CN110621935B

CN110621935B - Gas burner system with thermal sensor for protecting burner

Info

Publication number: CN110621935B
Application number: CN201880030137.8A
Authority: CN
Inventors: 马西莫·多拉
Original assignee: Sabaf SpA
Current assignee: Sabaf SpA
Priority date: 2017-05-09
Filing date: 2018-04-17
Publication date: 2022-06-14
Anticipated expiration: 2038-04-17
Also published as: CN110621935A; WO2018207040A1; ES2895378T3; EP3622219A1; EP3622219B1; IT201700050203A1

Abstract

The invention relates to a gas burner (10) system, in particular for gas cookers, in which the burner (10) is associated with a thermocouple (30) connected to a safety valve (50) by means of an electric circuit (40), in which the aforementioned safety valve (50) is maintained in a position allowing the gas to flow towards the burner (10) due to the current generated by the thermocouple (30) when the burner (10) is burning, characterized in that the burner (10) is further associated with a non-electric thermostat (20), the non-electric thermostat (20) being adapted to cut off the electric circuit (40) connecting the thermocouple (30) to the safety valve (50) whenever the temperature (T) inside the burner (10) exceeds a predetermined threshold value (Ts).

Description

Gas burner system with thermal sensor for protecting burner

Technical Field

The present invention relates to a thermostat for protecting a burner, in which the inflow of gas to the burner is regulated by a safety valve fed by an associated thermocouple which detects the presence of a flame in the burner itself.

Background

Known techniques, in particular in the field of gas burners for residential use, equip the burner with a safety valve, usually a solenoid valve (i.e. activated by an electromagnet), which remains in an open position to enable the gas to flow into the burner thanks to the current generated by a thermocouple associated with the same burner and arranged at one or more holes of the burner flame diffuser.

For example, the solenoid safety valve may be located in the inlet duct of a gas-regulating tap of a burner and may be kept in its closed position by means of a spring, the thrust of which can be temporarily overcome manually by the operator when opening the burner, or by an electromagnetic field generated by a current generated in the solenoid valve by a thermocouple once the burner is opened, thus preventing the inflow of gas inside the tap and inside the burner.

In terms of safety of use of the known burners, this solution does not prevent possible flashback, i.e. the presence of combustion inside the burner, which could damage the burner itself or constitute a potential risk to the user.

In the field of burners, during an emergency, there are various known solutions aimed at interrupting the flow of gas to the burner, for example to prevent flashback.

For example, document JP H07-4651A (in the name of rinniai) describes a combustion device equipped with a solution for closing the solenoid valve for the gas flow into the combustion device in the event of a fire or whenever the temperature of the combustion device should reach an abnormal value.

Such a system is equipped with an electric circuit which supplies the combustion sensor and the thermostat of the electric/electronic type and which is activated in the event of any abnormal combustion and/or abnormal temperature values detected in the combustion device.

One aspect of this solution is that, since it involves the use of thermostats of the electric/electronic type, it also requires power supply by an electrical system external to the combustion device and therefore cannot operate in the event of a power failure.

Alternatively, in particular in the field of burners for gas cookers, the flow of gas into the same burner is controlled whenever overheating of the hob or receiver heated by the burner is detected.

Document WO2016162526a1 describes a cooker burner equipped with a safety system intended to interrupt the delivery of gas whenever overheating of the cooking vessel located on the burner is detected.

For this reason, the burner comprises a thermoelectric device that generates a voltage to account for its overheating, and this thermoelectric device is positioned parallel to the thermocouple. By means of a diode (acting as a switch), the voltage generated by the thermoelectric device is applied to the valve as soon as a determined temperature threshold is reached and detected by the thermoelectric device.

Document US5769622A describes a device comprising a burner equipped with a temperature sensor located in the centre of a flame crown (flame corona). The temperature sensor comprises a PTC (positive temperature coefficient) thermistor adapted to detect the temperature of the pan located on the burner.

The resistance of the thermistor increases each time the temperature increases. As soon as the defined resistance threshold is reached, the voltage across the thermistor cuts off the supply current to the coil and thus closes the safety valve.

Document KR20140040909A describes a device comprising a control unit and a temperature sensor arranged to penetrate through the centre of the head of a cooking appliance in order to detect the temperature of a container used to cook food on a flame.

The control unit drives a relay intended to regulate the power supply of the magnets by means of which the gas delivery is activated.

This known device 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 power supply unit, and the relay is powered by the power supply unit.

Whenever the temperature of the upper plate of the bimetal switch falls within a predetermined temperature range, the switch immediately cuts off the power of the magnet of the control valve to prevent the container for cooking food from being overheated and to prevent possible generation of soot.

However, these types of solutions do not allow to control the burner when the temperature inside the burner reaches an abnormal value, for example in case of undesired flashback or other phenomena.

The object of the present invention is to increase the safety of use of the burner by solving the drawbacks of the prior art mentioned above.

A further object of the present invention is to realise a burner with high safety in use, in a simple and economical manner.

A further object of the present invention is still to achieve a burner, in particular for residential use, which prevents the delivery of gas to the burner itself both in the absence of flame at the holes of the relative flame diffuser and whenever the same burner should overheat (for example, due to backfiring).

Disclosure of Invention

These and other objects are achieved by a gas burner system for housing, in particular for gas cookers, of the type in which a thermocouple for detecting external flames is associated with the burner and is connected by an electric circuit to a safety valve, and in which the aforementioned safety valve is maintained in a position enabling the gas to flow towards the burner, due to the current generated by the thermocouple when the burner is burning, and therefore, in the absence of the current generated by the thermocouple, the safety valve returns to a position preventing the gas from flowing towards the burner, characterized in that a non-electric thermostat is further connected to the burner to detect the temperature of the burner itself, which is adapted to cut off the electric circuit connecting the thermocouple to the safety valve when the temperature inside the burner exceeds a predetermined threshold.

An advantage of such an embodiment is that the non-electric thermostat can intervene in the supply of the burner in the presence of phenomena that may cause an abnormal rise in temperature inside the burner.

Furthermore, this solution does not require the connection of a thermostat or safety valve to the external power supply line and is therefore not affected by any power outage.

Note that the expression "connected for detecting the temperature of the same burner" used for reference to the link between the thermostat and the burner here means that at least a portion sensitive to the temperature of the aforementioned thermostat is applied to the structure of the burner, such as the cup, the body or the mixer of the burner, or that this portion can also be applied within the burner itself, in order to directly detect the temperature of the burner.

Also, it will be apparent to the skilled person that the expression "non-electric thermostat" means that the thermostat used is of the mechanical type, for example a fluid expansion thermostat.

According to a preferred aspect of the invention, the gas burner system comprises at least one mixer with venturi effect (venturi mixer) obtained within the burner itself, and wherein a 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 electric circuit connecting the thermocouple to the safety valve whenever the temperature inside such a mixer with venturi effect exceeds a pre-specified threshold.

An advantage of such an embodiment is that the thermostat is positioned in an optimal way with respect to detecting the temperature inside the burner.

Preferably, the non-electric thermostat comprises a bulb fixed to the burner and wherein the bulb contains a fluid, for example a liquid, adapted to expand according to the temperature.

In this case, the expansion of the fluid, which is generally guided in a duct of reduced size, can act mechanically on the electric circuit connecting the thermocouple to the safety valve, so as to shut it off each time the burner reaches a certain temperature.

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

Preferably, the bulb is equipped with a bottom wall directed towards one of the ends of the venturi-type mixer.

An advantage of this embodiment is that in this way the bottom wall of the bulb is directly affected by the temperature inside the mixer.

Preferably, the fluid adapted to expand according to temperature is an oil.

As already mentioned, according to a preferred embodiment of the invention, the non-electric thermostat is provided with an inflatable element configured to cut off the electric circuit connecting the thermocouple to the safety valve each time the fluid contained in the bulb undergoes an expansion caused by the temperature inside the burner, when said temperature exceeds a pre-specified threshold.

According to a further embodiment of the invention, the non-electric thermostat is configured to act, through its own inflatable element, on a normally closed circuit breaker positioned in series with the thermocouple, breaking the electric circuit connecting the thermocouple to the safety valve.

An advantage of such an embodiment is that the non-electric thermostat makes it possible for the burner to operate under normal conditions and, in the presence of phenomena that may lead to an abnormal rise in temperature inside the burner, can nevertheless intervene in the supply of the burner.

According to a further alternative embodiment of the invention, the non-electric thermostat is configured to cut off the electric circuit connecting the thermocouple to the safety valve by acting through its own inflatable element to change the position of a shunt switch positioned in series with the thermocouple.

An advantage of such an embodiment is that it can apply a circuit fed by a thermocouple to the burner and operate whenever the temperature inside the burner exceeds a pre-specified threshold.

According to a further embodiment of the invention, the position of the shunt switch, which is achieved by the action of the non-electric thermostat, makes it possible to turn on the warning light.

An advantage of this solution is that it can inform the user of the presence of any anomalies within the burner.

According to still further embodiments of the present invention, the non-electric thermostat is configured to operate at a pre-specified temperature threshold between 250 ℃ and 400 ℃.

An advantage of such an embodiment is that the pre-specified temperature threshold can be chosen according to the application to ensure intervention of the non-electric thermostat in the event that, although below the temperature determined to be anomalous, the temperature determined to be normal is exceeded (even in particularly severe conditions) and the burner and/or its accessories and the hob may be damaged.

Further features of the invention can be derived from the dependent claims.

Drawings

Further characteristics and advantages of the invention will be evident from reading the following description, given for explanatory purposes and without limitation, with the aid of the figures illustrated in the attached table, in which:

FIG. 1 is an isometric view of a burner system provided with a thermostat according to an embodiment of the present invention;

FIG. 2 is a partial cross-sectional isometric view of the combustor system of FIG. 1;

FIG. 3 is an isometric view of a set of elements associated with the combustor system of FIGS. 1 and 2;

FIG. 4 is a schematic diagram of the major elements of FIG. 3;

FIG. 5 is a schematic view of a combustor system according to a further embodiment of the invention;

FIG. 6 is a schematic view of a combustor system according to yet another embodiment of the present invention;

FIG. 7 is a schematic view of a self-resetting system applied to a burner system; and

fig. 8 is a schematic view of a variation of the self-resetting system applied to a burner system.

Detailed Description

Referring first to fig. 1, a burner for gas cookers is shown, generally designated by the numeral 10, and comprising at least one venturi mixer 13 (more evident in the section of fig. 2) obtained inside the burner 10.

In particular, the burner 10 shown here, as shown by way of example in the solution of fig. 4, is of the type comprising a burner cup 11 intended to be confined below a hob (not shown) and equipped with a venturi mixer 13 of the axially flared type, on which there is an intermediate body 12 equipped with a distribution chamber and a plurality of flame diffusers adapted to define two or more flame crowns 60, closed by their relative upper covers. A similar burner may be implemented by the process described in EP2712334B, for example.

It is noted that although reference is made here to burners of similar type, any other gas burner for residential use can be used for implementing the invention, for example burners of the type equipped with a radial venturi mixer (for example in DE 3123751A) and/or equipped with only one flame crown.

Returning to the apparatus shown here, a valve tap 55, i.e. a tap equipped with a safety solenoid valve, connects the burner 10 to the gas supply pipe 90 and allows the gas to flow into the duct 54 through the outlet 52, the duct 54 being connected to the gas inlet 53 of the mixer 13 of the burner 10.

The thermocouple 30 is coupled to the burner 10 and is connected to the safety valve 50 by means of the electrical circuit 40.

The thermocouple 30 is located at the flame crown 60 of the burner 10.

The circuit 40 comprises an insulated cable 32, which insulated cable 32 extends from the hot junction 37 of the thermocouple 30 and is connected, by means of a normally closed circuit breaker (NC)70, to a branch 33 of the circuit 40, said branch 33 being in turn connected to the safety valve 50 or to a solenoid which activates an associated shutter (shutter) of the valve 50.

The second branch of the electrical circuit 40 includes a bare ground cable 34 that connects the thermocouple 30 to the safety valve 50.

Typically, the safety valve 50 is kept in the open position to allow the gas to flow towards the burner 10, for example by means of an electromagnet (actuating solenoid) connected to the electric circuit 40 and acting on the shutter of the valve 50, due to the electric current generated by the thermocouple 30 in the presence of a flame on the burner 10.

In contrast, it is known that whenever there is no flame on the burner, an electromagnet (solenoid) is not requested and the spring keeps the shutter of the valve 50 in the closed position to prevent the gas from flowing to the burner 10 and to avoid undesired gas leakage.

According to an aspect of the invention, the burner 10 is also associated or connected with a non-electric thermostat 20, the non-electric thermostat 20 allowing to detect the temperature of the same burner 10 and being further configured to interrupt the electric circuit 40 connecting the thermocouple 30 to the safety valve 50 whenever the temperature T inside the burner 10 exceeds a pre-specified threshold Ts.

The non-electric thermostat 20, or of the mechanical type, has its own temperature-sensitive portion that is directly fixed to a component of the burner 10 in order to easily detect its temperature, and preferably the non-electric thermostat 20 is located at one of the ends of the mixer 13 (shown for example in figures 1 and 2) and is configured to interrupt the electric circuit 40 that connects the thermocouple 30 to the safety valve 50 whenever the temperature T inside the mixer 13 exceeds a pre-specified threshold Ts.

Note that although in the embodiment shown herein the non-electric thermostat 20 is located at the end of the venturi mixer 13, the non-electric thermostat 20 may alternatively be disposed at any other location on the cup or body of the combustor 10 that allows for efficient detection of the temperature within the combustor 10.

Preferably, the non-electric thermostat 20 comprises a bulb 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 wherein the bulb 24 contains a fluid adapted to expand as a function of the temperature T.

In particular, according to a preferred aspect of the invention, bulb 24 of non-electric thermostat 20 is equipped with a bottom wall 25 facing one of the ends of venturi-type mixer 13.

As shown particularly in fig. 2 and 4, in the particular embodiment of the invention shown here, the bottom wall 25 of the bulb 24 of the non-electric thermostat 20 is arranged on a surface or part of the cup 11 of the burner 10 (for example, the closing cap of the venturi mixer 13), the flow of combustible gas-primary air mixture coming out from the head of the venturi mixer 13 being directed towards the surface or part of the cup 11 of the burner 10 before being directed towards the distribution chamber of the body 12 of the burner 10 and the relative flame diffuser.

Preferably, the fluid contained within the bulb 24 and adapted to expand in accordance with temperature is oil.

As shown in fig. 3 and 4, the non-powered thermostat 20 is provided with a capillary tube 22 terminating in an expandable bellows portion 26.

This configuration enables to interrupt the electric circuit 40 connecting the thermocouple 30 to the safety valve 40 when the fluid contained in the bulb 24 undergoes expansion due to the temperature T inside the burner 10 (when said temperature T exceeds a pre-specified threshold Ts).

In particular, in the event of an abnormal rise in the temperature T inside the burner 10, the fluid contained in the bulb 24 of the non-electric thermostat 20 expands and reaches, through the capillary tube 22, the expandable bellows portion 26, the bellows portion 26 acting on the normally closed circuit breaker (NC)70 to open it and thus open the branch of the electric circuit 40 connecting the hot junction 37 of the thermocouple 30 to the safety valve 50.

In this case, the solenoid of the valve 50 is no longer requested and the spring keeps the shutter of the valve 50 in the closed position to interrupt the flow of gas to the burner 10 and protect it from other temperature increases.

In one variation of the invention shown in fig. 5, the circuit 40 includes a shunt switch 80 positioned in series with the thermocouple 30, rather than a normally closed circuit breaker (NC) 70.

In this case, in the event of an abnormal rise in the temperature T inside the burner 10, the non-electric thermostat 20 can act on the shunt switch 80, so that the thermocouple 30 supplies an additional branch 71 of the circuit, this branch 71 being connected, for example, to a warning lamp 72, the warning lamp 72 indicating the occurrence of an abnormality.

Even in this case, the changed position of the diverter switch 80 ensures that the solenoid of the valve 50 is no longer requested and that the spring keeps the shutter of the valve 50 in the closed position to prevent gas from flowing to the burner 10.

In another variant of the invention shown in fig. 6, non-electric thermostat 20 is configured to activate auxiliary circuit 76 by intervention of auxiliary switch 75.

In particular, the auxiliary circuit 76 can be provided with an auxiliary power supply 78 adapted to supply the warning light 72.

Also in this case, in the event of an abnormal rise in the temperature T inside the burner 10, the non-electric thermostat 20 can act on the auxiliary switch 75 to activate the warning lamp 72, which warning lamp 72 indicates the occurrence of an abnormality.

In the preceding examples, the term warning light refers to any type of known optical and/or acoustic detector.

Preferably, non-electric thermostat 20 is configured to operate at a pre-specified temperature threshold Ts that is between 250 ℃ and 400 ℃.

Preferably, the temperature threshold is established so that the non-electric thermostat 20 can intervene at temperatures higher than the normal operating temperature, although lower than the temperature of abnormal operation (even in particularly severe conditions), for example caused by a fire at the injectors below the top of the hob, which may damage the burner and/or its accessories and the hob.

Still according to the invention, both the normally closed circuit breaker 70 and the auxiliary switch 75, as well as the shunt switch 80, can be equipped with a self-resetting system 90, 90' which is provided each time the temperature T inside the burner 10 drops to T_fBelow the threshold value, it is possible to return it to its initial position to reset the initial condition of the oil contained in the bulb 24 of the non-electric thermostat 20.

The self-resetting system 90 may be automated, for example by means of a suitably sized spring 92, as shown in fig. 7.

Alternatively, the self-reset system 90' may be manual, for example by means of a reset button 94, as shown in fig. 8.

Naturally, in both the described cases, the safety valve remains closed, since the thermocouple does not supply it with power due to the flame closure of the burner.

Thus, the effect of the self-resetting system 90, 90' is simply to turn the burner on again, but never automatically or without operator intervention.

Generally, once it is confirmed that the burner 10 is turned off, for example by means of the turning on of the warning light 72, the operator of the same burner must verify the cause of the intervention of the non-electric thermostat 20 and therefore of the turning off of the burner 10 operating in abnormal conditions.

After the problem is identified and resolved, the operator may turn the burner 10 on again, both in the case of automatic self-reset 90 and manual self-reset 90'. Whenever the cause is resolved, the burner 10 will operate normally again, otherwise the thermostat 20 will intervene again each time an anomaly occurs.

Furthermore, alternatively or in addition to the warning light 72, the auxiliary circuit 76 is also provided with any other warning means, such as the activation of a buzzer or a display.

Obviously, modifications and improvements may be added to the invention described, by chance or by specific motivation, without however departing from the scope of protection of the invention as claimed below.

Claims

1. A gas burner (10) system in which a thermocouple (30) is integrated with the burner (10) and connected to a safety valve (50) by an electrical circuit (40), wherein the safety valve (50) is maintained in a position allowing the gas to flow to the burner (10) due to the electric current generated by the thermocouple (30) when the burner (10) is burning, and in the absence of current generated by the thermocouple, the safety valve (50) is biased to return to a position preventing gas flow to the burner (10), characterized in that the non-electric thermostat (20) is further connected to the structure of the burner (10) to detect the temperature of the burner (10) itself, when the temperature (T) within the combustor (10) exceeds a predetermined threshold (Ts), the thermostat (20) is adapted to cut off an electrical circuit (40) connecting the thermocouple (30) to the safety valve (50).

2. Burner (10) system according to claim 1, comprising at least one venturi mixer (13) obtained inside the burner (10), characterized in that a non-electric thermostat (20) is arranged at one of the ends of the mixer (13), said non-electric thermostat (20) being designed to cut off the electric circuit (40) connecting the thermocouple (30) to the safety valve (50) when the temperature (T) inside said at least one mixer (13) exceeds a pre-specified threshold value (Ts).

3. Burner (10) system according to claim 1 or 2, characterized in that the non-electric thermostat (20) comprises a bulb (24) fixed to the burner (10), said bulb (24) containing a fluid suitable for expansion according to the temperature (T).

4. A burner (10) system according to claim 3, wherein the bulb (24) is provided with a bottom wall (25) facing one of the ends of the venturi mixer (13).

5. A burner (10) system according to claim 3, wherein the fluid adapted to expand according to temperature is oil.

6. A burner (10) system according to claim 3, characterized in that said non-electric thermostat (20) is provided with an expandable element (26) designed to cut off the electric circuit (40) connecting the thermocouple (30) to the safety valve (40) when the fluid contained in the bulb (24) undergoes expansion due to the temperature (T) inside the burner (10) when said temperature (T) exceeds a pre-specified threshold (Ts).

7. Burner (10) system according to claim 6, characterized in that the non-electric thermostat (20) is designed to act, through its own inflatable element (26), on a normally closed circuit breaker (NC) arranged in series with the thermocouple (30), breaking the electric circuit (40) connecting the thermocouple (30) to the safety valve (50).

8. Burner (10) system according to claim 7, characterized in that the non-electric thermostat (20) is designed to activate the auxiliary circuit (76) by the intervention of an auxiliary circuit breaker (75).

9. Burner (10) system according to claim 8, characterized in that the auxiliary circuit (76) is provided with an auxiliary power supply (78) adapted to power the warning light (72).

10. Burner (10) system according to claim 6, characterized in that the non-electric thermostat (13) is designed to act, through its own expandable element (26), to change the position of a shunt switch (80) arranged in series with the thermocouple (30), cutting off the electric circuit (40) connecting the thermocouple (30) to the safety valve (50).

11. Burner (10) system according to claim 10, characterized in that the position of the diverter switch (80) obtained by the action of the non-electric thermostat (13) allows the opening of the warning light (72).

12. A burner (10) system according to claim 1, wherein the non-electric thermostat (20) is designed to operate at a predetermined temperature threshold (Ts) between 250 ℃ and 400 ℃.