The present invention relates to a gas burner with multiple flame rings.

Single control gas burners with multiple concentric flame rings are known, i.e. burners in which the gas feed is controlled by a single tap. These generally comprise an injector holder cup, a flame divider resting on the injector holder cup and formed from two parts joined together to form an inner central portion and an outer annular portion, an annular cover which closes the annular portion of the flame divider, and a discoidal cover which closes the central portion of the flame divider.

Hence known gas burners with multiple concentric rings are formed from a total of five elements assembled together.

One of these known burners is described for example in EP-B1-0797048.

WO200605136 discloses a gas burner system for food cooking is described, comprising a pair of concentric burners , the gas to be supplied to the pair of burners being suitably mixed with air taken above the cooking top on which the burner system is mounted, so as to form an air-gas mixture for the pair of burners.

US2006121402 discloses a gas burner for cookers, of the type fitted to a cooking hob, comprising a central body having a first ring of flames and at least one external body, fluidly separated from said central body and substantially concentric with it, having at least one second (circumferential) ring of flames, as well as means for separately feeding the mixture of primary air and gas to the central body and to the external body.

An object of the invention is to provide a gas burner of multiple concentric ring type in which the number of components is reduced.

Another object of the invention is to provide a gas burner of multiple concentric ring type which is of limited overall height, such as to be able to be mounted on traditional built-in cooking hobs.

Another object of the invention is to provide a gas burner of multiple concentric ring type in which the primary air is drawn in from above the cooking hob, in order to prevent streaming, i.e. flame disturbance on sudden opening of the oven door or of a furniture item positioned below the cooking hob.

These and other objects which will be apparent from the ensuing description are attained according to the invention by a gas burner with multiple concentric rings as described in claim 1.

The present invention is further clarified hereinafter by means of some preferred embodiments thereof described with reference to the accompanying drawings, in which:

Figure 1

is an exploded perspective view of a first embodiment of the burner according to the invention, seen from above,

Figure 2

is an exploded perspective view thereof seen from below,

Figure 3

is a perspective view thereof in its assembled state, mounted on a cooking hob,

Figure 4

is a perspective view thereof shown in vertical section,

Figure 5

is a second embodiment thereof shown in the same view as Figure 4, and

Figure 6

shows a third embodiment thereof with three injectors.

As can be seen from the figures, the burner of the invention comprises, in the embodiment shown in Figures 1-4, three basic components consisting of the injector holder 2, the flame divider 4 and the cover 6.

The injector holder 2 is of essentially elongated extension and is shaped to define two cups 8 connected together by two baffles 10. The two cups are closed lowerly and laterally and are open at their top, where the lateral wall is provided with an outwardly jutting flange 12 for resting against the underside of the sheet metal of a cooking hob 14, to which the burner is fixed by screws.

The lateral wall of each cup 8 extends upperly beyond the flange 12 to form a rim 16 emerging from the cooking hob 14 and acting as the support element for the flame divider 4.

The injector holder 2 also comprises a gas feed conduit 18; it extends horizontally below the base of the two cups 8, it is open at one end for gas entry and communicates with two injectors 20 screwed centrally to the base of the cups.

The flame divider 4 rests on the injector holder 2 such that two of its downwardly jutting profiled projections 22 rest on the upper rims 16 of the two cups 8. These profiled projections 22 do not extend along the entire extension of the corresponding upper rims 16, but only along its two lateral portions and along its inner portion, such as to define between the flame divider 4 and the injector holder 2 two apertures for access of the primary air originating from above the cooking hob 14 into the two cups 8.

The flame divider 4 is centred about the injector holder 2 by projections 24, which extend downwards from the flame divider 2 and adhere via their outer vertical edge to the inner surface of the lateral wall of the two cups 8.

The flame divider 4 comprises an outer portion 26 of overall annular shape and an inner portion 28 of overall circular shape.

More particularly, the outer portion 26 presents an outer rim 30 which extends along a circumference, and an inner rim 32, of which a certain part extends along a circumference concentric with that of the outer rim 30, then it curves inwards to connect to the circular rim 34 of the inner portion 28. In this manner two substantially radial channels 36 are obtained providing fluidic connection between the inner circular portion 28 and the outer annular portion 26 of the flame divider 4. Hence these two portions are bounded by a single continuous rim, which comprises along its entire extension, with the exception of the parts relative to the two radial channels 26, a plurality of main ports 38 and secondary ports 40, which on the rim 30 form the outer ring of outwardly directed flames, on the rim 32 form the intermediate ring of inwardly directed flames, and on the rim 34 form the inner ring of outwardly directed flames.

The two rims bounding the radial channels 36 also present secondary apertures 42, the purpose of which is to transmit the flames from the intermediate ring to the inner ring.

In addition, in the outer portion 26 of the flame divider 4, two channels 43 are positioned provided with two small ports 44 for inter-ignition between the flames of the outer ring and those of the intermediate ring and inner ring.

The flame divider 4 also comprises two vertical conduits 46 which at their lower end face the two injectors 20 and open upperly at projections 48 which lowerly define two venture effect chambers bounded upperly by the cover 6, which rests on the flame divider 4 at four centring pegs 50 provided therein.

When the flame divider 4 rests via its profiled projections 22 on the upper rims 16 of the two cups 8, it is maintained spaced from the sheet metal of the cooking hob 14 by a distance such as to determine passages therewith for the secondary air intended for the inner portion 28 of the flame divider.

The cover 6 is formed in one piece and comprises an annular outer portion 52, a discoidal inner portion 54 and two profiled radial connection portions 56.

The burner of this embodiment operates in the following manner:

The gas entering from the conduit 18 leaves from the injectors 20 and enters the two vertical conduits 46 of the flame divider 4, to entrain the primary air drawn in from above the cooking hob 14 through the apertures defined by the outer part of the profiled projection 22 of each cup 8 and the overlying flame divider, in accordance with the path indicated by the arrows 58 in Figure 4.

The flow of gas and primary air which begins to mix in each of the vertical conduits 46 completes its mixing in the corresponding radial venturi chamber defined lowerly by the surface of the projection 48 and upperly by the cover 6.

The mixture obtained in this manner then propagates along the annular portion 26 of the flame divider 4 to feed the two rings of outer and intermediate flames thereof, then further propagates along the two radial conduits 36 to feed the central ring of flames of the inner portion 28.

From the aforegoing it is apparent that the burner of the invention is much more advantageous than traditional multi-flame ring burners, and in particular:

• it is formed from only three pieces, hence as the flame divider is of one-piece die-cast construction without machining, it is of simple and economical manufacture,
• the cover, even though intended for a three flame ring burner, is also formed in one piece, again making the burner manufacture simple and economical,
• because of the use of radial venturi mixing chambers, it is of small vertical height and easily installed in normal cooking hobs. The fact of having two mixing chambers means that a power can be developed which is much higher than traditional burners with a single radial venturi mixing chamber,
• finally, as the primary air is drawn in from above the cooking hob, it is virtually insensitive to streaming.

In the embodiment illustrated in Figure 5, the gas/primary air mixture of the burner of the invention generated by the two radial venturi chambers is conveyed into the inner central portion 28 of the flame divider 4 not through radial channels bounded by the flame divider and the cover, as in the preceding embodiment, but by two radial channels 60 bounded by the flame divider 4 and the injector holder 2. For this purpose the injector holder 2 is provided, in the connection portion between the two cups 8, with two radial channels 60 which connect the two radial venturi mixing chambers to the inner portion 28 of the flame divider 4, which is also provided with baffles 62 for upperly closing said channels 60.

In this embodiment the cover 6, the purpose of which is no longer to upperly bound the radial channels connecting the two mixing chambers to the inner portion 28 of the flame divider 4, can be formed in two separate parts, of which the outer part is of approximately annular shape and the inner part is of discoidal shape.

The embodiment shown in Figure 6 differs from the preceding embodiments by the addition, to the two cups 8 provided on their base with corresponding injectors, of a third central cup 8' provided on its base with a third injector 20', also communicating with the same gas feed conduit 18.

In this case the inner portion 28 of the flame divider 4 communicates with the cup 8' via its own vertical conduit 46', through which the gas/primary air mixture is fed.

The flame divider 4 rests only partly on the underlying injector holder 2, such as to define access apertures for the primary air originating from above the cooking hob.