GB883580A - Fluid flow control valve - Google Patents

Abstract

883,580. Hydraulic apparatus. FORD MOTOR CO. Ltd. Sept. 1, 1960, No. 30124/60. Class 69 (2). An hydraulic directional control valve comprises flow control devices 3, 4 arranged to control the quantity of fluid delivered to two or more services, and means 6 for selecting the delivery to each service, all the services utilizing a common dump valve 5 to exhaust fluid in excess of requirements. The control valve which may be used in a tractor hydraulic system for operating a single or double-acting motor in addition to the main tractor-lift system, consists of a spool 6 slidable in a bore connected by ports 7, 8 to a line 2 connected to a source of fluid pressure, ports 12, 13 which are connected to ports 22, 23 leading to the ends of a double-acting jack, a port 9 connected to valve gear controlling the tractor-lift system, and ports 37, 39 connected to a return line 38. Between the line 2 and each port 7, 8 is a throttle valve 3, 4 which may be of the needle valve, fixed orifice or, as shown, eccentric-type adjustable by a lever. The line 2 is also connected to one side of the dump valve 5 so that pressure in the line acts to move the spool thereof to an open position in opposition to a spring 20. The side of the spool on which the spring acts is joined by a passage 35 to the bore of the control valve. Between ports 12 and 22 and between ports 13 and 23 are check valves 15, 15<SP>1</SP> controlled by a shuttle 14. When the spool 6 is in its central position, fluid pressure from the line 2 passes through the throttle 3 and ports 8, 9 to the valve gear of the tractor lift system, the flow being controlled by the throttle 3. The pressure between ports 8, 9 is transmitted by passages 28, 29 in the spool of the control valve to the passage 35 so that the pressure differential across the throttle 3 acts on the valve to control the flow of excess fluid to the exhaust line 38. Since the port 8 is closed, fluid does not flow past the throttle 4 to the double-acting jack. When the spool 6 is moved in one direction or the other against the pressure of a spring 24, the port 9 is disconnected from port 8, so that the throttle 3 is inoperative, and the supply is connected by the throttle 4 and port 7 to one or other of ports 12, 13, the pressure at the high-pressure port acting to open its associated check valve to pass fluid to the jack, and move the shuttle 14 to open the check valve associated with the low-pressure port to permit exhaust fluid to pass from the jack to the port 37 or 39 and the return line 38.. The movement of the spool 6 moves a land 6b on the spool away from the passage 35 to enable the pressure downstream of the throttle to act on the dump valve 5 in opposition to the pressure upstream of the throttle. If the double-acting jack is replaced by a single-acting jack, the latter is connected to one or other of ports 22, 23, the remaining port being plugged.