U.S. patent application number 10/376419 was filed with the patent office on 2003-09-25 for low friction sleeve bearing.
This patent application is currently assigned to Minebea Co., Ltd.. Invention is credited to Akiyama, Motoharu, Hokkirigawa, Kazuo, Kawamura, Morinobu.
Application Number | 20030179963 10/376419 |
Document ID | / |
Family ID | 27767965 |
Filed Date | 2003-09-25 |
United States Patent
Application |
20030179963 |
Kind Code |
A1 |
Hokkirigawa, Kazuo ; et
al. |
September 25, 2003 |
Low friction sleeve bearing
Abstract
A sleeve bearing for use in water, the sleeve bearing having a
shaft and a sleeve. The sleeve or the shaft is made of a synthetic
resin composition obtained by uniformly dispersing fine powder of
RBC or CRBC in a resin. The sleeve bearing having a low coefficient
of friction in water.
Inventors: |
Hokkirigawa, Kazuo;
(Sendai-Shi, JP) ; Akiyama, Motoharu; (Nagano-Ken,
JP) ; Kawamura, Morinobu; (Nagano-Ken, JP) |
Correspondence
Address: |
SCHULTE ROTH & ZABEL LLP
ATTN: JOEL E. LUTZKER
919 THIRD AVENUE
NEW YORK
NY
10022
US
|
Assignee: |
Minebea Co., Ltd.
Nagano-Ken
JP
|
Family ID: |
27767965 |
Appl. No.: |
10/376419 |
Filed: |
February 28, 2003 |
Current U.S.
Class: |
384/97 |
Current CPC
Class: |
Y10S 384/907 20130101;
F16C 33/201 20130101; C08K 3/04 20130101; F16C 17/14 20130101; F16C
33/043 20130101 |
Class at
Publication: |
384/97 |
International
Class: |
F16C 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2002 |
JP |
2002-055307 |
Mar 1, 2002 |
JP |
2002-055308 |
Mar 7, 2002 |
JP |
2002-062412 |
Mar 7, 2002 |
JP |
2002-062406 |
Jun 17, 2002 |
JP |
2002-176436 |
Sep 18, 2002 |
JP |
2002-272147 |
Claims
We claim:
1. A sleeve bearing for use in water comprising: a shaft; and a
sleeve, wherein at least a portion of the sleeve or the shaft is
made of a synthetic resin composition obtained by uniformly
dispersing a powder of RBC or CRBC in a resin.
2. The sleeve bearing of claim 1 further comprising: grooves of a
spiral form made on the inner face of the sleeve or external
surface of the shaft.
3. The sleeve bearing of claim 1, wherein the synthetic resin
composition has a ratio by mass of the powder of RBC or CRBC to the
resin of 30 to 90:70 to 10.
4. The sleeve bearing of claim 3, wherein the resin is made of one
or more members of a group consisting of nylon 66, nylon 6, nylon
11, nylon 12, poly acetal, poly butylenes terephthalate, poly
ethylene terephthalate, poly propylene, poly ethylene, and poly
phenylene sulfide.
5. The sleeve bearing of claim 4, wherein the average particle
diameter of the powder of RBC or CRBC is 300 .mu.m or less.
6. The sleeve bearing of claim 5, wherein the average particle
diameter of the powder of RBC or CRBC is 10 to 50 .mu.m.
7. The sleeve bearing of claim 1 wherein the shaft is made of
rust-resistant steel series metal.
8. The sleeve bearing of claim 1, wherein the shaft is made of the
synthetic resin composition having a ratio by mass of the powder of
RBC or CRBC to the resin of 30 to 90:70 to 10.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This application claims priority based on the following
Japanese patent applications: 2002-055307, filed Mar. 1, 2002;
2002-055308, filed Mar. 1, 2002; 2002-062412, filed Mar. 7, 2002;
2002-062406, filed Mar. 7, 2002; -2002-176436, filed Jun. 17, 2002;
and 2002-272147, filed Sep. 18, 2002.
[0003] The present invention relates to a sleeve bearing for use in
water that has a low coefficient of friction in water. More
particularly the present invention relates to a sleeve bearing for
use in water which utilizes a synthetic resin composition obtained
by mixing RBC or CRBC in a form of fine powder of an average
particle diameter of 300 .mu.m or less and a resin.
[0004] 2. Description of the Related Art
[0005] A conventional sleeve bearing for use in water is made from
metal and is provided with a shield to prevent water from getting
into the sleeve bearing. Some conventional sleeve bearings are made
using commercially available PPS resin made by Idemitsu Sekiyu
Kagaku K., K. Co., Ltd. These conventional bearings do not provide
satisfactory wear characteristics. It is an object of this
invention to provide a sleeve bearing with improved wear
characteristics that does not require a shield when used in fluid,
for example, when used in a mixture of water and ethylene
glycol.
[0006] The objects are achieved by using rice bran--an
environmentally friendly ubiquitous raw material. Every year, the
total production of rice bran in the world is approximately thirty
three million tons of which Japan produces about 900,000 tons The
present invention uses a material made by improving upon a
materials described in an article by Mr. Kazuo Horikirigawa (Kinou
Zairyou (Functional Materials), May 1997 issue, Vol. 17, No. 5, pp
24 to 28). Mr. Kazuo Horikirigawa's article discloses a porous
carbon material made by using rice bran and called "RB ceramic"
(hereinafter referred to as "RBC"). RBC is a carbon material
obtained by mixing and kneading defatted rice bran and a
thermosetting resin, and then by molding the mixture and sintering
it in an inert gas atmosphere after drying the compact. Any
thermosetting resin including a phenol resin, a diaryl phthalate
resin, an unsaturated polyester resin, an epoxy resin, a polyamide
resin, or a triazine resin may be used. Phenol resin is the
preferred material. The mixing ratio between defatted rice bran and
the thermosetting resin is 50 to 90:50 to 10 by mass, 75:25 being
the preferred ratio. Sintering is done at 700.degree. C. to
1000.degree. C. for about 40 minutes to 120 minutes using, for
example, a rotary kiln.
[0007] CRB ceramic (hereinafter referred to as "CRBC") is a black
colored porous ceramic obtained by further improving RBC as
follows: after mixing and kneading defatted rice bran obtained from
rice bran and a thermosetting resin, and then preliminarily
sintering the mixture at a temperature of 700.degree. C. to
1000.degree. C. in an inert gas atmosphere, it is pulverized to
about 100 mesh or less, thereby preparing carbonized powder. Next,
the carbonized powder and a thermosetting resin are mixed and
kneaded, and after molding it under pressure of 20 Mpa to 30 Mpa,
the compact is again heat treated at a temperature of 500.degree.
C. to 1100.degree. C. in an inert gas atmosphere to obtain
CRBC.
[0008] RBC and CRBC have the following excellent
characteristics:
[0009] High hardness.
[0010] The surface of each particle is irregular.
[0011] Extremely small coefficient of thermal expansion.
[0012] The textural constitution is porous.
[0013] Conducts electricity.
[0014] The specific gravity is low and it is light in weight.
[0015] Extremely small coefficient of friction.
[0016] Excellent anti-wearing property.
[0017] As the raw material is rice bran, its adverse effects on the
earth's environment are minor, and it leads to the resource
saving.
SUMMARY OF THE INVENTION
[0018] The shortcomings of the prior art are overcome by using a
synthetic resin composition obtained by mixing the RBC or CRBC in
form of a fine powder of an average particle diameter of 300 .mu.m
or less, preferably 10 to 100 .mu.m, more preferably 10 to 50
.mu.m, and a resin. The synthetic resin composition displays
specific desirable sliding motion characteristics. In particular a
synthetic resin composition obtained by uniformly dispersing a fine
powder of RBC or CRBC, especially at a ratio by mass of fine powder
of RBC or CRBC : resin, of 30 to 90:70 to 10 displays surprisingly
good wear characteristics with a anti-rust property in water,
alcohol, ethylene glycol and a mixture thereof.
[0019] The typical process for the production of the synthetic
resin composition for making the sleeve bearing for use in fluid
includes kneading with a resin the fine powder of RBC or CRBC at a
temperature in the neighborhood of the melting point of the
synthetic resin, and thereby uniformly dispersing the fine powder
of RBC or CRBC in the resin. RBC and CRBC can also be made from
materials other than rice bran that can be a source of carbon. One
example of such material is bran of another grain such as oat.
Hence, as used herein, the terms RBC and CRBC are not limited to
materials made from rice bran.
[0020] Further features and advantages will appear more clearly on
a reading of the detailed description, which is given below by way
of example only and with reference to the accompanying drawings
wherein corresponding reference characters on different drawings
indicate corresponding parts.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a schematic drawing of a sleeve bearing.
[0022] FIG. 2 is an application example of the sleeve bearing.
[0023] FIG. 3 is one example of a shaft of a sleeve bearing.
[0024] FIG. 4 is one example of a sleeve bearing in which a spiral
groove is provided on the shaft thereof.
DETAILED DESCRIPTION
[0025] FIG. 1 shows a sleeve bearing. The sleeve bearing consists
of a shaft 1 and a sleeve 2. A synthetic resin composition obtained
by uniformly dispersing fine powder of RBC or CRBC in a resin is
molded, to make shaft 1 or sleeve 2. Generally, shaft 1 is made of
an alloy of a stainless steel family. If a hard shaft 1 is
required, quenching is carried out. As shown in FIG. 3, if
necessary, it is permissible to press a hard anti-rusting alloy 3
in portion of shaft 1. Non limiting examples of steel series metal
that may be used for making shaft 1 or sleeve 2 are stainless steel
type alloy of iron, nickel, chrome, and molybdenum. Any alloy, as
long as it is hard and difficult to rust, can be used. Furthermore,
it is also permissible to make a shaft with the above-mentioned
synthetic resin composition.
[0026] The RBC or CRBC used has an average particle diameter of 300
.mu.m or less. Average particle diameter of 10 to 100 .mu.m, more
preferably 10 to 50 .mu.m, allows a surface condition of a good
frictional coefficient to be formed, and is appropriate as a
material for a sleeve bearing for sliding motion in water.
[0027] Resins such as, for example, polyamide, polyester, and poly
olefin can be used with RBC or CRBC to obtain the synthetic resin
composition. Thermoplastic resins such as nylon 66 (poly
hexa-methylene adipamide), nylon 6 (poly capramide), nylon 11 (poly
undecane amide), nylon 12, poly acetal, poly butylenes
terephthalate, poly ethylene terephthalate, poly propylene, poly
ethylene, and poly phenylene sulfide can also be used with RBC or
CRBC to obtain the synthetic resin composition, nylon 66 being
preferred. These thermoplastic resins can be used alone or a
mixture of two or more may be used. Thermosetting resin alone or in
combination with other resins can be used with RBC or CRBC to
obtain the synthetic resin composition. Non-limiting examples of
such thermosetting resins are phenolc resin, diaryl phthalate
resin, an unsaturated polyester resin, an epoxy resin, a polyamide
resin, or a triazine resin. RBC can also be made from materials
other than rice bran that can be source of carbon. One example of
such material is bran of another grain such as oat. The ratio by
mass of fine powder of RBC or CRBC to resin is 30 to 90:70 to 10.
If the amount of a resin or a combination of resins exceeds 70% by
mass, the low frictional characteristics can not be achieved, on
the other hand, if a resin or a combination of resins is 10% by
mass or less, the molding becomes difficult.
[0028] The molding is in general done by extrusion molding or
injection molding. The preferred temperature of the mold die is on
a slightly lower side between the glass transition point and the
melting point of the resin. Furthermore, good frictional property
can be obtained by gradual cooling of the mold die.
[0029] The following examples explain the details of the present
invention.
EXAMPLE 1
Manufacturing Example of RBC Fine Powder
[0030] 750 grams of defatted rice bran and 250 grams of a phenol
resin in liquid form (Resol) were mixed and kneaded while heating
them at a temperature of 50.degree. C. to 60.degree. C. A uniform
mixture having plasticity was obtained. The mixture was baked for
100 minutes at a temperature of 900.degree. C. in a nitrogen
atmosphere in a rotary kiln, and the carbonated baked product thus
obtained was pulverized in a pulverizing machine, followed by
sieving with a sieve of 150 mesh, and thus fine powder of RBC
having an average particle diameter of 140 to 160 .mu.m was
obtained.
[0031] Example of Preparation 1 of a Composition of RBC Fine Powder
and a Resin
[0032] While heating at a temperature of 240.degree. C. to
290.degree. C., 500 grams of the RBC fine powder thus obtained and
500 grams of nylon 66 powder were mixed and kneaded. Thus a uniform
plastic mixture having 50% by mass of the RBC fine powder was
obtained.
[0033] Preparation of a Sleeve Bearing
[0034] The synthetic resin composition obtained by melting and
mixing the RBC fine powder and nylon 66 was injection molded,
thereby preparing a sleeve of 22 mm in outer diameter, 8 mm in
inner diameter, and 120 mm in length. A shaft of 7.95 mm in outer
diameter and 200 mm in length made of SUS 303 stainless alloy was
inserted into the molded sleeve, preparing a sleeve bearing as
shown in FIG. 1.
EXAMPLE 2
[0035] By using the method described in Example 1, RBC fine powder
of an average particle diameter of 140 to 160 .mu.m was
obtained.
[0036] Example of Preparation 2 of a Composition of RBC Fine Powder
and a Resin
[0037] While heating at a temperature of 240.degree. C. to
290.degree. C. 700 grams of the RBC fine powder thus obtained and
300 grams of nylon 66 powder were mixed and kneaded. Thus a uniform
plastic mixture having 70% by mass of the RBC fine powder was
obtained.
[0038] Preparation of a Sleeve Bearing
[0039] The synthetic resin composition obtained by melting and
mixing the RBC fine powder and nylon 66 was injection molded,
thereby preparing a sleeve of 22 mm in outer diameter, 8 mm in
inner diameter, and 20 mm in length. A shaft of 7.95 mm in outer
diameter and 200 mm in length made of SUS 304 stainless alloy was
inserted into the molded sleeve, preparing a sleeve bearing as
shown in FIG. 2.
EXAMPLE 3
Manufacturing Example 3 of RBC Fine Powder
[0040] 750 grams of defatted rice bran and 250 grams of a phenol
resin in a liquid form (Resol) were mixed and kneaded while heating
them at a temperature of 50.degree. C. to 60.degree. C. A uniform
mixture having plasticity was obtained. The mixture was baked for
100 minutes at a temperature of 1000.degree. C. in a nitrogen
atmosphere in a rotary kiln, and the carbonated baked product thus
obtained was pulverized in a pulverizing machine, followed by
sieving with a sieve of 400 mesh, and thus fine powder of RBC
having an average particle diameter of 40 to 50 .mu.m was
obtained.
[0041] Example of Preparation 3 of a Composition of RBC Fine Powder
and a Resin
[0042] While heating at a temperature of 240.degree. C. to
290.degree. C., 700 grams of the RBC fine powder thus obtained and
300 grams of nylon 66 powder were mixed and kneaded. Thus a uniform
plastic mixture having 70% by mass of the RBC fine powder was
obtained.
[0043] Preparation of a Sleeve Bearing
[0044] The synthetic resin composition obtained by melting and
mixing the RBC fine powder and nylon 66 was injection molded,
thereby preparing a sleeve of 22 mm in outer diameter, 8 mm in
inner diameter, and 120 mm in length. A shaft of 7.95 mm in outer
diameter and 200 mm in length made of SUS bearing steel was
inserted into the molded sleeve, preparing a sleeve bearing as
shown in FIG. 1.
EXAMPLE 4
Manufacturing Example of CRBC Fine Powder
[0045] 750 grams of defatted rice bran and 250 grams of a phenol
resin in a liquid form (Resol) were mixed and kneaded while heating
them at a temperature of 50.degree. C. to 60.degree. C. A uniform
mixture having plasticity was obtained. The mixture was baked for
60 minutes at a temperature of 900.degree. C. in a nitrogen
atmosphere in a rotary kiln. And the carbonated baked product thus
obtained was pulverized in a pulverizing machine, followed by
sieving with a sieve of 200 mesh, and thus fine powder of RBC
having an average particle diameter of 100 to 120 .mu.m was
obtained.
[0046] While heating at a temperature of 100.degree. C. to
150.degree. C., 750 grams of the RBC fine powder thus obtained and
500 grams of a phenol resin in a solid form (Resol) were mixed and
kneaded. Thus a uniform mixture having plasticity was obtained.
Then, the plastic material was molded under pressure into a sphere
of about 1 cm in diameter under a pressure of 22 Mpa. The
temperature of the mold die was 150.degree. C. The molded product
was taken out from the mold die and placed in a kiln, the
temperature of the molded product was raised to 500.degree. C. in a
nitrogen atmosphere at a rate of 1.degree. C. per minute, and it
was kept at 500.degree. C. for 60 minutes, and then sintered at
900.degree. C. for about 120 minutes. Then, the temperature was
lowered to 500.degree. C. at a rate of 2 to 3.degree. C. per
minute, and after reaching 500.degree. C. or lower, it was cooled
naturally while leaving it undisturbed. The CRBC molded product
thus obtained was pulverized in a pulverizing machine, followed by
sieving with a sieve of 500 mesh to obtain CRBC fine powder having
an average particle diameter of 20 to 30 .mu.m.
[0047] Example of Preparation of a Composition of CRBC Fine Powder
and a Resin
[0048] While heating at a temperature of 240.degree. C. to
290.degree. C., 500 grams of the CRBC fine powder thus obtained and
500 grams of nylon 66 powder they were mixed and kneaded. Thus a
uniform plastic mixture having 50% by mass of the CRBC fine powder
was obtained.
[0049] Preparation of a Sleeve Bearing
[0050] The synthetic resin composition obtained by melting and
mixing the CRBC fine powder and nylon 66 was injection molded into
a sleeve of 22 mm in outer diameter, 8 mm in inner diameter, and 20
mm in length. A 200 mm long shaft is made by pressing two
cylindrical members of 7.95 mm in outer diameter, 5.00 in inner
diameter and 20 mm in length and made of SUS 304 stainless alloy
into both ends of the shaft. The shaft was inserted into the molded
sleeves, preparing a sleeve bearing as shown in FIG. 3.
[0051] The compositions of RBC or CRBC and resins used in Example 5
through Example 9 were prepared by using the same RBC or CRBC fine
powder as produced in Example 1 through Example 4 and by dispersing
the fine powder of the RBC or the CRBC in synthetic resins under
the conditions as indicated in Table 1. In addition, for the sake
of comparison, commercially available PPS resin for pumps used in
water (made by Idemitsu Sekiyu Kagaku K., K. Co., Ltd.) was
used.
1 Table 1 Composition Composition Composition Composition
Composition 5 6 7 8 9 Ex. For comp. Types of RBC One used in One
used in One used in One used in One used in -- and CRBC Ex.4 Ex.3
Ex. 1 Ex.2 Ex.2 fine powder Synthetic Nylon 66 PBT PP PPS Nylon 66
PPS resin Finepowder: 70:30 50:50 70:30 50:50 30:70 -- resin (ratio
by mass) PBT: poly butylenes terephthalate PP: poly propylene PPS:
poly phenylene sulfide
[0052] The characteristics of the synthetic resin composition of
the RCB or CRBC fine powder and resin, and the PPS resin used in
the sleeve bearing for the use in water of Example 1 through
Example 9 are summarized in Table 2.
2 TABLE 2 Tensile Bending Bending strength strength elasticity
Resistivity Specific (MPa) (MPa) (GPa) (ohm cm) gravity Composition
of 64.6 98.6 6.12 4.9 E + 01 1.35 Ex. 1 Composition of 61.4 97.6
6.14 3.2 E + 01 1.38 Ex. 2 Composition of 76.5 120 8.85 2.1 E + 01
1.43 Ex. 3 Composition of 75.9 117 8.56 3.4 E + 01 1.38 Ex. 4
Composition of 58.2 105 4.12 3.3 E + 01 1.27 Ex. 5 Composition of
49.6 72.3 7.5 3.3 E + 01 1.46 Ex. 6 Composition of 22.7 44.3 6.5
3.8 E + 01 1.32 Ex. 7 Composition of 79.2 121 7.6 4.0 E + 01 1.48
Ex. 8 Composition of 57.3 101 4.3 2.7 E + 01 1.24 Ex. 9 PPS in Ex.
159 235 14.1 1.0 E + 16 1.75 For compar.
EXAMPLE 5
[0053] The synthetic resin composition 5 listed in Table 1 was
injection molded, thereby preparing a sleeve of 22 mm in outer
diameter, 8 mm in inner diameter, 120 mm in length and having a
spiral groove of 0.1 mm in depth on the inner side. A shaft of 7.95
mm in outer diameter and 200 mm in length made of SUS bearing steel
was inserted into the molded sleeves, preparing a sleeve bearing
shown in FIG. 1.
EXAMPLE 6
[0054] The synthetic resin composition 6 listed in Table 1 was
injection molded, thereby preparing a shaft of 7.95 mm in outer
diameter, and 200 mm in length. Sleeves 22 mm in outer diameter, 8
mm in inner diameter, and 120 mm in length were made from SUS
bearing steel. The sleeve was inserted on the shaft to form a
sleeve bearing as shown in FIG. 1.
EXAMPLE 7
[0055] The synthetic resin composition 7 listed in Table 1 was
injection molded, thereby preparing a shaft of 7.95 mm in outer
diameter, and 200 mm in length having a spiral groove of 0.1 mm in
depth. Sleeves 22 mm in outer diameter, 8 mm in inner diameter and
120 mm in length were made from SUS bearing steel. The sleeve was
inserted on the shaft to form a sleeve bearing as shown in FIG.
4.
EXAMPLE 8
[0056] The synthetic resin composition 8 listed in Table 1 was
injection molded, thereby preparing sleeves of 22 mm in outer
diameter, 8 mm in inner diameter, and 20 mm in length. A shaft of
7.95 mm in outer diameter and 200 mm in length made of SUS bearing
steel having a spiral groove of 0.1 mm in depth was inserted into
the sleeve, preparing a sleeve bearing as shown in FIG. 4.
EXAMPLE 9
[0057] The synthetic resin composition 9 listed in Table 1 was
injection molded, thereby preparing a shaft of 7.95 mm in outer
diameter, and 200 mm in length having a spiral groove of 0.1 mm in
depth. A sleeve 22 mm in outer diameter, 8 mm in inner diameter and
120 mm in length was made from SUS bearing steel. The sleeve was
inserted on the shaft to form a sleeve bearing as shown in FIG.
4.
[0058] Example for Comparison
[0059] The commercially available PPS resin for pumps for use with
water (made by Idemitsu Sekiyu Kagaku K., K., Co., Ltd.) was
injection molded, thereby preparing a sleeve of 22 mm in outer
diameter, 8 mm in inner diameter, and 120 mm in length. A shaft of
7.95 mm in outer diameter and 200 mm in length made of SUS 303
stainless alloy was inserted into the sleeve, preparing a sleeve
bearing as shown in FIG. 1.
[0060] The frictional characteristics in water of the sleeve
bearings for sliding motion in water obtained in Example 1 through
Example 9 and in Example for Comparison are summarized in Table
3.
3 TABLE 3 Ex. For Ex. 1 Ex. 2 Ex. 3 Ex.4 Ex. 5 Ex. 6 Ex. 7 Ex. 8
Ex. 9 compar Shape of Sleeve bearing spiral Frictional 0.212 0.198
0.259 0.221 0.231 0.288 0.232 0.288 0.268 0.406 coeff. .mu. A
Frictional 0.182 0.212 0.234 0.209 0.239 0.268 0.195 0.259 0.252
0.413 coeff. .mu. B Frictional 0.194 0.195 0.238 0.184 0.228 0.268
0.188 0.213 0.244 0.388 coeff. .mu. C Frictional 0.138 0.167 0.211
0.177 0.172 0.229 0.162 0.198 0.212 0.259 coeff. .mu. D Frictional
0.156 0.182 0.204 0.195 0.172 0.213 0.159 0.156 0.218 0.213 coeff.
.mu. E Frictional 0.148 0.153 0.204 0.152 0.153 0.187 0.168 0.177
0.196 0.248 coeff. .mu. F A. measured under the condition of a
sliding speed of 0.001 m/sec B. measured under the condition of a
sliding speed of 0.005 m/sec C. measured under the condition of a
sliding speed of 0.01 m/sec D. measured under the condition of a
sliding speed of 0.1 m/sec E. measured under the condition of a
sliding speed of 0.5 m/sec F. measured under the condition of a
sliding speed of 1 m/sec
[0061] As can be clearly seen from the results given in Table 3,
the sleeve bearings made of the synthetic resin compositions of
fine powder of RBC and CRBC and the resins have markedly excellent
frictional characteristics in water. These bearings can come into
direct contact with a liquid and do not have to be shielded from
the liquid.
[0062] While a preferred embodiment of the invention has been
described, various modifications will be apparent to one skilled in
the art in light of this disclosure and are intended to fall within
the scope of the appended claims.
* * * * *