Spark plug construction for lean mixture burning internal combustion engine

Abstract From the Canadian patent

An internal combustion engine has a main combustion chamber defined by a cylinder bore and its associated piston and a valved intake passage for introducing a lean fuel-air mixture in the combustion chamber. A novel spark plug mounted in the engine in place of the conventional spark plug has an apertured dome portion defining a limited size spark ignition chamber about the spark gap and a valved branch passage to the ignition chamber connected to a first fuel supply such as a rich fuel-air, mixture source to achieve ignition thereof in the ignition chamber causing a flame discharge which ensures ignition of another fuel mixture , such as a lean mixture in the main, combustion chamber. …