Constant-pressure carburetor

In a constant-pressure carburettor for an engine comprising walls forming an axially extending fuel air/mixture chamber which operates under reduced pressure, walls forming an axially extending air inlet duct upstream from and in general axial alignment with said mixing chamber, a vacuum controlled air intake valve between said air inlet duct and said mixing chamber, a suction duct downstream from said mixing chamber, a driver actuated throttle member between said mixing chamber and said suction duct, a float chamber, and fuel feed means through which fuel is drawn from said float chamber into said mixing chamber as required, the improvement wherein said fuel feed means comprises a fuel atomizer nozzle of high atomizing quality in one of said walls of said mixing chamber and opening obliquely into said mixing chamber with said nozzle located between and spaced from said air intake valve and said throttle member and directed in the downstream direction so that the fuel is directed obliquely across the axis of said mixing chamber toward the opposite surface thereof and in the downstream direction toward said throttle member, said atomizer nozzle having an axially extending central fuel supply passage with the axis of said passage at the outlet end thereof extending obliquely of the axis of said fuel air/mixing chamber and directed downwardly toward said throttle member and an annular atomizing air outlet concentrically surrounding the outlet end of said central fuel supply passage and constricting and throttling the supplied atomizing air whereby the velocity vectors of fuel and atomizing air at said outlets of said nozzle differ in magnitude and direction, proportioning means for regulating the flow through said central fuel supply passage, said proportioning means including an electronically controlled valve, and wall means in combination with said air inlet duct and said walls forming said mixing chamber forming a passage for supplying atomizing air to said atomizing air outlet of said nozzle, and heating means located in said walls of said mixing chamber downstream of said air intake valve and extending to said throttle member for heating the inner surface of said mixing chamber when the engine is cold and during normal operating conditions, said fuel atomizer nozzle is arranged to spray and atomize the fuel in the path of the air flow through said mixing chamber from said air inlet duct and any atomized fuel impinging on the heated surface of said mixing chamber is vaporized thereby avoiding precipitation of the fuel on the inner surface of said mixing chamber and affording a fine and large area distribution of the fuel mist within said mixing chamber.