Centrifugally operated evaporative emissions control valve system for internal combustion engines

Abstract

An evaporative emissions control system for small internal combustion engines. A control valve assembly includes a pair of control valves which are respectively associated with a fuel line and with a vent line which each connect the fuel tank and the carburetor of the engine. The control valve assembly is automatically operable responsive to the rotation of a rotatable member of the engine drive train, such as the crankshaft, camshaft, flywheel, governor assembly, or other rotatable member. In one embodiment, for example, the control valve assembly is driven from the flywheel. When the engine is not running, the flywheel is stationary and does not rotate, and the control valves automatically closes the vent line and the fuel line, thereby trapping fuel vapors within the fuel tank and blocking the supply of liquid fuel to the carburetor. Upon cranking of the engine for start up, a flyweight mechanism of the control valve is driven by rotation of the flywheel, and centrifugal force acting on the flyweight mechanism causes the control valve to automatically open the vent line and the fuel line, venting fuel vapors from the fuel tank through the vent line to the carburetor for consumption by the engine, and opening the supply of liquid fuel from the fuel tank to the carburetor.