DE20000259U1 - Gas stove top - Google Patents

Description

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WHl99-001

Gas stove top

The invention relates to a gas stove top having at least one gas burner. In particular, the invention relates to a gas stove top comprising a gas line for supplying gas to each burner, control valves adjustable by a user to allow, adjust and cut off the gas supply to the burner, a safety valve arranged in the gas line in series with the control valves and capable of cooperating with a flame sensor to automatically cut off the gas supply to the burner in the absence of flame, and flame ignition means controlled by the control valves which, during the ignition phase, on command from the user and even in the absence of flame, can keep the safety valve open to allow the gas supply to the burner during the ignition phase.

In the known so-called "gas-safe" gas stove tops, the arrangement of the control valve and the safety valve forms the so-called "valve connection" which contains a safety valve which is directly connected to a flame sensor, usually in the form of a thermocouple, which is located near the burner flame. This safety valve is opened by the pressure exerted by the user on the button of the valve connection and then held open by the electric current generated by the thermocouple located near the flame. When the flame is extinguished, the current required to keep the safety valve open is

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valve is not present; the safety valve then closes and interrupts the gas flow.

This known solution has the disadvantage of requiring the user's intervention during the ignition phase until the flame sensor intervenes to keep the safety valve open. In other words, the user must keep the button connected to the valve connector pressed for the time necessary to heat the thermocouple forming the flame sensor.

The object of the invention is to provide a gas stove top according to the preamble of claim 1, with which the aforementioned disadvantage is avoided in a simple and economical manner.

This object is achieved according to the invention in that the gas stove top additionally has an electronic control circuit which is connected to the control valve, the safety valve, the flame sensor and to the flame ignition means and can keep the safety valve open for a certain period of time in order to allow the automatic ignition of the flame based on an initial command from the user.

In the stove top according to the invention, a separation is made between the direct connection between the flame sensor and the safety valve by inserting an electronic control circuit which detects the presence or absence of a flame based on the voltage

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voltage signal from the sensor and which applies or does not apply this voltage signal to the safety valve according to the various conditions detected. Thanks to this control circuit, when the burner gas is ignited, the user only needs to give the control valves an initial command, which is preferably identical to that given for the known valve connections, namely pressing and turning the knob; the user no longer needs to keep the knob pressed because the electronic control circuit controls the ignition automatically.

Another disadvantage of the well-known gas stove top is the accidental extinguishing of the flame, caused for example by a gust of air. In this case, the gas supply to the burner is interrupted by the intervention of the safety valve, but the user is not informed of this and the burner gas cannot be re-ignited without the user's intervention.

The present invention also solves this technical problem because the electronic control circuit comprises means for automatically reigniting the flame, which come into effect after the flame has been extinguished during normal operation of the burner. These means can detect the normal operation of the burner, activate the flame ignition means when the absence of the flame has been detected and keep the safety valve open for a certain time.

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Further advantages and features of the gas stove top according to the invention will become apparent from the following detailed description of an embodiment. They show:

Fig. 1 is a general view of a gas stove top according to the invention, with only one gas burner being shown for reasons of clarity,

Fig. 2 is a block diagram of the electronic control circuit used in the gas stove top of Fig. 1, and

Fig. 3 is a schematic view of a display panel connected to the gas stove top of Fig. 1.

In Fig. 1, the gas stove top has the following components:

a flame sensor 10, preferably in the form of a thermocouple,
a valve arrangement, generally designated 12, consisting of a control valve 12a adjustable by means of a knob M and a safety valve 12b (solenoid valve), both valves being arranged in series in a gas line C supplying gas to the burner B,
a position sensor 14 connected to the control valve 12a, which detects two information positions of the button M, namely a signal for indicating the position of the button when it is pressed by the user and a signal for indicating the position of the button when it

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is not in the "0" position, i.e. when the knob has been turned and the valve arrangement allows the supply of gas to the burner,

an electronic control circuit 16, which is preferably formed by a microprocessor,

a user adaptation circuit 20 which provides information to the user and/or receives information or commands from the user.

According to a preferred embodiment of the gas stove top, the user adjustment circuit 20 has the following components:

a timer with a display unit 22 having two digits and four electroluminescent diodes (LEDs) for displaying the time for the automatic interruption function of the gas supply and for displaying which burner the timer is assigned to,
a safety button (associated with the corresponding LED) for the gas hob top, whereby this safety button is used to switch the gas hob top on or off and allows safety functions such as preventing use by children or quickly switching off the gas hob top when necessary (panic button),

a light alarm (LED) used to indicate an error condition that has occurred,

an acoustic alarm (buzzer) that provides the user with a range of information, such as alarm conditions, buzzer end, ignition failure, etc.

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The operation of the gas stove top according to the invention is as follows (Fig.2). When the button M is in the "0" position (closed), the control circuit 16 operating with a microprocessor 16a detects the position of the button by means of the "button rotation" signal; this control circuit then continues not to energize the safety valve 12b and leaves the ignition circuit 18 switched off. If in this state the button M is pressed to try to ignite the gas of the burner B, the control circuit 16 may detect an abnormal operation; the control circuit then does not activate the ignition circuit 18. It is also possible to inform the user of this abnormal operation, for example by switching on the buzzer.

When the knob M is turned, the control circuit 16 allows the possibility of ignition: as soon as the knob M is pressed, the control circuit, via an auxiliary circuit 13, energizes the safety valve 12b which had been opened by the user's pressure on the knob. Therefore, the user can now release the knob M immediately after having pressed the knob, without having to wait for the flame to ignite and the thermocouple 10 to heat up.

As soon as the pressure on the button M is detected, the control circuit 16 activates the ignition circuit 18 and this control circuit then begins to check, by means of a flame detection circuit 11, whether the gas from the burner B has ignited. As soon as the presence of a flame has been detected, the ignition circuit 18 is switched off, thus completing the ignition process.

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It should be noted that the ignition step cannot last beyond a certain time set in the control circuit 16 (for example 10 seconds). If the flame is not generated within this certain time, the safety valve 12b and the ignition circuit 18 are switched off, so that the gas flow in the gas line C is interrupted. The user is alerted to the ignition error by the audible and/or visual alarm (not shown). If the absence of the flame has been detected during the normal operation of the burner B (for example, if the flame has been blown out by a blast of air), the control circuit 16 starts a re-ignition process: the system repeats the ignition step by activating the ignition circuit 18. If the flame reappears within the certain time, the ignition circuit 18 is switched off again and the burner B can continue its function. If, on the other hand, the flame does not reappear within the certain time, the burner B is put into the safety state, the safety valve is closed and the user is informed by an audible or visual alarm.

To prevent constant re-ignition, even in the case of abnormal conditions (for example, when liquid boils over from a pot), the re-ignition attempts are limited to a certain number of attempts (for example, three) within a certain time (for example, one minute).

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To make the gas hob top safer, it is possible to insert an on-off switch (not shown) which allows the functions known as child safety lock or panic button to be carried out. When this switch is on, the control circuit 16 does not cause the safety valve 12b to open, even if the user turns the knob M; this control circuit then gives an audible or visual alarm to the user (child safety lock function). If this switch is turned on when the gas hob top is in operation, all the burners B are immediately switched off by closing the corresponding safety valves 12b (panic button function).

Another function that can advantageously be included in the gas stove top according to the invention is the timer function, which allows the user to program a cooking time for each burner, after which the burner is automatically switched off. In the gas stove top according to the invention, this function is carried out as follows: when a burner B is to be ignited in order to enter a cooking time, it is sufficient to press the corresponding button M. A timer display unit 22 (Fig. 3) immediately switches on, showing the time in minutes; also a second LED display 22a (four LEDs indicating the position of the burners) switches on, indicating the button pressed and the burner selected. By pressing button M again, the required time can be selected (a longer press corresponds to a longer cooking time).

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After the setting has been made, the display unit 22 continues to show the time remaining until the end of the cooking process, which time decreases continuously. At the end of the cooking time, the burner B is switched off because the control circuit 16 closes the safety valve 12b; the user is informed of this by an acoustic and/or visual alarm.

Another advantageous function is to ensure the operation of the gas cooker top even when it is not powered from the electrical network via a power supply circuit 15. As indicated in Fig. 2, a relay 24 is arranged in the control circuit 16: when the control circuit 16 is not powered from the network, the relay 24, which is normally in the operated state, brings the thermocouple 10 once again into contact with the winding of the safety valve 12b, so that an operation corresponding to the known valve arrangement is restored. Of course, the flame must then be ignited by using an external igniter.

The presence of the electronic control circuit 16 also enables other functions to be performed, such as checking the correct operation of the circuit, indicating errors and/or faults, indicating that the grill is still hot, etc.

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Claims (10)

1. Gas stove top with the following components - at least one gas burner (B), - a gas line (C) to supply each burner (B) with gas, - at least one control valve ( 12a ) which can be adjusted by a user to allow, adjust or interrupt a gas supply to the burner (B), - a safety valve ( 12b ) located in the gas line (C) in series with the control valve ( 12a ) and capable of cooperating with a flame sensor ( 10 ) to interrupt the gas supply to the burner (B) in the absence of a flame, and - flame ignition means ( 18 , 18a ) controlled by the control valve ( 12a ), said control valve being able to keep the safety valve ( 12b ) open during the ignition phase, at the user's request and even in the absence of the flame, in order to allow the gas supply to the burner during the ignition phase, characterized in that the gas cooker top additionally comprises an electronic control circuit ( 16 ) connected to the control valve ( 12a ), the safety valve ( 12b ), the flame sensor ( 10 ) and the flame ignition means ( 18 , 18a ), which is able to detect the ignition state of the control valve ( 12a ) and to keep the safety valve ( 12b ) open for a certain period of time in order to allow the automatic ignition of the flame following an initial command from the user. 2. Gas stove top according to claim 1, characterized in that the electronic control circuit ( 16 ) comprises alarm means capable of warning the user in the absence of ignition of the flame at the end of the predetermined period of time. 3. Gas stove top according to claim 1, characterized in that the electronic control circuit ( 16 ) comprises means for automatically reigniting the flame, which come into effect when the flame is accidentally extinguished during normal operation of the burner (B), and which can detect the state of normal operation of the burner (B), activate the flame ignition means ( 18 , 18a ) when the absence of a flame has been detected during normal operation of the burner (B), and keep the safety valve open for a certain time. 4. Gas stove top according to claim 3, characterized in that the electronic control circuit ( 16 ) comprises an auxiliary alarm means which warns the user if the re-ignition fails. 5. Gas stove top according to claim 3, characterized in that the electronic control circuit ( 16 ) can repeat the ignition process with a certain number of attempts. 6. Gas stove top according to claim 1, characterized in that the electronic control circuit ( 16 ) has a user-operable safety circuit which can keep the safety valves ( 12b ) of all burners (B) closed even when the control valves ( 12a ) are in the ignition state, or which can close the safety valves ( 12b ) during normal operation of the gas stove top in order to cause a rapid extinguishing of all burners (B). 7. Gas stove top according to claim 1, characterized in that the electronic control circuit ( 16 ) comprises a timer device which is associated with each burner (B), can be actuated by the user and can close the safety valve ( 12b ) of the burner (B) selected by the user after a certain time. 8. Gas stove top according to claim 7, characterized in that the timer device has a display panel which is associated with the gas stove top and has first display means ( 22 ) for setting the time by the user and second display means ( 22a ) for the burner (B) selected by the user. 9. Gas stove top according to claim 8, characterized in that the timer device comprises setting means associated with the setting buttons (M) for the control valves ( 12a ), the duration of the pressure on the button (M) of the selected burner (B) being proportional to the set time displayed by the first display means ( 22 ) on the display unit. 10. Gas stove top according to claim 1, characterized in that the electronic control circuit ( 16 ) has a normally-on relay ( 24 ) which, in the absence of electrical power supply for the gas stove top, can directly connect the flame sensor ( 10 ) to the safety valve ( 12b ) to allow manual ignition of the burner gas.