Method and apparatus for maintaining a constant ratio of gases in a mixture subject to steady state and intermittent flow conditions

A mixing device configured to combine flowing media received from elevated pressure sources, comprising:

• a housing which includes a plurality of inlet ports and a plurality of corresponding inlet pressure passages, each of said passages configured to communicate between said corresponding inlet port and a pressure gauge connection;
• a plurality of flow control orifices, each positioned downstream of and communicating with a corresponding said inlet port;
• a plurality of check valves, each positioned downstream of a corresponding said flow control orifice;
• a chamber in communication with said inlet ports, said chamber defined by a first piston upstream of a second piston;
• a control valve, connecting said chamber to an outlet port, configured to govern the flow of media exiting said chamber;
• a delay valve, connecting said inlet ports to said chamber, configured to govern the flow of media entering said chamber;
• said first and second pistons slidably mounted and positioned such that an exhaust port of said first piston communicates with an intake port of said second piston, each of said pistons including an outer surface of at least two diameters connected by a radial shoulder, each of said pistons including a hollow interior passage extending from an upstream intake port to a downstream exhaust port.

A mixing device configured to combine flowing media received from elevated pressure sources, comprising:

• a housing defining a plurality of inlet ports;
• a chamber within said housing in communication with said plurality of inlet ports via a plurality of corresponding flow control orifices;
• a plurality of check valves, each positioned downstream of a corresponding flow control orifice;
• and,
• a control valve connecting said chamber to an outlet port, said control valve opening in response to a decrease in pressure at said outlet port.

A method of reducing ratio errors in an intermittently flowing mixture, comprising the steps of:

• causing a control valve positioned between a flow passage and an outlet to open;
• permitting the pressure in said flow passage to drop significantly;
• and
• responsive to significantly dropped pressure,
• causing a delay valve, positioned between said flow passage and at least one flow orifice, to suddenly open.