GB1104849A - Improvements in or relating to oxygen regulators - Google Patents

Abstract

1,104,849. Regulating apparatus for respiration. WESTLAND AIRCRAFT Ltd. 13 Oct., 1966 [18 Oct., 1965], No. 44100/65. Heading AST. [Also in Division G3] An automatic regulating apparatus for an aviator's mask 1 comprises an oxygen supply valve 2, a (conventional) sensor 3 responsive to the partial pressure of the oxygen in the mask, a pressure transducer 4 responsive to the pressure difference between the inside and outside of the mask. a combined expiratory and air-intake valve 5, and an electronic control circuit 13 - - 22 arranged to vary the ratio of air to oxygen to maintain a desired partial pressure of oxygen in the mask. The signals from sensors 3, 4 are combined to produce from member 20 positive and negative pulses of which the latter cause the valves 2, 5 to be respectively closed and open during the expiratory period and the former cause the valves 2, 5 to be opened alternately during the inspiratory period to produce the mixture of air and oxygen required to maintain the desired partial pressure, which varies with the altitude of the aircraft to produce correcting signals from the sensor 3. The valves 2, 5 are electromagnetically controlled, Figs. 3 and 4 (not shown) and are opened during the respective marks and spaces of the positive pulse train produced during the inspiratory period, the mark/space ratio being varied by the signal from sensor 3 so that the system is fully automatic up to and including 100% oxygen. An altitude reference sensor 15 provides a bias to increase the amount of oxygen to prevent mask-seal leakage when a particular altitude is reached, the effect being that the transducer 4 then operates about a new datum pressure. The expiration phase is not affected. The electronic control also prevents opening of the valve 5 under "g" loading conditions, and members 4, 15 operate together to maintain the correct mask pressure in the event of cabin decompression. Should the altitude increase above that which can be accommodated by 100% oxygen admission during the inspiratory period, the partial pressure signal from amplifier 16 adjusts a safety pressure bias 19 which acts in conjunction with the transducer 4 to increase the oxygen pressure in the mask by prolonging the opening of the valve 2. Transducer 4 produces a variable capacitance signal, Fig. 2 (not shown).