Petrol tank filler cap on vehicle - is fitted with vacuum valve to admit air at low pressure and spring loaded safety valve to prevent normal escape of vapour

摘要

The filler cap has a pressure valve (13) which is kept on its seat by a helical spring (14). The valve is connected to the reservoir by the passage (16). The valve will open against the spring when the vapour pressure inside the tank exceeds a limit determined by the spring loading. The tank is protected against vacuum by the shifting valve (19) which is connected to the tank by the passage (27) and the bleed holes (9) is the passage (11). Inlet air is admitted through the passage (16) and a bleed hole in the passage (17).