Sealing butterfly valve

Abstract

The utility model discloses a sealing butterfly valve which comprises a valve body and a valve rod arranged in the valve body, padding is arranged between the upper portion of the valve rod and the valve body, a gland is arranged at the upper end of the padding in a pressing mode, a corrugated pipe is sleeved on the valve rod, the upper end of the corrugated pipe is fixedly connected with a pressing plate, the lower end of the corrugated pipe is fixedly connected with the valve rod, and the pressing plate is arranged at the lower end of the padding in a pressing mode. According to the scheme, the sealing performance of the butterfly valve is improved, so that the butterfly valve can be suitable for different working conditions; under the influence of special working conditions, the packing or the gland tends to loosen, and the corrugated pipe releases stored elastic enable to continuously press the packing, so that on one hand, the sealing performance of the packing is kept, and on the other hand, the gland can be kept loosen.

Description

Technical Field

[0001] The utility model relates to the technical field of butterfly valves, in particular to a sealed butterfly valve. Background Art

[0002] A butterfly valve, also called a flap valve, is a simple-structured regulating valve. A butterfly valve that can be used for the on-off control of a low-pressure pipeline medium refers to a valve in which the closing member (valve flap or butterfly plate) is a disc and rotates around the valve shaft to achieve opening and closing. The valve can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil products, liquid metals, and radioactive media. It mainly functions as a cut-off and throttling in a pipeline. The opening and closing member of the butterfly valve is a disc-shaped butterfly plate that rotates around its own axis in the valve body to achieve opening, closing, or regulation. In the butterfly valve, the upper part of the valve stem and the valve body are sealed by packing, and the packing is pressed tightly by a fastener to prevent the medium inside the butterfly valve from leaking out. When affected by special working conditions, the packing or fastener inside the butterfly valve will become loose, reducing the sealing effect of the packing and causing a risk of medium leakage in the butterfly valve.

[0003] For example, Chinese Patent Publication No. CN105822776A, publication date August 3, 2016, titled "A Hard Sealed Butterfly Valve", includes a valve body and a valve stem. A guide ring is provided between the lower part of the valve stem and the valve body, a graphite packing is provided between the upper part of the valve stem and the valve body, a packing gland is pressed on the graphite packing, the lower end of the valve stem is placed on a bottom cover fixed to the valve body, a valve plate is fixedly connected to the valve stem, a valve plate pressing ring presses a valve plate sealing ring on the side wall of the valve plate, and the valve plate sealing ring is in sealing cooperation with the protrusion in the inner cavity of the valve body.

[0004] The disadvantages of the existing patent are that the packing or fastener inside the existing butterfly valve is prone to looseness under special working conditions, reducing the sealing effect of the packing and causing a risk of medium leakage in the butterfly valve. Summary of the Utility Model

[0005] The purpose of the utility model is to solve the problem that the packing or fastener inside the existing butterfly valve is prone to looseness under special working conditions, resulting in medium leakage inside the butterfly valve, and to provide a sealed butterfly valve that improves the sealing performance of the butterfly valve.

[0006] To achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A sealed butterfly valve includes a valve body and a valve stem disposed within the valve body. There is a packing between the upper part of the valve stem and the valve body. The upper end of the packing is pressed by a gland. A bellows is sleeved on the valve stem. The upper end of the bellows is fixedly connected to a pressing plate, and the lower end of the bellows is fixedly connected to the valve stem. The pressing plate presses on the lower end of the packing. In this solution, the sealed butterfly valve is used to improve the sealing performance of the butterfly valve, enabling the butterfly valve to be applicable to different working conditions. Traditional butterfly valves are sealed by packing, and the packing is tightened by a gland. Due to factors such as vibration and external forces in special working conditions, the packing or the gland may become loose, resulting in the problem of the packing becoming loose or the pressing block becoming loose and causing the packing to become loose, deteriorating the sealing performance of the butterfly valve and posing a risk of external leakage of the medium inside the butterfly valve. In this solution, the elastic bellows presses the packing, and the bellows maintains a continuous pressure on the packing to prevent the problem of the packing becoming loose and reducing the sealing performance of the butterfly valve. The bellows evenly presses the packing through the pressing plate provided at the upper end of the bellows. The bellows presses the pressing plate in the circumferential direction, and the pressing plate generates a uniform and continuous pressure on the lower end face of the packing. When affected by special working conditions, if the packing or the gland shows a tendency to become loose, the bellows releases the stored elastic energy and continuously presses the packing. On the one hand, it maintains the sealing performance of the packing, and on the other hand, it can also prevent the gland from becoming loose. It solves the problem that the packing or fasteners inside the existing butterfly valve are prone to become loose under special working conditions, reducing the sealing effect of the packing and posing a risk of medium leakage in the butterfly valve.

[0008] Preferably, the pressing plate is sleeved on the valve stem, and the pressing plate is coaxially arranged with the valve stem. The pressing plate is sleeved on the valve stem, and the upper end face of the pressing plate cooperates with the lower end face of the packing. The pressing plate evenly and continuously presses the packing in the circumferential direction through the elastic force of the bellows, preventing the packing from becoming loose and reducing the sealing performance of the butterfly valve.

[0009] Preferably, a shoulder is provided on the inner wall of the valve body facing the packing, and the pressing plate presses on the shoulder. The inner wall of the pressing plate cooperates with the outer wall of the valve stem, and the outer wall of the pressing plate cooperates with the inner wall of the valve body. The shoulder is used for the initial positioning of the packing and the pressing plate. The pressing plate is limited on the shoulder. In the initial state after installation, the packing presses the pressing plate on the shoulder, and the bellows maintains a continuous pressure on the pressing plate.

[0010] Preferably, a receiving cavity is provided between the valve body and the valve stem, and the bellows is located within the receiving cavity. The receiving cavity is used to accommodate the bellows to prevent collision between the bellows and the inner wall of the valve body.

[0011] Preferably, the lower end of the bellows is hermetically connected to the valve body, and the upper end of the bellows is hermetically connected to the pressing plate. The upper and lower ends of the bellows are hermetically connected, strengthening the sealing performance between the inner side of the packing and the valve stem; the cooperation between the pressing plate and the shoulder strengthens the sealing performance between the outer side of the packing and the valve body.

[0012] Preferably, a positioning groove is provided at the lower end of the pressing plate. The pressing plate is sleeved on the upper end of the corrugated pipe through the positioning groove, and the upper end of the corrugated pipe is matched with the positioning groove. The positioning groove facilitates the connection between the pressing plate and the corrugated pipe, and the corrugated pipe is welded to the lower end of the pressing plate. The positioning groove is coaxially arranged with the corrugated pipe.

[0013] Preferably, the gland is pressed against the upper end of the packing through the locking cover. The lower end of the gland extends into the valve body, and the locking cover is locked to the upper end of the valve body through bolts.

[0014] Preferably, a disc spring is provided between the gland and the locking cover. The disc spring has elasticity, and the disc spring can exert pressure on the gland. In special working conditions, when the packing, gland, locking cover or bolt becomes loose, the disc spring releases the stored elastic potential energy, so that the packing remains in a continuously compressed state, maintaining the sealing effect of the butterfly valve and keeping the gland or locking cover stable and not loose.

[0015] On the other hand, the disc spring and the corrugated pipe act on the packing simultaneously to prevent the packing from moving up excessively, so that the packing is located at a proper position in the valve body, and both ends of the packing have continuous and uniform pressure, preventing the packing from leaking outside the valve body.

[0016] Preferably, the locking cover is divided into an abutting part and a locking part. The abutting part is pressed on the upper end of the gland, and the locking part is locked to the upper end of the valve body through bolts. The disc spring is sleeved on the abutting part. The upper end of the disc spring abuts against the lower end of the locking part, and the lower end of the disc spring abuts against the upper end of the gland. The disc spring is sleeved on the abutting part. The pressure of the gland on the packing is mainly locked and pressed by the locking cover. In special working conditions, when the packing, gland, locking cover or bolt becomes loose, the disc spring releases the stored elastic potential energy, so that the packing remains in a continuously compressed state, maintaining the sealing effect of the butterfly valve and keeping the gland or locking cover stable and not loose.

[0017] Preferably, the corrugated pipe is coaxially arranged with the valve stem, and the pressing plate is coaxially arranged with the corrugated pipe. The corrugated pipe uniformly compresses the packing through the pressing plate arranged at the upper end of the corrugated pipe. The corrugated pipe compresses the pressing plate in the circumferential direction, and the pressing plate generates uniform and continuous pressure on the lower end face of the packing.

[0018] Therefore, the utility model has the following beneficial effects: it is used to improve the sealing performance of the butterfly valve, so that the butterfly valve can be applied to different working conditions; when affected by special working conditions, when the packing or gland has a tendency to become loose, the corrugated pipe releases the stored elastic energy and continuously compresses the packing. On the one hand, the sealing performance of the packing is maintained, and on the other hand, the looseness of the gland can also be maintained. Description of the Drawings

[0019] Figure 1It is a schematic structural diagram of the first embodiment of the present utility model.

[0020] Figure 2 It is a schematic structural diagram of the second embodiment of the present utility model.

[0021] As shown in the figure:

[0022] Valve body 1, shaft shoulder 1.1,

[0023] Valve stem 2, packing 3, gland 4, bellows 5, pressing plate 6,

[0024] Locking cover 7, abutting portion 7.1, locking portion 7.2,

[0025] Bolt 8, disc spring 9. Specific implementation manner

[0026] To make the objectives, technical solutions and advantages of the embodiments of the technical solutions of the present utility model clearer, the present utility model will be further described below in conjunction with the accompanying drawings and specific implementation manners.

[0027] Embodiment 1, as Figure 1 shown, a sealing butterfly valve includes a valve body 1 and a valve stem 2 disposed inside the valve body 1. There is a packing 3 between the upper part of the valve stem 2 and the valve body 1. The upper end of the packing 3 is pressed by a gland 4. A bellows 5 is sleeved on the valve stem 2. The upper end of the bellows 5 is fixedly connected to a pressing plate 6. The lower end of the bellows 5 is fixedly connected to the valve stem 2. The pressing plate 6 presses on the lower end of the packing 3.

[0028] In the prior art, a butterfly valve, also called a flap valve, is a simple-structured regulating valve. A butterfly valve that can be used for the on-off control of a medium in a low-pressure pipeline refers to a valve in which the closing member (valve flap or butterfly plate) is a disc and rotates around the valve shaft to achieve opening and closing. The valve can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil products, liquid metals, and radioactive media. It mainly functions as a cut-off and throttling in a pipeline. The closing member of the butterfly valve is a disc-shaped butterfly plate that rotates around its own axis inside the valve body 1 to achieve opening, closing or regulation. In the butterfly valve, the upper part of the valve stem 2 and the valve body 1 are sealed by a packing 3, and the packing 3 is tightened by a fastener to prevent the medium inside the butterfly valve from leaking. When affected by special working conditions, the packing 3 or the fastener inside the butterfly valve will become loose, reducing the sealing effect of the packing 3 and causing a risk of medium leakage in the butterfly valve. To solve the problem that the packing 3 or the fastener inside the existing butterfly valve is prone to looseness under special working conditions, resulting in medium leakage inside the butterfly valve, a sealing butterfly valve with improved sealing performance of the butterfly valve is provided.

[0029] A sealing butterfly valve in the above embodiments is used to improve the sealing performance of the butterfly valve so that the butterfly valve can be applied to different working conditions. The traditional butterfly valve is sealed by packing 3, and the packing 3 is pressed by a pressing plate 6. The packing 3 or the pressing plate 6 loosens under the influence of factors such as vibration and external force in special working conditions, resulting in the loosening of the packing 3 or the loosening of the pressing block causing the loosening of the packing 3, which deteriorates the sealing performance of the butterfly valve and there is a risk of medium leakage inside the butterfly valve. In this solution, the packing 3 is pressed by an elastic corrugated pipe 5, and the corrugated pipe 5 maintains a continuous pressure on the packing 3 to prevent the problem of the packing 3 loosening and reducing the sealing performance of the butterfly valve. The corrugated pipe 5 evenly presses the packing 3 through the pressing plate 6 provided at the upper end of the corrugated pipe 5. The corrugated pipe 5 presses the pressing plate 6 in the circumferential direction, and the pressing plate 6 generates a uniform and continuous pressure on the lower end surface of the packing 3. When affected by special working conditions, if the packing 3 or the gland 4 has a loosening tendency, the corrugated pipe 5 releases the stored elastic energy to continuously press the packing 3. On the one hand, it maintains the sealing performance of the packing 3, and on the other hand, it can also prevent the gland 4 from loosening. It solves the problem that the packing 3 or fasteners inside the existing butterfly valve are prone to loosen under special working conditions, reducing the sealing effect of the packing 3 and causing a risk of medium leakage in the butterfly valve.

[0030] In this embodiment, as Figure 1 shown, the pressing plate 6 is sleeved on the valve stem 2, and the pressing plate 6 is coaxially arranged with the valve stem 2. The pressing plate 6 is sleeved on the valve stem 2, and the upper end surface of the pressing plate 6 cooperates with the lower end surface of the packing 3. The pressing plate 6 evenly and continuously presses the packing 3 in the circumferential direction through the elastic force of the corrugated pipe 5 to prevent the packing 3 from loosening and reducing the sealing performance of the butterfly valve.

[0031] The inner wall of the valve body 1 is further optimized. As Figure 1 shown, a shoulder 1.1 facing the packing 3 is provided on the inner wall of the valve body 1. The pressing plate 6 is pressed on the shoulder 1.1. The inner wall of the pressing plate 6 cooperates with the outer wall of the valve stem 2, and the outer wall of the pressing plate 6 cooperates with the inner wall of the valve body 1. The shoulder 1.1 is used for the initial positioning of the packing 3 and the pressing plate 6. The pressing plate 6 is limited on the shoulder 1.1. In the initial state after installation, the packing 3 presses the pressing plate 6 on the shoulder 1.1, and the corrugated pipe 5 maintains a continuous pressure on the pressing plate 6.

[0032] In this embodiment, as Figure 1 shown, there is a receiving cavity between the valve body 1 and the valve stem 2, and the corrugated pipe 5 is located in the receiving cavity. The receiving cavity is used to accommodate the corrugated pipe 5 to prevent the corrugated pipe 5 from colliding with the inner wall of the valve body 1.

[0033] The connection of the corrugated pipe 5 is further optimized. As Figure 1 shown, the lower end of the corrugated pipe 5 is hermetically connected to the valve body 1, and the upper end of the corrugated pipe 5 is hermetically connected to the pressing plate 6. The upper and lower ends of the corrugated pipe 5 are hermetically connected, which strengthens the sealing performance between the inner side of the packing 3 and the valve stem 2; the cooperation between the pressing plate 6 and the shoulder 1.1 strengthens the sealing performance between the outer side of the packing 3 and the valve body 1.

[0034] The pressing plate 6 is further optimized. For example, Figure 1 as shown, a positioning groove is provided at the lower end of the pressing plate 6. The pressing plate 6 is sleeved on the upper end of the bellows 5 through the positioning groove, and the upper end of the bellows 5 is matched with the positioning groove. The positioning groove facilitates the connection between the pressing plate 6 and the bellows 5, and the bellows 5 is welded to the lower end of the pressing plate 6. The positioning groove is coaxially arranged with the bellows 5.

[0035] Specifically, the gland 4 is pressed against the upper end of the packing 3 through the locking cover 7. The lower end of the gland 4 extends into the valve body 1, and the locking cover 7 is locked to the upper end of the valve body 1 through the bolt 8.

[0036] In this embodiment, the bellows 5 is coaxially arranged with the valve stem 2, and the pressing plate 6 is coaxially arranged with the bellows 5. The bellows 5 uniformly presses the packing 3 through the pressing plate 6 provided at the upper end of the bellows 5. The bellows 5 presses the pressing plate 6 in the circumferential direction, and the pressing plate 6 generates a uniform and continuous pressure on the lower end face of the packing 3.

[0037] In summary, this embodiment has the following beneficial effects: it is used to improve the sealing performance of the butterfly valve, so that the butterfly valve can be applied to different working conditions; when affected by special working conditions, if the packing 3 or the gland 4 has a loosening tendency, the bellows 5 releases the stored elastic energy and continuously presses the packing 3. On the one hand, it maintains the sealing performance of the packing 3, and on the other hand, it can also maintain the looseness of the gland 4.

[0038] On the basis of the basic structure in Embodiment 1, in Embodiment 2, Embodiment 1 is further optimized. For example, Figure 2 as shown, a sealing butterfly valve includes a valve body 1 and a valve stem 2 arranged in the valve body 1. There is a packing 3 between the upper part of the valve stem 2 and the valve body 1. The upper end of the packing 3 is pressed by a gland 4. A bellows 5 is sleeved on the valve stem 2. The upper end of the bellows 5 is fixedly connected with a pressing plate 6, the lower end of the bellows 5 is fixedly connected with the valve stem 2, and the pressing plate 6 is pressed on the lower end of the packing 3. Specifically, as Figure 2 shown, the gland 4 is pressed against the upper end of the packing 3 through the locking cover 7. The lower end of the gland 4 extends into the valve body 1, and the locking cover 7 is locked to the upper end of the valve body 1 through the bolt 8. A disc spring 9 is arranged between the gland 4 and the locking cover 7. The disc spring 9 has elasticity, and the disc spring 9 can form a pressure on the gland 4. When in special working conditions, if the packing 3, the gland 4, the locking cover 7 or the bolt 8 becomes loose, the disc spring 9 releases the stored elastic potential energy, so that the packing 3 remains in a continuously pressed state, maintaining the sealing effect of the butterfly valve and keeping the gland 4 or the locking cover 7 stable and not loose.

[0039] On the other hand, the disc spring 9 and the bellows 5 act on the packing 3 simultaneously to prevent the packing 3 from moving upwards excessively, so that the packing 3 is located at a suitable position in the valve body 1, and both ends of the packing 3 have continuous and uniform pressure to prevent the packing 3 from leaking outside the valve body 1.

[0040] Furthermore, for example, Figure 2As shown in the figure, the locking cover 7 is divided into an abutting portion 7.1 and a locking portion 7.2. The abutting portion 7.1 is pressed on the upper end of the gland 4, and the locking portion 7.2 is locked with the upper end of the valve body 1 through bolts 8. The disc spring 9 is sleeved on the abutting portion 7.1. The upper end of the disc spring 9 abuts against the lower end of the locking portion 7.2, and the lower end of the disc spring 9 abuts against the upper end of the gland 4. The disc spring 9 is sleeved on the abutting portion 7.1. The pressure of the gland 4 on the packing 3 is mainly locked and pressed through the locking cover 7. When in special working conditions, if the packing 3, gland 4, locking cover 7 or bolts 8 become loose, the disc spring 9 releases the stored elastic potential energy, so that the packing 3 remains in a continuously compressed state, maintaining the sealing effect of the butterfly valve and keeping the gland 4 or locking cover 7 stable and not loose.

[0041] A sealing butterfly valve in the above embodiment is used to improve the sealing performance of the butterfly valve, so that the butterfly valve can be applied to different working conditions. The traditional butterfly valve is sealed by the packing 3, and the packing 3 is pressed by the pressing plate 6. Due to factors such as vibration and external force in special working conditions, the packing 3 or the pressing plate 6 becomes loose, resulting in the problem that the packing 3 becomes loose or the pressing block becomes loose and causes the packing 3 to become loose, deteriorating the sealing performance of the butterfly valve and posing a risk of external leakage of the medium inside the butterfly valve. In this solution, the elastic bellows 5 presses the packing 3, and the bellows 5 maintains a continuous pressure on the packing 3 to prevent the problem that the packing 3 becomes loose and reduces the sealing performance of the butterfly valve. The bellows 5 evenly presses the packing 3 through the pressing plate 6 provided at the upper end of the bellows 5. The bellows 5 presses the pressing plate 6 in the circumferential direction, and the pressing plate 6 generates a uniform and continuous pressure on the lower end surface of the packing 3. When affected by special working conditions, if the packing 3 or the gland 4 has a tendency to become loose, the bellows 5 releases the stored elastic energy and continuously presses the packing 3. On the one hand, the sealing performance of the packing 3 is maintained, and on the other hand, the looseness of the gland 4 can also be maintained. It solves the problem that the packing 3 or fasteners inside the existing butterfly valve are prone to become loose under special working conditions, reducing the sealing effect of the packing 3 and posing a risk of medium leakage in the butterfly valve.

[0042] In this embodiment, as Figure 2 shown, the pressing plate 6 is sleeved on the valve stem 2, and the pressing plate 6 is coaxially arranged with the valve stem 2. The pressing plate 6 is sleeved on the valve stem 2, and the upper end surface of the pressing plate 6 cooperates with the lower end surface of the packing 3. The pressing plate 6 evenly and continuously presses the packing 3 in the circumferential direction through the elastic force of the bellows 5 to prevent the packing 3 from becoming loose and reducing the sealing performance of the butterfly valve.

[0043] The inner wall of the valve body 1 is further optimized. As Figure 2 shown, a shoulder 1.1 facing the packing 3 is provided on the inner wall of the valve body 1. The pressing plate 6 is pressed on the shoulder 1.1. The inner wall of the pressing plate 6 cooperates with the outer wall of the valve stem 2, and the outer wall of the pressing plate 6 cooperates with the inner wall of the valve body 1. The shoulder 1.1 is used for the initial positioning of the packing 3 and the pressing plate 6. The pressing plate 6 is limited on the shoulder 1.1. In the initial state after installation, the packing 3 presses the pressing plate 6 on the shoulder 1.1, and the bellows 5 maintains a continuous pressure on the pressing plate 6.

[0044] In this embodiment, as Figure 2 shown, there is a receiving cavity between the valve body 1 and the valve stem 2, and the bellows 5 is located in the receiving cavity. The receiving cavity is used to accommodate the bellows 5 to prevent collision between the bellows 5 and the inner wall of the valve body 1.

[0045] The connection of the bellows 5 is further optimized. As Figure 2 shown, the lower end of the bellows 5 is hermetically connected to the valve body 1, and the upper end of the bellows 5 is hermetically connected to the pressing plate 6. The upper and lower ends of the bellows 5 are hermetically connected, which strengthens the sealing performance between the inner side of the packing 3 and the valve stem 2; the pressing plate 6 cooperates with the shoulder 1.1, which strengthens the sealing performance between the outer side of the packing 3 and the valve body 1.

[0046] The pressing plate 6 is further optimized. As Figure 2 shown, the lower end of the pressing plate 6 is provided with a positioning groove. The pressing plate 6 is sleeved on the upper end of the bellows 5 through the positioning groove, and the upper end of the bellows 5 cooperates with the positioning groove. The positioning groove facilitates the connection between the pressing plate 6 and the bellows 5, and the bellows 5 is welded to the lower end of the pressing plate 6. The positioning groove is coaxially arranged with the bellows 5.

[0047] Specifically, as Figure 2 shown, the gland 4 is pressed against the upper end of the packing 3 by the locking cover 7. The lower end of the gland 4 extends into the valve body 1, and the locking cover 7 is locked to the upper end of the valve body 1 by bolts 8.

[0048] In this embodiment, as Figure 2 shown, the bellows 5 is coaxially arranged with the valve stem 2, and the pressing plate 6 is coaxially arranged with the bellows 5. The bellows 5 uniformly presses the packing 3 through the pressing plate 6 provided at the upper end of the bellows 5. The bellows 5 presses the pressing plate 6 in the circumferential direction, and the pressing plate 6 generates a uniform and continuous pressure on the lower end face of the packing 3.

[0049] In summary, this embodiment has the following beneficial effects: it is used to improve the sealing performance of the butterfly valve, so that the butterfly valve can be applied to different working conditions; when affected by special working conditions, if the packing 3 or the gland 4 has a loosening tendency, the bellows 5 releases the stored elastic energy to continuously press the packing 3. On the one hand, it maintains the sealing performance of the packing 3, and on the other hand, it can also maintain the looseness of the gland 4.

[0050] The above specific embodiments are only the preferred embodiments of the present invention, and do not limit the specific implementation scope of the present invention. Any equivalent changes made according to the shape and structure of the present invention should be included in the protection scope of the present invention.

Claims

1. A sealed butterfly valve, comprising a valve body and a valve stem arranged in the valve body, characterized in that: A packing is arranged between the upper part of the valve stem and the valve body, a gland is pressed on the upper end of the packing, a bellows is sleeved on the valve stem, a pressure plate is fixedly connected to the upper end of the bellows, the lower end of the bellows is fixedly connected to the valve stem, and the pressure plate is pressed on the lower end of the packing.

2. A sealing butterfly valve according to claim 1, characterized in that: The pressing plate is sleeved on the valve stem, and the pressing plate and the valve stem are coaxially arranged.

3. A sealing butterfly valve according to claim 2, characterized in that: The inner wall of the valve body is provided with a shaft shoulder facing the packing, the pressure plate is pressed tightly on the shaft shoulder, the inner wall of the pressure plate cooperates with the outer wall of the valve stem, and the outer wall of the pressure plate cooperates with the inner wall of the valve body.

4. A sealing butterfly valve according to claim 1, 2 or 3, characterized in that: An accommodating cavity is provided between the valve body and the valve stem, and the bellows is located in the accommodating cavity.

5. A sealing butterfly valve according to claim 1, 2 or 3, characterized in that: The lower end of the bellows is sealed and connected to the valve body, and the upper end of the bellows is sealed and connected to the pressure plate.

6. A sealing butterfly valve according to claim 1, 2 or 3, characterized in that: A positioning groove is provided at the lower end of the pressing plate, and the pressing plate is sleeved on the upper end of the bellows through the positioning groove, and the upper end of the bellows cooperates with the positioning groove.

7. A sealing butterfly valve according to claim 1, 2 or 3, characterized in that: The gland is pressed onto the upper end of the packing by a locking cover, the lower end of the gland extends into the valve body, and the locking cover is locked onto the upper end of the valve body by bolts.

8. A sealing butterfly valve according to claim 7, characterized in that: A butterfly spring is arranged between the pressure cover and the locking cover.

9. A sealing butterfly valve according to claim 8, characterized in that: The locking cover is divided into an abutment portion and a locking portion, the abutment portion is pressed on the upper end of the pressure cover, the locking portion is locked with the upper end of the valve body by bolts, the butterfly spring is sleeved on the abutment portion, the upper end of the butterfly spring abuts against the lower end of the locking portion, and the lower end of the butterfly spring abuts against the upper end of the pressure cover.

10. A sealing butterfly valve according to claim 1, 2 or 3, characterized in that: The bellows is coaxially arranged with the valve stem, and the pressure plate is coaxially arranged with the bellows.

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