Magnetic holder

Claim 2

A magnetic holder for releasably retaining a ferromagnetic object, comprising: a core member composed of a magnetically semi-hard material capable of magnetic retention after magnetization without substantial reduction, said material consisting essentially of a semi-hard spinodal-decomposition type magnetic alloy having a coercive force not greater than 600 oersted; coil means disposed in inductive relation to said member for the magnetization and demagnetization of said core member; a source of an essentially unidirectional momentary short-duration electrical pulse connectable to said coil means; and a single multiposition switch between said coil means and said source, said switch having a pair of operative positions and being operable in a first of said positions for passing said essentially unidirectional momentary short-duration electrical pulse from said source through said coil means in a first direction to retentively magnetize said core member and thereby enable it to retain said object for an entire holding duration after disappearance of said pulse, said switch being operable in its second position for passing a subsequent essentially unidirectional momentary short-duration electrical pulse from said source through said coil means in a second direction opposite to the first direction to permanently demagnetize said core member.

Claim 3

A magnetic holder for releasably retaining a ferromagnetic object, comprising: a core member composed of a magnetically semi-hard material capable of magnetic retention after magnetization without substantial reduction, said material consisting essentially of a semi-hard spinodal-decomposition type magnetic alloy having a coercive force not greater than 600 oersted; coil means disposed in inductive relation to said member for the magnetization and demagnetization of said core member; a source of an essentially unidirectional momentary short-duration electrical pulse connectable to said coil means; and a single multiposition switch between said coil means and said source, said switch means having a pair of operative positions and being operable in a first of said positions for passing said essentially unidirectional momentary short-duration electrical pulse from said source through said coil means in a first direction to retentively magnetize said core member and thereby enable it to retain said object for an entire holding operation after disappearance of said pulse, said switch being operable in its second position for passing a subsequent single essentially unidirectional momentary short-duration electrical pulse from said source through said coil means in a second direction opposite to the first direction to permanently demagnetize said core member, said source of a unidirectional momentary short-duration electrical pulse comprising a direct-current source and a capacitor for charging by said DC source and for discharging through said coil means upon said switch being brought into each of said first and second positions to provide said essentially unidirectional momentary short-duration electrical pulse through said coil means in the first and second directions respectively.

Claim 4

A magnetic holder for releasably retaining a ferromagnetic object, comprising: a core member composed of a magnetically semi-hard material capable of magnetic retention after magnetization without substantial reduction, said material consisting essentially of a semi-hard spinodal-decomposition type magnetic alloy having a coercive force not greater than 600 oersted; coil means disposed in inductive relation to said member for the magnetization and demagnetization of said core member; a source of an essentially unidirectional momentary short-duration electrical pulse connectable to said coil means; and a single multiposition switch between said coil means and said source, said switch means having a pair of operative positions and being operable in a first of said positions for passing said essentially unidirectional momentary short-duration electrical pulse from said source through said coil means in a first direction to retentively magnetize said core member and thereby enable it to retain said object for an entire holding operation after disappearance of said pulse, said switch being operable in its second position for passing a subsequent single essentially unidirectional momentary short-duration electrical pulse from said source through said coil means in a second direction opposite to the first direction to permanently demagnetize said core member, said source of a unidirectional momentary short-duration electrical pulse comprising a direct-current source and a capacitor for charging by said DC source and for discharging through said coil means upon said switch being brought into each of said first and second positions to provide said essentially unidirectional momentary short-duration electrical pulse through said coil means in the first and second directions respectively.