Abstract: A pair of parallel moving surfaces, such as may be used for construction of an adjustable height table or seat are connected by a plurality of pantographs or “lazy tongs” mechanisms, each driven from a differentially threaded control rod. By suitable gearing connections among them, the pantographs are caused to operate in concert, and thus to keep the surfaces parallel as the distance between them is continuously varied. By appropriate mounting of the pantograph ends, the mechanisms are allowed to fold closer together at the minimum separation distance, thereby further minimizing this separation. The use of a set of springs assists in expansion from this minimized separation situation. The overall result is a simply operated mechanism for the continuous separation adjustment of a pair of parallel moving surfaces, together with the maximization of the range of separation adjustment between the two surfaces, concomitant with a minimization of the size and weight of the overall apparatus.

Abstract: A pair of parallel moving surfaces, such as may be used for construction of an adjustable height table or seat are connected by a plurality of pantographs or “lazy tongs” mechanisms, each driven from a differentially threaded control rod. By suitable gearing connections among them, the pantographs are caused to operate in concert, and thus to keep the surfaces parallel as the distance between them is continuously varied. By appropriate mounting of the pantograph ends, the mechanisms are allowed to fold closer together at the minimum separation distance, thereby further minimizing this separation. The use of a set of springs assists in expansion from this minimized separation situation. The overall result is a simply operated mechanism for the continuous separation adjustment of a pair of parallel moving surfaces, together with the maximization of the range of separation adjustment between the two surfaces, concomitant with a minimization of the size and weight of the overall apparatus.