EP1099905A1 - Household cooking hob gas burner - Google Patents

Abstract

The gas burner for a domestic hob has a burner head (3) with branches (4) having openings (6) for the primary air fed by a passage (12). The head is raised above the base plate. Secondary air is fed by a second passage extending through the base plate and having ducts to allow vertical flow of the secondary air along the central head. The secondary air flow ducts have raised lugs 99) between each branch pair at the level of the base plate and defining a vertical surface.

Description

The invention relates to a gas burner for a hob. domestic, and more specifically a secondary air star burner.

In secondary air burners, a partial premix of combustible gas and air is produced upstream of the flames and the complement of air necessary for combustion is taken from the ambient air located at neighborhood of flames. Secondary air is therefore the air taken from the vicinity flames as opposed to primary air premixed with gas upstream flames.

Gas burners on a domestic cooktop include a burner head located above a hearth plate. The air and gas premix (primary mixture) escapes through orifices located on the periphery of the burner head. This type of burner requires generally that a free space is provided in the vicinity of the flames so as not to not disturb the arrival of secondary air. If secondary air does indeed arrive not in the vicinity of the flames in sufficient quantity, combustion is incomplete and produces toxic gases, including carbon monoxide (CO). This free space imposes a minimum height between the hearth plate and the flames and between the flames and the bottom of the container. Free space sufficient also requires simple shapes for the burner head which is generally circular.

However, a better distribution of the temperature is obtained over the bottom of the container in the star-shaped gas burners. The term 'star' is here taken in the broad sense. It is any burner including a burner head with several branches extending from a central body, these branches can take any form. In this type of burner, the branches are provided with primary mixture outlet ports which are the flame exit ports. On the other hand, we are trying to reduce the height between the hearth plate and the flame level, in order to present more aesthetic burners, and to reduce the height between the flame level and the container, in order to gain heating efficiency. We can get like this self-supporting burners, i.e. burners on the head of which the container can be placed directly, and therefore no longer requires a grid to place the container. In all these cases, the problem of supply of secondary air to the flames.

The invention solves these difficulties and proposes a gas burner in star, whose height between the hearth plate and the level of the flames as well between the flame level and the container can be reduced to minimum, while ensuring an optimal supply of air to the flames secondary.

For this, the invention relates to a burner for a hob domestic including a burner head with several branches provided orifices for the primary mixture, and extending from a central body, the head being slightly raised compared to a hearth plate, the burner further comprising a passage for the primary mixture in communication with said head, and an independent secondary air passage of passage for the primary mixture. The burner is characterized in that said secondary air passage takes place through an opening in the plate hearth, positioned substantially under the central body of the head, and in this that it further comprises means for channeling the secondary air allowing between two branches, a substantially vertical flow of the flow secondary air along the central body.

Thus, in the burner according to the invention, even if it is a self-supporting burner, secondary air supply can be carried out at the same time from below the flames, thanks to the secondary air which flows in under the branches, and over the flames, thanks to the air secondary which is channeled between the branches.

• la figure 1, une vue partielle d'un exemple de brûleur selon l'invention ;
• la figure 2, le schéma d'une bague formant un exemple de réalisation des moyens de canalisation de l'air secondaire ;
• la figure 3, une vue de dessus d'un exemple de réalisation du brûleur selon l'inventions ;
• la figure 4, le schéma vu en coupe d'un autre exemple de bague formant des moyens de canalisation.

Other advantages and characteristics of the invention will appear on reading the description which follows, illustrated by the figures which represent:

• Figure 1, a partial view of an example of a burner according to the invention;
• FIG. 2, the diagram of a ring forming an exemplary embodiment of the means for channeling the secondary air;
• Figure 3, a top view of an embodiment of the burner according to the invention;
• Figure 4, the diagram seen in section of another example of ring forming channeling means.

In these figures, the homologous elements are indexed by the same benchmarks.

FIG. 1 represents a partial view of an example of a burner according to the invention. The burner 1 is mounted on a hearth plate 2. It comprises a burner head 3 with several branches 4 extending from a central body 5, and thus forming a star burner. In Figure 1, only two branches are represented. The shape of the central body, as well as that of the branches and the number of these branches is arbitrary. For example, the central body has a substantially circular shape and the branches, in shape elongated, at least three in number, are evenly distributed along of the circumference of the central body 5. The branches are provided with holes 6 for the primary mixture. The shape of these holes defines the shape of the flames. In the example of Figure 1, these holes are shaped rectangular, giving 7 flat and wide flames. The head can be formed in one piece, or a first piece forming a gas train and covered by a hat with a shape substantially identical to that of the ramp and covering it. Head 3 is slightly raised relative to the hearth plate 2, for example by means of feet 8 placed at the ends of the branches. The burner also conventionally includes a passage for the primary mixture in communication with the head for supplying primary mixture of orifices. It can also include a device ignition device, a flame detection device, not shown here, or other conventional means of operating a gas burner.

According to the invention, the burner further comprises an air passage secondary independent of the passage for the primary mixture and which takes place through an opening in the hob. This opening is positioned substantially under the central body of the head in order to provide air secondary to the flames of all the branches. As the head is raised above the hearth plate, secondary air from the opening can flow under the branches, allowing a supply of secondary air flames from below. This flow is materialized in Figure 1 by arrows in thin line.

According to the invention, the burner further comprises means for secondary air ducting allowing between two branches, a substantially vertical flow of air flow along the central body. The Applicant has in fact shown that the channeling of the secondary air flow the along the central body, that is to say in the hollow which separates two branches, provides secondary air to the flames from above, allowing better combustion. Secondary air flow from above is materialized in the example of Figure 1 by arrows in thick line.

Thus in the burner according to the invention, the air supply secondary flames is carried out both from below and by the above. This effect is particularly advantageous in the case of flames wide and flat, as in the example in Figure 1, because in in this case, the secondary air has very little access to the sides of the flame.

The channeling means comprise for example a set of high slots 9, each high slot being positioned between two branches, on the hearth plate, and has a substantially wall vertical so that secondary air from the opening is channeled substantially vertically.

Alternatively, the secondary air passage opening extends beyond the central body 5 of the burner, and leaves between the branches secondary air inlet passages not covered by said central body. The means of channeling, for example the high slots previously described, are for example positioned directly at the edge of the opening, ensuring the channeling of the secondary air flow which is already substantially vertical at the outlet of the opening.

Advantageously, the effect of secondary air flow over flames can be reinforced by deflection means which allow, between two branches, to fold the secondary air flow along branches, substantially above the orifices. Certainly, the deviation of secondary air can be supplied by the container itself when, in the in the case of a self-supporting burner, it can be placed directly on the head 3 of the burner. But when the container is not in place or is not supported directly by the head, it is advantageous to provide these means of deviation. They are for example formed, as illustrated in FIG. 1, substantially horizontal fins 10, located in a plane above the orifices and which extend between the branches, from the central body 5 of the burner.

The applicant has shown that in the presence of means of diversion of the device according to the invention, good flow of secondary air between the branches was obtained for example with a high niche height slightly less than the height of the orifices 6, as illustrated in Figure 1. Very good combustion is then obtained with a distance only about 10 mm between the hearth plate and the flame level, defined by the plane of the orifices, and a substantially identical distance between the level of the flames and the top of the burner head where the means of diversion.

FIG. 2 illustrates means of channeling the burner according to the invention formed of a ring 11. The ring is circular, placed on the hearth plate 2, substantially centered with respect to the central body of the burner (not shown). In the example in Figure 2, the opening for the secondary air passage is substantially circular and extends beyond the central body of the burner, so that the ring can fit on the periphery of the opening. In this example, the pass for mixing primary is carried out by a collector 12 in communication with the body central and centered substantially in the opening. Secondary air passage is therefore done through the space 13 around the collector. Advantageously, the collector being of substantially circular section, centered on the opening, the space 13 is homogeneous around the collector, and the secondary air is uniformly distributed around the collector along a substantially axis parallel to that of the burner.

The ring 11 is in this example formed by high slots 9 alternated with low slots 112. The top slots are positioned between the branches (not shown), and allow a flow substantially vertical secondary air between the branches, along the body central, as explained above. The low slots are position under the branches. Their height is such that they do not prevent the secondary air flow under the branch. Low slots have before a whole anti-overflow function. Indeed, if liquid elements by example are spilled on the hearth plate, they will not be able to infiltrate the opening of the plate, thanks to the presence of the high slots between the branches, and that of the lower slots, under the branches. In Figure 2, the secondary air flows are shown diagrammatically by arrows. The arrows in thin lines represent the secondary air flow at the low slots, under the branches, and which will allow the feeding of the flames in secondary air from below. The thick line arrows represent the secondary air flow at the top slots, between the branches, along the central body and which will allow the feeding of flames in secondary air from above.

Figure 3 shows a top view of an example burner according to the invention. The burner 1 is here a star burner with five branches (4), distributed around a central body 5 of substantially circular shape. The head, formed of the central body and branches, is slightly raised by relation to the hearth plate by means of the feet 8, positioned at the ends branches. As in the previous example, the passage for the primary mixing is ensured by a manifold 12, centered on an opening in the hearth plate 2 and leaving, all around, a space 13 for the passage secondary air. A ring 11, of the type described in FIG. 2, is positioned on the periphery of the opening. It includes slots high 9 between the branches, and low slots 112 under the branches. As in the previous example, the arrows in thin lines symbolize the secondary air flow under the branches, to supply the flames from below, while the thick arrows symbolize supply of secondary air to the flames from above. In this example, secondary air deflection means are provided. They are formed here of a ring 14, positioned on the burner head, or directly integrated in the burner head, and whose external diameter is greater than that of the central body, thus making it possible to reduce the secondary air channeled thanks to to the slots 9 of the ring 11 along the branches, substantially above orifices.

Figure 4 shows in section, another example of a ring 11 forming channeling means, and which also has an anti-overflow effect. As before, the ring has slots high 9, positioned between the branches (not shown), each with a substantially vertical wall to create a flow substantially vertical of the secondary air flow. As in the previous example, the passage for the primary mixture is ensured by a manifold 12, centered in an opening in the hearth plate 2, and leaving, all around, a space 13 for the passage of secondary air. In this example, the ring 11 does not have low slots. It has a flange 113 which rests on the hearth plate 2. In the variant of FIG. 4, the ring 11 is fitted with a gutter 114 which extends around the opening, at a level lower than that of the hearth plate 2. This gutter allows collect any liquids or dirt that may come from the containers of cooking, thus presenting an anti-overflow effect. Space 13 for the secondary air passage therefore takes place between the manifold 12 and the gutter 114, under the central body of the burner head (not shown). Of means are provided here to first deflect secondary air in a substantially homogeneous horizontal flow all around the collector. it is for example a substantially horizontal ring 121 placed around collector 12, slightly above the level of the plate hearth. The secondary air flow (symbolized with arrows in thick lines) which meets the high slots 9 is then deflected vertically, forming, between the branches of the burner, the substantially vertical flow along the central body (not shown). The secondary air flow (symbolized with arrows in thin line) which does not meet the slots 9 forms the flow substantially horizontal which passes under the branches.

The gutter 114 is in this example integral with the ring 11. It could be an independent piece, placed around the opening in the hearth plate.

Of course, the invention is not limited to the examples described previously. In particular, it applies to any form of burner in secondary air star and allows, in a simple way, a very good supply of flames with secondary air, whatever the shape of these flames.

Claims (10)

Burner (1) for domestic hob comprising a burner head (3) with several branches (4) provided with orifices (6) for the primary mixture, and extending from a central body (5), the head being slightly raised compared to a hearth plate (2), a passage for the primary mixture in communication with said head, and an air passage secondary independent of the passage for the primary mixture, characterized in that said passage takes place through an opening in the hearth plate, positioned substantially under the central body of the head, and in that it further comprises means for channeling the secondary air allowing between two branches, a substantially vertical flow of the flow secondary air along the central body. Burner according to claim 1, characterized in that said channeling means comprise a set of high slots (9), each high slot being positioned between two branches, at the level of the hearth plate, and having a substantially vertical wall, allowing between two branches, the substantially vertical flow of the air flow secondary. Burner according to claim 2, characterized in that the channeling means are formed by a ring (11) positioned on the hearth plate, substantially centered with respect to the central body of the burner, and having between said branches said high slots (9). Burner according to claim 3, characterized in that the ring also has a low slot (112) under each branch, said slot bottom having an anti-overflow effect and being of a height such that does not prevent the flow of secondary air under the branch. Burner according to one of claims 3 or 4, characterized in the opening in the hearth plate being circular, the ring (11) fits on the periphery of the opening in the hearth plate. Burner according to one of Claims 2 to 5, characterized in that that the height of the high slots (9) between two branches is slightly lower than that of the burner head ports. Burner according to one of the preceding claims, characterized in that the passage for the primary mixture is effected by a manifold (12) in communication with the central body and centered substantially in said opening, the passage of secondary air taking place in the free space (13) around the collector. Burner according to claim 7, characterized in that it further comprises a gutter (114) having an anti-overflow effect and extending all around the opening, the secondary air passage is between the collector (12) and the gutter. Burner according to one of the preceding claims, characterized in that it further comprises means for deflecting secondary air allowing, between two branches, to fold the secondary air flow along branches, substantially above the orifices. Burner according to claim 9, characterized in that said deflection means comprise fins (10) substantially horizontal, located in a plane above the orifices and which extend between the branches, from the central body of the burner.

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