KR20030004009A - Butterfly valve - Google Patents

Abstract

PURPOSE: To provide a butterfly valve, in which a valve element peripheral portion almost simultaneously abuts on protrusions of a seat ring. CONSTITUTION: By gradually varying inclination of a pressure contact surface 28 of the protrusion 26, the pressure contact surface 28 in the vicinity of a valve shaft 3 is sharply inclined, and the surface 28 far from the valve shaft 3 is gently inclined. The abutting portion 31 of the pressure contact surface 28 abutting on the peripheral portion of the valve element 2 is expanded to an opening direction side more in a portion far from the valve shaft 3 than in the vicinity of the valve shaft 3. The peripheral portion of the valve element 2 almost simultaneously abuts on an abutting portions of protrusions 26 of the peripheral portion of the valve element 2.

Description

Butterfly valves {BUTTERFLY VALVE}

The present invention relates to a butterfly valve for rotating the valve body equipped in the valve box around the valve shaft to adjust the opening and closing of the valve and the flow rate.

In general, a butterfly valve rotates a substantially disk-shaped valve body provided in a valve box around a valve shaft in a radial direction of the valve body to control opening and closing of the valve or adjusting the flow rate. The seat ring which consists of rubber-like elastic bodies is attached to it. This seat ring is press-contacted by the periphery of the valve body which rotates around the valve shaft so that the plate surface is perpendicular to the flow path direction (in the closing direction) when the valve is closed, and seals between the valve box inner peripheral surface and the valve body.

8 shows an example of the sheeting. The seat ring 101 is formed in a ring shape having a substantially U-shaped cross section in which the outer surface side is opened, and the outer surface side thereof is fitted to the projection on the inner circumferential surface of the valve box and mounted on the valve box. Moreover, the inner peripheral surface is provided with the protrusion 102 which protrudes in the continuous direction continuously in the circumferential direction, and this protrusion 102 is pressed against the periphery of the valve body 103, and seals between the valve bodies 103. As shown in FIG.

In the seat ring of the type which is press-contacted radially outward of the flow path by the periphery of the valve body, the periphery of the valve body causes the seat ring to radially outwardly flow the flow path until the periphery of the valve body contacts and obtains a predetermined amount of pressure contact deformation. Since the surface slides toward the closing direction while being press-contacted at, the torque required for closing the valve is increased by the frictional force at this time.

On the other hand, in the seat ring 101 shown in FIG. 8, since the protrusion 102 of the inner peripheral surface is pressed and sealed in the closing direction at the peripheral part of the valve body 103, the frictional force at the time of valve closing is minimized, The torque required for valve closing can be reduced.

In short, in this seating, the valve body 103 in the closed state X rotates in the closing direction around the valve shaft 104, whereby the valve body 103 is in contact with the protrusion 102 ( Y), and the valve body 103 further rotates in the closing direction to reach the closed state Z. When moving from the contact state (Y) to the closed state (Z), the periphery of the valve body (103) slides the surface of the projection (102), but does not actively pressurize in the radially outward direction of the flow path. The friction force becomes small.

In the closed state Z, the reaction force which tries to return the periphery of the valve body 103 to the closing direction in the part (range of height H) pushed in the closing direction of the protrusion 102 arises, and this reaction force overcomes the fluid pressure. It is sealed by putting it out.

Since the reaction force is increased in accordance with the pressure contact deformation amount L when the valve body 103 moves from the contact state Y to the closed state Z, the pressure contact deformation amount L of the protrusion 102 is increased in the circumferential direction. The protrusions 102 have the same cross-sectional shape in the circumferential direction so as to be substantially constant. When the projection 102 is viewed in the direction of the valve shaft 104, the contact portion 105 forms a straight line parallel to the axis 106 of the projection 102 and the valve body in the closed state Z. It is substantially parallel to the periphery of 103, and the space | interval becomes a press contact deformation amount (L).

By the way, when viewed in the valve axis direction, the periphery of the valve body forms a straight line through the valve shaft, and the straight line of the periphery of the valve body rotates around the valve shaft. Since the straight line of the valve body peripheral part does not overlap with the straight line formed by the contact part, at the time of valve closing, the peripheral part of the valve body does not contact the protrusion at the same time, and the contact timing is shifted depending on the distance from the valve shaft.

In short, the amount of movement of the periphery of the valve body when the valve body is rotated around the valve shaft is proportional to the distance from the valve shaft in the direction orthogonal to the valve shaft, and the movement amount is equal to the compression strain L. Since the rotational movement angle of the sieve becomes larger in the vicinity of the valve shaft than in the vicinity of the central shaft between the valve shafts, when the central portion is in the contact state Y, the protrusion is pressed against the valve shaft to some extent.

However, even in the state of being press-contacted with the protrusion near the valve shaft, it cannot be sealed until the valve body peripheral part contacts the protrusion near the center, so that the valve body peripheral part contacts near the valve shaft and then comes in contact with the center part. The pressure welding of the projection near the valve shaft does not contribute to the seal and is a factor that unnecessarily increases the torque at the time of closing the valve.

In addition, when the flow rate is reduced by rotating the valve body in the closing direction, the peripheral portion of the valve body easily comes into contact with the protrusion in the vicinity of the valve shaft, so there is a concern that the sealing may deteriorate at this portion.

1 is a front view of a butterfly valve of the present invention.

FIG. 2 is a cross-sectional view along the line A-A in FIG.

3 is a valve axial cross-sectional view of the seat ring.

Fig. 4 is a cross sectional view at right angles to the valve shaft of the seat ring.

Fig. 5 is a sectional view of the main portion showing the form in which the periphery of the valve body presses the protrusions.

6 is a view for explaining the relationship between the press contact state near the boss and near the center between the bosses.

7 is a diagram for explaining the relationship between reaction force and pressure of the pressure contact surface.

8 is a sectional view of principal parts of a conventional seat ring.

(Explanation of symbols for the main parts of the drawing)

One … Valve box 2. Valve body

3…. Valve shaft 4.. Seat ring

23. Boss section 26. Stone

27. Top 28. Pressure contact

29. Protective face 31. Contact

In view of the above problems, the present invention is installed on the inner circumferential surface of the valve box of the butterfly valve, the valve rod so as to face each other in the radial direction of the flow path, assuming a seat ring for sealing between the inner circumferential surface of the valve box when the valve is closed. Two valve shaft holes for penetrating are formed, and a boss portion is formed around the valve shaft hole, and the boss portions project continuously inward in the circumferential direction so as to be press-contacted in the closing direction at the valve periphery at the time of valve closing. The present invention provides a seat ring formed with a protrusion, and a seat ring aimed at bringing the contact portion of the protrusion into contact with the periphery of the valve body at about the same time, and a butterfly valve equipped with the seat ring.

When the contact portion has a curved shape bulging away from the boss in the circumferential direction, it is different from the case where the same cross-sectional protrusion is adopted in the circumferential direction, and the valve body periphery can be brought into contact with the contact portion of the protrusion approximately simultaneously. In other words, in the case where the protrusions have the same cross-sectional shape in the circumferential direction and the contact portion is parallel to the axis of the protrusion, the valve body peripheral portion moving in the closing direction first contacts the protrusion near the boss portion, and thereafter, Although the part which contacts the part which fell apart is bulged, the part of the valve body periphery contacts the contact part of a protrusion substantially equally in the circumferential direction by bulging the part which separated from the boss part.

Further, if the cross-sectional area of the part which is pressed against the valve body peripheral part during closing of the valve and pushed out in the closing direction is approximately the same in the circumferential direction, in the part where the pressure contact deformation in the closing direction is small, as much as that The height of adhesion of the wand becomes large, and the sealing function can be made substantially the same in the circumferential direction.

In other words, by bulging the contact portions of the protrusions in the open direction side, the amount of pressure contact deformation in the closing direction of the protrusions from the contact state to the closed state becomes larger at the center portion away from the boss portion than at the boss portion, and the protrusions at the periphery of the valve body. However, the reaction force per unit area of the portion of the valve body which is brought into close contact with the valve body in the closing direction is small in the vicinity of the boss and increases in the vicinity of the center. However, since the adhesion height is increased by that amount, the sealing function becomes substantially the same in the circumferential direction.

When the valve is closed, the slope of the inclined surface in the circumferential direction is changed so that the inclined surface is the inclined surface in the opening direction side of the protrusion which is pressed against the periphery of the valve body, and that the vicinity of the boss portion is a steep gradient and the portion away from the boss portion is a toy gradient. The cross-sectional area of the part pushed in at the periphery of the valve body at the time and pushed in the closing direction can be made substantially the same in the circumferential direction.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of a butterfly valve concerning this invention is described using drawing. 1 is a front view of a butterfly valve of the present invention, Figure 2 is a cross-sectional view A-A. 3 is a valve axial cross-sectional view of the seat ring, Figure 4 is a valve shaft perpendicular to the seat ring.

This butterfly valve inserts the inside into the connection part of the pipe through which a fluid flows, and controls opening / closing of a flow path and adjustment of a flow volume, and the ring-shaped valve box 1 which presses in both the axial direction (flow path direction) in both pipes is The valve body 2 provided inside the valve box 1 and the valve body 2 through the center of the valve box 1 in a direction perpendicular to the valve shaft 3 (the flow path direction). And one side and the other valve rods 3a and 3b rotatably supported around the shaft) and the inner circumferential surface of the valve box 1 to seal between the inner circumferential surface of the valve box 1 and the valve body 2. The seat ring 4 is provided.

The valve box 1 is forced, for example, and the projection 7 which holds the cylindrical flange 6 inwardly is provided on the inner circumferential surface of the cylindrical valve box main body 5 which is pressed in the flow direction in both pipes. It is formed continuously in the circumferential direction. In the center portion of the inner circumferential surface of the protrusion 7, a ring-shaped groove is formed in which the shifting fixing portion 19 of the seat ring 4 described later is inserted to restrict the shift in the flow direction of the seat ring 4. .

In the direction of the valve shaft 3, one side and the other side of the valve box 1 protrude to one side and the other bearing 8a, 8b, through which the shaft hole penetrates from the outer side to the inner circumferential surface of the projection 7, and outward. One side and the other side valve rods 3a and 3b, which are inserted into the shaft hole, are rotatably supported.

In the part projecting outward from the valve box body 5 of the one-side bearing 8a, for example, a forced and cylindrical valve rod cover 9 is inserted thereinto, integrated with the one-side bearing 8a, and the inside of the one-side bearing 8a. The valve rod 3a is intended to pass through the insertion. An outer circumferential flange 10 is fixed to one end of the valve rod cover 9, and the outer circumferential flange 10 is made of, for example, a synthetic resin for preventing separation of one side of the valve rod 3a, and is separated into two parts. (11) is provided with the screw (12).

Further, positioning pieces 13 are formed on both sides of the one-side bearing 8a in the circumferential direction of the valve box body 5. In this positioning piece 13, a bolt through hole 14 is formed, and when the pipe is connected, the valve box 1 is positioned by passing a pipe connecting bolt through the bolt through hole 14. The box 1 can be easily sandwiched between pipes.

On the outer side surface of the other bearing 8b, for example, a steel cover plate 15 is secured with a screw 17 between the thin plate 16 made of a rubber-like elastic body, and the other side of the valve rod 3b While preventing the separation, the outer side of the shaft hole is closed so that fluid does not leak out through the shaft hole.

The valve body 2 is, for example, forced, and has a substantially disk shape having a straight line smaller than the inner diameter of the protrusion 7 of the valve box 1, and the valve box 1 having its radial direction aligned with the barb shaft 3. Equipped inside). The valve body 2 rotates around the valve shaft 3, opens the flow path by directing the plate surface in a direction parallel to the flow path direction, and opens the flow path by directing the plate surface in a direction perpendicular to the flow path direction. The flow rate is controlled by appropriately changing the angle of the plate surface.

In the valve shaft 3 direction, one side and the other side valve rod coupling parts 18a and 18b of the bag shape are formed in the vicinity of the peripheral edge of one side and the other side of the valve body 2, and this one side and the other side valve rod coupling The valve body 2 is supported inside the valve box 1 by engaging the portions 18a and 18b with the vicinity of the tip portions of the one side and the other side valve rods 3a and 3b. In addition, the hole of one side valve-rod coupling part 18a becomes substantially square, and the hole of the other side valve rod coupling part 18b is circular.

The one side valve rod 3a is forcibly made into a rod-shaped cross section, for example, and is internally inserted into the one side bearing 8a and the valve rod cover 9. One end of this one side valve rod 3a is formed in a substantially square cross section, protrudes from the valve rod cover 9, is provided with a handle (not shown), and the one side valve rod 3a is formed around its shaft (valve). It can be rotated about the axis (3).

In addition, the other end part vicinity of one side valve rod 3a is formed in substantially square cross section, protrudes inward of the valve box 1, and is a substantially square hole of the one side valve rod coupling part 18a of the valve body 2. The valve body 2 can be rotated about the valve shaft 3 by rotating the one side valve rod 3a around the shaft.

In the circular cross section of one side valve rod 3a, the groove | channel which continues in the circumferential direction is formed in the part located near one side edge part of the valve rod cover 9. In order to fit the groove into the inner edge portion, two separate release blocking members 11 having a circular hole are provided on the outer circumferential flange 10 to prevent the separation of one side valve rod 3a. .

The other side valve rod 3b is, for example, forced and has a circular cross section, and is inserted into the other side bearing 8b. One side end part of this other side valve rod 3b protrudes inwardly of the valve box 1, and is engaged with the circular hole of the other side valve rod coupling part 18b of the valve body 2, 2) is rotatably supported around the valve shaft 3. The other end of the other valve rod 3b is pressed by a cover plate 15 fixed to the outer surface of the other bearing 8b via a thin plate 16 made of rubber-like elastic body, and in the axial direction thereof. Movement is regulated.

The seat ring 4 is formed of a rubber-like elastic body in a ring-shaped cross-section having a substantially U-shape in which the outer surface side is opened, and the outer side thereof is bent inwardly so as to enclose the flange 6 of the protrusion 7. It is attached to the inner peripheral surface of the valve box 1. The outer diameter of the main body of the seat ring 4 is large enough to fit in the valve box body 5, and the inner diameter thereof is larger than the diameter of the valve body 2.

In the center part of the outer surface side of the seat ring 4, the shift part 19 is protruded continuously in the circumferential direction, it fits in the ring-shaped groove | channel formed in the projection 7 of the valve box 1, and a valve The shift | offset | difference to the flow path direction accompanying opening and closing of this is prevented.

Two valve shaft holes 20 for penetrating one side and the other valve rods 3a and 3b are formed at positions facing each other in the flow path radial direction of the seat ring 4 (positions through which the valve shaft 3 passes). It is. On the inner circumferential surface of the valve shaft hole 20, a valve rod seal portion 21 protruding continuously in the circumferential direction is formed near the center in the valve shaft 3 direction, and one side penetrating the valve shaft hole 20 and Sealing is performed between the other side valve rods 3a and 3b. In addition, a ring-shaped reinforcing material 22 is embedded around the valve shaft hole 20.

The boss | hub part 23 for sealing between the valve bodies 2 of the valve shaft 3 vicinity is formed in the periphery of the valve shaft hole 20 inwardly. The boss portion 23 has a substantially circular sliding surface 24 on which the cross sections of one side and the other valve rod engaging portions 18a and 18b of the valve body 2 slide, and the seat ring from the sliding surface 24. (4) It consists of the taper part 25 which rubs on the inner peripheral surface of a main body. The sliding surface 24 is concave so that the sliding surface 24 and the end surface of the one side and the other side valve rod coupling parts 18a and 18b of the valve body 2 may contact each other, and the one side and the other side valve rod coupling part The cross sections of 18a and 18b become convex spherical shapes, and both are formed in substantially the same size.

Between the boss part 23 of one side and the other side, the protrusion 26 which protrudes in an inner direction continuously in the circumferential direction is formed. The protrusion 26 includes the top 27 on the inner side thereof, the pressure contact surface 28 on the open direction (the direction in which the valve body 2 moves when the valve is opened), and the closing direction (at the time of closing the valve). The cross section holding the protective surface 29 on the side of the valve body 2 is formed to have a substantially large cross section. In addition, since the valve opens and closes by rotational movement of the valve body 2 around the valve shaft 3, in the two projections 26 between the maintenance parts 23, the opening direction and the closing direction are opposite to each other.

The top 27 has a height from the inner circumferential surface of the main body of the seat ring 4 constant in the circumferential direction, is parallel to the flow path direction, and becomes a part of the cylindrical surface having a constant width in the flow path direction. The inner diameter of the cylinder formed by the top portion 27 is smaller than the diameter of the valve body 2 so that the periphery of the valve body 2 can press the protrusion 26. This top portion 27 is positioned from the position (protrusion axis) of the valve shaft 3 so that the entire protrusion 2 is not easily deformed when the protrusion 26 is pressed against the periphery of the valve body 2. It is formed in a predetermined width toward the closing direction.

The pressure contact surface 28 becomes an inclined surface which rubs the inner peripheral surface of the main body opening direction side of the seat ring 4 from the top part 27, and is press-contacted by the peripheral part of the valve body 2 in the closing direction. The pressure-contacting surface 28 is a curved surface convex inward so as to be parallel to the flow path direction in the vicinity of the top 27, the vicinity of the boss 23 is a steep gradient, the central portion between the boss 23 is a toy gradient It is formed by gradually changing the gradient in the circumferential direction.

By the change of this gradient, the vicinity of the tip end (intersection with the main body inner circumferential surface of the seat ring 4) of the pressure contact surface 28 is the distance from the valve shaft 3 in the direction orthogonal to the valve shaft 3. In proportion to, the central portion between the bosses 23 is curved in the open direction. In addition, when viewed from the valve shaft 3 direction, near the tip of the pressure-contacting surface 28 forms a straight line inclined near the center between the bosses 23 on the opening direction side.

The protective surface 29 becomes an inclined surface with a constant gradient from the top portion 27 to the inner peripheral surface of the main body of the seat ring 4 in the closing direction, and the pressure contact surface 28 is pressed against the periphery of the valve body 2. At this time, the entire projection 26 is protected from deformation in the closing direction.

Next, the form when the protrusion of the seat ring seals between valve bodies is demonstrated. Fig. 5 is a sectional view of the main part showing the form in which the periphery of the valve body presses the protrusions; Fig. 6 is a diagram for explaining the relationship between the contact state between the boss part and the center part between the boss parts; Fig. 7 is the reaction force and the fluid pressure of the pressure contact face. A diagram illustrating the relationship between

When the valve body 2 in the open state X rotates around the valve shaft 3 in the closed direction and moves to the contact state Y, the closed side edge end 30 of the valve body 2 protrudes. It comes in contact with the pressure contact surface 28 of (26). At this time, the angle θ formed by the plate surface of the valve body 2 with respect to the direction orthogonal to the flow path direction is small, and the edge end 30 of the valve body 2 in the closed direction side from the inner circumferential surface of the seat ring 4. The height h toward the inner side is almost equal to the difference R1-R2 between the radius R1 of the inner circumferential surface of the seat ring 4 main body and the radius R2 of the radius 2. That is, on the pressure contact surface 28, the part of predetermined height h from the main body inner peripheral surface of the seat ring 4 turns into the contact part 31. As shown in FIG.

As for the contact part 31, the gradient of the press contact surface 28 changes gradually, the center part between the boss | hub parts 23 becomes a curved shape bulging toward the closing direction side, and the edge part 30 of the valve body 2 in the closing direction side edge part 30 is shown. ) Contacts the contact portion 31 of the pressure contact surface 28 substantially simultaneously. In short, when viewed from the valve shaft 3 direction, the contact portion 31 is a straight line in which the central portion between the bosses 23 is inclined toward the opening direction side through the valve shaft 31, and is closed on this straight line. As the straight line formed by the directional edge end 30 almost overlaps, the closing edge side 30 of the valve body 2 is in contact with the contact portion 31 at the same time.

Then, when the valve body 2 rotates and reaches from the contact state Y to the closed state Z, the straight line which the periphery of the valve body 2 forms by looking toward the valve axis 3 direction is a protrusion. It becomes substantially parallel to the axis line of (26), and the projection 26 is press-contacted by the pressure contact deformation amount L in the closing direction at the periphery of the valve body 2. At this time, a part of the protrusions 26 are pushed in the closing direction and in close contact with the periphery of the valve body 2 in the contact height H so as to return the valve body 2 to the opening direction. We seal between (2).

In the closed state Z, the fluid on the upstream side penetrates into the close contact portion between the protrusion 26 and the periphery of the valve body 2 and flows out downstream while spreading widely on the close contact portion. The pressure P of the fluid gradually decreases along the contact surface due to frictional resistance, and the fluid pressure P is the size S per unit area of the reaction force of the protrusion 26 returning the valve body 2. ) In the lower rotational position, intrusion of fluid is prevented, and the gap between the periphery of the valve body 2 is sealed.

In short, the fluid pressure P can be made small by increasing the contact height H, or the fluid pressure P which can prevent intrusion by increasing the size S per unit area of reaction force of the protrusion 26 is increased. This improves the sealing function.

Since the size S per unit area of the reaction force of the protrusion 26 which returns the valve body 2 becomes large according to the pressure contact deformation amount L, this pressure contact deformation amount L and adhesion height H are made large, By increasing the cross-sectional area A of the protruding portion of the protrusion 26, the sealing function is improved. In addition, the cross-sectional area A of the pushed-out part of the protrusions 26 uses the pressure contact deformation amount L and the adhesion height H, and it is (A1) = (L * H / 2).

The pressure contact deformation amount L increases as the bulging toward the open direction side of the contact portion 31 increases, and the adhesion height H increases according to the gradient of the pressure contact surface 28. Here, the pressure-contacting surface 28 of the protrusion 26 gradually changes the gradient so that the vicinity of the boss portion 23 becomes a sudden gradient, and the contact portion 31 is bulged toward the open direction near the center between the boss portions 23. It has a shape, and the contact height H becomes small at the position where the crimp contact strain L is large, and the contact height H becomes large at the position where the crimp contact strain L is small. For this reason, the cross-sectional area A becomes substantially the same in the circumferential direction, and the sealing function is substantially the same in the circumferential direction.

Moreover, the press-fitted projection 26 is deformed so that the closing direction side of the peripheral part of the valve body 2 may bulge, and it adheres to the surface of the closing direction side of the valve body 2 peripheral part. On the other hand, in the opening direction side rather than the closing direction side edge edge part 30, it is tensioned to the closing direction side by some frictional force of the valve body 2, and some clearance gap is formed between the cross sections of the valve body 2. Therefore, between the valve body 2 is sealed by the close contact of the surface of the periphery of the valve body 2 with the protrusion 26. As shown in FIG.

According to the above configuration, the protrusion 26 has a shape in which the contact portion 31 is bulging in the open direction near the center between the bosses 23, and at the time of closing the valve, the periphery of the valve body 2 It contacts the contact part 31 substantially simultaneously. Therefore, the torque required before the whole periphery of the valve body 2 contacts the protrusion 26 becomes small.

Moreover, the gradient of the contact surface 28 gradually changes so that the protrusion 26 may become a toy grade in the vicinity of the boss | hub part 23, and the toy grade near the center part between the boss | hub parts 23, and the pressure contact surface 28 is a toy In the part of a ship, the contact part 31 is made to bulge in the opening direction side. Therefore, the portion pushed away from the periphery of the valve body 2 at the time of valve closing has a cross-sectional area A determined by the contact height H and the pressure contact deformation amount L to the periphery of the valve body 2 in the circumferential direction. In the circumferential direction, the sealing function can be made substantially the same.

In addition, this invention is not limited to the said embodiment, A suitable change can be added within the scope of the present invention. For example, the top part 27 of the protrusion 26 may not only make the width constant, but may change the center part between the boss | hub parts 23 so that it may bulge to an opening direction side. In this case, the periphery of the valve body 2 can be brought into contact with the projection 26 at substantially the same time without changing the gradient of the pressure contact surface 28.

In addition, the top portion 27 of the protrusion 26 not only makes the height from the inner circumferential surface of the main body of the seat ring 4 constant, but also changes its height, so that the periphery of the valve body 2 at the time of closing the valve. The cross-sectional area of the portion which is pressed in the closed direction and pushed in the closing direction may be substantially the same in the circumferential direction. In this case, the sealing function can be made substantially the same in the circumferential direction without changing the gradient of the pressure contact surface 28.

As will be apparent from the above description, according to the present invention, the pressure contact portion can be brought into contact with the protrusion at the same time by making the pressure contact portion bulging in the open direction side. As a result, it is possible to eliminate the pressure contact until the contact with the projection of the periphery of the valve body is completed, thereby avoiding the unnecessary torque that does not contribute to the seal. In addition, when the valve body is rotated around the valve shaft to reduce the flow rate, the periphery of the valve body in the vicinity of the valve shaft can be prevented from contacting the protrusion, and the durability thereof can be improved.

In addition, by gradually changing the gradient of the pressure contact surface to increase the contact height of the portion where the pressure contact deformation is small, the cross-sectional area of the part that is press-contacted at the periphery of the valve body 2 and pushed in the closing direction at the time of valve closure is approximately in the circumferential direction. It is possible to make the same, and this sealing function can be made substantially the same in the circumferential direction, and there can be no useless unnecessary welding.

Claims (4)

It is mounted on the inner circumferential surface of the valve box of the butterfly valve, and when the valve is closed, the seat ring seals between the inner circumferential surface of the valve box and the valve body, and two valve shaft holes for penetrating the valve rod are formed to face each other in the radial direction of the flow path. A protrusion is formed between the boss portions around the valve shaft hole in a continuous direction in the circumferential direction, and is formed with a protrusion which is pressed in the closing direction from the periphery of the valve body when the valve is closed, and the periphery of the valve body is in contact with the protrusion. The seat ring characterized in that the portion away from the boss in the circumferential direction is bulging toward the open direction so that the periphery of the valve body contacts almost simultaneously. The seat ring according to claim 1, wherein the protrusion has a cross-sectional area of about a portion pressed against the periphery of the valve body and pushed in the closing direction at the time of closing the valve in the circumferential direction. The said protrusion is an inclined surface on the side of the opening direction which is pressed against the periphery of the valve body at the time of valve closing, and this inclined surface is a steep slope at the vicinity of the boss and a toy separated from the boss. A seat ring, characterized in that formed by changing the gradient in the circumferential direction so as to double. The butterfly valve provided with the seat ring as described in any one of Claims 1-3.