Patent Publication Number: US-2011074197-A1

Title: Chair

Description:
BACKGROUND OF THE INVENTION 
     a) Field of the Invention 
     The present invention relates to a chair, and more particularly to a chair which is linked to rearward tilt of a chair back, allowing a chair seat to be raised. 
     b) Description of the Prior Art 
     In spite that a chair which is linked to rearward tilt of a chair back for lowering a chair seat is more and more popular, in terms of a chair which is linked to sway of the chair back and allows a chair seat to be displaced synchronously, on the contrary, there is also a chair which is linked to the rearward tilt of the chair back for raising the chair seat. 
     For the chair that is linked to the rearward tilt of the chair back for raising the chair seat, there is an ergonomic chair structure disclosed in an international patent publication No. WO 00/74531. As shown in  FIG. 36  and  FIG. 37 , the chair includes the pintle  101 , the base  102  that is supported by the pintle  101 , the back support  104  that is installed on the back  103 , the seat support  106  that is installed on the seat  105 , the horizontal pivot point  107  that is connected on the base  102  to tilt the back support  104  rearwards, the support arm  108  that is located on the base  102  to connect the seat support  106 , and the horizontal pivot point  109  that connects the back support extension  112  of the back support  104  to the seat support  106 . After the back  103 , which was put upright as shown in  FIG. 36 , is tilted rearwards as shown in  FIG. 37 , the horizontal pivot point  109  will be raised. Besides, through the rising of the horizontal pivot point  109 , the support arm  108 , which was tilted forwards, can be raised. As a result, the linkage is generated with the rearward tilt of the back  103 , thereby allowing the seat  105  to be raised. 
     In this chair, the force that lowers the seat  105  becomes the force for putting the back  103  upright. As a result, the weight of the occupant who sits on the seat  105  will result in the resistance against the rearward tilt of the back  103 . Therefore, the heavier the occupant is, the larger the force will be needed to tilt the back  103  rearwards for resulting in the counter force, which is formed when the back  103  is tilted rearwards, to be fitted with the weight of the occupant. 
     However, there indeed exists following issues and shortcomings required to be improved, upon using the aforementioned chair. 
     For the conventional chair, when the seat  105  is raised, the support arm  108  will rotate at the center through the horizontal pivot point  110  at the underside, to change from the forward tilt condition to the upright condition, as shown by a curve C in  FIG. 27 , which is a stage that the support arm  108  starts to be putted upright. In other words, at the stage that the back starts to be tilted rearwards, the seat  105  will be changed into the maximum liftable condition. As shown by the curve C in  FIG. 27 , in the process that the occupant tilts the back  103  rearwards, the counter force at the initial stage of the process will be the largest, and is then decreased. For this kind of chair, a larger force is required when the back  103  starts to be tilted; whereas, the occupant should recline hard on the back  103 . Nevertheless, when the back  103  is tilted to a certain extent, the counter force will be weakened suddenly, allowing the back  103  to be easily tilted abruptly. As a result, the counter force is not configured appropriately. 
     On the other hand, as this kind of chair uses the support arm  108  which connects the front half of the seat support  106  with the base  102 , more parts are required correspondingly. In other words, the support arm  108  will become the necessary accessory, and the horizontal pivot points  110 ,  111  should be also installed on the support arm  108 . Therefore, the parts will be increased, manufacturing cost will be increased and a more complex structure will be induced. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide a chair which includes a pintle; a base which is supported by the aforementioned pintle; a back support which is installed on a back; a seat support which is installed on a seat; a first swaying pivot which is located on the aforementioned base to connect with the aforementioned back support; a second swaying pivot, which is located in front of the aforementioned first swaying pivot, is at a same level as that of the first swaying pivot, is displaced upwards or above the first swaying pivot, and connects the aforementioned seat support on the base in an upward or downward sway manner; a third swaying pivot, which is located between the first swaying pivot and the second swaying pivot, is displaced at a location higher than a connecting line that connects the first swaying pivot and the second swaying pivot, such that the aforementioned back is support and the seat support can be connected to sway upwards and downwards, and that the third swaying pivot can be linked with rearward tilt of the back support to raise; and a sliding structure, which is linked with rising of the aforementioned third swaying pivot, allowing the second swaying pivot to be guided along a rear upper slant direction. 
     Accordingly, when the back and the back support are tilted rearwards with the first swaying pivot as a center, a rear side is swayed immediately. Therefore, the third swaying pivot will be raised, and the second swaying pivot will be displaced along the rear upper slant direction, in association with the rising of the third swaying pivot. As a result, the seat support, which is supported by the second swaying pivot and the third swaying pivot, will be raised entirely. Accordingly, weight of an occupant that operates along a direction for lowering the seat support will result in a counter force against the rearward tilt of the back. Under this condition, the second swaying pivot will be guided to move along the rear upper slant direction by a function of the sliding structure. Hence, in a stage that the rearward tilt starts, the seat support will not be raised significantly and then slightly, and in an initial stage that the back is tilted rearwards, the rising of the seat support will not be enhanced quickly, thereby preventing from a condition that an extremely large counter force occurs suddenly and then diminishes, at the initial stage that the back is titled rearwards. 
     Another object of the present invention is that in a chair of the present invention, the sliding structure will guide the second swaying pivot along a straight line, or to be protruded out of a circular arc at an underside. As a result, when the back starts to be tilted rearwards, from the initial stage to a final stage that the back is tilted rearwards; a rising rate of the second swaying pivot will be equalized, and gradually increased following the rearward tilt of the back. At this time, if a rearward tilt angle of the back is increased by θ, and a rising distance of the second swaying pivot is assumed to be h, then the rising rate of the second swaying pivot will be h/θ. Therefore, the rising of the seat will be equalized as shown by a curve A, or be gradually increased as shown by a curve B, upon tilting the back rearwards. Accordingly, the counter force will be equalized as shown by the curve A, or be gradually increased as shown by the curve B. 
     Still another object of the present invention is to provide a locking structure on the base for fixing the back support. As a result, the back support can be prevented from being tilted rearwards by an operation of the locking structure, and after the operation of the locking structure has been released, the back support can be restored to a condition that it can be tilted rearwards. 
     Yet still another object of the present invention is to provide a locking structure which is provided with a swaying unit to fix the back support, a support arm to sway the swaying unit, and an operating structure to displace the support arm, such that under a condition that sway of the swaying unit, which is located on the support arm, is restricted, and when the operating structure is operated, an elastic deformation is formed to absorb a displacement of the swaying unit for accumulating energy, thereby swaying the swaying unit. 
     Accordingly, by the operation of the operating structure, the support arm will sway the swaying unit to fix the back support or to release the fixing state. In other words, after the locking structure has started to operate, the rearward tilt of the back support will be prohibited; or the back support can be tilted rearwards as the operation of the locking structure is released. When the back support is titling rearwards, the sway of the swaying unit is restricted due to the back support. Under this condition, through controlling the operating structure, an elastic deformation part which is disposed on the support arm will be deformed elastically to absorb the displacement of the swaying unit for accumulating energy, without swaying the swaying unit reluctantly. Besides, once the back support, which was titled rearwards originally, is putted upright, the swaying unit can sway. Therefore, under a condition that the elastic deformation part is restored to its original shape after being deformed elastically, the swaying unit will sway. 
     To enable a further understanding of the said objectives and the technological methods of the invention herein, the brief description of the drawings below is followed by the detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a side view of a first embodiment of a chair of the present invention, wherein a back is not tilted rearwards. 
         FIG. 2  shows a side view of a chair of the present invention, wherein a back is tilted rearwards. 
         FIG. 3  shows cutaway views of a base, a back support, and a seat support of a chair of the present invention, with (A) being a state that the back support is not tilted rearwards, and (B) being a state that the back support is titled rearwards. 
         FIG. 4  shows a plan view of a back support that is assembled to a base. 
         FIG. 5  shows a cutaway view along a line V-V of  FIG. 3 , for describing a height adjustment structure. 
         FIG. 6  shows a cutaway view of an enlarged installation part of an operating rod of a height adjustment structure. 
         FIG. 7  shows a side view of a second embodiment of a chair of the present invention. 
         FIG. 8  shows cutaway view of a locking structure of a chair of the present invention, with (A) being a state that a back support is not fixed, and (B) being a state that the back support is fixed. 
         FIG. 9  shows a plan view of a locking structure of a chair of the present invention. 
         FIG. 10  shows a turn-over unit of a locking structure of a chair of the present invention, with (A) being a front view of a state that a back support is not fixed, and (B) being a front view of a state that a back support is fixed. 
         FIG. 11  shows a cutaway view of a swaying unit of a locking structure of a chair of the present invention, wherein the swaying unit is installed on a base. 
         FIG. 12  shows a front view of a seat installation part which is fixed on a back support. 
         FIG. 13  shows a front view of an armrest installation part which is fixed on a seat support. 
         FIG. 14  shows a side view of an embodiment, excluding a sliding structure. 
         FIG. 15  shows a side view of an embodiment, excluding a counter force structure. 
         FIG. 16  shows a side view of a counter force structure and another embodiment. 
         FIG. 17  shows a bottom view of a first type of a representative installation structure of a seat. 
         FIG. 18  shows a cutaway view along a line A-A of  FIG. 17 . 
         FIG. 19  shows a cutaway view along a line B-B of  FIG. 17 . 
         FIG. 20  shows a bottom view of a second type of a representative installation structure of a seat. 
         FIG. 21  shows a cutaway view along a line A-A of  FIG. 20 . 
         FIG. 22  shows a bottom view of a third type of a representative installation structure of a seat. 
         FIG. 23  shows a side view of an installation structure of  FIG. 22 . 
         FIG. 24  shows a front view of an installation structure of  FIG. 22 . 
         FIG. 25  shows a top view of a fourth type of a representative installation structure of a seat. 
         FIG. 26  shows a cutaway view along a line A-A of  FIG. 25 . 
         FIG. 27  shows a graph of variations between a rearward tilt angle of a back and a seat height of the prior art. 
         FIG. 28  shows a graph of variations between a rearward tilt angle of a back and a resulted counter force. 
         FIG. 29  shows a cutaway view of another embodiment of an installation structure of an operating rod of a height adjustment structure. 
         FIG. 30  shows a cutaway view of a locking structure and another embodiment wherein a back support is not fixed. 
         FIG. 31  shows a cutaway view of a locking structure wherein a back support is fixed. 
         FIG. 32  shows a plan view of a locking structure. 
         FIG. 33  shows a cutaway view along a line X-X of  FIG. 32 . 
         FIG. 34  shows a cutaway view along a line Y-Y of  FIG. 33 . 
         FIG. 35  shows a cutaway view along a line Z-Z of  FIG. 33 . 
         FIG. 36  shows a side view of a conventional chair of the prior art, wherein a back is not tilted rearwards. 
         FIG. 37  shows a side view of a chair of the prior art, wherein a back is tilted rearwards. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 to 6 , showing a first embodiment of a chair of the present invention, a chair is provided with a pintle  1 ; a base  2 , which is supported by the pintle  1 ; a back support  4 , which is installed on a back  3 ; a seat support  6 , which is installed on a seat  5 ; a first swaying pivot  7 , which is connected at the base  2  to tilt the back support  4  rearwards; a second swaying pivot  8 , which is connected at the base  2  to sway the seat support  6  upwards and downwards; a third swaying pivot  9 , which connects the back support  4  and the seat support  6  to sway the back support  4  and the seat support  6  upwards and downwards, and which is linked to rearward tilt of the back support  4 , such that the third swaying pivot  9  can be raised along with the back support  4 ; and a sliding structure  10 , which is linked to rising of the third swaying pivot  9  to guide the second swaying pivot  8  along a rear upper slant direction. 
     The base  2  is latched on a top of the pintle  1 , and a bottom plate  2   a  of the base  2  is provided with a cylinder  2   b,  a diameter of which is gradually reduced from bottom to top. In addition, an interior of the pintle  1  is provided with a pneumatic spring  18  to adjust height, a top of this pneumatic spring  18  is protruded out of an upper end of the pintle  1 , and a circumference at an upper part of the pneumatic spring  18  is a slant surface with a diameter being gradually reduced from bottom to top. As a result, the base  2  can be installed on the top of the pintle  1  by inserting the upper part of the pneumatic spring  18  into the cylinder  2   b  from top to bottom. Rear half parts of left and right side plates  2   c,    2   b  of the base  2  are provided with through-holes for transfixing with the first swaying pivot  7 , and front half parts are provided with through-holes for transfixing with the second swaying pivot  8 . In this embodiment, the through-hole of the second swaying pivot  8  is a long hole to serve as the sliding structure  10 . In addition, the long hole will be described as the sliding structure  10 , hereafter. 
     As the seat support  6  supports the seat  5 , it can freely sway and be freely installed slidingly on the base  2 . The seat support  6  is constituted by an upper plate  6   a  above the base  2 , and a pair of left and right side plates  6   b,    6   c  that are hung down from two side edges of the upper plate  6   a.  These parts are formed by bending a piece of board material. In terms of the seat  5 , the seat  5  is installed on the upper plate  6   a  by screws. In addition, the left and right side plates  6   b,    6   c  are disposed at exterior sides of the side plates  2   c,    2   d  of the base  2 , and central positions of the left and right side plates  6   b,    6   c  of the seat support  6  are provided with through-holes for transfixing with the third swaying pivot  9 , whereas front half parts are provided with through-holes for transfixing with the second swaying pivot  8 . 
     The back support  4  is to support the back  3 , and hence, the back support  4  can be installed on the base  2  in a manner that it can sway freely. The back support  4  is constituted by the side plates  2   c,    2   d  of the base  2 , a pair of left and right side plates  4   a,    4   b  between the side plates  6   b,    6   c  of the seat support  6 , and a support plate  4   c  between the left and right side plates  4   a,    4   b.  A front half and a rear half of the support plate  4   c  are formed with an elevation difference, with the front half being higher, and the rear half lower. The rear half of the support plate  4   c  is loaded with loadings  4   d  at the rear halves of the left and right side plates  4   a,    4   b,  and the loadings  4   d  are fixed by welding or like. By this configuration, the loadings  4   d  will be integrally formed with the left and right side plates  4   a,    4   b,  as well as the support plate  4   c.  By welding or like, an installation plate  11  which is fixed on the back  3  is fixed on the rear half of the support plate  4   c  by bolts or like. The front half of the support plate  4   c  is extended to a level higher than that of the rear half, and is disposed above the base  2 . Central positions of the left and right side plates  4   a,    4   b  of the back support  4  are provided with through-holes for transfixing with the first swaying pivot  7 , and the front halves are provided with through-holes for transfixing with the third swaying pivot  9 . 
     The first swaying pivot  7  is transfixed into the through-holes of the base  2 , and the through-holes located at the back support  4 , to connect the back support  4  at the base  2 , and to allow the back support  4  to be tilted rearwards. A front end of the first swaying pivot  7  is latched with a pull preventer  12 . The second swaying pivot  8  is transfixed into the sliding structures  10  of the base  2 , and the through-holes located at the seat support  6 , to connect the base  2 , such that the seat support  6  can sway upwards and downwards. A front end of the second swaying pivot  8  is latched with the pull preventer  12 . The third swaying pivot  9  is transfixed into the through-holes of the seat support  6 , and the through-holes located at the back support  4 , to connect the seat support  6  with the back support  4 , allowing the seat support  6  and the back support  4  to sway. A front end of the third swaying pivot  9  is latched with the pull preventer  12 . 
     The sliding structure  10 , such as the long through-hole extended linearly along the rear upper slant direction, is latched with push buttons  13  made by polyacetal at its peripherals, allowing the second swaying pivot  8  to smoothly slide. An angle of the sliding structure  10  is preferably toward the rear upper slant direction, for example, tilting by about 40°-70°, with the best configuration being tilting along the rear upper slant direction at about 55°. Moreover, the length of the sliding structure  10  will be 25 mm under the condition that it is tilted along the rear upper slant direction at 55°, and the second swaying pivot  8 , for example, will be raised by about 20 mm. 
     The second swaying pivot  8  is disposed in front of the first swaying pivot  7 , and is at a level higher than that of the first swaying pivot  7 . The second swaying pivot  8 , following the displacement of the third swaying pivot  9 , is guided and displaced to the sliding structure  10 , with its range of displacement being in front of the first swaying pivot  7  and above the first swaying pivot  7 . However, if the second swaying pivot  8  is disposed in front of the first swaying pivot  7 , and is at a same level as that of the first swaying pivot  7 , then it can be also guided from this position to the sliding structure  10  along the rear upper slant direction. Besides, even under this condition, the second swaying pivot  8  will be displaced in front of the first swaying pivot  7 . Moreover, the third swaying pivot  9  is disposed between the first swaying pivot  7  and the second swaying pivot  8 , and is located above a connecting line L that connects the first swaying pivot  7  and the second swaying pivot  8 . The third swaying pivot  9  will be displaced following with rearward tilt of the back support  4 , with its range of displacement being located between the first swaying pivot  7  and the second swaying pivot  8 , and above the connecting line L that connects the first swaying pivot  7  and the second swaying pivot  8 . 
     On the other hand, when the second swaying pivot  8  is at the range below the first swaying pivot  7 , no displacement will occur. As a result, the second swaying pivot  8  can be smoothly raised along with the rearward tilt of the back support  4 . Assuming that the second swaying pivot  8  is disposed below the first swaying pivot  7 , when the third swaying pivot  9  is above the connecting line L that connects the first swaying pivot  7  and the second swaying pivot  8 , and is below the first swaying pivot  7 , the third swaying pivot  9  will sway toward the rear upper slant direction with the first swaying pivot  7  as an axis, following with the rearward tilt of the back support  4 . Therefore, a force of forward operation will be developed on the second swaying pivot  8 , prohibiting the second swaying pivot  8  from sliding toward the rear upper slant direction, and allowing the range of displacement of the second swaying pivot  8  to be above the first swaying pivot  7  or at the same level as that of the first swaying pivot  7 , so as to avoid the aforementioned condition and to enable the second swaying pivot  8  to be smoothly raised following with the rearward tilt of the back support  4 . 
     A counter force structure  14  is disposed between the base  2  and the back support  4 . By exerting a force on a top of the back support  4 , the counter force structure  14  will press the back support  4  to restore to an original position when the back support  4  is tilted rearwards. Referring to  FIG. 3 , the counter force structure  14  is constituted by a coil spring  15  and spring plates  16  at two ends of the coil spring  15 . The spring plate  16  at an upper side is folded and latched into a periphery of an axis  17  in the spring plate  16  at a lower side, and a distance between the upper side spring plate  16  and the lower side spring plate  16  will be changed following an extension or compression of the coil spring  15 . The lower side spring plate  16  is provided with a concaved part  16   a,  and the upper side spring plate  16  is provided with a convex part  16   b.  By latching the concaved part  16   a  into a convex part  2   g  of the base  2 , and inserting the convex part  16   b  into a concaved part  4   g  on the back support  4 , the counter force structure  14  can be installed between the base  2  and the back support  4 . The counter force structure  14  is disposed at a rear side of the first swaying pivot  7 , and once the back support  4  is tilted rearwards, the coil spring  15  will be compressed, thereby resulting in the counter force. 
     Furthermore, as the pneumatic spring  18 , which is used to adjust the height, has been used very commonly, it will not be described further. The pneumatic spring  18  operates through a height adjustment structure  19 . The height adjustment structure  19  in this embodiment is composed of an operating rod  20  and an installation tool  21  which is installed at the base  2  to sway the operating rod  20 . The operating rod  20  includes an operating stick which is bended into a crank shape, an extension part  20   a  which is extended along a breadth direction of the chair for installing an operating plate  22 , an shaft branch  20   b  which is extended toward a rear side from the extension part  20   a,  and an operating part  20   c  which is extended toward the breath direction of the chair from a front end of the shaft branch  20   b.  The shaft branch  20   b  and the operating part  20   c  are collected in the base  2 , and the extension part  20   a  is protruded out of an exterior side of the base  2  from a long through-hole  2   h  on the right side plate  2   c  of the base  2 . By two pieces of relieving arches  2   i  disposed at the base  2 , and the installation tool  21  of the relieving arch  2   j  which is disposed between the relieving arches  2   i,  the shaft branch  20   b  can be supported and turned over. In other words, concaved locations of the two relieving arches  2   i,  and concaved locations of the installation tool  21  will clamp the shaft branch  20   b  from top to bottom, so as to constitute a bearing. The operating part  20   c  is stuffed into the convex part  18   a  of the pneumatic spring  18  to form an operable state. The long through-hole  2   h  of the base  2  forms a swaying shape for the operating rod  20 . As shown by a solid line in  FIG. 5 , the operating rod  20  presses down the extension part  20   a  by its weight, thereby rising up the operating part  20   c.    
     Once an occupant has reclined on the back  3 , the coil spring  15  of the counter force structure  14  is compressed, and in a mean time, the back  3  and the back support  4  are tilted rearwards with the first swaying pivot  7  as a center. As a result, the third swaying pivot  9  will be raised. In addition, linkage is formed along with the rising of the third swaying pivot  9 , allowing the second swaying pivot  8  to be guided to the sliding structure  10  and be displaced along the rear upper slant direction. In other words, as the second swaying pivot  8  and the third swaying pivot  9  are raised, the seat support  6  and the seat  5  are raised too. As the seat is taken by the occupant, and the weight of the occupant becomes a force to restrain the rising of the seat  5 , a force that tilts the back  3  rearwards will correspondingly become a counter force. 
     A chair, a counter force of which as shown by a curve A or a curve B in  FIG. 28 , can almost have an equalized counter force without a limitation to a rearward tilt angle of the back  3 , or can have a counter force which is gradually increased as the rearward tilt angle of the back  3  increases. After the occupant has reclined on the back  3  and tilted the back  3  to a maximum extent, the back  3  will not be easily tilted suddenly, thereby improving comfortableness while being seated. As a result, it is preferably to configure the counter force as that of the curve A or B in  FIG. 28 . 
     In the chair of this embodiment, the sliding structure  10  will guide the second swaying pivot  8  toward the rear upper slant direction in a straight line. In addition, the third swaying pivot  9  will be displaced toward the rear upper slant direction along a circumference with the first swaying pivot  7  as a center. Accordingly, a relationship between an increment θ of the rearward tilt angle of the back  3  and a rising distance h of the second swaying pivot  8  will be constant, and from the back  3  starts to be tilted rearwards, to an initial stage and to a final stage of the rearward tilt, all of the rising rates (h/θ) of the second swaying pivot  8  will be equalized. To put it another way, the positions of the first, second, third swaying pivots  7 ,  8 ,  9  and the tilt angle of the sliding structure  10  will equalize the rising rates (h/θ) of the second swaying pivot  8  when the back support  4  is tilted rearwards. Therefore, as shown by the curve A in  FIG. 27 , as the tilt angle of the back support  4  increases, the seat support  6  and the seat  5  will be slowly rising at a certain distance, and the resulted counter force will become a constant. As a result, at a moment when the occupant tilts the back  3  rearwards, there will be no large change to the counter force, and the back  3  can be tilted rearwards continuously with almost the same force. That is to say, for the chair as shown in  FIG. 36 , the back will be easily tilted due to that the counter force is weakened suddenly, after the back has been tilted to a certain extent; whereas, for the chair of the present invention, this condition can be prevented, thereby improving comfortableness in using the chair. 
     Referring to  FIGS. 1 to 6 , in terms of the positions of first, second, third swaying pivots  7 ,  8 ,  9 , and the tilt angle of the sliding structure  10 , when the back support  4  starts to be tilted rearwards, the rising rate (h/θ) of the second swaying pivot  8  will become equalized. In other words, under a condition that the back support  4  is not tilted rearwards, the third swaying pivot  9  is disposed at about 40° in a front upper slant direction of the first swaying pivot  7 , and the second swaying pivot  8  is disposed at about 7° in a front upper slant direction of the first swaying pivot  7 , if viewing from a side of the chair. Moreover, viewing from the side of the chair, the third swaying pivot  9  is disposed at about 10° in a rear upper slant direction of the second swaying pivot  8 . In addition, viewing from the side of the chair, the sliding structure  10  is tilted about 55° toward the rear upper slant direction. Under this condition, once the back support  4  is tilted rearwards, the third swaying pivot  9  will be displaced to a position within about 60° in the front upper slant direction of the first swaying pivot  7 , and the second swaying pivot  8  will be displaced to a position within about 15° in the front upper slant direction of the first swaying pivot  7 . However, the relationship among the positions of first, second, third swaying pivots  7 ,  8 ,  9 , and the tilt angle of the sliding structure  10  is not limited to the aforementioned angles, as long as that when the back support  4  is tilted rearwards, the rising rate (h/θ) of the second swaying pivot  8  can be equalized. 
     On the other hand, once the occupant stops reclining on the back  3  and gets up, the coil spring  15  of the counter force structure  14  will be extended, allowing the back support  4  to be putted up forwards. 
     This chair is constituted through the sliding structure  10  to guide the third swaying pivot  9 , allowing the chair to be composed simply, and thereby controlling an increase of manufacturing cost. 
     The adjustment of height of the seat  5  is disclosed hereafter. As shown by a solid line in  FIG. 5 , under a condition that the operating rod  20  is not operated by the occupant, the operating rod  20  will lower down the extension part  20   a  by its weight, thereby raising the operating part  20   c.  As a result, the convex part  18   a  of the pneumatic spring  18  will not operate, its length cannot be changed, the length of the pintle  1  will remain at a constant, and the height of the seat  5  will also remain at a constant. 
     Once the occupant puts lifts up the operating plate  22  of the operating rod  20 , the operating rod  20  will sway with the shaft branch  20   b  as a center, as shown by a dotted line in  FIG. 5 . At this time, the operating part  20   c  will be pressed down into the convex part  18   a  of the pneumatic spring  18 . As a result, the length of the pneumatic spring  18  can be adjusted, and the length of the pintle  1  can be changed to adjust the height of the seat  5 . Next, after the occupant has released the operating rod  20 , the operating rod  20  will be restored to a non-operating state by its weight. 
     A second embodiment of the present invention is described hereafter. Besides, in this detailed description and drawings, as a same part is marked by a same numeral, the repeated description will be omitted. Referring to  FIGS. 7 to 13 , the base  2  is provided with a locking structure  23  to fix the back support  4 . The locking structure  23  is provided with a swaying unit  45  to fix the back support  4 , a support arm  46  to sway the swaying unit  45 , and an operating structure  44  to displace the support arm  46 . The operating structure  44 , such as a turn-over unit (called the turn-over unit  44  hereafter) is connected to the support arm  46  which sways and displaces the swaying unit  45 . However, the operating structure is not limited to the turn-over unit  44 , and any structure is acceptable as long as that it enables the support arm  46  to be displaced forwards and rearwards (omitting the drawings). In addition, in this embodiment, an operating plate  47  of the turn-over unit  44  is provided. 
     The turn-over unit  44  is disposed between the left side plate  2   d  and a wall plate  2   n  of the base  2 , is latched into an axis  48 , and cannot be turned over correspondingly. A spring  49  which can press the turn-over unit  44  toward the wall plate  2   n  is disposed between the side plate  2   d  and the turn-over unit  44 . The axis  48  is supported on the side plate  2   d  of the base  2 , and is protruded outwards from the left side plate  2   d,  in a manner that it can turn over freely. The operating plate  47  is installed on the protruded portion of the axis  48 . 
     The turn-over unit  44  is provided with an arm  44   a  and a brake  44   b.  Referring to  FIG. 8(A)  and  FIG. 10(A) , the turn-over unit  44  is turned over from an initial position toward a locking position as shown in  FIG. 8(B)  and  FIG. 10(B) . As a result, the turn-over unit  44  will enable the arm  44   a  to be folded toward a tilted surface  51  of the wall plate  2   n  and to be turned over at a same time. At this time, the tilted surface  51  will be protruded toward the side plate  2   d  from an initial position where the arm  44   a  is in touch with and a locking position where the arm  44   a  is in touch with, so as to press the turn-over unit  44 , compress the spring  49 , and move toward the side plate  2   d.  The arm  44   a  is connected to the support arm  46  which can sway. Once the turn-over unit  44  is restored to an original position from the locking position, the brake  44   b  will find tune the side plate  2   d  to prevent the turn-over unit  44  from excessively turning over. 
     The swaying unit  45  includes left and right side plates  45   a,    45   b,  and a connection plate  45   c  that connects the two side plates  45   a,    45   b.  The left and right side plates  45   a,    45   b  are provided with shafts  45   d,  concaved parts  2   p  on the base  2  are inserted with the shafts  45   d,  a cover plate  52  is enclosed at a top and is fixed on the base  2  by screws  53 . The swaying unit  45  is installed on the base  2  in a manner that it can sway with the shafts  45   d  as centers. An upper end of the swaying unit  45  is located in front of the shafts  45   d.  As a result, when the swaying unit  45  sways at a rear side, the upper end of the swaying unit  45  will be raised and latched into a concaved part  4   h  of the back support  4 . Under this condition, the upper end of the swaying unit  45  will enter into a range of rearward tilt of the back support  4 . 
     Referring to  FIG. 8(A) , under a condition that the turn-over unit  44  is restored to the initial position, the support arm  46  will pull up the swaying unit  45  toward a front side, and the upper ends of the side plates  45   a,    45   b  will be moved out from the concaved part  4   h  of the back support  4 . In other words, as the side plates  45   a,    45   b  are moved out of the range of rearward tilt of the back support  4 , the back support  4  can be tilted rearwards. To put it differently, the back  3  will not be locked. 
     On the other hand, as shown in  FIG. 8(B) , once the turn-over unit  44  has been turned over to the locking position, the support arm  46  will allow the swaying unit  45  to sway rearwards. As a result, the upper ends of the side plates  45   a,    45   b  will be latched into the concaved part  4   h  of the back support  4 . In other words, the side plates  45   a,    45   b  will enter into the range of rearward tilt of the back support  4 , thereby restricting the rearward tilt of the back support  4 . To put it another way, the back  3  is locked. 
     On the other hand, in this embodiment, a support plate  4   c  of the back support  4  is divided into a front half  4   ca  and a rear half  4   cb.  The front half  4   ca  is formed by bending a piece of board material, and the rear half  4   cb  is integrally formed with the left and right side plates  4   a,    4   b.  In other words, the rear half  4   cb  and the side plates  4   a,    4   b  are formed by bending the board material, and the front half  4   ca  is integrally fixed with the left and right side plates  4   a,    4   b  by welding or like. 
     Furthermore, in this embodiment, as shown in  FIG. 6  and  FIG. 29 , the shaft branch  20   b  of the operating rod  20  of the height adjustment structure  19  is emplaced in the concaved locations of the two relieving arches  2   i,  and at a same time, the location between the relieving arches  2   i  is clamped by the plan-shape installation tool  21  from top to bottom, so as to support the operating rod  20  in a manner that the operating rod  20  can be turned over. 
     Seat installation parts  37 , for example, are fixed by welding or like on a top of the seat support  6 . The seat installation parts  37  are provided at a front and a rear place. A seat shell  38  is fixed by the seat installation parts  37 , and the seat  5  is installed on the seat support  6  with screws, for example. Moreover, on the seat support  6  is provided with armrest installation parts  39  to install the armrests which are fixed by welding or like. Besides, as seen by the chair of this embodiment, the armrests do not need to be installed even there are the armrest installation parts  39 . 
     Even that the chair of this embodiment is the same as that in  FIG. 1 , when the occupant starts to tilt the back  3  rearwards, there will be no condition that the counter force will be increased in the middle of tilting, and the back  3  can be tilted continuously almost with the same force, thereby increasing comfortableness in using the chair. Moreover, by using the sliding structure  10  to guide the third swaying pivot  9 , the chair can be constituted simply, thereby controlling the increase of the manufacturing cost. 
     On the other hand, the aforementioned embodiment is only one of the proper embodiments of the present invention, and is not the necessary embodiment of the present invention. As long as they will not deviate from the features of the present invention, all kinds of variations can be available within the range. 
     For example, in the aforementioned description, although the sliding structure  10  guides the second swaying pivot  8  along a straight line, it can also guide non-linearly. As shown in  FIG. 14 , the second swaying pivot  8  is guided to an underside in a protruded arc-shape manner. In other words, the sliding structure  10  of the base  2  can be also formed as the underside protruded arc-shape structure. Under this condition; the rising rate (h/q) of the second swaying pivot  8  will be gradually increased following the rearward tilt of the back  3 . As a result, referring to the curve B in  FIG. 27 , the rising of the seat  5  will be gradually enlarged following the increase of the rearward tilt angle of the back  3 . Therefore, as shown by the curve B in  FIG. 28 , the resulted counter force will be gradually enlarged. Even under this condition, when the occupant reclines on the back  3  to tilt the back  3  rearwards, he or she can feel comfortable, thereby increasing comfortableness while being seated. Under this condition, as long as the positions of first, second, third swaying pivots  7 ,  8 ,  9 , and the shape and curvature of the sliding structure  10  can allow the rising rate (h/q) of the second swaying pivot  8  to be increased gradually when the back support  4  is tilted rearwards, then there will be no special limitation. 
     Furthermore, in the aforementioned description, if the counter force structure  14  cannot adjust the intensity of the resulted counter force, then it is still acceptable as long as that the intensity of the resulted counter force is adjustable. Referring to  FIG. 15  or  FIG. 16 , on a top of the bottom plate  2   a  of the base  2  is provided with adjustment screws  40 . By changing amounts of protrusion at front ends of the adjustment screws  40 , a pre-stress of the coil spring  15  of the counter force structure  14  is adjusted, and the intensity of the resulted counter force can be adjusted. This way is acceptable. Under this condition, as shown in  FIG. 15 , on a top of a handle  41  is provided with the adjustment screws  40 . Through the handle  41  to turn over and operate, the amounts of protrusion of the adjustment screws  40  can be adjusted without stages, or the intensity of the counter force can be adjusted. On the other hand, as shown in  FIG. 16 , at a base end of an operating rod  42  is provided with the adjustment screws  40 . Through a swaying operation of the operating rod  42 , the amounts of protrusion of the adjustment screws  40 , or the intensity of the counter force, can be adjusted in, for example, three stages. Besides, on the bottom plate  2   a  of the base  2 , a bottom plate  43  with screw through-holes  43   a  can be fixed by welding or like. The adjustment screws  40  are latched into the screw through-holes  43   a,  and are protruded from the through-holes  2   m  of the bottom plate  2   a  toward the spring plate  16  at the lower side of the counter force structure  14 . 
     Moreover, the locking structure  23  can be also a type which is provided with a spring part in a mechanism and keeps its own functions. Referring to  FIGS. 30 to 35 , on the support arm  46 , and under a condition that the sway of the swaying unit  45  is limited, when the operating structure  44  is operated, an elastic deformation is formed to absorb and accumulate energy that sways and displaces the swaying unit  45 . At a same time, once the sway of the swaying unit  45  is possible, an elastic deformation part (or a spring part)  56  can be also designed to develop a function for swaying the swaying unit  45 . In this embodiment, the configuration disposed is to bend a middle part of the support arm  46  into the U-shape elastic deformation part  56 . Nevertheless, the shape of the elastic deformation part  56  is not only limited to this shape, as described hereafter, as long as that the shape can absorb the displacement energy accumulated to sway the swaying unit  45 , and can develop the swaying energy, then there will be no special limitation. 
     In this embodiment, the turn-over unit  44  of the operating structure is disposed between the left side plate  2   d  and the wall plate  2   n  of the base  2 , and is latched into the axis  48  to prohibit from being turned over. In other words, by inserting the convex part  48   a  which is located at the axis  48  into the concaved part  44   d  which is located at the through-hole  44   c  of the turn-over unit  44 , the turn-over unit  44  will be latched into the axis  48  without being turned over. A fixing part  57  is located between the turn-over unit  44  and the bottom plate  2   a  of the base  2 , and is formed by an elastic material, such as resin, which enables the convex part  57   d  between the concaved parts  57   a,    57   b  to be pressed down by installing the through-hole  57   c,  to latch the convex part  44   e  at a bottom of the turn-over unit  44  into the concaved part  57   a  or  57   b  of the fixing part  57 . In this manner, the turn-over unit  44  will be fixed at the initial position, as shown in  FIG. 30 , or fixed at the locking position, as shown in  FIG. 31 . By pressing down the concaved part  57   d,  the convex part  44   e  of the turn-over unit  44  can move between the concaved parts  57   a  and  57   b.  As a result, the turn-over unit  44  can be turned over between the initial position and the locking position. The fixing part  57  is latched into the concaved part  2   t  of the bottom plate  2   a  of the base  2 . 
     The arm  44   a  is disposed on the top of the turn-over unit  44 . The support arm  46  is connected at the place close to the front end of the arm  44   a  in a manner that the support arm  46  can sway. The other end of the support arm  46  is connected at the side plate  45   b  of the swaying unit  45 , in a manner that the support arm  46  can sway. 
     The axis  48  is inserted into the through-hole  58  on the side plate  2   d  of the base  2 , and the through-hole  61  on the wall plate  2   n,  such that an inner end of the axis  48  can be supported by a wall plate  2   w  and the operating rod  20  with the installation tool  21  which can sway, in a manner that the axis  48  can be turned over freely. The axis  48  is provided with a convex part  48   b,  and the convex part  48   b  is inserted into the concaved part  58   a  of the through-hole  58  of the side plate  2   d,  so as to allow the axis  48  to be turned over by an angle, and to allow the convex part  48   b  to move from a side of the concaved part  58   a  to the other side. In other words, the turn-over unit  44  will be restricted from being turned over to the locking position (as shown in  FIG. 34 ) from the initial position. If the base  2  is made by a metal, then it will exceed the range of turning over, allowing the force of reluctantly turning over to be fed into the axis  48 , and the through-hole  58  or the concaved part  58   a  will still not be expanded, thereby limiting the turning-over angle of the axis  48 . As a result, the turn-over unit  44  can be prevented from excessively turning over, the swaying unit  45  can be prevented from excessively swaying, and the installation part at the inner end of the axis  48  can be prevented from being loaded. 
     As shown in  FIG. 35 , the inner end of the axis  48  is loaded on a top of a section  59  of the wall plate  2   w.  Close to the inner end of the axis  48  is formed with a trench  48   c  on which is inserted with a fixing piece  21   a  of the installation tool  21  from top. By this way, the inner end of the axis  48  can be supported through the wall plate  2   w  and the installation tool  21 , in a manner that the axis  48  can sway. Moreover, through inserting the fixing piece  21   a  into the trench  48   c,  the axis  48  can be prevented from withdrawing. The axis  48  is supported by the operating rod  20  with the installation tool  21 , in a manner that the axis  48  can sway, which can reduce an amount of parts, and can reduce an assembly engineering, thereby reducing the manufacturing cost. 
     The operating handle  60  is fixed at an exterior end of the axis  48 . Holding the operating handle  60  and turning it over, can turn over the turn-over unit  44 . However, if the operating handle  60  is changed into the operating rod (not shown in the drawings) that is installed at the axis  48 , then the turn-over unit  44  can be operated by the operating rod. 
     In this embodiment, a top of the back support  4  is provided with a convex part  4   i,  allowing the swaying unit  45  to be located outside the swaying range under a condition that the back support  4  is not tilted rearwards, and to the swaying unit  45  will be located outside the swaying range, and enter into the swaying range once the back support  4  is tilted rearwards. 
     Referring to  FIG. 30 , when the turn-over unit  44  is restored to the initial position, the support arm  46  will guide the swaying unit  45  to the front, and the upper ends of the side plates  45   a,    45   b  will be escaped from the concaved parts  4   h  of the back support  4 . Hence, as shown by an arrow T in  FIG. 30 , the back support  4  can be tilted rearwards. In other words, the back  3  is not locked. 
     On the other hand, as shown in  FIG. 31 , once the turn-over unit  44  is turned over to the locking position, the support arm  46  will sway the swaying unit  45  toward the rear side. As a result, the upper ends of the side plates  45   a,    45   b  will be latched into the concaved parts  4   h  of the back support  4 . Under this condition, when the back support  4  is to be tilted rearwards, the back support  4  will be in touch with the swaying unit  45 , thereby prohibiting the back support  4  from being tilted rearwards. In other words, the back  3  is locked. 
     When the turn-over unit  44  is at the initial position, the swaying unit  45  is pulled back to the front, as shown by the arrow T in  FIG. 30 , and the back support  4  is tilted rearwards, the convex part  4   i  of the back support  4  will enter into the swaying range of the swaying unit  45 . Under this condition, after the operating handle  60  is controlled to sway the swaying unit  45  toward the rear side a little, the swaying unit  45  will be in touch with the convex part  4   i,  and cannot sway rearwards further. At this condition, the operating handle  60  is controlled to further turn over the swaying unit  45 , and the elastic deformation part  56  of the support arm  46  will be deformed elastically, to absorb the accumulated displacement energy that sways the swaying unit  45 . As a result, under this condition, once the back support  4 , which has been tilted rearwards, is put upright, the convex part  4   i  will be escaped from the swaying range of the swaying unit  45 , and the swaying unit  45  can sway rearwards. The elastic deformation part  56 , which was deformed elastically, will be restored to its original shape, and at a same time, develop its accumulated energy to sway the swaying unit  45  rearwards. Accordingly, under a condition that the back  3  is not able to be locked, the swaying unit  45  cannot still sway even by conducting the locking operation. Therefore, the structures can be prevented from being damaged. Moreover, even that the swaying unit  45  cannot sway, the operation that turns over the turn-over unit  44  can be still conducted, and the swaying unit  45  can sway automatically when it is able to sway. Hence, one can conduct the operation without needing to care whether the back support  4  is tilted rearwards. As a result, the chair can be used more freely. 
     Moreover, when the back  3  is locked by using the locking structure  23  (as shown by a state in  FIG. 31 ), and once the occupant reclines on the back  3 , the swaying unit  45  will sway rearwards immediately. Under a condition that the upper ends of the side plates  45   a,    45   b  are latched into the concaved parts  4   h  of the back support  4 , when the back support  4  is to be tilted rearwards, the support plate  4   c  of the back support  4  will be in touch with the swaying unit  45 . As a result, the support plate  4   c  is changed into a state of pressing the swaying unit  45  which is not able to be pulled back to the front. Under this condition, when the operating handle  60  is controlled to turn over the turn-over unit  44  to the initial position, the elastic deformation part  56  of the support arm  46  will be deformed elastically to absorb the accumulated displacement energy that sways the swaying unit  45 . Hence, at this condition, once the occupant stops reclining on the back  3 , the support plate  4   c  will be escaped from the swaying unit  45 , allowing the swaying unit  45  to be pulled back to the front. Accordingly, the elastic deformation part  56 , which was deformed elastically, will be restored to its original shape, and develop the accumulated energy to pull back the swaying unit  45  to the front. Therefore, under a condition that the back  3  is not able to be released form the locking state, the swaying unit  45  cannot still sway even by conducting the unlocking operation. As a result, the structures can be prevented from being damaged. In addition, even that the swaying unit  45  cannot sway, the operation to turn over the turn-over unit  44  can be still conducted, and the swaying unit  45  can sway automatically when it can. Accordingly, one can conduct the operation without needing to care whether the back support  4  is tilted rearwards, and the chair can be used more freely. 
     Furthermore, referring to  FIGS. 17 to 19 , on a seating accessory of the seat support  6 , the seat shell  38  can be also fixed with screws. In other words, on a top of a concaved position  38   a  of the seat shell  38  is disposed with the seat support  6 , and screws  54  can be used to fix the seat shell  38  and the seat support  6 . 
     Moreover, referring to  FIG. 20  and  FIG. 21 , on the seating accessory of the seat support  6 , in addition to that the screws are used to fix the seat shell  38 , armrest installation accessories  39  can be also fixed on the seat support  6  by welding or like. In other words, the top of concaved position  38   a  of the seat shell  38  is disposed with the seat support  6 , and at a same time when the screws  54  are used to fix the seat shell  38  and the seat support  6 , the armrest installation accessories  39  can be disposed to install the armrests. 
     Moreover, referring to  FIGS. 22 to 24 , on the seating accessory of the seat support  6 , the seat installation part  37  can be also fixed by welding or like; whereas, at a same time, a seating plate  55  can be fixed at the seat installation part  37  with screws. 
     Moreover, referring to  FIG. 25  and  FIG. 26 , the second swaying pivot  8  and the third swaying pivot  9  can be also extended, and the second swaying pivot  8  can be connected with the third swaying pivot  9  by a seat enhancement accessory of the seat support  6 . At a same time, a hook  38   b  is formed on the seat shell  38 , to hook at the first swaying pivot  8  and the third swaying pivot  9 , thereby assembling the seat shell  38  at the seat support  6 . 
     The present invention is provided with following advantages:
         1. At the stage that the back starts to be tilted, the operation that the seat rises significantly and then rises slightly can be prevented. As a result, the condition that the back is easy to be tilted by the quick weakening of the counter force after the back is tilted from a certain extent can be avoided, thereby improving the comfortableness in using the chair. Besides, by using the sliding structure to guide the third swaying pivot, the chair can be constructed simply to reduce the manufacturing cost.   2. The sliding structure guides the second swaying pivot in a straight line or to be protruded out of the circular arc at the underside. As a result, at the moment that the back is tilted rearwards, the rising of the seat will be equalized as shown by the curve A in  FIG. 27 , or be enlarged gradually as shown by the curve B in  FIG. 27 . As a result, almost the equalized counter force can be acquired disregarding the rearward tilt angle as shown by the curve A in  FIG. 28 . On the other hand, as shown by the curve B in  FIG. 28 , when the rearward tilt angle of the back increases, the counter force can be changed. Therefore, when the occupant reclines on the back to tilt the back rearwards, a constant counter force can be maintained, or a proper counter force can be maintained depending on the angle of the back, thereby improving the comfortableness while being seated.   3. The chair of the present invention is provided with the elastic deformation part that absorbs the relative displacement between the operating structure and the swaying unit to accumulate as energy. As a result, when the sway of the swaying unit is restricted, the swaying unit will not sway reluctantly, thereby preventing the structures from being damaged. In addition, even that the swaying unit cannot sway; the operation can be still conducted through the operating structure. Under the condition that the swaying unit cannot sway, the operating structure is controlled and when the swaying unit can sway, it will sway automatically. Therefore, the operation of the operating structure can be conducted without needing to care whether the back is tilted rearwards, and the chair can be used more freely.       

     It is of course to be understood that the embodiments described herein is merely illustrative of the principles of the invention and that a wide variety of modifications thereto may be effected by persons skilled in the art without departing from the spirit and scope of the invention as set forth in the following claims.