A wind load pressure sensor

Abstract

This application relates to the field of wind load technology for building surfaces, and discloses a wind load pressure sensor, comprising a housing, a mounting base, and an electrical protective cover fixed to the mounting base. A pressure-sensitive element is mounted on the top of the electrical protective cover, and a signal amplification circuit is connected to the bottom of the pressure-sensitive element. A signal wire fixing connector is connected to the bottom of the signal amplification circuit, and the signal wire fixing connector penetrates the outer wall of the electrical protective cover. A waterproof and breathable plug is installed on the opening on the side of the electrical protective cover away from the signal fixing connector. The compact housing design of this application facilitates installation, improves the accuracy of wind pressure data testing, extends service life, and comprehensively protects sensor performance.

Description

Technical Field

[0001] This application relates to the field of wind load technology on building surfaces, and in particular to a wind load pressure sensor. Background Technology

[0002] A wind load pressure sensor is a sensor specifically designed to measure the pressure exerted by airflow on engineering structures; it is also known as a wind dynamic pressure sensor. The significance of studying wind loads lies in disaster prevention and mitigation. Firstly, as the wind-bearing area of ​​a building structure increases, the wind pressure becomes more uneven, and the wind load cannot be ignored. Secondly, the wide frequency range of wind loads may cause resonance and flutter in the structure. In addition, many other factors exist, making long-term monitoring of wind load pressure crucial for the safe maintenance of buildings.

[0003] The existing wind load has the following problems:

[0004] 1. The range of wind load pressure measurement is usually between -1kPa and 10kPa. Temperature drift has a great impact on the accuracy of small-range sensors. The temperature drift caused by ambient temperature to the sensor leads to a decrease in measurement accuracy.

[0005] 2. Existing wind load pressure sensors use lightning rods for lightning protection. However, the large shape of the lightning rod itself can affect the smooth flow of wind and cause inaccurate wind pressure data.

[0006] 3. Installation is inconvenient; the use of a mounting base makes on-site installation cumbersome and increases the workload.

[0007] 4. Due to its large size, it is extremely inconvenient to install in some high-speed rail stations or subway stations. Utility Model Content

[0008] To overcome the problems existing in the prior art, this application provides a wind load pressure sensor.

[0009] The wind load pressure sensor provided in this application adopts the following technical solution:

[0010] A wind load pressure sensor includes a housing, which includes a mounting base and an electrical protective cover fixed on the mounting base. A pressure-sensitive element is mounted on the top of the electrical protective cover, and a signal amplification circuit is connected to the bottom of the pressure-sensitive element. A signal wire fixing connector is connected to the bottom of the signal amplification circuit. The signal wire fixing connector penetrates the outer wall of the electrical protective cover, and a waterproof and breathable plug is installed on the opening on the side of the electrical protective cover away from the signal fixing connector.

[0011] By adopting the above technical solution, when airflow generates wind load acting on the sensor, the pressure-sensitive element located at the top of the electrical protective cover first comes into contact with the wind. As the core sensitive component, the pressure-sensitive element's internal material properties determine that it can undergo corresponding physical changes according to the magnitude of the pressure it bears, specifically manifested as a change in resistance. This change in resistance is linearly related to the magnitude of the wind load pressure applied to the pressure-sensitive element, thus converting the physical quantity of wind load pressure into an electrical signal. Next, the weak electrical signal generated by the pressure-sensitive element is transmitted to the signal amplification circuit connected to its bottom. Since the initial electrical signal is relatively weak, which is not conducive to long-distance transmission and accurate measurement, the signal amplification circuit amplifies the weak electrical signal through its internal amplification module, enhancing the signal strength and stability, so as to obtain more accurate wind load pressure information subsequently. The amplified electrical signal is transmitted through a signal cable fixing connector. The signal cable fixing connector penetrates the outer wall of the electrical protective cover; it not only serves to fix and connect the signal cable but also ensures the stability and sealing of the electrical signal during transmission, preventing interference from external environmental factors and ensuring that the signal can be accurately transmitted to subsequent data processing equipment. In terms of sensor structural design, a waterproof and breathable plug installed on the opening of the electrical protective cover away from the signal fixing connector effectively prevents external moisture from entering the sensor, allowing air to pass freely. This ensures that the pressure-sensitive element and signal amplification circuit are not affected by rainwater or condensation, and maintains communication with the atmosphere. In areas with large diurnal temperature differences, the wind load pressure sensor also features a breathable plug, preventing condensation inside. Furthermore, the sensor's housing structure, including the mounting base and electrical protective cover, simplifies the installation process compared to traditional mounting base methods. The mounting base can be directly fixed to the structure to be installed, reducing cumbersome on-site installation steps and lowering the workload. Simultaneously, its overall design optimizes the external dimensions, making it more suitable for installation in space-constrained locations such as high-speed rail stations and subway stations compared to traditional sensors.

[0012] Preferably, the top of the pressure-sensitive element is made of stainless steel corrugated membrane, and the stainless steel corrugated membrane is provided with annular steps around its perimeter, the height of which is 0.2-0.5mm.

[0013] Preferably, a gap is provided between the pressure-sensitive element and the electrical protective cover, and the gap is filled with a first sealing ring.

[0014] Preferably, the pressure-sensitive element includes an upper part and a lower part, wherein the outer diameter of the upper part is smaller than the outer diameter of the lower part, and a sealing groove for accommodating the first sealing ring is formed on the four sides of the lower part.

[0015] By adopting the above technical solution, the top of the pressure-sensitive element is a stainless steel corrugated diaphragm. The pressure-sensitive element and the electrical protective cover are fitted together with a sealing ring to ensure a sealed and waterproof seal. When installed on a building, the pressure-sensitive diaphragm will not be damaged by extreme weather such as hail, and it is protected from bird bites. The 0.2-0.5mm annular step design around the corrugated diaphragm ensures that the pressure-sensitive element protects the diaphragm during assembly. The gap between the pressure-sensitive element and the electrical protective cover is filled with a first sealing ring, and the sealing groove on the lower part of the four sides provides precise installation space for the sealing ring, ensuring that the sensor has good sealing performance in various environments and preventing external moisture, dust and other impurities from intruding and interfering with the measurement. The outer diameter design of the pressure-sensitive element, which is smaller at the top and larger at the bottom, together with the sealing ring, further enhances the installation stability and sealing reliability, enabling the pressure-sensitive element to stably convert wind load pressure into an electrical signal, which is then accurately output after processing by the signal amplification circuit, providing accurate data for wind load pressure measurement.

[0016] Preferably, the surface of the signal amplification circuit is coated with conformal coating, and the signal amplification circuit is equipped with a lightning protection circuit.

[0017] By adopting the above technical solution, the conformal coating on the surface of the signal amplification circuit forms a dense protective film, which can effectively resist the corrosion of harsh environmental factors such as salt spray, humidity, and mold, and prevent circuit components from short-circuiting, oxidizing, or other failures due to environmental influences, ensuring the long-term stable operation of the signal amplification circuit in complex environments. The built-in lightning protection circuit (which is existing technology and will not be elaborated here) can respond quickly to the instantaneous high-voltage pulse generated by lightning strikes, guiding the excessive voltage to a safe path for release through current shunting and voltage limiting, preventing irreversible damage to the signal amplification circuit from the lightning high voltage. This ensures that the amplification circuit can continuously and reliably amplify the weak electrical signal from the pressure-sensitive element, enabling stable signal transmission through the signal line, thereby ensuring that the wind load pressure sensor can still accurately measure and operate normally in harsh weather and complex environments.

[0018] Preferably, the electrical protection cover adopts a cylindrical structure, and the mounting base at the bottom of the electrical protection cover adopts a circular structure. The outer diameter of the circular structure is larger than the outer diameter of the cylindrical structure, and the portion of the circular structure located on the outer side of the cylindrical structure has mounting holes arranged in a circular array.

[0019] By adopting the above technical solution, the cylindrical electrical protective cover provides a neat and compact protective space for the internal pressure-sensitive elements, signal amplification circuits, and other core components, effectively preventing the intrusion of external debris and ensuring the normal operation of internal components. The outer diameter of the circular mounting base at the bottom is larger than that of the cylinder, and the outer part of the base has a circumferential array of mounting holes. A skirt-type three-hole mounting system is used for installation and fixation, resulting in a stable triangular structure that eliminates the need for mounting clamps and facilitates on-site drilling. The electrical protective cover and the mounting base are joined using aurora welding, which is simple, aesthetically pleasing, and robust. The mounting holes also allow for the use of bolts and other connectors to firmly install the sensor on various building structure surfaces. The circumferential array distribution of the mounting holes ensures uniform stress during installation, enhancing the stability of the sensor after installation.

[0020] Preferably, the waterproof and breathable plug includes a central expanded polytetrafluoroethylene (ePTFE) film and a surrounding mounting frame. The ePTFE film is a multi-layer composite film with decreasing pore size. The mounting frame is sealed to the inside of the opening via a second sealing ring.

[0021] Preferably, the frame of the waterproof and breathable plug adopts a two-section structure with different diameters, including a small diameter section and a large diameter section. The small diameter section is adapted to the inner diameter of the opening, and an elastic limiting ring is installed at the free end of the small diameter section. The second sealing ring is located between the elastic limiting ring and the large diameter section.

[0022] By adopting the above technical solution, the waterproof and breathable plug achieves efficient waterproofing, breathability, and stable installation through the coordinated operation of its various structures. The central multi-layer composite expanded polytetrafluoroethylene film, with its decreasing pore size design, acts like a precision filter, blocking external moisture, dust, and other impurities from entering while allowing air molecules to pass through smoothly. This ensures that the pressure-sensitive element can sense changes in external wind load pressure in real time. The surrounding mounting frame uses a two-section structure with different diameters. The smaller diameter section matches the inner diameter of the electrical protection cover opening and, together with the elastic limiting ring at the free end, can generate moderate elastic deformation during installation, easily embedding into the opening and providing a stable pre-tightening force. The larger diameter section forms a limit on the outside to prevent the sealing plug from being over-embedded. The second sealing ring around the mounting frame is located between the elastic limiting ring and the larger diameter section. Under the compression of the elastic limiting ring, it tightly fits the inner side of the opening, further enhancing the sealing performance and effectively preventing external moisture intrusion without affecting the breathability function. This ensures that the sensor can stably and accurately measure wind load pressure in complex environments.

[0023] In summary, this application includes at least one of the following beneficial technical effects:

[0024] 1. This application simplifies the installation process by using the design of the mounting base and electrical protection cover, allowing direct installation through the mounting holes on the mounting base. This reduces the cumbersome steps and workload of on-site installation and effectively solves the problem of inconvenient installation. At the same time, the compact structure also reduces the overall size, making it easier to install in places with limited space, such as high-speed rail stations and subway stations.

[0025] 2. This application uses a three-proof coating on the surface of the signal amplification circuit to effectively prevent moisture, salt spray, mold and other substances from corroding the circuit components and extend the service life of the sensor; it has an internal lightning protection circuit, which replaces the traditional lightning rod and avoids the problem that the large size of the lightning rod affects the smooth flow of wind, thus leading to inaccurate wind pressure data. At the same time, it achieves reliable lightning protection, ensuring that the sensor can work normally in severe weather and ensuring the accuracy of the measurement data.

[0026] 3. The waterproof and breathable plug in this application, through the design of a multi-layer composite membrane, a two-section frame, and an elastic limiting ring, ensures good breathability while effectively preventing external dust, moisture, and other impurities from entering the sensor, maintaining a stable internal environment, reducing the impact of environmental factors on sensor performance, ensuring measurement accuracy, and being securely installed at the opening of the electrical protection cover, further improving the sensor's waterproof and dustproof performance and ensuring stable operation of the sensor in complex environments. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of a wind load pressure sensor;

[0028] Figure 2 This is a top view of a wind load pressure sensor;

[0029] Figure 3 yes Figure 2 Sectional view of AA in the middle;

[0030] Figure 4 yes Figure 3 Enlarged view of point A in the middle.

[0031] Explanation of reference numerals in the attached drawings: 1. Housing; 11. Mounting base; 111. Mounting hole; 12. Electrical protection cover; 121. Opening; 2. Pressure-sensitive element; 21. Stainless steel corrugated membrane; 22. Annular step; 23. First sealing ring; 24. Upper part; 25. Lower part; 251. Sealing groove; 3. Signal amplification circuit; 4. Signal line fixing connector; 5. Waterproof and breathable plug; 51. Expanded polytetrafluoroethylene film; 52. Mounting frame; 53. Second sealing ring; 54. Small diameter section; 541. Elastic limiting ring; 55. Large diameter section. Detailed Implementation

[0032] The following is in conjunction with the appendix Figure 1-4This application will be described in further detail.

[0033] This application discloses a wind load pressure sensor.

[0034] Reference Figure 1 , Figure 2 , Figure 3 and Figure 4A wind load pressure sensor includes a housing 1, which includes a mounting base 11 and an electrical protective cover 12 fixed to the mounting base 11. A pressure-sensitive element 2 is mounted on the top of the electrical protective cover 12, and a signal amplification circuit 3 is connected to the bottom of the pressure-sensitive element 2. A signal wire fixing connector 4 is connected to the bottom of the signal amplification circuit 3, and the signal wire fixing connector 4 penetrates the outer wall of the electrical protective cover 12. A waterproof and breathable plug 5 is installed on the opening 121 of the electrical protective cover 12 away from the signal fixing connector. When airflow generates a wind load acting on the sensor, the pressure-sensitive element 2 at the top of the electrical protective cover 12 first comes into contact with the wind. As the core sensitive component, the internal material properties of the pressure-sensitive element 2 determine that it can undergo corresponding physical changes according to the magnitude of the pressure it bears, specifically a change in resistance. This change in resistance is linearly related to the magnitude of the wind load pressure applied to the pressure-sensitive element 2, thus converting the physical quantity of wind load pressure into an electrical signal. The weak electrical signal generated by the pressure-sensitive element 2 is then transmitted to the signal amplification circuit 3 connected to its bottom. Because the initial electrical signal is relatively weak, it is not conducive to long-distance transmission and accurate measurement. The signal amplification circuit 3 amplifies the weak electrical signal through its internal amplification module, enhancing the signal strength and stability, so as to obtain wind load pressure information more accurately. The amplified electrical signal is transmitted through the signal line fixing connector 4. The signal line fixing connector 4 penetrates the outer wall of the electrical protection cover 12. It not only serves to fix and connect the signal line, but also ensures the stability and sealing of the electrical signal during transmission, preventing external environmental factors from interfering with signal transmission, and ensuring that the signal can be accurately transmitted to the subsequent data processing equipment. In terms of the sensor's structural design, a waterproof and breathable plug 5 is installed on the opening 121 on the side of the electrical protection cover 12 away from the signal fixing connector. The waterproof and breathable plug 5 can effectively prevent external moisture from entering the sensor, allowing air to pass freely, ensuring that the pressure-sensitive element 2 and the signal amplification circuit 3 are not affected by rainwater and condensation, and maintaining communication with the atmosphere; in areas with large day-night temperature differences, the wind load pressure sensor has a breathable plug, so that condensation will not occur inside the wind load pressure sensor. Furthermore, the sensor's housing structure 1, including a mounting base 11 and an electrical protection cover 12, simplifies the installation process compared to traditional mounting base methods. The mounting base 11 can be directly fixed to the structure to be installed, reducing cumbersome on-site installation steps and lowering the workload. Simultaneously, its overall design optimizes the external dimensions, making it more suitable for installation in space-constrained locations such as high-speed rail stations and subway stations compared to traditional sensors.

[0035] Reference Figure 1 , Figure 2 and Figure 3The pressure-sensitive element 2 has a stainless steel corrugated membrane 21 at its top, and an annular step 22 with a height of 0.3 mm is provided around the stainless steel corrugated membrane 21. A gap is provided between the pressure-sensitive element 2 and the electrical protection cover 12, and the gap is filled with a first sealing ring 23. The pressure-sensitive element 2 includes an upper part 24 and a lower part 25, wherein the outer diameter of the upper part 24 is smaller than the outer diameter of the lower part 25, and a sealing groove 251 for accommodating the first sealing ring 23 is opened on the periphery of the lower part 25. The pressure-sensitive element 2 has a stainless steel corrugated membrane 21 at its top, and the pressure-sensitive element 2 is attached to the electrical protection cover 12 and has a sealing ring to ensure a sealed and waterproof seal. When installed on a building, the pressure-sensitive membrane will not be damaged by extreme weather such as hail, and it is protected from bird pecking. The design of the 0.3 mm annular step 22 around the corrugated membrane ensures that the pressure-sensitive element 2 protects the corrugated membrane during assembly. The gap between the pressure-sensitive element 2 and the electrical protective cover 12 is filled with the first sealing ring 23, and the sealing groove 251 on the four sides of the lower part 25 provides a precise installation space for the sealing ring, ensuring that the sensor has good sealing performance in various environments and preventing external moisture, dust and other impurities from intruding and interfering with the measurement. The outer diameter design of the pressure-sensitive element 2, which is smaller at the top and larger at the bottom, together with the sealing ring, further enhances the installation stability and sealing reliability, enabling the pressure-sensitive element 2 to stably convert wind load pressure into an electrical signal, which is then accurately output after being processed by the signal amplification circuit 3, providing accurate data for wind load pressure measurement.

[0036] Reference Figure 1 , Figure 2 and Figure 3 The signal amplification circuit 3 is coated with conformal coating and incorporates a lightning protection circuit. The conformal coating forms a dense protective film that effectively resists corrosion from harsh environmental factors such as salt spray, humidity, and mold, preventing short circuits and oxidation of circuit components due to environmental influences. This ensures the long-term stable operation of the signal amplification circuit 3 in complex environments. The built-in lightning protection circuit (a current technology, which will not be elaborated upon here) responds quickly to instantaneous high-voltage pulses generated by lightning strikes. It guides the excessive voltage to a safe path for release through current shunting and voltage limiting, preventing irreversible damage to the signal amplification circuit 3. This ensures the amplification circuit can continuously and reliably amplify the weak electrical signal from the pressure-sensitive element 2, allowing for stable signal transmission via the signal line. This guarantees the wind load pressure sensor can still accurately measure and operate normally in harsh weather and complex environments.

[0037] Reference Figure 1 and Figure 2The electrical protective cover 12 adopts a cylindrical structure, and the mounting base 11 at the bottom of the electrical protective cover 12 adopts a circular structure. The outer diameter of the circular structure is larger than that of the cylindrical structure, and the outer part of the circular structure has mounting holes 111 arranged in a circular array. The cylindrical electrical protective cover 12 provides a neat and compact protective space for the internal core components such as the pressure-sensitive element 2 and the signal amplification circuit 3, which can effectively prevent the intrusion of external debris and ensure the normal operation of the internal components. The outer diameter of the bottom circular mounting base 11 is larger than that of the cylinder, and the outer part of its circular array has mounting holes 111. It adopts a skirt-type three-hole hole mounting and fixing, and the triangular structure is stable, eliminating the need for mounting clamps and facilitating on-site drilling. The electrical protective cover 12 and the mounting base 11 are connected by aurora welding, which is simple, beautiful and strong. At the same time, the mounting holes 111 facilitate the use of bolts and other connecting parts to firmly install the sensor on various building structure surfaces. The circumferential array distribution of the mounting holes 111 ensures uniform force during installation and enhances the stability of the sensor after installation.

[0038] Reference Figure 2 , Figure 3 and Figure 4 The waterproof and breathable plug 5 includes a central expanded polytetrafluoroethylene (ePTFE) film 51 and a surrounding mounting frame 52. The ePTFE film 51 is a multi-layer composite film with decreasing pore sizes. The mounting frame 52 is sealed to the inside of the opening 121 via a second sealing ring 53. The frame of the waterproof and breathable plug 5 has two sections with different diameters: a small-diameter section 54 and a large-diameter section 55. The small-diameter section 54 is fitted to the inner diameter of the opening 121, and an elastic retaining ring 541 is installed at the free end of the small-diameter section. The second sealing ring 53 is located between the elastic retaining ring 541 and the large-diameter section 55. Through the coordinated operation of these structures, the waterproof and breathable plug 5 achieves efficient waterproofing and breathability while ensuring stable installation. The central multi-layer composite expanded polytetrafluoroethylene film 51, with its decreasing pore size design, acts like a precision filter, blocking external moisture, dust, and other impurities from entering while allowing air molecules to pass through smoothly. This ensures that the pressure-sensitive element 2 can sense changes in external wind load pressure in real time. The surrounding mounting frame 52 adopts a two-section structure with different diameters. The smaller diameter section 54 is adapted to the inner diameter of the opening 121 of the electrical protection cover 12. With the elastic limiting ring 541 at the free end, it can generate moderate elastic deformation during installation, easily embedding into the opening 121 and providing a stable pre-tightening force. The larger diameter section 55 forms a limit on the outside to prevent the sealing plug from being over-embedded. The second sealing ring 53 around the mounting frame 52 is located between the elastic limiting ring 541 and the larger diameter section 55. Under the compression of the elastic limiting ring 541, it fits tightly against the inside of the opening 121, further enhancing the sealing performance and effectively preventing external moisture intrusion without affecting the air permeability. This ensures that the sensor can stably and accurately measure wind load pressure in complex environments.

[0039] Working Principle: When the wind load pressure sensor is working, the stainless steel corrugated diaphragm 21 and annular step 22 at the top of the pressure-sensitive element 2 first sense the change in external wind load pressure and convert it into an electrical signal. Subsequently, the generated weak electrical signal is transmitted to the signal amplification circuit 3 at the bottom. After amplification, it is led out to external equipment through the signal cable fixing connector 4. Throughout the process, the electrical protection cover 12, the mounting base 11, and the waterproof and breathable plug 5 work together. The multi-layer composite membrane of the waterproof and breathable plug 5 maintains the internal and external air pressure balance and prevents dust. The two-section frame is tightly sealed. The structural design of the electrical protection cover 12 and the mounting base 11 not only facilitates installation but also provides physical protection for the internal components. At the same time, the conformal coating on the surface of the signal amplification circuit 3 and the internal lightning protection circuit resist environmental corrosion and lightning strikes, ensuring the stable operation of all components of the sensor and guaranteeing the accuracy of signal conversion, processing, and transmission.

[0040] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A wind load pressure sensor, characterized by: The device includes a housing (1), which includes a mounting base (11) and an electrical protective cover (12) fixed on the mounting base (11). A pressure-sensitive element (2) is installed on the top of the electrical protective cover (12), and a signal amplification circuit (3) is connected to the bottom of the pressure-sensitive element (2). A signal line fixing connector (4) is connected to the bottom of the signal amplification circuit (3). The signal line fixing connector (4) penetrates the outer wall of the electrical protective cover (12), and a waterproof and breathable plug (5) is installed on the opening (121) of the electrical protective cover (12) away from the signal fixing connector.

2. A wind load pressure sensor according to claim 1, wherein: The pressure-sensitive element (2) has a stainless steel corrugated membrane (21) at its top, and the stainless steel corrugated membrane (21) has an annular step (22) around its perimeter, with the height of the annular step (22) being 0.2-0.5 mm.

3. A wind load pressure sensor according to claim 2, wherein: A gap is provided between the pressure-sensitive element (2) and the electrical protective cover (12), and the gap is filled with a first sealing ring (23).

4. A wind load pressure sensor according to claim 3, wherein: The pressure-sensitive element (2) includes an upper part (24) and a lower part (25), wherein the outer diameter of the upper part (24) is smaller than the outer diameter of the lower part (25), and a sealing groove (251) for accommodating the first sealing ring (23) is provided on the four sides of the lower part (25).

5. A wind load pressure sensor according to claim 1, wherein: The signal amplification circuit (3) is coated with a three-proof paint, and the signal amplification circuit (3) is equipped with a lightning protection circuit.

6. A wind load pressure sensor according to claim 1, wherein: The electrical protective cover (12) adopts a cylindrical structure, and the mounting base (11) at the bottom of the electrical protective cover (12) adopts a circular structure. The outer diameter of the circular structure is larger than the outer diameter of the cylindrical structure, and the part of the circular structure located on the outside of the cylindrical structure has mounting holes (111) arranged in a circular array.

7. A wind load pressure sensor according to claim 1, wherein: The waterproof and breathable plug (5) includes a central expanded polytetrafluoroethylene film (51) and a surrounding mounting frame (52). The expanded polytetrafluoroethylene film (51) is a multi-layer composite film with decreasing pore size. The mounting frame (52) is sealed to the inside of the opening (121) by a second sealing ring (53).

8. A wind load pressure sensor according to claim 7, wherein: The waterproof and breathable plug (5) has a frame with two sections of different diameters, including a small diameter section (54) and a large diameter section (55). The small diameter section (54) is adapted to the inner diameter of the opening (121), and an elastic limiting ring (541) is installed on the free end of the small diameter section. The second sealing ring (53) is located between the elastic limiting ring (541) and the large diameter section (55).

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