Semi-closed circuit underwater breathing apparatus ratio regulator
An apparatus for adjusting the partial pressure of gaseous mixtures comprises a housing and piston. The housing defines a chamber coupled to an oxygen metering orifice, diluent metering orifice, vent port and gas outlet. The oxygen metering orifice provides oxygen to the chamber and the diluent metering orifice provides diluent gas to the chamber. The piston is movably positioned in the chamber and includes first and second sealing devices. The chamber is sectioned into a mixing chamber, a diluent chamber and a reference chamber located between the mixing chamber and diluent chamber. The diluent chamber receives a diluent gas referenced at ambient pressure and the reference chamber is charged with a gas having a reference pressure. The piston changes positions within the chamber depending on a force balance created by a pressure differential between the reference pressure and ambient pressure.
1. An apparatus for adjusting the partial pressure of gaseous mixtures, comprising:
a. a housing defining a chamber fluidly coupled to each of an oxygen metering orifice, diluent metering orifice and gas outlet, the oxygen metering orifice configured to provide oxygen to the chamber from an oxygen inlet, the diluent metering orifice configured to provide diluent gas to the chamber from a diluent inlet; and
b. a piston movably positioned in the chamber, the piston including first and second sealing devices thereby sectioning the chamber into a mixing chamber fluidly coupled to the oxygen metering orifice and the gas outlet, the mixing chamber configured to selectively receive oxygen and diluent gas; a diluent chamber fluidly coupled to the diluent inlet and the diluent metering orifice, the diluent chamber configured to receive a diluent gas; and a reference chamber disposed between the mixing chamber and the diluent chamber, the reference chamber configured to by charged with a gas having a reference pressure;
wherein the piston is configured to change positions within the chamber depending on a force balance created by a pressure differential between the reference pressure and the diluent gas pressure so as to output a mix gas having a proper oxygen-to-diluent gas ratio.
2. The apparatus of claim 1 wherein the piston further includes an internal leak path whereby the diluent chamber fluidly communicates with the mixing chamber upon leaking of diluent gas past the second sealing device.
3. The apparatus of claim 2 wherein the piston further includes a third sealing device interposed between the first and second sealing devices and wherein the internal leak path is located between the second and third sealing devices.
4. The apparatus of claim 1 further comprising a valve actuation assembly between the diluent inlet and the diluent chamber, the valve actuation assembly coupled to the piston whereby movement of the piston actuates the valve actuation assembly so as to selectively open or close a valve, the valve configured to inject diluent gas from the diluent inlet to the diluent chamber when open.
5. The apparatus of claim 1 wherein the chamber further includes a vent port fluidly coupling the reference chamber to ambient, the vent port being sealed after seating of the piston in the chamber during assembly of the apparatus so as to maintain the reference chamber at the reference pressure during use.