Butterfly valve

Abstract

A butterfly valve 1 comprises a cylindrical valve main body 2, a valve seat 3 provided on the inner peripheral surface of the valve main body 2 and provided with two opposing through-holes 3a, a disk-shaped valve body 10 configured come into close contact with the valve seat 3 to close a flow passage, a valve shaft 4 that penetrates through the through-holes 3a of the valve seat 3 and rotatably supports the valve body 10 in relation to the valve main body 2, and a sliding contact member 20 provided on the valve body 10 so as to be in close sliding contact with the valve seat 3 during rotation of the valve body 10. The sliding contact member 20 is configured to reduce friction resistance with the valve seat 3 or the amount of wear of the valve seat during rotation of the valve body 10 more than when the sliding contact member 20 is not provided.

Description

Butterfly Valve

[0001] The present invention relates to a butterfly valve.

[0002] Generally, a butterfly valve comprises a cylindrical valve body, a rubber valve seat provided on the inner circumferential surface of the valve body with two opposing through-holes, a disc-shaped valve element configured to fit tightly against the valve seat to close the flow path, and a valve stem that passes through the through-hole in the valve seat and rotatably supports the valve element relative to the valve body. In a butterfly valve, the valve element rotates in conjunction with the rotation of the valve stem, thereby opening and closing the flow path through the valve body.

[0003] A butterfly valve is known in which an O-ring seals the gap between the valve stem and the through-hole of the valve body into which the valve stem is inserted, preventing fluid from leaking to the outside (see Patent Document 1). Specifically, the butterfly valve described in Patent Document 1 has a cylindrical member called a cylindrical seal member disposed in the through-hole relative to the valve stem, with O-rings attached to the inner and outer circumferential surfaces of the cylindrical member. This prevents fluid from leaking along the through-hole.

[0004] Furthermore, because the valve seat is made of rubber, the elastic deformation of the rubber creates a seal between the area surrounding the through-hole of the valve seat and the valve disc that abuts on that area, and between the inner surface of the through-hole of the valve seat and the valve stem inserted into the through-hole. In other words, the restoring force caused by the elastic deformation of the valve seat causes the valve seat to tightly contact the valve disc or valve stem, preventing fluid from flowing into the through-hole of the valve seat and, ultimately, into the through-hole of the valve body.

[0005] JP 2012-57740 A

[0006] The area around the through-hole of the valve seat is constantly compressed by the valve disc abutting against that area. In other words, because the valve disc is constantly compressed, a surface pressure is generated at the abutting area due to a restoring force, thereby achieving a reliable seal. The opening and closing of the butterfly valve, i.e., the rotation of the valve disc around the valve stem, gradually wears the rubber valve seat. In particular, the area around the through-hole of the valve seat is more susceptible to wear than other areas that the valve disc separates from when the butterfly valve opens, because it is constantly subjected to surface pressure. When the area around the through-hole of the valve seat becomes significantly worn due to repeated opening and closing operations, the surface pressure decreases compared to before the wear, and as a result, the sealing performance also decreases.

[0007] An object of the present invention is to provide a butterfly valve that can maintain sealing performance around the through-hole of the valve seat relative to the valve body.

[0008] According to one aspect of the present invention, there is provided a butterfly valve comprising: a cylindrical valve body; a valve seat provided on the inner peripheral surface of the valve body and having two opposing through holes; a disk-shaped valve element configured to fit closely against the valve seat to close a flow path; a valve stem that passes through the through hole in the valve seat and rotatably supports the valve element with respect to the valve body; and a sliding contact portion provided on the valve element so as to fit closely and slide against the valve seat when the valve element rotates, wherein the sliding contact portion is configured to reduce frictional resistance with the valve seat or the amount of wear of the valve seat when the valve element rotates, compared to when the sliding contact portion is not provided.

[0009] The sliding contact portion may be a member separate from the valve body. The sliding contact portion may be an injection-molded product having an annular parting line formed on its surface, and the valve seat and the valve body may be in close contact with each other at least radially outward from the parting line. The sliding contact portion may have a protruding mating convex portion formed in an annular shape, and the valve body may have a mating recess formed to fit into the mating convex portion. A seal portion may be provided that is configured to bring the mating convex portion and the mating recess into close contact in the radial direction. The seal portion may be a protrusion provided on either the mating convex portion or the mating recess, or an elastic member arranged between the mating convex portion and the mating recess.

[0010] According to the aspects of the present invention, a common effect is achieved in that a butterfly valve is provided that can maintain sealing performance around the through-hole of the valve seat relative to the valve body.

[0011] Fig. 1 is a front cross-sectional view of a butterfly valve according to an embodiment of the present invention when the valve is closed. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. Fig. 3 is a perspective view of a sliding contact member. Fig. 4 is an exploded perspective view of a valve body and a sliding contact member. Fig. 5 is an enlarged perspective view of the valve body and the sliding contact member. Fig. 6 is a partially cross-sectional perspective view of the valve body and the sliding contact member. Fig. 7 is a partially cross-sectional view of the vicinity of the sliding contact member in Fig. 2. Fig. 8 is an enlarged perspective view of the valve body and the sliding contact member showing the contact portion with the valve seat. Fig. 9 is a partially cross-sectional view of the valve body and the sliding contact member showing another seal portion. Fig. 10 is a perspective view of another sliding contact member.

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Corresponding components throughout the drawings are designated by common reference numerals.

[0013] Fig. 1 is a front cross-sectional view of a butterfly valve 1 according to an embodiment of the present invention in a closed state, and Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. The butterfly valve 1 comprises a generally annular or cylindrical valve body 2 having two upper and lower protrusions, a valve seat 3 having two opposing through-holes 3a formed on the inner circumferential surface of the valve body 2, a disk-shaped valve element 10 configured to close a flow path by tightly contacting the valve seat 3, two valve stems 4 that pass through the through-holes 3a in the valve seat 3 and rotatably support the valve element 10 relative to the valve body 2, a synthetic resin bushing 5 fitted onto each of the valve stems 4, a handle 7 connected to one of the valve stems 4 via a gear mechanism 6, and a valve stem holder 8 disposed at the bottom of the valve body 2 and supporting the other valve stem 4. The butterfly valve 1 further comprises an annular sliding member 20 as a sliding contact portion provided on the valve element 10 so as to come into close sliding contact with the valve seat 3 when the valve element 10 rotates. The sliding contact member 20 is attached to the valve body 10 by fitting.

[0014] The valve body 2 is made of a synthetic resin material, and a reinforcing metal insert 9 is included around the through-hole through which the valve stem 4 is inserted. The gear mechanism 6 is a conventional type consisting of a cylindrical worm and a worm wheel. Rotational torque applied to the handle 7 is transmitted to the valve stem 4 via the gear mechanism 6. To transmit the rotational torque applied to the handle 7 to the valve disc 10 via the valve stem 4, the valve stem 4 is rotatably supported by the valve body 2 via a bushing 5, but is non-rotatably connected to the valve disc 10. The valve disc 10 is integrally formed from a synthetic resin profile 11 that forms a disk-shaped outer shape and a metal core 12 surrounded by the profile 11. The profile 11 and core 12 are integrally molded, for example, by injection molding. The valve disc 10 may be formed solely from the profile 11, omitting the core.

[0015] FIG. 3 is a perspective view of the sliding contact member 20. The sliding contact member 20 has a flat, annular sliding contact portion 21 and a cylindrical fitting rib 22 as a fitting protrusion. The central axis of the fitting rib 22 coincides with the center of the annular sliding contact portion 21. The outer diameter of the fitting rib 22 is slightly smaller than the diameter of the sliding contact portion 21. Two recesses 23 cut out to a uniform depth are formed on the end face of the fitting rib 22 opposite the sliding contact portion 21. The two recesses 23 are arranged symmetrically with respect to the central axis of the fitting rib 22. An annular inclined surface 24 is formed on the inner surface on the radially inner side of the sliding contact portion 21. The inclined surface 24 serves to guide the valve stem 4 when the valve stem 4 is inserted into the insertion hole of the valve disc 10 with the sliding contact member 20 attached to the valve disc 10.

[0016] 4 is an exploded perspective view of the valve body 10 and the sliding contact member 20, FIG. 5 is an enlarged perspective view of the valve body 10 and the sliding contact member 20, FIG. 6 is a partial cross-sectional perspective view of the valve body 10 and the sliding contact member 20, FIG. 7 is a partial cross-sectional view of the vicinity of the sliding contact member 20 in FIG. 2, and FIG. 8 is an enlarged perspective view of the valve body 10 and the sliding contact member 20 showing the contact portion with the valve seat 3.

[0017] The disc-shaped valve element 10 is formed with two insertion holes 13 into which two valve stems 4 are respectively inserted. A stem seal portion 14 is formed around each of the insertion holes 13, protruding from the surrounding area. An outer seal portion 15 is formed on the outer circumferential surface of the valve element 10, similarly protruding from the surrounding area, to connect the two stem seal portions 14. When the butterfly valve 1 is closed, the stem seal portion 14 and the outer seal portion 15 come into close contact with the valve seat 3 over the entire circumference, thereby closing the flow path.

[0018] A fitting recess 16 configured as a recess into which the fitting rib 22 can fit is formed around the insertion hole 13 and radially inside the shaft seal portion 14. Two protrusions (not shown) complementary to the recesses 23 of the sliding contact member 20 are formed inside the fitting recess 16. When the sliding contact member 20 is fitted into the fitting recess 16 of the valve body 10, the recesses 23 of the sliding contact member 20 mesh with the two protrusions formed in the fitting recess 16. Therefore, the sliding contact member 20 engages with the valve body 10 around the central axis. When the valve body 10 rotates, the sliding contact member 20 rotates integrally with the valve body 10.

[0019] An O-ring 30 is disposed inside the fitting recess 16 of the valve body 10, between the valve body 10 and the sliding contact member 20. Specifically, an annular accommodating recess 17 is formed on the radially inner inner wall of the fitting recess 16 ( FIG. 7 ). The O-ring 30 is disposed in the accommodating recess 17 between the inner wall of the fitting recess 16 and the radially outer inner wall of the fitting rib 22 of the sliding contact member 20. When the sliding contact member 20 is fitted to the valve body 10, the O-ring 30 disposed in the accommodating recess 17 prevents fluid from leaking into the insertion hole 13 through the fitting surfaces of the valve body 10 and the sliding contact member 20. In other words, the O-ring 30 constitutes a seal that radially seals the fitting rib 22, which is a fitting protrusion, and the fitting recess 16. The O-ring 30 may be disposed between the radially inner inner wall of the fitting recess 16 and the radially outer outer wall of the fitting rib 22 of the sliding contact member 20. Instead of the O-ring 30, another elastic member capable of realizing sealing properties may be used.

[0020] The sliding contact member 20 is a sliding contact portion provided on the valve disc 10 so as to come into close sliding contact with the valve seat 3 when the valve disc 10 rotates. In particular, the sliding contact member 20 always comes into close sliding contact with the valve seat 3 from the fully closed state to the fully open state of the butterfly valve 1. In other words, the shape and size of the sliding contact member 20 are determined so as to cover at least a part of the part of the valve disc 10 that always comes into close sliding contact with the valve seat 3 from the fully closed state to the fully open state of the butterfly valve 1.

[0021] The sliding contact member 20 is configured to reduce the frictional resistance with the valve seat 3 or the amount of wear on the valve seat 3 when the valve disc 10 rotates, compared to when the sliding contact member 20 is not provided. Specifically, the material of the sliding contact member 20 is determined so that the frictional resistance between the valve seat 3 and the sliding contact member 20 when the valve disc 10 rotates is lower than the frictional resistance between the valve seat 3 and the contour forming member 11 of the valve disc 10. The sliding contact member 20 is also formed from a material that is less abrasive than the valve seat 3. The sliding contact member 20 is formed, for example, by injection molding from a synthetic resin material, but may also be formed from a metal material.

[0022] The valve body 2 is formed from a synthetic resin material such as polypropylene, polyvinylidene fluoride, polyvinyl chloride, phenolic resin, or polydicyclopentadiene, or a metal such as stainless steel or aluminum. The valve seat 3 is formed from a synthetic resin material such as ethylene propylene diene rubber or fluororubber. The profile-forming member 11 of the valve disc 10 is formed from a synthetic resin material such as polypropylene, polyvinylidene fluoride, polyvinyl chloride, phenolic resin, or polydicyclopentadiene, or a metal such as stainless steel or aluminum. In contrast, the sliding contact member 20 is formed from a synthetic resin material such as PTFE (polytetrafluoroethylene), high-density polyethylene, ultra-high molecular weight polyethylene, polyacetal, or MC nylon, or fibers of these synthetic resin materials or a metal-reinforced material. In particular, when the valve disc 10 is formed from metal, the sliding contact member 20 is preferably formed from a metal-reinforced material.

[0023] The butterfly valve 1 has the sliding contact member 20, which can suppress wear on the valve seat 3 caused by repeated opening and closing operations. As a result, it is possible to suppress a decrease in surface pressure due to the restoring force of the compressed valve seat 3, and maintain the sealing performance around the through hole 3a of the valve seat 3 against the valve body 10. Furthermore, because the sliding contact member 20 is an integrally formed annular member, it can be manufactured more simply and inexpensively than the seal structure described in Patent Document 1.

[0024] 7, the valve disc 10 abuts against the valve seat 3, and the periphery of the through-hole 3a of the valve seat 3 is compressed by elastic deformation. That is, the valve seat 3 is compressed by the sliding contact member 20 and the surrounding portion of the valve disc 10. In FIG. 8, the portion of the valve disc 10 including the sliding contact member 20 that abuts against the elastically deformed valve seat 3 is indicated by diagonal lines. FIG. 8 differs from FIG. 5 only in the addition of diagonal lines.

[0025] When the sliding contact member 20 is formed by injection molding, a parting line formed by the mold is formed in a ring shape on the surface of the sliding contact portion 21. Depending on the position of the parting line and the sealing position between the valve seat 3 and the valve disc 10, leakage from the primary side to the secondary side may occur through the periphery of the parting line, which is raised higher than the surrounding area, even when the butterfly valve 1 is closed. However, as shown in FIG. 8 , the portion of the valve disc 10 around the sliding contact member 20 directly abuts and tightly contacts the valve seat 3. In other words, the valve seat 3 and the valve disc 10 are tightly contacted at least radially outward of the parting line of the sliding contact member 20. Therefore, even if a parting line is located on the surface of the sliding contact portion 21 of the sliding contact member 20, tight contact between the valve seat 3 and the portion of the valve disc 10 around the sliding contact member 20 prevents fluid leakage.

[0026] 7 and 8, the portion of the valve disc 10 around the sliding contact member 20 directly contacts the valve seat 3, and this portion is more susceptible to wear than the portion of the valve seat 3 that contacts the sliding contact member 20. However, since the portion of the valve disc 10 around the sliding contact member 20 is further away from the central axis of the valve disc 10, in terms of the restoring force due to compression at the portion of the valve seat 3 that this portion contacts, its contribution to the surface pressure that affects the sealing performance is small.

[0027] When the valve disc 10 rotates, a rotational torque is applied to the sliding contact member 20 due to frictional resistance with the valve seat 3. However, the engagement between the convex portion in the fitting recess 16 of the valve disc 10 and the concave portion 23 of the sliding contact member 20 prevents the sliding contact member 20 from rotating relative to the valve disc 10. Note that if the sliding contact member 20 rotates integrally with the valve disc 10 due to the fit between the valve disc 10 and the sliding contact member 20 or due to frictional resistance with the seal portion, i.e., the O-ring 30, the convex portion of the valve disc 10 and the concave portion 23 of the sliding contact member 20 may be omitted. The convex portion of the valve disc 10 and the concave portion 23 of the sliding contact member 20 may be omitted so that the valve disc 10 and the sliding contact member 20 do not rotate integrally. To ensure integral rotation, it is sufficient to have at least one convex portion of the valve disc 10 and one concave portion 23 of the sliding contact member 20, and three or more convex portions and concave portions 23 of the valve disc 10 may be included. As a rotation prevention portion to allow the valve body 10 and the sliding contact member 20 to rotate integrally, an additional recess may be provided within the mating recess 16 of the valve body 10, and a protrusion may be provided on the end face of the mating rib 22 of the sliding contact member 20.

[0028] 9 is a partial cross-sectional view of the valve body 110 and the sliding contact member 120 showing another sealing portion. The valve body 110 differs from the above-described valve body 10 in that it does not have a housing recess 17 within the fitting recess 16. Therefore, an O-ring is not disposed on the valve body 110. The sliding contact member 120 differs from the above-described sliding contact member 20 in the shape of the fitting rib. The fitting rib 22 of the sliding contact member 120 has an annular protrusion 125 on its outer circumferential surface. The annular protrusion 125 has a cylindrical outer circumferential surface 125a. The outer diameter of the outer circumferential surface 125a of the annular protrusion 125 is slightly larger than the inner diameter of the radially outer inner wall of the fitting recess 16 of the valve body 110 into which the sliding contact member 120 fits.

[0029] Therefore, when the sliding contact member 120 is fitted to the valve body 110, the annular protrusion 125 prevents fluid from leaking into the insertion hole 13 through the fitting surfaces of the valve body 110 and the sliding contact member 120. In other words, the annular protrusion 125 forms a seal that radially seals the fitting rib 122, which is the fitting protrusion, and the fitting recess 116. The seal formed by the annular protrusion 125 of the sliding contact member 120 can be constructed more inexpensively than a seal using an O-ring 30.

[0030] In addition to the sealing portion provided by the annular protrusion 125, a sealing portion provided by the above-mentioned O-ring 30 may also be arranged. The annular protrusion 125 may be provided on the inner peripheral surface of the fitting rib 22. The annular protrusion 125 may be provided on the inner wall radially outward of the fitting recess 16 of the valve body 110, rather than on the sliding contact member 120. In short, the sealing portion is a protrusion provided on either the fitting protrusion or the fitting recess, or an elastic member arranged between the fitting protrusion and the fitting recess.

[0031] FIG. 10 is a perspective view of another sliding contact member 220. The sliding contact member 220 differs from the aforementioned sliding contact member 20 only in the shape of the sliding contact portion 221. That is, while the surface of the sliding contact portion 21 that contacts the valve seat 3 in the sliding contact member 20 is flat ( FIG. 4 ), the surface of the sliding contact portion 221 that contacts the valve seat 3 in the sliding contact member 220 is a convex curved surface. Specifically, in a cross section along the radial direction, i.e., a cross section taken along a plane passing through the central axis of the sliding contact member 220, the contour of the surface of the sliding contact portion 221 is arc-shaped. More specifically, the surface of the sliding contact portion 221 is formed in an annular shape including a first spherical surface whose radius of curvature is the radius of the arc in the cross section. The center of the first spherical surface is located on the central axis. On the other hand, the portion of the valve disc to which the sliding contact member 220 is attached near the sliding contact member 220 is also formed as a surface including the first spherical surface. Furthermore, for a valve seat used together with a valve disc to which the sliding contact member 220 is attached, at least the periphery of the through hole of the valve seat, which comes into contact with the surface of the sliding contact portion 221 of the sliding contact member 220, is formed as a concave curved surface that is approximately complementary to the surface of the sliding contact portion 221, i.e., a concave curved surface that includes the surface of a first spherical surface. Note that the periphery of the through hole of the valve seat may also be a concave curved surface that includes the surface of a second spherical surface having a larger radius than the first spherical surface.

[0032] The surface of the sliding portion 221 of the sliding member 220 is a part of a sphere and the surface of the corresponding valve seat is a concave curved surface that is approximately complementary to the part of the sphere, i.e., the sealing surface is a part of a sphere, so that the life of the valve seat can be extended and the sealing torque can be reduced.

[0033] In the above-described embodiment, the sliding contact member is attached to the valve body by an engaging rib of the sliding contact member, but any structure for attaching the sliding contact member to the valve body may be adopted. For example, in the above-described embodiment, the engaging rib serving as the engaging convex portion is cylindrical, but the engaging convex portion may be a plurality of protrusions, and the engaging concave portion is configured to engage with the engaging convex portion. Also, while the valve body has a separate sliding contact member as the sliding contact portion, the sliding contact portion may be formed integrally with the valve body by two-color molding or the like. Furthermore, in the above-described embodiment, the sliding contact portion is provided on the valve body side, but a separate or integrated sliding contact portion may be provided on the valve seat side.

[0034] REFERENCE SIGNS LIST 1 butterfly valve 2 valve body 3 valve seat 3a through hole 4 valve stem 5 bushing 6 gear mechanism 7 handle 8 valve stem holder 9 insert member 10 valve body 11 contour forming member 12 core material 13 insertion hole 14 stem seal portion 15 outer seal portion 16 fitting recess 17 accommodation recess 20 sliding contact member 21 sliding contact portion 22 fitting rib 23 recess 24 inclined surface 30 O-ring

Claims

1. A butterfly valve comprising: a cylindrical valve body; a valve seat provided on the inner circumferential surface of the valve body and having two opposing through holes; a disk-shaped valve element configured to fit tightly against the valve seat to close a flow path; a valve stem passing through the through hole of the valve seat and rotatably supporting the valve element with respect to the valve body; and a sliding contact portion provided on the valve element so as to fit tightly and slide against the valve seat when the valve element rotates, wherein the sliding contact portion is configured to reduce the frictional resistance with the valve seat or the amount of wear of the valve seat when the valve element rotates, compared to when the sliding contact portion is not provided.

2. A butterfly valve as set forth in claim 1, wherein the sliding contact portion is a separate member from the valve body.

3. A butterfly valve as described in claim 2, wherein the sliding contact portion is an injection molded product having an annular parting line formed on its surface, and the valve seat and the valve body are in close contact with each other at least radially outward of the parting line.

4. A butterfly valve as claimed in claim 2 or 3, wherein the sliding contact portion has a protruding mating convex portion formed in an annular shape, and the valve body has a mating concave portion formed to fit into the mating convex portion.

5. A butterfly valve as set forth in claim 4, further comprising a seal portion configured to bring said mating protrusion and said mating recess into close contact in the radial direction.

6. A butterfly valve as set forth in claim 5, wherein the sealing portion is a protrusion provided on one of the mating protrusion or the mating recess, or an elastic member disposed between the mating protrusion and the mating recess.