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BACKGROUND OF THE INVENTION
The present invention relates to a constant-flow fluid controlling valve
for automatically controlling the rate of flow of fluid passing
therethrough to thereby maintain a constant rate of fluid flow even when
fluctuations in fluid pressure take place at either the inlet or outlet
side of the valve.
In a known constant-flow fluid controlling valves of the diaphragm or
piston type, when fluid pressure on the inlet side increases or when fluid
pressure on the outlet side decreases, increasing the rate of fluid flow
through a restriction installed in a flow passage on the inlet side and
also increasing the pressure differential across the restriction, the
diaphragm or piston moves, moving a valve stem connected thereto to
thereby reduce the rate of flow of fluid passing through the controlling
valve. When fluid pressures are well balanced as described above, the
following equation holds:
(P.sub.1 -P.sub.2).times.S=F-W
where
P.sub.1 =pressure on the upstream side of the restriction.
P.sub.2 =pressure on the downstream side of the restriction.
S=effective area of the diaphragm.
F=pulling force of a spring exerting on the valve stem.
W=sum of all the weights of an inner valve and the parts attached thereto
in fluid.
The above equation can be changed into the equation
##EQU1##
Since the pressure differential created across the restriction is held
constant, the controlling valve is capable of sending the fluid at a
constant rate of fluid flow.
However, the difference in magnitude between the upward and downward forces
acting on the inner valve must be nullified, irrespective of the values
for the pressures P.sub.1 and P.sub.2, in order that the above equation
should be made to hold.
In other words, it is essential that a constant-flow fluid controlling
valve should be designed in such a way that friction between a valve stem
and the parts guiding it is reduced to a minimum and also that an inner
valve is not moved up and down in a vertical line as result of pressures
received directly from the fluid.
The valve of the present invention is an automatic flow controlling valve
embodying such conception and thus maintaining a constant rate of fluid
flow by utilizing the energy itself of the fluid flowing therethrough.
SUMMARY OF THE INVENTION
The valve according one embodiment of to the present invention is an
automatic constant-flow fluid controlling valve having a valve casing, a
partition wall formed therewithin to partition the valve casing into an
inlet-side chamber and an outlet-side chamber, a valve port made in the
horizontal part of the partition wall, a valve stem movable relative to
the valve port and fitted with a valve plug adapted to open and close the
valve port. A diaphragm is mounted on the top of the valve stem. An
inlet-side flow passage of the valve is divided by a restriction into a
pre-chamber and a post-chamber. A lower pressure-differential chamber
separated from the inlet-side chamber by a valve-plug guiding member is
formed between the diaphragm and the valve plug; a part of the fluid from
the post-chamber of the restriction is caused to flow through a strainer
into the lower pressure-differential chamber; and the fluid pressures
acting on the upper and lower surfaces of the valve plug are made to be
equal in magnitude and opposite to each other.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical cross-sectional view of an automatic flow controlling
valve according to one embodiment of the invention.
FIG. 2 is a top view of the guide bushing 21 shown in FIG. 1.
FIG. 3 is an enlarged vertical cross-sectional view of a valve seat 24 and
a lower annular or circumferential edge of the valve plug 8 shown in FIG.
1.
FIG. 4 is an enlarged vertical cross-sectional view of the narrow passage
34 shown in FIG. 1.
FIG. 5 is a vertical cross-sectional view of an automatic flow controlling
valve having a modified construction, but also embodying the features of
the invention.
FIG. 6 is a vertical cross-sectional view of an automatic flow controlling
valve having another modified construction, but also embodying the
features of the invention.
FIG. 7 is an enlarged vertical cross-sectional view of the valve stem 67
shown in FIG. 6.
FIG. 8 is a vertical cross-sectional view of an automatic flow controlling
valve having a further modified construction, but also embodying the
features of the invention.
FIG. 9 is a vertical cross-sectional view of an autmoatic flow controlling
valve having a still further modified construction, but also embodying the
featrures of the invention.
In the drawings, the same reference characters are employed to designate
identical parts.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiment 1
With reference now to FIGS. 1, 2, 3, and 4 of the drawings there is
illustrated a valve casing 1 which is divided by a partition wall 2
therewithin into an inlet side chamber 3 and an outlet side chamber 4. A
restriction 5 is provided in the inlet side flow passage to partition it
into a pre-chamber 5a and post-chamber 5b the setting of the area for
fluid flow through the restriction 5 being adjusted by means of an
adjusting member 33. A valve port 6 is formed in the horizontal part of
the partition wall 2, the upper periphery of the valve port 6 constituting
a valve seat 24 having an inwardly inclined surface as shown in FIG. 3.
The valve port 6 is opened and closed by the respective separation and
contacting of the tapered edge 32 of a cylindrical valve plug 8 from and
with the valve seat 24. A hollow valve stem 7 extends through the valve
port 6 in the direction of the vertical axis of the valve casing 1. The
cylindrical valve plug 8 serving to open and close the valve port 6 is
fixedly mounted on the valve stem 7 by means of a transverse support plate
25. The transverse support plate 25 is dimensioned in such a way that the
axial fluid-pressure receiving areas of its upper and lower surfaces are
equal to each other. The cylindrical valve plug 8 also is dimensioned in
such a way that the axial fluid-pressure receiving areas of the upper and
lower annular edges of a cylindrical member 26 are equal to each other. A
diaphragm 9 partitions a pressure-differential chamber into an upper
pressure-differential chamber 12 and a lower pressure-differential chamber
13 and is secured to the upper end of the valve stem 7 by means of
retainers 10 and 11, the upper and lower pressure-differential chambers 12
and 13 respectively receiving back pressure and positive pressure. The
valve stem 7 is fitted at its lower end with a strainer 15 having
filtering medium 14. The strainer 15 is housed in an easily attachable and
detachable strainer case 16, the strainer case 16 being joined by
threading to the valve casing 1 at its bottom circular end. It is
preferred to employ a transparent strainer case because the inside can
then be seen through the strainer case from the outside. A valve-plug
guiding member 17 fitted at its lower part with a sliding-contact ring 18
is joined by threading on the upper inner peripheral surface of the valve
casing 1, thus separating the lower pressure-differential chamber 13 from
the outlet-side chamber 4. The inner peripheral surface of the valve plug
8 is slidable on the sliding-contact ring 18. Since the pressure P.sub.2
of the fluid flowing from the strainer 15 through the hollow valve stem 7
and a plurality of communicating holes 23 into the valve-plug guiding
member 17 and the lower pressure-differential chamber 13 is greater than
the fluid pressure P.sub.3 within the outlet-side chamber 4, the fluid
leaks along a sliding-contact surface X and through a clearance space
between the valve-plug guiding member 17 and the valve plug 8 into the
outlet side chamber 4. During this time, because the fluid entering the
valve-plug guiding member 17 and the lower pressure-differential chamber
13 has been filtered through the strainer 15 before flowing into the
hollow valve stem, there is no possibility of hindering the valve plug 8
from moving up and down smoothly due to the introduction of impurities
into the sliding contact surface X. The pre-chamber 5a of the restriction
5 and the upper pressure-differential chamber 12 communicate with each
other through a branch flow-passage 19. A spring case 27 positioned
coaxially over the valve stem 7 forms with the diaphragm 9 the upper
pressure-differential chamber 12. A spring 20 is mounted coaxially within
the spring case 27 between the upper end thereof and the top of the valve
stem 7. A guide bushing 21 serves to guide the lower part of the valve
stem 7. As shown in FIG. 2, a plurality of concave recesses 22 are formed
in the inner periphery of the guide bushing 21 so that the area of the
sliding-contact surface between the bushing and the valve stem 7 may be
reduced. The guide bushing 21 is so constructed to reduce frictional
resistance with the valve stem 7 and also to prevent the introduction of
impurities therebetween. The numerals 30 and 31 respectively designate
inlet and discharge pipes and the numerals 28 and 29 respectively
designate for flanges attachment to the inlet pipe 30 and the discharge
pipe 31. The, the action of the controlling valve of this embodiment will
now be described. The major portion of the fluid A which has reached the
inlet 3 flows sequentially through pre-chamber 5a, restriction 5,
post-chamber 5b, inlet side chamber 3, and the valve port 6 into the
outlet side chamber 4 and is discharged through the outlet 4.
Concurrently, a part of the fluid which has entered pre-chamber 5a flows
through the branch flow-passage 19 into the upper pressure-differential
chamber 12 and a part of the fluid which has entered the pre-chamber 5b
flows through the strainer 15, the valve stem 7, and the communicating
holes 23 into the lower pressure-differential chamber 13. If the fluid
pressures within the pre- and post-chambers 5a and 5b respectively are
represented by P.sub.1 and P.sub.2, then the back pressure within the
upper pressure-differential chamber 12 becomes equal to the fluid pressure
P.sub.1 because the upper pressure-differential chamber 12 communicates
with the prechamber 5a. The fluid pressure within the lower
pressure-differential chamber 13 has the pressure P.sub.2 because the
fluid pressure inside the lower pressure-differential chamber 13 is the
same as that inside the post-chamber 5b. Therefore, when fluctuations in
pressure differential take place across the restriction 5, pressure
differentials of equal value are generated between the upper and lower
pressure-differential chambers 12 and 13. The diaphragm 9 operates, to
move the valve stem 7 upwardly or downwardly to automatically regulate the
rate of fluid flow through the valve in accordance with such fluctuations
in pressure differential. During this time the upper and lower surfaces of
the transverse support plate 25 has applied thereto the same fluid
pressure as P.sub.2 inside the lower pressure-differential chamber 13 and
the same fluid pressure P.sub.2 inside the post-chamber 5b, the fluid
pressures applied on the upper and lower surfaces of the transverse
support plate 25 thus compensating each other and thereby cancelling out.
If the fluid pressure inside the outlet side chamber 4 is represented by
P.sub.3, fluid pressure P.sub.3 is exerted axially to each of the
circumferential upper and lower edges of the cylindrical member 26 of the
valve plug 8, these fluid pressures of P.sub.3 secure to compensate each
other and cancel out. Consequently the valve plug 8 is not at all
influenced by fluctuations in flow rate and fluid pressure, and only the
up and down movement of the diaphragm 9 caused by fluctuations in the
pressure differential of (P.sub.1 -P.sub.2) is transmitted by means of the
valve stem 7 to the valve plug 8, thereby permitting it to adjust the
degree of opening of the valve to automatically regulate the rate of fluid
flow therethrough.
As described above, in the controlling valve of this embodiment, the rate
of the fluid flow can be held nearly constant by adjusting the degree of
opening of the restriction 5 to a desired point by means of an adjusting
member 33 provided with a scale. The fluid pressures acting on the valve
plug 8 compensate one another and cancel out owing to the operation of the
diaphragm 9 caused by the action of the positive and back pressures
thereon as described above which permits an accurate supply of fluids at a
constant rate of flow. Further the adverse effect of impurities in the
fluids is prevented by removing the impurities through the strainer 15 at
the sacrifice of a small reduction in the degree of accuracy caused by the
change in effective area depending on the up and down movement of the
diaphragm 9. There is no possibility of introducing impurities between the
inner peripheral surface of the valve plug 8 and the sliding-contact
surface of the slide guide-ring 18 positioned on the peripheral surface of
the valve-plug guiding member 17, the fluid entering the lower
pressure-differential chamber 13 having been filtered through the strainer
15 before being permitted to flow into the inner valve. The dust and dregs
having been removed, the valve plug 8 can move up and down smoothly and
surely in a vertical line, to effectively close the valve port 6 and to be
trouble free. Furthermore, because the strainer 15 is covered with the
easily attachable and detachable strainer case 16, cleaning and exchanging
it can be easily carried out. The materials for the slide guide-ring 18
and the guide bushing 21 are selected from those that can reduce the
coefficient of friction between the sliding-contact surfaces thereby
enabling the degree of accuracy of the valve stem 7 and the valve plug 8
which move up and down to increase.
Since the upper periphery of the valve port 6, constituting the valve seat
24, is tapered on its inner surface as shown in FIG. 3, stream lines are
uninterrupted by virtue of the taper throughout the cross-sectional area
of the intermediate flow passage formed between the valve seat 24 and a
lower tapered edge 32 of the cylindrical member 26, independently of the
speed of the fluid or whether the lower annular or circumferential edge of
the cylindrical member 26 is square or is tapered as shown in FIG. 3.
Therefore the balance between axial fluid pressures acting on the valve
plug 8 can be always maintained accurately, the operation of the valve
plug 8 caused by the action of the diaphragm 9 can be effectively
performed, and positive closing of the valve port 6 can be expected when
the lower tapered edge 32 of the cylindrical member 26 comes into close
contact with the tapered valve seat 24, thereby providing a controlling
valve of a high degree of accuracy.
In this embodiment, when a part of the branch flow-passage 19 leading to
the upper-differential chamber 12 is formed into a narrow fluid passage 34
as shown in FIG. 4, then the problem of a hunting phenomenon of diaphragm
9 caused by fluctuations in fluid pressure can be avoided.
That is to say, since the rate of flow of a fluid flowing into and from the
upper pressure-differential chamber 12 is reduced by interposing the
narrow flow passage 34 between the branch flow-passage 19 and the upper
pressure-differential chamber 12, for example, even when a sharp increase
in fluid pressure occurs in the pre-chamber 5a and is transmitted through
the branch flow-passage 19 to the upper pressure-differential chamber 12,
the fluid does not flow rapidly at a high flow-rate according to the
increased fluid pressure into the upper pressure-differential chamber 12,
but instead flows thereinto at a low flow-rate. The resultant gentle
application of fluid pressure on the diaphragm 9 causes it to operate
slowly or to move downwardly and slowly. Hence, even if fluctuations in
fluid pressure occur on the inlet side 3 and are transmitted to the upper
pressure-differential chamber 12, the gentle operation of the diaphragm 9
eliminates the possibility of hunting moving the valve plug 8 upwardly and
downwardly with stability and certainty to automatically regulate the rate
of fluid flow through the valve very effectively.
Embodiment 2
The fluid flow controlling valve of this embodiment has a modified
construction and includes a cylindrical valve plug serving to open and
close a valve port positioned as to move up and down in a vertical line
freely; no difference in magnitude existing between the axial opposite
forces acting on the valve plug irrespective of fluctuations in the flow
rate and pressure of the fluid.
Referring to FIG. 5 there is described a valve casing 1 made into a flat
bottomed valve casing by omitting strainer 15 and strainer case 16 shown
in FIG. 1. A valve port 6 is made in the horizontal part of a partition
wall 2 provided within the valve casing 1. Over the valve port 6 there is
positioned a cylindrical valve plug 35 for opening and closing the valve
port 6. The valve plug 35 is secured by means of a horizontal spider 36 to
a vertical valve stem 37, the vertical valve stem 37 having its axis
common to the valve casing 1 and the valve port 6. Filtering medium 40
such as wire gauze is placed between each of the legs of the horizontal
spider 36. The valve plug 35 is dimensioned in such a way that the areas
of the fluid pressure-receiving surfaces of the upper and lower edges of
its peripheral wall are equal to each other. A diaphragm 9 is provided
within a pressure-differential chamber and is mounted on the top of the
valve stem 37 by means of metallic retainers 10 and 11, partitioning the
pressure-differential chamber into an upper pressure-differential chamber
12 and a lower pressure-differential chamber 13. A cylindrical, valve-plug
guiding member 38 is joined by threading to the upper inner peripheral
surface of the valve casing 1, separating the lower pressure-differential
chamber 13 from an outlet-side chamber 4 and also having on its lower
outer peripheral surface a slide guide-ring 39 facilitating the sliding of
the inner peripheral surface of the valve plug 35 to freely thereon.
The action of the controlling valve of this embodiment will now be
described. The major portion of the fluid which has reached inlet 3 flows
through a pre-chamber 5a of a restriction 5, and as described in
connection with FIG. 1, a post-chamber 5b. The fluid then flows through,
an inlet side chamber 3, valve port 6, and an intermediate flow passage
between the valve plug 35 and a valve seat 24 into an outlet side chamber
for discharge 4. At this time, in the same manner as that of the preceding
embodiment, some part of the fluid is introduced through a branch
flow-passage 19 into the upper pressure-differential chamber 12. Part of
the fluid is filtered through the filtering medium 40 positioned within
the valve plug 35 and flows through an annular clearance 41 between the
valve stem 37 and an internal flange of the valve-plug guiding member 38,
and through an annular opening 42 between the metallic retainer 11 and the
valve-plug guiding member 38 into the lower pressure-differential chamber
13. Hence the up and down movement of the diaphragm 9 is transmitted
through the valve stem 37 to the valve plug 35 to regulate the rate of
fluid flow through the valve in the same manner as described in connection
with FIG. 1 in accordance with changes in the pressure differential
P.sub.1 -P.sub.2.
Embodiment 3
The construction of the fluid flow controlling valve of this embodiment is
such that a variable-area orifice that adjusts the area of a flow passage
for fluids passing therethrough is formed in place of the restriction 5 of
the first and second embodiments on the inlet side of the valve. A branch
flow passage leading to an upper pressure-differential chamber is provided
on the upstream side of the orifice and a bypass leading to a lower
pressure-differential chamber and a valve port are provided on the
downstream side of the orifice. The variable orifice is set for the
desired flow-rate before the rate of fluid flow is regulated by means of a
valve plug having a diaphragm to be held constant.
Referring to FIGS. 6 and 7 there is shown a box-type valve casing 51 having
on its inlet side an inlet conduit 52. The inlet conduit 52 has
therewithin a flow passage 53 of larger diameter and a flow passage 54 of
smaller diameter. The flow passage 53 and the flow passage 54 communicate
with each other through a smaller-diameter hole or orifice 55. The lower
tapered end 80 of an orifice adjusting stem 56 is cooperable with the hole
55. The orifice adjusting stem 56 is so positioned loosely through a
larger-diameter hole 57 made in the side wall of the inlet conduit 52 as
to slide therewithin. The upper threaded part of the stem 56 is engaged
with threads on the inner peripheral surface of a guide bushing 58 fixedly
positioned above the larger-diameter hole 57. An orifice adjusting
mechanism is constructed in such a way that the lower tapered end 80 of
the orifice adjusting stem 56 is made to contact with and separate from
the smaller-diameter hole 55 by turning a handwheel 59 surmounting and
integral with the stem 56 to adjust the cross-sectional flow area for
through the orifice 55. The handwheel 59 has proximate thereto a dial and
whereby the setting of the rate of flow can be adequately adjusted. The
hole orifice 55 communicates through the flow passage 54 with a flow
passage 60 formed in the lower thicker portion of the valve casing 51 and
communicates further through a valve port 62 with an outlet-side flow
passage 61. A pressure-differential chamber is formed within the upper
part of valve casing 51 and is partitioned by a diaphragm 64 into an upper
pressure-differential chamber 63 and a lower pressure-differential chamber
81. The upper pressure-differential chamber 63 communicates through a flow
passage 65 with the flow passage 53 of larger diameter, namely the
upstream side of the restriction orifice 55. The lower
pressure-differential chamber 81 communicates through a flow passage 66
leading to the flow passage 60 with the flow passage 54 of smaller
diameter, namely the downstream side of the restriction 55. The diaphragm
64 is secured to about the middle of a valve stem 67 by means of a
metallic retainer 68, the lower part of the valve stem 67 being so
inserted closely within a guide hole 70 formed in a valve guide 69 as to
slide freely therewithin. The annular space between the outer
circumferential surface of the flange of the valve guide 69 and the inner
circumferential surface of the lower pressure-differential chamber 81 is
filled with filtering medium 82 such as wire gauze, thus constituting a
strainer. The upper part of the valve stem 67 is positioned coaxially
within a spring case 71 surmounting the valve casing 51, and a spring
retainer 72 is attached to the upper end of the valve stem 67. A coil
spring 74 is so interposed compressively between the lower surface of the
spring retainer 72 and the upper surface of a ceiling plate 73 of the
valve casing 51 as to bias the valve stem 67 upwardly. The valve stem 67
is positioned loosely through a central hole 75 formed in the plate 73,
the central hole 75 allowing the spring case 71 and the upper
pressure-differential chamber 63 to communicate with each other. The lower
part of the valve stem 67 constitutes a valve plug 76. The lower end of
the valve plug 76 is opposed to a valve seat 83 formed in the upper
periphery of the valve port 62, the valve port 62 being formed between the
flow passage 60 and the outlet-side flow passage 61. The detailed
structure of the valve plug 76 is shown in FIG. 7. The valve plug is
formed into a cylindrical tube 78, the cylindrical tube 78 being closed at
its upper end and opened at its lower end. The upper end of the
cylindrical tube 78 constitutes a shoulder 79 and the lower end of the
cylindrical tube 78 is shaped into an inclined surface 77. Further the
cylindrical tube 78 is dimensioned to have its inner diameter D.sub.2 made
to be equal to the outer diameter D.sub.1 of the valve stem 67.
The action of the controlling valve of this embodiment will now be
described. When the area for fluid flow through the restriction 55 is
adequately set by turning the handwheel 59 and a fluid W is allowed to
enter the inlet conduit 52, then major portion of the fluid W flows
through the restriction 55, the flow passages 54 and 60, and the valve
port 62 into the outlet-side flow passage 61 and leaves through an outlet.
The remainder of the fluid W flows through passages 65 and 66 into the
upper and lower pressure-differential chambers 63 and 81 respectively. If
fluid pressures on the upstream and downstream sides of the restriction 55
respectively are taken to be P.sub.1 and P.sub.2, then fluid pressures
acting on the upper and lower surfaces of the diaphragm 64 respectively
become P.sub.1 and P.sub.2. If pressure on the downstream side of the
valve port 62 is taken to be P.sub.3, then the pressures P.sub.2, P.sub.3,
and P.sub.3 respectively are applied on the ceiling surface, shoulder 79
and inclined circumferential surface 77 of the cylindrical tube 78 of the
valve plug 76. When the rate of fluid flow through the inlet conduit 52 is
increased or decreased, thereby increasing or decreasing the pressure
P.sub.1, the diaphragm 64 thus moves upwardly or downwardly, bringing the
valve plug 76 close to or moving it away from the valve port 62 and also
decreasing or increasing the cross-sectional area of the intermediate flow
passage formed between the valve port 62 and the lower annular or
circumferential edge of the cylindrical tube 78 of the valve plug 76 so
that fluids passing through the valve will have a constant rate of fluid
flow. When pressures are well balanced as described above, the following
equation holds:
(P.sub.1 -P.sub.2).times.S=F-W
where
P.sub.1 =pressure on the upstream side of the restriction 55.
P.sub.2 =pressure on the downstream side of the restriction 55.
S=effective area of the diaphragm 64.
F=pulling force of the coil spring 74 exerted on the valve stem 67.
W=sum of all the weights of the inner valve and the parts attached thereto
in the fluid W.
The above equation can be changed into the equation
##EQU2##
The rate Q of fluid flow through the restriction 55 can be expressed by the
equation
##EQU3##
where H=.sub.1 -P.sub.2 =a constant value.
g=acceleration of gravity.
K=coefficient of exit.
a=cross-sectional fluid flow area through orifice or restriction 55.
This equation consequently gives
Q.varies.a.
Hence the rate Q of fluid flow is held constant unless the area for fluid
flow through the restriction 55 is altered. Because a pressure as high as
the fluid pressure P.sub.3 is applied on the lower inclined peripheral
surface 77 of the cylindrical tube 78 of the valve plug 76, pressures
exerted on the upper and lower edges 79 and 77 of the cylindrical tube
become nearly equal to each other. The valve plug 76 thus is not affected
very much by fluctuations in pressure differential (P.sub.2 -P.sub.3)
created across the valve port 62, but is accurately driven substantially
only by the displacement movement of the diaphragm 64 caused by
fluctuations in pressure differential created across the restriction 55,
which thereby permits the rate of fluid flow through the valve to be held
constant.
Embodiment 4
The construction of the fluid flow controlling valve of this embodiment is
such that a box-shaped partition wall defining on its one side an inlet is
provided within a valve casing, partitioning it into an inlet-side chamber
and an outlet-side chamber; a round hole and a valve port respectively are
made in the upper and lower horizontal parts of the partition wall; a
valve stem is positioned through the round hole and the valve port, the
valve stem being fitted at its upper end with a diaphragm, having a valve
plug to open and close the valve port and a pressure-receiving slide
member slidable on the inner peripheral surface of a guide bushing
inserted into the round hole. The valve stem is movable with the up and
down movement of the diaphragm; the fluid passing through a radial
clearance between the inner peripheral surface of the guide bushing and
the outer peripheral surface of the pressure-receiving slide member after
having been purified through a strainer before flowing into the radial
clearance.
In the fluid flow controlling valve of this embodiment, because the fluid
passing through the radial clearance between the outer peripheral surface
of the pressure-receiving slide member and the inner peripheral surface of
the guide bushing has been purified through the strainer before flowing
into the radial clearance, the slide member can slide smoothly on the
inner surface of the guide bushing, resulting in accurate automatic
control.
Referring to FIG. 8 there is shown a valve casing 91 provided therewithin
with a box-shaped partition wall 92. The partition wall 92 is opened at
its one side and partitions the valve casing 91 into an inlet-side chamber
93 and an outlet-side chamber 94. A restriction 96 that provides an
adjustment of fluid flow rate therethrough is positioned in a flow passage
between the outlet-side chamber 94 and an outlet 95. This setting can be
adjusted by the use of an externally located dial (not shown in the
drawing). A round hole 97 and a valve port 98 respectively are made in the
upper and lower horizontal parts of the partition wall 92. A guide bushing
99 is screwed into the round hole 97. The guide bushing 99 is provided
with an integral strainer 100. The strainer 100 has on its entire
peripheral side a filtering medium 101 such as wire gauze and projects
from the upper horizontal part of the partition wall 92 into the
inlet-side chamber 93 and communicates therewith. A hole 112 is made in
the bottom 111 of the strainer 100 and a valve stem 102 described later is
positioned slidably therethrough. By making the diameter of the hole 112
adequately larger than the outer diameter of the valve stem 102, a
sufficient radial clearance is allowed to exist between the hole 112 and
the peripheral surface of the valve stem 102 so as to prevent the close
contact thereof with the hole 112 as well as the clogging of the radial
clearance by impurities, which might otherwise interfere with the up and
down movement of the valve stem 102. Since the fluid which has entered the
strainer 100 is allowed to flow in the directions of the arrow heads,
there is no possibility of the fluid entering the strainer 100 through the
radial clearance between the hole 112 and the peripheral surface of the
valve stem 102; that is to say, the whole of the fluid entering the inside
of the strainer 100 has been purified through the filtering medium 101
before flowing into the inside of the strainer 100.
The valve stem 102 extends slidably through the valve port 98 and through
the hole 122 made in the strainer 100 and is provided with a
pressure-receiving slide member 103 slidable on the inner peripheral
surface of the guide bushing 99 and with a cylindrical inner valve 104
which is adapted to open and close the valve port 98. The upper half of
the inner valve 104 constitutes a cylindrical valve plug 113 and is
cooperable with a valve seat 118 of the valve port 98. The lower half of
the inner valve 104 has a slightly smaller diameter than the outer
diameter of the valve plug 113 and constitutes a mounting member 114 for
attachment thereof to the valve stem 102. The peripheral surface of the
mounting member 114 is slidable on the inner peripheral surface of a tube
member 115 inserted into a round hole made in a bottom plate 116 of the
valve casing 91. The mounting member 114 of the inner valve 104 and the
pressure-receiving slide member 103 are dimensioned in such a way that all
of the pressure-receiving areas of their respective upper and lower
surfaces are equal to one another. A diaphragm 106 is secured to the upper
end of the valve stem 102 by means of metallic retainer 105, thereby
defining an upper pressure-differential chamber 107 and a lower
pressure-differential chamber 108. The lower pressure-differential chamber
108 communicates with the outlet-side chamber 94. The upper extremity of a
spring 109 housed within a spring case 117 is connected to the lower
extremity of the valve stem 102, the valve stem 102 being biased
downwardly by the spring 109. A branch flow-passage 110 is provided
between the restriction 96 and outlet 95 to the upper
pressure-differential chamber 107. The outlet-side chamber 94 and the
spring case 117 communicate with each other through a branch flow-passage
120.
The action of the fluid flow controlling valve of this embodiment will now
be described. The fluid which has reached the inlet flows through the
inlet-side chamber 93 and valve port 98 into the outlet-side chamber 94
and leaves through the restriction 96 and through the outlet 95. A part of
the fluid which has reached the outlet 95 is introduced through the branch
flow-passage 110 into the upper pressure-differential chamber 107. When
the rate of fluid flow increases on the inlet side and thereby the fluid
pressure inside the outlet-side chamber 94 immediately upstream of the
restriction 96 become higher than that at the outlet 95, moving the
diaphragm 106, the valve stem 102, and the cylindrical inner valve 104
upwardly, the cross-sectional area of an intermediate fluids flow passage
formed between the valve port 98 and the upper annular or circumferential
edge of the cylindrical valve plug 113 is decreased so as to limit the
rate of fluid flow through the valve. When the rate of fluid flow is
limited in this manner and the pressure-differential between the upper and
lower pressure-differential chambers 107 and 108 approaches zero, the
diaphragm 106 resumes its position to automatically regulate the rate of
fluid flow through the valve. If the pressures inside the inlet- and
outlet-side chambers 93 and 94 respectively are represented by P.sub.1 and
P.sub.2, then the pressure P.sub.1 is applied on the upper surface of the
mounting member 114 and also on the lower surface of the
pressure-receiving slide member 103, and the pressure P.sub.2 is applied
on the lower surface of the mounting member 114 and also on the upper
surface of the pressure-receiving slide member 103. Because the
pressure-receiving areas of the upper surface of the mounting member 114
and the lower surface of the pressure-receiving slide member 103 are equal
to each other, the pressures acting on them are equal in magnitude and
opposite to each other, compensating and cancelling out each other.
Similarly the pressures acting on the lower surface of the mounting member
114 and on the upper surface of the pressure-receiving slide member 103
are equal in magnitude and opposite to each other, compensating and
cancelling out each other. Further, the pressure P.sub.2 acts on the upper
and lower circumferential edges of the cylindrical valve plug 113,
compensating and cancelling out each other. Therefore all of the pressures
which the cylindrical inner valve 104 and the pressure-receiving slide
member 103 receive compensate and thereby cancel out one another. The
cylindrical inner valve 104 thus is not influenced at all by fluctuations
in flow rate and fluid pressure, and only the up and down movement of the
diaphragm 106 is transmitted thereto by means of the valve stem 102. A
single inner valve, namely the cylindrical inner valve 104 thus
automatically regulates the rate of fluid flow through the valve
effectively. Although pressure P.sub.1 inside the inlet-side chamber 93 is
higher than P.sub.2 inside the outlet-side chamber and thereby 94 gives
rise to the leakage of fluids from the higher-pressure side to the lower
pressure-side through radial clearance 119 between the inner peripheral
surface of the guide bushing 99 and the outer peripheral surface of the
pressure-receiving slide member 103 in the directions of arrow heads, the
purification of fluids through the filtering medium 101 results in no
possibility of dust and dregs being introduced into the radial clearance
119, which permits the valve stem 102 to move smoothly up and down.
As described above, the fluid flow controlling valve of this embodiment is
able to always supply fluids at a constant rate of flow and as results in
accurate, effective, and trouble-free operation, the fluid entering the
radial clearance 119 is purified through the strainer 100 before flowing
into the guide bushing 99, which prevents the introduction of impurities
into the radial clearance 119, reduces the friction between the
pressure-receiving slide member 103 and the guide bushing 99, and thus
permits the valve stem 102 to move smoothly up and down.
Embodiment 5
Referring to FIG. 9 there is shown a valve casing 121 partitioned with a
partition wall 122 therewithin into an inlet-side flow passage 123 and an
outlet-side flow passage 124. A valve seat 126 is provided in the
horizontal part of the partition wall 122. An umbrella-shaped restriction
adjusting member 127 for adjusting the cross-sectional flow area of a
restriction 125 cooperates with the valve seat 126 and when spaced
therefrom forms therewith the restriction 125, constituting a first
intermediate flow passage for fluids passing through the valve. Section
128 of the adjusting member 127 is joined by threading to the valve casing
121 in the bottom thereof. Handle 130 is integral with a shank 129 of the
adjusting member 127. Turning of the handle causes the adjusting member
127 to move up and down relative to valve port 131 formed with the valve
seat 126 so that the setting of the rate of fluid flow through the valve
can be adjusted as desired. A chamber on the other side of the partition
wall 122 constitutes a post-chamber 150 of the restriction 125. The lower
annular or circumferential edge 151 of a valve plug 132 is cooperable with
valve seat 126 provided in the horizontal part of the partition wall 122
and forms with the valve seat 126 a second intermediate flow passage for
fluids passing through the valve. The valve plug 132 has a cylindrical
form and is closed at its upper extremity by means of a top plate 133. The
top plate 133 of the valve plug 132, a bellows-diaphragm 134, and a
retainer plate 135 are secured together to the lower end of a valve stem
136 with the bellows-diaphragm 134 sandwiched between the retainer plate
135 and the top plate 133. The upper half of the valve plug 132 is
positioned coaxially within a lower pressure-differential chamber 139 and
is made to contact loosely with the inner surface of a liner 140 through
the medium of the bellows-diaphragm 134. The peripheral part 141 of the
bellows-diaphragm 134 is sandwiched between the upper peripheral part of
the lower pressure-differential chamber 139 and the lower surface of a
flange 142 of a spring case 143. The bellows-diaphragm 134 serves to
separate the lower pressure-differential chamber 139 from an upper
pressure-differential chamber 144 within the spring case 143. The
inlet-side flow-passage 123 and the upper pressure-differential chamber
144 communicate with each other through a branch flow-passage 138 and a
flow passage 145 in the flange 142. The valve stem 136 is positioned
coaxially within the spring case 143 which is sealed with a bonnet 148 and
is biased upwardly by a spring 146, the upper end of the spring 146 being
secured to the valve stem 136 a short distance below the upper end
thereof.
The action of the fluid flow controlling valve of this embodiment will now
be described. The major portion of the fluid which has reached an inlet
flows through the inlet-side flow passage 123, the pre-chamber 149 of the
restriction 125, the restriction 125 the valve port 131 and through the
second intermediate flow passage into the post-chamber 150 of the
restriction 125 and leaves through the outlet-side flow passage 125 and
through an outlet a part of the fluid in the inlet-side flow passage 123
is introduced through the branch flow-passage 138 and through the flow
passage 145 formed in the flange 142 into the upper pressure-differential
chamber 144. If fluid pressures in the inlet-side flow passage 123 and the
post-chamber 150 of the restriction 125 respectively are taken to be
P.sub.1 and P.sub.2, then the fluid pressures P.sub.1 and P.sub.2
respectively act within the upper pressure-differential chamber 144 and
the lower pressure-differential chamber 139. Therefore, when fluctuations
in pressure differential take place across the restriction 125, that is,
the first intermediate flow passage 125, creating between the upper and
lower pressure-differential chambers 144 and 139 pressure differentials
equalling the values of the varying pressure differentials across the
restriction 125, the bellows-diaphragm 134 thus operates, moving the valve
stem 136 and the valve plug 132 upwardly and downwardly to automatically
regulate the rate of flow of fluids passing through the valve port 131. At
this time, If fluid pressure in the outlet-side flow passage 124 is taken
to be P.sub.3, the fluid pressure P.sub.3 is applied on the inner surface
and outer exposed surface of the valve plug 132 and also to the lower
annular or circumferential edge 151 thereof. However, since the pressures
acting on such parts compensate each other and thereby cancel out, the
valve plug 132 is not affected by fluctuations in the rate of fluid flow
and in fluid pressure only the up and down movement of the
bellows-diaphragm 134 is transmitted through the valve stem 136 to the
valve plug 132.
As described above, in the fluid flow controlling valve of this embodiment,
the setting of the cross-sectional flow area of the restriction 125, that
is, the first intermediate flow passage through the valve is adjusted to a
desired value by means of the restriction adjusting member 127. The upward
and downward motion of the valve plug 132 fitted with the
bellows-diaphragm 134 is automatically caused by fluctuations in pressure
differential across the restriction 125 to thereby main | | |
