Abstract: System and method for interrupting the delivery of microwave power to a microwave cavity when a door to the cavity is opened and an interlock switch fails to operate. A switch actuated by movement of the door applies an overload current to an overload protector in the filament circuit of the generator which supplies microwave power to the cavity, thereby interrupting the filament current and shutting down the generator.

Abstract: Microwave drying system and method in which arcing is detected by a sudden drop in electric field strength within the drying chamber. An electric signal corresponding to field strength is provided and, in one disclosed embodiment, is compared with a reference signal which varies with changes in field strength which occur more slowly than changes due to arcing. The two signals are compared, and an output signal is provided if the two signal differ by more than a predetermined amount. This permits the sudden drop which accompanies arcing to be distinguished from more gradual changes in the electric field which occur, for example, as moisture is evaporated from the clothing or other articles being dried.

Abstract: System and method for processing extruded sponge rubber products and the like by simultaneously heating the products with microwave energy and impinging jets of high velocity hot air on the products. In one disclosed embodiment, the extruded sponge rubber parts are passed through a series of impingement rings in a microwave cavity, and each of the rings has a plurality of inwardly facing nozzles for directing jets of air in a radial direction toward the parts. Rollers transport the parts between the rings and can be driven at different speeds to accommodate elongation of the rubber parts as they expand. The microwave power is applied in pulses to provide more uniform heating of the parts, and the time base of the pulses can be changed without having to readjust the on-time of the pulses to maintain the on-time as a given percentage of the time base.

Abstract: Turntable for rotating food being cooked in a microwave oven, including a rotatable platform upon which the food is mounted and a drive motor positioned to the side of the platform. The turntable is made of a material having a low loss tangent at microwave frequencies, and the drive motor is surrounded by a shielding enclosure which reflects microwaves. In one of the disclosed embodiments, the turntable can also be used in conventional ovens.

Abstract: Microwave oven and method in which the microwave energy pattern and the load are moved relative to each other, and the rate of movement is varied to control the amount of heating in different portions of the load. In some embodiments, a rotator causes the microwave energy pattern to be modulated within the oven cavity. The microwave power at different points in the oven cavity is measured with the rotator in different angular positions, and the angular velocity of the rotator is varied so that the rotator spends more time in angular positions where more heating is required. In other embodiments, the load is rotated, and the angular velocity of the load is varied so that the load spends more time in angular positions where additional heating is required.

Abstract: System and method for applying microwave power of substantially constant frequency and variable power level to a work load. A microwave power source having an operating frequency which varies with power level is operated at a substantially constant power level and frequency. Power from the source is applied to a dummy load, and a portion of the power is diverted away from the dummy load to the work load to vary the amount of power applied to the work load without changing the power level or frequency at which the source is operated.

Abstract: Apparatus and method for applying microwave energy to a material in a resonant cavity. The Q of the cavity is reduced to broaden the bandwidth of the system by passing a portion of the microwave energy from the cavity through an iris plate to a dummy load positioned outside the cavity. Tuning stubs are provided to tune the cavity to resonance.

Abstract: Turntable for rotating food being cooked in a microwave oven, including a rotatable platform upon which the food is mounted and a drive motor positioned to the side of the platform. The turntable is made of a material having a low loss tangent at microwave frequencies, and the drive motor is surrounded by a shielding enclosure which reflects microwaves. In one of the disclosed embodiments, the turntable can also be used in conventional ovens.

Abstract: A microwave oven is incorporated in a coffee bean roasting system and includes a rotatable microwave transparent tube or drum positioned within the same and at an angle to the horizontal, through which coffee beans are introduced at an upper end and flow in continuous agitation to the lower end while being subjected to microwave fields within the oven. At the lower end of the oven a separate section is preferably provided for subjecting the coffee beans to selective treatment during the final stages of the roasting process. In one form utilizing a unitary structure the separate section is provided by a conductive septum which separates the oven into sections in which the power level is different. In the last section the power level is adjusted to control the final critical phase of the roasting process. The oven terminates into a cooling and quenching chamber from which the beans are delivered through a microwave trap to a further cooling stage to rapidly reduce their temperature to well below roasting.

Abstract: Microwave oven and method utilizing an oven cavity having two feed ports, one of which supplies microwave energy from the magnetron to the cavity. Energy reflected back into the first port is returned to the cavity through the second port.

Abstract: A system for heating objects by means of microwave energy in an assembly line fashion is disclosed herein and utilizes a specific microwave oven assembly especially suitable for this purpose. The oven assembly is designed to receive within its heating cavity a continuously or intermittent changing section of a conveyance mechanism, even though the cavity may be effectively sealed off from the ambient surroundings during its heating operation. In this manner, objects, even relatively large objects, can be conveyed into the cavity of the oven assembly where they are heated, then automatically conveyed out from the cavity in an assembly line fashion.

Abstract: A method and apparatus is disclosed for controlling the temperature rise of a material placed in a microwave oven in which use is made of a correlation between the power delivered to the load and the residual field within the oven at a position spaced away from the load. By sensing the strength of the electromagnetic field, electronic circuitry is provided for evaluating the time required to achieve a given temperature rise of the material being heated.