D E S C R I P T I O N

The present invention relates to an innovative power adjustment system for atmospheric gas burners with multiple injectors for cooking tops, in particular household cooking tops.

By atmospheric burner it is meant a burner where the air-gas mixture is obtained by the effect of the gas supply pressure using the principle of the tube ejector of Venturi and without the aid of fans.

The ejectors are extremely simple, economical and reliable devices and it is for this reason that they are used for the air-fuel gas mixing in the burners of cooking tops. Substantially all of the household gas cooking tops currently on the market use atmospheric burners.

In the tube ejector of Venturi (hereinafter simply "ejector"), the pressure energy of a motor fluid available at a nozzle located at the inlet of a Venturi tube is transformed into kinetic energy; the high-velocity jet coming out from the nozzle induces and drags an induced fluid flow at a lower pressure; both flows are conveyed within the Venturi groove where they mix and recover part of the pressure; then the mixing continues in a diverging section (which is the Venturi diffuser) where additional kinetic energy is recovered in static pressure. At the outlet of the diffuser, fuel gas and combustion air are substantially completely mixed.

The most widespread, universally accepted and most traditional technical solution to make a gas burner of a cooking top is the one with "vertical Venturi" (hereinafter, identified with the abbreviation STD); however, in recent years, alternative solutions to the STD one have developed, in particular burners with horizontal Venturi or "linear" configuration, herein referred to as "LIN".

This configuration includes a Venturi with a completely linear development arranged horizontally and parallel to the cooking top (conversely, in the STD burners the STD diffuser is instead radial). The linear diffuser leads to a further mixing chamber that occupies the internal volume of the burner wherein the mixing of primary air and fuel gas continues and completes Figure 2c shows a comparison between the two types in section.

The adjustment of the thermal power of the STD or LIN burner is generally carried out by means of a manual rotary valve for adjusting the flow of fuel gas (hereafter simply "adjusting valve") located upstream of the Venturi ejector; by continuously reducing the supply pressure to the ejector a continuous adjustment of said thermal power between a minimum and 100% of the nominal power is obtained.

Each adjusting valve of each of the burners, is keyed and sealed, as known, on the "ramp tube" (also called "manifold") of the fuel gas supply circuit of a cooking top, and usually carries also a safety valve, directly connected to the thermocouple (flame sensor) that keeps it in the open position when the flame is ignited and releases it in its "normally closed" position at its switching off (see figure 1).

At the ignition of the burner, an external mechanical action (typically the pressure that precedes the rotation of the control knob of the burner) forces the safety valve from its "normally closed" to the open position.

While the linear movement safety valves carry special sealing members (gaskets), the adjusting valves ("taps") are plug valves the sealing whereof is guaranteed by the presence of lubricating grease in the gap between the rotating trim and the seat, these members being generally made by chip removal from brass or aluminium blanks; unsuitable for serving as a safety device. It is known, since some years, that burners equipped with more than one ejector (also called "special burners" or "poly-injectors") exist that feed separately more than one "flame generation zone" (hereinafter called, for convenience of description "flame zone"), for example multiple concentric crowns of flames. Said "special burners" are in fact multiple burners comprising "n" injectors (typically n = 2 or 3, more rarely 4) often provided with as many "special valves" capable of feeding separately or simultaneously in a continuous or discontinuous manner all the injectors of the single burner.

Each crown of flames of the special burner normally requires a dedicated gas supply line that develops from the corresponding special valve to the injector and, at least in some cases, of a corresponding igniter (and relative flame sensor) with clear drawbacks in terms of structural complexity and overall dimensions. Even the adjustment of the thermal power of those special burners appears complex and delicate.

It can be assumed, for example, having to manage an STD multi-burner comprising two concentric crowns of flames (one internal centripetal and one external centrifugal), each separately fed by its own Venturi ejector and adjusted by a single special adjusting valve operable by the user through a control knob; turning the control knob starting from the OFF position the innermost crown is enabled and the thermal power thereof is continuously adjusted from its maximum (i.e., the crown ignites at full power) to its minimum, when a small unstable angular sector is reached, followed by the enabling of the outer crown and the concomitant switching off of the first. Continuing with the rotation of the knob, a progressive decrease of the thermal power of the outer crown is observed until a second unstable angular sector is reached; insisting with the rotation the two concentric crowns of flames are then simultaneously enabled with the possibility of their continuous adjustment from 100% of the nominal power to 0%.

The modulation curve resulting from such typical management of a special burner is by portions continuous and strongly non-linear, as clearly visible in figure 3a, where the abscissa shows the angle of rotation of the special valve control, while the ordinate indicates the corresponding thermal power of the burner; there should be noted the three operating zones of the special burner. This modulability of the power may be overabundant compared to the practical needs, being it sufficient, as also in the electric cookers, a discrete adjustment with a sufficient number of "steps" (see Fig. 3b), while its implementation may result, especially for users with little experience, non-intuitive and not always easy and immediate to understand.

For said burners it is also desirable to increase safety against fuel gas leaks found in case of accidental and sudden switching off of the flame or their malfunctioning.

The main object of the present invention is to provide a "special" atmospheric burner suitable for use for cooking tops, household in particular, which eliminates at least partly the drawbacks listed above.

More precisely, the main object of the present invention is to provide a sequential adjustment system of the thermal power of a "special" household burner with multiple injectors adapted to increase safety against the inadvertent access of fuel gas to the burner.

A further object of the present invention is to provide a simplification and a reduction of the overall dimensions of the supply and control line of the burners of a cooking top, preferably "special burners".

A further object of the present invention is to achieve the previous objects through innovative pneumatic or electronic or electromechanical controls.

A further object of the present invention is to control and manage the ignition of the plurality of flame zones of the special burner by means of a single igniter and flame sensor.

Further features and advantages of the present invention shall be better highlighted by the following description of an atmospheric burner for cooking tops in accordance with the main claims, articulated in possible variants in accordance with the dependent claims and illustrated, by way of a non-limiting example, with the aid of the annexed drawing tables, wherein:

- Fig. 1 schematically shows a conventional layout of a cooking top and a safety valve according to the prior art.

- Fig. 2a shows, in a graphical legend, arrows symbolizing air-gas mixtures of different titre and inflow rate that are used by way of example, without any intent to provide quantitative data, in other figures;

- Figs 2b and 2c schematically show, respectively, a typical Venturi ejector according to the prior art for an atmospheric burner and a comparison between a burner with horizontal Venturi configuration and a burner with vertical Venturi configuration;

- Figs. 3a and 3b show, respectively, the modulation curves of the thermal power of a conventional burner and of a "special burner" according to the invention;

- Figs 4a, 4b, 4c, 4d, 4e, 4f and 4g schematically show a "special burner" and the relevant feeding and control system according to different variants of the invention;

- Fig. 5 shows the ignition and modulation diagram of the thermal power of the "special burner" of Fig. 4a;

- Fig. 6 shows an ignition and modulation diagram of the thermal power of the "special burner" of Fig. 4c;

- Fig. 7 shows the ignition and modulation diagram of the thermal power of the "special burner" of Fig. 4d;

- Fig. 8 shows, in multiple cutaway views, a component of the control line of the "special burner" of the invention;

- Fig. 9 shows, in a cutaway view and according to a possible variant, a power and modulation button of the thermal power of the "special burner" of the invention;

- Fig. 10 shows a cooking top implementing multiple "special burners" according to a first variant of the invention;

- Fig. 1 1 shows a cooking top implementing multiple "special burners" according to a second variant of the invention;

- Fig. 12 shows a cooking top implementing multiple "special burners" according to a further variant of the invention;

- Fig. 13 shows a cooking top implementing multiple "special burners" according to a further variant of the invention;

- Fig. 14 shows a cooking top implementing multiple "special burners" according to a last variation of the invention.

Unless otherwise specified, any possible spatial reference in this report such as the terms vertical/horizontal or lower/upper refers to the position in which the elements are located in the annexed figures while spatial terms such as previous/subsequent, upstream/downstream should be understood with reference to the direction of circulation of the flows of airforms.

In Fig. 2a arrows are drawn, each of which symbolizes a flow of mixture of a different speed and titre. These arrows are used in many of the subsequent figures to exemplify without any intent to provide quantitative indications, the substantial state of the air, gas and mixture thereof at various points upstream, downstream and inside the illustrated burners.

With the purpose of highlighting some features instead of others, not necessarily what described in the annexed drawings is perfectly scaled.

Moreover, the figures show only the essential elements for the purposes of the invention.

In the annexed figures (see, for example, Fig. 4a) of the household atmospheric burner 1 of the invention there are shown: the cup 14 which defines therein the air-fuel gas mixing chamber, a plurality "n" of contiguous flame generation zones FLn each served by its own "Venturi" ejector EJ.n adapted to the above mixing and at the inlet whereof corresponding injectors INJ.n for the supply of fuel gas are positioned.

Each "Venturi" ejector EJ.n comprises, as is known (see, for example, Fig. 2b), a first converging section 10 (or simply the "convergent") wherein the pressure energy of the fuel gas available at injector INJ.n is transformed into kinetic energy and wherein a combustion air flow is carried over by said high speed fuel gas jet; a groove 1 1 where the fuel gas and the combustion air are mixed recovering part of the pressure energy; a final diverging section 12 (also called Venturi "diffuser 12") along which said mixing continues and where additional kinetic energy is recovered in static pressure.

Although in the annexed figures the ejectors EJ.n are shown of the STD type (i.e., as already anticipated, with "vertical Venturi") nothing prevents them, for the purposes of the invention, from being of the LIN type, that is with "horizontal Venturi", or in any case arranged about the body of the burner.

Moreover, although not explicitly illustrated, the flame zones FL„ fed by said ejectors EJ.n may consist, without distinction, in a plurality of concentric crowns of flames or have other shapes as long as contiguous, each one to all the subsequent (e.g., without any limiting intent, four concentric crowns or contiguous "groups of slots" FL _! , FL ² , FL ₃ , FL ₄ ).

At at least one flame zone FLn, hereinafter referred to as main FL] , a known ignition device IGN (also called "igniter IGN") is provided, for example of the piezoelectric type.

Said contiguous flame zones FLn are adjacent to one another such that none (except, as will be seen, the main one FL may be fed and activated by its own dedicated ejector EJ.n without there being at least one adjacent flame zone FLn already ignited.

In this way, the pilot flame functionality that keeps turned on and systematically propagates the flame to all the slots of a traditional burner STD and/or LIN is again proposed.

By ensuring the continuity of the flame zones FL„, the need of using multiple flame sensors FD, one for each flame zone FL„ is also avoided.

For the special burner 1 of the invention, it is therefore provided only one flame sensor FD at the flame zone FLi, herein referred to as "main", already equipped, as seen, with the igniter IGN.

For simplicity of description, said flame sensor shall be hereinafter referred to as "flame detector FD".

The thermal power of such a special burner 1 (also called "poly-injector burner 1 ") is exclusively a function of the number of flame zones FL„ simultaneously active.

In other words, the burner 1 operates at the minimum power P _m j _n when only the main flame zone FLi is activated while it reaches its maximum power P _max when all its flame zones FL„ are simultaneously enabled.

It is clear that, in the case of ejectors EJ.n all identical to each other the modulation ratio Y of the special burner 1 (equal, as known, to the ratio between its maximum and minimum power) will be equal to the total number of flame zones FLn. Obviously, for the purposes of the invention, nothing prevents from providing ejectors EJ.n even different from each other.

Reference numeral 2, moreover, denotes a push-button panel, comprising at least one button 20. n for the activation of said special burner 1 and for its modulation in power.

As it will be seen, said push-button panel 2 may be of the electromechanical or electronic or pneumatic type and is connected to the injectors INJ.n of the special burner 1 by means of at least one control line 3, 3.n.

More precisely, according to the invention, a single control line 3 adapted to serve all the injectors INJ.n of the burner 1 (see. Figs. 4c, 4d. 4e, 4f) or. alternatively, as many dedicated control lines 3, 3.1 ... 3.n as said injectors INJ.n (i.e. one for each injector INJ.n) as shown in Fig. 4a or 4b may be provided. Said at least one control line 3.n may be connected directly to the at least one button 20. n of said push-button panel 2 or, according to some variants (of the electric type), to an electrical control circuit CMD capable of receiving specific control signals from the same push-button panel 2 (said circuit CMD, as shall be seen, being capable of receiving signals also from the flame detector FD and sending second signals to the igniter IGN and to a valve of the burner 1 , which shall be referred to as "safety SV").

From here on. the push-button panel 2 and the at least one injectors INJ.n control line 3 assembly shall be referred to as "control system" of the burner 1.

The different types and architectures of said control system 2 shall be referred to shortly with the description of some preferred and functional embodiments thereof.

Although said push-button panel 2 is shown in the annexed figures of the type comprising at least one mechanical button, nothing prevents it from providing, without any exhaustive intent, rotary or linear potentiometers or any other type of control known to manufacturers and designers of cooking tops.

Moreover, according to the invention, a single gas supply line 4 (also referred to as "adduction line 4") serves the entire plurality of injectors INJ.n of the special burner 1. arranged in series to each other.

Said supply line 4 is shut-off by a known and conventional safety valve SV against gas leaks found in case of accidental and sudden switching off of the flame or malfunctioning of the burner 1.

As clearly shown in the annexed figures, said safety valve SV is placed upstream of the plurality of injectors INJ.n of the special burner 1.

Even if well known to the man skilled in the art, it is useful to specify that said safety valve SV (e.g., an electro-actuator) is piloted by the push-button panel 2 of the burner 1 to switch from a "normally closed" to an "open" configuration, suitable for the passage of fuel gas, and that is maintained as such as long as the above flame detector FD senses at least one active flame zone FL„. The absence of such signal will determine, on the contrary, the closing of said safety valve SV and the subsequent shut-off of the supply line 4, thus interrupting the supply of fuel gas to the special burner 1.

Appropriate and known wirings 50, 51 connect respectively the safety valve SV and the flame detector FD to the push-button panel 2 while a cable 52 controls the ignition of the igniter IGN.

According to another important aspect of the invention, each injector ENJ.n of the burner 1 is equipped with a special shutter device 6 (see in particular Fig. 8). "normally closed", but capable of allowing or preventing, on command, the exit of the gases towards the corresponding ejector EJ.n for the activation of the relative flame zone FLn but at the same time ensuring its passage towards the next injector INJ.n (with respect to the travelling direction of the gas along the only one supply line 4).

Said shutters 6 are interlocked to the flame detector FD.

Although in the figures annexed to the present disclosure said shutter device 6 and injector INJ.n are represented as strongly integrated to each other to form a single valve body, nothing prevents that they can also be logically and physically separate elements.

According to the invention, each injector INJ.n, besides feeding the corresponding ejector EJ.n, thus acts also as a gas shut-off valve ensuring a further safety against gas leaks towards the external household environment with the burner 1 switched off or in the event of accidental switching off of the flame. As already anticipated, the linear shutters in the closed position ensure an intrinsically better sealing of the corresponding conventional adjusting taps.

Even in case of failure of the safety valve SV, the inadvertent or undesired access of gas to the burner 1 is prevented by the presence of the shutter device 6, normally closed, on board of each injector INJ.n.

Known electromechanical or pneumatic actuators 7 guide the switching of the shutter device 6 from its natural closed to open configuration of the injector INJ.n and vice versa.

Without any exhaustive intent, suitable electric actuators 7 may be of the type (only schematically shown in the annexed figures) comprising a coil substantially wound around the shutter device 6 and capable of converting the electric signal generated and transmitted to it by the push-button panel 2 through the aforesaid at least one control line 3 (in this case, therefore, of electrical type) into an electromagnetic field, causing a linear movement thereof.

Obviously nothing prevents the possibility of providing, alternatively, pneumatic actuators 7 utilizing pressurized or depressurized air as energy carrier and capable of moving said shutter device 6 by means of a pressure (or actually, as it shall also be seen, vacuum) generated by acting on the at least one button 20. n of the push-button panel 2 that therefore behaves as a proper volumetric pump. In both cases, as shall be seen, the presence of a stationary spring of said actuator 7 allows, when the electric or pneumatic pulse generated through the push-button panel 2 ceases, the return of the shutter device 6 to its rest position coinciding with that "normally closed".

The possible configurations of such actuators 7 and shutter device 6 of each injector INJ.n shall be referred to in the description.

The essence of the invention is already outlined, consisting in a special burner 1 comprising a plurality of injectors INJ.n:

- fed in series from a single supply line 4 of fuel gas

- each adapted to serve a specific and dedicated flame zone FL„ of the special burner 1

- the activation whereof, necessary to allow the sequential ignition of said flame zones FLn and a modulation of the thermal power of the same said special burner 1 , is assigned to at least one control line 3 connected to a pushbutton panel 2 comprising at least one button 20. n capable of being pressed according to a suitable and specific ignition sequence and/or mode

The special burner 1 of the invention implements, moreover, a double security level (or system) against gas leaks in case of incomplete ignition thereof or accidental switching off of the flame ensured, on the one hand, by the safety valve SV located along said fuel gas supply line 4 upstream of the same said plurality of injectors INJ.n and, on the other hand, by each of the same injectors INJ.n that by means of their respective shutter devices 6 act, as seen, as shut-off valves, said safety valve SV and shutter devices 6 being capable of closing instantaneously (or remaining closed) in the absence of a flame signal detected by at least one flame detector FD of the special burner 1.

At this point, the typical ignition sequence of a special burner 1 as described above shall be described.

As the special burner 1 ignites (by pressing the relevant ignition button), acting on the push-button panel 2, the "normally closed" safety valve SV of the fuel gas supply line 4 is forcibly opened, the shutter device 6 of the first injector INJ. l is retracted, thereby opening the access of the gas to the corresponding ejector EJ. l , and the igniter IGN for the ignition of the flame in the main flame zone FLi is activated.

Once the combustion in the main flame zone FLi starts, the flame detector FD creates an electric voltage (which is a function, as known, of the local temperature reached therein) that keeps both the safety valve SV and the injector INJ.l in open position.

The main flame zone FLi therefore remains ignited and the special burner 1 , as anticipated, is at its minimum thermal power.

Conversely, if the user stops the ignition procedure before the flame stabilizes, the absence of a flame signal detected by the above detector FD causes the simultaneous and instant closing of the safety valve SV and injector INJ. l , doubly inhibiting the passage of gas to the burner 1.

The adjustment of the level of thermal power of the special burner 1 of the invention goes through the successive and incremental enabling of the other ejectors EJ.n through the opening of the shutter devices 6 of the corresponding injectors INJ.n and in such a way that each pair of consecutively fed flame zones FLn are adjacent to each other (see the "steps" modulation curve of Fig. 3b).

Although already mentioned, that is, said modulation of the thermal power of the special burner 1 is subject to the contiguity of its flame zones FLn, meaning that a flame zone FL _n cannot be fed and activated by its own dedicated ejector EJ.n without there being at least one adjacent flame zone already ignited; e.g., the flame zone FL ₂ may be enabled, only after the activation of the contiguous main flame zone FLi and so on for the subsequent flame zones FL ₃ , FL ₄ of the special burner 1.

Similar considerations apply also in case of decrease of the thermal power of the burner 1 , i.e in case it is necessary to proceed with the sequential and progressive switching off of one or more of its flame zones FLn. Summarizing what described thus far, of the special burner 1 , therefore, there are identified:

- a main flame zone FLi equipped with igniter IGN and relevant flame detector FD and fed by the corresponding at least one injector INJ. l

- further one or more flame zones FLn, each fed by at least one respective injector INJ.n

where:

- said main flame zone FLi is fed first

- said additional one or more flame zones FL„ are fed and activated in sequence one after the previous

- each pair of flame zones FLn, including the main one, which are fed in sequence are adjacent to each other.

Fig. 4a shows in more detail a first version of the control system of the special burner 1.

Said control system provides a common electromechanical push-button panel 2 comprising a number of buttons 20.n, 20.1....20.4 equal to that of the activatable flame zones FLn where said number of zones is less or equal to the number of injectors INJ.n of the special burner 1.

More precisely, each button 20.n is connected by means of one own control line 3, 3.1....3.4 to the corresponding injector INJ.n or to as many groups of injectors INJ.n; as many control lines 3.n are therefore provided as the flame zones, each of which is equipped with at least one injector INJ.n of the special burner 1 to be managed.

Each button 20. n of the push-button panel 2 is therefore capable of enabling the corresponding flame zone FLn according to the sequence previously described in general terms, by simply using known switching means for electrical signals. At least one of said buttons 20. n of the push-button panel 2, is connected, besides to the corresponding injector INJ.n (or, as it shall be understood, to the corresponding group of injectors INJ.n"), as anticipated, also to the igniter IGN and flame detector FD of the special burner 1 and to the safety valve SV of the fuel gas supply line 4.

Said button 20. n is that 20.1 adapted to enable the main flame zone FLi of the burner 1 , where said zone FLi is that expected to ignite first.

A push thereof will command, therefore, the opening of said safety valve SV and the at least one main injector INJ. l and the simultaneous activation of the igniter IGN capable of "igniting" (through the known spark produced thereby) the air- fuel mixture intended to said main flame zone FL^

Once the ignition of the burner has taken place and stabilized, the repeated and sequential pressing of the other buttons 20. n of the push-button panel 2 will result in the progressive activation of the contiguous flame zones FLn and the consequent increase in the thermal power of the same burner 1.

The switching off of a previously activated flame zone FLn and the corresponding reduction in power of the burner 1 , are achieved, on the contrary, by means of the pushing of any button 20. n of ignition of a flame zone FL„ not immediately contiguous to that to deactivate.

For example, the switching off of the second flame zone FL of the special burner 1 (previously activated through button 20.2) will be achievable by pressing the button 20.4 dedicated to the enabling of the fourth and last flame zone FL ₄ (see position of the representation of a user "hand" at point (iv) of Fig. 5).

The previous logic of operation is just an example of the countless possibilities offered by the proposed adjustment system and can be safely achieved with common electromechanical devices already available to a man skilled in the art Even for the electronic variant of Fig. 4b, each injector 12.n is controlled by a special and dedicated control line 3; 3.1....3.4....3.n.

However, according to this construction variant, said control lines 3.n are connected directly to an electrical control circuit CMD capable of:

- receiving signals from the push-button panel 2 and the flame detector FD through the cables 53, 51 , respectively

- sending by means of wirings 52, 50 control signals to the igniter IGN and the safety valve SV of the fuel gas supply line 4 to the burner 1. More precisely, according to this variant, the push-button panel 2 may comprise a pair of buttons 20. n represented symbolically in Fig. 4b by a first key (+) 20.1 and by a second key (-) 20.2 connected to said electrical control circuit CMD; with a first pressing of the key (+) 20.1 there will be, therefore, the activation of the main flame zone FLi while each subsequent pressing will result in the enabling of those contiguous until the desired thermal power for the special burner 1 is reached.

It will be referred to as electrical control circuit CMD to recognize if the pressing exerted on said button (+) 20.1 corresponds to that for the first ignition of the special burner 1 or to that for increasing the power thereof depending on whether the flame signal from the flame detector FD is received or not.

On the contrary, at each pressing of the key (-) 20.2 the electrical control circuit CMD will manage the sequential switching off of the flame zones FL„ already activated until the minimum thermal power of the burner 1 or its final switching off is reached.

In the ignition and power modulation versions of a special burner 1 mentioned so far, there is, as seen, always a unique one-to-one connection between each button 20. n of the push-button panel 2 and the shutter device 6 of each injector INJ.n; as seen, in fact, each button 20.n of the push-button panel 2 is connected to the corresponding injector INJ.n through single and separate control lines 3.n. This makes the assembly of a plurality of special burners 1 in a cooking top rather complex and expensive.

In order to overcome this problem a simplified variant of the control system of the special burner 1 , shown in Fig. 4c, is therefore proposed.

According to such variant, the actuators 7 that move the shutter devices 6 of each injector INJ.n are all connected in series to each other by a single control line 3. in this example of the pneumatic type (exactly as the injectors INJ.n with their own dedicated gas supply line 4).

According to such variant, therefore, all the shutter devices 6 of each injector INJ.n work at the same pneumatic pressure, function of the subsequent pushes exerted on the push-button panel 2 of the special burner 1.

As clearly shown also in Fig. 6, according to this variant, said push-button panel 2 may comprise at least one button 20.1 , called "ignition", adapted to activate the igniter IGN and to allow the switching of the safety valve SV from its "normally closed" to "open" position (activating, as a consequence, the main flame zone FLO and at least one button 20.2, called "selection", which behaves, as anticipated, as a "compression" volumetric pump adapted to discretely increase the pressure of the control line 3 at each repeated pushing thereof so as to sequentially activate, in the manners that shall be described, the contiguous flame zones FLn of the special burner 1.

On the other hand, by pressing all the way down and holding said selection button 20.2 a discharge orifice opens that lets the air leak from the control line 3, quickly and interactively reducing the pressure thereof with the consequences that will be described shortly.

According to this variant, a further safety discharge device consists of a "normally open" discharge solenoid valve DV in communication with the external household environment pilotable by the ignition button 20.1 and kept in a closed position by the flame detector FD.

In the absence of flame in the main flame zone FLi or in case of accidental switching off thereof, said discharge solenoid valve DV returns to its normally open position discharging the compressed air and causing the closing of all the shutter devices 6 of the injectors INJ.n that the control line 3 serves; this ensures, as a consequence, an additional level of security for the special burner 1.

At this point a first possible architecture for the injectors INJ.n, and the relevant shutter devices 6 of the pneumatic control type, represented in multiple views in Fig. 8 shall be described in greater detail and precision.

More precisely, of said injector INJ.n there are shown: a nozzle 80 and a gas compartment 81 connected to the fuel gas supply line 4 while of said shutter device 6 there are shown a pneumatic chamber 60 in fluid communication with the above pneumatic control line 3 and the shutter "pin" 61 capable of being moved from a "normally closed" to an "open" position (and vice versa) of the nozzle 80 by means, e.g., of the above pneumatic actuator 7.

Said actuator 7 may comprise a pneumatic piston 70 and a mechanically adjustable stationary spring 71 with settable preload to keep its piston in a "normally closed" position, e.g., by means of a threaded ring nut 72 or a screw. According to a possible variant, said piston 70 may alternatively consist in a known bistable piston.

Sealing members 62 keep the pneumatic chamber 60 and gas compartment 81 strictly separate.

The pneumatic chamber 60,- adjacent to the gas compartment-Si- of the injector INJ.n, is in overpressure relative to the outside environment so as to avoid the emission of fuel gas to the outside (e.g., in the cooking top) in case of damage/or wear of the sealing members 62.

By suitably managing the pressure level inside the pneumatic chamber 60 it is therefore possible to systematically limit or eliminate the pressure gradient between fuel gas and the fluid (usually compressed air) of the pneumatic control line 3 astride of the sealing member 62. This is accomplished by ensuring an operating pressure of the pneumatic control line of the shutters 6 close to the fuel gas supply pressure, for example through two non-return valves (not shown): one in series to the leakage device of the pneumatic control line 3, preferably coincident with the above discharge valve DV; the other at the exit of the air inlets 26.

By adjusting the opening of said non-return valves to the fuel gas supply pressure and suitably setting the preloads of the above stationary spring 71 of each actuator 7:

- with the special burner 1 ignited (e.g., by simultaneously pressing the power 20.1 and selection 20.2 buttons), each subsequent pressing of the selection button 20.2 will correspond to a discrete increase in the pressure in the control line 3 up to the minimum level necessary for the opening of the first closed shutter in the sequence of the shutter devices 6 of each injector INJ.n - with the special burner 1 ignited by pressing the selection button 20.2 all the way down (which, as seen, works as a volumetric pump) it is possible to obtain a decrease in pressure to the various shutter devices 6 of the injectors INJ.n that one by one sequentially close until the minimum pressure of the pneumatic control line is reached (equal, actually, to that of gas supply). With the special burner 1 switched off, therefore, the pressure gradient between pneumatic chamber 60 and gas compartment 81 is zeroed and with it the risk of gas leak to the external household environment.

The overpressure generated in the pneumatic chamber 60 in order to keep the special burner 1 ignited would lead, in case of damage of the sealing member 62, to an air leak towards the gas compartment 81 , however without particular problems, since it would reduce automatically the pressure of the pneumatic control line 3 inducing the sequential and simultaneous closing of the shutters 6 of the injectors INJ.n

In the event that the minimum pressure of the pneumatic control line is equal to the atmospheric one, in case of damage of the sealing member 62 of the injector INJ.n, there would be a fuel gas leak inside said pneumatic line 3; this does not constitute any danger because said pneumatic line 3 has a very low internal volume, is watertight and leaks a very small amount of fuel gas.

With the burner 1 switched off, then, SV is, as seen, in the "closed" position and the gas eventually leaked in the control line 3 flows away through the discharge valve DV or remains confined along the same line if said valve DV is equipped with the above non-return valve adjusted to the gas pressure.

However, the shutter devices 6 of the plurality of injectors INJ.n are located, as seen, in the "normally closed" position thereby preventing the inflow of fuel gas towards the respective injectors INJ.n; said ignition and power modulation system of a special burner 1 is therefore intrinsically safe.

An ignition (or switching off) and adjustment diagram of the thermal power of a special burner 1 according to such variant is shown in Fig. 6 and provides by way of a non-limiting example the following steps: once the special burner 1 is activated to its minimum thermal power (that is, the only main zone FLi is enabled; see (i) and (ii) in Fig. 6). a further succession of presses of the latter will correspond to the ignition of the immediately contiguous flame zone FL ₂ (see (iii) in Fig. 6); a possible later and prolonged pressing on the same selection button 20.2 will lead, on the contrary, to the deactivation of the last activated flame zone FL,, (in this case the second flame zone FL ₂ ) and to a consequent reduction of its power level (see (iv) in Fig. 6).

If said special burner 1 was already at the minimum power (only the area FLi ignited), that prolonged full pressing of the selection button 20.2 will result in its final switching off.

The pneumatic control system for the ignition of the special burner 1 of the invention may be, alternatively, also of the "vacuum type"; Fig. 9 therefore shows the relative button 20. n.

According to this variant the at least one button 20.n of the push-button panel 2 is a tubular body comprising an outer liner 21 fixed to a support (e.g., to the aesthetic face of a cooking top P) in turn comprising a connecting channel 22 to the pneumatic control line 3 and a relative non-return valve VNR1.

A movable key 23 is capable of shifting vertically, when pressed, within said fixed liner 21 so as to open, for the reasons which will be clarified shortly, said "normally closed" valve VNR1.

Once the pressing of the key 23 ends, an inner pre-compressed spring 28 is capable of returning said valve VNR1 to the "normally closed" position.

Between the bottom 230 of said key 23 and that of said outer liner 21 there is located a sealed chamber 24 for the pneumatic control line 3. said chamber 24 varying its volume according to the above vertical shifting of the key 23 of the button 20. n.

By partially pushing the key 23 (partial pressing is to be understood as an insufficient push to bring the button all the way down), within said collection chamber 24 a vacuum is thus generated that opens the non-retum valve VNR1 and draws air from the pneumatic line 3 (which depresses); subsequently releasing the same key 23, said non-return valve VNR1 will close immediately through the precompressed recovery spring 27, said recovery spring 27 being capable of recompressing the collection chamber 24 up to opening a discharge valve VRN2 located at the bottom 230 thereof.

Such sequence can be repeated to further increase the vacuum of the control line 3.

Pushing the key 23 all the way down, the alignment of the lateral grooves 25 of the outer liner 21 with as many air inlets 26 of said sealed chamber 24 is obtained so as to allow ambient air to penetrate in the pneumatic control line 3 recompressing it;- this corresponds to the closing of the shutter devices-6 of the injectors ENJ.n served by said control line 3.

It should be noted that the at least one button 20. n for the "compression" pneumatic system previously described and shown in Fig. 8 may be constructively identical to this "vacuum" one except for the inversion of the direction of operation of the two valves VNR1 and VNR2.

A particular application of said vacuum pneumatic control is shown in Fig. 4f according to which the activation of the special burner 1 is managed by a single button 20.n capable of acting on a microswitch MT of an electromechanical control group SWT, suitably connected and/or wired to the igniter IGN, to the discharge DV and safety SV valve capable of intercepting the fuel gas supply line 4.

According to such version, starting from the special burner 1 in OFF configuration, with a first partial push on button 20. n, exerted for a predetermined period of time (preferably in the order of some seconds), said electromechanical group SWT provides, by means of specific signals along suitable dedicated connecting wirings, for closing the discharge valve DV, simultaneously opening the safety valve SV and enabling the igniter IGN for the ignition of the main flame zone FLi.

When said button 20. n is released, the same electromechanical group SWT cuts off the signal to the igniter IGN as well as to said discharge DV and safety valves SV.

If the ignition of the special burner 1 has taken place, the above flame detector FD shall keep the discharge valve DV in "closed" configuration and the safety one SV in "open" position; otherwise the safety valve SV is immediately closed interrupting, as seen, the gas flow to the burner 1 , while the discharge valve DV is opened to restore the pressure along the pneumatic control line 3 of the injectors INJ.n, avoiding gas leaks.

It is not necessary to dwell on the modulation of the thermal power of the special burner 1 (sequential ignition/switching off of the contiguous flame zones FL„) being it totally similar to what seen and described so far.

Instead, it is necessary to specify that preferably the triggering of the igniter IGN takes place with a pre-set delay time relative to the pressing on the button thus avoiding unnecessary ignitions thereof also during the modulation of the thermal power of the special burner 1 of the invention.

The same optimization and simplification of the control line of the injectors INJ.n of the special burner 1 of the invention, as anticipated, may also be obtained by providing electrically and/or electronically managed shutter devices 6.

According to this variant shown schematically in Fig. 4e, the actuators 7 of each shutter 6 are preferably:

- known actuators of the electric type comprising, as said, excitation coils of relative electromagnets, electrically connected in parallel to each other, and dimensioned to accept a predetermined range of voltage values

- connected in series to each other and fed by a same electric line 3 (e.g, of the single wire type).

An electrical control circuit CMD, connected to the push-button panel 2, transforms each pressing on button 20.1 and/or 20.2 into a voltage signal that increases or decreases discretely, obtaining a modulation of the thermal power of the special burner 1 (see steps (i), (ii), (iii), (iv) of Fig. 7), similarly to what achievable with the pneumatic system described above. The simultaneous pressure of the two buttons 20.1 , 20.2 with the burner 1 switched off determines, instead, the ignition (more precisely, the activation of the main flame zone FL _l5 as shown in (i) of Fig. 7).

More precisely, the opening or closing of each injector INJ.n may be obtained by providing different alternative solutions.

For example, in case of electroactuators 7 different for each injector INJ.n it will be sufficient to dimension the winding of their coil differently to obtain the tripping of the relevant shutter 6 only at the appropriate level of voltage signal coming from the electrical control circuit CMD.

The same result may be obviously obtained by providing identical electroactuators for all the shutters 6 of the injector INJ.n but differently dimensioned stationary springs to obtain the tripping of the relative shutter device 6 only at an appropriate level of the electrical signal (for example, voltage or current) coming from said electrical control circuit CMD; more precisely, as said level of the voltage signal generated by the pressing of the button increases all the electroactuators 7 will exceed in sequence the resisting force of the relative stationary spring by activating the shutter 6.

Vice versa, for the reduction of power of the special burner 1 , at each decrease step of the control signal managed by the control card CMD each stationary spring will exceed the electromagnetic force of the respective electroactuator 7 thereby closing the shutter device 6 whereon they rest.

It is obviously possible also a combination of the above two solutions.

According to a further alternative, it is possible to provide electroactuators 7 and stationary springs all identical to each other. In such a case, the sequential opening or closing (more generally the '"tripping") of the shutter is obtained by simply adjusting the preloads of their stationary springs on different values. Finally, it is possible to provide the possibility of using more advanced electroactuators 7 such as, for example, linear stepping motors or the like; in this case, the control line 3 would become an actual data BUS, where the master is the push-button panel 2 and the relative electrical control circuit CMD (which becomes an actual electronic card having calculation capabilities) and the slaves are the actuators 7 of the shutters 6 of the injectors INJ.n that would thereby be networked together.

This entails further advantages relating to the mutual diagnostics and. ultimately, to a higher security and reliability level of the whole.

Fig. 4g finally shows a last variant of the control and adjustment system of a special burner 1.

Said variant provides an electrical control circuit CMD of the special burner 1 connected, on one side, to a push-button panel 2 comprising a single button 20 therefore capable of functioning both as a power and selection button and on the other side to the single electrical control line 3 of the injectors INJ.n.

In this case, a short pressing of said button 20 shall correspond to a power reduction (or switching off of the burner 1 if it is the only main flame zone FLi to be active), while a long press corresponds to an increase in said power. It shall be the electrical control circuit CMD to recognize if a long press on the button corresponds or not to the first ignition (that of the main flame zone FLi) according to the reception or not of the flame signal sent by the flame detector FD, to which it is connected.

In case of prolonged pressing with burner 1 in OFF position, in fact, the electrical control circuit CMD opens the safety valve SV feeding the burner 1 with fuel gas, enables the igniter IGN, to which it is connected, and sends the signal for opening the injector INJ. l installed upstream of the main flame zone FLi through said electrical control line 3.

As for the pneumatic case already covered, when the button 20 is released, if the ignition has been successful, the signal generated and coming from the flame detector FD will keep the safety valve SV open; otherwise, the electrical control circuit CMD will close said safety valve SV and the injector INJ. l of the main flame zone FL^

At this point it is possible to describe logics of management of cooking tops integrating a plurality of said special burners 1 and relative ignition and modulation systems described above.

In the examples to follow, reference shall be always made, without any limiting intent, to electrical/electronic variants of the control and adjustment system for special burners 1 with the understanding that all that shall be said may also be extended to the pneumatic versions.

By way of an example only, Fig. 10 shows a cooking top P comprising four special burners 1 of the type just described, each in its turn comprising four injectors INJ.n feeding, as seen, an equal number of flame zones FLn. The cooking top illustrated has three security levels; a first security level (called "base level") is ensured by a known general safety solenoid valve SSV ("normally closed") capable of cutting off the general line L for the supply of fuel gas (represented in Fig. 10 by the thick grey line and from which, downstream of the same valve SSV, a plurality of gas supply lines 4 is branched, one for each single burner 1 , represented in the figure in "dotted line") when no special burner 1 is ignited. A second security level is represented by the safety valves SV (as seen, "normally closed" as well ) supplied with each burner 1 and adapted to interrupt the fuel supply line of the single burner 1 (dotted line of Fig. 10) in the absence of the confirmation signal from its flame detector FD; a third security level guaranteed by the shutters 6 of each injector L J.n connected in series through a single control line 3 (see dashed-dotted line of Fig. 10), the electrical control circuit CMD that transmits a closing signal when the flame detector FD detects the accidental switching off of the flame or when the burner 1 is switched off.

This redundancy may advantageously be used to make simplified versions of the cooking top P always comprising at least two security levels. Even in the absence of the general safety valve SSV, in fact, the security against fuel gas leaks in the absence of flame would be guaranteed by at least the safety valve SV of each special burner 1 and by each shutter of the plurality of injectors INJ.n that feed it.

A further simplified variant, illustrated in Fig. 1 1 , provides the absence of the safety valve SV of the single special burner 1. Even in this case a basic level of security is still guaranteed through the general safety valve SSV and a second security level guaranteed by the shutters 6 of the injectors INJ.n of each special burner 1. In this case, all flame detectors FD of the plurality of special burners 1 of the cooking top P are directly connected, through cables 55, to the general safety valve SSV thus capable to return to the "normally closed" position already in the event of accidental switching off of the flame of one of said burners 1 of the cooking top P.

The distinction between accidental or voluntary switching off of each special burner 1 is guaranteed by the electric control circuit CMD according to reception or not of the flame signal by the respective flame detectors to which, as seen, it is connected.

Fig. 12 shows a further variant according to which the safety function consisting in the closing of the injectors INJ.n in the event of accidental switching off of the flame, rather than being assigned to the electrical control circuit CMD, is attributed to special safety relays K (for example, dual input of which one timed), normally open, one for each special burner 1. In this version, the safety function of disabling the injectors INJ.n in the event of accidental switching off of the flame (missing signal from the flame detector FD) has been attributed to normally open special safety relays K(i) (for example of the solid state type). Each relay is connected in series to its injectors INJ.n control line 3 so as to cut it off in case of absence of flame; while the flame signal from said detector FD is able to keep them in the closed position. To allow the first ignition, the CMD group will provide a first signal (e.g. a voltage) to the control line 3 of the injectors of the burner of level L _K closely below the minimum level of activation of the injector INJ. l (that shall be called Li). The signal level L must be able to close K(i) but not sufficient to open the first injector of the series. The device K(i) can be equipped with such a timing that, after a few seconds from the first reception of the signal L . K(i) it can be kept closed only by the signal of the flame detector FD and, in the absence of this, returns to the open position forcing the user to repeat the procedure of first ignition. In this way overlaps between the control signal of the power level of the burner (Li< L ₂ < L ₃ < L ₄ ) and the ignition signal L (where L < LI) are avoided.

Moreover, nothing prevents from providing a further construction variant (see Fig. 13) comprising a safety functional group SFT which is assigned the task of constantly receiving the flame signals from the flame detectors FD of each special burner 1 of the cooking top P and to compare them with the information of the ignition state of said burners 1 coming from the electronic control board CMD.

According to this variant, in the event of accidental switching off of a special burner 1 , the safety functional group SFT will command the closure of the general safety valve SSV.

Through the data line 56 that connects it to the electrical control circuit CMD, the safety functional group SFT is also able to force said general safety valve SSV in "open" configuration in case of first ignition of the burner 1 (that is, as repeatedly said, of his main flame zone FLj). Said data line 56 finally allows the electrical control circuit CMD to receive the information on flame presence and to close, through the relative control lines 3 of the shutters, all the injectors INJ.n in case of accidental switching off or failed ignition of the burner 1.

Fig. 14 finally shows one last construction variant for a cooking top P which comprises:

- a single gas supply line 4, downstream of the general safety valve SSV, which connects all the injectors INJ.n of all the special burners 1 , by feeding them in succession (by way of a non-limiting example, starting from injector INJ. l of the special burner 1 indicated as BRN1 to the injector INJ.4 of the special burner 4 of the cooking top P indicated as BRN4)

- a single control line 3 continues that, from the electronic control circuit CMD, joins in a sequence all the special burners 1 of the same cooking top P (rather than having as many dedicated control lines as the burners 1 of the cooking top P, as in the constructive examples of Figs. 10-13), said single control line 3 serving, as seen, all the injectors INJ.n of each burner. Said control line 3 is a BUS that connects all the electric actuators 7 that are of the bistable type (or the like) that become interlocked and addressed by the CMD device.

It is clear that in the practical embodiment of the invention numerous modifications and further variants may be provided, all falling within the same inventive concept. All the various components and details previously described may also be replaced by technically equivalent elements.

For example, in the case of very wide flame zones FL„, by injector INJ.n it may be also meant a group of injectors INJ.n, all serving the same flame zone FLn, with the understanding that said group of injectors INJ.n is piloted like a single injector E J.n.

With the control and management system of a special burner 1 of the invention the stated objects are achieved, in particular the possibility of a discrete and intuitive adjustment of the thermal power (shown in Fig. 3b) thereof that is easy and immediate to understand even for users with little experience. The presence of a single fuel gas supply line 4 for the special burner 1 and, for the variants that provide for it, of a single electrical/electromechanical or pneumatic control line 3, for all the injectors DNJ.n thereof also allows a considerable construction simplification of the cooking tops implementing said special burners 1 with undoubted advantages even from an economic point of view. The use of injectors INJ.n integrating a relative shutter device 6. normally closed with the burner switched off or in case of accidental switching off of the flame finally ensures an additional level of security against fuel gas leaks and escapes.