GB940581A - A valve assembly for breathing apparatus - Google Patents

Abstract

940,581. Respiratory appliances. SIERRA ENGINEERING CO. May 30, 1960, No. 19042/60. Heading A5T. A valve assembly for breathing apparatus having a fixed main oxygen supply in an airplane and an auxiliary supply carried by the pilot, the main supply connection being closed automatically on severance from the main supply when the pilot leaves the plane leaving only the auxiliary supply operative, comprises a hollow body having a main supply inlet connected to one end, a valve in the inlet which is spring urged to close the inlet, an auxiliary supply inlet communicating with the hollow body at a point removed from the main supply inlet and a second spring normally urging an auxiliary valve to close the inlet but allowing the valve to open when the main supply valve is closed. As shown, a body 14 on which a master hose is mounted at one end 25 has screwed into the opposite end a main supply inlet 42 which receives a hose (not shown) connected to a fixed main supply of oxygen. A valve element 54 carrying a stem 51 bears against a seat 55 in its closed position. A guide 50 mounted on the stem is slidable in grooves 49 in the inlet 42 and acts as a stop for a spring 65 the other end of which abuts against a shoulder 66 adjacent the valve seat 55. A relief valve element 57 is normally urged by a spring 58 weaker than the spring 65 into a position covering apertures 56 in the valve element 54. A hose (not shown) from a portable auxiliary oxygen supply is connected to an auxiliary supply inlet 29 which is screwed into a connection 26 on the body 14 and comprises a valve seat 31 against which a valve element 32 is urged by a spring 33. During operation with either gas supply the expired gases are exhaled through an exhaust valve (not shown) on the mask. Mounting the fixed supply hose on the member 42 moves the guide 50 into recesses in a retaining ring 47 and the valve element 54 into the open position. On removal of the supply hose the valve element 54 closes under the action of the spring 65. The portable supply hose is already connected to the inlet 29 and since the pressure on the body 14 fell on closure of the main valve gas pressure in the hose unseats the valve element 32. If pressure in the body now becomes excessive, the relief valve element 57 opens. When the pilot reaches a lower altitude, the ambient pressure may overcome the main valve spring 65 and ambient air be mixed with the oxygen in the body 14.