EP0236223A1 - Ionization chamber smoke detector - Google Patents
Ionization chamber smoke detector Download PDFInfo
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- EP0236223A1 EP0236223A1 EP87400420A EP87400420A EP0236223A1 EP 0236223 A1 EP0236223 A1 EP 0236223A1 EP 87400420 A EP87400420 A EP 87400420A EP 87400420 A EP87400420 A EP 87400420A EP 0236223 A1 EP0236223 A1 EP 0236223A1
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- smoke detector
- chamber
- ions
- ionization chamber
- detector according
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- 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
- G08B17/11—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using an ionisation chamber for detecting smoke or gas
- G08B17/113—Constructional details
Definitions
- the invention relates to devices intended to detect the presence of smoke, dust or similar particles in the ambient atomosphere, devices comprising an ionization chamber whose internal volume is placed in communication with said atmosphere and means for measuring the current. ionic created in this room.
- Said ionization chamber itself comprises a source of ionizing radiation, generally constituted by a radioactive substance ⁇ or ⁇ , capable of ionizing the air contained in the chamber, two electrodes framing at least a portion of the volume thus ionized and means to apply a DC voltage between these two electrodes, which creates the ion current to be measured between said electrodes.
- a source of ionizing radiation generally constituted by a radioactive substance ⁇ or ⁇ , capable of ionizing the air contained in the chamber, two electrodes framing at least a portion of the volume thus ionized and means to apply a DC voltage between these two electrodes, which creates the ion current to be measured between said electrodes.
- the variation of this intensity is used to detect such a presence and to trigger an alarm as soon as the concentration of the polluting agent exceeds a predetermined threshold.
- Such a device is preferably used to detect fires from the fumes they give off and, to simplify the description, but of course not limiting, the polluting agent will be designated by the word "smoke”.
- the movement of ambient air in the immediate vicinity of a detector device of the type in question can alter the detections it provides.
- the object of the invention is, above all, to remedy these various drawbacks.
- the smoke detector devices with an ionization chamber are essentially characterized in that they comprise at least one ion reservoir independent of said chamber arranged and arranged so as to be swept by at least one part. disturbing air currents before they pass through at least part of the ionization chamber.
- the smoke detector device has a strong symmetry of revolution around an axis so as to be lend to almost omnidirectional penetration of ambient smoke
- the ion reservoir is placed inside the ionization chamber, preferably in a central position of this chamber
- the ionization chamber is in a central position relative to the ion reservoir, which comprises at least two portions framing or surrounding this chamber
- the ion reservoir consists of a conductive cage containing a source of ionizing radiation and having good transparency both to the radiations emitted by this source, to the ions generated by these radiations, to the disturbing air currents and to the particles of smoke to detect
- - the cage consists of crossed semi-circular arches
- - the cage constitutes one of the two electrodes of the ionization chamber
- the source of ionizing radiation which generates the ions in the ionization chamber is the same as that which generates the ions in the ion reservoir
- the invention includes, apart from these main provisions, certain other provisions which are preferably used at the same time and which will be more explicitly discussed below.
- FIGS 1 and 2 of this drawing, very schematically show a smoke detector established according to the invention, Figure 1 corresponding to operation without wind and Figure 2, to operation with wind.
- Figures 3 and 4 also schematically show two variants according to the invention of such a smoke detector, during its operation without wind.
- Figures 5 and 6 show respectively in axial section and in external view an embodiment of such a detector according to the invention.
- the ionization or measurement chamber 1 comprises two electrodes 2 and 3 (FIG. 1) delimiting between them a volume A in which there is a radioactive substance 4.
- This substance ionizes the air contained in volume A by creating positive and negative ions therein represented by the signs + and - respectively.
- a continuous electric voltage V is applied between the two electrodes, which creates an electric field E, and consequently an ion current, between these electrodes, as indicated by the small arrows leaving the ions.
- Means are also provided for measuring the resulting electric current, which remains constant under normal conditions, that is to say in the absence of smoke in volume A.
- the measured electric current then decreases and this decrease is used to trigger an alarm signal when it crosses a predetermined threshold.
- volume A is swept by wind or current of violent air C (FIG. 2), some of the ions 5 contained between the electrodes 2 and 3, ions designated by the reference 51, are entrained by this wind and extracted from the chamber 1.
- said wind is made to cross, before it crosses the chamber, a reservoir 6 of ions 7 independent of this chamber.
- the characteristics of the reservoir 6 are chosen (location, concentration of the ions, etc.) so that the ion compensation obtained inside the chamber 1 is total during the manifestation of the winds C, of predetermined speed, with respect to - against which we essentially want to protect the detector.
- the number of 71 ions sampled per unit of time in the tank 6 and introduced into the chamber 1 by such winds C is equal to that of the 51 ions extracted from said chamber during the same duration and by the same winds.
- the reservoir 6 is preferably delimited by a cage of conductive material forming a Faraday cage and containing a radioactive source suitable for ionize the volume of air inside this cage.
- the latter must be at the same time permeable to winds C, whether or not charged with the smoke to be detected, to radiation emitted by the source and to ions 71 entrained by these winds towards the outside of said cage.
- the ion reservoir 6 is located next to the chamber 1 and the ion compensation described above then implies that the winds C circulate in a well-defined direction.
- the ion reservoir 6 is located inside the chamber 1, in a central position, so as to be necessarily swept by the winds in all cases before they describe the end of their walk in the room, - according to the second formula, it is the chamber 1 which is inside the ion reservoir 6, or at least which is framed by two portions of such a reservoir situated respectively at its inlet and at its outlet in such a way that, in all cases, the winds to be neutralized begin by crossing a portion of the ion reservoir before sweeping the chamber.
- the detector as a whole is given a strong symmetry of revolution about an axis so that it lends itself to almost omnidirectional penetration of ambient smoke.
- FIGS 5 and 6 show in more detail an embodiment according to this last characteristic and to the first of the two formulas above.
- the ionization chamber 1 is here delimited externally by a flat and circular plate 8 made of insulating material and by a hemispherical dome 9 made of metal or metallized plastic, dome, the circular edge of which is attached to the periphery of the plate 8.
- Said plate 8 is intended to be fixed against a wall or a ceiling delimiting a room to be monitored or even against the internal face of an air conditioning pipe to be controlled.
- the dome is perforated by annular series of lights 10 making its interior volume communicate with the ambient atmosphere.
- a cage 11 made of metal or metallized plastic which, like the dome, has a hemispherical shape and is centered in the center of this dome.
- This cage is advantageously composed of a plurality of semi-circular arches crossed at their vertices.
- the cage 11 is connected to the positive pole of a direct current source 12 by means of a measurement and alarm assembly known per se and symbolized by the rectangle 13 and the dome 9 is grounded.
- This cage and this dome then respectively play the roles of the two electrodes 2 and 3 above.
- a frustoconical deflector 14 disposed inside the dome just opposite a series of lights 10 so as to deflect towards the cage the air currents introduced into the chamber through these lights and reduce their input speed.
- the measurement involves exclusively the ionization chamber which is constituted by the curved zone A comprised between the cage 11 and the dome 9.
- the ions formed in this area by ionizing radiation from source 4 form a ion current between the two electrodes formed by the two surfaces 9 and 11 and any presence of smoke in the immediate vicinity of the device results in penetration of this smoke into said zone and therefore in a reduction of the ion current in the above manner above described, reduction which triggers an alarm signal when it exceeds a predetermined threshold.
- the radiation emitted by the substance 4 ionizes the volume B inside the cage 11 and the ions thus formed in this cage remain trapped there, constituting a "reserve” of these ions.
- the characteristics of the cages are determined so that the ion compensation obtained is optimal during the manifestation of the winds against which we especially want to protect the detector.
- the electrodes were made of stainless steel or metallized plastic, - the voltage V was + 8 volts, -the external electrode was in the form of a cylindrical perforated cover of revolution 45 mm in diameter, - the ion reservoir was in the form of an internal semi-spherical cage of revolution 30 mm in diameter, - and the smoke detection obtained remained very insensitive to air currents in the sense that the speed of these air currents had to exceed 11 m / sec for the disturbance of the measurement current due to said air currents to reach 10 % of the value of this current.
- This detector has many advantages over those previously known, in particular with regard to the efficiency of the compensation with respect to the winds, the simplicity and the reliability.
- 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 variants, in particular: - those where the plate 8 of the embodiment of Figures 5 and 6 would be conductive instead of being insulating, then being isolated from the dome 9 by an insulating ring and can itself constitute one of the two electrodes of the ionization chamber, the inner cage can then be brought to the same potential as said plate or to a different potential, preferably lower if the cage is still inside the dome, - And those where the perforated dome 9 above would have a shape other than those hemispherical and cylindrical of revolution explained above, for example a parallelepiped shape, the shape of the cage 11 can of course be modified accordingly.
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Abstract
Il s'agit d'un détecteur de fumée comportant une chambre d'ionisation (1). Pour compenser l'enlèvement des ions (51) entraînés hors de la chambre par les courants d'air violents (C) traversant cette chambre, on enrichit préalablement ces courants d'air en ions (71) en leur faisant traverser une réserve d'ions (6) avant leur introduction dans ladite chambre.It is a smoke detector comprising an ionization chamber (1). To compensate for the removal of the ions (51) entrained out of the chamber by the violent air currents (C) passing through this chamber, these air currents are enriched beforehand with ions (71) by making them pass through a reserve of ions (6) before their introduction into said chamber.
Description
L'invention est relative aux dispositifs destinés à détecter la présence de fumées, poussières ou particules analogues dans l'atomosphère ambiante, dispositifs comportant une chambre d'ionisation dont le volume intérieur est mis en communication avec ladite atmosphère et des moyens pour mesurer le courant ionique créé dans cette chambre.The invention relates to devices intended to detect the presence of smoke, dust or similar particles in the ambient atomosphere, devices comprising an ionization chamber whose internal volume is placed in communication with said atmosphere and means for measuring the current. ionic created in this room.
Ladite chambre d'ionisation comprend elle-même une source de radiations ionisantes, généralement constituée par une substance radioactive α ou β , propre à ioniser l'air contenu dans la chambre, deux électrodes encadrant une portion au moins du volume ainsi ionisé et des moyens pour appliquer une tension électrique continue entre ces deux électrodes, ce qui crée le courant ionique à mesurer entre lesdites électrodes.Said ionization chamber itself comprises a source of ionizing radiation, generally constituted by a radioactive substance α or β, capable of ionizing the air contained in the chamber, two electrodes framing at least a portion of the volume thus ionized and means to apply a DC voltage between these two electrodes, which creates the ion current to be measured between said electrodes.
La présence d'une fumée ou autre agent polluant dans la chambre considérée se traduit par fixation des particules constitutives de cet agent sur les ions présents dans cette chambre, ce qui les alourdit, les ralentit et réduit l'intensité du courant ionique correspondant.The presence of smoke or other polluting agent in the chamber in question results in the fixation of the constituent particles of this agent on the ions present in this chamber, which weighs them down, slows them down and reduces the intensity of the corresponding ion current.
La variation de cette intensité est exploitée pour détecter une telle présence et pour déclencher une alarme dès que la concentration de l'agent polluant dépasse un seuil prédéterminé.The variation of this intensity is used to detect such a presence and to trigger an alarm as soon as the concentration of the polluting agent exceeds a predetermined threshold.
Un tel dispositif sert de préférence à détecter les incendies à partir des fumées qu'ils dégagent et, pour simplifier la description, mais à titre bien entendu non limitatif, on désignera dans ce qui suit l'agent polluant par le mot "fumée".Such a device is preferably used to detect fires from the fumes they give off and, to simplify the description, but of course not limiting, the polluting agent will be designated by the word "smoke".
Les mouvements de l'air ambiant à proximité immédiate d'un dispositif détecteur du genre en question peuvent altérer les détections qu'il assure.The movement of ambient air in the immediate vicinity of a detector device of the type in question can alter the detections it provides.
En effet un courant d'air balayant le volume intérieur de la chambre d'ionisation emporte avec lui certains des ions qui cheminent entre les deux électrodes de cette chambre, ce qui réduit le courant ionique même en l'absence de fumée : cet enlèvement d'ions peut à la limite déclencher de fausses alarmes.Indeed a draft sweeping the volume inside the ionization chamber takes with it some of the ions that pass between the two electrodes of this chamber, which reduces the ion current even in the absence of smoke: this removal of ions can ultimately trigger false alarms .
Pour remédier à un tel inconvénient, un certain nombre de solutions ont déjà été proposées, d'ordre mécanique (telles qui l'addition de chicanes ou volets déflecteurs pour réduire la violence des vents admis dans la chambre) et/ou d'ordre électrique (telles que la réalisation d'électrodes de forme telle que les particules et ions entraînés par les courants d'air soient envoyés dans des régions où règne un fort champ électrique).To remedy such a drawback, a certain number of solutions have already been proposed, of a mechanical nature (such as the addition of baffles or deflector flaps to reduce the violence of the winds admitted into the room) and / or of an electrical nature. (such as the realization of electrodes of shape such that the particles and ions entrained by the air currents are sent in regions where a strong electric field prevails).
Mais ces solutions présentent toutes des inconvénients tels que la réduction de la sensibilité du détecteur et/ou l'augmentation du prix et de la fragilité.However, these solutions all have drawbacks such as reducing the sensitivity of the detector and / or increasing the price and the brittleness.
L'invention a pour but, surtout, de remédier à ces différents inconvénients.The object of the invention is, above all, to remedy these various drawbacks.
A cet effet les dispositifs détecteurs de fumée à chambre d'ionisation selon l'invention sont essentiellement caractérisés en ce qu'ils comprennent au moins un réservoir d'ions indépendant de ladite chambre agencé et disposé de façon à être balayé par au moins une partie des courants d'air perturbateurs avant leur passage dans au moins une partie de la chambre d'ionisation.To this end, the smoke detector devices with an ionization chamber according to the invention are essentially characterized in that they comprise at least one ion reservoir independent of said chamber arranged and arranged so as to be swept by at least one part. disturbing air currents before they pass through at least part of the ionization chamber.
Au cours du balayage de ce réservoir, les courants d'air considérés prélèvent certains des ions présents dans ledit réservoir, puis ils introduisent ces ions dans la chambre, ce qui compense les ions entraînés hors de cette chambre par ces mêmes courants d'air.During the scanning of this reservoir, the air currents considered take off some of the ions present in said reservoir, then they introduce these ions into the chamber, which compensates for the ions entrained out of this chamber by these same air currents.
Dans des modes de réalisation préférés, on a recours en outre à l'une et/ou à l'autre des dispositions suivantes :
- le dispositif détecteur de fumée présente une forte symétrie de révolution autour d'un axe de façon à se prêter à une pénétration quasiment omnidirectionnelle des fumées ambiantes,
- le réservoir d'ions est disposé à l'intérieur de la chambre d'ionisation, de préférence en une position centrale de cette chambre,
- la chambre d'ionisation se trouve en une position centrale par rapport au réservoir d'ions, lequel comporte au moins deux portions encadrant ou entourant cette chambre,
- le réservoir d'ions est constitué par une cage conductrice contenant une source de radiations ionisantes et présentant une bonne transparence à la fois aux rayonnements émis par cette source, aux ions engendrés par ces rayonnements, aux courants d'air perturbateurs et aux particules de fumée à détecter,
- la cage est constituée par des arceaux semi-circulaires croisés,
- la cage constitue l'une des deux électrodes de la chambre d'ionisation,
- la source de radiations ionisantes qui engendre les ions de la chambre d'ionisation est la même que celle engendrant les ions du réservoir d'ions,
- la source de radiations ionisantes est constituée par une substance radioactive,
- des déflecteurs sont prévus pour diriger au moins une partie des courants d'air provenant de l'extérieur vers le réservoir d'ions avant leur introduction dans au moins une partie de la chambre d'ionisation.In preferred embodiments, use is also made of one and / or the other of the following arrangements:
- the smoke detector device has a strong symmetry of revolution around an axis so as to be lend to almost omnidirectional penetration of ambient smoke,
the ion reservoir is placed inside the ionization chamber, preferably in a central position of this chamber,
the ionization chamber is in a central position relative to the ion reservoir, which comprises at least two portions framing or surrounding this chamber,
the ion reservoir consists of a conductive cage containing a source of ionizing radiation and having good transparency both to the radiations emitted by this source, to the ions generated by these radiations, to the disturbing air currents and to the particles of smoke to detect,
- the cage consists of crossed semi-circular arches,
- the cage constitutes one of the two electrodes of the ionization chamber,
the source of ionizing radiation which generates the ions in the ionization chamber is the same as that which generates the ions in the ion reservoir,
- the source of ionizing radiation consists of a radioactive substance,
deflectors are provided for directing at least part of the air currents coming from the outside towards the ion reservoir before their introduction into at least part of the ionization chamber.
L'invention comprend, mises à part ces dispositions principales, certaines autres dispositions qui s'utilisent de préférence en même temps et dont il sera plus explicitement question ci-après.The invention includes, apart from these main provisions, certain other provisions which are preferably used at the same time and which will be more explicitly discussed below.
Dans ce qui suit, l'on va décrire plusieurs modes de réalisation de l'invention en se référant au dessin ci-annexé d'une manière bien entendu non limitative.In what follows, several embodiments of the invention will be described with reference to the attached drawing, of course in a non-limiting manner.
Les figures 1 et 2, de ce dessin, montrent très schématiquement un détecteur de fumée établi selon l'invention, la figure 1 correspondant à un fonctionnement sans vent et la figure 2, à un fonctionnement avec vent.Figures 1 and 2, of this drawing, very schematically show a smoke detector established according to the invention, Figure 1 corresponding to operation without wind and Figure 2, to operation with wind.
Les figures 3 et 4 montrent encore schématiquement deux variantes conformes à l'invention d'un tel détecteur de fumée, lors de son fonctionnement sans vent.Figures 3 and 4 also schematically show two variants according to the invention of such a smoke detector, during its operation without wind.
Les figures 5 et 6 montrent respectivement en coupe axiale et en vue extérieure un mode de réalisation d'un tel détecteur conforme à l'invention.Figures 5 and 6 show respectively in axial section and in external view an embodiment of such a detector according to the invention.
D'une façon connue en soi, la chambre d'ionisation ou de mesure 1 comprend deux électrodes 2 et 3 (figure 1) délimitant entre elles un volume A dans lequel se trouve une substance radioactive 4.In a manner known per se, the ionization or measurement chamber 1 comprises two
Cette substance ionise l'air contenu dans le volume A en y créant des ions 5 positifs et négatifs représentés respectivement par les signes + et -.This substance ionizes the air contained in volume A by creating positive and negative ions therein represented by the signs + and - respectively.
Une tension électrique continue V est appliquée entre les deux électrodes, ce qui crée un champ électrique E, et par suite un courant ionique, entre ces électrodes, ainsi qu'indiqué par les petites flèches partant des ions.A continuous electric voltage V is applied between the two electrodes, which creates an electric field E, and consequently an ion current, between these electrodes, as indicated by the small arrows leaving the ions.
Des moyens sont en outre prévus pour mesurer le courant électrique résultant, lequel demeure constant en régime normal, c'est-à-dire en absence de fumée dans le volume A.Means are also provided for measuring the resulting electric current, which remains constant under normal conditions, that is to say in the absence of smoke in volume A.
Si une fumée, provenant par exemple d'un incendie, est introduite dans ce volume A, les particules de cette fumée se fixent sur les ions 5, ce qui les alourdit et les ralentit.If smoke, for example from a fire, is introduced into this volume A, the particles of this smoke become fixed on the ions 5, which weighs them down and slows them down.
Le courant électrique mesuré décroît alors et cette décroissance est exploitée pour déclencher un signal d'alarme quand elle franchit un seuil prédéterminé.The measured electric current then decreases and this decrease is used to trigger an alarm signal when it crosses a predetermined threshold.
Si le volume A est balayé par un vent ou courant d'air violent C (figure 2), certains des ions 5 contenus entre les électrodes 2 et 3, ions désignés par la référence 5₁, sont entraînés par ce vent et extraits de la chambre 1.If volume A is swept by wind or current of violent air C (FIG. 2), some of the ions 5 contained between the
Si aucune précaution n'est prise pour remédier à cet enlèvement d'ions par balayage, il en résulte une réduction du courant ionique engendré dans la chambre 1 et cette réduction peut être la cause de fausses alarmes.If no precautions are taken to remedy this removal of ions by scanning, this results in a reduction in the ion current generated in chamber 1 and this reduction can be the cause of false alarms.
Pour remédier audit enlèvement, selon l'invention, on exploite le phénomène même qui est à l'origine de cet enlèvement, savoir l'entraînement ou balayage d'ions par le vent, pour introduire dans la chambre d'ionisation de nouveaux ions en compensation de ceux enlevés.To remedy said removal, according to the invention, the very phenomenon which is at the origin of this removal, namely the entrainment or sweeping of ions by the wind, is exploited to introduce new ions into the ionization chamber. compensation for those removed.
A cet effet, on fait traverser par ledit vent, avant sa traversée de la chambre, un réservoir 6 d'ions 7 indépendant de cette chambre.For this purpose, said wind is made to cross, before it crosses the chamber, a reservoir 6 of ions 7 independent of this chamber.
Cette traversée se traduit par un entraînement ou balayage d'ions hors dudit réservoir, ions désignés par la référence 7₁, lesquels ions sont ensuite introduits dans la chambre 1.This crossing results in a drive or scanning of ions out of said reservoir, ions designated by the reference 7₁, which ions are then introduced into chamber 1.
On choisit les caractéristiques du réservoir 6 (emplacement, concentration des ions ...) de façon telle que la compensation ionique obtenue à l'intérieur de la chambre 1 soit totale lors de la manifestation des vents C, de vitesse prédéterminée, vis-à-vis desquels on désire essentiellement protéger le détecteur.The characteristics of the reservoir 6 are chosen (location, concentration of the ions, etc.) so that the ion compensation obtained inside the chamber 1 is total during the manifestation of the winds C, of predetermined speed, with respect to - against which we essentially want to protect the detector.
En d'autres termes, le nombre des ions 7₁ prélevés par unité de temps dans le réservoir 6 et introduits dans la chambre 1 par de tels vents C est égal à celui des ions 5₁ extraits de ladite chambre pendant la même durée et par les mêmes vents.In other words, the number of 7₁ ions sampled per unit of time in the tank 6 and introduced into the chamber 1 by such winds C is equal to that of the 5₁ ions extracted from said chamber during the same duration and by the same winds.
Le réservoir 6 est de préférence délimité par une cage en matériau conducteur formant une cage de Faraday et contenant une source radioactive propre à ioniser le volume d'air intérieur à cette cage.The reservoir 6 is preferably delimited by a cage of conductive material forming a Faraday cage and containing a radioactive source suitable for ionize the volume of air inside this cage.
Cette dernière doit être à la fois perméable aux vents C, chargés ou non de la fumée à détecter, aux rayonnements émis par la source et aux ions 7₁ entraînés par ces vents vers l'extérieur de ladite cage.The latter must be at the same time permeable to winds C, whether or not charged with the smoke to be detected, to radiation emitted by the source and to ions 7₁ entrained by these winds towards the outside of said cage.
Dans le schéma des figures 1 et 2, le réservoir d'ions 6 est situé à côté de la chambre 1 et la compensation ionique décrite ci-dessus implique alors que les vents C circulent dans un sens bien déterminé.In the diagram of FIGS. 1 and 2, the ion reservoir 6 is located next to the chamber 1 and the ion compensation described above then implies that the winds C circulate in a well-defined direction.
Pour assurer une telle compensation pour au moins deux directions opposées de la circulation des vents C, on a recours de préférence à l'une ou l'autre des deux formules schématisées sur les figures 3 et 4 :
- selon la première formule, le réservoir 6 d'ions se trouve à l'intérieur de la chambre 1, en une position centrale, de façon à être obligatoirement balayé par les vents dans tous les cas avant qu'ils décrivant la fin de leur parcours dans la chambre,
- selon la seconde formule, c'est la chambre 1 qui se trouve à l'intérieur du réservoir 6 d'ions, ou tout au moins qui est encadrée par deux portions d'un tel réservoir situées respectivement à son entrée et à sa sortie de façon telle que, dans tous les cas, les vents à neutraliser commencent par traverser une portion de réservoir d'ions avant de balayer la chambre.To ensure such compensation for at least two opposite directions of the circulation of the winds C, recourse is preferably had to one or the other of the two formulas shown diagrammatically in FIGS. 3 and 4:
- according to the first formula, the ion reservoir 6 is located inside the chamber 1, in a central position, so as to be necessarily swept by the winds in all cases before they describe the end of their walk in the room,
- according to the second formula, it is the chamber 1 which is inside the ion reservoir 6, or at least which is framed by two portions of such a reservoir situated respectively at its inlet and at its outlet in such a way that, in all cases, the winds to be neutralized begin by crossing a portion of the ion reservoir before sweeping the chamber.
De préférence encore, on donne au détecteur dans son ensemble une forte symétrie de révolution autour d'une axe de façon qu'il se prête à une pénétration quasiment omnidirectionnelle des fumées ambiantes.More preferably, the detector as a whole is given a strong symmetry of revolution about an axis so that it lends itself to almost omnidirectional penetration of ambient smoke.
Les figures 5 et 6 montrent plus en détail un mode de réalisation conforme à cette dernière caractéristique et à la première des deux formules ci-dessus.Figures 5 and 6 show in more detail an embodiment according to this last characteristic and to the first of the two formulas above.
La chambre d'ionisation 1 est ici délimitée extérieurement par une plaque plane et circulaire 8 en matière isolante et par un dôme hémisphérique 9 en métal ou matière plastique métallisée, dôme dont le bord circulaire est rapporté sur la périphérie de la plaque 8.The ionization chamber 1 is here delimited externally by a flat and circular plate 8 made of insulating material and by a
Ladite plaque 8 est destinée à être fixée contre une paroi ou un plafond délimitant un local à surveiller ou encore contre la face interne d'une conduite de climatisation à contrôler.Said plate 8 is intended to be fixed against a wall or a ceiling delimiting a room to be monitored or even against the internal face of an air conditioning pipe to be controlled.
Le dôme est perforé par des séries annulaires de lumières 10 faisant communiquer son volume intérieur avec l'atmosphère ambiante.The dome is perforated by annular series of
A l'intérieur du dôme 9 est placée une cage 11 en métal ou matière plastique métallisée qui présente comme le dôme une forme hémisphérique et est centrée au centre de ce dôme.Inside the
Cette cage est avantageusement composée d'une pluralité d'arceaux semi-circulaires croisés en leurs sommets.This cage is advantageously composed of a plurality of semi-circular arches crossed at their vertices.
Au centre commun du dôme et de la cage se trouve la substance radioactive 4.At the common center of the dome and the cage is the radioactive substance 4.
La cage 11 est reliée au pôle positif d'une source de courant continu 12 par l'intermédiaire d'un ensemble de mesure et d'alarme connu en soi et symbolisé par le rectangle 13 et le dôme 9 est mis à la masse.The cage 11 is connected to the positive pole of a direct
Cette cage et ce dôme jouent alors respectivement les rôles des deux électrodes 2 et 3 ci-dessus.This cage and this dome then respectively play the roles of the two
On voit encore sur la figure 5 un déflecteur tronconique 14 disposé à l'intérieur du dôme juste en regard d'une série de lumières 10 de façon à dévier vers la cage les courants d'air introduits dans la chambre à travers ces lumières et à réduire leur vitesse d'entrée.We also see in Figure 5 a
Le fonctionnement du détecteur ainsi décrit est le suivant.The operation of the detector thus described is as follows.
Au repos, la mesure fait intervenir exclusivement la chambre d'ionisation qui est constituée par la zone incurvée A comprise entre la cage 11 et le dôme 9.At rest, the measurement involves exclusively the ionization chamber which is constituted by the curved zone A comprised between the cage 11 and the
Les ions formés dans cette zone par les radiations ionisantes provenant de la source 4 forment un courant ionique entre les deux électrodes constituées par les deux surfaces 9 et 11 et toute présence de fumée à proximité immédiate de l'appareil se traduit par une pénétration de cette fumée dans ladite zone et donc par une réduction du courant ionique de la manière ci-dessus décrite, réduction qui déclenche un signal d'alarme lorsqu-elle dépasse un seuil prédéterminé.The ions formed in this area by ionizing radiation from source 4 form a ion current between the two electrodes formed by the two
Simultanément, les radiations émises par la substance 4 ionisent le volume B intérieur à la cage 11 et les ions ainsi formés dans cette cage y demeurent prisonniers, constituant une "réserve" de ces ions.Simultaneously, the radiation emitted by the substance 4 ionizes the volume B inside the cage 11 and the ions thus formed in this cage remain trapped there, constituting a "reserve" of these ions.
Tant que l'atmosphère ambiante demeure calme, la pénétration de la fumée dans la zone A se fait calmement et ne se traduit par aucun entraînement d'ions de l'intérieur de la cage 11 à l'extérieur de celle-ci.As long as the ambient atmosphere remains calm, the penetration of the smoke into zone A takes place calmly and does not result in any entrainment of ions from the inside of the cage 11 outside of the latter.
En revanche, lorsqu'un vent créé à proximité de l'appareil se présente devant celui-ci, il y est introduit à travers les lumières 10, traverse la zone incurvée A, puis pénètre aussitôt dans la cage 11.On the other hand, when a wind created close to the device comes before it, it is introduced there through the
En traversant cette cage, il la balaye et prélève un certain nombre des ions qui s'y trouvent en réserve.While crossing this cage, it sweeps it and takes a certain number of the ions which are there in reserve.
Il s'échappe ensuite de ladite cage en entraînant les ions ainsi prélevés et, lorsqu'il traverse à nouveau la zone A, il l'enrichit avec ces ions prélevés dans la cage.It then escapes from said cage by entraining the ions thus removed and, when it again crosses zone A, it enriches it with these ions removed from the cage.
Finalement il s'échappe hors de la chambre en entraînant avec lui quelques-uns des ions circulant dans la zone A, mais le nombre des ions finalement extraits hors de cette zone par le vent considéré ne diffère pas sensiblement de celui des ions apportés par ce vent dans cette zone : il y a donc compensation ionique et la mesure n'est par perturbée par ledit vent.Finally it escapes from the chamber, carrying with it some of the ions circulating in zone A, but the number of ions finally extracted from this zone by the wind considered does not differ appreciably from that of the ions brought by this wind in this zone: there is therefore ion compensation and the measurement is not disturbed by said wind.
Les caractéristiques des cages (dimensions, positions, formes, composition) sont déterminées de façon telle que la compensation ionique obtenue soit optimale lors de la manifestation des vents vis-à-vis desquels on désire surtout protéger le détecteur.The characteristics of the cages (dimensions, positions, shapes, composition) are determined so that the ion compensation obtained is optimal during the manifestation of the winds against which we especially want to protect the detector.
Dans des modes de réalisation ayant donné toute satisfaction et cités uniquement à titre illustratif,
- les électrodes étaient constituées en acier inoxydable ou en matière plastique métallisée,
- la tension V était de + 8 volts,
-l'électrode extérieure se présentait sous la forme d'un capot perforé cylindrique de révolution de 45 mm de diamètre,
- le réservoir d'ions se présentait sous la forme d'une cage interne semi-sphérique de révolution de 30 mm de diamètre,
- et la détection de fumée obtenue demeurait très peu sensible aux courants d'air en ce sens que la vitesse de ces courants d'air devait dépasser 11 m/sec pour que la perturbation du courant de mesure due auxdits courants d'air atteigne 10 % de la valeur de ce courant.In embodiments having given all satisfaction and cited only by way of illustration,
- the electrodes were made of stainless steel or metallized plastic,
- the voltage V was + 8 volts,
-the external electrode was in the form of a cylindrical perforated cover of revolution 45 mm in diameter,
- the ion reservoir was in the form of an internal semi-spherical cage of revolution 30 mm in diameter,
- and the smoke detection obtained remained very insensitive to air currents in the sense that the speed of these air currents had to exceed 11 m / sec for the disturbance of the measurement current due to said air currents to reach 10 % of the value of this current.
En suite de quoi, et quel que soit le mode de réalisation adopté, on dispose finalement d'un détecteur de fumée dont la constitution et le fonctionnement résultent suffisamment de ce qui précède.As a result of which, and whatever the embodiment adopted, there is finally a smoke detector whose constitution and operation result sufficiently from the above.
Ce détecteur présente de nombreux avantages par rapport à ceux antérieurement connus, en particulier en ce qui concerne l'efficacité de la compensation vis-à-vis des vents, la simplicité et la fiabilité.This detector has many advantages over those previously known, in particular with regard to the efficiency of the compensation with respect to the winds, the simplicity and the reliability.
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 la plaque 8 du mode de réalisation des figures 5 et 6 serait conductrice au lieu d'être isolante, étant alors isolée du dôme 9 par un anneau isolant et pouvant constituer elle-même l'une des deux électrodes de la chambre d'ionisation, la cage intérieure pouvant alors être portée au même potentiel que ladite plaque ou à un potential différent, de préférence inférieur si la cage est encore intérieure au dôme,
- et celles où le dôme perforé 9 ci-dessus présenterait une forme autre que celles hémisphérique et cylindrique de révolution explicitées ci-dessus, par exemple une forme parallélèpipédique, la forme de la cage 11 pouvant être bien entendu modifiée en conséquence.As is obvious, and as already follows from the foregoing, 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 variants, in particular:
- those where the plate 8 of the embodiment of Figures 5 and 6 would be conductive instead of being insulating, then being isolated from the
- And those where the
Claims (10)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8602567 | 1986-02-25 | ||
| FR8602567A FR2594953B1 (en) | 1986-02-25 | 1986-02-25 | SMOKE DETECTOR WITH IONIZATION CHAMBER |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0236223A1 true EP0236223A1 (en) | 1987-09-09 |
| EP0236223B1 EP0236223B1 (en) | 1991-01-30 |
Family
ID=9332497
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP87400420A Expired - Lifetime EP0236223B1 (en) | 1986-02-25 | 1987-02-25 | Ionization chamber smoke detector |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4864141A (en) |
| EP (1) | EP0236223B1 (en) |
| AU (1) | AU595292B2 (en) |
| CA (1) | CA1275744C (en) |
| DE (1) | DE3767734D1 (en) |
| ES (1) | ES2019645B3 (en) |
| FR (1) | FR2594953B1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2746184A1 (en) * | 1996-03-15 | 1997-09-19 | Lewiner Jacques | SMOKE DETECTOR WITH ELECTRICAL IONIZATION OF AIR |
| WO2014016473A1 (en) | 2012-07-24 | 2014-01-30 | Finsecur S.A. | Smoke detector |
| US9201051B2 (en) | 2010-12-31 | 2015-12-01 | Finsecur | Method and device for detecting smoke |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5384462A (en) * | 1992-12-08 | 1995-01-24 | Levitt; Roy C. | Process and apparatus for localizing a source of charged particles using an electric field |
| US6215851B1 (en) | 1998-07-22 | 2001-04-10 | Northrop Grumman Corporation | High current proton beam target |
| US6606899B1 (en) * | 2000-07-07 | 2003-08-19 | Air Products And Chemicals, Inc. | Total impurity monitor for gases |
| US20030180591A1 (en) * | 2001-03-29 | 2003-09-25 | Steven Danyluk | Contact potential difference ionization battery |
| GB0613882D0 (en) * | 2006-07-12 | 2006-08-23 | Kidde Ip Holdings Ltd | Smoke detector |
| US7735910B2 (en) * | 2007-03-10 | 2010-06-15 | Honda Motor Co., Ltd | Plasma wind deflector for a sunroof |
| US8735858B2 (en) * | 2010-04-30 | 2014-05-27 | Hewlett-Packard Development Company, L.P. | Ionic devices with interacting species |
| US9437093B2 (en) | 2011-10-06 | 2016-09-06 | Microchip Technology Incorporated | Differential current measurements to determine ION current in the presence of leakage current |
| US9823280B2 (en) | 2011-12-21 | 2017-11-21 | Microchip Technology Incorporated | Current sensing with internal ADC capacitor |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1185495A (en) * | 1957-10-24 | 1959-07-31 | Device for detecting and controlling variations in the composition of a gas, usable in particular as a fire predetector | |
| FR1575343A (en) * | 1967-08-02 | 1969-07-18 | ||
| EP0111012A1 (en) * | 1982-06-07 | 1984-06-20 | Nohmi Bosai Kogyo Co., Ltd. | Ionization type of smoke sensor |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH475614A (en) * | 1968-06-18 | 1969-07-15 | Cerberus Ag Werke Fuer Elektro | Ionization fire alarms |
| CH508251A (en) * | 1970-07-23 | 1971-05-31 | Cerberus Ag | Ionization fire alarms |
| AU423137B2 (en) * | 1970-11-09 | 1972-04-04 | Nittan Company Limited | Ionization smike detector |
| CH551057A (en) * | 1973-04-17 | 1974-06-28 | Cerberus Ag | IONIZATION ALARM. |
| US4171486A (en) * | 1977-08-31 | 1979-10-16 | Emhart Industries, Inc. | Ionization smoke detector with controlled sensitivity |
| US4185196A (en) * | 1978-01-13 | 1980-01-22 | General Electric Company | Ionization smoke detector having improved stability and sensitivity |
| US4227085A (en) * | 1978-10-05 | 1980-10-07 | Electrometer Corporation | Ionization-type particle detector |
| US4488044A (en) * | 1981-11-20 | 1984-12-11 | Pittway Corporation | Ionization chamber for smoke detector and the like |
| US4564762A (en) * | 1984-05-16 | 1986-01-14 | Pyrotector, Inc. | Smoke detector |
-
1986
- 1986-02-25 FR FR8602567A patent/FR2594953B1/en not_active Expired
-
1987
- 1987-02-19 US US07/016,378 patent/US4864141A/en not_active Expired - Lifetime
- 1987-02-19 CA CA000530144A patent/CA1275744C/en not_active Expired - Lifetime
- 1987-02-24 AU AU69177/87A patent/AU595292B2/en not_active Ceased
- 1987-02-25 ES ES87400420T patent/ES2019645B3/en not_active Expired - Lifetime
- 1987-02-25 EP EP87400420A patent/EP0236223B1/en not_active Expired - Lifetime
- 1987-02-25 DE DE8787400420T patent/DE3767734D1/en not_active Expired - Lifetime
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1185495A (en) * | 1957-10-24 | 1959-07-31 | Device for detecting and controlling variations in the composition of a gas, usable in particular as a fire predetector | |
| FR1575343A (en) * | 1967-08-02 | 1969-07-18 | ||
| EP0111012A1 (en) * | 1982-06-07 | 1984-06-20 | Nohmi Bosai Kogyo Co., Ltd. | Ionization type of smoke sensor |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2746184A1 (en) * | 1996-03-15 | 1997-09-19 | Lewiner Jacques | SMOKE DETECTOR WITH ELECTRICAL IONIZATION OF AIR |
| WO1997035287A1 (en) * | 1996-03-15 | 1997-09-25 | Jacques Lewiner | Electric air ionisation smoke detector |
| US9201051B2 (en) | 2010-12-31 | 2015-12-01 | Finsecur | Method and device for detecting smoke |
| WO2014016473A1 (en) | 2012-07-24 | 2014-01-30 | Finsecur S.A. | Smoke detector |
| US9286780B2 (en) | 2012-07-24 | 2016-03-15 | Finsecur | Smoke detector |
Also Published As
| Publication number | Publication date |
|---|---|
| ES2019645B3 (en) | 1991-07-01 |
| US4864141A (en) | 1989-09-05 |
| FR2594953A1 (en) | 1987-08-28 |
| EP0236223B1 (en) | 1991-01-30 |
| DE3767734D1 (en) | 1991-03-07 |
| AU6917787A (en) | 1987-08-27 |
| FR2594953B1 (en) | 1989-05-05 |
| AU595292B2 (en) | 1990-03-29 |
| CA1275744C (en) | 1990-10-30 |
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