EP1016823B1 - Gas burner supplied with secondary forced air - Google Patents

Description

The present invention relates to air supply secondary of a gas burner according to the preamble of claim 1. Such a burner is known from document EP-A-0 581 655. Two main families can be distinguished gas burners. In the first family burners, gas fuel and all of the air needed for combustion is mixed upstream of the flames. These burners are called premix burners total. In the second family burners, a partial gas premix and air is produced upstream of the flames and the necessary air supplement during combustion is taken from the ambient air located in the vicinity of flames. These burners are called partial premix burners or secondary air burners. Secondary air is the air taken in the vicinity of flames as opposed to the so-called primary air premixed with gas upstream of flames. The invention is an improvement of secondary air burners. She is particularly useful in gas burners used in cooking domesticated.

In domestic cooking, gas burners have a burner located above a hearth plate. The air and gas premix escapes through orifices located at the periphery of the burner head. The fact taking secondary air near the flames requires that a space be free in the vicinity of the flames so as not to disturb the arrival of secondary air and the evacuation of burnt gases. Indeed if the air secondary does not reach the flames in sufficient quantity, or if the gases can not escape, combustion is incomplete and produced including carbon monoxide (CO) which is a toxic gas. A sufficient free space requires a first free height of around 30 mm between the hearth plate and the flames for the supply of secondary air and a second free height of the order of 15 mm between the flames and the bottom a cooking utensil heated by the burner. Sufficient free space also imposes simple shapes for the burner head which is generally circular.

The object of the invention is to allow freedom from these constraints in order to produce burner heads closer to the plate hearth and various forms.

To achieve this object, the invention relates to a gas burner according to claim 1.

An advantage linked to the invention is to be able to do without grids usually used to place and hold kitchen utensils away from the burner head. Thanks to the invention, it is thus possible to pose the cookware directly on a burner body.

Another advantage linked to the invention is that it does not require tolerances too tight for forced air flow, unlike gas burners total premix, which use means to force the primary air flow and which require precise adjustment of the air flow in relation to the flow of gas.

• la figure 1 représente schématiquement un exemple de forme de tête de brûleur en vue de dessus.
• la figure 2 représente un brûleur à gaz comportant une couronne de flammes ;
• la figure 3 représente un brûleur à gaz comportant trois couronnes de flammes.

The invention will be better understood on reading several embodiments illustrated by means of the attached drawing in which:

• FIG. 1 schematically represents an example of a burner head shape seen from above.
• FIG. 2 represents a gas burner comprising a crown of flames;
• FIG. 3 represents a gas burner comprising three crowns of flame.

Figure 1 shows a five-pointed star. The lines forming the outline of the star represent the position of the flames of the burner. The position of the flames is only given here, by way of example, for show the freedom of form which allows the invention. Indeed, food forced into air provides sufficient secondary air to all the burner flames, which the air supply would not allow secondary by natural convection. For example, in Figure 1, a zone A of the flames located in one of the returning angles of the star would not not properly supplied with secondary air by natural convection. Through against, thanks to the invention, the quantity of secondary air is sufficient in the zone A.

For a better understanding of the invention, the modes of embodiment described using FIGS. 2 and 3 disclose burners of revolution. It is understood that the invention is not limited to these burners and can be implemented whatever the shape of the burner.

The gas burner shown in Figure 2 is assembled through of a hearth plate 1. The burner comprises a burner head 2 and a burner cap 3 located above the hearth plate 1. The head of burner 2 and the burner cap 3 form a burner body. The head of burner 2 and the burner cap 3 are, in FIG. 1, parts of revolution around an axis 4 substantially perpendicular to the hearth plate 1. It is of course possible that the axis 4 is not perpendicular to the hearth plate 1. Below the hearth plate 1 the burner has gas supply means. These gas supply means comprise an injector 5 as well as means 6 for adjusting the flow of gas. These means 6 advantageously comprise a tap whose control can be electrical or mechanical. Injector 5 injects gas in a structure called venturi 7 belonging to the burner. Venturi 7 sucks said primary air in its vicinity and performs a premix of air and gas. The venturi 7 is connected to a channel 8 belonging to the burner head 2. The channel 8 is substantially of axis 4. Downstream of the venturi 7, the air premix and gas is routed through channel 8 to a space 9 located between a face upper 10 of the burner head 2 and a lower face 11 of the cap of burner 3. The space 9 has substantially the shape of a disc of axis 4. The premix circulates in space 9 away from axis 4. The premix escapes from the burner through orifices 12 produced for example by means of slots located in the burner head 2. The slots are covered by the underside 11 of the burner cap 3. The premix is ignited at the outlet of the orifices 12.

Advantageously, the burner cap 3 has a face upper 25 on which a cooking utensil can be placed directly cooking (not shown) without the intermediary of a grid, as usually used in domestic cooktops for laying the utensil. To do this, it is necessary that the orifices 12 are located slightly lower than the upper face 25, in order to spare between orifice 12 and the utensil sufficient space for the flame to be develop properly.

The burner also includes air supply means secondary. Advantageously, these means are separated from the means primary air supply to the burner so that the two air flows, air primary and secondary air do not disturb each other. Ways secondary air supply means include forcing the displacement of air, for example by means of a fan 13 located under the hearth plate 1. The fan 13 blows air into a chamber 14 located it also under the hearth plate 1. The chamber 14 is for example formed between the hearth plate 1 and a substantially planar lower face 22 and perpendicular to axis 4. A contour 23 closes the chamber by connecting the face lower 22 than the hearth plate 1. The chamber 14 has two orifices 15 and 24. The orifice 24 is for example located in the lower face 22. The separation of primary air and secondary air is achieved by means of the lower face 22. The movement of air is forced, for example by means from the fan 13, towards the interior of the chamber 14 through the orifice 24. The air escapes from the chamber 14 through the orifice 15. The orifice 15 is by example made through the hearth plate 1 around the duct 8. After be out of the orifice 15, the air escapes between the top of the hearth plate 1 and the underside of the burner head 2. The air then moves away from axis 4 to move towards the flames 16. This air is called secondary air. Primary air contains about 40 to 60% of the oxygen necessary for combustion, the air secondary provides additional air for combustion full of gas. The speed of the secondary air in the vicinity of the flames 16 tends to evacuate the burnt gases.

The orifice 15 is advantageously calibrated and the dimension is dimensioned. chamber 14 and the orifice 15 so that the secondary air flow is sufficient, when the gas flow rate, adjusted by the means 6 for adjusting the gas flow rate, is maximum. The orifice 15 is also dimensioned so that the secondary air speed is not too great to the point of disturbing the flames 16 even when the means 6 for adjusting the gas flow injects a minimum gas flow into the burner.

Advantageously, the chamber 14 can supply several burner body simultaneously in secondary air. Room 14 has then a single orifice 24 through which the fan 13 draws air into the chamber 14 and as many orifices 15 as there are burner bodies. The different burner bodies can have different powers. The dimensioning of each orifice 15 is then a function of the power of the burner body which it supplies. One can advantageously arrange the shape and dimensions of the chamber 14 to obtain a speed of substantially equal displacement of air towards each burner body.

The invention is here described in relation to a gas burner of revolution where the flames 16 are distributed angularly, in a plane perpendicular to axis 4, constantly. So that the secondary air is also distributed steadily, it is advantageous that the orifice 15 is circular and of axis 4. If, on the contrary, the flames 16 are not distributed constantly, a particular shape can be provided for the orifice 15, shape adapted to the distribution of the flames 16. It is also possible to provide one or several deflectors in the vicinity of orifice 15 in order to distribute the air secondary according to the distribution of the flames 16.

The air flow through the fan 13 is controlled for example by controlling the speed of the fan 13. Control means 17 for fan 13 can be connected to a pressure sensor 18 measuring the pressure of the air in chamber 14. We can control the fan so that the air pressure in the chamber 14 is substantially constant. The pressure sensor 18 allows also to detect a possible problem in the air flow secondary. For example when the orifice 15 is blocked, the pressure measured by the sensor 18 increases and the control means 17 tend to reduce the speed of fan 13, below a limit value defined at construction, which makes it possible to highlight a defect in operation and for example cutting off the gas supply using means 6 gas flow adjustment. When the air pressure in the room is substantially constant, several burner bodies can be supplied at using a single fan 13. The control means 17 can also be connected to means 19 for controlling the power of the burner, so that the fan 13 is controlled according to the power control of the burner. The means 19 for controlling the burner power are connected to the means 6 for adjusting the gas flow rate and control them directly. The means 19 for controlling the burner power include: example a rotary button or a keyboard operated by a user. When the gas flow from the injector 5 is minimum, the air flow is reduced secondary and when the gas flow rate from injector 5 is maximum, increases the secondary air flow by acting on the means 17 of fan control. Control secondary air flow accordingly of the burner power control provides a quantity of air secondary just necessary. This variant requires a fan 13 per burner body.

The fan control means 17 can both be connected to the pressure sensor 18 and to the means 19 for controlling the burner power, so that the secondary air pressure inside the chamber is a function of the burner power control. Knowing the dimensions of the orifice 15, this variant makes it possible to control the secondary air flow rate at the burner power control.

The control means 17 may include a circuit electronic. Advantageously, in order to cool this circuit, it can be placed on the way of the air flow driven by the fan 13. More usually many cooktops have circuits electronics that need to be cooled, for example by means of a fan. In these hobs, it is advantageous to use only one single fan to cool the electronic circuits and to create a forced air current, conform to the invention.

The burner shown in Figure 3 includes all of the elements shown in Figure 2. For simplicity these elements will bear the same topological references and will not be described a second time. The orifices 12 shown in FIG. 2 are located on a ring with an axis 4. The burner shown in Figure 2 then has a single crown of flames 16. Unlike figure 2 the burner shown in figure 3 comprises several crowns of flames 16, for example all concentric of axis 4. For the realization of a burner comprising several crowns of flame, we can take inspiration from the embodiment described in the European patent application: EP 552 135.

In Figure 3, three flame rings 16 are shown. The space 9 is capable of supplying the three crowns with premix flames 16 of the burner. Secondary air supply to the crown outermost flame 16, is done identically in the two figures 2 and 3. On the other hand, to supply the two most flame crowns interior, at least one channel 20 with axis 21 is provided, this channel crosses right through the burner head 2 and the cap 3, the axis 21 is for example parallel to axis 4. The channel 20 thus makes it possible to supply secondary air to the two innermost crowns of flame 16. We have to size the channel 20 so that sufficient secondary air is supplied to all of the flame crowns 16.

So that the burnt gases from the flames, especially 16 interior flame crowns can escape, it is necessary to raise the kitchen utensil either by means of a grid or, if wishes to do without a grid, by means of an arrangement of the hat burner 3 as for example shown in FIG. 3. This arrangement has a boss 26 in the part of the burner cap 3 located at the interior of the innermost flame crown 16. The utensil of kitchen will be placed directly on the boss 26, which saves a space 27 between the burner cap 3 and the kitchen utensil and at the outside of the innermost flame crown 16. Space 27 allows the burnt gases from the 16 most flame crowns interior to be evacuated. The space 27 can be annular and of axis 4. It can just as well be interrupted by slots 28 of the same height as the boss 26, in order to improve the stability of the cookware when it is placed on the burner cap 3.

Claims (8)

1. Gas burner including means (5, 6) of feeding gas, means of feeding with primary air and means (13, 14, 15, 24) of feeding secondary air, the means of feeding with secondary air including means (13) for forcing displacement of the air, characterised in that the means to force displacement of the air include means (17) to control the air flow.
2. Gas burner as in Claim 1, characterised in that the means (13, 14, 15, 24) of feeding secondary air are separate from the means of feeding primary air.
3. Gas burner as in either of the preceding claims, characterised in that the means for forcing displacement of the air include a chamber (14), a fan (13) blowing the air into the chamber and a calibrated orifice (15) allowing the air to exit from the chamber in the direction of the flames (16) of the burner.
4. Device as in Claim 3, characterised in that the chamber (14) is placed under a hearth plate (1), in which the orifice (15) is situated in the hearth plate (1), and in which, on its exit from the orifice (15), the air is displaced between the hearth plate (1 ) and a burner jet (2).
5. Device as in either of Claims 3 or 4, characterised in that the fan (13) is controlled such that the pressure in the chamber (14) is constant.
6. Device as in either of Claims 3 or 4, characterised in that the fan (13) feeds air to a single burner whose power can be varied by means of a controller (19), and in which control of the fan (13) is dependent on the burner power controller.
7. Device as in either of Claims 3 or 4, characterised in that the fan (13) feeds air to a single burner whose power can be varied by means of a controller (19), and in which the fan (13) is controlled such that the secondary air flow is dependent on the burner power controller.
8. Device as in any of the preceding claims, characterised in that the burner has a number of jets (16), all fed by the means (13, 14, 15, 24) of feeding the secondary air.

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