US3491222A - Microwave heating applicator - Google Patents

Microwave heating applicator Download PDF

Info

Publication number
US3491222A
US3491222A US609525A US3491222DA US3491222A US 3491222 A US3491222 A US 3491222A US 609525 A US609525 A US 609525A US 3491222D A US3491222D A US 3491222DA US 3491222 A US3491222 A US 3491222A
Authority
US
United States
Prior art keywords
cavity resonator
waveguide
vaned
waveguides
applicator
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US609525A
Other languages
English (en)
Inventor
Fred Kohler
Norman H Williams
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Varian Medical Systems Inc
Original Assignee
Varian Associates Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Varian Associates Inc filed Critical Varian Associates Inc
Application granted granted Critical
Publication of US3491222A publication Critical patent/US3491222A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • H05B6/78—Arrangements for continuous movement of material

Definitions

  • the applicator is a microwave heating apparatus having a circular multimode waveguide capable of propagating electromagnetic fields of difierent mode patterns coupled thereto from an excited rectangular multimode cavity resonator.
  • the multimode waveguide includes two axially spaced apart, open ended sections on the order of 37 ⁇ long.
  • the waveguide sections extend perpendicularly from coupling holes at the center of opposite sides of the rectangular cavity resonator.
  • a vaned mode stirrer having a plurality of vanes circumferentially spaced about the coupling holes to radially extend into the cavity resonator is rotatably mounted between the long sides of the cavity resonator.
  • the vaned mode stirrer is rotated to periodically change the mode pattern within the cavity resonator and preferentially couple and rotate TE modes in the multimode waveguide sections whereby a work piece is uniformly heated as it is advanced through the open ended waveguide sections.
  • the present invention relates to apparatus for heating materials by high frequency electromagnetic fields. More particularly, it relates to such an apparatus which is able to uniformly heat a continuously moving work piece.
  • Microwave heating of materials with high frequency electromagnetic fields is a common and, in certain instances, the best suited method of heating materials. How- 'ever, for several reasons, the practical utility of microwave heating techniques has been severely limited, particularly with respect to industrial applications. For example, often it is desired to uniformly heat a work piece of relatively large dimensions, i.e., a work piece having a dimension on the order of x, the free space wavelength of the applied energy. Generally, it has been the practice to place such work pieces in excited cavity resonators or waveguides. Normally, the standing wave pattern produced in such devices includes localized regions of maximum and minimum electric field intensity separated bydistances equal to M4.
  • portions thereof located in the vicinity of maximum electric field intensity will be heated to a substantially greater extent than those portions located in the vicinity of minimum electric field intensity. This results in hot-spots being created in the work piece at locations separated by distances of ) ⁇ /2, hence, non-uniform heating of the work piece.
  • those applicators including a rotating fan or moveable diaphragm mode stirrer are characterized by other disadvantages which severely limit their field of use, particularly, at high power levels.
  • the mode stirrer is set into motion by a motor located external of the cavity resonator.
  • the motor drive is coupled to the fan mode stirrer through the walls of the cavity resonator by suitable coupling means.
  • the coupling means allows electromagnetic energy to escape from the cavity resonator to be lost to the surroundings.
  • arcing occurs between the moving and stationary parts of the coupling means. If the heating is to be conducted in a contamination free environment, such arcing can not be tolerated.
  • the microwave heating applicator of the present invention includes a multimode cavity resonator arranged to excite a waveguide to propagate electromagnetic waves. Enhanced efficiency of operation is obtained by employing a multimode waveguide, Le, a waveguide of'a size capable of propagating electromagnetic waves of different mode patterns.
  • the work piece to be heated is introduced into the waveguide.
  • an open ended waveguide having two axially spaced sections is used for heating a continuously moving work piece.
  • the multimode cavity resonator is coupled to excite the multimode waveguide as the work piece is advanced through the waveguide.
  • the vaned mode stirrer comprises a plurality of circumferentially spaced outwardly extending vanes rotatably mounted within the cavity resonator.
  • the vaned mode stirrer is mounted between axially spaced sections with its vanes radially extending into the cavity resonator.
  • the uniformity of the total heat energy available to all portions of the waveguide is enhanced.
  • the total heat energy available to all portions of the waveguide is made uniform.
  • Another object of this invention is to provide a microwave heating applicator which supplies uniform total heat energy to all regions of the applicator which are intended for receiving work pieces.
  • Yet another object of this invention is to provide a microwave heating applicator suitable for uniformly heating work pieces having dimensions which are on the order of the free space wavelength of the applied energy.
  • Still a further object of this invention is to provide a microwave heating applicator for high power heating applications.
  • FIGURE 1 is a perspective view of one embodiment of the applicator of the present invention.
  • FIGURE 2 is a front elevation cross-section view of the applicator of FIGURE 1.
  • FIGURE 3 is a cross-section of the vaned mode stirrer taken along lines 33 of FIGURE 2.
  • FIGURE 4 is a block diagram of a system for heat treating materials employing the applicator of the present invention.
  • the microwave heating applicator of the present invention includes first and second axially spaced open-ended waveguides 11 and 12 of aluminum or other conductive material.
  • Each waveguide has a cross-section in the plane normal to the direction of propagation of electromagnetic waves of a size sufficient to support a plurality of modes of propagation.
  • multimode waveguides can be used in the practice of the present invention, propagating electromagnetic waves in various mode patterns and uniform heating of a work piece passed through the multimode waveguides 11 and 12 is facilitated by using circular waveguides.
  • the diameter of the circular multimode waveguide is selected to be greater than the dominant mode cutoff diameter, and preferably larger than x.
  • the length of each of the waveguides 11 and 12 is selected to insure efficient heating of the work piece passed therethrough, and to minimize the escape of electromagnetic energy to the surroundings. A length greater than t and, preferably, of about 3k, is satisfactory for common materials.
  • the multimode Waveguides 11 and 12 are excited to propagate electromagnetic waves by a multimode cavity resonator 13 of aluminum or other conductive material.
  • the size and configuration of the resonator 13 are selected so that a large number of different mode patterns can be excited therein.
  • a rectangular cavity resonator is employed having side walls 14 and 16, end walls 17 and 18, top wall 19, and bottom wall 21 secured together, as by heliarc welding, to define enclosure 22.
  • the height, width and depth dimensions of the enclosure 22 are made large compared to A, for example, approximately 10x x 3/ ⁇ x 7 and non-integral multiples of each other so as to maximize the number of difierent modes which can be excited therein.
  • the multimode waveguides 12 and 13 are secured to extend outward from the center of opposite resonator side walls 14 and 16.
  • the rectangular configuration of the cavity resonator 13 insures the presence of an electromagnetic field at the coextending axes of the cavity resonator 13 and waveguides 11 and 12.
  • Each of the resonator side walls 14 and 16 is provided with a circular aperture 23 at its center for communicating the cavity resonator 13 to the waveguides 11 and 12.
  • the cavity resonator 13 and waveguides 11 and 12 are constructed of thin aluminum sheets /3 inch thick.
  • an aluminum disc 26 A inch thick and 24 inches in diameter, is secured at each of the resonator side walls 14 and 1-6 by screws 27 which threadingly engage tapped holes in the side walls 14 and 16.
  • Each aluminum disc 26- defines an aperture 28 in registry with the aperture 23 of the side wall to which the disc 26 is secured.
  • Each pair of registered apertures 23 and 28 snugly receives one of the ends 31 and 32 of the open ended waveguides 11 and 12.
  • the waveguide ends 31 and 32 serve as coupling holes communicating the waveguides 11 and 12 to enclosure 22.
  • Each of the waveguides 11 and 12 are secured in place by four aluminum gussets 33, 4 inch thick, 12 inches long and 8 inches high. The gussets are secured to the discs 26 and Waveguides 11 and 12 by heliarc Welding.
  • end wall 17 is demountably fastened to the cavity resonator 13. As illustrated in FIGURE 1, end wall 17 is secured to the top, bottom and side walls of the cavity resonator 13 by screws 34 which threadingly engage the resonator walls to fasten the folded edge portion 36 of end wall 17 thereto.
  • the multimode cavity resonator 13 and waveguides 11 and 12 are excited by introducing electromagnetic energy into cavity resonator 13 at waveguide feed 37.
  • the waveguide feed 37 is positioned at least ) ⁇ /2 from the adjoining walls and at an angle of, for example, 45 with the adjoining walls.
  • mode stirring means 41 is provided to periodically change the electromagnetic field distribution in the multimode cavity resonator 13 and waveguides 11 and 12. Any of the various prior art techniques may be employed to accomplish the mode pattern changing.
  • one embodiment of the microwave heating applicator of the present invention preferably, employs a novel vaned mode stirrer 41 which serves both to change the field distribution and couple electromagnetic energy from the cavity resonator 13 to the multimode waveguides 11 and 12. More particularly, the vaned mode stirrer 41 comprises a plurality of circumferentially-spaced radially-extending generally-rectangular vanes 42-49 of 0.05 inch thick aluminum.
  • the vanes 42-49 are fastened at opposite ends thereof, for example, by heliarc welding, to axially spaced inch aluminum split rings 51 and 52 at regular circumferentially-spaced locations.
  • the split ring halves are demountably fastened together by nuts 53 and bolts 54.
  • the vaned mode stirrer 41 is rotatably mounted within the cavity resonator 13 to extend between the resonator side walls 14 and 16 in axial alignment with the multimode waveguide-s 11 and 12.
  • the inside diameter of the vaned mode stirrer 41 is adjusted to be equal to the diameter of the multimode circular waveguides 11 and 12.
  • each of the vanes 42-49 are provided with recesses 56 and 57 respectively along the inwardly facing edge 58 thereof.
  • the outer surfaces of the ends 31 and 32 of waveguides 11 and 12 facing recesses 56 and 57 define circumferential recesses 61 and 62 opposite recesses 56 and 57.
  • the vaned mode stirrer 41 is rotatably supported at the waveguide ends 31 and 32 by annular Teflon bushings 63 and 64 and are snugly seated in the recesses 56 and 57 to turn loosely in circumferential recesses 61 and 62.
  • Teflon is a trademark designating tetrafluoroethylene fluorocarbon resins.
  • the vaned mode stirrer 41 is spaced from the waveguide ends and cavity resonator by at least M4.
  • an inlet port 66 and air duct 60 are provided in the top wall 19 of the cavity resonator for coupling an air blower 65 (see FIG- URE 4) to direct an air flow against the vaned mode stirrer 41.
  • Other mechanical and electrical means can be employed to drive the vaned mode stirrer 41.
  • such means require either mechanically coupling through the cavity resonator walls or through the waveguides.
  • coupling through the cavity resonator walls creates arcing and energy loss problems, particularly at high power levels.
  • coupling through the waveguides requires surrounding the work piece with a hollow drive shaft.
  • the presence of such a drive shaft prevents any excess fluid that might be present from escaping the vicinity of the work piece whereas the open structure illustrated in the figures allows such fluid to escape.
  • the air flow drive means has the additional advantages of ventilating the cavity resonator 13 and, if hot air is used, aiding in the heating process as the work piece is being treated.
  • the electromagnetic field distribution within the cavity resonator 13 and waveguides 11 and 12 is periodically changed.
  • the periodic variation in the electromagnetic field distribution is controlled by the rate at.which the vaned mode stirrer 41 is rotated and the extent of the changes in the electrical shape of the enclosure 22 created by the revolving vaned mode stirrer 41.
  • the mode patterns coupled to the waveguides 11 and 12 are determined by the radial and longitudinal extent of the vanes and the chord distance between adjacent vanes of the vaned mode stirrer 41.
  • the radial extent of the vanes becomes a less critical factor on coupling of electromagnetic energy from the resonator 13 to the waveguides 11 and 12.
  • the electrical shape of the enclosure 22 as seen by the electromagnetic field established therein is made to assume a variety of forms.
  • the number of mode patterns which can be created in the enclosure 22 is increased significantly above the number that would be possible with a vaned mode stirrer having vanes of uniform radial extent.
  • vanes 42 and 46 were long, vanes 43, 45, 47 and 49 were A3). long, and vanes 44 and 48% long.
  • Such a vaned mode stirrer produces a periodic variation in the mode pattern of two cycles per revolution of the vaned mode stirrer 41.
  • the vaned mode stirrer 41 further serves to couple electromagnetic energy to excite the waveguides 11 and 12 to propagate electromagnetic waves.
  • the vaned mode stirrer 41 is rotated, the electromagnetic wave pattern established within and between the waveguides 11 and 12 is caused to rotate.
  • the period of revolution of the wave pattern is equal to the period of revolution of the mode stirrer 41 divided by number of cycles of variation in the lengths of the vanes comprising the vaned mode stirrer 41.
  • the chord length between adjacent vane-s of the vaned mode stirrer is made less than A the cutoff wavelength of the electromagnetic energy propagated between adjacent vanes.
  • the length is ⁇ /2.
  • traps 69 and 71 are mounted at each of the outer ends of the waveguides to absorb escaping radiation.
  • Each of the lossy wall waveguides 69 and 71 includes an aluminum waveguide 72 enclosing a coiled hose 73 for carrying water. The coiled hose is retained Within the waveguide 72 by end tabs 74.
  • the hoses 73 of each of the lossy wall waveguides 69 and 71 are serially connected by connecting hose 76.
  • a pump and reservoir (not shown) are connected between couplers 77 and 78 to circulate water through the serially connected hoses 73.
  • the lossy wall waveguides 69 and 71 are fastened in place by supporting bars 79 secured to gussets 33 and supporting strap 81 secured to the cavity resonator 13.
  • the outer end 68 of the Waveguide 12 and the outer end (not shown) of waveguide 11 respectively extend into the adjacent lossy wall waveguides 71 and 69 a distance of M4. It has been found that under normal operating conditions with an input of 20 kw. of applied power to the cavity resonator 13, fifty feet of common garden hose coiled into a length of two feet reduced the energy escaping from the waveguides 11 and 12 to substantially below the level of 10 mw/cm. which level has come to be accepted as the standard for a non-hazardous condition.
  • a microwave heating applicator constructed in accordance with FIGURES 1-3 was operated to cure a continuously moving epoxy impregnated fiber glass tube 82 having an outside diameter of 5 inches and a wall thickness of inch.
  • the dimensions of the multimode cavity resonator 13 were 18 inches wide, 48 inches high and 48 inches long.
  • Each of the multimode circular waveguides 11 and 12 were 16 inches long and had an inside diameter of 6 inches.
  • a klystron source 83 energized by a power supply 84 and operated at 2450 mc. to deliver 20 kw. of power to the cavity resonator 13 was coupled by waveguide 86 to waveguide feed 37.
  • the klystron source 83 could be coupled to the cavity resonator 13 through a directional coupler 87.
  • the directional coupler 87 would be coupled to a detector 88, e.g., a power meter, which responds to signals received therefrom to provide a signal to activate a relay 89 to deenergize the klystron source 83.
  • a detector 88 e.g., a power meter
  • the microwave heating applicator can be used to accomplish other types of microwave heating.
  • the applicator can be used to simultaneously dielectrically and inductively heat carbon, or if desired inductively heat conductors.
  • the microwave heating applicator has been found to be particularly adept at dielectric heating of materials.
  • the microwave heating applicator could be employed to heat stationary work pieces positioned within the Waveguides 11 and 12 and cavity resonator 13.
  • the outer ends 67 and 68 could be closed, for example, by a shorting piece or water load.
  • a plurality multimode cavity resonator could be coupled to the waveguide in a staged fashion if it is necessary to extend the heating time.
  • Such staged cavity resonators would be connected by waveguides sufficiently long, e.g., 3A, to prevent coupling between the staged cavity resonators.
  • the present invention is not intended to be limited except by the terms of the following claims.
  • a microwave heating applicator comprising at least one multimode cavity resonator adapted to receive electromagnetic energy from a source and excite nonpropagating electromagnetic field patterns in said cavity, a multimode waveguide coupled to receive electromagnetic energy from said multimode cavity resonator and establish propagating electromagnetic field patterns therein, and mode stirrer means within said cavity resonator for changing the electromagnetic field distribution within said cavity resonator and preferentially coupling selected ones of said modes [within said cavity to said multimode waveguide said .mode stirrer means being a vaned mode stirrer including a plurality of circumferentially spaced conductive vanes extending radially outward from and along the axis of said stirrer with the distance between the most proximate parts of adjacent vanes being no greater than Ac the cutoff wavelength of the applied electromagnetic energy propagated between said adjacent vanes.
  • said multimode waveguide includes first and second axiallyaligned waveguide sections, said waveguide sections coupled to said cavity resonator at opposite sides thereof.
  • a microwave heating applicator comprising at least one multimode cavity resonator adapted to receive electromagnetic energy from a source for exciting electromagnetic field patterns therein, a .multimode waveguide coupled to receive electromagnetic energy from said multimode cavity resonator for establishing electromagnetic field patterns therein, and means for changing the electromagnetic field distribution within said cavity resonator, said multimode Waveguide including first and second axially aligned waveguide sections, said waveguide sections coupled to said cavity resonator at opposite sides thereof, said means for changing the electromagnetic field distribution within said cavity resonator being a vaned mode stirrer including a plurality of circumferentially spaced conductive vanes extending outward from and along the axis of the vaned mode stirrer to define a space bounded by said vanes, said vaned mode stirrer being rotatably mounted within said cavity resonator to have said space bounded by said vanes in alignment with said axially-aligned waveguides to allow a work piece to pass through said space.
  • vanes are generally rectangular slats circumferentially spaced about a circular locus to radially extend from the axis of the vaned mode stirrer into said cavity resonator, said axis of said vaned mode stirrer aligned with the axes of said waveguide sections, and said vanes are circumferentially disposed to provide a periodic variation in the radial extent of the circularly disposed vanes.
  • chord distance between adjacent vanes is not greater than M2.
  • the applicator according to claim 10 further comprising means to direct an air flow against said vaned mode stirrer to rotate same.
  • the applicator according to claim 13 further comprising a lossy wall waveguide mounted at the end of said open ended waveguide sections distal said cavity resonator to absorb electromagnetic energy escaping from said waveguide sections.
  • the applicator according to claim 15 further comprising a lossy wall waveguide mounted at the end of said waveguide extending outside of said cavity resonator to absorb electromagnetic energy escaping from said waveguide end.
  • said lossy wall waveguide includes a tubular conductive member defining an inside surface, and a dielectric fluid conduit disposed along inside surface for conveying fluid for absorbing the electromagnetic energy escaping from said waveguide end.
  • said dielectric fluid conduit is a helically-coiled hose disposed in axial alignment within said tubular conductive mem ber.
  • a microwave applicator comprising a multimode cavity resonator adapted to receive electromagnetic energy from a source for exciting electromagnetic field patterns therein; and a vaned mode stirrer for rotation about an axis within said cavity resonator, said vaned mode stirrer comprising a slat radially displaced from said axis and extending outwardly from and in the direction of said axis, means for rotatably mounting said vaned mode stirrer about said axis within said cavity resonator, whereby said slat is moved through an annular path about said axis, and means for supporting a work piece in the space bounded by said annular path.
  • vaned mode stirrer includes slats of different dimensions in the outwardly-extending direction and each of which have a dimension in the direction of the axis of said vaned mode stirrer greater than 2.
  • the applicator according to claim 19 further comprising at least one waveguide mounted to receive and propagate electromagnetic energy from said multimode cavity resonator.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Constitution Of High-Frequency Heating (AREA)
US609525A 1967-01-16 1967-01-16 Microwave heating applicator Expired - Lifetime US3491222A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US60952567A 1967-01-16 1967-01-16

Publications (1)

Publication Number Publication Date
US3491222A true US3491222A (en) 1970-01-20

Family

ID=24441166

Family Applications (1)

Application Number Title Priority Date Filing Date
US609525A Expired - Lifetime US3491222A (en) 1967-01-16 1967-01-16 Microwave heating applicator

Country Status (4)

Country Link
US (1) US3491222A (fr)
DE (1) DE1615504A1 (fr)
FR (1) FR1551509A (fr)
GB (2) GB1221795A (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3626838A (en) * 1969-11-24 1971-12-14 Dorran Electronics Inc Continuous microwave grain cooker
US4341937A (en) * 1980-11-28 1982-07-27 General Electric Company Microwave oven cooking progress indicator
US20080302787A1 (en) * 2005-07-11 2008-12-11 William Robertson Cunningham Erskine Vessel, Heating Apparatus and Method of Heating a Feedstock

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2288958A1 (fr) * 1974-10-21 1976-05-21 Desmarquest & Cec Installation pour le traitement par zone de produits de forme allongee
KR0140461B1 (ko) * 1994-07-12 1998-06-01 김광호 전자렌지

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2909635A (en) * 1957-07-29 1959-10-20 Raytheon Co Electronic oven systems
US3263052A (en) * 1963-09-11 1966-07-26 Cryodry Corp Power distribution system for microwave process chambers
US3281568A (en) * 1963-11-12 1966-10-25 Thermowave Corp Oven control system
FR1476179A (fr) * 1966-04-15 1967-04-07 Atlas Werke Appareil de chauffage par énergie à haute fréquence
US3365562A (en) * 1962-12-17 1968-01-23 Cryodry Corp Apparatus and process for microwave treatment
US3439143A (en) * 1966-12-08 1969-04-15 Litton Precision Prod Inc Microwave oven having a mode stirrer located within the waveguide

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2909635A (en) * 1957-07-29 1959-10-20 Raytheon Co Electronic oven systems
US3365562A (en) * 1962-12-17 1968-01-23 Cryodry Corp Apparatus and process for microwave treatment
US3263052A (en) * 1963-09-11 1966-07-26 Cryodry Corp Power distribution system for microwave process chambers
US3281568A (en) * 1963-11-12 1966-10-25 Thermowave Corp Oven control system
FR1476179A (fr) * 1966-04-15 1967-04-07 Atlas Werke Appareil de chauffage par énergie à haute fréquence
US3439143A (en) * 1966-12-08 1969-04-15 Litton Precision Prod Inc Microwave oven having a mode stirrer located within the waveguide

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3626838A (en) * 1969-11-24 1971-12-14 Dorran Electronics Inc Continuous microwave grain cooker
US4341937A (en) * 1980-11-28 1982-07-27 General Electric Company Microwave oven cooking progress indicator
US20080302787A1 (en) * 2005-07-11 2008-12-11 William Robertson Cunningham Erskine Vessel, Heating Apparatus and Method of Heating a Feedstock

Also Published As

Publication number Publication date
DE1615504A1 (de) 1970-06-11
FR1551509A (fr) 1968-12-27
GB1221794A (en) 1971-02-10
GB1221795A (en) 1971-02-10

Similar Documents

Publication Publication Date Title
US5869817A (en) Tunable cavity microwave applicator
US3526737A (en) Microwave heating apparatus
US3715551A (en) Twisted waveguide applicator
US3478188A (en) Multimode cavity resonator with two coupling holes at wall corners
US3916137A (en) Multi-mode microwave cavity feed system
WO2010090120A9 (fr) Dispositif de chauffage par micro-ondes
US4406937A (en) Microwave device for the heat treatment of powdery or granular materials
US3431381A (en) Dual stirrer assembly
US4463239A (en) Rotating slot antenna arrangement for microwave oven
US3491222A (en) Microwave heating applicator
US3673370A (en) Microwave applicator system with cylindrical resonant cavity
US3462575A (en) Microwave heating device
US4684776A (en) Method and apparatus for uniform microwave bulk heating of thick viscous materials in a cavity
US3439143A (en) Microwave oven having a mode stirrer located within the waveguide
CN103650637B (zh) 微波加热装置
WO2013005438A1 (fr) Dispositif de chauffage par micro-ondes
US3521019A (en) Microwave heating cavity with a venetian blind mode stirrer
US2937259A (en) Ultra-high frequency heating apparatus
KR101104832B1 (ko) 마이크로파 에너지로의 소재 노출 장치
US3463894A (en) Microwave drying system using phase shifters
US3474212A (en) Multimode cavity resonator with triangular coupling holes
PL168000B1 (pl) Sposób i zespól do ogrzewania czynnika za posrednictwem pradu elektrycznegoo wysokiej czestotliwosci PL PL PL
US3430022A (en) Microwave oven
US3665142A (en) System for applying microwave energy to a lossy cylindrical object
US4185182A (en) Microwave oven apparatus