Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
1999-10-27
2001-04-17
Hannon, Thomas R. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C029S413000
Reexamination Certificate
active
06217222
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a notching construction and method that facilitates fracture of an otherwise solid cross section. More particularly, the present invention pertains to a notching construction and method that facilitates fracture of an outer ring of a spherical plain bearing.
BACKGROUND OF THE INVENTION
In the description of the background of the present invention that follows reference is made to certain structures and methods, however, such references should not necessarily be construed as an admission that these structures and methods qualify as prior art under the applicable statutory provisions.
It is often desirable to separate a bearing ring into different pieces by intentionally fracturing the ring at a desired location.
One such bearing ring that is advantageously fractured at one or more locations along its circumference is an outer ring of a spherical plain bearing. Spherical plain bearings are used in numerous applications, such as in construction and other equipment.
FIG. 1A
is a plan view of a spherical plain bearing
200
. The bearing
200
generally comprises a continuous inner ring member
202
and an outer ring member
204
. The outer ring
204
as illustrated in
FIG. 1A
is “double fractured” or segmented into two pieces that can be moved apart and mounted over the inner bearing ring
202
. When mounting of the outer ring
204
is complete, the free ends
205
of the double fractured ring are brought together and the gaps between the two ring parts are closed.
FIG. 1B
is a cross-sectional view taken along the section line
1
B—
1
B of
FIG. 1A
, and illustrates certain features of the inner bearing ring
202
. The inner bearing ring
202
generally includes a substantially cylindrical inner surface
206
, and optionally having an inner peripheral groove
208
which distributes lubricant along the inner surface
206
, the edge surface
210
and the outer arcuate surface
212
of the inner bearing ring
202
. The outer arcuate surface
212
of the inner bearing ring
202
may optionally be provided with an outer peripheral groove
213
disposed therein. A through hole (not shown) radially interconnecting the inner and outer peripheral grooves
208
and
213
may also be provided for allowing lubricant to flow between the grooves
208
and
213
.
FIG. 1C
is a sectional partial perspective view of the outer bearing ring
204
, prior to fracture. The outer bearing ring
204
generally comprises an inner arcuate surface
214
that receives the outer arcuate surface
212
of the inner bearing ring
202
in a nested relationship. The edge surfaces
216
of the outer bearing ring
204
each extend radially, and are interconnected by a substantially cylindrical outer peripheral surface
218
. An outer peripheral groove
220
may be provided in the outer peripheral surface
218
of the outer bearing ring
204
to distribute lubricant along the outer peripheral surface
218
.
A notched area
222
is provided in the outer bearing ring
204
by any suitable material removal technique, such as sawing or milling. The notched area
222
does not extend completely through the bearing ring
204
. A centrally-located blind hole
224
or a multiple number of blind holes across the surface
218
may also be provided in the outer bearing ring
204
. The blind hole
224
may be formed by any suitable material removal technique, such as drilling. Although only one notched region
222
and accompanying blind hole
224
are shown in
FIG. 1C
, typically a substantially identical construction is provided on the diametrically opposite side of the outer bearing ring
204
.
FIG. 1D
is a cross-sectional view taken along the section line
1
D—
1
D of FIG.
1
C and illustrates certain features of the notched area
222
. A gap or space
226
on either side of the cross-section of the outer ring
204
represents the area where the material of the outer ring
204
has been removed to form the notched area
222
. As illustrated by gap
226
in
FIG. 1D
, only a portion on either side of the cross-section of outer ring
204
is removed. That portion of the cross-section that remains defines an interconnecting region or fracture region
228
which is represented by the cross-hatched area shown in FIG.
1
D. The interconnecting region
228
is bounded by the inner arcuate surface
214
, a portion of the edge surfaces
216
, the arcuate surfaces
230
on either side of the cross section, and a portion of outer substantially cylindrical surface
218
. The blind hole
224
may be provided in the region
228
.
The outer ring
204
with the above-described construction is case or surface hardened and then fractured. The outer ring
204
is fractured along the interconnecting region
228
to form two ring parts having separated ends
205
(FIG.
1
A). The outer ring
204
is fractured by the application of mechanical force to the outer periphery of the ring in the notched area(s)
222
.
By providing the interconnecting region
228
with a relatively small cross-sectional area the case hardening or surface hardening treatment can more easily penetrate through the entire interconnecting region
228
and cause this region to become sufficiently “brittle”, thus facilitating fracturing. In addition, the blind hole
224
is provided to further facilitate the penetration of the case or surface hardening treatment through the cross section.
The fracture mechanics of this construction can be better understood by reference to
FIGS. 1E-1H
. Typically, a pair of notches N
1
, N
2
is formed at both axial sides of the ring
204
. As a mechanical force MF is applied to the outer periphery of the ring
204
, cracks A, B originate within the interconnecting region
228
at points IE A
o
, B
o
in the vicinity of the notches N
1
, N
2
, respectively. These cracks A, B propagate toward each other.
Under ideal circumstances, cracks A, B propagate toward each other until the leading end or tip of one crack A, B runs into the leading end or tip of the other crack B to thereby define a fracture plane F corresponding to a line interconnecting B
o
, B and A
o
, A, as illustrated in FIG.
1
F. However, it has been discovered that in practice this rarely occurs. Instead, a fracture pattern similar to that illustrated in FIG.
1
G and/or
FIG. 1H
often occurs.
As shown in
FIG. 1G
, the cracks A, B propagate toward one another, but the leading ends or tips of the cracks pass one another and do not intersect. Instead, the leading end of one crack B may eventually run into or intersect a portion of the other crack A at a point spaced from the leading end of the other crack A. The distance between this point of intersection and the leading end of the crack being intersected A defines a secondary fracture SF which represents a residual fracture or crack that is not needed to form the fracture plane across the cross section of the outer ring
204
.
Alternatively, as shown in
FIG. 1H
, the leading end of one crack may never entirely intersect the body of the other crack. Instead, an offset crack OC can form between the leading end of one crack B, with this offset crack C then intersecting the body of the other crack A. This forms a secondary fracture SF between the point where offset crack OC intersects the body of the crack A and the leading end of the crack being intersected A.
These secondary or residual fractures define a weakness in the cross-section of the outer ring
204
and can further propagate, possibly causing a chip of material to be dislodged from the outer ring
204
. This can result in a reduction in service life of the bearing and the equipment in which the bearing is installed.
After the outer ring
204
has been fractured at the region
228
, the resulting free ends
205
have a surface area defined by the area of the region
228
. The free ends
205
are brought into contact with each other after the outer ring has been placed over the inner ring
202
. Because the area of the region
228
is relatively small, by virtue of the amount a significant amount of mat
Cutler Mark J.
Mattson Arthur
Meyer Jerry
Meyers Keith
Winkel David A.
Burns Doane Swecker & Mathis L.L.P.
Hannon Thomas R.
SKF USA Inc.
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