The invention relates to a mechanical assembly (2), said mechanical assembly (2) comprising, in addition to a leaf spring, at least one further spring element, the elastic restoring force of the at least one further spring element and the elastic restoring force of the one or more leaf springs supporting the seat shell (S) with a total restoring force, and/or the mechanical assembly (2) comprising at least two leaf springs and at least two supports, each support being associated with one of the leaf springs, and at least two supports being displaceable beneath the leaf springs by means of an adjustment mechanism and being displaceable on their trajectories by different extents.