D E S C R I P T I O N

The present invention relates to valves for regulating the thermal power of gas burners of the blown or premix type.

In particular, the burners according to the present invention are suitable for serving as burners for gas cookers of cooktops.

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 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 required to obtain an STC mixture;

- "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 even lean mixture.

Premix burners are well 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 still 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 fed by a single fan; each burner provides for 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 feed each burner with the stoichiometric air flow rate needed to the power set at the moment.

The main object of the present invention is to provide a regulation valve for the regulation of the thermal power of a blown burner where, at least for some variants, such regulation is in steps.

A further object of the present invention, is to feed a blown burner directly with the fuel mixture instead of separately with fuel gas and combustion air.

A further object, at least of some variants of the present invention, is to provide an electromagnetically actuated regulation valve.

A further object, at least of some variants of the present invention, is to provide a regulation valve that regulates at least three power steps.

A further object, at least of some, variants of the present invention, is to provide a regulation valve that has pre-calibrated inlets orifices preset and easily selectable for multiple types of gases, preferably methane and LPG.

A further object, at least of some variants of the present invention, is to provide a regulation valve which is of quick mounting and without screws on the fuel gas and primary air feeding ducts.

- Fig. 1 shows a plan and schematic view of the main elements of a possible cooktop utilizing means according to the invention, some general, others according to a first main variant;

- Fig. 2 is a detail of Fig. 1 ;

- Figs. 3. a to 3.e show, in various views and sections, a valve for the regulation of the power of a burner according to a second main variant of the invention mounted on an air and gas distribution ramp always according to the same variant;

- Figs. 4. a to 4.d show the sections indicated in Fig. 3.b and their details;

- Figs. 5. a to 5.c show an axonometric and exploded view of the elements of Figs. 3. a to 3.e;

- Figs. 6. a to 6.c show, according to views, sections or axonometries, the elements of Figs. 3. a to 3.e;

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 shown in the figures while any relative spatial reference such as the terms previous/subsequent, upstream/downstream should be understood with reference to the direction of circulation of the flows of airforms. Fig. 1 (and Fig. 2 for greater clarity of some details) shows a cooktop PC with blown burners BRN which, by way of an example, are three and of identical characteristics but only because they actually want to show three different possible operating states of a single blown burner BRN, it being understood that such cooktop PC may comprise one or more of such blown burners BRN.

The figure shows the fan FAN that supplies with primary air said one or more blown burners BRN (hereinafter simply referred to as burners BRN) through an air duct 401. The latter is part of a ramp 4 that comprises also a gas duct 402 that instead supplies the same burners BRN with the fuel gas.

The figure then shows the 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 shut- off solenoid valve SSV and/or shut-off solenoid valves SV of the single burners. The figure also shows a possible control dashboard CC that has functional links, consisting in exchange of signals and/or input, with a possible command unit CMD which, in turn, has functional links with at least the valves 1 for the regulation of 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 figure, 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.

The object of the invention is a feeding unit 1-4 comprising:

- a ramp 4 for supplying with gas and air one or more burners BRN

- and one or more valves 1 connected to said ramp 4 and each intended for the regulation of the power of a corresponding one of said one or more burners BRN.

For shortness, from here on, valves 1 for the regulation of the power according to the invention shall be referred to as mix valves 1.

For simplicity of description reference shall substantially always be made to a mix valve 1 and to a corresponding burner BRN, it being understood, as mentioned, that said ramp 4 may serve a plurality of burners BRN through the corresponding mix valves 1.

The burner BRN, which is a blown and preferably premix burner, is fed with an air-gas mixture that forms inside a mixing chamber 2 that is part of said mix valve 1.

The mixing chamber 2 is sealed towards the outside environment except for passages consisting of a mix outlet 201 connected from a mix pipe 202 to the burner BRN and air and gas inlets from corresponding air orifices 403 and gas orifices 404. From now on, by sealed mixing chamber 2 it is meant a mixing chamber 2 made sealed except for said passages 201 , 403, 404.

According to the invention, the mix valve .1 provides for a plurality of shutter assemblies 3. Each shutter assembly 3 comprises a shutter 301 capable of being piloted to two stable positions ON/OFF where;

- in OFF position it keeps simultaneously closed corresponding air orifices 403 and gas orifices 404 associated thereto;

- in ON position it keeps simultaneously open the same associated air orifices 403 and gas orifices 404;

- said air orifices 403 and gas orifices 404 are openings that put in communication the air duct 401 and the gas duct 402 with the mixing chamber 2, respectively, and which have passage sections suitably calibrated, considering the predetermined gas and air supply pressures and the nature of the gas, to provide, through each shutter assembly 3, the amount of gas and air required to form a mix that ensures a predetermined partial power of value

Pp-

Accordingly, the total power Ptot delivered at a given time by each burner BRN is equal to the sum of the partial powers Pp due to the shutters 301 in the ON position at that time and the- maximum power Pmax of each burner BRN is obtained when all its shutters 301 are in the ON position.

Preferably, said stable ON and OFF positions are obtained by the fact that in said shutter assembly 3 the shutter 301 is constrained to a stem 302 piloted by a coil 303 which, energized, brings the shutter 301 in the ON position in contrast with a compression spring 304 which, when the coil 303 is de-energized, keeps the shutter 301 in the OFF position.

The variation in steps of the power of a burner BRN is obtained by imposing the appropriate ON or OFF position to each shutter 301 of the plurality of shutter assemblies 3 which the mix valve 1 has.

According to an embodiment that meets most of the practical needs, such a plurality of shutter assemblies 3 is a pair of shutter assemblies 3, of which the first with passage sections of the associated air 403 and gas 404 orifices set up for a predetermined partial power Ppl and the second similarly set up for a partial power Pp2 greater than ^" Ppl so as to obtain increasing powers with any step; by choosing in particular Pp2 = 2Ppl such step becomes uniform equal to Ppl and the power is modulable from 0 to 3 times Ppl .

However, if the adjustment in steps of the power is not required but only an "all or nothing" power such plurality of shutter assemblies 3 may consist of a single shutter assembly 3. This is the case of small power burners BRN useful for special purposes that shall not be covered herein. Therefore, hereinafter and in the accompanying figures, the description makes particular reference to mix valves 1 comprising a pair of shutter assemblies 3 without wishing to limit the scope of the invention.

According to a first main variant of the invention, illustrated in Figs. 1 and 2 the mix valve 1 is suitable for being mounted on a ramp 4:

- the air 401 and gas 402 ducts whereof, one inside the other, preferably with the gas duct 402 internal to the air duct 401 ;

- the ones and/or the others of said air 403 and gas 404 orifices may comprise a stretch of corresponding tube 413 (not present in the figures) and 414 that starts from the corresponding air 401 or gas 402 duct up to the front of the corresponding shutter 301 ;

- said tubes 413 and 414 being concentric to each other obviously with the tube 413/414 respectively on the outside corresponding to that external of the ducts 401/402;

the mix valve 1 having shutters 301 suitable for opening/closing such type of air 403 and gas 404 orifices.

According to such variant, the adaptation of each burner BRN to each type of gas and/or power provided is possible by mounting concentric tubes 413 and 414 of appropriate passage section although such interchangeability option is not shown in Figures 1 and 2 for graphical simplicity. According to a very advantageous second main variant of the invention, illustrated in Figs. 3 to 6:

- the ramp 4 provides for a mounting wall 405 the outer surface whereof is flat and whereon the mix valves 1 may be constrained so as to ensure that the corresponding mixing chambers 2 are sealed;

- the ramp 4 provides for an air duct 401 and a first gas duct 402 which run side by side and have the said mounting wall 405 as part of their walls;

- the ramp 4 may further provide a second gas duct 402 arranged symmetrically to the first relative to the air duct 401 and also sharing the same mounting wall 405;

- said air orifices 403 and gas orifices 404 are holes that pass through the said mounting wall 405.

Preferably, at said mounting wall 405, the cross section of the air duct 401 is sufficiently narrow to allow said air 403 and gas 404 orifices associated with each shutter 301 to be close enough to each other in order to make the simultaneous plugging thereof by the same shutter 301 constructively simple. Advantageously (see Fig. 6. a) in said first and possible second gas duct 402 additional gas orifices 404" suitable for further types of gas GAS2 (for example, LPG) and to be used as an alternative to each other according to the type of gas available may also be provided, associated with each shutter assembly 3, in addition to first gas orifices 404' suitable for a first type of gas GAS1 (for example, natural gas).

To this end, preferably with respect to other possible geometries that solve the problem:

- all the gas orifices 404 associated to a shutter 301 are arranged at the same radial distance from the corresponding air orifice 403;

- gas orifices 404 specific for the same gas may be provided in pairs (that is, the pairs of gas orifices 404 due to the presence of not only the first but also, possibly, the second gas duct 402) are in a diametrically opposed position relative to the corresponding air orifice 403; - a selective sealing member 406 that selectively closes all the gas orifices 404/404" relating to the gas GAS1/GAS2 not in use while leaving around the gas orifices 4047404" relating to the gas GAS1/GAS2 in use a space sufficient to allow the shutter 301 to take the ON/OFF positions in their regard without interferences with the same selective sealing member 406;

- all such gas orifices 404 are spaced, angularly from each other by a measure sufficient to allow the selective opening/closing thereof without having necessarily to interfere with the other gas orifices 404.

In order to set up the feeding unit 1 -4 for said first and second type of gas GAS 1 and GAS2 it is possible, as an alternative to the above to provide that the two gas ducts 402 are a first and a second gas duct, 4027402", respectively, each dedicated to the only gas GAS1/GAS2, respectively, and each carry ng exclusively the gas orifices 4047404", respectively, specific to the gas GAS1/GAS2 to which it is dedicated.

In such case, the preferred solution to select the gas duct 402 dedicated to the gas in use provides that:

- all the gas orifices 404' associated to a shutter 301 are arranged at the same radial distance from the corresponding air orifice 403 of the gas orifices 404" associated to the same shutter 301 ;

- all said gas orifices 404' associated to a shutter 301 are in a diametrically opposed position relative to the corresponding air orifice 403 to the gas orifices 404" associated to the same shutter 301 ;

- the selective sealing member 406 is always provided, which selectively closes all the gas orifices 4047404" relating to the gas GAS1/GAS2 not in use while leaving around the gas orifices 4047404" relating to the gas GAS1/GAS2 in use a space sufficient to allow said shutter 301 to take the ON/OFF positions in their regard without interferences with the same selective sealing member 406;

Advantageously:

- such selective sealing member 406 is a sealing disc: - capable of being irremovably fastened against the mounting wall 405 at the time of fixing thereon the mix valve 1, centred relative to the associated air orifice 403 and in a suitable angular position;

- of outer diameter sufficient to cover such gas orifices 404 entirely;

- carrying an opening 407 at the centre that leaves free only the associated air orifice 403 and the associated gas orifices 404V404" relating to the gas in use;

- while the shutter 301 is capable of being constrained to the angular position necessary to cover the air orifice 403 and all the gas orifices 404 left free by the selective sealing member 406 and has an outline which excludes interferences with the opening 407.

According to such variant, it is possible to adapt the cooktop PC to the type of gas in use among those provided by making operational the corresponding gas orifices 404 and leaving unchanged the air orifices 403 but setting the required air pressure that must be ensured by the fan FAN.

Preferably, the ramp 4 is obtained from a profile of material having suitable physical and mechanical characteristics; in particular the ramp 4 is obtained from an aluminium alloy profile.

What described thus far for the second main variant makes it easy to provide means for the quick fixing of the mix valves 1 to the ramp 4.

To this end, on the ramp 4 two guides 409 are provided (for example, obtained with the aid of two ribs 408) in which the appendices 102 of a foot 101 being part of the mix valve 1 can engage slidingly and by shape coupling. Geometry of the guides 409 and foot 101 are such as to ensure that the mixing chamber 2 may be sealed by suitable sealing members, once the positioning of the mix valve 1 has taken place.

Usefully (see at least Fig. 6. a), in order to further facilitate the mounting of the mix valve 1 such two ribs 408 may be locally interrupted so as to allow a bayonet coupling of the mix valve 1. The bayonet coupling is a shape coupling which, as is known, provides, along special guides, an approach of a first and second element and then a relative sliding of the first relative to the second element where in this case first and second element are the mix valve 1 and the ramp 4.

It should be noted that these types of coupling that provide for the said relative sliding are allowed by the fact that in the second main variant the air 403 and gas 404 orifices are simple holes that therefore do not produce projections.

The cited document AN2015 A000041 teaches the criteria by which the speed of the fan FAN may be regulated when the ON/OFF state of all the shutters 301 present in the cooktop PC changes.

Summarizing, there is provided a control unit that knows the load/flow loss characteristic curves of the cooktop PC for every possible combination of the ON/OFF state of all the shutters 301 of the burners BRN but also knows, for inputs sent and/or signals received by the same burners BRN, the actual ON/OFF state and therefore it is able to change the rotation speed of the fan FAN bringing it to the value that knows as appropriate to that state.

It has already been said that, through each air orifice 403, in order to guarantee the predetermined invariant partial power Pp (as well as for proper combustion), a predetermined amount of air must be guaranteed that depends on the type of gas in use. Such a predetermined amount of air is ensured by a predetermined pressure upstream of each air orifice 403 and obviously, regardless of the load losses of the air along the ramp 4 (that can be made very small with adequate section of the air duct 401), equal for all the air orifices 403 fed. In other words, all the air orifices 403 of each shutter assembly 3 must be fed with a same pressure that depends only on the type of gas in use.

Therefore, what it is obtained according to the teachings of document AN2015A000041 is to keep air the feeding pressure constant without measuring it directly.

A simple and direct method to ensure the predetermined powers is then that of - continuously controlling the delivery pressure of the fan FAN;

- verifying any deviations from the preset value p. target required by the type of gas in use;

- in case of deviation, changing the rotation speed of the fan FAN until reaching a delivery pressure equal to the preset value p.target.

This can be achieved by means that comprise a pressure gauge and a speed regulator as well as by the appropriate reception, storage and data output means. In fact, when the ON/OFF state of all the shutters 301 changes, the load/flow loss characteristic curve of the cooktop PC changes and therefore the delivery pressure of the fan FAN changes, the rotation speed being equal but changing the latter, the required delivery pressure is restored.

According to such method, no functional link is necessary that from the mix valves 1 leads, directly or indirectly, to the fan FAN but it may not prevent transient flame fluctuations or even possible switching offs at every change of the ON/OFF state, especially if important and not gradual.

Using, instead, the teachings of document AN2015A000041, such transient fluctuations are avoided because the command unit CMD knows in advance the possible effects of each change of the ON/OFF state requested to it through the control dashboard CC and may, simultaneously or slightly in advance on the ON/OFF state changes that it determines itself, intervene on the fan FAN by changing the speed thereof with the appropriate promptness and gradualness so that substantially the delivery pressure remains constant. By contrast, the predetermined speed imposed to the fan FAN may be inaccurate or not exactly reached for some reason.

A solution that substantially eliminates such drawback is therefore:

- first, bringing the fan FAN, through the command unit CMD, to the predetermined speed provided for the particular ON/OFF state;

- then, continuously controlling the delivery pressure of the fan FAN in order to keep it, as said above, to the preset value p.target.

It is seen, in general, that the mix valve 1 lends itself to numerous piloting methods: the control dashboard CC and/or the command unit CMD are very useful but not necessary the mix valve 1 being able to be piloted directly and manually according to many known means while the preset value p.target of the pressure can be ensured independently with the said means that comprise a pressure gauge and a speed regulator of the fan FAN.