JP3075700B2 - Dual plate check valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer-type dual plate check valve having two semi-disc-shaped valve elements, which have increased corrosion resistance of a main body, an opening ratio of a valve seat, and reduced pressure loss. About.

[0002]

2. Description of the Related Art Conventionally, a pair of semi-disc-shaped valve bodies are pivotally supported on a main body by a single hinge pin while being urged by a spring.
Normally, the valve body is urged and held to the closed position by the spring force of the spring,
The valve body is rotated to the valve-open position against the spring force of the spring by the fluid pressure of the normal flow to allow the flow of the fluid, while when a reverse flow occurs, the valve body is caused by the spring force of the spring. 2. Description of the Related Art A wafer type dual plate check valve in which a valve is quickly closed is known, and an example thereof is shown in FIG.

In FIG. 5, two semicircular valve elements 3a and 3b rotatably supported by a hinge (pin) 2 on a housing (main body) 1 are wound around the hinge pin 2 and both ends are formed of two sheets. The coil springs 4 respectively abutted on the back surfaces of the valve bodies are urged in the valve closing direction (the direction in which the two valve bodies themselves open). In the figure, reference numeral 5 denotes a stop pin installed at a position sandwiched between the back surfaces of both valve bodies when the valve is opened;
Is a flat planar valve seat, and 7 is a central rib (post) provided upstream of the hinge pin 2.

[0004] The hinge pin 2 and the stop pin 5
Usually, each is inserted into a hole formed in the housing 1 and fixed to the housing 1, and is fixed by a screw plug 8 attached from the outside of the housing. The screw plug 8 needs to be easily detachable so that parts such as the pin itself, the valve bodies 3a and 3b, and the spring 4 can be easily replaced as needed.

On the other hand, conventionally, there has been a problem that these plugs 8 may be loosened due to, for example, long-term vibration, causing leakage, and may be loosened due to thermal expansion or contraction due to a temperature difference. Leaks can also be localized corrosion and
This was caused by the threads of the plug 8 being exposed to corrosive conditions that would leak or relax.

As an improvement over the above-mentioned problems, it is disclosed in Japanese Patent Publication No. Hei 5-78712, which is shown in FIG. This inserts into diametrically opposed and axially extending slots formed in the inner wall of an annular housing 11 to form insertion members 12, each of which has two through transverse holes. The hinge member 13 and the stop pin 14 are fitted and assembled, and the insertion member 12
Is held in place by a ring 15, usually wedge-shaped in cross section, which fits into a corresponding slot in one end of the inner surface of the housing and is provided with a diametrically opposed countersunk screw 16 Is held inside the slot. The hinge pin 13 has a valve plate 17a,
17b is rotatably supported, and a spring (spring) 18
Urged in the valve closing direction. The joint area between the retaining ring 15 and the housing 11 is a gasket 19
The reference numeral 11b denotes the downstream end surface 11a of the
And the ring 15 and the housing 11
The gasket 19 blocks the leak between them. In the figure, reference numeral 10 denotes a pipe flange.

[0007]

In the above-described conventional dual plate check valve (FIG. 5), the hinge pin 2 and the stop pin 5 are inserted into holes formed in the housing 1 and the screw plug 8 is provided. Therefore, external leakage occurs due to long-term vibration, temperature difference, and local corrosion, and a means for preventing the external leakage is required.

FIG. 6 shows a circuit diagram of FIG.
However, the inner surface (fluid passage) of the conventional wafer type dual plate check valve is a rigid material, that is, an as-cast state of a cast product, so that expensive materials such as corrosion-resistant stainless steel are used. At present, there is not much corrosion resistance except for. Also in this case, FIG.
The strut (not shown), which crosses in the housing diametrical direction and is similar to the strut (center rib) 7 in (b), is located in the flow passage, which causes a maximum cause of fluid resistance, and thus causes a problem that the aperture ratio is reduced. I was

Furthermore, the hinge pin 13 and the stop pin 1
And a wedge-shaped ring for holding the insertion member 12 at a predetermined position when disposing the insertion member 12 without taking into consideration the sealing performance between the pins 13 and 14. It is necessary to install the gasket 19 at the substantially central portion of the gasket 19 installed at the joint area between the housing 15 and the housing 11. Unless the gasket 19 is properly provided at this specified position, external leakage may occur. There was a problem that it could not be stopped.

The present invention solves the above-mentioned problems of the prior art, can endure the use of various corrosive fluids, and has a fluid accompanying wear and damage due to vibration and impact at the main body supporting portions of the hinge pin and the stop pin. It is an object of the present invention to provide a dual-plate check valve which prevents the occurrence of external leakage of the valve.

[0011]

Means taken by the present invention to solve the above-mentioned problems include a hinge pin and a stop pin installed diametrically across a fluid passage of a hollow cylindrical body made of a rigid material. 2 that is pivotally supported by the hinge pin to selectively open or close the fluid passage of the main body;
In a dual plate check valve comprising a pair of semi-disc-shaped valve bodies and a spring for constantly biasing the valve bodies in a closing direction, a reinforcing member is integrated with the entire inner peripheral surface of the hollow cylindrical main body. A seat ring made of vulcanized elastic material is inserted and supported, and both ends of the hinge pin and the stop pin are supported by a reinforcing material of the seat ring, and both ends of the hinge pin and the stop pin are pivotally supported inside the main body. It is characterized by doing.

[0012] Further, the rotating surfaces of the two semi-disc-shaped valve elements pivotally supported by the hinge pin and the seat ring are brought into surface contact with each other to form a primary seal and to be inserted into the hinge pin insertion portion of the seat ring. A secondary seal is formed by providing a shaft sealing mechanism.

[0013] The seating surfaces of the outer peripheral edges of the pair of two valve bodies on the seat ring are inclined surfaces, and the diametrical seating surfaces of the valve bodies are flat surfaces. To
It is characterized in that projections are provided which come into contact with each other when the valve is opened.

Further, both end surfaces of the seat ring inserted into the entire inner peripheral surface of the hollow cylindrical main body are enlarged and extended in the axial direction so as to function as a gasket at the time of disposing the valve. The surface is enlarged in the diametric direction to prevent external leakage of fluid from the hinge pin portion and the stop pin portion.

[0015]

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 is a sectional view showing 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.

In FIG. 1, reference numeral 21 denotes a hollow cylindrical body, which has a cylindrical fluid passage 22 formed therethrough, and is a wafer-shaped body disposed to be sandwiched between flanges of piping pipes (not shown). It has a structure. In the center of the fluid passage 22 of the main body 21, a pair of semi-disc-shaped valve bodies 24 (24a, 24b) are rotatably provided via hinge pins 23 fixed across the main body 21 in the diameter direction. It is pivoted. The valve element 24 includes a spring 25 wound around the hinge pin 23.
It is urged in the direction to always close by receiving the elastic force of
The fact that the stop pin 26 is provided in parallel with the hinge pin 23 is not different from the conventional one (FIG. 5).

In the present invention, the hollow cylindrical main body 21 is provided.
Both ends are made slightly thicker than the middle part and reinforced from the cross-sectional shape, and are formed on the entire inner peripheral surface thereof with an elastic material such as rubber or soft elastic synthetic resin integrally vulcanized with the reinforcing material 27. The seat ring 28 is inserted (fitted and attached). The entire inner peripheral surface of the main body 21 or only the both ends may be processed with increased accuracy so that the outer peripheral surface of the reinforcing member 27 that is in contact with the inner peripheral surface of the main body 21 is preferable to be inserted. Alternatively, the middle portion of the reinforcing member 27 except for the end portion may be recessed.

As described above, the seat ring 2 is
The seat ring (valve seat) is completed by integrally vulcanizing the elastic material of No. 8, and the seat ring 28 is provided inside the intermediate portion between the inlet portion 28a and the outlet portion 28b when the valve is closed. The inclined surface 24c of the outer peripheral edge of the two valve bodies 24 and the inclined valve seat portion 28c that is in contact with the adhesive are integrally formed, extend to the inlet / outlet end surfaces of the main body 21, and are sandwiched between flanges of a piping pipe (not shown). When it is installed, it acts as a flange gasket. Seat ring inlet portion 28a and outlet portion 28 of inlet-side fluid passage 22 of seat ring 28
The thickness of the elastic material b may be thinner than the inclined portion 28c. Further, the inclined portion 28 of the seat ring is used.
The abutment angle of the inclined surface 28d of c is about 60 degrees, so that the surface pressure and impact caused by the seating of the valve body 24 are absorbed together with the inclined surface 27a of the reinforcing member 27. Assuming that the inclination angle is 60 °, the inclination angle of the valve element peripheral portion 24c is 6 °.
By processing the angle slightly larger than 0 °, the contact portion is located above the inclined surface 28d of the seat ring, and the contact surface is reduced, thereby ensuring the sealing performance.

As described above, since the seating of the valve element is caused by the bias of the spring and the reverse flow of the secondary pressure, the valve body is formed thicker than the other parts in consideration of vibration, impact, etc. on the inclined surface 28d. At the same time, the reinforcing member inclined portion 27a is also formed in the same shape and integrally.

As described above, the seat ring connecting portion 28e with the piping flange (not shown) is a portion that comes into contact with the mating flange surface at the time of disposition, and is formed by bending from a cylindrical portion. The outer shape of the part is shown in an enlarged scale in FIG.
It is slightly larger than the reinforcing member 27 and serves as a packing for preventing external leakage in the event that fluid leaks from the pin portions 23 and 26 of the hinge pin and the stop pin. Also,
It is formed so as to extend by α from the width of the main body 21 in the axial direction, and serves as a gasket between piping flanges (not shown) at the time of installation, thereby eliminating the need for a commonly used auxiliary material (gasket) and reducing costs. We are trying to decrease.

The elastic material of the seat ring 28 is made of EPDM having corrosion resistance and heat resistance, NBR having oil resistance, and IIR having acid resistance so that it can be changed and replaced depending on fluid conditions.
In addition, a material such as CR having weather resistance is prepared, and the surface hardness of the inner peripheral surface of the seat ring 28 is HS70 to 90 in JIS A spring hardness, preferably HS80 inside and outside.

The valve element 24 attached to the inside of the seat ring 28 is composed of two semi-disc-shaped valve elements 24a and 24b, and the bases of these two valve elements are displaced (shifted) to the rear side. A plurality of bearing bosses 29a, 2 formed respectively.
9b (in the embodiment shown in FIG. 2, the bearing boss 29a of the valve body 24a is disposed outside in the diametric direction (the direction of the hinge pin 23), and the bearing boss 29b of the valve body 24b is disposed inside. ) Is rotatably supported by being inserted through a hinge pin 23 fixedly attached to the main body 21, and the pressure of the fluid flowing from the inlet (the lower portion in FIG. 1) of the fluid passage 22 causes The valve is rotated in the outlet direction like the right valve body 24b in FIG. 1 so that both valves are simultaneously opened, and the flow path 22 is opened.

At the time of opening the valve, a stop pin 26 is provided to prevent the valve body from rotating too far. However, immediately before the stop pin abuts on the valve body boss seat 24d, the center of the rear surface 24e of the valve body is substantially removed. The convex portion 24f formed integrally with the portion is brought into contact first, and the vibration to the stop pin 26 portion,
Shock, etc. are mitigated. Further, the convex portion 24f can also be used as a cutting claw at the time of processing the valve body, thereby improving the accuracy of the valve body outer peripheral inclined surface 24c.

On the other hand, when the valve body is closed, both valve bodies 24a, 24a,
An inclined surface 24c formed on the outer peripheral edge of the valve seat 24b is provided with a valve seat inclined portion 28 integrally formed inside the elastic seat ring 28.
c is attached to the inclined surface 28d,
At this time, the hinge pin 2 of the pair of two valve bodies 24a, 24b
When the valve is closed, the flat seating planes 24g formed so as to abut each other on the diametrical end surfaces parallel to the end surfaces 3a. It plays a role of alleviating the surface pressure and impact with the inclined surface 28d of 28.

As shown in FIG. 2, a spring 25 for urging the valve bodies 24a and 24b in the valve closing direction is attached to the center of the hinge pin 23 where the bearing bosses 29a and 29b are not provided. Wound so as to face each other, and the spring 25
The bushes 30 and 3 are provided to prevent the bearing boss 29b and the spring 25 from interfering with each other at the time of rotation.
1 for smooth rotation of the valve body 24.

Further, the boss flat surface 24h of the valve element 24 which rotates through the hinge pin 23 comes into surface contact with the surface contact portion 28f of the seat ring 28 to serve as a primary seal, and when the hinge pin 23 is vertical. Acts as a thrust bearing. A shaft sealing portion 28g having a trapezoidal cross section formed in the circumferential direction of the fitting surface with the hinge pin 23 and the stop pin 26.
(FIG. 3) plays a role of sealing the shafts of the pins 23 and 26, and at the same time, mitigating vibration, impact, and the like when the valve is closed or opened.

Further, a bearing 32 provided on the supporting portion of the reinforcing member 27 for supporting both ends of the pins 23 and 26 is provided.
These pins function as radial bearings when they are horizontal. In FIG. 1A, reference numeral 24j denotes a front surface of the valve body, and 24k denotes a rotation locus of the valve body.

FIG. 3 is an enlarged sectional view of a main part of the portion A (boss portion) in FIG. 2. A left side A of the line YY 'shows an assembled state where the hinge pin 23 is inserted, and a right side B is a hinge pin. 23 shows a state before the insertion of No. 23.

FIG. 4 is an enlarged sectional view of a main part showing another embodiment of the part A in FIG. 2. On the left side of the line Y--Y ", a reinforcing member 27 supporting the end of the hinge pin 23 is provided. The lower end surface of the bearing 32, the seat ring 28 and the hinge pin 2
An O-ring 33 is provided so as to be in contact with three of the three,
The shaft sealing action of the pin 23 is performed. Also Y-
On the right side of the Y ″ line, an O-ring 33 is provided on the peripheral surface of the hinge pin 23 penetrating the reinforcing member 27 to perform a shaft sealing action on the pin portion. The same applies to 26.

On the other hand, the fishing bolt 34 is
6 is fixed to the main body in the same direction as that of the pin 6 so that the orientation (vertical or horizontal) of each pin can be confirmed at the time of disposition.
Generally, in a horizontal pipe, when the pins are arranged in a horizontal direction, the acting force of the valve body at the upper part and the valve body at the lower part are not the same, and the valve body is simultaneously opened and closed. Requires a different spring force, which may cause problems for actual specification conditions.

On the other hand, when the respective pins are similarly arranged in the vertical direction in the horizontal piping, the valve bodies are arranged symmetrically, and the acting force on the valve bodies becomes the same. As a result, the opening and closing of the valve is the same, and there is little problem. Also, when the pipes are provided in a vertical pipe, the pins are in the horizontal direction, but there is no problem.

In these descriptions, since each pin is arranged vertically or horizontally, the valve body and the seat ring are used as thrust receivers of the surface contact portion 28f so as to receive the valve body's own weight and receiving pressure. In a horizontal state, the bearing 32 is inserted into the seat ring reinforcing member 27 as described above to receive the load on each pin.

The hollow cylindrical main body 21 is formed of a rigid metal material, and is formed of a non-metallic 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.
Further, the reinforcing member 27 is usually formed of a rigid metal material, and is formed of a non-ferrous metal material.

According to the above-described embodiment (embodiment), a seat ring 28 made of an elastic material integrally vulcanized and formed with a reinforcing material 27 is inserted into the entire inner peripheral surface of a main body 21 made of a rigid material. Applicable to corrosive fluids, it can correspond to a wide range of fluid specifications, and the elasticity and reinforcing material are vulcanized together, so that the thickness change between the cylindrical part and the inclined part can be set freely, and It exhibits the characteristics of each member such as the reinforcing effect by vulcanization, and has a synergistic effect. In addition, there is a cost advantage due to the effect of mass production as a part, which leads to a low price of the whole product, and it is easy to assemble and replace parts such as a seat ring and a valve body which are highly likely to be damaged.

By removing the diametrical column (central rib) provided at the inlet of the conventional valve and forming the seat of the valve element at the time of closing the valve on the inclined surface 28d from the flat surface, the fluid passage is formed. 22 is also enlarged, and pressure loss (fluid resistance) can be reduced.

The hinge pin 23 and the stop pin 26
Are supported by the seat ring reinforcing member 27,
Since both ends of these pins are pivotally supported inside the main body 21, the shaft sealing portions of these two pins are formed inside the main body 21, and it is not necessary to use a plug or the like from the outside. In addition, it is possible to reliably prevent leakage to the outside of the flow path, and to play two roles of a buffering effect such as vibration and impact acting on these pins.

Further, 2 supported by the hinge pin 23
The rotating surfaces of the two semi-disc-shaped valve bodies 24 and the seat ring 28 are brought into surface contact 28f to form a primary seal, and a shaft sealing mechanism 28g is provided at a hinge pin insertion portion of the seat ring 28 to provide a secondary seal. Is formed, the thrust bearing action of the valve body and external leakage along the hinge pin can be prevented.

A diametrical seating surface 24g of the valve body 24 is also provided.
Is a flat surface, so that excessive impact due to backflow pressure on the inclined surface 28d of the seat ring at the time of closing the valve is reduced,
In addition, approximately in the center of the back surface 24e of the valve bodies 24a and 24b,
By providing the protruding portions 24f that come into contact with each other when the valve is opened, the two boss seats 24d are
The protrusions 24f abut each other immediately before abutment of the stopper 6, preventing impact vibration of the stop pin 26 and the like, and reducing external leakage from the pin portion. On the other hand, there is also an advantage as a manufacturing (working) method that can be used as a cutting seat for cutting the outer periphery of the valve body and the like by the two boss seats 24d. This is the same for the projection 24f.

The connecting portion 28e of the seat ring 28 is made slightly larger (α + α) than the width of the main body 21 so as to function as a gasket when the gasket is tightened, so that the outer diameter of the connecting portion 28e is similarly determined. Is slightly larger than the inner diameter of the main body 21 to prevent the fluid temporarily leaking from the pin portions 23 and 26 from leaking out of the main body.

Further, by using a non-metallic material for the main body, it is possible to achieve further weight reduction, mass production, and aesthetic sensation. Further, by mixing a coloring pigment, the coating work after the product can be performed. Can be omitted.

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. 5) 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 and a stop pin installed diametrically across a fluid passage of a hollow cylindrical body made of a rigid material, and two pivotally supported by the hinge pin to selectively open or close the fluid passage of the body. A pair of semi-disc-shaped valve elements,
In a dual plate check valve provided with a spring that constantly biases the valve body in a closing direction, a seat ring made of an elastic material integrally vulcanized and molded with a reinforcing material is inserted into the entire inner peripheral surface of the hollow cylindrical main body. The following effects are achieved by fitting, supporting both ends of the hinge pin and the stop pin with the reinforcing material of the seat ring, and pivotally supporting both ends of the hinge pin and the stop pin inside the main body. You.

(I) The present invention is also applied to corrosive fluids, and can correspond to a wide range of fluid specifications.

(Ii) Since the elastic material and the reinforcing material are integrally vulcanized, the characteristics of each member such as a change in the thickness of the cylindrical portion and the inclined portion and a reinforcing effect by the integrated vulcanization are exerted and synergized. effective.

(Iii) Since the shaft sealing portions of the hinge pin and the stop pin are formed inside the main body, there is no need to use a plug or the like from the outside, so that leakage to the outside of the flow path is reliably prevented. At the same time, it can play two roles of a buffering effect such as vibration and impact acting on these pins.

(Iv) There is a cost advantage due to the effect of mass production as a part, which leads to a low price of the whole product, and parts other than the main body such as a seat ring and a valve body which are highly likely to be damaged are assembled in advance and the main body is assembled. , Assembly is facilitated.

Further, the rotating surfaces of the two semi-disc-shaped valve bodies pivotally supported by the hinge pins and the seat ring are brought into surface contact with each other to form a primary seal, and a shaft seal is formed in the hinge pin insertion portion of the seat ring. By providing the mechanism and forming the secondary seal, it is possible to prevent external leakage of fluid along the hinge pin, and to have a thrust bearing effect of the valve body and a radial bearing effect by the support of the reinforcing material.

The seating surface of the outer peripheral edge of the pair of two valve bodies on the seat ring is an inclined surface, the diametrical seating surface of the valve body is a flat surface, and a substantially central portion of the back surface of each valve body. To
By providing the convex portions that come into contact with each other when the valve is opened, the opening ratio in the flow path can be reduced by the seating portion formed on the inclined surface in conjunction with the removal of the column portion provided at the inlet portion of the conventional valve. In addition to the above, a more effective seal can be exhibited. In addition, the diametrical seating plane of the valve body reduces excessive impact on the inclined surface of the seat ring when the valve is closed, and the convex portion provided on the back of each valve body provides impact vibration at the stop pin when fully opened. Etc. can be prevented.

Further, both end surfaces of the seat ring inserted into the entire inner peripheral surface of the hollow cylindrical main body are enlarged and extended in the axial direction, and both end surfaces of the seat ring are enlarged in the diameter direction. In addition to serving as a gasket for the pipe flange, it has the effect of preventing fluid temporarily leaking from the pin portion from leaking out of the main body.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view showing a fully closed state (left side) and a fully opened state (right side) of a dual plate check valve according to an embodiment (example) of the present invention, and FIG. It is a principal part expanded sectional view of B part of (a).

2 shows a fully closed state in an upper half part in a sectional view taken along line II-II in FIG. 1, and a lower half part shows a fully closed state in a top view in FIG.

FIG. 3 is an enlarged sectional view of a main part of a portion A in FIG. 2; A on the left side of line YY 'shows a state after hinge pin assembly, and B on the right side shows a state before hinge pin assembly.

FIG. 4 is an enlarged sectional view of a main part showing another example of the part A in FIG. 2, wherein a left side and a right side of a YY ″ line show different embodiments.

5A and 5B show a conventional example, in which FIG.
(B) is a sectional side view.

6A and 6B show different conventional examples, wherein FIG. 6A is a front view and FIG.
Is a sectional side view of a main part.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Main body 22 Fluid passage 23 Hinge pin 24, 24a, 24b Valve 24c Peripheral inclined surface 24d Boss seat 24e Back surface 24f Convex portion 24g Diameter plane 24h Boss plane 25 Spring 26 Stop pin 27 Seat ring reinforcing member 27a Reinforcement inclined portion 28 Seat ring 28a Seat ring inlet 28b Seat ring outlet 28c Seat slant 28d Seat slant 28e Connection 28f Surface contact 28g Shaft seal 29,29a, 29b Boss 30,31 Bush 32 Bearing 33 O-ring 34 Fishing bolt

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F16K 1/00-1/226 F16K 15/00-15/20 F16K 27/02 F16K 47/02

Claims (4)

(57) [Claims] 1. A hinge pin and a stop pin installed across a fluid passage of a hollow cylindrical body made of a rigid material in a diameter direction, and are rotatably supported by the hinge pin to selectively open a fluid passage of the body. Or, in a dual plate check valve comprising a pair of two semi-disc-shaped valve bodies to be closed and a spring for constantly biasing the valve body in the closing direction, the entire inner peripheral surface of the hollow cylindrical body is A seat ring made of an elastic material integrally vulcanized and molded with a reinforcing material is inserted and supported, and both ends of the hinge pin and the stop pin are supported by the reinforcing material of the seat ring. Dual plate check valve that is pivotally supported inside. 2. A primary seal is formed by bringing the rotating surfaces of two semi-disc-shaped valve bodies pivotally supported by a hinge pin and a seat ring into surface contact with each other, and a shaft seal is formed in a hinge pin insertion portion of the seat ring. The dual plate check valve according to claim 1, wherein a secondary seal is formed by providing a mechanism. 3. An inclined surface is used as a seating surface of an outer peripheral edge of a pair of two valve bodies with respect to a seat ring, and a diametrical seating surface of each of the valve bodies is a flat surface. 3. The dual plate check valve according to claim 1, further comprising a plurality of projections which are in contact with each other when the valve is opened. 4. The seat ring, which is inserted into the entire inner peripheral surface of the hollow cylindrical main body, is extended and extended in the axial direction so as to function as a gasket when disposing the valve. The dual plate check valve according to any one of claims 1 to 3, wherein a surface is enlarged in a diameter direction to prevent external leakage of fluid from the hinge pin portion and the stop pin portion.