Fuel tank filler cap with improved vent

Claim 1

A fuel tank cap having an air vent through which vapor can leave and air can enter the tank and means to prevent liquid fuel in the tank from being expelled through the air vent, comprising: A. an inverted cup-shaped portion adapted for detachable connection to the neck of a fuel tank inlet; B. walls fixed with respect to said inverted cup-shaped portion defining at least two superimposed coaxial substantially cylindrical compartments above the top of said inverted cup-shaped portion, and a bottom compartment beneath said superimposed compartments, each of said compartments having a side wall and said bottom compartment also having a bottom wall which together with its side wall separates the bottom compartment from the interior of the inverted cup-shaped portion; C. the upper one of two of said directly superimposed compartments being smaller in diameter than the lower one and its side wall having a flange projecting laterally outward from its lower marginal edge; D. the wall that separates said directly superimposed compartments having its peripheral portion underlying said laterally projecting flange and being spaced therefrom a short distance to form a shallow annular space which communicates with the upper one of said directly superimposed compartments; E. port means in said peripheral portion of the wall that separates said directly superimposed compartments communicating the lower one of said compartments with said shallow annular space and forming the only communication between said directly superimposed compartments; F. the wall separating the lowermost one of said superimposed compartments from the bottom compartment having port means spaced from the common axis of said compartments through which the compartments at the opposite sides of said wall are communicated; G. port means in a wall of said bottom compartment communicating the same with the interior of the fuel tank on which the cap is mounted; H. a centrally located port in the top of the uppermost of said superimposed compartments; and I. fibrous material filling said superimposed compartments.