US2851952A - Hydraulic pumps - Google Patents

Description

Sept. 16, 1958 E. L'. LANE 2,851,952

' HYDRAULIC PUMPS P Filed June 27, 1957 5 sheets-sheet 1 ATTORNEYS E. L. LANE HYDRAULIC PUMPS Sept. 16v, 1958 Filed June 27, 1957 5 Sheets-Sheet 2 INVENTOR ATTORNEYS Sept. 16, 1958 E. L. LANE 2,851,952

HYDRAULIC PUMPS v Filed June 2v, 1957` 5 sheets-sheet s rIl IIA

6 INVENTOR (5w/mq. 55W, BY

ATTOR N E YS Sept. 16, 1958 E. 1 LANE 2,851,952

HYDRAULIC PUMPS v Filed June 27, 1957 5 Sheets-Sheet ATTOR NEYS Sept. 16, 1958 E. l.. LANE Y HYDRAULIC PUMPS 5 Sheets-Sheet 5 Filed June 27, 1957 ATroRNEYs United States Pate-nto a The object-ofthe invention is the provision of an improved-constructional arrangementof variable delivery hydraulic pump, of the type having aplurality of cylinders arrangedfin communicating pairs, whereby. it is. possible to obtainra high :operating -output "pressure Handhigh volumetric etiiciency, an output delivery infinitely variable -between zero and-'fullv capacity, and certain other valuable -advantages which will be apparent 'from the following description.

According to the invention a variable vdeliveryhydraulic Apumpof the type specified is characterised by an arrangefment whereby the pistons vof each communicating pair of cylinders are respectively driven from a common 'shaft i through -the -media of eccentrics the" sheaves whereof are `mounted -on the shaft'andconnected thereto byhelical splines `of opposite hand, such' that'anaxial adjustment -of the shaft produces a relative angular `.displacement of the eccentrics and-consequently a-va'riation ofithe volumetric output.

One embodiment-ofA theinvention, and certain minor y-rnodilications thereoaarel illustratedV in and are hereinafter described with-*reference to the accompanying dia- ^`grammatic drawings. EIn said `-drawings, Fig v1 `is a longitudinal section of `the'pump, Figs. 2 and `3 are respectively sections of the lines II-II and III-#III of `Fig. l, Fig. .4v is a sectionon `the line IV-IV of'Fig.'3,

Fig. 5 is a fragmentary elevation'jof'alternative,manual means for effecting an axial adjustment of thedriving shaftfand Fig. 6 is a section on the line VI-VIof Fig.`5. Fig. 7 illustrates apparatus `for controlling the pump by hydraulic servo mechanism, and Fig. 8 illustrates further alternative control means,.dcpending in lthis case The pump depicted in Figs. l1 to 4 comprises a' block 10 housing five equiangularly spaced connected pairs of cylinders 11, 12, each pair being'sealed by individual Apistons 13, 14'and furnished Awith a single inlet valve` 15 and a single outlet valve'16,-both said valves being of the seated type. rThe output valves 16 communicate by means of an annular duct' 161 Vwith theL pump delivery routlet 162. The Acylinders are disposed radially about `an axially mounted driving shaft117 which may be coupled at 171 toanelectricmotor or otherprime mover 1(not shown), and having spl-ined thereon two eccentrics 18, 19 which are respectively locatedoppositethe inner ends of the pistonsvl, 14, which latter are karranged to' bear against grooved reaction rings 20, '21 mounted on the yeccentric sheaves by needle bearings 22,22, thefarrangement being such that the pistons are reciprocated intheir cylinders `by the throw of the eccentrics. l Each eccentric is -preferably made as an extension of a tubular shaft.23, supported by a pair of taper roller anti-friction bearings 24, 24.

The splines 25, whereby the eccentrics 18, 19 receive rotarymotion fromtheidriving shaft 17 at equal speeds are helical and of respectively opposite hand, and the arrangement is such that,the effect of imparting` an axial movement tothe driving.,shaft117 is toproduce a rotary movement of the ,eccentric ;18 relative to "the other 19; provision is made for an axial shaft-adjustment sufficient to move each eccentricsthrough'an angle 2,851,952 4"Patteinliced Sept. .16, 1958 .of so that the conditions may be varied from a relative disposition of the eccentrics of 180, in which the stroke ofthe pistons 13 exactly balances that of the v`,pistons14 andthe output delivery has a'zero value, to an eccentric settinglin which the pressure strokeof lthe pistons 13' and 14 coincides and -the output delivery is accordingly at a maximum. Any relativesettingof the veccentrics between .these limits will provide'a'proportional -delivery rate.

`'"lhe'inlet may be connected-to a 'reservoir'so 5that suction lift can be obtained, and in such'an arrangement return springs will be required to maintainV thepistons13, 14 in operativecontact'with the' eccentrics `18, '19. Such an `arrangement may uhowever be vdisadvantageous 'and it'isconsidered preferable to 'supply hydraulic uidto lthe inletvalve 15 by-,the gear-type `constant-.delivery feed purr-1p"`i1lustrated kat the right-hand end of Figp'l, 'a1id"in"Fig.` 3, which-'comprises a lgear V26iixed onthe 4"shaft "171, 'atgear 27 meshing with the gear'26 and Aarranged'to pumpdiquid'en'tering thegear chamber 28 'at `29 throughthe'duct 30 by ythe 'passage 31 into" the fannularheader duct 32, whence the liquid has access to* the inlet valves 15. *By these means the useof'return springs4 for they pistons is rendered unnecessary, 'whilst cavita'tionv and' starvation offlow to theV variable'delivery -pump Vare avoided "and the resultant lhigh volumetric --iciencyfprolongs thet'working life of the valves. "The `inlet pressure maybemaintained byv employing a feed *pump havinga volumetric output greater Vthan the maxi- 'mumow through the variable delivery pump, and passing the surplus feed to exhaust at 33 (Fig.` 3). Conveniently, the inleti'header Ai32 may be provided-with a'relief valve lof fthe 4balanced `type offering a I constant ihydraulic nresistance atz 'varying' rates of flow, such resistance `being determined'-by-external means-f adjustment. fBy 'this ar-rangement -aback pressure Iis maintained in the -inlet 'header32. i

In Acasefthe driving shaft i7, being relatively unstable, "should-'tend to amplifysundesirable vibration forces `due toexcessive working clearances in the transmission-fiele- `ments- (caused erg. by wear or inaccuracies- -in manufac- A-tur`e),itfrnay'be desirable to attach to the-end of'a vcylin'dricalextension -34 of said-shaft17 the-pistonrod "L35 and pistonf36 of an' oil-filled double-acting dash-pot37. Asupply'of oil is led from the header l32 through Vthe passage 33 and a pipe 39 to either side of the dash-pot piston*36,an'd the dash-pot cylinder is` maintained `filled vvwith oil by-check-valvesll), "41when the pump is at rest, lthe-piston' lbeing-in hydraulic balance and air being exclude'd notwithstanding possible 'oil-leakage.

Whenltne -axialzpo'sition of the shaft 17 is such'asto *provide `a given output delivery, the vcentripetal forces acting-through eacheccentric 18,119 react axiallywi'thin the shaft, which is. therefore substantially -in'iequilibr-ium.

' YAny out-f-balance force tending to displace the-shaft axially y-m-ust overcome the resistance in-either direction 'f'fspringebiassed valves 42, #i3 of small yoriiicefwhich flareprovide'd' inthe'dash-'p'ot piston-36. Thus, each such 1-vlve'42,='43will subject the oil in 'the dashpot to ay unit fpressurewhieh,multiplied by the annular area-aroundf'the fpi'stonero'd 35, willl resist axial `movement of thel shaft: 17.

'fThe'shft 17. is operated for control purposesr by ymeans Rois-a levera44riarrangedto rotate a-r pinion 45 meshingwith la rack-246 'onf the shaft-extension V34 and acting through thrustlbea'ringsl147,548. Suchform of control means'has a high lmeohanical'-advantage capable of overcoming'the re'sistancefof the dashpot valves 42, 43 Aand thereby enables control to be effected manually Awithout `undue lelo'rt.

=-An"alte1nativefdevce for operating the lhelicalshaft17 i'for:zcontrol purposes is Vshown in Figs. 5 vand l6. -In'this .:case1a11=gear quadrant-549 securedto Van'extension v-of the pinion 45 is rotated by a worm 50 and handwheel 51. Stops may be fitted to bear against the quadrant 49 and limit its movement. With this arrangement the dashpot assembly 35, 36, 37 may be dispensed with.

Which ever of the aforedescribed means for axial adjustment of the shaft 17 is employed, the effect of such adjustment is to alter the phase relationship of the eccentrics 18, 19 and therefore of the pistons 13, 14, with the result that the volumetric output of the pump is regulated accordingly.

The radial pumping action of the pistons 13, 14 at high pressure, and the consequent reaction of the liquid upon the helical splines 25, 25, are resisted by the combined axial and journal anti-friction bearings 24, 24. This arrangement enables advantage to be taken of the centrifugal pumping characteristics of taper roller bearings which are used in this situation, as illustrated in Fig. l. A small volume of the surplus oil from the feed pump is tapped from the header 32 and metered through the passages 52 controlled by the needle-valve 53 (Fig. 4) to the chamber 54 containing the bearings 24 and eccentrics 18, 19. Said passages 52 feed oil between the taper roller bearings 24 which circulate oil to the innermost bearing 55 of the feed pump, the thrust bearings 47, 48, and most important, to the eccentrics 18, 19 and their needleroller supported reaction rings 20, 21. This llow is drained to exhaust through passages 56, 56 in which are provided light check-valves 57, 57 which keep the pressure in the transmission chamber 54 slightly above atmosphere to exclude air and ensure the regular replacement of oil, thus maintaining its lubricity.

It is a particular advantage of the present pump construction that it lends itself, due to the rectilinear characteristics of the control element and to the fact that the helically-splined shaft 17 is maintained in equilibrium whilst transmitting considerable power, to remote control by suitable pneumatic, electric, hydraulic and mechanical media, without locking the element.` Thus, in the embodiment illustrated in Fig. 7, there is a manuallyoperable control valve 58 arranged to feed surplus oil fed from the header 32 via the pipe 59 to a double-acting hydraulic ram 6%) which is axially attached to a rack member 61 meshing with a quadrant 62 operably associated with the pinion 45 by which the rack 46 on the extension 34 of the driving shaft 17 is adjusted. As will be evident from Fig. 1, the position of the control valve 58 will be effective to select the direction of movement of the ram 60 and therefore the direction of adjustment of the shaft 17.

Fig. 8 illustrates means by which the rate of delivery of the pump may be controlled. The pinion 45 is connected to a quadrant 63 which meshes with a slidably mounted rod 64 which latter is biassed to a position corresponding to preset or full delivery by a spring 65 compressed between the housing 66 and a collar 67 on said rod 64. On increase of output pressure in the delivery outlet 162, such pressure is made to act, through the pipe 68 upon a single-acting ram constituted by the end of the dashpot piston rod 35 (for its equivalent), in opposition to the force exerted by the spring 65, and on overcoming the latter, to move the shaft 17 to a position of zero, or reduced, delivery. A useful feature of this control arrangement is that should oil escape from the pressurised system during such high-pressure period, the resulting drop in delivery pressure will cause the spring-biassed driving shaft 17 to move and enable the pump to make up losses and restore the desired pressure. The position of the rod 64 may be preset by adjusting the knurled nuts 69, 69 on the screw-threaded extension 70 of said rod.

What I claim as my invention and desire to secure by Letters Patent is:

l. A variable delivery hydraulic pump comprising a plurality of cylinders arranged in communicating pairs, means for supplying liquid to each pair of cylinders, an exhaust valve for each pair of cylinders, a driving-shaft,

a piston in each cylinder, there being on said driving-shaft in respect of each pair of cylinders two eccentric sheaves each in helically splined relationship with the shaft, each piston being arranged to bear against the periphery of one such sheave, means for shifting said shaft axially in relation to the sheaves for producing relative rotation thereof, and means for damping axial displacement of said shaft in both directions, said damping means including a dash-pot, a double-acting piston in said dash-pot and attached to said shaft for axial movement therewith, a port at each end of the dash-pot, means supplying low pressure liquid to said ports, two ducts through the piston for connecting the compartments of the dash-pot on opposite sides of the piston, and in each such duct a singleacting self-seating valve for restricting ow of fluid through the duct, said valves being arranged to operate in `opposite direction.

2. A variable delivery hydraulic pump comprising a plurality of pumping units, each said unit including two inter-communicating cylinders, a driving-shaft, said units being equiangularly assembled about said driving-shaft radially thereof, a header, means for supplying liquid to said header, inlet-valves respectively connecting the header with said units, an exhaust valve in each unit, a piston in each cylinder, there being on said driving-shaft in respect of each assembly of units two eccentric sheaves each in helically splined relationship with the shaft, each piston being arranged to bear against the periphery of one such sheave, means for shifting said shaft axially in relation to the sheaves for producing relative rotation thereof, and dash-pot means for damping axial displacement of said shaft in both directions, said damping means including a dash-pot, a double-acting piston in said dashpot and attached to said shaft for axial movement therewith, a port at each end of the dash-pot, means supplying l low pressure fluid to said ports, two ducts through the piston for connecting the compartments of the dash-pots on opposite sides of the piston, in each such duct a singleactingA self-seating valve for restricting ilowy of fluid through the duct, said valves being arranged to operate in opposite directions.

3. A variable delivery hydraulic pump comprising a plurality of cylinders arranged in communicating pairs, means for supplying liquid to each pair of cylinders, an exhaust valve for each pair of cylinders, a driving-shaft, a piston in each cylinder, there being on said driving-shaft in respect of each pair of cylinders two eccentric sheaves each in helically splined relationship with the shaft, each piston being arranged to bear against the periphery of one such sheave, taper roller bearings supporting said shaft, means supplying lubricant fluid to said bearings, the arrangement of said bearings being such that said lubricant is delivered thereby to working parts of the pump, means for shifting said shaft axially in relation to the sheaves for producing relative rotation thereof, and means for damping axial displacement of said shaft in both directions, said damping means including a dashpot, a double-acting piston in said dash-pot and attached to said shaft for axial movement therewith, a port at each end of the dash-pot, means supplying low pressure liquid to said ports, two ducts through the piston for connectlng the compartments of the dash-pot on opposite sides of the piston, and in each such duct a single-acting self-seating valve for restricting flow of fluid through the duct, said valves being arranged to operate in opposite direction.

References Cited in the file of this patent UNITED STATES PATENTS 886,047 Flinn Apr. 28, 1908 1,719,693 Ernst `luly 2, 1929 2,172,103 Kotaki Sept. 5, 1939 2,327,787 Heintz Aug. 24, 1943 2,605,707 Worlidge Aug. 5, 1952 2,642,804 Bowers June 23, 1953

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