Electrically switchable magnet system

• US 6,229,422 B1
• Filed: 11/22/1999
• Issued: 05/08/2001
• Est. Priority Date: 04/13/1998
• Status: Expired due to Fees

• Current Assignee: Walker Magnetics Group, Inc. (IMI Holding Corp.)
• Original Assignee: Walker Magnetics Group, Inc. (IMI Holding Corp.)
• Inventors: Pignataro, Dominic F.
• Primary Examiner(s): Donovan, Lincoln
• Application Number:
  US09/444,891
• Time in Patent Office: 533 Days
• Field of Search: 335/289, 335/290, 335/291, 335/285-288, 335/274
• US Class Current: 335/289
• CPC Class Codes: H01F 2007/208 combined with permanent magnets
• CPC Class Codes: H01F 7/206 Electromagnets for lifting, handling or transporting of magnetic pieces or material electromagnets for guidance of vehicles, workpieces B65G21/2009; for magnetic suspension or levitation H02N15/00

Abstract

In the switchable magnet system disclosed herein, a central pole piece is backed by at least two permanent magnets having substantially different energies (H_c) so that one of the magnets is relatively switchable or reversible and the other is not. A magnetically permeable frame provides a peripheral pole face at least on either side of the central pole face and a backing plate bridging the central pole piece over the permanent magnets. A coil surrounds the first and second permanent magnets insde of the peripheral pole face. According, energization of the coil in one direction can reverse the polarization of the first magnet, thereby effectively short circuiting flux produced by the second magnet and terminating holding, while energization of the coil in the opposite direction can polarize the first magnet in parallel with the second magnet, thereby to effect holding.

Claims

1. A switchable holding magnet system comprising:

a central pole piece providing a central pole face;

a magnetically permeable frame providing a peripheral pole face at least on either side of said central pole face and a backing plate bridging said central pole piece;

between said backing plate and said central pole piece,

a first, switchable permanent magnet and,

beside said first permanent magnet, a second permanent magnet having an energy (Hc) which is substantially higher than that of said first permanent magnet; and

a coil surrounding both said first and second permanent magnets inside of said peripheral pole face;

whereby energization of said coil in one direction can reverse the polarization of said first magnet and thereby effectively short circuit flux produced by said second magnet and terminate holding while energization of said coil in the opposite direction can polarize said first magnet in parallel with said second magnet thereby to effect holding.

2. A switchable holding magnet system as set forth in claim 1 wherein said first magnet is an alnico alloy.

3. A switchable holding magnet system as set forth in claim 1 wherein said second magnet is a neodymium alloy.

4. A switchable holding magnet system comprising:

magnetically permeable means providing a pair of elongate parallel pole faces;

a central pole piece providing an elongate central pole face parallel to and coplanar with said pair of pole faces;

magnetically permeable frame means bridging between said pair of pole faces;

between said frame and said central pole piece,

a first, switchable permanent magnet and,

beside said first permanent magnet, a second permanent magnet having an energy (Hc) which is substantially higher than that of said first permanent magnet; and

a coil surrounding both said first and second permanent magnets;

whereby energization of said coil in one direction can reverse the polarization of said first magnet and thereby terminate holding while energization of said coil in the opposite direction can polarize said first magnet in parallel with said second magnet thereby to effect holding.

5. A switchable holding magnet system as set forth in claim 4 wherein said first magnet is an alnico alloy and said second maagnet is a neodymium alloy.