EP2166288A1 - Open stove - Google Patents

Abstract

The fireplace (1) has a housing (11) connected to an exhaust gas discharge system (15). A capillary tube (19) having a thermistor wire is in proximity of an upper edge (21) of a visible opening (13) of the housing and extends over an entire horizontal width of the visible opening. The capillary tube outputs a temperature-dependent sensor signal to a control circuit (25). The circuit provides an activation signal during increasing temperature of the capillary tube to introduce a measure counteracting an exhaust gas emission to the opening and/or release a warning signal.

Description

The invention relates to an open hearth furnace with a housing containing the combustion chamber and to be connected to an exhaust gas discharge system, which has at least one side of a view from the outside into the combustion chamber releasing viewing opening.

Such stoves are known in various configurations as decorative fireplaces in living spaces. The viewing opening provides a view of the combustion chamber from the installation room so that the observer can observe the flames and the embers when the stove is in operation. In the context of the present application, the term "wood-burning stove" in the broadest sense is intended to include open fireplaces in or connected to flue gas ducts in rooms.

As a fuel comes in the classic open fireplaces in particular wood in question. Meanwhile, increasingly find gas-heated open fireplaces of interest, in particular so-called decorative fireplaces, which in the fireplace floor area z. B. rust-shaped gas distribution valves a gas supply means for introducing fuel gas into the combustion chamber. On these rusty gas distribution valves z. As fireproof logs, lava stones or the like. Are, which mediate the combustion of the gas fireplace the illusion of wood combustion or solid fuel. In fact, the combustion of the fuel gas flowing into the combustion chamber takes place around such fuel dummies. The resulting exhaust gases normally flow upwards over the exhaust gas discharge system, so that they can finally reach the outside through the chimney.

Due to unfavorable weather conditions and / or draft in the installation room of the open fireplace, however, it may happen that the exhaust of the exhaust gas through the discharge system is insufficient and exhaust gas passes directly through the viewing port of the open stove into the installation room. This can create a dangerous situation for people in the room, as the usually toxic fumes are inhaled by the people concerned. The influx of exhaust gas into the installation room can take place gradually and unnoticed by the persons located in the installation room of the stove for longer periods of time. This situation can occur in both gas-fired and wood-fired open hearth furnaces.

The present invention has for its object to provide an open fireplace of the type mentioned, in which the risk of health hazards of persons in the installation room is significantly reduced by directly exiting exhaust gas or even completely excluded.

To solve this problem, it is proposed to further develop an open stove with the features mentioned above that in the vicinity of the upper edge of the viewing port preferably outside the combustion chamber, a temperature-sensitive exhaust gas outlet sensor arrangement is provided which extends at least approximately over the entire horizontal width of the viewing port and is determined and arranged to deliver its temperature-dependent sensor signal to a control circuit of the stove, wherein the control circuit is adapted to determine a temperature increase of the exhaust gas outlet sensor assembly beyond a tolerance an activation signal for initiating an exhaust gas outlet at the opening counteracting measure and / or for triggering to provide a warning signal.

If exhaust gas from the combustion chamber of the stove in the firing mode emerge from the viewing port, the hot exhaust gas will immediately rise upwards in the cooler air of the installation room and will flow out close to the upper edge of the viewing port. The invention is based on the idea, the area of the upper edge of the viewing aperture outside the Hot zone of the combustion chamber to monitor temperature changes. Hot zone is understood to mean, in particular, the combustion chamber region, which in normal operation is regularly penetrated by the exhaust gases flowing to the exhaust gas discharge system or by the fire during uninterrupted combustion operation. If the temperature in this upper edge region rises significantly relative to the ambient temperature, this is an indication that exhaust gas exits through the viewing opening into the installation space. Since the temperature-sensitive exhaust gas outlet sensor assembly monitors the viewing opening of the stove substantially over its entire horizontal width in the upper edge region to such a temperature increase, the backup system of exhaust gas outlet sensor assembly, control circuit and downstream components can also respond if the exhaust outlet limited only to a narrow horizontal region of the viewing port should be.

In principle, it would be conceivable to have a row or chain of several exhaust gas outlet sensors extending over the horizontal width of the viewing opening. However, preference is given to an exhaust gas outlet sensor arrangement with a uniform sensor which extends over at least 75%, preferably over 100%, of the horizontal width of the viewing opening at its upper edge outside the hot zone of the combustion chamber, preferably completely outside the combustion chamber. Such an elongated sensor is normally optically inconspicuous to accommodate and does not require much circuit complexity for its connection to the downstream evaluation system of control circuit and components connected thereto. Wire-shaped or tubular sensors are therefore preferably used.

Particularly suitable for exhaust gas outlet monitoring, a capillary tube with an outwardly closed cavity and a sensor gas therein has proven to be connected to the tube, a pressure sensor for monitoring the pressure of the sensor gas and for providing the sensor signal for the control circuit. The sensor gas can be air. When heating the capillary tube experiences in a in Essentially constant volume enclosed sensor gas pressure increase, which can be directly perceived by the pressure sensor, such as a pressure cell, and passed to the control circuit after signal conversion as an electrical signal. Such a capillary tube can be installed inconspicuously on the upper edge of the viewing opening of the stove in a horizontal orientation. Test measurements have shown that such a sensor arrangement of capillary tube and pressure sensor is very sensitive to the exhaust gas outlet at the fireplace view opening.

Instead of such a capillary tube with pressure sensor and alternative sensor arrangements come into question, such as a thermistor wire whose temperature-dependent change in the electrical resistance is monitored by the control circuit. The thermistor wire is of a typical temperature sensing resistor material, e.g. B. a platinum alloy formed. As thermistors come thermistor or PTC in question. An advantage of a thermistor wire as an exhaust gas outlet sensor is that the metrological detection and evaluation of temperature changes is possible easily and with little effort.

Another alternative is a thermal expansion element in the form of a wire or a rod in question, wherein a force transducer detects temperature-induced changes in length of the thermal expansion element and emits a corresponding sensor signal to the control circuit.

As a further alternative, a so-called stretch thermocouple comes into question. Such a path thermocouple comprises a plurality of individual thermocouples, which may vary in number and spacing from each other and which are housed in a common elongated shell (distributed over its length).

In one embodiment, the individual thermocouples are electrically connected in parallel. They allow the detection of a rapid increase in temperature at every point of the track thermocouple.

According to a further embodiment, the individual thermocouples are connected in series, wherein the connection points are thermally insulated. Even such a variant allows the rapid detection of temperature changes.

There are in the context of the inventive concept various ways of responding to the finding of exhaust gas outlet at the viewing port of the stove. In the simplest case, an audible and / or visual warning signal could be given, which then points people in the installation room of the stove on the hazardous situation. The control circuit would thus be followed in this case, an acoustic and / or optical alarm.

According to one embodiment of the invention, the stove may have an automatically operable door, preferably a sliding door with a controllable by the control circuit closing mechanism. In the event of detection of exhaust gas outlet at the viewing opening of the stove, the control circuit can then deliver the activation signal to the closing mechanism to activate it and thus bring the door in the closed position to seal the viewing opening to the installation room. The automatically operable door may be a transparent refractory disc, which is normally recessed into an open position in a receptacle.

An alternative or additional measure could be the activation of a smoke extraction device in the chimney or in the exhaust gas discharge system of the stove. The forcibly increasing the exhaust of the exhaust gas discharge system can prevent the exhaust gas outlet at the viewing port or at least significantly reduce.

With special advantages, the invention can also be realized in gas-operated open stoves. As a the exhaust gas outlet at the opening counteracting Measure comes in this case, the interruption of the gas supply to the combustion chamber of the stove in question. For this purpose, a z. B. electrically or magnetically controlled shut-off valve provided in the gas supply line, wherein the activation signal of the control circuit in the event of leakage of exhaust gas to the viewing port of the stove activates the shut-off valve for shutting off the gas supply line.

In order to avoid that the safety system already triggers a measure or warning signal counteracting the exhaust gas outlet at the viewing port due to short-term temporary temperature changes at the exhaust gas outlet sensor arrangement, the control circuit can be designed such that it does not emit the activation signal unless it exceeds the tolerance Temperature increase of the exhaust gas outlet sensor assembly has detected over a predetermined minimum period of time. This minimum time can be z. B. be a few minutes.

The invention will be explained in more detail below with reference to the figures. In the figures, two different types of stoves according to the invention as embodiments are shown partly schematically.

Fig. 1 shows an operated with fuel gas as an open fireplace 1 according to the invention in a perspective and partly schematic representation.

In the bottom region of the combustion chamber 5 of the stove 1 is a rust-like ausgestalteter gas distributor 3 with (not visible) gas outlet nozzles. On the rust-like gas distributor 3 are refractory solid fuel dummies and / or stones 7, which are surrounded by the flames 9 of the burning gas in the combustion chamber 5.

The stove 1 may be any suitable oven housing, for. B. have a masonry housing with or without furnace insert. In the examples shown here is of a bricked housing 11 with a viewing port 13 assumed that the view of the flames 9 in the combustion chamber 5 releases the viewer in the installation room of the stove 1. The combustion chamber 5 is connected via an exhaust gas discharge system 15 to the chimney of the building in question. Normally exhaust gas escapes from the combustion chamber 5 directly into the exhaust gas discharge system 15 and then passes through the chimney into the open air. One option could be to monitor the train of the chimney or the exhaust gas discharge system 15 in a conventional manner and set the stove operation at critical low train or turn on a chimney in the chimney. However, it has been shown in practice that even with normal chimney draft situations can occur which lead to a discharge of exhaust gas from the combustion chamber 5 through the sight opening 13 into the installation room, as at 17 in Fig. 1 is indicated. This can be z. B. happen in unfavorable draft in the installation room. In order to prevent such leakage of exhaust gas 17 from the viewing port 13, the following safety measures are provided. A capillary tube 19 extends horizontally over the entire horizontal width of the viewing port 13 at the upper edge 21 outside of the combustion chamber 5. The capillary tube 19 contains trapped in its cavity air, which experiences a pressure increase in temperature increase. This increase in pressure is detected by means of a pressure cell 23, which is connected to a control circuit 25. The control circuit 25 controls an electrically actuatable shut-off valve 27, which is indicated in the chimney housing area shown broken out, and which is located in the main supply line 29 for the gas supply to the gas distributor 3 and thus to the combustion chamber 5. Exceeds the detected by the pressure cell 23 sensor gas pressure in the capillary tube 19 a comparison pressure value in a significant manner over a predetermined period of z. B. two minutes, the control circuit 25 is its activation signal to the shut-off valve 27 from to transfer the latter in the blocking position. Thus, the gas supply to the combustion chamber 5 is interrupted and the fire 9 goes out, so that further exhaust gas outlet is suppressed.

It would also be conceivable to partially throttle the gas supply in the event make a continuously or gradually adjustable shut-off valve and trigger a full closure of the gas supply only when even after the throttling still exhaust leakage should take place in critical extent. However, the spontaneous full shut-off of the gas supply is preferred in the event of detection of exhaust gas outlet at the sight opening 13. For safety reasons, the re-starting of the stove should require an active measure of an operator. However, it would also be conceivable to automatically restart after a certain waiting time. If exhaust emissions continue to be detected, the subsequent waiting period can be extended.

As already mentioned above, instead of the gas-filled capillary tube, a thermistor wire can also be provided as a temperature measuring resistor in a comparable installation position on the stove. Furthermore, as an alternative, a wire or tube with a relatively large coefficient of thermal expansion in question, wherein a miniature force transducer monitors the force or voltage occurring during thermal expansion in order to derive therefrom the sensor signal.

In the over-corner stove 1 according to Fig. 2 are elements with elements in Fig. 1 correspond in their function, with correspondingly the same reference numerals, so that their explanation to the description of the embodiment according to Fig. 1 can be referenced.

The over-corner stove 1 has interspersed view openings 13. In particular, in such an over-corner fireplace 1 according to Fig. 2 can a lateral draft, as indicated by the arrow 31, lead to exhaust gas outlet 17 at a respective viewing port 13. To be able to reliably detect this state, the rod-shaped sensor 19 is also guided at the upper edge 21 of the viewing openings 13 via the corner. As already mentioned, this can be a capillary tube with sensor gas content, a temperature measuring resistance wire or / and a thermal expansion element. In the example of Fig. 2 is the sensor element 19 in a decorative linkage 33 integrated. The functioning of the stove after Fig. 2 corresponds to the operation of the stove according to Fig. 1 ,

The figures show two embodiments of a gas-fired stove. However, the invention is not limited thereto. It can also be used in woodburning stoves. In such a case comes as a the exhaust gas outlet at the opening 13 counteracting measure z. B. the forcible reinforcement of the chimney draft by a chimney or the like. Or the obstruction of the viewing opening 13 with a window or the like. In question.

Claims (9)

Open hearth with a combustion chamber (5) containing and to an exhaust gas discharge system (15) to be connected housing (11) on at least one side of the view from the outside into the combustion chamber (5) releasing opening (13),
characterized in that in the vicinity of the upper edge (21) of the opening (13) a temperature-sensitive exhaust gas outlet sensor arrangement (19) is provided, which extends at least approximately over the entire horizontal width of the opening (13) and is intended and set up her output temperature-dependent sensor signal to a control circuit (25), wherein the control circuit (25) is adapted, upon detection of a temperature increase of the exhaust gas outlet sensor assembly (19) beyond a tolerance, an activation signal for initiating an exhaust gas outlet at the opening (13) counteracting measure or / and to provide a warning signal. An open-hearth furnace according to claim 1, characterized in that it is a gas stove having a gas supply means (3, 29) for introducing fuel gas into the combustion chamber (5), wherein the gas supply means (3, 29) by the activation signal of the control circuit ( 25) has activatable shut-off device (27) for interrupting the gas supply to the combustion chamber (5). An open-hearth furnace according to claim 1 or claim 2, characterized in that the control circuit (25) is such that it does not emit the activation signal until it has detected over the tolerance exceeding temperature increase of the exhaust gas outlet sensor assembly (19) over a predetermined minimum period of time. An open-hearth furnace according to one of the preceding claims, characterized in that the exhaust gas outlet sensor arrangement (19) has a tube (19), in particular a capillary tube, extending at least approximately over the entire horizontal width of the opening (13) at its upper edge (21) outwardly closed cavity and a sensor gas therein, in particular air, wherein on the tube (19) a pressure sensor (23) for monitoring the pressure of the sensor gas and for providing the sensor signal for the control circuit (25) is connected. An open hearth furnace according to one of the preceding claims, characterized in that the exhaust gas outlet sensor arrangement comprises at least one thermistor wire extending at least approximately over the entire horizontal width of the opening at its upper edge, wherein the control means for monitoring the temperature-dependent change in the electrical resistance of the thermistor wire is set up. An open-hearth furnace according to one of the preceding claims, characterized in that the exhaust gas outlet sensor arrangement comprises at least one elongated thermal expansion element in the form of at least one wire or rod extending at least approximately over the entire horizontal width of the opening at its upper edge and on a force transducer for detection is connected by temperature-dependent changes in length of the thermal expansion element, wherein the force transducer is adapted to output the sensor signal to the control device. Open stove according to one of the preceding claims, characterized in that it comprises an automatically operable door with a controllable by the control circuit closing mechanism for closing the opening on demand, wherein the Locking mechanism is adapted to transfer the door in the closed position when the control circuit outputs the activation signal. An open hearth furnace according to one of the preceding claims, characterized in that the control circuit is connected to a smoke extraction device for the forced exhaust of exhaust gas in the exhaust gas discharge system. An open-hearth furnace according to one of the preceding claims, characterized in that the exhaust gas outlet sensor arrangement comprises at least one track thermocouple which extends at least approximately over the entire horizontal width of the opening at its upper edge.

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