US4404500A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Projection television apparatus
Assignee: US Philips Corp
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Filing: 1981-06-04
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Granted: 1983-09-13
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Expires: 2001-06-04
Abstract
Abstract In projection television apparatus in order to prevent burning of the phosphor screen of at least one of the television projection tubes a display is not produced should there be an interruption or substantial reduction in the deflection current through one of the line or field deflection coils. Each deflection coil is connected in series with sensing means for separately sensing the deflection current flowing therethrough. In the event of one of the currents through one of the deflection coils being interrupted or substantially reduced means responsive to said sensing means prevents picture information from being applied to the control grids of the projection tubes.
Inventors
- 👤 Richard G. Stow
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 02:58
CPC Classifications
H; H04; H04N; H04N3/00; H04N3/10; H04N3/16; H04N3/20; H04N5/00; H04N5/74; H04N5/7408
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
181 words
Projection television apparatus having a plurality of projection television tubes each adapted to produce a display of a different colour for projection, each projection tube having a line deflection coil and a field deflection coil for deflecting an electron beam when generated in each projection tube in two orthogonal directions, the said line deflection coils being connected in parallel branches connected to a line output stage for providing line deflection current through said line deflection coils, the said field deflection coils being connected to a field output stage for providing field deflection current through said field deflection coils, and protection means for protecting a projection tube in the event of the cessation of or substantial reduction in the line deflection current through the line deflection coil corresponding to said projection tube, said projection means comprises sensing means connected in series with each line deflection coil for separately sensing the line deflection current therethrough, and means responsive to said sensing means for preventing the electron beams from falling on the screens of the projection tubes upon the occurrence of the said event.
Claim 2
Dependent Claim
181 words
Projection television apparatus having a plurality of projection television tubes each adapted to produce a display of a different colour for projection, each projection tube having a line deflection coil and a field deflection coil for deflecting an electron beam when generated in each projection tube in two orthogonal directions, the said line deflection coils being connected in parallel branches connected to a line output stage for providing line deflection current through said line deflection coils, the said field deflection coils being connected to a field output stage for providing field deflection current through said field deflection coils, and protection means for protecting a projection tube in the event of the cessation of or substantial reduction in the line deflection current through the line deflection coil corresponding to said projection tube, said projection means comprises sensing means connected in series with each line deflection coil for separately sensing the line deflection current therethrough, and means responsive to said sensing means for preventing the electron beams from falling on the screens of the projection tubes upon the occurrence of the said event.
Claim 3
Dependent Claim
94 words
Projection television apparatus as claimed in claim 1, in which said field deflection coils are connected in parallel branches, and wherein said protection means additionally comprises further sensing means connected in series with each field deflection coil for separately sensing the field deflection current therethrough, and means responsive to said further sensing means for preventing the electron beam from falling on on the screen of the projection tubes in the event of the cessation of or a substantial reduction in the field deflection current through the field deflection coil corresponding to one projection tube.
Claim 4
Dependent Claim
122 words
Projection television apparatus as claimed in claim 1, comprising a control stage and wherein said sensing means comprises a plurality of transformers the primary of each transformer being connected in series with a corresponding line deflection coil while the secondary is connected to an associated transistor such that the associated transistor conducts in the presence of a normal line deflection current but is non-conducting in the even of the cessation of or substantial reduction in the line deflection current through the corresponding line deflection coil, said transistor being connected to said control stage such that in the event of one of said transistors being non-conducting said control stage prevents picture information from being applied to the control grids of the projection tubes.
Claim 5
Dependent Claim
125 words
Projection television apparatus as claimed in claim 1 or 2 wherein said further sensing means comprises a plurality of further transformers the primary of each further transformer being connected in series with a corresponding field deflection coil while the secondary is connected to an associated further transistor such that the associated transistor conducts in the presence of a normal field deflection current but is non-conducting in the event of the cessation of or substantial reduction in the field deflection current through the corresponding field deflection coil, said further transistors being connected with said control stage such that in the event of one of said further transistors being non-conducting said control stage prevents picture information from being applied to the control grids of the projection tubes.
References Cited (Backward Citations)
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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) | 1986-09-12 | 1987-03-14 | 1987-09-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-09-12 | 1991-03-14 | 1991-09-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-09-12 | 1995-03-14 | 1995-09-13 | $7700.00 | Window Closed / Lapsed |