CA1138937A - Combination microwave and convection oven - Google Patents
Combination microwave and convection ovenInfo
- Publication number
- CA1138937A CA1138937A CA000338612A CA338612A CA1138937A CA 1138937 A CA1138937 A CA 1138937A CA 000338612 A CA000338612 A CA 000338612A CA 338612 A CA338612 A CA 338612A CA 1138937 A CA1138937 A CA 1138937A
- Authority
- CA
- Canada
- Prior art keywords
- oven
- burner
- vapor
- accordance
- air
- 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
- H05B6/647—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
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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
Abstract
ABSTRACT OF THE DISCLOSURE
A combination microwave and convection oven in which a gas burner positioned outside the oven provides heated combustion products which are drawn from the burner area along with vapor from an outlet of the oven by a blower system and the combined output of the blower system is blown into the oven through an oven inlet region in the oven wall. Both the oven outlets and the oven inlet are formed of holes substantially less than one-half wave-length in diameter. A predetermined portion of the blower output system is blown through an exhaust vent thereby creating slight negative pressures in the oven and in the burner plenum to accurately control the air flow through the burner.
A combination microwave and convection oven in which a gas burner positioned outside the oven provides heated combustion products which are drawn from the burner area along with vapor from an outlet of the oven by a blower system and the combined output of the blower system is blown into the oven through an oven inlet region in the oven wall. Both the oven outlets and the oven inlet are formed of holes substantially less than one-half wave-length in diameter. A predetermined portion of the blower output system is blown through an exhaust vent thereby creating slight negative pressures in the oven and in the burner plenum to accurately control the air flow through the burner.
Description
:~3~7 Background of the Invention Microwave ovens have had electric heaters positioned inside the oven to ai~ in the cooking and/or browning process and have had electrically heated air or air used to cool electrical com-ponents such as magnetrons, power supplies, or magnetrons directed through the oven to aid in controlling vapors produced by a food body.
However, attempts to use the products of combustion in cooking regions excited with microwave energy have been generally unsatis-factory. Open gas flames in the oven can, among other things, act as sources of ionization which can absorb large portions of the microwave energy.
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Summary of the Invention In accordance with this invention there is disclosed an oven which can be heated by combustion products blown into the oven by a blower system which draws heated vapor comprising the combustion products from a burner plenum and controls the air drawn through the burner, More specifically, the blower system blows the mixture of vapor drawn from the oven and the vapor comprising the burner products of combustion and second-ary air back into the oven with a small portion of the mixture being blown out an exhaust vent to create a slight negative pressure in the burner plenum so a predetermined amount of air will enter the burner.
This invention further discloses that the temperature of the vapors blown into the oven can be controlled by a thermostatic switch which controls an on/off cycle of the burner.
This invention further provides that the output of the oven circulation blower enters the oven through the back wall adjacent the upper oven surface. Such a direction of heated vapor into the oven has been iEound to substantially improve heating pattern uni-formity and to assist in browning the upper surfaces of food pro-ducts such as pastries or cakes or meat products by microwave energy while using less circulation blower power than other con-convection ovens.
In accordance with this invention the burner heats a region of a burner plenum during the time when the burner is energized and the oven circulating blower system draws air through a gas burner, and draws vapor from the oven to heat the vapor and to circulate the heated vapor through the oven. However, when the burner is off, for example, during the period when a thermostat senses that the oven temperature has reached a value corresponding ~3~
to that which has been manually selected for a cooking temperature, the circulating ~an continues to draw air through the burner plenum where it is heated by the hea~ed region of the burner plenum.
In accordance with this invention it has been discovered that a very rapid rate of cooking of a food body can occur even when the oven is first energized and the walls are still cool. The uni-formity of the cooking pattern is believed to occur due to the velocity of air being directed into the top of the oven from two counter rotating fans spaced behind the oven wall so that the oven inlet duct has a uniform pattern of air issuing from all parts thereof.
Further in accordance with this invention each motor driving one of the oven recirculating blowers is separated from the re-circulating blower by a second blower on the same shaft as the recirculating blower. The second blower prevents thermal energy leaking along the motor shaft by conduction from heating the motor. Rather the second blower draws air over the motor to cool the motor and supplies the air to an exhaust vent where it is mixed with the portion of the vapor output from the oven circu-lating blower to cool said portion prior to venting.
This invention is particularly useful in a microwave oven wherein the burner is outside the microwave enclosure and the vapor, drawn from the oven is blown back into the oven through the oven wall region having multiple apertures whose maximum dimensions are less than one-half of a free space wavelength of the microwave energy and hence prevent the escape of microwave energy into the blower system or burner.
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In accordance with the present invention, there is provided in com--bination: a conductive enclosure supplied with microwave energy; and a burner and means for drawing air through said burner and blowing vapor comprising said air and the products of combustion of said burner into 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, 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 while exhausting from said system a portion of the vapor passi.ng through said circulating means.
In accordance with the present invention, there is further provided in combination: a conducti.ve enclosure supplied with microwave energy through a rotating radiator; a gas burner; and means for drawing air through s~id burner and for blowing a major portion of the vapor comprisi.ng said air and the products of combustion of said burner through said enclosure while blowing a sufficient portion of said vapor out a vent to control the amount of said air drawn through saicl burner.
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Brief Description of the Drawings Other and further embodiments of the invention will become apparent as the description thereo:E 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 front view of the oven illustrated in FIG. l; and FIG. 3 illustrates an enlarged sectional view o-E the micro-wave radiator structure of FIG. I taken along line 3-3 oE FIG. 1.
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Description of the Preferred Embodiment Referring now to E~IG. 1 there is shown a combination gas convection and microwave stove 10 embodying the invention. Stove 10 comprises an oven cavity 12 which is closed by a door 14 during operation. Cavity 12 has elongated vapor inlet region 16 through which heated vapor is directed into the oven 12, and a vapor outlet region 18 through which vapor is drawn out of the enclosure 12 into a blower input plenum 20. A rack 22 made ! for example, of steel rods is supported on bumps 24 formed in the side walls of the enclosure 12 so that the position of the rack 22 may be changed in accordance with well-known oven practice. Positioned below rack 22 is a rotatable microwave energy radiator 26 which directs microwave energy up through the apertures in rack 22 and through a support plate 28, positioned in the middle of rack 22, and through a dish 30 containing a food body 32 such as a roast of meat. Dish 30~ as well as plate 28, are preferably substantially transparent to microwave energy so that the lower region of food body 32 and the interior portions thereoE may be heated effectively by microwave energy.
Regions 16 and 18 pre~erably have a plurality of apertures 34 whose maximum dimensions are substantially less than a half wavelength of the free space wavelength of the microwave energy ; radiated into cavity 12. Preferably apertures 34 haviny maximum dimensions of, for example, less than a tenth of the free space wavelength of the microwave energy radiated into oven 12 by radiator 26 so that microwave energy radiated into enclosure 12 will not escape through regions 16 or 18~
Radiator 26 may comprise, for e~ample, a plenum 36 whose upper surface 38 contains a plurality of apertures 40 through which microwave energy is radiated upwardly into oven 12. A
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central conductor 42 of a coaxial line 44 supports plenum 36 by being attached to the center of upper plate 38. Conductor 42 extends downwardly through the outer conductor 46 of coaxial line 44 and through a waveguide 48 to a microwave choke and bearing assembly 50. An extensi.on of conductor 42 is rotated by a motor 52 below waveguide 48.
Microwave energy from a magnetron 54 is fed through wave-guide 48 and coaxial line 44 to radiator 26. A blower 56 blows a:ir passed the fins 58 of magnetron 54 to cool the magnetron, but none of this air passes through waveguide 48. A cover 60 of microwave transparent material is supported over radiator 26 on centering bumps 62 on the bottom o:f oven 12 to cover radiator 26 and thereby prevent food juices or other material from being dropped on radiator 26. However, any desired microwave feed structure, radiator, and/or door seal could be used.
When closed, door 14 is preferably sealed to enclosure 12 by a high temperature vapor seal with a microwave choke struc-ture positioned between said vapor seal and the interior of enclo-sure 12 50 t}-at microwave energy rad.iated into oven 12 -i~ 1argely prevented from bci.ng absorl)cd Irom the higll tcml)cr.ltl:lrc v~po:r seal Ilowever, any microwave energy passing through sa-id choke section is substanti.ally absorbed by the high tempera-ture vapor seal. ~hen door 14 is closed, a latch is mecllanically moved to lock door 14 shut and to permit energization of the magnetron 48. In accordance wi.th this invention a slight negative pressure is produced within plenum 20 by a blower system comprising two centrifugal blowers ~ i3~
64 which draw vapor out of cavity 12 through apertures 34 into plenum 20 and blows it out into plenums 66 surrounding blowers 64 and supplying region 16. The upper ends of plenum 66 are connected to an opening through which a small portion of the output of blowers 64 pass through an outlet vent 68 where the air is mixed with the air blown by a second set of blowers 70.
Blowers 70 draw cool ajr in from the back of the stove 10 to cool the air in duct 72 which exits through a screened aperture 74 in the top of the stove above the cooking surface thereof.
As shown in FIG.'s 1 and 2, each of the apertured regions 18 supplies vapors from the oven sucked to a different blower 64 and each blower 64 is driven along with one of the blowers 70, by a separate motor 76 which is supported from a bac~ wall 78 of the oven. A partition 80 between the two blowers 64 prevents tangential interaction of the vapor output of the blowers 64.
Blowers 64 preferably rotate in opposite directions to cause the air between the blowers to move upwardly adjacent par-tition 80.
It should be clearly understood that a single blower could be used in place of the dual blowers 64 and the plenum 66 could have ducting systems to direct the vapor through openings 16 into the oven. However, it has been found that the dual counter rotating blower system can improve the uniformity of convection heating in the overl.
A burner system 90 positioned at the bottom of stove 10 in a compartment behind and below enclosure 12 comprises a horizontal apertured tube 92 extending substantially the entire width of the oven and fed through vertical tubular member 94 with a gas-primary mixture supplied with gas through a gas valve 96. Second-ary air is regulated by the spacing of a plate 98 from the bottom of the entrance of the burner plenum. A pressure regulator 100 $~
connected to a gas line input 102 supplies gas valve 96. When the oven is turned on, an igni~or 108 is electrically energized and heats to a temperature which will ignite an air-gas mixture whereupon valve 98 opens, thereby causing said mixture to emanate from the apertures in tube 92 and producing a flame in burner plenum 106. Flue gas products in plenum 106 are drawn into plenum 20 along with excess secondary air by blowers 64 where the combustion products and secondary air are mixed with vapor drawn through apertures 34 from enclosure 12.
Burner 90, preferably run with excess secondary air to reduce the temperature of the products of combustion, is below 3,000 F so that substantially no oxide products of nitrogen are produced and combustion is substantially complete. Preferably sufficient excess secondary air is drawn into plenum 106 by the negative pressure in plenum 20 to produce a temperature in burner plenum 106 of l,200 F to 2,000 F. Plenums 20 and 106 extend ; substantially the full width of the back of enclosure 12 so that the burner plenum temperature is suhstantially uniform across said width. Thus, since the blower speed is constant, the slight negative pressure in combustion plenum 106 is substantially con-stant and accurately regulates the burner primary and secondary air drawn into the combustion chamber. The gas fed into the chamber is also constant due to pressure regulator 100 so that the excess air is accurately controlled.
A plurality of top gas burners llO is provided which operate as convention gas surface burners in accordance with well-known practice. Thermal insulation 112 is provided around the enclosure 12 and around the burner plenum 106 to reduce loss of thermal energy from the entire stove lO. A skin 114 of, for example, sheet metal surrounds the enclosure 12, the blower region, and the burner and microwave supply region.
During operation, the temperature of the enclosure vapor is sensed by a temperature sensor bulb 120 mounted, for example, in the oven on a bracket 122 below the vapor inlet 16 from the plenum 66.
The positioning of sensor 120 is preferably chosen so that it is not directly in the entering hot vapor stream from inlet 16 but rather senses the temperature of the vapor circu~
lating in the enclosure 12. The location of sensor 120 may be selected so that the oven heating cycles have reasonable time periods for burner on and burner off and the temperature range fluctuate large amounts. When the oven is ener~ized, the recircu-lating blowers 64 run continuously and when the burner 90 is energized, heat is delivered in the form of hot vapor substantially directly to the food body 32 in enclosure 12 and a substantially uniform heating pattern occurs.
Microwave energy power level and timer are controlled, for example, by a control panel 130 containing a timer 132 a power level 134, and on/off buttons 136 and 13~. In addition, a light 140 positionecl outside oven 12 but illuminating oven 12 through a light transparent high temperature ceramic 142 and a microwave shielding screen 144 may be provided. The microwave system may be energized, for example, from a 110 volt 60 cycle AC supply.
In accordance with this invention there is disclosed the discovery that browning of a Eood body such as roast 32 can be controlled by blowing hot vapor through inlet region 16 while radiating full power of microwave energy into the oven. This effect appears to occur due to surface effects of the velocity of hot air drying molsture from the surface of the food body and can occur with microwave energy being more readily absorbed by the dry food body surface to brown the food body surface, and _g _ therefore, an added broiler unit is not necessaryO
An example of power levels for effective food body 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 heating rate of about 5,000-15,000 BTU's per hour. Such power levels will bake and/or brown a cake in a few minutes.
This completes the description of the preferred embodiments of the invention. Although preferred embodiments have been described, it is believed that numerous modifications and altera-tions thereto would be apparent to one having ordinary skill in the art without departing from the spirit and scope of the inven-tion. For example, the oven may be fed through apertures located ; in regions other than the back wall, other systems for supplying microwave energy to the oven may be used and other types of circulating systems and burners may be used. Accordingly, it is intended that this invention be not limited to the particular details of the embodiment illustrated herein except as defined by the appended claims.
However, attempts to use the products of combustion in cooking regions excited with microwave energy have been generally unsatis-factory. Open gas flames in the oven can, among other things, act as sources of ionization which can absorb large portions of the microwave energy.
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Summary of the Invention In accordance with this invention there is disclosed an oven which can be heated by combustion products blown into the oven by a blower system which draws heated vapor comprising the combustion products from a burner plenum and controls the air drawn through the burner, More specifically, the blower system blows the mixture of vapor drawn from the oven and the vapor comprising the burner products of combustion and second-ary air back into the oven with a small portion of the mixture being blown out an exhaust vent to create a slight negative pressure in the burner plenum so a predetermined amount of air will enter the burner.
This invention further discloses that the temperature of the vapors blown into the oven can be controlled by a thermostatic switch which controls an on/off cycle of the burner.
This invention further provides that the output of the oven circulation blower enters the oven through the back wall adjacent the upper oven surface. Such a direction of heated vapor into the oven has been iEound to substantially improve heating pattern uni-formity and to assist in browning the upper surfaces of food pro-ducts such as pastries or cakes or meat products by microwave energy while using less circulation blower power than other con-convection ovens.
In accordance with this invention the burner heats a region of a burner plenum during the time when the burner is energized and the oven circulating blower system draws air through a gas burner, and draws vapor from the oven to heat the vapor and to circulate the heated vapor through the oven. However, when the burner is off, for example, during the period when a thermostat senses that the oven temperature has reached a value corresponding ~3~
to that which has been manually selected for a cooking temperature, the circulating ~an continues to draw air through the burner plenum where it is heated by the hea~ed region of the burner plenum.
In accordance with this invention it has been discovered that a very rapid rate of cooking of a food body can occur even when the oven is first energized and the walls are still cool. The uni-formity of the cooking pattern is believed to occur due to the velocity of air being directed into the top of the oven from two counter rotating fans spaced behind the oven wall so that the oven inlet duct has a uniform pattern of air issuing from all parts thereof.
Further in accordance with this invention each motor driving one of the oven recirculating blowers is separated from the re-circulating blower by a second blower on the same shaft as the recirculating blower. The second blower prevents thermal energy leaking along the motor shaft by conduction from heating the motor. Rather the second blower draws air over the motor to cool the motor and supplies the air to an exhaust vent where it is mixed with the portion of the vapor output from the oven circu-lating blower to cool said portion prior to venting.
This invention is particularly useful in a microwave oven wherein the burner is outside the microwave enclosure and the vapor, drawn from the oven is blown back into the oven through the oven wall region having multiple apertures whose maximum dimensions are less than one-half of a free space wavelength of the microwave energy and hence prevent the escape of microwave energy into the blower system or burner.
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In accordance with the present invention, there is provided in com--bination: a conductive enclosure supplied with microwave energy; and a burner and means for drawing air through said burner and blowing vapor comprising said air and the products of combustion of said burner into 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, 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 while exhausting from said system a portion of the vapor passi.ng through said circulating means.
In accordance with the present invention, there is further provided in combination: a conducti.ve enclosure supplied with microwave energy through a rotating radiator; a gas burner; and means for drawing air through s~id burner and for blowing a major portion of the vapor comprisi.ng said air and the products of combustion of said burner through said enclosure while blowing a sufficient portion of said vapor out a vent to control the amount of said air drawn through saicl burner.
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Brief Description of the Drawings Other and further embodiments of the invention will become apparent as the description thereo:E 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 front view of the oven illustrated in FIG. l; and FIG. 3 illustrates an enlarged sectional view o-E the micro-wave radiator structure of FIG. I taken along line 3-3 oE FIG. 1.
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Description of the Preferred Embodiment Referring now to E~IG. 1 there is shown a combination gas convection and microwave stove 10 embodying the invention. Stove 10 comprises an oven cavity 12 which is closed by a door 14 during operation. Cavity 12 has elongated vapor inlet region 16 through which heated vapor is directed into the oven 12, and a vapor outlet region 18 through which vapor is drawn out of the enclosure 12 into a blower input plenum 20. A rack 22 made ! for example, of steel rods is supported on bumps 24 formed in the side walls of the enclosure 12 so that the position of the rack 22 may be changed in accordance with well-known oven practice. Positioned below rack 22 is a rotatable microwave energy radiator 26 which directs microwave energy up through the apertures in rack 22 and through a support plate 28, positioned in the middle of rack 22, and through a dish 30 containing a food body 32 such as a roast of meat. Dish 30~ as well as plate 28, are preferably substantially transparent to microwave energy so that the lower region of food body 32 and the interior portions thereoE may be heated effectively by microwave energy.
Regions 16 and 18 pre~erably have a plurality of apertures 34 whose maximum dimensions are substantially less than a half wavelength of the free space wavelength of the microwave energy ; radiated into cavity 12. Preferably apertures 34 haviny maximum dimensions of, for example, less than a tenth of the free space wavelength of the microwave energy radiated into oven 12 by radiator 26 so that microwave energy radiated into enclosure 12 will not escape through regions 16 or 18~
Radiator 26 may comprise, for e~ample, a plenum 36 whose upper surface 38 contains a plurality of apertures 40 through which microwave energy is radiated upwardly into oven 12. A
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central conductor 42 of a coaxial line 44 supports plenum 36 by being attached to the center of upper plate 38. Conductor 42 extends downwardly through the outer conductor 46 of coaxial line 44 and through a waveguide 48 to a microwave choke and bearing assembly 50. An extensi.on of conductor 42 is rotated by a motor 52 below waveguide 48.
Microwave energy from a magnetron 54 is fed through wave-guide 48 and coaxial line 44 to radiator 26. A blower 56 blows a:ir passed the fins 58 of magnetron 54 to cool the magnetron, but none of this air passes through waveguide 48. A cover 60 of microwave transparent material is supported over radiator 26 on centering bumps 62 on the bottom o:f oven 12 to cover radiator 26 and thereby prevent food juices or other material from being dropped on radiator 26. However, any desired microwave feed structure, radiator, and/or door seal could be used.
When closed, door 14 is preferably sealed to enclosure 12 by a high temperature vapor seal with a microwave choke struc-ture positioned between said vapor seal and the interior of enclo-sure 12 50 t}-at microwave energy rad.iated into oven 12 -i~ 1argely prevented from bci.ng absorl)cd Irom the higll tcml)cr.ltl:lrc v~po:r seal Ilowever, any microwave energy passing through sa-id choke section is substanti.ally absorbed by the high tempera-ture vapor seal. ~hen door 14 is closed, a latch is mecllanically moved to lock door 14 shut and to permit energization of the magnetron 48. In accordance wi.th this invention a slight negative pressure is produced within plenum 20 by a blower system comprising two centrifugal blowers ~ i3~
64 which draw vapor out of cavity 12 through apertures 34 into plenum 20 and blows it out into plenums 66 surrounding blowers 64 and supplying region 16. The upper ends of plenum 66 are connected to an opening through which a small portion of the output of blowers 64 pass through an outlet vent 68 where the air is mixed with the air blown by a second set of blowers 70.
Blowers 70 draw cool ajr in from the back of the stove 10 to cool the air in duct 72 which exits through a screened aperture 74 in the top of the stove above the cooking surface thereof.
As shown in FIG.'s 1 and 2, each of the apertured regions 18 supplies vapors from the oven sucked to a different blower 64 and each blower 64 is driven along with one of the blowers 70, by a separate motor 76 which is supported from a bac~ wall 78 of the oven. A partition 80 between the two blowers 64 prevents tangential interaction of the vapor output of the blowers 64.
Blowers 64 preferably rotate in opposite directions to cause the air between the blowers to move upwardly adjacent par-tition 80.
It should be clearly understood that a single blower could be used in place of the dual blowers 64 and the plenum 66 could have ducting systems to direct the vapor through openings 16 into the oven. However, it has been found that the dual counter rotating blower system can improve the uniformity of convection heating in the overl.
A burner system 90 positioned at the bottom of stove 10 in a compartment behind and below enclosure 12 comprises a horizontal apertured tube 92 extending substantially the entire width of the oven and fed through vertical tubular member 94 with a gas-primary mixture supplied with gas through a gas valve 96. Second-ary air is regulated by the spacing of a plate 98 from the bottom of the entrance of the burner plenum. A pressure regulator 100 $~
connected to a gas line input 102 supplies gas valve 96. When the oven is turned on, an igni~or 108 is electrically energized and heats to a temperature which will ignite an air-gas mixture whereupon valve 98 opens, thereby causing said mixture to emanate from the apertures in tube 92 and producing a flame in burner plenum 106. Flue gas products in plenum 106 are drawn into plenum 20 along with excess secondary air by blowers 64 where the combustion products and secondary air are mixed with vapor drawn through apertures 34 from enclosure 12.
Burner 90, preferably run with excess secondary air to reduce the temperature of the products of combustion, is below 3,000 F so that substantially no oxide products of nitrogen are produced and combustion is substantially complete. Preferably sufficient excess secondary air is drawn into plenum 106 by the negative pressure in plenum 20 to produce a temperature in burner plenum 106 of l,200 F to 2,000 F. Plenums 20 and 106 extend ; substantially the full width of the back of enclosure 12 so that the burner plenum temperature is suhstantially uniform across said width. Thus, since the blower speed is constant, the slight negative pressure in combustion plenum 106 is substantially con-stant and accurately regulates the burner primary and secondary air drawn into the combustion chamber. The gas fed into the chamber is also constant due to pressure regulator 100 so that the excess air is accurately controlled.
A plurality of top gas burners llO is provided which operate as convention gas surface burners in accordance with well-known practice. Thermal insulation 112 is provided around the enclosure 12 and around the burner plenum 106 to reduce loss of thermal energy from the entire stove lO. A skin 114 of, for example, sheet metal surrounds the enclosure 12, the blower region, and the burner and microwave supply region.
During operation, the temperature of the enclosure vapor is sensed by a temperature sensor bulb 120 mounted, for example, in the oven on a bracket 122 below the vapor inlet 16 from the plenum 66.
The positioning of sensor 120 is preferably chosen so that it is not directly in the entering hot vapor stream from inlet 16 but rather senses the temperature of the vapor circu~
lating in the enclosure 12. The location of sensor 120 may be selected so that the oven heating cycles have reasonable time periods for burner on and burner off and the temperature range fluctuate large amounts. When the oven is ener~ized, the recircu-lating blowers 64 run continuously and when the burner 90 is energized, heat is delivered in the form of hot vapor substantially directly to the food body 32 in enclosure 12 and a substantially uniform heating pattern occurs.
Microwave energy power level and timer are controlled, for example, by a control panel 130 containing a timer 132 a power level 134, and on/off buttons 136 and 13~. In addition, a light 140 positionecl outside oven 12 but illuminating oven 12 through a light transparent high temperature ceramic 142 and a microwave shielding screen 144 may be provided. The microwave system may be energized, for example, from a 110 volt 60 cycle AC supply.
In accordance with this invention there is disclosed the discovery that browning of a Eood body such as roast 32 can be controlled by blowing hot vapor through inlet region 16 while radiating full power of microwave energy into the oven. This effect appears to occur due to surface effects of the velocity of hot air drying molsture from the surface of the food body and can occur with microwave energy being more readily absorbed by the dry food body surface to brown the food body surface, and _g _ therefore, an added broiler unit is not necessaryO
An example of power levels for effective food body 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 heating rate of about 5,000-15,000 BTU's per hour. Such power levels will bake and/or brown a cake in a few minutes.
This completes the description of the preferred embodiments of the invention. Although preferred embodiments have been described, it is believed that numerous modifications and altera-tions thereto would be apparent to one having ordinary skill in the art without departing from the spirit and scope of the inven-tion. For example, the oven may be fed through apertures located ; in regions other than the back wall, other systems for supplying microwave energy to the oven may be used and other types of circulating systems and burners may be used. Accordingly, it is intended that this invention be not limited to the particular details of the embodiment illustrated herein except as defined by the appended claims.
Claims (12)
1. In combination:
a conductive enclosure supplied with microwave energy; and a burner and means for drawing air through said burner and blowing vapor comprising said air and the products of combustion of said burner into said enclosure.
a conductive enclosure supplied with microwave energy; and a burner and means for drawing air through said burner and blowing vapor comprising said air and the products of combustion of said burner into said enclosure.
2. The combination in accordance with Claim 1 wherein:
said vapor comprises vapor drawn from said oven and combined with said products of combustion.
said vapor comprises vapor drawn from said oven and combined with said products of combustion.
3. An oven system comprising:
a conductive enclosure having an access opening and a closure member, 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 while exhausting from said system a portion of the vapor passing through said circulating means.
a conductive enclosure having an access opening and a closure member, 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 while exhausting from said system a portion of the vapor passing through said circulating means.
4. The oven in accordance with Claim 3 wherein:
said vapor comprises said products of combustion and excess air drawn through said burner.
said vapor comprises said products of combustion and excess air drawn through said burner.
5. the oven in accordance with Claim 4 wherein:
microwave energy is supplied to the interior of said oven.
microwave energy is supplied to the interior of said oven.
6. The oven in accordance with Claim 3 wherein:
the air drawn through said burner is controlled by said circulating means.
the air drawn through said burner is controlled by said circulating means.
7. In combination:
a conductive enclosure supplied with microwave energy through a rotating radiator;
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 while blowing a sufficient 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;
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 while blowing a sufficient portion of said vapor out a vent to control the amount of said air drawn through said burner.
8. The combination in accordance with Claim 7 wherein:
said vapor comprises vapor drawn from said oven and combined with said air and products of combustion.
said vapor comprises vapor drawn from said oven and combined with said air and products of combustion.
9. The combination in accordance with Claim 7 wherein:
said conductive enclosure has an access opening closed by a closure member sealed to said access opening by a microwave seal.
said conductive enclosure has an access opening closed by a closure member sealed to said access opening by a microwave seal.
10. The combination in accordance with Claim 7 wherein:
the amount of excess air drawn through burner is 50 to 150 percent of that required for complete combustion of said gas.
the amount of excess air drawn through burner is 50 to 150 percent of that required for complete combustion of said gas.
11. The combination in accordance with Claim 7 wherein:
microwave energy is supplied to the interior of said oven through a coaxial line.
microwave energy is supplied to the interior of said oven through a coaxial line.
12. The combination in accordance with Claim 7 wherein:
said gas burner comprises a ribbon type burner.
said gas burner comprises a ribbon type burner.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US96360478A | 1978-11-24 | 1978-11-24 | |
| US963,604 | 1978-11-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1138937A true CA1138937A (en) | 1983-01-04 |
Family
ID=25507444
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000338612A Expired CA1138937A (en) | 1978-11-24 | 1979-10-29 | Combination microwave and convection oven |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS5575131A (en) |
| AU (1) | AU529868B2 (en) |
| BE (1) | BE880134A (en) |
| CA (1) | CA1138937A (en) |
| CH (1) | CH642734A5 (en) |
| DE (1) | DE2946798A1 (en) |
| FR (1) | FR2442405A1 (en) |
| IT (1) | IT1162691B (en) |
| NL (1) | NL7908527A (en) |
| ZA (1) | ZA796074B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3599420A1 (en) * | 2018-07-23 | 2020-01-29 | Lg Electronics Inc. | Cooking appliance |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1138533A (en) * | 1978-11-20 | 1982-12-28 | Bernard J. Weiss | Microwave and convection oven |
| JPS596322Y2 (en) * | 1979-04-24 | 1984-02-27 | リンナイ株式会社 | high frequency cooker |
| DE3049922C2 (en) * | 1979-04-24 | 1983-11-10 | Rinnai Kk | Microwave oven with gas or electric burner underneath - for alternative baking and has fan shaft carrying both circulation and suction fans |
| JPS6440680U (en) * | 1987-09-08 | 1989-03-10 | ||
| JPS6444167U (en) * | 1987-09-14 | 1989-03-16 | ||
| JPH0712265U (en) * | 1993-08-13 | 1995-02-28 | 株式会社アビオン | Business card |
| EP3503680B1 (en) | 2011-08-31 | 2022-01-19 | Goji Limited | Object processing state sensing using rf radiation |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2910566A (en) * | 1958-06-23 | 1959-10-27 | Raytheon Co | Microwave ovens |
| DE1492600A1 (en) * | 1964-02-03 | 1970-03-26 | Cryodry Corp | Method and device for treating substances with microwaves |
| JPS4930957Y1 (en) * | 1970-12-16 | 1974-08-21 | ||
| JPS5125354Y2 (en) * | 1972-07-04 | 1976-06-28 | ||
| 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 |
| CH591049A5 (en) * | 1975-12-17 | 1977-08-31 | Elektromaschinen Ag | |
| GB1538851A (en) * | 1976-04-14 | 1979-01-24 | Boc International Ltd | Microwave heating |
| US4109488A (en) * | 1976-11-22 | 1978-08-29 | Bj-Hughes Inc. | Shock absorbing rotary drive coupling |
| US4211909A (en) * | 1978-05-15 | 1980-07-08 | Sanyo Electric Co., Ltd. | Combination microwave and gas oven |
| JPS5718577Y2 (en) * | 1978-08-03 | 1982-04-19 | ||
| CA1138533A (en) * | 1978-11-20 | 1982-12-28 | Bernard J. Weiss | 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
- 1979-10-29 CA CA000338612A patent/CA1138937A/en not_active Expired
- 1979-11-08 AU AU52630/79A patent/AU529868B2/en not_active Ceased
- 1979-11-12 ZA ZA00796074A patent/ZA796074B/en unknown
- 1979-11-19 FR FR7928473A patent/FR2442405A1/en active Granted
- 1979-11-19 BE BE0/198192A patent/BE880134A/en not_active IP Right Cessation
- 1979-11-20 IT IT50862/79A patent/IT1162691B/en active
- 1979-11-20 DE DE19792946798 patent/DE2946798A1/en active Granted
- 1979-11-22 JP JP15193179A patent/JPS5575131A/en active Granted
- 1979-11-22 NL NL7908527A patent/NL7908527A/en not_active Application Discontinuation
- 1979-11-23 CH CH1047679A patent/CH642734A5/en not_active IP Right Cessation
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3599420A1 (en) * | 2018-07-23 | 2020-01-29 | Lg Electronics Inc. | Cooking appliance |
| US11221146B2 (en) | 2018-07-23 | 2022-01-11 | Lg Electronics Inc. | Cooking appliance |
Also Published As
| Publication number | Publication date |
|---|---|
| ZA796074B (en) | 1980-10-29 |
| IT1162691B (en) | 1987-04-01 |
| NL7908527A (en) | 1980-05-28 |
| AU529868B2 (en) | 1983-06-23 |
| FR2442405B1 (en) | 1984-03-23 |
| IT7950862A0 (en) | 1979-11-20 |
| CH642734A5 (en) | 1984-04-30 |
| DE2946798A1 (en) | 1980-06-04 |
| AU5263079A (en) | 1980-05-29 |
| JPS5575131A (en) | 1980-06-06 |
| DE2946798C2 (en) | 1988-10-27 |
| BE880134A (en) | 1980-03-17 |
| FR2442405A1 (en) | 1980-06-20 |
| JPS6131777B2 (en) | 1986-07-22 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |