Telescopic crane boom having corrugated boom sections

摘要

A large light-weight telescopic crane boom comprises a plurality of relatively movable boom sections, such as base, intermediate, outer, and fly sections, and each section comprises top and bottom walls and a pair of spaced apart side walls. In each pair of relatively movable adjacent boom sections wherein one (inner) section is telescopically receivable within another (outer) section, the inner surface of the side walls of the outer section and the outer surface of the side walls of the inner section comprise longitudinally extending corrugations or projections which interengage and whereby the inner section is slideably supported on the outer section. The corrugations or projections on each wall surface are arranged in two (upper and lower) sets, one above and the other below, the longitudinal neutral axis of the crane boom. When the inner section is telescoped within the outer section and the crane boom is not loaded, the upper set of corrugations of the inner section rest in slideable engagement on the upper set of corrugations of the outer section. When the inner section is extended relative to the outer section and the crane boom is loaded, the inner section flexes downward sufficiently so that the lower set of corrugations of the inner section also rest on the lower set of corrugations of the outer section to thereby distribute the load and increase the area of slideable engagement between the two boom sections. Mating surfaces of projections which are subject to sliding engagement are coated with anti-friction material to facilitate boom extension and retraction whether loaded or unloaded.