HYDRAULIC CIRCUIT FOR MOVING UP AND DOWN WORKING EQUIPMENT

摘要

PROBLEM TO BE SOLVED: To reduce the cost of a main hydraulic circuit by making a control valve for moving up and a control valve for moving down be operated by a pilot valve. SOLUTION: This circuit has a sub-control valve Vh for connecting and disconnecting a supply and discharge hydraulic passage 33 which connects a control valve 18 for moving up and a control valve 19 for moving down which are connected in parallel and are operated by a hydraulic pilot valve to a single motion type moving up-and-down cylinder 10 and has operation valves 25, 26 for moving up and moving down which switch between a control valve 18 for moving up and a control valve 19 for moving down. A first hydraulic circuit y1 for connecting the control valve 18 for moving up to the control valve 19 for moving-down, a second hydraulic circuit y2 for connecting the sub-control valve Vh to both operation valves 18, 19 and a third hydraulic circuit y3 for supplying pilot hydraulic pressure to both operation valves 18, 19 are connected via a shuttle valve 23 for checking the first hydraulic circuit y1 and the second hydraulic circuit y2.