Rebreather system with depth dependent flow control and optimal PO.sub.2 d e
First Claim
1. In a semi-closed circuit rebreather system of the type comprising an oxygen rich gas source and a diluent gas source, configured to provide a breathing gas mix to a flow loop including a counterlung, a method for adaptively controlling flow rates of said oxygen rich and said diluent gasses so as to provide the partial pressure of oxygen of the breathing gas mixture within a specified range comprising;
- providing a first, oxygen rich gas source having a first oxygen fraction, FO.sbsb.2 ;
providing a second diluent gas source having a second oxygen fraction, FAIR ;
providing first and second flow control means, coupled respectively to said first oxygen rich gas source and said second diluent gas source, the flow control means individually adjustable for controlling gas flow from their respective gas sources to the counterlung flow loop; and
adaptively adjusting said first and second flow control means so as to vary flow rates from the oxygen rich gas source and the diluent gas source in a manner solely dependent on ambient pressure expressed as a function of diving depth.
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Accused Products
Abstract
A method and apparatus for a self contained underwater breathing apparatus in which a breathing gas is supplied to a flow loop from two separate gas sources each having a different oxygen fraction, and each controlled by separate mass flow controllers having variable flow rate. The mass controller flow rates are adaptively adjustable to deliver gas at variable flow rates which depend solely on a function of depth. An algorithm determines these specific flow rates from each of the tanks at particular depths, such that the gas flow from an oxygen rich gas source decreases as a function of depth, while the gas flow from a diluent gas source increases as a function of depth, so as to maintain the oxygen partial pressure in the flow loop within a specific pre-deternined range. The algorithm allows calculation of an optimum oxygen partial pressure, for a particular dive, which allows construction of a dive profile which maximizes bottom time while taking into account no-decompression time at depth, tank capacity limited time, and single-dive and daily pulmonary oxygen toxicity limits.
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Citations
30 Claims
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1. In a semi-closed circuit rebreather system of the type comprising an oxygen rich gas source and a diluent gas source, configured to provide a breathing gas mix to a flow loop including a counterlung, a method for adaptively controlling flow rates of said oxygen rich and said diluent gasses so as to provide the partial pressure of oxygen of the breathing gas mixture within a specified range comprising;
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providing a first, oxygen rich gas source having a first oxygen fraction, FO.sbsb.2 ; providing a second diluent gas source having a second oxygen fraction, FAIR ; providing first and second flow control means, coupled respectively to said first oxygen rich gas source and said second diluent gas source, the flow control means individually adjustable for controlling gas flow from their respective gas sources to the counterlung flow loop; and adaptively adjusting said first and second flow control means so as to vary flow rates from the oxygen rich gas source and the diluent gas source in a manner solely dependent on ambient pressure expressed as a function of diving depth. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A semi-closed circuit rebreather apparatus of the type comprising a flow-loop including a counterlung and a carbon dioxide scrubber canister, the rebreather further comprising:
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a first gas supply, comprising an oxygen rich compressed gas, the oxygen rich gas further having a pre-determined oxygen fraction, FO.sbsb.2 ; a second gas supply, comprising a diluent gas, the diluent gas having a pre-determined oxygen fraction, FAIR, less than the oxygen fraction, FO.sbsb.2, of the oxygen rich gas; first and second pressure regulators, respectively coupled between the first and second gas supplies and the flow loop of the rebreather; a first flow controller for controlling the flow rate of oxygen rich gas to the counterlung, coupled between the first pressure regulator of the first gas supply and the rebreather flow loop, the first flow controller having a variable flow rate and adaptively adjusting the oxygen rich gas flow rate to the counterlung in a manner solely dependent on a function of depth; and a second flow controller for delivering diluent gas to the counterlung, coupled between the second pressure regulator of the diluent gas supply and the rebreather flow loop, the second flow controller having a variable flow rate and adaptively adjusting the diluent gas flow rate to the counterlung in a manner solely dependent on a function of depth, so as to substantially extend dive time. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification