Wave shielding device for microwave oven

Claim 1

In a microwave oven of the type having an internal heating chamber, which chamber has an entrance opening in one face thereof, an irradiating means for supplying microwave energy to the heating chamber, the microwave energy having both a fundamental frequency and higher order harmonics thereof, and a door movably attached to the heating chamber and adapted to cover completely the entrance opening of the heating chamber when the door is in a closed position, a microwave leakage shielding device comprising: the heating chamber having a metallic flange surrounding the entrance opening, the door having first and second juxtaposed choke sealing cavities formed therein and having a common wall therebetween, the common wall including a series of tuning posts and intervening spaces therebetween, the series of tuning posts and spaces having a periodicity based upon a TE mode for obtaining microwave leakage damping effects. the first, outermost choke sealing cavity having a width of about 1/4 of the wavelength of the fundamental frequency of the microwave energy for preventing leakage of the fundamental frequency of the microwave energy from the microwave oven, the second, innermost choke sealing cavity having a width substantially less than 1/4 of the wavelength of the fundamental frequency of the microwave energy for preventing the leakage of the higher order harmonics of the microwave energy from the microwave oven, and the door also having first and second metallic surfaces thereon each of which makes surface-to-surface contact with the metallic flange on the heating chamber when the door is in the closed position to form first and second capacitive seals therebetween to prevent leakage of microwave energy from the microwave oven, the first capacitive seal being at the periphery of the door and the second capacitive seal being disposed inwardly of the second choke sealing cavity, whereby the microwave leakage shielding device exhibits an excellent capability for preventing leakage of microwave energy from the microwave oven because four separate microwave leakage shielding effects are combined and which is convenient to assemble into the microwave oven while maintaining a pleasing appearance for the microwave oven.