Eccentric butterfly valve

Abstract

To provide an eccentric butterfly valve having improved strength while reducing the weight of a valve element, reliably sealing a fluid when the valve is closed by suppressing deflection and deformation due to fluid pressure, and improving a Cv value even when a high-pressure fluid flows by allowing the fluid to flow while straightening the flow when the valve is opened.SOLUTION: A valve element 4 is mounted in a body 2 by one stem 3 so as to be opened and closed in an eccentric state. The stem is fixed to the 4a side of one side surface of the valving element in a state that at least the vicinity of its center is exposed, and vertical ribs 20 are provided on both sides in the vicinity of the 3a of the exposed portion of the stem in the valving element substantially in parallel with the stem. Each of the vertical ribs is provided in a shape that gradually increases in height from the vane portion 30 side of the valving element toward the stem side in the height direction from the one side surface of the valving element, and the height H1 portion of the highest portion of each of the vertical ribs is provided at a position lower than the height H2 portion of the highest exposed portion of the stem and higher than the position of the central shaft C of the stem.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an eccentric butterfly valve that is particularly suitable for use in the flow of high-pressure fluids. [Background technology]

[0002] Conventionally, eccentric butterfly valves, such as double eccentric butterfly valves, have been known as butterfly valves suitable for high-pressure fluids. In such eccentric butterfly valves, the stem is attached eccentrically to the disk, and this eccentric structure allows for improved watertightness and high sealing performance even at high pressures compared to central butterfly valves. Among these, eccentric butterfly valves are known for improving the strength of the disk to suppress deflection and deformation in the face of high-pressure fluids and ensure sealing performance when the valve is closed.

[0003] The applicant has filed a patent application for an eccentric butterfly valve of this type, disclosed in Patent Document 1. In this eccentric butterfly valve, bosses are provided on the upper and lower sides of one surface of the disk in the mounting direction, and the disk is attached to the body by a single stem through these bosses so as to be freely opened and closed. In this case, the stem is inserted into the upper and lower bosses of the disk and attached to the upper and lower mounting portions of the body. This structure, in which the disk is attached by a single stem, allows the disk to be attached with improved strength in the direction perpendicular to the stem axis (fluid flow direction) compared to a structure in which the upper and lower sides of the disk are attached to the upper and lower mounting portions of the body by two upper and lower stems. This increases strength around the boundaries between the disk and the upper and lower mounting portions, suppressing stress concentration due to fluid pressure and preventing deflection and damage to the disk, even when high-pressure fluid flows.

[0004] The disk has a hollowed-out shape near the center between the upper and lower bosses, and this hollowed-out portion exposes the center of the stem that passes through the upper and lower bosses to the flow path. By hollowing out the portion between the upper and lower bosses in this way, when drilling holes for inserting stems in the upper and lower bosses, the holes can be drilled while being accurately centered relative to the upper and lower bosses, making the drilling process easier. Furthermore, the hollowed-out shape also makes it possible to reduce the overall weight of the disk and the amount of material used.

[0005] In Patent Document 1, in order to compensate for the reduction in strength of the disk due to the above-mentioned reduction in weight, flat vertical ribs are formed on both sides of the boss portion of the disk, and these vertical ribs connect the boss portions to each other. The vertical rib has a generally tapered surface that slopes from the stem mounting side to the valve wing side of the disk, and is formed to a height that rises slightly above the disk surface. In this case, the apex of the tapered surface of the vertical rib on the stem side is located closer to the disk surface than the central axis of the stem, i.e., the vertical rib is located at a height lower than the central axis of the stem in the height direction from the disk surface.

[0006] By providing such flat vertical ribs, the eccentric butterfly valve of Document 1 maintains the thin-walled state of the disc and maintains its light weight, while using these vertical ribs to reinforce the disc when attaching the stem, ensuring strength and dispersing the stress applied to the center of the disc due to fluid pressure. Furthermore, by forming the vertical ribs in a manner that prevents the creation of sharp irregularities between them and the disk surface, the flow of fluid is restricted toward the hollowed-out portion of the disk surface on the side where the vertical ribs are formed, thereby minimizing fluid resistance when the valve is opened. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-47858 Summary of the Invention [Problem to be solved by the invention]

[0008] In the case of the eccentric butterfly valve of Patent Document 1 mentioned above, the apex of the tapered surface of the vertical rib is positioned lower than the central axis of the stem in the height direction from the surface of the disc. Therefore, when the valve is open, part of the fluid flowing from the valve blade side of the disc toward the vertical rib may be guided along the tapered surface of the vertical rib, and then proceed from the apex of the tapered surface toward the gap between the stem and disc. If the fluid directly penetrates into the gap between the stem and the disk in this way, the fluid will flow as if it is caught in the narrow area between the stem and the disk, and there is a risk that this will cause turbulence around this area.

[0009] In addition to the above, part of the remaining fluid flowing from the valve blade side of the disc toward the vertical rib directly hits the surface of the exposed part of the stem from the flow path direction. At this time, because the surface of the stem is steeply inclined relative to the side of the valve body, the flow is not smoothly rectified near the surface of the stem when the fluid tries to get over the stem, and there is a risk of turbulence occurring around this area.

[0010] These turbulent flows can make it difficult to maintain a straight flow of fluid in and around the gap between the stem and disc, which is sandwiched between the longitudinal ribs on both sides, and around the surface of the exposed part of the stem. In this case, the fluid flow between the disc and the flow path in the body becomes less smooth, and this tendency becomes more pronounced as the fluid pressure increases and the valve diameter increases, leading to a decrease in the Cv value.

[0011] In response to this phenomenon, the applicant focused on the height and shape of the vertical ribs of the eccentric butterfly valve, and by using the vertical ribs to ensure strength in the area between the bosses and thereby improving the strength of the entire disc, the applicant was able to develop an eccentric butterfly valve that, by appropriately setting the height and shape of the vertical ribs, rectifies the flow of fluid passing particularly near the vertical ribs when the valve is open, improving the Cv value and allowing the fluid to flow smoothly.

[0012] The present invention was developed to solve the above-mentioned problems, and its purpose is to provide an eccentric butterfly valve with excellent flow characteristics that improves the Cv value even when high-pressure fluids are flowing by reducing the weight of the valve disc while improving its strength, suppressing deflection and deformation due to fluid pressure to reliably seal the fluid when the valve is closed, and rectifying the fluid flow when the valve is open. [Means for solving the problem]

[0013] In order to achieve the above object, the invention of claim 1 is an eccentric butterfly valve in which a valve disc is attached eccentrically within a body by a single stem so as to be able to open and close freely, the stem is fixed to one side of the valve disc with at least the vicinity of its center exposed, vertical ribs are provided on both sides of the valve disc near the exposed part of the stem and approximately parallel to the stem, each of these vertical ribs is gradually higher in the height direction from the valve wing side of the valve disc towards the stem side, and the height of the highest part of each of these vertical ribs is lower than the height of the highest exposed part of the stem and is higher than the position of the central axis of the stem.

[0014] The invention of claim 2 is an eccentric butterfly valve in which at least the exposed portion of the stem has a substantially circular cross section in a direction perpendicular to its central axis, and when a tangent is formed on the outer surface of the exposed portion of the stem at an angle of 45° to the perpendicular direction to one side of the valve body, the height of the highest part of each vertical rib from one side of the valve body is higher than the height from one side of the valve body to the tangent point.

[0015] The invention of claim 3 is an eccentric butterfly valve in which each vertical rib is provided in a direction perpendicular to the central axis of the stem, from at least a position near both sides of the stem fixed to the valve body to a position that exceeds half the distance from the central axis of the stem to the edge of the valve wing.

[0016] The invention of claim 4 is an eccentric butterfly valve in which the distance between the opposing surfaces of the vertical ribs on the stem insertion side is wider than the diameter of the insertion hole provided in the valve body for inserting the stem.

[0017] The invention according to claim 5 is an eccentric butterfly valve in which horizontal ribs are formed in the vicinity of the upper and lower sides of the vertical ribs of the valve body, extending in the direction of the valve wing portions and intersecting the vertical ribs.

[0018] The invention of claim 6 is an eccentric butterfly valve in which the vertical ribs have a gradient that changes in height in a direction perpendicular to the central axis of the stem in relation to a change in the direction from the valve wing edge toward the stem, and the gradient change is gentler near the valve wing edge and near the stem than the gradient change between them. [Effects of the Invention]

[0019] According to the invention of claim 1, the valve disc is rotatably mounted within the body by a single stem, and vertical ribs are provided on both sides of the stem near its exposed portion, generally parallel to the stem, thereby reducing the weight of the valve disc and particularly increasing the strength of the valve disc in the vertical direction, which is the direction of the stem's central axis, thereby improving the strength of the valve disc as a whole and suppressing deflection and deformation, so that the fluid is reliably sealed when the valve is closed, even when a high-pressure fluid flows. Each vertical rib is gradually increased in height from the valve disc's wing side toward the stem side in the height direction from one side of the valve disc, and the height of the highest point of each vertical rib is lower than the height of the highest exposed point of the stem and higher than the position of the central axis of the stem, so that the valve disc can be provided with a smooth transition from the highest point of the vertical rib to the highest exposed point of the stem in the direction of fluid flow. As a result, when the valve is open, when fluid flows across the stem on one side of the valve disc where the stem is attached, the fluid gently climbs over the stem, preventing it from flowing into the gap between the valve disc and the stem or directly hitting the exposed part of the stem from the flow path. This allows the fluid to flow smoothly and prevents turbulence such as vortices from occurring. This makes it possible to provide an eccentric butterfly valve that is compatible with fluids and has excellent high-pressure flow characteristics, while ensuring the strength of the valve disc and improving the Cv value. Furthermore, by providing a vertical rib on the structure that exposes the stem, the valve disc can be easily manufactured by casting without using a core.

[0020] According to the invention of claim 2, at least the exposed portion of the stem is formed to have a substantially circular cross section in a direction perpendicular to its central axis, and when a tangent line is formed on the outer peripheral surface of the exposed portion of the stem at an angle of 45° to the perpendicular to one side surface of the valve disc, the height of the highest point of each longitudinal rib from one side surface of the valve disc is higher than the height from the one side surface of the valve disc to the tangent line, so that when the change in curvature between these curved surfaces in the direction of fluid flow in the valve disc is kept small, a gently sloping flow path can be formed by gently connecting one end side of the longitudinal rib to the other end side in the flow path direction on the side where the vertical ribs are formed. This streamlined flow path allows the fluid that has passed through the vertical ribs to smoothly overcome the stem when the valve is open, further improving the Cv value.

[0021] According to the invention of claim 3, the width of the vertical ribs formed on the valve disc is secured to be large on the wing side, and the vertical ribs have a sufficient reinforcing effect on the valve disc, improving the strength of the valve disc. Moreover, by providing each vertical rib in a shape that gradually increases in height from the wing side of the valve disc toward the stem side, the weight increase of the valve disc is minimized and the amount of material used when forming the valve disc is also reduced.

[0022] According to the invention of claim 4, the distance between the opposing surfaces of the vertical ribs on the stem side is set to be wider than the diameter of the stem insertion hole. This prevents the tools such as blades and drills from coming into contact with the vertical ribs when drilling the stem insertion hole, thereby enabling the production of a highly accurate valve body.

[0023] According to the invention of claim 5, horizontal ribs are formed near the upper and lower sides of the vertical ribs in the valve body, extending toward the valve wing portion in a direction intersecting the vertical ribs, thereby reinforcing the valve body in the valve wing direction, i.e., horizontally, and, together with the reinforcement by the vertical ribs in the central axis direction of the stem, i.e., vertically, the strength of the entire valve body can be synergistically improved.

[0024] According to the invention of claim 6, the gradient of the vertical ribs changes with the change in height in the direction from the valve wing edge toward the stem, and this gradient change is gentler near the valve wing edge and near the stem than between them, so that the flow direction of the fluid attempting to go over the stem does not change suddenly, further suppressing the generation of turbulence due to vortices, etc. In particular, by easing the flow just before the stem, where the fluid tends to flow along the surface of the object, the flow near the stem becomes almost parallel to the surface of the valve disc, allowing the fluid to go over the stem smoothly. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a perspective view showing an embodiment of an eccentric butterfly valve of the present invention. [Figure 2] FIG. 2 is a perspective view showing the valve body in FIG. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] 4 is a cross-sectional view taken along the line AA in FIG. 3. [Figure 6] FIG. 4 is a bottom view of FIG. 3. [Figure 7] 4(a) is a BB end view of Fig. 3, and (b) is a partially enlarged cross-sectional view of (a). [Figure 8] FIG. 1 is a schematic diagram illustrating the analysis of the flow trajectory of an eccentric butterfly valve. [Figure 9] 10 is a graph showing the relationship between the valve opening and the Cv value. DETAILED DESCRIPTION OF THE INVENTION

[0026] An embodiment of an eccentric butterfly valve according to the present invention will be described in detail below with reference to the drawings. Fig. 1 is a perspective view of an embodiment of the butterfly valve of the present invention, and Figs. 2 to 7 show the valve body in Fig. 1.

[0027] In FIG. 1, an eccentric butterfly valve (hereinafter referred to as valve body 1) according to an embodiment of the present invention comprises a body 2, a stem 3, and a valve element 4, and is provided with various diameters, such as large diameters of about 350A to 600A, or diameters less than half the diameter of 600A, and can be used even if the flow path direction is reversed, making it a so-called dual-flow valve.

[0028] The body 2 is formed in a short cylindrical shape and has a flow path 10 inside. The upper and lower parts of the body 2 are provided with mounting portions 11 for mounting the stem 3, and these mounting portions 11 are each provided with a stem insertion hole 12. The valve element 4 is attached to the body 2 in an eccentric state so that it can be opened and closed freely by the single stem 3 inserted into the stem insertion hole 12.

[0029] As will be described later, the stem 3 is attached to the valve body 4 with the central portion thereof exposed to the outside. At least the exposed portion 3a of the stem 3 is provided with a substantially circular cross section in a direction perpendicular to the central axis C of the stem 3, and in this example, the entire stem 3 is provided with a substantially circular cross section in its longitudinal direction.

[0030] 2 to 7, the valve disc 4 is formed in a substantially circular disk shape, and a vertical rib 20 is provided near the center of one side surface 4a thereof. An upper boss portion 21 and a lower boss portion 22 are provided near the top and bottom of the valve disc 4 on the upper and lower sides of this vertical rib 20, i.e., on the side of the mounting portion 11 to the body 2, so as to be continuous with the upper and lower sides of the vertical rib 20. With this structure, a gap portion 23 having a substantially rectangular shape in a plan view is provided in the area surrounded by the upper and lower boss portions 21, 22 and the left and right vertical ribs 20, and the center of the stem 3 attached to the valve disc 4 is exposed within this gap portion 23. In this way, the upper and lower boss portions 21, 22 are provided in a structure divided into upper and lower portions via the vertical rib 20 in the attachment direction of the stem 3 to the valve disc 4.

[0031] In this embodiment, the upper and lower boss portions 21, 22 are positioned relative to the valve body 4 so that the stem 3 can be held offset from the center of the valve body 4 by double eccentricity, and the stem 3 fixed to the valve body 4 through the upper and lower boss portions 21, 22 is attached to the body 2, so that the valve main body 1 is configured as a double eccentric butterfly valve.

[0032] In this example, the upper and lower boss portions 21, 22 respectively have small boss portions 21a, 22a located near the top and bottom of the valve body 4 and large boss portions 21b, 22b that are larger than the small boss portions 21a, 22a and located closer to the center of the valve body 4, and these are formed by integrating different substantially rectangular parallelepiped shapes. In particular, the large boss portions 21b, 22b are provided so as to be higher from one side surface 4a of the valve body 4 than the small boss portions 21a, 22a.

[0033] The upper and lower boss portions 21, 22 each have an insertion hole 24 on the side facing the stem insertion hole 12 of the body 2, through which the stem 3 can be inserted. Each boss portion 21, 22 has a through hole 25 formed on the outer periphery, into which a tapered pin 27 can be inserted.

[0034] The stem 3 is inserted into the insertion hole 24 and fixed at the upper and lower boss portions by tapered pins 27, and connected to the valve element 4. As a result, the stem 3 and the valve element 4 are integrated with reduced vibration, and the valve element 2 is provided so that its rotation can be accurately controlled relative to the flow path 10 by the stem 3.

[0035] The vertical ribs 20 are formed integrally with the upper and lower boss portions 21, 22 so as to connect these boss portions 21, 22 from both sides thereof, and are provided on both sides near the exposed portion 3a of the stem 3 attached to the valve body 4 so as to be approximately parallel to the stem 3. By providing the vertical ribs 20 between the upper and lower boss portions 21, 22 in this way, the valve body 4 is reinforced by these vertical ribs 20 in the attachment direction of the stem 3.

[0036] The configuration of the vertical rib and upper and lower boss portions in this manner provides the aforementioned gap 23 in the valve body 4, which removes a portion of the valve body 4 near its center by this gap 23. The stem 3 described above is fixed to one side surface 4a of the valve body 4, with its approximately circular cross-section near its center exposed to the outside by the gap 23. In the gap 23, rounded surfaces 26 are formed at each of the four corners near the boundary between the vertical rib 20 and the upper and lower boss portions 21, 22, and these rounded surfaces 26 disperse stress that would otherwise be applied to the gap 23.

[0037] The vertical ribs 20 are formed thin in the thickness direction of the valve body 4, and furthermore, the upper surfaces 20a thereof are provided in a substantially arc shape. The vertical ribs 20 having these upper surfaces 20a make it possible to reduce fluid resistance when the fluid flows near the vertical ribs 20 when the valve is open.

[0038] The vertical ribs 20 on both sides of the stem 3 are provided in a substantially symmetrical shape around the central axis C of the stem 3. Each of these vertical ribs 20 is provided in a shape with a gradient that gradually increases in height from the valve wing portion 30 side toward the stem 3 side in the height direction from one side surface 4a of the valve body 4, and in this embodiment, as shown in Figures 7(a) and 7(b), is formed to an appropriate length so that the upper surface 20a side has a substantially arc shape.

[0039] More specifically, each vertical rib 20 has a gradient that changes in height in a direction perpendicular to the central axis C of the stem in response to a change in the direction from the valve wing edge 31 toward the stem 3, and is shaped so that this gradient change is gentler near the valve wing edge 31 and near the stem 3 than the gradient change between them.

[0040] In this way, the vertical ribs 20 have an approximately arc-shaped upper surface 20a and are shaped so that the stem 3 side is thicker than the valve wing portion 30.As a result, even though there is a gap 23 between these vertical ribs 20, the strength of the stem 3 side is ensured even when stress is applied to the valve wing portion 30 in the bending direction.

[0041] In the height direction from one side 4a of the valve body 4, the height H1 of the highest part of the vertical rib 20 is lower than the height H2 of the highest exposed part 3a of the stem 3 and is higher than the position of the central axis C of the stem 3. In this case, it is desirable to set the height H1 relative to the height H2 so that the height H1 of the highest part of the vertical rib 20 is higher than a position 30% lower than the diameter of the stem 3 in the height direction.

[0042] In the figure, tangent line S to stem 3 is a line drawn on outer peripheral surface 3b of exposed portion 3a of stem 3 at an angle θ of 45° with respect to the perpendicular direction to one side surface 4a of valve body 4. Valve body 4 is formed so that height H1 of the highest part of the vertical rib from one side surface 4a of valve body 4 is higher than height H3 from one side surface 4a of valve body 4 to tangent point P of tangent line S. In this example, for a valve with a diameter of φ400 mm and a stem with a diameter of φ42 mm, the difference between the height H1 of the highest part of the vertical rib and the height H3 to the contact point P is set to approximately 3 mm.

[0043] The vertical ribs 20 are provided in a direction perpendicular to the central axis C of the stem 3 in the valve body 4 (towards the valve wing 30), from positions near both sides of the stem 3 fixed to the valve body 4 to a position beyond point E, which is half the distance from the central axis C to the valve wing edge 31. In this example, each vertical rib 30 is formed with a length of width W from positions near both sides of the stem 3 to point E in the direction of the valve wing edge 31. In this embodiment, the valve wing portion 30 refers to the portion of the valve body 4 that forms the valve wing side, and the valve wing edge portion 31 refers to the portion of the valve wing portion 30 that is located furthest from the central axis C of the stem 3 in the valve wing direction.

[0044] The opposing surfaces 32 of the vertical ribs 20 on the stem 3 insertion side are arranged substantially parallel to each other with a gap G therebetween, and this gap G is set to be wider than the diameter φD of the stem insertion hole 24 of the valve body 4 for inserting the stem 3. Furthermore, these opposing surfaces 32 are connected to each other by a semicircular portion 33 on the base end side, and this semicircular portion 33 is set to have a diameter slightly larger than the outer diameter of the stem. Due to this shape, when the stem 3 is placed between the vertical ribs 20, the outer periphery of the stem 3 does not come into contact with the opposing surfaces 32 or the semicircular portion 33, and the stem 3 is attached to the valve body 4 with a gap R between them.

[0045] 3, the vertical ribs 20 not only improve the rectification of the fluid when the valve is open, as will be described later, but also improve the strength of the valve body 4 in the direction in which it bends and deforms vertically by being integrally connected to the upper and lower boss portions 21, 22 in the mounting direction of the stem 3. Furthermore, the vertical ribs 20 are formed at the distance W in the direction of the valve wing portions 30, and their upper surfaces 20a are formed in a substantially arc shape, thereby improving the strength of the valve body 4 in the direction in which it bends and deforms horizontally. As described above, the vertical ribs 20 ensure strength in both the mounting direction of the stem 3 in the valve body 4 and the direction of the valve wing portion 30, thereby comprehensively improving the bending strength of the entire valve body 4 against high-pressure fluid.

[0046] Near the upper and lower sides of the vertical rib 20 of the valve body 4, horizontal ribs 40 are integrally formed, extending to the valve wing portion 30 where they intersect with the vertical rib 20. In this example, horizontal ribs 40 are provided on both side surfaces of each large boss portion 21b, 22b of the upper and lower boss portions 21, 22, so that a total of four horizontal ribs 40 are formed on the valve body.

[0047] The horizontal ribs 40 are formed so as to have a gentle taper from the large bosses 21b, 22b toward the valve wings, with the leading end of this tapered portion positioned slightly away from the end of the valve wings. The horizontal ribs 40 are formed with an appropriate thickness in the vertical direction of Figure 3 to improve the rigidity of the valve body 4 toward the valve wings 30, and are desirably formed with an outer shape that prevents stress from concentrating near the upper and lower bosses 21, 22 or the vertical ribs 20 when a bending force is applied to the valve wings 30. At the portions connecting to the large bosses 21b, 22b, the upper surfaces of the horizontal ribs 40 are higher from one side surface 4a of the valve body 4 than the highest portion of the vertical ribs 20.

[0048] Here, when fluid pressure is applied to the valve disc 4, the valve wing 30 side is deformed so as to bend toward the secondary side because the valve disc 4 is supported near its center by a single stem 3, and the degree of bending becomes greater toward the valve wing tip 31 side. From the viewpoint of suppressing the occurrence of such bending, it is advantageous to make the transverse ribs 40 as tall and thick as possible, but this also increases the weight of the valve disc 4. Therefore, it is preferable to keep the height and thickness of the transverse ribs 40 to the minimum necessary. Since the stress caused by the bending of the valve disc 4 increases closer to the stem 3 side, it is preferable to form the transverse ribs 40 in a right-angled triangular shape, for example, to accommodate this.

[0049] As described above, in the valve body 4, upper and lower boss portions 21, 22 are provided on the upper and lower sides of the vertical rib 20, respectively, in the stem mounting direction, and horizontal ribs 40 are provided from the vertical rib 20 toward the valve wing portion 30, thereby reinforcing the entire valve body 4 in the vertical and horizontal directions.

[0050] In the above embodiment, a double eccentric butterfly valve has been described as an example of the eccentric butterfly valve that constitutes the valve body 1, but other types of eccentric butterfly valves may also be used. For example, a triple eccentric butterfly valve may also be configured in the same manner as described above.

[0051] As long as the vertical rib is shaped so that it gradually becomes higher from the valve wing side toward the stem side, the shape of its upper surface can be any shape other than an approximately arc shape, and for example, it may be shaped approximately tapered. On the other hand, in FIG. 6, the horizontal ribs are provided so that their upper surfaces have a substantially tapered shape, but they may also be formed so that their upper surfaces have a substantially arcuate shape.

[0052] Furthermore, the void portion may have a shape other than a generally rectangular shape in plan view, and may have, for example, a generally elliptical shape in plan view.

[0053] Next, the operation of the eccentric butterfly valve of the present invention in the above embodiment will be described. 1 to 7, the eccentric butterfly valve of the present invention has vertical ribs 20 provided on both sides of the valve body 4 near the exposed portion 3a of the stem 3, approximately parallel to the stem 3, thereby increasing the strength of the valve body 4 mainly in the vertical direction (direction of the stem central axis C) and suppressing deflection and deformation due to forces in a direction intersecting the stem central axis C.

[0054] Each vertical rib 20 is formed in a generally tapered shape in the height direction from one side 4a of the valve body 4, gradually increasing in height from the valve wing portion 30 side toward the stem 3 side, and the height H1 of the highest part of each vertical rib 20 is lower than the height H2 of the highest exposed part 3a of the stem 3 and is formed at a position higher than the position of the central axis C of the stem 3. Therefore, the inclination direction of the arc part formed near the highest part of the vertical rib 20 and the arc part formed by the exposed part 3a of the stem 3 is aligned, and when the imaginary line T shown by the dotted line from the highest part of each vertical rib 20 to the highest exposed part 3a of the stem is connected, these are smoothly connected and the inclination can be made small. Therefore, when the valve is open, on one side surface 4a of the stem mounting side of the valve body 4, when fluid flows from the valve wing portion 30 side in a direction intersecting with the stem 3, this prevents the fluid from entering the gap R between the stem 3 and the valve body 4 or from directly hitting the exposed portion 3a of the stem 3, rectifying the flow as it tries to get over the stem 3 and making it less likely that turbulent flows such as vortices will occur. This makes it possible to improve the Cv value.

[0055] Furthermore, the height H1 of the highest point of each vertical rib 20 from one side surface 4a of the valve disc 4 is set at a higher position than the height H3 from one side surface 4a of the valve disc 4 to the tangent point P of the tangent line S at an angle θ of 45°, and in this example, for a stem diameter of φ42 mm (a valve with a φ400 mm size), the difference between the height H1 of the highest point of the vertical rib and the height H3 to the tangent point is set to 3 mm. This allows the stem 3 to be attached to the valve disc 4 with an arc portion of the stem (the outer periphery of the stem) that is a very small proportion of the stem diameter protruding in the flow path direction from the height H1 of the highest point of the vertical rib, preventing this protruding portion from causing significant flow resistance.

[0056] Due to this very slight height difference of 3 mm, when the highest part of the longitudinal rib 20 and the highest exposed part of the stem 3 are connected by an imaginary line T, they form a gently sloping streamlined part. As a result, the fluid that flows along the upper surface 20a of the longitudinal rib 20 on the inlet side (right side in FIG. 7) flows smoothly by moving along the imaginary line T, and the fluid that passes through the imaginary line T is guided by the upper surface 20a of the longitudinal rib 20 on the outlet side (left side in FIG. 7). In this way, turbulence near the exposed part 3a of the stem 3 is suppressed.

[0057] In the present embodiment, the difference between heights H1 and H2 is set to 3 mm as described above, which makes it possible to achieve a better Cv value and improve flow characteristics compared to when the difference is set to a value greater or less than 3 mm. For example, if the difference between heights H1 and H2 is set to a value greater than 3 mm, the amount of fluid that directly hits the exposed portion 3a of the stem increases, which may increase the likelihood of turbulence occurring around this area. On the other hand, if the difference between heights H1 and H2 is set to a value less than 3 mm, the fluid tends to flow more easily in the direction of the gap R between the stem 3 and the valve body 4, which may increase the likelihood of turbulence occurring around this area. It should be noted that this value of "3 mm" is a suitable value for the valve element 4 shown in this example, and the suitable value will vary as appropriate depending on the size of the valve element, etc.

[0058] Furthermore, each longitudinal rib 20 extends from at least a position near both sides of the stem 3 fixed to the valve disc 4 to a distance W that is more than half the distance from the central axis C of the stem 3 to the wing edge 31. This reinforces the valve disc 4. Furthermore, as described above, the longitudinal ribs 20 are gradually elevated from the wing 30 side toward the stem 3 side. Furthermore, the height H1 of the highest point of each longitudinal rib 20 is lower than the height H2 of the highest exposed point of the stem 3. Therefore, sufficient strength is ensured despite the longitudinal ribs 20 having such a low height H1. Therefore, even when the valve body 1 has a large diameter and high-pressure fluid flows through its flow path 10, deflection or deformation toward the wing 30 can be reliably prevented. In this case, the upper surface 20a of each longitudinal rib 20 is generally arc-shaped and its thickness is kept to a minimum, thereby minimizing the weight of the valve disc 4 while adequately reinforcing the valve disc 4. This minimizes the operating torque of the valve disc 4 and improves operability.

[0059] The valve disc 4 has upper and lower bosses 21, 22 connected by vertical ribs 20 on the left and right sides, with a gap 23 provided near the center. Therefore, when a valve disc 4 of the same shape is produced by casting, even though a gap is provided near the center, the upper part of the gap is open, eliminating the need for a core or the like and facilitating demolding. Therefore, even when the valve body 1 has a larger diameter, the valve disc 4 can be easily produced without compromising castability. Furthermore, after the valve disc 4 is formed by casting or the like, the gap 23 facilitates post-processing such as deburring.

[0060] Here, the valve element 4 of this embodiment has a stem fixed in the vertical direction along the vicinity of the center thereof, and is held by the body 2 via this stem 3. However, in the case of the present embodiment, where the upper and lower boss portions 21, 22 are separated, the valve body 4 is not supported by the stem 3 in the gap portion 23 between these boss portions 21, 22, and therefore the rigidity of this portion is inferior.

[0061] Therefore, when fluid pressure is applied to the valve body 4, a force is applied in a direction that tries to bend the valve body 4 in a direction that intersects with the central axis P of the stem 3 (a force that tries to bend the stem 3), as described below, and a bending in the bending direction tends to occur near the void portion 23, which has lower rigidity than other areas. In other words, in a structure in which the upper and lower boss portions 21, 22 are separated, there is a risk that the strength against forces tending to bend the valve body 4 will be weaker than if the vertical ribs were provided continuously in the vertical direction.

[0062] In contrast to this, in this embodiment, the upper and lower boss portions 21, 22 of the valve body 1 are connected and integrated by the vertical rib 20, which improves the strength of the valve body 4 mainly in the direction of the central axis C (the attachment direction of the stem 3). Combined with the strength of the single stem 3 inserted into the insertion hole 24 of the boss portions 21, 22, it is possible to suppress deflection of the valve body 4 due to high-pressure fluid and prevent bending, etc.

[0063] However, if the stem is divided into upper and lower halves, rattle is likely to occur at the respective mounting points of the upper and lower stems. Specifically, if the upper stem and the upper boss hole of the valve disc, and the lower stem and the lower boss hole of the valve disc, are respectively loose-fitted, clearances will occur between the respective mounting positions, making the valve disc more susceptible to significant movement due to fluid pressure, particularly when high-pressure fluid flows. In this case, designing the seat on the valve seat side becomes difficult, and if the seat is designed to accommodate both fluid flows, it will be difficult to prevent leakage when the valve is closed.

[0064] In contrast, as described above, the valve body 1 of this embodiment is configured such that the valve element 4 is attached to a single stem 3, which prevents rattling near the upper and lower mounting positions of the stem 3 and also prevents movement of the valve element 4 due to the fluid. This simplifies the design of the valve seat and makes it easy to accommodate both types of flow.

[0065] Furthermore, by providing the upper and lower boss portions 21, 22 in an upper and lower divided structure, when forming the insertion hole 24 for the stem 3 in the valve body 4, the processing can be easily performed by drilling holes from the upper and lower sides of these boss portions 21, 22 toward the position of the divided portion near the center of the valve body 4 using tools such as blades or drills, and the insertion hole 24 can be formed in a short time.

[0066] Furthermore, the distance G between the opposing surfaces 32 of the vertical ribs 20 on the stem 3 insertion side is set to be wider than the hole diameter φD of the insertion hole 24, so that when the insertion hole 24 is drilled with a tool, the tool is prevented from coming into contact with the inside of the vertical rib 20, and tool vibration is suppressed, enabling high-precision production.

[0067] In addition to the above-mentioned vertical ribs 20, the valve body 4 is formed with horizontal ribs 40 on the bosses 21, 22 at the top and bottom of the vertical ribs 20, extending in a direction intersecting the vertical ribs 20 to the vicinity of the valve wings 30. These horizontal ribs 40 improve the strength of the valve body 4, mainly in the direction of the valve wings 30, and can suppress deflection near the valve wings 30 even when subjected to high-pressure fluid, preventing bending. Furthermore, the horizontal ribs 40 are formed on the large bosses 21b, 22b, which are larger than the small bosses 21a, 22a. Therefore, when stress acts on the bosses 21, 22 from the valve wings 30, the large bosses 21b, 22b ensure sufficient strength and can suppress deflection and deformation of the vertical ribs 20. The vertical and horizontal reinforcement provided by these vertical ribs 20 and horizontal ribs 40 reduces the stress acting on the valve body 4, thereby keeping the displacement of the valve body 4 low even when subjected to high-pressure fluids, thereby providing excellent durability.

[0068] In particular, when reinforcing the valve body 4 with ribs, it is important that the ribs have a sufficient height to withstand the force that deflects the valve body 4. In this embodiment, the horizontal ribs 40 are connected to the large bosses 21b, 22b, which are higher than the small bosses 21a, 22a, and have a shape that gradually increases in height toward the large bosses 21b, 22b. This ensures that the horizontal ribs 40 are as high as possible without interfering with the flow of fluid, thereby maximizing the reinforcing effect of the horizontal ribs 40 against the deflection of the valve body 4.

[0069] In this embodiment, the small bosses 21a, 22a are provided with sloped connecting portions 41 at their connecting portions with the valve disc 4, where the height from one side surface 4a of the valve disc 4 gradually increases from the valve wing 30 side toward the small bosses 21a, 22a. By providing such gently sloped connecting portions 41, the fluid flowing near the surface of the valve disc 4 is guided by the sloped connecting portions 41, allowing it to smoothly overcome the small bosses 21a, 22a. Furthermore, the small bosses 21a, 22a are lower in height than the large bosses 21b, 22b, and have rounded portions 42 at their corners, making them less likely to obstruct the flow of fluid.

[0070] As described above, by providing the sloped connection portion 41 and the curved portion 42, the small boss portions 21a, 22a have a generally streamlined cross section, allowing the fluid to flow smoothly in the vicinity thereof while suppressing the occurrence of turbulence, etc. Moreover, while keeping the height of the small boss portions 21a, 22a low, the gradient connection portions 41 are provided along the entire length of both sides of the small boss portions 21a, 22a in the direction of the stem central axis C, thereby ensuring the strength of the small boss portions 21a, 22a by means of these gradient connection portions 41.

[0071] To summarize the above, the valve disc 4 of the double eccentric butterfly valve of this embodiment has a shape in which upper and lower bosses 21, 22 for fixing the stem 3, the stem 3, a vertical rib 20 for reinforcement against bending, and a horizontal rib 40 are provided on one side of the valve disc 4. Of these, the vertical rib 20 is gradually raised from the valve wing 30 side of the valve disc 4 toward the stem 3 side, and the height of its highest point is higher than the height of the highest exposed part of the stem 3, and of the upper and lower bosses 21, 22, the small bosses 21a, 22a are lower than the large bosses 21b, 22b, and a gradient connection part 41 is provided, which results in smooth fluid flow, particularly when the valve is fully open, and excellent flow characteristics such as a high Cv value. On the other hand, with such a shape, the vertical ribs 20 suppress deflection and deformation due to forces in the direction transverse to the stem central axis C, and the horizontal ribs 40 suppress deflection near the valve wing portions 30 of the valve body 4, thereby providing an excellent reinforcing effect for the valve body 4. In this way, the valve body 4 of this embodiment not only has flow characteristics and strength, but also, as described above, can be easily manufactured by casting, and therefore has all the characteristics primarily required of a double eccentric butterfly valve. [Example]

[0072] Next, an embodiment of the eccentric butterfly valve according to the present invention will be described. First, the flow path of a fluid flowing through the valve body of the above embodiment was analyzed, and then the flow path of a comparative example was similarly analyzed for comparison with this valve body.

[0073] FIG. 8 shows a schematic diagram of the analysis of the flow trajectories of these eccentric butterfly valves. 8(a) shows the flow state of a test specimen of the valve body 1 of the present invention when the specimen is fully open. In this case, the height of the highest point of the vertical rib is lower than the height of the highest exposed point of the stem, and is higher than the central axis of the stem. On the other hand, Figure 8(b) shows the flow state of the comparative eccentric butterfly valve when it is fully open. In this case, the height of the entire vertical rib is higher than the height of the highest exposed part of the stem. In both Figures 8(a) and 8(b), the valve has a diameter of 400A, and the flow of fluid from right to left through this valve is shown by a flow trajectory.

[0074] In Figure 8(a), it can be seen that the test specimen suppresses large changes in flow, such as vortices, particularly when the fluid passes near the vertical ribs, and that the fluid flows to the secondary side while being rectified after passing through the valve disc.

[0075] On the other hand, in the comparative example of Fig. 8(b), the vertical ribs are higher than the stem, and therefore, when the fluid passes near the vertical ribs, a large vortex is generated around the vertical ribs and their secondary side, compared to the case of Fig. 8(a). In this way, it can be confirmed that the fluid flows while generating turbulence after passing through the valve body.

[0076] Figure 9 is a graph showing an analysis of the change in Cv value according to the valve opening when the valve opening is increased from a closed state for the test specimen in Figure 8(a) and the comparative example in Figure 8(b). In the graph, the horizontal axis represents the valve opening (degrees), and the vertical axis represents the Cv value relative to the valve opening. The maximum target value for the Cv value when fully open is set to 100 (%), and the relative value (0 to 90%) to this target value is shown on the vertical axis as a percentage. In both the test specimen and the comparative example, the valve diameter is 350A, and in the figure, 350A (comparative example) is the comparative example, 350A (test specimen 1) is the test specimen 1 of the valve body of the present invention, and 350A (test specimen 2) is the test specimen 2, which is a design modification of test specimen 1.

[0077] In the graph, for specimens 1 and 2, the Cv value increases proportionally as the valve opening increases, and the Cv value reaches its maximum when the valve opening is 90 degrees (fully open). The maximum Cv value at this time is approximately 91% of the target value (100%).

[0078] On the other hand, in the case of the comparative example, the Cv value increases as the valve opening increases, just like the test sample. However, the Cv value is maximum at a valve opening of approximately 80 degrees and decreases at a valve opening of 90 degrees. This is thought to be because the vertical ribs are higher than the stem, resulting in greater fluid resistance in the valve disc at a valve opening of 90 degrees (fully open) than at 80 degrees. In this case, the maximum Cv value at a valve opening of approximately 80 degrees is approximately 78% of the target value (100%).

[0079] As can be seen, the comparative example was unable to secure the maximum Cv value when the valve was fully open at 90 degrees, whereas the two test products were able to achieve the maximum Cv value when fully open, demonstrating the ideal flow characteristics for a valve. Furthermore, when comparing these maximum Cv values, the comparative example was approximately 78% while the test products were approximately 91%, demonstrating that a higher Cv value could be achieved when fully open than the comparative example, and that the test products were able to significantly improve the flow characteristics compared to the comparative example. Furthermore, it can be confirmed that even at openings other than fully open, particularly at valve openings of 60 degrees or more, the test sample can achieve a higher Cv value than the comparative example at the same valve opening.

[0080] From the above, it can be said that the test valve, which is an eccentric butterfly valve of the present invention, is able to allow fluid to flow smoothly while rectifying the flow as an eccentric butterfly compared to the comparative example, and can exhibit excellent flow rate characteristics and improve the Cv value.

[0081] The above describes in detail the embodiments of the present invention, but the present invention is not limited to the description of the above embodiments, and various modifications can be made within the scope of the spirit of the invention described in the claims of the present invention. [Explanation of symbols]

[0082] 1 Valve body 2 Body 3 Stem 3a Exposed area 3b Outer surface 4 Valve body 4a one side 20 Vertical ribs 24 Stem insertion hole 30 Valve blade part 31 Valve wing edge 32 Opposite surface of vertical rib 40 Horizontal rib C center axis G interval H1 Height of the highest point of the vertical rib H2 Height of the most exposed part of the stem H3 Height from one side of the valve body to the point of contact of the tangent line S tangent φD: Diameter of the stem insertion hole

Claims

1. an eccentric butterfly valve in which a valve disc is eccentrically mounted within a body by a single stem so as to be able to open and close freely, the stem being fixed to one side of the valve disc with at least the vicinity of its center exposed, vertical ribs being provided on both sides of the valve disc near the exposed part of the stem and generally parallel to the stem, each of these vertical ribs being gradually higher in height from the one side of the valve disc from the valve wing side towards the stem side, the height of the highest part of each of these vertical ribs being lower than the height of the highest exposed part of the stem and being higher than the position of the central axis of the stem.

2. 2. The eccentric butterfly valve according to claim 1, wherein at least the exposed portion of the stem has a substantially circular cross section in a direction perpendicular to the central axis thereof, and when a tangent line is formed on the outer peripheral surface of the exposed portion of the stem at an angle of 45° with respect to a direction perpendicular to the one side surface of the valve body, the height of the highest portion of each of the vertical ribs from the one side surface of the valve body is higher than the height from the one side surface of the valve body to the tangent line.

3. 3. An eccentric butterfly valve according to claim 1, wherein each of the longitudinal ribs is provided in a direction perpendicular to the central axis of the stem, from at least a position near both sides of the stem fixed to the valve body to a position exceeding half the distance from the central axis of the stem to the edge of the valve wing.

4. 2. An eccentric butterfly valve according to claim 1, wherein the distance between opposing surfaces of the vertical ribs on the stem insertion side is set to be wider than the diameter of an insertion hole provided in the valve body for inserting the stem.

5. 2. An eccentric butterfly valve according to claim 1, wherein horizontal ribs are formed in the valve body near the upper and lower sides of the vertical ribs, the horizontal ribs intersecting the vertical ribs and extending in the direction of the valve wings.

6. 2. The eccentric butterfly valve according to claim 1, wherein the vertical rib has a slope that changes in height in a direction perpendicular to the central axis of the stem from the valve wing edge toward the stem, and the slope change is gentler near the valve wing edge and near the stem than between them.

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