Anti-drainback valve for filter

Claim 1

FLUID FILTER DEVICE COMPRISING A CASING HAVING AN OPEN END PORTION; A FILTER ELEMENT DISPOSED WITHIN SAID CASING; A COVER MEMBER FOR CLOSING SAID OPEN END PORTION, SAID COVER MEMBER HAVING A CENTRAL OUTLET OPENING AND A SUBSTANTIAL CONE-SHAPED PORTION DIVERGING FROM SAID OUTLET OPENING TOWARD THE INTERIOR OF SAID CASING AND TERMINATING IN AN ANNULAR PERIPHERY DISPOSED BETWEEN THE CENTRAL AXIS OF SAID CASING AND THE INNER SURFACE THEREOF, SAID CONESHAPED PORTION HAVING AT LEAST ONE INLET OPENING THEREIN ADJACENT SAID ANNULAR PERIPHERY; A FLEXIBLE VALVE DISC OVERLYING THE SURFACE OF SAID CONE-SHAPED PORTION FACING THE INTERIOR OF SAID CASING, THE CENTRAL PORTION OF SAID DISC BEING SECURED ADJACENT SAID OUTLET OPENING OF SAID COVER MEMBER AND SPACED APART FROM AND OVERLYING SAID CONESHAPED PORTION AT A LOCATION POSITIONED FURTHER FROM THE INTERIOR OF SAID CASING THAN SAID ANNULAR PERIPHERY, SAID VALVE DISC BEING ADAPTED TO FLEX AND ABUT SAID SURFACE ADJACENT THE ANNULAR PERIPHERY OF SAID INNER CONE-SHAPED PORTION TO BLOCK FLOW FROM THE INTERIOR OF SAID CASING TOWARD SAID INLET OPENING; AND A DIAPHRAGM SPRING OVERLYING THE SURFACE OF SAID VALVE DISC FACING THE INTERIOR OF SAID CASING, MEANS FOR POSITIONING SAID SPRING WITH THE CENTRAL PORTION OF SAID SPRING SPACED APART FROM SAID VALVE DISCAND THE OUTER PERIPHERAL PORTION OF SAID SPRING URGING SAID VALVE DISC TOWARD THE SURFACE OF SAID CONE-SHAPED PORTION ADJACENT SAID ANNULAR PERIPHERY THEREOF.