CN109820363B

CN109820363B - Chair

Info

Publication number: CN109820363B
Application number: CN201910240786.7A
Authority: CN
Inventors: 王江林; 潘星; 莫伟清; 宋洪平
Original assignee: Henglin Home Furnishings Co Ltd
Current assignee: Henglin Home Furnishings Co Ltd
Priority date: 2019-03-28
Filing date: 2019-03-28
Publication date: 2023-12-12
Anticipated expiration: 2039-03-28
Also published as: CN109820363A

Abstract

The invention discloses a chair, which comprises a supporting part, a seat part, a backrest seat and a backrest, wherein the seat part and the backrest seat are arranged on the supporting part; the upper part of the backrest is hinged with the upper part of the backrest seat, and the lower part of the backrest is in sliding connection with the backrest seat through a sliding component and realizes multi-gear sliding stop; according to the technical scheme, the upper part of the backrest is hinged with the upper part of the lumbar backrest, the lower part of the lumbar backrest is connected with the backrest in a sliding manner, so that the lumbar backrest has independence relative to the backrest, namely, the lumbar backrest can be adjusted according to the self requirements of a human body no matter whether the chair is in a vertical state or in a backward tilting state, and the lumbar backrest is adjusted to a position which is comfortable to the human body.

Description

Chair

Technical Field

The invention belongs to the field of seats, and particularly relates to a chair.

Background

The chair is an important rest tool for providing weight for a human body when the human body is at home or at office or reading, basically has a seat part for supporting buttocks of the human body, and enables legs to be temporarily pressed due to the support, and the common chair is provided with a back seat part, so that the back of the human body can be leaned. However, the chair does not fully support all the body positions, and there is still no adequate support for the lumbar position when the back is reclined and the buttocks are under. Thus, more commonly, the backrest seat is often formed with appropriate protrusions at the lumbar region to provide support to the lumbar region.

The existing seats can adjust the seat back seat according to the needs of the human body in an angle range, however, the degree of the back bulge required by the human body in the lying and sitting states is different, and the comfort level of sitting is basically considered in the prior art, so that the waist is still unsupported when the human body is in the lying state on the seat, and the fatigue is felt when the human body is in the lying state on the seat for a long time.

Chinese patent publication No. CN201875327U discloses a chair comprising a back support and a back; the connecting part of the chair back is fixedly connected with the supporting part of the back support, and at least one of the connecting part and the supporting part is made of elastic materials; the first limiting part of the chair back is movably connected with the second limiting part of the back support, and the first limiting part can move for a preset distance relative to the second limiting part; the connecting part and the first limiting part are distributed up and down, and the chair back is also provided with a waist rest. The chair provided by the patent limits the leaning angle of the chair back through the mutual matching of the first limiting part and the second limiting part, and enables the backrest to move when the chair back leans, so that the backrest can still prop against the waist of a person even in a lying state, but the waist of the chair moves forwards along with the leaning of the chair back, namely the movement displacement of the waist of the chair is fixed and cannot be changed, and the chair cannot adjust the required supporting force of the waist of the person according to different conditions of the person, such as tired conditions, favors of each person and different heights of each person.

Disclosure of Invention

In order to solve the technical problems, the invention provides the chair, the supporting force of the backrest on the waist of a human body can be adjusted according to the needs of the human body, and the degree of the bulge of the backrest can also follow the change along with the tilting angle of the chair back, so that the back and the waist of the human body are always in a supported state, and the human body is always in a comfortable state.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

a chair comprises a supporting part, a seat part, a backrest seat and a backrest, wherein the seat part and the backrest seat are arranged on the supporting part, the backrest is arranged on the backrest seat, and the backrest is provided with a backrest part; the upper part of the backrest is hinged with the upper part of the backrest seat, and the lower part of the backrest is in sliding connection with the backrest seat through a sliding component and realizes multi-gear sliding stop.

Preferably, the sliding component comprises a first connecting block, a second connecting block, a sliding block, a first limiting block and a second limiting block, wherein the first connecting block is fixedly connected with the backrest or integrally formed, the first limiting block is fixedly connected with the lower part of the backrest seat or integrally formed, the second connecting block is fixedly connected with the first limiting block, the sliding block is hinged with the first connecting block and slides on the first limiting block, a serrated gear part is arranged on the first limiting block, a first limiting part is arranged at the front edge of the gear part, a first buckle is arranged on the sliding block, the front end of the second limiting block is hinged with the sliding block, and the rear end of the second limiting block moves up and down and can be positioned on the sliding block or the first limiting block: when the rear end of the second limiting block falls down to be engaged with the gear part on the first limiting block for limiting, the sliding block and the backrest are limited to move backwards; when the sliding block moves forwards to the front edge of the gear part, the rear end of the second limiting block is jacked up by the first limiting part on the first limiting block, and the rear end of the second limiting block is positioned by the first buckle on the sliding block; when the sliding block moves backwards to a proper position, the rear end of the second limiting block is positioned and released with the first buckle on the sliding block, and the rear end of the second limiting block falls down.

More preferably, the first buckle for positioning the second limiting block on the sliding block is arranged on the extension arm at the rear part of the sliding block, and the first buckle is in buckle fit with the rear end face of the second limiting block.

More preferably, the sliding block is provided with a first hinge hole, a second hinge hole and a sliding part, a plurality of first mounting holes are formed in two sides of the upper surface of the first limiting block, two sliding grooves are formed in the inner side of each first mounting hole, the inner sides of the two sliding grooves are provided with saw-toothed gear parts, the sliding block is hinged to the first connecting block through a rotating shaft penetrating through the first hinge hole, the sliding block is hinged to the second limiting block through a rotating shaft penetrating through the second hinge hole, the sliding block is in sliding fit with the sliding grooves in the first limiting block through the sliding part, and the second connecting block is fixedly connected with the first limiting block through a fastening piece and the first mounting hole.

More preferably, the sliding block is provided with a second limiting part for limiting the second limiting block to turn upwards.

More preferably, the second limiting block is provided with a first limiting hole, a second buckle and a third buckle, the first limiting hole is matched with the second limiting part, the second buckle is matched with the first buckle to enable the second limiting block to be positioned on the sliding block, and the third buckle can be meshed with the serrated gear part to enable the second limiting block to be fixed on the first limiting block.

More preferably, a third limiting part is arranged on the second connecting block, and the third limiting part can enable the rear end of the second limiting block to overturn downwards so as to be separated from the positioning of the first buckle.

More preferably, the upper portion of the backrest seat is provided with two fourth buckles, the fourth buckles are located at the left side and the right side of the upper portion of the backrest seat, the upper portion of the backrest is provided with two fifth buckles, the fifth buckles are located at the left side and the right side of the upper portion of the backrest, and the fifth buckles and the fourth buckles are buckled to achieve hinge connection of the upper portion of the backrest and the upper portion of the backrest seat.

Preferably, the upper surface of the first limiting part is an arc surface, and the lower surface of the sliding block is an arc surface corresponding to the upper surface of the first limiting part.

Preferably, the support part is provided with a second mounting hole, the backrest seat is hinged with the support part through the second mounting hole, and the support part is fixedly connected with the chair footing through the support air rod.

Preferably, the headrest is further provided with a headrest, the headrest is fixed on the backrest through a connecting assembly, the connecting assembly comprises a third connecting block and a connecting plate, the connecting plate is hinged with the headrest, the connecting plate penetrates through the third connecting block and is fixed on the third connecting block, the third connecting block is fixedly connected to the backrest, and the lower portion of the connecting plate can be propped against the backrest seat along with the rotation of the backrest.

By adopting the technical scheme, the upper part of the backrest seat is hinged with the upper part of the backrest seat, and the lower part of the backrest seat is connected with the backrest seat in a sliding way, so that the backrest has independence relative to the backrest seat, namely, the backrest can be adjusted according to the self requirements of a human body no matter the chair is in a vertical state or in a backward tilting state, namely, the backrest is adjusted to a position which is comfortable for the human body, and meanwhile, the whole structure is simple and the cost is low.

Drawings

FIG. 1 is a schematic view of the chair according to the present invention;

FIG. 2 is an exploded view of the chair of the present invention;

FIG. 3 is a schematic view of the first stopper of the chair according to the present invention;

FIG. 4 is a schematic view of a second stopper of the chair according to the present invention;

FIG. 5 is a schematic view of the structure of the chair slider of the present invention;

FIG. 6 is a schematic view of the structure of the second connection block of the chair of the present invention;

FIG. 7 is a schematic diagram of a slide assembly shift of the present invention;

FIG. 8 is a second schematic illustration of a shift of the slide assembly of the present invention;

FIG. 9 is a third schematic illustration of a shift of the slide assembly of the present invention;

FIG. 10 is a fourth schematic illustration of a shift of the slide assembly of the present invention;

FIG. 11 is a schematic view of the structure of the chair support of the present invention;

FIG. 12 is a schematic illustration of an embodiment of a chair according to the present invention;

figure 13 is a schematic representation of a chair embodiment of the present invention.

Reference numerals illustrate: 1. a support part; 2. a back rest seat; 3. a backrest seat; 4. a seat; 5. a headrest; 11. a second mounting hole; 12. a second limiting slot; 13. the second hinge seat; 6. a connection assembly; 61. a third connecting block; 62. a connecting plate; 21. a fourth buckle; 75. a first limiting block; 751. a first mounting hole; 752. a chute; 753. a gear position section; 754. a first limit part; 23. a first hinge base; 7. a sliding assembly; 71. a first connection block; 72. a second connection block; 73. a slide block; 74. a second limiting block; 31. a fifth buckle; 731. a first hinge hole; 732. a second hinge hole; 733. a first buckle; 734. a second limit part; 735. a sliding part; 741. a first limiting hole; 742. a second buckle; 743. a third buckle; 721. and a third limit part.

Detailed Description

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "inner", "outer", "vertical", "horizontal", "top", "bottom", "inner", "clockwise", "counterclockwise", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more, unless otherwise clearly defined.

In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present invention, unless expressly stated or limited otherwise, a first feature "above" or "below" a second feature may include both the first and second features being in direct contact, as well as the first and second features not being in direct contact but being in contact with each other through additional features therebetween. Moreover, a first feature being "above," "over" and "on" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is higher in level than the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly under and obliquely below the second feature, or simply means that the first feature is less level than the second feature.

A chair as shown in fig. 1 and 2, comprising a support part 1, a seat part 4, a backrest seat 2 and a backrest 3, wherein the seat part 4 and the backrest seat 2 are mounted on the support part 1, the backrest 3 is mounted on the backrest seat 2, and the backrest 3 has a backrest part; the multifunctional backrest is characterized in that the upper part of the backrest 3 is hinged with the upper part of the backrest seat 2, and the lower part of the backrest 3 is in sliding connection with the backrest seat 2 through a sliding component 7 and realizes multi-gear sliding stop. Namely, the backrest seat 2 can lean backwards by taking the supporting part 1 as a fulcrum, so that a person can lie on a chair conveniently, the backrest 3 can also rotate by taking the hinging point of the upper part and the backrest seat 2 as a fulcrum, the lower part of the backrest 3 can slide relative to the backrest seat 2, the backrest 3 can slide and stop in multiple gears in the sliding process, and the backrest 3 can conveniently adjust the supporting force of the backrest 3 to the waist of the person according to the self requirement.

The sliding component 7 comprises a first connecting block 71, a second connecting block 72, a sliding block 73, a first limiting block 75 and a second limiting block 74, wherein the first connecting block 71 is fixedly connected with the backrest 3 or integrally formed, the first limiting block 75 is fixedly connected with the lower portion of the backrest seat 2 or integrally formed, the second connecting block 72 is fixedly connected with the first limiting block 75, the sliding block 73 is hinged with the first connecting block 71 and slides on the first limiting block 75, a serrated gear portion 753 is arranged on the first limiting block 75, a first limiting portion 754 is arranged on the front edge of the gear portion 753, a first buckle 733 is arranged on the sliding block 73, the front end of the second limiting block 74 is hinged with the sliding block 73, and the rear end of the second limiting block 74 moves up and down and can be positioned on the sliding block 73 or the first limiting block 75: when the rear end of the second limiting block 74 falls down to engage with the gear portion 753 on the first limiting block 75 for limiting, the slider 73 and the backrest 3 are limited to move backward; when the slider 73 moves forward to the front edge of the gear portion 753, the rear end of the second stopper 74 is pushed up by the first stopper portion 754 on the first stopper 75, and the rear end of the second stopper 74 is positioned by the first buckle 733 on the slider 73; when the slider 73 moves backward to the position, the rear end of the second stopper 74 is released from the first buckle 733 on the slider 73, and the rear end of the second stopper 74 falls down.

Since there are various ways in which the specific embodiments of the chair may be used, the following detailed description will be made with reference to the specific embodiments:

the chair shown in fig. 12 comprises a supporting part 1, a back rest seat 2, a back rest 3, a seat 4 and a head rest 5, wherein the supporting part 1 is movably connected with the bottom end of the back rest seat 2, and the back rest seat 2 can rotate for a preset angle relative to the supporting part 1; the upper part of the backrest seat 2 is hinged with the upper part of the backrest 3, and the lower part of the backrest 3 is connected with the backrest seat 2 in a sliding way; the backrest 3 can be stopped at a plurality of positions in the sliding process, one side of the seat 4 is hinged with the backrest seat 2, and the other side of the seat 4 is hinged with the supporting part 1; the headrest 5 is fixed on the backrest 3 by a connecting assembly 6.

The backrest is in a state of not leaning backwards, and the backrest 3 is in a state of minimum supporting force to the human body, and the backrest 3 can adjust the supporting force to the human body according to the actual requirement of the human body.

The headrest 5 is fixed on the backrest 3 through the connecting component 6, the connecting component 6 comprises a third connecting block 61 and a connecting plate 62, the connecting plate 62 is hinged with the headrest 5, the connecting plate 62 penetrates through the third connecting block 61 and is fixed on the third connecting block 61 through bolts and nuts, the third connecting block 61 is fixedly connected on the backrest 3 through bolts and nuts, and the lower part of the connecting plate 62 can prop against the backrest seat 2 along with the rotation of the backrest 3.

The support part 1 shown in fig. 11 is provided with a second mounting hole 11 and a second limiting long hole 12, the backrest seat 2 is mounted on the second mounting hole 11 and the second limiting long hole 12 through a positioning pin, the backrest seat 2 rotates around the second mounting hole 11 as a circle center, the rotation angle of the backrest seat 2 is limited by the second limiting long hole 12, the limiting long hole is an arc long hole, and the positioning pin is positioned at the leftmost end of the arc long hole because the backrest is in a state of not leaning backwards.

The right upper part of the supporting part 1 is also provided with a second hinging seat 13, and the second hinging seat 13 is used for hinging with the seat 4.

The supporting plate supporting part 1 is fixedly connected with the chair footing through a supporting air rod.

The upper portion of the backrest seat 2 is provided with two fourth buckles 21, the fourth buckles 21 are located on the left side and the right side of the upper portion of the backrest seat 2, the upper portion of the backrest 3 is provided with two fifth buckles 31, the fifth buckles 31 are located on the left side and the right side of the upper portion of the backrest 3, the fifth buckles 31 and the fourth buckles 21 are buckled to enable the upper portion of the backrest 3 to be hinged to the upper portion of the backrest seat 2, the lower portion of the backrest seat 2 is further provided with a first hinge seat 23, and the first hinge seat 23 is used for being hinged to the seat 4.

It is particularly noted that the upper surface of the first limiting block 75 needs to have a certain radian, or the fifth buckle 31 can move a certain distance relative to the fourth buckle 21, so that the lower portion of the backrest 3 can slide smoothly relative to the backrest seat 2, and in this embodiment, the upper surface of the first limiting block 75 preferably has a certain radian.

As shown in fig. 3, a plurality of first mounting holes 751 are formed on two sides of the upper surface of the first limiting block 75, two sliding grooves 752 are formed on the inner sides of the first mounting holes 751, and the serrated gear parts 753 are formed on the inner sides of the two sliding grooves 752.

The slider 73 shown in fig. 5 is provided with a first hinge hole 731, a second hinge hole 732, a sliding portion 735, a second limiting portion 734 and a first buckle 733, the slider 73 is hinged to the first connecting block 71 through a rotation shaft passing through the first hinge hole 731, the slider 73 is hinged to the second limiting block 74 through a rotation shaft passing through the second hinge hole 732, the slider 73 is in sliding fit with a sliding groove 752 on the first limiting block 75 through the sliding portion 735, the second connecting block 72 is fixedly connected with the first limiting block 75 through a fastener and a first mounting hole 751, the second limiting portion 734 is used for limiting the second limiting block 74 to turn upwards, and the first buckle 733 is arranged on an extension arm at the rear portion of the slider 73.

It is particularly noted that, because the upper portion of the backrest 3 is hinged to the upper portion of the backrest seat 2, in order to enable the slider to slide smoothly on the first limiting portion, the upper surface of the first limiting portion 75 is an arc surface, and the lower surface of the slider 73 is an arc surface corresponding to the upper surface of the first limiting portion 75.

The second limiting block 74 shown in fig. 4 is provided with a first limiting hole 741, a second buckle 742 and a third buckle 743, the first limiting hole 741 is matched with the second limiting portion 734, the second buckle 742 is matched with the first buckle 733 to fix the second limiting block 74 on the sliding block 73, and the third buckle 743 is engaged with the serrated gear portion 753 to fix the second limiting block 74 on the first limiting block 75.

The second connecting block 72 shown in fig. 6 is provided with a third limiting portion 721, and the third limiting portion 721 can enable the second limiting block 74 to flip down to be separated from the slider 73.

As shown in fig. 7, at this time, the backrest 3 is in a state of minimum supporting force to the human body, at this time, the third buckle 743 is engaged with the leftmost gear portion 753, and in this embodiment, five layers of gear portions 753 are preferable, of course, the number of gear portions 753 may be increased or decreased appropriately, that is, the pitch of the serrated gear portion 753 is decreased in an increasing manner, and in order to ensure that the second stopper 74 can be firmly engaged with the gear portion 753, the tooth height of the gear portion 753 should be increased appropriately, that is, the pitch of the serrated gear portion 753 is increased in a decreasing manner.

The external gear shifting mode of the embodiment is as follows: when a human body is completely attached to the backrest 3, the whole backrest 3 is provided with a pressure, so that the gear shifting function of the chair is limited, the gear shifting can be performed only when the human body cannot be completely attached to the backrest 3, at the moment, the gear shifting can be performed only by applying proper pressure to the headrest 5, the gear shifting mode can be that the human body presses the headrest 5 by standing by hands, the gear shifting can be performed also when the human body is in a lying state, the waist is lifted, and the gear shifting can be performed by applying pressure to the headrest 5 by using the head or the shoulders.

The specific gear shifting process of the sliding assembly 7 in this embodiment is as follows: the lower part of the backrest 3 slides outwards to drive the first connecting block 71 to slide outwards, the first connecting block 71 drives the sliding block 73 to move outwards due to the fact that the first connecting block 71 is hinged with the sliding block 73 through the first rotating shaft and the first hinging hole 731, the sliding part 735 slides in the sliding groove 752 to limit the moving track of the sliding block 73, the sliding block 73 drives the second limiting block 74 to move outwards due to the fact that the sliding block 73 is hinged with the second limiting block 74 through the second rotating shaft and the second hinging hole 732, and in the moving process, the third clamping buckle 743 on the second limiting block 74 is continuously meshed with different parts of the serrated gear part 753 due to the action of self gravity, namely gear conversion is carried out.

And when the pressure is stopped to be applied to the headrest 5 or the pressure is stopped to be applied to the lower part of the backrest 3, the gear shifting can be completed, and the gear shifting is convenient and quick.

When the maximum gear position shown in fig. 8 is reached, the backrest 3 is in a state of maximum supporting force to the human body, and at this time, the third fastener 743 on the second stopper 74 is engaged with the rightmost gear position portion 753.

When pressure is continuously applied to the headrest 5, the second limiting block 74 still moves towards and contacts with the first limiting part 754, and smooth transition is achieved between the first limiting part 754 and the gear part 753, so that the second limiting block 74 can move obliquely upwards along the first limiting part 754 smoothly until the backrest 3 rotates, the connecting plate 62 abuts against the backrest seat 2, the backrest 3 cannot rotate any more, and a neutral state as shown in fig. 9 is achieved, at this time, the second buckle 742 on the second limiting block 74 is buckled with the first buckle 733 on the sliding block 73, so that the second limiting block 74 is fixed on the sliding block 73, and the second limiting part 734 is matched with the first limiting part 754 to limit the second limiting block 74 to overturn upwards.

Applying pressure to the lower part of the backrest 3 or pulling the headrest 5 to enable the backrest 3 to slide leftwards, at the moment, the second limiting block 74 is fixed on the sliding block 73 and cannot contact with the first limiting block 75, when the sliding block 73 continues to slide leftwards, the second limiting block 74 is driven to contact with the third limiting block 721 on the second connecting block 72, the contact area of the third limiting block 721 and the second limiting block 74 is an arc surface, at the moment, the third limiting block 721 can start to apply downward overturning force to the second limiting block 74, and as the sliding block 73 continues to slide inwards, the leftmost end is reached, namely the state of fig. 10 is reached, at the moment, the downward overturning force applied by the third limiting block 721 to the second limiting block 74 is maximum, so that the second limiting block 74 is separated from the sliding block 73 and overturns downwards, and the minimum gear position shown in fig. 7 is reached, and one cycle is completed.

As shown in fig. 13, the backrest 3 is in a reclined state, and the backrest 3 is in a state of having the greatest supporting force to the human body, that is, the third fastener 743 on the second limiting block 74 is engaged with the outermost gear portion 753, and of course, the backrest 3 can also adjust the supporting force to the human body according to the actual requirement of the human body, that is, the third fastener 743 is engaged with the gear portion 753 of other parts.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives, and variations may be made in the above embodiments by those skilled in the art without departing from the spirit and principles of the invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A chair comprises a supporting part (1), a seat part (4), a backrest seat (2) and a backrest (3), wherein the seat part (4) and the backrest seat (2) are arranged on the supporting part (1), the backrest (3) is arranged on the backrest seat (2), and the backrest (3) is provided with a lumbar rest part; the multifunctional backrest is characterized in that the upper part of the backrest (3) is hinged with the upper part of the backrest seat (2), and the lower part of the backrest (3) is in sliding connection with the backrest seat (2) through a sliding component (7) and realizes multi-gear sliding stop;

the sliding component (7) comprises a first connecting block (71), a second connecting block (72), a sliding block (73), a first limiting block (75) and a second limiting block (74), wherein the first connecting block (71) is fixedly connected with the backrest (3) or integrally formed, the first limiting block (75) is fixedly connected with the lower part of the backrest seat (2) or integrally formed, the second connecting block (72) is fixedly connected with the first limiting block (75), the sliding block (73) is hinged with the first connecting block (71) and slides on the first limiting block (75), a serrated gear part (753) is arranged on the first limiting block (75), a first limiting part (754) is arranged at the front edge of the gear part (753), a first buckle (733) is arranged on the sliding block (73), the front end of the second limiting block (74) is hinged with the sliding block (73), and the rear end of the second limiting block (74) moves up and down and can be positioned on the sliding block (73) or the first limiting block (75). When the rear end of the second limiting block (74) falls down to be engaged with the gear part (753) on the first limiting block (75) for limiting, the sliding block (73) and the backrest (3) are limited to move backwards; when the sliding block (73) moves forwards to the front edge of the gear part (753), the rear end of the second limiting block (74) is jacked by the first limiting part (754) on the first limiting block (75), and the rear end of the second limiting block (74) is positioned by the first buckle (733) on the sliding block (73); when the sliding block (73) moves backwards to a proper position, the rear end of the second limiting block (74) is positioned and released with the first buckle (733) on the sliding block (73), and the rear end of the second limiting block (74) falls down;

the supporting part (1) is fixedly connected with the chair bottom foot through a supporting air rod.

2. A chair according to claim 1, characterized in that a first catch (733) for positioning the second stopper (74) on the slider (73) is provided on the extension arm at the rear of the slider (73), the first catch (733) being in catch engagement with the rear end face of the second stopper (74).

3. The chair according to claim 1, wherein the sliding block (73) is provided with a first hinge hole (731), a second hinge hole (732) and a sliding part (735), two sides of the upper surface of the first limiting block (75) are provided with a plurality of first mounting holes (751), two sliding grooves (752) are formed in the inner sides of the first mounting holes (751), the toothed gear part (753) is formed in the inner sides of the two sliding grooves (752), the sliding block (73) is hinged with the first connecting block (71) through a rotating shaft penetrating through the first hinge hole (731), the sliding block (73) is hinged with the second limiting block (74) through a rotating shaft penetrating through the second hinge hole (732), the sliding block (73) is in sliding fit with the sliding grooves (752) in the first limiting block (75), and the second connecting block (72) is fixedly connected with the first limiting block (75) through a fastener and the first mounting hole (751).

4. A chair according to claim 1, wherein the slider (73) is provided with a second limiting portion (734) for limiting the upward turning of the second limiting block (74).

5. The chair according to claim 4, wherein the second limiting block (74) is provided with a first limiting hole (741), a second buckle (742) and a third buckle (743), the first limiting hole (741) is matched with the second limiting portion (734), the second buckle (742) is matched with the first buckle (733) so that the second limiting block (74) is positioned on the sliding block (73), and the third buckle (743) can be meshed with the serrated gear portion (753) so that the second limiting block (74) is fixed on the first limiting block (75).

6. A chair according to claim 1, wherein the second connecting block (72) is provided with a third limiting part (721), and the third limiting part (721) can enable the rear end of the second limiting block (74) to turn downwards to be separated from the positioning of the first buckle (733).

7. A chair according to claim 1, wherein the upper part of the backrest seat (2) is provided with two fourth buckles (21), the fourth buckles (21) are positioned on the left and right sides of the upper part of the backrest seat (2), the upper part of the backrest (3) is provided with two fifth buckles (31), the fifth buckles (31) are positioned on the left and right sides of the upper part of the backrest (3), and the fifth buckles (31) and the fourth buckles (21) are buckled so as to realize the hinging of the upper part of the backrest (3) and the upper part of the backrest seat (2).

8. The chair according to claim 1, wherein the upper surface of the first limiting portion (754) is an arc surface, and the lower surface of the slider (73) is an arc surface corresponding to the upper surface of the first limiting portion (754).

9. A chair according to claim 1, further comprising a headrest (5), wherein the headrest (5) is fixed to the backrest (3) by a connecting assembly (6), the connecting assembly (6) comprises a third connecting block (61) and a connecting plate (62), the connecting plate (62) is hinged to the headrest (5), the connecting plate (62) passes through the third connecting block (61) and is fixed to the third connecting block (61), the third connecting block (61) is fixedly connected to the backrest (3), and the lower portion of the connecting plate (62) can abut against the backrest seat (2) along with the rotation of the backrest (3).