Crosslinked polyethylene insulated power cable with anti-seismic function

Abstract

The invention relates to the technical field of power cables, and provides a cross-linked polyethylene insulated power cable with an anti-seismic function, which comprises a cable body, the cable body is composed of a plurality of stranded wires, an insulating layer is arranged outside each wire, a filling layer and a belting layer are sequentially arranged outside the plurality of wires, and the insulating layer is arranged outside the plurality of wires. The cable comprises a cable body and further comprises a sheath layer, fixing seats, upper fixing frames, supporting assemblies and buffering assemblies, the sheath layer comprises an inner sheath and an outer sheath, the cable body is provided with a plurality of fixing seats, each fixing seat is provided with one upper fixing frame, the supporting assemblies are arranged between each fixing seat and the corresponding upper fixing frame, each fixing seat is provided with one buffering assembly, and the buffering assemblies are arranged on the supporting assemblies. According to the technical scheme, the problem that in the prior art, when a cross-linked polyethylene insulated power cable is arranged near a factory workshop or in a tunnel or other positions where vibration is likely to be generated, vibration can affect the cable through the ground or a supporting structure, and the cable is damaged is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power cables, and in particular to a cross-linked polyethylene insulated power cable with earthquake resistance. Background Art

[0002] Cross-linked polyethylene insulated power cable is a commonly used power transmission cable. It plays an important role in the power system. It is mainly used to transmit the electricity generated by power plants to various end users through transmission lines. Cross-linked polyethylene insulated power cable is generally composed of conductors, insulation layers and outer sheaths. Among them, the conductor is generally made of copper and other materials for transmitting electric energy. The insulation layer is used to protect the electric field inside the cable from external interference. The outer sheath is used to resist ultraviolet rays and reactions with external chemicals.

[0003] When cross-linked polyethylene insulated power cables are installed near factory workshops or in tunnels, a large number of mechanical equipment in the factory workshops, such as large punching machines, crushers, vibrating screens, etc., will generate strong vibrations during operation. When installed in tunnels, when trains pass by, especially when the trains are in the process of braking or starting, strong vibrations will also be generated. Especially in the tunnel environment, these vibrations will be transmitted to the cross-linked polyethylene insulated power cables through the ground or supporting structures, which will not only cause damage to the cables, but also cause the internal conductors of the cables to loosen. Summary of the Invention

[0004] The present invention proposes a cross-linked polyethylene insulated power cable with earthquake resistance, which is used to solve the problem in the prior art that when the cross-linked polyethylene insulated power cable is installed in a location prone to vibration, such as near a factory workshop or in a tunnel, the vibration will affect the cable through the ground or supporting structure, causing damage to the cable.

[0005] The technical solutions of the present invention are as follows: A cross-linked polyethylene insulated power cable with earthquake resistance, comprising a cable body, wherein the cable body is composed of a plurality of twisted conductors, each of the conductors is provided with an insulating layer on the outside, a plurality of the conductors are provided with a tape layer on the outside, and a filling layer is provided between the tape layer and the plurality of the conductors, and further comprising: A sheath layer, the sheath layer comprising an inner sheath and an outer sheath, the outer portion of the tape layer being sequentially coated with the inner sheath and the outer sheath, and an anti-seismic structure for buffering being provided between the inner sheath and the outer sheath, as well as inside the inner sheath; A fixing seat and an upper fixing frame, wherein the cable body is provided with a plurality of the fixing seats, each of the fixing seats is mounted with the upper fixing frame, and the cable body is located between the fixing seats and the upper fixing frame; A support assembly is provided between each of the fixing seats and the upper fixing frame, and is used to install the cable body; A buffer component is installed on each of the fixing seats to disperse the vibrations applied to the cable body.

[0006] On the basis of the above solution, in order to reduce the possibility of the cable body being affected by vibration, the seismic structure includes: an armor layer, the armor layer being arranged between the inner sheath and the outer sheath, the armor layer being composed of a plurality of steel wires; Rubber ropes, wherein a plurality of rubber ropes are arranged inside the inner sheath and the plurality of rubber ropes are twisted together; Wherein, the twisting direction of the steel wires in the armor layer is opposite to the twisting direction of the rubber ropes.

[0007] Based on the above solution, the support assembly includes: Rubber support pads, a group of rubber support pads is provided between each fixing seat and the upper fixing frame, two rubber support pads are symmetrically provided in each group, and the axial dimension of each rubber support pad is greater than the axial dimension of the upper fixing frame and the fixing seat; Grooves, each of the rubber support pads is provided with a plurality of grooves at equal distances on the outside; Raised ridges, each of the fixing seats and each of the upper fixing frames are provided with a plurality of raised ridges at equal distances, and the plurality of raised ridges on the fixing seats and the upper fixing frames correspond to and fit with the plurality of grooves on the rubber support pad in a one-to-one manner; Mounting grooves, each of the rubber support pads has a plurality of mounting grooves formed in a circumferential shape, a buffer support pad is fixedly mounted in each mounting groove, and each buffer support pad is provided with a hollow structure; Wherein, the buffer support pad is filled with non-Newtonian fluid.

[0008] Based on the above solution, the buffer assembly includes: A plug-in rack, the bottom of each fixing seat is fixedly mounted with the plug-in rack; A lower fixing frame is provided at the bottom of each of the plug-in frames.

[0009] On the basis of the above scheme, it also includes a mounting ring and a buffer pad, each of the lower fixed frames is fixedly mounted with the mounting ring, multiple mounting rings correspond one-to-one to multiple plug-in frames and are fixedly connected, each of the lower fixed frames is fixedly mounted with the buffer pad, and the top of the buffer pad abuts against the bottom of the plug-in frame.

[0010] The working principle and beneficial effects of the present invention are: 1. In the present invention, the twisting direction of the steel wires in the armor layer is opposite to that of the rubber ropes. When the cable body is subjected to vibration or other external forces, the steel wires and rubber ropes in the armor layer will generate a certain reverse force, thereby reducing the displacement or deformation of the overall structure, avoiding material fatigue caused by local stress concentration, thereby buffering the impact of vibration on the conductors, and reducing the possibility of deformation or rupture of the cable body due to external stress changes.

[0011] 2. In the present invention, when the cable body is affected by sudden vibration, the influence of the vibration and the cable body is eliminated through the cooperation of the rubber support pad and the buffer support pad, and through the setting of the non-Newtonian fluid filled inside the buffer support pad, when subjected to vibration, the non-Newtonian fluid becomes thicker due to the increase in shear force, and changes from "liquid" to "similar to solid" to consume the energy of the vibration, and the original fluidity is restored until the vibration force weakens, thereby protecting the cable body and reducing the damage to the cable body caused by sudden vibration.

[0012] 3. In the present invention, when the vibration is transmitted to the lower fixing frame through the cable bracket, the setting of the buffer pad and the mounting ring can eliminate the influence of the vibration on the plug-in frame to a certain extent, thereby reducing the possibility of the vibration being transmitted to the fixing seat through the cable bracket, increasing the shock resistance of the fixing seat, and thus improving the shock resistance of the cable body.

[0013] 4. In the present invention, by setting up an anti-seismic structure, the damage to the cable body caused by the vibration energy acting on the cable body is reduced and the stress is dispersed, thereby preventing cable structure damage and material fatigue. By cooperating with the support component and the buffer component, the buffer support pad is filled with non-Newtonian fluid, thereby alleviating the damage to the cable body caused by vibration when sudden vibration occurs. At the same time, in conjunction with the internal buffer pad, the vibration transmitted from the ground or the bracket is eliminated, the impact on the fixed seat is reduced, and the overall anti-seismic performance is enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the structure of the cable body, the seismic-resistant structure and the supporting assembly in the present invention; Figure 3 It is a cross-sectional structural diagram of the outer sheath and the support assembly in the present invention; Figure 4 It is a schematic diagram of the exploded structure of the support assembly in the present invention; Figure 5 Schematic diagram of the structure of the rubber support pad in the present invention; Figure 6 It is a cross-sectional structural diagram of the supporting assembly and the buffer assembly in the present invention; Figure 7 It is a cross-sectional structural diagram of the cooperation between the fixing seat and the upper fixing frame in the present invention; Figure 8 It is a schematic cross-sectional structural diagram of the buffer assembly in the present invention.

[0016] In the figure: 1. Wire; 2. Insulation layer; 3. Tape layer; 4. Filling layer; 5. Inner sheath; 6. Outer sheath; 7. Fixing seat; 8. Upper fixing frame; 9. Armor layer; 10. Rubber rope; 11. Rubber support pad; 12. Groove; 13. Ridge; 14. Mounting slot; 15. Buffer support pad; 16. Plug-in frame; 17. Lower fixing frame; 18. Mounting ring; 19. Buffer pad; 20. Nut; 21. Screw. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0018] like Figures 1 to 8 As shown, this embodiment proposes a cross-linked polyethylene insulated power cable with earthquake resistance, including a cable body, which is composed of a plurality of twisted conductors 1. Each conductor 1 is provided with an insulating layer 2 on the outside, wherein the insulating layer 2 is made of cross-linked polyethylene, a tape layer 3 is provided on the outside of the plurality of conductors 1, and a filling layer 4 is provided between the tape layer 3 and the plurality of conductors 1. The cable also includes a sheath layer, a fixing seat 7, an upper fixing frame 8, a support assembly and a buffer assembly. The sheath layer includes an inner sheath 5 and an outer sheath. The outer portion of the sheath 6 and the tape layer 3 are sequentially covered with an inner sheath 5 and an outer sheath 6. An anti-seismic structure for buffering is provided between the inner sheath 5 and the outer sheath 6, as well as inside the inner sheath 5. The anti-seismic structure includes an armor layer 9 and a rubber rope 10. The armor layer 9 is provided between the inner sheath 5 and the outer sheath 6. The armor layer 9 is composed of a plurality of steel wires. A plurality of rubber ropes 10 are provided inside the inner sheath 5. The plurality of rubber ropes 10 are twisted together, wherein the twisting direction of the steel wires in the armor layer 9 is opposite to the twisting direction of the rubber rope 10.

[0019] Among them, nuts 20 are fixedly installed at both ends of each fixing seat 7, and screws 21 are provided at both ends of each upper fixing frame 8. The screws 21 are adapted to the nuts 20. When the upper fixing frame 8 is installed on the fixing seat 7, the screws 21 and nuts 20 are matched, and the screws 21 are screwed into the corresponding nuts 20 to complete the fixation.

[0020] Specifically, when laying cables in a tunnel, it is necessary to first install the corresponding cable bracket, and then use a cable car or other equipment to move the prepared cable body to the designated position. The cable car releases the line, and after releasing the line to a certain distance, the cable body is moved to the cable bracket position. At this time, each cable bracket is installed with a corresponding buffer component. Due to the setting of the buffer component, the relative position of the cable body can be fixed by the fixing seat 7 and the upper fixing frame 8.

[0021] When fixing the relative position of the cable body, first place the cable body on the fixing seat 7 on the top of the buffer assembly, then install the support assembly on the position corresponding to the cable body and the fixing seat 7, then place the support assembly on the cable body on the corresponding fixing seat 7, and fix the relative position between the support assembly and the fixing seat 7 through the structure of the support assembly, and then place an upper fixing frame 8 on the corresponding support assembly. At this time, the two sides of the bottom of the upper fixing frame 8 correspond to the two sides of the fixing seat 7 respectively. At this time, the screw 21 is passed through the side of the upper fixing frame 8, and the screw 21 can be used to fix the relative position between the upper fixing frame 8 and the fixing seat 7 through the matching nut 20. Therefore, the position of the support assembly can be fixed by the setting of the upper fixing frame 8. During operation, when the vibration is transmitted to the cable body through the cable bracket due to various reasons such as the passage of a train or natural disasters in the tunnel, the cable body will be damaged due to the vibration. At this time, the setting of the buffer assembly can reduce the possibility of vibration being transmitted to the fixing seat 7 through the cable bracket, thereby increasing the seismic resistance of the fixing seat 7, and the setting of the support assembly further reduces the impact of vibration on the cable body.

[0022] Through the arrangement of the armor layer 9 and the rubber rope 10, the armor layer 9 is composed of several steel wires, which is mainly used to resist external mechanical stress such as extrusion and stretching, and prevent the cable from being damaged by vibration. The rubber rope 10 forms a buffer layer through its own elasticity, which is mainly used to absorb internal vibration energy, thereby reducing the risk of wear or breakage of the core wire due to vibration, thereby enhancing the seismic performance, and, as Figure 2 As shown, since the twisting direction of the steel wires in the armor layer 9 is opposite to that of the rubber rope 10, when the cable body is subjected to vibration or other external forces, the steel wires in the armor layer 9 and the rubber rope 10 will generate a certain reverse force, thereby reducing the displacement or deformation of the overall structure, avoiding material fatigue caused by local stress concentration, and thus eliminating the impact of vibration on the cable body.

[0023] like Figures 3 to 6As shown, a plurality of fixing seats 7 are provided on the cable body, and an upper fixing frame 8 is installed on each fixing seat 7. The cable body is located between the fixing seat 7 and the upper fixing frame 8. A support assembly is provided between each fixing seat 7 and the upper fixing frame 8 for installing the cable body. The support assembly includes a rubber support pad 11, a groove 12 and a ridge 13. A group of rubber support pads 11 are provided between each fixing seat 7 and the upper fixing frame 8. Each group of rubber support pads 11 is symmetrically provided with two, and the axial size of each rubber support pad 11 is larger than the axial size of the upper fixing frame 8 and the fixing seat 7. In terms of size, a number of grooves 12 are evenly spaced on the outside of each rubber support pad 11, and a number of ridges 13 are evenly spaced on each fixing seat 7 and each upper fixing frame 8. The several ridges 13 on the fixing seat 7 and the upper fixing frame 8 correspond to and adapt to the several grooves 12 on the rubber support pad 11 one by one, and also include mounting grooves 14. A number of mounting grooves 14 are circumferentially opened inside each rubber support pad 11, and a buffer support pad 15 is fixedly installed inside each mounting groove 14, and the interior of each buffer support pad 15 is set to a hollow structure.

[0024] Specifically, when the cable body is placed on the fixing seat 7 on the top of the buffer assembly, the two rubber support pads 11 are installed on the cable body at the corresponding position. After the two rubber support pads 11 are installed, the inner side walls of the two rubber support pads 11 are in contact with the outer sheath 6 of the cable body, and the several buffer support pads 15 inside the rubber support pad 11 are in contact with the cable body, and the several grooves 12 outside the two rubber support pads 11 are aligned, then the corresponding upper fixing frame 8 can be moved to the installation position. At this time, the grooves 12 of the two rubber support pads 11 are adapted and engaged with the corresponding ridges 13 on the fixing seat 7, and at the same time engaged with the ridges 13 on the upper fixing frame 8, thereby fixing the axial position of the rubber support pads 11.

[0025] Since the axial dimensions of the rubber support pad 11 are larger than the axial dimensions of the upper fixing frame 8 and the fixing seat 7, that is, after the rubber support pad 11 is installed, both ends of the rubber support pad 11 extend a certain distance from the edge of the upper fixing frame 8, such as Figure 5 As shown, the closer the protruding end of the rubber support pad 11 is to the edge, the thinner it becomes. When the cable body needs to be bent, the protruding thin edge can deform accordingly with the deformation of the cable body, thereby avoiding excessive bending of the cable due to rigid constraints at the fixed point, and reducing the possibility of damage to the outer sheath 6 of the cable body.

[0026] like Figures 6 to 8As shown, each fixing seat 7 is equipped with a buffer assembly for dispersing the vibration of the cable body. The buffer assembly includes a plug-in frame 16 and a lower fixing frame 17. A plug-in frame 16 is fixedly installed at the bottom of each fixing seat 7. A lower fixing frame 17 is provided at the bottom of each plug-in frame 16. It also includes a mounting ring 18 and a buffer pad 19. A mounting ring 18 is fixedly installed on each lower fixing frame 17. Multiple mounting rings 18 correspond one-to-one to multiple plug-in frames 16 and are fixedly connected. A buffer pad 19 is fixedly installed inside each lower fixing frame 17, and the top of the buffer pad 19 abuts against the bottom of the plug-in frame 16.

[0027] Specifically, when the vibration is transmitted to the lower fixing frame 17 through the cable bracket, the buffer pad 19 and the mounting ring 18 can alleviate the influence of the vibration on the plug-in frame 16 to a certain extent.

[0028] In order to further alleviate the impact of vibration on the cable body, a buffer support pad 15 (such as Figure 4 As shown) and cushion 19 (as Figure 8 The hollow structure inside the cable (as shown) is filled with a non-Newtonian fluid. It should be noted that the non-Newtonian fluid here is a shear-thickening fluid. When the cable body is affected by sudden vibration, the non-Newtonian fluid thickens due to the increased shear force, changing from a "liquid" state to a "quasi-solid" state, thereby consuming the vibration energy. It will not restore its original fluidity until the vibration force weakens, thereby protecting the cable body and reducing damage to the cable body caused by sudden vibration.

[0029] It should be added that the amount of non-Newtonian fluid filled is preferably 80% to 90% of the hollow structure, which not only ensures the flow space of the non-Newtonian fluid, but also avoids the expansion and rupture of the buffer support pad 15 due to excessive filling.

[0030] The working principle or usage process of this application is as follows: When laying cables in a tunnel, it is necessary to first install the corresponding cable bracket, and then use a cable car or other equipment to move the prepared cable body to the designated position. The cable car pays out the line, and after paying out the line to a certain distance, the cable body is moved to the cable bracket position. At this time, each cable bracket is installed with a corresponding lower fixing frame 17, a plug-in frame 16 and a fixing seat 7. At this time, the relative position of the cable body can be fixed by the fixing seat 7 and the upper fixing frame 8.

[0031] When fixing the relative position of the cable body, first place the cable body on the corresponding fixing seat 7, and then install the two rubber support pads 11 on the cable body in the corresponding positions. After the two rubber support pads 11 are installed, the inner side walls of the two rubber support pads 11 abut against the outer sheath 6 of the cable body, and the several buffer support pads 15 inside the rubber support pads 11 all abut against the cable body, and the several grooves 12 outside the two rubber support pads 11 correspond to each other, and the corresponding upper fixing frame 8 can be moved to the installation position. At this time, the grooves 12 of the two rubber support pads 11 are adapted and engaged with the corresponding ridges 13 on the fixing seat 7, and at the same time, they are engaged with the ridges 13 on the upper fixing frame 8, which plays the role of fixing the axial position of the rubber support pads 11. At this time, the two sides of the bottom of the upper fixing frame 8 correspond to the two sides of the fixing seat 7 respectively. At this time, the screws 21 are passed through the side of the upper fixing frame 8, and the relative position between the upper fixing frame 8 and the fixing seat 7 can be fixed by the screws 21 through the cooperation of the nut 20 adapted thereto.

[0032] During operation, when vibration is transmitted to the cable body through the cable bracket due to various reasons such as the passage of a train or natural disasters in the tunnel, the cable body will be damaged due to the vibration. At this time, through the setting of the buffer support pad 15 and the buffer pad 19, when the vibration is transmitted to the lower fixing frame 17 through the cable bracket, the setting of the buffer pad 19 and the mounting ring 18 can eliminate the influence of the vibration on the plug-in frame 16 to a certain extent, thereby reducing the possibility of vibration being transmitted to the fixing seat 7 through the cable bracket, and increasing the seismic resistance of the fixing seat 7.

[0033] Furthermore, the hollow structure inside the buffer support pad 15 and the buffer pad 19 is filled with a non-Newtonian fluid (shear-thickening fluid). When the cable body is affected by sudden vibration, the non-Newtonian fluid thickens due to the increase in shear force, changing from a "liquid state" to a "quasi-solid state", thereby consuming the vibration energy. The original fluidity will not be restored until the vibration force weakens, thereby protecting the cable body and reducing the damage to the cable body caused by sudden vibration. Through the arrangement of the armor layer 9 and the rubber rope 10, the armor layer 9 is composed of several steel wires, which are mainly used to resist external mechanical stress such as extrusion and stretching, and prevent structural damage of the cable due to vibration. The rubber rope 10 forms a buffer layer through its own elasticity, which is mainly used to absorb internal vibration energy, thereby reducing the risk of wear or breakage of the core wire due to vibration, thereby enhancing the seismic performance. Moreover, since the twisting direction of the steel wires in the armor layer 9 is opposite to that of the rubber rope 10, when the cable body is subjected to vibration or other external forces, the steel wires of the armor layer 9 and the rubber rope 10 will generate a certain reverse force, thereby reducing the displacement or deformation of the overall structure, avoiding material fatigue caused by local stress concentration, and further eliminating the impact of vibration on the cable body.

[0034] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A cross-linked polyethylene insulated power cable with earthquake resistance, comprising a cable body, wherein the cable body is composed of a plurality of twisted conductors (1), each of the conductors (1) is provided with an insulating layer (2) on the outside, a plurality of the conductors (1) are provided with a tape layer (3) on the outside, and a filling layer (4) is provided between the tape layer (3) and the plurality of the conductors (1), characterized in that: Also includes: A sheath layer, the sheath layer comprising an inner sheath (5) and an outer sheath (6), the outer portion of the wrapping layer (3) being covered with the inner sheath (5) and the outer sheath (6) in sequence, and an anti-seismic structure for buffering is provided between the inner sheath (5) and the outer sheath (6), as well as inside the inner sheath (5); A fixing seat (7) and an upper fixing frame (8), wherein a plurality of the fixing seats (7) are provided on the cable body, and each of the fixing seats (7) is mounted with the upper fixing frame (8), and the cable body is located between the fixing seat (7) and the upper fixing frame (8); A support assembly is provided between each of the fixing seats (7) and the upper fixing frame (8) and is used for mounting the cable body; A buffer component is installed on each of the fixing seats (7) to disperse the vibrations received by the cable body.

2. The cross-linked polyethylene insulated power cable with earthquake resistance according to claim 1, characterized in that: The earthquake-resistant structure comprises: an armor layer (9), the armor layer (9) being arranged between the inner sheath (5) and the outer sheath (6), the armor layer (9) being composed of a plurality of steel wires; Rubber rope (10), a plurality of rubber ropes (10) are arranged inside the inner sheath (5), and the plurality of rubber ropes (10) are twisted together; The twisting direction of the steel wires in the armor layer (9) is opposite to the twisting direction of the rubber rope (10).

3. The cross-linked polyethylene insulated power cable with earthquake resistance according to claim 1, characterized in that: The support assembly comprises: A rubber support pad (11), wherein a group of the rubber support pads (11) is provided between each of the fixing seats (7) and the upper fixing frame (8), and each group of the rubber support pads (11) is symmetrically provided with two rubber support pads (11), and the axial dimension of each of the rubber support pads (11) is greater than the axial dimension of the upper fixing frame (8) and the fixing seat (7); Grooves (12), each of the rubber support pads (11) is provided with a plurality of grooves (12) at equal distances on the outside; The ridges (13) are evenly spaced on each of the fixing seats (7) and each of the upper fixing frames (8). The ridges (13) on the fixing seats (7) and the upper fixing frames (8) correspond to and fit in with the grooves (12) on the rubber support pad (11).

4. The cross-linked polyethylene insulated power cable with earthquake resistance according to claim 3, characterized in that: It also includes mounting grooves (14), each of the rubber support pads (11) is provided with a plurality of mounting grooves (14) in a circumferential shape, each of the mounting grooves (14) is fixedly installed with a buffer support pad (15), and each of the buffer support pads (15) is provided with a hollow structure.

5. The cross-linked polyethylene insulated power cable with earthquake resistance according to claim 1, characterized in that: The buffer assembly comprises: A plug-in frame (16), wherein the bottom of each fixing seat (7) is fixedly mounted with the plug-in frame (16); A lower fixing frame (17) is provided at the bottom of each of the plug-in frames (16).

6. The cross-linked polyethylene insulated power cable with earthquake resistance according to claim 5, characterized in that: It also includes a mounting ring (18) and a buffer pad (19), wherein each lower fixing frame (17) is fixedly mounted with the mounting ring (18), a plurality of mounting rings (18) correspond one-to-one to a plurality of plug-in frames (16) and are fixedly connected, and each lower fixing frame (17) is fixedly mounted with the buffer pad (19), and the top of the buffer pad (19) abuts against the bottom of the plug-in frame (16).

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