US3907467A

US3907467A - Rotary vane machine with fluid flow paths on each vane side

Info

Publication number: US3907467A
Application number: US504534A
Authority: US
Inventors: Ulf Christer Ekenberg; Johan Paul Strom; Ragnar Georg Jonsson
Original assignee: US Philips Corp
Current assignee: NobelTech Electronics AB
Priority date: 1971-11-12
Filing date: 1974-09-09
Publication date: 1975-09-23
Anticipated expiration: 1992-09-23

Abstract

A hydraulic vane motor having rotor vanes radially displaceable in slots, in which a pressure chamber is disposed in the inner part of each slot. The outer edge of a vane is pressed against a work portion of a cam profile by fluid pressure acting on the bottom of the vane. Radially directed flow paths along the broad sides of each vane, plus a small circumferential movement of the vane in the slot, provide different flow resistances on the opposite sides of the vane.

Description

United States Patent Ekenberg et al.

[4 1 Sept. 23, 1975 ROTARY VANE MACHINE WITH FLUID FLOW PATHS ON EACH VANE SIDE Inventors: Ulf Christer Ekenberg; Johan Paul Strom; Ragnar Georg Jonsson, all of Jakobsberg, Sweden Assignee: U.S. Philips Corporation, New

York, NY.

Filed: Sept. 9, 1974 Appl. No.: 504,534

Related US. Application Data Continuation of Ser. No. 305,297, Nov. 10, 1972, abandoned.

Foreign Application Priority Data Nov. 12, 1971 Sweden 14491/71 US. Cl 418/82; 418/268 Int. C1. F01C l/00; F03C 3/00; F04C 1/00;

FOlC 21/00 Field of Search 418/267, 268, 82, 184

References Cited UNITED STATES PATENTS 3/1945 Tucker et a1. 418/268 2,435,279 2/1948 Hubucker 418/268 3,076,415 2/1963 Farron 418/268 3,086,475 4/1963 Rosaen 418/268 3,609,071 9/1971 Brown 418/267 3,627,456 12/1971 Gerlach 418/268 Primary Examiner-John J. Vrablik Attorney, Agent, or FirmFrank R. Trifari; David R. Treacy [57] ABSTRACT A hydraulic vane motor having rotor vanes radially displaceable in slots, in which a pressure chamber is disposed in the inner part of each slot. The outer edge of a vane is pressed against a work portion of a cam profile by fluid pressure acting on the bottom of the vane. Radially directed flow paths along the broad sides of each vane, plus a small circumferential movement of the vane in the slot, provide different flow resistances on the opposite sides of the vane.

4 Claims, 7 Drawing Figures US Patent Sept. 23,1975 Sheet 1 of 2 3,907,467

US Patent Sept. 23,1975 Sheet 2 of2 3,907,467

Fig.2

ROTARY VANE MACHINE WITH FLUID FLOW PATHS ON EACH VANE SIDE This is a continuation of Ser. No. 305,297, filed Nov. 10, 1972, now abandoned.

This invention relates to hydraulic machines, and more particularly to vane motors for use in position servo applications. Such a motor has a stator including a stator ring provided with a cam profile, two side members, and a rotor enclosed in said stator transferring the torque to an output shaft and carrying radially displaceable vanes in slots. Each slot has a pressure chamber at its inner part. The outer edge of each vane during the work moment of the vane is pressed against a corresponding work length of the cam profile thereby preventing pressure medium from overflowing between the outer edges of the active vanes and the stator ring from the high pressure to the low pressure side of the vane.

The seal between the vanes and the stator ring is a source of difficulty in machines of this type. If the motor is intended to develop high torque at start and at low speed, which is necessary for position servo purposes, these difficulties are increased because it is then not possible to gain an advantage from the centrifugal force on the vanes to provide an adequate seal.

The solution to this problem is to provide a force which presses each vane against a corresponding work length of the cam profile of the stator ring only during the work movement of the vane. It is desirable that the resultant force directed upwards just exceeds zero, whereby the frictional drag between vanes and stator ring and the accompanying wearing of the vanes and the cam profile will be minimized, so the motor will operate at the highest possible efficiency.

It is known to spring load the vanes in such a manner that they are continuously pressed against the cam protile. In a machine of said type this solution means that the vanes are pressed against the cam profile by the total spring force when the vanes are inactive, and thus are not influenced by-an inwardly directed hydraulic force. This solution causes high frictional forces and consequently great wearing of the vanes and the cam profile.

It is also known to use a hydraulic pressure derived from the high pressure side of the machine for providing an outward force. For this purpose it is possible to use the total high pressure by feeding pressure medium from the high pressure side of the machine through channels into the pressure chamber in each slot, or a part of the high pressure bypassing the pressure medium through pressure reducing valves before reaching the pressure chamber. The pressure in the pressure chamber acts on the inner edge of each vane to provide an outwardly directed force. ln the first case the force on each vane during the work movement of the vane is unsuitably great, and causes high friction and wearing. In the second case additional features are necessary to reduce the pressure, thus making the machine more complicated, which in turn gives rise to greater manufacturing cost. When a vane motor is used for servo purposes the second case design is inappropriate, because the use of pressure reducing valves in the regulating process easily can give rise to oscillations in the servo system.

The invention eliminates the above mentioned drawbacks and provides by means of simple techniques an appropriate force action on the vanes during the work movement. According to the invention flow paths are radially arranged along the broad sides of each vane and the corresponding boundary surfaces of each slot, to permit a predetermined overflow of pressure medium from the high pressure side to the low pressure side of the vane through the pressure chamber provided in the inner part of each slot, thereby controlling the pressure in the pressure chamber and in consequence providing an outwardly directed predetermined force acting on each vane during its work movement.

By permitting a controlled flowing through of pressure medium from the high pressure side of the vane to its low pressure side a stable condition at each vane is provided making it possible to accurately predetermine the action of forces on each vane.

According to the invention appropriate force action .on each vane is provided by dimensioning the flow paths in such a manner that the flow paths on the high pressure side and the low pressure side of said vane present diffferent flow resistances. The difference in flow resistance may be provided by dimensioning the thickness of each vane and the width of the corresponding slot such that the vane, under influence from the pressure medium, is displaced in the direction of rotation in such a way that a gap is still provided between the vane and the low pressure side boundary surface of the slot when the vane is pressed against said boundary surface.

If the machine is to be used for position servo purposes the motor necessarily must be able to work reversibly i.e., in both directions of rotation. In accordance with the invention this is achieved simply by constructing each vane and the corresponding slot in an essentially symmetrical manner with respect to a plane through the machine axle and through the center of said slot, hereinafter referred to as the radial plane. Upon reversing the motor, the vanes are brought into contact with the opposite boundary surfaces of the corresponding slots which means that the greater and smaller flow resistances change sides.

According to the invention it is also advantageous to shape the vanes such that the ratio between the total radial length of each vane and the corresponding length of that portion of the vane which protrudes from the slot is such that the mean part of the surface area of the low pressure side of said vane situated in the slot is brought into contact with a corresponding surface area of the boundary surface of the slot when said vane is pressed against the boundary surface.

According to one embodiment of the invention the broad sides of each vane are essentially plane parallel as are the corresponding boundary surfaces of the associated slot, and the flow paths are provided by recessing plane parallel grooves in a radial direction in each of the broad sides. The outer edge of each vane is straight in the axial direction and provided with a longitudinal rounding off.

According to another embodiment of the invention the flow paths are provided by distance means on the broad sides of the vanes and/or the corresponding boundary surfaces of the slots, or by recessings in said broad sides and/or said boundary surfaces.

The invention will be more fully described in connection with a preferred embodiment of a reversible vane motor according to the invention, having reference to the drawings, in which:

FIG. 1 is a sectional view of one side of a motor with one of the side members eliminated;

FIG. 2 shows schematically a sectional view along the shaft and a radial plane of said shaft; and

FIGS. 3a, 3b, 3c, 3d and 3e are different views of a vane according to the invention.

Referring to FIG. 1, a sectional view is shown of a motor along the direction of the shaft. The shaft 1 is fastened to the rotor 2. Along its periphery the rotor 2 is provided with radial slots at the edge 3, each of which slots closest to the shaft terminating in a pressure chamber 4. The slots 3 and the pressure chambers 4 extend straight through the rotor in an axial direction (FIG. 2). A vane 5 is provided in each of said slots 3. The vanes 5 are in contact with the cam profile 7 shaped in the stator ring 6. A number of work chambers 8 are distributed along the circumference of the stator ring 6 between the cam profile 7 and the rotor 2. Each of the work chambers 8 is coupled to a channel for feeding of and a channel for removal of pressure medium. If the direction of rotation is the direction shown by the arrow then pressure medium from the high pressure side of the machine is fed through the channel 9 to the work chambers 8 respectively. This feeding is carried out through communication channels from channel 9 to the front part of the work chambers 8 respectively through a number of grooves in the stator ring 6 formed by recesses beside each other along the axial width of the stator ring and having a shape shown by the dotted lines 10. Removal of pressure medium is carried out through identical grooves 11 provided in the back part of each work chamber, said grooves communicating with a channel which corresponds to channel 9.

The cam profile 7 of the stator ring is composed of sets of identical profile parts a-e, the number of which sets corresponds to the number of work chambers 8. Parts a-e are in turn composed of several portions, namely: the rest portion a-b at which each vane 5 is in an inserted position and performs no work; the project portion b-c at which each vane 5 is successively projected to its work position; the work portion c-d at which each vane is in the work position and performs useful work; the insert portion d-e at which each vane is successively inserted to its rest position.

During the time each vane 5 runs over the project portion bc the outer edge 19 of the vane (FIG. 3) is acted upon by pressure medium from the high pressure side, which causes a force acting on said vane in an inward radial direction, tending to insert said vane in the corresponding slot 3. For compensation of this force and for instant feeding of the volume of pressure medium which is required for projection of each vane 5, the corresponding pressure chamber 4 during this moment is in communication with the high pressure side of the machine through a channel 12 in one of the side members which channel communicates the channel 9 is tangent to a broad side of a vane 5. The figure also shows that the bottom of each pressure chamber 4 is provided with two radially directed holes for the compression springs 14.

The shape of the vane 5 is obvious from FIG. 3, which shows that said vane 5 on the whole is symmetrically shaped with exception for the outer edge 19 which in opposition to the inner edge 18 shows a longitudinal round off. The inner edge of said vane 18 is completely flat. Each of the two

broad sides

15 and 16 contains two grooves 17, the depths of which are exaggerated in the drawing.

In operation of the motor, a pressure medium, usually oil of any adequate quality, is fed to each work chamber 8 from the high pressure side of the machine through a channel, such as the channel 9; in each of the work chambers 8 the pressure medium is caught by those vanes 5 which are in work position, so that said vanes 5 are exposed on the one broad side to the high pressure and on the other broad side to the low pressure. The difference in pressures gives rise to a force acting on said vanes in work position so that said vanes are displaced in the direction of rotation and bring with them the rotor 2, transferring the torque to the shaft 1. When said vanes 5, respectively, reach the end of the work portions, a next set of vanes 5 have already reached the respective work positions and then take over the work movement. Thereafter the process is repeated in the manner described.

When a vane 5 passes point c on its profile portion a-e the communication between the channel 12 and the pressure chamber 4 is broken. This means that the pressure in the pressure chamber decreases rapidly because of leakage, for example between the rotor 2 and the side members, which in turn means that the vane 5 is no longer hydrostatically balanced. From this it follows that the vane at this moment is no longer acted upon by any outwardly directed force. The proportionately weak action of the compression springs 14 may in this connection be disregarded. For the vane to continue to be in contact with the cam profile 7 an outwardly directly force greater than the inwardly directed force is required.

According to the invention said outwardly directed force is provided by permitting passage of pressure medium from the high pressure side of the vane through grooves 17 in the vane (FIG. 3) and through the work chamber 4 to the low pressure side of said vane. The pressure in the pressure chamber 4 amounts to a value between the pressure values on the high pressure and the low pressure side of the vane in dependence on the sizes of the flow paths.

Assuming that the pressure on the high pressure side of the vane is P,, the pressure on the low pressure side of the vane is P the pressure in the pressure chamber P and the cross-section of the vane in the direction of the shaft is Y, as a consequence of the symmetrical shape of the rounded off outer edge of the vane 19 that said vane is acted upon by an inwardly directed force r (P +P )'Y and the outwardly directed force P -Y.

From this follows that the condition for hydrostatic balancing of the vane is P V2 (P,+P which is satisfied when the flow resistance between the high pressure side and pressure chamber equals the flow resistance between the pressure chamber and low pressure side, if leakage is disregarded.

In practice it turns out that the vanes 5 under their movements in and out in the corresponding slots 3 are acted upon by frictional forces which are not completely predictable, and it also appears that consideration must be given to leakage; e.g., between the rotor and the side members. Therefor it is necessary to provide a flow of pressure medium to the pressure chamber to such an extent that these factors are compensated and that in addition some excess of outwardly directed hydraulic force is obtained to ensure sealing between the vane and the cam profile. This excess force should have a value such that the wear of the vanes and cam profile is minimized.

Consequently in the pressure chamber 4 a pressure is desired which satisfies the condition A (P,+P P P,. According to the invention this relationship is satisfied by dimensioning the flow paths to and from the pressure chamber in such manner that the required difference in flow resistance is obtained.

The requirement on reversibility, i.e. that the machine shall be able to work with the dame efficiency in both directions of rotation, is achieved in this embodiment of the invention by means of the completely symmetrical shaping of the vanes 5, the slots 3 and the cam profile 7, and the feeding and removal channels for the pressure medium.

The mentioned necessary difference in flow resistance of the flow paths to and from the pressure chambers 4 is provided by dimensioning of the thickness of the vanes (T, FIG. 3) relative to the widths of the slots (B, FIG. 1) such that each vane in the work position is displaced in the direction of rotation. This displacement causes the flow path on the high pressure side of the vane to be increased by the gap formed between the broad side of the vane and the corresponding boundary surface on the slot. Furthermore, because the portion of each vane which protrudes into the work chamber has a ratio to the total radial length of said vane such that said vane will be displaced with its broad side parallel to said slot, so that one of the broad sides of said vane lies close to a corresponding boundary surface of said slot, a change in flow resistance is achieved which will always be of a predetermined magnitude.

The flow of pressure medium from the high pressure side through the pressure chambers to the low pressure side which follows from the shaping of the vane has been shown to bring about very stable pressure conditions in the pressure chambers. The flow is, of course, kept below a value such that it will influence the torque delivered by the motor. The flow resistance of a column can be shown to be reciprocally proportional to the third power of the height of the column. This means that the dimensions of the grooves 17 and of the column which is formed by the displacement of the vane are of the order of magnitude of some hundredths of a millimeter, which in turn gives an indication of the amount of said flow.

The simple and totally symmetrical shaping of the vanes and corresponding slots means that the manufacturing can be carried out by known techiques at low cost. A further advantage is that thelow number of movable parts simplifies assembly and disassembly of the motor. Endurance tests of a motor according to the described embodiment has shown very good operating properties.

What is claimed is:

1. A reversible direction hydraulic machine comprising a stator and a rotor, said stator having a cam profile defining work chambers, said rotor connected to a shaft and enclosed within said stator, said rotor having a plurality of radially extending symmetrical slots spaced thereabout and a respective pressure chamber located radially inward from each slot and communicating therewith, said rotor also comprising a radially displaceable vane carried in each of said slots, each vane being symmetrical with respect to a radial plane and having two narrow sides transverse to said plane and two broad sides, a portion of said vane protruding from said slot for contact with said cam profile so as to prevent a working medium from flowing between an outer edge of said vane and said cam profile from a high pressure side of the vane to a low pressure side, said rotor having at least one flow path means symmetrically arranged about each broad side of each vane for permitting said working. medium to flow between the work chamber and the respective pressure chamber, each vane having a thickness slightly less than the width of the respective slot, said flow path means being in addition to space between said vane and said slot due to said lesser thickness of the vane has been inserted after the comma. said slot having a depth and said vane having a total radial length such that the broad side of said vane on the low pressure side is brought into area contact with a corresponding side of said slot without tilting of said vane, whereby a total flow path between the work chamber and the pressure chamber on the high pressure side of said vane has a flow resistance less than that on the low pressure side of said vane, and upon reversal of the machine the opposite broad side of said vane will become the low pressure side and be in area contact with a corresponding side of the slot.

2. A hydraulic machine as claimed in claim 1 wherein said flow path means comprises a passage region provided between each broad side of said vane and a corresponding side of said slot.

3. A hydraulic machine as claimed in claim 1 wherein said flow path means comprise a recess in each broad side of each vane.

4. A hydraulic machine as claimed in claim 3 wherein said broad sides of each of said vanes are substantially plane parallel sides, said recesses are radially extending parallel grooves, the outer edge of each vane being axially straight and transversely rounded, and wherein the sides of each slot corresponding to said broad sides are plane parallel sides.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3907467 DATED September 23, 1975 INVENTOR(S) ULF CHRISTER EKENBERG ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 10, "slots at the edge 3" should be --slots 3 Column 3, line 11, "slots closest should be -slots at the edge closest-- Claim 1, lines 24 and 25, delete "has been inserted after the comma Signed and Salad this twenty-third Day of March 1976 [SEAL] A ttes t:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner oflarenls and Trademarks

Claims

1. A reversible direction hydraulic machine comprising a stator and a rotor, said stator having a cam profile defining work chambers, said rotor connected to a shaft and enclosed within said stator, said rotor having a plurality of radially extending symmetrical slots spaced thereabout and a respective pressure chamber located radially inward from each slot and communicating therewith, said rotor also comprising a radially displaceable vane carried in each of said slots, each vane being symmetrical with respect to a radial plane and having two narrow sides transverse to said plane and two broad sides, a portion of said vane protruding from said slot for contact with said cam profile so as to prevent a working medium from flowing between an outer edge of said vane and said cam profile from a high pressure side of the vane to a low pressure side, said rotor having at least one flow path means symmetrically arranged about each broad side of each vane for permitting said working medium to flow between the work chamber and the respective pressure chamber, each vane having a thickness slightly less than the width of the respective slot, said flow path means being in addition to space between said vane and said slot due to said lesser thickness of the vanehas been inserted after the comma. said slot having a depth and said vane having a total radial length such that the broad side of said vane on the low pressure side is brought into area contact with a corresponding side of said slot without tilting of said vane, whereby a total flow path between the work chamber and the pressure chamber on the high pressure side of said vane has a flow resistance less than that on the low pressure side of said vane, and upon reversal of the machine the opposite broad side of said vane will become the low pressure side and be in area contact with a corresponding side of the slot.