Variable venturi type carburetor

Claim 1

A variable-venturi type carburetor having an intake passage, comprising means comprising a suction piston disposed in said intake passage and adapted to be moved in a path of movement in dependency on the flow rate of intake air sucked into an engine through said intake passage, a canister, a carburetor housing forming an internal passage communicating with said intake passage, a vent passage, a valve chamber communicating with said internal passage and with said vent passage, respectively, and a fuel float chamber communicating with said vent passage and with said valve chamber via said vent passage, means comprising an external passage for communicating said valve chamber with said canister, said internal passage communicating between said valve chamber and the intake passage of said carburetor, means comprising a rod valve disposed in said valve chamber for alternately communicating either said external passage with said vent passage via said valve chamber or said internal passage with said vent passage via said valve chamber depending on predetermined conditions of the engine, and spring means for biasing said rod valve such that said rod valve in normal condition closes communication between said external passage and said vent passage, said rod valve having a projecting end portion projecting into said intake passage spaced from and under said suction piston in the normal condition in the path of movement of said suction piston, said end portion constituting means for being pressed directly by said suction piston only when said suction piston is lowered in a direction opposite to the direction of biasing of said spring means, overcoming the force of said spring means so as to interrupt communication between said internal passage and said vent passage.