GB664348A - Improvements in pressure regulating means for aircraft cabins - Google Patents

Abstract

664,348. Fluid-pressure servomotor control systems; valves. GARRETT CORPORATION. Feb. 13, 1948 [Jan. 10, 1947], No. 4317/48. Class 135. Pressure regulating means for aircraft cabins comprises an airflow duct 10, a valve 11 for regulating the flow in the duct under the control of mechanism responsive to the air flow, and control means 41 responsive at least to the pressure outside the cabin for modifying the action of the said mechanism so as to control the cabin pressure. As shown, a butterfly valve 11 is actuated through rack and pinion mechanism 15, 21 by a spring-loaded diaphragm 22, chambers 37, 38 on opposite sides of which are connected to the inlet and throat respectively of a venturi 14. A check valve 13t opens to admit air at ram pressure from a passage 13 for ventilation purposes when pressurisation is not required. The chamber 38 communicates with the throat of the venturi through a conduit 16 and through two valves 27, 30 arranged in parallel. The valve 27 is normally closed and limits the pressure differential between the chamber 38 and the throat of the venturi. The valve 30 also regulates this pressure differential and is actuated by the mechanism 41 which comprises a diaphragm 31 having a chamber 42 on its upper side exposed to a pressure which is substantially the pressure in the cabin 9 by means of a conduit 17 leading to a pressure orifice 36, and a chamber 43 on its lower side exposed to ambient atmospheric pressure through a port or ports 46. The diaphragm 31 is connected to a spring-loaded evacuated metallic bellows 32 of substantially equal effective area, the latter being supported on a cage 34 having an internal flange 34a to limit the expansion of the bellows as the altitude increases, and a rib 34<SP>1</SP> pressed against a flange 45 by a spring 35 until the pressure in the chamber 42 overcomes the spring. The cage 34 is guided by a pin 34b. Specification 521,623 is referred to.