US3562635A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus and method for detecting defects in magnetic tape
Assignee: International Business Machines Corp
•
Filing: 1968-10-16
•
Granted: 1971-02-09
•
Expires: 1988-10-16
Abstract
Abstract This invention detects tape defects down to and in the order of 10-5 inches in diameter or depth. This detection is achieved by recording DC test signals that do not saturate the tape, but instead provide a gradient of DC magnetization through the tape. The detection of very small or very shallow defects is further enhanced by use of an integrating amplifier in the faultdetecting circuit connected to the test read head. The output of the integrating amplifier is a signal which is very similar to the surface appearance of the tape.
Inventors
- 👤 Gerald R Parker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 22:19
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/72; G01N27/82; G01N27/90; B; B01; B01J; B01J27/00; B01J27/20; B01J27/22; B01J27/224; C; C07; C07C; C07C17/00; C07C17/093; C07C17/15; C07C17/152; C07C17/156
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
96 words
Apparatus for detecting defects in a flexible magnetic storage medium comprising: means for recording in the medium a DC magnetic field whose strength varies as a function of depth into the medium whereby the magnetization of the medium normally varies as a gradient through the thickness of the medium, but where, if a defect in the medium is present, a portion of the magnetization gradient is lost; means for detecting magnetic flux differences between adjacent areas of the medium, the flux differences being due to differences in the magnetization gradient in adjacent areas of the medium.
Claim 2
Dependent Claim
96 words
Apparatus for detecting defects in a flexible magnetic storage medium comprising: means for recording in the medium a DC magnetic field whose strength varies as a function of depth into the medium whereby the magnetization of the medium normally varies as a gradient through the thickness of the medium, but where, if a defect in the medium is present, a portion of the magnetization gradient is lost; means for detecting magnetic flux differences between adjacent areas of the medium, the flux differences being due to differences in the magnetization gradient in adjacent areas of the medium.
Claim 3
Dependent Claim
80 words
The apparatus of claim 1 wherein said detecting means comprises: transducing means for generating an electric signal from magnetic flux differences between adjacent areas of the medium, said transducing means having a frequency response of predetermined slope; means for amplifying the electric signal generated by said transducing means, said amplifying means having a frequency response inverse to the frequency response of said transducing means so that the total frequency response of said transducing means and said amplifying means is flat.
Claim 4
Dependent Claim
72 words
Apparatus for detecting defects in flexible magnetic storage medium comprising the apparatus of claim 1 and, in addition: means for saturating the medium with a strong DC magnetic field before said recording means records a DC magnetic field in the medium, the direction of the magnetic field applied to the medium by said saturating means being opposite to the direction of the magnetic field applied to the medium by said recording means.
Claim 5
Dependent Claim
42 words
Apparatus for detecting defects in a flexible magnetic storage medium comprising the apparatus of claim 1 and, in addition: means for saturating the medium with a strong AC magnetic field before said recording means records a DC magnetic field in the medium.
Claim 6
Dependent Claim
129 words
In magnetic tape testing apparatus having a write head, a read head, and driving means to move the tape first past the write head and then the read head, apparatus for testing tape comprising: means for energizing the write head with a DC signal just strong enough for the write head to produce a magnetic field in the tape that varies as a function of depth into the tape whereby the magnetization of the tape normally varies as a gradient through the thickness of the tape, but where, if a defect is present, a portion of the magnetization gradient is lost; means for monitoring the read head for changes in magnetic flux in the read head caused by differences in the magnetization gradient in successive areas of the tape.
Claim 7
Dependent Claim
129 words
In magnetic tape testing apparatus having a write head, a read head, and driving means to move the tape first past the write head and then the read head, apparatus for testing tape comprising: means for energizing the write head with a DC signal just strong enough for the write head to produce a magnetic field in the tape that varies as a function of depth into the tape whereby the magnetization of the tape normally varies as a gradient through the thickness of the tape, but where, if a defect is present, a portion of the magnetization gradient is lost; means for monitoring the read head for changes in magnetic flux in the read head caused by differences in the magnetization gradient in successive areas of the tape.
Claim 8
Dependent Claim
49 words
The apparatus of claim 5 wherein said monitoring means comprises: integrating means for integrating the signal from the read head, the integrating function being inverse to the differentiating function of the read head so that the output of said integrating means varies directly with flux in the read head.
Claim 9
Dependent Claim
48 words
Apparatus for testing tape comprising the apparatus of claim 5 and, in addition: erase means for DC erasing the tape before the tape passes under the write head, the magnetic field from said erase means being in the opposite direction to the magnetic field from the write head.
Claim 10
Dependent Claim
28 words
Apparatus for testing tape comprising the apparatus of claim 5 and, in addition: erase means for AC erasing the tape before the tape passes under the write head.
Claim 11
Independent Claim
122 words
A method for testing a flexible magnetic storage medium for defects comprising the steps of: writing in the medium with a DC magnetic field whose strength varies as a function of depth into the medium; storing a gradient of magnetization in the medium according to the strength of the DC magnetic field, whereby the magnetization varies as a gradient through the thickness of the medium except where a defect in the medium permits only a portion of the gradient to be stored; reading changes in the magnetic field from one area to an adjacent area of the medium, said changes being due to defects which permitted only a portion of the magnetization gradient to be stored in the area of the defect.
Claim 12
Independent Claim
122 words
A method for testing a flexible magnetic storage medium for defects comprising the steps of: writing in the medium with a DC magnetic field whose strength varies as a function of depth into the medium; storing a gradient of magnetization in the medium according to the strength of the DC magnetic field, whereby the magnetization varies as a gradient through the thickness of the medium except where a defect in the medium permits only a portion of the gradient to be stored; reading changes in the magnetic field from one area to an adjacent area of the medium, said changes being due to defects which permitted only a portion of the magnetization gradient to be stored in the area of the defect.
Claim 13
Dependent Claim
64 words
The method of claim 9 wherein said reading step comprises the steps of: differentiating the magnetic field produced by the gradient of magnetization in each area of the medium so that changes in the gradient from area to adjacent area produce a signal; integrating the signal so that the integrated signal varies directly with the magnetic field from the magnetization gradient in the medium.
Claim 14
Dependent Claim
54 words
A method of testing a flexible magnetic storage medium comprising the steps of claim 9 and, in addition: saturating the medium with a DC field before writing on the medium so that before the writing the magnetization of the medium is opposite in direction to the field applied to the medium during the writing.
Claim 15
Dependent Claim
34 words
A method of testing a flexible magnetic storage medium comprising the steps of claim 9 and, in addition: erasing the medium with an AC signal that saturates the medium before writing on the medium.
References Cited (Backward Citations)
US2221570A
Cited
US2528290A
Cited
US2937368A
Cited
US2995701A
Cited
SU151091A1
Cited
GB1076168A
Cited
US3432747A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-02-08 | 1974-08-10 | 1975-02-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-02-08 | 1978-08-10 | 1979-02-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-02-08 | 1982-08-10 | 1983-02-09 | $7700.00 | Window Closed / Lapsed |