Abstract: A flow control valve assembly, for preventing the pressure oil confined in an inlet port of a valve housing from pulsating and for additionally performing a safety valve function without employing a separate safety valve, has a valve housing which is easy in machining thereof and neat in construction. In the valve housing of the flow control valve assembly is formed a valve-receiving bore (21) in which a poppet (32) and a second spool valve (51), serving as a safety valve, are axially aligned with each other in series. In the valve housing (20), a hydraulic operating oil flows to a communication port (39) of the poppet (32) through an inlet port (23) formed in the valve housing (20), and then further flows to a back-pressure chamber portions (38a, 38b) of the poppet (32) through a variable orifice (44). The pressure oil, having been received in the back-pressure chamber portion (38b), flows out of the portion (38b) to an outer peripheral portion of the second spool valve ( 51).

Abstract: An integrated hydraulic system for use in a construction work vehicle has three hydraulic pumps for supplying hydraulic fluid into a steering mechanism and work implement operating actuators. One of the pumps is a steering pump for supplying through a steering circuit hydraulic fluid into the steering mechanism. Another pump is a work implement pump for selectively supplying hydraulic fluid through a work implement circuit by the interposition of a pilot operated directional control valve into the steering circuit and/or the work implement circuit. Still another pump is an auxiliary pump for selectively supplying hydraulic fluid through an auxiliary circuit by the interposition of the directional control valve into the steering circuit and/or the work implement circuit. The directional control valve is controlled by a pressure differential across a restrictor provided in the steering circuit.

Abstract: A control system has two fixed-displacement pumps for supplying pressurized fluid to a pair of steering cylinders via a steering valve and to a pair of implement cylinders via an implement valve. Connected next to the pumps is a demand valve which is pilot operated to deliver to the steering cylinder pair the pressurized fluid from only one pump upon slight displacement of the steering valve and the pressurized fluid from both pumps upon greater displacement of the steering valve. The demand valve is further pilot operated to deliver to the implement cylinder pair the pressurized fluid from only one pump when the implement valve is actuated in a direction to lower the implement assembly, and the pressurized fluid from both pumps when the implement valve is actuated in a direction to raise the implement assembly.