Guide rail type vacuum heat treatment furnace

Abstract

The utility model relates to a guide rail type vacuum heat treatment furnace, belongs to the technical field of vacuum heat treatment furnaces, and aims to solve the problem of how to improve the disassembly and assembly convenience of a guide rail. The guide rail type vacuum heat treatment furnace comprises a furnace body and two guide rail assemblies arranged in the furnace body. At least two positioning holes are formed in the bottom of the inner wall of the furnace body; each guide rail assembly comprises a main rail, an auxiliary rail, idler wheels, supporting columns and limiting pins. The extending directions of the main rails and the auxiliary rails are both parallel to the length direction of the furnace body, the two main rails of the two guide rail assemblies are both in a regular L shape and are horizontally opposite, and the two guide rail assemblies are combined to form a limiting groove of a material box; the roller is rotationally connected between the main rail and the auxiliary rail through a pin shaft; the bottoms of the supporting columns are inserted into the corresponding positioning holes, the top of each supporting column is provided with a supporting face and a limiting protrusion located on the supporting face, and the limiting protrusions extend between the rolling wheels. Limiting pins for limiting the supporting columns from shaking are installed on the two sides of the limiting protrusion correspondingly.

Description

Technical Field

[0001] This application relates to the field of vacuum heat treatment furnace technology, and in particular to a guide rail type vacuum heat treatment furnace. Background Technology

[0002] Guide rails are crucial components within vacuum heat treatment furnaces, supporting and guiding material boxes to ensure smooth movement during high-temperature heat treatment and prevent misalignment or jamming. In existing technologies, guide rail installation in vacuum heat treatment furnaces typically involves two methods: welding and bolting. Welding involves directly welding the guide rail to the furnace wall or support beams; while this method offers high stability, disassembly is difficult. Bolting, on the other hand, uses pre-embedded bolts or adjustable brackets to fix the guide rail inside the furnace body. While this method facilitates adjustment and replacement, it requires tightening numerous bolts in the confined space inside the furnace, making the process cumbersome. Therefore, providing a vacuum heat treatment furnace with easily detachable and removable guide rails is a pressing technical problem that needs to be solved by those skilled in the art.

[0003] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Utility Model Content

[0004] (a) Technical problems to be solved

[0005] This application provides a guide rail type vacuum heat treatment furnace, which can solve the problem of how to improve the convenience of guide rail assembly and disassembly in the prior art.

[0006] (II) Technical Solution

[0007] To solve the above-mentioned technical problems, this application provides the following technical solution:

[0008] A guide rail vacuum heat treatment furnace is provided, the guide rail vacuum heat treatment furnace includes: a furnace body and at least one set of two guide rail assemblies disposed opposite to each other in the furnace body along the length direction of the furnace body;

[0009] The bottom of the inner wall of the furnace is provided with at least two positioning holes corresponding to each of the guide rail assemblies;

[0010] Each of the rail assemblies includes:

[0011] The main rail and the auxiliary rail extend in directions parallel to the length of the furnace body. The two main rails of the two guide rail assemblies are both L-shaped and horizontally opposite each other. The two guide rail assemblies are combined to form the limiting groove of the material box.

[0012] The roller is rotatably connected between the main rail and the auxiliary rail via a pin.

[0013] A support column, the bottom end of which is inserted into the corresponding positioning hole, and the top of which has a support surface for supporting the main rail and the auxiliary rail of a guide rail assembly, and a limiting protrusion located on the support surface, the limiting protrusion extending into the space between two adjacent rollers;

[0014] Limiting pins are provided on both sides of the limiting protrusion. The two ends of the limiting pins are respectively connected to the main rail and the auxiliary rail, and are used to limit the swaying of the support column along the extension direction of the main rail.

[0015] In some embodiments, the inner wall of the furnace is welded or integrally formed with a positioning seat, and the positioning seat is provided with the positioning hole.

[0016] In some embodiments, the support column includes a support section and a plug-in section, the support section and the plug-in section are coaxially arranged and detachably connected, the support section is provided with the support surface and the limiting protrusion, and the bottom end of the plug-in section is inserted into and limited to the inside of the positioning hole.

[0017] In some embodiments, the bottom end of the support section and the top end of the insertion end are provided with a threaded hole and a matching external thread, respectively.

[0018] In some embodiments, a retaining edge extending along the height direction is provided on one side of the main rail, and the retaining edges in the two guide rail assemblies are arranged parallel to each other, so that a limiting groove for the material box is formed between the retaining edges in the two guide rail assemblies.

[0019] In some embodiments, the main rail is provided with a clearance slope on the side opposite to the secondary rail, and the clearance slope faces the inner wall of the vacuum heat treatment furnace.

[0020] In some embodiments, each of the guide rail assemblies is provided with at least two support columns and at least three rollers, wherein the at least two support columns are spaced apart along the length of the main rail, and the distance between two adjacent support columns is less than 1 / 2 of the length of the material box.

[0021] In some embodiments, one end of the limiting pin extends horizontally through the sub-rail, and the other end abuts against the side wall of the main rail. The limiting pin is fitted with a collar, which is made of graphite or carbon-carbon composite material and is configured as a buffer and shock-absorbing structure between the limiting pin and the limiting protrusion.

[0022] (III) Beneficial Effects

[0023] Compared with the prior art, the beneficial effects of the technical solution provided in this application include at least the following:

[0024] The guide rail vacuum heat treatment furnace of this application uses the insertion and connection between the bottom end of the support column and the positioning hole, eliminating the need for welding or bolt tightening. During installation, simply align the support column with the positioning hole and insert it to complete the fixation. During disassembly, simply pull out the guide rail assembly, reducing the number of operation steps and making assembly and disassembly more convenient. The positioning holes are symmetrically distributed along the length of the furnace body, and their axis is perpendicular to the furnace body, ensuring that the insertion direction of the guide rail assembly is perpendicular to the furnace body axis, avoiding manual angle adjustment and achieving rapid alignment. Furthermore, the mechanical insertion method between the bottom end of the support column and the positioning hole replaces traditional welding and bolt connections, allowing for assembly and disassembly without tools, further improving the convenience of guide rail assembly and disassembly.

[0025] Because the guide rail assembly adopts a modular design, when a single guide rail is damaged, it can be directly replaced without the need for complete disassembly. If the roller or support column of a certain guide rail assembly fails, only that guide rail assembly needs to be pulled out and replaced, while other guide rail assemblies can remain in use, thereby reducing the amount of maintenance work during use.

[0026] Equally important, the positioning holes of the guide rail vacuum heat treatment furnace of this application are symmetrically arranged, and the number of guide rail components is adjustable, so that the overall length of the rail can be adjusted according to the type or model of the material box, making it more versatile. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is an exploded view of the guide rail vacuum heat treatment furnace in the embodiments of this application;

[0029] Figure 2 This is a front view of the guide rail type vacuum heat treatment furnace in the embodiment of this application;

[0030] Figure 3 yes Figure 2 A schematic diagram of section A in the middle;

[0031] Figure 4 This is a perspective view of the guide rail assembly in an embodiment of this application;

[0032] Figure 5 This is a top view of the guide rail assembly in an embodiment of this application;

[0033] Figure 6 yes Figure 5 Sectional view of section B;

[0034] Figure 7 yes Figure 5Sectional view of section C.

[0035] Figure label:

[0036] Furnace body 1, positioning hole 11, positioning seat 12;

[0037] Guide rail assembly 2, main rail 21, secondary rail 22, roller 23, support column 24, limit pin 25, flange 211, limit groove 212, clearance slope 213, installation gap 221, pin shaft 231, support surface 240, support section 241, plug section 242, limit protrusion 243, collar 251;

[0038] Material box 3; rack 4.

[0039] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0041] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0042] The existing guide rail installation methods for vacuum heat treatment furnaces typically include two types: welding and bolting. Welding involves directly welding the guide rail to the inner wall of the furnace or the support beam. While this method offers high stability, it is difficult to disassemble. Bolting, on the other hand, involves fixing the guide rail inside the furnace body using pre-embedded bolts or adjustable brackets. Although this method facilitates adjustment and replacement, it requires tightening a large number of bolts in the confined space inside the furnace, making the operation cumbersome.

[0043] To address the aforementioned technical problems, this embodiment provides a guide rail type vacuum heat treatment furnace. (See reference...) Figures 1 to 7 As shown, Figure 1 This is an exploded view of the guide rail type vacuum heat treatment furnace in the embodiments of this application. Figure 2 This is a front view of the guide rail type vacuum heat treatment furnace in the embodiments of this application. Figure 3 yes Figure 2 A schematic diagram of section A in the middle. Figure 4 This is a perspective view of the guide rail assembly in an embodiment of this application. Figure 5 This is a top view of the guide rail assembly in an embodiment of this application. Figure 6 yes Figure 5 Sectional view of section B in the middle. Figure 7 yes Figure 5 Sectional view of section C.

[0044] The guide rail vacuum heat treatment furnace of this embodiment includes: furnace body 1 and at least one set of two guide rail assemblies 2 arranged opposite to each other.

[0045] Furnace body 1 is a core component of the heat treatment process, such as Figure 1 As shown, it is horizontally fixed to the frame 4 by means of bolts or welding. The furnace body 1 can adopt an existing mature heat treatment furnace structure; for example, it has a horizontally opening and closing furnace door on one side (to better show the interior of the furnace, the furnace door is shown in the image). Figure 1 (Not shown in the text).

[0046] The furnace body 1 and at least one set of guide rail assemblies disposed within the furnace body 1, each set of guide rail assemblies comprising two guide rail assemblies arranged opposite each other along the length direction of the furnace body 1. The at least one set of guide rail assemblies 2 may be one set or multiple sets, and multiple sets of guide rail assemblies 2 may be arranged along the length direction of the furnace body 1 and installed within the furnace body 1.

[0047] The bottom of the inner wall of the furnace body 1 is provided with at least two positioning holes 11 corresponding to each guide rail assembly. Two sets of positioning holes 11 corresponding to two oppositely arranged guide rail assemblies 2 are symmetrically arranged along the length direction of the furnace body 1. The axis of each positioning hole 11 is perpendicular to the length direction of the furnace body 1 and parallel to the height direction of the furnace body 1. The two rows of positioning holes 11 correspond to the two guide rail assemblies 2 respectively. For example, when the number of the at least one set of guide rail assemblies 2 is multiple, the spacing between the multiple sets of positioning holes corresponding to the multiple sets of guide rail assemblies 2 is the same.

[0048] like Figure 3 and Figure 4 As shown, each of the guide rail assemblies 2 includes a main rail 21, a secondary rail 22, a roller 23, a support column 24, and a limiting pin 25.

[0049] The extension directions of the main rail 21 and the auxiliary rail 22 are both parallel to the length direction of the furnace body 1; the two main rails 21 of the two guide rail assemblies 2 are both L-shaped and horizontally opposite each other, so that the two guide rail assemblies 2 combine to form the limiting groove 212 of the material box 3.

[0050] The main rail 21 and the auxiliary rail 22 are arranged opposite each other, forming an installation gap 221 between them. The installation gap 221 is used to install the rollers 23, the limiting protrusions 243, and the limiting pins 25. The length direction of the installation gap 221 is parallel to the axis of the furnace body 1. The rollers 23 are arranged along the length direction within the installation gap 221. The rollers 23 are rotatably connected to both the main rail 21 and the auxiliary rail 22 via pins 231. At the same time, the pins 231 can also limit the relative displacement of the main rail 21 and the auxiliary rail 22.

[0051] When the material box 3 is moved through the furnace door on one side of the furnace body 1 onto the two sets of guide rail assemblies 2, the main rail 21, rollers 23, and auxiliary rail 22 together support the material box 3. When the material box 3 needs to be moved further horizontally into the furnace body 1, the rollers 1 can reduce resistance. The two main rails 21 of the two guide rail assemblies 2 are both L-shaped and horizontally opposite each other, so that the two guide rail assemblies 2 combine to form the limiting groove 212 of the material box 3. The limiting groove 212 guides the material box 3 to move along a preset path to prevent deviation or jamming; the retaining edge 211 enhances the structural rigidity of the main rail 21 and resists high-temperature deformation.

[0052] The bottom end of the support column 24 in the guide rail assembly 2 is inserted into and confined within the corresponding positioning hole 11. The top of the support column 24 has a support surface 240 and a limiting protrusion 243 located in the central area of ​​the support surface 240 and extending into the installation gap 221; the support surface 240 contacts the bottom surfaces of the main rail 21 and the auxiliary rail 22 to provide support, so that the load-bearing capacity of the main rail 21, the auxiliary rail 22 and the roller 23 can be distributed on the furnace body 1 through the support column 24. Each limiting protrusion 243 has a limiting pin 25 on each side of the length direction of the installation gap 221, and the limiting pin 25 is used to limit the swaying of the support column 24 in the extension direction of the main rail 21.

[0053] For example, each of the guide rail assemblies 2 is provided with at least two support posts 24 and at least three rollers 23.

[0054] For example, see Figure 3 As shown, the bottom end of the support column 24 can be confined within the positioning hole 11 in the following ways: the bottom end of the support column 24 is similar in size to the inner side of the positioning hole 11, with a clearance fit; or the bottom end of the support column 24 is provided with a radial flange, the outer diameter of which is slightly larger than the inner diameter of the positioning hole 11, and after insertion, it is interference-fitted; or the bottom end of the support column 24 is provided with an existing elastic claw, which opens and engages with the hole wall after being inserted into the positioning hole 11, and retracts when the claw is pressed when it is pulled out.

[0055] In one embodiment where the positioning hole 11 is provided on the inner wall of the furnace body 1, see [reference needed]. Figure 3As shown, the positioning seat 12 is fixed to the inner wall of the furnace body 1 by welding or integral molding. The positioning seat 12 has positioning holes 11. The positioning seat 12 and the positioning holes 11 are symmetrically distributed on both sides of the furnace body 1. The diameter of the positioning holes 11 matches the bottom size of the support column 24. The positioning seat 12 enhances the local strength of the furnace body 1 and prevents the furnace body 1 from deforming and failing in the area of ​​the positioning holes 11 due to high temperature or local stress. At the same time, the symmetrical distribution of the positioning seats 12 ensures that the guide rail assembly 2 is evenly stressed after installation, reducing the risk of uneven load on the furnace body 1.

[0056] The positioning hole 11 can be a blind hole structure with an elastic gasket inside. The elastic gasket is made of a high-temperature resistant material. When the insertion section 242 is inserted, the compression gasket 113 forms a pre-tightening force to prevent the support column 24 from shaking.

[0057] For adjustable guide rail height, please refer to... Figure 3 and Figure 6 As shown, the support column 24 includes a support section 241 and a plug-in section 242, which are coaxially arranged and detachably connected. The support section 241 has a support surface 240, and its top end has a limiting protrusion 243 that extends into the installation gap 221. The bottom end of the plug-in section 242 is inserted into and limited to the inside of the positioning hole 11. For example, the bottom end of the support section 241 has an internal threaded hole, and the top end of the plug-in section 242 has an external thread, and the two are fixed by a threaded connection; or, the bottom end of the support section 241 has an external thread, and the top end of the plug-in section 242 has an internal threaded hole. Before installation, the plug-in section 242 of the corresponding length can be selected according to the preset height of the guide rail to meet the support and guidance requirements of different material boxes. At the same time, the segmented design facilitates the replacement of damaged parts, such as worn plug-in section 242, without the need to completely disassemble the guide rail assembly 2. The threaded connection not only realizes the detachable function but also allows for fine-tuning of the height to adapt to the different material box transmission requirements.

[0058] It should be noted that guide ribs or guide grooves can be provided in the insertion section 242.

[0059] Furthermore, a guide groove (not shown) can be provided on the inner wall of the positioning hole 11, and a guide rib can be provided on the outer side of the part of the support column 24 inserted into the positioning hole 11, or a guide rib can be provided on the inner wall of the positioning hole 11, and a guide groove can be provided on the outer side of the part of the support column 24 inserted into the positioning hole 11. When the insertion section 242 is inserted into the positioning hole 11, it is locked by the cooperation of the guide rib and the guide groove.

[0060] In some implementations of main track 21, see [link / reference]. Figure 3 and Figure 4As shown, a retaining edge 211 extending along the height direction is provided on one side of the main rail 21. The retaining edge 211 makes the longitudinal cross-section of the main rail 21 of the two sets of guide rail assemblies 2 horizontally opposite positive L-shapes. The horizontal extension direction of the retaining edge 211 is parallel to the horizontal extension direction of the main rail 21. A limiting groove for supporting the material box 3 is formed between the retaining edges 211 of the two sets of guide rail assemblies 2. The width of the formed limiting groove 212 is greater than the width of the material box 3 to guide the material box to move along a preset path. The limiting groove 212 guides the material box 3 to move along the preset path to prevent deviation or jamming; the retaining edge 211 enhances the structural rigidity of the main rail 21 and resists high-temperature deformation.

[0061] In some implementations of main track 21, see [link / reference]. Figure 3 and Figure 4 As shown, the main rail 21 has a clearance slope 213 on the side opposite to the secondary rail 22, with the clearance slope 213 facing the inner wall of the furnace body 1 of the vacuum heat treatment furnace. The clearance slope 213 is used to make way for the inner wall of the furnace body 1 during installation, reducing the risk of collision. The clearance slope 213 can be directly obtained during the casting of the main rail 21.

[0062] To improve the support performance of the guide rail support assembly, please refer to... Figure 4 and Figure 7 As shown, each guide rail assembly 2 is provided with at least two support columns 24. In each guide rail assembly 2, the support columns 24 are distributed at intervals along the length direction of the main rail 21, and the distance between adjacent support columns 24 is less than 1 / 2 of the length of the material box 3. This support reduces the deflection deformation of the guide rail and ensures the smooth transmission of the long material box 3.

[0063] In some embodiments, one end of the limiting pin 25 extends horizontally through the sub-rail 22, and the other end abuts against the side wall of the main rail 21.

[0064] In some embodiments, a collar 251 is sleeved on the outer side of the limiting pin 25, see reference. Figure 4 As shown, the collar 251 is configured as a buffer and shock-absorbing structure between the limiting pin 25 and the support column 24, and the collar 251 covers the contact area between the limiting pin 25 and the support column 24. The collar 251 is made of graphite or carbon-carbon composite material. The collar 251 can absorb the vibration energy of the guide rail, reduce noise, reduce the impact on the support column 24 and the positioning hole 11, and extend the service life of the support column 24 and the positioning hole 11.

[0065] During installation of the guide rail type vacuum heat treatment furnace, the bottom end of the support column 24 of the guide rail assembly 2 is aligned with the positioning hole 11 on the inner wall of the furnace body 1 and inserted vertically until the flange of the insertion section 242 is engaged inside the positioning hole 11 to complete the limiting. Then, the main rail 21, secondary rail 22, roller 23, and limiting pin 25 are installed as a whole. The limiting protrusion 243 is inserted through the installation gap 221, so that the limiting protrusion 243 is located between the two limiting pins 25, the main rail 21, and the secondary rail 22. The bottom surfaces of the main rail 21 and the secondary rail 22 are in close contact with the support surface 240 of the support column 24. When disassembling the guide rail type vacuum heat treatment furnace, the guide rail assembly 2 is lifted by directly pulling out the limiting pin 25, thus disengaging the guide rail assembly 2 from the positioning hole 11.

[0066] In summary, the guide rail vacuum heat treatment furnace of this application achieves its functionality through the insertion and connection of the bottom end of the support column 24 with the positioning hole 11, eliminating the need for welding or bolt tightening. During installation, simply align the support column 24 with the positioning hole 11 and insert it to complete the fixation. Disassembly is achieved by directly pulling out the guide rail assembly 2, reducing operational steps and making assembly and disassembly more convenient. Specifically, there are two positioning holes 11, symmetrically distributed along the length of the furnace body 1, with their axes perpendicular to the furnace body 1. This ensures that the insertion direction of the guide rail assembly 2 is perpendicular to the axis of the furnace body 1, avoiding manual angle adjustment and enabling rapid alignment. Furthermore, the mechanical insertion of the bottom end of the support column 24 with the positioning hole 11 replaces traditional welding and bolt connections, allowing for tool-free assembly and disassembly, thus improving the ease of guide rail assembly and disassembly.

[0067] Because the guide rail assembly 2 adopts a modular design, when a single guide rail is damaged, it can be directly replaced without the need for complete disassembly. If the roller 23 or support column 24 of a certain guide rail assembly 2 fails, only the guide rail assembly 2 needs to be pulled out and replaced, while other guide rail assemblies 2 can remain in use, thereby reducing the amount of maintenance work during use.

[0068] Equally important, the positioning holes 11 of the guide rail vacuum heat treatment furnace of this application are symmetrically arranged, and the number of guide rail components 2 is adjustable, so that the overall length of the rail can be adjusted according to the type or model of the material box, making it more versatile.

[0069] The above description is merely an optional embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A guide rail type vacuum heat treatment furnace, characterized in that, The utility model relates to a vacuum heat treatment furnace, including: a furnace body and at least one set of two guide rail assemblies arranged oppositely along the length direction of the furnace body in the furnace body; a bottom of an inner wall of the furnace body is provided with at least two positioning holes corresponding to each of the guide rail assemblies; each of the guide rail assemblies includes: a main rail and a sub rail, the extension directions of the main rail and the sub rail are parallel to the length direction of the furnace body, the two main rails of the two guide rail assemblies are both in the shape of a right L and horizontally opposite, and the two guide rail assemblies combine to form a limiting groove of a material box; a roller is rotatably connected between the main rail and the sub rail through a pin shaft; a support column is inserted into the corresponding positioning hole at a bottom end and has a support surface at a top portion for supporting the main rail and the sub rail of one guide rail assembly and a limiting protrusion on the support surface, the limiting protrusion extends into between two adjacent rollers; limiting pins are arranged on both sides of the limiting protrusion, the two ends of the limiting pins are connected with the main rail and the sub rail respectively, and the limiting pins are used for limiting the support column from shaking along the extension direction of the main rail.

2. The guided-arc vacuum heat treatment furnace according to claim 1, wherein The inner wall of the furnace body is welded or integrally formed with a positioning seat, and the positioning seat is provided with the positioning holes.

3. The guided-arc vacuum heat treatment furnace according to claim 1, wherein The support column includes a support section and a plug-in section, the support section and the plug-in section are coaxially arranged and detachably connected, the support section is provided with the support surface and the limiting protrusion, and the bottom end of the plug-in section is inserted into and limited to the inside of the positioning hole.

4. The guided-ship vacuum thermal treatment furnace according to claim 3, characterized in that, The bottom end of the support section and the top end of the plug-in section are provided with a threaded hole and a matching external thread respectively.

5. The guided-arc vacuum thermal processing furnace according to any one of claims 1 to 4, wherein One side of the main rail is provided with a stop edge extending along the height direction of the main rail, and the stop edges of the two guide rail assemblies are arranged in parallel relative to each other, so that the stop edges of the two guide rail assemblies form a limiting groove of a material box.

6. The guided-arc vacuum thermal processing furnace according to any one of claims 1 to 4, wherein The side of the main rail away from the sub rail is provided with a give-way inclined surface, and the give-way inclined surface faces the inner wall of the furnace body of the vacuum heat treatment furnace.

7. The guided-arc vacuum thermal processing furnace according to any one of claims 1 to 4, wherein Each of the guide rail assemblies is provided with at least two support columns and at least three rollers, the at least two support columns are distributed at intervals along the length direction of the main rail, and the interval between adjacent two support columns is less than 1 / 2 of the length of the material box.

8. The guided-arc vacuum thermal processing furnace according to any one of claims 1 to 4, wherein One end of the limiting pin extends horizontally through the sub rail, the other end abuts against the side wall of the main rail, the limiting pin is provided with a sleeve ring, the sleeve ring is made of graphite or carbon-carbon composite material and is configured as a buffer and damping structure between the limiting pin and the limiting protrusion.

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