A seat with adjustable backrest angle

Abstract

The utility model discloses a backrest angle adjustable seat, including base and with base's hinge backrest, still include for adjusting the elastic component of the included angle between base and backrest and for providing backrest supporting force, wherein initial state, the included angle of base and backrest front is acute angle, and elastic component exists initial pre -tightening force in initial state, along with backrest from initial angle counterclockwise rotation, the force of elastic component to human body gradually increases, and the increasing rate is first increase later reduces. The utility model discloses through elastic component dynamic self -adaptation and provide a supporting force for human waist, thereby make human body keep in comfortable and correct sitting posture, solve the problem that present seat can not dynamically provide supporting force for waist.

Description

Technical Field

[0001] This utility model relates to the field of chair technology, and in particular to a seat with an adjustable backrest angle. Background Technology

[0002] Currently, office workers spend over 8 hours a day sitting (more than 60% of their day), and the prolonged use of chairs lacking ergonomic design leads to a high incidence of spinal diseases. Most office workers suffer from cervical spondylosis, lumbar disc herniation, or chest and back pain due to prolonged sitting, and the number of lumbar spine patients continues to rise. A healthy, ergonomically designed office chair can effectively reduce the probability of developing these diseases, making a healthy and comfortable office chair particularly important for office workers. However, most existing office chair backrests have a fixed shape and cannot dynamically adapt to changes in the curvature of the lumbar spine; when users lean forward or backward, the lower back is unsupported, causing pressure to concentrate on a single vertebral segment, accelerating intervertebral disc deformation. Utility Model Content

[0003] Purpose of the utility model: The purpose of this utility model is to provide a seat with an adjustable backrest angle, which provides a support force to the human waist through the dynamic adaptive elastic component, thereby allowing the human body to maintain a comfortable and correct sitting posture, and solving the problem that existing seats cannot dynamically provide lumbar support.

[0004] Technical solution: To achieve the above objectives, this utility model discloses a seat with an adjustable backrest angle, including a base and a backrest hinged to the base, and an elastic component for adjusting the angle between the base and the backrest and for providing backrest support. In the initial state, the angle between the base and the front of the backrest is an acute angle, and the elastic component has an initial preload in the initial state. As the backrest rotates counterclockwise from the initial angle, the force exerted by the elastic component on the human body gradually increases, and the rate of increase is first increased and then decreased.

[0005] Optionally, the upper end of the elastic component is hinged to the back of the backrest, and the lower end of the elastic component is hinged to the rear end of the base. The hinge point between the elastic component and the base is located behind the hinge point between the backrest and the base. The elastic component can extend and retract under the pressure of the backrest.

[0006] Optionally, the elastic component includes a telescopic cylinder hinged to the backrest via an upper connector and to the base via a lower connector, a threaded tube sleeved on the outside of the cylinder barrel of the telescopic cylinder, a nut threaded to the outer circumference of the threaded tube, a handle sleeve whose lower end is fixed to the outer circumference of the nut, a travel limiting sleeve whose lower end is sleeved to the upper end of the handle sleeve and whose upper end abuts against the lower surface of the upper connector, and a compression spring sleeved on the outside of the threaded tube, wherein one end of the compression spring abuts against the end face of the nut and the other end of the compression spring abuts against the stepped surface of the travel limiting sleeve; rotating the handle sleeve causes the nut to rotate, and the rotation adjusts the engagement position with the threaded tube, thereby adjusting the preload of the compression spring.

[0007] Optionally, the upper end of the travel limiting sleeve and the upper connector are connected to an appearance shielding member for covering the connector.

[0008] Optionally, the upper end of the travel limiting sleeve is provided with a first magnet, and the appearance shield is provided with a second magnet that attracts the first magnet.

[0009] Optionally, the elastic component includes a torsion spring pivot for hinged backrest and base, a double torsion spring sleeved on the torsion spring pivot, and a torsion spring limiting member located at the bottom of the backrest. The middle torsion arm of the double torsion spring contacts the back of the backrest, and the two end torsion arms of the double torsion spring pass through the base and are fixed to the base. In the initial state, the double torsion spring is compressed, generating an initial preload force, which pushes the backrest to rotate forward, and the torsion spring limiting member abuts against the base.

[0010] Optionally, a torsion spring pad that fits against the backrest surface is provided at the position where the middle torsion arm of the double torsion spring contacts the back of the backrest.

[0011] Optionally, the bottom surface of the base is provided with a torsion spring fixing plate for fixing the torsion arms at both ends of the double torsion spring.

[0012] Optionally, the base includes a breathable cushion on the upper surface of the base and an anti-slip component on the lower surface of the base, wherein the base includes a hollow ring structure and a mesh fabric fixed to the hollow ring structure.

[0013] Optionally, the anti-slip element is a silicone pad or a raised textured feature on a base.

[0014] Beneficial effects: Compared with the prior art, this utility model has the following advantages: This utility model realizes real-time position adjustment of the lumbar support component through elastic components, which can adapt to changes in human sitting posture and actively conform to the lumbar curve; it provides a support force to the human waist through dynamic adaptation of elastic components, thereby keeping the human body in a comfortable and correct sitting posture, solving the problem that current lumbar support cushions and chairs cannot dynamically provide lumbar support; this utility model can be easily folded and stored, reducing logistics and warehousing costs. Attached Figure Description

[0015] Figure 1 This is a simplified schematic diagram of the principle of this utility model;

[0016] Figure 2 This is an axonometric view of the present invention;

[0017] Figure 3 This is a side view of the present invention;

[0018] Figure 4 This is a detailed axial side view of the present invention;

[0019] Figure 5This is a diagram illustrating the folded state of this utility model;

[0020] Figure 6 This is a cross-sectional view of the elastic component of this utility model;

[0021] Figure 7 This is a detailed drawing of the base plate of this utility model;

[0022] Figure 8 Here are detailed drawings of the elastic component of this utility model;

[0023] Figure 9 This is a force analysis diagram of the human body according to the present invention;

[0024] Figure 10 This is a schematic diagram of Embodiment 2 of the present invention;

[0025] Figure 11 Axial view of Embodiment 2 of this utility model Figure 1 ;

[0026] Figure 12 Axial view of Embodiment 2 of this utility model Figure 2 ;

[0027] Figure 13 Axial view of Embodiment 2 of this utility model Figure 3 ;

[0028] In the diagram: Base 1, Base 101, Hollow Ring Structure 1011, Mesh Fabric 1012, Breathable Seat Cushion 102, Anti-slip Part 103, Backrest Hinge Shaft 104, Elastic Component Hinge Shaft 105; Backrest 2, Elastic Component 3, Upper Connector 301, Lower Connector 302, Telescopic Cylinder 303, Screw Tube 304, Nut 305, Handle Sleeve 306, Travel Limit Sleeve 307, Compression Spring 308, Appearance Covering Part 309, Torsion Spring Rotary Shaft 310, Double Torsion Spring 311, Torsion Spring Limiting Part 312, Torsion Spring Pad 313, Torsion Spring Fixing Plate 314, Torsion Spring Fixing Part 315, First Magnet 316, Second Magnet 317. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the scope of the present utility model.

[0030] It should be understood that this invention can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of this invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of the components may be exaggerated. The same reference numerals denote the same components throughout.

[0031] Example 1: As Figure 1 , Figure 2 and Figure 3 As shown, this embodiment of an adjustable backrest seat includes a base 1, a backrest 2, and an elastic component 3. The backrest 2 is hinged to the base 1. The elastic component 3 is used to adjust the angle between the base 1 and the backrest 2, and also to provide support for the backrest 2. In the initial state, the angle between the front of the base 1 and the backrest 2 is an acute angle, and the elastic component has an initial preload. As the backrest rotates counterclockwise from the initial angle, the force exerted by the elastic component 3 on the human body gradually increases, with the rate of increase first increasing and then decreasing. When a person sits on a chair, there is generally a certain distance between them and the backrest. If the person does not actively recline, that is, if the angle between the waist and thigh is less than 90 degrees, a force supporting the waist cannot be generated. In this invention, the angle between the front of the base 1 and the backrest 2 is set to an acute angle so that the waist can generate a forward thrust as long as it remains upright. Moreover, even with small adjustments and movements of the waist, the backrest and lumbar support can still follow the body's adjustments and continuously provide a supporting force for the waist, thereby achieving the best effect.

[0032] The base 1 and backrest 2 are connected via a rotating joint. An elastic component 3 is connected to both the base 1 and backrest 2 via rotating joints. The rotating joint connecting the base 1 and backrest 2 is located in the rear half of the base, while the rotating joint connecting the base 1 and elastic component 3 is located at the rear edge of the base. In the absence of external force, the elastic component 3 forms an acute angle with the base 1. The backrest 2 can rotate around its hinge point with the seat cushion 1. When the backrest 2 rotates, the spring component 3 deforms. When a person leans back against the backrest 2, they exert a backward force on it. As the backrest 2 rotates counterclockwise under this force, the elastic force of the elastic component 3 gradually increases, and the angle between the elastic component 3 and the base 1 increases. At this time, the back of the person also experiences a forward force on the lumbar spine from the backrest 2. This ensures that the backrest 2 consistently provides support, creating a sense of back support and reducing pressure on the lumbar spine. This invention can improve posture problems, ensuring an optimal sitting position and alleviating lumbar spine issues caused by improper posture. When the elastic component 3 is in its initial position, there is an initial preload. The stiffness of the elastic component 3 and the initial preload can be adjusted.

[0033] like Figure 7As shown, the base 1 includes a base 101, a breathable seat cushion 102, an anti-slip component 103, a backrest hinge shaft 104, and an elastic component hinge shaft 105. The base 1 is hinged to the backrest 2 via the backrest hinge shaft 104, which is located in the rear half of the base 101 and is used for hinged connection with the backrest 2. The lower end of the elastic component is hinged to the base 1 via the elastic component hinge shaft 105, which is located at the rear edge of the base 1 and is used for hinged connection with the elastic component 3. The upper surface of the base 1 is provided with the breathable seat cushion 102, and the lower surface of the base 1 is provided with the anti-slip component 103. The base 101 is made of engineering plastics such as PP, possessing good resistance to deformation and toughness. The breathable seat cushion 102 is fixed to the base 101, and the specific fixing method can be quick-release structures such as glue, magnetic adsorption, clips, or Velcro. The breathable seat cushion 102 is integrally molded from a 30% open-cell mesh polyurethane foam, or alternatively, a honeycomb mesh TPE material. The breathable seat cushion 102 is elastic and breathable, providing excellent support for the buttocks and improving seating comfort. The upper front edge of the breathable seat cushion 102 is 4cm high (H1=4cm) from the base 101, and the upper rear edge is 2cm high (H2=2cm), forming an angle α=5°. An anti-slip element 103 is located at the bottom of the base 101, effectively preventing the chair from sliding. The anti-slip element 103 is an embedded 3mm thick silicone pad with a friction coefficient μ≥0.8, or it can be a textured feature on the bottom of the base 101, or an anti-slip structure such as rubber anti-slip dots. The base 101 includes a hollow ring structure 1011 and a mesh fabric 1012 fixed to the hollow ring structure 1011. The base 101 adopts a rigid-flexible coupling design, resulting in better compatibility with chairs and sofas of different materials. The mesh fabric 1012 is fixed to the hollow ring structure 1011 using ultrasonic welding or adhesive methods. The hollow ring structure 1011 is made of PP plastic and, due to the absence of structural components in the center, possesses good toughness, allowing it to conform well to various non-flat surfaces such as ergonomic chairs, sofas, and other similar objects. The mesh fabric 1012 can be a mesh-shaped polymer material, a fabric with some elasticity, or a thinner plastic component. When a person sits on the mesh fabric 1012, it will slightly concave and deform, better conforming to the buttocks. When the base 101 is placed on a flexible ergonomic chair, the mesh fabric 1012 can retain the original flexibility of the ergonomic chair as much as possible. The structure of the base 101 provides better comfort and breathability.

[0034] The backrest 2 is hinged to the elastic component 3 through the rear pivot hole 210, and the backrest 2 is hinged to the backrest hinge shaft 104 of the base 1 through the bottom pivot hole 211. The backrest has a certain arc shape. When it is not fixedly connected to the elastic component, the backrest can rotate clockwise, so that the entire backrest and lumbar support are folded and close to the base; this can reduce its packaging volume, facilitate transportation, and reduce transportation costs.

[0035] like Figure 5 As shown, the backrest 2 has a certain arc. When not hinged to the elastic component 3, the backrest 2 can rotate clockwise, causing the entire backrest 2 to fold and fit snugly against the base 1. This reduces its packaging volume, facilitates transportation, and lowers transportation costs. Folding parameters: Folded thickness 12~18cm, unfolded structural safety factor ≥2.5.

[0036] like Figure 4 As shown, the upper end of the elastic component 3 is hinged to the back of the backrest 2, and the lower end of the elastic component 3 is hinged to the rear end of the base 1. The hinge point between the elastic component 3 and the base 1 is located behind the hinge point between the backrest 2 and the base 1. The elastic component 3 can extend and retract under the pressure of the backrest 2.

[0037] like Figure 6 and Figure 8 As shown, the elastic component 3 includes an upper connector 301, a lower connector 302, a telescopic cylinder 303, a screw tube 304, a nut 305, a handle sleeve 306, a stroke limit sleeve 307, a compression spring 308, and an appearance shield 309. The lower end of the telescopic cylinder 303 is hinged to the elastic component hinge shaft 105 of the base 1 via the lower connector 302, and the upper end of the telescopic cylinder 303 is hinged to the pin in the rear rotating shaft hole 210 of the backrest 2 via the upper connector 301. The screw tube 304 is sleeved on the outside of the cylinder barrel of the telescopic cylinder 303, and the screw tube 304 is interference-fitted with the cylinder barrel. The outer circumference of the screw tube 304 is threaded with a nut 305. The lower end of the handle sleeve 306 is fixedly connected to the outer circumference of the nut 305. The lower end of the travel limit sleeve 307 is sleeved with the upper end of the handle sleeve 306. The upper end of the travel limit sleeve 307 abuts against the lower surface of the upper connector 302. The compression spring 308 is sleeved on the outside of the screw tube 304. One end of the compression spring 308 abuts against the end face of the nut 305, and the other end of the compression spring 308 abuts against the stepped surface of the travel limit sleeve 307. Rotating the handle sleeve 306 causes the nut 305 to rotate. Rotation adjusts the engagement position with the screw tube 304 and adjusts the preload of the compression spring 308. The appearance shielding part 309 is fixed to the travel limit sleeve 307 by magnetic attraction or snap fastener, and is used to cover the appearance of the upper connector 301. Specifically, the upper end of the travel limit sleeve 307 is provided with a first magnet 316, and the appearance shielding part 309 is provided with a second magnet 317 that is attracted to the first magnet.

[0038] The handle sleeve 306 can control the initial preload of the elastic component 3 by adjusting the pre-deformation of the compression spring 308. The compression spring 308 and the telescopic cylinder 303 are compressible; when the backrest 2 rotates counterclockwise, the compression spring 308 and the telescopic cylinder 303 are compressed, and the entire elastic component 3 shortens. The function of the elastic component 3 is to provide a clockwise rotational force to the backrest 2, ensuring an initial force when the human body contacts the backrest.

[0039] The telescopic cylinder 303 and the compression spring 308 can only deform axially and will not bend due to external forces. The telescopic cylinder 303 has a pneumatic pressure of 100N, an outer diameter of 15mm, and a length of 220mm. The compression spring 308 has a length of 100mm. The telescopic cylinder 303 provides some elastic force and also acts as a radial limiter. The compression spring supplements the elastic force and allows for easy adjustment of the preload by changing the initial compression distance.

[0040] Because of the travel limitation, the telescopic cylinder 303 and the travel limit sleeve 307 allow for forward and backward limits on the rotation of the backrest 2. By selecting appropriate travel for the telescopic cylinder 303 and the travel limit sleeve 307, or by adjusting the fixed position of the connector 302, the optimal maximum and minimum angles between the backrest 2 and the base 1 can be obtained. In this specific embodiment, the maximum and minimum angles are 80° and 150°, respectively. The minimum angle range limitation ensures that, under the initial preload of the spring, the angle between the backrest and the base still conforms to the most comfortable angle for a person sitting on it. The maximum angle range limitation prevents the backrest from being excessively pressed backward, causing the elastic element to exceed its travel range and undergo plastic deformation and failure. It also ensures that heavy individuals will not completely press down on the backrest, thus preventing the risk of falls or injury.

[0041] like Figure 9 As shown, assuming the seat is in its initial state, the initial elastic force of the elastic component 3 on the backrest 2 is... The distance between the hinge point between the backrest and the base and the hinge point between the elastic component and the backrest is The distance between the hinge point between the backrest and the elastic component and the hinge point between the backrest and the base is The distance between the hinge point of the elastic component and the backrest and the hinge point of the elastic component and the base is The initial angle between the backrest 2 and the base 1 is... The initial angle between the elastic component 3 and the base 1 is When the human body applies a backward force to the backrest 2, the backrest 2 rotates counterclockwise. Angle becomes , Angle becomes , and remain unchanged. shortened to .

[0042] In the initial state: After deformation: The force F1 of the elastic component 3 changes as follows after deformation: The force of elastic component 3 after deformation: The force exerted by the elastic component on the human body in the forward direction: As the backrest rotates counterclockwise from its initial angle, the force exerted on the human body by the elastic component 3 gradually increases, with the rate of increase first increasing and then decreasing.

[0043] Example 2: The structure of Example 2 is the same as that of Example 1, except that: Figure 10 As shown, the elastic component 3 adopts a torsion spring structure, connected to both the base 1 and the backrest 2. The rotation center of the torsion spring and the revolute joint of the backrest 2 are on the same straight line. The backrest 2 can rotate around its hinge point with the base 1, and the spring component 3 deforms when the backrest 2 rotates. When a person leans back against the lumbar support 4, the person exerts a backward force on the backrest 2. When the backrest 2 rotates counterclockwise under this force, the elastic component 3 is compressed, and the elastic force gradually increases. Figure 11 , Figure 12 and Figure 13 As shown, the elastic component 3 includes a torsion spring shaft 310, a double torsion spring 311, a torsion spring limiting member 312, a torsion spring pad 313, and a torsion spring fixing plate 314. The torsion spring shaft 310 is used to hinge the backrest 2 and the base 1. The torsion spring shaft 310 is also the hinge shaft between the backrest 2 and the base 1. The double torsion spring 311 is sleeved on the torsion spring shaft 310. The torsion spring limiting member 312 is provided at the bottom front of the backrest. The torsion spring pad 313 is provided at the position where the middle torsion arm of the double torsion spring 311 contacts the back of the backrest, and is in contact with the back surface of the backrest. The two torsion arms of the double torsion spring pass through the base and are fixed to the base. In the initial state, the double torsion spring is compressed, generating an initial preload force, which pushes the backrest 2 to rotate forward, and the torsion spring limiting member 312 abuts against the base.

[0044] The double torsion spring 311 is made of spring steel and has an axially symmetrical shape. Both the left and right sides of the torsion spring can provide torsional force. The left and right sides of the torsion spring are fitted onto the torsion spring shaft 310 of the base 1. The torsion arms at both ends of the double torsion spring are fixed to the base 1, and the middle torsion arm is fixed to the backrest 2.

[0045] The diameter of the torsion spring shaft is slightly smaller than the inner diameter of the torsion spring. This serves two purposes: firstly, it prevents the torsion spring from wobbling excessively; secondly, during the compression of the torsion spring, the inner diameter of the torsion spring will decrease, and being slightly smaller prevents the torsion spring from locking the shaft with slight compression. By setting an appropriate size difference, when the backrest reaches its maximum rotation angle, the inner diameter of the torsion spring shrinks to match the diameter of the torsion spring shaft, causing it to lock and preventing the shaft from continuing to rotate backward, thus achieving the purpose of rear limit.

[0046] When a torsion spring rotates around its axis, especially in the "tightening" direction (the direction that increases the number of coils), its internal coils tighten, resulting in a decrease in the effective inner diameter, which is: D. min =(D0*N) / (N+(θ / 360°)), where: D minD0 is the minimum inner diameter of the torsion spring after a certain angle of twist, in mm; D0 is the initial inner diameter of the torsion spring, i.e., the inner diameter of the torsion spring in its free state, in mm; N is the effective number of coils of the torsion spring; θ is the torsion angle of the torsion spring, in degrees, assuming the chair can rotate a maximum of 90°; the outer diameter of the torsion spring's pivot must be less than the minimum inner diameter D calculated above. min To avoid suffocation, it is necessary to... min A safety clearance C is provided between the outer diameter of the torsion spring shaft and the outer diameter D of the torsion spring shaft. sleeve_max =D min -C, if the safety clearance is too small, friction or even jamming may occur due to machining tolerances, surface roughness, fine dust, or insufficient lubrication. If the safety clearance is too large, the torsion spring will shift its center and wobble during rotation, affecting motion accuracy and stability, and may even produce abnormal noise and additional wear. The recommended safety clearance C range is: C = (0.003~0.006) * D0.

[0047] The backrest 2 has a torsion spring limiting component 312 at its bottom. In the initial state, the backrest and the base form an acute angle of approximately 90 degrees. At this time, the double torsion springs are compressed, and the torsion springs have preload, which will cause the backrest to rotate forward. At this point, the torsion spring limiting component 312 will interfere with the base, thus limiting the maximum forward position that the backrest can reach in the initial state. The torsion spring limiting component 312 can also be other adjustment mechanisms, such as using a ratchet to achieve an adjustable initial position of the backrest.

[0048] To prevent excessive stress concentration at the contact points between the torsion spring and the backrest and base, which could damage the plastic parts, a torsion spring pad 313 is installed at the contact point between the torsion spring and the backrest. The torsion spring pad 313 is flush with the curved surface of the backrest and is fixed to the backrest. The torsion spring pad 313 contacts the torsion spring, and the torsion spring transmits force to the torsion spring pad 313, which then distributes the force to the backrest. The two ends of the torsion spring pass through the base, and a torsion spring fixing plate 314 is installed at the contact point with the bottom of the base. The torsion spring fixing plate 314 is fixed to the base, and the two ends of the torsion spring are fixed to the torsion spring fixing plate 314 by torsion spring fixing parts 315 to prevent the torsion spring from shifting back and forth. There are two double torsion springs, symmetrically distributed, which apply force to both ends of the backrest.

[0049] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A seat with an adjustable backrest angle, comprising a base (1) and a backrest (2) hinged to the base (1), characterized in that: It also includes an elastic component (3) for adjusting the angle between the base (1) and the backrest (2) and for providing support for the backrest (2). In the initial state, the angle between the front of the base (1) and the backrest (2) is an acute angle, and the elastic component has an initial preload in the initial state. As the backrest (2) rotates counterclockwise from the initial angle, the force exerted by the elastic component (3) on the human body gradually increases, and the rate of increase is first increased and then decreased.

2. The adjustable backrest angle seat according to claim 1, characterized in that: The upper end of the elastic component (3) is hinged to the back of the backrest (2), and the lower end of the elastic component (3) is hinged to the rear end of the base (1). The hinge point between the elastic component (3) and the base (1) is located behind the hinge point between the backrest (2) and the base (1). The elastic component (3) can extend and retract under the pressure of the backrest (2).

3. A seat with an adjustable backrest angle according to claim 2, characterized in that: The elastic component (3) includes a telescopic cylinder (303) hinged to the backrest (2) via an upper connector (301) and hinged to the base (1) via a lower connector (302), a threaded tube (304) sleeved on the outside of the cylinder barrel of the telescopic cylinder (303), a nut (305) threaded to the outer circumference of the threaded tube (304), a handle sleeve (306) whose lower end is fixed to the outer circumference of the nut, and a handle sleeve (306) whose lower end is sleeved to the upper end of the handle sleeve (306) and whose upper end abuts against the upper connector (304). 301) The travel limit sleeve (307) on the lower surface and the compression spring (308) sleeved on the outside of the screw tube (304), wherein one end of the compression spring (308) abuts against the end face of the nut (305) and the other end of the compression spring (308) abuts against the stepped surface of the travel limit sleeve (307); rotate the handle sleeve (306), the handle sleeve (306) drives the nut (305) to rotate, rotate to adjust the engagement position with the screw tube (304), and adjust the preload of the compression spring (308).

4. A seat with an adjustable backrest angle according to claim 3, characterized in that: The upper end of the travel limiting sleeve (307) and the upper connector (301) are connected to an appearance shield (309) for shielding the connector.

5. A seat with an adjustable backrest angle according to claim 4, characterized in that: The upper end of the travel limiting sleeve (307) is provided with a first magnet (316), and the appearance shielding part (309) is provided with a second magnet (317) that attracts the first magnet.

6. A seat with an adjustable backrest angle according to claim 1, characterized in that: The elastic component (3) includes a torsion spring shaft (310) for hinged backrest (2) and base (1), a double torsion spring (311) sleeved on the torsion spring shaft (310), and a torsion spring limiting member (312) located at the bottom of backrest (2). The middle torsion arm of the double torsion spring (311) contacts the back of backrest (2), and the two torsion arms of the double torsion spring (311) pass through the base (1) and are fixed to the base (1). In the initial state, the double torsion spring (311) is compressed, generating an initial preload force, pushing the backrest (2) to rotate forward, and the torsion spring limiting member (312) abuts against the base.

7. A seat with an adjustable backrest angle according to claim 6, characterized in that: The middle torsion arm of the double torsion spring (311) is provided with a torsion spring pad (313) that is in contact with the back of the backrest (2) at the position where it contacts the back of the backrest (2).

8. A seat with an adjustable backrest angle according to claim 6, characterized in that: The bottom surface of the base (1) is provided with a torsion spring fixing plate (314) for fixing the torsion arms at both ends of the double torsion spring (311).

9. A seat with an adjustable backrest angle according to claim 1, characterized in that: The base (1) includes a base (101), a breathable seat cushion (102) on the upper surface of the base (101), and an anti-slip component (103) on the lower surface of the base (101). The base (101) includes a hollow ring structure (1011) and a mesh fabric (1012) fixed on the hollow ring structure (1011).

10. A seat with an adjustable backrest angle according to claim 9, characterized in that: The anti-slip component (103) is a raised textured feature on a silicone pad or base (101).

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