Controllable permanent magnetic chuck

Claim 1

A PERMANENT-MAGNETIC CHUCK CAPABLE OF BEING RENDERED MAGNETICALLY OPERATIVELY AND INOPERATIVE, COMPRISING A POLE PIECE ASSEMBLY HAVING A MAGNETIC GRIPPING SURFACE AND PROVIDED WITH FIRST SOFT IRON BARS MUTUALLY ARRANGED SIDE BY SIDE, AND NON-MAGNETIC SEPARATOR BARS BETWEEN SAID FIRST IRON BARS, THE WIDTHS OF SAID SEPARTOR BARS BEING LESS THAN THE WIDTHS OF SAID FIRST SOFT IRON BARS, A MAGNET SYSTEM DISPOSED BENEATH SAID POLE PIECE ASSEMBLY AND COMPRISING PERMANENT MAGNETS MUTUALLY ARRANGED SIDE BY SIDE AND MAGNETIZED IN A DIRECTION PARALLEL TO SAID MAGNETIC GRIPPING SURFACE, OTHER SOFT IRON BARS LOCATED IN SAID MAGNET SYSTEM BETWEEN ADJACENT ONES OF SAID PERMANENT MAGNETS AND DEFINING WITH SAID FIRST SOFT IRON BARS MUTUAL CONTACTING SURFACES WHEN SAID CHUCK IS IN OPERATIVE CONDITION, SAID POLE PIECE ASSEMBLY AND SAID MAGNET SYSTEM BEING DISPLACEABLE RELATIVE TO ONE ANOTHER ALONG AND PAST SAID CONTACTING SURFACES INTO OPERATIVE AND INOPERATIVE CONDITION IN A DIRECTION PARALLEL TO THE DIRECTION OF MAGNETIZATION OF THE PERMANENT MAGNETS, THE RESPECTIVE FIRST AND OTHER SOFT IRON BARS HAVING EQUAL CROSS SECTIONAL DIMENSIONS AT THEIR MUTUAL CONTACTING SURFACES, THE CROSS SECTION OF SAID PERMANENT MAGNETS IN SAID DIRECTION OF MAGNETIZATION DECREASING GRADUALLY FROM THE BASE OF THE MAGNET SYSTEM UP TO THE POLE PIECE ASSEMBLY, AND THE CROSS SECTION OF SAID OTHER SOFT IRON BARS CORRESPONDINGLY INCREASING.