Patent ID: 8338765

Claim:
A self-supporting field director structure for use in heating an article in a microwave oven, the field director structure comprising: a plurality of vanes, each vane extending radially outwardly from a central axis, each vane having a first major surface and a second major surface, and a radially inner and a radially outer end, each vane being angularly adjacent to two other vanes, each vane having a predetermined thickness dimension, a plurality of bracing members, each bracing member extending between adjacent vanes and being attached to the confronting major surfaces of the vanes to which they are adjacent; 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 and the radially outer end of each vane are covered by the electrically conductive material of the 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.