Abstract: A valve assembly controls fluid flow between first and second ports of a hydraulic actuator and each of a supply line and a return line. A first electrohydraulic proportional valve is connected between the supply line and the first port, and second electrohydraulic proportional valve is connected between the supply line and the second port. A first counterbalance valve couples the second port to the return line and operates in response to pressure created by the first electrohydraulic proportional valve and the first port. A second counterbalance valve couples the first port to the return line and operates in response to pressure created by the second electrohydraulic proportional valve and the second port. Thus operation of the first counterbalance valve is slaved to the first electrohydraulic proportional valve, and the second counterbalance valve is slaved to the second electrohydraulic proportional valve.

Abstract: A solenoid operated valve has a valve body with a plurality of ports and a spool slidable within the body to interconnect the ports in different combinations. A solenoid, which is coupled to drive the spool, has a coil wound on an annular bobbin with a tube of an electrically conductive, non-magnetic metal within the bobbin. A first pole piece extends into one end of the tube and a second pole piece extends into another end of the tube. A separate bushing is located in an aperture in each pole piece. Each bushing has a tubular body with a first end section that has a larger outer diameter than a second end section and the second end section that has a smaller inner diameter than the first end section. The solenoid further includes an armature that is slidably received in the bushings and engaging the spool.

Abstract: A hydraulic fluid is supplied from a tank to a plurality of actuators by a variable displacement pump which produces an output pressure that is a constant amount greater than a pressure at a control input. A mechanism senses the greatest pressure among the workports to provide a first load-dependent pressure and a second load-dependent pressure which is greater than the first load-dependent pressure when the pump operates a maximum flow capacity. Each valve section includes a pressure compensating valve which controls the fluid flow to the associated actuator in response to a pressure differential between the metering orifice and either the first or second load-dependent pressures. When the pump operates at maximum flow capacity, actuators connected to the valve sections in which the pressure compensating valve responds to the first load-dependent pressure receive the fluid flow on a priority basis as compared to the other valve sections.

Abstract: An improved pressure-compensated hydraulic system for feeding hydraulic fluid to one or more hydraulic actuators. A remotely located, variable displacement pump provides an output pressure equal to input pressure plus a constant margin. A pressure compensation systems requires that a load-dependent pressure be provided to the pump input through a load sense circuit. A reciprocally spooled, multiported isolator transmits the load-dependent pressure to the pump input but prevents fluid in the load sense circuit from leaving the load sense circuit and flowing through a relatively long conduit leading to the remotely located pump. In a multi-valve array, at least one valve section has a backflow-preventing shuttle valve which prevents backflow through the pressure compensation system if a main relief valve is operative.