EP0457948B1 - Microwaveapparatus - Google Patents

Microwaveapparatus Download PDF

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Publication number
EP0457948B1
EP0457948B1 EP19900109863 EP90109863A EP0457948B1 EP 0457948 B1 EP0457948 B1 EP 0457948B1 EP 19900109863 EP19900109863 EP 19900109863 EP 90109863 A EP90109863 A EP 90109863A EP 0457948 B1 EP0457948 B1 EP 0457948B1
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Prior art keywords
chamber
microwave
movable
wall
resonator
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EP19900109863
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German (de)
French (fr)
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EP0457948A1 (en
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Lothar Dr. Schuh
Friedrich Dr. Harbach
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ABB Patent GmbH
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ABB Patent GmbH
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Priority to DE90109863T priority Critical patent/DE59004441D1/en
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    • 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
    • H05B6/80—Apparatus for specific applications

Definitions

  • Microwave devices with a multimode chamber with at least one movable resonator wall are shown in FIGS. 2 and 3 of GB-A-926 958 and described in the associated description part.
  • the movable wall is designed as a reflector of an infrared radiator that bounces around a pivot point at a small angle.
  • the rocking movement results in an oscillating movement of wave maxima in the resonator chamber.
  • the resonator volume practically does not change, so that the number of modes remains constant. There is only a slight change in the field distribution.
  • DE-B 11 86 570 shows a microwave device which does not have a multimode resonator for receiving a workpiece, but rather a slot radiator through which a workpiece to be heated is passed.
  • the slot radiator is the exit opening of a waveguide into which a magnetron feeds.
  • the waveguide is to be regarded as a single-mode chamber.
  • the field strength maximum of the radiation characteristic at the outlet opening moves back and forth. This is achieved by a movable short-circuit slide in the waveguide.
  • DE-B 24 62 853 discloses a microwave device with a plurality of microwave generators for providing the microwave energy. Given the dimensions of the chamber acting as a resonator and an operating frequency of a few GHz, standing waves are formed. For example, the usual operating frequency of 2.45 GHz corresponds to a free space wavelength of approximately 12 cm. The resulting stationary wave nodes and wave bellies cause disturbing field inhomogeneities, which lead to the fact that, for example, larger ceramic components are heated differently locally and sinter inhomogeneously. This leads to unusable workpieces or even to their complete destruction.
  • the invention is based on the object of specifying a microwave device which has a highly homogeneous field distribution during a heating or sintering process in the volume of a workpiece.
  • the resonator can preferably be designed with chamber walls arranged parallel to one another, of which one chamber wall is designed to be movable and can be set in repetitive lifting movements.
  • curved walls can also be provided to achieve special field configurations.
  • cylindrical resonators or resonators with hollow mirror-shaped walls are possible.
  • the microwave device according to the invention has the advantage that the microwave field is homogenized, so that even complex-shaped parts can be heated homogeneously.
  • the sintered material is not set in motion.
  • a single waveguide can be used with the interposition of a circulator. This will have no effect on the generators.
  • the invention proposes to have at least one resonator wall perform a movement, preferably a stroke movement, with a low frequency, that is to say to allow it to vibrate.
  • a movement preferably a stroke movement
  • a low frequency that is to say to allow it to vibrate.
  • a wall is designed to be adjustable so that the desired wave propagation (resonance) can be set before the heating process is carried out (see Ceramic Bulletin, page 1603, paragraph 2 and page 1604, paragraph 2).
  • the movable wall of the single-mode chamber is therefore only intended for adjustment, ie. for setting the location of the maximum power of the standing wave in the chamber.
  • the chamber wall movement according to the invention a field distribution which is more homogeneous on average over time than can be achieved with known measures, for example rotary blades.
  • the characteristic of the standing waves is influenced to a large extent by the position of the chamber walls.
  • a contactless lambda quarter short-circuit structure ensures that the chamber wall can be moved without friction and that no microwave radiation can escape through leaks.
  • the device can be operated with both continuous and pulsed microwave energy.
  • the pulse frequency and pulse shape can run synchronized with the wall movement as well as being stochastic.
  • a variable or fixed stroke frequency in the range from 0.1 to 100 Hz and a stroke amplitude in the range from approximately 0.5 to 20 cm are preferred for the wall movement.
  • the drawing shows schematically the structure of a microwave device according to the invention.
  • the device contains a metallic chamber 1 made, for example, of stainless steel, which has fixed walls 2 and a movable wall 3.
  • the dimensions of the chamber are approximately 60 x 60 x 60 cm3.
  • the movable wall 3 is coupled to a controllable reciprocating piston engine 5 via a push rod 4.
  • the rod 4 is supported by a ball bearing 6.
  • a gap 7 is expedient between the movable wall 3 and the fixed walls 2, which is approximately 1 to 2 mm wide.
  • the edge of the movable wall 3 is designed as a quarter-wave short-circuit slide 8.
  • a high-frequency insulation ring 10 can be attached to the part 9 of the lambda quarter short-circuit slide 8 that is turned toward the outside.
  • a high-frequency insulation ring 10 can be designed, for example, as a plastic ring or as a brush with microwave-absorbing properties.
  • This additional safety device has no mechanical guiding or supporting function, so that even when this safety device is used, there is a practically contactless movement of the movable wall 3 in the chamber 1.
  • a second quarter-wave short-circuit slide 11 is arranged on the push rod 4.
  • a microwave-impermeable metal grille 12 with a corresponding mesh size and a stable pipe duct 13 for the push rod 4 is provided for shielding on the chamber 1 in front of the movable wall 3.
  • the existing structural parts for moving and guiding the movable wall 3, such as rod 4, ball bearing 6 and bushing 13, must be made sufficiently stable to ensure a constant narrow gap 7 during wall movement.
  • a ventilation channel 14 is installed in one of the fixed walls 2, the diameter-length ratio of which is approximately 1: 3.
  • the opening of the ventilation channel 14 is secured by a metallic ventilation grille 15 against the escape of microwave radiation.
  • a ceramic molded body 16 to be sintered is arranged within the chamber 1 in a microwave-transparent container 17.
  • the molded body 16 is surrounded by heat-insulating and microwave-transparent fiber mats 18, which consist, for example, of aluminum oxide ceramic.
  • the movable wall 3 is set in a repetitive lifting movement and microwave energy is fed in via the waveguide 25.
  • the standing waves caused by the chamber dimensions and the interferences given by several modes are continuously changed. It creates other waveforms, which results in a spatially and temporally changing plurality of power maxima, which leads to homogeneous heating of the molded body 16.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Constitution Of High-Frequency Heating (AREA)

Description

MikrowelleneinrichtungMicrowave facility

Die Erfindung bezieht sich auf eine Mikrowelleneinrichtung mit einer Mehrmodenkammer, die wenigstens eine bewegliche Kammerwand aufweist. Die Mikrowelleneinrichtung ist vorgesehen zur raschen und homogenen Erwärmung und zur Sinterung keramischer Bauteile. Für diesen Zweck wird eine Mikrowelleneinrichtung mit einer relativ großen Ofenkammer und einer hohen Mikrowellenleistung benötigt.The invention relates to a microwave device with a multi-mode chamber, which has at least one movable chamber wall. The microwave device is intended for rapid and homogeneous heating and for sintering ceramic components. For this purpose, a microwave device with a relatively large oven chamber and a high microwave power is required.

Mikrowelleneinrichtungen mit einer Mehrmodenkammer mit wenigstens einer beweglichen Resonatorwand sind in den Figuren 2 und 3 der GB-A-926 958 dargestellt und im zugehörigen Beschreibungsteil beschrieben. In beiden dort dargestellten Ausgestaltungen der Mehrmodenkammer ist die bewegliche Wand als Reflektor eines Infrarotstrahlers gestaltet, der um einen Drehpunkt in einem kleinen Winkel wippt. Durch die Wippbewegung wird eine oszillierende Bewegung von Wellenmaxima im Resonatorraum erreicht. Das Resonatorvolumen ändert sich jedoch praktisch nicht, so daß auch die Anzahl der Moden konstant bleibt. Es kommt nur zu einer geringfügigen Änderung der Feldverteilung.Microwave devices with a multimode chamber with at least one movable resonator wall are shown in FIGS. 2 and 3 of GB-A-926 958 and described in the associated description part. In both of the configurations of the multimode chamber shown there, the movable wall is designed as a reflector of an infrared radiator that bounces around a pivot point at a small angle. The rocking movement results in an oscillating movement of wave maxima in the resonator chamber. However, the resonator volume practically does not change, so that the number of modes remains constant. There is only a slight change in the field distribution.

Der DE-B 11 86 570 ist eine Mikrowelleneinrichtung zu entnehmen, die keinen Mehrmoden-Resonator zur Aufnahme eines Werkstücks aufweist, sondern einen Schlitzstrahler, an dem ein zu erwärmendes Werkstück vorbeigeführt wird. Der Schlitzstrahler ist die Austrittsöffnung eines Hohlleiters, in den ein Magnetron einspeist. Der Hohlleiter ist als Einmoden-Kammer aufzufassen. Das Feldstärkemaximum der Strahlungscharakteristik an der Austrittsöffnung bewegt sich hin und her. Dies wird durch einen beweglichen Kurzschlußschieber im Hohlleiter erreicht.DE-B 11 86 570 shows a microwave device which does not have a multimode resonator for receiving a workpiece, but rather a slot radiator through which a workpiece to be heated is passed. The slot radiator is the exit opening of a waveguide into which a magnetron feeds. The waveguide is to be regarded as a single-mode chamber. The field strength maximum of the radiation characteristic at the outlet opening moves back and forth. This is achieved by a movable short-circuit slide in the waveguide.

Aus der DE-B 24 62 853 ist eine Mikrowelleneinrichtung mit mehreren Mikrowellengeneratoren zur Bereitstellung der Mikrowellenenergie bekannt. Bei den gegebenen Abmessungen der als Resonator wirkenden Kammer und bei einer Betriebsfrequenz von einigen GHz kommt es zur Ausbildung von stehenden Wellen. Beispielsweise entspricht der üblichen Betriebsfrequenz von 2,45 GHz eine Freiraum-Wellenlänge von etwa 12 cm. Die damit gegebenen stationären Wellenknoten und Wellenbäuche bewirken störende Feldinhomogenitäten, die dazu führen, daß beispielsweise größere keramische Bauteile örtlich unterschiedlich erwärmt werden und inhomogen sintern. Dies führt zu unbrauchbaren Werkstücken oder gar zu deren vollständigen Zerstörung.DE-B 24 62 853 discloses a microwave device with a plurality of microwave generators for providing the microwave energy. Given the dimensions of the chamber acting as a resonator and an operating frequency of a few GHz, standing waves are formed. For example, the usual operating frequency of 2.45 GHz corresponds to a free space wavelength of approximately 12 cm. The resulting stationary wave nodes and wave bellies cause disturbing field inhomogeneities, which lead to the fact that, for example, larger ceramic components are heated differently locally and sinter inhomogeneously. This leads to unusable workpieces or even to their complete destruction.

In der DE-B 24 62 853 ist eine von Haushalts-Mikrowellengeräten bekannte Abhilfemaßnahme, nämlich ein rotierender Reflektorflügel erwähnt. Bei Hochtemperaturanwendungen ist allerdings die Wirksamkeit des Drehflügels, der eine kontinuierliche Änderung der Feldverteilung verursachen soll, unbefriedigend. Wirksamer sind dagegen Drehteller oder andere Vorrichtungen, welche eine Ortsänderung eines zu erwärmenden Sintergutes innerhalb der Kammer bewirken. Da Sintergut gegen Erschütterungen empfindlich ist, sind auch Drehtelleranordnungen, welche Erschütterungen verursachen, nicht geeignet. Zur Lösung des Problems der ungleichmäßigen Feldverteilung wird in der DE-B 24 62 853 vorgeschlagen, mehrere Generatoren mit einzeln regelbaren Magnetrons vorzusehen, welche jeweils über in den Ofenraum ragende Antennen einspeisen. Bei hohen Magnetronleistungen und verlustarmem Erwärmungsgut kommt es jedoch zu einer Rückstrahlung von Mikrowellenenergie ins Magnetron, wodurch dieses zerstört werden kann.DE-B 24 62 853 mentions a remedy known from household microwave devices, namely a rotating reflector wing. In high-temperature applications, however, the effectiveness of the rotary wing, which is said to cause a continuous change in the field distribution, is unsatisfactory. On the other hand, turntables or other devices that cause a change in the location of a sintered material to be heated within the chamber are more effective. Since sintered goods are sensitive to vibrations, turntable arrangements which cause vibrations are also unsuitable. To solve the problem of uneven Field distribution is proposed in DE-B 24 62 853 to provide several generators with individually controllable magnetrons, each of which feeds in via antennas projecting into the furnace space. With high magnetron outputs and low-loss heating material, however, microwave energy is reflected back into the magnetron, which can destroy it.

Der Erfindung liegt die Aufgabe zugrunde, eine Mikrowelleneinrichtung anzugeben, die eine in hohem Maß homogene Feldverteilung während eines Erwärmungs- oder Sinterprozesses im Volumen eines Werkstücks aufweist.The invention is based on the object of specifying a microwave device which has a highly homogeneous field distribution during a heating or sintering process in the volume of a workpiece.

Diese Aufgabe wird gelöst durch eine Mikrowelleneinrichtung mit einer als Resonator wirkenden, mit mehreren metallischen Kammerwänden gebildeten Mehrmodenkammer, in die ein zu erwärmendes Werkstück einsetzbar ist und in die Mikrowellenenergie einspeisbar ist, wobei

  • a) wenigstens eine beweglich ausgeführte Kammerwand vorhanden ist und
  • b) Mittel vorhanden sind, die bewirken, daß die bewegliche Kammerwand während des Betriebes der Mikrowelleneinrichtung in eine repetierende Bewegung versetzbar ist, und wobei
  • c) Mittel zur Hochfrequenz-Abdichtung der beweglichen Kammerwand gegenüber festen Kammerwänden vorhanden sind, so daß bei Bewegung der beweglichen Kammerwand eine Änderung des Resonatorvolumens gegeben ist.
This object is achieved by a microwave device with a multi-mode chamber acting as a resonator and formed with a plurality of metallic chamber walls, into which a workpiece to be heated can be inserted and into which microwave energy can be fed, wherein
  • a) at least one movable chamber wall is present and
  • b) means are provided which bring about that the movable chamber wall can be set in a repetitive movement during the operation of the microwave device, and wherein
  • c) Means for high-frequency sealing of the movable chamber wall from fixed chamber walls are present, so that there is a change in the resonator volume when the movable chamber wall is moved.

Der Resonator kann vorzugsweise mit parallel zueinander angeordneten Kammerwänden ausgeführt werden, von denen eine Kammerwand beweglich ausgeführt ist und in repetierende Hubbewegungen versetzbar ist. Anstelle von parallel zueinander angeordneten plattenförmigen Wänden eines z.B. quaderförmigen Resonators können auch gebogene Wände vorgesehen werden, um besondere Feldkonfigurationen zu erzielen. Möglich sind z.B. zylinderförmige Resonatoren oder Resonatoren mit hohlspiegelförmigen Wänden.The resonator can preferably be designed with chamber walls arranged parallel to one another, of which one chamber wall is designed to be movable and can be set in repetitive lifting movements. Instead of plate-shaped walls of a cuboid resonator arranged parallel to one another, curved walls can also be provided to achieve special field configurations. For example, cylindrical resonators or resonators with hollow mirror-shaped walls are possible.

Die erfindungsgemäße Mikrowelleneinrichtung hat den Vorteil, daß eine Vergleichmäßigung des Mikrowellenfeldes erreicht wird, so daß auch komplex geformte Teile homogen erwärmt werden können. Das Sintergut wird dabei nicht in Bewegung versetzt. Bei Verwendung mehrerer Generatoren kann unter Zwischenschaltung eines Zirkulators mit einem einzigen Hohlleiter eingespeist werden. Eine Rückwirkung auf die Generatoren wird dadurch vermieden.The microwave device according to the invention has the advantage that the microwave field is homogenized, so that even complex-shaped parts can be heated homogeneously. The sintered material is not set in motion. When using several generators, a single waveguide can be used with the interposition of a circulator. This will have no effect on the generators.

Mit der Erfindung wird vorgeschlagen, wenigstens eine Resonatorwand eine Bewegung, vorzugsweise eine Hubbewegung mit einer niedrigen Frequenz ausführen zu lassen, also schwingen zu lassen. Aus Ceramic Bulletin, Vol. 68, No. 9, 1989, Seite 1601 bis 1606, insbesondere Figur 2 und zugehörigem Text ist bekannt, eine Kammerwand einstellbar zu gestalten. Dabei ist jedoch keine betriebsmäßige Bewegung der Kammerwand zur Änderung der Feldverteilung vorgesehen. Es handelt sich dort um eine Einmoden-Kammer, welche zum Fügen von Keramikteilen vorgesehen und nicht zum Sintern größerer Keramikteile geeignet ist. Zum Verbinden von Keramikteilen wird eine hohe Erwärmung an der Verbindungsstelle benötigt. Deshalb ist dort eine Wand einstellbar gestaltet, um die gewünschte Wellenausbreitung (Resonanz) vor der Durchführung des Erwärmungsvorgangs einstellen zu können (vgl. Ceramic Bulletin, Seite 1603, Absatz 2 und Seite 1604, Absatz 2). Die bewegliche Wand der Einmoden-Kammer ist also lediglich zum Justieren vorgesehen, dh. zur Einstellung des Ortes des Leistungsmaximums der stehenden Welle in der Kammer. Eine Anregung im Falle einer Mehrmoden-Kammer durch eine repetierende Bewegung einer Kammerwand eine Änderung der Feldverteilung während des Erwärmungsvorgangs zu bewirken, ist dort nicht zu entnehmen.The invention proposes to have at least one resonator wall perform a movement, preferably a stroke movement, with a low frequency, that is to say to allow it to vibrate. From Ceramic Bulletin, Vol. 68, No. 9, 1989, pages 1601 to 1606, in particular FIG. 2 and the associated text, it is known to design an adjustable chamber wall. However, there is no operational movement of the chamber wall to change the field distribution. It is a single-mode chamber which is intended for joining ceramic parts and is not suitable for sintering larger ceramic parts. A high level of heating at the connection point is required to connect ceramic parts. Therefore, a wall is designed to be adjustable so that the desired wave propagation (resonance) can be set before the heating process is carried out (see Ceramic Bulletin, page 1603, paragraph 2 and page 1604, paragraph 2). The movable wall of the single-mode chamber is therefore only intended for adjustment, ie. for setting the location of the maximum power of the standing wave in the chamber. There is no suggestion in the case of a multi-mode chamber that a repetitive movement of a chamber wall causes a change in the field distribution during the heating process.

Es hat sich gezeigt, daß mit der erfindungsgemäßen Kammerwandbewegung eine im zeitlichen Mittel homogenere Feldverteilung als mit bekannten Maßnahmen, z.B. Drehflügeln, erreicht werden kann. Die Charakteristik der stehenden Wellen wird nämlich in hohem Maße von der Position der Kammerwände beeinflußt. Mit einer kontaktlosen Lambda-Viertel-Kurzschlußstruktur wird erreicht, daß die Kammerwand ohne Reibung bewegt werden kann und daß keine Mikrowellenstrahlung durch Lecks nach außen dringt. Zur besseren Steuerung des Erwärmungsvorganges kann die Einrichtung sowohl mit kontinuierlicher wie auch gepulster Mikrowellenenergie betrieben werden. Die Pulsfrequenz und Pulsform können sowohl mit der Wandbewegung synchronisiert ablaufen, wie auch stochastisch sein. Für die Wandbewegung wird eine veränderliche oder feste Hubfrequenz im Bereich von 0,1 bis 100 Hz und eine Hubamplitude im Bereich von etwa 0,5 bis 20 cm bevorzugt.It has been shown that with the chamber wall movement according to the invention a field distribution which is more homogeneous on average over time than can be achieved with known measures, for example rotary blades. The characteristic of the standing waves is influenced to a large extent by the position of the chamber walls. A contactless lambda quarter short-circuit structure ensures that the chamber wall can be moved without friction and that no microwave radiation can escape through leaks. For better control of the heating process, the device can be operated with both continuous and pulsed microwave energy. The pulse frequency and pulse shape can run synchronized with the wall movement as well as being stochastic. A variable or fixed stroke frequency in the range from 0.1 to 100 Hz and a stroke amplitude in the range from approximately 0.5 to 20 cm are preferred for the wall movement.

Eine ausführlichere Beschreibung erfolgt nachstehend anhand eines in der Zeichnung dargestellten Ausführungsbeispiels.A more detailed description is given below with reference to an embodiment shown in the drawing.

Die Zeichnung zeigt schematisch den Aufbau einer erfindungsgemäßen Mikrowelleneinrichtung. Die Einrichtung enthält eine z.B. aus Edelstahl gefertigte metallische Kammer 1, welche feste Wände 2 und eine bewegliche Wand 3 aufweist. Die Abmessungen der Kammer betragen etwa 60 x 60 x 60 cm³. Die bewegliche Wand 3 ist über eine Schubstange 4 mit einem steuerbaren Hubkolbenmotor 5 gekoppelt. Die Stange 4 ist mit einem Kugellager 6 gelagert. Um eine freie Beweglichkeit der beweglichen Wand 3 in der Kammer 1 zu gewährleisten, ist ein Spalt 7 zwischen der beweglichen Wand 3 und den festen Wänden 2 zweckmäßig, der etwa 1 bis 2 mm breit ist. Um einen Austritt von Mikrowellenstrahlung als Leckstrahlung zu verhindern, ist der Rand der beweglichen Wand 3 als Lambda-Viertel-Kurzschlußschieber 8 ausgebildet. Außerdem kann als zusätzliche Sicherung an dem zur Außenseite gekehrten Teil 9 des Lambda-Viertel-Kurzschlußschiebers 8 ein Hochfrequenz-Isolationsring 10 angebracht werden. Ein solcher Hochfrequenz-Isolationsring 10 kann beispielsweise als Kunststoffring oder als Bürste mit mikrowellenabsorbierenden Eigenschaften ausgeführt werden. Diese zusätzliche Sicherheitseinrichtung hat keine mechanische Führungs- oder Abstützungsfunktion, so daß auch bei Verwendung dieser Sicherheitseinrichtung eine praktisch berührungslose Bewegung der beweglichen Wand 3 in der Kammer 1 gegeben ist. Als weitere Sicherheitsmaßnahme ist an der Schubstange 4 ein zweiter Lambda-Viertel-Kurzschlußschieber 11 angeordnet. Außerdem ist zur Abschirmung an der Kammer 1 vor der beweglichen Wand 3 ein mikrowellenundurchlässiges Metallgitter 12 mit entsprechender Maschenweite mit einer stabilen Rohrdurchführung 13 für die Schubstange 4 vorhanden. Die zur Bewegung und Führung der beweglichen Wand 3 vorhandenen Konstruktionsteile, wie Stange 4, Kugellager 6 und Durchführung 13, müssen ausreichend stabil ausgeführt sein, um einen gleichbleibend schmalen Spalt 7 während der Wandbewegung zu gewährleisten.The drawing shows schematically the structure of a microwave device according to the invention. The device contains a metallic chamber 1 made, for example, of stainless steel, which has fixed walls 2 and a movable wall 3. The dimensions of the chamber are approximately 60 x 60 x 60 cm³. The movable wall 3 is coupled to a controllable reciprocating piston engine 5 via a push rod 4. The rod 4 is supported by a ball bearing 6. In order to ensure free movement of the movable wall 3 in the chamber 1, a gap 7 is expedient between the movable wall 3 and the fixed walls 2, which is approximately 1 to 2 mm wide. In order to prevent leakage of microwave radiation, the edge of the movable wall 3 is designed as a quarter-wave short-circuit slide 8. In addition, a high-frequency insulation ring 10 can be attached to the part 9 of the lambda quarter short-circuit slide 8 that is turned toward the outside. Such a high-frequency insulation ring 10 can be designed, for example, as a plastic ring or as a brush with microwave-absorbing properties. This additional safety device has no mechanical guiding or supporting function, so that even when this safety device is used, there is a practically contactless movement of the movable wall 3 in the chamber 1. As a further safety measure, a second quarter-wave short-circuit slide 11 is arranged on the push rod 4. In addition, a microwave-impermeable metal grille 12 with a corresponding mesh size and a stable pipe duct 13 for the push rod 4 is provided for shielding on the chamber 1 in front of the movable wall 3. The existing structural parts for moving and guiding the movable wall 3, such as rod 4, ball bearing 6 and bushing 13, must be made sufficiently stable to ensure a constant narrow gap 7 during wall movement.

Wegen des bei der Hubbewegung der beweglichen Wand 3 nötigen Druckausgleichs in der Kammer 1 ist in einer der festen Wände 2 ein Entlüftungskanal 14 angebracht, dessen Durchmesser-Längen-Verhältnis etwa 1 : 3 beträgt. Die Öffnung des Entlüftungskanals 14 wird durch ein metallisches Entlüftungsgitter 15 gegen einen Austritt von Mikrowellenstrahlung gesichert.Because of the pressure equalization in the chamber 1 necessary for the lifting movement of the movable wall 3, a ventilation channel 14 is installed in one of the fixed walls 2, the diameter-length ratio of which is approximately 1: 3. The opening of the ventilation channel 14 is secured by a metallic ventilation grille 15 against the escape of microwave radiation.

Ein zu sinternder keramischer Formkörper 16 ist innerhalb der Kammer 1 in einem mikrowellentransparenten Behälter 17 angeordnet. Der Formkörper 16 ist mit wärmedämmenden und mikrowellentransparenten Fasermatten 18 umgeben, die beispielsweise aus Aluminiumoxidkeramik bestehen.A ceramic molded body 16 to be sintered is arranged within the chamber 1 in a microwave-transparent container 17. The molded body 16 is surrounded by heat-insulating and microwave-transparent fiber mats 18, which consist, for example, of aluminum oxide ceramic.

Zur Temperaturmessung ist ein Meßkopf 19 eines Hochtemperatur-Thermometers an der Oberfläche des Formkörpers 16 angeordnet und über einen Lichtleiter 20 und eine Durchführung 21 in der Kammer 1 mit einer Steuer- und Regeleinrichtung 22 für Mikrowellengeneratoren 23 verbunden. Mit dieser Einrichtung wird die gegebenenfalls über Zirkulatoren 24 und über Hohlleiter 25 in die Kammer 1 eingespeiste Mikrowellenenergie unter Vermeidung unzulässiger Temperaturen oder Temperaturgradienten entsprechend vorgegebener Temperatur-Zeitprofile gesteuert. Die Mikrowellenleistung beträgt typisch mehrere Kilowatt.For temperature measurement, a measuring head 19 of a high-temperature thermometer is arranged on the surface of the molded body 16 and connected to a control and regulating device 22 for microwave generators 23 via an optical fiber 20 and a bushing 21 in the chamber 1. This device is used to control the microwave energy which may be fed into the chamber 1 via the circulators 24 and the waveguide 25 while avoiding inadmissible temperatures or temperature gradients in accordance with predetermined temperature-time profiles. The microwave power is typically several kilowatts.

Zur Durchführung eines Sintervorgangs wird die bewegliche Wand 3 in eine sich wiederholende Hubbewegung versetzt und Mikrowellenenergie über die Hohlleiter 25 eingespeist. Als Folge der sich andauernd ändernden Reflexionsbedingungen in der Kammer 1 werden die durch die Kammerabmessungen bedingten stehenden Wellen und die durch mehrere Moden gegebenen Interferenzen dauernd verändert. Es entstehen dabei auch andere Wellenformen, wodurch sich eine sich räumlich und zeitlich ändernde Vielzahl von Leistungsmaxima ergibt, welche zu einer homogenen Erwärmung des Formkörpers 16 führt.To carry out a sintering process, the movable wall 3 is set in a repetitive lifting movement and microwave energy is fed in via the waveguide 25. As a result of the constantly changing reflection conditions in the chamber 1, the standing waves caused by the chamber dimensions and the interferences given by several modes are continuously changed. It creates other waveforms, which results in a spatially and temporally changing plurality of power maxima, which leads to homogeneous heating of the molded body 16.

Claims (1)

  1. Microwave device having a multi-mode chamber (1) acting as resonator and formed with a number of metallic chamber walls (2, 3), into which chamber a workpiece (16) to be heated can be inserted and into which microwave energy can be fed, there being
    a) at least one chamber wall (3) constructed to be movable, and there being
    b) means (4, 5, 22) which cause a repetitive movement to be impartable to the movable chamber wall (3) during the operation of the microwave device,
    characterized in that there are
       c) means (7 to 10) for radio-frequency sealing of the movable chamber wall (3) with respect to fixed chamber walls (2) so that a change in the resonator volume is given when the movable chamber wall (3) moves.
EP19900109863 1990-05-23 1990-05-23 Microwaveapparatus Expired - Lifetime EP0457948B1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE90109863T DE59004441D1 (en) 1990-05-23 1990-05-23 Microwave facility.
EP19900109863 EP0457948B1 (en) 1990-05-23 1990-05-23 Microwaveapparatus

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19900109863 EP0457948B1 (en) 1990-05-23 1990-05-23 Microwaveapparatus

Publications (2)

Publication Number Publication Date
EP0457948A1 EP0457948A1 (en) 1991-11-27
EP0457948B1 true EP0457948B1 (en) 1994-01-26

Family

ID=8204023

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900109863 Expired - Lifetime EP0457948B1 (en) 1990-05-23 1990-05-23 Microwaveapparatus

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EP (1) EP0457948B1 (en)
DE (1) DE59004441D1 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2627730B2 (en) * 1993-09-23 1997-07-09 エルジー電子株式会社 Automatic matching device for microwave oven
DE19700140A1 (en) * 1997-01-04 1998-07-09 Gero Hochtemperaturoefen Gmbh Kiln for high temperature treatment of materials with low dielectric loss factor
MY123981A (en) * 1997-08-26 2006-06-30 Samsung Electronics Co Ltd Microwave oven having a cooking chamber reflecting microwaves at varying angles
IT1304897B1 (en) * 1998-09-08 2001-04-05 Gaudenzio Borelli MICROWAVE OVEN FOR COOKING CERAMIC MATERIAL UNDER PRESSURE
DE102006052169A1 (en) * 2006-11-02 2008-05-08 Ivan Dr. Imenokhoyev Microwave device i.e. microwave oven, for heating goods, has chamber type applicator with hood and base plate, which limits chamber volumes, where hood has concave inner surface surrounding goods to be warmed in dome shaped manner

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB926958A (en) * 1957-12-10 1963-05-22 Miwag Mikrowellen A G Improvements in apparatus for heating substances and objects by means of micro-waves
DE1186570B (en) * 1958-10-01 1965-02-04 Robert Bosch Elektronik Ges Mi Slot radiator for the heating of dielectric materials
FR2053592A5 (en) * 1969-07-10 1971-04-16 Kriz Francois Rotary plastisol moulding device
FR2315986A1 (en) * 1975-07-04 1977-01-28 Olivier Jean RESONANT PROCESS AND REACTOR FOR TREATING MATERIAL WITH ELECTROMAGNETIC WAVES
US4054768A (en) * 1976-08-06 1977-10-18 White Donald A System for increasing visibility and microwave distribution within a microwave oven
US4361744A (en) * 1981-01-12 1982-11-30 Despatch Industries, Inc. Microwave process unit

Also Published As

Publication number Publication date
DE59004441D1 (en) 1994-03-10
EP0457948A1 (en) 1991-11-27

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