US4004185A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electric lighting systems
Assignee: Thomas Ashworth and Co Ltd
•
Filing: 1975-04-25
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Granted: 1977-01-18
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Expires: 1995-04-25
Abstract
Abstract A method and apparatus of lighting a cold cathode electric gas discharge lamp in which the lamp is connected across the secondary winding of a voltage step-up transformer, and the primary winding of the transformer is energized with a chopped D.C. voltage having a frequency of at least 12 kHz and a voltage which provides an output voltage from the secondary winding having an R.M.S. value no greater than 700 volts.
Inventors
- 👤 Harry Edmondson
- 👤 Walter Whittaker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 06:29
CPC Classifications
H; H01; H01F; H01F38/00; H01F38/08; H01F38/10; H02; H02M; H02M3/00; H02M3/22; H02M3/24; H02M3/28; H02M3/325; H02M3/335; H02M3/338; H05; H05B; H05B41/00; H05B41/14; H05B41/26; H05B41/28; H05B41/282; H05B41/2821; H05B41/2822; Y; Y10; Y10S; Y10S315/00; Y10S315/07
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
77 words
A method of lighting a cold cathode electric gas discharge lamp having a length of at least one foot, comprising connecting the lamp across the secondary winding of a voltage step-up transformer, energizing the primary winding of the transformer with a chopped D.C. voltage having a frequency of at least 12 kHz and a voltage which provides an output voltage from the secondary winding of the said transformer having an R.M.S. value no greater than 700 volts.
Claim 2
Independent Claim
77 words
A method of lighting a cold cathode electric gas discharge lamp having a length of at least one foot, comprising connecting the lamp across the secondary winding of a voltage step-up transformer, energizing the primary winding of the transformer with a chopped D.C. voltage having a frequency of at least 12 kHz and a voltage which provides an output voltage from the secondary winding of the said transformer having an R.M.S. value no greater than 700 volts.
Claim 3
Dependent Claim
28 words
A method of lighting a cold cathode electric gas discharge lamp according to claim 1 in which the frequency lies in the range 20 kHz to 60 kHz.
Claim 4
Dependent Claim
25 words
A method of lighting a cold cathode electric gas discharge lamp as claimed in claim 1, in which the frequency is at least 15 kHz.
Claim 5
Dependent Claim
115 words
A lighting unit comprising a cold cathode electric gas discharge lamp having a length of at least one foot and a power unit therefor, the power unit comprising an inverter circuit including an output transformer having the discharge lamp connected across its secondary winding, a transistor having its main current-carrying electrodes connected between a D.C. power supply and the input of the primary winding and oscillating circuit means connected between the outlet of the primary winding and the control electrode of the transistor for oscillating at a predetermined frequency of at least 12 kHz and for supplying to the cold cathode electric discharge lamp a voltage having an R.M.S. value no greater than 700 volts.
Claim 6
Dependent Claim
115 words
A lighting unit comprising a cold cathode electric gas discharge lamp having a length of at least one foot and a power unit therefor, the power unit comprising an inverter circuit including an output transformer having the discharge lamp connected across its secondary winding, a transistor having its main current-carrying electrodes connected between a D.C. power supply and the input of the primary winding and oscillating circuit means connected between the outlet of the primary winding and the control electrode of the transistor for oscillating at a predetermined frequency of at least 12 kHz and for supplying to the cold cathode electric discharge lamp a voltage having an R.M.S. value no greater than 700 volts.
Claim 7
Dependent Claim
18 words
A lighting unit as claimed in claim 4 in which the said frequency is at least 15 kHz.
Claim 8
Dependent Claim
30 words
A lighting unit according to claim 4 in which the primary winding of the transformer is wound with wire having a gauge in the range 24 SWG to 30 SWG.
Claim 9
Dependent Claim
24 words
A lighting unit according to claim 6 in which the gauge of the primary winding is in the range 24 SWG to 26 SWG.
Claim 10
Dependent Claim
31 words
A lighting unit according to claim 4 in which the transformer includes a pair of C-shaped saturable magnetic cores having their open ends facing one another to form a magnetic loop.
Claim 11
Dependent Claim
16 words
A lighting unit as claimed in claim 8 including an air gap in the magnetic loop.
Claim 12
Dependent Claim
19 words
A lighting unit according to claim 9 in which the width of the gap does not exceed 3 mm.
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) | 1980-01-18 | 1980-07-19 | 1981-01-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-01-18 | 1984-07-19 | 1985-01-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-01-18 | 1988-07-19 | 1989-01-18 | $7700.00 | Window Closed / Lapsed |