US3204566A

US3204566A - Vane type hydraulic mechanism with balanced stator walls

Info

Publication number: US3204566A
Application number: US201607A
Authority: US
Inventors: Feroy Arne
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-06-11
Filing date: 1962-06-11
Publication date: 1965-09-07
Anticipated expiration: 1982-09-07

Description

Sept. 7, 1965 A. FEROY 3,204,566

VANE TYPE HYDRAULIC MECHANISM WITH BALANCED STATOR WALLS Filed June 11, 1962 IN V N TOR A m 5 0P0) United States Patent 3,204,566 VANE TYl E HYDRAULIC MECHANISM WITH BALANCED STATOR WALLS Arne Ferny, 20017 42ml 8., Kent, Wash. Filed June 11, 1962, Ser. No. 201,607 9 Claims. (Cl. 103-136) The present invention relates to a rotary hydraulic mechanism of the vane type operable either as a pump or as a motor, and more particularly to such a mechanism equipped with means for automatically maintaining optimal axial running clearances at the faces of the rotor over the entire range of operating pressures and speed.

it is an object of this invention to provide a hydraulic mechanism of the vane type having a stator housing including a pair of stator end plates, wherein each of said stator end plates comprises integral stator wall, rim and hub portions, with an annular balancing ring engaging the cylindrical hub portion, and with means for communicating the back side of the annular balancing ring on the side of the rotor Where leakage is likely to occur with the system high pressure fluid, so that the balancing ring automatically maintains the desired clearance at the rotor face by balancing the moments on the stator wall portion about its cylindrical line of connection with the cylindrical rim portion.

One of the principal problems existing in hydraulic mechanisms of the vane type is leakage at the faces of the rotor. There are several known methods of preventing such leakage, but each of them possesses various disadvantages and, in general, have not been very satisfactory. For example, one known way in which leakage is prevented at the faces of the rotor is by interposing a floating pressure plate on the side of the rotor where leakage is likely to occur, i.e. between the associated stator end plate and rotor face, and subjecting the entire back surface of the pressure plate to the system high pressure fluid. Sealing forces are thus developed against such floating pressure plate urging the same towards the rotor face. However, this method is unsatisfactory because the sealing forces that are developed extend over the entire area of the back surface of the pressure plate while the unbalancing forces that tend to cause leakage at the rotor face extend over approximately fifty percent or less of the area of the front surface of the pressure plate. This results in approximately fifty percent or more of the sealing forces being unopposed and causes the pressure plate to buckle or deflect inwardly slightly in the regions of such unopposed sealing forces, resulting in the clearances in such regions being too small and causing the pressure plate to contact and rub the rotor face. Seeondly, since the pressure plate is full floating, a relatively large sealing force is required to prevent such leakage.

In accordance with the present invention, no floating plate is interposed between the rotor face and the stator end plate, but rather the rotor face is in direct sealing engagement with the inner face of said stator wall portion. Importantly, also, the stator wall portion is made integral with the remaining portions of the stator end plate so that such stator wall portion has one-piece rigidity and resists a relatively large portion of the unbalancing forces by such rigidity alone. The sealing or balancing forces that are required are consequently relatively small and are applied only where they are most needed and can do the most good, i.e. adjacent the center portion of the stator wall portion where maximum deflection tends to occur. The sealing or balancing forces are provided by an annular balancing ring having an annular action surface engaging an annular reaction surface formed on the cylindrical hub portion of the stator end plate. The system high pressure fluid is automatically applied to the back surface of a balancing ring to create the balancing forces only when balancing is required. The area of the pressure surface on the back side of the pressure ring determines the magnitude of the balancing force and is chosen to be of the size required to create a force that will substantially balance the moments on the stator wall portion.

Since a given hydraulic mechanism according to the present invention is preferably constructed to operate either as a pump or as a motor, and since such a hydraulic mechanism is reversible, a balancing ring is preferably provided at each end of the mechanism.

A'hydraulic mechanism constructed in accordance with the present invention has an operating pressure of sub stantially 2000 p.s.i., for example, while a hydraulic mechanism similar in construction but not provided with balancing rings would be limited to an operative pressure of approximately p.s.i. because a higher operating pressure would cause leakage at the rotor face. Therefore, it is a further object of this invention to provide an improved hydraulic mechanism of the vane type which has a greater pressure capability due to the provision of means for automatically maintaining optimal axial running clearances at the faces of the rotor.

A still further object of this invention is to provide a hydraulic mechanism of the above described character which is economically manufactured, simply constructed, is durable in use, and is eflicient in operation throughout a wide range of operating pressures.

These and other objects, features, and advantages of the present invention will be apparent from the following description, appended claims and annexed drawings.

Referring to the drawings wherein like reference characters designate like parts throughout the several views:

FIG. 1 is a view in cross section, taken substantially along line 11 of FIG. 2 of a vane type hydraulic mechanism incorporating balancing rings in accordance with the present invention;

FIG. 2 is a view in cross section of the mechanism shown in FIG. 1, taken through the rotor and cam ring substantially along line 2--Z of FIG. 1, and showing the general configuration of the working chambers and the division of the working chambers into compartments by the vanes;

FIG. 3 is a view in cross section of the mechanism shown in FIG. 1, taken substantially along line 33 thereof; FIG. 4 is a view in cross section of the mechanism shown in FIG. 1, taken substantially along line 44 thereof;

FIG. 5 is an enlarged fragmentary view of a portion of FIG. 1 showing the relationship of the balancing ring to the stator Wall and a retaining ring.

FIG. 1 shows the hydraulic mechanism of the present invention as including a stator housing 10 and a rotor 12 mounted for rotation within the stator housing lit).

The stator housing 10 consists of two parallel spaced stator end plates or

end sections

14, 16 and a cam ring or housing ring portion 18 positioned between them. The

stator plates

14, 16 are secured to the cam ring 18 by a circular array of bolts 20 whose heads are received in counterbores formed in the

stator plates

14, 16.

The cam ring 18 is conventional er se, employing four constant radius sections A, B, C, and D separated by transition zones E, F, G, H, as shown in FIG. 2; with the radiuses of sections A and B being relatively equal, and the r-adiuses of sections C and D being relatively equal. In sections C and D, which are termed idle zones, the curvature of the cam surface substantially coincides with that of the rotor 12. In sections A and B and in the transition zones E, F, G, H, the curvature of the cam surface is sharper than the curvature of the rotor 12 resulting in the formation of two, radially opposed, generally crescent shaped working chambers 22, 24.

The rotor 12 is provided with radial slots 26 spaced around its periphery, and each of such radial slots 26 is provided with a reciprocating vane 28. The reciprocating vanes 28 serve to divided the working chambers 22, 24 into a plurality of compartments 29 whose volumes first increase and then decrease as the vanes 28 sweep through the working chambers 22, 24 during an operation cycle. The reciprocating vanes 28 are in sliding .and sealing engagement at their opposite side faces with the inner surfaces of

stator wall portions

30, 32 of the

stator end plates

14, 16 and at their outer ends with the cam surface 19 of the cam ring 18.

When the mechanism is to be operated as a motor, push rods (not shown) or their equivalent should be provided for urging the vanes 28 against the cam surface 19. A suitable push rod arrangement is shown and described in my prior US. Patent No. 2,929,365, issued on March 22, 1960. When the mechanism is operated as a pump such means for biasing the vanes 28 are not needed because the vanes will be held against the cam surface by centrifugal force.

A generally toroidal-shaped fluid manifold is formed in each of the stator end plates 14, and, for descriptive purposes, the fluid manifold formed in stator plate 14 is termed the inlet manifold and is designated 34 and the fluid manifold formed within stator plate 16 is termed the outlet manifold and is designated 36.

Stator end plate 14 includes in addition to stator wall portion a cylindrical peripheral rim portion 38, an annular back flange portion 4i) and a cylindrical hub portion 42. The cylindrical hub portion 42 has two axially extending sections of unequal diameter connected by a radially extending annular reaction surface 44. In a similar manner, stator late 16 is provided with a peripheral cylindrical rim portion 46, an annular back flange portion 48, a cylindrical hub portion and an annular reaction surface 52. In axial cross-section

stator end plates

14, 16 closely resemble the letter E. Of course it is to be understood that each stator end plate is of one-piece construction and that each portion thereof is an integral part of the adjoining portion.

Inlet manifold 34 communicates with a source of hydraulic fluid by way of an inlet passageway 54 (FIG. 3) and With the Working chamber 22, 24 by way of kidney-shaped inlet valve ports 56, provided axially through stator wall portion 30. At the opposite end of the rotor the working chambers 22, 24 communicate with the outlet manifold 36 by way of kidney-shaped outlet valve ports 58 formed axially through stator wall portion 32. k

The outlet manifold 36 in turn communicates with a point of use or discharge by means of an outlet passageway 60 (FIG. 4). The rotor 12 is spline connected to a shaft 62 which is mounted for rotation by means of bearing 64, 66 positioned inside of the cylindrical hub portions 42, 59, respectively. A seal 68 surrounds the shaft 62 where it leaves the stator housing 10.

The alignment of the valve ports is such that the inlet valve ports 56 trail the outlet valve ports 58 with respect to the direction of rotation and, of course, are the first to communicate with a given compartment 29 as the rotor 12 rotates in the direction indicated by the arrow R in FIG. 2. The relative alignment of the inlet valve ports 56 and the outlet valve ports 58 is indicated in FIG. 2, wherein the inlet valve ports 56 are shown as they appear in the sectional view which FIG. 2 presents, and the outlet valve ports 58 are shown in phantom.

Considering the operation of the mechanism in so far as it has been described, and considering further that the mechanism is operating as a motor, hydraulic fluid under pressure is delivered through inlet passageway 54 into the inlet manifold 34, completely filling the same. From the inlet manifold 34 the fluid flows through the inlet valve ports 56 into the compartments 2? (FIG. 2), com

pletely filling the same and exerting a pressure on all of their interior surfaces. The remaining compartments 29 are in communication with the outlet manifold 36 which is at atmospheric pressure, and so the pressures on the two sides of the vanes 28' are not equal but rather are unbalanced in the counter-clockwise direction creating tangential forces, indicated by force arrows, F, P which cause counter-clockwise rotation of the rotor 12.

Similarly, the high fluid pressure in compartments 29' is not balanced in the direction of the stator wall 32 because the outlet manifold 36 positioned on the opposite side of stator wall portion 32 is at atmospheric pressure. The pres-sure differential creates unbalancing forces which are exerted against said stator wall portion 32 in the outward direction. The resultant of such unbalancing forces lies radially inboard of the rigid connection of stator wall 32 with cylindrical rim portion 46, thereby giving such un'balancing forces a moment arm and establishing an unbalancing turning moment in the outward direction about the line of junction of stator wall portion 32 with cylindrical rim portion 46. If such turning moment were not balanced, it would cause the stator wall portion 32 to slightly bow or deflect outward, causing leakage at the face of rotor 12.

Referring again to FIG. 1, in accordance with the present invention, the outward deflection of stator wall portion 32 is resisted to a large extent by the rigid, integral construction of stator end plate 16 itself. In addition, a pressurized balancing ring 7i; is provided contiguous the back side of stator wall portion 32 to exert balancing forces on said stator wall portion 32. The mean diameter of the balancing ring '70 is made smaller than the diameter of the rotor so that the resultant of the balancing forces lies inboard a substantial distance from the resultant of the urn-balancing forces. Therefore, the balancing forces have larger moment arms than the un'balancing forces, and small balancing forces can balance the moment produced by the larger unbalancing forces.

Referring to FIG. 5, the balancing ring 70 is shown to have an action surface 72 which bears against the reaction surface 52 of the cylindrical hub portion 50. An 0 ring '74 is provided in the outer cylindrical surface of the balancing ring 78 to provide a seal between such surface and the inner cylindrical surface of annular back flange portion 4-8. In similar fashion, 0 rings 76, 78 are provided in recesses formed in the radially offset cylindrical inner surfaces of ring '73 to provide a seal between such surfaces and the cylindrical surfaces of cylindrical hub portion 5t against which they fit. A retaining ring 3%) is secured to stator plate 16 by means of bolts 82. Such retaining ring 80 is provided with an annular flange portion 84 dimensioned to fit behind the balancing ring 79 within the annular opening defined between the cylindrical rim portion 46 and the cylindrical hub portion 59. The flange portion 84 is provided with 0

rings

86, 88 for sealing the engagement of its surfaces with respective surfaces of the cylindrical rim portion 36 and the cylindrical hub portion 5%).

An annular groove 90 is formed along the back surface of balancing ring 70 so as to define an annular chamber 92 between such balancing ring 79 and the adjoining end surface of flange portion 84. Ports 94 are provided through balancing ring 7t) for communicating annular chamber 92 with similar ports :96 formed through stator wall 32 near its center. As most clearly shown in FIG. 4, ports 36 terminate into kidney-shaped grooves 98 formed in the innerface of stator wall portion 32. Grooves 98 are in fluid receiving communication with the lower portions of the Vane slots 26 below the vanes 23. Such lower portions of the vane slots 26 communicate at their other ends with kidney-shaped grooves 100 formed in the innerface of stator wall 30. Ports 192 are provided for communicating the grooves 1% with the inlet manifold 34. Therefore, ports Hi2, grooves N0, the lower portions of vane slots 26, grooves 98, ports 96 and ports 94 altogether define a fluid flow path for conducting the high pressure fluid from the inlet manifold 32 to the annular chamber 92 during operation of the mechanism so that the balancing ring 70 is forced by such high pressure fluid against stator wall 32, creating a balancing moment on such stator wall 32 in opposition to the unbalancing moment created by the unbalancing forces in the high pressure compartments, thereby preventing undesirable deflection of the stator wall and accompanying fluid leakage.

It is quite obvious that when the mechanism is operated as a pump, the manifold pressures will be reversed, i.e. the pressure of the fluid in manifold 34 is low and the pressure of the fluid in manifold 36 is high. Consequently, when the mechanism is operated as a pump, and the direction of flow remains the same, stator wall 3b is the wall that is subjected to the unbalancing forces and is the wall that must be balanced. Therefore, a balancing ring 1% identical in construction with balancing ring 70 is provided adjacent stator wall portion 30 and is provided with the annular grooves, ports, O-rings, etc. which are identical to those associated with balancing rings 7% so that such balancing ring Hi4 functions in exactly the same manner as balancng ring 70.

Of course it is to be realized that the hydraulic mechanism of this invention is completely reversible and reversing is accomplished simply by reversing the direction of flow through the meohansm. The provision of a balancing ring at each end of the mechanism provides means for automatically maintaining optimum axial running clearances regardless of the direction of rotation.

Having thus described the invention it is clear that the objects as stated have been attained in a simple and practical .manner. While a particular embodiment of the invention has been shown and described, it is understood that changes may he made in the construction and the arrangement of the various parts without departing from the spirit and scope of the invention as expressed in the following claims.

I claim:

1. A rotary hydraulic mechanism of the vane type comprising a vaned rotor rotatable in a working chamber defined by an oval cam ring between stator end plates affixed to said cam ring, with an annular main-fold and hydraulic fluid passageways provided in each of said stator end plates, and with one of said manifolds containing high pressure fluid and the other containing low pressure fluid, and further with the high pressure manifold communicating with a portion of the working chamber and the low pressure manifold communicating with the remaining portion of the working chamber; such low pressure stator end plate comprising integral rim and hub portions, having in conjunction therewith an annular balancing ring engaging said hub portion, and high pressure fluid delivery means in communication with the back of said annular balancing ring, causing the balancing ring to exert a balancing moment on said hub portion and in turn on said stator wall portion to counteract the tendency of the stator wall portion to be deflected by the high fluid pressure in said working chamber.

2. A rotary hydraulic mechanism of the vane type comprising a vaned rotor rotatable in a fluid pressurized working chamber defined by an oval cam ring between stator end plates aflixed to said cam ring, with high pressure and low pressure fluid inlet and outlet mainfolds and valve ports provided in respective stator end plates; said low pressure stator end plate comprising integral wall, rim and hub portions, having in conjunction therewith an annular balancing ring engaging said hub portion, with high pressure fluid delivery means in communication with the back of said annular balancing ring, causing the balancing ring to exert a balancing moment on said hub portion and in turn on said stator wall portion to counteract the tendency of the stator wall to be deflected by the fluid pressure in said working chamber.

3. In a hydraulic mechanism, a plurality of revolving fluid compartments bounded at their respective axial ends by a pair of axially spaced stator walls, at least one of said stator walls having a cylindrical rim portion integral with and extending axially from its periphery on the side thereof opposite from said compartment; meansestablishing a high pressure in some of said compartments; means establishing a low pressure in others of said compartments including a low pressure manifold contiguous the last mentioned stator wall on the side thereof opposite from the compartments, a portion of said stator wall being interposed between the high pressure fluid compartments and the low pressure fluid manifold and thereby subjected to a pressure differential producing unbalancing forces tending to deflect said stator wall outwardly; annular means contiguous with said stator wall on the low pressure manifold side thereof substantially radially inboard of the unbalancing forces; and means delivering high pressure fiuid behind said annular means to that the latter exerts an axially inwardly directed balancing force against said stator wall of such a magnitude that deflection of said stator wall is prevented.

4. A hydraulic mechanism of the van type having a plurality of revolving increasing and decreasing volume compartments bounded at their axial ends by stator walls, each stator wall integrally connecting at its outer periphery to a cylindrical rim member, a high pressure fluid manifold located on the opposite side of one of said stator walls in the vicinity of the compartments, a low pressure fluid manifold located adjacent the opposite side of the other stator wall in the vicinity of the compartments, means communicating some of the compartments with the high pressure manifold, means for communicating the remaining compartments with the low pressure fluid manifold, a balancing ring positioned contiguous the stator wall associated with the low pressure fluid manifold on the side thereof opposite from said compartments and substantially radially inboard of said compartments, and means for communicating the high pressure manifold with the back side of said balancing ring so that the high pressure fluid forces the balancing ring axially against the stator wall and resist deflection of such stator wall.

5. A hydraulic mechanism of the vane type comprising a stator housing and a vane rotor mounted for rotation within said housing, the housing including a pair of axially spaced stator end plates and a cam ring interposed between said stator end plates, each of said stator end plates having hub, stator wall, rim and back flange portions, with the hub portion integrally connecting to the stator wall portion, the stator wall portion integrally connected to the rim portion, the rim portion inte rally connected to the back flange portion and an annular opening being formed between the back flange and hub portions, an annular balancing ring snugly located within said annular opening and having an annular surface engaging a surface of said hub portion and an annular groove formed in the back surface thereof, a retaining ring having an annular tang-e portion snugly located within said annular opening behind said balancing ring, said annular flange portion having a surface abutting the grooved surface of the balancing ring and partially defining therewith an annular chamber, means for fastening said retaining ring to said back flange portions, and means for delivering a high pressure fluid into said annular chamber.

6. A rotary hydraulic mechanism comprising a rotor mounted for rotation within a housing consisting of a pair of stator end plates and a housing ring portion interconnected therebetween, at least one of said stator end plates being characterized by a generally annular stator wall situated contiguous a face of the rotor, a generally annular back flange spaced axially outboard of said stator wall, a generally cylindrical. peripheral rim portion integrally interconnected between said stator wall and said back flange, and a generally cylindrical hub portion integrally connected at one end thereof to the inner periphery of said generally annular stator wall and extending outwardly therefrom generally concentrically with said peripheral rim portion, with the integral construction of the back flange, peripheral rim, stator Wall and hub portions giving said stator end plate one-piece rigidity, a generally annular balancing ring situated between the back flange and hub portions of said stator end plate and forming with said back flange, rim, stator wall and hub portions a generally toroidal fluid manifold within the stator end plate with an action surface on the inboard side of said balancing ring and a related reaction surface on a contiguous portion of said stator end plate, means removably interconnected between said back flange and hub portions of said stator end plate outboard of the balancing ring with a fluid chamber being defined between the outboard side surface of the balancing ring and an opposed surface of said means, with the second stator end plate also containing a fluid manifold, with at least one Working chamber being defined between the outer periphery of the rotor and the inner surface of said housing ring portion, radially extending means dividing said working chamber into compartments, means communicating some of the compartments and the fluid manifold in the second stator end plate with a high pressure fluid, means communicating others of the compartments and the fluid manifold in the first stator end plate with a low pressure fluid, and means communicating high pressure fluid to the said fluid chamber defined behind the balancing ring of the first stator end plate.

7. A rotary hydraulic mechanism comprising a rotor mounted for rotation within a housing consisting of a pair of stator end plates and a housing ring portion interconnected therebetween, each of said stator end plates being characterized by a generally annular stator wall situated contiguous a face of the rotor, 21 generaliy annular back flange spaced axially outboard of said stator wall, a generally cylindrical peripheral rim portion integrally interconnected between said stator wall and said back flange and a cylindrical hub portion integrally connected to the inner periphery of said generally annular stator wall and extending outwardly therefrom generally concentric with said peripheral rim portion, with the integration of the back flange, peripheral rim, stator wall and hub portions giving the stator end plates one-piece rigidity, a generally annular balancing ring situated between the back flange and-hub portions of each stator end late and forming with said back flange, rim, stator wall and hub portions a generally toroidal fluid manifold with an action surface on the inboard side of each balancing ring and with a related reaction surface on a contiguous portion of each stator end plate, means removably interconnected between said back flange and hub portions of each stator end plate outboard of the balancing ring with a fluid chamher being defined between opposed surfaces of the balancing ring and the said means, at least one working chamber being defined between the outer periphery of the rotor and the inner surface of said housing ring portion, radially extending means dividing said working chamber into compartments, means communicating some of the compartments and the fluid manifold in one of the stator end plates with a high pressure fluid, means communicating others of the compartments and the fluid manifold in the other stator end plate with a low pressure fluid, and means communicating high pressure fluid to the said fluid chamber situated behind the balancing ring of the stator end plate containing the manifold which is in communication with the low pressure fluid.

8. A rotary hydraulic mechanism comprising a housing and a rotor journaled for rotation in said housing, at least one working chamber being formed between said rotor and portions of said housing, ieans'dividing said working chamber into a plurality of compartments, said housing including end plates, each of which is characterized by one-piece, integral construction and comprises an annular stator wall portion situated contiguously of a face of the rotor and extending between generally cylindrical, concentrically related rim and hub portions, said hub portion having an outwardly facing reaction surface, a generally annular-shaped balancing ring having an action surface in contact with said reaction surface, a fluid manifold in each stator end plate, means communicating some of the compartments and the fluid manifold in one of the stator end plates with a high pressure fluid, means communicating others of the compartments and the fluid manifold in the other stator end plate with a low pressure fluid, and means communicating high pressure fluid to the outboard side of the balancing ring of the stator end plate containing the manifold which is in communication with the low pressure fluid, exerting an inwardly directed force on said balancing ring and in turn on said hub portion.

9. A rotary hydraulic mechanism comprising a housing and a rotor in said housing forming at least one compartmented working chamber therewith, said housing including an end plate of one-piece integral construction comprisins a cylindrical hub portion and an annular stator wall portion extending radially outwardly from said hub portion, contiguous a face of said rotor, said mechanism further comprising a balancing ring abuttingly engaging an axially outboard facing part of said hub portion, means forming a fluid manifold in said end plate including the balancing ring and the hub and stator wall portions of said end plate, means communicating the fluid manifold and some of the compartments of the compartmented working chamber with a high pressure fluid, and means communicating others of the compartments and the axially outboard facing side of the balancing ring with a relatively low pressure in comparison with the pressure in said manifold.

References (Ii ed by the Examiner UNITED STATES PATENTS KARL I. ALBRECHT, Primary Exaiitiner.

LAURENCE V. EFNER, Examiner.

Claims

1. A ROTARY HYDRAULIC MECHANISM OF THE VANE TYPE COMPRISING A VANED ROTOR ROTATABLE IN A WORKING CHAMBER DEFINED BY AN OVAL CAM RING BETWEEN STATOR END PLATES AFFIXED TO SAID CAM RING, WITH AN ANNULAR MAINFOLD AND HYDRAULIC FLUID PASSAGEWAYS PROVIDED IN EACH OF SAID STATOR END PLATES, AND WITH ONE OF SAID MANIFOLDS CONTAINING HIGH PRESSURE FLUID AND THE OTHER CONTAINING LOW PRESSURE FLUID, AND FURTHER WITH THE HIGH PRESSURE MANIFOLD COMMUNICATING WITH A PORTION OF THE WORKING CHAMBER AND THE LOW PRESSURE MANIFOLD COMMUNICATING WITH THE REMAINING PORTION OF THE WORKING CHAMBER; SUCH LOW PRESSURE STATOR END PLATE COMPRISING INTEGRAL RIM AND HUB PORTIONS, HAVING IN CONJUNCTION THEREWITH AN ANNULAR BALANCING RING ENGAGING SAID HUB PORTION, AND HIGH PRESSURE FLUID DELIVERY MEANS IN COMMUNICATION WITH THE BACK OF SAID ANNULAR BALANCING RING, CAUSING THE BALANCING RING TO EXERT A BALANCING MOMENT ON SAID HUB PORTION AND IN TURN ON SAID STATOR WALL PORTION TO COUNTERACT THE TENDENCY OF THE STATOR WALL PORTION TO BE DEFLECTED BY THE HIGH FLUID PRESSURE IN SAID WORKING CHAMBER.