GB734631A - Pressure regulating mechanism for enclosures such as aircraft cabins - Google Patents

Abstract

734,631. Fluid-pressure servo motor-control systems. GARRETT CORPORATION. April 2,1953 [April 15, 1952], No. 9165/53. Class 135. Mechanism for controlling the pressure in an enclosure such as an aircraft cabin comprises an outflow valve 27 actuated by the pressure in an operating chamber 33, having an inlet connection and an outlet connection, one of which is controlled by relay means 16 which in turn are controlled by the pressure in a control pressure chamber 41 having an inlet connection and an outlet connection, one of which is controlled by pilot valve means responsive to the control chamber pressure. Power-operated means are also provided for opening the valve positively at any time and further means are provided for closing the valve quickly in an energency. As shown, the outflow valve 27 is generally similar to that described in Specification 672,929 and controls an opening 13 in the wall 11 of an aircraft cabin 10. The outflow valve is balanced as regards atmospheric pressure and is sealed with respect to a casing 25 forming part of the operating pressure chamber 33 by a flexible diaphragm 31. The chamber 33 is connected to the cabin through a restricted orifice 34 and to the relay means through a conduit 40. A spring 33a tends to close the outflow valve. The control pressure chamber 41 communicates with the cabin through a restriction 68 and with the atmosphere through one or more pilot valves actuated by one or more known pressure control devices. As shown, the pilot valve 53 is actuated by an isobaric control mechanism 44 and the pilot valve 63 by a differential pressure control mechanism 45. Each comprises a spring-loaded lever such as 49 supporting the pilot valve. The lever of the isobaric control' is operated by an evacuated capsule 46 and that of the differential pressure control by a spring-loaded diaphragm 57 exposed on one side to control chamber pressure and on the other side to ambient atmospheric pressure through a conduit 60. The relay means comprises a spring-loaded diaphragm 70 clamped to the base 42 of the chamber 41 by a discshaped housing 72 and exposed on its upper side to the control chamber pressure and on its lower side to the pressure in the conduit 40 and therefore to the operating chamber pressure. The relay valve member 78 which serves to connect the conduit 40 with the ambient atmosphere (or in some cases with a source of vacuum) has a stem 81 pressed against the diaphragm 70 by a spring 90 weaker than a spring 88 in the control pressure chamber 41. Other forms of pressure control device and various combinations of pressure control device may be used for the control pressure chamber 41. Thus a pressure ratio control device may be employed. Also the chamber 75 below the diaphragm 70 may be connected directly to the cabin instead of to the conduit 40. The outflow valve may be opened positively at any time by mechanism 100 comprising an electric motor driven actuator 101 having a rotatable sleeve 109 adapted to move axially a screw 110 connected to a yoke 113 by a removable cross-pin 112. The stem 114 of the yoke has a head 115 capable of limited movement in a cylinder 116 connected to the outflow valve by a stem 117 having a guide 119 in a fixed baffle 35. The sleeve 109 is moved in one direction or the other by energization of one of the motor coils 107, 108 on moving a switch member 104 against one or other of the fixed contacts 105, 106. The lostmotion between the head 115 and the ends of the cylinder 116 permits normal operation of the outflow valve by the relay means. The pin 112 may be withdrawn from the yoke 113 and the screw 110 to permit the outflow valve to be closed rapidly. The pin 112 is connected to a clevis 125 connected to a cable 126. A collar on the pin 112 slides on a bar connecting the ends of the clevis 125. The cable 126 is also connected to the arm 140 of a three-way coke 130 adapted to connect the chamber 33 direct to the cabin when the pin 112 is withdrawn. As both sides of the outflow valve assembly are now at cabin pressure, the spring 33a closes the out flow vaive.