US5128643A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for producing a region of low magnetic field
Assignee: Individual
•
Filing: 1990-09-24
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Granted: 1992-07-07
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Expires: 2010-09-24
Abstract
Abstract A magnetic shield is presented comprising a shell of ferromagnetic material, augmented by one or more shielding magnets. The shielding magnets may be permanent magnets, electromagnetic coils, or other sources of magnetic flux. These shielding magnets are placed in close proximity to the shell, on the surface facing the region to be shielded, and are arranged to cancel any magnetic flux penetrating through the ferromagnetic shell into the region to be shielded. This invention provides magnetic protection for an exterior region when the shield is assembled around a magnet whose external field is to be contained, such as an MRI magnet. This invention also provides protection within an interior volume which is to be protected from an exterior source such as the Earth's magnetic field. The method by which the invention is applied is an iterative one, in which the shielding magnets are applied to substantially cancel the leakage field and then adjusted to minimize the remaining field in the shielded region. The invention is expected to be useful in containing the fringing field of medical imaging magnets as well as other applications.
Inventors
- 👤 David E. Newman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 14:37
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/42; G01R33/421
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
108 words
A device for shielding a selected region from magnetic fields produced by a magnetic field source, said device comprising a shell comprised of ferromagnetic material and at least one shielding magnet, said shell comprising a body that defines a boundary between the volume containing said selected region and the volume containing said magnetic field source, said at least one shielding magnet being provided on a surface of said shell between said shell and said selected region, and said at least one shielding magnet being oriented so as to produce a magnetic flux in said selected region generally opposite to said magnetic fields produced by said magnetic field source.
Claim 2
Independent Claim
108 words
A device for shielding a selected region from magnetic fields produced by a magnetic field source, said device comprising a shell comprised of ferromagnetic material and at least one shielding magnet, said shell comprising a body that defines a boundary between the volume containing said selected region and the volume containing said magnetic field source, said at least one shielding magnet being provided on a surface of said shell between said shell and said selected region, and said at least one shielding magnet being oriented so as to produce a magnetic flux in said selected region generally opposite to said magnetic fields produced by said magnetic field source.
Claim 3
Dependent Claim
19 words
The device of claim 1 wherein said at least one shielding magnet is comprised of a permanently magnetized material.
Claim 4
Dependent Claim
20 words
The device of claim 1 wherein said at least one shielding magnet is comprised of electroconductive material carrying electrical current.
Claim 5
Dependent Claim
37 words
The device of claim 1 wherein said shell comprises a body that defines a substantially enclosed volume, said selected region of space being contained within said volume, and said magnetic field source being exterior to said volume.
Claim 6
Dependent Claim
37 words
The device of claim 1 wherein said shell comprises a body that defines a substantially enclosed volume, said magnetic field source being contained within said volume, and said selected region of space being exterior to said volume.
Claim 7
Independent Claim
115 words
A method of producing a low magnetic field in a selected region proximate to a source of magnetic field, said method comprising the steps of: placing a shell comprised of ferromagnetic material so as to substantially separate the volume containing said selected region from the volume containing said source of magnetic field, measuring the magnetic field in said selected region, placing at least one shieldinng magnet in close proximity to said shell to substantially cancel said magnetic field in said selected region, and alternately measuring the magnetic field in said selected region and adjusting said at least one shielding magnet until said measurements indicate that a desired degree of magnetic field reduction has been achieved.
Claim 8
Independent Claim
115 words
A method of producing a low magnetic field in a selected region proximate to a source of magnetic field, said method comprising the steps of: placing a shell comprised of ferromagnetic material so as to substantially separate the volume containing said selected region from the volume containing said source of magnetic field, measuring the magnetic field in said selected region, placing at least one shieldinng magnet in close proximity to said shell to substantially cancel said magnetic field in said selected region, and alternately measuring the magnetic field in said selected region and adjusting said at least one shielding magnet until said measurements indicate that a desired degree of magnetic field reduction has been achieved.
Claim 9
Dependent Claim
20 words
The method of claim 6 wherein said at least one shielding magnet is comprised of electroconductive material carrying electrical current.
Claim 10
Dependent Claim
19 words
The method of claim 7 wherein said at least one shielding magnet is adjusted by varying said electrical current.
Claim 11
Dependent Claim
18 words
The method of claim 6 wherein said at least one shielding magnet is comprised of permanently magnetized material.
Claim 12
Dependent Claim
23 words
The method of claim 9 wherein said at least one shielding magnet is adjusted by varying the magnetization of said permanently magnetized material.
Claim 13
Dependent Claim
22 words
The method of claim 6 wherein said at least one shielding magnet is adjusted by changing the location of said shielding magnet.
Claim 14
Dependent Claim
26 words
The method of claim 6 wherein said at least one shielding magnet is adjusted by changing the orientation of said shielding magnet relative to said shell.
Claim 15
Independent Claim
94 words
A device for shielding a selected region from the external magnetic field of a MRI magnet, said device comprising a shell comprised of ferromagnetic material and defining a volume substantially enclosing said MRI magnet, said device further comrising at least one shielding magnet provided in close proximity to the exterior surface of said shell, said shielding magnet being interposed between said shell and said selected region, and said shielding magnet being oriented so as to generate in said selected region a magnetic flux generally opposite to said external magnetic field of said MRI magnet.
Claim 16
Independent Claim
94 words
A device for shielding a selected region from the external magnetic field of a MRI magnet, said device comprising a shell comprised of ferromagnetic material and defining a volume substantially enclosing said MRI magnet, said device further comrising at least one shielding magnet provided in close proximity to the exterior surface of said shell, said shielding magnet being interposed between said shell and said selected region, and said shielding magnet being oriented so as to generate in said selected region a magnetic flux generally opposite to said external magnetic field of said MRI magnet.
Claim 17
Dependent Claim
19 words
The device of claim 13 wherein said at least one shielding magnet is comprised of a permanently magnetized material.
Claim 18
Dependent Claim
20 words
The device of claim 13 wherein said at least one shielding magnet is comprised of electroconductive material carrying electrical current.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-07-07 | 1996-01-06 | 1996-07-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-07-07 | 2000-01-06 | 2000-07-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-07-07 | 2004-01-06 | 2004-07-07 | $7700.00 | Window Closed / Lapsed |