Abstract:
A combination oven for cooking with heat and steam provides a boiler system for creating steam and includes a smoker appliance for generating smoke flavor during the cooking process. An oven controller detecting the use of the smoke appliance institutes a flushing and filling of the boiler after such use to reduce the transfer of smoke flavors to food that is subsequently cooked in the oven.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to ovens, and in particular to ovens, such as combination ovens, that may provide cooking with steam derived from a boiler unit. 
     Combination ovens provide the ability to cook food using a combination of techniques, typically including both convection and steam. As is understood in the art, convection cooking may employ a fan near the oven heater that circulates heated air throughout the cooking cavity. Steam cooking introduces steam into the cooking cavity, for example, by employing a jet of water to spray water on a convection fan and/or heater (in a “boiler-less” design) such as is described in U.S. Pat. No. 6,188,045 assigned to the assignee of the present invention and hereby incorporated by reference. 
     An alternative technique for steam cooking employs a boiler providing a boiler chamber separated from the cooking cavity through a port that may communicate steam from the boiler chamber into the cooking cavity. The boiler holds a volume of water and a separate heater that heats the volume of water to the boiling point under the control of the oven control system. Boiler designs are described, for example, in U.S. Pat. No. 7,755,005 assigned to the assignee of the present invention and also hereby incorporated by reference. 
     Combination ovens are versatile and normally used to prepare a range of different foods. in order to prevent flavor transfer between earlier and later foods cooked in the combination oven, the oven may provide for a cleaning cycle in which the interior is cleaned with water, steam, and/or other cleaning materials in between different cooking sessions. A built in spray hose may be provided for the purpose of keeping the oven interior clean and/or an internal set of spray nozzles may be activated by the user as part of a cleaning cycle. 
     in order to further increase the versatility of such combination ovens, a smoker accessory may be provided. for example, comprising a tray that may hold woodchips and heat them with a contained electrical resistance heater. Combination ovens providing smoking capability are described in U.S. Pat. Nos. 7,317,173 and 7,157,668 both assigned to the assignee of the present invention and incorporated by reference. 
     A cleaning cycle is typically employed in between cooking cycles of the combination oven including cooking cycles employing a smoking process to reduce the transfer of flavors to subsequently cooked foods. 
     SUMMARY OF THE INVENTION 
     The present inventors have determined that significant smoke flavor may be absorbed within the water of a boiler used in a combination oven, making conventional cleaning of  t he oven interior insufficient to ensure extremely low transfer of smoke flavors between foods. This absorption appears to be the result of absorption into the water of the boiler which is then released in a subsequent steam cycle. Accordingly, the present invention provides an automatic boiler flush cycle before a subsequent cooking cycle when it has been determined that the smoking accessory has previously been used. 
     Specifically, one embodiment the present invention provides a combination oven including an insulated housing including a door closing over a cooking cavity and a cooking cavity heater communicating with the cooking cavity to heat the cooking cavity. A boiler chamber defines a volume for holding water and provides a port communicating between the volume and the cooking cavity and holds a boiler heater positioned to heat water in the volume of the boiler chamber. The boiler chamber communicates with an electronically actuable water valve communicating between a water source and the boiler chamber to provide water thereto and an electronically actuable drain valve communicating between the boiler chamber and a drain. The oven further includes a smoker appliance electronically controllable to introduce a vaporizable smoke material into the cooking cavity. An electronic computer communicates with the water valve, drain valve, and smoker appliance and executes a program stored in memory to activate the smoker appliance during a cooking cycle, and further, based on activation of the smoker appliance, to activate the water valve and drain valve after the cooking cycle to flush and refill the boiler chamber. 
     It is thus a feature of at least one embodiment of the invention to prevent the transfer of smoke flavor to subsequent foods prepared in a combination oven having a boiler. Whereas it might be expected that very little smoke would pass into the boiler unit because of its small port that is typically discharging steam, the present inventors have determined that the capacity of the boiler water to absorbed smoke particularly when the boiler is not used and to later release that smoke flavor when the steamer is used, provides a path of transferring smoke between cooked foods. A forced flushing of this water breaks this path. 
     The electronic computer may further activate the water valve and drain valve to flush and refill the boiler chamber based on an event other than activation of the smoker appliance such as elapsed time since the last flushing and refilling of the boiler chamber or a number of cooking cycles since the last flushing and refilling of the boiler chamber. 
     It is thus a feature of at least one embodiment of the invention to provide a flush cycle for the removal of smoke flavor in distinction from a flush cycle used to prevent the buildup of lime on the boiler walls. 
     The flushing and refilling of the boiler chamber may first substantially fully drain the boiler chamber and then refill the boiler chamber. 
     It is thus a feature of at least one embodiment of the invention to provide for a flushing process distinct from normal water makeup during the boiler operation in which complete water exchange is provided. 
     The smoker appliance may be a container having a resistance element for heating the contents of the container with electrical current wherein the electrical current is controlled by the electronic computer. 
     It is thus a feature of at least one embodiment of the invention to provide a smoker appliance whose operation may automatically be detected by the oven controller for the purpose of automatic boiler flushing 
     The cooking cavity may be sealed against airflow into and out of the cavity except through a pressure relief vent. 
     It is thus a feature of at least one embodiment of the invention to provide decreased flavor transfer in closed system ovens. 
     The cooking cavity may further include an internal sprayer receiving a source of water for spraying inside of the cooking cavity for cleaning the cooking cavity. 
     It is thus a feature of at least one embodiment of the invention to provide a flavor transfer prevention mechanism extending beyond normal cleaning of the cooking cavity. 
     The boiler chamber may include baffle plates providing a serpentine path for water vapor out of the boiler chamber. 
     It is thus a feature of at least one embodiment of the invention to maintain a water charge in the boiler even when the boiler is not used to prevent flavor accumulation on the high surface area interior of the boiler chamber, shielding that surface with the water charge which may be then drained according to the present invention. 
     The boiler chamber provides a single port communicating with the cooking cavity. 
     It is thus a feature of at least one embodiment of the invention to address unexpected flavor accumulation within the closed boiler chamber. 
     These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a combination oven showing the cooking cavity and a smoker tray prior to installation on a smoker heating element at a back wall of the cooking cavity and showing a port from the cooking cavity to a boiler chamber; 
         FIG. 2  is a simplified diagram of a cleaning system for the cooking cavity such as may operate in tandem with a boiler flushing cycle of the present invention; 
         FIG. 3  is a perspective view of the boiler chamber attached to the side of the cooking cavity; 
         FIG. 4  is a block diagram of the principal components of the boiler chamber of  FIG. 2  as controlled by an electronic oven controller; and 
         FIG. 5  is a flowchart of a program executed by the controller  FIG. 3  for implementation of an additional boiler flush cycle after a cooking cycle that uses smoke. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , combination oven  10 , according to one embodiment of the present invention, may provide a housing  12  defining a cooking cavity  14  within the housing  12 . Sidewalls of the cooking cavity  14  may provide for rack supports  11  holding conventional cooking racks for supporting pans or trays of food. 
     The cooking cavity  14  may be accessed through a door  16  connected by a hinge at one vertical side of the cooking cavity  14 . The door  16  may close over the cooking cavity  14  during the cooking operation as held by a latch assembly  15  (visible on the door  16  only). In the closed position, the door  16  may substantially seal against the cooking cavity  14  by compressing a gasket  17  surrounding an opening of the cooking cavity  14  in the housing  12 . 
     At one side of the cooking cavity  14 , the housing  12  may expose a control panel  23  accessible by a user standing at a front of the oven  10 . The control panel  23  may present conventional electronic controls such as switches, buttons, a touchscreen or the like that may receive oven control data from the user as will be described below. 
     Referring now also to  FIG. 2 , a motor-driven convection fan  18  is typically positioned within the housing  12  in communication with the cooking cavity  14  to direct a stream of air across a heater element  20  into the cooking cavity  14 . The heater element  20  may surround the convection fan  18  and may be an electric resistance element or a heat exchanger tube receiving heat from a gas flame or the like. 
     A bottom wall  31  of the cooking cavity  14  may provide a drainpipe  25  extending downwardly from the bottom wall  31  to a water trap  30  positioned beneath the bottom wall  31 . The drainpipe  25  may extend vertically (as shown) or may extend horizontally for a short distance before or after it is received within the water trap  30 . 
     In either case, the drainpipe  25  allows steam and water vapor to enter the water trap  30  from the otherwise sealed cooking cavity  14 , the water trap  30  providing a generally enclosed box whose upstanding sidewalls retain a pool of water having a water level  36 . The lower end of the drainpipe  28  passes downward through the water level  36  stopping above its bottom wall  33 . An exit port  38  to the side of the drainpipe  28  provides a passageway out of the water trap  30  from a point above the water level  36 . Generally, therefore, the water trap  30  seals the cooking cavity  14  from the free flow of air into or out of the cooking cavity  14  unless a pressure difference exists sufficient to displace the water within the drainpipe  25  so as to allow gases to bubble through water to pass between the drainpipe  24  and exit port  38 . In this respect, the water trap  30  provides an excess pressure relief valve. 
     A boiler  22 , as will be described below, may be located to the side of the cooking cavity  14 , typically opposite the convection fan  18 . Generally the boiler  22  provides steam  24  into the cooking cavity  14  through a steam port  26  positioned near the top of the boiler  22 . 
     Ovens of this type are commercially available from Alto-Shaam Inc. of Menomonee Falls, Wisc. and are described generally in U.S. Pat. No. 6,188,045 “Combination Oven with Three Stage Water Atomizer”, and the above-referenced patent is hereby incorporated by reference. 
     Referring now to  FIGS. 2 and 3 , a lower portion of the boiler  22  may admit electrical heaters  40  to heat the water within the boiler  22  to boiling point to generate steam. Inwardly extending baffles  42  on the opposed inner walls of the boiler  22  are positioned to prevent steam bubbles generated at the heaters  40  from carrying water out of the port  26  while nevertheless allowing steam  24  to pass upward and out of that port  26 . The outer surfaces of the boiler  22  and the cooking cavity  14  are covered with an insulating material  44  such as fiberglass to minimize heat loss from these elements out of the housing  12 . 
     Referring now to  FIG. 4 , an electric water valve  46  may communicate with a source of water  48 , for example, filters attached to a water main or the like, so that the electric water valve  46  may control water flow into the boiler  22  through an entrance pipe  50  positioned near the top of the boiler chamber  22 . The entrance pipe  50  may be positioned so as to not discharge water through the port  26  (when the first electric water valve  46  is open) but nevertheless to permit water to spray down the inside of the boiler  22  above the normal level of water within the boiler  22 . A second electric water valve  52  may communicate with an exit pipe  54  positioned at the bottom of the boiler  22  to conduct water (when the second electric water valve  52  is open) from the boiler  22  to a drainpipe  56  that may lead to a building water drain or the like. 
     An upper and lower water sensor  58  and  60  may extend through one wall of the boiler  22  into the volume of the boiler  22  to detect the presence of water at first and second vertically displaced locations about a desired water level and hence to allow determination of a water height  62  within the boiler chamber to above, below, or between the first and second water sensors  58  and  60 . 
     Referring momentarily also to  FIG. 2 , each of valve  46  and  52 , heaters  40 , and water sensors  58  and  60  may be in electrical communication with a controller  64  that also provides electrical connections to other controllable elements of the oven  10 , for example, including a motor  65  driving the fan  18 , the heater elements  20  and the motor  65 . The controller  64  may provide for an electronic computer  70  and an electronic memory  72  holding within it a stored program  74  whose operation will be described below allowing it to control these various electrical components. 
     The controller  64  may provide electrical communication with a heating element  76  being part of a smoker appliance  78  including a tray  80  fitting over the heating element holding woodchips  82  or the like therein. Operation of the heating element  76  under control of the controller  64  heats the woodchips  82  until they begin to smoke to impart a smoky flavor to the food in the cooking cavity  14 . In addition, the controller  64  may receive electrical signals from one or more temperature sensors  77  positioned in the cooking cavity  14 . 
     During operation of the oven  10 , the controller  64  receives data input from a user through the control panel  23 . Such data may include, for example, an input  75  indicating a desire to use a smoking process during a cooking cycle. Other inputs may include cooking temperatures, the use of steam, the use of convection, the identification of recipes associated with particular combinations of cooking conditions and cooking schedules. According to methods well understood in the art, the controller  64  then provides electrical signals to equipment of the oven  10  during a cooking cycle according to these user inputs and the oven sensors. As is generally understood in the art, a cooking cycle normally consists of one session of heating the cooking cavity  14  up to a cooking temperature for cooking food and ultimately cooling the cooking cavity  14  after cooking for removal of the food therefrom. 
     Referring now to  FIG. 5 , in this control process, the program  74  executed by the controller  64  may generally check for user input at decision block  81  indicating a desire to operate the oven  10  to cook a particular food and the conditions for the oven operation. As noted, this input may provide direct control of the oven (for example setting a temperature, the use of steam, the use of the convection fan  18 , and/or the use of the smoker appliance  78  or the like) or maybe a selection of a pre-programmed cycle selecting among these different features or a recipe which denotes a particular set of operating conditions. 
     At process block  83 , the particular cooking cycle may be implemented, for example, through feedback control of the heater elements  20  (shown in  FIG. 2 ) based on readings of the temperature sensors  77 . During this cooking cycle, steam and/or convection fan operation may be employed and cooking timers implemented in the program to control the timing of these operations during the cooking cycle. 
     When steam is desired as part of the cooking cycle of process block  83 , the heaters  40  may be activated and the water level monitored by means of sensors  58  and  60  to activate water valve  46  to make up water into the boiler  22  when sensor  60  indicates that the water level has dropped below the height of sensor  60 . The water continues to be added until sensing occurs at higher water sensor  58 . Steam  24  is expelled from the boiler  22  by the inherent expansion of water when it passes from the liquid to the gaseous state. 
     At the conclusion of the cooking cycle, as determined by this decision block  84 , the program may proceed to decision block  86  to determine whether there has been smoke usage during the cooking cycle. This may be readily determined by a flag set by the controller  64  when the heating element  76  is activated during a cooking cycle. If smoke has been employed, then at process block  98 , a cleaning cycle may be implemented followed by a filling and flushing of the boiler  22 . 
     Referring momentarily to  FIG. 2 , in one embodiment, the cleaning cycle may instruct the user to place cleaning materials into the water trap  30  which serves as a reservoir for cleaning liquid. Liquid in the water trap  30  is then recycled by a pump  88  to a sprayer head  91  positioned at the top of the cooking cavity  14  which sprays the cleaning solution about the cooking cavity  14  for a predetermined period of time as determined by the controller  64 . 
     Referring to  FIG. 4  during the flush and fill cycle, valve  52  is fully opened for a period of time sufficient to hilly drain the boiler  22  and then the valve  52  is closed and valve  46  is opened until the boiler cavity is again filled as indicated by a sensing of sensor  58  and  60 . 
     This process of draining and then refilling the boiler cavity is then repeated as indicated by process block  92 . 
     If at decision block  86  a smoke cycle was not employed (or if the processes of process blocks  90  and  92  have been completed after the smoke cycle) at decision block  94 , the program determines whether a regular flushing of the boiler  22  should be performed such as is intended to prevent lime build up on the internal surfaces of the boiler  22  caused by inherent concentration of impurities with boiling away of water. This determination normally looks at length of time since the last flushing or a number of cooking cycles since the last flushing. If that limit has been exceeded, program  74  proceeds at process block  92  for single flushing and filling. Otherwise the program proceeds back to loop at decision block  81 . 
     Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “front”, “back”, “rear”, “bottom” and “side”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. 
     When introducing elements or features of the present disclosure and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. ft is also to be understood that additional or alternative steps may be employed. 
     References to “a controller” and “a processor” should be understood to include one or more microprocessors that can communicate in a stand-alone and/or a distributed environment(s), and can thus be configured to communicate via wired or wireless communications with other processors, where such one or more processor can be configured to operate on one or more processor-controlled devices that can be similar or different devices. Furthermore, references to memory, unless otherwise specified, can include one or more processor-readable and accessible memory elements and/or components that can be internal to the processor-controlled device, external to the processor-controlled device, and can be accessed via a wired or wireless network. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein and the claims should be understood to include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims, All of the publications described herein, including patents and non-patent publications, are hereby incorporated herein by reference in their entireties.