Patent Publication Number: US-2023136782-A1

Title: Two-Level Rapid Cooking Oven and Multi-Tiered Rack Assembly for the Same

Description:
TECHNICAL FIELD 
     Example embodiments generally relate to ovens and, more particularly, relate to provision of cookware appliances for providing multiple tiers within an oven that is enabled to cook using radio frequency (RF). 
     BACKGROUND 
     Combination ovens that are capable of cooking using more than one heating source (e.g., convection, steam, microwave, etc.) have been in use for decades. Each cooking source comes with its own distinct set of characteristics. Thus, a combination oven can typically leverage the advantages of each different cooking source to attempt to provide a cooking process that is improved in terms of time and/or quality. More recently, ovens with improved capabilities relative to cooking food with a combination of controllable RF energy and convection energy have been introduced. Unlike the relatively indiscriminate bombarding of food product, which generally occurs in microwave cooking, the use of controllable RF energy can enable a much more fine-tuned control of the cooking process. This fine-tuned control of the cooking process can lead to superior results in vastly shortened time periods. 
     The improved speed and accuracy of cooking with RF can be advantageous in many contexts. However, these ovens also have unique characteristics by virtue of the features made available in connection with the application of the heat sources involved. Cooking sequences must be organized in light of the expected results associated with each energy source that is to be employed. That said, factors such as air speed, time, temperature, and sequencing may not be the only factors that impact cooking characteristics. In this regard, internal characteristics of the oven structure may also impact the cooking characteristics. As such, any effort to add multiple cooking locations within the oven may impact the cooking characteristics. 
     Accordingly, it may be desirable to develop structures to provide an oven capable of utilizing the advantages of RF cooking, but nevertheless be flexible enough to permit cooking of food product at either a single location or at multiple locations (e.g., multiple tiers or levels) within a cooking chamber of the oven. 
     BRIEF SUMMARY OF SOME EXAMPLES 
     In an example embodiment, an oven is provided. The oven may include a cooking chamber, a convective heating system configured to provide heated air into the cooking chamber, a radio frequency (RF) heating system configured to provide RF energy into the cooking chamber, a bottom tier rack that is removable from and insertable into the cooking chamber to be supported at a bottom wall of the cooking chamber, and a top tier rack that is removable from and insertable into the cooking chamber to be supported by the bottom tier rack. The bottom tier rack includes a first frame including a plurality of first frame members that surround a first grate structure. The top tier rack includes a second frame including a plurality of second frame members that surround a second grate structure. Each of the bottom tier rack and the top tier rack may define a lateral gap proximate to sidewalls of the cooking chamber and a rear gap proximate to a back wall of the cooking chamber to permit, along with the first and second grate structures, airflow vertically through, along sides, and along a back of the bottom and top tier racks, respectively. 
     In another example embodiment, multi-tier rack assembly for use in an oven including a cooking chamber, a convective heating system configured to provide heated air into the cooking chamber, and a radio frequency (RF) heating system configured to provide RF energy into the cooking chamber may be provided. The assembly may include a bottom tier rack and a top tier rack. The bottom tier rack may be removable/insertable relative to the cooking chamber to be supported at a bottom wall of the cooking chamber. The bottom tier rack may include a first frame including a plurality of first frame members that surround a first grate structure. The top tier rack may be removable/insertable to be supported by the bottom tier rack. The top tier rack may include a second frame including a plurality of second frame members that surround a second grate structure. Each of the bottom tier rack and the top tier rack may define a lateral gap proximate to sidewalls of the cooking chamber and a rear gap proximate to a back wall of the cooking chamber to permit, along with the first and second grate structures, airflow vertically through, along sides, and along a back of the bottom and top tier racks, respectively. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG.  1    illustrates a perspective view of an oven capable of employing at least two energy sources according to an example embodiment; 
         FIG.  2    illustrates a functional block diagram of the oven of  FIG.  1    according to an example embodiment; 
         FIG.  3    shows a cross sectional view of the oven from a plane passing from the front to the back of the oven according to an example embodiment; 
         FIG.  4    is a top view of an attic region of the oven in accordance with an example embodiment; 
         FIG.  5    is a block diagram of control electronics for providing the electronic circuitry for controlling RF application in the oven in accordance with an example embodiment; 
         FIG.  6    illustrates a control console interface for selecting a recipe for execution with batches at different locations in accordance with an example embodiment; 
         FIG.  7    is a perspective view of a top tier rack in accordance with an example embodiment; 
         FIG.  8    is a perspective view of a bottom tier rack in accordance with an example embodiment; 
         FIG.  9    illustrates a perspective view of the top and bottom tier racks showing how the top tier rack interfaces with the bottom tier rack in accordance with an example embodiment; 
         FIG.  10    illustrates a front view of the top and bottom tier racks showing relative height differences between the top tier rack and the bottom tier rack in accordance with an example embodiment; and 
         FIG.  11    illustrates placement of the top and bottom tier racks within a cooking chamber of the oven in accordance with an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Some example embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all example embodiments are shown. Indeed, the examples described and pictured herein should not be construed as being limiting as to the scope, applicability or configuration of the present disclosure. Rather, these example embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like reference numerals refer to like elements throughout. Furthermore, as used herein, the term “or” is to be interpreted as a logical operator that results in true whenever one or more of its operands are true. As used herein, operable coupling should be understood to relate to direct or indirect connection that, in either case, enables functional interconnection of components that are operably coupled to each other. 
     Some example embodiments may improve the cooking performance of an oven and/or may improve the operator experience of individuals employing an example embodiment. In this regard, since some example embodiments may provide the operator with increased flexibility and versatility relative to food item positioning, the operator may take better advantage of the characteristics of the oven. As an example, the operator may place food items so that RF cooking and browning characteristics may be utilized to place items more or less within the airflow path of the heated airstream (e.g., that may be used for product browning) by controlling food product elevation. Alternatively or additionally, elevation or positioning of food product using racks designed with specific RF and airflow restriction characteristics in mind within the oven may avoid having one item or the racks themselves block energy from being communicated to another item. Further still, elevation or positioning of food products may alter the RF cross section of certain items. Thus, in some cases, a better cooked product may be achieved in terms of consistent heating (and in some cases also browning) by providing an ability to disperse food items over elevated cooking platforms within the oven. 
       FIG.  1    illustrates a perspective view of an oven  100  according to an example embodiment. As shown in  FIG.  1   , the oven  100  may include a cooking chamber  102  into which a food product may be placed for the application of heat by any of at least two energy sources that may be employed by the oven  100 . The cooking chamber  102  may include a door  104  and an interface panel  106 , which may sit proximate to the door  104  when the door  104  is closed. The door  104  may be operable via handle  105 , which may extend across the front of the oven  100  parallel to the ground. In some cases, the interface panel  106  may be located substantially above the door  104  (as shown in  FIG.  1   ) or alongside the door  104  in alternative embodiments. In an example embodiment, the interface panel  106  may include a touch screen display capable of providing visual indications to an operator and further capable of receiving touch inputs from the operator. The interface panel  106  may be the mechanism by which instructions are provided to the operator, and the mechanism by which feedback is provided to the operator regarding cooking process status, options and/or the like. 
     In some embodiments, the oven  100  may include one or multiple racks or may include rack (or pan) supports  108  or guide slots in order to facilitate the insertion of one or more racks  110  or pans holding food product that is to be cooked. In an example embodiment, air delivery orifices  112  may be positioned proximate to the rack supports  108  (e.g., just below a level of the rack supports in one embodiment) to enable heated air to be forced into the cooking chamber  102  via a heated-air circulation fan (not shown in  FIG.  1   ). The heated-air circulation fan may draw air in from the cooking chamber  102  via a chamber outlet port  120  disposed at a back or rear wall (i.e., a wall opposite the door  104 ) of the cooking chamber  102 . Air may be circulated from the chamber outlet port  120  back into the cooking chamber  102  via the air delivery orifices  112 . After removal from the cooking chamber  102  via the chamber outlet port  120 , air may be cleaned, heated, and pushed through the system by other components prior to return of the clean, hot and speed controlled air back into the cooking chamber  102 . This air circulation system, which includes the chamber outlet port  120 , the air delivery orifices  112 , the heated-air circulation fan, cleaning components, and all ducting therebetween, may form a first air circulation system within the oven  100 . The air delivery orifices  112  may form a rectangular array of holes in the back wall that are proximate to a bottom wall of the cooking chamber  102 , and the chamber outlet port  120  may be a circular array of holes in a middle portion of the back wall. In some cases, another array of air delivery orifices similar in shape to that of the air delivery orifices  112  of  FIG.  1   , but positioned proximate to a top wall of the cooking chamber  102  may also be provided. 
     In an example embodiment, food product placed on a pan or one of the racks  110  (or simply on a base of the cooking chamber  102  in embodiments where racks  110  are not employed) may be heated at least partially using radio frequency (RF) energy. Meanwhile, the airflow that may be provided may be heated to enable further heating or even browning to be accomplished by convection. Of note, a metallic pan may be placed on one of the rack supports  108  or racks  110  of some example embodiments. However, the oven  100  may be configured to employ frequencies and/or mitigation strategies for detecting and/or preventing any arcing that might otherwise be generated by using RF energy with metallic components. 
     Meanwhile, in some example embodiments, an elevated rack insert may be provided to sit on top of the rack  110  shown in  FIG.  1    to provide a second cooking location that is elevated and thereby creates a second tier on which food products or pans may be placed. An example of such an elevated rack insert is described in greater detail in reference to  FIG.  7    below. However, in alternative embodiments, the rack  110  of  FIG.  1    may also be replaced by a separate removable rack insert, an example of which is shown in  FIG.  8   . In such an example, there may be no need for rack supports  108 , and the rack supports  108  and rack  110  may be entirely omitted. 
     In an example embodiment, the RF energy may be delivered to the cooking chamber  102  via an antenna assembly  130  disposed proximate to the cooking chamber  102 . In some embodiments, multiple components may be provided in the antenna assembly  130 , and the components may be placed on opposing sides of the cooking chamber  102 . The antenna assembly  130  may include one or more instances of a power amplifier, a launcher, waveguide and/or the like that are configured to couple RF energy into the cooking chamber  102 . 
     The cooking chamber  102  may be configured to provide RF shielding on five sides thereof (e.g., the top, bottom, back, and right and left sides), but the door  104  may include a choke  140  to provide RF shielding for the front side. The choke  140  may therefore be configured to fit closely with the opening defined at the front side of the cooking chamber  102  to prevent leakage of RF energy out of the cooking chamber  102  when the door  104  is shut and RF energy is being applied into the cooking chamber  102  via the antenna assembly  130 . 
     In an example embodiment, a gasket  142  may be provided to extend around the periphery of the choke  140 . In this regard, the gasket  142  may be formed from a material such as wire mesh, rubber, silicon, or other such materials that may be somewhat compressible between the door  104  and a periphery of the opening into the cooking chamber  102 . The gasket  142  may, in some cases, provide a substantially air tight seal. However, in other cases (e.g., where the wire mesh is employed), the gasket  142  may allow air to pass therethrough. Particularly in cases where the gasket  142  is substantially air tight, it may be desirable to provide an air cleaning system in connection with the first air circulation system described above. 
     The antenna assembly  130  may be configured to generate controllable RF emissions into the cooking chamber  102  using solid state components. Thus, the oven  100  may not employ any magnetrons, but instead use only solid state components for the generation and control of the RF energy applied into the cooking chamber  102 . The use of solid state components may provide distinct advantages in terms of allowing the characteristics (e.g., power/energy level, phase and frequency) of the RF energy to be controlled to a greater degree than is possible using magnetrons. However, since relatively high powers are necessary to cook food, the solid state components themselves will also generate relatively high amounts of heat, which must be removed efficiently in order to keep the solid state components cool and avoid damage thereto. To cool the solid state components, the oven  100  may include a second air circulation system. 
     The second air circulation system may operate within an oven body  150  of the oven  100  to circulate cooling air for preventing overheating of the solid state components that power and control the application of RF energy to the cooking chamber  102 . The second air circulation system may include an inlet array  152  that is formed at a bottom (or basement) portion of the oven body  150 . In particular, the basement region of the oven body  150  may be a substantially hollow cavity within the oven body  150  that is disposed below the cooking chamber  102 . The inlet array  152  may include multiple inlet ports that are disposed on each opposing side of the oven body  150  (e.g., right and left sides when viewing the oven  100  from the front) proximate to the basement, and also on the front of the oven body  150  proximate to the basement. Portions of the inlet array  152  that are disposed on the sides of the oven body  150  may be formed at an angle relative to the majority portion of the oven body  150  on each respective side. In this regard, the portions of the inlet array  152  that are disposed on the sides of the oven body  150  may be tapered toward each other at an angle of about twenty degrees (e.g., between ten degrees and thirty degrees). This tapering may ensure that even when the oven  100  is inserted into a space that is sized precisely wide enough to accommodate the oven body  150  (e.g., due to walls or other equipment being adjacent to the sides of the oven body  150 ), a space is formed proximate to the basement to permit entry of air into the inlet array  152 . At the front portion of the oven body  150  proximate to the basement, the corresponding portion of the inlet array  152  may lie in the same plane as (or at least in a parallel plane to) the front of the oven  100  when the door  104  is closed. No such tapering is required to provide a passage for air entry into the inlet array  152  in the front portion of the oven body  150  since this region must remain clear to permit opening of the door  104 . 
     From the basement, ducting may provide a path for air that enters the basement through the inlet array  152  to move upward (under influence from a cool-air circulating fan) through the oven body  150  to an attic portion inside which control electronics (e.g., the solid state components) are located. The attic portion may include various structures for ensuring that the air passing from the basement to the attic and ultimately out of the oven body  150  via outlet louvers  154  is passed proximate to the control electronics to remove heat from the control electronics. Hot air (i.e., air that has removed heat from the control electronics) is then expelled from the outlet louvers  154 . In some embodiments, outlet louvers  154  may be provided at right and left sides of the oven body  150  and at the rear of the oven body  150  proximate to the attic. Placement of the inlet array  152  at the basement and the outlet louvers  154  at the attic ensures that the normal tendency of hotter air to rise will prevent recirculation of expelled air (from the outlet louvers  154 ) back through the system by being drawn into the inlet array  152 . Furthermore, the inlet array  152  is at least partially shielded from any direct communication path from the outlet louvers  154  by virtue of the fact that, at the oven sides (which include both portions of the inlet array  152  and outlet louvers  154 ), the shape of the basement is such that the tapering of the inlet array  152  is provided on walls that are also slightly inset to create an overhang  158  that blocks any air path between inlet and outlet. As such, air drawn into the inlet array  152  can reliably be expected to be air at ambient room temperature, and not recycled, expelled cooling air. 
       FIG.  2    illustrates a functional block diagram of the oven  100  according to an example embodiment. As shown in  FIG.  2   , the oven  100  may include at least a first energy source  200  and a second energy source  210 . The first and second energy sources  200  and  210  may each correspond to respective different cooking methods. In some embodiments, the first and second energy sources  200  and  210  may be an RF heating source and a convective heating source, respectively. However, it should be appreciated that additional or alternative energy sources may also be provided in some embodiments. 
     As mentioned above, the first energy source  200  may be an RF energy source (or RF heating source) configured to generate relatively broad spectrum RF energy or a specific narrow band, phase controlled energy source to cook food product placed in the cooking chamber  102  of the oven  100 . Thus, for example, the first energy source  200  may include the antenna assembly  130  and an RF generator  204 . The RF generator  204  of one example embodiment may be configured to generate RF energy at selected levels and with selected frequencies and phases. In some cases, the frequencies may be selected over a range of about 6 MHz to 246 GHz. However, other RF energy bands may be employed in some cases. In some examples, frequencies may be selected from unlicensed frequency (e.g., the ISM) bands for application by the RF generator  204 . 
     In some cases, the antenna assembly  130  may be configured to transmit the RF energy into the cooking chamber  102  and receive feedback to indicate absorption levels of respective different frequencies in the food product. The absorption levels may then be used to control the generation of RF energy to provide balanced cooking of the food product. Feedback indicative of absorption levels is not necessarily employed in all embodiments however. For example, some embodiments may employ algorithms for selecting frequency and phase based on pre-determined strategies identified for particular combinations of selected cook times, power levels, food types, recipes and/or the like. In some embodiments, the antenna assembly  130  may include multiple antennas, waveguides, launchers, and RF transparent coverings that provide an interface between the antenna assembly  130  and the cooking chamber  102 . Thus, for example, four waveguides may be provided and, in some cases, each waveguide may receive RF energy generated by its own respective power module or power amplifier of the RF generator  204  operating under the control of control electronics  220 . In an alternative embodiment, a single multiplexed generator may be employed to deliver different energy into each waveguide or to pairs of waveguides to provide energy into the cooking chamber  102 . 
     In an example embodiment, the second energy source  210  may be an energy source capable of inducing browning and/or convective heating of the food product. Thus, for example, the second energy source  210  may a convection heating system including an airflow generator  212  and an air heater  214 . The airflow generator  212  may be embodied as or include the heated-air circulation fan or another device capable of driving airflow through the cooking chamber  102  (e.g., via the air delivery orifices  112 ). The air heater  214  may be an electrical heating element or other type of heater that heats air to be driven toward the food product by the airflow generator  212 . Both the temperature of the air and the speed of airflow will impact cooking times that are achieved using the second energy source  210 , and more particularly using the combination of the first and second energy sources  200  and  210 . 
     In an example embodiment, the first and second energy sources  200  and  210  may be controlled, either directly or indirectly, by the control electronics  220 . The control electronics  220  may be configured to receive inputs descriptive of the selected recipe, food product and/or cooking conditions in order to provide instructions or controls to the first and second energy sources  200  and  210  to control the cooking process. In some embodiments, the control electronics  220  may be configured to receive static and/or dynamic inputs regarding the food product and/or cooking conditions. Dynamic inputs may include feedback data regarding phase and frequency of the RF energy applied to the cooking chamber  102 . In some cases, dynamic inputs may include adjustments made by the operator during the cooking process. The static inputs may include parameters that are input by the operator as initial conditions. For example, the static inputs may include a description of the food type, initial state or temperature, final desired state or temperature, a number and/or size of portions to be cooked, a location of the item to be cooked (e.g., when multiple trays or levels are employed), a selection of a recipe (e.g., defining a series of cooking steps) and/or the like. 
     In some embodiments, the control electronics  220  may be configured to also provide instructions or controls to the airflow generator  212  and/or the air heater  214  to control airflow through the cooking chamber  102 . However, rather than simply relying upon the control of the airflow generator  212  to impact characteristics of airflow in the cooking chamber  102 , some example embodiments may further employ the first energy source  200  to also apply energy for cooking the food product so that a balance or management of the amount of energy applied by each of the sources is managed by the control electronics  220 . 
     In an example embodiment, the control electronics  220  may be configured to access algorithms and/or data tables that define RF cooking parameters used to drive the RF generator  204  to generate RF energy at corresponding levels, phases and/or frequencies for corresponding times determined by the algorithms or data tables based on initial condition information descriptive of the food product and/or based on recipes defining sequences of cooking steps. As such, the control electronics  220  may be configured to employ RF cooking as a primary energy source for cooking the food product, while the convective heat application is a secondary energy source for browning and faster cooking. However, other energy sources (e.g., tertiary or other energy sources) may also be employed in the cooking process. 
     In some cases, cooking programs or recipes may be provided to define the cooking parameters to be employed for each of multiple potential cooking stages or steps that may be defined for the food product and the control electronics  220  may be configured to access and/or execute the cooking programs or recipes (all of which may generally be referred to herein as recipes). In some embodiments, the control electronics  220  may be configured to determine which recipe to execute based on inputs provided by the user except to the extent that dynamic inputs (i.e., changes to cooking parameters while a program is already being executed) are provided. However, in other examples, the user may directly select a recipe for execution. The recipe may be descriptive of items to be cooked, and information about such items in their initial and/or final state (e.g., level of doneness). Meanwhile, the control electronics  220  may determine specific details regarding frequency, phase, temperature, fan speed, time, etc. However, the user may also provide some input regarding the details in some cases. 
     In an example embodiment, an input to the control electronics  220  may also include browning instructions. In this regard, for example, the browning instructions may include instructions regarding the air speed, air temperature and/or time of application of a set air speed and temperature combination (e.g., start and stop times for certain speed and heating combinations). The browning instructions may be provided via a user interface accessible to the operator, or may be part of the cooking programs or recipes. 
     As discussed above, the first air circulation system may be configured to drive heated air through the cooking chamber  102  to maintain a steady cooking temperature within the cooking chamber  102 . Meanwhile, the second air circulation system may cool the control electronics  220 . The first and second air circulation systems may be isolated from each other. However, each respective system generally uses differential pressures (e.g., created by fans) within various compartments formed in the respective systems to drive the corresponding air flows needed for each system. While the airflow of the first air circulation system is aimed at heating food in the cooking chamber  102 , the airflow of the second air circulation system is aimed at cooling the control electronics  220 . As such, cooling fan  290  provides cooling air  295  to the control electronics  220 , as shown in  FIG.  2   . 
     The structures that form the air cooling pathways via which the cooling fan  290  cools the control electronics  220  may be designed to provide efficient delivery of the cooling air  295  to the control electronics  220 , but also minimize fouling issues or dust/debris buildup in sensitive areas of the oven  100 , or areas that are difficult to access and/or clean. Meanwhile, the structures that form the air cooling pathways may also be designed to maximize the ability to access and clean the areas that are more susceptible to dust/debris buildup. Furthermore, the structures that form the air cooling pathways via which the cooling fan  290  cools the control electronics  220  may be designed to strategically employ various natural phenomena to further facilitate efficient and effective operation of the second air circulation system. In this regard, for example, the tendency of hot air to rise, and the management of high pressure and low pressure zones necessarily created by the operation of fans within the system may each be employed strategically by the design and placement of various structures to keep certain areas that are hard to access relatively clean and other areas that are otherwise relatively easy to access more likely to be places where cleaning is needed. 
     The typical airflow path, and various structures of the second air circulation system, can be seen in  FIG.  3   . In this regard,  FIG.  3    shows a cross sectional view of the oven  100  from a plane passing from the front to the back of the oven  100 . The basement (or basement region  300 ) of the oven  100  is defined below the cooking chamber  102 , and includes an inlet cavity  310 . During operation, air is drawn into the inlet cavity  310  through the inlet array  152  and is further drawn into the cooling fan  290  before being forced radially outward (as shown by arrow  315 ) away from the cooling fan  290  into a riser duct  330  (e.g., a chimney) that extends from the basement region  300  to the attic (or attic region  340 ) to turn air upward (as shown by arrow  315 ). Air is forced upward through the riser duct  330  into the attic region  340 , which is where components of the control electronics  220  are disposed. The air then cools the components of the control electronics  220  before exiting the body  150  of the oven  100  via the outlet louvers  154 . The components of the control electronics  220  may include power supply electronics  222 , power amplifier electronics  224  and display electronics  226 . 
     Upon arrival of air into the attic region  340 , the air is initially guided from the riser duct  330  to a power amplifier casing  350 . The power amplifier casing  350  may house the power amplifier electronics  224 . In particular, the power amplifier electronics  224  may sit on an electronic board to which all such components are mounted. The power amplifier electronics  224  may therefore include one or more power amplifiers that are mounted to the electronic board for powering the antenna assembly  130 . Thus, the power amplifier electronics  224  may generate a relatively large heat load. To facilitate dissipation of this relatively large heat load, the power amplifier electronics  224  may be mounted to one or more heat sinks  352 . In other words, the electronic board may be mounted to the one or more heat sinks  352 . The heat sinks  352  may include large metallic fins that extend away from the circuit board to which the power amplifier electronics  224  are mounted. Thus, the fins may extend downwardly (toward the cooking chamber  102 ). The fins may also extend in a transverse direction away from a centerline (from front to back) of the oven  100  to guide air provided into the power amplifier casing  350  and past the fins of the heat sinks  352 . 
       FIG.  4    illustrates a top view of the attic region  340 , and shows the power amplifier casing  350  and various components of the antenna assembly  130  including a launcher assembly  400  and waveguides of a waveguide assembly  410 . Power is provided from the power amplifier electronics  224  to each launcher of the launcher assembly  400 . The launcher assembly  400  operably couples a signal generated by the power amplifiers of the power amplifier electronics  224  into a corresponding one of the waveguides of the waveguide assembly  410  for communication of the corresponding signal into the cooking chamber  102  via the antenna assembly  130  as described above. In an example embodiment, each instance of the waveguide assembly  410  may have a corresponding RF entry point  420  located near a bottom portion of the waveguide and in a sidewall of the cooking chamber  102  (see  FIG.  3   ) to provide the RF into the cooking chamber  102 . A cover that is invisible to RF, but restricts the flow of air may be provided over the RF entry points  420 . In an example embodiment, the RF entry points  420  may be at a predetermined height within the cooking chamber  102 . 
     The power amplifier electronics  224  are defined by a plurality of electronic circuitry components including opamps, transistors and/or the like that are configured to generate waveforms at the corresponding power levels, frequencies and phases that are desired for a particular situation or cooking program. In some cases, the cooking program may select an algorithm for control of the power amplifier electronics  224  to direct RF emissions into the cooking chamber  102  at selected power levels, frequencies and phases. One or more learning processes may be initiated to select one or more corresponding algorithms to guide the power application. The learning processes may include detection of feedback on the efficacy of the application of power at specific frequencies (and/or phases) into the cooking chamber  102 . In order to determine the efficacy, in some cases, the learning processes may measure efficiency and compare the efficiency to one or more thresholds. Efficiency may be calculated as the difference between forward power (P fwd ) and reflected power (P refl ), divided by the forward power (P fwd ). As such, for example, the power inserted into the cooking chamber  102  (i.e., the forward power) may be measured along with the reflected power to determine the amount of power that has been absorbed in the food product (or workload) inserted in the cooking chamber  102 . The efficiency may then be calculated as: Efficiency (eff)=(P fwd −P refl )/P fwd . 
     As can be appreciated from the description above, the measurement of the efficiency of the delivery of RF energy to the food product may be useful in determining how effective a particular (e.g., a current) selection for a combination (or pair) of frequency and phase parameters of RF energy applied into the cooking chamber  102  is at delivering heat energy to the food product. Thus, the measurement of efficiency may be useful for selecting the best combination or algorithm for application of energy. The measurement of efficiency should therefore also desirably be as accurate as possible in order to ensure that meaningful control is affected by monitoring efficiency. 
       FIG.  5    is a block diagram of control electronics  220  for providing the electronic circuitry for instantiation of power cycling during oven operation in accordance with an example embodiment. In some embodiments, the control electronics  220  may include or otherwise be in communication with processing circuitry  600  that is configurable to perform actions in accordance with example embodiments described herein. As such, for example, the functions attributable to the control electronics  220  may be carried out by the processing circuitry  600 . 
     The processing circuitry  600  may be configured to perform data processing, control function execution and/or other processing and management services according to an example embodiment of the present invention. In some embodiments, the processing circuitry  600  may be embodied as a chip or chip set. In other words, the processing circuitry  600  may comprise one or more physical packages (e.g., chips) including materials, components and/or wires on a structural assembly (e.g., a baseboard). The structural assembly may provide physical strength, conservation of size, and/or limitation of electrical interaction for component circuitry included thereon. The processing circuitry  600  may therefore, in some cases, be configured to implement an embodiment of the present invention on a single chip or as a single “system on a chip.” As such, in some cases, a chip or chipset may constitute means for performing one or more operations for providing the functionalities described herein. 
     In an example embodiment, the processing circuitry  600  may include one or more instances of each of a processor  610  and memory  620  that may be in communication with or otherwise control a device interface  630  and the user interface  570 . As such, the processing circuitry  600  may be embodied as a circuit chip (e.g., an integrated circuit chip) configured (e.g., with hardware, software or a combination of hardware and software) to perform operations described herein. However, in some embodiments, the processing circuitry  600  may be embodied as a portion of an on-board computer. 
     The user interface  570  (which may be embodied as, include, or be a portion of the interface panel  106 ) may be in communication with the processing circuitry  600  to receive an indication of a user input at the user interface  570  and/or to provide an audible, visual, mechanical or other output to the user (or operator). As such, the user interface  570  may include, for example, a display (e.g., a touch screen such as the interface panel  106 ), one or more hard or soft buttons or keys, and/or other input/output mechanisms. 
     The device interface  630  may include one or more interface mechanisms for enabling communication with connected devices  650  such as, for example, other components of the oven  100 , sensors of a sensor network of the oven  100 , removable memory devices, wireless or wired network communication devices, and/or the like. In some cases, the device interface  630  may be any means such as a device or circuitry embodied in either hardware, or a combination of hardware and software that is configured to receive and/or transmit data from/to sensors that measure any of a plurality of device parameters such as frequency, phase, temperature (e.g., in the cooking chamber  102  or in air passages associated with the second energy source  210 ), air speed, and/or the like. As such, in one example, the device interface  630  may receive input at least from a temperature sensor that measures the temperatures described above, or receives input from any of the other parameters described above, in order to enable communication of such parameters to the processing circuitry  600  for the performance of certain protective or control functions. Alternatively or additionally, the device interface  630  may provide interface mechanisms for any devices capable of wired or wireless communication with the processing circuitry  600 . In still other alternatives, the device interface  630  may provide connections and/or interface mechanisms to enable the processing circuitry  600  to control the various components of the oven  100 . 
     In an example embodiment, the memory  620  may include one or more non-transitory memory devices such as, for example, volatile and/or non-volatile memory that may be either fixed or removable. The memory  620  may be configured to store information, data, cooking programs, recipes, applications, instructions or the like for enabling the control electronics  220  to carry out various functions in accordance with example embodiments of the present invention. For example, the memory  620  could be configured to buffer input data for processing by the processor  610 . Additionally or alternatively, the memory  620  could be configured to store instructions for execution by the processor  610 . As yet another alternative, the memory  620  may include one or more databases that may store a variety of data sets responsive to input from the sensor network, or responsive to programming of any of various cooking recipes. Among the contents of the memory  620 , applications may be stored for execution by the processor  610  in order to carry out the functionality associated with each respective application. In some cases, the applications may include control applications that utilize parametric data to control the application of heat by the first and second energy sources  200  and  210  as described herein. In this regard, for example, the applications may include operational guidelines defining expected cooking speeds for given initial parameters (e.g., food type, size, initial state, location, and/or the like) using corresponding tables of frequencies, phases, RF energy levels, temperatures and air speeds. Thus, some applications that may be executable by the processor  610  and stored in memory  620  may include tables defining combinations of RF energy parameters and air speed and temperature to determine cooking times for certain levels of doneness and/or for the execution of specific cooking recipes. Accordingly, different cooking programs can be executed to generate different RF and/or convective environments to achieve the desired cooking results. In still other examples, data tables may be stored to define calibration values and/or diagnostic values, as described above. Alternatively or additionally, the memory  620  may store applications for defining responses to stimuli including the generation of protective actions and/or notification functions. 
     The processor  610  may be embodied in a number of different ways. For example, the processor  610  may be embodied as various processing means such as one or more of a microprocessor or other processing element, a coprocessor, a controller or various other computing or processing devices including integrated circuits such as, for example, an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), or the like. In an example embodiment, the processor  610  may be configured to execute instructions stored in the memory  620  or otherwise accessible to the processor  610 . As such, whether configured by hardware or by a combination of hardware and software, the processor  610  may represent an entity (e.g., physically embodied in circuitry—such as in the form of processing circuitry  600 ) capable of performing operations according to example embodiments of the present invention while configured accordingly. Thus, for example, when any instance of the processor  610  is embodied as an ASIC, FPGA or the like, the processor  610  may be specifically configured hardware for conducting the operations described herein. Alternatively, as another example, when the processor  610  is embodied as one or more executors of software instructions, the instructions may specifically configure the processor  610  to perform the operations described herein. 
     In an example embodiment, the processor  610  (or the processing circuitry  600 ) may be embodied as, include or otherwise control the control electronics  220  and/or the power amplifier electronics  224 . As such, in some embodiments, the processor  610  (or the processing circuitry  600 ) may be said to cause each of the operations described in connection with the control electronics  220  and/or the power amplifier electronics  224  by directing the control electronics  220  and/or the power amplifier electronics  224 , respectively, to undertake the corresponding functionalities responsive to execution of instructions or algorithms configuring the processor  610  (or processing circuitry  600 ) accordingly. As an example, the control electronics  220  may be configured to control the responses to various stimuli associated with executing the learning procedure discussed above and directing RF application within the oven  100  based on the learning procedure. Moreover, the control electronics  220  may be configured to determine efficiency parameters and take protective actions based on the efficiency parameters, or based on individual ones of the values, measurements and/or parameters that are determined by or received at the control electronics  220  for execution of the learning procedure. In some cases, a separate instance of a processor (or processors) and memory may be associated with different parts of the control electronics  220  (e.g., including separate processors for the control of the power amplifier electronics  224  amongst potentially others). 
     In an example embodiment, the control electronics  220  may also access and/or execute instructions for control of the RF generator  204  and/or the antenna assembly  130  to control the application of RF energy to the cooking chamber  102 . Thus, for example, the operator may provide static inputs to define the type, mass, quantity, or other descriptive parameters (e.g., a recipe) related to the food product(s) disposed within the cooking chamber  102 . The control electronics  220  may then utilize the static inputs to locate an algorithm or other program for execution to define the application of RF energy and/or convective energy to be applied within the cooking chamber  102 . The control electronics  220  may also monitor dynamic inputs to modify the amount, frequency, phase or other characteristics of the RF energy to be applied within the cooking chamber  102  during the cooking process, and may also perform protective functions. The control electronics  220  may also execute instructions for calibration and/or fault analysis. Accordingly, for example, the control electronics  220  may be configured to act locally to protect the power amplifier electronics  224  via stopping RF application to the cooking chamber  102 , via making adjustments to components to provide calibrated outputs, and/or via alerting the user when various abnormal or correctable situations are detected. 
     As noted above, in some cases it may be desirable to cook on multiple levels within the cooking chamber  102 . In some cases, the characteristics of RF absorption and/or airflow experienced by food products placed in each respective one of the multiple levels may be different. To account for such differences, the control electronics  220  of some example embodiments may employ a location management module  670 . The location management module  670  may be may be any means such as a device or circuitry operating in accordance with software or otherwise embodied in hardware or a combination of hardware and software (e.g., processor  610  operating under software control, the processor  610  embodied as an ASIC or FPGA specifically configured to perform the operations described herein, or a combination thereof) thereby configuring the device or circuitry to perform the corresponding functions of the location management module  670  as described herein. In this regard, the location management module  670  may be configured to employ location-specific recipe variants, or execute recipes in consideration of location and alter certain recipe parameters based on the location of the food product to which the recipe is being applied. 
     In order to account for different locations, the location management module  670  of some example embodiments may provide the user with an ability to inform the location management module  670  as to the location of food items within the cooking chamber  102 . To accomplish this, the location management module  670  may be operably coupled to the user interface  570  to receive information indicative of the type or identity of food product being cooked according to a given recipe, and the corresponding location of the food product within the cooking chamber  102 .  FIG.  6    illustrates an example control console  700  that may be provided for such purposes in accordance with an example embodiment. However, it should be appreciated that other specific interface consoles may be used in alternative embodiments. Moreover, in some cases, the location management module  670  may use RF feedback measurements to determine the location of food products automatically. 
     As shown in  FIG.  6   , the control console  700 , which may also be referred to as a recipe execution interface, may be displayed via the user interface  570 . The control console  700  may indicate the selected recipe  710  and the selected item count  720  for items being cooked according to the selected recipe  710 , along with a location indication  722 . The location indication  722  may indicate a specific location within the cooking chamber  102  at which the selected item count  720  is physically situated. In the example of  FIG.  6   , the specified location for the location indication  722  is level 1. Level 1 may correspond to a lower level or tier within the cooking chamber  102  as described in greater detail below. The items positioned at level 1, or more generally all items located at the location indicated by the location indication  722  may be considered to be a first batch or group of items or food products that are all assumed to experience similar cooking parameters during execution of the selected recipe  710 . 
     If another location is to be specified, the user may actuate a batch modification indicator  724  to add additional batches at corresponding locations that are specified. In this regard, a second selected item count  726  is shown to indicate the number of items provided at a second specific location (indicated by second location indication  728 ) within the cooking chamber  102 . In the example of  FIG.  6   , the specified location for the second location indication  728  is level 2. Level 2 may correspond to an upper level or tier within the cooking chamber  102  as described in greater detail below. The items positioned at level 2, or more generally all items located at the location indicated by the second location indication  728  may be considered to be a second batch or group of items or food products that are all assumed to experience similar cooking parameters during execution of the selected recipe  710 . However, the cooking parameters experienced at level 1 may be different than those experienced at level 2. Such difference may be accounted for by the location management module  670  as described in greater detail below. 
     The selected recipe  710  may correspond to specific oven settings  730  that are defined by the selected recipe  710 . In this example, the oven settings  730  may include settings for fan speed, temperature (of the cooking chamber  102 ), and RF power level. However, in alternative embodiments, other or additional operational parameters may be included in the oven settings  730 . The fan speed, temperature and RF power level defined by the selected recipe  710  may be provided into the cooking chamber  102  with the intent that hot air and RF energy are distributed in such a way as to most efficiently cook food products placed in the cooking chamber  102 . However, it can be appreciated that hot air may be provided via the air delivery orifices  112  located in the back wall of the cooking chamber  102 , and that RF energy is provided via the RF entry points  420  at a predetermined height within the cooking chamber  102 . Thus, some localized differences in temperature, airflow and/or RF energy may be experienced within the cooking chamber  102 . The location management module  670  may therefore account for the location of each batch (e.g., level 1 vs. level 2), and modify the selected recipe  710  as needed to ensure similar, repeatable, and consistent cooking results regardless of the location within the cooking chamber  102 . 
     To accomplish this, the location management module  670  may include data tables, or other content that is descriptive of cooking parameter (e.g., airflow, temperature and/or RF energy) variations that may occur in the cooking chamber  102  with certain food types or specific food items at the different locations (e.g., level 1 or level 2) within the cooking chamber  102 . Since recipes may specify the food type or specific food items being cooked, such information may be obtained from the selected recipe  710 . The number of such items (e.g., as indicated by the selected item count  720  and the second selected item count  726 ) may further indicate a change to cooking parameters that may be accounted for by the location management module  670 . In a typical situation, the location management module  670  may not alter fan speed, temperature or RF energy applied into the cooking chamber  102 , but may instead modify the time at which food items are retained at their respective locations relative to a nominal cooking time defined by the selected recipe  710 . As such, time, which is relatively easy to monitor and manage for each location separately, may be controlled instead of undertaking the otherwise potentially complicated task of trying to alter the other cooking parameters within the cooking chamber  102 , which may create other modifications to the selected recipe  710 . 
     In relation to separately tracking cooking times as modified by the location management module  670 , the control console  700  may also include a first progress indicator  740  that may be used to track progress relative to completion of the selected recipe  710  for the first batch. The first progress indicator  740  may, in some cases, provide a textual or other indication of the full time commitment associated with execution of the selected recipe  710  at the location indication  722  (i.e., level 1). In other words, the nominal cooking time of the selected recipe  710  may be modified slightly by the location management module  670  to account for the location of the first batch. Meanwhile, a first status indicator  750  may be provided with the first progress indicator  740  to demonstrate what portion of the full time commitment associated with execution of the selected recipe  710  has already been executed for the food product at level 1, as indicated by the location indication  722 . In the depicted example, the first status indicator  750  is a bar that grows in size proportional to the fraction of the full time commitment associated with execution of the selected recipe  710  that has transpired. Thus, for example, if the selected recipe  710  calls for a 5 minute full time commitment, the entire space of the first progress indicator  750  may represent 5 minutes plus or minus any modification inserted by the location management module  670 . Meanwhile, the first status indicator  750 , which fills about 90% of the first progress indicator  850 , may indicate that about 4.5 minutes (or 90% of approximately 5 minutes) has transpired toward completion of the selected recipe  710 . In some cases, the first status indicator  750  may include text defining a percentage completion and/or defining elapsed time (e.g., in hours, minutes and/or seconds). Similarly, a second progress indicator  760  and second status indicator  770  may be provided for operating similar to the first progress indicator  740  and the first status indicator  750  described above, except for food product located at level 2, as indicated by the second location indication  726 . Thus, the second progress indicator  740  may also be adjusted from the nominal cooking time defined by the selected recipe  710  to account for any location specific factors associated with the food product being at level 2, as indicated by the second location indication  726 . 
     The control console  700  may also include an action selector  780 . In this example, the action selector  780  includes selectable symbols for start (or cook), pause, and stop operations. A selected one of the symbols may be highlighted to indicate its having been actively selected. However, other presentation and selection paradigms are also possible, including dedicated buttons, a single selectable operator, or many other possible specific instantiations of action selectors. When the action selector  780  is selected for starting (or unpausing), cooking may be initiated. 
     As noted above, the inclusion of the location management module  670  may enable the user to cook according to the same recipe (i.e., the selected recipe  710 ) at multiple levels while accounting for any location-based differences in cooking parameters via modifying the selected recipe  710  slightly. To any extent absorption of RF or cooking speed is dependent upon the level (or other location) that is specified, the location management module  670  may also be configured to make modification calculations in consideration of the rates of absorption of RF associated with (or specified to) the location specified for the food product. To be sure that the conditions in the data tables employed by the location management module  670  remain accurate, the respective locations (e.g., a first location corresponding to level 1, and a second location corresponding to level 2, and any subsequent levels and locations that may be added) should be accurately known and consistently repeatable. To achieve such repeatability, one or more elevated rack inserts may be provided for insertion into the cooking chamber  102  to define the different tiers (e.g., level 1, level 2, and any other levels if more inserts are used) at consistent heights, and with consistent and advantageous physical features that have predictable impacts on the cooking parameters (e.g., air flow, temperature and RF power).  FIGS.  7 - 11    illustrate examples of such elevated rack inserts in accordance with an example embodiment. In this regard,  FIG.  7    illustrates a perspective view of a top tier rack  800  according to an example embodiment.  FIG.  8    illustrates a perspective view of a bottom tier rack  830  according to an example embodiment.  FIG.  9    shows the top tier rack  800  and bottom tier rack  830  prior to stacking of the racks.  FIG.  10    illustrates a front view of the top tier rack  800  and bottom tier rack  830  prior to stacking of the racks, and  FIG.  11    shows a front view of the top tier rack  800  and bottom tier rack  830  stacked and within the cooking chamber  102 . 
     The top tier rack  800  and the bottom tier rack  830  are each individually examples of a cookware appliance that may be used in connection with the oven  100  of  FIG.  1   . However, it should be appreciated that the combination of the top tier rack  800  and the bottom tier rack  830  is itself also a cookware appliance that may be useable in connection with the oven  100 . When combined, the resulting cookware appliance of  FIG.  11    is embodied as a multiple-tier elevated rack assembly  900 . Although  FIG.  11    shows the multiple-tier elevated rack assembly  900  having two tiers, some embodiments may include more than just two tiers. 
     As shown in  FIGS.  7 - 11   , the top tier rack  800  and the bottom tier rack  830  may each be substantially rectangular in shape (when viewed from above or below) to substantially match a shape of the cooking chamber  102  when viewed in a horizontal cross section. However, various aspects of the shape and structure of the top tier rack  800  and the bottom tier rack  830  are provided to specifically influence (or avoid influencing) impacts on airflow and RF energy distribution in the cooking chamber  102 , and to position the top tier rack  800  and the bottom tier rack  830  strategically in elevation within the cooking chamber  102 . Some aspects of these structures and shapes will be described below. 
     In this regard, for example the top tier rack  800  includes a frame  802  that extends around a periphery of a top surface or supporting surface of the top tier rack  800 . The frame  802  includes a first frame member  804 , a second frame member  806 , a third frame member  808  and a fourth frame member  810 . The first frame member  804  extends substantially perpendicular to the second and fourth frame members  806  and  810 , which each connect (at respective ends thereof) to portions of the first frame member  804  near respective opposite ends of the first frame member  804 . The first frame member  804  also extends substantially parallel to the third frame member  808 . The third frame member  808  extends between the opposite ends of the second and fourth frame members  806  and  810  relative to the ends of the second and fourth frame members  806  and  810  that connect to the first frame member  804 . The second and fourth frame members  806  and  810  also extend substantially perpendicular to the third frame member  808 . 
     The top tier rack  800  further includes a grate structure  812  that is disposed to lie in the same plane as the frame  802  and cover an entirety of the area defined between the frame members of the frame  802 . The grate structure  812  of  FIG.  4    is formed as a grid of rectangular holes that are formed between members that extend parallel relative to respective ones of the frame members at a constant interval therebetween. The constant interval, and spacing, of the rectangular holes are designed to make the top tier rack  800  effectively appear solid relative to the RF frequencies employed by the oven  100 . In some embodiments, the grate structure  812  may include wires, bars, or other members that extend substantially parallel (and/or perpendicular) to the first and third frame members  804  and  808  and substantially perpendicular (or parallel) to the second and fourth frame members  806  and  810 . The grate structure  812  may be integrally formed between the frame members. However, in other cases, the grate structure  812  may be joined to the frame members by welding, by being pinched between portions of the frame members, or by another form of adhesion. 
     The first and third frame members  804  and  808  may be elongated past respective ends of the second and fourth frame members  806  and  810  to create a lateral gap  814  that will be formed between each of the first and fourth members  806  and  810  and a corresponding nearest one of the sidewalls  816  of the cooking chamber  102 . Meanwhile, front legs  818  may extend substantially perpendicularly away from opposite ends of the first frame member  804  in a downward direction. Similarly, rear legs  820  may extend substantially perpendicularly away from opposite ends of the third frame member  808  in the downward direction. In an example embodiment, the front legs  818  may extend downwardly proximate to the sidewalls  816  of the cooking chamber  102 . Meanwhile, the rear legs  820  may be spaced apart from the sidewalls  816  as shown in  FIG.  11   . As such, the third frame member  808  may be slightly shorter than the first frame member  804 . Whereas the first frame member  804  may have a length that is substantially equal to a distance between the sidewalls  816 , the third frame member  808  may be shorter than the distance between the sidewalls  816 . 
     At distal ends of the front and rear legs  818  and  820 , respective feet  822  may be formed. The feet  822  may extend substantially perpendicular to the direction of extension of the front and rear legs  818  and  820  (inwardly and away from the sidewalls  816  of the cooking chamber  102 ). The feet  822  may rest on the rack  104  of  FIG.  1   , or the bottom tier rack  830  of  FIG.  8   , as shown in  FIG.  11   . In an example embodiment, the feet  822  may include protruding members  824  that extend downward past the feet  822  in the same direction as the direction of extension of the front and rear legs  818  and  820 . The protruding members  824  may engage a portion of the rack  104  or bottom tier rack  830  as described in greater detail below, and as shown in  FIG.  11   . 
     As best seen in  FIG.  7   , the third frame member  808  may further include a shoulder member  826  that extends along a portion of the third frame member  808  that is coextensive with the grate structure  812 . The shoulder member  826  may extend perpendicularly away from the third frame member  808  in an upward direction (i.e., opposite the direction of extension of the front and rear legs  818  and  820 ). The shoulder member  826  may also be spaced apart from a back wall of the cooking chamber  102  when the top tier rack  800  thereby creating a rear gap  828  between the back wall of the cooking chamber  102  and the shoulder member  826 . The shoulder member  826  may prevent insertion of a pan or any food item all the way to the back wall of the cooking chamber  102 , since such insertion may otherwise block airflow. The holes of the grate structure  812 , the rear gap  828  and the lateral gaps  814  may each be formed to allow airflow to move with minimal obstruction through the cooking chamber  102 , and more particularly through and around the top tier rack  800 . 
     The bottom tier rack  830  may include a frame  832  that is structured in similar fashion to the structure described above for the frame  802  of the top tier rack  800 , so a specific description of the structure of the first frame member  834 , second frame member  836 , third frame member  838  and fourth frame member  840  would be redundant and will not be repeated. However, it should be noted that the first and third frame members  834  and  838  of the bottom tier rack  830  may each be the same length. Grate structure  842  is also similarly structured to the grate structure  812  described above, so details will not be repeated. Lateral gaps  844  are also formed similar to the lateral gaps  814  described above. The bottom tier rack  830  also includes a shoulder member  846  that is situated and structured similar to the shoulder member  826  above, including the formation of rear gap  848  similar to rear gap  828  described above. 
     The bottom tier rack  830  differs from the top tier rack  800 , however, in relation to the support structures that are provided for the components of the bottom tier rack  830  described above. In this regard, rather than employing separate legs and feet disposed in respective corners of the frame  832 , the bottom tier rack  830  employs a support assembly  850  that is shaped to match a corresponding shape of the lower internal corners of the cooking chamber  102 . In this regard, sidewalls  816  of the cooking chamber  102  may intersect a bottom wall  852  of the cooking chamber  102  at respective rounded corners  854 . One instance of the support assembly  850  may therefore extend from respective first ends of the first and third frame members  834  and  838 , and the other instance of the support assembly  850  may extend from opposite respective second ends of the first and third frame members  834  and  838 . As shown in  FIG.  8   , receiving slots  851  may be formed proximate to respective opposite ends of the third frame member  838  and receiving orifices  853  may be formed proximate to respective opposite ends of the first frame member  834  to receive the protruding members  824  of the feet  822  of the top tier rack  800  in order to prevent any sliding of the top tier rack  800  relative to the bottom tier rack  830 . 
     In this example embodiment, the cooking chamber  102  is formed to have the rounded corners  854  at the intersection of the bottom wall  852  and the sidewalls  816  since sharp, perpendicular corners are more difficult to clean. The rounded corners  854  present an easier surface to keep clean at a portion of the cooking chamber  102  that is most susceptible (contrary to the top corners) to becoming fouled by drippings and splatter of the food product during cooking or insertion into/removal from the cooking chamber  102 . When inserted into the cooking chamber  102 , the support assembly  850  may substantially cover an entirety of the otherwise exposed surfaces of the rounded corners  854 . The support assembly  850  would then receive any drippings or splatter, and could be cleaned outside the cooking chamber  102  more easily after removal thereof, while keeping the rounded corners  854  themselves substantially clean. 
     The support assembly  850  has a height (H1) that is sufficient to elevate the grate structure  342  above a top level of the air delivery orifices  112  in the back wall of the cooking chamber  102 . Meanwhile, a height (H2) of the front and rear legs  818  and  820  of the top tier rack  800  may be between 2 and 2.5 times the height (H1) of the support assembly  850 . As shown in  FIG.  11   , setting the relative heights in this way (in addition to ensuring that the air deliver orifices  112  are not blocked, as noted above) provides a consistent and known positioning of the elevation of the top tier rack  800  relative to the RF entry points  420  formed in the sidewalls  816 . In this regard, the entry points  420  may, in some cases, at least partially overlap with the grate structure  812  of the top tier rack  800 . In other words, part of the opening that defines the RF entry points  420  may extend in the sidewalls  816  below the grate structure  812  and part of the opening may extend above the grate structure  812 . The lateral gaps  814  of the top tier rack  800  (and in some cases also the lateral gaps  844  of the bottom tier rack  830 ) may be formed to be about one half a wavelength in length. Thus, the grate structure  812  (and the second and fourth frame members  806  and  810 ) may be positioned at least ½ wavelength away from the RF entry points  420 . This strategic positioning may ensure that the RF energy inserted into the cooking chamber  102  is not obstructed in its ability to fill the cooking chamber  102  evenly, even when the top tier rack  800  is inserted in the cooking chamber  102 . 
     As can be appreciated from the descriptions above, the lateral gaps  814  and  844 , the rear gaps  828  and  848 , and the holes in the grate structures  812  and  842  may support (or at least minimize inhibition of) general airflows within the cooking chamber  102  and more specifically of vertical airflows upward (or downward) through the grate structures  812  and  842 . Meanwhile, the relative heights of the top tier rack  800  and the bottom tier rack  830  are selected to strategically place the top tier rack  800  relative to RF entry points  420  to avoid any negative impacts on RF distribution in the cooking chamber  102 . Example embodiments therefore enable the efficient use of space inside the cooking chamber  102  to define more capacity for simultaneously cooking food items of different respective batches at corresponding different locations. Moreover, the location management module  670  may be configured to account for any known differences associated with RF absorption at each of the different locations. 
     In an example embodiment, the frame members, the grate structure, legs, feet, and/or support assembly of the top tier rack  800  and bottom tier rack  830  may be made from aluminum. However, alternative materials may be used in other embodiments, such as, for example, stainless steel. 
     In an example embodiment, an oven (and/or a multi-tiered rack assembly of the oven) may be provided. The oven may include a cooking chamber, a convective heating system configured to provide heated air into the cooking chamber, a radio frequency (RF) heating system configured to provide RF energy into the cooking chamber, a bottom tier rack that is removable from and insertable into the cooking chamber to be supported at a bottom wall of the cooking chamber, and a top tier rack that is removable from and insertable into the cooking chamber to be supported by the bottom tier rack. The bottom tier rack includes a first frame including a plurality of first frame members that surround a first grate structure. The top tier rack includes a second frame including a plurality of second frame members that surround a second grate structure. Each of the bottom tier rack and the top tier rack may define a lateral gap proximate to sidewalls of the cooking chamber and a rear gap proximate to a back wall of the cooking chamber to permit, along with the first and second grate structures, airflow vertically through, along sides, and along a back of the bottom and top tier racks, respectively. 
     In some embodiments, additional optional features may be included or the features described above may be modified or augmented. Each of the additional features, modification or augmentations may be practiced in combination with the features above and/or in combination with each other. Thus, some, all or none of the additional features, modification or augmentations may be utilized in some embodiments. For example, in some cases, the back wall of the cooking chamber may include air delivery orifices forming a rectangular array of holes in a back wall of the cooking chamber proximate to a bottom wall of the cooking chamber, and a height of the bottom tier rack may be sufficient to position the first grate structure above a top of the air delivery orifices. In an example embodiment, a height of the top tier rack is between about two and two and a half times the height of the bottom tier rack. In some cases, an RF entry point may be disposed in a sidewall of the cooking chamber via which the RF energy is distributed into the cooking chamber, and the height of the top tier rack may be sufficient to place the second grate structure such that a first portion of the RF entry point extends below the second grate structure, and a second portion of the RF entry point extends above the second grate structure. In an example embodiment, the lateral gap of each of the top tier rack and the bottom tier rack may be about one half wavelength relative to frequencies used to apply the RF energy. In some cases, the top and bottom tier racks may each include a shoulder member disposed proximate the back wall of the cooking chamber, the shoulder member being spaced apart from the back wall by the rear gap, and the shoulder member of each of the top and bottom tier racks may extend substantially perpendicularly away from a plane in which the first and second grate structures, respectively, lie. In an example embodiment, the top tier rack may include legs disposed at respective corners of the second grate structure, and feet that extend substantially perpendicular to the legs and substantially parallel to the second grate structure to lie on a portion of the first grate structure. In some cases, protruding members may extend from the feet to be inserted into corresponding openings formed proximate to respective corners of the bottom tier rack. In an example embodiment, an intersection of the sidewalls of the cooking chamber and a bottom wall of the cooking chamber forms rounded corners, and the first grate structure may be supported relative to the bottom wall by a support assembly, while the support assembly is shaped to conform to a shape of the rounded corners. In some cases, the support assembly may extend from the back wall of the cooking chamber to a front portion of the cooking chamber to substantially cover the rounded corners. In an example embodiment, holes formed in the first and second grate structures may be sized to make the first and second grate structures appear solid relative to frequencies used to apply the RF energy. In some cases, the oven may further include a location management module configured to employ location-specific recipe variants based on whether food product is located on the first grate structure of the second grate structure. Alternatively or additionally, the location management module may be configured to modify a nominal recipe based on whether food product is located on the first grate structure of the second grate structure. Alternatively or additionally, the location management module may be configured to separately track cooking progress for food items located on the first grate structure and the second grate structure, respectively. 
     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe exemplary embodiments in the context of certain exemplary combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. In cases where advantages, benefits or solutions to problems are described herein, it should be appreciated that such advantages, benefits and/or solutions may be applicable to some example embodiments, but not necessarily all example embodiments. Thus, any advantages, benefits or solutions described herein should not be thought of as being critical, required or essential to all embodiments or to that which is claimed herein. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.