Metal sealing butterfly valve

Abstract

The invention discloses a metal sealing butterfly valve, relates to the field of butterfly valves, and solves the contradiction between leakage and operation torque. The valve seat assembly comprises a main sealing ring, an auxiliary sealing ring and a pressing ring. The main sealing ring and the auxiliary sealing ring are coaxially arranged, and the main sealing ring is closer to the valve rod than the auxiliary sealing ring. Each of the main sealing ring and the auxiliary sealing ring comprises a spiral spring, the spiral springs are connected end to end to form a ring, and the peripheral surfaces of the spiral springs are coated with metal sheets; the main sealing ring makes contact with the butterfly plate to form sealing fit when the butterfly plate is closed, and the auxiliary sealing ring extrudes the main sealing ring under forward impact of a medium and makes contact with the butterfly plate to form sealing fit. The spiral spring is connected end to end to form an annular structure to serve as an elastic base body, the elastic deformation capacity similar to that of rubber is provided for the sealing ring, the metal sheet wrapping the periphery is matched, the high-temperature-resistant and high-pressure-resistant characteristics of metal materials are reserved, tight attachment of the sealing face is achieved through elastic compensation of the spring, and the leakage-proof capacity is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of butterfly valves, in particular to a metal sealing butterfly valve. Background Art

[0002] In industrial fluid control systems, butterfly valves, as simple, easy-to-operate regulating and shutoff devices, are widely used in numerous fields, including petroleum, chemical, power, and water treatment. Based on the sealing material, butterfly valves are primarily divided into two categories: soft-seal butterfly valves and metal-seal butterfly valves. These two categories differ significantly in their applicable operating conditions and performance. Soft-seal butterfly valves typically use non-metallic materials such as rubber, nylon, and polytetrafluoroethylene (PTFE) as their sealing rings. These valves offer excellent sealing performance and low opening and closing torque. However, their operating temperature and pressure ranges are severely limited by the inherent properties of the sealing material, making them incapable of meeting the requirements of high-temperature (e.g., exceeding 200-300°C) or high-pressure (e.g., exceeding 10-20 kgf / cm²) operating conditions. To meet these high-pressure and high-temperature requirements, metal-seal butterfly valves have emerged. Currently, metal-seal butterfly valves on the market can withstand operating pressures of 20-50 kgf / cm² and temperatures of 100-600°C, making them widely used in high-pressure and high-temperature systems.

[0003] However, the sealing structure design of existing metal-sealed butterfly valves has significant flaws: the metal sealing ring typically adopts a rigid integral structure, which is complex to process, difficult to manufacture, and expensive. More importantly, due to the poor elasticity of metal materials, it is difficult to form a tightly fitting sealing surface between the sealing ring and the valve disc. This not only makes it difficult to achieve low-leakage sealing requirements, but also increases torque during valve opening and closing, increasing operating energy consumption and the burden on the actuator. Furthermore, when operating conditions experience rapid pressure fluctuations or temperature changes, the rigid metal sealing ring cannot deform to compensate for the gap changes on the sealing surface, making leakage problems likely to occur, seriously affecting the safety and stability of the system. Although single eccentric, double eccentric and even triple eccentric structures can be used in the sealing structure design to improve sealing performance and reduce torque, the inherent problems of the above-mentioned metal-sealed butterfly valves, especially the contradiction between achieving low leakage and low operating torque, have always been the key bottleneck restricting their wider application in high-demand occasions. Summary of the Invention

[0004] Purpose of the present invention: In order to overcome the defects of the prior art, the present invention provides a metal-sealed butterfly valve that solves the contradiction between leakage and operating torque and can adapt to high-demand occasions of high temperature and high pressure.

[0005] The technical solution of the present invention comprises: a valve body, a valve stem and a butterfly plate, a flow channel is provided in the valve body, a valve seat assembly is provided in the flow channel, the valve seat assembly comprises a main sealing ring, a secondary sealing ring and a pressure ring, an installation cavity for accommodating the main sealing ring and the secondary sealing ring is formed between the inner wall of the pressure ring and the flow channel, the main sealing ring and the secondary sealing ring are coaxially arranged and the main sealing ring is closer to the valve stem than the secondary sealing ring; the main sealing ring and the secondary sealing ring both comprise a coil spring, the coil spring is connected head to tail in a ring shape, and the outer periphery of the coil spring is covered with a metal sheet; the main sealing ring contacts with the outer periphery of the butterfly plate to form a sealing fit when the butterfly plate is closed, and the secondary sealing ring squeezes the main sealing ring under the positive impact of the medium and contacts with the outer periphery of the butterfly plate to form a sealing fit.

[0006] The above technical solution is adopted, through the double-layer sealing structure of the main sealing ring and the auxiliary sealing ring, and the composite sealing ring structure of the coil spring and the metal sheet, to solve the core problems of the traditional metal sealed butterfly valve, such as insufficient sealing elasticity, large leakage and excessive torque; the coil spring is connected head to tail to form a ring structure as an elastic matrix, which provides the sealing ring with elastic deformation ability similar to rubber. Combined with the metal sheet wrapped around the outer periphery, it not only retains the high temperature and high pressure resistance of the metal material, but also achieves close fit of the sealing surface through the elastic compensation of the spring, thereby improving the leakage prevention ability; the main sealing ring directly forms a basic seal with the butterfly plate, and the auxiliary sealing ring further squeezes the main sealing ring under the positive impact of the medium, forming a dual protection mechanism of active sealing and medium impact auxiliary sealing, which significantly improves the sealing reliability, especially when the working pressure changes sharply, it can effectively prevent leakage.

[0007] In one possible design, the outer peripheral surface of the butterfly plate is a large spherical structure, and the sealing surfaces of the main sealing ring and the auxiliary sealing ring in contact with the butterfly plate are small spherical structures, and the two constitute a line contact sealing pair; the curvature radius of the large spherical structure is greater than the curvature radius of the small spherical structure.

[0008] With the above design, the line contact form ensures that the contact area of ​​the sealing surface is small during the opening and closing process, which can reduce frictional resistance and lower operating torque; and the difference in spherical curvature enables the sealing surface to achieve adaptive fit through slight deformation when pressure or temperature changes, avoiding the gap leakage problem caused by inconsistent deformation of traditional flat or conical seals. In this way, even if the sealing surface is slightly worn after long-term use, the spherical structure can still maintain effective line contact, thereby extending the service life of the sealing pair.

[0009] In a possible design, the bottom of the installation cavity is an inclined surface, and the inclined surface is inclined outward along the forward flow direction of the medium.

[0010] With the above design, when the medium impacts forward, the inclined surface guides the auxiliary sealing ring to produce extrusion deformation along the inclined direction, converting the medium pressure into additional pressing force on the main sealing ring, so that the main and auxiliary sealing rings and the butterfly plate fit more closely, and the medium pressure is used to achieve dynamic enhancement of the sealing performance, forming an adaptive sealing effect in which the higher the pressure, the more reliable the seal; this structure is particularly suitable for working conditions with large fluctuations in medium pressure. The matching relationship between the sealing force and the medium pressure can be adjusted by the preset design of the cavity bottom inclination angle, avoiding the problem of torque surge caused by excessive compression.

[0011] In one possible design, a corner groove is opened on the outer wall of the pressure ring, and an outer sealing ring is installed in the corner groove. The outer sealing ring has the same structure as the main sealing ring and also includes a coil spring and an outer metal sheet. The outer sealing ring contacts and seals with the corner groove wall and the inner wall of the flow channel respectively.

[0012] With the above design, the outer sealing ring compensates for the potential leakage risk outside the installation cavity of the traditional metal-sealed butterfly valve, and expands the sealing range from the core sealing surface of the butterfly plate and the sealing ring to the connection between the pressure ring and the valve body, thereby improving the overall sealing integrity of the valve.

[0013] In a possible design, the metal sheet is made of 316L stainless steel or a nickel-based alloy plate.

[0014] With the above design, 316L stainless steel has excellent resistance to intergranular corrosion, and nickel-based alloys exhibit stable mechanical properties and chemical stability at high temperatures above 600°C and in highly corrosive environments, ensuring that the metal sheets will not oxidize, become embrittled or corrode perforated during long-term use.

[0015] In one possible design, the metal sheet has a thickness in the range of 0.5 to 0.6 mm.

[0016] With the above design, the metal sheet in this thickness range can not only produce sufficient elastic deformation under the drive of the coil spring to ensure a tight fit of the sealing surface, but also provide sufficient impact strength and wear resistance to resist medium erosion and friction damage during the opening and closing process.

[0017] In one possible design, a sleeve is fixedly connected to the back of the butterfly plate, and the sleeve is sleeved on the outside of the valve stem, and a radial gap is provided between the sleeve and the valve stem; the sleeve is connected to the valve stem through a pin, and the pin is tightly fitted with the sleeve and can move relatively with the gap of the valve stem; the bottom and top of the flow channel are respectively provided with pressure platforms protruding inward, and the side of the pressure platform facing the sleeve is provided with a protrusion protruding in the direction of the sleeve; an eccentric groove is provided on the outer wall of the sleeve, and the groove depth of the eccentric groove gradually deepens in the closing direction of the butterfly plate; the protrusion is embedded in the eccentric groove and contacts with the bottom of the groove, so that: during the closing process of the butterfly plate, the protrusion moves relatively in the direction of the gradually shallowing groove depth, pushing the sleeve to drive the butterfly plate to move radially outward of the valve stem, and squeezing the valve seat assembly; during the opening process of the butterfly plate, the protrusion moves relatively in the direction of the gradually deepening groove depth, driving the sleeve to drive the butterfly plate to move radially inward of the valve stem and separate from the valve seat assembly.

[0018] The above design realizes adaptive radial displacement of the butterfly plate during the opening and closing process through the floating connection structure between the butterfly plate and the valve stem and the guiding mechanism of the eccentric groove and the protrusion, thereby optimizing the sealing performance and operating characteristics; during the closing process of the butterfly plate, the protrusion of the pressure platform moves in the direction of gradually shallowing the eccentric groove, and pushes the sleeve to drive the butterfly plate to move radially outward of the valve stem through mechanical guiding action, actively squeezing the main sealing ring and the auxiliary sealing ring, so that the sealing surface fitting pressure increases synchronously with the closing action, solving the problem of insufficient sealing force of traditional fixed-connection butterfly valves, and forming a dynamic sealing effect that becomes tighter as it is closed, further reducing the risk of leakage; during the opening process of the butterfly plate, the protrusion moves in the direction of gradually deepening the groove, driving the butterfly plate to move radially inward, realizing the gradual separation of the butterfly plate and the valve seat assembly, reducing the friction area and friction resistance of the sealing surface, reducing the opening and closing torque, and at the same time avoiding scratches and wear on the sealing surface in the initial opening stage, thereby extending the service life of the sealing ring.

[0019] In a possible design, the protrusion is an arc-shaped structure, and the bottom of the eccentric groove is a curved surface shape that matches the arc-shaped structure.

[0020] With the above design, the curved surface guide makes the protrusion slide more smoothly in the eccentric groove, eliminates the movement jamming phenomenon, and ensures that the butterfly plate displacement process is continuous and smooth.

[0021] In a possible design, a triangular reinforcing rib is connected to the press platform, and the reinforcing rib is fixedly connected to the inner wall of the flow channel.

[0022] With the above design, the reinforcing ribs of the triangular structure utilize the principle of triangle stability to effectively enhance the structural strength and rigidity of the press platen, prevent the press platen from bending or deforming due to long-term stress, and ensure that the position accuracy of the protrusion remains unchanged. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A cross-sectional view of the present invention in a closed state; Figure 2 For the present invention Figure 1A partial enlarged view of point A in the middle; Figure 3 It is a partial stereogram of the present invention; Figure 4 This is a partial structural diagram of the present invention in a closed state; Figure 5 This is a partial structural diagram of the present invention in an open state; Figure 6 A three-dimensional cross-sectional view of the present invention in a closed state; Figure 7 For the present invention Figure 6 A partial enlarged view of point B in the middle; Among them, 1. valve body; 11. flow channel; 12. pressure platform; 121. protrusion; 122. reinforcing rib; 2. valve stem; 3. butterfly plate; 31. sleeve; 311. eccentric groove; 32. radial clearance; 33. pin; 4. valve seat assembly; 41. main sealing ring; 42. secondary sealing ring; 43. pressure ring; 431. installation cavity; 432. inclined surface; 433. angle groove; 44. outer sealing ring; 411. coil spring; 412. metal sheet. DETAILED DESCRIPTION

[0024] This embodiment discloses Figures 1 to 3 The metal-sealed butterfly valve shown is designed to address the problems of high leakage, high operating torque, and difficulty adapting to high-temperature and high-pressure operating conditions of traditional metal-sealed butterfly valves. The following describes this embodiment in detail, combining its structural composition, material selection, manufacturing process, and operating principle.

[0025] The metal-sealed butterfly valve of this embodiment primarily comprises a valve body 1, a valve stem 2, a butterfly plate 3, and a valve seat assembly 4. The valve body 1 is forged from carbon steel or 316 stainless steel and defines a circular flow channel 11. The inner wall of the flow channel 11 is machined with a stepped mounting groove for mounting the valve seat assembly 4. The valve stem 2 extends through the bearing seats on either side of the valve body 1 and is sealed to the valve body 1 via a stuffing box. The stuffing is made of flexible graphite to ensure no leakage during the rotation of the valve stem 2. The butterfly plate 3 is fixed to the center of the valve stem 2 and rotates with the valve stem 2 to control the opening and closing of the flow channel 11. Its outer periphery is provided with a sealing surface that mates with the valve seat assembly 4. The valve seat assembly 4 is the core structure of the present invention and includes a primary seal ring 41, a secondary seal ring 42, a pressure ring 43, and an outer seal ring 44. The pressure ring 43 is bolted to the valve body 1. A mounting cavity 431 is formed between the inner wall of the pressure ring and a side wall of the flow channel 11 to accommodate the primary seal ring 41 and the secondary seal ring 42. The primary seal ring 41 and the secondary seal ring 42 are coaxially arranged, with the primary seal ring 41 closer to the valve stem 2 than the secondary seal ring 42, while the secondary seal ring 42 is located upstream of the medium flow direction. Both the primary seal ring 41 and the secondary seal ring 42 utilize a coil spring 411 as their elastic base. The coil spring 411 is connected end to end to form a ring structure, and its outer periphery is covered with a metal sheet 412.

[0026] The sealing surface of the butterfly plate 3 is a large spherical structure, while the contact surfaces of the main sealing ring 41 and the auxiliary sealing ring 42 are small spherical structures, and the two form a line contact sealing pair. The radius of curvature of the large spherical structure is greater than the radius of curvature of the small spherical structure. During the processing of the sealing surface of the butterfly plate 3, the surface is polished to reduce the roughness and ensure the sealing contact effect with the sealing ring. The outer surface of the small spherical metal sheet 412 is cold-pressed by a special grinding tool on the outer periphery of the metal sheet 412. After forming, it is subjected to non-destructive testing to ensure that there are no defects such as cracks and dents. Since the sealing pair is a spherical line contact, the required operating torque is small and the valve is easy to open and close.

[0027] The bottom of mounting cavity 431 is configured with an inclined surface 432 that slopes outward in the direction of the medium's forward flow. The preferred angle is 5-10 degrees. This structure utilizes medium pressure to enhance the sealing effect. During forward flow, inclined surface 432 converts fluid pressure into axial thrust on secondary seal ring 42, causing it to squeeze primary seal ring 41. During reverse flow, inclined surface 432 prevents secondary seal ring 42 from easily losing contact with primary seal ring 41, ensuring reverse sealing of primary seal ring 41.

[0028] An angled groove 433 is defined on the outer wall of the pressure ring 43, within which an outer sealing ring 44 is mounted. The outer sealing ring 44 has the same structure as the main sealing ring 41, comprising a coil spring 411 and a metal sheet 412. The cross-sectional diameter of the outer sealing ring 44 is slightly larger than the width of the angled groove 433 to ensure a close fit with the inner wall of the flow channel 11 of the valve body 1, preventing leakage of the medium through the assembly gap between the valve seat and the valve body 1.

[0029] In view of the extreme working conditions of high temperature, high pressure and corrosive media, the material selection is further optimized. The material of the metal sheet 412 is preferably 316L stainless steel or nickel-based alloy, and the thickness is controlled at 0.5~0.6mm to ensure sufficient elasticity and pressure resistance to adapt to high-demand environments. The coil spring 411 is wound with chromium-nickel alloy material and has excellent elastic recovery properties after heat treatment. The manufacturing process of the metal sheet 412 adopts the metal inert gas welding (MIG / MAG) process. MIG / MAG welding is an automatic gas-shielded arc welding method. The arc burns between the current carrier metal wire and the workpiece under the shield of protective gas. The metal wire fed by the machine acts as a welding rod and melts under its own arc. This welding method has the advantages of strong versatility and a wide range of applicable materials. It can be used for welding steel, non-alloy steel, low-alloy steel and high-alloy materials. It is particularly suitable for the welding processing of 0.5-0.6mm thin-gauge steel plates in this embodiment. When welding steel sheet metal 412, MAG welding is used, with a reactive shielding gas such as carbon dioxide or a mixture of 80% argon and 20% carbon dioxide. This effectively prevents defects such as burn-through and deformation during welding. It is important to note that welding must be performed indoors, or moisture-proof measures must be taken for outdoor workpieces to prevent moisture from affecting the shielding effect of the shielding gas and ensure the strength and sealing of the weld joint. The sheet metal 412 is wrapped around the outer periphery of the coil spring 411 through MIG / MAG welding, forming a tightly fitting annular seal. The weld seam is polished to ensure a smooth surface.

[0030] like Figures 4 to 7 As shown, a sleeve 31 is welded to the back of the butterfly disc 3. The inner diameter of the sleeve 31 is larger than the outer diameter of the valve stem 2. Sleeve 31 is placed over the valve stem 2 to create a radial clearance 32 of 0.5-1 mm, allowing the butterfly disc 3 to float freely in the radial direction relative to the valve stem 2. The sleeve 31 is connected to the valve stem 2 via a pin 33. The pin 33 and the pin hole of the sleeve 31 have an interference fit (tight fit), while the pin 33 and the pin hole of the valve stem 2 have a clearance fit. This ensures that torque from the valve stem 2 can be transmitted to the sleeve 31 through the pin 33 to drive the butterfly disc 3 to rotate, while allowing the butterfly disc 3 to undergo radial displacement relative to the valve stem 2.

[0031] The bottom and top of the flow channel 11 are respectively provided with a press platform 12 protruding inwardly. The press platform 12 protrudes radially along the flow channel 11, and the side facing the sleeve 31 is provided with a protrusion 121 protruding in the direction of the sleeve 31. The protrusion 121 is a curved structure, integrally formed with the press platform 12, and the surface is polished. An eccentric groove 311 is provided on the outer wall of the sleeve 31 at the position corresponding to the protrusion 121. The eccentric groove 311 extends circumferentially along the sleeve 31. The groove width is larger than the height of the protrusion 121, and the groove depth gradually deepens from 0 mm to 1-2 mm along the closing direction of the butterfly plate 3. The specific depth is adjusted according to the nominal diameter of the butterfly valve. The bottom of the eccentric groove 311 is a curved surface shape that matches the curved surface of the protrusion 121 to ensure that the two form a surface contact fit.

[0032] A triangular reinforcing rib 122 is welded to one side of the pressing platform 12 away from the protrusion 121 , one end of which is integrally connected to the pressing platform 12 , and the other end is welded and fixed to the inner wall of the flow channel 11 .

[0033] The working principle of the present application is: when the valve is closed, the valve stem 2 drives the butterfly plate 3 to rotate to the center position of the flow channel 11, and the large spherical sealing surface of the butterfly plate 3 first contacts the small spherical surface of the main sealing ring 41. Under the action of the preload force, the main sealing ring 41 is elastically deformed to form an initial line contact seal. When the medium flows in the forward direction, the positive pressure of the medium acts on the auxiliary sealing ring 42, pushing the auxiliary sealing ring 42 along the inclined surface 432 of the installation cavity 431 toward the main sealing ring 41, causing the main sealing ring 41 to further deform and fit tightly with the butterfly plate 3. At the same time, the auxiliary sealing ring 42 itself also forms a sealing contact with the butterfly plate 3, achieving a double seal and a medium-assisted seal. When the medium flows in the reverse direction, the auxiliary sealing ring 42 is not easily affected by axial displacement due to the inclined surface 432, and the main sealing ring 41 still maintains elastic contact to prevent the medium from flowing back. When the valve is open, the valve stem 2 drives the butterfly plate 3 to rotate. Since the butterfly valve adopts a floating structure for the butterfly plate 3, the butterfly plate 3 rotates while separating from the main and auxiliary sealing rings 42 during the rotation process, reducing friction and wear on the sealing surface and extending the service life of the sealing ring. When the working conditions experience a sudden change in pressure or temperature, the elastic restoring force of the coil spring 411 and the micro-deformation ability of the metal sheet 412 work together to ensure that the sealing ring always fits the sealing surface of the butterfly plate 3, effectively preventing leakage. In addition, during the closing process, when the butterfly plate 3 rotates from the open state to the closed state, the valve stem 2 drives the sleeve 31 and the butterfly plate 3 to rotate synchronously through the pin 33. At this time, the protrusion 121 of the pressure plate 12 moves relative to each other in the eccentric groove 311 along the direction of gradually shallowing the groove depth, that is, it moves relative to each other from the deep groove end to the shallow groove end of the eccentric groove 311. As the groove depth gradually decreases, the protrusion 121 generates a radial thrust on the bottom of the eccentric groove 311, pushing the sleeve 31 to drive the butterfly disc 3 to move radially outward from the valve stem 2, away from the center of the valve stem 2, and gradually increasing the fitting pressure between the sealing surface of the butterfly disc 3 and the primary and secondary sealing rings 41 and 42. When the butterfly disc 3 is fully closed, the displacement of the butterfly disc 3 reaches its maximum, and the sealing surface pressure reaches its peak, achieving a tight fit. During the opening process, when the butterfly disc 3 rotates from the closed state to the open state, the protrusion 121 moves relative to the eccentric groove 311 in the direction of the groove depth, that is, from the shallow groove end to the deep groove end. The gradual increase in the groove depth provides space for the sleeve 31 to move inward. Under the action of the medium, the sleeve 31 drives the butterfly disc 3 to move radially inward from the valve stem 2, closer to the center of the valve stem 2, causing the sealing surface of the butterfly disc 3 to gradually separate from the primary and secondary sealing rings 41 and 42 until there is essentially no contact friction in the open state, thereby reducing the opening and closing torque.

Claims

1. A metal-sealed butterfly valve, comprising a valve body (1), a valve stem (2) and a butterfly plate (3), wherein a flow channel (11) is provided in the valve body (1), and a valve seat assembly (4) is provided in the flow channel (11) in the valve body (1), characterized in that: The valve seat assembly (4) includes a main sealing ring (41), a secondary sealing ring (42) and a pressure ring (43). An installation cavity (431) for accommodating the main sealing ring (41) and the secondary sealing ring (42) is formed between the inner wall of the pressure ring (43) and the flow channel (11). The main sealing ring (41) and the secondary sealing ring (42) are coaxially arranged, and the main sealing ring (41) is closer to the valve stem (2) than the secondary sealing ring (42). The auxiliary sealing ring (42) includes a coil spring (411) connected head to tail in a ring shape, and the outer periphery of the coil spring (411) is covered with a metal sheet (412); the main sealing ring (41) contacts the outer periphery of the butterfly plate (3) to form a sealing fit when the butterfly plate (3) is closed, and the auxiliary sealing ring (42) squeezes the main sealing ring (41) under the positive impact of the medium and contacts the outer periphery of the butterfly plate (3) to form a sealing fit.

2. The metal-sealed butterfly valve according to claim 1, characterized in that: The outer peripheral surface of the butterfly plate (3) is a large spherical structure, and the sealing surfaces of the main sealing ring (41) and the auxiliary sealing ring (42) in contact with the butterfly plate (3) are small spherical structures, and the two constitute a line contact sealing pair; the curvature radius of the large spherical structure is greater than the curvature radius of the small spherical structure.

3. The metal-sealed butterfly valve according to claim 1 or 2, characterized in that: The bottom of the installation cavity (431) is an inclined surface (432), and the inclined surface (432) is inclined outward along the forward flow direction of the medium.

4. The metal-sealed butterfly valve according to claim 1, characterized in that: An angle groove (433) is provided on the outer wall of the pressure ring (43), and an outer sealing ring (44) is installed in the angle groove (433). The outer sealing ring (44) has the same structure as the main sealing ring (41) and also includes a coil spring (411) and an outer metal sheet (412). The outer sealing ring (44) contacts and seals the groove wall of the angle groove (433) and the inner wall of the flow channel (11).

5. The metal-sealed butterfly valve according to claim 1 or 4, characterized in that: The metal thin plate (412) is made of 316L stainless steel or a nickel-based alloy plate.

6. The metal-sealed butterfly valve according to claim 1 or 4, characterized in that: The thickness of the metal sheet (412) ranges from 0.5 to 0.6 mm.

7. The metal-sealed butterfly valve according to claim 1 or 2, characterized in that: The back of the butterfly plate (3) is fixedly connected to a sleeve (31), the sleeve (31) is sleeved on the outside of the valve stem (2), and a radial gap (32) is provided between the sleeve (31) and the valve stem (2); the sleeve (31) is connected to the valve stem (2) through a pin (33), the pin (33) is tightly fitted with the sleeve (31), and can be relatively moved with the gap of the valve stem (2); the bottom and top of the flow channel (11) are respectively provided with a pressing platform (12) protruding inward, and the side of the pressing platform (12) facing the sleeve (31) is provided with a protrusion (121) protruding in the direction of the sleeve (31); the outer wall of the sleeve (31) is opened An eccentric groove (311) is provided, and the groove depth of the eccentric groove (311) gradually deepens along the closing direction of the butterfly plate (3); the protrusion (121) is embedded in the eccentric groove (311) and contacts and cooperates with the groove bottom, so that: during the closing process of the butterfly plate (3), the protrusion (121) moves relatively in the direction of the groove depth gradually becoming shallower, pushing the sleeve (31) to drive the butterfly plate (3) to move radially outward of the valve stem (2), squeezing the valve seat assembly (4); during the opening process of the butterfly plate (3), the protrusion (121) moves relatively in the direction of the groove depth gradually becoming deeper, driving the sleeve (31) to drive the butterfly plate (3) to move radially inward of the valve stem (2), and separating from the valve seat assembly (4).

8. The metal-sealed butterfly valve according to claim 7, characterized in that: The protrusion (121) is a curved surface structure, and the bottom of the eccentric groove (311) is a curved surface shape that matches the curved surface.

9. The metal-sealed butterfly valve according to claim 7, characterized in that: A triangular reinforcing rib (122) is connected to the pressing platform (12), and the reinforcing rib (122) is fixedly connected to the inner wall of the flow channel (11).

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