EP0071123B1 - Microwave device for warming and/or drying flat materials passing through the device - Google Patents

Microwave device for warming and/or drying flat materials passing through the device Download PDF

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Publication number
EP0071123B1
EP0071123B1 EP82106440A EP82106440A EP0071123B1 EP 0071123 B1 EP0071123 B1 EP 0071123B1 EP 82106440 A EP82106440 A EP 82106440A EP 82106440 A EP82106440 A EP 82106440A EP 0071123 B1 EP0071123 B1 EP 0071123B1
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EP
European Patent Office
Prior art keywords
waveguide
web
microwave
halves
waveguide elements
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Expired
Application number
EP82106440A
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German (de)
French (fr)
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EP0071123A1 (en
Inventor
Hans Georg Dr. Fitzky
Franz Schmitt
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Agfa Gevaert AG
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Agfa Gevaert AG
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Publication of EP0071123A1 publication Critical patent/EP0071123A1/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
    • H05B6/78—Arrangements for continuous movement of material
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F5/00—Dryer section of machines for making continuous webs of paper
    • D21F5/16—Drying webs by electrical heating
    • D21F5/167—Microwave heating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B13/00—Machines and apparatus for drying fabrics, fibres, yarns, or other materials in long lengths, with progressive movement
    • F26B13/10—Arrangements for feeding, heating or supporting materials; Controlling movement, tension or position of materials
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B3/00—Drying solid materials or objects by processes involving the application of heat
    • F26B3/32—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action
    • F26B3/34—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action by using electrical effects
    • F26B3/347—Electromagnetic heating, e.g. induction heating or heating using microwave energy
    • 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
    • H05B2206/00—Aspects relating to heating by electric, magnetic, or electromagnetic fields covered by group H05B6/00
    • H05B2206/04—Heating using microwaves
    • H05B2206/046—Microwave drying of wood, ink, food, ceramic, sintering of ceramic, clothes, hair

Definitions

  • the present invention relates to a device for the uniform heating and / or drying of broad, thin sheets of paper, plastic, textiles or photographic materials using a microwave-powered energy transmitter which, for the passage of the material, consists of pipelines arranged symmetrically in two parts and arranged parallel to one another exists, which are connected to each other and whose length is matched to a whole number of half-waves (AI2), whereby in order to avoid undesired electromagnetic couplings between the pipe elements, the pipe elements are alternately offset by a fourth-pipe wavelength ( ⁇ / 4) and for feeding g of the individual pipe elements, separate microwave generators are used in connection with circulators.
  • a microwave-powered energy transmitter which, for the passage of the material, consists of pipelines arranged symmetrically in two parts and arranged parallel to one another exists, which are connected to each other and whose length is matched to a whole number of half-waves (AI2), whereby in order to avoid undesired electromagnetic couplings between the pipe elements, the pipe elements are alternately offset
  • microwaves offer higher specific heating outputs because the heat generated in the material due to the dielectric loss increases proportionally with the frequency.
  • Usual microwave dryers for sheet-like materials use meandering pipelines which are guided transversely to the web, the material being passed through slots in the pipeline, e.g. B. US 3,672,066, US 3,449,836, US 3,475,827.
  • Disadvantages of these arrangements are, particularly with a larger width and thickness of the material, the local inhomogeneity of the heating, in particular the exponential decrease in the intensity of the progressing in the pipeline due to the absorption in the material Wave, and the heating by standing waves, which are caused by reflection on the web edges and the pipe bends in the course of the meandering guidance of the rectangular tube.
  • Characteristic here are relatively sharply defined temperature maxima in the material at a distance of half the tube wavelength.
  • the quadratic field strength dependence of the dielectric losses contributes to the formation of local overheating.
  • the arrangement according to GB 2 042 703 A attempts to reduce the effect of standing waves in pipelines oriented transversely to the web direction by using two pipelines with different positions of the electrical field maxima in relation to the point of action of the material passing through.
  • the aim is a coincidence of the maximum field strength in the first pipeline with the minimum field strength in the second pipeline.
  • the invention has for its object to provide a device of the type mentioned above, with which it is possible in a simple manner, both uniformly across the width of the material heating and drying of the material, in particular the coatings of carrier materials, as well as when one maintenance of certain maximum temperatures to achieve the fastest possible drying.
  • the claimed method uses an arrangement of several parallel, two-part and short-circuited pipelines which are oriented in the web running direction .
  • the length of the individual pipelines is a multiple half the tube wavelength matched, the number of half-wavelengths is chosen so large that, taking into account the microwave absorption by the web material, there is an approx. 50% absorption when the microwave is first run through the tube system fed at the end.
  • the excitation in the pipeline is thereby. formed by a predominant proportion of continuous waves and a smaller proportion of standing waves. Due to the high damping of the standing wave (resonance), a critical adjustment of the individual pipe conductors to the frequency of the generator is not necessary.
  • Another key characteristic of the device is the parallel feeding of the individual pipelines by separate microwave generators and circulators, the individual control and regulation of the power supplied by iris couplers at the ends and the practically completely uniform heating of the material in the transverse direction by slightly interlacing the pipeline direction with respect to the Direction of the material.
  • Standing waves in the individual pipeline do not cause uneven heating of the material transversely to the running direction, because the piping is arranged in the running direction and differs only a few degrees with it.
  • All pipe halves are integrated in two mirror-symmetrical metal half-shells, one of which is designed to be hinged for the introduction of the material and for cleaning purposes. Maintaining maximum material temperatures is achieved by the constant control of the microwave excitation acting in each pipe and by the method of direct current heating, ie the same direction of travel of the material and the microwave fed in.
  • the parallel pipelines are connected to each other to suppress radiation and coupling with larger gap widths by conductive webs. These webs reduce the undesired electromagnetic coupling between the individual pipelines which are guided in parallel at a short distance.
  • the width of the webs is in the range of 20 to 200% of the gap width and is selected according to the microwave absorption by the material.
  • the individual pipelines represent highly damped microwave resonators that are operated at the frequency of the generator. The resonators are damped by the absorption of the material. Given the microwave absorption of the material, the damping of the resonance increases with the length of the tube. The shaft is almost completely absorbed in the material during one pass. For a given pipe length, the damping increases with the absorption of the material, e.g. B. with increasing water content.
  • the web width can therefore be chosen to be relatively small. Conversely, the web width must be chosen larger with low absorption of the material (low moisture).
  • the microwave will run back and forth with an absorption of more than 75%. This results in a relatively low ripple in the field profile along the pipe and the maximum electric field strength that occurs is severely limited, so that electrical discharges from metallic edges are avoided, which is of great importance when drying photographic material or thermally sensitive layers.
  • the high microwave absorption of the material is mainly in the initial stages of drying (wet area), with advanced drying and in the so-called residual moisture area (e.g. equilibrium moisture compared to the relative humidity of the ambient or entrained air) the microwave absorption can be less than 1 db / m fall off.
  • the undesired electromagnetic, mainly electrical coupling increases with less material absorption.
  • the web width is increased to up to 200% of the gap width between the half-shells.
  • a special possibility of suppressing the coupling between adjacent pipelines was found in a surprisingly simple manner by the alternating arrangement of the pipelines, that is to say by alternating displacement next to one another gender pipe around A14 in the longitudinal direction.
  • the coupling via the electrical component is suppressed to such an extent that the electrical and magnetic maxima of the standing wave component lie opposite one another in adjacent pipelines.
  • This type of arrangement is particularly advantageous when there is a high proportion of standing waves, ie with a short pipe length and / or low material absorption (residual moisture range).
  • the size of the permissible gap width between the half shells containing the pipe halves is ultimately limited by the radiation to the outside. Even with a very large web width (more than 200% of the gap width), the gap width must remain below half the free space wavelength. At 2450 MHz, values of 40 mm can be achieved in extreme cases. However, gap widths of 10 to 25 mm are preferred. With gap widths above about 20% of the free space wavelength, the distortion of the electrical field profile of the Hio wave results in an increasing decoupling of material passed through, so that at 2450 MHz gap widths over 25 mm are of little importance (for thin, dense materials up to approx. 1 mm). By using low frequencies, e.g. B. 915 MHz correspondingly larger gap widths can be realized.
  • the adjustment of the pipe elements to resonance with the feeding microwave takes place by means of short-circuit slides and / or dielectric rods in the pipe elements of both half-shells, which can be introduced more or less into the pipe elements by means of adjusting devices.
  • the coupling elements for microwave energy the so-called iris couplers, which determine the strength of the magnetic coupling between the rectangular pipe feed line coming from the generator and the pipe elements serve primarily to adjust the range of services across the web.
  • a low-reflection setting is preferably carried out with the variable iris coupler, the reflected power being checked at the output of the circulator. If the pipelines are tuned to resonate with the short-circuit slides, any heating profiles can be realized with the iris couplers, for example, the increased heating of the edge parts. Setting to the same heating power per cm of web width is preferred, it being possible to compensate for different output power of the generators.
  • the setting of the iris couplers can be done either manually or automatically, for example by checking the local web temperature
  • the arrangement of the iris couplers is preferably at a distance of a quarter tube wavelength from the end of the tube elements.
  • square-working detectors are arranged opposite the coupling point in the hinged half-shell. These are not only used to monitor the microwave excitation during operation, but they are also used to adjust the resonance tuning of the pipeline with the variably adjustable short-circuit slides.
  • the microwave energy is fed in on the inlet side of the web.
  • Effective use of the dryer or heating device includes rapid heating of the material on the inlet side to the maximum permissible material temperature and maintaining this value as evenly as possible during the passage through the effective range of the dryer.
  • the application of the so-called direct current principle meets this requirement.
  • the direction of travel of material and microwave radiation in the pipelines are rectified.
  • the microwave is fed in on the inlet side of the material.
  • the highest microwave power density on the inlet side causes a rapid rise in temperature in the material, while the microwave intensity, which exponentially decreases in the direction of travel in the pipeline, is used primarily to cover the heat of vaporization.
  • a particularly important feature of the arrangement according to the invention is the slight entanglement of the longitudinal direction of the pipeline with respect to the running direction of the material.
  • the setting of the angle it between the running direction of the material (web edge) and the longitudinal direction of the pipeline serves to achieve uniform heating across the web.
  • These strips of low heating become increasingly smaller as the angle ⁇ increases from zero until, depending on the web width, a value ⁇ ′ results in which there is a slight ripple in the local heating profile transverse to the web.
  • This optimal angle ⁇ ' is reached when there is an approximately 10 to 20% overlap of the strips of material captured by the pipelines.
  • the value ⁇ ' depends on the ratio of the gap width to the pipe dimension (narrow side) and to a small extent on the dielectric properties of the material.
  • the characteristic of the arrangement is therefore a possibility of adjusting the angle n during the operation of the dryer.
  • the microwave generators are set to frequencies of 915 MHz or 2450 MHz.
  • the entirety of the pipe halves of each half-shell is covered by a gas-tight cover with a thin, low-loss film to prevent contamination of the pipe ducts or condensation.
  • This cover lies directly on the surface of the half-shells and is continuously fixed in the area of the webs and on the edge of the half-shells by nozzle heads sunk at periodic intervals.
  • the nozzle heads located in the web area are used to supply trailing air, nitrogen and protective gases when flammable vapors are removed in order to ensure their removal without condensation.
  • the gases are fed from the back of the half-shells and can be tempered.
  • the microwave device 1 shows a microwave heating and / or drying device 1 in an expanded state in a simplified form.
  • the web 2 to be dried is moved through the device 1 from the left (arrow).
  • the microwave device 1 consists of two half-shells 1a, 1b which are hingedly connected to one another, for example with hinges.
  • Pipe conductors 3 are incorporated into the shells parallel to one another and are arranged at an angle IX with respect to the web running direction.
  • the entanglement 5 by the angle ex serves to achieve a uniform heating of the web 2 transversely to its direction of travel.
  • the angle can be adjusted either by changing the web running direction or by rotating the device 1 relative to the web running direction in such a way that the ripple of the local heating profile transverse to web 2 is minimal.
  • the setting 5 causes approximately a 10 to 20% overlap of the strips of material captured by the pipelines 3.
  • the energy is fed to the microwave device 1 from a microwave generator 6 via a circulator 7 and a rectangular pipeline 9 and transmitted to the pipeline 3 via an iris coupler 4.
  • short-circuit slides 8 are arranged in all pipelines 3 to tune the pipeline 3 for resonance.
  • FIG. 2 shows a partial section through the half-shells 1a, 1b of the microwave device 1 with mirror-symmetrical construction.
  • the tubular conductors 3 are rectangular and are interrupted by a gap S through which the web 2 is guided.
  • the pipe conductors 3 are formed by the shells 1a, 1b and the conductive webs 15.
  • the width b of each tubular conductor elements 3 of the construction of the H io -Feldtyps is correspondingly dimensioned. (The field type in the right pipe is of the H 10 (TE-10) mode).
  • the width f of the conductive webs 15 between the adjacent pipe halves 3 is between 20 and 200% of the gap width S.
  • FIG. 3 shows a microwave device 1 with all devices according to the invention.
  • the web 2 was cut and the upper half-shell 1 was partly cut and shown unfolded.
  • the web 2 is passed in the direction of the arrow over rollers through the device 1.
  • the energy for heating and drying the web 2 is generated by microwave generators 6 via circulators 7, rectangular feed lines 9 of the device 1 and fed into the pipeline 3 with iris couplers 4.
  • the iris couplers 4 determine the strength of the magnetic coupling between the rectangular pipe feed lines 9 coming from the generator 6 and the pipe elements 3, can be adjusted by adjusting devices 16 and protrude into the border area between the pipe elements 3 and 9.
  • the pipe elements 3 are drawn in dashed lines in the lower shell half 1a and the associated upper parts are shown in the upper shell half 1b.
  • the length of the pipe 3 short-circuited on both sides is n times half the tube wavelength A, where n can be between 2 and 20.
  • the resonance of the microwave energy in the device is set with short-circuit slides 8, which are adjustable with an adjusting device 17.
  • Dielectric tuning elements 14 can also be used for tuning.
  • square-working detectors 12 are arranged opposite the coupling point. These detectors 12 serve both to monitor the microwave energy during operation and to tune the resonance of the pipeline 3 with the short-circuit slides 8 or the dielectric tuning elements 14.
  • each half-shell 1a, 1b is covered by a gas-tight cover with a thin, low-loss film 10, preferably made of approx. 0.2 mm thick polytetrafluoroethylene (PTFE), reinforced with glass fabric, to prevent contamination of the pipe ducts or condensation.
  • PTFE polytetrafluoroethylene
  • This cover 10 lies directly on the surface of the half-shells 1a, 1b and is continuously fixed in the region of the webs and on the edge of the half-shells 1a, 1b by nozzle heads 11 sunk at periodic intervals.
  • the nozzle heads 11 located in the web area serve to supply air or gases when flammable vapors are removed in order to ensure their removal without the formation of condensation.
  • the drag air is supplied from the rear of the half-shells 1a, 1 and can be tempered beforehand.

Description

Die vorliegende Erfindung betrifft eine Vorrichtung zur gleichmäßigen Erwärmung und/ oder Trocknung breiter, dünner flächenhafter Bahnen aus Papier, Kunststoff, Textilien oder photographischer Materialien unter Verwendung eines mit Mikrowellen gespeisten Energie- übertragers, der zur Durchführung des Materials aus parallel zueinander angeordneten, symmetrisch zweigeteilten Rohrleitern besteht, die miteinander verbunden sind und deren Länge auf eine ganze Anzahl von Halbwellen (AI2) abgestimmt ist, wobei zur Vermeidung unerwünschter elektromagnetischer Kopplungen zwischen den Rohrleiterelementen alternierend ein Versatz der Rohrleiterelemente um eine Viertetrohrwellenlänge (Λ/4) vorgesehen ist und zur Spei- sung der einzelnen Rohrleiterelemente jeweils getrennte Mikrowellengeneratoren in Verbindung mit Zirkulatoren eingesetzt sind.The present invention relates to a device for the uniform heating and / or drying of broad, thin sheets of paper, plastic, textiles or photographic materials using a microwave-powered energy transmitter which, for the passage of the material, consists of pipelines arranged symmetrically in two parts and arranged parallel to one another exists, which are connected to each other and whose length is matched to a whole number of half-waves (AI2), whereby in order to avoid undesired electromagnetic couplings between the pipe elements, the pipe elements are alternately offset by a fourth-pipe wavelength (Λ / 4) and for feeding g of the individual pipe elements, separate microwave generators are used in connection with circulators.

Verfahren zur dielektrischen Erwärmung und Trocknung feuchter Materialien mittels hochfrequenter Felder sind bekannt. Sie verwenden einerseits Frequenzen im Bereich von 13 und 27 MHz, zum anderen werden Frequenzen im Mikrowellenbereich vorzugsweise 2450 MHz benutzt. Mit diesem Verfahren werden beispielsweise Papier, Textilien und Beschichtungen auf verschiedenen Trägern getrocknet. Gegenüber Hochfrequenzverfahren bieten Mikrowellen höhere spezifische Heizleistungen, weil die durch den dielektrischen Verlust erzeugte Wärmeentwicklung im Material proportional mit der Frequenz zunimmt.Methods for the dielectric heating and drying of moist materials using high-frequency fields are known. On the one hand they use frequencies in the range of 13 and 27 MHz, on the other hand frequencies in the microwave range are preferably used in the 2450 MHz range. This process is used, for example, to dry paper, textiles and coatings on various substrates. Compared to high-frequency processes, microwaves offer higher specific heating outputs because the heat generated in the material due to the dielectric loss increases proportionally with the frequency.

Übliche Mikrowellentrockner für flächenhafte Materialien verwenden mäanderförmig quer zur Bahn geführte Rohrleiter, wobei das Material durch Schlitze im Rohrleiter durchgeführt wird, z. B. US 3 672 066, US 3 449 836, US 3 475 827. Nachteile dieser Anordnungen sind besonders bei größerer Breite und Stärke des Materials die örtliche Inhomogenität der Erwärmung insbesondere die durch die Absorption im Material bedingte exponentielle Abnahme der Intensität der im Rohrleiter fortschreitenden Welle, und die Erwärmung durch stehende Wellen, die durch Reflexion an den Bahnkanten und den Rohrleiterkrümmern im Verlaufe der mäanderförmigen Führung des Rechteckrohrs entstehen. Charakteristisch sind hierbei relativ scharf begrenzte Temperaturmaxima im Material im Abstand der halben Rohrwellenlänge. Zur Ausbildung der lokalen Überhitzung trägt neben dem speziellen dielektrischen Verhalten des Materials (z. B. Zunahme des dielektrischen Verlustes (tg d) mit der Temperatur) vor allem die quadratischen Feldstärken-Abhängigkeit der dielektrischen Verluste bei. Die Auswirkung stehender Wellen in quer zur Bahnrichtung orientierten Rohrleitern wird in der Anordnung nach GB 2 042 703 A dadurch zu verringern versucht, daß zwei Rohrleiter mit unterschiedlicher Lage der elektrischen Feldmaxima bezogen auf die Einwirkungsstelle des durchlaufenden Materials verwandt werden. Insbesondere wird hierbei eine Koinzidenz von Feldstärken-Maximum im ersten Rohrleiter mit dem Feldstärke-Minimum im zweiten Rohrleiter angestrebt. Durch eine derartige Anordnung kann der Effekt stehender Wellen bezüglich einer ungleichmäßigen Erwärmung quer zur Bahn verringert werden, bei stärker absorbierendem Material und größeren Bahnbreiten bleibt dagegen das durch exponentielle Absorption der Welle bedingte Erwärmungsprofil bestehen.Usual microwave dryers for sheet-like materials use meandering pipelines which are guided transversely to the web, the material being passed through slots in the pipeline, e.g. B. US 3,672,066, US 3,449,836, US 3,475,827. Disadvantages of these arrangements are, particularly with a larger width and thickness of the material, the local inhomogeneity of the heating, in particular the exponential decrease in the intensity of the progressing in the pipeline due to the absorption in the material Wave, and the heating by standing waves, which are caused by reflection on the web edges and the pipe bends in the course of the meandering guidance of the rectangular tube. Characteristic here are relatively sharply defined temperature maxima in the material at a distance of half the tube wavelength. In addition to the special dielectric behavior of the material (e.g. increase in dielectric loss (tg d) with temperature), the quadratic field strength dependence of the dielectric losses contributes to the formation of local overheating. The arrangement according to GB 2 042 703 A attempts to reduce the effect of standing waves in pipelines oriented transversely to the web direction by using two pipelines with different positions of the electrical field maxima in relation to the point of action of the material passing through. In particular, the aim is a coincidence of the maximum field strength in the first pipeline with the minimum field strength in the second pipeline. With such an arrangement, the effect of standing waves with regard to uneven heating across the web can be reduced, whereas, with more absorbent material and larger web widths, the heating profile due to exponential absorption of the wave remains.

Aus der GB-PS 1 050 493 ist es auch schon be kannt, zum Erwärmen und/oder Trocknen von Bändern mittels Mikrowellen den Mikrowellenleiter nach dem H10-Typ zu erregen.From GB-PS 1 050 493 it is also known to be used to heat and / or dry tapes by means of microwaves to excite the microwave conductor according to the H 10 type.

Der Erfindung liegt die Aufgabe zugrunde, eine Vorrichtung der einleitend genannten Art zu schaffen, mit der es auf einfache Weise möglich ist, sowohl eine über die Breite des Materials möglichst gleichmäßige Erwärmung und Trocknung des Materials, insbesondere der Beschichtungen von Trägermaterialien, als auch bei Ein haltung bestimmter Höchsttemperaturen eine möglichst schnelle Trocknung zu erzielen.The invention has for its object to provide a device of the type mentioned above, with which it is possible in a simple manner, both uniformly across the width of the material heating and drying of the material, in particular the coatings of carrier materials, as well as when one maintenance of certain maximum temperatures to achieve the fastest possible drying.

Ausgehend von einer Vorrichtung der ein gangs genannten Art, ist diese Aufgabe erfin dungsgemäß dadurch gelöst, daß

  • a) die einzelnen Rohrleiterelemente in ihrer Längsrichtung parallel oder in einem kleinen Winkel (α) zur Laufrichtung der Bahn an geordnet sind,
  • b) die Anzahl der Rohrleiterelemente propor tional der Breite der Bahn gewählt ist, wobei der Proportionalitätsfaktor sich aus den Er fordernissen ergibt,
  • c) die Breite der einzelnen Rohrleiterelemente entsprechend der Ausbildung der H10-Feldtyps dimensioniert ist,
  • d) Zur Einstellung der in jedem Rohrleiterelement wirksamen Mikrowellenleistung magnetisch wirkende einstellbare Iriskoppler vorgesehen sind, die einen gleichmäßigen oder beliebigen Verlauf der zugeführten Mikrowellenleistung quer zur Bahnlaufrichtung ermöglichen.
Starting from a device of the type mentioned, this object is inventively solved in that
  • a) the individual pipe elements are arranged in parallel in their longitudinal direction or at a small angle (α) to the running direction of the web,
  • b) the number of tubular elements is selected proportionally to the width of the web, the proportionality factor resulting from the requirements,
  • c) the width of the individual pipeline elements is dimensioned in accordance with the design of the H 10 field types,
  • d) Magnetic-acting adjustable iris couplers are provided for setting the effective microwave power in each tubular conductor element, which enable a uniform or arbitrary course of the supplied microwave power transversely to the web running direction.

Es wurde gefunden, daß in überraschender Weise eine vollständig gleichmäßige Erwär mung quer zur Bahn resultiert, wenn parallel zur Laufrichtung der Bahn orientierte Rohrleitersysteme verwendet werden, wobei die Zahl der parallelen Rohrleiter proportional der Bahnbreite gewählt wird. Abweichend von vorbekannten Mikrowellentrocknern, bei denen das flächenhafte Material durch Schlitze in einem Rohrleiter geführt wird, der senkrecht zur Bahnlaufrichtung angeordnet ist, wird bei dem beanspruchten Verfahren eine Anordnung von mehreren parallel angeordneten, zweiteiligen und beiderseits kurz geschlossenen Rohrleitern verwendet, die in Bahnlaufrichtung orientiert sind. Die Länge der einzelnen Rohrleiter ist auf ein ganzes Vielfaches der halben Rohrwellenlänge abgestimmt, dabei ist die Zahl der Halbwellenlängen so groß gewählt, daß unter Berücksichtigung der Mikrowellen-Absorption durch das Bahn-Material eine ca. 50%ige Absorption beim ersten Durchlauf der Mikrowelle durch das am Ende gespeiste Rohrleitersystem erfolgt. Die Erregung im Rohrleiter wird dabei. durch einen überwiegenden Anteil an fortlaufenden Wellen und zu einem geringeren Anteil an stehenden Wellen gebildet. Durch die hohe Dämpfung der stehenden Welle (Resonanz) ist eine kritische Abstimmung der einzelnen Rohrleiter auf die Frequenz des Generators nicht erforderlich, insbesondere können kleinere Verstimmungen durch Materialien unterschiedlicher Feuchte toleriert werden. Ein weiteres wesentliches Kennzeichen der Vorrichtung ist die parallele Einspeisung der einzelnen Rohrleiter durch separate Mikrowellen-Generatoren und Zirkulatoren, die individuelle Steuerung und Regelung der zugeführten Leistung durch endseitig angebrachte Iriskoppler und die praktisch vollständig gleichmäßige Erwärmung des Materials in Querrichtung durch leichte Verschränkung der Rohrleiterrichtung gegenüber der Laufrichtung des Materials. Stehende Wellen im einzelnen Rohrleiter bewirken keine ungleichmäßige Erwärmung des Materials quer zur Laufrichtung, weil die Rohrleiter in Laufrichtung angeordnet sind und nur wenige Grade mit dieser differieren. Alle Rohrleiterhälften sind in zwei spiegelsymmetrische metallische Halbschalen integriert, von denen eine zur Einführung des Materials und zu Reinigungszwecken aufklappbar gestaltet ist. Die Einhaltung maximaler Materialtemperaturen wird durch die ständige Kontrolle der in jedem Rohrleiter wirkende Mikrowellen-Erregung und durch das Verfahren der Gleichstrom-Erwärmung, d. h. gleiche Laufrichtung von Material und eingespeister Mikrowelle, bewirkt.It has been found that, surprisingly, a completely uniform heating cross-web results when pipe systems are used which are oriented parallel to the direction of travel of the web, the number of parallel pipelines being selected in proportion to the web width. Deviating from previously known microwave dryers, in which the sheet-like material is guided through slots in a pipeline which is arranged perpendicular to the web running direction, the claimed method uses an arrangement of several parallel, two-part and short-circuited pipelines which are oriented in the web running direction . The length of the individual pipelines is a multiple half the tube wavelength matched, the number of half-wavelengths is chosen so large that, taking into account the microwave absorption by the web material, there is an approx. 50% absorption when the microwave is first run through the tube system fed at the end. The excitation in the pipeline is thereby. formed by a predominant proportion of continuous waves and a smaller proportion of standing waves. Due to the high damping of the standing wave (resonance), a critical adjustment of the individual pipe conductors to the frequency of the generator is not necessary. Another key characteristic of the device is the parallel feeding of the individual pipelines by separate microwave generators and circulators, the individual control and regulation of the power supplied by iris couplers at the ends and the practically completely uniform heating of the material in the transverse direction by slightly interlacing the pipeline direction with respect to the Direction of the material. Standing waves in the individual pipeline do not cause uneven heating of the material transversely to the running direction, because the piping is arranged in the running direction and differs only a few degrees with it. All pipe halves are integrated in two mirror-symmetrical metal half-shells, one of which is designed to be hinged for the introduction of the material and for cleaning purposes. Maintaining maximum material temperatures is achieved by the constant control of the microwave excitation acting in each pipe and by the method of direct current heating, ie the same direction of travel of the material and the microwave fed in.

Die parallel angeordneten Rohrleiter sind zur Unterdrückung der Ausstrahlung und Kopplung untereinander bei größeren Spaltweiten durch leitende Stege verbunden. Diese Stege verringern die unerwünschte elektromagnetische Kopplung zwischen den im geringem Abstand parallel geführten einzelnen Rohrleitern. Die Breite der Stege liegt im Bereich von 20 bis 200% der Spaltweite und wird entsprechend der Mikrowellenabsorption durch das Material gewählt. Die einzelnen Rohrleiter stellen stark gedämpfte Mikrowellen-Resonatoren dar, die auf der Frequenz des Generators betrieben werden. Die Dämpfung der Resonatoren erfolgt durch die Absorption des Materials. Bei gegebener Mikrowellen-Absorption des Materials ergibt sich eine mit der Länge des Rohrleiters zunehmende Dämpfung der Resonanz. Die Welle wird bereits bei einem Durchlauf fast völlig im Material absorbiert. Bei gegebener Rohrleiterlänge steigt die Dämpfung mit der Absorption des Materials, z. B. mit zunehmendem Wassergehalt, an.The parallel pipelines are connected to each other to suppress radiation and coupling with larger gap widths by conductive webs. These webs reduce the undesired electromagnetic coupling between the individual pipelines which are guided in parallel at a short distance. The width of the webs is in the range of 20 to 200% of the gap width and is selected according to the microwave absorption by the material. The individual pipelines represent highly damped microwave resonators that are operated at the frequency of the generator. The resonators are damped by the absorption of the material. Given the microwave absorption of the material, the damping of the resonance increases with the length of the tube. The shaft is almost completely absorbed in the material during one pass. For a given pipe length, the damping increases with the absorption of the material, e.g. B. with increasing water content.

Allgemein gilt, daß bei hoher Dämpfung nur eine geringe unerwünschte elektromagnetische Kopplung zwischen benachbarten Rohrleitern erfolgt: die Stegbreite kann daher relativ gering gewählt werden. Umgekehrt muß die Stegbreite bei geringer Absorption des Materials (geringe Feuchte) größer gewählt werden. Eine typische Ausführungsform verwendet bei Speisung der Rohrleiter mit einer Frequenz von 2450 MHz eine Spaltweite von 20 mm, eine Stegbreite von 20 mm und eine Länge der Rohrleiter von n = 10 Halbwellen. Mit dieser Dimensionierung können Materialien mit ca. 20 bis 200 g H20/M 2 (freies Wasser) wirksam erwärmt und getrocknet werden, wobei auch zur Begrenzung der Maximaltemperaturen mehrere Trockner hintereinander geschaltet werden können. Derartige wasserhaltige Materialien zeigen Absorptionen von mehr als 3 db/m. Wird also beispielsweise die Länge eines derartigen Rohrleiters zu 1 m festgelegt, so ergibt sich bei einem Hin- und Rücklauf der Mikrowelle eine Absorption von mehr als 75%. Damit wird eine relativ geringe Welligkeit des Feldverlaufs längs des Rohrleiters erzielt und die maximal auftretende elektrische Feldstärke wird stark begrenzt, so daß von metallischen Kanten ausgehende elektrische Entladungen vermieden werden, was bei der Trocknung von photographischem Material oder thermisch empfindlichen Schichten von großer Bedeutung ist.In general, with high damping there is only a slight undesired electromagnetic coupling between adjacent pipelines: the web width can therefore be chosen to be relatively small. Conversely, the web width must be chosen larger with low absorption of the material (low moisture). A typical embodiment uses a gap width of 20 mm, a web width of 20 mm and a length of the pipeline of n = 10 half-waves when feeding the pipeline with a frequency of 2450 MHz. With this dimensioning, materials with approximately 20 to 200 g H 2 O / M 2 (free water) can be effectively heated and dried, and several dryers can also be connected in series to limit the maximum temperatures. Such water-containing materials show absorptions of more than 3 db / m. If, for example, the length of such a pipeline is set to 1 m, the microwave will run back and forth with an absorption of more than 75%. This results in a relatively low ripple in the field profile along the pipe and the maximum electric field strength that occurs is severely limited, so that electrical discharges from metallic edges are avoided, which is of great importance when drying photographic material or thermally sensitive layers.

Die hohe Mikrowellen-Absorption des Materials liegt vor allem in den Anfangsstufen der Trocknung (Naßbereich) vor, bei fortgeschrittener Trocknung und im sogenannten Restfeuchtebereich (etwa Gleichgewichtsfeuchte im Vergleich zur relativen Feuchte der Umgebungs-oder Schleppluft) kann die Mikrowellenabsorption bis auf weniger als 1 db/m abfallen. Die Effizienz eines gleich langen Trockners fällt aber nur wenig mit geringer werdender Absorption des Materials, weil die Feldstärken in dem als Resonator fungierenden Rohrleiter infolge der geringeren Dämpfung ansteigen, wodurch ein Ausgleich eintritt: die im Material erzeugte dielektrische Verlustwärme P ist:

Figure imgb0001
mit eo, einer dimensionslosen Konstanten für die dielektrischen Eigenschaften im luftleeren Raum, rα = Frequenz, E = elektrische Feldstärke, s" dielektrischer Verlust. Bei sehr geringer Absorption durch das Material kann zum Ausgleich die Länge der Rohrleiter auf bis zu 20 Halbwellen und mehr vergrößert werden.The high microwave absorption of the material is mainly in the initial stages of drying (wet area), with advanced drying and in the so-called residual moisture area (e.g. equilibrium moisture compared to the relative humidity of the ambient or entrained air) the microwave absorption can be less than 1 db / m fall off. However, the efficiency of a dryer of the same length drops only slightly with a decrease in the absorption of the material, because the field strengths in the pipeline functioning as a resonator increase as a result of the lower damping, as a result of which there is a compensation: the dielectric loss heat P generated in the material is:
Figure imgb0001
 with eo, a dimensionless constant for the dielectric properties in a vacuum, rα = frequency, E = electric field strength, s "dielectric loss. With very little absorption by the material, the length of the pipeline can be increased to up to 20 half waves and more will.

Die unerwünschte elektromagnetische, vorwiegend elektrische Kopplung nimmt bei geringerer Materialabsorption zu. Zur Vermeidung der Erregung anderer Feldtypen und der Ausstrahlung am Rande des Trockners wird die Stegbreite auf bis zu 200% der Spaltbreite zwischen den Halbschalen erhöht. Eine besondere Möglichkeit der Unterdrückung der Kopplung zwischen benachbarten Rohrleitern ergab sich in überraschend einfacher Weise durch die alternierende Anordnung der Rohrleiter, das heißt durch wechselweise Verschiebung nebeneinanderliegender Rohrleiter um A14 in der Längsrichtung. Die Kopplung über die elektrische Komponente wird dadurch so stark unterdrückt, daß in benachbarten Rohrleitern die elektrischen und magnetischen Maxima des stehenden Wellenanteils einander gegenüberliegen. Diese Art der Anordnung ist vor allem bei hohem Anteil stehender Wellen, d. h. bei geringer Rohrleiterlänge und/oder geringer Materialabsorption (Restfeuchtebereich) von Vorteil.The undesired electromagnetic, mainly electrical coupling increases with less material absorption. To avoid the excitation of other field types and the radiation at the edge of the dryer, the web width is increased to up to 200% of the gap width between the half-shells. A special possibility of suppressing the coupling between adjacent pipelines was found in a surprisingly simple manner by the alternating arrangement of the pipelines, that is to say by alternating displacement next to one another gender pipe around A14 in the longitudinal direction. The coupling via the electrical component is suppressed to such an extent that the electrical and magnetic maxima of the standing wave component lie opposite one another in adjacent pipelines. This type of arrangement is particularly advantageous when there is a high proportion of standing waves, ie with a short pipe length and / or low material absorption (residual moisture range).

Die Größe der zulässigen Spaltweite zwischen den die Rohrleiterhälften enthaltenden Halbschalen wird letztlich durch die Abstrahlung nach außen begrenzt. Selbst bei sehr großer Stegbreite (mehr als 200% der Spaltweite) muß die Spaltweite unterhalb der halben Freiraumwellenlänge bleiben. Bei 2450 MHz sind Werte von im Extremfall 40 mm realisierbar. Bevorzugt sind jedoch Spaltweiten von 10 bis 25 mm. Bei Spaltweiten über etwa 20% der Freiraumwellenlänge ergibt sich durch die Verzerrung des elektrischen Feldverlaufs der Hio-Welle eine zunehmende Entkopplung von hindurchgeführten Material, so daß bei 2450 MHz Spaltweiten über 25 mm nur geringe Bedeutung haben (für dünne, dichte Materialien bis ca. 1 mm). Durch Verwendung niedriger Frequenzen, z. B. 915 MHz können entsprechend größere Spaltweiten realisiert werden.The size of the permissible gap width between the half shells containing the pipe halves is ultimately limited by the radiation to the outside. Even with a very large web width (more than 200% of the gap width), the gap width must remain below half the free space wavelength. At 2450 MHz, values of 40 mm can be achieved in extreme cases. However, gap widths of 10 to 25 mm are preferred. With gap widths above about 20% of the free space wavelength, the distortion of the electrical field profile of the Hio wave results in an increasing decoupling of material passed through, so that at 2450 MHz gap widths over 25 mm are of little importance (for thin, dense materials up to approx. 1 mm). By using low frequencies, e.g. B. 915 MHz correspondingly larger gap widths can be realized.

Bei Spaltweiten etwa von der Größe der halben Rohrleiterdimension ergibt sich in Richtung zur Flächennormalen ein besonders flacher Verlauf der elektrischen Feldstärke in Spaltmitte, der auch bei nicht exakter Materialführung in der Mitte eine relativ gleichmäßige Mikrowellenabsorption (Erwärmung) liefert.With gap widths of about half the size of the pipe, a particularly flat course of the electrical field strength in the middle of the gap results in the direction of the surface normal, which provides a relatively uniform microwave absorption (heating) even when the material is not exactly guided in the middle.

Die Rohrleiterelemente sind vorzugsweise gleich lang und besitzen eine Länge von einem Vielfachen der halben Wellenlänge der speisenden Mikrowelle, also n · A12, wobei n ein Faktor zwischen 2 und 20 sein kann (n = 2,3,4... 20).The pipeline elements are preferably of the same length and have a length of a multiple of half the wavelength of the feeding microwave, that is n · A12, where n can be a factor between 2 and 20 (n = 2,3,4 ... 20).

Die Abstimmung der Rohrleiterelemente auf Resonanz mit der speisenden Mikrowelle erfolgt durch Kurzschlußschieber und/oder dielektrische- Stäbe in den Rohrleiterelementen beider Halbschalen, die mittels Verstelleinrichtungen mehr oder weniger in die Rohrleiterelemente einbringbar sind.The adjustment of the pipe elements to resonance with the feeding microwave takes place by means of short-circuit slides and / or dielectric rods in the pipe elements of both half-shells, which can be introduced more or less into the pipe elements by means of adjusting devices.

Der Einstellung des Leistungsangebots quer zur Bahn dienen in erster Linie die Einkoppelelemente für die Mikrowellenenergie, die sogenannten Iriskoppler, die die Stärke der magnetischen Kopplung zwischen den vom Generator kommenden Rechteckrohrzuleitung und den Rohrleiterelementen bestimmen. Vorzugsweise wird mit dem variablen Iriskoppler eine reflexionsarme Einstellung vorgenommen, wobei die Kontrolle der reflektierten Leistung am Ausgang des Zirkulators erfolgt. Bei Abstimmung der Rohrleiter mit den Kurzschlußschiebern auf Resonanz, können mit den Iriskopplern beliebige Erwärmungsprofile realisiert werden, beispielsweise auch die erhöhte Erwärmung der Randpartien. Bevorzugt ist die Einstellung auf gleiche Heizleistung je cm Bahnbreite, wobei ein Ausgleich unterschiedlicher Abgabeleistung der Generatoren erfolgen kann. Die Einstellung der lriskoppler kann sowohl manuell erfolgen als auch automatisch geregelt werden, etwa über die Kontrolle der lokalen BahntemperaturThe coupling elements for microwave energy, the so-called iris couplers, which determine the strength of the magnetic coupling between the rectangular pipe feed line coming from the generator and the pipe elements serve primarily to adjust the range of services across the web. A low-reflection setting is preferably carried out with the variable iris coupler, the reflected power being checked at the output of the circulator. If the pipelines are tuned to resonate with the short-circuit slides, any heating profiles can be realized with the iris couplers, for example, the increased heating of the edge parts. Setting to the same heating power per cm of web width is preferred, it being possible to compensate for different output power of the generators. The setting of the iris couplers can be done either manually or automatically, for example by checking the local web temperature

Die Anordnung der Iriskoppler erfolgt vorzugsweise in einem Abstand von einer Viertelrohrwellenlänge vom Ende der Rohrleiterelemente entfernt.The arrangement of the iris couplers is preferably at a distance of a quarter tube wavelength from the end of the tube elements.

Zur Messung der in jedem Rohrleiter vorliegende Stärke der Mikrowellenintensität sind quadratisch arbeitende Detektoren gegenüber der Einkoppelstelle in der abklappbaren Halbschale angeordnet. Diese dienen nicht nur der Überwachung der Mikrowellenerregung im Betrieb, sondern sie werden auch zur Justierung der Resonanzabstimmung der Rohrleiter mit den variabel einstellbaren Kurzschlußschiebern verwendet.To measure the strength of the microwave intensity present in each pipeline, square-working detectors are arranged opposite the coupling point in the hinged half-shell. These are not only used to monitor the microwave excitation during operation, but they are also used to adjust the resonance tuning of the pipeline with the variably adjustable short-circuit slides.

Die Einspeisung der Mikrowellenenergie erfolgt in einer bevorzugten Ausführungsform auf der Einlaufseite der Bahn. Zum wirkungsvollen Einsatz des Trockners bzw. der Heizeinrichtung gehört eine schnelle Erwärmung des Materials auf der Einlaufseite auf die maximal zulässige Materialtemperatur und die möglichst gleichmäßige Erhaltung dieses Wertes während des Durchlaufs durch den Wirkungsbereich des Trockners. Dieser Forderung kommt die Anwendung des sogenannten Gleichstromprinzips entgegen. Die Laufrichtung von Material und Mikrowellenstrahlung in den Rohrleitern sind gleichgerichtet. Die Einspeisung der Mikrowelle erfolgt auf der Einlaufseite des Materials. Die auf der Einlaufseite vorhandene höchste Mikrowellen-Leistungsdichte verursacht einen schnellen Temperaturanstieg im Material, während die in Laufrichtung im Rohrleiter exponentiell abfallen de Mikrowellenintensität vorwiegend zur Dekkung der Verdampfungswärme dient.In a preferred embodiment, the microwave energy is fed in on the inlet side of the web. Effective use of the dryer or heating device includes rapid heating of the material on the inlet side to the maximum permissible material temperature and maintaining this value as evenly as possible during the passage through the effective range of the dryer. The application of the so-called direct current principle meets this requirement. The direction of travel of material and microwave radiation in the pipelines are rectified. The microwave is fed in on the inlet side of the material. The highest microwave power density on the inlet side causes a rapid rise in temperature in the material, while the microwave intensity, which exponentially decreases in the direction of travel in the pipeline, is used primarily to cover the heat of vaporization.

Durch dieses Prinzip wird der häufig vorliegenden Tendenz, daß die Temperatur des Materials auf der Austrittsseite des Trockners erheblich höher ist als in weiten Bereichen des Trockners, entgegengewirkt. Einzelheiten des Temperaturverlaufs des Materials beim Durchgang durch den Trockner hängen natürlich stark von den Materialeigenschaften und der Verweilzeit im Trockner ab.This principle counteracts the frequently occurring tendency that the temperature of the material on the outlet side of the dryer is considerably higher than in large areas of the dryer. Details of the temperature profile of the material as it passes through the dryer naturally depend strongly on the material properties and the residence time in the dryer.

Ein besonders wichtiges Merkmal der erfindungsgemäßen Anordnung stellt die leichte Verschränkung der Rohrleiterlängsrichtung in bezug auf die Laufrichtung des Materials dar. Die Einstellung des Winkels it zwischen der Laufrichtung des Materials (Bahnkante) und der Rohrleiterlängsrichtung dient zur Erzielung einer quer zur Bahn gleichmäßigen Erwärmung. Bei exakt paralleler Ausrichtung α = 0 würde sich im Bereich der Stege nur eine geringe Erwärmung ergeben. Diese Streifen geringer Erwärmung werden mit von Null wachsendem Winkel α zunehmend kleiner bis sich je nach Stegbreite ein Wert α' ergibt, bei dem eine geringste Welligkeit des lokalen Erwärmungsprofils quer zur Bahn er gibt. Dieser optimale Winkel α' ist erreicht, wenn eine etwa 10 bis 20%ige Überlappung der von den Rohrleitern erfaßten Materialstreifen vorliegt. Der Wert α' hängt vom Verhältnis der Spaltweite zur Rohrleiterdimension (Schmalseite) und in geringem Maße von den dielektrischen Eigenschaften des Materials ab. Kennzeichen der Anordnung ist daher eine Möglichkeit der Justierung des Winkels n während des Betriebs des Trockners.A particularly important feature of the arrangement according to the invention is the slight entanglement of the longitudinal direction of the pipeline with respect to the running direction of the material. The setting of the angle it between the running direction of the material (web edge) and the longitudinal direction of the pipeline serves to achieve uniform heating across the web. With exactly parallel alignment α = 0, there would be only a slight heating in the area of the webs. These strips of low heating become increasingly smaller as the angle α increases from zero until, depending on the web width, a value α ′ results in which there is a slight ripple in the local heating profile transverse to the web. This optimal angle α 'is reached when there is an approximately 10 to 20% overlap of the strips of material captured by the pipelines. The value α 'depends on the ratio of the gap width to the pipe dimension (narrow side) and to a small extent on the dielectric properties of the material. The characteristic of the arrangement is therefore a possibility of adjusting the angle n during the operation of the dryer.

Die Mikrowellengeneratoren werden in einer bevorzugten Ausführungsform auf Frequenzen von 915 MHz oder 2450 MHz eingestellt.In a preferred embodiment, the microwave generators are set to frequencies of 915 MHz or 2450 MHz.

Die Gesamtheit der Rohrleiterhälften jeder Halbschale ist durch eine gasdichte Abdeckung mit einer dünnen verlustarmen Folie zur Verhütung von Verschmutzungen der Rohrleiterkanäle oder Kondenswasserbildung abgedeckt. In Verbindung mit der aufklappbaren Konstruktion ergibt sich so eine einfache Möglichkeit der Reinigung des Trockners. Diese Abdeckung liegt unmittelbar auf der Oberfläche der Halbschalen auf und ist im Bereich der Stege und am Rande der Halbschalen durch in periodischen Abständen versenkt angebrachte Düsenköpfe durchgehend fixiert. Die im Stegbereich liegenden Düsenköpfe dienen der Zuführung von Schleppluft, Stickstoff und Schutzgasen bei der Abführung brennbarer Dämpfe, um deren Entfernung ohne Kondensbildung zu gewährleisten. Die Gase werden von der Rückseite der Halbschalen zugeführt und können temperiert werden.The entirety of the pipe halves of each half-shell is covered by a gas-tight cover with a thin, low-loss film to prevent contamination of the pipe ducts or condensation. In conjunction with the hinged construction, this provides an easy way of cleaning the dryer. This cover lies directly on the surface of the half-shells and is continuously fixed in the area of the webs and on the edge of the half-shells by nozzle heads sunk at periodic intervals. The nozzle heads located in the web area are used to supply trailing air, nitrogen and protective gases when flammable vapors are removed in order to ensure their removal without condensation. The gases are fed from the back of the half-shells and can be tempered.

Im folgenden wird eine Ausführungsform der Erfindung anhand von Zeichnungen näher beschrieben. Es zeigt

  • Fig. 1 eine Aufsicht auf die vereinfacht dargestellt aufgeklappte Vorrichtung,
  • Fig. 2 einen Teilschnitt durch die Vorrichtung längs der Linie AA in Fig. 1,
  • Fig. 3 eine teilweise aufgeschnittene Vorrichtung mit der Darstellung aller Elemente.
An embodiment of the invention is described in more detail below with reference to drawings. It shows
  • 1 is a plan view of the device shown in simplified form,
  • 2 shows a partial section through the device along the line AA in FIG. 1,
  • Fig. 3 is a partially cut device showing all the elements.

In Fig. 1 ist eine Mikrowellen-Erwärmungs-und/oder Trockeneinrichtung 1 in aufgeklapptem Zustand in vereinfachter Form dargestellt. Die zu trocknende Bahn 2 wird von links (Pfeil) durch die Vorrichtung 1 bewegt. Die Mikrowelleneinrichtung 1 besteht aus zwei Halbschalen 1a, 1b, die zum Beispiel mit Scharnieren aufklappbar miteinander verbunden sind. In die Schalen sind Rohrleiter 3 parallel zueinander eingearbeitet, die unter einem Winkel IX gegenüber der Bahnlaufrichtung verschränkt angeordnet sind. Die Verschränkung 5 durch den Winkel ex dient zur Erzielung einer gleichmäßigen Erwärmung der Bahn 2 quer zu deren Laufrichtung. In einer bevorzugten Ausführungsform ist der Winkel entweder durch Ändern der Bahnlaufrichtung oder aber durch Drehen der Vorrichtung 1 relativ zur Bahnlaufrichtung so einstellbar, daß eine geringste Welligkeit des lokalen Erwärmungsprofiles quer zur Bahn 2 entsteht. Die Schränkung 5 bewirkt etwa eine 10 bis 20%ige Überlappung der von den Rohrleitern 3 erfaßten Materialstreifen. Die Energie wird der Mikrowelleneinrichtung 1 von einem Mikrowellengenerator 6 über einen Zirkulator 7 und einer Rechteckrohrleitung 9 zugeführt und über Iriskoppler 4 auf die Rohrleiter 3 übertragen. Auf der der Energiezufuhrseite gegenüberliegenden Seite der Rohrleiter 3 sind zur Abstimmung der Rohrleiter 3 auf Resonanz Kurzschlußschieber 8 in allen Rohrleitern 3 angeordnet.1 shows a microwave heating and / or drying device 1 in an expanded state in a simplified form. The web 2 to be dried is moved through the device 1 from the left (arrow). The microwave device 1 consists of two half-shells 1a, 1b which are hingedly connected to one another, for example with hinges. Pipe conductors 3 are incorporated into the shells parallel to one another and are arranged at an angle IX with respect to the web running direction. The entanglement 5 by the angle ex serves to achieve a uniform heating of the web 2 transversely to its direction of travel. In a preferred embodiment, the angle can be adjusted either by changing the web running direction or by rotating the device 1 relative to the web running direction in such a way that the ripple of the local heating profile transverse to web 2 is minimal. The setting 5 causes approximately a 10 to 20% overlap of the strips of material captured by the pipelines 3. The energy is fed to the microwave device 1 from a microwave generator 6 via a circulator 7 and a rectangular pipeline 9 and transmitted to the pipeline 3 via an iris coupler 4. On the side of the pipeline 3 opposite the energy supply side, short-circuit slides 8 are arranged in all pipelines 3 to tune the pipeline 3 for resonance.

Fig. 2 zeigt einen Teilschnitt durch die spiegelsymmetrisch aufgebauten Halbschalen 1a, 1b der Mikrowellenvorrichtung 1. Die Rohrleiter 3 sind rechteckig ausgebildet und sind durch einen Spalt S, durch den die Bahn 2 geführt wird, unterbrochen. Die Rohrleiter 3 werden durch die Schalen 1a, 1b und die leitenden Stege 15 gebildet. Die Breite b der einzelnen Rohrleiterelemente 3 ist entsprechend der Ausbildung des Hio-Feldtyps dimensioniert. (Der Feldtyp im Rechtrohrleiter ist vom H10(TE-10)-Modus). Die Breite f der leitenden Stege 15 zwischen den benachbarten Rohrleiterhälften 3 beträgt zwischen 20 und 200% der Spaltweite S.FIG. 2 shows a partial section through the half-shells 1a, 1b of the microwave device 1 with mirror-symmetrical construction. The tubular conductors 3 are rectangular and are interrupted by a gap S through which the web 2 is guided. The pipe conductors 3 are formed by the shells 1a, 1b and the conductive webs 15. The width b of each tubular conductor elements 3 of the construction of the H io -Feldtyps is correspondingly dimensioned. (The field type in the right pipe is of the H 10 (TE-10) mode). The width f of the conductive webs 15 between the adjacent pipe halves 3 is between 20 and 200% of the gap width S.

In Fig. 3 ist eine Mikrowellenvorrichtung 1 mit allen Einrichtungen gemäß der Erfindung dargestellt. Zur Darstellung aller Teile wurde die Bahn 2 geschnitten und die obere Halbschale 1 zum Teil geschnitten und ausgeklappt dargestellt. Die Bahn 2 wird in Pfeilrichtung über Walzen durch die Vorrichtung 1 geleitet. Die Energie zur Erwärmung und Trocknung der Bahn 2 wird von Mikrowellengeneratoren 6 erzeugt über Zirkulatoren 7, Rechteckzuleitungen 9 der Vorrichtung 1 zugeführt und mit Iriskopplern 4 in die Rohrleiter 3 eingespeist. Die Iriskoppler 4 bestimmen die Stärke der magnetischen Kopplung zwischen den vom Generator 6 kommenden Rechteckrohrzuleitungen 9 und den Rohrleiterelementen 3, sind durch Stelleinrichtungen 16 einstellbar und ragen in den Grenzbereich zwischen den Rohrleiterelementen 3 und 9.3 shows a microwave device 1 with all devices according to the invention. To display all the parts, the web 2 was cut and the upper half-shell 1 was partly cut and shown unfolded. The web 2 is passed in the direction of the arrow over rollers through the device 1. The energy for heating and drying the web 2 is generated by microwave generators 6 via circulators 7, rectangular feed lines 9 of the device 1 and fed into the pipeline 3 with iris couplers 4. The iris couplers 4 determine the strength of the magnetic coupling between the rectangular pipe feed lines 9 coming from the generator 6 and the pipe elements 3, can be adjusted by adjusting devices 16 and protrude into the border area between the pipe elements 3 and 9.

Die Rohrleiterelemente 3 sind in der unteren Schalenhälfte 1a gestrichelt gezeichnet und die zugehörigen oberen Teile in der oberen Schalenhälfte 1b dargestellt. Durch die Anordnung der Rohrleiterelemente 3 in der Art, daß jedes zweite Element um eine Viertelrohrwellenlänge Λ/4 in Längsrichtung gegen das danebenliegende Element verschoben ist, ergibt sich eine besondere Möglichkeit der Unterdrückung der Kopplung zwischen benachbarten Rohrleitern 3. Die Länge der beidseits kurzgeschlossenen Rohrleiter 3 beträgt das n-fache der halben Rohrwellenlänge A, wobei n zwischen 2 und 20 liegen kann.The pipe elements 3 are drawn in dashed lines in the lower shell half 1a and the associated upper parts are shown in the upper shell half 1b. The arrangement of the pipe elements 3 in such a way that every second element is shifted in the longitudinal direction by a quarter pipe wavelength gegen / 4 in the longitudinal direction, there is a special possibility of suppressing the coupling between adjacent pipe 3. The length of the pipe 3 short-circuited on both sides is n times half the tube wavelength A, where n can be between 2 and 20.

Die Resonanz der Mikrowellenenergie in der Vorrichtung wird mit Kurzschlußschiebern 8 eingestellt, die mit einer Verstelleinrichtung 17 einstellbar ausgebildet sind. Zur Abstimmung können auch dielektrische Abstimmelemente 14 verwendet werden. Zur Messung der in jedem Rohrleiter 3 vorliegenden Stärke der Mikrowellenintensität sind quadratisch arbeitende Detektoren 12 gegenüber der Einkoppelstelle angeordnet. Diese Detektoren 12 dienen sowohl der Überwachung der Mikrowellenenergie im Betrieb als auch zur Resonanzabstimmung der Rohrleiter 3 mit den Kurzschlußschiebern 8 oder den dielektrischen Abstimmelementen 14.The resonance of the microwave energy in the device is set with short-circuit slides 8, which are adjustable with an adjusting device 17. Dielectric tuning elements 14 can also be used for tuning. To measure the strength of the microwave intensity present in each pipeline 3, square-working detectors 12 are arranged opposite the coupling point. These detectors 12 serve both to monitor the microwave energy during operation and to tune the resonance of the pipeline 3 with the short-circuit slides 8 or the dielectric tuning elements 14.

Die Gesamtheit der Rohrleiterhälften jeder Halbschale 1a, 1b ist durch eine gasdichte Abdeckung mit einer dünnen verlustarmen Folie 10, vorzugsweise aus ca. 0,2 mm starkem Polytetrafluoräthylen (PTFE), glasgewebeverstärkt, zur Verhütung von Verschmutzung der Rohrleiterkanäle oder Kondenswasserbildung abgedeckt. In Verbindung mit der aufklappbaren Konstruktion (Pfeil) ergibt sich so eine einfache Möglichkeit der Reinigung der Vorrichtung. Diese Abdekkung 10 liegt unmittelbar auf der Oberfläche der Halbschalen 1a, 1b auf und ist im Bereich der Stege und am Rande der Halbschalen 1a, 1b durch in periodischen Abständen versenkt angebrachte Düsenköpfe 11 durchgehend fixiert. Die im Stegbereich liegenden Düsenköpfe 11 dienen der Zuführung von Luft oder Gasen bei der Abführung brennbarer Dämpfe, um deren Entfernung ohne Kondensbildung zu gewährleisten. Die Schleppluft wird von der Rückseite der Halbschalen 1a, 1 zugeführt und kann vorher temperiert werden.The entirety of the pipe halves of each half-shell 1a, 1b is covered by a gas-tight cover with a thin, low-loss film 10, preferably made of approx. 0.2 mm thick polytetrafluoroethylene (PTFE), reinforced with glass fabric, to prevent contamination of the pipe ducts or condensation. In conjunction with the hinged construction (arrow), this results in a simple possibility of cleaning the device. This cover 10 lies directly on the surface of the half-shells 1a, 1b and is continuously fixed in the region of the webs and on the edge of the half-shells 1a, 1b by nozzle heads 11 sunk at periodic intervals. The nozzle heads 11 located in the web area serve to supply air or gases when flammable vapors are removed in order to ensure their removal without the formation of condensation. The drag air is supplied from the rear of the half-shells 1a, 1 and can be tempered beforehand.

Claims (10)

1. Apparatus for uniformly heating and/or drying wide, thin, sheet-like webs of paper, plastics, textiles or photographic materials using an energy transmitter supplied with microwaves which consists of waveguides which are arranged parallel to each other and are divided into two symmetric parts between which the material can be passed and which are interconnected and whose length is made to equal an integral number of half-waves (Λ/2), the waveguide elements being alternately displaced by a quarter of a waveguide wavelength (A/4) for the avoidance of undesired electromagnetic coupling between the waveguide elements and separate microwave generators being used, in conjunction with circu- lators, to supply each of the individual waveguide elements, characterised in that
a) the individual waveguide elements (3) are, in their longitudinal direction, arranged parallel to or at a small angle (a) to the direction of travel of the web (2),
b) the number of waveguide elements (3) is selected so as to be proportional to the width of the web (2), the proportionality factor being based on the required conditions,
c) the width (b) of the individual waveguide elements (3) is of a size corresponding to the configuration of the Hio mode and
d) magnetically-acting adjustable iris couplers (4) are provided for adjusting the microwave power acting in each waveguide element (3), which couplers allow a uniform or any desired pattern of the supplied microwave power transversely to the direction of travel of the web.
2. Apparatus according to Claim 1, characterised in that several waveguide halves (3) are arranged parallel to each other and are attached to each other by means of parallel conductive ridges (15) to form a continuous shell half (1a, 1b).
3. Apparatus according to Claim 1, characterised in that the energy transmitter consists of two shell halves (I a, 1 b) which are constructed in a mirror-symmetric manner and each contain all of the waveguide halves (3) and the shell halves (1a, 1b) are hingedly connected to each other on one longitudinal side of the energy transmitter and there is a stationary shell half (1a) and a folding shell half (1b).
4. Apparatus according to Claim 1, characterised in that the width (f) of the conductive ridges (15) between the adjacent waveguide halves (3) is between 20% and 200% of the width of the gap (S) between the mutually corresponding waveguide halves (3).
5. Apparatus according to Claim 1, characterised in that the width of the gap (S) between the waveguide halves (3) or the shell halves (1a, 1b) is between 2% and 40% of the free space wavelength of the supplying microwaves.
6. Apparatus according to Claim 1, characterised in that the length of the individual waveguide elements (3) is the same and is n · Λ/2, where n = 2, 3, 4 to 20 and in order to tune each individual waveguide element (3) to be resonant with the supplying microwave the waveguide elements (3) in the two shell halves (1a, 1b) are each provided with a short-circuit plunger (8) and/or dielectric rods (14).
7. Apparatus according to Claim 1, characterised in that magnetically-acting iris couplers (4) are provided in the narrow sides of the rectangular structures of each of the waveguide elements (3) in the stationary shell half (1a) to allow variable transfer of the microwave energy into the waveguide elements (3), and the iris couplers (4) are arranged at a distance of a quarter of a waveguide wavelength (AI4) away from the end of the waveguide elements (3).
8. Apparatus according to Claim 1, characterised in that the supply (6, 7, 9) of the microwave energy is carried out at the feed end of the web (2) and that a detector (12) is provided at a point opposite the point of connection for the conti- nous monitoring and adjustment of the microwave excitation in each waveguide element.
9. Apparatus according to Claim 1, characterised in that the angle (α) between the longitudinal direction of the waveguide elements (3) and the direction of travel of the web (2) can be adjusted to allow uniform cross-sectional heating.
10. Apparatus according to Claim 1, characterised in that the surfaces of the two shell halves (1a, 1b) which face the web (2) are covered in a gastight manner with a protective film (10) which has a thickness of 0.1 to 0.5 mm and a low dielectric constant and the protective film (10) is fastened in the area of the ridges (15) by means of submerged nozzle heads (11), which are at the same time used for supplying gases for removing vapours from the web (2).
EP82106440A 1981-07-31 1982-07-17 Microwave device for warming and/or drying flat materials passing through the device Expired EP0071123B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3130358 1981-07-31
DE19813130358 DE3130358A1 (en) 1981-07-31 1981-07-31 DEVICE FOR HEATING AND / OR DRYING CONTINUOUS AREA MATERIALS WITH MICROWAVES

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EP0071123A1 EP0071123A1 (en) 1983-02-09
EP0071123B1 true EP0071123B1 (en) 1985-10-02

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EP (1) EP0071123B1 (en)
JP (1) JPS5826979A (en)
DE (2) DE3130358A1 (en)

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DE102008038215A1 (en) * 2008-08-18 2010-02-25 Siemens Aktiengesellschaft Method and device for drying a paper web
DE102013009064B3 (en) * 2013-05-28 2014-07-31 Püschner GmbH + Co. KG Continuous microwave furnace e.g. microwave oven, has microwave generator which is formed in microwave mode in specific mode orthogonally and is coupled with respective single mode microwave channel
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DE3266685D1 (en) 1985-11-07
DE3130358A1 (en) 1983-02-17
EP0071123A1 (en) 1983-02-09
JPS5826979A (en) 1983-02-17

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