The present design is of a variable posture component system seating device, also called a work chair, which integrates user selectable and adjustable components. The components consist generally of a short base, a long base, height adjustment mechanisms, a seat adjustment mechanism, a seat assembly,...http://www.google.co.uk/patents/US5542746?utm_source=gb-gplus-sharePatent US5542746 - Variable posture component system seating device
