169 Prall June 10, 1913 1,989,387 Vickers Jan. 29, 1935 2,344,879 Johnson Mar. 21, 1944 2,440,072 Booth Apr.. 20, 1948

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