HYDRAULIC CIRCUIT OF WORK MACHINE WITH TELESCOPIC ARM

摘要

PROBLEM TO BE SOLVED: To prevent the operating speed of an arm expandable cylinder and a bucket closing cylinder from slowing, because of the pressure loss of the oil path connected between a telescopic arm and a machine body and achieve proper pressure setting of a relief valve for preventing the expandable cylinder from buckling in a work machine the equipped with a telescopic arm. SOLUTION: The machine includes a bottom oil path connected between a bottom chamber of the arm expandable cylinder and the arm control valve of the machine body, and a opening/closing valve. The opening/closing valve which opens the tank oil path connected between the bottom chamber and a tank of the machine body, when the expandable cylinder is contracted is provided in the connecting part between the tank oil path and the bottom chamber in paralle to the bttom oil path.