EP0159798A1
Expired / Lapsed
EP
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Fire and explosion protection system
Assignee: Kidde Graviner Ltd
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Filing: 1985-03-15
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Granted: —
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Expires: 2005-03-15
Abstract
Abstract The system discrimates between radiation produced by a hydrocarbon fire in an armored vehicle and radiation produced by the explosion of an armor-piercing ammunition round itself which does not cause a hydrocarbon fire. A radiation detector (10) sensitive to radiation, characteristic of a hydrocarbon fire, produces logic outputs if the radiation intensity exceeds a predetermined relatively low threshold (20) and is rising at at least a predetermined rate of rise (22). A detector (12) operating at 0.9 microns, at which the exploding ammunition round produces significant radiation, produces logic outputs if the radiation intensity exceeds a predetermined relatively low threshold (40) and if it is not falling at more than a predetermined rate (44). All these logic outputs are fed into a coincidence gate (28) whose output feeds a circuit (80) which produces an output only when the coincidence gate (28) produces an output for at least a predetermined period of time. A third radiation detector (14), in combination with the detector (12) and units (46) and (60), measures the colour temperature of the source being monitored, and inhibits the coincidence gate (28) if the colour temperature exceeds a predetermined value. This prevents the system reacting merely to muzzle flash from a gun. However, any such inhibition is permitted by a monostable (54) to last only for a predetermined period of time, so that the system can still detect a fire in the presence of high colour temperature sunlight. A medium threshold unit (48) is provided to produce an inhibit signal for a relatively short period of time if the output of the detector (12) exceeds a medium-level threshold. This primarily prevents the coincidence gate (28) from reacting to relatively prolonged signals from an indirectly viewed ammunition round and its hot fragments.
Inventors
- 👤 Richard V. Henry
- 👤 David N. Ball
- 👤 Robert L. Farquhar
- 👤 Vincent M. Rowe
- 👤 Peter L. Hutchins
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 05:19
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/12
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
272 words
A fire or explosion detection system for discriminating between (a) radiation produced by a source of fire or explosion to be detected and (b) radiation produced by a source of fire or explosion not to be detected, comprising first (12) and second (10) radiation detectors respectively responsive to radiation in first and second wavelength bands the second of which is a characteristic wavelength band for a source of fire or explosion to be detected, the first (12) and second (10) radiation detectors being operative to produce first and second radiation-intensity-dependent electrical signals respectively, an output arrangement (20,28,40,80) connected to monitor the first and second electrical signals and operative in dependence on the signal values and unless inhibited by an inhibiting signal to produce a fire or explosion indicating output when the signal values and the absence of the inhibiting signal indicate that the radiation is radiation produced by a source of fire or explosion to be detected, and a colour temperature-responsive inhibiting device (14,36,38,46,60) operative to monitor the colour temperature of the radiation received by at least the first radiation detector (12) to produce a said inhibiting signal when the colour temperature exceeds a predetermined colour temperature threshold, characterised in that the output arrangement comprises an arrangement (20,28,40,44) operative, unless inhibited by a said inhibiting signal, to produce the said fire or explosion indicating output only when, for at least a first predetermined period of time, the magnitudes of both the first and second signals exceed respective first and second predetermined thresholds and the magnitude of at least the said first electrical signal is not falling at more than a predetermined rate.
Claim 2
Dependent Claim
272 words
A fire or explosion detection system for discriminating between (a) radiation produced by a source of fire or explosion to be detected and (b) radiation produced by a source of fire or explosion not to be detected, comprising first (12) and second (10) radiation detectors respectively responsive to radiation in first and second wavelength bands the second of which is a characteristic wavelength band for a source of fire or explosion to be detected, the first (12) and second (10) radiation detectors being operative to produce first and second radiation-intensity-dependent electrical signals respectively, an output arrangement (20,28,40,80) connected to monitor the first and second electrical signals and operative in dependence on the signal values and unless inhibited by an inhibiting signal to produce a fire or explosion indicating output when the signal values and the absence of the inhibiting signal indicate that the radiation is radiation produced by a source of fire or explosion to be detected, and a colour temperature-responsive inhibiting device (14,36,38,46,60) operative to monitor the colour temperature of the radiation received by at least the first radiation detector (12) to produce a said inhibiting signal when the colour temperature exceeds a predetermined colour temperature threshold, characterised in that the output arrangement comprises an arrangement (20,28,40,44) operative, unless inhibited by a said inhibiting signal, to produce the said fire or explosion indicating output only when, for at least a first predetermined period of time, the magnitudes of both the first and second signals exceed respective first and second predetermined thresholds and the magnitude of at least the said first electrical signal is not falling at more than a predetermined rate.
Claim 3
Dependent Claim
75 words
A system according to claim 1, characterised by a threshold device (48) connected to compare the magnitude of the first radiation-intensity-dependent signal with a third predetermined threshold which is higher than the first predetermined threshold, so as to produce a further inhibiting signal for a predetermined period of time in response to the first radiation-intensity-dependent signal exceeding the third predetermined threshold, and a connection (74) connecting the further inhibiting signal to the output arrangement (28).
Claim 4
Dependent Claim
241 words
A fire or explosion detection system for discriminating between (a) radiation produced by a source of fire or explosion to be detected and (b) radiation produced by a source of fire or explosion not to be detected, comprising first (12) and second (10) radiation detecting devices respectively responsive to radiation at first and second wavelengths, the first of which is a wavelength produced by a source not to be detected, to produce first and second radiation-intensity-dependent electrical signals respectively, and an output arrangement (20,28,40,44,80) connected to monitor the first and second radiation-intensity-dependent electrical signals and operative, unless inhibited by an inhibiting signal, to produce a fire or explosion indicating output only when, for at least a first predetermined period of time, the magnitudes of both the first and second radiation-intensity-dependent electrical signals exceed respective first and second predetermined thresholds and the magnitude of at least the first radiation-intensity-dependent signal is not falling at more than a predetermined rate, characterised by a threshold device (48) connected to receive the first radiation-intensity-dependent electrical signal and to produce a medium threshold signal if the magnitude of the first radiation-intensity-dependent signal exceeds a predetermined threshold higher than the said first threshold, by an inhibiting device (72) responsive to initial production of the said medium threshold signal to produce a said inhibiting signal for a predetermined duration, and by a connection (74) connecting the inhibiting signal to inhibit the output means (28) for the said duration.
Claim 5
Dependent Claim
241 words
A fire or explosion detection system for discriminating between (a) radiation produced by a source of fire or explosion to be detected and (b) radiation produced by a source of fire or explosion not to be detected, comprising first (12) and second (10) radiation detecting devices respectively responsive to radiation at first and second wavelengths, the first of which is a wavelength produced by a source not to be detected, to produce first and second radiation-intensity-dependent electrical signals respectively, and an output arrangement (20,28,40,44,80) connected to monitor the first and second radiation-intensity-dependent electrical signals and operative, unless inhibited by an inhibiting signal, to produce a fire or explosion indicating output only when, for at least a first predetermined period of time, the magnitudes of both the first and second radiation-intensity-dependent electrical signals exceed respective first and second predetermined thresholds and the magnitude of at least the first radiation-intensity-dependent signal is not falling at more than a predetermined rate, characterised by a threshold device (48) connected to receive the first radiation-intensity-dependent electrical signal and to produce a medium threshold signal if the magnitude of the first radiation-intensity-dependent signal exceeds a predetermined threshold higher than the said first threshold, by an inhibiting device (72) responsive to initial production of the said medium threshold signal to produce a said inhibiting signal for a predetermined duration, and by a connection (74) connecting the inhibiting signal to inhibit the output means (28) for the said duration.
Claim 6
Dependent Claim
61 words
A system according to claim 3, characterised by a colour temperature-responsive inhibiting device (14,36,38,46,60) operative to monitor the colour temperature of the radiation received by at least the first radiation detector (12) to produce a said inhibiting signal when the colour temperature exceeds a predetermined colour temperature threshold and by a connection feeding this inhibiting signal to the output arrangement (28).
Claim 7
Dependent Claim
88 words
A system according to claim 1,2 or 4, characterised in that the colour temperature responsive inhibiting device comprises a third radiation detector (14) responsive to radiation in a third wavelength band to produce a third radiation-intensity-dependent electrical signal, the third wavelength band being so selected in relation to the said first wavelength band that a comparison of the first and third signals produces an output dependent on colour temperature, and a comparing arrangement (36,38,46,60) operative to compare the first and third signals to produce the said inhibiting signal.
Claim 8
Dependent Claim
27 words
A system according to claim 5, characterised in that the comparing arrangement comprises an arrangement (36,38,46) for measuring the ratio of the first and third electrical signals.
Claim 9
Dependent Claim
85 words
A system according to claim 6, characterised in that the comparing arrangement comprises logarithmic amplifiers (36,38) for respectively logarithmically amplifying the first and third electrical signals, a differencing arrangement (46) for measuring the difference between the outputs of the two logarithmic amplifiers (36,38) whereby to produce an output whose anti-logarithm is dependent on the ratio of the first and third electrical signals, and an arrangement (60) responsive to the anti-logarithm of the output of the said differencing arrangement (46) to produce the said inhibiting signal.
Claim 10
Dependent Claim
85 words
A system according to claim 1 or 2 or to any one of claims 4 to 7, characterised by a timing arrangement (54) connected to be responsive to the production of the said inhibiting signal by the colour temperature-responsive device (14,36,38,46,60) and to cancel that inhibiting signal after a predetermined time from its initial production so as then to permit production of the fire or explosion indicating output by the output arrangement (20,28,40,44,80) even when the said colour temperature exceeds the predetermined colour temperature threshold.
Claim 11
Independent Claim
71 words
A system according to any preceding claim, characterised by a rate of rise arrangement (22) operative to produce a rate of rise signal when the rate of rise of the said second radiation-intensity-dependent signal does not exceed a predetermined value, and a device (30) responsive to this rate of rise signal to produce another said inhibiting signal inhibiting the output arrangement (28) from producing the said fire or explosion indicating output.
Claim 12
Dependent Claim
98 words
A system according to claim 9, characterised by a saturation responsive device (24) responsive to the second radiation-intensity-dependent signal to produce a saturation signal when the magnitude of the second radiation-intensity-dependent signal reaches a level corresponding to electrical saturation of the second radiation detecting device (10), and in that the device (30) responsive to the rate of rise signal . comprises a device (30) connected to receive that signal and the saturation signal and arranged to produce an inhibiting signal for inhibiting the output arrangement only when neither the rate of rise signal nor the saturation signal exists.
Claim 13
Independent Claim
70 words
A system according to any preceding claim, characterised in that the output arrangement includes first (40) and second (20) threshold devices, the first threshold device (40) being connected to receive the first radiation-intensity-dependent signal and to compare its magnitude with the said first predetermined threshold, and the second threshold device (20) being connected to receive the second radiation-intensity-dependent signal and to compare its magnitude with the said second predetermined threshold.
Claim 14
Dependent Claim
67 words
A system according to claim 11, characterised by a modifying arrangement (50) responsive to the said first radiation-intensity-dependent electrical signal and connected to the first threshold device (40) to increase the predetermined value of the said first threshold so that it is higher after the first radiation detecting device (12) has responded to radiation than it is before the first radiation detecting device (12) has so responded.
Claim 15
Dependent Claim
33 words
A system according to claim 12, characterised in that the said modifying arrangement (50) comprises an integrator (50) for producing an output in dependence on the time integral of the first radiation-intensity-dependent signal.
Claim 16
Independent Claim
69 words
A system according to any preceding claim, characterised in that the output arrangement includes a logic gate (28) and a time delay arrangement (80) connected to receive the output of the logic gate (28) and operative to produce the said fire or explosion indicating output only when the output of the logic gate (28) has a predetermined logic value for at least the said first predetermined period of time.
Claim 17
Independent Claim
32 words
A system according to any preceding claim, characterised in that the said first wavelength band includes a wavelength at which a fire or explosion source not to be detected produces significant radiation.
Claim 18
Independent Claim
46 words
A system according to any preceding claim, characterised by an inhibiting device (42) responsive to the first radiation-intensity-dependent signal to produce another said inhibiting signal when the magnitude of the first radiation-intensity-dependent signal reaches a level corresponding to electrical saturation of the first radiation detecting device
Claim 19
Dependent Claim
15 words
(12), and a connection (56) connecting this other inhibiting signal to inhibit the output arrangement
Claim 20
Dependent Claim
15 words
(12), and a connection (56) connecting this other inhibiting signal to inhibit the output arrangement
Claim 21
Dependent Claim
1 words
(28).
Claim 22
Dependent Claim
1 words
(28).
Claim 23
Independent Claim
99 words
A system according to any preceding claim, characterised by a second output arrangement connected to monitor the first and second signals and operative, unless inhibited by a said inhibiting signal, to produce a second fire or explosion indicating output only when, for at least a particular predetermined period of time, the magnitude of the first signal exceeds a predetermined threshold which is lower than the first predetermined threshold, the magnitude of the second signal exceeds the said second predetermined threshold and the magnitude of at least the said first signal is not falling at more than a predetermined rate.
Claim 24
Dependent Claim
67 words
A system according to claim 17, characterised in that the second output arrangement comprises a logic gate and a time delay arrangement connected to receive the output of that logic gate and operative to produce the said second fire or explosion indicating output only when the output of the that logic gate has a predetermined logic value for at least the said particular predetermined period of time.
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