JPH10220603A - Dual plate check valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve which endures various kinds of corrosive fluid, prevent two valve bodies from being worn or damaged and producing metallic noises when they are closed, increase the rate of opening of a valve seat to reduce a pressure loss, and prevent the damage of a bearing when the valve is opened or closed. SOLUTION: A cylindrical sheet ring 16 made of an elastic material is provided on the whole inner peripheral surface of a fluid passage 12, a slant surface 16d is formed integrally inside the sheet ring 16, slant surfaces 14d formed on the outer peripheries of two semicircular valve bodies 14a, 14b supported by a hinge 13 are put into contact with the slant surface 16d when the slant surfaces 14d are closed, and a center rib is removed to increase the rate of opening of a valve seat. The valve body is mounted with a sub-valve body urged by a spring in a direction which closes the valve and opened when the pressure is small and a sub-valve body opened when the pressure of fluid in the exit side is excessively high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer which has two semi-disc-shaped valve bodies having corrosion resistance in a main body, and in particular, prevents a main part from being damaged when opening and closing the valve. Shape dual plate check valve.

[0002]

2. Description of the Related Art Conventionally, two semi-disc-shaped valve elements are axially supported on a main body by a single hinge pin while being urged by a spring, and the valve element is normally brought to a closed position by the elastic force of a spring. The valve body is biased and held, and the valve body is turned to the valve-opening position against the resilience of the spring by the fluid pressure of the normal flow to allow the flow of the fluid. A wafer type dual plate check valve in which a valve body is quickly closed by an elastic force is known, and is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 8-1660072.

As shown in FIG. 4, the dual plate check valve disclosed in the above publication has two semicircular valve bodies 3a and 3b rotatably supported on a main body 1 by hinge pins 2.
Is urged in the valve closing direction (the direction in which the two valve bodies themselves open) by the coil springs 4 wound around the hinge pins 2 and having both ends abutting against the back surfaces of the two valve bodies. I have. In the drawing, reference numeral 5 denotes a stopper pin installed at a position sandwiched between the rear surfaces of both valve bodies having a front surface 3c formed of a part of a spherical surface when the valve is opened, 6 a flat planar valve seat portion, and 7 a flat valve seat portion. A central rib 8 provided on the upstream side of the hinge pin 2 is a stopper provided on the back surface of both valve bodies, and an elastic cushioning material 8a protrudes from the center thereof.

The main body 1 is constructed as described above.
When the fluid does not flow through the inside, the two valve bodies 3a and 3b are spread 180 ° by the resilience of the spring 4 as shown by the solid line, and the pipes are completely closed, but in FIG. When the fluid flows toward the valve, the two valve bodies 3a and 3b open the pipeline as shown by the dotted line against the resilience of the spring 4, and at a normal flow rate, the two valve plates are closed at the center stopper. Abut on pin 5,
It is kept fully open. Also, when the water supply in the pipe is suddenly cut off due to an emergency stop of the pump, etc., the two valve plates 3a,
3b is designed to actuate quickly and reliably (close the valve) with spring force to protect the piping system from the backflow shock wave (water hammer), and constitute a small, lightweight and highly durable check valve. I have.

[0005]

The above-described known dual plate check valve (FIG. 4) has the following problems. (I) There is a difference in the opening (area) ratio of the valve seat portion with respect to the valve diameter of the inlet or the outlet of the main body 1, and this difference differs depending on the valve diameter. The opening ratio of the seat is 40 to 60%. For this reason, pressure loss (fluid resistance) occurs in the valve seat portion, and depending on the type of fluid, the effect is not small. In addition, there is a danger that the contact portion between the valve seat portion and the valve body becomes a fluid having a high flow velocity as a result of the pressure loss and is worn or damaged.

(Ii) Conventionally, in this type of dual plate check valve, the material of the seat of the valve body and the valve seat is a combination of a metal and an elastic body in order to ensure sealing performance and prevent noise. The mass (volume) of the elastic body could not be formed so large that there was a risk of damage such as wear, peeling or falling off of the elastic body.

(Iii) The hinge pin, which is the pivot axis of the valve body, and the main body and the bearing that support the pin have a risk of being worn or damaged as a result of being in contact with the fluid for many years. Also, similarly, the main body and the bearing that support the stopper pin that stops the valve body at the valve opening position have been in contact with the fluid for many years, and when the metal valve body abuts when fully opened. Metallic noise, abnormal noise, and the like were generated, and there was a risk that the bearing portion would be worn or damaged by the vibration of the stopper pin.

(Iv) Conventionally, in this type of dual-plate check valve, all the fluid passages of the hollow cylindrical main body are formed of a metal material, and the type of fluid is limited. There is a problem that fluids such as seawater, sewage, wastewater and the like cannot withstand long-term use. In recent years, there has been no check valve suitable for a pipe material having corrosion resistance (eg, rubber lining, resin coating, etc.).

(V) Hinge pin 2 for pivotally supporting two valve elements
The hammering phenomenon (chattering) which is assumed to be the largest cause of wear and damage of the shaft support portion of the main body 1 of the main body 1 is that when the fluid pressure or flow rate is extremely small, the fluid pressure, flow rate fluctuation, pulsation, etc. The opening and closing movement of the body becomes intense,
As a result, there has been a problem that the body supporting portions of the hinge pins and the stopper pins are deformed and damaged for many years.

Further, when the water supply in the piping is suddenly cut off due to an emergency stop of the pump or the like, the two valve bodies close quickly by spring force, and then the water in the outlet side piping tends to flow backward. In order to reduce the generated backflow shock wave (water hammer), a bypass passage that bypasses the upstream and downstream sides of the two valve bodies is provided in the main body, and the bypass passage is opened and closed by an on-off valve. Conventionally known (for example, see Japanese Utility Model Application Laid-Open No. 173776/1985), there is a problem that the structure becomes complicated because both the bypass passage and the on-off valve are provided in the main body.

The present invention solves the above-mentioned problems of the prior art, can endure the use of various corrosive fluids, and wears, damages and damages when two semi-disc-shaped valve bodies are closed. Prevents the generation of metallic noise, etc., increases the opening ratio of the valve seat, reduces pressure loss, and prevents external leakage of fluid. It is an object of the present invention to provide a dual plate check valve in which damage to a main part is prevented beforehand.

[0012]

Means taken by the present invention to solve the above-mentioned problems include a hinge pin installed diametrically across a fluid passage of a hollow cylindrical body made of a rigid material, and the hinge pin. A pair of two semi-disc-shaped valve bodies that are rotatably supported on the body and selectively open or close the fluid passage of the main body, and a spring that constantly biases the valve bodies in the closing direction. In the dual plate check valve provided, a cylindrical seat ring made of an elastic material is mounted on the entire inner peripheral surface of the fluid passage of the hollow cylindrical body, and the two semicircles are provided inside the seat ring. An outer peripheral edge portion of the plate-shaped valve body and a valve seat portion to be in an adhesive seat are integrally formed, a plurality of openings are provided in the pair of two semi-disc-shaped valve bodies, and the openings are closed by a spring. A sub-valve that is urged in the direction and opens when the inlet-side fluid is at a small pressure;
A sub-valve, which is urged in the closing direction by a spring and opens when the outlet fluid is in excess pressure, is attached.

Further, the valve seat portion integrally formed inside the cylindrical seat ring made of an elastic material is bonded to the inclined surfaces formed on the outer peripheral edges of the two semi-disc-shaped valve bodies when the valve is closed. It is formed by an inclined surface, and is characterized in that the above-mentioned two types of sub-valve elements are attached to a pair of two semi-disc-shaped valve elements.

[0014] Further, the rotating surfaces of the two semi-disc-shaped valve elements pivotally supported by the hinge pins and the seat ring are brought into surface contact, and a shaft sealing member is provided at the hinge pin insertion portion of the seat ring. The two types of sub-valves are fixed to a pair of two semi-disc-shaped valve bodies via a sleeve.

Further, the fluid at the time of full opening is directly divided into two along the front surface of the boss portion without providing a center rib on the upstream side of the boss portion of the two semi-disc-shaped valve bodies pivotally supported by the hinge pin. When fully closed, two semi-disc-shaped valve elements are configured so that the flat portions formed in the diameter direction of the two semi-disc-shaped valve elements are brought into contact with each other. It is characterized in that the above-mentioned two types of sub-valves are attached.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the embodiments shown in the drawings. FIG. 1 shows a fully closed state (left side of line YY) and a fully open state (right side of line YY) of a dual plate check valve according to an embodiment of the present invention, taken along line II of FIG. It is sectional drawing.

In FIG. 1, reference numeral 11 denotes a cylindrical main body, through which a cylindrical fluid passage 12 is formed.
It has a wafer-type structure that is disposed between flanges of a pipe pipe (not shown). In the center of the fluid passage 12 of the main body 11, a pair of two semi-disc-shaped valve bodies 14 (14a, 14b) are rotatably mounted via a hinge pin 13 fixed across the main body 11 in the diameter direction. It is pivoted.
The fact that the valve element 14 is urged in the direction to normally close the valve by receiving the elastic force of the spring 15 wound around the hinge pin 13 is the same as the conventional one (FIG. 4).

In the present invention, an elastic seat ring 16 is fitted and mounted on the entire inner peripheral surface of the main body 11, and the seat ring 16 has a cylindrical shape made of an elastic material such as rubber or soft elastic synthetic resin. When the valve is closed, the two valve bodies 14 are provided inside the intermediate portion between the inlet portion 16a and the outlet portion 16b.
And an inclined valve seat portion 16c that is in contact with the inclined surface 14d of the outer peripheral edge of the main body 11, is formed integrally, extends to the inlet / outlet end surfaces of the main body 11, and is disposed between the flanges of a piping pipe (not shown). At times, the connection portion 16e serves as a flange gasket. The thickness of the elastic material of the seat ring inlet portion 16a and the outlet portion 16b of the inlet-side fluid passage 12 of the seat ring 16 may be thinner than that of the inclined portion 16c. The contact angle between the inclined surface 16d of the inclined portion 16c of the seat ring and the inclined surface 16d is about 60 degrees, so that the surface pressure and impact caused by the seating of the valve body 14 are absorbed together with the main body inclined surface 11a.

The elastic material of the seat ring 16 is EPDM, which emphasizes corrosion resistance and heat resistance, and NB, which emphasizes oil resistance.
R and IIR, which emphasizes acid resistance, are compatible according to fluid specification conditions.
6 is JIS A spring hardness HS70-9
0, preferably inside and outside the HS80.

The valve element 14 attached to the inside of the seat ring 16 is composed of two semi-disc-shaped valve elements 14a and 14b. The bases of these two valve elements are displaced (shifted) to the rear side. A plurality of bearing bosses 17a, 1 formed respectively.
7b (in the embodiment shown in FIG. 2, the bearing boss 17a of the valve element 14a is disposed outside in the diameter direction (the direction of the hinge pin 13), and the bearing boss 17b of the valve element 14b is disposed inside thereof. ) Is rotatably supported by being inserted through a hinge pin 13 fixedly attached to the main body 11, and the pressure of the fluid flowing from the inlet (the lower part in FIG. 1) of the fluid passage 12 causes By turning in the outlet direction, both valves are simultaneously opened, and the flow path 12 is opened. FIG.
In the figure, 14e indicates a rotation locus, and the right valve body 14b indicates a fully open position.

When fully opened, the two valve bodies 14a and 14b have a rear seat 18 integrally formed on the back surface (exit surface) 14f of each valve body. Is stopped by contacting a stopper pin 19 attached to the motor. Further, in the present invention, the conventional center rib (7 in FIG. 4) is not provided on the upstream side, and the fluid at the time of full opening is configured to be directly divided into two along the front surface of the valve body boss portion 17, At this time, a curved surface 14c is formed on the front surface (inlet surface) 14g of both the valve bodies 14a and 14b so that the fluid flows smoothly.

On the other hand, as shown in FIG. 2, the spring 15 for urging the two valve bodies 14a and 14b in the valve closing direction includes a hinge pin 13 having no bearing bosses 17a and 17b for both valve bodies.
Are wound around the center of the shaft, and the long and short shaft side free ends 15a, 1
5b is locked to the back surfaces of the valve bodies 14a and 14b, respectively, to apply resilient force to the valve body 14 to maintain the sealing property when the valve is closed. Depending on the valve diameter, one or a plurality of springs 15 may be used, and bushes 20a and 20b may be inserted and the valve body 14 may be smoothly turned in order to prevent adjacent interference with the spring 15 or the bearing boss 17. I am trying to move.

When the valve is closed, the inclined surface 14d formed on the outer peripheral edge of both the valve bodies 14a and 14b is connected to the inclined surface 16d of the valve seat inclined portion 16c integrally formed inside the elastic seat ring 16.
The valve body inclined surface 14
d is a contact angle of 60 ° from the seat ring inclined surface 16d.
It is set slightly larger than inside and outside.

A pair of flat valve seats 14a, 14b are formed with flat seating flat surfaces 14h which are in contact with each other when the valve is closed, on the diametrical end faces parallel to the hinge pin 13 when the valve is closed. The inclined surface 14d of the valve body peripheral portion and the inclined surface 16d of the seat ring 16 play a role of reducing the surface pressure and impact.

Further, a pair of two semi-disc-shaped valve elements 14 are provided with a plurality of apertures, and one of the apertures has
As shown in FIG. 3 (a), a sub-valve element 21 which is urged in the closing direction by a coil spring 21a and is opened when the inlet-side fluid opens at a minute pressure is attached. As shown in (b), a sub-valve element 22 that is urged in the closing direction by a coil spring 22a and that opens when the outlet-side fluid is over-pressurized is attached.

The sub-valve element 21 shown in FIG.
A valve stem 21 disposed on the outlet side and penetrating through a valve stem guide 21c having a fluid passage 21b fitted into the opening of the valve element 14
d and is always in contact with a valve seat 21e formed around the opening by a coil spring 21a having a low spring force wound around the valve rod 21d. In the figure, 21f is a hexagon nut and 21g is a split pin.

The sub-valve element 22 shown in FIG. 3B is the same as the sub-valve element 21 described above, except that the sub-valve element 22 is disposed on the inlet side and has a coil spring 22a having a strong spring force. It is composed of components.

The above-mentioned sub-valve element 21 and sub-valve element 22 are usually provided at the portion A shown in the valve body 14a of FIG. 1 and the portion B shown in the valve body 14b, respectively. Valve element 14
a, 14b, two types of sub-valve 21
And 22 may be provided side by side.
1 and 22 may be provided on any of the two valve bodies 14a and 14b.

Further, the seat ring 16 against which the bearing boss 17 of the valve body 14 supported by the hinge pin 13 abuts.
As shown in FIG. 2, the inner rotation surface of the valve body 14 is formed so as to make a surface contact (primary seal) 16f. 13 (in the axial direction), the surface contact (primary seal) is made effective.

A packing 23 is provided at a contact portion between the seat ring 16 and the main body 11 along the hinge pin 13,
The packing 23 is pressed and fixed from the outside of the main body 11 in the hinge pin direction by a bearing sleeve 24, and the radial and thrust load of the hinge pin 13 is reduced by the plug 25.
It is to be received with.

Similarly to the hinge pin 13, the stopper pin 19 presses and fixes the packing from the outside of the main body 11 by a bearing sleeve, and reduces the radial and thrust vibrations of the stopper pin 19 in the plug 2.
6 and is relieved by the elastic body of the seat ring 16.

The hollow cylindrical main body 11 is formed of a rigid metal material, and is formed of a nonmetallic material such as a thermoplastic resin such as polyethylene, polypropylene and polystyrene and a thermosetting resin such as epoxy and phenol. Can be. Further, by adding glass fiber or carbon fiber to the above resin material, the strength can be further increased.

In addition, a seat ring 16 made of an elastic material can be attached to the entire inner peripheral surface of the main body 11 by integral vulcanization molding of a rigid material made of a metal material and the above-mentioned non-metal material. In this case, there are advantages such as the number of steps for fitting the seat ring 16 and the processing accuracy of the inner peripheral surface of the main body 11 can be reduced.

According to the above-described embodiment (embodiment), since the elastic seat ring 16 is attached to the entire inner peripheral surface of the main body 11 made of a rigid material, the material of the main body 11 can be made resistant to corrosive fluid. In addition to having a role of preventing corrosion, removing obstructions such as the center rib of the conventional valve, and forming the seating portion on a sloped (tapered) surface 16d from a flat surface,
The fluid passage 12 is also enlarged, and pressure loss (fluid resistance) can be reduced.

In addition, when the valve is closed, the valve seat in the conventional example is formed by an adhesive seat between the inclined surface 14d of the peripheral portion of both valve bodies 14a and 14b and the inclined surface 16d formed integrally inside the elastic seat ring. It is possible to eliminate the generation of the metal sound and the abnormal sound in the valve seat portion generated at the time of the contact.

Further, by arranging the bearing bosses 17a, 17b of the same shaped valve bodies 14a, 14b alternately in combination on the hinge pin 13, a pair of two valve bodies 14 can be formed. By increasing the accuracy of the contact between the ends, it is possible to prevent the movement, vibration, and the like in the direction of the hinge pin 13 when the valve is opened and closed.

In the dual plate check valve of the present invention, when the valve is closed, the flat plate portion 14h formed on the diametrical end surfaces of the semi-disc-shaped valve bodies 14a and 14b abuts on the valve body periphery. The impact between the inclined surface 14d of the portion and the valve seat inclined surface 16d integrally formed inside the seat ring can be reduced.

Further, by attaching two types of sub-valve elements 21 and 22 to a pair of two semi-disc-shaped valve elements, FIG.
, The small pressure on the inlet side passes through the fluid passage 21b, and opens when the surface pressure acting on the back surface (back surface) of the sub-valve element 21 exceeds the biasing force of the coil spring 21a in the valve closing direction. The fluid flows out from the seat 21e to the fluid passage 12 from the inlet side. At this time, the force of the coil spring 21a is calculated and manufactured depending on the valve opening pressure. The spring 21a is held by a hexagon nut 21f and fixed by a split pin 21g. In this way, the spring 21a of the valve 21 is set to be soft.

On the other hand, the sub-valve element 22 shown in FIG. 3 (b) is opened by an action similar to that described above at the time of excessive pressure exceeding the rated pressure, and the primary side of the fluid passage 12 is moved from the outlet side (secondary side). To drain. The spring force of the spring 22a is set to be harder than that of the spring 21a.

Thus, the hammering phenomenon (chattering) of the valve body and the like and the prevention of water hammer (water hammer) can be prevented, and the damage to the valve can be prevented.

Instead of making the outer peripheral edge of the pair of two semi-disc-shaped valve bodies inclined surfaces, a flat valve seat as in the conventional example (FIG. 4) can be used. ,
The opening ratio of the valve seat is inferior to that of the above-described embodiment as in the conventional example.

[0042]

As described above, according to the present invention,
A hinge pin installed diametrically across a fluid passage of a hollow cylindrical body made of a rigid material, and a pair of two hinged pins rotatably supported by the hinge pin to selectively open or close the fluid passage of the body. In a dual-plate check valve including a semi-disc-shaped valve element and a spring that constantly biases the valve element in a closing direction, the entire inner peripheral surface of the fluid passage of the hollow cylindrical body is formed of an elastic material. Attach a cylindrical seat ring
On the inner side of the seat ring, a valve seat portion is formed integrally with an outer peripheral edge portion of the two semi-disc-shaped valve bodies, and a plurality of the semi-disc-shaped valve bodies are provided on the pair of two semi-disc-shaped valve bodies. An opening is provided, and in the opening, a sub-valve urged by a spring in the closing direction and the inlet-side fluid is opened at a minute pressure, and a sub-valve urged by the spring in the closing direction and the outlet-side fluid is opened by an excessive pressure. The following effects are achieved by attaching the valve body.

(I) Various fluids having corrosive properties can be used.

(Ii) Metal noise or abnormalities generated when the valve is closed due to the contact between the peripheral portions of the two valve bodies and the valve seat formed integrally with the elastic seat ring mounted on the inner surface of the main body. Noise can be reduced and wear and damage in the valve seat can be prevented.

(Iii) the inlet side fluid is released when the pressure is very small,
A relief valve or bypass that prevents damage to the valve with the effect of a minute pressure relief valve that prevents hammering of the valve body, etc. and that opens when the outlet side fluid is overpressured, preventing the water hammer phenomenon of the valve body, etc. The valve effect can prevent the valve from being damaged.

Further, the valve seat portion formed integrally with the inside of the cylindrical seat ring made of an elastic material is bonded to the inclined surfaces formed on the outer peripheral edges of the two semi-disc-shaped valve bodies when the valve is closed. The above-mentioned effect (i) is obtained by forming an inclined surface and attaching the above-described two types of sub-valve elements to a pair of two semi-disc-shaped valve elements.
In addition to (iii), the opening ratio of the valve seat portion can be increased, and the pressure loss and the fluid resistance can be reduced in combination with the removal of the conventionally used central rib.

The two semi-disc-shaped valve elements pivotally supported by the hinge pins are brought into surface contact with the rotating surfaces of the seat ring, and a shaft sealing member is provided at the hinge pin insertion portion of the seat ring. The two types of sub-valve elements are fixed to the pair of semi-disc-shaped valve elements via a sleeve, and in addition to the above-described effects (i) to (iii), external leakage along the hinge pin is achieved. And can receive the radial load and thrust load applied to the hinge pin from the bearing bosses of the two valve bodies, and protect the through bearing of the main body that supports the hinge pin. As a result, the durability of the check valve can be increased.

Further, the fluid at the time of full opening is directly divided into two along the front surface of the boss portion without providing a center rib on the upstream side of the boss portion of the two semi-disc-shaped valve bodies pivotally supported by the hinge pin. When fully closed, two semi-disc-shaped valve elements are configured so that the flat portions formed in the diameter direction of the two semi-disc-shaped valve elements are brought into contact with each other. By attaching the two types of sub-valves described above, the above-described effects (i) to
In addition to (iii), not only can the fluid resistance and pressure loss at the inlet part be reduced, but also when the valve is closed,
It is possible to reduce the impact on the contact inclined surface formed on the valve body peripheral portion and the valve seat.

[Brief description of the drawings]

FIG. 1 shows a fully closed state (left side) and a fully opened state (right side) of a dual plate check valve showing one embodiment (example) of the present invention.
FIG. 3 is a sectional view taken along line II of FIG.

2 is a cross-sectional view taken along the line II-II of FIG. 1 showing a fully closed state, and the lower half is a top view of FIG.

3A is a cross-sectional side view of a minute pressure release valve provided with a sub-valve on the outlet side, and FIG. 3B is a cross-sectional side view of an excessive pressure release valve provided with a sub-valve on the inlet side.

FIG. 4 is a sectional view of a dual plate check valve showing a conventional example.

[Explanation of symbols]

 Reference Signs List 11 main body 11a main body inclined surface 12 fluid passage 13 hinge pin 14, 14a, 14b valve body 14c valve body curved surface 14d valve body inclined surface 14f valve body outlet surface 14g valve body inlet surface 14h valve body seating plane 15 spring 16 seat ring 16a seat ring Inlet part 16b Seat ring outlet part 16c Seat ring inclined part 16d Seat ring inclined surface 16e Seat ring connecting part 16f Seat ring plane contact part 17, 17a, 17b Bearing boss 18 Boss part 19 Stopper pin 20a, 20b Bush 21, 22 Secondary valve Body 21a, 22a Coil spring 21b, 22b Fluid passage 21c, 22c Valve stem guide 21d, 22d Valve stem 21e, 22e Valve seat 21f, 22f Hex nut 21g, 22g Split pin 23 Packing 24 Bearing sleeve 25, 26 Plug

Claims (4)

[Claims] 1. A hinge pin installed across a fluid passage of a hollow cylindrical body made of a rigid material in a diametrical direction, and a pivotally rotatably supported by the hinge pin to selectively open or close the fluid passage of the body. A pair of semi-disc-shaped valve bodies to be
A dual plate check valve having a spring that constantly biases the valve body in a closing direction, wherein a cylindrical seat ring made of an elastic material is mounted on the entire inner peripheral surface of the fluid passage of the hollow cylindrical body. On the inner side of the seat ring, a valve seat portion is formed integrally with an outer peripheral edge portion of the two semi-disc-shaped valve elements, and a plurality of the semi-disc-shaped valve elements are provided on the pair of two semi-disc-shaped valve elements. A sub-valve body which is urged in a closing direction by a spring and opens the inlet-side fluid at a minute pressure and an outlet-side fluid urged by a spring in a closing direction and opens at an excessive pressure. Dual plate check valve with sub-valve attached. 2. A valve seat portion integrally formed inside a cylindrical seat ring made of an elastic material is bonded to an inclined surface formed on the outer peripheral edge of two semi-disc-shaped valve bodies when the valve is closed. 2. The dual plate check valve according to claim 1, wherein the check valve is formed as an inclined surface. 3. The bearing according to claim 1, wherein the rotating surfaces of the two semi-disc-shaped valve bodies pivotally supported by the hinge pin and the seat ring are in surface contact with each other, and a shaft sealing member is provided at the hinge pin insertion portion of the seat ring. 3. The dual plate check valve according to claim 1, wherein the check valve is fixed via a sleeve. 4. A fully opened fluid is directly divided into two along the front surface of the boss portion without providing a center rib on the upstream side of the boss portion of the two semi-disc-shaped valve bodies pivotally supported by the hinge pin. 4. The device according to claim 1, wherein when the valve is fully closed, the flat portions formed in the diameter direction of the two semi-disc-shaped valve bodies are brought into contact with each other. The dual plate check valve according to claim 1.