Patent Publication Number: US-11382429-B2

Title: Backrest and chair

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is the U.S. national phase under 35 U.S.C. § 371 of International Application No. PCT/JP2019/021333 filed May 29, 2019, and further claims priority to Japanese Patent Application No. 2018-103537 filed May 30, 2018 wherein the entire disclosures of the foregoing applications are hereby incorporated by reference herein. 
     TECHNICAL FIELD 
     The present disclosure relates to a chair with a backrest. 
     BACKGROUND ART 
     There are conventional chairs configured to be stackable or nestable. In some cases, a backrest has a reduced thickness in a front-rear direction, in order to reduce a gap in the front-rear direction between chairs when the chairs are stacked. Patent Document 1 below discloses a backrest configured with a relatively thick frame and relatively thin plate-shaped members arranged within the frame. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: Japanese Unexamined Patent Application Publication No. 2010-51384 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In a backrest with a thick frame as disclosed in aforementioned Patent Document 1, the frame is likely to have a low flexibility. In particular, since left and right corners of the backrest are less likely to follow body movement, a seated person&#39;s action of turning around while keeping seated or stretching out the left or right hand rearward may be hindered. 
     In one aspect of the present disclosure, it is preferable to propose a backrest that is less likely to obstruct body movement. 
     Means for Solving the Problems 
     One aspect of the present disclosure provides a backrest for use in a chair, and comprises a back board arranged in a position to abut a back of a seated person on the chair. A first area including a laterally central area of the back board has a thickness greater than a thickness of a second area of the back board located closer to each of left and right ends than the first area. 
     This configuration allows the second area to be relatively deformable. Accordingly, particularly when a seated person turns the body rearward, movement of the seated person is less likely to be obstructed by the backrest. Also, when the seated person is seated in a normal posture (a posture of facing forward), the back can be supported by the first area having a relatively high rigidity. 
     In the above-described backrest, the back board may comprise a region having a thickness that gradually decreases upward. With this configuration, the back board becomes more deformable as a position becomes upper, and the backrest is less likely to obstruct movement of the body. 
     Also, in the above-described backrest, the back board may comprise a high rigidity portion provided at least in a lower area from a vertical center position at each of the left and right ends of the back board. The high rigidity portion has a rigidity higher than that of a surrounding area of the high rigidity portion in the back board. With this configuration, a lower portion of the backrest can securely support the backrest. Also, an upper portion of the backrest having high flexibility is less likely to obstruct movement of the body. 
     In the above-described backrest, the backrest may be connected to a seat body of the chair or a support body supporting the seat body by a connecting portion. The connecting portion may be connected to the first area in the backrest. With this configuration, connection with the seat body or the like is achieved using the first area having a relatively high rigidity, and thus the backrest can be held stably. 
     In the above-described backrest, at least the second area may comprise a flexible structure to improve flexibility of the back board. The first area may comprise no flexible structure. With this configuration, it is possible to achieve an increased flexibility of the second area, while inhibiting decrease in rigidity of the first area. 
     In the above-described backrest, the back board may comprise a projecting portion projecting rearward at an upper end of the back board. With this configuration, it is possible to hold the projecting portion to carry the backrest (and thus, the chair). 
     In the above-described backrest, the back board may comprise an area having a thickness gradually decreasing from a lateral center of the back board toward the left and right ends. With this configuration, the flexibility of the back board gradually changes toward the left and right ends of the back board. Accordingly, it is possible to reduce an uncomfortable feeling that may be caused to a seated person due to abrupt changes in flexibility of the back board. 
     In the above-described backrest, at least a part in a vertical direction of each of the left and right ends of the back board may be a portion having a smallest thickness at a same height of the back board. This configuration can achieve increased flexibility at the ends of the back board. 
     A main part of the above-described back board may be formed from a material that is a thermoplastic elastomer or a mixture including a thermoplastic elastomer. This configuration can achieve increased flexibility at the ends of the back board. 
     Another aspect of the present disclosure provides a chair that comprises the above-described backrest. Such chair can achieve the effects brought by the above-described backrest. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a front side perspective view of a chair of an embodiment. 
         FIG. 1B  is a rear side perspective view of the chair of the embodiment. 
         FIG. 2A  is a front view of the chair of the embodiment. 
         FIG. 2B  is a side view of the chair of the embodiment. 
         FIG. 2C  is a rear view of the chair of the embodiment. 
         FIG. 2D  is a plan view of the chair of the embodiment. 
         FIG. 2E  is a bottom view of the chair of the embodiment. 
         FIG. 3A  is a rear view of a backrest of the embodiment. 
         FIG. 3B  is a side view of the chair of the embodiment. 
         FIG. 3C  is a plan view of the backrest of the embodiment. 
         FIG. 4A  is a IVA-IVA sectional view of  FIG. 3B . 
         FIG. 4B  is a IVB-IVB sectional view of  FIG. 3B . 
         FIG. 5  is a V-V sectional view of  FIG. 2A . 
         FIG. 6A  is a front view showing a variation of the backrest. 
         FIG. 6B  is a VIB-VIB sectional view of  FIG. 6A . 
         FIG. 7  is a front view showing a variation of the backrest. 
         FIG. 8  is a front view showing a variation of the backrest. 
         FIG. 9A  is a front view showing a variation of the backrest. 
         FIG. 9B  is a IXB-IXB sectional view of  FIG. 9A . 
         FIG. 9C  is a sectional view showing another variation. 
         FIG. 10  is a front view showing a variation of the backrest. 
     
    
    
     EXPLANATION OF REFERENCE NUMERALS 
     
         
         
           
               1  . . . chair,  11  . . . support body,  13  . . . seat body,  15  . . . backrest,  31  . . . pipe body,  32  . . . front side connector,  33  . . . rear side connector,  35  . . . connecting portion,  41  . . . back board,  42  . . . pipe holder,  43  . . . projecting portion,  44  . . . bent portion,  51  . . . first area,  52  . . . second area,  53  . . . thinnest portion,  101  . . . backrest,  103  . . . first area,  105  . . . second area,  111  . . . backrest,  113  . . . high rigidity portion,  121  . . . backrest,  123  . . . first area,  125  . . . second area,  127  . . . connecting portion,  131  . . . backrest,  133  . . . back board,  135  . . . first area,  137  . . . second area,  139  . . . through hole,  141  . . . dimple,  151  . . . backrest,  153  . . . back board,  155  . . . first area,  157  . . . second area,  159  . . . slit 
           
         
       
    
     MODE FOR CARRYING OUT THE INVENTION 
     A description will be given of embodiments of the present disclosure with reference to the drawings. 
     1. Embodiment 
     1-1. Overall Configuration 
     As shown in  FIG. 1A  to  FIG. 2E , a chair  1  comprises a support body  11 , a seat body  13 , a backrest  15 , and other components. 
     In the present embodiment, configurations of respective components may be described using directions, such as a front-rear direction, a left-right (lateral) direction, and an up-down (vertical) direction, and these directions are indicated with respect to a user who is normally seated on the chair  1 . That is, front is a direction that the seated user faces. The chair  1  is left-right symmetric. 
     The support body  11  comprises paired left and right pipe bodies  31  each formed by bending a tubular metal pipe, and bar-shaped front side connector  32  and rear side connector  33  each connecting the paired pipe bodies  31 . The paired pipe bodies  31  each form a substantially rectangular ring shape when viewed from left or right side. The seat body  13  is supported by upper ends of the paired pipe bodies  31  and the rear side connector  33 . 
     The seat body  13  is substantially rectangular when seen in a plan view, and is configured to allow a user to be seated thereon. Left and right ends, and a rear end of the seat body  13  are connected to the respective upper ends of the paired pipe bodies  31  and the rear side connector  33 , and thereby the seat body  13  is fixed to the support body  11 . 
     Each of the paired pipe bodies  31  comprises a connecting portion  35  that deviates from the rectangular ring shape and projects upward from a portion connecting with the rear side connector  33 . The backrest  15  is connected to the support body  11  by the left and right connecting portions  35 , and thereby secured to the support body  11  through the left and right connecting portions  35 . 
     1-2. Configuration of Backrest 
     As shown in  FIG. 3A  to  FIG. 3C , the backrest  15  for use in a chair is substantially rectangular in a front view. Also, when viewed in a plan view, the backrest  15  forms a gentle curve such that both of left and right ends are positioned forward and a central part positioned rearward. 
     The backrest  15  comprises a back board  41 , paired pipe holders  42 , a projecting portion  43 , and a bent portion  44 . The back board  41  has a substantially rectangular shape. The paired pipe holders  42  are provided at left and right ends of the back board. The projecting portion  43  is provided at an upper end of the back board. The bent portion  44  is provided at a lower end of the back board. 
     The back board  41  is arranged in a position to abut the back of a seated person on the chair  1 . 
     A laterally central area of the back board  41  is a first area  51 , and areas located closer to the left and right ends of the back board  41  than the first area  51  are second areas  52 . As shown in  FIG. 4A  and  FIG. 4B , the first area  51  has a thickness L 1  greater than a thickness L 2  of the second area  52 . Also, as shown in  FIG. 4A , an upper area in a vertical direction of each of the left and right ends of the back board  41  is a thinnest portion  53  having a smallest thickness at a same height of the back board  41 . 
     More specifically, the thickness of the back board  41  gradually decreases from a lateral center of the back board  41  toward the left and right ends except for areas where the pipe holders  42  are formed. In other words, the thickness of the first area  51  is greater than the thickness of the second area  52 , and the thickness also varies within each of the first area  51  and the second area  52  depending on a lateral position therein. 
     A material for a main part of the back board  41  is a thermoplastic elastomer. The material for forming the back board  41  may be a mixture including a thermoplastic elastomer. 
     As shown in  FIG. 5 , the back board  41  has a thickness greatest at a lower end and gradually decreasing upward. As shown in  FIG. 5 , the thickness of the back board  41  decreases upward at any position along the lateral direction. 
     The paired pipe holders  42  are provided at the left and right ends of the back board  41  in a lower area from a vertical center position. The paired pipe holders  42  each have a greater thickness than a surrounding area, and protrude rearward from the back board  41 . The connecting portion  35  is inserted in each of the paired pipe holders  42 . Thus, the paired pipe holders  42  each have a higher rigidity than the surrounding area of the pipe holder  42  in the back board  41 . The paired pipe holders  42  each correspond to a high rigidity portion. 
     The projecting portion  43  is a plate-shaped portion projecting rearward across an entire laterally extending area of the upper end of the back board  41 . The bent portion  44  is a plate-shaped member projecting rearward across an entire laterally extending area of the lower end of the back board  41 . 
     1-3. Effects 
     According to the embodiment detailed above, the following effects can be obtained. 
     (1a) In the chair  1 , the second area  52  of the back board  41  is relatively more deformable than the first area  51 . Thus, for example, as indicated by two-dotted chain lines in  FIG. 3C , end portions of the back board  41  are easily elastically deformable rearward. Accordingly, for example, when a seated person turns the body rearward, movement of the seated person is less likely to be obstructed. Also, when the seated person faces forward, the first area  51  having a high rigidity sufficiently supports the back, and thus, it is possible to reduce impairment of the function of the backrest due to excessive flexibility of the backrest. 
     (1b) Since the back board  41  gradually becomes thinner upward, an upper part of the back board  41  has a relatively high flexibility. Accordingly, when a seated person moves the body, obstruction of the movement by the back board  41  can be significantly reduced. 
     (1c) The backrest  15  comprises the pipe holders  42  at two left and right positions of its lower end. The pipe holders  42  have high rigidity, and thus, provide high rigidity of a lower part of the backrest  15  that provides small influence on movements of a seated person, thereby allowing inhibition of unnecessary flexibility of the backrest  15 . 
     (1d) The backrest  15  comprises the projecting portion  43  and the bent portion  44 , and thus can inhibit deformation of the shape of the backrest  15  caused by an excessive reduction in rigidity of the backrest  15 . The backrest  15  is formed from a material containing an elastomer, and thus has a high flexibility. Even in this case, the projecting portion  43  and the bent portion  44  sufficiently achieve maintenance of the shape. 
     (1e) Since the backrest  15  comprises the projecting portion  43 , the projecting portion  43  can be used as a handhold for carrying the chair  1 . Particularly, it is useful when carrying a relatively light chair, such as a stacking chair and a pipe chair. 
     (1f) Since the thickness of the back board  41  gradually decreases from the lateral center of the back board  41  toward the left and right ends, it is possible to reduce an uncomfortable feeling caused to a seated person due to abrupt changes in flexibility of the back board  41 . Also, it is possible to inhibit concentration of stress at one place when a load is applied to the back board  41 , and thus to inhibit breakage of the back board  41 . 
     The phrase “the thickness gradually decreases” herein does not only mean smooth changes in thickness, but also includes multiple stepwise changes, for example, at three or more levels. Also, in some of the entire area, there may be an area with no change in thickness or an area having a locally large thickness. 
     (1g) The upper area above each of the paired pipe holders  42  at the left and right ends of the backrest  15  is the thinnest portion  53  having the smallest thickness at the same height. Since the left and right ends of the back board  41  do not have high rigidity as described above, reduction in flexibility at the both ends of the backrest  15  can be inhibited. 
     2. Other Embodiments 
     Although an embodiment of the present disclosure has been described above, it is to be understood that the present disclosure is not limited to the above-described embodiment, but may be in various forms within the technical scope of the present disclosure. 
     (2a) A specific configuration of the backrest is not limited to the configuration shown in the above-described embodiment. For example, the backrest is not required to be rectangular. Various shapes, such as a rounded shape, and a bilaterally asymmetric shape, may be employed for the backrest. Also, there is no limitation to the configuration of the projecting portion  43  or the bent portion  44 . For example, respective arrangement positions, projecting amounts, thicknesses, widths, etc. of the projecting portion  43  and the bent portion  44  may be specified optionally. Further, the backrest  15  may include one or none of the projecting portion  43  and the bent portion  44 . 
     (2b) In the above-described embodiment, an example configuration is shown in which the thickness of the back board  41  gradually decreases toward the left and right ends. However, there is no particular limitation to the specific configuration of the back board that includes the second area thinner than the first area. For example, there is no particular limitation to a specific size of the first area as long as the first area includes a laterally central area of the back board. The first area may be a relatively small area in a vicinity of the laterally central area. Also, there is no particular limitation to size of the second area, as long as the second area is located closer to each of the left and right ends than the first area. As in a backrest  101  shown in  FIG. 6A  to  FIG. 6B , a first area  103  and a second area  105  may have respective fixed thicknesses. Between the first area and the second area, there may be an area having a thickness greater or smaller than the thicknesses of the first area and the second area. The configuration of the back board may be such that the thickness decreases toward the left and right ends in a stepwise manner. The configuration may be such that the thickness of the back board gradually decreases across the back board along the lateral direction, or the configuration may be such that the thickness of the back board gradually decreases in a part of the back board along the lateral direction. 
     Further, the first area and the second area may cover the entire area of the back board in the vertical direction, or may cover a part of the area of the back board in the vertical direction. For example, the first area and the second area may cover a range except for an upper end portion and a lower end portion of the back board. 
     (2c) In the above-described embodiment, an example configuration is shown in which the thickness of the entire back board  41  gradually decreases upward. However, the back board need not be configured in such a manner across the entire area in the vertical direction as long as the back board includes a region in which the thickness gradually decreases upward. For example, the back board may include the aforementioned configuration in some part along the lateral direction of the back board, or may include the aforementioned configuration in some part along the vertical direction of the back board. In this regard, if at least the second area includes the aforementioned configuration, an effect can be obtained that obstruction of movement of a seated person is reduced. Further, the back board need not include a region in which the thickness gradually changes in the vertical direction. 
     (2d) In the above-described embodiment, an example configuration is shown in which the paired pipe holders  42  are provided, each as a high rigidity portion, from the lower end to the center. However, the configuration of the high rigidity portion is not limited to that in the above-described embodiment. For example, there is no particular limitation to a specific configuration of the high rigidity portion as long as the rigidity is higher than that of the surroundings. Specifically, the high rigidity portion may have a thickness greater than the surroundings. The high rigidity portion may be configured with a member having a rigidity higher than that of the surroundings of the high rigidity portion, or may include a member having a rigidity higher than that of the surroundings of the high rigidity portion. 
     The high rigidity portion may be provided at least in respective lower areas of at least the left and right ends of the back board. For example, as a backrest  111  shown in  FIG. 7 , high rigidity portions  113  may be provided in positions apart from respective lower ends of the left and right ends. In certain embodiments, as further shown in  FIG. 7 , upper areas from the vertical center of each of the left and right ends of the back board are reduced thickness portions  53  having the smallest thickness at a same (i.e., selected) height of the back board. Also, the high rigidity portions may be provided at respective upper areas of the left and right ends of the back board. Further, no high rigidity portions need to be provided at both ends in the lateral direction. 
     (2e) In the above-described embodiment, an example configuration is shown in which the connecting portion  35  is provided at each of the left and right ends of the back board. However, the position where the connecting portion is provided in the back board need not be located at the left and right ends. For example, as a backrest  121  shown in  FIG. 8 , a connecting portion  127  may be connected not to a second area  125  but to a first area  123 . 
     Also, the connecting portion may be connected to the seat body of the chair or the support body supporting the seat body. Further, the backrest and the seat body, or the backrest and the support body may be connected through another member along with the connecting portion. In other words, the connecting portion is a component to define a positional relationship between the seat body and the backrest of the chair. 
     (2f) The back board may comprise a flexible structure to achieve an improved flexibility. A configuration may be such that the flexible structure is provided in the second area and not provided in the first area. For example, a backrest  131  shown in  FIG. 9A  to  FIG. 9B  comprises through-holes  139  penetrating from a front surface to a rear surface of a back board  133  at least in a second area  137 . On the other hand, no through-hole is formed in a first area  135 . With this configuration of the back board, an improved flexibility of the second area  137  can be achieved by the through holes, and reduction in rigidity of the first area  135  can be inhibited. Also, since there is no through-hole in the first area  135  that is likely to abut a back in an ordinary posture, it is possible to inhibit a seated person from having an uncomfortable feeling by through-holes. It may be configured such that a hole diameter of the through hole  139  becomes smaller as the through hole  139  is positioned closer to a lateral outer side. It may be configured such that the hole diameter of the through hole  139  becomes smaller as the through hole  139  is positioned closer to a vertical upper side. Alternatively, it may be configured such that the hole diameter of the through hole  139  becomes larger as the through hole  139  is positioned closer to the lateral outer side. It may be configured such that the hole diameter of the through hole  139  becomes larger as the through hole  139  is positioned closer to the vertical upper side. 
     Further, as shown in  FIG. 9C , dimples  141  may be formed in place of the through hole  139 . In this case, it may be configured such that the dimple  141  becomes smaller as the dimple  141  is positioned closer to the lateral outer side. It may be configured such that the dimple  141  becomes smaller as the dimple  141  is positioned closer to the vertical upper side. Alternatively, it may be configured such that the dimple  141  becomes larger as the dimple  141  is positioned closer to the lateral outer side. It may be configured such that the dimple  141  becomes larger as the dimple  141  is positioned closer to the vertical upper side. 
     Moreover, as a backrest  151  shown in  FIG. 10 , at least a second area  157  may comprise slits  159  penetrating from a front surface to a rear surface of a back board  153 . A first area  155  need not comprise any slits. 
     (2g) In the above-described embodiment, an example configuration is shown in which the upper area from the vertical center of each of the left and right ends the back board is the thinnest portion  53  having the smallest thickness at the same height of the back board. However, the position of the thinnest portion  53  is not limited to the position in the embodiment, but may be at least any vertical part of the left and right ends of the back board to achieve flexibility in a periphery of the back board. Also, the thinnest portion  53  need not be provided to the backrest.