ES2895378T3 - Gas burner system with a thermosensor to protect the burner - Google Patents

Abstract

A system comprising a gas burner (10) and a non-electric thermostat (20), wherein the gas burner (10) comprises a thermocouple (30) which is combined with the burner (10) and which is connected with a safety valve (50) through an electrical circuit (40), in which said safety valve (50) is maintained in a position that allows gas flow to the burner (10) thanks to the electrical current generated the thermocouple (30) when the burner (10) turns on and in which, in the absence of the electrical current generated by the thermocouple, said safety valve (50) is pre-charged to return to a position that prevents gas flow to the burner (10), characterized in that the non-electric thermostat (20) is also connected to the structure of the burner (10) to detect the temperature of the burner itself, thermostat (20) that is adapted to break the circuit (40) that connects the thermocouple (30) to the safety valve (50) to interrupt said circuit (40) when the temperature (T) inside the burner (10) exceeds a predetermined threshold (Ts).

Description

DESCRIPTION

Gas burner system with a thermosensor to protect the burner

field of invention

The present invention relates to a system comprising a gas burner and a thermostat to protect the gas burner, the gas burner being of the type in which the gas inflow to the burner is regulated by means of a safety valve supplied by a thermocouple relevant that detects the presence of a flame in the burner itself.

Known Prior Art

The known technique, especially in the field of gas burners for domestic use, is to equip the burner with a safety valve, usually a solenoid valve (i.e. activated by an electromagnet) which is held in an open position to allow the influx of gas to the burner, thanks to the electrical current generated by a thermocouple combined with the same burner and arranged in one or more of the holes of the flame propagator of that burner.

For example, the solenoid safety valve can be placed in the inlet duct of the burner gas regulation tap and can be kept in its closed position, thus preventing the influx of gas into the tap and therefore , inside the burner, by means of a spring whose thrust can be temporarily overcome manually by an operator when lighting the burner or by the magnetic field generated in the solenoid valve by the current generated by the thermocouple once the burner is on. switched on.

With regard to the safety of use of known burners, this solution does not prevent the possible return of flame, that is, the presence of combustion inside the burner, from damaging the burner itself or constituting a potential risk for the user. .

In the field of burners, there are various known solutions intended to interrupt the flow of gas to a burner during emergency conditions, so as to prevent flashback.

For example, JP H07-4651 A (in the name of RINNAI) describes a combustion apparatus provided with a solution for closing a solenoid valve for gas inflow to the combustion apparatus in the event of a flare or whenever the temperature of the combustion apparatus reaches abnormal values.

Such a system is provided with an electrical circuit that feeds a combustion sensor and an electrical/electronic type thermostat, and which are activated in the event of any abnormal combustion and/or temperature values are detected in the combustion apparatus.

One aspect of such a solution is that, since it involves the use of an electrical/electronic type thermostat, it needs to be powered by an electrical system external to the combustion apparatus and, consequently, cannot operate in the event of electrical blackouts.

Alternatively, especially in the field of burners for gas cookers, the inflow of gas to the same burner is controlled whenever overheating of a stove, or of a container heated by the burner, is detected.

Document WO2016162526A1 describes a kitchen burner provided with a safety system designed to interrupt the gas supply whenever overheating of a cooking container placed on the burner is detected.

For this reason, the burner comprises thermoelectric voltage generating means to deal with its overheating and these are placed in parallel with a thermocouple. By means of a diode (acting as a switch), the voltage generated by the thermoelectric means is imparted through the valve once a certain temperature threshold value has been reached and detected by the thermoelectric means.

Document US5769622A describes an apparatus comprising a burner provided with a temperature sensor placed in the center of the crown of the flame. The temperature sensor comprises a PTC (positive temperature coefficient) thermistor adapted to detect the temperature of a pot placed on the burner.

The resistance of the thermistor increases whenever the temperature increases. Once a predetermined threshold resistance value is reached, the voltage across it breaks the supply current to the winding and consequently closes the safety valve.

Document KR20140040909A describes an apparatus comprising a control unit and a temperature sensor arranged to penetrate through the center of a kitchen stove to detect the temperature of a container used to cook food over the flame.

The control unit drives a relay in order to regulate the supply of a magnet through which a gas supply valve is activated.

This known apparatus comprises a bimetallic switch adapted to directly detect the temperature of the container used to cook the food. The switch is arranged between the relay and the supply unit through which the relay is powered.

Whenever the temperature of the top plate of the bi-metallic switch falls within a predetermined temperature range, the switch immediately cuts off power to the magnet that controls the valve to prevent the container used to cook food from overheating and possibly sooting.

JP 3595432 B2 shows the features specified in the preamble of claim 1.

However, these types of solutions do not make it possible to control the burner whenever the temperature inside the burner reaches abnormal values, such as in the case of unwanted return of flame or other phenomena.

The purpose of the present invention is to increase the safety of use of systems with gas burners by resolving the disadvantages of the prior art mentioned above.

Another purpose of the present invention is to implement a system with a gas burner with a high safety of use in a simple and economic way.

Another additional purpose of the present invention is to implement a system with a burner, specifically for domestic use, which prevents gas from being supplied to the burner itself both in the absence of a flame in the holes of the relevant flame propagator and whenever the same burner is overheating, such as due to flashback.

Brief summary of the invention

These and other purposes are achieved by a system of a gas burner and a non-electric thermostat for domestic use, and particularly for gas cookers, of the type in which a thermocouple detecting the external flame is combined with the burner and is connected with a safety valve through an electrical circuit, and in which the safety valve is held in a position that allows a flow of gas to the burner thanks to the electrical current generated by the thermocouple when the burner is turned on and, therefore, which, in the absence of the electrical current generated by the thermocouple, returns to a position that prevents gas flow to the burner, characterized in that the non-electric thermostat is also connected to the burner to detect the temperature of the burner itself, which thermostat it is adapted to break the circuit connecting the thermocouple with the safety valve to interrupt the circuit when the temperature inside the burner exceeds a predetermined threshold.

An advantage of such an embodiment is that it makes it possible to intervene on the supply of the burner in the presence of phenomena that could give rise to an abnormal increase in temperature inside the burner.

Furthermore, such a solution does not require connecting the thermostat or safety valve to an external power supply line and is therefore not affected by any blackouts.

It should be noted that the expression "connected for the detection of the temperature of the same burner", used with reference to the connection between the thermostat and the burner, means, in the present specification, that at least the temperature sensitive part of the The aforementioned thermostat is applied to the burner structure, such as the burner cup or body or mixer, or is also applied inside the burner itself to directly detect its temperature.

Also, as will be apparent to a person skilled in the art, the expression "non-electric thermostat" denotes that the thermostat used is of a mechanical type, such as a fluid expansion thermostat.

According to a preferred aspect of the present invention, the gas burner system comprises at least one mixer with a Venturi effect (Venturi mixer) obtained inside the burner itself and in which the non-electric thermostat is arranged at one of the ends of the mixer with Venturi effect, said non-electric thermostat being configured to interrupt the circuit connecting the thermocouple with the safety valve whenever the temperature inside said Venturi effect mixer exceeds a predetermined threshold.

An advantage of such an embodiment is that the thermostat is optimally positioned with respect to sensing the temperature inside the burner.

Preferably, the non-electric thermostat comprises a fire wand attached to the burner and wherein said fire wand contains a fluid, such as liquid, adapted to expand depending on temperature.

In this case, the expansion of the fluid generally channeled inside a conduit of reduced dimensions, can make it possible to mechanically act on the electrical circuit that connects the thermocouple with the safety valve to break it whenever the burner reaches a certain temperature.

As already mentioned, an advantage of such an embodiment is that it allows the thermostat to operate even in the absence of electrical current.

Preferably, the pyrometric wand is provided with a bottom wall facing towards one of the ends of the Venturi-type mixer.

An advantage of such an embodiment is that, in this way, the lower wall of the pyrometric wand is directly affected by the internal temperature of the mixer.

Preferably, the fluid adapted to be expanded according to temperature is oil.

According to a preferred embodiment of the invention, as already mentioned, the non-electric thermostat provides an expandable element configured to break the circuit that connects the thermocouple with the safety valve whenever the fluid contained in the pyrometric wand is subjected to expansion. resulting from the temperature inside the burner when the aforementioned temperature exceeds a predetermined threshold.

According to another embodiment of the invention, the non-electric thermostat is configured to break the circuit connecting the thermocouple with the safety valve by acting, through its own expandable element, on a normally closed switch placed in series with the thermocouple.

An advantage of such an embodiment is that it allows the burner to operate under normal conditions, and that it can intervene, however, on the supply of the burner in the presence of phenomena that could give rise to an abnormal increase in the temperature inside the burner.

According to another alternative embodiment of the invention, the non-electric thermostat is configured to break the circuit connecting the thermocouple with the safety valve by acting, through its own expandable element, to change the position of a bypass switch placed in series with the thermocouple.

An advantage of such an embodiment is that it makes it possible to apply electrical circuits powered by the thermocouple to the burner and which operate whenever the temperature inside the burner exceeds a predetermined threshold.

According to another embodiment of the invention, the position of the bypass switch, achieved by the effects of the non-electric thermostat, allows a warning light to be turned on.

An advantage of such a solution is that it makes it possible to warn a user of the presence of any anomaly inside the burner.

According to yet another embodiment of the invention, the non-electric thermostat is configured to operate at predetermined temperature thresholds ranging between 250°C and 400°C.

An advantage of such an embodiment is that the predetermined temperature threshold can be selected, depending on the applications, to guarantee that the non-electric thermostat intervenes in case of temperatures that exceed those determined for normal operations (even under particularly severe conditions), although lower. than those determined for abnormal operations and that may damage the burner and/or its accessories and stove.

Other features of the invention can be deduced from the dependent claims.

Brief description of the figures

Additional features and advantages of the invention will become apparent from a reading of the following description given for illustrative purposes and without limitation, with the aid of the figures illustrated in the attached tables, in which:

• figure 1 is an axonometric view of a burner system provided with the thermostat according to an embodiment of the invention;

• figure 2 is an axonometric view, partially in section, of the burner system of figure 1;

• figure 3 is an axonometric view of a set of elements associated with the burner system of figures • figure 4 is a schematic view of the main elements of figure 3;

• figure 5 is a schematic view of a burner system according to another embodiment of the invention;

• Figure 6 is a schematic view of a burner system according to yet another embodiment of the invention;

• figure 7 is a schematic view of an auto reset system applicable to the burner system; and

• Figure 8 is a schematic view of a variant of the auto-reset system applicable to the burner system.

Detailed description of some embodiments of the present invention

First, with reference to figure 1, a burner for gas cookers, globally denoted with the reference number 10, is represented and comprises at least one Venturi mixer 13 (more visible in the section of figure 2) obtained inside the burner 10.

In particular, the burner 10 illustrated herein, shown by way of example in the schematic of Figure 4, is of the type comprising a burner cup 11 intended to be retained under a stove (not shown) and provided with a Venturi mixer 13 of the type with axial development, on which there is an intermediate body 12 provided with a distribution chamber and a plurality of flame propagators adapted to define two or more flame crowns 60, which are closed by their relevant upper covers . A similar burner can be achieved, for example, by the process described in EP2712334B.

It should be noted that, although a similar type of burner is referred to herein, any other gas burner for domestic use, such as the type equipped with a radial Venturi mixer ( such as in document DE3123751A) and/or provided only with a crown of flame.

Returning to the equipment illustrated here, a valve tap 55, that is, a tap fitted with a safety solenoid valve, connects the burner 10 with a gas supply pipe 90 and allows, through an outlet 52, the flow into a conduit 54 connected to the gas inlet 53 of mixer 13 of burner 10.

A thermocouple 30 is combined with the burner 10 and connected, via an electrical circuit 40, with a safety valve 50.

Thermocouple 30 is placed in a flame crown 60 of burner 10.

The electrical circuit 40 comprises an insulated wire 32 which runs from a hot junction of the thermocouple 30 and which is connected, by means of a normally closed (NC) switch 70, to a branch 33 of the circuit 40, said branch 33 being connected to in turn, with the safety valve 50 or with the solenoid that activates the relevant shutter of such valve 50.

A second branch of electrical circuit 40 comprises a grounded bare wire 34 connecting thermocouple 30 to safety valve 50 .

In general, safety valve 50 is held in an open position to allow gas flow to burner 10, such as by means of an electromagnet (actuating solenoid) connected to electrical circuit 40 and acting on a valve shutter. 50, thanks to the electrical current generated by thermocouple 30 in the presence of a flame on burner 10.

As is known, instead, when there is no flame on the burner, the electromagnet (solenoid) is not used and a spring returns the valve shutter 50 to the closed position to block the flow of gas to the burner 10 and to prevent unwanted gas leaks.

According to one aspect of the invention, the burner 10 is also combined with, or connected to, a non-electric thermostat 20 that allows the temperature of the burner 10 itself to be sensed and is also configured to interrupt the circuit 40 that connects the thermocouple 30 to the temperature of the burner 10. safety valve 50 whenever the temperature T inside the burner 10 exceeds a predetermined threshold Ts.

The non-electric thermostat 20, or mechanical type, has its own temperature sensing section directly attached to a component of the burner 10, so as to easily detect the temperature thereof, and preferably, the non-electric thermostat 20 is placed in one from the ends of the mixer 13 (shown, for example, in Figures 1 and 2) and is configured to interrupt the circuit 40 connecting the thermocouple 30 with the safety valve 50 whenever the temperature T inside the mixer 13 exceeds a predetermined threshold Thes.

It should be noted that although in the embodiment illustrated herein the non-electric thermostat 20 is positioned at one end of the Venturi mixer 13, such non-electric thermostat 20 may alternatively be positioned in any of the other positions on the cup or body. burner 10 that allows the temperature within such burner 10 to be effectively sensed.

Preferably, the non-electric thermostat 20 comprises a fire rod 24 fixed to the burner 10, such as by means of a flange 15 fixed to the cup 11 of the burner 10, for example by means of screws 16, and in which the fire rod 24 contains a fluid adapted to be expanded depending on the temperature T.

In particular, according to a preferred aspect of the present invention, the pyrometric tube 24 of the non-electric thermostat 20 is provided with a lower wall 25 oriented towards one of the ends of the Venturi-type mixer 13 .

As shown particularly in Figures 2 and 4, the lower wall 25 of the pyrometric wand 24 of the non-electric thermostat 20, in the particular embodiment of the invention illustrated herein, is disposed on that surface, or component (such as a closing cap of the Venturi mixer 13), of the cup 11 of the burner 10 towards which the flow of the primary gas-air fuel mixture leaving the Venturi mixer 13 is directed before being directed towards the distribution chambers and the relevant flame spreaders.

Preferably, the fluid contained within the fire wand 24 and adapted to expand depending on temperature is oil.

As shown in Figures 3 and 4, the non-electric thermostat 20 provides a capillary tube 22 which terminates with an expandable bellows portion 26 .

Such a configuration makes it possible to interrupt the circuit 40 connecting the thermocouple 30 with the safety valve 40 when the fluid contained in the pyrometric wand 24 is subjected to expansion as a result of the temperature T inside the burner 10 when the aforementioned temperature T exceeds a predetermined threshold Ts. In particular, in the event of an abnormal increase in temperature T inside the burner 10, the fluid contained in the pyrometric tube 24 of the non-electric thermostat 20 expands and, through the capillary tube 22, reaches the expandable portion 26 of the bellows. and this acts on the normally closed (NC) switch 70 to open it and, thus, to open the branch of the electrical circuit 40 that connects the hot junction 37 of the thermocouple 30 with the safety valve 50. In this case, the electromagnet (solenoid) of the valve 50 is no longer used and the spring returns the valve shutter 50 to a closed position to interrupt the flow of gas to the burner 10 and to protect it from further increases in temperature.

In a variant of the invention, illustrated in Figure 5, circuit 40 comprises, instead of normally closed (NC) switch 70, a bypass switch 80 placed in series with thermocouple 30.

In this case, the non-electric thermostat 20 can act, in the event of an abnormal increase in the temperature T inside the burner 10, on the bypass switch 80, so that the thermocouple 30 feeds the additional branch 71 of the circuit, being connecting the branch 71, for example, with a warning light 72 that signals the incidence of an anomaly.

Even in this case, the changed position of the bypass switch 80 ensures that the electromagnet of the valve 50 is no longer called upon and that the spring returns the valve plug to a closed position to prevent gas flow to the burner 10.

In another variant of the invention, illustrated in Figure 6, the non-electric thermostat 20 is configured to additionally activate an auxiliary circuit 76 by means of an intervention of the auxiliary switch 75.

In particular, the auxiliary circuit 76 may provide an auxiliary supply 78 adapted to power a warning light 72.

Also in this case, the non-electric thermostat 20 can act, in the event of an abnormal increase in the temperature T inside the burner 10, on the auxiliary switch 75 to activate a warning light 72 signaling the incidence of an anomaly.

In the preceding examples, the expression warning light means any type of known optical and/or acoustic detector. Preferably, non-electric thermostat 20 is configured to operate at predetermined thresholds Ts of temperatures ranging from 250°C to 400°C.

Preferably, the temperature threshold is set so that the non-electric thermostat 20 can intervene at temperatures higher than normal operating temperatures (even in the case of particularly serious conditions), although lower than those of abnormal operations, such as those resulting from the ignition in the injector under the top of the stove, which could damage the burner and/or its accessories and the stove.

Still according to the invention, both the normally closed switch 70 and the auxiliary switch 75, as well as the bypass switch 80, can be provided with a self-resetting system 90, 90' that allows them to return to their initial position whenever the temperature T inside the burner 10 falls below such threshold value Tf to restart the initial conditions of the oil contained in the pyrometric rod 24 of the non-electric thermostat 20.

The self-resetting system 90 may be automatic, such as by means of a spring 92 of appropriate dimensions, as illustrated in Figure 7.

Alternatively, the auto reset system 90' may be manual, such as by means of a reset button 94, as illustrated in FIG. 8.

Naturally, in both cases described, the safety valve remains closed because the thermocouple does not supply it since the burner flame is off.

Therefore, the effect of the auto reset system 90, 90' is only to relight the burner, but never automatically or without operator intervention.

In general, once it has been confirmed that the burner 10 is off, such as by turning on the warning light 72, the operator of the same burner must verify the causes that gave rise to the intervention of the non-electric thermostat 20 and, therefore, therefore, to the shutdown of the burner 10 that operates under abnormal conditions.

After having identified and resolved the problem, both in the case of automatic 90 and manual 90' auto resets, the operator can relight the burner 10. Provided that the causes have been resolved, the burner 10 will operate normally again; if not, the thermostat 20 will intervene again each time an anomaly arises.

In addition, the auxiliary circuit 76 provides, as an alternative or in addition to the warning light 72, any other means of warning, such as an acoustic alert or the activation of a display means.

Obviously, modifications or improvements may be added to the described invention as a result of contingent or particular motivations, but without deviating from the scope of the invention claimed below.

Claims (12)

1. A system comprising a gas burner (10) and a non-electric thermostat (20), wherein the gas burner (10) comprises a thermocouple (30) that is combined with the burner (10) and is connected to a safety valve (50) through an electrical circuit (40), in which said safety valve (50) is kept in a position that allows gas flow to the burner (10) thanks to the electrical current generated by the thermocouple (30) when the burner (10) turns on and in which, in the absence of the electrical current generated by the thermocouple, said safety valve (50) is pre-charged to return to a position that prevents gas flow to the burner (10), characterized in that the non-electric thermostat (20) is also connected to the structure of the burner (10) to detect the temperature of the burner itself, which thermostat (20) is adapted to break the circuit (40) that connects the thermocouple (30) to the safety valve (50) to interrupt said circuit. ito (40) when the temperature (T) inside the burner (10) exceeds a predetermined threshold (Ts). 2. The system according to claim 1, of the type comprising at least one Venturi mixer (13) obtained inside said burner (10), characterized in that the non-electric thermostat (20) is arranged at one end of the mixer (13), said non-electric thermostat (20) being designed to break the circuit (40) that connects the thermocouple (30) with the safety valve (50) when the temperature (T) inside said at least one mixer (13) exceeds a predetermined threshold (Ts). 3. The system according to claim 1 or 2, characterized in that the non-electric thermostat (20) comprises a pyrometric rod (24) fixed to the burner (10), said pyrometric rod (24) containing a fluid adapted to be subjected to an expansion depending on the temperature (T). 4. The system (10) according to claims 2 and 3, characterized in that said pyrometric tube (24) is provided with a lower wall (25) oriented towards one of the ends of the Venturi mixer (13). 5. The system according to claims 3 or 4, characterized in that the adapted fluid that has to expand as a function of temperature is oil. 6. The system according to claims 3, 4 or 5, characterized in that the non-electric thermostat (20) provides an expandable element (26) designed to break the circuit (40) that connects the thermocouple (30) with the valve (40) security when the fluid contained in the pyrometric rod (24) is subjected to an expansion due to the temperature (T) inside the burner (10) when the aforementioned temperature (T) exceeds a predetermined threshold (Ts). 7. The system according to claim 6, characterized in that the non-electric thermostat (20) is designed to break the circuit (40) that connects the thermocouple (30) with the safety valve (50) acting, through its own element expandable (26), on a normally closed switch (NC) arranged in series with the thermocouple (30). The system according to claim 7, characterized in that the non-electric thermostat (20) is designed to additionally activate an auxiliary circuit (76) by means of the intervention of an auxiliary switch (75). The system according to claim 8, characterized in that the auxiliary circuit (76) provides an auxiliary power supply (78) adapted to supply a warning light (72). 10. The system according to claim 6, characterized in that the non-electric thermostat (13) is designed to break the circuit (40) that connects the thermocouple (30) with the safety valve (50) acting, through its own element expandable (26), to change the position of a bypass switch (80) arranged in series with the thermocouple (30). The system according to claim 10, wherein the position of the bypass switch (80), obtained by the effect of the non-electric thermostat (13), allows a warning light (72) to be turned on. 12. The system according to claim 1, characterized in that the non-electric thermostat (20) is designed to operate at predetermined temperature thresholds (Ts) between 250 °C and 400 °C.