An adjustable insulating assembly for discharge cleaning electrodes in a fusion device

Abstract

The invention belongs to the technology of discharge cleaning of fusion device, and specifically relates to an adjustable insulating component for discharge cleaning electrode of fusion device, comprising a horizontally fixed insulating connecting plate, a vertically fixed support, and coaxially installed insulating protection parts, insulating positioning parts and insulating load-bearing parts; the insulating load-bearing parts are assembled in reserved process holes of the insulating connecting plate, the insulating positioning parts are mounted above the insulating load-bearing parts, and the supports are coaxially mounted in axial through holes of the insulating load-bearing parts and the insulating positioning parts. The structure is simple and the assembly is simple. The component can be widely used for insulation connection of discharge cleaning of various fusion devices such as DC glow discharge cleaning, radio frequency / high frequency discharge cleaning and spiral wave discharge cleaning, and can also meet different insulation structures. The insulating positioning parts and the insulating load-bearing parts can meet the axial pressure bearing and radial load bearing requirements of discharge electrodes / antennas with large volume and weight.

Description

Technical Field

[0001] The invention belongs to the field of discharge cleaning technology for fusion devices, and in particular relates to an adjustable insulating component for discharge cleaning electrodes of fusion devices. Background Art

[0002] Discharge cleaning is one of the basic means to achieve good first wall conditions in fusion devices. Discharge cleaning generates plasma through different heating methods. The high-energy particles bombard the surface of the first wall so that the impurity particles adsorbed on the surface obtain energy that exceeds the binding energy of the wall surface, thereby achieving desorption from the wall surface, and then being discharged by vacuum exhaust to achieve the purpose of impurity removal. The main discharge cleaning methods in fusion devices include: DC glow discharge cleaning, radio frequency / high frequency discharge cleaning, and spiral wave discharge cleaning. In various types of discharge cleaning, the discharge electrode / antenna needs to achieve reliable insulation from the vacuum chamber and the inner wall of the vacuum chamber. Among them, it is particularly important that the insulating parts / components still need to maintain reliable insulation performance after repeated discharge operations. In addition, the trend of diversified discharge cleaning methods for fusion devices and the volume and weight of discharge electrodes / antennas increase with the increase in the scale of the device. Various types of insulation components with existing fixed methods are difficult to meet the requirements of large load-bearing, flexible adjustment, and repeated use. For the above reasons, a special adjustable insulation component suitable for various types of discharge cleaning is needed. Summary of the invention

[0003] The purpose of the present invention is to provide an adjustable insulating component for discharge cleaning electrodes of a fusion device, which has a wide range of applications, improved insulation performance, and can flexibly realize the positioning of the insulating component.

[0004] The technical solution of the present invention is as follows:

[0005] An adjustable insulating assembly for discharge cleaning electrodes of a fusion device comprises a horizontally fixed insulating connecting plate, a vertically fixed support, and coaxially mounted insulating protection parts, insulating positioning parts and insulating load-bearing parts; the insulating protection parts, insulating positioning parts and insulating load-bearing parts are all sheathed outside the support; the insulating positioning parts are mounted above the insulating load-bearing parts, and the insulating load-bearing parts are assembled in the reserved process holes of the insulating connecting plate; the support is coaxially mounted in the axial through holes of the insulating load-bearing parts and the axial through holes of the insulating positioning parts, and the upper and lower ends of the support extend out of the insulating protection parts located at the upper and lower parts, respectively.

[0006] The parts of the outer side of the insulating protection member extending out of the upper and lower ends of the support are fastened and limitedly locked by fixing nuts and locking nuts.

[0007] The insulating protection member structure is a cylindrical structure with an inner cavity and an open lower portion, a mounting hole is processed at the center of the upper surface, and the upper end of the support extends upward to the outside of the insulating protection member through the mounting hole; when the insulating protection member is located at the lower portion, its upper portion is open, a mounting hole is processed at the center of the lower surface, and the lower end of the support extends downward to the outside of the insulating protection member through the mounting hole.

[0008] The insulating positioning piece is installed in the inner cavity of the upper insulating protection piece, and is coaxially installed, and the installation surface of the insulating positioning piece is in close contact with the installation surface of the inner cavity of the insulating protection piece.

[0009] The insulating positioning piece is a columnar structure with an outer wall processed into a stepped shape, so that the outer wall has a shoulder, and a stepped through hole is processed along the axial direction, the upper inner surface of the through hole is in close contact with the supporting outer wall, and the lower inner surface of the through hole is in close contact with the upper outer wall of the insulating load-bearing piece.

[0010] The upper part and the lower part of the through hole have the same shape, and the cross-sectional area of ​​the lower part of the through hole is larger than that of the upper part of the through hole, so that the inner wall of the through hole is stepped.

[0011] The position of the shoulder of the insulating positioning piece is higher than the step position of the stepped through hole.

[0012] A portion of the insulating load-bearing member is located in the inner cavity of the lower insulating protection member, and is coaxially installed with the mounting surface of the insulating load-bearing member in close contact with the mounting surface of the inner cavity of the insulating protection member;

[0013] The insulating load-bearing member has a columnar main body, the upper end of which is mounted on the lower part of the stepped through hole of the insulating positioning member. The interior of the insulating load-bearing member is processed with a through hole along the axial direction, and the interior of the through hole is in close contact with the supporting outer wall.

[0014] The insulating load-bearing component has a load-bearing platform with a cross-sectional area larger than the cross-sectional area of ​​the column processed on the outer wall of the columnar main body.

[0015] The contact area between the upper surface of the load-bearing platform and the lower surface of the insulating connecting plate is greater than or equal to the cross-sectional area of ​​the support.

[0016] The vertical distance from the top of the insulating load-bearing member to the upper surface of the load-bearing platform is greater than the thickness of the insulating connecting plate.

[0017] The insulating protection member, insulating positioning member and insulating load-bearing member have the same cross-sectional shape at any height position, which is a circular, rectangular or polygonal cross-section.

[0018] The cross-sectional areas of the insulating positioning member and the insulating load-bearing member at any height position should be greater than or equal to the cross-sectional area of ​​the fixing nut or the support.

[0019] The insulating protection part, the insulating positioning part and the insulating load-bearing part are made of alumina, zirconium oxide or silicon nitride.

[0020] The insulating connecting plate and the support are made of metal materials SS304, SS316, SS316L, SS310 or Inconel625.

[0021] The upper end surface of the insulating positioning member and the lower end surface center of the insulating load-bearing member are both processed with a raised plane, and a circle of grooves are processed on the outside of the raised plane. The outer wall thickness of the groove is set to a, the height of the groove is set to c, and the height of the raised plane is set to b, satisfying a:b≤1:1, and b:c≤1:2.

[0022] The insulating positioning member is a columnar structure whose outer wall is processed into a stepped shape, so that the outer wall has a shoulder, and the insulating load-bearing member is a load-bearing platform whose cross-sectional area is larger than the cross-sectional area of ​​the columnar body.

[0023] The height difference from the shoulder to the lower edge of the upper insulating protection member, or the height difference from the lower edge of the load-bearing platform of the insulating load-bearing member to the upper edge of the lower insulating protection member, is defined as f;

[0024] The height difference between the lower edge of the upper insulating protection member and the upper surface of the insulating connecting plate, or the height difference between the upper edge of the lower insulating protection member and the lower surface of the insulating connecting plate, is defined as e;

[0025] The lateral distance from the inner wall of the insulating protection member to the side wall below the shoulder of the insulating positioning member, or the lateral distance from the inner wall of the insulating protection member to the outer wall of the load-bearing platform, is defined as d;

[0026] Satisfies d=e, and d:f≤1:3.

[0027] The remarkable effects of the present invention are as follows:

[0028] 1. The adjustable insulation component has a simple structure and is easy to assemble. It can be widely used in the insulation connection of various fusion device discharge cleaning such as DC glow discharge cleaning, radio frequency / high frequency discharge cleaning and spiral wave discharge cleaning, and can also meet different insulation structures (the reserved holes are circular, rectangular or polygonal, etc.).

[0029] 2 The insulating component can be flexibly positioned by fixing the nut and locking the nut, and the installation position can be adjusted.

[0030] 3. The insulating positioning parts and insulating load-bearing parts can meet the axial pressure-bearing and radial load-bearing requirements of discharge electrodes / antennas with large volume and weight.

[0031] 4 The assembled two-level insulation protection can ensure that the discharge electrode / antenna can maintain reliable insulation performance after multiple plasma discharge particle bombardment / impurity sputtering, and can be reused. The secondary insulation protection has basically completely shielded the contamination or damage of the surface of the insulating part by charged particles or impurity particles; the primary insulation protection further ensures that the particles that may pass through the secondary insulation protection cannot cause contamination or damage to the surface of the end groove of the insulating positioning part or the insulating load-bearing part. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of an adjustable insulating assembly for discharge cleaning electrodes of a fusion device;

[0033] Figure 2 It is a schematic diagram of an insulating positioning member;

[0034] Figure 3 It is a schematic diagram of an insulating load-bearing member;

[0035] Figure 4a It is a schematic diagram of the primary insulation protection of the adjustable insulation component;

[0036] Figure 4b for Figure 5a A partial enlarged view of

[0037] Figure 5a It is a schematic diagram of secondary insulation protection of an adjustable insulation component;

[0038] Figure 5b for Figure 5a A partial enlarged view of

[0039] In the figure: 1-insulation protection part; 2-insulation positioning part; 3-insulation load-bearing part; 4-locking nut; 5-fixing nut; 6-insulation connecting plate; 7-support;

[0040] 201. shoulder; 202. stepped through hole; 2021. upper part of through hole; 2022. lower part of through hole;

[0041] 301. Column; 302. Load-bearing platform. DETAILED DESCRIPTION

[0042] The present invention will be further described below through the accompanying drawings and specific implementation methods.

[0043] like Figure 1 As shown, the adjustable insulating assembly for discharge cleaning electrodes of a fusion device comprises: a coaxially mounted insulating protection member 1, an insulating positioning member 2 and an insulating load-bearing member 3; all three are sheathed outside a support 7;

[0044] Among them, the insulating positioning member 2 is installed above the insulating load-bearing member 3, the insulating load-bearing member 3 is assembled in the reserved process hole of the insulating connecting plate 6, the cylindrical support 7 is coaxially installed in the axial through hole of the insulating load-bearing member 3 and the axial through hole of the insulating positioning member 2, and the upper and lower ends of the support 7 extend out of the insulating protection member 1 located at the upper and lower parts through the corresponding mounting holes respectively;

[0045] The insulating load-bearing member 3 and the insulating positioning member 2 together form a physical separation between the insulating connecting plate 6 and the support 7;

[0046] The parts of the support 7 extending out of the upper and lower ends of the insulating protection member 1 are fastened and limitedly locked by the fixing nut 5 and the locking nut 4 .

[0047] like Figure 1 As shown, the structure of the insulating protection member 1 is a cylindrical shape with an inner cavity and an open lower part, a mounting hole is processed at the center of the upper surface, and the upper end of the support 7 extends upward to the outside of the insulating protection member 1 through the mounting hole; when the insulating protection member 1 is located at the lower part, its upper part is open, a mounting hole is processed at the center of the lower surface, and the lower end of the support 7 extends downward to the outside of the insulating protection member 1 through the mounting hole;

[0048] The entire insulating positioning member 2 is installed in the inner cavity of the upper insulating protection member 1, coaxially installed, and the mounting surface of the insulating positioning member 2 is in close contact with the mounting surface of the inner cavity of the insulating protection member 1;

[0049] A portion of the insulating load-bearing member 3 is located in the inner cavity of the lower insulating protection member 1, and is coaxially installed, and the mounting surface of the insulating load-bearing member 3 is in close contact with the mounting surface of the inner cavity of the insulating protection member 1;

[0050] like Figure 2 The structure of the insulating positioning member 2 shown is a columnar structure whose outer wall is processed into a stepped shape, so that the outer wall has a shoulder 201, and a stepped through hole 202 is processed along the axial direction, the inner surface of the upper part 2021 of the through hole is in close contact with the outer wall of the support 7, and the inner surface of the lower part 2022 of the through hole is in close contact with the outer wall of the upper end of the insulating load-bearing member 3; the upper and lower parts of the through hole have the same shape, and the cross-sectional size of the lower part is larger than the cross-sectional size of the upper part, so that the inner wall of the through hole is stepped; the position of the shoulder 201 of the insulating positioning member 2 is higher than the step position of the stepped through hole 202;

[0051] like Figure 3 The structure of the insulating load-bearing member 3 shown in the figure has a main body in the shape of a column 301, the upper end of the column is mounted on the lower part of the stepped through hole of the insulating positioning member 2, the interior of the insulating load-bearing member 3 is processed with a through hole along the axial direction, the interior of the through hole is in close contact with the outer wall of the support 7, and a load-bearing platform 302 having a cross-sectional area larger than the cross-sectional area of ​​the column is processed on the outer wall of the columnar main body of the insulating load-bearing member 3;

[0052] During installation, the insulating load-bearing member 3 is first assembled in the reserved process hole of the insulating connecting plate 6, and then the support 7 is installed through the through hole inside the insulating load-bearing member 3, with the upper and lower ends extending out;

[0053] Then, the insulating positioning member 2 is mounted outside the portion of the support 7 extending from the upper end thereof, and the inner surface of the through hole lower portion 2022 of the stepped through hole 202 of the insulating positioning member 2 is in close contact with the outer wall of the upper end of the insulating load-bearing member 3; the three are coaxially mounted; and the support 7 still passes through the through hole upper portion 2021 and extends upwardly from the insulating positioning member 2;

[0054] The portion of the support 7 extending out of the upper portion 2021 of the through hole passes through the mounting hole of the insulating protection member 1 located at the upper portion, and is fastened and locked in position by the fixing nut 5 and the locking nut 4;

[0055] The lower end of the support 7 extends out of the insulating load-bearing member 3 and passes through the mounting hole of the lower insulating protection member 1, and is fastened and locked by the fixing nut 5 and the locking nut 4;

[0056] like Figure 1 As shown, the insulating load-bearing member 3 and the insulating positioning member 2 not only form a physical isolation between the insulating connecting plate 6 and the support 7, but also adjust the relative distance between the insulating connecting plate 6 and the support 7 by moving the insulating load-bearing member 3, the insulating positioning member 2, and the upper and lower insulating protection members 1 along the axial direction of the support 7. When the appropriate position is reached, the position is locked by the fixing nut 5 and the locking nut 4.

[0057] The cross-sectional shapes of the insulating protection member 1, the insulating positioning member 2 and the insulating load-bearing member 3 at each height position are the same, and may be circular, rectangular or polygonal.

[0058] At the same time, the cross-sectional area of ​​the insulating positioning member 2 and the insulating load-bearing member 3 at any height position should be greater than or equal to the cross-sectional area of ​​the fixing nut 5 or the support 7, so that the insulating component can bear axial pressure.

[0059] The contact area between the upper surface of the load-bearing platform 302 of the insulating load-bearing member 3 and the lower surface of the insulating connecting plate 6 should be greater than or equal to the cross-sectional area of ​​the support 7, and the component can bear radial load.

[0060] In the insulating load-bearing member 3, the height (vertical distance) from its top to the upper surface of the load-bearing platform 302 must be greater than the thickness of the insulating connecting plate 6), further ensuring the effective use of the force when bearing weight, and at the same time further ensuring the accurate positioning and assembly of the insulating load-bearing member 3 and the insulating positioning member 2.

[0061] The insulating protection member 1 , the insulating positioning member 2 and the insulating load-bearing member 3 may be made of alumina (Al 2 O 3 ), zirconium oxide (ZrO 2 ) or silicon nitride (Si 3 N 4 ).

[0062] The locking nut 4, the fixing nut 5, the insulating connecting plate 6 and the support 7 are all made of metal materials compatible with the discharge operation of the fusion device (such as SS304, SS316, SS316L, SS310 or Inconel625).

[0063] like Figure 4a and Figure 4b As shown, the upper end surface of the insulating positioning member 2 and the lower end surface center of the insulating load-bearing member 3 are both processed with a raised plane 8, and a circle of grooves 9 are processed on the outer side of the raised plane 8, the outer wall thickness of the groove 9 is set to a, the height of the groove 9 is set to c, and the height of the raised plane 8 (that is, the height difference from the outer end surface of the raised plane 8 to the upper edge of the groove 9) is set to b;

[0064] In the upper part or the lower part of the entire device, the lengths of a, b, and c satisfy a:b≤1:1 and b:c≤1:2 respectively.

[0065] like Figure 5a and Figure 5b As shown, the height difference from the shoulder 201 of the insulating positioning member 2 to the lower edge of the upper insulating protection member 1, or the height difference from the lower edge of the load-bearing platform 302 of the insulating load-bearing member 3 to the upper edge of the lower insulating protection member 1, is defined as f;

[0066] The height difference between the lower edge of the upper insulating protection member 1 and the upper surface of the insulating connecting plate 6, or the height difference between the upper edge of the lower insulating protection member 1 and the lower surface of the insulating connecting plate 6, is defined as e;

[0067] The lateral distance from the inner wall of the insulating protection member 1 to the side wall below the shoulder 201 of the insulating positioning member 2, or the lateral distance from the inner wall of the insulating protection member 1 to the outer wall of the load-bearing platform 302, is defined as d;

[0068] In the upper part or the lower part of the entire device, d=e and d:f≤1:3 are satisfied respectively.

[0069] The insulating component as a whole is in a plasma operating environment for a long time, that is, low-temperature plasma cleaning and high-temperature plasma operation. The two-stage insulation protection design is based on the charged particle orbit theory. Under extremely harsh conditions, that is, high-temperature plasma operation, a single charged particle rotates with the Larmor radius and performs equal-pitch spiral motion. The secondary insulation protection sets the relative distance relationship between d, e and f, so that the charged particles passing through the slit between the insulating protection part 1 and the insulating connecting plate 6 can hit the inner wall of the insulating protection part 1 or the outer wall of the insulating positioning part 2, thereby realizing that the charged particles in spiral motion cannot pass through the continuous slit channel. Similarly, in the primary insulation protection, by setting the relative distance relationship between a, b and c, effective blocking of charged particles is achieved. The design of the two-stage insulation protection structure can fundamentally prevent the impact of charged particles on all slit surfaces, thereby achieving effective shielding of charged particles and avoiding the deposition of charged particles on the entire surface of the insulating component, thereby achieving the function of insulation protection of the combined component.

[0070] The assembled adjustable insulating component can play an excellent shielding role for particles escaping from plasma or impurities sputtered out during the cleaning discharge or operation of the fusion device by adopting a two-stage protection method.

[0071] The present invention is described in detail above with reference to the accompanying drawings and implementation examples, but the present invention is not limited to the above implementation examples. Various changes can be made within the knowledge of technicians in the field without departing from the purpose of the present invention. Any content not described in detail in the present invention can adopt the existing technology.

Claims

1. An adjustable insulating assembly for discharge cleaning electrodes of a fusion device, characterized in that: The invention comprises a horizontally fixed insulating connecting plate (6), a vertically fixed support (7), and coaxially mounted insulating protection parts (1), insulating positioning parts (2) and insulating load-bearing parts (3); the insulating protection parts (1), insulating positioning parts (2) and insulating load-bearing parts (3) are all mounted outside the support (7); the insulating positioning parts (2) are mounted above the insulating load-bearing parts (3), and the insulating load-bearing parts (3) are assembled in the reserved process holes of the insulating connecting plate (6); the support (7) is coaxially mounted in the axial through holes of the insulating load-bearing parts (3) and the axial through holes of the insulating positioning parts (2), and the upper and lower ends of the support (7) extend out of the insulating protection parts (1) located at the upper and lower parts respectively; The structure of the insulating protection member (1) is a cylindrical shape with an inner cavity and an open lower part, a mounting hole is processed at the center of the upper surface, and the upper end of the support (7) extends upward through the mounting hole to the outside of the insulating protection member (1); when the insulating protection member (1) is located at the lower part, its upper part is open, a mounting hole is processed at the center of the lower surface, and the lower end of the support (7) extends downward through the mounting hole to the outside of the insulating protection member (1); The insulating positioning member (2) is installed in the inner cavity of the upper insulating protection member (1), is installed coaxially, and the installation surface of the insulating positioning member (2) is in close contact with the installation surface of the inner cavity of the insulating protection member (1); The insulating positioning member (2) is a columnar structure whose outer wall is processed into a stepped shape, so that the outer wall has a shoulder (201), and a stepped through hole (202) is processed along the axial direction, the inner surface of the upper part (2021) of the through hole is in close contact with the outer wall of the support (7), and the inner surface of the lower part (2022) of the through hole is in close contact with the outer wall of the upper end of the insulating load-bearing member (3).

2. An adjustable insulating assembly for discharge cleaning electrodes of a fusion device as claimed in claim 1, characterized in that: The parts of the support (7) extending out of the upper and lower ends of the insulating protection member (1) are fastened and locked in position by means of a fixing nut (5) and a locking nut (4).

3. The adjustable insulating assembly for discharge cleaning electrodes of a fusion device as claimed in claim 1, characterized in that: The upper part (2021) of the through hole and the lower part (2022) of the through hole have the same shape, and the cross-sectional area of ​​the lower part (2022) of the through hole is larger than that of the upper part (2021) of the through hole, so that the inner wall of the through hole is stepped.

4. An adjustable insulating assembly for discharge cleaning electrodes of a fusion device as claimed in claim 3, characterized in that: The position of the shoulder (201) of the insulating positioning piece (2) is higher than the step position of the stepped through hole (202).

5. The adjustable insulating assembly for discharge cleaning electrodes of a fusion device as claimed in claim 1, characterized in that: A portion of the insulating load-bearing member (3) is located in the inner cavity of the lower insulating protection member (1), and is coaxially installed, with the installation surface of the insulating load-bearing member (3) in close contact with the installation surface of the inner cavity of the insulating protection member (1).

6. An adjustable insulating assembly for discharge cleaning electrodes of a fusion device as claimed in claim 5, characterized in that: The insulating load-bearing member (3) has a main body in the shape of a column (301), the upper end of which is mounted on the lower part of the stepped through hole of the insulating positioning member (2). A through hole is machined inside the insulating load-bearing member (3) along the axial direction, and the inside of the through hole is in close contact with the outer wall of the support (7).

7. An adjustable insulating assembly for discharge cleaning electrodes of a fusion device as claimed in claim 5, characterized in that: The insulating load-bearing member (3) has a load-bearing platform (302) whose cross-sectional area is larger than the cross-sectional area of ​​the column processed on the outer wall of the columnar main body.

8. An adjustable insulating assembly for discharge cleaning electrodes of a fusion device as claimed in claim 7, characterized in that: The contact area between the upper surface of the load-bearing platform (302) and the lower surface of the insulating connecting plate (6) is greater than or equal to the cross-sectional area of ​​the support (7).

9. An adjustable insulating assembly for discharge cleaning electrodes of a fusion device as claimed in claim 8, characterized in that: The vertical distance between the top of the insulating load-bearing member (3) and the upper surface of the load-bearing platform (302) is greater than the thickness of the insulating connecting plate (6).

10. An adjustable insulating assembly for discharge cleaning electrodes of a fusion device according to any one of claims 1 to 9, characterized in that: The insulating protection member (1), the insulating positioning member (2) and the insulating load-bearing member (3) have the same cross-sectional shape at any height position, which is a circular or polygonal cross-section.

11. An adjustable insulating assembly for discharge cleaning electrodes of a fusion device according to any one of claims 1 to 9, characterized in that: The cross-sectional areas of the insulating positioning member (2) and the insulating load-bearing member (3) at any height position should be greater than or equal to the cross-sectional area of ​​the fixing nut (5) or the support (7).

12. An adjustable insulating assembly for discharge cleaning electrodes of a fusion device according to any one of claims 1 to 9, characterized in that: The insulating protection part (1), the insulating positioning part (2) and the insulating load-bearing part (3) are made of alumina, zirconium oxide or silicon nitride.

13. An adjustable insulating assembly for discharge cleaning electrodes of a fusion device according to any one of claims 1 to 9, characterized in that: The insulating connecting plate (6) and the support (7) are made of metal materials such as SS304, SS316, SS316L, SS310 or Inconel625.

14. An adjustable insulating assembly for discharge cleaning electrodes of a fusion device according to any one of claims 1 to 9, characterized in that: The upper end surface of the insulating positioning member (2) and the lower end surface center of the insulating load-bearing member (3) are both processed with a raised plane (8), and a circle of grooves (9) are processed outside the raised plane (8), the outer wall thickness of the groove (9) is set to a, the height of the groove (9) is set to c, and the height of the raised plane (8) is set to b, satisfying a:b≤1:1, and b:c≤1:

2.

15. The adjustable insulating assembly for discharge cleaning electrodes of a fusion device as claimed in claim 1, characterized in that: The insulating positioning member (2) is a columnar structure whose outer wall is processed into a stepped shape, so that the outer wall has a shoulder (201); the insulating load-bearing member (3) has a load-bearing platform (302) whose cross-sectional area is larger than the cross-sectional area of ​​the columnar body processed on the outer wall of the columnar body; The height difference between the shoulder (201) and the lower edge of the upper insulating protection member (1), or the height difference between the lower edge of the load-bearing platform (302) of the insulating load-bearing member (3) and the upper edge of the lower insulating protection member (1), is defined as f; The height difference between the lower edge of the upper insulating protection member (1) and the upper surface of the insulating connecting plate (6), or the height difference between the upper edge of the lower insulating protection member (1) and the lower surface of the insulating connecting plate (6), is defined as e; The lateral distance from the inner wall of the insulating protection member (1) to the side wall below the shoulder (201) of the insulating positioning member (2), or the lateral distance from the inner wall of the insulating protection member (1) to the outer wall of the load-bearing platform (302), is defined as d; Satisfies d=e, and d:f≤1:3.

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