Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic oxygen compound
Reexamination Certificate
1999-10-18
2001-08-07
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic oxygen compound
C508S579000, C508S580000, C427S096400, C427S384000, C427S435000, C427S443000
Reexamination Certificate
active
06271186
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electrical contact lubricant composition designed to prevent or overcome a specific type of electrical contact failure.
Electrical contacts can fail by a number of different mechanisms but a common failure mechanism results from fretting, which is relative micro-motion vibration of the contact surfaces. The source of fretting motion comes from background mechanical, thermal or electrical disturbances. These vibration sources are almost always present in equipment that use electrical contacts. Fretting failure of an electrical contact surface can occur when the amplitude of the fretting motion is on the order of the size of the contacting surface asperities, which form the microscopic electrical contact paths at the contact surface. The asperity sizes and critical fretting amplitudes are typically on the order of 10 to 100 microns in magnitude. Fretting failure occurs when debris, either from the action of wear or from outside contamination, becomes lodged between contacting surface asperities and separates the asperities sufficiently to interrupt the flow of electric current. A contact lubricant that is effective against fretting failure must specifically treat the debris problem by keeping debris from accumulating and intruding into critical asperity contact points.
Many electrical contact lubricants have been proposed over the years, but such products are not specifically designed and tailored to inhibit or eliminate fretting failure of electrical contacts. Few, if any, of such contact lubricants have been demonstrated by extensive laboratory testing to significantly reduce fretting failure. The function of a typical lubricant, according to Webster's dictionary, is primarily to reduce friction and, to a lesser extent, to reduce heat and wear. A reduction in friction in the presence of background vibration will tend to increase the amplitude of fretting motion. An increase in fretting amplitude, with other factors held constant, has been shown experimentally to increase fretting failure. A contact lubricant designed to prevent or reduce fretting failure must focus on the elimination of debris build-up at the asperity contact points rather than on the reduction of friction. The use of almost any contact lubricant will reduce wear, and in turn, should reduce the amount of local debris produced by wear. However, debris that ultimately causes fretting failure can often result from outside sources of contamination rather than be the product of local wear. A contact lubricant that specifically addresses the reduction of elimination of fretting failure must focus primarily on the debris problem.
SUMMARY
It has been discovered that an electrical contact lubricant composition, consisting of a mixture of polyphenyl ether and polypropylene monobutyl ether, is able to dramatically improve the fretting failure resistance of new electrical contacts and is able to rejuvenate electrical contacts that have previously failed in service. This unique lubricant composition combines the strong clustering and surface adherence properties of polyphenyl ether with the continuous coating and debris removal properties of polyproplylene monobutyl ether to produce a synergistic effect in lubricant fretting resistance. In addition, this contact lubricant composition is able to recover or rejuvenate electrical contacts that have already experienced fretting failure, allowing these contacts to be returned to service. Although the combination of the two basic ingredients in this electrical contact lubricant might have been expected to offer some possible improvement in fretting resistance of electrical contacts, the large degree of improvement observed apparently results from a synergistic effect that was not anticipated and only became apparent after extensive laboratory fretting tests on many different materials. Further, the ability of this electrical contact lubricant to rejuvenate previously failed electrical contacts was totally unexpected and was discovered only by means of laboratory tests.
The composition of the electrical contact lubricant in this present invention consists of an optimum mixture of fifty volume percent polypropylene monobutyl ether combined with fifty volume percent polyphenyl ether. A composition mixture with as little as ten volume percent polyphenyl ether and the remainder being polypropylene monobutyl ether still exhibits significant fretting protection. The polypropylene monobutyl ether component is commercially available as UCON LB-1800-XY26 from Union Carbide Chemical Company, and the polyphenyl ether component is commercially available as OS-124 or OS-138 from SantoVac Fluids. Preparation of the contact lubricant from these two chemical components is performed by a simple mixing and stirring operation. Application of the lubricant to electrical contact surfaces is by conventional means such as brushing, dipping or by aerosol spray.
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Aukland Neil R.
Hardee Harry C.
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