U.S. patent application number 11/069983 was filed with the patent office on 2006-09-07 for pump device.
Invention is credited to Jun Taga.
Application Number | 20060198743 11/069983 |
Document ID | / |
Family ID | 36944281 |
Filed Date | 2006-09-07 |
United States Patent
Application |
20060198743 |
Kind Code |
A1 |
Taga; Jun |
September 7, 2006 |
Pump device
Abstract
A pump device has an impeller rotatable in a pump space, a
rotational shaft interconnecting a rotational drive source and the
impeller, a rotational shaft casing having a bearing assembly
and/or a seal assembly, a first blocking flow mechanism, having a
discharge section for discharging a portion of a main delivery
liquid introduced from the pump space as a first blocking flow, for
preventing a second blocking flow containing fine particles
produced by the bearing assembly and/or the seal assembly from
being entrained into the main delivery liquid, and a second
blocking flow mechanism for combining the second blocking flow with
the first blocking flow and discharging the second blocking flow
from the discharge section while preventing the first blocking flow
from being introduced.
Inventors: |
Taga; Jun; (Kawasaki-shi,
JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
36944281 |
Appl. No.: |
11/069983 |
Filed: |
March 3, 2005 |
Current U.S.
Class: |
417/423.1 |
Current CPC
Class: |
F04D 29/128 20130101;
F04D 29/108 20130101 |
Class at
Publication: |
417/423.1 |
International
Class: |
F04B 17/00 20060101
F04B017/00 |
Claims
1. A pump device comprising: an impeller rotatable in a pump space;
a rotational shaft interconnecting a rotational drive source and
said impeller; a rotational shaft casing having a bearing assembly
and/or a seal assembly; a first blocking flow mechanism, having a
discharge section for discharging a portion of a main delivery
liquid introduced from said pump space as a first blocking flow,
for preventing a second blocking flow containing fine particles
produced by said bearing assembly and/or said seal assembly from
being entrained into the main delivery liquid; and a second
blocking flow mechanism for combining said second blocking flow
with said first blocking flow and discharging said second blocking
flow from said discharge section while preventing said first
blocking flow from being introduced.
2. A pump device according to claim 1, wherein said first blocking
flow mechanism has a first blocking flow passage defined between
said rotational shaft and an inner circumferential surface of said
rotational shaft casing, and said second blocking flow mechanism
has a second blocking flow passage defined between said rotational
shaft and an inner circumferential surface of said rotational shaft
casing, said first blocking flow passage and said second blocking
flow passage being disposed in respective positioned on both sides
of said discharge section, said second blocking flow passage being
supplied with an inactive liquid as said second blocking flow from
a second blocking flow supply port which is open into said second
blocking flow passage.
3. A pump device according to claim 1, wherein said discharge
section comprises a blocking disk mounted on said rotational shaft
and a disk chamber defined in said rotational shaft casing and
housing said blocking disk therein.
4. A pump device according to claim 3, wherein a labyrinth is
provided in said disk chamber between an inner circumferential
surface of said disk chamber and said blocking disk.
5. A pump device according to claim 2, wherein said second blocking
flow has a higher liquid pressure than said first blocking flow at
said second blocking flow supply port.
6. A pump device according to claim 2, wherein said second blocking
flow passage is filled at all times with the inactive liquid
supplied from said second blocking flow supply port.
7. A pump device according to claim 1, wherein said first blocking
flow is discharged from said discharge section at a rate higher
than said second blocking flow, the rate of said second blocking
flow being at least 1.5 when the rate of said first blocking flow
is 1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a rotary pump device for
transporting a very highly-purity active liquid for use in a
process of fabricating semiconductor devices, liquid crystals,
etc., and more particularly to a pump device which is capable of
preventing metal ions and other fine particles from being produced
by isolating an active liquid, such as ultrapure water or the like,
and a metallic part of a pump mechanism from each other.
[0003] 2. Description of the Related Art
[0004] For achieving a high level of integration of semiconductor
devices, it is necessary to increase the purity of various liquids
used in the fabrication process and, in particular, to achieve
extremely lower content of impurities in those liquids. With regard
to ultrapure water that is used in a cleaning process for
semiconductor fabrication, the content of fine particles having a
size of 0.1 micron poses a problem and greatly affects the yield of
products. Particularly, it was a challenging task for pumps for
transporting ultrapure water to prevent fine particles from being
produced by the wear of rotary sliding components. The task has
been achieved by the inventor of the present application as
disclosed in Japanese patent No. 1807169, U.S. Pat. No. 5131806, or
Japanese laid-open patent publication No. H3-26897.
[0005] As the level of integration of semiconductor devices and the
performance of liquid crystals further increase, however, the
concentration of metal ions, which remain in ultrapure water, poses
a large problem. Today, the content of metal ions is required to be
1 PPT (Part Per Trillion) or less. Metal ions are caused to occur
when ultrapure water dissolves a metal in liquid-contacting regions
of devices including pumps, pipes, valves, etc. in a wet process.
It is understood that ultrapure water of highest purity having a
resistance of 18.20 M.OMEGA. or higher tends to elute highly active
ions of metal or the like.
SUMMARY OF THE INVENTION
[0006] In order to solve the above disadvantage, it has been
customary to apply a surface treatment, such as a lining or coating
of tetrafluororesin, to regions of devices, such as pumps, that are
brought into contact with ultrapure water. However, it is generally
difficult to apply a surface treatment, such as a lining of
tetrafluororesin, to rotary sliding components and seals of pumps.
Even if very chemically stable, highly hard SiC (silicon carbide)
is used for rotary sliding components and seals of pumps, it cannot
fully prevent ultrapure water from dissolving the metal. At
present, it has been attempted to use functional ultrapure water
containing a small amount of ozone (O.sub.3) or hydrogen fluoride
(HF). Use of functional ultrapure water, however, is problematic in
that metal and ceramics are exposed to a chemical attack, causing
the liquid-contacting regions in rotary sliding components of
pumps, i.e., bearings and seals, to suffer erosion due to elution
of metal and ceramics.
[0007] A pump device according to the present invention has an
impeller rotatable in a pump space, a rotational shaft
interconnecting a rotational drive source and the impeller, a
rotational shaft casing having a bearing assembly and/or a seal
assembly, a first blocking flow mechanism, having a discharge
section for discharging a portion of a main delivery liquid
introduced from the pump space as a first blocking flow, for
preventing a second blocking flow containing fine particles
produced by the bearing assembly and/or the seal assembly from
being entrained into the main delivery liquid, and a second
blocking flow mechanism for combining the second blocking flow with
the first blocking flow and discharging the second blocking flow
from the discharge section while preventing the first blocking flow
from being introduced.
[0008] In a preferred aspect of the present invention, the first
blocking flow mechanism has a first blocking flow passage defined
between the rotational shaft and an inner circumferential surface
of the rotational shaft casing, and the second blocking flow
mechanism has a second blocking flow passage defined between the
rotational shaft and an inner circumferential surface of the
rotational shaft casing, the first blocking flow passage and the
second blocking flow passage being disposed in respective
positioned on both sides of the discharge section, the second
blocking flow passage being supplied with an inactive liquid as the
second blocking flow from a second blocking flow supply port which
is open into the second blocking flow passage.
[0009] Preferably, the discharge section comprises a blocking disk
mounted on the rotational shaft and a disk chamber defined in the
rotational shaft casing and housing the blocking disk therein.
Further preferably, a labyrinth is provided in the disk chamber
between an inner circumferential surface of the disk chamber and
the blocking disk.
[0010] The second blocking flow preferably has a higher liquid
pressure than the first blocking flow at the second blocking flow
supply port.
[0011] The second blocking flow passage is preferably filled at all
times with the inactive liquid supplied from the second blocking
flow supply port.
[0012] The first blocking flow is preferably discharged from the
discharge section at a rate higher than the second blocking flow,
the rate of the second blocking flow being at least 1.5 when the
rate of the first blocking flow is 1.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a cross-sectional view of a pump device according
to an embodiment of the present invention; and
[0014] FIG. 2 is a cross-sectional view of a pump device according
to another embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] A pump device according to an embodiment of the present
invention has regions, other than rotary sliding components, such
as a bearing assembly and a seal assembly in a rotational shaft
casing, which are brought into contact with a main delivery liquid
(ultrapure water) and which have surfaces treated for erosion
resistance by a lining of tetrafluororesin or the like. In a first
blocking flow mechanism, a first blocking flow as a portion of a
main delivery liquid (ultrapure water) flowing from a pump space
into the rotational shaft casing is discharged out of the
rotational shaft casing through a first blocking flow passage
defined between a rotational shaft and an inner circumferential
surface of the rotational shaft casing, a discharge section
contiguous to the first blocking flow passage and disposed in the
rotational shaft casing closely to an impeller, and a discharge
passage communicated with the discharge section. Therefore, a
second blocking flow containing fine particles produced from the
rotary sliding components, such as the bearing assembly and the
seal assembly, as they are worn is blocked by the first blocking
flow against entry from the rotational shaft casing into the pump
space.
[0016] Specifically, in a second blocking flow mechanism, an
inactive liquid, such as ordinary tap water, which exhibits an
excellent lubricity to ultrapure water, flows as the second
blocking flow from a supply source into the rotational shaft
casing, and then flows through a second blocking flow passage
defined between the rotational shaft and an inner circumferential
surface of the rotational shaft into the discharge section of the
first blocking flow mechanism. Therefore, the first blocking flow
is prevented from entering into the rotary sliding components, such
as the bearing assembly and the seal assembly. In the rotational
shaft casing, the inactive liquid (water) delivered as the second
blocking flow into the rotational shaft casing flows along the
rotational shaft away from the first blocking flow mechanism, i.e.,
toward the rotary sliding components, such as the bearing assembly
and the seal assembly. Since a terminal end of the rotational shaft
casing, i.e., the end thereof close to a rotational drive source,
is sealed by a seal mechanism, the inactive liquid (water) fills
the rotational shaft casing including the rotary sliding
components, such as the bearing assembly and the seal assembly,
isolating the first blocking flow (ultrapure water) and the rotary
sliding components from each other.
[0017] The pressure of the second blocking flow of the inactive
liquid at a second blocking flow supply port is higher than the
pressure of the first blocking flow. However, the rate of the
second blocking flow may be lower than the rate of the first
blocking flow at all times, primarily at a level for allowing the
second blocking flow to operate as lubricating oil and exhibit a
cooling effect. Since the rate of the second blocking flow after it
has flowed into the rotational shaft casing is much lower than the
rate of the first blocking flow, the pressure of the second
blocking flow is gradually lowered toward the pressure of the first
blocking flow, and becomes equal to the pressure of the first
blocking flow when the second blocking flow is discharged in
combination with the first blocking flow. Consequently, the second
blocking flow does not flow toward and into the pump space on the
impeller side.
[0018] The inactive liquid (water), which forms the second blocking
flow, is supplied by a diaphragm that is actuatable pneumatically,
hydraulically or electrically, or a metering pump comprising a
plunger pump that is actuatable by an air cylinder. Tap water
having a suitable pressure may also be used as the inactive liquid.
If necessary, a supply passage interconnecting the supply source
and the rotational shaft casing may have a pressure regulating
valve, a flow regulating valve, an on-off valve, and the like.
[0019] Embodiments of the present invention will be described in
detail below with reference to the drawings. FIG. 1 is a
cross-sectional view of a pump device according to an embodiment of
the present invention.
[0020] As shown in FIG. 1, the pump device has an impeller 2
rotatable in a pump space 1, a rotational shaft 3 interconnecting a
rotational drive source M and the impeller 2, and a rotational
shaft casing 4 having a bearing assembly B and a mechanical seal
assembly S. The mechanical seal assembly S has a fixed ring S1 and
a rotary ring S2. Regions of the various components, other than the
bearing assembly B and the mechanical seal assembly S, which are
brought into contact with ultrapure water as a main delivery
liquid, are treated for erosion resistance by a lining of
tetrafluororesin or the like. The regions, which are treated for
erosion resistance, are indicated by bold solid lines in FIG.
1.
[0021] The rotational shaft casing 4 has a disk chamber 5a defined
therein by an inner circumferential surface thereof and positioned
between the impeller 2 and the bearing assembly B. A blocking disk
5b mounted on the rotational shaft 3 is rotatably housed in the
disk chamber 5a. The disk chamber 5a and the blocking disk 5b,
housed in the disk chamber 5a and made of fluororesin, make up a
discharge section 5 of a first blocking flow mechanism. The disk
chamber 5a communicates with a discharge passage 5c having flow
rate regulating mechanisms 5e, 5f. In this embodiment, a labyrinth
5d is provided between the inner circumferential surface of the
disk chamber 5a and the blocking disk 5b. However, as shown in FIG.
2, the labyrinth 5d may be dispensed with.
[0022] The first blocking flow mechanism is constructed of a first
blocking flow passage 6 which is defined as a gap between the
portion of the rotational shaft 3 extending from the pump space 1
to the disk chamber 5a and the inner circumferential surface of the
rotational shaft casing 4, the discharge section 5, and the
discharge passage 5c. The first blocking flow mechanism causes a
branched flow of ultrapure water as the main delivery liquid to
flow from the pump space 1 successively through the first blocking
flow passage 6, the discharge section 5, and the discharge passage
5c, preventing a liquid containing fine particles (a second
blocking flow) from entering from the bearing assembly B and the
mechanical seal assembly S into the pump space 1.
[0023] The pump device also has a supply source T of an inactive
liquid (water), a metering pump P, a second blocking flow supply
port 7 that is open at the inner circumferential surface of the
rotational shaft casing 4 between the bearing assembly B and the
mechanical seal assembly S, and a second blocking flow passage 8
which is defined as a gap between the portion of the rotational
shaft 3 extending from the bearing assembly B to the disk chamber
5a and the inner circumferential surface of the rotational shaft
casing 4. The supply source T, the metering pump P, the second
blocking flow supply port 7, and the second blocking flow passage 8
make up a second blocking flow mechanism. If the pump space 1 is
regarded as a front end, then the second blocking flow supply port
7 of the second blocking flow mechanism is positioned behind the
blocking disk 5b disposed at a terminal end of the first blocking
flow mechanism. An inactive liquid (water) supplied from the supply
source T flows as a second blocking flow successively through the
bearing assembly B, the second blocking flow passage 8, the
discharge section 5, and the discharge passage 5c, preventing the
first blocking flow (ultrapure water) coming from the discharge
section 5 of the first blocking flow mechanism from entering into
the bearing assembly B.
[0024] As described above, the second blocking flow is combined
with the first blocking flow in the discharge section 5 of the
first blocking flow mechanism, and flows out from the discharge
passage 5c. In this embodiment, the discharge section 5 is made up
of the disk chamber 5a and the blocking disk 5b, and the labyrinth
5d is provided in the disk chamber 5a, making it difficult for the
blocking blows to combine with each other and allowing the blocking
flows to flow as centrifugal flows due to the rotation of the
blocking disk 5b out from the discharge passage 5c. The first
blocking flow is thus fully prevented from entering into the
bearing assembly B.
[0025] The inactive liquid, which forms the second blocking flow,
maybe ordinary tap water, and is supplied under a higher pressure
and at a lower rate than the first blocking flow to the second
blocking flow passage 8 by the metering pump P. Since the second
blocking flow flows under a high pressure and at a low rate, it is
equalized in pressure to the first blocking flow in the discharge
section 5, and discharged out of the pump device through the flow
rate regulating mechanisms 5e, 5f provided in the discharge passage
5c. The ratio of the flow rates of the first and second blocking
flows, which are combined with each other, may be 1.5:1, or 50:1 or
100:1 in some cases. The direction of the blocking flows is
determined by the flow rate of the first blocking flow as a main
flow. The second blocking flow supplied to the pump device can
maintain a large discharge rate.
[0026] If the pump device is inactivated for a long time, fine
particles including metal ions produced from metal and ceramics of
liquid-contacting regions brought into contact with the delivery
liquid are entrained into the ultrapure water as the delivery
liquid. Therefore, for achieving the ultrahigh purity of ultrapure
water, whose metal ion concentration is required to be 1 PPT or
less, immediately after the pump device has started to operate, it
is necessary to clean the contaminated interior of the pump device
with a large amount of flushing ultrapure water at the time the
pump device starts to operate. However, the flushing process is
responsible for an excessive increase in the running cost of the
pump device.
[0027] According to this embodiment, after the pump device has
ceased to operate, the second blocking flow mechanism is
immediately inactivated to stop the second blocking flow containing
fine particles of metal and ceramics. At the same time, the main
pump is operated again to circulate the first blocking flow at a
rate, which is 1/10 or less of the ordinary rate, for thereby
reliably preventing fine particles including eluted ions of metal
and ceramics from entering into the pump space 1. Since the second
blocking flow mechanism is filled with the second blocking flow,
the first blocking flow does not enter into the bearing assembly B.
The second blocking flow mechanism may be operated continuously or
intermittently at a rate which is 1/2 of the ordinary rate. In this
embodiment shown in FIG. 1, a lip seal L1 is provided as a check
valve in the first blocking flow passage 6, and a lip seal L2 is
provided as a check valve in the second blocking flow passage
8.
[0028] When a small amount of blocking flow is thus passed
intermittently or continuously, ions of metal or the like, which
are produced when the pump device is inactivated, are prevented
from being spread into the entire pump device due to Brownian
movement, thereby keeping a highly pure environment in the pump
device.
[0029] FIG. 2 shows a pump device according to another embodiment
of the present invention. The pump device shown in FIG. 2 is
different from the pump device shown in FIG. 1 in that the bearing
assembly B is dispensed with, and the rotary ring S2 of the
mechanical seal assembly S is positioned closer to the impeller 2,
with the second blocking flow support port 7 being open in the
rotational shaft casing 4 between the blocking disk 5b and the
fixed ring S1 of the mechanical seal assembly S.
[0030] According to the present invention, with the above-described
arrangement and operation, fine particles produced in the rotary
sliding regions of the rotary pump are efficiently discharged at a
low cost, the main delivery liquid is effectively prevented from
entering into the rotary sliding regions, and fine particles, such
as metal ions or the like, are prevented from being produced due to
contact between the main delivery liquid, such as ultrapure water
or the like, and the rotary sliding regions of the pump device.
[0031] The present invention has been described above as having an
outside-type mechanical seal having a fixed ring disposed in a pump
chamber and a rotary ring and a spring disposed outside of the pump
chamber. However, the present invention is also applicable to an
inside-type mechanical seal mechanism having a rotary ring and a
spring disposed in a pump chamber.
[0032] The present invention is also applicable to a grand packing
mechanism or a lip seal mechanism which is a rotary sliding seal
mechanism other than the mechanical seal.
[0033] As described above, a pump device according to the present
invention for transporting ultrapure water or the like has a pump
space, an impeller rotatable in the pump space, a rotational shaft
interconnecting a rotational drive source and the impeller, and a
rotational shaft casing having a bearing assembly and a seal
assembly. The pump device has regions brought into contact with a
main delivery liquid and treated for erosion resistance by a lining
of tetrafluororesin or the like. The pump device also has a first
blocking flow mechanism for preventing worn fine particles produced
from rotary sliding components, such as the bearing assembly and
the seal assembly, brought into contact with a second blocking
flow, from being entrained into the delivery liquid, and a second
blocking flow mechanism for preventing a main delivery liquid from
entering from the pump space into regions, not treated for erosion
resistance, of the rotary sliding components.
[0034] The first blocking flow mechanism comprises a first blocking
flow passage defined by the rotational shaft and an inner
circumferential surface of the rotational shaft casing, a discharge
section disposed in the rotational shaft casing closely to the
impeller, for discharging a first blocking flow introduced as the
main delivery liquid from the pump space into the rotational shaft
casing, from the first blocking flow passage, and a discharge
passage communicated with the discharge section.
[0035] The second blocking flow mechanism comprises a supply source
for supplying a inactive liquid, having a lubricity, as the second
blocking flow, a second blocking flow passage for delivering the
second blocking flow into the rotational shaft casing having the
bearing assembly and the seal assembly positioned therein, the
second blocking flow passage being defined by the rotational shaft
and the inner circumferential surface of the rotational shaft
casing, a second blocking flow supply port defined in the
rotational shaft casing between an end of the rotational shaft
closely to the rotary sliding components and the discharge passage,
for combining the second blocking flow through the second blocking
flow passage with the first blocking flow and discharging the
second blocking flow from the discharge passage of the first
blocking flow mechanism, and a supply passage disposed between the
supply source and the second blocking flow supply port.
[0036] In the above pump device, the discharge section of the first
blocking flow mechanism comprises a blocking disk mounted on the
rotational shaft in an area where the opposite flows meet each
other, and a disk chamber defined in the rotational shaft casing
and housing the blocking disk therein.
[0037] A labyrinth is preferably provided in the disk chamber for
preventing the first blocking flow and the second blocking flow
from flowing into the second blocking flow passage and the first
blocking flow passage, respectively.
[0038] The regions not treated for erosion resistance in the
rotational shaft casing is preferably filled at all times with the
second blocking flow of the inactive liquid flowing in from the
second blocking flow supply port, for isolation from the main
delivery liquid having a strong chemical attack tendency which is
introduced from the first blocking flow passage.
* * * * *