Sealing caps

Claim 1

A two piece petrol cap assembly for application to the filler neck of an automobile petrol tank, said cap assembly comprising a one-piece overcap body and a one-piece plastic diaphragm, said cap body and diaphragm having mutually cooperating means to permit them to be relatively rotatably coupled together as a unit, said cap body having means adapted to mutually cooperate with securing means on the neck of said petrol tank, said diaphragm being substantially continuous and presenting an annular wall which extends radially outwardly and includes the outer margin of said diaphragm, said diaphragm in its relaxed condition when coupled with said overcap being spaced axially from said cap body in the vicinity of said annular wall, said diaphragm having another wall radially inwardly of said annular wall which extends a substantial distance angularly inwardly relative to the axis of said cap body and capable of being moved radially outward to form a continuous seal against the interior surface of said neck upon mounting of said cap and diaphragm unit on the neck of the petrol tank as said cap is progressively pressed onto the rim of said filler neck of said tank, the seal between the two wall of the diaphragm and the inner surface and rim of the neck being continuously maintained by said securing means operative between said cap head and filler neck, said diaphragm further having means abutting the cap body, said means having a fine labyrinthine passage over its outer surface and a small passage opening through the diaphragm to a radially inner portion of the passage.