Safety device for controlling the flames of a plurality of gas burners

Abstract

Safety device for flame control of a plurality of gas burners, wherein each burner (2i) comprises: - a thermocouple (30j) positioned to be hit by at least one flame (8) generated by said burner (2j) and inserted into a thermoelectric circuit that controls the gas supply to said burner (2i), - an electromagnet (20) belonging to said thermoelectric circuit and acting on the shutter element (16) of a solenoid valve (10j) provided in the gas supply conduit to said burner (2j), - electrical contact means (32i, 33i, 38i, 39i) powered by the mains voltage and configured to allow the flow of current in said thermoelectric circuit in the presence of said mains voltage and to prevent the flow of current in the absence of said mains voltage, - a Hall effect sensor (48) for monitoring the current generated by said thermocouple (30i), characterized by the fact that each burner (2j) comprises a first connection of the thermocouple (30j) associated with it to said electromagnet (20), and a second connection of the same thermocouple (30) to a Hall sensor (48) common to all burners (2i), in each of said first and second connections being inserted an electrical contact means (32j,33i,38i,39j), controlled by a single control unit (46) powered by the mains and configured to cyclically and temporarily close the electrical contact means (33i, 39i) inserted into said second connection of the thermocouple (30j) associated with that burner (2j) when said burner (2j) is active, and at the same time to open both the electrical contact means (32i,38i) inserted into the first connection of that same thermocouple (30j) and the electrical contact means (33j,39j) inserted into the second connection of all the other thermocouples (30j) associated with the other active burners (2j), said opening times of said electrical contact means (32i,38i) inserted into said first connection of all thermocouples (30j) being chosen to be shorter than the switching time of the solenoid valve (10j) associated with each of said electromagnets (20).

Description

[0001] SAFETY DEVICE FOR CONTROLLING THE FLAMES OF A PLURALITY OF GAS BURNERS

[0002] The present invention relates to a safety device for controlling the flames of a plurality of gas burners.

[0003] Gas burners are known and used in various applications, particularly in gas stoves and cooktops. They are generally equipped with a safety device to prevent gas leakage in the event of accidental flame extinguishment. This safety device typically includes a thermoelectric circuit with a thermocouple designed to be heated by one of the flames produced by the burner, a solenoid valve, which is inserted into the gas supply line to the burner and is equipped with a spring, that keeps it closed in the absence of external forces, and an electromagnet connected to the thermocouple, which opens the solenoid valve when energized by the current generated by the thermocouple heated by the burner flame.

[0004] To ignite these known burners, the user manually operates the adjustment knob of the valve, which regulates the gas flow, to open the electric valve by prevailing over the elastic reaction of the spring that keeps it closed. This action simultaneously causes the gas to flow from the burner and generates a flame ring. At least one of the flames in this ring hits the thermocouple, generating a voltage and causing a current to circulate through the winding of the electromagnet. The electromagnet maintains the solenoid valve open and supplies the flame with gas that continues to flow through the burner even after the user releases the knob, which also performs the function of adjusting the valve that controls the gas flow and thus the size of the flames. Obviously, to stop the burner from operating, the user only needs to turn the knob to the position that stops the gas flow.

[0005] If during the operation of the burner an accidental cause, such as a breath of air or liquid spilling from a pot placed on the burner itself, leads to its extinguishment, the thermocouple, no longer exposed to the flame, ceases to generate voltage at its terminals and no longer powers the electromagnet. Consequently, the electromagnet no longer acts on the solenoid valve, allowing the spring's elastic reaction to return it to the closed position, thereby stopping the gas flow, even if the valve remains open.

[0006] Gas burners are also known that are designed for timed extinguishment. In this case, the burner can be extinguished not only manually by the user or due to accidental causes as described above but also in a programmed manner through the timed opening of a normally closed contact of a relay controlled by a control unit.

[0007] In all these known burners, their operation does not require mains power, and if no accidental causes occur, they remain lit until the user intervenes to turn them off. Timed extinguishment is not possible because it would require the intervention of the control unit, which is inactive without mains power.

[0008] For this reason, and more generally for safety reasons, recent regulations require that gas burners with a safety device must not operate without mains power.

[0009] Safety devices that comply with this regulation are already known. They are based on the principle of incorporating an electrical contact in the circuit powering the electromagnet, which is supplied with the voltage generated by a thermocouple exposed to the flame of a burner. This electrical contact remains closed in the presence of mains power and opens in the absence of mains power. In these known safety devices the electrical contacts opens in the absence of mains power, interrupts the current generated by the thermocouple and closes the solenoid valve that controls the gas flow to the burner.

[0010] EP 288390 teaches the use of a mosfet in the circuit that powers the electromagnet with the voltage generated by the thermocouple. Unlike a mechanical contact, a mosfet avoids contact uncertainties due to oxidation, dirt, or vibrations.

[0011] US 2022 / 341593 teaches placing a voltage amplifier in parallel with this electrical contact, which may also be a mosfet. This amplifier powers the mosfet and keeps it temporarily in the conductive state even in the absence of mains power, in order to delay the moment of interruption of the electromagnet's intervention.

[0012] EP 3534069 teaches incorporating a mosfet in the circuit that powers the electromagnet with the voltage generated by the thermocouple to enable very rapid interruptions of that circuit. This allows for the measurement of the voltage across the thermocouple without causing the gas flow to stop, due to the mechanical inertia of the solenoid valve.

[0013] US 2019 / 078781 teaches including a mosfet in the electromagnet's power circuit, which opens the circuit in the absence of mains power and prevents gas flow to the burner.

[0014] US 10247418 teaches including a Hall sensor in the electromagnet's power circuit to monitor the current generated by the thermocouple.

[0015] An aim of the invention is to ensure that gas burners with safety devices meet the aforementioned regulatory requirements and to propose a gas burner of the described type that, in addition to operating normally with its safety device and eventually having programmed automatic extinguishment, can also be automatically turned off in the event of mains power failure. Another aim of the invention is to eliminate the risk that a gas burner remains lit following a suspension of mains power, i.e., when the control means normally provided are inactive.

[0016] Another aim of the invention is to propose a gas burner that is simple to manufacture and operates safely and reliably.

[0017] Another aim of the invention is to propose a gas burner in which it is possible to effectively control the operating parameters.

[0018] Another aim of the invention is to propose a configuration of multiple gas burners of the aforementioned type, all capable of providing the required performance without incurring the costs associated with individually producing each burner capable of independently providing the same performance.

[0019] All these aims, and others that will become apparent from the following description, are achieved according to the invention with a safety device for flame control of a plurality of gas burners as defined in claim 1.

[0020] The present invention is further clarified below in some of its preferred embodiments of practical realization, provided for purely illustrative and non-limiting purposes, with reference to the attached drawings, in which: figure 1 shows in schematic view the general principle of operation of a gas burner flame control device with a relay contact inserted in the thermoelectric circuit of its thermocouple, figure 2 shows it in the same view as fig. 1 , with the relay contact replaced by a mosfet, figure 3 shows it in schematic view with a mosfet and a Hall sensor inserted in the thermoelectric flame control circuit of a gas burner, figure 4 shows in schematic view a flame control device for a pair of gas burners according to the invention in a first embodiment, and figure 5 shows it in the same view in a different embodiment.

[0021] As shown in fig. 1 , a gas burner 2 equipped with a flame control device is supplied with gas through a conduit 4, which is delivered from an external source 5 through an opening 6 and generates a flame crown 8.

[0022] The opening 6 is controlled by a solenoid valve 10, which may include, for example, a movable axial stem 12 with a magnet 14 at one end and a shutter 16 in a central position, configured to close the opening 6 for a specific axial position of the stem 12, thereby preventing gas from passing to the burner 2. The shutter 16 may advantageously be associated with a solenoid spring 18, which in its resting state tends to keep the shutter in a closed position and is loaded when the shutter is moved from this position to be brought into an open condition.

[0023] The magnet 14 may be attracted by an electromagnet 20 comprising a ferromagnetic core 22 and a winding 24, whose ends are connected to the two terminals 26, 28 of a thermocouple 30 arranged to be exposed to one of the flames of the flame crown 8.

[0024] Preferably, one terminal 26 of the thermocouple 30 is connected to ground, similarly to one end of the winding 24 of the electromagnet 20, while the other terminal 28 is connected to a normally open electrical contact 32 of a relay 34, which is directly powered by the mains or by a control unit 36 powered by the mains.

[0025] The operation of the control device described is as follows: when the burner 2 is supplied with gas, its flame 8 reaches the thermocouple 30 and generates a small electrical voltage between its terminals 26 and 28. In this condition, the control unit 36 keeps the relay 34 activated and thus keeps its contact 32 closed, so that the voltage generated by the thermocouple 30 causes a current to circulate in the winding 24 of the electromagnet 20, which in turn keeps the magnet 14 attracted, and consequently keeps the shutter 16 of the solenoid valve 10 spaced from the opening 6, thereby keeping the solenoid valve itself open.

[0026] However, if there is a power outage during normal operation, the relay 34 deactivates and its contact 32 opens. In this situation, the current circulation in the electromagnet 20 is interrupted even though the thermocouple 30 is still exposed to the flame 8 generated by the burner 2, and this is in line with current safety regulations.

[0027] Fig. 2 illustrates a gas burner 2, where the safety device is designed such that the normally open electrical contact connected to the terminal 28 of the thermocouple 30 is constituted by a mosfet 38, which in particular has the Drain terminal 40 connected to said terminal 28, the Source terminal 42 connected to the winding 24 of the electromagnet 20, and the Gate 44 connected to a control unit 46 powered by the mains. At rest, i.e. , when the mosfet 38 is not activated by the control unit 46, it is in the off state.

[0028] The operation of the control device now described is similar to that described previously: when the burner 2 is supplied with gas, its flame 8 reaches the thermocouple 30 and generates a small electrical voltage between its terminals 26 and 28. In this condition, the control unit 46 keeps the mosfet 38 in the conducting state, and the voltage generated by the thermocouple 30 causes a current to circulate in the winding 24 of the electromagnet 20, which keeps the magnet 14 attracted and, consequently, keeps the solenoid valve 10 open.

[0029] Even in this case, if a power outage occurs during normal operation, the control unit 46 of the mosfet 38 is no longer powered, and the mosfet switches to the off state, interrupting the current flow in the electromagnet 20 even though the thermocouple 30 is still hit by the flame 8 generated by the burner 2.

[0030] It can be recognized that the intervention of the contact 32 of the relay 34 or the mosfet 38 immediately and automatically stops the gas supply in the event of a power outage, making the gas burner fully compliant with regulations. More specifically, if this objective is achieved with the mosfet 38, the solution is particularly advantageous due to the superior performance of an electronic component compared to an electromechanical one in terms of cost, durability, and reliability of operation.

[0031] The state of the art already provides for the use of a Hall effect sensor 48, or simply Hall sensor 48, in the thermoelectric control circuit of the burner 2, in addition to the means (contact 32 of relay 34 or mosfet 38) for interrupting the current flowing in it. The Hall sensor 48 functions to detect the current generated when the thermocouple 30 is exposed to the flame 8 and its terminals 26 and 28 are connected to the electromagnet 20 that operates the solenoid valve 10.

[0032] Fig. 3 schematically illustrates a burner 2 with its control device, which includes the thermocouple 30, a mosfet 38 connected with its Drain terminal 40 to terminal 28 of the thermocouple 30, a Hall sensor 48 connected to the Source terminal 42 of the mosfet 38, and the winding 24 of the electromagnet 20 that operates the solenoid valve 10 connected to the Hall sensor 48. In this fig. 3, the solenoid valve 10 is represented, for simplicity, with only the electromagnet 20 that operates it.

[0033] Both the mosfet 38 and the Hall sensor 48 are connected to the control unit 46, which contains a program for managing the operation of the burner 2 according to the specified modes.

[0034] From a general point of view, the function of the Hall sensor 48 is to detect the current generated by the thermocouple 30 and to provide the control unit 46 with information based on the detected values. This information allows the control unit to perform corresponding functions based on specific algorithms used by the program loaded into the control unit.

[0035] For example, in the event of a burner 2 shutdown due to an accidental cause, such as a breath of air or a power outage, the Hall sensor 48 can provide corresponding information to the user and can send a command to relight the burner 2 once the cause of the shutdown has been resolved. Alternatively, it can command the control unit 46 not to relight the burner 2 if the unit was set to automatic relighting. Additionally, it can provide information on the presence or absence of a pot on the burner 2, if the system's geometry allows detection of differences in the current generated by the thermocouple 30 based on the configuration of the flame 8, depending on whether a pot, plate, or similar item is present on the burner 2.

[0036] The invention aims to apply the principles now described to a configuration of multiple gas burners of the type described, typically found in a stovetop or gas range with multiple burners 2. Since the current cost of an electrical contact 32 or a mosfet 38 is significantly lower than the cost of a Hall sensor 48, the invention proposes an economically advantageous configuration. Specifically, the proposed solution is illustrated in figs. 4 and 5, which differ primarily to show in fig. 4 a configuration of two burners 2i equipped with electrical contacts 32i,33i and in fig. 5 a configuration of two burners 2i equipped with mosfets 38j,39j.

[0037] Since, apart from this difference, the operation of the two configurations of burners 2i is essentially identical, this description will refer for simplicity to the burner configuration illustrated in fig. 5, but it should also be understood to apply to the burner configuration 2i illustrated in fig. 4 by substituting the mosfets 38i,39i with the relay contacts 32i,33j.

[0038] With reference to fig. 5, it is provided that each burner 21 , 22 is associated with two mosfets 38, 39, specifically a first mosfet 38i , 382, inserted in the branch connecting the thermocouple 30i , 302 to the respective solenoid valve 10i , 2, and a second mosfet 39i , 392, inserted in the branch connecting the thermocouple 30i , 302 to a Hall sensor 48, which is also common to the other burner 22, 2i.

[0039] In this embodiment, the coordinated management of the various mosfets 38i, 39i by the control unit (not shown for simplicity) allows the current individually generated by the thermocouple 30i, 302 of each burner 2i , 22, when active, to pass cyclically or according to a predefined program of the control unit through the single Hall sensor 48, while the current generated by the thermocouple 3O2, 30i of the other burner 22, 2i (or by the thermocouples 30i of other burners 2j, in the case of more than two burners 2) is sent to the respective solenoid valve 101 , 102. Given the inertia of the solenoid valves 10i compared to the rapid response of the electrical contacts 32i, 33j, and even more so of the mosfets 38i, 39i (a few hundred psec), the time of interruption of the current flow through a solenoid valve 10j when the current is diverted to the Hall sensor 48 is so brief that it does not allow the solenoid valve itself to close, while being sufficient to measure the current generated by the thermocouple 30i. T o illustrate the cyclic operation of the mosfets 38i, 39i in the schematic of fig. 5, where the four mosfets are marked with numbers 38i, 39i , 382, 392 and the two thermocouples are marked with numbers 30i, 302, the following phases can be identified:

[0040] Phase 1 : mosfets 38i , 382 conducting and mosfets 39i, 392 off

[0041] The currents generated by both thermocouples 30i , 302 power the respective solenoid valves 101 , 2 and both burners 2i , 22 operate normally.

[0042] Phase 2: mosfets 38i , 392 off and mosfets 39i , 382 conducting.

[0043] The current generated by the left thermocouple 30i does not feed the respective solenoid valve 101 for a brief moment but reaches the Hall sensor 48 through mosfet 39i , while the right thermocouple 3O2 feeds the respective solenoid valve 102. This brief moment, during which the current generated by the left thermocouple 30i does not power the respective solenoid valve 101 , is too short to deactivate the solenoid valve itself and interrupt the gas supply to the left burner 2i , but is sufficient to be detected by the Hall sensor 48.

[0044] Phase 3: mosfets 38i , 392 conducting and mosfets 39i, 382 off

[0045] In this case, the situation is reversed compared to Phase 2, meaning that the current generated by the left thermocouple 30i powers the respective solenoid valve 10i, while the current generated by the right thermocouple 3O2 passes through the Hall sensor 48, but the duration of this phase is too brief to interrupt the operation of the right burner 22.

[0046] Phase 4: Same as Phase 1.

[0047] The same applies in the case of more burners 2. there is cyclic connectivity for each thermocouple 30i with the Hall sensor 48, so that it can detect the behavior of all the burners 2i at the predetermined frequency, using a single Hall sensor 48 and two mosfets 38i, 39i for each burner 2i to be monitored.

[0048] It may also be provided that the connection of the thermocouple 30i of the various burners 2i does not occur with a predetermined cycle but is controlled by the operator or based on a predefined program in the control unit.

Claims

C L A I M S1 . Safety device for flame control of a plurality of gas burners, wherein each burner (2i) comprises: a thermocouple (30j) positioned to be hit by at least one flame (8) generated by said burner (2j) and inserted into a thermoelectric circuit that controls the gas supply to said burner (2i), an electromagnet (20) belonging to said thermoelectric circuit and acting on the shutter element (16) of a solenoid valve (10j) provided in the gas supply conduit to said burner (2j), electrical contact means (32j, 33j, 38i, 39j) powered by the mains voltage and configured to allow the flow of current in said thermoelectric circuit in the presence of said mains voltage and to prevent the flow of current in the absence of said mains voltage, a Hall effect sensor (48) for monitoring the current generated by said thermocouple (30i), characterized by the fact that each burner (2j) comprises a first connection of the thermocouple (30j) associated with it to said electromagnet (20), and a second connection of the same thermocouple (30) to a Hall sensor (48) common to all burners (2i), in each of said first and second connections being inserted an electrical contact means (32j,33i,38i,39j), controlled by a single control unit (46) powered by the mains and configured to cyclically and temporarily close the electrical contact means (33i, 39i) inserted into said second connection of the thermocouple (30j) associated with that burner (2j) when said burner (2j) is active, and at the same time to open both the electrical contact means (32i,38i) inserted into the first connection of that same thermocouple (30j) and the electrical contact means (33j,39j) inserted into the second connection of all the other thermocouples (30j) associated with the other active burners (2j), said opening times of said electrical contact means (32i,38i) inserted into said first connection of all thermocouples (30j) being chosen to be shorter than the switching time of the solenoid valve (10j) associated with each of said electromagnets (20).

2. Device according to claim 1 characterized in that said Hall sensor (48) is controlled by the same unit (46) that controls said electrical contact means (32i,33i,38i,39i).

3. Device according to claim 1 and / or 2 characterized in that in said first connection of each thermocouple (30i) with the respective electromagnet (20), a normally open contact (32j) of a relay (34) controlled by said control unit (46) is inserted.

4. Device according to one or more of the preceding claims characterized in that in said first connection of each thermocouple (30j) with the respective electromagnet (20), a mosfet (38j) is inserted, configured to be in a non-conductive state at rest and to switch to a conductive state upon command from said control unit (46).

5. Device according to one or more of the preceding claims characterized in that in said second connection of each thermocouple (30j) with said Hall sensor (48) a normally open contact (33j) of a relay (34) controlled by said control unit (46) is inserted.

6. Device according to claim 5 characterized in that in said second connection of each thermocouple (30i) with said Hall sensor (48), a mosfet (39i) is inserted, configured to be in a non-conductive state at rest and to switch to a conductive state upon command from said control unit (46).

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