Patent GB-690033-A (GB)
Title: Mechanism for controlling the pressure in an enclosure
IPC: B64D13/04
Filed: 1949-10-05
Abstract: 690,033. Pressure cabins for aircraft. GARRETT CORPORATION. Oct. 5, 1949. [Feb. 24, 1949] No. 25583/49. Class 4. [Also in Group XXIX] A valve arrangement for eliminating or minimising pressure surges in, e.g., a pressurized aircraft cabin comprises a main pressure regulating valve 9, Fig. 3, an auxiliary outflow valve 11, means for co-ordinating the operation of the two valves and means for effecting the slow closure of the valve 11. Fig. 3 includes two main pressure regulating valves 9 which may be of the type described in Specification 655,601 [Group XXIX] and two auxiliary outflow valves 11. The valves 9 are opened positively by electric motor-operated jacks 68. Each of the valves 11 comprises a casing 20, Fig. 1, with an outlet 17 to the atmosphere and inlets 18, 19 open to the interior of an aircraft cabin 6 pressurized by a supercharger 7. The casing 20 contains a double beat valve 14, 15 supported by a spindle 21. The spindle is carried by a diaphragm 22 and a spider or diaphragm 26 and at one end engages the rod 38 of an electrically-operated jack 39 so as to be operated positively thereby in the valveopening direction. The diaphragm 22 completes a chamber 23 having a restricted connection 24 with the cabin. When the rod 38 is withdrawn to permit the valve 14, 15 to close, it does so only slowly as it takes time for the pressure in the chamber 23 to equalise with the high pressure then prevailing in the cabin. The jacks 39, 68 may be of the type described in U.S.A. Specification 2,407,537. Fig. 3 shows the jacks in a circuit with a landing switch 48, a manual switch 52, an auxiliary vent control switch 55 and a battery 45. Each switch has a valveopening contact O and a valve-closing contact C. The switch 48 engages its contact O only when the weight of the aircraft is on the landing gear so that on take-off, the valves 9 close immediately and the valves 11 close slowly subsequently. The switch 55 is operatively connected to the movable contact member 57 of a potentiometer arrangement 58 adapted to control the operation of auxiliary vent doors in the cabin. The arrangement is such that the switch 55 moves to the valve-opening contact O before the contact-member 57 moves over the resistance 61 to effect opening of the doors. Conversely the doors are closed before the valves. If closed, the valves may be opened at any time by means of the manual switch 52. In an alternative arrangement, both sets of valves are located on the outside of the cabin wall 80, Fig. 2, the main pressure regulating valves being of the type described in Specification 664,143, [Group XXIX], and the auxiliary outflow valves being constructed as shown in Fig. 2. The switches 48, 55 in this case are replaced by double pole, double throw switches and the circuit is modified so that the manual switch 52 controls the main valves 9 only. The auxiliary outflow valve comprises a valve member 84, Fig. 2, co-operating with a seat 82 and carried by an annular diaphragm 92. The diaphragm 92 is disposed within a guide or collar 93 and is clamped to a Z-section member 87 spaced from the cabin by bolts 86. The valve member 84, together with the diaphragm 92, the member 87 and a dome 90 forms a control pressure chamber 98 communicating with the cabin through a pipe 100 having a restriction 101. The valve member 84 is loaded in the closing direction by a spring 99 and its stem 94 is guided in ball bearings 97. An outlet from the chamber 98 to atmosphere is controlled by a solenoid-operated auxiliary valve 104 which in effect replaces the electrically-operated jack 39, Figs. 1 and 3. The valve member 84 is opened when the auxiliary valve opens, but when the auxiliary valve is closed by the spring 107, the main valve 84 only closes slowly due to the time taken for the pressure in the chamber 98 to equalise through the restriction 101 with cabin pressure. Specification 690,089 also is referred to.