A chair and its adjustable base

Abstract

This invention discloses a chair and its adjustable chassis, including a base, a top seat, a tail seat, a tension spring, a first adjustment seat, and a first mounting seat. The base and tail seat are hinged together by a first hinge axis, and the front part of the tail seat is hinged to the top seat by a second hinge axis, which is located above the front side of the first hinge axis. The bottom of the first adjustment seat is hinged to the base, and the top of the first adjustment seat is hinged to the first mounting seat and the top seat by a fourth hinge axis. One part of the tension spring is connected to the first mounting seat, and the other part of the tension spring is connected to the front part of the base, which makes the chassis more adjustable and thinner.

Description

Technical Field

[0001] This invention relates to the field of home furnishings, and more particularly to a chair and its adjustable base. Background Technology

[0002] The base of a chair, also known as the tray, is an important component that connects the seat, backrest, and legs. Modern swivel chair trays typically consist of an upper tray, lower support beam, pivot, and spring mechanism. Once the upper tray is fixed to the back of the swivel chair, the chair can tilt appropriately around the pivot and automatically return to its original position.

[0003] Patent document CN102846068B discloses a swivel chair chassis, including a base plate connected to a gas spring, which supports the entire chassis, seat, and backrest. A support plate is provided vertically on each of the left and right sides of the base plate, and the support plates are fixedly connected to the base plate. A seat plate for mounting the seat is provided horizontally above the two support plates. Support frames and backrest brackets inclined towards the front of the swivel chair are provided on the front and rear sides of the base plate, respectively. The lower parts of the support frames and backrest brackets are hinged to the two support plates. The front and rear sides of the seat plate are hinged to the tops of the support frames and backrest brackets, respectively. The backrest bracket is connected to the backrest via a connecting steel plate, and the backrest bracket is connected to an elastic reset device that tilts it towards the front of the swivel chair. Specifically, the support frame has a U-shaped structure, including two pins arranged parallel vertically, which are fixedly connected by two connecting rods arranged parallel horizontally; alternatively, a single connecting rod can also be used. The backrest bracket also has two pins arranged parallel vertically, which pass through the side plates on both sides of the backrest bracket. The pins at the lower ends of the support frame and backrest bracket are hinged to the support plate. The lower end of the seat plate has four lugs, which are hinged to the pins at the upper ends of the support frame and backrest bracket via these lugs. The elastic reset device is a spring, with one end connected to the pin at the upper end of the backrest bracket and the other end connected to the pin at the lower end of the support frame. In actual use, 2 to 4 springs can be used depending on the actual needs.

[0004] In the prior art, the front part of the seat plate and the front part of the base plate are hinged by two parallel connecting rods, and the rear end of the seat plate and the rear end of the base plate are hinged by the side plates on the left and right sides of the backrest bracket. The two ends of the spring are connected to the backrest bracket and the base plate respectively. When the chassis self-adjusts, the backrest bracket acts directly on the seat plate, so that the backrest bracket directly drives the seat plate to swing. In this way, the thickness of the chassis depends only on the length of the side plates, making the chassis relatively thick and heavy. Summary of the Invention

[0005] To address the problem of heavy chair trays in existing technologies, the present invention aims to provide a lighter and thinner chair and its adjustable chassis, which can adaptively adjust to make the chair more comfortable. Furthermore, during the adaptive adjustment process, the movement of the top seat relative to the tail seat is smaller, making the chair more stable.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: an adjustable chassis, including a base, a top seat, a tail seat for mounting a chair back, and a tension spring. The base and the tail seat are hinged together by a first hinge axis, and the top seat and the tail seat are hinged together by a second hinge axis. The tail seat includes two first connecting plates arranged symmetrically on the left and right sides. The two first connecting plates of the tail seat are hinged to the base by the first hinge axis, and the front parts of the two first connecting plates of the tail seat are hinged to the bottom of the top seat by the second hinge axis. The chassis also includes a first adjusting seat. The bottom of the first adjusting seat is hinged to the base by a third hinge axis, and the top of the first adjusting seat is hinged to the top seat by a fourth hinge axis. One end of the tension spring is connected to the fourth hinge axis, and the other end of the tension spring is connected to the base by an adjusting device.

[0007] Preferably, the system also includes a first mounting base, the top of which is hinged to the first mounting base via a fourth hinge shaft, and the first adjusting base is hinged to the top base via the fourth hinge shaft. One end of the tension spring is connected to the first mounting base, and the other end of the tension spring is connected to the front of the base via an adjusting device. The adjusting device includes a second adjusting base, on which a second mounting base is fixed. The two ends of the tension spring are respectively connected to the first mounting base and the second mounting base. An adjusting screw is threaded onto the second adjusting base, and the adjusting screw is mounted on the base and can rotate.

[0008] Preferably, the second adjusting seat has a bayonet, a nut is installed in the bayonet, and the adjusting screw passes through the nut and is threadedly connected; when the adjusting screw rotates, the nut can drive the second adjusting seat to move along the axis of the adjusting screw.

[0009] Preferably, a handle is fixed to one end of the adjusting screw, and a pin is radially fixed to the other end of the adjusting screw, with the handle located on the outside of the base.

[0010] Preferably, there are two tension springs arranged symmetrically on the left and right, two first mounting bases arranged symmetrically on the left and right, and two second mounting bases arranged symmetrically on the left and right.

[0011] Preferably, both the outer side of the first mounting base and the outer side of the second mounting base have spiral-shaped fixing grooves, and the two ends of the tension spring are respectively engaged in the fixing grooves of the first mounting base and the fixing grooves of the second mounting base.

[0012] Preferably, the base has a raised guide portion to prevent the second adjustment seat from moving laterally, and the bottom of the second adjustment seat has a downward-opening guide groove, and the guide portion of the base is inserted into the guide groove at the bottom of the second adjustment seat from bottom to top.

[0013] Preferably, the chassis is also provided with two upward-opening positioning slots, which extend backward through the base. The two first connecting plates of the tailstock are respectively inserted into the two positioning slots and are hinged to the base through the first hinge shaft.

[0014] Preferably, the base and top are made of plastic.

[0015] A chair comprising the aforementioned adjustable base.

[0016] The beneficial effects of the technical solution of the present invention are as follows: the chassis has an adaptive function, providing users with a better user experience. Since the force distribution in the chassis is not concentrated, the force on each component is more uniform, improving the service life and reliability of the chassis. During the adaptive adjustment of the chassis, the swing amplitude of the tail seat is much greater than that of the top seat, and the upward speed of the front part of the top seat is greater than that of the rear part of the top seat, making the support of the chair more stable. In the prior art, the chassis is usually made of metal, so in order to increase the aesthetics of the chair, a shell is usually needed to cover the chassis. However, in the technical solution of the present invention, both the top seat and the base are made of plastic, so even without a shell, the aesthetics of the chair can still be maintained, the weight of the chair can be reduced, the structure of the chair can be simplified, the manufacturing difficulty of the chassis can be reduced, and the diversity of chassis styles can be increased. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the adjustable chassis structure in this invention. Figure 1 ;

[0018] Figure 2 This is a schematic diagram of the adjustable chassis structure in this invention. Figure 2 ;

[0019] Figure 3 Schematic diagram of the chassis structure Figure 1 ;

[0020] Figure 4 Schematic diagram of the chassis structure Figure 2 ;

[0021] Figure 5 This is a schematic diagram of the second adjusting seat;

[0022] Figure 6 This is a schematic diagram of the base structure;

[0023] Figure 7 This is a schematic diagram of the structure of the first adjusting seat.

[0024] Reference numerals: 1. Base; 11. Baffle; 12. First connecting part; 13. Second blocking part; 14. Positioning groove; 15. Countersunk hole; 16. Mounting hole; 17. Guide part; 18. Through hole; 2. Tailstock; 21. Second connecting plate; 22. First connecting plate; 23. Third connecting plate; 3. Top seat; 31. Covering part; 4. First hinge shaft; 5. Second hinge shaft; 60. Fixed seat; 61. Third hinge shaft; 62. First adjusting seat; 621. Second connecting part; 622. Mounting port; 63. Fourth hinge shaft; 64. First mounting seat; 65. Tension spring; 66. Second adjusting seat; 662. Through hole; 663. Second mounting seat; 664. Bayonet; 665. Guide groove; 667. Pin; 67. Nut; 68. Adjusting screw; 69. Handle; 7. Lever. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below, examples of which are illustrated 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 intended to explain the present invention, and should not be construed as limiting the present invention.

[0026] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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. Therefore, they should not be construed as limitations on this invention.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more, unless explicitly defined otherwise.

[0028] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0029] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0030] The front, back, left, and right directions described in the following embodiments are consistent with the front, back, left, and right directions of the chair product. The side with the chair back is the back, and the side opposite the chair back is the front. The front and back are further divided into left and right.

[0031] Example

[0032] like Figure 1-4 The adjustable chassis shown includes a base 1 for connecting chair legs, a top mount 3 for mounting the chair seat, a tail mount 2 for mounting the chair back, and a tension spring 65 for adaptive adjustment. The base 1 and tail mount 2 are hinged together by a first hinge axis 4, and the top mount 3 and tail mount 2 are hinged together by a second hinge axis 5. The tail mount 2 includes two symmetrically arranged first connecting plates 22. The two first connecting plates 22 of the tail mount 2 are hinged to the base 1 by the first hinge axis 4, and the front of the two first connecting plates 22 of the tail mount 2 is connected to the bottom of the top mount 3 by the second hinge axis 5. The chassis also includes a first adjusting seat 62 and a first mounting seat 64. The bottom of the first adjusting seat 62 is hinged to the base 1 via a third hinge shaft 61, and the top of the first adjusting seat 62 is hinged to the first mounting seat 64 via a fourth hinge shaft 63. The fourth hinge shaft 63 is hinged to the top seat 3 and is located behind the second hinge shaft 5. One end of the tension spring 65 is connected to the first mounting seat 64, and the other end of the tension spring 65 is connected to the front of the base 1 via an adjusting device. The second hinge shaft 5 is located above the front of the first hinge shaft 4.

[0033] The chassis adaptive adjustment process is as follows: When the user sits in the chair with their back against the backrest, the backrest, under pressure, drives the tail seat 2 to swing around the first hinge shaft 4. When the tail seat 2 swings, the front of the tail seat 2 lifts the top seat 3 via the second hinge shaft 5, causing the top seat 3 to move backward and upward around the first hinge shaft 4. When the top seat 3 moves, it pulls the first mounting seat 64 and the first adjusting seat 62 via the fourth hinge shaft 63, causing the first adjusting seat 62 to swing backward around the third hinge shaft 61. This causes the first mounting seat 64 to move backward and stretch the tension spring 65, thus storing force in the tension spring 65. When the user leans forward or stands up, the tension spring 65 pulls the first mounting seat 64 back to its original position. The first mounting seat 64, via the fourth hinge shaft 63, pulls the top seat and the first adjusting seat 62 back to their original positions. The top seat 3, via the second hinge shaft 5, drives the tail seat 2 back to its original position. When the tail seat 2 returns to its original position, it can drive the backrest to move with the user's back.

[0034] With this configuration, in the above structure, the first hinge shaft is used as the fulcrum, and the first hinge shaft to the rear end of the tailstock forms the first lever arm; the first hinge shaft to the second hinge shaft forms the second lever arm; the second hinge shaft to the fourth hinge shaft forms the third lever arm; and the fourth hinge shaft to the third hinge shaft forms the fourth lever arm.

[0035] This design allows the chassis to be self-adaptive, providing a better user experience. Because the stress points within the chassis are not concentrated, the stress on each component is more even, improving the chassis's lifespan and reliability. Furthermore, by adjusting the length of each lever arm, the chassis becomes thinner and lighter overall, offering a wider adjustment range. Additionally, the connection structure between the tailstock, top mount, and base is not concentrated at the front or rear of the base, resulting in greater stability and better support rigidity during chassis adjustment.

[0036] To facilitate the installation of the tailstock 2, top seat 3, and base 1, in this embodiment, as follows: Figure 2 , Figure 5 , Figure 6 and Figure 7As shown, the base 1 has an open mounting cavity. On both the left and right sides of the mounting cavity are upward-opening positioning grooves 14. The positioning grooves 14 extend rearward and penetrate the base 1. Two first connecting plates 22 of the tailstock 2 are respectively inserted into the two positioning grooves 14, and the two first connecting plates 22 are respectively hinged to the middle position of the base 1 via first hinge shafts 4. The front parts of the two first connecting plates 22 are raised upward and extend beyond the base 1. A second hinge shaft 5 extends laterally to connect the two first connecting plates 22 to the top seat 3. The mounting cavity has two protrusions arranged on the left and right sides. A connecting portion 12 is provided. The bottom of the first adjusting seat 62 has two protruding second connecting portions 621 arranged left and right. The two first connecting portions 12 are located between the two second connecting portions 621. A third hinge shaft 61 passes through the first connecting portions 12 and the second connecting portions 621, hinged to the base 1 and the first adjusting seat 62. To facilitate the installation of the third hinge shaft 61, a through hole 18 coaxial with the third hinge shaft 61 is provided on the side of the base 1. Thus, the third hinge shaft 61 can be inserted into the mounting cavity through the through hole 18 to hinge the base 1 and the first adjusting seat 62. To increase the overall strength of the base, in this embodiment, crisscrossing reinforcing ribs are provided on the inner sides of the mounting cavity and the positioning groove 14.

[0037] To further expand the target audience for the chassis, such as Figure 2 , Figure 5 , Figure 6 and Figure 7 As shown, in this embodiment, the adjustment device includes a second adjustment seat 66, on which a second mounting seat 663 is fixed. The other end of the tension spring 65 is connected to the second mounting seat 663. An adjustment screw 68 is threaded onto the second adjustment seat 66, and the adjustment screw 68 is rotatably connected to the base 1. This allows for adjustment of the tension of the tension spring, improving the chassis's applicability and providing a better user experience.

[0038] To make the chassis's adaptive process more stable, in this embodiment, as follows: Figure 2-7 As shown, there are two tension springs 65 arranged symmetrically from left to right, two first mounting seats 64 arranged symmetrically from left to right, and two second mounting seats 663 arranged symmetrically from left to right. The top of the first adjusting seat 62 has two mounting holes 622, and one end of the first mounting seat 64 is inserted into the mounting hole 622. The fourth hinge shaft 63 passes laterally through the first adjusting seat 62 and the two first mounting parts 64, thereby hinged the two first mounting parts 64 to the first adjusting seat 62. The adjusting screw 68 is located between the two second mounting seats 663. In this way, the tensile force of the chassis can be increased, and the symmetrical arrangement of the tension springs can make the movement of the chassis more stable.

[0039] To prevent the second adjusting seat from shifting laterally, in this embodiment, as follows: Figure 4-6As shown, the mounting cavity of the base 1 has two protruding guide parts 17, which are located in front of the first connecting part 12. The bottom of the second adjusting seat 66 has two protruding first blocking parts, and the first blocking parts are provided with guide grooves 665 with downward openings. The two guide parts 17 are respectively inserted into the guide grooves of the two first blocking parts, so that the second adjusting seat 66 can only move in the longitudinal direction, avoiding the second adjusting seat from moving or rotating laterally.

[0040] To facilitate the installation of the tension spring, in this embodiment, as follows: Figure 4 and Figure 5 As shown, both the outer surface of the first mounting base 64 and the outer surface of the second mounting base 663 have spiral-shaped fixing grooves. The two ends of the tension spring 65 are respectively wound around the fixing grooves of the first mounting base 64 and the second mounting base 663. This facilitates the installation of the tension spring, makes it easier to adjust the angle of the first and second mounting bases, and reduces the difficulty of chassis assembly.

[0041] In this embodiment, as Figure 2 , Figure 4 and Figure 6 As shown, a second blocking part 13 protrudes from the mounting cavity of the base 1. The second blocking part 13 is located in front of the first connecting part 12 and is used to limit the forward tilt angle of the first adjusting seat 62. When the chassis is not under force, the tension spring 65 can pull the first adjusting seat 62 to press against the second blocking part 13. In this way, the tension spring can have sufficient preload to maintain a certain initial angle between the base and the first adjusting seat, reducing the difficulty of adaptive adjustment.

[0042] To facilitate the rotation of the screw, in this embodiment, as follows: Figure 2-6As shown, the second adjusting seat 66 has a through hole 662, and a nut 67 is also installed on the second adjusting seat 66. The inner hole of the nut 67 is connected to the through hole 662 of the second adjusting seat 66. The front part of the base 1 has a countersunk hole 15 that is connected to the mounting cavity. The countersunk hole 15 is rectangular. A fixing seat 60 with an inner hole is engaged in the countersunk hole 15. The front part of the fixing seat 60 has a protruding annular fifth blocking part. One end of the screw 68 is fixedly installed with a handle 69. The handle 69 has a protruding annular sixth blocking part. The fifth blocking part is inserted into the sixth blocking part. The other end of the screw 68 passes through the fifth blocking part, the inner hole of the fixing seat 60, and the through hole 662 of the second adjusting seat 66 and is threadedly connected to the nut 67 installed on the second adjusting seat 66. In order to prevent the nut 67 from falling off the screw 68, a pin 667 is also fixedly installed on the screw 68. To facilitate the installation of the nut, the second adjusting seat 66 also has a plurality of fourth blocking parts protruding around the through hole 662. The fourth blocking parts are located between the two second mounting seats 663. The plurality of fourth blocking parts form a bayonet 664 that matches the shape of the nut. The bayonet 664 is connected to the through hole 662. The nut 67 can be directly pressed into the bayonet 664 between the plurality of fourth blocking parts, thereby preventing the nut 67 from rotating. Located inside the plurality of fourth blocking parts, and abutting against the fourth blocking parts, the nut 67 can be directly pressed between the plurality of fourth blocking parts. The plurality of fourth blocking parts can prevent the nut 68 from rotating.

[0043] In this embodiment, as Figure 1-3 As shown, a baffle 11 is fixedly installed on the front of the base 1. The baffle 11 is located in front of the second hinge shaft 5. The baffle 11 can cover the structure between the top seat 3 and the base 1 from the front. The bottom of the top seat 3 is provided with two left and right blocking parts 31. The base 1 is between the two blocking parts 31. The blocking parts 31 can cover the structure between the top seat 3 and the base 1 from the left and right directions.

[0044] In this embodiment, the second adjustment seat 66 and the second mounting seat 663 are integrally formed. In order to further reduce the weight of the chassis, the integrally formed second adjustment seat 66 and the second mounting seat 66 are made of hard plastic such as nylon. The base 1 and the top seat 3 are also made of hard plastic.

[0045] In this embodiment, the base 1 is provided with a mounting hole 16 for mounting the gas spring, and the base 1 is also provided with a lever 7 for switching the gas spring on and off.

[0046] In this embodiment, as Figure 2-4As shown, the tailstock 2 also includes a second connecting plate 21 and a third connecting plate 23. The two first connecting plates 22 are fixedly connected to each other through the second connecting plate 21 and the third connecting plate 23. The second connecting plate 21 is located on the rear side of the base 1, and the third connecting plate 23 is located above the second adjusting seat 66. This increases the overall rigidity and stability.

[0047] A chair includes the aforementioned adjustable base, and also includes chair legs mounted on a base, a seat on a top seat, and a backrest on a tail seat.

[0048] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0049] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. An adjustable chassis, comprising a base (1), a top seat (3), a tail seat (2), and a tension spring (65), wherein the base (1) and the tail seat (2) are hinged via a first hinge shaft (4), and the top seat (3) and the tail seat (2) are hinged via a second hinge shaft (5), characterized in that: The tailstock (2) includes two first connecting plates (22) on the left and right. The two first connecting plates (22) of the tailstock (2) are hinged to the middle position of the base (1) through the first hinge shaft (4). The front part of the two first connecting plates (22) of the tailstock (2) is hinged to the bottom of the top seat (3) through the second hinge shaft (5). It also includes a first adjusting seat (62). The bottom of the first adjusting seat (62) is hinged to the base (1) through the third hinge shaft (61). The top of the first adjusting seat (62) is hinged to the top seat (3) through the fourth hinge shaft (63). The fourth hinge shaft (63) is located behind the second hinge shaft (5). One end of the tension spring (65) is connected to the fourth hinge shaft (63). The other end of the tension spring (65) is connected to the base (1) through the adjusting device. The second hinge shaft (5) is located above the front side of the first hinge shaft (4). It also includes a first mounting base (64), the top of the first adjusting base (62) is hinged to the first mounting base (64) through the fourth hinge shaft (63), the first adjusting base (62) is hinged to the top base (3) through the fourth hinge shaft (63), one end of the tension spring (65) is connected to the first mounting base (64), and the other end of the tension spring (65) is connected to the front of the base (1) through the adjusting device; the adjusting device includes a second adjusting base (66), a second mounting base (663) is fixed on the second adjusting base (66), both ends of the tension spring (65) are connected to the first mounting base (64) and the second mounting base (663) respectively, and an adjusting screw (68) is threaded on the second adjusting base (66), and the adjusting screw (68) is installed on the base (1) and can rotate.

2. The adjustable chassis according to claim 1, characterized in that: The second adjusting seat (66) has a bayonet (664) and a nut (67) is installed in the bayonet (664). The adjusting screw (68) passes through the nut (67) and is threadedly connected. When the adjusting screw (68) rotates, the nut (67) can drive the second adjusting seat (66) to move along the axis of the adjusting screw (68).

3. An adjustable chassis according to claim 2, characterized in that: A handle (69) is fixed to one end of the adjusting screw (68), and a pin (667) is radially fixed to the other end of the adjusting screw (68). The handle (69) is located on the outside of the base.

4. An adjustable chassis according to claim 1, characterized in that: There are two tension springs (65) arranged symmetrically on the left and right, two first mounting bases (64) arranged symmetrically on the left and right, and two second mounting bases (663) arranged symmetrically on the left and right.

5. An adjustable chassis according to claim 1, characterized in that: The outer side of the first mounting base (64) and the outer side of the second mounting base (663) both have spiral fixing grooves, and the two ends of the tension spring (65) are respectively locked in the fixing groove of the first mounting base (64) and the fixing groove of the second mounting base (663).

6. An adjustable chassis according to claim 1, characterized in that: The base (1) has a raised guide part (17) for preventing the second adjustment seat (66) from moving laterally. The bottom of the second adjustment seat (66) is provided with a guide groove (665) with an opening facing downward. The guide part (17) of the base (1) is inserted into the guide groove (665) at the bottom of the second adjustment seat (66) from bottom to top.

7. An adjustable chassis according to claim 1, characterized in that: The base (1) is also provided with two upward-opening positioning grooves (14), which extend backward through the base (1). The two first connecting plates (22) of the tailstock (2) are respectively inserted into the two positioning grooves (14) and are hinged to the base (1) through the first hinge shaft (4).

8. An adjustable chassis according to claim 1, characterized in that: The base (1) and the top (3) are made of plastic.

9. A chair, characterized in that: An adjustable chassis comprising any one of claims 1-8.

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