1. Technical Field
This invention relates to food heating devices and, more particularly, to a popcorn heating device for keeping popcorn warm after popping.
2. Prior Art
Modern day devices for heating foods and the like often include a rechargeable phase change material. Once charged with heat energy, the phase change material radiates heat energy to keep foods and other objects warm.
For delivery of food and other products, insulated boxes and thermal bags are currently used to keep the food warm while it is transported from one place to another. Typically, these bags and boxes also include a heat reflective material on their inner surfaces. Even though the food is stored in an insulated box or bag, the temperature of the food begins declining once the food is removed from the cooking device. Thermal bags and boxes only serve to reduce the rate at which the food loses heat and do not maintain the temperature of the food.
Phase change materials have been found to be particularly useful for food warming because they utilize their latent heats of fusion for thermal storage. The latent heat of fusion of a phase change material is substantially greater than the sensible heat capacity of the material. Upon melting and freezing, per weight, a phase change material absorbs and releases substantially more energy than a sensible heat storage material which is heated and cooled in the same temperature range.
In contrast to a sensible heat storage material which absorbs and releases heat energy essentially uniformly over a broad range of temperature, a phase change material absorbs and releases a large quantity of energy in the vicinity of its melting/freezing point in a controlled manner. In addition to its latent heat storage capacity, a phase change material also stores and releases sensible heat.
Various food warming devices containing phase change materials have been proposed. However, most of these devices are designed so that the phase change material is charged by heating the device in a convection oven. When heated in this manner, a lengthy period of time is required to charge the phase change material. Further, once these devices have been heated, they continue to lose heat as the phase change material discharges its stored heat energy.
Accordingly, a need remains for a heating device that is portable and that heats the food contained therein and maintains the predetermined heated temperature until the food is consumed and a user selectively turns the heating device off.
USPTO Backgrounds
USPTO Backgrounds