Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2001-01-16
2002-11-05
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
Reexamination Certificate
active
06474874
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a roller bearing used in apparatus causing large vibrations such as axles of railway vehicles or vibrating screens, that is, a roller bearing for use in places undergoing vibrations repeatedly at least in the radial direction of the bearing and, more in particular, it relates to a comb-shaped cage assembled in such a roller bearing.
Roller bearings have been used generally for supporting rotational shafts, for example, in vehicles and various industrial machines. A roller bearing comprises, for example, as shown in
FIG. 1
, an outer ring
1
having an outer ring raceway
1
a
at the inner circumferential surface, an inner ring
2
having an inner ring raceway
2
a
at the outer circumferential surface, a plurality of rollers
3
assembled such that they can roll between the outer ring raceway
1
a
and the inner ring raceway
2
a
, and a cage
4
interposed rotatably between the outer ring raceway
1
a
and the inner ring raceway
2
a
in a state of holding the plurality of the rollers
3
.
Each of the plurality of the rollers
3
are arranged in double rows between the outer ring raceway
1
a
and the inner ring raceway
2
a
, and the rollers
3
in each row are held by respective comb-shaped cage
4
. That is,
FIG. 1
illustrates an example having two comb-shaped cages
4
.
Each of the comb-shaped cages
4
comprises, as shown in FIG.
1
and
FIG. 2
, respectively, a circular portion
5
axially opposing to the end surface
3
a
of the roller
3
and a plurality of bar portions
7
protruding from one axial side of the circular portion
5
and arranged circumferentially being opposed to the rolling surface
3
b
of the roller
3
. A space surrounded by the circular portion
5
and the bar portions
7
,
7
is referred to as a pocket
8
for accommodating the roller
3
, and the roller
3
is held rotatably in the cage
4
by providing a predetermined gap between the cage
4
and the roller
3
.
In the roller bearing having the double rows of rollers
3
as described above, in a case where individual cage
4
is assembled on every row for each of the rollers
3
as shown in
FIG. 1
, comb-shaped cages of a configuration in which the bar portions
7
protrude only from one axial side of the circular portion
5
as shown in
FIG. 2
is used. On the other hand, in a case where the rollers
3
in the double rows are held by one cage, a comb-shaped cage of a configuration in which bar portions
7
protrude respectively from both axial sides of the circular portion
5
as shown in
FIG. 3
is used.
In the subsequent description, a comb-shaped cage of a configuration in which bar portions
7
protrude from one axial side of the circular portion
5
as shown in
FIG. 2
is sometimes referred to as a two component type, whereas a comb-shaped cage of a configuration in which bar portions
7
protrude from both axial sides of the circular portion
5
as shown in
FIG. 3
is sometimes referred to as a one component type.
By the way, when the roller bearing having the cage
4
as described above is used in places causing large vibrations repeatedly such as axles of vehicles, or driving apparatus, iron making rolling mills or vibrating screens, the cage
4
is vibrated repeatedly in the radial direction of the bearing and the bar portion
7
of the cage
4
collides against the rollers
3
again and again. Accordingly, load W′ is exerted in the radial direction by the collision from the roller
3
to the bar portion
7
of the cage
4
as shown in
FIG. 4
to deform the cage
4
as shown in FIGS.
4
(B), (C).
When the bending stress is loaded on the circular portion
5
and the bar portion
7
repeatedly, cracks occur in the circular portion
5
or the bar portion
7
which not only fractures the cage
4
but also sometimes makes the rotation of the bearing impossible during long time use.
Since the cracks occur at a connection portion between the circular portion
5
and the bar portions
7
, it is necessary for preventing fracture of the cage
4
thereby preventing deterioration for the bearing life, to moderate the bending stress caused to the connection portion by the load W′ in the radial direction.
Further, when the roller bearing having the cages
4
as described above is used in places where abrupt acceleration/deceleration or load fluctuations are repeated, since revolutional speed of the rolls
3
changes abruptly, the roller
3
collides against the bar portion
7
of the cage
4
again and again. A load W exerted in the circumferential direction by the collision is applied from the roller
3
to the bar portion
7
of the cage
4
as shown in
FIG. 2
to deform the cage
4
as shown in FIG.
5
.
When the bending stress is loaded on the circular portion
5
and the bar portion
7
repeatedly, cracks occur in the circular portion
5
or the bar portion
7
which not only fractures the cage
4
but also sometimes makes the rotation of the bearing impossible during long time use.
Since the cracks occur at a connection portion between the circular portion
5
and the bar portions
7
, it is necessary for preventing fracture of the cage
4
thereby preventing deterioration for the bearing life, to moderate the bending stress caused to the connection portion by the load W in the circumferential direction.
When the cage
4
is moved by the vibrations in the direction of a blank arrow in FIG.
4
(A), the cage
4
is deformed as shown in
FIG. 4
by the radial load W′ exerted from the roller
3
. That is, the load W′ is exerted on the bar portion
7
at a position opposed substantially to a central portion in the axial direction of the roller, while a load balancing the load W′ is exerted also to a connection portion between the circular portion
5
and the bar portion
7
and the circular portion
5
and the bar portion
7
undergo bending moments M
1
′, M
3
′, respectively, to deform as shown in FIGS.
4
(B), (C). Let the bending stress caused to an area A of the circular portion
5
in the connection portion between the circular portion
5
and the bar portion
7
be denoted by &sgr;
1
, the bending stress caused to an area C of the bar portion
7
in the connection portion between the circular portion
5
and the bar portion
7
be denoted by &sgr;
3
′, each of the bending stresses &sgr;
1
′, &sgr;
3
′ is expressed by the following equations based on the conditions for the balance of forces in view of the strength of materials:
&sgr;
1
′=M
1
′·e
1
′/I
1
′ (1)
&sgr;
3
′=M
3
′·e
3
′/I
3
′ (2)
I
1
′, I
3
′ each express the moment of inertia of area for each of the circular portion
5
and the bar portion
7
, and the moment of inertia of area I
1
′, I
3
′ are defined by the following equations:
I
1
′=∫
A1
y
1
2
dA
1
(3)
I
3
′=∫
A3
y
3
2
dA
3
(4)
A
1
, A
3
in the equations (3), (4) described above each expresses, respectively, the cross sectional areas for each of circular portion
5
, and the bar portion
7
.
Further, e
1
′, e
3
′ in the equations (1), (2) described above express the maximum values of distance from the center of the graph to the edge of the cross sectional area in each of the coordinate systems to be described later.
Further, the coordinate system for each of the moment of inertia of area I
1
′, I
3
′ is defined as below. That is, as shown in
FIG. 1
, the moment of inertia of area I
1
′ is in accordance with a y
1
-z
1
orthogonal coordinate system, on the cross section of the circular portion
5
, taking an axis y
1
in the direction of a normal line for the conical surface or cylindrical surface that defines the outer diametrical surface of the cage and taking an axis z
1
axially and in the direction of a tangential line for the conical surface or cylindrical surface, with respect to the center of the graph for the cross section as an origin,
Crowell & Moring Ltd.
Footland Lenard A.
NSK Ltd.
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