Knit seat back for an office chair

Abstract

A seat back for an office chair includes a knit material for extending over a structural frame. The knit material can be formed in a single knitting operation to include cushioning characteristics that vary across different regions of the knit material. The knit material may be a weft knit material having a first layer, a second layer, and a third layer, wherein the third layer is inlayed between the first and second layers and the inlay material is different from at least the first and second layers and provides a degree of cushioning between the first and second layers. The first and second layers are knit according to a predetermined pattern, the predetermined pattern determining crossing lines where the first and second layers cross one another and fix the third layer in position with respect to the first and second layers. The predetermined pattern is differentiated between regions of the back support, such that a first region of the back support has a higher density of crossing lines than a second region of the back support, the first region providing a different degree of cushioning than the second region.

1 . A seat back for a chair, comprising:
 a back frame; and   a weft knit material attached to the back frame, the weft knit material and back frame together forming a back support for a user, the knit material having a first layer formed from a first material, a second layer formed of a second material, and a third layer formed of a third material;   wherein the third layer is inlayed between the first and second layers;   wherein the first and second layers are knit according to a predetermined pattern, the predetermined pattern determining crossing lines where the first and second layers cross one another and tack the third layer in position with respect to the first and second layers;   wherein the predetermined pattern is differentiated between regions of the back support, such that a first region of the back support has a higher density of crossing lines than a second region of the back support, the first region providing a greater degree of support than the second region due to the higher density of crossing lines in the first region, and the second region providing a greater degree of cushioning than the first region due to the lower density of crossing lines in the second region.   
     
     
         2 . The seat back of  claim 1  wherein the first and second layers are the same material and the third layer is formed of a different material. 
     
     
         3 . The seat back of  claim 2  wherein, when the materials of the first, second and third layers are in an unstretched and unwoven state, the third layer has a thickness that is greater than the thickness of the first and second layers. 
     
     
         4 . The seat back of  claim 3  wherein the first region, with a higher density of crossing lines and a greater degree of support, is a lumbar region and the second region, with a lower density of crossing lines and a greater degree of cushions, is a thoracic region. 
     
     
         5 . The seat back of  claim 4  wherein the seat back includes a third region that is a shoulder region, the third region having a lower density of crossing lines than the second region. 
     
     
         6 . The seat back of  claim 5  wherein the predetermined pattern includes formation of a closed pattern in the lumbar region, the closed patterns interfitted with each other and defined by the crossing lines. 
     
     
         7 . The seat back of  claim 6  wherein the predetermined pattern includes the formation of a partially defined one of the closed patterns in the thoracic region. 
     
     
         8 . The seat back of  claim 7  wherein the predetermined pattern includes the formation of a partially defined one of the closed patterns in the shoulder region, wherein the partially defined closed pattern in the shoulder region is less defined than that of the thoracic region. 
     
     
         9 . The seat back of  claim 8  wherein the back support has an upper edge and a lower edge, and the back support defines a height between the upper and lower edges, wherein the first region, second region and third region each comprise about one-third of the height of the back support. 
     
     
         10 . The seat back of  claim 1  wherein the predetermined pattern gradually transitions from region to region. 
     
     
         11 . An office-type chair, comprising:
 a ground engaging base;   a height adjustable pedestal extending upwardly from the base;   a seat supported on the pedestal and forming a surface for supporting a user seated on the chair;   an upright back frame supported on one of the seat and the pedestal, the back frame extending upwardly from the seat;   a weft knit back support attached to the back frame and including a lower edge adjacent the seat, an upper edge opposite the lower edge, and a pair of lateral side edges, wherein the back support includes a forward layer formed of a first yarn, the forward layer facing the user, a rear layer formed of a second yarn, the rear layer opposite the forward layer, and an inlay between the forward layer and the rear layer;   wherein the forward layer and rear layer are knit with a predetermined pattern defined by cross points of the first and second yarns where the forward layer and rear layer are looped with one another and pinch the inlay to hold the inlay in place with respect to the forward and rear layers, wherein at the crossing points the inlay is flattened from a first inlay thickness to a second, narrower inlay thickness;   wherein the back support includes a first region and a second region, the first and second regions each located in positions associated with a particular position on the back of a user, the first region having an increase density of cross points than the second region to provide differentiation in cushioning between the first and second regions due to the reduced density of crossing points providing reduced flattening of the inlay within the second region.   
     
     
         12 . The chair of  claim 11  wherein the density of cross points decreases from the lower edge toward the upper edge. 
     
     
         13 . The chair of  claim 12  wherein the first and second yarns are formed from a first material and the inlay is formed from a second material. 
     
     
         14 . The chair of  claim 13  wherein the inlay is formed from at least one of: polyester, cotton, elastane, rayon, wool and nylon. 
     
     
         15 . The chair of  claim 14  wherein the predetermined pattern in the first region includes a series of adjacent generally closed shapes outlined by cross points. 
     
     
         16 . The chair of  claim 15  wherein the predetermined pattern in the second region includes a series of partially closed shapes. 
     
     
         17 . The chair of  claim 16  wherein the back support includes a third region including a series of partially closed shapes formed by the cross points. 
     
     
         18 . The chair of  claim 17  wherein the predetermined pattern gradually transitions from the generally closed shapes in the first region to the partially closed shapes in the second region. 
     
     
         19 . The chair of  claim 18  wherein the predetermined pattern extends substantially from the first lateral edge to the second lateral edge in each of the regions. 
     
     
         20 . A back support for an office type chair, comprising:
 a back support frame;   a first woven material attached to the back support frame; and   a second material woven with the first material as an inlay within the first material;   wherein the first and second materials are woven according to a predetermined knit pattern using a weft knitting process to form a first layer and a second layer of the first material, the first layer and the second layer crossing one another at cross points, the second material inlayed between the first and second layers such that it is held in position with respect to the first material at the cross points;   wherein the knitting program differentiates the number of cross points by at least a first region and a second region in order to provide cushioning levels that vary by region across the back support.