Control valve and electrical and hydraulic control system

Apparatus including an electrical and hydraulic control system for actuating a control valve,

• said control valve comprising
• a valve body having an elongate chamber, and an inlet and an outlet communicating with said chamber,
• a valve element longitudinally movably positioned in said chamber between the inlet and the outlet whereby movement in one direction opens communication between the inlet and the outlet and movement in the other direction closes communication between the inlet and the outlet,
• first and second pilot pistons positioned in said chamber and of equal cross-sectional areas, said first piston being positioned longitudinally on one side of the valve element and said second piston being positioned longitudinally on the other side of the valve element,
• first and second pilot ports extending into said chamber for admitting fluid behind the first and second pistons, respectively, for moving the valve element to either an open or closed position,
• third and fourth pilot pistons positioned in said chamber and of unequal cross-sectional areas less than the cross-sectional area of said first and second pistons, said third piston being positioned on said one side of the valve element and at least partially longitudinally outwardly of said first pilot port, and the fourth piston being positioned on said other side of the valve element and at least partially longitudinally outwardly of said second pilot port,
• third and fourth pilot ports extending into said chamber for admitting fluid behind the third and fourth pistons, respectively, for moving the valve to either an open or closed position,
• and said apparatus further including--
• a hydraulic fluid line connected to the inlet of said control valve and to the third and fourth pilot ports of said valve,
• a first electrically actuated valve means having an inlet and an outlet with the inlet connected to the hydraulic fluid line, said valve being open when electrically actuated and closed when electrically deactuated,
• a pilot valve having an inlet and an outlet and connected in hydraulic fluid line upstream of said third and fourth pilot ports, said pilot actuated by the first electrically actuated valve for moving the pilot valve to the closed piston when the first electrically actuated valve is electrically actuated,
• second and third electrically actuated valve means having an inlet and an outlet, said inlet being connected to the outlet of the first electrically actuated valve means and the outlets connected to the first and second pilot ports, respectively, of the control valve, said valves being open when electrically actuated and closed when electrically deactuated.