General Electric Company

James E Staats

Louis H Fitzmayer

Matthew S Miller

An excitation system structurally compatible with a low profile streamlined microwave oven appliance configuration, comprising a generally planar antenna member disposed between the bottom wall and a support shelf centered laterally in the oven cavity and extending over a substantial portion of the bottom wall. An open peripheral region is defined between the front, back, side and bottom oven cavity walls and the peripheral edge of the antenna member. A plurality of radiating apertures are formed in the antenna member and arranged in a triangular fashion such that straight lines connecting the centers of any three closely adjacent apertures intersect to define an equilateral triangle. Microwave energy is coupled from the magnetron to the center point of the antenna member, whereby microwave energy radiates from the apertures in the antenna member to heat items placed on a support shelf from below and energy propagates between the antenna member and the bottom cavity wall to the periphery of the antenna member from which it is radiated through the peripheral region into the interior of the cavity and reflected by the front, back, side and top cavity walls to the heat items on support shelf from above.

Triangular antenna array for microwave oven

An improved excitation system for a microwave oven employing a circular rotating disk antenna configured to radiate peripherally from its outermost edge to provide backgound radiation in the oven cavity. Primary microwave energy radiation is emitted from a pair of transverse radiating slots formed in the disk antenna. A first slot is positioned radially outwardly relative to the second slot. The first slot alternately functions as a relatively strongly coupled series and shunt radiating slot and the second slot concurrently alternately functions as a moderately coupled shunt and series slot with each quarter revolution of the disk antenna. Both slots are louvered for improved coupling to the load being heated in the cavity.

Rotating slot antenna arrangement for microwave oven

A microwave oven door seal arrangement for inhibiting microwave energy leakage employs an energy splitting and phase shifting device disposed proximate the door gap formed between the access opening to the oven cavity and the oven door. The energy splitting and phase shifting device initially splits the energy attempting to escape through the door gap between two intersecting transmission paths. An inner intersection is provided near the inner edge of the gap relatively near the cavity, at which point the energy splits between the two paths. An outer intersection is provided near the outer edge of the door gap relatively remote from the cavity, at which point the energy propagating along the two paths recombines. The paths differ in effective electrical length between these intersections by an odd integral multiple of one-half the wavelength of the energy resulting in a half wavelength phase difference at the point of recombination between the energy from one path and that from the other. Consequently, upon recombination at the outer intersection, the energy from one path substantially cancels the energy from the other, effectively inhibiting energy leakage beyond the region of the door gap.

Microwave oven door seal

A microwave oven having an energy distribution system which produces efficient and uniform heating by utilizing a plurality of slotted feed apertures through which energy enters the top and bottom walls of the cooking chamber over a large area. A support shelf is provided for carrying an object to be heated and a rectangular waveguide is located immediately below the shelf which includes a first set of slots in its top wall to heat by use of near field effects and a second set of slots in its side walls which radiate energy toward reflecting surfaces in the bottom wall for further reflection upwardly into the chamber. A further set of feed apertures are located to pass energy into the chamber through the top wall thereof.

Microwave oven with novel energy distribution arrangement

Apparatus and methods for determining the progress of a food load cooked within a microwave oven responsive to changes in dielectric or electrical load characteristics of the food load as it is heated. A particularly sensitive indication is provided by placing the food load between a microwave feed point and an RF voltage probe.

Microwave oven cooking progress indicator

A microwave cooking appliance having bypass waveguides oriented vertically within the cooking cavity to more evenly distribute microwave energy. The waveguides are supported from the sidewalls of the cavity and are provided with slots for supporting a food holding shelf. Microwave energy is introduced into the cavity through a feed aperture in the top wall and an energy directing plate is arranged opposite the opening to direct microwave energy toward the bypass waveguides.

Microwave oven with improved energy distribution

An electromagnetic wave energy seal arrangement for a microwave oven which incorporates juxtaposed conductive surfaces spaced apart by a gap which circumscribes the perimeter of an access opening to the oven cooking cavity. One of the conductive surfaces is located on the oven door, overlies a recessed channel in the door, and is provided with slots to inhibit longitudinal currents. The slots are configured to have a first average width near the slot entrance and a second larger average width adjacent the slot terminus to thereby better tailor the bandwidth of the slots for optimum operation to the specific microwave energy characteristics of the oven.

Slot configuration for choke seal

A pair of phase shift devices is provided for sealing a microwave oven against the leakage of microwave energy. Each phase shift device is in the form of a conductive channel member having sides of unequal width. The narrower channel side is positioned parallel to and slightly spaced from an inner surface of the door to define a capacitive gap therebetween. The wider channel side extends perpendicularly outwardly from one of the cavity walls and is effectively electrically connected thereto at the microwave frequency. The devices are particularly adapted to be used in combination with a metal mesh gasket seal and, when so used, not only serve as a backup for the metal mesh gasket but also reduce the likelihood of gasket failure. The nature of the phase shift device permits it to be easily retrofitted to a microwave oven already in service.

Phase shift device for microwave oven door seal

A counter-top microwave oven comprises an upstanding box-like metal wall structure defining a heating cavity, a microwave generator including a voltage quadrupler power supply, and transmission means including a probe antenna for radiating the microwaves into the heating cavity, the cavity being so dimensioned and the antenna being so positioned as to excite in said cavity preferred electromagnetic field modes for establishing preferred field patterns to achieve uniform heating of a variety of foods. The power supply includes capacitive and inductive means, having values designed to optimize the power factor, and switching means for selectively switching between low and high power modes. The heating cavity is dimensioned to produce two complementary modes of which establish an undistorted field pattern providing uniform heating over a distance greater than a wavelength of the source microwave energy, tuning means being provided to tune undesired modes off resonance.

Magnetron power supply and control circuit

A magnetron adapted for operation with an ungrounded power supply, has mounted thereon and tightly coupled thereto an external cavity resonator having coaxial first and second openings in opposite walls thereof. The magnetron has coaxial output connection members including a hollow outer connection member communicating with the interior of the cavity resonator through the first opening, and an internal connection member extending entirely through and beyond the resonator via the first and second openings. The cavity resonator is galvanically insulated from the magnetron by teflon insulation which provides capacitive coupling therebetween. The cavity is coupled to a load which may be grounded. The cavity resonator is formed from a closed section of wave guide, two embodiments of which are disclosed.

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Louisville, KY, United States of America

James E Staats