Abstract: A switchable magnetic chuck has a magnet assembly slidably arranged in a casing to magnetize and demagnetize a top plate disposed in an open side of the casing. The top plate is provided with main pole members and auxiliary pole members which are arranged alternatively in the sliding direction of the magnet assembly, separated respectively by a non-magnetic separator disposed between them. To smoothen the change-over operation, enhance magnetic force under the magnetized condition and reduce residual attraction under the demagnetized condition, each main pole member is formed on the side facing the magnet assembly with an extension extending between the auxiliary pole member adjacent thereto and the magnet assembly.

Abstract: A magnet assembly used as a magnetism generating source for attaching an article to a magnetic substance or for magnetically retaining a magnetic member. The magnet assembly consists of a cylindrical casing open at least at one end, a core disposed within the casing at a spacing from an inner wall thereof, with one end of the core aligned with the open end face of the casing, and a permanent magnet disposed between the core and the inner peripheral surface of the casing. The permanent magnet has one magnetic pole on an outer surface thereof opposing the inner peripheral surface of the casing, and the other magnetic pole opposite the magnetic pole on an inner surface thereof opposing the outer peripheral surface of the core, so that the open end face of the casing and the end face of the core serve as a magnetic attraction surface.

Abstract: A switchable permanent magnet holding device in which a permanent magnet rotatably disposed within a bore in a magnetic circuit block is rotated, so that the magnetism acting surfaces of the magnetic circuit block are brought into an exciting state for retaining a magnetic substance thereon and into a non-exciting state for releasing the magnetic substance therefrom. The permanent magnet is pressed against a stopper for impeding rotation thereof, due to a gyromagnetic force acting across the permanent magnet and the magnetic circuit block when the permanent magnet is rotated to a position in which the magnetism acting surfaces of the block become exciting.

Abstract: A magnetic base adapted to be secured to a magnetic substance attractively, wherein a permanent magnet 20 having a small reversible permeability .mu. is employed as a rotary magnet housed in a magnetic block 18 and rotated for switching magnetic active surfaces 24 of the block from an unexcited state to an excited state, thereby effecting a light and smooth rotation.