A box-type substation

Abstract

The utility model relates to the field of new energy power generation, especially a box type substation. The box type substation comprises a container, the container is equipped with a medium voltage chamber and an arc discharge assembly, a medium voltage cabinet is arranged in the medium voltage chamber; the arc discharge assembly comprises an arc discharge channel, a buffer chamber and a pressure relief device, the arc discharge channel extends along the height direction, the arc discharge channel has an input port and an output port, the output port is higher than the input port, the input port is communicated with the inside of the medium voltage cabinet, and the output port is communicated with the buffer chamber; the buffer chamber is arranged at the top of the container. When the medium voltage cabinet has an arc fault, arc products and high-temperature and high-pressure gas are guided by the arc discharge channel to the buffer chamber at the top of the container outside the medium voltage cabinet, the high-temperature and high-pressure gas diffuses to the surroundings when entering the buffer chamber from the arc discharge channel, the flow rate of the gas can be reduced, the pressure peak value is buffered, and the impact force of the arc products and the high-temperature and high-pressure gas on the pressure relief device and the external environment is reduced.

Description

Technical Field

[0001] This utility model relates to the field of new energy power generation, and in particular to a box-type substation. Background Technology

[0002] In new energy power generation systems, prefabricated substations integrate low-voltage switchgear, transformers, medium-voltage switchgear, and auxiliary power supplies into a single steel-structured container, providing a highly integrated power distribution solution for medium-voltage grid-connected scenarios in new energy power generation systems. When a short-circuit fault occurs inside the medium-voltage switchgear of a prefabricated substation, it generates enormous electric arc energy. The electric arc rapidly heats the surrounding air in a very short time, causing a sudden increase in internal pressure. To prevent the equipment from exploding due to internal overpressure, endangering personal safety and surrounding equipment, the traditional solution is to use a downward pressure relief method, adding an arc relief chamber to the foundation structure, which increases construction costs and prolongs construction time. Therefore, some existing prefabricated substations involve independent pressure relief channels and devices to safely guide and release high-temperature, high-pressure gas and arc products to the external environment. However, simply guiding pressure through a pressure relief channel to the pressure relief device for release to the external environment results in a large impact on the device and the external environment, posing a safety threat to nearby personnel and equipment. Utility Model Content

[0003] The main purpose of this utility model is to provide a prefabricated substation that aims to reduce the impact of electric arc products and high-temperature, high-pressure gases on the pressure relief device and the external environment.

[0004] To achieve the above objectives, this utility model proposes a prefabricated substation, which includes a container, a medium-voltage chamber and an arc-venting assembly, a medium-voltage switchgear inside the medium-voltage chamber, and the arc-venting assembly located outside the medium-voltage switchgear.

[0005] The arc venting assembly includes an arc venting channel, a buffer chamber, and a pressure relief device. The arc venting channel extends along the height direction and has an input port and an output port. The output port is higher than the input port. The input port is connected to the interior of the medium-pressure cabinet, and the output port is connected to the buffer chamber. The buffer chamber is located near the top of the container and has a pressure relief port located outside the medium-pressure chamber. The pressure relief device is located at the pressure relief port.

[0006] In the aforementioned prefabricated substation, the buffer chamber is provided with a buffer layer, which is composed of several sheet-like first energy absorption elements spliced ​​together, and each first energy absorption element is provided with multiple first through holes.

[0007] In the aforementioned prefabricated substation, two adjacent first energy absorption elements are arranged in a V-shape.

[0008] In the aforementioned prefabricated substation, the medium-voltage room is equipped with a cabinet base, and the medium-voltage cabinet is mounted on the cabinet base; the cabinet base is equipped with an arc-venting chamber, which is connected to the interior of the medium-voltage cabinet and the input port respectively.

[0009] In the aforementioned prefabricated substation, the input port is located on the side wall of the arc venting channel. The arc venting channel is provided with an arc guiding structure at the input port. The arc guiding structure includes several guide plates, which are spaced apart.

[0010] In a longitudinal section along the orientation direction of the input port, each guide vane has a first guide portion, a second guide portion, and a third guide portion. The first guide portion is perpendicular to the plane where the input port is located. The second guide portion connects the first guide portion and the third guide portion. The third guide portion is higher than the first guide portion and is parallel to the plane where the input port is located.

[0011] In the aforementioned box-type substation, the arc venting channel has a first sidewall and a second sidewall facing each other. The first sidewall is provided with a plurality of sheet-like second energy absorption elements. The plurality of second energy absorption elements are spaced apart along the height direction. The second energy absorption elements are inclined relative to the first sidewall. The bottom edge of the second energy absorption element is connected to the first sidewall. The top edge of the second energy absorption element is close to the middle of the arc venting channel.

[0012] The second sidewall is provided with a plurality of sheet-like third energy absorption elements, which are spaced apart along the height direction. The third energy absorption elements are inclined relative to the second sidewall, the bottom edge of the third energy absorption elements is connected to the second sidewall, and the top edge of the third energy absorption elements is close to the middle of the arc venting channel.

[0013] The second energy absorption element and the third energy absorption element are staggered in the height direction; both the second energy absorption element and the third energy absorption element are provided with multiple second through holes.

[0014] In the aforementioned prefabricated substation, both the arc venting channel and the buffer chamber are located within the medium-pressure chamber. The top of the buffer chamber extends at least partially to the outer top of the container, and the pressure relief port is located at the top of the buffer chamber.

[0015] In the aforementioned prefabricated substation, both the arc venting channel and the buffer chamber are located outside the medium-pressure chamber.

[0016] In the aforementioned prefabricated substation, the pressure relief port is positioned with its opening facing upwards or tilted upwards.

[0017] In the aforementioned prefabricated substation, the pressure relief port is provided with a surrounding edge, and the pressure relief device includes a cover plate and several connecting components. Each connecting component includes a connecting rod and a spring. The connecting component has a smooth rod portion and a boss portion. The boss portion is located at one end of the smooth rod portion, and the other end of the smooth rod portion passes through the surrounding edge and is fixedly connected to the cover plate. The spring is sleeved on the smooth rod portion, with one end of the spring abutting against the boss portion and the other end of the spring abutting against the surrounding edge.

[0018] The technical solution provided by this utility model can include the following beneficial effects:

[0019] The prefabricated substation provided in this embodiment guides the arc products and high-temperature, high-pressure gas upwards to the open space above through an independent arc-venting channel, buffer chamber, and pressure relief device. This eliminates the need for additional arc-venting space on the foundation structure, thus eliminating the dependence of the pressure relief function on the foundation structure. The foundation structure only needs to meet the load-bearing requirements, significantly reducing the difficulty, cost, and time of foundation construction, and greatly improving the applicability of prefabricated substations in complex terrain, geological conditions, and rapid deployment scenarios.

[0020] When an arcing failure occurs in the intermediate pressure cabinet, the arc products and high-temperature, high-pressure gas are guided through the arc-venting channel to a buffer chamber located outside the intermediate pressure cabinet and at the top of the container. As the high-temperature, high-pressure gas enters the buffer chamber through the arc-venting channel, it diffuses outwards, reducing the gas flow rate, buffering the pressure peak, and minimizing the impact of the arc products and high-temperature, high-pressure gas on the pressure relief device and the external environment. When the pressure in the buffer chamber exceeds the threshold, the pressure relief device automatically opens the pressure relief port, thereby discharging the arc products and high-temperature, high-pressure gas. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 This is a cross-sectional structural diagram of the prefabricated substation of this utility model;

[0023] Figure 2 This is a cross-sectional structural diagram of the medium-pressure chamber of this utility model;

[0024] Figure 3 This is a schematic diagram of the internal structure of the arc-extinguishing assembly of this utility model;

[0025] Figure 4 for Figure 2An enlarged structural diagram of region A in the embodiment;

[0026] Figure 5 for Figure 2 An enlarged structural diagram of region B in the embodiment;

[0027] Figure 6 This is a cross-sectional structural diagram of a prefabricated substation according to another embodiment of the present invention.

[0028] In the attached diagram: 1-Container, 2-Medium-pressure chamber, 21-Medium-pressure cabinet, 22-Cabinet base, 221-Arc venting chamber, 3-Arc venting assembly, 31-Arc venting channel, 311-Input port, 312-Output port, 313-First sidewall, 314-Second sidewall, 315-Second energy absorption element, 316-Third energy absorption element, 317-Second through hole, 318-Side enclosure, 32-Buffer chamber, 321-Arc venting... Pressure port, 322-buffer layer, 3221-first energy absorption element, 3222-first through hole, 33-pressure relief device, 331-cover plate, 332-connecting assembly, 3321-connecting rod, 3322-spring, 3323-smooth rod part, 3324-bore part, 34-arc guiding structure, 341-guide plate, 3411-first guide part, 3412-second guide part, 3413-third guide part. Detailed Implementation

[0029] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0030] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0031] In this utility model, unless otherwise explicitly specified and limited, the terms "connection," "fixing," etc., should be interpreted broadly. For example, "fixing" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0032] Furthermore, in this utility model, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the word "and / or" throughout the text means including three parallel solutions; taking "A and / or B" as an example, it includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0033] The following is combined Figures 1 to 6 This invention describes a prefabricated substation according to an embodiment of the present invention. The prefabricated substation includes a container 1, which has a medium-voltage chamber 2 and an arc-venting assembly 3. The medium-voltage chamber 2 contains a medium-voltage cabinet 21, and the arc-venting assembly 3 is located outside the medium-voltage cabinet 21. The arc-venting assembly 3 includes an arc-venting channel 31, a buffer chamber 32, and a pressure relief device 33. The arc-venting channel 31 extends along the height direction and has an input port 311 and an output port 312. The output port 312 is higher than the input port 311. The input port 311 is connected to the interior of the medium-voltage cabinet 21, and the output port 312 is connected to the buffer chamber 32. The buffer chamber 32 is located near the top of the container 1 and has a pressure relief port 321 located outside the medium-voltage chamber 2. The pressure relief device 33 is located at the pressure relief port 321.

[0034] The prefabricated substation provided in this embodiment guides the arc products and high-temperature, high-pressure gas upwards to the open space above through an independent arc-venting channel 31, buffer chamber 32, and pressure relief device 33. This eliminates the need for additional arc-venting space on the foundation structure, thus eliminating the dependence of the pressure relief function on the foundation structure. The foundation structure only needs to meet the load-bearing requirements, significantly reducing the difficulty, cost, and time of foundation construction, and greatly improving the applicability of prefabricated substations in complex terrain, geological conditions, and rapid deployment scenarios.

[0035] When an arcing failure occurs in the intermediate pressure cabinet 21, the arc products and high-temperature, high-pressure gas are guided through the arc venting channel 31 to the buffer chamber 32 located outside the intermediate pressure cabinet 21 and at the top of the container 1. As the high-temperature, high-pressure gas enters the buffer chamber 32 from the arc venting channel 31, it diffuses outwards, reducing the gas velocity, buffering pressure peaks, and minimizing the impact of the arc products and high-temperature, high-pressure gas on the pressure relief device 33 and the external environment. When the pressure in the buffer chamber 32 exceeds a threshold, the pressure relief device 33 automatically opens the pressure relief port 321, thereby discharging the arc products and high-temperature, high-pressure gas.

[0036] In a specific embodiment of this example, both the arc-venting channel 31 and the buffer chamber 32 are spaces enclosed by plates and have boundaries. The internal space of the buffer chamber 32 is sufficiently large, and the cross-section of the buffer chamber 32 is larger than that of the arc-venting channel 31. This allows the arc products and high-temperature, high-pressure gases entering from the arc-venting channel 31 to expand, thereby reducing the gas flow rate and buffering pressure peaks. For example, as... Figure 1 As shown, the arc venting channel 31 is a channel with a rectangular longitudinal section, and the buffer chamber 32 also has a rectangular longitudinal section.

[0037] Optionally, the buffer chamber 32 is provided with a buffer layer 322, which is composed of a plurality of sheet-like first energy absorption elements 3221 spliced ​​together, and each first energy absorption element 3221 is provided with a plurality of first through holes 3222. Figure 3 As shown, in this embodiment, after the high-temperature and high-pressure gas enters the buffer chamber 32, it passes through multiple first through holes 3222 to pass through the buffer layer 322, and then exits from the pressure relief port 321. The buffer layer 322 introduces a certain flow resistance, reducing the flow velocity of the high-temperature and high-pressure gas. Simultaneously, the first energy absorption element 3221 can absorb some of the impact energy, weakening the kinetic energy of the high-temperature and high-pressure gas, achieving a buffering effect, thereby reducing the impact force of arc products and high-temperature and high-pressure gas on the pressure relief device 33 and the external environment. For example, the first energy absorption element 3221 can be a damping plate; the high-temperature and high-pressure gas pushes the damping plate inward to absorb energy, thus absorbing and dissipating some of the impact energy. Preferably, as... Figure 3 As shown, the buffer layer 322 can also be configured with multiple layers.

[0038] Optionally, two adjacent first energy absorption elements 3221 are arranged in a V-shape. This increases the contact area between the buffer layer 322 and the high-temperature, high-pressure gas, which is beneficial for the first energy absorption elements 3221 to absorb and consume the energy of the high-temperature, high-pressure gas.

[0039] Optionally, the medium-pressure chamber 2 is provided with a cabinet base 22, and the medium-pressure cabinet 21 is mounted on the cabinet base 22. The cabinet base 22 is provided with an arc-venting chamber 221, which is connected to the interior of the medium-pressure cabinet 21 and the input port 311. In this embodiment, when an arcing failure occurs in the medium-pressure cabinet 21, the arc products and high-temperature, high-pressure gas are released from the medium-pressure cabinet 21 downwards into the arc-venting chamber 221 of the cabinet base 22, then through the arc-venting channel 31 into the buffer chamber 32, and finally discharged through the pressure relief port 321. Increasing the arc-venting chamber 221 increases the arc-venting space, thereby better cooling the arc. In a specific embodiment, the top of the cabinet base 22 and the top of the medium-pressure cabinet 21 can be provided with a connecting opening. The cabinet base 22 has an opening on its side wall near the arc-venting channel 31 corresponding to the input port 311, thereby enabling the arc-venting chamber 221 to be connected to the interior of the medium-pressure cabinet 21 and the input port 311.

[0040] Optionally, the input port 311 is disposed on the side wall of the arc-venting channel 31, and the top of the arc-venting channel 31 is disposed on the output port 312, which is connected to the buffer chamber 32 located above. The arc-venting channel 31 is provided with an arc guiding structure 34 at the input port 311. The arc guiding structure 34 includes a plurality of guide plates 341, which are spaced apart. In a longitudinal section along the orientation direction of the input port 311, each guide plate 341 has a first guide portion 3411, a second guide portion 3412, and a third guide portion 3413. The first guide portion 3411 is perpendicular to the plane where the input port 311 is located. The second guide portion 3412 connects the first guide portion 3411 and the third guide portion 3413. The third guide portion 3413 is higher than the first guide portion 3411 and is parallel to the plane where the input port 311 is located. In this embodiment, an arc guiding structure 34 is formed by setting multiple guide plates 341 near the input port 311 in the arc venting channel 31. This guides the arc products and high-temperature, high-pressure gas along a predetermined upward path, facilitating their introduction into the arc venting channel 31 for discharge. For example, as shown... Figure 3 and Figure 5 As shown, the guide plate 341 can be a plate that is bent twice to form the first guide part 3411, the second guide part 3412 and the third guide part 3413, thereby guiding the arc products and high temperature and high pressure gas to be discharged upward.

[0041] Optionally, the arc-venting channel 31 has opposing first sidewalls 313 and second sidewalls 314. The first sidewall 313 is provided with a plurality of sheet-like second energy-absorbing elements 315, which are spaced apart along the height direction. The second energy-absorbing elements 315 are inclined relative to the first sidewall 313, with their bottom edges connected to the first sidewall 313 and their top edges close to the middle of the arc-venting channel 31. The second sidewall 314 is provided with a plurality of sheet-like third energy-absorbing elements. Absorption element 316, a plurality of third energy absorption elements 316 are spaced apart along the height direction, the third energy absorption elements 316 are inclined relative to the second sidewall 314, the bottom edge of the third energy absorption element 316 is connected to the second sidewall 314, and the top edge of the third energy absorption element 316 is close to the middle of the arc venting channel 31; the second energy absorption element 315 and the third energy absorption element 316 are staggered in the height direction; both the second energy absorption element 315 and the third energy absorption element 316 are provided with a plurality of second through holes 317.

[0042] In this embodiment, the arc products and high-temperature, high-pressure gas entering the arc venting channel 31 pass sequentially from top to bottom through the inclined upward second energy absorption element 315 and third energy absorption element 316. The second and third energy absorption elements 315 and 316 absorb some energy, causing the energy to attenuate layer by layer, thus providing a certain buffering effect. The second through-hole 317 reduces turbulence. By setting the second energy absorption element 315 and third energy absorption element 316 in the arc venting channel 31, initial attenuation of the arc energy is achieved. For example, both the second and third energy absorption elements 315 and 316 can be damping sheets.

[0043] Optionally, both the arc-venting channel 31 and the buffer chamber 32 are disposed within the intermediate-pressure chamber 2, with the top of the buffer chamber 32 extending at least partially to the outer top of the container 1, and the pressure relief port 321 disposed at the top of the buffer chamber 32. This allows the arc-venting channel 31 and the buffer chamber 32 to be disposed within the intermediate-pressure chamber 2 while the pressure relief port 321 can be disposed outside the intermediate-pressure chamber 2.

[0044] Optionally, both the arc-venting channel 31 and the buffer chamber 32 are located outside the intermediate-pressure chamber 2. For example... Figure 6 As shown, by placing the arc venting channel 31 and the buffer chamber 32 outside the medium-pressure chamber 2, the medium-pressure chamber 2 has more space to arrange electrical cabinets or electrical components.

[0045] Optionally, the pressure relief port 321 is configured with its opening facing upwards or tilted upwards. This allows the arc products and high-temperature, high-pressure gases to be discharged upwards or tilted upwards into a wide space, reducing the threat to surrounding personnel and equipment.

[0046] Optionally, such as Figure 4 As shown, the pressure relief port 321 is provided with a surrounding edge 318. The pressure relief device 33 includes a cover plate 331 and several connecting components 332. Each connecting component 332 includes a connecting rod 3321 and a spring 3322. The connecting component has a smooth rod portion 3323 and a boss portion 3324. The boss portion 3324 is disposed at one end of the smooth rod portion 3323, and the other end of the smooth rod portion 3323 passes through the surrounding edge 318 and is fixedly connected to the cover plate 331. The spring 3322 is sleeved on the smooth rod portion 3323, with one end of the spring 3322 abutting against the boss portion 3324 and the other end of the spring 3322 abutting against the surrounding edge 318. Thus, when the pressure in the buffer chamber 32 exceeds a preset value, the cover plate 331 is lifted, thereby opening the pressure relief port 321. At this time, the spring 3322 is in a compressed state. When the pressure in the buffer chamber 32 returns to normal, the spring 3322 releases its elastic force, causing the cover plate 331 to close the pressure relief port 321, thus preventing rainwater and animals from entering the buffer chamber 32. Of course, in other embodiments, the pressure relief device 33 can also be a mechanical flap, a pressure relief valve, etc.

[0047] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. All equivalent structural transformations made under the concept of the present utility model and using the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present utility model.

Claims

1. A prefabricated substation, characterized in that: The prefabricated substation includes a container, the container is equipped with a medium-voltage chamber and an arc-extinguishing assembly, the medium-voltage chamber is equipped with a medium-voltage switchgear, and the arc-extinguishing assembly is located outside the medium-voltage switchgear; The arc venting assembly includes an arc venting channel, a buffer chamber, and a pressure relief device. The arc venting channel extends along the height direction and has an input port and an output port. The output port is higher than the input port. The input port is connected to the interior of the medium-pressure cabinet, and the output port is connected to the buffer chamber. The buffer chamber is located near the top of the container and has a pressure relief port located outside the medium-pressure chamber. The pressure relief device is located at the pressure relief port.

2. A prefabricated substation according to claim 1, characterized in that: The buffer chamber is provided with a buffer layer, which is composed of several sheet-shaped first energy absorption elements spliced ​​together, and each first energy absorption element is provided with multiple first through holes.

3. A prefabricated substation according to claim 2, characterized in that: The two adjacent first energy absorption elements are arranged in a V-shape.

4. A prefabricated substation according to claim 1, characterized in that: The medium-pressure chamber is equipped with a cabinet base, and the medium-pressure cabinet is mounted on the cabinet base; the cabinet base is equipped with an arc-venting chamber, which is connected to the interior of the medium-pressure cabinet and the input port respectively.

5. A prefabricated substation according to claim 4, characterized in that: The input port is located on the side wall of the arc venting channel. The arc venting channel has an arc guiding structure at the input port. The arc guiding structure includes a plurality of guide plates, which are spaced apart from each other. In a longitudinal section along the orientation direction of the input port, each guide vane has a first guide portion, a second guide portion, and a third guide portion. The first guide portion is perpendicular to the plane where the input port is located. The second guide portion connects the first guide portion and the third guide portion. The third guide portion is higher than the first guide portion and is parallel to the plane where the input port is located.

6. A prefabricated substation according to claim 1, characterized in that: The arc-venting channel has a first sidewall and a second sidewall with opposite sides. The first sidewall is provided with a plurality of sheet-like second energy-absorbing elements. The plurality of second energy-absorbing elements are spaced apart along the height direction. The second energy-absorbing elements are inclined relative to the first sidewall. The bottom edge of the second energy-absorbing element is connected to the first sidewall. The top edge of the second energy-absorbing element is close to the middle of the arc-venting channel. The second sidewall is provided with a plurality of sheet-like third energy absorption elements, which are spaced apart along the height direction. The third energy absorption elements are inclined relative to the second sidewall, the bottom edge of the third energy absorption elements is connected to the second sidewall, and the top edge of the third energy absorption elements is close to the middle of the arc venting channel. The second energy absorption element and the third energy absorption element are staggered in the height direction; both the second energy absorption element and the third energy absorption element are provided with multiple second through holes.

7. A prefabricated substation according to claim 1, characterized in that: Both the arc relief channel and the buffer chamber are located within the medium-pressure chamber. The top of the buffer chamber extends at least partially to the outer top of the container, and the pressure relief port is located at the top of the buffer chamber.

8. A prefabricated substation according to claim 1, characterized in that: Both the arc-venting channel and the buffer chamber are located outside the medium-pressure chamber.

9. A prefabricated substation according to claim 1, characterized in that: The pressure relief port is positioned with its opening facing upwards or tilted upwards.

10. A prefabricated substation according to claim 1, characterized in that: The pressure relief port is provided with a surrounding edge. The pressure relief device includes a cover plate and several connecting components. Each connecting component includes a connecting rod and a spring. The connecting rod has a smooth rod portion and a boss portion. The boss portion is located at one end of the smooth rod portion. The other end of the smooth rod portion passes through the surrounding edge and is fixedly connected to the cover plate. The spring is sleeved on the smooth rod portion. One end of the spring abuts against the boss portion, and the other end of the spring abuts against the surrounding edge.

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