Tank closure assembly

Claim 1

IN A TANK DOME FOR ATTACHMENT TO THE PERIPHERAL RING DEFINING THE FILLING OPENING OF A TANK, WHEREIN SAID TANK DOME INCLUDES A BASE FOR PERIPHERAL ENGAGEMENT UPON THE UPPER EDGE OF SAID RING, A CENTRAL OPENING IN SAID BASE, A CAP PIVOTALLY MOUNTED TO SAID BASE AND NORMALLY LATCHED SHUT TO CLOSE SAID CENTRAL OPENING, AND A VENT VALVE OF PREDETERMINED VENTING CAPACITY IN SAID CAP TO VENT SAID TANK THROUGH SAID CAP, THE IMPROVEMENT COMPRISING: A PLURALITY OF ELONGATED ANCHOR ELEMENTS SECURED AT THEIR UPPER EXTREMITIES TO SAID BASE AND DEPENDING THEREFROM THROUGH SAID FILLING OPENING; A PLURALITYA OF STOP MEANS ADJACENT THE LOWER EXTREMITIES OF SAID PLURALITY OF ANCHOR ELEMENTS; A PLURALITY OF LUGS AXIALLY SLIDABLY CARRIED BY SAID PLURALITY OF ANCHOR ELEMENTS ABOVE SAID STOP MEANS AND ENGAGING THE LOWER EDGE OF SAID RING; AND A PLURALITY OF BIAS MEANS BETWEEN SAID STOP MEANS AND SAID LUGS WHEREBY SAID BASE IS URGED AGAINST THE UPPER EDGE OF SAID RING TO SEAL SAID TANK AND YET IS MOVABLE AWAY FROM SAID RING AGAINST THE BIAS OF SAID BIAS MEANS TO VENT SAID TANK UPON DEVELOPMENT IN SAID TANK OF PRESSURES SUBSTANTIALLY EXCEEDING THE VENTING CAPACITY OF SAID VENT VALVE.