EP0369321B1 - Ventilateur à air circulé pour fours - Google Patents

Ventilateur à air circulé pour fours Download PDF

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Publication number
EP0369321B1
EP0369321B1 EP89120760A EP89120760A EP0369321B1 EP 0369321 B1 EP0369321 B1 EP 0369321B1 EP 89120760 A EP89120760 A EP 89120760A EP 89120760 A EP89120760 A EP 89120760A EP 0369321 B1 EP0369321 B1 EP 0369321B1
Authority
EP
European Patent Office
Prior art keywords
drive shaft
microwave oven
muffle
baking muffle
spring element
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 - Lifetime
Application number
EP89120760A
Other languages
German (de)
English (en)
Other versions
EP0369321A2 (fr
EP0369321A3 (en
Inventor
Reinhold Hopfensperger
Rolf Tungl
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alcatel Lucent Deutschland AG
Original Assignee
Alcatel SEL AG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Alcatel SEL AG filed Critical Alcatel SEL AG
Publication of EP0369321A2 publication Critical patent/EP0369321A2/fr
Publication of EP0369321A3 publication Critical patent/EP0369321A3/de
Application granted granted Critical
Publication of EP0369321B1 publication Critical patent/EP0369321B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • 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
    • H05B6/76—Prevention of microwave leakage, e.g. door sealings

Definitions

  • the invention relates to a microwave oven with a circulating air fan for circulating air in the baking muffle, in which an electric motor is fastened to the baking muffle rear wall by means of a bearing bracket and the drive shaft of the electric motor projects through an opening into the baking muffle.
  • the passage opening for the drive shaft in the back wall of the baking muffle is particularly critical, but also the drive shaft itself. In order to achieve a certain exit damping, the opening should not exceed a quarter of the wavelength of the high frequency. This condition can be met without major difficulties. It is much more difficult to get a grip on the part of the high frequency that comes out through the drive shaft.
  • the drive shaft acts as a radiator (part an antenna), whereby the baking muffle wall is used as an electrical counterweight.
  • the shortening factor is a function of the material and the diameter of the drive shaft. Part of the energy radiated by the drive shaft is damped by the stator package of the drive motor and the bearing brackets and converted into heat, but the free part can radiate unhindered.
  • a microwave oven is also known (DE-A-31 04 627) in which the muffle is designed to be microwave-proof.
  • a microwave throttle is arranged at the opening through which the drive shaft of the blower motor projects into the muffle, both inside and outside the muffle.
  • Each microwave choke consists of a cavity resonator, which are coupled to one another via the opening in the muffle rear wall and the drive shaft of the blower motor.
  • the microwave chokes create a high impedance in the area of the opening, as a result of which the microwave energy which wants to escape from the muffle is largely reflected.
  • the object of the invention is therefore to find an effective and inexpensive solution to prevent the radiation of high-frequency energy via the drive shaft.
  • the solution according to the invention consists in that a short circuit for high-frequency currents is arranged outside the baking muffle rear wall and the drive shaft.
  • the advantage of the invention is that a metal drive shaft is still used.
  • use is made of the fact that the skin effect is pronounced due to the high frequencies (of the order of about 2.5 GHz). This means that the electrical energy comes out of the baking muffle mainly via the surface of the drive shaft.
  • the high-frequency energy reaching the surface on the outside is picked up near the shaft by an electrically conductive element, for example a pair of clamping glasses, and short-circuited via the rear wall of the baking muffle.
  • an electrically conductive element for example a pair of clamping glasses
  • This not only ensures the shortest possible electrical path, but also ensures that tolerances due to production or operation (thermal expansion) are compensated for.
  • a further advantage of the invention results when the piece of the drive shaft protruding from the baking muffle is roughened and / or provided with an electrically poorly conductive layer. Due to the already mentioned skin effect, less high-frequency energy escapes through a roughened surface than through a smooth (dead-run effect!).
  • Fig. 1a 10 denotes a drive motor which is flanged via a three-armed bearing bracket 16 to the rear wall 11 of the baking muffle of a baking oven, which is only partially shown.
  • a drive shaft denoted by 12 projects through an opening 17 into the interior of the baking muffle and drives a fan wheel (not shown) there.
  • a conductive connection designated 13 Between baking muffle rear wall 11 and drive shaft 12 there is a conductive connection designated 13, in the exemplary embodiment described here, a pair of clamping glasses.
  • the clamping glasses 13 are attached to a socket 14.
  • a shielding plate 15 is also provided.
  • the arrangement shown works as follows: If high-frequency energy reaches the outside through the opening 17 from the interior of the baking muffle via the drive shaft 12, it is short-circuited via the conductive connection 13, in this case by means of a pair of clamps, via the back wall of the baking muffle. Since the energy transport of high-frequency energy from the interior of the baking muffle to the outside takes place essentially on the surface of the drive shaft due to the skin effect, this measure prevents high-frequency energy from reaching the bearing bracket or the motor.
  • the socket 14 is held by the shielding plate 15.
  • the purpose of the shield plate 15 is a further high-frequency shield.
  • the spring element 13 is attached to the socket 14.
  • the conductive connection 13 is connected to the three-armed bracket 16, so the socket is missing. It is essential that the high-frequency energy reaching the outside is short-circuited via the back wall of the baking muffle so that electrical energy cannot be emitted.
  • the use of a spring element as a conductive connection also compensates for manufacturing and operational tolerances.
  • One way to minimize the amount of high-frequency energy that escapes to the outside is to roughen the part of the drive shaft that lies outside the baking muffle and / or with an electrically poorly conductive layer (reference numeral 32, FIG. 1b) cover. These measures dampen both the transport of the RF energy from the rear wall (reduction in conductivity) and the radiation of the wave outside the baking muffle (dead-running effect).
  • 1b shows a drive shaft which is provided with knurling 31 and a plurality of grooves 30.
  • a graphite layer is suitable as a coating.
  • Fig. 2 shows a second embodiment of the invention.
  • the same reference numerals designate the same elements as in FIG. 1.
  • the bushing 14 carrying the spring element is here connected directly to the bearing bracket 16.
  • the difference between the two exemplary embodiments results from the different design of the baking muffle rear wall.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
  • Constitution Of High-Frequency Heating (AREA)
  • Electric Ovens (AREA)

Claims (9)

  1. Four à micro-ondes comportant un ventilateur de circulation de l'air pour recycler l'air dans le moufle du four, dans le cas duquel un moteur électrique (10) est fixé à la paroi arrière (11) du moufle du four au moyen d'un étrier porte-palier (16) et l'arbre d'entraînement (12) du moteur électrique (10) pénètre dans le moufle du four par une ouverture (17),
       caractérisé par le fait qu'à l'extérieur du moufle du four, entre la paroi arrière (11) du moufle du four et l'arbre d'entraînement (12) est disposé un court-circuit pour courants de haute fréquence.
  2. Four à micro-ondes selon la revendication 1,
       caractérisé par le fait que le court-circuit est constitué d'un élément formant ressort (13).
  3. Four à micro-ondes selon la revendication 2,
       caractérisé par une rondelle Belleville ou une monture de bridage comme élément formant ressort.
  4. Four à micro- ondes selon la revendication 2,
       caractérisé par une tôle de blindage (15) reliée, avec conduction, avec la paroi arrière (11) du moufle du four et l'élément formant ressort (13).
  5. Four à micro-ondes selon la revendication 2,
       caractérisé par un coussinet (14) pouvant coulisser librement sur l'arbre d'entraînement selon le sens axial et relié, avec conduction électrique, avec l'élément formant ressort (13).
  6. Four à micro-ondes selon la revendication 2,
       caractérisé par le fait que l'élément formant ressort (13) est fixé à l'étrier porte-palier (16).
  7. Four à micro-ondes selon la revendication 1,
       caractérisé par le fait que la partie de l'arbre d'entraînement (12) qui se trouve à l'extérieur du moufle du four (11) est rendue fortement rugueuse.
  8. Four à micro-ondes selon la revendication 7,
       caractérisé par le fait que la surface de l'arbre d'entraînement (12) est munie d'un moletage (31) et/ou de rainures obtenues au tour par saignée.
  9. Four à micro-ondes selon la revendication 8,
       caractérisé par le fait que la surface de l'arbre d'entraînement (12) est revêtue d'une couche (32) d'un matériau à grande résistance électrique.
EP89120760A 1988-11-12 1989-11-09 Ventilateur à air circulé pour fours Expired - Lifetime EP0369321B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3838447A DE3838447A1 (de) 1988-11-12 1988-11-12 Umluftgeblaese fuer backoefen
DE3838447 1988-11-12

Publications (3)

Publication Number Publication Date
EP0369321A2 EP0369321A2 (fr) 1990-05-23
EP0369321A3 EP0369321A3 (en) 1990-12-27
EP0369321B1 true EP0369321B1 (fr) 1995-03-01

Family

ID=6367073

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89120760A Expired - Lifetime EP0369321B1 (fr) 1988-11-12 1989-11-09 Ventilateur à air circulé pour fours

Country Status (3)

Country Link
US (1) US4973825A (fr)
EP (1) EP0369321B1 (fr)
DE (2) DE3838447A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3437443B2 (ja) * 1997-08-08 2003-08-18 シャープ株式会社 高周波加熱装置

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4053730A (en) * 1976-05-17 1977-10-11 Litton Systems Inc. Microwave oven shaft seal
US4211909A (en) * 1978-05-15 1980-07-08 Sanyo Electric Co., Ltd. Combination microwave and gas oven
US4358653A (en) * 1977-11-25 1982-11-09 Raytheon Company Combination microwave oven
US4335290A (en) * 1978-01-05 1982-06-15 Raytheon Company Microwave oven blower radiator
EP0006997B1 (fr) * 1978-07-12 1983-01-19 Bosch-Siemens HausgerÀ¤te GmbH Four à micro-ondes
US4308417A (en) * 1979-06-19 1981-12-29 International Computers Limited Electrical sealing device
DE3104627A1 (de) * 1980-07-23 1982-11-11 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Mikrowellenheizgeraet
DE3028352C2 (de) * 1980-07-25 1982-10-14 Bosch-Siemens Hausgeräte GmbH, 7000 Stuttgart Mikrowellenofen
US4485285A (en) * 1983-03-07 1984-11-27 Control Data Corporation Quarterwave choke for a microwave oven quartz lamp
US4687908A (en) * 1985-12-23 1987-08-18 Parallel Industries, Inc. Convection blower for conventional electric ovens
US4764651A (en) * 1987-09-23 1988-08-16 Whirlpool Corporation Grounding of stirrer bushing in a microwave oven
DE3810684A1 (de) * 1988-03-29 1989-10-19 Bosch Siemens Hausgeraete Geblaese fuer einen umluftherd

Also Published As

Publication number Publication date
US4973825A (en) 1990-11-27
DE3838447A1 (de) 1990-05-17
DE58909058D1 (de) 1995-04-06
EP0369321A2 (fr) 1990-05-23
EP0369321A3 (en) 1990-12-27

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