Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
1998-05-21
2001-03-27
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S624000
Reexamination Certificate
active
06206573
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to bearing assemblies having wear indicators, and more specifically, to bearing assemblies with wear indicators having a different hardness than the surrounding bearing structure to produce detectible and identifiable vibrations.
A wide variety of bearing assemblies are available for use in a seemingly endless number and types of machines. Bearing assemblies typically include at least two components that move relative to each other. For example, assemblies may include components which rotate or slide relative to another component. Wear and tear on bearing components, even those lubricated to facilitate relative movement, can ultimately lead to bearing failure. To prevent such failure, often it is desirable to detect and replace worn bearing members and components before catastrophic failure thereof.
Detecting bearing wear and/or replacing worn bearing components have taken a number of forms. For example, bearing assemblies may be manually disassembled or replaced at a predicted lifetime. Unfortunately, bearings that wear faster than predicted can fail prior to a scheduled repair or replacement. Bearings that wear slower than predicted may be replaced before the end of their useful life. For some bearings, physical or visual inspection will suffice. Clearly, however, such inspections provide little assistance when the bearing to be evaluated is out of view or buried within surrounding equipment. Such inspections also may be time consuming or unnecessarily interrupt operation of the machine containing the bearing.
The measurement of vibrations may also be used to determine when maintenance is required on mechanical systems. However, vibration analysis is not always effective in providing a signal prior to catastrophic device failure because excessive wear can occur under conditions where detectible and identifiable vibrations do not arise.
SUMMARY OF THE INVENTION
The present invention provides bearing assemblies and methods of manufacturing bearing assemblies which allow for reliable, non-intrusive wear detection.
In one embodiment, the present invention provides a bearing assembly including first and second bearing members adapted for movement relative to each other. The first bearing member includes an outer layer that is adapted to wear in response to the relative movement between the first and second bearing members. The first bearing member further includes an inner layer in contact with the outer layer. The inner layer includes a base portion having a first hardness and a plurality of spaced apart wear indicating regions having a second hardness, whereby the first hardness and second hardness are different. The wear indicating regions are adapted to produce a vibration after sufficient wear of the outer layer.
The first hardness may be greater than or less than the second hardness. In this manner, wear of the outer layer results in the inner layer becoming exposed. Since the wear indicating regions have a different hardness than the inner layer base portion, the second bearing member is exposed to alternating regions having different hardness. As a result, continued relative movement produces a vibration.
In one aspect, the outer layer comprises a nitridized metal. In another aspect, the outer layer comprises a carbonized metal. In still another aspect, the first and second bearing members comprise a ceramic.
In one aspect of the bearing assembly, the first bearing member is stationary and the second bearing member is adapted to move relative to the first bearing member. Alternatively, the second bearing member is stationary and the first bearing member is adapted to move relative to the second bearing member. Further, both the first and second bearing members could move in a manner which produces relative movement therebetween.
In one particular aspect, the wear indicating regions are spaced apart from each other so that the regions produce a vibration having a desired frequency when the relative movement between the first and second bearing members occurs at a particular rate. In this manner, detection of the desired vibration frequency indicates that the wear indicating regions are exposed and, thus, subjected to wear.
In one aspect, the second bearing member comprises a movable bearing and the first bearing member comprises a bearing race. In another aspect, the first and second bearing members comprise an axial bearing. In still another aspect, the first and second bearing members comprise a linear slide bearing. Alternatively, first and second bearing members comprise a thrust bearing.
In one particular aspect, the outer layer has a thickness that is equal to between about 50 percent and about 100 percent of a wear limit of the first bearing member. In this manner, vibrations are produced by the wear indicating regions before catastrophic failure of the first bearing member occurs. In one aspect, the wear indicating regions include regions formed by ion implantation. Alternatively, the wear indicating regions include regions formed by chemical vapor deposition.
In one embodiment of the present invention, a bearing assembly comprises a housing adapted to support first and second bearing members. The first and second bearing members are adapted for movement relative to each other. The first bearing member includes an outer layer adapted to wear in response to the relative movement between the first and second bearing members. The first bearing member further includes an inner layer in contact with the outer layer. The inner layer includes a base portion having a first hardness and a plurality of spaced-apart wear indicating regions each having a second hardness, and wherein the first and second hardnesses are different. Wear indicating regions are further adapted to produce a vibration after sufficient wear of the outer layer.
In one aspect of the bearing assembly, a vibration detector is provided, operably attached to the housing. The detector is adapted to detect vibrations caused by the wear indicating regions.
The present invention further provides a method of manufacturing a bearing assembly. The method includes the steps of forming a base portion of a first bearing member inner layer. A plurality of spaced-apart wear indicating regions are created in the base portion. The wear indicating regions have a hardness that is different than a hardness of the base portion. The method includes forming an outer layer over the base portion. A second bearing member is provided that is adapted to provide relative movement between the first and second bearing members.
In one aspect of the method, the wear indicating regions are created using an ion implantation technique. In another aspect of the method, the base portion is formed having a plurality of spaced-apart cavities. The wear indicating regions are created by filling the cavities with a material that is different than a base portion material. In one aspect of the method, the cavities are filled using a chemical vapor deposition technique to produce the wear indicating regions.
Other features and advantages of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawings.
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patent: 5381692 (1995-01-01), Winslow et al.
patent: 5433531 (1995-07-01), Thompson
patent: 5451110 (1995-09-01), Gams, Jr. et al.
patent: 5599112 (1997-02-01), Klein
patent: 5701119 (1997-12-01), Jurrias
Miller Gayle W.
Shelton Gail D.
Footland Lenard A.
LSI Logic Corporation
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