TWI824158B - Hydrostatic controller for maintaining constant fluid film gap - Google Patents

Abstract

Embodiments herein disclose a hydrostatic controller for maintaining a constant fluid film gap. The hydrostatic controller includes a fixed restrictor (106 or 402) configured to provide a fixed resistance in the hydrostatic controller. The fixed restrictor (106 or 402) is connected in series with a variable restrictor (108 or 404). The variable restrictor (108 or 404) is configured to provide a variable resistance in the hydrostatic controller. The variable restrictor (108 or 404) is connected in line with a recess pocket (112 or 410). The fixed resistance has a geometry of a capillary restrictor. The variable resistance comprises a geometry, wherein the geometry deforms to actively control a flow rate in the hydrostatic controller, wherein the geometry is provided by the circular member (102 or 406).

Description

Hydrostatic controller to maintain constant film gap

The present invention relates to a hydrostatic bearing system and, more particularly, to a hydrostatic controller for maintaining a constant fluid film gap in a hydrostatic bearing system. The present application is based on and claims priority to Indian Application No. 201941023121 filed on June 11 , 2019 and Indian Application No. 201941023123 filed on June 11 , 2019 , the disclosures of which are incorporated by reference into the present application.

The hydrostatic bearing system is a non-contact bearing system that guides fluids such as air, lubricating oil, etc. into its interior and obtains load capacity through restriction. Although the hydrostatic bearing system has advantages such as low friction and high movement accuracy due to the averaging effect, it has disadvantages such as low stiffness and low damping characteristics. In order to improve the stiffness of the hydrostatic bearing system, it is effective to reduce the bearing clearance. Additionally, in order to optimally design bearings with smaller bearing clearances, the amount of fluid flowing in the bearing system should be limited to correspond to the bearing clearance.

However, when reducing bearing clearance, the machining accuracy of the bearing should be improved. Therefore, there are limitations to improving bearing stiffness by reducing bearing clearance. To overcome this limitation, various variable limiting mechanisms have been proposed.

In one example, in an existing hydrostatic bearing system there is a working mechanism of a flow controller that uses a flat membrane and a spherical membrane in series, where the two different flow resistances have a thin limiting gap. The thin confinement gap is connected directly to one of the hydrostatic tanks. In the existing hydrostatic bearing system, the conventional liquid flow restrictor has a fixed liquid flow resistance, and when the oil chamber pressure in the hydrostatic tank changes, the flow rate will decrease. The flow equation is as follows, Q = (supply pressure-oil chamber pressure)/(fixed flow resistance).

Therefore, it is desirable to address the above-mentioned disadvantages or other disadvantages or at least provide a useful alternative.

In view of this, our inventors devoted themselves to further research, and began to carry out research and development and improvement, hoping to solve the above problems with a better invention, and after continuous testing and modification, the present invention came out.

A primary object of embodiments of the present invention is to provide a flow control unit for maintaining a constant fluid film gap in a hydrostatic bearing system.

Another object of embodiments of the present invention is to provide a hydrostatic bearing film thickness controller using a cylindrical tube diaphragm.

Accordingly, embodiments of the present invention disclose a hydrostatic pressure controller for maintaining a constant fluid film gap. The hydrostatic pressure controller includes a circular member and a fixed flow restrictor. The fixed flow restrictor is configured to provide a fixed flow resistance in the hydrostatic controller, wherein the fixed flow restrictor is connected in series with the variable flow restrictor. The variable flow restrictor is configured to provide variable flow resistance in the hydrostatic pressure controller. The variable flow restrictor is connected in a straight line with the oil chamber groove. Fixed flow resistance has the geometry of a capillary flow restrictor. Variable flow resistance includes geometry. The geometry deforms to actively control flow in the hydrostatic controller, where the geometry is provided by a circular member.

In one embodiment, variable flow resistance is provided using clearance formed by a circular member and an annular boss.

In one embodiment, the fixed flow restrictor is connected in series with the circular member through a variable flow restrictor and capillary system to create a pressure gradient across the circular member.

In one embodiment, the circular members are circular flat membranes and cylindrical tube membranes.

In one embodiment, the hydrostatic pressure controller is a flow control unit or a hydrostatic bearing film thickness controller.

In one embodiment, the circular members are circular flat membranes and cylindrical tube membranes.

Accordingly, embodiments of the present invention disclose a flow control unit for maintaining a constant fluid film gap in a hydrostatic bearing system. The flow control unit includes a circular flat membrane, an annular boss, and a fixed flow restrictor that provides a fixed flow resistance in the flow control unit. The fixed current limiter is connected in series with the variable current limiter. The variable flow restrictor provides variable flow resistance in the flow control unit, wherein the variable flow restrictor is connected in line with the oil chamber groove. Fixed flow resistance has the geometry of a capillary flow restrictor. Variable flow resistance includes geometries in which the geometry of the variable flow resistance deforms to actively control flow in a hydrostatic bearing system. The rounded flat membrane provides a variable flow resistance geometry. Variable flow resistance is provided using clearance formed by a circular flat membrane and annular bosses.

In one embodiment, fixed flow resistance enables the necessary pressure differential to be established across the circular flat membrane.

In one embodiment, a fixed flow resistance maintains the correct gradient of pressure difference across the circular flat membrane.

In one embodiment, the cross-section of the clearance is determined by the deformation of the circular flat membrane.

In one embodiment, the pressure difference across the circular flat membrane controls the amount of deformation in the circular flat membrane.

In one embodiment, a fixed flow resistance blocks fluid flow to control a large flow of fluid through the variable flow restrictor.

In one embodiment, clearance is provided at a specific supply pressure.

Accordingly, embodiments of the present invention disclose a hydrostatic bearing system that includes a sump, a pressure relief valve, a pump, a motor, an accumulator, a filter, a hydraulic power pack, a bearing tank, and a flow control unit. The flow control unit includes a circular flat membrane as a variable flow restrictor, an annular boss, and a fixed flow restrictor that provides a fixed flow resistance in the flow control unit. The fixed current limiter is connected in series with the variable current limiter. The variable flow restrictor provides variable flow resistance in the flow control unit, wherein the variable flow restrictor is connected in line with the oil chamber groove. Fixed flow resistance has the geometry of a capillary flow restrictor. Variable flow resistance includes geometries in which the geometry of the variable flow resistance deforms to actively control flow in a hydrostatic bearing system. The rounded flat membrane provides a variable flow resistance geometry. Variable flow resistance is provided using clearance formed by a circular flat membrane and annular bosses.

Accordingly, embodiments of the present invention disclose a hydrostatic bearing film thickness controller that includes a fixed flow restriction configured to provide a fixed flow resistance in the hydrostatic bearing film thickness controller. device. The fixed current limiter is connected in series with the variable current limiter. The variable flow restrictor is configured to provide variable flow resistance in the hydrostatic bearing film thickness controller, wherein the variable flow restrictor is in line connection with the oil chamber groove. Fixed flow resistance includes the geometry of the capillary flow restrictor. Variable flow resistance includes geometries where the geometry deforms to actively control flow in hydrostatic bearing film thickness controllers. This geometry is provided by a cylindrical tube diaphragm. The fixed flow restrictor is connected in series with the cylindrical tube diaphragm through a variable flow restrictor and capillary tube system to create a pressure gradient across the cylindrical tube diaphragm.

In one embodiment, the cylindrical tube diaphragm is configured such that stress changes across the cylindrical tube diaphragm are minimized.

In one embodiment, the cylindrical tube membrane is constructed with variable thickness to improve the bending characteristics of the cylindrical tube membrane.

In one embodiment, supply pressure on the inboard portion of the cylindrical tube diaphragm provides a projection in the cylindrical tube diaphragm towards a thin limiting clearance.

In one embodiment, variations in the gap in the cylindrical tube diaphragm are maintained by a thin restricted clearance of variable flow resistance.

In one embodiment, the supply pressure on the inner portion of the cylindrical tube diaphragm creates a narrow radial clearance portion. The narrow radial clearance section is directly connected to the oil chamber groove.

In one embodiment, the cylindrical tube diaphragm is configured such that the deformation is closer to the desired average deflection of the cylindrical tube diaphragm.

These and other aspects of embodiments of the present invention will be better appreciated and understood when considered in conjunction with the following description and accompanying drawings. It is to be understood, however, that the following description, while indicating preferred embodiments and numerous specific details thereof, is given by way of illustration and not limitation. Many changes and modifications may be made within the scope of embodiments of the invention without departing from the spirit of the invention, and embodiments of the invention include all such modifications.

Regarding the technical means of our inventors, several preferred embodiments are described in detail below along with the drawings, so that everyone can have a thorough understanding and recognition of the present invention.

Embodiments of the invention and its various features and advantageous details are explained more fully with reference to the non-limiting embodiments illustrated in the drawings and described in detail in the following description. Descriptions of well-known components and processing techniques are omitted to avoid unnecessarily obscuring embodiments of the invention. Furthermore, various embodiments described herein are not necessarily mutually exclusive, as some embodiments may be combined with one or more other embodiments to form new embodiments. Unless otherwise specified, the term "or" refers to a non-exclusive "or". The examples used in the present invention are merely intended to aid the understanding in a manner in which embodiments of the present invention can be implemented and to further enable those skilled in the art to which the present invention pertains to implement the embodiments of the present invention. Accordingly, these examples should not be construed as limiting the scope of embodiments of the invention.

The accompanying drawings are used to help easily understand various technical features, and it should be understood that the embodiments proposed by the present invention are not limited by the accompanying drawings. Accordingly, the invention is to be construed to extend to any modifications, equivalents, and alternatives other than those specifically set forth in the drawings. Although the present invention may use the terms first, second, etc. to describe various elements, these elements should not be limited by these terms. These terms are generally only used to distinguish one element from another element.

Accordingly, embodiments of the present invention disclose a flow control unit for maintaining a constant fluid film gap in a hydrostatic bearing system. The flow control unit includes a circular flat membrane, an annular boss, and a fixed flow restrictor that provides a fixed flow resistance in the flow control unit. The fixed current limiter is connected in series with the variable current limiter. The variable flow restrictor provides variable flow resistance in the flow control unit, wherein the variable flow restrictor is connected in line with the oil chamber groove. Fixed flow resistance has the geometry of a capillary flow restrictor. Variable flow resistance includes geometries in which the geometry of the variable flow resistance deforms to actively control flow in a hydrostatic bearing system. The rounded flat membrane provides a variable flow resistance geometry. Variable flow resistance is provided using clearance formed by a circular flat membrane and annular bosses.

Unlike conventional methods and systems, the flow control unit uses a circular flat membrane to control hydrostatic bearing film thickness. The flow control unit compensates by supplying more fluid to increase the bearing's load-carrying capacity and stiffness.

Furthermore, tube diaphragms are fixed around thin circular slots or thin confinement gaps and have many advantages over flat diaphragms as tube diaphragms can be easily attached, but flat diaphragms require a press fit to support the hydrostatic bearing film thickness The components of the controller are held at the edge of the membrane. The flow rate of the fluid depends on the pressure difference between the supply pressure and the oil chamber pressure and the flow resistance that limits the clearance. The liquid flow resistance of the clearance is controlled by changes in the limiting gap caused by the deflection of the tube diaphragm caused by the fixed flow resistance.

The variable flow resistance geometry is provided by a cylindrical tube diaphragm to deform and actively control flow in a hydrostatic bearing film thickness controller. Deflection of the tube diaphragm allows more fluid to enter the loaded oil chamber trough, thus regulating the stiffness and hydrostatic system membrane gap thickness.

Referring now to the drawings, and more particularly to Figures 1-4, there are shown preferred embodiments.

1 is a cross-sectional view of a flow control unit (100) for maintaining a constant fluid film gap in a hydrostatic bearing system (200) in accordance with an embodiment disclosed herein;

Generally speaking, a hydrostatic bearing system (200) is required due to its ability to achieve high stiffness. To achieve high stiffness, a flow control unit (100) is required to maintain a constant fluid film gap in the hydrostatic bearing system (200). In one embodiment, flow control unit (100) includes a circular flat membrane (102), an annular boss (104), and a fixed flow restrictor (106) configured to provide a fixed flow resistance in flow control unit (100) ). The fixed current limiter (106) and the variable current limiter (108) are connected in series. The variable flow restrictor (108) is configured to provide variable flow resistance in the flow control unit (100). The variable flow limiter (108) is connected in a straight line with the oil chamber groove (112) (ie, the bearing groove). Fixed flow resistance and variable flow resistance help regulate fluid flow in the flow control unit (100). Fixed flow resistance has the geometry of a capillary flow restrictor. Variable flow resistance includes geometries that can deform and thereby actively control flow. The rounded flat membrane (102) provides a variable flow resistance geometry. The fixed flow resistance enables the necessary pressure differential to develop across the circular flat membrane (102) so that the circular flat membrane (102) can deform as intended. Fixed flow resistance also blocks flow to prevent large flows of fluid from flowing past the fixed flow resistance. Fixed flow resistance also helps maintain the correct pressure differential gradient across the circular flat membrane (102) so that the circular flat membrane (102) does not deflect in the opposite direction than intended.

Furthermore, variable flow resistance is achieved via the clearance (110) formed by the circular flat membrane (102) and the annular boss (104). Clearance (110) is optimized for best performance at a given operating supply pressure of 25 bar. The cross-section of the clearance (110) is determined by the amount of membrane deformation. The higher the deformation of the membrane, the smaller the clearance cross-sectional area. The pressure differential across the circular flat membrane (102) helps control the amount of deformation of the circular flat membrane (102) and thereby the clearance (110). When the bearing clearance changes, the thin limiting clearance in the variable flow resistance of the control unit (100) changes to compensate for the change in clearance. An increase in load will increase the oil chamber pressure, thereby reducing the bearing film clearance. The control unit (100) compensates by supplying more fluid to increase the bearing capacity and stiffness. This represents a positive slope between pressure and fluid flow, which results in ideal performance, and this is achieved via the control unit (100).

As the oil chamber pressure increases, the flow control unit (100) uses a variable flow restrictor to cause a simultaneous increase in flow. This helps maintain bearing clearance height for sufficient stiffness so that the hydrostatic bearing system (200) can provide the required precision and accuracy.

Additionally, the thickness of the circular flat membrane (102) and the limiting gap can be used to control the performance of the variable flow resistance. The round flat membrane (102) is easy to install and secure. The design is easy to manufacture and implement.

A model of the flow control unit (100) was tested in the laboratory using a hydrostatic bearing test rig. The output performance shows an increase in flow when the load increases, which increases the oil chamber pressure and tends to increase the fluid flow resistance of the bearing groove, and the hydrostatic bearing film thickness will begin to decrease. This can be prevented by increasing the flow rate by an external flow control mechanism. Using a diaphragm to reduce the resistance to fluid flow in the bearing groove will help maintain a constant film thickness and achieve the desired performance.

Figure 2 is a schematic diagram of a hydrostatic bearing system (200) in accordance with an embodiment disclosed herein. The hydrostatic bearing system (200) includes a hydraulic power unit (214), an oil pool (202), a pressure relief valve (204), a pump (206), a motor (208), an accumulator (210), and a filter (212). ) and bearing groove (216) and flow control unit (100). The hydraulic power unit (214) is used to pressurize the oil, which generates supply pressure (Ps). Pressurized oil is supplied to a flow control unit (100) with fixed flow resistance (106) and variable flow resistance (102). The oil passes through the flow control unit (100) and proceeds to the oil chamber tank (112) where the oil chamber pressure (Pr) is generated.

Figure 3 is a cross-sectional view of a plurality of flow control units (100) connected in series and assembled into a single unit connected to a hydrostatic bearing system (200). The arrangement and functionality of the flow control unit (100) have been explained in conjunction with Figures 1 and 2.

The load carrying capacity and stiffness of the hydrostatic bearing system (200) depend on the fixed flow resistance of the flow control unit (100). The capillary flow restrictor is used as a fixed flow restrictor (106), and the parameters of the fixed flow restrictor (106) are mainly the diameter of the capillary tube and the length of the capillary tube.

Figure 4 is a cross-sectional view of a hydrostatic bearing film thickness controller (400) in accordance with a disclosed embodiment of the present invention. In one embodiment, the hydrostatic bearing film thickness controller (400) includes a fixed flow restrictor (402) configured to provide a fixed flow resistance in the hydrostatic bearing film thickness controller (400). The fixed flow limiter (402) and the variable flow limiter (404) are connected in series. A variable flow restrictor (404) is configured to provide variable flow resistance in the hydrostatic bearing film thickness controller (400), wherein the variable flow restrictor (404) is in-line with the oil chamber sump (410).

Additionally, fixed flow resistance has the geometry of a capillary flow restrictor. The variable flow resistance includes geometries that deform and thereby actively control flow. The variable flow restrictor geometry is provided by a cylindrical tube diaphragm (406). A fixed flow restrictor (402) modeled using a capillary system is connected in series with a variable flow resistance of the cylindrical tube diaphragm (406) to create a pressure gradient across the cylindrical tube diaphragm (406).

The design of the cylindrical tube diaphragm (406) is such that stress changes across the cylindrical tube diaphragm (406) are minimized. The length (411) of the cylindrical tube diaphragm (406) is designed with variable thickness to improve its bending characteristics. The cylindrical tube diaphragm (406) has a smaller cross-sectional thickness (412) on the edge of the cylinder (414) that tapers and increases to form a thicker middle portion of the other cylinder (413) cross section. The cylindrical tube diaphragm (406) is designed such that the deformation is closer to the desired average deflection of the cylindrical tube diaphragm (406) rather than having uneven deformation along its length. Supply pressure on the inside of the tube diaphragm (406) causes the tube diaphragm (406) to bulge toward the thin limiting clearance (408). Thin limited clearance (408) is directly connected to the bearing's oil chamber groove (410) and changes as the incoming oil chamber pressure changes. Deflection of the tube diaphragm (406) allows more fluid to enter the loaded oil chamber trough, thereby adjusting the stiffness and hydrostatic system film gap thickness. When the bearing clearance changes, the thin limiting clearance (408) in the variable flow resistance (i.e., the annular boss clearance) changes to compensate for the change in clearance. An increase in load will increase the oil chamber pressure, thereby reducing the bearing film clearance. The hydrostatic bearing film thickness controller (400) compensates by supplying more fluid to increase the bearing's load carrying capacity and stiffness. This represents a positive slope between pressure and fluid flow, which results in ideal performance, and this is achieved via the hydrostatic bearing film thickness controller (400).

The variable thickness reduces the maximum deflection that can be achieved while keeping the average deflection constant, so it can reduce the maximum gap without blocking the fluid passage, allowing for a greater percentage of the average gap thickness.

Tube diaphragms (406) are fixed around thin circular slots or thin restricted gaps and have many advantages over flat diaphragms because tube diaphragms (406) can be easily attached, but flat diaphragms require a press fit to perform hydrostatic A pressure bearing is held within the assembly of the film thickness controller (400) at the edge of the film. The flow rate of the fluid depends on the pressure difference between the supply pressure and the oil chamber pressure and the flow resistance that limits the clearance. The liquid flow resistance of the clearance is controlled by changes in the limiting gap caused by the deflection of the tube diaphragm caused by the fixed flow resistance.

The hydrostatic bearing film thickness controller (400) has been tested in a laboratory-fabricated single-slot hydrostatic bearing test rig where the fluid flow resistance of the bearing slots tends to increase. The oil chamber pressure changes. The hydrostatic bearing film thickness then begins to decrease, which can be prevented by increasing the flow rate via an external flow control mechanism (i.e. a tube diaphragm) to reduce the resistance to fluid flow in the bearing groove which will maintain a constant film thickness.

Embodiments of the present invention may be implemented using at least one software program that runs on at least one hardware device and performs network management functions to control elements.

The foregoing description of specific embodiments will sufficiently disclose the general nature of embodiments of the invention such that others, by applying current knowledge, may readily modify and/or adapt such specific embodiments for use without departing from the general concepts. various applications, and therefore such adaptations and modifications should and are intended to be included within the meaning and scope of equivalents to the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Accordingly, although embodiments of the invention have been described in terms of preferred embodiments, those of ordinary skill in the art to which this invention pertains will recognize that the embodiments of the invention can be practiced within the spirit and scope of the described embodiments of the invention. implemented through modifications within.

In summary, the technical means disclosed in the present invention can indeed effectively solve the problems of conventional knowledge and achieve the expected purposes and effects. They have not been published in publications or publicly used before the application and are of long-term progress. They are truly worthy of the title. The invention described in the Patent Law is correct, and I submit the application in accordance with the law. I sincerely pray that Jun will review it carefully and grant an invention patent. I am deeply grateful.

However, the above are only several preferred embodiments of the present invention, and should not be used to limit the scope of the present invention. That is, all equivalent changes and modifications made based on the patent scope of the present invention and the content of the invention specification are It should still fall within the scope of the patent of this invention.

[Invention] 100:Flow control unit 102: Round flat film 104: Annular boss 106: Fixed current limiter 108:Variable current limiter 110: Clearance 112: Oil chamber groove 200:Hydrostatic Bearing System 202:Youchi 204: Pressure relief valve 206:Pump 208:Motor 210: Accumulator 212:Filter 214:Hydraulic power unit 216:Bearing groove 400: Hydrostatic Bearing Film Thickness Controller 402: Fixed current limiter 404: Variable current limiter 406: Cylindrical tube diaphragm 408: Thin limit clearance 410: Oil chamber groove 411:Length 412: Smaller cross-sectional thickness 413:Another cylinder 414:Cylinder

[Fig. 1] is a cross-sectional view of a flow control unit for maintaining a constant fluid film gap in a hydrostatic bearing system according to an embodiment disclosed in the present invention; [Fig. 2] is a schematic diagram of a hydrostatic bearing system according to an embodiment disclosed in the present invention; [Fig. 3] is a cross-sectional view of a plurality of flow control units connected in series and assembled into a single unit connected to a hydrostatic bearing system according to an embodiment disclosed in the present invention; [Fig. 4] is a cross-sectional view of the hydrostatic bearing film thickness controller according to the disclosed embodiment of the present invention.

102: Round flat film

104: Annular boss

106: Fixed current limiter

108:Variable current limiter

110: Clearance

112: Oil chamber groove

Claims (13)

A flow control unit (100) for maintaining a constant fluid film gap in a hydrostatic bearing system (200), the flow control unit (100) includes: a circular flat membrane (102); an annular boss (104) ; a fixed flow restrictor (106) configured to provide a fixed flow resistance in the flow control unit (100), wherein the fixed flow restrictor (106) is combined with a variable flow restrictor (106); 108) Connected in series, the variable flow restrictor (108) configured to provide variable flow resistance in the flow control unit (100), wherein the variable flow restrictor (108) is in line with the oil chamber groove (112), wherein the fixed flow resistance has the geometry of a capillary flow restrictor, and wherein the variable flow resistance includes a geometry that deforms to actively control the Flow in a hydrostatic bearing system (200), wherein the geometry is provided by the circular flat membrane (102) for controlling the gap between the membrane and the annular boss (104); wherein using the The clearance (110) generated by the circular flat membrane (102) and the annular boss (104) provides the variable flow resistance; and the hydrostatic bearing system (200) includes: an oil pool (202); Pressure valve (204); pump (206); motor (208); Accumulator (210); filter (212); hydraulic power unit (214); bearing groove (216); flow control unit (100). The flow control unit (100) of claim 1, wherein the fixed flow resistance enables a necessary pressure difference to be formed across the circular flat membrane (102). The flow control unit (100) of claim 1, wherein said fixed flow resistance maintains a correct gradient of pressure differential across said circular flat membrane (102). The flow control unit (100) of claim 1, wherein the cross section of the clearance (110) is determined by the deformation of the circular flat membrane (102). The flow control unit (100) of claim 1, wherein the pressure difference across the circular flat membrane (102) controls the amount of deformation in the circular flat membrane (102). The flow control unit (100) of claim 1, wherein the fixed flow resistance blocks the fluid flow so as to control a large flow of the fluid flow through the variable flow restrictor (108). The flow control unit (100) of claim 1, wherein the clearance (110) is provided at a specific supply pressure. The hydrostatic bearing system (200) of claim 1, wherein the fixed flow resistance enables a necessary pressure difference to be established across the circular flat membrane (102). The hydrostatic bearing system (200) of claim 1, wherein said fixed flow resistance maintains a correct gradient of pressure differential across said circular flat membrane (102). The hydrostatic bearing system (200) of claim 1, wherein the cross-section of the clearance (110) is determined by the deformation of the circular flat membrane (102). The hydrostatic bearing system (200) of claim 1, wherein the pressure difference across the circular flat membrane (102) controls the amount of deformation in the circular flat membrane (102). The hydrostatic bearing system (200) of claim 1, wherein the fixed flow resistance blocks fluid flow to control a large flow of the fluid flow through the variable flow restrictor (108). The hydrostatic bearing system (200) of claim 1, wherein the clearance (110) is provided at a specific supply pressure.