Contained volatile liquids vapor retention system

Claim 1

A tank for storing and dispensing a volatile fluid comprising top, bottom, and side walls forming a closed chamber, fill pipe and discharge means for said chamber located on said tank, a flexible bag having top, bottom, and side walls corresponding generally to the top, bottom, and side walls of the tank on the inside thereof, an opening through one of the walls of the tank separate from said fill pipe, an opening in said bag conincident with the opening in the tank, a collar around the opening in the bag comprising a seal between the respective tank wall and the bag, and a breather valve operatively associated with said openings for passing air between the interior of said bag respectively filling and emptying said tank, said breather valve assembly comprising a body having a passage therethrough, a breather valve seat for said passage, a valve element operably associated with said valve seat and constantly open bleed passage means between the passage and the interior of the bag bypassing said valve seat, and means responsive to the level of liquid in the tank adapted to close the valve element on the valve seat when the liquid level reaches a pre-set elevation.