Mechanical extension structure of sofa and sofa

Abstract

This utility model discloses a mechanical extension structure for a sofa, including a base, a drive unit, two bases for mounting the seat cushion structure, and extension units respectively mounted on the two bases. The extension unit includes a leg assembly, a swing mechanism, and a backrest assembly. The swing mechanism includes a front support rod, a middle connecting rod, a rear support rod, a front swing rod assembly, a connecting rod assembly, and a rear swing rod assembly. One end of the front support rod and one end of the rear support rod are respectively hinged to the middle connecting rod, and the other end of the front support rod and the other end of the rear support rod are respectively hinged to the base. The middle connecting rods of the two swing mechanisms are connected by a synchronizing rod. The front swing rod assembly includes a front main swing rod with one end hinged to the base and a front auxiliary swing rod with one end hinged to the middle connecting rod. The front main swing rod and the front auxiliary swing rod are hinged together. The rear swing rod assembly includes a rear main swing rod with one end hinged to the base and a rear auxiliary swing rod with one end hinged to the middle connecting rod. The rear main swing rod and the rear auxiliary swing rod are hinged together. The front swing rod assembly is connected to the rear swing rod assembly through the connecting rod assembly.

Description

Technical Field

[0001] This utility model relates to the field of sofa technology, and in particular to the mechanical extension structure of a sofa and the sofa itself. Background Technology

[0002] Existing sofa mechanical extension structures include a base, a drive unit, two bases for mounting the seat cushion structure, and extension units respectively mounted on the two bases. Each extension unit includes leg components hinged to the base, a swing mechanism movably connected between the base and the base, and a backrest assembly. The mechanical extension structure has a sitting position and a reclining position. The drive unit extends the leg components to move the base and swing mechanism forward, switching the mechanical extension structure from the sitting position to the reclining position. Conversely, the drive unit retracts the leg components to move the base and swing mechanism backward, switching the mechanical extension structure from the reclining position to the sitting position. However, during the extension process, the swing mechanisms on both sides may exhibit asynchronous movement due to manufacturing errors, wear, or uneven force. This causes the sofa to tilt or twist when changing positions, resulting in an unsmooth transition, and in severe cases, jamming, requiring manual adjustment by the user, leading to a poor user experience. Utility Model Content

[0003] The technical problem to be solved by this utility model is to overcome the shortcomings of the existing technology and provide a mechanical extension structure and sofa for a sofa, which realizes the synchronous movement of the swing mechanism on both sides, effectively avoids the problem of unsmooth or even stuck posture switching, and improves the user experience.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] The sofa's mechanical extension structure includes a base, a drive unit, two bases for mounting the seat cushion structure, and extension units respectively mounted on the two bases. Each extension unit includes leg assemblies hinged to the bases, a swing mechanism movably connected between the bases and the bases, and a backrest assembly. The mechanical extension structure has a sitting position and a reclining position. The drive unit extends the leg assemblies to move the bases and swing mechanism forward, switching the mechanical extension structure from the sitting position to the reclining position. The swing mechanism includes a front support rod, a middle connecting rod, a rear support rod, a front swing rod assembly, and a connecting rod assembly. The front and rear swing arm assemblies are connected by hinges: one end of the front support rod and one end of the rear support rod are respectively hinged to the intermediate connecting rod; the other end of the front support rod and the other end of the rear support rod are respectively hinged to the base; the intermediate connecting rods of the two swing mechanisms are connected by a synchronizing rod; the front swing arm assembly includes a front main swing arm with one end hinged to the base and a front auxiliary swing arm with one end hinged to the intermediate connecting rod; the front main swing arm and the front auxiliary swing arm are hinged together; the rear swing arm assembly includes a rear main swing arm with one end hinged to the base and a rear auxiliary swing arm with one end hinged to the intermediate connecting rod; the rear main swing arm and the rear auxiliary swing arm are hinged together; the front swing arm assembly is connected to the rear swing arm assembly through a connecting rod assembly.

[0006] In this invention, the intermediate connecting rods of the two swing mechanisms are connected by a synchronizing rod. This synchronizing rod rigidly connects the two intermediate connecting rods, suppressing asymmetrical movement of the two swing mechanisms during posture switching in the mechanical extension structure. This ensures that the two swing mechanisms always maintain synchronized movement, thereby guaranteeing smoothness and dynamic stability. This prevents the sofa from tilting or twisting during posture switching, which can lead to unsmooth posture switching or even jamming, thus improving the user experience. Furthermore, in existing sofas, if the user's weight is biased to one side, the swing mechanism on that side will bear a greater load, while the other side may not provide sufficient support. Over time, the hinge points or connecting rods of the swing mechanism on one side are prone to wear, leading to loosening, abnormal noise, or even breakage. In this application, by setting a synchronizing rod, the user's weight is distributed to the swing mechanisms on both sides, reducing the problem of loosening, abnormal noise, or even breakage caused by wear on one side of the swing mechanism, thereby extending the service life of the mechanical extension structure.

[0007] In the aforementioned mechanical extension structure of the sofa, the two front auxiliary swing arms of the swing mechanism have bent portions extending in opposite directions, and the two ends of the synchronizing rod are respectively fixedly connected to the bent portions of the two front auxiliary swing arms; or, the two ends of the synchronizing rod are respectively fixedly connected to the intermediate connecting rod. When the two ends of the synchronizing rod are respectively fixedly connected to the bent portions of the two front auxiliary swing arms, the synchronous movement of the intermediate connecting rods on both sides can be indirectly controlled by controlling the synchronous movement of the front auxiliary swing arms on both sides. Since the movement of the front auxiliary swing arms directly affects the position of the intermediate connecting rod, compared with the synchronizing rod directly connecting to the intermediate connecting rod, this connection method can reduce the slight asynchrony caused by the gap at the hinge point of the intermediate connecting rod, and achieve more precise control of the synchronicity of the forward / backward movement of the base; in addition, the design of the bent portion also makes it easier to fix the synchronizing rod and reduces the assembly difficulty; when the two ends of the synchronizing rod are respectively fixedly connected to the intermediate connecting rod, the front auxiliary swing arms can adopt a simpler straight rod structure, reducing the processing difficulty of the front auxiliary swing arms.

[0008] In the aforementioned mechanical extension structure of the sofa, the mechanical extension structure also includes a drive rod. One end of the drive rod is hinged to the leg assembly, and the other end is hinged to either the intermediate connecting rod or the front support rod, so that the swing mechanism and the leg assembly are linked. Since the intermediate connecting rod is the core motion node of the swing mechanism, when the other end of the drive rod is hinged to the intermediate connecting rod, the tension of the drive rod can be directly applied to the intermediate connecting rod. Then, the movement of the intermediate connecting rod synchronously drives the front and rear support rods, ensuring that the rear swing arm assembly moves into position while also making the linkage between the base and the leg assembly smoother. When the other end of the drive rod is hinged to the front support rod, since the front support rod mainly controls the front movement of the base, this reduces the intermediate transmission link of force from the drive rod to the base, making it suitable for scenarios requiring rapid extension and retraction.

[0009] In the aforementioned mechanical extension structure of the sofa, the other end of the drive rod is hinged to the intermediate connecting rod. The connecting rod assembly includes a main connecting rod and a secondary connecting rod. The two ends of the main connecting rod are respectively hinged to the front secondary swing arm and the rear main swing arm. One end of the secondary connecting rod is connected to the other end of the front main swing arm, and the other end of the secondary connecting rod is hinged to the main connecting rod. Both the front and rear main swing arms are provided with limiting grooves. The base is also provided with a sitting support member. When the mechanical extension structure is in a sitting position, the sitting support member cooperates with the limiting groove to support the swing mechanism. When the mechanical extension structure is in a reclining position, the sitting support member disengages from the limiting groove. This design establishes a connection between the front and rear main swing arms via the main connecting rod. The secondary connecting rod constrains the movement trajectory of the front main swing arm, preventing instability of the quadrilateral mechanism. Compared to having no secondary connecting rod, the movement trajectory is more precise, preventing the rear end from tilting when the base moves forward. When the mechanical extension structure switches from a reclining position to a sitting position, the middle connecting rod, under the tension of the drive rod, drives the front and rear main swing arms to move synchronously. This ensures that both the front and rear main swing arms move into position and cooperate with the sitting support components in the sitting position, thereby increasing the stability of the sitting position and preventing collapse.

[0010] In the aforementioned mechanical extension structure of the sofa, the other end of the drive rod is hinged to the front support rod. The linkage assembly includes a main linkage and a secondary linkage. The two ends of the main linkage are respectively hinged to the front main swing arm and the rear secondary swing arm. One end of the secondary linkage is hinged to the front secondary swing arm, and the other end of the secondary linkage is hinged to the main linkage. Both the front main swing arm and the rear main swing arm are provided with limiting grooves. The base is also provided with a sitting support member. When the mechanical extension structure is in a sitting position, the sitting support member cooperates with the limiting groove to support the swing mechanism. When the mechanical extension structure is in a reclining position, the sitting support member disengages from the limiting groove. This design establishes a connection between the front main swing arm and the rear auxiliary swing arm via a main connecting rod. The auxiliary connecting rod constrains the movement trajectory of the front and auxiliary swing arms, preventing instability of the quadrilateral mechanism. Compared to designs without auxiliary connecting rods, the movement trajectory is more precise. Furthermore, the other end of the drive rod is hinged to the front support rod. Since the front support rod primarily controls the front movement of the base, this reduces the intermediate transmission links in the force transmission from the drive rod to the base, making it suitable for scenarios requiring rapid deployment and retraction. Finally, when the mechanical extension structure is in a seated position, the seated support abuts against the front and rear main swing arms, ensuring the stability of the seated position and preventing collapse.

[0011] In the aforementioned mechanical extension structure of the sofa, the base is a metal support frame, which includes two spaced-apart armrests, front and rear support legs mounted at both ends of the armrests, and a rear drive tube connecting the rear ends of the two armrests. Two leg assemblies are connected via the front drive tube, and a drive unit is installed between the rear and front drive tubes. The rear drive tube and the two armrests together form a frame. One end of the front main swing arm and one end of the rear main swing arm are hinged to the armrests, and the backrest assembly is hinged between the armrests and the base. Compared to existing wooden support frames, the metal support frame structure of this technical solution is simpler, more stable, lighter, and lower in cost. Furthermore, in existing technologies, the armrests are screwed onto the side panels of the wooden frame, which can cause the armrests to shift relative to the wooden frame, leading to asynchronous movement of the two swing mechanisms. This technical solution integrates the armrests onto the metal support frame, ensuring that the positions of the armrests on both sides are relatively fixed, further guaranteeing synchronous movement of the two swing mechanisms.

[0012] In the aforementioned sofa's mechanical extension structure, both the front and rear support legs are welded and fixed to the armrests. This design increases the reliability of the connection between the front and rear support legs and the armrests, thereby further enhancing the structural rigidity of the metal support frame.

[0013] In the aforementioned sofa's mechanical extension structure, both the front and rear support legs are U-shaped tubes with openings facing inwards from the frame. Positioning notches are provided on the adjacent side walls of both the front and rear support legs. The armrest panels extend through the positioning notches of the front and rear support legs respectively. This design, with U-shaped tubes opening inwards from the frame, reduces material costs for the support legs and prevents the openings from being exposed on the outside, thus improving the base's appearance. Before welding, the positioning notches of the front and rear support legs, respectively, through which the armrest panels extend, allow for pre-positioning of the front and rear support legs and the armrest panels, facilitating subsequent welding of the front and rear support legs to the armrest panels and reducing the difficulty of the welding operation.

[0014] In the aforementioned sofa's mechanical extension structure, a first reinforcing tube connects the two front support legs, and a second reinforcing tube connects the two armrests. The second reinforcing tube is located between the first reinforcing tube and the rear drive tube, and is positioned at the front of the armrests. This design allows the first reinforcing tube to provide lateral constraint on the two front support legs, preventing them from twisting or deforming laterally. The second reinforcing tube provides lateral constraint on the front of the armrests, preventing changes in the distance between the front of the two armrests from causing deformation of the extension unit and resulting in jamming during extension and retraction. Therefore, by incorporating both the first and second reinforcing tubes, the structural stability of the entire base is enhanced.

[0015] In the aforementioned sofa's mechanical extension structure, the armrest is a wave-shaped plate extending along its length. This design enhances the rigidity of the armrest, thereby increasing its structural strength, preventing deformation, and further ensuring the synchronization of the two swinging mechanisms.

[0016] In the aforementioned sofa's mechanical extension structure, both the front and rear legs have horizontally extending bottom walls with mounting holes for connecting the base legs. This design allows the front and rear legs to serve as mounting carriers for the base legs, facilitating their assembly onto the base using fasteners.

[0017] In the aforementioned sofa's mechanical extension structure, both the front and rear support legs are equipped with armrest mounting holes for connecting the armrest assembly. This design allows the armrest assembly to be secured to the front and rear support legs using fasteners, facilitating its installation.

[0018] In the aforementioned sofa's mechanical extension structure, both the front and rear support legs connected to one armrest panel have snap-fit ​​holes, while both the front and rear support legs connected to the other armrest panel have snap-fit ​​pins. The snap-fit ​​holes on adjacent mechanical extension structures engage with the snap-fit ​​pins. This design allows for the connection of adjacent sofas when multiple sofas are combined, as the snap-fit ​​pins engage with the snap-fit ​​holes, making the connection method relatively simple and convenient.

[0019] In the aforementioned sofa's mechanical extension structure, the height of the rear support legs is greater than the height of the front support legs, and both rear support legs have mounting holes for the rear end plate at their upper parts. This design allows the rear end plate of the sofa's backrest assembly to be connected to the rear end plate connection holes via fasteners, thus securing the rear end plate to the two rear support legs without requiring additional connectors on the rear support legs, thereby simplifying the base structure.

[0020] This utility model also discloses a sofa, including an armrest assembly, a backrest assembly, a seat cushion structure, and the mechanical extension structure described in any of the above technical solutions. The armrest assembly and the backrest assembly are both mounted on a base, and the seat cushion structure is mounted on the base.

[0021] These features and advantages of the present invention will be disclosed in detail in the following specific embodiments and accompanying drawings. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings:

[0023] Figure 1 This is a schematic diagram of the assembly of the mechanical extension structure in Embodiment 1 of this utility model;

[0024] Figure 2 for Figure 1 A magnified view of part A in the diagram;

[0025] Figure 3 This is a partial structural diagram of the mechanical extension structure in Embodiment 1 of this utility model;

[0026] Figure 4 for Figure 3 A magnified view of part B in the diagram;

[0027] Figure 5 This is a schematic diagram of the left-side swing mechanism in Embodiment 1 of this utility model;

[0028] Figure 6 This is a schematic diagram of the base structure in Embodiment 1 of this utility model;

[0029] Figure 7 This is a schematic diagram of the left side of the mechanical extension structure in Embodiment 1 of this utility model. Figure 1 ;

[0030] Figure 8 This is a schematic diagram of the left side of the mechanical extension structure in Embodiment 1 of this utility model. Figure 2 ;

[0031] Figure 9 This is a schematic diagram of the right front support leg in Embodiment 1 of this utility model;

[0032] Figure 10 This is a schematic diagram of the right rear support leg in Embodiment 1 of this utility model;

[0033] Figure 11 A partial structural diagram of the mechanical extension structure in Embodiment 2 of this utility model.

[0034] Figure label:

[0035] 100. Base; 101. First mounting hole; 102. Second mounting hole; 103. Third mounting hole; 104. Seating support; 105. Positioning notch; 106. Foot mounting hole; 107. Armrest mounting hole; 108. Snap-fit ​​hole; 109. Clip; 110. Armrest board; 120. Front support leg; 130. Rear support leg; 131. Rear end plate mounting hole; 140. Rear drive tube; 150. First reinforcing tube; 160. Second reinforcing tube;

[0036] 200. Base; 210. Connecting plate;

[0037] 300. Extension unit; 310. Leg assembly; 320. Swing mechanism; 3201. Limiting groove; 321. Front support rod; 322. Intermediate connecting rod; 323. Rear support rod; 324. Front swing arm assembly; 3241. Front main swing arm; 3242. Front auxiliary swing arm; 32421. Bending part; 325. Link assembly; 3251. Main connecting rod; 3252. Auxiliary connecting rod; 326. Rear swing arm assembly; 3261. Rear main swing arm; 3262. Rear auxiliary swing arm; 330. Backrest assembly;

[0038] 400, Synchronizing rod; 500, Drive rod; 600, Front drive tube. Detailed Implementation

[0039] This utility model provides a mechanical extension structure for a sofa, including a base, a drive unit, two bases for mounting the seat cushion structure, and extension units respectively mounted on the two bases. Each extension unit includes leg assemblies hinged to the bases, a swing mechanism movably connected between the bases and the bases, and a backrest assembly. The mechanical extension structure has a sitting position and a reclining position. The drive unit drives the leg assemblies to extend, causing the bases and swing mechanism to move forward, thus switching the mechanical extension structure from the sitting position to the reclining position. The swing mechanism includes a front support rod, a middle connecting rod, a rear support rod, and a front swing rod assembly. The linkage assembly and the rear swing arm assembly are provided. One end of the front support rod and one end of the rear support rod are respectively hinged to the intermediate connecting rod, and the other end of the front support rod and the other end of the rear support rod are respectively hinged to the base. The intermediate connecting rods of the two swing mechanisms are connected by a synchronizing rod. The front swing arm assembly includes a front main swing arm with one end hinged to the base and a front auxiliary swing arm with one end hinged to the intermediate connecting rod. The front main swing arm and the front auxiliary swing arm are hinged together. The rear swing arm assembly includes a rear main swing arm with one end hinged to the base and a rear auxiliary swing arm with one end hinged to the intermediate connecting rod. The rear main swing arm and the rear auxiliary swing arm are hinged together. The front swing arm assembly is connected to the rear swing arm assembly through the linkage assembly.

[0040] In this invention, the intermediate connecting rods of the two swing mechanisms are connected by a synchronizing rod. This synchronizing rod rigidly connects the two intermediate connecting rods, suppressing asymmetrical movement of the two swing mechanisms during posture switching in the mechanical extension structure. This ensures that the two swing mechanisms always maintain synchronized movement, thereby guaranteeing smoothness and dynamic stability. This prevents the sofa from tilting or twisting during posture switching, which can lead to unsmooth posture switching or even jamming, thus improving the user experience. Furthermore, in existing sofas, if the user's weight is biased to one side, the swing mechanism on that side will bear a greater load, while the other side may not provide sufficient support. Over time, the hinge points or connecting rods of the swing mechanism on one side are prone to wear, leading to loosening, abnormal noise, or even breakage. In this application, by setting a synchronizing rod, the user's weight is distributed to the swing mechanisms on both sides, reducing the problem of loosening, abnormal noise, or even breakage caused by wear on one side of the swing mechanism, thereby extending the service life of the mechanical extension structure.

[0041] The technical solutions of the present utility model will be explained and described below with reference to the accompanying drawings. However, the following embodiments are only preferred embodiments of the present utility model and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments in the implementation methods without creative effort are all within the protection scope of the present utility model.

[0042] 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", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more, unless otherwise expressly defined.

[0044] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., 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 or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of 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.

[0045] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0046] Example 1

[0047] like Figures 1 to 10 As shown, the mechanical extension structure of the sofa in this embodiment includes a base 100, a drive unit (not shown in the figure), two bases 200 for mounting the seat cushion structure, and extension units 300 respectively disposed on the two bases 200. The two bases 200 are spaced apart from each other on the left and right. The front ends of the two bases 200 and the rear ends of the two bases 200 are fixedly connected by connecting plates 210. Each base 200 is provided with an extension unit 300. The two extension units 300 are symmetrically arranged and have the same structure. The extension unit 300 includes a leg assembly 310 hinged to the base 200, a swing mechanism 320 movably connected between the base 200 and the base 100, and a backrest assembly 330. The leg assembly 310 and the backrest assembly 330 can be set with reference to the prior art, and will not be described in detail here. The mechanical extension structure in this embodiment has a sitting position and a lying position. The drive unit drives the leg assembly 310 to unfold, thereby moving the base 200 and the swing mechanism 320 forward, so that the mechanical extension structure switches from the sitting position to the lying position. The drive unit drives the leg assembly 310 to retract, thereby moving the base 200 and the swing mechanism 320 backward, so that the mechanical extension structure switches from the lying position to the sitting position. The drive unit can directly drive the swing mechanism 320 to move back and forth through the leg assembly 310, or the drive unit can indirectly drive the swing mechanism 320 through the leg assembly 310. For example, the drive unit drives the base 200 to move forward through the leg assembly 310, and the base 200 drives the swing mechanism 320 to move forward.

[0048] Since the two swing mechanisms 320 in this embodiment have the same structure, for ease of description, the left swing mechanism 320 will be used as an example for explanation. Figures 3 to 8 As shown, the left swing mechanism 320 includes a front support rod 321, a middle connecting rod 322, a rear support rod 323, a front swing rod assembly 324, a connecting rod assembly 325, and a rear swing rod assembly 326. One end of the front support rod 321 and one end of the rear support rod 323 are respectively hinged to the middle connecting rod 322, and the other end of the front support rod 321 and the other end of the rear support rod 323 are respectively hinged to the left base 200. Figure 5 , Figure 7 and Figure 8 Taking the direction shown as an example, the lower ends of the front support rod 321 and the rear support rod 323 are respectively hinged to the intermediate connecting rod 322, and the upper ends of the front support rod 321 and the rear support rod 323 are respectively hinged to the base 200 on the left side. Figure 1 and Figure 3 As shown, the intermediate connecting rod 322 of the two swing mechanisms 320 is connected by a synchronizing rod 400, as follows: Figure 5 , Figure 7 and Figure 8 As shown, the front rocker arm assembly 324 includes a front main rocker arm 3241 hinged at one end to the base 100 and a front auxiliary rocker arm 3242 hinged at one end to the intermediate connecting rod 322. The front main rocker arm 3241 and the front auxiliary rocker arm 3242 are hinged together. The rear rocker arm assembly 326 includes a rear main rocker arm 3261 hinged at one end to the base 100 and a rear auxiliary rocker arm 3262 hinged at one end to the intermediate connecting rod 322. (Refer to...) Figures 5 to 8 In the indicated direction, the lower end of the front main swing arm 3241 is hinged to the first mounting hole 101 on the base 100 via a pivot, the front auxiliary swing arm 3242 is hinged to the front end of the intermediate connecting rod 322, the front main swing arm 3241 is hinged to the upper end of the front auxiliary swing arm 3242, the lower end of the rear main swing arm 3261 is hinged to the second mounting hole 102 on the base 100 via a pivot, the lower end of the rear auxiliary swing arm 3262 is hinged to the rear end of the intermediate connecting rod 322, the upper end of the rear auxiliary swing arm 3262 is hinged to the upper end of the rear main swing arm 3261, and the front swing arm assembly 324 is connected to the rear swing arm assembly 326 via a connecting rod assembly 325.

[0049] In this embodiment, the intermediate connecting rods 322 of the two swing mechanisms 320 are connected by a synchronizing rod 400. This synchronizing rod 400 rigidly connects the two intermediate connecting rods 322. During posture switching in the mechanical extension structure, the synchronizing rod 400 suppresses asymmetrical movement of the two swing mechanisms 320, ensuring that they always maintain synchronized movement. This ensures smooth movement and dynamic stability, preventing the sofa from tilting or twisting during posture switching, which could lead to unsmooth posture switching or even jamming in severe cases, thus improving the user experience. Furthermore... When using existing sofas, if the user's weight is biased to one side of the sofa, the swing mechanism 320 on that side will bear a greater load, while the other side may not be fully supported. After long-term use, the hinge points or connecting rods of the swing mechanism on the side with greater force are prone to wear, which can lead to loosening, abnormal noise, or even breakage. In this embodiment, by setting a synchronizing rod 400, the user's weight can be distributed to the swing mechanisms 320 on both sides through the synchronizing rod 400, reducing the problem of loosening, abnormal noise, or even breakage caused by wear on the swing mechanism 320 on one side, thereby extending the service life of the mechanical extension structure.

[0050] Specifically, such as Figures 3 to 5 As shown, in this embodiment, the synchronizing rod 400 is a hollow metal tube, which can be a square tube or a round tube. The lower ends of the front auxiliary swing rods 3242 of the two swing mechanisms 320 have opposing bending portions 32421, that is, the lower end of the front auxiliary swing rod 3242 of the left swing mechanism 320 has a bending portion 32421 extending to the right, and the lower end of the front auxiliary swing rod 3242 of the right swing mechanism 320 has a bending portion 32421 extending to the left. The two bending portions 32421 are provided with first connecting holes. Screws pass through the left end of the synchronizing rod 400 and are fixed to the first connecting hole on the left bending portion 32421, and screws pass through the right end of the synchronizing rod 400 and are fixed to the first connecting hole on the right bending portion 32421. The connecting holes are fixed so that both ends of the synchronizing rod 400 are fixedly connected to the bent portions 32421 of the two front auxiliary swing rods 3242 respectively. At this time, the synchronous movement of the two front auxiliary swing rods 3242 can be indirectly controlled by controlling the synchronous movement of the two middle connecting rods 322. Since the movement of the front auxiliary swing rods 3242 directly affects the position of the middle connecting rod 322, compared with the synchronizing rod 400 directly connecting to the middle connecting rod 322, this connection method can reduce the slight asynchrony caused by the hinge gap of the middle connecting rod 322, and achieve more precise control of the synchronicity of the forward / backward movement of the base 200. In addition, the design of the bent portion 32421 also makes it easier to fix the synchronizing rod 400 and reduces the assembly difficulty.

[0051] It is understood that in other embodiments of this utility model, the two ends of the synchronizing rod can also be directly fixed to the middle connecting rods on both sides by screws, which allows the front auxiliary rocker arm to adopt a simpler straight rod structure and reduces the processing difficulty of the front auxiliary rocker arm; or, the two ends of the synchronizing rod can also be directly fixed to the front support rods on both sides by screws.

[0052] Furthermore, in this embodiment, the drive unit preferably drives the swing mechanism 320 to move back and forth directly through the leg assembly 310. The mechanical extension structure also includes a drive rod 500, one end of which is hinged to the leg assembly 310, and the other end of which is hinged to the front support rod 321. The hinge position between the front support rod 321 and the drive rod 500 is located near the lower end of the front support rod 321. Thus, the swing mechanism 320 and the leg assembly 310 on the same side are linked through the drive rod 500. Since the front support rod 321 mainly controls the front movement of the base 200, the intermediate transmission link of the drive rod 500 to the base 200 can be reduced, which is suitable for scenarios that require rapid deployment and retraction.

[0053] like Figures 4 to 8 As shown, the linkage assembly 325 in this embodiment includes a main linkage 3251 and a secondary linkage 3252. The two ends of the main linkage 3251 are hinged to the upper end of the front main swing arm 3241 and the upper middle part of the rear secondary swing arm 3262, respectively. The front end of the secondary linkage 3252 is hinged to the front secondary swing arm 3242, and the rear end of the secondary linkage 3252 is hinged to the main linkage 3251. Limiting grooves 3201 are provided on the rear side of both the front main swing arm 3241 and the rear main swing arm 3261. Two seating support members 104 (such as...) are also provided on the base 100. Figure 6 As shown), the sitting support 104 is a support rod detachably connected to the base 100. The support rod may consist only of the rod body, or it may consist of the rod body and a support ring sleeved on the outside of the rod body. In this embodiment, the support rod preferably includes the rod body and a support ring sleeved on the outside of the rod body. The stiffness of the support ring is different from that of the swing mechanism 320. When the mechanical extension structure is in the sitting position (e.g. Figure 4As shown, one seated support 104 is inserted into the limiting groove 3201 on the rear side of the front main swing arm 3241 and the support ring abuts against the groove wall of the limiting groove 3201. The other seated support 104 is inserted into the limiting groove 3201 on the rear side of the rear main swing arm 3261 and the support ring abuts against the groove wall of the limiting groove 3201. After the swing mechanism 320 is damaged, the movement of the front main swing arm 3241 and the rear main swing arm 3261 is restricted by the two seated support 104 to provide more stable support for the swing mechanism 320 and prevent the swing mechanism 320 from collapsing relative to the base 100. When the mechanical extension structure is in the lying position, the seated support 104 disengages from the limiting groove 3201. This design establishes the connection between the front main swing arm 3241 and the rear auxiliary swing arm 3262 through the main connecting rod 3251. The auxiliary connecting rod 3252 can constrain the motion trajectory of the front auxiliary swing arm 3242, preventing the quadrilateral-like mechanism composed of the intermediate connecting rod 322, the front auxiliary swing arm 3242, the rear auxiliary swing arm 3262 and the main connecting rod 3251 from becoming unstable. Compared with no auxiliary connecting rod, the motion trajectory is more accurate.

[0054] To further improve the stability of the mechanical extension structure in a seated position, such as Figure 7 As shown, in this embodiment, the base 100 is also detachably connected to two additional seating support members 104. One seating support member 104 is located below the secondary connecting rod 3252, and the other seating support member 104 is located behind the rear secondary swing rod 3262. The rear side of the rear secondary swing rod 3262 is provided with a groove. When the mechanical extension structure is in the seating position, one seating support member 104 supports the secondary connecting rod 3252, and the other seating support member 104 cooperates with the groove to support the rear secondary swing rod 3262. Thus, the four seating support members 104 provide four-point support for the swing mechanism 320, which can further provide more stable support for the swing mechanism 320 and prevent the swing mechanism 320 from collapsing relative to the base 100.

[0055] It should be noted that when the secondary connecting rod 3252 is hinged to the front secondary swing rod 3242, in order to avoid interference between the secondary connecting rod 3252 and the main connecting rod 3251 and the front main swing rod 3241, the front main swing rod 3241 needs to be lengthened so that the front end of the secondary connecting rod 3252 can be rotatably connected to the upper middle position of the front secondary swing rod 3242.

[0056] When the mechanical extension structure in this embodiment is in the sitting position, the upper end of the front auxiliary swing rod 3242 is hinged to the upper middle part of the front main swing rod 3241, and the lower end of the front main swing rod 3241 is located in front of the lower end of the front auxiliary swing rod 3242. Therefore, the front auxiliary swing rod 3242 and the front main swing rod 3241 form a support structure in the shape of a "V". Similarly, since the upper end of the rear auxiliary swing rod 3262 is hinged to the upper end of the rear main swing rod 3261, and the lower end of the rear main swing rod 3261 is located in front of the lower end of the rear auxiliary swing rod 3262, the rear auxiliary swing rod 3262 and the rear main swing rod 3261 also form a support structure in the shape of a "V". The "V" - shaped support structure has the function of relatively stable support. In addition, when the mechanical extension structure is in the lying position, the lower end of the front main swing rod 3241 is located behind the lower end of the front auxiliary swing rod 3242, and the lower end of the rear main swing rod 3261 is located behind the lower end of the rear auxiliary swing rod 3262; during the process of the mechanical extension structure changing from the sitting position to the lying position, the lower end of the front auxiliary swing rod 3242 moves from behind the lower end of the front main swing rod 3241 to in front of the lower end of the front main swing rod 3241, and the lower end of the rear auxiliary swing rod 3262 moves from behind the lower end of the rear main swing rod 3261 to in front of the lower end of the rear main swing rod 3261; during the process of the mechanical extension structure changing from the lying position to the sitting position, the lower end of the front auxiliary swing rod 3242 moves from in front of the lower end of the front main swing rod 3241 to behind the lower end of the front main swing rod 3241, and the lower end of the rear auxiliary swing rod 3262 moves from in front of the lower end of the rear main swing rod 3261 to behind the lower end of the rear main swing rod 3261. In this structure, the front main swing rod 3241 and the front auxiliary swing rod 3242 cooperate with each other, and the rear main swing rod 3261 and the rear auxiliary swing rod 3262 cooperate with each other to control the forward movement distance of the intermediate link 322, and the intermediate link 322 controls the forward movement distance of the base 200 through the front support rod 321 and the rear support rod 323.

[0057] In addition, as Figure 1 and Figure 6 shown, the base 100 in this embodiment is a metal support frame, which includes two armrest plates 110 arranged at intervals left and right, front feet 120 and rear feet 130 installed at the front and rear ends of the armrest plates 110, and a rear drive tube 140 connecting the rear ends of the two armrest plates 110. The armrest plates 110, front feet 120, rear feet 130 and rear drive tube 140 are all metal parts. The leg components 310 of the two extension units 300 are connected through the front drive tube 600 to realize the synchronous movement of the two leg components 310. The drive unit is installed between the rear drive tube 140 and the front drive tube 600. The drive unit in this embodiment includes a driver, and a telescopic drive rod is provided on the driver. One of the driver and the drive rod is hinged to the front drive tube 600, and the other is hinged to the rear drive tube 140.

[0058] In this embodiment, both ends of the rear drive tube 140 are fixed to the second connecting holes at the rear ends of the two armrest plates 110 by screws. Thus, the rear drive tube 140 and the two armrest plates 110 together form a frame. The first mounting hole 101, the second mounting hole 102, and the seating support 104 are all provided on the armrest plates 110. This allows the lower ends of the front main swing arm 3241 and the rear main swing arm 3261 to be hinged to the armrest plates 110, while the backrest assembly 330 and the third mounting hole 103 are hinged through a pivot. Compared with the existing wooden support frame, the metal support frame in this embodiment has a simple and stable structure, is lighter and thinner, and has a lower cost. In addition, in the prior art, the armrest plates are installed on the side plates of the wooden frame by screws, which can cause the armrest plates to shift relative to the wooden frame, resulting in the two swing mechanisms being out of sync. In this embodiment, by integrating the armrest plates 110 onto the metal support frame, the positions of the armrest plates 110 on both sides can be kept relatively fixed, thereby further ensuring the synchronous movement of the two swing mechanisms 320.

[0059] Preferably, in this embodiment, both the front support leg 120 and the rear support leg 130 are welded and fixed to the handrail plate 110. This design increases the connection reliability between the front support leg 120 and the handrail plate 110, as well as the connection reliability between the rear support leg 130 and the handrail plate 110, thereby further improving the structural rigidity of the metal support frame.

[0060] like Figure 6 , Figure 9 and Figure 10 As shown, both the front support leg 120 and the rear support leg 130 are U-shaped tubes with openings facing the inside of the frame. That is, the openings of the left front support leg 120 and the left rear support leg 130 are open to the right, while the openings of the right front support leg 120 and the right rear support leg 130 are open to the left. Each of the front support leg 120 and the rear support leg 130 includes a front side wall, a rear side wall, and a transition wall connecting the front side wall and the rear side wall. The front side wall, the rear side wall, and the transition wall are connected to form a U-shaped tube with openings. The side walls of the front support leg 120 and the rear support leg 130 that are close to each other are provided with positioning notches 105. That is, the rear side wall of the front support leg 120 and the front side wall of the rear support leg 130 are respectively provided with positioning notches 105 that run through the front and rear. The two ends of the handrail plate 110 pass through the positioning notches 105 of the front support leg 120 and the positioning notches 105 of the rear support leg 130, respectively. This design, with its U-shaped tube opening towards the inside of the frame, reduces the material cost of the legs and prevents the opening from being exposed on the outside, thus improving the appearance of the base 100. Before welding, the positioning notches 105 of the front leg 120 and the rear leg 130 are respectively passed through the two ends of the armrest plate 110, which allows for the pre-positioning of the front leg 120, the rear leg 130, and the armrest plate 110. This facilitates the subsequent welding of the front leg 120 to the armrest plate 110 and the rear leg 130 to the armrest plate 110, reducing the difficulty of the welding operation.

[0061] In this embodiment, the armrest 110 is a corrugated plate extending along its length, and the corrugated plate is made of stamped metal sheet. This design, by bending the armrest 110, enhances its rigidity and structural strength, preventing deformation and further ensuring the synchronization of the two swing mechanisms 320. It should be noted that the armrest 110 is partially arched to form multiple reinforcing bosses. The first mounting hole 101, the second mounting hole 102, the seating support 104, and the second connecting hole are all located on these reinforcing bosses to enhance the structural strength at the connection between the armrest 110 and the front main swing arm 3241 and the rear main swing arm 3261, and to enhance the stability of the seating support 104 in supporting the swing mechanism 320.

[0062] In addition, in this embodiment, a first reinforcing tube 150 is connected between the two front support legs 120, and a second reinforcing tube 160 is connected between the two handrails 110. The second reinforcing tube 160 is located between the first reinforcing tube 150 and the rear drive tube 140, and the second reinforcing tube 160 is located at the front of the handrail 110. Both the first reinforcing tube 150 and the second reinforcing tube 160 are hollow metal tubes. The two ends of the first reinforcing tube 150 are fixed to the rear side walls of the two front support legs 120 by screws, and the first reinforcing tube 150 is set lower than the armrest plate 110. The two ends of the second reinforcing tube 160 are fixed to the two armrest plates 110 by screws. With this design, the first reinforcing tube 150 can achieve lateral constraint on the two front support legs 120, avoiding the two front support legs 120 from twisting and deforming to the left and right. The second reinforcing tube 160 can achieve lateral constraint on the front part of the armrest plate 110, avoiding the change of the distance between the front parts of the two armrest plates 110, which would cause the extension unit 300 to deform and get stuck during the extension and retraction process. Thus, by setting the first reinforcing tube 150 and the second reinforcing tube 160, the structural stability of the entire base 100 can be enhanced.

[0063] Both the front support leg 120 and the rear support leg 130 have horizontally extending bottom walls with mounting holes 106 for connecting the feet. This design allows the front support leg 120 and the rear support leg 130 to serve as mounting carriers for the feet, facilitating the assembly of the feet onto the base 100 using fasteners.

[0064] Furthermore, both the front support leg 120 and the rear support leg 130 are provided with armrest mounting holes 107 for connecting the armrest assembly. The armrest assembly of the sofa is connected to the armrest mounting holes 107 by fasteners so that the armrest assembly is installed on the outside of the front support leg 120 and the rear support leg 130, thereby facilitating the installation of the armrest assembly.

[0065] In this embodiment, the transition walls of the front support leg 120 and the rear support leg 130, which are connected to one of the armrest panels 110, are each provided with snap-fit ​​holes 108. Similarly, the transition walls of the front support leg 120 and the rear support leg 130, which are connected to the other armrest panel 110, are each provided with snap-fit ​​pins 109. When the sofa is a single-seat sofa, armrest assemblies are provided on both sides of the base 100. When the sofa is an outer sofa position of a sectional sofa, an armrest assembly is provided on the outer side of the base 100 of the outer sofa position. The armrest assembly is located on the outer side of the armrest panel 110, while the other side is connected to the base 100 of the adjacent sofa position through the snap-fit ​​holes 108 and snap-fit ​​pins 109. In this case, no armrest assemblies are provided on either side of the base of the middle sofa position. With this design, when multiple sofas are combined, adjacent sofas can be connected through the snap-fit ​​pins 109 and snap-fit ​​holes 108, making the connection method simple and convenient.

[0066] Finally, in this embodiment, the height of the rear support leg 130 is greater than the height of the front support leg 120, and both rear support legs 130 have rear end plate mounting holes 131 on their upper parts. This design allows the rear end plate of the sofa backrest assembly to be connected to the rear end plate mounting holes 131 via fasteners, thus fixing the rear end plate onto the two rear support legs 130 without requiring additional connectors on the rear support legs 130, thereby simplifying the structure of the base 100.

[0067] It is understood that in other embodiments of this utility model, the front support and the rear support can also be metal tubes, the front support and the rear support are provided with mortise grooves, and the two ends of the handrail are provided with tenons, which are inserted into the mortise grooves and welded to fix them.

[0068] Example 2

[0069] like Figure 11 As shown, compared with Embodiment 1, the difference in this embodiment is that the other end of the drive rod 500 is hinged to the intermediate connecting rod 322, and the connecting rod assembly 325 includes a main connecting rod 3251 and a secondary connecting rod 3252. The front and rear ends of the main connecting rod 3251 are respectively hinged to the upper middle part of the front secondary swing rod 3242 and the upper middle part of the rear main swing rod 3261. One end of the secondary connecting rod 3252 is connected to the other end of the front main swing rod 3241, and the other end of the secondary connecting rod 3252 is hinged to the main connecting rod 3251. Figure 11In the indicated direction, the lower end of the front main swing arm 3241 is hinged to the first mounting hole 101 on the armrest plate 110 via a pivot, and the lower end of the rear main swing arm 3261 is hinged to the second mounting hole 102 on the armrest plate 110 via a pivot. The front end of the auxiliary connecting rod 3252 is connected to the upper end of the front main swing arm 3241, and the rear end of the auxiliary connecting rod 3252 is hinged to the main connecting rod 3251. The rear side of both the front main swing arm 3241 and the rear side of the rear main swing arm 3261 are provided with limiting grooves 3201. The armrest plate 110 is provided with a sitting support member 104. When the mechanical extension structure is in a sitting position, the sitting support member 104 cooperates with the limiting groove 3201 to support the swing mechanism 320. When the mechanical extension structure is in a reclining position, the sitting support member 104 disengages from the limiting groove 3201. This design establishes the connection between the front auxiliary swing arm 3242 and the rear main swing arm 3261 through the main connecting rod 3251. The auxiliary connecting rod 3252 can constrain the movement trajectory of the front main swing arm 3241, preventing the quadrilateral mechanism from becoming unstable. Compared with no auxiliary connecting rod, the movement trajectory is more accurate, avoiding the rear end from tilting when the base 200 moves forward.

[0070] It should be noted that in Embodiment 1, the structure of the swing mechanism 320 and its connection to the drive rod 500 via the front support rod 321 may result in incomplete movement of the front main swing rod 3241 and the rear main swing rod 3261 when in a seated position, causing the seat support member 104 to fail to provide stable support for the swing mechanism 320. However, in this embodiment, since the intermediate connecting rod 322 is the core motion node of the swing mechanism, when the other end of the drive rod 500 is hinged to the intermediate connecting rod 322, the tension of the drive rod 500 can be directly applied to the intermediate connecting rod 322. Then, the movement of the intermediate connecting rod 322 synchronously drives the front support rod 321 and the rear support rod 323, ensuring that the rear swing rod assembly 326 moves to the correct position while also making the linkage between the base 200 and the leg assembly 310 smoother. In other words, when the mechanical extension structure switches from a lying position to a sitting position, the intermediate connecting rod 322 is pulled by the drive rod 500, which drives the front main swing rod 3241 and the rear main swing rod 3261 to move synchronously. This ensures that the front main swing rod 3241 and the rear main swing rod 3261 move into position and cooperate with the sitting support 104 when in the sitting position, thereby increasing the stability of the sitting position and avoiding collapse.

[0071] It should be noted that the base in this embodiment is set with reference to Embodiment 1, and will not be described in detail here.

[0072] Example 3

[0073] This embodiment discloses a sofa, including an armrest assembly, a backrest assembly, a seat cushion structure, and the mechanical extension structure described in Embodiment 1 or 2. The armrest assembly is mounted on the front support leg 120 and the rear support leg 130 of the base 100 by fasteners. The rear end plate of the backrest assembly is mounted on the two rear support legs 130 of the base 100 by fasteners, and the seat cushion structure is mounted on two bases 200.

[0074] The above description is merely a preferred embodiment of this utility model. The protection scope of this utility model is not limited to the above embodiments. All technical solutions falling within the scope of this utility model's concept are protected. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of this utility model should also be considered within the protection scope of this utility model.

Claims

1. A mechanical extension structure for a sofa, comprising a base, a drive unit, two bases for mounting a seat cushion structure, and extension units respectively disposed on the two bases. Each extension unit includes leg components hinged to the bases, a swing mechanism movably connected between the bases and the bases, and a backrest assembly. The mechanical extension structure has a sitting position and a reclining position. The drive unit drives the leg components to extend, thereby moving the bases and the swing mechanism forward, allowing the mechanical extension structure to switch from the sitting position to the reclining position. Its features are: The swing mechanism includes a front support rod, a middle connecting rod, a rear support rod, a front swing rod assembly, a connecting rod assembly, and a rear swing rod assembly. One end of the front support rod and one end of the rear support rod are respectively hinged to the middle connecting rod, and the other end of the front support rod and the other end of the rear support rod are respectively hinged to the base. The middle connecting rods of the two swing mechanisms are connected by a synchronizing rod. The front swing rod assembly includes a front main swing rod with one end hinged to the base and a front auxiliary swing rod with one end hinged to the middle connecting rod. The front main swing rod and the front auxiliary swing rod are hinged together. The rear swing rod assembly includes a rear main swing rod with one end hinged to the base and a rear auxiliary swing rod with one end hinged to the middle connecting rod. The rear main swing rod and the rear auxiliary swing rod are hinged together. The front swing rod assembly is connected to the rear swing rod assembly through the connecting rod assembly.

2. The mechanical extension structure of the sofa as described in claim 1, characterized in that, The two front auxiliary swing arms of the two swing mechanisms have bent portions extending in opposite directions, and the two ends of the synchronizing rod are respectively fixedly connected to the bent portions of the two front auxiliary swing arms; or, the two ends of the synchronizing rod are respectively fixedly connected to the intermediate connecting rod.

3. The mechanical extension structure of the sofa as described in claim 1, characterized in that, The mechanical extension structure also includes a drive rod, one end of which is hinged to the leg assembly, and the other end of which is hinged to the intermediate connecting rod or the other end of which is hinged to the front support rod, so that the swing mechanism is linked with the leg assembly.

4. The mechanical extension structure of the sofa as described in claim 3, characterized in that, The other end of the drive rod is hinged to the intermediate connecting rod. The connecting rod assembly includes a main connecting rod and a secondary connecting rod. The two ends of the main connecting rod are respectively hinged to the front secondary swing rod and the rear main swing rod. One end of the secondary connecting rod is connected to the other end of the front main swing rod, and the other end of the secondary connecting rod is hinged to the main connecting rod. Both the front main swing rod and the rear main swing rod are provided with limiting grooves. The base is also provided with a sitting support member. When the mechanical extension structure is in a sitting position, the sitting support member cooperates with the limiting groove to support the swing mechanism. When the mechanical extension structure is in a lying position, the sitting support member disengages from the limiting groove.

5. The mechanical extension structure of the sofa as described in claim 3, characterized in that, The other end of the drive rod is hinged to the front support rod. The linkage assembly includes a main linkage and a secondary linkage. The two ends of the main linkage are hinged to the front main swing rod and the rear secondary swing rod, respectively. One end of the secondary linkage is hinged to the front secondary swing rod, and the other end of the secondary linkage is hinged to the main linkage. Both the front main swing rod and the rear main swing rod are provided with limiting grooves. The base is also provided with a sitting support member. When the mechanical extension structure is in a sitting position, the sitting support member cooperates with the limiting groove to support the swing mechanism. When the mechanical extension structure is in a lying position, the sitting support member disengages from the limiting groove.

6. The mechanical extension structure of the sofa as described in claim 1, characterized in that, The base is a metal support frame, which includes two spaced armrests, front and rear support legs installed at both ends of the armrests, and a rear drive tube connecting the rear ends of the two armrests. The two leg assemblies are connected through the front drive tube. The drive unit is installed between the rear drive tube and the front drive tube. The rear drive tube and the two armrests together form a frame. One end of the front main swing arm and one end of the rear main swing arm are both hinged to the armrests. The backrest assembly is hinged between the armrests and the base.

7. The mechanical extension structure of the sofa as described in claim 6, characterized in that, Both the front and rear support legs are welded and fixed to the handrail plate.

8. The mechanical extension structure of the sofa as described in claim 7, characterized in that, Both the front and rear support legs are U-shaped tubes with openings facing the inside of the frame. The side walls of the front and rear support legs that are close to each other are provided with positioning notches. The two ends of the handrail plate pass through the positioning notches of the front and rear support legs, respectively.

9. The mechanical extension structure of the sofa as described in claim 6, characterized in that, A first reinforcing tube is connected between the two front support legs, and a second reinforcing tube is connected between the two armrests. The second reinforcing tube is located between the first reinforcing tube and the rear drive tube and is located at the front of the armrest.

10. The mechanical extension structure of the sofa as described in claim 6, characterized in that, The handrail is a corrugated board that extends along its length.

11. The mechanical extension structure of the sofa as described in claim 6, characterized in that, Both the front and rear support legs have horizontally extending bottom walls, and the bottom walls are provided with foot mounting holes for connecting the feet.

12. The mechanical extension structure of the sofa as described in claim 6, characterized in that, Both the front and rear support legs are provided with handrail mounting holes for connecting the handrail assembly.

13. The mechanical extension structure of the sofa as described in claim 6, characterized in that, Both the front and rear support legs connected to one of the handrails are provided with snap-fit ​​holes, and both the front and rear support legs connected to the other handrail are provided with snap-fit ​​pins. The snap-fit ​​holes on the two adjacent mechanical extension structures are engaged with the snap-fit ​​pins.

14. The mechanical extension structure of the sofa as described in claim 6, characterized in that, The height of the rear support leg is greater than that of the front support leg, and the upper part of both rear support legs is provided with a rear sealing plate mounting hole.

15. A sofa, characterized in that, The sofa includes an armrest assembly, a backrest assembly, a seat cushion structure, and a mechanical extension structure of any one of claims 1 to 14, wherein the armrest assembly and the backrest assembly are both mounted on a base, and the seat cushion structure is mounted on the base.

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