US3295459A - Hydraulic pumps - Google Patents

Description

HYDRAUL I G PUMPS original Filed April 4,' 1965v 3 sheets-sheet' 1 lo ATTORNEYS Jan. 3, 1967 R. c. GRIFFITH 3,295,459

I HYDRAULIC PUMPS l original Filed April 4, 1963` 5 sheets-sheet 2IZO 5 ATORNEYS Jari. 3, 1967 R. c: GRIFFITH HYDRAULIC PUMPS ,3 Sheets-Sheet :5A

RAYMOND C. GRIFFITH ATroRNgYs Patented Jan. 3, 1967 3,295,459 HYDRAULIC PUMPS Raymond C. Griffith, 12683 Arnold St., Detroit, Mich. 4822s Original application Apr. 4, 1963, Ser. No. 271,050. Divided and this application Aug. 23, 1965, Ser. No.

6 Claims. (Cl. 10s- 161) 'Ihis application is a division of Ser. No. 271,050 tiled April 4, 1963 now U.S. Patent No. 3,225,701, which in turn was a continuation-impart of patent application Ser. No. 45,470, now abandoned.

This invention relates -to fluid pumps, and more particularly to pumps of the radial piston type.

The presentembodiment of the pump employs a chambered casing having a fixed valve face on a wall or side of the chamber, and formed with inlet and outlet ducts opening in said valve face. A rotatably driven shaft extends through the cham'ber and is concentrically connected to the shaft of a rotor operable in the chamber, the rotor carrying reciprocable pistons in radially extending cylinders.

Shoes carried at the outer ends of the pistons engage the annular peripheral surface of said chamber which has a cam ring disposed in eccentric relation to the shaft, whereby upon rotation of the rotor, the sliding ktravel of the shoes effects reciprocation of the pistons.

A valve face is formed on one side of the rotor and contacts face-to-face on the aforesaid fixed valve face. Ports extending from the piston cylinders open on the valve face of the rotor and alternately communicate with said intake and discharge ports of said casing. Such arrangement, as hereinafter explained, affords induction of fluid pressure through the discharge duct. The rotor in reaction to said pressure tends to shift axially and cause lseparation tbetween the rotor valve face and the fixed valve plate.

The above pump arrangement or assembly generally is to be found in prior art such as the T. R. Almond Patents Nos. 580,838 and 622,318, the Egersdorfer Patent No. 1,506,893, the I. C. Naylor et al. Patent No. 2,525,498, and the F. A. Serman Patents Nos. 2,797,643 and 2,833,225.

The Value in this type of pump is that it can 'be made inexpensively, is very durable, and theoretically should be able to produce high fluid flow and pressure.

However, the problem presented by the aforesaid separation between rotor face and valve plate has not been solved satisfactorily heretofore. Springs and other devices tending to hold the faces in contact either produce ununiform forces under varying discharge pressures or cause excessive Wearing of the faces,

A further problem, which I have recently uncovered is that no rotor shaft can satisfactorily be made to withstand forces of deection caused (1) by unbalanced piston reaction and (2) by unbalanced separating forces at the valve. The slightest, even immeasurable deiiections, produced on the most accurately centered and completely supported rotor and shaft cause uneven wear on the valve faces, particularly at high pressures and speeds, and leakage results due to non-intimate contact of the valve faces, lowering pump eciency. With two bearings, one at each side of the rotor, the bearings defect unevenly, with the same result.

Another pro'blem encountered heretofore in radial piston pumps is the `difficulty of maintaining the piston shoes in contact with the peripheral wall of the chamber under variable pressure conditions.

Retainer rings, such as those shown in the Ferris Patent No. 2,074,068, have been found unsatisfactory for various reasons. For example, wearing of parts occurs, and retaining forces are difficult to lbalance.

An object of this invention then is to provide for tran- Imission of pressure from the discharge duct to an end face of the shaft to oppose axial shift of the rotor and maintain contact with uniform frictional Contact throughout said engaged faces.

Another object of the invention is to provide Within the chamber annular means, substantially concentric wi-th the drum and engaging with -saidshoes to maintain said shoes in sliding engagement upon the annular drum.

A further object of the invention is to eliminate the problems of the aforementioned valve face separation by providing a new supporting means for the rotor so arranged that various innate forces operate to cancel each others deliection causing tendencies.

These and variousV other objects are attained by the construction hereinafter explained and illustrated in the accompanying drawings wherein FIG. 1 is a sectional elevation of a preferred pump taken on the rotational axis of the shaft.

FIG. 2 is a view in partial section on the line 2-2 of FIG. 1.

FIG. 3 is a fragmentary plan view of a part in the pump, namely, a preferred means for maintaining the shoes in contact with the peripheral wall of the chamber.

FIGJ4 is an end view, partially in section and with one end removed for clarity, of another preferred embodiment of the pump.

FIG. 5 is a cross section taken substantially on the line 5-5 of FIG. 4.

FIG. 6 is a perspecive View of a retaining ring utilized with the pump of FIGS. 4-5.

FIG. 7 is a longitudinal cross-Sectional View of another 'embodiment of the invention, and

FIG. 8 is a fragmentary cross-sectional view of still another modification of the invention.

Referring to FGS. 1-3, the reference character 1 designates a stator casing preferably having a cover plate 2 with which it jointly forms an annular chamber or stator recess 3 and retains a fluid seal 4. Screws V5, or the like, secure said cover V.plate to the casing.

A rotatably driven shaft 6 extends axially through the chamber, and has an end portion 7 journaling in needle bearings 8 provided in the cover plate. Theopposite end portion 9 of the shaft 6 extends through the casing and journals in needle bearingslt) provided therein. Theend Y portion 9 is provided with an extension 1.1 projecting from the casing to receive a drive connection (not shown). A nut 12 threads upon theend portion 9 to restrain theV shaft to limited axial motion.

The extension 11 passes through acap 13 secured to the casing by any means such asscrews 14. A recess 15 in said cap accommodates the nut 12, while an oppositely. formed recess 16 retains a Huid seal 17 which embraces said extension 11. In order to drain fluid which may reach the recess 15, the cap 13 is provided with a pipe tapped hole 18 to receive an appropriately threaded drain Iconnection (not shown).

The stator casing is formed with anintake duct 19 leading from the exterior of the casing to theend wall 3A of the chamber or recess 3. Adischarge duct 20 opens into said wall 3A of the chamber 3 in similar form and leads to the exterior of the casing. Avalve plate 21 is non-rotatably recessed into said wall of the chamber. Said plate overlies the wall 3A and has elongatedarcuate apertures 22 and 23 as indicated in FIG. 2, and whichy connect respectively with inlet andoutlet passages 19 and 20.

The chamber 3 houses a fluid pumping mechanism, including acylindrical rotor element 25 rigidly mounted 3 upon the shaft 6 for rotation by said shaft. Said rotor element is formed with avalve face 26 rotatably contacting thefixed valve plate 21. Saidrotor 25 is further formed with a plurality of angularly spaced radiallyelongated cylinder bores 27, from whichlateral passages 28 open upon saidvalve face 26.

Pistons 29 are reciprocably operable in thebores 27, and at their outer ends carryshoes 30. Such shoes are swivelly attached to the pistons and in the particular construction herein illustrated are formed with spherically socketed Shanks 31 affording a ball-joint connection 32 with said pistons. An annular insert orring 33 is concentrically fixed in the chamber 3,'and its inner annular surface provides acam surface 34 on which theshoes 30 ride. Therotor 25 is eccentric With respect to saidcam surface 34 of the stator casing 1, and theshoes 30 ride on the guide as thecylinder block 25 rotates.

To ensure constant contact of the shoes against thecam surface 34, a pair of axially spacedannular rings 35 straddle the shoes, engaging withshoulders 30A provided on 'the underside of said shoes as shown in FIGS. 1 and 2, to locate theshoes 30 with respect to thecam surface 34. To prevent dislodgment of the rings,elongated bars 36 extend between and rigidly interconnect the rings. Said ring and bar assembly loosely floats in the stator recess 3 and is supported solely by saidshoes 30,

practically eliminating frictional wear and effectively bal-V ancing and distributing the retaining forces among the pistons. At least one ofsuch bars 36 is constantly engaged by the leading edge of a shoe, so that the rings are rotated with the rotor. provided withroutwardly protrudingabutments 37, to assure contact with the leading edge of the shoe as shown in FIG. 2. Y

The end 7 of the shaft 6, which journals inthe cover plate or closure 2, projects slightly through said closure and is enclosed by acap 38 recessed as at 39 for such purpose. encircles the flange 41 of asleeve 42 insertedover the end of the shaft. The flange 41 has a close lit against the outer end face of the cover plate 2, and thecylindrical sleeve portion 42 is preferably made relatively thin. A'compression spring 41A bears against ange 41.

The end of thisdrive shaft is preferably recessed "as at 46A and a spring 4S seats'therein and bearsagainstthe cap 38, thus urging the shaft and rotor carried thereby axially so as to urge the end face of said rotor against the valve face of theinsert valve plate 21.

Itwill be understood thatpressure in theexhaust line 20 willrvary dependingn varying conditions in the system downstream of the pump. The spring tension of thespring 45 is substantially constant, andifconstructed strong enoughto-urge the rotor-into tightV engagement with the valve face ofplate 21 when pressure in the cx-V haust 20 is at a maximum, the pressure exerted thereby when the pressure inexhaust 20 is yat a minimum is too much, thereby resulting in high frictional losses and undue wear of engaging faces of said rotor and valve plate; I therefore have a spring strong enough to operate satisfactorily under low or minimum pressures and arrange for connecting the recess in saidcap 28 with theexhaust 20 so as to transfer exhaust pressure to recess 39. Any suitable means for connectingrecess 39 toexhaust passage 20 may be utilized and one such means is herein illustrated, comprising a conduit orpipe 46 leading from said exhaust to the fitting 47. It may be further noted that the fluid pressure inrecess 39 exerts a radial force against thesleeve 42 `tending to close this relatively thin sleeve portion about the rshaft and also a force axially against the flange 41. f

Rotation of the rotor 2S results in reciprocation of thepistons 29 due to the travel of theshoes 30 on the eccentrically disposedcam surface 34 oftheannular insert 33; Theports 28 in the rotor are alternatively com- The bars areV preferablyV fluid through theintake duct 19 and to expelit under pressure through thedischarge duct 20.

The rotor, in reaction to such pressure tends to shift axially Within the stator recess or chamber 3 against the pressure ofspring 45, tending to separate the contacting 1 faces of the rotor and end face ofvalve plate 21,1thus reducing the effective operation and output of the pump.

The arrangement whereby the conducting means trans-y l mits dischargey pressure to the end of the shaft, thus mam.`

tains the engagement of the rotor valve face upon thevalve plate face 26. The transmission and application Such cap retains a uid seal which tightly of said pressure in the manner described affords the ad` vantage that it is uniformly effective over the full contacting areas of the rotor valve face and the face of the vvalve plate.

pressure indischarge passage 20.

Although therotor 25 is preferably secured to the shafts by a shrink fit or otherwise fixed thereon, it is preferred to form aflange 44 on said shaft to guard against.

eventual slipping of the cylinder block axially of the shaft under the pressures discussed above.

The pressure transmitted to and directed upon the end of the shaft is generally adequate or sulcient to maintain the desired engagement of the faces of said rotor andvalve plate 21. Thespring 45 is preferably employed to react between said cap and the end of said shaft and to thereby act along with uid pressure transmitted to said shaft and to maintain said valve faces in contact. When utilizing the springr45, it is desirable to recessinto the cap a needle bearing 47 upon which the spring `may rotate.Screws 48 `or other suitable means removably secure thecap 38 to said rotor coverplate 2.

Where the described pump is to be used in pumping a liquid which can serve as a lubricant, thepistons 29 may be formed with pockets 49. A lubricatingpassagev 50 formed jointly in theball connection 32 and theshoes 30 may then conduct such liquid to the cam surface to4 lubricate same. p I

A drain hole 19A is preferably provided to drain excess fluid from chamber 3 to theintake passage 19.

In FIGS. 4-6, a more improved pump constructionais illustrated, in which a two-part casing 100, 101 is shownf:

In FIG; 4, the part 101 and elementscarried thereby are removed for clarity.Part 100 has a central insert 100A'`r provided with abore 102 and an annular valve face 103.

Part 100 is also recessed as at 104 to provide apumpingy 106 for rotatably supporting arotor 107 having acentral bore 108 splined as at 109 Vin the same radial planeas the 'bearing 106.

Adrive shaft 110 is supported -by a bearing 111 mounted on thepart 100 as shown and has a reduced portion face 103. The rotor has radial pumping chambers 1121 .in which reciprocatepistons 113 havingspherical end portions 114 supportingshoes 115.

Theshoes 115 slide on the eccentric`cam ring 105 as therotor 107 rotates, causing the pistons t0 reciprocate. Theshoes 115 each have radial sideslots 116in which are engaged annular retainer rings 117, one of which is illustrated in FIG. 6 as comprising a flat spring coil. The

rings 117 are radially compressible to enable them to be assembled to theshoes 115 and when so assembled they urge and hold theshoes 115 radially outwardly against. thecam ring 105.

The pressure is thus uniform throughthe operative range of the pump irrespective of variationsof saca-15A'Ports 120 communicate the inner ends of the chambers 112 'with the valve face 111, where they alternately register, as the rotor rotates, with arcuate inlet andoutlet ports 121, 122 respectively, assuming the rotor to be moving clockwise as viewed in FIG. 4. Thepart 100 has intake and dischargepassages 123, 124 as shown connecting with theports 121, 122.

Therotor 107, being supported only by onebearing 106 on one side, is in effect a free oating rotor, subjected to the action of two forces. One force, designated -by the arrow P, tends to separate the valve faces in the vicinity of the outlet port-s 120 since uid pressure produced by the piston is being discharged therethrough. This force P tends to deect the rotor from its axis.

The other force, designated by the arrow R, is produced by the radial Huid pressure reaction of thepistons 113 on the'u pumping strokes, and since the bearing is on only one side, the force R tends to deectthe rotor in the opposite direction to force P.

The area of the rotor face subject to pressure can be analyzed to determine a center locus having an average force Pave, which will be offset from the axis of the rotor a distance Pd. The forces produced by the pistons also have an average force Rave, 'and the radial axes of the pistons lie on a common plane offset from the center plane of thebearing 106 by a distance Rd. The products PafeXPd and REWXRd represent the moments of the two forces, and by proper choice of the axial offset of the bearing 106 lthese moments can be made equal so that the rotor will maintain a constant axis precisely normal to the valve face 103, even though the forces mentioned are individually unbalanced.

Of course, the rotor will have a tendency to move away from the valve face 103, the same as in the pump of FIG. 1, so pressure is admitted to the end 4of t-he casing part 101 through aport 125 as in the pump of FIG. 1, so pressure is admitted to the end of the casing part 101 through aport 125 as in the pump of FIG. 1.

The part 101 has a recess 126 carrying athrust element 127 bearing on the side of therotor 107 and the uid pressure is admitted to the side of the rotor, the bore S being closed by aplug 128, -by aport 129.

The area betweenelement 127 and the rotor subjected to fluid pressure preferably is about 5% less than the outer end area of theelement 127, which in turn yis about 5% more than the total effective area of the rotor valve face 111 subjected to fluid pressure.

Aspring 130 acts to urge the valve faces together on starting, when uid pressure is low.

FIG. 7 illustrates another method of counterbalancing Ithe valve separating forces, in which'a two-part casing 200, 201 has achamber 202 which is slightly inclined with respect to ashaft 203 supported at both ends bybearings 204, 205. Arotor 206 rotatable in the chamber 202 -has a central bore wiht anannular boss 207 spheroidal in cross-section as shown so that the rotor is in effect freefioating. Casingvalve ports 208, 209 open to aninclined side wall 210 of thechamber 202 for alternate registry withrotor ports 211 opening to oneside face 212 of therotor 206. In lthis modification, thelower port 209 is the pressure port.

Theshaft 203 has a ange 213 which eng-ages the side face 214 of the rotor opposite thevalve face 212. Fluid pressure is directed to the right-hand end of the shaft, but this pressure will be transmitted to the rotor as an unbalanced force, due to the inclination of the casing valve side rwall 210 against which the rotor is urged, the unbalanced force having a moment with respect to its axis equal and opposite to the moment of the valve face separating pressure with respect to its axis. Therotor 206 is driven from the ange 213 by a means such asla pin 215 engaged in aslot 216 in therotor 206.

In FIG. 8, a further modification is shown in a fragmentary View in which theshaft 250 is inclined with respect to thechamber 251 as in FIG. 7, but therotor 252 61 has a sphei'oidalannularl seat 253 engaged on a spheroidalannular shoulder 254 of theflange 255 from which therotor 252 is driven by yapin 256. Function and unbalanced forces will be the same here as in the modification of FIG. 7.

Although I have described but several embodiments of the invention, it will be apparent to those skilled in the art to which my invention pertains that various changes and modifications may be made therein without departing from the spirit of the invention or the scope of the appended claims.

I` claim:

1. A fluid pump comprising a stator casing structure, a power shaft supported -by said stator casing structure, a rotor secured on said shaft, said stator casing structure provided lwith a chamber having an annular peripheral cam surface eccentric to the shaft axis, said rotor having aA plurality of angularly spa-ced radially extending fluid pumping instrumentalities, each comprising a pump chamber and a pump plunger reciprocatingly supported by said rotor in said pump chamber, and a shoe movablyv carried on the Aouter end of the pump plunger and constructed to slidably contact the eccentric cam surface of said stator casing structure, uid intake and exhaust means for said pumping instrumentalities, and a free floating annular shoe retaining ring assembly disposed concentric with respect to the annular peripheralV cam surface of the stator casing chamber and engaged with said shoes to retain same in position for operable contact with said cam surface and to restrain said shoes from rotary displacement about the pump plunger axis, said ring assembly being rotatable with respect to said rot-or and to said stator casing structure, said free fioating annular shoe retaining ring assembly comprising a pair of axially spaced annular rings engaging the radially inner sides of said shoes, and means fixing said rings in said spaced relation with respect to each other, said means fixing said rings in spaced `relation comprising cross members secured to both rings and which extend intermediate adjacent shoes, one or more of said cross members being engaged lby a shoe to effect rotation of said retaining ring asembly with said rotor.

2. A fiuid pump comprising a stator casing structure, a power shaft supported by said stator casing structure, a rotor secured on said shaft, said stator casing structure provided with a chamber having an annular peripheral cam surface eccentric to the shaft axis, said rotor having a plurality of angularly spaced radially extending fiuid pumping instrumentalities, each comprising a pump chamber and a pump plunger reciprocatingly supported by said rotor in said pump chamber, and a shoe movably carried on the outer end of the pump plunger and constructed t0 slidably contact the eccentric cam surface of said stator casing structure, uid intake and exhaust means for said pumping instrumentalities, and a free floating annular shoe retaining ring assembly disposed concentric with respect to the annular peripheral cam surface of the stator casing chamber and engaged with said shoes to retain same in position for operable contact with said cam surface and to restrain said shoes from rotary displacement about the pump plunger axis, said ring assembly being rotatable with respect to said rotor and to said stator casing structure, said annu-lar retaining ring assembly comprising a pair of concentric rings disposed concentric with and radially spaced inwardly of the `cam surface of said stator casing structure, and axially spaced to straddle said shoes, and angularly spaced cross member abutments secured to said rings and extending intermediate said adjacent shoes.

3. A fiuid pump as set forth and described in claim 2 wherein said cross member abutments are provided with portions projected radially outwardly of the external circumferential surface of said rings whereby to provide for positive engagement with the leading edge of said shoes.

4. In a fluid pump of the type having a rotor peripherally encircled by an annular cam surface eccentric with re- 7 spect to the rotor axis and radially actuable pistons carried by the rotor, a retainer structure comprising (a) shoe elements carried by said pistons and slidably engaging said cam surface,

(b) an annular shoe retaining ring assembly disposed concentric with and inwardly spaced from said cam surface and slidably engaged with said shoes, said shoes being disposed between the ring assembly and the cam surface,

(c) said shoes and retaining ring assembly having means coacting to support said ring assembly solely by said shoes against radial and axial disengagement therefrom,

(d) said means comprising grooves disposed in said shoes in a common plane disposed normal to the rotor axis, and said ring assembly comprising a pair of at spring coils each having a pair of circumferentially spaced end portions and an intermediate portion which axially spaces said end portions whereby said ring assembly is radially compressible and engages in said grooves at a radially expande-d position.

5. In a fluid pump of the type having a rotor peripherally encircled by an annular cam-surface eccentric with respect to the rotor axis and radially actuable pistons carried by the rotor, a retainer structure comprising (a) shoe elements carried by said pistons and slidably engaging said cam surface,

(b) an annular shoe retaining ring assembly disposed l concentric with and inwardly spaced from said cam 1 surface and slidably engaged with said shoes, said l shoes being disposed between the ring assembly and the cam surface, Y (c) said shoes and retaining ring assembly having means coacting to support said ring assembly solely by said said cross members extend intermediate adjacent shoe elements with one or more of said cross members being engaged by a shoe element to eiect rotation of said ring assembly.

References Cited by the Examiner UNITED STATES PATENTS i 9/1915 Hele-Shaw 103-161 4/1934 Vickers 103-161 MARK NEWMAN, Primary Examiner.

R. M. VARGO, Assistant Examiner.

Claims (1)

1. A FLUID PUMP COMPRISING A STATOR CASING STRUCTURE, A POWER SHAFT SUPPORTED BY SAID STATOR CASING STRUCTURE, A ROTOR SECURED ON SAID SHAFT, SAID STATOR CASING STRUCTURE PROVIDED WITH A CHAMBER HAVING AN ANNULAR PERIPHERAL CAM SURFACE ECCENTRIC TO THE SHAFT AXIS, SAID ROTOR HAVING A PLURALITY OF ANGULARLY SPACED RADIALLY EXTENDING FLUID PUMPING INSTRUMENTALITIES, EACH COMPRISING A PUMP CHAMBER AND A PUMP PLUNGER RECIPROCATINGLY SUPPORTED BY SAID ROTOR IN SAID PUMP CHAMBER, AND A SHOE MOVABLY CARRIED ON THE OUTER END OF THE PUMP PLUNGER AND CONSTRUCTED TO SLIDABLY CONTACT THE ECCENTRIC CAM SURFACE OF SAID STATOR CASING STRUCTURE, FLUID INTAKE AND EXHAUST MEANS FOR SAID PUMPING INSTRUMENTALITIES, AND A FREE FLOATING ANNULAR SHOE RETAINING RING ASSEMBLY DISPOSED CONCENTRIC WITH RESPECT TO THE ANNULAR PERIPHERAL CAM SURFACE OF THE STATOR CASING CHAMBER AND ENGAGED WITH SAID SHOES TO RETAIN SAME IN POSITION FOR OPERABLE CONTACT WITH SAID CAM SURFACE AND TO RESTRAIN SAID SHOES FROM ROTARY DISPLACEMENT ABOUT THE PUMP PLUNGER AXIS, SAID RING ASSEMBLY BEING ROTATABLE WITH RESPECT TO SAID ROTOR AND TO SAID STATOR CASING STRUCTURE, SAID FREE FLOATING ANNULAR SHOE RETAINING RING ASSEMBLY COMPRISING A PAIR OF AXIALLY SPACED ANNULAR RINGS ENGAGING THE RADIALLY INNER SIDES OF SAID SHOES, AND MEANS FIXING SAID RINGS IN SAID SPACED RELATION WITH RESPECT TO EACH OTHER, SAID MEANS FIXING SAID RINGS IN SPACED RELATION COMPRISING CROSS MEMBERS SECURED TO BOTH RINGS AND WHICH EXTEND INTERMEDIATE ADJACENT SHOES, ONE OR MORE OF SAID CROSS MEMBERS BEING ENGAGED BY A SHOE TO EFFECT ROTATION OF SAID RETAINING RING ASSEMBLY WITH SAID ROTOR.

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