Roller bearing

A roller bearing with roller elements constructed as rollers (4) or balls arranged between an inner race (3) and an outer race (5), and with a thick-walled outer ring (6) if provided. The inner surface of the outer ring forms the outer race (5) and the outer surface is provided for direct rolling on a cylindrical matching roller path, and has a crowned contour (7) curved in longitudinal section. In accordance with the invention, the spherical crowned contour (7) of the outer ring (6) is formed from several arcs that pass smooth into one another whereby the radius of curvature of a central arc and the radius of curvature of an outer arc have in a ratio from 2 to 1 up to 5 to 1 in relation to one another.

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.

DETAILED DESCRIPTION OF THE INVENTION
 A roller bearing of the invention represented in FIG. 1 is constructed as a
 cam follower roller and contains a bolt 1 on one end of which a fastening
 thread 2 is formed. The other end of the bolt 1 forms a circular
 cylindrical inner race 3 for cylindrical rollers 4 as rolling elements of
 the roller bearing. Instead of the rollers 4, the use of balls is also
 possible. An outer race 5 is formed from the inner surface of a
 thick-walled outer ring 6 which surrounds the bolt 1 on its end which
 includes the inner race and the rollers 4. In FIG. 1, two different
 possibilities for constructing and arranging the rollers are represented.
 In the upper half, longer rollers 4 are shown which are directly adjacent
 to each other, while in the lower half, shorter rollers 4 are arranged
 axially spaced apart from each other. Thus, a cam follower roller with
 longer rollers 4 as well as a cam follower roller with short rollers 4 or
 with balls is conceivable.
 In accordance with the invention, the outer ring has a convex surface which
 appears as a crowned contour in cross section which is comprised by
 several arcs. Furthermore, the adjacent arcs pass smoothly into each
 other, thus having a common tangent on their adjacent ends. In the
 embodiment according to FIGS. 1 to 5, on the outer ring 6, the crowned
 contour 7 is formed from a central arc with a longer radius of curvature
 K.sub.1 and two adjacent arcs with a shorter radius of curvature K.sub.2.
 The radius of curvature K.sub.1 stands in a ratio from 2 to 1 up to 5 to 1
 with each radius of curvature K.sub.2. The length of the radius of
 curvature K.sub.1 and the width B of the outer ring 6 are preferably in a
 ratio from 3 to 1 up to 6 to 1 in relation to each other.
 In FIGS. 2 and 3, two different attitudes of the outer ring 6 of the bolt 1
 in relation to a matching roller path 8 are represented on which the outer
 ring 6 with its crowned contour 7 moves. The matching roller path 8 can be
 a cylindrical or flat surface. In FIG. 2, the axis of rotation of the
 outer ring 6 runs parallel to the matching roller path 8, while the axis
 in FIG. 3 is arranged inclined in relation to matching roller path 8. The
 outer ring is here thus arranged tipped with reference to the matching
 roller path 8.
 The outer ring 9 in accordance with FIG. 6 has a crowned contour 10 which
 is comprised by a total of five arcs. In any given case these follow from
 the center of the outer ring 9 to one end in the axial direction from an
 arc with the greatest radius of curvature K.sub.1, to an arc with a
 smaller radius of curvature K.sub.2, and from this to an arc with an even
 smaller radius of curvature K.sub.3. The magnitudes of the radii of
 curvature K.sub.1, K.sub.2 and K.sub.3 thus diminish monotonically from a
 greatest value in the center to the ends.
 In FIG. 5, two areas 12 of arcs with smaller radii of curvature K.sub.2 are
 connected with an area 11 of the arc with the greatest curvature radius
 K.sub.1. With the outer ring 9 represented in FIG. 6, further additional
 areas 13 of arcs with the smallest radii of curvature K.sub.3 follow in
 axial direction upon the corresponding areas 11 and 12.
 Experiments have shown that with outer rings with curved contours formed
 by. several arcs in accordance with the invention, the Hertzian stress
 arising in interaction with the matching roller path 8 is clearly
 diminished, and its threshold value is not exceeded even when the outer
 ring axis is tipped.
 REFERENCE NUMBER LIST
 1. Bolts
 2. Fastening thread
 3. Inner race
 4. Roller
 5. Outer race
 6. Outer ring
 7. Crowned contour
 8. Matching roller path
 9. Outer ring
 10. Spherical contour
 11. Area of the arc with the greatest radius of curvature
 12. Area of the curve with the smaller radius of curvature
 13. Area of the curve with the smallest radius of curvature
 K.sub.1 Radius of curvature
 K.sub.2 Radius of curvature
 K.sub.3 Radius of curvature
 B Width of the outer ring