CRAWLER EXTENSION CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a crawler extension circuit capable of retaining a posture that a blade is lowered in the widening work and the vehicle body is set afloat. SOLUTION: A vehicle body is set afloat from the other face by driving it to the lowering direction by hydraulic oil fed to the head side 25h of the blade cylinder 25 and a pair of crawler shoe belts widenably attached to the vehicle body is driven in the widening direction of the width by the hydraulic oil fed to the head side 31h of a widening cylinder 31. A condition under which hydraulic oil is supplied to the head side 25h of the blade cylinder 25 , and another condition in which the hydraulic oil is supplied to the head side 31h of the widening cylinder 31 can be interchanged to each other by a widening changeover valve 50. The widening changeover valve 50 has an overlap structure as a cylinder communication prevention means preventing communication between the head side 25h of the blade cylinder 25 in the changeover time and the head side 31h of the widening cylinder 31 in the inside. COPYRIGHT: (C)2004,JPO