The specification discloses a chair system wherein two different types of chairs, a shell chair and a sling chair, can be made using the same basic components and tooling. Spaced side rails support a separately molded plastic seat and back which can be upholstered with upholstery pads which do not cover...http://www.google.sh/patents/US4152023?utm_source=gb-gplus-sharePatent US4152023 - Chairs and method for making same
