Abstract: A microwave powered lamp wherein microwave energy is coupled to a cavity in which an electrodeless bulb is disposed, such that a rotating field of constant ellipticity is established in the cavity.

Abstract: An electrodeless lamp which couples strong microwave fields to a very small bulb of diameter about 1/2' or smaller. The lamp is operated in a mode which is independent of the height of the cavity and which provides electric field lines parallel to such height. The height of the cavity is substantially reduced as compared with prior lamps to provide strong coupling of the electric field to the bulb.

Abstract: An electrodeless lamp which couples to a small bulb and obtains a relatively high light output therefrom. A cavity which comprises a compound resonant structure including vestibule and reflector portions is provided. The combination of vestibule and reflector results in a condition of resonance throughout the cavity, whereby strong fields are coupled to the small bulb and a reflector is provided for directing and enhancing light output.

Abstract: A circularly polarized microwave oven. Microwave energy is coupled from a waveguide above the ceiling to the cavity by a rotatable vertical probe extending through a circular aperture in the cavity. A strip conductor closely spaced to the ceiling to limit radiation therefrom conducts the microwave current to an air dielectric patch antenna radially offset from the axis of the probe. A vertical section of the strip conductor spaces the patch antenna more than one-eighth wavelength from the ceiling which functions as a ground plane. The patch antenna is rectangular and the dimensions of its sides are selected to be respectively resonant above and below the operating frequency of the oven. More specifically, the dimensions are selected so that the orthogonal currents parallel to the rectangle sides produce orthogonal radiated components that are equal in magnitude and separated by 90.degree. in phase. Accordingly, the resonant patch or flag antenna radiates substantially circular polarization.

Abstract: A circularly polarized microwave oven. Microwave energy is coupled from a waveguide above the ceiling to the cavity by a rotatable vertical probe. A strip transmission line closely spaced to the ceiling to limit radiation therefrom conducts the microwave current from the probe to a helical strip antenna radially offset from the axis of the probe. The helical strip antenna has a cylindrical segment which has a downward slope from its feed end to gradually increase the spacing between the cylindrical segment and the ceiling which functions as a ground plane. The increase in radiative efficiency around the cylindrical segment caused by increasing the spacing to the ceiling offsets the magnitude of the current traveling wave diminishing as a result of radiation losses. Accordingly, the magnitude of the X and Y electric vectors are substantially equal over a relatively wide angle thus defining circular polarization.

Abstract: A bipolar digitizer (A/D converter) is disclosed which uses a single comparator circuit for initially determining the polarity of a sampled input signal and for thereafter comparing the absolute magnitude of the signal to an applied ramp voltage. The time required for the ramp voltage to exceed the magnitude of the sampled input signal is converted into a digital waveform representative of the magnitude of the sampled input signal. Resistive means are selectively connected in shunt with a signal storage capacitor to achieve bipolar signal compression and increased dynamic range.

Abstract: A metal rod rack shelf for a microwave oven wherein extension support rods are substantially prevented from being excited with high electric currents. The rack is embodied with quarter wavelength choking structures in the regions where the extension support rods connect to the rack mainframe. Accordingly, the effective short circuits in those regions are transformed to open circuits at a distance of one-quarter wavelength along the support rods. As a result, the support rods do not rise to high temperatures or radiate intense microwave fields that could cause melting of or arcing to microwave transparent brackets which mount to walls of the oven cavity and engage the rods.

Abstract: A microwave oven having a directional rotating antenna axially supported on an axis of one wall of a microwave oven cavity of the microwave oven which provides circularly symmetric uniform energy distribution of microwave energy within the microwave oven cavity and consistent heating of a product in the microwave oven cavity. The directional rotating antenna includes a two-by-two array of antenna elements where each element is an end driven half-wavelength resonating antenna element supported by a length of conductor perpendicular to the wall of the microwave oven cavity. A parallel plate transmission line connects to each of the supports, four of which join at a junction which connects to a cylindrical probe antenna. The probe antenna is excited by microwave frequency currents of a waveguide adjacent to the wall of the microwave oven cavity. The directional antenna is rotated by a moving stream of air circulated through the microwave oven cavity.

Abstract: A microwave oven having a directional rotating antenna axially supported on an axis of one wall of a microwave oven cavity of the microwave oven which provides circularly symmetric uniform energy distribution of microwave energy within the microwave oven cavity and consistent heating of a product in the microwave oven cavity. The directional rotating antenna includes a two-by-two array of antenna elements where each element is an end driven half-wavelength resonating antenna element supported by a length of conductor perpendicular to the wall of the microwave oven cavity. A parallel plate transmission line connects to each of the supports, four of which join at a junction which connects to a cylindrical probe antenna. The probe antenna is excited by microwave frequency currents of a waveguide adjacent to the wall of the microwave oven cavity. The directional antenna is rotated by a moving stream of air circulated through the microwave oven cavity.

Abstract: Method and apparatus for measuring gases dissolved in molten metal. Also disclosed are method and apparatus for dissolving gases in molten metal and a method of forming a gas permeable but molten metal impervious ceramic tube. A ceramic member is leached by an invention process so as to be selectively gas permeable. The member is inserted into molten metal to submerge the permeable portion. Then a vacuum is applied to the member and dissolved gases are measured by the change in pressure caused by gases entering from the molten metal. In another embodiment gas is applied to the submerged member to cause it to dissolve in the molten metal.

Abstract: Method and apparatus for measuring gases dissolved in molten metal. Also disclosed are method and apparatus for dissolving gases in molten metal and a method of forming a gas permeable but molten metal impervious ceramic tube. A ceramic member is leached by an invention process so as to be selectively gas permeable. The member is inserted into molten metal to submerge the permeable portion. Then a vacuum is applied to the member and dissolved gases are measured by the change in pressure caused by gases entering from the molten metal. In another embodiment gas is applied to the submerged member to cause it to dissolve in the molten metal.

Abstract: Microwave ovens typically have an oven cavity and a feed system for supplying microwaves through a feed opening into the cavity. Such ovens are inproved by providing a field stirrer rotatably mounted over and covering the feed opening. The field stirrer is a single conductive plate having a single radiating slot in the plate exposing only a portion of the feed opening to the cavity through the slot at any position of the plate during its rotation. The slot is in the shape of an arc or other shape which is tangentially longer than it is radially wide. The plate also has a plurality of wings, fins, or vanes outside the feed opening. The vanes and slot are arranged so that electrically identical positions of the plate occur only every full circle of rotation by virtue of bilateral symmetry at most. The plate is spaced from the feed opening and into the cavity by a sufficient distance to permit flow of microwave energy beneath the plate for distribution around the periphery of the plate and by the vanes.

Abstract: A microwave oven having a directional rotating antenna axially supported on an axis of one wall of a microwave oven cavity of the microwave oven which provides circularly symmetric uniform energy distribution of microwave energy within the microwave oven cavity and consistent heating of a product in the microwave oven cavity. The directional rotating antenna includes a two-by-two array of antenna elements where each element is an end driven half-wavelength resonating antenna element supported by a length of conductor perpendicular to the wall of the microwave oven cavity. A parallel plate transmission line connects to each of the supports, four of which join at a junction which connects to a cylindrical probe antenna. The probe antenna is excited by microwave frequency currents of a waveguide adjacent to the wall of the microwave oven cavity. The directional antenna is rotated by a moving stream of air circulated through the microwave oven cavity.

Abstract: Method and apparatus for measuring gases dissolved in molten metal. Also disclosed are method and apparatus for dissolving gases in molten metal and a method of forming a gas permeable but molten metal impervious ceramic tube. A ceramic member is leached by an invention process so as to be selectively gas permeable. The member is inserted into molten metal to submerge the permeable portion. Then a vacuum is applied to the member and dissolved gases are measured by the change in pressure caused by gases entering from the molten metal. In another embodiment gas is applied to the submerged member to cause it to dissolve in the molten metal.

Abstract: A high frequency oven having a door sealed to the oven by a seal which prevents the escape of high frequency energy between the door and the oven by acting as a choke to energy attempting to pass across the seal in which excitation of energy modes in a band of frequencies including the desired operating frequency range of the oven is controlled peripherally along the seal. An energy absorbing gasket surrounds the seal to absorb any energy passing outwardly from the energy seal.The questions raised in reexamination request No. 90/000,945, filed Jan. 29, 1986, have been considered and the results thereof are reflected in this reissue patent which constitutes the reexamination certificate required by 35 U.S.C. 307 as provided in 37 CFR 1.570(e).