LOAD HOLDING DEVICE FOR HYDRAULIC ACTUATOR CIRCUIT

摘要

PROBLEM TO BE SOLVED: To surely decrease the size of a holding valve opening in burst of a loading side conduit regardless of operation quantity of an operation lever so as to control falling speed of a load to be safe, in a load holding device for a hydraulic actuator circuit. SOLUTION: The holding valve 13 is provided between a bottom side and a hydraulic conduit 8a of a boom cylinder 1 and a pressure control valve 9 for controlling pressure of a pilot conduit 7a not to exceed a setting value when pressure in the hydraulic conduit 8a becomes equal to or lower than a predetermined value and a check valve 10 for preventing pressure transmission from the hydraulic conduit 8a to the pressure control valve 9 are provided between the pilot conduit 7a and the hydraulic conduit 8a. The pressure control valve 9 is, for example, a decompression valve which actuates when differential pressure of the pilot conduit 7a and pressure of an output side of the pressure control valve 9 becomes higher than a setting pressure of a spring 9a and conducts control (decompression) so that the differential pressure becomes equal to the setting pressure of the spring 9a. COPYRIGHT: (C)2008,JPO&INPIT