METHODS AND APPARATUS FOR HIGH-HEAT COOKING

A rack assembly is mountable within an oven cavity of a cooking appliance. The rack assembly includes a cooking stone; an insulating mat defining a recess configured to accommodate the cooking stone; and a rack configured to support the insulating mat. A superficial area of the insulating mat is at least 70% of a superficial area of the rack.

TECHNICAL FIELD

The present disclosure relates to methods and apparatus for high-heat cooking in an oven cavity of a cooking appliance and, more particularly, high-heat cooking in a confined portion of the oven cavity.

BACKGROUND

Domestic cooking appliances can include an oven cavity and one or more preprogrammed cooking operations for cooking food in the oven cavity. The maximum temperature setting for any cooking operation of a domestic appliance is typically about 550° F., because safety regulations require the oven door to automatically lock once the oven cavity reaches a temperature of about 600° F. However, various cooking operations may benefit from higher cooking temperatures. For example, in conventional methods of cooking pizza, a ceramic cooking stone is placed on a rack in the oven cavity, and a baking operation is performed to heat the oven cavity and cooking stone to a selected cooking temperature. The ideal cooking temperature of the cooking stone for brick-oven style pizza is preferably about 750° F. Thus, a conventional baking operation, even at its highest temperature setting, cannot heat the cooking stone up to its ideal cooking temperature.

BRIEF SUMMARY

According to a first aspect, a rack assembly is mountable within an oven cavity of a cooking appliance. The rack assembly includes a cooking stone; an insulating mat defining a recess configured to accommodate the cooking stone; and a rack configured to support the insulating mat. A superficial area of the insulating mat is at least 70% of a superficial area of the rack.

According to a second aspect, a cooking appliance includes a oven cavity, a broil element adjacent to an upper wall of the oven cavity, a rack within the oven cavity, and a cooking stone supported by the rack. A cooking operation for the cooking appliance includes a preheat stage during which the broil element is operated according to a preheat-power scheme in order to heat the cooking stone and air within the oven cavity; a reduced-power stage during which the broil element is operated according to a reduced-power scheme in order to reduce a heat output of the broil element while the cooking stone emits residual heat; and an increased-power stage during which the broil element is operated according to an increased-power scheme. The reduced-power scheme operates the broil element at less power than the preheat-power scheme, and the increased-power scheme operates the broil element at greater power than the reduced-power scheme.

DETAILED DESCRIPTION

Turning toFIG.1, an example cooking appliance10is illustrated having a housing12, a cooking compartment14that defines a cavity18, a door22pivotally attached to the housing12that provides selective access to the cavity18, and a control panel having a user interface30. The compartment14has a plurality of walls34that define the cavity18, including a lower wall34a, a left-side wall34b, a rear wall34c, a right-side wall34d(seeFIG.2) opposite to the left side wall34b, and an upper wall34e. Moreover, the left- and right-side walls34b,34dof the compartment14include multiple opposing pairs of rack supports38that are vertically spaced and can receive a rack assembly for supporting food items within the cavity18.

The appliance10further includes a plurality of heating elements40,50,60that are spaced about the cavity18and can be operated to heat the cavity18to perform various cooking operations. For example, the appliance10includes a lower heating element40(“bake element”) arranged at or adjacent to the lower wall34aof the compartment14, and which can be operated to perform a baking operation. An upper heating element50(“broil element”) can be arranged at or adjacent to the upper wall34eof the compartment14, and can be operated to perform a broiling operation. And a rear heating element60(“convection element”) can be arranged at or adjacent to the rear wall34cof the compartment14, and can be operated with a convection fan64to perform a convection cooking operation. The rear element60(sometimes referred to as a convection element) and the convection fan64typically are covered by a protective shroud66, and collectively form a convection system70of the appliance10.

Each heating element40,50,60may be an electric-resistive body (e.g., coil) that converts electrical energy supplied thereto into heat, or a gas burner that burns gas supplied thereto to generate heat. Moreover, each heating element40,50,60may be located within or outside of the cavity18, adjacent to its associated compartment wall34. Still further, the appliance10may comprise additional or fewer heating heater elements in other examples. Broadly speaking, the appliance10can include any configuration of one or more heating elements that includes a broil element50arranged at or adjacent to the upper wall34e.

The appliance10further includes a controller80(e.g., programmable logic controller) having a processor and memory, which is operatively coupled (e.g., via one or more wires, relays, digital gas valves, etc.) to the heating elements40,50,60such that the controller80can selectively and independently operate the heating elements40,50,60to perform various cooking operations. Moreover, the controller80is in communication with the user interface30, which has one or more input elements (e.g., switches, buttons, touchscreens, etc.) that a user can manipulate to provide one or more inputs (e.g., program selections, start commands, temperature settings, etc.) to the controller80. The user interface30also has one or more output elements (e.g., speakers, displays, lights, etc.) that can provide one or more outputs (e.g., program selection screens, cooking operation settings and statuses, sounds, lights, etc.) to convey information to the user.

The appliance10also includes a primary temperature sensor82(seeFIG.9) that is configured to measure temperature and provide an output to the controller80indicative of the measured temperature. The sensor82is used for controlling basic cooking operations and ensuring that the appliance10is in compliance with agency safety regulations. For example, the controller80may be configured to perform one or more cooking operations (e.g., baking, convection baking, etc.) based on feedback from the sensor82. Moreover, per industry regulations, the controller80can be configured to automatically lock the oven door22if a temperature measured by the sensor82exceeds a predetermined threshold (e.g., 600° F.) during any operation of the appliance10.

Lastly, the appliance10includes a door sensor84(seeFIG.1) that is configured to detect a position of the door22and provide an output to the controller80indicative of the detected position. For example, if the door22is in a closed position, the door sensor84can provide a positive signal to the controller80indicating that the door22is closed. Conversely, if the door22in an open position, the door sensor84can provide a zero signal to the controller80indicating that the door22is open.

Various example rack assemblies will now be described, which can be mounted within the cavity18to support food items for cooking.FIGS.2-5show a first example rack assembly100, whileFIGS.6-8show a second example rack assembly100′. As discussed further below, either one of the rack assemblies100,100′ can be mounted within the cavity18in close proximity to the broil element50, and is configured to partition and insulate an upper portion18aof the cavity18from a lower portion18bwhere the temperature sensor82is located. As such, the broil element50can be used to cook food within the upper portion18aat high temperature (e.g., 750° F.) without heating the lower portion18bup to a temperature that exceeds safety regulations and causes the oven door22to automatically lock.

Each rack assembly100,100′ is arranged relative to a set of axes X, Y, Z and includes a rack102, an insulating mat104, and a ceramic cooking stone106. The first and second axes X, Y are horizontal and perpendicular to each other, while the third axis Z is vertical and perpendicular to the first and second axes X, Y. Left and right directions of the rack assemblies100,100′ extend along the first axis X, while frontward and rearward directions of the rack assemblies100,100′ extend along the second axis Y (and thus perpendicular to the left and right directions). As discussed further below, the components of the rack assemblies100,100′ have various lengths and widths that are measured along the first and second axes X, Y, respectively.

As shown inFIGS.4and6, the cooking stone106of each rack assembly100,100′ comprises a monolithic body110of material such as, for example, ceramic, clay, cordierite, or cast iron. The body110in each rack assembly100,100′ is a rectangular-shaped body having a length L1and width W1. However, other shapes are possible such as, for example, square or circular.

As shown inFIGS.4and7, the insulating mat104of each rack assembly100,100′ is a generally rectangular body having an overall length L2and width W2. Moreover, the insulating mat104defines a recess118that is configured to accommodate the cooking stone106therein in the assembled rack assembly100,100′. In the first rack assembly100(seeFIG.4), the insulating mat104comprises a single metal sheet that is bent to form a receiving portion122and flanges124b,124dextending laterally from opposite sides of the receiving portion122. The receiving portion122has a bottom wall124and left- and right-side walls126b,126dthat extend upward from opposites sides of the bottom wall124, substantially perpendicular to the bottom wall124. The walls124,126b,126dof the receiving portion122define the recess118, and the left and right flanges132b,132dextend outward from the left- and right-side walls126b,126d, substantially parallel to the bottom wall124.

In the second rack assembly100′ (seeFIG.7), the insulating mat104comprises a single metal sheet that is stamped to form a rectangular body having a front panel132, an upper panel134, and a receiving portion136that defines the recess118. The front panel132has a front surface142that extends along a vertical plane that is parallel to or encompasses the first and third axes X, Z. Meanwhile, the upper panel134has an upper surface146that is sloped in the frontward and rearward directions. Specifically, the upper surface146is sloped such that a rear end of the upper surface146is elevated relative to a front end of the upper surface146. The receiving portion136includes a bottom wall154that extends along a horizontal plane that is parallel to or encompasses the first and second axes X, Y. Moreover, the receiving portion136includes left-, rear-, and right-side walls156b,156c,156dthat extend upward from a perimeter of the bottom wall154, substantially perpendicular to the bottom wall154.

For each rack assembly100,100′, the recess118of the insulating mat104has dimensions that approximate the dimensions of the cooking stone106, such that the stone106will fit securely in the recess118when mounted. For example, the recess118each rack assembly100,100′ has a substantially complementary shape compared to the cooking stone106, and has a length L3and width W3that approximate a length L1and width W1of the stone106, respectively (for the purposes of this disclosure, a first dimension can “approximate” a second dimension if the ratio between the first and second dimensions (or its inverse) is between 0.85 and 1.0, preferably between 0.90 and 1.0). The cooking stone106can be placed within the recess118of the insulating mat104and supported by its bottom wall124,154.

As assembled, the cooking stone106will be substantially in-register with the bottom wall124,154of insulating mat104, fitted snugly (but not necessarily with interference) between the left- and right-side walls126b,126d,156b,156d. In particular, the left- and right-side walls126b,126d,156b,156dof the insulating mat104can inhibit lateral movement of the cooking stone106relative to the insulating mat104in left and right directions, respectively. Moreover, the rear-side wall156cof the insulating mat104in the second rack assembly100′ can restrict rearward movement of the cooking stone106relative to the insulating mat104.

The rack102for each assembly100,100′ (seeFIGS.5and8) is defined by a plurality of metal wires170, which includes a front wire170a, a left wire170b, a rear wire170c, and a right wire170dthat extend within a primary plane Pi and collectively form a rectangular, outer frame176having a length L4and a width W4. The wires170further include a plurality of crosswires180that are supported by the outer frame176and extend horizontally along the rack102.

The rack102of the first assembly100(seeFIG.5) has a plurality of crosswires180b,180dthat extend within the primary plane Pi and define a well182configured to accommodate the receiving portion122of the insulating mat104therein. Moreover, the rack102includes a plurality of crosswires180ethat are recessed from the primary plane Pi and define a base of the well182in order to support the receiving portion122of the insulating mat104when seated therein. The well182preferably has dimensions that approximate the dimensions of the receiving portion122of the insulating mat104and cooking stone106such that they fit securely in the well182when mounted. For example, the well182in the illustrated embodiment has a length L5that approximates the lengths L6, L1of the receiving portion122and the cooking stone106, and a width W5that similarly approximates the widths W6, W1of the receiving portion122and the cooking stone106. This ensures a snug (though not necessarily with interference) fit.

Thus, the cooking stone106of the first assembly100can be seated within the receiving portion122of the insulating mat104, which in-turn can be seated within the well182of the rack102such that the bottom wall124of the receiving portion122rests on the central crosswires180e, and the left and right flanges132b,132dof the insulating mat104rest on the left- and right-crosswires180b,180dof the rack102, respectively. The crosswires180b,180d,180ewill thus support the insulating mat104and cooking stone106.

The rack102of the second assembly100′ (seeFIG.8), on the other hand, does not include any well. Instead, the crosswires180of that rack102all extend along the primary plane Pi and define a planar support platform for the insulating mat104. Thus, the cooking stone106of the second assembly100′ can be seated within the receiving portion136of the insulating mat104, which in-turn can be placed on the crosswires180of the rack102. Notably, the insulating mat104of the second assembly100′ is configured to elevate the cooking stone106relative to the rack102. Specifically, the insulating mat104is configured such that in the assembled state of the second rack assembly100′, the bottom wall154of the insulating mat104and the cooking stone106resting thereon are parallel to and spaced from the primary plane Pi of the rack102. Preferably, a distance between the bottom wall154/cooking stone106and the primary plane Pi will be 1 to 6 inches, and more preferably 1 to 3 inches. This spacing of the bottom wall154/cooking stone106from the primary plane Pi will elevate the cooking stone106relative to the rack102, thereby positioning the cooking stone106closer to the broil element50and enabling the broil element50to provide more-focused heat to the cooking stone106and any food supported thereon.

Each rack assembly100,100′ can be mounted in the oven cavity18by resting its rack102on the rack supports38(seeFIG.2) of the compartment's left- and right-side walls34b,34d. The rack102of each assembly100,100′ is preferably a “full width” rack having dimensions that approximate horizontal dimensions of the cavity12. In particular, the length L4of the rack's outer frame176can approximate a distance between the left- and right-side walls34b,34d. As such, the left- and right-side walls34b,34c,34dof the compartment14can restrict lateral movement of the rack102when mounted within the cavity18.

As mounted, the cooking stone106preferably will be substantially centered in the rack102between the left and right walls34b,34dof the compartment14, such that the cooking stone106is directly below the broil element50. Moreover, lateral movement of the cooking stone106can be inhibited by the rack102and/or insulating mat104.

For example, with respect to the first rack assembly100, the left- and right-crosswires180b,180dof the rack102(seeFIG.5) can inhibit lateral movement of the insulating mat104and cooking stone106relative to the rack102in left and right directions, respectively. Meanwhile, the front and rear crosswires180a,180cof the rack102can inhibit lateral movement of the insulating mat104and cooking stone106relative to the rack102in frontward and rearward directions, respectively.

With respect to the second rack assembly100′, the left-, rear-, and right-side walls156a,156b,156cof the insulating mat104can inhibit lateral movement of the cooking stone106relative to the mat104in left, rear, and right directions, respectively. Moreover, lateral movement of the insulating mat104(and cooking stone106) relative to the rack102can be inhibited by friction between the mat104and rack102. In some examples, the insulating mat104can have dimensions that approximate horizontal dimensions of the cavity12, such that lateral movement of the insulating mat104is restricted by the left-, rear-, and right-side walls34a,34b,34cof the compartment14. In particular, the length L2of the insulating mat104can approximate a distance between the left- and right-side walls34b,34d. Moreover, the width W2of the insulating mat104can approximate a depth of the rear-side wall34cfrom the door22when closed. Inhibiting lateral movement of the insulating mat104and cooking stone106can prevent those elements from shifting as food (e.g., pizza, steak, etc.) is slid onto or off of the cooking stone106during a cooking operation.

As noted above, each rack assembly100,100′ is configured to partition and insulate an upper portion18aof the cavity18from a lower portion18bwhere the temperature sensor82is located. In particular, the insulating mat104of each assembly100,100′ can have a superficial area (calculated by multiplying its overall length L2and width W2) that is preferably 80% or more, and more preferably 90% or more, of the rack's superficial area (calculated by multiplying the overall length L4and width W4of its outer frame176). Preferably, the overall length L2and width W2of the insulating mat104are approximate to or greater than the respective length L4and width W4of the rack102. As such, the insulating mat104will occupy a significant proportion of the area defined within the rack's outer frame176, and by extension of the lateral area of the oven cavity18itself, such that the insulating mat104partitions and insulates the upper portion18afrom the lower portion18b.

Moreover, the insulating mat104of each rack assembly100,100′ is preferably configured such that in the mounted state, the insulating mat104will be arranged relative to the primary temperature sensor82as shown inFIG.9. That is, the insulating mat104will be arranged in close proximity to and above the sensor82, such that the mat104is arranged directly between the sensor82and the broil element50. Accordingly, the insulating mat104can reflect direct radiation travelling downward from the broil element50back up toward the upper wall34e, thereby preventing that direct radiation from entering the lower portion18bof the cavity18and impinging on the sensor82. This enables the broil element50to heat the upper portion18ato a high temperature (e.g., 750° F.) without heating the sensor82and lower portion18bof the cavity18up to a temperature that exceeds safety regulations and causes the oven door22to automatically lock.

Various cooking operations are described further below that utilize the broil element50and either of the rack assemblies100,100′ described above to perform high-heat cooking in the upper portion18aof the oven cavity18. In some cases, it may be desirable to control a cooking operation based on temperature of the cooking stone106and/or the air within the upper portion18a. Moreover, it may be desirable to detect a presence of the rack assembly100,100′ in order to ensure it is properly mounted prior to and/or during a cooking operation. Accordingly, described below are various features that can facilitate detection of these parameters for regulating one or more cooking operations.

For example, as shown inFIG.9, the appliance10can include an auxiliary temperature sensor184that is configured to measure the air temperature within the upper portion18aand provide an electrical output to controller80indicative of its detected temperature.

The appliance10can further include a rack detection device188(shown schematically inFIG.9) that is configured to detect the presence of a rack assembly100,100′ within the cavity18and provide an output to the controller90that is indicative of a rack assembly's presence. The rack detection device188can be a switch (e.g., tactile switch, limit switch, etc.) that is physically triggered when a rack assembly100,100′ is place in or removed from the cavity18. Alternatively, the rack detection device188can be a contactless proximity sensor (e.g., Hall effect sensor, capacitive sensor, optical sensor, etc.) that is configured to a detect a presence of the rack assembly100,100′ when in close proximity thereto. The rack detection device188can be any device that is operable to provide an output to the controller80indicative of a rack assembly's presence.

Moreover, as shown inFIG.4, the cooking stone106of each rack assembly100,100′ can include a temperature sensor190that is configured to measure a temperature of the body110and provide an electrical output indicative of the measured temperature. For instance, the temperature sensor190in the present example is embedded within the body110such that the sensor is in direct thermal contact with the surrounding body110. Moreover, the cooking stone106includes a cable192for establishing an electrical connection between the sensor190and another device (e.g., the controller80). The cable192is electrically connected to the sensor190at one end and has a connector194(e.g., plug) at its other end that can mate with a corresponding connector196(seeFIG.9) of the appliance10to electrically connect the temperature sensor190and controller80. In this manner, the cable192can be plugged into the appliance10whenever it is desirable to use the cooking stone106and its temperature sensor190in a cooking operation, and disconnected from the appliance10whenever it is desirable to remove the cooking stone106from the appliance10(e.g., for cleaning or when not in-use).

In some examples, the connector196of the appliance10can correspond to the rack detection device188described above, since its output to the controller80is dependent on connection to (and thus the presence of) the cooking stone106. That is, the controller80can monitor an output from the connector196to determine if a rack assembly100,100′ is present within the oven cavity18. If the cooking stone106of a rack assembly100,100′ is connected to the connector196, the output of the connector196will correspond to the output of the temperature sensor190, which fluctuates based on temperature of the cooking stone106. Any positive output from the connector196can indicate that the cooking stone106is connected to the connector196, and a rack assembly100,100′ is presumably mounted within the cavity18in its assembled state. Conversely, a zero output from the connector196will indicate that no cooking stone106is connected to the connector196, and presumably neither rack assembly100,100′ is present within the cavity18.

Turning toFIG.10, a high-heat cooking operation200will now be described for cooking food items at high heat using the rack assembly100,100′ described above. The cooking operation200can be particularly useful for grilling or searing meats (e.g., steak) or cooking “fresh pizza” (pizza with uncooked, non-frozen dough).

The cooking operation200includes a rack detection stage202, a preheat stage204, an intermediate stage206, and a cooking stage208. The details of these stages202,204,206,208are described below and illustrated further inFIGS.11-14. As discussed further below, the cooking operation200will activate only the broil element50to heat the oven cavity18, without activating any other heating element or fan. Moreover, during the cooking operation200, the rack assembly100,100′ will preferably be mounted in the oven cavity18close to the broil element50, such that the cooking stone106is spaced about 8 inches or less below the broil element50, and more preferably 6 inches or less below the broil element50.

As discussed above, the insulating mat104of the rack assembly100,100′ will partition and insulate the upper portion18aof the oven cavity18from the lower portion18bwhere the temperature sensor82is located. The insulating mat104can thus reflect direct radiation travelling downward from the broil element50back up toward the upper wall34e, thereby preventing that direct radiation from entering the lower portion18bof the cavity18. The result is that the lower portion18band primary temperature sensor82never reach a temperature (e.g., 600° F.) that would require triggering the door lock as a result of agency regulations.

A user can initiate the first cooking operation200by entering a start command on the user interface30, which in turn will provide a start signal to the controller80that causes it to start performing the rack detection stage202. As shown inFIG.11, the rack detection stage202will monitor the output of the rack detection device188to determine if a rack condition Xr1is satisfied in which the rack assembly100,100′ is present within the oven cavity18. If the output indicates that the rack condition Xr1is satisfied (i.e., the rack assembly100,100′ is present), the controller80will proceed to and perform the preheat stage204. Conversely, if the output indicates that the rack condition Xr1is not satisfied (i.e., no rack assembly100,100′ is present), the controller80can either cease the cooking operation200or continue monitoring the output until it indicates that a rack assembly100,100′ is present.

The controller80will perform the preheat stage204(seeFIG.11) in response to completion of the rack detection stage202(which corresponds to the moment the rack condition Xr1is satisfied). Preferably, the preheat stage204will be performed without any food being present in the oven cavity18. During the preheat stage204, the controller80will operate the broil element50according to a preheat power scheme until a preheat condition Xp1is satisfied, at which point the preheat stage204will cease and the intermediate stage206will begin. For the purposes of this disclosure, a “power scheme” of a heating element can be any scheme that regulates power supplied to the heating element by regulating the rate of energy (e.g., electricity or gas) supplied thereto. For example, power can be regulated (i.e., adjusted or maintained) by continuously energizing the heating element with a constant rate of energy, continuously de-energizing the heating element, varying (e.g., cycling) the rate of energy supplied to heating element, or combinations thereof. The preheat power scheme in the present embodiment continuously energizes the broil element50at full power for the entire preheat stage204until the preheat condition Xp1is satisfied.

The preheat condition Xp1can be any condition that is predetermined to render the oven cavity18and/or cooking stone106sufficiently preheated for cooking. In particular, the preheat condition Xp1can be based on a predetermined temperature threshold and/or amount of time. For example, the preheat condition Xp1in the present embodiment corresponds to a condition in which a temperature Tm1measured by the sensor190of the cooking stone106is equal to or greater than a predetermined target temperature Tx1. For cooking fresh pizza, the target temperature Tx1will preferably be 700° F. or greater, and more preferably 750° F. or greater. In other examples, the preheat condition Xp1may correspond to a condition in which the broil element50has been operated according to the preheat power scheme for a predetermined amount of time (e.g., 20 minutes or more, and more preferably 24 minutes or more) sufficient to heat the cooking stone106up to a desirable temperature for the cooking operation.

The controller80will perform the intermediate stage206in response to completion of the preheat stage204(which corresponds to the moment the preheat condition Xp1is satisfied). At the beginning of the intermediate stage206(seeFIG.12), the controller80will operate the user interface30of the cooking appliance10to provide an indication that prompts a user to place a food item in the cavity18. In particular, the controller80will provide an electrical signal to the user interface30, which in turn will provide an output (e.g., light, image, sound, etc.) indicating (e.g., either explicitly or implicitly) that the preheat stage204is complete and a food item can be placed in the oven cavity18.

Moreover, during the intermediate stage206, the controller80will operate the broil element50according to an intermediate power scheme in order to keep the upper portion18aof the oven cavity18and the cooking stone106heated while the user places a food item on the cooking stone106in the oven cavity18. In particular, the controller80will continuously energize the broil element50for the entire intermediate stage206until an intermediate condition Xiis satisfied, at which point the intermediate stage206will cease and the cooking stage208will begin.

The intermediate condition Xican be any predetermined condition indicating or suggesting that food has been placed in the cavity18and is ready for the cooking stage208. For example, when a user opens the door22to insert a food item and then subsequently closes the door22, the door sensor84can provide an input signal to the controller80indicating that the door22has been opened and closed during the intermediate stage206. That input signal therefore suggests that a food item is in the cavity18and ready for cooking. Additionally or alternatively, the user can provide an input to the user interface30indicating that a food item is in the cavity18and ready for cooking, and the user interface30will provide a corresponding input signal to the controller80in response to the user input. Thus, the intermediate condition Xican correspond to a condition in which the controller80receives either of those input signals from the door sensor84and user interface30.

The controller80will perform the cooking stage208in response to completion of the intermediate stage206(which corresponds to the moment the intermediate condition Xiis satisfied). As discussed above, the preheat and intermediate stages204,206will operate the broil element50according to respective power schemes, thereby heating the cooking stone106and the air within the upper portion18aof the oven cavity18up to a high temperature (e.g., 700° F.). However, once a food item is placed on the cooking stone106and the cooking stage208begins, keeping the broil element50energized throughout the entire cooking stage208may cause an upper portion of the food item to cook faster than the bottom, since the combination of convective heat from the air and radiative heat from the broil element50will be greater than the conductive heat from the cooking stone106. This may cause the upper and lower portions of the food item to cook differently, resulting in the upper portion being overcooked and/or the lower portion being undercooked.

Accordingly, at the beginning of the cooking stage208, the controller80will perform a reduced-power stage210(seeFIG.13) that operates the broil element50according to a reduced-power scheme in order to reduce air temperature and a heat output of the broil element50. In particular, the reduced-power scheme will operate the broil element50at less power than the preheat- and intermediate-power schemes. For the purposes of this disclosure, a first power scheme can operate a heating element at less power than a second power scheme if the average or maximum power (i.e., rate of energy) supplied to the heating element during the first power scheme is less than the average or maximum power supplied to the heating element during the second power scheme. Conversely, a first power scheme can operate a heating element at greater power than a second power scheme if the average or maximum power supplied to the heating element during the first power scheme is greater than the average or maximum power supplied to the heating element during the second power scheme. For example, in the present embodiment, the preheat- and intermediate-power schemes will continuously energize the broil element50at full power, and the reduced-power scheme will continuously de-energize the broil element50. Thus, the reduced-power scheme will operate the broil element50at less power than the preheat- and intermediate-power schemes.

Operating the broil element50at the reduced-power scheme (e.g., continuously de-energized) will cause air temperature and the heat output of the broil element50to decrease (although the broil element50may still provide some heat output if, for example, it has residual heat and/or remains energized at a low level). Meanwhile, the cooking stone106will emit residual heat to conductively cook the food item resting thereon. Thus, the reduced-power stage210can begin cooking the lower portion of the food item while the cavity air and broil element50are providing relatively low heat output to the upper portion of the food item.

The reduced-power stage210will operate the broil element50according to the reduced-power scheme until a reduced-power condition Xrpis satisfied, at which point the reduced-power stage210will cease and the controller80will proceed to an increased-power stage212. The reduced-power condition Xrpcan be any predetermined condition in which the lower portion of the food item has been at least partially cooked and the upper portion of the food item is ready for additional heat to complete the cooking process. In particular, the reduced-power condition Xrpcan be based on a predetermined temperature threshold and/or amount of time. For example, the reduced-power condition Xrpin the present embodiment corresponds to a condition in which the broil element50has been operated according to the reduced-power scheme for a predetermined amount of time t1a(e.g., one minute). In other examples, the reduced-power condition X, can correspond to a condition in which a temperature measured by the auxiliary temperature sensor184of the appliance10is equal to or less than a predetermined target temperature.

The controller80will perform the increased-power stage212(seeFIG.14) in response to completion of the reduced-power stage210(which corresponds to the moment the reduced-power condition Xrpis satisfied). In this stage212, the controller80will operate the broil element50according to an increased-power scheme in order to increase a heat output of the broil element50and finish cooking the food item at high heat. In particular, the increased-power scheme will continuously energize the broil element50at full power for the entire increased-power stage212. Thus, the increased-power scheme will operate the broil element50at greater power than the reduced-power scheme.

During the increased-power stage212, the controller80can operate the user interface30to provide a notification to the user once the food item is finished cooking. In particular, the controller80can determine if a food condition Xf1is satisfied indicating or suggesting that the food item is finished cooking. The food condition Xf1can be based on a predetermined temperature threshold and/or amount of time. For example, the food condition Xf1in the present embodiment corresponds to a condition in which the broil element50has been operated according to the increased-power scheme for a predetermined amount of time t1b(e.g., one minute) sufficient to finish cooking the food item. In other examples, the food condition Xf1can correspond to a condition in which a temperature measured by a food probe is equal to or greater than a predetermined target temperature. In response to the food condition Xf1being satisfied, the controller80will provide an electrical signal to the user interface30, which in turn will provide an output (e.g., light, image, sound, etc.) indicating (e.g., either explicitly or implicitly) that the food item can be removed from the cavity18.

The increased-power stage212will continue operating the broil element50according to the increased-power scheme until either one of a first condition X1a, a second condition X1b, and a third condition X1cis satisfied, at which point the increased-power stage212will cease. For example, the first condition X1amay correspond to a condition in which the controller80receives an input signal to cancel the cooking operation200. More specifically, a user can enter a cancel command on the user interface30, which in turn will provide a corresponding input signal to the controller80. If this first condition X1ais satisfied, the controller80will cease the whole cooking operation200. In other words, the first condition X1aenables a user to manually end the cooking operation200.

Meanwhile, the second condition X1bmay correspond to a condition in which a predetermined amount of time (e.g., 5 minutes) has lapsed since the food condition Xf1was initially satisfied. If that second condition X1bis satisfied, the controller80will also cease the whole cooking operation200. In other words, the second condition X1benables the controller80to automatically cease the cooking operation200if no cancel command is provided by the user within the predetermined amount of time.

Lastly, the third condition X1cmay correspond to a condition in which the controller80receives an input signal to repeat the cooking operation200. More specifically, if a user wants to cook another food item using the cooking operation200, the user can enter a repeat command on the user interface30, which in turn will provide a corresponding input signal to the controller80. If this third condition X1cis satisfied, the controller80will cease the increased-power stage212and repeat the intermediate stage206in response to completion of the increased-power stage212. As discussed above, the intermediate stage206will operate the broil element50according to an intermediate power scheme in order to keep the upper portion18aof the oven cavity18and the cooking stone106heated while the user places a food item on the cooking stone106in the oven cavity18. Moreover, intermediate stage206will continue to operate the broil element50according to the intermediate power scheme until an intermediate condition Xiis satisfied, at which point the intermediate stage206will cease and the cooking stage208will begin. The controller80can continue alternating between the intermediate stage206and cooking stage208accordingly until the cooking operation200is ceased.

The cooking stage208of the high-heat cooking operation200described above is configured to temporarily operate the broil element50at a reduced-power scheme so that the cooking stone106has sufficient time to conductively heat the bottom portion of the food item before the upper portion is overcooked by the combination of convective heat from the air and radiative heat from the broil element50. However, in some examples, residual heat in the air and broil element50may still cause the upper portion to cook faster than the bottom portion, even while the broil element50is de-energized. Thus, described below is a second high-heat cooking operation300(seeFIG.15) that is designed to de-energize the broil element50before its cooking stage begins, in order to reduce residual heat in the air and broil element50before the food item is placed in the oven cavity18.

The high-heat cooking operation300comprises a rack detection stage302, a preheat stage304, a reduced-power stage306, an intermediate stage308, a cooking stage310, and a recovery stage312. The details of these stages are described below and illustrated further inFIGS.16-21. Similar to the first cooking operation200described above, the second cooking operation300will activate only the broil element50to heat the oven cavity18, without activating any other heating element or fan. Moreover, during the cooking operation300, the rack assembly100,100′ will preferably be mounted in the oven cavity18close to the broil element50, such that the cooking stone106is spaced about 8 inches or less below the broil element50, and more preferably 6 inches or less below the broil element50.

A user can initiate the second cooking operation300by entering a start command on the user interface30, which in turn will provide a start signal to the controller80that causes it to start performing the rack detection stage302. As shown inFIG.16, the rack detection stage302will monitor the output of the rack detection device188to determine if a rack condition Xr2is satisfied in which the rack assembly100,100′ is present within the oven cavity18. If the output indicates that the rack condition Xr2is satisfied (i.e., the rack assembly100,100′ is present), the controller80will proceed to and perform the preheat stage304. Conversely, if the output indicates that the rack condition Xr2is not satisfied (i.e., no rack assembly100,100′ is present), the controller80can either cease the cooking operation300or continue monitoring the output until it indicates that a rack assembly100,100′ is present.

The controller80will perform the preheat stage304(seeFIG.16) in response to completion of the rack detection stage302(which corresponds to the moment the rack condition Xr2is satisfied). Preferably, the preheat stage304will be performed without any food being present in the oven cavity18. During the preheat stage304, the controller80will operate the broil element50according to a preheat power scheme until a preheat condition Xp2is satisfied, at which point the preheat stage304will cease and the reduced-power stage306will begin.

The preheat power scheme in the present embodiment continuously energizes the broil element50at full power for the entire preheat stage304until the preheat condition Xp2is satisfied. The preheat condition Xp2can be any condition that is predetermined to render the oven cavity18and/or cooking stone106sufficiently preheated for the cooking operation300. In particular, the preheat condition Xp2can be based on a predetermined temperature threshold and/or amount of time. For example, the preheat condition Xp2in the present embodiment corresponds to a condition in which the temperature Tm1measured by the sensor190of the cooking stone106is equal to or greater than a predetermined target temperature Tx2. For cooking fresh pizza, the target temperature Tx2will preferably be 700° F. or greater, and more preferably 750° F. or greater. In other examples, the preheat condition Xp2may correspond to a condition in which the broil element50has been operated according to the preheat power scheme for a predetermined amount of time (e.g., 30 minutes or more, and more preferably 24 minutes or more) sufficient to heat the cooking stone106up to a desirable temperature for the cooking operation.

The preheat stage304will thus operate the broil element50according to a preheat power scheme that heats the cooking stone106and the air within the upper portion18aof the oven cavity18up to a high temperature (e.g., 700° F.). However, once a food item is placed on the cooking stone106and the cooking begins, keeping the broil element50energized throughout the cooking process may cause an upper portion of the food item to cook faster than the bottom, since the combination of convective heat from the air and radiative heat from the broil element50will be greater than the conductive heat from the cooking stone106. This may cause the upper and lower portions of the food item to cook differently, resulting in the upper portion being overcooked and/or the lower portion being undercooked. Moreover, even if the broil element50is de-energized at the start of cooking, residual heat in the air and broil element50may still cause the upper portion to cook faster than the bottom portion.

Accordingly, in the second cooking operation300, the controller80will perform a first reduced-power stage306(seeFIG.17) in response to completion of the preheat stage304(which corresponds to the moment the preheat condition Xpis satisfied). The reduced-power stage306will operate the broil element50according to a reduced-power scheme in order to reduce a heat output of the broil element50before food is placed in the cavity18. For instance, in the present embodiment, the reduced-power scheme will continuously de-energize the broil element50for the entire reduced-power stage306. Thus, the reduced-power scheme will operate the broil element50at less power than the preheat-power scheme of the preheat stage204.

Operating the broil element50at the reduced-power scheme (e.g., continuously de-energized) will cause the cavity temperature and the heat output of the broil element50to decrease (although the broil element50may still provide some heat output if, for example, it has residual heat and/or remains energized at a low level). Meanwhile, the cooking stone106will emit residual heat such that its heat output also decreases over time, but at a much slower rate than the combined heat output of the broil element50and cavity air. Thus, the reduced-power stage306can reduce heat output of the broil element50and cavity air while still maintaining a sufficiently high heat output for the cooking stone106.

The reduced-power stage306will operate the broil element50according to the reduced-power scheme until a reduced-power condition Xp1is satisfied, at which point the reduced-power stage306will cease and the controller80will proceed to the intermediate stage208. The reduced-power condition Xp1can be any predetermined condition in which the heat output of the broil element50and/or temperature of the cavity air has been sufficiently reduced for the cooking operation300. In particular, the reduced-power condition Xp1can be based on a predetermined temperature threshold and/or amount of time. For example, the reduced-power condition Xp1in the present embodiment corresponds to a condition in which the broil element50has been operated according to the reduced-power scheme for a predetermined amount of time t2a(e.g., one minute). In other examples, the reduced-power condition Xrp1can correspond to a condition in which an air temperature measured by the auxiliary temperature sensor184of the appliance10is equal to or less than a predetermined target temperature.

The controller80will perform the intermediate stage308in response to completion of the reduced-power stage306(which corresponds to the moment the reduced-power condition Xrp1is satisfied). At the beginning of the intermediate stage308(seeFIG.18), the controller80will operate the user interface30of the cooking appliance10to provide an indication that prompts a user to place a food item in the cavity18. In particular, the controller80will provide an electrical signal to the user interface30, which in turn will provide an output (e.g., light, image, sound, etc.) indicating (e.g., either explicitly or implicitly) that the reduced-power stage306is complete and a food item can be placed in the oven cavity18.

Moreover, during the intermediate stage308, the controller80will operate the broil element50according to an intermediate power scheme in order to keep the upper portion18aof the oven cavity18and the cooking stone106heated while the user places a food item on the cooking stone106in the oven cavity18. For example, the controller80can operate the broil element50based on a predetermined target temperature in order to achieve and/or maintain an oven cavity temperature about the target temperature. More specifically, the controller80can monitor an air temperature measured by the auxiliary temperature sensor184of the appliance10, and then operate (e.g., energize, de-energize, cycle, etc.) the broil element50based on the measured temperature and a closed-loop control algorithm (e.g., hysteresis, PID control, etc.) such that the measured air temperature maintains about the target temperature Tx. However, in other examples, the controller60may simply operate the broil element50according to a fixed power scheme (e.g., continuously energized or cycled) with open loop control.

The controller80will operate the broil element50according to the intermediate power scheme for the entire intermediate stage308until either one of a first intermediate condition Xii and a second intermediate condition X2iis satisfied, at which point the intermediate stage308will cease.

The first intermediate condition X1ican be any predetermined condition indicating or suggesting that food has been placed in the cavity18and is ready for the cooking stage310. For example, when a user opens the door22to insert a food item and then subsequently closes the door22, the door sensor84can provide an input signal to the controller80indicating that the door22has been opened and closed during the intermediate stage308. That input signal therefore suggests that a food item is in the cavity18and ready for cooking. Additionally or alternatively, the user can provide an input to the user interface30indicating that a food item is in the cavity18and ready for cooking, and the user interface30will provide a corresponding input signal to the controller80in response to the user input. Thus, the first intermediate condition X1ican correspond to a condition in which the controller80receives either of those input signals from the door sensor84and user interface30. In response to the first intermediate condition Xii, the controller80will cease the intermediate stage308and perform the cooking stage310(described further below).

If the first intermediate condition X1idoes not occur within a sufficient amount of time and the controller80continues to operate the broil element50according to the intermediate power scheme for an extended period of time, it is possible that the temperature of the cooking stone106will eventually drop to a temperature that is insufficient for high-heat cooking. Accordingly, the second intermediate condition X2ican correspond to a condition in which the broil element50has been operated according to the intermediate power scheme for an undesirable length of time. For example, the second intermediate condition X2iin the present embodiment corresponds to a condition in which the broil element50has been operated according to the intermediate-power scheme for a predetermined amount of time (e.g., 5 minutes). In other examples, the second intermediate condition X2ican correspond to a condition in which the temperature Tm1measured by the temperature sensor190of the cooking stone106is equal to or less than a predetermined target temperature.

In response to the second intermediate condition X2ibeing satisfied, the controller80will cease the intermediate stage308and perform the recovery stage312(seeFIG.19). In that stage312, the controller80will operate the broil element50according to a recovery power scheme until a recovery condition Xyis satisfied, at which point the recovery stage312will cease and the reduced-power stage306will restart.

The recovery power scheme in the present embodiment continuously energizes the broil element50at full power for the entire recovery stage312until the recovery condition Xyis satisfied. The recovery condition Xycan be any condition that is predetermined to render the cooking stone106sufficiently recovered for the cooking operation300. In particular, the recovery condition Xycan be based on a predetermined temperature threshold and/or amount of time. For example, the recovery condition Xyin the present embodiment corresponds to a condition in which the broil element50has been operated according to the recovery power scheme for a predetermined amount of time t2b(e.g., 3-5 minutes) sufficient to reheat the cooking stone106up to a desirable temperature for the cooking operation300. In other examples, the recovery condition Xycan correspond to a condition in which the temperature Tm1measured by the sensor190of the cooking stone106is equal to or greater than a predetermined target temperature.

The controller80will repeat the intermediate stage308in response to completion of the recovery stage312(which corresponds to the moment the recovery condition Xyis satisfied). If the second intermediate condition X2ioccurs again during operation of the intermediate stage308, the controller80will keep cycling through recovery and intermediate stages312,308until the first intermediate condition X1iis eventually satisfied during the intermediate stage308, at which point the controller80will cease the intermediate stage308and perform the cooking stage310.

In response to the first intermediate condition Xii being satisfied, the controller80will cease the intermediate stage308and perform the cooking stage310(seeFIG.20). At the beginning of the cooking stage310, the controller80will perform another reduced-power stage314that operates the broil element50according to a reduced-power scheme in order to reduce or limit a heat output of the broil element50during the beginning of the cooking stage310. In particular, the reduced-power scheme will continuously de-energize the broil element50for the entire reduced-power stage314. Thus, the reduced-power scheme will operate the broil element50at less power than the power schemes of the preheat, intermediate, and recovery stages304,308,312described above.

Operating the broil element50at the reduced-power scheme (e.g., continuously de-energized) will cause air temperature and the heat output of the broil element50to decrease. Meanwhile, the cooking stone106will emit residual heat to conductively cook the food item resting thereon. Thus, the reduced-power stage314can begin cooking the lower portion of the food item while the cavity and broil element50are providing relatively low heat output to the upper portion of the food item.

The reduced-power stage314will operate the broil element50according to the reduced-power scheme until a reduced-power condition Xrp2is satisfied, at which point the reduced-power stage314will cease and the controller80will proceed to an increased-power stage316. The reduced-power condition Xrp2can be any predetermined condition in which the lower portion of the food item has been at least partially cooked and the upper portion of the food item is ready for additional heat to complete the cooking process. In particular, the reduced-power condition Xrp2can be based on a predetermined temperature threshold and/or amount of time. For example, the reduced-power condition Xrp2in the present embodiment corresponds to a condition in which the broil element50has been operated according to the reduced-power scheme for a predetermined amount of time t2c(e.g., one minute). In other examples, the reduced-power condition Xrp2can correspond to a condition in which a temperature measured by the auxiliary temperature sensor184of the appliance10is equal to or less than a predetermined target temperature.

The controller80will perform the increased-power stage316(seeFIG.21) in response to completion of the reduced-power stage310(which corresponds to the moment the reduced-power condition Xrp2is satisfied). In this stage316, the controller80will operate the broil element50according to an increased-power scheme in order to increase a heat output of the broil element50and finish cooking the food item at high heat. In particular, the increased-power scheme will continuously energize the broil element50at full power for the entire increased-power stage316. Thus, the increased-power scheme will operate the broil element50at greater power than the reduced-power scheme.

During the increased-power stage316, the controller80can operate the user interface30to provide a notification to the user once the food item is finished cooking. In particular, the controller80can determine if a food condition Xf2is satisfied indicating or suggesting that the food item is finished cooking. The food condition Xf2can be based on a predetermined temperature threshold and/or amount of time. For example, the food condition Xf2in the present embodiment corresponds to a condition in which the broil element50has been operated according to the increased-power scheme for a predetermined amount of time (e.g., one minute) sufficient to finish cooking the food item. In other examples, the food condition Xf2can correspond to a condition in which a temperature measured by a food probe is equal to or greater than a predetermined target temperature. In response to the food condition Xf2being satisfied, the controller80will provide an electrical signal to the user interface30, which in turn will provide an output (e.g., light, image, sound, etc.) indicating (e.g., either explicitly or implicitly) that the food item can be removed from the cavity18.

The increased-power stage316will continue operating the broil element50according to the increased-power scheme until either one of a first condition X2a, a second condition X2b, and a third condition X2c is satisfied, at which point the increased-power stage316will cease. For example, the first condition X2amay correspond to a condition in which the controller80receives an input signal to cancel the cooking operation300. More specifically, a user can enter a cancel command on the user interface30, which in turn will provide a corresponding input signal to the controller80. If this first condition X2ais satisfied, the controller80will cease the whole cooking operation300. In other words, the first condition X2benables a user to manually end the cooking operation300.

Meanwhile, the second condition X2bmay correspond to a condition in which a predetermined amount of time (e.g., 5 minutes) has lapsed since the food condition Xf2was initially satisfied. If that second condition X2bis satisfied, the controller80will also cease the whole cooking operation300. In other words, the second condition X2benables the controller80to automatically cease the cooking operation300if no cancel command is provided by the user within the predetermined amount of time.

Lastly, the third condition X2c may correspond to a condition in which the controller80receives an input signal to repeat the cooking operation300. More specifically, if a user wants to cook another food item using the cooking operation300, the user can enter a repeat command on the user interface30, which in turn will provide a corresponding input signal to the controller80. If this third condition X2c is satisfied, the controller80will cease the increased-power stage316and begin the recovery stage312in response to completion of the increased-power stage316. As discussed above, the controller80will perform the intermediate stage308in response to completion of the recovery stage312, and then perform the cooking stage310if the first intermediate condition Xi, is satisfied during the cooking stage310. The controller80can continue cycling through the recovery, intermediate, and cooking stages312,308,310accordingly until the cooking operation300is ceased.

The rack assemblies100,100′ and high-heat cooking operations200,300described above can achieve a relatively high temperature (e.g., 750° F.) for cooking food items without heating the oven cavity18at-large up to a temperature that exceeds safety regulations and requires the oven door22to automatically lock. In particular, the assemblies100,100′ and cooking operations200,300can be particularly useful for cooking food items such a fresh pizza or steak, which can benefit from high cooking temperatures.

Turning toFIG.22, a third cooking operation400will now be described for cooking frozen pizza or other (typically frozen) food items. The cooking operation400includes a preheat stage402and a cooking stage404, and can be performed using any type of rack assembly mounted within the oven cavity. The rack assembly preferably will be mounted at a central elevation within the oven cavity18, although lower and higher elevations are possible in some embodiments.

A user can initiate the second cooking operation400by entering a start command on the user interface30, which in turn will provide a start signal to the controller80that causes it to start performing the preheat stage402. Preferably, the preheat stage402will be performed without any food being present in the oven cavity18. During the stage402, the controller80will continuously energize the bake element40and convection fan64until a temperature Tm2measured by the oven cavity sensor82is equal to or greater than a predetermined target temperature Ty1, at which point the preheat stage402will cease and the cooking stage404will commence. Moreover, upon completion of the preheat stage402, the controller80will provide an electrical signal to the user interface30, which in turn will provide an output (e.g., light, image, sound, etc.) indicating (e.g., either explicitly or implicitly) that the preheat stage402is complete and a food item can be placed in the oven cavity18. In other words, as in the prior embodiment the aforementioned output will trigger insertion of the food to be cooked by the user.

During the cooking stage404, the controller80will continuously energize the convection fan64while regulating operation of the bake element40to adjust or maintain the measured temperature Tm2relative to a predetermined target temperature Ty2. That is, the controller80will cycle the bake element40on and off based on a predetermined control algorithm (e.g., using PID or hysteresis control) to adjust or maintain the measured temperature Tm2such that it is close to the target temperature Ty2. Preferably, once the measured temperature Tm2reaches the target temperature Ty2, the cooking stage404will maintain the measured temperature Tm2within 15° F. of the target temperature Ty2, and more preferably within 10° F. of the target temperature Ty2. In other words, the measured temperature Tm2will fluctuate between peaks of high and low temperatures that are within 15° F. of the target temperature Ty2 or less, preferably for the entire cooking stage404; e.g., those peaks being the hysteresis bounds of the algorithm that controls the bake element40to maintain the target temperature close to the target temperature Ty2.

In some examples, the target temperatures Ty1, Ty2of the preheat and cooking stages402,404can correspond to a desired cooking temperature Td (e.g., 350° F.) that is selected on the user interface30and input to the controller80, such that the preheat stage402increases the measured temperature Tm2up to the desired cooking temperature Td and the cooking stage404maintains the measured temperature Tmabout that temperature. In other examples, one or both of the target temperatures Ty1, Ty2can be offset from the desired temperature Td by a predetermined offset to account for inaccuracies, inefficiencies, thermal inertias, sensor locations, or other conditions associated with the cooking appliance10.

In some examples, the cooking stage404can continue energizing the convection fan64and regulating operation of the bake element40in the manner described above indefinitely until the user cancels the cooking operation400by providing a cancel command on the user interface30, which in turn will provide a corresponding signal to the controller80. In other words, the cooking stage404will continue indefinitely until the controller80receives a cancel signal from the user interface30. In other examples, the cooking stage404can continue energizing the convection fan64and regulating operation of the bake element40for a predetermined amount of time that is either programmed into the controller80or set by a user on the user interface30.

By utilizing the convection fan64and bake element40as described above, the second cooking operation400can evenly thaw and cook a frozen pizza or other frozen food items. However, it is to be appreciated that various modifications can be made to the cooking operation400without departing from the scope of the disclosure. Broadly speaking, the cooking operation400can comprise any operation having a preheat stage that energizes the convection fan64and a heating element until the measured temperature Tm2reaches a predetermined target temperature, and a cooking stage that energizes the convection fan64and regulates operation of a heating element to maintain the measured temperature Tm2relative to a predetermined target temperature.

Illustrative embodiments have been described, hereinabove. It will be apparent to those skilled in the art that the above apparatuses and methods may incorporate changes and modifications without departing from the general scope of this disclosure. The disclosure is intended to include all such modifications and alterations disclosed herein or ascertainable herefrom by persons of ordinary skill in the art without undue experimentation.