Air frying system and method

Abstract

The present invention relates to the field of food preparation by cooking with hot air in combination with RF energy. A system (100) for cooking food comprises a holder (120) for holding food having breathable sides (121), a treatment chamber (145) that is RF opaque and preferably non-breathable, holding means (192, 192', 148, 148') for holding the holder inside the treatment chamber, RF antennas (155, 155') arranged to radiate RF energy into the treatment chamber to heat the food in the holder, a fan (156) for circulating air in the treatment chamber through the breathable sides and through the holder, and a heater (157) arranged to provide heat to the circulated air. 0), wherein a fan and heater are arranged to air-fry food within the holder, the processing chamber having an upper shell (146) having an upper rim forming an upper interior space and an access opening to the upper interior space, and a lower shell (147) having a lower rim forming a lower interior space and an access opening to the lower interior space, the upper and lower shells being arranged relative to one another in the closed position to enclose an interior space (193) including the upper and lower interior spaces, the radiated RF energy generating RF waves, the processing chamber being configured such that the RF waves have nodes substantially at the upper rim (190) and / or the lower rim (191) in the closed position.

Description

Detailed Description of the Invention

[0001] [Field of the Invention] The present invention relates to the field of food preparation by cooking with hot air, for example air fryers and methods of air frying, and more particularly to the field of air frying foods and methods for air frying foods. [Background of the invention] An air fryer is a kitchen appliance that cooks food by circulating hot air around it using a convection mechanism. A mechanical fan circulates hot air, up to 230°C, at high speeds around the food to cook the food and create a crispy layer. The crispy layer is usually thin to create the crispy effect while retaining moisture in the center of the food, which usually heats up by conduction.

[0002] Foods cooked in an air fryer are usually quiches, pies, spring rolls, croquettes, and even rolls and croissants, as well as sweets such as potato chips, which are often pre-fried in hot oil, chicken, chicken wings, fish, fish sticks, steaks, spare ribs, or french fries, which are often stored by quick freezing.

[0003] The drawback is that when a significant amount of frozen food is fried at once, known air fryers produce food that is fried or even burnt on the outside while the center of the food is still cold or even frozen, or known air fryers take a long time to cook. To avoid this problem, the food-holding chamber of modern air fryers is designed to be small, but adds another drawback. Another drawback is that modern air fryers are only suitable for home use due to the size of the food-holding chamber, and are not suitable for commercial use, such as in restaurants, bars, cafes, brasseries, cafeterias, fast food restaurants, etc. [Summary of the Invention] It is an object of the present invention to alleviate the above-mentioned drawbacks.According to a first aspect of the present invention, a system for cooking food comprises an apparatus comprising a radio frequency (RF) opaque layer, a holder for holding a food product, the holder having breathable sides, a treatment chamber arranged to be RF opaque and preferably non-breathable, a holding means for holding the holder inside the treatment chamber, an RF antenna arranged to radiate RF energy into the interior of the treatment chamber to heat the food product inside the holder, a fan for circulating air in the treatment chamber through the breathable sides and through the holder, and a heater arranged to provide heat to the circulated air, the fan and heater arranged to air fry the food product inside the holder, the RF opaque layer also being breathable and arranged substantially parallel to the breathable sides of the holder at least in use, the RF opaque layer separating the treatment chamber in use into a first area susceptible to RF energy from the RF antenna and a second area shielded against RF energy from the RF antenna, the fan being arranged in the second area.

[0004] The process of air frying involves cooking food by circulating hot air around the food in a system. The circulation of the hot air is forced by a fan that moves the air. The fan circulates, swirls and / or propels the hot air, which can be heated up to 230°C, at high speeds around the food, cooking the food and creating a crispy layer.

[0005] The breathable side should be able to transmit the typically high velocity, hot air as used in air fryers. Examples of breathable sides are meshes of certain plastics that can withstand high temperature air, metal layers with openings, or meshes of metal or other materials made, for example, from ceramic or other.

[0006] The non-ventilated sides or walls need only be impermeable to the hot air circulating at high velocity within the air fryer. They do not necessarily need to be airtight. The non-ventilated sides or walls must at least prevent the hot air from the inside from harming or burning anyone outside the system.

[0007] An RF opaque layer or wall is a layer that blocks the propagation of RF waves of a certain frequency or frequency band. The RF opaque layer or wall may be reflective, absorbing, diffusing, or a combination thereof. The RF opaque layer is typically RF opaque to at least some, and preferably all, frequencies of RF energy radiated by the RF antenna. The RF opaque layer may be a metal layer, a metal mesh, or the like. The RF opaque layer may be a metal layer with openings of a suitable size to prevent RF waves from leaking through the layer.

[0008] The treatment chamber usually has walls. The treatment chamber walls are RF-opaque and non-porous. This prevents the outside of the treatment chamber and people standing by the system from being exposed to any dangerous RF radiation and / or hot air during use. Since food needs to be brought into the treatment chamber and taken out again, the treatment chamber usually has openings. The treatment chamber may for example comprise two shell halves that fit together tightly. When combined, the two shells provide a treatment chamber that is RF-opaque and non-porous. Meanwhile, when the two shells are separated, the half shell that holds the food provides easy access to this food. Special shape and material considerations ensure that the RF-opaque walls prevent RF leakage in areas that are divided for openings in the treatment chamber or for access to motors, temperature sensors, or antennas, and it prevents RF leakage in those areas by confining the RF waves within the RF-opaque boundaries.

[0009] The inventors' insight is that tightly packed food pieces and / or large quantities of food pieces result in food that is cooked or even burnt on the outside while the inside remains cold or even frozen. The thermal conductivity of frozen food is different compared to the thermal conductivity of non-frozen food. The inventors' insight is that if the outside of a large food piece or tightly packed food gets hot, and if the temperature of the surrounding air is too high, then due to the difference in conductivity, only the outer shell of the food will be cooked. This adverse effect is amplified when the volume of food is large, preventing the use of prior art air fryers in commercial applications, such as those used in restaurants, bars, cafes, brasseries, cafeterias, fast food restaurants, etc.

[0010] The inventor's insight is that if the food product were to transition uniformly from the frozen to the non-frozen state, air frying could be used in the non-frozen state to obtain large quantities of typical air fried food products. Furthermore, the air fried food products would have a near crispy exterior and a uniformly cooked interior. The inventor's further insight is that uniform transition of large quantities of food products in a relatively short period of time would typically be achieved using RF waves that can penetrate large quantities of food products. RF waves penetrating the frozen food product would heat the food product uniformly, or at least for the interior of the food product, for a more uniform transition of the food product from the frozen to the non-frozen state.

[0011] Known fans are typically made of metals such as steel to provide an easy to manufacture and low cost fan. These fans distort RF waves. And even if the fan were made of plastic, which has a dielectric constant significantly different from the surrounding air, the fan would still block the RF waves. Furthermore, the shaft of the fan is typically made of metal, which also blocks RF waves. It was the inventor's insight to modify the arrangement of the components of the air fryer so that the air fryer could incorporate heating food with RF energy.

[0012] The system includes a treatment chamber for holding a food item within the treatment chamber, the system including components positioned such that the food item can be exposed to RF energy as well as the effect of an air fryer, which provides the technical effect of improving cooking uniformity of the cooked food item in a relatively short period of time.

[0013] The fan is located in an area of ​​the chamber that is not or only minimally exposed to RF energy or low levels of RF energy that do not or only only minimally interfere with the RF waves, so that the RF energy can be efficiently transferred to the food. In the context of the claims, the term area is used to identify the boundary where the RF energy is or where the RF energy is primarily located. Alternative expressions for area can be a part of the chamber, a portion of the chamber, a cavity of the chamber, a space of the chamber. The technical effect of the RF impermeable layer also being breathable and being located substantially parallel to the breathable side of the holder, at least during use, is that the enclosed space can be separated into two areas. The first area is accessible to hot air for the air frying effect and to the RF energy for heating the food, and the second area is accessible to hot air for the air frying effect. Now, by placing the food in the first area and the fan in the second area, the technical effect of the fan can be obtained without interfering with the RF waves.

[0014] Furthermore, in the context of this invention, the term approximately parallel or parallel is understood as two layers, or layers and sides, that overlap each other or are spaced apart by a certain distance. Two parallel layers may have a small angle, for example a few degrees, relative to each other. Usually, these deviations from parallelism are within the limits of the product.

[0015] In an embodiment of the invention, the supply of RF energy to the food within the holder is not dependent on the supply of heated air to the food within the holder. This provides the advantage that the food can be exposed to RF energy during the food's phase change from frozen to unfrozen, while the circulation of hot air can be stopped or minimized. This also provides the advantage of relying on the setting to cook the food in an unfrozen state, which can be done by hot circulating air and / or RF energy.

[0016] In an embodiment of the invention, the breathable sides are arranged to allow a vertical flow of air through the holder. The air is advantageously vertical through the food product. Depending on the system's settings and / or functionality, the vertical flow of air through the food product may be from top to bottom or bottom to top. Alternatively, the system may change the vertical direction of the air flow through the food product, for example in a pulsed manner from one vertical direction and then the opposite vertical direction.

[0017] In an embodiment of the invention, the breathable side of the holder is advantageously arranged as the breathable bottom surface, which provides an advantageous entry point for air flow into the food product. In an embodiment of the invention, the holder has an RF opaque layer. In a further advantageous embodiment of the invention, the RF opaque layer is the bottom surface of the holder, and preferably the RF opaque layer and the breathable side are integrated. This provides the advantage that the RF opaque layer and the breathable side are aligned by design to optimize the conductance of air through the RF opaque layer.

[0018] In an embodiment of the invention, the RF opaque layer is the top surface of the holder. Typically, the bottom surface of the holder also includes a breathable bottom surface to allow air to pass vertically through the holder and therefore through the food item held within the holder.

[0019] In an embodiment of the invention, the retaining means is at least partially RF opaque so as to form RF isolation in the process chamber together with the RF opaque layer during use. The holder typically leaves a space between the holder and the process chamber to allow air to circulate after passing through the holder. RF energy can leak through this space from the first region to the second region. The retaining means typically extends from the holder and at least partially fills the space between the holder and the process chamber. The retaining means may therefore advantageously extend the RF opaque layer to reduce leakage of RF energy into the second region.

[0020] In an embodiment of the invention, the heater is advantageously placed in the second area. The heater usually comprises metal parts or at least parts that affect RF waves. The heater is therefore optimally placed inside the second area where there is no or a small amount of RF energy and therefore the heater causes little disturbance of the RF waves. In particular, it is known that the grounding of the heater can cause disturbance of the RF waves if the heater is not in an area shielded from the RF waves. In an alternative embodiment, the heater is an indirect heater, which heats at least a part of the process chamber, which then conducts heat to the air passing along at least a part of the process chamber. This provides the advantage that the heater can be placed virtually anywhere outside the process chamber.

[0021] In an embodiment of the invention, the heater is at least partially RF opaque so as to form RF isolation within the process chamber together with the RF opaque layer during use. In a further embodiment, the retaining means is also advantageously part of the RF isolation means so as to improve RF shielding for reduction of RF energy in the second region, thereby minimizing disturbance of the RF waves of components in the second region.

[0022] In an embodiment of the invention, the system comprises an RF source provided for supplying RF energy to the RF antenna, a motor for driving a fan, a heating source for supplying energy to the heater, and a controller for controlling the amount of RF energy from the RF source, the speed of the motor, and the amount of radiated heat from the heater, the controller controlling the RF source, the motor, and the heater separately. The controller may advantageously control various parameters that result in optimal cooking results and a uniform transition of the food from a frozen to an unfrozen state in a minimum of time.

[0023] In an embodiment of the invention, the holder is a food basket. Typically, the food basket has a bottom surface made of an RF opaque mesh, such as a metal mesh, thereby advantageously incorporating breathable sides and an RF opaque layer.

[0024] According to another aspect of the invention, a system for cooking food comprises an RF opaque layer, a holder for holding a food product, the holder having breathable sides, a treatment chamber arranged to be RF opaque and non-breathable, a holding means for holding the holder inside the treatment chamber, an RF antenna arranged to radiate RF energy into the interior of the treatment chamber to heat the food product inside the holder, a fan for circulating air in the treatment chamber through the breathable sides and through the holder, and a heater arranged to provide heat to the circulated air, the RF opaque layer also being breathable and arranged substantially parallel to the breathable sides of the holder at least in use, the RF opaque layer separating the treatment chamber in use into an upper region susceptible to RF energy from the RF antenna and a lower region shielded from RF energy from the RF antenna, the fan being arranged in the lower region. This aspect of the invention provides similar advantages as discussed throughout the text for other aspects of the invention.

[0025] In an embodiment of the invention, the device comprises a motor for driving the fan, the motor being located below the treatment chamber. The motor is usually one of the largest objects or objects with the greatest mass in the device. Locating the motor low in the device provides the advantage of a low center of gravity, and therefore improves the mechanical stability of the device or system as a whole. This is particularly useful when the holder is being installed, removed, and / or partially placed outside the treatment chamber, but still remains in the treatment chamber or is connected to the device. The holder and the food in the holder may in this case destabilize or tilt the device. Locating the motor below the treatment chamber reduces the change in tilt of the device during installation, removal, and / or placement of the holder.

[0026] In an embodiment of the invention, the treatment chamber defines a vertical axis that is a substantial axis of symmetry, and the motor is aligned with this vertical axis. The system is also symmetrical about the vertical axis to a large extent. Hence, the air flow circulating inside the treatment chamber for the air frying effect is largely symmetrical and substantially doughnut-shaped. Positioning the fan relative to this largely doughnut shape advantageously simplifies facilitating this substantially doughnut-shaped air flow. Furthermore, positioning the motor with a substantially vertical axis provides the advantage of the motor shaft directly driving the fan, simplifying the design of the apparatus as well as the number of components of the apparatus, and therefore minimizing replacements for failures of the apparatus or the system as a whole.

[0027] In an embodiment of the invention, the process chamber defines a vertical axis that is a substantial axis of symmetry, the process chamber has a back surface having a first back end and a second back end, a triangle defines a vertical projection of the vertical axis, the first back end, and the second back end, and the center of gravity of the motor is located inside the triangle.

[0028] Locating the motor low in the device provides the advantage of a lower center of gravity and therefore improves the mechanical stability of the device or system as a whole. This is particularly useful when the holder is being installed, removed, and / or partially positioned outside and in front of the treatment chamber, but still remains in the treatment chamber or is connected to other parts of the device or system. The holder and the food within the holder may then destabilize or tilt the device. Locating the motor below the treatment chamber reduces changes in the tilt of the device during installation, removal, and / or placement of the holder.

[0029] This embodiment provides the added advantage that when the holder is coupled to the device during installation, removal, and / or deployment, while being positioned in front of the device, the motor acts as a counterweight, improving overall balance and preventing the device or system from tipping.

[0030] In an embodiment of the invention, the device comprises a shared shaft between the motor and the fan for direct drive of the fan, this embodiment provides the advantage of reducing the number of components and therefore replacements on failure.

[0031] In an embodiment of the invention, the holder is a food basket, preferably having an RF-opaque, breathable bottom, such as a metal mesh, and / or RF-transparent, non-breathable sides, such as certain plastics.

[0032] According to another aspect of the present invention, a system for cooking food includes an apparatus including a treatment chamber configured to be RF opaque and non-porous, the treatment chamber having a treatment chamber surface, an RF antenna positioned to radiate RF energy to at least a portion of the treatment chamber interior to heat the food within the treatment chamber, and an RF transparent layer having an RF transparent surface and sealing the RF antenna from a portion of the treatment chamber configured to hold the food. During preparation or cooking of food within the treatment chamber, the food may splash, crackle, bubble, or otherwise disperse due to, for example, gas generation within the food being cooked. Pieces of food or food splashes may impact the treatment chamber surface. These food pieces or food splashes must be removed in a timely and complete manner, as they may cause health problems for food subsequently cooked within the treatment chamber if not properly removed.

[0033] The RF antenna is edged and curved, usually sharply edged and curved, to radiate RF energy with the desired efficiency and RF mode. The edges and curves of the RF antenna make it difficult to clean. By covering the RF antenna with an RF transparent layer, food particles and food splashes cannot couple to the RF antenna. This seal is therefore intended to contain food debris or pieces originating from the food inside the processing chamber, preferably the inside of the holder.

[0034] In an embodiment of the invention, the system typically includes a fan, heater, and air ducts for circulating hot air inside the processing chamber for air frying, as specified in other aspects of the invention. Air frying can cause food to splatter, crackle, bubble, or get spattered. When air frying is combined with RF cooking, the benefits of improved cleaning become even more beneficial.

[0035] Uncovered RF antennas inside the processing chamber also provide a means of air frying, and while they do not heat the RF antenna enough to carbonize the food on the RF antenna, they can heat the RF antenna, making health issues even more significant. Therefore, uncovered RF antennas are typically difficult to clean. Furthermore, with the increased temperature inside the processing chamber, food particles or food splatters can bond more tightly to the uncovered RF antenna, making cleaning more difficult.

[0036] In an embodiment of the invention, the RF transparent layer is seamlessly joined to the treatment chamber surface to further improve the cleanability of the treatment chamber or to further facilitate the removal of food particles or food splashes. In an embodiment of the invention, the RF transparent surface is seamlessly joined to the treatment chamber surface to further improve the cleanability of the treatment chamber or to further facilitate the removal of food particles or food splashes. In an embodiment of the invention, at least an edge of the RF transparent surface is flush with the treatment chamber surface to further improve the cleanability of the treatment chamber or to further facilitate the removal of food particles or food splashes. In an embodiment of the invention, the treatment chamber has a protrusion, preferably an outward protrusion, and the RF antenna is located within the protrusion to further improve the cleanability of the treatment chamber or to further facilitate the removal of food particles or food splashes. In an embodiment of the invention, the RF transparent surface is planar, substantially planar, slightly undulating, or slightly curved to further improve the cleanability of the treatment chamber or to further facilitate the removal of food particles or food splashes. The amount of swell, or curvature, depends on the shape of the process chamber so as to seamlessly fit the curvature of the process chamber.

[0037] In an embodiment of the invention, the RF transparent surface is flush with the treatment chamber surface to further enhance cleanability of the treatment chamber or to further facilitate removal of food particles or food splashes. This embodiment combines particularly well with embodiments in which the RF transparent surface is planar and / or in which the treatment chamber has an outwardly protruding portion and the RF antenna is positioned on the protruding portion to provide a planar, generally planar, slightly undulating, or slightly curved surface to be cleaned.

[0038] In an embodiment of the invention, the RF antenna is a substantially planar antenna. This embodiment is particularly well combined with an embodiment in which the treatment chamber has an outward protrusion and the RF antenna is arranged on the protrusion so as to provide a planar surface to be cleaned. A planar or substantially planar RF antenna provides the advantage that the depth of the protrusion does not need to be too large.

[0039] In an embodiment of the invention, the RF antenna is an inverted-F or PIFA antenna, preferably an inverted dipole, also known as a slot antenna, or a number of such antennas. These are advantageous types of RF antennas, capable of transmitting within a desired frequency band, or in more than one frequency band, and are generally planar.

[0040] According to another aspect of the invention, a system for cooking food comprises an apparatus including an RF opaque layer, a holder for holding a food product, the holder having breathable sides, a treatment chamber arranged to be RF opaque and non-breathable, a holding means for holding the holder inside the treatment chamber, an RF antenna arranged to radiate RF energy into the interior of the treatment chamber to heat the food product inside the holder, a fan for circulating air in the treatment chamber through the breathable sides and through the holder, and a heater arranged to provide heat to the circulated air, the fan and heater arranged to air fry the food product inside the holder, the RF opaque layer also being breathable and arranged at least in use substantially parallel to the breathable sides of the holder, the RF opaque layer separating the treatment chamber in use into a first area susceptible to RF energy from the RF antenna and a second area shielded from RF energy from the RF antenna, the fan being arranged in the second area. This aspect of the invention provides similar advantages as discussed throughout the text for other aspects of the invention.

[0041] In an embodiment of the invention, the holder has a size such that during use, the holder uses only a portion of the first region such that the unused area of ​​the first region is sized and / or shaped to receive RF energy from the RF antenna to generate RF waves in the unused area to efficiently transfer the RF energy from the RF antenna to the food in the holder. The inventor's insight is that the food held in the holder impedes RF waves or the formation of RF waves. The unused area provides an advantageous transition space from the RF antenna and the food to efficiently transfer the RF energy from the RF antenna to the food. The inventor's experiments and simulations have shown that the unused space needs to be at least half of the first region, which is the area where RF energy can be available. In a further embodiment, the height of the holder is less than half the height of the first region or equal to half the height of the first region. Furthermore, experiments and simulations have shown that the holder can have a width and length that is comparable to 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 to circulate along the circulation path, typically passing vertically between the holder and the processing chamber and then being blown or sucked through the food in the holder for the air frying effect.

[0042] In an embodiment of the invention, the primary RF wave in the unused area is a standing RF wave. The size and / or shape of the first area is usually selected such that one or two standing waves are formed, at least for the length and width. The standing wave provides a means for efficient transfer of RF energy from the RF antenna to the food product at a well-defined location with high electromagnetic energy density. The standing wave may have a hotspot of energy. A further advantage would be to have two primary standing waves to spread the RF energy more uniformly inside the food product. The length and width of the first area may be selected slightly differently to promote the formation of two primary standing waves.

[0043] In an embodiment of the invention, the predominant standing RF wave in the unused region 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 may be beneficial since these modes require approximately the same length and width as the first region in order to be the predominant standing RF wave.

[0044] In an embodiment of the invention, the RF antenna operates in a frequency band that is completely transparent to the food in the holder, the food in the holder having a weight of more than 2Kg, preferably more than 3Kg, more preferably more than 4Kg. These amounts of food are typically used in commercial and not domestic applications. The frequency of the RF waves and the size and / or shape of the treatment chamber are advantageously selected and sized and / or shaped, respectively, to accommodate this amount of food in the holder.

[0045] In an embodiment of the invention, the RF antenna operates in a frequency band that completely penetrates the food in the holder, the frequency band being below 1 GHz, preferably in the 902-928 MHz range, or around 915 MHz. The amount of food as mentioned above must be penetrated by the RF waves to provide RF energy to the entire inside of the food. The 2.45 GHz frequency that is usually used is not very suitable, since the penetration depth is only in the centimeter range and therefore is not sufficient to penetrate a food block weighing more than 2 Kg. Choosing a lower frequency advantageously allows the RF waves to penetrate deeper into the food, instead of heating only the outer layer of the food. If the frequency is chosen so low that the RF waves traversing the food are only partially absorbed, the RF waves may subsequently bounce off the treatment chamber and / or the RF wall separating the first and second zones, to traverse the food again to be absorbed and thereby heat the food. This provides the advantage that the food is heated more uniformly, for example during the transition from frozen to unfrozen. This provides the added benefit that the food product is heated less in hot spots defined by standing waves and more by more random reflections which promote an even diffusion of the absorbed RF energy within the food product.

[0046] It is the inventor's insight based on extensive characterization of various foods and conditions that the 902-928 MHz frequency band has one or more advantages over other frequencies, such as the 2400-2500 MHz band. Also, in various countries, this frequency band of 902-928 MHz is a license-free band that can be used freely. However, in many other countries, very strict regulations apply for that frequency band, and measures must be taken to avoid electromagnetic interference. Therefore, selecting a frequency in this band advantageously facilitates compliance with those different requirements, and still achieves good performance, especially in the 915 MHz band for the United States, as well as in the global ISM band of 2.45 GHz. Therefore, by selecting a frequency in this band, the product is simplified, while this frequency band also brings advantages such as high penetration to the food in the holder.

[0047] In a further preferred embodiment, the main RF wave has a frequency below 1 GHz, preferably within the 902-928 MHz band, or around 915 MHz, and the main RF wave has at least one, preferably both, of TE mode 011 and / or TE mode 111. Experiments and tests by the inventors have shown that, with the above parameters, the length and width of the treatment chamber fall in the range of 250-380 mm, preferably in the range of 280-340 mm, more preferably around 306 mm. This dimension may also refer to the specific size of the RF-impermeable walls of the holder and may be adjusted according to the overall effective treatment chamber. The height of the first region during experiments and tests was around 180 mm, more specifically 192 mm, while the height of the holder was less than 60% of the height of the first region. Further, it was assumed that the dielectric constant of air is near 1, the dielectric constant of the RF transparent side of the holder is near 3-10 depending on the material of the holder, e.g., PTFE, PEEK, fiberglass, or ceramic, and the dielectric constant of frozen foods is near 80, while unfrozen but cold foods may have a dielectric constant near 3. Typically, as the temperature increases, the dielectric constant of the food settles near 80 for crispy crust, while it ends up near 40 for mostly water foods, e.g., hot snack foods with moisture inside. These dimensions are particularly well suited for commercial use, since they hold larger quantities of food. This embodiment may be useful for small general purpose or countertop devices, and may be further improved by selecting different lengths and widths for the first region, within the ranges specified above to advantageously spread the RF energy more uniformly. For larger devices beyond countertop placement, a frequency of 433 MHz may be selected to support quantities of food of 8 kg or more.

[0048] In a further preferred embodiment, the main RF wave has a frequency below 1 GHz, preferably in the band of 902-928 MHz, or around 915 MHz, and the main RF wave has a TM mode 110. Experiments and tests by the inventors have shown that, with the above mentioned parameters, the length and width of the treatment chamber fall in the range of 200-260 mm, preferably in the range of 220-240 mm, more preferably around 230 mm. The height of the first region during the experiments or tests was around 180 mm, while the height of the holder was less than half the height of the first region. Furthermore, it was assumed that the dielectric constant of air is around 1, the dielectric constant of the RF transparent side of the holder is 2 (PTFE), 3-4 (PEEK, glass fiber), around 4-10 (ceramic), and the dielectric constant of the food product ranges over a very wide range from 3 to 80, while very low values ​​hold for frozen foods and high values ​​may hold for non-frozen but cold foods. As the temperature increases, the dielectric constant drops, typically to around 40, which is true for mostly moist foods such as hot snack foods with moisture inside and crispy crusts. These dimensions are particularly well suited for commercial use as they hold larger amounts of food.

[0049] According to another aspect of the invention, a system for cooking food comprises a holder for holding a food product, the holder having breathable sides (121), a treatment chamber arranged to be RF opaque and preferably non-breathable, a holding means for holding the holder inside the treatment chamber, an RF antenna arranged to radiate RF energy into the interior of the treatment chamber to heat the food product inside the holder, a fan for circulating air in the treatment chamber through the breathable sides and through the holder, a heater arranged to provide heat to the circulated air, the fan and the heater arranged to air fry the food product inside the holder, the treatment chamber comprising an upper shell having an upper rim forming an upper interior space and an access opening to the upper interior space and a lower shell having a lower rim forming a lower interior space and an access opening to the lower interior space, the upper shell and the lower shell being arranged relative to each other to enclose an interior space including the upper interior space and the lower interior space in a closed position, the radiated RF energy generates RF waves, the treatment chamber being shaped such that the RF waves have nodes substantially at the upper rim and / or the lower rim in the closed position.

[0050] The upper and lower shells may alternatively be referred to as an upper pan and a lower pan, respectively.In a further embodiment of the invention, the upper and lower interior spaces together form an interior of the process chamber.

[0051] A node of an RF wave may be understood as a minimum value of RF energy and / or a volume of space where the RF energy is minimal, e.g. below a predefined reference value. The reference value may be 10% of the range between the maximum value of RF energy and the minimum value of RF energy. The RF energy may use a linear, decibel, or logarithmic scale. A node of an RF wave that is in contact with or adjacent to a conductive wall, e.g. a metal wall, induces a minimum current density area in the wall. It is the inventor's insight that the flow of current in the wall of the process chamber is disrupted, e.g. at the rim where the upper and lower shells are in contact or adjacent in the closed position. And when the flow of current in the wall of the process chamber is disrupted, the RF wave and, as a result, the standing wave is disrupted. By aligning the node of the RF wave, e.g. with one of the rims where the two shells meet, the disruption of the RF wave is reduced. This reduction of disruption allows for a reduction in the amount of radiated RF energy put into the RF wave to form the RF wave, or a standing RF wave. Therefore, the effect of placing or aligning the node of the RF wave with one of the rims results in a more efficient system and / or improved transfer of radiated RF energy from the RF antenna to the food item within the holder.

[0052] In an embodiment of the invention, the upper and lower shells are arranged relative to one another in an open position to allow the holder to be attached to and removed from the treatment chamber, which advantageously allows food to be transferred between the treatment chamber and the exterior.

[0053] In an embodiment of the invention, the upper shell has an upper shell height and the lower shell has a lower shell height, the upper shell height and the lower shell height are substantially the same. This embodiment advantageously instigates and / or promotes RF waves, e.g. standing RF waves, in the upper interior space, such that the change in the lower interior space, which typically holds the holder, preferably with food, benefits from RF waves in the lower interior space that may typically be absorbed by the food. In a preferred embodiment, the diameter of the second interior space is substantially slightly larger than 10 inches, such that a 10 inch pizza fits in the holder. In a preferred embodiment, the upper shell height and the lower shell 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 approximately 96 mm. In a preferred embodiment, the diameter and height of the upper shell and the lower shell are within the ranges mentioned above. The combination provides the advantage of instigating or promoting RF waves, e.g. standing RF waves or RF modes, that optimize the absorption of RF energy by the lower interior space, e.g. by the food in the holder.

[0054] In an embodiment of the invention, the upper and lower rims contact, join, and / or abut each other to form a treatment chamber that is RF-opaque and preferably non-permeable in the closed position. The rims are where the treatment chamber is usually closed and form joints or gaps. Furthermore, the RF waves induce currents in the walls of the treatment chamber. It is the inventor's insight that these currents are absent or minimal in the walls at the nodes of the RF waves and these currents are maximal in the walls at the antinodes of the RF waves. The upper and / or lower rims are advantageously located at the nodes, so that the effect of the upper and / or lower rims, preferably joints and / or gaps, is minimal for RF waves such as facilitated RF waves. The current embodiment advantageously allows for simplifying and / or adding mechanical tolerances to how the upper and lower shells are joined in the closed position. Furthermore, the RF waves are advantageously optimized since the loss of RF energy within the walls of the treatment chamber, especially where the upper and lower shells join or bond, is reduced or minimized. Certain RF modes, according to this embodiment TE mode xx1, TM mode xx1, and TM mode xx0, can result in standing RF waves, and further higher order TE and / or TM modes, usually at higher frequencies, e.g., 2450 MHz, will appear depending on the amount of food in the treatment chamber, e.g., food weight or food height, and the type of food ingredient applied, e.g., water, salt, protein, carbohydrate, sugar, or fat content.

[0055] In an embodiment of the invention, the process chamber, preferably the interior space, more preferably the interior space having a holder disposed therein, is configured such that the RF wave has a node substantially where the upper and lower shells contact, join and / or abut one another in the closed position. This embodiment further elaborates upon the above-mentioned embodiment providing or enhancing the advantages of the above-mentioned embodiment.

[0056] In an embodiment of the invention, the RF wave has a node that forms a plane substantially at the height where the upper and lower shells contact, join, and / or are adjacent to each other in the closed position. This embodiment facilitates the RF wave having a plane as a node, thereby advantageously mitigating the width and length, e.g., diameter, of the interior space of the process chamber, preferably the width and length, e.g., diameter, of the upper and / or lower shells.

[0057] In an embodiment of the invention, the retaining means (192, 192') is positioned adjacent the lower rim to contact the holder substantially at a node of the RF waves. The retaining means for retaining the holder also typically forms a joint or gap. The retaining means is also advantageously positioned in a space where the RF waves have a node to minimize absorption of RF energy at the joint or gap and / or blockage of the RF waves by the joint or gap.

[0058] In an embodiment of the invention, the holder in use within the process chamber is suspended from the holding means. This advantageously allows no joints or gaps to be created or be created in a position that would induce currents in the joints or gaps within the interior space of the process chamber. Thus, loss of RF energy through the holder and / or holding means is minimized.

[0059] According to another aspect of the invention, a system is based on one of the independent claims or embodiments, or on an aspect of the invention combined with any one or any number of the dependent claims, dependent embodiments. [Brief description of the drawings]

[0060] The invention will be elucidated and further elucidated with respect to embodiments described by way of example in the following description and with reference to the accompanying drawings, in which: FIG. [Figure 1] 1 shows a schematic cross-section of a first embodiment of a system according to the invention; [Diagram 2] 2 shows diagrammatically another cross-section of a first embodiment of a system according to the invention; [Diagram 3] 1 shows a schematic cross-section of a process chamber of a first embodiment of a system according to the invention; [Figure 4A] 2 shows a schematic view of a second cross section of the treatment chamber of the first embodiment of the system according to the invention. [Figure 4B] 3 shows a schematic view of a third cross section of the treatment chamber of the first embodiment of the system according to the invention. [Figure 4C] 3 shows a schematic view of a fourth cross section of the treatment chamber of the first embodiment of the system according to the invention. [Figure 4D] 5 shows a schematic view of a fifth cross section of the treatment chamber of the first embodiment of the system according to the invention. [Figure 4E] 6 shows a schematic view of a sixth cross section of the treatment chamber of the first embodiment of the system according to the invention. [Diagram 5] 3 shows a schematic cross-section of a second embodiment of a system according to the invention; [Figure 6] 1 shows a schematic cross-section of a first embodiment of a device according to the invention; [Figure 7] 1 shows diagrammatically a cross-sectional detail of a first embodiment of a device according to the invention; [Figure 8] 1 shows a schematic perspective view of a top corner of a first embodiment of a device according to the invention; [Figure 9] 2 shows a cross-sectional detail of an RF antenna of a first embodiment of a device according to the invention; [Figure 10A] 1 shows a schematic view of a seventh cross section of the process chamber 145 of the first embodiment of the system according to the invention. [Figure 10B] 8 shows a schematic diagram of an eighth cross section of the treatment chamber of the first embodiment of the system according to the invention. [Figure 10C] 9 shows a schematic ninth cross section of the treatment chamber of the first embodiment of the system according to the invention. [Figure 11] 3 shows a schematic cross-section of a third embodiment of a system according to the invention. [Figure 12] 10 shows a schematic cross-section of the treatment chamber of the first embodiment of the system according to the invention;

[0061] [Detailed Description of the Invention] The drawings are merely schematic and are not to scale. In the drawings, elements that correspond to elements already described will have the same reference numbers. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Figure 1 shows a schematic cross-section of a first embodiment of a system 100 according to the invention. The system comprises an RF opaque layer 110, a holder 120 and an apparatus 140. The holder has breathable sides 121. The apparatus comprises a process chamber 145, a holding means 148, 148', an RF antenna 155, 155', a fan 156 and a heater 157, 157'. The apparatus may further comprise a housing 141 housing all the features of the apparatus.

[0062] The treatment chamber of the device may comprise an upper shell 146 and a lower shell 147. The upper and lower shells may be positioned in a closed position where the upper and lower shells form a layer of the treatment chamber that is RF-opaque and non-permeable. The device is shown in the closed position with the holder disposed inside the treatment chamber. The holder may comprise a handle 125. The handle may partially protrude from the device for easy removal of the holder when the device or treatment chamber is in the open position. The open position of the device is such that when the upper and lower shells are separated, the holder can be removed from the device, more specifically from the treatment chamber, or positioned therein. In an alternative embodiment, the holder is retained within the lower shell when loading and unloading food products from the holder. In this alternative embodiment, the holder is separated from the lower shell only for cleaning purposes. In an alternative embodiment, the upper and lower shells may be the front door and rear shells, respectively. In yet another embodiment, the upper and lower shells may be the front shell and rear shell, respectively. In an embodiment of the holder, the holder comprises a removable handle 125. A removable handle provides the advantage of minimizing the number of excessively protruding elements of the holder so that it may be more easily stored in, for example, a dishwasher or cupboard.

[0063] The holding means is disposed inside the process chamber to position or locate the holder. The holder may be annular or rectangular and only supports the outer edges of the holder. The holder may be a layer that partially or completely covers the bottom of the holder. This layer may be non-permeable and / or RF opaque. In an alternative embodiment, the edge of the top shell is joined with the top edge of the holder to form an RF closed volume, while the non-permeable layer of the process chamber is separated from the RF opaque layer, the non-permeable layer of the process chamber surrounds the RF opaque layer of the process chamber, and the RF opaque layer of the process chamber and the RF opaque holder together form the first region. In this alternative embodiment, air may circulate in the space between the non-permeable layer and the RF opaque layer.

[0064] Although the embodiments have shown two RF antennas, the inventors have also contemplated embodiments using only one RF antenna. The inventors have also contemplated the use of multiple RF antennas to direct RF energy in a particular direction, such as toward a food item held in the holder. Furthermore, by using more than one RF antenna, at least one RF antenna can be used to provide RF energy, and one or more RF antennas that do not provide RF energy may be used to measure or detect the effectiveness of the transmission of RF energy toward the food item in the holder, or to identify characteristics of the food item in the holder. For example, to identify the state of the food item in the holder, such as frozen, unfrozen, or partially frozen and partially unfrozen. Next to the frozen and unfrozen states, more detailed measurements may also be used, such as identifying whether the food item is liquid or solid, to better direct RF energy to precise locations within the food item for a more uniform transition from frozen to unfrozen states, and for a more uniform cooking of the food item overall.

[0065] The fan regulates the speed of the air flow. The heater together with the fan regulates the temperature of the air flow. The temperature of the air flow will for example decrease when the speed of the air flow increases but also when the heater is switched off. The temperature of the air flow may range from a temperature above 100°C, for example from 100 to 250°C, preferably from 150 to 240°C, more preferably below 230°C. The fan and the heater are usually arranged for air frying.

[0066] The fan and heater are optimally shielded from RF waves when they are made of materials or may have a size and / or shape that mitigates, blocks, or weakens the RF waves from the RF antennas. Furthermore, the operation of the fan may exacerbate the effect of the fan on the RF waves. The RF opaque layer is therefore disposed inside the treatment chamber such that a portion of the treatment chamber is shielded from these one or more RF antennas and the RF waves radiated from these one or more RF antennas, this portion of the treatment chamber being named the second region 151. By shielding these portions, the RF waves may reach the food in the holder unhindered or with reduced attenuation for improved transfer of RF energy from the RF antennas to the food in the holder. The portion of the treatment chamber exposed to the RF waves is labeled the first region 150.

[0067] When the fan and heater are located in an RF shielded or low RF energy area, the airflow generated by the fan and heated by the heater should still be able to reach the food, as should the RF energy. The fan is positioned such that it directs the airflow through the food in the holder, through the breathable layer and / or non-breathable sides. The fan may blow air through the food or may draw air through the food. This also allows the fan to change the direction of the airflow from any side and / or angle for improved cooking and / or frying of the food.

[0068] The device comprises a motor 159. The motor may be located below the treatment chamber. FIG. 1 further shows a vertical axis of symmetry V of the device. The motor may be aligned with this axis of symmetry. In an alternative embodiment, the motor may be located towards the rear of the device to optimise balance and / or stability of the device, especially during loading and unloading of the holder with food therein. The positioning of the motor may balance the weight of the holder with food therein, especially when the holder is loaded onto the device out of alignment with the vertical axis V. The device may comprise a shaft 164 coupling the motor to the fan, which offers the advantage of a very simple and secure coupling. Alternatively, the motor may be indirectly coupled to the fan, which offers the advantage of a more flexible motor positioning.

[0069] 2 shows a schematic representation of another cross section of a first embodiment of a system 100 according to the invention. The system comprises an RF opaque layer 110, a holder 120 and an apparatus 140. The holder is shown on the outside of the apparatus. In this particular embodiment, the RF opaque layer 110 and the breathable bottom surface 121 of the holder are integrated. This has the technical effect that when the holder is removed, the heater and the fan may be easily accessible for cleaning.

[0070] FIG. 3 shows a schematic cross-section of the process chamber 145 of a first embodiment of a system according to the invention. The process chamber is shown without the housing and also without the device or holder that is placed in the process chamber. The figure shows possible locations of RF antennas. The figure shows in detail the locations where RF energy may leak out of the process chamber. Leakage may occur at the location of one or more RF antennas 155, 155'. Leakage may also occur where the upper and lower shells form the process chamber junction 144, 144'. A further leakage point may be the shaft opening 143 in the process chamber. The shaft opening allows the shaft to pass through to drive the fan. The shaft opening may be located in the lower shell. When this fan is located in a second area that is maximally free of RF energy to produce the technical effect described for the invention, this shaft may further act as an antenna to receive RF energy, usually a small amount of RF energy, exacerbating potential leakage along or through the shaft of the fan. The shaft typically includes a material that is a poor conductor of RF energy at the particular frequency or frequencies of RF energy or waves radiated by the RF antenna and used for cooking, and typically has so-called RF traps positioned around or within the shaft to confine the RF energy and waves within the process chamber.

[0071] Typically, leakage is an issue when RF wave frequencies are used outside the ISM bands, which are mostly freely available worldwide, whereas other frequencies are not. In particular, frequencies around 915 MHz are not freely available, for example in Europe. This requires that leakage should be minimized, preferably to a level that allows the system to be accepted worldwide or nearly worldwide.

[0072] All Figures 4 show diagrammatically a second cross section of the process chamber of the first embodiment of the system 100 according to the invention. For all Figures 4 furthermore a holder 120 and a fan 156 are shown arranged inside the device.

[0073] In Figure 4A, the region through which RF energy may propagate, can propagate, or can primarily propagate is hatched. This region within the process chamber is designated as a first region 150. The boundaries of the first region include the sides of the process chamber and RF opaque layers disposed within the process chamber. The length L and height H of the first region are indicated in Figure 4A.

[0074] In FIG. 4B, the areas where air may, could or will primarily circulate are hatched. The present invention also includes embodiments where only a portion of the treatment chamber is used to circulate hot air for cooking. An exemplary embodiment is one where the RF-opaque and breathable sides of the treatment chamber are separated or spaced apart. RF-opaque materials also have high thermal conductivity. This separation or spacing can be advantageous when RF-opaque and thermally conductive materials are used to prevent the outside of the treatment chamber from becoming too hot during use.

[0075] Figure 4C shows the first region, which is the hatched region in Figure 4A, minus the hatched region in Figure 4B. The result is a region into which primarily, or substantially, circulated hot air reaches, but into which RF energy or RF waves cannot enter or are largely minimized. This resultant region is termed second region 151.

[0076] Fig. 4D shows a schematic view of a fifth cross section of the treatment chamber of the first embodiment of the system according to the invention. The arrows in the figure show a typical air flow A of the air circulation through the food product and back along the side between the holder and the treatment chamber. The circulation is maintained by the use of a fan at the bottom of the treatment chamber.

[0077] Figure 4E shows a schematic view of a sixth cross section of the treatment chamber of the first embodiment of the system according to the invention, which is identical to Figure 4D except for the direction of the air flow A, which is reversed compared to Figure 4D.

[0078] FIG. 5 shows a schematic cross-section of a second embodiment of the system 100 according to the invention. In addition to the first embodiment, this embodiment also comprises an RF source 158 that supplies energy to the RF antenna for emitting RF waves or RF energy from the RF antenna. Furthermore, the system comprises a controller 160 and a motor 159. The motor is arranged to drive the fan. The motor is advantageously arranged outside the process chamber, since it may emit RF radiation that interferes with the RF waves. The heater may be arranged outside the process chamber or may be integrated with the side of the process chamber to provide heat to the air flow inside the process chamber, for example to conduct thermal energy through the side of the process chamber. In this embodiment, the heater is arranged inside the process chamber.

[0079] The controller may be arranged to receive input from an operator. The controller may be arranged to control the heater and fan to control the cooking effect of hot air flowing through or over the food. The controller may be arranged to control the RF source to control the amount of RF energy, the frequency of the RF waves and / or the RF mode of the RF waves to control the cooking effect of the RF energy radiated towards the food. The RF source may comprise an RF amplifier, e.g. a solid state amplifier, for precision control of the RF energy, e.g. stepless control of the radiated RF energy. The RF source may comprise an RF signal generator for generating the frequency of the RF waves.

[0080] The controller may use operator settings to control or set the RF source, fan and / or heater. Additionally or alternatively, the controller may use a sensor to determine the setting of the RF source. The sensor may be a temperature sensor, such as an IR sensor, to detect the temperature of the food inside the holder. The sensor may be a temperature sensor to detect the temperature of the circulated hot air to non-contact determine 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 to determine the RF energy radiated by another RF antenna and its effect on the food in the holder. Using multiple RF antennas as sensors may provide the controller with an accurate image of the amount of food in the holder, such as, for example, kilograms, as well as the texture of the food and / or the condition of the food, such as, for example, frozen, unfrozen, or partially frozen and unfrozen.

[0081] Figure 6 shows a schematic cross-section of a first embodiment of an apparatus 140 according to the invention. The location of the cross-section is indicated in Figure 1. The cross-section in Figure 1 is cut vertically and the cross-section in Figure 6 is cut horizontally. The apparatus comprises a process chamber 145, which may comprise a top shell 146. The apparatus may further comprise a housing 141. The housing typically provides a frame or structure for arranging the elements of the apparatus relative to one another. The length L and width W of a first area 150 inside the process chamber is indicated in Figure 6. The height at which the cross-section is cut is the height that may be designated as the unused area inside the process chamber.

[0082] The length, width and height dimensions of the first chamber greatly affect the attenuation or stimulation of the RF wave frequency and greatly affect the RF wave mode. The primary RF wave in the unused area is a standing RF wave. The size and / or shape of the first area, usually at least the length and width, is selected such that one or two standing waves are formed. The standing waves provide an efficient means of transferring RF energy from the RF antenna to the food product. The standing waves may have hot spots of energy. A further advantage may be to have two primary standing waves to spread the RF energy more evenly inside the food product. The length and width of the first area may be selected slightly different to facilitate the formation of two primary standing waves.

[0083] The predominant standing RF wave in the unused region 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 may be beneficial since these modes, in order to be the predominant standing RF wave, require approximately the same length and width as the first region.

[0084] The RF antenna may operate in a frequency band that is completely transparent to the food in the holder, the food in the holder having a weight of more than 2Kg, preferably more than 3Kg, more preferably more than 4Kg. These amounts of food are typically used in commercial and not domestic applications. The frequency of the RF waves and the size and / or shape of the treatment chamber are advantageously selected and sized and / or shaped, respectively, to accommodate this amount of food in the holder.

[0085] The RF antenna may operate in a frequency band that completely penetrates the food in the holder, the frequency band being below 1 GHz, preferably in the 902-928 MHz range, or around 915 MHz. The amount of food as mentioned above must be penetrated by the RF waves to provide RF energy throughout the food interior. The commonly used frequency of 2.45 GHz is not suitable, since the penetration depth is only in the centimeter range and therefore is not sufficient to penetrate a food block weighing more than 2 Kg. Choosing a lower frequency advantageously allows the RF waves to penetrate deeper into the food, instead of heating only the outer layer of the food. If a frequency is chosen that is so low that the RF waves traversing the food are only partially absorbed, the RF waves may subsequently bounce off the treatment chamber and / or the RF wall separating the first and second zones, to traverse the food again to be absorbed and thereby heat the food. This provides the advantage that the food is heated more uniformly, for example during the transition from frozen to unfrozen. This provides the added benefit that the food product is heated less in hot spots defined by standing waves and more by more random reflections which promote an even distribution of the absorbed RF energy within the food product.

[0086] It is the inventor's insight based on extensive characterization of various foods and conditions that the 902-928 MHz frequency band has one or more advantages over other frequencies, such as the 2390-2450 MHz band. Also, in various countries, this frequency band of 902-928 MHz is a license-free band that can be used freely. However, in many other countries, very strict regulations apply for that frequency band, and measures must be taken to avoid electromagnetic interference. Therefore, selecting a frequency in this band advantageously facilitates compliance with those different requirements, and still achieves good performance, especially in the 915 MHz band for the United States, as well as in the global ISM band of 2.45 GHz. Therefore, by selecting a frequency in this band, the product is simplified, while this frequency band also provides advantages such as high penetration to the food in the holder.

[0087] The main RF wave may have a frequency below 1 GHz, preferably within the 902-928 MHz band, or around 915 MHz, and the main RF wave has at least one, preferably both, of TE mode 011 and / or TE mode 111. Experiments and tests by the inventors have shown that, using the above parameters, the length and width of the treatment chamber fall in the range of 250-380 mm, preferably in the range of 280-340 mm, more preferably around 306 mm. This dimension may also refer to the specific size of the RF-impermeable wall of the holder, and may be adjusted according to the effective treatment chamber as a whole. The height of the first region during experiments and tests was around 180 mm, more specifically 192 mm, while the height of the holder was less than half of 60% of the height of the first region. Further, it was assumed that the dielectric constant of air is near 1, the dielectric constant of the RF transparent side of the holder is near 3-10 depending on the material of the holder, e.g., PTFE, PEEK, fiberglass, or ceramic, and the dielectric constant of frozen foods is near 80, while non-frozen but cold foods may have a dielectric constant near 3. Typically, as the temperature increases, the dielectric constant of the food settles near 80 for crispy crusts, while it eventually ends up near 40 for mostly water foods, e.g., hot snack foods with moisture inside. These dimensions are particularly well suited for commercial use, since they hold larger quantities of food. This embodiment may be useful for small general purpose or countertop devices, and may be further improved by selecting different lengths and widths for the first region, although the ranges specified above to advantageously spread the RF energy more uniformly. For larger devices that exceed countertop placement, a frequency of 433 MHz may be selected to support quantities of food of 8 kg or more.

[0088] The primary RF wave may have a frequency below 1 GHz, preferably within the 902-928 MHz band, or around 915 MHz, the primary RF wave having a TM mode 110. The inventor's experiments and tests have shown that, with the above parameters, the length and width of the treatment chamber fall in the range of 200-260 mm, preferably in the range of 220-240 mm, more preferably around 230 mm. The height of the first region during the experiments or tests was around 180 mm, while the height of the holder was less than half the height of the first region. Furthermore, it was assumed that the dielectric constant of air is around 1, the dielectric constant of the RF transparent side of the holder is around 2 (PTFE), 3-4 (PEEK, glass fiber), around 4-10 (ceramic), and the dielectric constant of the food product ranges over a very wide range from 3 to 80, while very low values ​​hold for frozen foods and high values ​​hold for non-frozen but cold foods. As the temperature increases, the dielectric constant drops, usually around 40, which is true for mostly moist foods, such as hot snack foods with moisture inside, and crispy crust 3, and foods around 80. These sizes are particularly well suited for commercial use, as they hold larger amounts of food.

[0089] Experiments have shown that the ratio of the length to the width of the first region is preferably around 1. Further experiments have shown that the ratio of the height to the length or width of the first region is preferably around 2. Further experiments have shown that the height of the holder, and therefore of the food product held in the holder, should also not exceed 60% of the height of the first region. These limitations are observed in order to generate RF waves sufficiently or very efficiently inside the treatment chamber.

[0090] 6 further illustrates a vertical axis V as a dot with a cross, such that the vertical axis is perpendicular to the plane of the cut. The device may further comprise a housing defining an outer edge of the device. The housing may have a back surface 161 defining a face of the device that generally faces away from the operator. The back surface generally faces a wall. The housing may have a front surface 163. The front surface is opposite the back surface and generally faces the operator. The back surface has a first back edge 162 and a second back edge 162'. The first back edge, the second back edge and the vertical axis define a triangle T.

[0091] 7 shows a schematic cross-sectional detail of a first embodiment of a device according to the invention, the detail showing the RF antenna 155' in the top right corner of FIG. The RF antenna may have a slot 178, a shielding box 175, an RF transparent layer 176, and an RF transparent surface 177. The slot 178 is not shown in FIG. 7, but is shown in FIG. 8, for example.

[0092] The RF antenna is supplied with energy or signals through an RF cable 170. The RF cable has a core 172 and a shield 171. The core typically carries the signal, while the shield prevents the core from radiating RF waves outside the RF cable. The RF cable may be a coaxial cable.

[0093] The RF antenna may be a slot antenna or an inverse antenna as shown. Other types of RF antennas may be used to radiate RF energy. The RF antenna may further include an RF transparent layer 176 having an RF transparent surface 177. The RF transparent surface prevents dust accumulation inside the shielding box and / or seals the inside of the shielding box for easy cleaning of the inside of the process chamber. The RF transparent layer preferably seamlessly connects with the inner surface of the process chamber. The RF transparent layer is preferably flush with the inner surface of the process chamber. The inside of the shielding box may be seen as a protrusion of the process chamber. The RF transparent layer is usually made of a material that readily allows the conduction of RF waves. The RF transparent layer therefore has an appropriate dielectric constant.

[0094] The RF antenna is connected to the slot antenna by connecting the RF cable core 172 to a second RF cable feed point 174 at an edge of the process chamber on one side of the slot and connecting the RF cable shield 171 to a first RF cable feed point 173 at another edge of the process chamber on the opposite side of the slot. The slot typically has a circumference with a length λ equal to the dominant wavelength of the RF waves to be generated.

[0095] 8 shows a schematic perspective view of a top corner of a first embodiment of a device according to the invention. The RF antenna 155, 155' is a slot-type antenna. The RF antenna has a slot 178 which may be curved as shown. Other slot shapes, e.g. straight, are envisaged by the inventors.

[0096] The process chamber 145 may comprise a top shell 146. The process chamber may comprise a side wall 146' and a top wall 146". The RF antenna may alternatively be located on the side wall. For clarity, the shielding box has been removed in this view and is therefore drawn with a dotted line, however it will be apparent to one skilled in the art that a shielding box would be placed over the RF antenna during use to prevent RF waves from escaping the process chamber enclosure.

[0097] Fig. 9 shows a schematic cross-sectional detail of an RF antenna of a first embodiment of the device according to the invention. The RF antenna is an example of an inverted antenna, more specifically a planar inverted antenna or PIFA. The RF antenna has a conductive antenna trace 180 that is meandered to reduce the overall length of the antenna. The RF antenna further has a ground plate 181. An RF cable 170, which may be a coaxial cable, may have a core 172 and a shield 171 that are respectively coupled to the antenna trace 180 via a second RF cable feed point 174 and to the ground plate 181 via a first RF cable feed point 173.

[0098] Fig. 10A shows a schematic seventh cross section of the process chamber 145 of the first embodiment of the system according to the invention. With reference to the previous figures, identical reference numbers may indicate identical features. The process chamber comprises a lower shell 147 and an upper shell 146. The lower shell has a lower rim 191 and the upper shell has an upper rim 190. The process chamber is shown in an open position. In this embodiment, the upper shell can be removed from the lower shell. The holder 120 is shown when held by a holding means arranged on the lower shell. Furthermore, the holder 120' is shown when separated from the process chamber. The holder 120 can be moved in the R direction to the position shown by the holder 120'.

[0099] Figure 10B shows a schematic eighth cross section of the process chamber of the first embodiment of the system according to the invention. With reference to Figure 10A, like reference numbers may indicate like features. The lower shell slides horizontally away from the upper shell to separate from the upper shell in the S direction.

[0100] Figure 10C shows a schematic ninth cross section of the process chamber of the first embodiment of the system according to the invention. With reference to Figure 10A, the same reference numbers may indicate the same features. In this embodiment, the upper shell is hinged to the lower shell.

[0101] 11 shows diagrammatically a cross-section of a third embodiment of a system according to the invention. With reference to the previous figures, identical reference numbers may indicate identical features. The apparatus comprises holding means 192, 192' arranged inside the process chamber. The holding means is arranged for suspending a holder 120.

[0102] 12 shows a schematic view of a tenth cross section of the process chamber of the first embodiment of the system according to the invention. With reference to the previous figures, identical reference numbers may indicate identical features. The process chamber 145 comprises an upper shell 145 and a lower shell 146 shown in a closed position. Furthermore, the holder 120 is at least partially disposed inside the process chamber. The space enclosed or enclosed by the process chamber is the interior space 193.

[0103] The term "substantially" herein will be understood by those of skill in the art, e.g., "substantially all radiation" or "substantially consisting of". The term "substantially" may also include embodiments using "entirely", "completely", "all", etc. Thus, in embodiments, the adjective substantially may be removed. Where applicable, the term "substantially" may relate to 90% or more, including 100%, such as 95% or more, particularly 99% or more, more particularly 99.5% or more. The term "comprises" also includes embodiments where the term "comprises" means "consists of".

[0104] The term "functionally" will be understood and clear to those skilled in the art. Both the terms "substantially" and "functionally" may include embodiments using "entirely", "completely", "all", etc. Thus, in embodiments, the adjective functionally may be removed. For example, when used as in "functionally parallel", those skilled in the art will understand that the adjective "functionally" includes the term substantially as described above. In particular, functionally should be understood to include configurations of features that allow those features to function as if the adjective "functionally" were not present. The term "functionally" is intended to include variations in the features it refers to, such that the combination of features operates or functions in the functional use of the features, possibly in combination with other features related in the present invention. For example, when an antenna is functionally coupled or functionally connected to a communication device, the received electromagnetic signal received by the antenna can be used by the communication device. The phrase "functionally", used as in "functionally parallel", is used to include not only exactly parallel, but also the embodiments encompassed by the phrase "substantially" above. For example, "functionally parallel" refers to embodiments in which the parts are, for example, parallel in function of operation. This includes embodiments that would be clear to one of ordinary skill in the art to operate as if they were parallel in the intended field of use.

[0105] In the foregoing specification, the invention has been described with reference to specific examples of embodiments of the invention. However, it will be apparent that various modifications or changes can be made therein without departing from the scope of the invention as outlined in the appended claims. For example, the shape may be of any type suitable for achieving the desired effect. Multiple devices that form functionally separate devices may be physically integrated into a single device.

[0106] However, other variations, modifications, and alternatives are also possible, and the specification and drawings are accordingly to be regarded in an illustrative rather than a restrictive sense.

[0107] In the claims, any reference signs placed in parentheses shall not be construed as limiting the claim. The words "comprising" or "including" do not exclude the presence of elements or steps other than those recited in the claim. Moreover, "a" or "an" as used herein 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 as implying that the introduction of another claim element by the indefinite article "a" or "an" limits any particular claim containing such introduced claim element to an invention containing only one such element, even when the same claim contains the introductory phrases "one or more" or "at least one" and an indefinite article such as "a" or "an". The same applies to the use of definite articles. Unless otherwise specified, terms such as "first" and "second" are used to arbitrarily distinguish between the elements that such terms describe. As such, these terms are not necessarily intended to indicate a temporal or other priority of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of those measures cannot be advantageously used.

[0108] [Embodiment] 1. A system (100) for cooking food, comprising: an RF opaque layer (110); -Breathable sides (121) a holder (120) for holding food, a treatment chamber (145) that is RF-tight and preferably non-breathable; holding means (148, 148') for holding the holder inside the treatment chamber, - an RF antenna (155, 155') arranged to radiate RF energy into the interior of the treatment chamber to heat the food product in the holder; a fan (156) for circulating air in the treatment chamber through the breathable side and through the holder, - a heater (157, 157') arranged to give heat to the circulated air, An apparatus (140) comprising: Equipped with a fan and a heater are positioned to air fry the food within the holder; The RF opaque layer is also breathable and is disposed generally parallel to the breathable side of the holder, at least during use; the RF opaque layer separates the process chamber, during use, into a first region (150) that is susceptible to RF energy from the RF antenna and a second region (151) that is shielded from RF energy from the RF antenna; The fan is disposed in the second region. System (100). 2. A system as described in embodiment 1, wherein the supply of RF energy to the food within the holder is not dependent on the supply of heated air to the food within the holder. 3. A system according to any of the preceding claims, wherein the breathable sides are positioned to allow vertical air flow (A) through the holder. 4. The system according to any one of the first to third embodiments, wherein the breathable side of the holder is a breathable bottom surface (121). 5. The system of any one of embodiments 1 to 4, wherein the holder has an RF opaque layer. 6. The system of embodiment 5, wherein the RF opaque layer is the bottom surface of the holder, and preferably the RF opaque layer and the breathable side are integral. 7. The system of embodiment 5, wherein the RF opaque layer is a top surface of the holder. 8. A system according to any of the preceding embodiments, wherein the retaining means is at least partially RF opaque so as to, in use, form RF isolation within the process chamber together with the RF opaque layer. 9. The system of any one of embodiments 1 to 8, wherein the heater is disposed in the second region. 10. The system of embodiment 9, wherein the heater is at least partially RF opaque to form RF isolation within the process chamber together with the RF opaque layer during use. 11.-An RF source (158) arranged to supply RF energy to the RF antenna; a motor (159) for driving the fan; a heat source for supplying energy to the heater; 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 radiated heat from the heater, the controller controlling the RF source, the motor, and the heater separately; The system according to any one of embodiments 1 to 10, comprising: 12. The system of any one of embodiments 1 to 11, wherein the holder is a food basket. 13. A system according to any one of embodiments 1 to 12, in which the system is combined with any feature from the claims section. [Explanation of symbols]

[0109] 100...system, 110...RF opaque layer, 120, 120'...holder, 121(4)...ventilated side, 125...handle of holder, 140...device, 141...housing, 143...axial opening, 144, 144'...joint shell, 145(5)...processing chamber, 146(31)...upper shell, 146'...side wall, 146"...top wall, 147(32)...top shell, 147(32)...side wall, 147 ...top shell, 147(32)...top shell, 147(32)...top shell, 147(32)...top shell, 147(32)...top shell, 147(32)...top shell, 147(32)...top shell, 147(32)...top shell, 147(32)...top shell, 147(32)...top shell, 147(32)...top shell, 148, 148' (6, 6')...retaining means, 150 (10)...first region, 151 (11)...second region, 155, 155' (7, 7')...RF antenna, 156 (8)...fan, 157, 157' (9, 9')...heater, 158 (15)...RF source, 159 (16)...motor, 160 (20)...controller, 161...back surface, 162, 162'...inner corners of process chamber, 162"...first rear end, 162'''...second rear end, 163...front surface, 164...axis, 170...RF cable, 171...RF cable shield, 172...RF cable core, 173...first RF cable feed point, 174...second RF cable feed point, 175...shielding box, 176...RF transparent layer, 177...RF transparent surface, 178...slot, 180...antenna trace, 181...ground surface, 190...upper rim, 191...lower rim, 192, 192'...holding means, 193...internal space, A...air flow, H...height of first region, L...length of first region, R...direction of holder removal, S...direction of shell separation, T...triangle, V...vertical axis, W...width of first region

Claims

1. A system (100) for cooking food, comprising: an RF opaque layer (110); A holder (120) for holding food, the holder having a breathable surface (121); - a treatment chamber (145) arranged to be RF-tight and non-breathable; holding means (148, 148') for holding said holder inside said treatment chamber, - an RF antenna (155, 155') arranged to radiate RF energy into the interior of the treatment chamber to heat the food product inside the holder; a fan (156) for circulating air inside the treatment chamber through the breathable surface and through the holder, a heater (157, 157') arranged to give heat to the circulated air, An apparatus (140) comprising: Equipped with the fan and the heater are positioned to air fry food within the holder; the RF impermeable layer is also breathable and is disposed generally parallel to the breathable surface of the holder, at least during use; the RF opaque layer, during use, separates the process chamber into a first region (150) that is susceptible to the RF energy from the RF antenna and a second region (151) that is shielded from the RF energy from the RF antenna; The fan is disposed in the second region. System (100).

2. 10. The system of claim 1, wherein the delivery of RF energy to the food within the holder is independent of the delivery of heated air to the food within the holder.

3. 3. The system of claim 1 or 2, wherein the air permeable surface is arranged to allow a vertical air flow (A) through the holder.

4. The system according to any one of claims 1 to 3, wherein the breathable surface of the holder is a surface that constitutes a bottom surface of the holder when the holder is held by the holding means.

5. The system of any one of claims 1 to 4, wherein the holder comprises an RF opaque layer.

6. The system described in claim 5, wherein the RF impermeable layer and the breathable surface are integrated together.

7. The system of claim 5 , wherein the RF opaque layer is formed on a top surface of the holder.

8. A system according to any one of the preceding claims, wherein the retaining means is at least partially RF opaque so as to, in use, form RF isolation within the process chamber together with the RF opaque layer.

9. The system of any one of claims 1 to 8, wherein the heater is disposed in the second region.

10. 10. The system of claim 9, wherein the heater is at least partially RF opaque so as to, during use, form RF isolation within the process chamber together with the RF opaque layer.

11. an RF source (158) provided for supplying RF energy to said RF antenna; A motor (159) for driving the fan; a heat source for supplying energy to the heater; 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 radiated heat from the heater, the controller controlling the RF source, the motor, and the heater individually; The system according to any one of claims 1 to 10, comprising:

12. The system according to any one of claims 1 to 11, wherein the holder is a food basket.

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