Atmospheric gas burner with at least one mixing tube integrated into the burner head

Abstract

Partially-aerated gas burner (1; 100) comprising a. burner base (20; 120) having at least one header (22; 122) for a fuel gas fluidically connected to at least one injection nozzle (26, 126), a burner head (10; 110) equipped with at least one distribution chamber (12; 112), at least one flame spreader (30; 130) shaped to be juxtaposed to said at least one distribution chamber (12; 112), as well as at least one Venturi-type mixing tube (15a, 15b; 115), which extends substantially horizontally and sequentially has an inlet section (151), a throat section (15G) and an expansion section (ISE), said inlet section (151) facing the at least one injection nozzle (26; 126), said burner base (20; 120), said burner head (10; 110) and said at least one flame spreader (30; 130) being overlapped on each other to form the burner (1; 100). Advantageously, said at least one Venturi -type mixing tube (15a, 15b; 115) is defined by an open tubular structure (13a, 13b; 113) and at least one partially closing plate (14a, 14b; 114), preferably substantially flat, to partially close this at least one open tubular structure (13a, 13b; 113), and this open tubular structure (13a, 13b; 113) forms a recess of the aforesaid at least one distribution chamber (12; 112), said at least one closing plate (14a, 14b; 114) partially closing said recess.

Description

[0001] ATMOSPHERIC GAS BURNER WITH AT LEAST ONE MIXING TUBE INTEGRATED INTO THE BURNER HEAD

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a partially-aerated gas burner, i.e. a gas burner also known as “atmospheric” burner, in which, in a special mixing tube of the burner, a jet of fuel gas is mixed with an amount of air (known as primary air) which is not enough to generate gas combustion, and this mixture of gas and primary air is then supplied with additional atmospheric air (known as secondary air) at the outflow holes of the burner, so that its combustion can be ignited and one or more flames produced.

[0004] Accordingly, this type of burner usually comprises a mixing tube, for example a Venturi tube, fed by an injection nozzle of a fuel gas, which produces the aforesaid mixture of gas and primary air, which reaches, for example by means of conduits, a flame spreader, i.e., an element equipped with a plurality of outflow holes from which this mixture flows out. Thanks to the supply of secondary air, this mixture of fuel gas and primary air can be burned and thus generate one or more flames, thanks to an ignition source, such as a spark plug or a pilot flame.

[0005] This type of gas burner is widely used in domestic environment as heat source for cooking food or, in any case, heating edible products, for example in cooktops or stoves. KNOWN PRIOR ART

[0006] It is well known to make this type of atmospheric burners in a modular, preferably reversible, manner, in which a burner base, and respective means for fastening to a cooking surface, a burner head, a flame spreader and a top cover are overlapped on each other.

[0007] Usually, the burner base, which sometimes takes the form of a cup, comprises at least one header to supply fuel gas (e.g., methane or LPG) fluidically connected to the distribution network or other fuel gas source, and at least one respective injection nozzle in turn fluidically connected to the aforesaid header. The burner head may comprise a Venturi-effect mixing tube facing the aforesaid injection nozzle to receive the jet of fuel gas, and at least one distribution chamber, for example in the form of an annular channel or cylindrical chamber, which, both connected fluidically to the mixing tube, are furthercoupled to the flame spreader and the respective top cover.

[0008] Venturi -effect mixing tubes, also referred to herein as " Venturi-type mixing tubes," comprise an inlet section which is normally convergent, a throat section with a reduced area, where the pressure is reduced and the velocity of the fluid flowing through this tube increases, and an expansion section in which the pressure is recovered and the fluid velocity decreases.

[0009] In the field of partially-aerated burners, Venturi -effect mixing tubes, known as "radial Venturis", in which the expansion section consists of a cylindrical chamber with a circular base and the fluid expands radially from the throat section, which in this case opens onto the lower base of the cylindrical chamber, are well known.

[0010] For example, the gas burner described in WO 2004 / 044490 Al owned by the Applicant comprises a burner head with a peripheral annular channel and a central chamber for distributing the gas-primary air mixture, in which the annular channel is fluidically connected to two mixing tubes that are an integral part of the burner head. The mixing tubes used are of the radial Venturi -effect type, in which the inlet section and the throat section of this Venturi-effect mixing tube extend along the same vertical axis, while the respective expansion section extends radially, in a horizontal direction.

[0011] Since these radial Venturi tubes extend partially vertically, the burner has a certain height.

[0012] Venturi mixing tubes, known as "axial Venturis", are also known, in which the expansion section is of truncated-cone type and extends along the same axis as the inlet section and the throat section. These axial Venturi tubes can be arranged with a substantially horizontal axis in order to reduce the height of the burner.

[0013] A variation of these axial Venturi mixing tubes provides that the Venturi mixing tube extends substantially on a plane, for example horizontal, and that this Venturi mixing tube comprises an expansion section that is not necessarily coaxial with the inlet and throat sections, although it necessarily provides a gradual widening of the fluid passage section.

[0014] For example, the burner described in Chinese utility model CN 210485711 U comprises a burner head equipped with an annular channel that is fed by two substantially axial Venturi-type mixing tubes, in which the respective expansion sections, which have apartially curved plan shape, open up in part to form two diametrically opposed recesses in the annular channel. The burner base is equipped with two injection nozzles which are fluidically connected to fuel gas supply headers and are capable of injecting fuel gas into the inlet sections of the two Venturi mixing tubes, respectively.

[0015] The geometry of this burner of CN 210485711 U provides that part of each Venturi-type mixing tube, in particular the respective inlet and throat sections, are made below the annular channel and are presumably attached to the burner head mechanically or by welding, while only the expansion section of each mixing tube opens partly into the annular channel of the burner head.

[0016] Although this type of burner is compact and space-saving, it is complex and costly to make due to the number of operations that must be performed and the precision of the machining that must be carried out, thus resulting economically disadvantageous.

[0017] Object of the present invention is to address the critical issues highlighted above by providing a compact, low-height, partially-aerated gas burner that is also simple to manufacture.

[0018] A further object of the present invention is to provide a gas burner that is economical and, at the same time, particularly efficient.

[0019] SUMMARY OF THE INVENTION

[0020] The present invention achieves these and other objects by means of the partially-aerated gas burner according to the first independent claim and the further dependent claims. The partially-aerated gas burner of the present invention comprises a burner base having at least one fuel gas header fluidically connected to at least one injection nozzle, a burner head equipped with at least one distribution chamber, preferably but not necessarily in the form of an annular channel, and at least one flame spreader shaped to be juxtaposed to this at least one distribution chamber, as well as at least one Venturi-type mixing tube (i.e., at least one Venturi-effect mixing tube) which extends substantially horizontally and sequentially has an inlet section, a throat section and an expansion section, wherein the inlet section faces the aforesaid at least one injection nozzle, and wherein the burner base, the burner head and the respective flame spreader are overlapped on each other to form the burner. Advantageously, the aforesaid at least one Venturi-type mixing tube is defined by an open tubular structure and at least onepreferably flat plate, or even variously shaped, partially closing this open tubular structure. Furthermore, this open tubular structure of the mixing tube is shaped to define a recess of the aforesaid at least one distribution chamber, and the respective plate is shaped to partially close this recess.

[0021] Preferably, this partially closing plate, which is shaped to partially close the respective open tubular structure of the aforesaid at least one mixing tube, leave at least one end region of the expansion section of the at least one mixing tube in fluidic communication with that, at least one distribution chamber of the burner head.

[0022] In practice, according to the invention, the at least one Venturi-type mixing tube comprises an upwardly open tubular structure that forms a discontinuity, and in particular a recess, in said distribution chamber with which the burner head is equipped, so that this burner head can preferably be integrally made without any undercuts and without the need to attach external components to this burner head.

[0023] By simply mounting the respective upper plate onto the recess that forms the open tubular structure of the Venturi-type mixing tube, while leaving at least one end region uncovered, i.e. a region distant from the respective throat section of the at least one mixing tube, the latter is completed, thus making this burner easy and economical to be made.

[0024] The possible use of mechanical constraining means for the aforesaid at least one partially closing plate of the at least one open tubular structure of the mixing tube makes it easy to assemble this at least one plate.

[0025] Furthermore, since the plate that partially closes the open tubular structure of the mixing tube is mounted inside the distribution chamber, any fluid leaks between the plate and the walls of the open tubular structure occur inside the distribution chamber itself, and therefore do not pose a potential hazard of unbumed gas mixture emissions outside the burner, as they are burned at the outlet of the flame spreader.

[0026] It should be noted that the term "distribution chamber" refers to any open structure in which, during burner use, the combustible mixture of gas-primary air flows in, flows through and flows out. As is well known, this distribution chamber can be cylindrical with a circular base, for example, or it can be shaped like an annular channel or have a toroidal shape, or other shapes.Furthermore, the term "plate" refers to any body with two dimensions that are larger than the third dimension. In the burner depicted herein, the shape of this plate may preferably be flat or alternatively it may be convex, semi-cylindrical, semi-conical or the like.

[0027] Finally, the expression "substantially horizontal", referred to the direction along which the Venturi-type mixing tube extends, means that, during use, this mixing tube, which is of substantially axial type, extends along a direction that may be horizontal or slightly inclined with respect to the horizontal.

[0028] According to a preferred aspect, the closing plate is substantially flat-shaped, so that it can be easily made, for example by blanking a metal sheet, and mounted at the respective open tubular structure of the Venturi-type mixing tube.

[0029] According to another preferred aspect of the present invention, the aforesaid at least one burner head's distribution chamber, for example in the form of an annular channel or in the form of a cylindrical chamber, comprises a bottom surface delimited by at least one side wall-— for example, in the case of an annular channel, this bottom surface is delimited by two facing side walls preferably circular in shape — which projects substantially orthogonally from the bottom surface in the opposite direction to that in which the recess or recesses formed by the open tubular structure of the mixing tube or Venturi-type mixing tubes extend. Advantageously, the open tubular structure of the aforesaid at least one mixing tube forms a recess in the bottom surface of the di strib uti on chamb er.

[0030] With this type of configuration, the geometry of the burner head is simplified, making it even easier to be made.

[0031] Furthermore, if the bottom surface of the distribution chamber lies substantially on a plane, or in any case the open tubular structure of the mixing tube opens onto a flat portion of the bottom surface, the at least one partially closing plate of the aforesaid at least one Venturi-type mixing tube is shaped to be arranged on that bottom surface or on that flat portion of the bottom surface of the distribution chamber, thus preferably restoring the continuity thereof, except for the opening that causes an end region of the expansion section of the at least one Venturi-type mixing tube to be in fluidic communication with the same distribution chamber of the burner head. Thisconfiguration is easy to implement and is also highly effective in terms of fluid dynamics.

[0032] If the closing plate is essentially flat, it will be of such dimensions as not to occlude the end region of the expansion section of the open tubular structure of the relative Venturi-type mixing tube, considering that in any case the closing plate must ensure the passage of fluid, i.e., the fuel gas - primary air mixture, from the expansion section of the Venturi-type mixing tube to the respective distribution chamber.

[0033] Furthermore, according to a preferred aspect of the present invention, the partially- aerated burner comprises two Venturi-type mixing tubes extending substantially horizontally, wherein each of the two mixing tubes sequentially comprises an inlet section facing a respective injection nozzle, a throat section and an expansion section, and wherein each of the two mixing tubes is defined by an open tubular structure and at least one respective partially closing upper plate to partially close the open tubular structure, and wherein the open tubular structure of each mixing tube forms, in the at least one burner-head's distribution chamber, for example in form of annular channel, a respective recess which is partially covered by the respective plate.

[0034] According to a further aspect of the present invention, a method for making a partially- aerated gas burner of the type set forth above is provided, the method comprising the following steps:

[0035] integrally making, without undercuts, by molding or forging, for example by die casting, the aforesaid burner head having, integral therewith, the aforesaid open tubular structure of at least one Venturi-type mixing tube projecting with a recess from the at least one distribution chamber, for example in the shape of an annular channel, of said burner head;

[0036] making said at least one upper closing, preferably flat, or alternatively curved or otherwise shaped, plate to partially close the open tubular structure;

[0037] constraining this at least one upper partially closing plate to the burner head at or near the open tubular structure of the aforesaid at least one mixing tube to partially close the respective open tubular structure.

[0038] BRIEF DESCRIPTION OF THE FIGURES

[0039] These and other characteristics of the present invention will be apparent by the detaileddescription of a related preferred embodiment provided herein by way of example and without limitations, with reference to the accompanying figures, in which:

[0040] Figure 1 is an axonometric view of a partially-aerated gas burner according to a first embodiment of the present invention;

[0041] Figure 2 is an exploded view of the burner of Figure I,

[0042] Figure 3 is a bottom view of the burner head of Figure 1;

[0043] Figure 4 is a top view of the burner head of Figure 1;

[0044] Figure 5 is a cross-section, transverse to the vertical axis of the burner head of Figure 1, taken on a plane below that of the bottom of the respective distribution chamber, which is in the form of an annular channel in this case;

[0045] Figure 6 is an axial sectional view of the burner, passing through part of a Venturi-type mixing tube;

[0046] Figure 7 is an exploded bottom view of a second embodiment of a gas burner according to the present invention,

[0047] Figure 8 is an axonometric top view of the burner head of Figure 7;

[0048] Figure 9 is a longitudinal - sectional bottom view of a burner head according to an aspect of the present invention, and

[0049] Figure 10 is an enlarged and partial view of the section A-A of Figure 9. DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

[0050] With reference first to the burner in Figures 1 to 6, and now with particular reference to Figures 1 and 2, the partially-aerated gas burner 1, according to an aspect of the present invention, comprises a burner base 20, a burner head 10 and a flame spreader 30, as well as, preferably but not necessarily, a spark plug 40 and a safety thermocouple 50, which can be combined with each other to form the complete burner 1. In particular, the flame spreader 30 can be overlapped on the burner head 10, which in turn can be overlapped on the burner base 20.

[0051] The burner base 20 comprises a shaped body 23 which comprises a header 22 for the fuel gas at the bottom and has housing seats for two turrets 25a, 25b which carry two respective injection nozzles 26a, 26b for the fuel gas. The injection nozzles 26a, 26b are fluidically connected to the header 22, which can be connected, in turn, via a known connection, to a fuel gas distribution duct coming from a respective distribution networkor to another source of fuel gas (for example, a pressurized cylinder).

[0052] This does not exclude embodiments in which the shaped body 23 may have housing seats for a single turret with a single respective injection nozzle for fuel gas, or may have seats for three or more turrets with their respective injection nozzles.

[0053] In this particular embodiment, the shaped body 23 of the burner base 20 also comprises housing seats to house the spark plug 40 and the safety thermocouple 50.

[0054] As is well known, the spark plug 40 is able to ignite combustion by emitting electric sparks and the thermocouple 50 provides an electrical signal only in the presence of a flame, thus allowing a safety valve to be activated, the safety valve interrupting the inflow of gas into the burner in the absence of an electrical signal from thermocouple 50.

[0055] The burner base 20 comprises, or is also combined with, an attachment surface 21 possibly consisting of a portion of a cooktop or an attachment plate or disc, and a mounting gasket 24 interposed between the attachment surface 21 and the shaped body 23, the attachment surface and the mounting gasket being also equipped with housing seats for the turrets 25a, 25b, the spark plug 40 and the safety thermocouple 50.

[0056] The attachment surface 21 may comprise means for fastening to a cooktop or may itself form part of the cooktop.

[0057] The burner head 10 is constrained, preferably in reversible manner, onto the burner base 20, the former having, inside it, a distribution chamber for the combustible mixture in this case consisting of an annular channel 12 and, outside it, a protective skirt 11, which is tapered upwards in this case.

[0058] This protective skirt 11 has the function of preventing or reducing the access of foreign material to the burner base 20 and, being configured to be spaced at a distance d from the attachment surface 21, also has the function of defining a passage for the primary air directed towards the injection nozzles 26a, 26b.

[0059] The annular channel 12 of the burner head 10 is open at the top and, in this preferred embodiment of the invention (see Figure 4), consists of a bottom surface 12a that lies predominantly on a single plane and is interposed between two circular side walls 12b, 12c, which project upward, substantially orthogonally, from the sides of the same bottom surface 12a.In alternative embodiments not shown herein, the burner base 20 may comprise more than one preferably concentric annular channel 12, and / or may additionally comprise a distribution chamber with a circular cross-section, preferably located centrally with respect to the annular channel 12.

[0060] The burner base 20 can further comprise a single distribution chamber having cylindrical shape with a circular base or any other shape, without thus departing from the protection scope of this patent. The burner 100 depicted with reference to Figures 7 and 8 is, as will be seen, a burner in which the respective distribution chamber is substantially cylindrical with a circular base.

[0061] A flame spreader 30, also annular in shape, is constrained on the burner head 10, preferably in a reversible manner, and overlaps the annular channel 12 of the burner head 10 itself at the top, thus completing the side walls of this annular channel 12 and, in this case, also closing them at the top.

[0062] In practice, the flame spreader 30 is shaped so as to be juxtaposed to the annular channel 12 of the burner head 10.

[0063] In the embodiment shown herein, the flame spreader 30 has a substantially circular cylindrical ring shape and is closed at the top by a top surface 31 that forms a top cover, in this case integrated into the flame spreader 30.

[0064] It should be specified that there are possible embodiments in which a top cover, or a set of elements constituting a top cover, can be separated from the flame spreader 30 and can therefore be overlapped and constrained, preferably reversibly, to the latter.

[0065] Furthermore, the flame spreader 30 can alternatively be made integrally with the burner head 10 and, in this case, have one or more removable top covers.

[0066] , As will be described below, the burner 100 of the embodiment illustrated with reference to Figures 7 and 8 provides that the respective flame spreader is made integrally with the burner head and a top cover is removably constrained above the fl me spreader. The flame spreader 30 has two substantially concentric rings of flame holes on its sides, an external one 32 and an internal one 33, which allow the combustible mixture of gas - primary air to flow outwards.

[0067] The presence of atmospheric air (secondary air) and the ignition provided, for example, by a spark fired by the spark plug 40 generate flames at the holes in the flame rings 32,33 of the flame spreader 30.

[0068] In alternative embodiments not shown herein, the presence of a single ring of flame holes is not excluded, nor is the presence of holes for generating flames also at the top surface 31 (cover) of the same fl me spreader 30.

[0069] It should be noted that the annular channel 12 of the burner head 10 and the flame spreader 30 with its top surface (cover) 31 define an annular volume for distributing the combustible mixture of gas - primary air to the external environment.

[0070] Now, referring also to the remaining accompanying figures, turning back to the burner head 10, the latter also includes two Venturi -effect mixing tubes integrated therein, namely two Venturi-type mixing tubes 15a, 15b arranged on the lower part of the burner head 10, substantially below the plane on which the bottom surface 12a of the respective annular channel 12 mainly lies.

[0071] The two Venturi-type mixing tubes 15a and 15b substantially extend horizontally, i.e., their main axes lie on a horizontal plane.

[0072] In other embodiments not shown herein, these Venturi-type mixing tubes may extend along an axis that is inclined, although only slightly, with respect to the horizontal. As shown schematically in Figure 5, each Venturi tube comprises, in a sequence that follows the fluid flow; an inlet section 151, which is preferably convergent and located downstream of the respective injection nozzle 26a or 26b, a throat section 15G, which has a fluid passage section that is narrower than the inlet section and results in decreased pressure and increased velocity, and a divergent expansion section 15E, with pressure recovery and decrease in fluid velocity.

[0073] As can be seen in particular in Figure 5, according to a preferred aspect of the present invention, the expansion section 15E of each Venturi-type mixing tube 15a, 15b is at least partially curved and follows at least in part the curve of the annular channel 12 of the burner head 10.

[0074] However, for reasons of effectiveness of the Venturi-type mixing tube, at least the inlet section 151 and the throat section 15G, and preferably at least the first portion of the expansion section 15E, extend axially, i.e., along a substantially straight line.

[0075] The inlet sections 151 of each mixing tube 15a, 15b face the respective injection nozzles 26a, 26b so as to receive, together with the respective throat sections 15G andexpansion sections 15E, a flow of fuel gas which, thanks to the entrainment effect of the gas jet and the vacuum effect produced by the Venturi effect, mixes with the primary air which flows between the protective skirt 11 of the burner head 10 and the attachment surface 21 of the burner base 20, thus forming an optimal fuel gas - primary air mixture. It should be noted that, in alternative embodiments, not explained herein, the burner head 10 may comprise a single Venturi-type mixing tube, preferably of the type described above but in any case substantially horizontal and equipped with an inlet section, a throat section and an expansion section. A similar embodiment, as will be seen, is illustrated in Figures 7 and 8 attached hereto.

[0076] According to an aspect of the present invention, each Venturi-type mixing tube 15a, 15b consists of an open tubular structure 13a, 13b that is partially closed at the top by a corresponding partially closing plate 14a, 14b, preferably flat.

[0077] Making the partially closing plates 14a, 14b substantially flat allows the burner to be made more easily, since these flat plates 14a, 14b can be simply made, for example by blanking a metal sheet or even by molding in a mold that is geometrically simple and thus easy to make, and also because this flat shape facilitates the assembly of these plates 14a, 14b at the respective open tubular structure 13a, 13b.

[0078] However, it cannot be excluded that the plates 14a, 14b, or at least one plate, may have a complex shape, for example with sections of different curvature and / or extent. In any case, the thickness of these plates is preferably smaller than the other two dimensions, so that they can be manufactured, preferably, by blanking a metal sheet and / or by molding.

[0079] Each open tubular structure 13a, 13b of the Venturi-type mixing tubes 15a, 15b is made, without interruption, as a recess of the annular channel 12, projecting downwardly from the latter.

[0080] Each open tubular structure 13a, 13b comprises, in sequence, an inlet section, a throat section and an expansion section of the respective Venturi-type mixing tube 15a, 15b, which are, however, open at the top.

[0081] These open tubular structures 13a, 13b can be made integrally with the burner head 10 since they do not create any undercut with respect to the annular channel 12, i.e., they do not have any acute-angle recess with respect to the extent of the annular channel 12,.This involves significantly simplified molding or forging and finishing operations for the burner head 10.

[0082] The respective partially closing plates 14a, 14b are shaped so that, once juxtaposed and secured to the burner head 10 at the relative open tubular structures 13a, 13b, they partially close the upper part of those recesses of the annular channel 12, i.e. partially close each of the open tubular structures 13a, 13b, so as to form the respective Venturi-type mixing tubes 15a, 15 b.

[0083] In particular, each of the partially closing plates 14a, 14b is shaped to partially cover the respective open tubular structure 13 a, 13b of the respective Venturi-type mixing tube 15a, 15b, leaving at least one end region of the expansion section 15E of the relative Venturi-type mixing tube 15a, 15b in fluid communication with the same annular channel 12 of the burner head 10.

[0084] This way, the gas - primary air mixture flows through the mixing tube 15a, 15b into the annular channel 12 and from there to the outside environment through the flame hole rings 32 and 33 of the flame spreader 30.

[0085] In the embodiment of the burner head 10 shown herein, in which the annular channel 12 comprises a bottom surface 12a that extends predominantly on a plane and is delimited by two upwardly projecting walls 12b, 12c, each open tubular structure 13a, 13b of each Venturi-type mixing tube 15a, 15b forms a recess in this bottom surface 12a of the annular channel 12 and each partially closing plate 14a, 14b is shaped to be arranged substantially on that plane along which the bottom surface 12a of the annular channel 12 extends.

[0086] In alternative embodiments, the bottom surface of the distribution chamber may comprise a flat portion in which at least one recess opens up, the latter consisting of the open tubular structure of a Venturi-type mixing tube.

[0087] Furthermore, it should be noted that this bottom surface of the distribution chamber can generally only be "substantially flat", that is to say that it can be flat or have a predefined curve.

[0088] As mentioned, the constraint of the partially closing plates 14a, 14b can be of mechanical type and, especially in the case of bottom surface 12a of the distribution chamber, in this case in the form of annular channel 12, that constraint of a plate 14a,14b can restore part of the bottom surface 12a that has the aforesaid recess consisting of the open tubular structure 13a, 13b of a Venturi-type mixing tube 15a, 15b.

[0089] For example, each substantially flat partially closing plate 14a, 14b can rest on lowered bosses located near or at the respective open tubular structure 13a, 13b of each Venturi-type mixing tube 15a, 15b, so as to be arranged on the same level as the plane along which the annular channel 12 mainly extends, i.e., in areas other than the recesses which are determined by the open tubular structures 13a, 13b.

[0090] The constraint between each upper partially closing plate 14a, 14b and the burner head 10 at the recesses defined by the open tubular structures 13a, 13b of the mixing tubes 15a, 15b is preferably made by mechanical constraining means, such as interlocking means to interlock complementary parts.

[0091] These constraining means may also be of the type involving interference between elastically deformable complementary' parts, or of the screwing-type or of another type known to those skilled in the art.

[0092] In the embodiment shown herein (see Figure 4), there are two holes 16a on each plate 14a, 14b that are interlockingly coupled to two corresponding pins or pegs 16b located near the respective open tubular structure 13a, 13b. Preferably, the holes 16a and the respective pins or pegs 16b are oriented in such a way as to allow' interlocking only if each plate 14a, 14b is properly oriented with respect to the respective open tubular structure 13a, 13b, and therefore with respect to the annular channel 12.

[0093] In general, the shape of the plates 14a, 14b and / or the shape of the respective means constraining to the annular channel 12 may be such as to allow a uniquely determined coupling in terms of relative orientation of each plate 14a, 14b with respect to the annular channel 12.

[0094] It should be noted that the coupling between each plate 14a, 14b and the respective open tubular structure 13a, 13b of each mixing tube 15a, 15b does not necessarily have to be fluid-tight, since any leaks, consisting mainly of an incomplete mixture of gas and primary air, remain confined within the annular channel 12 and the flame spreader 30 and are in any case burned at the outlet of the holes of the flame spreader 30 itself.

[0095] Indeed, the constraint between each plate 14a, 14b and the open tubular structure 13a,

[0096]

[0097] chamber, in this case in the form of an annular channel 12, so that any leaks of fuel gas or the combustible mixture of gas - primary air, even if only partially formed, do not flow directly to the outside of the burner but remain confined within the same annular channel 12.

[0098] This increases the safety of use of the burner 1 according to the present invention and makes it unnecessary to achieve a tight fluidic seal of every plate 14a, 14b on the open tubular structure 13a, 13b of the respective Venturi-type mixing tube 15a, 15b, thereby making the production of the burner 1 simpler and less expensive.

[0099] With reference now to the gas burner 100 of partially-aerated, i.e. atmospheric, type shown in Figures 7 and 8, similarly to the burner 1 in Figures 1 to 6, this burner 100 comprises a burner base 120 having a burner head 110 constrained thereon, which is enclosed at the top by a top cover 131.

[0100] According to an aspect of the present invention, the base 120, the head 110 and the top cover 131 of the burner 100 can be overlapped on top of each other and reversibly constrained to each other, i.e., in such a way that the burner 100 itself can be easily assembled and disassembled.

[0101] The base 120 of the gas burner 100, similarly to the gas burner 1, comprises a shaped body 123 that supports, at the bottom, a header 122 for the fuel gas coming from a public gas distribution network or from any source of fuel gas (for example a pressurized cylinder).

[0102] In this embodiment, this base 120 of the gas burner 100 comprises a housing seat for a spark plug 140, which is known per se. Although not visible, this burner base 120 may also comprise a housing seat for a safety thermocouple, which is also known per se. The base 120 also supports, on top, a turret 125 for a fuel gas injection nozzle 126. The turret 125 causes the header 122 to be in fluidic communication with the injection nozzle 126.

[0103] The burner head 110 comprises a distribution chamber 112 for the combustible mixture of gas - primary air w'hich essentially consists of a cylindrical body with a circular base and has a flame spreader 130 integrated around its perimeter.

[0104] The flame spreader 130 of this embodiment, which has an annular structure and a ring of variously shaped combustible mixture outflow holes, actually defines at least part ofthe side wall of the distribution chamber 112.

[0105] The distribution chamber 112 is completed by the top cover 131 constrained above the flame spreader 130.

[0106] It should be noted that in this embodiment, the top cover is overlapped on the flame spreader 130 and, when resting thereon, it is constrained thereto, thanks also to centering bosses 134a, 134b, 134c that project from the bottom wall of the distribution chamber 112 (see Figure 8).

[0107] The burner head 110 depicted herein further comprises a single Venturi-type mixing tube 115 which, similarly to each of the mixing tubes 15a, 15b described in relation to the gas burner 1 in Figures 1 to 6, is of the substantially horizontal type, i.e., it has a main axis which is horizontal or slightly inclined with respect to the horizontal, during use of the burner.

[0108] Also in this Venturi-type mixing tube 115, as in each of the mixing tubes 15a, 15b of the burner 1 described above, it is possible to identify, following its axial extent, an inlet section facing the injection nozzle 126 when the burner 100 is assembled, a throat section and an expansion section that has at least one end section in fluid communication with the distribution chamber 112.

[0109] The mixing tube 115, according to the principle already illustrated above for the mixing tubes 15a, 15b of the burner 1, allows the primary air coming from a volume specially created between the base 120 and the head 110 of the burner 100, to be mixed with the fuel gas injected by the injection nozzle 126.

[0110] Similarly to each Venturi-type mixing tube 15a, 15b of the embodiment shown in Figures 1 to 6, the mixing tube 115 comprises an open tubular structure 113 which, in this embodiment, is made uninterruptedly in the distribution chamber 112, in the form of a recess in a wail of the distribution chamber 112 itself. Preferably, this open tubular structure 113 of the mixing tube 115 is made in the bottom surface of the distribution chamber 112, so as to protrude downwardly from the latter, thereby effectively forming a lower recess of the distribution chamber 112 itself.

[0111] In this burner 100, too, this open tubular structure 113 can be made integrally with the head 110 of the gas burner 100, since the open tubular structure 113 does not create any- undercut with respect to the wall of the distribution chamber 112 from which itprotrudes, i.e., it does not have any acute-angle recess with respect to the extent of the distribution chamber 112.

[0112] The mixing tube 115, as already happened for each of the mixing tubes 15a, 15b described above, is completed by a partially closing plate 114 which is shaped to partially overlap the open tubular structure 113, so as to close this open tubular structure 113 at the top, except for an end region of the latter.

[0113] In this embodiment, this partially closing plate 114 is shaped so as to have curved bulges that are at least in part substantially symmetrical to those of the open tubular structure 113 and is configured so as to allow, when constrained to the open tubular structure 113, fluidic communication between the distribution chamber 112 and an end region of the outflow section furthest from the throat section of the mixing tube 115. In particular, the partially closing plate 114 comprises, at its region intended to be juxtaposed to the end region of the expansion section of the Venturi-type mixing tube 115, at least one slit 141 from which, in use, the combustible mixture formed in the same expansion section of the mixing tube 115 flow's out.

[0114] Thanks to the partially closing plate 114, which only partially closes the open tubular structure 113, the combustible mixture produced in the mixing tube 115 can flow' into the distribution chamber 112, flow therethrough and flow' out of the outflow' holes of the flame spreader 130 to be ignited, thanks also to the supply of secondary' air.

[0115] The partially closing plate 114 can be constrained to the distribution chamber 112 at the respective open tubular structure 113 by means of mechanical constraining means, for example of the type that are interlocked by elastically deformation.

[0116] In particular, in the embodiment shown herein (see Figure 9 in particular), these mechanical constraining means comprise a plurality of pegs projecting upward near the contour of the open tubular structure 113, which engage with respective coupling holes made along the perimeter edge of the partially closing plate 114 by means of an elastic¬ type interlocking, or by interference of elastically deformable complementary' parts. Again, the partially closing plate 114 is shaped so as to have a thin thickness compared to the other two dimensions so that it can be easily produced, for example, by simple operations of die forming a thin metal sheet.

[0117] With reference now' to Figures 9 and 10, a burner head 210 according to an aspect of thepresent invention is illustrated and comprises two Venturi-type mixing tubes 215 which are fed by a respective injection nozzle 226 and are shaped to feed, in turn, a gas - primary' air mixture to a respective distribution chamber 212, which is in turn fluidically connected to a flame spreader 230.

[0118] Each Venturi-type mixing tube 215 consists of an open tubular structure 213, which is made integrally with the head 210, below it, so as to form a recess of the distribution chamber 212, and at least one substantially flat closing plate 214 which is shaped to partially close the aforesaid recess.

[0119] Each Venturi-type mixing tube 215 comprises an inlet section 2151 facing the outflow hole of the respective injection nozzle 226, a throat section 15G having a fluid passage section that is reduced with respect to the inlet section 2151, and an expansion section 215E in which the fluid passage section gradually increases.

[0120] As shown in Figure 10, in this embodiment of the burner according to the present invention, the fluid passage section of each Venturi-type mixing tube 215, i.e., the section perpendicular to the main axis of the mixing tube, coincides with the fluid flow direction and is substantially square.

[0121] In particular, in this embodiment, the fluid passage section of at least the open tubular structure 213 of each Venturi-type mixing tube 215 has an at least partially square shape.

[0122] In an embodiment, at least the throat section 215G of the Venturi-type mixing tube 215 has substantially square shape, as shown in Figure 10.

[0123] Since the gas burners 1, 100 described herein have similar shapes, for the sake of completeness their operation will be described herein only with reference to gas burner 1 in Figures 1 to 6. A person skilled in the art will have no difficulty in correlating the following description of the operation of the burner 1 in Figures 1 to 6 with the burner 100 in Figures 7 and 8.

[0124] As will already be clear to the person skilled in the art, the operation of the gas burner 1 provides that, a jet of fuel gas, coming from the header 22 of the burner base 20, is injected by the injection nozzles 26a, 26b into the respective mixing tubes 15a, 15b, and that this gas, upon meeting the primary air that can flow into the volume between the protective skirt 11 of the burner head 10 and the attachment surface 21 of the burnerbase 20, mixes with this primary air, thus forming the fuel gas - primary air mixture that flows out of the holes of the flame spreader 30, where it can be ignited, thanks for example to the help of the spark plug 40, and then burn in a plurality of flames, thanks to the supply of secondary air from the atmosphere surrounding the burner 1.

[0125] According to an aspect, the burner 1 or the burner 100 of the present invention may be made according to a process comprising the following steps:

[0126] integrally making by molding or forging, without undercuts, the burner head 10 or 110 with each open tubular structure 13a, 13b, or 113 of each Venturi-type mixing tube 15a, 15b or 115 integrated therein, so that the open tubular structure is recessed while projecting downward from the distribution chamber of the same burner head 10 or 110, for example in form of an annular channel 12 or, as a further example, in form of a cylinder with a circular base 112. Preferably, this step can be performed by molding a metal material, such as aluminum;

[0127] making each upper partially closing plate 14a, 14b, or 14 for partially closing the respective open tubular structure 15a, 15b, or 15, preferably by blanking and / or die forming a metal sheet;

[0128] constraining, preferably mechanically by interlocking complementary parts, each upper plate 14a, 14b or 14 to the burner head 10 or 110 at or near the respective open tubular structure 13a, 13b or 113 of each mixing tube 15a, 15b or 115, to partially close this open tubular structure 13a, 13b or 113.

[0129] Those skilled in the art will understand that by integrally molding, or forging, part, of the structure of at least one Venturi-type mixing tube with the burner head, making upper closing plates, preferably substantially flat and therefore made, for example, by simple blanking, and assembling them to define the mixing tube according to the present invention, the partially-aerated gas burner described above can be made in a simple and economical manner.

[0130] It will be noted that the partially-aerated gas burner 1 and the partially-aerated gas burner 100 described herein are particularly suitable for use as burners for cooking or heating food products and can therefore be coupled to a cooktop or a free-standing stove.

Claims

CLAIMS1. Partially-aerated gas burner (1; 100) comprising a burner base (20; 120) having at least one header (22; 122) for a fuel gas fluidically connected to at least one injection nozzle (26; 126), a burner head (10; 110) equipped with at least one distribution chamber (12; 112), at least one flame spreader (30; 130) shaped to be juxtaposed to said at least one distribution chamber (12; 112), as well as at least one Venturi-type mixing tube (15a, 15b; 115), which extends substantially horizontally and sequentially has an inlet section (151), a throat section (15G) and an expansion section (15E), said inlet section (151) facing the at least one injection nozzle (26; 126), said burner base (20; 120), said burner head (10; 110) and said at least one flame spreader (30; 130) being overlapped on each other to form the burner (1; 100), characterized in that said at least one Venturi-type mixing tube (15a, 15b; 115) is defined by an open tubular structure (13a, 13b, 113) and at least one partially closing plate (14a, 14b; 114) to partially close said at least one open tubular structure (13a, 13b; 113), and in that the open tubular structure (13a, 13b; 113) forms a recess of said at least one distribution chamber (12; 112), said at least one closing plate (14a, 14b; 114) partially closing said recess.

2. Burner according to claim 1, characterized in that said at least one partially closing plate (14a, 14b) is substantially flat.

3. Burner according to any one of the preceding claims, wherein said at least one partially closing plate (14a, 14b; 114) is shaped to partially close the respective open tubular structure (13; 113) of said at least one Venturi-type mixing tube (15a, 15b; 115) while leaving at least one end region of said expansion section (15E) of the at least one Venturi-type mixing tube in fluidic communication with said at least one distribution chamber (12; 112) of the burner head (10; 110).

4. Burner according to any one of the preceding claims, wherein the expansion section (15E) of said at least one mixing tube (15a, 15b; 115) comprises at least one curved portion.

5. Burner according to any one of the preceding claims, wherein said at least one distribution chamber (12, 112) of the burner head (10; 110) comprises a bottom surface (12a) delimited by at least one projecting side wall (12b, 12c), and wherein said opentubular structure (13a, 13b; 113) of said at least one mixing tube (15a, 15b; 115) forms a recess of said bottom surface (12a) of the distribution chamber (12; 112).

6. Burner according to claim 5, wherein the bottom surface (12a) of said at least one distribution chamber (12, 112) upstream and downstream of the open tubular structure (13a, 13b; 113) of the at least one mixing tube lies substantially on the same, preferably flat, bottom surface (12a), the at least one partially closing plate (14a, 14b; 114) being shaped so as to be arranged on said surface of the distribution chamber (12; 112).

7. Burner according to any one of the preceding claims, comprising two Venturi-type mixing tubes (15a, 15b) extending substantially horizontally, each of the two mixing tubes sequentially comprising an inlet section (151) facing a respective injection nozzle (26a, 26b), a throat section (15G) and an expansion section (15E), wherein each of the two mixing tubes (15a, 15b) is defined by an open tubular structure (13a, 13b) and at least one respective partially closing plate (14a, 14b) to partially close the open tubular structure (13a, 13b), and wherein the open tubular structure (13a, 13b) of each mixing tube (15a, 15b) forms, in the at least one distribution chamber (12) of the burner head (10), a respective recess which is partially closed by the respective plate (14a, 14 b).

8. Burner according to any one of the preceding claims, wherein said at least one mixing tube (15a, 15b; 115) is made integrally with said burner head (10; 110).

9. Burner according to any one of the preceding claims, wherein said burner head (10; 110) comprises mechanical constraining means to constrain said at least one partially closing plate (14a, 14b; 114) to partially close the open tubular structure of said at least one Venturi-type mixing tube (15a, 15b; 115).

10. Burner according to claim 9, wherein said mechanical constraining means comprise at least one pin or peg (16b) and at least one respective hole (16a) for the interlocking coupling, preferably of elastic type, said at least one pin or peg projecting from the distribution chamber (12, 112) at the recess defined by the open tubular structure (13a, 13b; 113) of said at least one mixing tube (15a, 15b; 115) and said respective coupling hole being formed on the respective plate, or vice versa.

11. Burner according to any one of the preceding claims, characterized in thatsaid at least one partially closing plate (14a, 14 b; 114) and / or the respective constraining means to constrain said at least one partially closing plate to said at least one distribution chamber (12; 112) are shaped to allow exclusively an oriented constraint of said at least one plate with respect to the extent of said open tubular structure (13a, 13b; 113) of said at least one Venturi-type mixing tube (15a, 15b; 115).

12. Process for making a partially-aerated gas burner according to any one of claims 1 to 11, comprising the steps of:integrally making, without undercuts, by molding or forging, said burner head (10; 110) having said open tubular structure (13a, 13b, 113) of at least one Venturi-type mixing tube (15a, 15b; 115) integrated therewith, projecting with a recess from the at least one distribution chamber (12; 112) of said burner head;making said at least one partially closing plate (14a, 14b; 114) of said open tubular structure (13a, 13b; 113);constraining said at least one partially closing plate (14a, 14b; 114) to said burner head (10; 110) at, or near, the open tubular structure (13a, 13b; 113) of said at least one mixing tube (15a, 15b; 115) to partially close said open tubular structure.

13. Process according to claim 12, wherein said step of integrally making the burner head (10; 110) is carried out by molding a metal material.

14. Process according to claim 12 or 13, wherein said step of making said at least one plate (14a, 14b; 114) comprises a step of sheet metal blanking and / or molding.

15. Process according to any one of claims 11 to 14, wherein said step of constraining the at least one plate (14a, 14b; 114) to the burner head is carried out mechanically by interlocking, preferably elastically, complementary parts.

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