| 摘要 |
1,162,412. Automatic cabin pressure control. GARRETT CORP. Aug. 25, 1966 [Sept. 13, 1965], No.38237/66. Heading G3R. Signals, dependent in magnitude and sense on deviation of aircraft cabin pressure from a datum, control separate circuits to operate an A. C. motor at a corresponding speed in the appropriate sense to correct the deviation by adjustment of a damper controlling air outlet from the cabin. In Fig. 2, deviations of pressure in a pressurized cabin, from a value selected by the pilot, are detected by a unit 11 the electrical output of which is effective to correct deviations by controlling an A. C. motor 43 adjusting a shaped damper in an exhaust outlet of the cabin. According to the sense of deviation, a D. C. signal of one polarity or the other is applied through a line 69 or 71 to cause operation of the motor in one direction or the other. A transistor circuit 73 or 75 is thus controlled so that a blocking oscillator 81 or 81<1> operates to render a silicon controlled rectifier 83 or 83<1> conductive thereby causing the motor to run in the appropriate direction. Feedback circuits 87, 87<1> ensure that, for small pressure deviations, discrete groups of pulses are produced by the blocking oscillators, whereas for larger deviations the blocking oscillators operate continuously. Stabilizing rate feedback from a tachometer alternator 45 driven by motor 43 is demodulated at 59 and delayed at 61 before being combined with the output of unit 11. This feedback is also applied in A. C. form between a modulator 63 and a demodulator 67 in the control system. The stabilizing feedbacks may alternatively be derived from a resistance-condenser circuit having a suitable time constant, which integrates the pulses from both blocking oscillators. A switch 51, closed by the landing gear on landing, applies such a signal to the control system that the damper is opened to its limit. A further switch (not shown) disables the control system if the damper is operated manually. |
