Abstract: Longitudinal and transverse rows of pole pieces are flanked by pairs of rows of fixed permanent magnets in one direction and by movable permanent magnets in another direction and are mounted on a magnetic or nonmagnetic base plate. An actuating mechanism for the movable permanent magnets enables the displacement thereof by one pole pitch so that in one position all four sides of each pole piece are flanked by magnetic poles of the same polarity so that the flux lines close through the active face of the magnetic retention plate. In the other position, pairs of permanent magnets confronting the opposite sides of the pole pieces are of opposite polarity so that flux line closure is entirely within the body of the plate.

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.