Back construction for seating unit

Abstract

A chair includes a base having a control assembly operably supporting a seat assembly and also a back assembly for movement about a seat tilt axis and a back tilt axis, respectively. The back assembly includes a flexible sheet supported at upper/outer corners by a back support structure and hanging downwardly. The flexible sheet includes a lower portion coupled to the back support structure by a tensioner for holding the lower portion rearwardly. A vertically-adjustable lumbar mechanism is adjustably supported on the back support structure and operably engages the flexible sheet for flexing a lumbar area of the flexible sheet forwardly to provide an optimal ergonomic horizontal and vertical convex shape for postural lumbar support.

1 . A seating unit comprising: 
 a base including a control;    a backrest assembly pivotally attached to the control for movement between upright and reclined positions, the backrest assembly including a support component with an upper connecting member; and    a seat operably supported on the control for synchronous movement during movement of the backrest assembly between the upright and reclined positions;    the backrest assembly further including a back shell having an upper region, a lumbar region disposed below the upper region, and a lower region disposed below the lumbar region, the back shell being attached at a location above the lumbar region to the upper connecting member, the back shell further having an array of elongated openings through the back shell, some of the openings being positioned in the upper region and some of the openings being positioned in at least one of the other regions, a length of the openings in the upper region on average being shorter than an average length of the openings in the other region.    
   
   
       2 . The seating unit defined in  claim 1 , wherein the lumbar and lower regions both include openings.  
   
   
       3 . The seating unit defined in  claim 2 , wherein the openings in the upper, lumbar and lower regions each define a different pattern.  
   
   
       4 . The seating unit defined in  claim 2 , wherein the openings in the lower region are longer on average than the openings in the lumbar region.  
   
   
       5 . The seating unit defined in  claim 1 , wherein the back shell includes a flexible deformable flat sheet that includes the upper, lumbar, and lower regions,  
   
   
       6 . The seating unit defined in  claim 1 , wherein at least some of the openings in the upper and other regions include slots.  
   
   
       7 . The seating unit defined in  claim 1 , wherein the support component comprises a spine component.  
   
   
       8 . A backrest comprising: 
 a back shell with a surface configured and adapted to support a seated person; the back shell having an upper region, a lumbar region disposed below the upper region, and a lower region disposed below the lumbar region; the back shell including at least one upper connector located in the upper region that is adapted to support the back shell, the back shell including an array of first openings through the back shell in the upper region and including an array of additional openings in at least one of the other regions, with an average length of the first openings being shorter than an average length of the additional openings in the other region, at least the additional openings being elongated and providing flexibility to the back shell in the one region.    
   
   
       9 . The backrest defined in  claim 8 , wherein the lumbar and lower regions both include openings.  
   
   
       10 . The backrest defined in  claim 9 , wherein the openings in the upper, lumbar and lower regions each define a different pattern.  
   
   
       11 . The backrest defined in  claim 9 , wherein the openings in the lower region are longer on average than the openings in the lumbar region.  
   
   
       12 . The backrest defined in  claim 8 , wherein the back shell includes a flexible deformable flat sheet that includes the upper, lumbar, and lower regions,  
   
   
       13 . The backrest defined in  claim 8 , wherein at least some of the openings in the upper and other regions include slots.  
   
   
       14 . The backrest defined in  claim 8 , including a support component connected to the at least one upper connector.  
   
   
       15 . The backrest defined in  claim 14 , wherein the support component includes a spine component extending vertically parallel a central location on the back shell.  
   
   
       16 . A back shell comprising: 
 a polymeric component with a sheet portion having a front surface configured and adapted to support a seated person; the sheet portion having an upper region, a lumbar region disposed below the upper region, and a lower region disposed below the lumbar region; the sheet portion including an array of first, second, and third openings through the sheet portion in the upper, lumbar and lower regions, respectively, with an average length of the first openings being shorter than an average length of the second and being shorter than an average length of the third openings, at least the second openings being elongated and providing flexibility to the polymeric component in the lumbar region.    
   
   
       17 . The back shell defined in  claim 16 , wherein at least some of the first, second, and third openings include slots.  
   
   
       18 . The back shell defined in  claim 17 , wherein at least some of the slots extend at an angle to vertical.