Patent ID: 8431877

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 being angularly adjacent to two other vanes, each vane having a radially inner and a radially outer end, the vanes being attached to each other at their inner ends, each vane being formed from an electrically non-conductive outer jacket, the outer jacket having a predetermined coefficient of thermal expansion, and an inner layer of an electrically conductive material having a predetermined coefficient of thermal expansion that is different from the coefficient of thermal expansion of the outer jacket, the inner layer of electrically conductive material having an elongated edge thereon, each vane having a predetermined thickness dimension, the outer jacket having an overfolded portion that overlies the elongated edge of the inner layer and is adhered to electrically conductive material such that the inner layer and the outer jacket are arranged in a laterally symmetric fashion with the inner layer being substantially completely enclosed within the electrically non-conductive outer jacket, so that thermal expansion effects due to heating are equalized across the thickness of each vane.