EP0089288B1 - Device for heating sheet products by microwaves - Google Patents

Device for heating sheet products by microwaves Download PDF

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Publication number
EP0089288B1
EP0089288B1 EP83400518A EP83400518A EP0089288B1 EP 0089288 B1 EP0089288 B1 EP 0089288B1 EP 83400518 A EP83400518 A EP 83400518A EP 83400518 A EP83400518 A EP 83400518A EP 0089288 B1 EP0089288 B1 EP 0089288B1
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EP
European Patent Office
Prior art keywords
applicators
length
fact
microwaves
product
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EP83400518A
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German (de)
French (fr)
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EP0089288A1 (en
Inventor
André-Jean Berteaud
René Clement
Claude Merlet
Claude Leclercq
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Public Dit Centre National de la R Ets
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Centre National de la Recherche Scientifique CNRS
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Priority to AT83400518T priority Critical patent/ATE25315T1/en
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    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00Heating by electric, magnetic or electromagnetic fields
    • H05B6/64Heating using microwaves
    • H05B6/78Arrangements for continuous movement of material
    • H05B6/788Arrangements for continuous movement of material wherein an elongated material is moved by applying a mechanical tension to it

Definitions

  • the present invention relates to a device for the microwave treatment of sheet products.
  • It relates more particularly to the heat treatment or the drying of thin sheet products in motion, in particular at high speed and with a large sheet width.
  • One of the preferred applications of the invention is the drying of printing ink applied to sheet paper which runs continuously, for example at the outlet of a gravure printing machine.
  • Another preferred application of the invention is the drying of thin sheet wood, for example veneer lumber.
  • the energy intended for processing sheet products must be transmitted very quickly to these products and in a homogeneous manner.
  • the requirement for rapid energy transfer is essentially conditioned by a problem of space. In fact, the faster the energy transfer, the less cumbersome the processing device.
  • the requirement of a homogeneous treatment is essential for obtaining a sheet product of constant quality over the entire width to be treated.
  • This heating also leads to an increase in the duration of treatment, since it is often necessary to cool the product. On the other hand this heating can affect the quality of the product treated.
  • microwave when subjected to the action of electromagnetic energy in the microwave, can exhibit a relaxation phenomenon if the frequency range of the wave is suitably chosen.
  • microwave applies to electromagnetic waves with a frequency between about 0.1 GHz and 100 GHz.
  • microwaves are therefore particularly recommended for drying alcohol inks or water inks on sheets of paper, for example at the outlet of a gravure printing machine.
  • Microwave processing devices mainly consist of a frequency generator in a selected frequency band, as well as an applicator coupled to the generator and which serves as a guide to the microwaves produced by the generator.
  • microwave must therefore be understood, in the sense that it is used here, as applying to guided microwaves and not as designating a high frequency technique.
  • the electric field is multiplied by the square root of the overvoltage, the overvoltage being defined as the ratio between the total energy stored in the resonator and the energy dissipated per period (at a factor of 2 ⁇ ).
  • a resonant applicator makes it possible to obtain a higher coupling with the sheet product than in the case where a non-resonant applicator is used and, moreover, the same action on the sheet product can be obtained with a small footprint applicator.
  • the product to be treated is scrolled successively through a device which comprises at least two elongated microwave applicators, of the resonant type, with nodes and bellies of intensity along their main axis, and provided with passage openings for the movement of the product to be treated, the applicators having their main axes parallel to each other and being offset transversely to the direction of movement of the products by the quantity where n represents the total number of applicators and ⁇ g the wavelength of microwaves in the applicator.
  • the applicators are defined by a prismatic shape with rectangular section where a denotes the measurement of the side of the section of the rectangle which is perpendicular to the electric field and b denotes the measurement of the side of the section of the rectangle which is parallel to the electric field, said shape prismatic being delimited at one end by a short circuit and at the other end by a conductive wall with coupling iris.
  • Such a device is in particular described by GB-A-650 337 and FR-A-2 448 699.
  • the measurement of the side b can in fact be adjusted to an optimal value greater than a / 2 which makes it possible to greatly increase effectiveness of the applicator.
  • This jet of cold air is intended to sweep the substance, in particular the solvent of the ink which has migrated from the sheet product under the action of microwaves.
  • the device represented in FIG. 1 comprises two parallel microwave applicators 10 and 12 intended for the treatment of a sheet product 14 which scrolls continuously in the direction of the arrow F.
  • the applicators 10 and 12 comprise a waveguide standard, respectively 16 and 18 each supplied in fundamental mode by a generator, respectively 20 and 22, at 2.45 GHz delivering 1 kW of microwave power.
  • the measurement sides a are perpendicular to the plane of the sheet to be treated and the sides d are parallel to the plane of the sheet to be treated.
  • the waveguides 16 and 18 are coupled to the applicators 10 and 12 by a conductive wall, respectively 24 and 26, provided with a coupling iris, respectively 28 and 30.
  • the applicators 10 and 12 are prismatic housings of rectangular section , made of an electrically conductive material.
  • the two sides of the applicators 10 and 12 which are located perpendicular to the plane of the sheet product 14 are provided with rectangular openings 32, 34, 36 and 38 located halfway up the corresponding sides of the applicators.
  • the measurement of these sides is equal to the aforementioned measurement, that is to say 8.6 cm in the present case.
  • the measurement of the other sides of the rectangular section of the applicators 10 and 12 is equal to b.
  • This value b is an optimal value greater than a / 2 and the measurement d of the waveguides 16 and 18.
  • the measurement b is between 8 and 10 cm, preferably equal to 9.1 mc.
  • the applicators 10 and 12 are each delimited, at their end opposite to the wall 24 or 26, by a short circuit, respectively 40 and 42, which is constituted by a rectangular wall, of conductive material, which can slide in the applicator 10 or the applicator 12 under the action of a rod, respectively 44 and 46.
  • the respective positions of irises 28 and 30 and short circuits 40 and 42 are chosen so that the resonance of the guides is obtained and the ap pliers 10 and 12 are offset from each other by an amount X, / 4, transverse to the direction of travel.
  • the device shown in Figures 1 and 2 is particularly applicable to the drying of ink applied to sheet products at the outlet of a printing machine.
  • a blower 48 capable of directing cold air onto the solvent of the ink which has migrated from the sheet of paper under the action of microwaves .
  • the sheet of paper 14 passes, on leaving the applicators 10 and 12, on a roller 50 which allows it to be deflected upwards. This facilitates the ejection of the solvent under the action of the blower 48.
  • the application of the invention to the drying of printing inks with alcohol or water constitutes only a preferred example of application of the invention, and the invention can be applied other treatments, especially heat treatments.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Constitution Of High-Frequency Heating (AREA)
  • Drying Of Solid Materials (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Heating, Cooling, Or Curing Plastics Or The Like In General (AREA)
  • Treatment Of Fiber Materials (AREA)

Abstract

1. Device for treating sheet products by microwaves, comprising at least two elongate micro-wave applicators of the resonant type, with the nodes and antinodes of intensity the length of their principal axes, and provided with passage openings for conducting the product to be treated, the applicators having their principal axes parallel to each other and being spaced transversely in the direction of conduction of the product by an amount 1/2 lambda g/2 where n represents the total number of applicators and lambda g the wavelength of the microwaves in the applicator, the applicators being defined by a prismatic shape of rectangular section where a indicates the length of the side of the section of the rectangle which is perpendicular to the electrical field and b the length of the side of the rectangular section which is parallel to the electric field, said prismatic shape being limited at one end by a short circuit and at the other end by a conducting partition with a coupling iris, characterized by the fact that the length of the side b is in fact adjusted to an optimum value greater than a/2.

Description

La présente invention concerne un dispositif pour le traitement par micro-ondes de produits en feuille.The present invention relates to a device for the microwave treatment of sheet products.

Elle concerne plus particulièrement le traitement thermique ou le séchage de produits en feuille mince en mouvement, notamment à grande vitesse et à grande largeur de feuille.It relates more particularly to the heat treatment or the drying of thin sheet products in motion, in particular at high speed and with a large sheet width.

Une des applications préférentielles de l'invention est le séchage de l'encre d'imprimerie appliquée sur du papier en feuille défilant en continu, par exemple à la sortie d'une machine d'impression héliogravure.One of the preferred applications of the invention is the drying of printing ink applied to sheet paper which runs continuously, for example at the outlet of a gravure printing machine.

Une autre application préférentielle de l'invention est le séchage du bois en feuille mince, par exemple du bois de placage.Another preferred application of the invention is the drying of thin sheet wood, for example veneer lumber.

Pour de telles applications, l'énergie destinée au traitement des produits en feuille doit être transmise très rapidement à ces produits et d'une façon homogène. L'exigence d'un transfert d'énergie rapide est essentiellement conditionnée par un problème d'encombrement. En effet, plus le transfert d'énergie est rapide et moins le dispositif de traitement est encombrant.For such applications, the energy intended for processing sheet products must be transmitted very quickly to these products and in a homogeneous manner. The requirement for rapid energy transfer is essentially conditioned by a problem of space. In fact, the faster the energy transfer, the less cumbersome the processing device.

L'exigence d'un traitement homogène est essentielle pour l'obtention d'un produit en feuille de qualité constante sur toute la largeur à traiter.The requirement of a homogeneous treatment is essential for obtaining a sheet product of constant quality over the entire width to be treated.

Les procédés et dispositifs utilisés actuellement pour le traitement, en particulier pour le séchage, de produits en feuille font principalement appel à de l'air chaud ou à des rayonnements infrarouge. De tels procédés et dispositifs ont pour inconvénient d'être très coûteux en énergie et de conduire à un échauffement important du produit dans le cas du séchage.The methods and devices currently used for the treatment, in particular for drying, of sheet products mainly use hot air or infrared radiation. Such methods and devices have the drawback of being very costly in energy and of leading to significant heating of the product in the case of drying.

Cet échauffement entraîne également une augmentation de la durée de traitement, puisqu'on est souvent obligé de refroidir le produit. D'autre part cet échauffement peut nuire à la qualité du produit traité.This heating also leads to an increase in the duration of treatment, since it is often necessary to cool the product. On the other hand this heating can affect the quality of the product treated.

En dehors des procédés et dispositifs utilisant de l'air chaud ou des rayonnements infrarouge, on connaît également une technique plus récente qui consiste dans l'application de micro-ondes pour le traitement de produits sensibles aux micro-ondes, c'est-à-dire de produits présentant une polarité diélectrique permanente.Apart from the processes and devices using hot air or infrared radiation, there is also known a more recent technique which consists in the application of microwaves for the treatment of products sensitive to microwaves, i.e. - to say of products having a permanent dielectric polarity.

De tels produits, lorsqu'ils sont soumis à l'action d'une énergie électromagnétique en micro-ondes, peuvent présenter un phénomène de relaxation si la gamme de de fréquences de l'onde est convenablement choisie. On rappelera à ce propos que le terme «micro-ondes» s'applique à des ondes électromagnétiques de fréquence comprise entre environ 0,1 GHz et 100 GHz.Such products, when subjected to the action of electromagnetic energy in the microwave, can exhibit a relaxation phenomenon if the frequency range of the wave is suitably chosen. It will be recalled in this connection that the term "microwave" applies to electromagnetic waves with a frequency between about 0.1 GHz and 100 GHz.

La mise en oeuvre de ces phénomènes de relaxation diélectrique dans des produits polaires, c'est-à-dire eau, alcool, polymères etc. conduit à des transferts énergétiques à haut rendement, ne comportant pas nécessairement un échauffement important du produit dans le cas du séchage.The implementation of these dielectric relaxation phenomena in polar products, that is to say water, alcohol, polymers etc. leads to high efficiency energy transfers, not necessarily involving significant heating of the product in the case of drying.

Il en résulte par conséquent, que, dans des matériaux diélectriques convenables, c'est-à-dire ceux qui contiennent des molécules polaires ou des chaînes macromoléculaires dissymétriques, l'application des micro-ondes pour réaliser un traitement thermique ou un séchage répond au double objectif d'une grande rapidité de transfert d'énergie et d'un fort rendement énergétique dans le produit.It therefore follows that, in suitable dielectric materials, that is to say those which contain polar molecules or asymmetric macromolecular chains, the application of microwaves to carry out heat treatment or drying responds to the double objective of a high speed of energy transfer and a high energy yield in the product.

L'application des micro-ondes est donc particulièrement recommandée pour le séchage d'encres à l'alcool ou d'encres à l'eau sur des feuilles de papier, par exemple à la sortie d'une machine d'impression héliogravure.The application of microwaves is therefore particularly recommended for drying alcohol inks or water inks on sheets of paper, for example at the outlet of a gravure printing machine.

Les dispositifs de traitement aux micro-ondes se composent principalement d'un générateur de fréquences dans une bande de fréquences choisies, ainsi qu'un applicateur couplé au générateur et qui sert de guide aux micro-ondes produites par le générateur.Microwave processing devices mainly consist of a frequency generator in a selected frequency band, as well as an applicator coupled to the generator and which serves as a guide to the microwaves produced by the generator.

Le terme micro-ondes doit donc être compris, dans le sens où il est utilisé ici, comme s'appliquant à des micro-ondes guidées et non pas comme désignant une technique haute fréquence.The term microwave must therefore be understood, in the sense that it is used here, as applying to guided microwaves and not as designating a high frequency technique.

Le problème essentiel que l'on rencontre pour la mise en ceuvre des traitements aux micro-ondes est la réalisation d'un dispositif applicateur qui couple très efficacement le champ électrique de l'onde aux produits à traiter, et diverses solutions ont déjà été proposées à cet effet.The essential problem encountered in the implementation of microwave treatments is the production of an applicator device which very effectively couples the electric field of the wave to the products to be treated, and various solutions have already been proposed. for this purpose.

Les solutions proposées jusqu'à présent font appel le plus souvent au passage successif d'une onde progressive appliquée au moyen soit de guides repliés, soit de guides à fentes. Ces solutions connues permettent un traitement homogène sur toute la largeur de la feuille à traiter, mais elles conduisent malheureusement à un applicateur de micro-ondes encombrant, car le champ électrique de l'onde progressive possède une faible intensité.The solutions proposed so far most often call for the successive passage of a progressive wave applied by means of either folded guides or slotted guides. These known solutions allow homogeneous treatment over the entire width of the sheet to be treated, but they unfortunately lead to a bulky microwave applicator, since the electric field of the traveling wave has a low intensity.

Pour palier cet inconvénient et réduire l'encombrement de l'applicateur, on peut faire appel à un applicateur résonnant dont le champ électrique est nettement plus intense pour une même puissance micro-ondes injectée à l'entrée de l'applicateur. En effet, dans ce cas, le champ électrique est multiplié par la racine carrée de la surtension, la surtension étant définie comme le rapport entre l'énergie totale emmagasinée dans le résonna- teur et l'énergie dissipée par période (à un facteur de 2π près).To overcome this drawback and reduce the size of the applicator, one can use a resonant applicator whose electric field is significantly more intense for the same microwave power injected at the input of the applicator. In this case, the electric field is multiplied by the square root of the overvoltage, the overvoltage being defined as the ratio between the total energy stored in the resonator and the energy dissipated per period (at a factor of 2π).

L'utilisation d'un applicateur résonnant permet d'obtenir un couplage avec le produit en feuille plus élevé que dans le cas où on utilise un applicateur non résonnant et, en outre, la même action sur le produit en feuille peut être obtenue avec un applicateur de faible encombrement.The use of a resonant applicator makes it possible to obtain a higher coupling with the sheet product than in the case where a non-resonant applicator is used and, moreover, the same action on the sheet product can be obtained with a small footprint applicator.

Cependant, l'utilisation d'un applicateur résonnant unique présente un sérieux inconvénient en ce sens que le traitement n'est plus homogène sur toute la largeur du produit en feuille à traiter puisque le champ électrique présente des noeuds et des ventres d'intensité.However, the use of a single resonant applicator has a serious disadvantage in that the treatment is no longer homogeneous over the entire width of the sheet product to be treated since the electric field has nodes and bellies of intensity.

On évite les inconvénients précités par l'utilisation de plusieurs applicateurs résonnants en parallèle présentant entre eux un décalage de phase approprié.The aforementioned drawbacks are avoided by the use of several resonant applicators in parallel having an appropriate phase shift between them.

Plus particulièrement, on fait défiler le produit à traiter successivement à travers un dispositif qui comprend au moins deux applicateurs micro-ondes allongés, du type résonnant, avec des noeuds et des ventres d'intensité le long de leur axe principal, et munis d'ouvertures de passage pour le défilement du produit à traiter, les applicateurs ayant leurs axes principaux parallèles entre eux et étant décalés transversalement à la direction de défilement des produits de la quantité

Figure imgb0001
où n représente le nombre total d'applicateurs et λg la longueur d'ondes des micro-ondes dans l'applicateur.More particularly, the product to be treated is scrolled successively through a device which comprises at least two elongated microwave applicators, of the resonant type, with nodes and bellies of intensity along their main axis, and provided with passage openings for the movement of the product to be treated, the applicators having their main axes parallel to each other and being offset transversely to the direction of movement of the products by the quantity
Figure imgb0001
where n represents the total number of applicators and λg the wavelength of microwaves in the applicator.

On a pu constater que le produit en feuille ayant traversé successivement les n applicateurs a subi un traitement assez homogène sur toute la largeur de la feuille traitée.It has been observed that the sheet product having successively passed through the n applicators has undergone a fairly homogeneous treatment over the entire width of the treated sheet.

Bien qu'en fait l'homogénéité soit d'autant meilleure que n est grand, on a pu constater, en pratique, que l'utilisation de deux applicateurs en parallèle permettaient d'obtenir déjà un traitement relativement homogène.Although in fact the homogeneity is all the better as n is large, it has been observed, in practice, that the use of two applicators in parallel already makes it possible to obtain a relatively homogeneous treatment.

Les applicateurs sont définis par une forme prismatique à section rectangulaire où a désigne la mesure du côté de la section du rectangle qui est perpendiculaire au champ électrique et b désigne la mesure du côté de la section du rectangle qui est parallèle au champ électrique, ladite forme prismatique étant délimitée à une extrémité par un court-circuit et à l'autre extrémité par une paroi conductrice à iris de couplage.The applicators are defined by a prismatic shape with rectangular section where a denotes the measurement of the side of the section of the rectangle which is perpendicular to the electric field and b denotes the measurement of the side of the section of the rectangle which is parallel to the electric field, said shape prismatic being delimited at one end by a short circuit and at the other end by a conductive wall with coupling iris.

Un tel dispositif est en particulier décrit par le GB-A-650 337 et le FR-A-2 448 699.Such a device is in particular described by GB-A-650 337 and FR-A-2 448 699.

Mais surtout, et de façon caractéristique de l'invention, on a pu constater, de façon tout à fait surprenante, que la mesure du côté b peut être en fait ajustée sur une valeur optimale supérieure à a/2 qui permet d'augmenter fortement l'efficacité de l'applicateur.But above all, and characteristically of the invention, it has been found, quite surprisingly, that the measurement of the side b can in fact be adjusted to an optimal value greater than a / 2 which makes it possible to greatly increase effectiveness of the applicator.

Ainsi, dans le cas où l'on utilise un applicateur à partir d'un guide d'ondes standard qui, pour l'Europe, correspond à une forme prismatique de section rectangulaire où a = 8,6 cm et b = 4,3 cm, on a pu constater que la valeur optimale de b était comprise entre 8 et 10 cm et qu'en particulier elle pouvait être égale à 9,1 cm.Thus, in the case where an applicator is used from a standard waveguide which, for Europe, corresponds to a prismatic shape of rectangular section where a = 8.6 cm and b = 4.3 cm, we could see that the optimal value of b was between 8 and 10 cm and that in particular it could be equal to 9.1 cm.

Une telle constatation n'est nullement évidente, et même contraire aux préjugés de l'homme du métier qui cherche toujours à diminuer la valeur b du côté transversal pour tenter d'améliorer le couplage entre l'applicateur et le produit à traiter. En effet, l'augmentation de b entraîne une diminution du champ électrique, mais une amélioration du couplage entre le guide d'ondes et les générateurs et une augmentation du temps de séjour du produit en feuille dans le guide d'ondes.Such a finding is by no means obvious, and even contrary to the prejudices of those skilled in the art who always seek to decrease the value b on the transverse side in an attempt to improve the coupling between the applicator and the product to be treated. Indeed, the increase in b results in a decrease in the electric field, but an improvement in the coupling between the waveguide and the generators and an increase in the residence time of the sheet product in the waveguide.

Le guide d'ondes standard étant prévu pour fonctionner dans le mode TE,,, l'augmentation de la mesure d pour obtenir la valeur optimale précitée permet d'approcher les conditions de résonance du mode TEo2.Since the standard waveguide is designed to operate in the TE mode, increasing the measurement d to obtain the aforementioned optimal value makes it possible to approach the resonance conditions of the TE o2 mode.

Il peut être préférable, pour certaines applications, en particulier pour le séchage d'encre d'imprimerie de prévoir une soufflerie apte à diriger un jet d'air froid sur le produit en feuille après son séchage au travers des applicateurs. Ce jet d'air froid est destiné à balayer la substance, en particulier le solvant de l'encre qui a migré du produit en feuille sous l'action des micro-ondes.It may be preferable, for certain applications, in particular for the drying of printing ink, to provide a blower capable of directing a jet of cold air onto the sheet product after it has dried through the applicators. This jet of cold air is intended to sweep the substance, in particular the solvent of the ink which has migrated from the sheet product under the action of microwaves.

D'autres caractéristiques et avantages de l'invention seront mieux compris à la lecture de la description détaillée qui suit et qui se réfère au dessin annexé, donné uniquement à titre illustratif, et sur lequel:

  • - La figure 1 est une vue en perspective d'un dispositif de traitement selon l'invention comportant deux applicateurs micro-ondes en parallèle; et
  • - la figure 2 est une vue schématique de côté du dispositif de la figure 1 incorporant une soufflerie à la sortie des applicateurs.
Other characteristics and advantages of the invention will be better understood on reading the detailed description which follows and which refers to the appended drawing, given solely by way of illustration, and in which:
  • - Figure 1 is a perspective view of a processing device according to the invention comprising two microwave applicators in parallel; and
  • - Figure 2 is a schematic side view of the device of Figure 1 incorporating a blower at the outlet of the applicators.

Le dispositif représenté sur la figure 1 comporte deux applicateurs micro-ondes parallèles 10 et 12 destinés au traitement d'un produit en feuille 14 qui défile en continu dans la direction de la flèche F. Les applicateurs 10 et 12 comportent un guide d'ondes standard, respectivement 16 et 18 alimenté chacun en mode fondamental par un générateur, respectivement 20 et 22, à 2,45 GHz délivrant 1 kW de puissance micro-ondes. Les guides d'ondes 16 et 18 sont des guides standards (standard européen) de section rectangulaire présentant un côté de mesure a = 8,6 cm et un côté de mesure d = 4,3 cm. Les côtés de mesure a sont perpendiculaires au plan de la feuille à traiter et les côtés d sont parallèles au plan de la feuille à traiter. Les guides d'ondes 16 et 18 sont couplés aus applicateurs 10 et 12 par une paroi conductrice, respectivement 24 et 26, munie d'un iris de couplage, respectivement 28 et 30. Les applicateurs 10 et 12 sont des boîtiers prismatiques de section rectangulaire, réalisés en une matière conductrice de l'électricité. Les deux côtés des applicateurs 10 et 12 qui sont situés perpendiculairement au plan du produit en feuille 14 sont munis d'ouvertures rectangulaires 32, 34, 36 et 38 situées à mi-hauteur des côtés correspondants des applicateurs. La mesure de ces côtés est égale à la mesure a précitée, c'est-à-dire à 8,6 cm dans le cas présent. La mesure des autres côtés de la section rectangulaire des applicateurs 10 et 12 est égale à b. Cette valeur b est une valeur optimale supérieure à a/2 et à la mesure d des guides d'ondes 16 et 18. Dans cet exemple particulier, la mesure b est comprise entre 8 et 10 cm de préférence égale à 9,1 mc.The device represented in FIG. 1 comprises two parallel microwave applicators 10 and 12 intended for the treatment of a sheet product 14 which scrolls continuously in the direction of the arrow F. The applicators 10 and 12 comprise a waveguide standard, respectively 16 and 18 each supplied in fundamental mode by a generator, respectively 20 and 22, at 2.45 GHz delivering 1 kW of microwave power. The waveguides 16 and 18 are standard guides (European standard) of rectangular section having a measurement side a = 8.6 cm and a measurement side d = 4.3 cm. The measurement sides a are perpendicular to the plane of the sheet to be treated and the sides d are parallel to the plane of the sheet to be treated. The waveguides 16 and 18 are coupled to the applicators 10 and 12 by a conductive wall, respectively 24 and 26, provided with a coupling iris, respectively 28 and 30. The applicators 10 and 12 are prismatic housings of rectangular section , made of an electrically conductive material. The two sides of the applicators 10 and 12 which are located perpendicular to the plane of the sheet product 14 are provided with rectangular openings 32, 34, 36 and 38 located halfway up the corresponding sides of the applicators. The measurement of these sides is equal to the aforementioned measurement, that is to say 8.6 cm in the present case. The measurement of the other sides of the rectangular section of the applicators 10 and 12 is equal to b. This value b is an optimal value greater than a / 2 and the measurement d of the waveguides 16 and 18. In this particular example, the measurement b is between 8 and 10 cm, preferably equal to 9.1 mc.

Les applicateurs 10 et 12 sont délimités chacun, à leur extrémité opposée à la paroi 24 ou 26, par un court-circuit, respectivement 40 et 42, qui est constitué par une paroi rectangulaire, en matière conductrice, pouvant coulisser dans l'applicateur 10 ou l'applicateur 12 sous l'action d'une tige, respectivement 44 et 46.The applicators 10 and 12 are each delimited, at their end opposite to the wall 24 or 26, by a short circuit, respectively 40 and 42, which is constituted by a rectangular wall, of conductive material, which can slide in the applicator 10 or the applicator 12 under the action of a rod, respectively 44 and 46.

Les positions respectives des iris 28 et 30 et des court-circuits 40 et 42 sont choisies de façon que la résonnance des guides soit obtenue et les applicateurs 10 et 12 sont décalés l'un par rapport à l'autre d'une quantité X,/4, transversalement à la direction du défilement.The respective positions of irises 28 and 30 and short circuits 40 and 42 are chosen so that the resonance of the guides is obtained and the ap pliers 10 and 12 are offset from each other by an amount X, / 4, transverse to the direction of travel.

A titre indicatif, on a obtenu de bons résultats avec des dimensions d'iris de 3,8 x 9,1 cm.As an indication, good results have been obtained with iris dimensions of 3.8 x 9.1 cm.

Le dispositif représenté sur les figures 1 et 2 est particulièrement applicable au séchage d'encre appliquée sur des produits en feuille à la sortie d'une machine d'impression. A la sortie du dispositif de l'invention, il est préférable d'adjoindre une soufflerie 48 apte à diriger de l'air froid sur le solvant de l'encre qui a migré de la feuille de papier sous l'action des micro-ondes. Comme représenté sur la figure 2, et dans le cas où la face imprimée est dirigée vers le bas, la feuille de papier 14 passe, à sa sortie des applicateurs 10 et 12, sur un rouleau 50 qui permet de la dévier vers le haut. Ceci facilite l'éjection du solvant sous l'action de la soufflerie 48.The device shown in Figures 1 and 2 is particularly applicable to the drying of ink applied to sheet products at the outlet of a printing machine. At the outlet of the device of the invention, it is preferable to add a blower 48 capable of directing cold air onto the solvent of the ink which has migrated from the sheet of paper under the action of microwaves . As shown in FIG. 2, and in the case where the printed face is directed downwards, the sheet of paper 14 passes, on leaving the applicators 10 and 12, on a roller 50 which allows it to be deflected upwards. This facilitates the ejection of the solvent under the action of the blower 48.

Avec le dispositif tel que représenté sur les figures 1 et 2, qui délivre une puissance totale de 2 kW, et des applicateurs 10 et 12 qui ont une largeur b = 4,3 cm, on a pu obtenir des vitesses de séchage de 30 à 40 m par minute avec une encre à solvant alcool et de 20 m par minute avec une encre à l'eau, à condition d'appliquer une ventilation d'air à la sortie des deux applicateurs. Dans ce cas particulier, la largeur de la feuille 14 était voisine de 50 cm, mais il est bien entendu que le dispositif n'est pas limité à une largeur de traitement particulière. En optimisant la mesure b du côté transversal des applicateurs 10 et 12, et en particulier avec b = 9,1 cm, on a pu multiplier par un facteur de 2 la vitesse de séchage par rapport aux vitesses obtenues avec un guide standard, c'est-à-dire dans le cas où le côté transversal est égal à d (c'est-à-dire 4,3 cm pour le standard européen).With the device as shown in FIGS. 1 and 2, which delivers a total power of 2 kW, and applicators 10 and 12 which have a width b = 4.3 cm, it was possible to obtain drying speeds of 30 to 40 m per minute with alcohol solvent ink and 20 m per minute with water ink, provided that air ventilation is applied at the outlet of the two applicators. In this particular case, the width of the sheet 14 was close to 50 cm, but it is understood that the device is not limited to a particular processing width. By optimizing the measurement b on the transverse side of the applicators 10 and 12, and in particular with b = 9.1 cm, we were able to multiply by a factor of 2 the drying speed compared to the speeds obtained with a standard guide, c ' i.e. in the case where the transverse side is equal to d (i.e. 4.3 cm for the European standard).

Il est bien entendu que l'invention n'est pas limitée au mode de réalisation particulièrement décrit et représenté et qu'on peut imaginer d'autres variantes de réalisation sans sortir du cadre de l'invention. Ainsi, on peut faire appel à des applicateurs dérivant de guides standards non européens, en particulier du standard américain de 3,4 x 7,2 cm.It is understood that the invention is not limited to the embodiment particularly described and shown and that one can imagine other alternative embodiments without departing from the scope of the invention. Thus, it is possible to use applicators derived from non-European standard guides, in particular from the American standard of 3.4 x 7.2 cm.

D'autre part, l'application de l'invention au séchage des encres d'imprimerie à l'alcool ou à l'eau ne constitue qu'un exemple préférentiel d'application de l'invention, et on peut appliquer l'invention à d'autres traitements, en particulier à des traitements thermiques.On the other hand, the application of the invention to the drying of printing inks with alcohol or water constitutes only a preferred example of application of the invention, and the invention can be applied other treatments, especially heat treatments.

Claims (4)

1. Device for treating sheet products by microwaves, comprising at least two elongate microwave applicators of the resonant type, with the nodes and antinodes of intensity the length of their principal axes, and provided with passage openings for conducting the product to be treated, the applicators having their principal axes parallel to each other and being spaced transversely in the direction of conduction of the product by an amount
Figure imgb0003
where n represents the total number of applicators and λg the wavelength of the microwaves in the applicator, the applicators being defined by a prismatic shape of rectangular section where a indicates the length of the side of the section of the rectangle which is perpendicular to the electrical field and b the length of the side of the rectangular section which is parallel to the electric field, said prismatic shape being limited at one end by a short circuit and at the other end by a conducting partition with a coupling iris, characterized by the fact that the length of the side b is in fact adjusted to an optimum value greater than a
2. Device according to the claim 1, characterized by the fact that the length of the side b is adjusted to approach the conditions of resonance of the mode TEa2.
3. Device according to one of claims 1 and 2, characterized by the fact that the rectangular section has a length a of 8.6 cm and a length b contained between 8 and 10 cm, in particular of 9.1 cm.
4. Device according to one of claims 1 to 3, characterized by the fact that it comprises a bellows intended to direct a jet of cold air onto the sheet product after its passage across the applicators.
EP83400518A 1982-03-16 1983-03-14 Device for heating sheet products by microwaves Expired EP0089288B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT83400518T ATE25315T1 (en) 1982-03-16 1983-03-14 PLANT FOR TREATMENT OF SHEET PRODUCTS BY MICROWAVES.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8204398A FR2523797B1 (en) 1982-03-16 1982-03-16 METHOD AND DEVICE FOR MICROWAVE PROCESSING OF SHEET PRODUCTS
FR8204398 1982-03-16

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EP0089288A1 EP0089288A1 (en) 1983-09-21
EP0089288B1 true EP0089288B1 (en) 1987-01-28

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EP (1) EP0089288B1 (en)
AT (1) ATE25315T1 (en)
DE (1) DE3369626D1 (en)
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Publication number Priority date Publication date Assignee Title
FR2673936B1 (en) * 1991-03-14 1993-12-24 Snecma INSTALLATION FOR HEAT TREATMENT OF PARTS OF COMPOSITE MATERIAL WITH CERAMIC MATRIX, HEATED BY MICROWAVE WAVES AND METHOD OF IMPLEMENTING SAME.
US5423260A (en) * 1993-09-22 1995-06-13 Rockwell International Corporation Device for heating a printed web for a printing press
US5631685A (en) * 1993-11-30 1997-05-20 Xerox Corporation Apparatus and method for drying ink deposited by ink jet printing
WO2000004746A1 (en) 1998-07-16 2000-01-27 The Board Of Regents, The University Of Texas System Method and apparatus for rapid drying of coated materials with close capture of vapors
GB201406657D0 (en) 2014-04-14 2014-05-28 Pera Technology Ltd Heating apparatus and method

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Publication number Priority date Publication date Assignee Title
GB633916A (en) * 1946-10-04 1949-12-30 Westinghouse Electric Int Co Improvements in or relating to dielectric heating apparatus
GB650337A (en) * 1948-12-20 1951-02-21 Gen Electric Co Ltd Improvements in or relating to high frequency electric heating apparatus
FR1264758A (en) * 1960-07-29 1961-06-23 Ass Elect Ind Device for ultra high frequency heat treatment
US3052856A (en) * 1961-12-22 1962-09-04 John L Carter Ferrite power divider
US3247472A (en) * 1963-03-06 1966-04-19 Bell Telephone Labor Inc Microwave devices exhibiting mode conversion using a resonantly biased gyromagnetic material
US3564458A (en) * 1969-10-28 1971-02-16 Canadian Patents Dev Branched waveguide transitions with mode filters
GB2042703A (en) * 1979-02-06 1980-09-24 Ciba Geigy Ag Drying of Web Material

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DE3369626D1 (en) 1987-03-05
ATE25315T1 (en) 1987-02-15
EP0089288A1 (en) 1983-09-21
FR2523797A1 (en) 1983-09-23
FR2523797B1 (en) 1985-09-27

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