US3797003A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Warning circuits for intermittently flashable lamp
Assignee: CAV Ltd
•
Filing: 1972-06-05
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Granted: 1974-03-12
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Expires: 1992-06-05
Abstract
Abstract A warning circuit for use with a lamp which in use is connected to an intermittent source of electric supply, the warning circuit comprising means for sensing the current flow through the lamp during the on period of the supply and further means operable when the current falls below a predetermined value, indicative that the lamp has failed for providing an indication of such failure.
Inventors
- 👤 A Ramshaw
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 18:32
CPC Classifications
B; B60; B60Q; B60Q11/00; B60Q11/005
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
144 words
A warning circuit for a lamp which in use, is connected to an intermittent source of electric supply the circuit comprising in combination a resistor connected in series with said lamp and the intermittent source of electric supply, switch means for sensing the voltage developed across said resistor during the on periods of said supply, an electromagnetic relay, said switch means switching on to energise said relay when the voltage drop due to current flow developed across said resistor falls below a predetermined value during an on period of said supply, a pair of relay contacts forming part of said relay, said relay contacts when said relay is energised maintaining current flow through said resistor from a further source of supply during the off periods of said first mentioned supply and a warning lamp for providing an indication of the operation of the relay.
Claim 2
Dependent Claim
144 words
A warning circuit for a lamp which in use, is connected to an intermittent source of electric supply the circuit comprising in combination a resistor connected in series with said lamp and the intermittent source of electric supply, switch means for sensing the voltage developed across said resistor during the on periods of said supply, an electromagnetic relay, said switch means switching on to energise said relay when the voltage drop due to current flow developed across said resistor falls below a predetermined value during an on period of said supply, a pair of relay contacts forming part of said relay, said relay contacts when said relay is energised maintaining current flow through said resistor from a further source of supply during the off periods of said first mentioned supply and a warning lamp for providing an indication of the operation of the relay.
Claim 3
Dependent Claim
29 words
A warning circuit as claimed in claim 1 in which said switch means comprises a transistor having the operating coil of said relay connected in its collector emitter path.
Claim 4
Dependent Claim
31 words
A warning circuit as claimed in claim 2 in which the operating coil of the relay and the collector emitter path of the transistor are connected in parallel with the lamp.
Claim 5
Dependent Claim
33 words
A warning circuit as claimed in claim 3 including means for determining the base potential of the transistor whereby the voltage across the resistor at which the transistor switches on can be determined.
Claim 6
Dependent Claim
33 words
A warning circuit as claimed in claim 4 in which the means for determining the base potential of the transistor comprises a potential divider network connected in parallel with said first mentioned supply.
Claim 7
Dependent Claim
32 words
A warning circuit as claimed in claim 5 in which said potential divider network includes a diode to provide compensation for changes in the operating characteristics of the transistor with temperature variations.
Claim 8
Dependent Claim
40 words
A warning circuit as claimed in claim 6 in which said potential divider network includes a Zener diode whereby compensation for varying lamp current will be obtained as a result in fluctuation of the voltage of said first mentioned supply.
Claim 9
Dependent Claim
23 words
A warning circuit as claimed in claim 1 in which said warning lamp is connected in parallel with said pair of relay contacts.
Claim 10
Dependent Claim
29 words
A warning circuit as claimed in claim 8 in which said first mentioned source of supply comprises an interrupter switch connected in series with a steady source of supply.
Claim 11
Dependent Claim
28 words
A warning circuit as claimed in claim 9 in which said relay contacts are of the normally open type and are connected in parallel with said interrupter switch.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-03-11 | 1977-09-10 | 1978-03-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-11 | 1981-09-10 | 1982-03-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-11 | 1985-09-10 | 1986-03-12 | $7700.00 | Window Closed / Lapsed |