EP2578947A1

EP2578947A1 - Gas cooking top with safety system

Info

Publication number: EP2578947A1
Application number: EP12187055.4A
Authority: EP
Inventors: Tiziano Lacche'
Original assignee: Indesit Co SpA
Current assignee: Whirlpool EMEA SpA
Priority date: 2011-10-03
Filing date: 2012-10-02
Publication date: 2013-04-10
Also published as: ITTO20110882A1

Abstract

The present invention relates to a cooking appliance comprising at least one flat gas burner (105, 106, 107, 108), a cover (104) that closes on top of the flat burner (105, 106, 107, 108), a gas supply line (201) and a first gas circuit (202) supplying gas to the flat burner (105, 106, 107, 108), and at least one ionization flame detector (305, 306, 307, 308) associated with the flat burner and adapted to generate a signal dependent on the presence of a flame at the flat burner. The cooking appliance further comprises cover closure sensing means (212), adapted to output a signal when the cover (104) is closed, and two electrovalves (209, 210) arranged in series and adapted to stop the gas flow towards the flat burner, and further comprising control means (211, 213) operationally connected to the two electrovalves (209, 210) and to the ionization flame detector, and adapted to cause the closing of the two electrovalves (209, 210) depending of the signal received from the ionization flame detector, wherein the control means (213) are also operationally connected to the closure sensing means (212) and are adapted to cause the closing of at least one (210) of the two electrovalves (209, 210) depending of the second signal received from the closure sensing means (212).

Description

[TECHNICAL FIELD]

The present invention relates to the field of cooking appliances, wherein the heat required for cooking food is provided by gas combustion.
In particular, the invention relates to a cooking appliance according to the preamble of claim 1.

[PRIOR ART]

Cooking tops are currently known which comprise one or more gas burners and which are equipped with safety systems for stopping the gas flow to the burners in the event that combustion problems arise at burner level.
For example, US patent 7,044,729 B2 relates to a cooking appliance comprising a burner and a thermostat valve for burner adjustment. The cooking appliance described in US 7,044,729 B2 comprises an electronic module that outputs a voltage signal to a safety valve, which stays open depending on the signal supplied by a thermocouple associated with the burner flame.
Patent GB2249382A relates to a cooking appliance comprising a burner and a tap; the cooking appliance further comprises a cut-off valve that controls the gas flow to the burner, and a thermocouple that generates an opening signal when heated by the burner flame, wherein the cut-off valve is further controlled by an electric pulse generator controlled by a switch associated with the tap.
Patent EP964326B1 relates to a cooking appliance comprising a manually operated valve supplying gas to a burner, and an electromagnetic valve that shuts off the gas line if the burner flame goes out. The electromagnetic valve is connected to an electronic control unit, which closes the electromagnetic valve if the burner does not become ignited within a predetermined number of ignition pulses. The ignition sensor of the cooking top is of the flame ionization type, and is associated with the ignition spark plug of the burner. However, the above-described known cooking appliances cannot control the safety of some kinds of cooking devices, such as, for example, cooking tops comprising a cover adapted to cover at least one of the cooking top's burners.
Current safety regulations require that the gas flow to the burners of a cooking appliance comprising a cooking top fitted with a cover be inhibited when the cover is down.
The reasons for this safety requirements are apparent. In fact, if there was still a flame under the cover, the cover itself would become very hot, thus representing a danger for the user; also, the interspace under the cover could become saturated with gas, which might cause an explosion should the user raise the cover and provide the oxygen necessary for burning the gas accumulated therein.

[OBJECTS AND SUMMARY OF THE INVENTION]

The present invention aims at overcoming some of the problems of known cooking appliances.
In particular, it is one object of the present invention to provide a cooking appliance that implements a safety system which is alternative to those according to the prior art and more efficient in ensuring safety of operation of a cooking top comprising a cover, in particular when the cover is closed.
The present solution also aims at providing a safety system for a cooking appliance comprising a cooking top with a cover, wherein the safety system of the cooking appliance comprises a small number of elements having an effective configuration, thus ensuring increased simplicity and reduced costs of the cooking appliance while complying with the safety regulations in force.
This and other objects of the present invention are achieved through a cooking appliance incorporating the features set out in the appended claims, which are intended to be an integral part of the present description.
One idea at the basis of the present invention is to provide a cooking appliance comprising at last one flat burner, a cover adapted to be positioned, when closed, on top of the flat burner, a gas supply line supplying gas to the flat burner, at least one ionization flame detector for the flat burner, adapted to generate a signal dependent on the presence of a flame at the flat burner, and a cover closure sensor, adapted to switch a signal when the cover is closed. The cooking appliance further comprises two safety electrovalves arranged in series, adapted to cut off the gas supply line, and control means operationally connected to the two electrovalves, to the ionization flame detector, and to the cover closure sensor; the control means are adapted to cause the closing of both electrovalves depending on the signal received from the ionization flame detector, and of at least one of the electrovalves depending on the signal from the cover closure sensor.
The cooking appliance according to the invention is thus provided with an efficient and reliable safety system, which allows stopping the gas flow to the flat burner if the flame gets extinguished or the cover is closed, thus ensuring increased simplicity and reduced costs of the appliance while complying with the safety regulations in force, which require a replication of the on-off valves and the presence of a cut-off valve that comes into play when the cover is closed.
In a preferred embodiment, a cooking appliance according to the present invention further comprises a cooking cavity, which comprises at least one second burner and one second ionization flame detector adapted to generate a second signal dependent on the presence of a flame at the second burner. The second burner is supplied by a second gas supply line, which branches off from the main gas supply line in the line portion comprised between the two electrovalves.
Therefore, the present invention is advantageously applicable to gas cookers comprising a cooking top and at least one oven, thus effectively preventing any accidental gas leakage from all the burners of the gas cooker, while only requiring the use of three electrovalves that can be controlled by the control means of the cooking top.
Further objects and advantages of the present invention will become more apparent from the following detailed description and from the annexed drawings.

[BRIEF DESCRIPTION OF THE DRAWINGS]

Some preferred and advantageous embodiments will now be described by way of non-limiting example with reference to the annexed drawings, wherein:

Figure 1 shows a cooking appliance comprising a cooking top according to the present invention;
Figure 2 diagrammatically shows an example of embodiment of a cooking appliance comprising a cooking top according to the present invention.

The drawings show different aspects and embodiments of the present invention and, where appropriate, similar structures, components, materials and/or elements in the various drawings are designated by the same reference numerals.

[DETAILED DESCRIPTION OF THE INVENTION]

Figure 1 shows an example of embodiment of a cooking appliance 101. The cooking appliance 101 comprises a cooking top 103 and a cooking cavity 102. The cooking top 103 further comprises a cover 104; when the cover 104 is in the open configuration (as shown in Figure 1), the cooking top 103 is accessible and shows a plurality of flat burners 105, 106, 107 and 108, the power of which is adjusted by suitable valves that can be controlled by the user through the knobs 109. When the cover 104 is closed again by the user, it covers the flat burners 105, 106, 107 and 108, thereby making them no longer accessible.
Safety regulations require that, when the cover 104 is closed, the flat burners 105, 106, 107 and 108 cannot be turned on or stay on; therefore, when the cover 104 is closed, the gas supply to said burners is stopped in manners that will be further explained below.
The cooking cavity 102, e.g. an oven, comprises a burner (not shown in the drawing), the power of which is adjusted through a user-operated knob 110, which is preferably associated with a thermostat.
The flat burners 105, 106, 107 and 108 of the cooking top 103 and the burner 109 of the cooking cavity 102 are supplied with fuel gas through a supply line that will be described more in detail below.
Figure 2 diagrammatically shows the internal configuration of the cooking appliance 101.
The gas supply line 201 provides the fluidic connection that supplies fuel gas to the burners of the cooking appliance 101. In this embodiment, the line 201 branches off into a first branch 202, which supplies each flat burner 105, 106, 107 and 108 of the cooking top 103, and a second branch 203, which supplies the burner (not shown) of the cooking cavity 102. In general, in Figure 2 a continuous line represents a gas supply line, whereas a dashed line represents an electric/electronic connection.
The supply branch 202 comprises a plurality of adjuster valves 205, 206, 207 and 208, which are adapted to adjust the flow of gas supplied to the flat burners 105, 106, 107 and 108, with which they are respectively associated, so as to adjust the heating power of the burner themselves. Preferably, the flow rate is adjustable through a knob that can be operated by a user by referring to indications shown on a graduated scale. Preferably, the adjuster valves 205, 206, 207 and 208 lack any dedicated safety systems and can only be operated manually.
Likewise, the supply branch 203 comprises a thermostat 204, i.e. a valve adapted to adjust the flow of gas supplied to the burner of the cooking cavity 102, so as to adjust the temperature in the cavity with which the burner 102 is associated. Preferably, the thermostat 204 is a mechanical one and comprises a diaphragm that adjusts the gas flow rate; preferably, the flow rate is adjustable through a knob that can be operated by the user by referring to indications shown on a graduated scale. Preferably, the thermostat 204 lacks a dedicated safety valve and must be operated manually.
In order to implement the safety functions required by the regulations, according to which the gas flow to the burners must be stopped if the flame thereon gets extinguished, the cooking appliance 101 comprises a pair of valves 209 and 210, wherein the valve 209 is placed on the supply line 201, whereas the valve 210 is arranged in series with respect to the valve 209 on the branch 202 that supplies the flat burners 105, 106, 107 and 108 of the cooking top 103. The valve 210 is located upstream of the above-described adjuster valves 205, 206, 207 and 208, so that it can stop the gas flow in the whole branch 202. The valves 209 and 210 are in a number of two because, for safety reasons, it is preferable to provide a replication of the gas line interruption: in fact, should one valve malfunction, the other valve will still be able to interrupt the gas flow to the burners, if necessary.
The valves 209 and 210 are adapted to be electrically controlled by a control of the cooking appliance 101, and will therefore be referred to below as "electrovalves". Preferably, said electrovalves 209 and 210 comprise an electric motor or actuator. Alternatively, said electrovalves 209 and 210 are solenoid valves, wherein the current flow through a solenoid associated with the valve is such as to vary the opening of the valve itself. Preferably, solenoid electrovalves are such as to stay closed in the absence of current.
The cooking appliance 101 further comprises control means 211 for controlling the safety devices. These control means 211 comprise at least one electronic board; therefore, in the following description the terms "board" or "electronic board" will be used to indicate the control means 211 as a whole.
The valves 209 and 210 are operationally associated with the electronic board 211 of the cooking appliance 101.
The board 211 is adapted to, among other things, cause the closing of the electrovalves 209 and 210. The electrovalves 209 and 210 stay normally open during the operation of the flat burners 105, 106, 107 and 108 of the cooking top 103; however, in the event that the flame thereon goes out and cannot be restored within a suitable time, the board 211 will cause the closing of the safety electrovalves 209 and 210, thereby stopping the gas flow to the flat burners 105, 106, 107 and 108.
To this end, the cooking appliance 101 further comprises a plurality of ionization flame detectors 305, 306, 307 and 308, which are adapted to detect the presence of a flame at the flat burners 105, 106, 107 and 108 with which they are respectively associated.
The ionization flame detectors 305, 306, 307 and 308 are adapted to output an electric signal to the board 211, so as to signal any situations requiring attention, e.g. if the flame of one of the burners of the cooking top accidentally goes out.
In this way, when the flame at one burner goes out, the ionization flame detector will detect such a condition and will send a signal to the board 211.
If the flame goes out accidentally and unexpectedly, i.e. not because of a user command, the board 211 will preferably re-ignite the flame through a known igniter device (not shown) controlled by the board 211, in order to restore the operation set by the user. If reignition is unsuccessful within times set by the regulations, the board 211 will cause the closing of the electrovalves 209 and 210, thereby stopping the gas flow along the supply branch 202.
The cooking top 101 further comprises a closure sensor 212 adapted to detect the closure of the cover 104, i.e. adapted to determine the (open/closed) configuration of the cover. Preferably, the closure sensor 212 comprises an electromechanical switch, i.e. a pushbutton actuated by the closed cover.
As an alternative, the closure sensor 212 comprises a magnetic proximity switch adapted to detect the presence of a portion corresponding to the cover 104, and hence the closure thereof.
The cooking appliance 101 further comprises control means 213 for controlling the safety devices associated with the closure of the cover 104. In this case as well, these control means 213 comprise at least one electronic board; therefore, in the following description the terms "board" or "electronic board" will be used to indicate the control means 213 as a whole. As will be apparent to those skilled in the art, the control means 211 and 213 may be implemented either through a single control board or through a larger number of control boards, although in the present description reference is made, for clarity, to two separate control boards 211 and 213.
The board 213 is operationally connected to the closure sensor 212, and is adapted to detect the signal sent by the latter and relating to the closure of the cover 104. If the closure sensor 212 detects that the cover 104 has been closed and is covering the cooking top 103, the board 213 will cause the closing of the electrovalve 210, thereby stopping the gas flow to the flat burners 105, 106, 107 and 108 of the cooking top 103.
Therefore, the electrovalve 210 operates as a cut-off valve, by excluding the branch 202 from the gas supply line 201. In this manner, a safety system is created which prevents the burners of the cooking top from igniting accidentally when the cover is closed.
In a preferred embodiment, the cooking appliance 101 further comprises the cooking cavity 102, with which a burner (not shown) is associated. The burner of the cooking cavity 102 is monitored by an additional ionization flame detector 302, which, as previously described, sends a signal to the electronic board 211.
The cooking appliance 101 further comprises an electrovalve 214, arranged upstream of the thermostat 204 that adjusts the temperature in the cooking cavity 102.
In particular, the electrovalve 214 is placed past the point where the branch 203 branches off the gas supply line 201, i.e. it is in such a position as to be able to stop the gas flow to the cooking cavity 102.
Also the electrovalve 214 is controlled by the board 211, which is adapted to cause the closing thereof depending on the signal supplied by the ionization flame detector 302 associated with the burner of the cooking cavity 102. Therefore, in this embodiment of the cooking appliance 101, the thermostat 204 that adjusts the temperature in the cooking cavity 102 does not need a dedicated safety valve and is compliant with the regulations, since the electrovalves 209 and 214 are replicated and ensure safety redundancy. Preferably, the safety system implemented by the electronic board 211 that controls the electrovalves 209, 210 and 214 is activated when the user decides to turn on one of the burners by operating the corresponding knobs of the adjuster valve or of the thermostat, which are fitted with a rotary electric contact that sends an activation signal to the electronic board 211.
The safety system implemented by the electronic board 213 that only controls the cut-off valve 210 is preferably always active, so as to detect the closure of the cover 104 whether the flat burners are on or off.
Furthermore, in a preferred embodiment of the present invention the cooking appliance 101 implements a "T0 ignition" function, which means that, when a user wants to turn on a burner, he/she will not need to continuously press the adjuster knob to enable the supply of gas to the burner. The "T0 ignition" function is implemented by the control means of the cooking appliance 101 in accordance with known methods.
In addition, the cooking appliance 101, while implementing the "T0 ignition" function, temporarily suspends the operation of the safety system implemented by the board 211 for the first ignition instants, i.e. for a predetermined period of time following the instant at which the user issued the ignition command.
During this predetermined ignition time, the electronic board 211 further issues a command that suspends the command for closing the safety electrovalves (although a flame has not yet been generated) only within the time window defined by said predetermined time. Once ignition has successfully occurred, the electronic board 211 will continue to operate by monitoring the safety conditions as previously described. Should any problems arise during the ignition stage, the electronic board would right away cause the closing of the electrovalves, as already described.
It is clear that the man skilled in the art may conceive further variants of the present invention, different from the non-limiting example described herein, without however departing from the protection scope as defined by the appended claims.
It would be possible, in fact, to equip the heating appliance with additional safety electrovalves, controlled by the electronic board, implementing redundant safety functions. Moreover, a cooking appliance according to the present invention may comprise or not a cooking cavity in addition to a cooking top, or said cooking cavity may be heated by electric means, as opposed to one or more gas burners.
It is also apparent that the invention can be extended to cooking appliances comprising further heating elements, such as electric coils, microwave generators, steam cooking systems, or the like.
It should also be understood that, when the cooking top is said to comprise a "cover", said cover may be any element adapted to be positioned over the burners for both aesthetical and functional reasons, and that said cover may be made of any material, e.g. plastic or glass, and must not necessarily be hinged or otherwise mechanically constrained to the cooking top.

Claims

A cooking appliance comprising at least one flat gas burner (105, 106, 107, 108), a cover (104) adapted to be positioned, when closed, on top of said at least one flat burner (105, 106, 107, 108), a gas supply line (201) and a first gas circuit (202) supplying gas to said at least one flat burner (105, 106, 107, 108), and at least one ionization flame detector (305, 306, 307, 308) respectively associated with said at least one flat burner (105, 106, 107, 108) and adapted to generate a first signal dependent on the presence of a flame at said at least one flat burner (105, 106, 107, 108), characterized in that it further comprises cover closure sensing means (212) adapted to output a second signal if said cover (104) is closed, and two electrovalves (209, 210) arranged in series and adapted to stop the gas flow towards said at least one flat burner, and further comprising control means (211, 213) operationally connected to said two electrovalves (209, 210) and to said at least one ionization flame detector (205, 206, 207, 208), and adapted to cause the closing of said two electrovalves (209, 210) depending on said first signal received from said at least one ionization flame detector (305, 306, 307, 308), wherein said control means (213) are also operationally connected to said closure sensing means (212) and are adapted to cause the closing of at least one (210) of said two electrovalves (209, 210) depending on said second signal received from said closure sensing means (212).
A cooking appliance according to claim 1, further comprising at least one cooking cavity (102) and a second gas circuit (202) supplying gas to at least one second burner adapted to heat said cooking cavity (102), and further comprising a third electrovalve (203) and at least one second ionization flame detector (302) respectively associated with said second burner of said cooking cavity (102) and adapted to generate a third signal dependent on the presence of a flame at said second burner of said cooking cavity (102), wherein a first one (209) of said two electrovalves is positioned on said main gas supply line (201), a second one (201) of said two electrovalves is positioned on said first gas circuit (202), and wherein said third electrovalve (203) is positioned on said second gas circuit (203), wherein said control means (211, 213) are operationally connected to said at least one second ionization flame detector (302) and are adapted to cause the closing of said first (209) and said third (214) electrovalves depending on said third signal received from said at least one second ionization flame detector (302).
A cooking appliance according to claim 2, wherein said first gas circuit (202) supplying gas to said at least one flat burner (105, 106, 107, 108) and said second gas circuit (202) supplying gas to said at least one second burner of said cooking cavity (102) branch off from said main gas supply line (201) downstream of said first electrovalve (209), and wherein said first gas circuit (202) comprises said second electrovalve (210), and wherein said second gas circuit (203) comprises said third electrovalve (214).
A cooking appliance according to any one of claims 1 to 3, wherein said control means (211) are adapted to control, upon a user's command, the ignition of at least one flat burner (105, 106, 107, 108), and are adapted to keep said electrovalves (209, 210) open for a predetermined period of time during said ignition, independently of the signal received from said ionization flame detectors (305, 306, 307, 308) within said predetermined period of time.
A cooking appliance according to any one of claims 1 to 4, wherein said control means comprise at least one electronic board (211, 213).
A cooking appliance according to any one of claims 1 to 5, wherein said closure sensing means (212) comprise an electromechanical switch.
A cooking appliance according to any one of claims 1 to 5, wherein said closure sensing means (212) comprise a magnetic proximity switch.
A cooking appliance according to one of claims 1 to 7, wherein each of said two electrovalves (209, 210) comprises at least one electric motor.
A cooking appliance according to one of claims 1 to 7, wherein each of said two electrovalves (209, 210) comprises at least one solenoid.