Sofa seat stretching device and method

Abstract

The invention relates to the technical field of sofa seats, in particular to a sofa seat stretching device and method, and provides a sofa seat stretching device aiming at the problem that when an existing sofa seat stretching device is unfolded, a supporting structure is not stable enough, the sofa seat stretching device comprises a main body frame, and a movable driving plate is arranged at the lower end of the main body frame; a leg bracket is arranged at the front end of the driving plate, a back plate is arranged on one side of the upper end of the main body frame, each supporting structure comprises two extending supporting rods, and when the driving plate moves towards one side, the leg bracket can move forwards and can also move upwards after moving forwards to a designated position; when the driving plate moves towards one side, the back plate can be turned over downwards, and the two extending supporting rods move towards the outer side; when the device is unfolded, the bottom supporting structures synchronously extend towards the two sides, the contact area between the supporting span and the ground is remarkably increased, the rollover risk caused by gravity center shifting is reduced, potential safety hazards of an existing device are fundamentally eliminated, and the sense of safety of a user in the using process is improved.

Description

Technical Field

[0001] This invention relates to the field of sofa and chair technology, and in particular to a sofa and chair extension device and method. Background Technology

[0002] In the furniture industry, extendable sofas and chairs are widely used in homes and offices due to their ability to meet diverse comfort needs such as sitting and lying down. These sofas and chairs are typically equipped with an extension mechanism, allowing users to switch between different functions by adjusting the seat angle and extending the leg rest. However, the bottom support structure design of existing extension mechanisms has significant flaws: most support structures use a fixed frame or a unidirectional telescopic design, resulting in limited support span and concentrated support points when extended, leading to insufficient overall support stability. When a user lies down and the center of gravity shifts, the seat is prone to tipping over due to support imbalance, posing a safety hazard. Furthermore, existing support structures cannot be effectively folded down after the mechanism is closed, often taking up additional indoor space and reducing adaptability to space-constrained environments such as small apartments. These problems seriously affect the safety and space utilization of functional sofas; therefore, this paper proposes a sofa and chair extension mechanism to solve these problems. Summary of the Invention

[0003] This invention addresses the problem of insufficient stability in the support structure of existing sofa chair extension devices when they are extended. It provides a sofa chair extension device in which the bottom support structure extends synchronously to both sides when the device is extended, significantly increasing the support span and the contact area with the ground. This makes the support points more evenly distributed, effectively dispersing the force on the seat, reducing the risk of tipping over due to center of gravity shift, fundamentally solving the safety hazards of existing devices, improving the user's sense of security during use, and effectively solving the problems mentioned in the background art.

[0004] The technical solution adopted by the present invention to solve the above problems is as follows: A sofa seat extension device includes a main frame, a movable drive plate at the lower end of the main frame, a leg support at the front end of the drive plate, a back panel on one side of the upper end of the main frame, and two sets of support legs at the lower end of the main frame. Each set of support legs has a support structure at its lower end, and each support structure includes two extension support rods. When the drive plate moves to one side, the leg support can move forward and then move upward after moving forward to a designated position. When the drive plate moves to one side, the back panel can be flipped downward and the two extension support rods can be moved outward.

[0005] The lower end of the main frame is also provided with a telescopic rod, and the drive plate is installed at the telescopic end of the telescopic rod.

[0006] Each of the extended support rods includes an upper support rod and a lower support rod, both of which are slidably connected to the inner wall of the support leg. Rollers are provided on one side of the upper support rod and the other side of the lower support rod.

[0007] The lower support rods are all fixed to the lower end of the drive plate. The support structure also includes a spur gear that is rotatably connected to the support leg. The upper and lower sides of the outer surface of the spur gear are meshed with a spur rack. The spur racks are all fixed to the inner walls of the corresponding upper and lower support rods. The lower inner wall of each set of support legs is provided with a base plate, and the lower end of the base plate is provided with an anti-slip pad.

[0008] The drive plate is hinged with a main swing arm that can swing up and down, and the drive plate is also hinged with a secondary swing arm that is parallel to the main swing arm and of the same length. The leg bracket is hinged to the other end of the main swing arm and the secondary swing arm.

[0009] A drive seat is slidably connected to one end face of the drive plate. The inner wall of the drive seat is provided with a main pin that can move up and down. The inner wall of the main swing rod is provided with a first keyway that cooperates with the main pin.

[0010] The lower end of the main frame is also provided with a guide plate, and the inner wall of the guide plate is provided with horizontal grooves and oblique grooves that cooperate with the main pin.

[0011] A U-shaped seat is slidably connected to the support leg. The inner wall of the U-shaped seat has a long keyway that matches the main pin. A support plate is fixed to the U-shaped seat, and a handrail is fixed to the upper end of the support plate.

[0012] The back plate is hinged to the inner wall of the main frame. A crank is coaxially fixed to the lower end of the back plate, and a secondary pin is fixed to one side of the support plate. A second keyway that mates with the secondary pin is opened on the inner wall of the crank.

[0013] A method of using a sofa seat extension device includes the following steps: S1. Control the drive plate to move to one side, and the drive plate simultaneously drives the leg bracket to move outward of the main frame; S2. When the leg bracket moves to the preset designated position, the drive plate continues to drive the leg bracket to move upward until the leg bracket is flush with the upper end of the main frame. S3. During the movement of the drive board, the back panel is simultaneously rotated downwards, so that the back panel is in an inclined state suitable for the user to lie down. S4, the drive plate synchronously moves the extension support rods in the two sets of support structures outward, so that the support structure unfolds to increase the support span and the contact area with the ground.

[0014] Compared with the prior art, the present invention has the following advantages: In use, when the drive plate moves to one side, it drives the leg support to extend to that side. After moving to the designated position, it can move upward again, aligning the leg support with the top of the main frame, allowing the user to lie down on the sofa seat. When the drive plate moves to one side, it also causes the back panel to flip downward, extending the entire device. This also allows the two extension support rods to move outward, extending the support structure to both sides, providing better support for the user and making the device more stable. The stability of this sofa seat extension device is significantly improved. When the device extends, the bottom support structure extends synchronously to both sides, significantly increasing the support span and the contact area with the ground, making the support points more evenly distributed and effectively dispersing the weight of the seat. The chair's load-bearing capacity is reduced, minimizing the risk of tipping over due to center of gravity shift. This fundamentally solves the safety hazards of existing devices, enhancing user safety. It boasts superior spatial adaptability; the support structure retracts synchronously with the device's closing motion, fitting snugly against the main sofa / seat structure without occupying additional storage space. This perfectly suits space-constrained environments such as small apartments and offices, enhancing the product's practicality. Operation is remarkably convenient; the support structure's extension and retraction are linked to the seat's extension and closure, automatically switching between support states without manual adjustment, simplifying the operation process. The simple and compact design does not compromise the sofa / seat's overall aesthetics or comfort, combining safety, practicality, and convenience. Attached Figure Description

[0015] Figure 1 This is a first axonometric view of a sofa seat extension device according to the present invention.

[0016] Figure 2 This is a second axonometric view of a sofa seat extension device according to the present invention.

[0017] Figure 3 This is a schematic diagram of the installation of the telescopic rod of a sofa seat extension device according to the present invention.

[0018] Figure 4 This is a schematic diagram of the installation of the guide plate of a sofa seat extension device according to the present invention.

[0019] Figure 5 This is a schematic diagram of the installation of the drive plate of a sofa seat extension device according to the present invention.

[0020] Figure 6 This is a schematic diagram of the installation of the extension support rod of a sofa seat extension device according to the present invention.

[0021] Figure 7 This is a schematic diagram of the installation of the main swing arm of a sofa seat extension device according to the present invention.

[0022] Figure 8This is a schematic diagram of the main pin installation of a sofa seat extension device according to the present invention.

[0023] Figure 9 This is a schematic diagram of the armrest installation of a sofa seat extension device according to the present invention.

[0024] Numbering in the diagram: 1-Main frame, 2-Support leg, 3-First support rod, 4-Telescopic rod, 5-Second support rod, 6-Drive plate, 7-Base plate, 8-Anti-slip mat, 9-Extension support rod, 10-Roller, 11-Rack and pinion, 12-Spur gear, 13-Main swing rod, 14-Secondary swing rod, 15-Leg bracket, 16-Drive seat, 17-Main pin, 18-First keyway, 19-Guide plate, 20-Horizontal groove, 21-Angled groove, 22-U-shaped seat, 23-Long keyway, 24-Panel, 25-Handrail, 26-Secondary pin, 27-Crank, 28-Secondary keyway, 29-Back plate. Detailed Implementation

[0025] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0026] like Figures 1-9 As shown, the present invention provides a sofa seat extension device, including a main frame 1. The lower end of the main frame 1 is provided with a movable drive plate 6, and the front end of the drive plate 6 is provided with a leg support 15. The upper side of the main frame 1 is provided with a back panel 29. The lower end of the main frame 1 is also provided with two sets of support legs 2. Each set of support legs 2 is provided with a support structure at its lower end. Each support structure includes two extension support rods 9. When the drive plate 6 moves to one side, the leg support 15 can move forward and then move upward after moving forward to a designated position. When the drive plate 6 moves to one side, the back panel 29 can be flipped downward and the two extension support rods 9 can be moved outward.

[0027] like Figures 1-4As shown, the main frame 1 is the supporting skeleton of the sofa chair. The main frame 1 is existing technology. Support legs 2 are fixed to both sides of the lower end of the main frame 1. Each set of support legs 2 consists of three legs, evenly distributed on both sides of the lower end of the main frame 1. A drive plate 6 can drive the leg support 15, back panel 29, and extension support rods 9 to move, thus controlling the extension, unfolding, or retraction of the support structure. The leg support 15 supports the user's lower limbs. In its normal state, the leg support 15 is located inside the lower end of the main frame 1, i.e., in a retracted state. When the drive plate 6 moves to one side, it drives the leg support 15 to move out to one side and then moves upwards after reaching a designated position, making the leg support 15 flush with the upper end of the main frame 1, allowing the user to lie down on the sofa chair. When the drive plate 6 moves to one side, it also causes the back panel 29 to flip downwards, at which point the entire device is in an extended state. It also causes the two extension support rods 9 to move outwards, i.e., the support structure unfolds to both sides, allowing the user to use the chair. This sofa chair extension device offers superior support, resulting in greater stability. Its stability is significantly enhanced; the bottom support structure extends synchronously to both sides when the device is extended, significantly increasing the support span and ground contact area. This makes the support points more evenly distributed, effectively dispersing the force on the chair and reducing the risk of tipping over due to center of gravity shift. This fundamentally solves the safety hazards of existing devices, improving user safety. It also boasts superior spatial adaptability; the support structure retracts synchronously with the device's closing motion, fitting snugly against the main structure of the sofa chair without occupying additional storage space. This perfectly suits small apartments, offices, and other space-constrained environments, enhancing the product's practicality. Furthermore, its ease of operation is outstanding. The extension and retraction of the support structure are linked to the chair's extension and closing motions, allowing for automatic switching of support states without manual adjustment. This simplifies the operation process. The compact and simple design does not compromise the overall aesthetics or comfort of the sofa chair, combining safety, practicality, and convenience.

[0028] The lower end of the main frame 1 is also provided with a telescopic rod 4, and the drive plate 6 is installed on the telescopic end of the telescopic rod 4.

[0029] like Figures 1-3 As shown, a first support rod 3 is fixedly connected to the inner side of the two support legs 2, and a telescopic rod 4 is fixedly connected to the first support rod 3. One or two drive plates 6 can be set. When two are set, the device operates more stably. A second support rod 5 is fixedly connected to the inner end face of the two drive plates 6, and the telescopic end of the telescopic rod 4 is fixedly connected to the second support rod 5. When the telescopic rod 4 extends or retracts, it can move the drive plate 6. The telescopic rod 4 can be an electric rod, a hydraulic rod, or a pneumatic rod. The telescopic rod 4 is existing technology and will not be described in detail.

[0030] Each of the extended support rods 9 includes an upper support rod and a lower support rod, both of which are slidably connected to the inner wall of the support leg 2. Rollers 10 are provided on one side of the upper support rod and the other side of the lower support rod.

[0031] like Figures 4-6 As shown, the upper and lower support rods can slide left and right on the inner wall of the support leg 2. The roller 10 is rotatably connected to one side of the corresponding upper and lower support rods. The roller 10 can contact the ground. When the upper and lower support rods move outward, the roller 10 can reduce its friction with the ground.

[0032] The lower support rods are all fixed to the lower end of the drive plate 6. The support structure also includes a spur gear 12 that is rotatably connected to the support leg 2. The upper and lower sides of the outer surface of the spur gear 12 are meshed with a spur rack 11. The spur rack 11 is fixed to the inner wall of the corresponding upper and lower support rods. The lower inner wall of each support leg 2 is provided with a base plate 7, and the lower end of the base plate 7 is provided with an anti-slip pad 8.

[0033] like Figures 5-6 As shown, the base plate 7 is fixed to the inner wall of the lower end of the support leg 2, and the lower support rod is slidably connected to the upper end of the base plate 7, which is equivalent to the lower support rod being slidably connected to the inner wall of the support leg 2. The base plate 7 strengthens the contact between the support leg 2 and the ground, and the anti-slip pad 8 prevents the device from sliding with the ground, making the device more stable in the designated position. The inner wall of the spur gear 12 is fixed with a rotating shaft, which is rotatably connected to the inner wall of the middle support leg 2. When the lower support rod moves, the upper support rod can move to the other side through the meshing of the spur rack 11 and the spur gear 12, that is, the support structure unfolds. When the drive plate 6 moves to one side, it can drive the lower support rod to one side and the upper support rod to the other side, thereby unfolding the support structure. Similarly, when the drive plate 6 is reset, the support structure can be folded up without occupying space.

[0034] The drive plate 6 is hinged with a main swing rod 13 that can swing up and down. The drive plate 6 is also hinged with a secondary swing rod 14 that is parallel to the main swing rod 13 and of the same length. The leg bracket 15 is hinged to the other end of the main swing rod 13 and the secondary swing rod 14.

[0035] like Figure 7 As shown, by setting the main swing rod 13 and the auxiliary swing rod 14 parallel and of equal length, the leg support 15 can always be kept in a horizontal state. That is, the drive plate 6, the main swing rod 13, the auxiliary swing rod 14, and the leg support 15 indirectly form a parallelogram mechanism. When the drive plate 6 moves forward or backward, it can drive the main swing rod 13, the auxiliary swing rod 14, and the leg support 15 to move forward or backward synchronously. When the main swing rod 13 flips up and down, under the limit of the auxiliary swing rod 14, it can drive the leg support 15 to move up or down, and the leg support 15 always maintains a horizontal state when moving up or down.

[0036] A drive seat 16 is slidably connected to one end face of the drive plate 6. The inner wall of the drive seat 16 is provided with a main pin 17 that can move up and down. The inner wall of the main swing rod 13 is provided with a first keyway 18 that cooperates with the main pin 17.

[0037] like Figure 7 As shown, the drive seat 16 can slide up and down on the inner wall of the drive plate 6, that is, the limiting main pin 17 can only move up and down at the front end of the drive plate 6. When the drive plate 6 moves to one side, it can drive the drive seat 16, the main pin 17, etc. to move to one side. When the main pin 17 moves up and down, it can drive the main rocker arm 13 to swing up and down through engagement with the first keyway 18.

[0038] The lower end of the main frame 1 is also provided with a guide plate 19, and the inner wall of the guide plate 19 is provided with a horizontal groove 20 and an inclined groove 21 that cooperate with the main pin 17.

[0039] like Figure 4 and Figure 7 As shown, the guide plate 19 is fixed to the inner wall of the upper end of the two corresponding support legs 2. The upper end of the drive plate 6 is slidably connected to one side end face of the guide plate 19, limiting the drive plate 6 to move stably to one side. Through the engagement of the main pin 17 with the transverse groove 20 and the inclined groove 21, the main swing rod 13 can be controlled to swing upward when it moves to the designated position. That is, when the drive plate 6, the main pin 17, the leg bracket 15, etc. move to one side, the main pin 17 will first engage with the transverse groove 20, that is, the corresponding main pin 17 will not move upward or downward, but will maintain horizontal forward movement, that is, the corresponding The leg bracket 15 will move forward from its lowest position. When the drive plate 6, the leg bracket 15, etc. move forward to make the main pin 17 enter the inner wall of the inclined groove 21, as the drive plate 6, the main pin 17, etc. continue to move forward, the main pin 17 can move forward and upward at the same time, and the corresponding leg bracket 15 can move forward and upward at the same time, so that the leg bracket 15 moves to the front end of the main frame 1, and the device can be unfolded and used. Similarly, when the drive plate 6 moves backward to reset, the corresponding leg bracket 15 can move backward and downward to reset to the initial position.

[0040] A U-shaped seat 22 is slidably connected to the support leg 2. The inner wall of the U-shaped seat 22 is provided with a long keyway 23 that cooperates with the main pin 17. A support plate 24 is fixedly connected to the U-shaped seat 22, and a handrail 25 is fixedly connected to the upper end of the support plate 24.

[0041] like Figures 8-9As shown, the U-shaped seat 22 and the support plate 24 are slidably connected to the support leg 2, limiting the movement of the U-shaped seat 22, the support plate 24, and the armrest 25 to only up and down. Through the engagement of the long keyway 23 and the main pin 17, when the main pin 17 moves back and forth, it can move back and forth along the inner wall of the long keyway 23, meaning the corresponding U-shaped seat 22 will not move up and down. When the main pin 17 moves up and down, through engagement with the long keyway 23, it can drive the U-shaped seat 22, the support plate 24, and the armrest 25 to move up and down synchronously, thereby allowing the armrest 25 to move upwards for user use. This prevents the user from slipping off to one side when lying on the sofa seat, further improving safety. When the main pin 17 moves downwards to reset, it allows the armrest 25 to move downwards and retract.

[0042] The back plate 29 is hinged to the inner wall of the main frame 1. A crank 27 is coaxially fixed to the lower end of the back plate 29. A secondary pin 26 is fixed to one side of the support plate 24. A second keyway 28 that cooperates with the secondary pin 26 is opened on the inner wall of the crank 27.

[0043] like Figures 8-9 As shown, a pivot is fixed to the inner wall of the back plate 29 and the crank 27. The pivot is rotatably connected to the inner wall of the main frame 1. When the crank 27 swings, it can drive the back plate 29 to swing up and down, that is, control the back plate 29 to swing down to unfold or swing up to close. When the support plate 24 moves up or down, it can drive the auxiliary pin 26 to move up or down. When the auxiliary pin 26 moves up, it can drive the crank 27 to flip up and the back plate 29 to flip down to unfold through engagement with the second keyway 28. Similarly, when the auxiliary pin 26 moves down, it can drive the back plate 29 to flip up to close. That is, when the drive plate 6 moves forward, it can drive the leg support 15 to move forward and also drive the leg support 15 to move up to a designated position, that is, at the same height as the main frame 1. At the same time, the extension support rod 9 can move outward to unfold to support the device and can also drive the armrest 25 to move upward to protect the user. The back plate 29 flips down to unfold, allowing the user to lie on the back plate 29.

[0044] A method of using a sofa seat extension device includes the following steps: S1. Control the drive plate 6 to move to one side, and the drive plate 6 simultaneously drives the leg bracket 15 to move outward from the main frame 1. S2. When the leg support 15 moves to the preset designated position, the drive plate 6 continues to drive the leg support 15 to move upward until the leg support 15 is flush with the upper end of the main frame 1. S3. During the movement of the drive board 6, the back panel 29 is simultaneously rotated downwards, so that the back panel 29 is in an inclined state that is suitable for the user to lie down. S4 and drive plate 6 move the extension support rods 9 in the two sets of support structures outward in a synchronous linkage, so that the support structure unfolds to increase the support span and the contact area with the ground; thus completing the linkage operation of the device extension and the support structure unfolding.

[0045] In use, when the drive plate 6 moves to one side, it drives the leg support 15 to extend to one side. After moving to a designated position, it can move upwards again, making the leg support 15 flush with the upper end of the main frame 1, allowing the user to lie on the sofa seat. When the drive plate 6 moves to one side, it also causes the back panel 29 to flip downwards, putting the entire device in an extended state. Furthermore, it allows the two extension support rods 9 to move outwards, extending the support structure to both sides, providing better support for the user and making the device more stable. This sofa seat extension device significantly improves support stability. When the device extends, the bottom support structure extends synchronously to both sides, significantly increasing the support span and the contact area with the ground, resulting in a more even distribution of support points. This design effectively distributes the force on the seat, reducing the risk of tipping over due to a shift in the center of gravity. It fundamentally solves the safety hazards of existing devices, enhancing user safety. It also boasts superior spatial adaptability; the support structure retracts synchronously with the device's closing motion, fitting snugly against the main structure of the sofa seat without taking up additional storage space. This makes it perfectly suited for space-constrained environments such as small apartments and offices, enhancing the product's practicality. Furthermore, its ease of operation is outstanding. The extension and retraction of the support structure are linked to the seat's extension and closure, allowing for automatic switching of support states without manual adjustment. This simplifies the operation process. The compact and simple structural design does not compromise the overall aesthetics or comfort of the sofa seat, combining safety, practicality, and convenience.

Claims

1. A sofa seat extension device, comprising a main frame (1), characterized in that: The lower end of the main frame (1) is provided with a movable drive plate (6), the front end of the drive plate (6) is provided with a leg bracket (15), the upper end of the main frame (1) is provided with a back plate (29), and the lower end of the main frame (1) is also provided with two sets of support legs (2). Each set of support legs (2) is provided with a support structure at its lower end. The support structure includes two extension support rods (9). When the drive plate (6) moves to one side, the leg bracket (15) can move forward and then move upward after moving forward to a designated position. When the drive plate (6) moves to one side, the back plate (29) can be flipped downward and the two extension support rods (9) can be moved outward.

2. The sofa seat extension device as described in claim 1, characterized in that: The lower end of the main frame (1) is also provided with a telescopic rod (4), and the drive plate (6) is installed on the telescopic end of the telescopic rod (4).

3. The sofa seat extension device as described in claim 1, characterized in that: Each of the extended support rods (9) includes an upper support rod and a lower support rod. The upper support rod and the lower support rod are slidably connected to the inner wall of the support leg (2). Rollers (10) are provided on one side of the upper support rod and the other side of the lower support rod.

4. The sofa seat extension device as described in claim 3, characterized in that: The lower support rods are all fixed to the lower end of the drive plate (6). The support structure also includes a spur gear (12) that is rotatably connected to the support leg (2). The upper and lower sides of the outer surface of the spur gear (12) are meshed with a rack (11). The rack (11) is fixed to the inner wall of the corresponding upper support rod and lower support rod. The lower inner wall of each support leg (2) is provided with a base plate (7). The lower end of the base plate (7) is provided with an anti-slip pad (8).

5. The sofa seat extension device as described in claim 1, characterized in that: The drive plate (6) is hinged with a main swing rod (13) that can swing up and down. The drive plate (6) is also hinged with a secondary swing rod (14) that is parallel to the main swing rod (13) and of the same length. The leg bracket (15) is hinged to the other end of the main swing rod (13) and the secondary swing rod (14).

6. The sofa seat extension device as described in claim 5, characterized in that: A drive seat (16) is slidably connected to one end face of the drive plate (6). The inner wall of the drive seat (16) is provided with a main pin (17) that can move up and down. The inner wall of the main swing rod (13) is provided with a first keyway (18) that cooperates with the main pin (17).

7. A sofa seat extension device as described in claim 6, characterized in that: The lower end of the main frame (1) is also provided with a guide plate (19), and the inner wall of the guide plate (19) is provided with a horizontal groove (20) and an inclined groove (21) that cooperate with the main pin (17).

8. A sofa seat extension device as described in claim 6, characterized in that: The support leg (2) is slidably connected to a U-shaped seat (22). The inner wall of the U-shaped seat (22) is provided with a long keyway (23) that cooperates with the main pin (17). A support plate (24) is fixedly connected to the U-shaped seat (22), and a handrail (25) is fixedly connected to the upper end of the support plate (24).

9. A sofa seat extension device as described in claim 8, characterized in that: The back plate (29) is hinged to the inner wall of the main frame (1). A crank (27) is coaxially fixed to the lower end of the back plate (29). A secondary pin (26) is fixed to one side of the support plate (24). A second keyway (28) that cooperates with the secondary pin (26) is opened on the inner wall of the crank (27).

10. The method of using the sofa seat extension device as described in claim 1, characterized in that: Includes the following steps: S1. Control the drive plate (6) to move to one side, and the drive plate (6) simultaneously drives the leg bracket (15) to move outward to the outside of the main frame (1); S2. When the leg bracket (15) moves to the preset designated position, the drive plate (6) continues to drive the leg bracket (15) to move upward until the leg bracket (15) is flush with the upper end of the main frame (1). S3. During the movement of the drive plate (6), the back plate (29) is simultaneously rotated downwards, so that the back plate (29) is in an inclined state that is suitable for the user to lie down. S4, the drive plate (6) synchronously moves the extension support rods (9) in the two sets of support structures outward, so that the support structure unfolds to increase the support span and the contact area with the ground.

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