Patent Publication Number: US-2022232981-A1

Title: Multi-gear supporting and adjustment mechanism, and adjustable seat

Description:
RELATED APPLICATIONS 
     This application is a § 371 application of PCT/CN2020/089596 filed May 11, 2020, which claims priority from Chinese Patent Application No. 201910435788.1 filed May 23, 2019, each of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention pertains to the field of daily necessities and relates to a multi-gear adjustable support mechanism and an adjustable seat comprising the multi-gear adjustable support mechanism. 
     BACKGROUND OF THE INVENTION 
     Some daily appliances have support components. For example, seats such as chairs have backrests, which can support the waist and back of the user in a sitting state, and make the user feel comfortable. When users use these daily appliances, they usually adopt a posture that they feel comfortable. Accordingly, the support angles required by the users are different. 
     In order to generate a sufficient supporting force for different angles, the prior art discloses support mechanisms for adjusting angles, and these support mechanisms are suitable for these daily appliances. For example, an angle adjustment mechanism is provided between the cushion and the backrest of a car seat. And the user can manually or electrically adjust the angle of the backrest. This kind of support and adjustment mechanisms is relatively free in angle adjustment, but usually with complicated structure, large volume and high cost. Therefore, this kind of support and adjustment mechanisms is usually used in vehicles, train seats and other transportation, and it is difficult to be used in daily life. In contrast, there are also some relatively simple support mechanisms for angle adjustment in the prior art. For example, the sit board and the back plate of the seat are connected by a rotating shaft, and then a strut and a multi-gear member that cooperates with the strut (for example, a gear element with a plurality of grooves corresponding to different angle gears, etc.) is used to achieve angle adjustment. This type of support mechanism and the seat containing the support mechanism have the advantages of simple structure and low cost, but the seat is relatively inconvenient to use. And the user needs to operate with both hands after leaving the seat to adjust the angle. 
     SUMMARY OF THE INVENTION 
     The objective of the present invention is to provide a multi-gear adjustable support mechanism and an adjustable seat that are simple in structure and easy to use. The present invention adopts the following technical solutions. 
     The present invention provides a multi-gear adjustable support mechanism, characterized by comprising: 
     a base plate; 
     a support plate, which is rotatably installed on the base plate; 
     a support element, which is rotatably installed on the plate, and has a support crossbar part for supporting the support plate so as to support the support plate at a different angle from the base plate; a gear forming element, fixed on the support plate, on which a plurality of support gears arranged in a predetermined direction and corresponding to the different angles between the base plate and the support plate are formed; and a gear control element, which controls the movement of the support crossbar part on the gear forming element so that the support element supports the support plate in different the support gears, wherein the gear forming element has a moving surface which carries the movement of the support crossbar part, a plurality of gear grooves respectively corresponding to the support gears and capable of accommodating the support crossbar part are formed on the moving surface, and a limiting part corresponding to an unlock gear for unlocking is formed on the moving surface, the gear control element is movably arranged on the gear forming element in the predetermined direction, and the gear control element has a first abutting part which can abut against the support crossbar part and is positioned at an end of the gear control element close to the limiting part, and the gear control element has a platform part which is far from the limiting part and corresponding to the gear grooves, the support crossbar part abuts against the first abutting part and drives the gear control element to move when moving towards the limiting part in the predetermined direction, so as to make the platform part at least aligned with the moving surface which is positioned at the gear groove closest to the limiting part when the support crossbar part reaches the limiting part, thereby allowing the support crossbar part to move on the surface of the platform part and crosses the gear grooves when the support cross bar part returns from the limiting part. 
     Further, the end of the gear control element away from the limiting part has a second abutting part capable of abutting against the support crossbar part, and the support crossbar part abuts against the second abutting part and drives the gear control element to move when the support crossbar part moves in a direction away from the limiting part. 
     Further, the gear control element also has a recess positioned between the first abutting part and the platform part, the shape of the recess matches the shape of the gear groove, when the support gear crossbar part moves along the predetermined direction and drives the gear control element to move by abutting against the first abutting part, the recess is sequentially aligned with each of the gear grooves along with the movement of the gear control element, so that once the support crossbar part stops moving, the support crossbar part can enter the gear groove along the surface of the first abutting part and the recess, thereby entering corresponding the support gear. 
     Further, the number of the recesses is multiple and not greater than the number of the gear grooves, and the distance between adjacent the recesses is the same as the distance between adjacent the gear grooves. 
     Further, the multi-gear adjustable support mechanism further comprises a crossbar guiding element, which is used to provide the support crossbar part a tendency force that makes the support crossbar part to move into the gear groove, so that when the recess is aligned with the gear groove and the support crossbar part reaches the gear groove, the support crossbar part automatically enters the gear groove under the action of the tendency force. 
     Further, the crossbar guiding element is a hook-shaped element fixed on the support crossbar part, a first magnet element extending along the predetermined direction and distributed at least at each of the gear grooves is provided at the gear forming element, and a second magnet element is fixed on the hook-shaped element, the first magnet element and the second magnet element are attracted to each other by magnetic force, thereby generating the tendency force. 
     Further, a second magnet element is fixedly arranged on the gear control element, and the second magnet element and the first magnet element are attracted to each other by magnetic force, so that the gear control element is attracted to the gear forming element and can move relative to the gear forming element. 
     Further, the first magnet element is a magnetic metal sheet, and the second magnet element is a permanent magnet. 
     Further, the support control component further comprises a cover element covering the gear forming element. 
     Further, the crossbar guiding element is a sheet-shaped element that is fixed on the cover element by a plurality of springs and is in contact with the support crossbar part, the springs are all compression springs, and apply a force toward the second element on the crossbar guiding element, so that the crossbar guiding element applies the tendency force on the support crossbar part. 
     Further, the gear forming element is provided with a groove part extending along the predetermined direction, and the groove part is provided with a guiding groove extending along the predetermined direction, and the gear control element is movably arranged on the gear forming element through the guiding groove. 
     Further, the gear control element is provided with a fixture block embedded in the guiding groove, so that the gear control element can be movably arranged on the gear forming element in an up-and-down direction. 
     Further, the inner side of the guiding groove is further provided with an inner groove part corresponding to the gear groove, and the depth of the part of the inner groove corresponding to the gear groove is lower than the depth of the gear groove, both sides of the platform part are provided with third extension parts that are overlaid on the guiding groove, and the distance between the ends of two the third extension parts is greater than the width of the groove part, so that the gear control element can slide on the guiding groove by two the third extension parts. 
     Further, the widths of the platform part and the first abutting part are both smaller than the distance between the guiding grooves and at the same time greater than the distance between the inner groove parts, so that the support crossbar part drives the first abutting part to move, and the gear control element rotates through the shaft formed by two the extension parts when the first abutting part reaches the gear groove, so that the platform part and the first abutting part enter the gear groove, thereby guiding the support crossbar part to enter the gear groove. 
     Further, the length of the platform is greater than the distance between the ends of the gear grooves on both sides of the predetermined direction, so that the platform part is aligned with the moving surface positioned at the gear groove when the support crossbar part reaches the limiting part, thereby allowing the support crossbar part to cross all the gear grooves by the platform part. 
     Further, the multi-gear adjustable support mechanism further comprises a cover element, covering the gear forming element, wherein the first abutting part is provided with a second extension part extending toward the cover element, the cover element is provided with a pressing piece extending toward the gear control element, and the pressing piece is pressed against the second extension part, thereby generating a tendency force that pushes the part of the gear control element comprising at least the first abutting part toward the gear forming element, the tendency force pushes the first abutting part toward the inner groove part when the gear control element is driven by the support crossbar part and reaches the gear groove, so that the platform part inclines and guides the support crossbar part into the gear groove. 
     Further, the support element further has two connecting rod parts respectively extending from both sides of the support crossbar part, and the ends of two the connecting rod parts away from the support crossbar part are hinged on the base plate. 
     The present invention provides an adjustable seat, comprising: a sit board, corresponding to the buttocks of the user; a waist board, corresponding to the waist of the user; and the aforementioned multi-gear adjustable support mechanism, wherein one of the base plate and the support plate is installed on the sit board or is integrally formed with the sit board, and the other of the base plate and the support plate is installed on the waist board or is integrally formed with the waist board. 
     According to the multi-gear adjustable support mechanism provided by the present invention, the gear forming element is formed with gear grooves corresponding to each support gear and the limiting part corresponding to the unlock gear. The movement control element is movably arranged in the gear forming element. The movement control part further has the platform part that is aligned with the moving surface of the gear forming part and the first abutting part that can abut against the support crossbar part and is located close to the end of the limiting part. Thus, when the support crossbar part moves from top to bottom to the limiting part, the support crossbar part can drive the movement control element to reach the limiting part by abutting against the first abutting part, and the platform part is aligned with the gear groove that is closest to the limiting part. Thereby, when the support crossbar part returns from the limiting part (that is, when the support crossbar part moves from bottom to top), the support crossbar part is blocked by the platform part and cannot enter the gear groove. That is, when the support crossbar part passes through all the support gears and returns from the unlock gear, the support crossbar part will not enter the corresponding gear again. Correspondingly, according to the adjustable seat provided by the present invention, the adjustable seat contains the aforementioned multi-gear adjustable support mechanism. The sit board and the base plate are integrally formed, and the waist board and the support plate is integrally formed. Thereby, when the user uses the adjustable seat, there is no need to manually pull the support element out of the gear groove. In order to unlock the waist board and readjust the gear, the user only needs to turn the waist board. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic structural diagram of the adjustable seat according to embodiment  1  of the present invention. 
         FIG. 2  shows a schematic side view of the structure of the adjustable seat according to embodiment 1 of the present invention. 
         FIG. 3  shows a schematic diagram of an exploded structure of the adjustable seat according to embodiment 1 of the present invention. 
         FIG. 4  shows a schematic cross-sectional structure diagram of the multi-gear adjustable support mechanism of embodiment 1 of the present invention. 
         FIG. 5  shows a schematic structural diagram of the gear forming element according to embodiment 1 of the present invention. 
         FIG. 6  shows a schematic structural diagram of the movement control element according to embodiment 1 of the present invention. 
         FIG. 7  shows a schematic structural diagram of a crossbar guiding element of embodiment 1 of the present invention. 
         FIG. 8  shows a schematic structural diagram of the adjustable seat in different states according to embodiment 1 of the present invention. 
         FIG. 9  shows a partial structural diagram of the part of the multi-gear adjustable support mechanism of the adjustable seat in different states of  FIG. 8 . 
         FIG. 10  shows a schematic cross-sectional structure diagram of the multi-gear adjustable support mechanism according to embodiment 2 of the present invention. 
         FIG. 11  shows a schematic cross-sectional structure diagram of the multi-gear adjustable support mechanism according to embodiment 3 of the present invention. 
         FIG. 12  shows a schematic diagram of the structure of the gear control element of embodiment 3 of the present invention. 
         FIG. 13  shows a schematic structural view of the gear forming element of embodiment 3 of the present invention. 
         FIG. 14  shows a partial structural diagram of the multi-gear adjustable support mechanism of the adjustable seat in different states of embodiment 3 of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention is further described in the following embodiments with reference to the drawings, and not only limited to these embodiments. 
     In the following embodiments, the description of the direction is based on the direction in which the user sits on the adjustable seat. That is, the front refers to the direction in which the user faces, and the back refers to the direction in which the user&#39;s back is facing away. The up and down directions respectively refer to the up and down directions of the user, and the left and right directions respectively refer to the left and right directions of the user. 
     Embodiment 1 
       FIG. 1  shows a schematic structural diagram of the adjustable seat according to embodiment  1  of the present invention. 
       FIG. 2  shows a schematic side view of the structure of the adjustable seat according to embodiment 1 of the present invention. 
       FIG. 3  shows a schematic diagram of an exploded structure of the adjustable seat according to embodiment 1 of the present invention. 
     As shown in  FIGS. 1 to 3 , the adjustable seat  100  of embodiment 1 comprises the sit board  10 , the waist board  20  and the multi-gear adjustable support mechanism  30 . 
     Wherein, the sit board  10  corresponds to the user&#39;s buttocks, and supports the user&#39;s buttocks during use. In the present embodiment, the bottom surface of the sit board  10  is a flat surface, so the adjustable seat  100  of the present embodiment can be placed on other adjustable seats with support legs by the sit board  10  and can be used in conjunction with these adjustable seats. 
     The waist board  20  corresponds to the user&#39;s waist, and is used to support the user&#39;s waist during use. 
     In the present embodiment, the waist board  20  is formed in a curved shape adapted to the waist of human body. 
       FIG. 4  shows a schematic sectional view of the structure of the multi-gear adjustable support mechanism according to embodiment 1 of the present invention. 
     As shown in  FIGS. 1 to 4 , the multi-gear adjustable support mechanism  30  comprises the base plate  31 , the support plate  32 , the support element  33 , the gear forming element  34 , the gear control element  35 , the crossbar guiding element  36 , the cover element  37 , the first magnet element  38  and the second magnet element  39 . 
     The base plate  31  is formed integrally with the sit board. The upper part of the support plate  32  is formed integrally with the waist board, and the lower part of the support plate  32  comprises two connecting parts  321  extending downwards. These two connecting parts  321  are installed on the base plate  31  through the rotating shaft  311 , so that the support plate  32  can rotate relative to the base plate  31 . And correspondingly, the waist board  20  can also rotates relative to the sit board  10 . 
     The support element  33  is used to support the support plate  32 , so that the support plate  32  is stabilized at a certain angle after rotating relative to the base plate  31 . At this time, the waist board  20  is also stabilized at a certain angle relative to the sit board  10 , and the waist board  20  can support the waist of the user at this angle. 
     The support element  33  has a support crossbar part  331  for supporting the support plate  32 . Two ends of the support crossbar part  331  are respectively provided with two connecting rod parts  332 . The ends of the two connecting rod parts  332  away from the support crossbar part  331  are respectively installed in the mounting hole parts  312  provided on the base plate  31 , so that the support element  33  can rotate relative to the base plate  31 , and thereby supporting the support plate  32  at different positions by the support crossbar part  331 . 
     Specifically, the two mounting hole parts  312  are arranged opposite to each other. The lower ends of the two connecting rod parts  332  are respectively provided with extension portions extending outward horizontally. The extension portions are respectively embedded in the mounting hole parts  312 , so that the support element  33  can rotate with the connection of the two mounting hole parts  312  as a rotation axis. 
     In addition, compared to the shaft  311  for installing the connecting parts  321  of the support plate  32 , the mounting hole parts  312  for installing connecting rod part  332  are located at a more rear position on the base plate  31 . Therefore, when the user sits on the adjustable seat  100  and leans the waist on the waist board  20 , the support element  33  can support the support plate  32  and waist board  20  from behind the support plate  32 , thereby supporting the waist board  20 . 
     In this embodiment, a plurality of support positions can be formed after the support crossbar part  331  supports the support plate  32 . Correspondingly, the waist board  20  has a plurality of stable angles after being supported by the support crossbar part  331 . In other words, the support crossbar part  331  has a plurality of positions that support the waist board  20 . 
       FIG. 5  shows a schematic structural diagram of a gear forming element according to embodiment 1 of the present invention. 
     As shown in  FIGS. 3 to 5 , the gear forming element  34  in fixed on the rear surface of the support plate  32  by bolts. A plurality of gear grooves  341  are formed on the surface (that is, the moving surface) of the gear forming element  34  away from the support plate  32 , and the gear grooves  341  are arranged in a top-to-down direction. The support crossbar part  331  is in contact with the moving surface and can move up and down along the moving surface, thereby entering different gear grooves  341 . 
     In this embodiment, four gear grooves  341  are provided. Each gear groove  341  is semi-circular when viewed from its side. The diameter of each gear groove  341  matches the diameter of the support crossbar part  331 , so that the support crossbar part  331  can be accommodated in each gear groove  341  when it enters thereof. 
     As shown in  FIGS. 2 and 5 , the support element  33  supports the support plate  32  from behind the support plate  32 . Therefore, when the support crossbar part  331  is accommodated in the gear grooves  341 , the connecting rod part  332  and the support plate  32  forms an acute angle. The force generated by the user&#39;s waist leaning against the waist board  20  is applied to the support crossbar part  331  by the support plate  32  and the gear forming element  34 , so that the support crossbar part  331  and the inner surface of the gear groove  341  tightly abuts each other, and a triangular stress structure is formed between the support plate  32 , the support element  33  and the base plate  31 . Even if the user leans the waist backward forcibly, there will be no relative movement between the support plate  32  and the support element  33  (correspondingly, the angle of the waist board  20  will not change). In this state, the position of the support crossbar part  331  is limited by the gear grooves  341 , and the support crossbar part  331  cannot move upward and move out of the gear grooves  341 . That is, the support crossbar part  331  is limited by the gear grooves  341 . 
     Thereby, each gear groove  341  corresponds to a plurality of positions where the support crossbar part  331  can be limited. When the support crossbar part  331  is limited by different gear grooves  341 , the support crossbar part  331  supports the support plate  32  and the waist board  20  at different angles and different positions, correspondingly. Therefore, different gear grooves  341  actually corresponds to different support gears. 
     As described above, due to the limit of the gear grooves  341 , a triangular stress structure is formed among the support plate  32 , the support element  33  and the base plate  31  when they are used together. Therefore, applying a backward force to the waist board  20  does not allow the support crossbar part  331  to move upward out of the corresponding gear groove  341 . However, when the user leans the user&#39;s upper body forward slightly so that the waist no longer leans against the waist board  20 , and stretches the user&#39;s hand to turn the waist board  20  forward at the same time, the support crossbar part  331  can be moved downward relative to the support plate  32  and waist board  20 , thereby leaving the gear grooves  341 . 
     In this embodiment, the lower end of the gear forming element  34  has a limiting part  342 . The limiting part  342  is a protrusion extending outward from the surface of the gear forming element  34  away from the support plate  32 . When the support crossbar part  331  moves downward along the surface of the gear forming element  34  and reaches the limiting part  342  at the lower end, the support crossbar part  331  is limited by the limiting part  342  and cannot continue to move downward. In this state, when the user stops pulling the waist board  20  forward and pulls the waist board  20  backward instead, since there is no recessed part such as the gear groove  341  at position of the limiting part  342 , the support crossbar part  331  can be moved upward relative to the waist board  20  and the support plate  32  along with the user&#39;s action, and thereby leaving the limiting part  342 . Therefore, the limiting part  342  also corresponds to a gear, that is, the unlock gear. 
     In addition, the upper end of the gear forming element  34  also has a limiting protrusion  343  for blocking the support crossbar part  331 , which stops the support crossbar part  331  from moving upward when the support crossbar part  331  reaches the uppermost position. 
       FIG. 6  shows a schematic diagram of the structure of the movement control element according to embodiment 1 of the present invention. 
     As shown in  FIGS. 3, 5 and 6 , the middle portion of the gear forming element  34  is provided with a groove part  344 . The groove part  344  extends in an up and down direction. The upper end of the groove part  344  extends to the limiting protrusion  343 , and the lower end of the groove part  344  extends to the limiting part  342 . The width of the gear control element  35  matches the width of the groove part  344 , and the gear control element  35  is accommodated in the groove part  344 . 
     Therefore, the gear control element  35  can move inside the groove part  344  and in an up and down direction. In addition, the groove part  344  divides the gear forming element  34  into two portions, therefore each gear groove  341  comprises of two groove portions. The two groove portions are respectively positioned on portions formed by dividing the gear forming element  34  by the groove part  344 . 
     The gear control element  35  is provided with the first abutting part  351 , the recess  352 , the platform part  353  and the second abutting part  354 . They are arranged on the surface of the gear control element  35  close to the support crossbar part  331 , and they are arranged in sequence from bottom to top. The limiting part  342  is positioned at the lower end of the gear control element  35 , meanwhile the gear control element  35  is positioned in the groove part  344  and the groove part  344  is positioned at the middle portion of the gear forming element  34 . Therefore, the first abutting part  351  is positioned at an end close to the limiting part  342  (that is, the lower end), and meanwhile the second abutting part  354  is positioned at an end away from the limiting part  342  (that is, the upper end). 
     The gear control element  35  has a certain thickness. So, when the gear control element  35  is placed in the groove part  344 , the first abutting part  351  and the second abutting part  354  both protrude outward relative to the moving surface of the gear forming element  34 . Meanwhile, the surface of the platform part  353  is aligned with the moving surface, and the recess  352  is recessed inward relative to the moving surface. The shape and size of the recess  352  match the shape and size of gear groove  341 . Therefore, when the gear control element  35  moves to such position that the recess  352  and the gear groove  341  are aligned, the support crossbar part  331  can enter the gear groove  341 . And when the gear control element  35  moves to such position that the platform part  353  and the gear groove  341  are aligned, the surface of the platform part  353  and the moving surface at the gear groove  341  (that is, the moving surface portions of the upper and lower sides of the gear groove  341 ) are aligned. In this state, the support crossbar part  331  is blocked by the platform part  353 . The support crossbar part  331  can only along the surface of the platform part  353 , and cannot enter the gear groove  341 . In addition, a portion of the surface of the recess  352  adjacent to the first abutting part  351  has a smooth transition. 
     In the present embodiment, one recess  352  is provided, and the length of the platform part  353  (that is, the size in the up and down direction) is greater than the diameter of the gear groove  341 . 
       FIG. 7  shows a schematic structural diagram of the crossbar guiding element according to embodiment 1 of the present invention. 
     As shown in  FIG. 7 , in the present embodiment, the crossbar guide element  36  is a hook-shaped element. The hook part of the crossbar guide element  36  is fixed on the support crossbar part  331 , so that the crossbar guide element  36  is fixed to the support crossbar part  331 . 
     As shown in  FIGS. 1 to 4 , the cover element  37  covers the gear forming element  34 . The two ends of the cover element  37  are fixed on the support plate  32  by bolts. The cover element  37  is used to prevent the gear control element  35 , the crossbar guiding element  36  and etc. from falling off. 
     The first magnet element  38  is in the shape of a sheet, and is arranged in the groove part  344  and positioned at the bottom of the groove part  344 . The length and width of the first magnet element  38  match the length and width of the groove part  344 . Therefore, the first magnet element  38  also extends in an up and down direction. The upper end of the first magnet element  38  extends to the uppermost gear groove  341 , and the lower end extends to the limiting part  342 . 
     The second magnet element  39  is cylindrical. In the present embodiment, two second magnet elements  39  are provided, and they are respectively fixed on the crossbar guiding element  36  and the gear control element  35 . 
     In the present embodiment, the first magnet element  38  is a magnetic metal piece. The first magnet element  38  and a permanent magnet can attract each other, but the first magnet element  38  itself does not have magnetism. The second magnet element  39  is a permanent magnet and has magnetism. The second magnet element  39  and a magnetic metal piece can attract each other. Therefore, the gear control element  35  is movably arranged in the groove part  344  by the magnetic attraction of the first magnet element  38  and the second magnet element  39 . 
     Similarly, the second magnet element  39  on the crossbar guiding element  36  and the first magnet element  38  attract each other magnetically, so that the crossbar guiding element  36  applies a force toward the gear forming element  34  on the support crossbar part  331 . When the support crossbar part  331  reaches the position of the gear groove  341  and is not blocked by the platform part  353 , the force causes the support crossbar part  331  to move toward the gear groove  341 , so that the support element  33  automatically enters the gear groove  341  without the interference of the user. 
     In the present embodiment, the second magnet element  39  on the crossbar guiding element  36  is exposed from the surface of the crossbar guiding element  36  close to the first magnet element  38 . When the support crossbar part  331  enters the gear groove  341 , the surface of the second magnet element  39  is in contact with the first magnet element  38 . Therefore, once the support crossbar part  331  enters the gear groove  341 , the second magnet element  39  and the surface of the first magnet element  38  slightly collide and make a sound. The sound reminds the user that the corresponding support gear is in place. 
     In addition, when the support crossbar part  331  moves on the moving surface or on the surface of the platform part  353 , since the support crossbar part  331  does not enter the gear groove  341 , there is a certain distance between the second magnet element  39  on the crossbar guiding element  36  and the first magnet element  38 . At this time, the second magnet element  39  on the crossbar guiding element  36  and the first magnet element  38  still attract to each other and a force is generated thereof. The force makes the support crossbar part  331  always have a tendency to move toward the first magnet element  38 , so that the support crossbar part  331  is always attached to the moving surface or the surface of the platform part  353 . 
     The operating principle of the adjustable seat  100  of the present embodiment will be described below with reference to the drawings. 
       FIG. 8  shows a schematic structural diagram of the adjustable seat in different states of embodiment 1 of the present invention.  FIG. 9  shows a partial structural diagram of the multi-gear adjustable support mechanism of the adjustable seat in different states of  FIG. 8 . In  FIGS. 8 and 9 , arrows D 1  and D 2  respectively indicate the direction in which the user pulls the waist board  20  to make it rotate, and S 1 , S 2 , S 3 , and S 4  indicate different states of the adjustable seat  100  respectively. 
     As shown in  FIGS. 8 and 9 , the state S 1  is the state that the adjustable seat  100  is in one support gear. In this state, support crossbar part  331  is positioned in one of the gear grooves  341 , and supports the support plate  32  and the waist board  20  in a fixed angle. Since a plurality of gear grooves  341  and corresponding support gears are provided, four S 1  states are provided, and only one of the S 1  states is shown in the drawings. 
     When the use turns the waist board  20  forward, the waist board  20  rotates forward so that the support crossbar part  331  moves downward relative to the support plate  32 . When the support crossbar part  331  moves downward and reaches the first abutting part  351 , the support crossbar part  331  abuts against the first abutting part  351  and drives the gear control element  35  to move downward. When the recess  352  is aligned with the next gear groove  341 , the attraction force between the second magnet element  39  on the crossbar guiding element  36  and the first magnet element  38  makes the support crossbar part  331  have a tendency to move into the gear groove  341 . Therefore, the support crossbar part  331  enters the gear groove  341 , that is, the support crossbar part  331  enters the next support gear. In addition, the portion of the recess  352  adjacent to the first abutting part  351  is a smooth transition, therefore the portion of the support crossbar part  331  that abuts against the first abutting part  351  can also slide into the recess  352  smoothly along the adjacent portion. It is equivalent to entering the gear groove  341  aligned with the recess  352 . 
     After entering the next support gear described above, if the user continues to turn the waist board  20 , the support crossbar part  331  further enters the support gear after next according to the aforementioned process. The support crossbar part  331  stops when it moves downward to the limiting part  342  and is limited by the limiting part  342 . At this time, the adjustable seat  100  is in the state S 2 . 
     The limiting part  342  is not provided with the gear grooves  341 , therefore the support crossbar part  331  cannot enter the support gear or continue to move downward. When the user releases the user&#39;s hands, the waist board  20  and the support plate  32  both rotate slightly backwards due to gravity (the user can also turn the waist board  20  backwards by hand to rotate it backwards, or lean the waist on the waist board  20  so as to rotate the waist board  20  backwards by applying a force from the waist). As a result, the support crossbar part  331  moves upward relative to the support plate  32 . 
     When the support crossbar part  331  moves upward to the seconds abutting part  354 , the support crossbar part  331  abuts against the seconds abutting part  354  and drives the gear control element  35  to move upward. The state of this movement process is shown in S 3 . In this state, the support crossbar part  331  is in contact with the platform part  422 . Therefore, when moving to each of the gear grooves  341 , the support crossbar part  331  cannot enter the gear groove  341  due to the blocking of the platform part  422 , so that the support crossbar part  331  crosses each of the gear grooves  341  and moves upward to the uppermost limiting protrusion (equivalent to the first support gear). As a result, the adjustable seat  100  reaches the state S 4 , that is, the reset state. 
     In this state, the user can turn the waist board  20  forward again, so that the support crossbar part  331  enters each gear groove  341  in turn. The user can also stop turning the waist board  20  when the angle feels appropriate, so that the support crossbar part  331  is limited in the corresponding gear groove  341  after entering thereof. That is, the adjustable seat  100  returns to a different S 1  state. 
     In the above process, when the support crossbar part  331  reaches the limiting part  342  and cannot continue to move downward, the user can turn the waist board  20  backward to move the support crossbar part  331  to the uppermost limiting protrusion. As a result, the adjustable seat reaches state S 4 , so that it can be adjusted from the uppermost support gear. On the other hand, when the adjustable seat  100  is in state S 3 , the user can also stop turning the waist board  20  backward at any time during the turning backward process and start to turn the waist board  20  forward again. In this state, the support crossbar part  331  will move downward from the current position and leave the second abutting part  354  and the platform part  353 . If the recess  352  is aligned with a certain gear groove  341  at this time, the support crossbar part  331  enters the gear groove  341  and stops at the corresponding support gear. If the recess  352  is not aligned with any of the gear grooves  341  at this time, the support crossbar part  331  will move long the moving surface to the first abutting part  351  and abut against the first abutting part  351 , thereby driving the gear control element  35  to move downward until the recess  352  is aligned with a certain gear groove  341  and enter the gear groove  341 . Therefore, the adjustable seat  100  of the present embodiment can be adjusted midway. That is, the user can stop turning the waist board  20  backward any time during the adjustment, and turn the waist board  20  forward again to make the support crossbar part  331  enter the closest support gear. 
     According to the multi-gear adjustable support mechanism provided in the present embodiment, the gear forming element is formed with gear grooves corresponding to each support gear and a limiting part corresponding to the unlock gear. The movement control element is movably arranged on the gear forming element. The movement control element also has a platform part that is aligned with the moving surface of the gear forming element and a first abutting part that abuts against the support crossbar part and is positioned at an end close to the limiting part. Therefore, when the support crossbar part moves from top to bottom to the limiting part, the support crossbar part can drive the movement control element to the limiting part by abutting against the first abutting part. As a result, the platform part is aligned with the gear groove that is closest to the limiting part, so that the surface of the platform part is aligned with the moving surface that is positioned at the gear groove. Thus, when the support crossbar part returns from the limiting part (that is, when moving from bottom to top), the support crossbar part is blocked by the platform part and cannot enter the gear groove. That is, after the support crossbar part has passed all the support gears, it will not enter the corresponding gear when returning from the unlock gear. Correspondingly, according the adjustable seat provided by the present embodiment, the multi-gear adjustable support mechanism is contained, the sit board and the base plate is integrally formed, and the waist board and the support plate is integrally formed. Therefore, when the user uses the adjustable seat, there is no need to manually pull the support element out of the gear grooves, but only to turn the waist board to unlock the waist board and adjust the gears again. 
     Further, the movement control element in the present embodiment also has a second abutting part at one end away from the limiting part. The second abutting part can abut against the support crossbar part. In this way, when the support crossbar part returns from the limiting part (that is, moving from bottom to top), the movement control element is driven and always moves with the support crossbar part, so that the platform part always blocks the support crossbar part from entering the gear grooves, and the support crossbar part can return to the uppermost end without entering any of the gear grooves. In addition, a recess is provided between the platform part and the first abutting part, and the connecting portion of the recess and the first abutting part is a smooth transition. Therefore, when the support crossbar part abuts against the first abutting part and drives the movement control element to move downward, the recess is aligned with each of the gear grooves in turn, so that the support crossbar part enters each of the gear grooves in turn, and the adjustable seat is adjusted to each of the support gears. 
     The multi-gear adjustable support mechanism further comprises a crossbar guiding element that applies a force toward the gear forming element and the waist board. The force causes the support crossbar part to enter the gear groove when the support crossbar part moves to the gear groove and the recess is aligned with the gear groove. 
     In general, in the multi-gear adjustable support mechanism provided by the present embodiment, the gear forming element, the movement control element and the crossbar guiding element cooperate with each other. Therefore, when adjusting the gears, the user only needs to turn the waist board forward or backward, and make the adjustment direction between the support gears opposite to the resetting direction (that is, the direction of adjusting the support gears is that the support crossbar part moves from top to bottom, corresponding to the user moving the waist board forward; and the direction of resetting is that the support crossbar part moves from bottom to top, corresponding to the user moving the waist board backward or the user leaning on the waist board to make the waist board rotate). The user can adjust or reset the support gears without complicated operation. 
     In addition, the forced applied by the crossbar guiding element to the support crossbar part is achieved by the attraction between the magnetic elements, and the combination between the movement control element and the gear forming element is also achieved by the attraction force between the magnet elements. Therefore, there is no need to provide additional mechanically connected parts or structures between the parts. The structure is relatively simple and easier to manufacture. 
     Embodiment 2 
     In embodiment 2, the same reference numbers are used and the same descriptions are omitted for the same structures as in embodiment 1. 
       FIG. 10  shows a schematic cross-sectional structure diagram of the multi-gear adjustable support mechanism according to embodiment 2 of the present invention. 
     As shown in  FIG. 10 , in embodiment 2, the multi-gear adjustable support mechanism  30  comprises the base plate  31  (not shown in  FIG. 10 ), the support plate  32 , the support element  33 , the gear forming element  34 , the gear control element  35 , the crossbar guiding element  36 , the cover element  37  and the springs  41 . 
     The main difference between the present embodiment and embodiment 1 is that the tendency force on the support crossbar part  331  toward the gear forming element  34  and the support plate  32  is not provided by the mutual attraction between the magnet elements, but by the elastic deformation force of the spring. 
     Specifically, the crossbar guiding element  36  of the present embodiment is a sheet-shaped element fixed on the cover element  37  by a plurality of springs  41 . The sheet-shaped element is in contact with the support crossbar part  331 . The upper end of the sheet-shaped element is close to the limiting protrusion  343 , and the lower end is close to the limiting part  342 . The springs  41  are all compression springs and apply forces toward the support plate  32  on the crossbar guiding element  36 . The forces in turn causes the crossbar guiding element  36  to press on the surface of the support crossbar part  331 , which in turn presses the support crossbar part  331  on the moving surface of the gear providing element  41 . As a result, the support crossbar part  331  can only move along the moving surface, and when it reaches the gear grooves  341 , it will automatically enter one of the gear grooves  341  under the influence of the forces of the springs and the crossbar guiding element  36 . 
     In addition, in the present embodiment, the gear control element  35  is no longer arranged in the groove part  334  by the attractive force of the first magnet element  38  and the second magnet element  39 , but is movably arranged in the groove part  334  through the guiding groove  345 . Specifically, the inner surface of the groove part  344  is provided with a guiding groove  345  extending in the up and down direction. The guiding groove  345  is formed by sinking the surface of the groove part  344 , so its cross-section has a concave shape. The gear control element  35  is provided with a fixture block embedded in the guiding groove  345 , so that the gear control element  35  is movably arranged in the groove part  334 , and the gear control element  35  can move in an up and down direction. 
     Compared with embodiment 1, in the present embodiment, the tendency force that forces the support crossbar part  331  to move along the moving surface and enter the gear grooves is provided by the compression springs and the sheet-shaped element that is in contact with the support crossbar part  331 . Since the springs may be weakened during long-term use, the service life is relatively shorter. However, since the price of the springs is lower than that of the permanent magnets (especially permanent magnets with strong magnetic force), the manufacturing cost is relatively lower. 
     In the same way, the gear control element  35  is fixed in the groove part  344  by the structure of the guiding groove and the fixture block, but not by the attraction force of the magnet elements. The service life of such mechanical structure is relatively short. But the mechanical structure does not require magnetic metal sheets or permanent magnets, thereby reducing the manufacturing cost. 
     Embodiment 3 
     In embodiment 3, the same reference numbers are used and the same descriptions are omitted for the same structures as in embodiment 1. 
     Compared with embodiment 1 and 2, the difference of the present embodiment is mainly in the structure of the gear control element  35  and the corresponding way of guiding the support crossbar part  331  into the gear grooves  341 . In the present embodiment, no recess  352  or similar structure is formed on the gear control element  35 . The gear control element  35  guides the support crossbar part  331  into the gear grooves  341  not by means of aligning the recess  352  and the gear groove  341 , but by means of steering. The specific structure and operation principle are explained below with reference to the drawings. 
       FIG. 11  shows a schematic cross-sectional structure diagram of the multi-gear adjustable support mechanism according to embodiment 3 of the present invention. 
     As shown in  FIG. 11 , the multi-gear adjustable support mechanism  30  of embodiment 3 comprises the base plate  31  (not shown in  FIG. 11 ), the support plate  32 , the support element  33 , the gear forming element  34 , the gear control element  35  and the cover element  37 . 
       FIG. 12  shows a schematic diagram of the structure of the gear control element according to embodiment 3 of the present invention. 
     As shown in  FIGS. 11 and 12 , the gear control element  35  is provided with the first abutting part  351 , the platform part  353  and the second abutting part  354  that arranged in sequence from bottom to top on the surface of the gear control element  35  close to the support crossbar part  331 . 
     In the present embodiment, the first abutting part  351  is provided with a first extension part  335  extending in a direction away from the platform part  353  (that is, downward) and a second extension part  356  extending toward the cover element  37 . Each side of the platform part  353  is provided with a third extension part  357  extending to the side. The end of the second abutting part  354  is provided with a fourth extension part  358  extending toward the first abutting part  351 . Therefore, the gear control element  35  as a whole presents an open ring-like structure. 
     In addition, the third extension parts  357  are both located at a position of the platform part  353  close to the second abutting part  354 . The end of the second extension part  356  is also provided with a first protrusive block  359  with a triangular cross-sectional shape. 
     In other words, compared with the gear control element  35  of embodiment 1, the gear control element  35  of the present embodiment does not have a recess  352 , but has the first extension part  355 , the seconds extension part  356 , the third extension parts  357  and the protrusive block  359  in addition. Correspondingly, since no recess  352  is provided, the first abutting part  351  and the platform part  353  are directly connected to each other, and the connection part of the two presents a smooth transition surface. 
     In addition, the length of the platform part  353  of the present embodiment is longer, and it is greater than the distance between the upper end of the uppermost gear groove  341  and the lower end of the lowermost gear groove  341 . 
       FIG. 13  shows a schematic structural diagram of the gear forming element of embodiment 3 of the present invention. 
     As shown in  FIGS. 11 and 13 , the gear forming element  34  is formed with two gear grooves  341 , and the groove part  344  extending in the length direction (that is, in the up and down direction) is provided in the middle portion of the gear forming element  34 . The groove part  334  divides the gear forming element  34  into two portions. The inner edges of the two portions (that is, the edges adjacent to the groove part  344 ) are partially formed with a guiding groove  345 . The guiding groove  345  is formed by sinking the inner edges of the two portions of the gear forming element  34  respectively, so its cross-sectional shape is L-shaped, which is different from embodiment 2. 
     Two inner groove parts  346  corresponding to the gear grooves  341  are respectively provided on the inner side of the two guiding grooves  345 . The inner groove parts  346  are formed by further sinking the inner edges of the two portions of the gear forming element  34 , and their cross-sections are also L-shaped. In addition, the depth of the portion of the inner groove parts  346  corresponding to the gear grooves  341  (that is, the distance between the deepest part of the depression corresponding to the gear grooves  341  and the surface of the gear forming element  34 ) is lower than the depth of the two gear grooves  341 , and the depth of the lower end of the inner groove parts  346  (that is, the end close to the limiting part  342 ) is lower. 
     In the present embodiment, the distance between the ends of the two third extension parts  357  is greater than the width of the groove part  344 . The two third extension parts  357  are placed on the guiding groove  345 , so that the gear control element  35  can slide on the the guiding groove  345  by the third extension parts  357 , so as to be movably arranged in the groove part  344 . The shape of the gear grooves  341  is also different from the previous two embodiments. Specifically, the upper surface of the gear grooves is arc-shaped, and the lower surface extends downward obliquely. This shape makes it easier for the support crossbar part  331  to slide out from the lower surface of the gear grooves  341  when the support crossbar part  331  moves downward, thereby leaving the gear grooves  341 . 
     Further, the width of the gear control element  35  (including the width of the platform part  353  and the first abutting part  351 ) is smaller than the distance between the guiding grooves  345 , and larger than the distance between the inner groove parts  346  at the same time. Therefore, when moving to the junction of the inner groove parts  346  and the guiding groove  345  (that is, point X in  FIG. 13 ), the platform part  353  and the first abutting part  351  can move along the inner groove parts  346  so as to enter the gear grooves  341 . In contrast, the third extension parts  357  cannot move along the inner groove parts  346 , but can only move along the guiding groove  345 , and the third extension parts  357  cannot enter the gear grooves  341 . 
     The surfaces of the third extension parts  357  close to the guiding groove  345  are arc-shaped, so the gear control element  34  can also be rotated with the shaft formed by the two third extension parts  357  as a rotation axis. That is, when moving to point X, the gear control element  34  rotates through the shaft formed by the two third extension parts  357 , so that the platform part  353  and the first abutting part  351  enter the gear grooves  341 . 
     As shown in  FIG. 11 , the cover element  37  of the present embodiment is provided with a pressing piece  371  extending toward the second extension part  356 . The end of the cover element  37  is further provided with a second protrusive block  372  with a polygonal cross-section. The pressing piece  371  and the second extension part  356  press against each other, and both have a certain elasticity. Therefore, the force of the pressing piece  371  pressing on the second extension part  356  forms a tendency force that pushes the lower portion of the gear control element  35  (that is, the second extension part  356 , the first abutting part and etc.) toward the gear forming element  34 . 
       FIG. 14  shows a partial structural diagram of the multi-gear adjustable support mechanism of the adjustable seat in different states of embodiment 3 of the present invention. The support plate  32  is omitted in  FIG. 14 , and at the same time, S 5 , S 6 , S 7 , and S 8  correspond to different states of the adjustable seat  100  respectively. 
     As shown in  FIG. 14 , S 5  shows a state in which the support crossbar part  331  is positioned in the upper gear groove  341 . S 6  shows a state in which the support crossbar part  331  is positioned in the lower gear groove  341 . Each gear grooves  341  corresponds to a support gear. Therefore, S 5  and S 6  are the states where the adjustable seat  100  is in the support gears, which is equivalent to state S 1  of embodiment 1. 
     In the state of S 5 , the support crossbar part  31  and the first abutting part  351  are both positioned in the upper gear groove  341 . When the user turns the waist board  20  forward to make it rotate forward in direction D 1  as shown in  FIG. 8 , the support crossbar part  31  moves downward along the guiding groove  345 . At the same time, the support crossbar part  31  abuts against the first abutting part  351  and drives the gear control element  35  to move downward together with it. The lower surfaces of the gear grooves  341  are inclined, so the support crossbar part  31  can easily move out of the gear grooves  341  and drive the gear control element  35  to move out together with it. 
     When reaching the lower gear groove  341 , the crimping action of the pressing piece  371  and the second extension part  356  generates a tendency force that pushes the lower portion of the gear control element  35  to the gear forming element  34 , so the lower portion of the gear control element  35  (including the first abutting part  351 ) can only approach the inner groove parts  346  or move along the surface of the inner groove parts  346 . Therefore, the lower portion of the gear control element  35  faces the bottom of the inner groove parts  346 , while the upper portion thereof is always placed on the guiding groove  345  by the third extension parts  357 . At this time, the platform part  353  is inclined from the guiding groove  345  to the bottom of the inner groove parts  346 . 
     The support crossbar part  331  is sandwiched between the platform part  353  and the second extension part  356 . Therefore, when the platform part  353  is in the aforementioned inclined state, the support crossbar part  331  moves along the platform part  353 , and is guided into the lower gear groove  341  by the platform part  353 , and reaches the state shown in S 6 . 
     When the user further turns the waist board  20  to make the support crossbar part  331  further move downward relative to the gear control element  35 , the support crossbar part  331  abuts against the first abutting part  351  and drives the gear control element  35  to move downward continuously, so that the gear control element  35  moves out of the lower gear groove  341 . Then, the support crossbar part  331  reaches the limiting part  342  and drives the first abutting part  351  to reach the limiting part  342 . Since the depths of the inner groove parts  346  are relatively shallow, the first abutting part  351  moves along the inner groove parts  346  and reaches the limiting part  342 . At this time, the surfaces of the first protrusive block  359  and the second protrusive block  372  abut against each other. In this state, the pressing piece  371  and the second extension part  356  also press against each other. The elastic deformation force of the pressing piece  371  and the second extension part  356  makes the surfaces of the first protrusive block  359  and the second protrusive block  372  press against each other, and it is not easy to shift between the two surfaces. Therefore, the lower end portion of the gear control element  35  is stabilized at the position of the limiting part  342 , and reaches the state shown in S 7 . In addition, in this state, the first extension part  355  abuts on the surface of the cover element  37 , so that the gear control element  35  shown in state S 7  is more stable and less likely to be shifted. 
     In the state shown in S 7 , when the user turns the waist board  20  backward, the gear control element  35  is not easily shifted in this state. Therefore, when the support crossbar part  331  moves upward relative to the gear forming element  34 , the support crossbar part  331  leaves the first abutting part  351  and moves upward along the platform part  353 . The length of the platform part  353  is greater than the distance of the upper end of the uppermost gear groove  341  and the lower end of the lowermost gear groove  341 , therefore the platform part  353  is aligned with all the gear grooves  341  at this time, equivalent to that the surface of the platform part  353  is aligned with the moving surface among the gear grooves  341  and other portions. Therefore, the support crossbar part  331  moves on the surface of the platform part  353  so as to pass all the gear grooves  341  at one time and move upward. 
     When reaching the second abutting part  354 , the support crossbar part  331  abuts against the second abutting part  354  and drives the gear control element  35  to move upward. At this time, the driving force that drives the support crossbar part  331  and the gear control element  35  to move upward is provided by the user turning the waist board  20 . Therefore, the driving force can overcome the elastic deformation force of the pressing piece  371  and the second extension part  356 , so that the first protrusive block  359  is separated from the second protrusive block  372 . As a result, the gear control element  35  further moves upward and reaches the limiting protrusion  343 , reaching the state shown in S 8 . 
     In the state shown in S 8 , if the user turns the waist board  20  to make the support crossbar part  331  to move downward relative to the gear forming element  34 , the support crossbar part  331  abuts against the first abutting part  351  and drives the gear control element  35  to move downward together. When the gear control element  35  passes the point X, the lower portion of the gear control element  35  moves along the surface of the inner groove parts  346  due to the pressing action of the pressing piece  371  and the second extension part  356 . As a result, the support crossbar part  331  is guided into the gear grooves  341 , returning to the state shown in S 5 . 
     Therefore, when using the seat  100  of the present embodiment, if the user needs to adjust the angle between the sit board  10  and the waist board  20  (equivalent to the angle between the support plate  32  and the base plate  31 ), the user only needs to lean the upper body forward so that the waist temporarily leaves the waist board, and then move the waist board  20  backhand so that the support crossbar part  331  enters the corresponding gear groove  341 . During the process, the user does not need to leave the seat  100 , nor to bend or twist the waist. 
     Compared with embodiment 1 or 2, in the present embodiment, the form of recesses formed on the gear control element  35  is not used to guide the support crossbar part  331 . Meanwhile, the force toward the gear forming element  34  that drives the gear control element  35  is not provided by magnet elements or springs, but by the elastic deformation force of the pressing piece  371  and the second extension part  356 . 
     The structure of the present embodiment is simpler than that of embodiment 2, and does not require magnet elements as in embodiment 1, therefore with a lower cost than embodiment 1. 
     However, the platform part  353  of the gear control element  35  requires a certain length to ensure that all the gear grooves  341  are covered. When the number of the gear grooves  341  is large, the length of the platform part  353  will be too long. To ensure that the inclination angle of the platform part  353  is suitable for guiding the support crossbar part  331  into the gear grooves  341 , the inner groove parts  346  need to be make deeper. In this case, the platform part  353  is too long and the inner groove parts  346  are too deep, therefore the movement and rotation of the gear control element  35  are not smooth enough. It is even difficult to smoothly guide the support crossbar part  331  into or out of the gear grooves  341 . Therefore, under the premise of ensuring smooth use, the multi-gear adjustable support mechanism  30  of the present embodiment should not be made into a form with a large number of gears. Generally, 2 to 4 gears are sufficient. 
     In addition, the platform part  353  of the present embodiment allows the support crossbar part  331  to pass over all the gear grooves  341  at one time. Therefore, when the support crossbar part  331  reaches the unlock gear, the support crossbar part  331  can only move upward to the uppermost gear groove  341  and continue to move upward. In this way, the gear control element is driven to move upward, and the first protrusive block and the second protrusive block are separated. After the first protrusive block and the second protrusive block are separated, the support crossbar part  331  can enter each gear groove  341  in sequence again. Therefore, the multi-gear adjustable support mechanism cannot achieve midway adjustment, and the flexibility of use is not as good as embodiment 1 or 2. 
     The aforementioned embodiments are only used to illustrate the specific implementations of the present invention, and the multi-gear adjustable support mechanism and the adjustable seat of the present invention are not limited to the scope of the aforementioned embodiments. 
     In embodiment 1 and 2, a recess is provided on the movement control element. However, in the present invention, a plurality of recesses can be provided on the movement control element to achieve the same gear controlling effect, as long as the number of the recesses is not greater than that of the gear grooves. When a plurality of recesses is provided on the movement control element, the length of the whole movement control element will be longer than that of the embodiments. But as long as the length is not greater than the distance of the uppermost gear and the limiting part, the recesses can make the support crossbar part drive the movement control element to move up or down by abutting the first abutting part or the second abutting part respectively, thereby achieving gear adjustment or resetting. 
     In each embodiment, the gear forming element is fixedly arranged on the support plate. However, in the present invention, the gear forming element can also be integrally formed with the support plate. 
     In addition, four gear grooves are provided in embodiment 1 and 2, while two gear grooves are provided in embodiment 3. However, in the present invention, fewer or more gear grooves can be provided, such as three or five, so as to provide more support gears for the user to choose. Especially in the form of embodiment 1, the gear control element is arranged on the gear forming element by magnetic force, and the tendency force between the support crossbar part and the crossbar guiding element is also provided by magnetic force. In this form, the number of the gear grooves is not as limited as in embodiment 3, therefore it is suitable for occasions with a large number of gears. 
     In addition, in the embodiments, the support plate is integrally formed with the waist board, and the base plate is integrally formed with the sit board. In the present invention, the corresponding relationship can be altered. That is, the support plate is integrally formed with the sit board, and the base plate is integrally formed with the waist board. In this form, the gear grooves and limiting part on the gear forming element are not distributed in the up and down direction, but in a front and back direction. Correspondingly, when the user turns the waist board, the support crossbar part moves in the front and back directions (rather than the up and down directions) on the moving surface of the gear forming element to enter each support gear. Such an adjustable seat also has the same function of adjusting and resetting the support gears as the embodiments and has basically the same effect. However, it is necessary to leave enough space on the sit board for the support plate. As a result, the adjustable seat has a relatively larger length in the front-to-rear direction and takes a correspondingly larger floor area. Therefore, the adjustable seat is not as portable as the adjustable seats in the aforementioned embodiments. 
     In the embodiments, the adjustable seat is provided with waist board and sit board. The user sits directly on the sit board while using, and the user&#39;s waist leans on the waist board. In the present invention, a sit surface made of flexible material can be further provided to improve the comfort of the adjustable seat. The sit surface can be continuously covered on the sit board and the waist board, and does not affect the rotation of the waist board. The user feels comfortable by contacting with the flexible material. 
     In the embodiments, the lower surface of the sit board is flat, therefore the adjustable seat of the aforementioned embodiments can be used on other adjustable seats. However, in the present invention, the sit board can be further provided with supporting legs, which allows the adjustable seat of the present invention to be put directly on the ground. More than that, the waist board of the embodiments only corresponds to and supports the user&#39;s waist. However, the waist board of the present invention can be extended and provided with accessory parts such as a neck pillow, so that the adjustable seat can also support the user&#39;s other body parts such as the neck, thereby further improving the comfort of use. In this structure, due to the larger size of the waist board the corresponding increase in weight, each member of the gear control component should be made of higher-strength materials.