Abstract A magnetic circuit made of a permanent magnet of high coercivity material, for example, barium ferrite ceramic material having a coercive force sufficiently high that the domains of the permanent magnet will not be reversed, and an electrical coil wound closely around the permanent magnet over its entire length. The electrical coil may be excited by a direct current of value and direction such that the magnetic field from the permanent magnet will be partially or completely neutralized, however, the domains of the permanent magnet will not be reversed and when the current in the coil is reversed from the first condition, the strength of the magnet becomes equal to the combined magnetic field from the permanent magnet and the magnetic field from the coil. This magnetic circuit is particularly useful for use in lifting magnets, although it is also applicable to magnets used for separating, holding, or otherwise exerting an external magnetic influence.
A magnetic circuit comprising a permanent magnet, a coil, said coil being adapted to have a direct current pass therethrough and to produce A magnetic field through said permanent magnet, said permanent magnet being made of a magnetic material having a sufficiently high coercive force that the magnetic domains of said material will not change substantially when said current from said coil is passed therethrough in a direction to produce a field of a direction opposing said permanent magnet field, said coil being adapted to have the said current therethrough reversed whereby its magnetic field aids the field of said permanent magnet and therefore produces a stronger magnet.
Claim 2
Dependent Claim
108 words
A magnetic circuit comprising a permanent magnet, a coil, said coil being adapted to have a direct current pass therethrough and to produce A magnetic field through said permanent magnet, said permanent magnet being made of a magnetic material having a sufficiently high coercive force that the magnetic domains of said material will not change substantially when said current from said coil is passed therethrough in a direction to produce a field of a direction opposing said permanent magnet field, said coil being adapted to have the said current therethrough reversed whereby its magnetic field aids the field of said permanent magnet and therefore produces a stronger magnet.
Claim 3
Dependent Claim
29 words
The magnetic circuit recited in claim 1 wherein said permanent magnetic material is a material having a coercive force equal to or greater than 4,400 ampere turns per inch.
Claim 4
Dependent Claim
25 words
The magnetic circuit recited in claim 1 wherein said coil covers the outside surface of said permanent magnet to the extreme ends of said magnet.
Claim 5
Dependent Claim
43 words
The magnetic circuit recited in claim 3 wherein said ends of said magnet are adapted to attract a magnetic material thereto whereby said magnet may be used as a lifting magnet and means on said magnet for attaching it to a lifting member.