A quick-release structure for street light maintenance

Abstract

This application relates to the field of lighting device technology, and in particular to a quick-release structure for street light maintenance, including a connecting cylinder, a lamp cover, a housing, and a quick-release assembly. The connecting cylinder is used to connect to a lamp post. The lamp cover is detachably mounted on the connecting cylinder, and a locking element is provided between the lamp cover and the connecting cylinder. The housing is detachably mounted on the lamp cover, and a lighting panel and a control unit electrically connected to a control system are provided on the housing. A conductive element for transmitting current is provided between the lamp cover and the housing. The quick-release assembly includes a connecting rod rotatably mounted on the lamp cover, and an L-shaped buckle rotatably mounted on the connecting rod. The buckle is elastic. A slot is provided on the housing for the buckle to rotate and engage. A temporary pivot is provided between the housing and the lamp cover, which allows the housing to rotate and is detachably mounted on the lamp cover. This application has the effect of improving the efficiency of street light maintenance.

Description

Technical Field

[0001] This application relates to the field of lighting device technology, and in particular to a quick-release structure for street light maintenance. Background Technology

[0002] Streetlights, as an important part of urban infrastructure, provide illumination for roads and public places. Their core functions include ensuring nighttime traffic safety and beautifying the urban environment. In order to ensure that streetlights do not affect the normal driving of vehicles on the road, streetlights on both sides of the road usually have a long lamp post.

[0003] Traditional street light maintenance methods typically require maintenance personnel to use ladders or aerial work platforms to approach the lights, then use tools such as screwdrivers to remove the fixing bolts before the lights can be replaced or repaired.

[0004] However, maintenance personnel need to use specialized equipment to align the fixing bolts when disassembling them, and there are usually multiple fixing bolts on streetlights. This results in maintenance personnel spending a long time on repairs. Furthermore, with the acceleration of urbanization, the number of streetlights along the roads is constantly increasing, which also increases the demand for streetlight maintenance. Ultimately, this leads to low maintenance efficiency for streetlights along the roads, which is a shortcoming. Utility Model Content

[0005] To address the issue of low maintenance efficiency in traditional streetlights, this application provides a quick-release structure for streetlight maintenance.

[0006] The quick-release structure for street light maintenance provided in this application adopts the following technical solution:

[0007] A quick-release structure for street light maintenance includes a connecting cylinder, a lamp cover, a housing, and a quick-release assembly. The connecting cylinder is used to connect to a lamp post. The lamp cover is detachably mounted on the connecting cylinder, and a locking element is provided between the lamp cover and the connecting cylinder. The housing is detachably mounted on the lamp cover, and a lighting panel and a control unit electrically connected to a control system are provided on the housing. A conductive element for transmitting current is provided between the lamp cover and the housing. The quick-release assembly includes a connecting rod rotatably mounted on the lamp cover, and an L-shaped buckle rotatably mounted on the connecting rod. The buckle is elastic. A slot is provided on the housing for the buckle to rotate and engage. A temporary rotating element is provided between the housing and the lamp cover, which allows the housing to rotate and is detachably mounted on the lamp cover.

[0008] By adopting the above technical solution, when streetlights need to be repaired, workers approach the streetlights using a ladder, then rotate to open the latch. The latch disengages from the slot through deformation. At this time, under the restraint of the temporary transfer piece, the housing rotates open, and the conductive parts disconnect the current. The control unit inside the housing is exposed to the outside of the lamp cover and housing, which facilitates maintenance personnel to carry out maintenance. When the housing needs to be replaced, workers remove the housing again using the temporary transfer piece, and maintenance personnel can directly replace it. This process is simple and convenient, greatly improving the maintenance efficiency of maintenance personnel.

[0009] Optionally, the temporary rotating component includes pin plates symmetrically arranged on both sides of the lamp cover, with a connecting shaft slidably passing through the pin plates. A fixing plate is provided on the housing, and a connecting hole for the connecting shaft to be inserted is provided on the fixing plate. A retaining ring is provided on the connecting shaft, and a compression spring is supported between the side of the retaining ring facing away from the fixing plate and the pin plate. A lever is provided on the connecting shaft on the side of the pin plate facing away from the compression spring, and the axis of the lever is perpendicular to the axis of the connecting shaft.

[0010] By adopting the above technical solution, when the housing is opened by rotating around the axis of the connecting shaft and the housing needs to be replaced, the maintenance personnel push the lever, which drives the connecting shaft to slide synchronously until the connecting shaft is disengaged from the connecting hole on the fixed plate. During this process, the compression spring is continuously compressed. Then the maintenance personnel can remove the old housing and install the new housing to complete the housing replacement. This process is simple and convenient.

[0011] Optionally, the conductive element includes a plug protrusion disposed on the lamp cover, and a plug recess disposed on the housing. The plug protrusion is used to engage with the plug recess. When the housing is fastened to the lamp cover, current flows from the plug protrusion to the plug recess.

[0012] By adopting the above technical solution, when the maintenance personnel replace the housing, they rotate the housing so that it snaps onto the lamp cover. During this process, the concave end of the plug on the housing will fit onto the convex end of the plug on the lamp cover. At this time, the current can flow from the convex end of the plug on the lamp cover through the concave end of the plug on the housing to the lighting board and control unit on the housing, thereby enabling the lighting board to work.

[0013] Optionally, a limiting plate is provided on the lamp cover, and a limiting groove for accommodating the lever is provided on the limiting plate.

[0014] By adopting the above technical solution, during the reinstallation of the housing, the maintenance personnel first turn the lever into the limiting groove on the limiting plate. At this time, the compression spring is compressed. Then, the maintenance personnel align the connecting hole on the fixing plate on the housing with the connecting shaft. Finally, the lever is turned out of the limiting groove, the compression spring returns to its deformation, and the connecting shaft is inserted into the connecting hole on the fixing plate, thus completing the installation of the housing.

[0015] Optionally, the lamp cover is provided with a lower frame, the housing is provided with an upper frame, the control unit is located within the frame of the upper frame, and the upper frame is provided with a sealing strip for abutting against the lower frame.

[0016] By adopting the above technical solution, after the housing is fastened to the lamp cover, the upper frame will press the sealing strip tightly against the lower frame, and the area around the control unit will be sealed, thereby reducing the impact of rainwater on the control unit.

[0017] Optionally, the locking component includes an angle control bolt threaded onto the lamp cover, the cross-section of the connection between the connecting cylinder and the lamp cover is arc-shaped, and the connecting cylinder has a waist-shaped groove for the angle control bolt to pass through.

[0018] By adopting the above technical solution, when it is necessary to change the illumination angle of the lighting panel, the maintenance personnel loosen the angle control bolts, then adjust the fixed angle of the lamp cover on the connecting cylinder, and finally tighten the angle control bolts again, so that the lamp cover is pressed tightly on the connecting cylinder.

[0019] Optionally, the lamp cover is provided with an illumination angle scale line, which is close to the connecting cylinder.

[0020] By adopting the above technical solution, maintenance personnel can easily adjust the illumination angle of streetlights on both sides of the road, which helps to improve the lighting effect of the road.

[0021] Optionally, both the connecting cylinder and the lamp cover are provided with meshing teeth, and the meshing teeth on the connecting cylinder are used to mesh with the meshing teeth on the lamp cover.

[0022] By adopting the above technical solution, the possibility of accidental slippage between the connecting cylinder and the lamp cover is reduced, which helps to improve the stability of the street light's illumination angle.

[0023] Optionally, a fall-prevention plate is slidably sleeved on the connecting shaft. The fall-prevention plate is located between the retaining ring and the fixing plate. A protruding plate is provided on the fall-prevention plate, which is used to abut against the fixing plate.

[0024] By adopting the above technical solution, during the process of the maintenance personnel opening the housing, the housing drives the fixing plate to rotate synchronously until the housing separates from the protruding plate on the anti-fall plate. At this time, the compression spring pushes the anti-fall plate to slide, and the protruding plate on the anti-fall plate abuts against the fixing plate. At this time, the housing can no longer be fastened to the lamp cover, which facilitates the maintenance personnel to carry out maintenance. After the maintenance is completed, the maintenance personnel push the anti-fall plate and then slowly rotate the housing until the protruding plate on the anti-fall plate abuts against the fixing plate again. Then the lamp cover can be easily fastened.

[0025] In summary, this application includes at least one of the following beneficial technical effects:

[0026] 1. When streetlights need repair, workers approach the streetlight using a ladder, then rotate to open the latch. The latch deforms and disengages from the slot. At this point, under the restraint of the temporary transfer piece, the housing rotates open, and the current is disconnected from the conductive parts. The control unit inside the housing is exposed to the outside of the lamp cover and housing, making it convenient for maintenance personnel to carry out repairs. When the housing needs to be replaced, workers remove the housing using the temporary transfer piece, and maintenance personnel can directly replace it. This process is simple and convenient, greatly improving the maintenance efficiency of maintenance personnel.

[0027] 2. When the housing is opened by rotating around the axis of the connecting shaft and the housing needs to be replaced, the maintenance personnel push the lever. The lever drives the connecting shaft to slide synchronously until the connecting shaft is disengaged from the connecting hole on the fixed plate. During this process, the compression spring is continuously compressed. Then the maintenance personnel remove the old housing and install the new housing to complete the housing replacement. This process is simple and convenient.

[0028] 3. After the maintenance personnel replace the housing, they rotate the housing so that it snaps onto the lamp cover. During this process, the concave end of the plug on the housing will fit onto the convex end of the plug on the lamp cover. At this time, the current can flow from the convex end of the plug on the lamp cover through the concave end of the plug on the housing to the lighting board and control unit on the housing, thereby enabling the lighting board to work. Attached Figure Description

[0029] Figure 1 This is a structural schematic diagram of an embodiment of this application.

[0030] Figure 2 This is a schematic diagram showing the positional relationship between the lamp cover and the control unit when the housing is opened in an embodiment of this application.

[0031] Figure 3 This is a cross-sectional view used in the embodiments of this application to illustrate the positional relationship between the buckle, the protruding end of the plug, and the recessed end of the plug.

[0032] Figure 4 yes Figure 4 Enlarged view of section A.

[0033] Explanation of reference numerals in the attached drawings: 1. Connecting cylinder; 2. Lamp cover; 3. Housing; 4. Quick-release assembly; 41. Connecting rod; 42. Buckle; 43. Slot; 44. Temporary transfer piece; 441. Pin plate; 442. Connecting shaft; 443. Fixing plate; 444. Connecting hole; 445. Retaining ring; 446. Compression spring; 447. Lever; 5. Locking piece; 51. Angle control bolt; 52. Waist-shaped groove; 6. Lighting panel; 7. Control unit; 8. Conductive component; 81. Plug protrusion; 82. Plug concave end; 9. Limiting plate; 10. Limiting groove; 11. Lower frame; 12. Upper frame; 13. Sealing strip; 14. Illumination angle scale line; 15. Engaging teeth; 16. Anti-fall plate; 17. Protruding plate. Detailed Implementation

[0034] The following is in conjunction with the appendix Figures 1-4 This application will be described in further detail.

[0035] This application discloses a quick-release structure for street light maintenance.

[0036] Reference Figure 1 A quick-release structure for street light maintenance includes a connecting cylinder 1, a lamp cover 2, and a housing 3. The connecting cylinder 1 is used to be bolted to the lamp post. The lamp cover 2 is detachably arranged on the connecting cylinder 1. A locking element 5 is arranged between the lamp cover 2 and the connecting cylinder 1. The locking element 5 includes an angle control bolt 51 threadedly connected to the lamp cover 2.

[0037] Reference Figure 1 The cross-section of the connection between the connecting cylinder 1 and the lamp cover 2 is arc-shaped. The connecting cylinder 1 has a waist-shaped groove 52 for the angle control bolt 51 to pass through. The length of the waist-shaped groove 52 is much larger than the diameter of the angle control bolt 51. The lamp cover 2 has an integrally formed illumination angle scale line 14. The illumination angle scale line 14 is close to the connecting cylinder 1 and located at the waist-shaped groove 52. Both the connecting cylinder 1 and the lamp cover 2 are welded with meshing teeth 15. The meshing teeth 15 on the connecting cylinder 1 are used to mesh with the meshing teeth 15 on the lamp cover 2.

[0038] When it is necessary to uniformly adjust the illumination angle of the streetlights, the maintenance personnel loosen the angle control bolt 51 so that the lamp cover 2 can rotate freely until it is in the appropriate position. Then, the maintenance personnel tighten the angle control bolt 51, and the meshing teeth 15 on the lamp cover 2 will gradually mesh with the meshing teeth 15 on the connecting cylinder 1.

[0039] At this time, the lamp cover 2 is kept at a fixed angle under the restriction of the meshing teeth 15. Then, the maintenance personnel observe the scale indicated by the illumination angle scale line 14 at this time, and then adjust the corresponding illumination angle scale line 14 on the other street lights to be the same.

[0040] Reference Figure 1 and Figure 2The housing 3 is detachably arranged on the lamp cover 2. The lighting board 6 and the control unit 7, which are electrically connected to the control system, are bolted to the housing 3. The control unit 7 is a circuit board and electrical components that control the lighting board 6. The lamp cover 2 has an integrally formed lower frame 11, and the housing 3 has an integrally formed upper frame 12. The control unit 7 is located inside the frame of the upper frame 12. A sealing strip 13 is glued to the upper frame 12. The sealing strip 13 is used to abut against the lower frame 11.

[0041] Reference Figure 2 , Figure 3 and Figure 4 A quick-release assembly 4 is arranged between the lamp cover 2 and the housing 3. The quick-release assembly 4 includes a connecting rod 41 rotatably connected to the lamp cover 2. The connecting rod 41 is U-shaped in general. A buckle 42 with an L-shaped cross-section is rotatably connected to the connecting rod 41. The buckle 42 can be made of plastic material and is elastic. The housing 3 has a slot 43 for the buckle 42 to rotate and engage. A temporary rotating part 44 is arranged between the housing 3 and the lamp cover 2. The temporary rotating part 44 is used to rotate the housing 3 and is detachably arranged on the lamp cover 2.

[0042] Reference Figure 2 and Figure 4 The temporary rotating part 44 includes pin plates 441 symmetrically welded to both sides inside the lamp cover 2. A connecting shaft 442 is slidably passed through the pin plate 441. The connecting shaft 442 is rotatably connected to the pin plate 441. A fixing plate 443 is bolted to the housing 3. A connecting hole 444 is provided on the fixing plate 443 for the connecting shaft 442 to be inserted. A retaining ring 445 is snapped onto the connecting shaft 442. The retaining ring 445 can be a C-type retaining ring in the prior art.

[0043] Reference Figure 4 A compression spring 446 is supported between the side of the retaining ring 445 facing away from the fixing plate 443 and the pin plate 441. A lever 447 is integrally formed on the connecting shaft 442 on the side of the pin plate 441 facing away from the compression spring 446. The axis of the lever 447 is perpendicular to the axis of the connecting shaft 442. A limiting plate 9 is integrally formed on the lamp cover 2. A limiting groove 10 for accommodating the lever 447 is provided on the limiting plate 9.

[0044] Reference Figure 2 A fall-prevention plate 16 is slidably sleeved on the connecting shaft 442. The fall-prevention plate 16 is located between the retaining ring 445 and the fixing plate 443. A protrusion plate 17 is provided on the fall-prevention plate 16, which is used to abut against the fixing plate 443.

[0045] Reference Figure 2 and Figure 3A conductive element 8 for transmitting current is arranged between the lamp cover 2 and the housing 3. The conductive element 8 includes a plug protrusion 81 that is attached to the lamp cover 2 and a plug concave end 82 that is attached to the housing 3. The lighting board 6 and the control unit 7 are both electrically connected to the plug concave end 82. The plug protrusion 81 is used to plug into the plug concave end 82. When the housing 3 is fastened to the lamp cover 2, the current flows from the plug protrusion 81 to the plug concave end 82.

[0046] When streetlights need repair, maintenance personnel approach the streetlights using a ladder, and then rotate to open the latch 42. The latch 42 will disengage from the slot 43 due to its own deformation. During this process, the connecting rod 41 will rotate at the corresponding angle.

[0047] Then the maintenance personnel push the housing 3, and the housing 3 will rotate and open around the axis of the connecting shaft 442. During this process, when the housing 3 drives the fixing plate 443 to rotate synchronously, until the housing 3 separates from the protrusion 17 on the anti-fall plate 16, the compression spring 446 pushes the anti-fall plate 16 to slide, and the protrusion 17 on the anti-fall plate 16 abuts against the fixing plate 443.

[0048] At the same time, the housing 3 will cause the plug recess 82 to separate from the plug protrusion 81 on the lamp cover 2, the control unit 7 and the lighting board 6 will be de-energized, the control unit 7 will be exposed to the maintenance personnel's view, and then the maintenance personnel can carry out maintenance.

[0049] When it is necessary to replace the control unit 7 and the lighting panel 6 on the housing 3, the maintenance personnel push the lever 447. The lever 447 drives the connecting shaft 442 to slide synchronously until the connecting shaft 442 disengages from the connecting hole 444 on the fixing plate 443. Then the maintenance personnel turn the lever 447 to the limiting groove 10 on the limiting plate 9. During this process, the compression spring 446 is compressed. After that, the maintenance personnel install the new housing 3 on the lamp cover 2.

[0050] After the maintenance is completed, the maintenance personnel push the anti-fall plate 16 and then slowly rotate the housing 3 until the protrusion 17 on the anti-fall plate 16 abuts against the fixing plate 443 again. Then the maintenance personnel rotate the lever 447 to disengage the lever 447 from the limiting groove 10 on the limiting plate 9. The compression spring 446 returns to its original shape and pushes the connecting shaft 442 to insert into the connecting hole 444 on the fixing plate 443. Finally, the housing 3 is rotated to make the housing 3 fasten onto the lamp cover 2.

[0051] At this time, the plug recess 82 on the housing 3 will be re-attached to the plug protrusion 81 on the lamp cover 2. At this time, the sealing strip 13 is deformed by the upper frame 12 and the lower frame 11. Then, the buckle 42 is rotated so that the buckle 42 is once again engaged in the slot 43 on the housing 3, thus completing the replacement process of the housing 3.

[0052] The implementation principle of a quick-release structure for street light maintenance in this application embodiment is as follows: When it is necessary to uniformly adjust the illumination angle of the street light, the maintenance personnel loosen the angle control bolt 51 so that the lamp cover 2 can rotate freely until it reaches the appropriate position. Then, the maintenance personnel tighten the angle control bolt 51, and the meshing teeth 15 on the lamp cover 2 will gradually mesh with the meshing teeth 15 on the connecting cylinder 1.

[0053] At this time, the lamp cover 2 is kept at a fixed angle under the restriction of the meshing teeth 15. Then, the maintenance personnel observe the scale indicated by the illumination angle scale line 14 at this time, and then adjust the corresponding illumination angle scale line 14 on the other street lights to be the same.

[0054] When streetlights need repair, maintenance personnel approach the streetlights using a ladder, and then rotate to open the latch 42. The latch 42 will disengage from the slot 43 due to its own deformation. During this process, the connecting rod 41 will rotate at the corresponding angle.

[0055] Then the maintenance personnel push the housing 3, and the housing 3 will rotate and open around the axis of the connecting shaft 442. During this process, when the housing 3 drives the fixing plate 443 to rotate synchronously, until the housing 3 separates from the protrusion 17 on the anti-fall plate 16, the compression spring 446 pushes the anti-fall plate 16 to slide, and the protrusion 17 on the anti-fall plate 16 abuts against the fixing plate 443.

[0056] At the same time, the housing 3 will cause the plug recess 82 to separate from the plug protrusion 81 on the lamp cover 2, the control unit 7 and the lighting board 6 will be de-energized, the control unit 7 will be exposed to the maintenance personnel's view, and then the maintenance personnel can carry out maintenance.

[0057] When it is necessary to replace the control unit 7 and the lighting panel 6 on the housing 3, the maintenance personnel push the lever 447. The lever 447 drives the connecting shaft 442 to slide synchronously until the connecting shaft 442 disengages from the connecting hole 444 on the fixing plate 443. Then the maintenance personnel turn the lever 447 to the limiting groove 10 on the limiting plate 9. During this process, the compression spring 446 is compressed. After that, the maintenance personnel install the new housing 3 on the lamp cover 2.

[0058] After the maintenance is completed, the maintenance personnel push the anti-fall plate 16 and then slowly rotate the housing 3 until the protrusion 17 on the anti-fall plate 16 abuts against the fixing plate 443 again. Then the maintenance personnel rotate the lever 447 to disengage the lever 447 from the limiting groove 10 on the limiting plate 9. The compression spring 446 returns to its original shape and pushes the connecting shaft 442 to insert into the connecting hole 444 on the fixing plate 443. Finally, the housing 3 is rotated to make the housing 3 fasten onto the lamp cover 2.

[0059] At this time, the plug recess 82 on the housing 3 will be re-attached to the plug protrusion 81 on the lamp cover 2. At this time, the sealing strip 13 is deformed by the upper frame 12 and the lower frame 11. Then, the buckle 42 is rotated so that the buckle 42 is once again engaged in the slot 43 on the housing 3, thus completing the replacement process of the housing 3.

[0060] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A quick release structure for street light maintenance, characterized by: The assembly includes a connecting cylinder (1), a lamp cover (2), a housing (3), and a quick-release assembly (4). The connecting cylinder (1) is used to connect to the lamp post. The lamp cover (2) is detachably mounted on the connecting cylinder (1). A locking element (5) is provided between the lamp cover (2) and the connecting cylinder (1). The housing (3) is detachably mounted on the lamp cover (2). A lighting panel (6) and a control unit (7) electrically connected to the control system are provided on the housing (3). A conveying mechanism is provided between the lamp cover (2) and the housing (3). The current-conducting component (8) and the quick-release assembly (4) include a connecting rod (41) rotatably mounted on the lamp cover (2), a buckle (42) with an L-shaped cross-section rotatably mounted on the connecting rod (41), the buckle (42) being elastic, a slot (43) for the buckle (42) to be rotatably engaged on the housing (3), and a temporary rotating member (44) is provided between the housing (3) and the lamp cover (2), the temporary rotating member (44) being used to rotate the housing (3) and detachably mount it on the lamp cover (2).

2. The quick-release structure for street light maintenance according to claim 1, characterized in that: The temporary rotating part (44) includes pin plates (441) symmetrically arranged on both sides of the lamp cover (2). A connecting shaft (442) is slidably passed through the pin plates (441). A fixing plate (443) is provided on the housing (3). A connecting hole (444) for the connecting shaft (442) to be inserted is provided on the fixing plate (443). A retaining ring (445) is provided on the connecting shaft (442). A compression spring (446) is supported between the side of the retaining ring (445) facing away from the fixing plate (443) and the pin plate (441). A lever (447) is provided on the connecting shaft (442) on the side of the pin plate (441) facing away from the compression spring (446). The axis of the lever (447) is perpendicular to the axis of the connecting shaft (442).

3. The quick-release structure for street light maintenance according to claim 2, characterized in that: The conductive component (8) includes a plug protrusion (81) disposed on the lamp cover (2) and a plug recess (82) disposed on the housing (3). The plug protrusion (81) is used to engage with the plug recess (82). When the housing (3) is fastened to the lamp cover (2), the current flows from the plug protrusion (81) to the plug recess (82).

4. The quick-release structure for street light maintenance according to claim 2, characterized in that: The lamp cover (2) is provided with a limiting plate (9), and the limiting plate (9) is provided with a limiting groove (10) for accommodating the lever (447).

5. The quick-release structure for street light maintenance according to claim 1, characterized in that: The lamp cover (2) is provided with a lower frame (11), the housing (3) is provided with an upper frame (12), the control unit (7) is located inside the upper frame (12), the upper frame (12) is provided with a sealing strip (13), and the sealing strip (13) is used to abut against the lower frame (11).

6. The quick-release structure for street light maintenance according to claim 1, characterized in that: The locking component (5) includes an angle control bolt (51) threaded onto the lamp cover (2). The cross-section of the connection between the connecting cylinder (1) and the lamp cover (2) is arc-shaped. The connecting cylinder (1) has a waist-shaped groove (52) through which the angle control bolt (51) passes.

7. A quick-release structure for street light maintenance according to claim 6, characterized in that: The lamp cover (2) is provided with an illumination angle scale line (14), which is close to the connecting cylinder (1).

8. A quick-release structure for street light maintenance according to claim 6, characterized in that: Both the connecting cylinder (1) and the lamp cover (2) are provided with meshing teeth (15), and the meshing teeth (15) on the connecting cylinder (1) are used to mesh with the meshing teeth (15) on the lamp cover (2).

9. A quick-release structure for street light maintenance according to claim 2, characterized in that: A fall-prevention plate (16) is slidably sleeved on the connecting shaft (442). The fall-prevention plate (16) is located between the retaining ring (445) and the fixing plate (443). A protruding plate (17) is provided on the fall-prevention plate (16), and the protruding plate (17) is used to abut against the fixing plate (443).

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