NL2005105C2 - Gas hob with inside burner. - Google Patents

Description

Gas hob with inside burner

The invention relates to a gas hob for cooking appliances. The invention also relates to a method of heating a pan.

5

Nowadays, most people use a gas hob for cooking meals. A known gas hob comprises a gas burner having a number of gas outlets and some sort of support for supporting a pan or a pot or any other type of cooking tool. When leaving the gas burner, the gas-air mixture needs extra air for a complete combustion. The extra air must arrive by natural draft. This natural draft 10 can be done with an air supply, from above or under a drip tray.

Once ignited, the gas will flame and the flames will heat up the pan. However, also a lot of heat will flow along the bottom of the pan and will escape at the side. As a result a lot of energy is actually wasted.

It is the object of the present invention to improve the heat transfer to a pan.

15 This object is achieved by providing a gas hob for cooking appliances, the gas hob comprising a plurality of gas outlets surrounding a cavity, and gas supply means for forcing gas or a gas/air mixture through said plurality of gas outlets in the direction of the cavity. Due to the inside orientations of the flames less cold outside air has to be heated up which results in a higher flame temperature and better combustion. The so-called ‘inside burner’ keeps the 2 0 combustion in the centre under the pan and gives the heat gases more time to transfer the heat to the pan.

In an embodiment, the gas outlets are arranged in a wall which is curved in one dimension so that, in use, adjacent flames converge. Because of the converging flames a significant improvement of the modulation range and a better combustion and a higher flame temperature 25 can be realized. In a particular embodiment the wall has a substantially conical shape. Due to a conical shape, the wall has an angle in one plane while being circular in another plane perpendicular to the first plane. The angle between the wall and a plane defined by an upper opening of the conical wall may have a value between 30 and 90 degrees and more preferably between 40 and 50 degrees. This will result in flames being directed inwardly while also being 3 0 oriented more or less towards the bottom of the pan.

In an embodiment a distance between adjacent gas outlets is smaller than 3 mm. Such a narrow distribution of flames will result in a cooperation of the individual flames resulting in a very effective heat source.

In a particular embodiment, the gas hob comprises supporting means for supporting a 35 pan. These supporting means are arranged to space a bottom of the pan relative to at least some of the plurality of outlets at a distance smaller than 2 cm. This relatively small distance 2 between the pan and the outlets result in a better heat transfer as compared to the state of the art.

The gas hob may comprise gas mixing means for premixing gas and air before the gas and air is forced through said gas outlets. The mixing means may comprise a premix chamber 5 or tube having a gas inlet and an air inlet. By premixing gas and air before it exits the gas outlets, the combustion is more complete and no additional air (i.e. oxygen) is needed so that the distance between the pan and the burner can be minimized.

In an embodiment the gas hob comprises a pre-heat compartment arranged in close vicinity of the gas outlets for preheating the gas or the gas/air mixture before reaching said gas 10 outlets. Pre-heating the gas or mixture will give a better combustion and a higher yield.

In an embodiment the gas hob comprises obstruction means for obstructing heat that flows underneath a pan placed on said gas hob. It should be noted that the obstruction is not complete and that eventually the produced gasses can leave the space under the pan. The obstruction means may comprise one or more rings arranged around the gas burner. One or 15 more of these rings may function as a support for the pan as well. In an embodiment, a ring comprises knobs or other spacing members to support the pan. By partly obstruction the heat flow under the pan, an increase in turbulence of the flow is realized. By producing a turbulence, the total flow under the pan can transfers heat to the pan, not only an upper flow as was the case in the state of the art gas hobs.

2 0 The invention also relates to a method of heating a pan by forcing gas or a gas/air mixture through a plurality of gas outlets in the direction of a cavity surrounded by said plurality of gas outlets, and then igniting the gas or the gas/air mixture when leaving the outlets.

Further details and advantages of the present invention will become clear to the reader 2 5 after reading the description of the embodiments described below with reference to the accompanying drawings, in which:

Figure 1 shows a perspective cut-away view of a pan placed on a gas hob according to an embodiment; 30 Figure 2 shows a cut-away side view of the embodiment of Figure 1 showing the pan placed on the gas hob;

Figure 3 shows a cross section of part of the gas hob of Figure 1;

Figure 4 shows a top view of the embodiment of Figures 1 and 2;

Figure 5 shows a schematic view of a gas hob according to an embodiment.

3

Figure 1 shows a perspective cut-away view of a pan 1 placed on a gas hob 2 according to an embodiment. The pan 1 is filled with a fluid 3 e.g. water. The gas hob 2 comprises a gas burner 4 having an inlet 5 and a plurality of outlets 6. In this embodiment the gas burner is integrated in a plate 7. Around the gas burner 4 underneath the pan 1, two rings 8, 9 are 5 arranged. In this embodiment the rings 8, 9 are arranged on the plate 7.

Figure 2 shows a cut-away side view of the embodiment of Figure 1 showing the pan 1 placed on the gas hob 2. The gas hob comprises a compartment 11 and a pre-heat compartment 12. The compartment 11 and the pre-heat compartment 12 are separated by a wall 13 in which some through holes are arranged to let the gas flow homogeneous into the pre-10 heat compartment 12.The pre-heat compartment is arranged underneath the gas outlets 6 so that heat coming from the flames will heat up the gas/air mixture before it flows out off the gas outlets 6. By preheating the gas/air mixture, the gas will be combusted in a more efficient and cleaner way.

In Figure 2 arrows show the flow of gas through the inlet 5, the compartment 11 and the 15 pre-heat compartment 12. Once combusted, the gas will form flames heating up the pan 1 and the fluid 3. The arrows between the gas hob 2 and the pan 1 indicate the heat flow. In this embodiment, two rings 8, 9 are arranged around the gas hob 2. The rings 8, 9 or other obstacles will form an obstacle for the heat before it can escape from underneath the pan 1. By obstructing the heat, a turbulence of heated air will be created which will result in a better heat 2 0 transfer to the pan 1. In this embodiment, the outer ring 8 comprises small extensions 15 for supporting the pan 1. The outer ring 8 thus functions both as a heat obstructer and as a pan support. The extensions 15 may be integrated into the ring 8 forming a single body made of e.g. iron or any other heat resistant material. It should be noted that the rings 8, 9 also cover the hot combustions gas from influences of cold air from outside the rings 8, 9.

2 5 Figure 3 shows a cross section of part of the gas hob 2. A top plate 16 transcends downward into a conical wall 18 in which a plurality of gas outlets 6 is arranged. Only four of them are shown. At the bottom the conical wall 18 is closed by a bottom plate 20. The conical wall 18 makes an angle a with the vertical. In the example of Figure 3 the angle a is about 45 degrees. In this way a cavity 22 is formed by the side wall 18 and the bottom plate 20. It should 3 0 be noted that the cavity 22 is a space which is open from above, and as such forms a tray or bin. The cavity 22 in this example is conical shaped because of the conical side wall 18, but it may have all sorts of forms depending on the shape of the side wall 18 and the presence and shape of the bottom plate 20. When leaving out the bottom plate 20, the side wall 18 may form a cone open from above but it may also be partly open at the bottom to form a sink connected 35 to a drain.

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The gas/air mixture is forced from the pre-heat compartment 12 through the plurality of gas outlets 6 in the direction of the cavity 22. Due to the inward direction of the outlets 6, the generated flames will be directed inward. Therefore the gas burner 2 of this invention is called an ‘inside burner’. Due to the inside orientations of the flames less cold outside air has to be 5 heated up which results in a higher flame temperature and a better and a more stable combustion. The inside burner 2 keeps the combustion in the centre under the pan 1, see Figure 2, and gives the heat gases more time to transfer the heat to the pan 1. By directing the flames inside, the heat is at first instance directed towards the centre of the bottom of the pan 1. Since the heat will be blocked by the bottom of the pan 1, it will be redirected toward the 10 periphery of the bottom of the pan 1, see arrows in Figure 2. The angle a between the wall 18 and a plane 24 which is defined by an upper opening of the conical wall 18 may have a value between 30 and 90 degrees, and more preferably between 40 and 50 degrees. The angle a between 40 and 50 degrees result in flames that are directed towards the centre of the bottom of the pan 1 but do not heat up the bottom plate 20 too much.

15 Figure 4 shows a top view of the embodiment of Figure 1 and 2. As can be seen from

Figure 4, the plate 20 is disc shaped. The outlets 6 are distributed substantially all over the wall 18. Many configurations are possible. For example outlets arranged in a number of concentric circles or randomly distributed. In the example of Figure 4, the outlets 6 are aligned in a radial way with lines of three outlets interchanged by lines of four outlets.

2 0 Seen from above, the conical side wall 18 looks circular. In other words, it is curved in one dimension, i.e. in the plane of the paper. Due to this curvature, the flames generated at the outlets 6 will converge. This convergence will improve the modulation range of the gas hob and will result in a better and more stable combustion and a higher flame temperature, which is an advantage. Other curvatures are possible such as oval shapes etcetera. Preferably, a distance 25 between adjacent gas outlets 6 is smaller than 3 mm. This will result in an effective flame even at low gas outlet ranges.

In an embodiment, the pan supporting means 8, 15 are arranged to space the bottom of the pan 1 relative to at least some of the outlets 6 at a distance smaller than 2 cm. Such a small distance will result in a better heat transfer as compared to the state of the art.

30 Figure 5 shows a schematic view of a gas hob 2 according to an embodiment. In Figure 5 gas premix tube 30 is positioned upstream of the inlet 5 of the gas hob 2. The gas-air mixture may be produced by means of a fan, not shown in Figure 5.

Air, see arrow 31 and gas, see arrow 32, are mixing before the mixture is entering the inlet 5. Although the invention is not limited to the use of premixing air with gas, the big 3 5 advantage of this pre-mixing is that the gas and the air can be mixed completely. As a result the combustion is more complete and a higher yield will be realized. Furthermore, by using the pre- 5 mixed burner technique, the distance between the pan 1 and the flames can be decreased.

Such a decrease in distance will result in a better heat transfer as was mentioned above.

Because the flames produced are pointed towards each other, a significant improvement of the modulation range of the burner is realized, besides a better and more stable combustion 5 and a higher flame temperature. Due to the inside position of the flames and to the pre-mixed system, no cold outside air has to be heated up which results in a higher flame temperature and a better heat transfer to the pan as well. The arising combustion gases will be forced to the bottom of the pan. Creating turbulence underneath the pan will increase the heat transfer.

In the above the term pan is used, but it should be noted that instead of a pan a pot or any 10 other cooking utensils may be heated to cook. The term pan is meant to embrace all those varieties of cooking utensils. Furthermore, it should be noted that the invention is not limited to a ring of outlets. The outlets may also be arranged in a square or triangle. Also, the gas outlets do not need to be arranged in a closed loop such as a circle, but may as well be arranged for example in groups which are distant from each other or in two opposed walls of a square 15 formed by four straight wall parts. So the terms ‘surrounding the cavity’ in the description above do not necessarily mean fully surrounding.

It is emphasized that the present invention can be varied in many ways, of which the alternative embodiments as presented are just a few examples. These different embodiments are hence non-limiting examples. The scope of the present invention, however, is only limited by 2 0 the subsequently following claims.

Claims (11)

Gas cooker for cooking, the gas cooker comprising: - a number of gas outlets surrounding a cavity; 5. gas supply means for controlling gas or a gas / air mixture through the gas outlets in the direction of the cavity. A gas hob according to claim 1, wherein the gas outlets are arranged in a wall which is curved in one dimension so that neighboring flames converge during use. 10 3. Gas hob as claimed in claim 2, wherein the wall has a substantially conical shape. 4. Gas hob as claimed in claim 3, wherein an angle α between the wall and a surface defined by an upper opening of the conical wall has a value of between 30 and 90 degrees, and more preferably between 40 and 50 degrees. Gas hob according to one or more of the preceding claims, wherein a distance between adjacent gas outlets is less than 3 mm. 20 Gas hob according to one or more of the preceding claims, wherein the gas hob comprises support means for supporting a pan, wherein the support means are adapted to keep a bottom of the pan at a distance from at least some of the gas outlets with a distance less than 2 cm. 25 7. Gas hob according to one or more of the preceding claims, wherein the gas hob comprises gas mixing means for premixing gas and air before the gas and air are sent through the gas outlets. A gas hob according to claim 7, wherein the gas mixing means comprises a premix chamber or a premix tube with a gas inlet and an air inlet. 9. Gas hob according to one or more of the preceding claims, wherein the gas hob comprises a preheating compartment arranged close to the gas outlets for preheating the air or the gas / air mixture before it reaches the gas outlets. Gas hob according to one or more of the preceding claims, wherein the gas hob comprises obstruction means for obstructing the heat that flows under a pan placed on the gas hob. A method for heating a pan, the method comprising: - directing gas or a gas / air mixture through a plurality of gas outlets in the direction of a cavity surrounded by the plurality of gas outlets; - igniting the gas or gas / air mixture when it leaves the outlets.