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US3609364A
Expired / Lapsed
US
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Hydrogen fire detection system with logic circuit to analyze the spectrum of temporal variations of the optical spectrum
Assignee: National Aeronautics and Space Administration
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Filing: 1970-02-02
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Granted: 1971-09-28
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Expires: 1990-02-02
Abstract
Abstract A hydrogen fire detector for use on a high altitude rocket. A hydrogen fire is detected by the ultraviolet radiation of the hot oxygen-hydrogen radical produced by hydrogen combustion, while the device selectively filters out ultraviolet radiation from other sources. The detection system senses both temporal variation and steady state radiation. Discrimination against engine exhaust plume radiation is accomplished by monitoring temporal variation. Solar discrimination is accomplished by a two-color technique whereby radiation is detected by two photomultiplier tubes, one filtered to accept visible radiation and the other filtered to accept ultraviolet radiation. The photomultiplier tubes control input to logic that produces an output signal only when a hydrogen fire is viewed.
Inventors
- 👤 Robert L Proffit
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 19:10
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/12
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
36 words
The hydrogen fire detection system of claim 1 wherein said photomultiplier means comprises two photomultiplier units, one of said units being filtered to accept ultraviolet light and the other unit being filtered to accept visible light.
Claim 2
Dependent Claim
62 words
comparison means connected to said summing means for comparing each said sum with a different presettable reference voltage and producing an output corresponding to each said sum, each said output being a first fixed voltage if said sum exceeds its corresponding said reference voltage and being a second fixed voltage if said sum is less than its corresponding said reference voltage; and
Claim 3
Dependent Claim
42 words
an AND gate connected to said comparison means for receiving said outputs from said comparison means, said AND gate being adjusted to produce a fire output signal only when all of said outputs of said logic means equal said first fixed voltage.
Claim 4
Dependent Claim
86 words
The hydrogen fire detection system of claim 2 wherein said filter means comprise: a. a high band-pass ultraviolet filter capable of passing high-frequency ultraviolet radiation, said high band-pass filter being directly connected to said ultraviolet photomultiplier unit; b. a low band-pass ultraviolet filter capable of passing low-frequency ultraviolet radiation, said low band-pass filter being connected directly to said ultraviolet photomultiplier unit; and c. a low band-pass visible filter capable of passing low-frequency visible radiation, said low band-pass filter being connected directly to said visible photomultiplier unit.
Claim 5
Dependent Claim
361 words
The hydrogen fire detection system of claim 3 wherein said summing means comprises: a. a first logic amplifier having a first input connection to said high band-pass ultraviolet filter and said low band-pass visible filter, for providing a first input signal comprising the sum of high-frequency ultraviolet radiation from a rocket engine plume and visible radiation from the sun, said first logic amplifier having a second input connection to said low band-pass ultraviolet filter for providing a second input signal comprising the suM of low-frequency ultraviolet radiation from a diffuse hydrogen fire, a rocket engine plume, and the sun, said first logic amplifier summing said first and second input signals to produce an output signal; b. a second logic amplifier having a first input connection to said low band-pass visible filter for providing a first input signal comprising visible radiation from the sun, said first input connection of said second logic amplifier being a tap to said first input connection to said low band-pass visible filter of said first logic amplifier, said second logic amplifier having a second input connection to said low band-pass ultraviolet filter for providing a second input signal comprising the sum of low-frequency ultraviolet radiation from a diffuse hydrogen fire, a rocket engine plume, and the sun, said second logic amplifier summing said first and second input signals to produce an output signal; c. a third logic amplifier having a first input connection for providing a fixed reference signal, said third logic amplifier having a second input connection to said low band-pass ultraviolet filter for providing a second input signal comprising the sum of low-frequency ultraviolet radiation from a diffuse hydrogen fire, a rocket engine plume, and the sun, said third logic amplifier summing said first and second input signals to produce an output signal; d. a diode in said first input connection of said first logic amplifier to said low band-pass visible filter, between said first input connection to said first logic amplifier and said tapped first input connection to said second logic amplifier, for preventing the signal from said high band-pass ultraviolet filter from reaching said tapped first input connection to said second logic amplifier.
Claim 6
Dependent Claim
121 words
The hydrogen fire detection system of claim 4 wherein said comparison means comprises: a. a plume logic comparison amplifier connected to said first logic amplifier; b. a sun logic comparison amplifier connected to said second logic amplifier; c. a fire logic comparison amplifier connected to said third logic amplifier; d. each of said comparison amplifiers having a presettable reference voltage input, each said comparison amplifier being adjusted so as to compare said output sum from its own said logic amplifier with its own presettable reference voltage input, for producing an output of a first fixed voltage when said output sum exceeds said reference voltage input and a second fixed voltage when said output sum is less than said reference voltage input.
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) | 1974-09-27 | 1975-03-29 | 1975-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-27 | 1979-03-29 | 1979-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-27 | 1983-03-29 | 1983-09-28 | $7700.00 | Window Closed / Lapsed |