Driving screw and a method for forming lubricating film thereon

Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Internally threaded fastener element – e.g. – nut – etc. – Including lubricating means

Patent

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Details

411432, 411534, 411903, F16B 3700, F16B 3708

Patent

active

060072865

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention concerns a driving screw and a method for forming a lubricant film thereon. Particularly, the present invention concerns a suitable driving screw for use in an environment, where a conventional grease or oil is not available, such as in vacuum environment, clean environment, corrosion environment, and the like.


BACKGROUND ART

As the aforementioned environment, for example, a transporting system, etc., which is installed in a semiconductor manufacturing plant, may be exemplified, however, under such environment, if a grease will be used as lubricant for the driving screw, an inconvenient drawback, such as a deterioration of the lubricating property or contamination in the operational environment, may be caused according to an evaporation of an oily component from the grease.
Under such circumstances, hitherto, at least either part in moving faces of screw stem and nut, or surface of ball, is conventionally coated with a solid lubricant, such as soft metal, which includes gold, silver, lead, copper, etc., carbon, and molybdenum bisulfide in a form of film.
In the case of using the coating film made of the above mentioned solid lubricant, a dusting caused by a slight slipping of the lubricant film due to rolling and sliding motion of the ball, may be reduced to a lower level, compared with the case where grease is used, however, in which case said level is still in considerably inadequate level, particularly under the clean environment. In particular, under heavier load condition, a dusting amount is remarkably increased.
Besides these, the present invention has been carried out in coating solid lubricant, in which fluoride resin is mixed with a binder, onto at least one of sliding face between screw stem and nut, and a surface of the ball. In this case, a dusting amount may be significantly reduced compared with the above discussed conventional case.
However, even in said coating film above, dusting due to wear, other than spalling and falling of the lubricant, is remarkably increased under the relatively heavy axial load condition, resulting in shortening of the dusting life. Furthermore, if spalling and falling of the lubricating film are occurring, a lubricating function at rolling and sliding sites may be deteriorated, thereby causing trouble with respect to the operable life, such as being liable of causing adhesion due to contact between metallic parts, and accelerating abrasive wear, as well, whereas, in the environment wherein corrosive gas is present, each constitutional element, which causes spalling and falling of the lubricating film, may be attacked.
Accordingly, an object of the present invention is to provide suppressing dusting and improving in lubricating property of the driving screw, resulting in prolonging life thereof.


DISCLOSURE OF THE INVENTION

The first embodiment of the driving screw according to the present invention is composed of screw stem, and nut, which are to be spirally attached, and is to provide plural movement bodies, which are related to screwing parts between the screw stem and nut, and on these elements, a solid film of fluoride containing polyurethane compound is formed in a position of at least rolling and sliding parts.
The second embodiment of the driving screw according to the present invention is composed of screw stem, and nut, which are to be screwed, and is to provide plural movable bodies, which are related to screwing parts between the screw stem and nut, and these elements are made of metallic material, on which a solid film of fluoride containing polyurethane compound is formed in a position of at least rolling and sliding parts.
The third embodiment of the driving screw according to the present invention is composed of screw stem, and nut, which is to be screwed, and is to form a solid film of fluoride containing polyurethane compound in at least any position of rolling and sliding parts.
In this connection, said solid film preferably has three dimensional network structure, and is preferably contained in disper

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