CA1105567A - Radiating mode stirrer for microwave heating system - Google Patents
Radiating mode stirrer for microwave heating systemInfo
- Publication number
- CA1105567A CA1105567A CA291,677A CA291677A CA1105567A CA 1105567 A CA1105567 A CA 1105567A CA 291677 A CA291677 A CA 291677A CA 1105567 A CA1105567 A CA 1105567A
- Authority
- CA
- Canada
- Prior art keywords
- radiating
- accordance
- enclosure
- microwave energy
- energy
- 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
- 238000010438 heat treatment Methods 0.000 title claims abstract description 18
- 230000005855 radiation Effects 0.000 claims abstract description 21
- 239000004020 conductor Substances 0.000 claims description 13
- 230000005540 biological transmission Effects 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 6
- 230000010287 polarization Effects 0.000 claims description 5
- 230000005684 electric field Effects 0.000 claims description 3
- 238000003756 stirring Methods 0.000 description 18
- 235000013305 food Nutrition 0.000 description 6
- 238000010411 cooking Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000007664 blowing Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 101100257800 Ipomoea batatas WAXY gene Proteins 0.000 description 1
- 239000002196 Pyroceram Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 235000015220 hamburgers Nutrition 0.000 description 1
- 235000019692 hotdogs Nutrition 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 235000013372 meat Nutrition 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/64—Heating using microwaves
- H05B6/72—Radiators or antennas
- H05B6/725—Rotatable antennas
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/64—Heating using microwaves
- H05B6/647—Aspects related to microwave heating combined with other heating techniques
- H05B6/6482—Aspects related to microwave heating combined with other heating techniques combined with radiant heating, e.g. infrared heating
Abstract
Abstract of the Disclosure A microwave heating system having a rotary multiport microwave radiator positioned in a cavity and having radiating ports at different distances from the axis of rotation which direct overlapping radiation patterns at a body to be heated.
A combination heater may be used having a resistive heater positioned in regions around the outside of the rotary struc-ture to supply heat to the body.
A combination heater may be used having a resistive heater positioned in regions around the outside of the rotary struc-ture to supply heat to the body.
Description
11(~5567 Background of the Invention Microwave ovens have used cavities containing mode stir-ring structures to provide varying electric field patterns in the cooking area of the oven by introducing microwave energy into a cavity, which generally has interior dimensions large with respect to a wavelength of the microwave frequency, and moving conductive elements in the cavity to reflect the energy and vary the patterns so that points of maximum voltage gra-dients are continuously shifted in the cavity to more uniformly heat different sizes and shapes of bodies. Such a reflective mode stirrer, which is designed for one set of load conditions such as heating hamburgers or hot dogs, does not produce the same effectiveness in uniformly heating a large body such as a roast or a wide relatively planar body such as a pie.
Coaxial feeds of microwave energy into microwave heating cavities with mode stirrers rotating concentric with the feed have still provided that the mode stirring be by reflection from metal members moving with respect to the food body as shown, for example, in U.S. patent No. 3,436,507, issued on April 1, 1969 to H. A. Puschner.
'~' ll(~S567 Summary of the Invention The present invention provides for a mode stirrer in a microhave oven with microwave energy radiated directly into the oven cavity from a plurality of movable antenna regions in the mode stirring structure so that the electric field mode patter~s are varied predominantly by varying the position of the radia-tion patterns radiating from the antenna regions.
This invention further provides that the radiating antennae are ports in the mode stirring structure which are positioned within the cavity such that the radiation pattern of each of the ports covers a region wherein the body to be heated is placed, and such ports are moved with respect to said region so that a substantial portion of radiation is absorbed by the body to be heated without reflection from the cavity walls. More speci-fically, this invention provides that such radiation patterns are formed by ports rotating about a common axis at different distances from said axis, hence providing different toroidal re-gions of impingement on the body being heated. In addition, the radiating ports preferably are positioned along radii from the axis of rotation which are separated by substantially equal an-gles so that coupling and/or interference between the radiating beam patterns prior to impingement on reflecting walls of the oven is minimized. In addition, the radiating ports are prefera-bly oriented to produce substantial radiation parallel to said axis.
This invention further provides that such a radiation mode pattern provides a region outside the primary radiation pattern prior to reflection of the oven walls in which additional heating elements such as resistance heaters or flame burner structures may be positioned. More specifically, a resistance heating unit ~lass67 may be formed with a substantially arcuate shaped portion and be positioned below a mode stirring structure in the oven cavity and having a radius of curvature larger than the maximum distance from the axis of rotation of the mode stirring structure to trans-fer heat by radiation and/or convection through the air to a body to be heated without interfering with the primary radiation pat-terns of the mode stirring structure.
This invention further provides that air may be circulated within the oven by a blower or fan action of the mode stirring structure to assist in the transfer of heat by conduction through the air from the resistive heater and/or to assist in maintaining the oven substantially free of surface wall deposits from con-densed gases driven off from the body being heated.
This invention provides for a coaxial feed structure which rotates with respect to a body to be heated about an axis sub-stantially concentric with the coaxial feed while radiating mi-crowave energy in a direction predominantly parallel to said axis whereby annular rings of substantially equal energy radiation are produced concentric with said coaxial feed.
This invention further provides for supplying energy through said feed to a heating cavity having a reflective wall substan-tially perpendicular to said axis of rotation spaced from said radiating mode stirrer, with the ports of said stirrer being positioned at different distances from said axis whereby energy reflected from said wall substantially cancels upon re-entering said feed structure and, hence, is prevented from feeding back to the energy source. More specifically, this invention provides for positioning said ports on radii from said axis which are spaced apart by 120 degrees to form a three-phase radiating sys-tem, and the magnitude of the power radiated from each port is lla~s~7 chosen by choosing the dimensions of the radiating ports, with said radiating ports being at different distances along said radii whereby energy reflected from said surface returns to the coaxial radiator at different phases and amplitudes which substantially cancel.
In accordance with the invention there is provided a microwave heating system comprising: a conductive enclosure; a source of microwave energy; a primary radiating structure positioned in said enclosure and sup-plied with microwave energy from said source by an energy transmission structure comprising a conductive member extending through an aperture in a wall of said enclosure; and said radiating structure comprising means for simultaneously radiating a plurality of microwave energy primary radiation patterns having different polarizations from said structure toward a region in said enclosure containing a body to be he~ted while producing relative motion between said radiating~,structure and'said enclosure.
In accordance with another aspect of the invention there is pro-vided the method of supplying ~ rowave energy to a body comprising the steps of: supporting said body in a region of space; and supplying said region with microwave energy by simultaneously radiating a plurality of primary ra-diation patterns having different polarizations into said region from a com-mon source through means comprising a coaxial transmission line having a cen-tral conductor supporting means for producing said primary radiation patterns while moving said radiators with respect to said body, ll(~S567 Brief Description of the Drawings Other and further objects and advantages of the invention will become apparent as the description thereof progresses, reference being had to the accompanying drawings wherein:
Fig. 1 illustrates a vertical sectional view taken along line 1-1 of Fig. 2 of a microwave oven embodying the invention;
Fig. 2 illustrates a horizontal sectional view of the oven illustrated in Pig. 1 taken along line 2-2 of Fig. l;
Fig. 3 illustrates an enlarged view of the mode stirrer section of Fig. l;
Fig. 4 illustrates an enlarged detail of the mode stirrer section of Fig. 2; and Fig. 5 illustrates a further embodiment of the invention.
ll(~SS67 Description of the Preferred Embodiment Referring now to Figs. 1 and 2, there is shown a microwave oven 10 comprising a cooking enclosure 12 formed of metal and having a door 14 which closes an access opening in the enclosure 12.
Positioned in oven 10 is a microwave energy feed structure 16 comprising a flat plate structure 18 having slots 20 therein through which microwave energy radiates into the interior of the oven. A microwave feed cavity formed by a plate 22 positioned below plate 18 and connected to plate 18 by an outer wall mem-ber 24 is supplied with microwave energy by a coaxial line 26 whose outer conductor 28 is fixed with respect to the oven and whose inner conductor 30 extends outside the oven to a motor 32 which rotates feed structure 16 about an axis concentric with coaxial feed 26.
Outer conductor 28 of coaxial line 26 is connected to wave-guide 34 while inner conductor 30 extends through the waveguide 34 to feed microwave energy from the waveguide 34 through the feed structure 16 into the enclo~ure 12. Waveguide 34 is sup-plied with microwave energy from a magnetron 36 in accordancewith well-known practice.
As shown in detail in Figs. 3 ~ 4 impedance matching struc-tures 38 and 40 around coaxial feed 30 provide transitional im-pedance matching between the waveguide 34 and the coaxial line 26 and between the coaxial line 26 and the microwave feed struc-ture 30. Structure 38 also acts with conductor 30 as a choke to prevent microwave energy from leaking out toward motor 32.
The openings 20 are radiating antennae, also referred to as radiating ports, positioned at different distances from the axis of rotation of the structure i6 and are shown, for example, 11(~55ti7 as three openings oriented about said axis at lZ0-degree angles with respect to each other. The ports 20 are spaced from the axis of rotation 16, for example, by different dis-tances.
While distances of ports Z0 from said axis may be other than those shown~ such distances preferably differ by amounts which cause energy reflected from the opposite oven wall to cancel in the stirrer feed cavity due to out of phase summa-tion at the center conductor 30. In addition, the apertures 20 are preferably spaced at right angles to radii of the axis of rotation as elongated slots perpendicular to said radii, with the length of said slots being on the order of a wavelength of the energy and the width of the slots being less than a quarter wavelength of the energy so that the radiation from the slots will be in the TEM mode with the el-ectric lines parallel to the radii through the axis of rota-tion of the structure.
The power radiated from each port 20 is dependent on the width of that port, and any desired pattern can be achieved by selecting the port width. However, the radiating port furthest from the axis of rotation preferably radiates the most power. Also, the distance from the axis of rotation to the center of the innermost slot at the end of the slot is preferably nearly as great as the distance radially from the axis of rotation to the center of the closest portion of the next slot and, similarly, the distance of the end portions of the middle slot are less than the distance from the axis of rotation to the closest point of said furthest slot so that when the structure 16 rotates, the areas of the slots sweep out overlapping toroidal regions.
il~t5S67 A wire grill 46 having opening dimensions greater than a wave-length of said radiation is positioned above the radiating struc-ture 16. The position of grill 46 is adjustable by the structure 46 being slid in and out between bumps 48 and the side walls of the enclosure 12.
Positioned on support rack 46 is a dielectric plate 50 of, for example, pyroceram having a dielectric constant at the micro-wave frequency which is greater than unity and may be, for exam-ple, on the order of ten depending on the particular ceramic. Due to the difference in dielectric constant, the field pattern radia-ted from the slots 20 is caused to converge slightly into a food body 52 supported thereon. Food body 52, as shown, is supported in a dish 54 and may constitute, for example, a roast of meat or other food bodies to be heated or cooked.
Positioned around the outside of rotating feed 16 are resis-tive heating elements 56 and 58 which may be used before, after, or during the application of microwave energy to the food body 52.
Elements 56 and 58 may, for example, in a typical oven have a re-sistive heating capacity of one kilowatt per element and heat ~he oven and the body by radiation as well as by convection.
The motor 32 and feed structure 34 are positioned outside the enclosure 12 whose outside is preferably insulated, for example, by insulation 60 held in place by an outer oven skin 62. Therefore the waveguide structure 34 and coaxial oven feed are not overheated when the resistance heating elements are operating. ~n addition, cooling air is supplied by a blower 64 driven by an electric motor 66 which cools the anode of magnetron 36 by blowing air past fins on the magnetron and cools waveguide structure 34 by blowing air into waveguide structure 34 through apertures 68 in the waveguide structure ~lQSS67 34. A portion of the air is blown through the coaxial feed 26 and Ollt into the oven through ports 20 to aid in circuia-tion of the heat in the oven and to exhaust cooking gases through apertures 70 in the enclosure 12, such vapors being processed in a canister 72 in accordance with well-known practice so that the air exhausted from canister 72 may be exhausted directly into the kitchen.
Referring now to Fig. 5, there is shown a modification of the invention wherein two rotary feed mode stirring struc-tures are positioned in a microwave heating cavity 80. More specifically, microwave heating cavity 80 has a mode stirring, structure 82 positioned in the bottom thereof fed thro~gh the floor of the cavity by a coaxial line 84 and rotated by a central conductor 86 of the coaxial line driven by a motor 88 through a belt 90. An upper mode stirring structure 92 is similarly fed with microwave energy through a coaxial line 94 and rotated by central conductor 96 of coaxial line 94 whi,ch is driven by a motor 98 through a belt 100.
Mode stirring radiating structures 82 and 92 which are similar to structure 16 are rotated about a common axis in op-posite directions so that the field patterns radiating from the ports 20 in the faces 18 of the mode stirrers cross each other as the mode stirrers rotate thereby creating additional pattern variation. The port sizes and structures for the mode stirrer may be, for example, like those disclosed for Figs. 1, 2, 3 and 4. However, other sizes and shapes may be used.
Bodies to be heated 102 are preferably supported on a shelf 104 which is transparent to the radiated energy from stirrer 82 so that the bodies 102 are positioned substantially equidistant between the radiating mode stirrers 82 and 92, the bodies 102 11~}5Sti7 being inserted or removed from the cavity 80 through a door 106 having a microwave seal 108 between the periphery of the door and thc adjacent wall.
Microwave energy radiated into cavity 80 may be in the frequency range having a free space wavelength from one to 100 centimeters. For the batch processor shown herein as, 91S
megahertz is preferable while for smaller bodies 52, 2450 mega-hertz may be preferable. The microwave energy is supplied to upper and lower coaxial lines 94 and 84 through waveguide sec-tions 110 and 112, respectively, which are fed from a common microwave source 114, such as a magnetron, through a waveguide 116 and a T-section 118. In such a structure, microwave energy radiated, for example, from the upper mode stirring radiator 92 has a portion which passes through food bodies 102 without absorption to impinge on lower radiator 82 and a portion there-of is coupled bac~ through coaxial line 84 to the waveguide 110. However, since such energy on reaching the T section 118 will have only a fraction thereof coupled back to the magnetron 114 with the rest being coupled to the waveguide portion 110 and back to the mode stirring radiator 92, the isolation of the magnetron 114 from energy fed back rrom the cavity is greater than that which would occur if only one of the mode stirring radiators 82 and 92 were used. For this reason, the magnetron 114 may have its output coupled closer to the wave-guide 116 and hence closer to its maximum efficiency operating conditions without changes in the energy absorption produced by different points of the heating cycle of the load 102 or different loads, causing excess reflection of power to the mag-netron 114 which could damage the magnetron by overheating.
11(35567 While the magnetron 114 is shown herein as cooled by air from a blower 120, a water cooled magnetron could be used and, in any event, some of the air from the blower 10 is preferably co~pled into the waveguide 116 through ports 122 to be directed through the waveguides 110 and 112 and the coaxial lines 84 and 94 into the cavity 80 to carry away gases produced by the heating which are exhausted through an outlet canister 124.
This completes the description of the embodiments of the invention illustrated herein. However, many modifications thereof will be apparent to persons skilled in the art without departing from the spirit and scope of this invention. For example, the mode stirring radiators could be moved in paths other than circular, the feeds to the mode stirring structures could be other than coaxial lines such as, for example, wave-guides, and the structure could be used in continuous processing applications in which a conveyor belt moves bodies to be heated past the rotary mode stirring radiators. Accordingly, it is desired that this invention be not limited by the parti-cular details illustrated herein except as defined by the appended claims.
Coaxial feeds of microwave energy into microwave heating cavities with mode stirrers rotating concentric with the feed have still provided that the mode stirring be by reflection from metal members moving with respect to the food body as shown, for example, in U.S. patent No. 3,436,507, issued on April 1, 1969 to H. A. Puschner.
'~' ll(~S567 Summary of the Invention The present invention provides for a mode stirrer in a microhave oven with microwave energy radiated directly into the oven cavity from a plurality of movable antenna regions in the mode stirring structure so that the electric field mode patter~s are varied predominantly by varying the position of the radia-tion patterns radiating from the antenna regions.
This invention further provides that the radiating antennae are ports in the mode stirring structure which are positioned within the cavity such that the radiation pattern of each of the ports covers a region wherein the body to be heated is placed, and such ports are moved with respect to said region so that a substantial portion of radiation is absorbed by the body to be heated without reflection from the cavity walls. More speci-fically, this invention provides that such radiation patterns are formed by ports rotating about a common axis at different distances from said axis, hence providing different toroidal re-gions of impingement on the body being heated. In addition, the radiating ports preferably are positioned along radii from the axis of rotation which are separated by substantially equal an-gles so that coupling and/or interference between the radiating beam patterns prior to impingement on reflecting walls of the oven is minimized. In addition, the radiating ports are prefera-bly oriented to produce substantial radiation parallel to said axis.
This invention further provides that such a radiation mode pattern provides a region outside the primary radiation pattern prior to reflection of the oven walls in which additional heating elements such as resistance heaters or flame burner structures may be positioned. More specifically, a resistance heating unit ~lass67 may be formed with a substantially arcuate shaped portion and be positioned below a mode stirring structure in the oven cavity and having a radius of curvature larger than the maximum distance from the axis of rotation of the mode stirring structure to trans-fer heat by radiation and/or convection through the air to a body to be heated without interfering with the primary radiation pat-terns of the mode stirring structure.
This invention further provides that air may be circulated within the oven by a blower or fan action of the mode stirring structure to assist in the transfer of heat by conduction through the air from the resistive heater and/or to assist in maintaining the oven substantially free of surface wall deposits from con-densed gases driven off from the body being heated.
This invention provides for a coaxial feed structure which rotates with respect to a body to be heated about an axis sub-stantially concentric with the coaxial feed while radiating mi-crowave energy in a direction predominantly parallel to said axis whereby annular rings of substantially equal energy radiation are produced concentric with said coaxial feed.
This invention further provides for supplying energy through said feed to a heating cavity having a reflective wall substan-tially perpendicular to said axis of rotation spaced from said radiating mode stirrer, with the ports of said stirrer being positioned at different distances from said axis whereby energy reflected from said wall substantially cancels upon re-entering said feed structure and, hence, is prevented from feeding back to the energy source. More specifically, this invention provides for positioning said ports on radii from said axis which are spaced apart by 120 degrees to form a three-phase radiating sys-tem, and the magnitude of the power radiated from each port is lla~s~7 chosen by choosing the dimensions of the radiating ports, with said radiating ports being at different distances along said radii whereby energy reflected from said surface returns to the coaxial radiator at different phases and amplitudes which substantially cancel.
In accordance with the invention there is provided a microwave heating system comprising: a conductive enclosure; a source of microwave energy; a primary radiating structure positioned in said enclosure and sup-plied with microwave energy from said source by an energy transmission structure comprising a conductive member extending through an aperture in a wall of said enclosure; and said radiating structure comprising means for simultaneously radiating a plurality of microwave energy primary radiation patterns having different polarizations from said structure toward a region in said enclosure containing a body to be he~ted while producing relative motion between said radiating~,structure and'said enclosure.
In accordance with another aspect of the invention there is pro-vided the method of supplying ~ rowave energy to a body comprising the steps of: supporting said body in a region of space; and supplying said region with microwave energy by simultaneously radiating a plurality of primary ra-diation patterns having different polarizations into said region from a com-mon source through means comprising a coaxial transmission line having a cen-tral conductor supporting means for producing said primary radiation patterns while moving said radiators with respect to said body, ll(~S567 Brief Description of the Drawings Other and further objects and advantages of the invention will become apparent as the description thereof progresses, reference being had to the accompanying drawings wherein:
Fig. 1 illustrates a vertical sectional view taken along line 1-1 of Fig. 2 of a microwave oven embodying the invention;
Fig. 2 illustrates a horizontal sectional view of the oven illustrated in Pig. 1 taken along line 2-2 of Fig. l;
Fig. 3 illustrates an enlarged view of the mode stirrer section of Fig. l;
Fig. 4 illustrates an enlarged detail of the mode stirrer section of Fig. 2; and Fig. 5 illustrates a further embodiment of the invention.
ll(~SS67 Description of the Preferred Embodiment Referring now to Figs. 1 and 2, there is shown a microwave oven 10 comprising a cooking enclosure 12 formed of metal and having a door 14 which closes an access opening in the enclosure 12.
Positioned in oven 10 is a microwave energy feed structure 16 comprising a flat plate structure 18 having slots 20 therein through which microwave energy radiates into the interior of the oven. A microwave feed cavity formed by a plate 22 positioned below plate 18 and connected to plate 18 by an outer wall mem-ber 24 is supplied with microwave energy by a coaxial line 26 whose outer conductor 28 is fixed with respect to the oven and whose inner conductor 30 extends outside the oven to a motor 32 which rotates feed structure 16 about an axis concentric with coaxial feed 26.
Outer conductor 28 of coaxial line 26 is connected to wave-guide 34 while inner conductor 30 extends through the waveguide 34 to feed microwave energy from the waveguide 34 through the feed structure 16 into the enclo~ure 12. Waveguide 34 is sup-plied with microwave energy from a magnetron 36 in accordancewith well-known practice.
As shown in detail in Figs. 3 ~ 4 impedance matching struc-tures 38 and 40 around coaxial feed 30 provide transitional im-pedance matching between the waveguide 34 and the coaxial line 26 and between the coaxial line 26 and the microwave feed struc-ture 30. Structure 38 also acts with conductor 30 as a choke to prevent microwave energy from leaking out toward motor 32.
The openings 20 are radiating antennae, also referred to as radiating ports, positioned at different distances from the axis of rotation of the structure i6 and are shown, for example, 11(~55ti7 as three openings oriented about said axis at lZ0-degree angles with respect to each other. The ports 20 are spaced from the axis of rotation 16, for example, by different dis-tances.
While distances of ports Z0 from said axis may be other than those shown~ such distances preferably differ by amounts which cause energy reflected from the opposite oven wall to cancel in the stirrer feed cavity due to out of phase summa-tion at the center conductor 30. In addition, the apertures 20 are preferably spaced at right angles to radii of the axis of rotation as elongated slots perpendicular to said radii, with the length of said slots being on the order of a wavelength of the energy and the width of the slots being less than a quarter wavelength of the energy so that the radiation from the slots will be in the TEM mode with the el-ectric lines parallel to the radii through the axis of rota-tion of the structure.
The power radiated from each port 20 is dependent on the width of that port, and any desired pattern can be achieved by selecting the port width. However, the radiating port furthest from the axis of rotation preferably radiates the most power. Also, the distance from the axis of rotation to the center of the innermost slot at the end of the slot is preferably nearly as great as the distance radially from the axis of rotation to the center of the closest portion of the next slot and, similarly, the distance of the end portions of the middle slot are less than the distance from the axis of rotation to the closest point of said furthest slot so that when the structure 16 rotates, the areas of the slots sweep out overlapping toroidal regions.
il~t5S67 A wire grill 46 having opening dimensions greater than a wave-length of said radiation is positioned above the radiating struc-ture 16. The position of grill 46 is adjustable by the structure 46 being slid in and out between bumps 48 and the side walls of the enclosure 12.
Positioned on support rack 46 is a dielectric plate 50 of, for example, pyroceram having a dielectric constant at the micro-wave frequency which is greater than unity and may be, for exam-ple, on the order of ten depending on the particular ceramic. Due to the difference in dielectric constant, the field pattern radia-ted from the slots 20 is caused to converge slightly into a food body 52 supported thereon. Food body 52, as shown, is supported in a dish 54 and may constitute, for example, a roast of meat or other food bodies to be heated or cooked.
Positioned around the outside of rotating feed 16 are resis-tive heating elements 56 and 58 which may be used before, after, or during the application of microwave energy to the food body 52.
Elements 56 and 58 may, for example, in a typical oven have a re-sistive heating capacity of one kilowatt per element and heat ~he oven and the body by radiation as well as by convection.
The motor 32 and feed structure 34 are positioned outside the enclosure 12 whose outside is preferably insulated, for example, by insulation 60 held in place by an outer oven skin 62. Therefore the waveguide structure 34 and coaxial oven feed are not overheated when the resistance heating elements are operating. ~n addition, cooling air is supplied by a blower 64 driven by an electric motor 66 which cools the anode of magnetron 36 by blowing air past fins on the magnetron and cools waveguide structure 34 by blowing air into waveguide structure 34 through apertures 68 in the waveguide structure ~lQSS67 34. A portion of the air is blown through the coaxial feed 26 and Ollt into the oven through ports 20 to aid in circuia-tion of the heat in the oven and to exhaust cooking gases through apertures 70 in the enclosure 12, such vapors being processed in a canister 72 in accordance with well-known practice so that the air exhausted from canister 72 may be exhausted directly into the kitchen.
Referring now to Fig. 5, there is shown a modification of the invention wherein two rotary feed mode stirring struc-tures are positioned in a microwave heating cavity 80. More specifically, microwave heating cavity 80 has a mode stirring, structure 82 positioned in the bottom thereof fed thro~gh the floor of the cavity by a coaxial line 84 and rotated by a central conductor 86 of the coaxial line driven by a motor 88 through a belt 90. An upper mode stirring structure 92 is similarly fed with microwave energy through a coaxial line 94 and rotated by central conductor 96 of coaxial line 94 whi,ch is driven by a motor 98 through a belt 100.
Mode stirring radiating structures 82 and 92 which are similar to structure 16 are rotated about a common axis in op-posite directions so that the field patterns radiating from the ports 20 in the faces 18 of the mode stirrers cross each other as the mode stirrers rotate thereby creating additional pattern variation. The port sizes and structures for the mode stirrer may be, for example, like those disclosed for Figs. 1, 2, 3 and 4. However, other sizes and shapes may be used.
Bodies to be heated 102 are preferably supported on a shelf 104 which is transparent to the radiated energy from stirrer 82 so that the bodies 102 are positioned substantially equidistant between the radiating mode stirrers 82 and 92, the bodies 102 11~}5Sti7 being inserted or removed from the cavity 80 through a door 106 having a microwave seal 108 between the periphery of the door and thc adjacent wall.
Microwave energy radiated into cavity 80 may be in the frequency range having a free space wavelength from one to 100 centimeters. For the batch processor shown herein as, 91S
megahertz is preferable while for smaller bodies 52, 2450 mega-hertz may be preferable. The microwave energy is supplied to upper and lower coaxial lines 94 and 84 through waveguide sec-tions 110 and 112, respectively, which are fed from a common microwave source 114, such as a magnetron, through a waveguide 116 and a T-section 118. In such a structure, microwave energy radiated, for example, from the upper mode stirring radiator 92 has a portion which passes through food bodies 102 without absorption to impinge on lower radiator 82 and a portion there-of is coupled bac~ through coaxial line 84 to the waveguide 110. However, since such energy on reaching the T section 118 will have only a fraction thereof coupled back to the magnetron 114 with the rest being coupled to the waveguide portion 110 and back to the mode stirring radiator 92, the isolation of the magnetron 114 from energy fed back rrom the cavity is greater than that which would occur if only one of the mode stirring radiators 82 and 92 were used. For this reason, the magnetron 114 may have its output coupled closer to the wave-guide 116 and hence closer to its maximum efficiency operating conditions without changes in the energy absorption produced by different points of the heating cycle of the load 102 or different loads, causing excess reflection of power to the mag-netron 114 which could damage the magnetron by overheating.
11(35567 While the magnetron 114 is shown herein as cooled by air from a blower 120, a water cooled magnetron could be used and, in any event, some of the air from the blower 10 is preferably co~pled into the waveguide 116 through ports 122 to be directed through the waveguides 110 and 112 and the coaxial lines 84 and 94 into the cavity 80 to carry away gases produced by the heating which are exhausted through an outlet canister 124.
This completes the description of the embodiments of the invention illustrated herein. However, many modifications thereof will be apparent to persons skilled in the art without departing from the spirit and scope of this invention. For example, the mode stirring radiators could be moved in paths other than circular, the feeds to the mode stirring structures could be other than coaxial lines such as, for example, wave-guides, and the structure could be used in continuous processing applications in which a conveyor belt moves bodies to be heated past the rotary mode stirring radiators. Accordingly, it is desired that this invention be not limited by the parti-cular details illustrated herein except as defined by the appended claims.
Claims (14)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A microwave heating system comprising:
a conductive enclosure;
a source of microwave energy;
a primary radiating structure positioned in said enclosure and sup-plied with microwave energy from said source by an energy transmission struc-ture comprising a conductive member extending through an aperture in a wall of said enclosure; and said radiating structure comprising means for simultaneously radi-ating a plurality of microwave energy primary radiation patterns having different polarizations from said structure toward a region in said enclosure containing a body to be heated while producing relative motion between said radiating structure and said enclosure.
a conductive enclosure;
a source of microwave energy;
a primary radiating structure positioned in said enclosure and sup-plied with microwave energy from said source by an energy transmission struc-ture comprising a conductive member extending through an aperture in a wall of said enclosure; and said radiating structure comprising means for simultaneously radi-ating a plurality of microwave energy primary radiation patterns having different polarizations from said structure toward a region in said enclosure containing a body to be heated while producing relative motion between said radiating structure and said enclosure.
2. The system in accordance with Claim 1 wherein:
said structure comprises a plurality of radiators which rotate about a common axis extending longitudinally through said conductor.
said structure comprises a plurality of radiators which rotate about a common axis extending longitudinally through said conductor.
3. The system in accordance with Claim 1 wherein:
said radiators are supplied with said energy through means compris-ing a coaxial transmission line comprising said conductive member.
said radiators are supplied with said energy through means compris-ing a coaxial transmission line comprising said conductive member.
4. The system in accordance with Claim 2 wherein:
said radiating structure is supported by said conductive member which forms the central conductor of a coaxial line supplying microwave energy from said source to said radiating means.
said radiating structure is supported by said conductive member which forms the central conductor of a coaxial line supplying microwave energy from said source to said radiating means.
5. The method of supplying microwave energy to a body comprising the steps of:
supporting said body in a region of space; and supplying said region with microwave energy by simultaneously radi-ating a plurality of primary radiation patterns having different polarizations into said region from a common source through means comprising a coaxial transmission line having a central conductor supporting means for producing said primary radiation patterns while moving said radiators with respect to said body.
supporting said body in a region of space; and supplying said region with microwave energy by simultaneously radi-ating a plurality of primary radiation patterns having different polarizations into said region from a common source through means comprising a coaxial transmission line having a central conductor supporting means for producing said primary radiation patterns while moving said radiators with respect to said body.
6. The method in accordance with Claim 5 wherein:
said step of supplying said region comprises rotating said radiators about an axis through said body.
said step of supplying said region comprises rotating said radiators about an axis through said body.
7. The method in accordance with Claim 5 wherein:
said step of radiating said patterns into said region comprises supplying said energy through a coaxial transmission line to a rotary struc-ture containing said radiators.
said step of radiating said patterns into said region comprises supplying said energy through a coaxial transmission line to a rotary struc-ture containing said radiators.
8. The method in accordance with Claim 7 wherein:
said step of supplying said energy comprises supplying said coaxial transmission line with microwave energy from a magnetron.
said step of supplying said energy comprises supplying said coaxial transmission line with microwave energy from a magnetron.
9. The method in accordance with Claim 6 wherein:
said radiators are ports positioned at different distances from said axis of rotation.
said radiators are ports positioned at different distances from said axis of rotation.
10. In combination:
an enclosure containing means for supporting a body to be heated;
means comprising a conductor extending through an aperture in said enclosure for simultaneously radiating directional microwave energy primary radiation patterns having different electric field polarizations toward said body from a plurality of regions simultaneously supplied with microwave energy from a common source; and means for moving said regions with respect to said enclosure.
an enclosure containing means for supporting a body to be heated;
means comprising a conductor extending through an aperture in said enclosure for simultaneously radiating directional microwave energy primary radiation patterns having different electric field polarizations toward said body from a plurality of regions simultaneously supplied with microwave energy from a common source; and means for moving said regions with respect to said enclosure.
11. The combination in accordance with Claim 10 wherein:
said supporting means comprises a dielectric member.
said supporting means comprises a dielectric member.
12. The combination in accordance with Claim 10 wherein:
said radiating means is positioned below said supporting means.
said radiating means is positioned below said supporting means.
13. The combination in accordance with Claim 10 wherein:
said enclosure contains resistive heating means spaced from said supporting means and positioned around said radiating means.
said enclosure contains resistive heating means spaced from said supporting means and positioned around said radiating means.
14. The combination in accordance with Claim 10 wherein:
said body supporting means is positioned in the direct radiation patterns of said radiating means.
said body supporting means is positioned in the direct radiation patterns of said radiating means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA370,448A CA1114455A (en) | 1976-12-23 | 1981-02-09 | Radiating mode stirrer heating system |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US75406476A | 1976-12-23 | 1976-12-23 | |
| US754,064 | 1976-12-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1105567A true CA1105567A (en) | 1981-07-21 |
Family
ID=25033347
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA291,677A Expired CA1105567A (en) | 1976-12-23 | 1977-11-24 | Radiating mode stirrer for microwave heating system |
Country Status (5)
| Country | Link |
|---|---|
| JP (2) | JPS5380037A (en) |
| CA (1) | CA1105567A (en) |
| DE (2) | DE2757710C2 (en) |
| FR (1) | FR2375791A1 (en) |
| GB (1) | GB1591140A (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE415317B (en) * | 1978-01-02 | 1980-09-22 | Husqvarna Ab | MICROWAVE HEATER FOR TREATING A DISCOVERED, Aqueous Container |
| CA1125378A (en) * | 1978-04-03 | 1982-06-08 | Bernard J. Weiss | Combination microwave oven control system |
| CA1134449A (en) * | 1978-12-01 | 1982-10-26 | John M. Osepchuk | Microwave oven having rotating conductive radiators |
| US4421968A (en) * | 1978-12-01 | 1983-12-20 | Raytheon Company | Microwave oven having rotating conductive radiators |
| US4392038A (en) * | 1979-01-16 | 1983-07-05 | Raytheon Company | Self-cleaning microwave convection oven |
| US4350859A (en) * | 1980-05-05 | 1982-09-21 | Raytheon Company | Microwave oven feed system |
| DE3024178C2 (en) * | 1980-06-27 | 1982-10-14 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Microwave heating device |
| US4430538A (en) | 1980-08-28 | 1984-02-07 | Tokyo Shibaura Denki Kabushiki Kaisha | High-frequency heating device |
| US4431889A (en) * | 1981-11-09 | 1984-02-14 | Raytheon Company | Combination microwave and convection oven |
| JPS58112298A (en) * | 1981-12-25 | 1983-07-04 | 松下電器産業株式会社 | High frequency heater |
| US4458126A (en) * | 1982-03-30 | 1984-07-03 | General Electric Company | Microwave oven with dual feed excitation system |
| JPS58169793A (en) * | 1982-03-30 | 1983-10-06 | 松下電器産業株式会社 | High frequency heater |
| CA1262374A (en) * | 1985-06-24 | 1989-10-17 | Ryuji Igarashi | High-frequency heating apparatus having a rotating waveguide |
| DE3738267A1 (en) * | 1987-11-11 | 1989-05-24 | Miele & Cie | Microwave oven |
| DE3742375A1 (en) * | 1987-12-14 | 1989-06-22 | Bosch Siemens Hausgeraete | Oven with a cooking chamber which can be closed by an oven door, for cooking food |
| IT1236295B (en) * | 1989-11-29 | 1993-02-02 | Zanussi Grandi Impianti Spa | COMBINED MICROWAVE COOKING OVEN AND FORCED CONVENTION |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2912554A (en) * | 1959-04-03 | 1959-11-10 | Gen Electric | Electronic oven shelf arrangement |
| GB977777A (en) * | 1962-02-02 | 1964-12-16 | Lyons & Co Ltd J | Improvements in or relating to radio frequency ovens |
| US3536507A (en) * | 1968-02-08 | 1970-10-27 | Raymond E Davis | Hydraulic cementitious mixtures |
| JPS4837532B1 (en) * | 1969-12-01 | 1973-11-12 | ||
| US3746823A (en) * | 1972-02-28 | 1973-07-17 | L Whiteley | Electronic cooking appliance |
| SE369026B (en) * | 1973-03-07 | 1974-07-29 | Husqvarna Vapenfabriks Ab | |
| GB1439260A (en) * | 1973-07-13 | 1976-06-16 | Modern Electronic Products Inc | Electronic cooking appliance |
| US3867605A (en) * | 1973-08-06 | 1975-02-18 | Welbuilt Corp | Microwave oven |
| US4121078A (en) * | 1975-04-30 | 1978-10-17 | Matsushita Electric Industrial Co., Ltd. | Microwave heating apparatus |
| GB1543980A (en) * | 1975-05-19 | 1979-04-11 | Matsushita Electric Ind Co Ltd | Microwave heating apparatus |
| CA1118844A (en) * | 1977-11-02 | 1982-02-23 | Bernard J. Weiss | Combination microwave oven with a multi-port radiator |
-
1977
- 1977-11-24 CA CA291,677A patent/CA1105567A/en not_active Expired
- 1977-12-12 GB GB5166177A patent/GB1591140A/en not_active Expired
- 1977-12-23 FR FR7739078A patent/FR2375791A1/en active Granted
- 1977-12-23 JP JP15546577A patent/JPS5380037A/en active Pending
- 1977-12-23 DE DE19772757710 patent/DE2757710C2/en not_active Expired
- 1977-12-23 DE DE19777739400 patent/DE7739400U1/en not_active Expired
-
1984
- 1984-05-28 JP JP7854384U patent/JPS6029840Y2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| FR2375791B1 (en) | 1984-04-27 |
| GB1591140A (en) | 1981-06-17 |
| FR2375791A1 (en) | 1978-07-21 |
| JPS5380037A (en) | 1978-07-15 |
| DE7739400U1 (en) | 1980-04-24 |
| DE2757710C2 (en) | 1983-12-22 |
| DE2757710A1 (en) | 1978-06-29 |
| JPS6029840Y2 (en) | 1985-09-07 |
| JPS6019192U (en) | 1985-02-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |