FR2568907A1

FR2568907A1 - Snowfall detector

Info

Publication number: FR2568907A1
Application number: FR8413103A
Authority: FR
Original assignee: BERNIE MICHEL
Current assignee: BERNIE MICHEL
Priority date: 1984-08-13
Filing date: 1984-08-13
Publication date: 1986-02-14

Abstract

Device intended to give out a warning signal at the first appearance of snowfall. The invention comprises a light source giving out approximately parallel rays 1 which light up the non-reflecting control target 6 and a photosensitive cell 3 directed towards the said target and supplying an electrical signal as soon as the said target 6 receives falling snow which reflects the light given out by the source 1 towards the cell 3, which signal, when amplified, enables a warning to be transmitted over a long distance. The invention may be used for detecting any snowfall as soon as it starts on roads, in order to enable them to be immediately cleared so as to keep them passable at all times.

Description

DETECTEUR DE CHUTE DE NEIGE. SNOWFALL DETECTOR.

Dans certaines circonstances, il est utile de détecter les chutes de neige dès leur première apparition. Par exemple, entre autres applications, dans les Travaux Publics, afin de mobiliser rapidement les moyens de dégagement des voies de communication dès les premières chutes de neige de façon a ne pas laisser se former des congères ou afin d'éviter la formation de plaques de glace. In certain circumstances, it is useful to detect snowfall when it first appears. For example, among other applications, in Public Works, in order to quickly mobilize the means of clearing the communication routes from the first snowfall so as not to allow snowdrifts to form or to avoid the formation of plaques ice.

Un dispositf connu, qui poursuit ce même but, fonctionne par gravité. Un plateau convexe est suspendu a un fléau équilibré. Les premiers flocons de neige qui tombent sur ce plateau déséquilibrent le fléau qui agit -sur un contact permettant ainsi l'émission d'un signal qui est exploité comme il convient. A known device, which pursues this same goal, operates by gravity. A convex plate is suspended from a balanced beam. The first snowflakes that fall on this plateau unbalance the plague which acts on a contact thus allowing the emission of a signal which is exploited as it should.

Un tel dispostif présente évidemment l'inconvénient que le déséquilibre peut être obtenu par tout autre chose que la neige, si même la pluie ne l'influence pas par suite de la convexité du plateau. Mais un insecte, un oiseau, ou simplement une feuille morte peuvent provoquer l'alarme intempestive. Obviously, such a device has the disadvantage that the imbalance can be obtained by anything other than snow, if even the rain does not influence it due to the convexity of the plateau. But an insect, a bird, or simply a dead leaf can cause the nuisance alarm.

Le dispositif objet de l'invention permet d'éviter cet inconvénient. The device which is the subject of the invention makes it possible to avoid this drawback.

Il permet en effet de déclencher un signal électrique dès l'apparition des premiers flocons de neige sans pouvoir être perturbé par des objets quelconques, car son fonctionnement est base sur le contraste entre la couleur noire du support de contrôle et la parfaite blancheur de la neige, contraste que seule la neige peut donner.It makes it possible to trigger an electrical signal as soon as the first snowflakes appear without being able to be disturbed by any objects, because its operation is based on the contrast between the black color of the control support and the perfect whiteness of the snow. , contrast that only snow can give.

Pour cela, une surface de contrôle de petites dimensions, non réfléchissante, est soumise a un éclairage constant de faible intensité, capable de provoquer la réaction d'une cellule sensible a la lumière lorsque cet éclairage est perçu par elle sous l'effet de la reflexion provoque par l'apparition des flocons de neige sur ladite surface de contrôle, engendrant ainsi un signal électrique qui, amplifié par un circuit électronique est capable d'être perçu a distance sous forme d'un signal lumineux ou sonore. For this, a small, non-reflecting control surface is subjected to constant lighting of low intensity, capable of causing the reaction of a light-sensitive cell when this lighting is perceived by it under the effect of the reflection caused by the appearance of snowflakes on said control surface, thus generating an electrical signal which, amplified by an electronic circuit is capable of being perceived at a distance in the form of a light or sound signal.

Les dessins annexés, donnes a titre d'exemple seulement, montrent un mode de réalisation de l'objet de l'invention. The accompanying drawings, given by way of example only, show an embodiment of the subject of the invention.

La figure 1 est une vue schématique en élévation de face du dispositif objet de l'invention. Figure 1 is a schematic front elevational view of the device object of the invention.

La figure 2 est une vue schematique en elevation de face de l'élément servant de support de la neige observee, selon un autre mode de réalisation. Figure 2 is a schematic elevational front view of the element serving as support for the snow observed, according to another embodiment.

La figure 3 est une vue schématique en plan, vue de dessous, du même élément, selon un autre mode de réalisation. Figure 3 is a schematic plan view, seen from below, of the same element, according to another embodiment.

La figure 4 est une vue schématique en élévation de profil, du même élément, selon un autre mode de réalisation. Figure 4 is a schematic side elevational view of the same element, according to another embodiment.

La figure 5 est une vue schématique du groupe electronique de traitement du signal produit par l'apparition de la neige sur la cible. FIG. 5 is a schematic view of the electronic group for processing the signal produced by the appearance of snow on the target.

Tel qu'il est représenté (fiv. 1) le dispositif comporte une source lumineuse 1 de faible intensité, avantageusement constituée par une diode électroluminescente, dite LED, située à l'intérieur d'une enceinte tubulaire 2 noircie intérieurement, de faible diamètre par rapport à sa longueur, de façon à limiter la surface éclairée à la section d'un faisceau lumineux de la largeur du tube, sans l'intervention d'un système optique focalisateur. As shown (fiv. 1) the device comprises a light source 1 of low intensity, advantageously constituted by a light-emitting diode, called LED, located inside a tubular enclosure 2 internally blackened, of small diameter by relative to its length, so as to limit the illuminated surface to the section of a light beam of the width of the tube, without the intervention of a focusing optical system.

Il comporte d'autre part une cellule 3 sensible a la lumière telle qu'une cellule photo-resistante, du type cellule au sulfure de cadmium, qui est particulièrement sensible aux longueurs d'ondes emises dans le jaune et vert par la LED. La cellule phota-resistante 3 est elle-même contenue a l'intérieur du tube 4 noirci aussi intérieurement et de faible diamètre par rapport à sa longueur de manière aussi à n'être sensible qu'a la lumière reçue parallèlement à son axe sans qu'il soit nécessaire la non plus d'utiliser un système optique focalisateur.It further comprises a light-sensitive cell 3 such as a photoresist cell, of the cadmium sulfide cell type, which is particularly sensitive to the wavelengths emitted in yellow and green by the LED. The photoresist cell 3 is itself contained inside the tube 4 also blackened internally and of small diameter with respect to its length so as to be sensitive only to the light received parallel to its axis without 'it is also necessary to use a focusing optical system.

L'extrémité inférieure des tubes 2 et 4 est munie d'un bord rabattu extérieurement 40 afin d'éviter que le givre ne s'accumule à la bouche de ces tubes et ne les obstrue, inhibant leur fonctionnement. The lower end of the tubes 2 and 4 is provided with an externally folded edge 40 in order to prevent the frost from accumulating at the mouth of these tubes and from obstructing them, inhibiting their operation.

Les deux tubes 2 et 4 ainsi équipés sont organises sur le bras 5 de manière que leur ouverture convergent vers le point commun 6 situé sur la sole 7 qui constitue donc la cible de contrôle sur laquelle la neige peut librement se deposer. The two tubes 2 and 4 thus equipped are organized on the arm 5 so that their opening converges towards the common point 6 located on the sole 7 which therefore constitutes the control target on which the snow can freely settle.

La sole 7 est munie en ce point 6 d'une surface non réfléchissante tel qu'un flocage parfaitement noir 8 ou tout autre materiau ou revêtement ayant meme pouvoir absorbant de la lumière. The floor 7 is provided at this point 6 with a non-reflecting surface such as a perfectly black flocking 8 or any other material or coating having the same light absorbing capacity.

Le bras 5 est lui-même monte de façon reglable en hauteur sur le support vertical -9 de manière situer à des hauteurs variables le plan de la cible d'observation 6 sur laquelle convergent les tubes 2 et 4, ce qui permet de regler l'épaisseur de neige satisfaisant aux conditions d'alerte. The arm 5 is itself adjustable in height on the vertical support -9 so as to locate at variable heights the plane of the observation target 6 on which the tubes 2 and 4 converge, which makes it possible to adjust the snow depth satisfying the warning conditions.

L'ensemble, parfaitement noirci, mat, exterieurement est contenu dans l'enceinte 10 verticale ouverte a son sommet, noirci mat aussi interieurement afin que la cellule 3 ne reçoive aucun autre rayonnement réfléchi que celui provenant de la cible 6. The assembly, perfectly blackened, mat, externally is contained in the vertical enclosure 10 open at its top, blackened mat also internally so that the cell 3 does not receive any other reflected radiation than that coming from the target 6.

L'enceinte 10 est elle-même suspendue au support 9 de manière a laisser un espace libre entre sa base et la sole 7 afin d'éviter au maximum les tourbillons d'air qui pourraient survenir à l'intérieur de cette enceinte, qui nuiraient a l'amoncellement naturel de la neige sur la cible 6. The enclosure 10 is itself suspended from the support 9 so as to leave a free space between its base and the floor 7 in order to avoid as much as possible the air vortices which could occur inside this enclosure, which would harm the natural accumulation of snow on target 6.

Selon un autre mode de réalisation (fig.2) la cible 6 sur laquelle convergent la source lumineuse 1 et la cellule photosensible 3 est située sur une sangle continue 11, de couleur noir mat, tendue entre les rouleaux 12 et 13, dont l'un est moteur, ladite sangle 11 circulant sous la platine 14 percée d'une ouverture à travers laquelle la cible 6 est observee. According to another embodiment (FIG. 2) the target 6 on which the light source 1 and the photosensitive cell 3 converge is located on a continuous strap 11, of matt black color, stretched between the rollers 12 and 13, the one is motor, said strap 11 circulating under the plate 14 pierced with an opening through which the target 6 is observed.

La platine 14 est aussi montée sur le support vertical 9 de manière a ce que sa distance verticale par rapport a la sangle 11 puisse être reglee en même temps que la hauteur par rapport à elle des organes detecteurs. The plate 14 is also mounted on the vertical support 9 so that its vertical distance relative to the strap 11 can be adjusted at the same time as the height relative to it of the detector members.

Le rouleau moteur 12 peut être anime soit par un moteur électriq- ue soit par un électro-aimant qui manoeuvre une roue a rochets selon une methode connue. Ledit organe moteur est lui-même mis en mouvement par le signal emis pa la cellule 3 et amplifié. Son mouvement, qui provoque l'avancement de la sangle 11 s'arrête automatiquement après que la neige accumulée sur la cible, et qui a provoqué l'excitation du système, a disparu de la zone cible 6, supprimant ainsi spontanément l'excitation du système. The drive roller 12 can be driven either by an electric motor or by an electromagnet which operates a ratchet wheel according to a known method. Said motor member is itself set in motion by the signal emitted by cell 3 and amplified. Its movement, which causes the advancement of the strap 11 stops automatically after the snow accumulated on the target, and which caused the excitation of the system, has disappeared from the target zone 6, thus spontaneously suppressing the excitation of the system.

Selon un autre mode de réalisation (fig.3) l'élément récepteur de la neige, soumis à l'observation de la cellule photosensible 3 est le disque découpé 15 présentant une succession de pales qui peuvent se placer alternativement sous l'ouverture correspondante dont est munie la platine 14 et à travers laquelle l'observation est faite. According to another embodiment (fig. 3) the snow receiving element, subjected to the observation of the photosensitive cell 3 is the cut disc 15 having a succession of blades which can be placed alternately under the corresponding opening, is provided with the plate 14 and through which the observation is made.

Le mouvement de ce disque est obtenu au moyen du moteur 16 mis en mouvement par le signal émis par la cellule 3 et amplifié. Ce mouve ment permet de substituer une pale nue à la pale chargée de neige qui a provoqué l'émission du signal. The movement of this disc is obtained by means of the motor 16 set in motion by the signal emitted by the cell 3 and amplified. This movement makes it possible to substitute a bare blade for the blade loaded with snow which caused the emission of the signal.

Ce mouvement est arrêté par le contact 17 monté en parallèle avec le contact automatique d'alarme 35 (fig.5) déclenché par la neige. Ce contact 17, qui est ouvert au repos sous la pression d'une pale, se ferme des que le signal d'alarme 35 ayant mis l'élément moteur 16 en mouvement ladite pale 15 s'efface. Et il s'ouvrira de nouveau sous la pression d'une pale suivante qui le rencontrera après que la temporisation du signal d'alarme aura ouvert le contact automatique 35. Une pale se trouvera donc ainsi toujours parfaitement située sous la cible 6. This movement is stopped by the contact 17 mounted in parallel with the automatic alarm contact 35 (fig.5) triggered by snow. This contact 17, which is open at rest under the pressure of a blade, closes as soon as the alarm signal 35 having set the motor element 16 in motion, said blade 15 disappears. And it will open again under the pressure of a next blade which will meet it after the delay of the alarm signal has opened the automatic contact 35. A blade will therefore always be perfectly located under the target 6.

Ce dispositif est complété par la brosse ou la lame élastique 18 qui balaie la surface des pales au cours de leur rotation. This device is completed by the brush or the elastic blade 18 which sweeps the surface of the blades during their rotation.

Selon encore un autre mode de réalisation (fig.4) la cible est constituee par le plateau 19 qui est observé à travers l'orifice adéquat pratiqué sur la platine 14, et qui peut se déplacer par translation parallèle sous ledit orifice au moyen de l'élément moteur qui transmet son mouvement au plateau 19 par l'intermédiaire de la bielle 21. Le contact 17, qui coopère avec la came 20 située sur l'arbre moteur, est ouvert à chaque tour de ladite came assurant ainsi le retour du plateau 19 à sa position d'origine selon le même processus qui vient d'être décrit, la came 20 jouant le règle de la pale 15, etle balai 23 effectuant le nettoyage du plateau 19 au cours de sa translation. According to yet another embodiment (fig. 4) the target is constituted by the plate 19 which is observed through the suitable orifice made on the plate 14, and which can move by parallel translation under said orifice by means of the motor element which transmits its movement to the plate 19 by means of the connecting rod 21. The contact 17, which cooperates with the cam 20 located on the motor shaft, is open at each revolution of said cam thus ensuring the return of the plate 19 in its original position according to the same process which has just been described, the cam 20 playing the blade rule 15, and the brush 23 cleaning the plate 19 during its translation.

Le signal électrique qui traverse la cellule photosensible 3, dont la résistance diminue sous l'effet du rayonnement émis par la LED et réfléchi par la neige, est amplifié (fig.5) par l'amplificateur 24 dont la broche d'entrée positive o; est polarisée par la potentiomètre P1 à une tension fixe, et la broche d'entrée négative ,! est située entre le pont diviseur composé de la résistance R3 et de la cellule photo-résistante 3 qui, en l'absence d'éclairement présente une résistance très importante maintenant la broche p à une tension élevée.Des que la cellule 3 est éclairée, par le rayonnement réfléchi par la neige, provenant de la LED 1 qui est toujours sous tension, sa résistance chute ainsi que, de ce fait, la tension au niveau de la broche dont le potentiel passe au dessous du seuil préréglé de la broche oc. La broche de sortie r passe alors à l'état 1, ce qui permet, à travers la diode zener 28, la polarisation du transistor (NPN) 29 qui permet à son tour la décharge de la capacité 30 a travers la diode 31. The electrical signal which passes through the photosensitive cell 3, the resistance of which decreases under the effect of the radiation emitted by the LED and reflected by the snow, is amplified (fig. 5) by the amplifier 24 whose positive input pin o ; is biased by potentiometer P1 at a fixed voltage, and the negative input pin,! is located between the divider bridge made up of the resistor R3 and the photoresist cell 3 which, in the absence of illumination has a very significant resistance keeping pin p at a high voltage. As soon as cell 3 is lit, by the radiation reflected by the snow, coming from the LED 1 which is always under tension, its resistance drops as well as, therefore, the tension at the level of the pin whose potential passes below the preset threshold of the pin oc. The output pin r then goes to state 1, which allows, through the zener diode 28, the bias of the transistor (NPN) 29 which in turn allows the discharge of the capacitor 30 through the diode 31.

Le temporisateur 32 permet de retarder l'émission du signal ainsi cree afin d'éviter qu'un eclairement passager etranger a l'appareil, un éclair par exemple, ou le passage d'un phare de voiture, ne provoque intempestivement le signal si même cette lumière intense instantanee venait a influencer la cellule photo-résistante 3. Il est de ce fait nécessaire que l'éclairement de la cellule 3 persiste au-del de cette temporisation prévue pour retarder l'émission du signal. The timer 32 makes it possible to delay the emission of the signal thus created in order to prevent a foreign passenger illumination from the device, a flash for example, or the passage of a car headlight, from inadvertently causing the signal even if this intense instantaneous light came to influence the photoresist cell 3. It is therefore necessary that the illumination of cell 3 persists beyond this time delay provided to delay the emission of the signal.

Le temporisateur 33, quant a lui, determine la duree du signal émis qui, grâce a cela, dans le cas où la cible est fixe (fig.l), s'arrête malgrè la persistance de l'excitation de la cellule 3, après le temps suffisant pour que la transmission téléphonique ait pu avoir lieu afin de menager la source d'energie lorsque celle-ci est autonome. Et dans le cas où la cible 6 est mobile (fig.2,3 et 4), ce temporisateur 33 permet au contraire de faire persister le signal au-del de l'enlèvement de la neige provoqué par l'effacement de la cible, afin de maintenir le signal durant le temps nécessaire a la transmission téléphonique.C'est alors qu'intervient l'interrupteur 17 manoeuvré par la pale 15 de la figure 3 ou par la came 20 de la figure 4, monté en parallèle avec l'interrupteur de signal 34 (fig. 5) manoeuvré lui-même par le relai 35 qui constitue la sortie du circuit electronique d'amplification. The timer 33, meanwhile, determines the duration of the transmitted signal which, thanks to this, in the case where the target is fixed (fig.l), stops despite the persistence of the excitation of cell 3, after sufficient time for the telephone transmission to take place in order to protect the energy source when it is autonomous. And in the case where the target 6 is mobile (fig. 2,3 and 4), this timer 33 on the contrary allows the signal to persist beyond the removal of the snow caused by the erasure of the target, in order to maintain the signal for the time necessary for telephone transmission. This is where the switch 17 operated by the blade 15 in FIG. 3 or by the cam 20 in FIG. 4 comes into action, mounted in parallel with the signal switch 34 (fig. 5) operated by relay 35 which constitutes the output of the electronic amplification circuit.

En effet, dans chacun de ces deux derniers modes de réalisation (fig.3 et 41 I'arrêt de l'organe moteur doit se faire en un point précis, celui où une nouvelle pale est amené sous l'ouverture de la platine 14 (fig.3) ou celui où le plateau 19 est ramene sous cette même ouverture (fig.4). Ceci est obtenu grâce à cet interrupteur 17 monté en parallèle avec l'interrupteur de signal 34. Tous deux sont ouverts dans leur position de repos.L'excitation de la cellule 3 par la présence de la neige provoque donc, à travers le circuit électronique, la fermeture du contact 34 qui permet l'émission du signal d'alarme par le moyen de tout organe de transmission adequat branche aux wr bornes 38 et 39 et simultanement fait demarrer l'élément moteur 16, monte en parallèle avec le circuit de transmission, en vue d'enlever la neige responsable de l'émission du signal, ce qui a pour effet secondaire de manoeuvrer la pale 15 (fig.3) ou la came 20 (fig.4), donc de fermer le contact 17 qui leur est lie et qui est lui-même monte en parallèle avec le contact 34.In fact, in each of these last two embodiments (fig. 3 and 41, the engine member must be stopped at a precise point, that where a new blade is brought under the opening of the plate 14 ( fig.3) or the one where the plate 19 is brought back under this same opening (fig.4) This is obtained thanks to this switch 17 mounted in parallel with the signal switch 34. Both are open in their rest position The excitation of cell 3 by the presence of snow therefore causes, through the electronic circuit, the closing of contact 34 which allows the emission of the alarm signal by means of any adequate transmission device connected to wr terminals 38 and 39 and simultaneously starts the motor element 16, rises in parallel with the transmission circuit, with a view to removing the snow responsible for the emission of the signal, which has the secondary effect of operating the blade 15 ( fig.3) or the cam 20 (fig.4), therefore to close the contact 17 which is linked to them and that i is itself mounted in parallel with contact 34.

L'action de l'élément moteur 16 s'exercera donc aussi longtemps que le relai 35 maintiendra fermé le contact 34 et, au delà de la fermeture de ce contact contrôlée par le temporisateur 33, aussi longtemps qu'une pale 15 (fig.3) ou que la came 20 (fig.4) n'aura pas ouvert a nouveau le contact 17 en ramenant au point precis de la cible un support liberé de neige. The action of the motor element 16 will therefore be exerted as long as the relay 35 keeps the contact 34 closed and, beyond the closing of this contact controlled by the timer 33, as long as a blade 15 (fig. 3) or that the cam 20 (fig.4) will not have opened the contact 17 again by bringing back to the precise point of the target a support released from snow.

L'ensemble peut être almenté par le secteur a travers le pont redresseur 36 qui fourni un courant de 12 volts régulé par le régulateur 37, ou directement par une bâtterie qui permet son implantation en tous lieux. The assembly can be supplied by the sector through the rectifier bridge 36 which supplies a current of 12 volts regulated by the regulator 37, or directly by a battery which allows its implantation in all places.

L'invention n'est pas limitée a l'exemple ou aux exerlples qui en ont été donnés, toute variante, considérée comme équivalence, ne pouvant en limiter la portée. The invention is not limited to the example or to the examples which have been given thereof, any variant, considered as equivalence, which cannot limit its scope.

L'invention peut être utilisée pour détecter les chutes de neige dans des points précis, éloignés des centres d'intervention et permettre à ceux-ci d'organiser le dégagement immédiat des voies de communication routières ou ferroviaires avant que l'accumulation de la neige ne gêne la circulation et que leur dégagement ne devienne trop difficile. The invention can be used to detect snowfall in specific points, far from intervention centers and allow them to organize immediate clearance of road or rail communication routes before the accumulation of snow. does not obstruct the circulation and that their release does not become too difficult.

Claims

CLAIMS 1) - Device for detecting snowfall, Characterized by the fact that it comprises a light source (1) illuminating a target (6) which naturally absorbs all of the light emitted by said source and a detector system of light (3) constantly oriented in such a way that it is capable of receiving the light reflected by the target as soon as the latter receives a reflecting body such as snow.

20) - Device according to claim 1,

Characterized by the fact that the light source (1) consists of a light-emitting diode placed at the upper end of a non-reflecting tube (2) internally open at its base, of small diameter relative to its length, oriented axially towards the target (6); the light detector system being the photo-sensitive cell (3) placed at the upper end of an internally non-reflecting tube (4), of small diameter relative to its length, open at its base, oriented axially towards said target (6).

3) - Device according to claim 2,

Characterized by the fact that the tubes (2) and (4) which respectively support the light source (1) and the light detector system (3) are each provided at their lower end with an externally folded edge (40) intended to prevent the closing of their lower opening by frost formation at this level.

4) - Device according to all of claims 1 to 3,

Characterized by the fact that the converging supports (2) and (4), which respectively contain the light source (1) and the photo-sensitive cell (3), are mounted on the same support (9) which makes them simultaneously adjustable in height compared to the observed target.

5) - Device according to claim 4,

Characterized by the fact that the target (6) is constituted by a continuous non-reflective strap (11), stretched between the movable rollers (12) and (13), capable of parading in line with practical light in the plate (14) at the aiming point of the photosensitive cell (3), said strap (II) being moved by means of the motor element (12) set in motion by the electrical signal emitted by the cell (3) and amplified , said movement stopping after the translational movement of said strap (II) has removed the snow it was carrying from the target field.

60) - Device according to claim 4,

Characterized by the fact that the target (6) is constituted by a succession of blades, such as (15), situated around the same axis, said non-reflecting blades being able to rotate so as to pass successively under the practical window in this purpose in the plate (14) at the point of convergence of the tubes (2) and (4), said blades being moved by the motor element (16) set in motion by the electrical signal emitted by the cell (3) and their precise positioning being ensured by the switch contact (17) which is operated by the passage of each blade which here acts as a cam; the simple blade (18) sweeping the snow deposited on the cam which leaves the target (6).

7) - Device according to claim 4,

Characterized by the fact that the target (6) is constituted by a flat non-reflecting surface (19) capable of being displaced by horizontal parallel translation under the opening made for this purpose in the plate (14) at the point of convergence of the tubes (2) and (4), said flat surface being driven by a motor element actuating the connecting rod (21) and also comprising the cam (20) which, by actuating the switch contact (17) ensures the element stops motor (16) so that the plate (19) is always returned to its original position after the signal transmitted by the cell (3) has itself ceased; the flexible blade (23) sweeping the snow carried by the plate (19) during each movement of the latter.

8) - Device according to one. any of claims 5 to 7,

Characterized by the fact that the motor element is an electromagnet actuating a ratchet wheel, this constituting the rotary motor element driving the support of the target.

9) - Device according to any one of claims 6 or 7,

Characterized by the fact that the switch (17), which is open in the rest position, is operated by the mechanical member set in motion by the motor element so as to stop the rotation of said element at a precise point where the support intended to receive snow and cleaned of any deposit is perfectly positioned under the opening made on the plate (14) at the point of convergence of the light source (1) and the photo-sensitive cell (3), said switch ( 17) being mounted in parallel with the switch (34) driven by the relay (35) output of the signal transmitter circuit which ensures the starting of the motor only mounted itself in parallel with the external receiver alarm circuit of the signal.

10) - Device according to any one of the preceding claims,

Characterized by the fact that the electronic circuit for amplifying the signal transmitted by the light-sensitive cell (3) is provided at its output with the timer (32) which ensures the delay in the emission of the signal long enough for a only instantaneous excitation of the cell (3) does not cause the emission of an untimely signal, and of the timer (33) which regulates the duration of the emission of the signal long enough also to allow the execution of the telephone transmission when this is planned.