Patent Publication Number: US-2018051888-A1

Title: Oven appliance surface element with no onboard sensor

Description:
FIELD OF THE INVENTION 
     The present disclosure relates generally to oven appliances and methods for oven appliance operation. In particular, the present disclosure is directed to the use of resistance sensors in oven appliances, and methods which utilize such technology. 
     BACKGROUND OF THE INVENTION 
     Oven appliances are frequently utilized in a variety of settings to cook food items. During operation of an oven appliance, relatively high temperatures can be generated, for example, in the cooking chamber or on the cooktop of the oven appliance. Further, heating elements of a cooktop can retain heat for some time after deactivation. As such, it is desired to provide an indication that the cooktop surface is relatively hot to inform users of the hot surface condition. For example, a hot surface indicator light can be used. The current approach is to determine if the cooktop surface is relatively hot by directly measuring the temperature of the heating element(s) thereon using onboard temperature sensors, i.e., sensors or a thermal switch mounted on the heating element(s). 
     The presence of such onboard temperature sensors necessarily increases the size of the cooktop relative to the total volume of the oven appliance. However, it is desired to provide a greater oven capacity, e.g., as measured by the cubic feet of volume provided inside the a cooking chamber of the oven. For a given size cabinet of the oven appliance, the possible volume of the cooking chamber therein is limited by, e.g., the amount of space within the cabinet taken up by the cooktop and associated sensors. 
     Accordingly, improved oven appliances and methods for operating oven appliances are desired. In particular, oven appliance and methods which provide a hot surface indication while increasing oven capacity would be advantageous. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In accordance with one embodiment, an oven appliance is provided. The oven appliance includes a cabinet defining a cooking chamber, the cooking chamber configured for receipt of items to be cooked and a cooktop disposed on the cabinet, the cooktop comprising at least one heating element. The oven appliance also includes an indicator light, a resistance sensor spaced from the heating element, and a controller in communication with the heating element, the resistance sensor, and the indicator light, the controller operable to store a cool resistance value of the heating element, to illuminate the indicator light when the heating element is turned on, to keep the indicator light illuminated after the heating element is turned off, to monitor the resistance of the heating element after it is turned off, and to turn off the indicator light when the resistance of the heating element equals the cool resistance value. 
     In accordance with another embodiment, a method for operating an oven appliance is provided. The method includes activating a heating element, illuminating an indicator light when the heating element is activated, deactivating the heating element, keeping the indicator light illuminated after the heating element is deactivated, monitoring resistance of the heating element after the heating element is deactivated, and turning off the indicator light when the resistance of the heating element equals a cool resistance value of the heating element. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  provides a perspective view of an oven appliance according to an exemplary embodiment of the present subject matter. 
         FIG. 2  provides a section view of the oven appliance of  FIG. 1  taken along the  2 - 2  line of  FIG. 1 . 
         FIG. 3  provides a perspective view of an exemplary embodiment of an oven appliance cooktop according to an exemplary embodiment of the present subject matter. 
         FIG. 4  provides a perspective view of another exemplary embodiment of an oven appliance cooktop according to another exemplary embodiment of the present subject matter. 
         FIG. 5  provides a flowchart of a method for operating an oven appliance according to an exemplary embodiment of the present subject matter. 
         FIG. 6  provides a flowchart of a method for operating an oven appliance according to an exemplary embodiment of the present subject matter. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
       FIG. 1  provides a perspective view of an oven appliance  10  according to an exemplary embodiment of the present subject matter.  FIG. 2  provides a section view of oven appliance  10  taken along the  2 - 2  line of  FIG. 1 . As may be seen, e.g., in  FIGS. 3 and 4 , oven appliance  10  defines a vertical direction V, a lateral direction L and a transverse direction T. The vertical direction V, the lateral direction L and the transverse direction T are mutually perpendicular and form an orthogonal direction system. Oven appliance  10  is provided by way of example only and is not intended to limit the present subject matter in any aspect. Thus, the present subject matter may be used with other oven appliance configurations, e.g., that define one or more interior cavities for the receipt of food and/or having different pan or rack arrangements than what is shown in  FIG. 2 . Further, the present subject matter may be used in a stand-alone cooktop, a hot plate, or any other suitable appliance. 
     Oven appliance  10  generally includes a cooking assembly. The cooking assembly may include one or more heating elements. For example, in some embodiments, the cooking assembly, and thus the oven appliance  10  includes an insulated cabinet  12  with an interior cooking chamber  14  defined by an interior surface  15  of cabinet  12 . Cooking chamber  14  is configured for the receipt of one or more food items to be cooked. Oven appliance  10  includes a door  16  rotatably mounted to cabinet  12 , e.g., with a hinge (not shown). A handle  18  is mounted to door  16  and assists a user with opening and closing door  16  in order to access cooking chamber  14 . For example, a user can pull on handle  18  to open or close door  16  and access cooking chamber  14 . 
     Oven appliance  10  can include a seal (not shown) between door  16  and cabinet  12  that assists with maintaining heat and cooking fumes within cooking chamber  14  when door  16  is closed as shown in  FIG. 2 . Multiple parallel glass panes  22  provide for viewing the contents of cooking chamber  14  when door  16  is closed and assist with insulating cooking chamber  14 . A baking rack  24  is positioned in cooking chamber  14  for the receipt of food items or utensils containing food items. Baking rack  24  is slidably received onto embossed ribs or sliding rails  26  such that rack  24  may be conveniently moved into and out of cooking chamber  14  when door  16  is open. 
     A gas fueled or electric bottom heating element  40  (e.g., a gas burner or a bake gas burner) is positioned in cabinet  12 , e.g., at a bottom portion  30  of cabinet  12 . Bottom heating element  40  is used to heat cooking chamber  14  for both cooking and cleaning of oven appliance  10 . The size and heat output of bottom heating element  40  can be selected based on the e.g., the size of oven appliance  10 . 
     A top heating element  42  is also positioned in cooking chamber  14  of cabinet  12 , e.g., at a top portion  32  of cabinet  12 . Top heating element  42  is used to heat cooking chamber  14  for both cooking/broiling and cleaning of oven appliance  10 . Like bottom heating element  40 , the size and heat output of top heating element  42  can be selected based on the e.g., the size of oven appliance  10 . In the exemplary embodiment shown in  FIG. 2 , top heating element  42  is shown as an electric resistance heating element. However, in alternative embodiments, a gas, microwave, halogen, or any other suitable heating element may be used instead of electric resistance heating element  42 . 
     As shown in  FIG. 2 , in some embodiments, a cooling air flow passageway  28  can be provided within cabinet  12  between cooking chamber  14  and cooktop  100 . For example, a portion of passageway  28  may be between cooking chamber  14  and cooktop  100  along a vertical direction V. Passageway  28  is shown schematically in the figures. As will be understood by one of skill in the art using the teachings disclosed herein, cooling air flow passageway  28  may have a variety of configurations other than as shown. Air flowing through passageway  28  can provide convective cooling. 
     Referring now to  FIGS. 3 and 4 , the oven appliance  10  additionally includes a cooktop  100 . Cooktop  100  may be disposed on the cabinet  12  such that the total volume of cabinet  12  is generally divided between the cooking chamber  14  and cooktop  100 . As shown, cooktop  100  may include a top panel  104 . By way of example, top panel  104  may be constructed of glass, ceramics, enameled steel, and combinations thereof. Heating assemblies  106 , e.g., electric heating elements, may be mounted, for example, below the top panel  104 . While shown with four heating assemblies  106  in the exemplary embodiment of  FIGS. 3 and 4  (as well as  FIG. 1 ), cooktop appliance  100  may include any number of heating assemblies  106  in alternative exemplary embodiments. Heating assemblies  106  can also have various diameters. For example, each heating assembly of heating assemblies  106  can have a different diameter, the same diameter, or any suitable combination thereof. Each heating assembly may include one or more heating elements  108 , such that in some exemplary embodiments, the cooktop  100  includes at least one heating element  108 . Relays (not shown) can selectively activate the associated heating elements  108  as desired. Activation of a heating element  108  can cause electricity to be flowed to that heating element  108 , which in turn can cause the heating element  108  to generate heat. This heat may be transferred through the top panel  104  to utensils positioned on the top panel  104 . The operation of heating elements  108 , such as through operation of relays, may be controlled by a processing device such as controller  50 . 
     Still referring to  FIGS. 1 through 3 , oven appliance  10  may further include a user interface panel  120 , which may be located as shown within convenient reach of a user of the oven appliance  10 . User interface panel  120  is generally a component that allows a user to interact with the oven appliance  10  to, for example, turn various heating elements (such as heating elements  40 ,  42 ,  108 ) on and off, adjust the temperature of the heating elements, set built-in timers, etc. A user interface panel  120  may include a user-interface  122  and a graphical display  124 , which may be separate from or integrated with the user-interface element  122 . The user-interface element  122  may include analog control elements, e.g., knobs or dials, or more preferably the user interface control elements can be all digital control elements, for example, a touchscreen comprising a plurality of elements thereon, as illustrated in  FIGS. 3 and 4 . Various commands for a user to select through such touching may be displayed by touchscreen  122 , and detection of the user selecting a specific command by touching a distinct location on the touchscreen  122  may be detected by the controller  50 , which is in communication with the touchscreen  122 , based on electrical signals from the touchscreen  122 . Graphical display  124  may generally deliver certain information to the user, which may be based on user selections and interaction with the touchscreen  122 , such as whether a particular heating element is activated and/or the level at which the heating element is set. 
     Heating elements  108  can retain heat for some time after deactivation. In some embodiments, one or more hot surface indicator lights  126  can be used to inform a user that the cooktop surface is still relatively hot even after deactivation. In some embodiments one or more indicator lights  126  can be provided on or near the user interface panel  120 , as illustrated in  FIG. 3 . In embodiments where the indicator lights  126  are provided on the user interface panel  120 , the indicator lights  126  may be provided separately from the graphical display  124  or as a part of the graphical display  124 . In some embodiments, an indicator light  126  can be provided proximate to each heating assembly  106  or heating element  108 , as illustrated in  FIG. 4 . In such embodiments, an equal number of indicator lights  126  as heating elements  108  may be provided. Alternatively, other suitable locations on appliance  10  may be utilized. In each of the various embodiments, every heating element  108  corresponds to an indicator light  126 , and in some embodiments, a single indicator light  126  may correspond to multiple heating elements  108 . For example, appliance  10  may include only a single indicator light  126  which may correspond to all heating elements  108 , or appliance  10  may include two or more indicator each of which corresponds to at least one heating element. One such exemplary embodiment may include two indicator lights  126 , e.g., one corresponding to a left side subset of heating elements  108  and the other corresponding to a right side subset of heating elements  108 . 
     Oven appliance  10  may include a controller  50  which generally controls operation of the various components of the oven appliance  10 . Controller  50  may include a memory and microprocessor, such as a general or special purpose microprocessor operable to execute programming instructions or micro-control code associated with a cleaning cycle. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory. The memory may be a separate component from the processor or may be included onboard within the processor. Alternatively, controller  50  may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software. User interface panel  120  and other components of oven appliance  10  may be in communication with controller  50  via one or more signal lines or shared communication busses. 
     Notably, controller  50  may be in communication with the user interface  122 , graphical display  124 , indicator lights  126 , and one or more heating elements. Accordingly, input signals received from the user interface  122  may be provided to and interpreted by the controller  50 , and the controller  50  may output corresponding control signals to the heating elements to operate the heating elements as desired. Additionally, the controller  50  may include or be connected to one or more sensors or switches which transmit sensed values or discrete signals to the controller and the controller may output control signals to the indicator lights  126  to selectively illuminate or deactivate one or more of the indicator lights  126  based on the sensed values. 
     In some embodiments, such as the examples illustrated in  FIGS. 1, 3, and 4 , one or more resistance sensors  140  may be provided, which may be an equal number of resistance sensors  140  as heating elements  108 . The sensors  140  may be positioned proximate the user interface  122 , such as within the user interface panel  120 . Resistance sensor  140  may alternatively be within the user interface panel  120  and distal from the user interface  122 , or in any other suitable location. The resistance sensor(s)  140  may be in communication with the controller  50  and in some embodiments may be integrated with the controller  50 , e.g., on a control board spaced from the heating element(s)  108 , such as within user interface panel  120 . A resistance sensor  140  is in communication with one or more heating elements  108  to measure the resistance of the heating elements  108 . Resistance sensor  140  is also in communication with the indicator lights  126 , directly in some embodiments, and/or via the controller  50  in additional embodiments, to transmit signals to the indicator lights  126  based on the sensed resistance of the heating elements  108 . 
     In certain embodiments, heating elements  108  can be electrical resistance heating elements, for example as illustrated in  FIGS. 3 and 4 . In such embodiments, the resistance value of the electrical resistance heating elements  108  will change with temperature. As such, the use of resistance sensor(s)  140  enables indirect measurement of the temperature of the heating elements  108  which, as may be seen in, e.g.,  FIG. 1 , can be performed remotely by a resistance sensor  140  located away from the heating element  108 . By eliminating the need for direct temperature measurement, there is no sensor mounted to the heating element, i.e., there are no sensors onboard the heating elements. Since there are no sensors onboard the heating elements  108 , additional space between the cooktop  100  and the cooking chamber  14  is available within the cabinet  12 . This additional space can be used to provide several possible advantages. For example, an unobstructed air flow path  28  for convection cooling may be provided, i.e., air flow path  28  can be provided such that there are no sensors in the air flow path  28  between the cooktop  100  and the cooking chamber  14 . As a further example, the oven chamber  14  can be larger in proportion to the overall size of the cabinet  12  as well as or instead of the air flow path  28 . 
     In some embodiments, the controller  50  can be configured to detect the operational status of each heating element  108 , e.g., whether the heating element  108  is on or off. The controller  50  may also, in some embodiments, include a real-time clock or otherwise be configured to measure time. As illustrated, e.g., in  FIG. 5 , in one or more embodiments, a method  200  of operating a cooktop appliance  10  can include the controller configured to determine that a heating element  108  has been deactivated at step  210  and measure the time T OFF  since the heating element  108  was last activated at step  220 . Further, in one or more embodiments, the controller  50  may be configured to perform step  230  of comparing the time since last activation, T OFF , to a threshold time, T, which can be, for example about 120 minutes, about 150 minutes, about 180 minutes, or more, or less so long as the threshold time T is long enough for the heat from heating element  108  to substantially dissipate. Threshold time T may for example, be empirically determined for appliance  10 . It is generally understood that the heat from heating element has substantially dissipated when the temperature of the heating element  108  and/or cooktop  100  is less than about 150° C. In such embodiments, when the time since last activation T OFF  is greater than or equal to threshold time T, it can be determined thereby that the heating element  108  is cool and the controller  50  and/or resistance sensor  140  may be configured to perform step  240  of measuring the resistance of the heating element  108  at that time and step  250  of defining the measured resistance as a cool resistance R C , of the heating element  108 . Further, some embodiments of the controller  50  may be configured to perform step  260  of storing the cool resistance R C  in a computer memory. Cool resistance R C  can also be measured when oven appliance  10  is manufactured or installed, i.e., before initial activation of heating element  108 . Cool resistance R C  can, after being initially determined, remain as a programmed value or be continuously calibrated and updated after activations of heating element(s)  108 . 
     As illustrated for example in  FIG. 6 , a method  300  can include, when a heating element  108  is turned on at step  310 , illuminating associated indicator light  126  at step  312 . In some embodiments, the controller  50  may also be configured to send a signal to the indicator light  126  to activate the indicator light. Additionally or in the alternative, the indicator light  126  may in certain embodiments otherwise be configured to illuminate when the heating element  108  is activated such as by a direct connection between the heating element  108  and the indicator light  126 . The indicator light  126  can also be configured to remain illuminated at step  322  after the heating element  108  is deactivated at step  320  and to remain illuminated until the temperature of cooktop surface  100  reaches a relatively cool temperature of about 150° C. or less, i.e., T OFF  exceeds T. The controller  50  can be configured to determine that the heating element  108  is cool based on the resistance of the heating element. When the heating element  108  is deactivated, the controller and/or resistance sensor  140  are configured to initiate a resistance monitoring step  330  that includes measuring the resistance of the heating element  108  over time, which measurement can be continuous or at selected time intervals. In some embodiments the resistance monitoring step may further include  340  comparing the measured resistance value, R, to the cool resistance value R C  and continuing to measure the resistance of heating element  108  until R equals R C , at which point step  350  of deactivating the corresponding indicator light  126  may be performed. In some embodiments wherein more than one heating element  108  is provided, a plurality of heating elements  108  may be activated at the same time. In such embodiments, the resistance monitoring step may further include monitoring the resistance of a selected one of the plurality of heating elements  108  after all of the heating  108  elements are turned off, and to turn off the indicator light  126  when the resistance of the selected heating element  108  equals the cool resistance value, wherein the selected one of the plurality of heating elements  108  may be the last heating element  108  to be turned off. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.