US3742474A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Flame detector
Assignee: Cerberus AG
•
Filing: 1971-04-07
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Granted: 1973-06-26
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Expires: 1991-04-07
Abstract
Abstract The output from a photosensitive transducer, such as a photo diode or the like, exposed to a flame, is applied to a circuit which is capable of filtering out regularly recurring a-c components to distinguish the randomly occurring components upon flame detection from regularly recurring variations of light sensed by the transducer, for example due to reflections from rotating machines, line disturbances and the like. The circuit includes a demodulator and filter, having a pass range of about 2-40 Hz to demodulate the signal, and a further detector circuit detecting randomly recurring components within a lower frequency range, for example 1 Hz or less and providing an output signal if a certain threshold is exceeded. Signals arising in the circuit can be used to additionally control the sensitivity of the flamesensitive detector.
Inventors
- 👤 P Muller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 05:40
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/12
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
119 words
Flame detector having photo-sensitive transducer means responsive to flame radiation, and an electrical recognition circuit connected to said transducer means, deriving its input signal therefrom, and producing an output signal representative of presence, or absence of a flame, said circuit comprising means discriminating between regularly, periodically recurring components and randomly, non-periodically occurring components of the input signal applied to said recognition circuit by said transducer comprising an amplitude detector providing an output representative of amplitude variations occurring in the output signal; and meanS responsive to the detector output detecting randomly, non-periodically recurring components in the output within a predetermined frequency range; said circuit providing said output signal when the predetermined low-frequency range, randomly occurring components exceed a pre-set value.
Claim 2
Dependent Claim
119 words
Flame detector having photo-sensitive transducer means responsive to flame radiation, and an electrical recognition circuit connected to said transducer means, deriving its input signal therefrom, and producing an output signal representative of presence, or absence of a flame, said circuit comprising means discriminating between regularly, periodically recurring components and randomly, non-periodically occurring components of the input signal applied to said recognition circuit by said transducer comprising an amplitude detector providing an output representative of amplitude variations occurring in the output signal; and meanS responsive to the detector output detecting randomly, non-periodically recurring components in the output within a predetermined frequency range; said circuit providing said output signal when the predetermined low-frequency range, randomly occurring components exceed a pre-set value.
Claim 3
Dependent Claim
22 words
Flame detector according to claim 1, wherein said circuit comprises a band pass filter having a high frequency cut-off below 50 Hz.
Claim 4
Dependent Claim
20 words
Flame detector according to claim 1, wherein the pass range of the low-pass filter is between 2 and 40 Hz.
Claim 5
Dependent Claim
26 words
Flame detector according to claim 1, wherein the amplitude detector includes an amplitude deomdulator providing an output representative of the ampltidue envelope of the input signal.
Claim 6
Dependent Claim
42 words
Flame detector according to claim 4, wherein the circuit comprises a bandpass filter having a frequency pass range of about 2-50 Hz and the amplitude demodulator includes low-pass filter means having a high-frequency cut-off below the low-frequency cut-off of the bandpass filter.
Claim 7
Dependent Claim
24 words
Flame detector according to claim 5, wherein the low-pass filter means has a high range cut-off in the order of 1 Hz or less.
Claim 8
Dependent Claim
22 words
Flame detector according to claim 6, including an RC network and a parallel resistance-capacity network connected, in parallel, to said RC network.
Claim 9
Dependent Claim
23 words
Flame detector according to claim 1, wherein the electrical recognition circuit comprises an integrator and a threshold detector connected to said amplitude detector.
Claim 10
Dependent Claim
50 words
Flame detector according to claim 4, wherein said amplitude demodulator includes a rectifier to provide an output signal therefrom which has a d-c and an a-c component; and said circuit further comprises means sensing the level of said d-c component and indicating when said d-c level exceeds a predetermined value.
Claim 11
Dependent Claim
29 words
Flame detector according to claim 1, including power supply means for said transducer; and means controlling the power applied to said transducer as a function of the output signal.
Claim 12
Dependent Claim
46 words
Flame detector according to claim 9, including ower supply means for said transducer; and means controlling the power applied to said transducer as a function of the output signal, said power supply means controlling the power applied to said transducer being responsive to said d-c component.
Claim 13
Dependent Claim
43 words
Flame detector according to claim 11, wherein said power supply control means comprises a transistor having said transducer connected in circuit with the emitter-collector path of the transistor; and means controlling the conductivity of said transistor as a function of said d-c component.
Claim 14
Dependent Claim
14 words
Flame detector according to claim 1, wherein the discriminator means comprises a frequency discriminator.
Claim 15
Dependent Claim
29 words
Flame detector according to claim 13, wherein the frequency discriminator comprises a square wave pulse generating circuit and a circuit responsive to the flanks of the square wave pulses.
Claim 16
Dependent Claim
23 words
Flame detector according to claim 14, wherein the square wave pulse generating circuit comprises a pair of oppositely poled, series connected Zener diodes.
Claim 17
Dependent Claim
28 words
Flame detector according to claim 14, wherein the frequency discriminator comprises a low-pass filter providing an output amplitude representative of the rate of recurrence of pulses applied thereto.
Claim 18
Dependent Claim
41 words
Flame detector according to claim 8, wherein the integrator and threshold detector are set to provide an output signal if, and only if the output signal of said amplitude detector repsresentative of randomly occurring low-frequency components persist beyond a predetermined duration.
Claim 19
Dependent Claim
39 words
Flame detector according to claim 17, wherein said integrator and threshold detector includes a condenser; said rectifier being connected to charge said condenser with half waves of one polarity; and said threshold detector detects the charge on said condenser.
Claim 20
Dependent Claim
32 words
Flame detector according to claim 18, wherein the threshold detector includes a thyristor controlled by the charge on said condenser; and means detecting current flow through the anode-cathode path of said thyristor.
Claim 21
Dependent Claim
123 words
Flame detector having photosensitive transducer means responsive to flame radiation, and an electrical recognition circuit connected to said transducer means deriving its input signal therefrom and producing an output signal representative of the presence, or absence of a flame, said circuit comprising means discriminating between regularly periodically recurring components and randomly non-periodically occurring components of the input signal applied to said recognition circuit by said transducer comprising an amplitude detector providing an output representative of amplitude variations occurring in the input signal; and an amplitude demodulator providing an output representative of the ampltidue envelope of the input signal, and means responsive to said output providing a flame detection output signal when low-frequency, randomly occurring amplitude variations in the envelope exceed a pre-set value.
Claim 22
Dependent Claim
123 words
Flame detector having photosensitive transducer means responsive to flame radiation, and an electrical recognition circuit connected to said transducer means deriving its input signal therefrom and producing an output signal representative of the presence, or absence of a flame, said circuit comprising means discriminating between regularly periodically recurring components and randomly non-periodically occurring components of the input signal applied to said recognition circuit by said transducer comprising an amplitude detector providing an output representative of amplitude variations occurring in the input signal; and an amplitude demodulator providing an output representative of the ampltidue envelope of the input signal, and means responsive to said output providing a flame detection output signal when low-frequency, randomly occurring amplitude variations in the envelope exceed a pre-set value.
Claim 23
Dependent Claim
42 words
Flame detector according to claim 20, wherein the circuit comprises a bandpass filter having a frequency pass range of about 2-40 Hz and the amplitude demodulator includes low-pass filter means having a high-frequency cut-off below the low-frequency cut-off of the bandpass filter.
Claim 24
Dependent Claim
23 words
Flame detector according to claim 20, wherein the electrical recognition circuit comprises an integrator and a threshold detector connected to said amplitude detector.
Claim 25
Dependent Claim
50 words
Flame detector according to claim 20, wherein the amplitude demodulator includes a rectifier to provide an output signal therefrom which has a d-c and an a-c component; and said circuit further comprises means sensing the level of said d-c component and indicating when said d-c level exceeds a predetermined value.
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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) | 1976-06-25 | 1976-12-25 | 1977-06-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-06-25 | 1980-12-25 | 1981-06-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-06-25 | 1984-12-25 | 1985-06-26 | $7700.00 | Window Closed / Lapsed |