Corrugated pipe upward expanding type angle valve for phosgene-containing medium

Abstract

The invention relates to a corrugated pipe upward expanding type angle valve for a phosgene-containing medium. The valve body is provided with a first port and a second port which are communicated with each other; the valve seat is mounted at the first port of the valve body, the valve seat extends into and is mounted at an outlet channel of the reaction equipment, and a first sealing assembly is arranged between the valve seat and the outlet channel; the valve element assembly comprises a valve rod movably connected into the valve body in the axial direction and a valve element connected with the valve rod and capable of making sealing contact with the valve seat. The upper cover is installed at the end, away from the valve element, of the valve seat. The first end of the corrugated pipe is mounted on the upper cover, and the second end of the corrugated pipe is mounted on the valve rod; and the corrugated pipe protection sleeve is installed in the inner cavity of the valve body and surrounds the corrugated pipe, and a second sealing assembly and a third sealing assembly are correspondingly arranged between the corrugated pipe protection sleeve and the upper cover and between the corrugated pipe protection sleeve and the valve rod. And the safety of the angle valve under the working condition of a high-toxicity medium is realized.

Description

Technical Field

[0001] The invention relates to the technical field of control valves, in particular to a bellows upward expansion type angle valve for a phosgene-containing medium. Background Art

[0002] NDI (1,5-naphthalene diisocyanate) is an important chemical raw material, mainly used in the production of high-performance polyurethane materials. NDI is widely used in the automotive, aerospace, construction, and electronic and electrical fields due to its excellent mechanical properties and chemical corrosion resistance. In its preparation process, 1,5-naphthalene diamine (NDA) is used as one of the raw materials to react with phosgene to synthesize NDI. This step is a key link in the entire synthesis process. Phosgene is a toxic gas that is extremely harmful to the human body. Therefore, during the reaction of phosgene, strict safety measures must be taken to prevent leakage and environmental pollution. This places extremely high demands on the sealing performance and stability of the valve. Traditional valves have deficiencies in sealing performance, stability, and ease of maintenance, and are difficult to meet actual production needs. Summary of the invention

[0003] To this end, the present invention provides a bellows upward expansion angle valve for phosgene-containing media, which greatly improves the safety and reliability of the angle valve, reduces the difficulty of operation and maintenance, and realizes the safety of the angle valve under highly toxic media working conditions.

[0004] In order to solve the above technical problems, the present invention provides a bellows upward expansion angle valve for phosgene-containing medium, comprising: The valve body is provided with a first opening and a second opening which are communicated with each other; A valve seat is installed at the first opening of the valve body, the valve seat extends into and is installed at the outlet channel of the reaction device, and a first sealing component is arranged between the valve seat and the outlet channel; A valve core assembly, comprising a valve stem movably connected to the valve body along the axial direction and a valve core connected to the valve stem and capable of sealing contact with the valve seat, wherein the valve core can connect or disconnect the interior of the reaction device with the first port under the action of the valve stem; An upper cover is mounted on an end of the valve seat away from the valve core; A bellows, comprising a first end and a second end axially opposite to each other, wherein the first end of the bellows is mounted on the upper cover, and the second end of the bellows is mounted on the valve stem; A bellows protective sleeve is installed in the inner cavity of the valve body and surrounds the bellows. A second sealing component and a third sealing component are correspondingly arranged between the bellows protective sleeve and the upper cover and between the bellows protective sleeve and the valve stem.

[0005] In one embodiment of the present invention, the reaction device is equipped with a mounting flange having the outlet channel, and the valve seat includes a cylindrical body and a mounting disk extending from an axial end of the cylindrical body, and the mounting disk is mounted on the mounting flange and abuts against the valve body.

[0006] In one embodiment of the present invention, a flange is extended axially outwardly along the mounting flange, and the mounting plate is provided with a groove suitable for the flange to be embedded.

[0007] In one embodiment of the present invention, the first sealing assembly includes at least two first sealing rings arranged between the outer circle of the cylindrical body and the inner wall of the outlet channel.

[0008] In one embodiment of the present invention, a first spiral wound gasket is arranged between the groove and the flange and / or between the mounting plate and the valve body.

[0009] In one embodiment of the present invention, the valve core is provided with a mounting hole arranged in a stepped manner, a portion of the side walls of the mounting hole is provided with a threaded structure, and a mounting portion is provided at the end of the valve stem close to the valve core, the mounting portion includes a mounting head extending into the mounting hole, a portion of the cylindrical surface of the valve stem, and a groove arranged between the mounting head and the portion of the cylindrical surface of the valve stem and used to install a split ring, and a portion of the cylindrical surface of the valve stem is provided with a threaded sleeve threadedly connected to the mounting hole.

[0010] In one embodiment of the present invention, a sealing cone surface is provided on the outer periphery of the valve core, and a cone surface sealing pair is formed between the sealing cone surface and the valve seat.

[0011] In one embodiment of the present invention, a guide block is welded to the inner cavity of the valve body, and the valve stem is slidably connected to the guide block.

[0012] In one embodiment of the present invention, the upper cover is provided with a filling hole, the valve stem passes through the filling hole and is connected to an external actuator, the first end of the bellows is connected to the bottom periphery of the filling hole by welding, and the second end of the bellows is connected to the valve stem by welding.

[0013] In one embodiment of the present invention, the outer wall of the bellows protective sleeve is closely attached to the inner cavity wall of the valve body, the bellows protective sleeve comprises a first end and a second end which are arranged opposite to each other, the first end of the bellows protective sleeve radially extends outward to have a convex edge located between the upper cover and the valve body, and the second sealing assembly comprises a second spiral wound gasket respectively located between the convex edge and the upper cover and between the convex edge and the valve body; The second end of the bellows protective sleeve is provided with a guide sleeve extending radially inward to the cylindrical surface of the valve stem, and the third sealing assembly includes at least two second sealing rings arranged between the inner hole of the guide sleeve and the valve stem.

[0014] The above technical solution of the present invention has the following advantages compared with the prior art: The bellows upward expansion angle valve for phosgene-containing media described in the present invention prevents the medium from accumulating between the valve seat and the flange gap of the equipment by arranging at least two perfluoroether O-rings between the outer circle of the valve seat and the inner wall of the outlet channel of the reaction equipment. The bellows itself forms an isolated sealing barrier between the valve stem and the inner cavity of the valve body to prevent phosgene from penetrating into the external environment. The bellows protective sleeve is in close contact with the inner cavity wall of the valve body, and the second and third sealing components (wound gasket, universal plug ring, perfluoroether O-ring, etc.) are respectively arranged between the bellows and the upper cover, the valve body, and the valve stem to achieve multiple seals and further improve the anti-leakage performance.

[0015] The bellows of the present invention moves with the valve stem through axial flexible deformation, and the valve stem plays the role of transmitting the opening and closing action and force of the valve core; at the same time, the bellows itself acts as a metal sealing barrier to prevent the internal medium of the valve body from leaking outward. The bellows protective sleeve surrounds the outside of the bellows, fits tightly with the valve body, and is provided with multiple sealing components. Even if the bellows body is accidentally damaged, the bellows protective sleeve and the second and third sealing components thereon can form a second line of defense, further reducing the risk of leakage.

[0016] At least two perfluoroether O-rings are arranged between the valve seat and the outlet channel of the reaction equipment to form a redundant seal; at the same time, a spiral wound gasket can be additionally arranged between the flange and the groove to further enhance the sealing effect and prevent the medium from being retained in the gap between the valve seat and the flange of the equipment. A guide sleeve extending radially inward is arranged at the first end of the bellows protective sleeve, and at least two sealing rings such as a universal plug ring and a perfluoroether O-ring are arranged between the guide sleeve and the valve stem to form another redundant sealing structure.

[0017] The valve core and valve stem of the present invention adopt a split structure, which is connected and positioned by a threaded sleeve and a split ring. When in use, only the threaded sleeve and the split ring need to be disassembled to realize the rapid replacement or maintenance of the valve core assembly, without having to disassemble the valve stem, bellows and other components as a whole, thus shortening the maintenance cycle and reducing the difficulty of maintenance.

[0018] A conical sealing pair is adopted between the end of the valve core and the valve seat of the present invention, which can meet the bidirectional VI level sealing requirements, and the valve core can be replaced independently, with lower maintenance costs.

[0019] When the valve stem of the present invention slides in the inner cavity (flow channel) of the valve body, it is guided by a guide block welded in the valve body. For an angle valve with a long rod structure, the guide block can effectively prevent lateral vibration or deflection of the valve stem, thereby improving the stability and reliability of the opening and closing action and reducing the wear of internal parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0021] Figure 1 It is a structural diagram of a bellows upward-spreading angle valve for a phosgene-containing medium according to the present invention.

[0022] Figure 2 yes Figure 1 Enlarged view of part I.

[0023] Figure 3 yes Figure 1 Enlarged view of part II.

[0024] Figure 4 yes Figure 1 Enlarged view of part III.

[0025] Description of the Figures in the Specification: 1. Valve core assembly; 1.1. Valve core; 1.2. Split ring; 1.3. Threaded sleeve; 1.4, valve stem; 1.4.1, mounting head; 2, first sealing assembly; 2.1, first sealing ring; 3, valve seat; 4, first spiral wound gasket; 5. Valve body; 5a. First port; 5b. Second port; 5.1. Guide block; 6. Third sealing assembly; 6a. Pan-Seal ring; 6b. Second sealing ring; 8. bellows protective sleeve; 8a. guide sleeve; 9. bellows; 10. second sealing assembly; 10a. second spiral wound gasket; 11. upper cover; 12. Second nut; 13. Second stud; 14. First stud; 15. First nut; 16. Mounting flange; 17. Reaction equipment. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0027] In the present invention, if directions (up, down, left, right, front and back) are described, it is only for the convenience of describing the technical solution of the present invention, and does not indicate or imply that the technical features referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, it cannot be understood as a limitation of the present invention.

[0028] In the present invention, "several" means one or more, "multiple" means more than two, "greater than", "less than", "exceed" and the like are understood to exclude the number itself; "above", "below", "within" and the like are understood to include the number itself. In the description of the present invention, if there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0029] In the present invention, unless otherwise clearly defined, the words "set", "install", "connect" and the like should be understood in a broad sense, for example, they can be directly connected or indirectly connected through an intermediate medium; they can be fixedly connected or detachably connected or integrally formed; they can be mechanically connected or electrically connected or able to communicate with each other; they can be the internal connection of two elements or the interaction relationship between two elements. Those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0030] Reference Figure 1 As shown, a bellows 9 upward expansion angle valve for a phosgene-containing medium of the present invention comprises: The valve body 5 is provided with a first opening 5a and a second opening 5b which are communicated with each other; The valve seat 3 is installed at the first opening 5a of the valve body 5. The valve seat 3 extends into and is installed at the outlet channel of the reaction device 17 (such as a reactor), and a first sealing component 2 is arranged between the valve seat 3 and the outlet channel. The medium (phosgene) flows from the reaction device 17 through the valve seat 3 and the first opening 5a and out from the second opening 5b. A valve core assembly 1, comprising a valve stem 1.4 movably connected to the valve body 5 along the axial direction and a valve core 1.1 connected to the valve stem 1.4 and capable of sealing contact with the valve seat 3, wherein the valve core 1.1 can, under the action of the valve stem 1.4, connect or disconnect the interior of the reaction device (17) with the first opening 5a; An upper cover 11 is mounted on an end of the valve seat 3 away from the valve core 1.1; The bellows 9 comprises a first end and a second end which are axially opposite to each other, wherein the first end of the bellows 9 is mounted on the upper cover 11, and the second end of the bellows 9 is mounted on the valve stem 1.4; The bellows protective sleeve 8 is installed in the inner cavity of the valve body 5 and surrounded by the bellows 9. A second sealing component 10 and a third sealing component 6 are correspondingly arranged between the bellows protective sleeve 8 and the upper cover 11 and between the bellows protective sleeve 8 and the valve stem 1.4.

[0031] It is understandable that the bellows 9 can be made of metal material through its flexible deformation in the axial direction, move with the valve stem 1.4, and under the action of the actuator, the valve core 1.1 is moved through transmission to control the flow of the medium.

[0032] Through the above arrangement, the bellows 9 not only transmits the movement of the valve stem 1.4, but also plays a sealing role. Its internal partition prevents the medium from penetrating; and cooperates with the bellows protective sleeve 8 arranged externally to further ensure that the medium does not leak along the control path.

[0033] In one embodiment, referring to Figure 2 As shown, the reaction device 17 is installed with a mounting flange 16 having the outlet channel, and the valve seat 3 includes a cylindrical body and a mounting disk extending from an axial end of the cylindrical body. The mounting disk is installed on the mounting flange 16 and abuts against the valve body 5.

[0034] Specifically, a flange is extended axially outwardly along the mounting flange 16 , and the mounting plate is provided with a groove suitable for the flange to be embedded.

[0035] A flange is provided on the mounting flange 16 of the reaction device 17, and a corresponding groove is provided on the mounting plate of the valve seat 3, so that fast and accurate alignment installation can be achieved; and a spiral wound gasket is added between the groove and the flange and between the valve body 5 and the mounting plate to further ensure the close fit of the mounting surface. This method simplifies the alignment operation when the equipment side is connected to the valve, shortens the installation cycle, and also reduces the potential leakage risk caused by assembly errors. In addition, the valve seat 3 is directly inserted into the outlet channel in the reaction device 17, and the transition of the medium between the valve seat 3 and the valve body 5 is smoother, and the dead angle and deposition area of ​​the medium are reduced, which is conducive to the rapid transportation and discharge of the medium (phosgene).

[0036] In one embodiment, referring to Figure 2 As shown, the first sealing assembly 2 includes at least two first sealing rings 2.1 arranged between the outer circle of the cylindrical body and the inner wall of the outlet channel. The first sealing ring 2.1 is a perfluoroether O-ring. The perfluoroether O-ring has stable performance in high temperature and highly toxic environments, has excellent corrosion resistance and aging resistance, and meets the requirements of harsh working conditions.

[0037] The two first sealing rings 2.1 form a redundant seal, which can prevent the medium from accumulating between the valve seat 3 and the flange gap of the equipment.

[0038] In one embodiment, a first spiral wound gasket 4 is provided between the groove and the flange and / or between the mounting plate and the valve body 5. The first spiral wound gasket 4 is pre-tightened and sealed by a first stud 14 and a first nut 15 provided between the valve seat 3 and the valve body 5. In one embodiment, the valve core 1.1 is provided with a mounting hole arranged in a stepped manner, a part of the side wall of the mounting hole is provided with a threaded structure, and a mounting portion is provided at the end of the valve stem 1.4 close to the valve core 1.1, and the mounting portion includes a mounting head 1.4.1 extending into the mounting hole, a part of the cylindrical surface of the valve stem 1.4, and a groove arranged between the mounting head 1.4.1 and a part of the cylindrical surface of the valve stem 1.4 and used to install the split ring 1.2, and a part of the cylindrical surface of the valve stem 1.4 is provided with a threaded sleeve 1.3 threadedly connected to the mounting hole. In addition, the mounting head 1.4.1 is an arc surface and abuts against the bottom wall of the mounting hole.

[0039] The valve core 1.1 and the valve stem 1.4 are of split design and are fastened together by a threaded sleeve 1.3, so they are easy to disassemble and assemble and maintain.

[0040] In one embodiment, a sealing cone surface is provided on the outer periphery of the valve core 1.1, and a cone surface sealing pair is formed between the sealing cone surface and the valve seat 3, which can meet the bidirectional VI level sealing requirements.

[0041] In one embodiment, referring to Figure 3 As shown, a guide block 5.1 is welded in the inner cavity (in the flow channel) of the valve body 5, and the valve stem 1.4 is slidably connected to the guide block 5.1, thereby improving the guiding stability of the slender valve stem 1.4.

[0042] Reference Figure 1 As shown, the upper cover 11 is provided with a packing hole, the valve stem 1.4 passes through the packing hole and is connected to the external actuator, the first end of the bellows 9 is connected to the bottom periphery of the packing hole by welding, and the second end of the bellows 9 is connected to the valve stem 1.4 by welding (separated from the inside of the bellows 9). The bellows 9 adopts a positive structure, with one end welded to the valve stem 1.4 and the other end welded to the upper cover 11, meeting the ISO 15848 A-level leakage grade requirements. The structure is compact, firm and reliable, and can avoid micro-leakage at the connection between the bellows 9 and the valve stem 1.4 to the greatest extent, meeting the high-level sealing requirements required for toxic and highly corrosive media such as phosgene.

[0043] It should be noted that the provision of the bellows 9 enables effective sealing between the inner cavity of the valve body 5 and the upper cover 11 , and the bellows protective sleeve 8 further improves the sealing performance.

[0044] Reference Figure 4As shown, in one embodiment, the outer wall of the bellows protective sleeve 8 is tightly attached to the inner cavity wall of the valve body 5, the bellows protective sleeve 8 includes a first end and a second end arranged opposite to each other, the first end of the bellows protective sleeve 8 radially extends outward to have a convex edge located between the upper cover 11 and the valve body 5, the second sealing assembly 10 includes a second wound gasket 10a respectively located between the convex edge and the upper cover 11 and between the convex edge and the valve body 5; the second wound gasket 10a is pre-tightened and sealed by a second stud 13 and a second nut 12 arranged between the upper cover 11 and the valve body 5.

[0045] The second end of the bellows protective sleeve 8 is provided with a guide sleeve 8a extending radially inward to the cylindrical surface of the valve stem 1.4. The third sealing assembly 6 includes at least two second sealing rings 6b arranged between the inner hole of the guide sleeve 8a and the valve stem 1.4. The second sealing rings 6b may include a pan seal ring 6a and a perfluoroether O-ring. The redundant sealing design ensures the reliability of sealing for highly toxic phosgene medium.

[0046] At least two sealing rings, such as a pan seal ring 6a and a perfluoroether O-ring, are arranged between the guide sleeve 8a and the valve stem 1.4 to form another redundant sealing structure.

[0047] It should be noted that the sealing rings (Vansil ring 6a, perfluoroether O-ring, etc.) used in this embodiment can be flexibly selected from other suitable sealing materials according to the corrosiveness of the medium such as phosgene and the process temperature and pressure requirements.

[0048] During operation, the valve seat 3 is installed at the first opening 5a of the valve body 5, one end of which enters the outlet channel of the reaction device 17, and a first sealing component 2 (for example, a sealing ring composed of a perfluoroether O-ring and a redundant design) is arranged between the channel to ensure a tight fit between the device and the valve seat 3 to prevent leakage of the medium (such as toxic phosgene).

[0049] In actual working conditions, the phosgene medium enters the first port 5a of the valve body 5 through the valve seat 3 from the reaction device 17, and then is transferred to the second port 5b by the flow channel in the valve body 5, so as to realize the smooth delivery of the medium. The valve core assembly 1 is composed of a valve stem 1.4 that moves in the axial direction and a valve core 1.1 connected to the valve stem 1.4. Driven by the valve stem 1.4, the valve core 1.1 realizes axial reciprocating motion in the valve body 5, thereby forming a tight seal (or disengaging the seal state) with the valve seat 3, and plays the role of opening or closing the flow passage of the phosgene medium.

[0050] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A bellows (9) upward expansion angle valve for a phosgene-containing medium, characterized in that: include: A valve body (5) is provided with a first opening (5a) and a second opening (5b) which are communicated with each other; A valve seat (3) is installed at the first opening (5a) of the valve body (5); the valve seat (3) extends into and is installed at the outlet channel of the reaction device (17), and a first sealing component (2) is provided between the valve seat and the outlet channel; A valve core assembly (1) comprising a valve stem (1.4) movably connected to the valve body (5) in the axial direction and a valve core (1.1) connected to the valve stem (1.4) and capable of sealing contact with the valve seat (3); the valve core (1.1) can, under the action of the valve stem (1.4), connect or disconnect the interior of the reaction device (17) with the first opening (5a); An upper cover (11) is mounted on an end of the valve seat (3) away from the valve core (1.1); A bellows (9) comprising a first end and a second end arranged axially opposite to each other, the first end of the bellows (9) being mounted on the upper cover (11), and the second end of the bellows (9) being mounted on the valve stem (1.4); A bellows protective sleeve (8) is installed in the inner cavity of the valve body (5) and surrounds the bellows (9), and a second sealing assembly (10) and a third sealing assembly (6) are provided between the bellows protective sleeve (8) and the upper cover (11) and between the bellows protective sleeve and the valve stem (1.4) respectively.

2. The bellows (9) upward expansion angle valve for phosgene-containing media according to claim 1, characterized in that: The reaction device (17) is provided with a mounting flange (16) having the outlet channel. The valve seat (3) comprises a cylindrical body and a mounting plate extending from an axial end of the cylindrical body. The mounting plate is mounted on the mounting flange (16) and abuts against the valve body (5).

3. The bellows (9) upward expansion angle valve for phosgene-containing media according to claim 2, characterized in that: A flange extends axially outwardly along the mounting flange (16), and the mounting plate is provided with a groove suitable for fitting the flange.

4. The bellows (9) upward expansion angle valve for phosgene-containing media according to claim 2, characterized in that: The first sealing assembly (2) comprises at least two first sealing rings (2.1) arranged between the outer circle of the cylindrical body and the inner wall of the outlet channel.

5. The bellows (9) upward expansion angle valve for phosgene-containing media according to claim 3, characterized in that: A first wound gasket (4) is provided between the groove and the flange and / or between the mounting plate and the valve body (5).

6. The bellows (9) upward expansion angle valve for phosgene-containing media according to claim 1, characterized in that: The valve core (1.1) is provided with a mounting hole arranged in a stepped manner, and a part of the side wall of the mounting hole is provided with a threaded structure. The end of the valve stem (1.4) close to the valve core (1.1) is provided with a mounting portion, and the mounting portion includes a mounting head (1.4.1) extending into the mounting hole, a part of the cylindrical surface of the valve stem (1.4), and a groove arranged between the mounting head (1.4.1) and a part of the cylindrical surface of the valve stem (1.4) and used for mounting a split ring (1.2), and a part of the cylindrical surface of the valve stem (1.4) is provided with a threaded sleeve (1.3) threadedly connected to the mounting hole.

7. The bellows (9) upward expansion angle valve for phosgene-containing media according to claim 1, characterized in that: The outer periphery of the valve core (1.1) is provided with a sealing cone surface, and a cone surface sealing pair is formed between the sealing cone surface and the valve seat (3).

8. The bellows (9) upward expansion angle valve for phosgene-containing media according to claim 1, characterized in that: A guide block (5.1) is welded to the inner cavity of the valve body (5), and the valve stem (1.4) is slidably connected to the guide block (5.1).

9. The bellows (9) upward expansion angle valve for phosgene-containing media according to claim 1, characterized in that: The upper cover (11) is provided with a packing hole, the valve stem (1.4) passes through the packing hole and is connected to an external actuator, the first end of the bellows (9) is connected to the bottom periphery of the packing hole by welding, and the second end of the bellows (9) is connected to the valve stem (1.4) by welding.

10. The bellows (9) upward expansion angle valve for phosgene-containing media according to claim 1, characterized in that: The outer wall of the bellows protective sleeve (8) is tightly attached to the inner wall of the valve body (5), the bellows protective sleeve (8) comprises a first end and a second end which are arranged opposite to each other, the first end of the bellows protective sleeve (8) radially extending outwards to have a convex edge located between the upper cover (11) and the valve body (5), and the second sealing assembly (10) comprises a second spiral wound gasket (10a) located between the convex edge and the upper cover (11) and between the convex edge and the valve body (5), respectively; The second end of the bellows protective sleeve (8) is provided with a guide sleeve (8a) extending radially inward to the cylindrical surface of the valve stem (1.4), and the third sealing assembly (6) comprises at least two second sealing rings (6b) arranged between the inner hole of the guide sleeve (8a) and the valve stem (1.4).

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