Bearings – Rotary bearing – Plain bearing
Patent
1994-10-03
1996-04-09
Hannon, Thomas R.
Bearings
Rotary bearing
Plain bearing
384276, 384295, F16C 2702
Patent
active
055055451
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a sliding bearing, essentially consisting of a plastic sleeve, which has a separate press-fit area and sliding area, where the sliding area has a smaller inside diameter than the press-fit area, and the press-fit area has a larger outside diameter than the sliding area.
Sliding bearings of this kind are essentially used in situations where good sliding properties with low-noise running and low wear are desired. Above all, sliding bearings made of plastic are corrosion-resistant, generate little noise, are extremely abrasion-resistant and can be lubricated with oil, grease, emulsions or even water. They are generally press-fitted into steel bushes or directly in the bearing seat.
Due to the fact that the plastics used for these bearings, such as polyamide, have a coefficient of thermal expansion which is approximately 10 times higher than that of metals, and are also hygroscopic, the use of plastic sliding bearings results in very large tolerances. This means that plastic bearings expand considerably during operation due to their hygroscopicity and their high coefficient of thermal expansion. In order to avoid the bearing from seizing, use of this type of bearing requires a clearance larger than that of sliding bearings made of metal. This is considered to be very unfavourable, particularly in situations where very small tolerances are required.
A type of sliding bearing of this kind is known from U.S. Pat. No. 4,208,075, for example. The sliding bearing described there is primarily designed for linear movements. It consists of a teflon sleeve divided into segments on both sides, where the individual segments protrude alternately inward and outward. The sliding area of the bearing is formed by collar-like projections protruding into the sleeve. The press-fit area of the bearing, i.e. the outer surface of the sleeve, is designed for a specially shaped bearing seat. For this purpose, the outer segments also have collar-like extensions projecting outward, which grip and snap into a groove in the bearing seat. The inward-protruding projections form a clearance region between the inner surface of the sleeve and the shaft, and the outward-protruding projections form a clearance between the outer surface of the sleeve and the bearing seat. The sliding area and press-fit area are separated from one another in the radial direction.
The task of the present invention is to create a sliding bearing made of plastic with improved running properties which requires substantially less clearance than conventional plastic sliding bearings.
In accordance with the invention, this task is solved in that the press-fit area and the sliding area are offset in the axial direction and axially separated from one another, the press-fit area has an outside diameter roughly equal to the inside diameter of the bearing seat, and the sliding area is formed by webs essentially extending in the axial direction, which rest against the shaft and are interconnected in continuous fashion by a thin, flexible film in the axial direction.
The sliding bearing according to the invention permits virtually clearance-free shaft mounting, where the effects of moisture and temperature have absolutely no influence on the running properties of the bearing. This is achieved through the separation of the retaining and sliding tasks, and through the segmented division of the sliding area. The expansion of the bearing material due to moisture and temperature can be compensated for by the segmented division of the sliding area. This means that material expansion in the radial direction can be distributed in the circumferential direction of the sliding bearing. In addition, the sliding bearing according to the invention requires little maintenance, i.e. no lubricant whatsoever is required. This guarantees the stability of the bearing, particulary during linear movements. The continuous interconnection of the webs via a flexible, thin film reliably prevents the webs from being forced apart or twisted when the bearing is subjected to great loa
REFERENCES:
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patent: 3929392 (1975-12-01), Ogino
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patent: 4208075 (1980-06-01), Templeton
patent: 4790672 (1988-12-01), Komplin
Louis Halberstadt, "Polyurethane Bearings", in Machine Design, Jun. 1963, pp. 151, 152.
Patent Abstract of Japan, Sliding Bearing, JP 1-216121 (A) M-898 Nov. 24, 1989 vol. 13/No. 528.
Hannon Thomas R.
Igus Spritzgussteile fur die Industrie GmbH
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