Pressurized fluid feed system

PCT No. PCT/JP94/01607 Sec. 371 Date Mar. 15, 1996 Sec. 102(e) Date Mar. 15, 1996 PCT Filed Sep. 28, 1994 PCT Pub. No. WO95/09282 PCT Pub. Date Apr. 6, 1995A pressurized fluid feed system including a pressure compensating valve and directional control valve disposed between a hydraulic pump and a boom cylinder, and a pressure compensating valve and a directional control valve disposed between the hydraulic pump and a turning motor. Each pressure compensating valve comprise a check valve section and a pressure reduction valve section. The check valve section has an inlet port connected to the said hydraulic pump, an outlet port connected to the directional control valve, a spool for establishing and blocking communication between the inlet and outlet ports and a pressure chamber for applying pressure to the spool. The pressure reduction valve section has a first port connected to the said hydraulic pump, a second port connected to a reservoir, and a spool for establishing and blocking communication between the first and second ports. The check valve section of the pressure compensating valve for the turning motor allows a variable flow rate when the turning motor is singly operated and is moved to provide a fixed throttled flow when the boom cylinder and the turning motor are simultaneously operated. There is a check valve (118) connected between the pump and both the pressure chamber (63a) and the first port (42), which prevents communication between the pump and both the pressure chamber and the first port, when the boom cylinder and the turning motor are simultaneously operated.