Note: Descriptions are shown in the official language in which they were submitted.
~5~fl4
BACICGROUND OF THE INVENTION
This inventi.on relates generally to self-lubricating
.` bearings and bearing liners and more particularly has reference
~o bearing liners containing felted fibers.
No prior art bearing liners have felted fibers in coMbi-
nation with dry resin having no surface bonding to the felted
~ibers, wherein the intertangled relationship of the felted fi.bers
~ithin the resin mechanically entraps the felted fibers in the
rcsin. Consequently, many problems rcmain in the prior art
~levices.
~'';
':
~s~
Prior art bearing liners having polytetrafluoro-
ethylene fibers randomly dispersed in a resin matrix lack
resistance to tensile forces tending to pull the fibers out of
the resin matrix. Another problem which exists in prior art
bearing liners using randomly dispersed or woven polytetra-
fluoroethylene fibers is that such liners do not have a
uniform composition. The characteristics of the liners become
less desirable as the liners wear. Since the polytetrafluoro-
ethylene gathers predominantly on the bearing surface, the
liners become progressively less rich in polytetrafluoro-
ethylene as wear progresses. Still another problem lies in
the prior art process of etching the polytetrafluoroethylene
fibers in bearing liners. Etching increases the bondability
of the fibers but detracts from the desirability of the fibers
as a bearing liner material. A further problem lies in the
limited utility of prior art bearings with polytetrafluoro-
ethylene liners. These bearings are limited to applications
involving heavy loading at low speed.
SUMMARY OF T~E INVENTION
~0 The present invention overcomes many of the problems
which exist in the prior art devices. The present invention
provides, in preferred form, a bearing having a low-friction
bearing liner including felted fibers in combination with
cured resin having no surface bonding to the felted fibers.
The intertangled relationship of the felted fibers within the
resin mechanically entraps the felted fibers in the resin and
prevents tensile forces from pulling the fibers out of the
resin.
Preferably, the felted fibers are felted polytetra-
fluoroethylene fibers. The liner is attached to a bearing
member by bonding the resin to the bearing member. The bonding
process has no adverse effects on the characteristics of the
~S~L7q~
polytetrafluoroethylene ~ibers.
Felting the polytetrafluoroethylene fibers provides
, the liner with a substantially uniform composition. The liner
is rich in polytetrafluoroethylene throughout its thickness.
Liner wear does not diminish the self-lubricating properties
of the bearing liner surface.
Additional fibers having high heat transfer capabil-
ity and high strength characteristics can be included in the
liner to improve its thermal and mechanical properties.
Additionally, fibrous fabric can be felted to the felted
fibers. Sintered polytetrafluoroethylene particles added to
the bearing surface of the liner improve the low-friction
characteristics of the liner. Pressing and heating sinters
particles mechanically worked into the liner.
The heaxing liners are formed by air-drying resin-
impregnated sheets of felted fibrous material. The resin may
be cured in a heated platen press before assembly of the
bearing. The liner is then attached to the bearing by curing
an additional layer of resin applied to the liner to thereby
~0 bond the liner to the bearing.
The bearing is assembled by deforming bearing members
to form an interference fit between the members an~ a bearing
liner disposed therebetween. When liners having uncured
resin are used, parting compound must be applied to one of
the bearing members to prevent the liner from bonding to that
member. The bearing assembly is then baked to cure the
resin and bond the liner to the bearing member to which no
parting compound is applied.
,~.
3L~Si~74g~
Similar liners are disclosed for bushes and bushings.
Methods for attaching these liners are also disclosed.
The bearing liners of the present invention can be
used in a variety of applications. The liners perform
particularly well with light loading at high speed.
Objects of the invention are, therefore, to provide an
improved self-lubricating sheet of material, ~o provide an improved
bearing liner, to provide an improved self-lubricating bearing,
to provide an iMproved method of making self-lubricating sheets of
material and bearing liners, to provide an improved method of
making lined bearings, bushes and bushings, to provide a bearing
liner having a uniform composition, to provide a bearing liner
that is highly resistant to tensile forces terld;ng to pull self-
lubricating fibers out of the liner, and to provide a polytetra-
fluoroethylene bearing liner that is readily bondable to bearing
members.
Another object of the invention is to provide a sheet of
material having felted fibers in combination with dry resin having
no surface bonding to the felted fibers, wherein the intertangled
~lationship of the felted fibers within the resin mechanically
cntraps the felted fibers in the resin.
Still another object is to provide a method for making
b~arings having low-friction surfaces including forming outer bearing
members with inner bearing surfaces and inner bearing members with
outer bearing surfaces, forming bearing liners with low-friction
surfaces including adhesive resin dried to a tack-free s-stage~
coating the bearing surfaces of one of the bearing members with
parting compound, placing the bearing ]iners between the bcaring
~ ... ... _ . . . . .. . .. . . . . .
7~
surfaces of the beariny membe~s, assembling the bcarings, swaging
the assembled bearings to pcovide an interference fit between the
bearing liners and the bearing members, applying resin-curing heat
to the assembled bearings, and curing the resin to thereby bond
the bearing liners to the bearing members to which parting compound
was not applied, the parting compound inhibiting the bond between
the bearing liners and the bearing members to which the parting
compound is applied.
These and other and further objects and features of the
invention are apparent in the disclosure which includes the above
and below specifications and claims and drawings.
.. ~ .. . . . . .. . . ....... . . .
~S47~9~
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 shows a bearing in sectional form produced by
the present method prior to assembly.
FIGURE 2 shows the bearing of FIGURE i, also in sectional
~orm, in its assemhled state.
FIGURE 3 is an enlarged sectional elevation of one embodiment
of the bearing liner of the present invention.
FIGURE 4 is an enlarged sectional elevation of another
embodiment o the bearing liner of the present invention.
FIGURE 5 is an enlarged sectional elevation of still another
embodiment of the bearing liner of the present invention including
fibrous fabric.
FIGURE 6 is an enlarged sectional elevation of still another
embodiment of the bearing liner of the present invention -
including fibrous fabric.
FIGURE 7 is an enlarged sectional elevation of yet another
embodiment of the bearing liner of the present invention including
ibrous fabric.
FIGURE 8 is an enlarged sectional elevation of still another
~O embodiment of tlle bearing liner of the present invention including
sintered particles.
FIGURE 9 is an enlarged sectional elevation of yet another
embodiment of the bearing liner of the present invention including
sintered particles.
` FIGURE 10 shows a bearing, in sect;onal form, in its
assem~led state inc]uding a backing layer.
FIGURE 11 is a perspective view of a bushing having a self-
lubricating liner.
-- 7 --
744
FIGURE 12 is a sectionaL view of the bushings shown in
F IGURE ll .
FIGURE 13 is a perspective view of a bush having a self-
lubricating overlay.
FIGURE 14 is a sectionaL view of the bush shown in FIGURE
~547~a~
DETAILED DESCRIPTION OF THE DRAWINGS
Referring to FIGURE 1, there is shown a typical spherical-
type bearing 10 in an unassembled state. The spherical bearing 10
comprises three parts, including an outer bearing member 12, an
inner bearing rnember 14 and a bearing liner 16. The outer bearing
member 12 is a cylindrical bearing member having a concave inner
bearing surface 18. The inner bearing member 14 is a spherical
bearing member having a convex outer bearing surface 20. The
convex outer bearing surface 20 is curved opposite the concave
inner bearing surface 18. The bearing members 12 and 14 are
formed of any suitable bearing material, preferably a metallic
material.
The inner bearing member 14 is provided with a central
bore 22 through which typically a bolt (not shown) is placed
therethrough for operationally attaching the inner bearing member
14 to an associated machine, element, apparatus, or the like (not
shown). The outer bearing member 12 is typically provided with
; an outer cylindrical surface 24 which generally provides the
assembling surface to which the outer bearing member 12 is
attached to its associated machine, element, apparatus, or the
like (not shown).
To enhance the bearing characteristics of the bearing lo,
a bearing liner 16 is provided between the inner and outer bearing
members 12 and 14 and is typically bonded or otherwise suitably
attached to one of the bearing member 12 and 14. In the preferred
embodiment, the bearing liner 16 is bonded to the concave inner
surface 18 of the outer bearing member 12. It i.s appreciated
that the bearing liner 16 could be bonded to the convex outer
surface 20 of the inner bearing member 14 instead.
_ g _
~5~
In the preferred embodiment, the bearing liner 16 has a
self-lubricating bearing surface 26 that provides omnidirectional
sliding contact between the inner and outer bearing members 12 and
14. The backing surface 28 of the bearing liner 16 is bonded to
the concave inner surface 18 of the outer bearing member 12.
Preferably, the bearing liner 16 has a uniform composition. Such
composition prevents changes in the characteristics of the bearing
sur~ace 26 as tlle bear;ng liner wears.
One erl~bodiment of a bearing liner 16 used in the present
invention is shown in FIGURE 3. The liner 16 includes felted
fibers 30 in combination with synthetic resin 32. Preferably,
the resin 32 impregnates sheets 34 formed of the felted fibers 30.
The felted sheets 34 are prepared by processes well known
in the art. Generally, sheets are prepared by forming a non-
woven batt of the fibers 30, needle punching the batt and heat-
shrinking the resulting product to form a felted sheet of material
34. In an alternate process, non-woven batts of fibers are prcssed
and then heated to form the sheets of felted fibers. The fibers
30 are either lightly felted or thickly fe]ted by methods well
~0 known in the art.
Preferably, the felted fibers 30 are formed of polytetra-
fluoroethylene. Polytetrafluoroethylene is a very slippery material
and, because of this, felted sheets 34 of polytetrafluoroethylene
fibers have excellent self-lubricating properties. It is appreciated
ho~ever, that the sheets 34 may be formed of various other self-
lubricating fibers. Carbon fibers, for example, have been used
satisfactorily in the present invention. In addition, the fibers
30 can include a mixture of self-lubricating fibers and various
other fibers. For example, the polytetrafluoroethy]ene fibers can
-- 10 --
~i9L74~
be mixed with fibers having higher heat transfer capabilities
than polytetrafluoroethylene to improve the overall performance
of the bearing liner 16 at high temperatures. Carbon fibers
have such properties. Alternatively', the polytetrafluoro-
ethylene fibers can be mixed with fibers having greater
strength than polytetrafluoroethylene to improve the overall
strength of the bearing liner 16. Glass', dacron and synthetic
fibers are suitable high strength fibers. In addition', one
or more extender fibers can be added to increase the bulk
of the liner 16 and thereby reduce manufacturing costs.
As mentioned before', the sheets 34 of felted
fibers 30 are impregnated with a suitable resin mate-rial 32.
The resin will typically impregnate substantially the enti~re
sheet 34 of felted fibers 30. By impregnating substantially
all of the felted fibers 30', the completed bearing liner 16
has a substantially uniform composition.
The ratio of fibers 30 to resin 32 affects the
properties of the bearing liner 16. As the amount of resin
increases, the coefficient of friction of the liner 16 increases.
On the other hand, excessive amounts of fibers adversely affect
the strength and wear characteristics of the liner 16. The
completed liner 16 should include at least 25% by weight of
resin. Best results have been achieved with liners 16 having
55% by weight of fibers and 45% by weight of resin. The
weight ratios are determined by weighing the sheet of fibers
before and after it is impregnated with dry resin.
The resin 3~ preferably includes a resin
manufactured by H. B. Fuller', of St. Paul, Minnesota, designated
as their Resiweld* R7119. This vinyl phenolic base resin is
initially in a liquid state but dries to a tack-free B-stage
upon exposure to air at ambient temperature. In the B-stage,
the resin remains active - 11 -
* Trademark for epoxy resins
3L~Sg74~
and can still be polymerized or cured. The liquid resin has aviscosity which enables the resin to flow and thoroughly impregnate
the sheets of felted fibers at ambient conditions. After the
sheet of fibers is fully impregnated, the liquid resin is dried
to a tack-free B-stage. The drying process can be carried out
more quickly if the resin-impregnated sheet is heated in a
circulating air environment.
The resin 32 adds strength to the bearing liner 16 by
mechanically locking the fibers 30 in a resin matrix 32. The
f;bers 30 are formed into felted sheets 34 and, because of this,
the fibers 30 are intertangled in the resin matrix and resist
tellsile forces tending to ~ull the fibers 30 out of the bearing
liner 16. I~hen assembly of the spherical bearing 10 is completed,
the resin 32 is cured in a manner which will be explained ]ater.
However, when polytetrafluoroethylene fibers 30 are used in the
bearing liner 16 there is no chemical bonding between the fibers
30 and the resin 32. This is due to the reluctance of polytetra-
fluoroethylene materials to bond to other materials.
The bearing liner 16 in the present invention has numerous
additional embodiments.
In the embodiment shown in FIGUR~ 4, the bearing liner 36
has a first sheet of felted fibers 40 felted to a second sheet of
felted fibers 44. The fibers 38 in the first sheet 40 and the
fibers 42 in the second sheet 44 are formed of diverse materials.
Any of the fiber materials or mixtures of fiber materials
mentioned above are suitable. ~owever,
at least one of the sheets 40 and 44 is formed of felted polytetra-
fluoroe~hylene fibers. Preferably, the surface of the bearing liner
- 12 -
._ . . .. ~ , ~ . ...
~L~S~4
36 which acts as the self-lubricating bearing surface is
formed of polytetra~luoroethylene fibers.
FIGURES 5-7 illustrate an alternate embodimen-t of
the bearing liner wherein sheets of fibrous fabric are felted
to sheets of felted fibers.
The bearing liner 48, shown in FIGURE 5, includes a
sheet 50 of felted fibers 52 felted to a sheet 54 of fibrous
fabric 56. The composite sheet is impregnated with resin 58.
The sheet 54 of fibrous fabric 56 can be woven fibrous fabric,
knitted fibrous fabric or non-woven fibrous fabric. The
felted fibers 52 and the fabric fibers 56 are formed of self-
lubricating material, preferably polytetrafluoroethylene.
In the embodiment shown in FIGURE 6, the liner 60
includes a sheet 62 of fibrous fabric 64 positioned between
sheets 66 and 68 of felted fibers 70 and 72 and felted thereto.
Resin 74 impregnates the entire composite sheet. The liner 76,
shown in FIGURE 7, includes a sheet 78 of felted fibers 80
positioned between sheets 82 and 84 of fibrous fabric 86 and
88 and felted thereto. Resin 90 impregnates the entire
composite sheet. In both embodiments, the felted fibers and
fabric fibers are formed of self-lubricating material,
preferably polytetrafluoroethylene.
The bearing liner 92 shown in FIGURE 8 includes
sintered particles 94 dispersed in the portion of a sheet 96
of felted fibers 98 adjacent the bearing surface 100. Resin
102 impregnates the entire sheet 96 and mechanically entraps
the felted fibers 98 and the sintered particles 94 in a resin
matrix. The sintered particles 94 are in flaked form ox
powdered form. Preferably, the sintered particles 94 are
sintered polytetrafluoroethylene powder particles. The felted
fibers 98 are fibers formed of self-lubricating material,
preferably polytetrafluoroethylene.
- 13 -
X
~S4~4
Alternately, any of the fiber materials or mixtures of
fiber materials mentioned in the discussion of the liner 16 shown
in FIGURE 3 are suitable for use in the liners 48, 60 and 76
shown in FIGURES 5-7.
The properties and functions of the resin used in the
liners shown in FIGURES 4-7 are similar to the prope.rties of the
resin used in the liner shown in FIGURE 3. Furthermore, the ratio
of fibers to resin and the uniformity of liner composition
discussed in reference to the liner shown in FIGURE 3 are equally
applicable to the liners shown in FIGURES 4-7.
The bearing liner 104 shown in FIGURE 9 is a variation of
the lincr 92 shown in FIGURE 8. Sintered particles 106 impregnate
the entire sheet 108 of felted fibers 110. No rcsin is used. The
sintered particles 106 and the felted fibers 110 are formed of
self-lubricating material, preferably polytetrafluoroethylene.
Alternately, any of the fiber materials or mixtures of fiber
materials mentioned in the discussion of the liner ]6 shown in
FIGURE 3 are suitable materials for the felted fibers. The
sintered polytetrafluoroethylene parti.cles 106 have no chcmical
bollding to the felted fibers 110. The felted fibers 110 are
intcrtangled within the sintered particle 106 matrix and are
thereby mechanically locked within the matrix. The bearing liner
104 is very ~lcxible but has sufficient strength to resist tensile
forces tending to pull the fibers 110 out of the liner 104. The
li.ner is parti.cularly usefuL i.n low load appli.cati.ons and for
vibration iso].ation. Tile
- 14 -
~3L5~4~
particles 106 are impregnated into the sheet 108 of felted fibers
110 by combining the particles 106 with the fibers 110 on one side
of the sheet 108 and then working the particles 106 into the
sheet 108. Alternately, the particles 106 are
combined with the fibers 110 on two opposite sides of the sheet
108 and then are worked into the sheet 108 from the opposite sides
simultaneously.
The sintered self-lubricating particles 94 and 106 in the
bearing liners 102 and 104 shown in FIGURES 8 and 9 tend to
decrease the overall coefficient of friction of the bearing liners
92 and 104. When the bearing liner 92 shown in FIGURE 8 is used
in the present invention, the resin 102 is cured during assembly
of the spherical bearing 10. However, when the felted fibers 98
are formed of polytetrafluoroethylene material, the curing process
does not form a chemical bond between the fibers 98 and the resin
102. The fibers 98 are mechanically locked in the resin matrix
in the manner described with respect to the bearing liner 16 shown
I in FIGURE 3.
! The bearing liners shown in FIGURES 3-9 are used in bearings
in the manner shown in FIGURES 1 and 2. In one embodiment of the
in~ention, the bearing liners are formed with uncured resin which
is bondable to the bearing members when cured. The llner is
attached to the bearing memher by placing the liner in contact
with the member and curing the resin. The process is more
fully described later. Preferably, the
bearing members are formed of a metallic material and the resin is
a resin bondable to metal. Alternatively, the bearing liners are
formed of a first resin which bonds to a second resin applied to
the bearing lirler when cured. The second resin is a resin bondable
4g
to the bearing members when cured. The process for attaching the
liner to the bearing member is similar to the process just mentioned
Again, preferably the bearing members are formed of a metallic
material and the resin is a resin bondable to metal. In still
another embodiment of the invention, the resin in the bearing
liners is cured before the bearing is assembled. The bearing
liner is attached to the bearing member by either of two methods.
First, a layer of adhesive material, for example, resin, is applied
to the backing surface of the bearing liner. The adhesive secures
the bearing liner to the desired bearing member. In the second
method, a backing layer is connected to the backing surface of the
bearing liner by any appropriate means. Compositions of backing
layers and methods for attaching backing layers to bearing liners
are well known in the art. A layer of adhesive material, for
example,.resin, is then applied to the surface of the backing layer
adjacent the bearing member to which the bearing liner is to be
attached. Pre~erably, the bearing members are formed of a metallic
material and the resin is a resin bondable to metal. The first
method is described in greater detail later. Both methods
preferably use an adhesive resin identical to the resin included
in the bearing liner. In both methods, the liner is attached to
the bearing member by placing the adhesive surface in contact
with the member and curing the resin.
If the latter method is used with the bearing liner
shown in FIGURE 5, the best results are achieved if the backing
layer is connected to the sheet 50 of felted fibers 52
since the felted fibers can be bonded to the backing layer more
easily than the fibrous fabric.
- 16 -
1~4744
An assembled bearing having a bearing liner 112 with a
backing member 114 Is shown in FIGURE 10. ~s previously des-
cribed, the bearing liner is formed into sheets having a substan-
tially uniform composition. The bearing surface of the bearing
liner 112 remains uniform despite liner wear caused by rotation
of the inner bearing member 14 across the bearing liner 112.
FIGURES 11-14 show the bearing liners of the present
invention used with bushes and bushings.
A bushing 116 having an inner cylindrical surface 118 is
shown in FIGURES 11 and 12. A bushing liner 120 connected to the
inner surface 118 of the bushing 116 has a low~friction bushing
surface 122 remote from the inner surface 118 of the bushing 116.
FIGURES 13 and 14 show a cylindrical bush 124 having an
outer cylindrical bush surface 126. A bush liner 128 attached
to the outer surface 126 of the bush 124 provides a low-friction
bush surface 130 remote from the outer surface 126 of the bush 124.
It is understood that all of the el~bodiments of the bcaring
liners of the present invent:ion shown in FIGUR~S 3-9 can be used
with a bush or a bushing in the manner shown in FIG~RES 11-14.
METI-IOD
The bearing liner shown in FIGURE 3 is formed by applying
; liquid adhesive resin to a sheet of fibrous material.
Preferably, the material is formed of poly~etrafluoroethylene
fibers. The resin is preferably applied to opposite sides of the
sheet. Alternatively, the resin i5 applied to only one side of
the sheet.
thoroughly
The material is/impregnated with the resin appLied to the
sl~eet either by capillary action or by calendaring. Both methods
5~4
of impregnation are well-known in the art. When the resin is
applied to both sides of the sheet of fibers yreater uniformity
of composition and eveness and thoroughness of impregnation results.
The resin is selected so that impregnation can take place at
ambient conditions. Impregnation is further enhanced by any of
the resin curing processes described below. Once the resin is
dried, it is very difficult to add additional resin by capillary
action or by calendaring. Consequently, the proper amount of
resin should be applied to the liner on the first coating.
After impregnation, the resin is dried to a tack-free
B-stage. In the preferred method, the resin is dried by exposing
the resin-impregnated material to an ambient environment.
Alternatively, the resin is dried by heating the resin-impregnated
` material in a circulating air environment.
Generally, the method set out above can be used in making
all of the various embodiments of the bearing liner of the present
invention shown in FIGURES 3-8.
As previously mentioned, uncured resin in a bearing liner
can be cured either during assembly of the bearing or prior to
assembly of the bearing.
Prior to assembly, the resin in the bearing liner shown
in FIGURES 3-8 is cured by heating and pressing the resin-
impregnated material. Initially, polytetrafluoroethylene slip
sheets are positioned between the resin-impregnated material
and the working surfaces of platen presses. The slip sheets
prevent the material from bonding to the platen presses when the
resin is cured. The material is then pressed and
heated by the platen presses. The
- 18 -
S~L7~
required temperature and pressure for curing depends on the resin
used. With the specific resin mentioned above, a temperature of
about 350 F. and a pressure of about 400 to 800 psi. is required
to cure the resin. This temperature and pressure is maintained
for about 30 minutes. The pressing and heating of the material
need not commence in any particular se~uence. In one process,
- the platen presses are heated before pressing the material. In
an alternative - process, the presses apply pressure to the
material and are heated while pressing. However, the prescribed
temperature and pressure should co-exist for the prescribed duration.
If desired, a plurality of bearing liners can be cured
simultaneously. A stack of alternating ploytetrafluoroethylene
slip sheets and sheets of resin-impregnated material are placed
between the working surfaces of platen presses. Slip sheets are
placed adjacent the working surfaces to prevent bonding to the
platen presses. The stack is heated and pressed as described above.
The slip sheets positioned between the sheets of material prevent
the sheets of material from bonding to each other.
The bearing shown in FIGURE 9 is formed by applying loose,
particulate material to the surface of a sheet of felted fibrous
material. The particles are then mechanically worked into the
material by any known process. Preferably, the particles are
worked into substantially all the material, thereby forming a
bearing liner having a uniform composition. The particles are
then sintered by pressing the particle-impregnatec1 material in a
heated platen press.
The bearing liner shown in FIGURE 8 is formed by a process
similar to the process used to form the bearing liner shown in
FIGURE 9. However, the particles are worked into only a portion
of the material when forming the liner shown in FIGURE 8. The
- 19 ~
~4'7~4
resin is com~ined with the particle-impregnated material after
sintering and cured in the manner already described.
The process of forming a completed bearing is shown
in Figures 1 and 2. As will become apparent, two separate
processes are available. Both processes can use any of the
various bearing liner embodiments shown in Figures 3-8.
One process is needed to assemble a bearing
having a bearing liner with resin which is cured during
assembly of the complete bearing. One advantage o~ not curing
1~ the liner before assembly is that the liner remains flexible
and therefore can be easily manipulated to fit complex bearing
s'hapes. Initially, inner and outer bearing members 12 and 14
are formed. A parting compound is applied to the bearing
! member to which the bearing liner 16 is not to be bonded.
As is known', a parting compound inhibits and prevents the
resin from bonding to the surface to which the compound is
applied. Generally, the parting compound is a dry lubricant
of the Teflon* variety. Preferably', the parting compound is
applied to the outer surface 20 of the inner bearing member 14.
A bearing liner having uncured resin dried to a tack-free B-stage
is cut to dimensions compatible with the dimensions of the
surface of the bearing member to which the liner is to be
attached. The liner is then coiled into a cylindrical shape
and positioned between the outer bearing member 12 and the inner
bearing member 14 as shown in Figure 1. The outer beaxing member
12 and/or the inner bearing member 14 are suitably deformed to
bring the various bearing parts into an interference fit
relationship. In the assembled state, the bearing 10 appears
as shown in Figure 2.
3~ Typically', the outer bearing member 12 is contracted
and compressed about the inner bearing member 14 by swaging.
~ 20 -
* A trademark of E.I. Dupont de Nemours for tetrafluoroethylene
resins.
~3L5i4744
Alternatively, the inner member 14 could be expanded within the
outer bearing member 12. ~dditionally, both the inner bearing
member 14 and the outer bearing member 12 could be deformed to
form an assembled bearing 10 as shown in F~GURE 2.
The assembled bearing with its respective parts in an
interference fit relationship is then placed in a suitable oven
or heating apparatus to bake the bearings and, more particularly,
the liner disposed therein to cure the resin. Typically, the
tempera~ure would be elevated in the oven or heating apparatus
to a level approximately 350 - 375 F., and this level of heat
would be maintained for a period of rom one to three hours.
After this heating period has been completed, the resin in the
bearing liner 16 will be cured and will form the bond between the
backing surface 2~ of the liner 16 and the inner surface 18 of
the outer bearing member 12. The parting compound which was
applied to the convex outer surface 20 of the inner bearing
member 14 will prevent the resin from bonding to said surface 20,
~hereby allowing the inner bearing member 14 to be rotatably
supported within the bearing liner 16.
~0 The resin becomes fluid during the curing process. This
enàbles the liner 16 to accurately conform to the shape of the
~onvex outer surface 20 of the inner bearing member
i 1~. Some small degree of shrinkage of the liner 16 may be
encountered during the baking or heating of the bearing which
will tend to reduce the interference fit between the inner
bearing member 14 and the ]iner 16. The desired bearing tolerance
between the inner bearing member 14 and the liner 16 can be
achievcd by loosening the inner member 14 with respect to the
liner 16. Such loosening might include impacting and~or pressure
roLling the assembled bearing.
- 21 -
3L~5~a~4~L
The bond between the bearing liner and the bearing
member is improved by chemically cleaning the bearing surface
of the bearing member before placing the bearing liner between
the bearing members. The cleaning process involves sand blasting
or pickling the bearing surface followed by washing, rinsing
and drying. To further improve bonding,
ehe cleaned bearing surface is immediately coated with liquid
adhesive resin. The resin is dried to a tack-free B-stage before
placing the bearing liner 16 between the bearing members 12 and
14. Preferably, the resin is identical to the resin included in
the bearing liner. Additionally, the backing surface 28 of the
bearing liner 16 may be coated with a similar resin dried to a
tack-free B-stage.
Bonding is also improved by resin-coating a bearing
surface that has not been cleaned or by resin-coating the backing
surface of the liner without coating or cleaning the bearing
surface.
The second method of assembling the bearing is used when
the bearing liner contains resin which is cured prior to assembly
of the bearing. The inner and outer bearing members 12 and 14
are formed as shown in FIGURE 1 in the manner previousLy described.
In addition, a bearing liner having cured resin is forrlled in the
manner previously described. The bearing liner is cut to
dimensions compatible with the dimensions of the surface of the
bearing member to which the liner is to be attached. The said
surface an~ the adjacent surface of the liner are then coated
with a liquid adhesive resin that is subsequently dried to a
tacX-frce B-stage. Preferably the bearirlg liner 16 is
attached to the inner surface 18 of the outer bearing member 12.
- 22 -
~S47~:
The bearing liner is then coiled into a cylindrical shape and
placed between the ~earing members as shown in FIGURE 1. The
outer bearing member 12 and/or the inner bearing mcmber 14 are
then suitably deformed in the manner described above to bring
the various bearing parts into interference fit relation-
ship. The assembled bearing is then placed in a heating apparatus
to bake the bearing assembly and, more particularly, the coating
of resin applied to the bearing member to cure the resin. After
the heating period has been completed, the resin will be cured and
will form the bond between the liner and the inner surface 18 of
the bearing member 12. The bearing assembly is then loosened in
the manner previously described.
The bond betwcen the bearing liner 16 and the inner
surface 18 of the bearing member12 is improved by coating the
backing surface 28 of the bearing liner 16 with liquid resin
subsequently dried to a tack-free B-stage before placing the
bearing liner 16 between the bearing members 12 and 14.
Different processes are used to make the bush and
bushings shown in FlGURES 11-14.
In forming the bushing, initially a bushing member 116
~ith an inner cylindrical surface 118 is formed. A bushing
liner 120 with a low friction surface 122 is formed and includes
adhesive resin dried to a tack-free B-stage. A parting compound
is applied to the outer cylindrical surface of a mandrel. The
parting compound prevents t}le resin in the liner 120 from bonding
to the mandrel. Thercafter, the liner 120 is placed between the
it~ner surface 118 of the bushing member 116 and the outer surface
of the mandrel. The bushing mernber 116 is suitably deformed to
l~ring the bushing mel~er 116, the liner 120 and the mandrel into
~i474g~
an interference fit relationship. The deforming processes men-
tioned above are adequate in this appLication. The assembly is
then placed in a suitable heatin~ apparatus to bake the liner to
cure the resin. After this heating process has been completedi
the resin will be cured and will form the bond between the liner
and the inner surface 118 of the bushing 116. The parting com-
pound which was applied to the mandrel will prevent the resin
from bonding to the mandrel thereby allowing the mandrel to be
'I withdrawn from the completed bushing.
The method for making the bushes shown in FIGURES 13 and
14 is similar to the method ~or making the bushings shown-in
FIGURES 11-12. The inner cylindrical surface of an arbor is
coated with parting compound. The bush overlay 128 is positioned
between the inner surface of the arbor and the outer surface 126
of the bush 124. The bush 124 is then deformed to form an
I interference fit between the bush 124, the overlay 128 and the
'i arbor. The assembly is then baked to cure the resin in the over-
lay 128 and bond the overlay to the outer surface 126 of the
bush 124. The completed lined bush is then withdrawn from the
arbor.
Any of the various liners shown in FIGURES 3-8 can be
used as bushing liners and bush overlays.
While the invention has been described with reference to
a specific embodiment, the exact nature and scope of the invention
is defined in the following claims.
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