GB651330A - Improvements in or relating to means for steadily varying the pressure of air in a closed room such as an aircraft cabin - Google Patents

Abstract

651,330. Regulating cabin pressure. SOC. NATIONALE DE CONSTRUCTIONS AERONAUTIQUES DU SUD-OUEST. June 5,1947, No. 14927. Convention date, June 6, 1946. [Class 4] [Also in Group XXIX] Apparatus for producing a gradual variation of pressure in an aircraft cabin in which an excess pressure prevails with reference to the external atmosphere following a disturbance of the steady state conditions prevailing comprises a balanced valve, itself controlling, or acting as a pilot valve to a main valve controlling the exhaust of air from the cabin, the balanced valve being mechanically loaded and subject to the action of a member responsive to the differential of the pressures in the cabin and in a further chamber communicating with the cabin through a restricted passage. In an embodiment, the cabin P2 communicates with a control chamber 1 through a restriction 2, and the chamber 1 communicates through a restricted passage 4 with the inside of a bellows 3 situated in the cabin. The bellows is thus subject to the differential of the cabin and control chamber pressures, and it actuates a double-beat valve 5 which allows the excess pressure in the cabin to flow through a conduit 9 to atmosphere or to the main valve actuator. The balanced valve is loaded by a spring 6 and the loading can be adjusted by a lever 7 and ratchet 7a. During ascent of the aircraft, spring 6 is placed in compression and during descent, it is placed in tension. If the flow of air from the cabin is small, this air escapes to atmosphere past or through a leaky piston 12 in a cylinder 13. If the flow from the cabin is so great that it cannot leak away sufficiently quickly, a pressure will be built up under the piston 12 and the latter will rise and open a valve 11 allowing a larger flow from the cabin. Bellows 3 may be situated inside chamber 1. In a modification for maintaining a constant pressure in the cabin when a predetermined altitude is reached, the air flowing through conduit 9 must first open a bellows-type relief valve before it can flow to the cylinder 13, and in a further modification, the relief valve is connected to the cylinder in parallel with the control valve 5 so that a varying controlled pressure or a constant pressure can be maintained in the cabin at will. Specification 646,287 is referred to.