Conveyorized microwave heating chamber with dielectric wall structure

Abstract

Apparatus (11, 11a, 11b, 11c) for heating substances (16, 16a, 16b, 16c) with microwave energy has a microwave containment housing (12, 12a) formed at least in part of thick microwave absorbent dielectric material (39, 39a, 39b) such as concrete or ceramic tile among other examples. Such materials are usually obtainable locally thereby avoiding the high costs of prefabricating all metal chamber components at a distant factory and shipping the bulky structure to the installation site. Unproductive absorption of microwave in the dielectric material is minimized, when necessary, by conductive elements (29, 29b, 42a, 42b, 64a, 64b, 67a, 67b) which reflect microwave energy. In the preferred form, such elements include a high strength metal conveyor (21, 21a, 21b, 21c, 21d, 29e, 21f) and means (68, 68a, 72, 73, 74) are provided, when necessary, to counteract underheating which may sometimes occur where substances contact a metal surface in a microwave field. The dielectric housing construction enables structural simplifications in conveyor entrance and exit tunnels (17, 18) and in access doors (53). The construction may include a series of separately energized, electrically isolated heating modules (13c, 13d, 13e, 13f) along the conveyor to increase processing capacity and to enable differing power levels at successive heating stages.