Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2001-10-30
2002-05-14
Pelham, Joseph (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S413000, C219S494000
Reexamination Certificate
active
06388235
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to the art of cooking and, more particularly, to a control system for regulating bake and broil heating elements of a convection cooking appliance in a manner which reduces a required preheat time without increasing a power rating for the appliance.
2. Discussion of the Prior Art
Conventional cooking appliances generally perform cooking operations through radiant heating developed from bake and/or broil elements. Such types of cooking appliances can take various forms, mainly ranges and wall ovens. When utilizing a conventional cooking appliance, the oven is initially controlled to proceed through a preheat cycle in order to reach a desired cooking temperature. Often times, a signal is provided to a user when the preheat cycle is complete in order to indicate when the food to be cooked can be placed in the oven. In some cases, both the bake and broil elements are actuated during the preheat cycle. Even though the broil element may have a higher wattage rating, the operation of this element is still limited for heat distribution, power and other reasons.
Certain known types of cooking appliances incorporate internal fans which operate during certain cooking periods. Therefore, these known cooking appliances can perform convection cooking operations. Convection cooking is actually more prevalent in microwave and other types of ovens which do not require preheating. However, utilizing convection heating in a cooking appliance including bake and broil elements is also known.
Regardless of the existence of these known arrangements, there still exists a need in the art of cooking appliances to reduce the preheat time of an oven having bake and broil elements. However, in addressing this problem, it is considered imperative that the wattage rating not be increased due to set standards on the manufacture of such appliances, as well as accepted building codes.
SUMMARY OF THE INVENTION
The present invention is directed to a rapid preheat system and method for a convection cooking appliance. More specifically, a rapid preheat control system is provided in a cooking appliance having a oven cavity, bake and broil elements for heating the oven cavity, and a fan for developing an air flow current within the oven cavity for convection purposes. The preheat control system regulates the operation of the bake and/or broil elements, as well as the fan, in a manner which minimizes the required time to preheat the oven cavity for a cooking operation, particularly a baking operation, while specifically avoiding the need to increase the overall power rating of the cooking appliance.
Although the invention could be applied to both electric and gas cooking appliances, the most preferred embodiment of the invention takes the form of an electric range. In accordance with the invention, a control algorithm is employed to actuate the broil element a higher percentage of time, as compared to the bake element, during a preheat operation. Actually, in one preferred embodiment, 100% of the heat emanates from the broil element, while the convection fan is operated either continuously or in a pulsating manner to quickly establish an even heat distribution in the oven cavity. In other embodiments, a portion of the preheat can come from the bake element, but simply in a much lower percentage than the broil element. When utilizing the present preheat control system in a known cooking appliance programmed to perform a baking operation, it has be found that the input power could be increased up to more than 50% without resizing the circuit breaker for the appliance.
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 accompanying drawing.
REFERENCES:
patent: 3358122 (1967-12-01), Torrey
patent: 3808402 (1974-04-01), Rea
patent: 4687908 (1987-08-01), Thorne
patent: 5534678 (1996-07-01), Bowles et al.
patent: 5688422 (1997-11-01), Landwehr et al.
patent: 5767488 (1998-06-01), Barger et al.
McFarland James Coty
Sauter Kenneth E.
Diederiks & Whitelaw PLC
Maytag Corporation
Pelham Joseph
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