A lumbar support mechanism

Abstract

The present invention discloses a lumbar support mechanism, which is arranged on a chair back frame; the lumbar support mechanism comprises a lumbar support frame, a lumbar support surface layer fixed on the lumbar support frame; the lumbar support frame comprises an upper frame, a lower frame, two upper side frame portions, two lower side frame portions, and two middle side frame portions made of elastic materials and connected to the upper side frame portions and the lower side frame portions; the side frame gradually bulges forward from the upper end of the upper side frame portion, the lower end of the lower side frame portion to the middle side frame portion; the lower frame has at least one connecting seat arranged on the chair back frame. The present invention has the beneficial effect that the lumbar can be fully supported at all times in different sitting postures of the user, thereby improving comfort.

Description

Technical Field

[0001] The invention relates to a lumbar support mechanism, belonging to the technical field of chairs. Background Art

[0002] Many chairs, especially office chairs, are provided with a lumbar support mechanism to support the user's waist.

[0003] For example, a patent application with publication number CN211431832U discloses a lumbar support adjustment mechanism, which is characterized in that it includes a back frame, a support assembly and a lumbar support assembly; the back frame includes vertical rods spaced apart on the left and right, a back frame cross bar is connected between the middle parts of the left and right vertical rods, a bracket is provided in the middle of the back frame cross bar, and the bracket extends downwardly beyond the back frame cross bar; the support assembly is arranged on the bracket, the support assembly includes a support seat, the support seat and the bracket are slidably matched; and the middle position of the lumbar support assembly is rotatably matched with the support seat.

[0004] The lumbar support component can be rotated and adjusted to achieve adaptive support for the human waist. However, the lumbar support component itself cannot be adjusted, especially the support surface of the lumbar support component cannot be adjusted, so the integrity of the lumbar support cannot match the diverse sitting postures of users. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a lumbar support mechanism which can fully support the waist of the user in different sitting postures and improve the comfort.

[0006] The present invention is achieved through the following technical solutions.

[0007] A lumbar support mechanism is arranged on a chair back frame; the lumbar support mechanism comprises a lumbar support frame and a lumbar support surface layer fixed on the lumbar support frame; the lumbar support frame comprises an upper frame, a lower frame, two upper side frame portions, two lower side frame portions, and two middle side frame portions made of elastic material and connecting the upper side frame portions and the lower side frame portions; the side frame gradually bulges forward from the upper end of the upper side frame portion, the lower end of the lower side frame portion to the middle side frame portion; the lower frame has at least one connecting seat arranged on the chair back frame.

[0008] As a further improvement of the present invention, slots are respectively provided at the upper and lower ends of the middle part of the side frame; and plug-ins are respectively provided at the lower end of the upper part of the side frame and the upper end of the lower part of the side frame and are inserted into corresponding slots.

[0009] As a further improvement of the present invention, the middle part of the side frame is provided with a fastening rod which passes through the middle part of the side frame and the insert block on the left and right sides, and the two ends of the fastening rod are respectively provided with locking structures which are attached to the left and right side surfaces of the middle part of the side frame.

[0010] As a further improvement of the present invention, a plurality of grooves are provided on the surface of the middle portion of the side frame facing the chair back frame, so as to reduce the deformation compression amount when the middle portion of the side frame is bent and deformed.

[0011] As a further improvement of the present invention, a mounting plate is provided on the front of the chair back frame, and a through slot extending from front to back is provided on the mounting plate; a mounting seat is provided on the front of the mounting plate, and a connecting seat is connected to the mounting seat; a connecting frame is provided at the rear end of the mounting seat, which passes through the through slot and extends into the chair back frame; a support plate is provided on the part of the connecting frame located in the chair back frame, and an elastic buffer is provided between the support plate and the mounting plate to support both.

[0012] As a further improvement of the present invention, the elastic buffer is configured as a columnar structure made of elastic material; the back side of the mounting plate and the front side of the support plate are respectively provided with sleeve structures that sleeve on both ends of the columnar structure.

[0013] As a further improvement of the present invention, the connecting seat and the mounting seat are rotatably connected, and the rotation axes of the two extend in the left-right direction; the connecting seat is provided with an adjustment groove and a plurality of positioning holes formed on the adjustment groove and having a width greater than the adjustment groove; the mounting plate is provided with a mounting frame located above the mounting seat, and the mounting frame is provided with an adjustment rod extending in the left-right direction, the adjustment rod passes through the adjustment groove or the positioning hole, and can be moved axially for adjustment; the adjustment rod has an adjustment portion adapted to the adjustment groove, and a positioning portion adapted to the positioning hole.

[0014] As a further improvement of the present invention, a rotational rebound structure supporting the mounting bracket and the connecting seat is provided between the mounting bracket and the connecting seat, and the rotational rebound structure is used to apply elastic force to the connecting seat so that the connecting seat is rotationally reset when the adjusting portion is located in the adjusting groove.

[0015] As a further improvement of the present invention, the mounting frame has frame plates spaced apart on the left and right, the connecting seat has a lug located between the two frame plates, and the adjustment slot and the positioning hole are arranged on the lug; the adjusting rod passes through the two frame plates, and one end of the adjusting rod is provided with a pressing structure for pressing the adjusting rod to move axially, and when the pressing structure abuts against the corresponding frame plate, the adjusting portion is located in the positioning hole or the adjusting slot; the other end of the adjusting rod is provided with a limiting structure, and when the limiting structure abuts against the corresponding frame plate, the positioning portion is located in the positioning hole; the adjusting rod is sleeved with an adjusting rebound structure, and its two ends respectively support the pressing structure and the corresponding frame plate, and the adjusting rebound structure is used to apply elastic force to the pressing structure so that the limiting structure abuts against the corresponding frame plate.

[0016] As a further improvement of the present invention, the top of the mounting seat has two seat plates spaced apart from each other on the left and right sides, and the two seat plates are respectively abutted against the inner surfaces of the two frame plates.

[0017] Beneficial effects of the present invention:

[0018] 1. By setting the middle part of the side frame with elastic material, the overall support effect of the lumbar support surface layer on the waist can be dynamically adjusted according to the change of the depth of the user leaning against the chair back frame and the physiological curve of the lumbar spine of different users, thereby improving the user's comfort;

[0019] 2. By setting up the connecting frame and the support plate, the lumbar support mechanism can match the user's different sitting postures (front and back positions), so that the lower part of the surface layer, the middle part of the surface layer, and the upper part of the surface layer can be dynamically adjusted to always support the user's lower waist, middle waist, and upper waist; in addition, by setting up elastic buffer parts, the dynamic adjustment of the lower part of the surface layer can be buffered, thereby comprehensively improving the user's comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings to help understand the purpose and advantages of the present invention, wherein:

[0021] Figure 1 It is a front view of the lumbar support mechanism;

[0022] Figure 2 is a side view of the lumbar support mechanism;

[0023] Figure 3 This is a schematic diagram of the partial disassembly of the waist support frame;

[0024] Figure 4 It is a front view of the connecting seat and the mounting frame;

[0025] Figure 5 A three-dimensional schematic diagram of the connecting seat and the mounting frame

[0026] Figure 6 It is a side view of the connecting seat, the connecting frame and the supporting plate;

[0027] Figure 7 It is a three-dimensional schematic diagram of the lug and the adjustment rod. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below based on the accompanying drawings and implementation examples.

[0029] The directional terms such as up, down, left, right, front, back, front, back, top, bottom, etc. mentioned or may be mentioned in this specification are defined relative to the structures shown in the drawings. The words "inside" and "outside" refer to the direction toward or away from the geometric center of a specific component, respectively. They are relative concepts, and therefore may change accordingly according to different locations and different usage conditions. Therefore, these or other directional terms should not be interpreted as restrictive terms.

[0030] Reference Figure 1-Figure 7A lumbar support mechanism is provided on a chair back frame 1, and comprises a lumbar support frame 2 and a lumbar support surface layer 5 fixed on the lumbar support frame 2. The lumbar support surface layer 5 is generally made of mesh, genuine leather and artificial leather, among which mesh is more commonly used, having good air permeability and elasticity, and the user is more comfortable when supported on the mesh. The mesh is preferably woven from multiple layers of polyester material, which is more cost-effective in production and manufacturing.

[0031] The waist support frame 2 includes an upper frame 21, a lower frame 22, and two side frames 23, which are enclosed together to form a frame-like structure. The side frames 23 further include a side frame upper portion 231, a side frame middle portion 233, and a side frame lower portion 232 that are sequentially connected. The upper frame 21, the lower frame 22, the two side frame upper portions 231, and the two side frame lower portions 232 of the waist support frame 2 are all made of hard materials, specifically polypropylene, which has good hardness and certain toughness, and as the main structure of the waist support frame 2, can provide stable support for the waist.

[0032] The middle part 233 of the side frame is made of elastic material, specifically rubber material, and has good compression deformation and elastic reset performance. The side frame 23 gradually bulges forward from the upper end of the side frame upper part 231, the lower end of the side frame lower part 232 to the middle part 233 of the side frame. When viewed from the side, the side frame 23 presents an arc-shaped structure. The lower frame 22 of the lumbar support frame 2 has at least one connecting seat 31, and the connecting seat 31 is arranged on the chair back frame 1. Considering the stability of the lumbar support mechanism as a whole connected to the chair back frame 1, especially to avoid the left and right ends of the lumbar support mechanism from shaking back and forth when the user's waist is leaning on the lumbar support structure, two connecting seats 31 are arranged, and they are symmetrically arranged with respect to the lower frame 22.

[0033] The edge of the waist support frame 2 is provided with a slot (not shown in the figure), and the edge of the waist support surface layer is inserted into the slot so that the waist support surface layer 5 is fixed on the waist support frame 2. The upper frame 21, the lower frame 22, the upper part of the side frame 231, and the lower part of the side frame 232 are made of hard materials, so the clamping strength is better, while the middle part 233 of the side frame is made of elastic material, so the clamping strength is relatively weak. Glue can be applied to the slot of the middle part 233 of the side frame to improve the clamping strength, so that the fixing strength of the middle part 233 of the side frame to the waist support surface layer is basically the same as that of the other parts. Even if the fixing strength of the middle part 233 of the side frame is still weaker than that of the other parts, since the middle part 233 of the side frame only occupies a small part of the waist support frame, the impact on the overall fixed connection strength of the waist support surface layer is also very small.

[0034] The lumbar support surface layer 5 is divided into an upper surface layer 51, a middle surface layer 52, and a lower surface layer 53, wherein the edge of the upper surface layer 51 is fixed to the upper frame 21 and the upper portions 231 of the two side frames, the edge of the lower surface layer 53 is fixed to the lower frame 22 and the lower portions 232 of the two side frames, and the edges of the middle surface layer 52 are respectively fixed to the middle portions 233 of the two side frames. When the user's waist is against the lumbar support mechanism, the user's middle waist is supported on the middle surface layer 52, the lower waist near the back is supported on the upper surface layer 51, and the lower waist near the buttocks is supported on the lower surface layer 53. If the user completely leans on the chair back frame 1, that is, when the user's back is against the chair back frame 1, the middle part 233 of the side frame will be compressed and deformed, causing the two upper parts 231 of the side frames, the upper frame 21 and the upper part 51 of the surface layer to flip backwards. In this process, the curvature of the surface of the middle part 52 of the surface layer increases, so the support strength of the middle part 52 of the surface layer for the middle waist can remain unchanged, and the lower part 53 of the surface layer and the upper part 51 of the surface layer also always keep in contact with the lower waist and the upper waist. In general, by setting the middle part 233 of the side frame of elastic material, the overall support effect of the lumbar support surface layer 5 for the waist can be dynamically adjusted according to the change of the depth of the user leaning against the chair back frame 1 and the physiological curve of the lumbar spine of different users, thereby improving the comfort of the user.

[0035] In addition, the middle waist area roughly corresponds to the area from the third to the fifth lumbar vertebrae of the human body. Therefore, when the user leans against the chair back frame 1 and the curvature of the arc of the middle portion 52 of the surface layer increases, the sharpness and stimulation of the middle portion 52 of the surface layer supporting the area from the third to the fifth lumbar vertebrae are correspondingly enhanced, which is very suitable for users with lumbar discomfort.

[0036] The upper and lower ends of the middle part 233 of the side frame are respectively provided with slots 2-1, and the lower end of the upper part 231 of the side frame and the upper end of the lower part 232 of the side frame are respectively provided with plug-in blocks 2-2 inserted into the corresponding slots 2-1. Through the insertion and coordination of the plug-in blocks 2-2 and the slots 2-1, and the lumbar support surface layer is simultaneously fixed to the upper part 231 of the side frame, the middle part 233 of the side frame, and the lower part 232 of the side frame, the connection between the middle part 233 of the side frame and the upper part 231 of the side frame and the lower part 232 of the side frame is better, and loosening of the middle part 233 of the side frame can be avoided.

[0037] In order to further enhance the connection firmness between the middle part 233 of the side frame and the upper part 231 and the lower part 232 of the side frame, the middle part 233 of the side frame is provided with a fastening rod 2-3, and the fastening rod 2-3 passes through the middle part 233 of the side frame and the plug block 2-2 on the left and right sides, and locking structures 2-4 are respectively provided at both ends, and the two locking structures 2-4 are respectively abutted against the left and right sides of the middle part 233 of the side frame. The locking structure 2-4 can be slightly tightened so that the part of the side of the side frame 23 that is affixed is slightly squeezed inward and deformed, thereby improving the fastening effect. The fastening rod 2-3 and the locking structure 2-4 are preferably made of metal materials, such as stainless steel, to further improve their fastening effect. More specifically, the locking structure 2-4 can be set as a knob, which is sleeved on the end of the fastening rod 2-3 and the two are threadedly matched.

[0038] The middle portion 233 of the side frame is in an arc-shaped structure, and its bending degree will increase when it is deformed by pressure. Therefore, the deformation compression of the inner arc surface of the middle portion 233 of the side frame is relatively large. This part is more prone to aging after long-term use. Therefore, a plurality of grooves 2331 are provided on the surface of the middle portion 233 of the side frame facing the chair back frame 1. The grooves 2331 extend in the left-right direction and are arranged side by side, thereby reducing the deformation compression of the middle portion 233 of the side frame when it is bent and deformed, which is beneficial to extending the service life of the middle portion 233 of the side frame.

[0039] The seat back frame 1 is provided with a mounting plate 11, which is in the shape of a square plate that is wide at the top and bottom and narrow at the left and right, and is fixedly connected to the front of the seat back frame 1 by fasteners. The mounting plate 11 is provided with a through slot 12 that passes through the front and back, and there are two through slots 12, which are spaced apart from the left and right and extend vertically. The front of the mounting plate 11 is provided with a mounting seat 32, and a connecting seat 31 is connected to the mounting seat 32. The area behind the seat back frame 1 corresponding to the mounting plate 11 is a hollow structure, and a connecting frame 33 is provided at the rear end of the mounting seat 32, and the connecting frame 33 passes through the through slot 12 and extends into the hollow area of ​​the seat back frame 1. The part of the connecting frame 33 located in the seat back frame 1 is provided with a support plate 34, and an elastic buffer 35 is provided between the support plate 34 and the mounting plate 11 to support the two. The support plate 34 is in the shape of a square plate that is wide at the top and bottom and narrow at the left and right, and there are two elastic buffers 35, which are spaced apart from each other from top to bottom, so that its supporting effect on the support plate 34 is more stable.

[0040] When the waist support mechanism is not under stress, under the elastic force of the elastic buffer 35, the distance between the support plate 34 and the mounting plate 11 is the largest, that is, the mounting seat 32 is closely attached to the mounting plate 11, and the waist support mechanism is at the rearmost position. When the user sits on the seat and leans back, the lower waist is fully supported by the lower part 53 of the surface layer. At this time, if the user leans back, the middle part 233 of the side frame is compressed and bent, so that the curvature of the surface middle part 52 increases, and the upper part 51 of the surface layer flips backward, and the middle waist and upper waist are fully supported by the middle part 52 and the upper part 51 of the surface layer. When the user sits forward and there is a gap between the lower waist and the lower part 53 of the surface layer, if the user leans back at this time, the middle waist and the upper waist are pressed on the middle part 52 and the upper part 51 of the surface layer respectively, so that the middle part 233 of the side frame is compressed and bent, and the upper part 51 of the surface layer flips backward and keeps supporting the upper waist, and the rebound characteristics of the middle part 233 of the side frame will exert a forward force on the lower part 232 of the side frame, so that the lower part 53 of the surface layer flips forward until it supports the lower waist. In this process, the distance between the mounting plate 11 and the support plate 34 is continuously reduced, so that the elastic buffer 35 is gradually compressed, which plays a buffering role, avoids the lower part 53 of the surface layer from quickly hitting the lower waist, and improves the user's comfort. In general, by providing the connecting frame 33 and the support plate 34, the lumbar support mechanism can match the user's different sitting postures (front and back positions), so that the lower part 53 of the surface layer, the middle part 52 of the surface layer, and the upper part 51 of the surface layer can be dynamically adjusted to always support the user's lower waist, middle waist, and upper waist; in addition, by providing the elastic buffer 35, the dynamic adjustment of the lower part 53 of the surface layer can be buffered, thereby comprehensively improving the user's comfort.

[0041] Furthermore, the elastic buffer 35 is configured as a columnar structure made of elastic material, and specifically a rubber column can be used; the back of the mounting plate 11 and the front of the support plate 34 are respectively provided with a sleeve structure 351 that sleeves on both ends of the columnar structure to prevent it from falling off.

[0042] The connecting seat 31 and the mounting seat 32 are rotatably connected, and the rotation axis of the two extends in the left-right direction. The connecting seat 31 is provided with an adjustment slot 311 and a plurality of positioning holes 312 formed on the adjustment slot 311 and having a width greater than the adjustment slot 311. In the present application, the positioning holes 312 are circular and are provided with two, respectively formed at the two ends of the adjustment slot 311. The number and layout of the positioning holes 312 can be reasonably set according to the application requirements of the product. The mounting plate 11 is provided with a mounting frame 41 above the mounting seat 32. The mounting frame 41 is provided with an adjustment rod 42 extending in the left-right direction. The adjustment rod 42 passes through the adjustment slot 311 or the positioning hole 312 and can be moved and adjusted in the axial direction. The adjustment rod 42 has a 421 adapted to the adjustment slot 311 and a positioning portion 422 adapted to the positioning hole 312. When the positioning part 422 is inserted into the positioning hole 312, the lumbar support mechanism is in a locked state. When the adjusting rod 42 is pulled axially so that 421 is located in the positioning hole 312, 421 can slide from the positioning hole 312 into the adjusting groove 311, so that the connecting seat 31 can be rotated and adjusted around its rotation axis. When 421 slides into another positioning hole 312, the adjusting rod 42 is pulled in the opposite direction so that the positioning part 422 is inserted into the positioning hole 312, thereby locking the lumbar support mechanism again. Through the rotation adjustment of the connecting seat 31, the front and rear position of the middle part 52 of the surface layer can be adjusted. In combination with the user's sitting posture (front and back), when the user's waist is completely against the lumbar support surface layer 5, the curvature of the surface middle part 52 will be different, thereby adjusting the sharpness of the middle part 52 of the surface layer to the third lumbar vertebra to the fifth lumbar vertebra area. For users with lumbar discomfort, the connecting seat 31 can be rotated and adjusted so that the position of the middle part 52 of the surface layer is more forward.

[0043] Furthermore, a rotational rebound structure 43 supporting the mounting frame 41 and the connecting seat 31 is provided between the mounting frame 41 and the connecting seat 31. The rotational rebound structure 43 is used to apply elastic force to the connecting seat 31, so that the connecting seat 31 is rotated and reset when the 421 is located in the adjustment groove 311. After the rotational reset, the position of the middle part 52 of the surface layer is the most forward. Therefore, the initial state of the lumbar support mechanism of the present application is more suitable for users with lumbar discomfort. In addition, the rotational rebound structure 43 is preferably a compression spring.

[0044] More specifically, the mounting frame 41 has frame plates 411 spaced apart from each other on the left and right sides, the connecting seat 31 has a lug 313 located between the two frame plates 411, the adjusting slot 311 and the positioning hole 312 are arranged on the lug 313, the adjusting rod 42 passes through the two frame plates 411, and one end of the adjusting rod 42 is provided with a pressing structure 42-1 for pressing to make the adjusting rod 42 move axially, and when the pressing structure 42-1 abuts against the corresponding frame plate 411, the 421 is located in the positioning hole 312. 12 or adjustment slot 311, the other end of the adjustment rod 42 is provided with a limiting structure 42-2, when the limiting structure 42-2 abuts against the corresponding frame plate 411, the positioning portion 422 is located in the positioning hole 312, the adjustment rod 42 is sleeved with an adjustment rebound structure 42-3, the two ends of which respectively support the pressing structure 42-1 and the corresponding frame plate 411, the adjustment rebound structure 42-3 is used to apply elastic force to the pressing structure 42-1, so that the limiting structure 42-2 abuts against the corresponding frame plate 411. The pressing structure 42-1 is arranged at the outer end of the adjustment rod 42, which is convenient for users to press.

[0045] In addition, the top of the mounting seat 32 has two seat plates 321 spaced apart from each other. The two seat plates 321 are respectively abutted against the inner surfaces of the two frame plates 411. The frame plates 411 guide the seat plates 321, so that the forward and backward movement of the connecting frame 33 is smoother.

[0046] Finally, it should be noted that the above implementation cases are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned implementation cases, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned implementation cases, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the implementation cases of the present invention.

Claims

1. A lumbar support mechanism, arranged on a chair back frame; the lumbar support mechanism comprises a lumbar support frame and a lumbar support surface layer fixed on the lumbar support frame; characterized in that: The waist support frame includes an upper frame, a lower frame, two upper side frames, two lower side frames, and two middle side frames made of elastic material and connecting the upper side frames and the lower side frames; the side frames gradually bulge forward from the upper end of the upper side frame, the lower end of the lower side frame to the middle of the side frames; the lower frame has at least one connecting seat arranged on the seat back frame; the front side of the seat back frame is provided with a mounting plate, and the mounting plate is provided with a through slot running through the front and back; the front side of the mounting plate is provided with a mounting seat, and the connecting seat is connected to the mounting seat; the rear end of the mounting seat is provided with a connecting frame passing through the through slot and extending into the seat back frame; the part of the connecting frame located in the seat back frame is provided with a support plate, and an elastic buffer supporting the two is provided between the support plate and the mounting plate; the connecting seat and the mounting seat are rotatably connected, and the rotation axis of the two extends in the left-right direction; the connecting seat is provided with an adjustment slot, a plurality of positioning holes formed on the adjustment slot and having a width greater than the adjustment slot ; The mounting plate is located above the mounting seat and a mounting bracket is provided, and the mounting bracket is provided with an adjusting rod extending in the left and right directions, the adjusting rod passes through the adjusting slot or the positioning hole, and can be moved and adjusted in the axial direction; the adjusting rod has an adjusting portion adapted to the adjusting slot and a positioning portion adapted to the positioning hole; the mounting bracket has a frame plate spaced apart from the left and right, the connecting seat has a lug located between the two frame plates, and the adjusting slot and the positioning hole are arranged on the lug; the adjusting rod passes through the two frame plates, and one end of the adjusting rod is provided with a pressing structure for pressing so that the adjusting rod moves axially when the pressing structure abuts against the corresponding frame plate; the other end of the adjusting rod is provided with a limiting structure, and when the limiting structure abuts against the corresponding frame plate, the positioning portion is located in the positioning hole; the adjusting rod is sleeved with an adjusting rebound structure, and its two ends respectively support the pressing structure and the corresponding frame plate, and the adjusting rebound structure is used to apply elastic force to the pressing structure so that the limiting structure abuts against the corresponding frame plate.

2. The lumbar support mechanism according to claim 1, characterized in that: Slots are respectively arranged at the upper and lower ends of the middle part of the side frame; and plug-in blocks which are inserted into corresponding slots are respectively arranged at the lower end of the upper part of the side frame and the upper end of the lower part of the side frame.

3. The lumbar support mechanism according to claim 2, characterized in that: The middle part of the side frame is provided with a fastening rod which passes through the middle part of the side frame and the insert block on the left and right sides, and the two ends of the fastening rod are respectively provided with locking structures which are close to the left and right side surfaces of the middle part of the side frame.

4. The lumbar support mechanism according to claim 1, characterized in that: A plurality of grooves are arranged on the surface of the middle portion of the side frame facing the chair back frame, so as to reduce the deformation compression amount when the middle portion of the side frame is bent and deformed.

5. The lumbar support mechanism according to claim 1, characterized in that: The elastic buffer is a columnar structure made of elastic material; the back of the mounting plate and the front of the support plate are respectively provided with sleeve structures for sleeve-connecting the two ends of the columnar structure.

6. The lumbar support mechanism according to claim 1, characterized in that: A rotational rebound structure supporting the mounting frame and the connecting seat is provided between the mounting frame and the connecting seat, and the rotational rebound structure is used to apply elastic force to the connecting seat so that the connecting seat is rotated and reset when the adjusting portion is located in the adjusting groove.

7. The lumbar support mechanism according to claim 6, characterized in that: The top of the mounting seat is provided with two seat plates spaced apart from each other, and the two seat plates are respectively abutted against the inner surfaces of the two frame plates.

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