Variable venturi downdraft carburetor

A downdraft variable venturi carburetor for an internal combustion engine, comprising:

• a hollow carburetor body having an upwardly open air intake end and a downwardly open end adapted to be mounted to an intake manifold of an internal combustion engine and a fuel-air mixing chamber intermediate the ends for receiving and guiding air in a downstream flow from the intake and through the downwardly open end and into the manifold;
• an annular fuel dispensing orifice encircling the fuel mixing chamber within the body;
• means for supplying fuel to the orifice at a plurality of angularly spaced locations in response to operation of the engine;
• a first movable venturi member located centrally within the body along an upright axis for axial movement therein within the mixing chamber;
• wherein the first venturi member is substantially bell-shaped and includes a reduced end facing the intake end;
• a convex portion curving down and outwardly from the reduced end to a downstream edge;
• a first axial rim extending downstream from the downstream edge of the convex portion;
• a first outwardly beveled portion extending downstream from the first axial rim;
• and an inwardly beveled portion extending downstream from the first outwardly beveled portion;
• a second venturi member defining the orifice and located coaxially with and radially adjacent to the first venturi member;
• wherein the first and second venturi members together form an annular restricted air passage downwardly adjacent to the fuel dispensing orifice;
• and
• throttle means for axially moving the first venturi member relative to the second venturi member to enlarge and reduce the restricted air passage and thereby increase and decrease the flow of air and fuel through the mixing chamber.