Variable venturi carburetor

A carburetor for an internal combustion engine, comprising carburetor body means, induction passage means formed through said body means, a related source of fuel, variable venturi means situated in said induction passage means for variably determining a variably openable venturi throat, a fuel passage means comprising metering restriction means between said source of fuel and said induction passage and discharging fuel into said passage adjacent said venturi throat, the dominant metering characteristic of said carburetor being venturi depression at said throat proportional to the square of the airflow through said throat, fuel flow through said restriction means proportional to the square root of said metering depression, resulting in fuel flow directly proportional to airflow, said variable venturi means comprising a first fixed venturi section and a second variably positionable venturi section, said first venturi section and said second venturi section cooperating to define said variably openable venturi throat therebetween, variably positional throttle valve means situated in said induction passage means downstream of said variable venturi means, connecting means operative interconnecting said throttle valve means and said second variably positionable venturi section for causing said second venturi section to assume opening positions determined by the position of said throttle valve means and correspondingly determine the effective opening of said variably openable venturi throat over the entire range of throttle movements from closed throttle to wide open throttle, said restriction means comprising calibrated orifice metering means and calibrated valve metering means, said calibrated orifice metering means and said calibrated valve metering means being relatively movable with respect to each other in order to thereby cooperatively define an effective fuel metering area, and one of said calibrated metering means being directly positioned by said second variably positionable venturi section and not any portion of said connecting means in order to thereby assure said effective fuel metering area to be totally dependent upon the actual position of said second variably positionable venturi section and thereby assure said effective fuel metering area to be correct for the then existing effective opening of said variably openable venturi throat, said connecting means comprising first and second lost motion means, said first lost motion means enabling said throttle valve means to at times move in the throttle opening direction without absolutely causing a corresponding movement of said second venturi section, and said second lost motion means enabling said second venturi section to move toward a further reduced venturi throat opening after said throttle valve means has attained a curb idle position.