Microwave heating apparatus having two cavities and method of using the same

Apparatus for heating an underlying material having multiple layers, said apparatus comprising:

• an enclosure capable of substantially containing microwave energy therein having a top and at lest one sidewall integral with said top and extending downwardly therefrom to a lowermost rim, and an applicator means integral with said sidewall, said enclosure defining a first cavity;
• a source of microwave radiation capable of emitting microwave energy into said enclosure;
• and
• shielding means fixed to said lowermost rim of said enclosure and capable of extending to an underlying surface of the non-metallic material, said shielding means and said applicator means together defining a second cavity, said shielding means capable of substantially containing microwave energy in the second cavity;
• said applicator means for receiving and converting a portion of microwave energy from said source to thermal energy and for transmitting said thermal energy into the second cavity, said applicator means capable of transmitting a portion of microwave energy into the second cavity;
• the first cavity being adjacent the second cavity with said applicator means separating the first and second cavities;
• whereby a discrete layer of the underlying material becomes heated initially primarily from the thermal energy and becomes heated subsequently from both the thermal energy and the microwave energy.

A method of heating an underlying material comprising the steps of:

• directing microwave energy into a first cavity defined in part by a semi-conductive member having overlying and continuous thermal insulating means associated therewith;
• converting some of the microwave energy into thermal energy by the semiconductor member;
• directing the converted thermal energy and the unaltered microwave energy into a second cavity adjacent the first cavity;
• and
• matching the impedance of the second cavity with that of the underlying material.

A method of heating an underlying material having multiple layers comprising the steps of:

• directing microwave energy into a first cavity defined in part by a semiconductor member having overlying and contiguous thermal insulating means associated therewith;
• converting some of the microwave energy into the thermal energy by the semiconductive member;
• directing the converted thermal energy and the unaltered microwave energy into a second cavity adjacent the first cavity;
• and
• matching the impedance of the second cavity with that of a discrete layer of the underlying material whereby the discrete layer becomes heated, substantially to the exclusion of adjacent layers, initially primarily from the thermal energy and becomes heated subsequently from both the thermal energy and the microwave energy.

A method of heating an underlying material comprising the steps of:

• directing microwave energy into a first cavity defined in part by a semiconductive member having overlying and contiguous thermal insulating means associated therewith;
• converting part of the microwave energy into thermal energy by the semiconductive member;
• directing the thermal energy into a second cavity adjacent the first cavity;
• focusing part of the microwave energy onto the underlying material;
• and
• matching the impedance of the second cavity with that of a discrete layer of the underlying material.