CA1113547A - Primary choke system for microwave oven - Google Patents
Primary choke system for microwave ovenInfo
- Publication number
- CA1113547A CA1113547A CA315,802A CA315802A CA1113547A CA 1113547 A CA1113547 A CA 1113547A CA 315802 A CA315802 A CA 315802A CA 1113547 A CA1113547 A CA 1113547A
- Authority
- CA
- Canada
- Prior art keywords
- seal
- oven
- microwave energy
- enclosure
- vapor
- 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
Links
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
- H05B6/76—Prevention of microwave leakage, e.g. door sealings
- H05B6/763—Microwave radiation seals for doors
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
- F24C15/00—Details
- F24C15/02—Doors specially adapted for stoves or ranges
- F24C15/021—Doors specially adapted for stoves or ranges sealings for doors or transparent panel
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Constitution Of High-Frequency Heating (AREA)
- Electric Ovens (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A self-cleaning combination electric heat and microwave oven em-ploying a common cavity for cooking food with microwave energy and/or elec-tric resistance heating having a door with a resilient heat seal and a two-part microwave energy seal in which a slotted choke structure is positioned between the heat seal and the oven interior with a secondary microwave energy seal being positioned between the heat seal and the outside of the oven.
A self-cleaning combination electric heat and microwave oven em-ploying a common cavity for cooking food with microwave energy and/or elec-tric resistance heating having a door with a resilient heat seal and a two-part microwave energy seal in which a slotted choke structure is positioned between the heat seal and the oven interior with a secondary microwave energy seal being positioned between the heat seal and the outside of the oven.
Description
Background of the Invention In the aforementioned copending application, there is disclosed a combination microwave oven using a rotating radiator for microwave energy. However, resistance heat from heating ele~ents positioned around the rotating radiator, for cooking or for self cleaning, requires a hot vapor seal; and hence, secondary microwave energy absorbing seals such as carbon loaded plastic or plastic filled on cover chokes will be too hot if placed before the vapor seal.
In addition, if a conventional high temperature vapor seal alone is used, it absorbs large amounts of microwave energy.
~3~`7 Summary of the Invention In accordance with this invention, there is provided a microwave energy seal for a high temperature oven in which a primary choke has a slotted wall and is positioned between a heat seal and the oven inte~ior.
More specifically, the slotted choke is inset into the periphery of the oven access aperture with the slots in a wall which is common to the choke section and the input trans-mission line extending between the interior of the oven and the choke section.
A second microwave energy seal is positioned between the heat seal and the outside of the oven.
In accordance with this invention, a food b~dy is positioned on a rack in the radiation patterns from-the rotating Tadiator so that a substantial portion of the micro-wave energy is absorbed on passing through the food body first time prior to Teflection from walls of the oven.
Therefore, high efficiency heating may be achieved with micro-wave energy even though the walls of the oven are made of inexpensive material such as enamelled steel 9 which also acts as a load to magnetron when a food body is absent to prevent the build-up of electric fields in the oven to a level where arcing could occur. In accordance with this invention, the magnetron may be tightly coupled to the oven through a coupling mechanism such as a waveguide and coaxial transition thereby increasing the efficiency of conversion of input power electrical energy to microwave energy coupled into the body to be heated.
~ore specifically, in the case of light loads OT if the oven is energizedS with no food body positioned therein, microwave energy radiation into the oven and refl~cted back to a multi-.
`7 port rotating radiator from the opposite wall such as the top wall of the oven will arrive at a comnlon junction such as the central conductor of a coaxial line transition with substantially different phases so that relatively low amounts of energy are coupled back into the magnetron and large portions of the energy are reflected back into the oven where the energy is absorbed by the walls of the oven.
This invention further discloses that when a high temperature micro-wave choke seal is placed between a high temperature vapor seal and the interior of a microwave oven such a choke will remain uncontaminated with condensed cooking vapors and may, hence, use air as the principle dielectric medium. In addition~ such a structure may be made of sheet steel coated with enamel.
In accordance with the present invention there is provided in com-bination: an enclosure having an interior supplied with microwave energy;
said enclosure having an access aperture and a closure member; mea~ns for pre-venting the escape of hot vapor from said enclosure between said closure member and the periphery of said aperture comprising a high temperature vapor seal; said high temperature vapor seal comprising a substantially resilient -conductive member covered with a substantially nonconductive layer resiliently and conformably contacting said periphery; and said sealing means further com-prising a microwave energy slotted choke cavity which is substantially filled with heated vapor from said enclosure and is positioned between the enclosure interior and said high temperature vapor seal with the input to said choke cavity being unobstructed by any vapor seal.
In accordance with the present invention there is also provided in combination: an enclosure having an access opening and a closure member;
means for supplying said enclosure with microwave energy from a source; a microwave energy sealing structure comprising wall regions of said access -opening and said closure member having an input transmission line section coupled between a choke section and the interior of said enclosure; said choke member at the point of coupling of said input transmission line to the interi-or of said enclosure being filled with vapor from said enclosure; said trans- -R
.. . .
mission line section providing a low impedance between said peripheral wall section and said closure section in the frequency range of said source while preventing coupling of energy from said input section into said choke section in modes propagating along said choke section around the periphery of said access opening; and a high temperature vapor seal of resilient conductive material covered with a layer of substantially insulating material which con-tacts regions of said wall and closure members.
In accordance with the present invention there is also provided a high temperature seal for microwave ovens comprising: portions of a microwave oven wall member and portions of a door for said oven; said portions being formed of conductive material and comprising a transmission line structure extending from the interior of said oven to a structure providing a high im- ~-pedance at the microwave frequency of said oven in a coupling region which contains heated vapor from said oven; a resilient high temperature vapor seal-ing structure contacting the wall of said oven and the periphery of said door adjacent said transmission line structure coupling region and formed of an outer layer of tubular woven insulating material supported on a tubular layer of woven wire mesh; and said transmission line structure providing means com-prising slots for inhibiting the transmission of microwave energy in said 20. transmission line structure around the periphery of said door.
~ :.
- 3a ~
S~ 7 In accordancc with thc present invention there is also provided in combination: an enclosure supplied with microwave energy having an access aperture and a closure member; means for vapor sealing said closure member to the periphery of said aperture comprising a hot vapor seal; a slotted choke microwave energy seal positioned between the oven interior and said hot vapor seal; and the cavity of said choke being substantially filled with vapor from said enclosure; means comprising a rotating primary radiator of said microwave energy positioned within said enclosure for simultaneously radiating a plurali-ty of separate patterns having different polarizations of said microwave energy into said enclosure.
- 3b - : .
3~
Brief Description of the Drawings Other and further objects and advantages of this invention will be apparent as the description thereof progresses reference being had to the accompanying drawings wherein:
FIG. 1 illustrates a partially broken away vertical sectional view of a combination microwave oven embodying the invention;
FIG. 2 illustrates a fragmentary transverse sectional . view of the door heat seal of FIG. 1 taken along line 2-2 of ~:IG. l;
FIG. 3 illustrates an expanded fragmenta~y ve~tical sectional view of the oven microwave seal of FIG. 1 taken along line 3-3 of FIG. 1.
PIG. 4 illustra~es an expanded transverse sectional view of the oven heat seal illustrated in FIG. 2 taken along line 4-4 of FIG. 2;
FIG. 5 illust'rates an expanded fTagmentary vertical sectional view of the door hinge and seal shown in FIG. 1; and FIG. 6 illustrates an expanded view of the woven microwave seal of FIG. 3.
: - 4 -3~s~`7 Description o the Preferred Embodiment Referring now to FIGS. 1 and 2, there is sholrn a microwave cavity 10 closed by a door 12 and supplied with microwave energy from a rotating radiator 14 in the bottom of the oven. Radiator 14 is fed l~ith microwave energy from a magnetron 16 through a waveguide 18 and a coaxial line 20 having a central conductor 22 rigidly connected to rotating radiator 14 and extending through waveguide 18 to a gear reduction motor 24.
Motor 24 is attached to the bottom of waveguide 18 and Totates central conductor 22 to rotate radiator 14. Coaxial line 20 has an outer conductor 26 r~igidly connec~ed to the upper wall of waveguide 18 and extending through the bottom wall of enclosure 10 into a plenum 28 in radiator 14.
As shown more specifically in FIG. 5, plenum 28 comprises an upper plate 30 connected to central conductor 22 and having a plurality of ports 32 therein spaced at different distances at the axis of conductor 22. Microwave energy is radiated from plenum 28 into the oven enclosuTe 10 through ports 32.
A lower plenum cover 38 of radiator 14, which prevents radiation of microwave energy radially outwardly and directs it through the ports 32, and the lower surface of cover 38 is positioned sufficiently above the bottom wall of enclosure 10 for radiator 14 to rotate freely. An aperture in cover 38 matches the upper end of outer coaxial conductor 26.
As in FIGS. 1 and 5, a substantially conical waveguide to coaxial line transition member 40 is formed with a slotted choke surrounding central conductor 22. Transition 40 exbends from the bottom wall upwardly along conductor 22 for distances equal to an effective electrical quarter wavelength at the frequency of magnetron 1~ so that it produces a choking action .
~ 7' to energy attempting to escape from waveguide 18 toward motor 24. A sleeve bearing 42 of dielectric materiàl is positioned between transition 40 and conductor 22 to insure against arcing in the bearing, and a metal thrust bearing 44 supports the lower end of shaft 22 with a reduced portion of shaft 22 extending through bearing 44 and connecting to the shaft of motor 24.
The ends of waveguide 18 are closed by shorting membeTs 46 which are positioned to provide impedance matching between the output probe 48 of magnetron 16 and central conductor 22 in accordance with well-known practice.
EneTgy reflected back to the ports 32, for example, from the top wall of the microwave cavity 10 will couple into the ports 32 dependent upon the polarization and will propagate t~ward the common junction at central conductor 22. However, as a result of the different distances that the waves travel from conductors 22 to ports 32, distance differences are double the length differences. The waves will arrive at central conductor 22 in different phases preferably selected so that substantial cancellation of the electrical field vector will occur thereby causing central conductor 22 to reflect such energy back through ports 32 into the cavity 10. As a result, a substantial isolation of the magnetron from reflected waves occurs. Furthermore, while this effect is preferably chosen to be maximized when the microwave cavity has no food body positioned therein and the geometry of the oven is fixed, substantial amounts of cancellation will occur for light loads such as small food bodies which do not absoTb substantially all the microwave radiation on the first pass of the microwave energy through the food body. Under these conditions it, therefore, is possible to couple magnetron `7 16 to the oven cavity 10 as tightly while maintaining low microwave energy field gradients and, hence, low wall losses in the waveguide 18. Such a match is achieved primarily by selecting the position of the waveguide end shorting members 46.
~ ven 10 is preferably made of relatively lossy or energy absorbing material which may absorb, for example, a few percent of microwave energy impinging thereon and reflecting therefrom. Such material may be, for example, conventional sheet steel used in conventional ovens and coated with conven- -tional enamel, which will withstand temperatures above 1,000F
in accordance with well-known practice.
~roiler and heating units 34 a~d 36 may be positioned adjacent the upper and lower walls of the cavity 10 held by conventional fastners 38 in accordance with well-known practice.
However, in the case of the heating unit 36, it preferably is formed in arcuate shape so that its closest portion is positioned around, and spaced from, the periphery of radiator 14 so as not to interfere with the pattern of microwave energy radiated therefrom.
Elements 34 and 36 extend through the back wall of cavity 10 and have the outer covering of the calrod unit grounded to the wall of ca~ity 10 ta avoid leakage of microwave energy at these points.
A food body 58 positioned, for example, on a rack 60 above radiator 14 in a dish 62 of material which is trans-parent to microwave energy such as pyroceram. Rack 60 may be9 ~or example, a welded wire rod having apertures substantially greater than ~/2 and adjustably supported at different levels in cavlty 10 by means of grooves 64 in the si~e walls of cavity 10 or in any other desired manner.
, . . , . . . ., . - .
~3;:s~ 7 Air from blower 50 is blown in a conventional manner through the cooling fins of magnetron 16 and then into oven 10, for example, through waveguide 18 via apertures 52 in shorting plates 46, transmission line 20, and the space between the bottom of enclosure 10 and the plate 38. The air circulates past calrod heater 36 to conduct that air past food body 58 during cooking. The air then exits through a canister 54 at the top of the oven to the center of a surface burner unit 56.
During the oven's self-cleaning cycle with food body 58 removed, the tempera~ure of the oven is raised to 750F-1,000F
by energizing calrod unit 36 to vaporize deposits on the wall of oven 10 and to blow the vapor out through heated canister 54 which may contain a catalyst to complete oxidation of the vapor in accordance with well-Xnown practice.
Door 12 has a heat seal 66, shown in greater detail in FIG. 4 as a tube o woven fiberglass 68 over a tubular w~ven spring steel mesh 70, positioned between the oven wall suTface and the door surface to prevent escape of hot gas from the oven.
~Ieat seals for self-cleaning ovens are well-known and are generally made of high temperature woven glass over a resilient material such as spring steel. While in accordance with this invention it has been found that such heat sealing structures can also substantially reduce leakage of microwave energy from an oven using both resistance heaters and microwave energy either together or sequentially, such a seal can produ~e arcing or pitting or can absorb excessive amounts of microwave energy.
In accordance with this invention, a microwave energy sealing structure 72 is positioned between the interior of the , 3~g 7 oven and the heat seal 66. A slotted choke microwave energy sealing structure 72 on door 12 prevents microwave energy from leaking out of oven 10 around the periphery of door 12. Choke structure 72 may be of the type described in patent number 3,767,884 by Osepchuk, et al, having an input section 74 coupled between the interior of the oven and a choke section 76 having a common slotted wall 78 to prevent peripheral transmission of micTowave energy around seal 72.
By the use of a slotted choke structure, leakage of microwave energy to heat seal 66 is further reduced over that encountered with a conventional unslotted choke stTucture and, hence, lleat seal 66 may be used, which is selected primarily for high temperature applications like conventional heat seals in self-cleaning ovens.
In accordance with this invention, as shown more specifically in FIG. 2, a second microwave energy sealing struct~re 80 is positioned outside the heat seal 66. Structure 80 comprises a second slotted choke made up of an output transmission line section 82 formed between a conductive edge 84 of door 12 and a slotted common wall 86 between said output-transmission line structure and a choke structure 88 coupled to said output transmission line structure 82 at a region 90 through a member 92 which is transparent to microwave energy. Coupling region 90 is also coupled back through transmission line section 94 to the heat seal 6S and, hence, to input transmission line section 74 of the microwave energy sealing structure 72.
Door 12, upon opening, swings downward on hinge 96 as shown in FIG. 1. Therefore, door edge 84 moves parallel to slotted wall member 86 covered by nylon member 92; and slotted wall member 78 moves parallel to the wall region 98 of the oven `7 enclosure 10 so that substantial motion of the top of the oven door, for example, by jiggling the handle can occur without microwave leakage. For example, the top of door 12 can open as much as a quarter of an inch so that interlock switches ~not shown) mechanically actuated by door movement can de-energize magnetron 16 prior to sufficient motion of the door to allow any substantial leakage of microwave energy from the ovsn.
As illustrated herein, a second microwave energy seal 80 is formed as a choke unit on each side of the oven door and an alternate foTm of secondary microwave energy seal structure 102 is used at the top and bottom of the door. ~eal structure 102 comprises a second resilient structure positioned between a surface 104 of the oven dooT and a surface 106 of the oven wall region adjacent the oven opening. As shown in greater detail in ~IG. 3, sealing structures 102 are positioned above and below the oven aperture closed by the door 12, and may be formed of tubular Tesilient elements made up of tubular spring mesh 108 to provide the resiliency covered by a woven ~ubular member 110 of a structure providing a conductive surface to the microwave energy and providing substantial microwave energy absorption to energy leaking through heat seal 66. More specifically, as shown in PIG. 6, an enlarged portion of the structure 108 comprises a plurality of threads having fiberglass cores 112 each individually wrapped with a ribbon of metal foil 114 such as stainless steel and then woven into tubular form. Such a structure has been found to absorb any stray microwave energy either of harmonics of the predominant microwave frequency exciting the oven 10 or a low level fundamental frequency or sidebands of the fundamental frequency. This absorbing effect ,~.
is particularly useful when used with wall members 104 and 106 of said steel as used in conventional ovens and coated with a thin ceramic 116 in accordance with conventional practice.
Coating 116, as shown in FIG. 4, also is used in the region of the high temperature seal and induces some microwave energy loss in this region.
Preferably, heat seal 66 extends around the oven door attached thereto by any desired means such as rivets or screws (not shown) but may, if desired, be attached to the oven wall member. Heat seal 66 appears as a relatively low impedance capacitive gap to microwave energy and is preferably placed as close as possible to the point of coupling of the input section 74 of seal 72 to the choke section 76. Such coupling region may, for example, be regarded as the region between the ends of the slotted common wall fingers 78 and the portion 118 of1 the door 12 which forms one wall of the choXe section 66. Such coupling region illustrated herein~ for example, at 120, is regarded as a high impedance region and the closely adjacent low impedance region of heat seal 66 may be regarded as in series with the high impedance region 120. From the foregoing it may be seen that an efficient high temperature combined microwave energy and vapor seal is provided for a combination oven which may be readily self-cleaned using any desired high temperature sel~-cleaning process. Self-cleaning may be carried out without damage to the microwave energy seals or coupling structures for supplying microwave energy from a magnetron to an oven.
Conventional oven skin of metal 122 may be provided surrounding the oven and decorative trim elements such as 124 and a control console 126 are provided in accordance with well-known prac~ice.
3~
In addition, a light 128 may be used to illuminate the interior of the oven 10 by positioning the light above the oven enclosure and shining it through a metal mesh 130 covered by a pyrex member 132 in the top wall of the oven.
This completes the description of the invention disclosed herein. However, many modifications thereof will be appaTent to peTsons of ordinary skill in the art without departing fTom the spiTit and scope of this invention. For example, microwave heating structures otheT than the rotating radiator 14 could be used; materials other than enamel-coated steel could be used foT the oven; and other sources of conventional heat such as hot air or gas burners could be used in place of the electrical heating units 34 and 36. Accordingly, it is intended that this invention be not limited by the particulaT details illustrated herein except as defined by the appended claims.
In addition, if a conventional high temperature vapor seal alone is used, it absorbs large amounts of microwave energy.
~3~`7 Summary of the Invention In accordance with this invention, there is provided a microwave energy seal for a high temperature oven in which a primary choke has a slotted wall and is positioned between a heat seal and the oven inte~ior.
More specifically, the slotted choke is inset into the periphery of the oven access aperture with the slots in a wall which is common to the choke section and the input trans-mission line extending between the interior of the oven and the choke section.
A second microwave energy seal is positioned between the heat seal and the outside of the oven.
In accordance with this invention, a food b~dy is positioned on a rack in the radiation patterns from-the rotating Tadiator so that a substantial portion of the micro-wave energy is absorbed on passing through the food body first time prior to Teflection from walls of the oven.
Therefore, high efficiency heating may be achieved with micro-wave energy even though the walls of the oven are made of inexpensive material such as enamelled steel 9 which also acts as a load to magnetron when a food body is absent to prevent the build-up of electric fields in the oven to a level where arcing could occur. In accordance with this invention, the magnetron may be tightly coupled to the oven through a coupling mechanism such as a waveguide and coaxial transition thereby increasing the efficiency of conversion of input power electrical energy to microwave energy coupled into the body to be heated.
~ore specifically, in the case of light loads OT if the oven is energizedS with no food body positioned therein, microwave energy radiation into the oven and refl~cted back to a multi-.
`7 port rotating radiator from the opposite wall such as the top wall of the oven will arrive at a comnlon junction such as the central conductor of a coaxial line transition with substantially different phases so that relatively low amounts of energy are coupled back into the magnetron and large portions of the energy are reflected back into the oven where the energy is absorbed by the walls of the oven.
This invention further discloses that when a high temperature micro-wave choke seal is placed between a high temperature vapor seal and the interior of a microwave oven such a choke will remain uncontaminated with condensed cooking vapors and may, hence, use air as the principle dielectric medium. In addition~ such a structure may be made of sheet steel coated with enamel.
In accordance with the present invention there is provided in com-bination: an enclosure having an interior supplied with microwave energy;
said enclosure having an access aperture and a closure member; mea~ns for pre-venting the escape of hot vapor from said enclosure between said closure member and the periphery of said aperture comprising a high temperature vapor seal; said high temperature vapor seal comprising a substantially resilient -conductive member covered with a substantially nonconductive layer resiliently and conformably contacting said periphery; and said sealing means further com-prising a microwave energy slotted choke cavity which is substantially filled with heated vapor from said enclosure and is positioned between the enclosure interior and said high temperature vapor seal with the input to said choke cavity being unobstructed by any vapor seal.
In accordance with the present invention there is also provided in combination: an enclosure having an access opening and a closure member;
means for supplying said enclosure with microwave energy from a source; a microwave energy sealing structure comprising wall regions of said access -opening and said closure member having an input transmission line section coupled between a choke section and the interior of said enclosure; said choke member at the point of coupling of said input transmission line to the interi-or of said enclosure being filled with vapor from said enclosure; said trans- -R
.. . .
mission line section providing a low impedance between said peripheral wall section and said closure section in the frequency range of said source while preventing coupling of energy from said input section into said choke section in modes propagating along said choke section around the periphery of said access opening; and a high temperature vapor seal of resilient conductive material covered with a layer of substantially insulating material which con-tacts regions of said wall and closure members.
In accordance with the present invention there is also provided a high temperature seal for microwave ovens comprising: portions of a microwave oven wall member and portions of a door for said oven; said portions being formed of conductive material and comprising a transmission line structure extending from the interior of said oven to a structure providing a high im- ~-pedance at the microwave frequency of said oven in a coupling region which contains heated vapor from said oven; a resilient high temperature vapor seal-ing structure contacting the wall of said oven and the periphery of said door adjacent said transmission line structure coupling region and formed of an outer layer of tubular woven insulating material supported on a tubular layer of woven wire mesh; and said transmission line structure providing means com-prising slots for inhibiting the transmission of microwave energy in said 20. transmission line structure around the periphery of said door.
~ :.
- 3a ~
S~ 7 In accordancc with thc present invention there is also provided in combination: an enclosure supplied with microwave energy having an access aperture and a closure member; means for vapor sealing said closure member to the periphery of said aperture comprising a hot vapor seal; a slotted choke microwave energy seal positioned between the oven interior and said hot vapor seal; and the cavity of said choke being substantially filled with vapor from said enclosure; means comprising a rotating primary radiator of said microwave energy positioned within said enclosure for simultaneously radiating a plurali-ty of separate patterns having different polarizations of said microwave energy into said enclosure.
- 3b - : .
3~
Brief Description of the Drawings Other and further objects and advantages of this invention will be apparent as the description thereof progresses reference being had to the accompanying drawings wherein:
FIG. 1 illustrates a partially broken away vertical sectional view of a combination microwave oven embodying the invention;
FIG. 2 illustrates a fragmentary transverse sectional . view of the door heat seal of FIG. 1 taken along line 2-2 of ~:IG. l;
FIG. 3 illustrates an expanded fragmenta~y ve~tical sectional view of the oven microwave seal of FIG. 1 taken along line 3-3 of FIG. 1.
PIG. 4 illustra~es an expanded transverse sectional view of the oven heat seal illustrated in FIG. 2 taken along line 4-4 of FIG. 2;
FIG. 5 illust'rates an expanded fTagmentary vertical sectional view of the door hinge and seal shown in FIG. 1; and FIG. 6 illustrates an expanded view of the woven microwave seal of FIG. 3.
: - 4 -3~s~`7 Description o the Preferred Embodiment Referring now to FIGS. 1 and 2, there is sholrn a microwave cavity 10 closed by a door 12 and supplied with microwave energy from a rotating radiator 14 in the bottom of the oven. Radiator 14 is fed l~ith microwave energy from a magnetron 16 through a waveguide 18 and a coaxial line 20 having a central conductor 22 rigidly connected to rotating radiator 14 and extending through waveguide 18 to a gear reduction motor 24.
Motor 24 is attached to the bottom of waveguide 18 and Totates central conductor 22 to rotate radiator 14. Coaxial line 20 has an outer conductor 26 r~igidly connec~ed to the upper wall of waveguide 18 and extending through the bottom wall of enclosure 10 into a plenum 28 in radiator 14.
As shown more specifically in FIG. 5, plenum 28 comprises an upper plate 30 connected to central conductor 22 and having a plurality of ports 32 therein spaced at different distances at the axis of conductor 22. Microwave energy is radiated from plenum 28 into the oven enclosuTe 10 through ports 32.
A lower plenum cover 38 of radiator 14, which prevents radiation of microwave energy radially outwardly and directs it through the ports 32, and the lower surface of cover 38 is positioned sufficiently above the bottom wall of enclosure 10 for radiator 14 to rotate freely. An aperture in cover 38 matches the upper end of outer coaxial conductor 26.
As in FIGS. 1 and 5, a substantially conical waveguide to coaxial line transition member 40 is formed with a slotted choke surrounding central conductor 22. Transition 40 exbends from the bottom wall upwardly along conductor 22 for distances equal to an effective electrical quarter wavelength at the frequency of magnetron 1~ so that it produces a choking action .
~ 7' to energy attempting to escape from waveguide 18 toward motor 24. A sleeve bearing 42 of dielectric materiàl is positioned between transition 40 and conductor 22 to insure against arcing in the bearing, and a metal thrust bearing 44 supports the lower end of shaft 22 with a reduced portion of shaft 22 extending through bearing 44 and connecting to the shaft of motor 24.
The ends of waveguide 18 are closed by shorting membeTs 46 which are positioned to provide impedance matching between the output probe 48 of magnetron 16 and central conductor 22 in accordance with well-known practice.
EneTgy reflected back to the ports 32, for example, from the top wall of the microwave cavity 10 will couple into the ports 32 dependent upon the polarization and will propagate t~ward the common junction at central conductor 22. However, as a result of the different distances that the waves travel from conductors 22 to ports 32, distance differences are double the length differences. The waves will arrive at central conductor 22 in different phases preferably selected so that substantial cancellation of the electrical field vector will occur thereby causing central conductor 22 to reflect such energy back through ports 32 into the cavity 10. As a result, a substantial isolation of the magnetron from reflected waves occurs. Furthermore, while this effect is preferably chosen to be maximized when the microwave cavity has no food body positioned therein and the geometry of the oven is fixed, substantial amounts of cancellation will occur for light loads such as small food bodies which do not absoTb substantially all the microwave radiation on the first pass of the microwave energy through the food body. Under these conditions it, therefore, is possible to couple magnetron `7 16 to the oven cavity 10 as tightly while maintaining low microwave energy field gradients and, hence, low wall losses in the waveguide 18. Such a match is achieved primarily by selecting the position of the waveguide end shorting members 46.
~ ven 10 is preferably made of relatively lossy or energy absorbing material which may absorb, for example, a few percent of microwave energy impinging thereon and reflecting therefrom. Such material may be, for example, conventional sheet steel used in conventional ovens and coated with conven- -tional enamel, which will withstand temperatures above 1,000F
in accordance with well-known practice.
~roiler and heating units 34 a~d 36 may be positioned adjacent the upper and lower walls of the cavity 10 held by conventional fastners 38 in accordance with well-known practice.
However, in the case of the heating unit 36, it preferably is formed in arcuate shape so that its closest portion is positioned around, and spaced from, the periphery of radiator 14 so as not to interfere with the pattern of microwave energy radiated therefrom.
Elements 34 and 36 extend through the back wall of cavity 10 and have the outer covering of the calrod unit grounded to the wall of ca~ity 10 ta avoid leakage of microwave energy at these points.
A food body 58 positioned, for example, on a rack 60 above radiator 14 in a dish 62 of material which is trans-parent to microwave energy such as pyroceram. Rack 60 may be9 ~or example, a welded wire rod having apertures substantially greater than ~/2 and adjustably supported at different levels in cavlty 10 by means of grooves 64 in the si~e walls of cavity 10 or in any other desired manner.
, . . , . . . ., . - .
~3;:s~ 7 Air from blower 50 is blown in a conventional manner through the cooling fins of magnetron 16 and then into oven 10, for example, through waveguide 18 via apertures 52 in shorting plates 46, transmission line 20, and the space between the bottom of enclosure 10 and the plate 38. The air circulates past calrod heater 36 to conduct that air past food body 58 during cooking. The air then exits through a canister 54 at the top of the oven to the center of a surface burner unit 56.
During the oven's self-cleaning cycle with food body 58 removed, the tempera~ure of the oven is raised to 750F-1,000F
by energizing calrod unit 36 to vaporize deposits on the wall of oven 10 and to blow the vapor out through heated canister 54 which may contain a catalyst to complete oxidation of the vapor in accordance with well-Xnown practice.
Door 12 has a heat seal 66, shown in greater detail in FIG. 4 as a tube o woven fiberglass 68 over a tubular w~ven spring steel mesh 70, positioned between the oven wall suTface and the door surface to prevent escape of hot gas from the oven.
~Ieat seals for self-cleaning ovens are well-known and are generally made of high temperature woven glass over a resilient material such as spring steel. While in accordance with this invention it has been found that such heat sealing structures can also substantially reduce leakage of microwave energy from an oven using both resistance heaters and microwave energy either together or sequentially, such a seal can produ~e arcing or pitting or can absorb excessive amounts of microwave energy.
In accordance with this invention, a microwave energy sealing structure 72 is positioned between the interior of the , 3~g 7 oven and the heat seal 66. A slotted choke microwave energy sealing structure 72 on door 12 prevents microwave energy from leaking out of oven 10 around the periphery of door 12. Choke structure 72 may be of the type described in patent number 3,767,884 by Osepchuk, et al, having an input section 74 coupled between the interior of the oven and a choke section 76 having a common slotted wall 78 to prevent peripheral transmission of micTowave energy around seal 72.
By the use of a slotted choke structure, leakage of microwave energy to heat seal 66 is further reduced over that encountered with a conventional unslotted choke stTucture and, hence, lleat seal 66 may be used, which is selected primarily for high temperature applications like conventional heat seals in self-cleaning ovens.
In accordance with this invention, as shown more specifically in FIG. 2, a second microwave energy sealing struct~re 80 is positioned outside the heat seal 66. Structure 80 comprises a second slotted choke made up of an output transmission line section 82 formed between a conductive edge 84 of door 12 and a slotted common wall 86 between said output-transmission line structure and a choke structure 88 coupled to said output transmission line structure 82 at a region 90 through a member 92 which is transparent to microwave energy. Coupling region 90 is also coupled back through transmission line section 94 to the heat seal 6S and, hence, to input transmission line section 74 of the microwave energy sealing structure 72.
Door 12, upon opening, swings downward on hinge 96 as shown in FIG. 1. Therefore, door edge 84 moves parallel to slotted wall member 86 covered by nylon member 92; and slotted wall member 78 moves parallel to the wall region 98 of the oven `7 enclosure 10 so that substantial motion of the top of the oven door, for example, by jiggling the handle can occur without microwave leakage. For example, the top of door 12 can open as much as a quarter of an inch so that interlock switches ~not shown) mechanically actuated by door movement can de-energize magnetron 16 prior to sufficient motion of the door to allow any substantial leakage of microwave energy from the ovsn.
As illustrated herein, a second microwave energy seal 80 is formed as a choke unit on each side of the oven door and an alternate foTm of secondary microwave energy seal structure 102 is used at the top and bottom of the door. ~eal structure 102 comprises a second resilient structure positioned between a surface 104 of the oven dooT and a surface 106 of the oven wall region adjacent the oven opening. As shown in greater detail in ~IG. 3, sealing structures 102 are positioned above and below the oven aperture closed by the door 12, and may be formed of tubular Tesilient elements made up of tubular spring mesh 108 to provide the resiliency covered by a woven ~ubular member 110 of a structure providing a conductive surface to the microwave energy and providing substantial microwave energy absorption to energy leaking through heat seal 66. More specifically, as shown in PIG. 6, an enlarged portion of the structure 108 comprises a plurality of threads having fiberglass cores 112 each individually wrapped with a ribbon of metal foil 114 such as stainless steel and then woven into tubular form. Such a structure has been found to absorb any stray microwave energy either of harmonics of the predominant microwave frequency exciting the oven 10 or a low level fundamental frequency or sidebands of the fundamental frequency. This absorbing effect ,~.
is particularly useful when used with wall members 104 and 106 of said steel as used in conventional ovens and coated with a thin ceramic 116 in accordance with conventional practice.
Coating 116, as shown in FIG. 4, also is used in the region of the high temperature seal and induces some microwave energy loss in this region.
Preferably, heat seal 66 extends around the oven door attached thereto by any desired means such as rivets or screws (not shown) but may, if desired, be attached to the oven wall member. Heat seal 66 appears as a relatively low impedance capacitive gap to microwave energy and is preferably placed as close as possible to the point of coupling of the input section 74 of seal 72 to the choke section 76. Such coupling region may, for example, be regarded as the region between the ends of the slotted common wall fingers 78 and the portion 118 of1 the door 12 which forms one wall of the choXe section 66. Such coupling region illustrated herein~ for example, at 120, is regarded as a high impedance region and the closely adjacent low impedance region of heat seal 66 may be regarded as in series with the high impedance region 120. From the foregoing it may be seen that an efficient high temperature combined microwave energy and vapor seal is provided for a combination oven which may be readily self-cleaned using any desired high temperature sel~-cleaning process. Self-cleaning may be carried out without damage to the microwave energy seals or coupling structures for supplying microwave energy from a magnetron to an oven.
Conventional oven skin of metal 122 may be provided surrounding the oven and decorative trim elements such as 124 and a control console 126 are provided in accordance with well-known prac~ice.
3~
In addition, a light 128 may be used to illuminate the interior of the oven 10 by positioning the light above the oven enclosure and shining it through a metal mesh 130 covered by a pyrex member 132 in the top wall of the oven.
This completes the description of the invention disclosed herein. However, many modifications thereof will be appaTent to peTsons of ordinary skill in the art without departing fTom the spiTit and scope of this invention. For example, microwave heating structures otheT than the rotating radiator 14 could be used; materials other than enamel-coated steel could be used foT the oven; and other sources of conventional heat such as hot air or gas burners could be used in place of the electrical heating units 34 and 36. Accordingly, it is intended that this invention be not limited by the particulaT details illustrated herein except as defined by the appended claims.
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In combination:
an enclosure having an interior supplied with microwave energy;
said enclosure having an access aperture and a closure member;
sealing means for preventing the escape of hot vapor from said enclosure between said closure member and the periphery of said aperture comprising a high temperature vapor seal;
said high temperature vapor seal comprising a substantially resil-ient conductive member covered with a substantially nonconductive layer resiliently and conformably contacting said periphery; and said sealing means further comprising a microwave energy slotted choke cavity which is substantially filled with heated vapor from said en-closure and is positioned between the enclosure interior and said high temper-ature vapor seal with the input to said choke cavity being unobstructed by any vapor seal.
an enclosure having an interior supplied with microwave energy;
said enclosure having an access aperture and a closure member;
sealing means for preventing the escape of hot vapor from said enclosure between said closure member and the periphery of said aperture comprising a high temperature vapor seal;
said high temperature vapor seal comprising a substantially resil-ient conductive member covered with a substantially nonconductive layer resiliently and conformably contacting said periphery; and said sealing means further comprising a microwave energy slotted choke cavity which is substantially filled with heated vapor from said en-closure and is positioned between the enclosure interior and said high temper-ature vapor seal with the input to said choke cavity being unobstructed by any vapor seal.
2. In combination:
an enclosure having an access opening and a closure member;
means for supplying said enclosure with microwave energy from a source;
a microwave energy sealing structure comprising wall regions of said access opening and said closure member having an input transmission line section coupled between a choke section and the interior of said enclosure;
said choke member at the point of coupling of said input transmission line to the interior of said enclosure being filled with vapor from said en-closure;
said transmission line section providing a low impedance between said peripheral wall section and said closure section in the frequency range of said source while preventing coupling of energy from said input section into said choke section in modes propagating along said choke section around the periphery of said access opening; and a high temperature vapor seal of resilient conductive material covered with a layer of substantially insulating material which contacts regions of said wall and closure members.
an enclosure having an access opening and a closure member;
means for supplying said enclosure with microwave energy from a source;
a microwave energy sealing structure comprising wall regions of said access opening and said closure member having an input transmission line section coupled between a choke section and the interior of said enclosure;
said choke member at the point of coupling of said input transmission line to the interior of said enclosure being filled with vapor from said en-closure;
said transmission line section providing a low impedance between said peripheral wall section and said closure section in the frequency range of said source while preventing coupling of energy from said input section into said choke section in modes propagating along said choke section around the periphery of said access opening; and a high temperature vapor seal of resilient conductive material covered with a layer of substantially insulating material which contacts regions of said wall and closure members.
3. The combination in accordance with Claim 2 wherein:
said vapor seal comprises tubular wire mesh covered with insulating material.
said vapor seal comprises tubular wire mesh covered with insulating material.
4. The combination in accordance with Claim 2 wherein:
said peripheral wall regions and regions of said closure member con-tacted by said resilient member are formed of cold-rolled steel coated with enamel.
said peripheral wall regions and regions of said closure member con-tacted by said resilient member are formed of cold-rolled steel coated with enamel.
5. The combination in accordance with Claim 2 wherein:
said oven is supplied with said microwave energy through a rotating multi-port radiating structure providing a plurality of simultaneous microwave energy primary radiation patterns which are cyclically moved within the interior of said oven.
said oven is supplied with said microwave energy through a rotating multi-port radiating structure providing a plurality of simultaneous microwave energy primary radiation patterns which are cyclically moved within the interior of said oven.
6. The combination in accordance with Claim 5 wherein:
a body to be heated is supported substantially directly into the paths of said radiation patterns.
a body to be heated is supported substantially directly into the paths of said radiation patterns.
7. A high temperature seal for microwave ovens comprising:
portions of a microwave oven wall member and portions of a door for said oven;
said portions being formed of conductive material and comprising a transmission line structure extending from the interior of said oven to a structure providing a high impedance at the microwave frequency of said oven in a coupling region which contains heated vapor from said oven;
a resilient high temperature vapor sealing structure contacting the wall of said oven and the periphery of said door adjacent said transmission line structure coupling region and formed of an outer layer of tubular woven insulating material supported on a tubular layer of woven wire mesh; and said transmission line structure providing means comprising slots for inhibiting the transmission of microwave energy in said transmission line structure around the periphery of said door.
portions of a microwave oven wall member and portions of a door for said oven;
said portions being formed of conductive material and comprising a transmission line structure extending from the interior of said oven to a structure providing a high impedance at the microwave frequency of said oven in a coupling region which contains heated vapor from said oven;
a resilient high temperature vapor sealing structure contacting the wall of said oven and the periphery of said door adjacent said transmission line structure coupling region and formed of an outer layer of tubular woven insulating material supported on a tubular layer of woven wire mesh; and said transmission line structure providing means comprising slots for inhibiting the transmission of microwave energy in said transmission line structure around the periphery of said door.
8. The seal in accordance with Claim 7 wherein:
said slots are positioned in said door structure and are spaced a-part by a distance of less than one half of a wavelength at the predominant frequency of said microwave energy.
said slots are positioned in said door structure and are spaced a-part by a distance of less than one half of a wavelength at the predominant frequency of said microwave energy.
9. The seal in accordance with Claim 8 wherein:
a second microwave choke seal is positioned outside said high temper-ature vapor seal.
a second microwave choke seal is positioned outside said high temper-ature vapor seal.
10. The seal in accordance with Claim 7 wherein:
a second microwave choke seal is coupled to the output of said vapor seal.
a second microwave choke seal is coupled to the output of said vapor seal.
11. The seal in accordance with Claim 10 wherein:
said second seal is provided with means for inhibiting the trans-mission of microwave energy at said frequency around the periphery of said door.
said second seal is provided with means for inhibiting the trans-mission of microwave energy at said frequency around the periphery of said door.
12. In combination:
an enclosure supplied with microwave energy having an access aper-ture and a closure member;
means for vapor sealing said closure member to the periphery of said aperture comprising a hot vapor seal;
a slotted choke microwave energy seal positioned between the oven interior and said hot vapor seal; and the cavity of said choke being substantially filled with vapor from said enclosure;
means comprising a rotating primary radiator of said microwave energy positioned within said enclosure for simultaneously radiating a plural-ity of separate patterns having different polarizations of said microwave energy into said enclosure.
an enclosure supplied with microwave energy having an access aper-ture and a closure member;
means for vapor sealing said closure member to the periphery of said aperture comprising a hot vapor seal;
a slotted choke microwave energy seal positioned between the oven interior and said hot vapor seal; and the cavity of said choke being substantially filled with vapor from said enclosure;
means comprising a rotating primary radiator of said microwave energy positioned within said enclosure for simultaneously radiating a plural-ity of separate patterns having different polarizations of said microwave energy into said enclosure.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US85510777A | 1977-11-25 | 1977-11-25 | |
| US855,107 | 1977-11-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1113547A true CA1113547A (en) | 1981-12-01 |
Family
ID=25320374
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA315,802A Expired CA1113547A (en) | 1977-11-25 | 1978-11-03 | Primary choke system for microwave oven |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5475643A (en) |
| AU (1) | AU518080B2 (en) |
| CA (1) | CA1113547A (en) |
| CH (1) | CH637794A5 (en) |
| DE (2) | DE2848658C2 (en) |
| FR (1) | FR2410224A1 (en) |
| NL (1) | NL7811594A (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2946767A1 (en) * | 1979-11-20 | 1981-06-11 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | COMBINED OVEN FOR MICROWAVE AND CONVENTIONAL RESISTANCE HEATING |
| JPS6116637Y2 (en) * | 1980-05-28 | 1986-05-22 | ||
| JPS5933793A (en) * | 1982-08-18 | 1984-02-23 | 松下電器産業株式会社 | High frequency heating device |
| NL8302366A (en) * | 1983-07-04 | 1985-02-01 | Hoogovens Groep Bv | FIRE-RESISTANT SEALING CORD. |
| DE3607557A1 (en) * | 1986-03-07 | 1987-12-23 | Bosch Siemens Hausgeraete | MICROWAVE OVEN |
| US6497953B1 (en) | 1998-10-09 | 2002-12-24 | Cabot Corporation | Polymeric fibers and spinning processes for making said polymeric fibers |
| DE102004003406A1 (en) * | 2004-01-23 | 2005-08-18 | Electrolux Schwanden Ag | A method for constructing a door for microwave ovens has an inner frame forming a quarter wavelength pocket around the opening and a smaller gap to the housing |
| DE102014201426A1 (en) | 2014-01-27 | 2015-07-30 | BSH Hausgeräte GmbH | Cooking appliance |
| DE102014107581A1 (en) * | 2014-05-28 | 2015-12-03 | Rational Aktiengesellschaft | Cooking device with microwave seal |
| DE102014112354A1 (en) | 2014-08-28 | 2016-03-03 | Miele & Cie. Kg | Cooking appliance |
| DE102015223022A1 (en) * | 2015-11-23 | 2017-05-24 | BSH Hausgeräte GmbH | Haushaltsgargerät |
| EP4543143A1 (en) * | 2023-10-20 | 2025-04-23 | Electrolux Appliances Aktiebolag | Oven door for a domestic oven having a microwave heating function |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1312486A (en) * | 1961-10-20 | 1962-12-21 | Cie Francaise De Micro Ondes | Microwave oven interference suppression devices |
| US3651300A (en) * | 1971-01-25 | 1972-03-21 | Matsushita Electric Industrial Co Ltd | Microwave heating apparatus with radiation control and monitoring |
| BE791916A (en) * | 1971-11-30 | 1973-03-16 | Raytheon Co | HIGH-FREQUENCY ENERGY HEATING APPLIANCE |
| US3812316A (en) * | 1973-03-28 | 1974-05-21 | Gen Electric | Door seal gasket for combined microwave and self-cleaning oven |
| ZA742105B (en) * | 1973-05-02 | 1975-03-26 | Amana Refrigeration Inc | Multilength microwave oven choketype energy seal |
| US3846608A (en) * | 1974-02-11 | 1974-11-05 | Litton Systems Inc | High temperature resistant door seal for a microwave oven |
| CA1030613A (en) * | 1974-06-14 | 1978-05-02 | Amana Refrigeration | Microwave energy oven seal |
| US4059742A (en) * | 1975-07-09 | 1977-11-22 | Litton Systems, Inc. | Microwave seal for combination cooking apparatus |
| US4013861A (en) * | 1975-08-13 | 1977-03-22 | The Frymaster Corporation | Microwave oven door seal |
| CA1118844A (en) * | 1977-11-02 | 1982-02-23 | Bernard J. Weiss | Combination microwave oven with a multi-port radiator |
| CA1114453A (en) * | 1977-11-25 | 1981-12-15 | Bernard J. Weiss | Combination microwave and resistively heated oven |
-
1978
- 1978-10-27 AU AU41127/78A patent/AU518080B2/en not_active Expired
- 1978-11-03 CA CA315,802A patent/CA1113547A/en not_active Expired
- 1978-11-09 DE DE19782848658 patent/DE2848658C2/en not_active Expired
- 1978-11-09 DE DE19787833340 patent/DE7833340U1/en not_active Expired
- 1978-11-09 JP JP13838878A patent/JPS5475643A/en active Pending
- 1978-11-22 CH CH1199778A patent/CH637794A5/en not_active IP Right Cessation
- 1978-11-24 NL NL7811594A patent/NL7811594A/en not_active Application Discontinuation
- 1978-11-24 FR FR7833200A patent/FR2410224A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| DE2848658C2 (en) | 1983-04-21 |
| AU518080B2 (en) | 1981-09-10 |
| NL7811594A (en) | 1979-05-29 |
| DE2848658A1 (en) | 1979-05-31 |
| AU4112778A (en) | 1980-05-01 |
| FR2410224A1 (en) | 1979-06-22 |
| CH637794A5 (en) | 1983-08-15 |
| DE7833340U1 (en) | 1980-04-17 |
| JPS5475643A (en) | 1979-06-16 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4410779A (en) | Combination microwave oven control system | |
| US4421968A (en) | Microwave oven having rotating conductive radiators | |
| CA1113547A (en) | Primary choke system for microwave oven | |
| AU619919B2 (en) | Improved microwave-powered heating device | |
| US4880952A (en) | Heat cooking oven having flat heater units on the outside of the walls thereof | |
| US3810248A (en) | Microwave heating apparatus | |
| US4342896A (en) | Radiating mode stirrer heating system | |
| US3974354A (en) | Microwave utensil with reflective surface handle | |
| CA2096893C (en) | Wave guide system of a microwave oven | |
| US2888543A (en) | Electronic heating apparatus | |
| US4358653A (en) | Combination microwave oven | |
| JPS6029840Y2 (en) | microwave heating device | |
| US2827537A (en) | Electronic heating apparatus | |
| CA1163682A (en) | Microwave oven feed system | |
| US4211910A (en) | High frequency heating apparatus with improved door arrangement | |
| CA1118844A (en) | Combination microwave oven with a multi-port radiator | |
| CA1125378A (en) | Combination microwave oven control system | |
| CA1134449A (en) | Microwave oven having rotating conductive radiators | |
| US4314127A (en) | Microwave oven with rotating multiport radiator | |
| US3364331A (en) | Energy distribution system | |
| US3562471A (en) | Microwave oven and antenna structure therefor | |
| CA1114453A (en) | Combination microwave and resistively heated oven | |
| US4412117A (en) | Microwave oven feed system | |
| CA1127720A (en) | Microwave heating apparatus with a z-shape waveguide | |
| CA1125380A (en) | Microwave heating apparatus with a thermally insulated tunnel |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |