Fail-safe permanent magnet lifting device with a movable bias keeper

Claim 1

IN A FAIL-SAFE PERMANENT MAGNET LIFTING DEVICE, THE COMBINATION COMPRISING, A CENTER POLE PIECE OF MAGNETIC MATERIAL, A PAIR OF PERMANENT MAGNETS POSITIONED ON OPPOSITE SIDES OF SAID CENTER POLE PIECE AND HAVING FACE PORTIONS ABUTTING SAID CENTER POLE PIECE ADJACENT FACE PORTIONS, A PAIR OF END POLE PIECES OF MAGNETIC MATERIAL POSITIONED ON OPPOSITE SIDES OF SAID PAIR OF PERMANENT MAGNETS AND HAVING FACE PORTIONS ABUTTING SAID ADJACENT PERMANENT MAGNET FACE PORTIONS, A COIL EXTENDING AROUND SAID CENTER POLE PIECE AND CONNECTED TO A SOURCE OF DIRECT CURRENT THROUGH A SWITCHING MEANS OPERABLE TO ENERGIZE SAID COIL AND TO REVERSE THE DIRECTION OF CURRENT FLOW THROUGH SAID COIL, SAID CENTER POLE PIECE AND SAID PAIR OF END POLE PIECES HAVING TOP WALLS ARRANGED IN SUBSTANTIALLY THE SAME PLANE, SAID CENTER POLE PIECE AND SAID PAIR OF END POLE PIECES HAVING BOTTOM WALLS ARRANGED IN SUBSTANTIALLY THE THE SAME PLANE, MECHANICAL MEANS CONNECTING AND RIGIDLY SECURING SAID END POLE PIECES, SAID PAIR OF PERMANENT MAGNETS AND SAID CENTER POLE PIECE TO EACH OTHER AS A UNITARY MASS TO RETAIN SAID RESPECTIVE TOP WALLS AND BOTTOM WALLS IN THE SAME PLANE, A KEEPER PLATE OF MAGNETIC MATERIAL POSITIONED ON THE TOP WALLS OF SAID END POLE PIECES AND CENTER POLE PIECE,