A front and back translation type backrest chair

Abstract

The utility model discloses a front and back translation type backrest chair, including chair seat subassembly and chair back subassembly, and the chair back subassembly includes back support and backrest, and the chair seat subassembly includes base, and the back support includes vertical support for installing backrest, and the sliding seat is connected with vertical support, and the sliding seat is connected on the base and slides back and forth, be equipped with drive assembly between the sliding seat and the base, and the drive assembly includes swing lever and telescopic drive part, and the swing lever includes first swing lever and second swing lever respectively with the rotation connection of base and sliding seat, and the second swing lever is connected with first swing lever and slides, when the telescopic drive part telescopic shorter length, the swing lever can drag the sliding seat and slide longer distance, and the telescopic drive part of length shorter can also drive chair back subassembly and carry out the backrest support of large range in the front and back direction, satisfy the backrest demand, and the cost and assembly difficulty of backrest chair have been reduced.

Description

Technical Field

[0001] This utility model relates to the field of seating, and in particular to a backrest chair with front-to-back translational movement. Background Technology

[0002] Chairs currently available on the market have a backrest tracking function, which is typically used for children learning to sit. When the child's back changes position, the chair back can automatically follow and support the back.

[0003] For example, in the chair patent with publication number CN220675602, the backrest and the gas spring are linked by a connecting rod, and an outer cover is connected to the connecting rod. The outer cover is used to connect the backrest. The connecting rod is hinged to the second connecting rod of the transmission assembly. The lower end of the chair is provided with a mounting seat, and the gas spring and the transmission assembly are both set in the mounting seat. The gas spring can push the first connecting rod in the transmission assembly to move, causing the backrest to rotate back and forth and form a backrest support. However, when the backrest rotates back and forth, the angle of the backrest support surface relative to the seat surface will change. It does not move completely in the back and forth direction and cannot fully fit the back during the backrest support process.

[0004] Based on this, if the goal is to achieve the purpose of backrest lateral movement for back support, theoretically, the backrest bracket can be slidably connected to the mounting base in the front-back direction, and then the gas spring in the mounting base can be directly connected to the outer cover. However, this requires the piston rod extension stroke of the gas spring to be roughly matched with the front-back sliding stroke of the backrest bracket. Therefore, the length of the gas spring needs to be designed to be larger, which increases the manufacturing cost of the seat. In addition, the gas spring occupies a lot of front-back space in the mounting base, and the assembly difficulty of the larger gas spring will also increase. Summary of the Invention

[0005] This utility model provides a backrest-following chair with front-to-back translation. By setting a telescopic drive and a swing rod between the base and the sliding seat of the backrest support, and positioning the telescopic drive between the swing rod and the connection between the base and the sliding seat, when the telescopic drive extends or retracts a short length, the swing rod can drag the sliding seat a longer distance. This allows the shorter telescopic drive to drive the backrest assembly to provide a wide range of backrest support in the front-to-back direction, meeting the backrest-following requirements and reducing the cost and assembly difficulty of the backrest-following chair.

[0006] The technical solution of this utility model is implemented as follows: A backrest chair with front-to-back translational movement includes a seat assembly and a backrest assembly. The backrest assembly includes a back support and a backrest. The seat assembly includes a base. The back support includes an upright support for mounting the backrest and a sliding seat connected to the upright support. The sliding seat is slidably connected to the base. A drive assembly is provided between the sliding seat and the base. The drive assembly includes a swing rod and a telescopic drive member. The swing rod includes a first swing rod and a second swing rod that are rotatably connected to the base and the sliding seat, respectively. The second swing rod is slidably connected to the first swing rod. The telescopic drive member acts on the first swing rod or the second swing rod. The position of the telescopic drive member is between the rotatable connection position of the second swing rod and the sliding seat and the rotatable connection position of the first swing rod and the base. The telescopic drive component can rotate the swing arm by extending and retracting itself, while simultaneously causing the second swing arm to slide relative to the first swing arm, thereby linking the sliding seat to move back and forth and changing the front and back position of the chair back assembly.

[0007] Preferably, the extension stroke of the telescopic drive is less than the forward and backward sliding stroke of the sliding seat; the telescopic drive can drive the sliding seat to slide a longer distance with a shorter extension and retraction distance, thus meeting the backrest's forward and backward support requirements.

[0008] Preferably, the base is a hollow structure, and the drive component is disposed inside the base; and the drive component is disposed between the base and the sliding seat; thus avoiding exposure of the drive component and making the seat look simple and beautiful.

[0009] Preferably, the seat assembly includes a seat and a base disposed at the lower end of the seat, wherein the base is either the base or the seat.

[0010] Preferably, the first swing arm is a hollow tubular component, and the second swing arm is slidably connected inside the tubular component.

[0011] Preferably, the base and the sliding seat are slidably connected by a guide rail. The guide rail is a through-type guide groove on the base and is symmetrical on the left and right. The sliding seat is provided with a side extension corresponding to the position of the guide groove. A pin is slidably connected in both guide grooves. Both ends of the pin pass through the corresponding guide groove and are connected to the corresponding side extension. The second rocker arm is rotatably connected to the sliding seat through the pin to pull the sliding seat to move back and forth.

[0012] Preferably, the telescopic drive component is a gas spring whose length can be changed by telescopic movement; one end of the gas spring is hinged to the base, and the other end of the gas spring is hinged to the first or second rocker arm; to prevent the piston rod of the gas spring from jamming when it extends or retracts.

[0013] Preferably, the telescopic drive component is a mechanical spring that can change its length under the action of external force; the mechanical spring can also generate sufficient elastic driving force for the swing rod, and at the same time, the mechanical spring is low in cost and easy to maintain.

[0014] Preferably, the mechanical spring is a tension spring, with one end connected to the base and the other end connected to the first or second rocker arm.

[0015] A forward-backward translating type chair includes a seat assembly and a backrest assembly. The backrest assembly includes a back support and a backrest. The seat assembly includes a base. The back support includes an upright support for mounting the backrest and a sliding seat connected to the upright support. The sliding seat is slidably connected to the base in the forward-backward direction. A drive assembly is provided between the sliding seat and the base. The drive assembly includes a swing rod rotatably connected to the base and a telescopic drive member acting on the swing rod. The swing rod has a strip groove extending along its own length. A pin with a circular cross-section is connected to the sliding seat. The pin passes through the strip groove to form a sliding fit. The telescopic drive member acts on the swing rod at a position between the connection position of the pin and the sliding seat and the rotational connection position of the base and the swing rod. The telescopic drive component can rotate the swing arm by its own telescopic movement, and through the sliding engagement of the pin and the strip groove, it can move the sliding seat back and forth and change the front and back position of the chair back assembly.

[0016] The beneficial effects of this utility model, which adopts the above technical solution, are as follows: In this invention, the swing arm includes a first swing arm and a second swing arm that are slidably connected to each other. The first and second swing arms are rotatably connected to the base and the sliding seat, respectively, forming two hinged ends. When the swing arm rotates, the second swing arm can slide relative to the first swing arm to adapt to the front-to-back position changes of the sliding seat and prevent the swing arm from jamming. At the same time, the telescopic drive is located between the two hinged ends. The telescopic drive can extend and retract a small length to allow the sliding seat to slide a large length. This allows the backrest chair to meet the needs of the back support and backrest to move a large range in the front-to-back direction and provide backrest support by only setting a telescopic drive with a small length. The smaller telescopic drive is also cheaper and easier to install in the corresponding position of the backrest chair.

[0017] In another type of backrest chair, the swing arm and the sliding seat are connected by a circular cross-section pin and a slot, allowing the swing arm to swing while sliding relative to the sliding seat to adapt to changes in the sliding seat's position and prevent jamming during rotation. At the same time, the telescopic drive is located between the pin and the sliding seat connection and the swing arm and the base rotation connection. The telescopic drive can extend or retract a small length to allow the sliding seat to slide a large length, achieving the same effect. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the front-to-back sliding backrest chair. Figure 2 This is a schematic diagram showing the chair back assembly in a rearward position. Figure 3This is a cross-sectional view of the drive assembly when the backrest assembly is in the rearmost position. Figure 4 This is a schematic diagram showing the chair back assembly in a forward position. Figure 5 This is a cross-sectional view of the drive assembly when the backrest assembly is in the forward position. Figure 6 This is a schematic diagram showing the shape of the chair when the seat and base are separated. Figure 7 This is a schematic diagram showing the drive components installed inside the base; Figure 8 This is a cross-sectional view of the drive assembly on the backrest chair in Embodiment 2; Figure 9 This is a schematic diagram of the telescopic drive component being a tension spring in Example 3; Figure 10 This is a schematic diagram of the telescopic drive component being a compression spring in Example 3; Figure 11 A simplified diagram illustrating the principle that a gas spring can drive a sliding block to slide a relatively large distance with a short extension or retraction. The reference numerals in the attached figures are as follows: 1-seat, 11-mounting groove, 2-back support, 2a-sliding seat, 2b-upright support, 21-backrest, 22-side extension, 23-guide groove, 3-base, 31-guide groove, 32-accommodating groove, 4-swing rod, 41-first swing rod, 42-second swing rod, 43-pin, 44-strip groove, 45-push seat, 5-gas spring, 5a-tension spring, 5b-compression spring. Detailed Implementation

[0019] To better understand the above-mentioned objectives, features, and advantages of this utility model, the present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0020] Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0021] This utility model has multiple embodiments, the specific embodiments of which are as follows: Example 1: As Figure 1-7 , Figure 11As shown, this embodiment provides a backrest chair with front-to-back translation, including a seat assembly and a backrest assembly. The backrest assembly includes a back support 2 and a backrest 21. The seat assembly includes a base. In this embodiment, the back support 2 is located at the rear of the seat assembly. The back support 2 includes a vertical support 2b for mounting the backrest 21 and a sliding seat 2a connected to the vertical support 2b. In this embodiment, the sliding seat 2a is located at the bottom end of the vertical support 2b, and the two form a back support 2 with an "L" shaped cross section. The sliding seat 2a is slidably connected to the base in the front-to-back direction. A driving assembly is provided between the sliding seat 2a and the base. The driving assembly includes a swing rod 4 and a telescopic driving component that can change its own length by extension and retraction. The definition of the telescopic driving component in this utility model is mainly based on whether it can change its own length, and does not only refer to telescopic structures that are nested together. That is to say, the telescopic driving component can be a telescopic structure that is nested together, or it can be a component that changes its own length under the action of external force. The swing arm 4 includes a first swing arm 41 and a second swing arm 42 that are rotatably connected to the base and the sliding seat 2a, respectively; the second swing arm 42 is slidably connected to the first swing arm 41; a telescopic drive acts on the first swing arm 41 or the second swing arm 42; and the position of the telescopic drive is between the rotatable connection position of the second swing arm 42 and the sliding seat 2a and the rotatable connection position of the first swing arm 41 and the base. The telescopic drive component can push the swing arm 4 to rotate by its own telescopic movement, while simultaneously causing the second swing arm 42 to slide relative to the first swing arm 41, thereby linking the sliding seat 2a to move back and forth and changing the front and back position of the chair back assembly.

[0022] Furthermore, such as Figure 11 As shown, in this embodiment, the swing arm 4 rotates around the rotational connection point between the first swing arm 41 and the base. The distance between the rotational connection point between the second swing arm 42 and the sliding seat 2a and the rotational center is greater than the distance between the action position of the telescopic drive on the first swing arm 41 or the second swing arm 42 and the rotational center. When the telescopic drive extends by a length of a, causing the entire swing arm 4 to swing at a predetermined angle, the connection point between the second swing arm 42 and the sliding seat 2a can move by a length of b, which is significantly greater than a. Therefore, in this embodiment, the extension stroke of the telescopic drive can be less than the forward and backward sliding stroke of the sliding seat 2a. This allows the length of the telescopic drive to be designed to be shorter, enabling the telescopic drive to extend a shorter distance to drive the sliding seat to slide a longer distance, thus meeting the backrest's forward and backward support requirements. At the same time, since the telescopic drive only needs to extend a short stroke, a telescopic drive with a shorter stroke can be selected, thereby reducing the cost and volume of the telescopic drive, reducing assembly difficulty, and making it easier to install in the corresponding position.

[0023] Furthermore, in this embodiment, the second swing rod 42 is slidably connected to the first swing rod 41 along the length direction of the first swing rod 41. The first swing rod 41 and the second swing rod 42 can be straight rods as shown in the figure of this utility model, or sheet-like parts with a certain left and right width, or other shapes that can satisfy smooth sliding. In this embodiment, in order to ensure the stability of the sliding connection between the first swing rod 41 and the second swing rod 42, the first swing rod 41 is a hollow tubular part, and the second swing rod 42 is slidably connected inside the tubular part. Thus, the second swing rod 42 can extend and retract relative to the first swing rod 41.

[0024] Furthermore, to facilitate the placement of the drive assembly, the base in this embodiment has a hollow structure, and the drive assembly is disposed within the base; moreover, the drive assembly is positioned between the base and the sliding seat 2a; this avoids exposing the drive assembly, making the seat appear simple and aesthetically pleasing; even further, as... Figure 6-7 As shown, the chair seat assembly includes a chair seat 1 and a base 3 disposed at the lower end of the chair seat 1. The base can be the chair seat 1, and a hollow groove can be provided on the chair seat 1, with the drive component disposed inside the groove; alternatively, the base 3 can be a hollow structure, with the drive component disposed inside the base 3. In this embodiment, the drive component is disposed inside the base 3 for explanation. Specifically, to reduce the abruptness of the base 3 at the lower end of the chair seat 1, a mounting groove 11 is provided at the lower end of the chair seat 1, and the base 3 is disposed at the mounting groove 11 to reduce the portion of the base 3 protruding from the lower end of the chair seat 1; at the same time, the base 3 is provided with an accommodating groove 32 with an upper opening, and the drive component is disposed inside the accommodating groove 32 and will not be exposed, ensuring the seat has a simple and beautiful appearance; in addition, a guide groove 23 is provided on the sliding seat 2a of the backrest 2, and the base 3 is disposed inside the guide groove 23, so that the sliding seat 2a can slide in the front-back direction without moving in the left-right direction.

[0025] Furthermore, to make the sliding connection between the base and the sliding seat 2a more stable, the base and the sliding seat 2a are slidably connected by a guide rail. The guide rail is a guide groove 31 that runs through the base and is symmetrical from left to right. The sliding seat 2a is provided with a side extension 22 corresponding to the position of the guide groove 31. A pin 43 is slidably connected in both guide grooves 31. Both ends of the pin 43 pass through the corresponding guide grooves 31 and are connected to the corresponding side extensions 22. The second rocker arm 42 is rotatably connected to the sliding seat 2a through the pin 43 to pull the sliding seat 2a to move back and forth.

[0026] Furthermore, the telescopic drive component is a gas spring 5 whose length can be changed by telescopic movement. The gas spring 5 includes a cylinder and a piston rod slidably connected to the cylinder. To prevent the piston rod of the gas spring 5 from jamming during telescopic movement, in this embodiment, one end of the gas spring 5 is hinged to the base, and the other end of the gas spring 5 is hinged to the first rocker arm 41 or the second rocker arm 42. When the gas spring 5 is hinged, the outer end of the piston rod can be hinged to the base, and the outer end of the cylinder can be hinged to the first rocker arm 41 or the second rocker arm 42. Alternatively, the positions of the outer end of the piston rod and the outer end of the cylinder can be interchanged. This allows the gas spring 5 to rotate adaptively during the telescopic movement of the piston rod, preventing jamming.

[0027] Furthermore, in this embodiment, the gas spring 5 can be a normally open gas spring located at the rear of the linkage assembly. A normally open gas spring has a piston rod that always extends outwards, which can push the swing rod 4 to rotate forward, causing the sliding seat 2a to always have a tendency to slide forward. When the occupant leans back against the backrest 21, the sliding seat 2a will slide backwards and the piston rod will elastically retract, causing the backrest 21 to provide elastic support for the back. Alternatively, the gas spring 5 can be a normally closed gas spring located at the front of the linkage assembly. A normally closed gas spring has a piston rod that always retracts inwards, which can pull the swing rod 4 to rotate forward, causing the sliding seat 2a to always have a tendency to slide forward. The trend is such that when the occupant leans back against the backrest 21, the sliding seat 2a slides backward and the piston rod extends elastically, so that the backrest 21 provides elastic support to the back. In addition, to facilitate control of the sliding position of the sliding seat 2a, each gas spring 5 in this embodiment is preferably a self-locking gas spring with a self-locking device. The self-locking device of the self-locking gas spring is connected to a pull wire, and the other end of the pull wire is connected to a control switch. The control switch can control the piston rod to unlock or lock at the corresponding position. After the sliding seat 2a slides to the corresponding position, it can switch between the locked and unlocked states. The principle and structure of the self-locking device are existing technologies and will not be described in detail here.

[0028] Example 2: Figure 8As shown, this embodiment differs from the above embodiments in that it provides a different structure for a front-to-back translational backrest chair, which also includes a seat assembly and a backrest assembly. The backrest assembly includes a back support 2 and a backrest 21; the seat assembly includes a base, and the back support 2 includes an upright support 2b for mounting the backrest 21 and a sliding seat 2a connected to the upright support 2b. The sliding seat 2a is slidably connected to the base in the front-to-back direction; a driving assembly is provided between the sliding seat 2a and the base, and the driving assembly includes a swing rod 4 rotatably connected to the base and a telescopic driving member acting on the swing rod 4. The difference is that the swing rod 4 in this embodiment is a single rod structure, wherein the swing rod 4 is provided with a strip groove extending along its own length direction. 44. A circular cross-section pin 43 is connected to the sliding seat 2a, and the pin 43 is inserted into the strip groove 44 to form a sliding fit. The position where the telescopic drive acts on the swing rod 4 is between the connection position of the pin 43 and the sliding seat 2a and the rotational connection position of the base and the swing rod 4. In this way, the swing rod 4 can rotate with the pin 43 as the rotational support axis as the center, and can also slide relative to the pin 43. This also avoids the swing rod 4 getting stuck when rotating, achieving the same effect as the above embodiment. Therefore, the telescopic drive in this embodiment can also push the swing rod 4 to rotate through its own telescopic extension, and the sliding seat 2a moves back and forth and changes the front and back position of the chair back assembly through the sliding fit between the pin 43 and the strip groove 44.

[0029] Example 3: As Figure 9-10 As shown, this embodiment differs from the previous embodiment in that the telescopic drive component in this embodiment is a mechanical spring that can change its length under external force. The mechanical spring can also generate sufficient elastic driving force on the swing rod 4. Furthermore, the mechanical spring is low in cost and easy to maintain. The mechanical spring can be a tension spring 5a, with one end connected to the base and the other end connected to the first swing rod 41 or the second swing rod 42. Specifically, when the mechanical spring is a tension spring 5a, the tension spring 5a is positioned at the front of the connecting rod assembly. To facilitate the installation of the tension spring 5a, a hanging lug can be provided on the first swing rod 41 or the second swing rod 42, and a hanging lug can also be provided on the base, so that both ends of the tension spring 5a are hooked onto the corresponding hanging lugs. Simultaneously, the mechanical spring... Alternatively, a compression spring 5b can be used. For example, the compression spring 5b can be placed on the rear side of the swing rod 4. To facilitate the installation of the tension spring 5a and prevent it from bending, a tube structure can be set on the base. One end of the compression spring 5b is inserted into the tube, and the other end protrudes outside the tube and is supported on the corresponding first swing rod 41 or second swing rod 42. To accommodate the rotation trajectory of the first swing rod 41 or second swing rod 42, a push seat 45 can also be rotatably connected to the first swing rod 41 or second swing rod 42. The push seat 45 has an annular boss. The other end of the compression spring 5b is sleeved on the push seat 45 and acts on the annular boss. When the swing rod 4 rotates, the push seat 45 can rotate adaptively, so that the direction of the thrust of the compression spring 5b remains unchanged, and the compression spring 5b is prevented from bending when deformed.

[0030] Furthermore, when the telescopic drive component uses a mechanical spring, in order to facilitate the unlocking and locking of the back support 2 and the backrest 21 in the front and rear positions, a gear control mechanism can be set between the base and the sliding seat 2a. This mechanism includes multiple gear slots spaced apart on the base and a locking component movably set on the sliding seat 2a. The locking component can also be connected to a pull wire, and the locking component can be engaged or disengaged with the corresponding gear slot by pulling the pull wire through a control switch, thereby locking or unlocking the position of the back support 2 and the backrest 21.

[0031] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the inventive spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A backrest chair with forward and backward translational movement, characterized in that, The chair includes a seat assembly and a backrest assembly. The backrest assembly includes a back support (2) and a backrest (21). The seat assembly includes a base. The back support (2) includes a vertical support (2b) for mounting the backrest (21) and a sliding seat (2a) connected to the vertical support (2b). The sliding seat (2a) is slidably connected to the base. A drive assembly is provided between the sliding seat (2a) and the base. The drive assembly includes a swing rod (4) and a telescopic drive. The swing rod (4) includes a first swing rod (41) and a second swing rod (42) that are rotatably connected to the base and the sliding seat (2a) respectively. The second swing rod (42) is slidably connected to the first swing rod (41). The telescopic drive acts on the first swing rod (41) or the second swing rod (42). The position of the telescopic drive is between the rotatable connection position of the second swing rod (42) and the sliding seat (2a) and the rotatable connection position of the first swing rod (41) and the base. The telescopic drive can push the swing arm (4) to rotate by its own telescopic movement, while the second swing arm (42) slides relative to the first swing arm (41), so as to link the sliding seat (2a) to move back and forth and change the front and back position of the chair back assembly.

2. The backrest chair with forward and backward translation as described in claim 1, characterized in that: The telescopic drive has a shorter telescopic stroke than the sliding stroke of the slide block (2a).

3. The backrest chair with forward and backward translation as described in claim 1, characterized in that: The base is a hollow structure, and the driving component is disposed inside the base; and the driving component is disposed between the base and the sliding seat (2a).

4. The backrest chair with forward and backward translation as described in claim 1, characterized in that: The chair seat assembly includes a chair seat (1) and a base (3) disposed at the lower end of the chair seat (1), wherein the base is either the base (3) or the chair seat (1).

5. The backrest chair with forward and backward translation as described in claim 1, characterized in that: The first pendulum (41) is a hollow tubular component, and the second pendulum (42) is slidably connected inside the tubular component.

6. The backrest chair with forward and backward translation as described in claim 1, characterized in that: The base and the sliding seat (2a) are slidably connected by a guide rail. The guide rail is a guide groove (31) that runs through the base and is symmetrical on the left and right. The sliding seat (2a) is provided with a side extension (22) corresponding to the position of the guide groove (31). A pin (43) is slidably connected in both guide grooves (31). Both ends of the pin (43) pass through the corresponding guide groove (31) and are connected to the corresponding side extension (22). The second rocker arm (42) is rotatably connected to the sliding seat (2a) through the pin (43) to pull the sliding seat (2a) to move back and forth.

7. The backrest chair with forward and backward translation as described in claim 1, characterized in that: The telescopic drive component is a gas spring (5) whose length can be changed by telescopic movement; one end of the gas spring (5) is hinged to the base, and the other end of the gas spring (5) is hinged to the first swing rod (41) or the second swing rod (42).

8. The backrest chair with forward and backward translation as described in claim 1, characterized in that: The telescopic drive component is a mechanical spring that can change its length under the action of external force.

9. The backrest chair with forward and backward translation as described in claim 8, characterized in that: The mechanical spring is a tension spring (5a), one end of which is connected to the base, and the other end of which is connected to the first rocker arm (41) or the second rocker arm (42).

10. A backrest chair with forward and backward translational movement, characterized in that, The chair includes a seat assembly and a backrest assembly. The backrest assembly includes a back support (2) and a backrest (21). The seat assembly includes a base. The back support (2) includes a vertical support (2b) for mounting the backrest (21) and a sliding seat (2a) connected to the vertical support (2b). The sliding seat (2a) is slidably connected to the base in the front-back direction. A drive assembly is provided between the sliding seat (2a) and the base. The drive assembly includes a swing rod (4) rotatably connected to the base and a telescopic drive member acting on the swing rod (4). The swing rod (4) is provided with a strip groove (44) extending along its own length direction. A pin (43) with a circular cross-section is connected to the sliding seat (2a). The pin (43) is inserted into the strip groove (44) to form a sliding fit. The telescopic drive member acts on the swing rod (4) at a position between the connection position of the pin (43) and the sliding seat (2a) and the rotational connection position of the base and the swing rod (4). The telescopic drive can push the swing arm (4) to rotate through its own telescopic movement, and through the sliding engagement of the pin (43) and the strip groove (44), it can move the sliding seat (2a) back and forth and change the front and back position of the chair back assembly.

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