GB589201A - Improvements in and relating to aircraft cabin pressure control arrangements - Google Patents

Abstract

589,201. Automatic control systems for aircraft cabins. BRITISH THOMSONHOUSTON CO., Ltd. March 19, 1945, No. 6854. Convention date, March 20, 1944. [Class 38 (iv)] Fluid pressure control.-In an arrangement for controlling the air pressure in an aircraft cabin, compressed air, controlled by a valve 14, Fig. 1, is fed into a cabin 12 via a conduit 13 and discharged via a restriction 18 and a valve 17. Between altitudes 10,000 and 35,000 feet the pressure is maintained constant by means of a bellows 29 connected between the restriction 18 and the valve 17 and co-operating with a similar but evacuated bellows 33 containing a spring, to move one end of a switch arm 25 in accordance with the absolute pressure in the cabin and so control a reversible servomotor operating the outlet valve. The effect of measuring the pressure between the restriction 18 and the valve 17 instead of in the cabin is to prevent hunting. At an altitude of 35,000 feet a bellows 37, responsive to altitude pressure, expands and a spring 41 begins to act on the other end of the lever 25 to effect a drop in the pressure as shown by the part CD, Fig. 2. At the altitude represented by the point D, the spring 41 is fully compressed and a pin 40 engages with the lever 25, thus, at higher altitudes, the valve 17 is responsive to changes in the of cabin pressure to altitude pressure.