Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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RAILWAY BEARING BACKING RING
Field of the Invention
[00011 This invention relates to anti-friction bearings and more particularly,
in one
embodiment, to tapered roller bearings.
Background of the Invention
[00021 Anti-friction bearings (also commonly known as rolling-contact
bearings), such as
ball bearings and tapered roller bearings, are commonly used in various
industrial applications.
Like any other moving mechanical component, bearings eventually experience
wear related
degradation. Because bearings are a high-value item, it is general practice to
recondition worn
bearing assemblies. Bearing assemblies removed from service for reconditioning
are cleaned,
inspected for defects, and "repaired as required. The bearing is reassembled
and prior to release,
undergoes a quality-control inspection. Bearing assemblies passing quality-
control inspection
are ready to be pressed onto a shaft (e.g., a railcar axle).
[00031 Certain types of bearing assemblies, however, lack a means for
retaining the backing
ring to the bearing assembly. As it is desirable to press fit the bearing
assembly and the backing
ring onto the journal as a unit, the absence of a retaining means to affix
these two components
can prove problematic for their efficient installation.
Summary of the Invention
[00041 A bearing assembly is presented having a compressible, adhesive gasket
to affix the
bearing backing ring to the bearing cone of a bearing assembly. The adhesive
gasket facilitates
the press fit of the bearing assembly and backing ring, as a unit, onto the
journal of a shaft (e.g.,
a railcar axle) in a single operation.
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[0005] The compressible, adhesive gasket has a body formed, in one embodiment,
with a
compressible, closed cell, polymer foam. In this embodiment, the body of the
gasket is coated
with a pressure sensitive adhesive.
[0006] The adhesive gasket, in one embodiment, has an annular shape to fit
around part of
the backing ring and into a gap between the backing ring and the bearing cone.
The
compressible nature of the adhesive gasket helps ensure uniform gasket contact
over potentially
rough, nonparallel, and uneven surfaces presented between the backing ring and
the bearing
cone. Disposing the adhesive gasket in the gap allows the bearing assembly to
have a series of
abutting solid metal components from the backing ring to the retaining cap,
allowing the preload
compression on the bearing assembly exerted by the retaining cap to remain
isolated and
unaffected by any deterioration in the adhesive gasket.
Brief Description of the Figures
[0007] Various embodiments of a bearing assembly with a novel compressible,
adhesive
gasket are described and illustrated in the accompanying figures. The figures
are provided as
examples only and are not intended to be considered as limitations to the
invention.
Consequently, the bearing assembly and gasket are illustrated by way of
example and not by
limitation in the accompanying figures in which:
[0008] FIG. I is a sectional view of one embodiment of the bearing assembly;
[0009] FIG. 2 is an enlarged sectional view of the bearing assembly
illustrated in FIG. 1;
[0010] FIG. 3 is a detailed sectional view of one embodiment of the adhesive
gasket depicted
in the bearing assembly embodiment illustrated in FIG. 1; and
[0011] FIG. 4 is a sectional view of the installation of a bearing assembly
onto a journal with
a bearing press.
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Detailed Description
[0012] Referring to FIG. 1, an exemplary bearing assembly 10 is illustrated.
In this
embodiment, the bearing assembly 10 is a tapered roller bearing of the type
commonly used in
railway applications to support a railcar wheel. The bearing assembly 10
described in the
following embodiments, however, may be adapted for use in many other common
industrial
applications. Consequently, the bearing assembly 10 illustrated and described
below in relation
to a tapered roller bearing assembly for a railcar wheel is for convenience
only.
[0013] The bearing assembly 10 is typically preassembled before being mounted
on a shaft
11 (e.g., a railcar axle). At the free end of the shaft 11, a journal 12
terminates in a slightly
conical, tapered guide 13 to facilitate installation of the bearing assembly
10 onto the journal 12.
The bearing assembly 10, in one embodiment, is press fit on the journal 12
which is machined to
very close tolerances to accurately accommodate the press fit.
[0014] The journal 12 terminates at its inboard end in a contoured fillet 18
leading to a
shoulder 19 on the shaft 11. A dust guard 14 having a cylindrical surface
extends axially inward
from the shoulder 19. A backing ring 22 having a contoured inner surface is
affixed to a
complementary surface of the fillet 18. The fillet 18 and the adjacent
shoulder 19 affix the
bearing assembly 10 against axially inward displacement.
[0015] The backing ring 22, in some embodiments, also has a collar 26
extending axially
inward and concentrically over the outer cylindrical surface 15 of the dust
guard 14. The collar
26, in some embodiments, develops an interference fit with the outer
cylindrical surface 15 of the
dust guard 14.
[0016] A bearing retaining cap 20 having a plurality of threaded bores is
mounted at the free
end of the shaft 11 to the journal 12 with threaded cap screws or bolts 21.
The bearing retaining
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cap 20 and the backing ring 22 cooperatively clamp the bearing assembly 10
into position on the
journal 12. The bearing retaining cap 20 directly abuts the bearing cone 38 of
the bearing
assembly 10 and develops a compressive preload on the bearing assembly.
[0017] The bearing assembly 10 is preassembled from a number of individual
components.
The bearing assembly 10 includes a bearing cup 31 having raceways 32, 34
formed on the inner
surface of the bearing cup. The raceways 32, 34 cooperate with bearing cones
38, 40 to capture
and support two rows of tapered rollers 42, 44 respectively. In some
embodiments, cages 46, 48
maintain the spatial position of the rollers 42, 44 within the raceways 32,
34. A center spacer 47
is positioned between the bearing cones 38, 40 to maintain the cones in
accurately spaced
position relative to one another and allow for proper bearing lateral
clearance.
[0018] Bearing seal cases 50, 52 cover the ends of the bearing assembly 10,
protecting the
bearing from external contaminants and sealing the lubricant within the
bearing assembly. The
bearing seal cases 50, 52 depicted in FIG. 1 are a type of cone riding bearing
seal which is
mounted on the bearing cone 38, 40 and the bearing cup 31.
[0019] Referring to FIG. 2, the inboard end of the bearing assembly 10 of FIG.
1 and in
particular, the bearing seal case 52 is illustrated in a detailed sectional
view. The bearing seal
cases 50, 52 are identical, consequently, in the following discussion, all
references to the bearing
seal case 52 on the inboard side of the bearing assembly 10 can be applied to
the outboard
bearing seal case 50.
[0020] The bearing seal 52 comprise two components: an outer seal case 54 and
an inner seal
case 56. The outer seal case 54 is affixed to the bearing cup 31. In one
embodiment, the outer
seal case 54 may be affixed to the bearing cup 31 with an interference fit
between the large
diameter open end section 51 and the counterbore 33 in the bearing cup 31.
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[0021] Alternatively, in another embodiment, the outer seal case 54 may have a
retaining lip
53 adapted to snap into an undercut retaining groove 37 in the bearing cup 31.
This design
allows the outer seal case 54 to be releaseably retained on the bearing
assembly 10.
[0022] The inner seal case 56 is a generally cylindrical housing affixed to
the bearing cone
40 on the standout 43 of the bearing cone. The inner seal case 56 has a wear
surface 57 to
provide a similar functionality as wear rings found in other types of bearing
assemblies.
[0023] A seal body 60 (typically of elastomeric construction) is attached to
the outer seal
case 54 and is urged against the wear surface 57 of the inner seal case 56 to
form a dynamic seal
between the stationary and moving bearing assembly components.
[0024] Tapered roller bearing assemblies and backing rings for railcar axles
are generally
pressed onto the journal of the rail car axle. As noted above, the backing
ring 22 is a separate
and loose component from the bearing assembly 10, particularly in many short
design, such as
Class K, bearings. These bearing assemblies are reconditioned often today and,
the lack of an
attachment means has proven problematic for their reassembly onto railcar
axles after
reconditioning.
[0025] A novel method and apparatus are presented to facilitate, in a single
press fit
operation, the installation of a bearing assembly onto a journal. To prevent
the disengagement of
the backing ring 22 from the bearing assembly 10, a special adhesive gasket 90
is positioned
between the backing ring 22 and the bearing cone 40 in a manner preventing
loss of compressive
preload on the bearing assembly.
[0026] The adhesive gasket 90 may take any shape, but an annular shaped gasket
covers the
greatest available surface area between the bearing cone 40 and the backing
ring 22, maximizing
the adhesive force connecting the bearing assembly with the backing ring. The
annular shape
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also facilitates the placement of the adhesive gasket 90 between the backing
ring 22 and the
bearing cone 40 to avoid interruption of the solid metal bearing stack between
the bearing
retaining cap 20 and the backing ring 22. This isolates the gasket 90 from the
bearing stack,
preventing any gasket degradation from affecting the preload compression on
the bearing stack.
[0027] In this embodiment, the bearing stack is a series of abutting metallic
components
including: the bearing retaining cap, bearing cones, the center spacer, and
the backing ring. Any
compressible material interposed in this solid metal bearing stack may
degrade, resulting in the
loss or reduction of the clamping force (i.e., compressive preload) exerted by
the retaining cap on
the bearing assembly and backing ring. A loss of bearing stack compressive
preload loosens the
bearing assembly and the backing ring; which in turn accelerates wear related
degradation and
can eventually lead to bearing, shaft, or backing ring failure.
[0028] To preclude this possible loss of compression, the annular adhesive
gasket 90 is
placed over and radially outward of the annular boss 23 of the backing ring
22. The annular boss
23 extends from the axially outward directed surface of the backing ring 22
and directly abuts the
bearing cone 40, maintaining the metal to metal series of contacts between the
bearing retaining
cap and the backing ring. The annular boss 23 projecting from the backing ring
22 has an outer
cylindrical surface having an outer diameter smaller than the outer diameter
of the cone back
face 41. As a result, a circumferential gap 25 is created between the cone
back face 41 and the
backing ring 22.
[0029] The adhesive gasket 90 is disposed in gap 25. The outside diameter of
the adhesive
gasket 90, in one embodiment, is radially inward from the outside diameter of
the cone back face
41 to prevent overlap and adhesion to the bearing seal 52. The adhesive gasket
90, in one
embodiment, may abut the outer cylindrical surface of the annular boss 23.
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[0030] Referring to FIG. 3, the adhesive gasket 90 is depicted in detail. In
one embodiment,
the adhesive gasket 90 comprises a compressible polymeric annular gasket body
92 with an
adhesive 94 (e.g., an acrylic adhesive or epoxy resin) applied to the inboard
and outboard
directed end surfaces.
[0031] The annular gasket body 92, in one embodiment, may comprise any number
of
polymeric foam materials, open or closed cell. In one embodiment, the
compressible annular
gasket body 92 is a closed cell polyethylene material (e.g., Ethafoam (9).
Other types of polymer
foams may also be used, including cross-linked polyethylene and polyurethane
foams depending
upon the tensile strength requirements of the bearing assembly components.
[0032] Because the gasket body 92 is formed from a compressible polymeric
material, in one
embodiment, the thickness of the adhesive gasket 90 may be dimensionally
oversized to ensure
full contact with both the backing ring and the bearing cone. Any voids formed
from the rough
or uneven surfaces between the backing ring and the bearing cone are filled by
the adhesive
gasket as the bearing retaining cap compresses the bearing stack, allowing the
gasket to make
full contact with both the backing ring and the bearing cone.
[0033] A variety of different adhesives 94 may be employed on the adhesive
gasket 90. In
one embodiment, the inward and outward directed surfaces of the gasket body 92
are coated with
an adhesive 94, such as a pressure sensitive adhesive (e.g., an acrylic resin
adhesive). Other
types of adhesives 94 may also be used such as epoxy resins.
[0034] Certain adhesives 94 may require protection from activation (e.g.,
pressure activation)
and protection from contamination. An acrylic resin adhesive applied to the
gasket surfaces may
be protected prior to its application, with a releasable liner 96 (e.g., paper
backing). The
releasable liner 96 may comprise both a release coating (e.g., silicone) (not
shown) and the liner
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(e.g., paper). The releasable liner 96 is removed immediately prior to its
application to the
bearing assembly.
[00351 In one embodiment, the annular shape of the adhesive gasket 90
establishes a
continuous, circumferential boundary between the backing ring 22 and the
bearing cone 40. In
one embodiment, the polymeric materials used in the construction of the
adhesive gasket 90
(both the body 92 and the adhesive 94) are moisture resistant, providing a
moisture resistant
boundary around the outer circumferential joint produced by the abutment of
the annular boss to
the cone back face.
[00361 A number of different procedures may be used in conjunction with the
adhesive
gasket to facilitate the press fit of a bearing assembly onto a shaft with a
bearing press.
Referring to FIG. 4, a typical bearing press 100 for press fitting a bearing
assembly 10 is
illustrated.
[00371 The first step, in one embodiment, of the press fit procedure is to
attach the adhesive
gasket 90 around the annular boss 23 of the backing ring 22. The adhesive
gasket 90 should not
overlap the axially outward directed surface of the annular boss 23 to insure
preload compression
can be maintained after installation on the bearing assembly 10.
[00381 In one embodiment of the process, the bearing assembly 10 and the
backing ring 22
are pressed together to activate the pressure sensitive adhesive on the gasket
90 and affix these
bearing components together. The bearing assembly unit (i.e., bearing assembly
10 and backing
ring 22) may now be placed over a pilot sleeve 130 which is part of the
bearing press 100. The
pilot sleeve 130 holds the bearing assembly 10 by the internal diameter of the
bearing cones 38,
40 and backing ring 22 while the bearing assembly unit is pressed onto the
journal 12.
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[0039] In another embodiment of the press fit process, the bearing assembly 10
and the
backing ring 22 (with the adhesive gasket attached) are separately placed onto
a pilot sleeve 130.
Sufficient pressure is then exerted between the backing ring 22 and the
bearing assembly 10
while on the pilot sleeve 130 to activate the pressure sensitive adhesive and
affix the components
together.
[0040] The bearing press 100 with its pilot sleeve 130 (including the bearing
assembly and
backing ring) is then aligned concentrically with the end of the journal 12.
The journal is now
ready to receive the bearing assembly 10 and backing ring 22. The bearing
press 100 has a press
ram 110 for applying force to the assembly sleeve 120 (another component of
the bearing press
100) which telescopes over the pilot sleeve 130 and pushes the bearing
assembly 10 and the
backing ring 22 off the pilot sleeve and onto the journal 12. The bearing
assembly 10 and the
backing ring 22 are pressed axially inward onto the journal 12 until the
contour surface 27 of the
backing ring 22 is in complementary relation with the fillet 18. The
installation process is then
complete and the bearing press 100 is removed from the journal.
[0041] Typically the press ram 110 of the bearing press 100 is hydraulically
driven. The
press fit developed between the bearing assembly 10 and the journal 12 is
predetermined by the
dimensional tolerances of the axle and the bearing components pressed onto the
axle. To ensure
the integrity of the press fit, certain technical specifications must be met
related to the peak
pressure and force achieved during the press fit operation to ensure a tight
fit. The satisfaction of
these technical specifications is typically verified using measurements taken
from pressure
gauges attached to the bearing press.
[0042] While the invention has been illustrated with respect to several
specific embodiments,
these embodiments are illustrative rather than limiting. Various modifications
and additions
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could be made to each of these embodiments as will be apparent to those
skilled in the art.
Accordingly, the invention should not be limited by the above description or
of the specific
embodiments provided as examples. Rather, the invention should be defined only
by the
following claims.
