EP0772852A1 - Improvements relating to optical smoke detectors - Google Patents

Improvements relating to optical smoke detectors

Info

Publication number
EP0772852A1
EP0772852A1 EP95926440A EP95926440A EP0772852A1 EP 0772852 A1 EP0772852 A1 EP 0772852A1 EP 95926440 A EP95926440 A EP 95926440A EP 95926440 A EP95926440 A EP 95926440A EP 0772852 A1 EP0772852 A1 EP 0772852A1
Authority
EP
European Patent Office
Prior art keywords
pulses
frequency
threshold
detector
microprocessor
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.)
Granted
Application number
EP95926440A
Other languages
German (de)
French (fr)
Other versions
EP0772852B1 (en
Inventor
Jacques Lewiner
Eugeniusz Smycz
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ORWIN
Original Assignee
Smycz Eugeniusz
Orwin
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Smycz Eugeniusz, Orwin filed Critical Smycz Eugeniusz
Publication of EP0772852A1 publication Critical patent/EP0772852A1/en
Application granted granted Critical
Publication of EP0772852B1 publication Critical patent/EP0772852B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/103—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device
    • G08B17/107—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device for detecting light-scattering due to smoke

Definitions

  • the invention relates to devices intended to detect the presence of smoke with a view in particular to carrying out surveillance of a room with regard to fire risks and, for this purpose, to automatically trigger an alarm, especially sound, when the density of the smoke detected exceeds a predetermined threshold.
  • a capacitor is charged during periods T using a low intensity electric current, then this capacitor is discharged at the end of each of said periods for times t and the pulses are applied to a light source of duration t thus generated, which result in light pulses of the same duration forming the light brush.
  • an alarm signifying a fire risk is not triggered until after having verified that the trigger threshold programmed in advance remains exceeded during several successive light pulses (see the document EP-A-0011 205). If the difference between said successive light pulses reaches or exceeds 5 or 10 seconds, the duration of such a security check can reach half a minute or more, which is prohibitive.
  • the object of the invention is, above all, to eliminate this drawback while benefiting from the great savings due to the formation of the light brush used for detection using brief pulses spaced over time.
  • the smoke detector devices of the kind in question according to the invention also comprise means for forming the incident light control brush using current pulses also spaced in time, and they are essentially characterized by what they further include means for automatically increasing the frequency of emission of said pulses at the first manifestation of a detection representative of a breach of the predetermined threshold by the density of the fumes to be checked, the possible triggering of an alarm then being controlled as a function of the signals produced by the detector in response to several of the successive pulses emitted at the frequency increased, said means then being neutralized again if the examination of said signals reveals a return to order of the situation and only in this case.
  • the means for emitting the light pulses constituting the incident brush comprise a source of direct current and a light source connected to the terminals of the current source by means of at least one electronic switch and the means for increasing the frequency of the pulses when the threshold predetermined by the response signal of the detector are exceeded comprise an amplifier of this signal response, an analog-digital converter, a microprocessor comprising the threshold recorded in an appropriate memory, and a circuit, associated with the microprocessor and possibly integrated therein, capable of increasing the operating frequency of the switch as soon as exceeding the threshold by the response signal and as long as this exceeding lasts, the microprocessor includes means for detecting ter, in particular by a derivative calculation, the direction of the evolution of the amplitudes of the detector response signals corresponding to successive pulses emitted at the increased frequency, and means for setting off the alarm if this direction is increasing and only in this case, the assembly constituted by the microprocessor and the circuit for controlling the frequency of emission of the
  • the invention includes, apart from these main provisions, certain other arrangements which are preferably used at the same time and which will be more explicitly discussed below.
  • FIG. 1, of this drawing shows very schematically the component, of a detection device established according to the invention, in which the optical detection proper is carried out.
  • FIG. 2 is a simplified diagram of the entire detection device according to the invention.
  • FIG. 3 shows in more detail another component of this device, namely its circuit for controlling the frequency of emission of the light pulses.
  • Figures 4, 5 and 6 are diagrams each showing, on the one hand at the top, the incident light pulses and, on the other hand at the bottom, the detector response signals for respectively three different situa ⁇ tions.
  • the detector comprises a housing 1 mounted on a base 2 and pierced with windows 3 suitable for delivering passage to a smoke F to be checked.
  • These windows 3 are associated with baffles (not shown) making it possible to prohibit the introduction of light into the housing as much as possible and thus to form a dark room inside this housing.
  • the housing contains a clean light source L to emit a light brush P in the dark room, and a detector D placed in a shadow area of this room with respect to the source L.
  • the X particles composing this smoke constitute small mirrors capable of reflecting light: some of the rays thus reflected reach detector D and the intensity of the latter's response is all the more higher than the density of the smoke considered is itself higher.
  • the incident light brush P is not emitted continuously, but in the form of pulses I (FIG. 4) whose durations t are relatively small, being in particular of the order of 100 microseconds to 1 millisecond, the periods T which elapse between the successive pulses I are themselves relatively long, and in particular of the order of 5 to 10 seconds.
  • each overshoot should be threshold detected on the basis of an incident light pulse is confirmed on several subsequent pulses and such verification may prove to be too long in practice: the gain of one minute, even half a minute, may be prove extremely valuable for extinguishing the start of a fire.
  • the invention makes it possible to benefit both from the considerable savings due to the light emission in the form of short and repeated pulses at a relatively slow rate and the security of a response delivered only after a multiplied verification, while limiting the obtaining of this response to a very small duration, which may be of the order of a second.
  • the emission frequency of the light pulses is automatically increased as soon as an abnormal threshold crossing has been detected on the basis of an incident pulse emitted at the normal low frequency.
  • FIG. 2 There is shown diagrammatically in FIG. 2 a device making it possible to obtain such a result.
  • This device comprises: - an amplifier 4 collecting the output of the detector D, the assembly constituted by a microprocessor 5 and an analog-digital input converter 6, assembly receiving the output of the amplifier 4 and comprising, recorded in a memory , the threshold S whose exceeding by the signal leaving the detector D and amplified by amplifier 4 means a dangerous density of smoke F, a circuit 7 receiving the output of the assembly
  • the circuit 7 for controlling the frequency of emission of the pulses I comprises meanwhile (see FIG. 3), in a manner known per se: the capacitor C above, mounted across the terminals of the current source 8 by means of the resistor R above so as to be gradually charged by this source, with a speed and at a level dependent on the value of said resistor, and a circuit 9 connecting the light source L to the terminals of the capacitor C by means of an electronic switch 10 and a resistor 11.
  • Said circuit 7 further comprises here: mounted in parallel on the resistor R, at least one other resistor 12 of value less than that of this resistor R, said other resistor 12 can even be limited to a single conductor 13 of low resistance, the switching on at will of one or other of the resistors in parallel (R, 12, 13 ...) being controlled by an electronic switch 14, and s electrical connections symbolized by the arrows 15 and 16 and associated with appropriate control means to transform the instructions prepared by the microprocessor 5 into corresponding commands, either from the switch 14 alone, or from this switch and the switch 10, in the '' assumption that the latter would not be organized so as to close automatically for a short time each time the charge of the capacitor C exceeds a predetermined threshold.
  • the light source L emits light pulses I spaced apart by identical and relatively long periods T (FIG. 4) which are generated by automatic discharges chronicles of the capacitor C, which is continuously charged continuously by the current source 8.
  • T time
  • V voltage signals
  • this amplitude remains less than that of the threshold S recorded in the microprocessor 5 (taking account, of course, of the amplification coefficient imposed by the amplifier 4) so that this microprocessor does not generate any control signal on its outputs 15, 16 disrupt the normal succession of standby cycles.
  • the microprocessor immediately delivers on its outputs 15, 16 an order of increase in the frequency of emission of the light pulses, this frequency being for example multiplied by a coefficient of the order of 10.
  • the decision to trigger the alarm or to return to the standby state is postponed until a change in the controlled amplitudes of the responses V n is detected in one or the other direction.
  • the alarm is automatically triggered at the end of a minimum duration T. which can itself have a value all the greater as the difference between the constant value of the response pulses V n and the threshold S is smaller.
  • the incident impulses I'i, I ' 2 ... are given increasing values themselves: 1'experience indeed shows that the resulting variation of amplitudes of the corresponding response signals V '., V' 2 ... is greater than the variation of the amplitudes of the incident pulses.
  • Each of the two switches 10 and 14 described above is advantageously constituted by a transistor or by a semiconductor with three electrodes, the control electrode of which is connected to the corresponding output (16 or 15) of microprocessor 5, said transistors or the like which can even be integrated into this microprocessor, as well as the resistors (11, 12, R) with which they are associated.
  • This constitution, or better still this integration, makes it possible to act in a particularly fine manner on the values of the frequencies and / or amplitudes of the pulses l lf I 2 ... to be generated.
  • the invention is in no way limited to those of its modes of application and embodiments which have been more especially envisaged; on the contrary, it embraces all the variants thereof, in particular those where a part of the microprocessor 5 above would be replaced by a comparator (not shown) receiving on one of its inputs the output of the amplifier 4 and on its other input, an electrical signal representative of the threshold S, the output of this comparator then being applied to the circuit 7, preferably by means of the assembly constituted by a microprocessor and by an analog-digital converter, assembly allowing a processing of signals particularly simple and efficient.

Abstract

The device for detecting the presence of smoke (F) comprises a dark chamber (1) into which the smoke to be detected passes, a source (L) capable of producing in said chamber a light beam formed from pulses of short duration spaced from one another by identical much longer intervals, a detector (D) for generating response signals related to successive light pulses being partially reflected by the smoke, and means for comparing these signals with a threshold and setting off an alarm if the threshold is exceeded by several successive signals. The device also comprises means (4-8, 15, 16) for automatically increasing the pulsing frequency as soon as a signal exceeding the threshold is detected. Optional triggering of an alarm is then initiated on the basis of the signals generated by the detector in response to successive pulses at the increased frequency.

Description

Perfectionnements aux détecteurs optiques de fumées.Improvements to optical smoke detectors.
L'invention est relative aux dispositifs destinés à détecter la présence de fumées en vue notamment d'effec- tuer la surveillance d'un local vis-à-vis des risques d'incendie et, à cet effet, de déclencher automatiquement une alarme, notamment sonore, lorsque la densité des fumées détectées dépasse un seuil prédéterminé.The invention relates to devices intended to detect the presence of smoke with a view in particular to carrying out surveillance of a room with regard to fire risks and, for this purpose, to automatically trigger an alarm, especially sound, when the density of the smoke detected exceeds a predetermined threshold.
Elle vise plus particulièrement, parmi ces détecteurs, ceux qui mettent en oeuvre un effet optique en exploitant, à l'aide d'un détecteur approprié, la réflexion d'un pinceau lumineux relativement intense sur certaines des particules composant les fumées à contrôler, fumées circulant dans une chambre noire qui contient ledit détecteur.It is more particularly aimed, among these detectors, at those which implement an optical effect by using, using an appropriate detector, the reflection of a relatively intense light brush on some of the particles composing the fumes to be checked, fumes circulating in a dark room which contains said detector.
Vu l'intensité du pinceau lumineux, si celui-ci était émis en permanence, la consommation électrique résultante du dispositif serait très importante.Given the intensity of the light brush, if it was emitted permanently, the resulting electrical consumption of the device would be very high.
Pour écarter cet inconvénient, il a déjà été proposé d'émettre ledit pinceau sous la forme d'impulsions lumineuses de courte durée t espacées les unes des autres de périodes identiques T beaucoup plus longues, les durées t étant par exemple de l'ordre de la milliseconde ou de 100 microsecondes et les périodes T, de l'ordre de 5 à 10 secondes, la détection étant alors effectuée sur la base de signaux électriques de réponse élaborés par le détec¬ teur uniquement au cours des durées t, les valeurs de ces signaux étant comparées à tour de rôle à une valeur représentative du seuil ci-dessus de façon à déclencher l'alarme en cas de dépassement.To overcome this drawback, it has already been proposed to emit said brush in the form of light pulses of short duration t spaced from one another with identical periods T much longer, the durations t being for example of the order of the millisecond or 100 microseconds and the periods T, of the order of 5 to 10 seconds, the detection then being carried out on the basis of electrical response signals produced by the detector only during the durations t, the values of these signals being compared in turn with a value representative of the above threshold so as to trigger the alarm in the event of overshooting.
Pour créer lesdites impulsions de durée t, on opère de préférence comme suit : on charge pendant les périodes T un condensateur à l'aide d'un courant électri¬ que de faible intensité, puis on décharge ce condensateur à la fin de chacune desdites périodes pendant des temps t et on applique sur une source lumineuse les impulsions de courant de durée t ainsi engendrées, lesquelles se traduisent par les impulsions lumineuses de même durée formant le pinceau lumineux.To create said pulses of duration t, it is preferably carried out as follows: a capacitor is charged during periods T using a low intensity electric current, then this capacitor is discharged at the end of each of said periods for times t and the pulses are applied to a light source of duration t thus generated, which result in light pulses of the same duration forming the light brush.
En général, pour éviter les déclenchements d'alarme intempestifs qui pourraient être provoqués par un éclairage brusque du détecteur, dû par exemple au balayage du dispositif par un faisceau lumineux intense lui-même créé directement à partir d'une torche manuelle ou indirectement par réflexion du soleil sur une surface vitrée déplacée à la vue du dispositif, on ne déclenche une alarme signifiant un risque d'incendie qu'après avoir vérifié que le seuil de déclenchement programmé à l'avance demeure dépassé durant plusieurs impulsions lumineuses successives (voir le document EP-A-0011 205). Si l'écart entre lesdites impulsions lumineuses successives atteint ou dépasse les 5 ou 10 secondes, la durée d'un tel contrôle de sécurité peut atteindre la demi-minute ou davantage, ce qui est prohibitif.In general, to avoid nuisance alarms which could be caused by sudden lighting of the detector, due for example to the scanning of the device by an intense light beam itself created directly from a manual torch or indirectly by reflection from the sun on a glass surface moved when the device is visible, an alarm signifying a fire risk is not triggered until after having verified that the trigger threshold programmed in advance remains exceeded during several successive light pulses (see the document EP-A-0011 205). If the difference between said successive light pulses reaches or exceeds 5 or 10 seconds, the duration of such a security check can reach half a minute or more, which is prohibitive.
L'invention a pour but, surtout, de supprimer cet inconvénient tout en bénéficiant de la grande économie due à la formation du pinceau lumineux exploité pour la détection à l'aide d'impulsions brèves espacées dans le temps.The object of the invention is, above all, to eliminate this drawback while benefiting from the great savings due to the formation of the light brush used for detection using brief pulses spaced over time.
A cet effet, les dispositifs détecteurs de fumée du genre en question selon l'invention comprennent encore des moyens pour former le pinceau lumineux incident de contrôle à l'aide d'impulsions de courant également espacées dans le temps, et ils sont essentiellement caractérisés en ce qu'ils comportent en outre des moyens pour augmenter automatiquement la fréquence d'émission desdites impulsions dès la première manifestation d'une détection représentative d'un dépassement du seuil prédéterminé par la densité des fumées à contrôler, le déclenchement éventuel d'une alarme étant alors commandé en fonction des signaux élaborés par le détecteur en réponse à plusieurs des impulsions successives émises à la fréquence augmentée, lesdits moyens étant ensuite à nouveau neutralisés si l'examen desdits signaux révèle un retour en ordre de la situation et seulement dans ce cas. Dans des modes de réalisation préférés, on a recours en outre à l'une et/ou à l'autre des dispositions suivantes : les moyens pour émettre les impulsions lumineu¬ ses constitutives du pinceau incident comprennent une source de courant continu et une source lumineuse branchée aux bornes de la source de courant par l'intermédiaire d'au moins un interrupteur électronique et les moyens pour augmenter la fréquence des impulsions lors des dépasse¬ ments du seuil prédéterminé par le signal de réponse du détecteur comprennent un amplificateur de ce signal de réponse, un convertisseur analogique-numérique, un microprocesseur comprenant le seuil enregistré dans une mémoire appropriée, et un circuit, associé au micropro¬ cesseur et éventuellement intégré à celui-ci, propre à augmenter la fréquence d'actionne ent de l'interrupteur dès dépassement du seuil par le signal de réponse et tant que dure ce dépassement, le microprocesseur comprend des moyens pour détecter, notamment par un calcul de dérivée, le sens de l'évolution des amplitudes des signaux de réponse du détecteur correspondant aux impulsions successives émises à la fréquence augmentée, et des moyens pour déclencher 1'alarme si ce sens est croissant et seulement dans ce cas, l'ensemble constitué par le microprocesseur et le circuit de commande de la fréquence d'émission des impulsions constitutives du pinceau lumineux incident est agencé de façon telle que les amplitudes de celles, de ces impulsions, qui sont émises à la fréquence augmentée croissent dans le temps, - l'ensemble du microprocesseur et du circuit de commande de la fréquence d'émission des impulsions constitutives du pinceau lumineux incident est agencé de façon telle que les largeurs et/ou amplitudes de celles, de ces impulsions, qui sont émises à la fréquence augmen¬ tée soient supérieures à celles des impulsions qui étaient émises auparavant à fréquence normale.To this end, the smoke detector devices of the kind in question according to the invention also comprise means for forming the incident light control brush using current pulses also spaced in time, and they are essentially characterized by what they further include means for automatically increasing the frequency of emission of said pulses at the first manifestation of a detection representative of a breach of the predetermined threshold by the density of the fumes to be checked, the possible triggering of an alarm then being controlled as a function of the signals produced by the detector in response to several of the successive pulses emitted at the frequency increased, said means then being neutralized again if the examination of said signals reveals a return to order of the situation and only in this case. In preferred embodiments, recourse is also had to one and / or the other of the following arrangements: the means for emitting the light pulses constituting the incident brush comprise a source of direct current and a light source connected to the terminals of the current source by means of at least one electronic switch and the means for increasing the frequency of the pulses when the threshold predetermined by the response signal of the detector are exceeded comprise an amplifier of this signal response, an analog-digital converter, a microprocessor comprising the threshold recorded in an appropriate memory, and a circuit, associated with the microprocessor and possibly integrated therein, capable of increasing the operating frequency of the switch as soon as exceeding the threshold by the response signal and as long as this exceeding lasts, the microprocessor includes means for detecting ter, in particular by a derivative calculation, the direction of the evolution of the amplitudes of the detector response signals corresponding to successive pulses emitted at the increased frequency, and means for setting off the alarm if this direction is increasing and only in this case, the assembly constituted by the microprocessor and the circuit for controlling the frequency of emission of the pulses constituting the incident light brush is arranged in such a way that the amplitudes of those, of these pulses, which are emitted at the increased frequency increase over time, - the entire microprocessor and the control circuit of the pulse transmission frequency constituting the incident light brush is arranged in such a way that the widths and / or amplitudes of those of these pulses which are emitted at the increased frequency are greater than those of the pulses which were previously emitted at normal frequency.
L'invention comprend, mises à part ces disposi¬ tions principales, certaines autres dispositions qui s'utilisent de préférence en même temps et dont il sera plus explicitement question ci-après. Dans ce qui suit, l'on va décrire quelques modes de réalisation préférés de l'invention en se référant au dessin ci-annexé d'une manière bien entendu non limita¬ tive.The invention includes, apart from these main provisions, certain other arrangements which are preferably used at the same time and which will be more explicitly discussed below. In what follows, we will describe some preferred embodiments of the invention with reference to the accompanying drawing in a manner of course not limita¬ tive.
La figure 1, de ce dessin, montre très schémati- que ent le composant, d'un dispositif de détection établi selon l'invention, dans lequel est effectuée la détection optique proprement dite.FIG. 1, of this drawing, shows very schematically the component, of a detection device established according to the invention, in which the optical detection proper is carried out.
La figure 2 est un schéma simplifié de l'ensemble du dispositif de détection selon l'invention. La figure 3 montre de façon plus détaillée un autre composant de ce dispositif, savoir son circuit de commande de la fréquence d'émission des impulsions lumineuses.FIG. 2 is a simplified diagram of the entire detection device according to the invention. FIG. 3 shows in more detail another component of this device, namely its circuit for controlling the frequency of emission of the light pulses.
Les figures 4, 5 et 6 sont des diagrammes faisant apparaître chacun, d'une part en haut, les impulsions lumineuses incidentes et, d'autre part en bas, les signaux de réponse du détecteur pour respectivement trois situa¬ tions différentes.Figures 4, 5 and 6 are diagrams each showing, on the one hand at the top, the incident light pulses and, on the other hand at the bottom, the detector response signals for respectively three different situa¬ tions.
D'une façon connue en soi, le détecteur comprend un boîtier 1 monté sur un socle 2 et percé de fenêtres 3 propres à livrer passage à une fumée F à contrôler.In a manner known per se, the detector comprises a housing 1 mounted on a base 2 and pierced with windows 3 suitable for delivering passage to a smoke F to be checked.
Ces fenêtres 3 sont associées à des chicanes (non représentées) permettant d'interdire au maximum les introductions de la lumière dans le boîtier et ainsi de former à l'intérieur de ce boîtier une chambre noire.These windows 3 are associated with baffles (not shown) making it possible to prohibit the introduction of light into the housing as much as possible and thus to form a dark room inside this housing.
Le boîtier contient une source lumineuse L propre à émettre un pinceau lumineux P dans la chambre noire, et un détecteur D placé dans une zone d'ombre de cette chambre vis-à-vis de la source L.The housing contains a clean light source L to emit a light brush P in the dark room, and a detector D placed in a shadow area of this room with respect to the source L.
Si aucune fumée n'est présente dans le boîtier lors de l'émission du pinceau incident P, celui-ci n'est pratiquement pas réfléchi vers le détecteur D et la réponse de ce dernier est très faible, voire pratiquement nulle.If no smoke is present in the housing during the emission of the incident brush P, the latter is practically not reflected towards the detector D and the response of the latter is very weak, or even practically zero.
Si au contraire le boîtier contient de la fumée, les particules X composant cette fumée constituent des petits miroirs propres à réfléchir la lumière : certains des rayons ainsi réfléchis atteignent le détecteur D et 1'intensité de la réponse de ce dernier est d'autant plus élevée que la densité de la fumée considérée est elle-même plus élevée.If, on the contrary, the housing contains smoke, the X particles composing this smoke constitute small mirrors capable of reflecting light: some of the rays thus reflected reach detector D and the intensity of the latter's response is all the more higher than the density of the smoke considered is itself higher.
Comme dit plus haut, le pinceau lumineux incident P n'est pas émis en continu, mais sous la forme d'impul¬ sions I (figure 4) dont les durées t sont relativement petites, étant notamment de l'ordre de 100 microsecondes à 1 milliseconde, les périodes T qui s'écoulent entre les impulsions I successives étant elles-mêmes relativement longues, et notamment de l'ordre de 5 à 10 secondes.As said above, the incident light brush P is not emitted continuously, but in the form of pulses I (FIG. 4) whose durations t are relatively small, being in particular of the order of 100 microseconds to 1 millisecond, the periods T which elapse between the successive pulses I are themselves relatively long, and in particular of the order of 5 to 10 seconds.
Avec de tels rapports de durée, on peut engendrer, par charges et décharges successives, à l'aide d'un interrupteur, d'un circuit résistance R-capacité C approprié (figure 3), circuit dont le condensateur C est monté aux bornes de la source lumineuse L à exciter, des impulsions de courant de 1 Ampère à partir d'un courant moyen de charge dont l'intensité est seulement de 100 microampères ou même inférieure.With such duration ratios, it is possible to generate, by successive charges and discharges, using a switch, an appropriate R-capacitance resistance circuit C (FIG. 3), circuit whose capacitor C is mounted across the terminals. of the light source L to be excited, pulses of current of 1 Ampere from an average charge current whose intensity is only 100 microamperes or even lower.
On obtient de cette façon une réduction très importante de la consommation électrique des détecteurs considérés, le rapport de cette réduction dépassant généralement 5000. Comme également dit plus haut, pour éviter toute alarme intempestive, il convient que chaque dépassement de seuil détecté sur la base d'une impulsion lumineuse incidente soit confirmé sur plusieurs impulsions subsé¬ quentes et une telle vérification peut se révéler trop longue dans la pratique : le gain d'une minute, voire d'une demi-minute, peut se révéler extrêmement précieux pour éteindre le début d'un incendie.In this way, a very significant reduction in the electrical consumption of the detectors considered is obtained, the ratio of this reduction generally exceeding 5000. As also said above, to avoid any untimely alarm, each overshoot should be threshold detected on the basis of an incident light pulse is confirmed on several subsequent pulses and such verification may prove to be too long in practice: the gain of one minute, even half a minute, may be prove extremely valuable for extinguishing the start of a fire.
L'invention permet de bénéficier à la fois de 1'économie considérable due à l'émission lumineuse sous la forme d'impulsions brèves et répétées à un rythme relativement lent et la sécurité d'une réponse délivrée seulement après une vérification multipliée, tout en limitant à une durée très petite, pouvant être de l'ordre de la seconde, l'obtention de cette réponse.The invention makes it possible to benefit both from the considerable savings due to the light emission in the form of short and repeated pulses at a relatively slow rate and the security of a response delivered only after a multiplied verification, while limiting the obtaining of this response to a very small duration, which may be of the order of a second.
A cet effet, selon l'invention, on augmente automatiquement la fréquence d'émission des impulsions lumineuses dès qu'un dépassement anormal de seuil a été détecté sur la base d'une impulsion incidente émise à la fréquence basse normale.To this end, according to the invention, the emission frequency of the light pulses is automatically increased as soon as an abnormal threshold crossing has been detected on the basis of an incident pulse emitted at the normal low frequency.
La vérification multipliée ci-dessus évoquée est alors réalisée à l'aide des impulsions émises à la fréquence augmentée : cette vérification est donc beaucoup plus rapide que précédemment et peut permettre de lever beaucoup plus vite l'incertitude en ce qui concerne l'origine de l'anomalie ; la réponse du dispositif de détection est donc beaucoup plus rapide sans que la fiabilité de cette réponse soit diminuée en rien.The above-mentioned multiplied verification is then carried out using pulses emitted at the increased frequency: this verification is therefore much faster than previously and can make it possible to remove the uncertainty as far as the origin of the anomaly; the response of the detection device is therefore much faster without the reliability of this response being in any way diminished.
On a schématisé sur la figure 2 un dispositif permettant d'obtenir un tel résultat. Ce dispositif comprend : - un amplificateur 4 recueillant la sortie du détecteur D, l'ensemble constitué par un microprocesseur 5 et un convertisseur d'entrée analogique-numérique 6, ensemble recevant la sortie de l'amplificateur 4 et comprenant, enregistré dans une mémoire, le seuil S dont le dépassement par le signal sortant du détecteur D et amplifié par l'amplificateur 4 signifie une densité dangereuse de fumée F, un circuit 7 recevant la sortie de l'ensembleThere is shown diagrammatically in FIG. 2 a device making it possible to obtain such a result. This device comprises: - an amplifier 4 collecting the output of the detector D, the assembly constituted by a microprocessor 5 and an analog-digital input converter 6, assembly receiving the output of the amplifier 4 and comprising, recorded in a memory , the threshold S whose exceeding by the signal leaving the detector D and amplified by amplifier 4 means a dangerous density of smoke F, a circuit 7 receiving the output of the assembly
5-6 et propre à commander la fréquence d'émission des impulsions lumineuses émises par la source L, circuit qui peut faire partie au moins partiellement dudit ensemble5-6 and suitable for controlling the frequency of emission of the light pulses emitted by the source L, a circuit which can be at least partially part of said set
5-6, et une source de courant électrique 8 alimen¬ tant les différents composants ci-dessus. Le circuit 7 de commande de la fréquence d'émis¬ sion des impulsions I comprend quant à lui (voir figure 3), d'une façon connue en soi : le condensateur C ci-dessus, monté aux bornes de la source de courant 8 par l'intermédiaire de la résistance R ci-dessus de façon à être progressivement chargé par cette source, avec une vitesse et à un niveau dépendant de la valeur de ladite résistance, et un circuit 9 connectant la source lumineuse L aux bornes du condensateur C par l'intermédiaire d'un interrupteur électronique 10 et d'une résistance 11. Ledit circuit 7 comprend en outre ici : montées en parallèle sur la résistance R, au moins une autre résistance 12 de valeur inférieure à celle de cette résistance R, ladite autre résistance 12 pouvant même se limiter à un simple conducteur 13 de faible résistance, la mise en circuit à volonté de l'une ou l'autre des résistances en parallèle (R, 12, 13...) étant commandée par un commutateur électronique 14, et des liaisons électriques symbolisées par les flèches 15 et 16 et associées à des moyens de commande appropriés pour transformer les instructions élaborées par le microprocesseur 5 en commandes correspondantes, soit du commutateur 14 seul, soit de ce commutateur et de l'interrupteur 10, dans l'hypothèse où ce dernier ne serait pas organisé de façon à se fermer automatiquement pendant une courte durée chaque fois que la charge du condensateur C dépasse un seuil prédéterminé.5-6, and a source of electric current 8 alimen¬ both the above components. The circuit 7 for controlling the frequency of emission of the pulses I comprises meanwhile (see FIG. 3), in a manner known per se: the capacitor C above, mounted across the terminals of the current source 8 by means of the resistor R above so as to be gradually charged by this source, with a speed and at a level dependent on the value of said resistor, and a circuit 9 connecting the light source L to the terminals of the capacitor C by means of an electronic switch 10 and a resistor 11. Said circuit 7 further comprises here: mounted in parallel on the resistor R, at least one other resistor 12 of value less than that of this resistor R, said other resistor 12 can even be limited to a single conductor 13 of low resistance, the switching on at will of one or other of the resistors in parallel (R, 12, 13 ...) being controlled by an electronic switch 14, and s electrical connections symbolized by the arrows 15 and 16 and associated with appropriate control means to transform the instructions prepared by the microprocessor 5 into corresponding commands, either from the switch 14 alone, or from this switch and the switch 10, in the '' assumption that the latter would not be organized so as to close automatically for a short time each time the charge of the capacitor C exceeds a predetermined threshold.
Le fonctionnement de l'ensemble est le suivant. En temps normal, c'est-à-dire en absence de fumée F dans le boîtier 1, la source lumineuse L émet des impulsions de lumière I espacées de périodes T identiques et relativement longues (figure 4) qui sont engendrées par les décharges automatiques chroniques du condensateur C, lequel est chargé progressivement en permanence par la source de courant 8. Ces impulsions de lumière se traduisent à la sortie du détecteur D par des signaux de tension V (figure 4) de très faible amplitude : cette amplitude demeure inférieure à celle du seuil S enregistré dans le micropro¬ cesseur 5 (en tenant compte, bien entendu, du coefficient d'amplification imposé par l'amplificateur 4) de sorte que ce microprocesseur n'engendre sur ses sorties 15, 16 aucun signal de commande susceptible de perturber la succession normale des cycles de veille.The operation of the assembly is as follows. In normal times, that is to say in the absence of smoke F in the housing 1, the light source L emits light pulses I spaced apart by identical and relatively long periods T (FIG. 4) which are generated by automatic discharges chronicles of the capacitor C, which is continuously charged continuously by the current source 8. These light pulses are translated at the output of the detector D by voltage signals V (FIG. 4) of very low amplitude: this amplitude remains less than that of the threshold S recorded in the microprocessor 5 (taking account, of course, of the amplification coefficient imposed by the amplifier 4) so that this microprocessor does not generate any control signal on its outputs 15, 16 disrupt the normal succession of standby cycles.
Dès qu'une bouffée de fumée F suffisamment dense a pénétré dans le boîtier 1, l'émission d'une impulsion lumineuse, dite I0, par la source L se traduit, du fait de la réflexion de certains rayons lumineux composant cette impulsion sur des particules X de cette fumée, par élaboration par le détecteur D d'une impulsion de tension V0 (figure 5).As soon as a sufficiently dense puff of smoke F has penetrated into the housing 1, the emission of a light pulse, called I 0 , by the source L is reflected, due to the reflection of certain light rays composing this pulse on particles X of this smoke, by development by the detector D of a voltage pulse V 0 (FIG. 5).
Si cette tension V0 est supérieure au seuil S, le microprocesseur délivre immédiatement sur ses sorties 15, 16 un ordre d'accroissement de la fréquence d'émission des impulsions lumineuses, cette fréquence étant par exemple multipliée par un coefficient de l'ordre de 10.If this voltage V 0 is greater than the threshold S, the microprocessor immediately delivers on its outputs 15, 16 an order of increase in the frequency of emission of the light pulses, this frequency being for example multiplied by a coefficient of the order of 10.
Cet accroissement est obtenu en modifiant la position du commutateur 14 de façon à remplacer dans le circuit RC la résistance R par l'une des résistances plus petites 12, 13 ou autres. A chacune des impulsions subséquentes ll f I2, I3... qui succèdent alors à fréquence accélérée à l'impulsion incidente I0 correspond une réponse de tension Vl f V2,This increase is obtained by modifying the position of the switch 14 so as to replace in the circuit RC the resistance R by one of the smaller resistors 12, 13 or others. Each of the subsequent pulses l lf I 2 , I 3 ... which then follow the pulse at accelerated frequency incident I 0 corresponds to a voltage response V lf V 2 ,
V3 • • •V3 • • •
L'examen des valeurs de ces réponses est capital pour déterminer si le dépassement de seuil observé lors de l'émission de l'impulsion incidente I0 était fugace et aurait donc donné lieu à une fausse alerte si elle avait été seule prise en considération ou si, au contraire, il s'agissait bien d'un début d'incendie devant donner lieu à l'émission d'une alarme. Pour le premier cas en effet, lesdites valeurs successives vont en décroissant et repassent rapidement au-dessous du seuil S : dans ce cas, le microprocesseur 5 élabore des instructions pour faire revenir le commuta¬ teur 14 en sa position initiale de veille. Dans le second cas, les valeurs successives en question vont en croissant : c'est bien là une confirma¬ tion du danger initialement détecté et le microprocesseur est agencé de façon à exciter alors une alarme de toute nature désirable, notamment sonore. Le sens de l'évolution des valeurs successives ci- dessus peut être déterminé par le calcul d'une dérivée dans le microprocesseur.Examination of the values of these responses is essential to determine whether the threshold exceeded observed during the emission of the incident pulse I 0 was fleeting and would therefore have given rise to a false alert if it had been taken into account alone or if, on the contrary, it was indeed the start of a fire which should give rise to the issue of an alarm. For the first case, in fact, said successive values decrease and quickly pass back below the threshold S: in this case, the microprocessor 5 prepares instructions for returning the commutator 14 to its initial standby position. In the second case, the successive values in question are increasing: this is indeed a confirmation of the danger initially detected and the microprocessor is arranged so as to then activate an alarm of any desirable nature, in particular sound. The direction of the evolution of the successive values above can be determined by the calculation of a derivative in the microprocessor.
Si lesdites valeurs successives V:, V2... demeurent constantes, l'ambiguïté peut demeurer plus longtemps. Plusieurs solutions peuvent alors être envisagées pour lever cette ambiguïté.If said successive values V :, V 2 ... remain constant, the ambiguity may remain longer. Several solutions can then be envisaged to resolve this ambiguity.
Selon une première solution, on diffère la décision de déclenchement de l'alarme ou de retour à l'état de veille jusqu'à détection d'une évolution des amplitudes contrôlées des réponses Vn dans l'un ou l'autre sens.According to a first solution, the decision to trigger the alarm or to return to the standby state is postponed until a change in the controlled amplitudes of the responses V n is detected in one or the other direction.
Selon une autre solution, on déclenche automati¬ quement l'alarme au bout d'une durée minimum T. qui peut elle-même avoir une valeur d'autant plus grande que la différence entre la valeur constante des impulsions de réponse Vn et le seuil S est plus petite. Selon encore une autre variante destinée à affiner la réponse de l'ensemble, on donne aux impulsions inciden¬ tes I'i, I'2... des valeurs elles-mêmes croissantes : 1'expérience montre en effet que la variation résultante des amplitudes des signaux de réponse correspondants V'., V'2... est supérieure à la variation des amplitudes des impulsions incidentes.According to another solution, the alarm is automatically triggered at the end of a minimum duration T. which can itself have a value all the greater as the difference between the constant value of the response pulses V n and the threshold S is smaller. According to yet another variant intended to refine the response of the set, the incident impulses I'i, I ' 2 ... are given increasing values themselves: 1'experience indeed shows that the resulting variation of amplitudes of the corresponding response signals V '., V' 2 ... is greater than the variation of the amplitudes of the incident pulses.
C'est ce qui a été représenté sur la figure 6. On pourrait également, dans le même but, donner aux durées et/ou aux amplitudes individuelles des impul¬ sions des valeurs encore constantes, mais supérieures à celles des impulsions I émises à cadence basse lors de chaque période normale de veille.This is what has been shown in FIG. 6. One could also, for the same purpose, give the durations and / or the individual amplitudes of the pulses values still constant, but greater than those of the pulses I emitted at a rate low during each normal sleep period.
Chacun des deux interrupteurs 10 et 14 ci-dessus décrits est avantageusement constitué par un transistor ou par un semi-conducteur à trois électrodes dont l'élec¬ trode de commande est reliée à la sortie correspondante (16 ou 15) du microprocesseur 5, lesdits transistors ou analogues pouvant même être intégrés dans ce microproces- seur, ainsi que les résistances (11, 12, R) auxquelles ils sont associés.Each of the two switches 10 and 14 described above is advantageously constituted by a transistor or by a semiconductor with three electrodes, the control electrode of which is connected to the corresponding output (16 or 15) of microprocessor 5, said transistors or the like which can even be integrated into this microprocessor, as well as the resistors (11, 12, R) with which they are associated.
Cette constitution, ou mieux encore cette intégra¬ tion, permet d'agir d'une manière particulièrement fine sur les valeurs des fréquences et/ou amplitudes des impulsions ll f I2... à engendrer.This constitution, or better still this integration, makes it possible to act in a particularly fine manner on the values of the frequencies and / or amplitudes of the pulses l lf I 2 ... to be generated.
De même, pour déterminer avec précision les instants de décharge du condensateur C, on prévoit avantageusement un circuit propre à mesurer la tension réelle à chaque instant aux bornes dudit condensateur, circuit pouvant faire partie, lui aussi, de l'ensemble 5- 6 : cette mesure de tension permet de s'affranchir des erreurs qui pourraient résulter du vieillissement des circuits.Likewise, in order to determine with precision the instants of discharge of the capacitor C, provision is advantageously made for a circuit capable of measuring the real voltage at each instant across the terminals of said capacitor, a circuit which may also be part of the assembly 5-6: this voltage measurement eliminates errors that could result from aging circuits.
En suite de quoi, et quel que soit le mode de réalisation adopté, on obtient finalement un dispositif de détection optique de fumée dont la constitution et le fonctionnement résultent suffisamment de ce qui précède. Ce dispositif présente par rapport à ceux actuel¬ lement connus de nombreux avantages et en particulier celui d'une réponse fiable rapide, sans pratiquement aucune augmentation de la consommation moyenne en courant électrique, laquelle demeure extrêmement faible.As a result of this, and whatever the embodiment adopted, an optical smoke detection device is finally obtained, the constitution and the operation result sufficiently from the above. This device has many advantages over those currently known, and in particular that of a rapid reliable response, with practically no increase in the average consumption of electric current, which remains extremely low.
Comme il va de soi, et comme il résulte d'ailleurs déjà de ce qui précède, l'invention ne se limite nullement à ceux de ses modes d'application et de réalisation qui ont été plus spécialement envisagés ; elle en embrasse, au contraire, toutes les variantes, notamment celles où une partie du microprocesseur 5 ci-dessus serait remplacée par un comparateur (non représenté) recevant sur une de ses entrées la sortie de l'amplificateur 4 et sur son autre entrée, un signal électrique représentatif du seuil S, la sortie de ce comparateur étant alors appliquée sur le circuit 7, de préférence par l'intermédiaire de 1'ensemble constitué par un microprocesseur et par un convertisseur analogique-numérique, ensemble permettant un traitement de signaux particulièrement simple et performant. As goes without saying, and as it already follows from the above, the invention is in no way limited to those of its modes of application and embodiments which have been more especially envisaged; on the contrary, it embraces all the variants thereof, in particular those where a part of the microprocessor 5 above would be replaced by a comparator (not shown) receiving on one of its inputs the output of the amplifier 4 and on its other input, an electrical signal representative of the threshold S, the output of this comparator then being applied to the circuit 7, preferably by means of the assembly constituted by a microprocessor and by an analog-digital converter, assembly allowing a processing of signals particularly simple and efficient.

Claims

REVENDICATIONS
1. Dispositif pour détecter la présence de fumées (F), comprenant une chambre noire (1) qui reçoit les fumées à détecter, une source (L) propre à émettre dans cette chambre un pinceau lumineux (P) formé d'impulsions de courte durée espacées les unes des autres de périodes identiques beaucoup plus longues, un détecteur (D) propre à élaborer des signaux de réponse (V) liés aux réflexions partielles des impulsions lumineuses successives sur certaines des particules (X) composant les fumées conte¬ nues dans la chambre, et des moyens pour comparer ces signaux de réponse à un seuil prédéterminé (S) et pour déclencher une alarme en cas de dépassement de ce seuil par plusieurs desdits signaux de réponse successifs, caractérisé en ce qu'il comprend en outre des moyens pour augmenter automatiquement la fréquence d'émission desdites impulsions dès la première manifestation d'une détection représentative d'un dépassement du seuil prédéterminé par la densité des fumées (F), le déclenchement éventuel d'une alarme étant alors commandé en fonction des signaux (V) élaborés par le détecteur en réponse à plusieurs des impulsions successives émises à la fréquence augmentée, lesdits moyens étant ensuite à nouveau neutralisés si l'examen desdits signaux révèle un retour en ordre de la situation et seulement dans ce cas.1. Device for detecting the presence of smoke (F), comprising a dark room (1) which receives the smoke to be detected, a source (L) capable of emitting in this room a light brush (P) formed of short pulses duration spaced from each other of much longer identical periods, a detector (D) capable of developing response signals (V) linked to the partial reflections of successive light pulses on some of the particles (X) composing the fumes contained in the chamber, and means for comparing these response signals with a predetermined threshold (S) and for triggering an alarm in the event of this threshold being exceeded by several of said successive response signals, characterized in that it further comprises means to automatically increase the transmission frequency of said pulses at the first manifestation of a detection representative of an overshoot of the threshold predetermined by the density smoke (F), the possible triggering of an alarm being then controlled as a function of the signals (V) produced by the detector in response to several of the successive pulses emitted at the increased frequency, said means then being neutralized again if the examination of said signals reveals a return to order of the situation and only in this case.
2. Dispositif de détection selon la revendication 1, caractérisé en ce que les moyens pour émettre les impulsions lumineuses constitutives du pinceau incident (P) comprennent une source de courant continu (8, C), et une source lumineuse (L) branchée aux bornes de la source de courant par l'intermédiaire d'au moins un interrupteur électronique (10, 14) et en ce que les moyens pour augmenter la fréquence des impulsions lors des dépasse- ments du seuil prédéterminé (S) par le signal de réponse (V) du détecteur (D) comprennent un amplificateur (4) de ce signal de réponse, un convertisseur analogique-numéri¬ que (6), un microprocesseur (5) comprenant le seuil enregistré dans une mémoire appropriée, et un circuit (7, 15, 16), associé au microprocesseur et éventuellement intégré à celui-ci, propre à augmenter la fréquence d'actionnement de l'interrupteur dès dépassement du seuil par le signal de réponse et tant que dure ce dépassement.2. Detection device according to claim 1, characterized in that the means for emitting the light pulses constituting the incident brush (P) comprise a direct current source (8, C), and a light source (L) connected to the terminals from the current source by means of at least one electronic switch (10, 14) and in that the means for increasing the frequency of the pulses when the predetermined threshold (S) is exceeded by the response signal ( V) of the detector (D) comprise an amplifier (4) of this response signal, an analog-digital converter (6), a microprocessor (5) comprising the threshold recorded in an appropriate memory, and a circuit (7, 15, 16), associated with the microprocessor and possibly integrated therein. ci, suitable for increasing the actuation frequency of the switch as soon as the threshold is exceeded by the response signal and as long as this exceeding lasts.
3. Dispositif de détection selon la revendication 2, caractérisé en ce que le microprocesseur (5) comprend des moyens pour détecter, notamment par un calcul de dérivée, le sens de l'évolution des amplitudes des signaux de réponse (V) du détecteur (D) correspondant aux impul¬ sions successives émises à la fréquence augmentée, et des moyens pour déclencher l'alarme si ce sens est croissant et seulement dans ce cas.3. Detection device according to claim 2, characterized in that the microprocessor (5) comprises means for detecting, in particular by a derivative calculation, the direction of the evolution of the amplitudes of the response signals (V) of the detector ( D) corresponding to the successive pulses emitted at the increased frequency, and means for triggering the alarm if this direction is increasing and only in this case.
4. Dispositif de détection selon l'une quelconque des revendications 2 et 3, caractérisé en ce que l'ensem¬ ble constitué par le microprocesseur (5) et le circuit (7, 15, 16) de commande de la fréquence d'émission des impulsions constitutives du pinceau lumineux incident (P) est agencé de façon telle que les amplitudes de celles, de ces impulsions, qui sont émises à la fréquence augmen¬ tée croissent dans le temps.4. Detection device according to any one of claims 2 and 3, characterized in that the assembly constituted by the microprocessor (5) and the circuit (7, 15, 16) for controlling the transmission frequency pulses constituting the incident light brush (P) is arranged in such a way that the amplitudes of those of these pulses, which are emitted at the increased frequency, increase over time.
5. Dispositif de détection selon l'une quelconque des revendications 2 et 3, caractérisé en ce que l'ensem¬ ble du microprocesseur (5) et du circuit (7, 15, 16) de commande de la fréquence d'émission des impulsions constitutives du pinceau lumineux incident (P) est agencé de façon telle que les largeurs et/ou amplitudes de celles, de ces impulsions, qui sont émises à la fréquence augmentée, soient supérieures à celles des impulsions qui étaient émises auparavant à fréquence normale. 5. Detection device according to any one of claims 2 and 3, characterized in that the assembly of the microprocessor (5) and the circuit (7, 15, 16) for controlling the frequency of transmission of the pulses constituting the incident light brush (P) is arranged in such a way that the widths and / or amplitudes of those of these pulses, which are emitted at the increased frequency, are greater than those of the pulses which were previously emitted at normal frequency.
EP95926440A 1994-07-29 1995-07-27 Improvements relating to optical smoke detectors Expired - Lifetime EP0772852B1 (en)

Applications Claiming Priority (3)

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FR9409473 1994-07-29
FR9409473A FR2723233B1 (en) 1994-07-29 1994-07-29 IMPROVEMENTS ON OPTICAL SMOKE DETECTORS
PCT/FR1995/001014 WO1996004627A1 (en) 1994-07-29 1995-07-27 Improvements relating to optical smoke detectors

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DE69506417D1 (en) 1999-01-14
JPH11509341A (en) 1999-08-17
US5864293A (en) 1999-01-26
WO1996004627A1 (en) 1996-02-15
ES2126915T3 (en) 1999-04-01
EP0772852B1 (en) 1998-12-02
FR2723233A1 (en) 1996-02-02
FR2723233B1 (en) 1996-10-04

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