A structural support shell for a tilt-back chair has a back portion, a seat portion, and a flexible compression zone extending between the back and seat portions in an integrally molded, one-piece unit. The chair has a base with a recline control pivoting recline control lever. The seat portion of the...http://www.google.de/patents/US5662381?utm_source=gb-gplus-sharePatent US5662381 - Chair construction and method of assembly
