Raute Oyj

Jerzy Piotrowski

Jaakko Vilo

Pete Ristola

In a microwave heating apparatus, the fundamental TEmode of the standard waveguide () having a standard rectangular cross-section is fed into an elongated heating cavity () having an enlarged rectangular cross-section in which the shorter side of the standard waveguide is enlarged to a length which can accommodate the desired width of a board () to be heated. A pair of lateral slots () is provided parallel in the opposite enlarged walls () of the heating cavity () to form a track for the board () to travel across the cavity. As the initially longer sidewall () of the standard waveguide is unchanged, the fundamental mode is not affected but the electric field is uniformly distributed along the width of the board () traversing the electric field and the cavity. As a result, wider products can be heated and a more uniform heating pattern can be achieved.

Apparatus for microwave heating of planar products

The invention relates to a microwave waveguide element for matching a standard waveguide input port to an enlarged waveguide output port. In the waveguide element, a plurality of intermediate waveguide segments is cascaded in the propagation direction of the microwave energy to first split the waveguide element into two symmetrical waveguide branches and then combine the branches at the output port. Thus, the width of the waveguide element is gradually enlarged and the input port is matched to the output port. The intermediate waveguide segments are preferably dimensioned such that respective characteristic impedances are approximately matched with each other for the fundamental mode.

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Warsaw, Poland

Jerzy Piotrowski