Backrest assembly of seat and seat

Abstract

The utility model discloses a backrest assembly of a seat and the seat. The backrest assembly of the seat comprises a fixed bracket, a movable bracket, a backrest and a locking piece, a guide part extending up and down is arranged on the fixed support, the movable support is installed on the guide part in a sliding mode, the locking piece is arranged between the movable support and the fixed support, and the locking piece is movably matched with the movable support so that the locking piece can move relative to the movable support between a first position and a second position in the left-right direction; the backrest comprises a top cross beam and a bottom cross beam, the top cross beam is installed on the movable support in a sliding mode, and an elastic supporting piece is arranged between the top cross beam and the movable support; an elastic piece is arranged between the bottom cross beam and the movable support and gradually inclines upwards from front to back, the upper end of the elastic piece is fixedly connected to the movable support, and the lower end of the elastic piece is fixedly connected to the bottom cross beam. According to the utility model, the backrest is arranged on the movable bracket in a floating manner, so that the backrest can adapt to different sitting postures of a user, and the comfort of the seat is improved.

Description

Technical Field

[0001] This utility model relates to the field of seating technology, specifically to a seat back assembly and a seat. Background Technology

[0002] The backrests of existing office chairs and gaming chairs are usually fixed to a backrest bracket, using the support surface of the backrest to conform to the user's back to provide support. In order to make the backrest conform to the user's back better, existing chairs are usually ergonomically designed, with the support surface of the backrest being shaped into a curved surface that is similar to the human back. While this can provide good support for the user's back when the user maintains a correct sitting posture, when the user changes their sitting posture slightly, the backrest fixed to the backrest bracket is difficult to adapt to the change in the user's sitting posture, resulting in a significant reduction in the comfort of the chair. Utility Model Content

[0003] The purpose of this invention is to provide a backrest assembly and a seat that can adapt to changes in the user's sitting posture and improve the comfort of the seat.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] The seat back assembly includes a fixed bracket, a movable bracket, a backrest, and a locking mechanism;

[0006] The fixed bracket is provided with a guide portion that extends vertically. The movable bracket is slidably mounted on the guide portion so that the movable bracket can move relative to the fixed bracket in the vertical direction. The locking member is provided between the movable bracket and the fixed bracket. The locking member is movably engaged with the movable bracket so that the locking member can move relative to the movable bracket in the left-right direction between a first position and a second position. When the locking member is in the first position, it is engaged with the fixed bracket to lock the movable bracket and the fixed bracket together. When the locking member is in the second position, it is disengaged from the fixed bracket so that the movable bracket has the freedom to move relative to the fixed bracket in the vertical direction.

[0007] The backrest includes a top crossbeam and a bottom crossbeam. The top crossbeam is slidably mounted on a movable support so that the top crossbeam can move relative to the movable support in the front-back direction. An elastic support is provided between the top crossbeam and the movable support, which is used to apply forward elastic stress to the top crossbeam. An elastic plate is provided between the bottom crossbeam and the movable support. The elastic plate gradually tilts upward from front to back. The upper end of the elastic plate is fixedly connected to the movable support, and the lower end is fixedly connected to the bottom crossbeam.

[0008] Preferably, the elastic sheet includes a first connecting portion extending upward from its upper end and a second connecting portion extending downward from its lower end. The first connecting portion is fixed to the movable bracket by bolts, and the second connecting portion is fixed to the bottom crossbeam by bolts. The thickness of the elastic sheet gradually increases from its middle part to its two ends.

[0009] Preferably, the movable support is provided with two guide columns that are staggered in the left-right direction, and the extension direction of the guide columns is consistent with the front-back direction. Two guide sleeves are fixed on the top crossbeam, and the two guide sleeves are slidably sleeved on the two guide columns respectively.

[0010] Preferably, the elastic support is a spring sleeved on the guide post, the guide post is provided with a stepped surface, and the two ends of the spring abut against the stepped surface and the rear end surface of the guide sleeve, respectively.

[0011] Preferably, the guide post is provided with a guide hole extending rearward from its front end, and the guide sleeve is provided with a guide post that slides through the guide hole.

[0012] Preferably, the fixed bracket includes a fixed seat and a fixed plate located on the front side of the fixed seat, the fixed plate being detachably fixedly connected to the fixed seat; the guide part includes two guide grooves disposed on the fixed plate and extending in the vertical direction, the rear side of the movable bracket is provided with two sliders, the two sliders being slidably embedded in the two guide grooves respectively, the rear side of the fixed plate is provided with a detachable stop fixed on the slider, and the fixed plate is limited between the stop and the movable bracket.

[0013] Preferably, the fixed bracket is provided with a vertically extending guide groove, the guide groove including a first sidewall and a second sidewall opposite to the first sidewall, the first sidewall being provided with a plurality of locking grooves arranged in the vertical direction; the movable bracket is provided with a mounting groove, the locking member is embedded in the mounting groove and configured to swing between a first position and a second position within the mounting groove, the locking member being provided with a locking pin protruding from the mounting groove and extending into the guide groove, when the locking member is in the first position, the locking pin is engaged in one of the locking grooves, when the locking member is in the second position, the locking pin disengages from the locking groove and is placed in the guide groove; an elastic member is provided between the movable bracket and the locking member, the elastic member being used to apply elastic stress to the locking member so that the locking member always maintains the tendency to swing towards the first position.

[0014] Preferably, the upper end face of the mounting groove has an upwardly recessed first recess, and the lower end face of the mounting groove has a downwardly recessed second recess. The locking member includes a rotating end at its upper end and a locking end at its lower end. The rotating end is fitted into the first recess and configured to rotate within the first recess so that the locking member can swing between a first position and a second position. The guide groove includes an upper end face and a lower end face. The portion of the guide groove between the uppermost locking groove and the upper end face forms a guide portion. The guide portion is used to limit the guide portion when the locking pin slides to the guide portion. The locking member is held in the second position. The upper end face is used to push the locking pin downward so that the locking end of the locking member is engaged in the second recess. The lower end face is used to push the locking pin upward so that the locking end of the locking member is disengaged from the second recess. The locking groove includes a baffle extending from the first sidewall of the guide groove away from the second sidewall and an inclined guide wall extending from the end of the baffle away from the second sidewall to the first sidewall. The inclined guide wall is used to push the locking pin towards the second sidewall when the locking pin is in the locking groove and moves upward. The baffle of the bottommost locking groove smoothly transitions with the lower end face of the guide groove.

[0015] Preferably, a cover plate is detachably fixed on the movable bracket, the cover plate covers the outside of the mounting groove, and the cover plate is provided with a through hole for the locking pin to pass through.

[0016] Seats, including the backrest assembly of the aforementioned seats.

[0017] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0018] In this invention, the top crossbeam of the backrest is slidably mounted on a movable bracket, and an elastic support member applies forward elastic stress to the top crossbeam. The bottom crossbeam of the backrest is connected to the movable bracket by an elastic sheet, thereby allowing the backrest to float on the movable bracket. The bottom crossbeam can move relative to the movable bracket in the front-to-back direction, and can also produce a slight displacement in the vertical direction. Combined with the vertical adjustability of the movable bracket relative to the fixed bracket, the backrest can adapt to different sitting postures of the user. Furthermore, when the user's sitting posture changes, the floating backrest quickly adapts to the changes in the user's sitting posture, allowing the backrest to better fit the user's back, thereby improving the comfort of the seat. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of this utility model;

[0020] Figure 2 This is a cross-sectional view of the present invention;

[0021] Figure 3 for Figure 2 Enlarged view of point A in the middle;

[0022] Figure 4For this Figure 1 Schematic diagram of the movable support structure;

[0023] Figure 5 for Figure 1 Schematic diagram of the middle fixing plate;

[0024] Figure 6 for Figure 1 Schematic diagram of the central locking component;

[0025] Figure 7 This is a schematic diagram of the working state of this utility model;

[0026] Figure 8-10 This is a schematic diagram of the adjustment process of this utility model.

[0027] Wherein: 10, fixed bracket; 11, fixed seat; 12, fixed plate; 121, guide groove; 13, guide groove; 131, first side wall; 132, second side wall; 133, upper end face; 134, lower end face; 135, guiding part; 14, locking groove; 141, baffle wall; 142, inclined guide wall; 20, movable bracket; 21, guide post; 211, stepped surface; 212, guide hole; 22, spring. 23. Spring; 24. Slider; 25. Stop; 26. Mounting groove; 27. First recess; 28. Second recess; 29. ​​Cover plate; 30. Backrest; 31. Top crossbeam; 32. Bottom crossbeam; 33. Guide sleeve; 34. Guide post; 45. Elastic sheet; 46. First connecting part; 47. Second connecting part; 58. Locking element; 59. Locking post; 50. Rotating end; 51. Locking end; 62. Spring. Detailed Implementation

[0028] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. Unless otherwise specified, the materials and equipment used in this embodiment are all commercially available. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0029] In the description of this application, it should be understood that the terms "upper," "lower," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In the description of this application, "a plurality of" means two or more, unless otherwise precisely specified.

[0030] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "connected," "linked," and "connected" should be interpreted broadly. For example, they can refer to a fixed connection, a connection through an intermediary, or a connection within two elements or an interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0031] like Figure 1 , 2 As shown in Figures 3, 4, and 5, this utility model provides a seat backrest assembly, which includes a fixed bracket 10, a movable bracket 20, a backrest 30, and a locking member 50. The fixed bracket 10 is provided with a guide portion that extends in the vertical direction. The movable bracket 20 is slidably mounted on the guide portion, giving the movable bracket 20 the freedom to move relative to the fixed bracket 10 in the vertical direction. The fixed bracket 10 remains relatively fixed to the seat cushion. The backrest 30 is mounted on the movable bracket 20, allowing the backrest bracket 30 to move relative to the seat cushion in the height direction, thereby changing the height between the backrest 30 and the seat cushion.

[0032] The locking member 50 is disposed between the movable bracket 20 and the fixed bracket 10. It is movably engaged with the movable bracket 20, allowing the locking member 50 to move relative to the movable bracket 20 in the left-right direction between a first position and a second position. When the locking member 50 is in the first position, it is engaged with the fixed bracket 10, locking the movable bracket 20 and the fixed bracket 10 together, thereby limiting the vertical movement of the movable bracket 20 relative to the fixed bracket 10. When the locking member 50 is in the second position, it is disengaged from the fixed bracket 10, giving the movable bracket 20 the freedom to move vertically relative to the fixed bracket 10. In other words, by operating the locking member 50 accordingly, the movable bracket 20 and the fixed bracket 10 can be kept relatively fixed to meet the needs of normal use of the seat. The height of the movable bracket 20 can also be adjusted to adjust the vertical position of the backrest 30.

[0033] The backrest 30 includes a top crossbeam 31 and a bottom crossbeam 32. The top crossbeam 31 is slidably mounted on the movable support 20, allowing the top crossbeam 31 to move relative to the movable support 20 in the front-back direction. Elastic support members are provided inside the top crossbeam 31 and the movable support 20, and a forward elastic stress is always applied to the top crossbeam 31 through the elastic support members. An elastic plate 40 is provided between the bottom crossbeam 32 and the movable support 20. The elastic plate 40 gradually tilts upward from front to back, wherein the upper end of the elastic plate 40 is fixedly connected to the movable support 20 and the lower end is fixedly connected to the bottom crossbeam 32. The elastic plate 40 provides elastic support to the bottom crossbeam 32. The elastic plate 40 can be made of plastic or metal material with a certain deformation capacity.

[0034] In this invention, the top crossbeam 31 of the backrest 30 is slidably mounted on the movable bracket 20, and a forward elastic stress is applied to the top crossbeam 31 by an elastic support member. The bottom crossbeam 32 of the backrest 30 is connected to the movable bracket 20 by an elastic sheet 40, thereby allowing the backrest 30 to float on the movable bracket 20. The bottom crossbeam 32 can move relative to the movable bracket 20 in the front-back direction and can also produce a slight displacement in the vertical direction. Combined with the vertical adjustability of the movable bracket 20 relative to the fixed bracket 10, the backrest 30 can adapt to different sitting postures of the user. When the user's sitting posture changes, the floating backrest 30 quickly adapts to the user's posture changes, so that the backrest 30 fits the user's back better, thereby improving the comfort of the seat.

[0035] The aforementioned elastic sheet 40 includes a first connecting portion 41 extending upward from its upper end and a second connecting portion 42 extending downward from its lower end. The first connecting portion 41 is fixedly connected to the movable bracket 20 by bolts, and the second connecting portion 42 is fixedly connected to the bottom crossbeam 32 by bolts. The thickness of the elastic sheet 40 gradually increases from the middle to both ends. The elastic sheet 40 is detachably fixed to the movable bracket 20 and the backrest 30 by bolts. An elastic sheet 40 with appropriate elastic stress can be selected according to actual needs. When the elastic sheet 40 is damaged, it can be easily replaced with a new elastic sheet 40. The elastic sheet 40 is designed with a structure that is thin in the middle and thick at both ends, making the elastic sheet 40 easy to deform, thereby making the backrest 30 float more widely and more easily adapting to changes in the user's sitting posture.

[0036] The movable support 20 is provided with two guide posts 21, which are staggered in the left and right direction and extend in the same direction as the front and back. The top crossbeam 31 is fixed with two guide sleeves 33, which are respectively fitted onto the two guide posts 21, thereby movably installing the top crossbeam 31 on the movable support 20. The guide posts 21 and guide sleeves 33 cooperate to guide the front and back movement of the top crossbeam 31. The aforementioned elastic support is a spring 22 sleeved on the guide post 21. The guide post 21 has a stepped surface 211. The rear end of the spring 22 abuts against the stepped surface 211, and the front end abuts against the rear end face of the guide sleeve 33, thereby applying a forward elastic stress to the guide sleeve 33. To prevent the guide sleeve 33 from detaching from the guide post 21, a limiting screw can be fixed on the guide sleeve 33. The nut at the rear end of the limiting screw is hooked onto the guide post 21. When the guide sleeve 33 moves forward relative to the guide post 21 to the maximum displacement, the nut of the limiting screw is limited by the guide post 21, preventing the guide sleeve 33 from continuing to move forward.

[0037] The guide post 21 is provided with a guide hole 212 extending rearward from its front end, and the guide sleeve 33 is provided with a guide post 331 extending rearward inside. The guide post 331 is movably inserted into the guide hole 212. In this way, the guide hole 212 and the guide post 331 cooperate with each other to guide the front and back movement of the top crossbeam 31 in one step. The fit gap formed between the guide post 21 and the guide sleeve 33, and the fit gap formed between the guide post 331 and the guide hole 212, allows the top crossbeam 31 to have a slight up and down swing amplitude when moving back and forth, so that the elastic sheet 40 can deform in the front and back direction and the up and down direction, so that the backrest 30 can not only float in the front and back direction, but also float slightly in the up and down direction.

[0038] To facilitate the assembly of the fixed bracket 10 and the movable bracket 20, the fixed bracket 10 of this utility model includes a fixed base 11 and a fixed plate 12 located on the front side of the fixed base 11. The fixed plate 12 is fixed to the fixed base 11 by bolts or other detachable means. The guide part includes two guide grooves 121 provided on the fixed plate 12 and extending in the vertical direction. Two sliders 23 are provided on the rear side of the movable bracket 20. The two sliders 23 are slidably embedded in the two guide grooves 121 respectively. A stop block 24 is provided on the rear side of the fixed plate 12 and is detachably fixed on the slider 23. The fixed plate 12 is limited between the stop block 24 and the movable bracket 20, thereby preventing the movable bracket 20 from detaching from the fixed bracket 10.

[0039] See Figure 4 , Figure 5 , Figure 6 and Figure 7As shown, the fixed bracket 10 is provided with a vertically extending guide groove 13. Specifically, the guide groove 13 is provided on the surface of the fixed plate 12 facing the movable bracket 20. The guide groove 13 includes a first side wall 131 and a second side wall 132 opposite to the first side wall 131. The first side wall 131 is provided with a plurality of locking grooves 14 arranged in the vertical direction. The movable bracket 20 is provided with a mounting groove 25, and the locking member 50 is embedded in the mounting groove 25, so that the locking member 50 can be within the mounting groove 25. The part swings between the first position and the second position. The locking member 50 is provided with a locking post 51 that protrudes from the mounting groove 25 and extends into the guide groove 13. When the locking member 50 is in the first position, the locking post 51 is engaged in one of the slots 14, locking the fixed plate 12 and the movable bracket 20. When the locking member 50 is in the second position, the locking post 51 disengages from the slot 14 and slides inside the guide groove 13, allowing the movable bracket 20 to move up and down relative to the fixed plate 12.

[0040] A spring 60 is also provided between the movable bracket 20 and the locking member 50. The spring 60 is used to apply an elastic stress to the locking member 50, so that the locking member 50 always tends to swing towards the first position. In this way, under the action of the elastic stress of the spring 60, the locking pin 51 on the locking member 50 can always be kept in one of the slots 14. When it is necessary to adjust the height of the backrest 30, the locking member 50 is moved towards the second position, so that the locking pin 51 is placed in the guide groove 13, and the movable bracket 20 can be moved up and down.

[0041] In a preferred embodiment, a first recessed position 251 is provided on the upper end face of the mounting groove 25, and a second recessed position 252 is provided on the lower end face of the mounting groove 25. The locking member 50 includes a rotating end 52 located at its upper end and a locking end 53 located at its lower end. The rotating end 52 is embedded in the first recessed position 251, allowing the rotating end 52 to rotate within the first recessed position 251, thereby allowing the locking member 50 to swing between a first position and a second position, and subsequently allowing the locking pin 51 on the locking member 50 to swing left and right. The guide groove 13 includes an upper end face 133 and a lower end face 134. The uppermost slot 14 on the guide groove 13 and the upper end face 133 are connected by a locking groove 14. A guide portion 135 is formed. When the locking pin 51 slides into the guide portion 135, the guide portion 135 guides the locking pin 51, limiting its swing and keeping the locking member 50 in the second position. When the locking pin 51 continues to move upward inside the guide portion 135 and contacts the upper end face 133, the upper end face 133 pushes the locking pin 51 downward. The locking member 50, in the second position in the left-right direction, moves downward relative to the movable bracket 20, causing the locking end 53 on the locking member 50 to move downward and engage in the second recess 252. At this time, the second recess 252 and the locking end 53 cooperate to limit the locking member 50 in the left-right direction. In the second position of the direction, when the locking member 50 is in this state, it moves downward with the movable bracket 20 until the locking member 50 contacts the lower end face 134 of the guide groove 13. At this time, the locking member 50 is pushed upward by the lower end face 134, causing the locking end 53 of the locking member 50 to disengage from the second recess 252. At this time, the degree of freedom of the locking member 50 to swing left and right is no longer limited by the second recess 252. Under the elastic stress of the spring 60, the locking member 50 can swing to the first position. The locking groove 14 and the locking pin 51 cooperate with each other, so that when they slide up and down, they form a one-way motion mechanism. That is, when the locking pin 51 is inside the locking groove 14, it only allows the movable bracket 20 to move upward. The movable bracket 20 is not allowed to move downward. Specifically, the locking groove 14 includes a first side wall 131 of the guide groove 13 extending away from the second side wall 132, a baffle 141, and an inclined guide wall 142 extending from the end of the baffle 141 away from the second side wall 132 to the first side wall 131. When the locking pin 51 is in the locking groove 14 and the movable bracket 20 moves upward, the inclined guide wall 142 squeezes the locking pin 51, causing the locking pin 51 to gradually move towards the second side wall 132. The locking pin 51 gradually disengages from the locking groove 14 and moves into the guide groove 13. The baffle 141 of the bottommost locking groove 14 smoothly transitions with the lower end face 134 of the guide groove 13.

[0042] like Figure 7As shown, when the locking member 50 is in the first position, and the locking pin 51 is engaged in one of the locking slots 14, the locking member 50 locks the degree of freedom of the movable bracket 20 to move downward relative to the fixed bracket 10. The baffle 141 of the locking slot 14 supports the locking pin 51 and provides stable support for the locking pin 51. When it is necessary to adjust the position of the backrest 30, the movable bracket 20 is lifted upward, and the locking pin 51 disengages from the locking slot 14. After moving upward a certain distance, it is engaged in the corresponding locking slot 14, thus completing the upward adjustment of the backrest 30.

[0043] See Figure 8 , Figure 9 and Figure 10 As shown, when the backrest 30 needs to be adjusted downwards, the movable bracket 20 can be pulled upwards, causing the locking member 50 to move upwards with the movable bracket 20 to the top of the guide groove 13. The guide part 135 restricts the locking pin 51, keeping the locking member 50 in the second position. Continuing to move the movable bracket 20 upwards, the upper end face 133 of the guide groove 13 pushes the locking pin 51 downwards, causing the locking member 50 to move downwards relative to the movable bracket 20. The locking end 53 on the locking member 50 is inserted into the second recess 252, keeping the locking member 50 in the second position. At this time, the locking member 50 no longer restricts the movable bracket 20 relative to the second position. With the fixed bracket 10 having the freedom to move downwards, the movable bracket 20 is moved downwards, which causes the locking member 50 to move downwards. When the locking pin 51 of the locking member 50 contacts the lower end face 134 of the guide groove 13, the lower end face 134 pushes the locking pin 51 upwards, and the locking end 53 of the locking member 50 disengages from the second recess 252. Then, under the elastic stress of the spring 60, the locking member 50 swings from the second position to the first position, causing the locking pin 51 to swing into the lowest locking groove 14. Then, according to the required height, the movable bracket 20 is moved upwards, and the downward adjustment of the backrest 30 is completed.

[0044] A cover plate 26 is detachably fixed on the movable bracket 20. The cover plate 26 covers the outside of the mounting groove 25. A through hole is provided on the cover plate 26 for the locking pin 51 to pass through, so that the locking pin 51 passes through the through hole and extends into the guide groove 13. The rotating end 52 and the locking end 53 of the locking member 50 are both located inside the cover plate 26.

[0045] It should be noted that the spring 60 mentioned above, as an elastic element, applies elastic stress to the locking element 50. It can also be replaced by other elastic elements to keep the locking element 50 always swinging towards the first position.

[0046] The seat of this utility model includes the backrest assembly of the aforementioned seat. The other structures of the seat are the same as those in the prior art and will not be described in detail here.

[0047] Finally, it should be noted that the above embodiments are only optional embodiments of this utility model and should not be used to limit the scope of protection of this utility model. Any non-substantial changes and substitutions made by those skilled in the art based on this utility model shall fall within the scope of protection claimed by this utility model.

Claims

1. A seat back assembly, characterized in that, Includes fixed bracket, movable bracket, backrest, and locking components; The fixed bracket is provided with a guide portion that extends vertically. The movable bracket is slidably mounted on the guide portion so that the movable bracket can move relative to the fixed bracket in the vertical direction. The locking member is provided between the movable bracket and the fixed bracket. The locking member is movably engaged with the movable bracket so that the locking member can move relative to the movable bracket in the left-right direction between a first position and a second position. When the locking member is in the first position, it is engaged with the fixed bracket to lock the movable bracket and the fixed bracket together. When the locking member is in the second position, it is disengaged from the fixed bracket so that the movable bracket has the freedom to move relative to the fixed bracket in the vertical direction. The backrest includes a top crossbeam and a bottom crossbeam. The top crossbeam is slidably mounted on a movable support so that the top crossbeam can move relative to the movable support in the front-back direction. An elastic support is provided between the top crossbeam and the movable support, which is used to apply forward elastic stress to the top crossbeam. An elastic plate is provided between the bottom crossbeam and the movable support. The elastic plate gradually tilts upward from front to back. The upper end of the elastic plate is fixedly connected to the movable support, and the lower end is fixedly connected to the bottom crossbeam.

2. The seat back assembly as claimed in claim 1, characterized in that, The elastic sheet includes a first connecting portion extending upward from its upper end and a second connecting portion extending downward from its lower end. The first connecting portion is fixed to the movable bracket by bolts, and the second connecting portion is fixed to the bottom crossbeam by bolts. The thickness of the elastic sheet gradually increases from its middle part to its two ends.

3. The seat back assembly as claimed in claim 1, characterized in that, The movable support is equipped with two guide columns that are staggered in the left and right directions. The extension direction of the guide columns is the same as the front and back directions. Two guide sleeves are fixed on the top crossbeam, and the two guide sleeves are slidably sleeved on the two guide columns.

4. The seat back assembly as described in claim 3, characterized in that, The elastic support is a spring sleeved on the guide post. The guide post has a stepped surface, and the two ends of the spring abut against the stepped surface and the rear end surface of the guide sleeve, respectively.

5. The seat back assembly as claimed in claim 4, characterized in that, The guide post is provided with a guide hole extending backward from its front end, and the guide sleeve is provided with a sliding guide post that passes through the guide hole.

6. The seat back assembly as claimed in claim 1, characterized in that, The fixed bracket includes a fixed base and a fixed plate located on the front side of the fixed base. The fixed plate is detachably fixed to the fixed base. The guide part includes two guide grooves provided on the fixed plate and extending in the vertical direction. Two sliders are provided on the rear side of the movable bracket. The two sliders are slidably embedded in the two guide grooves. A stop block is provided on the rear side of the fixed plate and is detachably fixed on the slider. The fixed plate is limited between the stop block and the movable bracket.

7. The seat back assembly as claimed in claim 1, characterized in that, The fixed bracket is provided with a guide groove extending vertically, the guide groove including a first side wall and a second side wall opposite to the first side wall, the first side wall being provided with a plurality of locking grooves arranged in the vertical direction; the movable bracket is provided with a mounting groove, the locking member is embedded in the mounting groove and configured to swing between a first position and a second position within the mounting groove, the locking member being provided with a locking pin protruding from the mounting groove and extending into the guide groove, when the locking member is in the first position, the locking pin is engaged in one of the locking grooves, when the locking member is in the second position, the locking pin disengages from the locking groove and is placed in the guide groove; an elastic member is provided between the movable bracket and the locking member, the elastic member being used to apply elastic stress to the locking member so that the locking member always maintains the tendency to swing towards the first position.

8. The seat back assembly as claimed in claim 7, characterized in that, The upper end face of the mounting groove has an upwardly recessed first recess, and the lower end face of the mounting groove has a downwardly recessed second recess. The locking member includes a rotating end at its upper end and a locking end at its lower end. The rotating end is fitted into the first recess and configured to rotate within the first recess so that the locking member can swing between a first position and a second position. The guide groove includes an upper end face and a lower end face. The portion of the guide groove between the uppermost locking groove and the upper end face forms a guide portion. The guide portion is used to limit the guide portion when the locking pin slides to the guide portion so that the lock... The stop is held in the second position. The upper end face is used to push the locking pin downward so that the locking end of the stop is engaged in the second recess. The lower end face is used to push the locking pin upward so that the locking end of the stop is disengaged from the second recess. The locking groove includes a baffle extending from the first sidewall of the guide groove away from the second sidewall and an inclined guide wall extending from the end of the baffle away from the second sidewall to the first sidewall. The inclined guide wall is used to push the locking pin towards the second sidewall when the locking pin is in the locking groove and moves upward. The baffle of the bottommost locking groove smoothly transitions with the lower end face of the guide groove.

9. The seat back assembly as claimed in claim 8, characterized in that, A cover plate is detachably fixed to the movable bracket. The cover plate covers the outside of the mounting groove and has a through hole for the locking pin to pass through.

10. A seat, characterized in that, Includes the backrest assembly of the seat as described in any one of claims 1-9.

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