US3629645A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Television receiver protective system for preventing screen burn
Assignee: GTE Sylvania Inc
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Filing: 1969-08-19
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Granted: 1971-12-21
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Expires: 1989-08-19
Abstract
Abstract In a television receiver in which a television signal source is DC coupled to the cathode of a picture tube and circuit means including a brightness control is connected between the control grid of the picture tube and a power supply, a protective system for preventing screen burn comprising a diode with parallel capacitor connected between the variable tap of the brightness control and ground, the diode being rendered conducting in response to applied horizontal blanking pulses. Upon cessation of blanking pulses from a threshold controlled source, the brightness control tap is disconnected from ground, thereby causing the control grid voltage to increase and thus increase the beam current to discharge the high voltage stored on the picture tube before scan collapse.
Inventors
- 👤 Thomas Lester Taylor
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 21:42
CPC Classifications
H; H04; H04N; H04N3/00; H04N3/10; H04N3/16; H04N3/20
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
230 words
In electrical apparatus including a cathode-ray tube having a plurality of electrodes, a signal source DC coupled to a first one of said plurality of electrodes, electron beam deflection apparatus associated with said cathode-ray tube, power supply means having an input coupled to a power source and an output coupled to said signal source and said electron beam deflection apparatus for energizing said signal source and said electron beam deflection apparatus, and circuit means coupled intermediate said power supply means and a second one of said plurality of electrodes of said cathode-ray tube for energizing said second one of said plurality of electrodes, a protection system comprising: switching means for coupling said circuit means to a potential reference level; and energy sourcE means, including a potential threshold means for detecting a change in potential level upon decoupling of said power supply means from said power source, coupling said power supply means to said switching means for maintaining said switching means in a first operating state when said power supply means is coupled to said power source and for switching said switching means to a second operating state prior to complete deenergization of said beam deflection apparatus upon decoupling of said power supply means from said power source, said switching means and said circuit means cooperatively maintaining electron beam current in said cathode-ray tube during deenergization of said beam deflection apparatus.
Claim 2
Dependent Claim
230 words
In electrical apparatus including a cathode-ray tube having a plurality of electrodes, a signal source DC coupled to a first one of said plurality of electrodes, electron beam deflection apparatus associated with said cathode-ray tube, power supply means having an input coupled to a power source and an output coupled to said signal source and said electron beam deflection apparatus for energizing said signal source and said electron beam deflection apparatus, and circuit means coupled intermediate said power supply means and a second one of said plurality of electrodes of said cathode-ray tube for energizing said second one of said plurality of electrodes, a protection system comprising: switching means for coupling said circuit means to a potential reference level; and energy sourcE means, including a potential threshold means for detecting a change in potential level upon decoupling of said power supply means from said power source, coupling said power supply means to said switching means for maintaining said switching means in a first operating state when said power supply means is coupled to said power source and for switching said switching means to a second operating state prior to complete deenergization of said beam deflection apparatus upon decoupling of said power supply means from said power source, said switching means and said circuit means cooperatively maintaining electron beam current in said cathode-ray tube during deenergization of said beam deflection apparatus.
Claim 3
Dependent Claim
47 words
The protection system of claim 1 wherein said switching means comprises a semiconductor device having a first electrode connected to said circuit means and a second electrode connected to said potential reference level, and a capacitor connected across the first and second electrodes of said semiconductor device.
Claim 4
Dependent Claim
57 words
The combination of claim 1 wherein said switching means comprises a diode having a first electrode connected to said circuit means and a second electrode connected to said potential reference level, and a capacitor connected across the first and second electrodes of said diode, said energy source means being coupled to the first electrode of said diode.
Claim 5
Dependent Claim
40 words
The protection system of claim 3 wherein said circuit means includes a potentiometer for controlling the potential on the second electrode of said cathode-ray tube, and said potentiometer has a variable tap connected to the first electrode of said diode.
Claim 6
Dependent Claim
51 words
The protection system of claim 3 wherein said protection system is employed in a television receiver, and said energy source means comprises a source of blanking pulses and said potential threshold means, said source of blanking pulses being coupled to the first terminal of said diode through said potential threshold means.
Claim 7
Dependent Claim
42 words
The protection system of claim 5 wherein said circuit means includes a brightness control potentiometer for adjusting the potential on the second electrode of said cathode-ray tube, and said potentiometer has a variable tap connected to the first electrode of said diode.
Claim 8
Dependent Claim
26 words
The protection system of claim 6 wherein said potential threshold means comprises a neon bulb serially connected between said source of blanking pulses and said diode.
Claim 9
Dependent Claim
93 words
The protection system of claim 7 wherein the first and second electrodes of said cathode-ray tube are the cathode and control grid, respectively, said source of blanking pulses derives the horizontal blanking pulses for said television receiver and is AC coupled to the control grid of said cathode-ray tube, said circuit means further includes a plurality of resistors serially connected between said control grid and means coupled to said power supply means, and said potentiometer has a terminal connected to the junction of two of said series resistors and is branched out therefrom.
Claim 10
Dependent Claim
40 words
The protection system of claim 8 wherein said circuit means further includes a second power supply coupled to said first mentioned power supply means, said plurality of resistors being serially connected between said control grid and said second power supply.
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) | 1974-12-20 | 1975-06-21 | 1975-12-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-12-20 | 1979-06-21 | 1979-12-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-12-20 | 1983-06-21 | 1983-12-21 | $7700.00 | Window Closed / Lapsed |