Mechanical connection of concrete precast piles and method

Abstract

This invention discloses a mechanical connector and method for precast concrete piles, including a connecting clamp installed in a concave connecting groove to connect the pile end plates of two piles into one unit. The connecting clamp has at least one opening forming a micro-elastic unit connecting clamp with variable dimensions; a pile end plate for installing the connecting clamp and a pile sleeve clamp connected to the pile end plate for installing the connecting clamp; the end plate for installing the connecting clamp is slotted to reserve the clamp installation position; the upper end of the pile sleeve clamp has a radially inwardly formed radial protrusion, the top surface of which is on the same horizontal plane as the pile end face of the precast pile; the pile end plate and the pile sleeve clamp are welded together to form one unit, and an assembly weld is formed between the bottom surface of the pile end plate and the inner surface of the radial protrusion of the pile sleeve clamp; the bottom side surface of the pile end plate or the ground surface of the end plate and the radial protrusion of the pile sleeve clamp cooperate to form a concave connecting groove. This invention has a fast connection speed, strong environmental adaptability, and is safe and reliable, ensuring the tensile strength after the two piles are joined, and solving the problems of insufficient quality, tensile pull-out bearing capacity, and bending resistance of traditional pile foundation connections.

Description

Technical Field

[0001] This invention relates to connection technology for precast reinforced concrete pile foundations, and in particular to mechanical connectors and methods for precast concrete piles. Background Technology

[0002] The precast concrete pile industry has become a diversified sector, producing a wide variety of products including pipe piles, hollow square piles, solid square piles, irregularly shaped piles, interlocking piles, U-shaped piles, and sheet piles. These are widely used in industrial and civil construction, municipal engineering, metallurgy, ports, highways, and other fields. The vertical bearing capacity of pile foundations is no longer the primary evaluation indicator; on-site engineering projects increasingly demand stringent requirements for the vertical tensile loads of piles. However, under current technological conditions, welded end plates are commonly used in engineering projects. This welding method has several drawbacks: firstly, welding quality cannot be guaranteed, the requirements for weld seams are high, and rust prevention at the weld joints cannot be guaranteed; secondly, welding splicing is time-consuming, requiring a cooling period after welding. Furthermore, while mechanical connections are also used in existing projects, one method involves sealing the joints of multiple socket connectors with adhesive. This connection method cannot achieve a unified structural bearing capacity with the pile body; integral connections, due to their unreasonable structural bearing capacity, result in bulky construction, high costs, and difficult installation.

[0003] CN220225279U and CN219886799U propose using clamps inserted into the end plate. However, the clamps are divided into at least two parts, and the dimensions and methods for designing the clamp thickness are not clearly defined. This results in high clamp design rigidity, high installation precision requirements, and significant difficulties in on-site construction. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a mechanical connector for precast concrete piles, which addresses the problems of unreliable quality of traditional pile foundation connections, insufficient tensile strength and bearing capacity, and high cost of existing mechanical connections. It is simple and convenient to install and improves on-site construction efficiency.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] The mechanical connector for precast concrete piles includes a pile end plate embedded in the end face of the precast pile, the pile end plate having end plate holes for riveting and connecting with the prestressed steel bars inside the precast pile; it also includes a pile sleeve hoop embedded in the end of the precast pile, the pile sleeve hoop having two circumferentially formed anti-pull-out ribs for engaging with the pile body of the precast pile, and the upper end of the pile sleeve hoop having a radially inwardly formed radial L-shaped protrusion for engaging with the periphery of the end face of the precast pile, the top surface of the radial L-shaped protrusion being at the same level as the end face of the precast pile; the pile end plate is welded to the pile sleeve hoop before the precast pile is precast, and an assembly weld is formed between the bottom surface of the pile end plate and the inner surface of the radial protrusion of the pile sleeve hoop; the bottom surface of the pile end plate and the radial L-shaped protrusion of the pile sleeve hoop cooperate to form a connecting groove; a connecting clamp for engaging and connecting the pile end plates of the upper and lower sections of the precast pile into one piece is fitted in the connecting groove, and the connecting clamp has at least one connecting clamp opening.

[0007] To optimize the above technical solution, the specific measures also include:

[0008] The bottom surface of the aforementioned pile end plate is formed with an L-shaped groove in a closed loop. The upper end of the pile sleeve hoop is formed with a radially protruding edge for locking onto the periphery of the precast pile end face. The top surface of the radially protruding edge is on the same horizontal plane as the pile end face of the precast pile. The L-shaped groove and the radially protruding edge of the pile sleeve hoop cooperate to form a connecting groove.

[0009] The aforementioned pile end plate has a rectangular notch-shaped connecting groove machined around its perimeter at the bottom surface of the pile end plate; an assembly weld left by welding is formed between the bottom surface of the pile end plate and the inner wall of the top of the pile sleeve hoop.

[0010] The aforementioned pile end plate has welding notches processed around its top surface to form a weldable pile end plate. When two precast pile sections are joined, the welding notches of the two precast pile end plates fit together to form a welding bevel for easy welding. This welding bevel contains a connecting weld formed by welding the two pile end plates together. The aforementioned connecting clamp consists of a connecting clamp with at least one opening; the connecting clamp has two snap-fit ​​parts for snapping into the corresponding connecting slots of the two precast pile sections, and a locking cavity is formed between the two snap-fit ​​parts for locking the periphery of the two precast pile end plates.

[0011] The L-shaped groove of the aforementioned pile end plate is machined with anti-slip teeth. Correspondingly, the buckle of the connecting clamp is machined with anti-slip teeth for anti-slip contact with the anti-slip teeth in the L-shaped groove.

[0012] The aforementioned connecting clamps are connected end to end in a closed loop and are fitted into the connecting groove. The opening of the connecting clamp has a weld seam that is integrally welded to the side of the end plate.

[0013] The aforementioned connecting clamp is fitted into the connecting groove. The thickness of the clamp should not exceed the thickness of the end plate, so that the clamp has slight elasticity in the circumferential direction, which can expand the clamp opening and increase the circumferential dimension of the clamp. This allows the clamp to be fitted into the lower precast pile head before installation. After splicing the upper precast pile, the clamp can be installed in the connecting groove.

[0014] The thickness and dimensions of the connecting clamp must satisfy the finite element analysis requirements for the tensile bearing capacity of the thin plate. The equations are as follows:

[0015]

[0016] In the formula, b is the minimum inner radius of the clamp, a is the outer radius of the clamp, and D is the bending stiffness of the clamp plate. The thickness of the clamp that meets the tensile bearing capacity is determined by the above equations, the durability of the steel is estimated, and the minimum thickness and the size of the clamp opening are determined.

[0017] Compared with existing technologies, the mechanical connector for precast concrete piles of the present invention mainly includes a pile end plate, a pile sleeve, and a connecting clamp. The pile sleeve is pre-embedded at the end of the precast pile. The connecting clamp is an integral connector with only one opening. A connecting groove is formed between the pile end plate and the pile sleeve. When two piles are joined, the integral connecting clamp is inserted into the connecting groove to achieve a quick connection of the two precast pile sections. It has high bearing capacity, safe and reliable connection, and saves time and labor.

[0018] This invention reduces the connection time between precast piles while ensuring the tensile strength after connection. It solves the problems of unreliable connection quality and insufficient tensile strength in traditional pile foundations. Attached Figure Description

[0019] Figure 1 This is a structural schematic diagram of the pile-to-pile connection of the present invention and a partially enlarged schematic diagram of point I;

[0020] Figure 2 yes Figure 1 A partially enlarged cross-sectional view (1-1) of the schematic diagram of the weldless pile end plate splicing of the present invention, type 1 of the slot;

[0021] Figure 3 yes Figure 1 A partial enlarged cross-sectional view of the weldable pile end plate of the present invention, type 1, groove, in the present invention, shown in section 1-1;

[0022] Figure 4 yes Figure 1 A partial enlarged cross-sectional view of the weldless pile end plate of the present invention, type 2, in the present invention, shown in section 1-1;

[0023] Figure 5 yes Figure 1A partial enlarged cross-sectional view of the weldable pile end plate of the present invention, slot type 2, in the present invention, shown in section 1-1;

[0024] Figure 6 yes Figure 1 A partial enlarged cross-sectional view of the non-welding pile end plate of the present invention, type 3 of the slot, in the present invention, shown in section 1-1;

[0025] Figure 7 yes Figure 1 A partial enlarged cross-sectional view of the weldable pile end plate of the present invention, type 3, in the present invention, shown in section 1-1;

[0026] Figure 8 This is a schematic diagram of the circular and square end plates of the present invention;

[0027] Figure 9 yes Figure 8 Cross-sectional view of the weldless pile end plate of slot type 1 and a partially enlarged schematic diagram of part II;

[0028] Figure 10 yes Figure 8 Cross-sectional view of the weldable pile end plate of slot type 1 and a partially enlarged schematic diagram of section III;

[0029] Figure 11 This is a schematic diagram of the structure of the slot type 1 of the present invention with a partial pile end plate with anti-slip tooth surface;

[0030] Figure 12 This is a schematic diagram and a side sectional view of the groove-type pile sleeve of the present invention;

[0031] Figure 13 yes Figure 8 Cross-sectional view of the weldless pile end plate of slot type 2 and a partially enlarged schematic diagram of point IV;

[0032] Figure 14 yes Figure 8 Cross-sectional view of the weldable pile end plate of slot type 2 and a partially enlarged schematic diagram of section V;

[0033] Figure 15 This is a schematic diagram of the structure of the slot type 2 of the present invention with a partial pile end plate with anti-slip tooth surface;

[0034] Figure 16 This is a schematic diagram and a side sectional view of the two-pile sleeve of the present invention with a slot form;

[0035] Figure 17 yes Figure 8 Cross-sectional view of the weldless pile end plate of slot type 3 and a partial enlarged schematic diagram of point VI;

[0036] Figure 18 yes Figure 8Cross-sectional view of the weldable pile end plate of slot type 3 and a partially enlarged schematic diagram of section VII;

[0037] Figure 19 This is a schematic diagram of the structure of the slot type 3 of the present invention with a partial pile end plate with anti-slip tooth surface;

[0038] Figure 20 This is a schematic diagram and a side sectional view of the three-pile sleeve with a slotted design of the present invention.

[0039] Figure 21 This is a schematic diagram of the circular and square connecting clamps of the present invention;

[0040] Figure 22 yes Figure 21 Cross-sectional structural diagram;

[0041] Figure 23 yes Figure 21 Schematic diagram of the connecting clamp with anti-slip teeth

[0042] Figure 24 This is an installation diagram of the circular and square connecting clamps of the present invention when connecting piles;

[0043] Figure 25 This is a schematic diagram of the structure of the circular and square connecting clamps welded together in the present invention 1;

[0044] Figure 26 This is a schematic diagram of the structure of the circular and square connecting clamps welded together in the second manner according to the present invention;

[0045] Figure 27 This is a schematic diagram of the circular and square connecting clamps with threaded holes of the present invention;

[0046] Figure 28 This is a schematic diagram of the connection structure of the present invention with a threaded hole connecting clamp. Detailed Implementation

[0047] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0048] Figures 1 to 28 This is a schematic diagram of the structure of the present invention.

[0049] The attached reference numerals are as follows: assembly weld F1, connecting weld F2, clamp weld F3, clamp and end plate weld F4, clamp groove K1 for installing clamp, welding groove K2 for end plate bevel splicing, precast pile 1, prestressed steel bar 11, pile end plate 2, end plate hole 2a, end plate connecting groove surface 21, anti-slip tooth surface 21a, unit L-shaped groove 211, welding bevel 22, pile sleeve 3, pull-out rib 3a, radial L-shaped protrusion 31, radial protrusion 32, connecting clamp 4, connecting clamp opening 41, anti-slip tooth part 41a, snap part 411, snap cavity 412, clamp connecting assembly 5, connecting plate 51, circular bolt hole 51a, elongated bolt hole 51b, connecting bolt 52.

[0050] like Figure 1 and Figure 28 As shown, the present invention provides a mechanical connector for precast concrete piles, which includes a pile end plate 2 embedded in the end face of the precast pile 1. From Figure 8 , Figure 9 , Figure 24 , Figure 25 , Figure 26 and Figure 27 As can be seen from the images, the pile end plate 2 has multiple end plate holes 2a formed with equal arcs. The pile end plate 2 is riveted to the prestressed steel bars 11 on the reinforcing cage inside the precast pile 1 before the precast pile 1 is precast. A key feature of this invention is that a pile sleeve hoop 3 is also pre-embedded at the pile end of the precast pile 1. For example... Figure 12 As shown, the pile sleeve 3 has two circumferentially formed anti-pull-out ribs 3a for being inserted into the pile body of the precast pile 1, and the upper end of the pile sleeve 3 also has a radially inwardly formed radially L-shaped protrusion 31 for being inserted into the periphery of the end face of the precast pile 1. Figure 1 As shown, after the precast pile 1 is precast, the top surface of the radial L-shaped protrusion 31 is on the same horizontal plane as the pile end face of the precast pile 1. The pile end plate 2 is welded to the pile sleeve 3 before the precast pile is precast. The slot type 1 of this invention, from... Figure 3 and Figure 4 As can be seen, the bottom surface of the pile end plate 2 is welded and fixed to the inner side of the radial L-shaped protrusion 31 of the pile sleeve hoop 3, forming an assembly weld F1 left by the welding. Figure 1 As shown, when the two precast pile sections 1 are joined vertically, the pile end plates 2 of the two precast pile sections 1 correspond to each other, as shown. Figure 2 As shown, a connecting clamp 4 can be inserted into the connecting groove K1 of the two precast pile sections 1, locking the two pile end plates 2 around its circumference, thus achieving a quick connection between the two precast pile sections 1. Since the diameter of the connecting clamp 4 must match the diameter of the pile end plate 2, during installation, the connecting clamp 4 can be placed first on the lower section of the precast pile 1, such as... Figure 24 As shown, the upper section of precast pile 1 is then connected to it. Figure 1 Then install as follows Figure 2 As shown.

[0051] In the embodiments, the card slot form 2 of the present invention is as follows: Figure 13 As shown, an L-shaped groove 21 is formed in a closed loop around the bottom surface of the pile end plate 2. (As indicated...) Figure 16 As shown, the upper end of the pile sleeve 3 has a radially inwardly formed radially protruding edge 32 for engaging with the periphery of the pile end face of the precast pile 1. The top surface of the radially protruding edge 32 is on the same horizontal plane as the pile end face of the precast pile 1; as shown Figure 4 As shown, the connecting clamp 4 can be inserted into the connecting groove K1 formed by the L-shaped slot 21 and the radial protrusion 32 of the pile sleeve clamp 3.

[0052] In the embodiments, the card slot type 3 of the present invention is as follows: Figure 17 As shown, a rectangular notch-shaped connecting groove 21 is machined around the periphery of the pile end plate 2, immediately adjacent to the bottom surface of the pile end plate 2; as shown... Figure 6 , Figure 20 As shown, the bottom surface of the pile end plate 2 and the inner wall of the top of the pile sleeve hoop 3 are assembled and welded to form a weld F1, and the connecting clamp 4 is inserted into the connecting groove 21.

[0053] In the embodiments, the pile end plate 2 of the present invention can be divided into a non-welding pile end plate 2 and a weldable pile end plate 2. The non-welding pile end plate 2 is as follows: Figure 9 , Figure 13 and Figure 17 As shown, when the two piles are connected, it is as follows: Figure 2 , Figure 4 , Figure 6 As shown, the pile end plates 2 of the two precast piles 1 do not need to be welded together; they can be directly snapped into the connecting clamp 4. To prevent the connecting clamp 4 from coming off, the interfaces of the clamp openings 41 are welded together to form a complete connecting clamp 4. Figure 25 As shown, the connecting clamp 4 is closed-loop clamped in the connecting groove K1, and the openings 41 of the connecting clamp have a clamp weld seam F3 formed by welding them together.

[0054] like Figure 10 , Figure 14 and Figure 18 This invention shows another structure of the pile end plate 2, namely a weldable pile end plate, wherein a welding notch 22 is machined around the perimeter of the top surface of the pile end plate 2, as shown in the figure. Figure 1 As shown, when the welding notches 22 of the end plates 2 of the two precast piles 1 are fitted together, the two welding notches 22 can form a welding bevel K2 to ensure welding quality and facilitate welding. Figure 3 , Figure 5 , Figure 7 As shown, after the pile end plates 2 of the two pile sections are welded together, the resulting weld bevel K2 contains a connecting weld F2 formed because the piles are welded together as a single unit. After welding, as... Figure 25 As shown, the connecting clamp 4 is then inserted into the connecting clamp groove K1, and the openings 41 of the connecting clamp have a clamp weld seam F3 formed by welding them together.

[0055] In the embodiments, the connecting clamp 4 of the present invention is preferably composed of a circular ring or a square frame with a connecting clamp opening 41; such as Figure 21 , Figure 22 As shown, the connecting clamp 4 has two snap-fit ​​parts 411 for snapping into the corresponding connecting slots K1 of the two precast piles, and a snap cavity 412 is formed between the two snap-fit ​​parts 411 for locking the periphery of the pile end plate 2 of the two precast piles 1.

[0056] To further increase the friction between the connecting clamp 4 and the connecting groove K1, and to prevent the connecting clamp 4 from rotating circumferentially relative to the pile end plate 2. Figure 11 , Figure 15 and Figure 19 As shown, the present invention can also have an anti-slip toothed surface 21a machined in the L-shaped groove 21 of the pile end plate 2. Accordingly, as Figure 22 As shown, the buckle part 411 of the connecting clamp 4 is machined with anti-slip teeth 41a for anti-slip contact with the anti-slip tooth surface 21a in the L-shaped groove 21.

[0057] In this invention, during pile splicing, the opening 41 of the connecting clamp 4 can be pried open by a certain size using opening pliers, such as... Figure 24 As shown, the connecting clamp 4 can be fitted onto the lower pile head of the connecting pile. Then, after the upper pile sections are joined, the connecting clamp 4 is inserted into the groove. The open-end clamps are removed, and the sections are welded together to form a complete connecting clamp 4. Alternatively, it can be done as follows: Figure 27 As shown, the clamp connection assembly 5 is used to connect two adjacent unit connection clamps 41 to form a complete connection clamp 4.

[0058] In the embodiments, as shown Figure 26 As shown, during pile splicing, the connecting clamp 4 is fitted into the clamp slot K1, and the two ends of the connecting clamp opening 41 are welded and fixed to the side of the end plate 2 at the corresponding end. After welding, the two ends of the connecting clamp opening 41 and the end plate 2 are welded together to form the clamp and end plate weld F4.

[0059] In the embodiments, as shown Figure 27 As shown, the connecting clamp 4 is installed in the connecting groove K1, and the two ends of the connecting clamp opening 41 are fixedly connected into a whole by the clamp connecting assembly 5.

[0060] The clamp connecting assembly 5 of the present invention includes a connecting plate 51 and a connecting bolt 52 for fixing the connecting plate 51 to the connecting clamp 4. When the clamp connecting assembly 5 is used to connect the connecting clamp opening 41, as follows: Figure 27As shown, the connecting clamp 4 of the present invention needs to be machined with threaded holes 41b at both ends for screwing with the connecting bolt 52. Accordingly, as shown... Figure 28 As shown, the connecting plate 51 has two bolt holes for the connecting bolts 52 to pass through. One bolt hole is a circular bolt hole 51a, and the other is an elongated bolt hole 51b. The elongated bolt hole 51b is an adjustable bolt hole, which can be used to adjust the installation distance between the two bolt holes during actual installation.

[0061] It should be understood that although the above embodiments provide a relatively detailed textual description of the present invention, these textual descriptions are merely descriptions of the design concept of the present invention, and not limitations thereof. Any combination, omission, or modification that does not exceed the design concept of the present invention falls within the protection scope of the present invention.

Claims

1. A mechanical connector for precast concrete piles, comprising a connecting clamp (4) for connecting precast piles (1) into a single unit, wherein the connecting clamp (4) is composed of at least one connecting clamp opening (41); a pile end plate (2) pre-embedded on the pile end face of the precast pile (1), wherein the pile end plate (2) is formed with an end plate hole (2a) for riveting and connecting with the prestressed steel bars (11) inside the precast pile (1); characterized in that: It also includes a pile sleeve hoop (3) pre-embedded in the pile end of the precast pile (1). The pile sleeve hoop (3) has two pull-out ribs (3a) circumferentially formed on it for being inserted into the pile body of the precast pile (1). The upper end of the pile sleeve hoop (3) has a radially inwardly formed radial L-shaped protrusion (31) for being inserted into the periphery of the pile end face of the precast pile (1). The top surface of the radial L-shaped protrusion (31) is on the same horizontal plane as the pile end face of the precast pile (1). The pile end plate (2) is welded to the pile sleeve hoop (3) before the precast pile is precast. The bottom surface of the pile end plate (2) and the inner side of the radial L-shaped protrusion (31) of the pile sleeve hoop (3) form an assembly weld (F1) left by welding. The bottom surface of the pile end plate (2) and the radial L-shaped protrusion (31) of the pile sleeve hoop (3) cooperate to form a connecting groove (K1).

2. The mechanical connector for precast concrete piles according to claim 1, characterized in that: The bottom surface of the pile end plate (2) is formed with an L-shaped groove (21) in a closed loop. The upper end of the pile sleeve (3) is formed with a radial protrusion (32) for locking on the periphery of the pile end face of the precast pile (1). The top surface of the radial protrusion (32) is on the same horizontal plane as the pile end face of the precast pile (1). The L-shaped groove (21) and the radial protrusion (32) of the pile sleeve (3) cooperate to form a connecting groove (K1).

3. The mechanical connector for precast concrete piles according to claim 1, characterized in that: A rectangular notch-shaped connecting groove (21) is machined on the periphery of the pile end plate (2) at the bottom surface adjacent to the pile end plate (2); an assembly weld (F1) left by welding is formed between the bottom surface of the pile end plate (2) and the inner wall of the top of the pile sleeve hoop (3).

4. The mechanical connector for precast concrete piles according to claims 1, 2, and 3, characterized in that: The top surface of the pile end plate (2) is processed with welding notches (22) to form a weldable pile end plate. When two precast piles (1) are joined together, the welding notches (22) of the pile end plates (2) of the two precast piles (1) are matched to form a welding groove (K2) that is easy to weld. The welding groove (K2) has a connecting weld (F2) formed by welding the two pile end plates (2) together.

5. The mechanical connector for precast concrete piles according to claim 1, characterized in that: The connecting clamp (4) consists of a circular connecting clamp with an opening (41); the connecting clamp (4) has two snap-fit ​​parts (411) for snapping into the corresponding connecting slots (K1) of the two precast piles, and a snap cavity (412) is formed between the two snap-fit ​​parts (411) for snapping around the periphery of the pile end plate (2) of the two precast piles (1).

6. A mechanical connection for precast concrete piles as claimed in claim 1, wherein: The connecting clamp (4) consists of a square connecting clamp with an opening (41); the square connecting clamp (4) has two buckling parts (411) on its four sides for engaging in the corresponding connecting grooves (K1) of the two precast piles, and a clamping cavity (412) for engaging the four sides of the pile end plate (2) of the two precast piles (1) is formed between the two buckling parts (411). The four corners of the square connecting clamp (4) are not provided with buckling parts (411).

7. The mechanical connector for precast concrete piles according to claims 1, 2, 3, characterized in that: The L-shaped groove (21) of the pile end plate (2) is machined with anti-slip tooth surface (21a), and correspondingly, the buckle part (411) of the connecting clamp (4) is machined with anti-slip tooth surface (41a) for anti-slip contact with the anti-slip tooth surface (21a) in the L-shaped groove (21).

8. The mechanical connector for precast concrete piles according to claims 5 and 6, characterized in that: The connecting clamp (4) is connected end to end and locked in the connecting groove (K1). The thickness of the connecting clamp (4) should not exceed the thickness of the end plate according to the elastic force design of the thin plate. This allows the clamp to have slight elasticity in the circumferential direction, which can expand the clamp opening (41) and increase the circumferential size of the clamp (4). Before installation, the clamp (4) can be fitted into the head of the lower precast pile (1). After splicing the upper precast pile (1), the clamp can be installed in the connecting groove (K1).

9. A mechanical connection for precast concrete piles according to claim 5, 6, characterised in that: The connecting clamp (4) is connected end to end in a closed loop and is clamped in the connecting groove (K1). The opening (41) of the connecting clamp and the side of the end plate have a clamp weld seam (F3) formed by welding together.

10. The mechanical connector for precast concrete piles according to claim 5, 6, characterized in that: The connecting clamp (41) is connected end to end in a closed loop and is clamped in the connecting groove (K1). The opening (41) of the connecting clamp is fixedly connected to the connecting clamp assembly (5) to form a whole. The connecting clamp assembly (5) includes a connecting plate (51) and a connecting bolt (52) for fixing the connecting plate (51) to the connector of the connecting clamp (4). The connecting clamp (4) is machined with a threaded hole (41b) for screwing with the connecting bolt (52). The connecting plate (51) is machined with two bolt holes for the connecting bolt (52) to pass through. One of the two bolt holes is a circular bolt hole (51a) and the other is a long bolt hole (51b).

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