US4135219A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Demagnetizer for a magnetic head of a recording-reproducing device
Assignee: TDK Corp
•
Filing: 1977-07-20
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Granted: 1979-01-16
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Expires: 1997-07-20
Abstract
Abstract A demagnetizer for a magnetic head for a recording/reproducing device. The demagnetizer includes an electromagnet for producing an alternating magnetic field which gradually decreases in intensity. The demagnetizer is mounted in a case formed in the shape of a tape cassette. The electromagnet is resiliently held within the case adjacent to the opening for the magnetic head to be demagnetized. The electromagnet is energized by an oscillating drive circuit, the output of which is controlled by a capacitor.
Inventors
- 👤 Keiichi Yoshizawa
- 👤 Isamu Nakao
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:35
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/465; G11B23/00; G11B23/02; G11B23/04
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
114 words
A demagnetizer for demagnetizing the magnetic head of a conventional cassette-type recording-reproducing device, comprising a case formed in the shape of a conventional tape cassette, said case having an opening for the insertion therein of said magnetic head, an electromagnet positioned in said case adjacent to said opening for applying a magnetic field to said magnetic head, a driving circuit for energizing said electromagnet to produce said magnetic field so that said field gradually decreases in intensity, and biasing means for resiliently urging said electromagnet against said magnetic head within said cassette opening so that said electromagnet and magnetic head are maintained in stationary position with respect to each other during a demagnetizing operation.
Claim 2
Dependent Claim
114 words
A demagnetizer for demagnetizing the magnetic head of a conventional cassette-type recording-reproducing device, comprising a case formed in the shape of a conventional tape cassette, said case having an opening for the insertion therein of said magnetic head, an electromagnet positioned in said case adjacent to said opening for applying a magnetic field to said magnetic head, a driving circuit for energizing said electromagnet to produce said magnetic field so that said field gradually decreases in intensity, and biasing means for resiliently urging said electromagnet against said magnetic head within said cassette opening so that said electromagnet and magnetic head are maintained in stationary position with respect to each other during a demagnetizing operation.
Claim 3
Dependent Claim
18 words
A demagnetizer according to claim 1, wherein said biasing means comprises a spring member mounted within said case.
Claim 4
Dependent Claim
36 words
A demagnetizer according to claim 2, wherein said driving circuit is positioned within said case and includes a switch for controlling the energization of said circuit, and said spring member includes means for actuating said switch.
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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) | 1982-01-15 | 1982-07-17 | 1983-01-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-01-15 | 1986-07-17 | 1987-01-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-01-15 | 1990-07-17 | 1991-01-16 | $7700.00 | Window Closed / Lapsed |