A retractable writing board structure and a seat for retractable stand

Abstract

The utility model relates to the technical field of seat storage, and discloses a storage type writing board structure, including handrail, support seat, rear swing arm, front swing arm and writing board, the rear swing arm is sleeve structure, and the rear end of front swing arm inserts inside rear swing arm and is equipped with pivot on the rear end of front swing arm, is equipped with the slide groove that supplies pivot to extend on the circumference wall of rear swing arm, is equipped with torsional spring in rear swing arm, and forms the spacing boss on support seat. The storage type writing board structure provided by the utility model can rotate the front swing arm to get rid of spacing, swing the rear swing arm and the front swing arm together, and lower the swing mode when the seat is folded and laid flat, and the design of maintaining the writing board flat and close to the handrail with the help of torsional spring overcomes the defect that the overall thickness of the seat is too large and the limited space between the steps cannot be adapted due to the inadaptability or unreasonable folding structure of the traditional writing board, ensures that the retractable stand seat will not be interfered by the writing board structure when being recycled, and improves the space utilization of the retractable stand.

Description

Technical Field

[0001] This utility model relates to the field of seat storage technology, and in particular to a retractable writing board structure and a seat for a telescopic grandstand. Background Technology

[0002] In modern public spaces, retractable grandstands are highly favored for their ability to flexibly adjust space utilization. When a retractable grandstand needs to be retracted after use, the seats on each step must first be folded flat to compress the overall thickness and avoid interference when subsequent steps are folded against the wall and stored on the same plane. At this point, the seats will be stored in the narrow gap between two steps.

[0003] To enhance the user experience during events and conferences, adding writing pads to retractable grandstand seats for writing and reading has become a common functional improvement. However, existing technologies have significant drawbacks: traditional seats with writing pads, when folded down, significantly increase the overall thickness of the seat due to the presence of the writing pad structure. For example, some seats use fixed-mount writing pads, which protrude from the seat surface even when the seat is folded, making it impossible for the seat to fit the limited spacing between steps; while some writing pads with folding capabilities cannot fully conform to the seat body after folding, or due to unreasonable folding structure design, the overall thickness exceeds the tolerance range of the step spacing.

[0004] It is evident that existing technologies still need improvement and enhancement. Utility Model Content

[0005] In view of the shortcomings of the prior art, the purpose of this utility model is to provide a retractable writing board structure and a seat for a telescopic grandstand, so as to solve the technical problem that the overall thickness of the seat with the writing board when it is flattened cannot meet the spacing range of the telescopic grandstand steps.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A retractable writing tablet structure includes an armrest, a support base mounted on the armrest, a rear swing arm connected to the support base for vertical swing, a front rotating arm rotatable relative to the rear swing arm, and a writing tablet fixed to the front end of the front rotating arm. The rear swing arm is a sleeve structure, the rear end of the front rotating arm is inserted into the rear swing arm, and a rotating shaft is provided on the rear end of the front rotating arm. A groove is provided on the peripheral wall of the rear swing arm for the rotating shaft to extend and for limiting the rotation amplitude of the rotating shaft. A torsion spring is provided inside the rear swing arm, one end of which is fixedly connected to the rear swing arm, and the other end is fixedly connected to the front rotating arm. The torsion spring is used to drive the rotating shaft on the front rotating arm to return to a laterally extended state, while the writing tablet is correspondingly flattened. A limiting shoulder is formed on the support base to limit the downward swing of the rotating shaft in the laterally extended state. By rotating the front rotating arm, the rotating shaft can be freed from the limitation of the limiting shoulder, allowing the rear swing arm, the front rotating arm, and the writing tablet to swing downward and close to the armrest.

[0008] As a further improvement to the above technical solution, the front swing arm includes a rear axle section, a middle axle section and a connecting box connected in sequence, and the top cover plate of the connecting box is connected to the bottom surface of the writing board by screws.

[0009] As a further improvement to the above technical solution, the armrest is provided with a magnet for magnetically attracting the connecting box.

[0010] As a further improvement to the above technical solution, a gasket is provided between the magnet and the handrail.

[0011] As a further improvement to the above technical solution, the connecting box is provided with anti-collision rubber blocks.

[0012] As a further improvement to the above technical solution, a through hole is provided on the peripheral wall of the rear axle section of the front swing arm for the rotating shaft to pass through, a threaded hole is provided on the rear end face of the rear axle section, and a locking hole corresponding to the threaded hole is provided in the middle of the rotating shaft. The first fixing screw is screwed into the threaded hole and the locking hole in sequence.

[0013] As a further improvement to the above technical solution, the rear swing arm is provided with a first insertion hole for inserting one end of the torsion spring for positioning, and the central shaft section of the front swing arm is provided with a second insertion hole for inserting the other end of the torsion spring for positioning.

[0014] As a further improvement to the above technical solution, the support base is provided with a pivot and the pivot is fixed by a second fixing screw, and the rear swing arm is provided with an adapter hole that cooperates with the pivot.

[0015] As a further improvement to the above technical solution, the support base is composed of multiple steel plates spliced ​​together and the multiple steel plates are tightly connected by rivets.

[0016] A seat for a retractable grandstand includes a base, a flip structure disposed on the base, the aforementioned retractable writing board structure, armrests symmetrically arranged with respect to the armrests in the retractable writing board structure, a backrest disposed between the two armrests, and a seat cushion capable of returning to fit the backrest. The two armrests are mounted on the flip structure and can be flipped at a 90° angle to achieve upright or flattened positions.

[0017] The beneficial effects of this utility model are as follows: Compared with the prior art, the storage writing board structure provided by this utility model can overcome the limitation by rotating the front swing arm and swinging the rear swing arm and the front swing arm together when the seat is folded down. At the same time, the design of keeping the writing board flat and close to the armrest by the torsion spring overcomes the defects of traditional writing boards that cannot fit or have unreasonable folding structure, resulting in excessive overall thickness of the seat and inability to adapt to the limited spacing between steps. This ensures that the writing board structure will not interfere with the retractable grandstand seat when it is retracted, and improves the space utilization of the retractable grandstand. Attached Figure Description

[0018] Figure 1 A perspective view of the storage writing board structure provided by this utility model.

[0019] Figure 2 Explosion of the storage writing board structure provided by this utility model Figure 1 .

[0020] Figure 3 Explosion of the storage writing board structure provided by this utility model Figure 2 .

[0021] Figure 4 A structural diagram of the seat provided by this utility model in use.

[0022] Figure 5 This is a structural diagram of the seat provided by this utility model in a folded state.

[0023] Figure 6 This is a structural diagram of the seat provided by this utility model in its fully flat and stowed state.

[0024] Figure 7 This is a structural diagram showing the seats on the retractable grandstand in their fully flat, stowed state when it is retracted.

[0025] Key component symbols: 1-Armrest, 2-Support base, 21-Pivot, 22-Second fixing screw, 24-Limiting shoulder, 3-Rear swing arm, 31-Torsion spring, 32-First insertion hole, 33-Adapter hole, 34-Slide groove, 4-Front swing arm, 41-Rear axle section, 42-Central axle section, 43-Connecting box, 431-Top cover plate, 44-Anti-collision rubber block, 45-Through hole, 46-Threaded hole, 47-Second insertion hole, 5-Writing board, 61-Spinning shaft, 62-Locking hole, 63-First fixing screw, 71-Magnet, 72-Washer, 82-Backrest, 83-Seat cushion, 84-Flip structure, 85-Base, 9-Retractable grandstand, 91-Steps, 10-Seat. Detailed Implementation

[0026] This utility model provides a retractable writing board structure and a seat 10 for a retractable grandstand 9. To make the purpose, technical solution, and effects of this utility model clearer and more explicit, the following describes this utility model in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this utility model and are not intended to limit the scope of protection of this utility model.

[0027] Please see Figures 1 to 3 This utility model provides a retractable writing board structure, including a handrail 1, a support base 2 mounted on the handrail 1, a rear swing arm 3 connected to the support base 2 for vertical swing, a front rotating arm 4 rotatable relative to the rear swing arm 3, and a writing board 5 fixed to the front end of the front rotating arm 4; the rear swing arm 3 is a sleeve structure, the rear end of the front rotating arm 4 is inserted into the rear swing arm 3 and a rotating shaft 61 is provided on the rear end of the front rotating arm 4, and a groove 34 is provided on the peripheral wall of the rear swing arm 3 for the rotating shaft 61 to extend out and for limiting the rotation amplitude of the rotating shaft 61. The rear swing arm 3 is provided with a torsion spring 31. One end of the torsion spring 31 is fixed to the rear swing arm 3, and the other end is fixed to the front swing arm 4. The torsion spring 31 is used to drive the rotating shaft 61 on the front swing arm 4 to return to the lateral extension state, while the writing board 5 is in the flattened state. The support base 2 forms a limiting shoulder 24 to restrict the downward swing of the rotating shaft 61 in the lateral extension state. By rotating the front swing arm 4, the rotating shaft 61 can be freed from the limitation of the limiting shoulder 24, so that the rear swing arm 3, the front swing arm 4 and the writing board 5 can swing downward and close to the armrest 1.

[0028] When the user needs to use the writing tablet 5, the pivot 61 on the front rotating arm 4 is located above the limiting shoulder 24 of the support base 2. Under the weight of the writing tablet 5 and the action of the torsion spring 31, the pivot 61 is reset to the lateral extension state. At this time, the writing tablet 5 is in a flat state. The limiting shoulder 24 on the support base 2 restricts the pivot 61 from swinging downward, so that the writing tablet 5 is stably kept in a horizontal use position, providing the user with a flat surface for writing and reading.

[0029] When the writing tablet 5 needs to be stored, the user flips the writing tablet 5 outward, thereby causing the front rotating arm 4 to rotate, which in turn causes the rotating shaft 61 to slide along the groove 34 on the periphery of the rear swing arm 3. Since the groove 34 restricts the rotation range of the rotating shaft 61, the rotating shaft 61 switches from a horizontally extended state to a non-horizontal state (such as oblique or vertical), thereby getting rid of the restriction of the limiting shoulder 24. At this time, without the limiting restraint, under the action of gravity and the external force of the storage operation, the rear swing arm 3, the front rotating arm 4 and the writing tablet 5 can swing downward together, gradually approaching the armrest 1, and finally storing the writing tablet 5 next to the armrest 1. In this process, the torsion spring 31 also plays a key role. On the one hand, the torsion spring 31 drives the rotating shaft to reset, so that the writing board is reset to a flat position. On the other hand, when the seat 10 is flat, it can overcome the weight of the writing board to a certain extent through its own elastic force, so that the writing board 5 remains flat and avoids sagging due to its own weight. This ensures that the writing board 5 can be closely attached to the armrest 1, greatly reducing the overall thickness of the seat 10 after folding, so that the seat 10 can be stored in the narrow gap between the steps 91.

[0030] Compared to traditional seats 10 with writing pads 5, the storage writing pad structure provided by this utility model can overcome the limitation of the front swing arm 4 when the seat 10 is folded down, and the rear swing arm 3 and the front swing arm 4 swing down in coordination. At the same time, the torsion spring 31 keeps the writing pad 5 flat and close to the armrest 1. This overcomes the defects of traditional writing pads 5, which cannot fit or have an unreasonable folding structure, resulting in the overall thickness of the seat 10 being too large and unable to adapt to the limited spacing between the steps 91. This ensures that the retractable grandstand 9 seat 10 will not be interfered with by the writing pad 5 structure when it is retracted, and improves the space utilization of the retractable grandstand 9.

[0031] The torsion spring 31 not only ensures that the writing tablet 5 automatically resets and remains stable during use, eliminating the need for additional user intervention to fix it, but also helps the writing tablet 5 fit snugly against the armrest 1 during storage. Users can easily store the writing tablet 5 by simply rotating the front rotating arm 4, making operation convenient. Furthermore, the sliding groove 34's limitation on the rotation range of the rotating shaft 61 and the limiting shoulder 24 further ensure the stability of the entire structure during use and storage, effectively preventing the writing tablet 5 from wobbling or accidentally folding.

[0032] Specifically, the front swing arm 4 includes a rear axle section 41, a middle axle section 42, and a connecting box 43 connected in sequence. The top cover plate 431 of the connecting box 43 is connected to the bottom surface of the writing board 5 by screws. The front swing arm 4 adopts a structure in which the rear axle section 41, the middle axle section 42, and the connecting box 43 are connected in sequence. The segmented design of each part makes it easier to operate during production and assembly. Specifically, the rear axle section 41 and the middle axle section 42 are integrally machined, and the connecting box 43 is connected to the middle axle section 42 by welding. In particular, the top cover plate 431 of the connecting box 43 is connected to the bottom surface of the writing board 5 by screws. This connection method is simple and direct. During installation, only tightening the screws is needed to fix the writing board 5 to the front swing arm 4. During disassembly, unscrewing the screws can separate the two. Whether it is the initial production assembly or the later replacement of the writing board 5, it can greatly improve work efficiency and reduce the difficulty of installation and maintenance.

[0033] In a preferred embodiment, the armrest 1 is provided with a magnet 71 for magnetically attracting the connecting box 43. When the seat 10 is folded for storage, the writing tablet 5, along with the lower part of the front swing arm 4, is close to the armrest 1. At this time, the magnet 71 on the armrest 1 will generate a strong magnetic attraction force on the connecting box 43, which can actively and firmly attract the connecting box 43 to the surface of the armrest 1, so that the writing tablet 5 and the seat 10 are closely fitted. The magnetic attraction of the magnet 71 provides additional fastening force, which works in conjunction with the torsion spring 31 to overcome the sagging tendency of the writing tablet 5 due to its own weight, ensuring that the writing tablet 5 is fully fitted to the armrest 1 for storage, and preventing the writing tablet 5 from detaching and affecting the normal flat storage of the seat 10 when it is flat.

[0034] In a preferred embodiment, a spacer 72 is provided between the magnet 71 and the armrest 1. Different batches or models of components such as the armrest 1 and writing board 5 may have slight differences in size and shape. The heightening function of the spacer 72 effectively compensates for these dimensional errors, allowing the magnet 71 and the connecting box 43 to achieve optimal adsorption and fit. For components with positional deviations due to processing precision, precise fitting can be achieved by increasing or decreasing the thickness of the spacer 72, avoiding the impact of component size mismatch on the magnetic attraction effect and the normal use of the writing board 5. This significantly enhances the compatibility of the entire retractable writing board structure with components of different specifications, improving the flexibility and adaptability of product manufacturing.

[0035] During the storage of the writing tablet 5, the front rotating arm 4 causes the writing tablet 5 to swing downwards. When the connecting box 43 comes into contact with the armrest 1 or other adjacent components, a large impact force is easily generated. Therefore, the connecting box 43 is equipped with anti-collision rubber blocks 44. These anti-collision rubber blocks 44 effectively absorb and buffer the impact force generated during the collision. By dispersing energy through deformation, they reduce the damage to the connecting box 43, armrest 1, and magnet 71, preventing deformation, cracking, or damage to components due to collision. This protects the integrity of the entire storage writing tablet structure, extends the service life of each component, and ensures the stability and reliability of the product during long-term use. After the anti-collision rubber blocks 44 collide with the magnet 71, the writing tablet 5 flips inwards to reset under the action of the torsion spring 31.

[0036] The support base 2 is fixed to the armrest 1 by mounting screws. The support base 2 has a pivot 21, which is secured by a second fixing screw 22. The rear swing arm 3 has a transition hole 33 that mates with the pivot 21. This connection method makes the assembly and disassembly of the rear swing arm 3 and the support base 2 extremely simple. The tightening effect of the second fixing screw 22 on the pivot 21, combined with the precise fit between the transition hole 33 and the pivot 21, provides a stable rotation fulcrum for the rear swing arm 3. During frequent unfolding and retraction of the writing tablet 5, the rear swing arm 3 swings up and down around the pivot 21. This structure effectively disperses the stress generated by the swing, preventing the rear swing arm 3 from shaking or falling off due to loose connections. Even under long-term use or external impact, the tight fit between the pivot 21 and the transition hole 33 remains stable, ensuring precise and reliable linkage between the rear swing arm 3, the front swing arm 4, and the writing tablet 5, significantly improving the reliability and service life of the entire retractable writing tablet structure.

[0037] To meet strength requirements, the support base 2 is composed of multiple steel plates joined together and tightly connected by rivets. Compared to plastic parts, the combination of multiple steel plates in the support base 2 allows for a more complex and stable mechanical structure through reasonable layout and stacking. This effectively disperses and bears various stresses generated during use from the rear swing arm 3, front swing arm 4, and writing board 5, greatly improving the overall strength and load-bearing capacity of the support base 2. Even when the user frequently uses the writing board 5 for writing, placing items, or during the unfolding and folding of the seat 10, the multi-steel-plate structure of the support base 2 remains stable, preventing deformation and damage due to insufficient strength. This ensures the reliable operation of the entire folding writing board structure and extends the product's lifespan.

[0038] The torsion spring 31 is fitted onto the rear axle section 41 of the front swing arm 4. The rear swing arm 3 has a first insertion hole 32 for inserting one end of the torsion spring 31 for positioning, and the central axle section 42 of the front swing arm 4 has a second insertion hole 47 for inserting the other end of the torsion spring 31 for positioning. The torsion spring 31 is positioned by inserting into the first insertion hole 32 of the rear swing arm 3 and the second insertion hole 47 of the central axle section 42 of the front swing arm 4, and is simultaneously fitted onto the rear axle section 41 of the front swing arm 4. This installation method allows for quick and accurate determination of the torsion spring 31's position. During production and assembly, workers do not need complex calibration operations; they only need to insert both ends of the torsion spring 31 into the corresponding insertion holes and then fit it onto the rear swing arm 3 to complete the installation, greatly simplifying the installation process. Compared to traditional torsion spring 31 installation methods, this reduces installation time and labor costs, significantly improves production efficiency, and reduces the risk of torsion spring 31 malfunction due to installation errors.

[0039] The rear axle section 41 of the front swing arm 4 has a through hole 45 on its peripheral wall for the rotating shaft 61 to pass through. The rear end face of the rear axle section 41 has a threaded hole 46, and the middle part of the rotating shaft 61 has a locking hole 62 corresponding to the threaded hole 46. The first fixing screw 63 is screwed into the threaded hole 46 and the locking hole 62 in sequence. During installation, the rear axle section 41 of the front swing arm 4 is first inserted into the rear swing arm 3. Then, the rotating shaft 61 is installed into the through hole 45 through the slide groove 34. The first fixing screw 63 has been pre-installed on the front swing arm 4 but has not been tightened. Then, a screwdriver is used to insert into the first insertion hole 32 of the rear swing arm 3 and tighten the first fixing screw 63 to complete the fixation. This simple and direct connection method, compared with the complex welding, riveting and other fixing methods, greatly improves the work efficiency of production assembly and subsequent maintenance, and reduces the difficulty of manual operation and time cost.

[0040] This connection method provides stable support and constraint for the pivot 61, effectively preventing it from loosening, shifting, or falling off during use. Even when the writing pad 5 is frequently rotated, retracted, or subjected to external forces, the pivot 61 remains stable, ensuring smooth linkage between the rear swing arm 3, the front swing arm 4, and the writing pad 5. This maintains the stability and reliability of the entire retractable writing pad structure, avoiding structural failures and safety hazards caused by a loose pivot 61.

[0041] Understandably, after tightening the first fixing screw 63, when inserting one end of the torsion spring 31 into the first insertion hole 32, a tool can be used to extend from the adapter hole 33 into the interior of the rear swing arm 3 for auxiliary alignment.

[0042] Please see Figures 4 to 7The present invention also provides a seat 10 for a telescopic grandstand 9, including a base 85, a flip structure 84 disposed on the base 85, the aforementioned storage writing board structure, armrests 1 symmetrically disposed with the armrests 1 in the storage writing board structure, a backrest 82 disposed between the two armrests 1, and a seat cushion 83 capable of returning to fit the backrest 82. The two armrests 1 are mounted on the flip structure 84 and can be flipped at a 90° angle to achieve upright or flat position.

[0043] When the seat 10 is in use, the seat cushion 83 unfolds naturally, the backrest 82 provides back support for the user, the two armrests 1 are symmetrically installed on the flip structure 84 and are in an upright state, and the writing board 5 in the storage writing board structure is flattened under the action of the torsion spring 31. The user can use the writing board 5 to write, read and perform other operations as needed. At this time, the seat 10 provides the user with a comfortable space for watching games and attending conferences.

[0044] When the retractable grandstand 9 needs to retract the seat 10, the seat cushion 83 returns to its original position against the backrest 82. First, by flipping the writing board 5, the front rotating arm 4 of the retractable writing board structure is rotated, allowing the pivot 61 to break free from the limitation of the support seat 2's limiting shoulder 24. The rear swing arm 3, the front rotating arm 4, and the writing board 5 swing downwards under the action of gravity and external force. At the same time, the torsion spring 31 and the magnet 71 work together to keep the writing board 5 flat and tightly attached to the armrest 1, completing the storage of the writing board 5. Subsequently, the flipping structure 84 is operated, causing the two armrests 1 installed on it, along with the stored writing board 5 structure, to flip and flatten at a 90° angle. The thickness of the entire seat 10 is greatly reduced, and all components are compactly stored on top of the base 85. This ensures that when the subsequent steps 91 are closed against the wall and stored on the same plane, they will not interfere with other seats 10 or steps 91.

[0045] The seat 10 provided by this utility model has all the advantages of a retractable writing board structure, allowing the writing board 5 to be stored tightly against the armrest 1. Combined with the ability to flip and flatten the armrest 1, seat cushion 83, and backrest 82, the overall thickness of the seat 10 is significantly reduced, perfectly fitting the narrow gaps between the steps 91. This effectively solves the problem of difficult storage of the seat 10 in the retractable grandstand 9, significantly improving the space utilization of the grandstand and facilitating its rapid retraction and deployment. This seat 10 not only has the seating function of a conventional seat 10, but also adds a flexible writing board 5 structure, providing users with additional functions such as writing and reading during viewing events and attending conferences, meeting diverse user needs.

[0046] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0047] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0048] It is understood that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of this utility model, and all such substitutions or changes should fall within the protection scope of this utility model.

Claims

1. A retractable writing tablet structure, characterized by, The device includes an armrest, a support base mounted on the armrest, a rear swing arm connected to the support base for vertical swing, a front swing arm that can rotate relative to the rear swing arm, and a writing board fixed to the front end of the front swing arm. The rear swing arm is a sleeve structure. The rear end of the front swing arm is inserted into the rear swing arm and has a pivot on its rear end. The peripheral wall of the rear swing arm has a groove for the pivot to extend and for limiting the rotation amplitude of the pivot. A torsion spring is provided inside the rear swing arm. One end of the torsion spring is fixed to the rear swing arm, and the other end is fixed to the front swing arm. The torsion spring is used to drive the pivot on the front swing arm to return to a laterally extended state, while the writing board is correspondingly flattened. The support base has a limiting shoulder for limiting the downward swing of the pivot in the laterally extended state. By rotating the front swing arm, the pivot can be freed from the limitation of the limiting shoulder, allowing the rear swing arm, the front swing arm, and the writing board to swing downward and close to the armrest.

2. The retractable writing tablet structure of claim 1, wherein The front swing arm includes a rear axle section, a middle axle section, and a connecting box connected in sequence. The top cover of the connecting box is connected to the bottom surface of the writing board by screws.

3. The retractable writing board structure according to claim 2, characterized in that, The handrail is equipped with magnets for magnetically attracting the connecting box.

4. The retractable writing board structure according to claim 3, characterized in that, A gasket is provided between the magnet and the handrail.

5. The retractable writing board structure according to claim 2, characterized in that, The connecting box is equipped with anti-collision rubber blocks.

6. The retractable writing board structure according to claim 1, characterized in that, The rear axle section of the front swing arm has a through hole on its peripheral wall for the swing shaft to pass through. The rear end face of the rear axle section has a threaded hole. The middle part of the swing shaft has a locking hole corresponding to the threaded hole. The first fixing screw is screwed into the threaded hole and the locking hole in sequence.

7. The retractable writing board structure according to claim 2, characterized in that, The rear swing arm is provided with a first insertion hole for inserting one end of the torsion spring for positioning, and the central shaft section of the front swing arm is provided with a second insertion hole for inserting the other end of the torsion spring for positioning.

8. The retractable writing board structure according to claim 1, characterized in that, The support base is provided with a pivot and the pivot is fixed by a second fixing screw. The rear swing arm is provided with an adapter hole that mates with the pivot.

9. The retractable writing board structure according to claim 1, characterized in that, The support base is composed of multiple steel plates spliced ​​together and the steel plates are tightly connected by rivets.

10. A seat for a retractable grandstand, characterized in that, The invention includes a base, a flip structure disposed on the base, a storage writing board structure as described in any one of claims 1-9, armrests symmetrically arranged with the armrests in the storage writing board structure, a backrest disposed between the two armrests, and a seat cushion capable of returning to fit the backrest. The two armrests are mounted on the flip structure and can be flipped at a 90° angle to achieve upright or flat position.

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