GB724801A - Improvements in or relating to protective oxygen respirators providing circulation of the respiration air - Google Patents

Abstract

724,801. Respiratory appliances. AUERGES. AKT.-GES. Feb. 23, 1953 [Feb. 23, 1952], No. 5033/53. Class 81 (2). A closed circuit respirator has a scavenging port opened by the exhalation valve and means for ensuring that the system contains a high proportion of oxygen on being taken into use. The inhalation and exhalation valves are mounted in a unit comprising a casing 4, Fig. 3, divided into two compartments by a partition 5. Air from the breathing bag is received through a connection 15 and passes to the mask through the inhalation valve 14. Air from the mask enters through a connection 2 and passes through exhalation valve 32 and pipe 8 to the carbon dioxide absorber and back to the breathing bag. On each occasion that the valve member 32 is raised it also opens a tube 10 leading to atmosphere through a restricted orifice 12, so that a small proportion of the contained air is expelled at each exhalation, thereby reducing the proportion of nitrogen retained. The main oxygen control valve, comprising a seating 44, Fig. 4, and plunger 46 is actuated through a connection 50 by a diaphragm 40 through the middle of which is a passage 52 restricted by a choke 54. The chamber 55 surrounding the latter is closed by a valve 58, 59 which is opened by inward movement of a second diaphragm 61. When oxygen is first turned on, it enters the control valve through duct 42 and, owing to the presence of choke 54, it causes a temporary excess pressure on the lower side of diaphragm 40 which opens the main valve 46 and allows a flow of oxygen into the system until the pressures on the two sides of the diaphragm are equalised, thus ensuring that a high proportion of oxygen exists before breathing commences. In order that there may be a minimum of stagnant air in the breathing bag at this time, a light spring is provided to maintain the bag in the collapsed condition when out of use. Oxygen from the control valve passes through a tube 21 to a connection 20, Fig. 3, adjacent to the inhalation valve and, at each inhalation, the reduction in pressure in the chamber 13 is communicated through port 16 and pipe 17, Fig. 4, to cause inward movement of the diaphragm 61 and venting of the space 55. This disturbs the balance of pressure on the two sides of diaphragm 40 and the main valve 46 is accordingly opened to admit a further supply of oxygen.