Container hoisting equipment with anti-skid function for port

Abstract

The present application relates to container hoisting technical field, concretely is a kind of port container hoisting equipment with antiskid function, including hanger and the turnover plate being set to the front face both ends and back both ends of hanger, the outside of four lock head top is fixedly installed with connecting plate, one end of four connecting plate top is rotatably installed with transmission rod, the bottom and top of four hollow seats are respectively provided with first drive mechanism and second drive mechanism, the top of four installation supports is provided with adjusting mechanism, the inside of four hollow seats is provided with connecting mechanism.The beneficial effects of the present application are to solve the problem of the need for repairing or replacing damaged air cylinder in the prior art, the entire hoisting equipment downtime, affecting the container hoisting efficiency, the port container crane remote control system is directly connected with the hoisting device, and the hoisting device is controlled by remote command to complete the container lifting, transfer and lowering action.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of container hoisting, in particular to a port container hoisting device with anti-skid function. BACKGROUND

[0002] The hoisting of a container is mainly carried out by a lifting appliance. The lifting appliance is placed on the container, the four lower locks of the lifting appliance are adjusted to be in position with the corner fittings of the four corners of the container, the four locks are embedded in the four corner fittings of the container, then the four lifting rings at the upper corners of the lifting appliance are connected with a wire rope, and the wire rope is connected with a shackle and a crane for hoisting. The port container crane remote control system is directly connected with the hoisting device, and the hoisting device is controlled by remote instructions to complete the hoisting, transfer and lowering of the container.

[0003] A container lifting appliance for detecting the orientation of a container door is disclosed in Chinese patent application No. CN202410752844.5. When the container is hoisted, the locks provided on the lifting appliance body are first aligned with the corner castings, and then the locks are inserted into the corner castings to realize the connection of the lifting appliance and the container.

[0004] However, the rotation of the locks in the above-mentioned application completely depends on the cylinder as the driving member. When the cylinder is damaged, the entire locking function will immediately fail, the locks cannot rotate, and the container corner fittings cannot be separated or locked. At this time, if the hoisting of the container is to be continued, the damaged cylinder needs to be repaired or replaced immediately, and the entire hoisting device will be shut down, affecting the hoisting efficiency of the container. SUMMARY

[0005] The present application aims to provide a port container hoisting device with anti-skid function to solve the problems raised in the background.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solution: a port container hoisting device with anti-skid function, comprising a lifting frame and flip plates provided on the front and back ends of the lifting frame, fixed seats and mounting brackets are fixedly installed at both ends of the inside of the lifting frame, locks are rotatably installed in the inside of the four fixed seats, connecting plates are fixedly installed on the outside of the top ends of the four locks, transmission rods are rotatably installed at one end of the top of the four connecting plates, hollow seats are rotatably installed at one end of the four transmission rods away from the corresponding locks, guide rods one are slidably sleeved in the inside of both ends of the four hollow seats, the guide rods one are fixedly installed on the top of the corresponding mounting brackets, first driving mechanisms and second driving mechanisms are respectively provided on the bottom and top of the four hollow seats, adjusting mechanisms are provided above the four mounting brackets, and connecting mechanisms are provided in the inside of the four hollow seats.

[0007] Preferably, the connecting mechanism comprises a connecting rod and a positioning assembly, the connecting rod is slidingly arranged in the hollow seat, the two ends of the top of the connecting rod are fixedly provided with a plurality of evenly distributed clamping strips, one side of the connecting rod is fixedly provided with a T-shaped extension plate, and one end of the connecting rod is provided with a positioning hole.

[0008] Preferably, the positioning assembly comprises a U-shaped support, a top rod and two positioning blocks arranged above and below, the two ends of the U-shaped support are slidingly provided with guide rods two, the outer parts of the two guide rods two are sleeved with springs one, the two guide rods two are fixedly arranged in the hollow seat, one side of the U-shaped support away from the two positioning blocks is fixedly provided with a trapezoidal plate, one end of the two positioning blocks is slidingly provided with two guide rods three, the four guide rods three are fixedly arranged in the hollow seat, the outer parts of the four guide rods three are sleeved with springs two, the two positioning blocks are matched with the positioning hole, the top rod is slidingly arranged in the hollow seat, one side of the top rod is rotatably provided with a pull rod, and one end of the pull rod away from the top rod is rotatably connected with the positioning block above.

[0009] Preferably, the adjusting mechanism comprises an adjusting plate, the two ends of the T-shaped extension plate are arranged above the adjusting plate, one end of the adjusting plate is slidingly provided with a guide rod four, the guide rod four is fixedly arranged at the top of the mounting support, the other end of the adjusting plate is threadedly connected with a threaded rod one, the bottom of the threaded rod one is rotatably connected with the mounting support, and the top end of the threaded rod one is rotatably connected with the hanging bracket.

[0010] Preferably, the first driving mechanism comprises a gas cylinder, the gas cylinder is fixedly arranged in the interior of the hanging bracket, the telescopic shaft end of the gas cylinder is fixedly provided with a connecting block, the interior of the connecting block is provided with a connecting slot, and the connecting slot is matched with the connecting rod.

[0011] Preferably, the second driving mechanism comprises a receiving plate, one end of the receiving plate is internally threadedly connected with a threaded rod two, the threaded rod two is rotatably arranged in the interior of the hanging bracket, the interior of one end of the receiving plate away from the threaded rod two is slidingly sleeved with a guide rod five, the guide rod five is fixedly arranged in the interior of the hanging bracket, the bottom of the receiving plate is provided with a plurality of evenly distributed clamping grooves at the two ends, the plurality of clamping grooves are matched with the plurality of clamping strips respectively, one side of the threaded rod two is fixedly provided with a turbine, one side of the turbine is engaged with a worm, and the worm is rotatably arranged in the interior of the hanging bracket.

[0012] Preferably, the two ends of the top of the hanging bracket are symmetrically provided with two indicating grooves, the top of the four receiving plates is fixedly provided with indicating blocks, and the four indicating blocks are arranged in the interiors of the respective corresponding indicating grooves.

[0013] Preferably, the lower part of the four mounting supports is provided with a limiting base, the bottom of the four limiting bases is fixedly connected with the hanging bracket, the inside of the four limiting bases is provided with a limiting groove, and the four connecting blocks are arranged in the limiting grooves.

[0014] Compared with the prior art, the present application has the following advantages:

[0015] In the present application, in the case of cylinder damage, the corresponding lock head can be adjusted by the second driving mechanism to rotate the lock head to disengage or lock the container corner fittings, solving the problem in the prior art that the damaged cylinder needs to be repaired or replaced, resulting in downtime of the entire lifting equipment and affecting the efficiency of container lifting.

[0016] In the present application, under the action of the connecting mechanism, no matter where the damaged cylinder pushes the connecting block, the corresponding connecting rod can be connected with the second driving mechanism above it, and when the cylinder and the connecting block are reinstalled in the hanging bracket, the connecting rod can be connected with the connecting block by pushing the connecting block with the cylinder, without the need for workers to adjust the position of the connecting rod and the connecting block. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the present application;

[0018] Figure 2 It is a schematic diagram of the end structure of the hanging bracket of the present application;

[0019] Figure 3 It is a schematic diagram of the local three-dimensional structure of the present application;

[0020] Figure 4 It is a schematic diagram of the bottom structure of the receiving plate of the present application;

[0021] Figure 5 It is a local sectional view of the present application;

[0022] Figure 6 It is a schematic diagram of the top structure of the mounting support of the present application;

[0023] Figure 7 It is a schematic diagram of the structure of the first driving mechanism of the present application;

[0024] Figure 8 It is a schematic diagram of the structure of one side of the hollow seat of the present application;

[0025] Figure 9 It is a schematic diagram of the structure of the other side of the hollow seat of the present application;

[0026] Figure 10 Figure is the schematic diagram of the connecting plug rod and U-shaped support structure of the present application;

[0027] Figure 11 Figure is the schematic diagram of the U-shaped support structure of the present application;

[0028] Figure 12 Figure is the schematic diagram of the two positioning block structure of the present application;

[0029] Figure 13 Figure is the schematic diagram of the connecting plug rod structure of the present application.

[0030] In the drawings, the components represented by each number are listed as follows: 1, hanger; 2, turnover plate; 3, fixed seat; 4, lock head; 5, connecting plate; 6, transmission rod; 7, hollow seat; 8, mounting support; 9, guide rod one; 10, connecting plug rod; 11, clamping strip; 12, T-shaped extension plate; 13, positioning hole; 14, U-shaped support; 15, guide rod two; 16, indicating block; 17, spring one; 18, trapezoidal plate; 19, positioning block; 20, guide rod three; 21, spring two; 22, adjusting plate; 23, guide rod four; 24, threaded rod one; 25, air cylinder; 26, connecting block; 27, connecting plug groove; 28, bearing plate; 29, threaded rod two; 30, guide rod five; 31, clamping groove; 32, turbine; 33, worm; 34, limiting base; 35, limiting groove; 36, jacking rod; 37, pull rod; 38, indicating groove. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0032] The present application provides a technical solution: as Figure 1 - Figure 13The illustrated container hoisting equipment with anti-skid function for port comprises a hanging frame 1, turnover plates 2 arranged at the front ends and back ends of the hanging frame 1, fixed seats 3 and mounting brackets 8 arranged at the two ends in the hanging frame 1, lock heads 4 rotatably arranged in the four fixed seats 3, connecting plates 5 fixedly arranged at the top ends of the four lock heads 4, transmission rods 6 rotatably arranged at one end of the four connecting plates 5, hollow seats 7 rotatably arranged at the other end of the four transmission rods 6, guide rods one 9 slidably arranged in the two ends of the four hollow seats 7, the guide rods one 9 being fixedly arranged at the top of the corresponding mounting bracket 8, first driving mechanisms and second driving mechanisms arranged at the bottom and top of the four hollow seats 7 respectively, adjusting mechanisms arranged above the four mounting brackets 8, and connecting mechanisms arranged in the four hollow seats 7.

[0033] The connecting mechanism comprises a connecting plug rod 10 and a positioning assembly. The connecting plug rod 10 is slidably arranged in the hollow seat 7. A plurality of evenly distributed clamping strips 11 are fixedly arranged at the two ends of the top of the connecting plug rod 10. A T-shaped extension plate 12 is fixedly arranged on one side of the connecting plug rod 10. A positioning hole 13 is arranged at one end of the connecting plug rod 10.

[0034] The positioning assembly comprises a U-shaped bracket 14, a top rod 36, and two positioning blocks 19 arranged above and below. Guide rods two 15 are slidably arranged at the two ends of the U-shaped bracket 14. Spring one 17 is sleeved on the outside of the two guide rods two 15. The two guide rods two 15 are fixedly arranged in the hollow seat 7. A trapezoidal plate 18 is fixedly arranged on the side of the U-shaped bracket 14 away from the two positioning blocks 19. Two guide rods three 20 are slidably arranged at one end of the two positioning blocks 19. The four guide rods three 20 are fixedly arranged in the hollow seat 7. Spring two 21 is sleeved on the outside of the four guide rods three 20. The two positioning blocks 19 are matched with the positioning hole 13. The top rod 36 is slidably arranged in the hollow seat 7. A pull rod 37 is rotatably arranged on one side of the top rod 36. The end of the pull rod 37 away from the top rod 36 is rotatably connected with the positioning block 19 above.

[0035] The adjusting mechanism comprises an adjusting plate 22. The two ends of the T-shaped extension plate 12 are arranged above the adjusting plate 22. A guide rod four 23 is slidably arranged at one end of the adjusting plate 22. The guide rod four 23 is fixedly arranged at the top of the mounting bracket 8. A threaded rod one 24 is threadedly connected with the other end of the adjusting plate 22. The bottom of the threaded rod one 24 is rotatably connected with the mounting bracket 8. The top end of the threaded rod one 24 is rotatably connected with the hanging frame 1.

[0036] The first driving mechanism comprises a gas cylinder 25. The gas cylinder 25 is fixedly arranged in the inside of the hanging frame 1. A connecting block 26 is fixedly arranged at the telescopic shaft end of the gas cylinder 25. A connecting slot 27 is arranged in the inside of the connecting block 26. The connecting slot 27 is matched with the connecting plug rod 10.

[0037] The second driving mechanism comprises a receiving plate 28, a threaded rod two 29 is internally screwed at one end of the receiving plate 28, the threaded rod two 29 is rotatably installed in the interior of the hanger 1, a guide rod five 30 is slidably sleeved at the interior of the end of the receiving plate 28 away from the threaded rod two 29, the guide rod five 30 is fixedly installed in the interior of the hanger 1, a plurality of clamping grooves 31 are formed at both ends of the bottom of the receiving plate 28 and are uniformly distributed, the plurality of clamping grooves 31 are matched with the plurality of clamping strips 11 respectively, a turbine 32 is fixedly installed on one side of the threaded rod two 29, a worm 33 is engaged on one side of the turbine 32, and the worm 33 is rotatably installed in the interior of the hanger 1.

[0038] Two indicating grooves 38 are symmetrically formed at both ends of the top of the hanger 1, and four indicating blocks 16 are fixedly installed at the top of the four receiving plates 28 and are arranged in the interiors of the respective indicating grooves 38.

[0039] A limiting base 34 is arranged below each of the four mounting brackets 8, the bottom of each of the four limiting bases 34 is fixedly connected with the hanger 1, a limiting groove 35 is formed in the interior of each of the four limiting bases 34, and the four connecting blocks 26 are arranged in the interiors of the four limiting grooves 35.

[0040] Working principle: in use, the top of the hanger 1 is connected with four steel wires, and then the four steel wires are connected with hooks in a crane, the hanger 1 is moved to the top of a container by the crane, in the process of descending of the hanger 1, the inclined surfaces of the four turnover plates 2 are in contact with the corresponding corner fittings in the container, due to the effect of the inclined surfaces, a temporary friction force is generated on the contact surface between the four turnover plates 2 and the inclined surfaces of the corner fittings by part of the gravity of the hanger 1, the friction force can assist the hanger 1 to position the container and slow down the horizontal sliding trend of the hanger 1, so as to gain time for the final accurate positioning, so that the four turnover plates 2 have a certain anti-skid effect.

[0041] After the four lock heads 4 are correspondingly arranged with the four corner fittings in the container, the four first driving mechanisms are operated, and the movement process of one of the driving mechanisms is as follows: the cylinder 25 is started to drive the connecting block 26 to move, at this time, the interior of the connecting slot 27 has one connecting rod 10, so that the hollow seat 7 and the transmission rod 6 outside the connecting rod 10 are synchronously moved while the connecting block 26 moves, the hollow seat 7 slides along the two guide rods one 9, and the transmission rod 6 drives the lock head 4 to rotate; the movement processes of the other three driving mechanisms are the same as above, and the four lock heads 4 are connected with the respective corner fittings by rotating.

[0042] In the process of lifting the container, if a certain cylinder 25 fails to drive the corresponding lock head 4 to rotate, the corresponding adjusting mechanism and second driving mechanism are operated first, and the corresponding connecting mechanism is also operated. The movement process is as follows: first, the threaded rod 24 is rotated, and under the action of the guide rod 4, the adjusting plate 22 gradually rises close to the T-shaped extension plate 12. In the process of the adjusting plate 22 rising, the trapezoidal plate 18 is acted on, and the trapezoidal plate 18 is driven to move the U-shaped support 14 along the two guide rods 2 under the action of force. One side of the U-shaped support 14 acts on the two positioning blocks 19 respectively, and the two positioning blocks 19 are away from the connecting plug rod 10. The corresponding spring 2 extends, and the lower positioning block 19 is separated from the positioning hole 13. When the adjusting plate 22 contacts the T-shaped extension plate 12, the T-shaped extension plate 12 drives the connecting plug rod 10 to move upward synchronously with the continuous upward movement of the adjusting plate 22. At the same time, the adjusting plate 22 is not in contact with the trapezoidal plate 18, so that the trapezoidal plate 18 drives the U-shaped support 14 to reset under the action of the two springs 1. When the connecting plug rod 10 moves to the top, the connecting plug rod 10 is completely separated from the connecting slot 27. At this time, the corresponding transmission rod 6 is separated from the first driving mechanism, and the worker can take out the cylinder 25 for repair in the subsequent process. When the connecting plug rod 10 moves to the top, the multiple clamping strips 11 at the top of the two ends are respectively inserted into the corresponding clamping groove 31 inside, so as to realize the butt joint between the connecting plug rod 10 and the receiving plate 28. In addition, the upper positioning block 19 is clamped into the positioning hole 13 under the action of the corresponding spring 2. Finally, the worker rotates the worm 33, thereby driving the turbine 32 and the threaded rod 2 to rotate. Under the action of the guide rod 5, the receiving plate 28 moves, thereby driving the hollow seat 7 below to move. The corresponding transmission rod 6 acts, so that the lock head 4 can be controlled again to rotate and separate or connect with the angle piece;

[0043] When the damaged cylinder 25 is reinstalled inside the hanger 1, first, the cylinder 25 is fixed inside the hanger 1, and the connecting block 26 is placed inside the limiting groove 35, ensuring that the cylinder 25 is at the shortest stroke, then the threaded rod 24 is reversed, and the adjusting plate 22 is reset, at this time, the connecting plug rod 10 cannot move downward under the action of the upper positioning block 19, and as the cylinder 25 pushes the connecting block 26 to move, when the connecting block 26 touches the jacking rod 36, the jacking rod 36 is forced to move upward, and the pull rod 37 is forced to pull the upper positioning block 19 to slide, so that the upper positioning block 19 is separated from the positioning hole 13, at this time, the connecting plug rod 10 moves downward under the action of gravity, and as the connecting block 26 continues to move, when the connecting plug rod 10 corresponds to the connecting plug groove 27, the connecting plug rod 10 descends to the bottom and enters the connecting plug groove 27, realizing the connection with the first driving mechanism, and at this time, the lower positioning block 19 is clamped into the positioning hole 13 under the action of the corresponding spring 21, fixing the position of the connecting plug rod 10; when the other three cylinders 25 are damaged, the operation process is the same as above;

[0044] In the present application, for the damaged cylinder 25, the connecting block 26 connected by the cylinder 25 is disconnected from the connecting plug rod 10 by operating the corresponding connecting mechanism, at the same time, the connecting plug rod 10 is connected with the upper second driving mechanism, so that the position of the connecting plug rod 10 and the hollow seat 7 outside it can be adjusted by the second driving mechanism, and then the corresponding transmission rod 6 and the lock head 4 are adjusted, so that in the case of damaged cylinder 25, the second driving mechanism can be used to adjust the lock head 4 to rotate and separate or lock the container corner fittings, solving the problem that the damaged cylinder 25 needs to be repaired or replaced in the prior art, causing the whole hoisting equipment to stop, affecting the efficiency of container hoisting, and the port container crane remote control system is directly connected with the hoisting device, and the hoisting device completes the container lifting, transfer and lowering actions through remote command control; at the same time, under the action of the connecting mechanism, no matter where the damaged cylinder 25 pushes the connecting block 26, the corresponding connecting plug rod 10 can be connected with the second driving mechanism above it, and when the cylinder 25 and the connecting block 26 are reinstalled inside the hanger 1, the connecting plug rod 10 and the connecting block 26 can be connected by using the cylinder 25 to push the connecting block 26, without the need for workers to adjust the position of the connecting plug rod 10 and the connecting block 26.

[0045] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting; it is not intended to exclude myriad other embodiments of the present application that other inventors can develop based on the same general inventive concepts embodied by the described embodiments. That is, although the present application is described in terms of particular embodiments and illustrative figures, it should be apparent that the scope of the present application is not limited to these specific embodiments.

[0046] While the embodiments of the application have been shown and described herein, it will be understood by those skilled in the art that many changes, modifications, substitutions and alterations to these embodiments can be made without departing from the principles and spirits of the application, and it is intended that the scope of the application be limited solely by the scope of the appended claims and the equivalents thereof.

Claims

1. A port container lifting device with anti-slip function, comprising a lifting frame (1) and flip plates (2) disposed at both ends of the front and back of the lifting frame (1), characterized in that: The hanger (1) has a fixed seat (3) and a mounting bracket (8) fixedly installed at both ends. The four fixed seats (3) are rotatably installed with lock heads (4). The top of the four lock heads (4) is fixedly installed with connecting plates (5). The top of the four connecting plates (5) is rotatably installed with transmission rods (6). The ends of the four transmission rods (6) away from their respective lock heads (4) are rotatably installed with hollow seats (7). The interiors of the four hollow seats (7) are slidably fitted with guide rods (9). Multiple guide rods (9) are fixedly installed on the top of their respective mounting brackets (8). The bottom and top of the four hollow seats (7) are respectively provided with a first driving mechanism and a second driving mechanism. The top of the four mounting brackets (8) is provided with an adjustment mechanism. The interiors of the four hollow seats (7) are provided with a connecting mechanism. The connecting mechanism includes a connecting rod (10) and a positioning component. The connecting rod (10) is slidably disposed inside the hollow seat (7). Multiple evenly distributed clips (11) are fixedly installed at both ends of the top of the connecting rod (10). A T-shaped extension plate (12) is fixedly installed on one side of the connecting rod (10). A positioning hole (13) is opened at one end of the connecting rod (10). The positioning assembly includes a U-shaped bracket (14), a top rod (36), and two positioning blocks (19) arranged vertically. Guide rods (15) are slidably fitted at both ends of the U-shaped bracket (14). Springs (17) are fitted on the outside of the two guide rods (15). The two guide rods (15) are fixedly installed inside the hollow seat (7). A trapezoidal plate (18) is fixedly installed on the side of the U-shaped bracket (14) away from the two positioning blocks (19). One end of each positioning block (19) is slidably fitted. Two guide rods (20) are fitted on the hollow seat (7). All four guide rods (20) are fixedly installed inside the hollow seat (7). Springs (21) are fitted on the outside of the four guide rods (20). The two positioning blocks (19) cooperate with the positioning holes (13). The top rod (36) is slidably installed inside the hollow seat (7). A pull rod (37) is rotatably installed on one side of the top rod (36). The end of the pull rod (37) away from the top rod (36) is rotatably connected to the positioning block (19) located above.

2. The port container lifting equipment with anti-slip function according to claim 1, characterized in that: The adjustment mechanism includes an adjustment plate (22), with both ends of the T-shaped extension plate (12) located above the adjustment plate (22). One end of the adjustment plate (22) is slidably mounted with a guide rod four (23), which is fixedly mounted on the top of the mounting bracket (8). The other end of the adjustment plate (22) is threadedly connected with a threaded rod one (24), the bottom of which is rotatably connected to the mounting bracket (8), and the top of which is rotatably connected to the hanger (1).

3. A port container lifting device with anti-slip function according to claim 1, characterized in that: The first driving mechanism includes a cylinder (25), which is fixedly installed inside the hanger (1). A connecting block (26) is fixedly installed at the telescopic shaft end of the cylinder (25). A connecting slot (27) is provided inside the connecting block (26), and the connecting slot (27) cooperates with the connecting rod (10).

4. A port container lifting device with anti-slip function according to claim 1, characterized in that: The second driving mechanism includes a receiving plate (28), with a threaded rod (29) internally threaded at one end of the receiving plate (28). The threaded rod (29) is rotatably installed inside the hanger (1). A guide rod (30) is slidably sleeved at the end of the receiving plate (28) away from the threaded rod (29). The guide rod (30) is fixedly installed inside the hanger (1). Multiple evenly distributed slots (31) are provided at both ends of the bottom of the receiving plate (28). The multiple slots (31) cooperate with multiple clips (11). A worm gear (32) is fixedly installed on one side of the threaded rod (29). A worm (33) meshes on one side of the worm gear (32). The worm (33) is rotatably installed inside the hanger (1).

5. A port container lifting device with anti-slip function according to claim 4, characterized in that: The top of the hanger (1) has two symmetrically opened indicator slots (38) at both ends, and the top of the four support plates (28) is fixedly installed with indicator blocks (16), and the four indicator blocks (16) are respectively set inside their respective indicator slots (38).

6. A port container lifting device with anti-slip function according to claim 3, characterized in that: Each of the four mounting brackets (8) is provided with a limiting base (34) below it. The bottom of each of the four limiting bases (34) is fixedly connected to the hanger (1). Each of the four limiting bases (34) has a limiting groove (35) inside it. The four connecting blocks (26) are respectively located inside the four limiting grooves (35).

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