HYDRAULIC CONTROL VALVE FOR HEAVY CONSTRUCTION EQUIPMENT MACHINE

摘要

PURPOSE: A hydraulic control valve for heavy construction equipment machine is provided to enhance safety by controlling the operation of a hydraulic cylinder when a lock valve has a defect in operation. CONSTITUTION: In case of stopping a hydraulic cylinder(9) without applying pilot pressure(Pa), a subsidiary spool(5) and a direction control valve(10) return to the initial position. The communication of an inlet path(8) with a tank(13) is cut off, thus the actuating oil in the inlet port is supplied to a back chamber via a port. Due to the large size of the section of the back chamber than that of the seat of a lock poppet(2), large load of the back chamber is applied on under the same pressure. The lock poppet contacts to a lock valve body(12) and the actuating oil doesn't flow. The hydraulic cylinder doesn't operate and the load applied on the hydraulic cylinder is protected and maintained. Thereby, the contractive operation of the hydraulic cylinder is prevented.