US3740574A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ionic flame monitor
Assignee: Combustion Engineering Inc
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Filing: 1971-12-30
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Granted: 1973-06-19
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Expires: 1991-12-30
Abstract
Abstract A protection circuit for an ionic flame monitor to insure that high voltage AC signals appearing across the flame electrodes and arising from sources other than a flame will not be effective to provide a false output indication of flame presence. The flame monitor is sensitive to AC signals above a certain frequency or above a certain voltage to indicate flame presence. Non-flame AC signals having voltages above or below the certain frequency, but above the certain voltage are prevented from indicating flame presence if their voltage is above a second certain level which is above that of most flame signal voltages. A voltage level detection circuit clamps the monitor output circuitry to a ''''no-flame'''' condition whenever the AC signal voltage is above the second certain level.
Inventors
- 👤 J Taylor
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 20:26
CPC Classifications
F; F23; F23N; F23N5/00; F23N5/02; F23N5/12; F23N5/123
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
256 words
In a flame monitor for determining the presence or absence of a flame within a flame zone through detection of a flame generated AC signal, a pair of electrode means spaced from one another and disposed within said flame zone to be in contact with said flame when present; circuit means operatively connected to said electrode means for applying a direct current potential between said electrode means to develop a flame generated AC signal additionally appearing between said electrode means when a flame is present; coupling means having an input and an output and adapted for passing to said output thereof AC signal energy characteristic of AC signal energy applied to said input thereof; means electrically connecting said electrode means with said coupling means input for applying AC signal energy thereto; flame switch circuit means having an input circuit operatively connected to the output of said coupling means and responsive to signal energy appearing thereat for providing an output response commensurate with flame presence when the magnitude of said signal energy is at least as great as a certain value and providing an output response commensurate with flame absence when the magnitude of said energy is less than said certain value; and clamping means operatively connected between said electrode means and said flame switch circuit means and responsive to AC voltage magnitude for effecting said flame switch circuit means output response commensurate with flame absence when the AC voltage across said electrodes exceeds a predetermined level, regardless of the signal energy passed by said coupling means.
Claim 2
Dependent Claim
256 words
In a flame monitor for determining the presence or absence of a flame within a flame zone through detection of a flame generated AC signal, a pair of electrode means spaced from one another and disposed within said flame zone to be in contact with said flame when present; circuit means operatively connected to said electrode means for applying a direct current potential between said electrode means to develop a flame generated AC signal additionally appearing between said electrode means when a flame is present; coupling means having an input and an output and adapted for passing to said output thereof AC signal energy characteristic of AC signal energy applied to said input thereof; means electrically connecting said electrode means with said coupling means input for applying AC signal energy thereto; flame switch circuit means having an input circuit operatively connected to the output of said coupling means and responsive to signal energy appearing thereat for providing an output response commensurate with flame presence when the magnitude of said signal energy is at least as great as a certain value and providing an output response commensurate with flame absence when the magnitude of said energy is less than said certain value; and clamping means operatively connected between said electrode means and said flame switch circuit means and responsive to AC voltage magnitude for effecting said flame switch circuit means output response commensurate with flame absence when the AC voltage across said electrodes exceeds a predetermined level, regardless of the signal energy passed by said coupling means.
Claim 3
Dependent Claim
92 words
The apparatus of claim 1 wherein said clamping means include AC voltage level detection means connected across said electrode means for developing a switching voltage when AC voltage exceeding said predetermined level appears across said electrode means; and switch means responsive to the presence of said switching voltage for clamping the input circuit of said flame switch circuit means to a maximum electrical energy level less than that required to provide said response commensurate with flame presence, whereby the output response of said flame switch circuit means is commensurate with flame absence.
Claim 4
Dependent Claim
171 words
The apparatus of claim 2 wherein said flame generated AC signal applied to the input of said coupling means comprises AC electrical energy above a certain frequency and having an AC voltage substantially entirely within a range less than said predetermined level and said coupling means include filter means operatively connected between the input and output of said coupling means for attenuating the input signal of said coupling means to an output magnitude less than that required to provide said response commensurate with flame presence when said coupling means input signal is less than said certain frequency and said predetermined level of AC voltage and for passing the input signal of said coupling means to the output thereof at a magnitude at least as great as said certain value required to provide said response commensurate with flame presence when said AC flame signal is present and the AC voltage at said input is below said predetermined level and when said AC voltage present at said input is above said predetermined level.
Claim 5
Dependent Claim
72 words
The apparatus of claim 3 wherein said voltage level detection means include at least one gas filled discharge device having a breakdown potential no greater than said predetermined level of AC voltage and resistance means for developing said switching voltage, said resistance means and said discharge device being connected in series across said pair of electrode means and said switching voltage being that across said resistance means when said discharge device conducts.
Claim 6
Dependent Claim
64 words
The apparatus of claim 3 wherein said voltage level detection means include, in series, threshold discharge means for conducting only when a potential thereacross exceeds said predetermined level of AC voltage; means for isolating said threshold discharge means from said DC potential established between said pair of electrode means; and impedance means for developing thereacross said switching voltage when said threshold discharge means conducts.
Claim 7
Dependent Claim
89 words
The apparatus of claim 5 wherein said switch means for clamping said input circuit of said flame switch circuit means comprise an electronic switch having first, second, and third electrodes, said first electrode being operatively connected to said impedance means across which is developed said switching voltage and acting to close a circuit between said second and third electrodes when said switching voltage is applied thereto and said second and third electrodes respectively being connected to ground potential and to the input circuit of said flame switch circuit means.
Claim 8
Dependent Claim
115 words
The apparatus of claim 6 wherein said flame switch circuit means include a load relay for providing a response commensurate with flame presence when energized and triggerable gating means for gating energizing power to said load relay when triggered by a trigger signal, said gating means comprise a silicon controlled relay having an anode, cathode, and a trigger electrode and wherein energizing power is passed by circuit means from a power source to said relay by a current path through said anode and cathode in a triggered conductive state, said trigger signal being provided by that signal energy connected to the input circuit of said flame switch circuit means and being above said predetermined level.
References Cited (Backward Citations)
US2766440A
Cited
US3437884A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-06-18 | 1976-12-18 | 1977-06-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-06-18 | 1980-12-18 | 1981-06-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-06-18 | 1984-12-18 | 1985-06-19 | $7700.00 | Window Closed / Lapsed |