FLUID PRESSURE CIRCUIT HAVING BOOSTER CIRCUIT FOR OPERATING WORKING MEMBER FOR CIVIL ENGINEERING MACHINERY

摘要

PURPOSE: To provide the hydraulic circuit guaranteeing an efficiency in an anticavitation valve, by providing a re-supply circuit with a valve for feeding a boost to the anticavitation valve from the main supply source of a hydraulic fluid. CONSTITUTION: A signal is output to a booster valve 33 which signal is showing that a pressure in a re-supply circuit 26 has reduced down lower than a given back pressure corresponding to a value of elastic thrust load. A shuttle of a booster valve 33 comprising a normally-closed two-way pressure reducing valve is forced to move to an open position, so that the valve 33 is opened by the action of elastic thrust load. A boost is fed to an anticavitation valve 28 from the main supply source 8 of a hydraulic fluid and is also fed to a rotary-operating hydraulic motor 2a, 2b, and 2c for carrying out a rotary operation of a turret which holds thereon working members.