Electric heating – Heating devices – With power supply and voltage or current regulation or...
Reexamination Certificate
2001-02-15
2003-05-27
Paschall, Mark (Department: 3742)
Electric heating
Heating devices
With power supply and voltage or current regulation or...
C219S218000, C219S413000, C219S492000, C099S333000, C099S468000
Reexamination Certificate
active
06570138
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to warming chambers, and in particular, relates to a method and apparatus for anticipating and correcting for temperature fluctuations due to, for example, opening the door of the chamber.
2. Description of the Related Art
In order to enable restaurants and other food establishments to provide fresh food in bulk, it is necessary to precook the food items and subsequently place them in a warming chamber for preservation before being served. Conventional warming chambers are in widespread use and include an enclosed cavity having a heating element that is operable to direct heat into the chamber. The heating element receives signals from control circuitry operating in conjunction with a temperature sensor, such as a thermostat, to maintain the temperature of the cavity at a desired level. The warming chamber includes a door that is placed at the front end of the warming cavity and that may be opened and closed to provide access to the food products within the chamber. Many such warming chambers include humidity control to maintain the moisture content within the cavity in relation to the equilibrium water activity of the food product, and to further achieve the desired final characteristics of the food product.
Most such warming chambers contain racks within the cavity that support the food products to be heated. However, when the door is opened to either remove or insert the products into the cavity, heated air escapes into the ambient environment and is typically replaced by the cool ambient air. The actual temperature of the chamber is typically measured by a thermostat, which is located toward the back of the chamber so as to avoid being damaged by the products held on these racks or the racks themselves. As a result of the thermostat placement, there is considerable delay before the thermostat senses the heat loss within the warming chamber. The resulting delay in actuating the heating element produces a rapid cooling within the chamber, even after the door is closed, which adversely affects the quality of the food products that are stored therein.
What is therefore needed is a method and apparatus for anticipating and correcting for rapid heat loss in advance that would otherwise occur due to opening the door of a warming chamber.
BRIEF SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, a method for anticipating heat loss in a warming cavity having 1) a door that is disposed at an open end of the cavity and that is movable from a closed position, thereby enclosing the cavity, to an open position, thereby exposing the open end of the cavity, 2) at least one heating element operable to supply heat to the warming cavity so as to maintain the cavity substantially at a set temperature, and 3) a temperature sensor disposed within the cavity at a location remote from the open end, wherein the temperature sensor is operable to measure an actual temperature within the cavity. The method includes automatically determining that the door is open prior to the temperature sensor detecting a drop in the sensed temperature within the cavity, and activating the at least one heating element to heat the cavity towards a target temperature greater than the set temperature.
This and other aspects of the invention are not intended to define the scope of the invention for which purpose claims are provided. In the following description, reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration, and not limitation, a preferred embodiment of the invention. Such embodiment does not define the scope of the invention and reference must be made therefore to the claims for this purpose.
REFERENCES:
patent: 4404462 (1983-09-01), Murray
patent: 4614860 (1986-09-01), Kativois
patent: 5025132 (1991-06-01), Fortmann et al.
patent: 5715745 (1998-02-01), Blanton, Jr. et al.
patent: 5771789 (1998-06-01), Davis
Hansen William J.
Lemcke Michael
Redanz David J.
Alto-Shaam, Inc.
Paschall Mark
Quarles & Brady LLP
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