U.S. patent application number 14/021679 was filed with the patent office on 2014-03-13 for bellows pump.
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 Tomohiro Adachi, Atsushi Nakano.
Application Number | 20140072465 14/021679 |
Document ID | / |
Family ID | 49165486 |
Filed Date | 2014-03-13 |
United States Patent
Application |
20140072465 |
Kind Code |
A1 |
Adachi; Tomohiro ; et
al. |
March 13, 2014 |
Bellows Pump
Abstract
A bellows pump including in its pump case (5) a pair of plastic
bellows (6) that expand and contract to alternatingly execute an
output stroke that sends fluid out of pump chambers (7) defined by
the bellows and a suction stroke that supplies fluid to the pump
chambers. Metal actuation plates (10) are provided in the pump case
so as to be movable in the axial direction, and these actuation
plates are fixedly connected to the bottom walls (6a) of the
bellows in peripheral portions thereof so that the opposed end
faces (10c, 6g) of the actuation plates and fluid-contact portions
(6f), which are at the center of the bottom walls of the bellows
and come into contact with fluid in the pump chambers, are set in a
close contact to each other. The close-contact portions are sealed
by O-rings (15).
Inventors: |
Adachi; Tomohiro;
(Osaka-shi, JP) ; Nakano; Atsushi; (Osaka-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nippon Pillar Packing Co., Ltd. |
Osaka |
|
JP |
|
|
Assignee: |
Nippon Pillar Packing Co.,
Ltd.
Osaka
JP
|
Family ID: |
49165486 |
Appl. No.: |
14/021679 |
Filed: |
September 9, 2013 |
Current U.S.
Class: |
417/472 |
Current CPC
Class: |
F04B 43/0036 20130101;
F04B 45/02 20130101; F04B 45/022 20130101; F04B 43/1136 20130101;
F04B 43/084 20130101 |
Class at
Publication: |
417/472 |
International
Class: |
F04B 43/00 20060101
F04B043/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 10, 2012 |
JP |
2012-198289 |
Claims
1. A bellows pump adapted to cause a plastic bottom-closed
cylindrical bellows with aperture portions thereof connected to a
pump case to expand and contract in an axial direction thereof,
thereby alternating between an output stroke in which fluid is sent
from a pump chamber defined by the bellows to an output passage
through an output check valve and a suction stroke in which fluid
is supplied from a suction passage to the pump chamber through a
suction check valve, wherein: metal actuation plates are provided
in the pump case so as to be movable in an axial direction thereof,
the actuation plates and bottom walls of the bellows are fixedly
connected in peripheral portions thereof, opposed end faces of the
actuation plates and the fluid-contact portions are set in a close
contact with each other, the fluid-contact portions being central
areas of the bottom walls of the bellows and coming into contact
with fluid in the pump chamber, and said close-contact portions are
sealed with annular sealing members.
2. A bellows pump adapted to cause a plastic bottom-closed
cylindrical bellows with aperture portions thereof connected to a
pump case to expand and contract in an axial direction thereof,
thereby alternating between an output stroke in which fluid is sent
from a pump chamber defined by the bellows to an output passage
through an output check valve and a suction stroke in which fluid
is supplied from a suction passage to the pump chamber through a
suction check valve, wherein: metal actuation plates are provided
in the pump case so as to be movable in an axial direction thereof,
the actuation plates and bottom walls of the bellows are fixedly
connected in peripheral portions thereof, sealed spaces are
provided between opposed end faces of the actuation plates and
central areas of the bottom walls of the bellows, said spaces being
sealed by annular sealing members, and said sealed spaces are
filled with incompressible fluid.
3. The bellows pump according to claim 1, wherein the annular
sealing members O-rings, and said O-rings are held in engagement
with O-ring grooves formed in either one of the bottom walls of the
bellows and the actuation plates.
4. The bellows pump according to claim 2, wherein the annular
sealing members O-rings, and said O-rings are held in engagement
with O-ring grooves formed in either one of the bottom walls of the
bellows and the actuation plates.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a bellows pump used for
feeding and circulating chemicals (e.g., chemicals and the like
employed in fabrication processes of semiconductors, liquid
crystals, and organic EL (electroluminescence) elements) and
slurries containing solid components and other slurry components
(e.g., polishing fluid used in CMP (chemical mechanical polishing)
machines (semiconductor wafer surface-polishing machines, in which
CMP methods are used)).
[0003] 2. Description of the Related Art
[0004] Of the bellows pumps of the type described above, one that
is well-known includes a plastic, bottom-closed cylindrical bellows
with its aperture portions connected to a pump case so as to be
caused to expand and contract in the axial direction. With the
repeated extension and contract, this bellows pump is adapted to
alternate between an output stroke, during which fluid is sent from
a pump chamber formed by the surrounding bellows to an output
passage through an output check valve, and a suction stroke, during
which the fluid is supplied from a suction passage to the pump
chamber through a suction check valve (see, e.g., FIG. 1 of
Japanese Patent Application Laid-Open (Kokai) No. 2002-174180 or
FIG. 2 of Japanese Patent Application Laid-Open (Kokai) No.
2012-122380)
[0005] In such a bellows pump, during the output stroke, the pump
chamber is compressed, and/or during the suction stroke, the pump
chamber is decompressed (negatively pressurized), which creates a
risk that the bottom wall of the plastic bellow could be subject to
deformation, such as buckling and the like. For example, during the
output stroke, in which the bellows is actuated to contract, there
is a risk that the bottom wall of the bellows may be pushed out and
buckle in a convex shape under the pressure of the pump chamber. On
the other hand, conversely, during the suction stroke, in which the
bellow is actuated to expand, the pump chamber is negatively
pressurized, thereby creating a risk that the bottom wall of the
bellows may be sucked in and buckle in a concave shape.
Alternatively, when an air-cylinder mechanism (see paragraph 0024
below) is used as a means for actuating the bellows to expand and
contract, there is a risk that the bottom walls of the plastic
bellows could be subject to deformation such as buckling and the
like under the action of the pressurized air supplied to the
intake/discharge spaces. For example, on the output stroke, during
which the bellows is actuated to contract, the pressure in the
intake/discharge space becomes lower than the pressure in the pump
chamber, thereby creating a risk that the bottom wall of the
bellows may be pushed in by the pressurized air supplied to the
intake/discharge space and may buckle in a concave shape into the
pump chamber. Thus, when the bottom walls of the bellows undergoes
deformation in this manner, the bellows pump is unable to achieve
the proper pump functionality because of the unstable bellows-pump
flow rates (output-fluid volumes) and circulating-fluid volumes,
generation of random fluctuations, and the like.
[0006] In such a bellows pump, the pump chamber is compressed on
the output stroke and/or on the suction stroke the pump chamber is
decompressed (negatively pressurized), creating a risk that the
bottom walls of the plastic bellows could be subject to
deformation, such as buckling and the like. For example, during the
output stroke, in which the bellows is actuated to contract, there
is a risk that the bottom wall of the bellows may be pushed out and
buckle in a convex shape under the pressure of the pump chamber,
and, conversely, during the suction stroke, in which the bellows is
actuated to expand, the pump chamber is negatively pressurized,
thereby creating a risk that the bottom wall of the bellows may be
sucked in and buckle in a concave shape. Thus, when the bottom
walls of the bellows undergoes deformation in this manner, the
bellows pump cannot achieve proper pump functionality because of
substantial changes in pump-chamber volume, unstable bellows-pump
flow rates (output-fluid volumes) and circulating-fluid volumes,
generation of random fluctuations, and the like.
[0007] As disclosed in FIG. 1 of Japanese Patent Application
Laid-Open (Kokai) No. 2002-174180 and in FIG. 2 of Japanese Patent
Application Laid-Open (Kokai) No. 2012-122380, in bellows pumps,
actuation plates provided so as to be movable in the axial
direction are attached to the bottom walls of the bellows, so that
these actuation plates can work as a means for guiding the
axial-direction motion (contractile actuation) of the bellows or as
a means for synchronizing the contractile actuations of the two
bellows in a double-acting bellows pump. Accordingly, using
actuation plates that are made of metal can allow the bottom walls
of the bellows, which can be easily deformed because they are made
of plastic, to be reinforced.
[0008] However, as seen from FIG. 1 of Japanese Patent Application
Laid-Open (Kokai) No. 2002-174180 and in FIG. 2 of Japanese Patent
Application Laid-Open (Kokai) No. 2012-122380, the bottom walls of
the bellows are attached to the actuation plates only in the
peripheral portions thereof, which is why the above-described
deformation induced by the pump-chamber pressure fluctuations
during the output stroke and/or suction stroke cannot be prevented
in the central portion of the bottom wall of the bellows, that is,
in the portion not attached to the actuation plate. For example,
when the pump chamber is negatively pressurized during the suction
stroke, there is a risk that the central portion of the bottom wall
of the bellows, which is not secured to an actuation plate, is
subject to buckling deformation (and can be deformed in a concave
shape) into the pump chamber by the action of the suction force
produced by the negative pressure.
BRIEF SUMMARY OF THE INVENTION
[0009] Accordingly, in the light of the above-described
circumstances, the object of the present invention is to provide a
bellows pump that is capable of reliably preventing deformation,
such as buckling, of the bottom wall of a bellows due to pressure
fluctuations in the pump chamber during the output stroke and/or
suction stroke and that can achieve proper pump functionality,
providing stable flow rates (output-fluid volumes) and
circulating-fluid volumes and eliminating random fluctuations.
[0010] In order to accomplish the above-described object, the
present invention provides, in particular, the configuration (1) or
the configuration (2) below for a bellows pump that is adapted, by
causing plastic bottom-closed cylindrical bellows with its aperture
portions connected to the pump case to expand and contract in the
axial direction, to alternate between the output stroke that sends
fluid from a pump chamber, defined by the surrounding bellows, to
an output passage through an output check valve and the suction
stroke that supplies fluid supplied from a suction passage to the
pump chamber through a suction check valve.
[0011] (1) A metal actuation plate supported by the pump case so as
to be movable in the axial direction and the bottom wall of the
bellows are fixedly connected in their peripheral portions, and
opposed end faces of the actuation plate and the central area of
the bottom wall of the bellows, that is, a fluid-contact portion
that comes into contact with the fluid in the pump chamber, are
provided in a close contact with each other, with such a
close-contact portion being sealed by an annular sealing
member.
[0012] (2) A metal actuation plate supported by the pump case so as
to be movable in the axial direction and the bottom wall of the
bellows are fixedly connected in their peripheral portions, and a
sealed space is formed by an annular sealing member provided
between the opposed end faces of the actuation plate and the
central area of the bottom wall of the bellows, that is, a
fluid-contact portion that comes into contact with the fluid in the
pump chamber, with such a sealed space being filled with an
incompressible fluid.
[0013] In a preferred embodiment of the bellows pump of the present
invention, the annular sealing member is an O-ring, and this said
O-ring is held in engagement with an O-ring groove formed in the
actuation plate or in the bottom wall of the bellows.
[0014] In the bellows pump of the present invention configured as
described in (1) above, the fluid-contact portion, that is, the
central area of the bottom wall of the bellows, is in a close
contact with the actuation plate in a sealed state, and as a
result, the fluid-contact portion and the actuation plate are
always held in a state of inseparable close contact regardless of
any pressure fluctuations occurring in the pump chamber. In
addition, in the bellows pump of the present invention configured
as described in (2) above, the sealed space formed between the
actuation plate and the fluid-contact portion, that is, the central
area of the bottom wall of the bellows, is filled with
incompressible fluid, and as a result, the sealed space filled with
such incompressible fluid functions as a type of rigid body, and as
a result, regardless of any pressure fluctuations in the pump
chamber, the fluid-contact portion, as well as the sealed space
acting as a rigid body and the actuation plate, are held in such a
state that they are in a mutually inseparable close contact.
[0015] As seen from the above, in either one of configurations (1)
and (2), the fluid-contact portion of the bottom wall of the
bellows is reinforced by the metal actuation plate against the
pressure of the pump chamber, and deformation of the fluid-contact
portion of the bottom wall of the bellows caused by the pressure
fluctuations in the pump chamber can be reliably prevented.
Alternatively, when the means used in the bellows pump of the
present invention for actuating the bellows to expand and contract
is an air-cylinder mechanism (see paragraph 0024 below), the
pressurized air supplied to the intake/discharge space for
actuating the bellows to expand and contract is prevented from
getting between the bottom wall of the plastic bellows and the
metal actuation plate, thereby reliably preventing deformation of
the bottom wall of the plastic bellows that is caused by the
pressurized air supplied to the intake/discharge space. For this
reason, the volume of the pump chamber during the suction stroke
and during the output stroke does not vary due to the deformation
of the bottom wall of the bellows while the flow rate (output-fluid
volume) and circulating-fluid volume produced by the pump remains
stable, and the pump can achieve proper pump functionality. In
addition, the bottom wall of the bellows itself does not have to
possess a strength sufficient to prevent deformations induced by
pump-chamber pressure fluctuations; accordingly, in the case of
configuration (2), as well as in the case of configuration (1), the
bottom wall of the bellows can be made as thin as possible, and
this can ensure that the weight of the bellows is significantly
reduced.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0016] FIG. 1 is a cross-sectional side view illustrating one
example of the bellows pump according to the present invention.
[0017] FIG. 2 is a cross-sectional front view of the main portion
taken along the line II-II in FIG. 1.
[0018] FIG. 3 is a cross-sectional side view illustrating a
modification of the bellows pump according to the present
invention.
[0019] FIG. 4 is an enlarged view of the main portion of FIG.
3.
[0020] FIG. 5 is a cross-sectional front view taken along the line
V-V in FIG. 3.
[0021] FIG. 6 is a cross-sectional side view illustrating another
modification of the bellows pump according to the present
invention.
[0022] FIG. 7 is an enlarged view of the main portion of FIG.
6.
[0023] FIG. 8 is a cross-sectional front view taken along the line
VIII-VIII in FIG. 6.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The modes for carrying out the present invention will be
described specifically with reference to the drawings.
[0025] FIG. 1 is a cross-sectional side view showing an example of
the bellows pump according to the present invention, and FIG. 2 is
a cross-sectional front view of the main portion taken along the
line II-II in FIG. 1. It should be noted that in the description
below the phrase "left and right" is intended to mean "left and
right in FIG. 1".
[0026] The bellows pump shown in FIG. 1 (hereinafter referred to as
"first pump) is a horizontal double-acting bellows pump used for
feeding and circulating fluid (e.g., chemicals and the like
employed in the fabrication processes of semiconductors, liquid
crystals, organic EL elements, and the like). The bellows pump is
comprised of a pump case 5 comprised of a pump head 3, having an
output passage 1 and a suction passage 2 formed therein, and a pair
of left and right cylinder cases 4, 4 provided on both sides
thereof. The bellows pump further includes: a pair of left and
right bellows 6, 6 respectively disposed inside of each one of the
cylinder cases 4 so as to make expansion and contraction (thus
being expandable and contractable) in the axial direction
(horizontal direction) of the pump head 3; a pair of left and right
pump chambers 7, 7 defined by being surrounded by the respective
bellows 6; a pair of left and right output check valves 8, 8
mounted to the pump head 3 in a protruding fashion into each one of
the pump chambers 7; and a pair of left and right suction check
valves 9, 9 provided in the pump head 3 so as to protrude into each
one of the pump chambers 7. This bellows pump is adapted, by
alternatingly actuating the two or a pair of bellows 6, 6 to expand
and contract, to simultaneously carry out an output stroke that
sends fluid out of one of the pump chambers 7 to the output passage
1 through the output check valve 8, and a suction stroke that
supplies fluid from the suction passage 2 into the other pump
chamber 7 through the suction check valve 9. It should be noted
that, with the exception of their left- and right-hand symmetrical
structure, the two cylinder cases 4, 4, two bellows 6, 6, two pump
chambers 7, 7, two output check valves 8, 8, and two suction check
valves 9, 9 making up the bellows pump have identical structures to
each other.
[0027] The pump head 3 is shaped like a disk that has therein an
output passage 1 connected to a fluid-feed line and a suction
passage 2 connected to a fluid-supply line, and, as shown in FIG.
1, an upstream end of the output passage 1 and a downstream end of
the suction passage 2 are open on the left and right sides
thereof.
[0028] As seen from FIG. 1 to FIG. 4, each cylinder case 4 is a
bottom-closed cylindrical casing mounted to the pump head 3. The
pump case 5 is thus made of the pump head 3 and the two cylinder
cases 4, 4; and the space inside the pump case 5 is split into two
in a side-to-side direction with the pump head 3 in between.
[0029] As shown in FIG. 1 and FIG. 2, each bellows 6 is a
bottom-closed cylinder made of plastic, and its peripheral wall 6a
has a bellows configuration with a zigzag cross-section. By being
expanded and contracted in the axial direction (side-to-side
horizontal direction), it enlarges and reduces the volume of the
pump chamber 7. The open-end portion 6b of each one of the bellows
6 is intimately secured or connected to the pump head 3, with the
space inside the bellows 6 defining the pump chamber 7 closed by
the pump head 3. Though it depends on the consistency and other
characteristics of the fluid handled by the pump, fluororesins
(such as polytetrafluoroethylene (PTFE) and perfluoroalkoxy (PFA)
fluororesins and the like are preferably used as the materials to
make the bellows 6. In the shown example, PTFE is employed. The
bottom wall 6c of each one of the bellows 6 is a disk-like part
that has a constant thickness (thickness in the axial direction)
and an outer diameter that matches that of the peripheral wall 6a
(the maximum diameter thereof), and the end portion 6d of a trough
part of the peripheral wall 6a is coupled to the bottom wall
6c.
[0030] As shown in FIG. 1, a disk-shaped actuation plate 10 made of
metal (such as stainless steel) is fixedly attached to the bottom
wall 6c of each bellows 6. Each actuation plate 10 is comprised of
a thin-walled disk-shaped main portion 10a and a thick-walled
annular coupling portion 10b formed in the peripheral portion
thereof, and this actuation plate 10 is fixedly attached to the
bottom wall 6c of the bellows 6 in such a manner that the main
portion 10a of the actuation plate 10 is abutted in a close contact
to the bottom wall 6c of the bellows 6 and the bottom wall 6c is
fitted into the annular coupling portion 10b. In other words, the
thickness of the bottom wall 6c of the bellows 6 is set to be
identical to or somewhat greater than the thickness (the thickness
in the axial direction) (or depth) of the annular coupling portion
10b of the actuation plate 10, and the peripheral portion 6e (which
is of the bottom wall 6c and located more outboard of the portion
used for coupling to the end portion 6d of the trough part of the
peripheral wall 6a) of the bottom wall 6c of the bellows 6 is
clamped between the main portion 10a of the actuation plate 10 and
a mounting plate 11 mounted to the coupling portion 10b of the
actuation plate 10. Accordingly, as shown in FIG. 1, the bottom
wall 6c of the bellows 6 and actuation plate 10 are connected and
integrated in the peripheral portion thereof such that the bottom
wall 6c of the bellows is in a close contact with the main portion
10a of the actuation plate 10.
[0031] By way of connecting the actuation plates 10, 10 and the
bellows 6, 6 together with a plurality of (e.g., four) coupling
rods 12, the two bellows 6, 6 are actuated in synchronism to expand
and contract in opposite directions. In another words, as
illustrated in FIG. 1, the two bellows 6, 6 are operatively
connected to the actuation plates 10 such that when one of the
bellows 6 is in its most contracted state, the other bellows 6 is
in its most expanded state, and when one of the bellows 6 is
actuated to contract, the other bellows 6 is actuated to expand in
unison therewith.
[0032] The plurality of coupling rods 12 connect the coupling
portions 10b, 10b, that are the peripheral portions of the
actuation plates 10, 10, at locations spaced apart at regular
intervals in the circumferential direction; and by way of thus
coupling the two actuation plates 10, 10 with these coupling rods
12, the attachment of the bottom wall 6c of each bellows 6 to each
actuation plate 10 is obtained. More specifically, the coupling
rods 12, which are provided inside the cylinder cases 4, 4, are
held in the pump case 5 so as to be movable in the axial direction
by means of O-rings 13; and with nut members 14 threadably mounted
to and engaged with the distal threaded portions 12a that pass
through the coupling portions 10b of the actuation plates 10 and
the mounting plates 11, the two actuation plates 10, 10 are coupled
together while fixedly connecting the bottom wall 6c of each
bellows 6 to each of the actuation plates 10. The thickness of the
main portion 10a of the actuation plate 10 is set to have a
strength sufficient to prevent the deformation under the action of
the pressure in the pump chamber 7, at least during the suction
stroke and output stroke; and it is preferable that the main
portion 10a of the actuation plate 10 be as thin as possible as
long as such strength to prevent deformation can be ensured.
[0033] The means used for actuating the bellows 6 to expand and
contract include, generally, piston-cylinder mechanisms, crank
mechanisms, air-cylinder mechanisms, and the like; and in the shown
embodiment, an air-cylinder mechanism is employed. More
specifically, the actuating means is adapted to actuate the bellows
6 to expand and contract in the axial direction by supplying and
discharging pressurized air 4c through intake/discharge ports 4a
formed in the bottom walls of the cylinder cases 4 to/from
intake/discharge spaces 4b formed between the cylinder cases 4 and
the actuation plates 10 and bellows 6. The intake and discharge of
air through the two intake/discharge ports 4a, 4a is carried out
synchronously in an alternating manner, such that when pressurized
air 4c is supplied to the intake/discharge space 4b through one of
the intake/discharge ports 4a, air is simultaneously discharged
from the other intake/discharge port 4a, and as a result of which
the contractile actuation of the two bellows 6, 6, that is, the
contractile actuation of the two pump chambers 7, 7, is carried out
in synchronism in opposite directions. In other words, a suction
stroke (or an output stroke) in one of the pump chambers 7 is
carried out in synchronism with an output stroke (or a suction
stroke) in the other pump chamber 7, and the switching between an
output stroke (a stroke in which fluid is sent from the pump
chamber 7 to the output passage 1 through the output check valve 8)
and a suction stroke (a stroke in which fluid is supplied from the
suction passage 2 to the pump chamber 7 through the suction check
valve 9) in the two pump chambers 7, 7 is carried out
simultaneously. FIG. 1 illustrates the final state of the suction
stroke in the left-side pump chamber 7 and the output stroke in the
right-side pump chamber 7.
[0034] As shown in FIG. 1, each output check valve 8 is configured
such that on the suction stroke, during which the bellows 6 is
actuated to expand (the volume of the pump chamber 7 changes so as
to expand), the valve plug 8b is held in the closed position under
the urging force of the spring 8a, while on the output stroke,
during which the bellows 6 is actuated to contract (the volume of
the pump chamber 7 changes so as to contract), the valve plug 8b is
displaced to the open position against the urging force of the
spring 8a by the high pressure in the pump chamber 7. Furthermore,
as shown in FIG. 1, each suction check valve 9 is configured such
that on the output stroke, during which the bellows 6 is actuated
to contract, the valve plug 9b is held in the closed position by
back pressure (the pressure of the pump chamber 7) and by the
urging force of the spring 9a, while on the suction stroke, during
which the bellows 6 is actuated to expand, the valve plug 9b is
displaced to the open position against the urging force of the
spring 9a as a result of a pressure drop in the pump chamber 7.
[0035] Of the components making the bellows pump above, those
coming into contact with fluid are formed by the materials suited
to the characteristics of the fluid to be handled, etc. In the
shown example, those components coming into contact with fluid are
made of fluororesin-base plastics, such as polytetrafluoroethylene,
that have superior corrosion resistance and resistance to
chemicals.
[0036] As seen from the above, in the first pump, the opposed end
faces 10c, 6g of the actuation plate 10 and the central area of the
bottom wall 6c of the bellows 6 are in a close contact with each
other as shown in FIG. 1. In other words, the actuation plate 10
and the fluid-contact portion 6f (the portion of the bottom wall 6c
located more inboard of the portion used for coupling to the end
portion 6d of the trough part of the peripheral wall 6a) that comes
into contact with the fluid in the pump chamber 7 make a close
contact relationship with each other. In addition, the
close-contact portions 10c, 6g are sealed with an annular sealing
member 15. In the shown example, the annular sealing member 15 is
an O-ring made of an incompressible elastic material (such as
fluororubber), and this O-ring 15 is held in engagement within an
O-ring groove 15a formed in the bottom wall 6c of the bellows.
[0037] Accordingly, even if the pressure in the pump chamber 7
varies following the contractile actuation (contractile changes in
pump-chamber volume) of the bellows 6, the bottom wall 6c of the
bellows is not deformed, and such problems as described in the
section of the Related Art above do not arise, and proper pump
functionality is achieved.
[0038] More specifically, in the pump chamber 7 (e.g., the
left-side pump chamber in FIG. 1) that is in a suction stroke, the
suction stroke, during which the bellows 6 is actuated to expand,
reduces the pressure in the pump chamber 7 and makes it negative,
thereby creating the risk that the central area, that is, the
fluid-contact portion 6f, of the bottom wall 6c of the bellows
having only its peripheral portion 6e connected to the actuation
plate 10 may be sucked into the negatively pressurized pump chamber
7 and buckle in a concave shape. However, the fluid-contact portion
6f of the bottom wall 6c of the bellows is in a close contact with
the main portion 10a of the actuation plate 10 and, at the same
time, the close-contact portions 6g and 10c are sealed by the
O-ring 15; accordingly, it does not separate from the main portion
10a of the actuation plate 10 under the action of the
above-described suction force produced by the negative pressure. In
other words, the fluid-contact portion 6f of the bottom wall 6c of
the bellows is held in a state of inseparable close contact with
the main portion 10a of the actuation plate 10. Therefore, the
suction force that acts on the fluid-contact portion 6f of the
bottom wall 6c of the bellows is received by the main portion 10a
of the metal actuation plate 10, and thus there is no risk that the
fluid-contact portion 6f deforms during the suction stroke.
[0039] On the other hand, in the other pump chamber 7 (e.g., the
right side pump chamber in FIG. 1) that is in an output stroke, the
output stroke, during which the bellows 6 is actuated to contract,
increases pressure in the pump chamber 7 and brings the chamber
under high pressure, thereby creating the risk that the central
area, that is, the fluid-contact portion 6f, of the bottom wall 6c
of the bellows having only its peripheral portion 6e connected to
the actuation plate 10, may be subject to buckling deformation in a
convex shape under the action of the pushing force produced by the
pressure in the pump chamber 7. However, the fluid-contact portion
6f of the bottom wall 6c of the bellows is in a close contact with
the main portion 10a of the actuation plate 10; accordingly, the
above-described pushing force acting on the fluid-contact portion
6f is received by the main portion 10a of the metal actuation plate
10, and thus there is no risk that the fluid-contact portion 6f
deforms during the output stroke.
[0040] As seen from the above, in the first pump, the bottom walls
6c of the bellows are prevented from being deformed by the pressure
of the pump chambers 7 during the suction stroke or the output
stroke. As a result, problems such as unstable flow rates
(output-fluid volumes) and circulating-fluid volumes, and
generation of random fluctuations due to substantial changes in
pump-chamber volume do not arise, and proper pump functionality is
achieved.
[0041] Furthermore, in the first pump, the fluid-contact portion 6f
of the bottom wall 6c of each of the bellows is reinforced by the
actuation plate 10 as described above. Accordingly, the bottom
walls 6c of the bellows do not need to be so thick as to possess
enough strength to withstand the pressure in the pump chambers 7,
and the bottom walls 6c can be those that have a thickness that is
necessary and sufficient for being connected to the actuation
plates 10 via the mounting plates 11, distal threaded portions 12a
of the coupling rods 12, and nut members 14. Accordingly, in
comparison with the conventional bellows pump described in the
section of the Related Art above, the bottom walls 6c of the
bellows can be made as thin as possible, and thus the weight of the
bellows 6 can be reduced.
[0042] Incidentally, the configuration of the bellows pump
according to the present invention is not limited to the one
described above and can be suitably improved and modified without
deviating from the principles of the present invention.
[0043] In the configuration of the first pump shown in FIG. 1, the
two actuation plates 10, 10 are coupled via the coupling rods 12
which are movably supported by the pump case 5 in the axial
direction, so that each actuation plate 10 is supported by the pump
case 5 via the coupling rods 12 so as to be movable in the axial
direction; and further, by way of coupling each actuation plate 10
to the coupling rods 12, the actuation plate 10 is connected to the
bottom wall 6c of the bellows 6 with the mounting plate 11 in
between. However, in the present invention, as a modification, the
means used for supporting the actuation plates 10 in the pump case
5 and the means used for attaching the actuation plates 10 to the
bottom wall 6c of the bellows can be, as shown in FIG. 3 to FIG. 5,
separate and independent.
[0044] FIG. 3 is a cross-sectional side view illustrating a
modification of the bellows pump of the present invention, and FIG.
4 is an enlarged view of the main portion of FIG. 3, and further
FIG. 5 is a cross-sectional front view taken along the line V-V in
FIG. 3. With the exception of the following features, the bellows
pump illustrated in FIG. 3 (hereinafter referred to as "second
pump") is a horizontal double-acting bellows pump of the same
configuration as the first pump. For the components that are
identical to those of the first pump, the same reference numbers
are in FIG. 3 to FIG. 5 as those in FIG. 1 and FIG. 2, and detailed
descriptions thereof are omitted.
[0045] As shown in FIG. 3 and FIG. 4, in the second pump, the
bottom wall 6c of each bellows 6 and the actuation plate 10 are
shaped as disks of the same diameter with a fixed thickness
(thickness in the axial direction). The bottom wall 6c of the
bellows and the actuation plate 10 are connected in a state of
close contact by threadably engaging and fastening a plurality of
connecting bolts 16 passing through their peripheral portions 6e,
10e to a mounting plate 17. In the shown example, as seen from FIG.
5, the peripheral portion 6e of the bottom wall 6c of the bellows 6
and the peripheral portion 10e of the actuation plate 10 are
connected by eight (8) connecting bolts 16 arranged
circumferentially at evenly spaced intervals. In addition, the
thickness of the actuation plate 10 is set to possess a strength
sufficient to prevent deformation under the action of the pressure
in the pump chamber 7, at least during the suction stroke and
output stroke, and it is preferable that the actuation plate 10 be
as thin as possible as long as such strength to prevent deformation
can be ensured.
[0046] An actuation shaft 20, which passes through and is supported
by the bottom wall of the cylinder case 4 so as to be movable in
the axial direction through the medium of an O-ring 18 and a
bearing ring 19, is integrally formed in the central area of each
one of the actuation plates 10. A disk-shaped coupling plate 21 is
fixedly secured to the end of each actuation shaft 20 outside the
cylinder case 4. The two coupling plates 21, 21 are disposed
outside the cylinder cases 4, 4 and coupled together by an
appropriate number of coupling rods 12, 12 (in the shown example
two (2)) that are provided in the pump case 5 so as to be movable
in the axial direction. Accordingly, because the two actuation
plates 10, 10 are coupled together via the actuating shafts 20, 20,
the coupling plates 21, 21, and the coupling rods 12, 12, the two
bellows 6, 6 are actuated to in synchronism expand and contract in
opposite directions. In other words, as illustrated in FIG. 3, the
two bellows 6, 6 are operatively coupled such that when one of the
bellows 6 is in its most contracted state, the other bellows 6 is
in its most expanded state, and when one of the bellows 6 is
actuated to contract, the other bellows 6 is actuated to expand in
unison therewith.
[0047] In the same manner as in the first pump, the actuating means
for actuating the bellows 6 to expand and contract is adapted to
actuate the bellows 6 to expand and contract in the axial direction
by supplying and discharging pressurized air through
intake/discharge ports (not shown) formed in the bottom walls of
the cylinder cases 4 to/from the intake/discharge spaces 4d formed
between the cylinder cases 4, actuation plates 10, and the bellows
6. The intake and discharge of the air to/from the two
intake/discharge spaces 4d, 4d is carried out synchronously in an
alternating manner, and, as a result, the contractile actuation of
the two bellows 6, 6, that is, the contractile actuation of the two
pump chambers 7, 7, is carried out synchronously in opposite
directions. In other words, a suction stroke (or an output stroke)
in one of the pump chambers 7 is carried out in synchronism with an
output stroke (or a suction stroke) in the other pump chamber 7,
and the switching between the output stroke (a stroke in which
fluid is sent from the pump chamber 7 to the output passage 1
through the output check valve 8) and the suction stroke (a stroke
in which fluid is supplied from the suction passage 2 to the pump
chamber 7 through the suction check valve 9) in the two pump
chambers 7, 7 is carried out simultaneously. FIG. 3 illustrates the
final state of the suction stroke in the left-side pump chamber 7
and the output stroke in the right-side pump chamber 7.
[0048] As seen from the above, in this second pump, in the same
manner as in the first pump, as seen from FIG. 3 and FIG. 4, the
opposed end faces 10c, 6g of the actuation plate 10 and the central
area of the bottom wall 6c of the bellows 6 are in a close contact
with each other. In other words, the actuation plate 10 and the
fluid-contact portion 6f (the portion of the bottom wall 6c located
more inboard of the portion used for being connected to the end
portion 6d of the trough part of the peripheral wall 6a) that comes
into contact with the fluid in the pump chamber 7 are in a closely
contact relationship with each other. In addition, the
close-contact portions 10c, 6g are sealed with the annular sealing
member 15. In the shown example, in the same manner as in the first
pump, the annular sealing member 15 is an O-ring made of an
incompressible elastic material (such as fluororubber), and this
O-ring 15 is held in engagement within the O-ring groove 15a formed
in the actuation plate 10. The central portion of the fluid-contact
portion 6f of the bottom wall 6c of each one of the bellows 6 is
formed with a round positioning protrusion 6h that closely fits
into a round recessed portion 10d formed in the central portion of
each one of the actuation plates 10, and thus the bottom walls 6c
of the bellows and the actuation plates 10 are abutted each other
in a concentric manner.
[0049] Accordingly, in the second pump as well, in the same manner
as in the first pump, even if the pressure in the pump chambers 7
varies following the contractile actuation (contractile changes in
pump-chamber volume) of the bellows 6, the bottom walls 6c of the
bellows do not deform since the bottom walls 6c of the bellows are
reinforced by the metal actuation plates 10, and such problems as
described in the section of the Related Art above do not arise, and
thus proper pump functionality is achieved. In the second pump,
since the coupling rods 12, 12 are disposed outside the cylinder
cases 4, 4, the volume of the intake/discharge spaces 4d are
smaller compared to the intake/discharge spaces 4b in the first
pump, and it is thus possible to reduce the volume of the
pressurized air used to actuate the bellows 6, 6 to expand and
contract.
[0050] In addition, in the second pump, the fluid-contacts 6f of
the bottom walls 6c of the bellows are reinforced by the actuation
plates 10. Accordingly, the bottom walls 6c of the bellows do not
need to be so thick as to possess enough strength to withstand the
pressure in the pump chambers 7, and what is required for the
bottom wall of the bellows 6 is that it has a thickness that is
necessary and sufficient to be attached to the actuation plates 10
by the connecting bolts 16 and the mounting plates 17. In view of
the above, in the same manner as in the first pump, the bottom
walls 6c of the bellows in the second pump can be made as thin as
possible in comparison with the conventional bellows pump described
in the section of the Related Art above, and it is possible to
reduce the weight of the bellows 6.
[0051] In addition, although the first and second pump are adapted
to bring the opposed end faces 10c, 6g of the actuation plates 10
and the fluid-contact portions 6f of the bottom walls 6c of the
bellows 6 into a close contact with each other while sealing these
close-contact faces 10c, 6g with the annular sealing members (the
O-ring) 15, sealed spaces 22 as shown in FIG. 6 to FIG. 8 that are
sealed by the annular sealing members 15 can be formed between the
opposed end faces 6g, 10c, so that the sealed spaces 22 are filled
with an incompressible fluid 23.
[0052] More specifically, FIG. 6 is a cross-sectional side view of
another modification of the bellows pump according to the present
invention, FIG. 7 is an enlarged view of the main portion of FIG.
6, and FIG. 8 is a cross-sectional front view taken along the line
VIII-VIII in FIG. 6. With the exception of the following features,
the bellows pump illustrated in FIG. 6 (hereinafter referred to as
"third pump") is a horizontal double-acting bellows pump of the
same configuration as the second pump. The reference symbols
identical to those of FIG. 3 and FIG. 5 are assigned to the
components identical to those of the second pump in FIG. 6 to FIG.
8, and detailed descriptions thereof are omitted.
[0053] As seen from FIG. 6 and FIG. 7, in the third pump, a round
recessed portion is formed in the outer surface of the
fluid-contact portion 6f of the bottom wall 6c of each one of the
bellows 6. In other words, the thickness (thickness in the axial
direction) of the fluid-contact portion 6f, that is, the central
area of the bottom wall 6c of the bellows, is made thinner than the
thickness of the peripheral portion 6e of the bottom wall 6c, and a
space 22 corresponding to the above-described round recessed
portion is formed between the opposed end faces 6g, 10c of the
fluid-contact portion 6f and the actuation plate 10. This space 22
is made into a sealed space by way of using the annular sealing
member 15 provided between the actuation plate 10 and the
peripheral portion 6e of the bottom wall 6c of the bellows 6. In
the same manner as in the second pump, the annular sealing member
15 is an O-ring, and this O-ring 15 is held in engagement within
the O-ring groove 15b formed in the actuation plate 10.
[0054] The sealed space 22 is completely filled with incompressible
fluid 23 (e.g., oil or another fluid).
[0055] Furthermore, as shown in FIG. 6 and FIG. 7, in this third
pump, the actuating shafts 20 are the separate elements from the
actuation plates 10, and each actuation plate 10 and each actuation
shaft 20 are integrally coupled by threadably fastening the
threaded portion 20a of the distal end of the actuation shaft 20 to
the internally threaded recessed portion 10f formed in the
actuation plate 10 while sealing the threaded connection portion
with an O-ring 24.
[0056] With the above structure of the third pump, in the pump
chamber 7 which is under the suction stroke (e.g., the left-side
pump chamber illustrated in FIG. 6), the bellows 6 is actuated to
expand, thus reducing the pressure in the pump chamber 7 and making
it negative, thereby creating a risk that the central area, that
is, the fluid-contact portion 6f, of the bottom wall 6c of the
bellows 6 having only its peripheral portion 6e attached to the
actuation plate 10 by two or more connecting bolts 16 may be sucked
into the negatively pressurized pump chamber 7 and subject to
buckling deformation in a concave shape. However, the sealed space
22 formed between the opposed end faces 10c, 6g of the actuation
plate 10 and the fluid-contact portion 6f of the bottom wall 6c of
the bellows is completely filled with the incompressible fluid 23,
such as oil and the like; accordingly, the sealed space 22 filled
with this incompressible fluid 23 can function as a type of rigid
body. As a result, even when the pump chamber 7 is negatively
pressurized, the fluid-contact portion 6f of the bottom wall 6c of
the bellows, the sealed space 22 that is filled with the
incompressible fluid 23 acting as a rigid body, and the actuation
plate 10 are all held in a state of inseparable mutual contact.
Accordingly, the fluid-contact portion 6f of the bottom wall 6c of
the bellows 6 does not deform into a concave shape by being pulled
into the pump chamber 7, and thus the volume of the pump chamber 7
does not change on the suction stroke.
[0057] On the other hand, in another pump chamber 7 which is under
the output stroke (e.g., the right pump chamber illustrated in FIG.
6), the bellows 6 is actuated to contract, thus increasing the
pressure in the pump chamber 7 and bringing the chamber under high
pressure, thereby creating a risk that the central area, that is,
the fluid-contact portion 6f, of the bottom wall 6c of the bellows
6 with its peripheral portion 6e only connected to the actuation
plate 10, may deform in a convex shape into the sealed space 22
under the action of the pushing force produced by the pressure in
the pump chamber 7. However, the sealed space 22, as described
above, can function as a type of rigid body filled with the
incompressible fluid 23, and the pushing force produced by the
pressure in the pump chamber 7 that acts on the fluid-contact
portion 6f of the bottom wall 6c of the bellows is received by the
metal actuation plate 10 through the medium of the sealed space 22
acting as a rigid body. Consequently, there is no risk that the
fluid-contact portion 6f may deform during the output stroke, and
the volume of the pump chamber 7 does not change on the output
stroke.
[0058] As seen from the above, as in the first and second pumps,
the bottom walls 6c of the bellows of the third pump are not
deformed by the pressure fluctuations in the pump chambers 7 during
the suction stroke or the output stroke. Accordingly, problems such
as unstable flow rates (output-fluid volumes) and circulating-fluid
volumes, and generation of random fluctuations due to substantial
changes in pump-chamber volume do not arise, and proper pump
functionality is achieved.
[0059] In addition, in the third pump, as described above, the
fluid-contact portions 6f of the bottom walls 6c of the bellows are
reinforced by the actuation plates 10 through the medium of the
sealed spaces 22. Accordingly, the bottom walls 6c of the bellows
may have a thickness that is necessary and sufficient for attaching
its peripheral portions 6e to the actuation plates 10 by means of
the connecting bolts 16 and mounting plates 17, and the thickness
of the fluid-contact portions 6f, that is, the central areas, can
be reduced even more compared to the first and second pumps, and
further the weight of the bellows 6 can be reduced
significantly.
[0060] It should be noted that in addition to applications
involving double-acting bellows pumps such as the first through
third pumps, the present invention is suitably applicable to
single-acting bellows pumps.
* * * * *