Method for clearance adjustment in a rolling bearing

The present invention refers to a method for clearance adjustment in a rolling bearing having an angle of contact close to 0.degree., and of the type incorporating a number of rollers provided between and in contact with two race tracks, said rollers and race tracks having longitudinal section profiles of essentially the same radii of curvature, said rollers thereby being axially movable along the race tracks without being hindred by axial limitations at the race tracks, in order to allow relative misalignment and axial displaceability of the race tracks.

The present invention refers to a method for clearance adjustment in a 
rolling bearing having an angle of contact close to 0.degree., and of the 
type incorporating a number of rollers provided between and in contact 
with two race tracks, said rollers and race tracks having longitudinal 
section profiles of essentially the same radii of curvature, said rollers 
thereby being axially movable along the race tracks without being hindred 
by axial limitations at the race tracks, in order to allow relative 
misalignment and axial displaceability of the race tracks. 
The method can be applied to any adjustable bearings having a contact angle 
of or close to 0.degree., e.g. to spherical roller bearings, but it is 
particularly favourable at bearings where the radius of curvature of the 
longitudinal section profiles of said roller and race track is bigger than 
the distance between the outer race track and and the axis of the bearing, 
as measured perpendicularly to the race track. The contact angle at 
bearings of the last-mentioned type is altered to such a small extent as 
compared to spherical bearings when subjected to axial adjustment that the 
axial load component is not worth mentioning. 
Bearings of the last-mentioned type are known e.g. from EPB1-0175858, and 
they combine different advantages from other types of bearings, such as 
axial freedom as a cylindrical roller bearing, self alignment as a 
spherical roller bearing and low section height as a needle roller 
bearing. 
The life and stiffness of a bearing is extensively dependent on the radial 
internal clearance of the bearing, and it therefore is desirable to 
optimize the internal clearance for obtaining an optimized life and 
stiffness. 
Conventional rolling bearings are generally delivered with different 
internal clearances, which is dependent of the specific application for 
which the bearing is intended. With regard to the field of application it 
is necessary for the bearing to have either a positive or negative 
operational clearance, which in some instances is achieved during 
mounting, e.g. for angular contact bearings and taper roller bearings. It 
is also possible to provide bearings with specially made bearing rings, 
which during manufacture are matched to produce a predetermined positive 
or negative clearance or preload value after mounting. This of course 
means that an extensive number of different bearings with different 
internal clearance must be kept in stock. 
The purpose of the present invention is to provide a method for clearance 
adjustment at bearings of the type referred to manufactured to have a 
reduced number of internal clearances, by which method it is possible to 
obtain an extensive range of clearance classes with efficient and simple 
steps, thereby reducing the requirement of keeping a big stock of bearings 
having different predetermined internal clearance. 
In a bearing of the type now referred to, this adjustment of the 
operational clearance is achieved according to the present invention by 
actively displacing the inner and outer race rings axially relative to 
each other. 
In a first embodiment of the invention one of the race rings of the bearing 
is manufactured with its centre displaced from the central position at 
half the distance between the ends of the rings. When such an 
unsymmetrical race ring in a first relation is displaced axially in one 
direction, the clearance is altered either to become greater or smaller, 
and by turning said one ring in reversed direction, the same direction of 
axial displacement will result in the same clearance adjustment but in 
reversed order, i.e. instead of becoming greater, the clearance will 
become smaller and vice versa. The same effect of course could be achieved 
by turning around the entire bearing at mounting, but this is not possible 
in cases where e.g. the inner race ring has a taper bore. 
In another embodiment according to the invention both race rings of the 
bearing are manufactured with their centres displaced from the central 
position at half the distance between the ends of the rings. When mounting 
such a ring in a first relation the clearance can be big, and by turning 
one of said rings in reverse direction it is possible to obtain another, 
much smaller clearance, whereby the single bearing by means of a simple 
turning around of one ring at assembly can cover two different clearance 
classes. 
According to a further embodiment of the invention such axial displacement 
can be further achieved by using separate spacer washers, which are 
positioned against the end face of one of the rings. By moving at least 
one such spacer washer to the opposite end face of the same race ring it 
is further possible to adjust the bearing clearance to cover two different 
clearance classes. 
According to a still another embodiment of the application it is possible 
to use split bearing housings having a bearing seat disposed in a 
non-centered position in the removable half of the bearing housing. By 
positioning the removable bearing housing half in oppositely reversed 
directions the bearing received in the bearing housing can be given two 
different internal clearances. In this case it is of course necessary that 
opposite half of the bearing housing has a free adjustment space for the 
axially movable bearing ring. 
Furthermore it is possible to combine the first embodiment as mentioned 
hereabove with anyone of the second and third embodiments as mentioned, 
thereby making it possible to achieve up to eight different clearances in 
a single bearing, when using e.g. the spacing washers according to the 
second embodiment on both race rings. 
In still another embodiment it is possible cause an incremental 
displacement of one of the race rings by providing said race ring with a 
guiding means extending helically along the envelope surface of the race 
ring opposed to the race track in the ring, providing means projecting 
from a fixed position in the confronting surface of the bearing housing or 
the shaft and arranged to engage said guiding means, rotating said race 
ring relative to said housing and/or shaft, thereby causing axial 
displacement of the race ring, as a result of cooperation between said 
helical guiding means and said projecting means.

In FIG. 1 is schematically illustrated a roller bearing of the type 
referred to in the preamble. The bearing comprises an outer race ring 1 
having an inner race track, an inner race ring 2 having an outer race 
track and rollers 3 disposed between said outer and inner race tracks. The 
curvatures of the race tracks and of the rollers are substantially equal 
and have a radius R, which in the embodiment illustrated is substantially 
bigger than the mean radius of the bearing. 
The centre of the outer race ring 1 in this embodiment is displaced axially 
thus that it is situated offset from the geometrical center of the ring, 
resulting in an unsymmetric ring. The outer race ring 1 thus has side 
faces 1a and 1b of different heights. 
With this embodiment of the invention it is possible to compensate for 
expansion, whereby displacement when the rings are arranged in the 
relation shown in FIG. 1 will give a certain compensation in one 
direction, whereas a simple turning around of the outer race ring 1, thus 
that side face 1a and side face 1b change place, will result in a 
possibility of obtaining a compensation of equal size, but in the opposite 
direction. 
In FIGS. 2a and 2b is schematically illustrated another embodiment 
according to the invention, wherein the centres of both race rings 1, 2 
are displaced axially thus that they are situated offset from the 
geometrical centers of the rings, resulting in unsymmetric rings. The 
outer race ring 1 thus has end faces la and lb and the inner race ring 2 
side faces 2a and 2b of different heights. With this embodiment of the 
invention it is possible to alter the internal clearance of the bearing by 
turning one of the rings in opposite axial direction. In this manner it is 
achieved a possibility to allow a single bearing to cover two different 
clearance classes, i.e. when the bearing race rings are positioned with 
their resp. centre aligned. 
When the outer race ring 1 is positioned in one axial direction, having its 
higher section end face 1a turned in one axial direction as in FIG. 2a, 
the bearing has its greatest internal radial clearance, whereas it when 
the outer race ring is turned 180.degree. with its bigger end face section 
in the opposite axial direction such as shown in FIG. 2b, the clearance is 
at its smallest. 
In another embodiment shown in FIGS. 3a and 3b there is used a separate 
spacer washer 4, which by being positioned against either axial end face 
of the race ring can adjust the mutual axial relation between the race 
rings thus that different, predetermined clearances can be obtained by 
shifting the washer 4 from one side to the other. Although shown only at 
the outer race ring, similar clearance adjustment effects may be obtained 
by positioning a washer at the inner race ring. 
In still another embodiment illustrated in FIGS. 4a and 4b a similar axial 
displacement between the race rings and thereby an adjustment of the 
internal clearance can be obtained by using a split bearing housing, where 
the removable housing half 5 has a non-centred bearing seat 6 in which the 
outer race ring 1 is received. By turning the removable bearing housing 
half 5 in opposite axial directions it is possible to make the same type 
of clearance adjustments as in the embodiments previously shown and 
described. 
As stated above it is also possible to combine e.g. the embodiments 
according to FIGS. 2 and 3 or FIGS. 2 and 4, thereby making it possible to 
obtain a larger number of clearance adjustment positions. 
In FIG. 5 is illustrated an outer race ring 1 of a bearing inserted with 
loose fit in a schematically illustrated bearing housing 5', and 
supporting a shaft 7. The outer envelope surface of the outer race ring 1 
is provided with a guide means in the form of a helical groove 8, which is 
arranged to cooperate with a means projecting from the housing in the form 
of a set screw 10. This set screw 10 engages in the helical groove 8 and 
causes the outer race ring 1 to move axially, if the race ring is rotated 
relative to the housing, thereby causing adjusting of the internal 
clearance of the bearing in a simple manner. For arresting the race ring 
in a desired position, there is provided in the bottom of the helical 
groove a series of spaced apart indentations 9 or the like. By tightening 
the set screw 10 its tip can be caused to engage one of these indentations 
9, thereby arresting the race ring in a position resulting in a desired 
internal clearance. For facilitating of the rotation of the outer race 
ring 1 relative to the housing 5', the side face of the ring 1 may be 
recessed 11 for engagement with a tool for rotating the ring. 
Although the drawings and the description have referred to one type of 
bearing, the method according to the invention can be used for different 
self-aligning bearings having contact angles close to 0.degree., as 
mentioned above. The invention is neither limited to the embodiments shown 
and described but can be varied and modified within the scope of the 
accompanying drawings. It thus is possible to provide the guiding means in 
the inner envelope surface of the inner race ring, and using a projecting 
means in form of a projecting nib fitted to the shaft and cooperating with 
said guiding means for effecting axial displacement of the inner race 
ring.