U.S. patent application number 10/321445 was filed with the patent office on 2004-06-24 for sealing mechanism of feeding device.
This patent application is currently assigned to Kabushiki Kaisha Kobe Seiko Sho(Kobe Steel, Ltd.). Invention is credited to Tsuge, Osamu, Whitten, Gilbert Y..
Application Number | 20040119210 10/321445 |
Document ID | / |
Family ID | 32592920 |
Filed Date | 2004-06-24 |
United States Patent
Application |
20040119210 |
Kind Code |
A1 |
Tsuge, Osamu ; et
al. |
June 24, 2004 |
Sealing mechanism of feeding device
Abstract
The present invention provides a sealing mechanism of a feeding
device for feeding lumps and/or powder to a moving-hearth heating
furnace. The feeding device includes a vibrating feeder having a
trough in which a hole for feeding the lumps and/or powder to the
furnace is formed and a duct for guiding the lumps and/or powder
dropped through the hole to a hearth of the heating furnace. The
sealing mechanism includes a water sealing mechanism having a skirt
plate, a weir plate, a side surface of the duct, and liquid. The
skirt plate is provided on the lower surface of the trough. The
weir plate is provided above a ceiling of the heating furnace. The
liquid is kept in a tank serving as a pool of liquid which is
formed by the side surface of the duct and the weir plate.
Inventors: |
Tsuge, Osamu; (Kobe-shi,
JP) ; Whitten, Gilbert Y.; (Charlotte, NC) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Kabushiki Kaisha Kobe Seiko
Sho(Kobe Steel, Ltd.)
Kobe-shi
JP
|
Family ID: |
32592920 |
Appl. No.: |
10/321445 |
Filed: |
December 18, 2002 |
Current U.S.
Class: |
266/177 |
Current CPC
Class: |
F27D 3/0032 20130101;
F27D 2003/0038 20130101; F27D 3/0033 20130101; F27B 13/06
20130101 |
Class at
Publication: |
266/177 |
International
Class: |
C21B 013/10 |
Claims
What is claimed is:
1. A sealing mechanism of a feeding device for feeding lumps and/or
powder to a moving-hearth heating furnace, the feeding device
comprising: a vibrating feeder including a trough in which a hole
for feeding the lumps and/or powder to the furnace is formed; and a
duct for guiding the lumps and/or powder dropped through the hole
to a hearth of the heating furnace, the sealing mechanism
comprising: a water sealing mechanism including a skirt plate, a
weir plate, a side surface of the duct, and liquid, wherein the
skirt plate is provided on the lower surface of the trough such
that the skirt plate surrounds the periphery of the upper end of
the duct and such that the lower end of the skirt plate is
positioned below the upper end of the duct, the weir plate is
provided above a ceiling of the heating furnace such that the weir
plate surrounds the periphery of the lower end of the skirt plate
and such that the upper end of the weir plate is positioned above
the lower end of the skirt plate, and the liquid is kept in a tank
serving as a pool of liquid which is formed by the side surface of
the duct and the weir plate such that the liquid surface is above
the lower end of the skirt plate.
2. The sealing mechanism according to claim 1, wherein the pool of
liquid is formed in an area including a feeding nozzle of the
trough when viewed from a side.
3. The sealing mechanism according to claim 1, wherein the pool of
liquid is formed in an area including the width of the hearth below
the trough when viewed from the top.
4. The sealing mechanism according to claim 1, wherein a feeding
nozzle is formed in the lower side of the trough such that the
nozzle extends downward along the edge of the opening of the hole
in the vibrating feeder and the upper end of the duct is positioned
between the lower end of the feeding nozzle and the lower surface
of the trough.
5. The sealing mechanism according to claim 1, wherein at least one
inlet for feeding the liquid and at least one outlet for
discharging the liquid is provided in the tank formed by the side
surface of the duct and the weir plate.
6. The sealing mechanism according to claim 1, wherein the liquid
is continuously or intermittently fed to or discharged from the
tank formed by the side surface of the duct and the weir plate.
7. The sealing mechanism according to claim 1, wherein a rotary
hearth furnace is used as the moving-hearth heating furnace.
8. The sealing mechanism according to claim 7, wherein the rotary
hearth furnace is used for producing metallic iron by reducing iron
oxide.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a sealing mechanism of a
vibrating feeder which is used for feeding material to a
moving-hearth furnace such as a rotary hearth furnace or a straight
grate. More specifically, the present invention relates to a
sealing mechanism for preventing gas inside a furnace from leaking
through a gap between the lower part of a vibrating feeder and the
upper part of a feeding duct extending through the ceiling of the
furnace.
[0003] 2. Description of the Related Art
[0004] A shaft furnace method represented by a Midrex process has
been known as a direct iron making in which reduced iron (metallic
iron) is obtained by directly reducing iron oxides such as iron ore
or iron oxide by using a carbonaceous material and a reducing gas.
In this type of direct iron making, a reducing gas produced from a
natural gas or the like is blown into a shaft furnace through a
tuyere in a lower portion of the shaft furnace and iron oxide is
reduced by using the reducing force of the reducing gas so as to
obtain metallic iron. Further, a reduced iron making process, using
a carbonaceous material such as coal as a reducing agent instead of
a natural gas, has drawn attention in recent years. Specifically, a
so-called SL/RN method has been put to practical use.
[0005] In recent years, the following metallic iron making method
using a carbonaceous material has been known. That is, in the
method, a mixture containing iron oxide such as iron ore and a
carbonaceous reducing agent such as coal is loaded onto the hearth
of a moving-hearth heating furnace such as a rotary furnace or a
straight grate. Then, the mixture is heated by a burner and a
radiant heat while moving in the heating furnace so that the iron
oxide is reduced by the carbonaceous reducing agent. The obtained
reduced iron is carburized, melt, aggregated, and is separated from
molten slag, and is cooled and solidified so that granular solid
metallic iron is taken out of the furnace.
[0006] When the mixture containing iron oxide and a carbonaceous
reducing agent is loaded into the moving-hearth heating furnace, a
vibrating feeder is used as a feeding device so that the width in
the width direction of the hearth and/or thickness of the mixture
loaded onto the hearth is even.
[0007] FIG. 4 is a schematic view showing a general feeding device
using a vibrating feeder. Material to be fed such as mixture, which
is reserved in a hopper 10, is fed through a quantity-adjusting
mechanism 8, which is provided in the hopper 10, to a trough 11 of
a vibrating feeder 12. The mixture on the trough 11 is sequentially
moved toward a hole 13 provided in the trough 11 by the vibration
generated by a vibrating device 7, while the thickness of a layer
of the mixture on the trough 11 is adjusted to become even in the
thickness. Then, the mixture is continuously fed from the hole 13
through a feeding nozzle 14 and a duct 15 onto a hearth 2.
[0008] In this type of feeding device, the trough vibrates, and
thus the feeding nozzle 14 provided on the lower surface of the
trough 11, the nozzle extending along the edge of the opening of
the hole, and the duct 15 extending through the ceiling 3 of the
furnace are in a non-contacting state (non-contacting portion) 19.
However, if the non-contacting portion 19 is not closed, a
high-temperature gas in the furnace may flow out through the
non-contacting portion or dust may scatter outside the furnace in
accordance with the exhaust gas. Further, the high-temperature gas
flowing out through the non-contacting portion may deteriorate
peripheral devices of the vibrating feeder. Also, the air outside
the furnace may flow into the furnace so that turbulence of
atmosphere may be caused in the furnace. Accordingly, in order to
overcome these problems, the feeding nozzle 14 and the duct 15 are
connected by using a rubber boot 20 so as to seal the
non-contacting portion.
[0009] However, in a sealing mechanism using a rubber boot, the
rubber boot is deteriorated due to the heat of the gas inside the
furnace or rising powder is adhered to the rubber boot so that the
elasticity of the rubber boot is decreased. Thus, the rubber boot
must be frequently checked and changed. Further, since the rubber
boot is provided in a relatively small space, a sufficient
operation space cannot be obtained and thus a setting operation and
a maintenance operation for the rubber boot are difficult to
perform. Also, the feeder must be placed at a high position in
order to obtain an operation space. However, when the feeder is set
at a high position, material fed by the feeder may be broken at the
hearth due to the shock of drop and the amount of rising dust
increases.
[0010] The present invention has been made in view of the
above-described problems, and the object of the present invention
is to provide a sealing mechanism in which maintenance can be
easily performed and a great sealing effect can be achieved.
SUMMARY OF THE INVENTION
[0011] The present invention provides a sealing mechanism of a
feeding device for feeding lumps and/or powder to a moving-hearth
heating furnace. The feeding device comprises a vibrating feeder
including a trough in which a hole for feeding the lumps and/or
powder to the furnace is formed; and a duct for guiding the lumps
and/or powder dropped through the hole to a hearth of the heating
furnace. The sealing mechanism comprises a water sealing mechanism
including a skirt plate, a weir plate, a side surface of the duct,
and liquid. The skirt plate is provided on the lower surface of the
trough such that the skirt plate surrounds the periphery of the
upper end of the duct and such that the lower end of the skirt
plate is positioned below the upper end of the duct. The weir plate
is provided above a ceiling of the heating furnace such that the
weir plate surrounds the periphery of the lower end of the skirt
plate and such that the upper end of the weir plate is positioned
above the lower end of the skirt plate. The liquid is kept in a
tank serving as a pool of liquid which is formed by the side
surface of the duct and the weir plate such that the liquid surface
is above the lower end of the skirt plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross-sectional view of a moving-hearth heating
furnace to which a feeding device provided with a sealing mechanism
of the present invention is set;
[0013] FIGS. 2A and 2B are plan views viewed from the top showing
the critical portion of the moving-hearth heating furnace to which
the feeding device provided with the sealing mechanism of the
present invention is set;
[0014] FIG. 3 is a cross-sectional view showing the critical
portion of the moving-hearth heating furnace to which the feeding
device provided with the sealing mechanism of the present invention
is set;
[0015] FIG. 4 is a cross-sectional view for illustrating a known
feeding device and sealing mechanism; and
[0016] FIG. 5 is a schematic view of a rotary hearth furnace used
as the moving-hearth heating furnace.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] The present invention provides a sealing mechanism of a
feeding device for feeding lumps and/or powder (hereinafter
referred to as material to be fed) to a moving-hearth heating
furnace. The feeding device comprises a vibrating feeder including
a trough in which a hole for feeding the material to the furnace is
formed; and a duct for guiding the material dropped through the
hole to a hearth of the heating furnace. The sealing mechanism
comprises a water sealing mechanism including a skirt plate, a weir
plate, a side surface of the duct, and liquid. The skirt plate is
provided on the lower surface of the trough such that the skirt
plate surrounds the periphery of the upper end of the duct and such
that the lower end of the skirt plate is positioned below the upper
end of the duct. The weir plate is provided above a ceiling of the
heating furnace such that the weir plate surrounds the periphery of
the lower end of the skirt plate and such that the upper end of the
weir plate is positioned above the lower end of the skirt plate.
The liquid is kept in a tank serving as a pool of liquid which is
formed by the side surface of the duct and the weir plate such that
the liquid surface is above the lower end of the skirt plate.
[0018] This sealing mechanism can be easily maintained and has a
great sealing effect.
[0019] Lumps and/or powder (material to be fed) which are to be fed
by using the feeding device of the present invention include a
powder or a mixed powder containing two or more types of powder, or
lumps prepared by forming the powder into an arbitrary form, such
as a pellet or a briquette. Also, material, sub material, and
additives of any type can be used. For example, the following
matter may be used as a material for reduced iron (metallic iron);
a mixed powder prepared by mixing an iron-oxide-containing powder
and a carbonaceous powder, which are used for producing reduced
iron (metallic iron), (another component may be contained); various
types of raw powder such as an iron-oxide-containing powder and a
carbonaceous powder; lumps prepared by forming the mixed powder
into an arbitrary form such as a pellet and a briquette; or various
types of sub material and additive such as a carbonaceous powder
laid on the hearth, a refractory powder, a slag powder, a
basicity-adjusting agent (for example, lime), a hearth-maintaining
material (for example, the same material as that of the hearth),
and a melting point-adjusting agent (alumina, magnesia, or the
like). Of course, the material to be fed is not limited to the
above-described examples and any types of powder or lumps may be
fed to the furnace. Therefore, the sealing mechanism of the present
invention may be provided to a feeding device for each material to
be fed.
[0020] As the moving-hearth heating furnace, a heating furnace
including a moving hearth, such as a rotary hearth furnace or a
straight grate may be used. Also, any types of furnace, for
example, a reducing furnace, a heating furnace, and reducing and
fusing furnace, may be used as the moving-hearth heating furnace.
Among them, a reducing and fusing furnace using a rotary hearth
furnace is desired and is particularly suitable for producing
metallic iron, because a process from reduction to fusion can be
efficiently performed inside the furnace.
[0021] Incidentally, a specific method of producing metallic iron
by using a moving-hearth heating furnace is disclosed in Japanese
Unexamined Patent Application Publication No. 2000-144224.
[0022] The above-described feeding device is used for feeding
material to a heating furnace and includes at least a hopper for
feeding material, a vibrating feeder, and a duct.
[0023] Hereinafter, the present invention will be described with
reference to the drawings. The present invention is not limited to
the embodiments described below, and the design can be modified as
long as the advantages of the present invention can be
achieved.
[0024] FIG. 5 is a schematic view of a dome-shaped rotary hearth
furnace having a doughnut-shaped rotary moving hearth. FIGS. 1 and
3 are cross-sectional views taken along the line A-A of FIG. 5, and
FIGS. 2A and 2B are plan views showing a feeding device-setting
part of the moving-hearth heating furnace viewed from the top.
[0025] In the figures, the moving-hearth heating furnace 1 includes
a hearth 2, to which material 9 (lumps in FIG. 1) is fed by a
feeding device. The material 9 is loaded in a hopper 10. The
material 9 is fed from the hopper 10 through a quantity-adjusting
mechanism 8 to a trough 11 of a vibrating feeder or to an indirect
conveying unit (not shown), such as a belt conveyer, which
communicates with the trough 11 of the vibrating feeder. Although
not shown, a frame is formed at the edges of the trough 11 in order
to prevent the material from dropping due to the vibration of the
trough 11.
[0026] In the vibrating feeder, a vibrating device 7 vibrates the
trough 11 so that the material on the trough 11 is allowed to move
toward a hole 13, which is provided in the trough 11.
[0027] As such a vibrating feeder, the following known feeders may
be used: for example, a shaking feeder, an electromagnetic
vibrating feeder, an electric-motor-driven vibrating feeder, and a
stick-slip feeder. Among them, an electromagnetic vibrating feeder
is recommended, in which the amount of material to be fed can be
adjusted so that the material is fed to the furnace constantly (for
example, with a constant width and uniform thickness).
[0028] The hole 13 through which the material is fed to the hearth
2 is formed in the trough 11. The shape, size, and position of the
hole 13 is not specified and may be determined according to the
application. For example, as shown in FIG. 2A, a plurality of
slit-shaped holes 13 may be formed in a staggered arrangement over
the width of the hearth 2. Alternatively, as shown in FIG. 2B, one
slit-shaped hole may be formed over the width of the hearth 2. In
order to evenly feed the material to the furnace over the width of
the hearth 2 and to prevent the material from falling over the
edges of the trough 11, it is preferable to form a plurality of
slit-shaped holes in a staggered arrangement or one slit-shaped
hole in a slanting direction over the width of the hearth 2, as
shown in FIGS. 2A and 2B. In particular, as shown in FIG. 2B, it is
desired that one slit-shaped hole 13 be formed in a slanting
direction with respect to the longitudinal direction of the trough
11 (that is, ends 13a and 13b of the hole 13 are positioned at ends
11a and 11b in the longitudinal direction of the trough 11,
respectively, so that the hole extends in a slanting direction with
respect to the width direction of the hearth 2) so that the two
ends 13a and 13b of the hole 13 are positioned at the two ends of
the hearth 2. Of course, a plurality of partitions may be provided
on the trough 11 as required so as to form paths for the material
to be fed. Although not shown in FIGS. 2A and 2B, a cover 11a is
desirably provided over the trough 11 so as to effectively shield
and seal the trough 11.
[0029] Preferably, a feeding nozzle 14 having an arbitrary length
is formed below the trough 11, the nozzle 14 extending downward
along the edge of the opening of the hole 13. The feeding nozzle 14
prevents the material dropping through the hole 13 from scattering
and functions as a guide for reliably guiding the material to a
duct 15. Therefore, the feeding nozzle 14 extends so that a lower
end 14a of the feeding nozzle 14 is positioned below an upper end
15a of the duct 15 and the upper end 15a of the duct 15 is placed
so as to surround the periphery of the nozzle 14.
[0030] The duct 15 extends through a ceiling 3 of the heating
furnace 1 and the upper end 15a of the duct 15 is positioned
between the lower end 14a of the feeding nozzle 14 and the lower
surface of the trough 11. Also, a lower end 15b of the duct 15 is
positioned above the hearth 2 of the heating furnace 1 such that
the duct 15 is open.
[0031] The feeding nozzle 14 provided in the trough 11 vibrates due
to the vibration of the trough 11 (for example, it vibrates in the
vertical and horizontal directions), and thus the vibrating feeder
and the duct 15 must always be prevented from coming into contact
so that the vibrating feeder (in particular, the feeding nozzle 14
and the trough 11) is not brought into contact with the duct 15. On
the other hand, when the vibrating feeder is not in contact with
the duct 15, high-temperature gas and dust in the furnace rise
through the duct 15 and flow out through the non-contacting
portions. Thus, the area of the non-contacting portions should be
as small as possible. Specifically, the distance between the lower
surface of the trough 11 and the upper end 15a of the duct 15 and
the distance between the periphery of the feeding nozzle 14 and the
duct 15 are preferably as short as possible, while maintaining the
above-described non-contacting state.
[0032] In the present invention, when the feeding nozzle 14 of the
vibrating feeder is not in contact with the duct 15, a water
sealing mechanism is provided so that high-temperature gas and dust
rising through the duct 15 do not flow out through the
non-contacting portions.
[0033] The specific configuration of the water sealing mechanism is
not limited as long as the flow of gas can be blocked at the
non-contacting portions.
[0034] The water sealing mechanism shown in FIG. 1 includes a skirt
plate 16, a weir plate 17, a side surface of the duct 15, and
liquid 18.
[0035] The skirt plate 16 functions as a weir for blocking the flow
of gas and is formed so as to surround the periphery of the upper
end 15a of the duct 15. Also, the skirt plate 16 is provided on the
lower surface of the trough 11 such that a lower end 16a of the
skirt plate 16 is positioned below the upper end 15a of the duct
15.
[0036] Herein, the skirt plate 16 may be provided at an arbitrary
position between the duct 15 and the weir plate 17. However, it is
desired to place the skirt plate 16 as close as possible to the
duct 15 in order to prevent a wide range of the trough 11 from
being heated by high-temperature gas rising through the duct 15.
Incidentally, the skirt plate 16 vibrates in accordance with the
vibration of the trough 11, and thus the skirt plate 16 should also
be placed so that it is not in contact with the duct 15 and the
weir plate 17.
[0037] The weir plate 17 also functions as a weir for holding the
liquid 18 and is formed so as to surround the periphery of the
lower end 16a of the skirt plate 16. Also, the weir plate 17 is
provided above the ceiling of the heating furnace 1 such that an
upper end 17a of the weir plate 17 is positioned above the lower
end 16a of the skirt plate 16.
[0038] A pool of liquid 18 for water sealing is held in a tank
formed by the side surface of the duct 15 and the weir plate 17. At
this time, in order to prevent leakage of high-temperature gas, the
lower end 16a of the skirt plate 16 must always be under the liquid
18 even when the trough 11 vibrates. Therefore, the liquid surface
must always be kept above the lower end 16a of the skirt plate 16
by adjusting the amount of the liquid 18. Incidentally, the liquid
18 is simply kept in the tank; the liquid 18 does not flow.
[0039] The liquid surface also vibrates due to the vibration of the
trough 11. Thus, it is desired to adequately set the length of the
duct 15, the skirt plate 16, and the weir plate 17 and the amount
of the liquid 18 so that the liquid 18 does not leak out of the
water sealing mechanism, for example, into the furnace, due to the
vibration.
[0040] As the sealing liquid, water and so on may be used. But
water is the best in terms of cost efficiency and safety. Of
course, known additives such as a boiling point adjusting agent and
a preservative may be added to the water.
[0041] The weir plate 17 should be placed near the periphery of the
skirt plate 16 in order to obtain a sealing effect by using the
above-described water sealing mechanism. By adopting such a water
sealing mechanism, high-temperature gas and dust in the furnace do
not leak through the non-contacting portions of the nozzle 14 and
the duct 15 to the atmosphere. Further, the above-described water
sealing mechanism can be maintained simply by changing the liquid.
Also, it is easy to visually check the water sealing status (level
of the liquid surface and condition of the liquid), and thus the
mechanism can be easily checked.
[0042] Preferably, in the above-described water sealing mechanism,
by forming the pool of liquid at an area including the feeding
nozzle 14 of the trough 11, as shown in FIG. 1, the trough 11
positioned above the pool of liquid is not heated More preferably,
the weir plate 17 is provided to surround the area including the
trough 11 and the width of the hearth 2 below the trough 11 so as
to form the pool of liquid, as shown in FIGS. 2A, 2B, and 3. Since
the heating furnace 1 is operated at high-temperature, the external
upper surface of the furnace 1 is heated to considerably high
temperature. However, by increasing the area of the pool of liquid
in the water sealing mechanism described above, a rise in
temperature at the ceiling of the heating furnace (outer side) is
suppressed and deterioration in the vibrating feeder including the
trough 11 can be advantageously prevented.
[0043] For example, when the weir plate 17 is provided near the
duct 15, as shown in FIG. 1, only the vicinity of the feeding
nozzle 14 is cooled, and thus the distance between the external
upper surface of the furnace 1 and the trough 11 cannot be reduced,
as described later.
[0044] On the other hand, as shown in FIGS. 2A, 2B, and 3, by
forming the pool of liquid over the whole area under the trough 11
corresponding to the width of the ceiling of the furnace, a rise in
temperature at the trough 11 above the pool of liquid can be
suppressed. In this way, by suppressing a rise in temperature at
the trough 11, the distance between the ceiling of the furnace and
the trough 11 can be set to be shorter than in the known art.
[0045] That is, when the material 9 on the trough 11 is heated by
the heat from the ceiling of the furnace, the quality of the
material declines or the trough 11 is deformed by the heat. Thus,
in the known art, the trough 11 is placed at a considerable
distance from the ceiling of the furnace in order to prevent this
problem.
[0046] For example, when metallic iron is produced by using the
above-described heating furnace, and when a mixed powder containing
a carbonaceous reductant and iron oxide is heated on the trough,
the carbonaceous material is vaporized and adheres to the inside of
the trough 11. Otherwise, the trough 11 is deformed by heat and
therefore the material cannot be fed evenly.
[0047] However, by forming the pool of liquid under the entire area
of the trough 11 so as to prevent a rise in temperature at the
trough 11, all of the above-described problems can be overcome. In
addition, since the distance between the trough 11 and the hearth 2
can be shortened, breaking of lumps due to impact upon dropping and
the amount of dust can be reduced.
[0048] The area of the pool of liquid which is formed below the
trough 11 and the amount of the liquid may be determined in
consideration of various factors such as heat resistance of the
material to be fed and the operating conditions of the heating
furnace. For example, a decline in quality of the material to be
fed can be sufficiently suppressed, depending on the operating
conditions, when the pool of liquid is formed below the trough 11,
such that the distance between the pool of liquid and the trough 11
corresponds to about half of the width of the ceiling of the
furnace.
[0049] More preferably, as described above, the weir plate 17 is
formed to surround the area including the trough 11 and the width
of the ceiling of the furnace which exists under the trough 11 so
that this area is regarded as the pool of liquid. Also, by
extending the area of the pool of liquid, the thickness of a
fireproof wall of the ceiling of the furnace at the corresponding
portion can be reduced. In order to further improve the increased
temperature suppressing effect, the amount of liquid (volume) per
unit area is preferably increased.
[0050] In order to suppress evaporation of the liquid due to a rise
in temperature of the liquid, the liquid in the pool of liquid
should be adequately changed. Therefore, as shown in FIGS. 2A and
2B, at least one inlet 21 through which the liquid is fed to the
tank including the side surface of the duct 15 and the weir plate
17 and at least one outlet 22 for discharging the liquid are
preferably provided, In this way, by providing the inlet 21 and the
outlet 22, the liquid can be easily changed, and thus maintenance
can be easily performed even in a relatively small space.
[0051] Preferably, the liquid is fed to or discharged from the tank
continuously or intermittently in order to prevent a decrease in
the cooling effect due to a rise in temperature and a decrease in
fluidity of the liquid due to mixing of dust. Also, a flow path or
a liquid conveyer may be provided so that the function of the
liquid as a cooling medium can be evenly ensured over the whole
area,
[0052] The feeding device according to the present invention is not
limited to the above-described embodiment, and improvements and
modifications are possible without deviating from the fundamental
principle of the present invention.
* * * * *