High-precision regulating valve

Abstract

The utility model discloses a high-precision regulating valve, and relates to the field of regulating valves. A traditional adjusting valve has the problems of low adjusting precision, response lag, poor working condition adaptability and the like. The valve comprises a valve body, a valve seat, a sleeve, a valve rod, a valve core, an adaptive ring, a valve cover, a bracket, a pneumatic straight stroke film actuator, an electrical valve positioner and an air filtering pressure reducing valve. The valve element is matched with a valve seat wedge angle structure, the electric valve positioner and the air filtering pressure reducing valve work cooperatively, precise adjustment is achieved, the air filtering pressure reducing valve purifies and stabilizes an air source, the electric valve positioner constructs a closed loop to control and correct the valve position, and the response speed and the control precision are effectively improved. A metal winding gasket and a V-shaped packing assembly are arranged at key positions of the valve, the sealing performance is enhanced, and the valve adapts to high-temperature, high-pressure and corrosive environments. The problems that a traditional valve is low in adjusting precision, slow in response and poor in adaptability are solved, and the valve is suitable for fluid control systems in multiple industries such as chemical engineering and energy.

Description

Technical Field

[0001] This utility model relates to the field of control valves, and in particular to a high-precision control valve. Background Technology

[0002] In industrial automation, the precise regulation of fluid control systems is crucial for the production stability and efficiency of industries such as chemical, energy, power, pharmaceutical, and food processing. As a core control component, the performance of control valves directly affects the accuracy and reliability of system parameter control. However, existing control valves suffer from several technological bottlenecks:

[0003] First, traditional control valves rely on mechanical structures or simple proportional control, resulting in slow actuator response, limited valve core design, and insufficient feedback system accuracy. This makes it difficult to meet the demands of high-frequency changing operating conditions. For example, in the flow control of chemical reactors, existing valves cannot quickly respond to flow regulation needs caused by temperature changes, easily leading to control deviations.

[0004] Secondly, the control mode dominated by external controllers suffers from signal acquisition and execution delays. When the system requires real-time closed-loop regulation, the lag in signal transmission and processing will cause the regulation action to lag behind changes in operating conditions. Especially in the pressure control scenario of high-pressure steam pipelines, the lag may cause system oscillations and affect equipment safety.

[0005] Furthermore, insufficient adaptability to special operating conditions is a common problem. In environments with high temperature, high pressure, corrosive media, or low flow rates, the sealing structure of traditional valves is prone to failure, leading to frequent issues such as valve core jamming, control drift, and leakage. For example, in the sterile fluid delivery systems of the pharmaceutical industry, the durability of existing valves cannot meet the requirements for long-term trouble-free operation, increasing cleaning validation and maintenance costs.

[0006] Furthermore, existing control valves have low modularity, poor compatibility with industrial control systems, and complex installation and maintenance. In the context of intelligent manufacturing trends, they lack real-time status feedback and self-diagnostic functions, making them difficult to integrate into digital operation and maintenance systems, resulting in low troubleshooting efficiency and significant downtime losses.

[0007] In summary, developing a control valve that combines high-precision regulation, rapid response, strong adaptability to operating conditions, and intelligent control is key to solving existing industrial fluid control problems. Utility Model Content

[0008] The technical problem to be solved and the technical task proposed by this utility model is to improve and refine the existing technical solutions, and to provide a high-precision regulating valve to achieve high-precision regulation with rapid response. To this end, this utility model adopts the following technical solution.

[0009] A high-precision regulating valve includes a valve body, a valve seat, a sleeve, a valve stem, a valve core, a valve cover, a bracket, a pneumatic linear diaphragm actuator, an electric valve positioner, and an air filter pressure reducing valve. The valve seat is located within the valve body, the sleeve is located on top of the valve seat and fixed within the valve body, the valve cover is located at the upper end of the valve body, the bracket is located on top of the valve cover, the pneumatic linear diaphragm actuator is located on the bracket, the electric valve positioner is fixed to the side of the bracket, the air filter pressure reducing valve is fixed to the side of the bracket, the air filter pressure reducing valve is connected to the electric valve positioner, the electric valve positioner is connected to the pneumatic linear diaphragm actuator, the push rod of the pneumatic linear diaphragm actuator is connected to the valve stem via a nut, the lower end of the valve stem is connected to the valve core, the valve core is located inside the sleeve, and the lower part of the valve core is matched with the vertical through hole in the middle of the valve seat via a wedge structure.

[0010] By working in concert with a pneumatic linear diaphragm actuator, an electric valve positioner, and an air filter pressure reducing valve, a complete process from air source processing and signal control to mechanical action is achieved. The air filter pressure reducing valve enhances the reliability and stability of the air source, effectively filtering impurities and moisture from compressed air while stabilizing the air pressure within the set range. This ensures smooth actuator operation and prevents valve malfunction or delayed response due to unclean air or pressure fluctuations. The electric valve positioner automatically adjusts and corrects the valve position in real time, significantly improving the system's dynamic control capabilities. This avoids the error accumulation and response lag problems that easily occur in traditional open-loop control, thereby effectively improving the valve's response speed and control accuracy. The electric valve positioner enables precise adjustment of fluid parameters, giving the valve the characteristics of fast response and high adjustment accuracy, making it suitable for fluid control in various industrial automation systems.

[0011] As a preferred technical means, a metal spiral wound gasket is provided between the bottom outer periphery of the valve seat and the valve body. By placing a metal spiral wound gasket between the bottom outer periphery of the valve seat and the valve body, and utilizing the good elasticity and sealing performance of the metal spiral wound gasket, fluid leakage from the connection between the valve seat and the valve body can be effectively prevented in high-temperature, high-pressure, and corrosive media environments. This enhances the overall sealing performance and operational reliability of the valve, and extends the service life of the valve under harsh operating conditions.

[0012] As a preferred technical approach: an adapter ring is provided on the upper part of the sleeve, which presses against the outer peripheral step of the upper end of the sleeve, and the lower end of the valve cover presses against the upper end of the valve body and the adapter ring. Providing an adapter ring on the upper part of the sleeve, compared to directly inserting the valve cover into the upper part of the valve body to press against the sleeve, reduces the coaxiality requirement for valve cover assembly and facilitates assembly.

[0013] As a preferred technical approach, a spiral wound gasket is installed between the adapter ring and the upper outer circumferential step of the sleeve. This improves the sealing effect at the connection between the sleeve and the adapter ring. The adapter ring presses against the upper outer circumferential step of the sleeve, and the spiral wound gasket deforms under pressure between the two, forming a reliable seal. This prevents the medium from leaking out from the connection between the sleeve and the adapter ring, ensuring the sealing of the internal fluid passage of the valve and improving the stability of the valve under complex operating conditions.

[0014] As a preferred technical approach: an annular groove is provided on the inner side of the upper end of the valve body and the adjacent area on the outer side of the adapter ring. A metal spiral wound gasket is placed in the annular groove. The lower end of the valve cover has a downwardly protruding pressure ring, which presses against the metal spiral wound gasket in the annular groove. The inner side of the lower end of the valve cover mates with the outer side of the upper end of the adapter ring. This further improves the sealing performance of the valve, effectively preventing media leakage from the joint between the valve body and the adapter ring. Moreover, the matching and limiting of the valve cover and the adapter ring enhances the stability of the entire valve structure, enabling the valve to withstand the influence of external factors such as high pressure and vibration during long-term operation and maintain a good working condition.

[0015] As a preferred technical approach, a 3-5mm gap exists between the lower and upper surfaces of the valve cover, located outside the pressure ring. This gap reduces the surface area of ​​the assembly, lowering assembly requirements. Furthermore, it provides a buffer space for deformation of the valve cover due to temperature changes during operation, preventing excessive stress between the valve cover and other components due to thermal expansion and contraction, thus preventing component damage. Simultaneously, it helps maintain the valve's sealing performance, ensuring normal operation of the valve under different temperature conditions.

[0016] As a preferred technical means: a V-shaped packing assembly is provided at the upper end of the valve cover. The V-shaped packing assembly is located on the outer periphery of the valve stem. The V-shaped packing assembly includes, from bottom to top, a packing pad, a V-shaped combined packing, a packing sleeve, and a packing pressure plate. The packing pad and the V-shaped combined packing are located in the inner cavity of the valve cover packing around the valve stem. The lower part of the packing sleeve is embedded in the inner cavity of the valve cover packing and presses the V-shaped combined packing. The packing pressure plate presses the packing sleeve and is fastened to the upper end face of the valve cover by a combination of multiple sets of fully threaded studs and nuts. The V-shaped combined packing can fit tightly against the valve stem, preventing the medium from leaking along the valve stem. The fastening effect of the packing sleeve and the packing pressure plate ensures the stability of the packing assembly, guarantees the stable operation of the actuator, and enables the valve to maintain good sealing effect and mechanical performance even during frequent opening and closing.

[0017] As a preferred technical means: the upper end of the valve cover is provided with a stepped shaft portion, and the lower end of the bracket is provided with a connecting shaft hole portion. The connecting shaft hole portion at the lower end of the bracket mates with the stepped shaft portion. The upper middle part of the stepped shaft portion is provided with external threads. After the connecting shaft hole portion at the lower end of the bracket is fitted into the stepped shaft portion, a round nut is screwed into the upper end of the stepped shaft portion for tightening. The valve cover and the bracket are connected by the stepped shaft portion, the connecting shaft hole portion, and the round nut, achieving a stable installation of the bracket and the valve cover. This connection structure not only facilitates installation and disassembly but also ensures the stability of the bracket during valve operation, allowing components such as pneumatic linear diaphragm actuators to be reliably installed on the bracket and function normally, providing a stable support structure for precise valve control.

[0018] Beneficial effects:

[0019] 1. By working in concert with a pneumatic linear diaphragm actuator, an electric valve positioner, and an air filter pressure reducing valve, a complete control process from air source processing and signal control to mechanical action is achieved. The air filter pressure reducing valve enhances the reliability and stability of the air source, effectively filtering impurities and moisture from compressed air while stabilizing the air pressure within the set range. This ensures smooth operation of the actuator and prevents valve malfunction or slow response due to unclean air or pressure fluctuations. The electric valve positioner can automatically adjust and correct the valve position in real time, significantly improving the system's dynamic control capabilities. This avoids the error accumulation and response lag problems that easily occur in traditional open-loop control, thereby effectively improving the response speed and control accuracy of valve regulation. The electric valve positioner enables precise adjustment of fluid parameters, giving the valve the characteristics of fast response and high adjustment accuracy, making it suitable for fluid control in various industrial automation systems.

[0020] 2. By installing metal spiral wound gaskets at various sealing points related to the valve and V-type packing assemblies around the valve stem, the excellent elasticity and sealing performance of the metal spiral wound gaskets effectively prevent fluid leakage from the connection between the valve seat and the valve body in high-temperature, high-pressure, and corrosive media environments. This enhances the overall sealing performance and operational reliability of the valve, extending its service life under harsh conditions. The V-type combined packing tightly fits the valve stem, preventing media leakage along the stem. The tightening action of the packing sleeve and packing plate ensures the stability of the packing assembly, guaranteeing the stable operation of the actuator. This allows the valve to maintain good sealing performance and mechanical properties even during frequent opening and closing. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of this utility model.

[0022] Figure 2 This is a partially cut-out front view structural diagram of this utility model.

[0023] Figure 3 This is a utility model Figure 2 Enlarged schematic diagram of part A in the middle.

[0024] Figure 4 This is a utility model Figure 2 Enlarged schematic diagram of section B in the middle.

[0025] Figure 5 This is a schematic diagram showing the separation of the valve cover and the bracket in this utility model.

[0026] In the diagram: 1. Valve body; 2. Valve seat; 3. Sleeve; 4. Valve stem; 5. Valve core; 6. Valve cover; 7. Adapter ring; 8. Bracket; 9. Pneumatic linear diaphragm actuator; 10. Electric valve positioner; 11. Air filter pressure reducing valve; 12. Auxiliary fixing bracket; 13. Push rod; 14. Opening nut; 15. Heavy-duty elastic cylindrical pin; 16. Packing gasket; 17. V-type combined packing; 18. Packing sleeve; 19. Packing pressure plate; 20. Metal spiral wound washer; 21. Round nut; 101. Medium inlet channel; 102. Medium outlet channel; 601. Pressure ring; 602. Stepped shaft; 801. Connecting shaft hole. Detailed Implementation

[0027] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings.

[0028] like Figures 1-4 As shown, a high-precision regulating valve includes a valve body 1, a valve seat 2, a sleeve 3, a valve stem 4, a valve core 5, a valve cover 6, a bracket 8, a pneumatic linear diaphragm actuator 9, an electric valve positioner 10, and an air filter pressure reducing valve 11. The valve seat 2 is located inside the valve body 1. The vertical through holes of the valve body 1 and the valve seat 2 connect the medium inlet channel 101 and the medium outlet channel 102 of the valve body 1. The sleeve 3 is located on the valve seat 2 and fixed inside the valve body 1. The valve cover 6 is located at the upper end of the valve body 1 and is fastened to the valve body 1 by eight sets of evenly distributed fully threaded studs and type II hexagonal nuts. The bracket 8 is connected and fixed to the valve cover 6. A linear diaphragm actuator 9 is fixed to the bracket 8. An air filter pressure reducing valve 11 is fixed to the side of the bracket 8. An electric valve positioner 10 is fixed to the side of the bracket 8 via an auxiliary fixing bracket 12. The air filter pressure reducing valve 11 is connected to the electric valve positioner 10, which in turn is connected to the pneumatic linear diaphragm actuator 9. The push rod 13 of the pneumatic linear diaphragm actuator 9 is connected to the valve stem 4 via a split nut 14. The lower end of the valve stem 4 is connected to the valve core 5 via a heavy-duty elastic cylindrical pin 15. The valve core 5 is located inside the sleeve 3. The lower part of the valve core 5 is sealed to the vertical through hole in the middle of the valve seat 2 via a 45-degree wedge structure. Sealing rings are installed at all sealing positions where the valve body 1 contacts other parts. A V-shaped packing assembly is installed between the upper end of the valve cover 6 and the outer circumference of the valve stem 4.

[0029] To achieve the V-type packing assembly structure, the V-type packing assembly, from bottom to top, includes a packing pad 16, a V-type combined packing 17, a packing sleeve 18, and a packing pressure plate 19. The packing pad 16 and the V-type combined packing 17 are located in the packing cavity of the valve cover 6 around the valve stem 4. The lower part of the packing sleeve 18 is embedded in the packing cavity of the valve cover 6 and presses the V-type combined packing 17 tightly. The packing pressure plate 19 presses the packing sleeve 18 tightly and is secured to the upper end face of the valve cover 6 by two sets of symmetrically arranged fully threaded studs and type II hexagonal nuts. The V-type combined packing can tightly fit the valve stem 4, preventing the medium from leaking along the valve stem 4. The fastening effect of the packing sleeve 18 and the packing pressure plate 19 ensures the stability of the packing assembly, guarantees the stable operation of the actuator, and allows the valve to maintain good sealing effect and mechanical performance even during frequent opening and closing. In this embodiment, the V-type combined packing is made of polytetrafluoroethylene and carbon fiber reinforced material composite.

[0030] During operation, external control systems such as DCS and PLC send control signals, which the electric valve positioner 10 receives in real time. The electric valve positioner 10 converts the electrical signal into a corresponding mechanical opening command. At the same time, it forms a closed-loop control circuit with the valve position feedback sensor, receives the feedback signal of the actual position of the valve core 5, compares the difference between the command and the actual position, and provides a basis for subsequent precise adjustment.

[0031] Compressed air enters the air filter and pressure reducing valve 11 as a power source, where it is purified and pressure stabilized. On the one hand, it filters out impurities and moisture from the compressed air, preventing these substances from affecting the normal operation of pneumatic components; on the other hand, it stabilizes the air pressure within a set range, ensuring a stable air supply. The treated air is then delivered to the electric valve positioner 10, providing power for its subsequent actions.

[0032] The electric valve positioner 10 adjusts the air circuit opening based on the received control and feedback signals, and outputs the regulated air pressure to the pneumatic linear diaphragm actuator 9. The diaphragm inside the pneumatic linear diaphragm actuator 9 is displaced under air pressure, pushing the push rod 13 to move linearly. Since the push rod 13 is tightly connected to the valve stem 4 via the opening and closing nut 14, the movement of the push rod 13 can drive the valve stem 4 to move up and down synchronously.

[0033] The valve stem 4 is connected to the valve core 5. The up-and-down movement of the valve stem 4 drives the valve core 5 to move axially within the sleeve 3. The valve core 5 and the valve seat 2 are fitted with a 45° wedge angle structure. When the valve stem 4 moves upward, the valve core 5 gradually disengages from the sealing surface of the valve seat 2 under the action of the wedge angle, the valve opens, and fluid begins to flow. As the height of the valve core 5 changes, the size of the flow channel changes, thereby regulating the flow rate. When the valve stem 4 moves downward, the valve core 5 gradually presses against the sealing surface of the valve seat 2 under the action of the wedge angle, ultimately forming a reliable seal and cutting off the fluid passage.

[0034] The built-in self-diagnostic module of the electric valve positioner 10 monitors the signal status in real time. Once an abnormal signal such as control signal interruption or excessive feedback signal deviation is detected, an early warning is immediately issued. At the same time, the closed-loop control circuit automatically adjusts and corrects the valve position in real time based on the feedback signal, continuously optimizing the position of the valve core 5 to ensure valve adjustment accuracy and keep the valve in optimal working condition, meeting the needs of industrial automation systems for precise control of fluid parameters.

[0035] This regulating valve, through the coordinated operation of a pneumatic linear diaphragm actuator 9, an electric valve positioner 10, and an air filter pressure reducing valve 11, achieves a complete control process from air source processing and signal control to mechanical action. The air filter pressure reducing valve 11 enhances air source reliability and stability, effectively filtering impurities and moisture from compressed air while stabilizing the air pressure within the set range. This ensures smooth actuator operation and prevents valve malfunction or delayed response due to unclean air or pressure fluctuations. The electric valve positioner 10 receives control signals in real time and possesses closed-loop feedback regulation capabilities, forming a closed-loop control loop with sensor signals. This allows for automatic real-time adjustment and correction of the valve position, significantly improving the system's dynamic control capabilities. It avoids the error accumulation and response lag problems common in traditional open-loop control, converting these errors into corresponding mechanical opening actions. This effectively improves the valve's response speed and control accuracy, meeting the needs of high-precision fluid control systems. The electric valve positioner 10 enables precise adjustment of fluid parameters, giving the valve fast response and high regulation accuracy, making it suitable for fluid control in various industrial automation systems.

[0036] Example 2

[0037] Unlike the above embodiment, as Figure 4 As shown, an adapter ring 7 is provided on the upper part of the sleeve 3. The adapter ring 7 presses against the outer peripheral step of the upper end of the sleeve 3, and the lower end of the valve cover 6 presses against the upper end of the valve body 1 and the adapter ring 7. By providing an adapter ring 7 on the upper part of the sleeve 3, the valve cover 6 does not need to extend downward into the valve body 1, which reduces the coaxiality requirement of the valve cover 6 assembly and makes assembly easier.

[0038] A metal spiral wound gasket 20 is provided between the adapter ring 7 and the upper outer peripheral step of the sleeve 3. An annular groove is provided on the inner side of the upper end of the valve body 1 and adjacent to the outer side of the adapter ring 7, and a metal spiral wound gasket 20 is provided within the annular groove. A downwardly protruding pressure ring 601 is provided at the lower end of the valve cover 6, pressing the metal spiral wound gasket within the annular groove. The inner side of the lower end of the valve cover 6 mates with the outer side of the upper end of the adapter ring 7. A metal spiral wound gasket 20 is provided between the bottom outer periphery of the valve seat 2 and the valve body 1. By providing metal spiral wound gaskets 20 at various sealing positions, compared to ordinary sealing rings, their elasticity and sealing performance are better adapted to high-temperature, high-pressure, and corrosive media working environments, effectively preventing fluid leakage from various connection points, enhancing the overall sealing performance and operational reliability of the valve, and extending the valve's service life under harsh conditions. In this embodiment, the metal spiral wound gasket has an alternating winding structure of stainless steel strip and flexible graphite layer.

[0039] To reduce assembly difficulty, a 4mm gap exists between the lower end face and the upper end face of the valve cover 6 located outside the pressure ring 601. This gap reduces the area of ​​the assembly composite surface, lowering the assembly difficulty. Furthermore, it provides a buffer space for deformation of the valve cover 6 due to temperature changes and other factors during operation, preventing excessive stress between the valve cover 6 and other components due to thermal expansion and contraction, thus preventing component damage. Simultaneously, it helps maintain the valve's sealing performance, ensuring normal operation of the valve under different temperature conditions.

[0040] Example 3

[0041] Unlike Embodiment 1 or 2 above, as Figure 1 , Figure 3 , Figure 5 As shown, the upper end of the valve cover 6 has a stepped shaft portion 602, and the lower end of the bracket 8 has a connecting shaft hole portion 801. The connecting shaft hole portion 801 at the lower end of the bracket 8 mates with the stepped shaft portion 602. The upper middle part of the stepped shaft portion 602 has external threads. After the connecting shaft hole portion 801 at the lower end of the bracket 8 is inserted downwards into the stepped shaft portion 602, the upper end of the stepped shaft portion 602 is screwed into the round nut 21 for fastening. The valve cover 6 and the bracket 8 are connected by the stepped shaft portion 602, the connecting shaft hole portion 801, and the round nut 21, achieving a stable installation of the bracket 8 and the valve cover 6. Compared with the traditional method of fixing with multiple bolts, this connection structure is easier to install and disassemble, ensuring the stability of the bracket 8 during valve operation. This allows components such as the pneumatic linear diaphragm actuator 9 to be reliably installed on the bracket 8 and function normally, providing a stable support structure for precise valve control.

[0042] The high-precision regulating valve shown above is a specific embodiment of this utility model, which has demonstrated the substantial features and progress of this utility model. According to actual use needs, equivalent modifications in shape, structure, etc. can be made to it under the guidance of this utility model, all of which are within the protection scope of this solution.

Claims

1. A high-precision regulating valve, characterized by: The utility model discloses a valve body, valve seat, sleeve, valve stem, valve core, valve cover, support, pneumatic straight stroke diaphragm actuator, electrical valve positioner and air filter pressure reducing valve, the valve seat is located in the valve body, the sleeve is located on the valve seat top and is fixed in the valve body, the valve cover is located on the valve body upper end, the support is located on the valve cover top, the pneumatic straight stroke diaphragm actuator is located on the support top, the electrical valve positioner is fixed to the support side, the air filter pressure reducing valve is fixed to the support side, the air filter pressure reducing valve is connected with the electrical valve positioner, the electrical valve positioner is connected with the pneumatic straight stroke diaphragm actuator, the push rod of pneumatic straight stroke diaphragm actuator is connected with the valve stem through open and close nut, the valve stem lower end is connected with the valve core, and the valve core is located in the sleeve, and the valve core lower part is matched with the vertical through hole of the valve seat middle through wedge angle structure.

2. A high precision control valve according to claim 1, characterized in that: The bottom outer periphery of the valve seat and the valve body are provided with a metal winding gasket.

3. A high precision control valve according to claim 2, characterized in that: The upper surface of the sleeve is provided with an adapter ring, which presses the outer peripheral step of the upper end of the sleeve, and the lower end of the valve cover is pressed against the upper end of the valve body and the adapter ring.

4. A high precision control valve according to claim 3, characterized in that: A metal winding gasket is arranged between the adapter ring and the outer peripheral step of the upper end of the sleeve.

5. A high accuracy control valve according to claim 4, characterised in that: The inner side of the upper end of the valve body and the adjacent area of the outer side of the adapter ring are provided with an annular groove, and a metal winding gasket is arranged in the annular groove.

6. A high precision control valve according to claim 5, characterised in that: The lower end of the valve cover has a downwardly protruding compression ring portion, which compresses the metal winding gasket in the annular groove.

7. A high precision control valve according to claim 6, characterised in that: The lower end surface of the valve cover outside the compression ring portion and the upper end surface of the valve cover have a gap of 3-5 mm therebetween.

8. A high precision control valve according to claim 7, characterised in that: The upper end of the valve cover is provided with a V-shaped packing assembly, which is located around the valve stem, and the V-shaped packing assembly sequentially includes a packing pad, a V-shaped combined packing, a packing pressing sleeve and a packing pressing plate from bottom to top. The upper end of the valve cover is provided with a stepped shaft portion, the lower end of the support is provided with a connecting shaft hole portion, the connecting shaft hole portion of the lower end of the support is matched with the stepped shaft portion, the middle upper portion of the stepped shaft portion is provided with an external thread, and after the connecting shaft hole portion of the lower end of the support is sleeved into the stepped shaft portion, the upper end of the stepped shaft portion is screwed into a circular nut for fastening.

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