Backrest height adjustment structure

Abstract

This invention provides a backrest height adjustment structure. [Solution] This invention primarily relates to a backrest height adjustment structure, and mainly consists of a locking tooth unit for the backrest member, a backrest bracket, and a height adjustment member that are combined with each other. The height adjustment member of this invention can be assembled independently on the backrest member and backrest bracket, forming a shared unit that can realize the height adjustment positioning and origin return functions of the seat backrest. As a result, the stability and smoothness of the operation process of the entire height adjustment structure are improved, the complicated structural assembly procedure is reduced, assembly is made easier, and manufacturing costs can be reduced.

Description

Technical Field

[0001] The present invention relates to a backrest lifting and adjusting structure.

Background Art

[0002] Modern people work from 9:00 am to 5:00 pm, and many tasks require operating a computer to create files and search for materials. A comfortable seat plays a very important role. However, a long-term unchanged sitting posture may cause low back pain for the sitter. The lumbar belt protectors currently on the market that claim to prevent the occurrence of low back pain have not yet been proven effective, and excessive dependence on the lumbar belt may have adverse effects. Regarding the low back pain that may be caused by the long-term static sitting posture of computer work users, it is necessary to consider selecting an appropriate seat. The inventor has applied for a chair backrest height adjustment structure of US Patent US9648955, the content of which mainly includes a frame, a back plate, and an adjustment member. The frame has an adjustment plate with a central groove, a limiting groove, and two slide grooves. The back plate is connected to the frame and has an opening. The adjustment member is connected between the frame and the back plate. The adjustment member includes a slide base having an engagement block provided in the opening, and the engagement block has a groove with a through hole provided therein. The position regulating member provided in the groove has an extension portion having a central axis located in the through hole and a position regulating axis located in the position regulating groove, and a C-shaped groove is formed around the central axis. The torque spring is provided in the C-shaped groove, and both ends thereof extend out of the C-shaped groove and are position-regulated by the groove. Two slide blocks are accommodated in the slide grooves, and both the slide blocks and the slide base are fixed on the back plate. However, the conventional structure is complicated, not easy to assemble, has a high component cost, has no stability during operation, and is likely to cause a failure defect where the engagement block of the slide base becomes stuck.

Prior Art Documents

Patent Documents

[0003] [Patent Document 1] Japanese Patent Publication No. 2025-60131 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The object of the present invention is to provide a backrest height adjustment structure that solves the problems of conventional structures, which are complicated, difficult to assemble, have high component costs, lack stability during operation, and are prone to failure defects such as the engagement block of the slide base becoming stuck. [Means for solving the problem]

[0005] The backrest height adjustment structure provided by the present invention includes a backrest bracket, the backrest bracket has an assembly chamber in the center, and a height adjustment space is provided above that communicates with the assembly chamber, the height adjustment space can be extended and retracted by incorporating a slide base of a backrest member into it, the slide base is provided with a locking tooth unit corresponding to the assembly chamber of the backrest bracket, the locking tooth unit has a positioning section, the positioning section is provided with a plurality of parallel positioning teeth, and in the center of each positioning tooth there is a vertically extending A sliding groove is provided, an upper stopper surface is provided at one end extending above the sliding groove, and a lower stopper surface is provided at the other end extending below the sliding groove, a lifting member is assembled between the assembly chamber of the backrest bracket and the locking tooth unit of the backrest member, the lifting member includes a lifting housing, lifting locking teeth and a leaf spring, the lifting housing is assembled and positioned within the assembly chamber of the backrest bracket, a housing chamber is provided inside the lifting housing, a clamping portion is provided inside the housing chamber, and Eccentric central holes are provided at the inner walls of both sides of the interior of the housing chamber, and the lifting locking teeth are installed with shaft holes passing through them, and the shaft holes can be made to protrude toward both sides after the rotation shaft is assembled, and the lifting locking teeth are movably pivoted in the eccentric central holes on both sides of the lifting housing by the rotation shafts provided separately on both sides and perform a swinging motion, and at least two locking tooth portions are provided on one outward-facing side of the lifting locking teeth, and the locking tooth portions can engage with or disengage from each of the positioning teeth of the backrest member, and the lifting locking teeth are the backrest An operating block is provided corresponding to the position of the slide groove of the member, and the operating block has an upper operating surface corresponding to the position of the upper stopper surface of the backrest member, and the lifting locking teeth can be swung by the upper stopper surface pushing the upper operating surface, thereby engaging and positioning with each of the positioning teeth of the backrest member, and the operating block has a lower operating surface corresponding to the position of the lower stopper surface of the backrest member, and the lifting locking teeth can be swung by the lower stopper surface pushing the lower operating surface,The locking teeth can be swung to disengage each of the positioning teeth of the backrest member, and the leaf spring has a clamping end at its upper end and a pressing top at its lower end. The clamping end is positioned by being clamped in the clamping portion of the lifting housing, and the pressing top abuts against the relative position of the rear end surface of the lifting locking teeth. [Effects of the Invention]

[0006] As a result, the present invention forms a single shared unit by assembling a single independent lifting member on a backrest member and backrest bracket, enabling lifting positioning and origin return functions. This improves the stability and smoothness of the structure during operation, prevents sticking failures during the lifting positioning process, reduces the complex structural assembly process, is advantageous for assembly, lowers manufacturing costs, and improves practical inventiveness. [Brief explanation of the drawing]

[0007] [Figure 1] This is a perspective view of the combined backrest height adjustment structure of the present invention. [Figure 2] This is an exploded perspective view of the backrest height adjustment structure of the present invention. [Figure 3] This is an exploded perspective view of the lifting member in the backrest height adjustment structure of the present invention. [Figure 4] This is a cross-sectional view of the side structure of the lifting member in the backrest lifting adjustment structure of the present invention. [Figure 5] This is a cross-sectional view of the side structure of the backrest height adjustment structure of the present invention. [Figure 6] This is an enlarged side view diagram illustrating the operation of the backrest height adjustment structure of the present invention. [Figure 7] This is another enlarged side view diagram illustrating the operation of the backrest height adjustment structure of the present invention. [Figure 8] This is another enlarged side view diagram illustrating the operation of the backrest height adjustment structure of the present invention. [Figure 9] Figure 8 is an enlarged diagram illustrating the operation of the lifting member structure. [Figure 10] This is an enlarged side view diagram illustrating the operation of the backrest height adjustment structure of the present invention. [Figure 11] Figure 10 is an enlarged diagram illustrating the operation of the lifting member structure. [Modes for carrying out the invention]

[0008] Figures 1 to 11 show preferred embodiments of the backrest height adjustment structure of the present invention. These embodiments are for illustrative purposes only and the patent application is not limited to these embodiments. The structure includes the following backrest bracket A.

[0009] The backrest bracket A has an assembly chamber A2 in the center, and a lifting space A1 communicating with the assembly chamber A2 is provided above it. The lifting space A1 can be expanded and contracted and slid by incorporating a slider B1 of the backrest member B. The slider B1 is provided with a locking tooth unit B2 corresponding to the assembly chamber A2 of the backrest bracket A. The locking tooth unit B2 includes a positioning section B5, and the positioning section B5 is provided with a plurality of parallel positioning teeth B51. In the center of each positioning tooth B51, there is a slide groove B52 extending in the vertical direction. An upper stopper surface B42 is provided at one end of the slide groove B52 extending upward. Above the upper stopper surface B42 is defined as an engagement section B4, and the engagement section B4 is provided with a plurality of engagement teeth B41, and one end extending downward of the slide groove B52 A lower stopper surface B62 is provided, and the space between the lower stopper surface B62 and the positioning teeth B51 is defined as a release section B6, and a guide groove B61 is provided in the release section B6, and an auxiliary frame B3 is installed at a predetermined position of the backrest member B within there, and an auxiliary assembly groove A5 is provided in the backrest bracket A corresponding to the position of the auxiliary frame B3, and the auxiliary frame B3 can be auxiliaryly assembled into the auxiliary assembly groove A5, and a lifting member 1 is assembled between the assembly chamber A2 of the backrest bracket A and the locking tooth unit B2 of the backrest member B, and a plurality of fitting blocks A4 are provided on both sides inside the assembly chamber A2 of the backrest bracket A, and a fitting groove A3 is provided between each of the fitting blocks A4, and the lifting member 1 includes the following lifting housing 10, lifting locking teeth 30 and leaf spring 20.

[0010] The lifting housing 10 is provided with a plurality of fitting assembly parts 11 corresponding to the fitting groove A3, and the fitting assembly parts 11 are fitted and assembled into the fitting groove A3, and the lifting housing 10 is positioned and assembled within the assembly chamber A2 of the backrest bracket A, and an assembly chamber 12 is provided inside the lifting housing 10, a guide arc part 14 is provided on the bottom surface of the assembly chamber 12, a clamping part 131 is provided above the inside of the assembly chamber 12, and the positions of the inner walls 13 inside the assembly chamber 12 are respectively A central hole 15 is provided, and a main hole region 16 is provided inside the eccentric hole 15. The main hole region 16 generally has the shape of a long groove, and the main hole region 16 has two reference center points, which are defined as the first eccentric center point M and the second eccentric center point N, respectively. A first locking portion 17 is provided at the upper corner position of the main hole region 16, and an upper locking hole region 18 is provided above the main hole region 16 in communication with it, and a second locking portion 19 is provided at the upper corner position of the upper locking hole region 18.

[0011] The lifting locking tooth 30 is provided with a shaft hole 35 that passes through it, and the shaft hole 35 can be made to protrude to both sides after the rotating shaft 40 is pivotally supported. The lifting locking tooth 30 is pivotally supported in the eccentric holes 15 on both sides of the lifting housing 10 by the rotating shafts 40 which are provided on both sides, and rotates. Here, the shaft hole 35 of the lifting locking tooth 30 is provided with a main shaft hole 36, and a protruding hole 37 is provided in communication with the main shaft hole 36 above, and an engaging portion 38 is provided at the corner position above the protruding hole 37. Furthermore, the rotating shaft 40 has a main shaft portion 41 corresponding to the position of the main shaft hole 36 of the shaft hole 35, a protruding portion 42 corresponding to the position of the protruding hole 37 of the shaft hole 35, and a locking angular portion 43 corresponding to the position of the engaging portion 38 of the shaft hole 35. The main shaft portion 41, the protruding portion 42, and the locking angular portion 43 of the rotating shaft 40 are assembled to fit together with the main shaft hole 36, the protruding hole 37, and the engaging portion 38 of the shaft hole 35 of the lifting locking tooth 30, and the rotating shaft 40 can rotate movably in the eccentric hole 15 of the lifting housing 10, and the locking tooth portion 31 of the lifting locking tooth 30 When the rotating shaft 40 swings and engages with each of the positioning teeth B51 of the backrest member B to position it, the center position of the main shaft portion 41 of the rotating shaft 40 is aligned with the second eccentric center point N of the eccentric hole 15, and the locking angular portion 43 of the rotating shaft 40 is engaged with and positioned by the first locking portion 17 of the eccentric hole 15. Conversely, when the locking teeth portion 31 of the lifting locking teeth 30 swings and disengages from each of the positioning teeth B51 of the backrest member B, the center position of the main shaft portion 41 of the rotating shaft 40 is aligned with the first eccentric center point M of the eccentric hole 15, and the locking angular portion 43 of the rotating shaft 40 is engaged with and positioned by the second locking portion 19 of the eccentric hole 15.

[0012] Furthermore, at least two locking tooth portions 31 are provided on one outward-facing side of the lifting locking tooth 30, and the locking tooth portions 31 can engage with or disengage from each of the positioning teeth B51 of the backrest member B, and the lifting locking tooth 30 is provided with an operating block 39 corresponding to the position of the slide groove B52 of the backrest member B, and the operating block 39 is provided with an upper operating surface 391 corresponding to the position of the upper stopper surface B42 of the backrest member B, and the lifting locking tooth 30 is provided with the upper stopper surface B42 By pushing the upper operating surface 391, the locking teeth 31 can be swung to engage with and position each of the positioning teeth B51 of the backrest member B. The operating block 39 is provided with a lower operating surface 392 corresponding to the position of the lower stopper surface B62 of the backrest member B. The lifting locking teeth 30 can be disengaged from each of the positioning teeth B51 of the backrest member B by the lower operating surface 392 being pushed by the lower stopper surface B62, causing the locking teeth 31 to swung.

[0013] Furthermore, the bottom of the lifting locking tooth 30 is provided with a guide arc surface 34 corresponding to the guide arc portion 14 of the lifting housing 10, and when the lifting locking tooth 30 swings inside the assembly chamber 12 of the lifting housing 10, the guide arc surface 34 of the lifting locking tooth 30 is guided in an arc shape by the guide arc portion 14 on the bottom surface of the assembly chamber 12 of the lifting housing 10 and slides.

[0014] Furthermore, an upper contact portion 33 and a lower contact portion 331 are provided at the rear end surface of the lifting locking tooth 30, and the upper contact portion 33 and the lower contact portion 331 are provided at positions adjacent to each other vertically.

[0015] The leaf spring 20 is manufactured from a high-elasticity manganese steel material, and the leaf spring 20 has good, sustainable, and non-fatiguing elasticity and toughness. A clamping end 21 is provided at the upper end of the leaf spring 20, and a pressing top 22 is provided at the lower end. The clamping end 21 of the leaf spring 20 is clamped and positioned by the clamping portion 131 of the lifting housing 10, and the pressing top 22 is movably abutted against the upper abutting portion 33 or the lower abutting portion 331 of the lifting locking teeth 30. When the locking tooth portion 31 of the lifting locking teeth 30 swings and meshes with and positions each of the positioning teeth B51 of the backrest member B, the pressing top 22 of the leaf spring 20 is displaced upward to press and position the upper abutting portion 33 of the lifting locking teeth 30. Conversely, when the locking tooth portion 31 of the lifting locking teeth 30 swings and disengages from each of the positioning teeth B51 of the backrest member B, the pressing top 22 of the leaf spring 20 is displaced downward to press and position the lower abutting portion 331 of the lifting locking teeth 30.

[0016] Preferably, when the clamping end 21 of the leaf spring 20 is clamped and positioned by the clamping portion 131 of the lifting housing 10, a clamping block 132 can be additionally provided at the bottom of the clamping portion 131 to strengthen the fixation.

[0017] As shown in FIG. 6, in the normal state, the engaging portion 32 of the engaging section of the locking tooth portion 31 of the lifting locking teeth 30 of the lifting member 1 meshes with and positions each of the positioning teeth B51 of the backrest member B, and the pressing top 22 of the leaf spring 20 presses and positions the upper abutting portion 33 of the lifting locking teeth 30. By elastically biasing the lifting locking teeth 30, the meshing and positioning between the lifting member 1 and each of the positioning teeth B51 are strengthened. Here, the central position of the main shaft portion 41 of the rotating shaft 40 is aligned with the second eccentric center point N of the eccentric hole 15. At the same time, the locking angular portion 43 of the rotating shaft 40 is engaged and positioned by the first locking portion 17 of the eccentric hole 15. In the figure, the operating block 39 of the lifting locking teeth 30 of the lifting member 1 ascends to the position of the upper stopper surface B42 of the slide groove B52, and at the same time, the locking tooth portion 31 of the lifting locking teeth 30 is meshed with the engaging teeth B41 of the engaging section B4.

[0018] As shown in FIG. 7, the locking tooth portion 31 of the lifting locking tooth 30 is engaged with each of the positioning teeth B51 of the backrest member B, and the user can relatively lift the lifting locking tooth 30 of the lifting member 1 downward by pulling the backrest member B upward to position it at an arbitrary height position of the positioning teeth B51 in the positioning section B5.

[0019] As shown in FIGS. 8 and 9, when the backrest member B is continuously pulled upward to the limit, the operating block 39 of the lifting locking tooth 30 of the lifting member 1 enters the guide groove B61 in the release section B6 of the backrest member B, and the lower stopper surface B62 in the release section B6 pushes the lower operating surface 392 of the operating block 39 to swing the locking tooth portion 31 of the lifting locking tooth 30 to disengage it from each of the positioning teeth B51 of the backrest member B. Simultaneously with the swinging, the central position of the main shaft portion 41 of the rotating shaft 40 is displaced to the first eccentric center point M of the eccentric hole 15, and the locking angular portion 43 of the rotating shaft 40 moves to and engages with the second locking portion 19 of the eccentric hole 15 to be positioned. Further, the pressing top portion 22 of the leaf spring 20 is displaced downward to press and position the lower contact portion 331 of the lifting locking tooth 30, and by making the leaf spring 20 in a standing state, the elastic biasing mode is released, and the lifting member 1 has only a lifting function and is in a state without any height positioning function.

[0020] As shown in Figures 10 and 11, when the backrest member B is continuously moved downward to its limit, it enters the origin return mode. The upper operating surface 391 of the operating block 39 of the lifting locking teeth 30 of the lifting member 1 first contacts the upper stopper surface B42 of the engagement section B4 of the backrest member B. Further force is applied to swing the locking tooth portion 31 of the lifting locking teeth 30, causing it to engage with each of the engagement teeth B41 of the engagement section B4 of the backrest member B. Here, the engagement teeth B41 do not have a slide groove B52 and only provide a return standby function for the locking tooth portion 31. After the locking tooth portion 31 moves downward and disengages from the engagement section B4, the locking tooth portion 31 is displaced to engage with the positioning teeth B51 at an arbitrary height. Simultaneously with the oscillation of the lifting locking teeth 30, the center position of the main shaft portion 41 of the rotating shaft 40 is displaced to the second eccentric center point N of the eccentric hole 15, and the locking angular portion 43 of the rotating shaft 40 moves to engage with and position the first locking portion 17 of the eccentric hole 15. Furthermore, the pressing top portion 22 of the leaf spring 20 is displaced upward to press against the upper contact portion 33 of the lifting locking teeth 30, thereby positioning it, and by tilting the leaf spring 20 and elastically biasing the lifting locking teeth 30, the lifting member 1 is returned to the function of lifting and positioning to any height relative to the backrest member B.

[0021] As a result, the present invention enables the realization of lifting positioning and origin return functions as a single shared unit by assembling a single independent lifting member 1 with the backrest member B and backrest bracket A, improving stability and smoothness during the operation of the structure and preventing defects such as sticking failures during the lifting positioning process. The present invention reduces the complex structural assembly process, simplifies assembly, lowers manufacturing costs, and improves practical inventiveness. [Explanation of Symbols]

[0022] 1 Lifting member 10 Lifting Housing 11. Fitting assembly section 12 Assembly Room 13 Both inner walls 131 Clamping part 132 Clamping Block 14 Guide arc section 15 Eccentric hole 16 Main hole area 17. First locking section 18 Upper locking hole area 19 Second locking section 20 leaf springs 21 Clamping end 22 Pressing top 30 Lifting and lowering locking teeth 31 Locking teeth 32 Engaging part 33 Upper contact part 331 Lower contact part 34 Guide arc surface 35 Shaft hole 36 Main shaft hole 37 Projection hole 38 Engaging part 39 Operating block 391 Upper working surface 392 Lower working surface 40 Rotation axis 41 Main shaft part 42 Protrusion 43 Locking angle portion A Backrest Bracket A1 Lifting space A2 Assembly room A3 Fitting groove A4 interlocking block A5 Auxiliary assembly groove B Backrest component B1 Slider B2 Locking Tooth Unit B3 Auxiliary Frame B4 Engagement section B41 Engaging tooth B42 Upper stopper surface B5 Positioning section B51 Positioning tooth B52 Slide groove B6 Departure Section B61 Guide groove B62 Lower stopper surface M 1st eccentric center point N 2nd eccentric center point

Claims

1. Including the backrest bracket, The backrest bracket has an assembly chamber in the center, and a lifting space is provided above it that communicates with the assembly chamber. The lifting space can be extended and retracted by incorporating the slide base of the backrest member into it. The slide base is provided with a locking tooth unit corresponding to the assembly chamber of the backrest bracket. The locking tooth unit has a positioning section, and a plurality of parallel positioning teeth are provided in the positioning section. A slide groove extending in the vertical direction is provided in the center of each positioning tooth. An upper stopper surface is provided at one end of the slide groove extending upward, and a lower stopper surface is provided at the other end extending downward. A lifting member is assembled between the assembly chamber of the backrest bracket and the locking tooth unit of the backrest member. The lifting member includes a lifting housing, a lifting locking tooth, and a leaf spring. The lifting housing is positioned in combination with the backrest bracket within the assembly chamber, and a storage chamber is provided inside the lifting housing, a clamping portion is provided inside the storage chamber, and eccentric central holes are provided at the positions of both inner walls inside the storage chamber. The lifting locking teeth are installed with shaft holes passing through them, and the shaft holes can be made to protrude toward both sides after the rotation shaft is assembled, and the lifting locking teeth are movably pivoted in eccentric central holes on both sides of the lifting housing by the rotation shafts provided separately on both sides, and perform a swinging motion, and at least two locking tooth portions are provided on one outward-facing side of the lifting locking teeth, and the locking tooth portions can engage with or disengage from each of the positioning teeth of the backrest member, and the lifting locking teeth are provided with operating blocks corresponding to the position of the slide grooves of the backrest member, and the operating blocks The block has an upper operating surface corresponding to the position of the upper stopper surface of the backrest member, and the lifting locking teeth can be positioned by the upper stopper surface pushing the upper operating surface, thereby causing the locking teeth to swing and engage with each of the positioning teeth of the backrest member; the operating block has a lower operating surface corresponding to the position of the lower stopper surface of the backrest member, and the lifting locking teeth can be disengaged from each of the positioning teeth of the backrest member by the lower stopper surface pushing the lower operating surface, thereby causing the locking teeth to swing and disengage from each of the positioning teeth of the backrest member. The leaf spring is provided with a clamping end at its upper end and a pressing top at its lower end, the clamping end is positioned by being clamped in the clamping portion of the lifting housing, and the pressing top abuts against the rear end surface of the lifting locking teeth at a relative position, in a backrest lifting adjustment structure.

2. The backrest height adjustment structure according to claim 1, wherein a plurality of fitting blocks are provided on both sides inside the assembly chamber of the backrest bracket, a fitting groove is provided between each of the fitting blocks, the lifting housing is provided with a plurality of fitting assembly parts corresponding to the fitting grooves, and the fitting assembly parts are fitted and assembled within the fitting grooves to be positioned.

3. The backrest lifting adjustment structure according to claim 1, wherein a main hole region is provided inside the eccentric central hole of the lifting housing, the main hole region has the shape of a long groove, the main hole region has two reference center points, the two reference center points are defined as a first eccentric center point and a second eccentric center point, a first locking portion is provided at the upper corner position of the main hole region, an upper locking hole region is provided communicating above the main hole region, and a second locking portion is provided at the upper corner position of the upper locking hole region.

4. The shaft hole of the lifting locking tooth is provided with a main shaft hole, a protruding hole is provided above the main shaft hole in communication with it, an engaging portion is provided at the corner position above the protruding hole, and the rotating shaft is provided with a main shaft portion corresponding to the position of the main shaft hole of the shaft hole, a protruding portion corresponding to the position of the protruding hole of the shaft hole, and a locking angular portion corresponding to the position of the engaging portion of the shaft hole of the rotating shaft, and the main shaft portion, protruding portion and locking angular portion of the rotating shaft are assembled to fit together with the main shaft hole, protruding hole and engaging portion of the shaft hole of the lifting locking tooth, and the rotating shaft is movable in the eccentric central hole of the lifting housing. The backrest height adjustment structure according to claim 1, wherein the rotating shaft is guided and rotated, and when the locking teeth of the lifting locking teeth oscillate and engage with and position each of the positioning teeth of the backrest member, the center position of the main shaft of the rotating shaft is aligned with the second eccentric center point of the eccentric central hole, and the locking angular portion of the rotating shaft is engaged and positioned with the first locking portion of the eccentric central hole; and conversely, when the locking teeth of the lifting locking teeth oscillate and disengage from each of the positioning teeth of the backrest member, the center position of the main shaft of the rotating shaft is aligned with the first eccentric center point of the eccentric central hole, and the locking angular portion of the rotating shaft is engaged and positioned with the second locking portion of the eccentric central hole.

5. The shaft hole of the lifting locking tooth is provided with a main shaft hole, a protruding hole is provided above the main shaft hole in communication with it, an engaging portion is provided at the corner position above the protruding hole, and the rotating shaft is provided with a main shaft portion corresponding to the position of the main shaft hole of the shaft hole, a protruding portion corresponding to the position of the protruding hole of the shaft hole, and a locking angular portion corresponding to the position of the engaging portion of the shaft hole of the rotating shaft, and the main shaft portion, protruding portion and locking angular portion of the rotating shaft are assembled to fit together with the main shaft hole, protruding hole and engaging portion of the shaft hole of the lifting locking tooth, and the rotating shaft is movable in the eccentric central hole of the lifting housing. The backrest height adjustment structure according to claim 3, wherein the rotating shaft is guided and rotated, and when the locking teeth of the lifting locking teeth oscillate and engage with and position each of the positioning teeth of the backrest member, the center position of the main shaft of the rotating shaft is aligned with the second eccentric center point of the eccentric central hole, and the locking angular portion of the rotating shaft is engaged and positioned with the first locking portion of the eccentric central hole; and conversely, when the locking teeth of the lifting locking teeth oscillate and disengage from each of the positioning teeth of the backrest member, the center position of the main shaft of the rotating shaft is aligned with the first eccentric center point of the eccentric central hole, and the locking angular portion of the rotating shaft is engaged and positioned with the second locking portion of the eccentric central hole.

6. The backrest height adjustment structure according to claim 1, wherein a guide arc portion is provided on the bottom surface of the assembly chamber of the lifting housing, a guide arc surface is provided on the bottom of the lifting locking tooth corresponding to the guide arc portion, and when the lifting locking tooth swings inside the assembly chamber of the lifting housing, the guide arc surface of the lifting locking tooth is guided in an arc shape and slides on the guide arc portion on the bottom surface of the assembly chamber of the lifting housing.

7. The rear end surface of the lifting locking tooth is provided with an upper contact portion and a lower contact portion corresponding to the position of the pressing top portion of the leaf spring, and the upper contact portion and the lower contact portion are provided in positions adjacent to each other vertically, and when the locking tooth portion of the lifting locking tooth swings and engages with and positions each of the positioning teeth of the backrest member, the pressing top portion of the leaf spring is displaced upward and presses against the upper contact portion of the lifting locking tooth to position it, and conversely, when the locking tooth portion of the lifting locking tooth swings and disengages from each of the positioning teeth of the backrest member, the pressing top portion of the leaf spring is displaced downward and presses against the lower contact portion of the lifting locking tooth to position it, as described in claim 1.

8. The backrest height adjustment structure according to claim 1, wherein an auxiliary bracket is installed at a predetermined position on the backrest member, and the backrest bracket is provided with an auxiliary assembly groove corresponding to the position of the auxiliary bracket, thereby enabling the auxiliary bracket to be auxiliaryly assembled within the auxiliary assembly groove.

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