Eccentric butterfly valve

Abstract

To provide an eccentric butterfly valve excellent in operability and capable of preventing the leakage by maintaining high sealability during closing the valve even when the pressure of high pressure fluid is in the direction of a positive flow or a reverse flow, maintaining the sealing performance even when the reverse-flow high pressure is especially applied thereto, and securing seal surface pressure between a seat ring and a disk.SOLUTION: In a body 21, a disk 23 journaled by a stem 22 is provided which can be sealed to a seat ring 24. On the inner diameter side of the seat ring, a flexible part 41 is formed, and between the flexible part and a seat retainer 25, a plat spring 26 is mounted. A point where the load characteristics of the plate spring is changed is set as a point of inflection, and during closing the valve, the spring load is applied to the flexible part while attaining an unloaded condition that a fluid pressure is not applied to the valve at the point of inflection. In the positive pressure, the load characteristics are changed over from the position of the point of inflection, and when the positive pressure becomes higher, the spring load becomes smaller. In the reverse pressure, as the reverse pressure is higher when the load characteristics are changed over from the position of the point of inflection, the spring load becomes greater.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an eccentric type butterfly valve suitable for high-pressure fluids, and more particularly to an eccentric type butterfly valve that can accommodate both forward and reverse flows. [Background technology]

[0002] Conventionally, eccentric butterfly valves are generally known as valves suitable for high-pressure fluids. For example, in a double eccentric butterfly valve, the valve stem is eccentric to the flow path relative to the valve body, and the center of rotation of the valve body is eccentric from the center of the valve aperture, thereby improving the sealing performance when the valve is closed compared to a central butterfly valve. Even with this type of valve, there is a demand for a valve that has improved sealing performance against not only positive pressure, which is pressure in the forward flow direction, but also against back pressure, which is pressure in the reverse flow direction. In order to handle such bidirectional pressure, which is so-called both flows, it is necessary to improve the valve seat sealing durability, especially in the reverse pressure direction.

[0003] As an eccentric butterfly valve that can accommodate both flow directions, for example, the applicant has filed an eccentric butterfly valve in Patent Document 1. In this eccentric butterfly valve 1, as shown in the partially enlarged schematic view of Fig. 8, an annular one-piece seat ring member 4 is interposed between a valve body 2 and a seat retainer member 3, and this seat ring member 4 has a flexible portion 5 on its inner diameter side that is flexible in either the forward or reverse flow direction. When this butterfly valve 1 is in the closed state and a positive flow occurs, the fluid pressure (positive pressure) causes the valve element 6 in the valve box 2 to move in a direction away from the seat ring member 4 (secondary side: to the right in the figure), but the self-sealing function caused by the fluid pressure causes the flexible part 5 to tilt toward the valve element 6 (to the right) while pressing against the valve element 6, thereby maintaining the sealing surface pressure between them and preserving the sealing ability of the valve seat. On the other hand, when backflow occurs, the fluid pressure (back pressure) causes the valve body 6 to move toward the seat ring member 4 (primary side: leftward in the figure) and press against the seat ring member 4, and the flexible portion 5 of the seat ring member 4 is pressed against the opposing surface of the seat retainer member 3 and compressed, thereby providing valve seat sealing in the event of back pressure.

[0004] In the double eccentric butterfly valve of Patent Document 2, the seat ring member is provided by combining a resin seat ring and a metal seat ring, and the tip side (flow path side) of this seat ring member is flexible depending on the flow direction of forward or reverse flow. The seat ring member is attached to the valve body via a seat retainer member, and a metal disc spring is attached between the seat ring portion and the seat retainer member. When this valve is in the closed state and a positive flow occurs, the positive pressure causes the valve disc to move away from the seat ring member, while fluid enters through the gap between the metal seat ring and the valve disc and presses against the seat ring member. This causes the tip of the resin seat ring to deform in response to the movement of the valve disc, pressing against the valve disc and maintaining the contact surface pressure between them to maintain the valve seat sealing. On the other hand, when a backflow occurs, the back pressure causes the valve disc to move toward the seat retainer member, applying a force in a direction that compresses the plastic seat ring, causing the plastic seat ring to move in that direction. In this case, the resilient force of the disc spring arranged on the back surface of the metal seat ring pushes back the metal seat ring and the plastic seat ring, maintaining the contact surface pressure between the plastic seat ring and the valve disc that is necessary to close the fluid, thereby preventing leakage when back pressure occurs.

[0005] Incidentally, such an eccentric type butterfly valve capable of handling both flows may be used, for example, as part of a pipeline for a central air conditioning system installed in a structure such as a high-rise building. FIG. 9(a) shows a schematic diagram of a typical centralized air conditioning system 10. In this centralized air conditioning system 10, a chiller (heat source unit) 11, a cooling tower (cooling tower) 12, and the like are placed underground or on the roof, and these are connected to a circulation-type piping 13. A vertical piping 14 in the piping 13 is provided with a branch flow path (not shown), and this branch flow path is connected to the air conditioning system (air conditioner) on each floor. When the centralized air conditioning system 10 is in operation, the cold and hot water for air conditioning cooled or heated by the heat source unit 11 circulates through the piping 13 and is sent to the air conditioning system on each floor through the branch pipes, thereby performing air conditioning such as cooling and heating of the entire building.

[0006] In this centralized air conditioning system 10, an eccentric type butterfly valve 1 corresponding to both flows described above may be used, in which case the butterfly valve 1 is disposed on the lower side (low-rise side) of vertical pipes 14, 14 on the upstream and downstream sides of pipe 13, respectively. Each butterfly valve 1 has connection flanges 15 attached to both its first and secondary ends by pipe bolts (not shown), and is interposed between the vertical pipes 14 via these connection flanges 15. Each butterfly valve 1 is provided with an automatic or manual opening / closing operation unit 16, and is arranged so as to be openable and closable by this opening / closing operation unit 16.

[0007] When the centralized air conditioning system in Figure 9(a) is in operation, cooled or heated cold or hot water is sent from the heat source unit 11 by the pump 17, and this cold or hot water circulates within the pipes 13, ascending the vertical pipe 14 on the left side of the figure and descending the vertical pipe 14 on the right side of the figure, and is supplied from the vertical pipe 14 through the horizontal pipes to each floor.

[0008] 9(b), when performing maintenance of the central air conditioning system 10, the central air conditioning system 10 is stopped and each of the upstream and downstream butterfly valves 1 is operated to a valve closed state by the opening / closing operation unit 16, and the connecting flange 15 and part of the piping 13 below the butterfly valves 1 (low-rise side) are removed to make the end of the butterfly valve 1 into a so-called dead end state. This separates the flow path below the butterfly valve 1, making it possible to perform cleaning of the inside of each piping above the butterfly valve 1 (high-rise side) or below. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 6144847 [Patent Document 2] JP 2007-78001 A Summary of the Invention [Problem to be solved by the invention]

[0010] In the case of an eccentric type butterfly valve with a seal structure such as that of Patent Document 1, when back pressure is applied in Fig. 8, the valve element 6 moves toward the seat ring member 4 according to the magnitude of the pressure, which increases the force applied to the flexible portion 5 of the seat ring member 4. If the back pressure increases at this time, the flexible portion 5 is crushed by the mounting surface of the seat retainer member 3, causing the flexible portion 5 to plastically deform beyond the allowable stress of the seat ring member 4, or the wear of the seat ring member 4 due to the operation of the valve element 6 increases, causing a significant decrease in the seal surface pressure, which may result in the valve seat being unable to perform its sealing function.

[0011] On the other hand, in the latter Patent Document 2, when back pressure occurs, the disc spring tries to push the seat ring member back to the secondary side, but because this pushing force acts almost constantly, when high back pressure occurs, the disc spring cannot withstand the pressure and deforms significantly, and may become unable to push back the seat ring member. In this case, excessive pushing force continues to be applied to the flexible part of the seat ring member, causing plastic deformation at the tip side, which may cause valve seat leakage.

[0012] In addition, in double eccentric butterfly valves, the pressure-receiving areas of the valve discs on the left and right sides of the stem are different, so in each of the above butterfly valves, a torque is generated on the stem in proportion to the magnitude of the fluid pressure, and in the event of back pressure, a torque is generated on the stem in the valve closing direction. The increase in seal surface pressure due to the movement of the valve disc and the increase in the unbalanced torque caused by the fluid pressure applied to the stem by the torque also increase, resulting in a large load torque during operation. This causes sudden operation (jumping) when starting to open from a fully closed state, especially during automatic operation, and this sudden operation can cause severe wear on the seat ring, leading to a decrease in durability.

[0013] Furthermore, when the eccentric butterfly valve is installed in the piping of a central air conditioning system in a high-rise building or other structure, in the case of a dead end state during maintenance in Fig. 9(b), gravity will be generated in the water in the piping 13, and the resulting water pressure will be applied to the valve bodies of the butterfly valves 1 on both sides. In this case, the butterfly valve 1 on the upstream side (left side in the figure) will be subjected to a back pressure in the direction of the arrow, and as the vertical piping becomes longer with the rise of the building, the back pressure fluid pressure will increase. On the other hand, because the connection flange 15 on the lower side of the butterfly valve 1 has been removed, the fastening force of the piping bolts that had been pressing the seat retainer member until then is completely lost, and the force pressing and holding the seat ring member between the valve body and the seat retainer member is only the fastening force of the retainer bolts for fastening the seat retainer member.

[0014] In this state, when high back pressure is applied to the butterfly valve 1, the valve disc movement increases significantly, and in Figure 8, the back pressure moves the valve disc 6 to the left, forcing the seat ring member 4 towards the seat retainer member 3, causing further severe plastic deformation. As the seat ring member 4 is pushed towards the seat retainer member 3, it separates from the valve body 2, and the sealing surface pressure on the back surface of the base end portion of the seat ring member 4 also decreases. If the sealing surface pressure at this base end portion decreases, it can lead to fluid leakage from this portion, or so-called back leakage. In addition, when the seat ring member 4 is initially tightened with the retainer bolt, if the tightening force is insufficient and the lower connection flange 15 is then removed in a dead end state, the retainer bolt will loosen and the seal surface pressure will decrease, which will reduce the seal surface pressure at the base end of the seat ring, making back leakage even more likely to occur.

[0015] The present invention was developed to solve the problems associated with the prior art, and has as its object to provide an eccentric type butterfly valve with excellent operability which maintains high sealing performance when the valve is closed whether the pressure of a high-pressure fluid is applied in either the forward or reverse flow direction, and in particular which maintains the sealing performance of the seat ring even when high pressure is applied due to a reverse flow, and which can ensure the sealing surface pressure between the seat ring and the disc to prevent leakage. [Means for solving the problem]

[0016] In order to achieve the above object, the invention according to claim 1 provides an eccentric butterfly valve in which a disk rotatably supported at an eccentric position via a stem within a cylindrical body is hermetically attached to a seat ring fixed within the body by a seat retainer, the valve comprising: an inner diameter side of the seat ring having a flexible portion that tilts in response to the displacement of the disk; an annular leaf spring is attached between the flexible portion and the seat retainer for resilient reaction between them; the seat retainer is provided on the upstream side of the leaf spring, and the seat ring is provided on the downstream side; the leaf spring has an outer diameter side that abuts against the seat retainer, and an inner diameter side that is closer to the seat ring than the abutting position against the seat retainer abuts against the flexible portion, allowing elastic deformation of the inner diameter side; and a point at which the load characteristics of the leaf spring change when positive pressure or reverse pressure is applied to the valve is defined as an inflection point; the leaf spring is: The load characteristic of the leaf spring is set to switch between a low load characteristic and a high load characteristic at the inflection point,When the valve is closed, at the inflection point, the valve is in an unloaded state where no fluid pressure is applied to the valve, but a spring load is applied to the flexible portion; when positive pressure is applied to the valve and the load characteristics switch from the inflection point position, as the positive pressure increases, the flexible portion maintains a tight contact with the disk while the inner diameter side of the leaf spring tilts downstream, thereby decreasing the spring load; and when reverse pressure is applied to the valve and the load characteristics switch from the inflection point position, as the reverse pressure increases, the inner diameter side of the leaf spring tilts upstream while avoiding contact with the seat retainer, thereby increasing the spring load.This is an eccentric butterfly valve.

[0017] The invention of claim 2 is an eccentric butterfly valve in which a fixed portion that is fixed between the body and the seat retainer is integrally formed on the outer diameter side of the flexible portion, and a gasket portion that is integrally connected to the annular periphery on the outer surface side of this fixed portion via a thin-walled portion is sandwiched between the body and the seat retainer.

[0018] The invention according to claim 3 is an eccentric type butterfly valve in which the seat ring is fastened and fixed between the body and the seat retainer by a fastening retainer bolt with the seat ring and the disk hermetically sealed.

[0019] The invention according to claim 4 relates to an eccentric butterfly valve in which a disk rotatably supported at an eccentric position via a stem within a cylindrical body is hermetically attached to a seat ring fixed within the body by a seat retainer, the seat ring being provided with a flexible portion on the inner diameter side thereof which tilts in response to the displacement of the disk, and a leaf spring is attached between the flexible portion and the seat retainer for mutually elastically biasing the flexible portion and the seat retainer, the leaf spring being a spring in which the disk is displaced toward the seat retainer in the flow path direction, and the load in the elastically biasing direction increases in response to the degree of tilt of the flexible portion due to the displacement of the disk, and when the flexible portion is elastically deformed, the leaf spring pressed by the flexible portion is elastically deformed while avoiding contact with the seat retainer, and an annular abutment surface is formed on the flexible portion on the side opposite the leaf spring which abuts against the leaf spring, and the annular abutment surface is The leaf spring is attached at different angles.This is an eccentric type butterfly valve provided with a tapered surface that is gently inclined at a predetermined angle from the vertical direction toward the outer diameter direction. Effect of the Invention

[0020] According to the invention of claim 1, an eccentric valve structure is provided and a flexible part is provided on the inner diameter side of the seat ring that tilts in response to the displacement of the disk, thereby providing high sealing performance when the valve is closed regardless of whether the pressure of the high-pressure fluid is applied in the forward or reverse flow direction. In this case, a leaf spring is attached between the flexible part and the seat retainer, and the load of this leaf spring in the spring direction increases depending on the degree of tilt of the flexible part, so that even when high pressure is applied due to reverse flow in particular, the sealing surface pressure between the seat ring and the disk can be increased depending on the magnitude of the pressure, thereby reliably preventing leakage. During elastic deformation of the flexible portion, the leaf spring deforms while avoiding contact with the seat retainer, so even if the flexible portion is excessively deformed by high back pressure, the flexible portion of the leaf spring is prevented from contacting the seat retainer, suppressing a sudden increase in the seal surface pressure, allowing deformation of the flexible portion while increasing the seal surface pressure to prevent leakage, preventing damage due to wear, breakage, plastic deformation, etc. of the seat ring, maintaining its elastic characteristics, and maintaining the valve seat sealing performance when back pressure and positive pressure are applied when the valve is closed. Moreover, the repulsive force of the leaf spring can reduce the load torque due to fluid pressure during back pressure. Therefore, sudden operation (jumping) of the disk during operation such as automatic operation is prevented, improving operability, and the resulting wear of the seat ring is prevented, improving durability. In this case, the point at which the load characteristics of the leaf spring change when positive pressure or reverse pressure is applied to the valve is defined as the inflection point, and when the leaf spring is closed, the valve is in an unloaded state where no fluid pressure is applied to the valve at the inflection point, but a spring load is applied to the flexible portion.When positive pressure is applied to the valve and the load characteristics switch from the inflection point position, as the positive pressure increases, the flexible portion maintains a tight contact with the disk while the inner diameter side of the leaf spring tilts downstream, thereby reducing the spring load.On the other hand, when reverse pressure is applied to the valve and the load characteristics switch from the inflection point position, as the reverse pressure increases, the inner diameter side of the leaf spring tilts upstream while avoiding contact with the seat retainer, thereby increasing the spring load.This configuration allows the inflection point to be set arbitrarily. By setting the inflection point in this way, a valve with the desired characteristics can be obtained by setting the low load characteristics just before the inflection point for use in the positive pressure region, and the high load characteristics after the inflection point for use in the reverse pressure region.By setting the inflection point at any position, it is possible to provide a valve that can exhibit appropriate sealing properties for different diameters, from small to large. The leaf spring is set so that its load characteristics switch between low load characteristics and high load characteristics at the inflection point, and the timing at which the load characteristics of the leaf spring are switched with respect to the fluid flow direction can be changed by changing the position of the inflection point. This makes it possible to provide a valve that can provide appropriate sealing performance for different bore sizes, from small to large, by setting the inflection point at any position.

[0021] According to the invention of claim 2, a gasket portion is formed on the outer periphery of the fixed portion via a thin portion, independent of the flexible portion and the fixed portion, and this gasket portion is sandwiched between the body and the seat retainer, thereby preventing back leakage from between the body and the seat retainer. In this case, even if thermal expansion occurs in the gasket portion when the fluid is at high temperature, the sealing between the body and the seat retainer is maintained when the temperature returns to normal. By providing the thin portion, deformation of the gasket portion due to thermal expansion does not adversely affect the fixed portion or the flexible portion, and the valve seat sealing due to stable deformation of the flexible portion can be maintained even in the case of a high-temperature fluid.

[0022] According to the invention of claim 3, the hermetic seal between the seat ring and the disk when the valve is closed can be ensured only by the fastening force by fastening the fastening retainer bolt, and there is no need to connect a separate member such as a flange pipe to press the seat retainer against the body. In this way, even if the installation side of the seat retainer is in a dead end state where the flow path ends, it can exhibit excellent sealing properties and prevent leakage when high back pressure occurs. Therefore, even when used as part of the piping of a high-rise building and excessive head pressure in the back pressure direction is applied, the seat ring can be prevented from being pushed out toward the seat retainer while keeping the seat retainer pressing force low while balancing with the elasticity of the leaf spring in response to the displacement of the disk, and it is possible to prevent a decrease in the seal surface pressure of the base end part of the seat ring and reliably prevent back leakage.

[0023] According to the invention of claim 4, an eccentric valve structure is provided and a flexible part is provided on the inner diameter side of the seat ring that tilts in response to the displacement of the disk, thereby providing high sealing performance when the valve is closed regardless of whether the pressure of the high-pressure fluid is applied in the forward or reverse flow direction. In this case, a leaf spring is attached between the flexible part and the seat retainer, and the load of this leaf spring in the spring direction increases depending on the degree of tilt of the flexible part. Therefore, even when high pressure is applied due to reverse flow, the sealing surface pressure between the seat ring and the disk can be increased depending on the magnitude of the pressure, thereby reliably preventing leakage. During elastic deformation of the flexible portion, the leaf spring deforms while avoiding contact with the seat retainer, so even if the flexible portion is excessively deformed by high back pressure, the flexible portion of the leaf spring is prevented from contacting the seat retainer, suppressing a sudden increase in the seal surface pressure, allowing deformation of the flexible portion while increasing the seal surface pressure to prevent leakage, preventing damage due to wear, breakage, plastic deformation, etc. of the seat ring, maintaining its elastic characteristics, and maintaining the valve seat sealing performance when back pressure and positive pressure are applied when the valve is closed. Moreover, the repulsive force of the leaf spring can reduce the load torque due to fluid pressure during back pressure. Therefore, sudden operation (jumping) of the disk during operation such as automatic operation is prevented, improving operability, and the resulting wear of the seat ring is prevented, improving durability. Furthermore, the flexible portion is formed with an annular contact surface on the side facing the leaf spring, the annular contact surface being in contact with the leaf spring. The leaf spring is attached at different angles. Since the annular contact surface is provided with a tapered surface that is gradually inclined at a predetermined angle from the vertical direction toward the outer diameter direction, the timing for switching the load characteristics of the leaf spring with respect to the fluid flow direction can be changed by changing the magnitude of this inclination angle in a valve of the same size. In this case, if the inclination angle of the annular contact surface is set large, it is suitable for a small-diameter valve with a small amount of disk movement, while if the inclination angle is set small, it is suitable for a large-diameter valve with a large amount of disk movement, since the repulsive force of the leaf spring can be exerted when a large back pressure is applied to the flexible part. In this way, by setting the magnitude of the inclination angle of the annular contact surface, it is possible to provide a valve that can exhibit appropriate sealing properties according to the difference in diameter from small to large. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a longitudinal sectional view showing an embodiment of an eccentric butterfly valve of the present invention. [Diagram 2] FIG. 2 is an enlarged schematic view of a main part of FIG. [Diagram 3] FIG. 4 is an enlarged schematic view showing a main part near a flexible portion. [Figure 4] FIG. 4 is an enlarged schematic view of a main part showing a state in which a positive pressure is applied to the liquid crystal display device shown in FIG. [Diagram 5] FIG. 4 is an enlarged schematic view of a main part showing a state in which a counter pressure is applied to the liquid crystal display device shown in FIG. [Figure 6] 4 is a graph showing the relationship between the deformation amount of a leaf spring and the spring load. [Figure 7] 2 is an enlarged schematic view of a main portion showing a state in which a back pressure is applied to the eccentric type butterfly valve of FIG. 1. FIG. [Figure 8] FIG. 1 is a partially enlarged schematic view showing the vicinity of a seat ring mounting portion of a conventional double eccentric butterfly valve. [Figure 9] FIG. 1 is a schematic diagram showing an example of a central air conditioning system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] An embodiment of the eccentric butterfly valve of the present invention will be described below with reference to the drawings. Fig. 1 shows one embodiment of the eccentric butterfly valve of the present invention, and Fig. 2 shows an enlarged schematic diagram of the main part near the seat ring mounting part in Fig. 1. The eccentric butterfly valve of the present invention (hereinafter referred to as valve body 20) is installed assuming an operating pressure of approximately 5 MPa for positive pressure and counter pressure.

[0026] In Fig. 1, the valve body 20 is provided with a size of, for example, a caliber of 300A, and includes a cylindrical body 21, a stem 22, a disk 23, a seat ring 24, a seat retainer 25, and a spring member 26, of which the body 21, the disk 23, and the seat retainer 25 are formed from metal materials such as stainless steel and cast steel. In the figure, the left side of the valve body 20 indicates the upstream side, and the right side indicates the downstream side. In response to the fluid pressure (positive pressure) generated when the fluid flows from the upstream side to the downstream side (forward flow), or the fluid pressure (back pressure) generated when the fluid flows from the downstream side to the upstream side (backflow), the seat ring 24 is deflected to the right or left to prevent fluid leakage when the valve is closed. Figs. 2 and 3 show the vicinity of the upper part of the disk 23 in the valve body 20, with the lower side indicating the inner diameter side of the valve body 20 and the upper side indicating the outer diameter side.

[0027] 1, the body 21 is provided with upper and lower mounting portions 30 for mounting the stem 22, and the disk 23 is journaled at an eccentric position within the body 21 via the stem 22 mounted on these mounting portions 30. The disk 23 is provided so as to be hermetically sealed against a seat ring 24 fixed within the body 21 by a seat retainer 25 when the valve is closed.

[0028] The disk 23 is formed in a substantially circular disk shape, and its outer periphery is provided with a valve body seal surface 31 that can abut and seal with the seat ring 24. Bosses 32 are formed to protrude from the upper and lower parts of one surface of the disk 23, and a hole 33 for mounting the stem 22 is formed in the bosses 32 so as to be eccentric from the sealing position. With the stem 22 inserted in the hole 33, the disk 23 is fixed integrally to the stem 22 by a tapered pin 34 at an eccentric position within the body 21 and rotatably supported. In this way, the valve body 20 of this example is a double eccentric type valve in which the stem 22 is eccentric with respect to the disk 23 and the center of rotation of the disk 23 is eccentric from the center of the valve bore.

[0029] 2 and 3, the seat ring 24 is molded into an annular shape from a resin material such as PTFE (polytetrafluoroethylene), and in this embodiment, PTFE containing a filler is used. The seat ring 24 has a ring-shaped base portion 40, a flexible portion 41, a fixed portion 42, and a gasket portion 43. Note that Fig. 2 shows the state of the valve body 20 after assembly, and no fluid pressure is applied.

[0030] The base portion 40 has a generally rectangular cross section and functions as a base for the seat ring 24. A flexible portion 41 is formed integrally on the inner diameter side of one side of the base portion 40, and a fixed portion 42 is formed integrally on the outer diameter side. A gentle inclined surface is formed on the inner peripheral surface of the base portion 40, continuing from a seal contact portion 45 of the flexible portion 41, which will be described later. The inclined surface may be linear or curved, or may have a recess, and is provided in an appropriate shape so as to exhibit flexibility when the disk 23 abuts against the flexible portion 41.

[0031] The flexible portion 41 is formed with a predetermined thickness on the inner diameter side of the base portion 40, and a seal contact portion 45 is provided on the side that comes into contact with the disk 23. The seal contact portion 45 is provided in an annular shape with a predetermined seal width and a C-shaped or R-shaped cross section, in a state where it is located closer to the seat retainer 25 than the bottom in the flow path direction of a space portion 46 provided between the fixed portion 42 and the flexible portion 41, and this seal width enables sealing by surface contact with the disk 23.

[0032] An annular abutment surface 50 that abuts against the spring member 26 is formed on the side of the flexible portion 41 facing the spring member 26. The annular abutment surface 50 is provided as a tapered surface that is gently inclined at a predetermined inclination angle θ from the vertical direction toward the outer diameter direction. The magnitude of the inclination angle θ can be set arbitrarily. When the inclination angle θ is small, the characteristics of the elastic force of the leaf spring 26 can be changed by slightly tilting the flexible portion 41, and when the inclination angle θ is large, the characteristics of the elastic force cannot be changed unless the flexible portion 41 is tilted greatly.

[0033] A plurality of radial through slits 50a are provided in the annular contact surface 50. By providing these slits 50a, the annular contact surface 50 guides a positive pressure fluid to the space 46 while being in contact with the leaf spring 26, and seals the valve seat by tightly contacting the seat ring 24 and the disc 23. In this embodiment, the slits 50a are provided at two locations on the annular contact surface 50 at intervals of 180°, but any number of slits 50a can be provided as necessary depending on the size of the bore of the valve body 20, etc.

[0034] The groove-shaped space 46 is provided on the outer diameter side of the flexible portion 41, and when the disk 23 moves or bends horizontally or inclined relative to the flow path direction due to positive or reverse pressure, thereby displacing in the flow path direction, the flexible portion 41 flexes through the space 46 and tilts in the flow path direction depending on the magnitude of the displacement, whereby the seal contact portion 45 abuts and seals with the valve body seal surface 31.

[0035] A fixed portion 42 is formed on the outer diameter side of the flexible portion 41 with a space 46 in between, and this fixed portion 42 is fixed between the body 21 and the seat retainer 25, thereby mounting the seat ring 24 to the valve body 20 in a non-removable state. The shape of the fixed portion 42 is not particularly limited as long as it does not prevent the flexible portion 41 from bending in the left-right direction (flow path direction), and in this example, the fixed portion 42 is provided with a rectangular cross section.

[0036] A thin wall portion 51 is formed on the annular periphery on the outer peripheral surface side of the fixed portion 42, and a hook-shaped gasket portion 43 is formed integrally with the fixed portion 42, following the thin wall portion 51. The gasket portion 43 is attached in a tight contact state to an attachment groove 52 formed in the seat retainer 25, and is sandwiched between the seat retainer 25 and the body 21 in this state, thereby making it possible to prevent fluid from leaking out from between them. The thin wall portion 51 is provided with a thickness of, for example, about 1 to 1.5 mm, which makes it possible to suppress the outflow of excess portions due to thermal expansion even when this thermal expansion occurs.

[0037] The spring member 26 is made of an annular flat leaf spring, and is formed with an outer diameter that allows it to be mounted between the seat ring 24 and the seat retainer 25, and is provided so that it can be mounted in a state in which they are resiliently biased against each other. The leaf spring 26 is disposed such that its outer diameter side abuts against the seat retainer 25 on the side facing the seat ring 24, and its inner diameter side from the abutment position on the seat retainer 25 side abuts against the flexible portion 41 on the side facing the seat ring 24. When the flexible portion 41 bends and tries to tilt, the annular abutment surface 50 abuts against the leaf spring 26, so that the leaf spring 26 tries to elastically deform from the inner diameter side, and the abutment position with the seat ring 24 gradually shifts from the inner diameter side to the outer diameter side as the amount of tilt of the flexible portion 41 increases. The material of the leaf spring 26 is stainless steel, and the thickness of the thin portion 51 is 1.35 mm when the nominal diameter B is 2 1 / 2 to 4, 1.45 mm when the nominal diameter B is 5 to 8, and 1.7 mm when the nominal diameter B is 10 to 12.

[0038] By providing the leaf spring 26, when the disk 23 is displaced toward the seat retainer 25 due to fluid pressure (counter pressure) and the flexible portion 41 tilts due to this displacement, the spring load in the elastic direction of the leaf spring 26 increases in a manner substantially proportional to the magnitude of this tilt. In this case, the leaf spring 26 deforms so that its inner diameter side tilts more significantly as the flexible portion 41 tilts.

[0039] The seat retainer 25 is formed in a substantially annular shape, and the aforementioned leaf spring 26 is disposed near the outer diameter side thereof, with the seat ring 24 being provided so as to be temporarily attached and mounted so as to sandwich the leaf spring 26. This allows the seat retainer 25, leaf spring 26, and seat ring 24 to be mounted in an integrated state to the body 21. In the seat retainer 25, an annular gap 53, an annular protruding portion 54, an annular abutting portion 55, an annular convex portion 56, an annular concave groove 57, an annular protruding portion 58, and a mounting concave groove 52 are provided on the mounting surface sides of the spring member 26 and the seat ring 24, in that order from the inner diameter side, and form a concave-convex shape.

[0040] The annular protrusion 54 is formed in a trapezoidal cross section capable of abutting against the leaf spring 26 at the mounting position of the leaf spring 26. An annular abutment portion 55 is provided at a position radially outward from the annular protrusion 54, and the leaf spring 26 can abut against the annular abutment portion 55 in a line contact state. As a result, the leaf spring 26 elastically deforms such that the inner diameter side thereof tilts toward the flow path, with the abutment portion with the annular abutment portion 55 as a fulcrum.

[0041] The gap 53 is formed on the inner diameter side of the annular contact portion 55, and is capable of housing the inclined portion on the inner diameter side of the leaf spring 26 that has been deformed by the pressure of the elastically deformed flexible portion 41 within this gap 53. The size of the gap 53 can be set arbitrarily by adjusting the height and width of the annular protrusion 54, and is a space large enough that the inner diameter tip side does not come into contact with the seat retainer 25 when housing the inner diameter side portion of the deformed leaf spring 26.

[0042] 6, the dashed line indicates an imaginary line when the leaf spring 26 comes into contact with the seat retainer 25 in the valve body 20 with the inflection point as the origin O, and at this time, the rate of increase in the spring load relative to the amount of deformation of the leaf spring increases abruptly, which may result in an excessive force being applied to the seat retainer 25 and plastic deformation of the seat ring 24. Therefore, by providing the gap 53, the inclined portion of the leaf spring 26 is prevented from coming into contact with the seat retainer 25, and the flexible portion 41 is not sandwiched between the disc 23 and the seat retainer 25, making it possible to prevent plastic deformation of the flexible portion 41.

[0043] 3, when a force is applied from flexible portion 41 to leaf spring 26 in the above-described state of contact between leaf spring 26 and annular contact portion 55, the force is applied to leaf spring 26 with annular contact portion 55 as a fulcrum. In this case, the outer diameter side end portion (position of point P2) of annular contact surface 50 is disposed on the inner diameter side of normal line H to leaf spring 26 at the position of contact between annular contact portion 55 and leaf spring 26.

[0044] In Fig. 2, the annular convex portion 56 is formed at a position facing the space portion 46 of the seat ring 24 on the outer diameter side of the annular protruding portion 54, and is provided with a length shorter than the depth of the space portion 46 and a thickness thinner than the width of the space portion 46 closer to the annular concave groove 57. The annular concave groove 57 is located at a position facing the fixing portion 42 of the seat ring 24, and is formed with a depth and width that allow the fixing portion 42 to be inserted and fixed on the outer diameter side of the annular convex portion 56. The annular protrusion portion 58 is located at a position facing the thin-walled portion 51, and is formed with a length and thickness that allow it to be inserted into an annular insertion space 59 provided between the fixing portion 42 and the gasket portion 43. The mounting concave groove 52 is located at a position facing the gasket portion 43, and is formed with a depth and width that allow the gasket portion 43 to be inserted and sealed tightly.

[0045] The seat ring 24 is mounted on the seat retainer 25 with the leaf spring 26 sandwiched therebetween, and at this time, the annular convex portion 56, the annular concave groove 57, the annular protrusion portion 58, and the mounting concave groove 52 of the seat retainer 25 face the space portion 46, the fixed portion 42, the thin portion 51, and the gasket portion 43 of the seat ring 24, respectively, and are in an assembled state. After the seat ring 24 and the seat retainer 25 are assembled, the fixed portion 42 is fixed in a fitted state in the annular concave groove 57, and thus the fixed portion 42 is positioned. Therefore, the flexible portion 41 is disposed at a predetermined position in the radial direction.

[0046] With the seat ring 24 disposed between the body 21 and the seat retainer 25 as described above, they are fastened together by the fastening retainer bolt 60. In this case, the body 21 and the seat retainer 25 are fastened in a state where their contacting surfaces are in surface contact by so-called metal touch. The retainer bolt 60 has a predetermined amount of fastening force, and after fastening, the valve body 20 does not require an external fastening force when the valve is closed, and a hermetic seal between the seat ring 24 and the disk 23 is maintained.

[0047] Due to the fastening force of this retainer bolt 60, when the valve is closed, the seal contact portion 45 presses the disk 23, the flexible portion 41 tilts slightly toward the seat retainer 25, and the inner diameter side of the leaf spring 26 is also pushed slightly toward the seat retainer 25. In this state, two forces are generated: a reaction force of the leaf spring 26 generated by the tilt of the flexible portion 41 and a warp in the seat ring 24 itself. These forces generate a seal surface pressure between the disk 23 and the seat ring 24.

[0048] The base portion 40, flexible portion 41, and fixed portion 42 of the seat ring 24 are not strictly limited by their shapes or functions. In other words, when the flexible portion 41 bends and tilts, not only the flexible portion 41 but also a part of the base portion 40 bends, and when a movement occurs in the flexible portion 41 due to a thermal change, the movement is mitigated by the fixed portion 42. In this way, for example, the fixed portion 42 has a function other than the function of fixing the seat ring 24. Also, for example, the gasket portion 43 has a function of fixing the seat ring 24 in addition to the function of preventing back leakage.

[0049] It is preferable that a crushed portion of a predetermined volume is provided as necessary in each portion of the fixing portion 42 and the gasket portion 43. In this case, the crushed portion is pressed to increase the surface pressure, thereby improving the sealing performance between the seat retainer 25 and improving the leak prevention function.

[0050] Next, the operation and function of the eccentric type butterfly valve of the present invention in the above embodiment will be explained using the graph in Figure 6, along with the mechanism when pressure is applied to the seat ring 24. Figure 6 shows the relationship between the amount of deformation when pressure is applied to the leaf spring 26 and the spring load generated according to this amount of deformation.

[0051] In the graph, the origin O where the load characteristics of the leaf spring 26 change when positive or negative pressure is applied to the valve is defined as an inflection point. At the origin O, the valve is in an unloaded state where no fluid pressure is applied, and the spring load of the leaf spring 26 at this time is a load F O The load characteristics due to the reaction force of the leaf spring 26 applied to the seat ring 24 differ between the positive pressure state and the reverse pressure state, with the origin O as the boundary, and with the position of the origin O as the reference, the left side of this origin O is the state when positive pressure is applied, and the right side is the state when reverse pressure is applied.

[0052] When the valve body 20 is in an open state (not shown), there is almost no tilt of the seat ring 24, and the force with which the leaf spring 26 presses the seat ring 24 is extremely small. When the valve body 20 begins to close from this state, the disk 23 presses the seat ring 24, tilting the leaf spring 26, so that the reaction force of the leaf spring 26 acts on the seat ring 24 side.

[0053] The spring member 26 is arranged so as to apply a slightly weak elastic force to the flexible portion 41 in the assembled state shown in FIG. 2. The elastic force F in this case is the spring load F in FIG. O 2, the elastic force of the spring member 26 is set to about 20 to 30% of the maximum elastic force.

[0054] Even when the valve body 20 is in the fully open state with positive pressure applied to it, the elastic force of the spring member 26 is applied to the flexible portion 41. However, the elastic force in this case is only to the extent that the spring member 26 is in contact with the flexible portion 41, and the spring load F at point B in FIG. B As shown in FIG. 1, the elastic force of the spring member 26 is set to 5 to 10% of the maximum elastic force.

[0055] In this way, in the present invention, the spring member 26 is always in contact with the flexible portion 41. As a result, in response to the inclination of the flexible portion 41, the spring member 26 immediately follows the movement of the flexible portion 41 in either the case of positive pressure or reverse pressure, resulting in good responsiveness.

[0056] 1 to 3 show the valve body 20 in a closed state, and an unloaded state in which no fluid pressure is applied to the valve body 20, that is, a state in which the fluid pressure on the valve body 20 at the origin O is 0 MPa. In this case, the valve body seal surface 31 of the disk 23 presses the seal contact portion 45 of the flexible portion 41 to the left, and the seat ring 24 deforms so that the flexible portion 41 tilts slightly to the left with its fixed portion 42 fixed and held between the body 21 and the seat retainer 25. At this time, a force due to the elasticity of the flexible portion 41 is applied to the leaf spring 26, and the spring load generated when the leaf spring 26 is deformed is applied to the flexible portion 41.

[0057] In this way, when in the state of the origin O, a force acts on the flexible portion 41 in the direction of the disk 23 due to its own flexibility and the elasticity of the leaf spring 26, causing the seal contact portion 45 to come into tight contact with the valve body seal surface 31 with a predetermined seal surface pressure, thereby providing sealing performance.

[0058] Since a substantially conical annular abutment surface 50 inclined at a predetermined inclination angle θ in the outer diameter direction is provided on the side of the flexible portion 41 facing the leaf spring 26, the inner diameter side of the flexible portion 41 is closer to the leaf spring 26, and in the unloaded state in this embodiment, the flexible portion 41 abuts against the leaf spring 26 in the range from point P1 on the inner diameter side to point P2 on the outer diameter side, as shown in Fig. 3. Thus, in the assembled state, i.e., in the unloaded state where no fluid is applied, the annular abutment surface 50 of the flexible portion 41 is in surface contact with the leaf spring 26 in the range from point P1 to point P2.

[0059] When positive or reverse pressure is applied to the valve body 20 from this state, the spring load changes depending on whether (1) positive or reverse pressure is applied to the leaf spring 26 or (2) the inclination angle θ of the annular contact surface 50 with respect to the leaf spring 26 is different. Therefore, we will consider these cases (1) and (2) separately.

[0060] (1) In the case where positive and reverse pressures are applied to the leaf spring 26, when positive and reverse pressures are applied to the valve body 20, the seat ring 24 is tilted by the fluid pressure, and the contact position with the leaf spring 26 changes depending on the degree of tilt of the seat ring 24. As a result, the load characteristics of the reaction force of the leaf spring 26 applied to the seat ring 24 changes as shown by the solid line in Figure 6, and one type of leaf spring 26 generates load characteristics with two types of spring constants.

[0061] Under positive pressure, the seat ring 24 is less likely to tilt, and in this case, as shown in FIG. 4, point P1 of the annular abutment surface 50 comes into contact with the contact surface 26a of the leaf spring 26, and the load applied from the leaf spring 26 to the seat ring 24 is relatively small. In the positive pressure state, the seat ring 24 is less tilted, and the annular contact surface 50 of the flexible portion 41 comes into contact with the leaf spring 26 in a substantially linear manner at point P1 on the inner periphery. This state is near α in FIG. 6, and the spring load applied from the leaf spring 26 to the seat ring 24 is the spring load F at the origin O. O It will be smaller than

[0062] On the other hand, in a reverse pressure state, as shown in FIG. 5, the seat ring 24 tilts more, and in this case, the annular contact surface 50 comes into contact with the leaf spring 26 at point P2, and the load applied from the leaf spring 26 to the seat ring 24 increases. In the reverse pressure state, the seat ring 24 falls more, and the annular contact surface 50 of the flexible portion 41 comes into contact with the leaf spring 26 in a substantially linear manner at point P2 on the outer periphery. This state is near β in FIG. 6, and the spring load applied from the leaf spring 26 to the seat ring 24 is the spring load F at the origin O. O It will be greater than. As described above, when pressure is applied to a particular leaf spring 26, the spring load has the characteristic that it changes gradually in the positive pressure region and changes more rapidly in the reverse pressure region compared to the positive pressure.

[0063] Describing in more detail the case where positive pressure or reverse pressure is applied to the valve body 20, when reverse pressure is applied, the disk 23 is displaced, causing the flexible portion 41 to tilt more, and the contact position between the flexible portion 41 and the leaf spring 26 gradually shifts toward point P2 on the outer diameter, as shown in Figure 5, and when further reverse pressure is applied, the load on the leaf spring 26 increases while the flexible portion 41 comes into line contact at point P2. In this way, when fluid pressure is applied to the seat ring 24, the seat ring 24 gradually tilts, and the contact position with the leaf spring 26 changes depending on the magnitude of the tilt.

[0064] By making line contact at point P2, the distance W (in this embodiment, this indicates the radial distance) between the annular abutment portion 55 and point P2 becomes constant, so that the moment expressed by the product of the distance W and the spring load F of the leaf spring 26 can be stably obtained, and the sealing performance with the disc 23 at the seal contact portion 45 of the flexible portion 41 can be reliably ensured.

[0065] At this time, the outer diameter side of the leaf spring 26 on the side facing the seat retainer 25 abuts against the seat ring 24, and the inner diameter side of the leaf spring 26 abuts against the seat retainer 25, so that the inner diameter side of the leaf spring 26 elastically deforms with the annular abutment portion 55 of the seat retainer 25 as a fulcrum.

[0066] On the other hand, when positive pressure in the direction of the arrow is applied to valve body 20 in the valve closed state, as shown in FIG. 4, the valve seat can be sealed at low pressure due to the sealing surface pressure generated by the warping of seat ring 24 and leaf spring 26 during assembly.

[0067] In this case, the disk 23 tends to move downstream (to the right) due to the fluid pressure, and the flexible portion 41 tends to tilt downstream while maintaining a tight contact with the disk 23. In this way, the sealing performance between the seal contact portion 45 and the valve body seal surface 31 is maintained. This downstream movement also reduces the magnitude of the spring load F by the leaf spring 26. And, on the positive pressure side in Figure 6, as the positive pressure increases, the amount of elastic deformation of the leaf spring 26 decreases, and the spring load also becomes smaller, and the load of the leaf spring 26 becomes extremely small near the maximum fluid pressure.

[0068] In this way, when the inclination of the flexible portion 41 is small, the leaf spring 26 is in contact with point P1 on the inner diameter side of the annular contact surface 50, and the load applied from this leaf spring 26 to the flexible portion 41 is small. When the deflection of the disk 23 and the warp of the stem 22 increase with an increase in fluid pressure, the disk 23 moves toward the secondary stem 22, reducing the seal surface pressure, and further, the warp of the leaf spring 26, which was slightly tilted at the time of assembly, decreases due to the movement of the disk 23, thereby reducing the spring load applied to the flexible portion 41 from the leaf spring 26. However, the flexible portion 41, which receives the fluid pressure, falls toward the disk 23, and the seal contact portion 45 presses against the disk 23, causing the seat ring 24 to function as a self-sealing member by itself, thereby maintaining the valve seat sealing performance.

[0069] When setting the inclination angle θ of the annular contact surface 50, taking into consideration the operation of the seat ring 24 during the above-mentioned reverse pressure and positive pressure, the inclination angle θ is set to 12° for small diameter valves (e.g., nominal diameter 65A to 80A), while the inclination angle θ is set to 4° for large diameter valves (e.g., nominal diameter 200A to 300A). This is because the movement amount of the disk 23 is smaller in small diameter valves, and it is necessary to ensure a large movement (rotational movement) of the flexible portion 41, and therefore the inclination angle θ is set larger than that for large diameter valves.

[0070] Here, when the back pressure is applied, the disk 23, the seat ring 24, and the leaf spring 26 tend to deform into the state shown by the two-dot chain line in Fig. 7. At this time, as shown in Fig. 3, the flexible portion 41 tilts in the direction of the arrow.

[0071] When the disk 23 and stem 22 are warped due to the fluid pressure and the disk 23 moves upstream toward the seat ring 24 (left side), this movement pushes the seat ring 24 toward the seat retainer 25, and the inner diameter side of the leaf spring 26 also tries to tilt. As the fluid pressure rises to a high pressure, the amount of movement of the disk 23 also increases, and the tilt of the flexible portion 41 of the seat ring 24 and the leaf spring 26 also increases significantly. The tilt of the flexible portion 41 is also affected by the counter pressure applied to the seat ring 24, and by tilting the leaf spring 26, a resilient force is applied from the leaf spring 26 in a direction that tries to return the fallen flexible portion 41 to its original state, ensuring sealing.

[0072] 3, when flexible portion 41 tilts in the direction of the arrow, its annular contact surface 50 abuts against leaf spring 26 in the range from point P1 to point P2, and at this time, under positive pressure, contact occurs mostly at point P1, and the force applied to flexible portion 41 has low load characteristics, but under reverse pressure, contact occurs from point P1 to point P2, and a load with high load characteristics is generated. Flexible portion 41 tilts while abutting against leaf spring 26 between point P1 and point P2 depending on the disk position of reverse pressure / positive pressure, and a spring load according to the amount of tilt is applied to flexible portion 41.

[0073] In particular, when back pressure is applied, the leaf spring 26 comes into contact at point P2 and the spring load from this leaf spring 26 increases, but the seat ring 24 is held in a balanced state with an appropriate sealing surface pressure, preventing excessive deformation of the flexible portion 41. As a result, even when the back pressure is large, plastic deformation, wear, and damage to the seat ring 24 are prevented, sealing performance is maintained, and the sealing surface pressure between the seat ring 24 and the disc 23 is secured, making it possible to reliably prevent seal leakage.

[0074] In the figure, if the distance from point P1, which is the contact point with leaf spring 26 when flexible portion 41 is at its minimum deformation, to annular abutment portion 55 is L1, and the distance from point P2, which is the contact point with leaf spring 26 when flexible portion 41 is at its maximum deformation, to annular abutment portion 55 is L2, then distance L1>distance L2, and as the amount of tilt of flexible portion 41 increases due to changes in fluid pressure on disk 23, the distance from annular abutment portion 55 to the position where force is applied becomes shorter. For this reason, as shown in Figure 6, as flexible portion 41 is tilted significantly due to back pressure, the load of leaf spring 26 also increases approximately proportionally, and therefore, even when excessive back pressure is applied to disk 23, the tilt of flexible portion 41 can be suppressed while improving the sealing surface pressure with disk 23.

[0075] Next, (2) the case where the inclination angle θ of the annular contact surface 50 with respect to the leaf spring 26 is different will be described. By changing the magnitude of the inclination angle θ, it is possible to change the timing (position of the inflection point) at which the load characteristics of the leaf spring 26 relative to the fluid flow direction are switched, with the valve body 20 of the same size. For example, if the inflection point is set at the position of the origin O1, then as shown by the dashed line in FIG. 6, the high load characteristic can be exhibited early on the positive pressure side to respond to the fluid pressure.

[0076] For these reasons, a valve with the desired characteristics can be obtained by arbitrarily setting the inflection point when forming the inclination angle θ of the spring member 26, setting the low load characteristics just before the inflection point for use in the positive pressure region, and setting the high load characteristics after the inflection point for use in the reverse pressure region. Setting the inclination angle θ of the annular abutment surface 50 large is suitable for small-diameter valves with a small amount of movement of the disc 23. On the other hand, setting the inclination angle θ small allows the repulsive force of the leaf spring 26 to work when a large reverse pressure is applied to the flexible portion 41, making it suitable for large-diameter valves with a large amount of movement of the disc 23. In this way, the inflection point (origin O) on the graph in FIG. 6 can be set at any position by changing the magnitude of the inclination angle θ of the annular abutment surface 50, making it possible to provide a valve that can exhibit appropriate sealing properties depending on the difference in diameter, from small to large.

[0077] As described above, the valve body 20 of the present invention has a flexible portion 41 formed on the inner diameter side of the seat ring 24, and the leaf spring 26 attached between this flexible portion 41 and the seat retainer 25. In this leaf spring 26, the spring load changes according to the degree of inclination of the flexible portion 41 due to the displacement of the disk 23, so that even when a high-pressure fluid of about 5 MPa positive pressure to 5 MPa reverse pressure is applied to the disk 23, the sealing performance when the valve is closed is maintained at a high level, and both the sealing performance at positive pressure and the sealing performance at reverse pressure are achieved, thereby reliably preventing leakage. At this time, by increasing or decreasing the spring load according to the magnitude of the fluid pressure, it is also possible to suppress excessive sealing surface pressure of the valve at high reverse pressure, thereby improving operability.

[0078] By providing the gap 53 on the inner diameter side of the annular contact portion 55, even if an excessive force is applied to the inner diameter side of the leaf spring 26 due to the inclination of the flexible portion 41 caused by the back pressure, the inclined portion deforms to escape into the gap 53 as shown by the two-dot chain line in Fig. 3, thereby preventing the inner diameter side of the leaf spring 26 from contacting the seat retainer 25. As a result, there is no risk of the deformed flexible portion 41 being pinched between the seat retainer 25, the leaf spring 26, and the disk 23, and the change in the amount of deformation of the leaf spring 26 when back pressure is applied in Fig. 6 is maintained approximately proportional, making it possible to prevent plastic deformation of the flexible portion 41 without a sudden increase in the seal surface pressure.

[0079] 3, by locating the outer diameter side end (position of point P2) of the annular contact surface 50 on the inner diameter side of the normal line H, the contact point between the flexible portion 41 and the leaf spring 26 is located on the inner diameter side of the normal line H at any point between point P1 and point P2. As a result, when a force is applied to the flexible portion 41 from the disk 23, a force in the clockwise direction is always applied to the contact point between the flexible portion 41 and the leaf spring 26, centered on the annular contact portion 55. Since the direction of this force matches the direction in which the inner diameter side of the leaf spring 26 deforms, it is possible to efficiently transmit the force from the flexible portion 41 to the leaf spring 26 to exert the spring load.

[0080] In contrast to this, if the outer diameter side end of the annular contact surface 50 is positioned on the outer diameter side of the normal line H, when a force is applied to the flexible portion 41 from the disk 23, a counterclockwise force acts on the contact point between the flexible portion 41 and the leaf spring 26, centered on the annular contact portion 55. Since this force is in the opposite direction to the deformation direction of the inner diameter side of the leaf spring 26, the movement of the leaf spring 26 will stop, and further, a force pressing the leaf spring 26 will act on the flexible portion 41, which may cause plastic deformation of the flexible portion 41. Therefore, as described above, it is preferable to position the outer diameter side end of the annular contact surface 50 (the position of point P2) on the inner diameter side of the normal line H.

[0081] It is more preferable to set the spring characteristic (spring constant) of the leaf spring 26 so that the spring load switches at an inflection point so as to be low in the positive pressure region and high in the reverse pressure region. The reason for this is that in the positive pressure region, as described above, the self-sealing function utilizing fluid pressure can be exerted, so even if the seat ring 24 itself sags and the restoring ability of the seat ring itself decreases, sealing is possible as long as there is a spring load that can obtain a minimum sealing surface pressure in the low positive pressure region. Furthermore, even in the medium to high pressure region, the self-sealing function increases, so that sealing performance is exerted with almost no spring load. For these reasons, the spring load of the leaf spring 26 during positive pressure need only be at a level that is generated slightly at low pressure and no load.

[0082] On the other hand, in the counter pressure region, it is necessary to support the flexible portion 41 which tilts due to the movement of the disk 23, and the seat ring 24 which tilts due to the fluid pressure, so the forces acting on these are kept in balance by the load of the leaf spring 26. Therefore, the spring load is set to increase as the fluid pressure increases.

[0083] In this embodiment, in order to satisfy the above-mentioned conditions in the positive pressure region and the reverse pressure region, an inflection point (origin O) is set at which the contact point between the flexible portion 41 and the leaf spring 26 shifts depending on the amount of inclination of the flexible portion 41 of the seat ring 24. With this inflection point as a boundary, a single leaf spring 26 can accommodate low load characteristics in which the rate of increase in the spring constant is low on the positive pressure region side of the leaf spring 26, and high load characteristics in which the rate of increase in the spring constant is high on the reverse pressure region side (after the inflection point).

[0084] The fixed portion 42 is integrally formed on the outer diameter side of the flexible portion 41, and the hook-shaped gasket portion 43 is integrally formed on the outer peripheral surface side of the fixed portion 42 via the thin portion 51, so that the gasket portion 43 is fixed in a fixed state independent of the fixed portion 42 and the flexible portion 41 between the body 21 and the seat retainer 25. Therefore, the gasket portion 43 is prevented from leaking out of excess heat expansion at high temperatures in the thermal cycle, and maintains its volume even when the temperature returns to normal, preventing back leakage.

[0085] When assembling the valve body 20, the seat ring 24 and the disk 23 are sealed together, and the body 21 and the seat retainer 25 are firmly fastened together in a metal-to-metal contact state by the retainer bolts 60. Since the seat ring 24 is not further fastened after fastening, there is no stress relaxation in the seat ring 24 that occurs when the piping bolts are removed, and the retainer bolts 60 do not loosen, so the fastened state is maintained. At this time, the compression rate and filling rate of the gasket portion 43 in the mounting groove 52 can be set to the minimum necessary to further improve the fastening force by the metal-to-metal contact.

[0086] In addition, by bringing the vicinity of the tap for the retainer bolt 60 of the body 21 and the entire surfaces of the seat retainer 25 into surface contact, it is possible to maintain the fastening force of the retainer bolt 60.

[0087] By tightening and fixing with the retainer bolt 60, it functions to support the seat ring 24 which tilts due to fluid pressure, to support the seat ring 24 and leaf spring 26 which tilt due to the disc 23, and to maintain the surface pressure of the gasket portion 43 to maintain sealing performance.

[0088] As described above, the sealing ability of the seat ring 24 against back pressure when the valve is closed can be maintained by just the tightening force of the retainer bolt 60, and therefore it is possible to prevent seat leakage and back leakage even when the upstream connection flange of the valve body 20 is removed to create a dead end state.

[0089] For this reason, for example, the valve body 20 of the present invention can be used in the vertical pipe 14 of the central air conditioning system 10 shown in Fig. 9. In this case, the cooling tower 12 is arranged on the upper side (high-rise side), and the valve body 20 is disposed on the lower side (low-rise side) of the vertical pipe 14 on the upstream and downstream sides of the pipe 13, and the valve body 20 is opened to put the central air conditioning system 10 in operation as shown in Fig. 9(a) or closed to put the central air conditioning system 10 in stop as shown in Fig. 9(b), in which case maintenance and the like can be performed.

[0090] In the state shown in Figure 9(b), during maintenance, the connection flange 15 and part of the piping 13 on the lower side of the valve body 20 are removed to make the lower side of the valve body 20 a dead end, which makes it possible to perform maintenance and cleaning inside each of the piping 13 above or below the valve body 20.

[0091] In this dead-end state, when the water pressure in the pipe 13 is applied to the valve body 20 by gravity, the back pressure becomes excessive due to the head pressure, especially in the valve body 20 on the left side of the figure (the valve arranged with the seat retainer 25 located at the bottom), as the vertical pipe 14 becomes longer with the rise of the building. Even against such excessive back pressure, the sealing surface pressure between the seat ring and the disc is maintained by the reaction force of the leaf spring by the tightening force of the retainer bolt alone, preventing leakage, and preventing back leakage from the gasket side. This prevents plastic deformation and wear of the seat ring, and maintains the valve seat sealing performance for a long period of time.

[0092] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention as described in the claims of the present invention. [Explanation of symbols]

[0093] 20 Valve body 21 Body 22 Stem 23 Jisk 24 Seat ring 25 Seat retainer 26 Leaf spring (spring component) 41 Flexible part 42 Fixed part 43 Gasket part 50 Annular contact surface 51 Thin section 53 Cavity 54 Annular protrusion 55 Annular abutment 60 Retainer bolt P1 point Point P2 (outer diameter end of annular contact surface) H normal

Claims

1. In an eccentric butterfly valve, a disk is rotatably supported at an eccentric position within a cylindrical body via a stem, and is hermetically sealed on a seat ring fixed within the body by a seat retainer. A flexible portion is formed on the inner diameter side of the seat ring, which tilts in response to the displacement of the disk. An annular leaf spring is attached between the flexible portion and the seat retainer, which resiliently urges them against each other. The seat retainer is provided on the upstream side of the leaf spring, and the seat ring is provided on the downstream side of the leaf spring. The leaf spring has an outer diameter side that abuts against the seat retainer, and an inner diameter side that is in contact with the flexible portion on the opposite side to the seat ring, and is elastically deformable on the inner diameter side. A point at which the load characteristics of the leaf spring change when positive pressure or reverse pressure is applied to the valve is defined as an inflection point. the leaf spring is set so that its load characteristics switch between low and high load characteristics at the inflection point, and when the valve is closed, a spring load is applied to the flexible portion while no fluid pressure is applied to the valve at the inflection point; when positive pressure is applied to the valve and the load characteristics switch from the inflection point, as the positive pressure increases, the flexible portion maintains a tight contact with the disk while the inner diameter side of the leaf spring tilts downstream, thereby decreasing the spring load; and when reverse pressure is applied to the valve and the load characteristics switch from the inflection point, as the reverse pressure increases, the inner diameter side of the leaf spring tilts upstream while avoiding contact with the seat retainer, thereby increasing the spring load.

2. 2. The eccentric type butterfly valve according to claim 1, wherein a fixed portion that is fixed between the body and the seat retainer is integrally formed on the outer diameter side of the flexible portion, and a gasket portion that is integrally connected to the annular periphery of the outer peripheral surface side of this fixed portion via a thin-walled portion is sandwiched between the body and the seat retainer.

3. 3. The eccentric type butterfly valve according to claim 1, wherein the seat ring is fastened between the body and the seat retainer by a fastening retainer bolt while the seat ring and the disk are hermetically sealed.

4. In an eccentric butterfly valve, a disk is rotatably supported in an eccentric position via a stem in a cylindrical body, and is hermetically sealed on a seat ring fixed in the body by a seat retainer. A flexible portion is formed on the inner diameter side of the seat ring, which tilts in response to the displacement of the disk. A leaf spring is attached between the flexible portion and the seat retainer to resiliently bias them together. The leaf spring is configured to displace the disk toward the seat retainer in the flow path direction, and the tilt of the flexible portion due to the displacement of the disk is controlled by a spring. an eccentric butterfly valve comprising: a spring whose load in the elastic direction increases according to its size; when the flexible portion elastically deforms, the leaf spring pressed by the flexible portion elastically deforms while being avoided from contacting the seat retainer; and an annular abutment surface that abuts against the leaf spring is formed on the opposite side to the leaf spring, and this annular abutment surface is provided by a tapered surface that is gradually inclined at a predetermined inclination angle from the vertical direction toward the outer diameter direction at a different angle relative to the attached leaf spring.

Images