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Pressure-actuated regulator to allow multiple bailout mixes to be used on the same DV at the correct depth
  [vote for,

When diving with a rebreather, or on open circuit SCUBA to great depths, it's common practice to carry one or more tanks with different gas mixes in, due to the issues of Nitrogen narcosis (shallow) and Oxygen toxicity (deeper). Use of the wrong mix at the wrong depth can cause hypoxia or hyperoxia, both dangerous conditions. Normally, multiple DVs (Demand Valve, the mouthpiece) are used, one for each cylinder. In an emergency situation, especially after a sudden loss of main gas supply and/or in a dark/murky environment, picking the wrong DV could be dangerous especially if it goes unnoticed.

The proposed regulator is a long cylinder containing a plunger, with a sealed chamber at one end and the other open to the surrounding water. As the external pressure increases, the gas in the sealed chamber is compressed, and the plunger moves down the cylinder. The position of the plunger can be determined for a range of pressures. The end of the plunger reaches through the sealed chamber and is attached to the line to the DV. The plunger is hollow, with the top end (facing the water) sealed and a narrow ring near the top connected to the central cavity. At points down the cylinder, openings in the walls connect to the first stage regulators atop the various cylinders.

As the diver descends, the plunger moves down the cylinder, moving the opening to the DV between the outlets for the various cylinders. When the diver needs to breath from one of the cylinders rather than his/her primary source, s/he simply needs to breath from the DV, which will be connected to the correct gas mix for the current pressure.

While the described mechanism uses an unsprung plunger, a spring assist or diaphragm-actuated mechanism could also be used. The core of the idea is a valve that changes inputs dependant on external pressure.

EdZ, Apr 10 2011

Illustration http://img20.images....us/i/multireg.png/
For those allergic to WORDS WORDS WORDS [EdZ, Apr 10 2011]


       I like it. better make sure it's reliable. maybe link it to your dive computer.
sninctown, Apr 10 2011

       Sounds good to me.   

       I wonder if you could also add odorants to the different gas mixtures, so you could tell if you were breathing the wrong one (peppermint, strawberry, fried onions...)
MaxwellBuchanan, Apr 10 2011

       The olfactants would have to survive high pressure without corroding the inside of the tank, but that would work, with the only limitation being you'd have to take a lungful and exhale through your nose to smell it.
EdZ, Apr 10 2011

       I think they'd be non-corrosive, at least at the concentrations needed. On the other hand, I have no idea what pressure does to your sense of smell - does anyone know? If you fart in your suit at 100ft, what's the result?   

       (Actually, I guess it's physiologically difficult to fart at 100ft.)
MaxwellBuchanan, Apr 10 2011

       //I wonder if you could also add odorants// Good for signaling changes, but not great for monitoring a steady state: olfactory fatigue.
mouseposture, Apr 10 2011

       Exactly. You want to know you've switched to the deep mix, you don't want to keep smelling gherkins for an hour. It's a plus.
MaxwellBuchanan, Apr 10 2011

       The deep mix would be gherkins; when you surfaced, you'd switch to a floral-scented mix. The mnemonic would be the lyric from _Gypsy_ "[everything's] coming up roses."
mouseposture, Apr 10 2011


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