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US4218722A
Expired / Lapsed
US
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Compact hand-held demagnetizing device
Assignee: TDK Corp
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Filing: 1978-11-01
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Granted: 1980-08-19
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Expires: 1998-11-01
Abstract
Abstract A compact hand-held demagnetizing device is used for demagnetizing a magnetic recording and reproducing head. It comprises a handle portion and a demagnetizing head. The handle portion contains a circuit for generating a decreasing alternating current for exciting a drive coil for the demagnetizing head. Means is provided to indicate the time when the demagnetizing operation is initiated or when the demagnetizing operation can be initiated and when the demagnetizing operation is completed.
Inventors
- 👤 Keiichi Yoshizawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 21:26
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/465
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
85 words
A compact hand-held demagnetizing device including a circuit contained in a handle portion for generating a decreasing alternating electric current, a drive coil excited by said current, a demagnetizing head extending from said handle portion and driven by said drive coil for generating a decreasing alternating demagnetizing magnetic field, and a manually operable switch for initiating the generation of said decreasing alternating current, characterized in that said device includes first luminescent means for indicating the time when the decreasing alternating current becomes substantially zero level.
Claim 2
Dependent Claim
85 words
A compact hand-held demagnetizing device including a circuit contained in a handle portion for generating a decreasing alternating electric current, a drive coil excited by said current, a demagnetizing head extending from said handle portion and driven by said drive coil for generating a decreasing alternating demagnetizing magnetic field, and a manually operable switch for initiating the generation of said decreasing alternating current, characterized in that said device includes first luminescent means for indicating the time when the decreasing alternating current becomes substantially zero level.
Claim 3
Dependent Claim
34 words
A compact hand-held demagnetizing device according to claim 1, wherein said device includes second luminescent means responsive to said manually operable switch to indicate the start of the generation of the decreasing alternating current.
Claim 4
Dependent Claim
59 words
A compact hand-held demagnetizing device according to claim 2, wherein said circuit includes a capacitor, means for charging said capacitor, oscillator means responsive to the discharging of said capacitor to generate the decreasing alternating current, and means responsive to the discharge of said capacitor to activate the first luminescent means when the potential of said capacitor becomes substantially zero.
Claim 5
Dependent Claim
25 words
A compact hand-held demagnetizing device according to claims 1, 2 or 3, wherein said demagnetizing head is angularly adjustable with respect to said handle portion.
Claim 6
Dependent Claim
43 words
A compact hand-held demagnetizing device according to claim 4 wherein said demagnetizing head has a pair of long legs extending away from said handle portion and said legs are bent at their middle portions in one direction and then in the other direction.
Claim 7
Dependent Claim
83 words
A compact hand-held demagnetizing device according to claim 1, wherein said circuit includes a capacitor, means for charging said capacitor, oscillator means responsive to the discharging of said capacitor to generate the decreasing alternating current, means responsive to the charging of said capacitor to activate the first luminescent means when the potential of said capacitor exceed a predetermined level and means responsive to the discharge of said capacitor to deactivate said first luminescent means when the potential of said capacitor becomes substantially zero.
Claim 8
Dependent Claim
22 words
A compact hand-held demagnetizing device according to claim 6, wherein said demagnetizing head is angularly adjustable with respect to said handle portion.
Claim 9
Dependent Claim
45 words
A compact hand-held demagnetizing device according to claim 6 or 7, wherein said demagnetizing head has a pair of long legs extending away from said handle portion and said legs are bent at their middle portions in one direction and then in the other direction.
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) | 1983-08-19 | 1984-02-18 | 1984-08-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-08-19 | 1988-02-18 | 1988-08-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-08-19 | 1992-02-18 | 1992-08-19 | $7700.00 | Window Closed / Lapsed |