Spherical bearing assembly with stress relief

A spherical bearing adapted for use in rod end connections and the like, characterized by an outer race member having opposite faces and a concave spherical inner race surface, and a ball-like inner member within the outer race member having a complementary convex spherical outer bearing surface. At each face of the outer race member is a pair of diametrically opposed segmental slots. The diametrically opposed slots in each face are in alignment with the slots of the other and extend transversely partially through the housing with transversely opposed slots being separated by an annular contact band which maintains substantially constant side clearance between the inner member and outer race member thereby to prevent the development of high stress concentrations in the outer race member during loading. In use, the opposed slots are necessarily aligned substantially at right angles to the line along which the bearing is subjected to loads.

BACKGROUND OF THE INVENTION 
The present invention relates generally to a spherical bearing including an 
outer race member or bearing housing layer a concave spherical inner race 
surface and a ball-like member within the outer race member having a 
complementary convex spherical outer bearing surface, and more 
particularly to such a spherical bearing utilized in a rod end connection 
or the like wherein the spherical bearing may be subjected to loads 
applied substantially along a line normal to the axis of the outer race 
member. 
In conventional spherical bearings of the type described, there is normally 
provided a slight radial clearance between the race of the outer race 
member and the outer bearing surface of the ball-like inner member, 
whereby when the spherical bearing is subjected to tensile loads applied 
substantially along a line normal to the axis of the outer race member 
such as may occur when utilized in a rod end connection, the sides of the 
race member at right angles to such line of force will move inwardly 
toward the ball-like member as such clearance is taken up and the race 
surface of the outer race member will become somewhat oval-shaped. Such 
movement results in bending stress in the outer race member, in addition 
to the direct tensile stress resulting from the applied tensile loads, 
which increases with the distance from the neutral bending axis of the 
outer race member. This distance, and consequently the tensile stress, is 
greatest at the intersection of the spherical bearing race and the bearing 
housing 90.degree. to the line of force, and experience has shown that 
fatigue failures originate at this intersection, leading to short cycle 
life of the outer race member and/or requiring greater fatigue strength 
design requirements. 
Early failures of the race member may occur in spherical bearings of the 
type oftentimes referred to in the trade as messerschmidt-type bearing 
which include a bearing housing and a truncated ball, with the bearing 
housing being slotted to form keyhole type slots through which the ball 
may be inserted and withdrawn for assembly and replacement purposes. 
Examples of such type of bearings may be found in U.S. Pat. No. 3,116,539, 
dated Jan. 7, 1964 and in U.S. Pat. No. 2,309,281, dated Jan. 26, 1943. In 
such spherical bearings, the keyhole slots are diametrically opposed and 
extend either halfway or entirely across the bearing race surface of the 
bearing housing. In those bearings where the keyhole slots extend halfway, 
fatigue failures may originate at points of high stress concentration in 
the non-slotted portion of the bearing housing. Moreover, where the 
keyhole slots extend entirely across the inner bearing race surface, 
points of high stress concentration will develop in the bearing housing as 
the increased clearances resulting from the slotting are taken up during 
loading of the spherical bearing in the aforedescribed manner. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, spherical bearing or outer race 
member cycle life may be increased by removing the portions of the bearing 
housing that are subject to high stress concentrations but without 
increasing the side clearance between the inner race surface of the race 
member and the outer bearing surface of the ball-like member. The race 
member is provided at each of its opposite faces at the sides of the eye 
90.degree. to the line of force with a pair of diametrically opposed 
axially extending segmental slots with the opposed slots in each face 
being aligned diametrically with those of the other. The diametrically 
opposed slots extend transversely partially across the race surface from 
each face with the pairs of slots on opposite faces being separated by an 
annular contact band which maintains substantially constant side clearance 
between the inner bearing race surface of the race member and the outer 
bearing surface of the ball-like member thereby providing side support for 
the ball-like member. The outer bearing housing may be formed with the 
slots or the slots may be subsequently machined in the bearing housing 
with the contact band comprising that portion of the bearing race surface 
left between the slots after slotting. In use, the diametrically opposed 
slots of each pair are aligned normal to the line of force along which 
tensile loads are applied. Accordingly, points of high stress 
concentration in the race member are eliminated without allowing further 
bending to occur due to the contact band which maintains substantially 
constant side clearance. 
It is therefore a principal object of the present invention to provide a 
spherical bearing with stress relief. 
It is another object to provide a spherical bearing in which the race 
member or bearing housing will not be subject to early fatigue failure. 
Still another object is to provide a spherical bearing with increased 
practical load limit. 
Yet another object is to provide such a spherical bearing that may be 
easily assembled or disassembled. 
Other objects and advantages of the present invention will become apparent 
as the following description proceeds. 
To the accomplishment of the foregoing and related ends the invention, 
then, comprises the features hereinafter fully described and particularly 
pointed out in the claims, the following description and the annexed 
drawing setting forth in detail a certain illustrative embodiment of the 
invention, this being indicative, however, of but one of the various ways 
in which the principles of the inventon may be employed.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A spherical bearing embodying the concepts of the present invention is 
designated generally by numeral 10 in FIGS. 1-6 of the attached drawing. 
The bearing 10 is shown in the form of a rod end assembly 12; however, it 
will become apparent that the spherical bearing of the invention may have 
other applications. Such rod end assembly 12 and thus the spherical 
bearing 10, may be utilized, for example, in aircraft control linkages 
where the rod end assembly may be subjected along its longitudinal axis to 
cyclical tensile loads T shown schematically in FIG. 1. 
The spherical bearing 10 comprises an outer race member or bearing housing 
14 which may be formed integrally with the rod 16, or formed separately 
and assembled therein as desired. The race member 14 has opposite planar 
faces 18 and 20 and a concave spherical inner bearing race surface 22 
which forms the eye of the race member 14. The spherical bearing 10 
further comprises an inner ball-like member 24 housed within the race 
member 14. The ball-like member 24 is similar to those found in prior art 
forms of spherical bearings and essentially has the shape of a truncated 
ball with central bore 26 and a convex spherical outer surface 28 which is 
complementary to and has a radius slightly less than that of the concave 
inner race surface 22 of the race member 14. 
In accordance with the present invention, the race member 14 is provided 
with two pairs of diametrically opposed slots 30 and 32 respectively at 
each of the faces 18 and 20. The slots 30 and 32 of each pair are aligned 
diametrically at right angles to the direction of the applied tensile 
loads T for reasons that will become more apparent below. Preferably, the 
slots 30 and 32 are cylindrical segmental cavities with a radius 
approximately that of the ball 24 and may be machined or formed into the 
eye of the race member 14 as shown. The slots 30 and 32 extend 
transversely partially across the bearing race surface with transversely 
opposed slots of opposite pairs being separated by an annular contact band 
34 at each side of the race member. The annular contact band 34 consists 
of that portion of the bearing race surface left between the transversely 
opposed slots after slotting and thus is a continuation of such race 
surface. The side clearance between the inner bearing race surface 22 and 
outer spherical surface 28 of the ball 24 is thereby not increased by the 
slotting. Although the race member is described as being machined and/or 
formed, it of course may be cast in the desired shape. 
In the preferred embodiment shown, the slots 30 of one pair preferably 
extend approximately halfway across the bearing race surface whereas the 
slots 32 of the other pair extend only partially halfway, or approximately 
1/3 the way across the bearing race surface, leaving a contact band 34 of 
approximately 1/6 the axial length of the bearing housing. The chordal 
width of the slots 30 is also at least as great as the axial length or 
thickness of the ball-like member 24 whereby the spherical bearing 10 may 
be conventionally assembled by inserting the ball-like member edgewise 
through slots 30 and rotating the same to the position shown in FIG. 1. Of 
course, the spherical bearing may be assembled by other methods with the 
contact band axially offset as shown or centrally disposed in the race 
member if preferred. 
Turning now to FIG. 6, the stress relief function of the invention will be 
appreciated. There is shown in FIG. 6 a sectional view of the race member 
14 taken along a diametrical plane thereof normal to the direction of the 
applied tensile loading indicated by arrows T in FIG. 1 with that portion 
of the race member 14 normally eliminated by slotting being outlined by 
dashed line 35. Hence, the combined sectioned area of the race member is 
illustrative of the race member without slotting in accordance with the 
invention, and thus without stress relief. As such race member is 
subjected to tensile loads, the sides of the race member at right angles 
to the line of applied force (at the top and bottom of the race member as 
seen in FIG. 6) will move laterally inwardly as any clearance between the 
inner race surface of the race member and outer surface of the ball-like 
member is taken up. Such inward movement results in bending stress in the 
race member which combines with the direct tensile stress to create areas 
of high stress concentration. Moreover, the stress from bending increases 
the greater the distance from the neutral bending axis X and is additive 
with the direct tensile stress inwardly of the neutral bending axis. 
Accordingly, points of maximum tensile stress occur at the intersection of 
the periphery of the race surface and the diametrical plane extending at 
right angles to the direction of the applied force indicated at 36. In 
addition, the portions of the race member adjacent these points of highest 
stress concentration are also subjected to high stress concentrations. 
The removal of these portions of high stress concentration by slotting at 
30 and 32 in the manner previously described greatly reduces the maximum 
tensile force because the points of maximum stress concentration will then 
occur at the radial innermost edges 37 of the remaining contact band 34 
whose distance from the neutral bending axis X is much less as shown. 
Moreover, as previously indicated, the presence of the contact band is 
important so that the clearance between the inner race surface of the race 
member and outer surface of the ball-like member is not increased by such 
slotting, such contact band maintaining such clearance and providing the 
required support for the ball in the region of the slots 90.degree. to the 
line of the applied force. An increase in side clearance would allow for 
greater bending resulting in the development of high stress concentrations 
in additional portions of the race member, thus nullifying the benefits 
derived from removal of the portions of the bearing housing normally 
subject to the high stress. 
Although the invention has been shown and described with respect to a 
certain preferred embodiment, it is obvious that equivalent alterations 
and modifications will occur to others skilled in the art upon the reading 
and understanding of the specification. The present invention includes all 
such equivalent alterations and modifications and is limited only by the 
scope of the claims.