D E S C R I P T I O N

The present invention relates to new concept compact cooktops employing gas burners of the premix type.

An air-gas mixture where the air and gas masses are in a mixture ratio (mixture titre) equal to the exact stoichiometric ratio STC for a complete combustion of _s the gas without residual oxygen is referred to as stoichiometric mixture. A mixture rich in gas, that is to say with a mixture ratio < STC, i.e. with lack of air, is herein referred to as "rich" mixture. A mixture poor in gas, that is to say with a mixture ratio > STC, i.e. with excess of air, is herein referred to as "lean" mixture. For a complete combustion, in practice, a mixture with a slight excess of air is required compared to the STC ratio theoretically sufficient.

Hereinafter, however, by "stoichiometric" titre mixture or "STC mixture" it is meant a mixture with that minimum slight excess of air necessary to ensure the complete combustion.

They are herein referred to as:

- "primary air", the combustion air mixed with a fuel gas upstream of the point where the combustion takes place;

- "secondary air", the combustion air optionally to be flown to the flame in order to complete the combustion;

- "stoichiometric air", the air necessary to obtain an STC mixture; - "atmospheric burner" a burner that requires both primary air, sucked by the fuel gas by Venturi effect, and secondary air recalled on the flames by natural draft;

- "blown burner", a burner where the primary air is supplied through a fan; - "premix burner" a blown burner where the supplied primary air is at least sufficient to produce an STC if not also lean mixture; it is known that the premix burners do not need secondary air that in fact is deleterious because it cools the flames.

Premix burners are widely known and widely used for example in the household boilers for room heating and instant generators of hot water. In such products a very wide and continuous power modulation is possible while always keeping the mixture to stoichiometric titre. According to this technology, a single fan serves a single burner and the power modulation takes place by simultaneously changing, according to a predefined relation, fuel gas flow rate and combustion air.

The recent document AN2015A000041 discloses important improvements in the power regulation of a plurality of premix burners relating to gas cookers of a gas cooktop. According to the document, all such burners may be supplied by a single fan; each burner provides the possibility of modulation of its power at least in steps from a minimum to a maximum power while keeping in regular combustion conditions (that is,, with STC mixture); the only one fan regulates its flow rate so as to supply each burner with the stoichiometric air flow rate required for the power set at the moment.

With reference to burners for cooktops, they are herein referred to as:

- "crown of flames" the flames distributed as a crown to the edges of the flame spreading cap of an atmospheric or blown burner, at the substantially radial fuel mixture outlet holes;

- "bed of flames" the flames that is possible to have on the whole surface of the flame spreading cap of a premix burner at the substantially vertical fuel mixture outlet holes. It is not possible to have such beds of flames in atmospheric or even blown but not premix burners because the innermost flames could not be reached by the secondary air essential for the complete combustion.

An object of the present invention is to improve the uniformity of heat distribution on the bottom of the cooking vessels.

A further object of the present invention is to provide a cooktop where multiple contiguous gas cookers can form a continuous bed of flames.

A further object of at least some variants of the present invention, is to create a wide cooking zone where the cooking vessels can be arranged in ways not forced by the position of the underlying burners.

A further object of at least some variants of the present invention, is to be able to vary the power supplied to the cooking vessels by simply moving their position. A further object of at least some variants of the present invention, is to be able to vary the power supplied to the cooking vessels by simply lifting and repositioning them.

A further object of at least some variants of the present invention, is to be able to vary the power supplied to a cooking vessel by acting on a single control dashboard regardless of the position of the cooking vessel.

Further features and advantages of the present invention shall be better highlighted by the following description of a feeding unit of a blown burner for cooktops in accordance with the main claim, 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 shows, in a plan view and schematically, the main elements of a possible cooktop employing means according to document AN2015A000041 ;

- Fig. 2, which is a detail of Fig. 1 , shows a first possible mix valve usable in a cooktop PC comprising a group of burners according to the invention;

- Fig. 3 shows a second possible mix valve usable in a cooktop PC comprising a group of burners according to the invention;

- Fig. 4 shows a further possible mix valve usable in a cooktop PC comprising a group of burners according to the invention;

- Fig. 5 shows in a plan view and schematically a cooktop employing a first possible embodiment of burners according to the invention simultaneously usable by a single cooking vessel;

- Fig. 6 shows in a plan view and schematically a cooktop employing a second possible embodiment of burners according to the invention simultaneously usable by a single cooking vessel;

- Figs. 7. a, 7.b show, in plan view and schematically, a cooktop serving more cooking vessels each of which may engage groups of one or more burners simultaneously;

- Fig. 7c shows symbolically the cooking vessels that may be positioned, in various ways, on the cooktop of Figs. 7. a, 7.b;

- Figs. 8. a, 8.b show two situations similar to those of Fig. 7. a with cooktops of similar functions, but very different appearance and employing two different combustion air supply means;

- Figs. 9. a, 9.b show, in the turned on and off state a possible embodiment of burner usable in the cooktops of Figs. 7 and 8;

- Figs. 10a, 10b show, in detail, possible embodiments of mix valves and various other components, respectively, only symbolically shown in the cooktop of Figs. 7a, 7b, 8a, 8b.

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

Fig. 1 , shows a cooktop PC according to an embodiment prior to the present invention but contains elements all usable by the same invention except for the premix burners BRN and the control dashboard CC depicted there that are different from those according to the invention. In the figure, a fan FAN supplies with primary air one or more premix burners BRN through an air conduit 401. The latter is depicted as part of a ramp 4 that also comprises a gas conduit 402 that instead supplies the same burners BRN with the fuel gas.

The passage section of the air conduit 401 is, preferably, large enough to make irrelevant the pressure drop of the air flow from the fan FAN to some air orifices 403 that shall be described later; this in order to consider the air pressure upstream of said air orifices 403 as substantially equal. To this end, as an alternative to what shown in figure, the air conduit 401 may consist of a plenum 401 substantially extended to the whole casing of the cooktop PC and capable of keeping, in any part thereof, the air substantially to the delivery pressure of the fan FAN.

The figure also shows possible known safety means comprising flame sensors FD that send flame presence or absence signals to a control unit SFT which, in turn, if necessary, provides for the opening/closing of a general gas shut-off solenoid valve SSV and/or fuel gas or mixture shut-off solenoid valves SV to the single burners BRN.

Depending on the variants of the invention, to the side of each flame detector FD, not shown, also an ignition device IGN (explicitly shown in Fig. 10b) may be present.

The figure shows that the control dashboard CC, as preferably also in the invention, has functional links, consisting in exchange of signals and/or inputs, with a command unit CMD which, in turn, has functional links with at least the means for regulating the power of the burners BRN in order to actuate them and/or know their status.

The fan FAN, in addition to the possible functional link with the command unit CMD, as shown in the figure and according to the teachings of document AN2015A000041 , may have, additionally or alternatively, a functional link with a delivery pressure gauge of the same fan FAN. Such option is not shown in the figures. However, it should be noted that the system is perfectly functioning even without any kind of feedback or control of the rotation speed of the fan FAN. It is sufficient for it to be designed to ensure the predefined delivery pressure to the predefined rotation speed when electrically powered. Sensors and feedback methods are only appropriate to prevent any fluctuations in the angular speed. With reference to Figs. 5 - 8, the object of the invention is a cooktop PC equipped with a plurality of premix burners BRN gathered in one or more cooking zones 5 also separate from each other, but where, in each zone 5 the two or more premix burners BRN present are one adjacent to the other in such a way that there can be substantial continuity between the flame spreading caps 6 of the contiguous burners and, in particular, whether such flame spreading caps 6 are shaped to produce a bed of flames, this goes substantially up to their edge so that there can be substantial continuity between beds of flames of contiguous flame spreading caps 6.

The use of premix burners BRN, it fact, does not pose fluid-dynamic constraints to the close proximity to each other of the respective beds of flame not requiring, as mentioned, the supply of secondary air.

Each premix burner BRN of the cooktop PC according to the invention has means for its regulation of power independent of the other premix burner BRN although in some variants such regulation of power takes place in a manner related to the regulation of the other contiguous switched on premix burners BRN.

The regulation of power may take place according to known methods and means or according to more alternative methods and innovative means depending on the variants.

Preferably, except for some useful variants that shall be illustrated, also the ignition of each premix burner BRN is independent of that of the others.

The means for supplying a premix burner BRN (hereinafter simply "burner BRN") usable in the invention comprise (see at least Figs. 2 to 4 and 9) the air conduit 401 (which, as seen, may be a plenum 401 ), the gas conduit 402, a mixing chamber 2 communicating with said air 401 and gas 402 conduits through one or more groups-orifices 403-404 and having a mixture outlet 201 towards the flame spreading cap 6.

Each of said groups-orifices 403-404 comprises one or more air orifices 403 and one or more corresponding gas orifices 404.

These one or more air 403 and gas 404 orifices consist of openings with suitably calibrated passage sections, considering the predetermined gas and air supply pressures and the nature of the gas, so that the corresponding group-orifices 403- 404 can provide, as a whole, the amount of gas and air required to form a mixture that ensures a predetermined and specific partial power of value Pp. Normally closed shutters 3 are also present, which:

- if the mixing chamber 2 has a single group-orifices 403-404, they are capable of keeping all at once either open or closed at least the corresponding gas orifices 404

- whereas, if the mixing chamber 2 has more than a group-orifices 403-404, they are capable of keeping all at once either open or closed all the corresponding both air 403 and gas 404 orifices.

A group-orifices 403-404 the one or more gas orifices 404 whereof are open or closed making it possible, as a result, the generation of a corresponding thermal power to the burner BRN is herein referred to as in an ON or OFF state.

The reason why, in the presence of a single group-orifices 403-404, it is sufficient that the shutters 3 intercept the corresponding gas orifices 404 and not also the corresponding air orifices 403 is that air can escape from the burner BRN even if turned off without any inconvenience while this would alter the composition of the mixture in the presence of more groups-orifices 403-404 individually settable in an ON or OFF state.

As said, the mixing chamber 2 may have n groups-orifices 403-404 each set up for an overall predetermined and specific partial power of value Pp.i where the suffix "i" indicates the i-th of the n groups-orifices 403-404.

In this way, the power of each burner BRN is adjustable in steps by imposing the appropriate ON or OFF state to each of the n orifices groups 403-404 of which the burner BRN is provided and its total power Ptot at a given time is equal to the sum of the partial powers Pp.i due to each of the n groups-orifices 403-404 in the ON state at that time while the maximum power Pmax is obtained when all the n groups-orifices 403-404 are in the ON state.

According to a remarkable embodiment that meets most of the practical needs, such plurality of groups-orifices 403-404 associated to a burner BRN is a pair (n = 2) of groups-orifices 403-404 of which the first set up for a predetermined partial power Pp.1 and the second similarly set up for a partial power Pp.2 suitably > Pp.1 so as to obtain, as known, four increasing powers Ptot: Ptot = P0 = 0; Ptot = Pmin = Pp.1 ; Ptot = Pmed = Pp.2; Pmax = Pp.1 + Pp.2. In particular, if Pp2 is the double of Ppl , uniformly increasing powers with increments equal to Ppl are obtained.

For the purposes of the invention, however, the regulation of power in steps may not be required but only an "all or nothing" power, and then such plurality of groups-orifices 403-404 is reduced to a single group-orifices 403-404 (n = 1). By way of example, some possible embodiments of said means for supplying a premix burner BRN suitable for the invention are now described.

Fig. 2 shows a mixing chamber 2 that can receive air and gas from corresponding air 401 and gas 402 conduits (the second highly preferably internal to the first) through two groups-orifices 403-404 each comprising only one air orifice 403 and only one gas orifice 404, concentric. Each group-orifices 403-404 is kept closed/open by a corresponding single shutter 3. Such apparatus therefore allows the burner BRN the four power steps already seen (including the OFF state of turned off burner BRN).

Fig. 3 shows a mixing chamber 2 that can receive air and gas from corresponding one air 401 and two gas 402 conduits (the second ones 402 side by side to the first 401 ) through two groups-orifices 403-404 each comprising one air orifice 403 and two gas orifices 404 flanked thereto. Each group-orifices 403-404 is kept closed/open by a corresponding single shutter 3. Even such apparatus therefore allows the four power steps.

Fig. 4 shows a mixing chamber 2 that can receive air and gas from corresponding air 401 and gas 402 conduits (the second inner to the first) through a single group-orifices 403-404 each comprising multiple air orifices 403 and multiple gas orifices 404. The group-orifices 403-404 is kept closed/open by a corresponding shutter 3 having the shape of a drawer shutter with a first gasket 301 that intercepts the gas orifices 404 and a possible second gasket 302, downstream of the first, that intercepts both the gas orifices 404 and the air orifices 403. Such apparatus allows only two power steps (Ptot = 0 or Ptot = Pmax).

Of course, also the mixing chambers 2 shown in Figs. 2 and 3 could provide a single group-orifices 403-404 if the only two power steps Ptot = 0 and Ptot = Pmax are sufficient.

The fact that in the examples shown a single shutter 3 opens/closes simultaneously all air 403 and gas 404 orifices of a group-orifices 403-404 is only an advantageous and non-essential option.

In all the examples shown so far, the mixing chamber 2 is in the proximity of the ramp 4 and provides a mixture outlet 201 that, as shown in Figs. 6, 7 and 8, is connected to the corresponding burner BRN either directly or through a possible mixture supply conduit 202.

Fig. 9, instead, shows a burner BRN the cup whereof incorporates a mixing chamber 2 wherein the gas, coming from the gas conduit 402 through a pipe interceptable by a shutter 3 (pipe and a shutter 3 not shown), enters from a gas orifice 404 while the air, coming from the air conduit 401 , enters from an air orifice 403 separately interceptable by the gas orifice 404.

Also in this version the mixing chamber 2 may provide more groups-orifices 403-404 each comprising one or more air orifices 403 with one or more corresponding gas orifices 404.

It should be noted that, whatever the embodiment and the position of the mixing chamber 2, if a single group-orifices 403-404 is provided therein, it is not necessary to provide for the plugging of the air orifices 403. As regards the mixing chamber 2 of Fig. 4, supplied by the drawer shutter 3, this can be obtained by simply not providing the second gasket 302. As regards the mixing chamber 2 incorporated in the cup of the burner BRN, advantageously the air orifices 403, devoid of corresponding shutters 3, can be supplied by an air conduit 401 consisting in said plenum 401.

The device comprising at least the already seen mixing chamber 2, groups- orifices 403-404 and corresponding shutters 3, a mixture outlet 201 means towards a corresponding flame spreading cap 6 to obtain one or more power levels Ptot adjustable in steps is hereinafter referred to as mix valve 1. The means included in the mix valve 1 may be physically joined or located in separate positions.

Figs. 9. a and 9.b, for example, show a remarkable variant where the air conduit 401 consists of the entire compartment of the cooktop; the mix valve 1 includes a normal gas shut-off valve (not shown) mounted on a gas conduit 402 and with a passage hole of diameter not calibrated and greater than that of the gas orifice 404 of the corresponding gas injector 404; the latter, instead, is mounted in the mixing chamber 2 that is incorporated in the cup 2 of the burner BRN with the advantage of being thus easily accessible for replacement.

In Fig. 9a, the burner BRN is shown "turned on" with consequent entry of air and fuel gas in the mixing chamber 2 while in Fig. 9b the same is shown "turned off and with the only inlet of combustion air.

Having described possible mix valves 1 , Fig. 5 shows, in a cooktop PC, one of multiple possible cooking zones 5 shaped according to a very particular possible first embodiment of the invention.

In the example of Figure 5 such cooking zone 5 consists of a single circular gas cooker 5; that is, it consists of a zone 5 designed to receive a single cooking vessel R consisting in this case in a pot. Such cooking zone 5 is composed of three burners BRN, specifically referred to as BRN 1 , BRN2 and BRN3 from the innermost to the outermost, concentric and with three separate but contiguous beds of flames and each independently supplied by a mix valve 1 thereof.

The particular variant shown provides burners BRN supplied by non-modulable mix valves 1 because they are provided with a single group-orifices 403-404 but the proposed gas cooker 5 has modulable power because it provides the sequential ignition of the three burners BRN, of increasing power from BRN 1 to BRN3, according to the BRN1 sequence then BRN1 + BRN2 then again BRN1 + BRN2 + BRN3 and vice versa.

Only one flame detector FD controls the central bed of flame (that of BRN1 ) that is also served by an ignition device (not shown) and that is switched on first and switched off last. In this way the central bed of flame serves as a pilot flame for the adjacent beds of flame.

The sequential ignition of the three burners BRN upon user's command is preferably carried out as described later in a very general form.

Gas cookers with at least two concentric and independently supplied atmospheric burners, designed for higher powers useful in a cooktop are already known but the burners must be spaced from one another by at least what necessary to allow, among them, the inflow of secondary air. As a result it is impossible to use one of the burners as a pilot flame and the power required imposes minimum plan sizes significantly higher than what permitted by the use of premix burners according to the invention precisely thank to the possibility of having beds of flame and these contiguous to each other. This allows to deliver equal powers to pots R of lesser diameter and with heat distribution significantly more uniform.

In the example of Figure 6, the cooking zone 5 consists, instead, in a rectangular gas cooker 5 that is a zone 5 designed to receive a single cooking vessel R such as a rectangular baking tray or a grill pan: even in this example, the cooking zone 5 provides three burners BRN (the central one referred to as BRN1 and each of the two lateral as BRN2) each independently supplied by a mix valve 1 thereof. In this example the three burners BRN have a rectangular shape and are placed adjacent to one another according to the longer side, which, preferably, is equal to twice the shorter side.

Also in this example, the central burner BRN1 may serve as a pilot flame and the ignition sequence then provides the progressive ignition of the active beds of flame extending them from a rectangular (that of BRN 1 ) to a square (BRN1 + a side BRN2) then again rectangular (BRN1 + both the side BRN2) surface.

By using modulable mix valves 1 (that is, each provided with at least two groups-orifices 403-404) the possibility of regulation of power becomes very articulated, being able to switch progressively, as in the previous example, to the ignition of the three burners starting from the central burner BRN1 but also including steps in which the power of each burner BRN can be increased: the combinations that may be chosen are many, e.g., turning on in progression the three burners BRN to the minimum power Pmin and then bringing them one by one to the average power Pmed and finally to the maximum Pmax or turning on first only the central burner BRN1 gradually bringing it from minimum to maximum power before activating with the same gradualness one or both side burner BRN2. It is clear that many criteria for the regulation of power are possible and very uniform thermal powers of the "beds of flames" can be guaranteed.

In the version of most general application, the invention provides that the one or more cooking zones 5 are composed, each,_of a matrix of an undefined number of burners BRN adjacent to one another each of which is served by a mix valve 1 thereof, an ignition device thereof and a flame detector FD thereof so that each burner BRN may, absolutely independently of the others, be ignited, modulated if served by a modulable mix valve 1 or excluded from the gas supply in case the flame accidentally extinguishes.

As a consequence, each cooking zone 5 is composed of a number of flame zones Z equal to the number of burners BRN present, each corresponding to the bed of flames of each flame spreading cap 6 and can simultaneously accommodate more vessels R variously arranged and subject to independent cooking processes. The cooktop PC, accordingly, may provide a single cooking zone 5. Figure 7. a shows a first possible layout of a cooking zone 5 that provides burners BRN with rectangular (in particular, square) flame spreading cap 6.

Figure 8 shows a second possible layout of a cooking zone 5 that provides burners BRN with hexagonal flame spreading cap 6; the layout is deliberately unusual to show the extreme composition flexibility of the cooktop PC that may also provide more cooking zones 5 separate to each other for any purpose, even aesthetic.

In both Figs. 7 and 8, for greater clarity, "active" flame zones Z are symbolically represented with grey surfaces while those "turned off are white.

Moreover, for graphical simplicity, a symbol in the shape of a triangle indicates the mix valve 1 according to possible embodiments thereof, while the symbol in the shape of two triangles with opposed points indicates for each flame zone Z the assembly flame detector FD, ignition device IGN and, as shall be seen just below, device for detecting S the presence/absence of the cooking vessel R. The complexity of such matrix of burners BRN usable in a plurality of states is manageable, according to various possible means and methods, through the command unit CMD.

A preferred method herein referred to as "position sensing" provides that in each flame zone Z a device for detecting S the presence/absence of the cooking vessel R is present. Such a device, resistant to the operating temperatures, is of the known type such as a contact or remote detector (e.g., magnetic or optical), and arranged so as to recognize the presence of the vessel only if this occupies a delimited central part of the flame zone Z. The detected presence of a vessel R for a predetermined time interval Διρ.οη (which, in order to avoid accidental switching on, may be of a few seconds) enables the ignition and maintenance of the flame in the corresponding burner BRN. The switching off of the flame takes place after that the presence of vessels is no longer detected for a predetermined time interval Atp.off of duration similar to Διρ.οη.

In this way it is possible to regulate the level of thermal power even if the mix valves 1 are not modulable by suitably arranging the vessel on the desired beds of flame. By shifting the vessel the beds of flame under the vessel are enabled/disabled automatically by increasing/decreasing the number of burners BRN switched on. This is exemplified in Figure 7.b, 7.c where the dashed lines indicate vessels R of various shape and variously positioned on the matrix of burners BRN. Of these, only those in grey correspond to switched on burners BRN because only their flame zone Z has the central part occupied by a pot. It is seen that it is possible to arrange the vessels in a variety of positions (including those along the edge of the cooking zone 5) that activate a significantly different number of burners BRN so as to be able to supply various overall powers in the range of those required for cooking.

It can be affirmed that the minimum and maximum powers required in a cooking process from a given vessel are substantially proportional to the surface of the bottom of the same container; therefore, we can talk about power density substantially independent of the size of the vessel. A possible criterion for choosing the power of each burner BRN is then that of setting it equal to the minimum power required by the wider vessel that can be positioned on the cooking zone 5 so as to be detected by only one flame zone Z. As shown in the map B of Fig. 7.b, such vessel R may be suitably moved to receive a double or quadruple power of the minimum. A larger vessel R that intercepts to the minimum four flame zones Z (see map A of Fig. 7.b) will receive a quadruple power whereto, however, substantially corresponds the same power density P.spec.min.

One of the main advantages of this solution with non-modulable mix valves 1 is the ease of use: the selection and modulation controls of the burners disappear completely, the user has only to enable/disable the entire cooktop PC (single command) upon switching on then place the cooking vessel(s) R on the desired burner(s) BRN and the command unit CMD, upon receiving the presence signal of one or more of the vessels R over one or more burners BRN, provides for supplying, igniting and maintaining the flames thereof.

The "position sensing" method can also manage cooking zones 5 composed of an undefined number of burners BRN served by mix valves 1 modulable by discrete levels.

In this case, the function logic must comprise and manage the concurrency and timing of the signals sent by the pot presence detectors.

To exemplify the first method before providing the general rules thereof, let's suppose to place a cooking vessel R (e.g., a pot) on a single i-th flame zone Z(i) served by a mix valve 1 with two groups-orifices 403-404 (then with four power steps Ptot), the system, after an appropriate time interval of stability of the above-mentioned vessel presence signal has elapsed, enables/switches on/keeps the zone Z(i) to a level Pmin (i.e., switching from P0 to Pmin); by lifting and quickly repositioning the vessel R the system detects the movement and increases the power by a discrete level (in this example it is switched from Pmin to Pmed); by repeating the lifting and quick repositioning the system switches to the immediate higher level (from Pmed to Pmax) and then, at each subsequent lifting and repositioning, repeats the cycle or reduces the power according to these possible sequences:

P0 ==> Pmin ==> Pmed ==> Pmax ==> P0 ==> Pmin ==>...

or

P0 ==> Pmin ==> Pmed ==> Pmax ==> Pmed ==> Pmin ==> ...

Quick lifting and/or repositioning means that it must take place in time intervals lesser than said Atp.off or Δίρ.οη necessary for the command unit CMD to interpret the movement as absence/presence of vessel R.

By definitively lifting or shifting the vessel R to the outside of the matrix of flames, the system still switches off Z(i).

On the contrary, assuming that the cooking is taking place with Z(i) to Pmed, if the vessel R is shifted so as to extend the coverage to an adjacent flame zone (formally: flame zone Z(i+1 )), the system recognizes the simultaneous continuous involvement of Z(i) and Z(i+1 ) and realises the condition: Z(i) to Pmin and Z(i+1) to Pmin.

By repeating the lifting + the quick repositioning of the vessel R on both the zones Z, the cyclic sequence according to the following two possible variants is again realised:

[Z(i) to Pmin and Z(i+1 ) to Pmin] ==> [Z(i) to Pmed and Z(i+1 ) to Pmed] ==> [Z(i) to Pmax and Z(i+1 ) to Pmax] ==> [Z(i) to P0 and Z(i+1) to P0] ==> ... or

[Z(i) to Pmin and Z(i+1 ) to Pmin]==> [Z(i) to Pmed and Z(i+1 ) to Pmed] ==> [Z(i) to Pmax and Z(i+1 ) to Pmax]==> [Z(i) to Pmed and Z(i+1 ) to Pmed]==> ... In general, the method for the regulation of power provides that:

- at each movement of the vessel R that indicates a change of the flame zones Z occupied, all such zones are switched to a power Pmin;

- at each lifting + quick repositioning of the vessel R which does not change the flame zones Z occupied, there is an increase by a step in the power of all the same flame zones where, once the maximum power Pmax is reached, the method proceeds further by power steps according to the following two possible variants:

- the cycle is repeated starting again from P0 and then rising again in power or

- the cycle is repeated symmetrical decreasing up to P0 and then rising again in power.

By appropriately setting, in the command unit CMD, the time intervals between a lifting and a subsequent repositioning that must be recognised as the user's request to change power and the minimum parking times on a flame zone Z that must be recognised as a user's choice to occupy that zone, the same user can train quickly to make the correct movements so that the same command unit CMD interprets his intentions correctly.

In particular, to avoid misinterpretations, these durations of time may be chosen sufficiently different from those related to certain usual cooking operations involving the shaking of the vessel such as "sauteing".

By suitably managing times and pauses, the system is able to distinguish all the possible intentions of the user and regulate both the cooking perimeter and the power level within the perimeter accordingly.

A completely different method from that of "position sensing" described thus far to handle the same cooking zones 5 herein referred to as "mapping" provides a control dashboard CC provided with a touchscreen type screen responsive to contact with a finger.

A map of the cooking zones 5 is drawn in the screen, with all the flame zones Z the ON/OFF state (switched On/Off) and, if in the ON state, the power level whereof, are on each of flame zone Z indicated with graphic symbols and/or colours.

For example:

- progressive numbers from 0 to n to indicate the power supplied starting from P0 = 0.

and/or

- white colour to indicate the OFF state; colour of different degrees of intensity depending on the power level if in the ON state.

The user, having identified on the map the flame zones F of his interest, selects them and determines their state by repeated taps on the image of the same zone implementing the already described cyclical variations of the power.

A preferred method, for its immediacy of interpretation provides own means both of the "position sensing" method and the "mapping" method.

In it the device for detecting the presence/absence S of the vessel R are provided and the said touchscreen type screen is provided. In it the flame zones Z are indicated with graphic symbols and/or of a different colour depending on whether the corresponding devices for detecting the presence/absence S signal them free or occupied (e.g., white or in colour, respectively, as already shown graphically in some of the annexed Figs.). This facilitates the user in identifying the exact position of the vessels and therefore the flame zones Z to regulate the power whereof whose level can always be indicated by the optical symbols already described.

The means indicated to manage the "mapping" method may be used only for monitoring the state of the flame zones Z without being able to change their state; in that case the touchscreen type screen is not necessary but just a normal liquid crystal display monitor.

A further remarkable variant of methods and means for the regulation of the flame zones Z involving a vessel R (herein referred to as "with selector key") provides that, in the act of positioning the vessel R, detected by one of the detection devices S, only the burner BRN barycentric to the same vessel R activates: that is, only one burner BRN at the centre of the "area concerned" from the surface of the vessel R switches on. A selection key "+" or a selection key "+"/"-" remains present adapted to select cyclically only in one (selection key "+") or both (selection key "+"/"-") direction one of more possible actions of the command unit CMD as explained below.

Pressing, for a time not less than a minimum time Atp, the said selection key, the command unit CMD increases/reduces the power supplied to the vessel R - by actuating/deactivating in a sequence the flame zones Z immediately adjacent to that barycentric and "sensed" as occupied by the same vessel R - and/or by increasing/reducing the power Ptot supplied by the same flame zones Z.

In this way the need for the "selection" command provided by the "mapping" method is avoided. The choice of the flame zones Z to actuate/deactivate in a sequence and/or of which increasing/reducing the power supplied Ptot is, preferably, carried out by the command unit CMD that can be programmed to follow the criterion of the more uniform distribution of the power supplied under the vessel R (that is, a distribution as symmetrical and even as possible around the barycentre of the "area concerned" by the vessel R).

In case of simultaneous presence of more vessels Rl , R2, R(i), Rn, a selection step of the vessel Rk is provided the underlying flame zones Z whereof must be must be involved with the regulation. This can be achieved through a click consisting in a short pressing exerted on the same said selection key for a time not exceeding a maximum time Ats < Atp. The click produces a temporary switching on (a few seconds) of a flame zone Z adjacent to a vessel R(i) that is the one on which the command unit CMD is currently set to vary the perimeter of the flames. If the vessel R(i) signalled is not that Rk on which it is wished to operate, further clicks shall be continued on the selection key cyclically followed by the selection, by the command unit CMD, of each of the other vessels R(i) of which the detection devices S have detected the presence and the corresponding switching on of a corresponding flame zone Z for signalling purposes. The user continues with the clicks until the command unit CMD selects the vessel Rk for which the user wants to change the power, which is what then obtains, as said, by keeping pressed for that predetermined minimum time Διρ the same selection key.

The flame zone Z that is temporarily switched on to signal the vessel R(i) on which the command unit CMD is currently set, is preferably among those not covered by the vessel R(i) so as to be easily visible.

In short, and in more general terms, the method provides a device for detecting the presence/absence S of the vessel R in each of flame zone Z and at least one selection key (preferably at least one selection key "+" and one selection key "-

")·

The quick (click) and repeated pressing of the said at least one selection key allows the cyclic selection, through the command unit CMD, of each of the vessel R(i), among all the n vessels R of which the devices for detecting the presence/absence S have detected the presence, up to selecting that Rk of which it is wished to vary the perimeter of the flames.

The command unit CMD signals the selected vessel R(i) with every click through a specific identification signal of said vessel R(i) which may consist in the switching on for a short duration of a burner BRN adjacent to said vessel R(i).

The pressing for at least a short predetermined minimum time of said at least one selection key causes the command unit CMD to cyclically vary the perimeter of the flames below the selected vessel Rk. In even more synthetic and more general terms, the "selector key" method provides

- the emission of a specific identification signal of the vessel R(i) on which the said command unit CMD is set at the moment to vary its supplied power; - the repeated pressing of a selection key, each pressing being exerted for maximum time lengths equal to Ats up to selecting the desired vessel Rk among the n vessels R(i) which are present on the cooktop PC;

- the subsequent continuous or repeated pressing of the same selection key for minimum time lengths equal to Δίρ > Ats up to selecting the power to be supplied that is desired for the same vessel Rk.

Finally, it may be provided that, for safety reasons, the command unit CMD inhibits the activation of additional burners BRN and/or power increments of burners BRN already switched on when the sum of the powers Ptot supplied by the already active burners BRN reaches a power equal to a predetermined limit value P.lim.

As already partially anticipated, it is highly preferred that the conduits conveying the airforms, that is to say the gas conduits 402, any air conduits 401 (if different from a plenum 401), any mix conduits 202 are of such sections and lengths to ensure that both the pressure of both air and gas at the inlet of the corresponding air 403 and gas 404 orifices and the mixture pressure to the flame spreading caps 6 are substantially independent of the position of the corresponding burner BRN otherwise each orifice 403 and 404 and each flame spreading cap 6 should have calibrated passages for the specific ad different supply pressures. This can be achieved both with air 401 , gas 402 and mixture 202 conduits with a passage section so wide to make negligible the pressure drop of the airforms therein and also with connections from the air 401 and gas 402 conduits to the flame spreading caps 6 of equal length (e.g., by spirally winding the conduits that lead to the burners BRN closest to the ramp 4.

Many variants are possible without departing from the scopes of the invention also considering the possible further combinations of the means and methods described.

Moreover, nothing prevents, on the other hand, that the power of each burner BRN is continuously adjustable by known means different from those indicated above. This is particularly easy at least for cooktops PC containing cooking zones 5 with a number of burners BRN in a sufficiently limited number to be easily manageable manually by the user.