Metal working – Method of mechanical manufacture – Process for making bearing or component thereof
Reexamination Certificate
2000-02-04
2001-06-05
Hughes, S. Thomas (Department: 3726)
Metal working
Method of mechanical manufacture
Process for making bearing or component thereof
C029S898120, C029S898130
Reexamination Certificate
active
06240641
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a direct-acting bearing and a process for forming a lubricating film on a direct-acting bearing. More particularly, the present invention relates to a direct-acting bearing which is suitable for use in, for example, a vacuum, clean or corrosive environment not permitting the use of any ordinary grease or oil.
BACKGROUND ART
A conveying system installed in an apparatus for manufacturing semiconductors can, for example, be mentioned as such an environment. If grease is used as a lubricant for a direct-acting bearing in such an environment, the evaporation of oily matter from the grease causes problems, such as a lowering of its lubricating property and the pollution of the environment.
In such an event, it has hitherto been usual to coat at least one of the track surface of a rail in the form of a shaft, or a cylindrical movable body, or the surfaces of rolling bodies with a film of a solid lubricant, such as a soft metal such as gold, silver, lead or copper, or carbon, or molybdenum disulfide. The coating film formed from a solid lubricant as stated above, however, comes off little by little with the rolling or sliding motions of the rolling bodies. This causes an amount of dust which is inadequate for, among others, a clean environment, though it is a smaller amount than when grease is used. The amount of dust which is formed increases particularly under a high load.
The application of this applicant has coated the components of a direct-acting bearing with a solid lubricant obtained by mixing a fluororesin with a binder, and has made it possible to reduce dusting drastically, as compared with the usual case described above.
Even this coating film, however, produces a large amount of dust by getting worn, as well as by peeling or chipping, and has a short dust-free life, if it is subjected to a relatively high radial load. Moreover, the peeling or chipping of the coating film decreases the life to the direct-acting bearing, since it has a lower lubricating effect on the rolling and sliding portions of the bearing and allows its components to stick together and become worn more easily as a result of metal to metal contact. If the environment contains a corrosive gas, it corrodes the components of the bearing in those portions thereof from which the coating film has peeled, or chipped.
It is, therefore, an object of the present invention to restrain dusting in a direct-acting bearing and improve its lubrication to enable it to have a long life.
SUMMARY OF THE INVENTION
Construction
A first direct-acting bearing according to the present invention comprises a rail in the form of a shaft, a movable body fitted slidably to it, and a plurality of rolling bodies disposed between the rail and the movable body so as to roll and circulate with their relative sliding motion. The bearing includes a solid film of a fluorine-containing polyurethane high molecular compound formed on at least the rolling and sliding portions of its components.
A second direct-acting bearing according to the present invention comprises a rail in the form of a shaft, a movable body fitted slidably to it, and a plurality of rolling bodies disposed between the rail and the movable body so as to roll and circulate with their relative sliding motion. The rail and movable body are formed from a metal, and includes a solid film of a fluorine-containing polyurethane high molecular compound formed on at least the track surfaces of the rail and movable body.
A third direct-acting bearing according to the present invention comprises a rail in the form of a shaft, and a movable body fitted slidably to it. The bearing includes a solid film of a fluorine-containing polyurethane high molecular compound formed on at least the rolling and sliding portions of its components.
The solid film mentioned above preferably has a three-dimensional network structure. The solid film preferably contains a flowable fluorine-containing polymer dispersed therein. Moreover, the flowable fluorine-containing polymer preferably has no functional group.
A first process for forming a lubricating film on a direct-acting bearing according to the present invention comprises the steps of forming a liquid film on at least the rolling and sliding portions of the components of a direct-acting bearing by using a solution obtained by diluting in a solvent a fluorine-containing polymer having an isocyanate group as a functional group; and curing the liquid film to form a solid film of a fluorine-containing polyurethane high molecular compound having a network structure.
A second process for forming a lubricating film on a direct-acting bearing according to the present invention comprises the steps of forming a liquid film on at least the rolling and sliding portions of the components of a direct-acting bearing by using a solution obtained by diluting in a solvent a mixture of a fluorine-containing polymer having an isocyanate group as a functional group and a fluorine-containing polymer containing at least one of hydroxyl, amino and carboxyl groups; and curing the liquid film to form a solid film of a fluorine-containing polyurethane high molecular compound having a network structure.
A third process for forming a lubricating film on a direct-acting bearing according to this invention comprises the steps of forming a liquid film on at least the rolling and sliding portions of the components of a direct-acting bearing by using a solution obtained by adding a fluorine-containing polymer having no functional group to a solution obtained by diluting in a solvent a fluorine-containing polymer having an isocyanate group as a functional group or a mixture thereof with a fluorine-containing polymer containing at least one of hydroxyl, amino and carboxyl groups; and curing the liquid film partially to form a solid film of a fluorine-containing polyurethane high molecular compound having a network structure, in which the fluorine-containing polymer having no functional group is dispersed and retains its fluidity.
The fluorine-containing polymer may, for example, be perfluoro polyether having no functional group.
Function
According to this invention, the fluorine-containing polyurethane high molecular compound forms a solid film in which its molecules are closely bonded together, and which is highly resistant to peeling and wear during the rolling and sliding motions of the components of the direct-acting bearing, while reducing their rolling and sliding resistance.
Particularly, if the solid film of the fluorine-containing polyurethane high molecular compound contains a fluorine-containing polymer dispersed therein, and retaining its flowability, the flowable fluorine-containing polymer comes out of the solid film of the fluorine-containing polyurethane high molecular compound, and contributes to its lubricating action.
Effects
The solid film of the fluorine-containing polyurethane high molecular compound employed in the direct-acting bearing of the present invention, and having only a restrained likelihood to peel off, chip or get worn, as compared with the conventional coating film, while producing only a reduced level of rolling and sliding resistance, has a prolonged dust-free life and an improved lubricating property, and thereby contributes to improving the working stability and life of the bearing.
Therefore, if the direct-acting bearing of the present invention is used in an environment in which a high accuracy of work is required, as in the process of semiconductor manufacture, it hardly damages a clean atmosphere, but contributes to achieving an improved yield of semiconductor products.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled
Hayashida Kazunori
Takebayashi Hiroaki
Toyota Hiroshi
Birch & Stewart Kolasch & Birch, LLP
Butler Marc C.
Hughes S. Thomas
Koyo Seiko Co. Ltd.
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