Eccentric butterfly valve

Abstract

Provided is an eccentric butterfly valve that, even when the diameter of the valve is increased, can: ensure the strength of an entire disc and achieve lightweight while distributing stress on the disc and relieving the stress; surely seal a high-pressure fluid; and improve a Cv value even when the high-pressure fluid flows by reducing deflection and deformation due to the fluid pressure and surely sealing the fluid when the valve is closed, and allowing the fluid to flow while rectifying the fluid when the valve is opened, and that thereby has excellent flow characteristics.　A disc 4 is mounted in a body 2 by a stem 3 so as to be openable and closable in an eccentric state. The disc has a vertical rib 20 through which one stem is inserted and held in the vicinity of the center of a surface on one side of the disc, and a lateral rib 40 formed to extend from the vertical rib to the vicinity of a valve blade end part 33 in a direction crossing the vertical rib. The vertical rib has an upper boss part 20a, a lower boss part 20b, and a side wall part 24 that connects both side parts in the vertical direction of the upper and lower boss parts such that the stem is exposed between the upper and lower boss parts.

Description

Eccentric butterfly valve

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

[0002] Conventionally, eccentric butterfly valves, such as double eccentric butterfly valves, have been known as butterfly valves suitable for high-pressure fluids. The applicant of this application has filed a patent application for this type of eccentric butterfly valve, the butterfly valve of Patent Document 1. In this butterfly valve, two bosses are provided on one side of the disk, one on the upper and one on the lower side in the mounting direction, and the disk is attached to the body by a stem that can be opened and closed freely through these upper and lower bosses.

[0003] The stem consists of a single stem with integral attachment portions for the upper and lower body mounting portions, and this stem is inserted through the upper and lower bosses and fixed to the upper and lower bosses with the central portion between them exposed to the flow path. In this way, by attaching the valve body to the body through the upper and lower bosses with a single stem, the axial strength of the disc is improved by this stem, and it is possible to suppress deflection of the disc mainly in the direction transverse to the axial direction when high-pressure fluid flows through the valve.

[0004] The butterfly valve further includes ribs extending from the boss of the disk toward both outer edges in a direction intersecting with the stem. These ribs increase the strength of the disk on the valve blade side and primarily suppress deflection of the disk on the valve blade side when high-pressure fluid flows through the valve.

[0005] As described above, the eccentric butterfly valve of Patent Document 1 can improve the strength of the entire valve disc, mainly in the stem axial direction and on the valve blade side of the disc, and ensures sealing performance by suppressing deformation and deflection of the valve disc due to the fluid pressure of the high-pressure fluid when the valve is closed. Moreover, by providing ribs, the structure can improve strength while reducing the overall thickness of the disc, thereby reducing the weight of the disc.

[0006] In the above-mentioned eccentric butterfly valve, the stem is attached eccentrically to the disk, and this eccentric structure allows for improved watertightness and sealing performance even under high pressure compared to central butterfly valves. Among these, eccentric butterfly valves are known that have improved strength to suppress bending and deformation of the disk in response to high-pressure fluids and ensure sealing performance when the valve is closed.

[0007] The applicant has filed a patent application for an eccentric butterfly valve of this type, disclosed in Patent Document 2. 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 through 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 boundary 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.

[0008] 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.

[0009] In Patent Document 2, to compensate for the reduction in disk strength due to the above-mentioned lightening, flat vertical ribs are formed on both sides of the boss portion of the disk, and these vertical ribs connect the boss portions together. The vertical ribs have a generally tapered surface that slopes from the stem mounting side to the valve blade side of the disk, and are formed to a height that slightly rises 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. In other words, the vertical rib is located at a height lower than the central axis of the stem in the height direction from the disk surface.

[0010] By providing such flat vertical ribs, the eccentric butterfly valve of Document 2 maintains the thin-walled state of the disk and maintains its light weight, while reinforcing the disk at the attachment of the stem with the vertical ribs to ensure strength and dispersing the stress applied to the center of the disk 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 in 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 open.

[0011] JP 2020-139583 A JP 2014-47858 A

[0012] Generally, when the flow path diameter of a butterfly valve is increased, the valve disc also becomes larger. In addition to the weight increase caused by the larger valve disc diameter, the addition of reinforcement sections to ensure strength can easily increase the weight even further. Furthermore, increasing the diameter increases the pressure-receiving area that receives the fluid, which in turn increases the rotational torque, potentially leading to reduced operability. In addition, the increased size and thickness of the valve disc also poses the problem of increased material usage during manufacturing. Therefore, when increasing the valve disc diameter (increasing the valve size), it becomes difficult to reduce the material used to construct the valve disc while maintaining strength against fluid pressure.

[0013] The above-mentioned problems are also common to eccentric butterfly valves such as those described in Patent Document 1. In particular, in eccentric butterfly valves designed for high sealing performance, even when the valve disc is made larger in diameter, it is necessary to ensure the strength of the entire valve disc and reliably prevent leakage when the valve is closed.

[0014] Therefore, the present applicant discovered that in an eccentric butterfly valve, the strength of the entire valve disc can be improved by increasing the strength of the area between the upper and lower bosses of the disc that support the stem while preventing stress concentration. That is, in a double eccentric butterfly valve, by providing a reinforcing structure on one side of the disc where the boss is formed that further improves strength in the valve axis direction and the valve blade direction, even when the disc is provided with a large diameter, it is possible to avoid an increase in the thickness of the entire valve disc, while still taking advantage of the structure in which a single stem is inserted into the boss to ensure the strength of the disc in the stem axis direction, thereby dispersing stress mainly in the valve axis direction and the valve blade direction, thereby further improving the strength of the entire valve disc and also achieving weight reduction.

[0015] In the case of the eccentric butterfly valve of Patent Document 2, 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 disk surface. Therefore, when the valve is open, part of the fluid flowing from the valve blade side of the disk 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 the disk. If the fluid directly enters the gap between the stem and the disk in this way, the fluid will be caught in the narrow area between the stem and the disk and may cause turbulence around this area.

[0016] 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.

[0017] The occurrence of these turbulent flows can make it difficult to maintain a straight flow of fluid in and around the gap between the stem and the 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.

[0018] 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.

[0019] 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 can ensure the strength of the entire valve body while dispersing and mitigating stress even when the valve diameter is increased, and can be made lighter, can reliably seal in high-pressure fluid, suppresses deflection and deformation due to fluid pressure to reliably seal in the fluid when the valve is closed, and rectifies the fluid flow when the valve is open, thereby improving the Cv value even when high-pressure fluid is flowing.

[0020] 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 stem so as to be able to open and close freely, and which has a vertical rib near the center of one side surface of the valve disc through which one of the stems is inserted and held, and a horizontal rib formed so as to extend from the vertical rib to near the end of the valve wing in a direction intersecting the vertical rib, and the vertical rib has an upper boss portion, a lower boss portion, and side wall portions connecting both vertical sides of the upper and lower boss portions so that the stem is exposed between the upper and lower boss portions.

[0021] The invention according to claim 2 is an eccentric butterfly valve in which the valve body has a gap surrounded by four sides by the opposing surfaces of the upper and lower boss portions and the left and right side wall portions, and the four corners of this gap are rounded.

[0022] The invention according to claim 3 is an eccentric butterfly valve in which the rounded surfaces at the four corners are arc-shaped curved surfaces, and the gap is provided in a substantially elliptical shape.

[0023] The invention according to claim 4 is an eccentric butterfly valve in which the horizontal ribs are formed integrally with the vertical ribs with a portion of their end face extending in the direction of formation from the vertical ribs reaching into the gap.

[0024] The invention according to claim 5 is an eccentric butterfly valve in which the horizontal ribs are formed from the side wall portion, and the base ends of the horizontal ribs on the side wall portion side are integrally formed with the side wall portion while being slightly offset inward from at least one or both of the end faces of the side wall portion in the length direction and the height direction.

[0025] The invention according to claim 6 is an eccentric butterfly valve in which the width between the left and right side wall portions is formed wider than the width of each of the upper and lower boss portions that accommodate the stem.

[0026] The invention of claim 7 is an eccentric butterfly valve in which a valve disc is attached eccentrically within the 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 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 being 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 being lower than the height of the highest exposed part of the stem and higher than the position of the central axis of the stem.

[0027] The invention of claim 8 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 peripheral 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 the one side of the valve body is higher than the height from the one side of the valve body to the tangent point.

[0028] The invention of claim 9 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 positions 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.

[0029] The invention of claim 10 is an eccentric butterfly valve in which the distance between the opposing surfaces of the vertical ribs on the stem insertion side is set to be wider than the diameter of the insertion hole provided in the valve body for inserting the stem.

[0030] The invention according to claim 11 is an eccentric butterfly valve in which horizontal ribs are formed near the upper and lower sides of the vertical ribs on the valve body, extending in the direction of the valve wing portions and intersecting the vertical ribs.

[0031] The invention of claim 12 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 between them.

[0032] According to the invention of claim 1, a valve disc has a vertical rib near the center of one side surface through which a stem is inserted and supported, and a horizontal rib extending from the vertical rib to the ends of the valve wings in a direction intersecting the vertical rib. The vertical rib has an upper boss portion, a lower boss portion, and side walls connecting the vertical ends of the upper and lower boss portions so that the stem is exposed between the upper and lower boss portions. This ensures the strength of the valve disc as a whole while dispersing stress applied to the valve disc through the side walls to alleviate stress, even when the valve diameter is increased, and also reduces the amount of material used in manufacturing the valve disc by reducing its weight, preventing a decrease in operability. In this case, the side walls reinforce the valve disc axially and the horizontal ribs reinforce the valve wings, ensuring the strength of the valve disc as a whole. This reduces the deflection of the valve disc due to high-pressure fluid, reliably preventing fluid leakage, and exhibits excellent sealing performance. The valve body is attached to the body in an eccentric position via a single stem so that it can be opened and closed freely. This single stem improves the axial strength of the valve body and prevents rattling at the stem mounting point and movement in the flow path direction, making it possible to accommodate both types of flow without having to provide a specially shaped seat.

[0033] According to the invention of claim 2, the valve disc has a gap surrounded on all four sides by the opposing surfaces of the upper and lower bosses and the left and right side walls, which makes it possible to reduce the weight of the valve disc. Moreover, by forming rounded surfaces at the four corners of the gap, stress concentration at the corners of the gap is prevented, improving the strength of the entire valve disc, mainly in the axial direction of the stem and the direction of the valve blades, thereby easing stress acting on the valve disc and reliably suppressing deformation of the valve disc even when high-pressure fluid flows.

[0034] According to the invention of claim 3, the rounded surfaces at the four corners are formed as arc-shaped curved surfaces, and the gap is formed in a generally elliptical shape. Therefore, when a load due to deflection of the valve body or the like is applied near the gap, the load is dispersed appropriately through the side wall and the horizontal ribs, preventing localized stress concentration and deformation or damage.

[0035] According to the invention of claim 4, the horizontal ribs are formed integrally with the vertical ribs in a state where a portion of the end face side reaches the gap portion in the forming direction from the vertical rib. This ensures the strength of the entire valve while making the length of the gap portion in the mounting direction of the valve body as large as possible, thereby significantly reducing the weight of the valve body. Furthermore, when a force in the bending direction is applied from the horizontal ribs, this force can be reliably dispersed to suppress deformation of the valve body.

[0036] According to the invention of claim 5, the horizontal rib is formed from the side wall portion, and the base end portion of the horizontal rib on the side wall portion side is formed integrally with the side wall portion while being slightly shifted inward from at least one or both of the end faces of the side wall portion in the length direction and height direction. This prevents the force from the horizontal rib from being concentrated on the end face side of the vertical rib, and distributes the stress acting on the vertical rib to prevent deflection.

[0037] According to the invention of claim 6, the width between the left and right side wall portions is formed wider than the width of each of the upper and lower boss portions that accommodate the stem, thereby suppressing a decrease in the strength of the entire valve body due to gaps, and even when the valve body is provided with a large diameter, its deflection can be suppressed, ensuring sealing performance.

[0038] According to the seventh aspect of the present invention, 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 the exposed portion thereof, substantially parallel to the stem, thereby reducing the weight of the valve disc and, in particular, increasing the strength of the valve disc in the vertical direction, which is the direction of the central axis of the stem, thereby improving the strength of the valve disc as a whole and suppressing the occurrence of deflection or deformation, so that the fluid is reliably sealed when the valve is closed, even when a high-pressure fluid flows through the valve disc. Each vertical rib is gradually increased in height from the valve wing side to 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 a smooth transition can be achieved from the highest point of the vertical rib to the highest exposed point of the stem in the direction of fluid flow through the valve disc. As a result, when the valve is open, when fluid flows over one side of the valve disc on the stem mounting side in a direction intersecting the stem, the fluid gently overcomes 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 direction, allowing the fluid to flow smoothly and preventing turbulence such as vortices. 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 in the configuration where the stem is exposed, the valve disc can be easily manufactured by casting without using a core.

[0039] According to the invention of claim 8, 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 streamlined 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 rib is formed. This streamlined flow path allows the fluid that has passed through the vertical rib to smoothly overcome the stem when the valve is open, further improving the Cv value.

[0040] According to the invention of claim 9, the width of the vertical ribs formed on the valve disc is secured to be large on the valve wing side, and the vertical ribs provide 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 valve wing side to the stem side of the valve disc, the weight of the valve disc is kept to a minimum and the amount of material used in forming the valve disc is also reduced.

[0041] According to the invention of claim 10, 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 or 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.

[0042] According to the invention of claim 11, 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.

[0043] According to the invention of claim 12, 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 the gradient change 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 making the gradient gentle just before the stem, where the fluid tends to flow along the surface of the object, the flow near the stem becomes approximately parallel to the surface direction of the valve disc, allowing the fluid to go over the stem smoothly.

[0044] 8 is a perspective view showing an embodiment of an eccentric butterfly valve of the present invention. (a) is a front view showing the valve disc in FIG. 1. (b) is a cross-sectional view taken along line A-A in (a). An enlarged perspective view of the valve disc. An enlarged perspective view of the valve disc from the valve wing direction. A perspective view showing another example of the valve disc. A perspective view showing another embodiment of the eccentric butterfly valve of the present invention. A perspective view of the valve disc in FIG. 6. A front view of the valve disc. A right side view of the valve disc. A cross-sectional view taken along line B-B in FIG. 8. A bottom view of FIG. 8. (a) is an end view taken along line C-C in FIG. 8. (b) is a partially enlarged cross-sectional view of (a). A schematic diagram of an analysis of the flow path of an eccentric butterfly valve. A graph showing the relationship between valve opening and Cv value.

[0045] An embodiment of an eccentric butterfly valve according to the present invention will be described in detail below with reference to the drawings. Figure 1 is a perspective view of an embodiment of the butterfly valve of the present invention, and Figures 2 to 4 show the valve body shown in Figure 1.

[0046] In the figure, an eccentric butterfly valve (hereinafter referred to as valve body 1) in an embodiment of the present invention comprises a body 2, a stem 3, and a valve element 4, and is provided with a large diameter of, for example, approximately 350A to 600A, making it usable even if the flow path direction is reversed, making it a so-called dual-flow valve.

[0047] 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 provided with a stem insertion hole 12. The valve element 4 is provided in the body 2 in an eccentric state so as to be able to open and close freely by a single stem 3 inserted into the stem insertion hole 12.

[0048] 2 to 4, the valve element 4 is formed in a substantially circular disk shape, and a vertical rib 20 for attaching the stem is provided near the center of one side of the valve element 4. In this embodiment, the vertical rib 20 is provided in a position relative to the valve element 4 that allows the stem 3 to be held in a state where it is offset from the center of the valve element 4 by double eccentricity, and the valve body 1 is thereby provided as a double eccentric butterfly valve.

[0049] The vertical rib 20 has an upper boss portion 20a, a lower boss portion 20b, and sidewall portions 24, and is provided in an upper and lower divided structure so that the stem 3 is exposed near the center in the longitudinal direction (the direction in which the stem 3 is attached to the valve body 4). An upper boss portion 20a and a lower boss portion 20b are provided near the top and bottom of the valve body 4, i.e., on the upper and lower mounting portions 11 sides of the body 2, and insertion holes 21 through which the stem 3 can be inserted are provided in positions of each boss portion 20a, 20b opposite the body-side stem insertion hole 12. The stem 3 is inserted into this insertion hole 21, and the valve body 4 is rotatably held relative to the stem insertion hole 12 by the single stem 3 through each boss portion 20a, 20b.

[0050] In this example, the upper and lower boss portions 20a, 20b are formed integrally with the valve body 4 in a boss-like manner, with a substantially rectangular parallelepiped shape, and each of the upper and lower boss portions 20a, 20b is provided with a through-hole into which a tapered pin (not shown) can be inserted so as to penetrate the stem 3 from the side. The valve body 4 and the stem 3 are connected at the upper and lower parts by the tapered pin, so that the valve body 4 can rotate integrally with the stem 3 with vibration suppressed.

[0051] The side wall portions 24 connect both sides of the upper and lower boss portions 20a, 20b in the vertical direction, i.e., in the direction in which the stem 3 is attached, and are formed integrally with the upper and lower boss portions 20a, 20b on both sides with appropriate width dimensions and thicknesses, and these side wall portions 24, 24 reinforce the space between the upper and lower boss portions 20a, 20b while the stem 3 is exposed between the upper boss portion 20a and the lower boss portion 20b.

[0052] The side wall portions 24 are preferably formed in a thin plate shape that can ensure bending strength and can be made lightweight. In other words, the vertical rib 20 is composed of at least upper and lower boss portions 20a, 20b and side wall portions 24, 24 that connect them, and in this example, a frame-like portion 25 that is approximately rectangular in plan view is provided near the center in the vertical direction, and block-shaped upper and lower boss portions 20a, 20b through which the stem 3 is passed are connected above and below this frame-like portion 25.

[0053] With this structure, the valve body 4 has a gap 26 surrounded on all four sides by the opposing surfaces 20c, 20d of the upper and lower boss portions 20a, 20b and the left and right sidewall portions 24, 24. The width W1 between the left and right sidewall portions 24, 24 is wider than the width W2 of each of the upper boss portion 20a and the lower boss portion 20b that accommodate the stem 3. This allows the upper and lower boss portions 20a, 20b to be the minimum size possible to pass the stem 3 through, while the sidewall portions 24 prevent the side surface of the tip of a machining tool from interfering with the inner surface of the gap 26 when machining the stem insertion hole 21, and also improves the strength of the valve body 4 near the center in the direction in which the stem 3 is attached.

[0054] A rounded surface 30 is formed at each of the four corners of the gap 26, and these rounded surfaces 30 prevent stress from concentrating at the four corners of the gap 26. These rounded surfaces 30 at the four corners are provided so as to smoothly connect to the opposing surfaces 20c, 20d of the upper and lower boss portions 20a, 20b that constitute the gap 26 and to the left and right side wall portions 24, 24. These rounded surfaces 30 have an arc shape with a longer base toward the left and right side wall portions 24, 24 than toward the upper and lower opposing surfaces 20c, 20d. In the most preferable case, the rounded surfaces 30 extend to the center of the side wall portions 24, so that the entire side wall portions 24 become arc-shaped curved surfaces with no flat portions.

[0055] The upper and lower opposing surfaces 20c, 20d can also be made into arc-shaped curved surfaces so that the gap 26 as a whole has a generally elliptical shape in a plan view, which is preferable from the standpoint of strength, but the upper and lower boss portions 20a, 20b are provided with stem insertion holes 21 by drilling holes from above and below toward the gap 26. In this case, it is advantageous for the upper and lower opposing surfaces 20c, 20d at the end of the penetration to be as close to flat as possible, so from the standpoint of machining, it is preferable that the upper and lower opposing surfaces 20c, 20d are not made into entirely curved surfaces, but that at least a portion (for example, near the center) remains flat.

[0056] Furthermore, it is preferable that the opening edge 31 of the gap 26 in the vertical rib 20 (the boundary edge between the gap 26 and the upper surface 27 (surface parallel to the valve wing direction) of the upper and lower boss portions 20a, 20b) also has a rounded shape. Since stress caused by the deflection of the valve body 4 tends to concentrate particularly at the corners, connecting this opening edge 31 in a rounded shape makes it easier to disperse the stress.

[0057] A transverse rib 40 is formed in a direction intersecting the upper and lower bosses 20a, 20b, extending from the side wall 24 to near the end (valve wing end) 33 of the valve wing 32. The transverse rib 40 is formed in a substantially right-angled triangular shape with bases on both sides of the valve wing 32, one base being located on the side wall 24 side, and the hypotenuse extending from the side wall 24 side is gently shaped in the valve wing direction, with the tip of the hypotenuse located slightly away from the end face of the valve wing 32. The transverse rib 40 should have an appropriate thickness to ensure its rigidity and an external shape that prevents stress from concentrating on the side wall 24 side when bending stress acts on the valve wing 32 side.

[0058] When fluid pressure is applied to the valve disc 4, the center portion is supported by the stem 3 and is therefore less likely to displace, and the valve wing 32 side deforms so as to bend toward the secondary side, with the degree of bending increasing toward the valve wing tip 33. From the viewpoint of suppressing such bending, it is advantageous to make the transverse ribs 40 taller and thicker, but this increases the weight of the valve disc 4 accordingly, so 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, the transverse ribs 40 can be shaped in the right-angled triangle as described above.

[0059] The lateral ribs 40 are formed integrally with the side wall 24 at four locations in total, from the top and bottom of the left and right sides of the side wall 24, generally toward the valve wings 32, and these four lateral ribs 40 reinforce the valve body 4 in the direction of the valve wings 32. In this case, the lateral ribs 40 should be provided near the outside of the four curved surfaces 30 provided in the gap 26, so as to be as far away as possible from the gap 26 in the vertical direction (the direction in which the stem 3 is attached), which makes it possible to widen the gap 26 in the vertical direction.

[0060] Furthermore, the horizontal ribs 40 are provided such that a portion of their end faces in the formation direction from the side wall portions 24 abuts on the gap portions 26. In this example, the horizontal ribs 40 are formed on the side wall portions 24 such that 1 / 3t to 1 / 2t of their plate thickness t abuts on the end portions of the gap portions 26.

[0061] The horizontal ribs 40 are formed on the side wall 24 with their base ends 41 on the side wall 24 side slightly offset inward by an appropriate offset width from both the lengthwise and heightwise end faces of the side wall 24. It is preferable that the base ends 41 on the side wall 24 side of the horizontal ribs 40 are also connected to the side wall 24 in a rounded shape on both the top surface 42 and the side surfaces 43 of the horizontal ribs 40.

[0062] As described above, the valve body 1 is reinforced as a whole by the upper and lower bosses 20a, 20b, the vertical rib 20 having the side wall 24, and the horizontal rib 40, to reduce deflection due to high-pressure fluid. In this case, as described above, the side wall 24 is provided to connect the upper boss 20a and the lower boss 20b, thereby improving the rigidity of the entire valve body.

[0063] In the above-mentioned valve body 50, the base end portion 41 of the horizontal rib 40 on the side wall portion 24 side only needs to be slightly offset inward from at least one or both of the longitudinal and vertical end faces of the side wall portion 24, and the magnitude of the offset can also be set arbitrarily depending on the diameter of the valve body, etc.

[0064] In the above embodiment, a double eccentric butterfly valve has been described as an example of an eccentric butterfly valve forming the valve body, but a triple eccentric butterfly valve can also be configured in the same manner as described above.

[0065] In this embodiment, the valve body 4 is reinforced by providing side walls 24 on both sides of the upper and lower boss portions 20a, 20b, but the valve body 4 can also be reinforced by something other than the side walls 24.

[0066] For example, Figure 5 shows another example of a valve body. In this valve body, the same parts as those in the previously described valve body are designated by the same reference numerals, and their description will be omitted. In this valve body 50, a plate-like member 51 is provided to connect the surfaces of the upper and lower boss portions 20a, 20b, and this plate-like member 51 reinforces the upper and lower boss portions 20a, 20b through a so-called bridging structure. In this case, as in the previously described configuration with the side wall portion 24, the weight of the valve body 50 can be reduced while the overall strength can be improved.

[0067] In the bridging structure of Figure 5, the upper and lower boss portions 20a, 20b of the vertical rib 20 are separated from each other, and a gap portion 52 is formed near the center. The stem 3 is exposed in this gap portion 52, but the upper and lower portions are connected to each other on the surface side of the vertical rib 20 by a plate-shaped bridging portion (plate-shaped member 51).

[0068] The bridging portion (plate-like member 51) is formed with an appropriate cross-sectional shape, and in this example, is provided with a cross-sectional shape indicated by dashed-dotted line hatching in the figure. In this structure, the stem 3 passes through the insertion holes 21 of the upper and lower boss portions 20a, 20b and is positioned below the bridging portion in the central gap 52, where it is laterally exposed. The plate-like member 51 has the same width as the upper and lower boss portions 20a, 20b. The back surface facing the stem 3 is provided with a groove 51a having an arc-shaped cross section extending along the stem 3 to avoid contact with the cross-sectional shape of the stem 3, indicated by the dashed line, so as not to interfere with the rotation of the stem 3. The thickness of the plate-like member 51 is not particularly limited, but forming the transverse ribs 40 integrally with the plate-like member 51 while ensuring that the thickness above the base end 41 of the transverse ribs 40 extends directly to the bridging portion tends to provide an excellent stress dispersion effect.

[0069] Next, the operation of the above-described embodiment of the eccentric butterfly valve of the present invention will be described. In Figures 1 to 4, the valve body 1 has a vertical rib 20 and a horizontal rib 40. The vertical rib 20 has upper and lower bosses 20a, 20b and a side wall 24. The upper and lower bosses 20a, 20b are not continuous across the entire top and bottom of the valve disc 4. Instead, the upper and lower bosses 20a, 20b are connected by the side wall 24 so that the stem 3 is exposed between the upper and lower bosses 20a, 20b. This configuration is advantageous when casting the valve disc 4, even when the valve body 1 has a large diameter. It also reduces the amount of material required to make the valve disc 4, thereby reducing its weight. Furthermore, the reduced weight reduces the increase in rotational torque required when operating the valve disc 4 via the stem 3, thereby minimizing deterioration in operability.

[0070] In this case, the side wall portion 24 is formed in a thin plate shape while ensuring bending strength, thereby maintaining the light weight of the valve body 4 and compensating for the strength of the portions of the upper and lower boss portions 20a, 20b where the stem 3 is exposed.

[0071] Here, the valve element 4 of this embodiment has the stem 3 fixed vertically along the vicinity of its center, and is fixed to the body 2 via this stem 3. However, in the case of a structure in which the upper and lower boss portions 20a, 20b are separated as in this embodiment, the valve element 4 is not supported by the stem 3 in the gap portion 26 between the upper and lower boss portions 20a, 20b, and therefore the rigidity of this portion is inferior.

[0072] Therefore, when fluid pressure is applied to the valve element 4, as will be described later, forces (forces in the direction of bending the stem 3) are applied in directions that tend to bend the axis-mounted sides (upper and lower sides) of the valve element 4 symmetrically about a line L that is perpendicular to the center line (central axis) P of the stem 3, and there is a risk of bending in the region of this gap 26, which has low rigidity. In other words, in a structure in which the upper and lower boss portions 20a, 20b are separated as in this embodiment, the strength against forces in the direction of bending the valve element 4 (stem 3) is likely to be weaker than in a case in which the vertical ribs are provided continuously in the vertical direction.

[0073] In contrast to this, in this embodiment, the upper and lower boss portions 20a, 20b of the valve body 1 are connected by the side wall portion 24 to form an integrated unit, thereby improving the strength of the valve element 4 mainly in the axial direction (the direction in which the stem 3 is attached). Combined with the strength provided by the single stem 3 inserted into the insertion holes 21 of the upper and lower boss portions 20a, 20b, it is possible to suppress bending of the valve element 4 in a direction perpendicular to the axial direction due to high-pressure fluid, thereby preventing bending of the valve element 4.

[0074] If the stem were divided into upper and lower halves, rattle would easily occur where the upper and lower stems were attached. 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, were loosely fitted, clearances would be created between their respective mounting positions, making the valve disc prone to significant movement due to fluid pressure, especially when high-pressure fluid flows. In this case, designing the seat on the valve seat side would be difficult, and if the seat were designed to accommodate both fluid flows, it would be difficult to prevent leakage when the valve is closed.

[0075] In contrast, in the valve body 1 of this embodiment, as described above, 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 fluid. This simplifies the design of the valve seat and makes it easy to accommodate both types of flow.

[0076] Furthermore, by providing the upper and lower boss portions 20a, 20b with an upper and lower divided structure, when forming the insertion hole 21 for the stem 3 in the valve body 4, the processing can be easily performed by drilling from the upper and lower sides of the upper and lower boss portions 20a, 20b toward the divided portion near the center of the valve body 4, and the insertion hole 21 can be formed in a short time. Moreover, compared to when the stem insertion hole is formed over the entire valve body, the distance from the upper and lower sides of the upper and lower boss portions 20a, 20b to the divided portion is shorter, so there is less runout of the drill during the hole drilling process, and the insertion hole 21 can be formed with high precision drilling.

[0077] In addition to the above-mentioned vertical ribs 20, the valve disc 4 is formed with horizontal ribs 40 extending from the side wall 24 to the vicinity of the valve wing end 33 in a direction intersecting the upper and lower bosses 20a, 20b, and these horizontal ribs 40 can improve the strength of the valve disc 4, mainly in the valve wing direction, and can suppress deflection of the valve disc 4 in the valve wing direction due to high-pressure fluid, preventing bending. Reinforcement in two directions by these vertical ribs 20 and horizontal ribs 40 keeps the displacement of the valve disc 4 low when high-pressure fluid flows, reduces stress acting on the valve disc 4, and exhibits excellent durability.

[0078] The action of forces when fluid pressure is applied to the above-mentioned valve disc will now be described in detail. In Figure 4, when fluid pressure, such as high-pressure fluid, is applied to the valve disc 4 from the upstream side of the flow path 10 when the valve body 1 is fully closed, the valve disc 4 is mainly subjected to a force F in a direction that tries to bend the valve wings 32 symmetrically around the center line P of the stem 3, and a force F' (a force that tries to bend the stem 3) in a direction that tries to bend the attachment side (upper and lower sides) of the valve disc 4 symmetrically around a line L that passes through the center of the valve disc 4 in Figure 2 and is perpendicular to the center line P of the stem.

[0079] In response to these problems, as described above, the horizontal ribs 40 ensure strength against the force F that tries to bend the valve wings 32 symmetrically with respect to the center line P of the stem 3, and the vertical ribs 20 ensure strength against the force F' that tries to bend the stem 3. The upper and lower bosses 20a, 20b are provided with side walls 24 that connect them and run continuously in the mounting direction of the stem 3, thereby increasing the section modulus against the force F' that tries to bend the stem 3. This significantly improves the strength against bending forces compared to a valve body that is flat and does not have side walls.

[0080] In this case, when force F acting in a direction tending to bend the valve wings 32 is applied to the valve wings 32 in a bending direction, force f acting to tilt the side wall 24 toward the stem 3 is applied strongly, particularly at the base end 41 where the horizontal rib 40 is attached to the side wall 24. This force f travels along the side wall 24 and concentrates near the boundary between the upper and lower boss portions 20a, 20b of the vertical rib 20 and the side wall 24. At this time, the force F described above acting in a direction tending to bend the valve wings 32 is also applied to the horizontal rib 40, and a large stress is applied particularly to the upper surface 42 thereof, which increases the force f near the boundary between the upper and lower boss portions 20a, 20b and the side wall 24.

[0081] On the other hand, when a force F' in a direction that tries to bend the stem 3 is applied to the vertical rib 20 in a direction that causes the vertical rib 20 to fall around a line L that is perpendicular to the center line P of the stem, a force f' that tries to bend the side wall portion 24 in its length direction due to force F' acts mainly near the boundary between the upper and lower boss portions 20a, 20b and the side wall portion 24 of the vertical rib 20. For these reasons, stress concentration is likely to occur near the four corners of the gap portion 26 surrounded on all four sides by the opposing surfaces 20c, 20d of the upper and lower boss portions 20a, 20b and the left and right side wall portions 24, 24, particularly on the upper surface side.

[0082] As described above, in this embodiment, the vertical ribs 20 and horizontal ribs 40 are provided on the valve body 4 to increase the rigidity of the valve body 4, thereby suppressing deflection of the valve body 4 when fluid pressure is applied and improving its strength. However, according to the inventors' studies, it has been found that, while providing these vertical ribs 20 and horizontal ribs 40 increases the overall rigidity, it also creates areas where stress concentration is more likely to occur.

[0083] Even if the rigidity of the valve body 4 can be increased, if there is a large difference between areas where stress is likely to concentrate and areas where it is not, cracks or breaks will be more likely to occur in the areas where stress is likely to concentrate, and sufficient durability may not be obtained. In this embodiment, in order to alleviate such stress concentration and further enhance the effect of improving the strength of the valve body 4 by providing the vertical ribs 20 and the horizontal ribs 40, the following structural features are devised.

[0084] That is, first, the upper and lower boss portions 20a, 20b are connected by the side wall portions 24, and a frame portion 25 having a generally rectangular shape in plan view is formed near the center of the valve body 4, with the upper boss portion 20a and the lower boss portion 20b extending vertically from the frame portion 25 and horizontal ribs 40 extending horizontally from the frame portion 25, and the stem 3 is positioned so that it passes through the upper and lower boss portions 20a, 20b and vertically through the center of the frame portion 25, thereby providing a structure that can easily resist forces in any of the vertical and horizontal directions that deflect the valve body 4. Furthermore, the gap 26 surrounded by the frame portion 25 has four rounded surfaces 30, which effectively alleviates the effects that tend to concentrate near the corners of the gap 26. In particular, by forming the rounded surfaces 30 so that the arcs on the upper and lower opposing surfaces are short and the arcs on the left and right side wall portions are long, it is possible to ease the formation of the insertion holes 21 for the upper and lower boss portions 20a, 20b while also alleviating stress.

[0085] Furthermore, when fluid pressure is applied from the stem 3 holding side, for example, the force of this fluid pressure acts in a direction that stretches the upper surfaces 27, 42 of the vertical ribs 20 and the horizontal ribs 40, and when fluid pressure is applied from the opposite side, the force acts in a direction that compresses the upper surfaces 27, 42 of the vertical ribs 20 and the horizontal ribs 40, so in either case, the stress tends to be concentrated on the upper surfaces 27, 42 of the vertical ribs 20 and the horizontal ribs 40. In contrast, in this embodiment, the vicinity of the upper opening of the gap 26 is also rounded, so that it is possible to disperse and alleviate the stress concentrated on the upper surfaces 27 of the vertical ribs 20 in the direction of the side wall 24.

[0086] Furthermore, horizontal ribs 40 are provided in the direction intersecting the vertical ribs 20, and it is advantageous in terms of strength that these horizontal ribs 40 are connected to the vertical ribs 20 at positions that do not overlap the gaps 26, i.e., that they are connected to the block-shaped portions of the upper and lower boss portions 20a, 20b. However, in this case, it is necessary to either move the horizontal ribs 40 as close to the top or bottom as possible, or to make the gaps 26 as small as possible. In the former case, the horizontal ribs 40 cannot be formed long enough in the direction of the valve wings 32, resulting in insufficient strength against bending, while in the latter case, it is necessary to form long insertion holes 21 through which the stem 3 passes in the upper and lower boss portions 20a, 20b, which is disadvantageous in terms of processing.

[0087] Therefore, in this embodiment, the horizontal ribs 40 are formed integrally with the side wall portions 24 in a state where 1 / 3t to 1 / 2t of the plate thickness t of the horizontal ribs 40 abuts on the end side of the gap portion 26. In this way, the horizontal ribs 40 can be formed so as to overlap as much as possible with the block-shaped portions of the upper and lower boss portions 20a, 20b, and can be provided within the width of the curved surface 30 even at the position where they overlap with the gap portion 26. This effectively alleviates the bending stress on the horizontal ribs 40 even if it is applied to the vertical ribs 20, and provides sufficient strength.

[0088] Furthermore, the transverse ribs 40 are formed integrally with the side wall 24, with their base ends 41 on the side wall 24 side slightly offset inward by an appropriate offset width from both the longitudinal and vertical end faces of the side wall 24. Therefore, when a force is applied to the side wall 24 from the transverse ribs 40 by the fluid, the stress that is greatest on the end face side of the transverse ribs 40 is absorbed by the opposing surface with the side wall 24, thereby reducing the maximum stress value applied from the transverse ribs 40 to the end face side of the side wall 24 and the overall magnitude of the stress applied from the transverse ribs 40 to the vertical ribs 20.

[0089] In particular, when bending stress is applied to the transverse ribs 40, the stress tends to be applied to their upper surfaces 42. Therefore, if the upper surfaces 42 are connected to the upper surfaces of the sidewalls 24 at the same height and the boundary between them is angular, the stress will concentrate at the corners, which will tend to cause damage. In contrast, by connecting the transverse ribs 40 to a position on the sidewalls where their upper surfaces 42 are lower than the upper surfaces of the sidewalls 24, the bending stress applied to the transverse rib upper surfaces 42 can be distributed across the surface of the sidewalls 24, which is extremely advantageous for stress relief. Furthermore, by connecting both the side surfaces 43 and the upper surfaces 42 of the transverse ribs 40 with rounded surfaces at the connection points between the transverse ribs 40 and the sidewalls 24, an even better stress relief effect can be achieved.

[0090] 2(b), it is preferable that the upper surface of each horizontal rib 40 extending on both sides of the vertical rib 20 is formed at an angle such that its extension line in the stem direction intersects near the center of the stem 3, as shown by the dashed line. In this way, when a force is applied in a direction that bends the horizontal rib 40, the stress can be supported by the virtual triangle formed on the upper surface of the horizontal rib 40, and high strength against bending can be exhibited.

[0091] Next, another embodiment of the eccentric butterfly valve will be described in detail with reference to the drawings. Figure 6 is a perspective view of the other embodiment of the butterfly valve, and Figures 7 to 12 show the valve body in Figure 6. In the following, parts that are the same as those in the above-mentioned embodiment will be designated by the same reference numerals, and their description will be omitted.

[0092] In FIG. 6, an eccentric butterfly valve (hereinafter referred to as valve body 101) in another embodiment comprises a body 2, a stem 3, and a valve element 104, and is provided with various diameters, for example, 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.

[0093] As will be described later, the stem 3 is attached to the valve body 104 with the vicinity of its center 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 P of the stem 3, and in this example, the entire stem 3 is provided with a substantially circular cross section in its longitudinal direction.

[0094] 7 to 12, the valve element 104 is formed in a generally circular disk shape, with a vertical rib 120 provided near the center of one side surface 104a thereof, and an upper boss portion 121 and a lower boss portion 122 provided adjacent to the top and bottom of the valve element 104 on the upper and lower sides of the vertical rib 120, i.e., on the side of the mounting portion 111 to the body 102, so as to be continuous with the upper and lower sides of the vertical rib 120. With this structure, a gap 123 having a generally rectangular shape in plan view is provided in the area surrounded by the upper and lower boss portions 121, 122 and the left and right vertical ribs 120, and the center of the stem 3 attached to the valve element 104 is exposed within this gap 123. In this way, the upper and lower boss portions 121, 122 are provided in a structure divided into upper and lower portions via the vertical rib 120 in the attachment direction of the stem 3 to the valve element 104.

[0095] In this embodiment, the upper and lower boss portions 121, 122 are positioned relative to the valve body 104 so that the stem 3 can be held offset from the center of the valve body 104 by double eccentricity, and the stem 3 fixed to the valve body 104 through the upper and lower boss portions 121, 122 is attached to the body 102, so that the valve main body 101 is configured as a double eccentric butterfly valve.

[0096] In this example, the upper and lower bosses 121, 122 respectively have small bosses 121a, 122a located near the top and bottom of the valve body 104, and large bosses 121b, 122b that are larger than the small bosses 121a, 122a and located closer to the center of the valve body 104, and these are formed as integrated, roughly rectangular parallelepiped shapes. In particular, the large bosses 121b, 122b are provided so as to be higher from one side surface 104a of the valve body 104 than the small bosses 121a, 122a.

[0097] The upper and lower boss portions 121, 122 each have an insertion hole 124 on the side facing the stem insertion hole 112 of the body 102, through which the stem 3 can be inserted. Each boss portion 121, 122 has a through hole 125 formed on the outer periphery, into which a tapered pin 127 can be inserted.

[0098] The stem 3 is inserted into the insertion hole 124 and fixed at the upper and lower boss portions by tapered pins 127, and connected to the valve element 104. As a result, the stem 3 and the valve element 104 are integrated with reduced vibration, and the valve element 104 is provided so that its rotation can be accurately controlled relative to the flow path 110 by the stem 3.

[0099] The vertical ribs 120 are formed integrally with the upper and lower boss portions 121, 122 so as to connect these boss portions 121, 122 from both sides thereof, and are provided on both sides near the exposed portion 3a of the stem 3 attached to the valve body 104 so as to be approximately parallel to the stem 3. By providing the vertical ribs 120 between the upper and lower boss portions 121, 122 in this way, the valve body 104 is reinforced by these vertical ribs 120 in the attachment direction of the stem 3.

[0100] The configuration of the vertical rib and the upper and lower boss portions provides the aforementioned gap 123 in the valve body 104, which removes a portion of the valve body 104 near its center. The stem 3 is fixed to one side surface 104a of the valve body 104, with its generally circular cross-section near its center exposed to the outside by the gap 123. In the gap 123, rounded surfaces 126 are formed at the four corners near the boundaries between the vertical rib 120 and the upper and lower boss portions 121, 122, and these rounded surfaces 126 disperse stress that would otherwise be applied to the gap 123.

[0101] The vertical ribs 120 are formed thin in the thickness direction of the valve body 104, and furthermore, the upper surfaces 120a thereof are provided in a substantially arc shape. The vertical ribs 120 having the upper surfaces 120a make it possible to reduce fluid resistance when the fluid flows near the vertical ribs 120 when the valve is open.

[0102] The vertical ribs 120 on both sides of the stem 3 are provided in a generally symmetrical shape around the central axis P of the stem 3. Each of these vertical ribs 120 is provided in a shape with a gradient that gradually increases in height from the valve wing portion 130 side toward the stem 3 side in the height direction from one side surface 104a of the valve body 104, and in this embodiment, as shown in Figures 12(a) and 12(b), is formed to an appropriate length so that the upper surface 120a side has a generally arc shape.

[0103] More specifically, each vertical rib 120 has a gradient that changes in height in a direction perpendicular to the central axis P of the stem in response to a change in the direction from the valve wing edge 131 toward the stem 3, and is shaped so that this gradient change is gentler near the valve wing edge 131 and near the stem 3 than the gradient change between them.

[0104] In this way, the vertical rib 120 has an approximately arc-shaped upper surface 120a and is shaped so that the stem 3 side is thicker than the valve wing portion 130.As a result, even though there is a gap 123 between these vertical ribs 120, the strength of the stem 3 side is ensured even when stress is applied to the valve wing portion 130 in the bending direction.

[0105] In the height direction from one side surface 104a of the valve body 104, the height H1 of the highest part of the vertical rib 120 is set to be lower than the height H2 of the highest exposed part 3a of the stem 3 and higher than the position of the central axis P of the stem 3. In this case, it is desirable to set the height H1 of the highest part of the vertical rib 120 relative to the height H2 so that the height H1 is higher than a position 30% lower than the diameter of the stem 3 in the height direction.

[0106] In the figure, a tangent line S to the stem 3 is a line drawn on the outer peripheral surface 3b of the exposed portion 3a of the stem 3 at an angle θ of 45° with respect to the perpendicular direction to one side surface 104a of the valve body 104. The valve body 104 is formed so that the height H1 of the highest part of the vertical rib from one side surface 104a of the valve body 104 is higher than the height H3 from one side surface 104a of the valve body 104 to the tangent point Q of the 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 tangent point Q is set to be approximately 3 mm.

[0107] The longitudinal ribs 120 are provided in a direction perpendicular to the central axis P of the stem 3 of the valve body 104 (toward the valve wing 130), extending from positions near both sides of the stem 3 fixed to the valve body 104 to a position beyond point E, which is half the distance from the central axis P to the valve wing edge 131. In this example, each longitudinal rib 120 is formed with a length of distance X from a position near both sides of the stem 3 to point E in the direction of the valve wing edge 131. In this embodiment, the valve wing 130 refers to the portion of the valve body 104 that forms the valve wing side, and the valve wing edge 131 refers to the portion of the valve wing 130 that is furthest from the central axis P of the stem 3 in the valve wing direction.

[0108] The opposing surfaces 132 of the vertical ribs 120 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 124 of the valve body 104 for inserting the stem 3. Furthermore, these opposing surfaces 132 are connected to each other by a semicircular portion 133 on the base end side, and this semicircular portion 133 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 120, the outer periphery of the stem 3 does not come into contact with the opposing surfaces 132 or the semicircular portion 133, and the stem 3 is attached to the valve body 104 with a gap R between them.

[0109] In Figure 8, the vertical ribs 120 not only function to improve the rectification of the fluid when the valve is open, as described below, but also improve the strength of the valve body 104 in the direction in which it tends to bend and deform vertically by being integrally connected to the upper and lower boss portions 121, 122 in the mounting direction of the stem 3. Furthermore, the vertical ribs 120 are formed at the aforementioned distance X in the direction in which the valve wings 130 are mounted, and their upper surfaces 120a are formed in a substantially arc shape, thereby improving the strength of the valve body 104 in the direction in which it tends to bend and deform horizontally. As such, the vertical ribs 120 ensure strength in both the mounting direction of the stem 3 and the direction in which the valve wings 130 are mounted on the valve body 104, thereby comprehensively improving the bending strength of the entire valve body 104 against high-pressure fluid.

[0110] Near the upper and lower sides of the vertical rib 120 of the valve body 104, horizontal ribs 140 are integrally formed, extending to the valve wing portion 130 where they intersect with the vertical rib 120. In this example, horizontal ribs 140 are provided on both side surfaces of each large boss portion 121b, 122b of the upper and lower boss portions 121, 122, and a total of four horizontal ribs 140 are formed on the valve body.

[0111] The horizontal ribs 140 are formed to have a gentle taper from the large bosses 121b, 122b 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 140 are formed to an appropriate thickness in the vertical direction of Figure 8 to improve the rigidity of the valve body 104 toward the valve wings 130, and are desirably formed with an outer shape that prevents stress from concentrating near the upper and lower bosses 121, 122 or the vertical ribs 120 when a bending force is applied to the valve wings 130. At the portions connecting to the large bosses 121b, 122b, the upper surfaces of the horizontal ribs 140 are higher from one side surface 104a of the valve body 104 than the highest portion of the vertical ribs 120.

[0112] Here, when fluid pressure is applied to the valve disc 104, the valve wing 130 side is deformed so as to bend toward the secondary side because the valve disc 104 is supported near its center by a single stem 3, with the degree of bending becoming greater toward the valve wing edge 131 side. From the viewpoint of suppressing the occurrence of such bending, it is advantageous to make the transverse rib 140 as tall and thick as possible, but this also increases the weight of the valve disc 104. Therefore, it is preferable to provide the transverse rib 140 with the minimum necessary height and thickness. Since the stress caused by the bending of the valve disc 104 increases closer to the stem 3 side, it is preferable to provide the transverse rib 140 in the shape of a right-angled triangle, for example, to accommodate this.

[0113] As described above, in the valve body 104, upper and lower boss portions 121, 122 are provided on the upper and lower sides of the vertical rib 120 in the direction of the stem mounting, and horizontal ribs 140 are provided in the direction from the vertical rib 120 to the valve wing portion 130, thereby reinforcing the entire valve body 104 in the vertical and horizontal directions.

[0114] In this embodiment, a double eccentric butterfly valve has been described as an example of the eccentric butterfly valve that constitutes the valve body 101, 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.

[0115] As long as the vertical ribs are gradually raised from the valve wing side toward the stem side, the shape of their upper surfaces may be any shape other than a generally arcuate shape, for example, they may be tapered. On the other hand, although the horizontal ribs are shown in Fig. 11 to have a generally tapered upper surface, they may also be formed to have a generally arcuate upper surface.

[0116] 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.

[0117] Next, the operation of the above-mentioned other embodiments of the eccentric butterfly valve will be described. In Figures 6 to 12, the eccentric butterfly valve has vertical ribs 120 provided on both sides of the valve body 104 near the exposed portion 3a of the stem 3, and these ribs are generally parallel to the stem 3. This increases the strength of the valve body 104 mainly in the vertical direction (the direction of the central axis P of the stem) and makes it possible to suppress bending and deformation due to forces in a direction intersecting the central axis P of the stem.

[0118] Each vertical rib 120 is formed in a generally tapered shape in the height direction from one side 104a of the valve body 104, gradually increasing in height from the valve wing portion 130 side toward the stem 3 side, and the height H1 of the highest part of each vertical rib 120 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 P of the stem 3. Therefore, the inclination direction of the arc portion formed near the highest part of the vertical rib 120 and the arc portion 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 120 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 104a of the stem mounting side of the valve body 104, when fluid flows from the valve wing portion 130 side in a direction intersecting with the stem 3, this prevents the fluid from proceeding into the gap R between the stem 3 and the valve body 104 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 turbulence such as a vortex will occur. This makes it possible to improve the Cv value.

[0119] Furthermore, the height H1 of the highest part of each vertical rib 120 from one side surface 104a of the valve disc 104 is set at a higher position than the height H3 from one side surface 104a of the valve disc 104 to the tangent point Q 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 part 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 104 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 part of the vertical rib, preventing this protruding portion from causing significant flow resistance.

[0120] Due to this very slight height difference of 3 mm, when the highest part of the longitudinal rib 120 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 120a of the longitudinal rib 120 on the inlet side (right side in FIG. 12) 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 120a of the longitudinal rib 120 on the outlet side (left side in FIG. 12). In this way, turbulence near the exposed part 3a of the stem 3 is suppressed.

[0121] In this embodiment, the difference between heights H1 and H2 is set to 3 mm as described above, which enables a better Cv value and improved flow characteristics compared to when the difference is greater or less than 3 mm. For example, if the difference between heights H1 and H2 is set to greater than 3 mm, the amount of fluid that directly contacts the exposed portion 3a of the stem increases, which may lead to turbulence occurring around this area. On the other hand, if the difference between heights H1 and H2 is set to less than 3 mm, the fluid tends to flow in the direction of the gap R between the stem 3 and the valve body 104, which may lead to turbulence occurring around this area. Note that this value of "3 mm" is a preferred value for the valve body 104 shown in this example, and the preferred value will vary depending on the size of the valve body, etc.

[0122] Furthermore, each vertical rib 120 extends from at least a position near either side of the stem 3 fixed to the valve body 104 to a position at a distance X that is more than half the distance from the central axis P of the stem 3 to the valve wing edge 131, thereby reinforcing the valve body 104. Moreover, as described above, the vertical ribs 120 are gradually increased in height from the valve wing 130 side toward the stem 3 side, and the height H1 of the highest part of the vertical rib 120 is lower than the height H2 of the highest exposed part of the stem 3, so that sufficient strength can be ensured even with the vertical ribs 120 having such a low height H1. Therefore, even if the valve body 101 has a large diameter and high-pressure fluid flows through its flow path 110, bending or deformation toward the valve wing 130 can be reliably prevented. In this case, the vertical ribs 120 have an upper surface 120a that is generally arc-shaped and have a minimum necessary thickness, thereby sufficiently ensuring the reinforcing function of the valve body 104 provided by the vertical ribs 120 and minimizing the increase in the overall weight of the valve body 104. This minimizes the operating torque of the valve body 104 and improves operability.

[0123] The valve disc 104 has upper and lower bosses 121, 122 connected by vertical ribs 120 on the left and right sides, with a gap 123 provided near the center. Therefore, when a valve disc 104 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 101 has a larger diameter, the valve disc 104 can be easily produced without compromising castability. Furthermore, after the valve disc 104 is formed by casting or the like, the gap 123 facilitates post-processing such as deburring.

[0124] As in the previously described embodiment, the problem of the structure in which the upper and lower boss portions 121, 122 are separated resulting in a weaker strength than if the vertical rib were continuous in the vertical direction is addressed in this embodiment by integrating the upper and lower boss portions 121, 122 of the valve body 101 by connecting them with the vertical rib 120, thereby improving strength mainly in the direction of the central axis P (the attachment direction of the stem 3). Combined with the strength provided by the single stem 3 inserted into the insertion hole 124 of the boss portions 121, 122, this makes it possible to suppress deflection of the valve body 104 due to high-pressure fluid and prevent bending, etc.

[0125] The distance G between the opposing surfaces 132 of the vertical ribs 120 on the stem 3 insertion side is set to be wider than the hole diameter φD of the insertion hole 124, so that when the insertion hole 124 is drilled with a tool, the tool is prevented from coming into contact with the inside of the vertical rib 120, and the vibration of the tool is suppressed, enabling high-precision manufacturing.

[0126] In addition to the above-mentioned vertical ribs 120, the valve body 104 is formed with horizontal ribs 140 on the bosses 121, 122 at the top and bottom of the vertical ribs 120, extending in a direction intersecting the vertical ribs 120 to the vicinity of the valve wings 130. These horizontal ribs 140 improve the strength of the valve body 104, mainly in the direction of the valve wings 130, and can suppress bending near the valve wings 130 even when subjected to high-pressure fluid. Furthermore, the horizontal ribs 140 are formed on the large bosses 121b, 122b, which are larger than the small bosses 121a, 122a. Therefore, when stress acts on the bosses 121, 122 from the valve wings 130, the large bosses 121b, 122b ensure sufficient strength and can suppress bending and deformation of the vertical ribs 120. The vertical and horizontal reinforcement provided by these vertical ribs 120 and horizontal ribs 140 reduces the stress acting on the valve body 104, thereby keeping the displacement of the valve body 104 low even when exposed to high-pressure fluid, thereby providing excellent durability.

[0127] In particular, when reinforcing the valve body 104 with ribs, it is important that the ribs have a sufficient height to withstand the force that deflects the valve body 104. In this embodiment, the horizontal ribs 140 are connected to the large bosses 121b, 122b, which are higher than the small bosses 121a, 122a, and have a shape that gradually increases in height toward the large bosses 121b, 122b. This ensures that the horizontal ribs 140 are as high as possible without interfering with the flow of fluid, thereby maximizing the reinforcing effect of the horizontal ribs 140 against the deflection of the valve body 104.

[0128] In this embodiment, the small bosses 121a, 122a are provided with gradient connecting portions 141 at their connection portions with the valve body 104, the gradient connecting portions 141 gradually increasing in height from the valve wing portion 130 toward the small bosses 121a, 122a from the side of the valve body 104. The provision of the gently sloping connecting portions 141 allows the fluid flowing near the surface of the valve body 104 to be guided by the gradient connecting portions 141 and smoothly overcome the small bosses 121a, 122a. Furthermore, the small bosses 121a, 122a are lower in height than the large bosses 121b, 122b, and have rounded portions 142 at their corners, making them less likely to obstruct the flow of fluid.

[0129] As described above, by providing the sloped connecting portion 141 and the rounded portion 142, the small boss portions 121a, 122a have a generally streamlined cross section, allowing the fluid to flow smoothly near these portions while suppressing the generation of turbulence, etc. Moreover, while keeping the height of the small boss portions 121a, 122a low, the sloped connecting portion 141 is provided on the entire sides of the small boss portions 121a, 122a along the central axis P of the stem, thereby ensuring the strength of the small boss portions 121a, 122a.

[0130] To summarize the above, the valve disc 104 of the double eccentric butterfly valve of another embodiment has a shape in which upper and lower bosses 121, 122 for fixing the stem 3, the stem 3, a vertical rib 120 for reinforcing against bending, and a horizontal rib 140 are provided on one side of the valve disc 104. Of these, the vertical rib 120 is gradually raised from the valve wing 130 side of the valve disc 104 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 121, 122, the small bosses 121a, 122a are lower than the large bosses 121b, 122b, and a gradient connection part 141 is provided, which results in smooth fluid flow, particularly when the valve is fully open, and excellent flow characteristics in which a high Cv value can be obtained. On the other hand, with such a shape, the vertical ribs 120 suppress deflection and deformation due to forces in the direction transverse to the central axis P of the stem, and the horizontal ribs 140 suppress deflection near the valve wing portions 130 of the valve body 104, thereby providing an excellent reinforcing effect for the valve body 104. In this way, the valve body 104 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.

[0131] Next, an example of the above-mentioned eccentric butterfly valve will be described. First, the flow path of a fluid flowing through the valve body of the other embodiment described above was analyzed, and then the flow path of a comparative example was similarly analyzed for comparison with this valve body.

[0132] Figure 13 shows a schematic diagram of the analysis of the flow trajectories of these eccentric butterfly valves. Figure 13(a) shows a test specimen using the valve body 101, illustrating the flow conditions of this test specimen when 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 higher than the center axis of the stem. Figure 13(b) shows a comparative eccentric butterfly valve, illustrating the flow conditions of this comparative specimen when fully open. In this case, the height of the entire vertical rib is higher than the height of the highest exposed point of the stem. In both Figures 13(a) and 13(b), the valve diameter is 400A, and the flow trajectories represent the flow of fluid through this valve from right to left.

[0133] In Figure 13(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 body.

[0134] On the other hand, in the comparative example shown in Fig. 13(b), since the vertical ribs are higher than the stem, 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 shown in Fig. 13(a). In this way, it can be confirmed that the fluid flows while generating turbulence after passing through the valve body.

[0135] Figure 14 is a graph showing the analytical results of the change in Cv value as the valve opening increases from a closed state for the test specimen (Figure 13(a)) and the comparative example (Figure 13(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 Cv value at full open is set to 100 (%), and the relative value (0-90%) to this target value is expressed as a percentage on the vertical axis. In both the test specimen and the comparative example, the valve bore is 350A. In the figure, 350A (Comparative Example) represents the comparative example, 350A (Test Specimen 1) represents Test Specimen 1 of the valve body 101, and 350A (Test Specimen 2) represents Test Specimen 2, which is a design modification of Test Specimen 1.

[0136] In the graph, for specimens 1 and 2, the Cv value increases proportionally as the valve opening increases, reaching a 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%).

[0137] On the other hand, in the case of the comparative example, the Cv value increases as the valve opening degree increases, just like the test sample. However, the Cv value is maximum at a valve opening degree of approximately 80 degrees and decreases at a valve opening degree of 90 degrees. This is thought to be because the vertical rib is higher than the stem, resulting in greater fluid resistance of the valve disc at a valve opening degree of 90 degrees (fully open) than at an opening degree of 80 degrees. In this case, the maximum Cv value at a valve opening degree of approximately 80 degrees is approximately 78% of the target value (100%).

[0138] As shown above, the comparative example was unable to secure the maximum Cv value when the valve was fully open at 90 degrees, whereas the two test specimens were able to achieve the maximum Cv value when fully open, demonstrating ideal flow characteristics as a valve. Furthermore, comparing these maximum Cv values, the comparative example achieved approximately 78% and the test specimens achieved approximately 91%, demonstrating a higher Cv value when fully open than the comparative example and significantly improved flow characteristics compared to the comparative example. Furthermore, even at openings other than fully open, particularly at valve openings of 60 degrees or greater, it was confirmed that the test specimens achieved higher Cv values ​​than the comparative examples at the same valve opening.

[0139] From the above, it can be said that the test valves of other embodiments of the eccentric butterfly valve are able to flow fluid smoothly while rectifying the flow as an eccentric butterfly compared to the comparative example, and can exhibit excellent flow characteristics and improve the Cv value.

[0140] 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.

[0141] 1, 101 Valve body 2 Body 3 Stem 3a Exposed portion 3b Outer circumferential surface 4, 104 Valve disc 20, 120 Longitudinal rib 20a Upper boss portion 20b Lower boss portion 20c, 20d Opposing surface 24 Side wall portion 25 Gap portion 30 Rounded surface 32 Valve wing 33 Valve wing end portion 40, 140 Horizontal rib 41 Base end portion 124 Stem insertion hole 130 Valve wing portion 131 Valve wing edge portion 132 Opposing surface of vertical rib G Spacing H1 Height of highest portion of vertical rib H2 Height of highest exposed portion of stem H3 Height from one side of valve disc to tangent point of tangent P Central axis S Tangent X Distance W1 Width between left and right side wall portions W2 Width of each of upper boss portion and lower boss portion φD Stem insertion hole diameter

Claims

1. An eccentric butterfly valve in which a valve disc is eccentrically attached within a body by a stem so that it can be opened and closed freely, the valve disc having a vertical rib through which one stem is inserted and held near the center of one side of the valve disc, and a horizontal rib extending from the vertical rib to near the end of the valve wing in a direction intersecting the vertical rib, the vertical rib having an upper boss portion, a lower boss portion, and side wall portions connecting both vertical sides of the upper and lower boss portions so that the stem is exposed between the upper and lower boss portions.

2. An eccentric butterfly valve as described in claim 1, wherein the valve body has a gap surrounded on all four sides by the opposing surfaces of the upper and lower boss portions and the left and right side wall portions, and rounded surfaces are formed at the four corners of this gap.

3. An eccentric butterfly valve as set forth in claim 2, wherein the rounded surfaces at the four corners are arcuate rounded surfaces, and the gap is provided in a generally elliptical shape.

4. An eccentric butterfly valve as claimed in claim 2 or 3, wherein the horizontal ribs are integrally formed with the vertical ribs with a portion of their end face extending into the gap in the forming direction from the vertical ribs.

5. An eccentric butterfly valve as described in claim 1, wherein the transverse rib is formed from the side wall portion, and a base end of the transverse rib on the side wall portion side is formed integrally with the side wall portion while being offset slightly inward from at least one or both of the end faces of the side wall portion in the length direction and height direction.

6. An eccentric butterfly valve as set forth in claim 2, wherein the width between the left and right side wall portions is formed wider than the width of each of the upper and lower boss portions which house the stem.

7. An eccentric butterfly valve in which a valve body is eccentrically attached 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 body with at least its central area exposed, vertical ribs are provided on both sides of the valve body near the exposed part of the stem and approximately parallel to the stem, each of these vertical ribs is gradually increased in height from the valve wing side of the valve body toward the stem side in the height direction from the one side of the valve body, 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.

8. An eccentric butterfly valve as described in claim 7, wherein at least the exposed portion of the stem has a generally circular cross section in a direction perpendicular to its central axis, and when a tangent is provided on the outer peripheral surface of the exposed portion of the stem at an angle of 45° to a direction perpendicular to the one side of the valve body, the height of the highest portion of each of the vertical ribs from the one side of the valve body is set at a higher position than the height from the one side of the valve body to the tangent point.

9. An eccentric butterfly valve as claimed in claim 7 or 8, wherein each of the vertical ribs is provided in a direction perpendicular to the central axis of the stem, from at least adjacent positions on 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.

10. An eccentric butterfly valve as described in claim 7, wherein the distance between the 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.

11. An eccentric butterfly valve as set forth in claim 7, wherein horizontal ribs are formed in the valve body near the upper and lower sides of the vertical ribs and extend in the direction of the valve wing portions so as to intersect with the vertical ribs.

12. An eccentric butterfly valve as described in claim 7, wherein the vertical rib has a gradient that changes in height in a direction perpendicular to the central axis of the stem from the edge of the valve wing toward the stem, and the gradient change is gentler near the edge of the valve wing and near the stem than between them.

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