Patent GB-563553-A (GB)
Title: Improvements in or relating to pressure control apparatus for aircraft pressure cabins and the like
IPC: B64D13/04
Filed: 1941-11-06
Abstract: 563,553. Fluid-pressure servomotor control systems. WESTLAND AIRCRAFT, Ltd., WIDGERY, W. M., RICHARDS, S. T. A., and BANNISTER, E. D. Nov. 6, 1941, Nos. 14320/41, 15826/41 and 9788/42. [Class 135] A valve device for controlling the pressure in the pressure cabin of an aircraft has a main control valve actuated by fluid pressure admitted from the cabin through a restricted orifice and exhausted to atmosphere through a small auxiliary valve actuated by an absolutepressure sensitive capsule and a differentialpressure-sensitive capsule interconnected so that the pressure in the cabin, between two chosen altitudes, rises and falls substantially with the surrounding air, but to a lesser extent and in such a manner that for each altitude within the said range a definite corresponding differential pressure always exists between the cabin and the outside air irrespective of the manoeuvres of the aircraft and the duration of its flight. In the form shown in Figs. 1 and 3, communication between the cabin and the outside air is controlled by a diaphragm valve 4 co-operating with a seat 3 formed in a casing 2 secured to the wall 1 of the cabin. A dome 13 clamped to the casing by bolts 6 provides a chamber 5 above the diaphragm in communication with the cabin through a restricted passage in a flanged tubular member 9 secured to the diaphragm. The chamber 5 is vented to atmosphere through a small valve 14 actuated by lever .22 pivoted at one end to lugs carried' by a stack of differential-pressure responsive capsules 19 and at the other end is held by a spring 23 against a pin in the end of a spindle actuated by a stack of absolutepressure responsive capsules 17. Movement of this end of the spindle is limited by a stop 24. The lever 22 also operates a C-shaped member 27 to close a switch 25 controlling a warning light or klaxon when the pressurefalls a predetermined amount below the chosen pressure. The casing 2 also houses a spring-loaded valve 30 adapted to open when the cabin pressure falls a predetermined amount below the outside pressure. A second spring-loaded valve 31 seats on the valve 30 and opens to relieve excessive pressure in the cabin. The valve 4 is loaded by a spring 10 housed in a tubular member 12 screwed into the dome 13 and in a modification the member 9 is fitted with a friction damper co-operating with a cylindrical recess in the member 12. In a modification, the capsules are arranged coaxially, the capsule 17 carrying the small auxiliary valve or is connected by a lever to an external valve. In another form, the capsule 19 is connected to the mid-point of a lever 22, while the capsule 17 is connected to one end and the valve 14 and switch 25 are actuated by the other end. In a more elaborate form the mountings for switch 25, valve 14 and stop 24 are provided with fine adjustments fitted with visual indicators. The loading adjustment for the valve 31 is provided with both coarse and fine adjustments and both coarse and fine adjustments are provided between the lever 22 and a lever actuating the switch 25. A lever operated by a flexible control from a .remote point is also provided for raising the stop 24. With very large aircraft or aircraft having several blowers, a single master control structure associated with the pressure cabin may control several relief valves associated, for example, with front, rear and fuselage turrets. According to the second Provisional Specification, the lever connecting the capsules acts through an adjustable roller on a second lever adapted to actuate the auxiliary valve. The roller may be replaced by a screw and lock-nut or, alternatively, a series of screws with lock-nuts may be provided on the lower lever to give a finite number of adjustable positions. This Specification also describes a modified form of control valve in which a valve disc with a rubber face bonded to it is free to float but is located sideways by means of the ball-like lower end of a spindle which accommodates the spring. The diaphragm is on the upper face of the valve disc and rests on a plate with numerous fingers pointing inwards. In a modification a piston replaces the diaphragm.