Even when compression stress is generated because a volume of a thermal insulation layer 2 is expanded due to oxidized by oxygen in the air, occurrence of cracks and fractures of the thermal insulation layer and a heating conductor 3 caused by the cracks are prevented by dispersing the compression stress....http://www.google.ca/patents/US7474590?utm_source=gb-gplus-sharePatent US7474590 - Pressure wave generator and process for manufacturing the same
