Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
1999-10-22
2001-07-31
Hannon, Thomas R. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S450000, C384S568000, C074S055000
Reexamination Certificate
active
06267510
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a roller bearing with roller elements constructed as rollers or balls arranged between an inner race and an outer race and with a thick-walled outer ring whose inner surface forms the outer race and whose outer surface is provided for direct rolling on a cylindrical or flat matching roller path and has a crowned (curved in longitudinal section) contour.
Roller bearings of this type are known as castors, support rollers and cam follower which, with their thick-walled outer rings, allow the transmission of high radial stresses to their matching bearing races, mostly curved disks or straight guide paths. The convex surfaces of the outer rings are crowned in shape in order to avoid additional edge stresses from alignment errors. Such a profiling is usually determined by a constant radius. Parallel to these crowned constructions, solutions with a cylindrical outer contour are also offered, which of course attain high edge loading even with small angle errors. Owing to the high radial stress, it is advantageous with outer rings with crowned contours to have as large a radius as possible in order to reduce the minimum Hertzian stress.
From published patent German application DE 42 00 381 A1, a roller bearing is known in connection with which not an outer ring, but rather the rollers used as roller elements are preferably constructed barrel-shaped. In the end regions, the contour of each roller is determined by a curvature radius r and then passes over at a fixed point into a cylindrical shape. The roller is here in any given case constructed as a hollow roller while the roller paths of the bearing races on which the rollers move are the cylinder surfaces of an inner and an outer bearing ring.
German patent DE 29 35 023 C2 shows a roller bearing in connection with which at least some of the rollers are provided with a convex surface which, in axial section, has at least three segments with different radii of curvature passing over into one another without sharp or rounded off edges along the entire roller contour. Furthermore, the segments have radii of curvature on both sides of the middle segment which are smaller than the radii of curvature of the middle segment itself. The bearing races of this previously known bearing are not, however, cylindrical, but are likewise constructed curved.
A thick walled outer ring which would be provided for rolling on a cylindrical matching roller path cannot be inferred from these two publications.
SUMMARY OF THE INVENTION
The object of the invention is to provide a roller bearing with a thick-walled outer ring with the crowned contour of the outer ring configured such that, when rolling the outer ring on the cylindrical matching roller path, the maximum Hertzian stress arising is diminished and its threshold value is not exceeded even during tipping of the outer ring axis.
This objective is accomplished in accordance with the invention in that the crowned contour of the outer ring is comprised of several arcs which pass smoothly into one another, whereby the longer radius of curvature of a central arc and the shorter radius of curvature of an outer arc have a ratio from 2 to 1 up to 5 to 1 in relation to each other. Due to such a crowned contour, the maximum value of the Hertzian stress arising, which occurs in connection with parallel arrangement of the outer ring axis in relation to the matching roller path, is not exceeded when during rolling operation of the outer ring, its longitudinal axis inclines toward the matching roller path such that a tipping of the outer ring on the matching roller path occurs.
The crowned contour of the outer ring can be composed of three arcs, whereby the longer radius of curvature of a central arc and the short radius of curvature of an outer arc, which in any given case is adjacent to the central arc, stand in a ratio from 2 to 1 up to 5 to 1 in relation to each other. It is also possible to compose the crowned contour of the outer ring from five arcs, whereby the magnitudes of the radii of curvature of the arcs in each case diminish from the center of the outer ring axially toward the outside. Finally, the crowned contour of the outer ring can also be composed of a great number of arcs whereby the magnitudes of the radii of curvature of the arcs diminish monotonically from a greatest value in the middle of the outer ring axially toward the ends.
With such a roller bearing, the length of the radius of curvature of a central arc and the width of the outer ring can stand in a ratio from 3 to 1 up to 6 to 1 in relation to each other. It can be constructed as a support roller whereby the inner race is the outer surface of an inner ring. It is also possible, however, for the roller bearing to be constructed as a cam follower roller whereby the inner roller path is the outer surface of a bolt on its one end and its other end has a fastening thread.
REFERENCES:
patent: 2947581 (1960-08-01), Van Dorn et al.
patent: 4456313 (1984-06-01), Hartnett et al.
patent: 4802775 (1989-02-01), Takata
patent: 4877340 (1989-10-01), Hoeprich
patent: 4929098 (1990-05-01), Takata et al.
patent: 5064298 (1991-11-01), Hibi et al.
patent: 5071265 (1991-12-01), Bowen et al.
patent: 5426988 (1995-06-01), Ohata et al.
patent: 5752775 (1998-05-01), Tsutsui et al.
Bode Helmut
Herber Georg
Schäfers Heinz
Weber Jorg
Hannon Thomas R.
Ina Walzlager Schaeffler OHG
Volpe & Koenig PC
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