Showing papers on "Fluid bearing published in 1981"

Design of high speed cylindrical NMR sample spinners

Abstract: Simple approximate solutions to compressible fluid flow problems are used to arrive at useful design equations for high‐speed spinning on cylindrical air bearings for NMR studies of solids. The optimum radial clearance is shown to depend on the 1/3 power of the rotor diameter, and is 0.027 mm for a 12‐mm rotor, with a surface speed of one half the speed of sound, c. The required air bearing hole diameter is about 0.3 mm with a square root dependence on the rotor diameter. A few general comments are made concerning turbine design, and a simple combination impulse‐reaction type is described which offers some improvement in drive efficiency. Drive air flow is shown to depend approximately on the square root of the rotor volume for a surface speed 0.5 c. Relevant data for a number of high strength materials including hard ceramics are tabulated, and limiting speeds are calculated. The design equations are verified for 8 and 12 mm rotors made from Al2O3 with wall thicknesses equal to 6% of the diameter.

Bearing device for rapidly rotating body

Abstract: PURPOSE:In a bearing device for the shaft of an engine supercharger or the like, to attain a high load carrying capacity against the thrust, by providing a radial air bearing and a magnetically repulsive thrust bearing in the bearing device. CONSTITUTION:Radial air bearings 4,4 having vortically-wound thin sheets 7 inside between housings 6 and a rotary shaft 3, which couples a turbine rotor 1 and a compressor impeller 2 to each other, are secured in a radial bearing section. A magnetically repulsive bearing, which comprises a rotary permanent magnet 8 secured between the bearings 4, 4 and magnetized in the axial direction of the shaft 3 and static permanent magnets 9a, 9b secured in the housing 9 of the bearing, is fixed in a thrust bearing section. The radial load on the rotary shaft 3 is borne by the air bearings 4, 4. The thrust load on the shaft 3 is countered by the repulsive magnetic force caused between the facing sides of the magnets 8, 9a, 9b. According to this constitution, the shaft 3 can rapidly be rotated out of contact with the thrust bearing.

Surface roughness effect on finite oil journal bearings

Abstract: A theoretical study of the performance of finite oil journal bearings is made, considering the surface roughness effect The total load supporting ability under such a condition derives from the hydrodynamic as well as asperity contact pressure These two components of load are calculated separately The average Reynolds equation for partially lubricated surfaces is used to evaluate hydrodynamic pressure An analytical expression for average film thickness is obtained and introduced to modify the average Reynolds equation The resulting differential equation is then solved numerically by finite difference methods for mean hydrodynamic pressure, which in turn gives the hydrodynamic load Assuming the surface height distribution as Gaussian, the asperity contact pressure is found The effect of surface roughness parameter, surface pattern, eccentricity ratio, and length to diameter ratio on hydrodynamic load and on side leakage is investigated It is shown that hydrodynamic load increases with increasing surface roughness when both journal and bearing surfaces have identical roughness structures or when the journal only has a rough surface The trend of hydrodynamic load is reversed if the journal surface is smooth and the bearing surface is rough

Isolated multiple core magnetic transducer assembly

Abstract: Disclosed herein is a magnetic transducer assembly including a plurality of magnetic cores affixed to a non-magnetic slider, the slider having a multiplicity of fluid bearing surfaces for supporting the magnetic transducer assembly on a fluid bearing proximate to a rotating surface such as a magnetic disc. Each magnetic core has a corresponding slider fluid bearing surface of equal width, the magnetic cores being affixed to the trailing edge of the fluid bearing surfaces. The slider provides additional fluid bearing surfaces intermediate the corresponding fluid bearing surfaces.

Molecular Mean Free Path Effects in Gas Lubricated Slider Bearings : 2nd Report, Experimental Studies

Abstract: The latest magnetic disk files require lightly loaded air-lubricated slider bearings operating with film thicknesses less than 0.5μm to achieve high recording density. This paper reports results on flying characteristics obtained from experiments with such air bearings, which are influenced considerably by slip-flow effects. Experiments are carried out in the range of 30 to 70% load reductions due to slip-flow. White light interferometric techniques for measuring the spacing between a rotating glass disk and the slider are improved. For load reductions less than 60%, experimental data agree well with the numerical solution of a modified Reynolds equation which takes into account the velocity-slip boundary conditions. It is verified that the modified Reynolds equation can be used to predict the static behavior of slider bearings in designing magnetic flying heads. An effective calculation technique for the Reynolds equation by the finite element method is presented.

Unbalance Response of a Two Spool Gas Turbine Engine With Squeeze Film Bearings

Abstract: This paper presents a dynamic analysis of a two-spool gas turbine helicopter engine incorporating intershaft rolling element bearings between the gas generator and power turbine rotors. The analysis includes the nonlinear effects of a squeeze film bearing incorporated on the gas generator rotor. The analysis includes critical speeds and forced response of the system and indicates that substantial dynamic loads may be imposed on the intershaft bearings and main bearing supports with an improperly designed squeeze film bearing. A comparison of theoretical and experimental gas generator rotor response is presented illustrating the nonlinear characteristics of the squeeze film bearing. It was found that large intershaft bearing forces may occur even though the engine is not operating at a resonant condition.

Performance of jet- and inner-ring-lubricated 35 millimeter bore ball bearings operating to 2.5 million DN

Abstract: Parametric tests were conducted with a 35 millimeter bore, angular contact ball bearing having a single outer land guided cage. Lubrication was achieved by flowing oil through axial grooves and radial holes machined in the inner ring of the bearing. Test conditions were a thrust load of 667 N (150 lb), shaft speeds from 48,000 to 72,000 rpm, and an oil inlet temperature of 394 K (250 F). Data from tests where the distribution of the total oil supplied to the inner ring was 50 percent for bearing lubrication and 50 percent for bearing inner ring cooling were compared with those where the distribution pattern was 25 percent lubrication and 75 percent cooling. Successful operation was experienced with both the 50-50 and 25-75 percent flow distribution patterns to 2.5 million DN. The 50-50 percent flow pattern provided the cooler bearing operation of the two inner ring lubricated bearings. The jet lubricated bearing had lower outer ring and higher inner ring temperatures than the inner ring lubricated bearings. Maximum power loss of 2.8 kW (3.7 hp) was experienced with the 25-75 percent flow distribution, and maximum percent cage slip of 7.0 occurred at 72,300 rpm with the 50-50 percent flow distribution.

A fluid bearing

Abstract: A fluid bearing comprises orifices (14) in fluid communication between a cavity (12) containing pressurised fluid in the periphery of the fluid bearing to support a flexible magnetic tape (16) under tension, and a tension sensor having a chamber (20) within the fluid bearing, a pressure transducer (28) for sensing the pressure of the fluid within the chamber (20), a first metered orifice (24) providing fluid communication between the chamber (20) and the periphery of the bearing, and a second metered orifice (22) providing fluid communication between the chamber (20) and the source (12) of pressurised fluid, so that the pressure transducer provides an indication of the tension in the tape.

Hydraulic pneumatic sewerage pipe cleaning appliance - has liquid or air bearings holding rotor floating operatively on fixed unit

Abstract: The rotor, driven by recoil jet nozzles, is mounted on a hollow spindle supplying pressure medium, in an appliance for cleaning pipes in sewerage pipe systems, with pressure- medium drive, and recoil inducing automatic forward movement The rotor (4) is held in its operative position, floating on the stationary component (1), by fluid or air bearings These can be in the form of an axial bearing (3), adjoined by radial bearings (10,11) on both sides, the former being a self-centering shock absorbing bearing for the rotor This is reliable and quiet, and requires less power in proportion to output

Air Bearings And Drive Systems In Single-Point Diamond Tool Machine Tools

Abstract: The paper discusses two topics that the author has found to be of importance in the appl-ication cf air bearings to diamond tool machine tools. The first topic discussed concernsthe potentially poor performance, in relation to a machine tool, of an air bearing journal,if it is designed for the maximum possible static load carrying capacity. The problem isassociated with a sometimes self- excited instability, associated with the compressibility of air. The second subject is concerned with two different types of non -influencing drivesystem , both of which have been used to promote a vibration -free mode of operation. One type of drive provides a uniform linear motion to an air bearing supported table on a diam-ond tool flycutter. The other type of drive has been used to provide angular velocity tothe Headstocks of both a diamond tool lathe and an aspheric generator.IntroductionThe reliable production of non- ferrous components, the surfaces of which have both theaccuracy of shape, and reflectivity necessary to satisfy the demands of the precision opti-cal industry, have placed, in turn, stringent demands upon the diamond tool machine tool.In order to satisfy these demands the machine tool designer has, among many other things,needed to pay particular attention to the quality of the main spindle bearing that he empl-oys, and also to ensure that the drive systems used do not impose vibrations, periodicerrors, or extraneous forces upon the main bearings or slideway systems.Over the past two or three decades, the hydrodynamic oil bearing, and occasionally thehydrostatic oil bearing have been the bearings most favoured in diamond tool machine tools.However, the last decade has seen, increasingly, the application of pressurised air bearingsto provide the main spindle bearing. All of the above bearing types have in common thebeneficial properties of fluid film bearings, i.e. an accuracy of rotation better than theaccuracy of manufacture of the components of which the bearings are made; and an absenceof the broad hand vibrations associated with rolling element bearings. These propertieshave been, of course, the reasons for the selection of fluid film bearings by the designersof diamond tool machine tools. However, if the designer decides to use an externallypressurised air bearing, possibly for the first time, it is, in the author's opinion, impor-tant for him to realize that an air bearing designed for the maximum static load carryingcapacity or maximum stiffness, may have a poor dynamic performance as a machine tool element,as the result of a phenomenen known as self excited pneumatic instability. This is not thecase with hydrostatic oil bearings, due to the incompressible nature of the fluid. The useof air, which is a compressible fluid, demands a bearing design philosophy which recognisesthis effect.A suggested approach to the design of air journal bearings is discussed below, as are twodifferent types of non- influencing drive that have been successfully employed on diamondtool machine tools.Air Journal bearingsThe static load carrying capacity of an externally pressurised air bearing is primarilya function of the pressure of supplied air and the bearing dimensions. The load carryingcapacity is also, but less importantly, a function of:-Orifice sizeNumber of orifices per rowNumber of rows (either one or two)Pocket diameterAxial position of rowIt should perhaps be acknowledged here that there are other types of externally pressurisedair bearings which do not use orifices as restrictors, but which will not be discussed inthis paper. Further, and for the purposes of simplification, this discussion is restrictedto the orifice compensated, or pocketed, type of bearing as shown in Figures 1 and 2.The designer, given a fixed conventional workshop air supply of say 551.5kNm2 (80LB /in2gauge), will want to satisfy himself that his journal bearing has a load carrying capacity

Hydrodynamic shaft bearing with concentric outer hydrostatic squeeze film bearing

Abstract: A bearing structure which incorporates the advantages of a hydrodynamic film and of a hydrostatic squeeze film. The structure uses an inner elongated cylindrical bearing member with a hydrodynamic bearing therein, and an outer bearing member axially encompasses the inner bearing member. Passageways and adjacent surface on such members establish fluid flow paths, hydrostatic pockets and squeeze film areas to support such inner bearing member.

Device for controlling the vertical motion of an air-supported spindle

Abstract: The spindle (1) can be moved axially relative to the fixed stepped piston (3) by varying the internal air pressure, these movements being controllable with extremely great precision since air bearings (3a, 3b) build up in the interior of the spindle (1). As a result, this arrangement is particularly suitable as a measuring spindle for length measurement and hardness testing.

Self-Alignment Systems for Heavily Loaded, Compliant, Hydrodynamic Air Bearings

Abstract: Internal and external self-alignment system for compliant-foil journal bearings have been developed and tested at 35000 rpm in ambient air These system have been shown to substantially improve the self-alignment capabilities of the compliant-foil bearings The standard bearings with center-split bump have a misaligned capacity of 007 degrees at 55 kPa and 003 degrees at 83 kPa Bearings with an internal self-alignment system were shown to have 015-degree misalignment capability at 55-kPa loading and 006 degrees at 90 kPa A bearing with an external self-alignment system tolerated 043 degrees of misalignment at 69 kPa and 037 degrees at 110 kPa Self-alignment capabilities of the bearings were improved at higher speed Limited testing at 288°C showed that the temperature had no influence on the bearing performance Presented at the 35th Annual Meeting in Anaheim, California, May 5–8, 1980

Spherical telescope or radar bowl mounting - has sphere supported on two rings by ball bearings or pads to permit pivoting in all directions

Abstract: The spherical telescope (1) mounting has a sphere (4) supported on a support block (13) and can pivot in all directions about its centre. The support has a number of independent pads supporting the sphere. Each has a shoe pressing on the sphere via ball bearings (11) or by fluid bearings. These are concentric with the sphere. The pads can be moved by a type of jack. The annular support block is placed below the sphere with its vertical axis passing through the sphere centre. There can be two movable rings (9,10) joined to the first and second pad groups.