Overfill limiting apparatus for fuel tanks

Claim 1

A motor vehicle fuel tank vent system comprising: a fuel tank; a filler tube extending into the fuel tank to a depth of penetration which provides a vapor space in the top of the tank and a certain head of fuel in the filler tube when the tank is full; a vapor storage means; vent line means connected between the fuel tank and the vapor storage means, and normally closed pressure operated valve means in the vent line, the valve means being opened by pressure in the fuel tank greater than the pressure developed when the tank is substantially full of fuel including the head of the fuel in the filler tube whereby overfilling of the tank is liMited and vapor is periodically allowed to flow from the tank to the vapor storage means as the valve means opens, the valve means including a vertically mounted valve body having an upright axial passage therein and including a lower inlet opening with a surface forming a closure seat and an upper outlet opening, and an axially movable valve closure member carried in the passage, the closure member being normally seated on the inlet seat due to its weight which is such relative to the head of the fuel in the fuel tank whereby closing of the valve occurs when the tank is full, the closure member being so shaped as to have first lateral portions thereof spaced from the passage wall to allow vapor to flow past the member and through the valve body when the closure member is raised from the seat by excess pressure in the tank and to have second lateral portions abutting the passage wall to position the closure member axially in the valve body above the valve seat.