US3872379A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Eddy current testing apparatus using slotted monoturn conductive members
Assignee: Magnetic Analysis Corp
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Filing: 1973-08-29
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Granted: 1975-03-18
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Expires: 1993-08-29
Abstract
Abstract One or more monoturn conductive members are employed having an inner aperture and an encircling surface with a slot extending from the aperture to the encircling surface. An encircling coil supplied with alternating or pulsed current produces current flow around the inner surface of the aperture and thereby produces a magnetic field to induce eddy currents in an object located in the aperture. Variations in the eddy currents are detected and indicated. Greater flux densities for a given coil and current, lower coil inductance and short magnetic fields can be produced. A detector coil may encircle a monoturn member. A pair of monoturn members with encircling coils may be used in null-type instruments, and more than two may be employed if desired. Arrangements for testing hot objects and objects of noncircular cross-section are described, and also coil assemblies usable with different monoturn members having different aperture size or shape.
Inventors
- 👤 Robert A Brooks
- 👤 John Paul Wallace
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 12:05
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/72; G01N27/82; G01N27/90; G01N27/9006; G01R; G01R27/00
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
147 words
Eddy current testing apparatus for the non-destructive testing of objects which comprises a. a monoturn conductive member having an inner aperture for receiving an object to be tested and a surface encircling the aperture and spaced therefrom, b. a slot in said member extending from said aperture to said encircling surface, c. a coil encircling said encircling surface for inducing current flow therein, d. means for supplying alternating or pulsed current to said coil, e. said monoturn conductive member being designed and adapted for producing current flow around the surface of said aperture opposite in direction to current flow in said encircling surface in response to said current in said coil and thereby produce a magnetic field to induce eddy currents in an object located in the aperture, f. and detecting and indicating means responsive to variations in said eddy currents for indicating variations in said objects.
Claim 2
Dependent Claim
147 words
Eddy current testing apparatus for the non-destructive testing of objects which comprises a. a monoturn conductive member having an inner aperture for receiving an object to be tested and a surface encircling the aperture and spaced therefrom, b. a slot in said member extending from said aperture to said encircling surface, c. a coil encircling said encircling surface for inducing current flow therein, d. means for supplying alternating or pulsed current to said coil, e. said monoturn conductive member being designed and adapted for producing current flow around the surface of said aperture opposite in direction to current flow in said encircling surface in response to said current in said coil and thereby produce a magnetic field to induce eddy currents in an object located in the aperture, f. and detecting and indicating means responsive to variations in said eddy currents for indicating variations in said objects.
Claim 3
Dependent Claim
60 words
Apparatus according to claim 1 in which said monoturn conductive member is designed and adapted for producing a flux density of the magnetic field in the region of said aperture with a given current in said coil which is substantially greater than the flux density which would be produced in said region in the absence of said monoturn conductive member.
Claim 4
Dependent Claim
28 words
Apparatus according to claim 1 in which the length of said aperture is small compared to the distance from the center of the aperture to said encircling surface.
Claim 5
Dependent Claim
35 words
Apparatus according to claim 1 in which the width of said encircling surface is greater than the length of said aperture and the length of said coil is greater than the length of the aperture.
Claim 6
Dependent Claim
33 words
Apparatus according to claim 1 in which said detecting and indicating means inclUdes a single detector coil encircling a surface of said monoturn conductive member which encircles said aperture and is spaced therefrom.
Claim 7
Dependent Claim
24 words
Apparatus according to claim 1 in which said detecting and indicating means includes a pair of axially-spaced detector coils in or adjacent said aperture.
Claim 8
Dependent Claim
169 words
Eddy current testing apparatus for the non-destructive testing of objects which comprises a. a monoturn conductive member having an inner aperture for receiving an object to be tested and a surface encircling the aperture and spaced therefrom, b. the length of said aperture being small compared to the distance from the center of the aperture to said encircling surface, c. a slot in said member extending from said aperture to said encircling surface, d. a coil encircling said encircling surface for inducing current flow therein, e. means for supplying alternating or pulsed current to said coil, f. said monoturn conductive member being designed and adapted for producing current flow around the surface of said aperture opposite in direction to current flow in said encircling surface in response to said current in said coil and thereby produce a magnetic field to induce eddy currents in an object located in the aperture, g. and detecting and indicating means responsive to variations in said eddy currents for indicating variations in said objects.
Claim 9
Dependent Claim
169 words
Eddy current testing apparatus for the non-destructive testing of objects which comprises a. a monoturn conductive member having an inner aperture for receiving an object to be tested and a surface encircling the aperture and spaced therefrom, b. the length of said aperture being small compared to the distance from the center of the aperture to said encircling surface, c. a slot in said member extending from said aperture to said encircling surface, d. a coil encircling said encircling surface for inducing current flow therein, e. means for supplying alternating or pulsed current to said coil, f. said monoturn conductive member being designed and adapted for producing current flow around the surface of said aperture opposite in direction to current flow in said encircling surface in response to said current in said coil and thereby produce a magnetic field to induce eddy currents in an object located in the aperture, g. and detecting and indicating means responsive to variations in said eddy currents for indicating variations in said objects.
Claim 10
Dependent Claim
24 words
Apparatus according to claim 7 in which said detecting and indicating means includes a pair of axially-spaced detector coils in or adjacent said aperture.
Claim 11
Dependent Claim
32 words
Apparatus according to claim 7 in which said detecting and indicating means includes a detector coil encircling a surface of said monoturn conductive member which encircles said aperture and is spaced therefrom.
Claim 12
Dependent Claim
35 words
Apparatus according to claim 7 in which the width of said encircling surface is greater than the length of said aperture and the length of said coil is greater than the length of the aperture.
Claim 13
Dependent Claim
26 words
Apparatus according to claim 10 in which said detecting and indicating means includes a pair of null connected axially-spaced detector coils in or adjacent said aperture.
Claim 14
Dependent Claim
137 words
Eddy current testing apparatus for the non-destructive testing of objects which comprises a. a pair of monoturn conductive members each having an inner aperture and a surface encircling the aperture and spaced therefrom, b. each of said members having a slot extending from said aperture to said encircling surface thereof, c. coil means encircling said encircling surfaces for inducing current flow therein, d. means for supplying alternating or pulsed current to said coil means to produce current flow around the surfaces of said apertures opposite in direction to current flow in said encircling surfaces respectively and thereby produce respective magnetic fields, e. whereby an object located in at least one of said apertures has eddy currents induced therein, f. and detecting and indicating means responsive to variations in said eddy currents for indicating variations in said objects.
Claim 15
Dependent Claim
137 words
Eddy current testing apparatus for the non-destructive testing of objects which comprises a. a pair of monoturn conductive members each having an inner aperture and a surface encircling the aperture and spaced therefrom, b. each of said members having a slot extending from said aperture to said encircling surface thereof, c. coil means encircling said encircling surfaces for inducing current flow therein, d. means for supplying alternating or pulsed current to said coil means to produce current flow around the surfaces of said apertures opposite in direction to current flow in said encircling surfaces respectively and thereby produce respective magnetic fields, e. whereby an object located in at least one of said apertures has eddy currents induced therein, f. and detecting and indicating means responsive to variations in said eddy currents for indicating variations in said objects.
Claim 16
Dependent Claim
37 words
Apparatus according to claim 12 for comparing different objects located in respective apertures of said monoturn members in which said detecting and indicating means including means for detecting differences between the eddy current flows in respective objects.
Claim 17
Dependent Claim
46 words
Apparatus according to claim 12 for comparing different objects located in respective apertures of said monoturn members in which said coil means includes separate coils encircling respective members, and said detecting and indicating means includes means responsive to differences between the currents flowing in said coils.
Claim 18
Dependent Claim
29 words
Apparatus according to claim 12 in which said detecting and indicating means includes a pair of detector coils encircling respective surfaces of said monoturn members which encircle respective apertures.
Claim 19
Dependent Claim
29 words
Apparatus according to claim 12 in which the length of said apertures is small compared to the distance from the centers of the aperTures to said encircling surfaces, respectively.
Claim 20
Dependent Claim
32 words
Apparatus according to claim 12 in which said pair of monoturn members are spaced side by side with the aperture thereof in alignment for passage therethrough of an object to be tested.
Claim 21
Dependent Claim
29 words
Apparatus according to claim 17 in which said detecting and indicating means includes a pair of detector coils encircling respective surfaces of said monoturn members which encircle respective apertures.
Claim 22
Dependent Claim
29 words
Apparatus according to claim 18 in which the length of said apertures is small compared to the distance from the centers of the apertures to said encircling surfaces, respectively.
Claim 23
Dependent Claim
155 words
Eddy current testing apparatus for the non-destructive testing of objects which comprises a. a plurality of monoturn conductive members each having an inner aperture and a surface encircling the aperture and spaced therefrom, b. each of said members having a slot extending from said aperture to said encircling surface thereof, c. said members being spaced side by side with the apertures thereof in alignment for passage therethrough of an object to be tested, d. coils encircling said encircling surfaces, respectively, e. means for supplying alternating or pulsed current to the coil of at least one of said members to induce current flow in the encircling surface thereof and produce current flow in the opposite direction around the inner surface of the aperture thereof and induce eddy currents in a said object, f. and means for utilizing signals from the coil of at least another of said members to produce indications of variations in said objects.
Claim 24
Dependent Claim
155 words
Eddy current testing apparatus for the non-destructive testing of objects which comprises a. a plurality of monoturn conductive members each having an inner aperture and a surface encircling the aperture and spaced therefrom, b. each of said members having a slot extending from said aperture to said encircling surface thereof, c. said members being spaced side by side with the apertures thereof in alignment for passage therethrough of an object to be tested, d. coils encircling said encircling surfaces, respectively, e. means for supplying alternating or pulsed current to the coil of at least one of said members to induce current flow in the encircling surface thereof and produce current flow in the opposite direction around the inner surface of the aperture thereof and induce eddy currents in a said object, f. and means for utilizing signals from the coil of at least another of said members to produce indications of variations in said objects.
Claim 25
Dependent Claim
54 words
Apparatus according to claim 20 in which said alternating or pulsed current is applied to the coils of a pair of alternate members in respective directions which produce current flow in opposite directions around the respective apertures, and signals from the coil of a member between said pair are utilized to produce said indications.
Claim 26
Dependent Claim
48 words
Apparatus according to claim 20 in which said alternating or pulsed current is applied to the coil of an intermediate member, and the coils of the members on each side of the intermediate member are connected in opposed relationship to produce the signals utilized to produce said indications.
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) | 1978-03-17 | 1978-09-16 | 1979-03-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-17 | 1982-09-16 | 1983-03-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-17 | 1986-09-16 | 1987-03-18 | $7700.00 | Window Closed / Lapsed |