Patent ID: 8455802

Claim:
A self-supporting field director structure for use in heating an article in a microwave oven, the field director structure comprising: a central support member having a plurality of slots formed therein, the central support member being formed of an electrically non-conductive material, and a plurality of vanes, each vane extending radially outwardly from a central axis through a respective slot in the central support member, each vane being angularly adjacent to two other vanes, each vane having a predetermined thickness dimension, each vane having a radially inner and a radially outer end, the radially inner end of each vane being spaced a predetermined separation distance from the central axis, each vane having a first major surface and a second major surface, and wherein each vane comprises: a substrate formed from an electrically non-conductive material having a predetermined coefficient of thermal expansion, and an electrically conductive wrapper having a predetermined coefficient of thermal expansion that is different from the coefficient of thermal expansion of the substrate, the wrapper wrapping the substrate so that a portion of the first and second major surfaces are covered and the radially inner end of each vane is wrapped by the electrically conductive wrapper, the wrapper and the substrate being arranged in a laterally symmetric fashion so that thermal expansion effects due to heating are equalized across the thickness of each vane.