Expanding and contracting operating the valve cylinder with the change operation

摘要

PROBLEM TO BE SOLVED: To prohibit the occurrence of resonance due to the coincidence of the natural frequency of a boom with the switching timing of a concrete piston. SOLUTION: A vibration detector 35 is installed at the end of a boom 5 for a concrete pump vehicle. When a detection signal from the vibration detector 35 is at a given value or more a instruction is given from a controller 36 so as to change the switching timings of a suction discharge valve provided in a concrete pump 3 and a concrete piston to be moved forward/backward in mid course. An offset between the natural frequency of the boom 5 and of the switching timing of the concrete piston causes the cancel of resonance.