U.S. patent application number 16/707167 was filed with the patent office on 2020-06-11 for bellows pump device.
This patent application is currently assigned to NIPPON PILLAR PACKING CO., LTD.. The applicant listed for this patent is NIPPON PILLAR PACKING CO., LTD.. Invention is credited to Atsushi NAKANO, Kazukiyo TESHIMA, Ai TOMOTOSHI.
Application Number | 20200182234 16/707167 |
Document ID | / |
Family ID | 70972638 |
Filed Date | 2020-06-11 |
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United States Patent
Application |
20200182234 |
Kind Code |
A1 |
NAKANO; Atsushi ; et
al. |
June 11, 2020 |
BELLOWS PUMP DEVICE
Abstract
A bellows pump device includes: a first electropneumatic
regulator 51 that adjusts a first air pressure of pressurized air
in a first discharge-side air chamber 21A of a first air cylinder
unit 27; a second electropneumatic regulator 52 that adjusts a
second air pressure of pressurized air in a second discharge-side
air chamber 21B of a second air cylinder unit 28; and a control
unit 6 that controls the first electropneumatic regulator 51 such
that the first air pressure is continuously decreased during a
period from a time when a second bellows 14 starts contracting
until a first bellows 13 comes into a most contracted state, and
controls the second electropneumatic regulator 52 such that the
second air pressure is continuously decreased during a period from
a time when the first bellows 13 starts contracting until the
second bellows 14 comes into a most contracted state.
Inventors: |
NAKANO; Atsushi; (Osaka,
JP) ; TOMOTOSHI; Ai; (Osaka, JP) ; TESHIMA;
Kazukiyo; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NIPPON PILLAR PACKING CO., LTD. |
Osaka |
|
JP |
|
|
Assignee: |
NIPPON PILLAR PACKING CO.,
LTD.
Osaka
JP
|
Family ID: |
70972638 |
Appl. No.: |
16/707167 |
Filed: |
December 9, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04B 43/088 20130101;
F04B 49/22 20130101; F04B 49/08 20130101; F04B 43/113 20130101 |
International
Class: |
F04B 43/08 20060101
F04B043/08; F04B 49/22 20060101 F04B049/22; F04B 49/08 20060101
F04B049/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 11, 2018 |
JP |
2018-231725 |
Claims
1. A bellows pump device comprising: a pump head having a suction
passage and a discharge passage for a transport fluid; a first
bellows and a second bellows mounted on the pump head so as to be
expandable/contractible independently of each other and configured
to suck the transport fluid from the suction passage thereinto by
expansion thereof and discharge the transport fluid therefrom to
the discharge passage by contraction thereof; a check valve
configured to permit flow of the transport fluid in one direction
in the suction passage and the discharge passage and block flow of
the transport fluid in another direction in the suction passage and
the discharge passage; a first driving unit having a first
suction-side fluid chamber and a first discharge-side fluid chamber
and configured to supply a pressurized fluid to the first
suction-side fluid chamber thereby causing the first bellows to
expand to a most expanded state, and supply the pressurized fluid
to the first discharge-side fluid chamber thereby causing the first
bellows to contract to a most contracted state; and a second
driving unit having a second suction-side fluid chamber and a
second discharge-side fluid chamber and configured to supply a
pressurized fluid to the second suction-side fluid chamber thereby
causing the second bellows to expand to a most expanded state, and
supply the pressurized fluid to the second discharge-side fluid
chamber thereby causing the second bellows to contract to a most
contracted state, wherein the second bellows contracts from the
most expanded state before the first bellows comes into the most
contracted state, and the first bellows contracts from the most
expanded state before the second bellows comes into the most
contracted state, the bellows pump device further comprising a
first fluid pressure adjustment unit configured to adjust a first
fluid pressure of the pressurized fluid in the first discharge-side
fluid chamber of the first driving unit, a second fluid pressure
adjustment unit configured to adjust a second fluid pressure of the
pressurized fluid in the second discharge-side fluid chamber of the
second driving unit, and a control unit configured to control the
first fluid pressure adjustment unit such that the first fluid
pressure is decreased stepwise or continuously during a period from
a time at which the second bellows starts contracting to a time at
which the first bellows comes into the most contracted state, and
control the second fluid pressure adjustment unit such that the
second fluid pressure is decreased stepwise or continuously during
a period from a time at which the first bellows starts contracting
to a time at which the second bellows comes into the most
contracted state.
2. The bellows pump device according to claim 1, wherein the
control unit controls the first fluid pressure adjustment unit such
that the first fluid pressure reaches zero before or when the first
bellows comes into the most contracted state, and controls the
second fluid pressure adjustment unit such that the second fluid
pressure reaches zero before or when the second bellows comes into
the most contracted state.
3. The bellows pump device according to claim 2, wherein the
control unit controls the first fluid pressure adjustment unit such
that the first fluid pressure reaches zero at the time at which the
first bellows comes into the most contracted state, and controls
the second fluid pressure adjustment unit such that the second
fluid pressure reaches zero at the time at which the second bellows
comes into the most contracted state.
Description
TECHNICAL FIELD
[0001] The present invention relates to a bellows pump device.
BACKGROUND ART
[0002] As a bellows pump used for feeding a transport fluid such as
a chemical solution or a solvent in semiconductor production,
chemical industries, or the like, a bellows pump which includes: a
pair of bellows configured to suck a transport fluid thereinto and
discharge the transport fluid therefrom by expanding/contracting
independently of each other; and air cylinders configured to cause
the respective bellows to expand/contract, by supplying/discharging
compressed air (see, for example, PATENT LITERATURE 1), has been
known. The bellows pump disclosed in PATENT LITERATURE 1 controls
drive of each air cylinder such that, before one bellows comes into
a most contracted state (end of discharge), the other bellows is
caused to contract from a most expanded state to discharge a
transport fluid.
[0003] By controlling drive of each air cylinder as described
above, at a time of switching from contraction of one bellows to
expansion thereof (from discharge of the transport fluid to suction
thereof), the other bellows has already contracted to discharge the
transport fluid. Accordingly, great fall of the discharge pressure
of the transport fluid at the time of switching can be reduced. As
a result, pulsation at the discharge side of the bellows pump can
be reduced.
CITATION LIST
Patent Literature
[0004] PATENT LITERATURE 1: Japanese Laid-Open Patent Publication
No. 2004-293502
SUMMARY OF INVENTION
Technical Problem
[0005] The above bellows pump includes a check valve that prevents
backflow of the transport fluid in a discharge process of
discharging the transport fluid by contraction of each bellows.
When one bellows is switched from a discharge process to a suction
process, the check valve that has opened in the discharge process
to permit discharge of the transport fluid is pressed to close by
the transport fluid discharged from the other bellows.
[0006] However, there is the following problem. Specifically, when
one bellows is switched from a discharge process to a suction
process, the other bellows has already contracted to discharge
high-pressure transport fluid as described above, and thus the
check valve is pressed to rapidly close by the high-pressure
transport fluid. Therefore, the impact generated when the check
valve rapidly closes is transmitted to the interior of a transport
fluid discharge pipe connected to the bellows pump, whereby, as
shown in FIG. 10, surge pressure (a portion surrounded by a broken
line in the drawing) is generated within the discharge pipe.
[0007] The present invention has been made in view of such
circumstances, and an object of the present invention is to provide
a bellows pump device that can reduce pulsation and inhibit
generation of surge pressure at the discharge side when switching
is made from discharge of a transport fluid to suction thereof.
Solution to Problem
[0008] (1) A bellows pump device according to the present invention
is a bellows pump device including: a pump head having a suction
passage and a discharge passage for a transport fluid; a first
bellows and a second bellows mounted on the pump head so as to be
expandable/contractible independently of each other and configured
to suck the transport fluid from the suction passage thereinto by
expansion thereof and discharge the transport fluid therefrom to
the discharge passage by contraction thereof; a check valve
configured to permit flow of the transport fluid in one direction
in the suction passage and the discharge passage and block flow of
the transport fluid in another direction in the suction passage and
the discharge passage; a first driving unit having a first
suction-side fluid chamber and a first discharge-side fluid chamber
and configured to supply a pressurized fluid to the first
suction-side fluid chamber thereby causing the first bellows to
expand to a most expanded state, and supply the pressurized fluid
to the first discharge-side fluid chamber thereby causing the first
bellows to contract to a most contracted state; and a second
driving unit having a second suction-side fluid chamber and a
second discharge-side fluid chamber and configured to supply a
pressurized fluid to the second suction-side fluid chamber thereby
causing the second bellows to expand to a most expanded state, and
supply the pressurized fluid to the second discharge-side fluid
chamber thereby causing the second bellows to contract to a most
contracted state, wherein the second bellows contracts from the
most expanded state before the first bellows comes into the most
contracted state, and the first bellows contracts from the most
expanded state before the second bellows comes into the most
contracted state, the bellows pump device further including a first
fluid pressure adjustment unit configured to adjust a first fluid
pressure of the pressurized fluid in the first discharge-side fluid
chamber of the first driving unit, a second fluid pressure
adjustment unit configured to adjust a second fluid pressure of the
pressurized fluid in the second discharge-side fluid chamber of the
second driving unit, and a control unit configured to control the
first fluid pressure adjustment unit such that the first fluid
pressure is decreased stepwise or continuously during a period from
a time at which the second bellows starts contracting to a time at
which the first bellows comes into the most contracted state, and
control the second fluid pressure adjustment unit such that the
second fluid pressure is decreased stepwise or continuously during
a period from a time at which the first bellows starts contracting
to a time at which the second bellows comes into the most
contracted state.
[0009] According to the present invention, before one bellows of
the first bellows and the second bellows comes into the most
contracted state, the other bellows contracts from the most
expanded state. Accordingly, at a time of switching from
contraction of the one bellows to expansion thereof (from discharge
of the transport fluid to suction thereof), the other bellows has
already contracted to discharge the fluid, and thus fall of the
discharge pressure at the time of switching can be reduced. As a
result, pulsation at the discharge side of the bellows pump device
can be reduced.
[0010] Moreover, the control unit controls the fluid pressure
adjustment unit corresponding to the discharge-side fluid chamber
corresponding to the other bellows such that the fluid pressure in
the discharge-side fluid chamber is decreased stepwise or
continuously during a period from a time at which the one bellows
starts contracting to a time at which the other bellows comes into
the most contracted state. Owing to this control, before the other
bellows comes into the most contracted state, the check valve that
permits flow of the transport fluid from the other bellows to the
discharge passage gradually moves in a valve closing direction from
a valve-open state. Accordingly, when the other bellows is switched
from the most contracted state to expansion, impact due to rapid
closing of the check valve can be alleviated. As a result, surge
pressure can be inhibited from being generated at the discharge
side of the bellows pump device when switching is made from
discharge of the transport fluid to suction of the transport
fluid.
[0011] (2) Preferably, the control unit controls the first fluid
pressure adjustment unit such that the first fluid pressure reaches
zero before or when the first bellows comes into the most
contracted state, and controls the second fluid pressure adjustment
unit such that the second fluid pressure reaches zero before or
when the second bellows comes into the most contracted state.
[0012] In this case, before or when the other bellows comes into
the most contracted state after the one bellows starts contracting,
the fluid pressure in the discharge-side fluid chamber
corresponding to the other bellows is stepwise or continuously
decreased and reaches zero. Since the fluid pressure in the
discharge-side fluid chamber is decreased as described above, the
check valve corresponding to the other bellows closes before or
when the other bellows comes into the most contracted state.
Accordingly, the check valve can be prevented from rapidly closing
when the other bellows is switched from the most contracted state
to expansion. As a result, surge pressure can be further inhibited
from being generated at the discharge side of the bellows pump
device when switching is made from discharge of the transport fluid
to suction of the transport fluid.
[0013] (3) Preferably, the control unit controls the first fluid
pressure adjustment unit such that the first fluid pressure reaches
zero at the time at which the first bellows comes into the most
contracted state, and controls the second fluid pressure adjustment
unit such that the second fluid pressure reaches zero at the time
at which the second bellows comes into the most contracted
state.
[0014] In this case, during the period from the time at which the
one bellows starts contracting to the time at which the other
bellows comes into the most contracted state, the fluid pressure in
the discharge-side fluid chamber corresponding to the other bellows
is stepwise or continuously decreased, and reaches zero at the time
at which the other bellows comes into the most contracted state.
Accordingly, the check valve corresponding to the other bellows
slowly closes as compared to the case where the fluid pressure
reaches zero before the other bellows comes into the most
contracted state. As a result, surge pressure can be further
inhibited from being generated at the discharge side of the bellows
pump device when switching is made from discharge of the transport
fluid to suction of the transport fluid.
Advantageous Effects of Invention
[0015] According to the present invention, when switching is made
from discharge of the transport fluid to suction of the transport
fluid, pulsation can be reduced and generation of surge pressure
can be inhibited at the discharge side.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 is a schematic configuration diagram of a bellows
pump device according to an embodiment of the present
invention.
[0017] FIG. 2 is a cross-sectional view of a bellows pump.
[0018] FIG. 3 is an explanatory diagram showing operation of the
bellows pump.
[0019] FIG. 4 is an explanatory diagram showing operation of the
bellows pump.
[0020] FIG. 5 is a time chart showing an example of control of
electropneumatic regulators by a control unit.
[0021] FIG. 6 is a graph showing the discharge pressure of a
transport fluid discharged from a discharge passage of the bellows
pump.
[0022] FIG. 7 is a time chart showing first to third modifications
for control of the electropneumatic regulator by the control
unit.
[0023] FIG. 8 is a time chart showing fourth and fifth
modifications for control of the electropneumatic regulator by the
control unit.
[0024] FIG. 9 is a time chart showing a sixth modification for
control of the electropneumatic regulator by the control unit.
[0025] FIG. 10 is a graph showing the pressure within a discharge
pipe to a conventional bellows pump.
DESCRIPTION OF EMBODIMENTS
[0026] Next, preferred embodiments of the present invention will be
described with reference to the accompanying drawings.
[Entire Configuration of Bellows Pump Device]
[0027] FIG. 1 is a schematic configuration diagram of a bellows
pump device according to an embodiment of the present invention.
The bellows pump device of the present embodiment is used, for
example, in a semiconductor production apparatus when an object to
be transported (transport fluid) such as a chemical solution or a
solvent is supplied in a certain amount. The bellows pump device
includes: a bellows pump 1; an air supply device 2 such as an air
compressor that supplies pressurized air (pressurized fluid) to the
bellows pump 1; a mechanical regulator 3, a first electropneumatic
regulator (first fluid pressure adjustment unit) 51, and a second
electropneumatic regulator (second fluid pressure adjustment unit)
52 that adjust the air pressure of the pressurized air; a first
solenoid valve 4; a second solenoid valve 5; and a control unit
6.
[0028] FIG. 2 is a cross-sectional view of the bellows pump 1
according to the present embodiment. The bellows pump 1 of the
present embodiment includes: a pump head 11 that is disposed at a
center portion; a pair of pump cases 12 that are mounted at both
sides of the pump head 11 in a right-left direction (horizontal
direction); a first bellows 13 and a second bellows 14 that are
mounted on side surfaces of the pump head 11 in the right-left
direction and within the respective pump cases 12; and a total of
four check valves 15 and 16 that are mounted on the side surfaces
of the pump head 11 in the right-left direction and within the
respective first and second bellows 13 and 14.
[Configurations of Bellows]
[0029] The first bellows 13 and the second bellows 14 are each
formed in a bottomed cylindrical shape from a fluorine resin such
as polytetrafluoroethylene (PTFE) or a
tetrafluoroethylene-perfluoro alkyl vinyl ether copolymer (PFA). A
flange portion 13a and a flange portion 14a are integrally formed
at open end portions of the first and second bellows 13 and 14 and
are hermetically pressed and fixed to the side surfaces of the pump
head 11. Peripheral walls of the first and second bellows 13 and 14
are each formed in an accordion shape, and are configured to be
expandable/contractible independently of each other in the
horizontal direction.
[0030] Specifically, each of the first and second bellows 13 and 14
is configured to expand/contract between a most expanded state
where an outer surface of a working plate 19 described later is in
contact with an inner side surface of a bottom wall portion 121 of
the pump case 12 and a most contracted state where an inner side
surface of a piston body 23 described later is in contact with an
outer side surface of the bottom wall portion 121 of the pump case
12. The working plate 19, together with one end portion of a
connection member 20, is fixed to each of outer surfaces of bottom
portions of the first and second bellows 13 and 14 by bolts 17 and
nuts 18.
[Configurations of Pump Cases]
[0031] An opening peripheral portion of the pump case 12
(hereinafter, also referred to as "first pump case 12A"), which is
formed in a bottomed cylindrical shape, is hermetically pressed and
fixed to the flange portion 13a of the first bellows 13.
Accordingly, a first discharge-side air chamber (first
discharge-side fluid chamber) 21A is formed within the first pump
case 12A such that a hermetic state thereof is maintained.
[0032] A first suction/discharge port 22A is provided in the first
pump case 12A and connected to the air supply device 2 via the
first solenoid valve 4, the first electropneumatic regulator 51,
and the mechanical regulator 3 (see FIG. 1). Accordingly, the first
bellows 13 contracts to the most contracted state by continuously
supplying the pressurized air from the air supply device 2 via the
mechanical regulator 3, the first electropneumatic regulator 51,
the first solenoid valve 4, and the first suction/discharge port
22A into the first discharge-side air chamber 21A.
[0033] An opening peripheral portion of the pump case 12
(hereinafter, also referred to as "second pump case 12B"), which is
formed in a bottomed cylindrical shape, is hermetically pressed and
fixed to the flange portion 14a of the second bellows 14.
Accordingly, a second discharge-side air chamber (second
discharge-side fluid chamber) 21B is formed within the second pump
case 12B such that a hermetic state thereof is maintained.
[0034] A second suction/discharge port 22B is provided in the
second pump case 12B and connected to the air supply device 2 via
the second solenoid valve 5, the second electropneumatic regulator
52, and the mechanical regulator 3 (see FIG. 1). Accordingly, the
second bellows 14 contracts to the most contracted state by
continuously supplying the pressurized air from the air supply
device 2 via the mechanical regulator 3, the second
electropneumatic regulator 52, the second solenoid valve 5, and the
second suction/discharge port 22B into the second discharge-side
air chamber 21B.
[0035] The connection member 20 is supported by the bottom wall
portion 121 of each pump case 12A, 12B so as to be slidable in the
horizontal direction, and the piston body 23 is fixed to another
end portion of the connection member 20 by a nut 24. The piston
body 23 is supported so as to be slidable in the horizontal
direction relative to an inner circumferential surface of a
cylindrical cylinder body 25, which is integrally provided on the
outer side surface of the bottom wall portion 121, with a hermetic
state maintained.
[0036] Accordingly, at the first pump case 12A side, a space
surrounded by the bottom wall portion 121, the cylinder body 25,
and the piston body 23 is formed as a first suction-side air
chamber (first suction-side fluid chamber) 26A of which a hermetic
state is maintained. In addition, at the second pump case 12B side,
a space surrounded by the bottom wall portion 121, the cylinder
body 25, and the piston body 23 is formed as a second suction-side
air chamber (second suction-side fluid chamber) 26B of which a
hermetic state is maintained.
[0037] In the cylinder body 25 at the first pump case 12A side, a
suction/discharge port 251 is formed so as to communicate with the
first suction-side air chamber 26A. The suction/discharge port 251
is connected to the air supply device 2 via the first solenoid
valve 4, the first electropneumatic regulator 51, and the
mechanical regulator 3 (see FIG. 1). Accordingly, the first bellows
13 expands to the most expanded state by continuously supplying the
pressurized air from the air supply device 2 via the mechanical
regulator 3, the first electropneumatic regulator 51, the first
solenoid valve 4, and the suction/discharge port 251 into the first
suction-side air chamber 26A.
[0038] In the cylinder body 25 at the second pump case 12B side, a
suction/discharge port 252 is formed so as to communicate with the
second suction-side air chamber 26B. The suction/discharge port 252
is connected to the air supply device 2 via the second solenoid
valve 5, the second electropneumatic regulator 52, and the
mechanical regulator 3 (see FIG. 1). Accordingly, the second
bellows 14 expands to the most expanded state by continuously
supplying the pressurized air from the air supply device 2 via the
mechanical regulator 3, the second electropneumatic regulator 52,
the second solenoid valve 5, and the suction/discharge port 252
into the second suction-side air chamber 26B.
[0039] Because of the above configuration, the first pump case 12A,
in which the first discharge-side air chamber 21A is formed, and
the piston body 23 and the cylinder body 25 that form the first
suction-side air chamber 26A, form a first air cylinder unit (first
driving unit) 27 that causes the first bellows 13 to perform
expansion/contraction operation continuously between the most
expanded state and the most contracted state.
[0040] In addition, the second pump case 12B, in which the second
discharge-side air chamber 21B is formed, and the piston body 23
and the cylinder body 25 that form the second suction-side air
chamber 26B, form a second air cylinder unit (second driving unit)
28 that causes the second bellows 14 to perform
expansion/contraction operation continuously between the most
expanded state and the most contracted state.
[Configurations of Detection Units]
[0041] A pair of proximity sensors 29A and 29B are mounted on the
cylinder body 25 of the first air cylinder unit 27. A detection
plate 30 to be detected by each of the proximity sensors 29A and
29B is mounted on the piston body 23 of the first air cylinder unit
27. The detection plate 30 reciprocates together with the piston
body 23, so that the detection plate 30 alternately comes close to
the proximity sensors 29A and 29B, whereby the detection plate 30
is detected by the proximity sensors 29A and 29B.
[0042] The proximity sensor 29A is disposed at such a position that
the proximity sensor 29A detects the detection plate 30 when the
first bellows 13 is in the most contracted state. The proximity
sensor 29B is disposed at such a position that the proximity sensor
29B detects the detection plate 30 when the first bellows 13 is in
the most expanded state. Detection signals of the respective
proximity sensors 29A and 29B are transmitted to the control unit
6. In the present embodiment, the pair of proximity sensors 29A and
29B form a first detection unit 29 that detects an
expanded/contracted state of the first bellows 13.
[0043] Similarly, a pair of proximity sensors 31A and 31B are
mounted on the cylinder body 25 of the second air cylinder unit 28.
A detection plate 32 to be detected by each of the proximity
sensors 31A and 31B is mounted on the piston body 23 of the second
air cylinder unit 28. The detection plate 32 reciprocates together
with the piston body 23, so that the detection plate 32 alternately
comes close to the proximity sensors 31A and 31B, whereby the
detection plate 32 is detected by the proximity sensors 31A and
31B.
[0044] The proximity sensor 31A is disposed at such a position that
the proximity sensor 31A detects the detection plate 32 when the
second bellows 14 is in the most contracted state. The proximity
sensor 31B is disposed at such a position that the proximity sensor
31B detects the detection plate 32 when the second bellows 14 is in
the most expanded state. Detection signals of the respective
proximity sensors 31A and 31B are transmitted to the control unit
6. In the present embodiment, the pair of proximity sensors 31A and
31B form a second detection unit 31 that detects an
expanded/contracted state of the second bellows 14.
[0045] The pressurized air generated by the air supply device 2 is
alternately supplied to the first suction-side air chamber 26A and
the first discharge-side air chamber 21A of the first air cylinder
unit 27 by the pair of proximity sensors 29A and 29B of the first
detection unit 29 alternately detecting the detection plate 30.
Accordingly, the first bellows 13 continuously performs
expansion/contraction operation.
[0046] In addition, the pressurized air generated by the air supply
device 2 is alternately supplied to the second suction-side air
chamber 26B and the second discharge-side air chamber 21B of the
second air cylinder unit 28 by the pair of proximity sensors 31A
and 31B of the second detection unit 31 alternately detecting the
detection plate 32. Accordingly, the second bellows 14 continuously
performs expansion/contraction operation. At this time, expansion
operation of the second bellows 14 is performed during contraction
operation of the first bellows 13, and contraction operation of the
second bellows 14 is performed mainly during expansion operation of
the first bellows 13. By the first bellows 13 and the second
bellows 14 alternately repeating expansion/contraction operation as
described above, suction and discharge of the transport fluid to
and from the interiors of the respective bellows 13 and 14 are
alternately performed, whereby the transport fluid is
transported.
[0047] The first and second detection units 29 and 31 are composed
of proximity sensors, but may be composed of other detection means
such as limit switches. In addition, the first and second detection
units 29 and 31 detect the most expanded states and the most
contracted states of the first and second bellows 13 and 14, but
may be configured to detect states in the middle of
expansion/contraction of the first and second bellows 13 and
14.
[Configuration of Pump Head]
[0048] The pump head 11 is formed from a fluorine resin such as
PTFE or PFA. A suction passage 34 and a discharge passage 35 for
the transport fluid are formed within the pump head 11. The suction
passage 34 and the discharge passage 35 are opened in an outer
peripheral surface of the pump head 11 and respectively connected
to a suction port and a discharge port (both are not shown)
provided at the outer peripheral surface.
[0049] The suction port is connected to a storage tank for the
transport fluid or the like, and the discharge port is connected to
a transport destination for the transport fluid. In addition, the
suction passage 34 and the discharge passage 35 each branch toward
both right and left side surfaces of the pump head 11, and have
suction openings 36 and discharge openings 37 that are opened in
both right and left side surfaces of the pump head 11. Each suction
opening 36 and each discharge opening 37 communicate with the
interior of the bellows 13 or 14 via the check valves 15 and 16,
respectively.
[Configurations of Check Valves]
[0050] The check valves 15 and 16 are provided at each suction
opening 36 and each discharge opening 37.
[0051] The check valve 15 (hereinafter, also referred to as
"suction check valve") mounted at each suction opening 36 includes:
a valve case 15a; a valve body 15b that is housed in the valve case
15a; and a compression coil spring 15c that biases the valve body
15b in a valve closing direction.
[0052] The valve case 15a is formed in a bottomed cylindrical
shape. A through hole 15d is formed in a bottom wall of the valve
case 15a so as to communicate with the interior of the bellows 13
or 14. The valve body 15b closes the suction opening 36 (performs
valve closing) by the biasing force of the compression coil spring
15c, and opens the suction opening 36 (performs valve opening) when
a back pressure generated by flow of the transport fluid occurring
with expansion/contraction of the bellows 13 or 14 acts
thereon.
[0053] Accordingly, the suction check valve 15 opens, when the
bellows 13 or 14 at which the suction check valve 15 is disposed
expands, to permit suction of the transport fluid in a direction
from the suction passage 34 toward the interior of the bellows 13
or 14 (in one direction). In addition, the suction check valve 15
closes, when the bellows 13 or 14 at which the suction check valve
15 is disposed contracts, to block backflow of the transport fluid
in a direction from the interior of the bellows 13 or 14 toward the
suction passage 34 (in another direction).
[0054] The check valve 16 (hereinafter, also referred to as
"discharge check valve") mounted at each discharge opening 37
includes: a valve case 16a; a valve body 16b that is housed in the
valve case 16a; and a compression coil spring 16c that biases the
valve body 16b in a valve closing direction.
[0055] The valve case 16a is formed in a bottomed cylindrical
shape. A through hole 16d is formed in a bottom wall of the valve
case 16a so as to communicate with the interior of the bellows 13
or 14. The valve body 16b closes the through hole 16d of the valve
case 16a (performs valve closing) by the biasing force of the
compression coil spring 16c, and opens the through hole 16d of the
valve case 16a (performs valve opening) when a back pressure
generated by flow of the transport fluid occurring with
expansion/contraction of the bellows 13 or 14 acts thereon.
[0056] Accordingly, the discharge check valve 16 opens, when the
bellows 13 or 14 at which the discharge check valve 16 is disposed
contracts, to permit outflow of the transport fluid in a direction
from the interior of the bellows 13 or 14 toward the discharge
passage 35 (in one direction). In addition, the discharge check
valve 16 closes, when the bellows 13 or 14 at which the discharge
check valve 16 is disposed expands, to block backflow of the
transport fluid in a direction from the discharge passage 35 toward
the interior of the bellows 13 or 14 (in another direction).
[Operation of Bellows Pump]
[0057] Next, operation of the bellows pump 1 of the present
embodiment will be described with reference to FIG. 3 and FIG. 4.
In FIG. 3 and FIG. 4, the configurations of the first and second
bellows 13 and 14 are shown in a simplified manner
[0058] As shown in FIG. 3, when the first bellows 13 contracts and
the second bellows 14 expands, the respective valve bodies 15b and
16b of the suction check valve 15 and the discharge check valve 16
that are mounted at the left side of the pump head 11 in the
drawing receive pressure from the transport fluid within the first
bellows 13 and move to the right sides of the respective valve
cases 15a and 16a in the drawing. Accordingly, the suction check
valve 15 closes, and the discharge check valve 16 opens, so that
the transport fluid within the first bellows 13 is discharged
through the discharge passage 35 to the outside of the pump.
[0059] Meanwhile, the valve body 15b of the suction check valve 15
mounted at the right side of the pump head 11 in the drawing moves
to the right side of the valve case 15a in the drawing due to a
suction effect by the second bellows 14. In addition, the valve
body 16b of the discharge check valve 16 mounted at the right side
of the pump head 11 in the drawing moves to the right side of the
valve case 16a in the drawing due to a suction effect by the second
bellows 14 and a pressing effect by the transport fluid discharged
from the first bellows 13 to the discharge passage 35. Accordingly,
the suction check valve 15 opens, and the discharge check valve 16
closes, so that the transport fluid is sucked from the suction
passage 34 into the second bellows 14.
[0060] Next, as shown in FIG. 4, when the first bellows 13 expands
and the second bellows 14 contracts, the respective valve bodies
15b and 16b of the suction check valve 15 and the discharge check
valve 16 that are mounted at the right side of the pump head 11 in
the drawing receive pressure from the transport fluid within the
second bellows 14 and move to the left sides of the respective
valve cases 15a and 16a in the drawing. Accordingly, the suction
check valve 15 closes, and the discharge check valve 16 opens, so
that the transport fluid within the second bellows 14 is discharged
through the discharge passage 35 to the outside of the pump.
[0061] Meanwhile, the valve body 15b of the suction check valve 15
mounted at the left side of the pump head 11 in the drawing moves
to the left side of the valve case 15a in the drawing due to a
suction effect by the first bellows 13. In addition, the valve body
16b of the discharge check valve 16 mounted at the left side of the
pump head 11 in the drawing moves to the left side of the valve
case 16a in the drawing due to a suction effect by the first
bellows 13 and a pressing effect by the transport fluid discharged
from the first bellows 13 to the discharge passage 35. Accordingly,
the suction check valve 15 opens, and the discharge check valve 16
closes, so that the transport fluid is sucked from the suction
passage 34 into the first bellows 13.
[0062] By repeatedly performing the above operation, the left and
right bellows 13 and 14 can alternately suck and discharge the
transport fluid.
[Configurations of Solenoid Valves]
[0063] In FIG. 1, the first solenoid valve 4 switches between:
supply/discharge of the pressurized air to/from one air chamber of
the first discharge-side air chamber 21A and the first suction-side
air chamber 26A of the first air cylinder unit 27; and
supply/discharge of the pressurized air to/from the other air
chamber. The first solenoid valve 4 is composed of, for example, a
three-position solenoid switching valve including a pair of
solenoids 4a and 4b. Each of the solenoids 4a and 4b is magnetized
on the basis of a command signal received from the control unit
6.
[0064] The second solenoid valve 5 switches between:
supply/discharge of the pressurized air to/from one air chamber of
the second discharge-side air chamber 21B and the second
suction-side air chamber 26B of the second air cylinder unit 28;
and supply/discharge of the pressurized air to/from the other air
chamber. The second solenoid valve 5 is composed of, for example, a
three-position solenoid switching valve including a pair of
solenoids 5a and 5b. Each of the solenoids 5a and 5b is magnetized
upon reception of a command signal from the control unit 6.
[0065] Although each of the first and second solenoid valves 4 and
5 of the present embodiment is composed of the three-position
solenoid switching valve, each of the first and second solenoid
valves 4 and 5 may be a two-position solenoid switching valve which
does not have a neutral position.
[0066] In FIG. 1, a first quick discharge valve 61 is disposed
between the first discharge-side air chamber 21A (first
suction/discharge port 22A) of the first air cylinder unit 27 and
the first solenoid valve 4 and adjacently to the first
discharge-side air chamber 21A. The first quick discharge valve 61
has a discharge port 61a through which the pressurized air is
discharged, and is configured to permit flow of the pressurized air
from the first solenoid valve 4 to the first discharge-side air
chamber 21A and to discharge the pressurized air flowing out from
the first discharge-side air chamber 21A, through the discharge
port 61a. Thus, the pressurized air within the first discharge-side
air chamber 21A can be quickly discharged through the first quick
discharge valve 61, not via the first solenoid valve 4.
[0067] Similarly, a second quick discharge valve 62 is disposed
between the second discharge-side air chamber 21B (second
suction/discharge port 22B) of the second air cylinder unit 28 and
the second solenoid valve 5 and adjacently to the second
discharge-side air chamber 21B. The second quick discharge valve 62
has a discharge port 62a through which the pressurized air is
discharged, and is configured to permit flow of the pressurized air
from the second solenoid valve 5 to the second discharge-side air
chamber 21B and to discharge the pressurized air flowing out from
the second discharge-side air chamber 21B, through the discharge
port 62a. Thus, the pressurized air within the second
discharge-side air chamber 21B can be quickly discharged through
the second quick discharge valve 62, not via the second solenoid
valve 5.
[Configuration of Control Unit]
[0068] The control unit 6 controls drive of each of the first air
cylinder unit 27 and the second air cylinder unit 28 of the bellows
pump 1 by switching the respective solenoid valves 4 and 5 on the
basis of detection results of the first detection unit 29 and the
second detection unit 31 (see FIG. 2).
[0069] Specifically, on the basis of the detection results of the
first detection unit 29 and the second detection unit 31, the
control unit 6 controls drive of the first and second air cylinder
units 27 and 28 such that: the second bellows 14 is caused to
contract from the most expanded state before the first bellows 13
comes into the most contracted state; and the first bellows 13 is
caused to contract from the most expanded state before the second
bellows 14 comes into the most contracted state.
[0070] Here, the term "before" the first bellows 13 comes into the
most contracted state means that a contraction progress position of
the first bellows 13 is closer to a contraction end position (most
contracted position) than to a contraction start position (most
expanded position), and more specifically means that a state where
the first bellows 13 has contracted up to 60% to 90% (preferably
60% to 70%, more preferably 66%) of a contraction period T12 (see
FIG. 5) from a time point of start of contraction of the first
bellows 13 to a time point at which the first bellows 13 comes into
the most contracted state. Similarly, the term "before" the second
bellows 14 comes into the most contracted state means that a
contraction progress position of the second bellows 14 is closer to
a contraction end position (most contracted position) than to a
contraction start position (most expanded position), and more
specifically means that a state where the second bellows 14 has
contracted up to 60% to 90% (preferably 60% to 70%, more preferably
66%) of a contraction period T22 (see FIG. 5) from a time point of
start of contraction of the second bellows 14 to a time point at
which the second bellows 14 comes into the most contracted
state.
[0071] Accordingly, at a time of switching from contraction of one
bellows to expansion thereof (from discharge of the transport fluid
to suction thereof), the other bellows has already contracted to
discharge the transport fluid. Thus, great fall of the discharge
pressure of the transport fluid at the time of switching can be
reduced. As a result, pulsation at the discharge side of the
bellows pump 1 can be reduced.
[Configurations of Electropneumatic Regulators]
[0072] In FIG. 1 and FIG. 2, the first electropneumatic regulator
51 is disposed between the mechanical regulator 3 and the first
solenoid valve 4. The first electropneumatic regulator 51 adjusts
the air pressure of the pressurized air in the first suction-side
air chamber 26A of the first air cylinder unit 27, and the air
pressure (first fluid pressure) of the pressurized air in the first
discharge-side air chamber 21A of the first air cylinder unit
27.
[0073] Similarly, the second electropneumatic regulator 52 is
disposed between the mechanical regulator 3 and the second solenoid
valve 5. The second electropneumatic regulator 52 adjusts the air
pressure of the pressurized air in the second suction-side air
chamber 26B of the second air cylinder unit 28, and the air
pressure (second fluid pressure) of the pressurized air in the
second discharge-side air chamber 21B of the second air cylinder
unit 28.
[0074] The electropneumatic regulators 51 and 52 are disposed at
the upstream sides of the solenoid valves 4 and 5, but may be
disposed at the downstream sides of the solenoid valves 4 and 5.
However, in this case, impact pressures generated when the solenoid
valves 4 and 5 are switched act at the primary sides of the
electropneumatic regulators 51 and 52. Thus, from the standpoint of
preventing breakdown of the electropneumatic regulators 51 and 52,
the electropneumatic regulators 51 and 52 are preferably disposed
at the upstream sides of the solenoid valves 4 and 5.
[0075] The electropneumatic regulators 51 and 52 only have to
adjust at least the air pressure of the pressurized air in the
discharge-side air chambers 21A and 21B. In addition, in the
present embodiment, the electropneumatic regulators 51 and 52,
which directly adjust the air pressure, are used as fluid pressure
adjustment units, but the air pressure may be adjusted indirectly
using an air flow rate adjusting valve which adjusts an air flow
rate, or a device that adjusts the pressure or flow rate of a gas
other than air (for example, nitrogen), a liquid, or the like may
be used.
[Examples of Control of Electropneumatic Regulators]
[0076] FIG. 5 is a time chart showing an example of control of the
electropneumatic regulator 51 (52) by the control unit 6 of the
present embodiment. In FIG. 5, the control unit 6 controls the
first electropneumatic regulator 51 such that the air pressure in
the first suction-side air chamber 26A of the first air cylinder
unit 27 is a constant value P during an expansion period T11 in
which the first bellows 13 expands.
[0077] In addition, the control unit 6 controls the first
electropneumatic regulator 51 such that the air pressure in the
first discharge-side air chamber 21A of the first air cylinder unit
27 is the constant value P during a first contraction time T121
from a contraction start time point t1 of the first bellows 13 to a
contraction start time point t2 of the second bellows 14 in the
contraction period T12 in which the first bellows 13 contracts.
[0078] Subsequently, the control unit 6 controls the first
electropneumatic regulator 51 such that, in the contraction period
T12, during a second contraction time T122 from the contraction
start time point t2 of the second bellows 14 to a contraction end
time point t3 at which the first bellows 13 comes into the most
contracted state, the air pressure in the first discharge-side air
chamber 21A is continuously decreased from P, and reaches zero
before or when the first bellows 13 comes into the most contracted
state. For example, the control unit 6 of the present embodiment
controls the first electropneumatic regulator 51 such that the air
pressure in the first discharge-side air chamber 21A is linearly
and continuously decreased from P, and reaches zero at the
contraction end time point t3 at which the first bellows 13 comes
into the most contracted state.
[0079] Meanwhile, the control unit 6 controls the second
electropneumatic regulator 52 such that the air pressure in the
second suction-side air chamber 26B of the second air cylinder unit
28 is the constant value P during an expansion period T21 in which
the second bellows 14 expands.
[0080] In addition, the control unit 6 controls the second
electropneumatic regulator 52 such that the air pressure in the
second discharge-side air chamber 21B of the second air cylinder
unit 28 is the constant value P during a first contraction time
T221 from the contraction start time point t2 of the second bellows
14 to a contraction start time point t1 of the first bellows 13 in
the contraction period T22 in which the second bellows 14
contracts.
[0081] Subsequently, the control unit 6 controls the second
electropneumatic regulator 52 such that, in the contraction period
T22, during a second contraction time T222 from the contraction
start time point t1 of the first bellows 13 to a contraction end
time point t4 at which the second bellows 14 comes into the most
contracted state, the air pressure of the second discharge-side air
chamber 21B is continuously decreased from P, and reaches zero
before or when the second bellows 14 comes into the most contracted
state. For example, the control unit 6 of the present embodiment
controls the second electropneumatic regulator 52 such that the air
pressure in the second discharge-side air chamber 21B is linearly
and continuously decreased from P, and reaches zero at the
contraction end time point t4 at which the second bellows 14 comes
into the most contracted state.
[0082] FIG. 6 is a graph showing the discharge pressure of the
transport fluid discharged from the discharge passage 35 of the
bellows pump 1 of the present embodiment. As shown in FIG. 6, it is
found that, by the control unit 6 controlling the first and second
electropneumatic regulators 51 and 52 as described above, great
fall of the discharge pressure at a time of switching from
contraction of one bellows to expansion thereof (from discharge of
the transport fluid to suction thereof) (portions surrounded by
broken lines in the drawing) can be reduced. In addition, when the
graph shown in FIG. 6 of the present embodiment is compared with
the graph shown in FIG. 10 of the conventional art, it is found
that occurrence of surge pressure can also be inhibited at the time
of switching.
Advantageous Effects of Present Embodiment
[0083] As described above, in the bellows pump device of the
present embodiment, before the one bellows 13 (14) comes into the
most contracted state, the other bellows 14 (13) contracts from the
most expanded state. Accordingly, at a time of switching from
contraction of the one bellows 13 (14) to expansion thereof (from
discharge of the transport fluid to suction thereof), the other
bellows 14 (13) has already contracted to discharge the fluid, and
thus fall of the discharge pressure at the time of switching can be
reduced. As a result, pulsation at the discharge side of the
bellows pump device can be reduced.
[0084] The control unit 6 controls the electropneumatic regulator
52 (51) corresponding to the discharge-side air chamber 21A (21B)
corresponding to the other bellows 14 (13) such that, during a
period from a time at which the one bellows 13 (14) starts
contracting to a time at which the bellows 14 (13) comes into the
most contracted state, the air pressure in the discharge-side air
chamber 21B (21A) is continuously decreased. Owing to this control,
before the other bellows 14 (13) comes into the most contracted
state, the discharge check valve 16 corresponding to the other
bellows 14 (13) gradually moves in the valve closing direction from
a valve-opened state. Accordingly, when the other bellows 14 (13)
is switched from the most contracted state to expansion, impact due
to rapid closing of the discharge check valve 16 can be alleviated.
As a result, surge pressure can be inhibited from being generated
at the discharge side of the bellows pump device when switching is
made from discharge of the transport fluid to suction of the
transport fluid.
[0085] Before or when the other bellows 14 (13) comes into the most
contracted state after the one bellows 13 (14) starts contracting,
the air pressure in the discharge-side air chamber 21B (21A)
corresponding to the other bellows 14 (13) is continuously
decreased and reaches zero. Since the air pressure in the
discharge-side air chamber 21B (21A) is decreased as described
above, the discharge check valve 16 corresponding to the other
bellows 14 (13) closes before or when the other bellows 14 (13)
comes into the most contracted state. Accordingly, the discharge
check valve 16 can be prevented from rapidly closing when the other
bellows 14 (13) is switched from the most contracted state to
expansion. As a result, surge pressure can be further inhibited
from being generated at the discharge side of the bellows pump
device when switching is made from discharge of the transport fluid
to suction of the transport fluid.
[0086] During the period from the time at which the one bellows 13
(14) starts contracting to the time at which the bellows 14 (13)
comes into the most contracted state, the air pressure in the
discharge-side air chamber 21B (21A) corresponding to the other
bellows 14 (13) is continuously decreased, and reaches zero at the
time at which the other bellows 14 (13) comes into the most
contracted state. Accordingly, the discharge check valve 16
corresponding to the other bellows 14 (13) slowly closes as
compared to the case where the air pressure reaches zero before the
other bellows 14 (13) comes into the most contracted state (see
FIG. 8). As a result, surge pressure can be further inhibited from
being generated at the discharge side of the bellows pump device
when switching is made from discharge of the transport fluid to
suction of the transport fluid.
[Modifications of Control of Electropneumatic Regulators]
[0087] FIG. 7 is a time chart showing a first modification, a
second modification, and a third modification for control of the
electropneumatic regulator 51 (52) by the control unit 6.
[0088] In the first modification shown by a solid line in FIG. 7,
the control unit 6 controls the electropneumatic regulator 51 (52)
such that, during the second contraction time T122 (T222) from the
contraction start time point t2 (t1) of the one bellows 14 (13) to
the contraction end time point t3 (t4) of the other bellows 13
(14), the air pressure in the discharge-side air chamber 21A (21B)
is decreased stepwise from P, and reaches zero at the contraction
end time point t3 (t4). In the first modification, the air pressure
is decreased in two steps, but may be decreased in three or more
steps.
[0089] In the second modification shown by an alternate long and
short dash line in FIG. 7, the control unit 6 controls the
electropneumatic regulator 51 (52) such that, during the second
contraction time T122 (T222) from the contraction start time point
t2 (t1) of the one bellows 14 (13) to the contraction end time
point t3 (t4) of the other bellows 13 (14), the air pressure in the
discharge-side air chamber 21A (21B) corresponding to the other
bellows 13 (14) is continuously decreased in a concave curve from
P, and reaches zero at the contraction end time point t3 (t4).
[0090] In the third modification shown by an alternate long and two
short dashes line in FIG. 7, the control unit 6 controls the
electropneumatic regulator 51 (52) such that, during the second
contraction time T122 (T222) from the contraction start time point
t2 (t1) of the one bellows 14 (13) to the contraction end time
point t3 (t4) of the other bellows 13 (14), the air pressure in the
discharge-side air chamber 21A (21B) corresponding to the other
bellows 13 (14) is continuously decreased in a convex curve from P,
and reaches zero at the contraction end time point t3 (t4).
[0091] Thus, in the first to third modifications in FIG. 7 as well,
the same advantageous effects as those of the above embodiment are
achieved. In the first modification, the control unit 6 controls
the electropneumatic regulator 51 (52) such that the air pressure
in the discharge-side air chamber 21A (21B) is linearly decreased
in each step, but may control the electropneumatic regulator 51
(52) such that the air pressure is decreased in a curve in each
step, as in the second modification or the third modification.
[0092] FIG. 8 is a time chart showing a fourth modification and a
fifth modification for control of the electropneumatic regulator 51
(52) by the control unit 6.
[0093] In the fourth modification shown by a solid line in FIG. 8,
the control unit 6 controls the electropneumatic regulator 51 (52)
such that, during a period from the contraction start time point t2
(t1) of the one bellows 14 (13) to a contraction halfway time point
t5 (t6) before the other bellows 13 (14) comes into the most
contracted state, the air pressure in the discharge-side air
chamber 21A (21B) is continuously decreased from P, and reaches
zero at the contraction halfway time point t5 (t6). Then, the
control unit 6 controls the electropneumatic regulator 51 (52) such
that, during a period from the contraction halfway time point t5
(t6) to the contraction end time point t3 (t4) of the other bellows
13 (14), the air pressure in the discharge-side air chamber 21A
(21B) is maintained at zero.
[0094] In the fifth modification shown by an alternate long and
short dash line in FIG. 8, the control unit 6 controls the
electropneumatic regulator 51 (52) such that, during the period
from the contraction start time point t2 (t1) of the one bellows 14
(13) to the contraction halfway time point t5 (t6) before the other
bellows 13 (14) comes into the most contracted state, the air
pressure in the discharge-side air chamber 21A (21B) is
continuously decreased from P, and reaches P' (0<P'<P) at the
contraction halfway time point t5 (t6). Then, the control unit 6
controls the electropneumatic regulator 51 (52) such that, during
the period from the contraction halfway time point t5 (t6) to the
contraction end time point t3 (t4) of the other bellows 13 (14),
the air pressure in the discharge-side air chamber 21A (21B) is
zero.
[0095] Thus, in the fourth and fifth modifications as well, similar
to the above embodiment, during the period from the time at which
the one bellows 14 (13) starts contracting to the time at which the
other bellows 13 (14) comes into the most contracted state, the air
pressure in the discharge-side air chamber 21A (21B) corresponding
to the other bellows 13 (14) is continuously decreased.
Accordingly, when switching is made from discharge of the transport
fluid to suction of the transport fluid, pulsation can be reduced
and generation of surge pressure can be inhibited at the discharge
side.
[0096] Moreover, before the other bellows 13 (14) comes into the
most contracted state after the one bellows 14 (13) starts
contracting, the air pressure in the discharge-side air chamber 21A
(21B) corresponding to the other bellows 13 (14) is continuously
decreased and reaches zero. Since the air pressure in the
discharge-side air chamber 21A (21B) is decreased as described
above, the discharge check valve 16 corresponding to the other
bellows 13 (14) closes before the other bellows 13 (14) comes into
the most contracted state. Accordingly, the discharge check valve
16 can be prevented from rapidly closing when the other bellows 13
(14) is switched from the most contracted state to expansion. As a
result, surge pressure can be further inhibited from being
generated at the discharge side of the bellows pump device when
switching is made from discharge of the transport fluid to suction
of the transport fluid.
[0097] FIG. 9 is a time chart showing a sixth modification for
control of the electropneumatic regulator 51 (52) by the control
unit 6. In this modification, the control unit 6 controls the
electropneumatic regulator 51 (52) such that, during the second
contraction time T122 (T222) from the contraction start time point
t2 (t1) of the one bellows 14 (13) to the contraction end time
point t3 (t4) of the other bellows 13 (14), the air pressure in the
discharge-side air chamber 21A (21B) is continuously decreased from
P, and reaches P'' (0<P''<P) at the contraction end time
point t3 (t4) at which the other bellows 13 (14) comes into the
most contracted state. At the contraction end time point t3 (t4),
if the corresponding solenoid valve 4 (5) is switched, the
pressurized air within the discharge-side air chamber 21A (21B) is
released to the atmosphere, and the air pressure in the
discharge-side air chamber 21A (21B) becomes zero from P''.
[0098] Thus, in the sixth modification as well, similar to the
above embodiment, during the period from the time at which the one
bellows 14 (13) starts contracting to the time at which the other
bellows 13 (14) comes into the most contracted state, the air
pressure in the discharge-side air chamber 21A (21B) corresponding
to the other bellows 13 (14) is continuously decreased.
Accordingly, when switching is made from discharge of the transport
fluid to suction of the transport fluid, pulsation can be reduced
and generation of surge pressure can be inhibited at the discharge
side.
[0099] In each of the modifications in FIG. 8 and FIG. 9, the
control unit 6 linearly and continuously decreases the air pressure
in the discharge-side air chamber 21A (21B) when controlling the
electropneumatic regulator 51 (52), but may decrease the air
pressure stepwise as in the first modification in FIG. 7, or may
continuously decrease the air pressure in a curve as in the second
or third modification in FIG. 7.
[0100] The embodiment disclosed herein is merely illustrative and
not restrictive in all aspects. The scope of the present disclosure
is defined by the scope of the claims rather than the meaning
described above, and is intended to include meaning equivalent to
the scope of the claims and all modifications within the scope.
REFERENCE SIGNS LIST
[0101] 6 control unit
[0102] 11 pump head
[0103] 13 first bellows
[0104] 14 second bellows
[0105] 15 suction check valve (check valve)
[0106] 16 discharge check valve (check valve)
[0107] 21A first discharge-side air chamber (first discharge-side
fluid chamber)
[0108] 21B second discharge-side air chamber (second discharge-side
fluid chamber)
[0109] 26A first suction-side air chamber (first suction-side fluid
chamber)
[0110] 26B second suction-side air chamber (second suction-side
fluid chamber)
[0111] 27 first air cylinder unit (first driving unit)
[0112] 28 second air cylinder unit (second driving unit)
[0113] 34 suction passage
[0114] 35 discharge passage
[0115] 51 first electropneumatic regulator (first fluid pressure
adjustment unit)
[0116] 52 second electropneumatic regulator (second fluid pressure
adjustment unit)
* * * * *