Electric heating – Microwave heating – Cookware
Patent
1992-03-02
1994-05-10
Leung, Philip H.
Electric heating
Microwave heating
Cookware
219759, 99DIG14, 426234, 426243, H05B 680
Patent
active
053109767
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a novel material useful in the microwave heating of foodstuffs.
BACKGROUND TO THE INVENTION
The use of microwave energy to reheat or cook food products for consumption is increasing. Many such food products have a crust. By virtue of its manner of heating, microwave energy does not brown or crispen the crust.
It is well known, for example, from U.S. Pat. No. 4,641,005, that a continuous thin metallic film, generally vapour-deposited aluminum, may be employed to convert a portion of microwave energy incident thereon into thermal energy and that such thermal energy may be employed to effect heating of foodstuffs, particularly for the crispening and browning of outer crust material.
It is also well known that thicker metal films of foil thickness, such as aluminum foil, effectively act to reflect substantially all microwave energy incident thereon, and so act as a shield to prevent microwave energy from passing to the food. Metal film is of foil thickness generally have a thickness of about 0.0001 to about 0.01 inch, typically approximately 0.00035 inch for commercially-available aluminum foil.
There is described in U.S. Pat. No. 4,230,924 a structure which achieves browning of a microwave-cooked foodstuff and comprises a flexible dielectric wrapping sheet having a flexible metallic coating thereon, which may be in the form of aluminum foil. The coating is subdivided into a number of individual metallic islands by criss-crossing non-metallic gaps provided by exposed dielectric strips on the wrapping sheet. The flexible dielectric wrapping sheet is in the form of paperboard. (There is another embodiment disclosed in this reference in which the metallic coating is in the form of a thin film on a polymeric film substrate). In this arrangement, the individual metal foil islands are sized approximately 5/8 inch on a side and the criss-crossing, non-metallic gaps vary from about 0.001 to about 0.0625 inch in width. As described in the patent, the laminate is partially transparent to microwave energy, since microwave energy is permitted to pass through the gaps into a food product wrapped in the laminate to effect dielectric heating. The adjacent metallic islands are said to act as the plates of a capacitor to generate differences in electrical potential therebetween, which results in electrical current flow between the islands through the dielectric substrate. The islands are said to modify the microwave field configuration to achieve an enhance heating of the outer surface of the foodstuff, to effect browning and crispening.
SUMMARY OF INVENTION
It has now surprisingly been found that a novel structure may be provided which comprises a substantially uniform arrangement of small dots of aluminum or other metal of foil thickness (i.e., about 0.0001 to about 0.01 inch) spaced apart a short distance from one another on a suitable dielectric substrate.
The novel structure is useful in the microwave cooking or reheating of foodstuffs for consumption, in that the structure achieves an intensification of the microwave energy field, guiding an enhanced proportion of the microwave energy in the cavity of the microwave oven into the foodstuff, despite including metal of microwave energy-reflecting thickness.
BRIEF DESCRIPTION OF DRAWING
FIG. 1 is a plan view of a microwave intensifier provided in accordance with one embodiment of the invention;
FIG. 2 is a sectional view of the microwave intensifier of FIG. 1 taken along line 2--2 of FIG. 1.
GENERAL DESCRIPTION OF INVENTION AND PREFERRED EMBODIMENT
Accordingly, in one aspect, the present invention provides an article of manufacture suitable for use in the microwave cooking of foodstuffs, which comprises a dielectric substrate and an arrangement of small dots of electroconductive material of microwave-reflecting thickness supported on the dielectric substrate and spaced apart a short distance one from another sufficient to effect guidance of an enhanced proportion of incident microwave energy through the substra
REFERENCES:
patent: 4676857 (1987-06-01), Scharr et al.
patent: 4713512 (1987-12-01), Wild et al.
patent: 4883936 (1989-11-01), Maynard et al.
patent: 4962293 (1990-10-01), Lackey
Beckett Industries Inc.
Leung Philip H.
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