US3564156A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for the production of magnetic tapes which cannot be erased
Assignee: Agfa Gevaert AG
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Filing: 1967-07-20
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Granted: 1971-02-16
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Expires: 1987-07-20
Abstract
Abstract Nonerasable copy of a magnetic recording is made by applying to the recording movable magnetizable particles to cause them to be attracted by and arranged in accordance with the stray fields of the recording, then fixing the particles in position with respect to each other, securing the fixed particles to a separate backing and removing the backing with the particles therein from the recording. When the particles are applied a magnetic field can also be impressed to render the magnetizing of the magnetizable particles more ideal, or the particles can be magnetized by cooling down from their Curie point. The application of a unidirectional magnetic field whose lines of force are perpendicular to the surface of the recording will also prevent frequency doubling.
Inventors
- 👤 Joachim Greiner
- 👤 Wolfgang Eichler
- 👤 Wilhelm Abeck
- 👤 Erich Muller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 19:30
CPC Classifications
G; G03; G03G; G03G5/00; G03G5/16
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
142 words
A process for the production of magnetic copies of a magnetic recording of acoustic signals comprising the steps of: a. applying a layer of a suspension of movable soft magnetizable particles having a coercive force of less than 15 Oe and a length of between 0.05 and 2./ in a solution of a film-forming binder agent to the magnetic recording carrying original magnetic information to cause the magnetizable particles to be attracted by the magnetic stray field of the magnetic information of the recording and to become arranged in accordance with the magnetic stray field of the original information; and b. drying the Said layer of the suspension to fix the magnetizable particles in position with respect to each other after they have become arranged, and then removing the dried layer with the particles from the recording carrying the original magnetic information.
Claim 2
Dependent Claim
142 words
A process for the production of magnetic copies of a magnetic recording of acoustic signals comprising the steps of: a. applying a layer of a suspension of movable soft magnetizable particles having a coercive force of less than 15 Oe and a length of between 0.05 and 2./ in a solution of a film-forming binder agent to the magnetic recording carrying original magnetic information to cause the magnetizable particles to be attracted by the magnetic stray field of the magnetic information of the recording and to become arranged in accordance with the magnetic stray field of the original information; and b. drying the Said layer of the suspension to fix the magnetizable particles in position with respect to each other after they have become arranged, and then removing the dried layer with the particles from the recording carrying the original magnetic information.
Claim 3
Dependent Claim
52 words
In the process of claim 1 the step of first applying to the surface of the magnetic recording a covering layer by vapor coating the surface of the magnetic recording using vapor containing a film-forming substance selected from the group consisting of vaporized aluminum, silicon dioxide, aluminum oxide and synthetic film-forming resins.
Claim 4
Dependent Claim
27 words
A process as defined in claim 1, wherein the ratio of magnetizable particle volume to the total volume of the dried layer is between 0.15 and 0.25.
Claim 5
Dependent Claim
17 words
A process as defined in claim 1, wherein step (a) is performed under idealizing magnetic recording conditions.
Claim 6
Dependent Claim
19 words
A process as defined in claim 1, wherein idealizing magnetic recording conditions are supplied by an alternating magnetic field.
Claim 7
Dependent Claim
33 words
A process as defined in claim 1, wherein a unidirectional magnetic field is applied during step (a), the field lines of the unidirectional field extent substantially perpendicularly to the surface of the recording.
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) | 1974-02-15 | 1974-08-17 | 1975-02-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-02-15 | 1978-08-17 | 1979-02-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-02-15 | 1982-08-17 | 1983-02-16 | $7700.00 | Window Closed / Lapsed |