Dipole permanent magnet structure

• US 5,635,889 A
• Filed: 09/21/1995
• Issued: 06/03/1997
• Est. Priority Date: 09/21/1995
• Status: Expired due to Term

• Current Assignee: Dexter Magnetic Technologies, Inc. (TSL Engineered Products LLC)
• Original Assignee: Dexter Magnetic Technologies, Inc. (TSL Engineered Products LLC)
• Inventors: Stelter, Richard E.
• Primary Examiner(s): Gellner, Michael L.
• Assistant Examiner(s): BARRERA, RAMON M
• Application Number:
  US08/532,385
• Time in Patent Office: 621 Days
• Field of Search: 335/296-306
• US Class Current: 335/306
• CPC Class Codes: H01F 7/0278 for generating uniform fields, focusing, deflecting electrically charged particles for magnetic separation by Lorentz force B03C1/023; specially adapted for NMR applications G01R33/383

Abstract

A dipole permanent magnet structure having a rectangular gap about a longitudinal axis, in which tapered pole pieces form opposing sides of the rectangular gap to permit establishing a magnetic field in the gap. Permanent magnets having a rectangular shape are coupled to the rear, or base, of each pole piece, and have a magnetic field oriented in the same direction as the pole pieces, perpendicular to longitudinal axis, thereby establishing a magnetic field between the pole pieces. Additional permanent magnets, including a pair of blocking magnets, are coupled to the aforementioned permanent magnets to form a magnetic circuit. The orientation of the magnetic field of each permanent magnet is generally aligned in the direction of the lines of flux in the magnetic circuit to maximize the flux density within the air gap created by formation of the permanent magnets. Moreover, the pair of blocking magnets each form an opposing side of the rectangular gap adjacent to the pole pieces to prevent fringing. The structure is thus capable of generating a magnetic field having a flux density greater than the residual flux density of the magnet material. Indeed, the gap flux density is limited only by the saturation flux density of the pole pieces. Thus, the permanent magnets can be made of magnet material having high coercivity and high saturation magnetization level. An embodiment of the magnet structure is capable of generating a magnetic field in the air gap having a flux density of 2.2 Tesla (22,000 Gauss).

Claims

1. A dipole permanent magnet structure having a rectangular gap centered about a longitudinal axis, wherein a pair of permeable pole pieces form two opposing sides of said rectangular gap, said structure comprising:

at least eight permanent magnets coupled about the longitudinal axis, wherein two of said permanent magnets each form a side normal to said two opposing sides of said rectangular gap to form said rectangular gap;

said permanent magnets each having a magnetic field, said magnetic field having an orientation; and

,

said orientation of said magnetic field of each of said permanent magnets aligned to form a magnetic circuit that generates a magnetic field in said rectangular gap having a flux density greater than the residual flux density of said magnetic field of each of said permanent magnets.

2. The dipole permanent magnet structure of claim 1 wherein said rectangular gap has equilateral sides.

3. The dipole permanent magnet structure of claim 1 wherein said rectangular gap is square.

4. The dipole permanent magnet structure of claim 1 wherein each of said eight permanent magnets is a rectangular block of magnet material.

5. The dipole permanent magnet structure of claim 4 wherein each of said eight permanent magnets is made of highly coercive magnet material.

6. The dipole permanent magnet structure of claim 4 wherein each of said eight permanent magnets has a high saturation magnetization level.

7. The dipole permanent magnet structure of claim 6 wherein each of said eight permanent magnets is comprised of rare earth permanent magnet material.

8. The dipole permanent magnet structure of claim 7 wherein said rare earth permanent magnet material is Samarium Cobalt.

9. The dipole permanent magnet structure of claim 7 wherein said rare earth permanent magnet material is Neodymium Iron Boron.

10. The dipole permanent magnet structure of claim 1 further comprising a permeable shell coupled to said permanent magnets parallel to said longitudinal axis to reduce leakage flux.

11. A dipole permanent magnet structure having a rectangular gap about a longitudinal axis, said structure comprising:

a first pole piece and a second pole piece forming opposing sides of said rectangular gap to permit a magnetic field having a flux density in said rectangular gap;

a first permanent magnet coupled to said first pole piece, having a magnetic field oriented toward said first pole piece;

a second permanent magnet coupled to said second pole piece, having a magnetic field oriented away from said second pole piece;

said first permanent magnet and said second permanent magnet forming said magnetic field in said rectangular gap;

a plurality of permanent magnets coupling said first permanent magnet and said second permanent magnet to form a magnetic circuit through said rectangular gap; and

said plurality of permanent magnets each having a magnetic field oriented to intensify said magnetic field in said rectangular gap, said magnetic field in said first permanent magnet, said second permanent magnet and each of said plurality of permanent magnets having a residual flux density, wherein said flux density in said rectangular gap is greater than said residual flux density.

12. The dipole permanent magnet structure of claim 11 wherein said rectangular gap forms an equilateral rectangle.

13. The dipole permanent magnet structure of claim 11 wherein said first permanent magnet, said second permanent magnet, and each of said plurality of permanent magnets is a rectangular block of magnet material.

14. The dipole permanent magnet structure of claim 13 wherein said first permanent magnet, said second permanent magnet, and each of said plurality of permanent magnets is made of highly coercive magnet material.

15. The dipole permanent magnet structure of claim 14 wherein said first permanent magnet, said second permanent magnet, and each of said plurality of permanent magnets has a high saturation magnetization level.

16. The dipole permanent magnet structure of claim 15 wherein said highly coercive magnet material is rare earth magnet material.

17. The dipole permanent magnet structure of claim 16 wherein said rare earth permanent magnet material is Samarium Cobalt.

18. The dipole permanent magnet structure of claim 16 wherein said rare earth permanent magnet material is Neodymium Iron Boron.

19. The dipole permanent magnet structure of claim 11 wherein said first pole piece and second pole piece are made of permeable magnet material.

20. The dipole permanent magnet structure of claim 19 wherein said permeable magnet material is 2V Permendur.

21. The dipole permanent magnet structure of claim 19 wherein said permeable material is Hiperco 50.

22. The dipole permanent magnet structure of claim 19 wherein said permeable material is low carbon steel.

23. The dipole permanent magnet structure of claim 11 wherein said first pole piece and second pole piece are tapered to reduce fringing flux between said first pole piece and said second pole piece.

24. The dipole permanent magnet structure of claim 11 wherein said plurality of permanent magnets each having a magnetic field oriented to intensify said magnetic field in said rectangular gap increases the flux density of said magnetic field in said rectangular gap so that said flux density of said magnetic field in said rectangular gap approaches the saturation flux density of said first pole piece and said second pole piece.

25. The dipole permanent magnet structure of claim 11 further comprising a permeable shell coupled to said first permanent magnet, said second permanent magnet, and said plurality of permanent magnets, parallel to said longitudinal axis to reduce leakage flux.

26. A dipole permanent magnet structure having a rectangular gap about a longitudinal axis, comprising:

a first pole piece and a second pole piece, each having a tip and a base, each said tip forming an opposing side of said rectangular gap to permit establishing a magnetic field between said each said tip;

a first rectangular permanent magnet (hereafter referred to as PM), coupled to said base of said first pole piece, said first rectangular PM having a magnetic field oriented toward said first pole piece and perpendicular to said longitudinal axis;

a second rectangular PM coupled to said base of said second pole piece, said second rectangular PM having a magnetic field oriented away from said second pole piece and perpendicular to said longitudinal axis, said first rectangular PM and said second rectangular PM thereby establishing a magnetic field between each said tip;

a first pair of rectangular PMs, each coupled to an opposing side of said first rectangular PM, each having a magnetic field oriented toward said first rectangular PM;

a second pair of rectangular PMs, each coupled to an opposing side of said second rectangular PM, each having a magnetic field oriented away from said second rectangular PM; and

,

a pair of blocking magnets, each forming an opposing side of said rectangular gap adjacent to each said tip to prevent fringing, each said blocking magnet coupling one of said first pair of rectangular PMs to one of said second pair of rectangular PMs, each said blocking magnet having a magnetic field oriented toward said one of said first pair of rectangular PMs to form a magnetic circuit between said first pole piece and said second pole piece.

27. The dipole permanent magnet structure of claim 26 wherein said first pole piece and said second pole piece are tapered from said base to said tip to prevent fringing, thereby increasing the flux density of said magnetic field between each said tip.

28. The dipole permanent magnet structure of claim 27 wherein each of said blocking magnets is tapered to be contiguous with said first pole piece and said second pole piece between said base and said tip of said first pole piece and said second pole piece.

29. The dipole permanent magnet structure of claim 27 wherein said first pole piece and said second pole piece are made of permeable material.

30. The dipole permanent magnet structure of claim 29 wherein said permeable material is 2V Permendur.

31. The dipole permanent magnet structure of claim 29 wherein said permeable material is Hiperco 50.

32. The dipole permanent magnet structure of claim 29 wherein said permeable material is low carbon steel.

33. The dipole permanent magnet structure of claim 26 wherein said first rectangular PM, said second rectangular PM, said first pair of rectangular PMs, said second pair of rectangular PMs, and said blocking magnets are made of highly coercive magnet material.

34. The dipole permanent magnet structure of claim 26 wherein said first rectangular PM, said second rectangular PM, said first pair of rectangular PMs, said second pair of rectangular PMs, and said blocking magnets have a high saturation magnetization level.

35. The dipole permanent magnet structure of claim 33 wherein said highly coercive material is rare earth magnet material.

36. The dipole permanent magnet structure of claim 35 wherein said rare earth magnet material is comprised of Samarium Cobalt.

37. The dipole permanent magnet structure of claim 35 wherein said rare earth magnet material is comprised of Neodymium Iron Boron.

38. The dipole permanent magnet structure of claim 26 further comprising a permeable shell coupled to said first rectangular PM, said second rectangular PM, said first pair of rectangular PMs, said second pair of rectangular PMs, and said pair of blocking magnets, parallel to said longitudinal axis to reduce leakage flux.

39. A dipole permanent magnet structure having a rectangular gap about a longitudinal axis, comprising:

a first pole piece and a second pole piece, each having

     1) a tip forming an opposing side of said rectangular gap,

     2) a base, and

     3) and two sides adjacent said tip and said base, partially tapered so that said base is wider than said tip;

a first rectangular permanent magnet coupled to said base of said first pole piece, having a magnetic field oriented in a direction toward said first pole piece;

a second rectangular permanent magnet coupled to said base of said second pole piece, having a magnetic field oriented in a direction away from said second pole piece;

a first pair of rectangular permanent magnets each coupled on opposing sides of said first pole piece and said first rectangular permanent magnet, each having a magnetic field oriented in a direction toward said first pole piece so that lines of flux enter said first pole piece from said first rectangular permanent magnet and said first pair of rectangular permanent magnets;

a second pair of rectangular permanent magnets each coupled on opposing sides of said second pole piece and said second rectangular permanent magnet, each having a magnetic field oriented in a direction away from said second pole piece so that lines of flux flow from said second pole piece to said second rectangular permanent magnet and said second pair of rectangular permanent magnets; and

,

a pair of blocking magnets, each forming an opposing side of said rectangular gap adjacent to each said tip, each said blocking magnet coupling one of said first pair of rectangular permanent magnets to one of said second pair of rectangular permanent magnets, each said blocking magnet having a magnetic field oriented toward said one of said first pair of rectangular permanent magnets to form a magnetic circuit between said first pole piece and said second pole piece.

40. The dipole permanent magnet structure of claim 39 further comprising a permeable shell coupled to said first rectangular permanent magnet, said second rectangular permanent magnet, said first pair of rectangular permanent magnets, said second pair of rectangular permanent magnets, and said pair of blocking magnets, parallel to said longitudinal axis to reduce leakage flux.