JPH1030735A - Double seal valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a structure of a valve opening/closing drive mechanism, and to safely use a double seal valve without generating the misoperation. SOLUTION: A seal valve is provided with a valve seat on a communication passage of an upper flow passage and a lower flow passage, a first valve disk to be engaged with an inner circumferential side of the valve seat is provided on a first valve stem 8, a second valve disk to be pushingly engaged with an upper side of the valve seat is provided on a second valve stem 10, the first valve stem 8 is connected to a valve opening/closing drive mechanism 28 in an interlocking manner, and the second valve disk follows the upward movement of the first valve stem 8. In the valve opening/closing drive mechanism 28, a spring bracket 31 on an upper part in a fixed cylinder 30 to which a piston 29 is fitted, and a second spring 32 and a spring restrain stopper 33 which is connected to the spring bracket 31 in an expandable manner to restrict the elongation of the second spring 32 in the prescribed range, are interposed between the spring bracket 31 and the piston 29.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double seal valve used for a liquid distribution line in a machine or a plant for food production, brewing, etc. The present invention relates to a valve structure for preventing the above.

[0002]

2. Description of the Related Art A general double seal valve of this type is provided with a valve seat in a communication path formed between an upper flow path and a lower flow path,
A first valve body that slides and engages on the inner peripheral side of the valve seat is provided on the first valve shaft, and a second valve body that presses and engages on the upper side of the valve seat is provided on the second valve shaft. By appropriately driving the shafts and the two valve shafts by the valve opening / closing drive mechanism, the first valve body and the second valve body are caused to execute a fully closed state in which the first valve body and the second valve body are closed and a fully open state in which both the valve bodies are opened. However, in addition to the valve fully closed state and the valve fully open state, the first valve body is slightly opened and the second valve body is partially closed, or the first valve body is closed and the second valve body is closed. A slightly opened valve portion opening state is described in, for example, Japanese Patent Application Laid-Open No. 7-253167.

[0003]

In the double seal valve described in the above-mentioned publication, two valve opening / closing drive mechanisms for executing a fully closed state of the valve, a fully opened state of the valve and a partially opened state of the valve are connected vertically. However, the cylinder of the upper valve opening / closing drive mechanism and the cylinder of the lower valve opening / closing drive mechanism are provided independently of each other via a partition that passes through the first valve shaft in an airtight state. A pair of upper and lower pistons in the upper cylinder,
Since three pistons, one piston, are arranged in the lower cylinder and slidably provided on both pistons and the piston rod in the upper cylinder, the hermetic seal is complicated in many places. In addition to the manufacturing difficulties, there is a difficulty in making the structure compact, and because the piston of the upper cylinder is provided in a free state,
There has been a problem that the valve may be caught at the time of the fully opening operation of the valve or the like, resulting in malfunction.

[0004] It is an object of the present invention to provide a double seal valve which enables the structure of a valve opening / closing drive mechanism to be made compact and which can be used safely without causing a malfunction.

[0005]

According to a first aspect of the present invention, there is provided a double seal valve comprising a valve seat in a communication passage formed between an upper flow path and a lower flow path. The first valve body 7 engaging with the inner peripheral side of the valve seat 6 is engaged with the first valve shaft 8, and the second valve body 9 engaging with the upper side of the valve seat 6 is engaged with the first valve. The second valve shaft 10 is slidable on the shaft 8 and is fitted so as to be constantly urged downward by the first spring 11. The first valve shaft 8 is connected to the valve opening / closing drive mechanism 28 in an interlocking manner. A double-sealed valve in which the second valve element 9 moves following the upward movement of the first valve shaft 8 by the operation of the valve opening / closing drive mechanism 28 when the valve is opened. An air cylinder in which a piston 29 fixed to the shaft 8 as a piston rod is inserted into a fixed cylinder 30 is provided. The only 31 arranged to receive the spring 3
1 and the piston 29, the piston 29 and the second
A second spring 32 having a greater spring force than the first spring 11 interposed between the valve shaft 10 and a second spring 32 fixed to the piston rod and connected to the spring receiver 31 so as to be able to expand and contract; And a spring limiting stopper 33 for limiting the extension of the piston to a certain range.
Air supply / discharge ports 34, 35 for supplying / discharging air to / from the upper and lower chambers 30a, 30b sandwiching the fuel cell 9 are provided.

According to a second aspect of the present invention, in the double seal valve according to the first aspect, a second valve body opening / closing drive mechanism comprising an air cylinder is provided below the valve opening / closing drive mechanism, and the second valve is provided. The body opening / closing drive mechanism 36 includes the fixed cylinder 30
A second cylinder 37 formed in communication with a lower part of the second piston 37 and a second piston 38 which is fitted inside the cylinder 37 and externally fitted on the second valve shaft 10 and moves up and down a predetermined stroke S1.
A third spring 39 for urging the second piston 38 to the lower limit position; and an air supply / discharge port 40 for supplying / discharging air to / from the lower chamber 37a of the second cylinder 37. The second valve shaft 10 moves upward against the urging force of the first spring 11 in accordance with the upward movement of the second piston 38 due to the supply of air to open the second valve body 9. It is characterized by.

According to a third aspect of the present invention, in the double seal valve according to the second aspect, the inner peripheral upper end portion 38b of the second piston 38 urged to the lower limit position by the third spring 39, and the first spring 11 and a stopper 43 provided at a required position of the second valve shaft 10 urged to the valve closing position by the second piston 38.
Is provided with an axial play S2 shorter than the stroke S1 of the second valve shaft 10 so that the stroke of the second valve shaft 10 is S1-S2.

[0008]

FIG. 1 is a longitudinal sectional view of a lower half of the double seal valve according to the present invention, which is divided into two parts by the line aa. FIG. 2 shows an upper half. In these figures, reference numeral 1 denotes an upper flow path, 2 denotes a lower flow path, and these flow paths 1 and 2 are formed in parallel or crossing directions with each other. Are formed, and an upper opening 4 and a lower opening 5 are formed in a portion coaxially opposed to the communication passage 3 in both the flow paths 1 and 2, and a valve seat 6 is mounted in the communication passage 3. . For example, a drinking liquid or a washing liquid flows through the upper flow path 1 and the lower flow path 2, respectively.

Reference numeral 7 denotes a first valve body which engages with the inner peripheral side of the valve seat 6, and is an intermediate portion of the first valve shaft 8 inserted from the upper opening 4 through the communication passage 3 toward the lower opening 5. It is formed integrally with the lower end of the shaft 8b. A hollow lower shaft portion 8c is integrally formed coaxially below the first valve body 7, and an upper shaft portion 8a is coaxially connected to the upper portion of the intermediate shaft portion 8b, usually by screw connection. (In FIGS. 1 and 2, the intermediate shaft portion 8b and the upper shaft portion 8a are illustrated as being integrally formed.) The upper shaft portion 8a, the intermediate shaft portion 8b, and the lower shaft portion 8
c forms the first valve shaft 8.

Reference numeral 9 denotes a valve seat located above the first valve body 7.
A second valve body which is pressed into engagement with the upper side of the first valve shaft from above and is integrally formed with the lower end portion of the second valve shaft 10 which is fitted over the upper shaft portion 8a to the intermediate shaft portion 8b of the first valve shaft 8. The second valve shaft 10 is constantly urged downward by a first spring 11 formed of a coil spring as described later, thereby pressing the second valve body 9 against the upper side of the valve seat 6. The second valve shaft 10 includes an upper shaft portion 10a and a lower shaft portion 10b screwed to the upper shaft portion 10a.
A second valve body 9 is formed at the lower end of the valve body.

As is apparent from FIGS. 3 and subsequent drawings, the first valve body 7 is provided with a main annular packing 12 slidably in contact with the inner peripheral side seating surface 6 a of the valve seat 6. The sub-annular packing 13 which is fitted and attached to the fitting groove 7a for fitting, and which is closer to the upper side surface 6b of the valve seat 6 from above than the second valve body 9, is fitted to the fitting groove 9a for packing attachment. Has been installed. The upper opening 4 of the upper flow path 1 is provided with an annular member 14 that slidably supports the lower shaft portion 10b of the second valve shaft 10 that protrudes upward from the upper opening 4.
The annular member 14 includes a base 15a of a yoke 15 and a packing 16 that is in close contact with the lower shaft 10b at the lower end thereof. The lower opening 5 of the lower flow path 2 is provided with an annular member 17 slidably supporting a lower shaft portion 8c of the first valve shaft 8 protruding downward from the lower opening 5. The member 17 is the large diameter base 1 of the sleeve 18.
8a, and a packing 19 that is in close contact with the lower shaft portion 8c at the upper end thereof.

As shown in FIG. 1, a cleaning liquid supply port 20 is provided in a lower shaft portion 10 b of the second valve shaft 10, and the cleaning liquid supply port 20 is connected to the first valve shaft 8 through a communication hole 21. The internal passage 22 communicates with an internal passage 22 provided in the intermediate shaft portion 8b, and the internal passage 22 communicates with a plurality of cleaning liquid ejection holes 23 provided radially at the lower end of the intermediate shaft portion 8b. When the cleaning liquid is supplied from the cleaning liquid supply port 20, the cleaning liquid
An annular chamber 24 formed between the first valve body 7, the second valve body 9, and the valve seat 6 enters the internal passage 22 of the intermediate shaft portion 8 b through the communication hole 21, and from each of the cleaning liquid ejection holes 23 at the lower end. After cleaning the inside of the annular chamber 23, the plurality of through holes 2
5, and is discharged to the outside from the discharge passage 26 inside the lower shaft portion 8c. In addition, a base 27 for connecting a cleaning liquid hose is attached to the cleaning liquid supply port 20 through the window 15 a of the yoke 15.

Referring to FIG. 2, reference numeral 28 in FIG. 2 denotes a first valve opening / closing drive mechanism for opening and closing the first valve body 7 and the second valve body 9. The upper shaft portion 8a of the first valve shaft 8 is an air cylinder in which a piston rod fixed to the upper shaft portion 8a is fitted into a fixed cylinder 30. A spring receiver 31 is disposed in the upper portion of the fixed cylinder 30. The piston 29 and the second valve shaft 10 are located between the spring receiver 31 and the piston 29.
A second spring 32 composed of a coil spring having a greater spring force than the first spring 11 interposed between the second spring 32 and the second spring 32 fixed to the piston rod 8a and connected to the spring receiver 31 so as to be able to expand and contract. A spring limiting stopper 33 for limiting the extension of the two springs 32 to a certain range is interposed. The fixed cylinder 30 is provided with an air supply for supplying and discharging air to upper and lower chambers 30a and 30b via a piston 29. Discharge ports 34 and 35 are provided.

The spring support 31 comprises a ring-shaped spring support body 31o for receiving one end of a second spring 32 and a cylindrical member 31a formed concentrically and integrally therewith. A cylindrical member 33a which is externally fitted to the piston rod (upper shaft portion 8a of the first valve shaft 8), fixed at a fixed position, and slidably fitted inside the cylindrical member 31a of the spring receiver 31; Normally, as shown in FIG. 2, the two cylindrical members 31a, 3
The engagement of the distal end engagement portions of 3a causes the spring receiver 31 and the stopper 33 to be connected in a state of maximum extension, thereby restricting the second spring 32 from further extending.

Therefore, according to the first valve opening / closing drive mechanism 28, when pressure air is not supplied to either of the upper and lower chambers 30a, 30b with the piston 29 of the fixed cylinder 30 interposed therebetween, FIG. Thus, the first interposed between the piston 29 and the upper shaft portion 10a of the second valve shaft 10
The first valve shaft 8 is urged upward and the second valve shaft 10 is urged downward by the urging force of the spring 11, and the first valve body 7 is moved through the main annular packing 12 to the inner circumferential side of the valve seat 6. The second valve body 9 closely engages with the upper side seating surface 6b of the valve seat 6 via the auxiliary annular packing 13 while being closely engaged with the seating surface 6a, and the valve is fully closed as shown in FIG. .

When pressure air is supplied to the lower chamber 30b of the fixed cylinder 30 from the air supply / discharge port 35, the piston 29 rises against the urging force of the second spring 32, and the stopper 33 The cylindrical member 33a contracts with respect to the cylindrical member 31a of the spring receiver 31, and the first valve shaft 8 starts to move upward, while the upper end of the first valve body 7 moves upward as shown in FIG. In contact with the lower portion on the inner peripheral side of the second valve element 9, the first valve element 7 pushes up the second valve element 9 and rises together in this abutting state, and the two valve elements 7, 9 are raised from the valve seat 6. And the stroke setting ring R fitted on the upper end side of the piston rod 8a is fixed to the upper wall 3 of the fixed cylinder 30.
By contact with 0c, the piston 29 reaches the upper limit position, and the first valve body 7 and the second valve body 9 are in the fully opened state as shown in FIG.

When the pressure air in the lower chamber 30b of the fixed cylinder 30 is discharged when the valve is fully opened, the spring receiver 31 is moved to the upper wall 30c of the fixed cylinder 30.
The piston 29 is lowered by the urging force of the second spring 32 while being pressed against the first valve shaft 8 and the second valve shaft 8.
When the valve shaft 10 moves downward, the first valve body 7 and the second valve body 9
The state returns to the fully closed state as shown in FIG. Note that the valve is fully closed (see FIG. 3).
The stroke Sa of the piston 29 in the fully opened state (see FIG. 5) and the stroke of the piston 29 in the fully opened state (see FIG. 5) are set by the stroke setting ring R which comes into contact with the upper wall portion 30c of the fixed cylinder 30.

When pressure air is supplied from the air supply / discharge port 34 to the upper chamber 30a of the fixed cylinder 30 in the fully closed state shown in FIGS. 1 and 2, the second spring 32 is actuated by the spring limiting stopper 33. Of the upper chamber 30a, the piston 29 is pushed downward, and descends together with the second spring 32 and the spring receiver 31, whereby the first valve shaft 8 is moved downward. The main annular packing 12 of the first valve body 7 slides downward on the inner peripheral side seating surface 6a of the valve seat 6 and separates as shown in FIG. Then, only the first valve element 7 is in a slightly opened valve part open state. In this way, by supplying the pressurized air to the upper chamber 30a of the fixed cylinder 30, the first valve shaft 8 can be moved down independently, and only the first valve body 7 can be partially opened. In this case, the piston 29 is
Starts descending from the position shown in FIG. 5, and stops by contacting the upper end of the second cylinder 37 described later. Accordingly, the stroke becomes Sb shown in the figure, and the first valve shaft 8 moves up and down independently of the second valve shaft 10 by this stroke Sb.

Below the first valve opening / closing drive mechanism 28, there is provided a second valve body opening / closing drive mechanism 36 also composed of an air cylinder. The second valve body opening / closing drive mechanism 36 is a fixed cylinder 30 of the first valve opening / closing drive mechanism 28.
A second cylinder 37 formed at a lower portion in communication with the second cylinder 37;
The second valve shaft 10 and the second cylinder 37
A second piston 38 which moves up and down by a predetermined stroke in a state of being externally fitted to the upper shaft portion 10a, and a third spring 39 comprising a coil spring for urging the second piston 38 to a lower limit position.
And an air supply / discharge port 40 for supplying / discharging air to / from the lower chamber 30a of the second piston 38. As can be seen from FIG. 2, the second cylinder 37 is connected to the lower end of the fixed cylinder 30 of the first valve opening / closing drive mechanism 28 by a screw connection.
The upper chamber 37b and the lower chamber 30b of the fixed cylinder 30 in the first valve opening / closing drive mechanism 28 are formed so as to communicate with each other.

In FIG. 2, reference numeral 41 denotes a stopper for regulating the lower limit position of the second piston 38.
The stopper 42 is formed on the lower wall side of the second cylinder 37 and restricts the upper limit position of the second piston 38.
Is formed on the upper wall side. Thus, the second piston 38 corresponds to the distance between the upper end 38 a on the outer peripheral side of the piston 38 and the upper limit position restricting stopper 42 between the lower limit position restricting stopper 41 and the upper limit position restricting stopper 42. The second piston 38 urged by the third spring 39 to the lower limit position.
Is shorter than the stroke S1 between the inner peripheral side upper end portion 38b and the stopper 43 projecting from the upper shaft portion 10a of the second valve shaft 10 urged to the valve closing position by the first spring 11. Since the axial play S2 is provided,
When the piston 38 moves up the stroke S1 from the lower limit position to the upper limit position, the second valve shaft 10 actually causes the difference (S1) between the stroke S1 of the second piston 38 and the axial play S2. -S2) It moves up by the amount.
As described above, the inner peripheral upper end 38 b of the second piston 38 urged to the lower limit position by the third spring 39 and the second spring 32
The stopper 4 on the side of the second valve shaft 10 urged to the valve closing position by the
3, an axial play S2 shorter than the stroke S1 of the second piston 38 is provided, so that the urging force of the second spring 32 is effectively applied to the second valve shaft 10 and
The valve body 9 can be securely pushed and engaged with the upper seat surface 6b of the valve seat 6.

In the second valve opening / closing drive mechanism 36, the state in which the second piston 38 is held at the lower limit position as shown in FIG. When the pressurized air is supplied to the lower chamber 37a, the second piston 38 starts to move upward.
The upper end 38b on the inner peripheral side of the
, The second valve shaft 10 remains held at the lowered position to close the second valve body 9. Thus, the second valve shaft 1
After the upper end 38b on the inner peripheral side of the second piston 38 hits the stopper 42, the upper end 38b is pushed up with the upward movement of the second piston 38, and the upper end 38 on the outer peripheral side of the piston 38
The valve a moves upward until it reaches the upper limit position restricting stopper 42, and as a result, as shown in FIG. 7, only the second valve body 9 is in a slightly open valve part open state. Also, the lower chamber 37a
The second piston 38 is moved to the third
While being pushed down by the spring 39, the second valve shaft 10 is moved down by the second spring 32, and the second valve body 9 is closed.

In the use of the double seal valve having the above-described configuration, when no pressure air is supplied to the lower chamber 30b of the fixed cylinder 30 in the first valve opening / closing drive mechanism 28, FIGS. As shown in FIG. 3, the first valve body 7 closely engages with the inner peripheral side seating surface 6 a of the valve seat 6 via the main annular packing 12, and the second valve shaft 10 is pushed down by the first spring 11 to thereby provide the second valve shaft 10. The valve body 9 presses and engages with the upper side seating surface 6b of the valve seat 6 via the sub annular packing 13,
The first valve body 7 and the second valve body 9 are both in a fully closed state in which both valves are closed, and the communication path 3 that connects the upper flow path 1 and the lower flow path 2 is connected to the first valve on the lower flow path 2 side. Is closed in a double sealed state by the body 7 and the second valve body 9 on the upper flow path 1 side,
Mixing of the liquid flowing in the upper flow path 1 and the liquid flowing in the lower flow path 2 is prevented.

The lower chamber 3 of the fixed cylinder 30
0b is supplied with the pressure air, as shown in FIG.
As the first valve body 7 pushes up the second valve body 9 and moves up together with the upward movement of the valve shaft 8, the two valve bodies 7, 9 are sufficiently separated upward from the valve seat 6 as shown in FIG. Such a valve is fully open,
Thereby, the communication path 3 is opened, and the upper flow path 1 and the lower flow path 2 can be communicated via the communication path 3.

When using a liquid that is difficult to wash, such as a highly viscous liquid, one of the first valve element 7 and the second valve element 9 should be closed, and the other should be slightly opened and opened. While washing the packing part with the cleaning liquid, the cleaning liquid is discharged. For example, high-viscosity drinking water is circulated through the upper flow path 1,
When the cleaning liquid is supplied to the lower flow path 2, when the pressurized air is supplied to the upper chamber 30 a of the fixed cylinder 30, the piston 29 descends together with the second spring 32 whose elongation is restricted by the increase in the pressure of the upper chamber 30 a. As a result, the first valve shaft 8 moves downward, and the main annular packing 12 of the first valve body 7 slides downward on the inner peripheral side seating surface 6a of the valve seat 6 to be separated, as shown in FIG. Then, only the first valve element 7 is in a slightly opened valve part open state. Thus, the cleaning liquid from the lower flow path 2 passes through the gap between the first valve element 7 and the valve seat 6 as shown by the arrow in FIG. Is introduced into an annular chamber 24 formed between the first valve body 7 and the valve seat 6, during which the main annular packing 12 of the first valve body 7 and the interior of the annular chamber 2 are washed, and then the lower portion of the first valve shaft 8 It is discharged to the outside through the discharge passage 26 inside the shaft portion 8c.

In the case where highly viscous drinking water flows through the lower flow path 2 and the washing liquid flows through the upper flow path 1, the second flow path is used.
When pressure air is supplied to the lower chamber 37a of the second cylinder 37 in the valve opening / closing drive mechanism 36, the second valve shaft 10 is pushed up by the piston 38 while the second piston 38 is moving upward, and the second piston 38 Moves upward by a predetermined stroke S1, so that the second valve shaft 10 moves in the axial play S2.
The valve is moved upward by the stroke (S1-S2) from which the minute has been subtracted, and as shown in FIG. 7, only the second valve body 9 is in a slightly open valve part open state. Thus, the cleaning liquid from the upper flow path 1 passes through the gap between the second valve body 9 and the upper seating surface 6b of the valve seat 6, as indicated by the arrow in FIG. After circulating in the annular chamber 24 formed between the second valve body 9 and the valve seat 6 to clean the sub-annular packing 13 portion of the first valve body 7 and the inside of the annular chamber 2, It is discharged to the outside through the discharge passage 26 inside the lower shaft portion 8c of the valve shaft 8.

[0026]

According to the double seal valve of the first aspect, the valve opening / closing drive mechanism for opening and closing the first valve body and the second valve body has a first valve shaft fixed to the piston rod as a piston rod.
An air cylinder in which three pistons are inserted into a fixed cylinder, wherein a spring receiver is disposed in an upper part of the fixed cylinder, and between the spring receiver and the piston, between the piston and the second valve shaft. A second spring having a spring force greater than that of the first spring interposed therebetween, and a spring limiting stopper fixed to the piston rod and connected to the spring receiver so as to be extendable and contractible to limit the extension of the second spring to a certain range. When pressure air is not supplied to either of the upper and lower chambers of the fixed cylinder, the first spring biases the first valve shaft upward and the second valve shaft downward. Then, the first valve body is engaged with the inner peripheral side of the valve seat, and the second valve body is engaged with the upper side of the valve seat, so that the valve is fully closed. When pressurized air is supplied to the lower chamber of the fixed cylinder, the piston rises against the urging force of the second spring, and the spring limiting stopper contracts with respect to the spring receiver, thereby causing the first valve shaft to move. Starts moving upward, and while the first valve body pushes up the second valve body and rises together, both the valve bodies are separated upward from the valve seat, and the valve is fully opened. When the pressure air in the lower chamber is released, the first valve shaft moves down to the original position by the urging force of the second spring, and
The valve body and the second valve body are both in a fully closed state in which the valve is closed.

Further, when the pressure air is supplied to the upper chamber of the fixed cylinder in the fully closed state of the valve, the extension of the second spring is restricted by the spring restricting stopper. As a result, the first valve shaft moves down against the first spring, and the first valve body is in an open state. Thus, by supplying the pressurized air to the upper chamber of the fixed cylinder, the first valve body is opened and the second valve body is in a partially opened state.

Therefore, according to the present invention, the valve opening / closing drive mechanism supplies and exhausts the pressure air to and from the lower chamber of the fixed cylinder, whereby the valve can be fully opened or closed. By supplying compressed air to the upper chamber of the cylinder, the first valve element opens and the second valve element opens.
The valve body can be in a partially open state in which the valve body is closed. In this valve opening and closing drive mechanism, only one piston is provided in the fixed cylinder and fixed to the piston rod. Therefore, only one airtight seal is required, which simplifies the structure and reduces the manufacturing cost. This can be simplified and the piston does not malfunction, so that the valve does not malfunction.

According to the second aspect of the invention, the second valve opening / closing drive mechanism is provided below the first valve opening / closing drive mechanism. Works like That is, when the pressure air is supplied to the lower chamber of the second cylinder from the state where the second piston is held at the lower limit position, the second piston is moved upward with the upward movement of the second piston.
The valve shaft is pushed up, and only the second valve body is opened, so that the valve portion is opened. Also, by releasing the pressure air in the lower chamber, the second piston is pushed down by the third spring, and the second piston is pushed down.
The valve shaft is moved downward by the second spring, and the second valve body is brought into the closed state.

Thus, according to the present invention, the second cylinder in the second valve opening / closing drive mechanism has a partition wall below the fixed cylinder of the first valve opening / closing drive mechanism as in the conventional device described at the beginning. Instead, it is formed so as to communicate with the fixed cylinder, so that the structure can be simplified and the size can be reduced, so that the production can be facilitated.

According to the third aspect, the inner peripheral upper end of the second piston biased to the lower limit position by the third spring, and the second valve shaft biased to the valve closing position by the second spring. By providing an axial play shorter than the stroke S1 of the second piston between the stopper and the stopper provided on the second valve body, the urging force of the second spring is effectively applied to the second valve shaft, and the second valve body is moved. It is possible to reliably press and engage the upper portion of the valve seat.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a lower half of a double seal valve according to the present invention, and an aa line is a dividing line with an upper half.

FIG. 2 is a longitudinal sectional view showing an upper half of the double seal valve.

FIG. 3 is a longitudinal sectional view showing a central portion of a double seal valve in a fully closed state of the valve.

FIG. 4 is a vertical cross-sectional view of a central portion of the double seal valve showing a state in which the valve has transitioned from a fully closed state to an open state.

FIG. 5 is a longitudinal sectional view showing a central portion of the double seal valve in a fully opened state.

FIG. 6 is a longitudinal sectional view showing a valve part opened state in which a first valve body is slightly opened.

FIG. 7 is a longitudinal sectional view showing a valve part opened state in which a second valve body is slightly opened.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper flow path 2 Lower flow path 3 Communication path 6 Valve seat 7 First valve body 8 First valve shaft 9 Second valve body 10 Second valve shaft 11 First spring 28 First valve opening / closing drive mechanism 29 Piston 30 Fixed Cylinder 30a Upper chamber 30b Lower chamber 31 Spring receiver 32 Second spring 33 Spring limiting stopper 34 Air supply / discharge port 35 Air supply / discharge port 36 Second valve opening / closing drive mechanism 37 Second cylinder 38 Second piston 39 Third spring 40 Air Supply / discharge port

Claims (3)

[Claims] A valve seat is provided in a communication passage formed between an upper flow passage and a lower flow passage, a first valve body engaging with an inner peripheral side of the valve seat is provided on a first valve shaft, and a valve seat is provided. A second valve body that is pressed and engaged with the upper side of the second valve shaft is provided on the second valve shaft that is slidable on the first valve shaft and is fitted so as to be constantly urged downward by the first spring; A double seal valve in which the first valve shaft is interlockedly connected to the valve opening / closing drive mechanism, and the second valve body follows the upward movement of the first valve shaft due to the operation of the valve opening / closing drive mechanism when the valve is opened; The valve opening / closing drive mechanism is composed of an air cylinder in which a piston fixed to the first valve shaft as a piston rod is inserted into a fixed cylinder, and a spring receiver is arranged at an upper portion in the fixed cylinder.
A second spring having a greater spring force than the first spring interposed between the piston and the second valve shaft is fixed between the spring receiver and the piston, and fixed to the piston rod and connected to the spring receiver. On the other hand, an air supply / discharge port for supplying / discharging air to / from both the upper and lower chambers sandwiching the piston is provided in the fixed cylinder. A double seal valve characterized by being provided. 2. A second valve body opening / closing drive mechanism comprising an air cylinder is provided below the valve opening / closing drive mechanism, and the second valve body opening / closing drive mechanism is formed in communication with a lower portion of the fixed cylinder. A second piston, which is internally fitted in the cylinder and externally fitted on the second valve shaft and moves up and down a predetermined stroke S1, and a third spring for urging the second piston to a lower limit position. An air supply / discharge port for supplying / discharging air to / from the lower chamber of the second cylinder, and the second valve shaft is attached to the first spring by the upward movement of the second piston by the supply of air to the lower chamber. 2. The double seal valve according to claim 1, wherein the double seal valve moves upward against the force to open the second valve body. 3. An inner peripheral upper end portion of the second piston biased to a lower limit position by a third spring and a required position of a second valve shaft biased to a valve closing position by the first spring. Between the stopper and the stopper, an axial play S2 shorter than the stroke S1 of the second piston is provided, so that the stroke of the second valve shaft is S1-S.
3. The double seal valve according to claim 2, wherein the number is 2.