Waist rest stepless adjusting mechanism

Abstract

The utility model discloses a waist rest stepless adjusting mechanism which comprises a backrest assembly and a waist rest assembly, and the waist rest assembly is installed on the front side of the backrest assembly through a connecting rod assembly. The connecting rod assembly comprises a front swing part and a rear swing part which are parallel front and back, the upper ends of the front swing part and the rear swing part are hinged to one of the backrest assembly and the waist rest assembly, and the lower ends of the front swing part and the rear swing part are hinged to the other one of the backrest assembly and the waist rest assembly; a locking device is further arranged in the connecting rod assembly and comprises a telescopic part, the two ends of the telescopic part are hinged to any two of the backrest assembly, the waist rest assembly, the front swing part and the rear swing part respectively, the telescopic part has a movable state and a locking state which can be switched, and the telescopic part can be locked in the movable state. The telescopic piece responds to front-back rotation of the front swing piece and the rear swing piece to stretch and change the length. In the locking state, the length of the telescopic piece is fixed, so that the front swing piece and the rear swing piece are restrained and cannot continue to rotate.

Description

Technical Field

[0001] The utility model relates to the technical field of seats, in particular to a lumbar support stepless adjustment mechanism. Background Art

[0002] Lumbar spine health is a common concern in today's society. Both children and adults need to study or work at a desk for a long time. Since the backrest of the chair cannot support the waist that bends forward, the waist is prone to fatigue when it is not supported for a long time, and even lumbar scoliosis occurs, which eventually leads to a series of lumbar diseases. In order to maintain lumbar spine health, existing chairs usually add a lumbar support to the backrest. When the user sits upright, the lumbar support fits and supports the user's waist, thereby effectively relieving waist fatigue and avoiding lumbar scoliosis. However, for users of different body shapes or sitting postures, there is more or less difference in the distance between their waist and the backrest. As a result, if the position of the lumbar support is fixed, the lumbar support may not fit the user's waist or the lumbar support may be pushed out too far forward, which will not meet the needs of the majority of users.

[0003] In order to solve the above problems, the existing patent provides a chair with a lumbar support adjustment function (application number: CN201710114538.9). The chair back is installed with a support member (i.e., a lumbar support) through a folding device. The folding device includes a fixed plate and a connecting arm. The fixed plate and the connecting arm are hinged so that the support member can be rotated forward and backward relative to the chair back to adjust the tilt angle; a pawl block is hinged on the fixed arm, and a ratchet block is fixed on the connecting arm. A ratchet structure is formed between the pawl block and the ratchet block. During the rotation of the support member, the teeth on the pawl block and the ratchet block are engaged in sequence, thereby realizing the gear adjustment of the support member.

[0004] Although the above solution achieves depth adjustment of the lumbar support, it has the following problems: the gear position between the support member and the chair back is adjusted through a ratchet structure, which means that the support member can only be fixed at several preset gears, which is a step-by-step adjustment and cannot achieve more precise adjustment, and the adjustment freedom is low. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desired to provide a lumbar support stepless adjustment mechanism, which connects the lumbar support assembly and the backrest assembly through two front and rear parallel swinging members, so that a parallel four-bar linkage structure is formed between the backrest assembly, the lumbar support assembly, the front swinging member and the rear swinging member, so that as the front swinging member and the rear swinging member rotate forward and backward, the lumbar support assembly can maintain the same posture and be pushed forward or retracted backward, thereby realizing the depth adjustment of the lumbar support assembly; the telescopic member can be fixed at any length and constrain the rotation of the front swinging member and the rear swinging member, that is, the lumbar support assembly can be fixed at any depth, which is stepless adjustment and has a high degree of adjustment freedom.

[0006] The effect of the utility model is achieved in this way:

[0007] The present application provides a lumbar support stepless adjustment mechanism, comprising a backrest assembly and a lumbar support assembly, wherein the lumbar support assembly is mounted on the front side of the backrest assembly through a connecting rod assembly; the connecting rod assembly comprises a front swinging member and a rear swinging member parallel to each other, one end of each of the front swinging member and the rear swinging member is hinged to one of the backrest assembly and the lumbar support assembly, and the other end of each of the front swinging member and the rear swinging member is hinged to the other of the backrest assembly and the lumbar support assembly; when the front swinging member and the rear swinging member swing back and forth, the lumbar support assembly is driven to move back and forth relative to the backrest assembly; a locking device is also provided in the connecting rod assembly, the locking device comprises a telescopic member, the two ends of the telescopic member are respectively hinged to any two components of the backrest assembly, the lumbar support assembly, the front swinging member and the rear swinging member, and the telescopic member has a switchable active state and a locked state. In the active state, the telescopic member responds to the forward and backward rotation of the front swinging member and the rear swinging member to extend and retract and change its length; in the locked state, the length of the telescopic member is fixed, so that the front swinging member and the rear swinging member are constrained and cannot continue to rotate, thereby keeping the lumbar support assembly and the backrest assembly relatively fixed.

[0008] Furthermore, the upper ends of the front and rear swing members are hinged to the backrest assembly, and the lower ends of the front and rear swing members are hinged to the lumbar support assembly. As a result, when the front and rear swing members rotate forward, the lumbar support assembly is not only pushed forward in the horizontal direction, but also simultaneously raised in the vertical direction. That is, the lumbar support assembly is pushed forward and upward as a whole, which provides a better lumbar support effect.

[0009] Furthermore, the telescopic member is a controllable gas spring, tilted from front to back and from low to high. The telescopic member constantly applies thrust to both ends, causing the front and rear swing members to consistently swing forward relative to the backrest assembly. This tilt not only improves transmission efficiency but also makes the rotation process smoother. Furthermore, by tilting the telescopic member backward, the thrust applied by the telescopic member is converted into a force that rotates the front or rear swing members forward, ensuring that the lumbar support assembly consistently tends to move forward. This eliminates the need for the user to manually adjust the position of the lumbar support assembly, making it easier to adjust the depth of the lumbar support assembly.

[0010] Furthermore, the top of the telescopic member and the top of the rear swing member are hinged to the rear side of the backrest assembly, while the bottom of the telescopic member and the bottom of the front swing member are hinged to the front side of the lumbar support assembly. The top and bottom ends of the telescopic member are respectively hinged to two diagonal positions of the parallelogram linkage structure, which improves transmission efficiency and makes the rotation of the front swing member smoother.

[0011] Furthermore, the telescopic member can also be a tension-type gas spring, a controllable gas spring, and be tilted from front to back and from high to low. The telescopic member constantly applies tension to both ends, causing the front and rear swing members to constantly swing forward relative to the backrest assembly. The tilted arrangement of the telescopic member improves transmission efficiency and smooths rotation. Furthermore, the telescopic member is tilted forward, so that the tension applied by the telescopic member is converted into a force that rotates the front or rear swing members forward, causing the lumbar support assembly to constantly move forward.

[0012] Furthermore, the top of the telescopic member and the top of the front swing member are hinged to the front side of the backrest assembly, while the bottom of the telescopic member and the bottom of the rear swing member are hinged to the rear side of the lumbar support assembly. The top and bottom ends of the telescopic member are respectively hinged to two diagonal positions of the parallelogram linkage structure, which allows the tension of the telescopic member to be better converted into the rotational force of the rear swing member, resulting in better transmission effect and smoother rotation of the rear swing member.

[0013] Furthermore, the backrest assembly includes a backrest body and an upper support member detachably connected to the backrest body, and the lumbar support assembly includes a lumbar support body and a lower support member detachably connected to the lumbar support body. The upper ends of the front and rear swing members are hinged to one of the upper and lower support members, and the lower ends of the front and rear swing members are hinged to the other of the upper and lower support members. This not only makes the overall seat installation and disassembly more convenient, but also allows the upper support member and backrest body, as well as the lumbar support body and lower support, to be manufactured separately, making manufacturing operations more convenient.

[0014] Furthermore, both the front and rear swing members are hollow structures, with openings on the sides of the front and rear swing members facing the telescopic member. The hollow portions of the front and rear swing members are combined to form a complete accommodating cavity, within which the telescopic member is located. This not only allows for a shorter spacing between the front and rear swing members, making the entire connecting rod assembly more compact and occupying less space, but also allows the telescopic member to be hidden within the accommodating cavity and not easily exposed, resulting in a more integrated and aesthetically pleasing appearance of the connecting rod assembly.

[0015] The lumbar support stepless adjustment mechanism provided by the present application connects the lumbar support assembly and the backrest assembly through two front and rear parallel swinging members, so that a parallel four-bar linkage structure is formed between the backrest assembly, the lumbar support assembly, the front swinging member and the rear swinging member, so that as the front swinging member and the rear swinging member rotate back and forth, the lumbar support assembly can maintain the same posture and push forward or retract backward, thereby realizing the depth adjustment of the lumbar support assembly; not only that, by arranging a telescopic member between the backrest assembly, the lumbar support assembly, the front swinging member and the rear swinging member, when adjusting the depth of the lumbar support assembly, the telescopic member is in an active state and expands and contracts as the front swinging member and the rear swinging member rotate; when the position of the lumbar support assembly needs to be fixed, the telescopic member enters a locked state and fixes the two sides of the parallel four-bar linkage structure, so that the front swinging member and the rear swinging member are constrained and cannot continue to rotate, thereby fixing the depth of the lumbar support assembly; the telescopic member can be fixed at any length, that is, the lumbar support assembly can be fixed at any depth, which is stepless adjustment with a high degree of adjustment freedom. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0017] Figure 1 A schematic diagram of the three-dimensional structure of the lumbar support stepless adjustment mechanism provided in an embodiment of the present application;

[0018] Figure 2 A schematic cross-sectional view of the lumbar support stepless adjustment mechanism when the lumbar support assembly provided in an embodiment of the present application is adjusted to the final position;

[0019] Figure 3 A schematic cross-sectional view of the lumbar support stepless adjustment mechanism when the lumbar support assembly provided in an embodiment of the present application is adjusted to the forward position;

[0020] Figure 4 A schematic diagram of the connection structure between the lumbar support assembly and the backrest assembly provided in an embodiment of the present application;

[0021] Figure 5 A schematic diagram of the connection structure between the connecting rod assemblies provided in an embodiment of the present application;

[0022] Figure 6 A schematic diagram of the connection structure between the lumbar support body and the lower support member provided in an embodiment of the present application;

[0023] Figure 7 A schematic diagram of the connection structure between the backrest body and the upper support member provided in an embodiment of the present application;

[0024] Figure 8 A schematic cross-sectional view of the connecting rod assembly when the telescopic member provided in an embodiment of the present application is tilted forward;

[0025] Figure 9 A schematic cross-sectional view of the telescopic member provided in an embodiment of the present application when connected between two adjacent rods;

[0026] Figure 10 Schematic diagram of the cross-sectional structure of the telescopic member provided in the embodiment of the present application when connected between two parallel rods

[0027] Figure 11 This is a schematic cross-sectional view of the lumbar support stepless adjustment mechanism when the upper end of the connecting rod assembly provided in an embodiment of the present application is connected to the lumbar support assembly.

[0028] The figures are marked as follows: 1-backrest assembly, 110-backrest body, 111-avoidance, 120-upper support member, 121-connecting part, 2-lumbar support assembly, 210-lumbar support body, 220-lower support member, 301-accommodating cavity, 310-front swing member, 320-rear swing member, 4-telescopic member. DETAILED DESCRIPTION

[0029] The present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the relevant utility model and are not intended to limit the utility model. It should also be noted that, for ease of description, only the portions relevant to the utility model are shown in the accompanying drawings.

[0030] Please refer to the attached Figure 1-11 The embodiment of the present application provides a lumbar support stepless adjustment mechanism, including a backrest assembly 1 and a lumbar support assembly 2, wherein the lumbar support assembly 2 is mounted on the front side of the backrest assembly 1 through a connecting rod assembly; the connecting rod assembly includes a front swinging member 310 and a rear swinging member 320 that are parallel to each other, the upper ends of the front swinging member 310 and the rear swinging member 320 are hinged to one of the backrest assembly 1 and the lumbar support assembly 2, and the lower ends of the front swinging member 310 and the rear swinging member 320 are hinged to the other of the backrest assembly 1 and the lumbar support assembly 2; when the front swinging member 310 and the rear swinging member 320 swing back and forth, the lumbar support assembly 2 is driven to move forward and backward relative to the backrest assembly 1 Movement; a locking device is also provided in the connecting rod assembly, which includes a telescopic member 4, the two ends of which are respectively hinged to any two components of the backrest assembly 1, the lumbar support assembly 2, the front swing member 310 and the rear swing member 320, and the telescopic member 4 has a switchable active state and a locked state. In the active state, the telescopic member 4 responds to the front and rear swing members 310 and 320 to rotate back and forth and telescope to change the length; in the locked state, the length of the telescopic member 4 is fixed, so that the front swing member 310 and the rear swing member 320 are constrained and cannot continue to rotate, thereby keeping the lumbar support assembly 2 and the backrest assembly 1 relatively fixed.

[0031] In this embodiment, the lumbar support assembly 2 and the backrest assembly 1 are connected by two front and rear parallel swinging members 310 and 320, so that a parallel four-link structure is formed between the backrest assembly 1, the lumbar support assembly 2, the front swinging member 310 and the rear swinging member 320. As the front swinging member 310 and the rear swinging member 320 rotate forward and backward, the lumbar support assembly 2 can maintain the same posture and be pushed forward or retracted backward, thereby realizing the depth adjustment of the lumbar support assembly 2; moreover, by 0, and when adjusting the depth of the lumbar support assembly 2, the telescopic member 4 is in an active state and telescopes with the rotation of the front swing member 310 and the rear swing member 320; when it is necessary to fix the position of the lumbar support assembly 2, the telescopic member 4 enters a locked state and fixes the two sides of the parallel four-bar linkage structure, so that the front swing member 310 and the rear swing member 320 are constrained and cannot continue to rotate, thereby fixing the depth of the lumbar support assembly 2; the telescopic member 4 can be fixed at any length, that is, the lumbar support assembly 2 can be fixed at any depth, which is stepless adjustment with a high degree of adjustment freedom.

[0032] Please refer to the attached Figure 2-3 In some embodiments of the present application, the upper ends of the front swing member 310 and the rear swing member 320 are both hinged to the backrest assembly 1, and the lower ends of the front swing member 310 and the rear swing member 320 are both hinged to the lumbar support assembly 2. When the front swing member 310 and the rear swing member 320 rotate forward, the lumbar support assembly 2 is not only pushed forward in the horizontal direction, but also simultaneously raised in the vertical direction. That is, the lumbar support assembly 2 is pushed forward and upward as a whole, which improves the lumbar support effect.

[0033] Of course, as attached Figure 11 As shown, in other embodiments of the present application, the upper ends of the front swing member 310 and the rear swing member 320 can also be hinged to the lumbar support assembly 2, and the lower ends of the front swing member 310 and the rear swing member 320 are both hinged to the backrest assembly 1; during the forward rotation of the front swing member 310 and the rear swing member 320, the lumbar support assembly 2 will also be pushed forward.

[0034] Please refer to the attached Figure 2-3 In some embodiments of the present application, the telescopic member 4 is a controllable gas spring, and the telescopic member 4 is tilted, with the tilting direction being from front to back and from low to high; the telescopic member 4 always applies thrust to both ends, so that the front swing member 310 and the rear swing member 320 always have a tendency to swing forward relative to the backrest assembly 1.

[0035] In this embodiment, by tilting the telescopic member 4, not only can the thrust of the telescopic member 4 be better converted into the rotational force of the front swing member 310 or the rear swing member 320, the transmission effect is better, and the rotation process is smoother; moreover, the telescopic member 4 is tilted backward, and the thrust applied by the telescopic member 4 can be converted into the force for the front swing member 310 or the rear swing member 320 to rotate forward, so that the lumbar support assembly 2 always has a tendency to move forward, so that when the user needs to adjust the depth of the lumbar support, it is only necessary to switch the telescopic member 4 from the locked state to the active state, and the telescopic member 4 will automatically push the lumbar support assembly 2 to a position that fits the user's waist, and then switch the telescopic member 4 back to the locked state to fix the lumbar support assembly 2 to the appropriate position, without the user manually adjusting the position of the lumbar support assembly 2, making the depth adjustment operation of the lumbar support assembly 2 easier.

[0036] Among them, the telescopic part 4 is controlled by a wire control device, which includes an adjustment switch and a pull rope connected between the adjustment switch and the controllable gas spring thimble. The user only needs to press the adjustment switch to drive the pull rope to squeeze or release the thimble of the gas spring to control the telescopic part 4 to switch between the locked state and the active state. The adjustment operation is very simple.

[0037] Of course, in other embodiments of the present application, the telescopic member 4 may also be a mechanism with a telescopic adjustment function, such as a hydraulic rod, an electric telescopic rod, etc.

[0038] Please refer to the attached Figure 2-3 In some embodiments of the present application, the top end of the telescopic member 4 and the top end of the rear swing member 320 are hinged to the rear side of the backrest assembly 1, and the bottom end of the telescopic member 4 and the bottom end of the front swing member 310 are hinged to the front side of the lumbar support assembly 2.

[0039] In this embodiment, a parallel four-bar linkage structure is formed between the backrest assembly 1, the lumbar support assembly 2, the front swing member 310 and the rear swing member 320, and the upper and lower ends of the telescopic member 4 are respectively hinged to the two diagonal positions of the parallel four-bar linkage structure, so that the thrust of the telescopic member 4 can be better converted into the rotational force of the front swing member 310, the transmission effect is better, and the rotation process of the front swing member 310 is smoother.

[0040] Among them, as attached Figure 9 As shown, the telescopic member 4 can also be hinged to any two adjacent components of the backrest assembly 1, the lumbar support assembly 2, the front swing member 310 and the rear swing member 320. The force applied by the telescopic member 4 to the front swing member 310 or the rear swing member 320 can be directly converted into a force for the front swing member 310 or the rear swing member 320 to rotate. Figure 10As shown, the telescopic member 4 can also be hinged to any two parallel components among the backrest assembly 1, the lumbar support assembly 2, the front swing member 310 and the rear swing member 320 (the telescopic member 4 is not arranged on the center line of the two parallel components). The force applied by the telescopic member 4 to both ends can force the distance between the two components to change, thereby forcing the front swing member 310 or the rear swing member 320 to rotate.

[0041] Please refer to the attached Figure 8 In some embodiments of the present application, the telescopic member 4 can also be a tension-type gas spring. The telescopic member 4 is a controllable gas spring. The telescopic member 4 is tilted, and the tilting direction is from front to back and from high to low. The telescopic member 4 always applies tension to both ends, so that the front swing member 310 and the rear swing member 320 always have a tendency to swing forward relative to the backrest assembly 1.

[0042] In this embodiment, by tilting the telescopic member 4, not only can the thrust of the telescopic member 4 be better converted into the rotational force of the front swing member 310 or the rear swing member 320, the transmission effect is better and the rotation process is smoother; moreover, the telescopic member 4 is tilted forward, and the pulling energy applied by the telescopic member 4 is converted into the force for the front swing member 310 or the rear swing member 320 to rotate forward, so that the lumbar support assembly 2 always has a tendency to move forward.

[0043] Please refer to the attached Figure 8 In some embodiments of the present application, the top end of the telescopic member 4 and the top end of the front swing member 310 are hinged together on the front side of the backrest assembly 1, and the bottom end of the telescopic member 4 and the bottom end of the rear swing member 320 are hinged together on the rear side of the lumbar support assembly 2. The upper and lower ends of the telescopic member 4 are respectively hinged to two diagonal positions of the parallelepiped linkage structure, so that the tension of the telescopic member 4 can be better converted into the rotational force of the rear swing member 320, resulting in a better transmission effect and a smoother rotation process of the rear swing member 320.

[0044] Please refer to the attached Figure 4-7 In some embodiments of the present application, the backrest assembly 1 includes a backrest body 110 and an upper support member 120 detachably connected to the backrest body 110, and the lumbar support assembly 2 includes a lumbar support body 210 and a lower support member 220 detachably connected to the lumbar support body 210; the upper ends of the front swing member 310 and the rear swing member 320 are both hinged to one of the upper support member 120 and the lower support member 220, and the lower ends of the front swing member 310 and the rear swing member 320 are both hinged to the other of the upper support member 120 and the lower support member 220.

[0045] In this embodiment, by setting the backrest assembly 1 and the lumbar support assembly 2 as a split structure, the front swing member 310 and the rear swing member 320 are connected to the upper support member 120 and the lower support member 220, which not only makes the installation and disassembly operations of the entire seat more convenient, but also the upper support member 120 and the backrest body 110 and the lumbar support body 210 and the lower support member 220 can be separately processed and manufactured, making the processing and manufacturing operations simpler.

[0046] Among them, preferably, the upper support member 120 is connected to the backrest body 110 by screw connection, and the lower support member 220 is also connected to the lumbar support body 210 by screw connection, which not only has high connection strength but also is easy to install and disassemble.

[0047] Please refer to the attached Figure 7 The backrest body 110 is an integrally formed structure made by injection molding. A recessed opening 111 is formed in the middle of the backrest body 110. The upper end of the upper support member 120 protrudes to form two symmetrical connecting portions 121, which are clamped to the upper edge of the recess 111 and secured by screws. Furthermore, the rear end of the upper support member 120 extends horizontally rearward beyond the recess 111. The top ends of the front and rear swing members 310 and 320 pass through the recess 111 and connect to the upper support member 120. When the front and rear swing members 310 and 320 rotate backward, the recess 111 clears them, allowing the lumbar support assembly 2 to rotate a greater distance backward and closer to the backrest body 110.

[0048] Please refer to the attached Figure 5 In some embodiments of the present application, both the front swing member 310 and the rear swing member 320 are hollow structures, with openings on the sides of the front swing member 310 and the rear swing member 320 facing the telescopic member 4. The hollow portions of the front swing member 310 and the rear swing member 320 are combined to form a complete accommodating cavity 301, and the telescopic member 4 is located within the accommodating cavity 301. This not only allows the distance between the front swing member 310 and the rear swing member 320 to be designed to be shorter, making the entire connecting rod assembly more compact and occupying less space, but also allows the telescopic member 4 to be hidden within the accommodating cavity 301 and not easily exposed, making the connecting rod assembly more integrated and beautiful in appearance.

[0049] Preferably, the front swing member 310 and the rear swing member 320 are made of sheet metal with a U-shaped cross-section, which is relatively easy to manufacture. Furthermore, the upper support member 120 and the lower support member 220 are also hollow structures, with the lower end of the upper support member 120 being open and the upper end of the lower support member 220 being open. This allows the upper and lower ends of the front swing member 310 and the rear swing member 320 to be inserted into the upper support member 120 and the lower support member 220 through the openings, further improving the overall compactness of the connecting rod assembly and making the appearance more simple and beautiful.

[0050] It should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like used above to indicate orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means more than three.

[0051] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the utility model disclosed in this application is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the concept of the utility model. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A lumbar support stepless adjustment mechanism, characterized in that: The invention comprises a backrest assembly (1) and a lumbar support assembly (2), wherein the lumbar support assembly (2) is mounted on the front side of the backrest assembly (1) through a connecting rod assembly; the connecting rod assembly comprises a front swinging member (310) and a rear swinging member (320) which are parallel to each other, one end of each of the front swinging member (310) and the rear swinging member (320) being hinged to one of the backrest assembly (1) and the lumbar support assembly (2), and the other end of each of the front swinging member (310) and the rear swinging member (320) being hinged to the other of the backrest assembly (1) and the lumbar support assembly (2); when the front swinging member (310) and the rear swinging member (320) swing forward and backward, the lumbar support assembly (2) moves forward and backward synchronously relative to the backrest assembly (1); the lumbar support assembly (2) is free from friction and is not movable. The extreme adjustment mechanism also includes a locking device, which includes a telescopic member (4), wherein both ends of the telescopic member (4) are respectively hinged to any two components of the backrest assembly (1), the lumbar support assembly (2), the front swing member (310) and the rear swing member (320), and the telescopic member (4) has a switchable active state and a locked state. In the active state, the telescopic member (4) responds to the front and rear swing members (310) and the rear swing member (320) to change its length; in the locked state, the length of the telescopic member (4) is fixed, so that the front swing member (310) and the rear swing member (320) are constrained and cannot continue to rotate, thereby keeping the lumbar support assembly (2) and the backrest assembly (1) relatively fixed.

2. The lumbar support stepless adjustment mechanism according to claim 1 is characterized in that: The upper ends of the front swing member (310) and the rear swing member (320) are both hinged to the backrest assembly (1), and the lower ends of the front swing member (310) and the rear swing member (320) are both hinged to the lumbar support assembly (2).

3. The lumbar support stepless adjustment mechanism according to claim 2 is characterized in that: The telescopic member (4) is a controllable gas spring. The telescopic member (4) is tilted in a direction from front to back and from low to high. The telescopic member (4) always applies thrust to both ends, so that the front swing member (310) and the rear swing member (320) always have a tendency to swing forward relative to the backrest assembly (1).

4. The lumbar support stepless adjustment mechanism according to claim 3 is characterized in that: The top end of the telescopic member (4) and the top end of the rear swing member (320) are hinged to the rear side of the backrest assembly (1), and the bottom end of the telescopic member (4) and the bottom end of the front swing member (310) are hinged to the front side of the lumbar support assembly (2).

5. The lumbar support stepless adjustment mechanism according to claim 2 is characterized in that: The telescopic member (4) is a controllable gas spring. The telescopic member (4) is tilted in a direction from front to back and from high to low. The telescopic member (4) always applies a pulling force to both ends, so that the front swing member (310) and the rear swing member (320) always have a tendency to swing forward relative to the backrest assembly (1).

6. The lumbar support stepless adjustment mechanism according to claim 5, characterized in that: The top end of the telescopic member (4) and the top end of the front swing member (310) are hinged to the front side of the backrest assembly (1), and the bottom end of the telescopic member (4) and the bottom end of the rear swing member (320) are hinged to the rear side of the lumbar support assembly (2).

7. The lumbar support stepless adjustment mechanism according to claim 1 is characterized in that: The backrest assembly (1) includes a backrest body (110) and an upper support member (120) detachably connected to the backrest body (110); the lumbar support assembly (2) includes a lumbar support body (210) and a lower support member (220) detachably connected to the lumbar support body (210); the upper ends of the front swing member (310) and the rear swing member (320) are both hinged to one of the upper support member (120) and the lower support member (220), and the lower ends of the front swing member (310) and the rear swing member (320) are both hinged to the other of the upper support member (120) and the lower support member (220).

8. The lumbar support stepless adjustment mechanism according to claim 1 is characterized in that: The front swing member (310) and the rear swing member (320) are both hollow structures. The front swing member (310) and the rear swing member (320) are both opened on one side facing the telescopic member (4). The hollow parts of the front swing member (310) and the rear swing member (320) are combined to form a complete accommodating cavity (301), and the telescopic member (4) is located in the accommodating cavity (301).

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