MICROWAVE FIELD DIRECTOR STRUCTURE HAVING VANES COVERED WITH A CONDUCTIVE SHEATH

摘要

A reusable self-supporting field director for use in heating an article in a microwave oven is characterized by a plurality of vanes, with each vane extending radially outwardly from a central axis. Each vane is angularly adjacent to two other vanes and is attached to each other at their inner ends. Each vane has a predetermined thickness dimension. Each vane each vane has a substrate formed from an electrically non-conductive material having a predetermined coefficient of thermal expansion, and an electrically conductive sheath having a predetermined coefficient of thermal expansion that is different from the coefficient of thermal expansion of the substrate. The sheath encases the substrate so that a portion of the first and second major surfaces and a portion of the first and second minor surfaces of each vane are covered by an electrically conductive material. The sheath and the substrate are arranged in a laterally symmetric fashion so that thermal expansion effects due to heating are equalized across the thickness of each vane.