CA1256509A - Microwave oven - Google Patents
Microwave ovenInfo
- Publication number
- CA1256509A CA1256509A CA000524109A CA524109A CA1256509A CA 1256509 A CA1256509 A CA 1256509A CA 000524109 A CA000524109 A CA 000524109A CA 524109 A CA524109 A CA 524109A CA 1256509 A CA1256509 A CA 1256509A
- Authority
- CA
- Canada
- Prior art keywords
- lamp
- microwave
- microwave energy
- lamps
- filament
- 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
Landscapes
- Control Of High-Frequency Heating Circuits (AREA)
- Electric Ovens (AREA)
- Resistance Heating (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A microwave oven consists of an oven cavity containing a turntable, a source of microwave energy and a waveguide for directing microwave energy into the oven cavity. Two lamp units accommodate tungsten-halogen lamps for browning food cooked by the microwave energy. To inhibit arcing through the lamps due to exposure to the microwave energy, support coils supporting the filament of each lamp are each formed from an incomplete turn of the coil to inhibit arcing between adjacent regions thereof. Other modifications to the lamps may also be provided to protect the lamps from exposure to the microwave energy.
A microwave oven consists of an oven cavity containing a turntable, a source of microwave energy and a waveguide for directing microwave energy into the oven cavity. Two lamp units accommodate tungsten-halogen lamps for browning food cooked by the microwave energy. To inhibit arcing through the lamps due to exposure to the microwave energy, support coils supporting the filament of each lamp are each formed from an incomplete turn of the coil to inhibit arcing between adjacent regions thereof. Other modifications to the lamps may also be provided to protect the lamps from exposure to the microwave energy.
Description
MICROWAVE OVEN
__ This invention relates to a microwave oven and in particular to such an oven including tungsten-halogen lamps as a means for browning food cooked by the microwave energy.
A microwave oven of this type is described in our copending 5 UK Patent Pubn. No. 2152790A, wherein, in one embodi~ent, two heating units, each containing two tungsten-halogen lamps, are located at predetermined positions ad~acent openings into the oven cavity, so that infra-red radiation generated by the lamps is emitted towards food within the oven cavity to effect optimum browning thereof. ~ach lamp comprises a tungsten filament supported by spiral supports within a sealed, halogenated quartz envelope.
To prevent damage to the lamps, it is necessary to protect them from the microwave energy within the cavity, and to this end the above-mentioned Patent Pubn. No. 2152790A describes in one embodiment the provision of a protective screen, positioned over the opening and having a number of apertures dimensioned to inhibit the passage of microwave energy through it 7 whilst permitting the passage of infra-red radiation. As alternative or additional protection for the lamps, a microwave choke arrangement may be used~ which consists of waveguides dimensioned and located relative to the lamps to inhibit transmission of microwave energy from within the oven cavity to the lamps.
However, the use of a choke arrangement alone may not be sufficient protection for the lamps, which still tend to be exposed to sufficient microwave energy to cause ionisation of ' : 2 the gaseou~ fill of the lamps. This can lead to arcing through the lamps ard/or the formation of localised hotspots, which may cause a break down in the regenerative halogen cycle, thereby substantially reduoing the operative life of the lamps~
It is therefore an ob~ect of the present invention to provide a microwave oven including an improved tungsten-halogen lamp, which is le~ vulnerable to damage, when exposed to microwave energy, by inhibiting arcing andtor the formation of localised hotspots within the lamp, which can result from exposure of conventional lamps to microwave energy.
In accordance with the present invention, there is provided a microwave oven comprising a source of microwave energy and at least one source of infra-red radiation, said at least one infr~-red source including an in~ra-red-emissive lamp comprising a tungsten filament supported by a number of spaced support coils within a halogenated tubular envelope, each of said coils consisting of a first wire portion attached at one end to said filament and extending at the other end to form a second wire portion curled around the inner wall of said envelope, said second wire portion consisting of an incomplete turn of the coil to inhibit arcing between adjacent regions thereof due to exposure to said microwave energy.
The gaseous fill of the tungsten-halogen lamp preferably consi~ts predominantly of nitrogen with a halogen additive to inhibit arcing between the ends and/or the filament of the lamps, which can occur if other gases, such as argon, are used instead of nitrogen.
Each end of the lamp filament within the envelope is provided with an electrical connection to connect the filament to a power supply located externally of the lamp~ and each electrical connection of the lamp filament is preferably positioned so as to be shielded from the microwave energy by a wall of a metallic casing accommodating the lamp, thereby inhibiting the formation of localised hotspots at the electrical connection.
The, invention will now be further described by way of .D~
: 3:
- - example only with reference to the accompanying drawings, wherein:- -Figure 1 shows a schematic sectional vie~J of a microwave oven incorporating tungsten-halogen lamp units, Figure 2 shows a more detailed schematic plan view of a lamp unit shown in Figure 1, incorporating the present invention, Figure 3 shows a sectional view through I-I in Figure 2, and Figure 4 shows a schematic E~erpective end view of part of another embodiment of a lamp unit.
A microwave oven9 shown in Figure 1, consists of an oven cavity 1 containing a turntable 2, upon which food is supported to be cooked by microwave energy emitted from a source (not shown) and directed into the oven cavity 1 by a conventional wav~guide 3, stirrer and~or other suitable means.
Two lamp units 4, 5 are positioned outside of the cavity 1 at predetermined locations adjacent respective openings in side wall 6 and top wall 7 of the cavity 1. Each lamp unit 4, 5 consists of a metallic casing 8 accommodating tungsten-halogen lamps, such as at 9, around which a thermally-insulative or ceramic material 10 is provided to alleviate dissipation of heat from the unit 4,5 and partially to reflect infra-red radiation emitted from the lamps, a~ well as providing support for the lamps.
The lamps 9 generate radiation in the near-infra-red range within a wavelength band of 0.8-~ m with a peak at approximately 1. ~ m.
A protective screen 11 is positioned over each opening into the cavity 1, the screen being formed from any suitable infra-red-transmis~ive material, such as glass ceramic, to prevent the lamps and the interior of the unit from being damaged and/or soiled by food particles or other cooking products di~sipated from food being cooked in the cavity 1.
Infra-red radiation emitted from the lamp~ 9 is thus directed into the oven cavity 1, through the screen 11, to brown food being cooked by the microwave energy, the lamp units 4, 5 being poisitioned at predetermined locations to achieve an : 4 optimum browning effect.
The protective screen 11 does not prevent exposure of the lamps to the microwave energy, so that microwave energy can be transmitted from the lamp filament to lamp leads 12 and thus to outside of the cavity 1, causing an unacceptable leakage of the microwave energy. To inhibit such leaks, the ends oP each lamp 9 is provided with a microwave attenuating device, attached to the casing 8, as shown in outline at 13, whlch will be described in more detail hereinafter.
One of the lamp units 4 is shown in more detail in the plan view of Figure 2, wherein like parts are labelled with like reference numerals, with respect to Figure 1~
Each lamp 9 of the unit 4 consists of a linear or coiled coil tungsten filament 14 supported within a tubular quartz envelope 15 by a number of spaced support coils, such as at 16, each consisting of a coiled wire having a first portion wrapped~
at one end, around the filament 14 and extending radially in the envelope to form a second portion curled around the inner wall of the envelope 15.
Each end of the filament 14 i~ electrically connected to the flying lead 12, or other suitable connector, for connection to a power supply for the lamp, via a molybdenum foil 17 and a tail wire 18 sealed within a pinch seal 19 oP the envelope 15.
End 20 of the tail wire 18 emergent from the pinch seal 19 is formed into a short coil, which is interlinked with the end turns of the filament 14 to provide the electrical connection.
The envelope 15 has a gaseous fill sealed therein, which fill includes a halogen additive, providing a regenerative halogen cycle to increase the longevity of the lamp filament.
The pinch seal at the ends of each lamp are preferably enclosed within a oeramic housing, such as at 21, the housing for pinch seal 19 having been removed to reveal the pinch seal construction. The ceramic housings 21 are provided to protect the pinch seals from mechanical damage and/or overheating by exposure to infra-red radiation from the filament.
As.indicated in Figure 1, the ends of the lamps are ~d l~ ~3 : 5 enclosed within a microwave attenuating device 13, the device at one end of the unit shown in Figure 2 having been removed for clarity.
One example of a suitable microwave attenuating device is shown in Figure 3, wherein the device 13 consists of a conventional quarter-wave choke. The choke consists of a metallic, short-circuited stub 22, having a rectangular cross-section9 which fits over ceramic end cap 23 of the lamp and surrounds lamp lead 24. The stub 22 has a length commensurate with a quarter of th~e wavelength of the microwave energy, which produces an electrical open-cirouit to propagating microwaves, thereby inhibiting their tran~mi3sion along the lamp lead 24. Preferably, the stub 22 enclo~es the end caps of both of the lamps in each unit, but each lamp may alternatively be provided with an individual stub.
The temperature of the pinch seals of the lamps should not exceed approximately 350C to prevent damage to the lamps due to overheating and, to this end, a number of holes (not shown) are preferably provided in some or all of the top and side walls and the base of the attenuating device 13 to increa~e air circulation and reduce thermal conduction from the oven cavity.
Although the microwave attenuating device 13 inhibits microwave leakage, it does not provide any protection for the lamps from the microwave energy and is thus insufficient by itself to inhibit damage to the lamps and a reduction in their operative life. Major causes of lamp failure due to exposure to microwave energy are arcing through the lamp, which occurs when the gaseous fill is ionised by the microwave energy, and the formation of localiAed hotspots within the lamp.
To substantially reduce the vulnerability of the lamps to the microwave energy, in accordance with the present invention, the lamps are provided with one or more modifications to alleviate the above problems of arcing and/or localised hotspots.
A first modification is to the support coils 16, which, in conventional tungsten-halogen lamps, each consists of more than one comp~ete turn, generally 4/3 turns, of the wire portion : 6 curled around the inner wall of the envelope. However, it has been found to be advantageous to reduce the coil length to less than one complete turn, preferably to 3/4 or 7/8 of a turn, as shown in Figure 2, thereby inhibiting arcing which tends to occur between adjacent turns of a conventional support coil, when the lamp is exposed to microwave energy. In a preferred construction, the coil diameter is 7.7-7.8mm and the gap left in the coil turn around the inner wall of the envelope i.9 2-3mm.
A second modification is to the gaseous fill of the lamps, which conventionally consists predominantly of an inert gas, usually argon, together with a halogen additive sufficient in quantity to provide the regenerative cycle. However, it has been found to be particularly advantageous to utilise a fill pre~ominantly of nitrogen with a halogen additive, which is less susceptible to ionisation by the microwave energy, and thus to arcing between the lamp ends and/or the filament, than conventionally used Pills.
A third modification of the lamps is to the positioning of the electrical connection between the tail wire 18 and the end of the filament 14. When this connection is exposed to relatively high intensities of microwave energy, it tends to form a localised hotspot, which may cause a visual di~turbance to a user of the microwave oven, as well as reducing the life of the lamp. To inhibit the formation of such a hotspot, the lamp is arranged such that the electrical connection is shielded from the microwave energy by positioning it adjacent a wall of the metallic casing 8, as shown by the connection between tail wire 18 and filament 14 adjacent wall 25 of the casing 8. The metallic wall 8 thus acts as a shield to protect the electrical connection from the microwave energy.
It can thus be envisaged that by using one or more, and preferably all three, of the above-described modifications, the vulnerability of the lamps to damage by microwave energy is substantially reduced, thus lncreasing the operative life of the lamps.
Figure 4 shows an alternative arrangement of the microwave : 7 attenuating device shown in Figures 1 to 3. Figure 4 show3 schematically an end perspective view of a lamp unlt~ showing two end caps 26, 27 o~ the lamps of the unit. In this arrangement, lamp leads 28, 29 extend laterally from the end caps 26, 27 respe¢tively and respectively pass through two microwave attenuating devices 30, 31. Between the two devices 30, 31 and surrounding the end caps 26, 27 is a metal mesh 32, which is attached to the metallic casing 8 o~ the unit. The mesh 32 permits sufficient cooling of the lamp ends, a3 well as inhibiting leakage of the microwave energy propogated along the lamp leads.
The microwave attenuating devices shown in the Figures may consist of any suitable arrangement, such as the quarter wave choke shown in Figures 2 and 3.
An alternative suitable device may include microwave absorbent materials, quch as ferrite, which absorbs microwaves as they propagate down the lamp leads. A conventional embodiment of such a device includes one or more ferrite bead~
threaded onto the lamp lead and then enclosed within a metallic sleeve.
__ This invention relates to a microwave oven and in particular to such an oven including tungsten-halogen lamps as a means for browning food cooked by the microwave energy.
A microwave oven of this type is described in our copending 5 UK Patent Pubn. No. 2152790A, wherein, in one embodi~ent, two heating units, each containing two tungsten-halogen lamps, are located at predetermined positions ad~acent openings into the oven cavity, so that infra-red radiation generated by the lamps is emitted towards food within the oven cavity to effect optimum browning thereof. ~ach lamp comprises a tungsten filament supported by spiral supports within a sealed, halogenated quartz envelope.
To prevent damage to the lamps, it is necessary to protect them from the microwave energy within the cavity, and to this end the above-mentioned Patent Pubn. No. 2152790A describes in one embodiment the provision of a protective screen, positioned over the opening and having a number of apertures dimensioned to inhibit the passage of microwave energy through it 7 whilst permitting the passage of infra-red radiation. As alternative or additional protection for the lamps, a microwave choke arrangement may be used~ which consists of waveguides dimensioned and located relative to the lamps to inhibit transmission of microwave energy from within the oven cavity to the lamps.
However, the use of a choke arrangement alone may not be sufficient protection for the lamps, which still tend to be exposed to sufficient microwave energy to cause ionisation of ' : 2 the gaseou~ fill of the lamps. This can lead to arcing through the lamps ard/or the formation of localised hotspots, which may cause a break down in the regenerative halogen cycle, thereby substantially reduoing the operative life of the lamps~
It is therefore an ob~ect of the present invention to provide a microwave oven including an improved tungsten-halogen lamp, which is le~ vulnerable to damage, when exposed to microwave energy, by inhibiting arcing andtor the formation of localised hotspots within the lamp, which can result from exposure of conventional lamps to microwave energy.
In accordance with the present invention, there is provided a microwave oven comprising a source of microwave energy and at least one source of infra-red radiation, said at least one infr~-red source including an in~ra-red-emissive lamp comprising a tungsten filament supported by a number of spaced support coils within a halogenated tubular envelope, each of said coils consisting of a first wire portion attached at one end to said filament and extending at the other end to form a second wire portion curled around the inner wall of said envelope, said second wire portion consisting of an incomplete turn of the coil to inhibit arcing between adjacent regions thereof due to exposure to said microwave energy.
The gaseous fill of the tungsten-halogen lamp preferably consi~ts predominantly of nitrogen with a halogen additive to inhibit arcing between the ends and/or the filament of the lamps, which can occur if other gases, such as argon, are used instead of nitrogen.
Each end of the lamp filament within the envelope is provided with an electrical connection to connect the filament to a power supply located externally of the lamp~ and each electrical connection of the lamp filament is preferably positioned so as to be shielded from the microwave energy by a wall of a metallic casing accommodating the lamp, thereby inhibiting the formation of localised hotspots at the electrical connection.
The, invention will now be further described by way of .D~
: 3:
- - example only with reference to the accompanying drawings, wherein:- -Figure 1 shows a schematic sectional vie~J of a microwave oven incorporating tungsten-halogen lamp units, Figure 2 shows a more detailed schematic plan view of a lamp unit shown in Figure 1, incorporating the present invention, Figure 3 shows a sectional view through I-I in Figure 2, and Figure 4 shows a schematic E~erpective end view of part of another embodiment of a lamp unit.
A microwave oven9 shown in Figure 1, consists of an oven cavity 1 containing a turntable 2, upon which food is supported to be cooked by microwave energy emitted from a source (not shown) and directed into the oven cavity 1 by a conventional wav~guide 3, stirrer and~or other suitable means.
Two lamp units 4, 5 are positioned outside of the cavity 1 at predetermined locations adjacent respective openings in side wall 6 and top wall 7 of the cavity 1. Each lamp unit 4, 5 consists of a metallic casing 8 accommodating tungsten-halogen lamps, such as at 9, around which a thermally-insulative or ceramic material 10 is provided to alleviate dissipation of heat from the unit 4,5 and partially to reflect infra-red radiation emitted from the lamps, a~ well as providing support for the lamps.
The lamps 9 generate radiation in the near-infra-red range within a wavelength band of 0.8-~ m with a peak at approximately 1. ~ m.
A protective screen 11 is positioned over each opening into the cavity 1, the screen being formed from any suitable infra-red-transmis~ive material, such as glass ceramic, to prevent the lamps and the interior of the unit from being damaged and/or soiled by food particles or other cooking products di~sipated from food being cooked in the cavity 1.
Infra-red radiation emitted from the lamp~ 9 is thus directed into the oven cavity 1, through the screen 11, to brown food being cooked by the microwave energy, the lamp units 4, 5 being poisitioned at predetermined locations to achieve an : 4 optimum browning effect.
The protective screen 11 does not prevent exposure of the lamps to the microwave energy, so that microwave energy can be transmitted from the lamp filament to lamp leads 12 and thus to outside of the cavity 1, causing an unacceptable leakage of the microwave energy. To inhibit such leaks, the ends oP each lamp 9 is provided with a microwave attenuating device, attached to the casing 8, as shown in outline at 13, whlch will be described in more detail hereinafter.
One of the lamp units 4 is shown in more detail in the plan view of Figure 2, wherein like parts are labelled with like reference numerals, with respect to Figure 1~
Each lamp 9 of the unit 4 consists of a linear or coiled coil tungsten filament 14 supported within a tubular quartz envelope 15 by a number of spaced support coils, such as at 16, each consisting of a coiled wire having a first portion wrapped~
at one end, around the filament 14 and extending radially in the envelope to form a second portion curled around the inner wall of the envelope 15.
Each end of the filament 14 i~ electrically connected to the flying lead 12, or other suitable connector, for connection to a power supply for the lamp, via a molybdenum foil 17 and a tail wire 18 sealed within a pinch seal 19 oP the envelope 15.
End 20 of the tail wire 18 emergent from the pinch seal 19 is formed into a short coil, which is interlinked with the end turns of the filament 14 to provide the electrical connection.
The envelope 15 has a gaseous fill sealed therein, which fill includes a halogen additive, providing a regenerative halogen cycle to increase the longevity of the lamp filament.
The pinch seal at the ends of each lamp are preferably enclosed within a oeramic housing, such as at 21, the housing for pinch seal 19 having been removed to reveal the pinch seal construction. The ceramic housings 21 are provided to protect the pinch seals from mechanical damage and/or overheating by exposure to infra-red radiation from the filament.
As.indicated in Figure 1, the ends of the lamps are ~d l~ ~3 : 5 enclosed within a microwave attenuating device 13, the device at one end of the unit shown in Figure 2 having been removed for clarity.
One example of a suitable microwave attenuating device is shown in Figure 3, wherein the device 13 consists of a conventional quarter-wave choke. The choke consists of a metallic, short-circuited stub 22, having a rectangular cross-section9 which fits over ceramic end cap 23 of the lamp and surrounds lamp lead 24. The stub 22 has a length commensurate with a quarter of th~e wavelength of the microwave energy, which produces an electrical open-cirouit to propagating microwaves, thereby inhibiting their tran~mi3sion along the lamp lead 24. Preferably, the stub 22 enclo~es the end caps of both of the lamps in each unit, but each lamp may alternatively be provided with an individual stub.
The temperature of the pinch seals of the lamps should not exceed approximately 350C to prevent damage to the lamps due to overheating and, to this end, a number of holes (not shown) are preferably provided in some or all of the top and side walls and the base of the attenuating device 13 to increa~e air circulation and reduce thermal conduction from the oven cavity.
Although the microwave attenuating device 13 inhibits microwave leakage, it does not provide any protection for the lamps from the microwave energy and is thus insufficient by itself to inhibit damage to the lamps and a reduction in their operative life. Major causes of lamp failure due to exposure to microwave energy are arcing through the lamp, which occurs when the gaseous fill is ionised by the microwave energy, and the formation of localiAed hotspots within the lamp.
To substantially reduce the vulnerability of the lamps to the microwave energy, in accordance with the present invention, the lamps are provided with one or more modifications to alleviate the above problems of arcing and/or localised hotspots.
A first modification is to the support coils 16, which, in conventional tungsten-halogen lamps, each consists of more than one comp~ete turn, generally 4/3 turns, of the wire portion : 6 curled around the inner wall of the envelope. However, it has been found to be advantageous to reduce the coil length to less than one complete turn, preferably to 3/4 or 7/8 of a turn, as shown in Figure 2, thereby inhibiting arcing which tends to occur between adjacent turns of a conventional support coil, when the lamp is exposed to microwave energy. In a preferred construction, the coil diameter is 7.7-7.8mm and the gap left in the coil turn around the inner wall of the envelope i.9 2-3mm.
A second modification is to the gaseous fill of the lamps, which conventionally consists predominantly of an inert gas, usually argon, together with a halogen additive sufficient in quantity to provide the regenerative cycle. However, it has been found to be particularly advantageous to utilise a fill pre~ominantly of nitrogen with a halogen additive, which is less susceptible to ionisation by the microwave energy, and thus to arcing between the lamp ends and/or the filament, than conventionally used Pills.
A third modification of the lamps is to the positioning of the electrical connection between the tail wire 18 and the end of the filament 14. When this connection is exposed to relatively high intensities of microwave energy, it tends to form a localised hotspot, which may cause a visual di~turbance to a user of the microwave oven, as well as reducing the life of the lamp. To inhibit the formation of such a hotspot, the lamp is arranged such that the electrical connection is shielded from the microwave energy by positioning it adjacent a wall of the metallic casing 8, as shown by the connection between tail wire 18 and filament 14 adjacent wall 25 of the casing 8. The metallic wall 8 thus acts as a shield to protect the electrical connection from the microwave energy.
It can thus be envisaged that by using one or more, and preferably all three, of the above-described modifications, the vulnerability of the lamps to damage by microwave energy is substantially reduced, thus lncreasing the operative life of the lamps.
Figure 4 shows an alternative arrangement of the microwave : 7 attenuating device shown in Figures 1 to 3. Figure 4 show3 schematically an end perspective view of a lamp unlt~ showing two end caps 26, 27 o~ the lamps of the unit. In this arrangement, lamp leads 28, 29 extend laterally from the end caps 26, 27 respe¢tively and respectively pass through two microwave attenuating devices 30, 31. Between the two devices 30, 31 and surrounding the end caps 26, 27 is a metal mesh 32, which is attached to the metallic casing 8 o~ the unit. The mesh 32 permits sufficient cooling of the lamp ends, a3 well as inhibiting leakage of the microwave energy propogated along the lamp leads.
The microwave attenuating devices shown in the Figures may consist of any suitable arrangement, such as the quarter wave choke shown in Figures 2 and 3.
An alternative suitable device may include microwave absorbent materials, quch as ferrite, which absorbs microwaves as they propagate down the lamp leads. A conventional embodiment of such a device includes one or more ferrite bead~
threaded onto the lamp lead and then enclosed within a metallic sleeve.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A microwave oven comprising a source of microwave energy and at least one source of infra-red radiation, said at least one infra-red source including an infra-red-emissive lamp comprising a tungsten filament supported by a number of spaced support coils within a halogenated tubular envelope, each of said coils consisting of a first wire portion attached at one end to said filament and extending at the other end to form a second wire portion curled around the inner wall of said envelope, said second wire portion consisting of an incomplete turn of the coil to inhibit arcing between adjacent regions thereof due to exposure to said microwave energy.
2. A microwave oven as claimed in Claim 1 wherein the gaseous fill of said envelope consists predominantly of nitrogen with a halogen additive to inhibit arcing between the ends of said lamp and/or said filament.
3. A microwave oven as claimed in Claim 1 wherein each infra-red source includes a metallic casing and each end of said filament is provided with an electrical connection to a power supply located externally of said lamp, each electrical connection being positioned so as to be shielded from the microwave energy by a wall of said metallic casing, thereby inhibiting the formation of localised hotspots at said electrical connection.
4. A microwave oven as claimed in Claim 1 wherein each end of said lamp is enclosed within a microwave attenuating device to inhibit leakage of microwave energy from the oven.
5. A microwave oven as claimed in Claim 4 wherein said microwave attenuating device consists of a quarter-wave choke.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB858529580A GB8529580D0 (en) | 1985-11-30 | 1985-11-30 | Microwave ovens |
| GB8529580 | 1986-07-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1256509A true CA1256509A (en) | 1989-06-27 |
Family
ID=10589098
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000524109A Expired CA1256509A (en) | 1985-11-30 | 1986-11-28 | Microwave oven |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPH0719660B2 (en) |
| CA (1) | CA1256509A (en) |
| GB (1) | GB8529580D0 (en) |
| ZA (1) | ZA868941B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009257619A (en) * | 2008-04-14 | 2009-11-05 | Panasonic Corp | Heating cooker |
-
1985
- 1985-11-30 GB GB858529580A patent/GB8529580D0/en active Pending
-
1986
- 1986-11-26 ZA ZA868941A patent/ZA868941B/en unknown
- 1986-11-26 JP JP27989286A patent/JPH0719660B2/en not_active Expired - Lifetime
- 1986-11-28 CA CA000524109A patent/CA1256509A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB8529580D0 (en) | 1986-01-08 |
| ZA868941B (en) | 1987-10-28 |
| JPS62145692A (en) | 1987-06-29 |
| JPH0719660B2 (en) | 1995-03-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |