Patent US4940920A successfully refreshed from Google Patents.
US4940920A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Device to shield mask cathode tubes from the earth's magnetic field
Assignee: Videocolor
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Filing: 1987-11-06
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Granted: 1990-07-10
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Expires: 2007-11-06
Abstract
Abstract To improve the trichromatic cathode tube shielding effect given by the frame-mask set and by a shielding material made with material of low magnetic permeability, the external conductors of a de-magnetization coil with two loops are made to pass in front of the fastening lugs and not behind the frit plane as was the case before, and the position of the internal conductors is set to obtain the best compromise.
Inventors
- 👤 Guiseppe Giannantonio
- 👤 Cesare De Paolis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 22:33
CPC Classifications
H; H01; H01J; H01J29/00; H01J29/003; H01J2229/00; H01J2229/0007; H01J2229/003; H01J2229/0046; H01J2229/0053
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
168 words
A device to shield mask cathode tubes with shielding screens made of low magnetic permeability material from the earth's magnetic field, said tube having two sides which are substantially horizontal and two sides which are substantially vertical in a normal operating position, said device comprising a demagnetization coil having two oblong-shaped loops with each loop having two large sides, the large sides of which are substantially horizontal, said two loops being fixed substantially on the cone of the cathode tube, and being arranged symmetrically on opposite sides with regard to a horizontal plane passing through the axis of the tube neck, said loops being further connected to a de-magnetizing current generator device, the two large sides of these loops which are furthest from each other being located on the screen side of the frit plane of the tube and the two large sides of these loops which are closest to each other are located midway between the side of the deflector nearest the screen and an anode button.
Claim 2
Independent Claim
168 words
A device to shield mask cathode tubes with shielding screens made of low magnetic permeability material from the earth's magnetic field, said tube having two sides which are substantially horizontal and two sides which are substantially vertical in a normal operating position, said device comprising a demagnetization coil having two oblong-shaped loops with each loop having two large sides, the large sides of which are substantially horizontal, said two loops being fixed substantially on the cone of the cathode tube, and being arranged symmetrically on opposite sides with regard to a horizontal plane passing through the axis of the tube neck, said loops being further connected to a de-magnetizing current generator device, the two large sides of these loops which are furthest from each other being located on the screen side of the frit plane of the tube and the two large sides of these loops which are closest to each other are located midway between the side of the deflector nearest the screen and an anode button.
Claim 3
Dependent Claim
30 words
A device according to claim 1, wherein said two large sides which are furthest from each other are located near the horizontal sections of an anti-implosion belt of the tube.
Claim 4
Dependent Claim
50 words
A device according to claim 2 wherein fastening lugs are fixed to the anti-implosion belt, at mid-width and wherein said two large sides which are furthest from each other pass between the fastening plane of the lugs and the mating face of the skirt with the envelope of the screen.
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) | 1993-07-09 | 1994-01-08 | 1994-07-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-07-09 | 1998-01-08 | 1998-07-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-07-09 | 2002-01-08 | 2002-07-10 | $7700.00 | Window Closed / Lapsed |