Magnetic floating roof seal

Claim 1

IN A TANK HAVING A VERTICAL CYLINDRICAL WALL OF MAGNETIC MATERIAL AND HAVING A FLOATING ROOF ANNULARLY SPACED FROM THE INNER SURFACE OF THE WALL, A SEAL FORMING A CLOSURE BETWEEN SAID ROOF AND SAID TANK IN THE ANNULAR SPACE THEREBETWEEN, SAID SEAL COMPRISING: A SHEET OF FLEXIBLE ELASTOMERIC MATERIAL HAVING PERMANENTLY MAGNETIZED MATERIAL INTEGRAL THEREWITH AND FORMED TO BE EFFECTIVELY CIRCUMFERENTIALLY ENDLESS, SAID SHEET HAVING UPPER AND LOWER PORTIONS OF VERTICALLY SPACED EDGES SEALINGLY SECURED TO RESPECTIVE UPPER AND LOWER PORTIONS OF SAID ROOF; ANNULARLY SPACED POSITIONERS EXTENDING OUTWARDLY OF SAID ROOF INTERMEDIATE OF SAID SHEET EDGES TO POSITION A SUBSTANTIAL PORTION OF THE OUTER SURFACE OF SAID SHEET IN SLIDABLE SEALING CONTACT WITH THE INNER SURFACE OF THE WALL OF SAID TANK; EACH POSITIONER HAVING A PAIR OF VERTICALLY SPACED, GENERALLY HORIZONTAL MEMBERS, SAID HORIZONTAL MEMBERS BEING CURVED TO CONFORM TO SAID TANK WALL AND BEING IN CONTACT WITH THE INNER SURFACE OF SAID SHEET; A VERTICAL MEMBER CONNECTING EACH PAIR OF RESPECTIVE HORIZONTAL MEMBERS; AND LINKS, EACH HAVING AN UPPER END PIVOTALLY CONNECTED TO A RESPECTIVE VERTICAL MEMBER AND HAVING A LOWER END PIVOTALLY CONNECTED TO SAID ROOF, SAID HORIZONTAL MEMBERS HAVING WEIGHTED PORTIONS THEREOF EXTENDING RADIALLY OUTWARDLY OF SAID CONNECTIONS TO FORCE SAID POSITIONERS DOWNWARDLY AND OUTWARDLY ON SAID LINKS.