EP0234961B1 - Einrichtung für schnelle Erkennung von Feuer - Google Patents

Einrichtung für schnelle Erkennung von Feuer Download PDF

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Publication number
EP0234961B1
EP0234961B1 EP87400011A EP87400011A EP0234961B1 EP 0234961 B1 EP0234961 B1 EP 0234961B1 EP 87400011 A EP87400011 A EP 87400011A EP 87400011 A EP87400011 A EP 87400011A EP 0234961 B1 EP0234961 B1 EP 0234961B1
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EP
European Patent Office
Prior art keywords
sensor
radiation
signal
pyroelectric sensor
pyroelectric
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP87400011A
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English (en)
French (fr)
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EP0234961A1 (de
Inventor
André Benhamou
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KIDDE DEXAERO
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Individual
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/18—Prevention or correction of operating errors
    • G08B29/183—Single detectors using dual technologies
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/12—Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions

Definitions

  • the invention relates to a rapid flame detection device, in particular an oil fire, in particular in an armored vehicle.
  • a rapid flame detection device in particular an oil fire, in particular in an armored vehicle.
  • Such a device is known for example from GB-A-2 142 757.
  • the fuel tank In a combat tank the fuel tank is generally inside the armored vehicle that this tank constitutes; It lines an important part of the walls.
  • the weapons used to attack these tanks are explosive charges with hollow charges which concentrate thermal energy at a point and act like a torch to pierce the armor.
  • the machine also passes through the fuel tank; as a result, this fuel vaporizes in the passenger compartment and ignites rapidly in an explosive manner.
  • the protection of persons inside the armored vehicle therefore requires automatic and rapid detection of a flame or an explosion in order to activate, also automatically and rapidly, a fire extinguisher in the passenger compartment.
  • the detection device must be particularly selective, that is to say that it does not risk triggering the extinguisher if there is no fire.
  • the electromagnetic radiation emission properties of the hydrocarbon combustion flames are generally used.
  • the spectrum of these flames extends from the ultraviolet (UV) domain to the infrared (IR) domain.
  • UV ultraviolet
  • IR infrared
  • the ultra-violet it is especially the solar radiation which can be confused with a hydrocarbon flame.
  • the shortest wavelength of solar UV radiation is 0.25 microns while the flames of hydrocarbons emit below this wavelength; under these conditions, a UV radiation detector sensitive to wavelengths less than 0.25 microns is usually used.
  • an infrared radiation detector is used to ensure that we are dealing with heating radiation.
  • the invention provides a detection device of the kind mentioned above which is simple to perform while reducing the risk of false alarms.
  • a pyroelectric sensor consists of a crystal, for example of lithium tantalate, one face of which receives the radiation to be detected. The application of radiation causes heating and the production of a charge of the capacitor.
  • Such a pyroelectric sensor was previously known for detecting fires; however, it has so far not been used for very rapid detection, as it is considered to be slow responding.
  • the inventor has found that by using the voltage signal of such a pyroelectric sensor, a signal of very high quality is obtained in a few milliseconds.
  • the pyroelectric sensor accumulates the thermal energy received and, therefore, behaves like an integrator (in the mathematical sense of the term), which makes it possible to obtain an excellent signal-to-noise ratio and reduces the risk of false alarms.
  • the discriminating power of the detection device is further increased because, in this wavelength zone, parasitic sources that constitute heat sources in common glass bulbs are even more eliminated: lighting lamps, photographic flash , etc ....
  • the flame detection device which will now be described in relation to the figures comprises, in known manner, a detector 10 of ultra violet radiation which is sensitive to wavelengths between 0.18 and 0.25 microns and which is thus sensitive to the radiation emitted by the flames of hydrocarbons but insensitive to solar radiation (the spectrum of which begins only at 0.25 microns approximately).
  • a pyroelectric sensor 11 of infrared radiation is also provided.
  • this sensor 11 does not deliver a signal when the infrared radiation it receives is of constant amplitude.
  • incident radiation of amplitude constant allows a signal to be obtained provided that this signal is the voltage across the capacitor that constitutes the pyroelectric crystal; this latter property results from the following considerations:
  • the behavior (in voltage) of the pyroelectric crystal is no longer integrative but derivative because, then, its temperature only varies if the power of the incident radiation varies.
  • FIG. 3a shows the amplitude variations I L as a function of time t of infrared radiation of constant wavelength. This radiation appears suddenly at time t0.
  • the voltage response of the pyroelectric sensor 11 is represented by curve 13 in FIG. 3b.
  • the time which elapses between the instant t0 and the instant t de, of maximum response V M is relatively short, of a few milliseconds, at most a hundred milliseconds.
  • Another advantage of a pyroelectric sensor which, in steady state, directly provides a rate of change signal, is that it does not require the use of a branch circuit. The production of the detection device is therefore simplified, which makes this device more reliable.
  • a filter In front of the lithium tantalate pyroelectric detector, a filter is placed which lets through only radiation of wavelengths between 4 and 4.5 microns approximately, which further increases the discriminating power. Indeed, at these wavelengths, the solar radiation is weakened due to the presence of carbon dioxide C02 in the atmosphere and the light sources contained in a current glass envelope do not emit infrared of these wavelengths, current glass stopping radiation from about 2.7 microns.
  • the signal V of the pyroelectric sensor 11 is applied to the input of a low-pass filter 16 whose high cut-off frequency is approximately 5 KHz. This eliminates false alarms that would result from short-lived spurious signals.
  • the output of the filter 16 is applied to the first input 171 of a comparator 17 whose second input 172 receives a signal representing a predetermined threshold.
  • This comparator 17 delivers a signal on its output 173 when the signals 171 and 172 are equal or when the signal on the input 171 is greater than the signal on the input 172.
  • the 173 output is connected to the first 181 input of a AND gate 18, the second input 182 of which receives a signal from a channel 19 for processing the signal supplied by the ultraviolet (UV) radiation detector 10.
  • This fly 19 comprises a relaxer circuit 20, which will be described in more detail in connection with FIG. 2, supplying pulses every 2 ms approximately when UV radiation is detected. These pulses are delivered to the counting input 21 of a counter 22 mounted as a comparator to transmit a signal on its output 23, which is connected to the input 182 of the gate 18, when the number 2 has been reached.
  • the output pulses of circuit 20 are also applied to the reset input (RESET) 24 of a divider by sixteen 25 whose input receives a clock signal supplied by an oscillator 26 of period 1.25 milliseconds .
  • the output of the divider 25 is connected to the reset input 27 of the counter 22.
  • the relaxer circuit 20 (fig. 2) is supplied by a voltage source which applies a potential of 500 volts to a terminal 30 of a resistor 31 of great value, for example 15 megohm (M ⁇ ), the other terminal of which is connected, on the one hand, to ground via a capacitor 32 and, on the other hand, to the first electrode 33 of the detector 10, the other electrode 34 of which is connected to ground via d '' a measurement resistor 35.
  • a voltage source which applies a potential of 500 volts to a terminal 30 of a resistor 31 of great value, for example 15 megohm (M ⁇ ), the other terminal of which is connected, on the one hand, to ground via a capacitor 32 and, on the other hand, to the first electrode 33 of the detector 10, the other electrode 34 of which is connected to ground via d '' a measurement resistor 35.
  • this circuit is as follows: when the sensor 10 does not receive ultraviolet radiation of wavelength between 0.18 and 0.25 microns this sensor constitutes an open circuit and the terminal 36 of the resistor 31 opposite the terminal 30 remains at the potential of 500 volts and the potential difference across the resistor 35 is zero. When ultraviolet radiation appears, ionization occurs inside the detector tube 10, which makes the space 33,34 conductive. Under these conditions the capacitor 32 discharges into the resistor 35 and, across the latter, a pulse therefore appears. When the potential of point 36 falls below the value of 350 volts the ionization in the tube 10 cannot be maintained meager the presence of ultraviolet radiation and this detector then constitutes an open circuit; under these conditions the capacitor 32 is recharged which allows, if the UV radiation subsite, the production of a new pulse.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)
  • Fire-Detection Mechanisms (AREA)

Claims (6)

  1. Einrichtung zur Schnellerkennung von Kohlenwasserstoff-Explosionen im Inneren eines gepanzerten Fahrzeugs, wobei die Einrichtung zur Schnellauslösung eines Feuerlöschers ausgelegt ist, dadurch gekennzeichnet, daß sie für eine Erkennung in einer Zeitspanne von höchstens 100 Millisekunden ausgebildet ist, sie einen Detektor in Form eines pyroelektrischen Sensors (11) enthält, dessen Ausgangssignal das Spannungssignal an den Anschlüssen des Sensors ist, welches durch Schaltungsmittel (16, 17) unter Verzicht auf eine Rechenschaltung zum Berechnen der Änderungsrate, z.B. eine Differenzierschaltung, ausgewertet wird.
  2. Einrichtung nach Anspruch 1, dadurch gekennzeichnet, daß sie ein dem pyroelektrischen Sensor (11) nachgeschaltetes Tiefpaßfilter (16) enthält, dessen obere Grenzfrequenz in der Größenordnung von 5 kHz liegt.
  3. Vorrichtung nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der pyroelektrische Sensor (11) auf Schwankungen der Strahlungsintensität im Infrarot-Spektrum anspricht, und der Detektor im Sensor vorgeschaltet ein Filter aufweist, welches nur solche Strahlen durchläßt, deren Wellenlänge etwa zwischen 4 und 4,5 Mikrometer liegt.
  4. Einrichtung nach irgendeinem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß der pyroelektrische Sensor einen Lithiumtantalat-Kristall enthält.
  5. Einrichtung nach irgendeinem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß sie einen zweiten Sensor (10) aufweist, der auf das Vorhandensein von durch die Flamme emittierter Ultraviolettstrahlung anspricht.
  6. Einrichtung nach Anspruch 5, dadurch gekennzeichnet, daß der zweite Sensor auf Ultraviolettstrahlung mit einer Wellenlänge von weniger als 0,25 Mikrometer anspricht.
EP87400011A 1986-01-10 1987-01-06 Einrichtung für schnelle Erkennung von Feuer Expired - Lifetime EP0234961B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8600319A FR2592976B1 (fr) 1986-01-10 1986-01-10 Dispositif de detection rapide d'incendie
FR8600319 1986-01-10

Publications (2)

Publication Number Publication Date
EP0234961A1 EP0234961A1 (de) 1987-09-02
EP0234961B1 true EP0234961B1 (de) 1993-10-13

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Application Number Title Priority Date Filing Date
EP87400011A Expired - Lifetime EP0234961B1 (de) 1986-01-10 1987-01-06 Einrichtung für schnelle Erkennung von Feuer

Country Status (5)

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US (1) US4861998A (de)
EP (1) EP0234961B1 (de)
DE (1) DE3787738T2 (de)
FR (1) FR2592976B1 (de)
IL (1) IL81222A (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9162095B2 (en) 2011-03-09 2015-10-20 Alan E. Thomas Temperature-based fire detection
CN106168507A (zh) * 2015-09-09 2016-11-30 河南联纵消防科技有限公司 一种紫外光传感器脉冲供电方法

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA938018A (en) * 1970-10-20 1973-12-04 Yamaka Eiso Infrared intensity detector using a pyroelectric polymer
CH519761A (de) * 1971-03-04 1972-02-29 Cerberus Ag Flammen-Detektor
US4415806A (en) * 1978-04-25 1983-11-15 Cerberus Ag Radiation detector for a flame alarm
DE2823410A1 (de) * 1978-04-25 1979-11-08 Cerberus Ag Flammenmelder
JPS5769492A (en) * 1980-10-18 1982-04-28 Horiba Ltd Flame sensor
US4384207A (en) * 1981-01-23 1983-05-17 Eltec Instruments, Inc. Differential pyroelectric detector
US4455487A (en) * 1981-10-30 1984-06-19 Armtec Industries, Inc. Fire detection system with IR and UV ratio detector
IL65517A (en) * 1982-04-18 1988-02-29 Spectronix Ltd Discrimination circuitry for fire and explosion suppression apparatus
IL65715A (en) * 1982-05-07 1993-02-21 Spectronix Ltd Fire and explosion detection apparatus
GB2142757B (en) * 1983-05-21 1986-11-26 Graviner Ltd Improvements in and relating to fire and explosion detection and suppression
GB2165641B (en) * 1984-10-13 1988-01-13 Graviner Ltd Measuring distance to a fire

Also Published As

Publication number Publication date
DE3787738T2 (de) 1994-02-03
EP0234961A1 (de) 1987-09-02
FR2592976A1 (fr) 1987-07-17
IL81222A (en) 1990-02-09
DE3787738D1 (de) 1993-11-18
FR2592976B1 (fr) 1988-10-07
IL81222A0 (en) 1987-08-31
US4861998A (en) 1989-08-29

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