Abstract: Many frozen foods are now sold on the market and also produced by household refrigerators, and most of these frozen foods are eaten after thawing or after cooking under heat subsequent to thawing. The importance of thawing is thus increasing more and more. This invention provides a heating apparatus of simple construction capable of effectively thawing a frozen food to meet the above demand. The heating apparatus of the present invention is based on the fact that the dielectric loss of a frozen food itself varies as the frozen food is progressively heated. In the heating apparatus, a signal wave is directed toward a frozen food, and the variation of the rate of absorption of the signal wave due to the dielectric loss of the food is measured, so as to automatically control the process of heating for thawing on the basis of the result of measurement.

Abstract: A novel high frequency heating apparatus for detecting the internal temperature of an object contained in a heating chamber and controlling the heating thereof is disclosed, in which the temperature change of the object is picked up as a change of the resistance value of a thermistor. The resistance change is converted into a change of the oscillation frequency of an oscillator and transmitted with the ultrasonic wave as a medium. The power supply for the transmitter circuit is provided in such a manner that the high frequency filled in the heating chamber for heating the object is received by an antenna and rectified by a diode. At the receiving end, this ultrasonic wave is picked up as a temperature signal of the object, and processed by a microcomputer, so that the temperature of the object is detected for heating control.

Abstract: A door seal arrangement for application to a high-frequency heating apparatus comprising a heating chamber having an access opening and an oven door for openably closing the access opening, for preventing leakage of electromagnetic wave energy through the peripheral area of the oven door. In this door seal arrangement, a plurality of reactance elements of a conductive metal material or a dielectric material having a high dielectric constant are disposed between the flat surfaces of the parallel plate transmission line constituted by the oven door and the heating chamber to extend along the access opening of the heating chamber thereby forming a series resonance circuit connected in parallel with the parallel plate transmission line provided by the oven door and the heating chamber.

Abstract: A microwave oven having special form of a microwave energy radiation arrangement.In order to heat uniformly materials to be cooked, the microwave energy radiation arrangement includes a rotatable conductive rod extending into an oven chamber through a hole located substantially in the center of one oven chamber wall, a rotating conductive arm having one end fixed on the rod so as to extend transversely thereto, and a conductive plate having the center thereof coincident with the axis of the rod and arrayed such that the rotating arm is interposed between the one wall and the conductive plate. Openings for radiating microwave energy into the oven chamber are formed at the periphery of the conductive plate.