Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions, a pump for supplying fluid to said actuator, a directional valve comprising pilot operated meter-in valves to which the fluid from the pump is supplied through first lines for controlling the direction of movement of the actuator, and a pilot operated meter-out valve associated with each opening of the actuator for controlling the flow out of said actuator. The pressure of fluid being supplied to the actuator by the meter-in valve is sensed and supplied to a line extending from the output of the meter-in valve. A valve is provided in this line to provide a force selectively on the meter-in valve opposing the movement of the meter-in valve by the pilot pressure. The valve may comprise either a modulating valve or a shut-off valve.

Abstract: A hydraulic control system for controlling a hydraulic actuator comprising a pump for supplying fluid to the actuator and a directional valve for controlling the flow of fluid to the actuator. The directional valve includes a poppet piston that provides a variable orifice. The position of the poppet piston is controlled by a pilot flow controlled by a pilot valve which may be controlled by a solenoid controller. The flow out of the pilot valve is connected to the outlet of the directional valve. A pressure compensator is provided between the inlet to the directional valve and the pilot valve and maintains the pilot flow to the pilot valve constant. The pressure of fluid being applied to the actuator by the directional valve is also sensed and caused to produce a force opposing the opening force applied to the pilot valve to result in a smooth and accurate control of the load.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving an element of the actuator in opposite directions, a pump for supplying fluid to the actuator. A meter-in valve individual to each opening is provided to which fluid from the pump is supplied and a pair of lines extending from the respective meter-in valves to the respective openings of the actuator. A controller alternately supplies pressure to the respective meter-in valves for controlling the direction of movement of the load. A second pair of lines extends from the first pair of lines to tank and a variable pressure relief valve is positioned in each line of the second pair of lines.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions, a pump system for supplying fluid, and a directional valve provided to which the fluid from the pump is supplied for controlling flow to and from the actuator. A pair of lines extends from the directional valve to the respective openings of the actuator. A controller alternately supplies a first fluid pilot pressure to pressure reducing valves associated with the directional valve for reducing the pressure from the pump system or any other source and supplying a second reduced pilot pressure to the directional valve for controlling the flow to and from the actuator. Preferably, the directional valve comprises a meter-in valve and a meter-out valve associated with each line to the actuator for controlling flow out of the actuator.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions and a variable displacement pump with loading sensing control for supplying fluid to said actuator. A pilot operated spool type meter-in valve is provided to which the fluid from the pump is supplied and a pilot controller alternately supplies fluid at pilot pressure to the meter-in valve for controlling the direction and displacement of movement of the meter-in valve and the direction and velocity of the actuator. A pair of lines extends from the meter-in valve to the respective openings of the actuator and a pilot operated meter-out valve is associated with each line of the actuator for controlling the flow out of the actuator when that line to the actuator does not have pressure fluid from the pump applied thereto.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions and a variable displacement pump with loading sensing control for supplying fluid to said actuator. A pair of meter-in valves are provided to which the fluid from the pump is supplied and a pilot controller alternately supplies fluid at pilot pressure to a meter-in valve for controlling the displacement of movement of the meter-in valve and the direction and velocity of the actuator. Alternately pilot pressure from the pilot controller is applied simultaneously to both of the meter-in valves in conjunction with the venting of one of two load drop check valves to provide a regenerative mode.

Abstract: A hydraulic control system comprising a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions, a pump for supplying fluid to said actuator, pilot operated meter-in valve means to which the fluid from the pump is supplied for controlling the direction of movement of the actuator, pilot operated meter-out valve means associated with each opening of the actuator for controlling the flow out of said actuator,and means for sensing a predetermined drop in a line supplying fluid to one opening of the actuator caused by a runaway load in one direction and operating the meter-out valve means to interrupt flow out of the other opening of the actuator.