GB612164A - Improvements relating to automatic air-flow control means, particularly for use on aircraft - Google Patents

Abstract

612,164. Fluid-pressure servomotor-control systems. SEGRAVE, C. R., WILLIAMS, T. B. GLYNNE-, and BARKER, H. H. May 14, 1946, No. 14505. [Class 135] An airflow control device, particularly for use on aircraft wherein a substantially constant weight of air is automatically supplied to an apparatus irrespective of changes in altitude of the aircraft and in the back pressure of the apparatus being supplied. As shown, a valve casing 1, housing a double-beat lift valve 4 normally held off its seat by a spring 8, is disposed in a duct having an intake 2 and an outlet 3 to the apparatus being supplied. The valve casing is surmounted by a diaphragm chamber 7 connected to the valve 4 by a spindle 6 and subjected on its underside, through ducts 19, 20, to the pressure in the outlet, and on its upper side to the intake pressure through ducts 13, 12, 10 under the control of a valve 14 normally held on its seat by a spring 15 and the back pressure of the apparatus through a duct 29, and a casing 28 having a connection 30 to the apparatus. The valve 14 has a stem 16 which coacts with a diaphragm 17 in a chamber 18 above the chamber 7. The underside of the diaphragm 17 is in open communication with the outlet 3, whilst its upperside is exposed to the back pressure through a hole 31, and also loaded by a spring 21, the pressure of which depends on the difference in pressure on the two sides of an evacuated bellows 26 in a casing 25 open to the atmosphere. In operation, air entering the intake 2 passes through the normally open valve 4 to the underside of the diaphragm 9, thus tending to close the valve 4, against the spring 8, the strength of which predetermines the weight of air passing. Should the pressure of the atmosphere decrease, e.g., through increase in altitude of the aircraft, the bellows 26 will expand downwards to move the diaphragm 17 into contact with the stem 16 of the valve 14 which is opened to permit air from the intake 2 to load the upperside of the diaphragm 9 and thereby increase the opening of the valve 4 to compensate for the decrease in pressure. Also, should the back pressure of the apparatus being supplied increase this increase will act on the upper side of the diaphragm 17 to open the valve 14 and on the upperside of the diaphragm 9, to increase the opening of the valve 4 to maintain the same pressure difference between the supply and back pressures of the apparatus.