Patent ID: 6857443

Claim:
A gas flow control mechanism for a gas blender comprising: a voltage sensitive orifice defining a passage for each gas to be controlled and having an inlet port in fluid communication with a gas source and an outlet port in fluid communication with a plenum for mixing at least two gases; a gas flow controlling means placed in a feed back loop to adjust at least a parameter or characteristic of a gas flow exiting from the orifice through the outlet port to a preset value; the gas flow controlling means comprising: a gas flow resistor in fluid communication with the gas exiting from the orifice and adapted to generate an output signal based on a gas flow characteristic; and a comparing means, responsive to the gas resistor flow signal, to continuously evaluate and monitor the characteristic of the gas exiting from the orifice, compare the same with the preset value and minimize any difference therebetween by adjusting current supplied to the orifice which in turn adjusts the gas flow therethrough to the preset value by adjusting the passage, including a normally open solenoid valve and a needle valve in parallel connection with the orifice and the controlling means, and providing a by-pass connection between the gas source and rotameter connected to the plenum.