Abstract: A height adjustable mechanism for supporting a work surface for vertical movement relative to a base includes a counterbalance mechanism for providing a force opposing a downward force tending to lower the work surface; a brake mechanism for releasably retaining the work surface in a desired vertical position; a user operated release mechanism for selectively releasing the brake mechanism to permit vertical movement of the work surface; and an interlock mechanism for preventing release of the brake mechanism if the force and the downward force are out of balance by some given extent.

Abstract: A mechanism for mounting a keyboard supporting surface on a base including a linkage for mounting the surface for vertical swinging movement relative to the base and for vertical tilting movement relative thereto, a lock device for simultaneously locking the surface against swinging and tilting movements, a counterbalance spring for opposing downwardly directed swinging movement of said surface and a return spring for opposing downwardly directed tilting movement of said surface.

Abstract: A counterbalance mechanism for vertically positioning a load includes auxiliary linkage means associated with an upper end of the mechanism for carrying a load and automatically varying the vertical angular orientation of the load incident to vertical movement of the load.