Patent Description:
Combination steam and convection ovens ("combi-ovens") cook using combinations of convection and steam. In convection cooking, heated air is circulated rapidly through the cooking compartment to break up insulating layers of air around the food, thereby increasing the rate of heat transfer. Steam enhances the rate of heat transfer to the food as a result of the high specific heat of water compared to dry air and can also reduce water loss from the food. Combi-ovens are described, for example, in <CIT> and <CIT> assigned to the assignee of the present invention.

Combi-ovens may have provisions for cleaning by introducing water into the cooking cavity together with a detergent. This water and detergent may be heated and circulated by the oven fan and heater as a high velocity, atomized mist.

Professional kitchens are often called upon to simultaneously prepare a wide variety of dishes each one optimally being cooked for different periods of time, temperatures, and humidity. For this purpose, a multicavity oven has been developed having independent cooking chambers introducing heated air through openings in divider shelves between the chambers. An upper divider shelf may deliver heated air downwardly on the food while a lower divider shelf delivers deliver air upwardly. Air is distributed through the shelves by channels within the shelves communicating with a fan and heating system of the oven. Ovens of this kind are commercially available from Alto-Shaam, Inc. of Menomonee Falls, Wisconsin, under the Vector trademark and subject to multiple pending patent applications including <CIT>; <CIT>; <CIT>; and <CIT>. A further multi-cavity oven is disclosed in <CIT>.

The present inventors have recognized that the atomized water and steam produced in conventional oven cleaning systems may be inadequate for removing stubborn oven residue and clearing air channels in the divider shelves of multicavity ovens. The present invention accordingly introduces a surge cleaning system in which the oven fans are modulated to first allow an accumulation of water in the lower divider shelf and then to rapidly discharge this water in one or more substantially unbroken streams, the streams carrying debris from the shelves and providing a consolidated inertial impact against oven walls that can promote deep cleaning. Counter intuitively, the inventors have recognized that intermittent operation of the fans during cleaning can promote improved cleaning results.

Specifically, the present invention provides a multi-cavity oven having a housing holding a cooking volume surrounded by insulated outer walls and at least one door that may open and close to provide access to the cooking volume. A set of shelves divides the cooking volume into cooking cavities, the shelves having air channels each leading from an air inlet to upwardly or downwardly directed airstream openings into adjacent cavities. At least one fan provides air through the air channels into the air inlets, and a water inlet communicates with a water valve to introduce water into the cooking cavities. A controller controls the oven to provide a first and second cleaning state. In the first state, the fan operates below a predetermined airflow rate to allow water from the water inlet to drain backward into and accumulate in the air channels and in the second state, the fan operates above the predetermined airflow volume to rapidly expel accumulated water from the air channel through the airstream openings in at least one stream.

It is thus one feature of at least one embodiment of the invention to provide improved cleaning over atomized water and air by allowing water accumulation that can provide for high inertial impact against oven surfaces and that can help carry material and debris out of the air channels of the shelves.

The air may enter the rear of the shelf opposite the door so that momentum of the water moving through the air channels before discharge through the airstream openings directs at least one stream toward the door. The door may provide a glass panel.

It is thus a feature of at least one embodiment of the invention to provide improved cleaning of the door allowing better viewing of food during cooking and improved oven aesthetics after cleaning.

The shelves may include a set of airstream openings spaced along two different perpendicular dimensions of the shelves each providing a stream of water.

It is thus a feature of at least one embodiment of the invention to provide for multiple focused streams of water that may have higher velocity.

The oven may further include a set of drains leading from the cavities and wherein the valve controls the water inlet to provide a greater flow of water into the cavity than a flow of water out of the cavity through the drains to allow accumulation of water in the air channels.

It is thus a feature of at least one embodiment of the invention to provide a system that can allow for water accumulation while observing the necessity of draining water after the cleaning process.

The oven may include a heater operating to heat the water circulating in the cavity through action of the fan. It is thus a feature of at least one embodiment of the invention to provide both high inertial and heated water streams for improved cleaning.

In a second embodiment of the invention, the oven may include a steam generator for generating steam for introduction into the cooking volume. In this embodiment the controller may (a) open the water valve to allow water to flow in through the water inlet while operating the circulating fan to circulate water and a detergent material through the cooking volume; (b) allow a draining of detergent and water from the cooking volume; and (c) introduce steam into the cooking volume to dissipate accumulated detergent foam.

It is thus a feature of at least one embodiment of the invention to eliminate residual bits of detergent foam which can remain in the oven cavities, generated by the high degree of air turbulence and yet floating on rather than flowing with discharged water. The inventors have determined that high temperature steam can disrupt the structure of such foam without the need for additional rinse cycles.

The controller may further operate to include a step before step (a) of introducing steam into the cooking volume to soften accumulated grease.

It is thus a feature of at least one embodiment of the invention to make use of steam available in ovens of this kind both for initial and final cleaning steps.

The controller may further operate to provide a rinse cycle after step (b) in which additional water is introduced through the water inlet into the cooking volume and circulated by the fan and then allowed to drain from the cooking volume, and a rinse cycle after step (c) in which additional water is introduced through the water inlet into the cooking volume and circulated by the fan and then allowed to drain from the cooking volume.

It is thus a feature of at least one embodiment of the invention to collapse detergent foam so that it can be successfully rinsed out of the oven with a second rinse cycle thus allowing optimization of rinse water.

In yet another embodiment of the invention, the oven may provide an exhaust conduit associated with each chamber and having an exhaust conduit valve leading between each chamber and air outside of the housing. The controller communicates with the exhaust conduit valves to control the exhaust conduit valves during the cooking mode to independently control exhaust from each chamber according to separate cooking schedules and to control the exhaust conduit valves during a cleaning mode to open the exhaust conduit valves and water inlet valve to allow circulation of cleaning water by the fan through the cavities and at least a portion of the exhaust conduits.

It is thus a feature of at least one embodiment of the invention to provide improved cleaning of exhaust channels used for rapid air exchange in ovens of this kind. The inventors have determined that opening the valves reduces an effective dead space of air trapped in the exhaust channels that prevents proper cleaning.

The exhaust conduit valve may be displaced from a respective chamber by a portion of the exhaust conduit.

It is thus a feature of at least one embodiment of the invention to allow proper cleaning of an exhaust channel when the exhaust conduit valve is positioned away from the cooking chamber for protection against heat and direct contamination.

The portion of the exhaust conduit before the exhaust conduit valve may exit downwardly from the cooking cavity.

It is thus a feature of at least one embodiment of the invention to prevent minor amounts of contamination in the exhaust conduit from breaking off and falling into subsequent food in preparation.

Each exhaust conduit may provide a separate channel from a respective chamber to outside air.

It is thus a feature of at least one embodiment of the invention to prevent intercommunication between the cooking chambers through the exhaust conduits that could provide flavor transfer during different cooking cycles in different cavities where one cavity is in an overpressure state and one cavity is in a relative under pressure state.

The exhaust conduits may exit to outside air at openings separated from each other by a divider wall extending along a direction of airflow from the conduits from the openings and beyond the openings.

It is thus a feature of at least one embodiment of the invention to allow the exhaust conduits to exit at a common location, for example, removed from the oven user, without risking cross-contamination in the atmospheres of the chambers. The divider plate provides increased separation between the exhaust conduits while exposing them to the outside air for diffusion.

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.

Referring now to <FIG>, a multi-zone, combi-oven <NUM> may provide for a housing <NUM> having upstanding insulated left and right outer sidewalls 14a and 14b and an upstanding outer insulated rear wall 14c extending between and joining opposed, generally horizontal insulated outer upper walls 14d and 14e. The walls <NUM> enclose a volume <NUM> opening toward the front and which may be covered by hinged door <NUM> when the door <NUM> is in a closed position as is generally understood in the art. The housing <NUM> may be supported on one or more legs <NUM> extending downwardly from a bottom surface of the bottom wall 14e.

The cooking volume <NUM> may be divided into multiple cooking cavities 20a-d. Although four cooking cavities are shown, the invention contemplates a range from <NUM> to <NUM> cooking cavities <NUM> in vertical, spaced separation. Each of the cooking cavities <NUM> is separated by a shelf 22a-c with shelf 22a separating cavities 20a and 20b, shelf 22b separating cavities 20b and 20c and shelf 22c separating cavities 20c and 20d.

Referring also to <FIG>, each shelf <NUM> may be made up of a separate upper and lower generally rectangular plenum 24a and 24b fitting horizontally in the cooking volume <NUM> with plenum 24a facing an upper cavity <NUM> and plenum 24b facing a lower cavity <NUM>. A single upper plenum 24a forms the bottom of the lowermost cavity 20d and a single lower plenum 24b forms the upper wall of the uppermost cavity 20a.

An outer surface of each plenum <NUM> provides a horizontally extending air distribution plate <NUM> having a set of airstream openings <NUM> distributed over its area to provide for substantially even airflow therethrough. In one embodiment, the airstream openings <NUM> in the air distribution plate <NUM> may provide a series of holes <NUM> joined by slots <NUM> extending in multiple rows from the left to the right side of the cavities <NUM> as described in <CIT> referenced above. Generally, a width of the slots <NUM> will be less than <NUM> inches and preferably less than <NUM> inches to reduce pressure loss in the channel <NUM> that could result from high slot area. The holes <NUM> are much larger than the slot <NUM> and maybe circular and may have a diameter ranging from <NUM> inches to <NUM> inches to provide airstreams that help shepherd the air from the slots <NUM> while also minimizing loss of air pressure. Slot lengths may vary between <NUM> to <NUM> inches and are preferably approximately <NUM> inches. The air distribution plate <NUM> is a thin sheet of metal, for example, stainless steel, with a thickness less than <NUM>/<NUM> inch and typically less than <NUM>/<NUM> inch, such as may be easily formed using laser cutting techniques.

Air enters through sidewalls of each of the plenums 24a and 24b at air inlets 32a and 32b, respectively, from corresponding outlets at the rear of each cavity. These air inlets <NUM> may be as little as <NUM><NUM>/<NUM> inches tall and preferably less than one inch tall. From the air inlets 32a and 32b, the air then passes through a horizontally extending channel <NUM> defined by an inner surface of the air distribution plates <NUM> and inner surface of a focusing wall <NUM> opposite the air distribution plate <NUM> about the channel <NUM>. The focusing wall <NUM> has a maximum separation from the air distribution plate <NUM> at the air inlet <NUM> and then curves inward toward the air distribution plate <NUM> as air conducted in the channel <NUM> escapes through the airstream openings <NUM> and less channel height is needed. This inward sloping of the focusing walls <NUM> for each of the plenums 24a and 24b together provides an additional insulation zone <NUM> between the barrier walls <NUM> of the upper and lower plenums 24a and 24b, respectively, minimizing shelf height but maximizing insulation value. The average separation of the barrier walls <NUM> may be approximately one inch varying from contact between the barrier walls to nearly <NUM> inches in separation. The invention contemplates an average separation of at least one-quarter inch and preferably at least one inch.

A peripheral wall <NUM> of each plenum <NUM> surrounds the air distribution plate <NUM> and the barrier wall <NUM> to corral air within the channel <NUM> in all directions except through the inlets <NUM> and the airstream openings <NUM>. Peripheral wall <NUM> also provides inwardly horizontally extending tabs <NUM> which may support a wire rack <NUM> at a separation of approximately <NUM>/<NUM> inch and at least <NUM>/<NUM> inch above the upper extent of the air distribution plate <NUM> of the upper plenum 24a. In one embodiment the wire rack <NUM> may be supported by more than one inch above the air distribution plate <NUM> and desirably more than <NUM> inches above the air distribution plate either through the use of a special wire rack <NUM> or extender tabs <NUM> (not shown). In this way, a cooking sheet or pan set on top of the shelf <NUM> rests on the wire rack <NUM> and does not block the airstream openings <NUM>. In a preferred embodiment, a separation <NUM> (shown in <FIG> and <FIG>) between the uppermost extent of the airstream openings <NUM> of the air distribution plate <NUM> of the upper plenum 24a and the lowermost extent of the airstream openings <NUM> of the air distribution plate <NUM> of the lower plenum 24b will be less than four inches, preferably less than three inches and desirably less than two inches providing an extremely compact shelf maximizing cavity space and minimizing total height. The cavities <NUM> (shown in <FIG> and <FIG>) will have a nominal height <NUM> between four and nine inches and preferably five inches or more defined by the distance between air distribution plates <NUM> bounding the upper and lower extent of the cavity <NUM>. In one nonlimiting example, each cavity may add a height of about seven inches to the oven so that three cavities may have a height of no more than <NUM> inches or at least no more than <NUM> inches, and four cavities may have a nominal height of <NUM> inches and no more than <NUM> inches.

Generally the shelves <NUM> may be constructed entirely of stainless steel for durability and ease of cleaning, and although the invention contemplates that thin insulating materials may also be incorporated into the shelves <NUM> in some embodiments, the invention contemplates that no nonmetallic shelf construction materials are required. The barrier walls <NUM> may be held within each plenum <NUM> with a "floating mounting" allowing sliding of the barrier walls <NUM> with respect to the other structures of the plenums <NUM>, for example, by creating a sliding fit between these components augmented by a natural flexure of the metal of the barrier walls <NUM> providing a light pressure between the barrier walls <NUM> and the ribs <NUM> and inwardly extending lips of the peripheral walls <NUM>.

Referring now to <FIG> each of the cavities <NUM> may be associated with a temperature sensor <NUM> communicating with a controller <NUM>, for example, being a microcontroller having one or more processor <NUM> executing programs and communicating with an associated memory <NUM>, holding an operating program <NUM> and various recipe schedules <NUM>. The temperature sensors <NUM> may be thermistors, resistive temperature sensors, or the like.

Each cavity <NUM> may also be associated with an airflow system <NUM> comprising a heater system, fan motor, and variable speed motor controller so that the controller <NUM> may independently control the airflow circulating through each cavity <NUM> through a continuous range and may control the temperature of that air through a continuous range of temperatures. The heater system may be, for example, an electric resistance heater such as a "cal" rod controlled by a solid-state relay or may be a heat exchanger of an electrically controllable gas burner system.

Optionally, each cavity <NUM> may have an electrically controllable wash water valve <NUM> communicating with a common water supply <NUM> so that water for cleaning may be introduced into the cavity by a signal to the controllable wash water valve <NUM> from the controller <NUM>. Additional steam control valve <NUM> may be operated to allow water to be introduced to the heating units of the airflow system <NUM> as will be discussed below to allow independent control of moisture according to a cooking schedule. Mechanisms for the introduction of controlled moisture into an oven cavity <NUM> suitable for the present invention are described, for example, in <CIT>; <CIT>; <CIT>; and <CIT> assigned to the assignee of the present application.

The controller <NUM> may also receive a signal from a door switch <NUM> (such as a limit switch or proximity switch) and may provide for input and output to an oven user through a user interface <NUM> such as a touch screen, graphic display, membrane switch or the like such as are well known in the art. A data connector <NUM> may communicate with the controller <NUM> to allow for the readily uploading of cooking schedules <NUM> over the Internet or by transfer from a portable storage device or the like.

One or more of the cavities <NUM> may also include a smoker <NUM>, for example, providing a compartment that may hold woodchips or the like to be heated by an electric element controlled by the controller <NUM> through corresponding solid-state relays. The construction of a smoker <NUM> suitable for the present invention is described, for example, in <CIT>; <CIT>; and <CIT> each assigned to the assignee of the present invention.

Referring now to <FIG>, the airflow system <NUM> of each cavity <NUM> (indicated generally by separating dotted lines) may include a separate fan <NUM> independently controlled by a variable speed motor and motor drive <NUM>. The fan <NUM> may be, for example, a squirrel cage fan and the motor a DC synchronous motor driven by a solid-state motor controller of a type known in the art. The use of separate fans <NUM> permits full segregation of the airflows within each cavity <NUM>. The use of a separate motor and motor drive <NUM> allows independent airspeed control of the air in each cavity <NUM>.

The airflow system <NUM> may also include a heater <NUM> and the air from each fan <NUM> may pass through a heater <NUM> to be received by a bifurcated manifold <NUM> which separates the heated airstream into an upper airstream <NUM> and lower airstream <NUM>. The upper airstream <NUM> passes into the channel <NUM> (shown in <FIG>) of a lower plenum 24b of an upper shelf <NUM> defining an upper wall of the cavity <NUM> and then exits from the channel <NUM> as a set of downwardly directed airstreams 72a from each of the airstream openings <NUM> (shown in <FIG>) distributed over the lower area of the plenum 24b. The lower airstream <NUM> passes into the upper channel <NUM> of upper plenum 24a of a lower shelf <NUM> defining a lower wall of the cavity <NUM> to exit from the channel <NUM> as a set of upwardly directed airstreams 72b from each of the airstream openings <NUM> (shown in <FIG>) distributed over the upper area of the plenum 24a.

The bifurcated manifold <NUM> may be designed to provide substantially greater airflow in the upper airstream <NUM> than the airflow of the lower airstream <NUM>, for example, by constrictions or orientation of the branches of the bifurcated manifold <NUM> with respect to the natural cyclic flow of the fan. In one example, the air may be split so that <NUM> to <NUM> percent of the heated air is allocated to the lower shelf sending air upward, and <NUM> to <NUM> percent of the heated air is allocated to the upper plenum pulling downward as described in <CIT> cited above.

This arrangement of fans, airflow system <NUM> and bifurcated manifold <NUM> is duplicated for each cavity <NUM>. In the uppermost cavity 20a only a single lower plenum 24b is provided at the top of that cavity 20a and in the lowermost cavity 20d only a single upper plenum 24a is provided, each being effectively one half of shelf <NUM>.

Referring now to <FIG>, in one embodiment, the fan <NUM> may be a centrifugal fan having a squirrel cage impeller mounted for rotation about a horizontal axis <NUM> extending from the right to left wall of the oven <NUM> with the fan <NUM> centered with respect to the volume of the cavity <NUM>. A steam generator <NUM>, also positioned rearward from each cavity <NUM> and leftward from the fan <NUM> (for example), provides a water injector <NUM> providing a conduit and nozzle directing a stream of water or water droplets onto a rotating spinner <NUM>. The spinner <NUM> may be mounted for rotation, independent of rotation fan <NUM>, driven by a speed-controlled motor <NUM>, or may make use of motor <NUM> with appropriate linkage.

The water injector <NUM> may disperse freshwater onto the rotating spinner <NUM> to break up the water and emit a fine spray of water that is heated by a helical heater tube of heater <NUM> surrounding the spinner <NUM>. Water to the water injector <NUM> may be controlled by an electronically controlled wash water valve <NUM>. In this way, the convection fan speed-controlled motor <NUM> and the spinner speed-controlled motor <NUM> are independently controlled to provide separate control of a heating of the oven cavity <NUM> and steam generation of the oven cavity <NUM>.

Referring still to <FIG>, air from the fan <NUM> as heated by the heater <NUM> may enter into the cavity <NUM> to heat contained food and then be drawn through a side vent <NUM> into a return duct <NUM> to again pass by the heater <NUM>. The size of the side vent <NUM> is such as to provide a slight constriction producing a low pressure in the return duct which may communicate with a fresh air conduit <NUM>, either directly or optionally controlled by valve <NUM>, providing air inlet from outside of the oven. Valve <NUM> may be controlled by the controller <NUM>.

Likewise, the cavity <NUM> will be at slightly higher pressure because of the size of the side vent <NUM> and may communicate with an exhaust conduit <NUM> controlled by valve <NUM> through controller <NUM> providing an exhaust of air and steam from the cavity <NUM> to the outside air as will be discussed below.

As noted above, wash water can be introduced into the cavity <NUM>, for example, through a spray nozzle in the cavity <NUM> or in the bifurcated manifold <NUM> or both. A system of drains <NUM> allows excess water to be drained into a holding reservoir <NUM> into which a detergent material <NUM> may be placed for cleaning. This reservoir <NUM> may provide water through a pump (not shown) to the wash water valve <NUM> for recycling cleaning water and may provide for a drain <NUM> and freshwater make up valve <NUM> leading to a freshwater supply as is generally understood in the art.

Referring now to <FIG>, the program <NUM> of the controller <NUM> (shown in <FIG>) implements a cleaning sequence beginning at a stage <NUM>, for example, as initiated by the user entering information through interface <NUM> (shown in <FIG>). At this time program <NUM> may communicate to the user that detergent material should be added to the reservoir <NUM> or placed within each of the cavities <NUM> by means of display of the interface <NUM> shown in <FIG>.

Once detergent has been added and the door is closed, as indicated by door switch <NUM> (shown in <FIG>), the heater <NUM> may be activated and steam water valve <NUM> opened to begin the production of steam generation as indicated during stage 122a. At this time, the wash water valves <NUM> are closed and the exhaust conduit valves <NUM> (shown in <FIG>) are opened to encourage cleaning steam to enter and soften material in the conduits <NUM>. The fan motor <NUM> is operated to assist in steam dispersion.

At the next stage 122b, wash water valves <NUM> are opened and steam water valve <NUM> closed while maintaining activation of the heater <NUM> so that heated water is introduced into each cavity <NUM> and circulated by the high-speed air from the fan <NUM>. This process produces a spray of detergent-infused, heated and atomized water coating all cleanable surfaces of the oven interior.

Referring now also to <FIG>, at the next stage 122c, surge cleaning begins and the fan <NUM> is turned off or lowered in speed so that water <NUM> introduced through wash water valves <NUM> and heated by heater <NUM> drains backwards into the upper plenums <NUM> through jet openings <NUM> to substantially fill the air channel <NUM>. In this regard the drains <NUM> may be sized or valved to allow sufficient water accumulation so that at least <NUM>% of the air channel <NUM> is filled and preferably there is a small amount of standing water over the openings <NUM>.

At the next stage <NUM>, the fan <NUM> may be turned on again quickly to high speed producing a sudden pressurized flow <NUM> of air into the channels <NUM> as shown in <FIG>. This ejects multiple continuous streams or slugs <NUM> of water and/or suds from the openings <NUM> which, in contrast to the atomized heated water, provide a scouring flow emptying channels <NUM> of debris and a contiguous mass of water providing high inertial impact to the surfaces of the oven. In this tsunami type flow, softened grease and the like may be removed. The momentum of the water within the air channel <NUM> prior to exiting encourages the cohesive streams of water <NUM> toward the glass <NUM> on the inner surface of the of the door <NUM> providing improved cleaning of this highly visible surface. In one embodiment, the streams of water <NUM> will have a contiguous extent from the openings <NUM> upward by one or more inches without substantial dispersion.

The steps of stages 122c and 122d may have a duration of approximately one minute and may be repeated multiple times, alternating between the accumulation of <FIG> and stage 122c and the rapid expulsion of slugs of water in a surge as shown in <FIG> per stage 122d.

At a next stage 122e, the wash water valve <NUM> and heater <NUM> are turned off and water is allowed to drain. The fan <NUM> is activated to help in this process.

After a suitable draining time, at stage 122f, a rinse is performed in which the wash water valve <NUM> is again activated optionally with the heater <NUM> and the fan <NUM> followed by second drain stage 122e.

At the conclusion of this draining, there may be bits of detergent foam remaining in the cavity <NUM> representing an extremely small amount of persistent material. At a successive foam elimination stage <NUM>, steam is again activated by turning on steam water valves <NUM>, heater <NUM>, and motor <NUM> without wash water through wash water valve <NUM> but with the fan <NUM> on to disperse the steam. The hot steam quickly expands the contained air pockets in any detergent foam structure breaking down the foam. This steam reduction step of stage 122a may be followed by an optional additional rinsing stage 122f and then a drying stage <NUM> where the fan <NUM> and heater <NUM> are activated without water or steam.

Referring now to <FIG>, during the cleaning process, the valves <NUM> of the exhaust conduits <NUM> may be opened as noted to encourage steam and cleaning solution into the proximate portions of the exhaust conduits <NUM> to clean cooking grease and the like from these portions which may have entered during exhaust cycles to be cooled by these conduit walls and condensed thereon. In one embodiment, the proximate portions of the exhaust conduits <NUM> may be angled downward from their connection to the cavities <NUM> so that any material not cleaned from the exhaust conduits <NUM> does not subsequently fall into the cavity <NUM>, for example, during subsequent heating when the material may possibly crack or flake off. After exiting at a downward angle, the exhaust conduits <NUM> may angle upward and be collected together through a chimney <NUM> to exit to the outside air <NUM>. The upward bend of the exhaust conduits <NUM> may include water drains or the like passing to reservoir <NUM> if necessary.

Referring now to <FIG>, as noted multiple exhaust conduits 98a-98c may be collected together within a tubular chimney <NUM> to be conducted to the outside air <NUM>. By collecting the exhaust conduits <NUM> in this manner, heated steam or the like exhausted from the cavities <NUM> may be safely directed away from users of the oven <NUM> to a single location. However it is important that there not be a possible cross-contamination path out of one exhaust conduit <NUM>, for example, from a cavity <NUM> cooking with steam at overpressure, to a second cavity <NUM> that, for example, might be cooling. In such cross-contamination undesirable orders and flavors can be transferred between foods being cooked in different cavities <NUM>. Accordingly a divider plate <NUM> may be provided at the end of the chimney <NUM> separating each of the openings <NUM> of the exhaust conduits <NUM> from each other and extending for a diffusion distance of at least <NUM> inch and desirably at least <NUM> inches along axes <NUM> defining the direction of discharge of air from the exhaust conduits <NUM>. In this diffusion distance <NUM> beyond the upper edge <NUM> of the chimney <NUM>, flow between exhaust conduits <NUM> is blocked in favor of diffusion into the outside air. In this respect the divider plate <NUM> may provide a simple set of divider walls extending radially at equal angles about the center of the chimney <NUM> to its periphery, the number of walls equal in number to the number of cavities <NUM> and positioned between each distal end of an exhaust conduit <NUM>.

As used herein the term fan is meant to include all motor driven devices for moving air including blowers fans and the like. 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.

References to "a controller" and "a processor" or "the microcontroller" and "the processor," can 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.

Claim 1:
A multi-cavity oven (<NUM>) comprising:
a housing (<NUM>) providing a cooking volume (<NUM>) surrounded by insulated outer walls (14a, 14b, 14c) and at least one door (<NUM>) that may open and close to provide access to the cooking volume (<NUM>);
a set of shelves (20a, 20b, 20c) dividing the cooking volume (<NUM>) into cooking cavities (20a, 20b, 20c, 20d), the shelves having air channels (<NUM>) each leading from an air inlet (32a, 32b) to upwardly or downwardly directed airstream openings (<NUM>) and into adjacent cavities (20a. 20b, 20c, 20d);
at least one fan (<NUM>) providing air through the air channels (<NUM>) into the air inlets (32a, 32b);
a water inlet communicating with a water valve (<NUM>) to introduce water into the cooking cavities (20a, 20b, 20c, 20d); characterised in that the oven comprises
a controller (<NUM>) communicating with the fan (<NUM>) and the water valve (<NUM>) to provide a first and second cleaning state wherein in the first state, the fan (<NUM>) operates below a predetermined airflow rate to allow water from the water inlet to drain backward into and accumulate in the air channels (<NUM>) and in a second state the fan (<NUM>) operates above the predetermined airflow volume to rapidly expel accumulated water from the air channel (<NUM>) through the airstream openings (<NUM>) in at least one stream.