Back mechanism of chair

Abstract

The invention relates to the technical field of furniture, in particular to a chair back mechanism which comprises a back frame, a waist jacking frame and a waist jacking driving device, the waist jacking frame is rotatably mounted on the back frame, the waist jacking driving device is located on one side of the waist jacking frame, the output end of the waist jacking driving device is connected with the waist jacking frame, and the output end of the waist jacking driving device is connected with the back frame. Therefore, the waist supporting frame is driven to rotate relative to the back frame. By moving the waist-supporting driving device from the right rear part of the waist-supporting frame to the side part, the driving assembly, which is the most heavy part in the traditional design, is successfully removed from the central core area of the backrest. Therefore, the design of the thickness of the whole backrest is not limited by the size of the driving mechanism any more, and the backrest can be thinner and lighter and more attractive in shape; tension springs, sponges and the like can be better arranged on the backrest and the waist part, so that the whole back part is more comfortable, and the overall comfort degree and the ergonomic experience of the backrest are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of furniture technology, specifically to a chair back mechanism. Background Technology

[0002] As people's demands for seating comfort continue to increase, electric chairs with lumbar support functions are becoming increasingly popular in the market. Current electric chairs typically integrate lumbar support mechanisms inside their backrests. The mainstream solutions mostly use airbags or electric push rods as the driving source, placing them directly behind the lumbar support cushion. Through their inflation and deflation or extension and retraction movements, they directly push the lumbar support forward, thereby achieving the function of supporting and massaging the user's lower back.

[0003] However, this "rear-drive" layout has obvious structural defects: the drive mechanism (such as airbags, motors, and push rods) itself has a certain volume, and its embedded installation inevitably increases the overall thickness of the backrest, making the backrest appear abnormally heavy and clumsy. This not only affects the overall aesthetics and sense of lightness of the chair, but more importantly, the thick backrest restricts the user's sitting posture and movement space to a certain extent, and also limits the design space for backrest comfort, thus weakening the comfort it aims to improve. For example, Chinese utility model patent with publication number CN218571801U discloses a chair and its lumbar support assembly, in which the lumbar support assembly connecting the lumbar support and the chair back has a complex structure and a large overall thickness; another example is Chinese utility model patent with publication number CN217937684U, which discloses an electric push rod type backrest following office chair, in which a cushion airbag and an electric push rod are set behind the lumbar support, greatly increasing the overall thickness of the backrest. Therefore, there is an urgent need for an innovative design that optimizes the drive layout while ensuring the lumbar support function, thereby achieving a thinner backrest and improved comfort. Summary of the Invention

[0004] The purpose of this invention is to provide a backrest mechanism for a chair, which aims to solve the technical problems of excessive backrest thickness, inability to release backrest space, and low overall comfort in the prior art.

[0005] To achieve the above objectives, the present invention proposes a backrest mechanism for a chair, comprising a back frame, a top waist frame, and a top waist drive device. The top waist frame is rotatably mounted on the back frame, and the top waist drive device is located on one side of the top waist frame and its output end is connected to the top waist frame to drive the top waist frame to rotate relative to the back frame.

[0006] Preferably, the top waist drive device includes a housing, a first drive motor, a first reduction gear set, and a rotating output rod. The first reduction gear set is installed inside the housing. The output shaft of the first drive motor extends into the housing, and the teeth on the output end mesh with the first reduction gear set. The rotating output rod is connected to the first reduction gear set and the top waist frame respectively.

[0007] Preferably, the first reduction gear set includes a first gear, a second gear, and a third gear. The first gear meshes with the teeth on the output shaft of the first drive motor. The second gear is disposed on one side of the first gear and is coaxial with the first gear. The number of teeth of the second gear is greater than the number of teeth of the first gear. The third gear is sleeved on the rotating output rod and meshes with the second gear.

[0008] Preferably, the top waist drive device includes a second drive motor and an angle adjuster, the output end of the angle adjuster is connected to the top waist frame, and the second drive motor can drive the angle adjuster to adjust the angle of the top waist frame.

[0009] Preferably, the back frame includes a first left rod, a first right rod, and a first connecting rod. The first left rod and the first right rod are opposite to each other and spaced apart. The two ends of the first connecting rod are respectively connected to the first left rod and the first right rod. The top waist frame is located between the first left rod and the first right rod.

[0010] Preferably, the top waist drive device is mounted on the first left rod, and the left side of the top waist frame is connected to the output end of the top waist drive device, while the right side is rotatably connected to the first right rod; or,

[0011] The top waist drive device is mounted on the first right rod, and the right side of the top waist frame is connected to the output end of the top waist drive device, while the left side is rotatably connected to the first left rod.

[0012] Preferably, the top waist frame includes a second left rod, a second right rod, a second connecting rod, and a first serpentine spring. The second left rod and the second right rod are opposite to each other and spaced apart. The two ends of the second connecting rod are respectively connected to the second left rod and the second right rod. Multiple first serpentine springs are provided between the second left rod and the second right rod.

[0013] Preferably, it further includes a headrest frame and a headrest driving device, wherein the headrest frame is rotatably mounted on the back frame and located above the top waist frame, and the headrest driving device is located on one side of the headrest frame and is used to drive the headrest frame to rotate relative to the back frame.

[0014] Preferably, the headrest drive device is mounted on the back frame or the headrest frame.

[0015] Preferably, a connecting piece is installed at the upper end of the back frame, and the headrest frame is rotatably mounted on the connecting piece.

[0016] Preferably, the structure of the headrest driving device is the same as that of the lumbar support driving device.

[0017] Preferably, the headrest frame includes a third left rod, a third right rod, a third connecting rod, and a second serpentine spring. The third left rod and the third right rod are opposite to each other and spaced apart. The two ends of the third connecting rod are respectively connected to the third left rod and the third right rod. Multiple second serpentine springs are provided between the third left rod and the third right rod.

[0018] This invention discloses a chair backrest mechanism, which has at least the following beneficial effects: By moving the lumbar support drive device from the rear of the lumbar frame to the side, the most bulky part in the traditional design—the drive assembly—is successfully removed from the central core area of ​​the backrest. This allows the overall backrest thickness to be designed without being limited by the size of the drive mechanism, resulting in a thinner, lighter, and more aesthetically pleasing design. Furthermore, the backrest and lumbar region can better accommodate springs and foam, making the entire backrest more comfortable and significantly improving the overall comfort and ergonomic experience of the backrest. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the backrest mechanism of a chair according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of another state of the backrest mechanism of a chair according to an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the structure of the back frame according to an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the top waist frame according to an embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the headrest frame according to an embodiment of the present invention;

[0025] Figure 6 This is a schematic diagram of the top-waist drive device according to an embodiment of the present invention;

[0026] Figure 7 for Figure 6 A schematic diagram of the structure after the outer shell has been removed.

[0027] Figure 8 This is a schematic diagram of the backrest mechanism of a chair according to another embodiment of the present invention;

[0028] Figure 9 This is a schematic diagram of the assembly structure of the back frame, top waist frame, and top waist drive device according to another embodiment of the present invention;

[0029] Figure 10 This is a schematic diagram of the assembly structure of the back frame, headrest frame, and headrest driving device according to another embodiment of the present invention;

[0030] Figure 11 This is a schematic diagram of the top waist drive device according to another embodiment of the present invention.

[0031] In the attached diagram: 1-back frame, 11-first left rod, 12-first right rod, 13-first connecting rod, 2-top waist frame, 21-second left rod, 22-second right rod, 23-second connecting rod, 24-first serpentine spring, 3-top waist drive device, 31-outer shell, 32-first drive motor, 33-first reduction gear set, 331-first gear, 332-second gear, 333-third gear, 34-rotation output rod, 35-second drive motor, 36-angle adjuster, 4-headrest frame, 41-third left rod, 42-third right rod, 43-third connecting rod, 44-second serpentine spring, 5-headrest drive device, 6-connecting piece, 7-mounting bracket.

[0032] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0035] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0036] Please see Figures 1 to 2 , Figures 8 to 9 A chair backrest mechanism includes a back frame 1, a lumbar support frame 2, and a lumbar support drive device 3. The back frame 1 is the basic frame of the chair backrest, and the lumbar support frame 2 is the basic frame of the lumbar support mechanism, providing strong support for the user's lower back. The lumbar support frame 2 is rotatably mounted on the back frame 1. When the lumbar support frame 2 rotates forward relative to the back frame 1, it supports the user's lower back, providing lumbar support and relaxation. The lumbar support drive device 3 is located on one side of the lumbar support frame 2. The output end of the lumbar support drive device 3 is connected to the lumbar support frame 2, driving the lumbar support frame 2 to rotate relative to the back frame 1. The lumbar support drive device 3 can be mounted on the back frame 1, fixing the lumbar support drive device 3 and the back frame 1 relatively fixed. The lumbar support frame 2 rotates relative to the back frame 1 through the power transmission of the lumbar support drive device 3. Of course, in other embodiments, the top waist drive device 3 can also be installed on the top waist frame 2, so that the top waist drive device 3 and the top waist frame 2 are relatively fixed, and the top waist frame 2 and the top waist drive device 3 are rotated together relative to the back frame 1 through the power transmission of the top waist drive device 3.

[0037] By moving the lumbar support drive unit 3 from the rear of the lumbar frame 2 to the side, the heaviest part in the traditional design—the drive assembly—is successfully removed from the central core area of ​​the backrest. This frees the design of the entire backrest thickness from the limitations of the drive mechanism size, allowing it to be made thinner and more aesthetically pleasing. Furthermore, the backrest and lumbar region can better accommodate springs and foam, resulting in greater comfort for the entire backrest and significantly improving overall comfort and ergonomics.

[0038] In some embodiments, please refer to Figure 3The back frame 1 includes a first left rod 11, a first right rod 12, and a first connecting rod 13. The first left rod 11 and the first right rod 12 are made of high-strength aluminum alloy square tubing, and are arranged parallel to each other at a certain distance, forming the left and right boundaries of the main body of the back frame 1. The first connecting rod 13 is also made of metal profile, and its left and right ends can be connected to the inner walls of the first left rod 11 and the first right rod 12 respectively by welding, riveting, or screws, thereby connecting the first left rod 11 and the first right rod 12 into a strong and stable overall frame structure. When there is one first connecting rod 13, it is specifically located at the lower part of the back frame 1. Of course, two first connecting rods 13 can also be provided. When there are two connecting rods, the two first connecting rods 13 are respectively located at the upper and lower parts of the back frame 1 to further enhance the stability of the overall structure. The top waist frame 2 is rotatably mounted between the first left rod 11 and the first right rod 12, that is, within the space enclosed by the first left rod 11, the first right rod 12, and the first connecting rod 13. This frame structure design allows the back frame 1 to achieve hollowing out while ensuring sufficient support strength and rigidity, greatly reducing the overall weight, and providing ample and concealed space for the arrangement of other functional components (such as drive mechanisms, wiring harnesses, etc.), maintaining the neat and simple appearance of the back mechanism.

[0039] The back frame 1, through the combination of the first left rod 11, the first right rod 12, and the first connecting rod 13, forms a robust and hollow mounting base, constituting a stable load-bearing frame capable of reliably bearing the torque and stress generated during the operation of the lumbar support mechanism, resulting in structural stability. The hollow nature of the back frame 1 provides natural space for the lateral installation of components such as the lumbar support drive device 3, a key foundation for achieving a thin backrest design. Compared to a solid plate structure, the back frame 1 significantly reduces weight while maintaining strength. The clear frame structure and well-defined positioning of each component facilitate the installation and adjustment of parts such as the lumbar support frame 2 and the lumbar support drive device 3.

[0040] Specifically, when the top waist drive device 3 is installed on the back frame 1, there are two different ways to install the top waist drive device 3: the top waist drive device 3 is installed on the first left rod 11 or the first right rod 12.

[0041] The first method: such as Figures 1 to 2 As shown, the top waist drive device 3 is fixedly mounted on the outer wall of the first left rod 11 of the back frame 1 via a mounting bracket 7. The left side of the top waist frame 2 is connected to the output end of the top waist drive device 3. At the same time, the right side of the top waist frame 2 is rotatably connected to the first right rod 12 via a pin structure. Thus, the right side of the top waist frame 2 acts as the fulcrum for rotation, while the left side rotates under the drive of the top waist drive device 3.

[0042] The second approach: As a symmetrical alternative, the top waist drive device 3 can also be selectively fixedly mounted on the first right rod 12 of the back frame 1. In this case, the right side of the top waist frame 2 is connected to the output end of the top waist drive device 3. The left side of the top waist frame 2 is rotatably connected to the first left rod 11 via a pin structure.

[0043] The placement of the lumbar support drive device 3 offers several advantages: Flexible layout and strong adaptability: It provides two mirror-symmetrical drive layout schemes, allowing for flexible selection of the drive device's installation on the left or right side based on the overall chair design, wiring harness routing, or production assembly habits, enhancing design adaptability and versatility; Simplified structure and optimized cost: Adopting a single-sided drive and simply supported method, only one drive device and one hinge point are needed to achieve the lumbar support function. Compared to a dual-sided synchronous drive scheme, this simplifies the structure and reduces manufacturing costs and control complexity; Rational mechanics and smooth operation: The drive side provides power, while the simply supported side provides stable rotational support. The clear mechanical model ensures the smoothness and reliability of the lumbar support frame 2's movement.

[0044] In some embodiments, please refer to Figure 4 The top waist frame 2, as the core component that directly contacts and supports the user's waist, comprises a second left rod 21, a second right rod 22, a second connecting rod 23, and a first serpentine spring 24. The second left rod 21 and the second right rod 22 are preferably made of lightweight yet strong materials (such as aluminum alloy or engineering plastics), and are arranged parallel to each other at a certain distance, together forming the left and right boundaries of the top waist frame 2. The number of second connecting rods 23 can be one or more, and their ends are fixedly connected to the inner walls of the second left rod 21 and the second right rod 22 by welding, riveting, or screwing, thereby connecting the second left rod 21 and the second right rod 22 into a stable rectangular or near-rectangular frame body, ensuring the integrity and strength of the structure.

[0045] Within the frame space enclosed by the second left rod 21, the second right rod 22, and the second connecting rod 23, multiple first serpentine springs 24 are provided. These first serpentine springs 24 are preferably made of high-carbon manganese steel wire, possessing good elastic recovery properties. They are arranged parallel to each other and laterally tensioned between the second left rod 21 and the second right rod 22. Each first serpentine spring 24 typically has hanging loops at both ends, which are securely installed and maintain preload by means of dedicated hooks or by directly fitting them onto pre-set protrusions or holes on the second left rod 21 and the second right rod 22.

[0046] When the user leans back, the lumbar region is compressed by multiple first serpentine springs 24, causing them to elastically deform and providing gentle, supportive force. When the pressure is released, the first serpentine springs 24 return to their original shape under their own elasticity. This structure integrates the stability of the frame with the comfort of the elastic elements. Its advantages are: excellent elasticity and high comfort: The multiple first serpentine springs 24 work together to provide a uniform and elastic support surface, which can well adapt to the lumbar curves of users of different body types, dynamically respond to lumbar movements, and enhance comfort. High breathability: The gaps between the first serpentine springs 24 and the hollow structure of the frame form natural ventilation channels, greatly improving air circulation in the back and avoiding stuffiness. Lightweight structure: Compared with solid plastic or wooden supports, this structure significantly reduces weight while ensuring sufficient support. Good durability: As a mature elastic element, the serpentine spring has excellent fatigue resistance and a long service life. Of course, in the finished chair, the top lumbar frame 2 is also wrapped with sponge to improve comfort.

[0047] In this invention, the top waist drive device 3 can have multiple embodiments, and the following two embodiments are provided for description.

[0048] First implementation method

[0049] Please see Figures 1 to 2 , Figure 6-7 The top-and-waist drive device 3 includes a housing 31, a first drive motor 32, a first reduction gear set 33, and a rotating output rod 34. The housing 31 is hollow, and the output end of the first drive motor 32 and the first reduction gear set 33 are both located inside the housing 31. The output shaft of the first drive motor 32 has teeth that mesh with the first reduction gear set 33. The rotating output rod 34 connects the first reduction gear set 33 and the top-and-waist frame 2. When the first drive motor 32 starts, its output shaft rotates; the teeth on the output shaft of the first drive motor 32 drive the first reduction gear set 33 to rotate, and finally, the rotating output rod 34 drives the top-and-waist frame 2 to rotate relative to the back frame 1, thus achieving the top-and-waist function. The top-and-waist drive device 3 has a compact structure, a high degree of integration, and is easy to assemble onto the back frame 1.

[0050] For details, please refer to Figure 7The first reduction gear set 33 includes a first gear 331, a second gear 332, and a third gear 333. The first gear 331 meshes with the teeth on the output shaft of the first drive motor 32. The second gear 332 is located on one side of the first gear 331 and is coaxial with the first gear 331; the second gear 332 and the first gear 331 are an integral structure, and the outer diameter of the second gear 332 is smaller than the outer diameter of the first gear 331. The number of teeth of the second gear 332 is greater than the number of teeth of the first gear 331. The third gear 333 is sleeved on the rotating output rod 34 and meshes with the second gear 332. The first drive motor 32 starts, and its output shaft rotates. The teeth on the output shaft of the first drive motor 32 drive the first gear 331 to rotate. The second gear 332 rotates synchronously with the first gear 331, and the rotation of the second gear 332 drives the third gear 333 to rotate. The third gear 333 is sleeved on the rotating output rod 34, so the rotating output rod 34 rotates synchronously with the third gear 333. One end of the rotating output rod 34 is connected to the top waist frame 2, thus ultimately realizing the rotation of the top waist frame 2 relative to the back frame 1. The first reduction gear set 33 is set in this way to reduce the rotation of the output shaft of the first drive motor 32, making the adjustment of the top waist frame 2 more stable and smooth. Moreover, the first reduction gear has a compact structure and can be easily assembled into the outer casing 31.

[0051] Second implementation method

[0052] Please see Figure 8 , Figure 9 and Figure 11 The top-waist drive device 3 includes a second drive motor 35 and an angle adjuster 36. The second drive motor 35 is mounted on the back frame 1, and the output end of the angle adjuster 36 is connected to the top-waist frame 2. The second drive motor 35 can drive the angle adjuster 36 to adjust the angle of the top-waist frame 2. Compared with the first embodiment, the top-waist drive device 3 in the second embodiment also includes an angle adjuster 36. In this embodiment, the output end of the second drive motor 35 is connected to the angle adjuster 36 for transmission. The angle adjuster 36 can reduce the speed of the output end of the second motor and transmit it to the top-waist frame 2. The angle adjuster 36 can be a commercially available electric angle adjuster, such as the D66-16 electric angle adjuster. In this embodiment, the second drive motor 35 can be a common motor, or the top-waist drive device 3 of embodiment one can be used as the second drive motor 35 of embodiment two. By setting the angle adjuster 36, not only can speed reduction be achieved, but the selection of the second drive motor 35 can also be more flexible, and the rotation of the top-waist frame 2 can be ensured to be smooth and stable.

[0053] In some embodiments, please refer to Figures 1 to 2 , Figure 8 and Figure 10The chair's backrest mechanism also includes a headrest frame 4 and a headrest drive mechanism 5. The headrest frame 4 is rotatably mounted on the back frame 1 and located above the lumbar support frame 2. The headrest drive mechanism 5 is located on one side of the headrest frame 4 and is used to drive the headrest frame 4 to rotate relative to the back frame 1. Based on the electric lumbar support, an electric headrest adjustment function has been added, achieving zoned intelligent support for the waist and neck, significantly improving the overall comfort and ergonomics of the chair. Positioning the headrest drive mechanism 5 to the side of the headrest frame 4, rather than directly behind it, avoids the headrest drive mechanism occupies space in the head support area, facilitating a thinner design for the headrest area and ensuring both aesthetics and comfort. The side-mounted drive mechanism is structurally sound, provides direct power transmission, and operates smoothly and reliably.

[0054] The headrest drive device 5 is mounted on the back frame 1 or the headrest frame 4. The headrest drive device 5 can be mounted on the back frame 1, so that the headrest drive device 5 and the back frame 1 are relatively fixed, and the headrest frame 4 rotates relative to the back frame 1 through the power transmission of the headrest drive device 5. Of course, in other embodiments, such as... Figure 1 and Figure 2 As shown, the headrest drive device 5 can also be installed on the headrest frame 4, so that the headrest drive device 5 and the headrest frame 4 are relatively fixed, and the headrest frame 4 and the headrest drive device 5 rotate together relative to the back frame 1 through the power transmission of the headrest drive device 5.

[0055] Please see Figure 5 The headrest frame 4, as a support component that directly contacts the user's head or neck, comprises a third left rod 41, a third right rod 42, a third connecting rod 43, and second serpentine springs 44. The third left rod 41 and the third right rod 42 are made of lightweight, high-strength materials (such as aluminum alloy profiles), and are arranged parallel to each other at a certain distance, forming the left and right vertical boundaries of the headrest frame 4. The third connecting rod 43 is located at the upper part of the headrest frame 4, and its two ends are fixedly connected to the inner walls of the third left rod 41 and the third right rod 42 by welding or screws, thereby connecting the third left rod 41 and the third right rod 42 into a sturdy rectangular frame body, ensuring the overall stability of the structure and sufficient bending strength. Within the frame space enclosed by the third left rod 41, the third right rod 42, and the third connecting rod 43, multiple second serpentine springs 44 are provided. These second serpentine springs 44 are made of highly elastic spring steel wire, and are arranged parallel to each other and laterally tensioned between the third left rod 41 and the third right rod 42. Each second serpentine spring 44 has lugs at both ends, which are fixed to preset mounting points on the third left rod 41 and the third right rod 42 by direct hooks or using connectors. When the user's head rests against the headrest, pressure is applied to the second serpentine spring 44, causing it to elastically deform, thereby providing a soft and conforming adaptive support. After the pressure is released, the second serpentine spring 44 quickly returns to its original shape.

[0056] Multiple second serpentine springs 44 together form a support surface with good elasticity and a certain degree of undulation, effectively dispersing head pressure and providing a slightly bouncy, comfortable feel, avoiding the discomfort caused by rigid support. The mesh-like gaps between the second serpentine springs 44 constitute an efficient airflow channel, greatly improving ventilation and heat dissipation in the head and neck area, keeping the area dry even after prolonged use. The frame combined with the spring structure achieves significant weight reduction while ensuring support strength, reducing the weight of the top of the back mechanism and facilitating drive and adjustment. The serpentine spring structure has excellent fatigue resistance, capable of withstanding long-term repeated compression and recovery, resulting in a long service life. This structural form, together with the previously mentioned top waist frame 2 (using the first serpentine spring 24), forms a unified design language and functional characteristics, enhancing the overall aesthetics of the product.

[0057] In some embodiments, please refer to Figure 1 and Figure 2 A connecting piece 6 is installed on the upper end of the back frame 1, and the headrest frame 4 is rotatably mounted on the connecting piece 6. A pair of connecting pieces 6 are provided on the upper end of the back frame 1. These connecting pieces 6 are preferably metal stampings or machined parts, and they are respectively fixedly installed on the inner sides of the first left rod 21 and the first right rod 22 at the upper end of the back frame 1 by screw connection. The two connecting pieces 6 are symmetrical and coaxial. Each connecting piece 6 has a hinge hole. In the illustrated embodiment, the lower end of the third right rod 42 of the headrest frame 4 is rotatably connected to the connecting piece 6 on the first right rod 21 via a pin structure; the headrest drive device 5 is installed on the third left rod 41, and the output end of the headrest drive device 5 is fixedly connected to the connecting piece 6 on the first left rod 11; when the headrest drive device 5 drives its output end to rotate, since the output end is fixedly connected to the connecting piece 6, the headrest drive device 5 and the headrest frame 4 rotate synchronously relative to the connecting piece 6 and the back frame 1. Of course, in other embodiments, the headrest drive device 5 can be mounted on the third right rod 42, and the lower end of the third left rod 41 of the headrest frame 4 can be rotatably connected to the connecting piece 6 on the first left rod 11 via a pin structure. In some embodiments, please refer to... Figure 1 , Figure 2 and Figure 8 The headrest drive device 5 has the same structure as the lumbar support drive device 3. Therefore, the specific structure of the headrest drive device 5 can be found in the above description of the lumbar support drive device 3, and will not be repeated here. The headrest drive device 5 and the lumbar support drive device 3 adopt the same structure, which significantly improves the standardization of the product, assembly efficiency, and ease of maintenance.

[0058] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A backrest mechanism for a chair, characterized in that, It includes a back frame (1), a top waist frame (2) and a top waist drive device (3). The top waist frame (2) is rotatably mounted on the back frame (1). The top waist drive device (3) is located on one side of the top waist frame (2) and its output end is connected to the top waist frame (2) to drive the top waist frame (2) to rotate relative to the back frame (1).

2. The backrest mechanism of a chair according to claim 1, characterized in that, The top waist drive device (3) includes a housing (31), a first drive motor (32), a first reduction gear set (33), and a rotating output rod (34). The first reduction gear set (33) is installed inside the housing (31). The output shaft of the first drive motor (32) extends into the housing (31), and the teeth on the output end mesh with the first reduction gear set (33). The rotating output rod (34) is connected to the first reduction gear set (33) and the top waist frame (2).

3. The backrest mechanism of a chair according to claim 2, characterized in that, The first reduction gear set (33) includes a first gear (331), a second gear (332) and a third gear (333). The first gear (331) meshes with the teeth on the output shaft of the first drive motor (32). The second gear (332) is disposed on one side of the first gear (331) and is coaxial with the first gear (331). The number of teeth of the second gear (332) is greater than the number of teeth of the first gear (331). The third gear (333) is sleeved on the rotating output rod (34) and meshes with the second gear (332).

4. The backrest mechanism of a chair according to claim 1, characterized in that, The top waist drive device (3) includes a second drive motor (35) and an angle adjuster (36). The output end of the angle adjuster (36) is connected to the top waist frame (2). The second drive motor (35) can drive the angle adjuster (36) to adjust the angle of the top waist frame (2).

5. The backrest mechanism of a chair according to claim 1, characterized in that, The back frame (1) includes a first left rod (11), a first right rod (12) and a first connecting rod (13). The first left rod (11) and the first right rod (12) are opposite to each other and spaced apart. The two ends of the first connecting rod (13) are respectively connected to the first left rod (11) and the first right rod (12). The top waist frame (2) is located between the first left rod (11) and the first right rod (12).

6. The backrest mechanism of a chair according to claim 5, characterized in that, The top waist drive device (3) is mounted on the first left rod (11), and the left side of the top waist frame (2) is connected to the output end of the top waist drive device (3), and the right side is rotatably connected to the first right rod (12); or, The top waist drive device (3) is installed on the first right rod (12). The right side of the top waist frame (2) is connected to the output end of the top waist drive device (3), and the left side is rotatably connected to the first left rod (11).

7. The backrest mechanism of a chair according to claim 1, characterized in that, The top waist frame (2) includes a second left rod (21), a second right rod (22), a second connecting rod (23), and a first serpentine spring (24). The second left rod (21) and the second right rod (22) are arranged opposite to each other and spaced apart. The two ends of the second connecting rod (23) are respectively connected to the second left rod (21) and the second right rod (22). Multiple first serpentine springs (24) are provided between the second left rod (21) and the second right rod (22).

8. The backrest mechanism of a chair according to claim 1, characterized in that, It also includes a headrest frame (4) and a headrest drive device (5), the headrest frame (4) being rotatably mounted on the back frame (1) and located above the top waist frame (2), and the headrest drive device (5) being located on one side of the headrest frame (4) and used to drive the headrest frame (4) to rotate relative to the back frame (1).

9. The backrest mechanism of a chair according to claim 8, characterized in that, The headrest drive device (5) is mounted on the back frame (1) or the headrest frame (4).

10. The backrest mechanism of a chair according to claim 8, characterized in that, A connecting piece (6) is installed at the upper end of the back frame (1), and the headrest frame (4) is rotatably installed on the connecting piece (6).

11. The backrest mechanism of a chair according to claim 8, characterized in that, The structure of the headrest drive device (5) is the same as that of the top waist drive device (3).

12. The backrest mechanism of a chair according to claim 8, characterized in that, The headrest frame (4) includes a third left rod (41), a third right rod (42), a third connecting rod (43), and a second serpentine spring (44). The third left rod (41) and the third right rod (42) are arranged opposite to each other and spaced apart. The two ends of the third connecting rod (43) are respectively connected to the third left rod (41) and the third right rod (42). Multiple second serpentine springs (44) are provided between the third left rod (41) and the third right rod (42).

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