CA1138533A - Microwave and convection oven - Google Patents
Microwave and convection ovenInfo
- Publication number
- CA1138533A CA1138533A CA000337966A CA337966A CA1138533A CA 1138533 A CA1138533 A CA 1138533A CA 000337966 A CA000337966 A CA 000337966A CA 337966 A CA337966 A CA 337966A CA 1138533 A CA1138533 A CA 1138533A
- Authority
- CA
- Canada
- Prior art keywords
- oven
- enclosure
- vapor
- microwave energy
- microwave
- 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
- H05B6/6408—Supports or covers specially adapted for use in microwave heating apparatus
- H05B6/6411—Supports or covers specially adapted for use in microwave heating apparatus the supports being rotated
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- 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
- F24C15/32—Arrangements of ducts for hot gases, e.g. in or around baking ovens
- F24C15/322—Arrangements of ducts for hot gases, e.g. in or around baking ovens with forced circulation
-
- 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
- H05B6/6473—Aspects related to microwave heating combined with other heating techniques combined with convection heating
-
- 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
Abstract
ABSTRACT OF THE DISCLOSURE
A combined microwave and convection heating oven in which microwave energy is prevented from escaping from the oven into the region where the va-por, which is circulated through the oven, is heated by the products of com-bustion from a gas burner.
A combined microwave and convection heating oven in which microwave energy is prevented from escaping from the oven into the region where the va-por, which is circulated through the oven, is heated by the products of com-bustion from a gas burner.
Description
Background of the Invention In microwave ovens, such as shown in Canadian Patent 1,125,378, January 8, 1982, B. J. Weiss, microwave heating is supplemented by auxilliary means such as an electric heating element positioned in the oven. However, if gas burners are positioned in the oven in place of the electric resistance heaters, it has been discovered that the microwave heating efficiency is very substantially reduced since the microwave energy is absorbed by the gas flame.
In addition, for cooking pattern uniformity it is desirable that there be no auxilliary heating units in the cavity which can alter the pat-tern of the modes in the cavity to reduce microwave heating pattern un;form-ity.
If auxilliary gas heating means is positioned in a separate region from the oven and vapor heated thereby is then circulated through the oven, microwave energy may be coupled from the oven into the separate region and may be absorbed by the gas flame. Microwave energy absorbed by the gas flame in the separate region thereby rèduces the overall microwave oven efficiency.
Summary of the Invention This invention provides for a combined convection and micro-wave oven in which the microwave energy is couplèd into a conduc-tive enclosure while vapor is blown into the oven enclosure through means for preventing escape of microwave energy from the enclosure.
More particularly, the vapor may be the products of combustion from a gas fired burner. Such products of combustion are circulated through the oven by a circulating blower through oven inlet and outlet regions. In accordance with this invention, both the inlet and outlet regions are formed of a plurality of apertures whose diameters are less than a half wavelength of the free space wavelength of the microwave energy and preferabIy less than a tenth of a wavelength of said microwave energy.
Preferably, microwave energy is fed into the enclosure from a different wall than that through which heated vapor is blown into the oven. More particularly in accordance with this invention a microwave oven has the microwave energy fed into the oven enclosure through the bottom wall. Preferably, the microwave energy is radiated through a rotating radiator in the enclosure. The radiato may provide a plurality of separate directive radiation patterns in the enclosure which are moved by rotation of said radiator and which are directed toward a body to be heated. The rotating radiatt is preferably covered with a transparent ceramic cover and the body to be heated positioned on a support rack above the radiator. The vapor heated by the products of combustion i5 directed into the ove by the ~lower through a region either in the upp`er rear wall in one embodiment of the invention or through a region in the top wall in another embodiment of the invention and vapor is withdrawn from the oven through a region in the lower portion of the enclosur~
In accordance with the present invention, there is provided in combination: a conductive enclosure; means for supplying said enclosure with microwave energy, and means for blowing a heated vapor into said enclosure through means which prevents the escape of microwave energy from said enclosure.
In accordance with the present invention, there is further provided a microwave oven comprising: a conductive enclosure having an access opening and a closure member, a seal for said closure member comprising a microwave choke section and a vapor seal section; means for directing separate patterns of microwave energy into said enclosure through a rotating radiator; and means for blowing a vapor heated by the products of combustion from a burner into said oven through means which prevents the escape of microwave energy from said enclosure.
In accordance with the present invention, there is further provided an oven system comprising: a conductive enclosure having an access opening and a closure member; means for supplying said enclosure with microwave energy and a seal for said closure member; and a burner and means for recirculating heated vapor comprising the products of combustion from said burner through said oven through means for preventing escape of said microwave energy into a region in which said vapor is heated while exhausting from said system a por-tion of the vapor passing through said circulating means, said recirculating means including means for blowing heated vapor into said enclosure through said means for preventing escape of said microwave energy.
In accordance with the present invention, there is further provided a microwave oven comprising: a conductive enclosure having an access opening and a closure member, a seal for said closure member comprising a microwave choke section and a vapor seal section; means for supplying said enclosure with microwave energy; means for recirculating heated vapor through said oven and a vapor heating region including means for blowing said heated vapor into said oven through means for preventing microwave energy in said enclosure from entering said vapor heating region; said oven and said vapor heating region ~eing separated by said means for preventing the escape of microwave energy from said oven into said recirculating means.
-~ - 2a -113~S33 Brief Description of the Drawings Other and further embodiments of ~he invention will become apparent as the description thereof progresses, reference being had to the accompanying drawings wherein:
FIG. 1 illustrates a partially broken away side elevation view of an oven embodying the invention;
FIG~ 2 illustrates a transverse sectional view of the micro-wave radiator structure of FIG. 1 taken along line 2-2 of FIG. l;
FIG~ 3 illustrates a transverse sectional view of a blower portion of the oven of FIG. 1 taken along line 3-3 of FIG. 1.
FIG. 4 illustrates a sectional view of the burner portion of the oven of FIG. 1 taken along line 3-3 of FIG. 1 and showing burner details;
FIG. 5 illustrates a vertical sectional view of an oven illus-trating an alternate embodiment of the invention; and FIG. 6 is a transverse sectional view of the burner and blower portion of the oven of FIG. 5 taken along line 6-6 of FIG. 5.
Description of the Preferred Embodiment Referring now to FIG.'s l through 4 there is shown a combi-nation gas convection and microwave stove 10 comprising an oven cavity 12 closed by a door 14.
Cavity 12 has elongated inlet region 16 through which heated vapor is directed into the oven 12. In accordance with this invention inlet region 16 provides means comprising apertures 20 for preventing the escape of microwave energy from cavity 12 and is preferably located in the back wall of the oven adjacent the top oven wall so that the hottest vapor enters adjacent to the top of the oven. Two vapor outlet regions 13 in approximately the middle of the back wall of oven 12 contain apertures 20 for preventing the escape of microwave energy and through which the vapor is drawn out of the oven. Apertures 2~ preferably have maximum dimension which are less than a half wavelength of the free space wavelength of the microwave energy radiated into cavity 12, and preferably are holes whose diameters are less than a tenth of the free space wavelength of the microwave energy.
Microwave energy is fed into oven cavity 12, which is a conductive enclosure, by a rotating.radiator 22 which may comprise, for example., a plenum 24 whose upper surface is a plate 26 which contains a plurality of apertures 28 through which microwave energy is radiated upwardly into enclosure 12. A
central conductor 30 of a coaxial line 32 supports plenum 24 by being attached to the center of plate 26. Conductor 30 extends downwardly from the lower end of coaxial line 32, through a waveguide 34, and through a microwave choke 36 having bearing assembly 38. An extension of conductor 30 is connected to motor 40 below waveguide 34 which rotates radiator 22 through central conductor 30.
Microwave energy from a magnetron 42 is fed through waveguide 34, coaxial line 32, and plenum 24 to be radiated upwardly from slots 28 into enclosure 12 as a plurality of separate directive radiation patterns. A
cover 44 of microwave transparent material is supported over radiator 22 on bumps 46 on the bottom of enclosure 12 to prevent food juices or other ma-terial from being dropped on radiator 22.
Door 14 contains a microwave choke region surrounded by a high tem-perature vapor seal so that most of the microwave energy is prevented from being absorbed from the high temperature vapor seal. However, microwave en-ergy passing through the choke section is substantially absorbed by the hightemperature vapor seal thereby preventing stray radiation from the oven.
In accordance with this invention circulation of vapor through en-closure 12 is produced by centrifugal blowers 48 which draw vapor out of cav-ity 12 through apertures 20 in regions 18 and blows it into plenums 50 sur-rounding blowers 48 supplying apertures 20. The upper ends of plenums 50 have an opening to a vent 52 through which a small portion of the output of blowers 48 is blown and is mixed with the air blown by a second set of blow-ers 54 driven by motors 56. Blowers 54 draw cool air in from the back of the oven 12 to cool the motors 56 and to mix with vapor from vent 52. The cooled vent vapor then exits through a screened aperture 58 in the top of the oven.
A burner system 60 is positioned at the bottom of oven 10 in a compartment adjacent the microwave generator and comprises a horizontal apertured tube 62 extending substantially the entire width of the oven 10. Tube 62 is fed a gas fuel and primary air mixture at one end by a vertical tubular member 64 whose lower end is supplied with air and with gas through a solenoid operated gas valve 66 and a pressure regulator 68. An electrically energize~
ignitor 70 ignites the mixture coming from the apertures in tube 62 in the presence of secondary air to produce flue gas products in burner plenum 72. The flue gas products are drawn into the region of the stove between blowers 48 and oven outlet regions 18 where the combustion products are mixed with vapor drawn from enclo sure 12. The burner i5 preferably run with excess air so that the temperature of the products of combustion is below 3,000 F, for example, between 1,200 F and 2,000 F, so that combustion is sub-tantially complete. This heated oxidizing atmosphere contacting vapor drawn from the enclosure 12 substantially immediately oxidize organic components of food vapors so that when they are blown back into the enclosure through region 1~ or up the vent 52 into the room they are substantially clean. The slight pressure differential between the inlet and outlet of the blowers 48 causes a slight negative pressure in combustion plenum 72 which accurately regulates the excess air in the gas-air mixture drawn into the combustion plenum 72.
A rack 74 made, for example, of steel rods is supported on bumps formed in the side walls of the enclosure 12 so that the position of ~he rack may be changed in accordance with well-known oven practice. Positioned below rack 74 is rotatable microwave energy radiator 22 which directs microwave energy up through the apertures in rack 74 and through microwave transparent plate 76 positioned in the middle of rack 74 and microwave trans-parent dish 78 to a food body 80 such as a roast of meat.
A plurality of top gas burners 82 are provided which operate as convention gas surface burners in accordance with well-known practice. Thermal insulation 84 is provided around the oven 12 and around the burner plenum 72 to reduce loss of energy from the oven. The entire oven has a skin 86 of, for example, sheet metal surrounding the oven 12, the blower, burner, and microwave supply regions.
During operation, the temperature of the enclosure vapor is sensed by a temperature bulb 88 mounted, for example, in the enclo sure 12 on a bracket below the vapor inlet region 16. The posi-tioning of temperature sensor 88 is preferably chosen so that it is not directly in the entering hot vapor stream from region 16 but rather measures the temperature of the vapor eddying around in the enclosure 12. Its location may be selected so that the oven heating cycles have reasonable time periods for burner on and burner of and the temperature range fluctuates large amounts.
When the oven burner blown into the oven at velocities of 500 to 1,000 feet per minute is energized, heat is delivered in the form of hot vapor along the top surface of enclosure 12 and a substantially uniform convection heating pattern occurs.
The power level and time of the microwave energy may be controlled, for example, by a control panel 90 containing a manually set timer 92 and a manually set power level 94. In addit a light 96 may be positioned outside enclosure 12 illuminating enclosure 12 through a light transparent high temperture ceramic plate and microwave shielding screen 98.
113~s33 Description of an Alternate Embodiment Referring now to FIG.'s 5 and 6 there is snown a combination gas convection and microwave stove 100 illustrating an alternate embodiment of the invention. Stove 100 comprises an oven cavity 102 of conductive me'al closed by a door 104.
In accordance with the invention, an apertured convection vapo inlet region 106 is preferably located in the top wall of oven cavity 102 so that vapor is directed downwardly from the top of the oven. Oven vapor outlet region 108 is an apertured region in the bottom of the back wall of oven cavity 102. A rack 110 is provided made, for example, of steel rods supported on bumps 112 formed in the side walls of the oven.
Positioned below rack 110 is a rotatable microwave energy radiator 114 which directs a plurality of separate microwave energy patterns up through the apertures in rack 110, through a microwave transparent support plate 116 positioned in the middle of rack 110 and through a microwave transparent dish 118 to a food body 120. Apertures in regions 106 and 108 have maximum dimensions substantially less than a half ~7avelength of the free space wavelength of said microwave energy which may have a fre~uency, for example, of 2.45 KMH and preferably said apertures are less than a tenth of the free space wavelength of the microwave energy. Door 104 has a microwave choke and vapor seal like that disclosed in the preferred embodiment, and hence microwave energy is prevented from escaping from oven 102.
Radiator 114 may comprise, for example, a plenum whose upper surface contains a plurality of apertures through which microwave energy is radiated upwardly into oven 102. A central conductor of a coaxial line supports radiator 114 by beinq attached to the center of the upper plate and by extending down-113~S33 wardly through a waveguide to be supported by a choke and bearing assembly, An extension of the central conductor is rotated by a motor below the waveguide while microwave energy from a magnetron is radiated through the waveguide, the coaxial line and the radiator 114 into the oven 102. A cover 122 of microwave transparent material is supported over radiator 114 to prevent food juices or other material from being dropped on the radiator.
Such a radiator with its feed and drive assembly is similar to that described in the preferred émbodiment.
In accordance with this invention, recirculation of vapor within the oven 102 is achieved by a motor 124 driving a centri-fugal blower 126 through a belt 128. Blower 126 sucks vapor from the oven 102 through region 108 and blows the vapor out through ducts 130 into the oven 102 through the apertures in top wall vapor inlet region 106. A small portion of the output of blower 126 is blown outwardly through outlet duct 132 to an exhaust duct where it is mixed with cool the air drawn in through vents 134,in the back of the stove 100 to cool the air in duct i32 which then exits through a screened aperture 136 in the top back of the stove.
A burner system 138, positioned at the bottom of stove 100, comprises a horizontal apertured tube 140 extending substantially the entire width of the oven and fed at one end by a vertical tubular member 142 whose lower end is supplied with air from vent 144 and with gas from a gas jet 146 controlled by a gas control valve 148 supplied with gas through a pressure regulator 150. An electrically energized ignitor 152 ignites the air-gas mixture emanating from the apertures in tube 14~ causing a flame in burner plenum 154 to produce flue gas products which are drawn through the blower 126 along with vapor drawn from the oven throug~
3~ vapor outlet apertured region 108 and the hea~ed output of blower 126 is blown into the oven.
An example of power levels for effective food body cooking or browning may be microwave energy applied at a rate of 500-800 watts or around 2,000-3,000 BTU's per hour and a gas burner sup-plying at a rate of 5,000-15,000 BT~'s per hour. Such power levels will cook and/or brown a cake in a few minutes. Since microwave energy is prevented from entering the burner plenum 154, the burner can be operated while microwave energy is being supplied to the oven.
This completes the description of the embodiments of the invention illustrated herein. However, numerous modifications thereof will be apparent to one having ordinary skill in the art without departing from the spirit and scope of the invention.
For example, the oven may be fed through apertures located in regions other than the top or back walls, the circulating blower may be inside the oven, and other systems for supplying microwave energy to the oven may be used. In addition, other types of burners such as ribbon or power burners may be used. Accordingly, it is intended that this invention be not limited to the embodi-ment of the invention described herein except as defined by the appended claims.
In addition, for cooking pattern uniformity it is desirable that there be no auxilliary heating units in the cavity which can alter the pat-tern of the modes in the cavity to reduce microwave heating pattern un;form-ity.
If auxilliary gas heating means is positioned in a separate region from the oven and vapor heated thereby is then circulated through the oven, microwave energy may be coupled from the oven into the separate region and may be absorbed by the gas flame. Microwave energy absorbed by the gas flame in the separate region thereby rèduces the overall microwave oven efficiency.
Summary of the Invention This invention provides for a combined convection and micro-wave oven in which the microwave energy is couplèd into a conduc-tive enclosure while vapor is blown into the oven enclosure through means for preventing escape of microwave energy from the enclosure.
More particularly, the vapor may be the products of combustion from a gas fired burner. Such products of combustion are circulated through the oven by a circulating blower through oven inlet and outlet regions. In accordance with this invention, both the inlet and outlet regions are formed of a plurality of apertures whose diameters are less than a half wavelength of the free space wavelength of the microwave energy and preferabIy less than a tenth of a wavelength of said microwave energy.
Preferably, microwave energy is fed into the enclosure from a different wall than that through which heated vapor is blown into the oven. More particularly in accordance with this invention a microwave oven has the microwave energy fed into the oven enclosure through the bottom wall. Preferably, the microwave energy is radiated through a rotating radiator in the enclosure. The radiato may provide a plurality of separate directive radiation patterns in the enclosure which are moved by rotation of said radiator and which are directed toward a body to be heated. The rotating radiatt is preferably covered with a transparent ceramic cover and the body to be heated positioned on a support rack above the radiator. The vapor heated by the products of combustion i5 directed into the ove by the ~lower through a region either in the upp`er rear wall in one embodiment of the invention or through a region in the top wall in another embodiment of the invention and vapor is withdrawn from the oven through a region in the lower portion of the enclosur~
In accordance with the present invention, there is provided in combination: a conductive enclosure; means for supplying said enclosure with microwave energy, and means for blowing a heated vapor into said enclosure through means which prevents the escape of microwave energy from said enclosure.
In accordance with the present invention, there is further provided a microwave oven comprising: a conductive enclosure having an access opening and a closure member, a seal for said closure member comprising a microwave choke section and a vapor seal section; means for directing separate patterns of microwave energy into said enclosure through a rotating radiator; and means for blowing a vapor heated by the products of combustion from a burner into said oven through means which prevents the escape of microwave energy from said enclosure.
In accordance with the present invention, there is further provided an oven system comprising: a conductive enclosure having an access opening and a closure member; means for supplying said enclosure with microwave energy and a seal for said closure member; and a burner and means for recirculating heated vapor comprising the products of combustion from said burner through said oven through means for preventing escape of said microwave energy into a region in which said vapor is heated while exhausting from said system a por-tion of the vapor passing through said circulating means, said recirculating means including means for blowing heated vapor into said enclosure through said means for preventing escape of said microwave energy.
In accordance with the present invention, there is further provided a microwave oven comprising: a conductive enclosure having an access opening and a closure member, a seal for said closure member comprising a microwave choke section and a vapor seal section; means for supplying said enclosure with microwave energy; means for recirculating heated vapor through said oven and a vapor heating region including means for blowing said heated vapor into said oven through means for preventing microwave energy in said enclosure from entering said vapor heating region; said oven and said vapor heating region ~eing separated by said means for preventing the escape of microwave energy from said oven into said recirculating means.
-~ - 2a -113~S33 Brief Description of the Drawings Other and further embodiments of ~he invention will become apparent as the description thereof progresses, reference being had to the accompanying drawings wherein:
FIG. 1 illustrates a partially broken away side elevation view of an oven embodying the invention;
FIG~ 2 illustrates a transverse sectional view of the micro-wave radiator structure of FIG. 1 taken along line 2-2 of FIG. l;
FIG~ 3 illustrates a transverse sectional view of a blower portion of the oven of FIG. 1 taken along line 3-3 of FIG. 1.
FIG. 4 illustrates a sectional view of the burner portion of the oven of FIG. 1 taken along line 3-3 of FIG. 1 and showing burner details;
FIG. 5 illustrates a vertical sectional view of an oven illus-trating an alternate embodiment of the invention; and FIG. 6 is a transverse sectional view of the burner and blower portion of the oven of FIG. 5 taken along line 6-6 of FIG. 5.
Description of the Preferred Embodiment Referring now to FIG.'s l through 4 there is shown a combi-nation gas convection and microwave stove 10 comprising an oven cavity 12 closed by a door 14.
Cavity 12 has elongated inlet region 16 through which heated vapor is directed into the oven 12. In accordance with this invention inlet region 16 provides means comprising apertures 20 for preventing the escape of microwave energy from cavity 12 and is preferably located in the back wall of the oven adjacent the top oven wall so that the hottest vapor enters adjacent to the top of the oven. Two vapor outlet regions 13 in approximately the middle of the back wall of oven 12 contain apertures 20 for preventing the escape of microwave energy and through which the vapor is drawn out of the oven. Apertures 2~ preferably have maximum dimension which are less than a half wavelength of the free space wavelength of the microwave energy radiated into cavity 12, and preferably are holes whose diameters are less than a tenth of the free space wavelength of the microwave energy.
Microwave energy is fed into oven cavity 12, which is a conductive enclosure, by a rotating.radiator 22 which may comprise, for example., a plenum 24 whose upper surface is a plate 26 which contains a plurality of apertures 28 through which microwave energy is radiated upwardly into enclosure 12. A
central conductor 30 of a coaxial line 32 supports plenum 24 by being attached to the center of plate 26. Conductor 30 extends downwardly from the lower end of coaxial line 32, through a waveguide 34, and through a microwave choke 36 having bearing assembly 38. An extension of conductor 30 is connected to motor 40 below waveguide 34 which rotates radiator 22 through central conductor 30.
Microwave energy from a magnetron 42 is fed through waveguide 34, coaxial line 32, and plenum 24 to be radiated upwardly from slots 28 into enclosure 12 as a plurality of separate directive radiation patterns. A
cover 44 of microwave transparent material is supported over radiator 22 on bumps 46 on the bottom of enclosure 12 to prevent food juices or other ma-terial from being dropped on radiator 22.
Door 14 contains a microwave choke region surrounded by a high tem-perature vapor seal so that most of the microwave energy is prevented from being absorbed from the high temperature vapor seal. However, microwave en-ergy passing through the choke section is substantially absorbed by the hightemperature vapor seal thereby preventing stray radiation from the oven.
In accordance with this invention circulation of vapor through en-closure 12 is produced by centrifugal blowers 48 which draw vapor out of cav-ity 12 through apertures 20 in regions 18 and blows it into plenums 50 sur-rounding blowers 48 supplying apertures 20. The upper ends of plenums 50 have an opening to a vent 52 through which a small portion of the output of blowers 48 is blown and is mixed with the air blown by a second set of blow-ers 54 driven by motors 56. Blowers 54 draw cool air in from the back of the oven 12 to cool the motors 56 and to mix with vapor from vent 52. The cooled vent vapor then exits through a screened aperture 58 in the top of the oven.
A burner system 60 is positioned at the bottom of oven 10 in a compartment adjacent the microwave generator and comprises a horizontal apertured tube 62 extending substantially the entire width of the oven 10. Tube 62 is fed a gas fuel and primary air mixture at one end by a vertical tubular member 64 whose lower end is supplied with air and with gas through a solenoid operated gas valve 66 and a pressure regulator 68. An electrically energize~
ignitor 70 ignites the mixture coming from the apertures in tube 62 in the presence of secondary air to produce flue gas products in burner plenum 72. The flue gas products are drawn into the region of the stove between blowers 48 and oven outlet regions 18 where the combustion products are mixed with vapor drawn from enclo sure 12. The burner i5 preferably run with excess air so that the temperature of the products of combustion is below 3,000 F, for example, between 1,200 F and 2,000 F, so that combustion is sub-tantially complete. This heated oxidizing atmosphere contacting vapor drawn from the enclosure 12 substantially immediately oxidize organic components of food vapors so that when they are blown back into the enclosure through region 1~ or up the vent 52 into the room they are substantially clean. The slight pressure differential between the inlet and outlet of the blowers 48 causes a slight negative pressure in combustion plenum 72 which accurately regulates the excess air in the gas-air mixture drawn into the combustion plenum 72.
A rack 74 made, for example, of steel rods is supported on bumps formed in the side walls of the enclosure 12 so that the position of ~he rack may be changed in accordance with well-known oven practice. Positioned below rack 74 is rotatable microwave energy radiator 22 which directs microwave energy up through the apertures in rack 74 and through microwave transparent plate 76 positioned in the middle of rack 74 and microwave trans-parent dish 78 to a food body 80 such as a roast of meat.
A plurality of top gas burners 82 are provided which operate as convention gas surface burners in accordance with well-known practice. Thermal insulation 84 is provided around the oven 12 and around the burner plenum 72 to reduce loss of energy from the oven. The entire oven has a skin 86 of, for example, sheet metal surrounding the oven 12, the blower, burner, and microwave supply regions.
During operation, the temperature of the enclosure vapor is sensed by a temperature bulb 88 mounted, for example, in the enclo sure 12 on a bracket below the vapor inlet region 16. The posi-tioning of temperature sensor 88 is preferably chosen so that it is not directly in the entering hot vapor stream from region 16 but rather measures the temperature of the vapor eddying around in the enclosure 12. Its location may be selected so that the oven heating cycles have reasonable time periods for burner on and burner of and the temperature range fluctuates large amounts.
When the oven burner blown into the oven at velocities of 500 to 1,000 feet per minute is energized, heat is delivered in the form of hot vapor along the top surface of enclosure 12 and a substantially uniform convection heating pattern occurs.
The power level and time of the microwave energy may be controlled, for example, by a control panel 90 containing a manually set timer 92 and a manually set power level 94. In addit a light 96 may be positioned outside enclosure 12 illuminating enclosure 12 through a light transparent high temperture ceramic plate and microwave shielding screen 98.
113~s33 Description of an Alternate Embodiment Referring now to FIG.'s 5 and 6 there is snown a combination gas convection and microwave stove 100 illustrating an alternate embodiment of the invention. Stove 100 comprises an oven cavity 102 of conductive me'al closed by a door 104.
In accordance with the invention, an apertured convection vapo inlet region 106 is preferably located in the top wall of oven cavity 102 so that vapor is directed downwardly from the top of the oven. Oven vapor outlet region 108 is an apertured region in the bottom of the back wall of oven cavity 102. A rack 110 is provided made, for example, of steel rods supported on bumps 112 formed in the side walls of the oven.
Positioned below rack 110 is a rotatable microwave energy radiator 114 which directs a plurality of separate microwave energy patterns up through the apertures in rack 110, through a microwave transparent support plate 116 positioned in the middle of rack 110 and through a microwave transparent dish 118 to a food body 120. Apertures in regions 106 and 108 have maximum dimensions substantially less than a half ~7avelength of the free space wavelength of said microwave energy which may have a fre~uency, for example, of 2.45 KMH and preferably said apertures are less than a tenth of the free space wavelength of the microwave energy. Door 104 has a microwave choke and vapor seal like that disclosed in the preferred embodiment, and hence microwave energy is prevented from escaping from oven 102.
Radiator 114 may comprise, for example, a plenum whose upper surface contains a plurality of apertures through which microwave energy is radiated upwardly into oven 102. A central conductor of a coaxial line supports radiator 114 by beinq attached to the center of the upper plate and by extending down-113~S33 wardly through a waveguide to be supported by a choke and bearing assembly, An extension of the central conductor is rotated by a motor below the waveguide while microwave energy from a magnetron is radiated through the waveguide, the coaxial line and the radiator 114 into the oven 102. A cover 122 of microwave transparent material is supported over radiator 114 to prevent food juices or other material from being dropped on the radiator.
Such a radiator with its feed and drive assembly is similar to that described in the preferred émbodiment.
In accordance with this invention, recirculation of vapor within the oven 102 is achieved by a motor 124 driving a centri-fugal blower 126 through a belt 128. Blower 126 sucks vapor from the oven 102 through region 108 and blows the vapor out through ducts 130 into the oven 102 through the apertures in top wall vapor inlet region 106. A small portion of the output of blower 126 is blown outwardly through outlet duct 132 to an exhaust duct where it is mixed with cool the air drawn in through vents 134,in the back of the stove 100 to cool the air in duct i32 which then exits through a screened aperture 136 in the top back of the stove.
A burner system 138, positioned at the bottom of stove 100, comprises a horizontal apertured tube 140 extending substantially the entire width of the oven and fed at one end by a vertical tubular member 142 whose lower end is supplied with air from vent 144 and with gas from a gas jet 146 controlled by a gas control valve 148 supplied with gas through a pressure regulator 150. An electrically energized ignitor 152 ignites the air-gas mixture emanating from the apertures in tube 14~ causing a flame in burner plenum 154 to produce flue gas products which are drawn through the blower 126 along with vapor drawn from the oven throug~
3~ vapor outlet apertured region 108 and the hea~ed output of blower 126 is blown into the oven.
An example of power levels for effective food body cooking or browning may be microwave energy applied at a rate of 500-800 watts or around 2,000-3,000 BTU's per hour and a gas burner sup-plying at a rate of 5,000-15,000 BT~'s per hour. Such power levels will cook and/or brown a cake in a few minutes. Since microwave energy is prevented from entering the burner plenum 154, the burner can be operated while microwave energy is being supplied to the oven.
This completes the description of the embodiments of the invention illustrated herein. However, numerous modifications thereof will be apparent to one having ordinary skill in the art without departing from the spirit and scope of the invention.
For example, the oven may be fed through apertures located in regions other than the top or back walls, the circulating blower may be inside the oven, and other systems for supplying microwave energy to the oven may be used. In addition, other types of burners such as ribbon or power burners may be used. Accordingly, it is intended that this invention be not limited to the embodi-ment of the invention described herein except as defined by the appended claims.
Claims (20)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In combination:
a conductive enclosure;
means for supplying said enclosure with microwave energy; and means for blowing a heated vapor into said enclosure through means for preventing microwave energy in said enclosure from entering a region where said vapor is heated.
a conductive enclosure;
means for supplying said enclosure with microwave energy; and means for blowing a heated vapor into said enclosure through means for preventing microwave energy in said enclosure from entering a region where said vapor is heated.
2. The combination in accordance with Claim 1 wherein:
said blowing means comprises a blower for said vapor through the enclosure.
said blowing means comprises a blower for said vapor through the enclosure.
3. A microwave oven comprising:
a conductive enclosure having an access opening and a closure member, a seal for said closure member comprising a microwave choke section and a vapor seal section;
means for supplying said enclosure with microwave energy;
means for recirculating heated vapor through said oven and a vapor heating region including means for blowing said heated vapor into said oven through means for preventing microwave energy in said enclosure from entering said vapor heating region;
said oven and said vapor heating region being separated by said means for preventing the escape of microwave energy from said oven into said recir-culating means.
a conductive enclosure having an access opening and a closure member, a seal for said closure member comprising a microwave choke section and a vapor seal section;
means for supplying said enclosure with microwave energy;
means for recirculating heated vapor through said oven and a vapor heating region including means for blowing said heated vapor into said oven through means for preventing microwave energy in said enclosure from entering said vapor heating region;
said oven and said vapor heating region being separated by said means for preventing the escape of microwave energy from said oven into said recir-culating means.
4. The microwave oven in accordance with Claim 3 wherein:
said vapor comprises the products of combustion.
said vapor comprises the products of combustion.
5. The microwave oven in accordance with Claim 4 wherein:
said choke section is positioned between said vapor seal and the interior of said oven.
said choke section is positioned between said vapor seal and the interior of said oven.
6. The microwave oven in accordance with Claim 4 wherein:
said products of combustion are produced by a gas burner.
said products of combustion are produced by a gas burner.
7. In combination:
a conductive enclosure and means for supplying said enclosure with microwave energy; and means for blowing a vapor comprising the products of combustion into said oven through means for preventing the coupling of microwave energy from said enclosure into a region producing said products of combustion.
a conductive enclosure and means for supplying said enclosure with microwave energy; and means for blowing a vapor comprising the products of combustion into said oven through means for preventing the coupling of microwave energy from said enclosure into a region producing said products of combustion.
8. The combination in accordance with Claim 7 wherein:
said blowing means comprises an oven circulating blower outside said oven supplied with vapor from said oven and supplied with said products of combustion from a gas burner.
said blowing means comprises an oven circulating blower outside said oven supplied with vapor from said oven and supplied with said products of combustion from a gas burner.
9. A microwave oven comprising:
a conductive enclosure having an access opening and a closure member, a seal for said closure member comprising a microwave choke section and a vapor seal section;
means for directing microwave energy into said enclosure through a rotating radiator; and means for blowing a vapor heated by the products of combustion into said oven through means which prevents the escape of microwave energy from said enclosure.
a conductive enclosure having an access opening and a closure member, a seal for said closure member comprising a microwave choke section and a vapor seal section;
means for directing microwave energy into said enclosure through a rotating radiator; and means for blowing a vapor heated by the products of combustion into said oven through means which prevents the escape of microwave energy from said enclosure.
10. A microwave oven in accordance with Claim 9 wherein:
said products of combustion are produced by a gas burner positioned outside said oven.
said products of combustion are produced by a gas burner positioned outside said oven.
11. A microwave oven in accordance with Claim 8 wherein:
said choke section is positioned between said vapor seal section and the interior of said enclosure.
said choke section is positioned between said vapor seal section and the interior of said enclosure.
12. A microwave oven in accordance with Claim 9 wherein said means for preventing the escape of microwave energy from said oven enclosure comprises a plurality of apertures in a wall of said enclosure whose maximum dimensions are substantially less than half of a free space wavelength of said microwave energy.
13. In combination:
a conductive enclosure and means for supplying said enclosure with microwave energy;
a burner; and means for drawing air through said burner and blowing vapor compris-ing said air and the products of combustion into said oven through means for preventing the coupling of microwave energy from said enclosure into a region producing said products of combustion.
a conductive enclosure and means for supplying said enclosure with microwave energy;
a burner; and means for drawing air through said burner and blowing vapor compris-ing said air and the products of combustion into said oven through means for preventing the coupling of microwave energy from said enclosure into a region producing said products of combustion.
14. An oven system comprising:
a conductive enclosure having an access opening and a closure member;
means for supplying said enclosure with microwave energy and a seal for said closure member; and a burner and means for recirculating heated vapor comprising the products of combustion from said burner through said oven through means for preventing escape of said microwave energy into a region in which said vapor is heated while exhausting from said system a portion of the vapor passing through said circulating means, said recirculating means including means for blowing heated vapor into said enclosure through said means for preventing escape of said microwave energy.
a conductive enclosure having an access opening and a closure member;
means for supplying said enclosure with microwave energy and a seal for said closure member; and a burner and means for recirculating heated vapor comprising the products of combustion from said burner through said oven through means for preventing escape of said microwave energy into a region in which said vapor is heated while exhausting from said system a portion of the vapor passing through said circulating means, said recirculating means including means for blowing heated vapor into said enclosure through said means for preventing escape of said microwave energy.
15. The oven in accordance with Claim 14 wherein:
said vapor comprises said products of combustion and excess air.
said vapor comprises said products of combustion and excess air.
16. In combination:
a conductive enclosure;
means for supplying said enclosure with microwave energy; and means for blowing a heated vapor into said enclosure through means which prevents the escape of microwave energy from said enclosure.
a conductive enclosure;
means for supplying said enclosure with microwave energy; and means for blowing a heated vapor into said enclosure through means which prevents the escape of microwave energy from said enclosure.
17. The oven in accordance with Claim 3 wherein:
air is drawn through a burner by means of said recirculating means.
air is drawn through a burner by means of said recirculating means.
18. A microwave oven comprising:
a conductive enclosure having an access opening and a closure member, a seal for said closure member comprising a microwave choke section and a vapor seal section;
means for directing separate patterns of microwave energy into said enclosure through a rotating radiator; and means for blowing a vapor heated by the products of combustion from a burner into said oven through means which prevents the escape of microwave energy from said enclosure.
a conductive enclosure having an access opening and a closure member, a seal for said closure member comprising a microwave choke section and a vapor seal section;
means for directing separate patterns of microwave energy into said enclosure through a rotating radiator; and means for blowing a vapor heated by the products of combustion from a burner into said oven through means which prevents the escape of microwave energy from said enclosure.
19. The microwave oven in accordance with Claim 9 wherein:
said burner is a gas burner positioned outside said oven.
said burner is a gas burner positioned outside said oven.
20. In combination:
a conductive enclosure supplied with microwave energy through a rotating radiator;
means for supplying said enclosure with microwave energy;
a gas burner; and means for drawing air through said burner and for blowing a major portion of the vapor comprising said air and the products of combustion of said burner through said enclosure through means for preventing escape of said microwave energy while blowing a portion of said vapor out a vent to control the amount of said air drawn through said burner.
a conductive enclosure supplied with microwave energy through a rotating radiator;
means for supplying said enclosure with microwave energy;
a gas burner; and means for drawing air through said burner and for blowing a major portion of the vapor comprising said air and the products of combustion of said burner through said enclosure through means for preventing escape of said microwave energy while blowing a portion of said vapor out a vent to control the amount of said air drawn through said burner.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US96234278A | 1978-11-20 | 1978-11-20 | |
| US962,342 | 1978-11-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1138533A true CA1138533A (en) | 1982-12-28 |
Family
ID=25505723
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000337966A Expired CA1138533A (en) | 1978-11-20 | 1979-10-18 | Microwave and convection oven |
Country Status (11)
| Country | Link |
|---|---|
| JP (1) | JPS5575130A (en) |
| AU (1) | AU528210B2 (en) |
| BE (1) | BE880131A (en) |
| CA (1) | CA1138533A (en) |
| CH (1) | CH642736A5 (en) |
| DE (1) | DE2946425A1 (en) |
| FR (1) | FR2441802A1 (en) |
| GB (1) | GB2035767A (en) |
| IT (1) | IT1120619B (en) |
| NL (1) | NL7908440A (en) |
| ZA (1) | ZA795933B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1138937A (en) * | 1978-11-24 | 1983-01-04 | William J. Day | Combination microwave and convection oven |
| CA1114262A (en) * | 1979-01-16 | 1981-12-15 | Raytheon Company | Gas burner convection oven |
| EP0099705B1 (en) * | 1982-07-17 | 1990-03-28 | Microwave Ovens Limited | Microwave ovens and methods of cooking food |
| US4507529A (en) * | 1983-06-29 | 1985-03-26 | General Electric Company | Food emission sensing |
| GB2179529B (en) * | 1985-08-02 | 1988-06-15 | Cannon Ind Ltd | Cooking ovens |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1492600A1 (en) * | 1964-02-03 | 1970-03-26 | Cryodry Corp | Method and device for treating substances with microwaves |
| US3789178A (en) * | 1972-10-18 | 1974-01-29 | Sage Laboratories | Microwave heating apparatus |
| US3884213A (en) * | 1973-03-30 | 1975-05-20 | Donald P Smith | Cooking apparatus |
| GB1538851A (en) * | 1976-04-14 | 1979-01-24 | Boc International Ltd | Microwave heating |
| US4211909A (en) * | 1978-05-15 | 1980-07-08 | Sanyo Electric Co., Ltd. | Combination microwave and gas oven |
| CA1138937A (en) * | 1978-11-24 | 1983-01-04 | William J. Day | Combination microwave and convection oven |
| CA1114262A (en) * | 1979-01-16 | 1981-12-15 | Raytheon Company | Gas burner convection oven |
| CA1138049A (en) * | 1979-01-16 | 1982-12-21 | William J. Day | Self-cleaning microwave convection oven |
-
1979
- 1979-10-18 CA CA000337966A patent/CA1138533A/en not_active Expired
- 1979-10-29 GB GB7937415A patent/GB2035767A/en not_active Withdrawn
- 1979-10-30 IT IT50697/79A patent/IT1120619B/en active
- 1979-11-01 AU AU52421/79A patent/AU528210B2/en not_active Ceased
- 1979-11-05 ZA ZA00795933A patent/ZA795933B/en unknown
- 1979-11-16 DE DE19792946425 patent/DE2946425A1/en not_active Withdrawn
- 1979-11-16 FR FR7928328A patent/FR2441802A1/en not_active Withdrawn
- 1979-11-19 BE BE0/198189A patent/BE880131A/en not_active IP Right Cessation
- 1979-11-19 NL NL7908440A patent/NL7908440A/en not_active Application Discontinuation
- 1979-11-20 CH CH1035679A patent/CH642736A5/en not_active IP Right Cessation
- 1979-11-20 JP JP15055079A patent/JPS5575130A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| IT7950697A0 (en) | 1979-10-30 |
| BE880131A (en) | 1980-03-17 |
| ZA795933B (en) | 1980-10-29 |
| NL7908440A (en) | 1980-05-22 |
| FR2441802A1 (en) | 1980-06-13 |
| JPS5575130A (en) | 1980-06-06 |
| DE2946425A1 (en) | 1980-05-29 |
| AU5242179A (en) | 1980-05-29 |
| GB2035767A (en) | 1980-06-18 |
| CH642736A5 (en) | 1984-04-30 |
| AU528210B2 (en) | 1983-04-21 |
| IT1120619B (en) | 1986-03-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |