EP0409738B1 - Back draught security device for flue breaker in a boiler with atmospheric burner - Google Patents

Abstract

The invention relates to a back draught security device for the flue breaker (9) of a boiler (1) with an atmospheric burner (3), comprising a control thermostat serving to detect an abnormal rise in temperature, and making it possible in this case rapidly to interrupt the electric supply of the burner, as well as a delay means which allows resetting with a given delay. According to an essential aspect of the invention, the thermostat (150) is arranged against a wall (17) of the flue breaker (9) in order to detect the heating of a predetermined zone of the latter which is greatly stressed in the event of back draught; the thermostat (150) acts directly on the electric supply of the burner (3) when this heating reaches a given threshold, and the delay is ensured by a thermal insulation device (160) arranged against said predetermined zone of the wall in order to slow its cooling, the thermal inertia of this insulation means being selected so that the delay obtained corresponds at least to the given delay time. Application to flue breaker boilers with atmospheric burners. <IMAGE>

Description

The invention relates to the field of gas or atmospheric burner boilers, and more particularly the overflow security of the draft hood of such boilers.

The terminology "overflow" commonly used by specialists in this field, covers the concept of accidental escape of hot gases (fumes), for example in the event of total or partial blockage of the exhaust duct, or of discharge caused by a downwind which momentarily reverses the direction of flue gas flow in the chimney.

In boilers with atmospheric burners, a mixture of gas and primary air (atmospheric induction) is admitted into the burner, and secondary air is drawn into the hearth during combustion. When the gases (fumes) reach the top of the fireplace, it is considered that complete combustion has been carried out. The hot gases thus transmit their heat to exchanger elements in which the water circulates from the central heating circuit, and the cooled gases are then conducted in what is called a "draft hood".

The draft hood of an atmospheric burner boiler can be arranged differently depending on the type of boiler concerned, but its functions remain essentially the same.

The presence of a draft hood is intimately linked to the open circuit operation of a boiler with atmospheric burner (the very low pressure regime is associated with large variations in volume), and the draft hood of a boiler with atmospheric burner is an important part of the boiler, especially since it must fulfill several functions.

The draft cutter firstly regulates the effect of variations in the chimney draft. The draft hood indeed has an opening which, in normal operation, allows suction of the outside air diluting the smoke by a supply of cold air. This dilution leads to a lowering of the dew point temperature of the combustion products to avoid condensation in the chimney.

The draft hood also intervenes in the event of an anomaly in the chimney draft conditions, allowing in this case a total or partial overflow of the fumes, thereby avoiding affecting the good combustion characteristics of the burner: this overflow manifested by the exit of hot gases through the lower opening which is used, in normal operation, to take in the cold dilution air. Thus, when the draft is insufficient, the gases are discharged into the room through the lower opening of the draft hood, without appreciable alteration of the combustion.

As typical cases of anomaly in the draft conditions, we can cite the total or partial obstruction of the chimney (the case of bird nests is typical to cause such an obstruction), but also the backflow caused by a strong downward wind. , for example 3 mls, which reverses for a more or less long time the direction of flow of the fumes in the chimney.

The problem of the discharge of smoke into the room concerned, a fortiori if the boiler is installed in rooms receiving people, has therefore led manufacturers to consider the need to provide overflow security.

It should be noted that the combustion gases contain on the one hand non-toxic carbon dioxide and water vapor, and on the other hand traces of extremely toxic carbon monoxide: the draft hood makes it possible to maintain these traces within strict limits set by specifically provided regulations or standards. However, in the event of prolonged overflow in a room with insufficient ventilation, pollution of the atmosphere may occur by increasing the level of carbon dioxide and carbon monoxide.

As a result, any device that interrupts the boiler in the event of inadvertent backflow further increases user safety.

The draft hood is often placed behind the hearth-exchanger unit, and is then in the form of a casing open above for connection to the chimney, and below for admitting dilution air, the fumes entering the casing by a associated side opening. Such an arrangement is entirely suitable for boiler room installations arranged in a cellar, where the problems of space and / or aesthetics are not critical.

However, when the boiler is installed in a living room, it is generally preferred, for reasons of aesthetics and size, a different arrangement of the draft hood, according to which the dilution opening of said draft hood is arranged. on the front of the boiler. One can also provide a draft hood located in the upper part of the boiler: in this case, the casing is for example of conical shape, and disposed directly above the outlet nozzle, leaving a lower annular clearance to define the dilution air passage.

Some countries, such as the Federal Republic of Germany for example, have already provided for regulations obliging manufacturers to equip all atmospheric burner boilers with a useful power of 10 to 50 kW with an overflow safety device capable of '' stop the burner within fixed times according to certain precise conditions, in the event of total or partial obstruction of the chimney, and this within two or six minutes.

In the event of a safety shutdown, there are two possible cases, depending on whether the boiler is restarted manually with the intervention of the user, or automatically. In the case of an automatic restart, a time delay corresponding to a minimum waiting time is provided to allow the room to be sanitized by natural ventilation: a waiting time of fifteen minutes is usually considered sufficient.

Automatic restart is the solution most often sought by manufacturers, for obvious reasons of ease of use.

However, after an initial intervention of the overflow safety device, and after the given waiting time has elapsed, it is possible that the causes which caused the overflow are still present: in this case, the safety must be reset again in action at next start.

The problem of designing an overflow safety device allowing automatic restarting of the boiler is currently the subject of active and in-depth studies.

There are already overflow safety devices with automatic reset, fitted to many atmospheric burner boilers.

These devices are of the type comprising a control thermostat serving to detect an abnormal rise in temperature corresponding to an anomaly in the draft conditions, and in this case making it possible to quickly cut off the electrical supply to the burner, as well as a delay means authorizing restarting the boiler after a given waiting time following the burner shutdown.

In general, manufacturers have so far proposed on the one hand to have the control thermostat inside the draft hood, in an area which remains at room temperature in normal operation, and which, in in case of overflow, undergoes a significant rise in temperature caused by an abnormal flow of hot gases, and on the other hand to realize the delay means in the form of a timed relay, interposed in the electrical circuit between the thermostat and the control of the burner gas valve.

The control thermostat (or thermostatic probe) is usually bimetallic and of the normally open type, and the time relay of the coil type.

Thus, as soon as the temperature rise exceeds the thermostat set point (for example 60 ° C), said thermostat closes, and the time relay is energized: this triggering automatically causes a cut in the electrical supply to the burner, and this cutoff is maintained for a given waiting time (for example fifteen minutes) thanks to the action of the timed relay.

However, such a design has many drawbacks, both technically and commercially, essentially inherent in the presence of the time relay and in the mode of operation of the thermostat.

• . en cas de défaillance du circuit électrique et/ou du thermostat, (par exemple une oxydation de la zone de contact dans la position de repos normalement ouverte du thermostat), l'absence de commande d'arrêt du brûleur provoque un débordement continu, avec le danger que cela comporte au niveau du confinement de l'ambiance ;
• . en cas de défaillance du relais temporisé (par exemple si la bobine du relais est grillée), la commande d'arrêt et/ou de réenclenchement du brûleur ne fonctionne pas (il convient d'ailleurs de noter qu'avec ce type de sécurité, on ne peut pas savoir en cours de fonctionnement si la sécurité est active ou non).

On the technical level, there are many risks of breakdown:

• . in the event of a fault in the electrical circuit and / or the thermostat (for example an oxidation of the contact area in the normally open rest position of the thermostat), the absence of a burner stop command causes a continuous overflow, with the danger that this entails in terms of containing the atmosphere;
• . in the event of a time relay failure (for example if the relay coil is burnt out), the burner stop and / or reset command does not work (it should also be noted that with this type of security, you cannot know during operation whether security is active or not).

On the commercial level, the presence of the timed relay puts a heavy burden on the cost of the safety device (as an indication, the timed relay accounts for almost 90% of the total cost of the systems currently marketed).

In document DE-A-31 37 740, typical of the prior art, is described an overflow safety device associated with the draft hood 8 of a boiler 1 with atmospheric burner 7 comprising a control thermostat 27 serving to detect a Abnormal rise in temperature corresponding to an anomaly in the draft conditions, and in this case making it possible to quickly cut off the electrical supply to the burner, as well as a delay means authorizing the restarting of the boiler after a given waiting time following the burner cut-out, with the thermostat 27 placed against a wall of the draft hood in order to detect the heating of a predetermined area of the latter which is highly stressed in the event of overflow, said thermostat acting directly on the electrical supply of the burner 7 when this heating reaches a given threshold.

The object of the invention is to provide an overflow safety device which does not have the aforementioned drawbacks.

The object of the invention is also to provide a safety device which is simple in structure and of high reliability, while being compatible with any regulations already in force.

The object of the invention is also to design a security device the cost of which is accessible, which is compatible with marketing a kit, and which can be mounted by a non-specialized user.

It is more particularly an overflow safety device associated with the draft hood of an atmospheric burner boiler comprising a control thermostat serving to detect an abnormal rise in temperature corresponding to an anomaly in the draft conditions, and allowing in this case to quickly cut off the electrical supply to the burner, as well as a delay means authorizing the restarting of the boiler after a given waiting time following the burner shutdown, the thermostat being placed against a wall of the cutter -drawing to detect the heating of a predetermined area thereof which is highly stressed in the event of an overflow, said thermostat acting directly on the electrical supply to the burner when this heating reaches a given threshold, characterized in that the delay is ensured by means d thermal insulation surrounding the thermostat, said insulation means being disposed against said predetermined area of the wall to slow the cooling, and having a thermal inertia such that the delay thus obtained corresponds at least to the given waiting time.

According to a preferred embodiment, the thermostat is a contact thermostat with a wide operating range, said range being adapted to the thermal inertia of the thermal insulation means.

More particularly, the thermostat is preferably chosen to open at around 60 ° C and to close at around 35 ° C.

In the particular case of a draft hood provided behind the boiler, it is advantageous for the thermostat to be arranged against the rear wall of said draft hood.

Preferably then, the thermostat is held in abutment against the rear wall of the draft hood, on the outside of the latter; advantageously in this case, the thermal insulation means is arranged outside the rear wall of the draft hood, so as not to disturb the flow in said draft hood.

It is also advantageous to provide that the thermal insulation means also keeps the thermostat in place, which considerably simplifies the installation of the safety device.

Preferably, the thermal insulation means consists of an insulating material surrounded by a cover fixed against the rear wall of the draft hood.

Advantageously in this case, the insulating material consists of a heat-insulating block having a central opening for housing the thermostat, possibly with a second heat-insulating block closing said central opening behind said thermostat.

According to a preferred embodiment, the second block of insulation is compressed in thickness, so as to have a spring effect making it possible to maintain the thermostat; alternatively, a spring can be arranged between the thermostat and the second heat-insulating block, in order to maintain said thermostat.

Advantageously, the first block of insulation is made of rock wool, while the second block of insulation is made of glass wool.

Preferably also, the cover carries a cable gland, from which a connection cable comes out through which the thermostat connection wires pass and an earth connection.

According to a particular embodiment, the insulating material is rectangular in shape, and has a thickness at least equal to 20 mm.

Furthermore, it is advantageous for the thermostat to be arranged in the vertical plane of symmetry of the draft hood passing through the axis of the nozzle connecting to the chimney, at a level corresponding to a zone of high stress in the event of overflow; preferably also, the thermostat is arranged at a level corresponding to a substantially constant distance from the lower edge of the draft hood, for different boilers but whose draft hood is of similar construction.

Advantageously, finally, the thermostat is of the normally closed type.

• la figure 1 est une coupe illustrant une chaudière à brûleur atmosphérique, munie d'un coupe-tirage disposé ici en arrière de ladite chaudière, conformément à une construction classique, et normalement équipée d'un dispositif de sécurité de débordement connu à thermostat et relais temporisé (non visible sur la figure) ;
• la figure 2 représente le montage électrique d'un dispositif de sécurité de débordement connu à thermostat et relais temporisé, et la figure 3 illustre schématiquement le fonctionnement de ce dispositif, avec une séquence de coupure du brûleur en cas de débordement ;
• la figure 4 est une coupe illustrant une chaudière du type de celle de la figure 1, mais équipée d'un dispositif de sécurité de débordement conforme à l'invention, monté ici à l'extérieur de la paroi arrière du coupe-tirage ;
• la figure 5 représente le montage électrique du dispositif de sécurité de débordement conforme à l'invention, à rapprocher du montage antérieur de la figure 2 (le thermostat constitue en fait le seul organe électrique), et la figure 6 illustre schématiquement le fonctionnement de ce dispositif, à rapprocher du fonctionnement antérieur illustré en figure 3 ;
• la figure 7 est une vue en plan illustrant le moyen d'isolation thermique entourant le thermostat, ce qui permet d'assurer la temporisation, ces deux organes constituant en réalité les composants essentiels du dispositif de sécurité de débordement objet de l'invention ;
• les figures 8a, 8b, 8c sont des coupes selon VIII-VIII de la figure 7, illustrant trois variantes de montage du thermostat, avec un maintien dudit thermostat assuré respectivement par un bloc central comprimé de calorifuge présentant un effet ressort, ou par un ressort disposé entre le thermostat et un bloc central de calorifuge, ou par vissage direct sur la paroi du coupe-tirage ;
• la figure 9 est une vue en perspective éclatée illustrant le montage du dispositif de l'invention sur le coupe-tirage d'une chaudière, et la figure 10 illustre le dispositif monté ;
• la figure 11 est une vue en perspective éclatée illustrant une variante du montage de la figure 9, selon laquelle le thermostat est vissé directement sur la paroi du coupe-tirage, et la figure 12 illustre le dispositif monté ;
• la figure 13 est une coupe illustrant la structure du thermostat avantageusement utilisé, du type normalement fermé.

Other characteristics and advantages of the invention will appear more clearly in the light of the description which follows and of the appended drawings, relating to a particular embodiment, with reference to the figures in which:

• Figure 1 is a section illustrating an atmospheric burner boiler, provided with a draft hood arranged here behind said boiler, in accordance with a conventional construction, and normally equipped with a known overflow safety device with thermostat and relay timed (not visible in the figure);
• FIG. 2 represents the electrical assembly of a known overflow safety device with thermostat and timed relay, and FIG. 3 schematically illustrates the operation of this device, with a burner cut-off sequence in the event of overflow;
• Figure 4 is a section illustrating a boiler of the type of that of Figure 1, but equipped with an overflow safety device according to the invention, mounted here outside the rear wall of the draft cutter;
• FIG. 5 represents the electrical assembly of the overflow safety device according to the invention, to be compared to the previous assembly of FIG. 2 (the thermostat in fact constitutes the only electrical member), and FIG. 6 schematically illustrates the operation of this device, to be compared to the previous operation illustrated in FIG. 3;
• Figure 7 is a plan view illustrating the thermal insulation means surrounding the thermostat, which ensures timing, these two bodies actually constituting the essential components of the overflow safety device object of the invention;
• Figures 8a, 8b, 8c are sections according to VIII-VIII of Figure 7, illustrating three variants of mounting the thermostat, with said thermostat being maintained respectively by a compressed central block of insulation having a spring effect, or by a spring disposed between the thermostat and a central block of insulation, or by direct screwing on the wall of the draft hood;
• Figure 9 is an exploded perspective view illustrating the mounting of the device of the invention on the draft hood of a boiler, and Figure 10 illustrates the device mounted;
• Figure 11 is an exploded perspective view illustrating a variant of the assembly of Figure 9, according to which the thermostat is screwed directly on the wall of the draft hood, and Figure 12 illustrates the device mounted;
• FIG. 13 is a section illustrating the structure of the thermostat advantageously used, of the normally closed type.

Figure 1 is a section illustrating a boiler with atmospheric burner, provided with a draft hood which is here arranged in the rear part of said boiler, in accordance with a conventional construction.

The boiler 1 thus comprises a body 2, in the lower part of which a burner 3 is provided, connected to a manifold 4 for the gas inlet. There is also a hearth 5, above which is provided a battery of exchanger elements 6. In the upper part of the heating body 2, an upper cover 7 is provided delimiting a confined outlet space 15, said upper cover having a hatch inspection 8, and extending, here backwards, by a draft hood 9 with which it communicates by a lateral opening 12. The draft hood 9 is in the form of a rectangular housing, open above the level a nozzle 10 for connection to the chimney, and lower at 11 for the entry of dilution air.

During normal operation, the path taken by the hot gases (fumes) is illustrated by continuous arrows starting from the hearth and passing through the exchanger, to exit in the upper part of the draft hood 9. This main flow is combined a flow of dilution air penetrating through the lower opening 11 of the draft hood 9. Also illustrated by hatched arrows 13 are the combustion air inlets in the lower part of the heating body 2, and by hatched arrows 14 the dilution air inlet at the bottom of the draft hood 9.

As explained above, the draft cutter 9 first of all makes it possible to regularize the effect of the variations in the draft of the chimney, and allows a dilution of the fumes by a supply of cold air. The draft hood 9 also intervenes in the event of anomalies in the chimney draft conditions, allowing in this case a total or partial overflow of the fumes thereby avoiding affecting the good combustion characteristics of the burner 3. In case of overflow, the hot gases then exit through the lower opening 11 of the draft hood 9, opening which is normally concerned by the cold dilution air.

Figures 2 and 3 illustrate the mounting and operating mode of an overflow safety device usually fitted to an atmospheric burner boiler of the type described above.

FIG. 2 thus makes it possible to distinguish the control thermostat 50, normally open, and a time relay 51 whose movable member 52 makes it possible to interrupt the line 54 serving for the supply of a gas valve of the burner 53 (the line 55 corresponds to neutral). It is important to note that the known overflow safety device thus uses two electrical members linked together, namely a control thermostat 50, and a time relay 51.

The operation of this overflow safety device is illustrated in FIG. 3, on which the mode of intervention of said device in the event of an overflow is shown.

In the left part of the diagram, the system is in an operating state corresponding to normal conditions: the control thermostat 50 is open, which corresponds to its rest position, so that the time relay 51 is not supplied. The sequence diagram 56 thus corresponds to normal walking; on the diagram giving the variations of the temperature of the control thermostat as a function of time, this results in a temperature curve 56 ′ entirely disposed below a predetermined overflow threshold, for example 60 ° C. In the event of abnormal heating, the control thermostat 50, disposed in the interior space 16 of the draft hood 9, closes suddenly when the threshold of 60 ° C is reached, which has the effect of acting on the relay timed 51 so that the movable member 52 thereof opens the circuit, which causes the burner to shut down: on the sequence diagram, this corresponds to a phase 57 of shutdown of the burner. The time relay 51 provides a given time delay, for example 15 min, during which the system cools freely, which corresponds to a segment 57 ′ on the temperature curve. At the end of 15 minutes, the time delay is released, and, if the abnormal conditions have stopped, the burner is automatically restarted if the abnormal conditions still exist, the control thermostat 50 closes again, for a new time delay by l time delay relay intervention 51.

The drawbacks of such a system, both technically and commercially, have already been mentioned previously.

Thus, according to the known prior art, it was only known to make an overflow safety device associated with the draft hood 9 of a boiler 1 with atmospheric burner 3, comprising a control thermostat 50 used to detect an abnormal rise in temperature corresponding to an anomaly in the draft conditions, and in this case making it possible to quickly cut the electrical supply to the burner 3, as well as a time delay means, generally produced in the form of a time relay 51, authorizing the restarting of boiler after a given waiting time following burner shutdown 3.

According to the invention, and as illustrated in FIG. 4, the draft hood 9 of the atmospheric burner boiler is equipped with an overflow safety device 100, in which the control thermostat 150 is arranged against a wall of the draft hood 9 in order to detect the heating of a predetermined area thereof which is highly stressed in the event of overflow, said thermostat acting directly on the electrical supply of the burner 3 when this heating reaches a given threshold; in addition, the delay is ensured by a thermal insulation means 160, surrounding the thermostat 150, said insulation means being disposed against said predetermined area of the wall to slow the cooling, and having a thermal inertia such as the delay thus obtained corresponds at least to the given waiting time.

It goes without saying that the particular arrangement of the draft hood which is illustrated in the figures (rear arrangement) is only one example: it would naturally be possible to associate the security device of the invention with a draft hood arranged on the front or upper part of the boiler.

Whatever the layout of the draft hood, the predetermined area of the wall whose temperature is to be detected must be chosen as being a highly stressed area in the event of overflow: we are in fact seeking to have a reaction that is both rapid at an increase in temperature, and reproducible.

Therefore, in the particular case of a draft hood placed behind the boiler, it appears advantageous to have the control thermostat against the rear wall of the draft hood, as illustrated in FIG. 4.

A fundamental difference is already apparent between the overflow safety device 100 according to the invention, and the prior devices: a single electrical member is used, namely the thermostat 150, the timing function being essentially ensured not by electro-mechanical means, but by purely static thermal insulation means, the operating range of the thermostat and the thermal inertia of the thermal insulation means being also chosen so that the delay obtained corresponds at least to given waiting time that could be obtained using a time relay. It will in particular be advantageous for the thermostat 150 to be a contact thermostat with a wide operating range, for example a thermostat opening at around 60 ° C and closing at around 35 ° C.

The simplification obtained, with the progress which results therefrom, emerges clearly from FIGS. 5 and 6 which are equivalent to FIGS. 2 and 3 previously described.

FIG. 5 illustrates the electrical mounting of the overflow safety device according to the invention, which is now extremely simplified, since the control thermostat 150 is the only electrical member inserted on the line 154 leading to the gas valve of the burner 153 (the dotted lines schematize the initial line, and the neutral line is referenced 155).

As can be seen in FIG. 6, when the operating conditions are considered to be normal, that is to say when the temperature detected by the control thermostat 150 remains below a predetermined threshold, for example 60 ° C, the control thermostat 150 is normally closed, which corresponds to a diagram 156 for the running sequence, and a diagram 156 'for the temperature sequence. In the event of heating estimated to be abnormal, the control thermostat 150 opens and immediately controls burner shutdown, by means of a rapid and direct action (no longer via a time relay) of said thermostat on the electrical supply of said burner. The predetermined area of the wall can then cool, the cooling however being slowed down by the thermal insulation means 160, which corresponds to a delay effect produced in a particularly original manner. During the stop sequence, the temperature diagram 157 ′ can thus correspond to the diagram 57 ′ which was obtained with a timed relay, between two extreme points denoted A and B. When the temperature of the predetermined zone of the wall reaches again a predetermined low threshold (for example 35 ° C.), the time delay is automatically suspended by closing the control thermostat 150, said thermostat then automatically controlling the restarting of the burner. The following diagrams 158 for the sequence, and 158 ′ for the temperature, then correspond to the respective diagrams which were obtained with the prior art.

It is clear that such a design has many technical advantages over previous designs: the main advantages result above all from the elimination of the time relay, ipso facto eliminating the risks of failure inherent in this electro-mechanical member.

In addition, unlike the prior art, one can always know during operation whether the security is active or not.

As indicated above, the control thermostat 150 is preferably a contact thermostat, chosen with a wide range: for example, it is possible to use a thermostat opening at 60 ° C ± 3 ° C, and closing at 35 ° C ± 6 ° C. It goes without saying that the operating range is in any case adapted to the thermal inertia of the thermal insulation means 160.

FIG. 13 is a section illustrating the structure of a contact thermostat advantageously used, of the normally closed type, thermostat which is normally found on the market. The thermostat 150 illustrated here thus comprises a housing 180, closed below by a flange 181 held by a capsule 182. The movable member of contact detection consists of a bimetallic disc 183 connected to a transmission axis 184. The switching arm 185, fixed by a member 188 to the housing 180, ends with a movable contact 186 normally at rest resting against the associated fixed contact 187.

We will now describe in more detail the structure and arrangement of the thermostat 150 and the thermal insulation means 160 ensuring the desired delay.

As illustrated in FIG. 4, the thermal insulation means 160 is preferably placed outside the rear wall 17 of the draft hood 9, which has the advantage of not disturbing the flow in said draft cutter. It goes without saying, however, that such an arrangement is only an example.

The thermostat 150 is preferably kept in abutment against the rear wall 17 of the draft hood 9, on the outside of the latter. One could certainly imagine making a hole in the rear wall 17 of the draft hood 9, allowing partial penetration of the control thermostat 150 inside the space 16 of said draft hood, which would influence the thermostat to both by the passage of hot gases inside the draft hood in the controlled area, and by the temperature of the predetermined area of the rear wall of the draft hood 9. It however appears preferable to avoid such an assembly, and to provide more simply a direct support of the control thermostat 150 against the wall of the draft hood 9, that is to say in this case against the rear wall 17 of said draft hood.

The control thermostat 150 can be screwed directly onto the rear wall 17 of the draft hood 9, or even, more simply, and in accordance with another advantageous aspect of the invention, be held in place by the thermal insulation means 160 himself.

FIG. 7 makes it possible to distinguish the means of thermal insulation 160, here essentially constituted by an insulating material 161, 162 surrounded by a cover 163 fixed against the rear wall 17 of the draft hood 9. FIG. 7 is a view from the interior side , to distinguish the control thermostat 150.

In accordance with what is illustrated in the section of FIG. 8a, the insulating material consists of a block of insulation 161 having a central opening 164 to house the thermostat 150, and here a second block of insulation 162 closing said opening central behind said thermostat.

FIG. 7 makes it possible to distinguish the circular central opening 164 here from the first heat-insulating block 161, making it possible to arrange the control thermostat 150 and the associated connection members: the control thermostat 150 has a contact end 165, a plate 166 having two holes 167 (usually for fixing the thermostat), connection members 168 extending laterally beyond the associated protective insulators 169. There is also a ground wire 170 fixed by an associated bolt 171. FIG. 7 also makes it possible to distinguish the two fixing bolts 172 allowing the assembly of this assembly in the rear part of the draft cutter.

Preferably, the second heat-insulating block 162 is compressed in thickness, so as to have a spring effect making it possible to maintain the thermostat 150 against the rear wall 17 of the draft hood 9. As an indication, it will be advantageous to use a heat-insulating block 162 made of glass wool, the aerated fibers of which allow significant compression to be obtained in thickness (for example with an initial thickness of 50 mm for a final thickness corresponding to that of the cover, that is to say say about 23 mm). The first heat-insulating block 161 has no function to maintain the thermostat to be filled, which makes it possible to choose an economical material, however having sufficient thermal inertia: in practice, we can be satisfied with such a material than rock wool.

For the system output means, as illustrated in the section of FIG. 8a, provision is made for the cover 163 to carry a cable gland 174, from which a connection cable 175 passes through which the connection wires 168 of the thermostat 150 pass. and the earth connection 170. Such a cable gland 174 is of known type and commonly encountered in trade: it makes it possible to eliminate any risk of untimely tearing of the connection cable, which would ipso facto remove the additional advantage provided by the safety device. The 175 cable will also be chosen in accordance with the standards or regulations in force.

The insulating material 161, 162 preferably constitutes an assembly of rectangular shape, and has a thickness at least equal to 20 mm: the dimensioning illustrated in FIGS. 7 and 8a corresponds to a rectangular panel of 185 mm x 270 mm, with a thickness of 23 mm.

The section in FIG. 8b illustrates another variant of mounting the control thermostat 150, with the said thermostat being maintained by a spring: a spring 176 is thus distinguished, compressed between the plate 166 of the thermostat and the central inner block of insulation 162 (the central block can in this case be made from an economical material, not necessarily capable of being compressed, such as rock wool).

According to another variant, as illustrated in the section of FIG. 8c, the control thermostat 150 can be screwed directly onto the rear wall 17 of the draft cutter 9. In this case, the bolts 173 inserted by the interior of the cutter draft, pass through the holes 167 of the plate 166 of the control thermostat 150, to open normally behind the cover 163. In this case, we can be satisfied with a single block of insulation 161, without the need to close the central opening 164 of said block. However, it should be noted that this latter assembly is in practice less favorable than the previous assemblies, because of the clearance clearance that the outer covering cover can have.

In all cases, it will naturally also be possible to provide an additional means of protection, to protect the insulators of the connection wires of the control thermostat: for example, it is possible to provide a disc, preferably made of polytetrafluoroethylene, mounted on the end of control thermostat contact.

Generally, the constituent material and the dimensioning of the thermal insulation means 160 will be chosen so as to confer a thermal inertia such that the time delay obtained in association with the thermostat 150 corresponds at least to the waiting time. given, thanks to a controlled slowing down of the cooling of the predetermined area of the wall of the draft hood. It goes without saying that it will always be preferable to arrange to hold as large a temperature as possible for the predetermined area of the wall of the draft hood.

Figure 9 provides a better understanding of the mounting mode of the overflow safety device according to the invention.

We can see in Figure 9, the draft hood 9 with its nozzle 10 for connection to the chimney and its lower opening 11, as well as its rear face 17 against which can be pressed and fixed the overflow safety functional unit, consisting by the control thermostat 150 and the thermal insulation means 160. We thus distinguish the control thermostat 150, with its connection wires ending in a connection cable 175, which passes through the central centrifugal disc 162, and the cover cover 163 by the associated cable gland 174.

We have assumed here that the control thermostat 150 is not maintained by direct screwing on the rear wall 17 of the draft hood 9, since its maintenance is ensured by the thermal insulation means itself. -even.

The installation is carried out in a very simple manner, since it suffices to make two holes in the rear wall 17 of the draft cutter 9 to allow the two fixing bolts 173 to be inserted from the rear. The distance d between these holes are naturally imposed, and the vertical setting a is determined case by case according to the dimensioning considered.

It is advantageous that the thermostat 150 is also arranged in the vertical plane of symmetry P of the draft hood 9 passing through the axis of the nozzle 10 for connection to the chimney, and is moreover arranged at a level corresponding to an area heavy load in case of overflow. In practice, the dimension a will be given on an operating manual, so that the thermostat 150 is in fact arranged at a level corresponding to an essentially constant distance from the lower edge of the draft hood 9, for different boilers but whose draft hood is of similar construction.

Installation is then very simple: once the two bolts 173 are in place, it suffices to bring the functional unit (constituted by the cover 163, the thermal insulation means 160 and the control thermostat 150) against the rear wall 17 of the draft cutter 9, thanks to associated holes and according to the spacing d concerned; then simply install two washers 172 ', and the nuts 172 to keep everything in place. The assembly thus assembled then corresponds to the assembly illustrated in FIG. 10.

In the variant of FIGS. 11 and 12, the positioning of the two holes to be made in the rear wall 17 of the draft cutter 9 is simply modified, so that the two bolts 173 can pass through the holes in the plate 166 of the control 150 In this case, since the maintenance of the control thermostat is ensured by direct screwing on the rear wall of the draft hood, it is very possible to use only one block of insulation 161, having an opening here rectangular 164 , to house the control thermostat and its connection devices.

Thus, once the two bolts 173 are in place, it suffices to arrange the control thermostat 150, then to apply the heat-insulating material 161 and the cover 163, so as to fix the whole by the nuts 172. A further distinction is made between the fixing of the mass member 170, ensured by an associated bolt 171. The assembly thus mounted corresponds to the assembly illustrated in FIG. 12.

It is easy to see that the mounting of the overflow safety device is extremely simple, and entirely within the reach of a non-specialist. This makes it possible to market the system as a kit. Earlier devices were never sold as a kit, however, and their installation absolutely required the intervention of a specialist. This also constitutes a non-negligible advantage of the invention, in addition to the technical advantages already explained above.

Finally, it should be emphasized that the reliability obtained is extremely high, given the low risk of failure (the risk of failure of the control thermostat is in practice almost zero, given that manufacturers commonly guarantee proper operation. for more than 100,000 cycles), and that the structure particularly simple security device makes available the advantage of this additional security to a large number of users.

The overflow safety device according to the invention thus has a large number of advantages, both technically and commercially.

Claims (17)

1. Combustion product discharge safety-device (100) associated with the draught-diverter (9) of a boiler (1) with an atmospheric burner (3) including a control thermostat serving to detect any abnormal rise in temperature relating to an abnormality in the draught conditions and making it possible in such case to cut off the electrical power supply to the burner rapidly, and a time delay device allowing the boiler to be restarted after a given waiting time following the boiler shut-down, the thermostat (150) being disposed against a wall (17) of the draught-diverter (9) in order to detect the overheating of a predetermined zone in the latter which is highly stressed in the event of spillage, the said thermostat acting directly on the electrical power supply to the burner (3) when such overheating reaches a given threshold, characterised in that the time delay is provided by a thermal insulation means (160) surrounding the thermostat (150), the said insulation means being disposed against the said predetermined zone of the wall in order to slow down the recooling thereof and having a thermal inertia such that the time delay thus obtained corresponds at least to the given waiting time.
2. Safety device according to Claim 1, characterised by the fact that the thermostat (150) is a contact thermostat with a wide operating range, the said range being suited to the thermal inertia of the thermal insulation means (160).
3. Safety device according to Claim 2, characterised by the fact that the thermostat (150) is preferably chosen so as to open at approximately 60°C and close again at approximately 35°C.
4. Safety device according to one of Claims 1 to 3, associated with a draught-diverter provided at the rear of the boiler, characterised by the fact that the thermostat (150) is disposed against the rear wall (17) of the draught-diverter (9).
5. Safety device according to Claim 4, characterised by the fact that the thermostat (150) is held in abutment against the rear wall (17) of the draught-diverter (9), on the external side of the latter.
6. Safety device according to Claim 4 or 5, characterised by the fact that the thermal insulation means (160) is disposed on the outside of the rear wall (17) of the draught-diverter (9), in order not to disturb the flow in the said draught-diverter.
7. Safety device according to Claims 4 to 6, characterised by the fact that the thermal insulation means (160) also holds the thermostat (150) in position.
8. Safety device according to one of Claims 1 to 7, characterised by the fact that the thermal insulation means (160) consists of an insulating material (161, 162) surrounded by a cover (163) fixed against the rear wall (17) of the draught-diverter (9).
9. Safety device according to Claim 8, characterised by the fact that the insulating material (161, 162) consists of a block of heat insulation (161) having a central opening (164) for housing the thermostat (150), optionally with a second block of heat insulation (162) closing off the said central opening behind the said thermostat.
10. Safety device according to Claims 7 and 9, characterised by the fact that the second block of heat insulation (162) is compressed in thickness, so as to have a spring effect enabling the thermostat (150) to be held.
11. Safety device according to Claims 7 and 9, characterised by the fact that a spring (176) is disposed between the thermostat (150) and the second block of heat insulation (162), in order to hold the said thermostat.
12. Safety device according to one of Claims 9 to 11, characterised by the fact that the first block of heat insulation (161) is made from rock wool, whilst the second block of heat insulation (162) is made from glass wool.
13. Safety device according to one of Claims 8 to 12, characterised by the fact that the cover (163) carries a stuffing box (174), from which emerges a connecting cable (175) through which the connecting wires (168) for the thermostat (150) and an earth connection (170) pass.
14. Safety device according to one of Claims 8 to 13, characterised by the fact that the insulating material (161, 162) is rectangular in shape and has a thickness of at least 20 mm.
15. Safety device according to one of Claims 1 to 14, characterised by the fact that the thermostat (150) is disposed in the vertical symmetry plane (P) of the draught-diverter (9) passing through the axis of the duct (10) connecting to the flue.
16. Safety device according to Claim 15, characterised by the fact that the thermostat (150) is disposed at a level corresponding to an essentially constant distance from the bottom edge of the draught-diverter (9), for boilers which are different but on which the draught-diverters are of similar designs.
17. Safety device according to one of Claims 1 to 16, characterised by the fact that the thermostat (150) is of the normally closed type.

Images