Butterfly Valve

Abstract

This butterfly valve (11) comprises a main valve body (13), a valve shaft (15) rotatably supported by the main valve body (13), a valve body (19) rotatably supported by the main valve body (13), and a bush (21) fitted on the valve shaft (15). The valve body (19) includes a core material (35) and a contour forming member (33) which is made of a resin material and surrounds the core material (35) to form the contour of the valve body, valve shaft holes (37, 39) that support the valve shaft (15) via the bush (21) are provided in the valve body (19), the contour forming member (33) has a shaft hole forming part (41) that forms inner peripheral surfaces of the valve shaft holes (37, 39), and the bush (21) and the valve shaft (15) have a shape in which a gap is formed between an inner peripheral surface of a part of the bush (21) located inside the shaft hole forming part (41) and an outer peripheral surface of a part of the valve shaft (15) located inside the shaft hole forming part (41).

Description

[Technical Field]

[0001] The present invention relates to a butterfly valve having a valve body in which a core material is covered with a resin material. [Background technology]

[0002] Conventionally, in fields handling corrosive fluids, butterfly valves have been used that combine corrosion resistance and strength by coating a metal core (insert) with a synthetic resin material with excellent corrosion and chemical resistance. Such butterfly valves are configured so that a valve stem, rotatably supported in a bearing hole in the valve body, passes through a through-hole in a seat ring attached to the inner circumferential surface of the internal flow path and is non-rotatably connected to the valve stem hole in the valve body, and the valve body rotatably supports the valve body within the internal flow path. Furthermore, butterfly valves have multiple seals to prevent fluid from leaking into the valve stem hole in the valve body or the bearing hole in the valve body, including a seal between the periphery of the valve stem hole on the outer periphery of the valve body and the periphery of the through-hole on the seating surface of the seat ring, a seal formed by contact between the outer periphery of the valve stem and the inner periphery of the through-hole in the seat ring, and a seal between the outer periphery of the valve stem and the bearing hole and the inner periphery of the valve stem hole.

[0003] When a butterfly valve is closed, fluid pressure in the internal flow path acts on the valve disc, pushing it toward the secondary side (downstream). This causes the valve stem connected to the valve disc to move toward the secondary side. The valve body's bearing bore typically has an inner diameter slightly larger than the valve stem's outer diameter to accommodate machining errors in the valve stem and bearing bore and to prevent the valve stem from seizing. This allows a gap between the inner circumferential surface of the bearing bore and the outer circumferential surface of the valve stem. Therefore, when fluid pressure acts on the valve disc, the valve stem moves toward the secondary side along with the valve disc by the gap. This movement of the valve stem also deforms the through-hole in the seat ring, creating a problem of increased fluid leakage through the resulting gap. Another problem is the difficulty of sealing between the outer circumferential surface of the rotating valve stem and the inner circumferential surfaces of the stationary valve body's bearing bore and the seat ring's through-hole.

[0004] To address these problems, as described in Patent Documents 1 and 2, for example, butterfly valves have been proposed in which a bushing extending from the bearing hole in the valve body to the stem hole in the valve disc is rotatably fitted onto the valve stem, the valve stem being rotatably supported in the bearing hole and the stem hole via the bushing, and a sealing member such as an O-ring is provided on the outer circumferential surface of the bushing to seal between the outer circumferential surface of the valve stem and the inner circumferential surfaces of the bearing hole in the valve body, the valve stem of the seat ring, and the stem hole in the valve disc. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 1475 / 1983 [Patent Document 2] Japanese Patent Application Publication No. 9-303575 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, when a butterfly valve having a valve disc formed by covering a metal core with a synthetic resin material and a valve stem supported in a bearing bore and a stem bore via a bushing is used in a piping line for corrosive liquids, the valve stem may be connected to the core to prevent damage to the valve disc when a large fluid pressure acts on the valve disc when the valve is closed. Furthermore, since corrosive liquids are handled, it is desirable to prevent liquid leaking from the internal flow path into the stem bore from coming into contact with the metal core of the valve disc when the seal around the valve stem wears and breaks the seal around the valve stem between the outer periphery of the valve disc and the valve seat surface of the seat ring. That is, it is desirable to completely cover the periphery of the core with a synthetic resin material so that the core is not exposed to the outside. To achieve this, the inner side of the stem bore must be made of the core, and the valve stem must be fixed non-rotatably to the core portion of the stem bore. The outer side of the stem bore must be made of only the synthetic resin material. The core must not be present around the opening of the stem bore facing the outer periphery of the valve disc. With this configuration, the periphery of the opening of the stem hole is made only of synthetic resin material, and the portion of the valve disc surrounding the opening of the stem hole is not reinforced by a core material.

[0007] On the other hand, when the fluid pressure acting on the valve disc pushes it toward the secondary side when the valve is closed, a bending moment is generated on the valve disc, and a reaction force from the valve stem is transmitted via the bushing to the inner circumferential surface of the stem hole, which supports the valve stem. However, because no reinforcing core material is provided around the opening of the stem hole, the reaction force acting on the valve disc from the valve stem via the bushing must be borne solely by the resin material portion. As a result, if the pressure acting on the valve disc from the fluid is large when the valve is closed, the reaction force from the valve stem can easily damage the portion of the valve disc surrounding the opening of the stem hole.

[0008] Therefore, the object of the present invention is to solve the problems present in the prior art by preventing the fluid pressure acting on the valve body when the valve is closed from being transmitted to the valve stem from the vicinity of the opening of the valve stem hole in the valve body made only of resin material in a butterfly valve having a valve body whose core is covered with a resin material, thereby suppressing damage to the valve body due to reaction force from the valve stem. [Means for solving the problem]

[0009] In view of the above object, the present invention provides a butterfly valve comprising: a valve body having an internal flow path formed therein; a valve stem rotatably supported by the valve body; a valve element disposed within the internal flow path and supported by the valve body via the valve stem so as to be rotatable about a rotation axis; and a bushing fitted onto the valve stem, wherein the valve element is composed of a core material and a profile forming member formed from a resin material and surrounding the core material to form the profile of the valve element; a valve stem hole is provided in the valve body to support at least a part of the valve stem via the bushing; the profile forming member has a shaft hole forming portion which forms a portion of the valve stem hole into which the bushing is inserted; and the bushing and the valve stem are In the bush Located within the shaft hole configuration portion Ru Department The inner surface of the In the valve stem Located within the shaft hole configuration portion Ru Department Between the outer surface of the across the entire area along the axis of rotation To provide a butterfly valve having a shape that forms a gap.

[0010] In the butterfly valve, the disc is composed of a core and a resin profile-forming member surrounding the core. The stem, supported by the valve body, is supported via a bushing in a stem hole-forming portion of the disc, which is part of the profile-forming member. A gap is formed between the inner circumferential surface of the bushing located within the stem hole-forming portion and the outer circumferential surface of the stem located within the stem hole-forming portion. When the butterfly valve is closed, fluid pressure acts on the disc, tending to move it toward the secondary side (downstream), generating a bending moment in the disc connected to the stem. When the inner circumferential surface of the bushing contacts the outer circumferential surface of the stem, a reaction force from the stem is transmitted via the bushing to the inner circumferential surface of the stem hole, which supports the stem. Because the stem hole-forming portion is made entirely of resin around the opening of the stem hole, the stem hole-forming portion is susceptible to damage due to fluid pressure applied to the disc when the valve is closed. However, in the above-mentioned butterfly valve according to the present invention, a gap is formed between the inner circumferential surface of the part of the bushing located within the shaft hole constituent part (more specifically, within the stem hole of the shaft hole constituent part) and the outer circumferential surface of the part of the valve stem located within the shaft hole constituent part (more specifically, within the stem hole of the shaft hole constituent part). Therefore, even if fluid pressure acts on the valve disc when the valve is closed and a bending moment is generated on the valve disc, the gap between the outer circumferential surface of the valve stem and the inner circumferential surface of the bushing within the shaft hole constituent part acts as a relief, preventing contact between the outer circumferential surface of the valve stem and the inner circumferential surface of the bushing, preventing the transmission of force from the valve disc to the valve stem and preventing the transmission of reaction force from the bushing to the shaft hole constituent part.

[0011] In the above-mentioned butterfly valve, it is preferable that an annular constriction is provided on the outer periphery of the part of the valve stem located within the shaft hole constituent part, and that the gap between the inner periphery of the bushing and the outer periphery of the valve stem within the shaft hole constituent part is formed by the constriction.

[0012] Furthermore, it is preferable that the constricted portion is formed so as to extend over the entire area along the rotation axis of the outer periphery of the part of the valve stem that faces the area where the inner periphery of the valve stem hole and the outer periphery of the bushing contact each other within the shaft hole configuration portion.

[0013] In one embodiment, the core material is of The shaft hole may include cylindrical shaft hole reinforcing portions at both ends in the direction, and the shaft hole reinforcing portions may be arranged so as to surround the valve shaft hole while being spaced apart from the inner surface of the valve shaft hole of the shaft hole configuring portion. [Effects of the Invention]

[0014] According to the present invention, a butterfly valve includes a disc comprising a core and a resin profile-forming member surrounding the core, and a stem supported by the valve body is supported via a bushing within a stem hole-forming portion of the disc, which is part of the profile-forming member, in the stem hole of the disc. A gap is formed between the inner circumferential surface of the bushing located within the stem hole-forming portion and the outer circumferential surface of the stem located within the stem hole-forming portion. Therefore, even if fluid pressure acts on the disc during valve closing, generating a bending moment on the disc, the gap between the outer circumferential surface of the stem and the inner circumferential surface of the bushing provides a clearance within the stem hole-forming portion, preventing contact between the outer circumferential surface of the stem and the inner circumferential surface of the bushing. This prevents force from being transmitted from the disc to the stem and prevents reaction force from being transmitted from the bushing to the stem hole-forming portion. As a result, the butterfly valve effectively prevents damage to the stem hole-forming portion, i.e., the resin portion near the opening of the stem hole. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a longitudinal cross-sectional view of a butterfly valve according to an embodiment of the present invention in a closed state, as viewed from the axial direction of a flow channel. FIG. [Figure 2] FIG. 2 is a partially sectional perspective view showing the valve body of the butterfly valve shown in FIG. 1. [Figure 3] 2 is a partial cross-sectional view showing a bearing portion of a valve body that supports a valve stem of the butterfly valve shown in FIG. 1. FIG. [Figure 4] 4 is a partially enlarged cross-sectional view showing the vicinity of an opening of a bearing portion of the valve body shown in FIG. 3. FIG. [Figure 5] FIG. 10 is a partially enlarged cross-sectional view showing a modified example of the bearing portion of the valve body. [Figure 6]6 is a partially enlarged cross-sectional view showing an opening and its vicinity in a modified example of the bearing portion shown in FIG. 5. FIG. [Figure 7] 2 is a partially enlarged cross-sectional view perpendicular to FIG. 1, showing an enlarged view of the vicinity of the opening of a stem hole for connecting the stem of the butterfly valve shown in FIG. 1 to the valve body. [Figure 8] FIG. 2 is a side view showing the valve stem of the butterfly valve shown in FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of a butterfly valve 11 according to the present invention will be described with reference to the drawings, but it goes without saying that the present invention is not limited to this embodiment.

[0017] First, the overall configuration of a butterfly valve 11 will be described with reference to Figures 1 and 2. Figure 1 is a longitudinal cross-sectional view of the butterfly valve as viewed from the axial direction of the flow path, showing the closed state. Figure 2 is a partially cutaway perspective view of the valve body of the butterfly valve shown in Figure 1.

[0018] The butterfly valve 11 comprises a generally hollow cylindrical valve body 13 having an internal flow passage 13a extending in the axial direction of the flow passage, a valve stem 15 rotatably supported by the valve body 13, an annular seat ring 17 attached to the inner periphery of the internal flow passage 13a, a valve element 19 disposed within the internal flow passage 13a, connected to the valve stem 15, and supported by the valve body 13 so as to be rotatable about the rotation axis R, and a synthetic resin bushing 21 rotatably fitted onto the valve stem 15. The internal flow passage 13a can be opened and closed by moving a valve seat 17d formed on the inner circumferential surface of the seat ring 17 and the outer circumferential edge of the valve element 19 toward and away from each other.

[0019] In the illustrated embodiment of the butterfly valve 11, the valve shaft 15 is composed of a first valve shaft 15a arranged on the upper side in Fig. 1 and a second valve shaft 15b arranged on the lower side in Fig. 1 along the rotation axis R, and the bushing 21 is also composed of a first bushing 21a rotatably fitted onto the first valve shaft 15a and a second bushing 21b rotatably fitted onto the second valve shaft 15b. The valve element 19 is rotatably supported on the valve body 13 by the first valve shaft 15a and the second valve shaft 15b via the first bushing 21a and the second bushing 21b, respectively. A drive unit (not shown) is connected to the first valve shaft 15a, and by rotating the first valve shaft 15a using the drive unit, the valve element 19 is rotated about the rotation axis R to open and close the valve. In the illustrated embodiment, the valve shaft 15 is composed of two valve shafts, a first valve shaft 15a and a second valve shaft 15b, but the first valve shaft 15a and the second valve shaft 15b may be integrally formed to form a single valve shaft 15. Similarly, the first bushing 21a and the second bushing 21b may be integrally formed to form a single bushing 21. The first valve shaft 15a and the second valve shaft 15b may be formed from a metal material such as cast iron, steel, carbon steel, copper, a copper alloy, brass, stainless steel, aluminum, or titanium, but the material is not particularly limited as long as it does not pose a problem in terms of strength.

[0020] The valve body 13 is made of a synthetic resin material. Examples of synthetic resin materials that can be used include polyvinyl chloride (PVC), polypropylene (PP), polyvinylidene fluoride (PVDF), polyethylene (PE), polyphenylene sulfide (PPS), polydicyclopentadiene (PDCPD), polytetrafluoroethylene (PTFE), acrylonitrile butadiene styrene (ABS resin), chlorinated polyvinyl chloride (PVC-C), perfluoroalkoxylalkane (PFA), polydicyclopentadiene (PDCPD), fiber-reinforced plastic (FRP), and other synthetic resin materials reinforced with glass fiber or the like. A substantially disk-shaped top flange 23 is provided at the top of the valve body 13. The valve body 13 also has a first bearing hole 25 and a second bearing hole 27 that face each other in the radial direction of the internal flow path 13a (the vertical direction in FIG. 1) and extend from the internal flow path 13a to the outside.

[0021] The first bearing hole 25 extends through the top flange 23. The first valve shaft 15a is inserted into the first bearing hole 25 with the first bushing 21a fitted thereon and is rotatably supported in the first bearing hole 25 via the first bushing 21a. The upper end of the first valve shaft 15a inserted into the first bearing hole 25 protrudes from the top flange 23 and can be connected to a drive unit installed on the top flange 23. The drive unit may be, for example, a lever-type drive unit, a gear-type drive unit, or an automatic drive unit. Meanwhile, the lower ends of the first valve shaft 15a and the first bushing 21a inserted into the first bearing hole 25 extend so as to protrude from the first bearing hole 25 toward the internal flow path 13a. Similarly, the second valve stem 15b is inserted into the second bearing hole 27 with the second bush 21b fitted thereon, and is rotatably supported in the second bearing hole 27 via the second bush 21b. The second bearing hole 27 has a lower end closed by a valve stem holder 29, and the lower ends of the second valve stem 15b and the second bush 21b inserted into the second bearing hole 27 abut against the valve stem holder 29. Meanwhile, the upper ends of the second valve stem 15b and the second bush 21b inserted into the second bearing hole 27 extend so as to protrude from the second bearing hole 27 toward the internal flow path 13a.

[0022] A reinforcing metal insert member 31 is included inside the valve body 13, spaced apart from and surrounding the first bearing hole 25 and the second bearing hole 27. The metal material used to form the insert member 31 is stainless steel for casting, but this is not limited thereto. The insert member 31 may be formed from another metal material similar to the valve stem 15, or from a non-metallic material, as long as it has a higher mechanical strength than the valve body 13.

[0023] In the embodiment shown in FIG. 1 , the insert member 31 has a generally cylindrical shape. Specifically, the insert member 31 includes a generally rectangular parallelepiped central portion, a cylindrical portion located farther from the internal flow path 13a than the central portion, and a base portion located closer to the internal flow path 13a than the central portion, larger than the cylindrical portion, and smaller than the central portion. A through-hole having a diameter larger than the first bearing hole 25 and the second bearing hole 27 is formed in the center of the cylindrical portion, the central portion, and the base. A bolt hole is formed in the central portion for threading a bolt when connecting the valve body 13 to a pipe. The insert member 31 having such a shape is disposed radially outward of the first bearing hole 25 and the second bearing hole 27 and spaced apart from each other. The reason the insert member 31 is embedded in the valve body 13 and not exposed in the first bearing hole 25 and the second bearing hole 27 is to prevent the metallic insert member 31 from coming into contact with the liquid even if a corrosive fluid enters the first bearing hole 25 and the second bearing hole 27.

[0024] The seat ring 17 is formed from an elastic material such as ethylene propylene rubber (EPDM), chloroprene rubber (CR), isoprene rubber (IR), chlorosulfonated rubber (CSM), nitrile rubber (NBR), styrene butadiene rubber (SBR), chlorinated polyethylene (CM), fluororubber (FKM), hydrogenated acrylonitrile butadiene rubber (HNBR), urethane rubber (U), silicone rubber (VMQ, FVMQ), ethylene propylene rubber (EPM), acrylic rubber (ACM), butyl rubber (IIR), or a material in which such an elastic member is coated with a fluororesin. However, these elastic materials are merely examples, and the material is not particularly limited as long as it does not pose a problem in terms of strength and corrosion resistance in the intended use. The seat ring 17 includes a ring body 17a having a generally cylindrical shape and extending in the central axis direction, and flange portions 17b (see FIG. 3) extending outward from both axial ends of the ring body 17a in a manner opposing each other, and a pair of through holes 17c, 17c are formed at radially opposing positions in the ring body 17a, through which the first valve shaft 15a and the second valve shaft 15b pass, respectively. An annular valve seat portion 17d is formed on the inner peripheral surface of the ring body 17a, and the outer peripheral edge of the valve element 19 abuts against the valve seat portion 17d, thereby sealing the gap between the inner peripheral surface of the seat ring 17 and the outer peripheral edge of the valve element 19, allowing the valve element 19 to close the internal flow path 13a.

[0025] The valve element 19 is disposed inside a seat ring 17 attached to the inner circumferential surface of the internal flow path 13a of the valve body 13. The valve element 19 is integrally formed from a contour-forming member 33 made of a synthetic resin material and having a generally disk-shaped outer shape, and a core member 35 made of a metal material and surrounded by the contour-forming member 33. The valve element 19 in this embodiment is molded by injecting the synthetic resin material forming the contour-forming member 33 into an injection mold in which the core member 35 is previously installed. In this embodiment, the contour-forming member 33 is formed from PVDF, which has high chemical resistance, but is not limited thereto. Other synthetic resin materials, such as PP, PVC, PE, PFA, and PDCPD, can also be used. In this embodiment, the core member 35 is formed from a casting aluminum alloy, but is not limited thereto. The core member 35 may be formed from a metal material similar to the valve stem, or from a non-metallic material, as long as it has a higher mechanical strength than the contour-forming member 33.

[0026] A first valve stem hole 37 and a second valve stem hole 39 are provided on the outer periphery of the valve body 19 at opposing positions along the rotation axis R, and the first valve stem hole 37 and the second valve stem hole 39 are formed coaxially with the rotation axis R. When the first valve stem 15a and the second valve stem 15b are integrally formed and the valve stem 15 is formed by a single valve stem 15, the first valve stem hole 37 and the second valve stem hole 39 are also formed as a single through-hole.

[0027] The first stem hole 37 includes a first large-diameter hole portion 37a having a relatively large diameter and including an open end (an opening to the internal flow path 13a), and a first small-diameter hole portion 37b having a relatively small diameter and extending further inward in the direction of the rotation axis R from the first large-diameter hole portion 37a. The inner circumferential surface of the first large-diameter hole portion 37a is formed by the contour forming member 33, while the inner circumferential surface of the first small-diameter hole portion 37b is formed by the core material 35. The first stem hole 37 receives the first stem 15a and the first bushing 21a, which protrude from the first bearing hole 25 of the valve body 13 and pass through the through-hole 17c of the seat ring 17. The first large-diameter hole portion 37a of the first stem hole 37 supports the first stem 15a via the first bushing 21a. The first bushing 21a is not inserted into the first small diameter hole 37b, but rather the tip end portion of the first valve shaft 15a (hereinafter referred to as the tip end) is directly inserted into the first small diameter hole 37b, so that the tip end of the first valve shaft 15a is non-rotatably fitted into the first small diameter hole 37b around the rotation axis R. For example, the tip end of the first valve shaft 15a and the first small diameter hole 37b can be non-rotatably fitted into each other by forming them to have complementary polygonal shapes or circular shapes with two chamfered sides. However, the method of fitting the first valve shaft 15a and the first small diameter hole 37b into each other is not limited as long as the tip end of the first valve shaft 15a and the first small diameter hole 37b can be non-rotatably fitted into each other. Since the first bushing 21a is not inserted into the first small diameter hole portion 37b, only the inner peripheral surface of the first large diameter hole portion 37a comes into contact with the outer peripheral surface of the first bushing 21a.

[0028] Similar to the first stem hole 37, the second stem hole 39 also includes a second large-diameter hole portion 39a with a relatively large diameter including an open end (an opening to the internal flow path 13a), and a second small-diameter hole portion 39b with a relatively small diameter extending further inward in the direction of the rotation axis R from the second large-diameter hole portion 39a. The inner circumferential surface of the second large-diameter hole portion 39a is formed by the contour forming member 33, while the inner circumferential surface of the second small-diameter hole portion 39b is formed by the core material 35. The second stem hole 39 receives the second stem 15b and the second bushing 21b, which protrude from the second bearing hole 27 of the valve body 13 and pass through the through-hole 17c of the seat ring 17. The second large-diameter hole portion 39a of the second stem hole 39 supports the second stem 15b via the second bushing 21b. The second bushing 21b is not inserted into the second small diameter hole 39b, but rather the tip end portion of the second valve stem 15b (hereinafter referred to as the tip end portion) is directly inserted and fitted into the second small diameter hole 39b. Because the second bushing 21b is not inserted into the second small diameter hole 39b, only the inner circumferential surface of the second large diameter hole 39a comes into contact with the outer circumferential surface of the second bushing 21b. Furthermore, since the second small diameter hole 39b does not need to transmit rotational torque between itself and the second valve stem 15b, it has a circular cross-sectional shape, which differs from the first small diameter hole 37b of the first valve stem hole 37 in this respect. However, the second small diameter hole 39b may have a configuration similar to that of the first small diameter hole 37b.

[0029] In the following description, the contour forming member 33 surrounding the first large diameter hole portion 37a and the second large diameter hole portion 39a, which forms the inner peripheral surfaces of these portions, may be specifically referred to as "axial hole forming portion 41".

[0030] As described above, the first stem hole 37 and the second stem hole 39 have similar configurations except for the different cross-sectional shapes of their first small-diameter hole portion 37b and second small-diameter hole portion 39b. Therefore, in the following explanation, the first stem hole 37 will be mainly used as a representative. The first stem 15a will be used as a representative for the stem, and the first bush 21a will be used as a representative for the bush. However, the explanations regarding the first stem 15a, the first bush 21a, and the first stem hole 37 can be applied to the second stem 15b, the second bush 21b, and the second stem hole 39, respectively. Furthermore, for simplicity, the ordinal number "first" included in the names of each component will be omitted. However, this does not apply when it is necessary to distinguish between "first" and "second."

[0031] In this embodiment, the bushings 21 (first bushing 21a and second bushing 21b) are made of PVDF, which has high resistance to corrosive fluids. A plurality of seal members 43, such as O-rings, are provided on the outer circumferential surface of the bushing 21a to prevent fluid from entering the interior of the valve body 19 and contacting the valve stem 15. In the embodiment shown in Fig. 1, four seal members 43 are arranged in the portion of the bushing 21a that is inserted into the large-diameter hole portion 37a of the valve stem hole 37.

[0032] The core material 35 includes a central portion 35a and roughly lattice-shaped main reinforcing portions 35b provided symmetrically around the central portion 35a. The upper and lower ends of the central portion 35a are provided with roughly tubular (preferably roughly cylindrical) shaft hole reinforcing portions 35c, 35c, respectively. In the illustrated embodiment, the shaft hole reinforcing portions 35c, 35c have a shape in which holes with diameters larger than the first and second valve shaft holes 37, 39 are formed in roughly rectangular parallelepiped portions provided at the upper and lower ends of the central portion 35a. Preferably, the shaft hole reinforcing portion 35c and the central portion 35a have the same outer shape. The shaft hole reinforcing portion 35c extends into the shaft hole constituent portion 41 that constitutes the large diameter hole portion 37a and surrounds at least a portion of the radially outer side of the large diameter hole portion 37a in the rotational axis direction, reinforcing the shaft hole constituent portion 41, which is made of a synthetic resin material. When the large-diameter hole portion 37a supports the shear force and bending moment generated on the valve disc 19 due to fluid pressure, the shaft hole reinforcing portion 35c supports the force acting from the valve stem 15 on the large-diameter hole portion 37a and the shaft hole constituent portion 41, thereby suppressing deformation of the shaft hole constituent portion 41. As a result, the seal formed by the seal member 43 between the inner circumferential surface of the large-diameter hole portion 37a and the outer circumferential surface of the bushing 21a can be reliably maintained. As shown in FIGS. 1 and 2, the shaft hole reinforcing portion 35c preferably has multiple through-holes 35d penetrating its inner and outer circumferential surfaces. These through-holes 35d function as passages for the synthetic resin material forming the shaft hole constituent portion 41 when the core 35 is placed in a mold and the profile-forming member 33 is injection-molded, thereby suppressing injection molding defects.

[0033] The shaft hole reinforcing portion 35c surrounds the radially outer side of the first valve stem hole 37 and the second valve stem hole 39, is disposed at a distance from the inner circumferential surfaces of the first valve stem hole 37 and the second valve stem hole 39, and is configured to be embedded in the shaft hole forming portion 41 so as not to be exposed inside the first valve stem hole 37 and the second valve stem hole 39. This is to prevent the metallic shaft hole reinforcing portions 35c, 35c from coming into contact with the liquid even if a corrosive fluid enters the first large diameter hole portion 37a of the first valve stem hole 37 and the second large diameter hole portion 39a of the second valve stem hole 39.

[0034] Next, the support structure of the valve stem 15 by the valve body 13 and the valve element 19 will be described in detail with reference to FIGS.

[0035] First, with reference to FIGS. 3 and 4, the structure of the support portion of the valve stem 15 by the valve body 13 in the butterfly valve 11 shown in FIG. 1 will be described in detail.

[0036] In the butterfly valve 11, the first bearing hole 25 and the first bushing 21a are configured to have shapes that form a gap (space) between the inner circumferential surface of the first bearing hole 25 and the outer circumferential surface of the first bushing 21a in a region adjacent to the opening where the first bearing hole 25, which supports the first valve stem 15a, opens to the internal flow path 13a. In one embodiment shown in Figures 3 and 4, material is removed from the outer circumferential surface of the first bushing 21a in a region adjacent to the opening of the first bearing hole 25, to form an annular constricted portion 45 extending circumferentially on the outer circumferential surface of the first bushing 21a, thereby forming an annular gap (space) between the inner circumferential surface of the first bearing hole 25 and the outer circumferential surface of the first bushing 21a. However, a gap may be formed between the inner circumferential surface of first bearing hole 25 and the outer circumferential surface of first bushing 21a by forming a circumferentially extending annular constricted portion 45 on the inner circumferential surface of first bearing hole 25 by removing material from the inner circumferential surface of first bearing hole 25 in a region adjacent to the opening of first bearing hole 25. The method for forming the gap between the inner circumferential surface of first bearing hole 25 and the outer circumferential surface of first bushing 21a is not particularly limited. However, providing constricted portion 45 on the inner circumferential surface of first bearing hole 25 may reduce the wall thickness around first bearing hole 25, which supports bending moments, and may reduce strength. Therefore, it is preferable to provide constricted portion 45 on the outer circumferential surface of first bushing 21a, which is easier to machine than first bearing hole 25 of valve body 13.

[0037] When the butterfly valve 11 is closed, fluid pressure acts on the disc 19, attempting to move the disc 19 toward the secondary side (downstream), generating a bending moment on the first stem 15a fixed to the disc 19. The first bearing hole 25 attempts to support the force of this bending moment via the first bushing 21a. If the inner circumferential surface of the first bearing hole 25 and the outer circumferential surface of the first bushing 21a are in contact at this time, stress concentration occurs near the opening of the first bearing hole 25. Furthermore, due to wear of the seat ring 17 or the like, fluid in the internal flow path 13a may break through the seal between the valve seat 17d around the through hole 17c of the seat ring 17 and the outer circumferential edge around the first stem hole 37 of the disc 19, as well as the seal between the inner circumferential surface of the through hole 17c of the seat ring 17 and the outer circumferential surface of the first bushing 21a, and enter between the first bearing hole 25 or the outer circumferential surface of the seat ring 17 and the inner circumferential surface of the internal flow path 13a. Even in such a case, to prevent the fluid in the internal flow path 13a from coming into contact with the metallic insert member 31, the insert member 31 is covered with the synthetic resin material of the valve body 13 so as not to be exposed to the outside, and is positioned at a distance from the inner circumferential surface of the first bearing hole 25 and the inner circumferential surface of the internal flow path 13a of the valve body 13. In other words, the insert member 31 is not present near the opening of the first bearing hole 25, and the area near the opening of the first bearing hole 25 is formed only from the synthetic resin material. As a result, the first bearing hole 25 cannot withstand the force due to the bending moment transmitted from the first valve stem 15a via the first bushing 21a, and may be damaged.

[0038] However, as described above, in the butterfly valve 11, a gap (space) is formed between the inner circumferential surface of the first bearing hole 25 and the outer circumferential surface of the first bushing 21a in the region adjacent to the opening of the first bearing hole 25. Therefore, even if fluid pressure acts on the valve element when the valve is closed and the first valve stem 15a applies a force due to a bending moment to the first bearing hole 25 via the first bushing 21a, the gap between the inner circumferential surface of the first bearing hole 25 and the outer circumferential surface of the first bushing 21a in the region adjacent to the opening of the first bearing hole 25 serves as a relief, preventing contact between the outer circumferential surface of the first bushing 21a and the inner circumferential surface of the first bearing hole and preventing transmission of the force due to the bending moment from the outer circumferential surface of the first bushing 21a to the inner circumferential surface of the first bearing hole 25. As a result, the butterfly valve 11 can suppress damage to the resin material portion of the valve body 13 near the opening of the first bearing hole 25.

[0039] When the valve element 19 is subjected to fluid pressure and the first bearing hole 25 supports the bending moment from the first valve stem 15a, the fulcrum is on the side opposite to the internal flow path 13a, so the displacement of the first valve stem 15a from the rotation axis R increases the closer it is to the internal flow path 13a. Therefore, it is preferable that the size of the gap (space) between the inner circumferential surface of the first bearing hole 25 and the outer circumferential surface of the first bushing 21a, i.e., the depth of the constricted portion 45, be formed in a tapered shape so that it increases the closer it is to the opening of the first bearing hole 25 to the internal flow path 13a. This makes it possible to minimize the amount of material loss.

[0040] If the size of the gap (space) between the inner circumferential surface of the first bearing hole 25 and the outer circumferential surface of the first bushing 21a, i.e., the depth of the constricted portion 45, is made too large, it will allow deformation (i.e., bending) of the first valve stem 15a, increasing the displacement of the valve element 19 and deteriorating the valve seat sealing. Therefore, it is preferable to adjust the gap, i.e., the amount of thickness reduction in the constricted portion 45, to an extent that the force due to the bending moment is not transmitted even if the valve element 19 is displaced when pressure is received from the fluid.

[0041] 4, in the butterfly valve 11, the insert member 31 extends in the direction of the rotation axis R to the radial outside of at least a portion of the constricted portion 45. By providing the insert member 31 to extend in the direction of the rotation axis R to the vicinity of the opening of the first bearing hole 25 in this manner, the strength of the periphery of the opening of the first bearing hole 25 is increased, and even if a greater fluid pressure acts on the valve body 19, the first bearing hole 25 can withstand the force due to the bending moment acting from the first valve stem 15a via the first bushing 21a. In order to increase the strength of the first bearing hole 25, it is preferable to make the thickness of the insert member 31 as thick as possible.

[0042] Similarly, in the butterfly valve 11, the second bearing hole 27 and the second bush 21b are also configured to have a shape that forms an annular gap (space) between the inner circumferential surface of the second bearing hole 27 and the outer circumferential surface of the second bush 21b in the region adjacent to the opening where the second bearing hole 27, which supports the second valve stem 15b, opens to the internal flow path 13a. The configurations and functions of the second bearing hole 27, the second bush 21b, and their surroundings are similar to those of the first bearing hole 25, the first bush 21a, and their surroundings described above, and therefore will not be described here.

[0043] Figures 5 and 6 show modified examples of the structure of the support portion of the valve stem 15 provided by the valve body 13 in the butterfly valve 11 shown in Figure 1. The configuration of the support portion of the valve stem 15 provided by the valve body 13 of this modified example differs from the configuration of the support portion of the valve stem 15 provided by the valve body 13 of the embodiment shown in Figures 3 and 4 in that a cylindrical insert member 31' has multiple through holes 31'a extending from the inner peripheral surface to the outer peripheral surface, and that although the insert member 31' extends to the radially outer side of the portion (necked portion 45) where an annular gap (space) is formed between the inner peripheral surface of the first bearing hole 25 and the outer peripheral surface of the first bushing 21a, the insert member 31' is shorter and thinner than in the embodiment shown in Figures 3 and 4; otherwise, the configuration of the support portion of the valve stem 15 provided by the valve body 13 of the embodiment shown in Figures 3 and 4 is similar. If the strength of the first bearing hole 25 is reinforced, it becomes possible to provide the constricted portion 45 on the inner peripheral surface of the first bearing hole 25.

[0044] The through hole 31'a of the insert member 31' functions as a passage for the synthetic resin material and prevents the occurrence of injection molding defects when the insert member 31' is placed in a mold and the synthetic resin material that forms the valve body 13 is injection molded. Furthermore, it is sufficient for the insert member 31' to extend radially outward from at least a part of the portion (necked portion 45) where a clearance space is formed between the inner circumferential surface of the first bearing hole 25 and the outer circumferential surface of the first bushing 21a in the direction of the rotation axis R, and the length and thickness of the insert member 31' can be designed as appropriate.

[0045] Although the above description has been given of the first bearing hole 25, the first bush 21a and their surroundings, the second bearing hole 27, the second bush 21b and their surroundings have the same configuration.

[0046] Next, with reference to FIGS. 7 and 8, the structure of the support portion of the valve stem 15 by the valve element 19 in the butterfly valve 11 shown in FIG. 1 will be described in detail.

[0047] In the butterfly valve 11, the first bushing 21a and the first valve shaft 15a are configured to have shapes that form a gap (space) between the inner circumferential surface of the portion of the first bushing 21a located radially inside the shaft hole constituent portion 41 of the profile forming member 33 and the outer circumferential surface of the portion of the first valve shaft 15a located radially inside the shaft hole constituent portion 41 of the profile forming member 33. In the embodiment shown in Fig. 7, material is removed from the outer circumferential surface of the portion of the first valve shaft 15a located within the shaft hole constituent portion 41 of the profile forming member 33, and a circumferentially extending annular constricted portion 47 is formed on the outer circumferential surface of the first valve shaft 15a as shown in Fig. 8, thereby forming a gap between the inner circumferential surface of the first bushing 21a and the outer circumferential surface of the first valve shaft 15a. However, a gap may be formed between the inner circumferential surface of the first bushing 21a and the outer circumferential surface of the first valve shaft 15a by forming a circumferentially extending annular constricted portion 47 on the inner circumferential surface of the first bushing 21a by removing material from the inner circumferential surface of a portion of the first bushing 21a located radially inside the shaft hole constituent portion 41 of the contour forming member 33. The method for forming a gap between the inner circumferential surface of the first bushing 21a and the outer circumferential surface of the first valve shaft 15a is not particularly limited. However, when the first bushing 21a is made of a resin material and the first valve shaft 15a is made of a metal material, the latter has higher strength, so it is preferable to provide the constricted portion 47 on the outer circumferential surface of the first valve shaft 15a.

[0048] When fluid pressure acts on the disc 19 while the butterfly valve 11 is closed, it attempts to move the disc 19 to the secondary side (downstream side), and the first stem hole 37 attempts to support the shear stress and bending moment generated in the disc 19 via the first bushing 21a. At this time, the reaction force from the first stem 15a supported in the first stem hole 37 is transmitted to the inner circumferential surface of the first stem hole 37 of the valve 19. When the inner circumferential surface of the first bushing 21a and the outer circumferential surface of the first stem 15a are in contact with each other in the first large diameter hole portion 37a of the first stem hole 37, the reaction force from the first stem 15a is transmitted to the inner circumferential surface of the first large diameter hole portion 37a of the first stem hole 37 via the first bushing 21a. The inner circumferential surface of the first large-diameter hole portion 37a is formed by the shaft hole constituent portion 41, and the shaft hole reinforcing portion 35c of the core material 35 is covered with the contour forming member 33 made of synthetic resin to prevent contact with liquid (i.e., the shaft hole reinforcing portion 35c is spaced apart from the inner circumferential surface of the first large-diameter hole portion 37a and the outer circumferential surface of the valve disc 19). Due to this configuration, the periphery of the opening of the shaft hole constituent portion 41 to the outside is formed solely from synthetic resin. Therefore, the first large-diameter hole portion 37a of the first stem hole 37 cannot withstand the reaction force (shear force and bending moment) transmitted from the first stem 15a via the first bushing 21a and may be damaged. However, in the butterfly valve 11, as described above, a gap (space) is formed between the inner circumferential surface of the shaft hole constituent portion 41, which forms the first large-diameter hole portion 37a, at a portion located radially inward, and the outer circumferential surface of the first stem 15a at a portion located radially inward of the shaft hole constituent portion 41. Therefore, even if fluid pressure acts on the valve element 19 when the valve is closed, generating a bending moment on the valve element 19, the gap between the outer circumferential surface of the first valve stem 15a and the inner circumferential surface of the first bushing 21a within the first large diameter hole portion 37a formed by the shaft hole constituent portion 41 serves as a relief, preventing contact between the outer circumferential surface of the first valve stem 15a and the inner circumferential surface of the first bushing 21a and preventing force from being transmitted from the outer circumferential surface of the first valve stem 15a to the first bushing 21a, and preventing force from being transmitted from the first bushing 21a to the shaft hole constituent portion 41. As a result, the butterfly valve 11 is able to prevent damage to the resin material portion (shaft hole constituent portion 41) near the opening of the first valve stem hole 37 of the valve element 19.

[0049] The constricted portion 47 is preferably formed so as to extend over the entire area along the rotation axis R of the portion of the outer peripheral surface of the first valve stem 15a that is located within the first large diameter hole portion 37a formed by the shaft hole constituent portion 41 (i.e., the outer peripheral portion of the portion of the first valve stem 15a that faces the area within the shaft hole constituent portion 41 where the inner peripheral surface of the first valve stem hole 37 and the outer peripheral surface of the first bushing 21a are in contact). In addition, to increase the strength of the shaft hole constituent portion 41, it is preferable that the thickness of the shaft hole reinforcing portion 35c of the core material 35 be made as thick as possible.

[0050] If the size of the gap (space) between the outer circumferential surface of the first valve stem 15a and the inner circumferential surface of the first bushing 21a, i.e., the depth of the constricted portion 47, is made too large, the displacement of the valve element 19 relative to the first valve stem 15a increases, deteriorating the valve seat sealing. Therefore, it is preferable to adjust the gap, i.e., the amount of thickness reduction of the constricted portion 47, to an extent that the force due to the bending moment is not transmitted even if the valve element 19 is displaced when pressure is received from the fluid.

[0051] Similarly, in the butterfly valve 11, both the second valve stem 15b and the second bushing 21b are configured to have shapes that form a gap (space) between the inner circumferential surface of the portion of the second bushing 21b located radially inside the shaft hole forming portion 41 of the contour forming member 33 and the outer circumferential surface of the portion of the second valve stem 15b located radially inside the shaft hole forming portion 41 of the contour forming member 33. The configurations and functions of the second valve stem 15b, second bushing 21b, second valve stem hole 39 and their surroundings are similar to the configurations and functions of the first valve stem 15a, first bushing 21a, first valve stem hole 37 and their surroundings described above, so description thereof will be omitted here.

[0052] Although the butterfly valve 11 according to the present invention has been described above with reference to the illustrated embodiment, the present invention is not limited to the illustrated embodiment. For example, in the illustrated embodiment, insert members 31 are provided around the first bearing hole 25 and the second bearing hole 27, and shaft hole reinforcing portions 35c are provided around the first stem hole 37 and the second stem hole 39, but these are not essential components and may not be provided. [Explanation of symbols]

[0053] 11 Butterfly valve 13 Valve body 13a Internal flow path 15 Valve stem 15a First valve stem 15b Second valve stem 19 Valve body 21 Bush 21a First Bush 21b Second Bush 25 First bearing hole 27 Second bearing hole 31 Insert member 31´ Insert member 33 Profile forming member 35 Core material 37 First valve stem hole 39 Second valve stem hole 41 Shaft hole configuration part 45 Waist 47 Waist

Claims

1. A butterfly valve comprising: a valve body having an internal flow path formed therein; a valve stem rotatably supported by the valve body; a valve element disposed within the internal flow path and supported by the valve body via the valve stem rotatably about a rotation axis; and a bushing fitted onto the valve stem, the valve body is composed of a core material and a contour forming member that is made of a resin material and surrounds the core material to form the contour of the valve body, and a valve stem hole that supports at least a part of the valve stem via the bush is provided in the valve body, the contour forming member has a shaft hole forming portion that forms an inner circumferential surface of a portion of the valve shaft hole into which the bush is inserted, a valve shaft having a shaft hole forming portion and a shaft inner surface, the shaft hole forming portion being spaced apart from the shaft shaft; a valve shaft having a shaft hole forming portion and a shaft inner surface, the shaft inner surface and the shaft outer surface being spaced apart from the shaft shaft;

2. 2. The butterfly valve according to claim 1, wherein an annular constricted portion is provided on an outer circumferential portion of a portion of the valve stem located within the shaft hole constituent portion, and a gap between an inner circumferential surface of the bushing and an outer circumferential surface of the valve stem within the shaft hole constituent portion is formed by the constricted portion.

3. 3. The butterfly valve according to claim 2, wherein the constricted portion is formed so as to extend over the entire area along the rotation axis of an outer periphery of a portion of the valve stem that faces an area where an inner periphery of the stem hole and an outer periphery of the bushing contact each other within the stem hole configuration portion.

4. 4. A butterfly valve according to claim 1, wherein the core material includes cylindrical shaft hole reinforcing portions at both ends in the direction of the rotation axis, and the shaft hole reinforcing portions are arranged to surround the stem hole at a distance from an inner circumferential surface of the stem hole of the shaft hole configuring portion.

Images