Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2002-09-23
2004-04-20
Leung, Philip H. (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S413000, C219S681000, C219S494000, C126S02100R
Reexamination Certificate
active
06723961
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to the art of cooking appliances and, more particularly, to a method for self-cleaning a convection cooking appliance.
2. Discussion of the Prior Art
In the art of cooking appliances, it has been heretofore proposed to enable an appliance to operate in a self-cleaning mode. For example, in a conventional range having a cooking cavity which can be heated by one or more cooking elements arranged within the cooking cavity to perform at least baking and broiling functions, it is known to operate one or more of the cooking elements to perform a pyrolytic self-cleaning operation in order to cleanse the walls of the cavity from grease and other food soils developed during normal cooking operations. In such a cooking arrangement, the cooking elements used to perform the cleaning process are located entirely within the cooking cavity.
In addition, it is known to provide a catalytic self-cleaning oven. In such an arrangement, the walls of the oven are coated with a catalytic material which provides for self-cleaning of the oven cavity during cooking operations. In performing any self-cleaning function, byproducts, including smoke, gases and other odorous fumes, are inherently produced. A typical oven cavity will be vented to permit the escape of these byproducts to the ambient surroundings. In some cases, a catalytic oxidation unit is provided in the vent to react with the flowing byproducts.
In still other self-cleaning arrangements, a combination of pyrolytic and catalytic cleaning is performed. Regardless of the fact that various self-cleaning systems have been proposed in the art, there still exists a need for an improved self-cleaning system for a cooking appliance which maximizes the elimination of byproducts, while also minimizing the necessary operating time for the self-cleaning mode. Particular concerns are raised in connection with the necessary operating time and byproduct elimination in a self-cleaning convection oven which essentially relies on a heated flow of recirculating air for raising the temperature in an oven cavity. In any event, there exists a particular need for an improved self-cleaning system for a convection cooking appliance, as well as an improved cleaning method for such a cooking appliance.
SUMMARY OF THE INVENTION
The present invention is directed to a self-cleaning sequence for a convection cooking appliance. The sequence utilizes high velocity air to heat an oven cavity and components/ducting of an air circulation passage to self-cleaning (pyrolitic) temperatures. In accordance with the most preferred embodiment of the invention, the self-cleaning sequence includes four stages: a vent catalyst pre-heating stage; a low molecular weight hydrocarbon bum-off stage; a high temperature cleaning stage; and a cool down stage.
In general, during the vent catalyst pre-heating stage, a door of the oven is locked and an oven vent catalyst is initially heated to facilitate conversion of smoke and various hydrocarbons into carbon dioxide and water. A high output heating element, such as a primary oven cavity heating element, is operated at 100% power. A variable speed blower is operated at a low range to direct a flow of heated air at the catalyst. Heating of the catalyst and, correspondingly, the oven cavity, continues until the catalyst reaches a predetermined temperature, e.g. 450-500° F.
In the next stage, the catalyst is energized to 100% as the blower speed is increased to about 70% of the maximum blower air flow rate. In addition, the primary heating element is heated until the temperature of the catalyst is substantially increased, preferably to about 750° F. Once the oven catalyst reaches the predetermined temperature, this temperature is maintained constant for a predetermined period of time, preferably in the order of 20 minutes.
In the third stage, the blower speed is increased to about 90-100% of the maximum blower air flow rate, and the oven cavity temperature is raised while the catalyst temperature is substantially increased, preferably to a minimum temperature of 900° F. At this point, the oven cavity temperature is maintained for a desired minimum time period, such as 60 minutes. In the overall convection arrangement of the preferred embodiment, the temperature of the oven cavity and the overall air circulation assembly is maintained above about 840° F. The actual duration of this high temperature cleaning stage can be adjusted by the operator in order to improve the overall cleaning process.
In the final stage, a cool down sequence is initiated. During this stage, all of the heating elements are turned off, while the blower is maintained activated. After the oven temperature drops below a prescribed amount, the oven door will unlock, signifying a termination of the self-cleaning operation. Additional objects, features and advantages of the present invention will become readily apparent from the following detailed description of a preferred embodiment thereof, when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views.
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Choat Jeffrey T.
Pace Timothy M.
Whipple, Jr. Robert Z.
Diederiks & Whitelaw PLC
Leung Philip H.
Maytag Corporation
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