EP1269080B1 - Device for installing a thermocouple - Google Patents

Description

• la fonction de "sécurité froide" en cas d'extinction de flamme.
• la fonction de "sécurité chaude" en cas de prise de feu à l'injecteur et ce. sans dispositif supplémentaire,
• une longévité de fonctionnement considérablement accrue grâce au refroidissement permanent par le mélange "frais" air-gaz de ce thermocouple très fortement chauffé au niveau de ses éléments proches de la chambre de combustion.

The invention relates to the installation means. through the interior of the air-gas mixture supply duct of a gas burner, of a conventional thermocouple in order to allow it to ensure both:

• the "cold safety" function in the event of flame extinction.
• the "hot safety" function in the event of ignition of the injector. without additional device,
• a considerably increased operating life thanks to the permanent cooling by the "fresh" air-gas mixture of this thermocouple very strongly heated at the level of its elements close to the combustion chamber.

The device is particularly intended for devices whose chamber combustion works in confinement at high temperatures and nevertheless requires the positioning of the thermocouple at the level of said chamber.

In the current state of the art, thermocouples are components of a well-known safety device presented externally in the form of a sheath metallic called external conductor ending, side exposed to heat, by a probe tip in a bulb forming a sheath subject to one socket, and to the other end by an electrical connection fitting to a safety valve.

Inside the bulb sheath, a specific metal segment different from that of the bulb sheath is welded at its end to the tip of the latter. This solder is called "hot solder". This segment is extended at its other end by another solder to an insulated conductive wire enclosed in the outer conductive tube. This second weld is called "cold weld". Finally, the internal thread joined to the outlet of the conductive tube, the connection fitting to the safety valve. Driver internal and external conductor are thus connected to an electromagnetic coil with inside a safety valve. When the bulb probe tip is subjected to the heat of a burner, the temperature difference between the hot weld and the cold junction generates an electron movement and the potential difference created generates a continuous micro-current whose electromotive force is able to induce. at solenoid level of the safety valve coil. an electromagnetic field sufficient to maintain in the attracted position, against the electromagnet of said coil a movable core carrying the opening-closing valve of the safety valve. If the tip of thermocouple probe cools when heat from the burner stops when it goes out, voluntarily or not, the difference in potential disappears, and therefore also the electromagnetic field, and the valve, recalled by a spring, returns in closed position. In the current state of the art, this safety device by thermocouple is entirely satisfactory in many applications where the configuration of gas combustion devices allows to have the thermocouple of so that only the hot solder of the probe tip is exposed to heat of a flame. This is mainly the case with pilot pilot lights or combustion torches not confined in a temperature raising enclosure. And if the temperature, at the probe tip only, does not exceed 600 ° C, the longevity of the thermocouple stays within the limits of a normal service life and does not pose any special problems if not of reasonable maintenance when the wear of the point of probe exposed to oxidative combustion of an open flame eventually destroys the weld hot thus eliminating the generation of the electro-motive force sought.

The situation is not as satisfactory or even acceptable in other applications, especially new ones, where it is not possible to limit exposure to heat from the single probe tip of the thermocouple and from containing more, this exposure to heat in a temperature gradient not exceeding, at maximum, 600 ° C. This is the case, by way of nonlimiting example, of the new combustion of "high temperature" infrared emitters in refractory metal grids where the configuration sought requires the introduction of the probe tip into a confined combustion chamber to reach temperatures more or less 950 ° C.

Under these conditions, not only does the probe tip of the bulb undergo a temperature going beyond its own limits of 600 ° C for its longevity, but also the socket to which this bulb is fixed is subjected by conduction to a temperature not acceptable. It is inside and at the level of this socket that the "cold" weld. This brought to too high a temperature, affects the value of the difference potential with "hot" solder. but above all, submits the alloy segment specific between these 2 welds to inexorable destruction by loss of material following a geometry in "pencil points" opposite by the top (in the image electric arc electrodes). this deterioration going until the definitive rupture of the segment at the 2 opposite points.

To this is added immediately. upstream of the socket, the driver's attack external which becomes porous and particularly sensitive to oxidation and corrosive action burnt gases released by neighboring combustion.

• renforcement du volume de la soudure chaude.
• traitement de surface par dépôt de nickel sur la douille et sur la partie du conducteur externe proche de la zone chaude. Quoiqu'il en soit. il faut constater que ces efforts d'amélioration ne portent que sur les effets et non sur la cause.

In these conditions of temperature and proximity. the service life of a conventional thermocouple is very significantly reduced. The efforts made to extend this lifespan essentially consists in delaying these destructive effects:

• reinforcement of the volume of the hot weld.
• surface treatment by depositing nickel on the socket and on the part of the external conductor close to the hot zone. Anyway. it should be noted that these improvement efforts relate only to the effects and not to the cause.

With regard to hot safety devices, in the event of a fire the injector the known electrical cut-off devices are of "mechanical" design, whether this interruption occurs by breaking a fuse or by opening a contact thermostatic. These devices obviously constitute an additional cost, with in addition the disadvantage of "pirate" shunting always possible by an unconscious user or imprudent.

For the purpose in particular of illustrating the above, we know the US document 2,710,055 which relates to a thermocouple placed in the body of a burner comprising a hot junction subjected to the heat of the burner and a cold junction subjected to the ventilation due to feed mixture. In this way, the temperature difference between the two junctions is increased thanks to the effect of the fresh air-gas flow and, during a flame extinction, the two junctions are necessarily cooled by the mixture Power. Such a burner does not have a hot safety device.

We also know the document GB 1,536,520 which relates to a burner in which the conductors of a thermocouple are arranged inside the conduit supply so that they are both sheltered from the heat of the burner and ventilated by the fresh feed mixture flow. The burner according to this document is devoid of hot security.

We also know the document GB 1,442,745 which relates to a thermocouple mounted in a burner to ensure both the cold safety function, the junction hot being subjected to the heat of the pilot flame, and hot safety in case of internal ignition, the cold junction being subjected to the heat caused by a internal combustion of the burner.

pour la sécurité froide :

• de traiter la cause de la détérioration précoce des thermocouples lorsque ceux-ci sont placés par nécessité au sein même d'enceintes de combustion portées à haute température atteignant plus ou moins 950 °C.

pour la sécurité chaude :

• de bénéficier des conséquences induites par les moyens d'agencement mis en oeuvre afin de traiter cette cause de détérioration, pour permettre aussi au thermocouple d'assurer la fonction, de sécurité chaude sans dispositif "mécanique" de coupure électrique.

The subject of the present invention is therefore:

for cold safety:

• to deal with the cause of the early deterioration of thermocouples when they are placed out of necessity within combustion chambers brought to high temperatures reaching more or less 950 ° C.

for hot safety:

• to benefit from the consequences induced by the arrangement means implemented in order to treat this cause of deterioration, to also allow the thermocouple to perform the function, of hot safety without "mechanical" device for electrical cut-off.

And therefore to obtain a long-term use overall with a conventional thermocouple duration at a minimum cost since it is used to provide both the functions of cold and hot safety on appliances with a confined combustion chamber having the advantage of generating high temperatures. These high temperatures are particularly sought for luminous infrared emitters in order to obtain the wavelengths electro-magnetic between 1.5 and 4 micrometers.

More specifically, the invention consists of a device for arranging a thermocouple from the inside of the air-gas pipe of a gas burner ensuring both cold safety and hot safety functions, said thermocouple comprising a external conductor ending in a probe tip in a sheath bulb subject to a socket, characterized in that the downstream part of the external conductor of the thermocouple, probe tip side, penetrates inside the mixture inlet pipe air-gas, in that the probe tip at the end of the bulb abuts on the internal surface of the contact area of the perforated wall of a diffusion chamber, and in that the arrangement device comprises a plate fixed transversely to the section of the outlet of the air-gas pipe. said plate having a dimension surface suitable for performing a function of localized air-gas flow slowdown screen level of the contact zone with the internal surface of the diffusion chamber, the base of the bulb support bushing also being propped up in the lumen of the guide and positioning plate. the wafer being subject either to the outlet of the air-gas duct, ie at the base of the diffusion chamber on the outlet side of the duct.

• à positionner le thermacouple, en le faisant entrer à l'intérieur du conduit d'arrivée du mélange air-gaz, pour faire déboucher la pointe de sonde. au bout du bulbe à l'intérieur de la chambre de diffusion au centre de la chambre de combustion, ou, s'il n'y a pas de chambre de diffusion, au débouché du conduit d'alimentation dans la chambre de combustion elle-même selon des détails d'agencements qui seront décrits plus loin dans un exemple additionnel avec l'aide de la figure 3,
• à guider le bulbe 4 de l'élément sensible (pointe de sonde) du thermocouple introduit dans le conduit l'alimentation en mélange air-gaz et assurer son positionnement exact. la pointe de sonde venant buter contre la paroi interne de la grille constituant la chambre de diffusion,
• à créer par un déflecteur au débouché du tube côté chambre de diffusion une mini-zone abritée du flux frais et rapide du mélange air-gaz non encore enflammé.

It is appropriate by a general presentation, to show the operating principle of the present invention. The device which is the subject of the present arrangements and combinations therefore consists of:

• to position the thermacouple, by bringing it inside the inlet pipe of the air-gas mixture, to unblock the probe tip. at the end of the bulb inside the diffusion chamber in the center of the combustion chamber, or, if there is no diffusion chamber, at the outlet of the supply duct in the combustion chamber itself even according to details of arrangements which will be described later in an additional example with the help of FIG. 3,
• guiding the bulb 4 of the sensitive element (probe tip) of the thermocouple introduced into the duct, supplying the air-gas mixture and ensuring its exact positioning. the probe tip abutting against the internal wall of the grid constituting the diffusion chamber,
• to create by a deflector at the outlet of the tube on the diffusion chamber side a mini-zone sheltered from the fresh and rapid flow of the air-gas mixture not yet ignited.

This mini-zone. calmer. constrained a plot of the grid wall of the diffusion chamber to blush very locally. On the other side of the grid, in fact, the air-gas mixture enters combustion near the grate in the sheltered mini-zone. It is precisely at this very place that the probe tip abuts against the reddened grid or only therefore, the hot solder end is stressed by the necessary heat and sufficient to generate the electromotive force sought and therefore to obtain the function "cold" safety thanks to the sheltered mini-zone. Temperature measurements, at the forefront probe, stay around 500 ° C. Upstream of the probe tip and the bulb, all the rest of the thermocouple being ventilated by the fresh air-gas flow sees its temperature set at a level much lower than that of the hot weld. this difference reaching several hundred degrees centigrade.

In addition, this ventilation by the new and fresh flow protects it from any contact with the surrounding gases of the neighboring combustion, gases all the more corrosive as they are extremely hot, and therefore very damaging to the thermocouple as to its longevity. To perform the hot safety function, without mechanical device additional, if the injector ignites, it is the heat of this internal combustion itself, in the air-gas duct before its outlet in the diffusion chamber which is used. This internal inflammation then surrounds the external conductor of the thermocouple which runs through the interior of the conduit to the socket where the solder is located Cold. The combustion zone having thus moved from the burner into the duct, the weld cold heats up while hot solder cools. The electromotive force collapses and the gas shutdown safety is automatic. With the means put implemented according to the invention, this temperature inversion is precisely the consequence from a fire socket to the injector, for an internal thermocouple. In this eventuality in effect, the air-gas mixture igniting in the duct and no longer in the combustion, the socket containing the cold junction becomes hotter than the assembly bulb and probe tip containing the hot solder. Within a period of around 15 to 45 seconds, depending on the characteristics of the components used, the cut-off electric interrupts the ignition. The brevity of this abnormal event does not affect enough the external conductor to seriously damage it and experience shows that there should be around ten successive accidents involving the ignition of the injector, and so that nine maintenance operations of a device were neglected, to have to replace the thermocouple.

For the convenience of description. it should be described, according to the preferred mode of achievement. the most common cases where the invention can be advantageously used. This is particularly the case for infrared emitting gas burners at high temperature. according to the combustion technique in a confined room. That does not exclude other types of burners for other applications as will be mentioned later.

Figure 1 shows in longitudinal section a first example of mode of realization of a thermocouple arrangement according to the invention, in a duct burner angled air-gas inlet.

FIG. 2 shows in longitudinal section a second example of a mode of realization of a thermocouple arrangement according to the invention, in a duct burner air-gas inlet not bent.

FIG. 3 represents in longitudinal section a third exemplary mode of realization of a thermocouple arrangement according to the invention, in a burner comprising a flat grid called "flame hook" at the outlet of the tube.

FIG. 4 shows in longitudinal section a fourth example of a mode of realization of a thermocouple arrangement according to the invention, in a duct burner angled air-gas inlet.

• côté amont, d'un conduit d'arrivée du mélange air-gaz, appelé aussi tube venturi 2. Ce tube venturi comporte à son extrémité d'entrée :
  • une prise d'air neuf.
  • une valve de sécurité d'arrivée du gaz 8, qui alimente un injecteur de gaz 9 fixé au bout d'un tube porte-injecteur 10. Cet ensemble est de type classique.
• côté aval, à son extrémité de sortie du mélange air-gaz, le tube venturi 2, coudé dans l'exemple décrit, comporte avant son débouché 7 dans la chambre de diffusion 5 une plaquette de positionnement et de guidage 11 de la pointe de sonde 3 en bout du bulbe 4 du thermocouple. Sur cette plaquette de positionnement 11 est ménagée une lumière 12 dans laquelle est engagé le bulbe 4 du thermocouple. Une fois cette plaquette traversée, la pointe de sonde 3 vient buter contre la surface interne 13 de la grille constituant la paroi de la chambre de diffusion 5. Cette solution d'assujettissement de la plaquette à la base du tube d'arrivée du mélange air-gaz est, dans l'exemple présent une solution commode.

With regard to FIG. 1, the relevant part of the burner, which is the subject of the description, essentially consists of:

• upstream side, an air-gas mixture inlet pipe, also called a venturi tube 2. This venturi tube has at its inlet end:
  • a fresh air intake.
  • a gas inlet safety valve 8, which supplies a gas injector 9 fixed to the end of an injector holder tube 10. This assembly is of conventional type.
• downstream side, at its outlet end of the air-gas mixture, the venturi tube 2, bent in the example described, comprises, before its outlet 7 in the diffusion chamber 5, a positioning and guide plate 11 of the probe tip 3 at the end of bulb 4 of the thermocouple. On this positioning plate 11 is formed a light 12 in which is engaged the bulb 4 of the thermocouple. Once this wafer has been crossed, the probe tip 3 abuts against the internal surface 13 of the grid constituting the wall of the diffusion chamber 5. This solution for securing the wafer to the base of the air mixture inlet tube -gaz is, in the present example, a convenient solution.

However, this solution is not exclusive. and it can be beneficial in other configurations, to fix the plate, not to the tube, but at the level of the chamber of diffusion itself, at its base of contact with the tube.

The main thing is that the function of guiding, positioning the bulb and contact with the grid of the diffusion chamber is ensured. whatever the means equivalent.

The guide and positioning plate is oriented across the movement longitudinal of the air-gas flow so that its surface forms a deflector at velocity flow to the outlet of the venturi tube. This creates a quieter flow mini-zone between the unexposed face of the wafer 11 and the internal surface portion 13 of the wall of the diffusion chamber because it is sheltered under the plate. This calmer flow, when it ignites on the external face of the grid of the diffusion chamber at the mini-zone. ignites at the bottom of the grid which then presents a small surface of localized reddening of the grid metal, precisely around the point of contact of the probe tip with grid. This is the aim sought to heat only the end of the hot welding of the probe tip without affecting the rest of the thermocouple by the effects harmful from too high a temperature. Interposition of a grid between the probe tip (hot welding) and the combustion flame also has the advantage of protect this point from deterioration favored by the oxidizing nature of a flame naked. Experience shows the importance of this factor on the loss of longevity of the spikes. thermocouple probe.

To complete the description of the precise thermocouple guide means, after its introduction upstream of the venturi tube to bring the probe tip to the center of the light 12 of the guide and positioning plate, it should be noted than the tubular section. concave inside, of the bent part of the tube (convex to outside), particularly suitable for automatic guidance of the probe tip. Like the talweg line of a channel, there is only one line of greatest slope, and a alone, at the bottom of the concavity of the tube. that the probe tip will slide necessarily towards the center of the light of the positioning plate, placed at plumb with this sliding line.

In the case of other device configurations. especially the burners comprising a non-bent venturi tube 2, whether vertical or oblique, FIG. 2 shows how the guide of introduction and positioning of the thermocouple by a sheath adjacent 18 can be secured as rigorously, thanks to the "channel" effect of inside the tube, immediately upstream of its outlet in the chamber diffusion.

It is then necessary to seal, as shown in Figure 2, around the conductor external of the thermocouple the free end of the adjacent sheath as well so as not to disrupt the air-gas flow than prevent any unwanted flow return by the sheath.

• de conserver l'effet de "rigole" à l'intérieur du tube. tel que décrit plus haut.
• de permettre à la partie aval du conducteur externe du thermocouple introduite par le fourreau à l'intérieur du tube et donc située au dessus de la douille 14 du thermocouple de bénéficier, sur une longueur suffisante pour son refroidissement. de la ventilation du flux frais air-gaz se dirigeant vers le débouché 7.

It may also prove to be advantageous to use an adjacent sheath 18 for introduction and positioning guide on an apparatus comprising a bent venturi tube. FIG. 4 illustrates this possibility, the adjacent sheath 18 joining the tube 2 at the most appropriate place of said tube, the essential being:

• to keep the "laughing" effect inside the tube. as described above.
• allow the downstream part of the external conductor of the thermocouple introduced by the sheath inside the tube and therefore located above the sleeve 14 of the thermocouple to benefit, over a length sufficient for its cooling. the ventilation of the fresh air-gas flow towards the outlet 7.

It should be noted that if the adjacent sheath 18 cannot be placed for a reason any in the longitudinal plane of symmetry of the bent tube. but laterally offset in a plane oblique to the longitudinal plane, the line of greatest slope forming "channel" is located in this oblique plane. Consequently. the wafer 11 and its bulb 12 for guiding the thermocouple bulb 4 must be arranged in this plane oblique since it contains the bottom line of "fun".

It is also suitable in the configuration shown in Figure 4 and as in the case of the non-bent tube of the configuration shown in FIG. 2. to close off, around the external conductor of the thermocouple the free end of the adjacent sheath 18 by a blocking and obturation element: beyond this free end of the sleeve the thermocouple external conductor is outside the air-gas duct and joins the safety valve 8 to which it is conventionally connected.

• par la face externe de la paroi de la chambre de diffusion citée plus haut. et
• par la face interne de l'enceinte extérieure de la dite chambre de combustion. C'est dans cet espace compris entre ces deux parois que se produit l'inflammation et la combustion du mélange air-gaz à haute température. cette dernière pouvant atteindre plus ou moins 950°C. On remarquera donc que le thermocouple se trouve bien, quant à lui, entièrement séparé de cet espace où a lieu la combustion, puisque, même sa pointe de sonde 3 est de l'autre côté de la chambre de diffusion.

The "combustion" part of the burner taken with reference to description with FIG. 1 finally comprises a combustion chamber 6 whose volume is defined:

• by the external face of the wall of the diffusion chamber mentioned above. and
• by the internal face of the external enclosure of said combustion chamber. It is in this space between these two walls that ignition and combustion of the air-gas mixture takes place at high temperature. the latter possibly reaching more or less 950 ° C. It will therefore be noted that the thermocouple is indeed well separated from this space where combustion takes place, since even its probe tip 3 is on the other side of the diffusion chamber.

To extend the application according to the invention to other burners, as shown in FIG. 3, normally not comprising a conical diffusion chamber, cylindrical or other, but only and at best a flat grid called "flame hook" at the outlet 7 of the tube 2. provision should be made at this level. following the same principle that that described above, a calm and protected space. This space is actually a mini-diffusion chamber 19 in finely perforated refractory metal with, at its entrance tube side, a plate 11 with insertion light 12 for the probe tip and the bulb. This plate must have an area less than the cross section of the mini-chamber diffusion to leave the fresh (therefore not ignited) flow of the air-gas mixture fill the interior volume of said mini-chamber through this entry. We reconstruct thus the protection conditions of the sensitive end of the thermocouple as well as obtains the desired ventilation of the socket and the external conductor of the thermocouple.

a) côté pointe de sonde en bout de bulbe :

la douille 14 d'assujettissement du bulbe 4 est utilisée sur ses premiers millimètres de jonction au bulbe comme palier d'appui dans la lumière 12 de la plaquette de guidage et de positionnement 11;

   la pointe de sonde, au niveau de sa soudure chaude 3, rencontre comme point de butée et d'appui la paroi interne de la chambre de diffusion;
   dans la présente description de la configuration préférée selon la figure 2, comme dans la configuration représentée figure 4, l'ensemble bulbe-douille du thermocouple se trouve calé. naturellement, par effet de "coin", entre ses deux points d'appui, ce calage étant favorisé par l'oblicité de la paroi conique de la chambre de diffusion 5;
   dans d'autres configurations comme par exemple celle d'une chambre de diffusion cylindrique 20, l'effet de "coin" de l'ensemble bulbe-douille contre la grille de la chambre de diffusion est avantageusement obtenu, par exemple par une protubérance cylindro-conique 21 sur la douille 14, à l'aplomb amont de la plaquette de guidage et de positionnement. Cette protubérance 21, qui peut être une bague enfilée en force sur la douille, en prenant appui sur la paroi interne du tube venturi. donne à l'ensemble bulbe-douille l'oblicité qui pourrait lui manquer en raison de la verticalité de la paroi cylindrique de la chambre de diffusion.

b) Côté entrée du tube venturi :

il convient d'immobiliser le conducteur externe du thermocouple afin d'empêcher son recul et garantir ainsi la permanence du contact en butée de la pointe de sonde contre la paroi interne 13 de la chambre de diffusion: cet assujettissement précis du conducteur externe par rapport au tube venturi est assuré par deux moyens commodes dans le cas de la configuration décrite :

• sur le tube venturi :
• une vis de serrage 15 au niveau de l'entrée d'air bloque dans la position adéquate le conducteur externe 16 du thermocouple 1 en le pressant contre le tube injecteur de gaz 10,
• sur le conducteur externe :
• une saillie-repère 17, formant butée. empêche le conducteur de s'engager plus profondément dans le tube. Elle sert aussi de repère de positionnement si cet engagement est au contraire insuffisant. Un moyen intéressant de réalisation de cette saillie-repère 17 consiste à utiliser un segment de gaine thermorétractable présentant l'avantage d'être aisément enfilé dans le thermocouple avant chauffage de rétraction et d'être rigoureusement positionné après ce chauffage. Il va de soi que tous autres moyens donnant un résultat équivalent peuvent être utilisés, particulièrement dans le cas d'autres configurations, l'essentiel étant d'assurer le maintien systématique du thermocouple interne dans la position adéquate d'assujettissement.

One can therefore use including in these other configurations a thermocouple of conventional constitution and arrange it as follows:

a) probe tip side at the end of the bulb:

the socket 14 for securing the bulb 4 is used on its first millimeters of junction with the bulb as a bearing in the lumen 12 of the guide and positioning plate 11;

the probe tip, at its hot weld 3, meets as an abutment and support point the internal wall of the diffusion chamber;
in this description of the preferred configuration according to Figure 2, as in the configuration shown in Figure 4, the bulb-socket assembly of the thermocouple is wedged. naturally, by "wedge" effect, between its two support points, this setting being favored by the obliquity of the conical wall of the diffusion chamber 5;
in other configurations such as that of a cylindrical diffusion chamber 20, the "wedge" effect of the bulb-socket assembly against the grid of the diffusion chamber is advantageously obtained, for example by a cylindrical protuberance -conical 21 on the socket 14, vertically upstream of the guide and positioning plate. This protuberance 21, which may be a ring forcibly threaded onto the sleeve, bearing on the internal wall of the venturi tube. gives the bulb-socket assembly the obliquity that it might lack due to the verticality of the cylindrical wall of the diffusion chamber.

b) Inlet side of the venturi tube:

it is necessary to immobilize the external conductor of the thermocouple in order to prevent its recoil and thus guarantee the permanence of the contact in abutment of the probe tip against the internal wall 13 of the diffusion chamber: this precise subjection of the external conductor relative to the Venturi tube is provided by two convenient means in the case of the described configuration:

• on the venturi tube:
• a clamping screw 15 at the air inlet blocks the external conductor 16 of the thermocouple 1 in the appropriate position by pressing it against the gas injector tube 10,
• on the external conductor:
• a reference projection 17, forming a stop. prevents the conductor from going deeper into the tube. It also serves as a positioning benchmark if this commitment is insufficient. An interesting means of producing this reference projection 17 consists in using a segment of heat-shrinkable sheath having the advantage of being easily threaded into the thermocouple before heating of shrinkage and of being rigorously positioned after this heating. It goes without saying that any other means giving an equivalent result can be used, particularly in the case of other configurations, the main thing being to ensure the systematic maintenance of the internal thermocouple in the adequate securing position.

Among these other means of subjugation and benchmarks, we can mention those shown in 22 and 23 in Figure 2 which also seal the free end of the adjacent sheath 18, as well as that represented at 24 and 25 in FIG. 4. The reference 25 is then a projection fixed on the external conductor of the thermocouple, downstream of the means of tightening and shutter 24, and therefore inside the sheath 18. The blocking of the conductor of the thermocouple and positioning of the probe tip 3 is ensured when the screw 24, through which the external conductor of the thermocouple passes, is screwed in fully.

In summary, by the detailed description above, the device and the means of exposed arrangements allow the use of a conventional thermocouple, by installing of its downstream part, probe tip side, inside the inlet pipe to the burner of the air-gas mixture. Its upstream part, meanwhile, opens to the outside, either at the end air-gas inlet of the bent venturi tube, either by an adjacent sheath joining said tube, whether straight or angled, upstream of its outlet inside the chamber diffusion.

• en s'affranchissant de la limite de température au dessus de laquelle la résistance matérielle du thermocouple n'est plus assurée.
• en utilisant, en cas de combustion interne dans le conduit d'arrivée du mélange air-gaz. l'inversion de température entre la soudure chaude et la soudure froide du thermocouple en raison de son échauffement à l'intérieur du conduit où le mélange air-gaz est entré en combustion. Le résultat est l'interruption rapide de cette prise de feu à l'injecteur par effondrement de la force électromotrice ayant pour conséquence finale la fermeture de l'arrivée du gaz à la valve de sécurité.

So are assured at once. after connection of the thermocouple to the safety valve, the cold safety and hot safety functions. in "high temperature" burners:

• by overcoming the temperature limit above which the material resistance of the thermocouple is no longer ensured.
• using, in the event of internal combustion in the inlet pipe of the air-gas mixture. the temperature inversion between the hot junction and the cold junction of the thermocouple due to its heating inside the duct where the air-gas mixture entered into combustion. The result is the rapid interruption of this ignition catch at the injector by collapse of the electromotive force having the final consequence of shutting off the gas supply to the safety valve.

Claims (6)

1. Device for installing a thermocouple (1) in the interior of the air-gas duct (2) of a gas burner so as to ensure the functions both of cold safety and of hot safety, said thermocouple comprising an external conductor, which terminates in a sensor point (3) in a bulb (4) forming a sleeve secured to a casing (14), characterised in that the downstream portion of the external conductor of the thermocouple, on the sensor point (3) side, is capable of penetrating into the interior of the inlet duct (2) for the air-gas mixture, in that the sensor point (3) at the end of the bulb (4) is capable of being supported on the internal surface of the contact zone (13) of the perforated wall of a diffusion chamber (5, 19), and in that the installation device comprises a small plate (11) secured transversely to the outlet section (7) of the air-gas duct (2), said small plate having an appropriately dimensioned surface, to fulfil the function of a localised retardant screen for the air-gas flow, at the level of the contact zone (13) with the internal surface of the diffusion chamber (5, 19), the base of the casing (14) for supporting the bulb (4) also being supported in the gap (12) of the small guiding and positioning plate (11), the small plate (11) being secured either to the outlet of the air-gas duct (2) or to the base of the diffusion chamber on the outlet (7) side of the duct.
2. Device according to Claim 1, characterised in that the casing for supporting the bulb (14) is provided with a protuberance (21), the profile of which determines the inclination and the adequate wedging of the sensor point (3) against the contact zone (13) of the internal surface of the wall of the diffusion chamber (5).
3. Device according to Claim 1 or 2, characterised in that, in the case where the body of the burner is organised about a vertical axis, with an air-gas duct (2) which is substantially vertical on the outlet (7) side, the downstream portion of the thermocouple, on the sensor point (3) side, is capable of penetrating into the interior of the air-gas duct (2) upstream of the outlet through an adjacent guide sleeve (18) which connects with said duct (2), the external conductor of the thermocouple then being integral, at the level of its marker-projection (22), with the free end of the adjacent sleeve through a locking and blocking element (23).
4. Device according to Claim 1 or 2, characterised in that, in the case where the body of the burner comprises a bent air-gas duct, the downstream portion of the thermocouple, on the sensor point (3) side, is capable of penetrating into the interior of said air-gas duct (2) through the upstream end of the Venturi tube (2) on the air-gas mixture inlet side, the external conductor (16) of the thermocouple (1) then being integral, at the level of its marker-projection (15), through a locking means (17).
5. Device according to Claim 1 or 2, characterised in that, in the case of apparatuses comprising a bent air-gas duct, the downstream portion of the thermocouple, on the sensor point side, is capable of penetrating into the interior of the air-gas duct, either through the end of this duct on the air-gas inlet side, or through an adjacent sleeve connecting with said duct, the upstream portion of the external conductor of the thermocouple, which comprises, at its end, the connection to the safety valve (8), being situated on the outside of the duct on the air-gas inlet side in every case.
6. Device according to Claim 1, characterised in that, in the case of burners which do not comprise a diffusion chamber but only, at best, a "flame-catcher" grille, a diffusion mini-chamber (19) and a small guiding and positioning plate (11) are integrated, at the level of the outlet (7) of the air-gas mixture duct (2), with the inlet of the combustion chamber (6).

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