US3671815A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Flame detection apparatus
Assignee: Columbia Gas System Service Corp
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Filing: 1972-06-20
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Granted: 1972-06-20
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Expires: 1992-06-20
Abstract
Abstract A gas flame produces a voltage between the burner and an electrode in the flame. This voltage is utilized in a circuit which produces a pulse signal to control a relay that indicates flame presence. Failure of any critical component in the circuit prevents the relay from operating.
Inventors
- 👤 Arthur C Eberle
- 👤 Lee H Darby
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 09:42
CPC Classifications
F; F23; F23N; F23N5/00; F23N5/02; F23N5/12; F23N5/123; F23N2231/00; F23N2231/10
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
125 words
A flame detection circuit comprising first and second terminals to be connected conductively to a flame; a field effect transistor having gate, source and drain electrodes, said first and second terminals being connected in series with said source and drain electrodes; a first series circuit comprising a capacitor and a resistor connected in series with said first and second terminals whereby said capacitor can be charged by voltage generated by said flame; means to apply current pulses to said gate of said field effect transistor to render the latter conductive at repetitive intervals to discharge said capacitor; regenerative means connected to said series circuit to be actuated by discharge current from said capacitor; and relay means connected to said regenerative means to be actuated thereby.
Claim 2
Dependent Claim
125 words
A flame detection circuit comprising first and second terminals to be connected conductively to a flame; a field effect transistor having gate, source and drain electrodes, said first and second terminals being connected in series with said source and drain electrodes; a first series circuit comprising a capacitor and a resistor connected in series with said first and second terminals whereby said capacitor can be charged by voltage generated by said flame; means to apply current pulses to said gate of said field effect transistor to render the latter conductive at repetitive intervals to discharge said capacitor; regenerative means connected to said series circuit to be actuated by discharge current from said capacitor; and relay means connected to said regenerative means to be actuated thereby.
Claim 3
Dependent Claim
94 words
The flame detection circuit of claim 1 comprising, in addition, a second capacitor; a rectifier to connect said second capacitor to a source of alternating voltage to be charged during alternate half cycles of said alternating voltage; and a silicon controlled rectifier having an anode-cathode circuit connected in series with said relay means and said second capacitor, said silicon controlled rectifier also having a gate connected to said regenerative means to be actuated thereby to cause said silicon controlled rectifier to discharge said second capacitor through said relay means when there is a flame.
Claim 4
Dependent Claim
37 words
The flame detection circuit of claim 2 in which said regenerative means actuates said silicon controlled rectifier to discharge said second capacitor only during alternate half cycles of said alternating voltage when said rectifier is not conductive.
Claim 5
Dependent Claim
72 words
The flame detection circuit of claim 1 in which said means to apply current pulses to said gate of said field effect transistor comprises a bilateral switch connected to a source of alternating current to supply said current pulses to said gate of said field effect transistor during peaks of said alternating current to supply said current pulses to said gate of said field effect transistor during peaks of said alternating current.
Claim 6
Dependent Claim
40 words
The flame detection circuit of claim 4 comprising, in addition, a second rectifier connected to said source of alternating current to generate a direct voltage and connected to the gate of said field effect transistor to provide direct bias therefor.
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) | 1975-06-20 | 1975-12-20 | 1976-06-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-20 | 1979-12-20 | 1980-06-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-20 | 1983-12-20 | 1984-06-20 | $7700.00 | Window Closed / Lapsed |