PERFECCIONAMIENTOS EN LOS BRAZOS TELESCOPICOS PARA GRUAS MOVILES O SIMILARES.

摘要

A mobile crane has a boom comprising a plurality of telescopic hollow boom sections. Hydraulic operating cylinders for the boom sections are housed within the boom and each is provided with its own remotely operable electrically controlled main valve. Hydraulic fluid is supplied to the valves by flexible hydraulic fluid hoses disposed between the side plates of adjacent boom sections and the hoses uncoil or coil in a frictionless manner as the sections are extended or retracted. Electric control wires for operating the electric wires are wrapped around the hoses and held in place thereon by heat-shrunk plastic tubing. The boom sections have a cross-sectional configuration which is that of an inverted A-frame or trapezoid to increase boom strength, to provide the maximum ratio between internal component space and weight, and to enable a more compact physical arrangement of the boom and boom hoist cylinders on the crane when the boom is in lowered position. The hydraulic cylinders are progressively smaller in size (proceeding from the base end of the boom to its remote end) to provide a balanced hydraulic system and pressure compensating valve means located between the source of fluid and the first (lowest) cylinder respond to pressure differentials thereat to dump or unload excess fluid as is required to maintain a predetermined pressure differential.