US3102181A - High-frequency heating furnaces operating with very high frequencies - Google Patents

High-frequency heating furnaces operating with very high frequencies Download PDF

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Publication number
US3102181A
US3102181A US26235A US2623560A US3102181A US 3102181 A US3102181 A US 3102181A US 26235 A US26235 A US 26235A US 2623560 A US2623560 A US 2623560A US 3102181 A US3102181 A US 3102181A
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United States
Prior art keywords
wall
open end
parabolic
wall portions
generator
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Expired - Lifetime
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US26235A
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English (en)
Inventor
Verstraten Jan
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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    • 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
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/02—Waveguide horns
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
    • H01Q19/10—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces
    • H01Q19/12—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces wherein the surfaces are concave
    • 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
    • H05B6/66—Circuits
    • H05B6/68—Circuits for monitoring or control
    • H05B6/688—Circuits for monitoring or control for thawing
    • 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
    • H05B6/701—Feed lines using microwave applicators
    • 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
    • H05B6/78—Arrangements for continuous movement of material

Definitions

  • the invention relates to devices for heating by means of electromagnetic waves of very high frequencies. More particularly, the invention relates to furnaces for heating with waves of the decimeter or centimeter range.
  • Furnaces of this type may comprise a very high-frequency generator, such as a magnetron generator, and a wave guide system, the output of the very highfrequency generator being connected to the waveguide system to conduct the oscillations of ultra high frequency to the outlet port of the waveguide system.
  • the objects to be heated are moved by means of a conveyor belt arranged at the outlet port of the waveguide.
  • the construction of the waveguide system has to tulfill particular requirements, particularly when the conveyor belt has a width of the order of a multiple of the wavelength of the heating oscillations; Under thiscondition heating the objects uniformly demands special precautions, particularly in the construction of the high-frequency furnace.
  • the invention has for its object to provide a highfrequency furnace of simple construction, which is particularly suited for heating objects by means of high freque-ncy electromagnetic waves and utilizes a conveyor belt having a width a multiple of the wavelength of the heating energy.
  • a turnace construction which is well shielded so that substantially no radiation of the heating energy takes place.
  • the high-frequency furnace according to the invention is characterized in that the waveguide system comprises a component having a parabolic cylinder surface and two parallel boundary surfaces'at right angles to the former. On the tfocal line of the parabolic cylinder surface there is arranged, a linear radiator which is coupled with the output circuit of the high-frequency generator.
  • a reflector is arranged between the linear 3,102,181 atented Aug. 27, 1963 or" the interior.
  • the objects 5 to be heated for example, individually baked biscuits, are conveyed on a conveyor belt 6, and passed along the output opening of the waveguide system 3.
  • Belt 6 may be driven in any suitable manner, such as by driving rollers '7.
  • tuning means 8 of well known construction are provided as part of the coaxial conductor system 2.
  • the conveyor belt 6 may have a width, [for example, of over 120 cms. and in order to produce uniform heating of the objects throughout the width of the conveyor belt, the waveguide system 3 is dimensioned to surround the conveyor belt.
  • the system 3 comprises a parabolic cylinder surface 9 and two parallel boundary surfaces 10, 11, at right angles to the former.
  • a linear radiator 12 is arranged at the focal line of the parabolic cylinder surface 9.
  • Reflector 18 reflects the direct rays emanating from the linear radiator in the direction of the output opening 4 back towards the parabolic cylinder surface 9.
  • the reflector 18 consists of a reflector rod arranged parallel to the linear radiator 12.
  • the conveyor belt 6 is guided in a direction substantially at right angles to the parallel boundary surfaces 10, 11 of the waveguide system 3.
  • the waveguide system 3 is closed by a closing wall 13, which extends beyond the output opening 4 along the conveyor belt 1 6 to form entrance and exit passages 14- for the conveyor radiator and the outlet opening of the waveguide system remote from the parabolic surface and serves to reflect toward the parabolic surface the energy normally directly radiating from the linear radiator in the direction of the outlet opening.
  • the conveyor belt is ⁇ guided in a direction which is substantially at right angles to the parallel boundary surfaces of the parabolic component.
  • FIG. 1 is a perspective view of one embodiment of a high-frequency furnace according to the invention.
  • FIGS. 2 and3 are a cross sectional view and a longitudinal. sectional view, respectively, of the high-frequency furnace according to the invention.
  • the high-frequency furnace shown in a perspective View in FIG. 1, having a power of, for example, two kilowatts, comprises a magnetron or other suitable generator 1, which is adapted to produce oscillations or a wavelength of, for example, 12 cms.
  • the output circuit of the generator 1 is connected via a coaxial conductor 2 to a waveguide system 3, to guide the ultra high-frequency oscillations towards the outputopeningd of the waveguide system 3.
  • the front wall of the system 3 has been partly broken away to illustrate the construction 'dividually baked biscuits.
  • Trough 15 is filled partially with absorbing material 17 to absorb the radiation of the linear radiator 12 which passes along the conveyor belt 6 (of. FIGS. 2 and 3), so that the magnetron generator 1, even in the absence of objects to be heated, is adequately loaded.
  • a suitable material for this purpose may be, for example,
  • the rays emanating from the linear radiator 12 are reflected in the direction of the output opening 4- of the waveguidesystem 3 by the parabolic surface 9 and the reflector 18.
  • a radiation characteristic of the cardioid type is obtained in planes at right angles to the linear radiator 12.
  • This radiation characteristic is obtained by a suitable choice of the dimensions of the system, for example by the adjustment of the linear radiator 12 and the reflector rod 18 and of their relative spacing, which in the embodiments shown, is about 0.2 times. the wavelength.
  • the simplified construction shown in FIG. 1 adequately provides a uniformity of the electro-magnetic field at the output opening 4 of the waveguide ,system 3, which is sufiicient for many puposes such as the heating of in- In those instances where a greater uniformity of magnetic field at the output opening 4is desired, for example, for drying tissues, a pluralparallel to the linear radiator 12.
  • a uniformity of the electro-magnetic field at the output opening 4 of the waveguide ,system 3 which is sufiicient for many puposes such as the heating of in- In those instances where a greater uniformity of magnetic field at the output opening 4is desired, for example, for drying tissues, a pluralparallel to the linear radiator 12.
  • the device described above has the practically important advantage that the rays emanating fromthe high-frequency furnace are minimized, since the linear radiator 12 irradiates a linearly polarized field, of which the direction of the electric field vector E is parallel to the direction of the linear radiator 12, so that the rays extend parallel to the output 4 of the waveguide system in the direction indicated in the figure by the ldot-and dash arrows 16.
  • the energy vector (Poynting vector) is at right angles to the electric field vector'E and hence has no component in the direction of movement of the conveyor belt 6, so that only stray rays can emanate from the waveguide system 3.
  • These rays are, moreover, attenuated in the inlet and outlet passages 14 of the conveyor belt 6, for example, the emanating radiation is attenuated by a factor ofabout 25 db.
  • the height of the waveguide system 3 from the conveyor belt may be, for example, 48 cms. and the width of the output opening 4 is 120 cms.
  • the distance between the linear radiator 12 and the reflector rod 18 is about 25 cms.
  • the distance between the two boundary surfaces 10, 11 is 24 cms. and the length of the passages 14 is 30 cms. and the height thereof is 5 cms.
  • a high frequency furnace comprising a high frequency generator and a wave guide system, said wave guide system comprising first, second and third wall portions defining an enclosure having an open end, said first wall portion having a parabolic shape and said second and third wall portions forming two parallel boundary surfaces at right angles to said wall of parabolic shape and extending beyond the focal line of said parabolic wall portion, wave energy radiating means arranged at the focal line of said parabolic wall, wave energy reflecting means interposed between said radiating means and said open end, means for coupling said generator to said radiating means, and means for supporting objects to be heated at saidopen end of said enclosure.
  • a high frequency furnace comprising a high frequency generator and a wave guide system, said wave guide system comprising first, second and third Wall port-ions defining an enclosure having an open end, said first wall .portionhaving a parabolic shape and said second and third wall portions forming two parallel boundary surfaces at right angles to said wall of parabolic shape and extending beyond the focal line of said parabolic wall portion, wave energy radiating means arranged at the focal line of said parabolic wall, wave energy reflecting means interposed between said radiating means and said open means, and means for supporting objects to be heated at said open end of said enclosure, said latter means comprising a conveyor belt member and means for moving said belt member across said open end in a direction substantially at right angles to said second and comprising first, second and third wall portions defining an enclosure having an open end, said first wall portion having a parabolic shape .and said second and third Wall por- -tions form-ing twoparallel boundary surfaces at right end, means for coupling said generator to said radiating angles to said Wall of parabolic shape, wave
  • a high frequency furnace comprising a high frequency generator and a wave guide system, said wave guide system comprising first, second and third wall portions defining an enclosure having an open end, said first wall portion having a parabolic shape and said second and third wall portions forming two parallel boundary surfaces at right angles to said wall of parabolic shape, wave energy radiating means arranged at the focal line of said parabolic wall, wave energy reflecting'means interposed between said radiating means and said open end, means for coupling said generator to said radiating means, means enclosing said open end and providing aligned openings in said second and third wall portions, a conveyor belt member extending through said aligned openings for supporting objects to be heated at said open end, and shield means enclosing said conveyor belt at portions thereof adwall portion having a parabolic shape and said second and third wall portions forming two parallel boundary surfaces at right angles to said wall of parabolic shape, wave energy radiating means arranged at the focal line of said parabolic wall, wave energy reflecting means interposed between said radiating means and
  • a high frequency furnace comprising a high frequency generator and a wave guide system, said wave guide system comprising first, second and third wallpo-rtions defining an enclosure having an open end, said first wall portion having a parabolic shape and said second and faces at right angles to said wall of parabolic shape, wave energy radiating means arranged at the focal line of said parabolic wall, means for coupling said generator to said radiating means, means for supporting objects to be heated at said open end .of said enclosure, and shield means enclosing said support means adjacent the open end of said waveguide system;
  • a high frequency furnace comprising a high frequency generator and a wave guide system, said Wave guide system comprising first, second and third wall portions defining an enclosure having an open end, said first wall portion having a parabolic shape and saidsecond and third wall portions forming two parallel boundary surfaces at right angles to said wall of parabolic shape and extending beyond the focal line of said parabolic Wall portion wave energy radiating means positioned at the focal line of said parabolic Wall and arranged to radiate a linearly polarized field in which the-direction of the electric field vector is substantially perpendicular to saidsec- P J means for moving said belt member across said open end in a direction substantially at right angles to said second and third wall portions.
  • a high frequency furnace comprising a high frequency generator and a wave guide system, said wave guide system comprising first, second and third wall portions defining an enclosure having an open end, said first wall portion having a parabolic shape and said second and third wall portions forming two parallel boundary surfaces at right angles to said wall of parabolic shape, Wave energy radiating means arranged at the focal line of said parabolic wall, means for coupling said generator to said radiating means, means enclosing said open end and providing aligned openings in said second and third wall portions, a conveyor belt member extending through said aligned openings for supporting objects to be heated at said open end, and shield means enclosing said conveyor belt at portions thereof adjacent said aligned openings.
  • a high frequency furnace comprising a high frequency generator and a wave guide system, said wave guide system comprising first, second and third wall portions defining an enclosure having an open end, said first Wall portion having'a parabolic shape and said second and third wall portions forming, two parallel boundary surfaces at right angles to said wall of parabolic shape, Wave energy radiating means arranged at the focal line of said parabolic wall, means for coupling said generator to said radiating means, means enclosing said open end and providing aligned openings in said second and third Wall pol-tions, a radiation absorbing body in said enclosing means, a conveyor belt member extending through said aligned openings for supporting objects to be heated at said open end and located between said radiation means and said absorbing body, and means for moving said belt member in a direction at right angles to said second and third wall portions.
  • High frequency heating apparatus comprising a high frequency generator and a waveguide system, said waveguide system comprising first, second and third wall portions defining an enclosure having an open end, said first Wall portion having a parabolic shape and said second and third wall portions forming two parallel boundary surfaces substantially at right angles to said wall of parabolic shape and extending beyond the focal line of said parabolic wall portion, wave energy radiating means comprising a linear radiating element arranged at the focal line of said parabolic wall, wave energy reflecting means mounted between said radiating means and said open end, said radiating and reflecting means coacting with said wave guide system to produce at said open end a linearly polarized field in which the direction of the electric field vector is substantially perpendicular to said second and third wall portions, means for coupling said generator to said radiating means, .and conveyor means for carrying objects to be heated past the open end of said I 6 enclosure in a direction substantially at right angles to said second and third wall portions.
  • a high frequency furnace comprising a high frequency generator for supplying electromagnetic energy having a predetermined wave length and a waveguide system, said waveguide system comprising first, second and third wall portions defining an enclosure having an open end, said first wall portion having a parabolic shape and said second and third wall portions forming two parallel boundary surfaces at right angles to said wall of parabolic shape, wave energy radiating means arranged at the focal line of said parabolic wall and including means to focus substantially all of the radiated energy at said parabolic wall, said parabolic wall portion being arranged to reflect substantially all of the energy emitted from said radiating means towards said open end so that at said open end in directions parallel to said second and third wall portions a substantially uniform electromagnetic field of substantially constant intensity is produced, said focal line lying within said waveguide enclosure, means for coupling said generator to said radiating means, and conveyor means having a width dimension greater than the wave length of said electromagnetic energy for carrying objects to be heated past the open end of said enclosure.
  • High frequency heating apparatus comprising a high frequency generator and a waveguide system, said Waveguide system comprising first, second, third and fourth wall portions defining an enclosure, said first wall portion having a parabolic shape, said second and third wall portions forming two parallel boundary surfaces substantially at right angles to said first wall, and said fourth wall forming a closing surface substantially at right angles to said second and third wall portions, said second and third Wall portions including substantially aligned inlet and outlet apertures for receiving objects to be heated, wave energy radiating means arranged at the focal line of said parabolic wall, means for coupling said generator to said radiating means, and conveyor means extending through said inlet and outlet apertures for carrying objects to be heated through said Waveguide enclosure.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Constitution Of High-Frequency Heating (AREA)
US26235A 1959-05-01 1960-05-02 High-frequency heating furnaces operating with very high frequencies Expired - Lifetime US3102181A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL238818 1959-05-01
NL248916 1960-02-29

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US3102181A true US3102181A (en) 1963-08-27

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US26235A Expired - Lifetime US3102181A (en) 1959-05-01 1960-05-02 High-frequency heating furnaces operating with very high frequencies

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US (1) US3102181A (xx)
CH (2) CH379022A (xx)
DE (2) DE1095967B (xx)
GB (2) GB873082A (xx)
NL (3) NL113091C (xx)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3209113A (en) * 1961-07-17 1965-09-28 Philips Corp Furnace for high-frequency heating with the aid of oscillations of very high frequency
US3271552A (en) * 1963-02-01 1966-09-06 Litton Prec Products Inc Microwave heating apparatus
US3397296A (en) * 1964-06-02 1968-08-13 Ass Elect Ind Heating of substances by electrical energy at microwave frequencies
US3566066A (en) * 1968-08-30 1971-02-23 Dunlop Co Ltd Apparatus for heating articles
US3571551A (en) * 1968-04-03 1971-03-23 Furukawa Electric Co Ltd High frequency heating apparatus
US4431888A (en) * 1978-12-21 1984-02-14 Amana Refrigeration, Inc. Microwave oven with improved feed structure
US6157013A (en) * 1997-01-31 2000-12-05 Commissariat A L'energie Atomique Microwave applicator and method for the surface scarification of contaminated concrete
US20030205576A1 (en) * 1999-12-07 2003-11-06 Drozd J Michael Cylindrical reactor with an extended focal region
US20030226643A1 (en) * 2001-11-26 2003-12-11 Maschinenfabrik J. Dieffenbacher Gmbh & Co. Apparatus for the heating of pressed stock in the manufacture of boards of material
EP1530015A3 (en) * 2003-11-04 2007-11-14 Ngk Insulators, Ltd. Microwave drying method

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3197601A (en) * 1962-01-26 1965-07-27 Uarco Inc Heat treating apparatus
US3242304A (en) * 1963-07-22 1966-03-22 Philips Corp High frequency heating apparatus
US3404620A (en) * 1966-08-22 1968-10-08 Microtherm Ltd Preparation of food products
SE441640B (sv) * 1980-01-03 1985-10-21 Stiftelsen Inst Mikrovags Forfarande och anordning for uppvermning medelst mikrovagsenergi

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2259318A (en) * 1937-04-24 1941-10-14 Westinghouse Electric & Mfg Co Ultra high frequency for therapeutic purposes
US2478241A (en) * 1945-07-09 1949-08-09 Chu Lan Jen Flat beam antenna
US2500752A (en) * 1946-06-01 1950-03-14 Gen Electric High-frequency dielectric heating in a resonant chamber
US2539511A (en) * 1942-07-08 1951-01-30 Sperry Corp Radar system test equipment
US2560218A (en) * 1950-04-22 1951-07-10 Rca Corp Submarine antenna structure
US2627571A (en) * 1948-11-02 1953-02-03 Gen Electric Choke joint high-frequency heater
US3027442A (en) * 1960-02-29 1962-03-27 Philips Corp High-frequency furnaces

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2259318A (en) * 1937-04-24 1941-10-14 Westinghouse Electric & Mfg Co Ultra high frequency for therapeutic purposes
US2539511A (en) * 1942-07-08 1951-01-30 Sperry Corp Radar system test equipment
US2478241A (en) * 1945-07-09 1949-08-09 Chu Lan Jen Flat beam antenna
US2500752A (en) * 1946-06-01 1950-03-14 Gen Electric High-frequency dielectric heating in a resonant chamber
US2627571A (en) * 1948-11-02 1953-02-03 Gen Electric Choke joint high-frequency heater
US2560218A (en) * 1950-04-22 1951-07-10 Rca Corp Submarine antenna structure
US3027442A (en) * 1960-02-29 1962-03-27 Philips Corp High-frequency furnaces

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3209113A (en) * 1961-07-17 1965-09-28 Philips Corp Furnace for high-frequency heating with the aid of oscillations of very high frequency
US3271552A (en) * 1963-02-01 1966-09-06 Litton Prec Products Inc Microwave heating apparatus
US3397296A (en) * 1964-06-02 1968-08-13 Ass Elect Ind Heating of substances by electrical energy at microwave frequencies
US3571551A (en) * 1968-04-03 1971-03-23 Furukawa Electric Co Ltd High frequency heating apparatus
US3566066A (en) * 1968-08-30 1971-02-23 Dunlop Co Ltd Apparatus for heating articles
US4431888A (en) * 1978-12-21 1984-02-14 Amana Refrigeration, Inc. Microwave oven with improved feed structure
US6157013A (en) * 1997-01-31 2000-12-05 Commissariat A L'energie Atomique Microwave applicator and method for the surface scarification of contaminated concrete
US20030205576A1 (en) * 1999-12-07 2003-11-06 Drozd J Michael Cylindrical reactor with an extended focal region
US6797929B2 (en) * 1999-12-07 2004-09-28 Industrial Microwave Systems, L.L.C. Cylindrical reactor with an extended focal region
US20030226643A1 (en) * 2001-11-26 2003-12-11 Maschinenfabrik J. Dieffenbacher Gmbh & Co. Apparatus for the heating of pressed stock in the manufacture of boards of material
US6831259B2 (en) * 2001-11-26 2004-12-14 Dieffenbacher Gmbh + Co. Kg Apparatus for the heating of pressed stock in the manufacture of boards of material
EP1530015A3 (en) * 2003-11-04 2007-11-14 Ngk Insulators, Ltd. Microwave drying method

Also Published As

Publication number Publication date
CH379022A (de) 1964-06-30
NL248916A (xx)
CH396252A (de) 1965-07-31
NL113091C (xx)
GB958392A (en) 1964-05-21
NL238818A (xx)
DE1148674B (de) 1963-05-16
GB873082A (en) 1961-07-19
DE1095967B (de) 1960-12-29

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