Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2002-12-13
2004-05-04
Pelham, Joseph (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S681000, C219S685000, C219S393000, C219S411000, C099S476000
Reexamination Certificate
active
06730881
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 cooking appliance including a variable speed, bi-directional forced airflow system capable of rapidly and effectively performing a convection cooking process.
2. Discussion of the Prior Art
The demand for cooking appliances possessing the ability to both rapidly and effectively cook a wide variety of food items is on the rise. Individuals and businesses who prepare food have long searched for the fastest and most efficient approach to cooking. However, the problem with designing an oven capable of rapidly and effectively cooking a food item is exacerbated by the wide array of consumer tastes. No single cooking process lends itself to efficiently cook the wide variety of food items desired by consumers.
For example, while conventional or radiant heat cooking is suitable to a wide assortment of food types, the overall cooking process, especially baking, can be quite slow. The pre-heat time, combined with the cook time, is longer than most businesses or consumers desire. In addition, the dry, hot environment associated with a convection oven tends to absorb moisture contained within the food item. As a result, the quality of the finished product can be less than desirable.
Microwave ovens, on the other hand, are capable of performing a rapid cooking operation. Unfortunately, the types of food items and cooking processes found to be suitable for microwave cooking are limited. At the present time, microwaves, by themselves, are often not suitable for baking or for preparing food items which require a crunchy texture. For instance, pastries and other doughy food items tend to become soggy after exposure to a microwave cooking process.
Yet another method of rapidly cooking a food item is through forced air convection. Forced air convection allows for cooking at lower temperatures as compared to conventional radiant cooking processes. It has been shown that, by directing forced air streams over a food item, the time required to perform the cooking process is reduced. The forced air streams serve to disrupt a thermal insulation layer about the food item which increases the heat transfer rate between the food item and its surroundings. While effective to a large degree, like microwave cooking, forced air is not suitable to all types of food items or cooking processes. Red meats, for example, do not withstand the effects of convection cooking very well, nor is convection cooking extremely effective for performing a baking process. Furthermore, not every food type or cooking process requires the same forced air flow. A flow rate which is too high or too low can detrimentally alter the overall quality of the finished food product.
Accordingly, a design that incorporates a forced air convection system capable of performing both convection and standard radiant bake cooking can enable a business or individual to cook an appetizing meal in a short time period. The optional incorporation of microwave cooking system can further reduce the cook time and, properly regulated, be used to effectively perform a variety of quality cooking operations. The prior art has many examples of ovens which combine several types of cooking processes. However, most are limited in the types of cooking processes performed. Accordingly, based on at least these reasons, there still exists a need in the art for a cooking appliance capable of rapidly and efficiently cooking food items, while being adaptable to effectively perform a variety of cooking processes for a wide range of foods.
SUMMARY OF THE INVENTION
The present invention is directed to a cooking appliance including an oven cavity having a plurality of zones, an electronic control unit adapted to receive inputs from a user and subsequently control a cooking operation based, at least in part, on the user inputs, and an accelerated cooking, forced air convection system. Specifically, the forced air convection system includes a bi-directional, variable speed fan motor and a central vented cover about which is arranged a halo heating element and a peripheral vent. In one arrangement, an air stream is directed through a distinct region disposed about the vented cover plate which acts to direct an air stream into each of the plurality of oven cavity zones after circulating within the oven cavity.
In a preferred embodiment, the forced air convection system of the present invention is operable in a plurality of modes depending upon a consumer preference. In a first or convection cooking mode, the bi-directional fan motor operates in a first or forward direction at a selectively variable speed. Particularly, forced air is directed through the fan cover into the oven cavity and returned through the peripheral vent. More specifically, forced air is directed into each of the oven cavity zones at a selectively variable flow rate. In a preferred form of the invention, an optimal flow rate is determined by the electronic control unit based upon a selected cooking process, food item or combination thereof.
The cooking appliance of the present invention is further operable in a second or radiant bake mode. In the radiant bake mode, the bi-directional fan motor operates in a second or reverse direction whereby air is drawn in from the oven cavity through the vented cover and returned to the oven cavity through the peripheral vent. When operating in the second mode, a uniform oven temperature is developed inside the oven cavity, preferably without causing the air stream to impinge directly upon the food.
Finally, the cooking appliance of the present invention is operable in a third or self-clean mode. After a consumer selects the self-clean mode, the bi-directional fan is operated in the first direction at a high speed. In addition, a top mounted broil element is activated to further improve the cleanability in the self-clean mode. In operation, the high speed air stream, in combination with the top broil element, delivers thermal energy to all zones of the oven cavity which serves to combust any accumulated soil, thereby reducing soil build-up within the oven cavity.
Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of a preferred embodiment when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views.
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Arntz Timothy J.
Whipple, Jr. Robert Z.
Diederiks & Whitelaw PLC
Maytag Corporation
Pelham Joseph
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