Butterfly valve

Abstract

The utility model relates to a butterfly valve which comprises a valve body, a valve seat is arranged in the valve body, a valve rod is arranged on the valve body on one side of the valve seat, a butterfly plate is arranged on the valve rod, a valve seat pressing ring is arranged on one side of the valve seat, and the shape of a part of an inner cavity of the valve body is matched with that of a part of the valve seat pressing ring. The valve seat pressing ring is of an annular structure formed by sequentially connecting a plurality of valve seat pressing plates end to end, a butterfly plate pressing ring is arranged on the butterfly plate, a sealing ring is arranged between the butterfly plate pressing ring and the butterfly plate, the sealing ring is attached to the valve seat, a valve rod limiting ring and at least two shaft sleeves are arranged on the valve rod and the valve body, and the valve rod limiting ring and the shaft sleeves are matched with each other. The butterfly plate is arranged on the valve rod, the shaft sleeves are evenly distributed on the two sides of the butterfly plate, the valve rod is made of Cr20MoV alloy steel, the valve body is made of 0Cr17Ni4Cu4Nb martensitic stainless steel, and the valve rod limiting ring and the shaft sleeves are made of 06Cr19Ni10 austenitic stainless steel. And the abrasion of the valve rod during rotation is reduced, so that the maintenance difficulty of equipment is reduced. The utility model has the advantages of convenient use and wide market prospect.

Description

Technical Field

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

[0002] The butterfly valve, also known as the flap valve, is a simple regulating valve that can be used for the switch control of low-pressure pipeline media. The butterfly valve refers to a valve with a disc as the closing part, which rotates around the valve axis 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, liquid metal and radioactive media. It mainly plays the role of cutting off and throttling on the pipeline. The butterfly valve opening and closing part is a disc-shaped butterfly plate, which rotates around its own axis in the valve body to achieve the purpose of opening and closing or regulating. The butterfly valve has the advantages of simple structure, light weight and small operating torque. Its weight is half of the same caliber ball valve and its size is half to one-third of it. Compared with other valves, butterfly valves consume less materials, are simple to process, have low manufacturing costs, and are easy to install and maintain. It is difficult for general valves to achieve large diameters. This is due to the complex structure, difficulty in manufacturing, and the huge size that brings problems to installation and use.

[0003] The butterfly valve is particularly suitable for large size and low pressure. It has a simple shape and the smallest span. Butterfly valves have been widely used in different fields of industry, but as a large-diameter steam butterfly valve used in steam turbines, it has different characteristics. It requires rapid closure and small full-close slippage in an emergency, as well as good adjustment performance. The action of the shut-off butterfly valve is that the actuator drives the valve stem to drive the disc plate to a closed state or a fully open state. In the closed state, the force applied by the medium to the disc plate is transmitted to the valve seat through the disc plate and then to the valve body. In this state, the disc plate fits tightly on the valve seat. In the fully open state, the medium is transported to the downstream of the valve body through the disc plate and the valve seat, and the center axis of the medium and the center axis of the disc plate are located on the same axis. The disc plate reaches balance under the action of the passing medium. The actuator applies force to the valve stem to drive the valve stem to rotate. The main thing to overcome is the reaction force brought by the passing medium. When the disc plate has not reached the maximum open position, the force of the medium on both sides of the disc plate is not balanced, and this force will eventually act on the valve stem. The valve stem and the valve body are in contact. Repeated opening or closing actions will cause serious wear of the valve body or valve stem, causing the butterfly valve to change its position in the closed state, causing the disc plate to be unable to fit tightly with the valve seat in the closed state, resulting in leakage. If the shut-off medium is a high-pressure medium, the force will increase with the increase of the medium pressure.

[0004] The biggest difference between the large-diameter steam butterfly valve used in steam turbines and ordinary butterfly valves is the different medium used. Since the steam delivered from the upstream steam turbine has a high pressure, it will give the valve stem that performs the rotation action a large pressure through the disc plate. The application of this pressure is mainly manifested in the process of driving the disc plate to perform the corresponding rotation action through the rotating valve stem, especially in the butterfly valve that needs to perform the adjustment function. This is because the adjustment function needs to be completed. The disc plate does not need to perform the maximum opening amount of the disc plate, but a part of the maximum opening amount of the disc plate. In this state, since the center axis of the disc plate and the center axis of the medium passing through are not located on the same axis, the force of the medium on both sides of the disc plate is not balanced, so the disc plate will be subjected to additional force exerted by the medium. Under the action of this additional force, if the valve stem needs to continue to perform the rotation action, the friction force on the valve stem can be imagined to be very large. Under the action of this friction, after the valve stem performs the adjustment action many times, it will be seriously worn, causing equipment damage and requiring repair. Therefore, in the prior art, there is room for structural improvement of shut-off butterfly valves and regulating butterfly valves when they are used under high-pressure media, thereby reducing the wear of the valve stem during rotation, thereby reducing the difficulty of equipment maintenance, and improving the market promotion of the corresponding butterfly valves. Summary of the invention

[0005] In view of the deficiencies in the prior art, the utility model provides a butterfly valve which reduces the wear of the valve stem when performing a rotation action and thereby reduces the difficulty of repairing the equipment, and is used to overcome the defects in the prior art.

[0006] The technical solution adopted by the utility model is: a butterfly valve, including a valve body, a valve seat is arranged in the valve body, a valve stem is arranged on the valve body on one side of the valve seat, a disc plate is arranged on the valve stem, a valve seat pressure ring is arranged on the side of the valve seat away from the valve stem, the shape of the inner cavity of the valve body is matched with the shape of the valve seat pressure ring, the valve seat pressure ring adopts a ring structure composed of a plurality of arc-shaped valve seat pressure plates connected end to end in sequence, a disc plate pressure ring is arranged on the disc plate, a sealing ring is arranged between the disc plate pressure ring and the disc plate, and the sealing ring is in contact with the valve seat The valve stem and the valve body are provided with a valve stem limiting ring and a shaft sleeve, the valve stem limiting ring adopts a ring structure composed of a plurality of arc-shaped limiting rods connected end to end in sequence, the number of the shaft sleeves is at least two, and the plurality of shaft sleeves are evenly distributed on both sides of the disc plate, the valve stem is made of alloy steel with a grade of Cr20MoV, the valve body is made of 0Cr17Ni4Cu4Nb martensitic stainless steel, and the valve stem limiting ring and the shaft sleeve are both made of 06Cr19Ni10 austenitic stainless steel.

[0007] Preferably, a first bracket is arranged above the valve body, the valve stem passes through the inner cavity of the first bracket, a first spiral wound gasket is arranged between the first bracket and the valve seat, a first fixing bolt is arranged on the first bracket and the valve body, a packing sealing groove is opened on the top of the first bracket, the packing sealing groove is located on the outer side of the valve stem, and the packing sealing groove is sequentially provided with a packing gasket, a sealing packing and a packing pressure ring from bottom to top, a packing pressure plate is arranged on the packing pressure ring and the valve stem, a first adjusting bolt is arranged on the packing pressure plate and the first bracket, and an adjusting nut is arranged on the first adjusting bolt above the packing pressure plate.

[0008] Preferably, a disc spring is provided on the first adjusting bolt between the adjusting nut and the packing pressure plate.

[0009] Preferably, a heat sink is provided on the first bracket below the sealing filler, and the number of the heat sinks is several. The heat sinks are evenly distributed on the first bracket in sequence along the direction from close to the sealing filler to far away from the sealing filler, and the diameters of the circumscribed circles of the heat sinks gradually decrease along the direction from close to the sealing filler to far away from the sealing filler.

[0010] Preferably, each of the valve seat pressure plates is provided with a positioning bolt, which is installed through the valve seat pressure plate, the inner end of the positioning bolt is in contact with the valve seat, and a second winding gasket is provided between the valve seat and the valve body.

[0011] Preferably, a second adjusting bolt is provided on the disc plate and the disc plate pressure ring, and a graphite gasket is provided between the disc plate and the sealing ring.

[0012] Preferably, a second bracket is arranged above the first bracket, and a rack is arranged on the second bracket. The rack adopts a strip structure that can perform horizontal sliding movement along the extension direction of the rack. Tooth grooves are arranged on the valve stem. The number of tooth grooves is several, and the several tooth grooves are evenly distributed in a star shape on the outside of the center axis of the valve stem. The tooth grooves and the rack are meshed, and the rack is transmission-connected with a hydraulic cylinder.

[0013] The beneficial effects of the utility model are as follows: first, the utility model utilizes the shaft sleeve arranged between the valve stem and the valve body and the valve stem limiting ring, the material of the valve stem is alloy steel with a grade of Cr20MoV, the material of the valve body is martensitic stainless steel of 0Cr17Ni4Cu4Nb, the material of the valve stem limiting ring and the shaft sleeve are both austenitic stainless steel of 06Cr19Ni10; the Mohs hardness of the valve stem and the valve body is greater than the Mohs hardness of the valve stem limiting ring and the shaft sleeve, so that the shaft sleeve and the valve stem limiting ring are more susceptible to wear than the valve stem and the valve body, and the shaft sleeve and the valve stem limiting ring are replaced during maintenance, thereby reducing the difficulty of maintenance.

[0014] Secondly, the disc plate and the disc plate pressure ring of the utility model are provided with a second adjusting bolt, and a graphite gasket is provided between the disc plate and the sealing ring; installing the graphite gasket facilitates sealing the gap between the disc plate and the sealing ring.

[0015] The utility model has the advantages of simple structure, convenient operation, ingenious design, greatly improved working efficiency, good social and economic benefits, and is a product that is easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the utility model.

[0017] Figure 2 for Figure 1 A partial enlarged schematic diagram of detail A.

[0018] Figure 3 for Figure 1 A partial enlarged schematic diagram of detail B.

[0019] Figure 4 It is a structural schematic diagram of the components of the utility model. DETAILED DESCRIPTION

[0020] like Figures 1 to 4 As shown, a butterfly valve comprises a valve body 1, a valve seat 2 is arranged in the valve body 1, a valve stem 3 is arranged on the valve body 1 on one side of the valve seat 2, a disc plate 4 is arranged on the valve stem 3, the valve seat 2 is provided with a valve seat pressure ring on the side away from the valve stem 3, the valve seat pressure ring adopts a truncated cone tubular structure, the shape of a part of the inner cavity of the valve body 1 matches the shape of the valve seat pressure ring part, the valve seat pressure ring adopts a ring structure composed of a plurality of arc-shaped valve seat pressure plates 5 connected end to end in sequence, a disc plate pressure ring 6 is arranged on the disc plate 4, a sealing ring 7 is arranged between the disc plate pressure ring 6 and the disc plate 4, and a sealing ring 7 is arranged between the disc plate pressure ring 6 and the disc plate 4. The sealing ring 7 fits the valve seat 2, and the valve stem 3 and the valve body 1 are provided with a valve stem limiting ring and a shaft sleeve 8. The valve stem limiting ring adopts a ring structure composed of a plurality of arc-shaped limiting rods 9 connected end to end in sequence. The number of shaft sleeves 8 is at least two, and the plurality of shaft sleeves 8 are evenly distributed on both sides of the disc plate 4. The material of the valve stem adopts alloy steel with a grade of Cr20MoV, the material of the valve body adopts 0Cr17Ni4Cu4Nb martensitic stainless steel, and the material of the valve stem limiting ring and the shaft sleeve are both 06Cr19Ni10 austenitic stainless steel. The valve stem 3 and the disc plate 4 are provided with fixing pins 34, and the number of the fixing pins 34 is several.

[0021] A first bracket 10 is arranged above the valve body 1, the valve stem 3 passes through the inner cavity of the first bracket 10, a first spiral wound gasket 11 is arranged between the first bracket 10 and the valve seat 2, a first fixing bolt 12 is arranged on the first bracket 10 and the valve body 1, a packing sealing groove 13 is opened on the top of the first bracket 10, the packing sealing groove 13 is located on the outer side of the valve stem 3, and the packing sealing groove 13 is sequentially arranged with a packing gasket 14, a sealing packing 15 and a packing pressing ring 16 from bottom to top, a packing pressing plate 17 is arranged on the packing pressing ring 16 and the valve stem 3, a first adjusting bolt 18 is arranged on the packing pressing plate 17 and the first bracket 10, and an adjusting nut 19 is arranged on the first adjusting bolt 18 above the packing pressing plate 17. Further, a disc spring 20 is arranged on the first adjusting bolt 18 between the adjusting nut 19 and the packing pressing plate 17. The number of the first adjusting bolts 18 is several, and the several first adjusting bolts 18 are evenly distributed in a star shape outside the central axis of the valve stem 3, and each first adjusting bolt 18 is correspondingly installed with an adjusting nut 19 and a disc spring 20. Thus, after the valve stem 3 performs a rotation action for many times, the elastic force released by the compression of the disc spring 20 is used to cause the packing pressure plate 17 to move toward the packing gasket 14 after the sealing packing 15 is worn, thereby driving the packing pressure ring 16 to move toward the packing gasket 14, thereby causing the sealing packing 15 to deform again to reach a sealing state. Further, the top shape of the packing pressure ring 16 adopts a truncated cone tubular structure, and the partial shape of the packing pressure plate 17 matches the shape of the top of the packing pressure ring 16; thereby, it is convenient for the packing pressure plate 17 to evenly apply a force to the packing pressure ring 16 toward the packing gasket 14. Further, the diameter of the circumscribed circle of the inner cavity at the bottom of the packing pressure ring 16 gradually increases as the height of the packing pressure ring 16 decreases. Thus, the shape of the inner cavity at the bottom of the packing pressure ring 16 is used to cause the sealing packing 15 to deform toward the valve stem 3. A plug 21 is provided on the valve body 1 below the valve stem 3, a bottom flange 22 is provided on the bottom surface of the plug 21, a third spiral wound gasket 23 is provided between the bottom flange 22 and the valve body 1, and a second fixing bolt 24 is provided on the bottom flange 22 and the valve body 1. The plug 21, the third spiral wound gasket 23 and the bottom flange 22 are used to seal the valve body 1 below the valve stem 3, and the second fixing bolt 24 is installed to facilitate the disassembly of the bottom flange 22, and to facilitate the disassembly of the valve stem 3 and the shaft sleeve 8 to repair the product.

[0022] When the medium passing through is high-pressure steam, the valve body 1 near the disc plate 4 and the valve seat 2 is in a high-temperature state, and the sealing packing 15 adopts a graphite sealing packing. Although the sealing packing 15 adopts a graphite sealing packing and can work under high temperature, it will also increase the wear of the sealing packing 15 during the rotation of the valve stem 3. Therefore, the product is provided with a heat sink 25 on the first bracket 10 below the sealing packing 15. The number of the heat sink 25 is several, and the heat sinks 25 are uniformly distributed on the first bracket 10 in the direction from close to the sealing packing 15 to far away from the sealing packing 15. The circumscribed circle diameters of the heat sinks 25 gradually increase from close to the sealing packing 15 to far away from the sealing packing 15. Since the rising airflow formed by the adjacent air after the valve body 1 is heated will be blocked by the heat sink 25 located at the bottom, it is also convenient to use the heat sinks 25 located above the bottom heat sink 25 to contact the adjacent air to cool the first bracket 10, thereby reducing the working temperature of the sealing packing 15.

[0023] Each of the valve seat pressing plates 5 is provided with a positioning bolt 26, and the number of the positioning bolts 26 is several. The positioning bolts 26 are installed through the valve seat pressing plate 5, and the inner end of the positioning bolt 26 is in contact with the valve seat 2. Installing several positioning bolts 26 is more convenient for adjusting the valve seat 2 to achieve force balance in the preset installation state; a second spiral wound gasket 27 is provided between the valve seat 2 and the valve body 1. The installation of the second spiral wound gasket 27 is convenient for sealing the gap between the valve seat 2 and the valve body 1. The second adjusting bolts 28 are provided on the disc plate 4 and the disc plate pressure ring 6, and a graphite gasket 29 is provided between the disc plate 4 and the sealing ring 7.

[0024] A second bracket 30 is arranged above the first bracket 10, and a rack 31 is arranged on the second bracket 30. The rack 31 adopts a strip structure that can slide horizontally along the extension direction of the rack 31. The valve stem 3 is provided with a tooth groove 32. The number of the tooth grooves 32 is several. The several tooth grooves 32 are evenly distributed in a star shape on the outside of the central axis of the valve stem 3. The tooth grooves 32 and the rack 31 are meshed. The rack 31 is connected to a hydraulic cylinder 33 in transmission. A limit slider 36 is arranged on the rack 31. The number of the limit sliders 36 is several. The several limit sliders 36 are provided with linear guides 35. The limit slider 36 located at the outermost side is connected to the output end of the hydraulic cylinder 33. The hydraulic cylinder 33 adopts a multi-stage hydraulic cylinder. Therefore, it is convenient to use the hydraulic pressure delivered by the hydraulic cylinder 33 to drive the rack 31 to move under the limit conditions of the limit slider 36 and the linear guide 35, thereby driving the valve stem 3 meshed with the rack 31 to rotate.

[0025] The usage of this product is as follows: Figures 1 to 4 As shown, the following steps are included:

[0026] After installing this product to the preset installation position, when this product is in the fully open state, the high-pressure steam delivered by the upstream steam turbine unit enters the inner cavity of the valve body 1 from the inlet end of the valve body 1 of this product, and then is discharged from the outlet end of the valve body 1 of this product through the valve seat 2. At this time, the central axis of the disc plate 4 is parallel to the flow direction of the high-pressure steam.

[0027] When this product is in the fully closed state, the high-pressure steam sent from the upstream steam turbine unit is blocked by the disc plate 4, and the disc plate 4 is tightly fitted on the valve seat 2 under the action of the high-pressure steam. The sealing ring 7 and the valve seat 2 are fitted to form a seal, and the gap between the disc plate 4 and the disc plate pressure ring 6 is sealed by the sealing ring 7, and the gap between the valve body 1 and the valve seat 2 is sealed by the second spiral wound gasket 27.

[0028] When the downstream needs this product to make adjustments to meet the high-pressure steam volume required by the downstream, this product first delivers hydraulic oil to the hydraulic cylinder 33 through the hydraulic station. The hydraulic cylinder 33 pushes the rack 31 to move horizontally, and the rack 31 drives the tooth groove 32 to move, thereby driving the valve stem 3 to rotate. The valve stem 3 drives the disc plate 4 to overcome the resistance brought by the high-pressure steam delivered from the upstream to rotate. The force delivered by the upstream high-pressure steam acts on the disc plate 4 and the valve stem 3 at the same time. The valve stem 3 drives the shaft sleeve 8 to rotate and stop according to the command. At this time, the upstream hydraulic station maintains the pressure of the hydraulic cylinder 33. Thereby, the disc plate 4 can obtain sufficient force to overcome the force applied to the disc plate 4 by the upstream high-pressure steam passing through the disc plate 4 and the valve seat 2. At this time, the disc plate 4 is not in a fully open state, and the central axis of the disc plate 4 and the central axis of the valve seat 2 are at a certain angle, resulting in unequal forces on both sides of the disc plate 4. In this process, the force transmitted by the disc plate 4 is transmitted to the shaft sleeve 8 and the valve stem limiting ring via the valve stem 3. In the process of performing a partial opening or partial closing action again, the shaft sleeve 8 and the valve stem limiting ring are in contact with the valve body 1, thereby reducing the wear of the valve body 1 and the valve stem 3.

[0029] When the shaft sleeve 8 and the valve stem limiting ring have run for a preset time, the bottom flange 22 is opened and the fixing pin 34 is removed, so that the valve stem 3, the disc plate 4, the shaft sleeve 8 and the valve stem limiting ring can be easily removed and the shaft sleeve 8 and the valve stem limiting ring can be replaced again for quick maintenance.

[0030] Through this embodiment, the shaft sleeve 8 and the valve stem limiting ring are arranged between the valve stem 3 and the valve body 1. The material of the valve stem 3 is alloy steel with a grade of Cr20MoV, the material of the valve body 1 is 0Cr17Ni4Cu4Nb martensitic stainless steel, and the material of the valve stem limiting ring and the shaft sleeve 8 are both 06Cr19Ni10 austenitic stainless steel; the Mohs hardness of the valve stem 3 and the valve body 1 is greater than the Mohs hardness of the valve stem limiting ring and the shaft sleeve 8, so that the shaft sleeve 8 and the valve stem limiting ring are more susceptible to wear than the valve stem 3 and the valve body 1. During maintenance, the shaft sleeve 8 and the valve stem limiting ring are replaced, thereby reducing the difficulty of maintenance.

[0031] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, any equivalent changes or modifications made based on the structures, features and principles described in the patent scope of the present invention should be included in the patent application scope of the present invention.

Claims

1. A butterfly valve, comprising a valve body (1), a valve seat (2) being arranged in the valve body (1), a valve stem (3) being arranged on the valve body (1) on one side of the valve seat (2), and a disc plate (4) being arranged on the valve stem (3), characterized in that: The valve seat (2) is provided with a valve seat pressure ring on the side away from the valve stem (3); the shape of a part of the inner cavity of the valve body (1) matches the shape of the part of the valve seat pressure ring; the valve seat pressure ring adopts a ring structure composed of a plurality of arc-shaped valve seat pressure plates (5) connected end to end in sequence; a disc plate pressure ring (6) is provided on the disc plate (4); a sealing ring (7) is provided between the disc plate pressure ring (6) and the disc plate (4); the sealing ring (7) and the valve seat (2) are in contact with each other; a valve stem limiting ring and a shaft sleeve ( 8), the valve stem limiting ring adopts a ring structure composed of a plurality of arc-shaped limiting rods (9) connected end to end in sequence, the number of the shaft sleeves (8) is at least two, and the plurality of shaft sleeves (8) are evenly distributed on both sides of the disc plate (4), the material of the valve stem (3) is alloy steel with a grade of Cr20MoV, the material of the valve body (1) is 0Cr17Ni4Cu4Nb martensitic stainless steel, and the material of the valve stem limiting ring and the shaft sleeve (8) are both 06Cr19Ni10 austenitic stainless steel.

2. The butterfly valve according to claim 1, characterized in that: A first bracket (10) is arranged above the valve body (1), the valve stem (3) passes through the inner cavity of the first bracket (10), a first spiral wound gasket (11) is arranged between the first bracket (10) and the valve seat (2), a first fixing bolt (12) is arranged on the first bracket (10) and the valve body (1), a packing sealing groove (13) is opened at the top of the first bracket (10), the packing sealing groove (13) is located on the outer side of the valve stem (3), a packing gasket (14), a sealing packing (15) and a packing pressure ring (16) are arranged in sequence from bottom to top in the packing sealing groove (13), a packing pressure plate (17) is arranged on the packing pressure ring (16) and the valve stem (3), a first adjusting bolt (18) is arranged on the packing pressure plate (17) and the first bracket (10), and an adjusting nut (19) is arranged on the first adjusting bolt (18) above the packing pressure plate (17).

3. The butterfly valve according to claim 2, characterized in that: A disc spring (20) is provided on the first adjusting bolt (18) between the adjusting nut (19) and the packing pressure plate (17).

4. The butterfly valve according to claim 2, characterized in that: A heat sink (25) is provided on the first bracket (10) below the sealing filler (15), and the number of the heat sinks (25) is a plurality. The plurality of heat sinks (25) are evenly distributed on the first bracket (10) in sequence along a direction from close to the sealing filler (15) to far away from the sealing filler (15), and the diameters of the circumscribed circles of the plurality of heat sinks (25) gradually decrease along a direction from close to the sealing filler (15) to far away from the sealing filler (15).

5. The butterfly valve according to claim 1, characterized in that: Each of the valve seat pressure plates (5) is provided with a positioning bolt (26), which is installed through the valve seat pressure plate (5), the inner end of the positioning bolt (26) is in contact with the valve seat (2), and a second wound gasket (27) is provided between the valve seat (2) and the valve body (1).

6. The butterfly valve according to claim 1, characterized in that: The disc plate (4) and the disc plate pressure ring (6) are provided with a second adjusting bolt (28), and a graphite gasket (29) is provided between the disc plate (4) and the sealing ring (7).

7. The butterfly valve according to claim 2, characterized in that: A second bracket (30) is arranged above the first bracket (10), and a rack (31) is arranged on the second bracket (30). The rack (31) is a strip-shaped structure capable of horizontal sliding movement along the extension direction of the rack (31). A tooth groove (32) is arranged on the valve stem (3). The number of the tooth grooves (32) is a plurality, and the plurality of tooth grooves (32) are evenly distributed in a star shape on the outside of the central axis of the valve stem (3). The tooth grooves (32) are meshed with the rack (31), and a hydraulic cylinder (33) is transmission-connected to the rack (31).

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