U.S. patent application number 10/106510 was filed with the patent office on 2003-09-25 for wearing ring and pump having the same.
Invention is credited to Kainuma, Yoshikazu, Onoda, Hiroshi.
Application Number | 20030180142 10/106510 |
Document ID | / |
Family ID | 29738228 |
Filed Date | 2003-09-25 |
United States Patent
Application |
20030180142 |
Kind Code |
A1 |
Onoda, Hiroshi ; et
al. |
September 25, 2003 |
Wearing ring and pump having the same
Abstract
In a pair of wearing rings, the inner-cylinder wearing ring (5a,
5b) or the outer-cylinder wearing ring (4a, 4b) is formed of a
carbon fiber reinforced plastic and constituted so that the
coefficient of thermal expansion in the radial direction is
-1.times.10.sup.-6/.degree. C. to 30.times.10.sup.-6/.degree. C.
This makes it possible to maintain a clearance between the case
wearing ring and the impeller wearing ring within a small fixed
range even when the temperature rises due to rotation and when a
high-temperature fluid is used. A pump provided with the wearing
ring is excellent in stability and has a good efficiency.
Inventors: |
Onoda, Hiroshi; (Tokyo,
JP) ; Kainuma, Yoshikazu; (Kanagawa, JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
29738228 |
Appl. No.: |
10/106510 |
Filed: |
March 25, 2002 |
Current U.S.
Class: |
415/172.1 |
Current CPC
Class: |
F04D 29/167
20130101 |
Class at
Publication: |
415/172.1 |
International
Class: |
F04D 029/16 |
Claims
1. An inner-cylinder wearing ring or an outer-cylinder wearing ring
each of which is used in a pair of wearing rings of the combination
of inner-cylinder side and outer-cylinder side; wherein, the
inner-cylinder wearing ring or the outer-cylinder wearing ring is
formed of a carbon fiber reinforced plastic and has a coefficient
of thermal expansion in the radial direction of
-1.times.10.sup.-6/.degree. C. to 30.times.10.sup.-6/.degree.
C.
2. An inner-cylinder wearing ring or an outer-cylinder wearing ring
according to claim 1, in which its coefficient of thermal expansion
in the radial direction is 3.times.10.sup.-6/.degree. C. to
20.times.10.sup.-6/.degree. C.
3. An inner-cylinder wearing ring or an outer-cylinder wearing ring
according to claim 1, in which the above-described carbon fiber
reinforced plastic contains carbon fibers oriented in the axial
direction and carbon fibers oriented in the circumferential
direction of the wearing ring and in which the ratio of (weight of
axial carbon fibers): (weight of circumferential carbon fibers) is
(1:10) to (100:10).
4. An inner-cylinder wearing ring or an outer-cylinder wearing ring
according to claim 3, in which the ratio of (weight of axial carbon
fibers): (weight of circumferential carbon fibers) is (15:85) to
(85:15).
5. An inner-cylinder wearing ring or an outer-cylinder wearing ring
according to claim 1, in which the carbon fibers in the carbon
fiber reinforced plastic which constitutes an outermost layer of
the inner-cylinder wearing ring or the outer-cylinder wearing ring
are a fabric.
6. An inner-cylinder wearing ring or an outer-cylinder wearing ring
according to claim 1, in which a matrix resin contained in the
carbon fiber reinforced plastic is a thermosetting resin.
7. An inner-cylinder wearing ring or an outer-cylinder wearing ring
according to claim 1, which is used in a pair of wearing rings in
which a metal wearing ring is used as an opposed wearing ring.
8. An inner-cylinder wearing ring or an outer-cylinder wearing ring
according to claim 1, in which the carbon fiber reinforced plastic
is fabricated of continuous carbon filaments whose tensile modulus
is in the range of 49 Gpa to 950 GPa.
9. An inner-cylinder wearing ring or an outer-cylinder wearing ring
according to claim 1, which is used in a pump provided with an
impeller having an impeller wearing ring and a pump casing having a
case wearing ring.
10. An inner-cylinder wearing ring according to claim 1.
11. An inner-cylinder wearing ring according to claim 1, which is
used in a pair of wearing rings in which a metal wearing ring is
used as an opposed wearing ring.
12. A pump having the inner-cylinder wearing ring or the
outer-cylinder wearing ring according to claim 9.
13. A pump having the inner-cylinder wearing ring according to
claim 9.
Description
TECHNICAL FIELD
[0001] The present invention relates to a wearing ring used in a
pump, water wheel and the like.
BACKGROUND ART
[0002] In a general impeller-type pump that handles fluids, as
shown in FIG. 1, an impeller 1 housed in cases (2a, 2b) is rotated
by a main shaft 3 connected to a motor (not shown), whereby flows
of fluid are taken from direction A, pressurized and discharged in
the circumferential direction of the impeller, and the flows of
fluid then join together within the cases and are discharged from
an outlet (not shown). As wearing rings which are used as a bearing
mechanism for the rotation of the impeller in the cases, case
wearing rings (4a, 4b) and impeller wearing rings (5a, 5b) which
are opposed thereto are paired and clearances provided between the
pairs are lubricated by the fluid handled to thereby ensure smooth
rotation. Thus, clearances are necessary. However, if the
clearances are too large, the volume of fluid that leaks from the
high-pressure side (outlet side) to the low-pressure side (suction
side) increases, resulting in reduced pump efficiency.
[0003] Conventional wearing rings are formed of metals, ceramics,
plastics, carbon, etc. Metal wearing rings are generally used
because metals are the most inexpensive materials of all. However,
in the case of small clearances, in particular, when a
high-temperature fluid is handled, the impeller wearing rings can
expand to a larger extent due to a temperature gradient and a
temperature rise by rotation, with the result that the impeller
wearing rings may sometimes come into contact with the case wearing
rings resulting in seizure. For this reason, when metal wearing
rings were used, it was necessary to design clearances of a large
size. For example, in the case of a cylindrical wearing ring having
a diameter of 80 mm, it is necessary that a clearance be about 0.4
mm (on diameter basis) and, therefore, this provided limitations to
an increase in pump efficiency.
[0004] It is reported that in order to prevent the seizure of metal
parts, one of a wearing ring pair is made of metal and the other is
made of a ceramic or plastic material. However, ceramics have a
drawback in that they are brittle and do not endure a long period
of use. Plastic-made wearing rings have a drawback in that when
they expand and come to the state of contact-sliding due to thermal
expansion and swelling, their slidability is poor and, furthermore,
a local temperature rise due to contact-sliding develops biting due
to fusion bonding in the interface.
[0005] Also, in the Japanese Patent Laid-Open No. S63-129175 is
described the fact that slidability is improved by using a
composite material composed of a plastic material and a carbon
fiber in the contact-sliding surfaces of a piston-type pump.
However, in the case of an impeller-type pump etc., lubrication is
performed by a fluid and, therefore, contact-sliding does not occur
under usual conditions. When carbon and other composite materials
are used, the slidability between these materials and metals may be
improved. However, when contact-sliding occurs in an impeller-type
pump, the pump efficiency decreases due to the increased loads and,
therefore, it is not happened to positively effect the
contact-sliding.
[0006] Also, in the Japanese Patent Laid-Open No. 2001-173660 is
described the fact that it is possible to obtain a sliding bearing
which has a high cooling effect, is very effective in removing
foreign matter from water containing the foreign matter, and can
operate under dry conditions (i.e., in the air) by using a sliding
member provided, on a sliding surface thereof, with grooves formed
through in the axial direction, the sliding member being fabricated
of a carbon-fiber reinforced plastic which is molded by heating and
hot working long carbon fibers wound in coil form with respect to
the shaft center. However, although the sliding characteristics and
the foreign matter removing effect are high, all carbon fibers are
wound in the circumferential direction with respect to the shaft
center, with the result that the following problems arise; that is,
(A) the sliding bearing is vulnerable to damage by shock of impact
of foreign matter, and (B) because the coefficient of thermal
expansion in the radial direction is small, clearances are deformed
by the heat generated by sliding during operation, making it
difficult to obtain a stable pump efficiency. Furthermore, although
according to this disclosure, various types of thermoplastic resins
can be used as plastics to be used, (C) when thermoplastic resins
are used, fusion bonding may sometimes occur under sliding
conditions under which local contact such as eccentricity occur.
Also, in the Japanese Patent Laid-Open No. H9-2643275 and Japanese
Patent Laid-Open No. 2001-231213 is described a bearing each
fabricated of a carbon fiber reinforced plastic which is formed
from long carbon fibers wound in coil shape with respect to the
shaft center by heating and hot working and problems similar to
those described above arise.
DISCLOSURE OF THE INVENTION
[0007] The object of the present invention is to provide a wearing
ring which enables a clearance between a case wearing ring and an
impeller wearing ring to be maintained within a small fixed range
even when the temperature rises due to rotation and when a
high-temperature fluid is used, and a pump which is provided with
the wearing ring, is excellent in stability and has a good
efficiency.
[0008] The present invention discloses the following items.
[0009] 1. An inner-cylinder wearing ring or an outer-cylinder
wearing ring each of which is used in a pair of wearing rings of
the combination of inner-cylinder side and outer-cylinder side;
wherein, the inner-cylinder wearing ring or the outer-cylinder
wearing ring is formed of a carbon fiber reinforced plastic and has
a coefficient of thermal expansion in the radial direction of
-1.times.10.sup.-6/.degree. C. to 30.times.10.sup.-6/.degree.
C.
[0010] 2. An inner-cylinder wearing ring or an outer-cylinder
wearing ring according to item 1, in which its coefficient of
thermal expansion in the radial direction is
3.times.10.sup.-6/.degree. C. to 20.times.10.sup.-6/.degree. C.
[0011] 3. An inner-cylinder wearing ring or an outer-cylinder
wearing ring according to item 1, in which the above-described
carbon fiber reinforced plastic contains carbon fibers oriented in
the axial direction and carbon fibers oriented in the
circumferential direction of the wearing ring and in which the
ratio of (weight of axial carbon fibers): (weight of
circumferential carbon fibers) is (1:10) to (100:10).
[0012] 4. An inner-cylinder wearing ring or an outer-cylinder
wearing ring according to item 3, in which the ratio of (weight of
axial carbon fibers): (weight of circumferential carbon fibers) is
(15:85) to (85:1).
[0013] 5. An inner-cylinder wearing ring or an outer-cylinder
wearing ring according to item 1, in which the carbon fibers in the
carbon fiber reinforced plastic which constitutes an outermost
layer of the inner-cylinder wearing ring or the outer-cylinder
wearing ring are a fabric.
[0014] 6. An inner-cylinder wearing ring or an outer-cylinder
wearing ring according to item 1, in which a matrix resin contained
in the carbon fiber reinforced plastic is a thermosetting
resin.
[0015] 7. An inner-cylinder wearing ring or an outer-cylinder
wearing ring according to item 1, which is used in a pair of
wearing rings in which a metal wearing ring is used as an opposed
wearing ring.
[0016] 8. An inner-cylinder wearing ring or an outer-cylinder
wearing ring according to item 1, in which the carbon fiber
reinforced plastic is fabricated of continuous carbon filaments
whose tensile modulus is in the range of 49 Gpa to 950 GPa.
[0017] 9. An inner-cylinder wearing ring or an outer-cylinder
wearing ring according to item 1, which is used in a pump provided
with an impeller having an impeller wearing ring and a pump casing
having a case wearing ring.
[0018] 10. An inner-cylinder wearing ring according to item 1.
[0019] 11. An inner-cylinder wearing ring according to item 1,
which is used in a pair of wearing rings in which a metal wearing
ring is used as an opposed wearing ring.
[0020] 12. A pump having the inner-cylinder wearing ring or the
outer-cylinder wearing ring according to item 9.
[0021] 13. A pump having the inner-cylinder wearing ring according
to item 9.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a sectional view of an example of the structure of
an impeller-type pump;
[0023] FIGS. 2(a) and 2(b) are drawings for explaining the
coefficient of thermal expansion in the radial direction;
[0024] FIG. 3 is a drawing of the relationship between the
discharge rate and pump efficiency of pumps in embodiments and in a
comparative example;
[0025] FIG. 4 is a drawing of the relationship between the
discharge rate and total pressure of pumps in embodiments and in a
comparative example; and
[0026] FIG. 5 is a drawing of the relationship between the
discharge rate and shaft power of pumps in embodiments and in a
comparative example.
DESCRIPTION OF SYMBOLS
[0027] 1 Impeller
[0028] 2a, 2b Case
[0029] 3 Main shaft
[0030] 4a Suction side case wearing ring
[0031] 4b Back side case wearing ring
[0032] 5a Suction side impeller wearing ring
[0033] 5bBack side impeller wearing ring
[0034] 7 Main body of impeller
[0035] 8 Main body of case
BEST MODE FOR CARRYING OUT THE INVENTION
[0036] As described above, the invention relates to an
inner-cylinder wearing ring or an outer-cylinder wearing ring each
of which is used in a pair of wearing rings of the combination of
inner-cylinder side and outer-cylinder side; wherein, the
inner-cylinder wearing ring or the outer-cylinder wearing ring is
formed of a carbon fiber reinforced plastic and has a coefficient
of thermal expansion in the radial direction of
-1.times.10.sup.-6/.degree. C. to 30.times.10.sup.-6/.degree- . C.
Preferably, which the coefficient of thermal expansion in the
radial direction is 3.times.10.sup.-6/.degree. C. to
20.times.10.sup.-6/.degree. C.
[0037] The coefficient of thermal expansion in the radial direction
is a numerical value determined with respect to a value of change
of the diameter of a wearing ring caused by thermal expansion or
contraction. That is, in the case of an inner-cylinder wearing
ring, as shown in FIG. 2(a), when the outside diameter .phi. of the
wearing ring changes to (.phi.+.DELTA..phi.), this value is
determined by .DELTA..phi./(.phi..mul- tidot..DELTA.t). In the case
of an outer-cylinder wearing rate, as shown in FIG. 2(b), this
value is similarly determined from a change in the inside diameter
.phi. of the wearing ring.
[0038] The inner-cylinder wearing ring or outer-cylinder wearing
ring of the invention is preferably used in a pump provided with an
impeller and a pump casing. And in this case, the inner-cylinder
wearing ring of the invention is used as an impeller wearing ring,
and the outer-cylinder wearing ring is used as a case wearing
ring.
[0039] In the invention, when a wearing ring expands thermally,
carbon fibers suppress the expansion and, therefore, the thermal
expansion of the wearing ring can be efficiently reduced.
[0040] Although the inner-cylinder wearing ring or outer-cylinder
wearing ring of the invention is most preferably used both on the
inner-cylinder and outer-cylinder of a pair of wearing rings, the
wearing ring of the present invention shows sufficient effect even
when used on one side only. In particular, a wearing ring of the
invention which is formed of a carbon fiber reinforced plastic is
preferably used on the side where thermal expansion poses a
problem. For example, when heat is apt to be applied to the
inner-cylinder wearing ring or when the inner-cylinder wearing ring
is apt to expand because an inner-cylinder substrate material has a
larger coefficient of thermal expansion, it is preferred that the
present invention be applied to the inner-cylinder wearing ring.
And on that occasion, an inexpensive, general metal wearing ring
can be used as an opposed wearing ring which is a counterpart of
the pair.
[0041] Although a wearing ring of the invention can be used on the
external peripheral surface of the piston of a suspension cylinder,
it can be most preferably used in an impeller-type pump which
handles fresh water, seawater, oil, etc. as a fluid.
[0042] FIG. 1 shows an example of pump of this structure. By paying
attention to the wearing ring portions, we will observe that the
suction-side impeller wearing ring 5a and the suction-side case
wearing ring 4a are arranged in a pair and that the back-side
impeller wearing ring 5b and the back-side case wearing ring 4b are
arranged in a pair. All of the wearing rings in this example are
formed in the form of cylinders having a prescribed thickness and
length, and attached to the main body of impeller 7 and the main
body of case 8, for example, as shown in FIG. 2.
[0043] In the pump of the invention, in the pairs of wearing rings,
i.e., in the pair of 4a and 5a or the pair of 4b and 5b, it is
necessary only that a wearing ring on one side be formed of a
carbon fiber reinforced plastic. However, when on the suction side,
for example, the wearing ring of the invention is applied to the
impeller wearing ring 5a and the case wearing ring 4a is made of
metal, it is generally preferable that also on the backside, in
consideration of similar thermal conditions, the wearing ring of
the invention be applied to the impeller wearing ring 5b and that
the case wearing ring 4b be made of metal
[0044] The shape of the pump is not limited to that shown in FIG. 1
and can be changed according to pump capacity, kind of fluid, etc.
For example, the diameter, thickness, axial length, etc. of wearing
ring can be appropriately changed. The shape of the inner-cylinder
or outer-cylinder wearing ring is generally cylindrical and the
cylindrical type is easy to form and is hence preferable. However,
other shapes known as the shape of wearing ring, for example, a
circular conical shape may be adopted. Incidentally, the terms
"outer cylinder" and "inner cylinder" used in this specification
are intended for a discrimination between a wearing ring on the
outer side and a wearing ring on the inner side, which form a pair,
and is not intended to indicate solely "cylindrical shaped" wearing
rings.
[0045] In a pair of wearing rings in which the inner-cylinder or
outer-cylinder wearing ring using the carbon fiber reinforced
plastic of the invention is used at least one side, it is possible
to efficiently suppress thermal expansion and, therefore, so long
as the center accuracy of the rotation axis is sufficiently
ensured, contact of one wearing rings with the other wearing ring
will not occur and seizure can be prevented even when clearances
are set to equal to or smaller than 0.5% of diameter and even to
equal to or smaller than 0.2% of diameter. In general, in
consideration of the problem of center accuracy of the rotation
axis, the clearance is not less than 0.02% and preferably not less
than 0.05%.
[0046] For example, in the case of a wearing ring having a diameter
of 80 mm, it is most preferable to set the clearance (difference in
the diameter between the outer-cylinder inside diameter and the
inner-cylinder outside diameter) to about 0.08 mm to about 0.15
mm.
[0047] Concretely, such wearing rings are formed as follows.
[0048] First, the carbon fiber reinforced plastic used in the
invention is obtained by impregnating carbon fibers with a matrix
resin to obtain a composite material.
[0049] Carbon fires used are those having a tensile modulus of 49
to 950 GPa and in particular, those having a tensile modulus of 230
to 620 GPa are preferable. In terms of the tensile strength, carbon
fibers having a value of 1150 to 4510 MPa are preferable and in
particular, those of 2450 to 4410 MPa are preferable. In terms of
the coefficient of thermal expansion of carbon fibers (coefficient
of linear expansion in the fiber direction), carbon fibers having a
value of -1.5.times.10.sup.-6/.degree. C. to
4.times.10.sup.-6/.degree. C. are preferable. By using carbon
fibers of such physical properties, the expansion of the matrix
resin is suppressed and the coefficient of thermal expansion of the
carbon fiber reinforced plastic itself is reduced and, at the same
time, the expansion and contraction of the substrate (main body of
impeller, main body of case) to which the wearing rings are
attached can be suppressed, with the result that the coefficient of
thermal expansion in the radial direction as the wearing rings can
be set to a desired value.
[0050] Pitch-base carbon fibers, PAN-base carbon fibers, etc. can
be used as the carbon fibers of the invention. As required, these
may be used in combination for making the carbon fiber reinforced
plastic. It is preferable to select carbon fibers so that a desired
coefficient of thermal expansion be obtained as wearing rings in
consideration of the places of use, the material for the opposed
counterpart of a pair of wearing rings.
[0051] As the carbon fibers, it is preferable to use continuous
carbon filaments rather than short fibers. By winding continuous
carbon filaments at least one turn in the circumferential direction
of the wearing ring (in the case of a cylindrical shape, in the
circumferential direction of the cylinder), the properties of
carbon fibers can be efficiently utilized and furthermore the
coefficient of thermal expansion in the radial direction as the
wearing ring can be set to a desired value. It is preferable that
in this manner, at least a portion of the carbon fibers in the
carbon fiber reinforced plastic which constitute the wearing ring
be substantially oriented in the circumferential direction.
Furthermore, it is preferable that in order to prevent cracks etc.
due to strains, carbon fibers oriented in the axial direction of
the wearing ring (direction of rotation axis) be also present.
[0052] Usually, it is necessary only that carbon fibers be oriented
in two directions, i.e., the circumferential and axial directions.
The composition ratio (weight ratio) of carbon fibers in the
circumferential direction to the carbon fibers in the axial
direction is 1:(0 to 10). The composition ratio (weight ratio) of
(carbon fibers in the axial direction): (carbon fibers in the
circumferential direction) is preferably (1:10) to (100:10),
especially preferably (15:85) to (85:15), and most preferably
(15:85) to (20:10).
[0053] Incidentally, the circumferential orientation and axial
orientation of carbon fibers may not always be precisely oriented
to the circumferential and axial directions of the wearing ring.
When 0.degree. is defined as the axial direction of the wearing
ring, the orientation of carbon fibers in the circumferential
directions may be .+-.60.degree. to 90.degree. and preferably
.+-.85.degree. to 90.degree., and the orientation of carbon fibers
in the axial directions may be 0.degree. to 45.degree. and
preferably 0.degree. to .+-.15.degree..
[0054] The volume content of carbon fibers in the carbon fiber
reinforced plastic is preferably about 45 to about 70% by volume
and especially preferably 55 to 65% by volume.
[0055] As a matrix resin that constitutes the carbon fiber
reinforced plastic along with carbon fibers, a heat-resistant resin
is preferable. Above all, polyether ether ketone resins, aromatic
polyester resins, polyphenylene oxide resins, polysulfone resins,
polyphenylene sulfide resins, polyamide imide resins, polyamide
bismaleimide resins, etc. can be exemplified as thermoplastic
resins; and phenol resins, epoxy resins, cyanate resins, urea
resins, diallyl phthalate resins, polyimide resins, silicone
resins, unsaturated polyester resins, etc. can be exemplified as
thermosetting resins.
[0056] In particular, thermosetting resins are preferable because
fusion bonding is not apt to occur even when heat is generated by
local contact due to eccentricity of axis. Especially preferred
thermosetting resins are epoxy resins, phenol resins, cyanate
resins and unsaturated polyester resins.
[0057] In order to form a wearing ring of a prescribed shape, a
suitable molding method for the shape and the properties of the
matrix resin may be used. Molding methods will be described below
concerning a cylindrical wearing ring, which is of a representative
shape. For example, according to a molding method called sheet
rolling molding, a sheet-like unidirectional prepreg or fabric
prepreg is formed by impregnating carbon fibers with a matrix resin
by a known method, a prescribed number of such prepregs are
laminated on a mandrel, and after that, the laminated product is
removed from the mandrel after setting by heating in the case of a
thermosetting resin, with the result that a cylindrical molded
product of carbon fiber reinforced plastic is obtained. After that,
the cylindrical molded product is cut to a prescribed length and is
ground and polished with a prescribed accuracy in order to make an
accurate clearance, whereby a cylindrical wearing ring is
obtained.
[0058] Also, by the filament winding lamination method, which is
known as another lamination method, a tow-prepreg obtained by
impregnating carbon fibers with a matrix resin can be laminated in
a necessary number of layers by winding the tow-prepreg while
orienting it. Also, a tow-prepreg may be woven to form a
cylindrical shape. Alternatively, carbon fibers may be woven into a
cylindrical shape and after that, the woven carbon fibers may be
impregnated with a matrix resin
[0059] In an embodiment of the invention, the preferable
cylindrical molded product is obtained, using sheet rolling
molding, by alternately repeating the sequence of lamination of 1
to 10 layer(s) of unidirectional prepreg in the circumferential
direction and the sequence of lamination of 1 to 10 layer(s) of
unidirectional prepreg in the axial direction. On that occasion,
the sheet-like prepreg is selected so that the thickness of each
layer becomes about 0.05 to about 0.3 mm after setting, and the
total number of layers is appropriately changed according to the
thickness of one layer and the thickness of the wearing ring. In
the case of a general thickness, the total number of layers is, for
example, 20 to 300 or so. Furthermore, it is preferable that as the
outermost layer of the wearing ring, which is the sliding surface
thereof, (at least either on the outer side or inner side of the
cylinder), a fabric prepreg be laminated in 1 to about 10 layers
and particularly in 1 to about 5 layers. When the outermost layer
is formed by a fabric prepreg, this provides the advantage that
fluff is not apt to be formed during grinding and polishing.
[0060] A wearing ring formed of a carbon fiber reinforced plastic,
which has been thus formed into a cylindrical shape, is attached to
a substrate (main body of case or main body of impeller), which has
been formed so as to allow the attaching of the wearing ring, and
after that, the wearing ring is used.
[0061] In this invention, when this wearing ring made of a carbon
fiber reinforced plastic is to be used in a pump, the wearing ring
may be used both as the case wearing ring and the impeller wearing
ring, but may be used either one of the both wearing rings, as
already described. Because in ordinary uses, high-temperature
fluids are often handled and the temperature rise by rotation is
larger on the impeller side. Therefore, when this wearing ring is
used either one of the case side and the impeller side, it is
generally preferable that the wearing ring be used on the impeller
side.
[0062] And when the wearing ring of the invention is used on one
side only, metals, ceramics, plastics, carbon, etc. can be used as
the material for the counterpart of a pair of wearing rings. In
particular, from the standpoint of workability and price, metals
are preferable and particularly, stainless steels such as SUS304
and SUS403 are preferable because they have high wear-resistance
and rust-resistance.
[0063] Embodiments
[0064] Next, the invention will be described in further detail by
referring to embodiments. The pump used in the evaluation is an
overhang centrifugal pump having the rating of a water head of 55
m, a capacity of 14 m.sup.3/h, an output of 3.70 kW and a number of
revolutions of 2900 rpm. The shape of the pump is almost the same
as that shown in FIG. 1. Although in the pump shown in FIG. 1 the
wearing ring pair on the suction side and the wearing ring pair on
the back side have different diameters and lengths, in the pump
used here both wearing ring pairs are of the same shape.
[0065] Furthermore, in the pump performance measurement in the
embodiments, by using water at about 20.degree. C. as a fluid, the
relationship between discharge rate and pump efficiency (simple
efficiency=water power/shaft power.times.100), the relationship
between discharge rate and total pressure, and the relationship
between discharge rate and shaft power were determined by the
methods specified in JIS.
[0066] <Embodiment 1>
[0067] Prepreg A of about 0.25 mm thickness having a carbon fiber
content of about 55% by volume was produced by impregnating the
carbon fiber made by Nippon Graphite Fiber Corporation XN-60 with a
moisture-resistance epoxy resin, and prepreg B with a lamination
thickness (thickness after lamination) of about 0.25 mm having a
carbon fiber content of about 50% by volume was produced by
impregnating the carbon fiber cloth made by Toray Industries, Inc.
CO6343 with a moisture-resistance epoxy resin. Prepreg B was wound
on a mandrel in 5 lamination layers of 0.degree. orientation,
prepreg A was wound in such a manner that 0.degree. oriented layer
and 90.degree. oriented layer are alternately wound to form a total
of 20 layers, prepreg B was further wound in 5 lamination layers of
0.degree. oriented layers, and after that, thermosetting was
effected. As a result, a cylindrical molded product having 102 mm
in outside diameter and 87 mm in inside diameter was obtained.
[0068] This cylinder made of a carbon fiber reinforced plastic was
cut to a predetermined length, ground and polished, and then worked
into a shape 101.0 mm in outside diameter, 88.5 mm in inside
diameter and 22.5 mm in length. After that, fixing-screw holes were
bored and a wearing ring made of a carbon fiber reinforced was
obtained. This wearing ring was attached to both of the suction
side and back side of the impeller. This impeller wearing ring had
a coefficient of thermal expansion in the radial direction of about
5.times.10.sup.-6/.degree. C.
[0069] On the other hand, a case wearing ring made of SUS403 having
an inside diameter of 101.1 mm was used both on the suction side
and the back side. That is, the clearance of the wearing rings is
0.1 mm in diameter. The performance of this pump, i.e., the
relationship between discharge rate and pump efficiency, the
relationship between discharge rate and total pressure, and the
relationship between discharge rate and shaft power are shown in
FIG. 3, FIG. 4 and FIG. 5, respectively. Seizure did not occur in
spite of this narrow clearance.
[0070] <Embodiment 2>
[0071] Prepreg B used in Embodiment 1 was also used in this
embodiment. Prepreg B (plain weave fabric) was wound on a mandrel
in 30 lamination layers so that the direction of carbon fibers
became 0.degree. orientation and 90.degree. orientation,
thermosetting was then effected and a cylindrical molded product
having 102 mm in outside diameter and 87 mm in inside diameter was
obtained. This cylinder was worked in the same manner as in
Embodiment 1 and a wearing ring of the same size as in Embodiment
1, i.e., 101.0 mm in outside diameter, 88.5 mm in inside diameter
and 22.5 mm in length was obtained. This wearing ring was attached
to both of the suction side and back side of the impeller. This
impeller wearing ring had a coefficient of thermal expansion in the
radial direction of about 10.times.10.sup.-6/.degree. C.
[0072] On the other hand, the same case wearing ring as in
Embodiment 1 was used. The performance of this pump is shown in
FIGS. 3, 4 and 5. Seizure did not occur in spite of this narrow
clearance
[0073] <Comparative Example 1>
[0074] Impeller wearing rings made of SUS403 with an outside
diameter of 100.7 mm and a length of 22.5 mm were used. On the
other hands, the same case wearing rings made of SUS403 having an
inside diameter of 101.1 mm as in Embodiment 1 were used. That is,
the clearance of the wearing rings is 0.4 mm in diameter. In both
the case wearing rings and the impeller wearing rings, the
coefficient of thermal expansion in the radial direction was about
19.times.10.sup.-6/.degree. C. The performance of this pump is
shown in FIGS. 3 to 5. Seizure did not occur.
[0075] <Comparative Example 2>
[0076] Impeller wearing rings made of SUS403 with an outside
diameter of 101.0 mm and a length of 22.5 mm were used and case
wearing rings made of SUS403 having an inside diameter of 101.1 mm
were used. That is, the clearance of the wearing rings is 0.1 mm in
diameter. However, seizure occurred during the operation of the
pump and stable pump operation was impossible.
[0077] As described above, according to the invention, it is
possible to provide a wearing ring which enables a clearance
between a case wearing ring and an impeller wearing ring to be
maintained within a small fixed range even when the temperature
rises due to rotation and when a high-temperature fluid is used,
and a pump which is provided with the wearing ring, is excellent in
stability and has a good efficiency.
* * * * *