Electric heating – Microwave heating – Cookware
Reexamination Certificate
2001-09-25
2003-11-18
Van, Quang T. (Department: 3742)
Electric heating
Microwave heating
Cookware
C219S725000
Reexamination Certificate
active
06649891
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a reusable, microwave transmissive, impact-resistant food container adapted for warming food in a microwave oven. The container is characterized by good chemical inertness to cold and hot food, when compared to plastic containers.
2. Background Information
Almost every household and workplace has a microwave oven in which to heat or cook food or liquids. In the typical microwave oven, a magnetron functions to generate microwave energy at a frequency of about 2.5 GHz. This energy is conveyed by a wave-guide to the interior of the oven to irradiate the food placed therein. Because food having some water content tends to absorb microwave energy, this gives rise to internal molecular motion, i.e., thermal energy, which heats the food. Some food products are heated more rapidly than others in a microwave oven; but in general the cooking of food or liquids by microwave energy is much faster than by conventional heating techniques, including infrared radiation. In heating or cooking food in a microwave oven, the food is placed in a receptacle made of a microwave-safe synthetic plastic, glass or other material which is transparent or non-reactive to microwave energy; hence, it is only the food that is heated.
The conventional microwave food heating containers are generally made of a microwave-safe plastic or glass or other microwave transparent material, but these containers have certain inherent disadvantages which have not hitherto been overcome.
Glass containers are highly favored for their transparency and wear resistance. Modern glass containers can be taken from a refrigerator and placed directly into a microwave oven for heating of food. Glass containers are scour resistant, easy to clean, and dishwasher safe. However, they have certain disadvantages. They are easy to break or chip. They are good conductors of heat, so food warmed in a glass container tends to cool rapidly after removal from the microwave oven. Further, because it is difficult to visually determine the temperature of a glass container, the accidental picking up a hot glass container can result in skin bums.
Plastic containers, on the other hand, are much more resistant to breakage than glass. However, they do not have the heft or brilliance of glass, and thus are considered to be less desirable food containers. Further, they tend to impart a “plastic” odor or taste to food items stored in plastic containers for long periods of time. Further, when heating food such as spaghetti sauce, the sauce tends to impregnate the plastic along the top of the spaghetti sauce where the sauce gets hottest during heating. Such rings can never be removed from the plastic and create such an unattractive appearance that the damaged cookware is usually discarded, even though functional. Further yet, plastic dishes are easily scratched or gouged if cleaned with scouring powders or cleaning utensils.
In U.S. Pat. No. 5,986,248, Matsuno et al describe a food container that is generally microwave-transparent, but that comprises one or more non-transmissive insular areas at selected locations of the container so as to improve the uniformity of microwave heating of the contained food. The non-transmissive islands are preferably formed from pieces of aluminum foil or use very thin vapor deposited aluminum films on plastic foil substrates.
It has been known from the bottle art that the advantages of; glass and plastic can be combined by making a single container having two layers, an outer layer of plastic and an inner layer of glass.
For example, U.S. Pat. No. 3,767,496 (Amberg et al) teaches putting a plastic skin on a glass bottle by shrinking a sheet of heat-shrink plastic onto the bottle. Information can be printed on the plastic outer layer, and the plastic helps protect the bottle to some limited degree from chipping. If the contents of the bottle are to be heated, they are removed and poured into a pot or other heating utensil.
U.S. Pat. No. 3,903,339 (Brockway et al) teaches a glass container coated with a plastic containment film for improving the mechanical service strength and shatter resistance of the glass container. The plastic forms a thin skin, only about 2 to 5 thousandths of an inch thick, that commonly escapes notice on a casual inspection of the product. This film protects the glass from scratches which weaken the glass.
U.S. Pat. No. 4,238,041 (Jonsson et al) teaches a plastic coated glass container, made by passing a heated bottle through a fluidized bed of plastic powder. The plastic melts and adheres to the bottle, providing a scratch resistant surface.
As is apparent from the above, bottles are small-mouthed containers traditionally associated with liquids, and particularly cool liquids. Bottles are not suitable for heating, because the small mouth of a bottle provides little room for escape of steam. If one were to attempt to boil liquids in a bottle, the liquids would be violently expelled from the bottle by the rapidly expanding steam bubbles. Further, bottles can not serve as containers for foods, because it would be difficult to remove solid food through the neck of a bottle. Thus, the application of thin films or coating layers of plastic onto bottles to improve impact resistance has had no relevance to the food container art.
U.S. Pat. No. 4,315,573 (Bradley et al) teaches a method of strengthening a single use, disposable glass shipping and delivery container such as a jar for containing foodstuffs. A thin sleeve of plastic, such as a foamed thermoplastic, is applied to the heel of the jar. This layer is indicated as improving both the thermal and physical shock strength of the glass, enabling the glass container to withstand cooling and microwave heating. The container is obviously a disposable container, and is not suitable as a reusable food container.
Paliotta et al, in U.S. 4,848,541, teach a shipping and display container for use with glass, ceramic, or other frangible cookware vessels. Their container may be made from three sheets of a thermoplastic material, one of which is configured as an outer plastic container into which the cookware vessel fits loosely; a second may be an impact protection sheet extending across the mouth of the cookware vessel between the cookware vessel and a lid; and the third of which extends above the lid so as to seal both the cookware vessel and the lid within the shipping container. The three sheets may be welded around a common periphery to form a plastic container that the purchaser has to cut apart and destroy in order to get access to the cookware vessel and lid.
Various attempts have been made to improve microwave cookware. The general strategy has been to provide a thermally insulating layer of air between two containers of similar materials, which are generally either glass or plastic. For example, in U.S. Pat. No. 4,847,459 Desai teaches a bowl-shaped plastic structure for use in microwave ovens. Desai's structure comprises two plastic shells separated by a sealed air chamber. Because the container is made of plastic, it has all the problems associated with plastic, as discussed above.
There is thus a need for a reusable food container which does not suffer any of the disadvantages of either glass or plastic, but offers the advantages of both.
It is an object of the present invention to provide a food container which can have a long useful life, which does not impart a plastic smell or taste to food contained therein even after long periods of time, which is more shatter resistant than glass, which is easily cleaned, and in which food can be heated in a microwave oven even immediately after removal from a refrigerator.
BRIEF SUMMARY OF THE INVENTION
In view of the foregoing disadvantages inherent in known food containers, a food container has been developed that is surprisingly free of the above mentioned disadvantages, and that offers a surprising number of advantages. Such a food container has significant and unexpe
Hauser Ray L.
Kitko Anne M
Kiewit David
Kitko Anne
Van Quang T.
LandOfFree
Microwavable food storage container does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Microwavable food storage container, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microwavable food storage container will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3147381