Patent ID: 7270143

Claim:
A variable orifice gas flow sensor for use with a gas in which moisture may be present, said sensor comprising: a housing having a gas flow passage therethrough, said gas flow passage being formed with a first port portion adjacent to one end of said passage and a second port portion adjacent to the other end of said passage, each of said port portions having a central axis, the flow area of one of said port portions transverse to the central axis differing from that of the other of said port portions, the central axis of one of said port portions being offset from the central axis of the other of said port portions in a direction normal to a gas flow direction through said gas flow passage; variable orifice means mounted in said gas flow passage intermediate to said first and second port portions, said variable orifice means having a gas flow limiting flapper mounted in an interior surface of said gas flow passage and extending into said gas flow passage for creating a gas flow opening in the passage, the size of said opening being variable responsive to gas flow in said gas flow passage; and a portion of said interior surface of said gas flow passage adjacent said variable orifice means being formed to slope away from a central axis of one of said portions in a direction extending away from said flapper to allow moisture from the gas to drain away from said portion of said interior surface adjacent to said variable orifice means.