Thermoelectric safety devices for gas combustion systems in the absence of flame

Abstract

A thermoelectric safety device for a gas combustion system in the absence of flame comprises: a thermocouple (2) configured to detect flame in a corresponding burner and generate voltage; a solenoid valve (7) electrically connected to the thermocouple (2); and a transistor (6) electrically connected between the thermocouple (2) and the solenoid valve (7), wherein the solenoid valve (7) is arranged to be directly connected to a field effect transistor. The device (1) comprises a booster (5) for supplying power to the transistor (6), wherein the transistor (6) is connected in parallel to the booster (5), wherein an output terminal (5a) of the booster (5) is arranged to be connected to a gate terminal (6a) of the transistor (6), and wherein the booster (5) is configured to boost the voltage generated in the thermocouple (2), wherein the obtained voltage can keep the transistor (6) closed so that the solenoid valve (7) is energized.

Description

Technical Field

[0001] The invention relates to a thermoelectric safety device for a gas combustion system in the absence of flame. Background Art

[0002] Cooking appliances with burners are known in the art, each of which has an associated thermocouple connected to a corresponding solenoid valve, so that when the thermocouple detects the presence of a flame in the burner, the thermocouple generates a thermal current that is able to keep the solenoid valve energized for a given time, thereby allowing gas to flow towards the corresponding burner.

[0003] EP 0288390 A1 also describes a circuit in which a MOSFET is arranged between the thermocouple and the solenoid valve, said MOSFET acting as a switch. Thus, according to previously established parameters, the MOSFET can open the circuit, thereby preventing the passage of current towards the solenoid valve and thus causing the solenoid valve to close the passage of gas towards the burner, regardless of the presence of a flame in the corresponding burner. In this type of circuit, the MOSFET must be powered by an external power source in order for it to operate as a closed switch, allowing the passage of current towards the solenoid valve.

[0004] JP H09 196362A describes a cooking appliance comprising a burner, a thermocouple associated with an electromagnetic valve, and a thermoelectric generator that supplies power to a battery via a booster. When the ignition operation is completed, the switch is disconnected so that the battery does not supply power to the ignition device, but the electromagnetic valve remains unchanged. When the combustion flame is reduced by the user setting the flame, the thermoelectromotive force of the thermoelectric generator is also reduced. When the output voltage of the booster drops from a level, the current to the battery is limited by a current limiter, wherein sufficient voltage is supplied to prevent the electromagnetic valve from disconnecting.

[0005] US 5,599,181A discloses a cooking appliance comprising: a burner; a thermocouple connected to a solenoid valve capable of energizing the solenoid valve in the presence of a flame in the burner; a thermoelectric generating element connected to a boost circuit; and a battery. The boost circuit allows boosting of the voltage generated by the thermoelectric generating element, which in turn is connected to the battery via a load switch and contacts of a multi-contact switch. If the battery energy level drops below a required level, the cooking appliance can restore a sufficient amount of energy to the battery without requiring other measures such as battery replacement. When the energy drops below a limit, only manual operation on a manual switch is required to efficiently recharge the battery using the opening / closing of the multi-contact switch.

[0006] WO 2019 / 166680A1 discloses a flame monitoring system, which includes: a thermocouple adapted to be arranged adjacent to a burner; and an electromagnetic gas valve adapted to open or close the passage of gas to the burner, the electromagnetic gas valve being electrically connected to the thermocouple, and the electromagnetic gas valve keeping the passage of the gas open when it receives a specific current from the thermocouple. The flame monitoring system also includes an interruption device, which is configured to interrupt the flow of current between the thermocouple and the electromagnetic gas valve during a predetermined time so that a voltmeter can measure the voltage of the thermocouple in an isolated state, and the predetermined time is the time for the electromagnetic gas valve to keep the passage of gas open by means of the actual inertia of the electromagnetic during the interruption. The flame monitoring system also includes an interruption device located between the thermocouple and the gas solenoid valve, which is configured to interrupt the current circulation between the thermocouple and the gas solenoid valve in the disconnected position and allow such circulation in the closed position. The interruption device includes a MOSFET and is configured to be in the disconnected position in the absence of power. The flame monitoring system of the invention includes an additional power supply circuit, which is configured to power such an interrupting device for a given time interval in the absence of power from the mains, and to use such power to arrange and / or maintain such an interrupting device in a closed position. Summary of the invention

[0007] The object of the present invention is to provide a thermoelectric safety device for use in gas combustion systems in the absence of flames.

[0008] The thermoelectric safety device includes: a thermocouple configured to detect a flame in a corresponding burner of the gas combustion system, the thermocouple generating a voltage; a solenoid valve electrically connected to the thermocouple and configured to allow gas to travel toward the corresponding burner when the solenoid valve is energized by the thermocouple; and a transistor electrically connected between the thermocouple and the solenoid valve. The solenoid valve is arranged to be directly connected to the transistor, which is a field effect transistor.

[0009] The thermoelectric safety device comprises a booster for supplying power to the transistor, the transistor is connected in parallel with the booster, and an output terminal of the booster is arranged to be connected to a gate terminal of the transistor. The booster is configured to boost the voltage generated in the thermocouple, and the obtained voltage can keep the transistor closed so that the solenoid valve is energized.

[0010] A thermoelectric safety device is thus obtained which can be activated regardless of the presence of a flame in the burner, which is self-powered and does not require it to be powered by any external power source.

[0011] In addition, the disengagement of the solenoid valve is controlled by the transistor, that is, before the solenoid valve is disengaged because insufficient current reaches the solenoid valve when the thermocouple cools down after the flame of the corresponding burner is turned off, the transistor is turned off, whereby current automatically fails to reach the solenoid valve and the solenoid valve is disengaged. Thus, a thermoelectric safety device is obtained that has a greater response time in the absence of a flame without substantially adversely affecting the time it takes the solenoid valve to be energized in the presence of a flame.

[0012] Additionally, once the transistor has been powered so that it operates as a closed switch, the overvoltage generated in the booster can be used for other functions such as a power light indicator of the flashing LED type, RFID or a battery charging system for use in gas cooking appliances.

[0013] These and other advantages and features of the present invention will become apparent in view of the accompanying drawings and detailed description of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 An electrical diagram of a thermoelectric safety device for a gas combustion system in the absence of flame according to the present invention is shown. DETAILED DESCRIPTION

[0015] Figure 1 An electrical diagram of a thermoelectric safety device 1 for a gas combustion system in the absence of a flame according to the present invention is shown. The thermoelectric safety device 1 comprises: a thermocouple 2 configured to detect a flame in a combustion system, in particular a flame in a burner of the combustion system; and a solenoid valve 7 electrically connected to the thermocouple 2 and configured to allow or prevent the gas from traveling toward the burner. In the presence of a flame, the thermocouple 2 heats up, generating a voltage capable of keeping the solenoid valve 7 energized, thereby allowing the gas to travel toward the corresponding burner. In the absence of a flame, the thermocouple 2 cools to the extent that it cannot generate a voltage capable of keeping the solenoid valve 7 energized, thereby preventing the gas from traveling toward the burner.

[0016] The gas combustion system is preferably a gas appliance incorporating a thermoelectric safety device 1. In particular, the gas appliance is a gas cooktop, although the thermoelectric safety device 1 may be incorporated into any other type of gas appliance known in the prior art (e.g., a gas stove). Furthermore, the gas appliance may include one burner or a plurality of burners, each burner including a corresponding thermoelectric safety device 1. Gas solenoid valves are known in the prior art, and it is therefore considered unnecessary to describe the gas solenoid valve in the present application.

[0017] The thermoelectric safety device 1 also includes a transistor 6 electrically connected between the thermocouple 2 and the solenoid valve 7. The transistor 6 acts as a switch, which allows the solenoid valve 7 to be acted on, regardless of whether the thermocouple 2 detects a flame. In other words, by means of a control not depicted, the solenoid valve 7 can be acted on to be de-energized despite the fact that the thermocouple 2 detects a flame in the burner.

[0018] The thermoelectric safety device 1 includes a booster 5 for powering a transistor 6, the booster 5 being configured to boost the voltage generated in the thermocouple 2, thereby obtaining a voltage at the output end of the booster 5 that can keep the transistor 6 closed so that the solenoid valve 7 is energized. The booster 5 is configured to boost the millivolt no-load voltage of the thermocouple 2 to a nominal voltage of the transistor 6, which is greater than about 1.5 V. The nominal voltage of the transistor 6 is preferably about 3 V.

[0019] The transistor 6 is a field effect transistor, preferably a MOSFET type transistor. The transistor 6 comprises a gate terminal 6a, a drain terminal 6b and a source terminal 6c, the output terminal 5a of the booster 5 being arranged to be connected to the gate terminal 6a of the transistor 6.

[0020] The transistor 6 functions as a switch. Specifically, when it operates in the cut-off region, there is no conduction between the source terminal 6c and the drain terminal 6b, so it operates as an open switch regardless of whether the thermocouple 2 detects the presence of flame. In the embodiment described, when the transistor 6 is supplied with a voltage starting from 1.5V, the transistor 6 allows current to pass, and when the transistor 6 reaches the nominal voltage, the transistor 6 operates as a closed switch.

[0021] When the thermocouple 2 detects the presence of a flame, it generates a voltage known as a no-load voltage, which is amplified by the booster 5. When the nominal voltage of the transistor 6 is reached, the transistor 6 operates as a closed switch, thereby allowing the solenoid valve 7 to be energized. From that point on, the thermocouple 2 changes from no-load operation to load operation. From that point on, virtually all the thermal current generated in the thermocouple 2 passes directly through the transistor 6, and the booster 5 consumes very little current.

[0022] When the flame is turned off, the thermocouple 2 begins to cool, generating less thermal current, at which time the transistor 6 is turned off, and the solenoid valve 7 is disengaged, thereby shutting off the flow of gas to the burner. The disengagement of the solenoid valve 7 is controlled by the transistor 6, that is, before the solenoid valve 7 is disengaged because insufficient current reaches the solenoid valve 7 when the thermocouple 2 cools after the flame of the corresponding burner is turned off, the transistor 6 is turned off, whereby the current automatically cannot reach the solenoid valve 7, and the solenoid valve 7 is disengaged.

[0023] Furthermore, once the transistor 6 has been powered so that it operates as a closed switch (i.e. when it is supplied with nominal voltage), the overvoltage generated in the booster 5 can be used for other functions, such as a power supply light indicator of the flashing LED type, RFID or a battery charging system for use in a gas cooking appliance.

Claims

1. A thermoelectric safety device for a gas combustion system in the absence of flame, the thermoelectric safety device comprising: a thermocouple (2), the thermocouple (2) being configured to detect a flame in a corresponding burner of the gas combustion system, the thermocouple (2) generating a voltage; a solenoid valve (7) electrically connected to the thermocouple (2) and configured to allow gas to flow toward the corresponding burner when the solenoid valve is energized by the thermocouple (2); and a transistor (6) electrically connected between the thermocouple (2) and the solenoid valve (7), the solenoid valve (7) being arranged to be directly connected to the transistor (6) and the disengagement of the solenoid valve (7) being controlled by the transistor (6), the transistor (6) being a field effect transistor. The thermoelectric safety device comprises a booster (5) for supplying power to the transistor (6), the transistor (6) being connected in parallel with the booster (5), and the output terminal (5a) of the booster (5) being arranged to be connected to the gate terminal (6a) of the transistor (6), the booster (5) being configured to boost the voltage generated in the thermocouple (2), and the obtained voltage can keep the transistor (6) closed so that the solenoid valve (7) is energized.

2. The thermoelectric safety device according to claim 1, wherein: The transistor (6) is a MOSFET.

3. A gas combustion system comprising at least one thermoelectric safety device according to any one of the preceding claims.

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