Patent GB-576243-A (GB)
Title: Improvements in or relating to control devices for hydraulic pressure systems
IPC: F16K17/06
Filed: 1943-06-24
Abstract: 576,243. Fluid-pressure servomotor - control systems. HAWORTH, L. June 24, 1943, No. 10216. [Class 135] A system for delivering liquid fuel under pressure to the jet or jets of an internal-combustion engine comprises a positive displacement pump without restriction in the supply line to the jets, a main relief valve spilling fuel from the pump delivery line to determine the pressure in that line, and means for applying, and automatically adjusting, a load to the relief valve opposing the load applied by the pressure. As shown, the delivery of a gear pump 10, Fig. 5, is controlled by a relief valve 43, the loading of which is adjusted by the pressure in a hydraulic system controlled by a second valve having a manually-adjustable loading. A chamber 44 connected to the delivery side of the pump can be closed by a valve 43 and, on starting up the engine, the pressure of the spring 40 loading the valve 43 is just sufficient to keep the valve closed. Some fuel from the delivery conduit passes through a restriction 52 to the back of a piston 41 carrying the valve 43 and the combined pressure of the fuel and the spring 40 on the back of the piston keeps the valve 43 closed and allows the pressure on the delivery side of the pump to build up. The fuel in the space at the back of piston 41 also flows through a conduit 53 to a chamber 54 normally closed by a further valve 58, but when the pressure of the fuel on the delivery side of the pump- and hence the speed of the internal-combustion turbine &c.-has increased sufficiently, the valve 58 will be forced open and fuel will escape through a conduit 57 to the front face of piston 41 and through conduit 49 to the inlet side of the pump. The spring loading of valve 58 is adjustable by a link mechanism 61, 64 which thus gives a manual adjustment for the speed of the engine. Fuel at the back of piston 41 also flows through a conduit 39 to a valve 20 which is centrifugally controlled to limit the maximum pressure of fuel delivered to the turbine and, hence, the speed of the turbine. This control operates when the valve 20 opens to allow fuel from conduit 39 to flow into chamber 56 and thence to the inlet side of the pump. The pump and the valves are incorcorporated in a casing, Fig. 1, the pump comprising inter-engaging gears 13, 14 on shafts 11, 15 of which shaft 11 is the driven shaft. Shaft 15 is hollow and carries an inner shaft 18 driven from shaft 11 at a slightly higher speed than shaft 15 by means of inter-engaging cogs 16, 17. At one end, shafts 15, 18 carry a centrifugal governor 28, as described in Specification 566,253, [Group XXVI], and when the speed of the pump exceeds a value determined by the loading of a spring 29, shaft 18 moves to the right and a sleeve 20 on its other end slides over a spigot 21 and ports in the sleeve and spigot are brought into coincidence to place conduit 39 in communication with chamber 56. The loadings of springs 29, 40 are adjustable by set-screws 34, 50 respectively. The speed of the engine can be reduced on any part of the engine attaining a maximum temperature by means of a temperature flask which communicates with a liquid-vapour capsule 69, Fig. 6, through a capillary pipe 70. When the capsule expands, it moves a valve 68 to allow a through passage from the chamber at the back of piston 41 to the pump inlet, thus relieving the pressure on the outlet side of the pump and reducing the speed of the engine. A drop in the pressure of the lubricating system may act on a similar valve to reduce the pressure on the outlet side of the pump 10. In a modification, the shaft 18 adjusts the spring loading of valve 58 and the ports associated with the sleeve on shaft 18 are omitted. Spring 29 is then adjusted manually.