Patent GB-839771-A (GB)
Title: Improvements in apparatus for controlling the supply of gas to a breathing device
IPC: A62B9/02
Filed: 1957-02-07
Abstract: 839,771. Respiratory apparatus. SVENSKA AKTIEBOLAGET GASACCUMULATOR. Feb. 7, 1957 [Feb. 16, 1956], No. 4233/57. Class 81 (2). [Also in Group XXIX] Apparatus.-Tne oxygen supply conduit 1 is connected to a pilot's mask or helmet 6 through an inlet valve 4 comprising a membrane 12 and a seat 13, a chamber 14 being connected with the conduit 1 by a nozzle 15 in the membrane 12 and having an outlet controlled by a valve 16 actuated by another membrane 17 via a lever 18. A chamber 20 on the outside of membrane 17 is connected to a pressure chamber 8 that is normally open to the atmosphere through a passage 21 controlled by a membrane valve 9, the membrane carrying a nozzle 22 connecting the chamber 8 with a space 23; the chamber 8 is also open to the surrounding atmosphere by a nozzle 24, a spring-loaded valve or a barometrically controlled restriction, not shown; the nozzles 22, 24 being so dimensioned that a pressure of about one-fifth of that in space 23 is present in chamber 8. Space 23 leads to a conduit 10 connected to a pressure suit activation of which is controlled by a valve 11 comprising a membrane 26 and seat 27 that opens and closes the communication of conduit 10 with a passage 29 branching from conduit 1; the membrane 26 has an interconnected valve disc 31 that co-operates with a seat 32 controlling the connection of conduit 10 to the atmosphere. The membrane 26 is normally seated by connecting its chamber 33 to conduit 1 via a restriction 34, the disc 31 being seated and membrane 26 being unseated when the pressure in chamber 33 is reduced to that of the atmosphere by manually opening orifices 36 or upon automatic opening of a valve disc 37 through movement of barometric bellows 40. The pressure suit may be connected to the mask conduit 5 and chamber 8, 20 may form one space. The mask exhalation valve 7 consists of a membrane 44 urged by a spring 46 on to a seat 45 whilst beyond the seat the membrane rests on a disc 47 incorporating apertures 48, an annular slot 49 being formed between the disc 47 and seat 45 so that normally the exhaled gas escapes to the atmosphere via the aperture 48 and slot 49. A chamber 50 at the back of membrane 44 is connected to chambers 8, 20 by a tube 51. Operation, (a) Normal conditions.-The pressure of the atmosphere is present in conduit 10 and chambers 20, 50 so that upon inhalation the pressure on the main surface of membrane 17 falls and the membrane moves to open valve 16 and cause a pressure reduction in chamber 14 whereupon the membrane 12 is unseated to enable oxygen from conduit 1 to flow to the mask until the inhalation ceases when the pressure rise behind the membrane 17 moves the latter to close the valve 16 whereby pressure builds up in chamber 14 through the nozzle 15 and seats the membrane 12. Upon exhalation the membrane 44 is lifted. (b) Emergency conditions.-Should the aircraft cabin pressure reduce to that of the atmosphere due to an explosive decompression, for example the bellows 40 actuate the disc 37 to reduce the pressure in chamber 33 and cause the valve 11 to operate, the membrane 26 unseating and the disc 31 seating so that conduit 10 and chambers 8, 20, 23 and 50 are connected to conduit 1, the pressure suit is activated, and the valve 9 closed; the membrane 17 is in consequence moved to effect the supply of oxygen to the mask whilst the higher pressure in chamber 50 allows the mask pressure to rise to the desired overpressure which when reached brings about closure of valve 16 and hence membrane 12, the latter opening and closing upon inhalation and exhalation as before but under the different pressure conditions described. Exhaled gas passes to the surrounding atmosphere via slots 49 only thus effecting an automatic change in the effective diameter of membrane 44 when changing from normal to over-pressure breathing.