Lined butterfly valve and method for manufacturing lined butterfly valve

A lined butterfly valve and manufacturing method, the lined butterfly valve including a valve disk (2) with a core metal (20) covered with a lining layer (22) provided rotatably inside a body (3) by a stem (5). The lining layer includes a front/back-side lining part (32) provided on each of front and back sides of the core metal and an outer circumferential lining part (33) provided on an outer circumferential side of the core metal. The front/back-side lining part is provided on each of the front and back sides of the core metal in which no occurrence of warpage is assumed so as to have a thickness T1, and the outer circumferential lining part has a thickness T2 from an outer circumferential end of the core metal to a tip seal surface of an outer circumferential end of the valve disk.

TECHNICAL FIELD

The present invention relates to a lined butterfly valve in which a valve disk and an inner circumferential surface of a valve box are resin-lined, and a method of manufacturing the lined butterfly valve.

BACKGROUND ART

For example, when a highly-corrosive fluid is caused to flow in a chemical plant or the like or as a butterfly valve for a food-related flow path, a so-called lined butterfly valve is often used which has a resin-lined metal-made core metal of a valve disk and has a resin seat ring attached on an inner circumferential surface of a valve box. In the valve of this type, normally, as a lining material, a fluororesin excellent in chemical resistance and heat resistance is used. This fluororesin is subjected to lining process, with a thickness on a certain degree to prevent permeation and penetration of a special fluid such as a chemical. On the other hand, fluororesin also has a property of low elasticity. Thus, at the timing when the valve is closed, it is desired to sufficiently ensure sealability between, in particular, a valve blade side in the valve disk and a portion near a seal part with a valve box side and, in turn, to prevent leakage over the entire circumference of the seal part on the outer circumferential side of the valve disk.

As a lined butterfly valve, for example, the Applicant has filed an application of the butterfly valve in PTL 1. In this valve disk of the valve, the disk-shaped core metal is provided with disk lining with fluororesin. This disk lining has a mildly tilted surface on each of both surface sides and, contiguously to this tilted surface, a taper surface having a predetermined angle is formed on a tip side of the valve blade. Between these taper surfaces on both surfaces, a seal part is provided which makes pressure-contact with and seals a seat liner when the valve is closed. These tilted surface, taper surface, and seal part are formed of the core metal and having a substantially equal material thickness. When the valve is closed, a high seal surface pressure is exerted to prevent leakage.

On the other hand, in the valve disk of the butterfly valve in PTL 2, a lining layer covers the outside of the reinforcing core metal. On the outer circumferential edge of this lining layer, a seal part with two stages having different radiuses of curvature is formed, the seal part being formed of a low-pressure seal part with a small radius of curvature and a middle-pressure or high-pressure seal part with a large radius of curvature. With this seal part, only the low-pressure seal part makes a pressure contact with the seat ring with a small bite at the time of low pressure, and the low-pressure seal part and the middle-pressure or high-pressure seal part makes a pressure contact with the seat ring with a large bite at the time of high pressure, thereby trying to reduce loads on the covering material.

When resin lining is provided to the core metal of these lined butterfly valves of PTL 1 and PTL 2, a lining molding die is generally used. When lining process is performed with the lining molding die, normally, the core metal is supported in a lateral orientation inside the molding die and, in this state, a lining material is injected to a cavity to perform lining process on the entire surface including the front and back surfaces of the core metal to produce the valve disk.

CITATION LIST

Patent Literatures

SUMMARY OF INVENTION

Technical Problem

However, when the lined butterfly valves of PTL1 and PTL 2 are formed to have a large diameter, the core metal of the valve disk also has a large diameter accordingly to increase weight. At the time of casing this core metal, warpage tends to occur mainly on the valve blade side. When lining is performed on the core metal with the lining molding die, a portion near the valve blade tends to flex downward by its self-weight when supporting the core metal. In lining molding, the core metal is arranged inside the resin mold and then a resin is suppled for molding. Thus, the core metal with warpage or flexure is arranged inside a resin lining having a certain outer shape. Because of these, it is difficult to provide lining uniformly on both surface sides of the core metal. In particular, on one surface side of the core metal near the valve blade, the lining thickness becomes insufficient and the core metal may be exposed to the surface and, on the other surface side, the lining thickness may be formed more than required. Of these, in a portion where the lining layer becomes insufficient, a possibility arises in which the fluid permeates or penetrates at the time of use.

In the valve disks of these valves, on the core metal, a tilted surface or taper surface on each of the front and back surface sides and a seal part for pressure contact with the seat liner are provided to have an approximately same thickness. To form these thicknesses as the same material thickness, it is required to form the core metal with high accuracy. However, to cover the surface of the core metal with the resin lining layer, variations tend to occur in resin molding. In particular, it is difficult to form a portion of the core metal near the outer circumference with a predetermined seal width. Thus, near the outer circumference of the core metal, an outer circumferential seal surface is often formed so as to extend from the front and back surfaces. In this case, in order to make the outer circumferential seal surface with a uniform predetermined width, it is required to finely set the shape of the core metal or, in some cases, in consideration of a crush margin of the outer circumferential seal surface in advance, it is required to cut out a superfluous extended portion of an outer circumferential seal portion with high accuracy.

Because of these, a lined butterfly valve has been desired in which a lining is easily formed with a thickness allowing permeation and penetration of chemical or the like to be prevented without providing of the core metal with high accuracy even if the lined butterfly valve is provided to have a large diameter, and a valve disk is provided which ensures sealability over the entire circumference when the valve is closed.

The present invention has been developed to solve the conventional problems, and has an object of providing a lined butterfly valve excellent in chemical resistance and heat resistance and in which, without provision of a core metal of a valve disk with high precision, a lining layer with a thickness sufficient for the core metal is ensured to prevent permeation and penetration of a fluid even if the valve is provided to have a large diameter, and a method of manufacturing the lined butterfly valve.

Solution to Problem

To achieve the above-described object, a first aspect of the invention is directed to a lined butterfly valve in which a valve disk with a core metal covered with a lining layer is provided rotatably inside a body by a stem, wherein the lining layer comprises s a front/back-side lining part provided on each of front and back sides of the core metal and an outer circumferential lining part provided on an outer circumferential side of the core metal, the front/back-side lining part is provided on each of the front and back sides of the core metal in which no occurrence of warpage is assumed, so as to have a thickness obtained by adding a predetermined lining thickness and a thickness equal to a maximum warp width assumed on a valve blade side of the core metal at at least an outer circumferential end position of the core metal, and the outer circumferential lining part has a thickness from an outer circumferential end of the core metal to a tip seal surface of an outer circumferential end of the valve disk being a thickness obtained by adding the predetermined lining thickness and a predetermined crush thickness.

A second aspect of the invention is directed to the lined butterfly valve, in which the outer circumferential lining part has a convex part protruding to an outer circumferential side of the valve disk, the convex part substantially annularly formed contiguously to an outer circumference of the valve disk, and an end face of the convex part on an outer circumferential side of the valve disk serves as the tip seal surface having a predetermined seal width.

A third aspect of the invention is directed to the lined butterfly valve, in which the core metal has an outer circumferential side surface part on its outermost circumference, and this outer circumferential side surface part has a width that can be opposed to a center part of the convex part in a thickness direction provided to the outer circumferential lining part even if warpage occurs with the maximum warp width assumed on the valve blade side of the core metal.

A fourth aspect of the invention is directed to the lined butterfly valve, in which each side surface part of the convex part with respect to the tip seal surface is formed of a tilted surface having an angle equal to or smaller than 10 degrees with respect to a pressure-contact seal direction of the tip seal surface.

A fifth aspect of the invention is directed to the lined butterfly valve, in which one set of washers with opposed to each other in a direction of insertion of the stem is attached in a shaft-mounting part where the stem is inserted, the one set of washers is formed of convex and concave shapes so that a surface pressure applied from the stem side to a boss part formed in the valve disk can be substantially equal even if a deviation or tilt occurs between the stem and the valve disk.

A sixth aspect of the invention is directed to the lined butterfly valve, in which the washer is formed of a convex-shaped washer including a convex spherical surface and a concave-shaped washer including a concave spherical surface with which the convex spherical surface is in surface contact, the convex-shaped washer and the concave-shaped washer are attached in a pressurized state in a mutually opposed direction by a spring-back force of a spring inserted in the shaft-mounting part.

A seventh aspect of the invention is directed to a lined butterfly valve in which a valve disk with a core metal covered with a lining layer is provided rotatably inside a body by a stem, wherein the lining layer comprises a front/back-side lining part provided on each of front and back sides of the core metal and an outer circumferential lining part provided on an outer circumferential side of the core metal, the front/back-side lining part has at least a predetermined lining thickness on each of the front and back sides of the core metal and has, at at least an outer circumferential end position of the core metal, in total on the front and back sides, a thickness obtained by doubling a thickness obtained by adding a thickness equal to a maximum warp width assumed on a valve blade side of the core metal to the predetermined lining thickness, and the outer circumferential lining part has a thickness from an outer circumferential end of the core metal to a tip seal surface of an outer circumferential end of the valve disk being a thickness obtained by adding the predetermined lining thickness and a predetermined crush thickness.

An eighth aspect of the invention is directed to a method of manufacturing the lined butterfly valve according to any one of the first through seventh aspects of the invention, wherein a stem or a stem jig is inserted in stem insertion holes provided to the core metal at opposing positions of a valve blade part of the core metal to fix the core metal and the stem or the stem jig to each other, the core metal is arranged in a space of molding a die for molding the lining layer, and, in a state in which the upper and lower stems or upper and lower stem jigs are held so that the core metal is fixed so as not to move in the molding space, a material for forming the lining layer is introduced into the molding space to form the lining layer on a surface of the core metal.

Advantageous Effects of Invention

From the first aspect of the invention, the lined butterfly valve is excellent in chemical resistance and heat resistance. The front/back-side lining part of the valve disk is provided on each of the front and back sides of the core metal in which no occurrence of warpage is assumed, so as to have a thickness obtained by adding a predetermined lining thickness and a thickness equal to a maximum warp width assumed on a valve blade side of the core metal at at least an outer circumferential end position of the core metal. Thus, even if warpage occurs in the core metal in practice, a lining portion with at least the predetermined lining thickness is ensured on the front and back sides of the valve disk. On the other hand, the outer circumferential lining part has a thickness obtained by adding the predetermined lining thickness and a lining thickness as a predetermined crush thickness. Thus, a lining portion with at least the predetermined lining thickness is ensured also on the outer circumferential side of the valve disk. Thus, even if the valve is provided to have a large diameter, a lining layer with a thickness sufficient for the core metal can be ensured to prevent permeation and penetration of the fluid. With this, without finely setting the shape of the core metal, it is possible to form the front/back-side lining part and the outer circumferential lining part each in a predetermined shape and, in particular, it is possible to easily form the outer circumferential side with the predetermined thickness and the predetermined width. With this outer circumferential side having a thickness and seal width required to ensure sealability, leakage from the outer circumferential side of the valve disk is prevented when the valve is closed and sealability can be exerted over the entire circumference of the valve disk.

From the second aspect of the invention, the convex part is formed on the outer circumferential lining part, and the end face of this convex part on the outer circumferential side serves as a tip seal surface having the predetermined seal width. Thus, irrespective of the outer diameter and thickness of the core metal, while the outer circumferential lining part is formed to have a necessary thickness, the predetermined seal width required for sealing can be provided to this convex part. Thus, even if the valve is formed to have a large diameter, the minimum-required outer circumferential seal part can be formed, and processing this part is easy.

From the third aspect of the invention, for the convex part of the outer circumferential lining part to exert favorable sealability, the outer circumferential part of the core metal preferably serves as a support. For this purpose, even if warpage occurs in the core metal, the outer circumferential side surfaces of the core metal are opposed preferably at least at the center of the convex part. In particular, a width is provided that can be opposed to the center part of the convex part in the thickness direction provided to the outer circumferential lining part. Thus, even if warpage occurs in the core metal, the convex part and the outer circumferential side surface of the core metal can be reliably opposed, and sealability by the convex part can be ensured.

From the fourth aspect of the invention, each side surface part is formed of a tilted surface having an angle equal to or smaller than 10 degrees with respect to the pressure-contact seal direction of the tip seal surface. Thus, variations in the seal width after lining formation are suppressed, and the outer circumferential seal part having a uniform seal width can be easily formed on the outer circumference of the valve disk. When the valve is closed and sealed, the outer circumferential seal part exerts a constant seal surface pressure over the outer circumference of the valve disk to reliably inhibit fluid leakage.

From the fifth aspect of the invention, even if a tilt or movement occurs on a valve disk side and a stem side in a state in which a fluid pressure is applied by the one set of washers, the attachment state between the valve disk side and the stem side is maintained to maintain smooth rotational operability. In this case, the washer is formed of a combination of convex and concave shapes, and a surface pressure equivalent to that before a tilt or movement occurs from the stem side to the boss part of the valve disk is applied, thereby ensuring sealability between these boss part and the body side and reliably inhibiting leakage even if the valve disk side and the stem side are tilted or moved.

From the sixth aspect of the invention, even if the convex-shaped washer and the concave-shaped washer are tilted or positionally deviated to each other, the convex spherical surface and the concave spherical surface are closely attached by the spring-back force of the spring. Thus, a uniform surface pressure acts over a wide range of contact positions, and excellent sealability can be exerted between the boss part and the body side.

From the seventh aspect of the invention, the lined butterfly valve is excellent in chemical resistance and heat resistance. The front/back-side lining part of the valve disk is provided on each of the front and back sides of the core metal in which no occurrence of warpage is assumed, so as to have a thickness obtained by adding a predetermined lining thickness and a thickness equal to a maximum warp width assumed on a valve blade side of the core metal at at least an outer circumferential end position of the core metal. Thus, even if warpage occurs in the core metal in practice, a lining portion with at least the predetermined lining thickness is ensured on the front and back sides of the valve disk. On the other hand, the outer circumferential lining part has a thickness obtained by adding the predetermined lining thickness and a lining thickness as a predetermined crush thickness. Thus, a lining portion with at least the predetermined lining thickness is ensured also on the outer circumferential side of the valve disk. Thus, even if the valve is provided to have a large diameter, a lining layer with a thickness sufficient for the core metal can be ensured to prevent permeation and penetration of the fluid. With this, without finely setting the shape of the core metal, it is possible to form the front/back-side lining part and the outer circumferential lining part each in a predetermined shape and, in particular, it is possible to easily form the outer circumferential side with the predetermined thickness and the predetermined width. With this outer circumferential side having a thickness and seal width required to ensure sealability, leakage from the outer circumferential side of the valve disk is prevented when the valve is closed and sealability can be exerted over the entire circumference of the valve disk.

From the eighth aspect of the invention, the stem or the stem jig is inserted and fixed in advance in the core metal, and this stem or the stem jig is held so as not to move the core metal, and the core metal is fixed in the space of molding a die for molding the lining layer (metal mold). The material of the lining layer is introduced into the molding space to form the lining layer. Thus, the core metal can be arranged at a correct position in the lining layer whose outer shape is defined in advance by the die (metal mold). Thus, it is possible to reliably form a lining layer having a necessary thickness to prevent permeation of the fluid even if warpage occurs in the core metal.

DESCRIPTION OF EMBODIMENTS

An embodiment of a lined butterfly valve in the present invention is described in detail below based on the drawings.FIG.1depicts a central cross-sectional view of an embodiment of the lined butterfly valve of the present invention,FIG.2(a)andFIG.2(b)depict a valve disk, andFIG.3depicts an enlarged sectional view of an A portion inFIG.2(b).

In the drawings, the lined butterfly valve (hereinafter referred to as a valve main body1) is provided to have, for example, a large diameter with a nominal diameter on the order of 350 A to 600 A, and is used as part of a pipeline in semiconductor manufacturing plants and food-related industries. The valve main body1includes a valve disk2, a substantially cylindrically-shaped body3, a seat liner4, and a stem5, and this stem5is formed of an upper stem5aand a lower stem5b.

The body3is molded from cast iron such as, for example, ductile iron, is provided to have an upper body3aand a lower body3bin a vertically dividable mode, and is provided so as to be integrally fixable with a bolt not depicted. The body3is provided with a flow path port10and a flange11. An inner circumferential side of the body3including these is covered with a seat liner4. On a shaft-insertion side of each of the stem5of the upper body3aand the lower body3b, a shaft-mounting part12is formed. Inside this shaft-mounting part12, a shaft-mounting hole13is provided. Into the respective shaft-mounting holes13, the upper stem5aand the lower stem5bare inserted. On a lower part of the upper stem5a, a polygonal rectangular part5cis formed.

The valve disk2has, on its center side, a substantially-disk-shaped core metal20formed of a metal material such as a stainless steel alloy. This core metal20is covered with a lining layer (lining part)22. This lining part22includes front/back-side lining parts32provided on front and back sides, respectively, of the core metal20, and an outer circumferential lining part33provided on an outer circumferential side of the core metal20.

On top and bottom sides of the valve disk2, stem insertion holes23are formed. In particular, in the stem insertion hole23on the top side, a rectangular hole part24is formed where the rectangular part5cof the stem5can fit. In the stem insertion hole23on the top side, the upper stem5ais inserted and attached so that the rectangular part56cfits in the rectangular hole part24. In the stem insertion hole23on the bottom side, the lower stem5bis inserted. With these, the valve disk2is inserted inside the body3in a state with the upper stem5aand the lower stem5bbeing shaft-mounted, and can open and close a flow path inside the body by rotation of the upper stem5a.

The lining part (lining layer)22is provided from, for example, a resin material such as a fluororesin of PFA (tetrafluoroethylene-perfluoro alkyl vinyl ether copolymer) or the like, and includes, in addition to the front/back-side lining parts32and the outer circumferential lining part33described above, a boss part30and a shaft-cylinder lining part on each of the upper and lower sides (top and bottom sides). The lining part22integrally covers the outer circumference on the front and back surfaces of the core metal20through communication parts21formed at appropriate positions on the core metal20and is formed in a state of being prevented from falling away from the core metal20.

A seal portion of the lining part22of the valve disk2with the seat liner4is formed of the boss part30near each of the top and bottom sides and a valve blade part31, which is a portion other than the boss part30. With the boss parts30, sealability on the top and bottom sides with the seat liner4is ensured from valve opening to valve-closed states. With the valve blade part31, sealability on a valve blade side with the seat liner4is ensured in a valve-closed state. As described above, when the valve is closed, with the boss parts30and the valve blade part31, sealability with the seat liner4can be exerted over the entire inner circumferential surface.

Here, when the lining part22is formed, as the valve main body1(core metal20) has a larger diameter, a larger warp tends to occur at the time of casting from the valve blade side of the core metal20centering on a rotation axis. When lining process is performed thereafter, a portion of the core metal20near the valve blade side tends to be deformed as being warped downward by its self-weight.

By contrast, inFIG.2andFIG.3, the front/back-side lining parts32are provided to have, on each of the front and back sides of the core metal20presumed to have no occurrence of warpage, a thickness T1obtained by adding a predetermined lining thickness TL1and a thickness equal to a maximum warp width WA assumed on the valve blade side of the core metal20, at least a position on an outer circumferential side of the core metal20. With these front/back-side lining parts32, the front and back surfaces are reliably covered also on the valve blade side of the core metal20. TheseFIG.2andFIG.3are drawings in which no warpage occurs in the core metal20, which is, so to say, in an ideal state. In practice, this state may not occur and warpage may occur in the core metal20. A mode in which warpage occurs in the core metal20will be described further below based onFIG.4. Also, while the front/back-side lining parts32having a uniform thickness are provided on the front and back sides of the core metal20in the present example, this is not necessarily restrictive. Since warpage of the core metal20tends to be larger toward the valve blade side, the thickness may be increased toward the valve blade side accordingly.

Specifically, in the case of a large-diameter butterfly valve having a nominal diameter on the order of 350 A to 600 A as in the present example, the predetermined lining thickness TL1of each of the front and back sides of the core metal20is desirably at least equal to or larger than 3 mm, and is provided to be on the order of 3 mm. On the other hand, the thickness equal to the maximum warp width WA assumed on the valve blade side of the core metal20is provided, with the maximum warp width near the valve blade centering on the rotation axis of the core metal20being assumed to be 2 mm, to be on the order of 2 mm, accordingly, on each of the front and back sides of the core metal20. With these, the front/back-side lining part32is provided, on each of the front and back sides of the core metal20in which no occurrence of warpage is assumed, to have the thickness T1on the order of 5 mm, which is a sum of the predetermined lining thickness TL1of 3 mm and the thickness of 2 mm equal to the maximum warp width WA assumed on the valve blade side of the core metal.

On the other hand, the outer circumferential lining part33is provided to have a thickness T2on the outer circumferential side of the core metal20from an outer circumferential end of the core metal20to a tip seal surface41of an outer circumferential end of the valve disk2. This thickness T2consists of a thickness obtained by adding a predetermined lining thickness TL2on the outer circumferential side of the core metal20and a predetermined crush thickness TC. With this outer circumferential lining part33, the outer circumferential side of the core metal20is covered.

Specifically, the predetermined lining thickness TL2on the outer circumferential side of the valve disk2is provided to be on the order of 3 mm, the predetermined crush thickness TC is added to this predetermined lining thickness TL2and, with these, the outer circumferential lining part33is configured. In the present example, the predetermined crush thickness TC is set to be on the order of 1 mm and, with these predetermined lining thickness TL2and predetermined crush thickness TC, a necessary thickness is allocated on the outer circumferential side of the valve disk2as a thickness for pressure-contact with the seat liner4and a crush margin.

Here, the “predetermined lining thickness” is a minimum thickness of the lining layer required so as not to let a fluid having a possibility of being in contact with the valve disk2permeate through the core metal20, and is varied depending on the material of the lining layer and the type of the fluid. Note that this “minimum thickness” is not required to be a value proved by a theory, verification, and so forth, and may have a customary value required at minimum in order not to let the fluid penetrate, based on the experiments of a person skilled in the art. Also, the “predetermined crush thickness” is an amount of irreversible crush that can occur when the seal portion of the valve disk2repeatedly makes contact with the seat liner4to be crushed when the valve disk2is opened and closed. This “predetermined crush thickness” can be set in consideration of the size of the valve disk2, the material of the lining part22, the amount of crush of the seal portion, and so forth.

Furthermore, “the maximum warp width assumed near the valve blade of the core metal20” is a deviation width of a design value from an end portion of the core metal20regarding warpage mainly near the valve blade having a possibility of occurrence in casting the core metal20or the like, when a maximum warp occurs in a predicted range.

On a seal side of the outer circumferential lining part33, a convex part (annular convex part40) is provided to have a predetermined height. This annular convex part40protrudes to the outer circumferential side of the valve disk2and is substantially annularly formed contiguously to the outer circumference of this valve disk2. On an end face of this annular convex part40on the outer circumferential side of the valve disk2, the tip seal surface41is formed. The tip seal surface41is provided to have a predetermined seal width W.

In this case, in consideration of also irreversible leakage occurring as a result of a contact with the valve seat of the seat liner4, the annular convex part40is set to have a predetermined height (predetermined crush thickness) allowing sufficient sealability to be maintained. As a result, in the outer circumferential lining part33, a layer having a predetermined lining thickness is formed on the outer circumferential side of the core metal20, and on its further outer circumferential side, the annular convex part40as a predetermined crush thickness is formed. With this structure, while the predetermined lining thickness is reliably ensured on the outer circumferential side of the core metal20, a minimum-required outer circumferential seal part can also be formed.

The predetermined seal width W means a large width required for the tip seal surface41as a main seal portion with the seat liner4of the annular convex part40to obtain sufficient sealability. This predetermined seal width W can also have a customary value for a person skilled in the art.

The annular convex part40of the present example is formed to have a height on the order of 1 mm with the predetermined seal width W on the order of 3 mm. The entire outer circumferential lining part33is provided to have a thickness on the order of 4 mm, which is a sum of the predetermined lining thickness (3 mm) and the predetermined crush thickness (1 mm).

In the sectional view of the valve disk2ofFIG.3, a side surface part42is provided on both sides (upper and lower sides in the drawing) toward the tip seal surface41of the annular convex part40, and each side surface part42is formed of a tilted surface tilted with respect to a pressure-contact seal direction of the tip seal surface41. An angle θ of the tip seal surface41with respect to the pressure-contact seal direction is provided to be equal to or smaller than 10 degrees.

That is, when the lining layer (lining part22) is formed on the core metal20, at the time of forming the lining part22, the annular convex part40is formed in advance significantly higher (larger to a right direction inFIG.3) than a scheduled height and, after forming, can be cut at a position with a height required for the annular convex part40. Here, if the angle θ is equal to or smaller than 10 degrees, both of the side surface parts42of the annular convex part before cutting become nearly parallel to each other, and a change of the width due to the cutting position between both of the side surface parts42can be decreased. Thus, the seal width W required for the tip seal surface41can be formed.

InFIG.3, while the thickness of the front/back-side lining part32(thickness from the surface of the core metal20to the outer surface of the lining part22) is larger than the thickness of the outer circumferential lining part33, the thickness of the lining part from the front/back-side lining part32over the annular convex part40is more preferably uniform. If the thickness of the lining part has a difference, at the time of forming the lining part, a contraction difference occurs due to a difference in thickness, and stress concentrates on the thinnest portion, which possibly becomes a portion where rupture tends to take place. In particular, while a root part of the annular convex part40is a portion where stress tends to concentrate, by making the thickness from the front/back-side lining part32via the outer circumferential lining part33to the annular convex part40uniform in this manner, stress concentration due to a difference in thickness tends not to occur, and rupture of the lining part22and so forth can be easily suppressed.

Between the tip seal surface41and both of the side surface parts42, an annular C-surface part45is formed. Thus, with the C-surface part45(C-chamfer) provided, an excessive force is prevented from being applied to part of the annular convex part40when the annular convex part40makes contact with the seat liner4. Furthermore, by setting the size and angle of the C-surface part45as appropriate, the seal width W of the tip seal surface41can also be set to have any size.

With the above-described lining part22formed on the valve disk2, even if warpage or flexure occurs in the core metal20, the thickness T1of the front/back-side lining part32and the thickness T2in the outer circumferential lining part33and the seal width W serve as a size reliably exerting sealability when the valve is closed. Furthermore, at this time, the outer circumferential lining part33is suppressed to have a minimum-required thickness for maintaining sealability.

With reference toFIG.4, a case is described below in which warpage or flexure occurs in the core metal20. In the drawing, a partially-omitted sectional view of the valve disk is depicted.FIG.4(a)depicts a state in which no warpage is present in the core metal of the present embodiment,FIG.4(b)depicts a state in which warpage occurs in the core metal of the present embodiment, andFIG.4(c)depicts a comparative example.

InFIG.4(a), a state is depicted in which the front/back-side lining part32is formed to have a uniform thickness with respect to the front and back sides of the core metal20and the outer circumferential lining part33is formed to have a uniform thickness on the outer circumferential side. In this case, these front/back-side lining part32and the outer circumferential lining part33are each ensured to have a sufficient thickness.

As depicted inFIG.4(b), even if warpage occurs upward, since the front/back-side lining part32has a thickness obtained by adding the thickness of the maximum warp width of the core metal20assumed in advance to the predetermined lining thickness, at least the predetermined lining thickness is ensured on the front/back-side lining part32on an upper surface side of the core metal20, and at least the predetermined lining thickness is also ensured on the outer circumferential lining part33. With these, permeation and penetration of the fluid can be prevented, and sealability with respect to the seat liner4when the valve is closed can be ensured.

In the case of a lining part25provided in the comparative example ofFIG.4(c), the lining thickness equal to the maximum warp width assumed on the valve blade side is not added on the front and back surfaces of the core metal20. On the outer circumferential side of the core metal20, the lining thickness having the predetermined seal thickness is not added. In this case, the front/back-side lining part on the upper surface side is short of the predetermined lining thickness. In particular, in this example, since the core metal20is exposed from an upper part of the front/back-side lining part25, permeation and penetration of the fluid cannot be prevented, and the thickness of the outer circumferential lining part is not sufficient. Thus, it is difficult to ensure sealability when the valve is closed.

When the valve disk2of the present embodiment is applied to the butterfly valve, the annular convex part40is crushed between itself and a seal surface on a body side, and sealability is exerted. Here, to obtain favorable sealability, it is preferable that an outer circumferential side surface part20aof the core metal20be reliably positioned so as to be opposed to the annular convex part40. With this, the state is preferably such that the annular convex part40is supported by the core metal20. Also, as described above, while warpage and flexure tend to occur in the core metal20as the diameter is larger, if the outer circumferential side surface part20aof the core metal20is deviated from the annular convex part40due to warpage or flexure of the core metal20, there is a possibility that sealability cannot be sufficiently obtained.

Thus, in the present example, the outer circumferential side surface part20aof the core metal20has a width that can be opposed to a center part of the annular convex part40in a thickness direction even if warpage occurs with the maximum warp width assumed on the valve blade side of this core metal20. For example, if warpage of the core metal20is assumed to occur on the order of 2 mm at maximum, the width of the outer circumferential side surface part20ais preferably set larger than 4 mm. Even if the core metal20warps by 2 mm at maximum, the center part of the annular convex part40is at a position opposed to the outer circumferential side surface part20aof the core metal20. Thus, a decrease in sealability due to warpage or flexure of the core metal20can be prevented.

The above-described valve disk2including the lining part22on the surface of the core metal20can be manufactured as follows, for example.FIG.6is a schematic explanatory drawing depicting a molding die of the butterfly valve. Although not depicted, a stem or a stem jig is inserted into a stem insertion hole to hold a lower die with the stem or the stem jig.

First, the core metal20is prepared, and the stem5or an upper/lower-part stem jig (not depicted) or the like having the same shape as the stem is inserted into the stem insertion hole23of each of the upper stem5aand the lower stem5bof this core metal20to fix the core metal20(for the stem insertion holes23of the core metal20, refer toFIG.1and so forth).

Next, from a state of being substantially horizontally laid down, the core metal20is arranged in a predetermined molding area D for resin molding in a lower metal mold100bof a die for molding (metal mold)100while the upper and lower stems5aand5bor upper/lower-part stem jigs (hereinafter, stem jigs) are held. Here, the upper and lower stems5aand5bor the stem jigs are fixed with a holding member or the like so that the core metal20does not move in a rotating direction. Here, the holding member may be fixed in any method as long as the core metal20does not rotate. For example, the holding member may fix the upper and lower stems5aand5bor the stem jigs so as to interpose them from both sides, or may be integral with the metal mold, with stem-holding concave parts provided in the metal mold.

Next, from above the lower metal mold100b, an upper metal mold100ais placed to fix the metal mold100with a fixing member (not depicted) or the like. Here, between the upper metal mold100aand the lower metal mold100band an area where the core metal20is arranged, a space S is provided to form the lining part22around this core metal20.

InFIG.6, after the inside of a pot200is filled with a resin material300, the resin material300is extruded by an extruding member201, and the resin material300is infused (introduced) into the inside of the space S through an infusion port100cprovided in the metal mold100. This resin material300is cured to form the lining part22which covers the core metal20.

Also, the metal mold100is provided with an annular step part100d. The resin material300is injected into this annular step part100d, and the annular convex part40can be formed on the outer circumferential side of the lining layer22of the core metal20.

After the resin material is sufficiently cured, the core metal20with the lining layer formed is taken out from the metal mold100, unnecessary portion of the annular convex part40formed on the outer circumference of the valve disk is cut out, and thereby a lined butterfly valve including the tip seal surface41having the predetermined seal width W can be manufactured.

Also, in the above-described method, by fixing and holding the upper and lower stems5aand5b, the stem jig, or the like, the core metal20can be arranged at an accurate position in the molding area D in the metal mold100. Thus, distortion, deviation, and so forth when the lining layer is formed can be prevented, and the lining part22having a necessary thickness can be easily formed.

In the present example, in particular, in the case of a butterfly valve having a large diameter, warpage and flexure tend to occur in the core metal20more than in a butterfly valve having a small diameter. To form the lining part22having a necessary thickness even if warpage or flexure occurs in the core metal, the shape of the lining part22is set to satisfy a predetermined condition. At the time of forming this lining part22, it is particularly important to accurately align the position of the core metal20in the molding area in the metal mold. In the above-described method, by fixing and holding the upper and lower stems5aand5b, the stem jig, or the like fixed to the core metal20, accurate alignment of the core metal20can be made in the metal mold100.

InFIG.5, the boss part30on the top/bottom side of the valve disk is arranged in a state of being pressure-contact sealed to the boss surface4dformed on the top/bottom side of the seat liner4attached to the body3. With these boss unit30and the boss surface4d, sealability in a boss portion from a valve opening state to a valve-closed state is ensured.

InFIG.1, the seat liner4is provided from a resin material such as PFA, which is identical to the same material as that of the lining part22of the valve disk2so as to have a predetermined material thickness and, as described above, is provided to cover the inner circumference side of the body3so as to allow high anti-corrosion and heat resistance characteristics to be exerted. The seat liner4has an annular part4aattached to an inner circumferential side of the body3and flange parts4bformed to protrude from an outer circumferential edge at both ends of this annular part4a. At the insertion positions of the upper and lower stems5aand5bof the annular part4a, cylindrical lining parts4c,4care integrally formed to protrude in a direction of attachment of the stem5. Into these cylindrical lining parts4c, the upper and lower stems5aand5bare inserted.

Provided in each of the above-described shaft-mounting parts12of the body3where the stem on the upper/lower side is inserted are a washer51, a ring body52, a sealing bushing53, an O ring54, a cylindrical bearing55. Furthermore, a spring56formed of a coil spring is inserted on the upper/lower side of each shaft-mounting part12. On the upper/lower part side, the valve disk2is rotatably attached inside the body3in a state of being covered with the lining part22and in a state of being shaft-sealed with the shaft-mounting part12.

In each of the upper and lower shaft-mounting parts12, one set of washers51with opposed to each other is attached in a direction of insertion of the upper stem5a/lower stem5b. The one set of washer is formed of a combination of concave and convex shapes so that, even if a deviation or tilt occurs between the stem5and the valve disk2, the state of the surface pressure applied from the stem5(upper and lower stems5a,5b) side to the boss part30of the valve disk2is substantially equivalent to a state in which this does not occur.

Specifically, each washer51is formed of a convex-shaped washer60and a concave-shaped washer61. The convex-shaped washer60has a convex spherical surface62on one surface side, and the concave-shaped washer61has a concave spherical surface63with which this convex spherical surface62is in surface contact on one surface side. By a spring-back force of the spring56inserted in the shaft-mounting part12, these convex-shaped washer60and concave-shaped washer61are attached in a pressurized state in a mutually opposed direction. The attachment structure of this washer51is provided to each of the upper and lower shaft-mounting parts12in a symmetrical attachment state.

When a fluid pressure is applied to the valve disk2, the valve disk2moves to its direction, and it is considered thereby that the stem5(the upper stem5aand the lower stem5b) is tilted centering on a center position of each of the upper and lower bearings55. Thus, in view of sliding with the spherical surface along the tilt of the stem5, by taking the center position of each the upper and lower bearings55as the center position of a sphere, a virtual spherical surface formed at the position of the washer51is matched with the spherical surface where the convex-shaped washer60and the concave-shaped washer61are opposed.

The stem5is tilted by, at maximum, a space that is present around its tip portion side and between itself and a space on the valve disk2side. Thus, the convex spherical surface62and the concave spherical surface63are formed to each have a shape to the extent of being able to support this tilt. For example, when the stem5is tilted at an angle of 1 degree at maximum, the convex spherical surface62and the concave spherical surface63each have a spherical surface shape, accordingly, supporting a tilt at an angle of 1 degree at maximum.

In the present example, the virtual spherical surface has a radius of 110 mm, and with this radius, the convex spherical surface62and the concave spherical surface63are each formed. With this, even if the stem5(the upper stem5aand the lower stem5b) is tilted to cause a deviation or tilt to occur between this stem5and the valve disk2, the surface pressure of the tilt of the bearing55is uniformly transmitted from the convex spherical surface62to the concave spherical surface63.

The convex spherical surface62and the concave spherical surface63are desired to be formed to be in a mode in which they easily slide over each other. In the present embodiment, the inner and outer circumferential diameters of the convex-shaped washer60are provided to be slightly smaller than the inner and outer circumferential diameters of the concave-shaped washer61, and an appropriate space is provided on each of the inner and outer circumferential sides of the convex-shaped washer60(not depicted). Thus, the convex-shaped washer60can easily swing in a circumferential direction with respect to the concave-shaped washer61.

The bearing55is arranged between the spring56and the ring body52. With this bearing55, the upper stem5aand the lower stem5bare each supported near the O ring54so as to be rotatable an in an aligning state.

The ring body52is provided to have a cylindrical shape made of a stainless steel allowing a position of the boss part30of the valve disk2near the outer circumference to be strongly pressurized from an upper side. While the valve disk2is made in a rotatable state, this ring body52is provided to allow the spring-back force of the spring56to be transmitted through the bearing55to a valve disk2side.

On an upper side of the upper body3a, a bearing member70rotatably supporting the upper stem5ais arranged as being locked with a retainer ring71. With this bearing member70, the spring56is retained in a state of springing back downward.

On the other hand, on a lower body3bside, a top member72is arranged as being locked with the retainer ring71. On this top member72, a bearing member73is placed which rotatably supports the lower stem5b. Via this bearing member73, the spring56is retained in a state of being able to spring back upward. With the above-described bearing members70and73and top member72, the upper and lower springs56,56are spring back to two directions of the valve disk2. On the inner and outer circumferences of the bearing member70and the top member72, dustproof and waterproof O rings74,74are respectively attached.

The sealing bushing53is formed of a resin material such as carbon-fiber-impregnated PTFE (polytetrafluoroethylene), and is provided as a seal portion between the ring body52, and the lining part22and the seat liner4. On a lower side of the sealing bushing53, an annular flange part53ais formed so as to be bent to an outer circumferential direction. An end face side of the ring body52is provided so as to be able to make contact with a flange part53a. With this, the ring body52pressurizes the seat liner4via the flange part53a.

With the above-described structure, in the valve main body1ofFIG.1, by pressurizing, via the ring body52, the seat liner4positioned at the boss part30on the top/bottom of the valve disk2with the spring-back force of the spring56provided to the shaft-mounting hole13of the body3, sealability of each of these top and bottom portions is ensured.

Note that, in the above-described embodiment, a partial thickness in accordance with warpage of the core metal20may be further added to the front/back-side lining part32and the outer circumferential lining part33or a thickness corresponding to the maximum warp width assumed on the entire surface of the core metal20may be added thereto.

The washer51can also be arranged at any position in the shaft-mounting part12. As long as a mode is such that the convex-shaped washer and the concave-shaped washer can slide over each other, their shape can be a taper shape other than the spherical shape, and they can be provided to have a reversed vertical positional relation. Also, these washers in one set may be provided in a mode of not swinging.

While a coil spring is used as the spring56, this is not meant to be restrictive and, for example, a disc spring or the like may be used.

Next, the operation of the lined butterfly valve of the present invention in the above-described embodiment is described. InFIG.1toFIG.3, the valve main body1includes the lining part22including the front/back-side lining parts32and the outer circumferential lining part33, and the core metal20is covered with this lining part22. Thus, chemical resistance and heat resistance can be maintained even if the diameter of the valve main body1is increased to be a nominal diameter on the order of 350 A to 600 A.

In this case, on each of the front and back sides of the core metal20, the front/back-side lining part32is set to have the thickness T1of 5 mm obtained by adding the predetermined lining thickness of 3 mm and the thickness of 2 mm equal to the maximum warp width assumed on the valve blade side of the core metal20. Thus, even if warpage occurs in the core metal20at the time of casting or lining process is performed with the lining molding die ofFIG.6and the valve blade side flexes downward by its self-weight to be deformed, the necessary lining thickness can be applied to the front and back sides of the core metal20. With the lining part32, permeation and penetration of the fluid can be reliably inhibited to ensure chemical resistance and heat resistance.

On the other hand, the outer circumferential lining part33is set to have the thickness T2of 4 mm obtained by adding the predetermine lining thickness of 3 mm on the outer circumferential side of the core metal20and the predetermined crush thickness of 1 mm, and the annular convex part40is formed on the seal side of the outer circumferential lining part33. Thus, without finely setting the shape of the core metal20, it is possible to easily form the outer circumferential seal part having the necessary seal width W, without consideration of the thickness and the taper shape of this core metal20on the outer circumferential end part side.

The predetermined seal width W of the annular convex part40is provided to be 3 mm, which is a width necessary for the valve disk2having the size as in the present embodiment. Thus, when the valve is closed, the outer circumferential lining part33including the annular convex part40is pressurized by the outer circumferential surface of the core metal20, and the tip seal surface41of the annular convex part40is brought into pressure contact with the annular seal surface43on the inner circumference of the seat liner4, thereby reliably preventing leakage.

Also, the outer circumferential side surface part20aof the core metal20is formed to have a width that can be opposed to the center part of the annular convex part40in the thickness direction even if warpage occurs with the maximum warp width assumed on the valve blade side of this core metal20. Thus, even if warpage of the core metal20is at maximum, the outer circumferential side surface part20aand the center part of the annular convex part40are always opposed to each other. Thus, a decrease in sealability can be prevented even if warpage or flexure occurs in the core metal20.

Furthermore, each of the side surface parts42of the annular convex part40is provided to be formed of a tilted surface so that the angle θ of the side surface part with respect to the pressure-contact seal direction of the tip seal surface41is 10 degrees. thus, the side surface part42of the annular convex part40is almost parallel in a relation with the pressure-contact seal direction of the tip seal surface41. Thus, the annular convex part40is formed to be slightly long at the time of molding and its superfluous portion is cut out, thereby easily processing it with the predetermined seal width W.

As depicted inFIG.5, the one set of washers51formed of the convex-shaped washer60and the concave-shaped washer61is inserted in each of the upper and lower shaft-mounting parts12, and the convex spherical surface62and the concave spherical surface63are pressurized by the spring-back force of the spring56. With this, even if the valve disk2moves and a tilt occurs in the stem5, the convex spherical surface62slides with respect to the concave spherical surface63to cause the convex-shaped washer60to be tilted together with the stem5. On the other hand, a predetermined orientation of the concave-shaped washer61is maintained. Thus, even if the pressurizing force by the spring56is applied so as to be tilted with respect to the boss surface4ddue to the tilt of the stem5, the pressurizing force is converted by the washer51into a force in a direction perpendicular to the boss surface4d. Without this washer51, the tilted pressurizing force by the spring56is applied to the boss surface4d, and the pressurizing force to the circular boss surface4ddoes not match in the circumferential direction, and leakage may possibly occur at a weak portion. By contrast, the pressurizing force is converted by the washer51perpendicularly to the boss surface4d, the force is uniformly applied in the circumferential direction of the boss surface4d.

From the above description, when the valve is closed, sealability on both of a boss portion side of the valve disk2and a valve blade portion side other than the boss portion is ensured and, for example, even if the diameter of the valve main body1is increased to be a nominal diameter on the order of 350 A to 600 A, sealing can be improved over the entire circumference of the entire circumference of the valve disk2.

While the embodiment of the present invention has been described in detail above, the present invention is not limited by the description of the embodiment and can be variously modified in a range not deviating from the spirit of the invention described in the claims of the present invention.

REFERENCE SIGNS LIST