Patent ID: 7011374

Claim:
A seat device for a chair, comprising: at least two outer sheet layers made of a stretchable elastic textile material, each of said outer sheet layers having a first marginal part surrounding substantially an entire area of a corresponding one of said outer sheet layers; an inner sheet layer of a textile material sandwiched by said outer sheet layers and having a second marginal part surrounding substantially an entire area of said inner sheet layer, said second marginal part being secured to said first marginal parts; and an attachment member associated with said first and second marginal parts and being adapted to be mounted on the chair; said entire area of said inner sheet layer being larger than said entire area of a respective one of said outer sheet layers so that said inner sheet layer creases when said outer sheet layers lay flat, said inner and outer sheet layers forming a concaved configuration when a pressure is exerted on said inner and outer sheet layers along a direction transverse to said inner and outer sheet layers; wherein said textile material of said inner sheet layer includes polyethylene terephthalate fibers.