US Patent 7658448 Adjustable chair construction

An adjustable chair construction is described which is particular in that the backrest is linked to the seat by means of at least one hinge construction, where said hinge construction on the seat comprises at least one first projecting member (23) having a curved or linear top section on which top section teeth are arranged, and on the back rest at least one second projecting member (82) having a curved or linear top section on which top section teeth are arranged, such that the teeth on one section mesh with the teeth on the other section, and that at least one connecting member (100) being pivotable fastened to the first and second projecting members (23, 82) maintains the teeth of the curved sections in meshed relationship.