JPH0587262A - Gas effluent prevention valve - Google Patents

Abstract

PURPOSE:To provide a gas effluent prevention valve which is constituted so as to prevent any hunting due to the valve opening motion of a valve element. CONSTITUTION:A valve element 4, partitioning off the inside of a cylinder chamber 6 to both first and second cylinder chambers 7 and 8, is usually held in a state of being opened by dint of pressing force of a coil spring 22 installed in the first cylinder chamber secondary pressure P2 is taken in the first cylinder chamber 7, and usually this secondary pressure P2 is taken in the second cylinder chamber 8. When this secondary pressure P2 is suddenly dropped by an excess flow rate at the downstream side, the primary pressure is taken in the second cylinder chamber 8, and thereby the valve element 4 performs its valve closing motion against the pressing force of the spring 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas outflow prevention valve,
In particular, the present invention relates to a gas outflow prevention valve configured to automatically close the valve to prevent outflow of gas when a large amount of gas flows out due to breakage of a downstream pipe.

[0002]

2. Description of the Related Art For example, a gas outflow prevention valve that automatically closes a large amount of gas when a downstream pipe is cut off is installed in the middle of a gas supply pipe for supplying city gas to each household. ing. An example of this type of gas outflow prevention valve is Japanese Patent Application No. 2-336379 (filed on Nov. 30, 1990) previously proposed by the present applicant.

In the proposed gas outflow prevention valve, the valve body sliding in the cylinder is urged in the valve closing direction by the coil spring in the cylinder, and when the flow rate is zero, the lower side of the valve body and the upper side of the valve body. The primary pressure P ₁ is introduced into the cylinder to press the valve body against the valve seat in the valve body to close the valve. Then, when the gas is used on the downstream side and the flow rate increases, the secondary pressure P ₂ on the downstream side is introduced into the cylinder and the valve body is pressed by the primary pressure P ₁ acting on the lower side to separate from the valve seat. It sits down, slides in the valve opening direction, and gas is supplied to the downstream side. However, when an accident such as pipe breakage occurs on the downstream side and the secondary pressure P ₂ on the downstream side suddenly decreases, the primary pressure P ₁ is introduced into the cylinder chamber and the valve body pushes the coil spring. The pressure causes the valve to slide in the valve closing direction to shut off the gas supply path.

[0004]

However, in the above gas outflow prevention valve, the valve body has a stepped piston shape,
When the flow rate increases from zero, the valve body gradually separates from the valve seat because the stepped portion of the valve body with zero flow rate closes the primary pressure introducing hole. Since the area is small, the valve opening operation is slow, but when the valve element slides in the valve opening direction by a certain distance, the pressure receiving area is expanded to the entire step portion of the valve element and the valve opening operation is accelerated. Therefore, hunting (vertical vibration) is likely to occur during the valve opening operation of the valve body.

Therefore, in the gas outflow prevention valve having the above structure, the pressure difference between the primary pressure P ₁ and the secondary pressure P ₂ temporarily increases with the opening operation of the valve, and this pressure difference causes the downstream pipe. If the pressure difference exceeds the pressure at the time of overflow due to damage or the like, there is a problem that the valve body closes the valve and shuts off the flow path even though it is not the actual overflow.

Further, the hunting causes the valve body to move up and down frequently, so that the seal member of the valve body and the seat member that abuts on the valve seat are easily worn and deformed to shorten the life. Further, the secondary pressure P ₂ fluctuates due to the hunting operation of the valve element, and the gas supply to the downstream side becomes unstable.

Therefore, an object of the present invention is to provide a gas outflow prevention valve which solves the above problems.

[0008]

According to the present invention, there is provided a valve main body having a valve seat in the middle of a passage through which gas passes, a small diameter portion which is seated on and off the valve seat of the valve main body, and a diameter larger than the small diameter portion. And a large diameter portion, the valve body opening and closing the flow path by the pressure difference between the primary pressure on the inflow side and the secondary pressure on the outflow side acting on the large diameter portion, and the large diameter of the valve body. Provided in a first cylinder chamber on the valve closing side and a cylinder that has first and second cylinder chambers defined in a portion and guides the large diameter portion of the valve body in the valve opening and valve closing directions. An urging member for urging the large-diameter portion of the valve element in the valve opening direction; a primary pressure introducing path for introducing the primary pressure into the second cylinder chamber on the valve opening side; A secondary pressure introducing passage for introducing pressure into the first and second cylinder chambers;
A diaphragm provided so as to define a secondary pressure introducing path and a secondary pressure introducing path and displaced according to a pressure difference between the primary pressure and the secondary pressure, and the primary pressure introducing according to the displacement of the diaphragm. A switching valve for communicating either one of the passage and the secondary pressure introducing passage with the second cylinder chamber; and when the secondary pressure suddenly decreases, the switching valve and the secondary pressure introducing passage due to displacement of the diaphragm. And a sub-valve body which connects the switching valve and the secondary pressure introducing passage by the return of the diaphragm when the secondary pressure is increased to a predetermined pressure.

[0009]

The normal valve body is held in the valve open position by the pressing force of the urging member provided in the first cylinder chamber, and when the secondary pressure drops suddenly due to overflow on the downstream side, the primary pressure Is introduced into the second cylinder chamber and the secondary pressure is introduced into the first cylinder chamber, so the valve closing operation is performed due to this pressure difference. Even if the flow rate increases from zero flow rate, the valve body does not operate with the valve open, so the valve opening operation due to the increase in flow rate is eliminated, and hunting during the valve opening operation is prevented.

[0010]

1 shows an embodiment of a gas outflow prevention valve according to the present invention. Note that FIG. 1 shows the open state of the gas outflow prevention valve.

In the figure, a valve body 1 is arranged, for example, in the middle of a gas supply pipe (not shown) for supplying city gas to each household, and an inlet port through which gas flows into the valve body 1. 1a
And a flow path 1c that communicates with the outflow port 1b through which the gas flows. In addition, the flow passage 1c is provided in the center of the inside of the valve body
Is provided, and a tubular valve seat member 2 is fitted into the opening 1e of the wall portion 1d and fixed by a screw 3.

Reference numeral 4 denotes a valve body functioning as a main valve, which has a flange-shaped piston portion 4a on an upper portion, and a packing 5 which is in contact with the valve seat member 2 when the valve is closed, is held on the bottom surface, and the packing member 5 moves upward, downward, that is, It is slidable in the valve opening and valve closing directions.

As will be described later, the valve body 4 moves up and down due to the pressure difference between the primary pressure P ₁ flowing into the valve body 1 and the secondary pressure P ₂ flowing out from the valve body 1 to open and close the flow passage 1c. To do.

Reference numeral 6 denotes a cylinder, which is an upper opening 1f of the valve body 1.
It is further fitted and is in contact with the step portion 1g. The cylinder 6 has a large diameter portion 6a into which the piston portion 4a of the valve body 4 fits and a small diameter portion 6b into which the outer periphery 4b of the valve body 4 fits, and guides the valve body 4 slidably.

The inside of the cylinder 6 is covered by the valve body 4 at the first position.
It is defined by the Linda chamber 7 and the second cylinder chamber 8
The first cylinder chamber 7 and the outlet 1b are connected to the da 6
A hole 6c is provided. Therefore, the first cylinder chamber 7
Secondary pressure P from the downstream side ₂Is always guided through the hole 6c
It is included. The outer circumference of the piston 4a has a first seal.
Airtight seal between the Linda chamber 7 and the second cylinder chamber 8
A sealing member 9 is provided.

A lid member 10 is fixed to the valve body 1 by a bolt 11 to close the upper opening 1f of the valve body 1 and clamp the cylinder 6 from above. A sheet member 12 communicating with the second cylinder chamber 8 is provided at the center of the lid member 10.
Is screwed on. The sheet member 12 has an annular packing 12a in the upper part, and a small hole 12b extending in the upper and lower directions penetrates through the central part thereof. Between the valve body 4 of the first cylinder chamber 7 and the cylinder 6, the valve body 4 is moved upward (in the valve opening direction).
A coil spring (urging member) 22 for urging the coil spring is interposed.

Reference numeral 13 is a primary pressure introducing hole, one end of which is an inlet 1.
It opens to the flow path 1c on the a side, and the other end communicates with a passage 10a formed in the lid member 10 in the lateral direction. Accordingly, the primary pressure introducing passage 13 is formed by the primary pressure introducing hole 13 and the passage 10a.

Reference numeral 14 is a filter which prevents foreign matter from entering the pipe. Further, one end of the flow path 10a is closed by the plug 15 to prevent the primary pressure P ₁ from leaking to the atmosphere.

Reference numeral 16 is an orifice for the flow near the outlet 1b.
It is inserted in the center of the road. As shown in Figure 2,
The space 16 is formed into a small-diameter disk shape, and is connected via a pipe 17.
Is held. Therefore, the secondary pressure P₂To detect
The pressure loss due to the refill 16 is small. Ori
Secondary pressure P generated on the back side on the downstream side of the fiss 16 ₂
The secondary pressure detection port 16a for detecting is opened.

One end of the pipe 17 has a secondary pressure detecting port 16a.
And the other end projects downward from the mounting member 18 fitted in the mounting hole 1h of the valve body 1. Further, one end of a pressure introducing pipe 19 is connected to the central hole 18a of the mounting member 18. The other end of the pressure introducing pipe 19 is connected to a joint 20 communicating with the passage 29a. Therefore, the orifice 16, the pipe 17, the mounting member 18, the pressure introducing pipe 1
9. A secondary pressure introducing passage 45 is formed from the passage 29a.

Further, the mounting member 18 is provided with a hole 18b which is branched from the central hole 18a and extends laterally. The hole 18b communicates with a hole 6c formed in the cylinder 6 through a hole 1i formed in the valve body 1. Therefore, from the holes 18b, 1i, 6c, the branch passage 46 of the secondary pressure introducing passage is formed.
Is formed.

Reference numeral 21 denotes a differential pressure detector, which is provided between the primary pressure introducing passage 47 and the secondary pressure introducing passage 45, and as described later, the secondary pressure P ₂ is reduced to reduce the secondary pressure P ₂ . Introduced into the second cylinder chamber 8, when the secondary pressure P ₂ suddenly decreases and the pressure difference between the primary pressure P ₁ and the secondary pressure P ₂ increases, the primary pressure P _{1 is transferred} to the second cylinder chamber 8 Is configured for introduction. The differential pressure detection unit 21 is generally connected to the first passage 10a.
Of the diaphragm chamber 23 and the second diaphragm chamber 24 communicating with the passage 29a, and the clamping plates 26a and 26b that are in contact with the upper and lower surfaces of the central portion of the diaphragm 25 by tightening the nut 37. Cylindrical guide member 27 and the guide member 2 that are fixed together
7 and a switching valve 28 penetrating the inside of the through hole 27a and slidable in the upper and lower directions.

The upper holding plate 26a is the diaphragm 2
5 by the upward movement of the opening 5 of the diaphragm retainer 29 described later.
9b is provided so as to close the lower holding plate 26b.
It is provided so as to close b.

As shown in FIG. 3, the guide member 27 is provided with a valve seat 27b at its upper end, and a seal member 27c for sealing the gap with the switching valve 28 is provided on the inner wall of the through hole 27a. The switching valve 28 opens in the first diaphragm chamber 23 and contacts the packing 12a of the seat member 12 and is a valve seat 28a.
And the guide member 27 is opened in the second diaphragm chamber 24.
It has a hole 28b bored on the side surface so as to be opened and closed by a passage, and a passage 28c for communicating the valve seat 28a with the hole 28b. The hole 28b is provided at a position that opens above the valve seat 27b of the guide member 27 when the valve seat 28a contacts the seat member 12.

Further, the switching valve 28 has a small diameter upper end portion 28d extending above the hole 28b, and a ring-shaped sub valve body 40 and a cylindrical body 41 are fitted to the upper end portion 28d. There is. The sub valve body 40 and the tubular body 41 are fixed to the upper end portion 28d by tightening a nut 42 that is screwed onto the end portion of the upper end portion 28d.

The sub-valve body 40 has a packing 40a embedded in the lower surface so as to abut the valve seat 27b, and an upper end portion 28d on the inner periphery of the upper surface.
A seal member 40b that seals the space between and is embedded. The tubular body 41 has a collar portion 41a at the upper end, and
A washer 43 is fitted on the outer periphery of the unit 1 so as to be vertically slidable. A coil spring 44 is interposed between the washer 43 and the sub valve body 40, and the sub valve body 40 is pressed by the step portion 28e of the switching valve 28 by the pressing force of the spring 44. still,
The switching valve 28 is urged downward by the spring force of the coil spring 35.

A diaphragm retainer 29 is fixed to the upper surface of the lid member 10 by a bolt (not shown) so as to sandwich the peripheral edge of the diaphragm 25. The other end of the pressure introducing pipe 19 is connected to the side surface of the diaphragm retainer 29 via a joint 20, and the pressure introducing pipe 19 communicates with the diaphragm chamber 24 via a passage 29a.

Reference numeral 32 is a spring retainer, which is a diaphragm retainer 29.
Is screwed into the upper opening 29c. This spring retainer 32
A coil spring 33 that presses the diaphragm 25 downward is interposed between the diaphragm 25 and the diaphragm 25.

In the gas outflow prevention valve having the above structure, the primary pressure P ₁ and the secondary pressure P ₂ are substantially equal when the gas is not used on the downstream side, that is, when the flow rate is zero. Therefore, the primary pressure introducing hole 13 and the passage 10a
Primary pressure P ₁ introduced into the first diaphragm chamber 23 through the pressure detecting port 16a of the orifice 16 and the pipe 1
7, the pressure difference from the secondary pressure P ₂ introduced into the second diaphragm chamber 24 via the pressure introducing pipe 19 and the passage 29a becomes almost zero.

Therefore, the diaphragm 25, which is pressed by the spring force of the spring 33, moves downward and the pressing plate 26a is closed.
The opening 10b of the switching valve 28 and the valve seat 2 of the switching valve 28.
8a contacts the packing 12a of the sheet member 12.

As a result, the connection between the first diaphragm chamber 23 and the second cylinder chamber 8 is cut off, and the second diaphragm chamber 23 is closed.
The diaphragm 24 and the second cylinder chamber 8 communicate with each other through the hole 28b and the passage 28c of the switching valve 28. That is, in the second cylinder chamber 8, the secondary pressure P ₂ from the second diaphragm 24 is applied to the hole 28 b of the switching valve 28 and the passage 28.
c, It is introduced through the sheet member 12.

However, as described above, when the flow rate is zero, P
_{Since 1} ≈P ₂ , the valve body 4 is moved upward by the spring force of the spring 22 and the packing 5 is separated from the valve seat member 2 to open the valve.

Next, the operation of the gas outflow prevention valve when gas is used on the downstream side will be described.

When gas is used on the downstream side, the outlet 1b
The gas filled inside also flows in the direction indicated by the arrow, and the secondary pressure P ₂ gradually decreases. At this time, the second cylinder chamber 8
As described above, the seat member 12, the switching valve 28, the second diaphragm chamber 24, the passage 29a, the pressure introducing pipe 19,
It communicates with the outflow port 1b through the pipe 17 and the pressure detection port 16a.

Therefore, while the gas is used and the pressure in the second cylinder chamber 8 is reduced, the holes 18b, 1i. Since the secondary pressure P ₂ is introduced via 6c, the pressure difference between the first and second cylinder chambers 7 and 8 is zero.

As a result, the pressing force of the coil spring 22 and the valve
Primary pressure P acting on the bottom side of body 4 ₁Due to piston part
The force to move 4a upwards is 2 in the second cylinder chamber 8.
Next pressure P₂Since it is larger than the pressing force of
Thus, the valve body 4 is held in the valve open position.

Therefore, the valve body 4 is normally in the valve open position (normally open), and is kept in the valve open state even when the flow rate gradually increases to zero. Hunting does not occur and the seal member 9 and the like are less likely to wear, and durability can be improved. In addition, it is possible to prevent the secondary pressure P ₂ on the downstream side from largely fluctuating and the gas supply becoming unstable due to hunting accompanying the valve opening operation. Further, when the valve body 4 moves up and down due to the hunting accompanying the valve opening operation of the valve body 4 and the flow rate on the downstream side suddenly increases, the valve body 4 operates to close the valve even though there is no overflow on the downstream side. It is prevented from doing.

When the use of the gas on the downstream side is stopped, the secondary pressure P _{2 at the} outlet 1b gradually rises to P ₂ ≈P ₁ . However, since the pressure in the first cylinder chamber 7 and the pressure in the second cylinder chamber 8 become substantially equal, the valve body 4 is in the valve open position while being moved upward by the spring force of the spring 22. As described above, when the use of gas is stopped and the flow rate is zero, the valve body 4 is held in the valve open position as described above.

Here, a case will be described in which a pipe (not shown) on the downstream side of the gas outflow prevention valve is cut due to some accident or the like and a large amount of gas flows out.

When a gas outflow accident occurs on the downstream side, a large amount of gas passes through the flow path 1c. As the flow rate of the gas flowing out of the outlet 1b increases, the negative pressure generated on the downstream side of the orifice 16 also increases.

Orifice 1 in the valve open state shown in FIG.
When a negative pressure is generated on the downstream side of 6, the secondary pressure P ₂ decreases.

As described above, since the second diaphragm chamber 24 communicates with the pressure detecting port 16a of the orifice 16, when the negative pressure increases due to the excessive flow rate, the pressure inside the second diaphragm chamber 24 suddenly decreases. As a result, FIG. 4 and FIG.
As shown in FIG. 2, the diaphragm 25 is the second diaphragm chamber 2
It moves upward due to the pressure difference between the secondary pressure P ₂ inside the valve 4 and the primary pressure P ₁ introduced into the first diaphragm chamber 23. As the diaphragm 25 moves upward, the guide member 27 moves the switching valve 28.
To close the hole 28b of the switching valve 28. Further, the guide member 27 moves upward to bring the valve seat 27b into contact with the packing 40a of the sub valve body 40.

Then, as the diaphragm 25 moves upward, the washer 43 comes into contact with the step portion 32a of the spring retainer 32.
When the diaphragm 25 further moves upward, the guide member 27 moves upward while keeping the valve seat 27b in contact with the packing 40a of the sub valve body 40, and eventually the upper holding plate 26a comes into contact with the diaphragm holding member 29 to close the opening 29b. To do.

As a result, the valve seat 27b is closed and the primary pressure P ₁ is prevented from leaking into the diaphragm chamber 24 through the gap between the guide member 27 and the switching valve 28. Therefore, the inside of the diaphragm chamber 24 is maintained at the secondary pressure P ₂ .

As the diaphragm 25 moves upward, the valve seat 28a of the switching valve 28 is separated from the packing 12a of the seat member 12.

Therefore, the secondary pressure introducing passage 45 is cut off.
The primary pressure introducing passage 47 is connected to the second cylinder chamber
Communicate with 8. That is, the primary pressure from the primary pressure introducing hole 13
Power P ₁Is the passage 10a, the first diaphragm chamber 23, the sea
It is supplied to the second cylinder chamber 8 via the contact member 12.

Then, the valve body 4 is provided with 2 of the first cylinder chamber 7.
Since the pressure difference between the primary pressure P ₁ follows the pressure P ₂ and the second cylinder chamber 8 is increased, seated on the valve seat member 2 and moves downward against the pressing force of the spring 22.

As a result, the flow path 1c is closed, and gas outflow is prevented.

When the valve body 4 contacts the valve seat member 2 as described above, the guide member 27 and the diaphragm chamber 2
Since the valve valve 4 and the valve 4 are blocked by the auxiliary valve body 40, the inside of the diaphragm chamber 24 is maintained at the same pressure as the secondary pressure P ₂ .

Therefore, even if the downstream piping is repaired,
The primary pressure P ₁ is not supplied to the diaphragm chamber 24, and the valve body 4 maintains the valve closed state in which it is seated on the valve seat member 2. Therefore, in order to close the gas outflow prevention valve, after confirming that the downstream pipe has been repaired, an inert gas (N ₂ gas) is introduced into the downstream pipe to set the secondary pressure P ₂ . Boost.

As the secondary pressure P ₂ rises, the diaphragm 2
Secondary pressure P ₂ of the diaphragm chamber 24 that presses 5 downward.
The resultant force between the spring 33 and the spring 33 is the primary pressure P of the diaphragm chamber 23.
_When the pressing force becomes greater than ₁ , the diaphragm 25 moves downward to bring the valve seat 28a of the switching valve 28 into contact with the packing 12a of the seat member 12, and the secondary pressure P is applied to the second cylinder chamber 8.
Introduce ₂ .

The first cylinder chamber 7 has holes 2c through 2
The next pressure P ₂ is introduced, and the valve body 4 automatically returns to the valve open state. The valve body 4 is now in a state where it can operate normally, and gas supply is restarted.

Further, in the above embodiment, the orifice is provided in the flow path for detecting the excessive flow rate, but the present invention is not limited to this, and any element other than the orifice may be provided as long as the change in the secondary pressure can be detected. Of course, it is also good.

[0054]

As described above, in the gas outflow prevention valve according to the present invention, since the valve body is normally held in the valve open position by the pressing force of the biasing member, the valve open is prevented even if the flow rate increases from zero. It is not necessary to operate, and hunting of the valve body due to the valve opening operation can be eliminated. Therefore, it is possible to prevent the valve body from erroneously closing the valve due to flow rate fluctuations caused by hunting of the valve body, to prevent wear of the seal member of the valve body and to prolong the service life. It is possible to prevent the gas supply from becoming unstable due to the fluctuation of the secondary pressure due to the hunting.

Further, when the secondary pressure suddenly decreases due to breakage of the downstream side pipe, the diaphragm is displaced by the pressure difference between the primary pressure and the secondary pressure, and the sub-valve element moves between the switching valve and the secondary pressure introducing passage. Since the valve is shut off, the valve body is seated on the valve seat of the valve body and switched to the closed state, and at the same time, the primary pressure from the primary pressure introducing passage is prevented from leaking to the secondary pressure introducing passage. Therefore, after the operation, the upstream gas is prevented from flowing out to the downstream pipe, and the recovery work of the damaged portion of the downstream pipe can be performed more safely.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a valve open state of an embodiment of a gas outflow prevention valve according to the present invention.

FIG. 2 is a view of an orifice as viewed from an outlet.

FIG. 3 is an enlarged vertical sectional view showing an enlarged differential pressure detection unit.

FIG. 4 is a vertical sectional view for explaining a valve closing operation.

FIG. 5 is a vertical cross-sectional view for explaining the valve closing operation of the differential pressure detection unit.

[Explanation of symbols]

 1 Valve Main Body 2 Valve Seat Member 4 Valve Body 6 Cylinder 7 First Cylinder Chamber 8 Second Cylinder Chamber 10 Lid Member 12 Seat Member 13 Primary Pressure Introducing Hole 16 Orifice 19 Pressure Introducing Pipe 21 Differential Pressure Detecting Section 22 Coil Spring 23 First diaphragm chamber 24 Second diaphragm chamber 25 Diaphragm 27 Guide member 28 Switching valve 40 Sub-valve element 45 Secondary pressure introducing passage 46 Branch passage 47 Primary pressure introducing passage

Claims (1)

[Claims] 1. A valve main body having a valve seat in the middle of a passage through which gas passes, a small diameter portion that is seated on and off the valve seat of the valve main body, and a large diameter portion that is larger in diameter than the small diameter portion. A valve body that opens and closes the flow passage by a pressure difference between a primary pressure on the inflow side and a secondary pressure on the outflow side that acts on the large diameter portion; and a first partition defined on the large diameter portion of the valve body. , A cylinder having a second cylinder chamber for guiding the valve element in the valve opening / closing direction, and a large diameter portion of the valve element provided in the first cylinder chamber on the valve closing side for opening the valve element. Urging member for urging in the direction, a primary pressure introducing passage for introducing the primary pressure into the second cylinder chamber on the valve opening side, and a secondary pressure for the first and second cylinder chambers. A secondary pressure introducing passage to be introduced, and a duct which is provided so as to define the primary pressure introducing passage and the secondary pressure introducing passage and is displaced according to a pressure difference between the primary pressure and the secondary pressure. An ear diaphragm, a switching valve that connects one of the primary pressure introducing passage and the secondary pressure introducing passage to the second cylinder chamber according to the displacement of the diaphragm, and when the secondary pressure suddenly decreases, The displacement of the diaphragm shuts off the connection between the switching valve and the secondary pressure introducing passage,
A gas outflow prevention valve, comprising: a sub-valve body which connects the switching valve and the secondary pressure introducing passage by returning the diaphragm when the secondary pressure is increased to a predetermined pressure.