Patent GB-726705-A (GB)
Title: Pressure regulating mechanism for enclosures such as aircraft cabins
IPC: B64D13/04
Filed: 1953-03-24
Abstract: 726,705. Fluid-pressure servomotor-control systems. GARRETT CORPORATION. March 24, 1953 [April 11, 1952], No. 8036/53. Class 135. Pressure control mechanism for enclosures such as aircraft cabins comprises an outflow valve 49 operated by a pressure-sensitive element 48, one side of which is subjected to enclosure pressure and the other side of which is subjected to the pressure in an operating chamber 68, the latter pressure being controlled by relay means 17 which include a pressure responsive member, such as the diaphragm 90, one side of which is subjected to the pressure in the operating chamber. Power-actuated means 18 are also provided for opening the outflow valve positively, the outflow valve being capable of quick release from these means to permit it to close. The pressure-sensitive element 48 comprises an annular diaphragm 63, the-inner periphery of which is clamped between a dished plate 51 and a cylindrical member 50. A further annular diaphragm 52 is clamped between the cylindrical member 50 and the valve member 49. The valve 49 has a frustoconical portion 80 ending in a knife-edge 81 adapted to engage the valve seat 24. The seat 24 is formed on the base 21 of a cage or housing 20 mounted in aperture 13 of an aircraft cabin 10 supplied by a supercharger 12. The valve 49 and the pressure responsive element are balanced as regards the atmospheric pressure acting through the opening 23. An axially disposed pedestal 29 and an annular flow directing wane 31 are supported by spider arms 30. A rod 36 secured to the centre of the coverplate 51 'is guided in the pedestal 29, the bottom of the bore 33 in the pedestal being vented to a chamber 60 formed between the plate 51 and a conical baffle 39 fixed to the pedestal 29 by screws 41. The baffle 39 has a ported skirt 43 and the inner edge of the diaphragm 52 is clamped to the top edge of the baffle. Cabin pressure has access to the chamber 60 through ports 61. The outer edge of the diaphragm 63 is .clamped between the top of the cage 20 and a flanged cover 66 to form the operating pressure chamber 68 to which cabin air has access through a restricted orifice 69. A light spring 71 loads the valve to the closed position. The relay means 17 is mounted on the cover 66, the pressure-responsive diaphragm 90 thereof being loaded by an adjustable spring 99 and clamped at its edge between a flange 92 on the cover 66 and a cap 95. The diaphragm 90 is connected by a lever 125 pivoted at 126 to a relay valve 120 operating in a housing 109. The valve 120 has a conical part adapted to engage a seat 116 in a ported seat member or cage 112 screwed into the .top of the housing 109. The valve 120 is guided in the cage 112 and a spring 123 acting on a disc 122 tends to move it to the open position. A conduit 107 connects the relay valve to a point of low pressure such as the outside of the cabin. The diaphragm chamber 96 of the relay means 17 is connected by a conduit 16 to a pressure regulator unit 15. This may include one or more of the units described in Specification 718,674 for maintaining the pressure in the chamber 98 of the unit 15 in accordance with a predetermined schedule. The chamber 98 has a bleed connection 140 with the cabin and is connected to the atmosphere by a conduit 141. The poweractuated means 18 is also mounted on the cover 66 and comprises a motor 150 driving a clutch member 153 on the motor shaft 152, Fig. 6. A clutch disc 156 with a peripheral groove 157 is pressed against the clutch member 153 by a spring and is rotatably connected with a shaft 165 having an enlarged portion 166 adapted to fit an aperture in the clutch housing 168. The disc 156 also has a stub shaft 162 rotatably supported in the motor shaft 152. The clutch members 153, 156 are positively connected by a pin 157 on the latter engaging a hole in the former. A flexible cable 158 is secured to the guide shaft 36 of the pressuresensitive element and is wound round the pulley or disc 156 to open the outflow valve positively when the motor is energized. At the same time a cam portion on the disc 153 opens a spring- closed lift valve adapted to connect the operating pressure chamber 68 with the interior of the cabin so that the outflow valve is not prevented from opening by pressure backing up in the chamber 68. The clutch members 153, 156 may be disengaged to close the outflow valve rapidly by pulling the shaft 165 to the right at the same time the enlarged portion 166 of the shaft leaves the aperture in the clutch housing and so connects the chamber 68 to the cabin. The cable .158 is normally slack so that the fluid pressure actuation of the outflow valve is not interfered with.