Breathing apparatus

Claim 1

A SERVO OPERATED OXYGEN DEMAND REGULATOR COMPRISING A CASING HAVING AN OXYGEN SUPPLY INLET, A DEMAND OUTLET AND AN OUTLET AIR INLET, A DEMAND VALVE SITUATED BETWEEN SAID SUPPLY INLET AND SAID DEMAND OUTLET TO CONTROL OXYGEN FLOW THEREBETWEEN, A MAIN DIAPHRAGM DISPOSED WITHIN SAID CASING AND SUBJECTED ON ONE SIDE THEREOF TO DEMAND OUTLET PRESSURE IN A MAIN CHAMBER AND ON THE OTHER SIDE TO PRESSURE AT OR ABOVE CABIN PRESSURE, LEVER MEANS FOR OPERATIVELY CONNECTING SAID MAIN DIAPHRAGM TO A SERVO VALVE, SAID SERVO VALVE BEING SUBJECTED ON ONE FACE THEREOF TO A SUBSTANTIALLY CONSTANT PRESSURE FROM A PRESSURE REDUCING VALVE DISPOSED BETWEEN SAID SUPPLY IN LET AND SAID SERVO VALVE, A SERVO CHAMBER FORMED WITHIN SAID CASING HAVING A PORTION OF ONE WALL FORMED BY A SECONDARY DIAPHRAGM OPERATIVELY CONNECTED TO SAID DEMAND VALVE, SAID SERVO CHAMBER BEING DISPOSED WITHIN SAID CASING IN A POSITION SUCH THAT OXYGEN FROM SAID SERVO VALVE PASSES INTO SAID SERVO CHAMBER FOR BUILDING UP PRESSURE THEREIN TO CAUSE SAID SECONDARY DIAPHRAGM TO DEFLECT AND OPEN SAID DEMAND VALVE, SAID PRESSURE REDUCING VALVE BEING ARRANGED TO DELIVER OXYGEN TO SAID SERVO VALVE AT A SUBSTANTIALLY CONSTANT PRESSURE BELOW A PREDETERMINED PRESSURE RANGE OF SAID INLET SUPPLY, AN AIR MIX INJECTOR COMPRISING A NOZZLE AND A MIXING TUBE, SAID NOZZLE BEING IN COMMUNICATING WITH SAID SERVO VALVE AND ARRANGED TO INJECT OXYGEN INTO SAID MIXING TUBE FROM SAID SERVO VALVE IN A MANNER AS TO INDUCE AMBIENT AIR INTO SAID MIXING TUBE FROM SAID AMBIENT AIR INLET, THE MIXTURE OF OXYGEN AND AIR FURTHER MIXING WITH THE OXYGEN FROM SAID DEMAND VALVE IN PASS OUT OF SAID DEMAND OUTLET.