Air frying system and method

Abstract

The present invention relates to the field of cooking food by combining hot air with RF energy. A system (100) for cooking food includes: a holder (120) for holding the food, which includes: a permeable side (121); a device (140) that includes: a processing chamber (145) that is arranged to be RF-impermeable and preferably airtight; holding members (192, 192', 148, 148') for holding the holder inside the processing chamber; RF antennas (155, 155') that are arranged to radiate RF energy into the interior of the processing chamber for heating the food inside the holder; a fan (156) for circulating air in the processing chamber through the permeable side and through the holder; and a heater (157) that is arranged to supply heat to the circulating air.

Description

Field of the Invention

[0001] The present invention relates to the field of cooking food by means of hot air, such as air fryers, and to methods for air frying, and more particularly to the field of air frying food and to methods for air frying food. Background Art

[0002] Air fryers are kitchen appliances that cook by circulating hot air around food using a convection mechanism. A mechanical fan circulates hot air up to 230 °C around the food at high speed, thereby cooking the food and creating a crispy layer. The crispy layer is typically thin to provide a crispy effect while retaining moisture in the food core. The food core is typically heated by conduction.

[0003] Food cooked in air fryers is typically snacks, such as potato chips, chicken, chicken wings, fish, fish fingers, steaks, ribs or French fries, which are usually pre-fried in hot oil, as well as quiches, pies, spring rolls, croquettes and even bread rolls and croissants. Most of these foods are stored frozen at low temperatures.

[0004] The disadvantage is that known air fryers, when frying a relatively large amount of low-temperature frozen food at one time, produce food that is externally fried or even burnt, but the food core is still cold or even frozen, or takes a long time to cook. To avoid this problem, the chamber for accommodating the food in current air fryers is designed to be small, which adds another disadvantage. Another disadvantage is that due to the size of the chamber for accommodating the food, current air fryers are only suitable for household use and not for commercial use, such as in restaurants, bars, coffee shops, beer houses, cafeterias, fast food restaurants, etc. Summary of the Invention

[0005] An object of the present invention is to alleviate the drawbacks mentioned above. According to a first aspect of the present invention, a system for making food comprises: a radio frequency (RF) - impermeable layer; a holder for holding food, comprising: a breathable side; a device comprising: a processing chamber which is arranged to be RF - impermeable and preferably air - impermeable; a holding member for holding the holder inside the processing chamber; an RF antenna which is arranged to radiate RF energy into the interior of the processing chamber for heating food inside the holder; a fan for circulating air in the processing chamber through the breathable side and through the holder; and a heater which is arranged to supply heat to the circulating air; wherein the fan and the heater are arranged to air - fry food inside the holder; wherein the RF - impermeable layer is also breathable and is at least in use arranged to be substantially parallel to the breathable side of the holder; wherein the RF - impermeable layer separates the processing chamber in a first region vulnerable to RF energy from the RF antenna and a second region shielding the RF energy from the RF antenna in use; and wherein the fan is arranged in the second region.

[0006] The process of air - frying is to cook by circulating hot air around the food inside the system. The circulation of hot air is driven by a fan that moves the air. The fan circulates, swirls, and / or propels the hot air, which can be heated to 230 °C around the food at high speed, thus cooking the food and creating a crispy layer.

[0007] The breathable side should be breathable for hot air, typically at high speed, as used in an air - fryer. Examples of the breathable side are specific plastic meshes capable of withstanding hot air, a metal layer or metal mesh with openings therein, or other materials such as made of ceramic or others.

[0008] The air - impermeable side or wall is indeed only air - impermeable to hot air circulating at high speed in an air - fryer. It does not necessarily have to be air - tight. The air - impermeable side or wall should at least prevent hot air from the inside from harming or burning people outside the system.

[0009] The RF - impermeable layer or wall is a layer that blocks the propagation of RF waves of a specified frequency or frequency range. The RF - impermeable layer or wall can reflect, absorb, scatter, or a combination of the foregoing. The RF - impermeable layer is typically RF - impermeable to at least a portion, preferably all frequencies, of the frequencies of the RF energy radiated by the RF antenna. The RF - impermeable layer can be a metal layer, a metal mesh, etc. The RF - impermeable layer can even be a metal layer with openings, the openings having sizes adapted to prevent RF wave leakage through the layer.

[0010] A processing chamber generally includes walls. The walls of the processing chamber are RF-impermeable and airtight. During use, they prevent a person standing outside the processing chamber and next to the system from being exposed to any dangerous RF radiation and / or hot air. Since food needs to be introduced into and removed from the processing chamber again, the processing chamber generally includes an opening. The processing chamber may include, for example, two housing halves that fit tightly together. The two housing halves provide an RF-impermeable and airtight processing chamber when assembled together. At the same time, when the two housing halves are separated, the housing half holding the food provides an opportunity to easily access this food. Special geometric and material considerations prevent RF leakage into areas where the RF-impermeable walls are divided for the chamber opening or for access to motors, temperature sensors, or antennas; it prevents RF leakage in those areas by confining RF waves within the RF-impermeable boundaries.

[0011] The inventors have recognized that the tight packing of food and / or a large amount of food results in food where the outside is cooked or even charred while the inside remains cold or even frozen. The thermal conductivity of frozen food is different compared to that of unfrozen food. The inventors have recognized that if the outside of a large piece of food or tightly packed food is heated, due to the difference in conductivity, only the outer shell of the food gets cooked when the temperature of the surrounding air is too high. If the volume of the food is large, this negative effect is amplified and prevents the use of prior art air fryers for commercial purposes, such as in restaurants, bars, coffee shops, beer houses, cafeterias, fast food restaurants, and so on.

[0012] The inventors have recognized that if food is to be uniformly transformed from a frozen state to a non-frozen state, air frying can be used in the non-frozen state to obtain a typical air-fried food of a larger volume. In addition, the air-fried food will have a crispy exterior and also obtain a uniformly cooked interior. The inventors have further recognized that a relatively large amount of food can be uniformly transformed in a relatively short time by using RF waves that can generally penetrate a larger amount of food. The RF waves that penetrate frozen food can heat the food uniformly or at least also inside the food to transform the food from a frozen state to an unfrozen state more uniformly.

[0013] Known fans are generally made of a metal such as steel to provide a fan that can be easily produced and is low-cost. These fans cause distortion of RF waves. And even if the fan is made of plastic with a significantly different dielectric constant from the surrounding air, the fan will still interfere with RF waves. In addition, the axles of the fans are generally made of metal and also interfere with RF waves. The inventors have recognized that the arrangement of the components of the air fryer can be changed so that the air fryer can be combined with heating food using RF energy.

[0014] The system includes a processing chamber for holding food inside the processing chamber, wherein the system has components arranged such that the food can be exposed to RF energy and an air frying effect. This has the technical effect of increasing the cooking uniformity of the cooked food in a relatively short time.

[0015] Since the fan is arranged in an area of the processing chamber that is not exposed to or minimally exposed to RF energy or low levels of RF energy such that it does not interfere or minimally interferes with the RF waves, the RF energy can be efficiently transmitted to the food. The term area in the context of the claims is used to identify the boundary within which the RF energy lies or is predominantly located. Alternative wordings for the area could be part of the processing chamber, section of the processing chamber, cavity of the processing chamber, or space of the processing chamber. The technical effect of the RF-impermeable layer is also breathable and is arranged at least in use substantially parallel to the breathable side of the holder; the enclosed space can be separated in two areas. The first area is accessible to the hot air with an air frying effect and the RF energy for heating the food. And the second area is accessible to the hot air with an air frying effect. Now, by arranging the food in the first area and the fan in the second area, the technical effect is obtained from the fan without interfering with the RF waves.

[0016] Additionally, in the context of the present invention, the terms substantially parallel or parallel should be understood as two layers or one layer and one side being placed on top of each other or at a distance from each other. The two parallel layers can have a small angle relative to each other, for example, a few degrees. Generally, these deviations from parallel are within the limits of production.

[0017] In an embodiment of the present invention, providing RF energy to the food inside the holder is independent of providing hot air to the food inside the holder. This provides the advantage that during the phase change of the food from frozen to unfrozen, the food can be exposed to RF energy while the circulation of hot air can be stopped or minimized. This also provides the advantage of cooking food in an unfrozen state depending on the setting, which can be done by hot circulating air and / or RF energy.

[0018] In an embodiment of the present invention, the breathable side is arranged to allow a vertical air flow through the holder. The air is advantageously a vertical air flow through the food. Depending on the setting and / or capabilities of the system, the vertical air flow through the food can be from top to bottom or from bottom to top. Alternatively, the system can change the vertical direction of the air flow through the food, for example, pulse control one vertical direction and then pulse control the opposite vertical direction.

[0019] In an embodiment of the present invention, the breathable side of the holder is advantageously arranged as a breathable bottom side. This provides a favorable entry point for the air flow to reach the food.

[0020] In an embodiment of the present invention, the holder includes a RF-impermeable layer. In a further advantageous embodiment of the present invention, the RF-impermeable layer is the bottom side of the holder, preferably where the RF-impermeable layer and the breathable side are integrated. It provides the following advantages: The RF-impermeable layer and the breathable side are aligned by a design for optimizing the conduction of air through the RF-impermeable layer.

[0021] In an embodiment of the present invention, the RF-impermeable layer is the top side of the holder. Generally, the bottom side of the holder also contains a breathable bottom side for allowing air to vertically pass through the holder and thus food is held inside the holder.

[0022] In an embodiment of the present invention, the holding member is at least partially RF-impermeable for use with the RF-impermeable layer to form an RF separation in the processing chamber. The holder generally leaves a space between the holder and the processing chamber for allowing air to circulate back after passing through the holder. RF energy can leak through this space from the first region to the second region. The holding member generally extends from the holder and at least partially bridges the space between the holder and the processing chamber. Thus, the holding member can advantageously extend the RF-impermeable layer for reducing the leakage of RF energy to the second region.

[0023] In an embodiment of the present invention, the heater is advantageously arranged in the second region. The heater generally includes a metal part or at least part that affects RF waves. Thus, the heater is preferably arranged inside the second region because there is no RF energy or only a small amount of RF energy; the heater causes minimal interference to RF waves. It should be noted that if the heater is not in a region shielded from RF waves, especially the grounding of the heater can cause interference to RF waves. In an alternative embodiment, the heater is an indirect heater where the heater heats at least a part of the processing chamber, and thus at least a part of the processing chamber conducts heat to the air passing along at least a part of the processing chamber. It provides the following advantages: The heater can actually be arranged at every position on the outside of the processing chamber.

[0024] In an embodiment of the present invention, the heater is at least partially RF-impermeable for use with the RF-impermeable layer to form an RF separation in the processing chamber. In another embodiment, the holding member is advantageously also part of the RF separation for improving the RF barrier for reducing the RF energy in the second region, thereby minimizing the interference to the components in the second region on the RF waves.

[0025] In an embodiment of the present invention, the system includes: an RF source arranged to provide RF energy to an RF antenna; a motor for driving a fan; a heater source for providing energy to a heater; and a controller for controlling the amount of RF energy from the RF source, the number of rotations of the motor, and the amount of radiant heat from the heater, wherein the controller independently controls the RF source, the motor, and the heater. The controller can advantageously control different parameters for providing an optimal cooking result in a minimum time and a homogeneous transition of the food from a frozen to an unfrozen state.

[0026] In an embodiment of the present invention, the holder is a food basket. Generally, the food basket has a bottom side made of an RF-impermeable mesh such as a metal mesh, thereby advantageously integrating a breathable side and an RF-impermeable layer.

[0027] According to another aspect of the present invention, a system for preparing food includes: an RF-impermeable layer; a holder for holding food, including: a breathable side; a device including: a processing chamber arranged to be RF-impermeable and airtight; a holding member for holding the holder inside the processing chamber; an RF antenna arranged to radiate RF energy into the interior of the processing chamber for heating the food inside the holder; a fan for circulating air in the processing chamber through the breathable side and through the holder; and a heater arranged to provide heat to the circulating air; wherein the fan and the heater are arranged for air frying the food inside the holder; wherein the RF-impermeable layer is also breathable and at least in use is arranged generally parallel to the breathable side of the holder; wherein the RF-impermeable layer separates the processing chamber in a top region vulnerable to RF energy from the RF antenna and a bottom region shielding the RF energy from the RF antenna during use; and wherein the fan is arranged in the bottom region. This aspect of the present invention provides the same advantages as those mentioned throughout the text for other aspects of the present invention.

[0028] In an embodiment of the present invention, the device includes a motor for driving the fan, wherein the motor is arranged below the processing chamber. The motor is typically one of the largest or most massive objects in the device. Arranging the motor in the device lower provides the advantage of a low center of gravity, thereby overall improving the mechanical stability of the device or system. This becomes particularly advantageous if the holder is partially located outside the processing chamber during loading, unloading, and / or placement but still rests on the processing chamber or is coupled to the device. In this case, the holder and the food in the holder can make the device unstable or cause the device to tilt. Placing the motor below the processing chamber reduces the change in tilt of the device during loading, unloading, and / or placement of the holder.

[0029] In an embodiment of the present invention, the processing chamber defines a vertical axis that is generally a line of symmetry, wherein the electric motor is aligned with this vertical axis. The system is for a more significant portion that is symmetric about the vertical axis. Thus, the air flow that circulates inside the processing chamber to achieve an air frying effect is mainly symmetric and generally in an annular shape. Arranging the fan into this main annular shape advantageously simplifies stimulating the air flow of this generally annular shape. In addition, arranging the electric motor generally along the vertical axis provides the advantage of a motor shaft that directly drives the fan, thereby simplifying the design of the device and the number of components of the device, and thus minimizing the variation of failures in the overall device or system.

[0030] In an embodiment of the present invention, the processing chamber defines a vertical axis that is generally a line of symmetry, wherein the processing chamber includes a back plate having a first back plate end and a second back plate end, wherein a triangle defines the vertical projection of the vertical axis, the first back plate end, and the second back plate end, and wherein the center of gravity point of the electric motor is arranged inside this triangle.

[0031] Arranging the electric motor in the device lower provides the advantage of a low center of gravity, thereby improving the mechanical stability of the device or system as a whole. This becomes particularly advantageous if the holder is partially outside and in front of the processing chamber during loading, unloading, and / or placement but still rests on the processing chamber or is connected to the rest of the device or system. In this case, the holder and the food in the holder can make the device unstable or cause the device to tilt. Placing the electric motor below the processing chamber reduces the change in tilt of the device during loading, unloading, and / or placing the holder.

[0032] This embodiment provides another advantage: If the holder connected to the device during loading, unloading, and / or placement is arranged in front of the device, the electric motor acts as a counterweight to improve balance, thereby preventing the device or system as a whole from tilting.

[0033] In an embodiment of the present invention, the device includes a shaft that is shared between the electric motor and the fan for directly driving the fan. This embodiment provides the advantage of reducing the number of components and thus reducing the variation of failures.

[0034] In an embodiment of the present invention, the holder is a food basket, preferably a food basket having a bottom side that is RF-impermeable and breathable, such as a metal mesh, and / or sides that are RF-impermeable and airtight, such as a specific plastic.

[0035] According to another aspect of the present invention, a system for making food comprises: an apparatus including: a processing chamber which is arranged to be RF-impermeable and airtight and includes a processing chamber surface; an RF antenna which is arranged to radiate RF energy into at least a portion inside the processing chamber for heating food inside the processing chamber; and an RF transparent layer which has an RF transparent surface and seals the RF antenna from a portion of the processing chamber arranged for holding food. During making or cooking food inside the processing chamber, due to, for example, gas formation inside the food during cooking, the food may splash, spatter, hiss, or splutter. Food residues or food splashes may impact the surface of the processing chamber. These food residues or food splashes should be removed promptly and thoroughly. If not properly removed, these can cause health problems for food cooked later inside the processing chamber.

[0036] The RF antenna is bevelled and curved, typically sharply bevelled and curved, for radiating RF energy with a desired efficiency and RF pattern. The bevelling and curving of the RF antenna make cleaning challenging. By covering the RF antenna with the RF transparent layer, food residues or food splashes cannot adhere to the RF antenna. Thus, it seals for sealing food inside the processing chamber, preferably splashes or residues from food inside the holder.

[0037] In an embodiment of the present invention, the system includes a fan, a heater, and an air path for circulating hot air inside the processing chamber for air frying as generally specified for other aspects of the present invention. Air frying can cause the food to splash, spatter, hiss, or splutter. When air frying is combined with RF cooking, the advantages of improved cleaning become even more beneficial.

[0038] Health problems become even more important because an uncovered RF antenna inside the processing chamber which also provides components for air frying can heat the RF antenna without heating the RF antenna hot enough to carbonize the food on the RF antenna. Thus, an uncovered RF antenna is generally challenging to clean. Additionally, due to the increased temperature inside the processing chamber, food residues or food splashes can adhere more strongly to the uncovered RF antenna, making cleaning even more difficult.

[0039] In embodiments of the present invention, the RF transparent layer seamlessly engages the processing chamber surface for further improving the cleaning of the processing chamber or simplifying the removal of food residues or food splashes. In embodiments of the present invention, the RF transparent surface seamlessly engages the processing chamber surface for further improving the cleaning of the processing chamber or simplifying the removal of food residues or food splashes. In embodiments of the present invention, at least an edge of the RF transparent surface is flush with the processing chamber surface for further improving the cleaning of the processing chamber or simplifying the removal of food residues or food splashes. In embodiments of the present invention, the processing chamber includes a protrusion, preferably an outward protrusion, wherein the RF antenna is disposed in the protrusion for further improving the cleaning of the processing chamber or simplifying the removal of food residues or food splashes. In embodiments of the present invention, the RF transparent surface is a flat, substantially flat, slightly rolled or slightly curved surface for further improving the cleaning of the processing chamber or simplifying the removal of food residues or food splashes. The amount of rolling or curvature depends on the shape of the processing chamber to seamlessly fit into the curved portion of the processing chamber.

[0040] In embodiments of the present invention, the RF transparent surface is flush with the processing chamber surface for further improving the cleaning of the processing chamber or simplifying the removal of food residues or food splashes. This embodiment combines well in particular with embodiments where the RF transparent surface is flat and / or where the processing chamber includes an outward protrusion, wherein the RF antenna is arranged to provide a flat, substantially flat, slightly rolled or slightly curved surface to be cleaned.

[0041] In embodiments of the present invention, the RF antenna is a substantially flat antenna. This embodiment combines well in particular with embodiments where the processing chamber includes an outward protrusion, wherein the RF antenna is arranged to provide a flat surface to be cleaned. The flat or substantially flat RF antenna has the advantage that the protrusion does not need to be too deep.

[0042] In embodiments of the present invention, the RF antenna is an inverted F antenna, or a PIFA antenna, preferably an anti-dipole known as a slot antenna or a plurality of such antennas. These are advantageous types of RF antennas that can transmit within the desired frequency range or over more than one frequency range and are substantially flat.

[0043] According to another aspect of the present invention, a system for making food comprises: an RF-impermeable layer; a holder for holding food, the holder comprising: a breathable side; a device comprising: a processing chamber which is arranged to be RF-impermeable and airtight; a holding member for holding the holder inside the processing chamber; an RF antenna which is arranged to radiate RF energy into the interior of the processing chamber for heating food inside the holder; a fan for circulating air in the processing chamber through the breathable side and through the holder; and a heater which is arranged to supply heat to the circulating air; wherein the fan and the heater are arranged for air frying food inside the holder; wherein the RF-impermeable layer is also breathable and is arranged to be generally parallel to the breathable side of the holder at least in use; wherein the RF-impermeable layer separates the processing chamber in a first region vulnerable to RF energy from the RF antenna and a second region shielding the RF energy from the RF antenna in use; and wherein the fan is arranged in the second region. This aspect of the present invention provides the same advantages as those mentioned throughout the text for the other aspects of the present invention.

[0044] In an embodiment of the present invention, the holder has a size such that, in use, the holder only occupies a section of the first region, such that the unoccupied section of the first region is sized and / or shaped to receive RF energy from the RF antenna for generating RF waves in the unoccupied section for efficiently transferring RF energy from the RF antenna to the food in the holder. The inventors have appreciated that the food held in the holder interferes with the formation of RF waves or RF waves. The unoccupied section effectively provides a favorable transition space from the RF antenna and the food for efficiently transferring RF energy from the RF antenna to the food. The experiments and simulations of the inventors have shown that the unoccupied space needs to be at least half of the first region, which is the region where RF energy can be obtained. In another embodiment, the height of the holder is less than or equal to half of the height of the first region. Additionally, experiments and simulations have shown that the holder can have a width and length comparable or close to the width and length of the first region. It should be borne in mind that the holder should have a width and length that still allows air circulation to achieve the air frying effect, and the air along the circulation path generally also passes vertically between the holder and the processing chamber and is then blown away or sucked through the food in the holder.

[0045] In an embodiment of the present invention, the main RF wave in the unoccupied section is an RF standing wave. The size and / or shape of the first region are selected, typically at least in terms of length and width, such that one or two standing waves are formed. The standing wave provides a means for efficiently transferring RF energy from the RF antenna to the food at well-defined locations with a high electromagnetic energy density. The standing wave may have energy hotspots. Another advantage may be having two main standing waves for more uniform diffusion of RF energy inside the food. To enhance the formation of the two main standing waves, slightly different lengths and widths of the first region may be selected.

[0046] In an embodiment of the present invention, the main RF standing wave in the unoccupied section may be an RF wave having TE mode 011, TE mode 111, and / or TM mode 110. In particular, the combination of TE mode 011 and TE mode 111 seems to be beneficial because these modes require substantially the same length and width of the first region to act as the main RF standing wave.

[0047] In an embodiment of the present invention, the RF antenna operates in a frequency range that fully penetrates the food in the holder, where the weight of the food in the holder exceeds 2 Kg, preferably 3 Kg, and more preferably exceeds 4 Kg. These food quantities are typically used in commerce and not for household use. The frequency for the RF wave and the size and / or shape of the processing chamber will advantageously be selected and sized and / or shaped respectively to accommodate this food quantity in the holder.

[0048] In an embodiment of the present invention, the RF antenna operates in a frequency range that fully penetrates the food in the holder, where the frequency range is below 1 GHz, preferably in the frequency band of 902 MHz to 928 MHz or around 915 MHz. As specified above, the food quantity must be penetrated by the RF wave to provide RF energy throughout the food. The commonly used frequency of 2.45 GHz is not very suitable because the penetration depth is only in the range of centimeters and is thus insufficient to penetrate a food mass weighing more than 2 Kg. Selecting a lower frequency advantageously allows the RF wave to penetrate deeper into the food rather than just heating the outer layer of the food. If the frequency is selected to be even low enough such that the RF wave passing through the food is only partially absorbed, the RF wave can then bounce back from the processing chamber and / or the RF barrier separating the first and second regions to pass through the food again for heating the food by absorption. This provides the advantage of more uniform heating of the food, for example, during the transition from frozen to unfrozen. This provides another advantage that the food is less heated, where the hotspots are determined by the standing waves and also by more randomized reflections, thus enhancing the uniform diffusion of the absorbed RF energy in the food.

[0049] Based on extensive characterization of various foods and conditions, the inventors have learned that the frequency range of 902 MHz to 928 MHz has one or more advantages compared to other frequencies in the range of, for example, 2400 MHz to 2500 MHz. Also, in various countries, this frequency band of 902 MHz to 928 MHz can be used free of charge, i.e., the unlicensed band. However, in many other countries, there are very strict regulations on this frequency range, and measures must be taken to prevent electromagnetic interference. Therefore, choosing a frequency within this range advantageously simplifies compliance with those different requirements and still achieves good performance, especially in the 2.45 GHz ISM band globally, rather than just in the 915 MHz band in the Americas. Thus, production is simplified by choosing a frequency within this range, and this frequency range also provides the benefit of highly penetrating the food in the holder.

[0050] In another preferred embodiment, the main RF wave has a frequency below 1 GHz, preferably within the 902 MHz to 928 MHz band or substantially 915 MHz, and the main RF wave has at least one TE mode 011 and / or TE mode 111, preferably both. The inventors' experiments and tests have shown that, with the previously mentioned parameters, the length and width of the processing chamber are in the range of 250 mm to 380 mm, preferably in the range of 280 mm to 340 mm, and more preferably about 306 mm. This size can also refer to a certain size of the RF-impermeable wall of the holder and can be adjusted according to the overall effective processing chamber. During the experiments and tests, the height of the first region is in the range of 180 mm, more specifically 192 mm, and the height of the holder is less than 60% of the height of the first region. Additionally, assuming the dielectric constant of air is about 1, the dielectric constant of the RF-permeable side of the holder is about 3 to 10 depending on the material of the holder such as PTFE, PEEK, fiberglass, or ceramic, and the dielectric constant of frozen food is about 80, while that of unfrozen but cold food can be about 3. Generally, as the temperature increases, for food products mainly based on water, such as hot fast food with a moist interior, the dielectric constant of the food eventually reaches about 40, while the crispy outer skin stabilizes at about 80. These sizes are very suitable for accommodating a larger amount of food, especially for commercial use. This embodiment can be effective for general equipment or countertop equipment of a compact size, which can be further enhanced by choosing different lengths and widths of the first region, but still within the range specified for advantageously more evenly diffusing RF energy, as previously specified. For larger equipment, in addition to countertop placement, a frequency of 433 MHz can also be selected to support food loads of 8 kg and larger.

[0051] In another preferred embodiment, the main RF wave has a frequency below 1 GHz, preferably in the frequency band of 902 MHz to 928 MHz or substantially 915 MHz, and the main RF wave has a TM mode 110. The experiments and tests of the present inventors have shown that, with the previously mentioned parameters, the length and width of the processing chamber are in the range of 200 mm to 260 mm, preferably in the range of 220 mm to 240 mm, and more preferably about 230 mm. During the experiments and tests, the height of the first region is in the range of 180 mm, while the height of the holder is less than half of the height of the first region. In addition, assuming the dielectric constant of air is about 1, the dielectric constant of the RF-permeable side of the holder is about 2 (PTFE), 3 to 4 (PEEK, fiberglass) to about 10 (ceramic), and the dielectric constant of food is in a very wide range of 3 to 80; it can be a very low number for frozen food and a high number for low-temperature but unfrozen food. As the temperature increases, the dielectric constant generally drops to about 40; this applies to food products mainly based on water, such as hot fast food with a moist interior and a crispy crust. These dimensions are very suitable for accommodating a larger amount of food, especially for commercial use.

[0052] According to another aspect of the present invention, a system for making food includes: a holder for holding food, including: a breathable side (121); a device including: a processing chamber arranged to be RF-impermeable and preferably airtight; a holding member for holding the holder inside the processing chamber; an RF antenna arranged to radiate RF energy into the interior of the processing chamber for heating the food inside the holder; a fan for circulating air in the processing chamber through the breathable side and through the holder; and a heater arranged to supply heat to the circulating air; wherein the fan and the heater are arranged for air frying the food inside the holder; wherein the processing chamber includes: a top shell including a top inner space and a top edge forming an access opening leading to the top inner space; and a bottom shell including a bottom inner space and a bottom edge forming an access opening leading to the bottom inner space; wherein in the closed position, the top shell and the bottom shell are arranged to each other to enclose an inner space including the top inner space and the bottom space; wherein the radiated RF energy generates RF waves; and wherein the processing chamber is shaped such that the RF waves have substantially nodes at the top edge and / or the bottom edge in the closed position.

[0053] The top shell and the bottom shell can alternatively be identified as the top plate and the bottom plate respectively. In another embodiment of the present invention, wherein the top inner space and the bottom inner space together form the interior of the processing chamber.

[0054] A node of an RF wave can be understood as a volume in space where the minimum value of RF energy and / or where the RF energy is the lowest, for example, when it is below a predefined threshold. The threshold can be 10% of the range between the maximum RF energy value and the minimum RF energy value. The RF energy can be in linear, dB, or logarithmic scale. A node of an RF wave in contact with or adjacent to a wall such as a conductive wall like a metal wall induces a minimum current density. A node of an RF wave in contact with or adjacent to a wall such as a conductive wall like a metal wall induces a region of minimum current density in the wall. The inventors have recognized that at an edge, for example, at a location where the top housing and the bottom housing are in contact with or adjacent to each other in the closed position, the current flow in the wall of the processing chamber is disturbed. And when the current flow in the wall of the processing chamber is disturbed, the RF wave and necessarily the standing wave are also disturbed. By aligning, for example, the node of the RF wave with one of the edges at the junction of the two housings, the interference with the RF wave is reduced. This reduction in interference allows the RF wave or the RF standing wave to be formed with a reduced amount of radiated RF energy placed in the RF wave. Thus, the effect of arranging or aligning the node of the RF wave with one of the edges provides higher efficiency to the system and / or improves the transfer of the radiated RF energy from the RF antenna to the food in the holder.

[0055] In an embodiment of the present invention, in the open position, the top housing and the bottom housing are arranged relative to each other to allow loading and unloading of the holder into and from the processing chamber. This advantageously allows for the transportation of food between the processing chamber and the outside.

[0056] In an embodiment of the present invention, the top housing has a top housing height; the bottom housing has a bottom housing height; and the top housing height and the bottom housing height are substantially the same. This embodiment advantageously facilitates and / or promotes RF waves, such as RF standing waves, in the top inner space such that the variations in the bottom inner space that typically hold a holder preferably with food benefit from the RF waves, with the advantage that the RF energy can generally be absorbed by the food in the bottom inner space. In a preferred embodiment, the diameter of the second inner space is substantially slightly greater than 10", for example, a 10" pizza will fit in the holder. In a preferred embodiment, the top housing height and the bottom housing height are in the range of 90 mm to 125 mm, preferably 90 mm to 115 mm, more preferably 90 mm to 100 mm, and most preferably substantially 96 mm. In a preferred embodiment, the diameter and height of the top housing and / or the bottom housing are within the aforementioned ranges. This combination provides the advantage of facilitating or promoting RF waves such as RF standing waves or RF modes, which optimizes the absorption of RF energy by the bottom inner space such as the food in the holder.

[0057] In an embodiment of the present invention, in the closed position, the top edge and the bottom edge are in contact with each other, engaged with each other, and / or adjacent to each other to form a processing chamber that is RF-impermeable and preferably airtight. These edges are typically where the processing chamber closes and forms a splice or gap. In addition, RF waves induce currents in the walls of the processing chamber. The inventors have recognized that these currents are absent or minimal in the walls at the positions where the RF waves have nodes, and these currents are maximum in the walls at the positions where the RF waves have antinodes. The top edge and / or the bottom edge are advantageously arranged at the positions of the nodes such that the top edge and / or the bottom edge, preferably the influence of the splice and / or the gap, has a minimal influence on RF waves such as the promoted RF waves. The current embodiment advantageously allows for simplification and / or an increase in the mechanical tolerances regarding how the top housing and the bottom housing are engaged in the closed position. In addition, since the loss of RF energy in the walls of the processing chamber, specifically where the top housing and the bottom housing are joined or connected, is reduced or minimized, the RF waves are advantageously optimized. Specific RF modes of the RF standing wave according to this embodiment can be the TE mode xx1, the TM mode xx1, and the TM mode xx0. Additional higher-order TE and / or TM modes will generally occur at higher frequencies such as 2450 MHz and depend on the food load in the processing chamber such as the food weight or food height and the type of the food composition applied such as the water, salt, protein, carbohydrate, sugar, or fat content.

[0058] In an embodiment of the present invention, the processing chamber, preferably the internal space, more preferably the internal space having a holder arranged in the processing chamber, is shaped such that the RF waves have nodes generally where the top housing and the bottom housing are in contact with each other, engaged with each other, and / or adjacent to each other in the closed position. This embodiment further details the previous embodiment, thereby providing or enhancing the advantages of the previous embodiment.

[0059] In an embodiment of the present invention, the RF waves have nodes that generally form a plane at the height where the top housing and the bottom housing are in contact with each other, engaged with each other, and / or adjacent to each other in the closed position. This embodiment promotes RF waves having a plane as a node, thereby advantageously relaxing the width and length of the inner space of the processing chamber, such as the diameter, preferably the width and length, such as the diameter, of the top housing and / or the bottom housing.

[0060] In an embodiment of the present invention, the holding members (192, 192') are arranged adjacent to the bottom edge (191) to contact the holder generally at the nodes of the RF waves. The holding members that hold the holder typically also form a splice or gap. The holding members are advantageously also arranged in a space where the RF waves have nodes for minimizing the absorption of RF energy at this splice or gap and / or interfering with the nodes of the RF waves through this splice or gap.

[0061] In an embodiment of the present invention, the holder when used inside the processing chamber hangs from the holding member. This advantageously allows no or minimal splices or gaps to occur at positions in the inner space of the processing chamber that induce current on the splices or gaps. Accordingly, the RF energy loss of the holder and / or the holding member is minimized.

[0062] According to another aspect of the present invention, the system is based on one of the independent claims, embodiments or aspects of the present invention and incorporates any one or any number of the dependent claims, dependent embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The present invention will be apparent from the following description and will be further elucidated with reference to the embodiments described by way of example in the accompanying drawings, in which: Figure 1 A cross-section of a first embodiment of a system according to the present invention is schematically shown; Figure 2 Another cross-section of a first embodiment of a system according to the present invention is schematically shown; Figure 3 A cross-section of a processing chamber of a first embodiment of a system according to the present invention is schematically shown; Figure 4A A second cross-section of a processing chamber of a first embodiment of a system according to the present invention is schematically shown; Figure 4B A third cross-section of a processing chamber of a first embodiment of a system according to the present invention is schematically shown; Figure 4C A fourth cross-section of a processing chamber of a first embodiment of a system according to the present invention is schematically shown; Figure 4D A fifth cross-section of a processing chamber of a first embodiment of a system according to the present invention is schematically shown; Figure 4E A sixth cross-section of a processing chamber of a first embodiment of a system according to the present invention is schematically shown; Figure 5 A cross-section of a second embodiment of a system according to the present invention is schematically shown; Figure 6 A cross-section of a first embodiment of an apparatus according to the present invention is schematically shown; Figure 7 Details of a cross-section of a first embodiment of an apparatus according to the present invention are schematically shown; Figure 8 A perspective view of the top corner of a first embodiment of an apparatus according to the present invention is schematically shown; Figure 9 Details of a cross-section of an RF antenna of a first embodiment of an apparatus according to the present invention are schematically shown; Figure 10A A seventh cross-section of a processing chamber 145 of a first embodiment of a system according to the present invention is schematically shown; Figure 10B An eighth cross-section of a processing chamber of a first embodiment of a system according to the present invention is schematically shown; Figure 10C A ninth cross-section of a processing chamber of a first embodiment of a system according to the present invention is schematically shown; Figure 11Schematically shows a cross-section of a third embodiment of a system according to the present invention; and Figure 12 Schematically shows a tenth cross-section of a processing chamber of a first embodiment of a system according to the present invention. The drawings are for illustrative purposes only and are not drawn to scale. In the figures, elements corresponding to those already described may have the same reference numerals.

[0064] List of reference numerals

[0065]

[0066] Detailed description

[0067] Figure 1 Schematically shows a cross-section of a first embodiment of a system 100 according to the present invention. The system includes a RF-impermeable layer 110, a holder 120, and a device 140. The holder includes a breathable side 121. The device includes a processing chamber 145, holding members 148, 148', RF antennas 155, 155', a fan 156, and heaters 157, 157'. The device may further include a housing 141 that houses all the features of the device.

[0068] The processing chamber of the device may include a top housing 146 and a bottom housing 147. The top housing and the bottom housing may be positioned in a closed position in which the top housing and the bottom housing form a RF-impermeable and airtight layer of the processing chamber. The device is shown in the closed position, in which the holder is arranged inside the processing chamber. The holder may include a handle 125. When the device or the processing chamber is in the open position, the handle may protrude partially out of the device to facilitate removal of the holder. The open position of the device is the position when the top housing and the bottom housing are separated such that the holder can be removed from the device or positioned in the device, more specifically positioned in the processing chamber. In an alternative embodiment, the holder remains in the bottom housing when loading and unloading food from the holder. In this alternative embodiment, for cleaning purposes, the holder is separated only from the bottom housing. In an alternative embodiment, the top housing and the bottom housing may be a front door and a back housing, respectively. In yet another embodiment, the top housing and the bottom housing may be a front housing and a back housing, respectively. In an embodiment of the holder, the holder includes a detachable handle 125. The detachable handle provides the advantage of minimizing the number of overhanging elements of the holder, such that it can be more easily assembled in, for example, a dishwasher or a cabinet.

[0069] The holding member is disposed inside the processing chamber for disposing or positioning the holder. The holder can be a ring or a rectangle that only supports the outer edge of the holder. The holder can be a layer that partially or completely covers the bottom of the holder. This layer can be airtight and / or RF-impermeable. In an alternative embodiment, the edge of the top housing is coupled to the top edge of the holder to form an RF-closed space, while the airtight layer of the processing chamber is separated from the RF-impermeable layer, where the airtight layer of the processing chamber encloses the RF-impermeable layer of the processing chamber, and where the RF-impermeable layer of the processing chamber and the RF-impermeable holder together form a first region. In this alternative embodiment, air can circulate back in the space between the airtight layer and the RF-impermeable layer.

[0070] The embodiments show two RF antennas, but the inventors also envision embodiments using only one RF antenna. The inventors also envision using multiple RF antennas for directing RF energy in a particular direction, such as in the direction of the food held in the holder. Additionally, in the case of using two or more RF antennas, at least one RF antenna can be used to supply RF energy, and one or more RF antennas that do not supply RF energy can be used to measure or sense the effectiveness of RF energy transmission towards the food in the holder, or can be used to determine the characteristics of the food in the holder. For example, for determining the state of the food in the holder as being, for example, frozen, unfrozen, or partially frozen and partially unfrozen. Additionally, more specific measurements can be used, which determine whether the food is liquid or solid in the frozen and unfrozen states, to even better direct the RF energy to the correct location inside the food for a more uniform transition of the food from the frozen to the unfrozen state and for more uniformly cooking the food overall.

[0071] The fan regulates the speed of the air flow. The heater, together with the fan, regulates the temperature of the air flow. If the speed of the air flow increases and if the heater is turned off, the temperature of the air flow will, for example, drop. The temperature range of the air flow can be between temperatures exceeding 100°C, such as 100°C to 250°C, preferably 150°C to 240°C, and more preferably below 230°C. The fan and the heater are typically arranged for air frying.

[0072] Because the fan and heater may be made of materials or have a size and / or shape that reduces, interferes with, or attenuates RF waves from the RF antenna, the fan and heater optimally shield RF waves. Additionally, the movement of the fan can exacerbate the fan's effect on RF waves. Accordingly, an RF-impermeable layer is disposed inside the processing chamber such that a portion of the processing chamber shields these one or more RF antennas and the RF waves emitted from these one or more RF antennas, and this portion of the processing chamber is labeled as the second region 151. By shielding these portions, RF waves can reach the food in the holder without being disturbed or less attenuated, for improved RF energy transfer from the RF antenna to the food in the holder. The portion of the processing chamber that is exposed to RF waves is labeled as the first region 150.

[0073] Because the fan and heater are disposed in an RF-shielded region or an RF low-energy region, the air stream generated by the fan and heated by the heater should still be able to reach the food as well as the RF energy. The fan is arranged such that the fan guides the air stream through the food in the holder via a breathable layer and / or an airtight side. The fan can blow air through the food or suck air through the food. This also allows the fan to change the direction of the air stream for improved cooking and / or frying of the food from all sides and / or angles.

[0074] The device may include an electric motor 159. The electric motor may be disposed below the processing chamber. Figure 1 A symmetric vertical axis V of the device is further shown. The electric motor may be aligned with this symmetric axle. In an alternative embodiment, the electric motor may be arranged closer to the back panel of the device for optimizing the balance and / or stability of the device, especially during loading or unloading of the holder with food in the holder. The placement of the electric motor can balance the weight of the holder and the food held in the holder, especially when the holder is placed on the device without being aligned with the vertical axis V. The device may include a shaft 164 that couples the electric motor to the fan, thereby providing the advantages of a very simple and secure coupling. Alternatively, the electric motor may be coupled to the fan, thereby indirectly providing the advantage of more freely positioning the electric motor.

[0075] Figure 2 Another cross-section of a first embodiment of a system 100 according to the present invention is schematically shown. The system includes an RF-impermeable layer 110, a holder 120, and a device 140. The holder is shown outside the device. In this particular embodiment, the RF-impermeable layer 110 and the breathable bottom side 121 of the holder are integrated. This has the technical effect that the heater and fan can be made easily accessible for cleaning when the holder is removed.

[0076] Figure 3Schematically shows a cross-section of a processing chamber 145 of a first embodiment of a system according to the present invention. The processing chamber is shown without a housing and without a holder disposed in the apparatus or the processing chamber. This figure shows possible positions of RF antennas. This figure details positions where RF energy can leak from the processing chamber. Leakage can occur at the positions of one or more RF antennas 155, 155'. Leakage can also occur where the top and bottom housings form processing chamber joints 144, 144'. Another leakage point can be the axle opening 143 in the processing chamber. The axle opening allows an axle to pass through for driving a fan. The axle opening can be disposed in the bottom housing. This axle can further act as an antenna for receiving RF energy, typically receiving a low amount of RF energy, since the fan is disposed in a second region that is as RF - energy - free as possible to provide the technical effects described for the present invention, thus exacerbating potential leakage along or through the fan axle. Typically, the axle comprises a material having a low conductivity property for RF energy at a specific frequency or at the frequency of the RF energy or RF waves transmitted by the RF antenna and used for cooking. And, typically, a so - called RF trap is provided around or in the axle to capture RF energy and RF waves inside the processing chamber.

[0077] When using RF waves at frequencies outside the ISM band, leakage is generally a problem. Although the ISM band is mostly available for free around the world, other frequencies are not. In particular, a frequency of approximately 915 MHz cannot be used for free in, for example, Europe. This requires that leakage should be minimized, preferably to an extent that the system is acceptable worldwide or almost worldwide.

[0078] All of FIG. 4 schematically shows a second cross - section of a processing chamber of a first embodiment of a system 100 according to the present invention. For all of FIG. 4, additionally, a holder 120 and a fan 156 are shown disposed inside the apparatus.

[0079] In Figure 4A the regions where RF energy may propagate, can propagate, or may mainly propagate are shaded. This region inside the processing chamber is labeled as the first region 150. The boundaries of the first region include the sides of the processing chamber and an RF - impermeable layer disposed inside the processing chamber. The length L and height H of the first region are shown in Figure 4A In

[0080] In Figure 4BIn which air may circulate, can circulate or the regions where it mainly circulates are shaded. It is shown that hot air can circulate through the entire processing chamber. The present invention also includes embodiments in which only a part of the processing chamber is used for circulating hot air for cooking. An exemplary embodiment is one in which the sides of the RF-impermeable and air-permeable processing chamber are separated or spaced apart. The RF-impermeable material may also have high thermal conductivity properties. This separation or spacing can be advantageous where the materials are both used as RF-impermeable and thermally conductive to prevent the outside of the processing chamber from getting hot during use.

[0081] Figure 4C Show subtracting from Figure 4A the shaded region in Figure 4B the first region. The result of the subtraction is, mainly is or substantially is the region where circulating hot air can be obtained but where RF energy or RF waves cannot reach or are greatly minimized. This resulting region is labeled as the second region 151.

[0082] Figure 4D Schematically shows a fifth cross-section of the processing chamber of a first embodiment of a system according to the present invention. The arrows in the figure show a typical air flow A of air that circulates through the food and returns along the side between the holder and the processing chamber. The circulation is maintained by using a fan at the bottom of the processing chamber.

[0083] Figure 4E Schematically shows a sixth cross-section of the processing chamber of a first embodiment of a system according to the present invention. Figure 4E Same as Figure 4D except that the direction of the air flow A is reversed compared to Figure 4D that.

[0084] Figure 5 Schematically shows a cross-section of a second embodiment of a system 100 according to the present invention. Additionally, for the first embodiment, this embodiment also includes an RF source 158 that feeds energy to the RF antenna for emitting RF waves or RF energy from the RF antenna. Further, the system includes a controller 160 and a motor 159. The motor is arranged to drive the fan. Since the motor can emit RF radiation that interferes with RF waves, the motor is advantageously arranged outside the processing chamber. The heater can be arranged outside the processing chamber or integrated into one side of the processing chamber to provide heat to the air flow inside the processing chamber, for example, conducting thermal energy through the said side of the chamber. In this embodiment, the heater is arranged inside the processing chamber.

[0085] The controller may be arranged to receive input from an operator. The controller may be arranged to control a heater and a fan for controlling the cooking effect of hot air passing through or along food. The controller may be arranged to control an RF source for controlling the amount of RF energy, the frequency of the RF waves, and / or the RF mode of the RF waves for controlling the cooking effect of the RF energy radiated towards the food. The RF source may include an RF amplifier, such as a solid-state amplifier, so as to control the RF energy with high precision, such as stepless control of the emitted RF energy. The RF source may include an RF signal generator for generating the frequency of the RF waves.

[0086] The controller may use the operator's settings to control or set the RF source, the fan, and / or the heater. Additionally or alternatively, the controller may use sensors to determine the settings of the RF source, the fan, and / or the heater. The sensor may be a temperature sensor, such as an IR sensor, which senses the temperature of the food inside the holder. The sensor may be a temperature sensor that senses the temperature of the circulating hot air for indirectly determining the temperature of the food in the holder by comparing the measured temperature with the amount of energy introduced by the heater and the air velocity generated by the fan. The sensor may be an RF antenna that does not emit RF energy for determining the RF energy emitted by another RF antenna and the effect on the food in the holder. Using multiple RF antennas as sensors can provide an accurate image of the amount of food in the holder, such as several kilograms, as well as the food texture and / or the food state, such as whether the food is frozen, unfrozen, or partially frozen and unfrozen, to the controller.

[0087] Figure 6 Schematically shows a cross-section of a first embodiment of an apparatus 140 according to the present invention. The position of the cross-section is shown in Figure 1 in. Figure 1 The cross-section of is taken vertically, Figure 6 The cross-section of is taken horizontally. The apparatus includes a processing chamber 145, which may include a top housing 146. The apparatus may further include an outer shell 141. The outer shell generally provides a framework or structure for arranging the elements of the apparatus to each other. The length L and width W of a first region 150 inside the processing chamber are shown in Figure 6 in. The height at which the cross-section is taken may be specified as the height of the unoccupied section inside the processing chamber.

[0088] The dimensions of the first chamber, namely the length, width, and height, very much affect the damping or stimulation of the frequency of the RF waves and very much affect the mode of the RF waves.

[0089] The main RF wave in the unoccupied section is an RF standing wave. The size and / or shape of the first region is selected, typically at least length and width, such that one or two standing waves are formed. The standing waves provide a means for efficiently transferring RF energy from the RF antenna to the food. The standing waves can have energy hotspots. Another advantage can be having two main standing waves for more uniform diffusion of RF energy within the food. To enhance the formation of the two main standing waves, the length and width of the first region can be selected to be slightly different.

[0090] The main RF standing wave in the unoccupied section can be an RF wave having TE mode 011, TE mode 111, and / or TM mode 110. In particular, the combination of TE mode 011 and TE mode 111 seems to be beneficial because these modes require substantially the same length and width of the first region to act as the main RF standing wave.

[0091] The RF antenna can operate in a frequency range that fully penetrates the food in the holder, where the weight of the food in the holder exceeds 2 Kg, preferably 3 Kg, and more preferably exceeds 4 Kg. These food amounts are typically used in commerce and not for household use. The frequency for the RF wave and the size and / or shape of the processing chamber will advantageously be selected and sized and / or shaped respectively to accommodate this food amount in the holder.

[0092] The RF antenna can operate in a frequency range that fully penetrates the food in the holder, where the frequency range is below 1 GHz, preferably within the 902 MHz to 928 MHz band or approximately 915 MHz. As specified above, the food amount must be penetrated by the RF wave to provide RF energy throughout the food. The commonly used frequency of 2.45 GHz is not suitable because the penetration depth is only in the range of centimeters and thus insufficient to penetrate a food mass weighing more than 2 Kg. Selecting a lower frequency advantageously allows the RF wave to penetrate deeper into the food rather than just heating the outer layer of the food. If the frequency is selected to be so low that the RF wave passing through the food is only partially absorbed, the RF wave can then bounce back from the processing chamber and / or the RF barrier separating the first and second regions for subsequent passage through the food again for heating the food by absorption. This provides the advantage of more uniform heating of the food during, for example, the transition from frozen to unfrozen. This provides another advantage that the food is less heated, where the hotspots are determined by the standing waves and also by more randomized reflections, thus enhancing the uniform diffusion of the absorbed RF energy in the food.

[0093] Based on extensive characterization of various foods and conditions, the inventors have learned that the frequency range of 902 MHz to 928 MHz has one or more advantages compared to other frequencies in, for example, the range of 2390 MHz to 2450 MHz. Also, in various countries, this frequency band of 902 MHz to 928 MHz can be used free of charge, i.e., the unlicensed band. However, in many other countries, there are very strict regulations on this frequency range, and measures must be taken to prevent electromagnetic interference. Therefore, choosing a frequency within this range advantageously simplifies compliance with those different requirements and still achieves good performance, especially in the 2.45 GHz ISM band globally, rather than just the 915 MHz band in the Americas. Thus, production is simplified by choosing a frequency within this range, and this frequency range also provides the benefit of highly penetrating the food in the holder.

[0094] The main RF wave can have a frequency below 1 GHz, preferably within the 902 MHz to 928 MHz band or substantially 915 MHz, and the main RF wave has at least one TE mode 011 and / or TE mode 111, preferably both. The inventors' experiments and tests have shown that, with the previously mentioned parameters, the length and width of the processing chamber are in the range of 250 mm to 380 mm, preferably in the range of 280 mm to 340 mm, and more preferably about 306 mm. This size can also refer to a certain size of the RF-impermeable wall of the holder and can be adjusted according to the overall effective processing chamber. During the experiments and tests, the height of the first region is in the range of 180 mm, more specifically 192 mm, and the height of the holder is less than 60% of the height of the first region. Additionally, assuming the dielectric constant of air is about 1, the dielectric constant of the RF-permeable side of the holder is about 3 to 10 depending on the material of the holder such as PTFE, PEEK, fiberglass, or ceramic, and the dielectric constant of frozen food is about 80, while the dielectric constant of unfrozen but cold food can be about 3. Generally, as the temperature increases, for food products mainly based on water, such as hot fast food with a moist interior, the dielectric constant of the food eventually reaches about 40, while the crispy outer skin stabilizes at about 80. These sizes are very suitable for accommodating a larger amount of food, especially suitable for commercial use. This embodiment can be effective for general equipment or countertop equipment of a compact size, which can be further enhanced by choosing different lengths and widths of the first region but still within the range specified for advantageously more evenly diffusing RF energy, as previously specified. For larger equipment, in addition to countertop placement, a frequency of 433 MHz can also be selected to support food loads of 8 kg and larger.

[0095] The main RF wave may have a frequency below 1 GHz, preferably within the 902 MHz to 928 MHz band or substantially 915 MHz, and the main RF wave has a TM mode 110. The experiments and tests of the present inventors have shown that, with the previously mentioned parameters, the length and width of the processing chamber are in the range of 200 mm to 260 mm, preferably in the range of 220 mm to 240 mm, and more preferably about 230 mm. During the experiments and tests, the height of the first region is in the range of 180 mm, while the height of the holder is less than half of the height of the first region. Additionally, assuming the dielectric constant of air is about 1, the dielectric constant of the RF-transparent side of the holder is about 2 (PTFE), 3 to 4 (PEEK, fiberglass) to about 10 (ceramics) and the dielectric constant of food is in a very wide range from 3 to 80; it can be a very low number for frozen food and a high number for cold but unfrozen food. As the temperature increases, the dielectric constant generally drops to about 40; this applies to food products mainly based on water, such as hot fast food with a moist interior and a crispy crust, and the dielectric constant of the food is about 80. These dimensions are very suitable for accommodating a larger amount of food, especially for commercial use.

[0096] Experiments have shown that the length-to-width ratio of the first region is preferably about 1. Other experiments have shown that the ratio of the height of the first region to the length or width is preferably about 2. Other experiments have shown that the height of the holder and thus also the height of the food held in the holder should not exceed 60% of the height of the first region. These limitations need to be observed in order to generate RF waves inside the processing chamber with sufficient or considerable efficiency.

[0097] Figure 6 It is further shown that the vertical axis V has a point of intersection therein because the vertical axis is perpendicular to the plane of the cross-section. The device may further include a housing that defines the outer edge of the device. The housing may include a back plate 161 that defines the face of the device that is usually facing away from the operator. The back plate usually faces the wall. The housing may include a front plate 163. The front plate is opposite to the back plate and usually faces the operator. The back plate has a first back plate end 162 and a second back plate end 162'. The first back plate end, the second back plate end, and the vertical axis define a triangle T.

[0098] Figure 7 Details of a cross-section of a first embodiment of a device according to the present invention are schematically shown. The details show Figure 1 an RF antenna 155' in the upper right corner of

[0099] The RF antenna may include a slot 178, a shield box 175, an RF-transparent layer 176, an RF-transparent surface 177. The slot 178 is not shown in Figure 7 but is shown, for example, in Figure 8 ​

[0100] The RF antenna is fed with energy or signals through an RF cable 170. The RF cable includes a core 172 and a shield 171. The core typically carries the signal, while the shield shields the core from emitting RF waves outside the RF cable. The RF cable can be a coaxial cable.

[0101] The RF antenna can be a slotted antenna or an inverted antenna as shown. Other types of RF antennas can be used to radiate RF energy. The RF antenna can further include an RF transparent layer 176 having an RF transparent surface 177. The RF transparent surface seals the interior of the shielded box to prevent dirt from accumulating inside the shielded box and / or to facilitate cleaning the interior of the processing chamber. The RF transparent layer is preferably seamlessly connected to the inner surface of the processing chamber. The RF transparent layer is preferably flush with the inner surface of the processing chamber. The interior of the shielded box can be regarded as a protrusion of the processing chamber. The RF transparent layer generally has a material that easily allows RF waves to conduct. Therefore, the RF transparent layer has a suitable dielectric constant.

[0102] The RF antenna is connected to the slotted antenna by connecting the RF cable core 172 to a second RF cable feed point 174 and connecting the RF cable shield 171 to a first RF cable feed point 173, where the second RF cable feed point is an edge of the processing chamber on one side of the slot, and the first RF cable feed point is another edge of the processing chamber on the opposite side of the slot. The slot has a circumference that is generally of length λ, which is equal to the wavelength of the main RF wave to be generated.

[0103] Figure 8 A perspective view of the top corner of a first embodiment of the device according to the present invention is schematically shown. The RF antennas 155, 155' are typed slotted antennas. The RF antenna includes a slot 178, which can be curved as shown. The inventors envision other slot shapes, such as straight.

[0104] The processing chamber 145 can include a top housing 146. The processing chamber can include side walls 146' and a top wall 146”. The RF antenna can alternatively be placed in the side wall. For clarity, the shielded box is left in this figure and is thus drawn as a dashed line, but those skilled in the art should be clear that in use, the shielded box is arranged around the RF antenna to prevent RF waves from escaping from the enclosure of the processing chamber.

[0105] Figure 9Schematically shows details of a cross-section of an RF antenna according to a first embodiment of an apparatus of the present invention. The RF antenna is an example of an inverted antenna, more specifically a planar inverted antenna or PIFA. The RF antenna includes a conductive antenna trace 180, which is meandered to shorten the total length of the antenna. The RF antenna further includes a ground plane 181. An RF cable 170, which may be a coaxial cable, may include a core 172 and a shield 171, and the core and the shield are respectively connected to the antenna trace 180 via a second RF cable feed point 174 and to the ground plane 181 via a first RF cable feed point 173.

[0106] Figure 10A Schematically shows a seventh cross-section of a processing chamber 145 according to a first embodiment of a system of the present invention. Referring to the previous figures, the same reference numerals may indicate the same features. The processing chamber includes a bottom housing 147 and a top housing 146. The bottom housing has a bottom edge 191, and the top housing has a top edge 190. The processing chamber is shown in an open position. In this embodiment, the top housing may be away from the bottom housing. A holder 120 is shown when held by a holding member disposed in the bottom housing. In addition, a holder 120' is shown when separated from the processing chamber. The holder 120 can be moved in the direction R to the position indicated by the holder 120'.

[0107] Figure 10B Schematically shows an eighth cross-section of a processing chamber according to a first embodiment of a system of the present invention. Referring to Figure 10A , the same reference numerals may indicate the same features. The bottom housing slides horizontally away from the top housing for separation from the top housing in the direction S.

[0108] Figure 10C Schematically shows a ninth cross-section of a processing chamber according to a first embodiment of a system of the present invention. Referring to Figure 10A , the same reference numerals may indicate the same features. In this embodiment, the top housing is hinged to the bottom housing.

[0109] Figure 11 Schematically shows a cross-section according to a third embodiment of a system of the present invention. Referring to the previous figures, the same reference numerals may indicate the same features. The apparatus includes holding members 192, 192' disposed inside the processing chamber. The holding members are arranged to suspend the holder 120.

[0110] Figure 12Schematically shows a tenth cross-section of a processing chamber of a first embodiment of a system according to the present invention. Referring to the previous figures, the same reference numerals may indicate the same features. The processing chamber 145 includes a top housing 145 and a bottom housing 146 shown in a closed position. In addition, the holder 120 is at least partially disposed inside the processing chamber. The space enclosed or sealed by the processing chamber is the internal space 193.

[0111] Those skilled in the art will understand the term "substantially" herein, for example, expressed as "substantially all emissions" or "substantially consisting of". The term "substantially" may also include embodiments having "entirely", "completely", "wholly", etc. Thus, in various embodiments, the modifier "substantially" may also be removed. Where applicable, the term "substantially" may also refer to 90% or higher, such as 95% or higher, particularly 99% or higher, and even more particularly 99.5% or higher, including 100%. The term "comprising" also includes embodiments in which the term "comprising" means "consisting of".

[0112] Those skilled in the art will understand and will be clear about the term "functionally". The terms "substantially" and "functionally" may also include embodiments having "entirely", "completely", "wholly", etc. Thus, in various embodiments, the modifier "functionally" may also be removed. For example, when used in "functionally parallel", those skilled in the art will understand that the modifier "functionally" includes the term "substantially" as explained above. Specifically, functionally should be understood to include the configuration of features that allows these features to act as if the modifier "functionally" were absent. The term "functionally" is intended to cover variations of the features it refers to, and such variations enable the combination of features to operate or function in the functional use of the features and other features that may be present in the present invention. For example, if an antenna is functionally coupled or functionally connected to a communication device, the received electromagnetic signal received by the antenna is available for use by the communication device. The word "functionally" as used, for example, in "functionally parallel" is used to cover both completely parallel and also the embodiments covered by the word "substantially" as explained above. For example, "functionally parallel" relates to embodiments that act as if the components were parallel during operation. This covers embodiments in which those skilled in the art clearly know that it operates as if it were parallel within its intended field of use.

[0113] In the foregoing specification, the present invention has been described with reference to specific examples of embodiments of the present invention. However, it will be apparent that various modifications and changes can be made to the present invention without departing from the scope of the present invention as set forth in the appended claims. For example, the shape can be any type of shape suitable for achieving the desired effect. Devices that functionally form separate devices can be integrated with a single physical device.

[0114] However, other modifications, variations and alternatives are also possible. Accordingly, this specification and the accompanying drawings are to be regarded in an illustrative rather than a restrictive sense.

[0115] In the claims, any reference signs placed in parentheses shall not be construed as limiting the claim. The word 'comprising' or 'including' does not exclude the presence of other elements or steps than those listed in a claim. Further, as used herein, the term 'a' or 'an' is defined as one or more than one. Also, the use of introductory phrases such as 'at least one' and 'one or more' in the claims shall not be construed to imply that another claim element introduced by the indefinite article 'a' or 'an' limits any particular claim containing such introduced claim element to inventions containing only one such element. This is the same for the use of the definite article. Terms such as 'first' and'second' are used to arbitrarily distinguish between elements so described, unless otherwise stated. Thus, these terms are not necessarily intended to indicate a temporal or other precedence of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.

[0116] Embodiments

[0117] 1. A system (100) for making food, comprising:

[0118] An RF-impermeable layer (110);

[0119] A holder (120) for holding the food, comprising:

[0120] - A gas-permeable side (121);

[0121] A device (140), comprising:

[0122] - A processing chamber (145) which is arranged to be RF-impermeable and preferably gas-impermeable;

[0123] - Holding members (148, 148') for holding the holder inside the processing chamber;

[0124] - RF antennas (155, 155') which are arranged to radiate RF energy into the interior of the processing chamber for heating the food inside the holder;

[0125] - A fan (156) for circulating air in the processing chamber through the breathable side and through the holder; and

[0126] - Heaters (157, 157') arranged to supply heat to the circulating air;

[0127] wherein the fan and the heaters are arranged for air frying the food inside the holder;

[0128] wherein the RF-impermeable layer is also breathable and is arranged to be generally parallel to the breathable side of the holder, at least in use;

[0129] wherein the RF-impermeable layer separates the processing chamber in a first region (150) vulnerable to RF energy from the RF antenna and a second region (151) shielding the RF energy from the RF antenna during use; and

[0130] wherein the fan is arranged in the second region.

[0131] 2. The system according to the previous embodiment, wherein supplying RF energy to the food inside the holder is independent of supplying hot air to the food inside the holder.

[0132] 3. The system according to any one of the preceding embodiments, wherein the breathable side is arranged to allow a vertical air flow (A) to pass through the holder.

[0133] 4. The system according to any one of the preceding embodiments, wherein the breathable side of the holder is a breathable bottom side (121).

[0134] 5. The system according to any one of the preceding embodiments, wherein the holder includes the RF-impermeable layer.

[0135] 6. The system according to the previous embodiment, wherein the RF-impermeable layer is the bottom side of the holder, preferably wherein the RF-impermeable layer and the breathable side are integrated.

[0136] 7. The system according to the previous embodiment 5, wherein the RF-impermeable layer is the top side of the holder.

[0137] 8. The system according to any one of the preceding embodiments, wherein the holding member is at least partially RF-impermeable for use with the RF-impermeable layer to form an RF separation in the processing chamber.

[0138] 9. The system according to any one of the preceding embodiments, wherein the heater is arranged in the second region.

[0139] 10. The system according to the previous embodiment, wherein the heater is at least partially RF-opaque for use with the RF-opaque layer to form an RF isolation in the processing chamber.

[0140] 11. The system according to any one of the previous embodiments, comprising:

[0141] - an RF source (158) arranged to supply RF energy to the RF antenna;

[0142] - a motor (159) for driving the fan;

[0143] - a heater source for supplying energy to the heater; and

[0144] - a controller (160) for controlling the amount of RF energy from the RF source, the number of rotations of the motor, and the amount of radiant heat from the heater, wherein the controller independently controls the RF source, the motor, and the heater.

[0145] 12. The system according to any one of the previous embodiments, wherein the holder is a food basket.

[0146] 13. The system according to any one of the previous embodiments, wherein the system is combined with any one of the features from the claims section.

Claims

1. A system (100) for making food, comprising: An RF-impermeable layer (110); A holder (120) for holding the food, comprising: - A breathable side (121); A device (140), comprising: - A processing chamber (145) which is arranged to be RF-impermeable and airtight; - Holding members (148, 148') for holding the holder inside the processing chamber; - RF antennas (155, 155') which are arranged to radiate RF energy into the interior of the processing chamber for heating the food inside the holder; - A fan (156) for circulating air in the processing chamber through the breathable side and through the holder; and - Heaters (157, 157') which are arranged to supply heat to the circulating air; Wherein the fan and the heaters are arranged for air frying the food inside the holder; Wherein the RF-impermeable layer is also breathable and is arranged to be generally parallel to the breathable side of the holder at least during use; Wherein the RF-impermeable layer separates the processing chamber in a first region (150) vulnerable to RF energy from the RF antennas and a second region (151) shielding RF energy from the RF antennas during use; and Wherein the fan is arranged in the second region.

2. The system according to the previous claim, wherein supplying RF energy to the food inside the holder is independent of supplying hot air to the food inside the holder.

3. The system according to any one of the preceding claims, wherein the breathable side is arranged to allow a vertical air flow (A) to pass through the holder.

4. The system according to any one of the preceding claims, wherein the breathable side of the holder is a breathable bottom side.

5. The system according to any one of the preceding claims, wherein the holder comprises the RF-impermeable layer.

6. The system according to claim 5, wherein the RF-impermeable layer is the bottom side of the holder, wherein the RF-impermeable layer and the breathable side are integrated.

7. The system according to the previous claim 5, wherein the RF-impermeable layer is the top side of the holder.

8. The system according to any one of the preceding claims, wherein the holding members are at least partially RF-impermeable for use with the RF-impermeable layer, thereby forming an RF separation in the processing chamber.

9. The system according to any one of the preceding claims, wherein the heaters are arranged in the second region.

10. The system according to claim 9, wherein the heaters are at least partially RF-impermeable for use with the RF-impermeable layer, thereby forming an RF separation in the processing chamber.

11. The system according to any one of the preceding claims, comprising: - An RF source (158) which is arranged to supply RF energy to the RF antennas; - A motor (159) for driving the fan; - A heater source for providing energy to the heater; and - A controller (160) for controlling the amount of RF energy from the RF source, the number of revolutions of the motor, and the amount of radiant heat from the heater, wherein the controller independently controls the RF source, the motor, and the heater.

12. The system according to any one of the preceding claims, wherein the holder is a food basket.

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