An assembled power grid harmonic detection filter

Abstract

The application relates to the technical field of filters, and discloses an assembled power grid harmonic detection filter, which comprises a bottom plate, a protection mechanism and a fixing limiting mechanism are arranged above the bottom plate, the protection mechanism comprises a protective shell, the back surface of the protective shell is fixedly connected with a hinge hinge, the front surface of the hinge hinge is fixedly connected with a protective top cover, a clamping block is clamped in the protective shell, and a sliding plate is slidably connected in the protective shell. The assembled power grid harmonic detection filter is characterized in that the fixing base, the first clamping groove, the second clamping groove, the fixing frame, the threaded rod and the lower pressing plate are matched with each other, the filter installation module can be assembled conveniently, when a component in the filter fails, the entire filter needs to be overhauled on a large scale, the entire filter needs to be replaced and maintained, and the corresponding harmonic detection and filtering module cannot be added, so that the harmonic detection precision is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of filter, in particular to an assembled power grid harmonic detection filter. BACKGROUND

[0002] The filter is a filter circuit composed of capacitors, inductors and resistors. The filter can effectively filter out specific frequency points in the power line or frequencies other than the frequency points, obtain a specific frequency power signal, or eliminate a specific frequency power signal. With the continuous development of solar photovoltaic power generation and wind power generation and other new energy power generation, these new energy power generation systems will also generate harmonics when connected to the power grid.

[0003] At present, the filter device nowadays is often integrated and directly installed on the device that needs to detect harmonics. When a component in the filter fails, the entire filter needs to be overhauled and replaced, which consumes a lot of manpower and material resources, reduces the harmonic detection efficiency, and when the factory adds new large power electronic devices, new harmonic frequencies are generated, and the corresponding harmonic detection and filtering modules cannot be added, resulting in a decrease in harmonic detection accuracy. SUMMARY

[0004] The present application aims to provide an assembled power grid harmonic detection filter to solve the problems in the background art.

[0005] In order to solve the above technical problems, the present application provides the following technical scheme: an assembled power grid harmonic detection filter, comprising a bottom plate, a protection mechanism and a fixed limiting mechanism are arranged above the bottom plate respectively;

[0006] The protection mechanism comprises a protective shell, the back surface of the protective shell is fixedly connected with a hinge hinge, the front surface of the hinge hinge is fixedly connected with a protective top cover, the inside of the protective shell is clamped with a clamping block, the inside of the protective shell is slidingly connected with a sliding plate, the front surface of the sliding plate is fixedly connected with a button and a limiting column, the back surface of the sliding plate is fixedly connected with a spring, the outer surface of the limiting column is in contact with the inner wall of the clamping block, the inner wall of the protective shell is fixedly connected with two dustproof filter plates and two ventilation ducts, the inner wall of each ventilation duct is fixedly connected with two filter screen plates, and the ends of each group of filter screen plates away from each other are fixedly connected with two fan leaves;

[0007] The fixed limiting mechanism comprises a fixed base, the upper surface of the fixed base is fixedly connected with four fixed frames, the inner walls of each group of fixed frames are threadedly connected with two threaded rods, the outer surfaces of each group of threaded rods are fixedly connected with two bearings, the bottom ends of each group of bearings are fixedly connected with two pressing plates, the bottom surfaces of each group of pressing plates are fixedly connected with six limiting blocks, the upper surface of the fixed base is respectively provided with a plurality of same first clamping grooves and a plurality of same second clamping grooves, three first clamping grooves are clamped with filter installation modules, the outer surfaces of each filter installation module are fixedly connected with two fixed plates, the upper surfaces of each group of fixed plates are provided with two grooves, the inner walls of each filter installation module are fixedly connected with four capacitor element bodies, three inductor element bodies and four resistor element bodies, the outer surface of the fixed base is fixedly connected with four first connecting terminals, the outer surfaces of each filter installation module are fixedly connected with two second connecting terminals, the inner walls of each group of grooves are in contact with the outer surfaces of limiting blocks, and the outer surfaces of each group of second connecting terminals are in contact with the inner walls of second clamping grooves.

[0008] Preferably, the outer surface of the protective shell is fixedly connected with two rain shielding plates, and the mutually close sides of the two rain shielding plates are fixedly connected with the mutually away sides of the two dustproof filter plates.

[0009] Preferably, the outer surface of each rain shielding plate is fixedly connected with two support frames, and the mutually close sides of each group of support frames are fixedly connected with the outer surface of the protective shell.

[0010] Preferably, the inner walls of each group of support frames are threadedly connected with four fixed bolts, and the outer surfaces of each group of fixed bolts are threadedly connected with the inner walls of the rain shielding plates.

[0011] Preferably, the inner walls of each hinge hinge are threadedly connected with four reinforcing bolts, the outer surfaces of two groups of reinforcing bolts are threadedly connected with the inner walls of the protective top cover, and the outer surfaces of the other two groups of reinforcing bolts are threadedly connected with the inner walls of the protective shell.

[0012] Preferably, the outer surfaces of each group of first connecting terminals are fixedly connected with two fixed rings, and the mutually close ends of each group of fixed rings are fixedly connected with the outer surface of the fixed base.

[0013] Preferably, the outer surfaces of each group of fixed plates are fixedly connected with four reinforcing blocks, and the mutually close sides of each group of reinforcing blocks are fixedly connected with the outer surface of the filter installation module.

[0014] Preferably, the upper surfaces of each group of fixed plates are fixedly connected with four limiting frames, and the mutually close sides of each group of limiting frames are fixedly connected with the outer surface of the filter installation module.

[0015] Preferably, the inner wall of each set of the limiting frame is threadedly connected with four fastening bolts, and the outer surface of each set of the fastening bolts is threadedly connected with the inner wall of the fixed plate.

[0016] Preferably, the outer surface of the spring is fixedly connected with two limiting rings, one of which is fixedly connected with the back surface of the sliding plate at one end close to the button, and the other of which is fixedly connected with the inner wall of the protective shell at one end away from the sliding plate.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] The present application can facilitate the opening and closing of the protective top cover through the cooperation between the button, the sliding plate, the limiting column, the clamping block, the spring and the hinge, thus achieving the purpose of convenience and quickness, enhancing the use effect of the device, and facilitating the staff to detect the filter detection device at any time. The rain shield, the dust filter plate, the ventilation duct and the fan blade can ventilate and cool the internal electrical elements of the protective shell, prevent the internal temperature of the device from being too high, and reduce the service life. The cooperation between the fixed base, the first clamping groove, the second clamping groove, the fixed frame, the threaded rod and the pressing plate can facilitate the assembly of the filter installation module, achieve the purpose of easy assembly, enhance the applicability of the device, and fix the position of the filter installation module through the groove and the limiting block, thus enhancing the stability of the device. When a component in the filter fails, the entire filter needs to be overhauled and replaced, which consumes a lot of manpower and material resources, reduces the harmonic detection efficiency, and when new large power electronic equipment is added to the factory, new harmonic frequencies are generated, and the corresponding harmonic detection and filtering modules cannot be increased, which reduces the harmonic detection accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a perspective view of the overall structure of the assembled power grid harmonic detection filter of the present application.

[0020] Figure 2 It is a structure diagram of the protective top cover of the present application.

[0021] Figure 3 It is a structure diagram of the threaded rod of the present application.

[0022] Figure 4 It is a structure diagram of the fixed frame of the present application.

[0023] Figure 5 It is a structure diagram of the fan blade of the present application.

[0024] Figure 6Structure diagram of the first clamping groove of the application;

[0025] Figure 7 Structure diagram of the lower pressing plate of the application;

[0026] Figure 8 Structure diagram of the fixed plate of the application;

[0027] Figure 9 Structure diagram of the second connecting terminal of the application;

[0028] Figure 10 Structure diagram of the sliding plate of the application.

[0029] Wherein: 1, bottom plate; 2, protection mechanism; 201, protective shell; 202, protective top cover; 203, button; 204, hinge; 205, dustproof filter plate; 206, ventilation pipeline; 207, clamping block; 208, filter screen plate; 209, fan blade; 210, sliding plate; 211, limiting column; 212, spring; 3, fixed limiting mechanism; 301, fixed base; 302, fixed frame; 303, threaded rod; 304, first connecting terminal; 305, filter installation module; 306, lower pressing plate; 307, limiting block; 308, fixed plate; 309, second connecting terminal; 310, first clamping groove; 311, second clamping groove; 312, bearing; 313, groove; 314, capacitor element body; 315, inductor element body; 316, resistor element body; 4, rain shield; 5, fixed ring; 6, fixed bolt; 7, support frame; 8, reinforcing bolt; 9, reinforcing block; 10, limiting frame; 11, fastening bolt; 12, limiting ring. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application. Embodiment one

[0031] Please refer to Figures 1-10The utility model provides an assembled power grid harmonic detection filter, including bottom plate 1, the top of bottom plate 1 is provided with protection mechanism 2 and fixed limiting mechanism 3 respectively, protection mechanism 2 includes protective housing 201, the back of protective housing 201 is fixedly connected with hinged joint 204, the front of hinged joint 204 is fixedly connected with protective top cover 202, the inside of protective housing 201 is clamped with clamping block 207, the inside of protective housing 201 is slidably connected with sliding plate 210, the front of sliding plate 210 is fixedly connected with button 203 and limiting column 211, the back of sliding plate 210 is fixedly connected with spring 212, the outer surface of limiting column 211 is in contact with the inner wall of clamping block 207, the inner wall of protective housing 201 is fixedly connected with two dustproof filter plates 205 and two ventilation ducts 206, the inner wall of every ventilation duct 206 is fixedly connected with two filter screen plates 208, and every group of filter screen plates 208 is fixedly connected with two fan blades 209 at the end away from each other,

[0032] The outer surface of protective housing 201 is fixedly connected with two rain shields 4, and the side face away from each other of the two rain shields 4 is fixedly connected with the side face away from each other of the two dustproof filter plates 205, rain can be prevented from entering the inside of protective housing 201 through the rain shield 4, so that the electrical elements in the inside are prevented from being damaged,

[0033] The outer surface of every rain shield 4 is fixedly connected with two support frames 7, and the side face close to each other of every group of support frames 7 is fixedly connected with the outer surface of protective housing 201, the rain shield 4 can be fixedly supported by protective housing 201 through the support frame 7, the stability of the device is enhanced, and the device is prevented from shaking during use,

[0034] The inner wall of every group of support frames 7 is screw-connected with four fixing bolts 6, the inner wall of every group of fixing bolts 6 is screw-connected with the inner wall of rain shield 4, the support frame 7 and the rain shield 4 can be fixed through the fixing bolt 6, and the support frame 7 and the rain shield 4 are effectively prevented from being unstable and deviating during work,

[0035] The inner wall of every hinged joint 204 is screw-connected with four reinforcing bolts 8, the inner wall of two groups of reinforcing bolts 8 is screw-connected with the inner wall of protective top cover 202, and the inner wall of the other two groups of reinforcing bolts 8 is screw-connected with the inner wall of protective housing 201, the hinged joint 204, protective housing 201 and protective top cover 202 can be reinforced through the reinforcing bolt 8, have stronger fixed limiting effect, and the position of the hinged joint 204, protective housing 201 and protective top cover 202 is prevented from deviating during use,

[0036] The outer surface of the spring 212 is fixedly connected with two limiting rings 12, one of which is fixedly connected with the back surface of the sliding plate 210 near one end of the button 203, and the other is fixedly connected with the inner wall of the protective shell 201 away from one end of the sliding plate 210. Through the limiting ring 12, the position of the spring 212 can be limited to prevent the position from being unstable during use.

[0037] The specific implementation of the embodiment is that: first, the sliding plate 210 is moved by pressing the button 203, then the limiting column 211 is moved, so that the limiting column 211 does not limit the position of the clamping block 207, thereby the protective top cover 202 can be opened, thereby the electrical elements can be conveniently assembled inside the protective shell 201, the applicability of the device is enhanced, and the assembly is facilitated. When the electrical elements inside the protective shell 201 generate a high temperature, the two fan blades 209 are rotated in the same direction, the inside of the protective shell 201 is ventilated and cooled, the use effect of the device is enhanced, and the problem that the high temperature inside the device reduces the service life is effectively avoided. Embodiment two

[0038] Please refer to Figures 1-10 The fixed limiting mechanism 3 comprises a fixed base 301, the upper surface of the fixed base 301 is fixedly connected with four fixed frames 302, the inner wall of each set of fixed frames 302 is threadedly connected with two threaded rods 303, the outer surface of each set of threaded rods 303 is fixedly connected with two bearings 312, the bottom end of each set of bearings 312 is fixedly connected with two downward pressing plates 306, the bottom surface of each set of downward pressing plates 306 is fixedly connected with six limiting blocks 307, the upper surface of the fixed base 301 is respectively provided with a plurality of same first clamping grooves 310 and a plurality of same second clamping grooves 311, three first clamping grooves 310 are clamped with filter installation modules 305, the outer surface of each filter installation module 305 is fixedly connected with two fixed plates 308, the upper surface of each set of fixed plates 308 is provided with two grooves 313, the inner wall of each filter installation module 305 is fixedly connected with four capacitor element main bodies 314, three inductor element main bodies 315 and four resistor element main bodies 316, the outer surface of each filter installation module 305 is fixedly connected with two second connecting terminals 309, the inner wall of each set of grooves 313 is in contact with the outer surface of the limiting block 307, and the outer surface of each set of second connecting terminals 309 is in contact with the inner wall of the second clamping groove 311.

[0039] The outer surface of each group of first connecting terminals 304 is fixedly connected with two fixed rings 5, and the end of each group of fixed rings 5 close to each other is fixedly connected with the outer surface of the fixed base 301. Through the fixed ring 5, the first connecting terminal 304 and the fixed base 301 can be fixed, and the position offset is avoided;

[0040] The outer surface of each group of fixed plates 308 is fixedly connected with four reinforcing blocks 9, and the side surface of each group of reinforcing blocks 9 close to each other is fixedly connected with the outer surface of the filter mounting module 305. Through the reinforcing block 9, the fixed plate 308 and the filter mounting module 305 can be reinforced, and a strong fixing effect is achieved to prevent the position from moving;

[0041] The upper surface of each group of fixed plates 308 is fixedly connected with four limiting racks 10, and the side surface of each group of limiting racks 10 close to each other is fixedly connected with the outer surface of the filter mounting module 305. Through the limiting rack 10, the position of the fixed plate 308 can be limited to prevent shaking during use;

[0042] The inner wall of each group of limiting racks 10 is threadedly connected with four fastening bolts 11, and the outer surface of each group of fastening bolts 11 is threadedly connected with the inner wall of the fixed plate 308. Through the fastening bolt 11, the limiting rack 10 and the fixed plate 308 can be reinforced to avoid the problem of sliding offset during use.

[0043] The specific implementation of the embodiment is that the filter mounting module 305 is first mounted in the first clamping groove 310 on the fixed base 301, then the second connecting terminal 309 is mounted in the second clamping groove 311, the bearing 312 is driven to move downward by rotating the threaded rod 303, then the pressing plate 306 is driven to move downward, and then the limiting block 307 is driven to move downward, so that the limiting block 307 can be clamped in the groove 313 on the fixed plate 308, thereby the position of the filter mounting module 305 can be fixed and limited, and the problem of unstable position deviation during work is effectively prevented. The components of the assembled filter are pre-made in the factory, and when installed on site, only simple assembly according to the design drawing is needed, and by mounting the capacitor element body 314, the inductor element body 315 and the resistor element body 316 in the independent filter mounting module 305, these filter mounting modules 305 have standard interfaces, and when installed in power grid substations and other places, workers can quickly combine each module together by connecting these interfaces, greatly shortening the installation time, and the efficiency is significantly improved compared with the traditional filter which needs complex wiring and element installation on site. When a component in the device fails, only the faulty filter mounting module 305 needs to be replaced and repaired, which is convenient for maintenance personnel to repair and replace, and the entire filter does not need to be overhauled. When the power grid scale expands or the harmonic situation changes and the filtering function needs to be increased, new filter mounting modules 305 can be easily added to meet the demand, which can effectively avoid the problem that when a component in the filter fails, the entire filter needs to be overhauled and replaced, which consumes a lot of manpower and material resources, reduces the harmonic detection efficiency, and when the factory adds new large power electronic equipment, new harmonic frequencies are generated, and corresponding harmonic detection and filtering modules cannot be added, which reduces the harmonic detection accuracy. Embodiment three

[0044] Please refer to Figures 1-10The specific implementation of the embodiment is that: first, the sliding plate 210 is moved by pressing the button 203, then the limiting column 211 is moved, so that the limiting column 211 does not limit the position of the clamping block 207, thereby the protective top cover 202 can be opened, thereby the electrical element can be conveniently assembled inside the protective shell 201, the applicability of the device is enhanced, and the assembly is facilitated. When the electrical element inside the protective shell 201 generates a high temperature, the two fan blades 209 are rotated in the same direction, the inside of the protective shell 201 is ventilated and cooled, the use effect of the device is enhanced, the problem that the service life is reduced due to the high temperature inside the device is effectively avoided. The filter mounting module 305 is installed in the first clamping groove 310 on the fixed base 301, then the second connecting terminal 309 is installed in the second clamping groove 311, the bearing 312 is lowered by rotating the threaded rod 303, then the lower plate 306 is lowered, and then the limiting block 307 is lowered, so that the limiting block 307 is clamped in the groove 313 on the fixed plate 308, thereby the position of the filter mounting module 305 is fixed and limited, and the problem of unstable position during work is effectively prevented. The components of the assembled filter are pre-made in the factory, and during on-site installation, only simple assembly according to the design drawing is required, and by installing the capacitor element body 314, the inductor element body 315 and the resistor element body 316 in the independent filter mounting module 305, these filter mounting modules 305 have standard interfaces, and when installed in power grid substations and other places, workers can quickly combine each module together by connecting these interfaces, greatly shortening the installation time, and the efficiency is significantly improved compared with the traditional filter which needs complex wiring and element installation on site. When a component in the device fails, only the faulty filter mounting module 305 needs to be replaced and repaired, which is convenient for maintenance personnel to repair and replace, and the entire filter does not need to be overhauled on a large scale. When the power grid scale expands or the harmonic situation changes and the filtering function needs to be increased, new filter mounting modules 305 can be conveniently added to meet the demand, which can effectively avoid the problem that when a component in the filter fails, the entire filter needs to be overhauled on a large scale, and the entire filter needs to be replaced and repaired, which consumes a lot of manpower and material resources, reduces the harmonic detection efficiency, and when the factory adds new large power electronic equipment, new harmonic frequencies are generated, and corresponding harmonic detection and filtering modules cannot be added, which reduces the harmonic detection accuracy.

[0045] It is to be noted that, in the present text, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0046] Finally, it should be noted that the above-mentioned only constitutes preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications, equivalent replacements, improvements and the like of the technical solutions described in the foregoing embodiments can still be made. Any modifications, equivalent replacements, improvements and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A prefabricated power grid harmonic detection filter, comprising a base plate (1), characterized in that: A protective mechanism (2) and a fixed limiting mechanism (3) are respectively provided on the top of the base plate (1); The protective mechanism (2) includes a protective shell (201), a hinge (204) fixedly connected to the back of the protective shell (201), a protective top cover (202) fixedly connected to the front of the hinge (204), a locking block (207) snapped into the inside of the protective shell (201), a sliding plate (210) slidably connected to the inside of the protective shell (201), and a button (203) and a limiting post (211) fixedly connected to the front of the sliding plate (210). A spring (212) is fixedly connected to the back of the sliding plate (210). The outer surface of the limiting post (211) is in contact with the inner wall of the locking block (207). Two dust filter plates (205) and two ventilation ducts (206) are fixedly connected to the inner wall of the protective shell (201). Two filter screens (208) are fixedly connected to the inner wall of each ventilation duct (206). Two fan blades (209) are fixedly connected to the ends of each set of filter screens (208) that are far apart from each other. The fixed limiting mechanism (3) includes a fixed base (301). Four fixed brackets (302) are fixedly connected to the upper surface of the fixed base (301). Two threaded rods (303) are threadedly connected to the inner wall of each set of fixed brackets (302). Two bearings (312) are fixedly connected to the outer surface of each set of threaded rods (303). Two lower pressure plates (306) are fixedly connected to the bottom end of each set of bearings (312). Six limiting blocks (307) are fixedly connected to the bottom surface of each set of lower pressure plates (306). Several identical first slots (310) and several identical second slots (311) are respectively opened on the upper surface of the fixed base (301). Filter mounting modules (305) are snapped into the interior of three of the first slots (310). Each filter... Two fixing plates (308) are fixedly connected to the outer surface of each filter mounting module (305). Two grooves (313) are opened on the upper surface of each fixing plate (308). Four capacitor element bodies (314), three inductor element bodies (315) and four resistor element bodies (316) are fixedly connected to the inner wall of each filter mounting module (305). Four first connection terminals (304) are fixedly connected to the outer surface of the fixing base (301). Two second connection terminals (309) are fixedly connected to the outer surface of each filter mounting module (305). The inner wall of each groove (313) is in contact with the outer surface of the limiting block (307). The outer surface of each second connection terminal (309) is in contact with the inner wall of the second slot (311).

2. The prefabricated power grid harmonic detection filter according to claim 1, characterized in that: Two rain shields (4) are fixedly connected to the outer surface of the protective shell (201). The side of the two rain shields (4) that are close to each other is fixedly connected to the side of the two dust filter plates (205) that are far away from each other.

3. The prefabricated power grid harmonic detection filter according to claim 2, characterized in that: Two support frames (7) are fixedly connected to the outer surface of each of the rain shields (4), and the side of each set of support frames (7) that is close to each other is fixedly connected to the outer surface of the protective shell (201).

4. The prefabricated power grid harmonic detection filter according to claim 3, characterized in that: Each set of support frames (7) has four fixing bolts (6) threadedly connected to the inner wall, and the outer surface of each set of fixing bolts (6) is threadedly connected to the inner wall of the rain shield (4).

5. A prefabricated power grid harmonic detection filter according to claim 1, characterized in that: Each of the hinges (204) has four reinforcing bolts (8) threaded to its inner wall. The outer surfaces of two sets of the reinforcing bolts (8) are threaded to the inner wall of the protective top cover (202), and the outer surfaces of the other two sets of the reinforcing bolts (8) are threaded to the inner wall of the protective outer shell (201).

6. The prefabricated power grid harmonic detection filter according to claim 1, characterized in that: Two fixing rings (5) are fixedly connected to the outer surface of each group of first connecting terminals (304), and the ends of each group of fixing rings (5) that are close to each other are fixedly connected to the outer surface of the fixing base (301).

7. A prefabricated power grid harmonic detection filter according to claim 1, characterized in that: Each set of fixed plates (308) has four reinforcing blocks (9) fixedly connected to its outer surface. The side of each set of reinforcing blocks (9) that is close to each other is fixedly connected to the outer surface of the filter mounting module (305).

8. A prefabricated power grid harmonic detection filter according to claim 1, characterized in that: Each set of fixed plates (308) has four limiting brackets (10) fixedly connected to its upper surface. The side of each set of limiting brackets (10) that is close to each other is fixedly connected to the outer surface of the filter mounting module (305).

9. A prefabricated power grid harmonic detection filter according to claim 8, characterized in that: Each set of the limiting frame (10) has four fastening bolts (11) threadedly connected to the inner wall, and the outer surface of each set of fastening bolts (11) is threadedly connected to the inner wall of the fixing plate (308).

10. A prefabricated power grid harmonic detection filter according to claim 1, characterized in that: Two limiting rings (12) are fixedly connected to the outer surface of the spring (212). One of the limiting rings (12) is fixedly connected to the back of the sliding plate (210) at the end near the button (203), and the other limiting ring (12) is fixedly connected to the inner wall of the protective shell (201) at the end away from the sliding plate (210).

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