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US3703958A
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Eddy current apparatus and method of application to a conductive material
Assignee: Massachusetts Institute of Technology
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Filing: 1969-08-11
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Granted: 1972-11-28
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Expires: 1989-08-11
Abstract
Abstract Eddy current apparatus is disclosed for applying a force to a conductive material. The apparatus employs two magnetic fields. The first, a background or soaking field, is continuous or slow rising and has a skin depth that is greater than the dimension of the material in the direction of field penetration. The second is fast-rising and has a skin depth that is less than said dimension. The two fields are timed or phased and oriented with respect to each other to produce the force in a desired direction. Thus, the conductive material can be particles in a slurry or a sheet of conductive material and the force applied thereto can be toward or away from the field source depending upon the timing or phasing of the fields and the orientation thereof.
Inventors
- 👤 Henry H Kolm
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 05:43
CPC Classifications
B; B03; B03C; B03C1/00; B03C1/02; B03C1/23; B03C1/24; G; G01; G01N; G01N19/00; G01N19/04; G01N27/00; G01N27/72; G01N27/82; G01N27/90; H; H01; H01F; H01F7/00; H01F7/06; H01F7/20; H01F7/202
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
133 words
Eddy current apparatus for applying a unidirectional force to a conductive material that comprises, in combination, means producing and introducing to the conductive material a background magnetic field having a skin depth much greater than the dimension of the conductive material in the direction of field penetration so as to penetrate through the conductive material, and means producing a second magnetic field having a skin depth that is comparable to or less than the dimension of the conductive material in the direction of field penetration thereby to induce eddy currents therein the second field upon introduction to said material being appropriately oriented with respect to the background field that interaction between the eddy currents induced thereby and the background field will produce a unidirectional force upon the conductive material in the desired direction.
Claim 2
Independent Claim
96 words
A method of applying a unidirectional force to a conductive material that comprises, introducing to the conductive material concurrent magnetic fields, one of the fields having a rise time that is slow enough to provide a skin depth tHat is substantially greater than the characteristic dimensions of the conductive material in the direction of field penetration and the other of the fields having a rise time that is short enough to provide a skin depth that is either comparable or less than to the characteristic dimension of the conductive material in the direction of field penetration.
Claim 3
Dependent Claim
66 words
A method as claimed in claim 3 in which the field having the slow rise time is a sinusoidally varying field in the lower sonic frequency range and the field having the fast rise time is a square wave, the square wave being periodically varying at a frequency equal to that of the sinusoidally varying field but being pi /2 radians out of time phase therewith.
Claim 4
Dependent Claim
27 words
A method as claimed in claim 3 that includes applying as one of the concurrent fields a slow rising pulsed field to act as a background field.
Claim 5
Dependent Claim
34 words
A method as claimed in claim 5 that includes applying as the other of the concurrent fields an abruptly rising, slower-falling spike-shaped pulse to occur at the time when the background field is maximal.
Claim 6
Dependent Claim
47 words
A method as claimed in claim 3 in which the two concurrent magnetic fields upon introduction to said material are timed and oriented with respect to each other to produce either a repulsive force or an attractive force depending on the timing and orientation of said fields.
Claim 7
Dependent Claim
73 words
Electric eddy-current apparatus operable to apply a unidirectional force to an electrically conductive material, that comprises, means for introducing to the conductive material concurrent time-varying fields, one of the fields being a sinusoidally varying field in the lower sonic frequency range and no greater than about 400 Hz and the other field being a square wave having a frequency equal to that of the sinusoidally varying field but out of time phase therewith.
Claim 8
Dependent Claim
103 words
Apparatus as claimed in claim 8 in which the means for producing the magnetic field comprises: first and second coils, a source of sinusoidally varying current electrically connected to the first coil to provide the sinusoidally varying field, and a source of square-wave current connected to the second coil to provide the square-wave field, the currents in the coils and the orientation of the coils with respect to one another being such that either a repulsive force or an attractive force can be applied to said material depending upon the timing and orientation of the magnetic fields produced by the electrically energized coils.
Claim 9
Dependent Claim
25 words
Apparatus as claimed in claim 9 in which the square wave field is pi /2 radians out of time phase with the sinusoidally varying field.
Claim 10
Independent Claim
152 words
A method of applying a unidirectional force to a conductive material, that comprises, establishing within a region of the conductive material a background magnetic field, the background field having a skin depth that is much greater than the dimension of the conductive material in the direction of field penetration, and introducing to said region a second, fast-rising and slow-falling,or slow-rising and fast-falling single pulse or repetitively pulsed magnetic field, the skin depth corresponding to the fast rise or fast fall respectively being comparable to or less than said dimension and the skin depth corresponding to the slow fall or slow rise respectively being large compared to said dimension, thereby to induce eddy currents within the conductive material which interact electromagnetically with the background field to produce a net force on the conductive material, the fields being oriented with respect to each other so as to produce a force in a desired direction.
Claim 11
Dependent Claim
127 words
Eddy current apparatus for applying a unidirectional force to a conductive material that comprises, in combination, means for producing and introducing to the material a background magnetic field adapted to penetrate through the magnetic material, and means for producing and introducing to the conductive material another magnetic field having a skin depth that is comparable to or less than the dimension Of the conductive material in the direction of field penetration to induce eddy currents within the material which interact electromagnetically with the background field to produce a net force on the conductive material, the magnetic fields being oriented with respect to each other to effect interaction between the background field and the induced eddy currents so as to produce a unidirectional force in a desired direction.
Claim 12
Dependent Claim
48 words
Eddy current apparatus as claimed in claim 12 in which the means for producing and introducing the eddy-current inducing field produces and introduces to the conductive material a spike-shaped pulse as shown in FIG. 5 of the drawing hereof or a series of pulses like said spike-shaped pulse.
Claim 13
Dependent Claim
44 words
Eddy current apparatus as claimed in claim 12 in which the means for producing and introducing the eddy-current inducing field produces and introduces to the conductive material a pulse whose rise time differs substantially from its fall time thereby to produce said unidirectional force.
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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) | 1975-11-28 | 1976-05-29 | 1976-11-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-11-28 | 1980-05-29 | 1980-11-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-11-28 | 1984-05-29 | 1984-11-28 | $7700.00 | Window Closed / Lapsed |