Abstract: 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.

Abstract: 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.

Abstract: A microwave excitation system for coupling microwave energy from a magnetron to a load via a waveguide of relatively compact dimensions open at one end for radiating energy therefrom and enclosed at the other end by a conductive end wall. A magnetron output probe extends axially into the waveguide through a central opening in the end wall of the waveguide. A cup-like member is mounted within the waveguide and inverted over the probe concentric therewith to capacitively couple microwave energy from the probe into the waveguide. The cup-like member is dimensioned to provide a matched load condition for the magnetron.

Abstract: A microwave oven with a dual feed excitation system comprising in one form of the invention a rotating antenna supported from the top cavity wall and a slotted radiating chamber supported from the bottom cavity wall. The antenna and radiating chamber are coupled to the magnetron output probe by a waveguide having a central section for receiving energy from the magnetron probe; a first section for coupling energy from the central section to the antenna and a second section for coupling energy from the central section to the radiating chamber. The fractional apportionment of the total energy from the magnetron between antenna and radiating chamber is a function of the impedance presented by each. The impedance of the antenna varies as the antenna rotates. The impedance of the chamber is particularly sensitive to food load parameters such as dielectric constant, which changes as the food cooks.

Abstract: This invention relates to electric heaters of the type consisting of a flat convoluted loop or coil adapted to be arranged in an opening in a cooktop and, more particularly, to a support system wherein means are provided for cushioning vibrations resulting from relative movement between the convoluted heater and the support system.

Abstract: An excitation system for a microwave oven in which a rotating microwave field is established in a waveguide section prior to being propagated into the microwave oven cavity. A circular waveguide has an internal L-shaped rotating antenna excited from a coupling probe in an attached rectangular waveguide to establish in the waveguide a stationary TM01 and a TE11 mode. These modes interact in the waveguide to give an asymmetric rotating waveguide field which is then propagated into the oven to provide a rotating field pattern of desirable average uniformity. The excitation circular waveguide is located in a central position on the bottom wall of the oven.

Abstract: A microwave oven with an electrically conductive surface such as a flat metal plate positioned parallel to the bottom of the oven cavity and spaced therefrom by approximately one tenth the wavelength in free space .lambda.a of the excitation microwave energy.The width of the plate is an odd multiple of a quarter wavelength (.lambda.a/4) and the depth is an even multiple of .lambda.a/4. Preferably the plate is spaced an odd multiple of .lambda.a/4 from the feed aperture at the top of the oven cavity.The edges of the plate are spaced from the vertical side walls of the oven cavity, at least in that region of the cavity where the microwave energy level would be greatest in the absence of the plate.

Abstract: A combined microwave and self-cleaning oven has a choke surrounding the oven liner with the opening of the choke cavity adjacent the lip of the liner. The choke cavity has a rib at each of several groundpoints to trap air within the cavity. This trapped air thermally insulates the oven liner lip region so that pyrolytic self-cleaning of the oven can be accomplished without the aid of a mullion heater. For best electrical effectiveness, the choke groundpoints are preferably spaced a distance of between one-half and one wavelength.

Abstract: A food temperature-sensing probe assembly for monitoring the internal temperature of food while it is being cooked in a microwave oven includes a disc-like reflector mounted on the probe housing at a predetermined distance from the tip of the probe housing. The probe housing is adapted to be driven into the food so that the reflector is adjacent to the food. The reflector serves to prevent overcooking of the food in a region immediately adjacent the probe. A spacer is mounted adjacent the reflector and extends toward the tip of the probe housing to space the reflector away from the food at least a predetermined minimum distance.

Abstract: Apparatus is disclosed for monitoring the internal temperature of food being cooked in the cooking cavity of a microwave oven with microwaves of a predetermined frequency having a predetermined wavelength .lambda. . The apparatus includes a needle-like temperature-sensing probe adapted for insertion into the food being cooked, the probe including a thermally-responsive electrical element positioned internally of the probe housing near the tip end. A flexible shielded cable having first and second ends and generally extending between the probe and the cooking cavity wall connects the probe to circuitry responsive to thermally-induced changes in a characteristic of the electrical element, and includes chokes at either or both ends of the cable, the chokes presenting a high impedance to microwave energy of wavelength .lambda. . The cable length is selected to be approximately equal to n .lambda./2, where n is any integer, when one choke is used, and approximately equal to n .lambda.

Abstract: Apparatus is disclosed for monitoring the internal temperature of food being cooked in the cooking cavity of a microwave oven with microwaves of a predetermined frequency having a predetermined wavelength .lambda.. The apparatus includes a needle-like temperature-sensing probe adapted for insertion into the food being cooked, the probe including a thermally-responsive electrical element positioned internally of the probe housing near the tip end. A flexible shielded cable connects the probe to circuitry responsive to thermally-induced changes in a characteristic of the electrical element, the cable shield being connected at one end to the probe housing and at the other end to a wall of the cooking cavity. The total effective electrical length of the probe and the cable, measured along the cable and probe from the cooking cavity wall to the distal end of the probe, is selected to be an integer multiple of one-half the predetermined wavelength .lambda..

Abstract: A self-cleaning microwave oven comprises a heating cavity, source means including a disc antenna and a rotating mode stirrer for exciting in the heating cavity two predetermined electromagnetic field modes, a first metal rack horizontally disposed near the bottom of the cavity and having spaced-apart rods extending parallel to the direction of the electric field of the two modes and terminating those modes, and a second metal rack horizontally disposable in a plurality of different positions above the first rack and having spaced-apart rods extending perpendicular to the direction of the electric field of the two modes and having no effect thereon.