Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B6/00—Heating by electric, magnetic or electromagnetic fields
  • H05B6/64—Heating using microwaves
  • H05B6/72—Radiators or antennas
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B6/00—Heating by electric, magnetic or electromagnetic fields
  • H05B6/64—Heating using microwaves
  • H05B6/70—Feed lines
  • H05B6/705—Feed lines using microwave tuning
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B6/00—Heating by electric, magnetic or electromagnetic fields
  • H05B6/64—Heating using microwaves
  • H05B6/70—Feed lines
  • H05B6/707—Feed lines using waveguides

Definitions

• the invention relates to a device for setting a microwave energy density distribution in an applicator forming a resonator chamber, in which the radiation generated by microwave generators is guided via waveguides to the applicator wall, and the use of this device.
• the microwave generator which can be a magnetron, for example, is arranged with its power supply separate from the applicator in which the microwave energy is to be effective.
• waveguides possibly along with other components, are used, via which the microwave energy is fed into the applicator cavity.
• the applicator In order to generate several modes with different phase positions in one applicator, with which a homogeneous field distribution is to be achieved, the applicator often has dimensions that are a multiple of the wavelength of the microwave that is fed in.
• the waveguide can be flanged to one side of a cuboid applicator.
• this has the disadvantage that, depending on the spatial extent of the sample groups located in the applicator, a sufficiently homogeneous field distribution can only be achieved in individual areas due to the field distribution. This is remedied by slotted graphite plates, via which microwaves are guided from a waveguide into the interior of the furnace; the waveguides are then located at the corners of the applicator space, the slots being arranged at different angles.
• the device according to claim 1 which is characterized in accordance with the invention in that a plurality of electrically conductive coupling pins are provided, each of which preferably protrudes vertically both into the waveguide space and into the applicator space.
• Such pin-shaped antennas allow a greater field homogeneity to be created in the resonator space, which is also still separated from the waveguide, so that gases generated in the resonator space cannot penetrate into the waveguide.
• This is particularly advantageous for the heat treatment of pre-pressed green compacts, which have been produced by powder metallurgy, for their dewaxing (debinding). The same applies to sintering processes that take place in a carburizing atmosphere.
• the coupling pins are arranged to be displaceable along their longitudinal axis, so that the desired field distribution can be set in the applicator loaded with the material to be heated.
• the desired field distribution can be set in the applicator loaded with the material to be heated.
• Field dependencies result both from the length of the coupling pin and here in particular the respective length fractions of the coupling pin that protrude into the waveguide and into the resonator space.
• the coupling pins can be inserted in the waveguide from both the wide and the narrow side.
• the waveguide and the coupling surface of the resonator chamber are preferably arranged with their longitudinal axes parallel to one another, so that a plurality of coupling pins arranged at equidistant distances from one another protrude with one end into the waveguide and with the other end into the resonator chamber.
• a dielectric is arranged around the wall bushing for the coupling pins.
• each of the coupling pins can be displaceably guided in a sleeve made of dielectric material and projecting through the wall of the waveguide and / or the applicator.
• the electrically conductive coupling pin is formed from a coupling rod and a sleeve surrounding it, in which the coupling rod is arranged so as to be longitudinally axially displaceable.
• the coupling pin at its end projecting into the waveguide can have a piece of a dielectric which extends this pin and which preferably projects through the waveguide diameter and is guided to the outside at a waveguide opening located at the opposite end.
• Graphite metal such as copper, aluminum, tungsten or molybdenum, metal alloys such as brass or steel or other alloys are suitable as the material for the coupling pin but must be correspondingly temperature-resistant, or an insulator with an electrical coating, which preferably consists of TiN.
• Boron nitride or a ceramic such as aluminum oxide, silicon nitride or quartz are selected as the material for the dielectric.
• the coupling pins each protrude in the area of the maxima of the microwave fed in there.
• the microwave can be coupled in capacitively or inductively.
• the geometry of the pin is cylindrical, the edges and corners of the pin preferably being rounded.
• the ratio of the opening diameter D in the waveguide through which the coupling pin is guided to the coupling pin diameter d is chosen so that the characteristic impedance is adapted.
• the piece goods to be treated by the microwave are arranged in the applicator resonance room on gratings which consist of rounded grating bars which are preferably oriented perpendicular to the electrical field of the microwave.
• the walls of the waveguide and the applicator which are adjacent or adjacent to one another are thermally insulated from one another.
• the device described can be used for the debinding of green compacts from a binder and one of the substances mentioned below and / or for the sintering of hard metals, cermets, steels produced by powder metallurgy or metallic or ceramic magnetic materials, in particular ferrites.
• Special application examples both with regard to the selection of the composite materials that can be produced by sintering in a microwave field and also procedural measures are given in WO 96/33830 and WO 97/26383.
• the device mentioned can also be used to generate a plasma, as is required, for example, in CVD coatings.
• FIG. 1 to 4 each show schematically differently arranged coupling pins and dielectrics and
• FIG. 5 shows a schematic view of the device according to the invention.
• a waveguide 10 with an upper wall 11 and a lower wall 12 are shown in cross section.
• the wall 21 of the applicator resonance chamber On the wall 12 of the waveguide 10 is the wall 21 of the applicator resonance chamber, of which the section shown is designated 20.
• the two walls 12 and 21 are each broken through at equidistant intervals a, the distances a corresponding to approximately half to a quarter of the wavelength of the microwave in the waveguide 10.
• a first variant (FIG. 1), the opening in the walls 12 and 21 is surrounded by a circular dielectric 30.
• the middle opening of the dielectric D, through which the electrically conductive coupling pin made of graphite 31 is passed, is selected relative to the diameter d of the cylindrical coupling pin so that the characteristic impedance is adapted.
• the coupling pin 31 protrudes with its two ends, on the one hand, into the resonator chamber 20 of the applicator and, on the other hand, into the waveguide interior 10.
• the coupling pin can be displaced axially in the direction of the double arrow 32.
• the coupling pin 33 can be displaced in the direction of the double arrow 34 in a sleeve 40 made of a dielectric.
• the sleeve 40 projects exclusively into the resonator chamber 20 of the applicator.
• the coupling pin 35 consists of a coupling rod 36 which can be displaced longitudinally and axially in the direction of the double arrow 37 in a sleeve 38 of electrically conductive material surrounding it in the direction of the double arrow 37.
• the coupling pin 39 is provided with an extension 41 made of a dielectric material at its end projecting into the waveguide 10.
• the one rod formed from parts 39 and 41 is axially displaceable along the donoel arrow 42.
• Graphite rods with a diameter d of 3 mm are arranged at a distance of 10 mm as electrically conductive coupling pins 31, 33, 36 and 39.
• FIG. 5 shows a schematic view of the structure of the device according to the invention, the essential parts of a short-circuit slide 49, a microwave generator 44, a waveguide 10 which is guided through an opening in the furnace wall 45 and the arrangement of the coupling pins 31 already described.
• the interior of the furnace, in which hard metal parts 48 are arranged on gratings, is shielded from the outside by thermal insulation 46.

Landscapes

• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Plasma Technology (AREA)
• Constitution Of High-Frequency Heating (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Radiation-Therapy Devices (AREA)
• Electrotherapy Devices (AREA)
• Powder Metallurgy (AREA)
• Electron Sources, Ion Sources (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=7629967

Family Applications (1)

Country Status (6)

Families Citing this family (11)

Family Cites Families (15)

• 2000
  • 2000-02-04 DE DE10005146A patent/DE10005146A1/de not_active Withdrawn
• 2001
  • 2001-01-19 WO PCT/DE2001/000259 patent/WO2001058215A1/fr active IP Right Grant
  • 2001-01-19 EP EP01911377A patent/EP1252802B1/fr not_active Expired - Lifetime
  • 2001-01-19 US US10/168,786 patent/US6630653B2/en not_active Expired - Fee Related
  • 2001-01-19 JP JP2001557337A patent/JP2003522392A/ja not_active Ceased
  • 2001-01-19 AT AT01911377T patent/ATE357124T1/de active
  • 2001-01-19 DE DE50112190T patent/DE50112190D1/de not_active Expired - Lifetime

Non-Patent Citations (1)

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