Cooking appliance for cooking on wood

Abstract

Cooking appliance (1) for cooking on wood, comprising: - a housing (50) having a housing base (51) and one or more housing side walls (52), wherein the housing base (51) has an opening (53); - a combustion chamber (10) arranged within the housing (50) and having a combustion chamber base (12) and one or more side walls of the combustion chamber (15), wherein the side walls of the combustion chamber (15) comprise, in an upper region, a number of air inlets (11) designed to suck air into the combustion chamber (10), - an intermediate space (20) arranged between the housing (50) and the combustion chamber (10); - an air distribution chamber (70) located within the housing and below the combustion chamber (10), the air distribution chamber (70) being in open communication with the intermediate chamber (20); - a mechanical fan (30) arranged beneath the housing and designed to generate an air flow through the opening in the housing base through the air distribution space to the intermediate space, wherein the combustion chamber base (12) has a number of air inlets (13) for drawing air from the air distribution chamber (70) into the combustion chamber (10), and wherein the side walls of the combustion chamber (15) have, in a lower region, a number of openings (14) designed for the discharge of wood gas from the combustion chamber (10) into the intermediate space (20), at least during use, wherein the combustion chamber (10) is box-shaped, and wherein the side walls of the combustion chamber (15) are rectangular and the housing side walls (52) are rectangular.

Description

[0001] The invention relates to a cooking appliance. The cooking appliance is designed for cooking with wood, such as wood pellets.

[0002] Cooking appliances for cooking with wood are known, among other things, from patent publication WO2016075646A1. This publication describes a cooking appliance with a housing consisting of a housing base and one or more housing side walls, wherein the housing base has an opening. A combustion chamber is arranged in the housing and comprises a combustion chamber base and one or more combustion chamber side walls, wherein the combustion chamber side walls comprise, in an upper region, a number of air inlets for the intake of air into the combustion chamber. Also in the housing, next to the combustion chamber, there is a space. In addition, an air distribution space has been created within the housing and beneath the combustion chamber. This air distribution space is in open communication with the intermediate space. A mechanical fan is constructed beneath the housing to generate an air flow through the opening in the housing base, through the air distribution space, and into the intermediate space.

[0003] The device of WO2016075646A1 can be filled with suitable biomass material such as wood pellets. After the fire has been lit, the fan can be switched on. The fan is adjustable and initially sets a low speed until the lower flame is hot and pyrolysis takes place. When the wood pellets begin to burn, a flaming pyrolysis front forms, which burns from top to bottom. The cooker therefore operates as a so-called Top Lit Up Draft (TLUD) cooker, in which the fuel contained in the combustion chamber burns from top to bottom during use. In the center of the combustion chamber is a special tube that is open from below. The tube contains a series of holes in a lower section and also in an upper section, see Fig. 10 of the publication. The holes are intended for air supply to the combustion chamber.

[0004] The fan directs the air to the housing and enters the cavity through the central hole in the housing. The air also enters the central tube and flows upwards into the combustion chamber. The air enters the combustion chamber through the duct and the first openings in the lower air intake area.

[0005] The hot air that has flowed through the central tube also enters the combustion chamber at the top through partially sealed slots in an air intake zone between the intermediate space and the combustion chamber. In addition, hot air rising through the tube enters the combustion chamber through the second row of openings at the top of the tube in the upper air intake zone.

[0006] The TLUD unit uses the limited oxygen from the lower air intake zone to pyrolyze the wood pellets and release volatile components such as combustible gases and tar from the wood, collectively known as wood gases. The forced airflow helps release the wood gases from the wood pellets. The wood gases are drawn upward by the fan, where they mix with the hot air inside the cabinet, which enters the combustion chamber through the upper air intake zone and from the intermediate space. The hot air and the gases are mixed depending on the pressure of the air entering the combustion chamber.

[0007] Due to the presence of the central tube in the device of WO2016075646A1, the construction is relatively complex. This is partly due to the special base of the tube, as shown in Fig. 10 of the publication. It should also be noted that with this design, the wood gases are directed upward through the combustion chamber, where they mix with the air from the other ducts. This solution causes the space filled with wood gas to increase as the wood pellets burn. This makes optimal mixing of wood gas and fresh air more difficult, resulting in a suboptimal combustion process at the top of the combustion chamber.

[0008] Patent publication WO2017202853A1 describes a cooking appliance for wood-fired cooking in which both the combustion chamber and the housing surrounding it are cylindrical. Such a construction is not easily available from a manufacturer as a kit and must therefore always be delivered assembled.

[0009] It is a purpose of the present invention to provide a cooker that solves at least one of the problems of existing technology.

[0010] This goal is achieved with a cooking appliance for cooking on wood, comprising: - a housing having a housing base and one or more housing side walls, wherein the housing base has an opening; - a combustion chamber arranged within the housing and having a combustion chamber floor and one or more combustion chamber side walls, wherein the side walls of the combustion chamber have, in an upper region, a number of air inlets designed to draw air into the combustion chamber; - a space arranged between the housing and the combustion chamber; - an air distribution chamber located within the housing and below the combustion chamber, the air distribution chamber being in open communication with the intermediate chamber; - a mechanical fan arranged beneath the casing and for generating an air flow through the opening in the casing base through the air distribution space to the intermediate space, wherein the combustion chamber base has a number of air inlets for drawing air from the air distribution chamber into the combustion chamber, and wherein the side walls of the combustion chamber have, in a lower region, a number of openings designed for the discharge of wood gas from the combustion chamber into the intermediate space, at least during use, where the combustion chamber is box-shaped, where the side walls of the combustion chamber are rectangular, and where the casing side walls are rectangular.

[0011] By piercing holes in the lower section of the side walls of the combustion chamber, the upward airflow in the space between them, due to the "Venturi effect," draws some of the wood gas from the combustion chamber through the lower row of holes. This allows the wood gas to enter the room, where it mixes with the air flowing from the distribution chamber through the room. The mixture of wood gas and air then flows through the upper row of holes into the combustion chamber. Combustion takes place immediately afterwards. This continues until all the wood pellets are consumed. This design allows for better mixing of wood gas and air, producing a better and warmer flame. Furthermore, it has been proven that an adjustable fan is no longer necessary.

[0012] It has been found that at the end of a cooking cycle, there is often less than 1% ash residue remaining (as a percentage of the initial weight of the fuel batch).

[0013] Because the combustion chamber is box-shaped and its side walls are rectangular, it's relatively easy to assemble, for example, as a kit. This also applies to the rectangular housing side walls.

[0014] In one embodiment, the air inlets in the combustion chamber floor are holes with a diameter of less than or equal to 4 mm. Such small dimensions allow the combustion chamber to be supplied with limited oxygen, allowing the desired pyrolysis to take place.

[0015] In one embodiment, the air inlets in the combustion chamber floor cover a total area in the range of 1%–2.5% of the total area of ​​the combustion chamber floor. These percentages have produced good results in prototype testing.

[0016] In one embodiment, the openings in the lower region of the combustion chamber's side walls are holes with a diameter in the range of 2-3 mm. The openings in the upper region of the combustion chamber's side walls are preferably larger than those in the lower region. In one embodiment, the openings in the upper region are holes with a diameter between 3-4 mm. Other dimensions are conceivable.

[0017] In one embodiment, the cooker comprises a control plate mounted in the air distribution area, the control plate having a central opening. This control plate stabilizes the airflow of the fan. The control plate ensures optimal distribution of the air drawn in by the fan via the holes in the base plate and the holes in the side walls of the combustion chamber.

[0018] In one embodiment, the cooker comprises a shielding plate arranged in the air distribution space and positioned directly above the opening of the housing bottom so that the mechanical fan is shielded from the heat of the combustion chamber.

[0019] In one version, the mechanical fan is designed to produce an air flow in the range of 0.008 - 0.016 m 3 / s. These values, combined with specially selected dimensions, ensured good pellet combustion with little or no soot formation.

[0020] As a design feature, the side walls are provided with bulges that can be inserted into recesses in other walls. These bulges are L-shaped, allowing them to be hooked into a recess in another wall. Please note that the combustion chamber can also be mounted in a similar manner if the combustion chamber walls also have the aforementioned bulges and recesses.

[0021] In one embodiment, the combustion chamber floor, combustion chamber side walls, and housing side walls are made of stainless steel. Stainless steel is strong, relatively lightweight, and non-flammable. Stainless steel is also easy to process as sheet material.

[0022] In one embodiment, the stove includes a jacket arranged around the housing. A jacket around the stove's housing protects the housing but also insulates it. This makes the stove less hot on the outside during use and also allows for more effective combustion.

[0023] Insulating material can be applied between the jacket and the housing, providing increased insulation.

[0024] These and other aspects of the invention will become apparent from and be explained on the basis of the embodiments described below with reference to the accompanying drawings, in which: Fig. 1 is an isometric view of a cooking appliance according to an embodiment of the invention; Fig. 2 a plan view of the cooking appliance of the embodiment of Fig. 1; Fig. 3 a broken side view of the cooking appliance on the line AA of Fig. 2; Fig. 4 a side view of the embodiment of the cooking appliance from Fig. 1, and Fig. Figure 5 shows a broken plan view of the embodiment of the Fig. 4 on the cut BB.

[0025] Fig. Figure 1 shows an isometric view of a cooking appliance 1 according to an embodiment of the invention. The cooking appliance 1 comprises a number of side plates 2, 3, a top plate 43, and a bottom plate 44. The cooking appliance 1 also comprises a number of feet 4, 5 mounted beneath the base plate 44. On the top plate 43 is a cooking burner, which consists, among other things, of a grid 7 supported by a number of grid supports 8. In this embodiment, four additional supports 9 have been installed at the corners of the grid 7. In the top plate 43, a number of openings 6 have been provided, which are designed to receive an extension from the side plates 2, 3. In the center of the top plate 43 is an opening for access to a combustion chamber 10. Figure 1 also shows a number of air inlets 11 in the side walls of the combustion chamber 10. The function of these air inlets 11 will be explained below.

[0026] Fig. 2 shows a plan view of the cooking appliance 1 of the version of Fig. 1. This top view shows the bottom wall 12 of the combustion chamber 10. The bottom wall 12 of the combustion chamber 10 has a number of air inlets 13. In this example, the air inlets 13 are round holes. In one version, the diameter of these holes is less than or equal to 4 mm. Please note that the holes can also have other shapes than round, such as oval, rectangular, or star-shaped. This also applies to the holes mentioned below.

[0027] Fig. Figure 3 shows a broken side view of the cooker 1 on the line AA of Fig. 2. 3 shows the side panels 3, which as such form a shell 60. Within the shell 60, a housing 50 has been arranged, comprising a housing base 51 and a plurality of housing side walls 52. In this example, the housing base 51 is formed by a portion of the base plate 44. The housing base 51 contains an opening 53. The insulating material 61 (see double shading) can be arranged between the shell 60 and the housing 50 so that the interior of the cooker is sufficiently insulated from the outside world. This also reduces the risk of burns for users who may touch the side of the cooker during use.

[0028] Fig. 3 shows the combustion chamber 10 already mentioned in more detail. In addition to the combustion chamber floor 12, the combustion chamber 10 also has a plurality of combustion chamber side walls 15, wherein the combustion chamber side walls 15 have a number of air inlets in an upper region, see 11, for the air entry into the combustion chamber 10.

[0029] The cooker 1 also includes a space 20 between the housing 50 and the combustion chamber 10. In this embodiment, the space 20 consists of an air duct with an inner wall formed by the side walls of the combustion chamber 10 and an outer wall formed by the side walls 52 of the housing 50.

[0030] Furthermore, the cooker 1 comprises an air distribution chamber 70, which is arranged within the housing 50 and below the combustion chamber 10. This air distribution chamber 70 is in open communication with the intermediate space 20.

[0031] In this embodiment, the cooker 1 consists of four threaded rods 19 which, together with a number of nuts, are designed to connect the various horizontally aligned plates, such as the upper plate 43, the lower plate 44 and the combustion chamber floor 12.

[0032] A mechanical fan 30 is arranged beneath the housing 50 and is designed to generate an airflow through the opening 53 of the housing base 51, through the air distribution chamber 70, and then to the intermediate space 20. Note that the space 20 is closed at the top by the upper plate 43. The mechanically forced airflow therefore exits the intermediate space 20 again via the air inlets 11 in the upper region of the combustion chamber side walls.

[0033] The combustion chamber floor 12 also includes a series of air inlets, see inlets 13. These inlets are designed to draw fresh air from the air distribution chamber 70 into the combustion chamber 10. A number of openings 14 are arranged in a lower area of ​​the combustion chamber side walls 15 for the discharge of wood gas from the combustion chamber 10 into the space between 20. The operation of the stove 1 will now be described in more detail below.

[0034] The oven 1 is particularly suitable for cooking with wood pellets. Alternatively, wood chips can also be used. The combustion chamber 10 can be filled with wood pellets from above. Preferably, the chamber 10 is filled with pellets (see shading) to approximately 2 cm below the upper row of holes 11 of the combustion chamber 10, see also dashed line 16. This ensures that the filling is as complete as possible, while the openings 11 are not blocked by the wood pellets. In the meantime or afterward, the user activates the fan to create a forced airflow through the cooking appliance 1. The wood pellets are then ignited, for example, with a firelighter, after which combustion begins. The airflow generated by the fan 30, which flows through the gap 20, is heated and passes through the upper row of holes 11 of the combustion chamber 10 into the upper part of the combustion chamber 10.

[0035] The fan is mounted on the base plate 44 and directs the air into the cooking appliance. Directly below the bottom of the combustion chamber is a plate 41 provided with a concentric round hole 18. The shielding plate 42 is mounted between the control plate 41 and the fan 30 and, in this design, has a round shape. The function of the shielding plate 42 is to protect the fan 30 from overheating in the combustion chamber. Furthermore, the shielding plate 42 ensures the distribution of the turbulent airflow generated by the fan 30, so that the airflow flows evenly into the intermediate space 20.

[0036] The control plate 41 regulates the air flow into the lower part of the combustion chamber 10 through the holes 13 in the floor of the combustion chamber 10. The air flow into the combustion chamber is further limited / determined by the diameter of the holes 13 and their number. In one design, the air inlets 13 in the combustion chamber floor 12 cover a total area in the range of 1% - 2.5% of the total area of ​​the combustion chamber floor 12. An appropriately selected, relatively small air flow through the holes 13 causes incomplete combustion (also called pyrolysis) of the wood pellets at the floor of the combustion chamber 10, which leads to the formation of wood gas. The holes 13 also ensure a longer glow time for the charcoal at the floor of the combustion chamber after all the wood pellets have been burned. This leads to a longer cooking time.

[0037] The upward air flow in the space 20 will, due to the “Venturi effect”, draw part of the wood gas from the combustion chamber 10 through the lower row of holes 14 of the combustion chamber (see dashed lines 80 in Fig. 3), so that the wood gas enters the intermediate space 20. The wood gas flows into the upper part of the room along with the upward air flow in space 20. The mixture of wood gas and air then flows through the top row of holes 11 into the combustion chamber 10. Combustion takes place immediately afterwards. This continues until all wood pellets are consumed.

[0038] The downward flow of wood gas through the wood pellets in the combustion chamber 10 ensures that the wood gas is preheated. The wood gas is then mixed with the air in the room 20. The preheating and thorough mixing ensure better combustion with fewer soot particles and fewer harmful gases due to incomplete combustion of the wood gas. The jacket 60 on the outside ensures that the air-wood-gas mixture cools down as little as possible. The higher the temperature of the air-wood-gas mixture, the better the combustion. The insulation 61 also ensures a longer effective cooking time.

[0039] Fig. 4 shows a side view of the design of the cooking appliance in Fig. 1. In this design, the shell 60 and the housing (not visible in Figure 4) are box-shaped. This design allows for the use of flat plates, such as flat stainless steel plates. Such a furnace can be easily assembled by the user as a kit.

[0040] Such a cooker can have different sizes. Practical dimensions for the width b1 are in the range of 15 cm - 20 cm, but other dimensions are also conceivable. Practical dimensions for the height h1 are in the range of 20 cm - 30 cm, but other dimensions are also conceivable. Fig. 4 also shows a line BB in which a cross section for the creation of Fig. 5 was created.

[0041] Fig. Figure 5 shows a broken plan view of the embodiment of the Fig. 4 on the cut BB. Fig.Figure 5 clearly shows the combustion chamber floor 12 of the combustion chamber 10. The combustion chamber floor 12 is formed by a base plate 12', which is attached to the threaded rods 19 at four corners with nuts. In this example, the holes 13 in the floor of the combustion chamber 12 are arranged in a grid, with one centrally located inward within a square of other holes. This configuration provided good results during prototype testing.

[0042] The mechanical fan can be a non-adjustable fan with a preset flow rate. In one version, the mechanical fan is designed to generate an airflow in the range of 0.008 - 0.016 m3 / s. These values, combined with specially selected dimensions, ensure good pellet combustion with little or no soot formation.

[0043] It should be noted that the fan is also an adjustable fan, where the user can control the ventilation to achieve optimal results.

[0044] The stove according to the invention is easy to operate and very economical in fuel consumption. During combustion, hardly any smoke or harmful combustion gases are released. In one embodiment, the stove consists of flat stainless steel plates and is therefore easy to manufacture and assemble. As a kit, it can be transported inexpensively due to its compact volume (plates).

[0045] Please note that the stove can also be filled with wood chips instead of wood pellets. In this case, too, appropriate mechanical ventilation ensures a downward flow of the wood gas through the combustion chamber, achieving optimal mixing of air and wood gas.

[0046] The present invention is described above based on a number of versions, as shown in the drawings. Modifications and alternative implementations of some parts or elements are possible and fall within the scope of protection as defined in the attached conclusions. It should be noted that the above embodiments only illustrate and do not limit the invention, and that a person skilled in the art will be able to design many alternative embodiments. In the conclusions, reference points in parentheses should not be interpreted as limiting the claim. The use of the verb "include" and its conjugations does not exclude the presence of elements or steps other than those recited in a claim. The article "a" preceded by an element does not exclude the presence of multiple such elements.The mere fact that certain features are mentioned in different dependent conclusions does not mean that a combination of these measures cannot be used to advantage. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2016075646A1 [0002, 0003, 0007] WO 2017202853A1

[0008]

Claims

[1] Cooking appliance (1) for cooking on wood, comprising: - a housing (50) having a housing base (51) and one or more housing side walls (52), wherein the housing base (51) has an opening (53); - a combustion chamber (10) arranged within the housing (50) and having a combustion chamber base (12) and one or more side walls of the combustion chamber (15), wherein the side walls of the combustion chamber (15) comprise, in an upper region, a number of air inlets (11) designed to suck air into the combustion chamber (10), - an intermediate space (20) arranged between the housing (50) and the combustion chamber (10); - an air distribution chamber (70) located within the housing and below the combustion chamber (10), the air distribution chamber (70) being in open communication with the intermediate chamber (20); - a mechanical fan (30) arranged beneath the housing and designed to generate an air flow through the opening in the housing base through the air distribution space to the intermediate space, wherein the combustion chamber base (12) has a number of air inlets (13) for drawing air from the air distribution chamber (70) into the combustion chamber (10), and wherein the side walls of the combustion chamber (15) have, in a lower region, a number of openings (14) designed for the discharge of wood gas from the combustion chamber (10) into the intermediate space (20), at least during use, wherein the combustion chamber (10) is box-shaped, and wherein the side walls of the combustion chamber (15) are rectangular and the housing side walls (52) are rectangular. [2] Cooking appliance according to claim 1, wherein the air inlets (13) in the bottom of the combustion chamber base (12) are holes with a diameter of at most 4 mm. [3] Cooking appliance according to claim 1 or 2, wherein the air inlets (13) in the combustion chamber floor (12) cover a total area in the range of 1% - 2.5% of the total area of ​​the combustion chamber floor (12). [4] Cooking appliance according to one or more of the preceding claims, wherein the openings (14) in the lower region of the side walls of the combustion chamber (15) are holes with a diameter in the range of 2 to 3 mm. [5] Cooking appliance according to one or more of the preceding claims, wherein the cooking appliance comprises a regulating plate (41) mounted in the air distribution space, wherein the regulating plate (41) is provided with a central opening (18). [6] Cooking appliance according to one or more of the preceding claims, wherein the cooker comprises a shielding plate (42) arranged in the air distribution chamber (70) and positioned directly above the opening of the housing base so that the mechanical fan is shielded from the heat of the combustion chamber (10). [7] Cooking appliance according to one or more of the preceding claims, wherein the mechanical fan (30) is designed to produce an air flow in a range of 0.008 - 0.016 m 3 / s is generated. [8] Cooking appliance according to one or more of the preceding claims, in which the housing side walls (52) and / or the side walls of the combustion chamber (15) have bulges which can be pushed into recesses of further side walls. [9] Cooking appliance according to claim 8, wherein the bulges are L-shaped. [10] Cooking appliance according to one or more of the preceding claims, in which the combustion chamber base (12), the side walls of the combustion chamber (15) and the housing side walls (52) are made of stainless steel. [11] Cooking appliance according to one or more of the preceding claims, wherein the cooking appliance comprises a cover (60) mounted around the housing. [12] Cooking appliance according to claim 11, wherein insulating material (61) has been applied between the housing (60) and the housing (50).

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