Patent Abstract:
The present invention discloses a chair, comprising a seat, a backrest and a chair base, wherein the backrest and the chair base are connected through a first connector that comprises a base holder rigidly connected to the chair base, a back holder secured to the backrest, a rotation holder, a first linkage bar, a second linkage bar and a third linkage bar. The present technical solution solves the problem caused in using a traditional chair which is pulling up of a user&#39;s clothes when the backrest of the chair is inclined backward. The present design of a linkage movement not only makes a user feel more comfortable, but also is more user-friendly, thereby avoiding the damage of the user&#39;s clothes.

Full Description:
CROSS REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    The present application claims the priority of Chinese patent application No. 201110033706.4 filed on Jan. 30, 2011, which application is incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to furniture, particularly to a chair. 
       BACKGROUND OF THE INVENTION 
       [0003]    As people&#39;s living standards improve, their demands for high quality life increase more and more. The traditional wooden or bamboo chairs are gradually replaced by those with elegant style and multifunctionality. Modern chairs are designed more and more user-friendly, which is to meet consumers&#39; needs for comfort and convenience. One of the modern chairs backrest tilt angle is adjustable which allows people to sit more comfortably by changing the angle between the seat and the backrest. However, during a backrest inclined backward, the turning center and turning radius of the backrest are different from those of the body, therefore a user&#39;s clothes is pulled up by the friction between the backrest and the user, which results in unpretty wrinkles or even damages of the clothes, or results in exposures of the user&#39;s waist which causes embarrassment on some occasions. Thus the purpose of the present invention is to provide a rotary chair which avoids the pulling up of a user&#39;s clothes when the backrest is inclined backward. 
       SUMMARY OF THE INVENTION 
       [0004]    The purpose of the present invention is to provide a chair, which solves the technical problem mentioned above through a linkage movement of the seat and the backrest. 
         [0005]    To achieve this objective, the present invention applies the following technical solution: 
         [0006]    A chair, comprising a seat, a backrest and a chair base, wherein the backrest and the chair base are connected through a first connector that comprises a base holder rigidly connected to the chair base, a back holder secured to the backrest, a rotation holder, a first linkage bar, a second linkage bar and a third linkage bar, wherein the rotation holder is pivotally connected to the base holder; the back holder is non-rigidly connected to the rotation holder through a linear sliding connection; one end of the first linkage bar is pivotally connected to the back holder, the other end of the first linkage bar is pivotally connected to the third linkage bar; one end of the second linkage bar is pivotally connected to the rotation holder, the other end of the second linkage bar is pivotally connected to the third linkage bar; an end of the third linkage bar is pivotally connected to the base holder, as a result, when the end herein is considered a near end, the pivot point of the first linkage bar and the third linkage bar is located at a far end of the third linkage bar and the pivot point of the second linkage bar and the third linkage bar is located in the middle of the third linkage bar; and a reposition mechanism utilized to move the backrest forward towards its original position during the backrest inclined backward and a position mechanism utilized to position the backrest at a tilt angle are installed on the chair base. 
         [0007]    In a preferred embodiment of the present invention, a guide rail is provided on the rotation holder, a sliding block is provided on the guide rail, and the sliding block is rigidly connected to the back holder. 
         [0008]    The seat is mounted on the chair base. But in a preferred embodiment of the present invention, the seat and the chair base are connected through a second connector that comprises a base support fixed to the chair base, a back support fixed to the backrest and a seat support secured to the seat, wherein the lower end of the back support is pivotally connected to the back end of the base support; the higher end of the back support is pivotally connected to the back end of the seat support; the front end of the seat support is pivotally connected to the higher end of the connecting plate; and the lower end of the connecting plate is pivotally connected to the front end of the base support. Thus the base support, the back support, the seat support and the connecting plate comprise a four-bar linkage. 
         [0009]    In a preferred embodiment of the present invention, the reposition mechanism includes a extension spring; one end of the extension spring is connected to the base support; a fixed lever is provided between the pivot point of the back support and the seat support and the pivot point of the back support and the base support; the other end of the extension spring is connected to the fixed lever; and the fixed lever penetrates the base support through a guide hole or a guide slot inside which the fixed lever is movable. Further in the preferred embodiment, a rotatable tensioning bolt is provided inside the base support; the tensioning bolt is screwed into the threads at an end of the extension spring; a rotatable adjusting lever is provided on the base support; and the adjusting lever is coupled to the cross shaft of the tensioning bolt. 
         [0010]    In a preferred embodiment of the present invention, the position mechanism comprises a finger clamp is on a fixed lever, a clamp tooth provided at the front end of the finger clamp, and a plurality of clamp slots fit to the clamp tooth respectively provided on the base support. Further in the preferred embodiment, a finger clamp control mechanism utilized to restrict the rotation of the finger clamp is provided on the base support or the back support. 
         [0011]    The back support of the second connector is pivotally connected to the rotation holder of the first connector. Otherwise, the back support of the second connector is non-rigidly connected to the backrest through a guide sliding slot and a sliding wheel. 
         [0012]    The above technical solution of the present invention solves the problem caused in using a traditional chair which is pulling up of a user&#39;s clothes when the backrest of the chair is inclined backward. The present design of the linkage movement not only makes a user feel more comfortable, but also is more user-friendly, thereby avoiding the damage of the user&#39;s clothes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a structure diagram of a chair in accordance with the present invention. 
           [0014]      FIG. 2  is a structure diagram of a chair in accordance with embodiment 1 of the present invention. 
           [0015]      FIG. 3  is a structure diagram of a first connector in accordance with embodiment 1 of the present invention. 
           [0016]      FIG. 4  is a structure diagram of a second connector in accordance with embodiment 2 of the present invention 
           [0017]      FIG. 5  is a top view of  FIG. 4 . 
           [0018]      FIG. 6  is a structure diagram of a finger clamp inside a second connector. 
           [0019]      FIG. 7  is a structure diagram of a chair in accordance with embodiment 3 of the present invention (backrest in original position). 
           [0020]      FIG. 8  is a structure diagram of a chair in accordance with embodiment 3 of the present invention (backrest inclined). 
           [0021]      FIG. 9  is a structure diagram of a chair in accordance with embodiment 4 of the present invention (backrest in original position). 
           [0022]      FIG. 10  is a structure diagram of a chair in accordance with embodiment 4 of the present invention (backrest inclined). 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Detailed Illustrations of preferred embodiments of the present invention are provided in the following. 
       Embodiment 1 
       [0024]    A chair as shown in  FIGS. 1 and 2 , comprising a seat  1 , a backrest  2  and a chair base, wherein the seat  1  and the backrest  2  are connected through a first connector  5 ; a wedge-shaped insert member is provided on the backrest  2 ; a wedge-shaped case member  4  fit to the insert member  3  is provided on the first connector  5 ; and the wedge-shaped insert member is inserted into the wedge-shaped case member. In this embodiment, one wedge-shaped insert member  3  is provided on each side of the backrest  2 , and each wedge-shaped insert member  3  is inserted into a case member  4  of the first connector  5  on each side of the seat  1  respectively. The connection of the backrest and the connector through a wedge-shaped inserting set offers advantages such as accurate positioning, secure fitting, easy assembly or disassembly, easy adjustment, etc. 
         [0025]    As shown in  FIGS. 2 and 3 , the first connector  5  comprises a base holder  58 , a back holder  52 , a rotation holder  54 , a first linkage bar  55 , a second linkage bar  56  and a third linkage bar  57 . In this embodiment, the base holder  58  is a part of the chair base and it is rigidly connected to the seat  1 ; the wedge-shaped case member  4  is provided on the back holder  52 ; the wedge-shaped insert members  3  on both sides of the backrest  2  are inserted into the case members  4 , thereby fixing the backrest  2  to the back holder  52 ; the rotation holder  54  is pivotally connected to the base holder  58 ; a guide rail  53  is provided on the rotation holder  54 ; a sliding block  51  is provided on the guide rail  53 ; the sliding block  51  is rigidly connected to the back holder  52 , thereby allowing the back holder  52  sliding linearly relative to the rotation holder  54  (Herein exists a plurality of specific structures of the sliding connector, such as a structure with said guide rail and said sliding block in reverse order, a structure employing a sliding slot and a sliding block, or even a structure employing a linear bearing or a linear shaft, whereof the sliding direction is parallel to radial direction of the rotation axis of the rotation holder). One end of the first linkage bar  55  is pivotally connected to the back holder  52 , and the other end of the first linkage bar  55  is pivotally connected to the third linkage bar  57 ; one end of the second linkage bar  56  is pivotally connected to the rotation holder  54 , and the other end of the second linkage bar  56  is pivotally connected to the third linkage bar  57 ; an end of the third linkage bar  57  is pivotally connected to the base holder  58 , as a result, when the end herein is considered a near end, the pivot point of the first linkage bar  55  and the third linkage bar  57  is located at a far end of the third linkage bar  57  and the pivot point of the second linkage bar  56  and the third linkage bar  57  is located in the middle of the third linkage bar  57 . Three linkage bars are provided in between the base holder  58 , the back holder  52  and the rotation holder  54  to comprise a linkage structure, wherein the base holder  58  is served as a reference for the rotation of the backrest, and the rotation holder  54  is utilized to achieve the rotation of the backrest. In the rotation process of the rotation holder  54 , the second linkage bar  56  actuates the third linkage bar  57  to rotate around the pivot point of the base holder  58  and the third linkage bar  57 , subsequently the rotation of the third linkage bar  57  actuates the movement of the first linkage bar  55 , and the displacement of the first linkage bar  55  actuates the slide of the pivotally connected back holder  52 , thereby achieving a linkage movement of the back holder  52  and the rotation holder  54 . The purpose of employing the linkage mechanism is to eliminate or reduce as much as possible the distance between the seat&#39;s inside edge (facing the caudal vertebrae of the body) and the backrest&#39;s bottom edge (facing the lumbar vertebrae of the body) while the backrest is inclined backward, and therefore avoids a user&#39;s discomfort. The specific size of each part included in the above linkage structure can be obtained through limited tests according to the actual needs by the technical stuff from the related field, and creative work is not necessary. 
         [0026]    The above structure achieves a linkage rotation and a linkage slide of the backrest, but as a chair whose backrest can be inclined backward, a reposition mechanism is also required to provide a force to always pull the backrest back to its original position when it is inclined backward. Such a mechanism may comprise an air spring (or an extension spring). One end of the air spring is non-rigidly connected to the seat (or the chair base), and the other end of the air spring is non-rigidly connected to the backrest (or the back holder  54 ). 
         [0027]    As a preferred embodiment of the present invention, a position mechanism is also required to position the backrest at a tilt angle when it is inclined backward. Such a position mechanism may comprise a rotary table with multiple positioning holes and a positioning spring pin. The rotary table is fixed on the pivot axis of the base holder  58  and the rotation holder  54  of the first connector  5  and provided to rotate synchronically with the rotation holder  54 , and the spring pin is provided on the seat or the base holder  58 . A gear positioning mechanism can be achieved by inserting the spring pin into one of the positioning holes. Similarly, the rotary table may be integrated to the rotation holder  54 . Furthermore, the pin-hole mechanism may be replaced by a ratchet pawl mechanism. 
       Embodiment 2 
       [0028]    A chair, comprising a seat, a backrest and a chair base, wherein the seat and the backrest are connected through a second connector as shown in  FIGS. 4 and 5 , which comprises a base support  62  fixed to the chair base, a back support  69  fixed to the backrest and a seat support  63  secured to the seat, wherein the lower end of the back support  69  is pivotally connected to the back end of the base support  62 , the higher end of the back support  69  is pivotally connected to the back end of the seat support  63 , the front end of the seat support  63  is pivotally connected to the higher end of a connecting plate  61 , and the lower end of the connecting plate  61  is pivotally connected to the front end of the base support  62 , therefore the base support  62 , the back support  69 , the seat support  63  and the connecting plate  61  comprise a four-bar linkage. When the backrest is inclined backward, the backrest actuates the back support  69  to rotate clockwise, subsequently the back support  69  actuates the seat support  63  along with the seat to move backward, thereby achieving a linkage movement of the backrest and the seat. As described in embodiment 1, the purpose of employing a linkage mechanism is to eliminate or reduce as much as possible the distance between the seat&#39;s inside edge (facing the caudal vertebrae of the body) and the backrest&#39;s bottom edge (facing the lumbar vertebrae of the body) while the backrest is inclined backward, and therefore avoids a user&#39;s discomfort. The specific size of each part included in the above linkage structure can be obtained through limited tests according to the actual needs by the technical stuff from the related field, and creative work is not necessary. 
         [0029]    The above structure achieves a linkage movement that the backrest&#39;s rotation actuates the seat&#39;s slide, but as a chair whose backrest can be inclined backward, a reposition mechanism is also required to provide a force to always pull the backrest back to its original position when it is inclined backward. In this embodiment, an extension spring  66  (may be an air spring or one or more parts that provides elasticity) is disposed to provide the reset force. One end of the extension spring  66  is connected to base support  62 , and the other end of the extension spring  66  is connected to the back support  69 . To ensure that the extension spring works effectively, preferably the connection point of the extension spring  66  and the back support  69  is placed between the two pivot points through which the back support  69  is connected to the seat support  63  and the base support  62  respectively. To limit the movement range of the four-bar linkage, a fixed lever  67  is provided inside the back support  69 . The fixed lever  67  penetrates the base support  62  through a guide hole (or a guide slot)  68  inside which the fixed lever  67  is movable, thus during the movement of the four-bar linkage, the guide hole (or the guide slot)  68  can limit the movement range of the back support  69  by limiting the movement range of the fixed lever  67 . To eliminate or decrease the collision probability and friction between the fixed lever  67  and the guide hole (or the guide slot)  68 , preferably a wear resistance sleeve or a rubber sleeve is provided inside the guide hole (or the guide slot)  68 , furthermore preferably shafts are provided at both ends of the fixed lever  67  to aid moving smoothly. To ease assembly and adjustment, the fixed lever  67  inside the back support  69  is connected to one end of the extension spring  66 ; a panel is provided inside the base support  62 ; a rotatable tensioning bolt  65  is provided on the panel; the tensioning bolt  65  is screwed into the other end of the extension spring  66 ; a rotatable adjusting lever  64  is provided on the base support  62 ; and the adjusting lever  64  is coupled to the cross shaft of the tensioning bolt  65 . Thus the rotation of the adjusting lever  64  will actuate the rotation of the tensioning bolt  65 , and further actuate the extension spring  66  connected to the tensioning bolt  65  to stretch or compress, thereby achieving the purpose of adjusting the force to reset the backrest. 
         [0030]    As a preferred embodiment of the present invention, a position mechanism is also required to position the backrest at a tilt angle when it is inclined backward. As shown in  FIG. 6 , such a position mechanism comprises a finger clamp  612  on the fixed lever  67 , a clamp tooth  615  provided at the front end of the finger clamp  612 , and a clamp slot base  616  provided on the base support  62 , wherein a plurality of clamp slots  617  fit to the clamp tooth  615  respectively are provided on the clamp slot base  616 . When the clamp tooth  615  on the finger clamp  612  fits into the clamp slot  617 , the movement of the fixed lever  67  is restricted and then the rotation of the back support  69  as well as the backrest is restricted, thereby achieving the purpose of positioning. The fixed lever  67  may float through the finger clamp  612  and preferably shafts are provided between the two. In this case, the fixed lever is static when the finger clamp rotates. In another case, the finger clamp  612  is tightened onto the fixed lever  67  and preferably shafts are provided between the fixed lever and the extension spring as well as the guide hole on the base support. Thus the fixed lever will rotate synchronically with the finger clamp. To ensure that the clamp tooth  615  fits into the clamp slot  617  firmly, preferably a finger clamp control mechanism utilized to restrict the rotation of the finger clamp  612  is provided on the base support  62  or (and) the back support  69 . Such a control mechanism may have different structures. In one case, a finger press member  611  utilized to restrict the rotation of the finger clamp  612  is placed above the finger clamp, and the finger press member  611  contacts the finger clamp  612  through a flat spring  614 ; a rotatable adjusting lever  618  is provided on the base support  62 ; and the finger press member  611  is fixed on the adjusting lever  618 . Thus with the aid of a position pin or a positioning stud a gear change mechanism is achieved by rotating the fixed lever  618  to press or release the finger clamp  612 . Correspondingly, an elastic reposition mechanism utilized to rotate the finger clamp  612  upward back to its original position is required to be provided on the finger clamp  612 . Such an elastic reposition mechanism may also have different structures. Preferably a torsion spring  613  is provided on the fixed lever  67 . One end of the torsion spring  613  is connected to the bottom of the finger clamp  612 , and the other end of the torsion spring  613  is connected to a pivot shaft  610  of the back support  69  and the base support  62 . In another case of the finger clamp control mechanism, an elastic mechanism is employed to always force the finger clamp  612  to rotate downward, thereby ensuring the clamp tooth  615  and the clamp slot  617  remain in fit position. Such an elastic mechanism may be achieved by reversing the above torsion spring. Thus one end of the torsion spring is connected to the top of the finger clamp  612 , and the other end of the torsion spring is connected to the pivot shaft  610 . Correspondingly, a rotatable control lever is provided on the base support  62  located in front of the finger clamp&#39;s  612  clamp tooth, and a toggle is fixed on the control lever, thereby allowing the back support  69  to rotate by rotating the control lever which pushes up the finger clamp  612  to separate the clamp tooth and the clamp slot. 
         [0031]    In both above embodiments, the movement range of the seat or the backrest is limited by their mechanisms, thus the range of the tilt angle is limited too. In the following two embodiments, a first connector and a second connector are used together, thus the range of the tilt angle is extended while the movement range of the seat or the backrest is maintained. To eliminate or reduce as much as possible the distance between the seat&#39;s inside edge (facing the caudal vertebrae of the body) and the backrest&#39;s bottom edge (facing the lumbar vertebrae of the body) during the backrest inclined backward, let the backrest and the seat move at the same time. Thus the movement range of the backrest or the seat is about half of that of the backrest or the seat moving individually while the range of the tilt angle is maintained. Of cause, the specific size of each part included in the linkage structures of the first and second connectors need adjusting to meet the actual requirements, which can be achieved by the technical stuff from the related field through limited tests according to the actual needs without creative work. 
       Embodiment 3 
       [0032]    A chair as shown in  FIGS. 7 and 8 , comprising a seat  1 , a backrest  2 , a chair base, a first connector descried in embodiment 1 and a second connector descried in embodiment 2, wherein both the base holder of the first connector and the base support  62  of the second connector are rigidly connected to the chair base; the seat  1  is rigidly connected to the seat support  63  of the second connector; the backrest  2  is rigidly connected to the back holder of the first connector; and the back support  69  of the second connector is pivotally connected to the rotation holder  54  of the first connector through a extension bar  7 . Please refer to embodiment 1 for the structure of the first connector and refer to embodiment 2 for the structure of the second connector. The position mechanism and reposition mechanism are described in embodiment 2 and not repeated herein. 
         [0033]      FIG. 7  shows the chair when the backrest  2  is in the original position. When a user tilts the backrest  2  backward, the backrest  2  rotates clockwise; the back support  69  of the second connector rotates downward; the seat support  63  actuates the seat  1  to move backward; and the rotation holder of the first connector actuates the backrest  2  to move downward through the second linkage bar, the third linkage bar, the first linkage bar and the back holder  52 , as shown in  FIG. 8 . 
       Embodiment 4 
       [0034]    A chair as shown in  FIGS. 9 and 10 , comprising a seat  1 , a backrest  2 , a chair base, a first connector descried in embodiment 1 and a second connector descried in embodiment 2, wherein both the base holder of the first connector and the base support  62  of the second connector are rigidly connected to the chair base; the seat  1  is rigidly connected to the seat support  63  of the second connector; the backrest  2  is rigidly connected to the back holder of the first connector; a extension bar  7  is provided on the back support  69  of the second connector; a guide sliding slot  21  is provided on the backrest  2 ; and a top end of the extension bar  7  is non-rigidly connected to the guide sliding slot  21  through a sliding wheel. Please refer to embodiment 1 for the structure of the first connector and refer to embodiment 2 for the structure of the second connector. The position mechanism and reposition mechanism are described in embodiment 2 and not repeated herein. 
         [0035]      FIG. 9  shows the chair when the backrest  2  is in the original position. When a user tilts the backrest  2  backward, the backrest  2  rotates clockwise; the back support  69  of the second connector rotates downward; the seat support  63  actuates the seat  1  to move backward; and the rotation holder of the first connector actuates the backrest  2  to move downward through the second linkage bar, the third linkage bar, the first linkage bar and the back holder  52 , as shown in  FIG. 10 .

Technology Classification (CPC): 0