Predicting Operational Behaviour of Abstract Programs During Formal Developments

Abstract

A seat backrest having a contourable upholstered portion supported by a rigid frame portion includes means to produce a desired supporting contour in the lumbar region of the seat occupant. The contour-producing means includes a lumbar pad, a pair of link members connecting the lumbar pad to the frame, and a double threaded shaft means operable by a seated occupant from the side of the backrest for moving and holding the link members in an infinite number of fixed, generally horizontal positions forward of the frame. The position of maximum lumbar support can be adjusted vertically by pivoting the link members and lumbar pad by means of a pin which is engaged with an angled slot in a sliding plate.