THERMOELECTRIC SAFETY ASSEMBLY

A thermoelectric safety assembly that includes a thermocouple configured to detect a flame in a burner and, in response to detecting the flame, generating an electrical voltage. The assembly includes an electromagnetic valve electrically connected to the thermocouple, and a transistor electrically connected between the thermocouple and the electromagnetic valve. The electromagnetic valve is arranged electrically connected with a field-effect transistor. The assembly also includes a voltage booster configured to power the transistor, the transistor being connected in parallel with the voltage booster. An output terminal of the voltage booster is arranged connected with a gate terminal of the transistor, the voltage booster being configured to boost the electrical voltage generated in the thermocouple, an electrical voltage being obtained that is capable of keeping the transistor closed such that the electromagnetic valve is energized.

TECHNICAL FIELD

The present invention relates to a thermoelectric safety device in the absence of flame for gas combustion systems.

BACKGROUND

Cooking appliances with burners are known in the art, each of which burners has associated a thermocouple connected to a respective electromagnetic valve, such that when the thermocouple detects the presence of flame in the burner, it generates a thermoelectric current which at a given time is capable of keeping the electromagnetic valve energized, allowing the passage of gas towards the corresponding burner.

EP 0288390 A1 furthermore describes electric circuits in which a MOSFET is arranged between the thermocouple and the electromagnetic valve, said MOSFET acting as a switch. So, depending on previously established parameters, the MOSFET can open the circuit, preventing the passage of current towards the electromagnetic valve, and therefore, making the electromagnetic valve close the passage of gas towards the burner, regardless of there being presence of flame in the corresponding burner. In electric circuits of this type, the MOSFET must be powered by an external power supply so that it operates as a closed switch for allowing the passage of current towards the electromagnetic valve.

JP H09196362 A describes a cooking appliance comprising a burner, a thermocouple associated with an electromagnetic valve, and a thermoelectric generating device which supplies a battery through a booster. When an ignition operation is completed, a switch opens so that the battery does not feed 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 generating device is reduced as well. When the output voltage of the power booster drops from one level, the current to the battery is limited through a current limiter, with sufficient voltage being supplied to prevent the electromagnetic valve from disconnecting.

U.S. Pat. No. 5,599,181 A 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 booster circuit, and a battery. The booster circuit allows to boost the voltage generated by the thermoelectric generating element which is in turn connected to the battery through a load switch and a contact of a multi-contact switch. The cooking appliance can restore a sufficient amount of energy to the battery if the battery energy level falls below a required level without other measures such as a battery replacement being necessary. Only manual operation on manual switches is required to efficiently use the ON/OFF of the multi-contact switch to recharge the battery when the energy has dropped below a limit.

WO 2019/166680 A1 discloses a flame monitoring system comprises a thermocouple adapted for being arranged next to the burner and an electromagnetic gas valve adapted for opening or closing a gas passage to said burner, the electromagnetic gas valve being electrically connected with the thermocouple and said electromagnetic gas valve keeping the gas passage open when it receives a specific current from the thermocouple. The flame monitoring system also comprises interruption means configured for interrupting current flow between the thermocouple and the electromagnetic gas valve during a predetermined time so that the voltage meter can measure the voltage of the thermocouple in vacuum, said predetermined time being such that the electromagnetic gas valve keeps the gas passage open during the interruption by means of the actual inertia of the electromagnetic. The flame monitoring system also includes interrupting means between the thermocouple and the gas electromagnetic valve configured to interrupt current circulation between the thermocouple and the gas electromagnetic valve in an open position and to allow such circulation in a closed position. The interrupting means comprises a MOSFET and is configured to be in the open position in the absence of power supply. The flame monitoring system of the invention comprises an additional power circuit configured to feed such interrupting means for a given time interval in the absence of power from the mains and to cause, with such power, such interrupting means to be arranged and/or maintained in the closed position.

SUMMARY

Disclosed is a thermoelectric safety device in the absence of the flame for gas combustion systems.

The thermoelectric safety device comprises a thermocouple configured to detect a flame in a corresponding burner of the gas combustion systems generating an electrical voltage, an electromagnetic valve electrically connected to the thermocouple and configured to allow the passage of gas towards the corresponding burner when the electromagnetic valve is energized by the thermocouple, and a transistor electrically connected between the thermocouple and the electromagnetic valve. The electromagnetic valve is arranged directly connected with the transistor, the transistor being a field-effect transistor,

The thermoelectric safety device comprises a voltage booster powering the transistor, the transistor being connected in parallel with the voltage booster and an output terminal of the voltage booster being arranged connected with a gate terminal of the transistor. The voltage booster is configured to boost the electrical voltage generated in the thermocouple, an electrical voltage being obtained capable of keeping the transistor closed such that the electromagnetic valve is energized.

A thermoelectric safety device is thus obtained which can be actuated regardless of whether there is the flame in the burner, this thermoelectric safety device being self-powered, it not being necessary to power it through any external power supply.

In addition, the disengagement of the electromagnetic valve is controlled by the transistor, i.e., before the electromagnetic valve is disengaged because the sufficient current does not reach it when the thermocouple is cooled down upon the flame of the corresponding burner being turned off, the transistor opens, whereby current automatically does not reach the electromagnetic valve and the electromagnetic valve is disengaged. Therefore, a thermoelectric safety device is obtained which has a greater response time in the absence of the flame without virtually penalizing the time taken for the electromagnetic valve to be energized in the presence of the flame.

In addition, the excess voltage generated in the voltage booster once the transistor has been powered so that it operates as a closed switch can be used for other functions such as powering luminous indicators of the blinking led type, RFID or battery charging systems used in gas cooking appliances.

These and other advantages and features will become evident in view of the figures and of the detailed description.

DETAILED DESCRIPTION

FIG. 1shows an electrical diagram of a thermoelectric safety device1in the absence of flame for gas combustion systems according to the invention. The thermoelectric safety device1comprises a thermocouple2configured to detect a flame8in the combustion system, in particular in a burner10of the combustion system, and an electromagnetic valve7electrically connected to the thermocouple2and configured to allow or prevent the passage of gas towards the burner. In the presence of flame the thermocouple2heats up, an electrical voltage capable of keeping the electromagnetic valve7energized being generated allowing the passage of gas towards the corresponding burner10. In the absence of flame the thermocouple2cools down to the point at which an electrical voltage capable of keeping the electromagnetic valve7energized cannot be generated, the electromagnetic valve7preventing the passage of gas towards the burner10.

The gas combustion system is preferably a gas appliance incorporating the thermoelectric safety device1. In particular, the gas apparatus may be a gas cooking top, although the thermoelectric safety device1could be incorporated to any other type of gas appliance known in the state of the art, a gas oven for example. Furthermore, the gas appliance can comprise a burner or a plurality of burners, each burner comprising the respective thermoelectric safety device1. Gas electromagnetic valves are known in the state of the art so their description in this application is not considered necessary.

The thermoelectric safety device1further comprises a transistor6electrically connected between the thermocouple2and the electromagnetic valve7. The transistor6acts as a switch, allowing acting upon the electromagnetic valve7regardless of whether the thermocouple2detects flame. In other words, by means of a non-depicted control, the electromagnetic valve7can be acted upon de-energizing it although the thermocouple2detects a flame in the burner.

The thermoelectric safety device1comprises a voltage booster5powering the transistor6, the voltage booster5being configured to boost the electrical voltage generated in the thermocouple2, there being obtained at the output of the voltage booster5an electrical voltage capable of keeping the transistor6closed such that the electromagnetic valve7is energized. The voltage booster5is configured to boost a no-load voltage of the thermocouple2of millivolts up to a nominal voltage of the transistor6, said nominal voltage being greater than approximately 1.5V. The nominal voltage of the transistor6is preferably approximately 3V.

The transistor6is a field-effect transistor, preferably a MOSFET type transistor. The transistor6comprises a gate terminal6a, a drain terminal6band a source terminal6c, an output terminal5aof the voltage booster5being arranged connected to the gate terminal6aof the transistor6.

The transistor6acts as a switch. In particular, when it operates in the cutoff region there is no conduction between the source terminal6cand the drain terminal6b, so it operates as an open switch regardless of whether or not the thermocouple2detects the presence of flame. In the described embodiment, the transistor6allows the passage of current when it is powered with a voltage from 1.5 V, operating as a closed switch when it reaches the nominal voltage.

When the thermocouple2detects the presence of flame it generates a voltage, referred to as no-load voltage, which is amplified through the voltage booster5. When the nominal voltage of the transistor6is reached, the transistor6operates as a closed switch, allowing the energization of the electromagnetic valve7. The thermocouple2passes from working with no-load to working with a load from that time. From that time, virtually all the thermoelectric current generated in the thermocouple2passes directly through the transistor6, the voltage booster5consuming very little current.

When the flame turns off, the thermocouple2starts to cool down and less thermoelectric current is generated. There comes a time in which the transistor6opens and the electromagnetic valve7is disengaged, closing the passage of gas towards the burner10. The disengagement of the electromagnetic valve7is controlled by the transistor6, i.e., before the electromagnetic valve7is disengaged because the sufficient current does not reach it when the thermocouple2cools down upon the flame of the corresponding burner being turned off, the transistor6opens, whereby current automatically does not reach the electromagnetic valve7and the electromagnetic valve7is disengaged.

In addition, the excess voltage which is generated in the voltage booster5once the transistor6has been powered so that it operates as a closed switch, i.e., when it is powered with the nominal voltage, can be used for other functions such as powering luminous indicators of the blinking led type, RFID or battery charging systems used in gas cooking appliances.