Movable stacking device

A movable stacking device comprising a substructure, a vertical mast vertically arranged thereon and composed of a fixed outer frame and an inner frame vertically guided by the outer frame, an operating platform vertically guided by the inner frame and comprising a base frame extending transversely to the substructure, a rotation head horizontally guided by the base frame and a fork means adapted to carry a load and being supported by the rotation head for rotation about a vertical shaft, the outer frame and the inner frame of the mast each consisting of two spaced channel or I-beam sections extending transversely to the substructure, the webs of said sections extending in longitudinal direction of the substructure, rollers or similar means being mounted on the sections of one frame which act on flanges of the adjacent sections of the other frame of the mast and further rollers or similar means being mounted on the operating platform which act on the flanges of the inner frame, characterized in that the outer frame and the inner frame each comprise in addition a vertical box girder, said box girders being arranged on behind the other on the longitudinal axis of the substructure, the box girder of the inner frame being vertically movable relative to the box girder of the outer frame by means of a guide means, but being unable to move transversely thereto, that the sections are each connected to the corresponding box girder by rigid transverse beams and that the side of the operating platform remote from the base frame comprises additional rollers or similar means cooperating with a vertically extending guide rail on the box girder of the inner frame.