The invention relates to an injector device for a gas burner of a household appliance. The injector device has a tube portion through which gas flows during operation of the gas burner. A wall portion delimits the tube portion. The wall portion has an opening through which gas exits the injector device during operation of the gas burner. The invention further relates to a gas burner with such an injector device and to a household appliance with at least one gas burner.

It is difficult to design gas burners of household appliances such as gas cookers or gas stoves or such as gas ovens in a way that the gas which exits an injector device or injector nozzle mixes with a sufficient quantity of primary air, i.e. with air which is present around the gas stream exiting the injector device. This primary is entrained or carried along with the gas stream exiting the injector device such that a mixture of primary air and gas or fuel is obtained. It is also difficult to obtain a mixture of primary air and gas, which has a sufficient homogeneity. This is in particular valid, if the mixture of gas or fuel and primary air is obtained in reduced or limited spaces, for example under a top sheet of the household appliance.

This is a very common problem for gas burners that are equipped with injectors with a high power flow rate such as wok burners. The reduced or limited space mainly constrains the dimensions of mixing elements such as a venturi tube located downstream of the injector and a mixture spreader through which the mixture of gas and primary air flows before the mixture is ignited. As a consequence, the limited quantity of primary air which is entrained by the gas stream exiting the injector and the poor homogeneity of the mixture negatively affects the burner performance. The consequences can for example comprise an unbalanced flame or a large yellow-tipped flame due to a lack of oxygen when the gas is burned. Further, stability issues can occur as a consequence.

Document WO 2005/073630 A1 describes a gas burner suitable for use with a wok. Herein, a manifold of the gas burner has a plurality of injector nozzles which are arranged at equal distances from each other on an inner periphery of a cup member of the manifold.

This requires quite a lot of space and makes the design of the gas burner rather complex. It is therefore an object of the present invention to provide an injector device of the initially mentioned kind, which improves the mixing of gas exiting the injector device with air, and to provide a gas burner with such an injector device and a household appliance with such a gas burner.

This object is solved by the subject matter of the independent claims. Advantageous configurations with convenient further developments of the invention are specified in the dependent claims.

The injector device according to the invention for a gas burner of a household appliance has a tube portion through which gas flows during operation of the gas burner. The injector device further has a wall portion delimiting the tube portion. The wall portion has at least two openings through which gas exits the injector device during operation of the gas burner. The at least two openings are configured to divide a single gas stream flowing through the tube portion during operation of the gas burner into separated gas streams. As the bulk gas stream flowing through the tube portion is divided into the separated, partial gas streams or gas jets, each one of the gas streams entrains air from the respective surroundings of the partial gas stream. Accordingly, a particularly large quantity of air is entrained by the gas streams exiting the injector device. As a consequence more air can be mixed with the gas within a limited space. Therefore, the mixing of the gas exiting the injector device with the air surrounding the gas streams is improved.

In particular, an increased inlet of primary air is achieved, as a particularly large quantity of air is entrained by the separated gas streams. And even in comparatively small or reduced spaces the mixture containing the gas and the primary air is very homogenous. Since the mixture is more homogenous the combustion is improved. In particular, the homogeneity of the mixture prior to leaving a burner body or mixture spreader of the gas burner is improved. This also leads to reduced emissions of pollutant greenhouse gases. Finally, a particularly large diversity of gas burner designs can be realized as the burner design is less constrained by space requirements.

Preferably, the at least two openings are configured such that the separated gas streams entrain a larger quantity of air surrounding the gas streams than a single gas stream having the same flow rate as the at least two gas streams together. In other words, dividing the single gas stream flowing through the tube portion into the plurality of gas streams or gas jets having the same fluid properties and velocity magnitudes will lead to gas streams with a reduced gas flow rate of each one of the separated gas streams. Because of the reduced quantities of the gas flow of each gas stream or gas jet the gas streams will be thinner, and their speeds will be reduced as the gas is mixed with the air surrounding the individual gas stream. Every gas stream or gas jet entrains the surrounding, stagnant fluid in the form of the (primary) air surrounding the gas streams. This increases the global or total air-entrainment capacity of the injector device during the operation of the gas burner. Thus, the above-mentioned advantages are further enhanced.

Preferably, the wall portion is configured as a top plate of the injector device. Consequently, the single gas stream flowing through the tube portion can be particularly well divided into the separated gas streams.

Preferably, the tube portion comprises an inlet section provided by a pipe member of the injector device and an end section provided by a second member, in particular by a hat-shaped member, connected to the pipe member in a detachable manner. This allows to configure or equip the injector device with a specific second member having a desired number, shape and distribution of openings or perforations in the wall portion. Thus, the number, shape and distribution of the openings leading to the formation of the separated gas streams can be readily adapted to the specific boundary conditions of the gas burner.

For example, the cross-sectional area of the at least two openings and/or the number of the openings and/or the shape of the openings and/or the distribution of the openings in the wall portion can be adapted to the specific conditions of the gas burner to achieve optimum results with respect to the entrainment of air and to the mixing of gas with the air or primary air. To achieve this, it is sufficient to detach the second member, in particular hat-shaped member, and to replace the second member by another second member, in particular hat-shaped member, which has adapted openings.

Preferably, the hat-shaped member has a flange portion which abuts on an end face of the pipe member. Thus, a very smooth transition between the inlet section and the end section is provided, which facilitates the flow of the single gas stream through the tube portion. Further, this facilitates mounting the hat-shaped member onto the pipe member.

Preferably, the hat-shaped member is detachably fixed to the pipe member by means of a holding element. Thus, a very tight connection between the hat-shaped member and the pipe member is achieved. The holding element can in particular have an internal thread which is in engagement with an external thread provided on an outer surface of the pipe member. In such a configuration screwing the holding element onto the pipe member securely fixes the hat-shaped member to the pipe member. Consequently, the hat-shaped member can also be readily detached by unscrewing the holding element from the pipe member.

The at least two openings can have the same shapes or different shapes. In a very simple configuration the at least two openings can have a round shape. Alternatively or additionally, the shape of the at least two openings can be rectangular and/or square and/or triangular. Further, the at least two openings can have a star-like shape. Such a shape leads to a rather large contact zone between the gas stream or fuel jet and the surrounding air. This is also valid for other polygonal shapes of the openings.

Also, a double coned shape of the at least two openings produces a particularly high entrainment of the surrounding air and therefore enhances the mixing of the gas with the air. Further, the openings or perforations can have an arched shape. The dimensions and/or the shape and/or the number of the holes or openings in the wall portion can be readily adapted to the requirements, in particular space requirements, of the gas burner to be equipped with the injector device.

The gas burner according to the invention has at least one injector device according to the invention. The at least one injector device is preferably arranged downstream of a venturi device of the gas burner. The venturi device is configured to entrain primary air from the surroundings of the injector device into a mixing zone of the gas burner. From this mixing zone a mixture of gas with the air can exit a mixture spreader of the gas burner towards the surroundings of the mixture spreader. Here the mixture is mixed with further, secondary air, and the mixture is ignited. In such a gas burner the mixing of gas exiting the at least one injector device with primary air is improved.

The household appliance according to the invention has at least one gas burner according to the invention. Preferably, the at least one injector device is arranged below a top sheet of the household appliance. The household appliance can in particular be a gas stove or gas cooker or a gas oven. The gas burner can in particular be configured as a wok burner. The advantages and preferred embodiments described with respect to the injector device according to the invention also apply to the gas burner according to the invention and to the household appliance according to the invention and vice versa.

The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of figures and/or shown in the figures alone are usable not only in the respectively specified combination, but also in other combinations or alone, without departing from the scope of the invention. Thus, implementations are also to be considered as encompassed and disclosed by the invention, which are not explicitly shown in the figures or explained, but arise from and can be generated by separated feature combinations from the explained implementations.

Therefore also embodiments and feature combinations shall be considered as disclosed, which do not have all the features of an originally formulated independent claim. Moreover, implementations and feature combinations are to be considered as disclosed, in particular by the implementations set out above, which extend beyond or deviate from the feature combinations set out in the relations of the claims.

Further advantages, features and details of the invention are apparent from the claims, the following description of preferred embodiments as well as based on the drawings in which features having analogous functions are designated with the same reference signs. Therein show:

Fig. 1 schematically a partial section view of a household appliance configured as a gas stove, wherein a gas burner of the gas stove has an injector device or injector nozzle with a plurality of holes or openings in a top plate of the injector nozzle;

Fig. 2 schematically an enlarged view of separated gas streams or gas jets exiting the injector nozzle, wherein the gas streams entrain air surrounding the gas streams into a venturi tube of the gas burner;

Fig. 3 a perspective section view of an example of the injector nozzle;

Fig. 4 a section view of the injector nozzle shown in Fig. 3; Fig. 5 a top view of the injector nozzle with one possible shape of the openings or holes provided in the top plate of the injector nozzle;

Fig. 6 a top view of the injector nozzle with another possible shape of the openings or holes provided in the top plate of the injector nozzle

Fig. 7 a top view of the injector nozzle with a further possible shape of the openings or holes provided in the top plate of the injector nozzle

Fig. 8 a top view of the injector nozzle with a further possible shape of the openings or holes provided in the top plate of the injector nozzle

Fig. 9 a top view of the injector nozzle with still another possible shape of the openings or holes provided in the top plate of the injector nozzle; and

Fig. 10 schematically the gas stove according to Fig. 1 , which has a plurality of gas burners.

The indications “upper", “lower", “top", “front”, “bottom”, “floor”, “horizontal”, “vertical”, “depth direction”,“width direction”,“height direction” and the like refer to the positions and orientations of the device or appliance in its intended use position with respect to an observer located in front of the device and regarding towards the device or appliance.

Fig. 1 schematically shows a section view of an upper part of a household appliance configured as a gas stove 1 which is further shown in Fig. 10. The gas stove 1 has a plurality of gas burners 2 which are also schematically indicated in Fig. 10.

As can be seen from Fig. 1 , the gas burner 2 which is partially shown in the section view in Fig. 1 , comprises an injector device or injector nozzle 3 which is arranged below a top plate or top sheet 4 of the gas stove 1 . The top sheet 4 can be a metal sheet. In a variant, the top sheet 4 can be made from glass. Supports 5 (see Fig. 10) for supporting a frying pan or a saucepan 6 are arranged on top of the top sheet 4, such that a bottom 7 of the saucepan 6 is arranged at a certain height 8 above the top sheet 4 and above the gas burner 2. An injector holder 9 holds the injector nozzle 3 and has air inlets 10 which allow primary air 1 1 to be mixed with gas 12 exiting the injector nozzle 3 during operation of the gas burner 2. The primary air 1 1 is illustrated by curved arrows in Fig. 1 , and the gas 12 flowing through the injector nozzle 3 is illustrated by straight arrows in Fig. 1. As the gas 12 exits the injector nozzle 3 the gas 12 entrains primary air 11 into a venturi tube 13 of the gas burner 2. The primary air 1 1 enters the venturi tube 13 through the air inlets 10.

The venturi tube 13 is provided by a base part 14 of a mixture spreader 15 of the gas burner 2. The mixture spreader 15 further comprises a cap 16 located on top of the base part 14. In a manner known as such the cap 16 has a plurality of outlets along its periphery, such that the mixture of the primary air 1 1 and the gas 12 leaves the mixture spreader 15 in radial direction during operation of the gas burner 2. A flow of the mixture towards these outlets is indicated by further arrows 17 in Fig. 1.

When the mixture of the primary air 11 and the gas 12 leaves the mixture spreader 15, the mixture is further mixed with secondary air 18 which is illustrated in Fig. 1 by further arrows. The combustion of the mixture takes place, when the mixture leaves the mixture spreader 15, wherein the mixture is further mixed with the secondary air 18. Accordingly, a flame 19 is schematically shown in Fig. 1 , which entrains the secondary air 18.

The fuel or gas 12 needs an exact (stoichiometric) quantity of air to be fully burned. To achieve this, the gas 12 is in in the first instance premixed with the primary air 1 1. The primary air entrainment is caused by fuel jets or gas streams 23 (see Fig. 2) in the area surrounding the injector nozzle 3 and the venturi tube 13.

However, it is difficult to get a sufficient quantity of primary air 1 1 and a sufficient homogeneity in the mixture of primary air 1 1 and gas 12 or fuel in the area of the venturi tube 13. This is mainly due to the limited space available below the top sheet 4. This can negatively affect the performance of the gas burner 2 with the result that the flames 19 around the mixture spreader 15 or burner body may be unbalanced, yellow tipped and not stable. Such problems are avoided by the utilization of the injector nozzle 3 shown in Fig. 1 , which will be described in more detail in the following.

As can be better seen from Fig. 2 the injector nozzle 3 has a tube portion 20 through which the gas 12 flows during operation of the gas burner 2. A wall portion which is configured as a top plate 21 of the injector nozzle 3 has at least two openings 22, as can also be well seen from Fig. 3. The gas 12 flowing through the tube portion 20 during operation of the gas burner 2 is indicated by straight arrows in Fig. 2 and Fig. 3. The openings 22 or holes are configured to divide a single gas stream flowing through the tube portion 20 into separated gas streams 23 leaving the injector nozzle 3 through the openings 22.

In the schematic illustration of Fig. 2 the injector nozzle 3 is shown to have two openings 22 or holes. However, the injector nozzle 3 may have as many holes or openings 22 as is considered necessary for a specific gas burner 2 or for the specific power rate or flow rate of the gas 12 being fed into the injector nozzle 3 of the gas burner 2. For example, depending on the type of gas 12 fed into the injector nozzle 3, i.e. depending on the type of gas 12 utilized, different flow rates and/or different pressures may exist. For example, methane is provided in Europe at a pressure of 20 mbar, and butane can be provided at 29 mbar or 50 mbar depending on the country. The injector nozzle 3 is configured to work with these types of pressures and these types of fuels or gases 12.

However, the arrangement and/or number and/or shape of the openings 22 provided in the top plate 21 is preferably adapted in order to divide the gas 12 flowing through the tube portion 20 into several gas streams 23 or gas jets, in particular dependent on the type of gas 12 utilized and/or the pressure of the gas 12 fed into the injector nozzle 3.

If the single stream of gas 12 flowing through the tube portion 20 is divided into, for example, the two gas streams 23 shown in Fig. 2, these gas streams 23 can have the same fluid properties and velocity magnitudes but a lower flow rate than the single gas stream. Thus, every gas stream 23 will entrain the stagnant primary air 1 1 surrounding each one of the gas streams 23. Dividing the single gas stream flowing through the tube portion 20 into the separated gas streams 23 therefore leads to an increase of the overall air entrainment capacity of the injector nozzle 3.

This is based on the finding that the quantity of primary air 1 1 which is sucked into the venturi tube 13 depends directly on the power rate of the injector nozzle 3. Dividing the gas stream flowing through the tube portion 20 into the plurality of gas streams 23 exiting the injector nozzle 3 divides the total power rate and thus increases the amount of primary air 1 1 entrained by the gas streams 23. This increases the capacity of the injector nozzle 3 to carry along primary air 1 1 surrounding the individual gas streams 23. The gas streams 23 are thinner than a single gas stream which would leave the injector nozzle 3 through a central, single hole of the same cross-sectional area as the sum of the cross-sectional areas of the openings 22. Therefore, the thinner gas streams 23 reduce their speed as the gas and the primary air 1 1 is mixed in the area below the venturi tube 13 and within the venturi tube 13. Consequently, even in a particularly reduced space for the venturi tube 13 a larger quantity of primary air 1 1 can be introduced into the mixture containing the gas 12 and the primary air 11. Further, the homogeneity of the mixture is improved prior to leaving the burner body or mixture spreader 15.

The shape and/or number and/or arrangement of the openings 22 provided in the injector nozzle 3 is preferably adapted to the type of gas 12 utilized and to the power rate or pressure with which the gas 12 is provided to the injector nozzle 3. For example, the heat value of the gas 12 (i.e. the energy per mass unit or volume unit) can be taken into account for calculating the total cross-sectional area of the holes or openings 22 to be provided in the top plate 21 of the injector nozzle 3. In general, the larger the number of the holes or perforations or openings 22 in the wall portion, in particular in the top plate 21 of the injector nozzle 3 is, the better is the capacity of the injector nozzle 3 to carry along primary air 1 1 , provided that the openings 22 are sufficiently spaced apart from each other to create the separated gas streams 23.

As can be well seen from Fig. 3, for example, the gas 12 which is fed into the tube portion 20 with overpressure first flows through an inlet section of the tube portion 20, which is provided by a pipe member 24. An end section of the tube portion 20 is provided by a hat-shaped member 25 which is connected to the pipe member 24 in a detachable manner. The hat-shaped member 25 has a flange portion 26 which is pressed against an end face 27 of the pipe member 24. To achieve this, a holding element 28 which has an internal thread is screwed onto the pipe member 24 which has an external thread provided on an outer surface 29 of the pipe member 24.

As can be seen from Fig. 5, for example, the holding element 28 can have a hexagon shape to facilitate screwing the holding member 28 onto the pipe member 24. By detaching the hat shaped member 25 from the pipe member 24 this part of the injector nozzle 3 can be easily changed, for example, depending on the type and/or pressure of gas 12 utilized in the gas burner 2 and/or depending on the desired air entrainment capacity of the injector nozzle 3. Openings 22 or holes of variable diameters, variable number, variable arrangements and variable shapes can therefore be provided by fixing the appropriate hat-shaped member 25 to the pipe member 24.

Possible shapes of the openings 22 are exemplarily shown in Fig. 6 to Fig. 9. For example, according to Fig. 6, the openings 22 can be configured as elongated slots, which are parallel to each other. Other square and/or rectangular shapes of the openings 22 are also possible.

As can be seen from Fig. 7, the openings 22 can also have a double coned shape such that a boundary of the openings 22 is not rectangular but has inwardly projecting triangles 33 at opposite sides of each one of the openings 22. These triangles 33 modify the generally square hole shape of the openings 22 shown in Fig. 7. This increases the length of the boundary of the opening 22 compared to a square shaped opening 22. Thus, there is a larger contact area between the gas stream 23 exiting the opening 22 and the primary air 1 1 which surrounds each one of the gas streams 23. This leads to a higher entrainment of primary air 1 1.

Such a rather long boundary of the opening 22 can also be achieved by a star-like shape of the openings 22 and/or a polygonal shape of the openings 22, wherein the star-like shape is exemplarily shown in Fig. 8.

Finally, Fig. 9 shows yet another shape of the openings 22. Accordingly, the openings 22 can also have an arched shape. However, other shapes, dimensions, and arrangements of the openings 22 provided in the wall portion or top plate 21 of the injector nozzle 3 can be provided in order to promote a good mixing of the gas 12 with the primary air 11.

As can be seen from Fig. 10, the gas stove 1 usually has operating elements 30 for operating the gas burners 2, which can be arranged in an upper part of an oven front 31 of the gas stove 1. Further, the gas stove 1 can have a cooking chamber 32 which may also be heated by gas.

LIST OF REFERENCE SIGNS

1 gas stove

2 gas burner

3 injector nozzle

4 top sheet

5 support

6 saucepan

7 bottom

8 height

9 injector holder

10 air inlet

1 1 primary air

12 gas

13 venturi tube

14 base part

15 mixture spreader

16 cap

17 arrow

18 arrow

19 flame

20 tube portion

21 top plate

22 opening

23 gas stream

24 pipe member

25 hat-shaped member

26 flange portion

27 end face

28 holding element

29 surface

30 operating element

31 oven front

32 cooking chamber

33 triangle