US3761206A

US3761206A - Fluid device

Info

Publication number: US3761206A
Application number: US00111989A
Authority: US
Inventors: B Fierstine
Original assignee: SHIVELY BROS Inc
Current assignee: SHIVELY BROS Inc
Priority date: 1971-02-02
Filing date: 1971-02-02
Publication date: 1973-09-25
Anticipated expiration: 1990-09-25

Abstract

A fluid device of the sliding vane type having a housing with low and high pressure operating passages, one of which is an inlet passage and the other an outlet passage. A rotor having radially extending vanes is rotatably mounted within a chamber defined by the inner surface of a cam ring and a pair of pressure plates operatively coupled to the opposite sides of the cam ring. The cam ring and pressure plates are mounted in the housing for rotation with the rotor, while means are provided for selectively increasing and/or decreasing relative rotational movement between the rotor and cam ring to control the amount of fluid displaced by the fluid device.

Description

United States Patent 1191 V Fierstine Sept. 25, 1973 [73] Assignee: Shively Bros., Inc., Flint, Mich. a

. part interest [22] Filed: Feb. 2, 1971 [21] Appl. No.: 111,989

[52] US. Cl 418/16, 418/26, 418/27, 418/173, 192/45, 192/91 A [51] Int. Cl...... F01c 21/16, F030 3/00, F04c 15/04 [58] Field of Search 418/16, 17, 23-27, 418/159, 173; 417/220; 192/58 R, 45, 91 A, 91 R [56] References Cited UNITED STATES PATENTS 3,208,570 9/1965 Aschauer 418/173 2,673,448 3/1954 Wheeler 418/24 3,103,893 9/1963 Henning etal. 418/27 2,880,677 4/1959 Grupen 418/23 3,134,471 5/1964 Croswhite .1 192/45 Primary ExaminerCarlt0n R. Croyle Assistant Examiner-Joan J. Vrablik Att0rneyl-1auke, Gifford & Patalidis ABSTRACT A fluid device of the sliding vane type having a housing with low and high pressure operating passages, one of which is an inlet passage and the other an outlet passage. A rotor having radially extending vanes is rotatably mounted within a chamber defined by the inner surface of a cam ring and a pair of pressure plates oper atively coupled to the opposite sides of the cam ring. The cam ring and pressure plates are mounted in the housing for rotation with the rotor, while means are provided for selectively increasing and/or decreasing relative rotational movement between the rotor and cam ring to control the amount of fluid displaced by the fluid device.

13 Claims, 10 Drawing Figures 63? 5/ aze PATENTED 3.761 .206

SHEEI 1 OF 5 INVENTOR BURTON A. FIERSTINE PATENTED SEP25 i975 ,SHEEI 2 OF 5 INVENTOR BURTON A. FIERSTINE PATENTEB SEP25|975 SHEET 3 OF 5 7 R O T N E V N BURTON A.F|ERSTINE- BY z/ m PATENTEB SEPZS I975 SHEET U 0F 5 INVENTOR BURTON A. FIERSTI NE PATENTEnszrzsma 3071 v2 7 SHEET 5 0F 5 SZO/ 5% INVENTOR BURTON A. FIERSTIN BY FLUID DEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to variable displacement rotary fluid devices and, in particular, to variable displacement pumps and motors of the sliding vane type, the displacement of which is adapted to be reduced in response to an increase in pressure.

2. Description of the Prior Art Heretofore, prior art fluid devices, such as pumps and motors of the sliding vane type, generally have comprised a stator fixedly mounted within a housing, the stator including a vane cam track within which is rotatably mounted a rotor carrying radially sliding vanes, which in conjunction with the cam track form fluid inlet and fluid outlet working zones, one of which is connected to a low pressure passageway, the other to a high pressure passageway dependent upon the pump or motor function of the device. In such prior art devices, the rotor is encased between a pair of stationary pressure plates which provide a means for directing pressure fluid to and from the fluid working zones.

The displacement, that is, the fluid output of the prior art pumps and motors of the vane type may be varied in a number of ways. The most common manner of varying the fluid output is to mount the rotor on a shaft eccentrically within the vane track defined by the stator. Means are then provided to move the stator transversely of the axis of rotation of the rotor to vary the amount of eccentricity between the rotating shaft and the vane track, and thereby vary the output flow of the pump. Such variable displacement pumps or motors are quite common and function in an acceptable manner, however they have several disadvantages which make them unsuited for many applications. In particular, these prior art pumps or motors require large housings to accommodate the displacement varying mechanisms; are generally expensive to manufacture; and are not useful in applications where the device is subjected to severe operating conditions, such as in aircraft applications. In addition, pumps or motors of this type can accommodate only one pumping or motoring chamber, that is, one inlet port and one outlet port, which limits its pumping or motoring capacity.

Other mechanisms, which vary the displacement of rotary vane type pumps, or motors, employ a rotatably mounted stator having its outer surface formed with a gear rack which is operatively coupled to a rotating screw mounted in the housing and so arranged that the stator can be rotated a limited angular distance with respect to the rotor to thereby change the pumping or motoring volume between the rotor and the cam track. Such prior art devices have the same disadvantages as hereinbefore described.

Still other variable displacement vane pumps have employed a split stator having a suitable mechanism operatively coupled to each split half of the stator for rotating the stator halves in opposite directions, causing the vanes to pump fluid from one side of the cam track to the other side. This method is effective to control the output flow of the pump, however pumps of this type have excessive leakage and require a continual high power input even when only a low output flow is desired.

It would therefore be desirable to provide a fluid device, particularly of the sliding vane type, wherein the output flow may be varied infinitely over a wide range from zero output flow to maximum design output flow.

SUMMARY OF THE INVENTION The present invention which will be described subsequently in greater detail comprises a fluid device, preferably of the sliding vane type, having a rotor rotatably mounted with a cam ring and between a pair of pressure plates, the cam ring and pressure plate being operatively coupled and adapted for rotation independent of the rotor. Means are provided for selectively increasing and/or decreasing relative rotational movement between the cam ring and the rotor to thereby control the output flow from the fluid device.

It is therefore an object of the present invention to provide a new, improved, efficient, and long wearing fluid device of the sliding vane type.

It is another object of the present invention to provide a variable displacement fluid device of the sliding vane type which is capable of both high pressure and high speed operation without excessive leakage.

Other objects, advantages, and applications of the present invention will become apparent to those skilled in the art of such fluid devices when the accompanying description of the best modes contemplated for practicing the invention are read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF TI-IEDRAWINGS The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like or equivalent parts throughout the several views, and in which:

FIG. 1 is a longitudinal cross-sectional view of a fluid device incorporating features of the present invention and taken on line 1--1 of FIG. 2;

FIG. 2 is a transverse cross-sectional view of the fluid device and taken on line" 22 of FIG'. '1;

FIG. 3 is'a transverse cross-sectional view of the fluid device taken on line 3-3 of FIG. 1;

FIG. 4 is a transverse cross-sectional view of the fluid device taken along line 44 of FIG. 1;

FIG. 5 is an enlarged fragmentary perspective view of FIG. 4;

FIG. 6 is a circuit diagram including a longitudinal cross-sectional view of a preferred control mechanism particularly adapted for use with the fluid device illustrated in FIG. 1;

FIG. 7 is a partially sectioned perspective view of a fluid device incorporating another embodiment of the present invention;

FIG. 8 is an exploded perspective fragmentary view of the fluid device illustrated in FIG. 7;

FIG. 9 is a longitudinal cross-sectional view of a modified fluid device similar to the fluid device shown in FIG. 1; and

FIG. 10 is a fragmentary pespective view of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 through 3, there is shown a fluid devicd 10 of the sliding vane type and which is described herein as being a fluid pump; however, the description is equally applicable to a fluid motor. The pump 10 comprises a cylindrical housing 11 having a body 12 and an end cover 14 secured to the body 12 by screws 16 extending through the cover 14 into threaded bores 17 provided in the body 12. The body 12 includes a pilot portion 18 having a mounting flange 19 (FIG. 2) with mounting holes 20 extending therethrough.

The body 12 has an enlarged cylindrical bore 24 in which there is rotatably mounted a cartridge unit 26 comprising a cam ring 28, a rotor 30 rotatably mounted within the cam ring 28, and a pair of

pressure plates

32 and 34, one positioned on each side of the rotor 30 and cam ring 28. Each

pressure plate

32 and 34 has identical inner faces 36 (FIG. 2), the outer peripheral portions of the inner faces 36 being in a sealing abutment with the opposite sides of the cam ring 28. The width of the rotor 30 is slightly less than the width of the cam ring 28 so as to provide a small running clearance between the inner faces 36 of the

pressure plates

32 and 34 and the opposite sides of the rotor 30. A plurality of bolts (shown only in FIGS. 2 and 3) extend through the

plates

32 and 34 and the cam ring 28 to engage nuts (not shown) to hold the cartridge unit 26 together, such that the members of the cartridge unit 26, other than the rotor 30, will rotate together as a unit in a manner which will be described in greater detail hereinafter.

The outer face 40 of the pressure plate 34 has a cylindrically shaped, axially extending flange 42, the outer periphery of which is rotatably mounted in a bearing 44 which, in turn, is supported in a recess 46 in the end cover 14. The pressure plate 32 has a similar cylindrically shaped, axially extending flange 48, the inner periphery of which is rotatably mounted on a bushing 50 which, in turn, is fixedly mounted within a bore 52 extending through the pilot portion of the body 12 to permit relative rotational movement between the pressure plate 32 and the body 12.

The rotor 30 is rotatably mounted within the cam ring 28 on a splined portion 54 (FIG. 3) ofa drive shaft 56 which, in turn, is rotatably mounted within bushing 50, cantilever style. The drive shaft 56 extends externally of the housing body 12 through an internal bore 60 within the pressure plate 32 and is supported for rotational movement with respect to the pressure plate 32 by bushing 50. A conventional seal 64 mounted within the pilot portion 18 and engaging the outer periphery of the drive shaft 56 is provided to prevent leakage along the drive shaft 56 during operation of the pump 10. An 0-ring seal 66 provided in a recess 68 in the outer face of the body portion 12 prevents leakage at the juncture of the end cover 14 and the body 12.

Referring to FIGS. 4 and 5, the outer periphery of flange 48 of the pressure plate 32 is illustrated as mounting an inner race 70 of a displacement controd mechanism 72. The inner race 70 is fixedly attached to the flange 48 by any suitable means, such as by a pressflt. The displacement control mechanism 72 further comprises an outer race 76, the outer periphery of which is press-fitted into a recess 74 at the inner end of the cylindrical bore 24, while the inner periphery 73 of the outer race 76 has a plurality of angularly spaced recesses 78 of a generally U-shaped cross-section with the base surfaces 79 thereof having a predetermined cam contour which will be described in greater detail hereinafter. Each recess 78 accommodates a roller bearing 80 biased toward one side of its associated recess by a spring 82. Although not shown, the outer periphery of the outer race 76 may be provided with a plurality of projecting flanges adapted to engage complementary recesses in the wall of the recess 74 so that the outer race 76 is restrained from relative rotational movement with respect to the housing body 12, however, the press-fit should suffice to restrain the outer race 76 from rotating.

The outer race 76 has a plurality of radially extending bores 86 (FIGS. 4 and 5), each of which communicates with one of the recesses 78 and slidably mounts actuating members 88, the inner ends 89 of which are adapted to engage one side of their respective roller bearing 80 and shift the same within their associated recesses 78 against the bias of springs 82 when the opposite ends 90 of each actuating member 88 is subjected to a control pressure communicated thereto through an annular recess 92 formed in the outer periphery of the outer race 76 which, in turn, is in fluid communication with a control port 96 through a radially extending passageway 94. The manner in which the displacement control mechanism 72 operates will be described in greater detail hereinafter.

As can best be seen in FIG. 1, the end cover 14 has an inlet supply port 102 with an inlet passage 104 leading therefrom and into an internal bore 105 extending axially through the pressure plate 34 for connection with a drill passageway 106 extending axially through the inner end of the drive shaft 56 and terminating at a plurality of radially extending passages 108 (FIGS. 1 and 2) which, in turn, communicate with an annular recess 110 formed on the inner periphery of the pressure plate bore 60 (FIGS. 1 and 2). Radially extending passageways 112 and 114 in the pressure plate 32 respectively communicate the inlet supply fluid from the annular recess 110 to a pair of diametrically opposed, arcuately shaped inlet port openings 116 and 118 (FIG. 2) provided on the inner face 36 of the pressure plate 32, while a pair of radially extending passageways 120 (only one of which is shown in FIG. 1) in pressure plate 34 communicate the inlet fluid from the bore 105 to another pair of diametrically opposed, arcuatedly shaped inlet port openings 119 and 121 (FIG. 3) provided in the inner face 36 of pressure plate 34. The

inlet port openings

116 and 118 in plate 32, and openings 119 and 121.in plate 34, are respectively axially opposed and will be described in greater detail hereinafter.

Still referring to FIG. 1, the pilot portion end of the body 12 has an outlet connection port 122 with an outlet passage 124 leading therefrom for connection to an annular recess 126 formed at the end of the housing bore 24 surrounding the bushing 50 and opening to the outer face of the pressure plate flange 48. Suitable seals provided at 128 prevent the passage of the pressure fluid between the juncture of the face 48 and the recess 74. The annular recess 126 communicates with a pair of passageways 130 (FIGS. 1 and 4) that extend in a generally axial direction through the pressure plate 32 and terminate at a pair of diametrically opposed, arcuately shaped fluid outlet port openings 132 and 134 (FIG. 2) on the inner face 36 of the pressure plate 32. There is also provided on the inner face 36 of the pressure plate 34 another pair of diametrically opposed, arcuatedly shaped fluid outlet port openings 136 and 138 (FIG. 3) which are axially aligned with the outlet ports 132 and 134 and in fluid communication with one another through axial passageways 139 extending through the cam ring 28.

The face of the flange 48 between seal 128 and the outer periphery of bushing 50 is normally subjected to high pressure fluid which generates a force upon the flange 48 tending to shift the entire cartridge unit 26 rightwardly, as viewed in FIG. 1, such that the outer face 40 of pressure plate 34 is in abutment with the bearing 44, which in conjunction with the bolts 35 maintain the

pressure plates

32 and 34 in a sealing contact with the outer peripheral side edges of the cam ring 28.

As can best be seen in FIG. 3, the inner surface of the cam ring 28 forms a cam track 140 which is substantially elliptical in shape and against which the outer ends of a plurality of vanes 142 are adapted to be maintained in a sliding contact. The vanes 142 are adapted for movement in and out of radial slots 144 provided in the rotor 30 when the rotor 30 is rotated within the cam ring 28 under the driving force of the drive shaft 56. The cam track contour and the outer periphery of the rotor 30 define two opposed working chambers indicated by the

numerals

146 and 148, each of which, for the purposes of convenience, may be divided into a fluid inlet zone and a fluid delivery zone. The fluid inlet zones are those portions of the working

chambers

146 and 148 registering with the opposed

fluid inlet openings

116, 118, 119 and 121 in the

pressure plates

32 and 34, while the fluid delivery zones are those portions of the working

chambers

146 and 148 registering with the opposed

fluid outlet ports

132, 134, 136 and 138 in the

pressure plates

32 and 34.

Assuming rotation is'in a counterclockwise direction as viewed in FIG. 3, the cam track 140 includes an inlet zone ramp extending from A to B (FIG. 3), a true arc portion extending from B to C, an outlet or delivery zone ramp extending from C to D, and another true are portion extending from D to E. The track is symmetrical about both its major and minor axis, and thus each of the ramps and true are portions from A to E are duplicated on the opposite portion of the cam track 140. As the ends of the vanes 142 traverse the inlet ramps, the vanes 142 move radially outwardly with respect to the rotor 30 when the vanes 142 traverse the outlet ramps, the vanes 142 move radially inwardly. Within the true are portions, the vanes generally partake of no radial movement, however, a slight cant may exist in the true arc portions, causing radial movement of the vanes 142 to provide proper compression and decompression of the fluid entering and leaving the ramp zones, respectively.

Still referringto FIG. 3, the inner ends of the vane slots 144 are enlarged to form in conjunction with the inner ends of the vanes 142 closed undervane pressure chambers 150 to which fluid under pressure is supplied for the purpose of maintaining the outer ends of the vanes 142 in a sliding abutment against the cam track 140 during a rotary cycle of the pump. Leaf-type springs (not shown) may be provided to initially bias the vanes 142 radially outward when the device functions as a fluid motor. Each

pressure plate

32 and 34 has, respectively, annular feed grooves 152 (FIGS. 1 and 2) and 154 (FIG. 1) formed therein. Fluid under pressure is supplied to the groove 152 within the pressure plate 32 through axial passageways 156, only one of which is clearly illustrated in FIG. 1. The annular groove 152 in pressure plate 32 is in fluid communication with underwave pressure chambers 150 and supplies fluid pressure thereto as the rotor rotates through a cycle of the device, while pressure fluid entering undervane chambers 150 is transmitted to the annular groove 154 in the pressure plate 34 to provide a proper pressure balance across the opposite sides of the rotor 30. Although not shown, it should be noted that the pressure directed to the undervane pressure chamber 150 may be selectively controlled by any suitable valve means to increase or decrease the driving force exerted on the cam ring 28 by the engagement of the outer ends of the vanes 142 as the rotor 30 rotates. During a normal pumping operation, a fluid, such as a hydraulic oil, enters the inlet connection 102, and travels through passage 104, bore 106, annular recess 1 10, passages 114 and 120, to the fluid

inlet port openings

116, 118, 119 and 121 on the opposite sides of the rotor 30. The symmetrical arrangement of the inlet ports on the opposite side of the

pressure plates

32 and 34 is to permit the fluid from the several inlet passages to enter the

pumping Zones

114 and 146 through the inlet port openings so as to completely fill the pumping zones as the vanes 142 traverse the inlet zone ramps extending from A to B. When the vanes 142 pass through the inlet ramp zone, hydraulic fluid is carried under the force of the vanes 142 to the outlet port openings 132-138, through the outlet connecting passages and exteriorly of the pump through the outlet connection port 122..The vanes 142, which initially engage the cam track due to the centrifugal force imposed thereon as the drive shaft 56 rotates the rotor 30, are maintained in a sliding engagement with the cam track 140 by the force of whatever pressure is communicated to the undervane chambers as hereinbefore described.

Referring now to FIG. 6, there is illustrated a conventional pressure compensator control valve which may be employed in conjunctionwith the displacement control mechanism 72 so as to vary the outward flow of the pump 10. Although a more detailed description of the control valve 160 may be had by reference to U.S. Pat. No. 3,272,135, the control valve 160 will be described herein for purposes of convenience. The pressure compensated control valve 160 comprises a body 162 having three ports 164,166 and 168. These ports are connected respectively by

lines

170, 172 and 174 to the pump outlet connection 122, the pump control port connection 96 and the inlet connection 102.

Connecting lines

170, 172 and 174 schematically indicate connections which would normally be effected by passages within the pump housing 11 terminating in a mounting pad upon which the valve body 162 would be mounted. The pump 10 is normally adapted to be driven by a prime mover 171 and draws fluid from a reservoir 173 to the inlet connection port 102 and directs pressure fluid from the outlet port 122 to a fluid motor 175 to drive the same. The motor 175 returns the fluid to reservoir 173.

The valve body 162 of the valve 160 includes a central bore 176 closed at one end by a plug 178 and at the other by a cover 180. A sleeve 182 is inserted in bore 176 and contains a valve bore 184 in which a valve spool 186 is slidably inserted. Spool 186 carries a first land 1188 which controls communication between ports 164 and 166, and a second land 190 which controls communication between ports 166 and 168.

A bore 192 extends through the end of sleeve 182 and slidably receives a sensing spool 194 which projects into a chamber 196 that is formed in part of the bore 176 and in part of a cavity 198 in the plug 178. Sensing spool 194 has a smaller diameter than valve spool 186. A spring 200 normally urges the sensing spool 194 into abutment with the valve spool 186, which, in turn, abuts a stop 202 on the cover 180. In the normally spring biased position of the valve spool 186, the land 188 isolates port 164 from port 166, while the land 190 permits communication between ports 166 and 168. The biasing force imposed by spring 200 can be adjusted through a support rod 204, and the volume of chamber 196 can be adjusted by threading the plug 178 further into or out of the body 162. If a greater volume is desired for chamber 196, a plug similar to plug 178 having a larger cavity 198 can be substituted.

The sleeve 182 includes a drilled passageway 206 extending in an axial direction from end to end, and in which is inserted a plug 208 having a sharp edged orifree 210 therein.

It can be seen that by slowly increasing the pump outlet pressure a point will be reached at which the outlet pressure of the right hand end of spool 186 will overcome the force of spring 200, plus the pressure in chamber 196 acting on the smaller area of the sensing spool 194 exposed to the pressure in chamber 196, causing spool 186 to shift so that the land 188 will make communication between ports 164 and 166; and thus porting high pressure fluid to the control port inlet 96 wherein the fluid pressure acts against the outer ends 90 of the actuating members 88 to shift the roller bearings 80 against the bias of the springs 82.

Referring now to FIGS. 1, 4 and 5, the contour of the base surfaces 79 of each of the recesses 78 formed in the outer race 76 is formed along a first radius R and second smaller radius R such that the angle formed between the tangents of R and R is a locking or wedge angle I When the roller bearings 80 are engaged at this point with the outer periphery of the inner race 70 and the inner periphery of the outer race 76 under the force of the springs 82, the roller bearings 80 prevent relative rotation between the inner and outer races.

As viewed in FIG. 4, the inner race 70 is adapted to rotate with the cartridge 26 in counterclockwise direction, thus it tends to aid the springs 82 in urging the roller bearings 80 into a wedging contact between the outer periphery of the inner race 70 and the base surfaces 79 of the outer race 76. Thus, when no pressure is being directed to the outer end 90 of each actuating member 88, the roller bearings 80 under the force of the springs 82 prevent relative rotation between the inner and outer races. Since the pressure plate 32 is fixedly attached to the cam ring 28, the cam ring 28 is restrained from rotational movement relative to the housing as the rotor 30, along with the vane 142 carried thereby, rotate to pump fluid in the manner hereinbefore described. To this extent, the pumping action thus described is functionally the same as a conventional pump of a sliding vane type.

When the demand for fluid pressure downstream from the outlet port connection 122 (at motor 175) drops, causing a pressure increase, the same will be sensed by the pressure control valve 160, which, in turn, will direct fluid under pressure from the port 166 through line 172 to the control port 196 wherein the fluid pressure will act against the outer end 90 of each of the actuating members 88 to cause the same to move the roller bearings 80 against the bias of the springs 82. As the roller bearings 80 are so moved away from the locking angle, the bearings 82 will slip relative to the inner and outer races permitting a certain amount of rotational movement between the inner and outer races. Since the inner race is operatively coupled to the cam ring 28, relative rotational movement of the cam ring 28 with respect to the housing will occur, that is, the cam ring 28 will tend to rotate in the same direction as the rotor under the force of the engaged ends of the vanes 142 in conjunction with the pressure acting against outlet ramps of the cam track 140, causing a reduction in the output of the pump 10 and a corresponding drop in pressure. The amount of rotation of the cam ring will be dependent upon the amount of slip between the bearings and the inner and outer races of the control mechanism 72. If the pressure sensed by the pressure control valve is sufficiently high, the actuating members 88 will cause the roller bearings 80 to disengage from the locking angle a sufficient distance to cause free relative rotation between the outer race 76 and inner race 70, whereby the engaged outer ends of the vanes 142 and the cam track will cause the cam ring 28 to rotate with the rotor 30 at substantially the same angular velocity. When the cam ring 28 is so rotating with the rotor 30, no pumping action can be had.

It can thus be seen that depending upon the amount of slip between the inner and outer races, which, in turn, is dependent upon the position of the roller bearings 80, the amount of fluid output and thus the pressure downstream of the outlet 122 can be controlled over an infinite range between a full flow condition wherein the bearings engage in a locking engagement with the inner and outer races to prevent the cam ring 28 from rotating, and a no-flow or zero flow condition wherein the roller bearings 80 are disengaged from a locking engagement and the cam ring 28 rotates with the rotor 30.

Referring now to FIGS. 7 and 8 wherein there is illustrated a second embodiment of the present invention in the form of a fluid pump 300 of the sliding vane type which comprises a cylindrical housing 311 having a body 312 and an end cover 314 with a threaded outer periphery 315. The body 312 has an enlarged cylindrical bore 324, the open end of which is threaded at 316 to receive the end cover 314. The body 312 includes a pilot portion 318 having a mounting flange 320 with threaded mounting holes 322 extending therethrough.

A cartridge unit 326 is rotatably mounted with the housing bore 324 and comprises (as viewed from left to right in FIGS. 7 and 8) an intake port plate 327, a pressure plate 332, a cam ring 328, a rotor 330 rotatably mounted within the cam ring 328, and a second pressure plate 334. A stationary pressure pickup plate 335 abuts the outer face of the pressure plate 334. The inner faces 336 of the pressure plates 332' and 334 axially opposing the sides of the cam ring 328 and rotor 330 are substantially identical with the outer peripheral portions of the inner faces 336 of the pressure plates being in a sealing abutment with the opposite peripheral side portions of the cam ring 328. The width of the rotor 330 is slightly less than the width of the cam ring 328 so as to provide a small running clearance between the inner faces 326 of the

pressure plates

332 and 334 and the opposing sides of the rotor 330. The intake port plate 327, the two

pressure plates

332 and 334 and the cam ring 328 are attached by dowel pins 329 extending through bores 331 in each member and are adapted to rotate with one another with respect to the housing in a manner which will be described hereinafter.

An enlarged cavity 337 formed between the outer side of the stationary pressure pickup plate 335 and the interior wall of the end cover 314 accommodates a spring 338 having one end bearing against the cover 314 and the other end bearing against the pressure pickup plate 335. The spring 338 exerts a force of sufficient magnitude against the pressure pickup plate 335 so as to bias the entire cartridge unit 326 toward the opposite end of the pump bore 324 and into engagement with a thrust bearing 339. Thrust bearing 339 comprises an outer race 340 fixedly mounted in the pump bore 324, while the outer face of the intake port plate 327 functions as the inner race of the thrust bearing. A plurality of needle bearings 341 are mounted between the races and function in the conventional manner to absorb thrust loads imposed thereon.

The rotor 330 is rotatably mounted within the cam I ring 328 on a splined portion 354 of an inner drive shaft 356 which, in turn, extends axially through and is rotatably supported by an outer drive shaft 357, cantilever style. The inner and outer shafts pass externally of the pump 300 through a bore 359 extending through the pilot portion 318. The outer shaft 357 is fixedly attached to the outer surface of the intake port plate 327 by a suitable means and preferably is integral therewith. A conventional seal 364, mounted within the pilot portion bore 359, engages the outer periphery of the outer drive shaft 357 to prevent fluid leakage the repast. A second seal (not shown) may be provided between the outer periphery of the inner shaft 356 and the inner surface of the outer shaft 357 to provide a similar sealing function. An -ring seal 366, provided in a recess 368 in the body portion 312, prevents leakage across the outer periphery of the pressure pickup plate 335 since the cavity 337 is normally subjected to high pressure fluid as will be described hereinafter.

The outer periphery of the cam ring 328 forms an inner race for needle bearings 370, while an outer race 372 is fixedly attached to the pump bore 324 by any suitable means, such as a press-fit. Thus, the cartridge unit 326 is adapted for freerotation within the needle bearings 370 independent of both the rotor 330 and the body 312. The cartridge unit 326 is adapted to be driven by the outer shaft 357, while the rotor 330 is adapted to be driven by the inner shaft. 356, each inde pendent of the other.

The flange portion 320 has an inlet supply port 374 with an inlet passage 376 leading therefrom and into an annular bore 378 surrounding the outer periphery of the outer shaft 357 for connection with a recess 380 in the outer face of the intake port plate 327. Referring to FIG. 8, it can be seen that the intake port plate recess has a plurality of axially extending passages 381 which fluidly communicate the recess 380 with a similar recess 383 formed on the outer face of the pressure plate 332. The pressure plate recess 383 fluidly communicates with a pair of diametrically opposed, arcuately shaped inlet port openings 382 formed on the inner face 336 through radially extending passageways 384. The inlet openings 382 communicate the inlet fluid to working chambers formed between the cam ring 328 and the outer periphery of the rotor 330. The inner face 336 of the pressure plate 332 is further provided with a second pair of diametrically opposed, arcuately shaped outlet port openings 386 which are displaced from the inlet port openings 382. The port openings 386 are also in communication with the working chambers. The inner face 336 of the pressure plate 332 is provided with two pairs of undervane ports 388 and 390 spaced respectively radially inward of the inlet and outlet port openings and which communicate with the undervane chambers 150 within the rotor.

The inner surface of the cam ring 328 forms a cam track 400 similar to the aforementioned cam track 140, while the rotor 330 has a plurality of radially extending vanes 402 adapted to engage the vane track 400; the

rotor 330, the vane track 400 and the vanes 402 being substantially similar in both construction and function to the rotor 30, vane track and vanes 142 hereinbefore described in the embodiment illustrated in FIGS. 1-6, and thus a further description of these components is not necessary.

The inner face 336 of the pressure plate 334 is similarly provided with a pair of diametrically opposed, arcuately shaped outlet port openings 404 that are axially opposed to and in communication with outlet port openings 386 in the pressure plate 332 through crossover passages 405 that extend axially through the cam ring 328. The diametrically opposed outlet portopenings 404 extend completely through the pressure plate 334 to the opposite side thereof and communicate with an annular pressure pickup groove 406 formed in the inner face of the stationary pressure pickup plate 335. The pressure pickup groove 406,'in turn, fluidly communicates with the cavity 337 through a plurality of axial passageways 408 extending completely through the plate 335. The cavity 337 provides a fluid connection to a'fluid outlet port 410 disposed in the rear portion of the body 312.

The inner face of pressure plate 334 is also provided with a pair of diametrically opposed, arcuately shaped inlet port openings 412 which are axially opposed to the inlet port openings 382 in pressure plate 332 and in communication therewith through axial cross-over passages 414 in the cam ring 328. The inner face of pressure plate 334 is further provided with two pairs of undervane ports 416 and 418 spaced, respectively, radially inward of the inlet and outlet openings; the undervane ports 416 being in direct fluid communication with the pressure pickup groove 406 through axial passage 419, while the undervane ports 418 communicate with the pressure pickup groove 406 through restricted axial passages'420. The undervane ports 418 are thus adapted to restrict the rate at which fluid is exhausted from the undervane chambers when the vanes traverse the outlet port openings, thereby generating an increased pressure in the undervane chambers 150 to bias the vanes outwardly as they traverse the outlet ramps. The undervane ports 388 and 390 in the pressure plate 334 provide for a proper pressure balance across the rotor 330.

The high pressure fluid within the cavity 337 generates a force acting on the outer side of the pressure pickup plate 335 to aid the spring 338 in maintaining the cartridge unit 326 in abutment with the thrust bearings 339 at the front of the pump. The inner face of the plate 335 also has a pair of radially spaced annular thrust faces 422 and 424 which slidingly abut with the opposing outer face of the pressure plate 334 and allow the pressure plate 334 to rotate as well as providing a fluid seal to prevent the leakage of high pressure fluid from the pressure pickup groove 406.

When the outer shaft 357 is held stationary and the inner shaft 356 is rotated so that there is rotational movement of the rotor with respect to the cam track of the cam ring 328, the pump 300 functions in a normal manner and fluid is pumped from the inlet port openings to the outlet port openings in the same manner as hereinbefore described with respect to the embodiment disclosed in FIGS. 1-5. By rotating the outer shaft 357 in the same direction and at the same angular velocity as the inner shaft 356, there will be no relative movement between the rotor 330 and the cam ring 328, and thus no pumping action can be achieved. By varying the speeds of the inner and outer shafts, the fluid output of the pump 300 can be controlled from a minimum or zero flow condition to a maximum or full flow condition or any intermediate desired flow. The primary difference between the pump and the pump 300 is in the manner in which rotation of the cam ring is obtained. In the pump 10, rotation of the cam ring is due to the engagement of the outer ends of the vanes 142 with the cam track 140 when the displacement control mechanism 72 is released, while rotation of cam ring of pump 300 is directly controlled externally of the pump 300 via outer shaft 357.

Referring now to FIGS. 9 and 10, wherein there is illustrated a fluid pump 500 which is substantially identical to the fluid pump 10 described hereinbefore with the exception that the pump displacement mechanism 72 has been replaced by a conventional roller bearing 502 which provides radial support for the pressure plate 32 and the input shaft 56. A modified pump displacement control mechanism 504, illustrated as being positioned around a modified cam ring 528, is adapted to control the relative rotational movement between the cam ring 528 and rotor 30.

The outer periphery of the cam ring 528 has a tapered surface 505 which forms an inner race on which a plurality of tapered roller members 508 are engaged. Each of the roller members 508 is disposed in one of a plurality of angularly spaced recesses 510 formed in the inner periphery of an outer race 512 which, in turn, is rotatably mounted in an annular recess 517 in housing bore 24 and restrained from rotational movement in excess of approximately 10 BY the engagement of radial projections 519 with enlarged slots 521 formed in the recess 517. Thus the outer race 512 can move a limited angular distance relative to the housing 1 l. The inner or base surface 513 of each recess 510 has a tapered contour engaging its associated tapered roller member 508. The base surface 513 of each recess 510 is formed by a first arcuate portion having a radius R, at the rear portion of the surface 513 and by a second arcuate portion having a smaller radius R at the front portion of the surface 513 such that the angle A (hereinafter referred to as the locking angle) between the tangents of the two arcuate portions is formed between and 25 and is preferably while an angle B (hereinafter referred to as the wedge angle) formed between the tapered surface of each roller member 508 and the axis of rotation is maintained between 6 and 12.

A spring 514 of a relatively light spring force is disposed in the rear portion of each recess 510 and is of a sufficient preload to hold its associated tapered roller member in full engagement with the cooperating tapers formed on the base surface 513 of the recess 510 and the outer periphery of the cam ring 528. The opposite end faces of each of the roller members 508 have, respectively, axially extending

pistons

518 and 520 which respectively slidably engage

bores

522 and 524. Each roller member 508 is held within its respective recess 510 in a fixed angular position with respect to the housing 1 l by the engagement of its associated

portions

518 and 520 in their

respective bores

522 and 524. Bore 522 communicates with a source of high pressure fluid such as the outlet port 166 of the pressure compensator through a passageway 526 and a control port 527, while bore 524 communicates with inlet port 102 through a passage 529 in the cover 12. The bore 524 further has a spring 530, one end of which bears against the inner wall of cover 12, while the other end bears against the outer end of the piston 520 to bias the piston 520, and thus its associated roller member 508, into a locking contact between the cam ring and the outer race to controllably limit relative rotational movement between the two members. The inlet pressure acting against the outer end of piston 520 aids the spring 530 in maintaining the roller members 508 in position while pressure acts against the outer end of the piston 522 to shift the same axially and thus to move the roller members against the bias of the spring and the force created against the piston 520 by the inlet pressure.

Thus movement of the roller members is a function of the pressure differential of the pump inlet and outlet. A rightward movement (as viewed in FIG. 9) of the roller members shifts the roller members out of a locking contact with the cam ring and the outer race. By controlling the amount of pressure acting on the outer face of the piston 522, the roller members may be preferentially axially displaced by a sufficient amount which will permit a desired amount of slip between the cam ring and the roller members to thereby permit the cam ring to rotate with the rotor and to decrease the pump displacement in the same manner as described hereinbefore. If the roller members are axially displaced a sufficient distance percent slip between the cam ring and roller is obtained, that is, the roller members are free to rotate within their associated recesses 510 and the cam ring will rotate in the same direction as the rotor and at substantially the same angular velocity, whereby the pump output flow may be decreased to zero.

Spring 530 is sufficient in itself to hold the roller members in full engagement with the cooperating tapers formed on the generally fixed outer race member and the outer peripheral surface of the cam ring, while spring 514 provides a force sufficiently large in opposition to the directional rotation desired by the cam ring, that is, in the direction of rotation of the rotor, so as to keep the roller members wedged within the 15 to 25 subtended circumferential locking angle. With no additional resultant forces acting on the roller members, the same will not rotate, therefore the cam ring will not rotate and pump delivery will be at its maximum or 100%- capacity.

An examination of the known net resolution of forces imparted to the cam ring by the rotor member while transferring increments of fluid from the inlet zones to the outlet zones indicate that, in a dynamic sense, the rotational forces tending to turn the cam ring with, and in the same direction as the rotor, vary but little for a given physical pump at constant low heads between 100 percent capacity (zero cam ring rotation, 100 percent slip) and zero delivery capacity (100 percent cam ring rotation, percent slip). Kinematically, however, the imposition of a resistance to flow, for example increasing the amount of head, requires a greatly magnified rotational resisting force at a steeply ascending rate in proportion to the ascending head, to maintain constant flow 0 percent slip), and thus for a given pump size at a constant head differential, rotational forces tending to turn the cam ring with the rotor vary but little with the volume pumped; for example, within the limits defined by the cam ring rotating at 1 percent of rotor speed (99 percent slip) and the cam ring rotating at 99 percent of rotor speed 1 percent slip). While, conversely, at constant volume and varying heads, the magnitude of the forces generally directing the cam ring to rotate with the rotor vary greatly with varying head differentials. In particular at constant head differential restraining, the force required to maintain a constant speed ratio in opposition to the cam ring rotating forces is at a substantially steady level of magnitude at constant cam ring to rotor slip relationships or speed ratios (between 1 percent and 99 percent slip). A change in speed ratio produces a temporarily greaterthan the steady state resultant force at a new speed ratio when the cam ring speed decreases and conversely less force when the cam ring speed increases. The absolute magnitude of the greater-than, or less-than, steady state force depends upon the rate of change in state (speed ratio) and the acting force motivating the speed ratio change. In other words, a speed ratio change between cam ring and rotor brought about or caused by mechanical interference with the rotation of the cam ring produces a magnification or multiplication of the required cam ring restraining forces of steady state operation than would a similar cam ring speed change brought about by a hydraulic head change at constant drag or resisting force opposing cam ring rotation. Provided, however, that the rate of hydraulic head change at the point of occurrence of said change do not produce resonant shock waves, hydraulic hammer, jump or the like.

These physical considerations produce a smoothly functioning, easily controllable variable displacement vane pump using the compounded angularly locking and axially controllable wedging action of the tapered roller members cooperating with the circumferentially rotating outer surface formed on the pump cam ring and a compounded angle, axial, and angularly acting non-rotating outer race.

'In the embodiments illustrated in FIGS. 1 and 9, the speed ratio, that is, the cam ring speed with respect to the rotor speed, is not constant. The cam ring speed may vary from zero speed to the rotor speed, and in the embodiment illustrated in FIGS. 7 and 8, the cam ring speed can be increased over that of the rotor speed by using a gear drive or other means whereby the cam ring speed can be one or more times the rotor speed.

It can thus be seen that the present invention has provided means of varying the displacement of a vane pump or motor which is simple and compact in its construction and meets the objects as herebefore stated.

What is claimed is as follows:

1. A fluid pressure energy translating device comprising a housing having low and high pressure operating passages, one of which is an inlet passage and the other an outlet passage;

a cam ring rotatably mounted in said housing and a cam track formed on the inner periphery of said cam ring;

a fluid responsive means rotatably mounted within said cam track and forming fluid inlet and fluid outlet zones therewithin, said fluid responsive means engaging said cam track for moving fluid between said zones;

means normally restraining rotational movement of said cam ring with respect to said fluid responsive means when said fluid responsive means is rotated;

means varying the amount of said restrainment to permit said cam ring to rotate with said fluid responsive means for controlling the amount of fluid moving between said zones;

means communicating one of said zones with one of said passages and the other of said zones with the other of said passages;

said normally restraining means comprising a nonrotatable member carried within said housing; a rotatable member operatively coupled to said cam ring and rotatable therewith; bearing means disposed between said members and movable between a first position engaging said members to decrease relative rotational movement between said mebers and then limit the amount of relative rotational movement between said cam ring and said fluid'responsive means, and a second positionin-' creasing relative rotational movement between said members; means normally biasing said bearing means toward said first position; and

one of said members having a plurality of angularly spaced recesses having a selected cam contour, said bearingmeans being a plurality of bearings each of a selected shape disposed within said recesses, each of said bearings engaging a portion of the other of said members movable in their respective 'recesses between said first position, wherein said bearings engage said cam contour and said portion of said other member in a wedge-like manner, and said second position.

2. The device defined in claim 1 further comprising means disposed in said recesses for normally biasing said bearings into said first position.

3. The device defined in claim 2 further comprising means for selectively moving said bearings toward said second position. I

4. The device defined in claim 1 wherein one of said members is radially spaced and concentrically disposed with respect to the other of said members.

5. The device defined in claim 4 wherein said recesses are formed in said non-rotatable member.

6. A fluid pressure energy translating device comprising a housing having low and high pressure operating passages, one of which is an inlet passage and the other an outlet passage;

said normally restraining means comprising a nonrotatable member carried within said housing; a rotatable member operatively coupled to said cam ring and rotatable therewith; bearing means disposed between said members and movable between a first position engaging said members to decrease relative rotational movement between said members and then limit the amount of relative rotational movement between said cam ring and said fluid responsive means, and a second position increasing relative rotational movement between said members; means normally biasing said bearing means toward said first position; and

said rotatable member being radially spaced from and concentric with said non-rotatable member, said non-rotatable member having a plurality of angularly spaced recesses with selected cam contours formed on the inner periphery of said nonrotatable member, said bearing means comprising a plurality of rotatable bearings each of a selected shape and disposed, within said recesses, each bearing being engaged with a portion of the outer periphery of said rotatable member and movable within their respective recesses between said first position wherein each of said bearings are wedged between their respective cam contours and the outer periphery of said rotatable member to prevent rotational movement betwen said members and said second position.

7. The device defined in claim 6 further comprising means for selectively moving said bearings toward said second position to control the amount of relative rotational movement between said member.

8. The device defined in claim 6 further comprising means disposed in each of said recesses for normally biasing its associated bearing into said first position.

9. The device defined in claim 8 wherein said means for selectively moving said bearing comprises a plurality of pressure responsive members carried by said nonrotatable member, each pressure responsive member being associated with one of said bearings and movable in response to a pressure increase to move said bearings against said normally biasing means and means communicating said high pressure operating passage to said pressure responsive member.

10. A fluid pressure energy translating device comprising a housing have low and high pressure operating passages, one of which is an inlet passage and the other an outlet passage;

the outer periphery of said cam ring having a preselected tapered contour, said normally restraining means comprising a non-rotatable surface having a tapered contour and radially outwardly spaced from said cam ring tapered contour; bearing means having a preselected tapred contour and movable between a first position engaging said tapered contours of said cam ring and said non-rotatable surface for restraining relative rotational movement between said cam ring between said cam track and said fluid responsive means and a second position permitting rotation of said cam ring with respect to said non-rotatable surface and means normally biasing said bearing means to said first position.

11. The device defined in claim 10 further comprising a non-rotatable member carried by said housing, said member having a plurality of angularly spaced recesses formed on the inner periphery thereof, said nonrotatable surfaces beingformed in said recesses, said bearing means being carried within said recesses and rotatable about an axis that is coaxial with the axis of rotation of said cam ring; said normally biasing means comprising a spring disposed on one side of each of said bearing means, said springs urging said bearing means into engagement with said tapered surfaces of said member and said cam ring; and each of said bearing means having pressure responsive surfaces which in response to a pressure increase are adapted to move said bearing means axially against the bias of said spring to said second position.

12. The device defined in claim 10 further comprising means for selectively moving said bearing means toward said second position.

13. The device defined in claim 10 further comprising means for selectively moving said bearing means, said means comprising a plurality of pressure responsive members carried by said housing and each associated with one of said bearing means and movable in response to a pressure increase to move said bearing means against said biasing means; means communicating said high pressure operating passage to said pressure responsive member.

Patent No. 61,206 Dated ptember 25, 1973 lnventor(s) Burton Fierstine is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 2, line '62, delete "devicd" and insert -device-.

Col. 3, line 52, delete "controd" and insert '-control-.

Col. 5, line' 66', delete "underwave" and insert undervane.

Col. 6, line l9,- deletell4" andinsert --144--.

Col. 9, line delete the re" and insert --there--;

line .47, delete ".(period)," after "shaft"; "line 62, after "communicate", delete "the" and insert with-.

Col. ll, line 414, delete "BY" and insert -by-. Col. 14, line "26, delete "m ebe rs and insert --members-. g

Col. 16, line" 22, delete "tapred" and insert '-tapered--.

Signed and sealed this 1st day of January 1974,

(SEAL) Attest:

EDWAR .FLET HER;JR. RENE" D. TEGTMEYTER' Attesting Officer Acting Commissioner of Patents F ORM Po-1p50 0-69) T v USCOMMYDC seam-ps9 UlS, covznumsm' PRINTING o rlcpz 1959 0-366-334

Claims

1. A fluid pressure energy translating device comprising a housing having low and high pressure operating passages, one of which is an inlet passage and the other an outlet passage; a cam ring rotatably mounted in said housing and a cam track formed on the inner periphery of said cam ring; a fluid responsive means rotatably mounted within said cam track and forming fluid inlet and fluid outlet zones therewithin, said fluid responsive means engaging said cam track for moving fluid between said zones; means normally restraining rotational movement of said cam ring with respect to said fluid responsive means when said fluid responsive means is rotated; means varying the amount of said restrainment to permit said cam ring to rotate with said fluid responsive means for controlling the amount of fluid moving between said zones; means communicating one of said zones with one of said passages and the other of said zones with the other of said passages; said normally restraining means comprising a non-rotatable member carried within said housing; a rotatable member operatively coupled to said cam ring and rotatable therewith; bearing means disposed between said members and movable between a first position engaging said members to decrease relative rotational movement between said mebers and then limit the amount of relative rotational movement between said cam ring and said fluid responsive means, and a second position increasing relative rotational movement between said members; means normally biasing said bearing means toward said first position; and one of said members having a plurality of angularly spaced recesses having a selected cam contour, said bearing means being a plurality of bEarings each of a selected shape disposed within said recesses, each of said bearings engaging a portion of the other of said members movable in their respective recesses between said first position, wherein said bearings engage said cam contour and said portion of said other member in a wedge-like manner, and said second position.

3. The device defined in claim 2 further comprising means for selectively moving said bearings toward said second position.

6. A fluid pressure energy translating device comprising a housing having low and high pressure operating passages, one of which is an inlet passage and the other an outlet passage; a cam ring rotatably mounted in said housing and a cam track formed on the inner periphery of said cam ring; a fluid responsive means rotatably mounted within said cam track and forming fluid inlet and fluid outlet zones therewithin, said fluid responsive means engaging said cam track for moving fluid between said zones; means normally restraining rotational movement of said cam ring with respect to said fluid responsive means when said fluid responsive means is rotated; means varying the amount of said restrainment to permit said cam ring to rotate with said fluid responsive means for controlling the amount of fluid moving between said zones; means communicating one of said zones with one of said passages and the other of said zones with the other of said passages; said normally restraining means comprising a non-rotatable member carried within said housing; a rotatable member operatively coupled to said cam ring and rotatable therewith; bearing means disposed between said members and movable between a first position engaging said members to decrease relative rotational movement between said members and then limit the amount of relative rotational movement between said cam ring and said fluid responsive means, and a second position increasing relative rotational movement between said members; means normally biasing said bearing means toward said first position; and said rotatable member being radially spaced from and concentric with said non-rotatable member, said non-rotatable member having a plurality of angularly spaced recesses with selected cam contours formed on the inner periphery of said non-rotatable member, said bearing means comprising a plurality of rotatable bearings each of a selected shape and disposed, within said recesses, each bearing being engaged with a portion of the outer periphery of said rotatable member and movable within their respective recesses between said first position wherein each of said bearings are wedged between their respective cam contours and the outer periphery of said rotatable member to prevent rotational movement betwen said members and said second position.

9. The device defined in claim 8 wherein said means for selectively moving said bearing comprises a plurality of pressure responsive members carried by said non-rotatable member, each pressure responsive member being associated with one of said bearings and movable in response to a pressure increase to move said bearings against said normally biasing means and means communicating said high pressure operating passage to said pressure responsive member.

10. A fluid pressure energy translating device comprising a housing have low and high pressure operating passages, one of which is an inlet passage and the other an outlet passage; a cam ring rotatably mounted in said housing and a cam track formed on the inner periphery of said cam ring; a fluid responsive means rotatably mounted within said cam track and forming fluid inlet and fluid outlet zones therewithin, said fluid responsive means engaging said cam track for moving fluid between said zones; means normally restraining rotational movement of said cam ring with respect to said fluid responsive means when said fluid responsive means is rotated; means varying the amount of said restrainment to permit said cam ring to rotate with said fluid responsive means for controlling the amount of fluid moving between said zones; means communicating one of said zones with one of said passages and the other of said zones with the other of said passages; the outer periphery of said cam ring having a preselected tapered contour, said normally restraining means comprising a non-rotatable surface having a tapered contour and radially outwardly spaced from said cam ring tapered contour; bearing means having a preselected tapred contour and movable between a first position engaging said tapered contours of said cam ring and said non-rotatable surface for restraining relative rotational movement between said cam ring between said cam track and said fluid responsive means and a second position permitting rotation of said cam ring with respect to said non-rotatable surface and means normally biasing said bearing means to said first position.

11. The device defined in claim 10 further comprising a non-rotatable member carried by said housing, said member having a plurality of angularly spaced recesses formed on the inner periphery thereof, said non-rotatable surfaces being formed in said recesses, said bearing means being carried within said recesses and rotatable about an axis that is coaxial with the axis of rotation of said cam ring; said normally biasing means comprising a spring disposed on one side of each of said bearing means, said springs urging said bearing means into engagement with said tapered surfaces of said member and said cam ring; and each of said bearing means having pressure responsive surfaces which in response to a pressure increase are adapted to move said bearing means axially against the bias of said spring to said second position.