US3718411A

US3718411A - Hydraulic motor

Info

Publication number: US3718411A
Application number: US00180317A
Authority: US
Inventors: F Pollman
Original assignee: Sundstrand Corp
Current assignee: Danfoss Power Solutions Inc
Priority date: 1971-09-14
Filing date: 1971-09-14
Publication date: 1973-02-27
Anticipated expiration: 1990-02-27

Abstract

A rotary hydraulic motor including a stator having a central cylindrical cavity with radial slots communicating with the cavity and containing reciprocable sealing rollers, a cam rotor in the cavity with a peripheral cam surface including a plurality of cam lobes with intervening lows engaging the sealing rollers to form displacement chambers, a pair of port plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the sides of the stator adjacent the roller slots, an annular array of alternate inlet and outlet ports in each port plate adjacent the roller slots in the stator, and a pair of pressure plates disposed against the surfaces of the port plates remote from the rotor and the stator. Pressure chambers around the periphery of the port plates reduce deflection of the plates, and pressure chambers behind each pressure plate seal the port plates in the housing. The rotor is constructed with passages communicating the inlet ports in the two port plates and passages communicating the outlet ports in the two port plates. Provision is made for supplying pressure acting in the outer ends of the slots to urge the rollers toward the cam.

Description

United States Patent 91 Pollman 1 Feb. 27, 1973 HYDRAULIC MOTOR [75] Inventor: Frederic W. Pollman, Rockford, Ill.

[73] Assignee: Sundstrand Corporation, Rockford,

Ill.

[22] Filed: Sept. 14, 1971 [21] Appl. No.: 180,317

[52] U.S. Cl. ..41 8/82, 418/131, 418/186, 418/225, 418/248, 418/249 [51] Int. Cl ..F0lc 1/00, F03c 3/00, F04c 1/00 [58] Field of Search....4l8/77, 79, 82, 131, 177, 183,

[56] References Cited UNITED STATES PATENTS 1,349,353 8/1920 Wilber.... ..418/248 2,078,887 4/1937 Wood.. ..4l8/248 3,016,021 l/1962 Rineer ..418/225 3,128,708 4/1964 l-lenning .......418/249 3,606,600 9/1971 Pollman ..418/131 Primary Examiner-William Freeh Assistant Examiner.lohn J. Vrablik Attorney-Alex A. Hofgren et al.

[57] ABSTRACT A rotary hydraulic motor including a stator having a central cylindrical cavity with I radial slots communicating with the cavity and containing reciprocable sealing rollers, a cam rotor in the cavity with a peripheral cam surface including a plurality of cam lobes with intervening lows engaging the sealing rollers to form displacement chambers, a pair of port plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the sides of the stator adjacent the roller slots, an annular array of alternate inlet and outlet ports in each port plate adjacent the roller slots in the stator, and a pair of pressure plates disposed against the surfaces of the port plates remote from the rotor and the stator. Pressure chambers around the periphery of the port plates reduce deflection of the plates, and pressure chambers behind each pressure plate seal the port plates in the housing. The rotor is constructed with passages communicating the inlet ports in the two port plates and passages communicating the outlet ports in the two port plates. Provision is made for supplying pressure acting in the outer ends of the slots to urge the rollers toward the cam.

30 Claims, 12 Drawing Figures 26 1 /55 0 i 4 fl i w 1? '52 i102) 109 t 1% \7 E .1 7

61 105 Z! 102/ 32575 70 004 104 3 J I? :2; do 71 g 4% PATENTEI] FEB 2 7 I975 SHEET 3 UP 4 PATENTED P1821 3.718.411

sum 1 or 4 HYDRAULIC MOTOR BACKGROUND OF THE INVENTION The present invention relates to a cam motor including a rotor formed with a peripheral cam surface including cam lobes and intervening lows rotatable in a stator chamber formed with radial slots containing reciprocable sealing rollers engaging the cam surface to provide displacement chambers between the cam lobes. In the past, there has been some work in connec tion with hydraulic cam motors. For example, prior U. S. Pat. Nos. 346,531, 762,126, 883,319, 2,492,687, 3,128,708 and 3,276,386 relate to constructions of the type under consideration here. However, there has not been great competitive activity, and the known prior constructions are subject to some disadvantages.

in particular, the prior art devices do not provide for both radial and axial pressure balancing in fluid translating devices of the type described. Further, the prior art devices do not provide for the porting of fluid directly to both sides of the rotor and stator so as to ensure adequate fluid flow relative to the displacement chambers. Additionally, the prior art constructions have lacked adequate means for maintaining the sealing rollers in contact with the rotating cam surface.

SUMMARY OF THE INVENTION According to the present invention, a cam motor is provided with a cam rotor having port plates secured to opposite sides in an arrangement in which the rotor and port plates rotate relative to a stator containing radial slots having reciprocable sealing rollers engaging the periphery of the rotor to form displacement chambers between the cam lobes on the rotor. In order to ensure adequate fluid flow relative to the displacement chambers, provision is made for porting fluid to and from the chambers at both sides of the rotor and stator by means of appropriate inlet and outlet ports provided in both of the port plates. In order to communicate the inlet ports in the two port plates, passages are provided through the rotor, and in order to communicate the outlet ports in the two port plates, other passages are provided in the rotor.

In order to urge the sealing rollers in the stator slots toward the cam surface for engagement therewith, provision is made for applying fluid pressure in the stator slots radially outside of the sealing rollers for purposes of creating a pressure differential acting to urge the rollers toward the cam.

More specifically, the cam, the inlet and outlet porting in the port plates, the slots in the stator, and the sealing rollers are constructed to restrict flow in and out of the porting radially inside of the rollers during contact of the rollers with low portions of the rises and falls of the cam, and to restrict flow in and out of the porting outside of the rollers during contact of the rollers with the high portions of the rises and falls of the cam, in a manner to create a pressure differential urging the rollers toward the cam during communication with the inlet ports and the outlet ports, so that the rollers follow the cam rises and falls.

Additionally, ports are provided between the inlet and outlet ports for supplying fluid at intermediate pressure to the slots in the stator outside of the rollers for urging the latter toward the cam during intervals between communication with the inlet and outlet ports to obtain sealing with minimum load.

In order to provide for pressure balancing, the motor construction additionally includes a pair of pressure plates disposed respectively beside the port plates, each including an annular pressure chamber communicating with inlet pressure and an annular pressure chamber communicating with outlet pressure, to urge the pressure plates toward the rotating assembly, thereby to seal the rotating assembly relative to the housing.

In order to control deflection of the port plates and reduce leakage, provision is made for peripheral chambers surrounding the port plates supplied with fluid at a pressure intermediate the inlet pressure and outlet pressure by means of leakage fluid escaping between the port plates and the stator due to clearance provided to facilitate rotation of the port plates relative to the stator.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view through a motor constructed according to the principles of the present invention, taken at about the line 11 on FIG.

FIG. 2 is a longitudinal sectional view through the motor approximately on the line 2-2 of FIG. 1;

FIG. 3 is a transverse sectional view, taken at about the line 3-3 of FIG. 2, showing the rotor, the stator, and the sealing rollers;

FIG. 4 is a transverse sectional view taken at about the line 4-4 of FIG. 2, showing the inlet and outlet recesses in the face of one port plate adjacent the rotor and stator;

FIG. 5 is a transverse sectional view, taken at about the line 55 of FIG. 2, showing the inlet and outlet recesses in the adjacent face of the other port plate;

FIG.,6 is a transverse sectional view, taken at about the line 6-6 of FIG. 2, showing the outside of the port plate illustrated in FIG. 5;

FIG. 7 is a transverse sectional view, taken at about the line 7-7 of FIG. 2, showing the outside of the port plate illustrated in FIG. 4;

FIG. 8 is a transverse sectional view taken at about the line 8-8 of FIG. 2, showing the inner surfaces of one of the pressure plates;

FIG. 9 is a transverse sectional view taken at about the line 99 of FIG. 2, showing the outer surface of the pressure plate illustrated in FIG. 8;

FIG. 10 is a transverse sectional view, taken at about the line 10-10 of FIG. 2, showing the inside of the end housing with inlet and outlet ports;

FIG. 11 is a transverse sectional view taken at about the line ]l1ll of FIG. 3, illustrating check valves in the rotor for purposes of draining leakage from the shaft to the low pressure side of the device; and

FIG. 12 is a fragmentary transverse sectional view taken at about the line l2-l2 of FIG. 3, illustrating spring means in the stator slots urging the sealing rollers toward the cam surface of the rotor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawings in more detail, a housing includes an end cover member 10 (FIGS. 1 and 2), an end cover member 12, and an intermediate spacer or stator member 14 adapted to be held in tightly assembled relationship by means of appropriate bolts 15 (FIG. 3). End housing member 10 is formed to receive appropriate bearings as at 17, and end housing member 12 is provided with bearings as at 18 which together provide rotatable support for a shaft 20 mounted in the bearings and including an end portion 21 projecting outwardly from the housing for appropriate connection with a device adapted to be driven when fluid under pressure is supplied to the housing to drive the motor. The end housing is normally closed at the left end of the motor, though it may include a threaded aperture as at 22 if desired. At the right end, the housing member 12 carries an appropriate shaft seal as at 24 to prevent leakage along the shaft outwardly of the housmg.

In order to supply hydraulic fluid to the housing and exhaust hydraulic fluid from the housing, the end housing member 10 is formed with a threaded axially extending port 26 at one side of the axis of the shaft, and an axially extending threaded port 28 at the opposite side of the axis of the shaft. Either of the ports 26 and 28 may function as the inlet port while the other functions as the outlet port. As seen best in FIG. 10, the longitudinal passage 26 terminates in an arcuately shaped kidney-shaped port 29 and the longitudinal passage 28 terminates in an arcuate kidney-shaped port 30. The arcuate port 29 is relatively widely spaced from the axis of the shaft, while the arcuate-shaped port 30 is relatively closely spaced to the shaft, and the ports serve to communicate the fluid to and from the fluid displacement mechanism, as will appear.

Referring now to FIG. 3, the stator member 14 is formed with a central cylindrical cavity 32, and around the entire peripheral wall of the cavity 32, the stator member 14 is formed with a plurality of equally spaced radially disposed slots 34 of similar configuration, each opening into the central cavity 32. Each of the slots 34 receives a reciprocable sealing member 36 in the form of a hollow rotatable tube or roller 36. Each of the rollers 36 is urged radially inwardly of the stator member by a coiled compression spring 37 seated in the slot 34. As best seen in FIG. 12, base of each coiled spring 37 is preferably seated in an aperture in a plate 38 which bears on the roller 36 and functions to maintain the spring longitudinally centered in the slot 34.

A cam-shaped rotor 40 is positioned in the stator cavity 32 and connected by splines as at 42 for rotation with the shaft 20 while free to move a limited amount longitudinally of the shaft. The cam rotor 40 is formed with a peripheral cam surface including a plurality of equally spaced cam lobes 43, four as illustrated, and intervening lows 45 between the lobes. The top surfaces of the lobes 43, as well as the surfaces of the lows 45, are concentric about the axis of the shaft 20 and provide dwell surfaces. The cam lows and the cam highs (lobes) are connected by rises 46 at the leading edges of the lobes, and falls 47 at the trailing edges of the lobes. The spaces between the cam lows and the wall of the cavity in the stator provide displacement chambers to which fluid under pressure may be supplied for driving the rotor and the shaft 20. The rollers 36 on the high and low dwell portions of the cam make sealing contact with the periphery of the cam and the walls of slots 34 in a manner to isolate alternate high pressure and low pressure chambers around the periphery of the cam. Provision of an even number of displacement chambers provides radial balance.

Displacement is defined by the radial difference between the seals at opposite ends of the high pressure zones on the periphery of the cam, and the arrangement is such that the seal at one end of each high pressure zone occurs at a roller positioned on a high dwell on the cam, and sealing at the opposite end of the high pressure zone occurs at a roller on a low dwell portion of the cam. In this manner, the displacement of the device is constant and the torque flow is even. In the illustration of FIG. 3, high pressure areas are indicated by inclined hatching, while areas at intermediate pressure are indicated by crossed hatching, and areas at low pressure are indicated by the absence of hatching. It should be understood that while springs 37 have been illustrated only in the slots at low pressure in order to avoid interference with the hatching, springs may be utilized in each of the slots 34 for biasing each of the rollers 36 toward the cam surface of the rotor.

In order to port fluid to and from the displacement chambers between the rotor and the stator, a pair of port plates are provided on opposite sides of the rotor as at 50 and 52 (FIGS. 1 and 2), the first of which is shown in more detail in FIGS. 4 and 7, and the latter of which is shown in more detail in FIGS. 5 and 6. The

port plates

50 and 52 are angularly aligned with the rotor 40 by means of dowel pins as at 53. The rotor and port plates are secured together by angularly spaced machine screws as at 54. The thickness of the rotor 40 axially is slightly greater than the thickness of the stator, and outwardly disposed portions of the

port plates

50 and 52 rotate past the slot 34 in the stator. By virtue of the limited clearance between the rotating port plates and the stationary stator, there is leakage of fluid between the port plates and the stator to the periphery of the port plates which are spaced from the periphery of the surrounding housing members, thereby providing peripheral pressure chambers as at 55 and 56 under pressure at a value intermediate the inlet pressure and the outlet pressure.

For purposes of describing the porting, it will be convenient to refer to particular ports as inlet, and to refer to other ports as outlet. Accordingly, with the cam rotating clockwise as illustrated in FIG. 3, reference is made to the port 28 in the housing member 10 and the kidney 30 therein as inlet porting, and reference is made to the port 26 and the kidney 29 as outlet porting. However, it should be understood that the ports may be reversed, and fluid may be supplied to the motor through the port 26 and exhausted through the port 28.

For purposes of porting fluid under pressure to the displacement chambers, the surface of the port plate 50 adjacent to the rotor and the stator is formed with a plurality of recesses 60 which are distinguished from each other by sufflxes -l, 2, 3 and 4. The ports 60 are equally spaced angularly around the axis of the shaft 20, and equally spaced between the inlet ports are a plurality of outlet ports 62-1, 62-2, 62-3 and 62-4. In order to supply fluid under pressure to the inlet recesses 60, the recesses 60-1 and 60-3 communicate with ports as at 64 extending through the plate 50, and the recesses 60-2 and 60-4 communicate with ports as at 65 through the port plate 50. In order to exhaust fluid from the outlet recesses 62, the recesses 62-1 and 62-3 communicate with ports as at 67 through the port plate 50, and the recesses 62-2 and 62-4 communicate with ports as at 68 through the port plate 50. As illustrated in FIG. 7, the remote side of the port plate 50 i from the rotor and stator is formed with an inner annular groove as at 70 communicating with the

inlet ports

64 and 65 in order to supply fluid to the recesses 60. A radially outwardly disposed annular groove 71 communicates with the

outlet ports

67 and 68 in order to exhaust fluid from the outlet recesses 62.

As best seen in FIGS. 1 and 2, pressure plates 74 and 76 are disposed outwardly from the

port plates

50 and 52. In order to port fluid to the inlet groove 70 in the port plate 50, the pressure plate 74 has a surface in contact with the port plate 50 formed with an inner annular groove as at 78 (FIG. 8) in register with the inner annular groove 70 in the port plate. Similarly, the pressure plate includes an outer annular groove 79 in register with the outer annular groove 71 in the port plate 50. Fluid is ported from the

inlet

30,28 to the groove 78 through an arcuate kidney-shaped port as at 80. Fluid is ported from the outer annular groove 79 in the pressure plate 74 to the outlet port 26,29 through an arcuate kidney-shaped port 82 in the pressure plate, which may be in two sections if desired. The-pressure plate 70 is preferably retained in the housing member 10 against rotation by means of a pair of dowel pins as at 84 (FIG. 2). Similarly, the pressure plate 76 is retained in position by dowel pins as at 86.

In operation, it will be understood that the housing member 10 is stationary and the pressure plate 74 is retained against rotation, while the rotor 40 and the port plate 50 are rotatable with the shaft 20. Fluid under pressure supplied through the

inlet port

28,30 flows through the arcuate porting 80 to the annular channel between the pressure plate 74 and the port plate 50 provided by the annular groove 78 in the pressure plate and the annular groove 70 in the port plate. In this manner, the annular channel functions as an inlet manifold for supplying fluid under pressure to the

rotating inlet ports

64 and 65 in the port plate 50, so that the inlet recesses 60 contain fluid under pressure. The fluid under pressure in the inlet recesses 60 is supplied to the displacement chambers between the rotor 40 and the stator 14 at the spaces between the cam lobes 43. The fluid under pressure acting on the cam surfaces 47 forces the rotor to turn, and the rotor causes rotation of the port plates and the shaft 20. Thus, the high pressure displacement chambers between the rotor and the'stator rotate with the rotor, and the rotor is driven with an even torque flow.

The inlet and outlet recesses 60 and 62 in the face of the port plate 50 have distinctive configurations. The basic configuration of each recess 60 corresponds to that illustrated at 60-4, which includes an outer kidney portion 60a adapted to communicate with the outer portions of the roller slots 34 as the port plate rotates, an inner inclined kidney portion 60b which conforms approximately to the cam fall portion 47 and communicates with the inner portions of the roller slots 34 in the stator, an intermediate radially disposed connecting channel 60c, and a radially inwardly directed channel 60d through which the inlet ports extend to the opposite face of the port plate. The configuration of the inlet recess 60-2 corresponds to that of the' inlet recess 60-4. The configuration of inlet recesses 60-1 and 60-3 is similar to that at 60-4, except that the inner channel d in recesses 60-1 and 60-3 is somewhat wider to accommodate ports 64 which are larger than ports 65.

In order to ensure adequate flow of fluid to and from the displacement chambers, the port plate 56 on the opposite side of the rotor is also formed with inlet and outlet recesses similar to those at 60 and 62 in the face of the port plate 50. In order to port fluid through the rotor 40 to the inlet recesses in the port plate 56, there are

passages

88 and 89 extending through the rotor and communicating with ports 64, which are larger than ports 65 in order to convey adequate fluid to both sides of the rotor.

The basic configuration of the outlet recesses 62 in the face of the port plate 50 is that at 62-1 and 62-3 which includes an outwardly located kidney 62a, and inwardly disposed kidney 62b which is inclined to follow the inclination of the cam rise surfaces 46, and a connecting radially disposed channel 620 through which

outlet ports

67 and 68 extend. Recesses 62-2 and 62-4 include a radially inwardly directed channel 62d.

In order to convey outlet fluid through the rotor between the outlet recesses in the port plate 52 and the port plate 50, the rotor is formed with passages 91 and 92 communicating respectively with the inwardly projecting portions 62d of the outlet recesses 62-2 and 62-4.

The inlet recesses in the face of the port plate 52 are designated -1, 100-2, 100-3 and 100-4, and the shapes correspond to those at 60-1, 60-2, 60-3 and 60-4 in the face of the port plate 50, except that the inwardly extending leg 100d of the inlet recess 100-4 in the face of the port plate 52 includes a finger extension 100e which functions as a check valve outlet for a purpose that will appear presently.

The outlet recesses in the face of the port plate 56 are designated 102-1, 102-2, 102-3 and 102-4, and the configuration of such recesses conforms substantially to the configuration of corresponding outlet recesses 62-1, 62-2, 62-3 and 62-4 in the face of the port plate 50, except that the recess 102-3 has an inwardly extending leg 102 with finger 102e adapted to communicate with a check valve outlet for purposes that will appear.

In order to properly distribute inlet fluid, the recesses 100-1 and 100-3 contain ports as at 104 through the port plate 52, and the recesses 100-2 and 100-4 include ports 105 through the port plate 52. In order to communicate the

ports

104 and 105 with each other, the pressure plate 76 is formed like the pressure plate 74 with an inner annular groove 106.

In order to properly distribute outlet fluid, the outlet recesses 102-1 and 102-3 are formed with ports 107 through the port plate 52, and the outlet recesses 102-2 and 102-4 are formed with outlet ports 108. In order to communicate the port 107 and the port 108 with each other, they communicate with an outer annular groove 109 in the face of the pressure plate 76.

In operation of the motor, there is some leakage of fluid at high pressure from the inlet recesses 60 and the inlet recesses 100 radially outwardly between the port plates and the stator so that fluid accumulates in the peripheral chambers 55 and 56 around the periphery of port plates and the pressure plates. There is some pres sure drop in the process of such leakage, but the pressure is higher than the pressure in the inlet recesses 62 and 102 in the faces of the port plates, so that there is some leakage from the peripheral chambers 55 and 56 to the recesses 62 and 102. The pressure in the peripheral chambers 55 and S6 is thus left at an intermediate value between the value of the high inlet pressure and the value of the low outlet pressure, and may be as high as 75 percent of inlet pressure.

The pressure of fluid in the peripheral chambers 55 and 56 is utilized for several purposes. More particularly, it will be understood that when the housing port 26 is utilized as the inlet port, the outer

annular grooves

79 and 109 in the pressure plates 74 and 76 are at high pressure which tends to resist deflection of the port plates due to pressure between the port plates and the stator. On the other hand, when the port 26 is the outlet port and the pressure in the outer

annular grooves

78 and 106 is low pressure, the intermediate pressure in the peripheral chambers 55 and 56 tends to leak to the

channels

79 and 109 and serves to resist deflection of the port plates.

Additionally, the pressure at intermediate value in the peripheral chambers 55 and 56 is utilized to aid in holding the sealing rollers 36 against the periphery of the cam surface. More particularly, the

port plates

50 and 52 are formed with radially disposed channels leading from the periphery of the port plate as at 120 at angularly spaced positions between the inlet and outlet recesses. Each radially extending channel 120 communicates with a kidney-shaped recess as at 122, and each of the kidneys 122 is radially positioned so that it communicates successively with outer portions of the radial slots 34 in the stator radially outwardly from the sealing rollers 36 so that intermediate pressure is delivered to the outer ends of the slots to urge the sealing rollers toward the cam surface. The use of intermediate pressure assures that the rollers provide sealing while imposing a minimum resistance to rotation.

In order to aid in holding the sealing rollers 36 against the cam surface of the rotor during communication with the inlet recesses and the outlet recesses, the porting is formed in a manner to create a pressure differential which includes a greater pressure radially outwardly from the roller urging the roller to maintain contact with the cam surface. In order to obtain the pressure differential, when the rollers are on the lower half of the rises and falls of the cam, axial flow in and out of the displacement chambers and the roller slots is restricted at positions radially inwardly from the rollers. When the rollers are positioned on the upper half of the rises and falls in the cam, axial flow in and out of the displacement chambers and the roller .slots is restricted radially outwardly from the rollers.

Considering first the pressure differential acting on the rollers exposed to low pressure adjacent the outlet ports, shown in FIG. 3 at approximately 30, 1 10, 210 and 290 from the upper center of the figure, it will be understood that as the cam rotates in a clockwise direction, it has the effect of forcing low pressure fluid axially out of the displacement chambers and the roller slots. Considering the roller at 30, for example, communicating with the outlet recesses 62-1 and 102-1, and located at the bottom of a cam rise 46 which it is about to climb, during contact of the roller with the upper half of the cam rise, axial flow from the roller slot radially outwardly from the roller is restricted relative to axial flow out radially inwardly from the roller, as a result of which the pressure tends to be greater on the outside of the roller to hold the roller against the cam surface at a time when it becomes a sealing roller, performing a function like that illustrated at 10. During contact of the roller with the lower half of the cam rise, axial flow from the displacement chamber and the roller slot is restricted relative to axial flow from the roller slot radially outwardly from the roller as a result of which the pressure tends to be greater under the roller and to lift the roller from the cam. However, at that moment, the roller is not a sealing roller as are the rollers on opposite sides of it, and it is of no consequence if the roller is lifted from the cam.

Considering now the rollers exposed to high pressure and at the top of a cam lobe, about to ride down a fall 47, such as the roller situated at in FIG. 3, inlet fluid at high pressure, as in the inlet recesses 60-1 and -1, tends to flow axially inwardly into the displacement chamber and the roller slot. As the roller rides down the lower half of the fall in the cam, flow axially into the displacement chamber and the roller slot is restricted inwardly of the roller relative to the in-flow outwardly of the roller, as a result of which the pressure tends to be greater radially outwardly from the roller to urge the latter toward the cam surface and maintain contact as it approaches a sealing function comparable to that of the roller illustrated at 50. As the roller rides down the upper half of the fall of the cam, axial flow into the displacement chamber and the roller slot tends to be restricted outwardly of the roller relative to the flow permitted inwardly of the roller as a result of which there tends to be a greater pressure underneath the roller lifting it off the cam, but at the moment the roller is not performing a sealing function and the seemingly adverse effect is of no consequence.

The flow restriction described above is a function of the porting provided by the cooperating action of the cam surface, the inlet and outlet recesses in the port plates, the roller slots and the rollers in the slots as the cam and the port plates rotate past the roller slots and the rollers. Referring to FIG. 5, where the cam and port plates would be rotating in a counterclockwise direction, and viewing the outlet recess 102-1, it can be seen that during contact of the roller with the lower half of the cam rise, flow axially outwardly from beneath the roller is restricted (due to limited access of the roller periphery with the kidney 102b) relative to flow axially outwardly from the roller (where a substantial length of slot 34 communicates with kidney 102a and channel 102c). Similarly, during the fall of the roller while passing the inlet port 100-4, flow axially into the chamber underneath the roller is restricted relative to flow axially into the slot radially outwardly from the roller. In order to aid in restricting flow axially inwardly and outwardly beneath each roller during contact with the lower half of each cam rise and fall, the radially inner end of each inlet and outlet kidney 60b, 62b, 100k and l02b in

port plates

50 and 52 is shallow (as indicated at 60f, 62f, 100f and 102]) relative to the remainder of the kidney with which it is associated. On the other hand, as the roller rides the upper half of the cam rises and falls, the roller itself is deep in the roller slot as a result of which access to the roller slot is restricted. In order to aid in restricting flow axially inwardly and outwardly radially outside each roller during contact with the upper half of each cam rise and fall, the end of each inlet and outlet kidney 60a, 62a, 100a and 102a adjacent the cam lobes 43 is shallow (as indicated at 60g, 62g, 100g and 102g) relative to the remainder of the kidney with which is is associated.

In order to urge the pressure balance plates 74 and 76 against the

port plates

50 and 52 for purposes of sealing the port plates relative to the housing, an inner annular pressure chamber is formed on each plate at 130 (FIG. 9) between an inner annular O-ring 132 and an intermediate annular O-ring 134. The annular chamber 130 on plate 74 communicates with the inlet pressure porting 28,30 (FIG. 1) in the housing member 10 to provide a sealing force urging the pressure plate 74 toward the port plates. The chamber 130 on plate 76 communicates with inlet pressure channel 106 through one or more ports as at 135 (FIG. 1). An outer annular chamber is provided at 136 (FIG. 9) between the intermediate O-ring 134 and an outer O-ring 138. The annular chamber 136 on plate 74 communicates with the outlet porting 26,29 (FIG. 1) in the housing member 10 to provide a force urging the pressure plate toward the port plates when the motor operation is reversed. Chamber 136 on plate 76 communicates with outlet groove 109 (FIG. 1) through ports as at 137.

In order to equalize pressure at opposite ends of the splined connection of the rotor to the shaft 20, the port plates 55 and 56 are each formed with a groove in the face of the plate adjacent the rotor, leading radially outwardly from the shaft cavity as at 140 for purposes of communicating with an axial passage 142 through the rotor.

In order to drain the shaft cavity of leakage fluid and prevent build-up of excessive pressure therein, the shaft cavity communicates with a pair of check valves 150 and 1152 (FIG. 11), one adapted to communicate with the inlet porting and one adapted to communicate with the outlet porting, so that the shaft cavity may be drained to the low pressure side of the system. The check valve 150 includes an axial bore 153 in the rotor 40 receiving a ball valve member spring-urged toward an inlet seat communicating with the shaft cavity by means of a radial groove 154 in the face of the port plate 50. Theoutlet end .of the check valve 150 communicates with the finger 102e (FIG. 5) extending from the outlet recess 102-3.

The check valve 152 includes an axial bore 156 in the rotor 40 receiving a ball member spring-urged toward an inlet seat communicating with the shaft cavity through a radial groove 157 in the face of the port plate 50. The outlet from the check valve 156 communicates with the finger le (FIG. extending from the inlet recess 1024. It will be understood that any undue pressure increase in fluid in the shaft cavity will be permitted to escape through the

check valve

150 or 152 which allows communication with low pressure.

I claim:

1. A rotary hydraulic fluid translating device, comprising, I

a. a housing,

b. a stator in the housing having a cylindrical cavity and a plurality of radially disposed slots with reciprocable sealing members therein,

c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes engageable with the sealing members to form displacement chambers,

a pair of plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the stator adjacent the slots therein and peripheral portions spaced from the surrounding housing to define peripheral pressure chambers,

e. an annular array of alternate inlet and outlet ports extending through one plate in communication with the cavity and slots in the stator,

f. means in the housing providing an inlet communicating with the inlet ports and an outlet communicating with the outlet ports as the rotor and the plates rotate, and

g. leakage paths between the stator and the rotating plates leading to the peripheral pressure chambers creating pressure in the chambers at a value intermediate the values of inlet and outlet pressures.

2. A rotary hydraulic fluid translating device as defined in claim 1, including passages porting intermediate pressure from the peripheral chambers to the slots in the stator radially outwardly from the sealing members.

3. A rotary hydraulic fluid translating device as defined in claim 1, including means providing a pressure differential across the sealing members acting in the outer ends of the slots tending to hold the members on the cam.

4. A rotary hydraulic motor, comprising,

a. a housing,

b. a stator in the housing having a central cylindrical cavity and a plurality of radial slots extending from the cavity with reciprocable sealing rollers therein,

c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes and intervening lows engaging the sealing rollers to form displacement chambers between the lobes,

d. a pair of port plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the sides of the stator adjacent the slots and peripheral portions spaced from the surrounding housing to define peripheral pressure chambers,

e. a shaft mounted in the housing and rotatable with the rotor and port plates,

f. an annular array of alternate inlet and outlet ports extending through each port plate in communication with the cavity and slots in the stator,

g. means in the housing providing an annular inlet groove communicating with the inlet ports and an annular 'outlet groove communicating with the outlet ports on rotation of the rotor and port plates, and

h. leakage paths between the stator and the port plates leading to the peripheral pressure chambers to provide pressure in the chambers at a value intermediate the inlet and outlet pressures and act ing on the surface of the port plates remote from the stator to reduce deflection of the plates.

5. A rotary hydraulic motor as defined in claim 4, including passages through the rotor communicating the inlet ports in the two port plates with each other and communicating the outlet ports in the two plates with each other.

6. A rotary hydraulic motor as defined in claim 4, ineluding,

a. a pair of pressure plates disposed respectively against the surface of the port plates remote from the rotor and stator,

. an inlet kidney through one pressure plate communicating with the annular inlet groove and an outlet kidney through one pressure plate communicating with the annular outlet groove,

c. means defining an annular pressure balance chamber behind each pressure plate in communication with inlet pressure, and

. means defining an annular pressure chamber behind each pressure plate in communication with outlet pressure.

7. A rotary hydraulic motor as defined in claim 6, including passages in each port plate porting intermediate pressure from the peripheral chambers to the slots in the stator radially outwardly from the sealing rollers.

8. A rotary hydraulic fluid translating device, comprising,

a. a housing,

c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes engageable with the sealing members to from displacement chambers,

d. a pair of plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the stator adjacent the slots therein and peripheral portions spaced from the surrounding housing to define peripheral pressure chambers at pressure intermediate inlet and outlet pressures,

f. means in the housing adjacent the surface of the ported plate remote from the rotor providing an annular inlet groove communicating with the inlet ports and an annular outlet groove communicating with the outlet ports as the ported plate rotates, and

g. passages porting intermediate pressure from one peripheral chamber to the slots in the stator radially outwardly from the sealing members between the inlet and outlet ports.

9. A rotary hydraulic fluid translating device as defined in claim 8, including means creating a pressure differential across the sealing members during exposure to the inlet and outlet ports acting in the outer ends of the slots to urge the members toward the cam.

10. A rotary hydraulic fluid translating device, comprising,

a. a housing,

c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes engageable with the members to form displacement chambers between the lobes,

d. a pair of plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the stator adjacent the slots therein,

e. an annular array of alternate inlet and outlet recesses in the face of each plate adjacent the slots in the stator,

f. an annular array of alternate inlet and outlet ports extending through each plate in communication with the recesses in such plates,

. means in the housing providing an inlet communicating with the inlet ports and an outlet communicating with the outlet ports as the rotor and the plates rotate, and

. passages through the rotor communicating the inlet recesses in said one plate with the inlet recesses in the other plate, and communicating the outlet recesses in said one plate with the outlet recesses in the other plate.

11. A rotary hydraulic fluid translating device as defined in claim 10, wherein,

a. peripheral portions of the rotating plates are spaced from the surrounding housing to define peripheral pressure chambers, and

. leakage paths between the stator and the rotating plates lead to the peripheral pressure chambers to create pressure therein at a value intermediate inlet and outlet pressures acting on the surface of the plates remote from the stator to reduce deflection of the plates.

12. A rotary hydraulic fluid translating device as defined in claim 10 including passages in each plate for porting intermediate pressure to the slots in the stator radially outwardly of the sealing members.

13. A rotary hydraulic fluid translating device as defined in claim 10 including means creating a pressure differential across the sealing members during exposure to the inlet and outlet ports acting in the outer ends of the slots to urge the members toward the cam.

14. A rotary hydraulic fluid translating device, comprising,

a. a housing,

c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes and intervening lows engaging the sealing members in the stator to form displacement chambers,

. a pair of plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the stator adjacent the slots therein,

e. an annular array of alternate inlet and outlet recesses in the face of one plate adjacent the slots in the stator and extending radially a distance from the outer end of the slots inwardly to the cam lows to supply and exhaust fluid relative to the displacement chambers and the slots,

f. an annular array of inlet ports extending through said one plate in communication with the inlet recesses and a radially spaced annular array of outlet ports through the plate in communication with the outlet recesses, and

. means in the housing at the opposite face of said one plate providing an annular inlet groove communicating with the inlet ports and a radially spaced annular outlet groove communicating with the outlet ports as the rotor and the plates rotate.

15. A rotary hydraulic fluid translating device as defined in claim 14, wherein the sealing members are rollers having a diameter slightly less than the width of the slots.

16. A rotary hydraulic fluid translating device as defined in claim 14, wherein, p

b. leakage paths between the stator and the rotating plates lead to the peripheral pressure chambers to create pressuretherein at a value intermediate inlet and outlet pressures acting on the surface of the plates remote from the stator to reduce deflection of the plates.

17. A rotary hydraulic fluid translating device as defined in claim 16, including passages porting intermediate pressure from the peripheral chambers to the slots in the stator radially outwardly from the sealing members.

'18. A rotary hydraulic fluid translating device, comprising,

' a. a housing,

b. a stator in the housing having a cylindrical cavity and a plurality of radial slots with reciprocable sealing rollers therein,

c. a rotor disposed in the stator cavity and having a peripheral cam surface including a plurality of cam lobes and intervening lows connected by rises and falls engaging the sealing rollers to form displacement chambers,

d. a pair of plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the stator adjacent the slots therein, 7

f. an annular array of alternate inlet and outlet ports extending through said one plate in communication with the inlet and outlet recesses, respectively,

. means in the housing at the opposite face of said one plate providing an annular inlet groove communicating with the inlet ports and an annular outlet groove communicating with the outlet ports on rotation of the rotor and plates, and

b. means creating a pressure differential across the sealing rollers acting in the outer ends of the slots to urge the rollers toward the cam.

19. A rotary hydraulic translating device as defined in claim 18, including springs in the slots urging the rollers toward the cam surface.

20. A rotary hydraulic fluid translating device as defined in claim 18 including means restricting flow in and out of said recesses inwardly of said rollers during contact of the rollers with lower portions of the cam rises and falls, and means restricting flow in and out of said recesses outwardly of said rollers during contact of the rollers with upper portions of the cam rises and falls.

211. A rotary hydraulic fluid translating device as defined in claim 20 including ports in said one plate intermediate the inlet and outlet recesses for supplying pressure to the slots in the stator radially outwardly from the sealing rollers.

22. A rotary hydraulic motor, comprising,

a. a housing,

b. a stator in the housing having a central cylindrical cavity and a plurality of radial slots extending from the cavity with loosely fitting reciprocable sealing rollers therein,

c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes and intervening lows engaging the sealing rollers to form displacement chambers,

e. a shaft mounted in the housing and rotatable with the rotor and port plates,

f. an annular array of alternate inlet and outlet recesses in the face of each port plate adjacent the slots in the stator,

g. an annular array of alternate inlet and outlet ports extending through each plate in communication with the recesses in such plate,

h. means providing an inlet communicating with the inlet ports and an outlet communicating with the outlet ports on rotation of the cam and port plates, and

i. said inlet and outlet recesses, said cam, said slots and said rollers being constructed to restrict flow in an out of said recesses inwardly of the rollers during contact of the rollers with low portions of the rises and falls of the cam, and to restrict flow in and out of said recesses outwardly of the rollers during contact of the rollers with the high portions of the rises and falls of the cam, thereby to create a pressure differential acting across the rollers acting in the outer ends of the slots to urge the rollers toward the cam.

23. A rotary hydraulic motor as defined in claim 22, including means for porting pressure to the slots radially outwardly from the rollers intermediate the inlet and outlet recesses.

24. A rotary hydraulic motor as defined in claim 23, including spring means in the slots urging the sealing rollers toward the cam surface.

25. A rotary hydraulic fluid translating device, comprising,

a. a housing,

c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes engageable with the sealing members in the stator to form displacement chambers between the lobes,

d. a pair of port plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the stator adjaent the slots therein and peripheral portions spaced from the surrounding housing to define peripheral pressure chambers,

e. an annular array of alternate inlet and outlet ports extending through each plate in communication with the cavity and slots in the stator,

f. a pair of pressure plates disposed respectively against the surfaces of the port plates remote from the rotor and stator,

means at each interface of the port plates and pressure plates providing an annular inlet groove communicating with the inlet ports and an annular outlet groove communicating with the outlet ports as the rotor and the plates rotate,

. an inlet kidney through each pressure plate communicating with the adjacent annular inlet groove and an outlet kidney through each pressure plate communicating with the adjacent annular outlet groove,

i. means defining an annular pressure chamber behind each pressure plate in communication with the inlet port therein and means defining an annular pressure chamber behind each pressure plate in communication with the outlet port therein, and

j. leakage paths between the stator and the rotating plates leading to the peripheral pressure chambers creating pressure in the chambers at a value intermediate the values of inlet and outlet pressures.

26. A rotary hydraulic fluid translating device as defined in claim 25, including passages in each port plate porting intermediate pressure from the peripheral chambers to the slots in the stator radially outwardly from the sealing members between inlet and outlet recesses.

27. A rotary hydraulic fluid translating device as defined in claim 25, including passages through the rotor communicating the inlet ports in the two port plates with each other and communicating the outlet ports in the two port plates with each other.

28. A rotary hydraulic motor, comprising,

a. a housing,

. a pair of port plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the sides of the stator adjacent the slots and peripheral portions spaced from the surrounding housing to define peripheral pressure chambers,

e. a shaft mounted in the housing and rotatable with the rotor and port plates f. an annular array of alternate inlet and outlet recesses in the face of each port plate adjacent the slots in the stator,

. an annular array of alternate inlet and outlet ports extending through each plate in communication with the recesses in such plate,

. a pair of pressure plates disposed respectively against the surfaces of the port plates remote from the rotor and stator,

. means at each interface of the port plates and pressure plates providing an annular inlet groove communicating with the inlet ports and an annular outlet groove communicating with the outlet ports as the rotor and the plates rotate,

j. an inlet kidney through each pressure plate communicating with the adjacent annular inlet groove, and an outlet kidney through each pressure plate communicating with the adjacent annular outlet groove, and

k. means defining an annular pressure chamber behind each pressure plate in communication with the inlet port therein and means defining an annular pressure chamber behind each pressure plate in communication with the outlet port therein.

29. A rotary hydraulic motor as defined in claim 28, wherein the alternate inlet and outlet recesses in the face of each plate extend radially a distance from the outer end of the slots in the stator inwardly to the cam lows, wherein the annular array of inlet ports through each port plate is radially spaced from the annular array of outlet ports through such plate and wherein the annular inlet groove at each interface of the port plates and pressure plates is radially spaced from the annular outlet groove at each interface of the port plates and pressure plates.

30. A rotary hydraulic motor as defined in claim 28, including passages through the rotor communicating the inlet recesses in the two port plates with each other and communicating the outlet recesses in the two port plates with each other.

Claims

1. A rotary hydraulic fluid translating device, comprising, a. a housing, b. a stator in the housing having a cylindrical cavity and a plurality of radially disposed slots with reciprocable sealing members therein, c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes engageable with the sealing members to form displacement chambers, d. a pair of plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the stator adjacent the slots therein and peripheral portions spaced from the surrounding housing to define peripheral pressure chambers, e. an annular array of alternate inlet and outlet ports extending through one plate in communication with the cavity and slots in the stator, f. means in the housing providing an inlet communicating with the inlet ports and an outlet communicating with the outlet ports as the rotor and the plates rotate, and g. leakage paths between the stator and the rotating plates leading to the peripheral pressure chambers creating pressure in the chambers at a value intermediate the values of inlet and outlet pressures.

4. A rotary hydraulic motor, comprising, a. a housing, b. a stator in the housing having a central cylindrical cavity and a plurality of radial slots extending from the cavity with reciprocable sealing rollers therein, c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes and intervening lows engaging the sealing rollers to form displacement chambers between the lobes, d. a pair of port plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the sides of the stator adjacent the slots and peripheral portions spaced from the surrounding housing to define peripheral pressure chambers, e. a shaft mounted in the housing and rotatable with the rotor and port plates, f. an annular array of alternate inlet and outlet ports extending through each port plate in communication with the cavity and slots in the stator, g. means in the housing providing an annular inlet groove communicating with the inlet ports and an annular outlet groove communicating with the outlet ports on rotation of the rotor and port plates, and h. leakage paths between the stator and the port plates leading to the peripheral pressure chambers to provide pressure in the chambers at a value intermediate the inlet and outlet pressures and acting on the surface of the port plates remote from the stator to reduce deflection of the plates.

6. A rotary hydraulic motor as defined in claim 4, including, a. a pair of pressure plates disposed respectively against the surface of the port plates remote from the rotor and stator, b. an inlet kidney through one pressure plate communicating with the annular inlet groove and an outlet kidney through one pressure plate communicating with the annular outlet groove, c. means defining an annular pressure balance chamber behind each pressure plate in communication with inlet pressure, and d. means defining an annular pressure chamber behind each pressure plate in communication with outlet pressure.

8. A rotary hydraulic fluid translating device, comprising, a. a housing, b. a stator in the housing having a cylindrical cavity and a plurality of radially disposed slots with reciprocable sealing members therein, c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes engageable with the sealing members to from displacement chambers, d. a pair of plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the stator adjacent the slots therein and peripheral portions spaced from the surrounding housing to define peripheral pressure chambers at pressure intermediate inlet and outlet pressures, e. an annular array of alternate inlet and outlet ports extending through one plate in communication with the cavity and slots in the stator, f. means in the housing adjacent the surface of the ported plate remote from the rotor providing an annular inlet groove communicating with the inlet ports and an annular outlet groove communicating with the outlet ports as the ported plate rotates, and g. passages porting intermediate pressure from one peripheral chamber to the slots in the stator radially outwardly from the sealing members between the inlet and outlet ports.

10. A rotary hydraulic fluid translating device, comprising, a. a housing, b. a stator in the housing having a cylindrical cavity and a plurality of radially disposed slots with reciprocable sealing members therein, c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes engageable with the members to form displacement chambers between the lobes, d. a pair of plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the stator adjacent the slots therein, e. an annular array of alternate inlet and outlet recesses in the face of each plate adjacent the slots in the stator, f. an annular array of alternate inlet and outlet ports extending through each plate in communication with the recesses in such plates, g. means in the housing providing an inlet communicating with the inlet ports and an outlet communicating with the outlet ports as the rotor and the plates rotate, and h. passages through the rotor communicating the inlet recesses in said one plate with the inlet recesses in the other plate, and communicating the outlet recesses in said one plate with the outlet recesses in the other plate.

11. A rotary hydraulic fluid translating device as defined in claim 10, wherein, a. peripheral portions of the rotating plates are spaced from the surrounding housing to define peripheral pressure chamberS, and b. leakage paths between the stator and the rotating plates lead to the peripheral pressure chambers to create pressure therein at a value intermediate inlet and outlet pressures acting on the surface of the plates remote from the stator to reduce deflection of the plates.

14. A rotary hydraulic fluid translating device, comprising, a. a housing, b. a stator in the housing having a cylindrical cavity and a plurality of radially disposed slots with reciprocable sealing members therein, c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes and intervening lows engaging the sealing members in the stator to form displacement chambers, d. a pair of plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the stator adjacent the slots therein, e. an annular array of alternate inlet and outlet recesses in the face of one plate adjacent the slots in the stator and extending radially a distance from the outer end of the slots inwardly to the cam lows to supply and exhaust fluid relative to the displacement chambers and the slots, f. an annular array of inlet ports extending through said one plate in communication with the inlet recesses and a radially spaced annular array of outlet ports through the plate in communication with the outlet recesses, and g. means in the housing at the opposite face of said one plate providing an annular inlet groove communicating with the inlet ports and a radially spaced annular outlet groove communicating with the outlet ports as the rotor and the plates rotate.

16. A rotary hydraulic fluid translating device as defined in claim 14, wherein, a. peripheral portions of the rotating plates are spaced from the surrounding housing to define peripheral pressure chambers, and b. leakage paths between the stator and the rotating plates lead to the peripheral pressure chambers to create pressure therein at a value intermediate inlet and outlet pressures acting on the surface of the plates remote from the stator to reduce deflection of the plates.

18. A rotary hydraulic fluid translating device, comprising, a. a housing, b. a stator in the housing having a cylindrical cavity and a plurality of radial slots with reciprocable sealing rollers therein, c. a rotor disposed in the stator cavity and having a peripheral cam surface including a plurality of cam lobes and intervening lows connected by rises and falls engaging the sealing rollers to form displacement chambers, d. a pair of plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the stator adjacent the slots therein, e. an annular array of alternate inlet and outlet recesses in the face of one plate adjacent the slots in the stator and extending radially a distance from the outer end of the slots inwardly to the cam lows to supply and exhaust fluid relative to the displacement chambers and the slots, f. an annular array of alternate inlet and outlet ports exteNding through said one plate in communication with the inlet and outlet recesses, respectively, g. means in the housing at the opposite face of said one plate providing an annular inlet groove communicating with the inlet ports and an annular outlet groove communicating with the outlet ports on rotation of the rotor and plates, and h. means creating a pressure differential across the sealing rollers acting in the outer ends of the slots to urge the rollers toward the cam.

21. A rotary hydraulic fluid translating device as defined in claim 20 including ports in said one plate intermediate the inlet and outlet recesses for supplying pressure to the slots in the stator radially outwardly from the sealing rollers.

22. A rotary hydraulic motor, comprising, a. a housing, b. a stator in the housing having a central cylindrical cavity and a plurality of radial slots extending from the cavity with loosely fitting reciprocable sealing rollers therein, c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes and intervening lows engaging the sealing rollers to form displacement chambers, d. a pair of port plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the sides of the stator adjacent the slots and peripheral portions spaced from the surrounding housing to define peripheral pressure chambers, e. a shaft mounted in the housing and rotatable with the rotor and port plates, f. an annular array of alternate inlet and outlet recesses in the face of each port plate adjacent the slots in the stator, g. an annular array of alternate inlet and outlet ports extending through each plate in communication with the recesses in such plate, h. means providing an inlet communicating with the inlet ports and an outlet communicating with the outlet ports on rotation of the cam and port plates, and i. said inlet and outlet recesses, said cam, said slots and said rollers being constructed to restrict flow in an out of said recesses inwardly of the rollers during contact of the rollers with low portions of the rises and falls of the cam, and to restrict flow in and out of said recesses outwardly of the rollers during contact of the rollers with the high portions of the rises and falls of the cam, thereby to create a pressure differential acting across the rollers acting in the outer ends of the slots to urge the rollers toward the cam.

25. A rotary hydraulic fluid translating device, comprising, a. a housing, b. a stator in the housing having a cylindrical cavity and a plurality of radially disposed slots with reciprocable sealing members therein, c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes engageable with the sealing members in the stator to form displacement chambers between the lobes, d. a pair of port plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the stator adjacent the slots therein and peripherAl portions spaced from the surrounding housing to define peripheral pressure chambers, e. an annular array of alternate inlet and outlet ports extending through each plate in communication with the cavity and slots in the stator, f. a pair of pressure plates disposed respectively against the surfaces of the port plates remote from the rotor and stator, g. means at each interface of the port plates and pressure plates providing an annular inlet groove communicating with the inlet ports and an annular outlet groove communicating with the outlet ports as the rotor and the plates rotate, h. an inlet kidney through each pressure plate communicating with the adjacent annular inlet groove and an outlet kidney through each pressure plate communicating with the adjacent annular outlet groove, i. means defining an annular pressure chamber behind each pressure plate in communication with the inlet port therein and means defining an annular pressure chamber behind each pressure plate in communication with the outlet port therein, and j. leakage paths between the stator and the rotating plates leading to the peripheral pressure chambers creating pressure in the chambers at a value intermediate the values of inlet and outlet pressures.

28. A rotary hydraulic motor, comprising, a. a housing, b. a stator in the housing having a central cylindrical cavity and a plurality of radial slots extending from the cavity with loosely fitting reciprocable sealing rollers therein, c. a rotor disposed in the stator cavity having a peripheral cam surface including a plurality of cam lobes and intervening lows engaging the sealing rollers to form displacement chambers, d. a pair of port plates secured to opposite sides of the rotor for rotation therewith including outwardly disposed portions slidably engaging the sides of the stator adjacent the slots and peripheral portions spaced from the surrounding housing to define peripheral pressure chambers, e. a shaft mounted in the housing and rotatable with the rotor and port plates, f. an annular array of alternate inlet and outlet recesses in the face of each port plate adjacent the slots in the stator, g. an annular array of alternate inlet and outlet ports extending through each plate in communication with the recesses in such plate, h. a pair of pressure plates disposed respectively against the surfaces of the port plates remote from the rotor and stator, i. means at each interface of the port plates and pressure plates providing an annular inlet groove communicating with the inlet ports and an annular outlet groove communicating with the outlet ports as the rotor and the plates rotate, j. an inlet kidney through each pressure plate communicating with the adjacent annular inlet groove, and an outlet kidney through each pressure plate communicating with the adjacent annular outlet groove, and k. means defining an annular pressure chamber behind each pressure plate in communication with the inlet port therein and means defining an annular pressure chamber behind each pressure plate in communication with the outlet port therein.