A bolt assembly for fabricated foundation pit support

Abstract

The application belongs to the technical field of building construction, and particularly relates to a bolt assembly for a fabricated foundation pit support, which comprises a first compression ring, a tensile-resistant flexible disc, a first adapter and a second compression ring; the first adapter is in the shape of a pipe cylinder; the first adapter comprises an inner connecting section, an outer convex ring and an outer connecting section; the inner connecting section is connected with an anchor rod, the outer connecting section is connected with the inner connecting section, and the outer convex ring is arranged between the two; the flexible disc is in the shape of a disc; the flexible disc is connected with the inner connecting section and a support plate, and is compressed by the second compression ring and the first compression ring; the flexible disc can be bent and deformed to adapt to the change in the relative position of the anchor rod and the support plate. The flexible disc made of rubber material is used to achieve the flexible connection between the support plate and the anchor rod, so that the load transferred between the support plate and the anchor rod can be reduced when the soil quality of the side wall of the foundation pit changes, the protection of the anchor rod and the support plate is realized, and the recycling and secondary use of part or all of the components of the support structure are facilitated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of building construction, and particularly relates to a bolt assembly for assembly type foundation pit support. BACKGROUND

[0002] In the existing building construction technology, the foundation pit support is often used to strengthen the structural stability of the foundation pit. For the temporary support that needs to be disassembled later, the disassemblability and the integrity of the parts are important. At present, for the temporary support structure with anchor rods, the hard connection relationship between the existing anchor rod and the support plate is often adopted. When the soil settlement, water accumulation and other problems occur later, the force borne by the anchor rod or the support plate will be directly transmitted to the other party, which is easy to cause the deformation or damage of the two, and affects the secondary use of the temporary support.

[0003] Therefore, it is necessary to design a bolt assembly that realizes flexible connection between the pipe and the support plate. SUMMARY

[0004] In order to solve the above problems existing in the prior art, the present application provides a bolt assembly for assembly type foundation pit support.

[0005] The technical scheme adopted by the present application is as follows:

[0006] A bolt assembly for assembly type foundation pit support, comprising a first compression ring, a tensile-resistant flexible disc, a first adapter and a second compression ring.

[0007] The foundation pit support comprises anchor rods and support plates, the support plates are used to abut against the side wall of the foundation pit, and the anchor rods are used to be inserted into the side wall of the foundation pit; the bolt assembly is used for the connection between the anchor rod and the support plate.

[0008] The first adapter is in the shape of a pipe; the first adapter comprises an inner connecting section, an outer protruding ring and an outer connecting section; the inner connecting section is used for detachable fixed connection with the anchor rod, the outer connecting section is connected to the outer end of the inner connecting section, and the outer protruding ring is arranged on the outer circumferential side of the connecting position of the inner connecting section and the outer connecting section.

[0009] The flexible disc is in the shape of a disc; the center of the flexible disc is connected with the inner connecting section, and the flexible disc is compressed onto the outer end face of the outer protruding ring by the second compression ring; the outer edge of the flexible disc is compressed onto the outer surface of the support plate by the first compression ring; the flexible disc can be bent and deformed, and can be stretched and deformed within a preset range to adapt to the change of the relative position of the anchor rod and the support plate.

[0010] As an alternative or supplement to the above bolt assembly: the inner connecting section is provided with an inner thread on the pipe wall, and the end of the anchor rod is provided with an outer thread, which is threadedly connected with the inner thread.

[0011] As an alternative or supplement to the above bolt assembly: the outer side wall of the inner connecting section is provided with a screw hole; the end of the anchor rod has a pipe mouth and the side wall is provided with a through hole, and the anchor rod is connected to the screw hole by a screw.

[0012] As an alternative or supplement to the above bolt assembly: the inner side of the outer connecting section is provided with an internal thread; the bolt assembly further comprises a second adapter, an end connector, a universal joint and a clamp connector; the second adapter comprises an external thread cylinder for threadedly connecting the outer connecting section and a T-shaped connector coaxially connected with the external thread cylinder; the end connector is rotationally connected with the T-shaped connector, the end connector is connected with the clamp connector through the universal joint, and the clamp connector is used to connect a pressing assembly for pressing against the outer surface of the support plate.

[0013] As an alternative or supplement to the above bolt assembly: the pressing assembly comprises a backing plate, a pressing seat and a force transmission rod; the backing plate is in the shape of a strip or a wedge, the pressing seat is connected perpendicularly to the middle part of the backing plate, the end of the force transmission rod is connected with the pressing seat, and the clamp connector is connected with the force transmission rod and can slide along the force transmission rod.

[0014] As an alternative or supplement to the above bolt assembly: the flexible disc is made of rubber material, and a fiber layer is embedded in the flexible disc.

[0015] As an alternative or supplement to the above bolt assembly: the anchor rod is a tubular structure composed of four pipe petals, and the end of the anchor rod away from the support plate is tapered; a pipe petal support is arranged in the anchor rod, and the pipe petal support is connected with the four pipe petals and can spread or gather the four pipe petals.

[0016] As an alternative or supplement to the above bolt assembly: the pipe petal support comprises an external thread pipe column, a sliding sleeve, a connecting rod and a clamping head; the external thread pipe column is in the shape of a pipe cylinder, and opposite external threads are arranged at both ends of the external thread pipe column; one sliding sleeve is threadedly connected to each end of the external thread pipe column; one clamping head is connected to the inner wall of each of the four pipe petals, and each clamping head is connected with two sliding sleeves through two connecting rods, and the connecting rod is rotationally connected with the sliding sleeve and the clamping head; when the external thread pipe column rotates, the sliding sleeves gather or separate from each other, so that the four pipe petals are spread or gathered.

[0017] As an alternative or supplement to the above bolt assembly: the inner wall of each of the four pipe petals is provided with a clamping groove, and the clamping groove comprises a rectangular groove section and a T-shaped groove section, and the T-shaped groove section communicates with the rectangular groove section; the clamping head is in the shape of a T, and the clamping head can be inserted into the rectangular groove section and slide into the T-shaped groove section to realize the clamping and fitting of the clamping head and the clamping groove.

[0018] As an alternative or supplement to the bolt assembly described above: the tool cooperating with the pipe flap support includes a disassembly operating rod and an expansion operating rod, the end of the disassembly operating rod is provided with a threaded head, and the end of the expansion operating rod is provided with a prismatic head; the inner hole of the outer threaded pipe column includes a prismatic hole section and a threaded hole section, the prismatic hole section cooperates with the prismatic head, and the threaded head cooperates with the threaded hole section.

[0019] The beneficial effects of the present application are: the flexible connection between the support plate and the anchor rod is realized by the flexible disc of the rubber material, the load transmitted between the support plate and the anchor rod can be reduced when the soil of the side wall of the foundation pit changes, the protection of the anchor rod and the support plate is realized, and the recycling and secondary use of part or all of the components of the support structure are facilitated. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced.

[0021] Fig. 1 is a cooperation structure diagram of the bolt assembly and the pressing assembly;

[0022] Fig. 2 is a detailed structure diagram of the bolt assembly;

[0023] Fig. 3 is a use state diagram of the bolt assembly;

[0024] Fig. 4 is a structure schematic diagram of an anchor rod;

[0025] Fig. 5 is a cooperation structure diagram of the pipe flap support and the expansion operating rod;

[0026] Fig. 6 is a cooperation structure diagram of the pipe flap support and the disassembly operating rod.

[0027] In the drawings: 1-support plate; 2-pipe flap support; 21-outer threaded pipe column; 22-sliding sleeve; 23-connecting rod; 24-clamping joint; 3-anchor rod; 31-pipe flap piece; 311-clamping groove; 4-bolt assembly; 41-first pressing ring; 42-flexible disc; 43-first adapter; 431-inner connecting section; 432-outer convex ring; 433-outer connecting section; 44-second pressing ring; 45-second adapter; 451-outer threaded cylinder; 452-T-shaped connecting head; 453-lateral through hole; 46-end connector; 47-universal coupling; 48-hoop connector; 5-pressing assembly; 51-pad; 52-pressing seat; 53-force transmission rod; 6-expansion operating rod; 61-prismatic head; 7-disassembly operating rod; 71-threaded head. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments will be described clearly and completely below with reference to the drawings. The described embodiments are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative labor on the basis of the embodiments in the present solution fall within the protection scope of the present solution.

[0029] Embodiment 1

[0030] As shown in the drawings, the present embodiment designs a bolt assembly 4 for a fabricated foundation pit support, which comprises a first compression ring 41, a tensile-resistant flexible disc 42, a first adapter 43 and a second compression ring 44 and the like. Figs. 1-3 The foundation pit support comprises an anchor rod 3 and a support plate 1. In use, the support plate 1 is abutted to the side wall of the foundation pit, thereby providing support for the side wall of the foundation pit, so as to reduce the collapse of the side wall of the foundation pit. The anchor rod 3 is used to be inserted into the side wall of the foundation pit and to provide a fulcrum for the fixation of the support plate 1. One support plate 1 is generally connected with one or more anchor rods 3, so as to ensure the stability of the installed support plate 1. The bolt assembly 4 is used for the connection between the anchor rod 3 and the support plate 1. In the prior art, an iron gasket and a nut are often used to realize the connection between the anchor rod 3 and the support plate 1. However, this structure is prone to mutual force transmission between the anchor rod 3 and the support plate 1, and the local pressure is relatively high, which is prone to cause damage to the foundation pit support and affect the secondary use.

[0031] The first adapter 43 is in the shape of a tube, thereby reducing the weight of the first adapter 43 and facilitating the connection with the second adapter 45. The first adapter 43 comprises an inner connecting section 431, an outer convex ring 432 and an outer connecting section 433. The inner connecting section 431 is used for detachably fixedly connecting with the anchor rod 3. The outer connecting section 433 is connected to the outer end of the inner connecting section 431. The outer convex ring 432 is arranged on the outer periphery side of the connection between the inner connecting section 431 and the outer connecting section 433. The inner connecting section 431, the outer convex ring 432 and the outer connecting section 433 are integrally formed.

[0032] The flexible disc 42 is in the shape of a disc. The center of the flexible disc 42 is connected with the inner connecting section 431. The flexible disc 42 is compressed by the second compression ring 44 to the outer end face of the outer convex ring 432, thereby realizing the connection between the flexible disc 42 and the first adapter 43. The second compression ring 44 is threadedly connected with the inner connecting section 431. The outer edge of the flexible disc 42 is compressed by the first compression ring 41 to the outer surface of the support plate 1, thereby realizing the connection between the flexible disc 42 and the support plate 1. The screw passing through the structure of the first compression ring 41, the flexible disc 42 and the support plate 1 can fix them together.

[0033]

[0034] ​The flexible disc 42 is made of rubber material, and a fiber layer is embedded in the flexible disc 42, so that the flexible disc 42 can be bent and deformed, and can be stretched and deformed within a preset range to adapt to the change of the relative position of the anchor rod 3 and the support plate 1. When the anchor rod 3 and the support plate 1 are dislocated, the deformation of the flexible disc 42 can be compensated, so as to reduce the transmission of the load between the anchor rod 3 and the support plate 1, better protect the anchor rod 3 and the support plate 1, reduce the damage of the two, and facilitate subsequent recycling and secondary use.

[0035] The inner connecting section 431 is provided with an internal thread on the pipe wall, and when the end of the anchor rod 3 is provided with an external thread, the internal thread is threadedly connected with the external thread. Or / and, the outer side wall of the inner connecting section 431 is provided with a screw hole; when the end of the anchor rod 3 is provided with a pipe opening and the side wall is provided with a through hole, the anchor rod 3 is connected to the screw hole through a screw. The inner connecting section 431 can be provided with a matching structure (such as the internal thread and the screw hole described above) corresponding to the connection of different anchor rods 3, so as to ensure the connection of the inner connecting section 431 and the anchor rod 3.

[0036] In addition, the bolt assembly 4 further comprises a second adapter 45, an end connector 46, a universal coupling 47 and a clamp connector 48. The second adapter 45 comprises an external thread cylinder 451 and a T-shaped connector 452, the inner side of the outer connecting section 433 is provided with an internal thread, the external thread cylinder 451 is used for threadedly connecting to the internal thread of the outer connecting section 433, and the T-shaped connector 452 is coaxially connected with the external thread cylinder 451; a lateral through hole 453 is arranged on the cylinder wall of the external thread cylinder 451, a rod can be inserted into the lateral through hole 453 to rotate the second adapter 45, and a hose can also be inserted into the lateral through hole 453 and extended into the anchor rod 3, so that the accumulated water in the anchor rod 3 is pumped out through the hose. The end connector 46 is rotationally connected with the T-shaped connector 452, and the end connector 46 can rotate about the center line of the T-shaped connector 452, so as to avoid the problem that the end connector 46 rotates synchronously when the second adapter 45 is rotated. The end connector 46 is connected with the clamp connector 48 through the universal coupling 47, and the universal coupling 47 can reduce the shear force borne by the anchor rod 3. The clamp connector 48 is used for connecting a pressing assembly 5, and the pressing assembly 5 is used for abutting against the outer surface of the support plate 1. Through the pressing assembly 5, the stress area of the support plate 1 can be increased, and the direct transmission of the load to the support plate 1 can be reduced.

[0037] The pressure-absorbing assembly 5 includes components such as a pad 51, a pressure-absorbing seat 52, and a force transmission rod 53. The pad 51 is in the shape of a strip or a wedge to increase the contact area. By varying the number, thickness, and shape of the pads 51, the pressure-absorbing assembly 5 can more reliably press against the support plate 1, thereby reducing the formation of shear force. The pressure-absorbing seat 52 is vertically connected to the middle of the pad 51 (connected by screws, welding, etc.). The two ends of the force transmission rod 53 are connected to the respective pressure-absorbing seats 52. The two pressure-absorbing seats 52 can have different heights, so that the supporting force direction of the force transmission rod 53 can also be different. The clamp connector 48 is connected to the force transmission rod 53 and can slide along the force transmission rod 53. Therefore, when the anchor rod 3 and the support plate 1 misalign, it can achieve self-adaptation to a certain extent, thereby reducing the problem of soil leakage due to overload of the support plate 1, and reducing the shear force between the anchor rod 3 and the support plate 1.

[0038] Example 2

[0039] like Figs. 1-6 As shown, based on the structure of Embodiment 1, the structure in this embodiment was designed to enable the disassembly of the anchor rod 3.

[0040] The anchor rod 3 is a tubular structure composed of four pipe-shaped segments 31. The end of the anchor rod 3 furthest from the support plate 1 is tapered, facilitating its insertion into the holes drilled in the sidewall of the foundation pit. Inside the anchor rod 3 is a pipe-shaped support 2, which is connected to the four pipe-shaped segments 31 and can open or close them. When closed, the four segments 31 come together; when opened, they separate, allowing them to press against the holes in the sidewall of the foundation pit, thus fixing the anchor rod 3. Water from the sidewall of the foundation pit can also seep into the anchor rod 3, facilitating unified pumping and reducing the probability of soil collapse at the foundation pit.

[0041] The pipe valve support 2 comprises an outer threaded pipe column 21, sliding sleeves 22, connecting rods 23 and clamping joints 24, etc. The outer threaded pipe column 21 is in the shape of a pipe cylinder, and opposite threads are arranged at both ends of the outer threaded pipe column 21. A stop ring can be welded at both ends of the outer threaded pipe column 21 to prevent the sliding sleeves 22 from sliding off the outer threaded pipe column 21. One sliding sleeve 22 is threadedly connected at each end of the outer threaded pipe column 21. Since the threads at both ends of the outer threaded pipe column 21 are opposite, and the threads of the sliding sleeves 22 are also opposite, when the outer threaded pipe column 21 rotates, the sliding sleeves 22 can move closer to each other or move away from each other. One clamping joint 24 is connected to the inner wall of each of the four pipe petals 31. Each clamping joint 24 is connected to two sliding sleeves 22 through two connecting rods 23. The two connecting rods 23 are in the shape of a spread-out V. The connecting rods 23 are rotationally connected to the sliding sleeves 22 and the clamping joints 24. When the outer threaded pipe column 21 rotates and the sliding sleeves 22 move closer to each other or move away from each other, the four clamping joints 24 move away from each other or move closer to each other, thereby driving the four pipe petals 31 to spread out or move closer to each other.

[0042] A clamping groove 311 is arranged on the inner wall of each of the four pipe petals 31. The clamping groove 311 comprises a rectangular groove section and a T-shaped groove section, and the T-shaped groove section is in communication with the rectangular groove section. The clamping joint 24 is in the shape of a T. The clamping joint 24 can be inserted into the rectangular groove section and slid into the T-shaped groove section to achieve the clamping connection of the clamping joint 24 and the clamping groove 311. The disassembly of the clamping joint 24 and the clamping groove 311 can achieve the separation of the pipe valve support 2 and the pipe petals 31, thereby facilitating the piece-by-piece disassembly of the pipe petals 31 and reducing the difficulty of disassembling the pipe petals 31.

[0043] The tool cooperating with the pipe valve support 2 comprises a disassembly operating rod 7 and an expansion and contraction operating rod 6. A threaded head 71 is arranged at the end of the disassembly operating rod 7, and a prismatic head 61 is arranged at the end of the expansion and contraction operating rod 6. The inner hole of the outer threaded pipe column 21 comprises a prismatic hole section and a threaded hole section. The prismatic hole section cooperates with the prismatic head 61, and the threaded head 71 cooperates with the threaded hole section. The diameter of the rod section of the expansion and contraction operating rod 6 is smaller than the diameter of the inscribed circle of the prismatic hole section and the threaded hole section.

[0044] Before the anchor rod 3 is inserted into the hole on the side wall of the foundation pit support, the pipe valve support 2 is connected with the anchor rod 3, and multiple pipe valve supports 2 can be arranged in the length direction of the anchor rod 3. When the prismatic head 61 of the expansion and contraction operating rod 6 is inserted into the prismatic hole section of the pipe valve support 2, the expansion and contraction operating rod 6 can control the rotation of the external thread pipe column 21, thereby controlling the four pipe valve pieces 31 to be expanded and tightly abut against the side wall of the hole. After the multiple pipe valve supports 2 are all expanded, the fixation of the anchor rod 3 can be realized. When the four pipe valve pieces 31 are expanded, the rotation of each external thread pipe column 21 can be performed in sequence, thereby reducing the mutual interference between different pipe valve supports 2. Similarly, the four pipe valve pieces 31 can be gathered by reversely rotating the expansion and contraction operating rod 6.

[0045] When the pipe valve pieces 31 are in the gathered state, the threaded head 71 of the disassembly operating rod 7 is connected to the threaded hole section of the external thread pipe column 21. The disassembly operating rod 7 can drive the pipe valve support 2 to move, so that the clamping joint 24 moves to the rectangular groove section. Then, the external thread pipe column 21 is rotated again, so that the clamping joint 24 exits the clamping groove 311, and the pipe valve support 2 can be taken out from the anchor rod 3 in sequence, thereby facilitating the piece-by-piece disassembly of the pipe valve pieces 31.

[0046] The above embodiments are only examples for clearly illustrating the made examples, and are not limitations on the embodiments; all the embodiments do not need to be exhausted here, and it is impossible to exhaust all the embodiments. The obvious changes or changes derived therefrom are still within the protection scope of the technology.

Claims

1. A bolt assembly for prefabricated foundation pit support, characterized in that: It includes a first clamping ring (41), a tensile flexible disc (42), a first adapter (43), and a second clamping ring (44); The foundation pit support includes anchor rods (3) and support plates (1). The support plates (1) are used to abut against the side wall of the foundation pit, and the anchor rods (3) are used to insert into the side wall of the foundation pit. The bolt assembly (4) is used to connect the anchor rods (3) and the support plates (1). The first adapter (43) is in the shape of a tube; the first adapter (43) includes an inner connecting section (431), an outer protruding ring (432) and an outer connecting section (433); the inner connecting section (431) is used for a detachable fixed connection with the anchor rod (3), the outer connecting section (433) is connected to the outer end of the inner connecting section (431), and the outer protruding ring (432) is disposed on the outer periphery of the connection between the inner connecting section (431) and the outer connecting section (433); The flexible disc (42) is disc-shaped; the center of the flexible disc (42) is connected to the inner connecting section (431) and is pressed onto the outer end face of the outer convex ring (432) by the second pressing ring (44); the outer edge of the flexible disc (42) is pressed onto the outer surface of the support plate (1) by the first pressing ring (41); the flexible disc (42) can be bent and deformed, and can be stretched and deformed within a preset range to accommodate the changes in the relative position of the anchor rod (3) and the support plate (1).

2. The bolt assembly for prefabricated foundation pit support according to claim 1, characterized in that: The inner connecting section (431) has an internal thread on its pipe wall, and the end of the anchor rod (3) has an external thread and is threaded to the internal thread.

3. The bolt assembly for prefabricated foundation pit support according to claim 1, characterized in that: The inner connecting section (431) has screw holes on its outer side wall; the end of the anchor rod (3) has a pipe opening and a through hole on its side wall, and the anchor rod (3) is connected to the screw holes by screws.

4. The bolt assembly for prefabricated foundation pit support according to claim 1, characterized in that: The inner side of the outer connecting section (433) is provided with an internal thread; the bolt assembly (4) also includes a second adapter (45), an end connector (46), a universal coupling (47), and a clamp connector (48); the second adapter (45) includes an external threaded cylinder (451) and a T-shaped connector (452), the external threaded cylinder (451) is used to thread the outer connecting section (433), and the T-shaped connector (452) is coaxially connected with the external threaded cylinder (451); the end connector (46) is rotatably connected with the T-shaped connector (452), the end connector (46) is connected to the clamp connector (48) through the universal coupling (47), and the clamp connector (48) is used to connect the pressure assembly (5), the pressure assembly (5) is used to press against the outer surface of the support plate (1).

5. The bolt assembly for prefabricated foundation pit support according to claim 4, characterized in that: The pressing assembly (5) includes a pad (51), a pressing seat (52), and a force transmission rod (53); the pad (51) is in the shape of a strip or a wedge, the pressing seat (52) is vertically connected to the middle of the pad (51), the end of the force transmission rod (53) is connected to the pressing seat (52), and the clamp connector (48) is connected to the force transmission rod (53) and can slide along the force transmission rod (53).

6. The bolt assembly for prefabricated foundation pit support according to claim 1, characterized in that: The flexible disk (42) is made of rubber material and has a fiber layer embedded in it.

7. The bolt assembly for prefabricated foundation pit support according to any one of claims 3-6, characterized in that: The anchor rod (3) is a columnar structure made up of four tube flaps (31). The end of the anchor rod (3) away from the support plate (1) is tapered. Inside the anchor rod (3) is a tube flap support (2). The tube flap support (2) is connected to the four tube flaps (31) and can open or close the four tube flaps (31).

8. The bolt assembly for prefabricated foundation pit support according to claim 7, characterized in that: The tube flap support (2) includes an externally threaded tube column (21), a sliding sleeve (22), a connecting rod (23), and a snap-fit ​​connector (24). The externally threaded tube column (21) is in the shape of a tube, and external threads with opposite thread directions are provided at both ends of the externally threaded tube column (21). A sliding sleeve (22) is threaded to each end of the externally threaded tube column (21). A snap-fit ​​connector (24) is connected to the inner wall of each of the four tube flaps (31). Each snap-fit ​​connector (24) is connected to two sliding sleeves (22) through two connecting rods (23). The connecting rods (23) are rotatably connected to the sliding sleeves (22) and the snap-fit ​​connectors (24). When the externally threaded tube column (21) rotates, the sliding sleeves (22) move together or apart, so that the four tube flaps (31) are spread apart or brought together.

9. The bolt assembly for prefabricated foundation pit support according to claim 8, characterized in that: The inner walls of the four tube flaps (31) are provided with snap-fit ​​grooves (311). The snap-fit ​​grooves (311) include rectangular grooves and T-shaped grooves, and the T-shaped grooves are connected to the rectangular grooves. The snap-fit ​​connector (24) is T-shaped and can be inserted into the rectangular grooves and slide into the T-shaped grooves to achieve snap-fit ​​engagement between the snap-fit ​​connector (24) and the snap-fit ​​grooves (311).

10. The bolt assembly for prefabricated foundation pit support according to claim 9, characterized in that: The tools that cooperate with the tube support (2) include a disassembly operating rod (7) and an expansion and contraction operating rod (6). The end of the disassembly operating rod (7) is provided with a threaded head (71), and the end of the expansion and contraction operating rod (6) is provided with a prism head (61). The inner hole of the external threaded tube (21) includes a prism hole section and a threaded hole section. The prism hole section cooperates with the prism head (61), and the threaded head (71) cooperates with the threaded hole section.

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