Abstract: A lift base for raising and lowering objects such as an ophthalmological chair comprises a piston rotatably and axially movable within a cylinder and connected to a base support which mounts the chair or other object. A sleeve keyed to the cylinder is movable axially relative thereto but locked against rotation. A locking assembly carried by the support is effective to move the sleeve between an unlocked position out of contact with the sleeve wherein both axial and rotational movement of the base support and piston is permitted, and a locked position into contact with the sleeve wherein rotational movement of the piston and base support is prevented but axial movement thereof is permitted.

Abstract: A base support for an examination/treatment chair permits lateral movement of the chair relative to a support for medical instruments and comprises a top plate laterally movable on wheel assemblies relative to a fixed bottom plate. A locking assembly interposed between the top and bottom plates includes a foot operated pivot arm which mounts a locking pin movable within a guide bore formed in the top plate and into a selected aperture formed in the bottom plate to adjust the position of the top plate, and in turn, the chair, relative to the bottom plate.