CN111067292A - Tray on chair and torsion spring torsion adjusting structure thereof - Google Patents

Abstract

The invention discloses a torsion adjusting structure of a torsion spring, which comprises a swinging block, a screw rod and at least one torsion spring, wherein a mandrel is arranged at one end of the swinging block in a penetrating manner, and the mandrel is sleeved with the torsion spring; the other end of the swinging block is fixedly connected with or integrally formed with a torsion adjusting block, the lower end of the torsion adjusting block is provided with a push block, and a screw rod penetrates through the push block and is in threaded connection with the push block; the lower terminal surface of torsion regulating block forms first inclined plane, and the up end of ejector pad forms the second inclined plane that offsets with first inclined plane, and the mobilizable trend of installing on the torsion regulating block and giving the torsion regulating block to the ejector pad direction motion of one end of torsional spring, and the screw rod rotates and drives the ejector pad horizontal motion, and the ejector pad horizontal motion makes the torsion regulating block carry out the up-and-down motion. The torsion adjusting structure of the torsion spring enables the push block to horizontally move by rotating the screw rod, and the torsion adjusting block moves up and down under the action force of the push block.

Description

Tray on chair and torsion spring torsion adjusting structure thereof

Technical Field

The invention relates to a chair tray structure, in particular to a chair tray and a torsion adjusting structure of a torsion spring of the chair tray.

Background

The chair tray with the functions of lifting the chair, tilting the chair seat and tilting the chair back usually comprises a middle tray set connected with a pneumatic rod, a flip cover connected with the chair back and a big tray set connected with the chair seat, and a reset torsion spring for resetting is usually arranged on a pivot connecting the big tray set and the middle tray set and a pivot connecting the flip cover and the big tray set. After a certain usage time, the torsion of the reset torsion spring changes to a certain degree, and if the torsion of the reset torsion spring is weakened, the functions of lifting the chair, inclining the chair seat, inclining the chair back and the like are further influenced. In the prior art, some chair trays are provided with a mechanism for adjusting the torsion force of the return torsion spring, however, there are still some disadvantages, including the following:

1. when the torsion of the reset torsion spring is adjusted, the torsion can be realized only by a large external force;

2. when the torsion of the torsion spring is fixed, a locking member is required, and the operation is complicated.

Patent document that the publication number is CN203576041U discloses a chair tray torsional spring torsion adjustment mechanism, locates the epaxial reset torsion spring of chair tray pivot including shell, chair tray pivot and cover, still includes the locating piece, cam and regulation pole, reset torsion spring one end is equipped with the L type bending segment, L type bending segment and locating piece looks butt, the locating piece is contradicted with the cam cambered surface with the opposite side that the L type bending segment was contradicted to be connected relatively and is connected, adjust pole and cam fixed connection and control cam circumferential direction, the locating piece is the cambered surface with the face of L type bending segment butt, aims at providing one kind and can adjust the chair tray torsional spring torsion adjustment mechanism of the operation of being convenient for use to reset torsion spring torsion. The adjusting mechanism adjusts the torsion of the torsion spring by rotating the cam and extruding the positioning block, and needs strong external force; in addition, the torsion of the torsion spring is fixed by matching the annular clamping teeth with the annular clamping tooth holes, and the operation is complex.

Patent document with publication number CN206324514U discloses a swivel chair tray torsion spring adjusting mechanism, which comprises a base, a middle seat and a rocker, wherein the middle seat is internally provided with a triangular push block, the triangular push block is connected with a transmission mechanism, the inclined surface of the triangular push block is contacted with a torsion spring adjusting block, one end surface of the torsion spring adjusting block is provided with a contact surface matched with the inclined surface of the triangular push block, the other end of the torsion spring adjusting block is connected with a torsion spring, and the torsion spring is connected with the middle seat. This adjustment mechanism passes through adjusting screw and promotes the triangle ejector pad and remove, triangle ejector pad drive torsional spring regulating block takes place the displacement and then realizes torsional spring torsion's regulation, however, the atress through to the torsional spring regulating block carries out the analysis, we can discover, the torsional spring regulating block receives the effort of two directions, including the power that is on a parallel with torsional spring regulating block direction of motion, and the power of perpendicular to torsional spring regulating block direction of motion, the former promotes the torsional spring regulating block and moves to the torsional spring direction, the latter has increased the frictional force between torsional force regulating block and the base, when the torsion of regulation torsional spring, need stronger external force, influence user's experience.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a tray on a chair and a torsion adjusting structure of a torsion spring of the tray.

In order to achieve the purpose, the invention provides the following technical scheme: a torsion adjusting structure of a torsion spring comprises a swinging block, a screw rod and at least one torsion spring, wherein a mandrel is arranged at one end of the swinging block in a penetrating mode, the swinging block can rotate relative to the mandrel, and the torsion spring is sleeved on the mandrel; the other end of the swinging block is fixedly connected with or integrally formed with a torsion adjusting block, the upper end of the torsion adjusting block is provided with a push block, and a screw rod penetrates through the push block and is in threaded connection with the push block; the upper end face of the torsion adjusting block forms a first inclined face, the lower end face of the pushing block forms a second inclined face which is abutted to the first inclined face, one end of the torsion spring is movably installed on the torsion adjusting block and gives a trend that the torsion adjusting block moves towards the direction of the pushing block, the screw rod rotates to drive the pushing block to move horizontally, the pushing block moves horizontally to enable the torsion adjusting block to move up and down, and the torsion adjusting block further compresses or relaxes the torsion spring.

The push block horizontally moves by rotating the screw rod, the torsion adjusting block moves up and down under the acting force of the push block, further, the torsion adjusting block changes the torsion of the torsion spring, when the torsion adjusting block moves up under the action of the push block, the torsion of the torsion spring is enhanced, and when the torsion adjusting block moves down under the action of the push block, the torsion of the torsion spring is weakened. Compared with the prior art, on one hand, the pushing block is driven to horizontally move through the rotation of the screw rod, so that the torsion adjusting block moves up and down, and the torsion of the torsion spring is adjusted; on the other hand, when the torsion of the torsion spring is fixed, other external force is not needed, the torsion spring gives the downward movement force to the torsion adjusting block, the force acts on the pushing block to decompose the force, the force comprises a component force in the vertical direction and a component force in the horizontal direction, and the component force in the horizontal direction acts on the screw rod to enable the pushing block and the screw rod to be relatively fixed, so that the torsion of the torsion spring is fixed.

Preferably, the torsion adjusting mechanism further comprises a limiting block arranged below the torsion adjusting block, a first groove used for limiting the torsion adjusting block up and down and accommodating the torsion adjusting block is formed in the limiting block, and a limiting plate part extends upwards from one end, far away from the torsion spring, of the limiting block; a second groove which is used for the sliding of the push block and is matched with the bottom shape of the push block is further formed in one side, located on the first groove, of the limiting block. Spacing board portion and second recess cooperate and are used for carrying out circumference spacing to the ejector pad, avoid it to take place circumferential direction.

Preferably, one end of the screw is provided with a driving mechanism for driving the screw to rotate, the driving mechanism comprises a handle and at least two gears, the gears are meshed with each other, a first gear is fixed on the handle, one end, close to the limiting block, of the handle is rotatably connected with the limiting block, a second gear is fixed on the screw, and the first gear is directly meshed with the second gear or is indirectly meshed with the second gear through at least one gear in a transmission mode. The screw rod is driven to rotate through the transmission of the gear, and the operation is labor-saving.

Preferably, the driving mechanism comprises a handle and two gears, a first gear is fixed on the handle, a second gear is fixed on the screw, the first gear and the second gear are meshed with each other, and the outer diameter of the first gear is larger than that of the second gear. The big gear wheel on the handle drives the small gear wheel on the screw rod to rotate, and the torsion of the torsion spring can be adjusted only by rotating the handle in a small range.

Preferably, in the horizontal direction, the second inclined plane of the push block inclines from top to bottom along the left-to-right direction, the second inclined plane is in a twisted shape, and the right end edge of the push block inclines from back to front to top to bottom; in the horizontal direction, the first inclined plane of torsion regulating block is followed from left to right direction and is from top to bottom inclined, and first inclined plane is the distortion form, and the right-hand member of torsion regulating block is followed from the backward place ahead to from top to bottom inclined.

When the swinging block rotates by taking the spindle as a center, the running track of one end, far away from the spindle, of the swinging block is an arc, namely, one end, far away from the spindle, of the swinging block can move forwards relative to the push block, if the second inclined plane of the push block and the first inclined plane of the torque adjusting block are of a planar structure, when the swinging block rotates, one end, far away from the torsion spring, of the torque adjusting block can tilt, further, the surface contact between the two is gradually changed into the contact between a line and a surface, when the swinging block is used for a long time, the inclined planes of the push block and the torque adjusting block can be damaged, even the line contact part can be gradually developed into a planar structure, further, the rotating resistance is increased, the swinging block is arranged into a twisted shape, the surface contact can be realized to the maximum extent, and the damage to the push block and the torque.

Preferably, a third groove is formed in the middle of the upper end of the torque force adjusting block; and a fourth groove is formed in the middle of the lower end of the push block. The probability that the side edge of the torque force adjusting block is abutted to the inclined surface of the push block is reduced, and the inclined surface can be well protected.

Preferably, two support columns extend along the axial direction of the mandrel from one end of the swinging block, which is far away from the torsion adjusting block, the support columns are sleeved on the mandrel, and the outer diameter of each support column is smaller than or equal to the inner diameter of the torsion spring. Avoid the torsional spring atress to take place the distortion when great, and then can protect the torsional spring.

Preferably, an arc-shaped groove is formed in the position, in contact with the torsion spring, of the torsion adjusting block, and one end of the torsion spring is movably installed at the lower end of the torsion adjusting block and embedded into the arc-shaped groove. The setting of arc recess can play spacing effect to the torsional spring, avoids it to take place the displacement of horizontal direction.

Preferably, the swing block comprises two torsion springs, wherein the two torsion springs are sleeved on the mandrel and are respectively arranged on two opposite sides of the swing block. The stress of the acted part is increased, and the stress is more uniform.

The utility model provides a tray on chair, includes as above torsional spring torsion regulation structure, the mobilizable installation of one end of torsional spring is on the torsion regulating block, and back of the chair swing subassembly is connected to the other end of torsional spring, and both ends rotate respectively about the mandrel and connect or fixed connection on the tray, and the screw rod rotates to be connected on the tray. In conclusion, the invention has the following beneficial effects:

1. the push block moves horizontally by rotating the screw rod, the torsion adjusting block moves up and down under the action of the push block, further, the torsion of the torsion spring is changed by the torsion adjusting block, when the torsion adjusting block moves up under the action of the push block, the torsion of the torsion spring is enhanced, and when the torsion adjusting block moves down under the action of the push block, the torsion of the torsion spring is weakened, so that the operation is simple;

2. when the torsion of the torsion spring is locked, other locking mechanisms are not needed;

3. the screw rod is driven to rotate through the transmission action of the gear, and the operation is labor-saving.

Drawings

FIG. 1 is a schematic structural diagram of a torsion adjusting structure of a torsion spring;

FIG. 2 is a schematic structural view of a torsion adjusting structure of a torsion spring with a limiting block;

FIG. 3 is a bottom view of FIG. 1;

FIG. 4 is a schematic diagram of a wobble block;

FIG. 5 is a schematic structural view of the push block;

FIG. 6 is a schematic diagram of another view of a wobble block;

FIG. 7 is a schematic structural diagram of a limiting block;

FIG. 8 is a schematic structural view of the chair with the torsion adjusting structure of the torsion spring mounted on the tray;

fig. 9 is a bottom view of fig. 8.

Reference numerals: 1. a swing block; 2. a screw; 3. a torsion spring; 4. a mandrel; 5. a torque force adjusting block; 6. a push block; 7. an arc-shaped groove; 8. a limiting block; 9. a first groove; 10. a limit plate part; 11. a second groove; 12. a handle; 13. a first gear; 14. a second gear; 15. a third groove; 16. a fourth groove; 17. a support pillar; 18. a chair back swing assembly.

Detailed Description

The invention is further described with reference to the accompanying drawings.

The embodiment discloses a tray on a chair and a torsion adjusting structure of a torsion spring of the tray, as shown in fig. 1-5, the tray comprises a swinging block 1, a screw rod 2 and at least one torsion spring 3, wherein a mandrel 4 is arranged at one end of the swinging block 1 in a penetrating manner, the swinging block 1 can rotate relative to the mandrel 4, and the torsion spring 3 is sleeved on the mandrel 4; the other end of the swinging block 1 is fixedly connected with or integrally formed with a torsion adjusting block 5, the upper end of the torsion adjusting block 5 is provided with a push block 6, and the screw rod 2 penetrates through the push block 6 and is in threaded connection with the push block 6; the upper end face of torsion regulating block 5 forms first inclined plane, the lower terminal surface of ejector pad 6 forms the second inclined plane that offsets with first inclined plane, and the mobilizable installation of one end of torsional spring 3 is on torsion regulating block 5 and give torsion regulating block 5 the trend of the motion of 6 directions of ejector pad, it is concrete, arc recess 7 has been seted up with the position of torsional spring 3 contact on the torsion regulating block 5, the one end of torsional spring 3 compresses tightly in the lower extreme of torsion regulating block 5 and imbeds arc recess 7, swing piece 1 is when rotating, be close to in torsion regulating block 5 on the torsional spring 3 in the position embedding arc recess 7 and by spacing in arc recess 7, arc recess 7's setting can play spacing effect to torsional spring 3, avoid it to take place the displacement of horizontal direction. The screw rod 2 rotates to drive the push block 6 to move horizontally, and the push block 6 moves horizontally to drive the torsion adjusting block 5 to move up and down. Preferably, the swing block comprises two torsion springs 3, wherein the two torsion springs 3 are sleeved on the mandrel 4 and are respectively arranged on two opposite sides of the swing block 1, so that the stress of the acted part can be increased, and the stress of the acted part is more uniform. The push block 6 moves horizontally by rotating the screw rod 2, the torsion adjusting block 5 moves up and down under the action of the push block 6, further, the torsion adjusting block 5 changes the torsion of the torsion spring 3, when the torsion adjusting block 5 moves up under the action of the push block 6, the torsion of the torsion spring 3 is enhanced, and when the torsion adjusting block 5 moves down under the action of the push block 6, the torsion of the torsion spring 3 is weakened. Compared with the prior art, on one hand, the pushing block 6 is driven to move horizontally by the rotation of the screw rod 2, so that the torsion adjusting block 5 moves up and down, and further the torsion of the torsion spring 3 is adjusted, the friction between the pushing block 6 and other parts is small, the torsion of the torsion spring 3 is adjusted in a labor-saving manner, and certainly, the pushing block 6 is driven to rotate by the rotation of the screw rod 2, but the rotation of the pushing block 6 is blocked by the interaction of the first inclined plane and the second inclined plane; on the other hand, when the torsion of the torsion spring 3 is fixed, no other external force is needed, the torsion spring 3 gives a downward movement force to the torsion adjusting block 5, the force acts on the pushing block 6 to decompose the force, and the force comprises a component force in the vertical direction and a component force in the horizontal direction, and the component force in the horizontal direction acts on the screw rod 2 to enable the pushing block 6 and the screw rod 2 to be fixed relatively, so that the torsion of the torsion spring 3 is fixed.

In order to avoid that the screw rod 2 drives the torsion adjusting block 5 to rotate simultaneously when rotating, as shown in fig. 1, 2 and 7, a limiting block 8 is arranged below the torsion adjusting block 5, a first groove 9 for limiting the torsion adjusting block 5 up and down and accommodating the torsion adjusting block 5 is formed in the limiting block 8, and a limiting plate part 10 extends upwards from one end of the limiting block 8 far away from the torsion spring 3; a second groove 11 which is used for the sliding of the push block 6 and is matched with the bottom shape of the push block 6 is further formed in one side of the limiting block 8, which is positioned on the first groove 9. The limiting plate part 10 and the second groove 11 are matched for circumferentially limiting the push block 6 and preventing the push block from circumferentially rotating. In fact, the first inclined plane on the torque force adjusting block 5 is matched with the second inclined plane on the pushing block 6, so that the pushing block 6 can be blocked to a certain extent to rotate circumferentially, and the limiting block 8 can further limit the circumferential rotation of the pushing block 6.

As shown in fig. 1, 2 and 3, one end of the screw rod 2 is further provided with a driving mechanism for driving the screw rod 2 to rotate, the driving mechanism includes a handle 12 and at least two gears, the gears are engaged with each other, a first gear 13 is fixed on the handle 12, one end of the handle 12 close to the limiting block 8 is rotatably connected with the limiting block 8, a second gear 14 is fixed on the screw rod 2, and the first gear 13 and the second gear 14 are directly engaged with each other or indirectly engaged with each other through at least one gear. The screw rod 2 is driven to rotate through the transmission of the gear, and the operation is labor-saving. Specifically, the driving mechanism comprises a handle 12 and two gears, a first gear 13 is fixed on the handle 12, a second gear 14 is fixed on the screw rod 2, the first gear 13 and the second gear 14 are meshed with each other, and the outer diameter of the first gear 13 is larger than that of the second gear 14. The big gear wheel on the handle 12 drives the small gear wheel on the screw rod 2 to rotate, and the torsion of the torsion spring 3 can be adjusted only by rotating the handle 12 with small amplitude.

As shown in fig. 4 and 5, in the horizontal direction, the second inclined plane of the push block 6 is inclined from top to bottom along the left-to-right direction, the second inclined plane is twisted, and the right end of the push block 6 is inclined from back to front to top to bottom; in the horizontal direction, the first inclined plane of torsion regulating block 5 is followed from left to right direction and is from top to bottom inclined, and first inclined plane is the twist form, and the right-hand member of torsion regulating block 5 is followed from the backward place ahead to from top to bottom inclined.

When the swinging block 1 rotates by taking the spindle 4 as the center, the running track of one end of the swinging block 1 far away from the spindle 4 is a circular arc, that is, one end of the swing block 1 far from the spindle 4 will be displaced backwards relative to the push block 6, if the second inclined plane of the push block 6 and the first inclined plane of the torque force adjusting block 5 are planar structures, when the swinging block 1 rotates, one end of the torsion adjusting block 5 far away from the torsion spring 3 can tilt, so that the surface contact between the two is gradually changed into the contact between a line and a surface, when the swinging block is used for a long time, the inclined surfaces of the push block 6 and the torsion adjusting block 5 can be damaged, even the line contact part can be gradually developed into a plane structure, and further the resistance of rotation is increased, and the first inclined surface and the second inclined surface are arranged in a twisted shape, so that surface contact can be realized to the maximum extent, and the damage to the push block 6 and the torsion adjusting block 5 is reduced. Preferably, a third groove 15 is formed in the middle of the upper end of the torque adjusting block 5; the fourth groove 16 is formed in the middle of the lower end of the push block 6, so that the probability that the side edge of the torque force adjusting block 5 abuts against the inclined surface of the push block 6 can be reduced, and the inclined surface can be well protected.

In addition, as shown in fig. 1, two supporting columns 17 extend along the axial direction of the spindle 4 from one end of the swinging block 1 far away from the torque force adjusting block 5, the supporting columns 17 are sleeved on the spindle 4, and the outer diameter of the supporting columns 17 is smaller than or equal to the inner diameter of the torsion spring 3, so that the torsion of the torsion spring 3 when the stress is large can be avoided, and the torsion spring 3 can be protected.

The utility model provides a tray on chair, as shown in fig. 8 and 9, includes as above the torsional spring torsion regulation structure, the mobilizable installation of one end of torsional spring 3 is on torsion regulating block 5, and back of the chair swing subassembly is connected to the other end of torsional spring 3, and both ends rotate respectively about spindle 4 to connect or fixed connection is on the tray, and screw rod 2 rotates to be connected on the tray. When the torsion adjusting structure of the torsion spring 3 is applied to the chair back tilting, one end of the torsion spring 3 is movably arranged at the lower end of the torsion adjusting block 5, the other end of the torsion spring 3 is connected with the swinging assembly, and the force of the chair back can be adjusted by rotating the screw rod 2.

The directions given in the present embodiment are merely for convenience of describing positional relationships between the respective members and the relationship of fitting with each other. The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.

Claims (10)

1. The utility model provides a torsional spring torsion adjusts structure which characterized by: the swing device comprises a swing block (1), a screw rod (2) and at least one torsion spring (3), wherein a mandrel (4) is arranged at one end of the swing block (1) in a penetrating mode, the swing block (1) can rotate relative to the mandrel (4), and the torsion spring (3) is sleeved on the mandrel (4); the other end of the swinging block (1) is fixedly connected or integrally formed with a torsion adjusting block (5), the upper end of the torsion adjusting block (5) is provided with a push block (6), and the screw rod (2) penetrates through the push block (6) and is in threaded connection with the push block (6); the upper end face of torsion regulating block (5) forms first inclined plane, the lower terminal surface of ejector pad (6) forms the second inclined plane that offsets with first inclined plane, just the trend that torsion regulating block (5) moved to ejector pad (6) direction is installed on torsion regulating block (5) and is given to torsion regulating block (5) to the mobilizable one end of torsional spring (3), and screw rod (2) rotate and drive ejector pad (6) horizontal motion, and ejector pad (6) horizontal motion makes torsion regulating block (5) carry out the up-and-down motion, and torsion regulating block (5) and then compression or lax torsional spring (3).

2. The torsion adjusting structure of a torsion spring according to claim 1, wherein: the torsion spring is characterized by further comprising a limiting block (8) arranged below the torsion adjusting block (5), a first groove (9) used for limiting up and down and accommodating the torsion adjusting block (5) is formed in the limiting block (8), and a limiting plate part (10) extends upwards from one end, far away from the torsion spring (3), of the limiting block (8); a second groove (11) which is used for the sliding of the push block (6) and is matched with the shape of the bottom of the push block (6) is further formed in one side of the limiting block (8) positioned in the first groove (9).

3. The torsion adjusting structure of a torsion spring according to claim 1 or 2, wherein: the one end of screw rod (2) is equipped with and is used for driving screw rod (2) pivoted actuating mechanism, actuating mechanism includes handle (12) and two at least gears, meshes mutually between the gear, fixed first gear (13) on handle (12), and is close to on handle (12) the one end and stopper (8) of stopper (8) rotate and are connected, fixed second gear (14) on screw rod (2), direct meshing or through the indirect transmission meshing of at least one gear between first gear (13) and second gear (14).

4. The torsion adjusting structure of a torsion spring according to claim 3, wherein: the driving mechanism comprises a handle (12) and two gears, a first gear (13) is fixed on the handle (12), a second gear (14) is fixed on the screw rod (2), the first gear (13) and the second gear (14) are meshed with each other, and the outer diameter of the first gear (13) is larger than that of the second gear (14).

5. The torsion adjusting structure of a torsion spring according to claim 1, wherein: in the horizontal direction, a second inclined plane of the push block (6) inclines from top to bottom along the left-to-right direction, the second inclined plane is in a twisted shape, and the right end of the push block (6) inclines from back to front along the top to bottom direction; in the horizontal direction, the first inclined plane of torsion regulating block (5) is followed from left to right direction and is from top to bottom inclined, and first inclined plane is the distortion form, and the right-hand member of torsion regulating block (5) is followed from the back to the place ahead to from top to bottom inclined.

6. The torsion adjusting structure of a torsion spring according to claim 5, wherein: a third groove (15) is formed in the middle of the upper end of the torque force adjusting block (5); and a fourth groove (16) is formed in the middle of the lower end of the push block (6).

7. The torsion adjusting structure of a torsion spring according to claim 1, wherein: one end of the swinging block (1) far away from the torsion adjusting block (5) is provided with two supporting columns (17) along the axial extension of the mandrel (4), the mandrel (4) is sleeved with the supporting columns (17), and the outer diameter of the supporting columns (17) is smaller than or equal to the inner diameter of the torsion spring (3).

8. The torsion adjusting structure of a torsion spring according to claim 1, wherein: arc recess (7) have been seted up with torsional spring (3) contact's position on torsion regulating block (5), the mobilizable lower extreme of installing in torsion regulating block (5) of one end of torsional spring (3) is embedded in arc recess (7).

9. The torsion adjusting structure of a torsion spring according to claim 1, wherein: the two torsion springs (3) are sleeved on the mandrel (4) and are respectively arranged on two opposite sides of the swinging block (1).

10. A tray on a chair is characterized in that: the torsion adjusting structure of the torsion spring comprises the torsion spring according to any one of claims 1 to 9, wherein one end of the torsion spring (3) is movably mounted on the torsion adjusting block (5), the other end of the torsion spring (3) is connected with the chair back swinging component, the left end and the right end of the spindle (4) are respectively connected with or fixedly connected with a tray in a rotating manner, and the screw rod (2) is connected with the tray in a rotating manner.

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