US4672346A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic field generating device for NMR-CT
Assignee: SUMOTOMO SPECIAL METAL CO Ltd
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Filing: 1985-04-04
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Granted: 1987-06-09
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Expires: 2005-04-04
Abstract
Abstract A magnetic field generating device for a nuclear magnetic resonance-computerized tomography comprising a pair of permanent magnets magnetized in the same direction with different-polarity poles opposing mutually to define an air gap, whose maximum energy product, (BH) max , is not less than 30 MGOe (240 KJ/m 3 ), on each of the opposing faces of the permanent magnets a magnetic pole segment being provided which has an annular projection and, as occasion demands, at least one central convex projection inside the annular projection, and the permanent magnets being coupled magnetically by a yoke to generate a magnetic field within the air gap. The present device is able to create a uniform and stable magnetic field, in spite of its small-sized body.
Inventors
- 👤 Toshinobu Miyamoto
- 👤 Hideya Sakurai
- 👤 Hiroo Hayashi
- 👤 Youichi Ohnishi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 21:05
CPC Classifications
C; C08; C08J; C08J5/00; C08J5/18; B; B29; B29C; B29C67/00; B29C67/20; G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/38; G01R33/383; H; H01; H01F; H01F7/00; H01F7/02; H01F7/0273; H01F7/0278; C08J2323/00; C08J2323/02
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
169 words
In a magnetic field-generating device which is used in nuclear magnetic resonance-computerized tomography and which includes a yoke and a pair of permanent magnets mounted in said yoke so as to leave an air gap therebetween that contains a magnetic field, said air gap being sufficiently large to enable a portion of a human body to be positioned therein, said pair of permanent magnets being magnetized in the same direction such that the facing surfaces thereof have opposite polarities, the improvement wherein a magnetic pole segment is positioned on the facing surface of each of said permanent magnets, each magnetic pole segment having a flat surface which faces the corresponding flat surface of the other magnetic pole segment and an annular projection which extends away from the flat surface, said magnetic pole segments providing a three-dimensionally uniform magnetic field in the air gap between said permanent magnets and wherein said permanent magnets provide an energy product (BH) max of not less than 30 MGO e (240 kJ/m 3 ).
Claim 2
Dependent Claim
169 words
In a magnetic field-generating device which is used in nuclear magnetic resonance-computerized tomography and which includes a yoke and a pair of permanent magnets mounted in said yoke so as to leave an air gap therebetween that contains a magnetic field, said air gap being sufficiently large to enable a portion of a human body to be positioned therein, said pair of permanent magnets being magnetized in the same direction such that the facing surfaces thereof have opposite polarities, the improvement wherein a magnetic pole segment is positioned on the facing surface of each of said permanent magnets, each magnetic pole segment having a flat surface which faces the corresponding flat surface of the other magnetic pole segment and an annular projection which extends away from the flat surface, said magnetic pole segments providing a three-dimensionally uniform magnetic field in the air gap between said permanent magnets and wherein said permanent magnets provide an energy product (BH) max of not less than 30 MGO e (240 kJ/m 3 ).
Claim 3
Dependent Claim
164 words
In a magnetic field-generating device which is used in nuclear magnetic resonance-computerized tomography and which includes a yoke and a pair of permanent magnets mounted in said yoke so as to leave an air gap therebetween that contains a magnetic field, said air gap being sufficiently large to enable a portion of a human body to be positioned therein, said pair of permanent magnets being magnetized in the same direction such that the facing surfaces thereof have opposite polarities, the improvement wherein a magnetic pole segment is positioned on the facing surface of each of said permanent magnets, each magnetic pole segment having a flat surface which faces the corresponding flat surface of the other magnetic pole segment, an annular projection which extends away from the flat surface, and a convex projection which is centered within the annular projection and extends away from the flat surface, said magnetic pole segments providing a three-dimensionally uniform magnetic field in the air gap between said permanent magnets.
Claim 4
Dependent Claim
164 words
In a magnetic field-generating device which is used in nuclear magnetic resonance-computerized tomography and which includes a yoke and a pair of permanent magnets mounted in said yoke so as to leave an air gap therebetween that contains a magnetic field, said air gap being sufficiently large to enable a portion of a human body to be positioned therein, said pair of permanent magnets being magnetized in the same direction such that the facing surfaces thereof have opposite polarities, the improvement wherein a magnetic pole segment is positioned on the facing surface of each of said permanent magnets, each magnetic pole segment having a flat surface which faces the corresponding flat surface of the other magnetic pole segment, an annular projection which extends away from the flat surface, and a convex projection which is centered within the annular projection and extends away from the flat surface, said magnetic pole segments providing a three-dimensionally uniform magnetic field in the air gap between said permanent magnets.
Claim 5
Dependent Claim
62 words
A magnetic field-generating device as set forth in claims 1 or 2, wherein the flat surfaces of said magnetic pole segments are separated by a distance Lg, wherein each magnetic pole segment is circular and has an outer diameter D 1 , wherein each annular projection has an inner diameter D 2 and a height H, and wherein D.sub.2 ≧1/2·D.sub.1 and H≦1/4·Lg.
Claim 6
Dependent Claim
22 words
A magnetic field-generating device as set forth in claims 1 or 2, wherein each of said annular projections has trapezoidal cross section.
Claim 7
Dependent Claim
23 words
A magnetic field-generating device as set forth in claims 1 or 2, wherein each of said annular projections has a triangular cross section.
Claim 8
Dependent Claim
25 words
A magnetic field-generating device as set forth in claims 1 or 2, wherein each of said annular projections has an inner surface which is curved.
Claim 9
Dependent Claim
34 words
A magnetic field-generating device as set forth in claim 2, wherein each annular projection has a height H, wherein each convex projection has a height H 3 , and wherein H.sub.3 /H=1/100 to 1/3.
Claim 10
Dependent Claim
26 words
A magnetic field-generating device as set forth in claim 2, wherein each convex projection is generally disc-shaped and has a cross section which is substantially trapezoidal.
Claim 11
Dependent Claim
37 words
A magnetic field-generating device as set forth in claim 2, wherein each convex projection is composed of a plurality of disks on top of one another, each higher disk having a smaller diameter than the disk therebelow.
Claim 12
Dependent Claim
33 words
A magnetic field-generating device as set forth in claim 2, wherein said pair of permanent magnets provide an energy product (BH) max of not less than 30 MGO e (240 kJ/m 3 ).
Claim 13
Dependent Claim
41 words
A magnetic field-generating device as set forth in claims 1 or 2, wherein said yoke comprises a cylindrical body portion, a top wall and a bottom wall, and wherein said permanent magnets are respectively mounted on said top and bottom walls.
Claim 14
Dependent Claim
48 words
A magnetic field-generating device as set forth in claims 1 or 2, wherein said yoke comprises a top plate, a bottom plate and a plurality of rods connected between said top and bottom plates, and wherein said permanent magnets are respectively mounted on said top and bottom plates.
Claim 15
Dependent Claim
20 words
A magnetic field-generating device as set forth in claims 1 or 2, wherein said yoke comprises a quadrilateral frame body.
Claim 16
Dependent Claim
24 words
A magnetic field-generating device as set forth in claims 1 or 2, including a leakage flux-repelling permanent magnet positioned around each magnetic pole segment.
Claim 17
Dependent Claim
31 words
A magnetic field-generating device as set forth in claims 1 or 2, wherein said yoke has an inner face, and including a leakage flux-repelling permanent magnet provided on said inner face.
Claim 18
Dependent Claim
23 words
A magnetic field-generating device as set forth in claims 1 or 2, including means for changing the distance between said magnetic pole segments.
Claim 19
Dependent Claim
25 words
A magnetic field-generating device as set forth in claims 1 or 2, including means for moving said magnetic pole segments in parallel to one another.
Claim 20
Dependent Claim
53 words
A magnetic field-generating device as set forth in claims 1 or 2, wherein said permanent magnets are mounted on respective portions of said yoke, and including magnetic field-adjusting members containing magnetic material which are adjustably mounted on said yoke portions so as to be movable in the magnetizing direction of said permanent magnets.
Claim 21
Dependent Claim
37 words
A magnetic field-generating device as set forth in claims 1 or 2, including magnetic field-adjusting members containing a magnetic material adjustably mounted on said yoke so as to be movable in and out of said air gap.
Claim 22
Dependent Claim
37 words
A magnetic field-generating device as set forth in claims 1 or 2, including magnetic field-adjusting members adjustably mounted on said yoke so as to be movable toward and away from the periphery of each magnetic pole segment.
Claim 23
Dependent Claim
21 words
A magnetic field-generating device as set forth in claims 1 or 2, including a heat insulating material surrounding said permanent magnets.
Claim 24
Dependent Claim
22 words
A magnetic field-generating device as set forth in claims 1 or 2, including a heat insulating material surrounding said magnetic pole segments.
Claim 25
Dependent Claim
20 words
A magnetic field-generating device as set forth in claims 1 or 2, including a heat insulating material surrounding said yoke.
Claim 26
Dependent Claim
19 words
A magnetic field-generating device as set forth in claims 1 or 10, including means to cool said permanent magnets.
Claim 27
Dependent Claim
30 words
A magnetic field-generating device as set forth in claim 2, wherein each convex projection includes at least one recess therein which is centered with respect to the associated annular projection.
Claim 28
Dependent Claim
39 words
A magnetic field-generating device as set forth in claims 1 or 2, wherein the yoke has two permanent magnet receiving portions, each of which projects toward the air gap so as to form a convex portion in the yoke.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-06-08 | 1990-12-08 | 1991-06-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-06-08 | 1994-12-08 | 1995-06-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-06-08 | 1998-12-08 | 1999-06-09 | $7700.00 | Window Closed / Lapsed |