Patent US4990877A successfully refreshed from Google Patents.
US4990877A
Expired / Lapsed
US
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Passive shimming assembly for MR magnet
Assignee: General Electric Co
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Filing: 1989-12-04
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Granted: 1991-02-05
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Expires: 2009-12-04
Abstract
Abstract A passive shim assembly for a magnet having a central bore is provided. The passive shim assembly includes a plurality of axially extending guide rails bonded directly to the bore of the magnet and equally spaced circumferentially. A plurality of arcuately shaped drawers are slidably mounted between adjacent channel pieces. A plurality of stacks of arcuate strips of magnetic flux conducting material demountably secured to each of the drawers, the strips extending in the circumferential direction.
Inventors
- 👤 Jay F. Benesch
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 04:37
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/38; G01R33/387; G01R33/3873
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
71 words
A passive shim assembly for a magnet having a central bore comprising: plurality of axially extending guide rails bonded directly to the bore of the magnet and equally spaced circumferentially; a plurality of arcuately shaped drawers slidably mounted between adjacent channel pieces; and a plurality of stacks of predetermined length arcuate strips of magnetic flux conducting material demountably secured to each of said drawers, said strips extending in the circumferential direction.
Claim 2
Dependent Claim
71 words
A passive shim assembly for a magnet having a central bore comprising: plurality of axially extending guide rails bonded directly to the bore of the magnet and equally spaced circumferentially; a plurality of arcuately shaped drawers slidably mounted between adjacent channel pieces; and a plurality of stacks of predetermined length arcuate strips of magnetic flux conducting material demountably secured to each of said drawers, said strips extending in the circumferential direction.
Claim 3
Dependent Claim
42 words
The shim assembly of claim 1 wherein said arcuate strips of magnetic flux conductive material comprises strips having different saturation magnetization, said strips with the lower saturation magnetization allowing fine tuning of the magnet field inhomogeneity with an easily handled shim size.
Claim 4
Dependent Claim
20 words
The shim assembly of claim 2, wherein said strips of magnetic flux conductive material comprises steel strips and nickel strips.
Claim 5
Dependent Claim
100 words
A passive shim assembly for a magnet having a central bore comprising: a plurality of arcuate shaped drawers; a plurality of axially extending guide rails for supporting two sets of drawers radially spaced apart from one another, said guide rails bonded directly to the bore of the magnet and equally spaced from one another circumferentially, said drawers slidably mounted between rails, with two drawers supported radially spaced apart between two rails; and a plurality of stacks of predetermined length arcuate strips of magnetic flux conducting material demountably secured to each of said drawers, said strips extending in the circumferential direction.
Claim 6
Dependent Claim
100 words
A passive shim assembly for a magnet having a central bore comprising: a plurality of arcuate shaped drawers; a plurality of axially extending guide rails for supporting two sets of drawers radially spaced apart from one another, said guide rails bonded directly to the bore of the magnet and equally spaced from one another circumferentially, said drawers slidably mounted between rails, with two drawers supported radially spaced apart between two rails; and a plurality of stacks of predetermined length arcuate strips of magnetic flux conducting material demountably secured to each of said drawers, said strips extending in the circumferential direction.
References Cited (Backward Citations)
US4893083A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-02-04 | 1994-08-06 | 1995-02-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-02-04 | 1998-08-06 | 1999-02-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-02-04 | 2002-08-06 | 2003-02-05 | $7700.00 | Window Closed / Lapsed |