GB1437378A - Apparatus for heating by microwave energy - Google Patents

Abstract

1437378 Microwave heating STIFTELSEN INSTITUTET FOR MIKROVAGSTEKNIK VID TEKNISKA HOGSKOLAN I STOCKHOLM 24 May 1974 [29 May 1972] 24983/73 Heading H5H A microwave heater comprises a body 12, made of dielectric material having low loss and a relative dielectric constant # r exceeding that of air, fed with microwaves and forming a leaky waveguide, which body has a constant cross-sectional thickness normal to the surface near which the material to be heated is placed, this thickness being such as to maintain the phase velocity of the microwave energy in the body lower than the velocity of light in air and being no greater than where C is the velocity of light in air and fg is the frequency of the microwave source, in order to prevent propagation of modes higher than the basic mode. In an embodiment in the form of a hot plate for cooking purposes the dielectric body is in the form of a plate backed by a metal layer 13 and can heat a pot 16 resting on its top surface. In another embodiment two similar plates oppose one another and an object to be heated can be pressed between them, Fig. 3, not shown. In yet another embodiment the plate is in the form of an arc fitting over part of the circumference of a rotatable cylinder which when heated passes on the heat to the material over which it is rolled, Fig. 4, not shown. Other embodiments describe cylindrical forms of the dielectric material, fed by waveguides or coaxial cables, used for heating liquids or powders, Figs. 5-8, not shown. In yet a further embodiment, Figs. 9, 10, not shown, the dielectric material is in a channel and forms a closure for the open end of the channel which serves as a waveguide, this configuration being used to heat ribbons or strands of material.