Patent GB-799635-A (GB)
Title: Improvements in closed circuit breathing apparatus
IPC: A62B7/04
Filed: 1954-12-20
Abstract: 799,635. Respiratory apparatus. AUERGES AKT.-GES. Dec. 20, 1954 [Dec. 19, 1953; March 13, 1954], No. 36776/54. Class 81 (2). A closed circuit breathing apparatus with a lung-controlled oxygen supply comprises an oxygen supply valve controlled by an auxiliary valve actuated by suction created as the respiration bag empties, and an oxygen supplementation valve controlled by pressure in the exhalation passages of the apparatus so as to open only during exhalation of the user. On inhalation through a breathing tube 13 connected with an inhalation chamber 10, a decrease in pressure in the inhalation chamber 10 and a respiration bag 8 is transmitted by a conduit 29 to a control chamber 28 of an auxiliary valve 24. A diaphragm 25, which forms one side of the control chamber 28 and is open to the atmosphere on the other side, moves to open the auxiliary valve 24 so that oxygen in a chamber 23 above a control diaphragm 20 of an oxygen supply valve 18 flows into the auxiliary valve control chamber 28 thus reducing the pressure in the chamber 23. The control diaphragm 20 of the oxygen supply valve 18 is thus caused to move to open the valve 18 so that oxygen flows via a conduit 31 into a tube 7 which connects an air purifier cartridge 6 with the breathing bag 8. Oxygen is supplied from a cylinder 14 via a stop valve 15 and a pressure reducing valve 16 to the oxygen supply valve 18 and enters the chamber 23 through a throttle aperture 22 in a valve element 19, which controls the oxygen supply valve 18, at such a rate that the pressure in chamber 23 is not sufficiently great to prevent the opening of the oxygen supply valve 18 when the auxiliary valve 24 is open. On exhaling into a breathing tube 1, inhalation valve 12 is closed and the pressure in an exhalation chamber 2 rises. The rise in pressure is transmitted by a conduit 39 to the control chamber 38 of an oxygen supplementation valve 32. A diaphragm 35, which forms one side of the control chamber 38 and is open to the atmosphere on the other side, rises to open valve 32 so that oxygen flows into the control chamber 38 through a throttle aperture 42 connected with the pressure reducing valve 16 by a conduit 33 and thence to the exhalation chamber 2. In a modification (not shown) the oxygen supply valve 18, auxiliary valve 24 and oxygen supplementation valve 32 are contained in the same valve box. In another modification (Fig. 3, not shown) the conduit connecting the inhalation chamber with the auxiliary valve is nested within a conduit between the oxygen supplementation valve and the exhalation chamber, a single screw connection being provided between the conduits and the inhalation and exhalation chambers. In another modification (Fig. 5, not shown) the conduit 29 between the inhalation chamber 10 and the auxiliary valve 24 is also openly connected with the control chamber 38 of the oxygen supplementation valve 32, a non- return scavenging valve which opens when the exhalation valve 4 opens being provided in the exhalation chamber 4. In another construction (Fig. 6, not shown) the oxygen supplementation valve is opened by pressure of exhaled air directly upon its control diaphragm which also serves as an exhalation valve.