Covers and seals for manway structures for tanks

Claim 1

IN A TANK INCLUDING A HOLLOW BODY, TUBULAR MANWAY STRUCUTRE CARRIED BY SAID BODY AND PROJECTING OUTWARDLY THEREFROM AND DEFINING A MANWAY EXTENDING THERETHROUGH INTO SAID BODY, THE OUTER END OF SAID MANWAY STRUCTURE TERMINATING IN A FIRST FLAT ANNULAR SEALING SURFACE SURROUDNING THE OUTER END OF THE MANWAY EXTENDING THERETHROUGH, A COVER CARRIED BY SAID MANWAY STRUCTURE AND MOUNTED THEREON FOR HINGED MOVEMENTS BETWEEN CLOSED AND OPEN POSITIONS WITH RESPECT TO THE OUTER END OF SAID MANWAY STRUCTURE, THE INNER SIDE OF SAID COVER BEING PROVIDED WITH A SECOND ANNULAR SEALING SURFACE DISPOSED RADIALLY INWARDLY FREOM THE PERIMETER THEREOF AND ARRANGEDIN COOPERATING POSITION WITH SAID FIRST SEALING SURFACE WHEN SAID COVER OCCUPIES ITS CLOSED POSITION, SAID SECOND SEALING SURFACE BEING STEPPED AND INCLUDING CONCENTRIC AND ADJACENT OUTER AND INNER FLAT ANNULAR PORTIONS, THE OUTER ANNULAR PORTON OF SAID SECOND SEALING SURFACE IN ITS COOPERATING POSITION BEING DISPOSED SUBSTANTIALLY PARALLEL TO SAID FIRST SEALING SURFACE AND SPACED CLOSELY ADJACENT THERETO AND OUTWARDLY A FIRST DISTANCE THEREFROM THE INNER ANNULAR PORTION OF SAID SECOND SEALING SURFACE IN ITS COOPERATING POSITION BEING DISPOSED SUBSTANTIALLY PARALLEL TO SAID FIRST SEALING SURFACE AND SPACED CLOSELY ADJACENT THERETO AND OUTWARDLY A SECOND DISTANCE THEREFROM, WHEREIN SAID SECOND DISTANCE IS GREATER THAN SAID FIRST DISTANCE, THE INNER SIDE OF SIAD COVER ALSO HAVING A NARROW ANNULAR SLOT FORMED THEREIN AND POSITIONED AT THE BOUNDARY BETWEEN THE OUTER AND INNER ANNULAR PORTIONS OF SAID SECOND SEALING SURFACE AND SURROUNDING THE INNER PORTION OF SAID SECOND SEALING SURFACE, THE AXIS OF SAID SLOT BEING PITCHED RADIALLY OUTWARDLY AT AN ACUTE ANGLE TO THE INNER PORTION OF SAID SECOND SEALING SURFACE, AND A NARROW ANNULAR SEALING GASKET FORMED OF FLEXIBLE MATERIAL AND CARRIED BY SAID COVER, SAID SEALING GASKET INCLUDING AN OUTER ANNULAR PORTION POSITIONED IN SAID SLOT AND AN INNER ANNULAR PORTION PROJECTING RADIALLY INWARDLY FROM SAID SLOT AND UNDERLYING THE INNER ANNULAR PORTION OF SAID SECOND SEALING SURFACE, THE INNER ANNULAR PORTION OF SAID SEALING GASKET BEING CLAMPED BETWEEN THE INNER ANNULAR PORTIONS OF SAID FIRST AND SECOND SEALING SURFACES WHEN SAID COVER OCCUPIES ITS CLOSED POSITION, THEREBY HERMETICALLY TO SEAL THE OUTER END OF THE MANWAY EXTENDING HERMETICALLY TO SEAL THE OUTER END OF THE MANWAY OCCUPIES IS CLOSED POSITION.