Patent GB-1422399-A (GB)
Title: Oxygen regulator
IPC: A62B7/14
Filed: 1973-10-24
Abstract: 1422399 Respiratory apparatus BENDIX CORP 24 Oct 1973 [24 Oct 1972] 49569/73 Heading AST An oxygen regulator for breathing apparatus used in aircraft comprises a housing 12 incorporating a mixing chamber 140 into which are fed oxygen via a first inlet port 14, a pressure-reducing piston 68 and a first valve 24, and ambient air via a second inlet port 16 and controlling means 28, an outlet port 18 supplying the oxygen/air mixture to a recipient, with an aneroid 30 responsive to changes in ambient air pressure adjusting the ratio of oxygen to air supplied. Oxygen entering via port 14 flows through a restricted opening 74 into a passageway 22 and causes the piston 68 to move against pressure of a spring 72, bringing a head 76 carried on piston 68 to abut a seat 80 and maintain the oxygen pressure at a predetermined value. Piston 68 is mounted on a shaft 32 carried in a bearing housing 42 and rotatable by a square head 58, and fixable in varying positions representative of OFF-ON, 100% oxygen and emergency positive pressure positions by a series of tactile detents 36 in a helical groove 34 engaging a resiliently mounted ball 222. The oxygen is communicated from passageway 22 via a passage 82 to a visual flow indicator 26, to a first valve 24 controlling oxygen entry into mixing chamber 140 via passages 100, and to the controlling means 28. Oxygen from passageway 22 passes into a chamber 98, around a seat 110 and through passages 100 into mixing chamber 140 until a subsidiary flow, delayed by a restriction 108, causes equalisation of pressures in chamber 98 and a chamber 104, a diaphragm 102 then closing off passages 100 and preventing oxygen flow into mixing chamber 140. Upon a reduction in pressure in chamber 140 due to the recipient's breathing, the reduced pressure is communicated via passages 142 and 160 to a first sensing chamber 116 divided from a first ambient chamber 136 by a diaphragm 132 which operates a lever arm 118 uncovering a passage 114 and allowing oxygen to flow from chamber 104 and releasing diaphragm 102 to permit oxygen to flow from chamber 98 into mixing chamber 140. The oxygen pressure reduction in chamber 104 is simultaneously communicated to the flow indicator 26 via a passage 225. A reduced pressure in mixing chamber 140 is also communicated via a passage 164 to a second sensing chamber 168 divided from a second ambient chamber 174 by a diaphragm 172 of the controlling means 28, oxygen being also transmitted to the controlling means 28 from passageway 22 via a passageway 200 and flowing into a first chamber 196, and, via a bleed screw 204, into a second chamber 198. Chambers 196, 198 are separated by a diaphragm 190 attached to a piston 188 carrying at its lower end a diaphragm 192 dividing chamber 196 from an ambient chamber 206 and separated from mixing chamber 140 by a disc 210 resiliently held on piston 188 engaging a seat 220. The resulting pressure differential between chambers 168 and 174 causes diaphragm 172 to operate a lever arm 176 uncovering an oxygen escape passage 186 to allow oxygen to flow from chamber 198 into chamber 168, the combined pressure in chambers 196 and 206 then raising piston 188 lifting disc 210 from its seat 220 and allowing ambient air from inlet port 16 to flow into mixing chamber 140. Variation of ambient air pressure due to a change in altitude is sensed by the aneroid 30 which varies the supply of air to chamber 140 by gradually closing off passage 164 by means of a cylindrical cover 240 carried on a shaft 146 attached to aneroid 30, and also varying the supply of oxygen from valve 24 into chamber 140 by moving a face 158 attached to shaft 146 and partially obscuring passage 142. A shaft 256 attached to aneroid 30 is also movable by a manual control 156 so that when the regulator is set to supply 100% oxygen, passage 164 is closed off by cover 240, and a lever spring arrangement 250 is pivoted causing its tip 262 to augment the ambient air pressure acting on diaphragm 132 to assist lever arm 118 to open passage 114 on a depletion of pressure in mixing chamber 140. The effect of altitude on the oxygen/air ratio may be varied by a screw 244 attached to aneroid 30.