Abstract: A constant force generator mechanism is described, comprising a rigid first link adapted to be fixed to a support, a rigid second link mounted for pivotable movement to the first link by a first hinge joint, and a spring link hingedly mounted to the first link by a second hinge joint and hingedly mounted to the second link by a third hinge joint. The spring link is one having a linear spring rate and a zero free length whereby, upon pivotting the second link with respect to the first link, the spring link generates a force whose component parallel to the first link at any given point on the second link is constant through the entire range of pivotable movement of the second link.Also described is a chair having a seat continuously adjustable by the above constant force generator mechanism.