US3211107A

US3211107A - Hydraulic pump or motor

Info

Publication number: US3211107A
Application number: US143476A
Authority: US
Inventors: Bush Vannevar
Original assignee: Stewart Warner Corp
Current assignee: Stewart Warner Corp
Priority date: 1961-10-06
Filing date: 1961-10-06
Publication date: 1965-10-12
Anticipated expiration: 1982-10-12
Also published as: GB1019294A; CH403490A

Description

Oct. 12, 1965 v. BUSH HYDRAULIC PUMP OR MOTOR 6 Sheets-Sheet 1 Filed 001;. 6. 1961 Oct. 12, 1965 V. BUSH HYDRAULIC PUMP 0R MOTOR Filed Oct. 6, 1961 6 Sheets-Sheet 2 Oct. 12, 1965 v. BUSH 3,211,107

HYDRAULIC PUMP OR MOTOR Filed 001:. a. 1961 e Sheets-Sheet s Haj.

5/ A 1 r a/we/ Oct. 12, 1965 v. BUSH HYDRAULIC PUMP OR MOTOR 6 Sheets-Sheet 4 Filed 001;. 6. 1961 Oct. 12, 1965 v. BUSH 3,211,107

HYDRAULIC PUMP R MOTOR I Filed Oct. 6. 1961 e Sheets-Sheet Mwew 7a,?

Vannewer 50:6

Oct. 12, 1965 v. BUSH 3,211,107

' HYDRAULIC PUMP OR MOTOR Filed Oct. 6. 1961 6 Sheets-Sheet 6 Y Z176. 7 g

United States Patent Office 3,211,107 Patented Oct. 12, 1965 3,211,107 HYDRAULIC PUMP R MOTOR Vannevar Bush, Jaffrey, N.H., assignor to Stewart- Warner Corporation, Chicago, Ill., a corporation of Virginia Filed (let. 6, 1961, Ser. No. 143,476 Claims. (Cl. 103-174) This invention relates to high pressure hydraulic units, and more particularly to hydraulic pump or motor units of the radial piston type having one or more variable volume chambers.

One device of this general type includes a housing, a rotatable eccentric, and two mating members movable relative to one .another to define each variable volume chamber. The first member reciprocates transversely of the housing while the second member moves on the eccentric in a circular path relative to the housing without rotating about its own axis. Relative reciprocation of the members varies the volume of the chamber and causes a torque about the eccentric mounting to convert between mechanical energy and fluid pressure energy. Inlet and outlet means alternately respond to movement of the members for communicating a working fluid to and from each chamber.

A major limitation of existing hydraulic units is the presence of surfaces which slide upon one another while being pressed together with forces per unit area that can be enormously greater than the fluid pressure. The sliding surfaces must be separated from each other by a lubricating film of fluid regardless of the magnitude of the forces pressing the surfaces together. If the supporting film is destroyed, metal-to-metal contact will occur and the life of the unit wil be greatly reduced. The use of a high-viscosity lubricating fluid, which cannot be readily squeezed out from between the surfaces, is impracticable because there would be excessive losses due to fluid friction. Thus, for maximum success, the lubricating film must have a load carrying capacity which increases proportionally to the biasing forces, or the pressure of the working fluid.

A second major limitation of existing hydraulic units is the presence of couples, or cocking moments, between mating members such as between the piston and cylinder and/or between either the piston or cylinder and its adjacent reaction member. These couples are caused by the manner in which reaction torque is transmitted to the machine. The parts are arranged so that the fluid pressure exerts an axial force on the piston moving in the cylinder. The force is absorbed by the reaction members acting on a moment arm to produce a torque about the center of the machine. The reaction torque must be transmitted from one opposing reaction member of the machine through the piston .and cylinder to the other opposing reaction member. Because of the arrangement of parts, there is a couple, or cocking moment, set up which causes the parts to be tilted with respect to each other. The moment arm of a particular couple may be very small, resulting in the application of extremely large forces. Moreover, due to the tilting, these large forces are applied over a very small area approaching line contact instead of area contact. These large forces and small or negligible areas result in enormously large forces per unit area, or pressures, which cannot be supported by an oil film. Metal-to-metal contact will then occur. Thus, it is desirable in a dependable hydraulic machine to eliminate all such couples.

Another limitation to full success of any hydraulic unit is leakage of the working fluid past the mating parts from the high pressure region or chamber to the low pressure region. Leakage is an important consideration since the amount of leakage is proportional to the fluid pressure. When the fluid pressure is low the volume of fluid leaked is generally small compared to the active volume of the high pressure region. But, as the pressure is increased, the fractional part of the working fluid that leaks rises, and at very high pressures it can become intolerable. Consequently, a high pressure hydraulic unit must have high resistance leakage paths past the mating parts between the high and low pressure regions.

Another limitation and potential problem of high pressure hydraulic units is porting the working fluid to and from each chamber. Generally, the chamber wall has a port that is covered and uncovered by a movable member supported on a lubricating film adjacent the wall. As the port is opened, high and low pressure regions are connected resulting in fluid flow through the port and possible displacement of the member into direct engagement with the wall. To minimize this condition it is desirable to port the chamber symmetrically of the member to equalize the high and low pressure regions on opposite sides of the member.

Cavitation of the working fluid within the fluid ports or passages is another problem relating to porting,-particularly Where the fluid is under low pressure, as is the intake fluid of a pump. In conventional high pressure hydraulic units of the radial piston type, the working fluid is communicated to and from the unit in relatively small passages surrounding the shaft. The shaft, or a coupled extension thereof rotating with the shaft, connects the passages through the fluid ports to the working chamber. All the structure defining the ports and passages is generally between the axis of the shaft and the working chambers. This necessarily results in a design wherein the passages are relatively small, and the ports are quite limited in dimensions. Since at high operating speeds there is insuflicient time to accelerate the low pressure fluid through the small ports and passages without causing cavitation it has been necessary to pressurize the intake fluid of a pump.

High pressure piston-type hydraulic units commonly operate at some specific unchangeable volumetric displacement per cycle. This is a definite drawback, since frequently it is desirable to vary the displacement per cycle for various power requirements, or for various cyclic frequencies. However, the variable displacement high pressure hydraulic units available in the past generally have been quite complicated and lacked dependability for long periods of industrial applications.

Accordingly, an object of this invention is to provide a high pressure hydraulic pump or motor unit having a combinationof design features that eliminates all couples, or cocking moments, between the adjacent parts caused by the working fluid pressure, and that yields fluid films capable of supporting separated from each other the mating surfaces of the adjacent parts, regardless of the magnitude of the working pressure.

Another object of this invention is to provide a high pressure hydraulic pump or motor in which leakage of the working fluid between the high and low pressure regions is minimized.

Another object is to provide a hydraulic unit in which each working chamber is ported symmetrically to eliminate side thrust of its port controlling member.

Another object is to provide a high speed hydraulic pump in which the low pressure fluid can be ported without cavitation.

Another object is to provide a high pressure hydraulic unit in which the volumetric displacement per cycle can be adjusted.

Another object is to provide a hydraulic unit that is easily fabricated while yet being dependable in operation.

The particular embodiments of this invention, both as to their structure and mode of operation, will be better understood by reference to the following specification including the drawings forming a part thereof wherein:

FIG. 1 is an elevational view of an embodiment of the hydraulic unit forming a part of this invention;

FIG. 2 is a section view taken on line 22 of FIG. 1;

FIG. 3 is an elevational view, partly in longitudinal section, as seen from line 33 of FIG. 2;

FIG. 4 is a perspective view of a cylinder member used in the hydraulic unit;

FIG. 5 is a perspective view of a piston member used in the hydraulic unit;

FIG. 6 is a perspective view of a guide block used in the hydraulic unit;

FIG. 7 is an elevational view of a manifold used in the hydraulic unit;

FIG. 8 is an elevational view as seen from the rear of FIG. 7;

FIG. 9 is an elevational view, partly in section, of a second embodiment of the hydraulic unit forming a part of the invention;

FIG. 10 is a sectional view taken on line 10-10 of FIG. 9;

FIG. 11 is an elevational view, partly in section, of a third embodiment of the hydraulic unit forming a part of this invention;

FIG. 12 is an enlarged view as seen from line 12-12 of FIG. 11;

FIG. 13 is an enlarged view as seen from line 1313 of FIG. 11;

FIG. 14 is an elevational view of a slotted separating port plate used in a fourth embodiment of this invention; and

FIG. 15 is a sectional view taken on line 15--15 of FIG. 14.

In general, a hydraulic unit utilizing the teachings of this invention includes a stationary housing centrally supporting a rotatable shaft having an eccentric thereon. The housing has concave pockets or channels, extending transversely of the shaft, which are open toward the eccentric. A cylinder member is matably received in each pocket and defines a central cylinder open towards the eccentric. A cruciform piston is rotatably mounted on the eccentric and has radial arms each of which is matably received in one of the cylinders. Upon rotation of the shaft each piston arm reciprocates within its cylinder to define a variable volume chamber, while each cylinder member simultaneously reciprocates within its pocket. Each variable volume chamber moves with its defining piston arm and cylinder member so that it is always disposed symmetrically thereof to eliminate reaction couples therebetween. A restricted passage intercommunicates the fluid chamber and the interface of the moving and reaction members to establish a pressurized supporting fluid film therebetween. The housing has peripherally located inlet and outlet ports associated with each fluid chamber that separately communicate with the chamber in certain operate positions of the mating members. The mating members all mate on relatively large surfaces supported spaced from each other on a film of fluid pressurized from the working fluid.

Referring now to the drawings, and particularly to FIGS. 1, 2 and 3, a preferred embodiment includes a housing 10 having spaced port plates 48 (FIG. 2) presenting mutually facing substantially parallel surfaces 14 that sandwich four spaced shoe members 50 (FIG. 3). Each shoe member 50 has an inwardly facing substantially straight surface 16 thereon extending between surfaces 14 of port plates 48. The opposite surfaces 16 preferably are parallel to each other and disposed at angles 90 from the adjacent surfaces 16. The spaced surfaces 14 of port plates 48 and the surfaces 16 of shoe members 50 define a generally enclosed rectangular cavity 17 within the housing 10. The cavity 17 may be described as comprising four channels or pockets 12 defined by the confronting surfaces 14 and each interconnecting surface 16 on the shoe members 50.

Each pocket 12 matably receives a cylinder member 18, the cylinder member being slidable along a path generally parallel to the interconnecting surface 16. Each cylinder member 18 (FIG. 4) is generally U-shaped, with spaced leg portions 20 defining mutually facing straight parallel surfaces 22. The surfaces 22, along with the spaced surfaces 14 of the pocket 12, define a recess or cylinder 19 open inwardly of housing 10.

A single cruciform piston member 24 (FIGS. 3 and 5) is disposed centrally of the cavity 17 and has four rigid arms 26 each matably received in respective cylinder 19. The piston 24 is mounted centrally on eccentric portion 28 of a shaft 30 rotatably supported by the housing 10. As shaft 30 rotates piston 24 moves in a circular path about the axis of the shaft without rotation about its own axis. The arms 26 of piston 24 mate with cylinder members 18 to move the cylinder member relative to the housing 10. Each piston arm 26 thereby reciprocates within its mating cylinder member 18 while simultaneously reciprocating the cylinder member along the respective surface 16. Since the opposite surfaces 16 are parallel to each other, the opposite cylinder members 18 move in the same direction at the same time. Each cylinder member 18 and its mating piston arm 26 defines a variable volume chamber 32.

The port plates 48 have two aligned inlet ports 34 and two aligned outlet ports 36 associated with each chamber 32 and terminating at spaced surfaces 14. The edges of inlet ports 34 and outlet ports 36 adjacent chamber 32 are preferably parallel to the confronting surfaces 22 of cylinder member 18 and spaced apart a distance slightly greater than the distance between the surfaces 22. This slight overlap reduces direct port-to-port leakage. The ports of each chamber 32 are positioned symmetrically of the top dead center position so that both the inlet and outlet ports are closed when the piston arm and cylinder member are in the top dead center position. The length of the adjacent edges of the ports are preferably as long as the stroke of piston arm 26.

As the shaft 30 rotates each cylinder member 18 reciprocates along the intermediate pocket surface 16, first to one side of its top dead center position, and then to the other side. The inlet ports 34 and outlet ports 36 are respectively uncovered or opened during each alternate half-revolution of shaft 30 by the lateral harmonic displacement of the cylinder member 18. The communicating openings between the respective ports and each variable volume chamber 32 define generally rectangular slots extending the length of the chamber 32. At all positions of each cylinder member 18 other than its top dead center positions and the small lateral displacement on both sides thereof corresponding to port overlap, either the inlet ports 34 or the outlet ports 36 are at least partially open.

The aligned inlet ports 34 (FIG. 3) are all located clockwise of the top dead center positions, while the aligned outlet ports 36 are all located counterclockwise of the top dead center positions. Consequently, the opposite chambers 32 are always out of phase with each other so that, while top chamber 32 (FIG. 3) is on the intake, the bottom chamber 180 away is on the exhaust. Similarly the side chambers 32 are in opposite phases with respect to each other while being out of phase from the top and bottom chambers.

Manifolds 40 (FIGS. 2, 7 and 8) communicate with hydraulic fluid sources (not shown) to supply the ports and chambers with a hydraulic fluid. Hydrauli fluid thus is admitted to each chamber 32 on the inward stroke of piston arm 26 toward shaft 30 and discharged from each chamber on the outward stroke of the piston arm sure multiplied by the piston area.

away from the shaft. This operation is the same when the unit is used as a pump or as a motor.

The pressure of the fluid in each of the chambers 32 causes a force to be exerted on the piston arm 26 and cylinder member 18. This force is exerted in a direction parallel to the longitudinal axis of piston arm 26 and is equal to the product of the fluid pressure and the area of the piston. Reaction to this force is absorbed by the eccentric 28 and shoe member 50. This reaction force acting on the effective moment arm of the eccentric 28 about the shaft 30 converts between pressure energy of the fluid and mechanical energy of the shaft.

Each fluid chamber 32 is always located symmetrically of a line disposed parallel to the direction of bias extending through the geometric centers of the reaction surfaces of the fluid biased

members

18 and 24 mated with its respective

reactive members

50 and 28. The entire reaction caused by the fluid in chamber 32 can be represented as being transmitted through these reaction centers. Since the reaction centers are also the geometric centers, the fluid biased members are uniformly biased against the

reaction members

28 and 50. Since there are no couples caused by the chamber fluid pressure between each fluid biased member and its reaction member, there will be no couples between the fluid biased

members

18 and 24 themselves. Thus none of the adjacent mating surfaces will be tilted relative to one another by the fluid pressures to affect line contact or to squeeze asymmetrically a lubricating fluid film from between the adjacent members.

Two members having mated adjacent surfaces biased together by a force applied to the members can be supported separated from each other by a lubricating fluid supplied continuously between the mated surfaces intermediate the edges thereof. Flow of the fluid to the edges of the mated surfaces establishes a lubricating fluid film between the surfaces. The roughness characteristics of the mated surfaces determine the minimum thickness of the fluid film required to prevent direct metal-to-metal contact. The flow characteristics of the lubricating fluid determine the fluid flow and pressures required to maintain the fluid filmat the minimum thickness.

The film pressure varies from a maximum intermediate the mated surfaces to a minimum at the edges thereof. The leakage of the film past the edges of the mated surfaces varies proportional to the supplied fluid pressure and to the cube of the film thickness. The load supporting capacity of the film varies proportional to the supplied fluid pressure and to the film area. At balanced conditions, the integrated mathematical product of the film pressure acting on the mating area between the members will equal the biasing force to maintain the members spaced from each other by the thickness of the film.

Since the fluid biasing force on

members

18 and 24 against the

reaction member

28 and 50 is proportional to the chamber pressure, it is desirable that a proportionately high pressure supply the lubricating film at the reaction area between the adjacent members. Passages 42 (FIGS. 2 and 3) of restricted cross-section in each of the fluid biased

members

18 and 24 extend from the chamber 32 to the interface of the

adjacent reaction members

28 and 50. A limited quantity of hydraulic fluid under a proportionately high pressure as that in chamber 32 continuously flows from chamber 32 through each passage 42 to the reaction area between the members.

This continuously flowing fluid under pressures proportional to the biasing force establishes the pressurized lubricating film between the adjacent members.

In order to support the load without metal-to-metal contact, the average pressure in the lubricating film multiplied by the film area must equal the chamber pres- The pressure in the chamber 32 is the sum of the pressure drops across the restriction 42 and across the fihn. If the film thickness should increase, the film resistance will decrease, thus increasing the fluid flow. The pressure drop across the restriction will thus increase to reduce the average film pressure. If the film thickness should decrease, the opposite will occur, i.e., the flow will decrease, the pressure drop across the restriction will decrease to increase the average film pressure. There is only one film thickness at which the average film pressure multiplied by the film area will equal the chamber pressure multiplied by the piston area. The film thickness will vary until this correct thickness is reached and balance is attained. If the film thickness should vary, for any reason, a net force will be exerted which will restore the film thickness to the correct value.

In design, it has been established that the restriction should be chosen so that the balance occurs at a film thickness on the order of 0.0005 inch. This is a much thicker film than might be needed from considerations of surface roughness because with properly finished surfaces the roughness will be approximately 0.000005 inch. Thinner films are not desirable because the force required to shear an oil film varies inversely with the film thickness and thus the friction losses increase substantially as the film thickness is reduced.

For a positive balance and thus a stable support of loads, it has been found that the pressure drop across the restriction 42 should be one-third to one-half of the chamber pressure. The reaction areas are then chosen to produce the desired film thickness. When the dimensions have been chosen so that stable operation occurs, the film thickness will not change appreciably with chamber pressure. When the chamber pressure is increased, the pressure drop across the restriction and the average film pressure both will increase, since the sum of these will always equal the chamber pressure. But the film thickness will remain nearly constant. This observed fact is extremely important because it permits operation at very high working pressures without squeezing out the oil film, thus avoiding metal-to-metal contact. Moreover, a stable oil film limits the high frictional losses which would otherwise occur with very thin films.

With the design just described oil is supplied to the film only as needed, thus limiting leakage and the resulting energy losses.

Metal-to-metal contact is avoided only when two conditions are met: (1) there is a stable film capable of supporting the load under all operating conditions, and (2) the load is applied symmetrically with respect to the film areas. Condition (1) is achieved as previously described. Condition (2) will require further explanation.

Referring to FIGURE 3, it will be noted that the useful force exerted by the fluid in the chamber 32 can act only along a line parallel to the longitudinal axis of the piston arm 26. This axis passes through the center of the eccentric 23 and symmetrically of the base of cylinder member 18, mat-able with shoe member 50. The force acting be tween the eccentric 28 and the shoe member 50 exerts a turning moment about the center of shaft 30 that is equal to the force multiplied by the eccentricity normal to the line of application of the force. As the eccentric 28 revolves, a point on the piston 26 moves in a circle while the cylinder member 18 oscillates along shoe member 50. The important point is that the torque is always transmitted to the machine by means of the centrally applied force between the moving eccentric 28 and the stationary sohe member 50 on a moment arm about shaft 30. There are no couples, or cocking moments, exerted between the members which tend to cock the piston in the cylinder or which tend to tilt the cylinder member 18 with respect to the shoe member 50. In existing hydraulic units these couples or cocking moments are present and often are very large in magnitude. Indeed, in many designs it is the only means of transmitting torque to the frame of the machine and hence is equal to the shaft torque. These couples and the resulting tilting moments result in forces being applied which are asymmetrical with respect "Z to the fluid film separating the members. Such asymmetrical application of force inevitably destroys the balance previously described and results in line contact between the metal surfaces.

Although the description and discussion have referred mainly to the fluid film between cylinder member 18 and shoe member 50, the same principles apply to the fluid film between the bore of the piston 24 and the eccentric It is thus seen that the combination of balanced oil films and the elimination of cocking moments yields a major advance in the design of hydraulic equipment.

Considering the construction of the unit more in detail, and referring specifically to FIGS. 2 and 3, housing includes spaced bearing plates 46 having inner sides which sandwich the outer sides of the above-mentioned spaced port plates 48. The inner sides of port plates 48 form the substantially flat parallel surfaces 14 of pockets 12. The port plates 48 are maintained separated by the previously mentioned four shoe members 50 and by four guide blocks 52 (FIG. 6). The guide blocks 52 each have spaced guide surfaces 56 which face and are spaced from two adjacent shoe member bearing surfaces 16. Bolts 58 and dowel pins 60 extend through aligned openings in the bearing plates 46, port plates 48, shoe members 50 and guide blocks 52 to secure them together rigidly.

Hubs 64 (FIG. 2) of bearing plates 46, land the port plates 48 have generally aligned central openings 66 extending completely through the housing 10. The peripheries of openings 66 in bearing plates 46 snugly receive the outer races of bearing units 68. The shaft extends through the aligned openings 66 in the bearing plates and port plates and engages the inner races of bearing units 68. Bearing units 68 preferably are self aligning double guide roller bearings which adequately support the shaft 30 against both longitudinal and lateral forces. The eccentric 28 is a generally cylindrical section integral with or keyed to shaft 30 intermediate the inner races of bearing units 68. The eccentric 28 is disposed to rotate within the central openings 66 of the port plates 48.

End plates 70 engage the hubs 64 of bearing plates 46 and have O-ring gaskets 71 disposed to ensure a sealed fit therebetween. Bolts (not shown) extend through openings in the end plates 70 into threaded taps in the hubs 64 to secure the two together. Each end plate 70 has a central aperture 72 through which the shaft 30 extends. Annular spacer elements 74 are tightly received on shaft 30 over interposed O-ring gaskets 75 and are rotatable as a unit with the shaft. Each spacer 74 is received in the end plate aperture 72 and rotatable therein in sealing relationship with O-ring gasket 77. A threaded bore 76 through each end plate 70 to the interior or sump space of the unit provides for connection to a hydraulic line (not shown).

Counter-weights 78, keyed to shaft 30 adjacent end plates 70, equalize the dynamic unbalance caused by the rotating piston 24 and reciprocating cylinder members 18. Since all of the moving parts follow predetermined paths in parallel planes, dynamic balancing can be achieved by the two counter-weights 78, as is well known in the art. Cup-shaped covers 80 each having a central base opening 79 and a peripheral slot 81 cover counter-weights 78 and end plates 70 and are secured to the end plates by appropriate means (not shown). Nuts 82 threaded onto the threaded portions of shaft 30 tightly engage interposed lock washers 83 and counter-weights 78.

Thus the eccentric 28, inner races of the bearing units 68, the spacers 74, and counter-weights 78 rotate as a unit with the shaft 30. It is to be understood that there is suflicient axial clearance between piston 24 and the hearing units 68 to permit relative rotation between the members without binding or excessive wear. Keyed portions 84 of shaft 30 project outwardly of end covers 80 for connection to a mechanical device such as a driving motor (not shown) or to a driven unit (not shown) depending whether the unit is used as a pump or motor.

Annular oil jacket 86 surrounds the unit 10 at its midportion and is sealed thereto by a pair of O-ring gaskets 87 disposed in annular notches in the bearing plates 46. Port plates 48 preferably have enlarged recesses 89 (FIG. 2) adjacent the ports remote from each chamber 32 which reduce the hydraulic flow resistance through each port. Passages 91 in bearing plates 46 intercommunicate recesses 89 in the port plates 48 with a plurality of uniformly spaced counterbored openings 93. The interior or sump space of the unit is completely sealed by the various O-ring gaskets. The only paths by which hydraulic fluid can enter or leave the unit is through the threaded bores 76 in the end plates 70 and the openings 93 in bearing plates 46.

Manifolds 40 connect each chamber communicating openings 93 with the appropriate intake or exhaust hydraulic source (not shown). Each manifold 40 has an inner tube 88 and an outer tube (FIGS. 2 and 7) having communicating pipes 92 projecting from the tubes towards the housing. A stepped flange 94 on the free end of pipe 92 is secured to bearing plate 46 against interposed Oring gasket 95 and into the counterbored opening 93. The manifolds 48 are identical so that adjacent pipes 92 are alternately connected to the inner and

outer tubes

88 and 90 to correspond to the alternate positioning of the inlet ports 34 and outlet ports 36 about the unit. Consequently, as viewed in FIG. 2 the outer tube 90 on the left manifold 40 and the inner tube 88 on the right manifold 40 are associated with the intake fluid, while inner tube 88 on the left manifold and the outer tube 90 on the right manifold are associated with the exhaust fluid. Passages 96 (FIGS. 1 and 7) extend from the intake and exhaust tubes in each manifold and secure T connections 1% between opposed flanges 98. The Ts 100 each have a threaded bore 101 which receive a tube (not shown) respectively connected to the intake and exhaust sources of fluid (not shown).

Consequently, any fluid directed to the intake T 100 is delivered to opposite sides of chamber 32 equally. The fluid is similarly exhausted from opposite sides of chamber 32 through two manifolds having equal fluid pressures. This symmetric porting of each chamber equalizes the high or low pressure regions on opposite sides of the cylinder member 18 and piston arm 26 to eliminate biasing fluid forces tending to move either member towards one port plate 48 or the other.

It can be noted in FIGS. 2 and 3 that the

fluid ports

34 and 36 and manifolds 40 are located on the periphery of the unit adjacent the chambers 32. This arrangement permits the cross-section of both the ports and manifolds to be large and of adequate sizecompared to the maximum volume of each chamber 32. Consequently, for each working stroke of any piston arm 26, the fluid in the manifold is displaced only a short distance. Even when the unit is operating at a high speed and each working stroke takes only a fraction of a second, the fluid in manifold 40 only needs to be accelerated slightly to keep up with the full volumetric displacement. This is particularly true since each chamber 32 is supplied by two manifolds through two ports. This porting arrangement reduces cavitation to such an extent that high speed pumping operations are generally possible without the necessity of having a pressurized intake.

FIG. 4 shows one of the cylinder members 18 in perspective. Each cylinder member 18 includes a generally U-shaped body portion having opposed flat parallel surfaces 102 closely matable when assembled in the pocket 12 with the surfaces 14 of port plates 48. The base portion has a straight surface 104 partly defined by protruding toes 106 having flat surfaces 108 therein oppositely facing and extending parallel to surface 164. The surface 104 mates with and reciprocates along bearing surface 16 of the shoe member 50 while the toes 9 106 extend between the guide surfaces 56 of the guide blocks 52 and the bearing surface 16. The distance between guide surfaces 56 and bearing surface 16 is slightly greater than the distance between the

surfaces

104 and 108 to provide for free cylinder member movement therebetween.

Surfaces

56 and 108 are engageable only when the unit has stopped and gravity or residual fluid pressure between the

surfaces

104 and 16 biases cylinder member 18 from surface 16.

Leg portions .20 define the mutually facing straight surfaces or'faces 22, previously mentioned, which extend parallel to each other and perpendicular to straight surface 104 symmetrically of its ends. Base surface 110 extends between surfaces 22 and surfaces 102. A shallow groove or slot 116 extends along the intermediate portion of bearing surface 104 spaced from the edges thereof and is interconnected with base surface 110 by aperture 118. An insert 120 secured within the aperture 118 has a through-bore of very small cross-section, generally only a few thousandths of an inch in diameter, which defines one of the above-mentioned restricted passages 42.

Generally C-shaped braces 122 fit over the free ends of legs 20 and engage flat surfaces 112 and ribs 114. Bolts 124 extend through interposed lock washers 126 and the apertures 125 in braces 122 into threaded taps 123 in surface 112. The braces 122 constrain the free ends of the legs 20 from cantilever type deflection when hydraulic pressure is generated in chamber 32. Surfaces 22, which define two sides of chamber 32, are located symmetrically from the ends of the cylinder member along the bearing surface 104. Thus fluid pressure in chamber 32 will uniformly bias the cylinder member 18 against shoe member 58, causing no couples tending to establish line contact between the

adjacent surfaces

16 and 104.

FIG. shows a preferred form of the cruciform piston 24, which includes hub 128 having central cylindrical through bore 130. Arms 26 project from hub 128 radially of the bore 130 and are spaced 90 apart. Each arm is of uniform rectangular cross-section defined by flat parallel surfaces 132- disposed perpendicular to the axis of said bore, straight parallel surfaces 134 disposed ferential groove or slot 138 in the periphery of throughbore 130 extends over an arc of approximately 70 equidistantly of the center of each piston arm 26. Opening 140 in each piston arm 26 extending between the slot 138 and surface 136, receives an insert 142 therein having a through passage of very small cross-section which defines one of the previously mentioned restricted passages 42.

During operation of the unit, hydraulic fluid enters each chamber 32 through inlet ports 34 and is discharged from the chamber through outlet ports 36. Regardless of whether the unit is used as a pump or motor, the fluid in each chamber 32 is under high pressure at some time during the cycle. The pressurized fluid acts on

surfaces

110 and 136 of the cylinder member and piston, respectively, to bias them apart in the direction of piston arm 26 and cylinder 19. Since each chamber 32 is symmetrically disposed with respect to the reaction areas of its defining moving

members

18 and 24, the fluid biasing force produces no couples between the members. Reaction of this biasing force is absorbed by shoe member 50 and by eccentric 28.

Each restricted passage 42 communicates limited quantities of high pressure fluid from the chamber 32 to

slots

116 and 138 in the inter-faces between the fluid biased

members

18 and 24 and the

reaction members

28 and 50. The hydraulic film varies in pressure somewhat linearly from its high at the slot to its low at the edges of the sur- 18 face. Even though piston 24 is biased toward eccentric 28, and the cylinder member 18 toward the shoe member 50, by the continuingly changing resultant force from the changing fluid pressures within chamber 32, a supporting fluid film is maintained between the mating adjacent surfaces. The reasons for this are two-fold, since: (1) each chamber 32 communicates directly with the above-mentioned reaction areas to establish a proportionately high pressure supporting film, and (2) there are no couples between any of the mating surfaces caused by the fluid pressure to reduce area contact to line contact. Consequently at all times the moving fluid biased members 18 and 24- are floated on hydraulic film-s adjacent the

respective reaction members

50 and 28.

The fluid forced from chamber 32 past the mating surfaces 102 and 14 is directed to the sump space. The fluid forced past the shoe member 50 and the cylinder member 18 is directed in part to the peripheral region 146 (FIG. 3) of the unit. The oil in the peripheral region 146 is circulated in the oil jacket 86 and admitted to the sump space between the guide blocks 52 and cylinder members 18. Slots 148 (FIG. 6) in the guide blocks decrease the flow resistance of the fluid to the sump space. The fluid collected in the sump space is communicated through bores 76 in end plates 70 to the reservoir of the hydraulic system.

Since each cylinder member 18 and piston arm 26 are matable With the spaced surfaces 14 of the pocket, the flow path from the high pressure of the low pressure region is long and of high resistance. The leakage from each chamber 32 thus is minimized. However, any leakage is not totally wasted as it lubricates the members for friction free movements relative to each other.

FIGS. 9 and 10 show a second embodiment similar in part to that already disclosed. Like components will thus be designated with the same reference numerals. The embodiment includes housing 10a having bearing plates 46a sandwiching a plurality of separating port plates 48a, shoe members 50a and guide blocks 52a. Housing 10a is secured together, and to supporting feet 154 by through bolts 58a. Shaft 38a extends through aligned openings in the bearing plates 46a and is supported for rotation with; in bearing units 68a. Three cylindrical eccentric portions 28a are keyed or otherwise formed adjacent each other on shaft 30a, the end or outer eccentrics being in phase, with respect to the longitudinal axis of the shaft, and 180 out of phase with the intermediate eccentric.

Cylinder members 18a reciprocate in pockets 12a defined by port plates 48a and shoe members 50a. Three pistons 24a each having four equally spaced radial arms 26a are respectively disposed on the eccentric portions 28a, with arms 26a matable with the cylinder members 18a. Rotation of shaft 30a reciprocates the three pistons 24a relative each mating cylinder member 18a while simultaneously reciprocating the cylinder member along bearing surface 16a. The reciprocating piston arms 26a and cylinder members 18a define the variable volume chambers 32a. Thus, each piston 24a and its mating cylinder members 18a, represent a stage similar to that of the fiirst embodiment.

Each chamber 32a is symmetrically ported in the manner substantially as that already disclosed. However, the inlet ports 34a and outlet ports 36a communicate respectively with internal radial passages and 162 in port plates 48a. The

passages

160 and 162 communicate respectively with spaced longitudinally extending

channels

164 and 166 through the port plates 48a and shoe mem bers 50a. Each of the

channels

164 and 166 extends to an annular inlet 168 or outlet 170 internal manifold in one or the other of the bearing plates 46a. Threaded bores 174 and 176 in the bearing plates communicate respectively with the inlet and outlet manifolds 168 and .170 providing ready connection means to the hydrauli sources (not shown).

The inlet annular manifold 168 thus communicates 1 1 with each longitudinal passage 164 which in turn communicates with the inlet ports 34a through the radial passages 160. Similarly, the outlet annular manifold 170 communicates with each outlet port 36a through longitudinal passages 166 and radial passages 162.

Each reciprocating cylinder member 18a alternately covers and uncovers the inlet and outlet ports for communicating the hydraulic source with the defined chamber 32a. As shown in FIG. 10, upper chambers 32a of the outer stages are on intake, while the lower chambers of the outer stages are on exhaust. Conversely the upper and lower chambers of the intermediate stage are on exhaust and intake, respectively.

Preferably the piston arm areas of surfaces 136a of the outer stages are equal, with their combined areas being equal to the piston arm areas of the inner stage. Since the strokes of each stage are the same, the fluid delivery and torque of the outer stages are equal to and 180 out of phase with the inner stage. Also, since the opposite piston arms of the inner and outer stages are simultaneously operating on the same phase of the cycle (either intake or exhaust), the opposed biasing forces of the stages do not appear as loads on the bearings 68a, but substantially cancel each other. Similarly the unit is balanced dynamically since the mass of the outer stages counteracts the mass of the inner stage.

FIGS. 11, 12 and 13 disclose a third embodiment which is particularly adaptable as a variable displacement hydraulic unit. A pair of

frames

180 and 182 secured together by bolts 184 clamp two

adjacent housings

186 and 188 snugly against one another. Shaft 30b is rotatably mounted on hearing units 68b and has two adjacent eccentric portions 281) in positional relationship 180 out of phase with respect to each other. Housing 186 is aligned with one eccentric 28b and is fixed rigidly to the frame 180. Housing 188 is aligned with the other eccentric 28b and is movable about shaft 301) relative to the fixed hous ing 186. The movable housing 188 is rotated by hand wheel 190 fixed on shaft 191 through mating worm gear 192 and annular rack 194 secured respectively to shaft 191 and housing 188.

The housings include spaced separating

plates

48b and 196, and 198 and 200, respectively, which sandwich shoe members 50b and guide blocks 52b to define the inwardly facing C-shaped pockets 12b. Cylinder members 18b and arms 26b of piston 24b are matably disposed in the pockets and reciprocate relative to each other to define variable volume chambers 32b. The pistons 24b in each housing are actuated by eccentric portions 28b on shaft 30b.

To simplify the disclosure of the fundamental operation of the unit each stage is shown to have only two chambers 32b. It will be understood, however, that the preferred embodiment will include more than two chambers per stage, presumably four equally spaced chambers as shown in the first two embodiments.

The separating plate 48b of fixed housing 186 has an inlet port 34b and an outlet port 36b associated with each chamber 321?, and is similar to the port plates previously described. Separating plate 196 of fixed housing 186 has shallow indentations or blind ports (not shown) aligned with the inlet ports 34b and outlet ports 36b of plate 48b. The shallow indentations balance in part the low pressure region in the chamber caused by porting of the fluid. The separating plates .198 and 200 of moving housing .188 have no inlet and outlet ports therein, but have openings and slots to be discussed hereinafter.

The separating plates 196 and 1 98 have adjacent surfaces that are substantially identical. The mating surfaces have a series of separately matched slots 2 extending circularly about the shaft b at given radii each through -an angle of approximately 90 as shown in phantom in FIG. 13. The matched slots of the plates overlap to form a continuous passage from one end of one slot to the opposite end of the other slot through a maxieliminating couples between the members.

mum angle equal to the arc of the two matched slots, minus the overlap, or [approximately 1 Openings .204 extend through each separating plate and communicate with the slots 202 therein. The openings 204 are spaced apart and at a common radius from the center of the plates to communicate the variable volume chambers 32b of one stage with like or corresponding chambers 32b of the other stage. Each chamber 32b of the stationary housing 186 thus has a continuous fluid communicating passage with the corresponding chamber 32b of the movable housing 188.

As shown in FIG. 13 the two housings are rotated an angle A relative to one another so that the intercommunicated chambers are in other than phase relationship. When angle A is equal to 0 the stages are in phase and the corresponding pistons of each stage move in the same direction at the same time relative to its mating cylinder member. Thus, the intercommunicated chambers 32b are on intake or on exhaust at the same time. Consequently, when inlet port 3412 in fixed housing 186 is open the fluid is communicated to the intercommunicated chambers 32b in the fixed and movable housings to fill both chambers completely. The reciprocating cylinder members of the stationary housing 186 control the porting to and from the chambers of both housings.

When the stages are in phase (when angle A is equal to 0) the total hydraulic flow to and from the unit is additive and is equal to the sum of the intercommunicated chamber volumes. As the housings are rotated relative to each other and angle A becomes larger than 0", the stages are actuated in out-of-phase relationship. The total fluid fiow to and from the unit will then be reduced. This is because the volume change of chambers 32b in fixed housing 186 is partially counteracted by a different volume change of its intercommunicated chambers 32b in moving housing .188 for an incremental rotation of the shaft 30b.

When the two stages are rotated so that angle A is equal to 180, the stages are in opposite phase relationship with respect to each other. The volume changes of the intercommunicated chambers are then substantially opposite each other for a given rotation of the shaft 3017. Consequently, the total volume to and from the unit is effectively reduced to zero. The hydraulic fluid in the unit is surged back and forth between the intercommunicated chambers in the stationary and movable housings.

Thus, the resultant how to and from the unit can be varied as desired from its maximum displacement (the sum of the two stages) when the stages are in phase to its minimum displacement (approximately zero) when the stages are 180 out of phase.

FIGS. 14 and 15 show a separating plate, corresponding to plate 198 of FIG. 11, operable for a variable displacement hydraulic unit having four equally spaced chambers for each stage. The plate has matched slots 205 on two different radii and chamber communicating openings 208. Radial passages 210 between the larger radius slots 206 and openings 208 align the openings 208 with the chambers 3212, while yet not interfering with the separate independent action of each slot. llug 212 closes the outer end of passage 210.

It is thus seen that the teachings of this invention have substantially eliminated the defects of prior hydraulic units. The fiuid pressures generated in the unit are transmitted through reaction centers of the various chamber defining members symmetrically of the members, thus The fluid biased members are floated spaced from the reaction members on a continuous pressurized fluid film. Each fluid chamber is defined by mating members having high resistance flow paths therebetween to minimum leakage. Fluid porting of each chamber is ample to eliminate cavitation. The various hydraulic units disclosed are reliable, while yet not prohibitive by construction cost or complex components.

Various embodiments disclosed herein have been built to operate at speeds up to 5,000 r.p.-m. and the fluid pressures up to 5,000 psi. A unit similar to that described in FIG. 1 having 1" square piston arms with a /2" stroke has a total displacement "of 2 cubic inches per revolution. The flow rate is approximately 45 gallons per minute at 125 hydraulic horsepower. The unit weighs but 65 pounds.

A unit as disclosed in FIG. 9 having intermediate stage piston arms /2" by /2" with the outer stage piston arms /2" x A" has approximately 40 gallons per minute fluid flow with 120 hydraulic horsepower. The unit weighs approximately 75 pounds.

While various specific embodiments have been shown, it will be obvious to those skilled in the art that many changes can be made without departing from the spirit of the invention. Thus, while the embodiments shown included stagm having two or four equally spaced chambers,

many other chamber combinations for each stage are possible. Thus a hydraulic unit having stages with three,

a first member received in the pocket and having a straight bearing surface matably adjacent the support surface and reciprocable thereon, a second member matable with the first member and the opposite surfaces of the pocket and movable relative thereto to define a variable volume chamber, said second member having a generally smooth bearing surface facing oppositely the first member bearing surface, a shaft supported for rotation in the housing and having a smooth support surface matably adjacent and movable relative to the second member bearing surface and movable toward and away from the housing support surface for moving the members relative to one another and to the housing, and inlet and outlet means in the opposite surfaces associated with the chamber for supplying hydraulic fluid to and from the chamber, each of the first and second members having a through passage of restricted cross-sectional area extending between its bearing surface and the chamber for establishing a pressurized film of hydraulic fluid between the matably adjacent surfaces to support the mem- 2. A hydraulic pump or motor comprising a housing including a pocket defined by opposite walls and an interconnecting wall, a generally U-shaped cylinder member matably received in the pocket and reciprocable therein and having leg portions defining a cylinder with the opposite walls of the pocket, a piston matably received in the cylinder and adapted to reciprocate therein in a direction transverse to the direction of reciprocation of said cylinder member, and means for reciprocating the piston in the cylinder to define a variable volume chamber while simultaneously reciprocating the cylinder member within the pocket, said opposite walls each having an inlet and an outlet port associated with the chamber positioned to be covered'by the cylinder member at certain operative positions and selectively opened by the cylinder member at other operative positions to communicate with the chamber.

3. A hydraulic pump or motor unit comprising a housing including three surfaces, two of which are spaced and parallel, the third of which extends perpendicularly between the two to define a generally C-shaped pocket, a cylinder member received in the pocket and defined by three surfaces two of which are spaced and parallel, the third of which extends perpendicularly between the two and matably with the third housing surface, said cylinder member being reciprocable in the pocket parallel to all of the surfaces, said cylinder member being U-shaped and having leg portions defining with the two spaced surfaces of the housing a cylinder of uniform cross-section extending perpendicular to the third surface, a piston having a generally uniform cross-section matably received within the cylinder and reciprocable relative thereto to define a variable volume chamber, means for reciprocating the piston relative to the cylinder member to vary the chamber volume between maximum and minimum volumes respectively at top dead center positions while alternately reciprocating the cylinder member across the top dead center positions to either side thereof, and aligned inlet and outlet ports disposed in the two spaced surfaces of the housing adapted to be covered by the cylinder member at the top dead center positions, and respectively opened by the cylinder member on opposite sides thereof to communicate with the chamber.

4. A hydraulic pump or motor comprising a housing including a plurality of inwardly facing pockets each defined by opposite walls and an interconnecting wall, a first member matably received in each pocket and reciprocable therein, a second member having a center through-bore and a corresponding plurality of radially projecting arms each matable with one of the first members and opposite walls to define with said first members and said opposite walls a plurality of chambers, a shaft having an eccentric matably received within the throughbore, said eccentric being operable upon rotation to dis place the second member in a circular path to reciprocate the arms with respect to the first members and to simultaneously reciprocate the first members within the pockets, the opposite walls of each pocket having aligned inlet ports and aligned outlet ports separately connectable to the respective chambers and covered by the respective members at certain operative positions within the pocket and selectively opened by the members at other operative positions to communicate with the chamber.

5. A hydraulic pump or motor comprising a housing including a plurality of inwardly facing pockets each having mutually facing parallel surfaces, a U-shaped cylinder member received in each pocket and reciprocable therein along a fixed path and defining with the housing surfaces a cylinder opened inwardly of uniform cross- .section extending perpendicular to the path, a piston having a center through-bore and a corresponding plurality of radially projecting arms having uniform crosssections each matably received in a respective cylinder, a shaft member having and eccentric matably received within the through-bore and operable upon rotation to displace the piston member in a circular path, to reciprocate the piston arms with respect to said cylinder members in a direction transverse to the direction of said fixed path to define variable volume chambers, said eccentric also being operable to reciprocate the cylinder members to the extremes of their respective paths, each chamber having a maximum and minimum volume respectively at an operative position of the cylinder member intermediate said extremes, each chamber having associated therewith aligned pairs of inlet and outlet ports in the opposite surfaces alternately covered and uncovered by the cylinder member in the positions thereof toward the opposite extremes of its path.

6. A hydraulic pump or motor unit comprising a housing, a shaft rotatably mounted centrally of the housing and having an eccentric portion thereon, said housing having a plurality of circumferentially spaced pockets open toward and symmetrical of the eccentric portion, each of said pockets being defined in part by mutually facing opposite walls, a generally U-shaped cylinder member matably received in each of the pockets, the leg portions of the cylinder members and the opposite sides of the pockets defining cylinders open towards the shaft, each cylinder member being movable in its pocket along a path extending transversely of the shaft, and a piston member rotatably mounted centrally on the eccentric portion and having radial arms matably received in the cylinders to reciprocate the piston arms within the cylinders to define variable volume chambers while simultaneously reciprocating the cylinder members along their respective paths, the opposite walls of each pocket having aligned inlet ports and aligned outlet ports alternately and separately opened by the cylinder member therein to communicate with the chamber.

7. A hydraulic pump or motor unit comprising a housing having spaced parallel surfaces interconnected by two pairs of parallel mutually facing bearing surfaces angularly disposed 90 with respect to each other, said surfaces defining four inwardly facing pockets, a U- shaped cylinder member received in each pocket, the base portion of said cylinder member having a bearing surface matably adjacent the housing bearing surface and reciprocable thereon, the leg portions of said cylinder member having mutually facing bearing faces extending perpendicular to the bearing surface, a rigid cruciform piston member having a central bore and four equally spaced radial arms matably received between the leg portions with each arm having peripheral surfaces engaging the bearing faces thereof and the spaced pocket surfaces, said arms being reciprocable relative to said leg portions to define four variable volume chambers, a shaft supported by the housing having an eccentric matably received within the bore and operable upon rotation to displace the piston member in a circular path within the housing to vary the chamber volumes while simultaneously reciprocating the cylinder members, and inlet and outlet port means in the spaced pocket surfaces on opposite sides of the piston member selectively opened by the reciprocating cylinder member to communicate with the chambers.

8. A hydraulic pump or motor comprising a housing having spaced parallel flat surfaces interconnected by a plurality of inwardly facing straight bearing surfaces to define inwardly facing pockets, a generally U-shaped cylinder member received in each pocket with its base portion having a straight bearing surface matably adjacent the inwardly facing bearing surfaces and its leg portions having spaced mutually facing faces extending perpendicular to the bearing surface, a piston disposed in the housing and having a central through-bore and a corresponding plurality of radially projecting arms having exterior surfaces matably received between the leg portions of each member and the pockets to define variable volume chambers therebetween, and a shaft supported centrally of the housing and having an eccentric received by and engaging the periphery of the through-bore and operable upon rotation thereof to displace the piston member in a circular path, thereby reciprocating the piston arms relative each member while simultaneously reciprocating the members in the pockets along paths parallel to the respective bearing surfaces, said housing having inlet and outlet ports associated with each pocket closed by the cylinder member therein at certain operative positions, and separately opened at other operative positions to communicate with each of the chambers, said members each having a through passage of restricted cross-sectional area extending between its bearing surface and the chamber, each of the piston arms having a through passage of restricted cross-sectional area extending between the periphery of the through-bore and the chamber.

9. A hydraulic pump or motor unit comprising a housing, a shaft rotatably secured centrally of the housing and having a plurality of axially spaced adjacent eccentric portions each disposed in out-of-phase positional relationship with its adjacent portion, said housing having a plurality of axially spaced cavities each associated with one of said eccentric portions, each of said cavities comprising a plurality of pockets opened toward said shaft each being defined in part by mutually facing opposite surfaces, a generally U-shaped cylinder member matably received in each of the pockets so that its leg portions along with the opposite surfaces of the pockets define a cylinder open towards the shaft, each cylinder member being movable in its pocket along a path extending transversely of the shaft, a piston rotatably mounted centrally on each eccentric portion and having radial arms projecting respectively toward the pockets associated with the respective eccentric portion, said arms being matably received in the cylinders and reciprocal therein upon rotation of the shaft to define variable volume chambers, said arms adapted to simultaneously reciprocate the cylinder members along their respective paths, the opposite surfaces of each pocket having aligned pairs of inlet and outlet ports alternately opened by the cylinder member therein to communicate with the chamber.

10. A hydraulic pump or motor unit, comprising a housing, a shaft rotatably supported by the housing centrally thereof, a plurality of bearing surfaces on the housing spaced radially of the shaft, a plurality of first members matable respectively, with each bearing surface and reciprocable thereon, a second member rotatably mounted on the shaft and having radially extending arms matable respectively, with each of the first members, means to move the second member relative to each of the first members to define a plurality of variable volume chambers spaced radially of the shaft, said housing defining aligned pairs of inlet and outlet ports for each chamber disposed on both sides of and adjacent the respective chamber, and inlet and outlet manifolds extending annularly of the shaft adjacent the respective ports for directing a hydraulic fluid to and from the unit, said ports and manifolds being of such size, compared to the working volume of each chamber, that the fluid acceleration therein is small for all operating speeds of the unit.

11. A hydraulic pump or motor unit, comprising a housing, a shaft rotatably supported by the housing centrally thereof, an eccentric secured to the shaft, a plurality of inwardly facing bearing surfaces on the housing spaced radially of the eccentric, a plurality of first members matable respectively, with each bearing surface and reciprocable thereon, a second member rotatably mounted on the eccentric and having radially extending arms projecting respectivey, normal to the bearing surfaces and matable with each of the first members therein, wherein rotation of the shaft moves the second member relative to each of the first members to define a plurality of variable volume chambers spaced radially of the shaft, aligned pairs of inlet and outlet ports for each chamber defined by the housing on both sides of each chamber and disposed adjacent the chambers longitudinally of the shaft, and inlet and outlet manifolds extending annularly of the shaft adjacent the respective ports on both sides of the chambers for directing a hydraulic fluid to and from the unit, said ports and manifolds being of such size, compared to the working volume of the chambers, that the fluid acceleration therein is small for all operating speeds of the unit.

12. A hydraulic pump or motor unit, comprising a housing having a plurality of inwardly facing pockets each defined by opposing walls and an interconnecting wall, a plurality of first members each matably received in one of the pockets and reciprocable therein along the interconnecting wall, a second member having a center throughbore and a corresponding plurality of radial projections extending normal to the respective interconnecting wall, each radial projection being matable with one of the first members and the opposing walls to define a plurality of fl d c ambers each disposed symmetrically of the first member with respect to the portion thereof mated with the interconnecting wall, a shaft rotatable in the housing, an eccentric on the shaft matably received in the throughbore and operable to displace the second member in a generally circular path and to reciprocate the first members within the pockets thereby varying the volume of the chambers, each of said opposing walls of each pocket having aligned inlet and outlet ports spaced apart in the direction of movement of the first member and adjacent the chamber adapted to communicate separately therewith at certain operative positions of the first and second members, and means including restricted through-passages in the first and second members extending between the chambers and the interfaces of the members, respectively, adjacent the interconnecting walls and eccentric.

13. A hydraulic pump or motor unit, comprising in combination, fluid biased means including a pair of mating members reciprocable in a first direction relative to one another to define a variable volume fluid chamber, reaction means opposing the fluid biased means and including a straight bearing surface extending in a second direction normal to the first direction and a cylindrical eccentric spaced therefrom in the first direction rotatable about an axis normal to the first and second directions, one of the mating members being reciprocable on the bearing surface in said second direction and the other of the members being translatable on the eccentric in a circular path about said axis, each of said members having a passage of restricted cross-section communicating with the fluid chamber and terminating at the interface adjacent the respective reaction means operable to establish by leakage a fluid film and to cause a pressure drop comparable to the pressure drop across the fluid film itself under normal film clearance and flow conditions, the fluid biased means mating with the reaction means in all relative positions thereof symmetrically of lines extending in the first direction through the center of the fluid chamber, means to rotate the eccentric about the axis for converting between fluid and mechanical energies, and means to port the fluid chambers.

14. A hydraulic pump or motor unit, comprising in combination, a plurality of fluid biased means each including a common member and an independent member mating therewith and reciprocable in a first direction relative thereto to define a variable volume chamber, said first directions all extending normal to a common axis, reactive means opposing each fluid biased means and including a cylindrical eccentric rotatable about said axis and a corresponding plurality of straight bearing surfaces spaced therefrom in the respective first direction and extending in a second direction generally normal to the first direction, the independent mating member of each fluid biased means being reciprocable on the bearing surface of the corresponding reaction means in said second direction and the common mating member being translatable on the eccentric in a circular path about said axis, each of the mating members having a passage of restricted cross-section communicating with its defined fluid chamber and terminating at the interface adjacent the respective reaction means operable to establish by leakage a fluid film at the interface, said passage causing a pressure drop under normal film clearance and flow conditions of approximately /s to /2 the pressure in the fluid chamber, the fluid biased means mating with its respective reaction means in all relative positions thereof symmetrically of lines extending in the corresponding first direction through the center of its defined fluid chamber, means to rotate the eccentric about the axis for converting between fluid and mechanical energies, and means to port the fluid chambers.

15. A hydraulic pump or motor unit, comprising in combination, a pair of mating members constituting respectively, a piston member and a cylinder member, said mating members being reciprocable relative to one another along a first path parallel to the longitudinal center axis of the piston to define a variable volume fluid chamber of a given cross-section normal to said first path, each of said mating members having a reaction area larger than said chamber cross-section and extending transversely to and symmetrically of said center axis, a pair of opposing members disposed outwardly of said mating members controlling the relative movement thereof, said opposing members each having an opposing reaction area complementary to and adjacent the reaction area of the adjacent mating member, one of said opposing members having a longitudinal center axis intersecting said firstmentioned axis and extending generally parallel to said mating member reaction areas, means to move the secondmentioned axis and the other of the opposing members relative to one another in a generally circular path about an axis parallel to said second-mentioned axis to vary the shortest distance between said opposing reaction areas while simultaneously displacing the axis defining said shortest distance in a second path transverse to said first path, and means to supply a fluid to said chamber, thereby biasing the mating members apart along said first path and against said opposing members with a force equal to a chamber fluid pressure acting on said chamber crosssection, each of said mating members having a through restricted passage between the chamber and the interface of its reaction area, said restricted passage being operable to communicate a limited quantity of fluid at a second pressure less than the chamber pressure to between the adjacent reaction areas to support the areas spaced from each other on a fluid film having an average pressure less than the second pressure, the mathematical product of the average film pressure acting on the respective adjacent reaction areas always seeking to equal the mathematical product of the chamber pressure acting on said chamber cross-section and the pressure drop across the restricted passage being /2, to /2 that of the fluid pressure in the chamber and being comparable to the pressure drop across the fluid film itself.

References Cited by the Examiner UNITED STATES PATENTS 360,057 3/87 Smith 121-52 388,522 8/88 Beauchemin 103-161 X 580,838 4/97 Almond 103-161 X 1,082,224 12/13 Crayssac 103-161 X 1,455,753 5/23 Mayer 121-52 1,630,953 5/27 Levine 121-52 1,757,483 5/30 Hele-Shaw et al 103-161 2,013,862 9/35 Schulz et al. 103-163 X 2,130,037 9/38 Skarlund 103-163 2,347,663 5/44 Carnahan 103-174 X 2,561,519 7/51 Leech 103-37 2,573,472 10/51 Martin 103-174 X 2,675,763 4/54 Muller 103-161 2,679,210 5/54 Muller 103-161 2,833,225 5/58 Sherman 103-161 2,851,952 9/58 Lane 103-37 2,968,287 1/61 Creighton 103-174 X 2,981,201 4/61 Holdener 103-163 FOREIGN PATENTS 554,287 2/23 France. 1,240,080 7/60 France.

321,313 11/29 Great Britain.

764,698 1/57 Great Britain.

827,756 2/ 60 Great Britain.

96,030 9/22 Switzerland.

LAURENCE V. EFNER, Primary Examiner.

ERNEST W. SWIDER UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 211, 107 October 12, 1965 Vannevar Bush It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 14, line 55, for "and" read an column 16, line 50, for "respectivey" read respectively Signed and sealed this 12th day of July 1966.,

(SEAL) Attest:

EDWARD J. BRENNER Attcsting Officer Commissioner of Patents

Claims

1. A HYDRAULIC PUMP OR MOTOR COMPRISING A HOUSING INCLUDING A POCKET DEFINED IN PART BY OPPOSITELY FACING SURFACES AND AN INTERCONNECTING STRAIGHT SUPPORT SURFACE. A FIRST MEMBER RECEIVED IN THE POCKET AND HAVING A STRAIGHT BEARING SURFACE MATABLY ADJACENT THE SUPPORT SURFACE AND RECIPROCABLE THEREON, A SECOND MEMBER MATABLE WITH THE FIRST MEMBER AND THE OPPOSITE SURFACES OF THE POCKET AND MOVABLE RELATIVE THERETO TO DEFINE A VARIABLE VOLUME CHAMBER, SAID SECOND MEMBER HAVING A GENERALLY SMOOTH BEARING SURFACE FACING OPPOSITELY THE FIRST MEMBER BEARING SURFACE, A SHAFT SUPPORTED FOR ROTATION IN THE HOUSING AND HAVING A SMOOTH SUPPORT SURFACE MATABLY ADJACENT AND MOVABLE RELATIVE TO THE SECOND MEMBER BEARING SURFACE AND MOVABLE RELATIVE TO THE SECOND KFROM THE HOUSING SUPPORT SURFACE FOR MOVING THE MEMBERS RELATIVE TO ONE ANOTHER AND TO THE HOUSING, AND INLET AND OUTLET MEANS IN THE OPPOSITE SURFACES ASSOCIATED WITH THE CHAMBER, FOR SUPPLYING HYDRAULIC FLUID TO AND FROM THE CHAMBER, EACH OF THE FIRST AND SECOND MEMBER HAV- L ING A THROUGH PASSAGE OF RESTRICTED CROSS-SECTIONAL AREA EXTENDING BETWEEN ITS BEARING SURFACE AND THE CHAMBER FOR ESTABLISHING A PRESSURIZED FILM OF HYDRAULIC FLUID BETWEEN THE MATABLY ADJACENT SURFACES TO SUPPORT THE MEMBERS ADJACENT BUT SPACED FROM THE RESPECTIVE SUPPORT SURFACES, AND THE PRESSURE DROP ACROSS EACH RESTRICTED PASSAGE BEING APPROXIMATELY 1/3 TO 1/2 OF THE FLUID PRESSURE ING THE CHAMBER UNDER NORMAL FILM CLEARANCE AND FLOW CONDITIONS.