Combined microwave and thermal drying apparatus
AssigneeMcDonnell Douglas Corporation
InventorsFrederick C. Wear, Garret G. Heil, Howard F. McKinney
Life of this patent
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Abstract
In a microwave drying cavity, a thermal radiator provides infrared radiation that complements the microwave radiation in effecting a more uniform drying of a product within the cavity. The radiator includes a metal plate having apertures of a trifoliate configuration and electrical resistance-type heaters embedded in the plate. The trifoliate apertures permit microwave radiation of universal polarization to pass through the plate, so the radiator may be placed close to the product without shielding the product from the microwave radiation.
Claims27
In combination with a vessel that encloses a chamber, a product that contains moisture and is supported in the chamber, and means for introducing microwave radiation into the chamber remote from the product to elevate the temperature of the moisture in the product so that moisture escapes from the product, the improvement residing in a thermal radiator within the chamber for directing infrared radiation toward product to also elevate the temperature of the product so as to contribute to the escape of moisture therefrom, said radiator comprising a substantially rigid metal plate positioned remote from location at which microwave energy is introduced into the chamber and having a major surface area presented toward the product, but being spaced from the product, the plate having a multitude of apertures configured to permit substantial amounts of microwave radiation of random polarization to pass through the plate and on to the product where the product is supported;
- and heating means attached to the plate for transferring heat into the plate, so as to elevate the temperature of the plate along the major surface area thereof that is prevented toward the product, whereby the plate directs thermal radiation to the product.
A thermal radiator that is essentially transparent to radiation having a multitude of polarizations, said radiator comprising a substantially rigid metal plate having substantial major surface areas and apertures of trifoliate configuration within it, the apertures extending completely through the plate and opening out of the plate at both of its major surface areas, each trifoliate aperture having three slots which radiate from a common center in different directions and being configured to permit microwave radiation of a multitude of polarizations to pass through the plate;
- and heating means attached to the plate for conducting heat into the plate and elevating the temperature of the plate, so that it emits infrared radiation from at least one of its major surface areas.
In combination with a vessel that encloses a chamber containing a region in which a moisture-bearing product is supported and with means for directing microwave energy into the chamber to remove moisture from the product, the improvement comprising a thermal radiator located in the chamber for directing infrared radiation toward the product to contribute to the removal of moisture from the product, said radiator comprising:
- a rigid metal plate having a major surface area presented toward the region of the chamber in which the product is supported, the plate further having apertures which permit substantial amounts of microwave radiation of random polarization to pass through the plate to the region of the chamber where the product is supported, the apertures being of trifoliate configuration and further being arranged in rows;
- and electrical resistance-type heaters embedded in the plate between at least some of the rows of trifoliate apertures for elevating the temperature of the plate, whereby the plate emits thermal radiation.
Dependencies are inferred from the claim text.