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US4802028A
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Method and apparatus for erasing a magnetic disc employing erasing signals having at least two different frequencies
Assignee: Sanyo Electric Co Ltd
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Filing: 1987-04-15
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Granted: 1989-01-31
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Expires: 2007-04-15
Abstract
Abstract When a recording track on a magnetic disc (10) is erased, a first erasing signal f 1 with an upper limit of frequency (10 MHz) in a recording signal band is supplied through a magnetic head 14 over a period T 1 . Since the erasing signal f 1 is attenuated and vibrated in a period T 12 , the residual component is minimized. A second erasing signal f 2 with an upper limit of frequency (20 MHz) which is outside of the recording signal band and can be recording and reproduced by the magnetic head is supplied through the magnetic head 14 over a period T 2 , so that the residual component of the erasing signal f 1 is erased. Since the erasing signal f 2 is attenuated and vibrated in a period T 22 , the residual component is minimized.
Inventors
- 👤 Takashi Ohnaka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 12:16
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/02; G11B5/024; G11B5/012; Y; Y10; Y10S; Y10S358/00; Y10S358/906
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
133 words
A method for erasing a signal in a recording track formed on a magnetic disc, comprising the steps of: erasing said recording track by supplying through a magnetic head having a single winding a first AC erasing signal having a first frequency and a first duration and performing a damping oscillation over at least a first predetermined damping oscillation period following a first predetermined stationary oscillation period during said first duration, and erasing again said recording track erased by said first AC erasing signal by supplying through said magnetic head a second AC erasing signal having a second frequency higher than said first frequency and a second duration and performing a damping oscillation over at least a second predetermined damping oscillation period following a second predetermined stationary oscillation period during said second duration.
Claim 2
Independent Claim
133 words
A method for erasing a signal in a recording track formed on a magnetic disc, comprising the steps of: erasing said recording track by supplying through a magnetic head having a single winding a first AC erasing signal having a first frequency and a first duration and performing a damping oscillation over at least a first predetermined damping oscillation period following a first predetermined stationary oscillation period during said first duration, and erasing again said recording track erased by said first AC erasing signal by supplying through said magnetic head a second AC erasing signal having a second frequency higher than said first frequency and a second duration and performing a damping oscillation over at least a second predetermined damping oscillation period following a second predetermined stationary oscillation period during said second duration.
Claim 3
Dependent Claim
18 words
A method in accordance with claim 1, wherein said first and second duration are equal to each other.
Claim 4
Dependent Claim
21 words
A method in accordance with claim 1, wherein said first and second predetermined damping oscillation periods are equal to each other.
Claim 5
Dependent Claim
61 words
A method in accordance with claim 1, wherein said first frequency is the frequency in the vicinity of an upper limit of the band of a signal recorded on said track, and said second frequency is an upper limit of frequency which is outside of the band of said recorded signal and can be recorded and reproduced by said magnetic head.
Claim 6
Dependent Claim
79 words
A method in accordance with claim 4, wherein said recorded signal includes a frequency-modulated luminance signal, said frequency-modulated luminance signal comprises a carrier wave component with a predetermined frequency, and a predetermined band with respect to said carrier wave component, and said second frequency is set such that the frequency of the difference between said second frequency and the predetermined frequency of said carrier wave component may be larger than an upper limit of frequency of said predetermined band.
Claim 7
Dependent Claim
52 words
A method in accordance with claim 5, wherein the predetermined frequency of said carrier wave component is in the vicinity of about 7 MHz, said predetermined band is in the range of about 2.5 to 11.5 MHZ, and said second frequency is set in the range of about 19 to 23 MHz.
Claim 8
Independent Claim
162 words
An apparatus for erasing a signal in a recording track formed on a magnetic disc, comprising: a magnetic head (14) having a single winding and used for at least erasing of said recording track, erasing signal forming means (22) for generating sequentially a first AC erasing signal having a first frequency and a first duration and performing a damping oscillation over at least a first predetermined damping oscillation period following a first predetermined stationary oscillation period during said first duration and a second AC erasing signal having a second frequency higher than said first frequency and a second duration and performing a damping oscillation over at predetermined damping oscillation period following a second predetermined stationary oscillation period during said second duration and outputting the same, means (48) for inputting an erase command signal, and means (SW1, SW2) responsive to said erase command signal for supplying said magnetic head with said first and second erasing signals output from said erasing signal forming means.
Claim 9
Independent Claim
162 words
An apparatus for erasing a signal in a recording track formed on a magnetic disc, comprising: a magnetic head (14) having a single winding and used for at least erasing of said recording track, erasing signal forming means (22) for generating sequentially a first AC erasing signal having a first frequency and a first duration and performing a damping oscillation over at least a first predetermined damping oscillation period following a first predetermined stationary oscillation period during said first duration and a second AC erasing signal having a second frequency higher than said first frequency and a second duration and performing a damping oscillation over at predetermined damping oscillation period following a second predetermined stationary oscillation period during said second duration and outputting the same, means (48) for inputting an erase command signal, and means (SW1, SW2) responsive to said erase command signal for supplying said magnetic head with said first and second erasing signals output from said erasing signal forming means.
Claim 10
Dependent Claim
61 words
An apparatus in accordance with claim 7, wherein said first frequency is the frequency in the vicinity of an upper limit of the band of a signal recorded on said track, and said second frequency is an upper limit of frequency which is outside of the band of said recorded signal and can be recorded and reproduced by said magnetic head.
Claim 11
Dependent Claim
134 words
An apparatus in accordance with claim 7, wherein said erasing signal forming means (22) comprises means (30) for generating the signal with said first frequency, means (32) for generating the signal with said second frequency, means (34) for defining said first duration, means (36) for defining said second duration, gain variable amplifier means (46), first switching means (SW4) for selecting the signal with said first frequency and applying the same to said gain variable amplifier means during said first duration, second switching means (SW5) for selecting the signal with said second frequency and applying the same to said gain variable amplifier means during said second duration, and means (38, 40, 42, 44, SW3) for defining said first and second predetermined periods and changing the gain of said gain variable amplifier means during the periods.
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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) | 1992-01-31 | 1992-08-01 | 1993-01-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-01-31 | 1996-08-01 | 1997-01-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-01-31 | 2000-08-01 | 2001-01-31 | $7700.00 | Window Closed / Lapsed |