Patent ID: 7744758

Claim:
A liquid filter comprising a cup-shaped housing with a liquid inlet and a liquid outlet in communication with a discharge chamber of said filter; a filter element sealingly disposed in said housing between the inlet and the outlet, and a one-piece barrier membrane disposed adjacent the opening of the cup-shaped housing so that the liquid inlet and the liquid outlet can be closed by the barrier membrane, wherein the barrier membrane includes a circular connecting plate having a first return flow barrier arranged on the radially outer edge thereof and a concentric second return flow barrier arranged radially inwardly thereof, the connecting plate is provided with connecting elements for detachably connecting the barrier membrane to an end disk of the filter element or to a cover plate, and the concentric second return flow barrier includes an outlet seal valve having a duckbill configuration, said duckbill constructed as a flexible tube continuation extending from said connecting plate into said discharge chamber, said flexible tube forming a pair of tilted, opposing, generally flat members converging to form a self-closing slit, said slit configured to sealably close said liquid outlet, wherein curved sidewalls of said flexible tube are operable to tension said flat members to maintain closure of said slit, wherein the duckbill is directed towards the interior of the filter element, wherein the duckbill is configured to be mechanically opened during installation.