Mechanism for suppressing vibrations of travelling crane

Abstract

A mechanism for effectively suppressing vibrations in travel of mobile type crane includes; a boom lifting hydraulic cylinder connected between a vehicle body of the mobile crane and a boom; a main hydraulic pump; a direction control valve for supplying the discharge oil of the main hydraulic pump selectively to and from a first load-supporting oil chamber and an opposingly located second oil chamber of the boom lifting cylinder. A vibration suppressing accumulator is connected between the boom lifting cylinder and the direction control valve; a first change-over valve is selectively switchable between a travel mode position for forming a closed circuit through the first and second oil chambers and a working mode position for supplying the oil pressure independently to and from the first and second oil chambers; a second change-over valve is selectively switchable between a travel mode position for communicating the accumulator with the closed circuit and a working mode position for blocking oil flow from the closed circuit to the accumulator. Also provided are; a boom position detectors; a first selector for switching on and off oil pressure supply to the second oil chamber from an auxiliary oil pressure source; and a second selector for switching on and off oil pressure supply to the accumulator from an auxiliary oil pressure source.