Patent ID: 7588297

Claim:
A support diaphragm for a backrest of a chair, comprising: a support frame including laterally spaced first and second support portions; a support material including a flexible sheet extending from and generally tensioned between the first support portion and the second support portion to form a front portion, and extending from and generally tensioned between the first support portion and the second support portion to form a back portion spaced from and in underlying relationship to the front portion, the front portion being configured as a backrest including a lumbar area fabricated from a generally non-stretchable material and a remaining area of the front portion fabricated from a generally stretchable material; and a strut coupled at a first lateral end to the front portion of the support material and coupled at a second lateral end to the back portion of the support material, the strut lengthwise extending along the support material in at least one predetermined direction relative to a direction of tension in the support material, the strut being configured to provide generally no resistance to movement of the front portion and the back portion toward each other when pressure is applied to the front portion, and a width of the strut between the first lateral end and the second lateral end being configured to provide a desired amount of contouring of the front portion of the support material.