초록

A permanent magnet assembly is disclosed that is adapted to provide a magnetic field across an arc-shaped gap. Such a permanent magnet assembly can be used, for example, to provide a time-varying magnetic field to an annular region.

대표청구항 ▼

1. A permanent magnet assembly comprising:an arc-shaped flux return section formed of magnetically permeable material and extending along a portion of an arc and having an upper portion with a first end and a second end, a lower portion with a first end and a second end, and a middle portion with a

1. A permanent magnet assembly comprising:an arc-shaped flux return section formed of magnetically permeable material and extending along a portion of an arc and having an upper portion with a first end and a second end, a lower portion with a first end and a second end, and a middle portion with a first end and a second end, wherein the first end of the upper portion is operatively coupled to the first end of the middle portion and the first end of the lower portion is operatively coupled to the second end of the middle portion; an upper arc-shaped permanent magnet section having a north end and a south end, wherein the north end of the upper arc-shaped permanent magnet section is operatively coupled to the second end of the upper portion of the arc-shaped flux return section; and a lower arc-shaped permanent magnet section having a north end and a south end, wherein the south end of the lower arc-shaped permanent magnet section is operatively coupled to the second end of the lower portion of the arc-shaped flux return section; wherein an arc-shaped gap is formed between the south end of the upper arc-shaped permanent magnet section and the north end of the lower arc-shaped permanent magnet section. 2. The permanent magnet assembly of claim 1 wherein the arc-shaped flux return section has a unitary construction.3. The permanent magnet assembly of claim 1 wherein the arc-shaped flux return section is formed of at least two pieces which are operatively connected to carry magnetic flux.4. The permanent magnet assembly of claim 1 wherein the upper arc-shaped permanent magnet section has a unitary construction and the lower arc-shaped permanent magnet section has a unitary construction.5. The permanent magnet assembly of claim 1 wherein at least one of the upper arc-shaped permanent magnet section and the lower arc-shaped permanent magnet section comprises at least two permanent magnet portions.6. The permanent magnet assembly of claim 1 wherein the arc-shaped gap has a rectangular cross-section.7. The permanent magnet assembly of claim 1 wherein the arc-shaped gap has a trapezoidal cross-section.8. The permanent magnet assembly of claim 1 further comprising at least one pole piece operatively coupled to the south end of the upper arc-shaped permanent magnet section.9. The permanent magnet assembly of claim 1 further comprising at least one pole piece operatively coupled to the north end of the lower arc-shaped permanent magnet section.10. The permanent magnet assembly of claim 1 further comprising at least one pole piece operatively coupled to the south end of the upper arc-shaped permanent magnet section and at least one pole piece operatively coupled to the north end of the lower arc-shaped permanent magnet section.11. A permanent magnet assembly comprising:a central flux return section formed of magnetically permeable material and having an upper portion with a first end and a second end, a lower portion with a first end and a second end, and a central portion with a first end and a second end, wherein the first end of the upper portion is operatively coupled to the first end of the central portion and the first end of the lower portion is operatively coupled to the second end of the central portion; an upper arc-shaped permanent magnet section having a north end and a south end, wherein the north end of the upper arc-shaped permanent magnet section is operatively coupled to the second end of the upper portion of the central flux return section; and a lower arc-shaped permanent magnet section having a north end and a south end, wherein the south end of the lower arc-shaped permanent magnet section is operatively coupled to the second end of the lower portion of the central flux return section; wherein an arc-shaped gap is formed between the south end of the upper arc-shaped permanent magnet section and the north end of the lower arc-shaped permanent magnet section. 12. The permanent magnet assembly of claim 11 wherein the central flux return section has a unitary construction.13. The permanent magnet assembly of claim 11 wherein the central flux return section is formed of at least two pieces which are operatively connected to carry magnetic flux.14. The permanent magnet assembly of claim 11 wherein the upper arc-shaped permanent magnet section has a unitary construction and the lower arc-shaped permanent magnet section has a unitary construction.15. The permanent magnet assembly of claim 11 wherein at least one of the upper arc-shaped permanent magnet section and the lower arc-shaped permanent magnet section comprises at least two permanent magnet portions.16. The permanent magnet assembly of claim 11 wherein the arc-shaped gap has a rectangular cross-section.17. The permanent magnet assembly of claim 11 wherein the arc-shaped gap has a trapezoidal cross-section.18. The permanent magnet assembly of claim 11 further comprising at least one pole piece operatively coupled to the south end of the upper arc-shaped permanent magnet section.19. The permanent magnet assembly of claim 11 further comprising at least one pole piece operatively coupled to the north end of the lower arc-shaped permanent magnet section.20. The permanent magnet assembly of claim 11 further comprising at least one pole piece operatively coupled to the south end of the upper arc-shaped permanent magnet section and at least one pole piece operatively coupled to the north end of the lower arc-shaped permanent magnet section.21. A permanent magnet assembly comprising:an upper flux return section formed of magnetically permeable material and having a middle section, a first end, and a second end; a first arc-shaped upper permanent magnet section having a south end, and a north end operatively coupled to the first end of the upper flux return section; a second arc-shaped upper permanent magnet section having a north end, and a south end operatively coupled to the second end of the upper flux return section; a lower flux return section formed of magnetically permeable material and having a middle section, a first end, and a second end; a first arc-shaped lower permanent magnet section having a north end, and a south end operatively coupled to the first end of the lower flux return section; and a second arc-shaped lower permanent magnet section having a south end, and a north end operatively coupled to the second end of the lower flux return section; wherein a first arc-shaped gap is formed between the south end of the first arc-shaped upper permanent magnet section and the north end of the first arc-shaped lower permanent magnet section and wherein a second arc-shaped gap is formed between the north end of the second arc-shaped upper permanent magnet section and the south end of the second arc-shaped lower permanent magnet section. 22. The permanent magnet assembly of claim 21 wherein the upper flux return section has a unitary construction and the lower flux return section has a unitary construction.23. The permanent magnet assembly of claim 21 wherein at least one of the upper flux return section and the lower flux return section is formed of at least two pieces which are operatively connected to carry magnetic flux.24. The permanent magnet assembly of claim 21 wherein the first arc-shaped upper permanent magnet section, the first arc-shaped lower permanent magnet section, the second arc-shaped upper permanent magnet section, and the second arc-shaped lower permanent magnet section all have a unitary construction.25. The permanent magnet assembly of claim 21 wherein at least one of the first arc-shaped upper permanent magnet section and the first arc-shaped lower permanent magnet section comprises at least two permanent magnet portions, and wherein at least one of the second arc-shaped upper permanent magnet section and the second arc-shaped lower permanent magnet section comprises at least two permanent magnet portions.26. The permanent magnet assembly of claim 21 wherein the first arc-shaped gap has a rectangular cross-section and the second arc-shaped gap has a rectangular cross-section.27. The permanent magnet assembly of claim 21 wherein the first arc-shaped gap has a trapezoidal cross-section and the second arc-shaped gap has a trapezoidal cross-section.28. The permanent magnet assembly of claim 21 further comprising at least one pole piece operatively connected to the south end of the first arc-shaped upper permanent magnet section and at least one pole piece operatively connected to the north end of the second arc-shaped upper permanent magnet section.29. The permanent magnet assembly of claim 21 further comprising at least one pole piece operatively coupled to the north end of the first arc-shaped lower permanent magnet section and at least one pole piece operatively coupled to the south end of the second arc-shaped lower permanent magnet section.30. The permanent magnet assembly of claim 21 further comprising at least one pole piece operatively coupled to the south end of the first arc-shaped upper permanent magnet section and at least one pole piece operatively coupled to the north end of the first arc-shaped lower permanent magnet section.31. A permanent magnet assembly comprising:a central permanent magnet section having a north end and a south end; an upper pole piece formed of magnetically permeable material and having a first end bearing an arc-shaped side pole piece portion having a pole face, and a second end bearing an arc-shaped side pole piece portion having a pole face; and a lower pole piece formed of magnetically permeable material and having a first end bearing an arc-shaped side pole piece portion having a pole face, and a second end bearing an arc-shaped side pole piece portion having a pole face; wherein a first arc-shaped gap is formed between the pole face of the arc-shaped side pole piece portion of the first end of the upper pole piece and the pole face of the arc-shaped side pole piece portion of the first end of the lower pole piece and a second arc-shaped gap is formed between the pole face of the arc-shaped side pole piece portion of the second end of the upper pole piece and the pole face of the arc-shaped side pole piece portion of the second end of the lower pole piece. 32. The permanent magnet assembly of claim 31 wherein the first arc-shaped gap has a rectangular cross-section and the second arc-shaped gap has a rectangular cross-section.33. The permanent magnet assembly of claim 31 wherein the first arc-shaped gap and the second arc-shaped gap each have a trapezoidal cross-section with an interior dimension and an exterior dimension, wherein the interior dimension is less than the exterior dimension.34. The permanent magnet assembly of claim 31 wherein the first arc-shaped gap and the second arc-shaped gap each have a trapezoidal cross-section with an interior dimension and an exterior dimension, wherein the interior dimension is greater than the exterior dimension.35. The permanent magnet assembly of claim 31 wherein the upper pole piece has a unitary construction and the lower pole piece has a unitary construction.36. The permanent magnet assembly of claim 31 wherein at least one of the upper pole piece and the lower pole piece is formed of at least two pieces which are operatively connected to carry magnetic flux.37. The permanent magnet assembly of claim 31 wherein the central permanent magnet section has a unitary construction.38. The permanent magnet assembly of claim 31 wherein the central permanent magnet section comprises at least two permanent magnet portions.39. A permanent magnet assembly comprising:an upper flux return section formed of magnetically permeable material and having a middle portion, a first end, and a second end; a first arc-shaped upper permanent magnet section having a south end, and a north end operatively coupled to the first end of the upper flux return section; a second arc-shaped upper permanent magnet section having a south end, and a north end operatively coupled to the second end of the upper flux return section; a lower flux return section formed of magnetically permeable material and having a middle portion, a first end, and a second end; a first arc-shaped lower permanent magnet section having a north end, and a south end operatively coupled to the first end of the lower flux return section; a second arc-shaped lower permanent magnet section having a north end, and a south end operatively coupled to the second end of the lower flux return section; and a central flux return section formed of magnetically permeable material and having a middle section, a first end operatively coupled to the middle portion of the upper flux return section, and a second end operatively coupled to the middle portion of the lower flux return section; wherein a first arc-shaped gap is formed between the south end of the first arc-shaped upper permanent magnet section and the north end of the first arc-shaped lower permanent magnet section and wherein a second arc-shaped gap is formed between the south end of the second arc-shaped upper permanent magnet section and the north end of the second arc-shaped lower permanent magnet section. 40. The permanent magnet assembly of claim 39 wherein the first arc-shaped gap has a rectangular cross-section and the second arc-shaped gap has a rectangular cross-section.41. The permanent magnet assembly of claim 39 wherein the first arc-shaped gap and the second arc-shaped gap each have a trapezoidal cross-section with an interior dimension and an exterior dimension, wherein the interior dimension is less than the exterior dimension.42. The permanent magnet assembly of claim 39 wherein the first arc-shaped gap and the second arc-shaped gap each have a trapezoidal cross-section with an interior dimension and an exterior dimension, wherein the interior dimension is greater than the exterior dimension.43. The permanent magnet assembly of claim 39 wherein the upper flux return section has a unitary construction, the central flux return section has a unitary construction, and the lower flux return section has a unitary construction.44. The permanent magnet assembly of claim 39 wherein at least one of the upper flux return section, the central flux return section, and the lower flux return section is formed of at least two pieces which are operatively connected together to carry magnetic flux.45. The permanent magnet assembly of claim 39 wherein the first arc-shaped upper permanent magnet section and the second arc-shaped upper permanent magnet section each have a unitary construction.46. The permanent magnet assembly of claim 39 wherein the first arc-shaped upper permanent magnet section and the second arc-shaped upper permanent magnet section each comprise at least two permanent magnet portions.47. The permanent magnet assembly of claim 39 wherein at least one of the first arc-shaped lower permanent magnet section and the second arc-shaped lower permanent magnet section has a unitary construction.48. The permanent magnet assembly of claim 39 wherein at least one of the first arc-shaped lower permanent magnet section and the second arc-shaped lower permanent magnet section comprises at least two permanent magnet portions.49. The permanent magnet assembly of claim 39 further comprising at least one pole piece operatively connected to the south end of the first arc-shaped upper permanent magnet section and at least one pole piece operatively connected to the south end of the second arc-shaped upper permanent magnet section.50. The permanent magnet assembly of claim 39 further comprising at least one pole piece operatively coupled to each of the north end of the first arc-shaped lower permanent magnet section and the north end of the second arc-shaped lower permanent magnet section.