Improvements relating to Pressure Reducing Valves

1,174,252. Pressure-reducing valves; fluid pressure brakes. DUNLOP CO. Ltd. 7 July, 1967 [9 July, 1966], No. 30930/66.- Headings F2F and F2V. A pressure-reducing valve for an aircraft braking system has a spool 5 slidable in a bore 3 of the body 2 to permit flow of fluid from inlet 10 to outlet 11. The spool has a bore 19 in which is slidably received a spring-loaded piston 16, the end 21 thereof being subject through ports 20 in the spool to inlet pressure that under normal conditions neutralizes the spring-loading. The inlet pressure acts on an area equal to that of the piston cross-section on the spool while the outlet pressure passes through bores 23, 24 and restriction 18 of a secondary relief valve 25 to act on the whole of the area of the spool end in chamber 26. The spool thus acts as a differential piston reducing the pressure of the fluid passing through the valve. If the inlet pressure drops the spring-loading 30 of the piston 16 compensates to prevent outlet pressure drop. A main relief valve 37 is provided and is connected to a fluid return opening 12 as is a leakage passage 36 which is connected via bore 35 to waist 33 of piston 16.