Seating unit with auxetic user support

Abstract

A seating unit includes a generally horizontal seat portion and a generally upright back portion. The back portion includes a flexible membrane or mesh extending in first and second directions. The mesh defines a generally upright user support surface. At least a portion of the mesh comprises an auxetic material having a negative Poisson's ratio whereby stretching of the auxetic portion of the mesh in at least one of the first and second directions causes the mesh to expand in the other of the first and second directions.

The invention claimed is: 
     
         1 . A seating unit comprising:
 a lower portion that is configured to support the seating unit;   a seating structure supported by the lower portion, wherein the seating structure includes a generally horizontal seat portion and a generally upright back portion, wherein at least one of the seat portion and the back portion includes frame portions defining a space therebetween and a flexible polymer membrane extending in first and second directions across the space, and wherein the polymer membrane is connected to the frame portions to define a user support surface, wherein at least a portion of the polymer membrane comprises an auxetic material having a negative Poisson's ratio whereby stretching of the auxetic portion of the polymer membrane in at least one of the first and second directions tends to cause the polymer membrane to expand in the other of the first and second directions.   
     
     
         2 . The seating unit of  claim 1 , wherein:
 the user support surface defines opposite edge portions adjacent to the frame portions, and at least one high pressure region that is spaced apart from the opposite edge portions, and wherein the polymer membrane is significantly more flexible at the high pressure region than it is at the opposite edge portions of the user support surface.   
     
     
         3 . The seating unit of  claim 2 , wherein:
 the polymer membrane defines a region outside of the high pressure region having a first thickness, and a second thickness in the high pressure region that is significantly less than the first thickness.   
     
     
         4 . The seating unit of  claim 2 , wherein:
 the polymer membrane comprises a polymer mesh having a plurality of links that are interconnected to form a pattern extending radially outwardly in a plurality of radial directions from a central portion of the high pressure region, and wherein stretching of the polymer mesh in the radial directions or in directions transverse to the radial directions tends to cause expansion of the polymer mesh in the other of the radial directions and the directions that are transverse to the radial directions.   
     
     
         5 . The seating unit of  claim 2 , wherein:
 the polymer membrane comprises a mesh having a plurality of links that are interconnected to form a pattern, and wherein the pattern is non-uniform to provide increased flexibility in the high pressure region.   
     
     
         6 . The seating unit of  claim 1 , wherein:
 the polymer membrane comprises a mesh having a central portion including a plurality of openings defining a plurality of auxetic cells;   the polymer membrane includes an integral ring having an outer perimeter and an inner boundary adjacent outermost ones of the openings defining the auxetic cells, wherein the ring defines a width between the outer perimeter and the inner boundary, and wherein the width is non-uniform.   
     
     
         7 . The seating unit of  claim 1 , wherein:
 the flexible polymer membrane comprises polypropylene.   
     
     
         8 . The seating unit of  claim 1 , wherein:
 the frame portions comprise polymer material that is integrally formed with the polymer membrane, and wherein the frame portions are significantly thicker than the polymer membrane and have significantly greater stiffness than the polymer membrane.   
     
     
         9 . The seating unit of  claim 1 , wherein:
 the frame portions are generally upright to define a back frame;   the back frame includes transverse upper and lower frame portions extending between and interconnecting the upright frame portions to form a perimeter frame defining a central opening; and wherein:   the flexible polymer membrane includes an upper edge that is spaced apart from the upper frame portion to define a gap therebetween.   
     
     
         10 . The seating unit of  claim 1 , wherein:
 the frame portions include first connecting structures; and wherein:   the flexible polymer membrane includes integrally formed second connecting structures that engage the first connecting structures and connect the polymer membrane to the frame portions.   
     
     
         11 . The seating unit of  claim 1 , wherein:
 the polymer membrane defines a user support face comprising a plurality of spaced apart support members that are interconnected by folded sheet portions configured to provide an auxetic material.   
     
     
         12 . A user support structure comprising:
 a flexible membrane defining front and rear faces and opposite edge portions, the flexible membrane including a high pressure region that is configured to support portions of a user's body when a user's body comes into contact with the high pressure region of the flexible membrane, the flexible membrane defining a lower pressure region adjacent the high pressure region, and wherein the high pressure region and the lower pressure region comprise auxetic material whereby stretching of the flexible membrane in a first direction tends to cause the material to expand in a second direction that is transverse to the first direction and wherein the flexible membrane is significantly more compliant in the high pressure region than the lower pressure region in response to a force that is applied to the front face of the flexible membrane.   
     
     
         13 . The user support structure of  claim 12 , including:
 a pair of spaced apart frame portions extending along the opposite edge portions of the flexible membrane, and wherein the opposite edge portions of the membrane are connected to the frame portions.   
     
     
         14 . The user support structure of  claim 13 , wherein:
 the frame portions extend horizontally and at least a portion of the front face of the flexible membrane faces upwardly to define a seat surface.   
     
     
         15 . The user support structure of  claim 13 , wherein:
 the frame portions extend upwardly and at least a portion of the front face of the flexible membrane faces forwardly to define a back support surface.   
     
     
         16 . The user support structure of  claim 12 , wherein:
 the flexible membrane comprises a polymer mesh.   
     
     
         17 . The user support structure of  claim 16 , wherein:
 the flexible membrane comprises an integrally formed polymer ring defining an outer peripheral edge of the flexible membrane.   
     
     
         18 . The user support structure of  claim 12 , wherein:
 the flexible membrane comprises a plurality of spaced apart support members that are interconnected by folded sheet portions configured to provide an auxetic material.   
     
     
         19 . A user support comprising:
 a polymer mesh including a plurality of links forming interconnected auxetic cells, each auxetic cell having a length defined along a first cell axis and a width defined along a second cell axis that is transverse to the first cell axis, and wherein each auxetic cell comprises a plurality of interconnected flexible links configured such that stretching of the auxetic cells along the length of the auxetic cells causes the width of the auxetic cells to increase, and wherein a plurality of the auxetic cells are arranged about a center in a generally circular pattern to provide a region having increased compliance.   
     
     
         20 . The user support of  claim 19 , wherein:
 the polymer mesh comprises polypropylene.