Sofa bed iron frame mechanism

Abstract

This invention relates to a sofa bed frame mechanism, comprising side panels, a back panel, a first frame, and a second frame connector. The first and second frames are hinged to each other via the hinge connector. The mechanism also includes a stabilizing rod assembly and an elastic connecting rod assembly. The first and second frames are hinged via the stabilizing rod assembly, and the second frame is connected to the side panel via the elastic connecting rod assembly. A back panel is located on the rear side of the second frame. The first and second frames can be stacked and folded or unfolded via the stabilizing rod assembly, and the elastic connecting rod assembly allows the second frame to switch between folded and unfolded states using inertia. This frame mechanism eliminates interference when folded and makes posture switching easier. Furthermore, it reduces packaging space during transport and shipping, saving costs.

Description

Technical Field

[0001] This invention relates to a sofa bed, specifically a sofa bed frame mechanism. Background Technology

[0002] In modern living environments, storage and comfort are emphasized. In densely populated cities and countries, storage and organization are no longer limited to everyday items. Furthermore, because living spaces are often limited, people tend to arrange their living environment more efficiently within these constraints. The bed is an essential household item. However, beds typically occupy a significant amount of space, often taking up considerable living room area.

[0003] To improve the efficient use of space, people have modified the way beds are used to gain more living space. This led to the development of the sofa bed. By transforming between a sofa and a bed, the sofa bed provides more living space, significantly improving space utilization and allowing people to enjoy a more comfortable living environment within limited spaces.

[0004] The existing sofa bed frame mechanism may encounter the following problems during use:

[0005] 1. The power assist spring in the original bed frame runs through the entire side panel. This increases frictional wear between the spring and the side panel and the upholstery during actual use. Furthermore, because it runs through the entire side panel, it increases the risk of injury, such as a hand being squeezed and injured by the power assist system if it reaches into the side panel.

[0006] 2. When the backrest is set to the unfolded horizontal position and is subjected to a large load, the backrest and the power assist system (spring and linkage) will rub against each other, which may damage or wear out the backrest and the power assist system (spring and linkage). Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of the prior art and provide a sofa bed frame mechanism that enables the conversion between a sofa and a bed by extending and folding two interconnected sofa bed frames and a rotatable backrest.

[0008] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0009] A sofa bed frame mechanism includes side panels, a back panel, a first frame, a second frame, a front support leg, a middle support leg, and a connector. The first and second frames are hinged to the connector, the first frame is hinged to the front support leg, and the middle support leg is fixed to the connector. The mechanism also includes a stabilizing rod assembly and an elastic connecting rod assembly. The first and second frames are hinged together via the stabilizing rod assembly, and the second frame is connected to the side panels via the elastic connecting rod assembly. A back panel is provided on the rear side of the second frame. The first and second frames can be stacked and folded or unfolded via the stabilizing rod assembly, and the elastic connecting rod assembly switches the second frame between the folded and unfolded states by applying tension.

[0010] The sofa bed frame mechanism described above includes a stabilizing rod assembly that is hinged to a first connecting rod and a second connecting rod. One end of the first connecting rod is hinged to the front support leg, and then to the first frame via the front support leg. The other end of the first connecting rod is hinged to one end of the second connecting rod and an extended iron plate on the connector. The other end of the second connecting rod is hinged to the mounting plate, which is hinged to the second frame and fixed to the side plate. In this way, the linkage mechanism forms a stable structure and also serves as a guide and limiter when relative rotation occurs between the first and second frames.

[0011] The sofa bed frame mechanism includes an elastic linkage assembly comprising an assist rod and an assist spring. One end of the assist spring is connected to the second frame, and the other end is connected to the end of the assist rod, while the other end of the assist rod is fixed to the side plate. Thus, when the second frame rotates, the elasticity of the assist spring provides additional force for the second frame to switch between a folded state and a flat state.

[0012] The sofa bed frame mechanism includes a third link, a spring assist, a spring assist fixing plate, and a hinge rod assembly. One end of the third link is connected to the second frame, and the other end is connected to one end of the hinge rod assembly. The other end of the hinge rod assembly is connected to the spring assist, which is connected to the side plate via the spring assist fixing plate. The spring assist fixing plate is located on the inner side of the side plate and below the second frame. The hinge rod assembly is also located on the inner side of the side plate. Thus, when the second frame rotates, the elasticity of the spring assist is transmitted to the second frame through the hinge rod assembly and the third link, providing additional force for the second frame to switch between a folded and unfolded state.

[0013] The sofa bed frame mechanism is described in which the first frame, the connector, and the second frame are hinged in sequence, so that the first frame and the second frame do not interfere with each other when stacked and folded. The connector is made of channel steel, which has a limiting function to prevent the first frame and the second frame from continuing to flip after they are flattened.

[0014] The aforementioned sofa bed frame mechanism also includes a backrest frame and a flipping mechanism. The flipping mechanism is connected to the backrest frame, side panel, or back panel, thereby allowing the backrest frame to flip and switch between an overlapping state with the second frame or an independent folded state.

[0015] The sofa bed frame mechanism includes a flipping mechanism comprising a third connecting rod, a locking spring, a support plate, a first support rod, a second support rod, and a back panel connector. The support plate is fixed to the side plate. One end of the third connecting rod is hinged to the support plate, and the other end of the third connecting rod is sequentially hinged to the back panel connector, the second support rod, and the first support rod. One end of the first support rod is hinged to the support plate. Thus, a backrest frame is mounted on the back panel connector, and a locking spring is positioned between the first and second support rods. The backrest frame flips around the support plate via the first and second support rods and the back panel connector. During this process, the locking spring provides tension to the backrest frame during the flipping motion.

[0016] The sofa bed frame mechanism includes a hinge, a hinge support plate, and a flip-up backrest. The flip-up backrest has a notch on its lower side that can fit together with the hinge support plate so that the hinge mounting surfaces are on the same horizontal plane. The flip-up backrest rotates around the hinge until it is horizontal and overlaps with the second frame.

[0017] The sofa bed frame mechanism has a limiting structure on the inner side of the support plate. The backrest frame can be flipped around the support plate by the first support rod, the second support rod and the back plate connector. When the backrest frame is flipped to the horizontal position, it overlaps with the second frame and the support plate respectively.

[0018] The sofa bed frame mechanism has a limiting block on the support plate that limits the third connecting rod in the folded state. At the same time, the limiting block limits the first support rod when the backrest frame flips upward from the horizontal position.

[0019] The sofa bed frame mechanism is provided with a limiting plate at the end of the first support rod or the second support rod, so that when the first support rod and the second support rod rotate relative to each other to a straight position, the limiting plate will limit the two and restrict further rotation.

[0020] The sofa bed frame mechanism described herein includes the spring fixing plate and the mounting plate as a single component.

[0021] The sofa bed frame mechanism has a limiting support groove on the support plate, which is used to limit and support the backrest frame.

[0022] The sofa bed frame mechanism proposed in this invention has the following advantages:

[0023] 1. The first frame and the second frame are connected by a stabilizer bar assembly, especially the connecting rod in the stabilizer bar assembly, so that when the first frame and the second frame are stacked together, there will be no friction or interference between them.

[0024] 2. The elastic linkage assembly assists the flipping motion of the second frame, making the attitude switching process of the first and second frames easier.

[0025] 3. The second frame and the backrest frame are made independent of each other, thereby reducing the overall size of the sofa bed frame and increasing its flexibility of use. For example, by using a combination of a flipping mechanism and a flexible linkage mechanism, the posture switching process between the second linkage mechanism and the backrest frame does not interfere with each other, thus facilitating operation for different users.

[0026] 4. The backrest frame, side panels, back panel, and first frame are designed to be relatively independent from the second frame. During transportation and packing, the backrest frame can be placed directly on the first and second frames in a folded state, thereby reducing packing space, facilitating packing and transportation, and saving costs.

[0027] 5. The backrest frame's flipping mechanism adopts a multi-turn point structure, which makes the backrest frame easy to flip and reduces the gap between it and other upholstered components such as the second frame, side panels, and back panel, thus improving user comfort.

[0028] 6. The flipping mechanism of the backrest frame, through the cooperation of the locking spring 9 and the limiting plate 18, enables the entire flipping mechanism to have a self-locking function in the open state. Specifically, it ensures that the first support rod and the second support rod, as well as the third connecting rod and the back panel connector, are in a straight line, thereby preventing accidental operation of the flipping mechanism. For example, it prevents accidental flipping of the backrest frame when a certain part is stepped on, especially the backrest part facing the headrest after the soft backrest is upholstered, making it more comfortable and safer for the user when lying down.

[0029] 7. The first frame 1 and the second frame 2 are suitable for various soft upholstery methods such as webbing, wooden strips, serpentine springs, bed sheets, etc. Attached Figure Description

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0031] Figure 1 This is a schematic diagram of the unfolded state of Example 1.

[0032] Figure 2 This is a schematic diagram of the unfolding process of the first and second frames in Example 1. Figure 1 .

[0033] Figure 3 This is a schematic diagram of the unfolding process of the first and second frames in Example 1. Figure 2 .

[0034] Figure 4 This is a schematic diagram of the unfolding process of the first and second frames in Example 1. Figure 3 .

[0035] Figure 5 This is a schematic diagram of the unfolding process of the first and second frames in Example 1. Figure 4 .

[0036] Figure 6 This is a schematic diagram of the unfolding process of the first and second frames in Example 1. Figure 5 .

[0037] Figure 7 This is a schematic diagram of the unfolding process of the first and second frames in Example 1. Figure 6 .

[0038] Figure 8 This is a schematic diagram of the unfolding process of the first and second frames in Example 1. Figure 7 .

[0039] Figure 9 This is a schematic diagram of the connection structure of the backrest frame and the flipping mechanism shown in the embodiment.

[0040] Figure 10 This is a schematic diagram of the operation process of the backrest frame and the flipping mechanism shown in the embodiment. Figure 1 .

[0041] Figure 11 This is a schematic diagram of the operation process of the backrest frame and the flipping mechanism shown in the embodiment. Figure 2 .

[0042] Figure 12 This is a schematic diagram of the folded state of the first and second frames as shown in the embodiment.

[0043] Figure 13 This is a schematic diagram of the unfolded state of Example 2. Detailed Implementation

[0044] Example 1

[0045] like Figure 1 As shown, a sofa bed frame mechanism includes a side panel 16, a back panel 21, a first frame 1, a second frame 2, a front support leg 13, a middle support leg 14, and a connector 17. The first frame 1 and the second frame 2 are respectively hinged to the connector 17, the first frame 1 is hinged to the front support leg 13, and the middle support leg 14 is fixed to the connector 17. The mechanism also includes a stabilizer assembly and an elastic linkage assembly. The first frame 1 and the second frame 2 are hinged together by the stabilizer assembly, and the second frame 2 is connected to the side panel 16 by the elastic linkage assembly. The back panel 21 is located on the rear side of the second frame 2. Figures 2-8 As shown, the first frame 1 and the second frame 2 are stacked and folded or flattened through a stabilizer bar assembly, and the elastic link assembly switches the second frame 2 between the folded and flattened states through tension.

[0046] In the aforementioned sofa bed frame mechanism, the stabilizing rod assembly includes a first connecting rod 4, a second connecting rod 5, a connector 17, and a mounting plate 15. The first frame 1 and the second frame 2 are hinged together via the connector 17. One end of the first connecting rod 4 is hinged to the front support leg 13, and then hinged to the first frame 1 via the front support leg 13. The other end of the first connecting rod 4 is hinged together with one end of the second connecting rod 5 and the extended iron plate on the connector 17. The other end of the second connecting rod 5 is hinged to the mounting plate 15. The mounting plate 15 is hinged to the second frame 2 and fixed to the side plate 16. Thus, the linkage mechanism forms a stable structure, which plays a guiding and limiting role when the first frame 1 and the second frame 2 are stacked, folded, or unfolded.

[0047] In the aforementioned sofa bed frame mechanism, the elastic linkage assembly includes an assist rod 7 and an assist spring 8; one end of the assist spring 8 is connected to the second frame 2, and the other end is connected to the end of the assist rod 7, which is fixed to the side plate 16; thus, when the second frame 2 rotates, the elastic force of the assist spring 8 provides additional action force for the second frame 2 to switch between the stacked and folded state and the flat state.

[0048] The above-mentioned sofa bed frame mechanism also includes a backrest frame 3 and a flipping mechanism. The flipping mechanism is connected to the backrest frame 3, the side panel 16 or the back panel 21 respectively, so that the backrest frame 3 can be flipped and switched between the state of overlapping with the second frame 2 or the state of independent folding.

[0049] like Figure 1 , Figures 9-11 As shown, in the above-mentioned sofa bed frame mechanism, the flipping mechanism includes a third connecting rod 6, a locking spring 9, a support plate 10, a first support rod 11, a second support rod 12, and a back panel connector 20. The support plate 10 is fixed on the side plate 16. One end of the third connecting rod 6 is hinged to the support plate 10, and the other end of the third connecting rod 6 is sequentially hinged to the back panel connector 20, the second support rod 12, and the first support rod 11. One end of the first support rod 11 is hinged to the support plate 10. Thus, a backrest frame 3 is set on the back panel connector 20, and a locking spring 9 is set between the first support rod 11 and the second support rod 12. The backrest frame 3 can be flipped around the support plate 10 through the first support rod 11, the second support rod 12, and the back panel connector 20. During this process, the locking spring 9 provides tension to the backrest frame 3 during the flipping process.

[0050] In the above-mentioned flipping mechanism, the inner side of the support plate 10 has a limiting structure. The backrest frame 3 is flipped around the support plate 10 by the first support rod 11, the second support rod 12 and the back plate connector 20. When the backrest frame 3 is flipped to the horizontal position, it overlaps with the second frame 2 and the support plate 10 respectively.

[0051] In the aforementioned flipping mechanism, the support plate 10 is provided with a limiting block 30 that limits the third connecting rod 6 in the folded state. At the same time, the limiting block 30 limits the first support rod 11 when the backrest frame 3 flips upward from the horizontal position.

[0052] In the above-mentioned flipping mechanism, a limiting plate 18 is provided at the end of the first support rod 11 or the second support rod 12, so that when the first support rod 11 and the second support rod 12 rotate relative to each other to a straight position, the limiting plate 18 limits both of them and restricts further rotation.

[0053] In the aforementioned flipping mechanism, the support plate 10 is provided with a limiting support groove 19, which is used to limit and support the backrest frame 3.

[0054] like Figure 12 As shown in Embodiment 1, the sofa bed frame mechanism connects the first frame and the second frame via connecting rods, so that the first frame and the second frame will not rub against or interfere with each other when they are folded up. Furthermore, the backrest frame, side panels, back panel, and the first frame and the second frame are designed to be relatively independent. During transportation and packaging, the backrest frame can be placed directly on the folded first frame and the second frame, thereby reducing packaging space, facilitating packaging and transportation, and saving costs.

[0055] Furthermore, the sofa bed frame mechanism shown in Embodiment 1 uses an elastic linkage assembly to assist the flipping action of the second frame 2, thereby making the posture switching process of the first frame and the second frame easier. At the same time, through the paired use of the flipping mechanism and the elastic linkage mechanism, the posture switching process between the second linkage mechanism and the backrest frame does not interfere with each other, thus facilitating operation for different users.

[0056] Furthermore, in the sofa bed frame mechanism shown in Embodiment 1, the backrest frame's flipping mechanism, through the cooperation of the locking spring 9 and the limiting plate 18, enables the entire flipping mechanism to have a self-locking function in the open state. Specifically, the first support rod and the second support rod, as well as the third connecting rod and the back panel connector, are all in a straight line, thereby preventing accidental movement of the flipping mechanism. For example, it prevents accidental flipping when a part of the backrest frame is stepped on, especially the backrest part facing the headrest after being upholstered, making it more comfortable and safer for the user when lying down.

[0057] However, in practice, it was found that the elastic link assembly in Embodiment 1 had problems such as poor force distribution, easy deformation of the spring, and potential interference with the side plates and frame. Therefore, based on Embodiment 1, the elastic link assembly was improved to form Embodiment 2.

[0058] Example 2

[0059] like Figure 13 As shown, a sofa bed frame mechanism includes a side panel 16, a back panel 21, a first frame 1, a second frame 2, a front support leg 13, a middle support leg 14, and a connector 17. The first frame 1 and the second frame 2 are respectively hinged to the connector 17, the first frame 1 is hinged to the front support leg 13, and the middle support leg 14 is fixed to the connector 17. The mechanism also includes a stabilizer assembly and an elastic linkage assembly. The first frame 1 and the second frame 2 are hinged together by the stabilizer assembly, and the second frame 2 is connected to the side panel 16 by the elastic linkage assembly. The back panel 21 is provided on the rear side of the second frame 2. The first frame 1 and the second frame 2 can be stacked and folded or unfolded by the stabilizer assembly, and the elastic linkage assembly allows the second frame 2 to switch between the folded and unfolded states by inertia.

[0060] In the aforementioned sofa bed frame mechanism, the stabilizing rod assembly includes a first connecting rod 4, a second connecting rod 5, a connector 17, and a mounting plate 15. The first frame 1 and the second frame 2 are hinged together via the connector 17. One end of the first connecting rod 4 is hinged to the front support leg 13, and then to the first frame 1 via the front support leg 3. The other end of the first connecting rod 4 is hinged together with one end of the second connecting rod 5 and the extended iron plate on the connector 17. The other end of the second connecting rod 5 is hinged to the mounting plate 15. The mounting plate 15 is hinged to the second frame 2 and fixed to the side plate 16. In this way, the linkage mechanism forms a stable structure, which plays a guiding and limiting role when the first frame 1 and the second frame 2 are stacked, folded, or unfolded.

[0061] In the aforementioned sofa bed frame mechanism, the elastic linkage assembly includes a third link 23, a booster spring 8, a booster spring fixing plate 25, and a hinge rod assembly 26. One end of the third link 23 is connected to the second frame 2, and the other end of the third link 23 is connected to one end of the hinge rod assembly 26. The other end of the hinge rod assembly 26 is connected to the booster spring 8, and the booster spring 8 is connected to the side plate 16 via the booster spring fixing plate 25. The booster spring fixing plate 25 is located on the inner side of the side plate 16 and below the second frame 2. Meanwhile, the hinge rod assembly 26 is located on the inner side of the side plate 16. Thus, when the second frame 2 rotates, the elasticity of the booster spring 8 is transmitted to the second frame through the hinge rod assembly 26 and the third link 23, providing additional force for the second frame 2 to switch between the folded and unfolded states.

[0062] In the aforementioned sofa bed frame mechanism, the assist spring fixing plate 25 and the mounting plate 15 are the same component.

[0063] The above-mentioned sofa bed frame mechanism also includes a backrest frame 3 and a flipping mechanism. The flipping mechanism is connected to the backrest frame 3, the side panel 16 or the back panel 21 respectively, so that the backrest frame 3 can be flipped and switched between the state of overlapping with the second frame 2 or the state of independent folding.

[0064] In the aforementioned sofa bed frame mechanism, the flipping mechanism includes a third connecting rod 6, a locking spring 9, a support plate 10, a first support rod 11, a second support rod 12, and a back panel connector 20. The support plate 10 is fixed to the side plate 16. One end of the third connecting rod 6 is hinged to the support plate 10, and the other end of the third connecting rod 6 is sequentially hinged to the back panel connector 20, the second support rod 12, and the first support rod 11. One end of the first support rod 11 is hinged to the support plate 10. Thus, a backrest frame 3 is set on the back panel connector 20, and a locking spring 9 is set between the first support rod 11 and the second support rod 12. The backrest frame 3 can then be flipped around the support plate 10 through the first support rod 11, the second support rod 12, and the back panel connector 20. During this process, the locking spring 9 provides tension to the backrest frame 3 during the flipping process.

[0065] In the above-mentioned flipping mechanism, the inner side of the support plate 10 has a limiting structure. The backrest frame 3 is flipped around the support plate 10 by the first support rod 11, the second support rod 12 and the back plate connector 20. When the backrest frame 3 is flipped to the horizontal position, it overlaps with the second frame 2 and the support plate 10 respectively.

[0066] A flip-up backrest is a modified form of the backrest frame, specifically referring to backrest frames developed after upholstery.

[0067] In the aforementioned flipping mechanism, the support plate 10 is provided with a limiting block 30 that limits the third connecting rod 6 in the folded state. At the same time, the limiting block 30 limits the first support rod 11 when the backrest frame 3 flips upward from the horizontal position.

[0068] In the above-mentioned flipping mechanism, a limiting plate 18 is provided at the end of the first support rod 11 or the second support rod 12, so that when the first support rod 11 and the second support rod 12 rotate relative to each other to a straight position, the limiting plate 18 limits both of them and restricts further rotation.

[0069] In the aforementioned flipping mechanism, the support plate 10 is provided with a limiting support groove 19, which is used to limit and support the backrest frame 3.

[0070] The above-described embodiment two is a partial improvement on embodiment one. Specifically, the elastic link assembly is replaced by several rods instead of the original single assist rod, thereby making the rods more flexible, improving the stress state of the elastic link assembly, and avoiding interference with surrounding components.

[0071] For the purposes of saving space or reducing production costs, a new installation method can be adopted between the backrest frame 3 and the back panel 21. Specifically, the flipping mechanism includes a hinge 22, a hinge support plate 28, and a flipping backrest 29. The flipping backrest 29 has a notch on its lower side, which can fit together with the hinge support plate 28 so that the surface of the hinge 22 is on the same horizontal plane. The flipping backrest 29 rotates around the hinge 22 until it is horizontal and overlaps with the second frame 2.

[0072] With respect to the above embodiments and their modifications, this application is not limited to the iron frame of the sofa bed, but also includes the state of the sofa bed iron frame after being connected by the upholstered panel, especially the end and side of the back panel being connected to the upholstered panel respectively.

Claims

1. A sofa bed frame mechanism, comprising a side panel (16), a back panel (21), a first frame (1), a second frame (2), a front support leg (13), a middle support leg (14), and a connector (17); the first frame (1) and the second frame (2) are respectively hinged to the connector (17), the first frame (1) is hinged to the front support leg (13), the middle support leg (14) is fixed to the connector (17), and further comprising a stabilizing rod assembly and an elastic connecting rod assembly; the first frame (1) and the second frame (2) are hinged together by the stabilizing rod assembly, the second frame (2) is connected to the side panel (16) by the elastic connecting rod assembly, and a back panel (21) is provided on the rear side of the second frame (2); the first frame (1) and the second frame (2) are stacked and folded or unfolded by the stabilizing rod assembly, and the elastic connecting rod assembly switches the second frame (2) between the folded and unfolded states by tension; characterized in that: The stabilizer bar assembly includes a first link (4), a second link (5), a connector (17), and a mounting plate (15); the first frame (1) and the second frame (2) are hinged together by the connector (17), one end of the first link (4) is hinged to the front support leg (13), and then hinged to the first frame (1) by the front support leg (13), the other end of the first link (4) is hinged together with one end of the second link (5) and the extended iron plate on the connector (17), the other end of the second link (5) is hinged to the mounting plate (15), the mounting plate (15) is hinged to the second frame (2), and the mounting plate (15) is fixed on the side plate (16); Thus, the linkage mechanism forms a stable structure and also plays a guiding and limiting role when relative rotation occurs between the first frame (1) and the second frame (2); the elastic linkage assembly includes an assist rod (7) and an assist spring (8); one end of the assist spring (8) is connected to the second frame (2) and the other end is connected to the end of the assist rod (7), and the assist rod (7) is fixed on the side plate (16); thus, when the second frame (2) rotates, the elasticity of the assist spring (8) provides additional force for the second frame (2) to switch between the folded state and the flat state.

2. The sofa bed frame mechanism according to claim 1, characterized in that: The elastic linkage assembly includes a third link (23), a booster spring (8), a booster spring fixing plate (25), and a hinge rod assembly (26). One end of the third link (23) is connected to the second frame (2), and the other end of the third link (23) is connected to one end of the hinge rod assembly (26). The other end of the hinge rod assembly (26) is connected to the booster spring (8), and the booster spring (8) is connected to the side plate (16) through the booster spring fixing plate (25). The booster spring fixing plate (25) is located inside the side plate (16) and below the second frame (2). Meanwhile, the hinge rod assembly (26) is located inside the side plate (16). Thus, when the second frame (2) rotates, the elasticity of the booster spring (8) is transmitted to the second frame through the hinge rod assembly (26) and the third link (23), providing additional force for the second frame (2) to switch between the folded state and the flat state.

3. The sofa bed frame mechanism according to claim 1, characterized in that: The first frame (1), the connector (17), and the second frame (2) are hinged in sequence, so that the first frame (1) and the second frame (2) do not interfere with each other when they are stacked and folded. The connector (17) is made of channel steel, so it has a limiting function to prevent the first frame (1) and the second frame (2) from continuing to flip after they are flat.

4. The sofa bed frame mechanism according to any one of claims 1 to 2, characterized in that: It also includes a backrest frame (3) and a flipping mechanism, which is connected to the backrest frame (3), side panel (16) or back panel (21) respectively, so that the backrest frame (3) can be flipped through the flipping mechanism and switched between a state of overlapping with the second frame (2) or an independent folding state.

5. The sofa bed frame mechanism according to claim 4, characterized in that: it can be flipped. The mechanism includes a hinged third connecting rod (6), a locking spring (9), a support plate (10), a first support rod (11), a second support rod (12), and a back panel connector (20). The support plate (10) is fixed on the side plate (16). One end of the third connecting rod (6) is hinged to the support plate (10), and the other end of the third connecting rod (6) is hinged to the back panel connector (20), the second support rod (12), and the first support rod (11) in sequence. One end of the first support rod (11) is hinged to the support plate (10). Thus, a backrest frame (3) is set on the back panel connector (20), and a locking spring (9) is set between the first support rod (11) and the second support rod (12). The backrest frame (3) is made to rotate around the support plate (10) through the first support rod (11), the second support rod (12), and the back panel connector (20). During this process, the locking spring (9) provides tension to the backrest frame (3) during rotation.

6. The sofa bed frame mechanism according to claim 4, characterized in that: it can be flipped. The mechanism includes a hinge (22), a hinge support plate (28), and a flip-up backrest (29). The flip-up backrest (29) has a notch on its lower side and can fit together with the hinge support plate (28) so that the mounting surface of the hinge (22) is on the same horizontal plane. The flip-up backrest (29) rotates around the hinge (22) until it is horizontal and overlaps with the second frame (2).

7. The sofa bed frame mechanism according to claim 5, characterized in that: The inner side of the support plate (10) has a limiting structure. The backrest frame (3) is rotated around the support plate (10) by the first support rod (11), the second support rod (12) and the back plate connector (20). When the backrest frame (3) is rotated to the horizontal position, it overlaps with the second frame (2) and the support plate (10) respectively.

8. The sofa bed frame mechanism according to claim 5, characterized in that: The support plate (10) is provided with a limiting block (30) to limit the third connecting rod (6) in the folded state. At the same time, the limiting block (30) limits the first support rod (11) when the backrest frame (3) is flipped upward from the horizontal position.

9. The sofa bed frame mechanism according to claim 5, characterized in that: A limiting plate (18) is provided at the end of the first support rod (11) or the second support rod (12), so that when the first support rod (11) and the second support rod (12) rotate relative to each other to a straight position, the limiting plate (18) limits both of them and restricts further rotation.

10. The sofa bed frame mechanism according to claim 1 or 2, characterized in that: The power spring fixing plate (25) and the mounting plate (15) are the same component.

11. The sofa bed frame mechanism according to claim 7, characterized in that: The support plate (10) is provided with a limiting support groove (19), which is used to limit and support the backrest frame (3).

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