Scraper structure and scraper conveyor

Abstract

The present application relates to the technical field of coal mining, and particularly relates to a scraper structure and a scraper conveyor. The scraper structure comprises a scraper main body, a chain connecting unit and a plurality of sets of symmetrically arranged buffer units. The chain connecting unit comprises a shuttle hole, the shuttle hole comprises a first connecting hole, a second connecting hole group and a third connecting hole group which are symmetrically distributed about the central axis of the first connecting hole. The chain on the scraper conveyor is selectively connected with the first connecting hole, the second connecting hole group or the third connecting hole group. The scraper conveyor can adapt to single chain, double center chain and double edge chain, greatly improves the working condition adaptability, and can switch the conveying form without replacing the scraper, thereby improving the equipment versatility. By arranging the buffer structure, the risk of the scraper being separated from the conveyor track due to the rebound of the chain or the scraper main body is reduced, and the normal conveying of the coal mine is avoided.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, and in particular to a scraper structure and a scraper conveyor. Background Technology

[0002] A scraper conveyor is a general-purpose device that continuously transports bulk materials such as coal lumps within a trough using scrapers uniformly fixed to a chain. It can transport powdery, granular, and small lump materials horizontally, inclined, and vertically, and is widely used in coal, metallurgy, power, mining, and material conveying lines. Its core transmission components are the scrapers and the drive chain, relying on the reliable connection between the scrapers and the chain to achieve material movement. Based on the number and arrangement of chains, scraper conveyors are mainly divided into four structures: single-chain, double-sided chain, double-center chain, and triple-chain. Different chain types require corresponding scrapers, resulting in relatively poor versatility.

[0003] Currently, the conveying angle of conventional scraper conveyors is determined by the number of chains and the chain spacing. One type of scraper is only compatible with one type of chain, resulting in a fixed conveying angle and limited adaptability to different working conditions. At the same time, existing scraper conveyors generally lack buffering and anti-jump structures, making them prone to deviation and derailment during operation due to chain impact or their own bouncing. This not only affects the stable operation of the equipment but also reduces the conveying efficiency and production safety in underground coal mines. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a scraper structure and a scraper conveyor, which solves the technical problems of poor adaptability of existing scrapers to working conditions and easy scraper bouncing and derailment, resulting in poor conveying stability.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0008] This invention provides a scraper structure, including a scraper body, a chain connecting unit, and multiple symmetrically arranged buffer units. The chain connecting unit includes a shuttle hole that extends through the scraper body. The shuttle hole includes a first connecting hole and a second and third group of connecting holes symmetrically distributed about the central axis of the first connecting hole. Each of the second and third connecting hole groups includes two symmetrically distributed connecting holes centered on the first connecting hole. The chain on the scraper conveyor can optionally connect with the first connecting hole, the second connecting hole group, or the third connecting hole group. The buffer unit includes a buffer channel, a compression spring, and a support base. The buffer channel extends through the scraper body, and the support base partially extends into the buffer channel. One end of the compression spring is connected to the top wall of the buffer channel, and the other end is connected to the top of the support base. Because the scraper structure has a first connecting hole, a second connecting hole group, and a third connecting hole group, it can adapt to various chain types such as single chains, double-center chains, and double-sided chains, significantly improving adaptability to working conditions. The conveying mode can be switched without replacing the scraper, reducing operating costs and improving equipment versatility. The buffer unit is used to buffer the impact force on the scraper body during its movement by compressing the deformation of the spring during its extension. This reduces the amount of bouncing during the movement of the scraper body and greatly reduces the risk of the scraper body falling off the scraper conveyor. By setting up the buffer structure, the risk of the scraper falling off the conveyor track due to the bounce of the chain or scraper body can be reduced, thus avoiding affecting the normal transportation of coal in the mine.

[0009] Preferably, the top of the scraper body protrudes upward to form a trapezoidal platform, which is located in the middle of the scraper body.

[0010] Preferably, symmetrically arranged raised tail fins are formed on both sides of the top of the scraper body.

[0011] Preferably, a V-shaped recess is formed between the protruding tail fin and the trapezoidal platform.

[0012] Preferably, the inclination of the inclined surface of the V-shaped recess on the side closest to the trapezoidal platform is 30°-60°.

[0013] Preferably, the chain connection unit further includes multiple sets of locking components; at least two bolt holes are provided in the radial direction of the shuttle hole of the scraper body, the axis of the shuttle hole is perpendicular to the axis of the bolt hole, and the locking components are provided in correspondence with the bolt holes; the locking components include a threaded rod and a nut, the threaded rod passes through the bolt hole and is connected to the nut to lock the chain.

[0014] Preferably, the bottom ends of the support base extending along the length direction are provided with limiting rods.

[0015] Preferably, multiple sets of buffer units are symmetrically arranged with the axis of the first connecting hole as the center of symmetry.

[0016] The present invention also provides a scraper conveyor, including the scraper structure described above, and further including at least one chain; the chain may optionally be connected to a first connecting hole, a second connecting hole group or a third connecting hole group.

[0017] (III) Beneficial Effects

[0018] The beneficial effects of this invention are:

[0019] This invention discloses a scraper structure comprising a scraper body, a chain connecting unit, and multiple symmetrically arranged buffer units. The chain connecting unit includes a shuttle hole extending through the scraper body. The shuttle hole includes a first connecting hole and a second and third connecting hole group symmetrically distributed about the central axis of the first connecting hole. Each of the second and third connecting hole groups includes two symmetrically distributed connecting holes centered on the first connecting hole. The chain on the scraper conveyor can optionally connect with the first connecting hole, the second connecting hole group, or the third connecting hole group. Because the scraper structure has the first, second, and third connecting hole groups, it can adapt to various chain types such as single chains, double-center chains, and double-sided chains, significantly improving adaptability to different working conditions. The conveying mode can be switched without replacing the scraper, reducing operating costs and improving equipment versatility.

[0020] The buffer unit includes a buffer channel, a compression spring, and a support base. The buffer channel runs through the scraper body, and the support base extends into the buffer channel, with its bottom surface forming a sliding surface that mates with the scraper conveyor track. One end of the compression spring is connected to the top wall of the buffer channel, and the other end is connected to the top of the support base. The buffer unit buffers the impact force experienced by the scraper body during its movement by using the deformation of the compression spring as it extends. This reduces the amount of bouncing during scraper body movement and significantly decreases the risk of the scraper body detaching from the scraper conveyor. By incorporating the buffer structure, the risk of the scraper detaching from the conveyor track due to chain or scraper body bouncing can be reduced, preventing disruption to normal coal mine transportation. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the scraper structure of the present invention (showing the chain);

[0022] Figure 2 This is a front view of the scraper structure;

[0023] Figure 3 This is an exploded view of the scraper structure;

[0024] Figure 4 This is a top view of the scraper structure.

[0025] [Explanation of Labels in the Attached Image]

[0026] 1: Scraper body; 11: Trapezoidal platform; 12: Protruding tail fin; 13: V-shaped recess; 14: Bolt hole;

[0027] 2: Chain connection unit; 21: First connecting hole; 22: Second connecting hole group; 23: Third connecting hole group; 24: Locking element; 241: Threaded rod; 242: Nut;

[0028] 3: Buffer unit; 31: Buffer channel; 32: Compression spring; 33: Support base; 34: Limiting rod;

[0029] 4: Chain. Detailed Implementation

[0030] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] This invention aims to address the technical shortcomings of existing scraper conveyor structures, such as limited chain type compatibility, poor adaptability to working conditions, and susceptibility to bouncing during operation. It provides a scraper structure and scraper conveyor with a reasonable structural design, excellent buffering performance, strong adaptability, and stable operation. By setting up a chain connection unit 2 and a buffer unit 3, the reliability and service life of the scraper structure under complex working conditions in underground coal mines are improved, ensuring continuous and efficient coal transportation.

[0032] Example 1

[0033] like Figures 1-4 As shown, this embodiment provides a scraper structure. The scraper structure is integrally molded from high-strength wear-resistant alloy material, which can adapt to the harsh working environment of coal mines, characterized by dampness, high dust, high impact, and high wear, and possesses excellent structural strength and fatigue resistance. The scraper structure includes a scraper body 1, a chain connecting unit 2, and multiple symmetrically arranged buffer units 3. Each component unit cooperates and works together to achieve multiple functions of the scraper structure, such as efficient conveying, reliable connection, and buffering to prevent jumping.

[0034] The chain connection unit 2 includes a shuttle hole that runs through the scraper body 1. The shuttle hole includes a first connecting hole 21 and a second connecting hole group 22 and a third connecting hole group 23 symmetrically distributed about the central axis of the first connecting hole 21. Both the second connecting hole group 22 and the third connecting hole group 23 include two symmetrically distributed connecting holes centered on the first connecting hole 21. The three groups of connecting holes are arranged in a layered symmetrical layout on the scraper body 1. The hole walls are all chamfered and smoothed to prevent sharp edges from scratching the chain 4 and to reduce the resistance of the chain 4 during insertion. The chain 4 on the scraper conveyor can optionally be connected with the first connecting hole 21, the second connecting hole group 22, or the third connecting hole group 23. No structural changes to the scraper body 1 are required; multiple chain types can be adapted simply by adjusting the insertion position of the chain 4, significantly improving the versatility and interchangeability of the scraper and reducing the amount of spare parts needed and the procurement cost of mining equipment.

[0035] Because the scraper structure is equipped with a first connecting hole 21, a second connecting hole group 22, and a third connecting hole group 23, it can be adapted to various chain types such as single chain, double-center chain, and double-sided chain, greatly improving its adaptability to working conditions. The conveying mode can be switched without replacing the scraper, reducing operating costs and improving equipment versatility. Under different mining conditions such as thin coal seams, medium-thick coal seams, and steeply inclined coal seams, this scraper can be quickly matched with scraper conveyors of the corresponding chain type, eliminating the need for custom-made scraper, effectively shortening the equipment installation and commissioning cycle and improving mine mining efficiency. In practical applications, the chain connecting unit 2 is used to fix the scraper structure and the scraper conveyor. During the operation of the scraper conveyor, the chain 4 connects to the scraper structure, driving the scraper structure to move cyclically, thereby transporting the coal blocks by pushing them.

[0036] When a single chain 4 passes through the first connecting hole 21, a single-chain conveying mode is formed. This single-chain mode is suitable for low-power, low-capacity, and short-distance scraper conveyors, offering advantages such as simple structure, convenient assembly and disassembly, and flexible turning. When two chains 4 pass through the second connecting hole group 22 respectively, a double-center chain conveying mode for coal blocks is formed. This double-center chain mode features balanced force and moderate load-bearing capacity, suitable for medium-capacity, medium-inclination fully mechanized mining faces. When two chains 4 pass through the third connecting hole group 23 respectively, a double-sided chain conveying mode is formed. This double-sided chain mode has strong load-bearing capacity and excellent resistance to eccentric loading, suitable for heavy-duty scraper conveyors with large capacity, large inclination angle, and long distances, effectively handling the impact of large coal blocks. The shuttle hole configuration not only simplifies the installation and disassembly of the chain 4 but also improves the overall operating efficiency of the scraper conveyor. By adjusting the way the chain 4 passes through different connecting holes, different conveying modes and coal block conveying strategies can be achieved, meeting the application requirements under different working environments and needs.

[0037] The buffer unit 3 includes a buffer channel 31, a compression spring 32, and a support base 33. The buffer channel 31 extends through the scraper body 1, and its smooth inner wall provides stable vertical movement space for the support base 33, preventing jamming. The support base 33 partially extends into the buffer channel 31. One end of the compression spring 32 is connected to the top wall of the buffer channel 31, and the other end is connected to the top of the support base 33. The compression spring 32 is made of high-strength alloy spring steel, possessing excellent elastic recovery and fatigue resistance, and can withstand repeated impacts for extended periods without plastic deformation, fracture, or failure. The upper part of the support base 33 has an inverted conical structure, which matches the lower part of the buffer channel 31. This inverted conical structure prevents the support base 33 from detaching from the buffer channel 31. The buffer unit 3 is used to buffer the impact force experienced by the scraper body 1 during its movement by utilizing the deformation of the compression spring 32 when it extends. This reduces the amount of bouncing during the movement of the scraper body 1 and greatly reduces the risk of the scraper body 1 falling off the scraper conveyor. The buffer unit 3 can absorb the impact and vibration energy in real time, converting rigid impacts into elastic buffers, effectively protecting the scraper, chain, and conveyor trough, and reducing the overall machine failure rate.

[0038] By setting up the buffer unit 3, the risk of the scraper detaching from the conveyor track due to bouncing of the chain 4 or the scraper body 1 can be reduced, thus avoiding disruption to the normal transportation of coal in the mine. Specifically, when the scraper body 1 is impacted, the scraper body 1 bounces upward, causing the compression spring 32 to extend. The kinetic energy generated by the deformation of the compression spring 32 dissipates the tension of the scraper body 1, significantly reducing the risk of the scraper body 1 falling off. The elastic force of the compression spring 32 can be flexibly selected according to the working conditions. A high-stiffness spring is used in high-impact conditions, while a low-stiffness spring is used in stable conveying conditions, improving buffer adaptability. The support base 33 not only provides stable support for the compression spring 32 but also ensures that the scraper body 1 can smoothly reset after being impacted. Simultaneously, the support base 33 is fixedly connected to the bottom of the compression spring 32, enhancing the overall structural stability and ensuring that the scraper device maintains good working condition during long-term use, improving the durability and reliability of the equipment.

[0039] In this embodiment, four sets of buffer units 3 are provided, symmetrically arranged with the axis of the first connecting hole 21 as the center of symmetry. Two sets are symmetrically distributed on each side, ensuring that the scraper body 1 experiences uniform force during operation, preventing problems such as excessive force on one side, tilting, or uneven wear. The symmetrical layout also ensures that the buffering effect is simultaneous, providing balanced buffering support regardless of the direction of impact on the scraper, further improving operational stability.

[0040] In practical applications, a wear-resistant layer is provided at the bottom of the scraper body 1. The wear-resistant layer is made of steel plate, which can effectively resist the wear of coal blocks on the bottom of the scraper body 1 during transportation and extend the service life of the scraper structure.

[0041] like Figure 2 As shown, the top of the scraper body 1 protrudes upward to form a trapezoidal platform 11. The trapezoidal platform 11 is located in the middle of the scraper body 1. The top of the trapezoidal platform 11 is flat, which facilitates the opening of subsequent bolt holes 14. The inclined surfaces on both sides facilitate the flow of coal. The overall structure has high rigidity and is not easily deformed. In this embodiment, the first connecting hole 21 is opened in the middle of the trapezoidal platform 11. The two connecting holes in the second connecting hole group 22 are symmetrically opened on the trapezoidal platform 11 with the axis of the first connecting hole 21 as the center. Since the two sides of the trapezoidal platform 11 are inclined guide surfaces, the guide surfaces allow the coal blocks to slide more smoothly along the two sides of the trapezoidal platform 11 during the movement of the scraper body 1, reducing the accumulation and jamming of coal blocks on the scraper body 1, improving the transportation efficiency of coal blocks and the operational stability of the scraper structure.

[0042] like Figure 1 As shown, symmetrically arranged raised tail wings 12 are formed on both sides of the top of the scraper body 1. The raised tail wings 12 are used to block the leakage of coal blocks. The edges of the raised tail wings 12 are rounded to reduce the friction and resistance of coal blocks during the scraping process, and at the same time prevent coal blocks from getting stuck between the tail wings and the scraper body 1. The raised tail wings 12 can maintain the good structural integrity and functional stability of the scraper body 1, thereby effectively extending the service life of the scraper.

[0043] like Figure 1 and Figure 2 As shown, a V-shaped recess 13 is formed between the protruding tail fin 12 and the trapezoidal platform 11. The V-shaped recess 13 has an upward opening and a smooth bottom transition, forming an overall flow channel structure that provides good guidance and prevents coal accumulation. The inclination angle of the inclined surface of the V-shaped recess near the trapezoidal platform 11 is 30°-60°, ensuring a good material guiding angle, balancing smooth flow and structural strength, and extending service life. In this embodiment, the inclined surface is preferably 45°, as this angle results in fast coal flow, prevents accumulation, optimizes the stress on the scraper structure, and achieves the best overall performance.

[0044] like Figure 1 and Figure 3As shown, the chain connection unit 2 also includes multiple sets of locking components 24. The number of locking components 24 matches the number of connecting holes and is evenly distributed to ensure that the chain 4 is subjected to consistent force and that no single point is subjected to excessive force. At least two bolt holes 14 are provided radially on each of the shuttle holes of the scraper body 1. The axis of the shuttle hole and the axis of the bolt hole 14 are perpendicular to each other. This perpendicular arrangement ensures that the direction of the locking force is orthogonal to the direction in which the chain 4 passes through, resulting in a more secure locking effect and effectively preventing axial movement of the chain 4. Each locking component 24 corresponds to one bolt hole 14. Each locking component 24 includes a threaded rod 241 and a nut 242. The threaded rod 241 passes through the bolt hole 14 and connects with the nut 242 to lock the chain 4. When chain 4 passes through the inside of the shuttle hole, select the chain ring that is laid flat in chain 4. The two ends of the chain ring are respectively connected to threaded rods 241. The lower end of threaded rods 241 is connected to the nut 242 at the bottom of scraper body 1, which can connect chain 4 to scraper body 1.

[0045] like Figure 2 As shown, the support base 33 has symmetrically arranged limiting rods 34 at both ends of its bottom extending along its length. The limiting rods 34 extend into pre-set grooves on the sliding surface of the scraper conveyor, constraining the width of the support base 33 on both sides and effectively suppressing excessive swaying of the scraper body 1 in the width direction. The groove is a T-shaped groove structure, with a gap between the two ends of the limiting rods 34 and the inner wall of the T-shaped groove. This gap provides redundancy for the limiting rods 34 when the support base 33 is impacted and vibrates, and also prevents the limiting rods 34 from dislodging from the groove during scraper body 1 movement, thus ensuring that the scraper body 1 is stably mounted on the sliding surface of the scraper conveyor via the limiting rods 34. In practical applications, the scraper structure is inserted into the sliding surface from one side of the scraper conveyor, with the limiting rods 34 located within the grooves.

[0046] Example 2

[0047] This embodiment provides a scraper conveyor, including the scraper structure in Embodiment 1, and also includes at least one chain 4, which can optionally be connected to the first connecting hole 21, the second connecting hole group 22 or the third connecting hole group 23.

[0048] When a single chain 4 passes through the first connecting hole 21, a single-chain conveying mode is formed, facilitating quick adjustment of the conveying direction by the scraper body 1. This single-chain mode is suitable for low-power, low-capacity, and short-distance scraper conveyors, offering advantages such as simple structure, convenient assembly and disassembly, and flexible turning. When two chains 4 pass through the second connecting hole group 22 respectively, a double-center chain conveying mode for coal blocks is formed. This mode features balanced force distribution and moderate load-bearing capacity, suitable for medium-capacity, medium-inclination fully mechanized mining faces. When two chains 4 pass through the third connecting hole group 23 respectively, a double-sided chain conveying mode is formed. This mode boasts strong load-bearing capacity and excellent resistance to eccentric loading, suitable for heavy-duty scraper conveyors with large capacity, large inclination angle, and long distances, effectively handling the impact of large coal blocks. The shuttle hole configuration not only simplifies the installation and disassembly of the chain 4 but also improves the overall operating efficiency of the scraper conveyor. By adjusting the way the chain 4 passes through different connecting holes, different conveying modes and coal block conveying strategies can be achieved, meeting the application requirements under different working environments and needs. The scraper conveyor of this invention can achieve multiple uses, quick switching, and stable operation, greatly improving equipment utilization and production efficiency.

[0049] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0050] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0051] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that they are in indirect contact through an intermediate medium. Furthermore, "above," "over," or "on top" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," or "beneath" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0052] In the description of this specification, the terms "one embodiment," "some embodiments," "embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0053] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A scraper structure, characterized in that, It includes a scraper body (1), a chain connecting unit (2), and multiple sets of symmetrically arranged buffer units (3); The chain connection unit (2) includes a shuttle hole, which is opened through the scraper body (1). The shuttle hole includes a first connecting hole (21) and a second connecting hole group (22) and a third connecting hole group (23) symmetrically distributed about the central axis of the first connecting hole (21). The second connecting hole group (22) and the third connecting hole group (23) each include two symmetrically distributed connecting holes centered on the first connecting hole (21). The chain (4) on the scraper conveyor can optionally be connected with the first connecting hole (21), the second connecting hole group (22) or the third connecting hole group (23). The buffer unit (3) includes a buffer channel (31), a compression spring (32) and a support seat (33). The buffer channel (31) is opened through the scraper body (1). The support seat (33) extends into the buffer channel (31). One end of the compression spring (32) is connected to the top wall of the buffer channel (31), and the other end of the compression spring (32) is connected to the top of the support seat (33).

2. The scraper structure as described in claim 1, characterized in that: The top of the scraper body (1) protrudes upward to form a trapezoidal platform (11), and the trapezoidal platform (11) is located in the middle of the scraper body (1).

3. The scraper structure as described in claim 2, characterized in that: The scraper body (1) has symmetrically arranged raised tail wings (12) on both sides of its top.

4. The scraper structure as described in claim 3, characterized in that: A V-shaped recess (13) is formed between the raised tail fin (12) and the trapezoidal platform (11).

5. The scraper structure as described in claim 4, characterized in that: The inclination of the inclined surface of the V-shaped recess on the side near the trapezoidal platform (11) is 30°-60°.

6. The scraper structure as described in claim 1, characterized in that: The chain connection unit (2) also includes multiple sets of locking elements (24); The scraper body (1) has at least two bolt holes (14) in the radial direction of the shuttle hole. The axis of the shuttle hole is perpendicular to the axis of the bolt hole (14). The locking member (24) is provided in a one-to-one correspondence with the bolt hole (14). The locking element (24) includes a threaded rod (241) and a nut (242), the threaded rod (241) passing through the bolt hole (14) and connecting to the nut (242) to lock the chain (4).

7. The scraper structure as described in claim 1, characterized in that: The support base (33) has limiting rods (34) at both ends of its bottom extending along the length direction.

8. The scraper structure as described in claim 1, characterized in that: Multiple sets of buffer units (3) are symmetrically arranged with the axis of the first connecting hole (21) as the center of symmetry.

9. A scraper conveyor, characterized in that: The scraper structure according to any one of claims 1-8 further includes at least one chain (4). The chain (4) may optionally be connected to the first connecting hole (21), the second connecting hole group (22), or the third connecting hole group (23).

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