Abstract: A magnetic chuck designed as a releasable holder for ferromagnetic workpieces comprises an orthogonal matrix of flat permeable pole pieces rising above a ferromagnetic base plate, the pole pieces forming rows parallel to their major faces and columns perpendicular thereto; the pole pieces of the two outermost rows contact the base while the other pole pieces are separated from the base by a nonpermeable layer. The rows of pole pieces alternate with rows of flat permanent magnets which follow one another with the same pitch as the pole pieces and are magnetized in the transverse direction with alternating polarity in each row. The magnets of every other row are fixedly aligned with the pole pieces of their columns while those of the remaining rows are longitudinally shiftable by one pitch to establish either a working position, with like magnet poles confronting each other across an intervening pole piece, or an inoperative position in which the magnet poles alternate within each column.

Abstract: A magnetic holder has a permanent magnet stator and a permanent magnet rotor, the magnetic mass of the latter being greater than that of the form and a play defining an air gap being provided between them so that the losses in the air gap compensate for the magnetic mass by which the rotor permanent magnet exceeds the stator permanent magnet.