Quick-disassembly desk stand

Abstract

The present invention relates to a quick-disassembly desk stand, comprising a longitudinal beam, a transverse beam, and table legs. The table legs are electrically liftable table leg columns. The table legs are assembled with the desktop stand via a quick-disassembly mechanism. The quick-disassembly mechanism includes a slot mechanism and a locking mechanism. The locking mechanism includes a rotating member and a fixed member respectively located on the table leg and the longitudinal beam. The rotating member and the fixed member are driven and matched via a spiral structure. The locking mechanism drives the table leg to move laterally via the forward and reverse rotation of the rotating member, thereby causing the clamping head to engage or exit the main body of the slot, thereby locking or releasing the assembly relationship between the table leg and the transverse beam and the longitudinal beam. The present invention does not require the use of screws or tools. The entire desk stand can be assembled and disassembled by simply rotating the rotating member installed on the longitudinal beam, which is beneficial for reducing packaging materials and costs.

Description

Technical Field

[0001] The invention belongs to the technical field of furniture equipment, in particular to a quickly disassembled office desk bracket. Background Art

[0002] With the development of the times, height-adjustable desks have become a new trend in modern office work. Lifting platforms, especially electric lift platforms, such as height-adjustable tables, are becoming increasingly popular in both office and home settings. However, because lifts take up a lot of space and are inconvenient to transport, manufacturers of electric lift tables often ship them unassembled, requiring consumers to assemble them themselves or have the manufacturer perform on-site assembly. Therefore, achieving rapid assembly and disassembly, or making assembly convenient for consumers, is a pressing issue for lifts and electric lifts.

[0003] Current lifting platforms or lifting desks typically include a tabletop and a desk support, which in turn includes a longitudinal beam, a transverse beam, and an electric lift leg column. Today's quick-disassembly desk supports typically weld the longitudinal and transverse beams together. Later assembly primarily involves the installation of the transverse beams and the electric lift leg columns. Currently, a more common method is to use a crank or cam mechanism to press the transverse beams and the electric lift leg columns together to securely connect them. This assembly process is complex and requires considerable effort during disassembly. Furthermore, since the longitudinal and transverse beams are welded together, they occupy a significant amount of packaging space, making packaging and transportation difficult and increasing the packaging and transportation costs of the product. This prior art is disclosed in Chinese patent document CN209359912U. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a quick-disassembly desk bracket, which can make the assembly and disassembly of the desk bracket faster and more convenient, thereby improving the overall assembly and disassembly efficiency.

[0005] The technical solution adopted by the present invention to solve its technical problems is: a quick-disassembly and assembly desk support, comprising a desktop support and table legs supporting the desktop support, the desktop support comprising a longitudinal beam and a transverse beam, the table legs being located at the intersection of the longitudinal beam and the transverse beam, and being assembled with the desktop support through a quick-disassembly and assembly mechanism, the quick-disassembly and assembly mechanism comprising a slot mechanism and a locking mechanism, the slot mechanism comprising a clamping head and a slot respectively located on the table leg and the transverse beam, the main body of the slot extending laterally, the table leg being assembled with the transverse beam by the clamping head being clamped into the main body of the slot, the locking mechanism comprising a rotating part and a fixing part respectively located on the table leg and the longitudinal beam, the rotating part being rotatably installed, the fixing part being fixedly installed, the rotating part and the fixing part being driven and matched by a spiral structure, the locking mechanism driving the table leg to move laterally through the forward and reverse rotation action of the rotating part, thereby causing the clamping head to clamp into or exit the main body of the slot, locking or releasing the assembly relationship between the table leg and the transverse beam.

[0006] It is further defined that the matching spiral structures on the rotating member and the fixed member specifically include a spiral groove and a pin embedded in the spiral groove.

[0007] It is further defined that the spiral groove has a back-stopping pit to prevent the rotating part from reversing. When the clamping head moves to the end of the stroke of the clamping groove, the pin shaft is clamped into the back-stopping pit to maintain the locking state of the table legs and the beam.

[0008] It is further defined that the rotating part and the fixed part are nested and matched inside and outside.

[0009] Furthermore, the locking mechanism further includes a return spring that acts on the rotating member to reset the rotating member to an unlocked position. In this unlocked position, the pin on the rotating member faces the front opening of the spiral groove, and the pin is inserted into the spiral groove through the front opening of the spiral groove. The return spring design facilitates quick insertion and insertion of the rotating member and the fixed member, thereby improving the ease of assembly of the desk stand.

[0010] One of the specific structures of the locking mechanism is: the rotating part includes a columnar part and an operating cantilever part extending from the columnar part, the columnar part is rotatable on the longitudinal beam through a rotating shaft, and two coaxially distributed pins are provided on the columnar part; the fixed part is a hollow cylinder, and the rotating part is embedded in the inner hole of the fixed part through the columnar part, and two spiral grooves for the pins to be embedded are provided on the outer periphery of the fixed part, and a rotation limiting structure is provided between the columnar part and the rotating shaft, which is used to rotationally limit the rotating part when the rotating part rotates to the unlocked position, and the return spring has a pre-tightening force when the rotating part is in the unlocked position, and the return spring is a torsion spring, and the return spring is provided between the columnar part of the rotating part and the rotating shaft.

[0011] It is further defined that the table legs are electric lift table leg columns, which include a lift column and a drive box on the top of the lift column. The drive box is assembled with the desktop bracket through a quick disassembly and assembly mechanism.

[0012] In order to reduce packaging materials and costs, it is further defined that the crossbeam and the longitudinal beam are separate structures, and the ends of the crossbeam are inserted and positioned on the longitudinal beam through the end positioning structure. When the locking mechanism locks the assembly relationship between the table legs and the crossbeam, the clamping head moves to the end of the stroke of the clamping slot, locking the insertion relationship between the crossbeam and the longitudinal beam.

[0013] It is further defined that the end positioning structure includes a base on the longitudinal beam, a longitudinally arranged positioning pin fixed on the base, and a plug-in positioning groove on the side wall of the cross beam that cooperates with the positioning pin. The head of the positioning pin has a limiting end cap. When in the locked state, the positioning pin is embedded in the plug-in positioning groove, and the base and the limiting end cap are respectively located on the inner and outer sides of the plug-in positioning groove.

[0014] It is further defined that there are two crossbeams, and the table legs are located between the two crossbeams. The table legs and each crossbeam are assembled through two slot mechanisms, and the two crossbeams are connected as a whole through a connecting plate. The slot of the slot mechanism includes an entrance part extending vertically downward and a main part extending laterally. The main part of the slot and the plug-in positioning groove at the end of the crossbeam are wide outside and narrow inside and are trumpet-shaped. The specific structure of the columnar part rotatable on the longitudinal beam through the rotating shaft is as follows: a convex ring is provided in the inner hole of the columnar part, and the columnar part rotates on the rotating shaft through the convex ring. A retaining ring is fixed at the head end of the rotating shaft by a screw, and the retaining ring is blocked outside the convex ring for axial limitation. The rotation limiting structure between the columnar part and the rotating shaft includes a limiting ring groove on the columnar part and a limiting pin on the rotating shaft. The limiting pin is embedded in the limiting ring groove for rotation limitation, and the head end of the limiting pin screwed into the rotating shaft is simultaneously against the side of the screw.

[0015] The beneficial effects of the present invention are: no screws are needed, no tools are needed, and the entire office desk bracket can be assembled and disassembled by rotating the rotating part installed on the longitudinal beam. At the same time, the detachable structure is conducive to reducing packaging materials and costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Figure 1 Schematic diagram of the assembly structure of Example 1 of the present invention (only the assembly relationship between the desktop bracket on one side and the electric lifting table leg column on the same side is shown through sectioning);

[0018] Figure 2 yes Figure 1 Exploded diagram;

[0019] Figure 3 1 is a schematic structural diagram of a rotating member according to embodiment 1 of the present invention;

[0020] Figure 4 is a schematic structural diagram of a fixing member according to embodiment 1 of the present invention;

[0021] Figure 5 1 is a structural schematic diagram of the rotating member and the fixed member in a locked state according to embodiment 1 of the present invention;

[0022] Figure 6 is a structural schematic diagram of the rotating member and the fixing member of Example 1 of the present invention in a locked state from another perspective;

[0023] Figure 7 1 is a structural diagram of the rotating member and the fixing member in the unlocked state according to the first embodiment of the present invention;

[0024] Figure 8 1 is a schematic structural diagram of a longitudinal beam according to embodiment 1 of the present invention;

[0025] Figure 9 is a cross-sectional view of a rotating member on a longitudinal beam according to embodiment 1 of the present invention;

[0026] Figure 10 2 is a schematic structural diagram of a rotating member according to embodiment 2 of the present invention;

[0027] Figure 11 It is a cross-sectional view of a rotating member according to Example 2 of the present invention.

[0028] In the figure: 1. Electric lifting table leg column, 1-1. Lifting column, 1-2. Drive box, 2. Crossbeam, 3. Longitudinal beam, 3-1. Side panel, 3-2. Top folding edge, 4. Slot, 5. Clamp, 6. Rotating part, 6-1. Columnar part, 6-1-1. Pin shaft, 6-2. Cantilever part, 7. Fixing part, 7-1. Spiral groove, 7-1-1. Retraction pit, 7-2. Mounting plate, 8. Return spring, 9-1. Base, 9-2. Locating pin, 9-2-1. Limiting end cap, 9-3. Plug-in positioning groove, 10. Convex ring, 11. Connecting plate, 12. Rotating shaft, 13. Retaining ring, 14. Screw, 15. Limiting ring groove, 16. Limiting pin. DETAILED DESCRIPTION

[0029] The present invention will now be further described with reference to the accompanying drawings, which are simplified schematic diagrams illustrating the basic structure of the present invention in a schematic manner, and thus only show components related to the present invention.

[0030] Example 1, as Figures 1 to 9 As shown, a quick-disassembly office desk stand includes a desktop stand and table legs supporting the desktop stand. The desktop stand includes a longitudinal beam 3 and a transverse beam 2. The table legs are located at the intersection of the longitudinal beam 3 and the transverse beam 2 and are assembled with the desktop stand through a quick-disassembly mechanism. The quick-disassembly mechanism includes a slot mechanism and a locking mechanism.

[0031] The slot mechanism includes a clamping head 5 and a clamping slot 4 located on the table leg and the beam 2 respectively. The main part of the clamping slot 4 extends laterally, and the table leg is assembled with the beam 2 by clamping the clamping head 5 into the main part of the clamping slot 4.

[0032] The card slot 4 of the card slot mechanism includes an entrance portion extending vertically downward and a main portion extending laterally. The main portion of the card slot 4 is wide on the outside and narrow on the inside and is in a trumpet shape.

[0033] The locking mechanism includes a rotating part 6, a fixing part 7 and a return spring 8 respectively located on the table leg and the longitudinal beam 3. The rotating part 6 can be rotatably installed, and the fixing part 7 is fixedly installed. The rotating part 6 and the fixing part 7 are driven and matched by a spiral structure. The locking mechanism drives the table leg to move laterally through the forward and reverse rotation action of the rotating part 6, thereby causing the clamping head 5 to be clamped into or out of the main part of the clamping slot 4, locking or releasing the assembly relationship between the table leg and the crossbeam 2.

[0034] The matched spiral structures on the rotating member 6 and the fixing member 7 specifically include a spiral groove 7-1 and a pin 6-1-1 embedded in the spiral groove 7-1.

[0035] The spiral groove 7-1 has a stop-retraction pit 7-1-1 to prevent the rotating part 6 from reversing. When the clamping head 5 moves to the end of the stroke of the clamping groove 4, the pin 6-1-1 is clamped into the stop-retraction pit 7-1-1, keeping the table legs and the beam 2 locked.

[0036] The rotating part 6 and the fixing part 7 are nested and matched inside and outside.

[0037] The more specific structure of the rotating member 6 and the fixed member 7 is as follows: the rotating member 6 includes a columnar portion 6-1 and an operating cantilever portion 6-2 extending from the columnar portion 6-1. The columnar portion 6-1 is rotatably mounted on the longitudinal beam 3 via a rotating shaft 12. The columnar portion 6-1 is provided with two coaxially distributed pins 6-1-1. The fixed member 7 is a hollow cylinder. The rotating member 6 is inserted into the inner hole of the fixed member 7 via the columnar portion 6-1. Two spiral grooves 7-1 for the pins 6-1-1 to be inserted are provided on the outer periphery of the fixed member 7. The retaining recess 7-1-1 is located at the end of the spiral groove 7-1 on the side close to the rotating member 6. A reset spring 8 acts on the rotating member 6 to drive the rotating member 6 to reset to the unlocked position. In this unlocked position, the pin 6-1-1 on the rotating member 6 faces the front end opening of the spiral groove 7-1, and the pin 6-1-1 is inserted into the spiral groove 7-1 through the front end opening of the spiral groove 7-1. The return spring 8 is a torsion spring, and is disposed between the columnar portion 6 - 1 of the rotating member 6 and the rotating shaft 12 .

[0038] like Figure 9 As shown, the specific structure of the columnar portion 6-1 rotatably mounted on the longitudinal beam 3 via the rotating shaft 12 is as follows: a convex ring 10 is provided in the inner hole of the columnar portion 6-1, the columnar portion 6-1 is rotatably mounted on the rotating shaft 12 via the convex ring 10, and a retaining ring 13 is fixed to the head end of the rotating shaft 12 via a screw 14, and the retaining ring 13 is blocked outside the convex ring 10 for axial limitation.

[0039] The table legs are electrically-operated lifting table leg columns 1, which include a lifting column 1-1 and a drive box 1-2 on top of the lifting column 1-1. The drive box 1-2 is assembled with the desktop bracket via a quick disassembly mechanism. The clamping head 5 is a trapezoidal protrusion on the drive box 1-2.

[0040] The crossbeam 2 and the longitudinal beam 3 are separate structures. The end of the crossbeam 2 is inserted and positioned on the longitudinal beam 3 through the end positioning structure. When the locking mechanism locks the assembly relationship between the table legs and the crossbeam 2, the clamping head 5 moves to the end of the stroke of the clamping slot 4, locking the insertion relationship between the crossbeam 2 and the longitudinal beam 3.

[0041] The end positioning structure includes a base 9-1 on the longitudinal beam 3 and a longitudinally arranged positioning pin 9-2 fixed on the base 9-1. The head of the positioning pin 9-2 has a limiting end cap 9-2-1, and the side wall of the cross beam 2 has a plug-in positioning groove 9-3 that cooperates with the positioning pin 9-2. When in the locked state, the positioning pin 9-2 is embedded in the plug-in positioning groove 9-3, and the base 9-1 and the limiting end cap 9-2-1 are respectively located on the inner and outer sides of the plug-in positioning groove 9-3.

[0042] Two crossbeams 2 are provided, with the table legs located between them. The legs are assembled with each crossbeam 2 via two slot mechanisms, and the two crossbeams 2 are connected as a single unit via a connecting plate 11. The longitudinal beam 3 includes a side panel 3-1 and a top flange 3-2 at the top of the side panel 3-1. The rotating member 6 and base 9-1 are located on the side panel 3-1.

[0043] The front end of the fixing member 7 has a mounting plate 7-2. The fixing member 7 is fixed to the drive box 1-1 through the mounting plate 7-2 and screws. The fixing member 7 is located inside the drive box 1-2.

[0044] The cross beam 21 is specifically a square tube.

[0045] This embodiment 1 has the following advantages:

[0046] First, no screws or tools are needed, and the entire desk stand can be assembled and disassembled simply by rotating the rotating member 6 mounted on the longitudinal beam 3;

[0047] Second, by operating the cantilever part 6-2 to rotate the rotating part 6, it is quick and labor-saving, which greatly reduces the installation workload of the installer and significantly improves the installation efficiency;

[0048] Third, simplify the assembly steps. During assembly, first insert the base 9-1 of the longitudinal beam 3 into the end hole of the transverse beam 2, and match the trumpet-shaped insertion positioning groove 9-3 with the positioning pin 9-2. Then, insert the clamping head 5 on the electric lifting table leg column 1 from bottom to top through the entrance part of the clamping groove 4 into the clamping groove 4. Under the reset action of the reset spring 8, the rotating member 6 is kept in the unlocked position. In this unlocked position, the pin 6-1-1 on the rotating member 6 is opposite to the front end opening of the spiral groove 7-1. It is only necessary to slightly move the electric lifting table leg column 1 horizontally to make the pin 6-1-1 enter the spiral groove 7-1. By operating the cantilever part 6-2, manually rotate the rotating member 6 in the forward direction to put the locking mechanism into the locked state. Figure 5 and 6As shown, the electric lifting table leg column 1 and the desktop bracket, the crossbeam 2 and the longitudinal beam 3 are quickly assembled without screws;

[0049] Fourth, the disassembly steps are simplified. During the entire disassembly process, it is only necessary to operate the cantilever part 6-2 to reversely rotate the rotating part 6 to the unlocking position, and the electric lifting table leg column 1 and the crossbeam 2 will automatically separate. Then, the clamping head 5 of the drive box 1-2 is withdrawn from the clamping slot 4 of the crossbeam 2 to complete the entire disassembly process, saving time and effort, and greatly improving the disassembly efficiency.

[0050] Fifth, the crossbeam 2 and the longitudinal beam 3 are designed to be split, and the crossbeam 2 and the longitudinal beam 3 are packaged after being disassembled, which reduces the packaging materials and costs, and the transportation cost of the entire office desk stand or lifting office desk will also be reduced.

[0051] Embodiment 2 is different from Embodiment 1 in that: a rotation limiting structure is provided between the columnar portion 6-1 and the rotating shaft 12, which is used to rotationally limit the rotating member 6 when the rotating member 6 rotates to the unlocked position. When the rotating member 6 is in the unlocked position, the return spring 8 has a preload force. The rotation limiting structure between the columnar portion 6-1 and the rotating shaft 12 includes a limiting ring groove 15 on the columnar portion 6-1 and a limiting pin 16 on the rotating shaft 12. The limiting pin 16 is embedded in the limiting ring groove 15 for rotation limiting. The head end of the limiting pin 16 screwed into the rotating shaft 12 is simultaneously pressed against the side of the screw 14 to prevent the screw 14 from loosening. Figure 10 and 11 shown.

[0052] Example 3 differs from Example 1 in that, by changing the return direction of return spring 8, return spring 8 functions to prevent rotation of rotating member 6, replacing the retaining recess 7-1-1 to maintain the locked state between the table legs and crossbeam 2. Compared to Example 1, this solution has the disadvantage of being less convenient for quick assembly. Of course, it is not ruled out that the locked state can also be maintained by using pluggable limit pins or by designing the helical angle to make the helical structure self-locking, preventing rotating member 6 from automatically reversing and unlocking in the locked position.

[0053] Example 4 differs from Examples 1 and 2 in that the crossbeam 2 and the longitudinal beam 3 are fixedly connected together by welding or other methods, and the locking mechanism drives the table legs to move laterally through the forward and reverse rotation of the rotating member 6, thereby causing the clamping head 5 to enter or exit the main part of the clamping slot 4, locking or releasing the assembly relationship between the table legs and the desktop bracket.

[0054] Example 5 differs from Examples 1 and 2 in that the positions of the clamping head 5 and the clamping slot 4 of the clamping mechanism are interchanged, with the clamping slot 4 located on the drive box 1-2 and the clamping head 5 located on the crossbeam 2. The positions of the rotating member 6 and the fixed member 7 of the locking mechanism are interchanged, with the rotating member 6 located on the drive box 1-2 and the fixed member 7 located on the longitudinal beam 3.

[0055] Embodiment 6 is different from Embodiments 1 and 2 in that the desktop support is a single beam.

Claims

1. A quick-disassembly desk stand, comprising a desktop stand and legs supporting the desktop stand, wherein the desktop stand comprises a longitudinal beam (3) and a transverse beam (2), the legs being located at the intersection of the longitudinal beam (3) and the transverse beam (2) and being assembled with the desktop stand via a quick-disassembly mechanism, characterized in that: The quick disassembly and assembly mechanism includes a slot mechanism and a locking mechanism. The slot mechanism comprises a clamping head (5) and a clamping slot (4) respectively located on the table leg and the crossbeam (2). The main part of the clamping slot (4) extends laterally. The table leg is assembled with the crossbeam (2) by clamping the clamping head (5) into the main part of the clamping slot (4). The locking mechanism comprises a rotating member (6) and a fixing member (7) respectively located on the table leg and the longitudinal beam (3). The rotating member (6) is rotatably mounted, and the fixing member (7) is fixedly mounted. The rotating member (6) and the fixing member (7) are driven and matched by a spiral structure. The locking mechanism drives the table leg to move laterally by the forward and reverse rotation of the rotating member (6), thereby causing the clamping head (5) to be clamped into or out of the main part of the clamping slot (4), thereby locking or releasing the assembly relationship between the table leg and the crossbeam (2). The matching spiral structures on the rotating member (6) and the fixed member (7) specifically include a spiral groove (7-1) and a pin (6-1-1) embedded in the spiral groove (7-1). The spiral groove (7-1) has a stopper recess (7-1-1) for preventing the rotating member (6) from reversing. When the clamping head (5) moves to the end of the stroke of the clamping groove (4), the pin (6-1-1) is clamped into the stopper recess (7-1-1). The rotating member (6) includes a columnar portion (6-1) and an operating cantilever portion (6-2) extending from the columnar portion (6-1). The columnar portion (6-1) is rotatable on the longitudinal beam (3) through a rotating shaft (12). Two coaxially distributed pins (6-1-1) are provided on the columnar portion (6-1). The fixed member (7) is a hollow cylinder. The rotating member (6) is embedded in the inner hole of the fixed member (7) through the columnar portion (6-1). Two spiral grooves (7-1) for the pins (6-1-1) to be embedded are provided on the outer periphery of the fixed member (7). The table leg is an electric lifting table leg column (1), which comprises a lifting column (1-1) and a drive box (1-2) on the top of the lifting column (1-1), and the drive box (1-2) is assembled with the desktop bracket through a quick disassembly mechanism.

2. The quick-disassembly desk stand according to claim 1, characterized in that: The rotating member (6) and the fixing member (7) are nested and matched inside and outside.

3. The quick-detachable desk stand according to claim 2, characterized in that: The locking mechanism further includes a reset spring (8), which acts on the rotating member (6) to drive the rotating member (6) to reset to an unlocked position. In the unlocked position, the pin (6-1-1) on the rotating member (6) faces the front end opening of the spiral groove (7-1), and the pin (6-1-1) is embedded in the spiral groove (7-1) through the front end opening of the spiral groove (7-1).

4. The quick-disassembly desk stand according to claim 3, characterized in that: A rotation limiting structure is provided between the columnar portion (6-1) and the rotating shaft (12), which is used to rotationally limit the rotating member (6) when the rotating member (6) rotates to the unlocked position. When the rotating member (6) is in the unlocked position, the return spring (8) has a preload force. The return spring (8) is a torsion spring, and the return spring (8) is arranged between the columnar portion (6-1) of the rotating member (6) and the rotating shaft (12).

5. The quick-detachable desk stand according to claim 1, characterized in that: The crossbeam (2) and the longitudinal beam (3) are separate structures. The end of the crossbeam (2) is inserted and positioned on the longitudinal beam (3) through the end positioning structure. When the locking mechanism locks the assembly relationship between the table legs and the crossbeam (2), the clamping head (5) moves to the end of the stroke of the clamping slot (4), locking the insertion relationship between the crossbeam (2) and the longitudinal beam (3).

6. The quick-detachable desk stand according to claim 5, characterized in that: The end positioning structure comprises a base (9-1) on the longitudinal beam (3), a longitudinally arranged positioning pin (9-2) fixed on the base (9-1), and a plug-in positioning groove (9-3) on the side wall of the crossbeam (2) that cooperates with the positioning pin (9-2). The head of the positioning pin (9-2) has a limiting end cap (9-2-1). When in a locked state, the positioning pin (9-2) is embedded in the plug-in positioning groove (9-3). The base (9-1) and the limiting end cap (9-2-1) are respectively located on the inner and outer sides of the plug-in positioning groove (9-3).

7. The quick-detachable desk stand according to claim 4, characterized in that: There are two crossbeams (2), and the table legs are located between the two crossbeams (2). The table legs and each crossbeam (2) are assembled through two slot mechanisms, and the two crossbeams (2) are connected into a whole through a connecting plate (11). The card slot (4) of the card slot mechanism comprises an entrance portion extending vertically downward and a main portion extending laterally. The main portion of the card slot (4) and the plug-in positioning groove (9-3) at the end of the crossbeam (2) are wide on the outside and narrow on the inside, forming a trumpet shape. The columnar portion (6-1) is rotatably mounted on the longitudinal beam (3) via a rotating shaft (12). The columnar portion (6-1) has a specific structure in which a convex ring (10) is provided in the inner hole of the columnar portion (6-1). The columnar portion (6-1) is sleeved on the rotating shaft (12) via the convex ring (10) and rotates. A retaining ring (13) is fixed to the head end of the rotating shaft (12) via a screw (14). The retaining ring (13) is retained outside the convex ring (10) for axial positioning. The rotation limiting structure between the columnar portion (6-1) and the rotating shaft (12) comprises a limiting ring groove (15) on the side of the columnar portion (6-1) and a limiting pin (16) on the side of the rotating shaft (12), wherein the limiting pin (16) is embedded in the limiting ring groove (15) for rotation limiting. The head end of the limit pin (16) screwed into the rotating shaft (12) is pressed against the side of the screw (14) at the same time.

Images