US3784777A - Microwave furnace for the treatment of sheets or plates made of a material absorbing said waves - Google Patents

Microwave furnace for the treatment of sheets or plates made of a material absorbing said waves Download PDF

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Publication number
US3784777A
US3784777A US00210801A US3784777DA US3784777A US 3784777 A US3784777 A US 3784777A US 00210801 A US00210801 A US 00210801A US 3784777D A US3784777D A US 3784777DA US 3784777 A US3784777 A US 3784777A
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slot
microwave
plate
microwave furnace
cavity
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US00210801A
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English (en)
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J Soulier
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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
    • H05B6/78—Arrangements for continuous movement of material
    • H05B6/788—Arrangements for continuous movement of material wherein an elongated material is moved by applying a mechanical tension to it

Definitions

  • a m1crowave furnace comprises a gulde w1th a slot of BC. [311GB a eng corresponding o e of a sheet is to be treated by being continuously moved through 53 i gi 2 I the guide.
  • a microwave generator is electrically coni 333 8l R nected to said guide and at least one metal plate is 1 o earc 5 81 placed in front of said slot.
  • the invention relates to a novelmicrowave furnace for the treatment of sheets or plates (i.e. workpieces) of great width and made of material absorbing said microwaves, said sheets or plates being made to travel through the furnace.
  • the novel furnace comprises a wave-guide, a slot, provided in said wave-guide, and having a length corresponding to the width of said sheet or plate, conveying means for moving said sheet or plate transversely with respect to said slot, a microwave generator electrically connected to said guide, and at least one metal plate placed in'front of said slot perpendicularly to the plane of and over the whole length of said slot.
  • the plate has one side turned towards the slot and said side has an inclination decreasing in the direction of the microwave generator.
  • FIG. 1 is a longitudinaldiagrammatic perspective section of a furnace according to the invention
  • FIG. 2 is a diagrammatic top plan view of-the furnace of FIG. 1, with portions omitted for the sake of clarity;
  • FIG. 3 is a longitudinal perspective section, illustrating a variant embodiment of FIG. 1;
  • FIG. 4 is a cross-sectional view illustrating a further development of the invention.
  • FIG. -5 is an elevation sectional view taken online V-V of FIG. 4; and I FIG. 6 is a diagrammatic view illustrating another development of the invention.
  • the furnace shown in the drawings comprises a wave-guide excited on the mode TEOl; this waveguide is hereinafter called resonant cavity.
  • the resonant cavity 1 is of a'parallelepipedal shape and into it protrudes the antenna'2 of a microwave generator 3 constituted, for example, of a magnetron and fed by a power source 4.
  • the inside of the resonant cavity 1 in which ultra high frequency waves are dissipated includes matching elements 5, for example constituted by rings or plates made of polytetraflu orethylene; in addition, the resonant cavity 1 is provided, at the end thereof opposite the end into which the antenna 2 protrudes, with an absorbing load 6 whose position can be modified'by an adjusting device 7, the control 8 of the latter being placed outside the cavity 1.
  • the upper wall of cavity 1 is provided with a slot 9 whose length corresponds to the width of a sheet to be heated, and which is of a material absorbing the micro waves; thewidth of sheet 10 can be for example from 0.25 m to 2.50 m or more.
  • Such materials are technically known as polar materials and are, for example, constituted by various thermoplastic and thermosetting rubbers and resins, which are, should the occasion and vinyl acetate, nitrile' rubbers or blends thereof, chloroprene rubbers, and others.
  • Slot 9 may have various widths, but its width should preferably be in the range of about 5 to 10 mm.
  • the furnace being designed to treat or heat a sheet 10 which travels continuously, means are provided for advancing the sheet, such as, for example, sets of cylinders ll, 12, bands or other suitable conveyingdevices.
  • a protective cover 13 be provided above the slot 9 and preferably over the whole width of the cavity wallhaving said slot.
  • This cover 13 is made of conductive metal and has its ends securedoutside of the cavity.
  • the furnace is also provided in front of slot 9 with a plate l4-made of conductive metal, for example aluminum, whose length is preferably equal to the length of said slot 9.
  • the side l4a'of the plate 14 facing slot 9 is oblique to delimit a downwards inclination facing the antenna 2 of the magnetron 3.
  • the plate 14 can be permanently placed into the cavity 1 so as to be supported by that inner wall of the cavity, which is opposite to the wall provided with the slot 9.
  • the microwave power transmitted from the antenna 2 then has a tendency to decrease along slot 9, in an exponential manner from this end portion towards the other end portion of the slot.
  • the magnetic field which is produced inside the resonant cavity 1 and which extends transversely with respect to said cavity has to pass around'plate 14 as represented by line Hm in FIG. 4. Consequently it will be noticed that the magnetic field becomes more and more concentrated at the vicinity of the slot 9 as the distance from the antenna 2 increases so that the resulting electrical field He which is shown on FIG. 4 and absorbed by the material of sheet 10, is made substantially constant over the whole width of said sheet. This prevents the edge of the sheet which is closet to the antenna 2 from being more heated than the rest and thus to tend to absorb more of the microwaves. As a result, the microwave energy applied to said sheet is more uniform over the whole lenght of the slot 9.
  • the plate 14 is adjustable by means of screw 16, it is possible to concentrate the magnetic field more or less the cavity 1, thus enabling heating of sheets 10 of various thickness or having different absorption coefficients (tg 8.).
  • the auxiliary load constituted by the piston 6 which is made of absorbing material prevents reflections which can cause return waves to be applied to the antenna 2 and consequently to themagnetron 3 with the resulting risks of destroying the same.
  • FIG. 3 illustrates a variantof the preceding embodiment wherein the plate 14 is replaced by several successive small plates 18, 18a 18n, each of them having a separate control means 19, 19a 19n.
  • the height of plates 18 to 18n is decreases or the control means 19 to 1% are designed in order that the top 18 18a, 18a of each plate be set off substantially in step shape, as "shown.
  • FIGS. 4 and show a development of the invention wherein the plate 14 of FIG. 1 or the various plates 18 to 18n of FIG. 3 are replaced by a part 20 of U-shaped cross section, said part 20 containing between the branches thereof a plate 21 made of polytetrafluorethylene or similar material.
  • the part 20 is, asabove mentioned, preferably adjustable upwards and downwards by means ofcontrol devices 22 which are for example, constituted by screws as shown.
  • the plate 21 is also adjustable upwards and downwards by means of a control component 23 which can be operated separately from those operating and lifting or lowering of the part 20.
  • the top 20a of the part 20 and also the top 21a of the plate 21 be parallel to each other. Due to this additional means it becomes possible, by adjusting the position of the plate 21 to adapt or match the impedance of the resonant cavity and, consequently, to prevent the formation of standing waves which are prejudicial to good operation.
  • the plate 14 it is also possible, as shown in FIG. 6, for the plate 14 to have a top 14b substantially shaped as an exponential curve. This isadvantageous when the exponential function of absorbtion decrease of a material having to be heated is exactly known. Actually, then, by replacing said function in the configuration of the top 14b of plate 14 it becomes possible to compensate the absorption decrease very accurately and, consequently, to obtain strictly uniform heating over the whole width of the sheet 10.
  • a microwavefurnace for the treatment of sheetshaped or plate-shaped workpieces whose material is capable of absorbing microwaves comprising a waveguide having a wall bounding an interior cavity and provided with a slot having a length corresponding to the width of the workpieces to be treated;
  • conveying means for conveying a workpiece to be treated exteriorly of said cavity across said slot transversely to the elongation thereof;
  • a microwave generator electrically connected with said wave-guide for producing in said cavity of the latter an electric field to which the successive increments of the advancing workpiece are to be exposed through said slot, and which tends to be nonuniformly absorbed over the surface area of said slot by the material of the workpiece;
  • field-equalizing means in said cavity for equalizing said electric field over the entire area of said-slot so that the material of the workpiece will uniformly absorb the field during advancement of the workpiece across said slot.
  • said field-equalizing means comprises at least one metal plate located in said wave-guide in front of the slot and extending normalto the plane and over the entire length of the same, said plate having a surface facing said slot and inclined in direction toward the same from the region of said microwave generator.
  • said plate comprises one portion of substantially U-shaped cross-section having an open side facing said slot, and another portion of material sensitive to microwaves arranged in said one portion and having said surface which faces said slot at said open side;
  • control means associated with said I other portions for moving the same toward and away from said slot normal to the plane of the same.
  • a microwave furnace as defined in claim 2, said wave-guide having another wall opposite the firstmentioned wall and provided with an opening through which said plate in'part extends to the exterior of said wave-guide; and further comprising a cupped cover fixed to the outer side of said other wall over said opening.
  • a microwave furnace for treating a workpiece in the form of an elongated band comprising a substantially electrically continuous cavity having a longitudinal axis and being bounded by circumferential walls;
  • a source of microwave power to energize the cavity for propagating therein microwave energy along said longitudinal axis
  • one longitudinally extending slot provided in one of said walls, said slot having a length substantially equal to the width of the elongated band
  • travelling means for moving said elongated band along its own longitudinal plane and transversally to said longitudinal axis in front of said slot and exteriorly of said cavity;
  • said at least one metal plate has a rectilinear wherein said at least one metal-plate has a U-shaped cross-sectional shape and is supported by means for adjusting the position thereof with respect to the slot.
  • a method of treating elongated sheet-shaped or plate-shaped workpieces of material capable of absorbing microwaves, with the aid of a microwave furnace comprising the steps of producing a microwave field in a microwave furnace having a wall provided with a slot;
  • a method as defined in claim 20, wh ereinthe step of equalizing said field comprises varying the field over the surface area of the respective increment exposed in said slot as a function which is the inverse of the exponential function of absorption decrease of the material of the workpiece.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Constitution Of High-Frequency Heating (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Heating, Cooling, Or Curing Plastics Or The Like In General (AREA)
US00210801A 1970-12-31 1971-12-22 Microwave furnace for the treatment of sheets or plates made of a material absorbing said waves Expired - Lifetime US3784777A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7047567A FR2120402A5 (no) 1970-12-31 1970-12-31

Publications (1)

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US3784777A true US3784777A (en) 1974-01-08

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US00210801A Expired - Lifetime US3784777A (en) 1970-12-31 1971-12-22 Microwave furnace for the treatment of sheets or plates made of a material absorbing said waves

Country Status (7)

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US (1) US3784777A (no)
JP (1) JPS5035256B1 (no)
CA (1) CA933600A (no)
DD (1) DD97117A1 (no)
DE (1) DE2162851A1 (no)
FR (1) FR2120402A5 (no)
GB (1) GB1368779A (no)

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3949328A (en) * 1974-03-22 1976-04-06 C.G.R.-Mev Variable-reflectivity device for varying output power of microwave generator
US4179595A (en) * 1976-08-19 1979-12-18 Saint-Gobain Industries Multimodal resonant cavity for very high frequency heating
US4259561A (en) * 1977-05-06 1981-03-31 Agence Nationale De Valorisation De La Recherche (Anvar) Microwave applicator
US4689459A (en) * 1985-09-09 1987-08-25 Gerling John E Variable Q microwave applicator and method
US4711983A (en) * 1986-07-07 1987-12-08 Gerling John E Frequency stabilized microwave power system and method
US4991539A (en) * 1986-07-28 1991-02-12 Sarda Jean Lucien Microwave unit for thermographic printing
US5371342A (en) * 1990-06-01 1994-12-06 Saitoh; Yoshiaki Electromagnetic-wave-operated heating apparatus having an electric field concentrating member
US6054696A (en) * 1997-01-06 2000-04-25 International Business Machines Corporation Feedback system to automatically couple microwave energy into an applicator
US6072167A (en) * 1997-01-06 2000-06-06 International Business Machines Corporation Enhanced uniformity in a length independent microwave applicator
US6121595A (en) * 1997-01-06 2000-09-19 International Business Machines Corporation Applicator to provide uniform electric and magnetic fields over a large area and for continuous processing
US6590191B2 (en) * 1999-07-12 2003-07-08 Industrial Microwaves Systems, Inc. Method and apparatus for electromagnetic exposure of planar or other materials
US6965099B1 (en) * 2000-08-28 2005-11-15 Georgia Tech Research Corporation Geometry for web microwave heating or drying to a desired profile in a waveguide
US20070131678A1 (en) * 2005-12-14 2007-06-14 Industrial Microwave Systems, L.L.C. Waveguide exposure chamber for heating and drying material
US20100282741A1 (en) * 2007-11-29 2010-11-11 Dow Global Technologies Inc. Method for controlling and optimizing microwave heating of plastic sheet
US20150136761A1 (en) * 2012-05-14 2015-05-21 Korea Electrotechnology Research Institute Microwave heating apparatus for uniformly heating objects based on near-cutoff condition
US20220268155A1 (en) * 2021-02-22 2022-08-25 Off-World, Inc. Microwave energy applicator

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2642335C2 (de) * 1976-09-21 1978-12-21 Ingenieurbuero Hermann Purfuerst Kg, 3004 Isernhagen Vorrichtung zum kontinuierlichen dielektrischen Erwärmen mittels Mikrowellenenergie
SE419494B (sv) * 1979-12-21 1981-08-03 Husqvarna Ab Genomstromningsvermare av mikrovagstyp innehallande en cylindrisk mikrovagsapplikator
DE3033012A1 (de) * 1980-09-02 1982-04-01 Paul Troester Maschinenfabrik, 3000 Hannover Vorrichtung fuer die trockene vernetzung von straengen aus elastomeren
US5279788A (en) * 1991-01-24 1994-01-18 Eisai Co., Ltd. Sterilizer for sealed container utilizing microwave
JP2011150911A (ja) * 2010-01-22 2011-08-04 Konica Minolta Holdings Inc マイクロ波加熱装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2869085A (en) * 1954-01-19 1959-01-13 Raytheon Mfg Co Selective absorbers
US3218583A (en) * 1963-08-30 1965-11-16 Textron Inc High frequency attenuator with constant phase shift
US3457385A (en) * 1966-07-07 1969-07-22 Canadian Patents Dev Apparatus for dielectric heating
US3555232A (en) * 1968-10-21 1971-01-12 Canadian Patents Dev Waveguides

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2869085A (en) * 1954-01-19 1959-01-13 Raytheon Mfg Co Selective absorbers
US3218583A (en) * 1963-08-30 1965-11-16 Textron Inc High frequency attenuator with constant phase shift
US3457385A (en) * 1966-07-07 1969-07-22 Canadian Patents Dev Apparatus for dielectric heating
US3555232A (en) * 1968-10-21 1971-01-12 Canadian Patents Dev Waveguides

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3949328A (en) * 1974-03-22 1976-04-06 C.G.R.-Mev Variable-reflectivity device for varying output power of microwave generator
US4179595A (en) * 1976-08-19 1979-12-18 Saint-Gobain Industries Multimodal resonant cavity for very high frequency heating
US4259561A (en) * 1977-05-06 1981-03-31 Agence Nationale De Valorisation De La Recherche (Anvar) Microwave applicator
US4689459A (en) * 1985-09-09 1987-08-25 Gerling John E Variable Q microwave applicator and method
US4711983A (en) * 1986-07-07 1987-12-08 Gerling John E Frequency stabilized microwave power system and method
US4991539A (en) * 1986-07-28 1991-02-12 Sarda Jean Lucien Microwave unit for thermographic printing
US5371342A (en) * 1990-06-01 1994-12-06 Saitoh; Yoshiaki Electromagnetic-wave-operated heating apparatus having an electric field concentrating member
US6054696A (en) * 1997-01-06 2000-04-25 International Business Machines Corporation Feedback system to automatically couple microwave energy into an applicator
US6072167A (en) * 1997-01-06 2000-06-06 International Business Machines Corporation Enhanced uniformity in a length independent microwave applicator
US6121595A (en) * 1997-01-06 2000-09-19 International Business Machines Corporation Applicator to provide uniform electric and magnetic fields over a large area and for continuous processing
US6590191B2 (en) * 1999-07-12 2003-07-08 Industrial Microwaves Systems, Inc. Method and apparatus for electromagnetic exposure of planar or other materials
US6965099B1 (en) * 2000-08-28 2005-11-15 Georgia Tech Research Corporation Geometry for web microwave heating or drying to a desired profile in a waveguide
US20070131678A1 (en) * 2005-12-14 2007-06-14 Industrial Microwave Systems, L.L.C. Waveguide exposure chamber for heating and drying material
US7470876B2 (en) 2005-12-14 2008-12-30 Industrial Microwave Systems, L.L.C. Waveguide exposure chamber for heating and drying material
US20100282741A1 (en) * 2007-11-29 2010-11-11 Dow Global Technologies Inc. Method for controlling and optimizing microwave heating of plastic sheet
US20150136761A1 (en) * 2012-05-14 2015-05-21 Korea Electrotechnology Research Institute Microwave heating apparatus for uniformly heating objects based on near-cutoff condition
US10660166B2 (en) * 2012-05-14 2020-05-19 Korea Electrotechnology Research Institute Microwave heating apparatus for uniformly heating objects based on near-cutoff condition
US20220268155A1 (en) * 2021-02-22 2022-08-25 Off-World, Inc. Microwave energy applicator

Also Published As

Publication number Publication date
JPS5035256B1 (no) 1975-11-14
DE2162851A1 (de) 1972-07-20
DD97117A1 (no) 1973-04-12
GB1368779A (en) 1974-10-02
CA933600A (en) 1973-09-11
FR2120402A5 (no) 1972-08-18

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