Showing papers on "Bearing (mechanical) published in 1992"

Dynamic analysis of geared rotors by finite elements

Abstract: A finite element model of a geared rotor system on flexible bearings has been developed. The model includes the rotary inertia of on shaft elements, the axial loading on shafts, flexibility and damping of bearings, material damping of shafts and the stiffness and the damping of gear mesh. The coupling between the torsional and transverse vibrations of gears were considered in the model. A constant mesh stiffness was assumed. The analysis procedure can be used for forced vibration analysis geared rotors by calculating the critical speeds and determining the response of any point on the shafts to mass unbalances, geometric eccentricities of gears, and displacement transmission error excitation at the mesh point. The dynamic mesh forces due to these excitations can also be calculated. The model has been applied to several systems for the demonstration of its accuracy and for studying the effect of bearing compliances on system dynamics.

Theoretical Analysis of Piston-Ring Lubrication Part I—Fully Flooded Lubrication

Abstract: A one-dimensional analysis for lubrication between the piston ring and cylinder wall has been developed. A fully flooded inlet condition and axisymmetric geometry are considered. The piston ring is treated as a reciprocating, dynamically-loaded bearing with combined sliding and squeeze motion. A system of two nonlinear differential equations is used to model the lubrication including the Reynolds cavitation boundary condition. A numerical procedure is then developed to obtain the cyclic variations of film thickness, frictional force, power loss, and oil flow across the ring. Results are presented for a typical automotive engine. The effects of ring profile, ring tension, and engine speed are examined. It is shown that this analysis can be used to study the influence of ring design parameters in order to improve the design of the ring pack in reciprocating engines.

Experimental Study of Tilting-Pad Journal Bearings—Comparison With Theoretical Thermoelastohydrodynamic Results

Abstract: Operating characteristics of four-shoe tilling-pad journal bearings of 100 mm diameter and 70 mm length are determined on an experimental device The load, between pad configuration, varies from 0 to 10,000 N and the rotational speed is up to 4000 rpm Forty thermocouples are used in order to measure bearing element temperatures (babbitt, shaft, housing and oil baths) The influence of operating conditions and preload ratio on bearing performances are studied

Floating bearing prosthetic knee

Abstract: A semiconstrained prosthetic knee for surgical replacement of a dysfunctional knee includes a tibial platform, a movable bearing element, and a femoral component. The femoral and tibial components are typically constructed of a cobalt-chromium alloy and each includes an extension for securing the component to the bone. The femoral component includes a polycentric convex bearing which slidably engages a movable bearing, typically constructed of high molecular weight polyethylene. The superior surface of the bearing element is designed to congruently slidably engage the inferior surface of the bearing portion of the femoral component throughout the flexion/extension range of the knee. The inferior surface of the femoral component is generally convex with two or more offset portions of varying radii of curvature matching complimentary superior surfaces of the bearing element. The inferior surface of the femoral component may have more than one radii of curvature at different points along the convex surface. The superior surface of the tibial platform is generally flat and includes at least one protrusion for controlling the movement of the bearing element.

Optical table active leveling and vibration cancellation system

Abstract: An optical table active leveling and vibration cancellation system is disclosed. The system includes an optical table with three active isolation devices connected to the optical table, and one sole pneumatic device, such that the table is supported on all four corners. Each of the isolation devices includes a pneumatic suspension device and an electromagnetic suspension device. The pneumatic suspension device includes a pressurized load chamber, a gimballed piston received in the pressurized load chamber and coupled to the walls of the pressurized load chamber by a thin walled diaphragm, and a support rod extending from the optical table to the floor level. The electromagnetic bearing suspension device includes a magnetic bearing rotor having two planar surfaces and a peripheral surface, and two magnetic bearing stators, the stators each defining a central aperture and each stator being in a spaced apart relationship from each of the rotor planar surfaces. The rotor is secured to the support rod. Each of the stators includes an annular coil of wire. The electromagnetic suspension system may also include four radial electromagnets spaced around the peripheral surface of the rotor. The radial electromagnets also include an annular coil of wire. The system also includes three proximity sensors mounted under the optical table to detect motion of the table in relation to the floor or another fixed reference, and generate a signal in response to the motion. The system also includes three accelerometers mounted underneath the optical table in a triangle. The accelerometers measure vibration of the table in relation to inertial space and generate a signal in response to the movement. A controller receives the signals from the sensors and accelerometers, and generates a second signal, used to activate the pneumatic and electromagnetic bearing suspension devices to provide active leveling and vibration cancellation of the optical table.

Rotational and translational bearing combination in biological joint replacement

Abstract: A joint prosthesis having a femoral element (16), a tibial element (12) and a bearing (20) for articulation therebetween is disclosed to further include an intermediate element (22). The intermediate element permits rotation of the bearing with respect to the tibial element and longitudinal translation of the bearing with respect to the intermediate element. Transverse translation of the bearing with respect to the intermediate element is precluded. In an alternative embodiment, the longitudinal translation may be limited either in the anterior or posterior direction.

Rear wheel steering device for vehicle

Abstract: PURPOSE:To prevent the engaging end section of a cross end from being dislocated in position at the time in position adjustment as well as to perform adjustment works accurately with ease by providing a bearing support section with a movable member, a housing, a spring member and an adjusting screw. CONSTITUTION:In assembling a rear wheel steering device, after respective parts have been assembled in, and when the engaging end section C of a cross lever 14a is supported by a bearing support section 38 in order to absorb errors in assembly, the engaging end section C is engaged with the engaging hole 62a of a movable member 62. Since the movable member 62 is moved while it is against the spring force of the spring member 63 or while it is being energized by the spring force of the spring member 63 with an adjusting screw 64 rotated, the support section of the engaging end C can thereby be accurately adjusted in position with ease. Furthermore, if the projected end of the adjusting screw 64 is fastened with a lock nut 65 after the position has been adjusted, the adjusting screw 64 is fixed, the adjusted position will thereby never be dislocated so as to be stabilized in position.

Materials for Tribology

Abstract: Steels. Metallurgy of steels. Selection. Pearlitic. Martensitic. Stainless. Tool. Bearing. Manganese. Selecting steels for mining and construction industries. 2. Copper Base Bearing Materials. Tin bronzes. Leaded tin bronzes. Copper lead. Aluminum bronze. Manganese bronze. Beryllium copper. Porous bronzes. Bearing properties of copper base materials. Gear bronzes. Electrical contacts. 3. Soft Metal Bearing Materials. Soft metals. Babbitts or whitemeal. Alloy selection and design. Zinc bearing alloys. Gold, silver and indium. 4. Cast Iron. Properties of cast irons. Metallurgy. Heat treatment. Surface hardening. Wear properties. High alloy. 5. Carbon Graphite. Usage in tribology. Wear of carbon graphite. Mechanical seals. Sleeve bearings. Thrust bearings and vanes. Carbon brushes. 6. Ceramics and Special Alloys. Ceramics. Structure and properties. Ceramic tools. Rolling contact bearings. Cermets. Glasses Refractory metals and alloys. Super alloys. Materials for nuclear reactors. 7. Polymeric Materials. Properties of polymers. Design of plastic bearings. Plastics used in tribology. Elastomers-rubber. Properties of elastomers. Design of elastomer bearings. Types of elastomers. Wear of rubber. References. Appendix. Index.

A Linear Theory of Vibrations Caused by Ball Bearings With Form Errors Operating at Moderate Speed

Abstract: A linear theoretical model is presented for the vibrations of a shaft bearing system caused by ball bearing geometrical imperfections. It is valid for low and medium speeds where ball centrifugal forces can be neglected. The excitation forces from each bearing are calculated and can serve as input to suitable rotor dynamics programs. Imperfections covered are radial and axial waviness of outer and inner rings, ball waviness and diameter distribution, nonuniform cage pocket distribution

Square and rectangular hollow sections subject to combined actions

Abstract: A large number of tests on a range of cold‐formed square and rectangular hollow sections subjected to pure bending, pure concentrated force and combined bending, and concentrated force are described. The concentrated force is applied by means of a bearing plate that acts across the full flange width of the section. The ratio (γ) of the bearing length to the width of the bearing plate used varies from 0.5 to 1.0 in order to show the effects of the bearing length on the failure loads. The current tests are compared with previous T‐joint tests performed at the University of Sydney on similar sections to demonstrate the significant reductions in failure loads and the more severe interaction between bending moment and concentrated force for the tests using bearing plates. The test results are compared with the existing Australian, European, and American design procedures. Improved design procedures are also proposed.

Rolling Element Bearing Fatigue Damage Propagation

Abstract: Rolling element bearing fatigue spalls were propagated for several test conditions well beyond the laboratory criteria of 6.5 square millimeters used in the author's laboratory. Usually mare than one mode of fatigue spall propagation is involued when large spalls develop. The information provided in this paper can be used to gain an appreciation of the total useful life of a bearing and to allow a more accurate diagnosis of fatigue spall damage

Process cartridge and image forming apparatus on which process cartridge is mountable

Abstract: A process cartridge mountable within an image forming apparatus, includes an image bearing member, process means acting on the image bearing member, a frame, and a first guide surface provided on the frame and adapted to guide a recording medium toward the image bearing member, and a second guide surface recessed more than the first guide surface and having width smaller than that of the first guide surface. With the above construction, it is possible to provide a process cartridge and an image forming apparatus within which such a process cartridge can be mounted, which can be made small-sized and light-weighted and which are easy to use.

An efficient method of passive emitter location

Abstract: The problem of locating a stationary emitter from passive bearing and frequency measurements taken by a moving and autonomously operating sensor along its trajectory is considered. The estimation procedure based on bearings only is quite different from that based on frequency measurements. From the Cramer-Rao (CR) analysis of the single-measurement case, the characteristic features of each method become transparent and an intuitive understanding of both methods is provided. One of the major results is that the orientation of the error ellipses of the bearings method (BM) and frequency method (FM) differ significantly. From this a considerable integration gain in accuracy results, when processing the combined set of bearing and frequency measurements. The results of the theoretical CR analysis are verified in a numerical simulation based on the maximum-likelihood (ML) estimation. The simulations demonstrate that a combined method is definitely superior to BM and FM with respect to the bias and the size of the error ellipses. >

Magnetic bearing structure providing radial, axial and moment load bearing support for a rotatable shaft

Abstract: A magnetic bearing structure utilizes two adjacent electromagnetic bearings to provide controlled radial, thrust and moment load support of a shaft relative to a housing. The first bearing generates a high density controllable magnetic field to radially flux couple the shaft to the housing. A second bearing generates a high density controllable magnetic field to axially flux couple the shaft to the housing. In a preferred form, the first bearing circumferentially surrounds the shaft and includes a stator ring associated with the housing which holds several electromagnetic coils radially spaced from the shaft. Power supplied to the coils generates a radially polarized electromagnetic field surrounding the shaft. A pair of additional electromagnetic coils, or permanent magnets, circumferentially extend around the shaft to generate an axially polarized, constant flux magnetic field. Substantially all of the magnetic flux generated by both flux generation sources is directed radially through a primary air gap between the shaft and the stator ring to provide radial support for the shaft. The second bearing includes two coil housings between which a thrust disc associated with the shaft extends. Two arcuate permanent magnets within the disc generate a constant flux radially polarized magnetic field. Three pairs of electromagnetic coils, each subtending a 120 degree arc, are placed within the coil housings to generate an axially polarized, controllable magnetic field. Magnetic flux generated by the permanent magnets and the paired electromagnetic coils axially couples the shaft to the housing.

Valve mechanism of internal combustion engine

Abstract: A drive shaft is synchronously rotated with a crankshaft of an internal combustion engine. A cylindrical hollow cam shaft is rotatably disposed about the drive shaft keeping a first cylindrical clearance therebetween. The cam shaft is formed with at least one cam that actuates an engine valve for opening and closing the same. A bearing bears a given portion of the cam shaft keeping a second cylindrical clearance therebetween. A movement transmitting mechanism transmits a torque of the drive shaft to the cam shaft while converting a rotation movement of the drive shaft to a swing movement of the cam shaft. The thickness of the first cylindrical clearance is smaller than that of the second cylindrical clearance.

A Survey of Magnetic Levitation and Magnetic Bearing Types

Abstract: Magnetic levitation has been studied mainly in two distinct fields of application, MAGLEV transportation and rotor bearings. A unitied overview, as it is attempted in this paper, reveals that there are many radically different types of magnetic levitation. A systematic classification of these basic levitation principles is proposed. It starts from the fundamental manner to obtain the magnetic force. The systematization derived in this manner aims at including all possible basic magnetic levitation types. As a result some little known levitation types are inc1uded, among them Lorentz-force bearings and tuned LC bearings. As a special feature, a new type of active bearing is presented, the so-called self-sensing active bearing using no gap sensor. This remarkable bearing type combines high static load and low hardware costs. Examples of realizations are given.

Thin drawer slide

Abstract: A thin profile drawer slide apparatus for slidably supporting a heavy drawer in an article of furniture, comprising outside channels for slidably attaching the apparatus to a drawer and an article of furniture, a plurality of bearings slidably retained in the channels by parallel, opposed bearing retainers, and by a one-piece, generally "I"-shaped intermediate slide member or retaining member unitarily formed with top and bottom parallel raceway means for guiding the bearing retainers. Use of a single intermediate slide member with raceways for four separate sets of bearings enables construction of a thin, strong drawer slide for carrying heavy loads.

Dynamic Analysis and Control of High Speed and High Precision Active Magnetic Bearings

Abstract: The successful operation of actively controlled magnetic bearings depends greatly on the electromechanical design and control system design. The function of the controller is to maintain bearing performance in the face of system dynamic variations and unpredictable disturbances. The plant considered here is the rotor and magnetic bearing assembly of a test apparatus. The plant dynamics consisting of actuator dynamics, rigid rotor dynamics and flexibility effects are described. Various components of the system are identified and their corresponding linearized theoretical models are validated experimentally

Prosthetic knee joint

Abstract: There is disclosed a prosthetic knee joint which comprises: a bicompartmental femoral component (1) capable of attachment to a femur and having a lateral and a medial articular bearing surface (4); a bicompartmental tibial component (20) capable of attachment to a tibia and having a medial (26) and a lateral (27) articular bearing surface; and a bicompartmental meniscal component (11) capable of acting as a bearing positioned between the bearing surfaces of the femoral (1) and tibial (20) components, wherein the tibial component (20) is provided between its medial (26) and lateral (27) articular bearing surfaces with a protruding member (22) having at least at its distal end a cross-sectional shape which has a parallel-sided intermediate region extending between two convexly arcuate end regions, and wherein the meniscal component (11) is provided with a recess (13) in which the protruding member (22) of the tibial component can be accommodated with play.

Flow-regulating hydrodynamic bearing

Abstract: A self-lubricating hydrodynamic spindle bearing for support of a spindle of a magnetic disk drive assembly includes a crankcase design which provides large reservoirs for oil storage with an air cover in communication with the ambient environment through an air vents provided by clearance seals formed between respective central passages of housing-sealing endcaps and the shaft. The crankcase reservoir volume is defined within the bearing so that natural body force effects cause the lubricant to be fed into the hydrodynamic bearing. A leak-preventing capillary trap of minimal continuous axial length may be provided at the clearance seal for passive capture of wandering lubricant when the bearing is at rest. Full evacuation of lubricant trapped at the clearance seal is achieved toward the interior of the housing by centrifugal pumping, e.g., the inboard side of the rotating part of the seal is coned and fluted such that the rotating centrifugal field will throw all statically trapped oil into the lubricant reservoir. A three way restrictive valve is provided to assure balanced feeding of lubricant to both ends of the spindle for either vertical or horizontal spindle orientation. A pressure-actuated bladder may be attached to the bearing to deliver a volume of lubricant to the bearing on demand.

Abrasive wear in lubricated contacts

Abstract: Despite the fact that many tribological components are designed to operate with a comparatively thick film of lubricant, bearing surfaces often still deteriorate with time as hard particulate contaminants are swept through the bearing gap. These particles may arise from the external environment or be wear debris from other pairs of surfaces lubricated by the same fluid. In order to investigate this phenomenon experimentally it is necessary to develop a predictable hydrodynamic film between the test surfaces which can be contaminated by small volumes of carefully graded particles. Here we describe the use of a foil bearing to generate such films between 10 and 50 µm thick to which contaminants such as finely divided diamond can be added. As the ratio of the characteristic particle size to film thickness is varied not only do the wear rates of the solid surfaces change but examination of the wear tracks suggests that very different mechanisms of material loss come into operation. When the size ratio is low the worn surface of the cylinder is covered by what appear to be small erosion pits; these display virtually no alignment in the direction of relative sliding and it appears that the particles tumble and roll freely through the gap. Above some critical value of the ratio the appearance of the surface changes dramatically to a grooved or micro-machined surface with all the grooves aligned in the sliding direction. A relatively simple theoretical model is developed, based on what happens to a typical particle, which goes some way to explaining these observations. As well as being consistent with the observed transition from `tumbling' to `grooving', the model can also explain why increasing the hardness differential between the hard and the soft surfaces does not always lead to a reduction in the damage to the harder member of the pair.

High performance bearing pad for thrust bearing

Abstract: Cylindrical bearing pads (60) are insertable into bearing pad recesses (59) formed in a receiving surface of a bearing pad retainer (56) in a load-carrying structure. The bearing pads have an insertion end (61) which is fixed into the bearing pad recess by brazing or by interference fitting and a bearing end (62) which projects from the receiving surface and terminates in a bearing face (63). The bearing face has a periphery which encircles the bearing face and an indentation (67) having a perimeter formed centrally in the bearing face. An annular flattened area encircles the indentation forming an effective bearing contact area between an outer border of the flattened area and the perimeter of the indentation. When the indentation is filled with drilling fluid, lubrication is provided to an opposed bearing face of an opposing bearing pad. The indentation can be filled with drilling fluid or some other material with a higher heat storage capacity than polycrystalline diamond to provide temperature modulation for storing heat produced at the bearing face. When filled with a material, the indentation also serves to dissipate heat to reducing the length of a path of heat when the heat is conducted to cooler areas of the bearing face. Alternate embodiments include bearing faces with single or plural indentations of various shapes.

Operational characteristics of microfabricated electric motors

Abstract: We report on the operational characteristics of LOCOS-based microfabricated radial-gap electric motors through lifetime tests, transient measurements, modeling, and parameter extraction. We have found that the reduction of static friction (stiction) in the bearings by the incorporation of a silicon nitride film permits these micromotors to spin in normal air ambients. Frictional drag from the bearing, which results from the electric-based side-pull of the rotor, is found to be the dominant rotor-retarding force and to lead to motor wearout after approximately 10 000 rotor revolutions. Furthermore, the frictional coefficient of the nitride-on-polysilicon micromotor bearing is determined to be 0.36 ± 0.04.

Composite bearing structure

Abstract: A composite bearing structure that has a high rotational accuracy and that can withstand high-speed rotation comprises first bearing means, second bearing means, third bearing means and fourth bearing means. The first bearing means supports a radial impact force which is applied to a rotator during rotation, and is formed by an inner ring (1) and an outer ring (2) consisting of silicon nitride ceramics sintered bodies. The second bearing means supports an axial load which is applied to the rotator while maintaining a prescribed clearance with the rotator, and is formed by a magnetic bearing body of two permanent magnets (12) and (13) which are thrust-directionally opposed to each other. The third bearing means maintains the radial rotational accuracy of the rotator, and is formed by a radial dynamic pressure producing groove (5) which is formed in a cylindrical surface of the inner ring (1). The fourth bearing means maintains the thrust-directional rotational accuracy of the rotator, and is formed by an air dome portion (100) which is confined in a semi-closed state by the inner ring (1), the outer ring (2) and a cover (4).

An analytical and experimental investigation of ball bearing retainer instabilities

Abstract: Factors contributing to the dynamic instability of ball retainers in precision bearings were investigated. A real-lime, rolling-element bearing dynamics simulation was written (PADRE-Planar Analysis of a Dynamic Retainer) for rapid evaluation of key bearing design factors. This code permits economic screening of a large number of bearing geometric parameters as a prelude to other more comprehensive dynamic bearing codes

Wire saw and slicing method using the same

Abstract: To keep, with a simple structure, roller bearing devices, rotatably supporting the end sections of two rollers, at the same and substantially constant temperature, working fluid is applied not only to the slicing sections, but also to roller bearing devices 14b, 14c, 16b, 16c, 18b and 18c. The flow rate of the working-fluid supply to nozzles 20, 22 for slicing-section is controlled in such a way that the temperature of the working fluid coming down from the slicing sections becomes a first preset temperature; and the flow rate of the working-fluid supply to nozzles 24-29 for bearing-section is controlled in such a way that the temperature of the working fluid coming down from the bearing sections becomes a second preset temperature.

Measurement of wear in polysilicon micromotors

Abstract: Two polysilicon variable-capacitance rotary side-drive micromotor types, including harmonic and salient-pole, are described. Voltages as low as 26 and 35 V across 1.5- mu m gaps are sufficient for operating the harmonic and salient-pole side-drive micromotors, respectively. Extended operation of the harmonic micromotors to near 100 million wobble cycles is studied at excitation frequencies of 10000 and 25000 r/min for operational durations of 150 and 71 h, respectively. The results of in situ quantitative studies indicate that, with micromotor operation, the rotor inner radius asperities wear out and the bearing clearance increases. This bearing wear is significant and results in changes in the gear ratio of the harmonic micromotors by as much as 22%. Typical gear ratios are near 90 at the start of harmonic micromotor operation and decrease to near 70 as the bearings wear out. For the salient-pole micromotors, wear particles are observed to form in the bearing and at the bushings. These wear particles adhere to the bushing surfaces and the area near the edge of the rotor inner radius. >

Quick release lock mechanisms

Abstract: Quick release lock mechanisms for releasably connecting an extension pole to a tool handle include an adaptor attached to an end of the extension pole having a smooth cylindrical outer end portion axially slidable into and out of an internally threaded bore in the tool handle. A bearing support is provided for the cylindrical outer end portion when fully inserted into the bare. Also, a non-rotatable connection is provided between the adaptor and tool handle when the cylindrical outer end portion is fully inserted into the bore to prevent relative rotation therebetween, arid a releasable latch prevents the cylindrical outer end portion from being withdrawn from the bore unless released.