JP3349071B2 - Flow path switching valve device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow path switching valve which is installed in a pipe connecting an emergency water storage tank and a water main pipe used in an earthquake disaster or the like to change respective flow paths. It concerns the device.

[0002]

2. Description of the Related Art Conventionally, an emergency water storage tank (tank) is provided in a basement of a road, a school yard, or a park, for example, in order to secure living water for local residents in the event of a disaster such as an earthquake, or to provide water for fire extinguishing. It is buried.

[0003] In this emergency water storage tank equipment, generally, as shown in FIG. 5, a bypass pipe P is provided in a water main pipe S, a water storage tank (tank) T is provided in the bypass pipe P, and a bypass pipe P is provided. Emergency shut-off valves 1 and 1 are provided on the outflow and inflow side of P, respectively, and an emergency open valve 2 is installed in the water main S between the bypass pipes P.
Is provided. In the figure, 3 is a fire hydrant, 4 is a manual pump, and 5 is an air valve.

In normal times, the emergency shutoff valves 1 and 1 are opened, the emergency release valve 2 is closed, and water flows as indicated by arrows a, b, c and d to store water in the water storage tank T. ,
Rotation is prevented by preventing water from stagnating in the water storage tank T. On the other hand, in an emergency (emergency) such as an earthquake,
The emergency shutoff valves 1 and 1 are closed, the emergency release valve 2 is opened, the flow of the water main S is secured, the water storage tank T is cut off from the water main S, and the water from the water storage tank T due to the siphon phenomenon is generated. Prevent runoff and secure water.

In this emergency water storage tank facility, various techniques for controlling the emergency shutoff valve 1 and the emergency release valve 2 by the water pressure of the water main S have been developed. For example, Japanese Utility Model No. 3018335. The gazette discloses one example. Further, as a similar prior art, as shown in FIG. 6, there is an emergency shutoff valve 1 and an emergency release valve 2 provided with two pilot valves 6,7.

In the prior art, for example, in the case of an emergency shutoff valve 1, two emergency return and shutoff pilot valves 6, 7 are attached to the emergency shutoff valve 1 interposed in a bypass pipe P, and the pilot The pressure is guided to the valves 6 and 7 from the upstream side of the emergency cutoff valve 1 via the pilot pipe t. Each pilot valve 6, 7 is provided with a diaphragm 6a, 7 respectively.
a, springs 6b and 7b for pressing the diaphragm, valve bodies 6c and 7c interlocked with the diaphragm via a valve rod, and valve seats 6d and 7d.

In normal times when the tap water pressure is equal to or higher than the required pressure, as shown in FIG. 6A, the tap water pressure is applied to both pilot valves 6, 7, and the diaphragms 6a, 7a are connected to springs 6b, 7b. In a compressed state, the valve element 6c moves away from the valve seat 6d, and the valve element 7c presses against the valve seat 7d, so that the emergency shut-off valve 1
No tap water pressure is applied to the cylinder valve 81a. For this reason,
Cylinder valve 81a, the inner external pressure P _1> P _2, and the
Apart from the valve seat 12, the shut-off valve 1 is open.

On the other hand, when the water pressure drops due to an earthquake or the like and becomes lower than the urging force of the springs 6b, 7b, as shown in FIG. 1B, the pilot valves 6, 7 are attached to the springs 6b, 7b. By the force, the valve body 6c contacts the valve seat 6d, the valve body 7c is separated from the valve seat 7d, and the water pressure is applied to the cylinder 81 (P ₁ ≒ P ₂ ). In this case, the diameter D ₂ of the emergency shut-off valve 1 of the valve seat diameter D ₁ and the cylinder 81 D ₁
<There is relationship _{D 2, π / 4 · D} 1 2 · P 1 <π / 4 · D
₂ ² · P ₂ + W (weight of the cylinder valve 81a)
The cylinder valve 81a contacts the valve seat 82 to close the pipe P.

When the water pressure in the pipe P returns and becomes equal to or higher than the set pressure, the diaphragms 6a and 7a bend upward and automatically return to the state shown in FIG.

[0010]

However, in the above-described flow path switching valve device, the operation of the shut-off valve 1 is a fully open / fully closed ON-OFF operation. In this case, a large amount of water flows into the water storage tank T at once, causing a sudden change in the flow rate of the water main S, red rust inside the water, and so-called red water is generated. was there.

Accordingly, an object of the present invention is to prevent the generation of red water due to a rapid change in the flow rate at the time of automatic return in an automatic return type flow path switching valve device.

[0012]

In order to solve the above-mentioned problems, the invention according to claim 1 is provided with a bypass pipe provided with an emergency water storage tank in the water main pipe, and the water main pipe and the bypass pipe are connected to each other. In the meantime, in an emergency water storage tank facility provided with a main valve that opens and closes the communication so that the flow of the water main pipe does not pass through the bypass pipe, and a pressure sensing pilot valve as the main valve, The main valve is operated by the pilot valve using the water pressure on the water storage tank side as its pilot pressure, and the water main pipe side of the main valve and the water storage tank side are connected via a differential pressure actuation valve. When the water pressure difference between the water main and the water tank is within the range of the set differential pressure, the closed state is maintained, and the water pressure on the water main is reduced. Open the tank when it becomes larger than the set pressure difference from the water pressure on the water tank side. Than it was.

In the emergency water storage tank equipment equipped with this flow path switching valve device, when returning from an emergency with the water pressure on the water storage tank side being low, the water pressure on the water main pipe side rises, and the water pressure on the water storage tank side increases. When the water pressure difference exceeds the set differential pressure of the differential pressure operated valve, the differential pressure operated valve opens with the main valve shut off between the water main pipe and the bypass pipe, and gradually fills the water storage tank via the water filling pipe. When the water pressure in the water tank reaches the set pressure of the pilot valve, the main valve operates and the flow of the water main is guided to the bypass pipe, so that the flow rate of the water main does not change suddenly. .

According to a second aspect of the present invention, the operating pressure of the pilot valve and the operating differential pressure of the differential pressure operating valve are each adjustable.

[0015] With this configuration, it is possible to change the shutoff pressure of the water storage tank in an emergency and the pressure at which the water storage tank is filled with water at the time of return.

According to a third aspect of the present invention, a manual valve located between the differential pressure actuated valve and the main water pipe side of the main valve is provided in the water filling pipe.

In this case, the above-mentioned water filling function is stopped by closing the manual valve, and it can be used as a manual return type. Further, when the manual valve is closed, the water pressure from the water main does not act on the differential pressure operated valve, so that the differential pressure operated valve can be maintained.

According to a fourth aspect of the present invention, the main valve has the following configuration (A), and the first and fourth ports of the main valve are bypass pipes or water mains, and the second and third ports are water mains. A pipe or a bypass pipe is connected, and a piston in a cylinder below the main valve is moved by applying the pilot pressure through the pilot valve.

Configuration (A) "A valve rod that slides on the same axis is provided in a valve box, and partition walls that cross the valve rod are provided at three axial positions of the valve rod. First, second, third, and fourth chambers are sequentially divided in the axial direction, ports are formed in the respective chambers, and communication holes through which the valve stem penetrates are formed in the partition walls. A first valve seat is provided on the periphery of the communication hole between the first chamber and the second chamber, and a second valve seat is provided on the periphery of the communication hole between the second chamber and the third chamber.
A third valve seat is provided on the periphery of the communication hole of the valve seat, the third chamber and the fourth chamber, and a valve body is provided on the valve rod to open and close the communication hole by coming into contact with and separating from the valve seat. Each valve element is the first
And when it comes into contact with the third valve seat, it separates from the second valve seat, and when it comes into contact with the second valve seat, it separates from the first and third valve seats. Provide an inserted cylinder and a piston in the cylinder that is linked to the valve stem. "

When the main valve is configured as described above, the flow path is switched by the axial movement of the valve rod, so that there is no need to provide a plurality of shutoff valves and open valves, and the structure can be simplified. Can be.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Flow path switching valve device shown in FIG. 1 is of the automatic recovery using 4 Kataguchi switching valve as the main valve V _1.

[0022] In this main valve V _1, 10 is a valve box, the first port (mouth) 11a and the second port (mouth) 11b
Divided body 10a having a third port (mouth) 11
c and the other divided body 10 having the fourth port (mouth) 11d
b, and a lid 10c of one of the divided bodies 10a. The two divided bodies 10a and 10b, and the one of the divided bodies 10a and the lid 10c are each provided with a bolt 1 with a packing (seal) 12 interposed therebetween.
3 are integrated. Bolts 13 are provided at appropriate positions around the periphery.

A valve rod 14 is inserted into the center of the valve box 10.
The valve stem 14 is supported movably in the axial direction by bearings 15a and 15b on the bottom surface of the lid 10c and the other divided body 10b. In the valve box 10, partition walls 16a, 16b, 16c are provided to cross the valve rod 14, and the first chamber 17a of the first port 11a, the second chamber 17b of the second port 11b, and the third chamber 11b of the third port 11c are provided. It is divided into four chambers of a third chamber 17c and a fourth chamber 17d of a fourth port 11d.

The partition walls 16a, 16b, 16c are formed with communication holes 18a, 18b, 18c through which the valve rod 14 penetrates, and the peripheral edges of the holes 18a, 18b, 18c are first, second, and third valves. The seats are 19a, 19b, and 19c. The valve stem 14 is provided with valve bodies 20a, 20b which are in contact with and separate from the valve seats 19a, 19b, 19c, and as shown by the solid line in the figure, the lower valve body 20b is in contact with the second valve seat 19b. When in contact with each other, the upper valve body 20a is separated from the first valve seat 19a, and the lower valve body 20b is
The upper valve body 20a comes into contact with the first valve seat 19a when it comes away from the valve seat 19b and comes into contact with the third valve seat 19c. Valve seats 19a, 19b, 1 of the valve bodies 20a, 20b
A seal 21 is provided on the contact surface with 9c to ensure watertightness.

The upper portion of the lid 10c of the valve box 10 is cylindrical, and a cylinder with a cover is screwed into the cylindrical portion to form a cylinder 22, into which the upper end of the valve rod 14 is inserted. The piston 23 is fixed to the end. This piston 23 is pushed downward by a spring 24.

[0026] In the main valve V _1, the lower side of the valve body 20b,
First valve seat 19a (communication hole 18a) and second valve seat 19b
(The communication hole 18b), the cover 10
When c is removed, the valve stem 14, each of the valve bodies 20a and 20b, and the valve seat can be taken out of the valve box 10, and maintenance such as replacement of the seat is very simple.

The main valve V ₁ is provided with a pilot valve V ₂ via a pilot pipe 25.
Manual valve 27a in between both valve V ₁ V ₂ of 5, 27b are interposed. Normally, one manual valve 27a is open and the other manual valve 27b is closed.

The pilot valve V ₂ has first, second, third,
It has fourth four ports 31a, 31b, 31c, 31d, and the diaphragm 34 is moved up and down by the pilot pressure acting on the cylinder 32 and the pressing force of the spring 33 via the fourth port 31d. The valve body 35 is selectively brought into and out of contact with the first valve seat 36a and the second valve seat 36b,
Port 31a and second port 31b or third port 31
(c) is a pressure sensing type three-way valve that switches the flow path so as to communicate with any one of (c) and (c), and its operating pressure can be adjusted by rotating a bolt (37) screwed above the spring (33).

[0029] The first port 31a of the pilot valve V ₂
And the fourth port 31d is connected to the first chamber 17a of the main valve V _1. The third port 31c is the spring 2 of the cylinder 22.
4 and the second port 31b is open.

The first chamber of the main valve V ₁ 17a and the second chamber 17
b and is connected with filling of water pipe 39, the differential pressure actuated valve V ₃ and the manual valve 40 is interposed in the filling of water pipe 39. Manual valve 4
0 is located between the differential pressure actuated valve V ₃ of the second chamber 17b.

The differential pressure actuated valve V _3, as shown in FIG. 2, the valve body having a first port 41a and the second port 41b 42
A valve seat 43 is formed therein, and a valve stem 4 penetrating the valve seat 43 is formed.
4 is provided with a valve body 45 which comes into contact with and separates from the valve seat 43, and is inserted through a spring receiver 46 screwed into the valve box 42 and a valve rod 44 to thereby provide a nut 47
The spring 49 is sandwiched between the spring press 48 and the spring press 49 which is positioned in the above. The spring 49 is covered with a cylindrical body 50 screwed into the spring receiver 46, and the valve body 45 is urged by the spring 49 in a direction approaching the valve seat 43. The flow path between the ports 41a and 41b is opened and closed by the pressure difference.
By rotating and changing the pressure 7, the operating differential pressure can be adjusted. Then, as shown in FIG. 1, each port 41a, 41b, the first chamber 1 of each main valve V ₁
7a and the second chamber 17b.

Further, the differential pressure operated valve V ₃ may be as shown in FIG. In the differential pressure actuated valve V ₃ shown in this figure, as the valve body 45 is shown in FIG. 2 contact or away from the opposite direction to the valve seat 43, valve stem 44 and spring bearing 46 is omitted,
A spring 49 is in direct pressure contact with the valve body 45. A hexagonal bolt 51 protruding from the tubular body 50 is provided on the spring retainer 48, and a nut 47 is screwed into the hexagonal bolt 51 outside the tubular body 50. In this case, as shown in FIG. 4, the first port 41a to the second chamber 17b of the main valve V _1,
The second port 41b is connected to the first chamber 17a.

[0033] When using the flow path switching valve device in emergency reservoir equipment described above, as shown in FIG. 1, the main valve V ₁
The first and fourth ports 11a and 11d are connected to a bypass pipe P provided with a water storage tank T, and the second and third ports 11b and 11c are connected to a water main pipe S, respectively.

[0034] In this connected state, there is a predetermined value in the water pressure in water mains S, even when normal of full capacity water tank T is, water pressure in the first chamber 17a of the main valve V ₁ is of the pilot valve V ₂ cylinder 32, and as shown by the solid line in FIG.
4 is bent upward, and the valve body 35 is in pressure contact with the second valve seat 36b. Therefore, the first port 31a to the third port 31
through c, the cylinder 2 of the hydraulic main valve V ₁ of the mains S
2, the piston 23 compresses the spring 24 and moves upward (top dead center position) as shown by the solid line in the figure, the valve rod 14 is also positioned upward, and the valve body 20b is moved to the second valve seat 19b. , And maintains a state where the valve body 20a is separated from the first valve seat 19a. In this state, the first chamber 17a and the second chamber 17b,
The third chamber 17c and the fourth chamber 17d communicate with each other, and water in the water main S is supplied to the first port 11a and the second port 11b.
Alternatively, the water flows between the third port 11c and the fourth port 11d, passes through the water storage tank T, and is distributed downstream. At this time, since the pressure difference between the water main S and the water storage tank T is very low, the valve body 45 of the differential pressure actuated valve V ₃ is pressed against the valve seat 43 by the spring 49 and the water is stored through the water filling pipe 39. The tank T is not charged.

On the other hand, in an emergency such as when an earthquake occurs, the water pressure in the water main S decreases, and the water pressure on the water storage tank T side also decreases accordingly. This water pressure drop, as shown in chain line drawing, the valve body 35 is deflected downward by the diaphragm 34 spring 33 of the pilot valve V ₂ is pressed against the first valve seat 36a away from the second valve seat 36b. Therefore, the cylinder 22 is opened to the outside through the third port 31c, the second port 31b, the main valve V _1, as in FIG chain line, the piston 23 is lowered by the spring 24 (bottom dead center position) , The valve stem 14 is also positioned below, so that the valve body 20b separates from the second valve seat 19b and abuts on the third valve seat 19c.
a contacts the first valve seat 19a. This state is the second room 1
7b communicates with the third chamber 17c, and the first and fourth chambers 17a,
7d is the one that is shut off from the second and third chambers 17b and 17c, and the water in the water main S flows between the second port 11b and the third port 11c to secure the water in the water storage tank T. Water is distributed downstream in the state. At this time, in the differential pressure actuated valve V ₃ , the water pressure on the water main S side is low, the differential pressure with the water storage tank T side is equal to or less than the set differential pressure, and the valve body 45 is pressed against the valve seat 43, differential pressure actuated valve V ₃ remains closed. This closed state is maintained as long as the water pressure on the water main S is low, even when the water in the water tank T is emptied due to the use of the water therein.

[0036] When the pressure difference between the water pressure is increased the water tank T side of the mains S is the set differential pressure of differential pressure actuated valve V _3, valve body 45 is a valve seat by compressing the spring 49 away from 43, the differential pressure actuated valve V ₃ becomes open, is filled with water to a water tank T through the filling of water pipe 39. However, in this apparatus, since the collected pilot pressure of the pilot valve V ₂ from the first chamber 17a located reservoir T side of the main valve V _1, the pilot valve V water in the water tank T is restored until reaching the _second operating pressure, the main valve V ₁ was remains is closed, water mains S is the mostly downstream flows between the second port 11b and third port 11c Water is distributed. in this way,
Filled with water to the water tank T is in the closed state of the main valve V _1, to be done gradually over a filling of water tube 39, never flow water main S abruptly changes.

[0037] Thereafter, when the water tank T is filled with water, the water pressure rises in the first chamber 17a, the differential pressure actuated valve V ₃ is closed, the pilot valve V ₂ is operated as described above, the pilot valve V ₂ via the water pressure is applied to the cylinder 22, by its required water pressure, the piston 23 is moved upward becomes the main valve V ₁ is fully opened, to return to the normal state shown in FIG solid. That is, even if the water pressure in the water main S is temporarily reduced for some reason, the state automatically returns to the state of flowing water to the water storage tank T.

Further, the shutoff pressure of the water storage tank T in an emergency and the pressure at which the water storage tank T is filled at the time of return are determined by the bolt 37 of the pilot valve V ₂ and the differential pressure operating valve V _{3, respectively.}
By rotating the nut 47 of FIG. Here, the steady-state pressure of the water main S is
Daytime 2.5 kgf / cm ^2, a nighttime 5.0 kgf / cm ² or so,
Cutoff pressure of the pilot valve V ₂ is 1.0 to 1.5 kgf / c
m ^2, operating differential pressure of the differential pressure actuated valve V ₃ is 0.5 to 1.0 kgf / c
or equal to m ² about. Further, since each of the above operations is performed in sequence only by the pressure in the water distribution pipe, there is no need to perform electric sequence control.

When the manual valve 40 is fully closed, the main valve V ₁ is not opened even if the water pressure of the water main S increases after the emergency shutoff, and the water tank T via the water filling pipe 39 is not opened. Since the water is not supplied to the tank, it does not automatically return to the normal state. In this case, it can be used as a manual return type that returns to a normal state by manually opening the manual valve 40.

[0040] In the closed state of the manual valve 40, the water pressure from the water main S side to the differential pressure actuating valve V ₃ is not applied, it is possible to perform maintenance of the differential pressure actuated valve V _3.

Further, in an emergency, one of the manual valves 27a
Is closed and the other manual valve 27b is opened, so that the water tank T and the water main S can be shut off. The manual valves 27a, 27b may be electromagnetic valves.

By the way, as shown in FIG.
In the case of using three valves 1 and 2, each valve 1,
The pilot pressures of the water tanks 1 and 2 are collected from the water storage tank T side, and the shutoff valves 1 and 1 are provided with the bypass valves as described above. The function of suppressing the rapid change of the flow rate of the water main S by gradually filling the water with water can be obtained.

[0043]

As described above, according to the flow path switching valve device of the present invention, when returning from an emergency in a state where the water pressure on the water tank is low, the water pressure on the water main is increased, and the water tank is increased. If the water pressure difference between the main valve and the bypass valve exceeds the set differential pressure of the differential pressure operated valve, the differential pressure operated valve opens with the main valve shut off between the water main pipe and the bypass pipe, and the water enters the water storage tank via the water filling pipe. When the water is gradually filled and the water pressure on the water storage tank reaches the set pressure of the pilot valve, the main valve operates and the flow of the water main is guided to the bypass pipe.
The flow rate of the water main does not change suddenly, and the generation of red water is prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of a flow path switching valve device according to the present invention.

FIG. 2 is a cross-sectional view of the differential pressure actuated valve according to the first embodiment.

FIG. 3 is a sectional view showing another embodiment of the differential pressure operated valve.

FIG. 4 is a cross-sectional view of a flow path switching valve device using the differential pressure operated valve according to the first embodiment;

FIG. 5 is an explanatory view of an emergency water storage tank facility.

FIG. 6 is a diagram illustrating the operation of a conventional example.

[Explanation of symbols]

P bypass pipe S mains T reservoir (tank) V ₁ main valve V ₂ pilot valve V ₃ differential pressure actuated valve 10 valve body 11a, 11b, 11c, 11d port (mouth) 14 valve stem 16a, 16b, 16c partition Wall 17a First chamber 17b Second chamber 17c Third chamber 17d Fourth chamber 18a, 18b, 18c Communication hole 19a First valve seat 19b Second valve seat 19c Third valve seat 20a, 20b Valve 22 Cylinder 23 Piston 24 Spring 25 Pilot pipe 39 Filling pipe 40 Manual valve

Continuation of the front page (56) References JP-A-8-226553 (JP, A) JP-A-9-196212 (JP, A) JP-A-9-32963 (JP, A) JP-A-4-102780 (JP) , A) Japanese Utility Model Showa 49-105956 (JP, U) Japanese Utility Model Hei 5-96661 (JP, U) Japanese Utility Model Utility Model 4-73667 (JP, U) Japanese Utility Model Utility Model 4-49274 (JP, U) Japanese Utility Model Utility Model 6-59673 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16K 11/00-11/24 F16K 17/00-17/168 F16K 17/36 F16K 31/12-31 / 42 E03B 7/00

Claims (4)

(57) [Claims] 1. A bypass pipe P having an emergency water storage tank T interposed therebetween is provided in a water main pipe S, and its communication is opened and closed between the water main pipe S and the bypass pipe P so that the water main pipe S can be opened and closed. in emergency water tank equipment in which a main valve V ₁ to a state impervious state through the bypass pipe P flows, and attaching a pressure sensitive pilot valve V ₂ to the main valve V _1,
Using the water pressure on the water storage tank T side as its pilot pressure, the main valve V ₁ is operated by the pilot valve V ₂ , and the water main S side of the main valve V ₁ and the water storage tank T side are connected. connected with filling of water pipe 39 which is interposed a differential pressure actuated valve V _3, the differential pressure actuated valve V _3, when the pressure difference between the water main S side and the water tank T side is in the range of under set differential pressure or is A flow path switching valve device in an emergency water storage tank facility, wherein a closed state is maintained, and when the water pressure on the water main pipe S side becomes higher than the water pressure on the water storage tank T side by more than a set differential pressure, it is opened. . 2. A channel switching in emergency reservoir facility according to claim 1, characterized in that a respective adjustable hydraulic differential pressure of the hydraulic pressure and the differential pressure actuated valve V ₃ of the pilot valve V ₂ Valve device. To wherein said filling of water pipes 39, claim 1 or, characterized in that interposed a manual valve 40 located between the differential pressure actuated valve V ₃ and the water mains S side of the main valve V ₁ 3. The flow path switching valve device in the emergency water storage tank equipment according to 2. The method according to claim 4, wherein said main valve V ₁ and the following configurations (A),
The first of the main valve V _1, the fourth port 11a, the bypass pipe 11d P or water mains S, second, third port 11b, 1
Connect the mains S or bypass pipe P to 1c, the main valve V ₁
The piston 23 in the following cylinder 22 in the emergency reservoir Arrangement according to any of claims 1 to 3, characterized in that the move by the application of the pilot pressure via the pilot valve V ₂ of Flow path switching valve device.
Configuration (A) “A valve rod 14 that slides on the same axis is provided in the valve box 10, and partition walls 16 a and 16 that cross the valve rod 14 are provided.
b, 16c are provided at three axial positions of the valve stem 14,
The inside of the valve box 10 is divided into first, second, third, and fourth four chambers 17a, 17b, 17c, and 17d in the axial direction, and ports 11a, 11b, and 11 are respectively provided in the respective chambers.
c, 11d, and communication holes 18a, 18b, 18c through which the valve rod 14 penetrates are formed in the respective partition walls, and a first hole is formed in the periphery of the communication hole 18a between the first chamber 17a and the second chamber 17b.
Communication hole 18 between valve seat 19a, second chamber 17b and third chamber 17c
b, the second valve seat 19b, the third chamber 17c, and the fourth chamber 17d
The third valve seat 19c is provided on the periphery of the communication hole 18c, respectively.
The valve stem 14 is provided with valve bodies 20a and 20b which contact with and separate from the respective valve seats to open and close the communication holes, and the respective valve bodies are brought into contact with the first and third valve seats 19a and 19c. ,
When separated from the second valve seat 19b and comes into contact with the second valve seat 19b, it is separated from the first and third valve seats 19a and 19c, and the valve rod 14 is inserted into the valve box 10. The cylinder 22 is provided, and a piston 23 interlocked with the valve rod 14 is provided in the cylinder 22. "