Closed circuit oxygen feed for underwater breathing appts. - has sprung bellows with needle valve to supply oxygen and further valve to control neutral gas supply below certain depth

摘要

The underwater breathing apparatus uses a closed circuit to recycle used air, this being provided with pure oxygen to maintain a constant ratio. It comprises a bellows (1, 2), hinged at one side and connected to the mouthpiece (9) through a filter (10) removing carbon dioxide. At the hinge end, a spring (4) actuates a diaphragm (5) in accordance with the volume (V) breathed into the bellows and the oxygen supply pressure. A needle valve (7, 8) apportions the correct amount of oxygen (02) to maintain balance. A buffer tank (C) is provided and, after a certain depth, the bellows opens a second valve (11, 12) to admit a proportion of neutral gas (N2).