Bridge crane for the emplacement of elongate prefabricated members of structures spanning a multiplicity of spaced-apart supports

Abstract

Precast beams or slabs of an elongate structure such as a bridge, viaduct or overpass are emplaced on spaced-apart piers by a bridge crane which comprises a framework consisting of a pair of parallel trusses interconnected by end portals and long enough to extend across three piers. Each truss has a bottom stringer formed on its underside with tracks engaged above each pier by rollers mounted on a pair of rocker arms which are part of an undercarriage movable on transverse guide rails. Top stringers of the trusses support a trolley carrying hoists for raising and lowering the transported castings. Longitudinal movement of the framework relative to the piers is brought about by a motor-driven capstan, carried on the framework, which is engaged by cables wound about deflecting rollers at the ends of the framework and on an anchor frame to which the ends of the cables are fastened, the anchor frame being secured to one of the undercarriages and carrying pulleys coacting with confronting deflecting rollers to form a tackle with a fourfold mechanical advantage.

Dependencies are inferred from the claim text.