Patent US3978520A successfully refreshed from Google Patents.
US3978520A
Expired / Lapsed
US
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Magnetic head cleaning tape and method
Assignee: 3M Co
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Filing: 1974-11-29
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Granted: 1976-08-31
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Expires: 1994-11-29
Abstract
Abstract Magnetic heads of color video tape recorder (vtr) machines are cleaned without harmful abrasion by means of a novel magnetic head cleaning tape carrying a color bar signal. Abrupt appearance of the color bar test pattern at the video monitor permits cessation of the cleaning operation immediately upon complete removal of foreign matter and without harmful abrasion of the heads.
Inventors
- 👤 John V. Nowicki
- 👤 John D. Hakanson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 19:53
CPC Classifications
H; H04; H04N; H04N17/00; H04N17/06; G; G11; G11B; G11B5/00; G11B5/41; Y; Y10; Y10S; Y10S15/00; Y10S15/12
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
126 words
Method of cleaning the magnetic heads of a video tape recorder having a video monitor, comprising playing in said recorder a magnetically recordable magnetic head cleaning tape having a surface coating comprising magnetizable particles in a hard non-magnetizable binder, said coating having an H c value of at least 300 oersteds and a B r value of at least 800 gauss, and having a surface roughness of between 5 × 10 - 2 and 12 × 10.sup. -2 (arithmetic average) and between 20 × 10.sup. -2 and 47 × 10.sup. -2 (peak-to-valley) micro-meters, and said tape carrying a magnetically recorded video test pattern; continuing the play until the display produced on said video monitor resolves into the clear synchronized test pattern; and then immediately stopping play.
Claim 2
Dependent Claim
126 words
Method of cleaning the magnetic heads of a video tape recorder having a video monitor, comprising playing in said recorder a magnetically recordable magnetic head cleaning tape having a surface coating comprising magnetizable particles in a hard non-magnetizable binder, said coating having an H c value of at least 300 oersteds and a B r value of at least 800 gauss, and having a surface roughness of between 5 × 10 - 2 and 12 × 10.sup. -2 (arithmetic average) and between 20 × 10.sup. -2 and 47 × 10.sup. -2 (peak-to-valley) micro-meters, and said tape carrying a magnetically recorded video test pattern; continuing the play until the display produced on said video monitor resolves into the clear synchronized test pattern; and then immediately stopping play.
Claim 3
Dependent Claim
33 words
Method of claim 1 wherein said magnetizable particles are magnetic chromium dioxide and wherein said H c value is at least 500 oersteds and said B r value is at least 1200 gauss.
Claim 4
Dependent Claim
24 words
Method of claim 2 wherein said recorded test pattern is a color bar test pattern and said recorder is a color video tape recorder.
Claim 5
Dependent Claim
90 words
As a new article of manufacture, a magnetic head cleaning tape product including a carrier having bonded thereto a coating comprising magnetizable particles in a hard non-magnetizable binder, said coating having an H c value of at least 300 oersteds and B r value of at least 800 gauss, and having a surface roughness of between 5 × 10.sup. -2 and 12 × 10.sup. -2 (arithmetic average) and between 20 × 10.sup. -2 and 47 × 10.sup. -2 (peak-to-valley) micro-inches; and said tape carrying a magnetically recorded video test pattern.
Claim 6
Dependent Claim
90 words
As a new article of manufacture, a magnetic head cleaning tape product including a carrier having bonded thereto a coating comprising magnetizable particles in a hard non-magnetizable binder, said coating having an H c value of at least 300 oersteds and B r value of at least 800 gauss, and having a surface roughness of between 5 × 10.sup. -2 and 12 × 10.sup. -2 (arithmetic average) and between 20 × 10.sup. -2 and 47 × 10.sup. -2 (peak-to-valley) micro-inches; and said tape carrying a magnetically recorded video test pattern.
Claim 7
Dependent Claim
34 words
Tape product of claim 4 wherein said magnetizable particles are magnetic chromium dioxide and wherein said H c value is at least 500 oersteds and said B r value is at least 1200 gauss.
Claim 8
Dependent Claim
16 words
Tape product of claim 5 wherein said recorded test pattern is a color bar test pattern.
Claim 9
Dependent Claim
12 words
Tape product of claim 5 wherein said coating includes non-magnetic abrasive particles.
References Cited (Backward Citations)
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US3789452A
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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) | 1979-08-31 | 1980-03-01 | 1980-08-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-08-31 | 1984-03-01 | 1984-08-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-08-31 | 1988-03-01 | 1988-08-31 | $7700.00 | Window Closed / Lapsed |