Showing papers on "Bearing (mechanical) published in 1993"

Earthquake-Resistant Design with Rubber

Abstract: 1 Seismic Isolation for Earthquake-Resistant Design.- 1.1 Introduction.- 2 Vibration Isolation.- 2.1 Introduction.- 2.2 Theory of Vibration Isolation.- 2.3 Frictional Vibration Isolators.- 3 Seismic Isolation.- 3.1 Review of Fixed-Base Structural Analysis.- 3.2 Linear Theory of Base Isolation.- 3.3 Isolation of Very Flexible Structures.- 4 Extension of Theory to Buildings.- 4.1 M-Degree-of-Freedom Equations of Motion.- 4.2 Modal Analysis of M-DOF System.- 4.3 Estimates of Displacements and Forces for M-DOF System.- 5 Earthquake Regulations for Seismically Isolated Structures.- 5.1 Introduction.- 5.2 1994 Uniform Building Code.- 5.3 Design Methods.- 5.4 Static Analysis.- 5.5 Dynamic Analysis.- 5.6 Computer Programs for Analysis of Seismically Isolated Structures.- 5.7 Other Requirements for Nonstructural Components.- 5.8 Review.- 5.9 Design Requirements for Isolators.- 5.10 Base-Isolated Structures under Extreme Earthquake Loading.- 6 Coupled Lateral-Torsional Response of Seismically Isolated Buildings.- 6.1 Introduction.- 6.2 Case I: Three Close Frequencies.- 6.3 Case II: Equal Lateral Frequencies, Distinct Torsional Frequency.- 7 Behavior of M?ltilayered Bearings Under Compression and Bending.- 7.1 Introduction.- 7.2 Shear Stresses Produced by Compression.- 7.3 Bending Stiffness of a Single Pad.- 7.4 Pure Compression of Single Pads with Large Shape Factors.- 7.5 Compression Stiffness for Circular Pads with Large Shape Factors.- 7.6 Compression Stiffness for Square Pads with Large Shape Factors.- 7.7 Bending Stiffness of Single Pads with Large Shape Factors.- 8 Buckling Behavior of Elastomeric Bearings.- 8.1 Stability Analysis of Bearings.- 8.2 Stability of Annular Bearings.- 8.3 Influence of Vertical Load on Horizontal Stiffness.- 8.4 Downward Displacement of the Top of a Bearing.- 8.5 A Simple Mechanical Model for Bearing Buckling.- 8.6 Postbuckling Behavior.- 8.7 Influence of Compressive Load on Bearing Damping Properties.- 8.8 Rollout Stability.- 9 Design Process for Multilayered Elastomeric Bearings.- 9.1 Preliminary Bearing Design Process.- 9.2 Experimental Studies of Elastomeric Isolator Performance.- 9.3 Compact Design Bearings.- Afterword.- References.- Appendix A.- A.I Base-Isolated Buildings and Projects in the United States.- A.2 Retrofit Base-Isolated Buildings and Projects in the United States.- Appendix B.- B.I N-PAD.- B.2 3D-BASIS.- B.3 SADSAP.- B.4 General Nonlinear Three-Dimensional Analysis Programs.

Dynamics of rotors and foundations

Abstract: 1 Introduction.- 2 The one Degree of Freedom System.- 3 Shaft with Central Disc.- 4 Shaft with Non Central Disc.- 5 The Short and the Long Rotor.- 6 Oil-Film Bearings.- 7 Rotors with Oil-film Bearings.- 8 Vertical Rotors.- 9 Rolling-element Bearings.- 10 Shaft Seals.- 11 Steam Whirl.- 12 Internal Damping.- 13 Non-circular Shafts.- 14 Computer Model.- 15 Influence Coefficients.- 16 Equation of Motion.- 17 Results.- 18 Static Bearing Loads.- 19 Foundation.- 20 Rotor and Foundation.- 21 Rough Calculations.- 22 Bending Stresses in Rotors.- 23 Cracked Rotors.- 24 Solution of the Equation of Motion.- 25 Program MADYN.- References.

Telescoping spinal fixator

Abstract: The invention is a telescoping spinal fixator having axially aligned upper and lower bearing elements which fit within opposing cavities in vertebrae. The respective bearing elements are maintained at an adjustable distance apart by a connecting rod with a rotatable collar axially mounted intermediate the two bearing elements for adjusting the distance between the bearing elements. In its collapsed configuration, the two bearing elements are aligned proximate to one another with just sufficient space to permit access to the adjustment collar, which is otherwise disposed within cavities in each of the bearing elements.

Modular knee joint prosthesis

Abstract: An implantable knee joint prosthesis which comprises a tibial tray, an articulating tibial insert attached to the tibial tray, and a femoral condylar component adapted to cooperatively bear upon the tibial insert. The femoral component has an intercondylar recess having parallel lateral side walls and posterior and anterior bearing members defining the boundaries of the recess. The tibial insert includes an eminence extending superiorly into the intercondylar recess and dimensioned and shaped to provide defined stabilization limits for preventing posterior-anterior dislocation while allowing limited translation and essentially free rotation and angulation throughout most of the total range of articulation. Metal reinforcements serve to secure the insert to the tray. Bearing surfaces of the eminence and the intercondylar recess are so shaped as to increase the area of contact between them as the degree of flexion of the leg increases to thereby limit the contact stress transmitted to the eminence and to reduce wear of the eminence.

Calculation of Stiffness and Damping Coefficients for Elastically Supported Gas Foil Bearings

Abstract: The stiffness and damping coefficients of an elastically supported gas foil bearing are calculated. A perfect gas is used as the lubricant, and its behavior is described by the Reynolds equation. The structural model consists only of an elastic foundation. The fluid equations and the structural equations are coupled. A perturbation method is used to obtain the linearized dynamic coefficient equations. A finite difference formulation has been developed to solve for the four stiffness and the four damping coefficients. The effect of the bearing compliance on the dynamic coefficients is discussed in this paper.

Image forming apparatus, process cartridge mountable within it and method for attaching photosensitive drum to process cartridge

Abstract: In order to prevent the eccentricity of a rotary shaft for rotatably supporting an image bearing member used with an image forming apparatus when the image bearing member is rotated, a projection is provided on an outer peripheral surface of the rotary shaft fitted into a fitting hole formed in a casing for securing the rotary shaft.

Bearing assembly monitoring system

Abstract: A bearing assembly monitoring system (10) provides continuous, real time monitoring of the operating condition of a powertrain support bearing assembly and real time alarm signals indicative of degradation and/or impending catastrophic failure thereof. One embodiment includes a vibration sensing device (12), first and second primary temperature sensing devices (14, 16, 18), an ambient temperature sensing device, vibration and temperature signal processing subcircuits (20, 22), and an alarm subsystem (24). The vibration sensing device (12) monitors complex vibration signals emanating from the bearing assembly (120, 130) and provides signals which are compared to reference voltages corresponding to higher than normal and excessive vibration levels. The temperature sensing devices (14, 16, 18) monitor the operating and ambient temperatures of the bearing asssembly and provide signals corresponding thereto. The temperature signal processing circuit (22) converts such temperature signals to differential temperature signals which are compared to a reference voltage corresponding to a temperature differential indicative of impending catastrophic failure.

Magnetic bearing control using fuzzy logic

Abstract: Presented in this paper is a fuzzy logic approach to improve the performance of a magnetic bearing control system. Classical, linear design techniques are most often used to control the natural instability of these bearings, but magnetic nonlinearities limit control effectiveness and the region of stable performance. Therefore, the idea here is to adjust the linear controller signal in such a way that nonlinear effects are better compensated. The relationships of attractive force to the electromagnet currents and air gap are described and compensated using fuzzy principles, rather than a precise model-based control approach. Computer simulations are used to confirm that a fuzzy description of nonlinear compensation does indeed improve system performance, without requiring an exact model of the bearing nonlinearities.

Verification of friction model of teflon bearings under triaxial load

Abstract: The writers presented in an earlier paper a mathematical model of friction of sliding bearings under conditions of compression and bidirectional motion. The model could account for the dependence of the coefficient of friction on the velocity and direction of sliding. The model was capable of reproducing the behavior observed in experiments with unidirectional motion, however, no experimental validation of the model was provided for bidirectional motion. The present paper presents experimental results on Teflon sliding bearings under simultaneous compression and high velocity bidirectional motion that provide a complete verification of the presented model. Furthermore, the experimental results show the existence of bidirectional interaction between the orthogonal components of the frictional force at the bearing interface. The importance of these effects is studied in the analysis of an isolated structure. The structure is subjected to a number of pairs of horizontal earthquake excitation components that ...

Friction‐Controllable Sliding Isolation System

Abstract: This paper describes the experimental and analytical study of a friction-controllable sliding base isolation system. To overcome the problems associated with conventional passive sliding isolation systems that have hindered their practical effectiveness, a hybrid sliding base isolation system is developed using friction-controllable bearings. This innovative hybrid system uses a variable friction force that is computer controlled by changing the pressure in the fluid chamber of the bearing. The variable friction force makes the sliding isolation system more effective in controlling the structural response under earthquakes with a broad range of intensity. A prototype hybrid sliding isolation system is physically developed and tested on a shaking table using a structural model equipped with this system. Control algorithms specially developed for controlling the frictional force that has an inherent nonlinear feature are used in this study, and their effectiveness is verified. Simulation of structural response under passive or hybrid control technique shows good agreement with the experimental results.

Bone fixation plate

Abstract: An implantable bone plate comprises a solid, circular rod member (10) having a plurality of bone-engaging members (12) spaced apart along the length thereof Each bone-engaging member is centered on the rod and has a bearing surface (20) for bearing against the surface of a bone Each bone-engaging member has a thickness not smaller than the thickness of the rod member and an aperture (22) normal to the bearing surface for receiving a bone screw (34)

A Parameter Identification Method for the Rotordynamic Coefficients of a High Reynolds Number Hydrostatic Bearing

Abstract: In identifying the rotordynamic coefficients of a high-Reynolds-number hydrostatic bearing, fluid-flow induced forces present a unique problem, in that they provide an unmeasureable and uncontrollable excitation to the bearing. An analysis method is developed that effectively eliminates the effects of fluid-flow induced excitation on the estimation of the bearing rotordynamic coefficients, by using power spectral densities. In addition to the theoretical development, the method is verified experimentally by single-frequency testing, and repeatability tests. Results obtained for a bearing are the twelve rotordynamic coefficients (stiffness, damping, and inertia coefficients) as functions of eccentricity ratio, speed, and supply pressure.

Turbine pump ring for drilling heads

Abstract: A drilling head for the controlled operation of the drill string while diverting well fluids from the well The drilling head incorporates a kelly drive and at least one stripper rubber which rotate with the drill string extending through the drilling head Rotation of the drive bushing and stripper rubber are controlled by bearings disposed in a bearing chamber of the drilling head through which lubricant is circulated to reduce friction and cool the bearings A turbine ring attached to the lock nut ring of the kelly drive circulates lubricant through the bearing chamber as it rotates in association with the drive assembly of the drilling head The turbine pump ring forces circulation of lubricant as the drive assembly rotates in addition to the circulation by the remove lubricant pump or in the event the remote pump fails to operate The turbine ring includes a plurality of angular slots to force circulation of the lubricant as the drive assembly rotates

Stability Boundary of Non-Linear Orbits Within Clearance Circle of Journal Bearings

Abstract: The transient, nonlinear study of journal bearing stability requires tracking the locus of the shaft center as a function of time. It is shown that there exists a boundary within the bearing clearance circle outside of which any initial condition would yield an unstable orbit. This is shown to be the case for operating speeds that are well below the threshold of instability according to the linearized stability analysis.

Spindle Bearing Systems for High-Speed Applications in Machine Tools

Abstract: Summary The operational speed of spindle bearing systems with angular contact ball bearings is limited amongst other factors by the highest permissible rotatory speed of the bearings. The revolution parameter limit of these bearings currently lies at about n*dm= 1.5*106 mm/min if lubricated by the principle of minimum oil quantity. This paper will introduce how, by applying oil-air minimum quantity lubrication using a new oil-air supply, the revolutionary parameter limit was able to be increased to approximately n*dm=1.8*106 mm/min. On the basis of test results it shows how the application of ceramic balls or coasted bearing elements reduces the surface wear under insufficient lubrication conditions and increases the life span of the bearing.

Implantable device for straightening and fixing vertebrae

Abstract: An implant for the spinal column for fixing the vertebrae, especially the cervical vertebra, on the anterior side, i.e., on the side of the esophagus, wherein the implant has screw holes for screwing together with the vertebra and has a multi-component design, and has at least two mounting plates, which are provided with at least two screw holes. The mounting plates are connected by an articulated bearing each to a spindle having right-hand and left-hand, self-locking threads with an angular shaft piece for actuating the spindle, wherein the mounting plates have a ribbed area on the side facing the vertebral bone W. The articulated bearing includes a bearing bush extending outwardly from each mounting plate and a bearing pin which has a threaded hole for engaging the spindle. The bushing has a hole allowing the spindle to pass through the bearing bush wherein pin is moveable within the bearing bush.

Rolling bearing seal assembly with a built-in sensor

Abstract: A rolling bearing seal assembly with a built-in sensor; the bearing including a first ring rotating in relation to a second ring, and a number of rolling bodies interposed between the first ring and the second ring and housed in a chamber defined between the two rings; and the seal assembly including at least one shielding element for closing the chamber and located facing the chamber and outside the bearing, and at least one sensor housed inside a seat formed inside the shielding element.

Image bearing member having an asymmetrically weighted base, process cartridge and image forming apparatus

Abstract: The present invention provides an image bearing member comprising an image bearing layer capable of bearing an image, a substrate for supporting the image bearing layer, and a weight portion arranged with the substrate asymmetrically with respect to a center of said substrate in a generatrix direction thereof.

Device for adjusting the angle of a keyboard

Abstract: An adjustable keyboard support device is provided having a tubular bearing element (1), secured to a housing bottom (5) of a keyboard. A generally L-shaped stand (2) is provided with two bearing pins (3, 4) which fit respectively into tube ends of the bearing element. The stand includes two U-brackets (6, 7) placed perpendicularly to one another. The two jointly pivotable U-brackets (6, 7) of different lengths. A locking element (8) extends from one of the U-brackets, engaging in the bearing element (1) for fixing the position in one of the two inclination angle settings.

Bearing Strength of Compressive Struts Confined by Plain Concrete

Abstract: To study transverse splitting of compresson struts due to spreading of compression, concrete cylinders of varying diameters and of varying heights were loaded over a constant size bearing area. The travel time of an ultrasonic pulse was used to indicate internal cracking, and measured cracking loads were compared to finite element predictions. It was found that when compression struts are confined by plain concrete, the maximum bearing stress to cause transverse splittting depends on the amount of confinement, as well as the aspect ratio of the compression strut. Design recommendations are given for the maximum nodal zone bearing stress to prevent diagonal tension failures in deep memebers with unreinforced compression struts. A simple example is provided to illustrate the suggested nodal stress limits for the design of a pile cap using a strut-and-tie model.

Gripper for a conveying device for conveying single-sheet or multiple-sheet printed products

Abstract: A gripper for conveying printed products is disclosed. The gripper has two gripper parts mounted so as to be pivotable on a shaft which, in turn, is mounted rotatably in a holder. Connected to this shaft so as to be fixed against rotation is closing lever which bears at its end a follower roller which interacts with fixed closing links or cams. Furthermore, a resting part for a compression spring is connected to the shaft via a spreader ring so as to be fixed against rotation. This compression spring is supported at its other end on a bearing part which is integral with the one gripper part. A pivot movement of the closing lever results in a corresponding clockwise pivoting of the resting part. As a result, pivoting of the one gripper part into the clamping position is brought about via the compression spring. This one gripper part is blocked in its clamping position in which the compression spring is compressed and exerts a corresponding clamping force.

Experimental Versus Theoretical Characteristics of a High-Speed Hybrid (Combination Hydrostatic and Hydrodynamic) Bearing

Abstract: The high-speed test facility designed and installed at Texas A&M to study water lubricated journal bearings has been successfully used to test statically an orifice compensated five-recess-hybrid (combination hydrostatic and hydrodynamic) bearing for two radial clearance configurations. Measurements of relative-bearing position, torque, recess pressure, flow rate, and temperature were made at speeds from 10,000 to 25,000 rpm and supply pressures of 6.89 MPa (1,000 psi), 5.52 MPa (800 psi), and 4.14 MPa (600 psi)

Journal bearing differential heating evaluation with influence on rotor dynamic behaviour

Abstract: The nature of differential heating across the journal of a hydrodynamically lubricated bearing has been investigated theoretically and an assessment made of the local thermal bend in the rotor at the bearing location. The energy balance for the system is time dependent and involves a stationary bearing component, an oscillating lubricant film, and a rotating, orbiting section of journal. Thermo-hydrodynamic solutions are developed which allow for temporal and spatial periodic variations of bearing, lubricant and journal temperatures. The influence of a synchronous journal orbit on the temperature distribution throughout the system is discussed. In particular, the relation between any prescribed orbit and the steady state temperature differential across the journal, resulting in steady state rotor bending, is established. The role played by such thermal bending in the onset of unstable synchronous whirl in the rotors of high-speed machines is outlined.

Automotive vehicle differential assembly

Abstract: A differential assembly having a driving case enclosing a pair of driving members operably coupled with a pair of driven members. The driven members are secured to output shafts and the driving members are forcibly driven by a driving shaft having its opposite ends in engagement with the driving case. The mid-section of the driving shaft passes through an eccentric or angled aperture formed by cooperating arcuate surfaces provided in opposing surfaces of the driving members. The driving members and the driven members are urged together respectively by double oppositely wound concentric springs bearing against a pin carried in an elongated hole coextensively provided in opposing surfaces of adjacent driving members of both pairs. Inspection and access openings are provided in passageways and in the oblong cross-section of part of the passageways.

Dynamic Characteristics of TEHD Tilt Pad Journal Bearing Simulation Including Multiple Mode Pad Flexibility Model

Abstract: An approach for incorporating the heat transfer and elastic deformation effects into dynamic coefficient calculation is presented. A global analysis method is used, which finds the equilibrium pad till angles at each eccentricity position and includes cross-film variable viscosity, heat transfer effects in the lubricant, elastic deformation, heat conduction effects in the pads, and elastic deformation effect in the pivots. Deflection modes are used to approximate deformation of the top surface of the pads. The dynamic coefficients of a single pad are calculated at the equilibrium state of the bearing, based on numerical perturbation with respect to the bearing degrees of freedom. These include journal position, pad rotation, pivot deformation, and modal coordinates. The stiffness and damping coefficients are calculated and show very good agreement with experimental and numerical results from the existing literature

Tilting pad journal bearing using directed lubrication

Abstract: In a tilting pad journal directly lubricated bearing the axially spaced apart sidewalls of the tilting pads are provided with extensions that have an axial space between them and contribute to defining the boundaries of a cool oil infeed well whose other boundaries are radially extending walls of adjacent pads or walls that are defined by slotting the leading ends of the pads. The pads are contained within the circular opening of a supporting ring member which has an oil infeed groove around its periphery. In line with each of the oil infeed wells there is an oil infeed passageway for delivering oil to the shaft surface exposed in the well by means of an interposed row of jets or orifices. Cool oil is fed into the wells, such that the interface between the bearing pad and the shaft, which only has oil from the well available to it, necessarily runs on cooler oil. The arrangement permits elimination of the conventional oil sealing rings which pre-existing bearings participate in defining a path or oil flow which results in all parts of the bearing assembly being totally immersed in oil with a consequence of increased power loss and heating due to shearing of the greater quantity of oil in the prior designs.

A bearingless method for induction machines

Abstract: A bearingless induction motor system that uses standard windings is proposed. The theoretical assumptions are tested experimentally using a four-pole, two-phase machine without one mechanical bearing. The basic idea is the modulation of the stator winding currents to achieve positioning and rotary forces. Shaft deviations smaller than 0.5 mm at speeds of 4000 rpm are reached during the initial laboratory tests. >