Patent Description:
Here and below, the term "domestic cooktop" means any outer surface intended to house one or more atmospheric gas burners, whether it belongs to a so-called built-in cooktop, a range or any other domestic cooking appliance.

In the field of atmospheric gas burners for cooktops, the use of safety devices has long been known, in order to determine both the presence of flame, through thermocouples connected to special safety taps and the temperature reached by the burner, through temperature sensors also connected, for example, to the gas tap.

These temperature sensors, or probes, can be arranged at the flame spreader of the burner so as to detect the temperature at the cooking container placed on the gas burner, and normally have the purpose of preventing the temperature from excessively rising, for example when there are no liquids in the cooking container, and/or keeping the temperature of the aforesaid cooking container as constant as possible, basically acting as thermostats connected to the gas supply tap.

In particular, it is known to arrange a temperature probe inside a gas burner for cooktops, so that this probe can come into contact with, or otherwise be placed adjacent to, the bottom of a cooking container, such as a pot or pan or a WOK pan, hereby detecting the temperature of the cooking container and preventing situations of excessive dry heating of the same cooking container when the sensor is connected, for example, to a shutter on the gas supply control tap.

In high power burners, or in any case in gas burners for cooktops equipped with at least one annular flame spreader, and in which, as a result, there is a venturi mixer whose dimensions are not necessarily small, due to bulkiness, the axis along which the venturi mixer extends must be far from the axis along which the temperature probe lies and the former must not intersect the latter.

It should be noted that the term "annular" herein generally means that a burner's flame spreader, and the respective distribution chamber of the fuel mixture, is arranged according to a closed line that surrounds a volume of atmospheric air and only preferably has circular shape and therefore, in this case, the annular flame spreader is substantially toroidal but can also have elliptical or rectangular shape or any other shape suitable for manufacturing a flame spreader that potentially allows at least one flame ring facing the central axis of the same burner to be obtained.

It should also be noted that here and below the term "venturi mixer" means and will mean a mixer comprising a Venturi duct, namely equipped with a divergent portion in which the fluid can gradually expand, preceded at least by a narrow section which, in turn, may be preceded by a gradually converging portion, within which an injector delivers a flow of pressurized fuel gas, thereby causing primary air to be drawn upstream of the narrow section or the convergent portion, if any, and to be mixed with the fuel gas. This Venturi duct can be of the axial type (comparable in other words to a traditional longitudinally extending Venturi tube) having horizontal or vertical symmetry, or of radial type, as described for example in <CIT>.

<CIT> describes an atmospheric gas burner for cooktops of the type comprising an annular flame spreader, with the respective distribution chamber, and an axial venturi mixer having horizontal axis, and in which there is a temperature probe arranged along an axis parallel to the central symmetry axis of the burner, at the outer perimeter of the flame spreader. The off-center position of the temperature probe is not the most suitable for correctly detecting the temperature of a cooking container arranged on that burner, due to its off-center position with respect to the center of the burner itself.

In order to better detect the temperature of the cooking container placed on top of such a burner equipped with at least one annular spreader, it is known to arrange the temperature probe in a central position of the burner, usually along the central symmetry axis (vertical symmetry axis) of the burner itself.

In this case, the respective venturi mixer feeding at least the annular flame spreader has to be necessarily asymmetrically arranged with respect to the central burner's symmetry axis, so that its own longitudinally extending axis is far from the aforesaid burner's central symmetry axis and does not intersect the latter.

<CIT> patent describes a gas burner for cooktops, of the partially aerated type, which comprises an outer circular annular flame spreader with two flame rings and a central annular flame spreader with one flame ring, and which is equipped with a temperature probe arranged along the central (vertical) symmetry axis of the burner, within the volume surrounded by the central annular flame spreader. This burner further comprises two substantially horizontally extending venturi mixers of the axial type, whose symmetry axes are arranged at the sides of the aforementioned burner's vertical central symmetry axis, and lie on straight lines substantially orthogonal thereto. One of these venturi mixers feeds the distribution chamber of the outer annular flame spreader having two flame rings, while the other feeds the distribution chamber of the central flame spreader having one flame ring, the latter being concentric to the former.

<CIT> would appear to provide that when the fuel mixture is fed to the distribution chamber from the outlet section of the respective venturi mixer, i.e. from that section at the end of the divergent portion, that mixture flows directly into that distribution chamber of the flame spreader. Another example of a gas burner for cooktops, with two venturi gas mixers, can be found in the document <CIT>.

This usually causes the fuel mixture to be unevenly distributed in the annular flame spreader and results in a possible unevenness of the flames developing in the flame ring(s) of this annular flame spreader.

Therefore, object of the present invention is to provide a gas burner for domestic use, and in particular an atmospheric gas burner for a cooktop, which allows a temperature probe to be used without affecting the performance of the burner itself.

These and other objects are achieved by a gas burner for domestic use according to one or more of the appended claims.

In particular, object of the present invention is a gas burner according to claim <NUM>. Preferred aspects are stated in the dependent claims.

According to an aspect of the invention, a gas burner for cooktops, of the type comprising at least one outer annular flame spreader, having a respective annular distribution chamber of the mixture, at least one first fluidic inlet for the fuel gas, at least one first axial venturi mixer, configured to receive as an input said gas from said first fluidic inlet and primary air from a first atmospheric air inlet. The annular distribution chamber is fluidically connected to the first venturi mixer through a partition chamber of the fuel mixture that leaves the first venturi mixer. The partition chamber is fluidically connected to at least two fluidic passages, which connect the first venturi mixer to two regions of the annular distribution chamber of the outer annular flame spreader, the two regions being oppositely arranged with respect to the first venturi mixer. The burner further comprises at least one ignition device to light the mixture that leaves the flame spreader. In addition, considering a plan view of the burner in use condition, the outer flame spreader defines a geometric figure having a centroid, and an axis orthogonal to the plan view and passing through the mentioned centroid is outside the first venturi mixer.

The "off-center" positioning of the first venturi mixer allows elements, such as sensors and in particular temperature sensors, to be arranged at the center of to the burner without interfering with the first venturi mixer itself.

Moreover, thanks to the partition chamber and the fluidic passages, the distribution of the mixture to the distribution chamber (or chambers) takes place in a uniform way, even though the first mixer is arranged "off-center" with respect to the burner itself.

It should be noted that a duct that allows primary air to enter can be (at least partially) obtained in the burner, or can be obtained in the cooktop the burner is intended to be coupled to.

It is further known to provide not only burners configured so that the primary air is drawn from the environment above the cooktop, but also burners configured so that the primary air is drawn from the environment below the cooktop.

Embodiments of the present invention are provided for both solutions, i.e. both burners with primary air drawn from above the cooktop and burners with primary air drawn from below the cooktop.

A flame spreader has also been referred to as "outer" and "annular". The definition of "annular" has been previously discussed.

The term "outer" means that, if the burner has more than one flame spreader, the field technician clearly understands that the outer flame spreader is the larger one, which encloses the other flame spreaders. In case of a single flame spreader, this flame spreader acts as outer flame spreader.

According to an aspect of the invention, the fluidic passages, which are typically arranged downstream of the venturi mixer when considering the feed direction of the mixture under normal use condition of the burner, have an end opening to inject the mixture into the distribution chamber. The end openings are arranged substantially symmetrically with respect to a plane comprising the aforementioned orthogonal axis. Typically, not only the end openings, but also the end portions of the fluidic passages (i.e. portions of the fluidic passages equipped with such end openings) are symmetrical with respect to that plane.

Typically, in a plan view, the outer flame spreader has substantially circular perimeter.

The first venturi mixer is arranged so as to have substantially horizontal axis, where "substantially" means that the axis of the first venturi mixer is typically a tilted axis with respect to a horizontal plane by an angle of less than <NUM> degrees, typically less than <NUM> degrees, considering the use condition of the burner.

The orthogonal axis is therefore placed at the center of the circumference defined by the outer flame spreader.

The axis of the first venturi mixer (projected on the plan view of the burner in use condition) is therefore placed at a circumference chord, i.e. placed at a straight line that intersects the circumference without passing through the center thereof.

According to an aspect of the invention, the burner comprises at least two fluidic gas inlets. The aforementioned first fluidic inlet is fluidically connected to the aforementioned first axial venturi mixer, typically so as to feed the outer flame spreader. A second fluidic gas inlet is connected to a second venturi mixer, also typically axial, preferably to feed a second flame spreader. The second venturi mixer is arranged outside the orthogonal axis, so as to surround it.

According to a different possible aspect, the burner comprises an annular chamber arranged outside the orthogonal axis so as to surround it, and fluidically connected to the fluidic passages. In these embodiments, not covered by the claims, there can be a single venturi mixer (i.e. the first mentioned venturi mixer) to feed several flame spreaders.

In particular, according to another aspect of the invention, the burner comprises one or more inner or central flame spreaders equipped with at least one respective distribution chamber that can be fluidically connected to the distribution chamber of said outer flame spreader through ducts. Advantageously, said first venturi feeds the distribution chambers of said at least one outer flame spreader and said one or more inner flame spreaders.

Again, said ducts connecting said respective distribution chamber of said one or more inner flame spreaders to said distribution chamber of said outer flame spreader comprise said annular chamber, in which said annular chamber is fed by said fluidic passages and is fluidically connected to said fluidic passages, so that part of the mixture passing through said fluidic passages is directed to said annular chamber.

As described above, the first axial venturi mixer is arranged so that its axis is substantially horizontal.

In the embodiment with two venturi mixers, the second venturi mixer is preferably arranged so that at least one portion thereof is substantially vertically arranged in the condition of use (i.e. at an angle greater than <NUM>°).

According to an aspect, the burner comprises a housing arranged at the orthogonal axis for a temperature sensor or probe. Preferably, a temperature sensor is arranged in this housing. This embodiment can be used both in the case of burner with a single venturi mixer and with two venturi mixers.

According to a possible aspect, the housing is arranged so that there is at least one plane orthogonal to the orthogonal axis (i.e. a plane that is typically horizontal when the burner is in use condition) and able to intersect both the first venturi mixer with a substantially horizontal axis and the aforementioned housing.

According to a particular aspect of the invention, said housing is arranged substantially concentrically to said at least one portion of said second venturi mixer.

This configuration provides the advantage of reducing the number of components the burner is composed of, because the sensor inside the housing no longer needs to be protected by special shields having only this specific function, or that are made on the cover, but a wall of a portion of the second mixer is exploited to obtain also the housing for the temperature sensor. Preferably, said vertical portion is arranged so as to surround said orthogonal axis, so that said second venturi, which is adapted to allow the passage of the mixture, defines a space outside said orthogonal axis, thus surrounding the latter. In particular, said portion of said second venturi comprises at least one outer wall and one inner wall arranged inside said inner wall; said housing is defined by the inner wall of said portion of said second venturi.

On the other hand, in case of a single venturi mixer, said housing is defined by the inner wall of said annular chamber.

This configuration, as in the case of two distinct venturi mixers, provides the advantage of reducing the number of components the burner is composed of, because the sensor inside the housing no longer needs to be protected by special shields having only this specific function, or that are made on the cover, but a wall of a mixing chamber for a burner having a single venturi mixer is exploited to obtain also the housing for the temperature sensor.

In all cases, a temperature sensor is arranged in said housing.

Hereinafter, referring to the appended figures, exemplary and non-limiting embodiments of the present invention will be described, wherein:.

A gas burner <NUM> for domestic use comprises at least one first fluidic gas inlet 2a (hereafter also "first inlet 2a") feeding gas to a first axial venturi mixer 3a (hereafter also "first venturi 3a"), visible for example in <FIG>.

The burner <NUM> and/or the cooktop having the burner <NUM> installed thereto (not shown in detail) are configured to form an inlet 4a for primary air (hereafter also "first air inlet 4a"), so as to form a mixture inside the first venturi 3a. In the embodiments shown, the first air inlet 4a is made on the burner <NUM>.

In particular, there are possible embodiments in which primary air is drawn from above the cooktop, such as the embodiment shown in <FIG>, and embodiments in which primary air is drawn from below the cooktop, such as the embodiment shown in <FIG>.

The first venturi 3a preferably has a substantially horizontal axis AV, i.e. axis AV tilted with respect to a horizontal plane (considering the condition of normal use of the burner) by an angle of less than <NUM>°, typically less than <NUM>°.

The first venturi 3a communicates with one or more distribution chambers <NUM> adapted to distribute the gas-air mixture to an outer flame spreader 6a, the latter being configured in a way known in the art to allow the gas mixture, adapted to be burnt, to come out. A distribution chamber <NUM> is delimited by the flame spreader 6a, i.e. it is made in a space delimited on the top by the flame spreader 6a. One or more inner flame spreaders 6b can also be provided, in a known way. These inner flame spreaders 6b typically have a respective distribution chamber <NUM>', which can be fluidically connected to the distribution chamber <NUM> of the outer flame spreader 6a through ducts. The outer flame spreader 6a defines in plan view a geometric figure F, typically a circumference.

The geometric figure F is shown in detail in <FIG>. It should be noted that for ease of viewing, the plan view in <FIG> has been oriented and rotated so as to be comparable with the orientation of the elements shown in <FIG>, which instead represents a bottom view of the burner <NUM>.

The geometric figure F shows a centroid G, considering an orthogonal axis A (hereafter also "axis A") passing through the centroid G (i.e. orthogonal to the view of <FIG>), the axis A does not intersect the first venturi 3a, i.e. it is outside the first venturi 3a.

Simplifying, considering the plan view of the burner <NUM> in use condition or in any case a horizontal plane, the centroid G (representing the projection of the axis A on this view or horizontal plane) is outside the projection of the first venturi 3a on this view or horizontal plane, as schematically shown in <FIG>.

The first venturi 3a has at least two fluidic passages <NUM>, <NUM> to supply the gas-air mixture to the distribution chamber <NUM>. The fluidic passages <NUM>, <NUM> are oppositely arranged with respect to the first venturi <NUM>, i.e. the first venturi 3a is substantially interposed between the fluidic passages <NUM>, <NUM>.

Both the fluidic passages <NUM>, <NUM> have an end opening 71a, 72a which allows the mixture to enter the distribution chamber <NUM>.

The end openings 71a, 72a are preferably symmetrical to a plane P (schematically shown in <FIG>), which comprises the axis A.

The end openings 71a, 72a are arranged at the end of an end portion 71b, 72b of the respective fluidic passage <NUM>, <NUM>. Preferably the end portions 71b, 72b are also symmetrical with respect to the same plane P.

According to the invention, the first venturi 3a ends in a partition chamber <NUM>, which is connected to both the fluidic passages <NUM>, <NUM>. It should be noted that, for ease of production, in a first production step, the partition chamber <NUM> is made to be open to the external environment. Then, a covering element 70b is applied to the partition chamber <NUM> in order to allow the mixture to flow towards the fluidic passages <NUM>, <NUM>, thus preventing the mixture from being dispersed in the environment.

According to a possible aspect of the invention, the partition chamber <NUM> is configured to initially divert the flow in a substantially radial direction out of the first venturi 3a.

Typically, the partition chamber <NUM> is connected to an initial portion 71c of a first fluidic duct <NUM> (in turn connected directly, as shown in the figures, or indirectly to the respective end portion 71b of the respective duct <NUM>), and to the end portion 72b of a second fluidic duct <NUM> of the aforementioned fluidic ducts <NUM>, <NUM>.

According to a preferred aspect, as in the embodiments shown in the figures, the burner <NUM> comprises at least one second venturi mixer 3b (hereafter also "second venturi 3b"). The second venturi 3b is, in its turn, typically an axial venturi mixer.

The second venturi 3b typically has at least one portion 30b (usually at the end portion of the second venturi) substantially vertically arranged, considering the condition of use.

The vertical portion 30b is arranged so as to surround the axis A, so that the second venturi 3b, which is adapted to allow the passage of the mixture, defines a space outside the axis A, thus surrounding the latter.

Therefore, the second venturi 3b typically has at least one outer wall 31b and one inner wall 32b that is placed inside the outer wall. The section of the second venturi 3b is therefore typically ring- or frame-shaped.

Therefore, on the burner <NUM> there is a second gas inlet 2b to feed gas to the second venturi 3b. Similarly, the burner <NUM> is configured so as to allow primary air to enter the second venturi 3b, through an air inlet 4b made on the burner <NUM> and/or on the cooktop to which the burner <NUM> is intended to be coupled.

The second venturi 3b can be directly connected to a respective distribution chamber <NUM>', even if embodiments in which there are ducts between the second venturi and the respective distribution chamber <NUM>' are not excluded.

The position of the first and second venturi 3a, 3b, and in particular the first and second inlets 2a, 2b, can be selected depending on the needs.

For example, in possible embodiments as shown in <FIG> and <FIG>, the inlets 2a, 2b can be substantially orthogonal to each other.

In possible variations, for example in the embodiment shown in <FIG>, the inlets can be arranged close together, being for example arranged with an angle of less than <NUM> degrees from each other.

According to possible embodiments not covered by the claims, for example like the one shown in <FIG>, the first venturi 3a can feed both the distribution chambers <NUM>, <NUM>' of two different flame spreaders, therefore the second venturi 3b is absent.

In particular, a central annular chamber <NUM> ("annular" having the previously discussed meaning) arranged substantially vertically around the orthogonal axis A can be provided. This annular chamber <NUM> is therefore substantially identical to the vertical portion of the second venturi 3b described in the preceding embodiments. However, unlike the latter, this annular chamber <NUM> is not connected to its own gas inlet but is fed by fluidic passages <NUM>, <NUM> similar to those described in the previous embodiments. In particular, the annular chamber <NUM> is fluidically connected to both the fluidic passages <NUM>, <NUM>, so that part of the mixture passing through these passages is directed to the annular chamber <NUM>.

Typically, a first duct 73a connects the annular chamber <NUM> to the first fluidic passage <NUM>, and a second different duct 73b connects the annular chamber <NUM> to the second fluidic passage. Preferably, the ducts 73a, 73b are not directly connected to each other. In addition, according to a preferred aspect, the ducts 73a, 73b are symmetrical with respect to the same symmetry plane P of the end openings 71a, 72a of the fluidic passages <NUM>, <NUM>.

The mixture leaving the first venturi 3a is then deflected by the partition chamber <NUM>, and then enters the fluidic passages <NUM>, <NUM>. From here part of the mixture is delivered to the outer flame spreader 6a, while part of the mixture is fed to the annular chamber <NUM> and then from here goes on to a flame spreader 6b (not shown in <FIG>, but for example similar to the flame spreader 6b shown in <FIG>).

The burner <NUM> according to the invention, both the burner with two venturi ducts 3a and 3b of the first embodiment and the burner with only one venturi duct 3a of the second embodiment, is further equipped with a housing <NUM> for a temperature sensor or probe <NUM>.

This housing <NUM> is arranged at the axis A, i.e. the axis A passes through the housing <NUM>.

According to a preferred aspect, the housing <NUM> is obtained concentrically to the second venturi 3b, or in any case so as to be surrounded by it. In particular, according to a possible aspect, the housing <NUM> is defined by the inner wall 32b of the portion 30b of the second venturi 3b, or by the annular chamber <NUM> in embodiments equipped with a single venturi, such as that of <FIG>.

The housing <NUM> is arranged substantially parallel, preferably co-axial, with the A-axis.

Preferably, part of the housing <NUM> flanks the first venturi 3a. In other words, the housing <NUM> is quite deep, so that part of the housing <NUM> is arranged laterally to the first venturi 3a. There is therefore at least one plane orthogonal to the axis A, intersecting both the housing <NUM> and the first venturi 3a.

In a known way, the burner <NUM> also has an ignition device <NUM> comprising for example an ignition spark plug and a thermocouple, which is adapted to allow the burner <NUM> to be lighted, i.e. to form a flame at the outer flame spreader 6a.

The use of the burner <NUM> is clear to the field technician from the above description. Briefly, primary air (shown in small dashes in <FIG>) and gas (shown in large dashes in <FIG>) enter the first venturi 3a, so as to form a mixture (shown in a dash-dot line). After that, the mixture is directed to the one or more fluidic passages <NUM>, <NUM> (e.g. through the partition chamber <NUM>), in order to reach the distribution chamber <NUM>. From here, the mixture flows out of the outer flame spreader 6a and is lighted by the ignition device <NUM>.

In this embodiment, in the case of an inner flame spreader 6b, the mixture reaches the annular chamber <NUM> through the ducts 73a, 73b, which are directly connected to the fluidic passages <NUM> and <NUM>. Next, the second distribution chamber <NUM>' supplies the mixture to the inner flame spreader 6b.

Claim 1:
Gas burner (<NUM>) for cooktops, of the type comprising at least one outer annular flame spreader (6a), having a respective annular distribution chamber (<NUM>) of the mixture, at least one first fluidic inlet (2a) for the fuel gas, at least one first axial venturi mixer (<NUM> a), configured to receive as an input said gas from said first fluidic inlet (2a) and primary air from a first atmospheric air inlet (4a), said at least one annular distribution chamber (<NUM>) being fluidically connected to said first venturi mixer (3a) through a partition chamber (<NUM>) of the fuel mixture leaving said first venturi mixer (3a), said partition chamber (<NUM>) being fluidically connected to at least two fluidic passages (<NUM>, <NUM>) connecting said first venturi mixer (3a) to two regions of said annular distribution chamber (<NUM>) of the outer annular flame spreader (6a) which are oppositely arranged with respect to said first venturi mixer (3a), and at least one ignition device (<NUM>) to light said mixture that leaves said outer flame spreader (6a), and wherein, considering a plan view of the burner (<NUM>) in use condition, said outer annular flame spreader (6a) defines a geometric figure (F) having a centroid (G), and wherein an axis (A) orthogonal to said plan view and passing through said centroid (G) is outside the first venturi mixer (3a), said gas burner being characterized in that it comprises at least one second fluidic gas inlet (2b), said first fluidic inlet (2a) being fluidically connected to said first venturi mixer (3a), and the second fluidic gas inlet (2b) being connected to a second venturi mixer (3b), said second venturi mixer (3b) being arranged outside said axis (A), so as to surround it.