EP0403002A1 - Method for electrostatic powder coating for coating an object with powdery or granular particles and device for implementing this method - Google Patents

Method for electrostatic powder coating for coating an object with powdery or granular particles and device for implementing this method Download PDF

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Publication number
EP0403002A1
EP0403002A1 EP90201486A EP90201486A EP0403002A1 EP 0403002 A1 EP0403002 A1 EP 0403002A1 EP 90201486 A EP90201486 A EP 90201486A EP 90201486 A EP90201486 A EP 90201486A EP 0403002 A1 EP0403002 A1 EP 0403002A1
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European Patent Office
Prior art keywords
particles
fluid
electrostatic field
support
jet
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EP90201486A
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German (de)
French (fr)
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EP0403002B1 (en
Inventor
Jean-Luc Houssaye
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Tremplin SA
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Tremplin SA
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Priority to AT90201486T priority Critical patent/ATE99996T1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/18—Processes for applying liquids or other fluent materials performed by dipping
    • B05D1/22—Processes for applying liquids or other fluent materials performed by dipping using fluidised-bed technique
    • B05D1/24—Applying particulate materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05C19/00—Apparatus specially adapted for applying particulate materials to surfaces
    • B05C19/02—Apparatus specially adapted for applying particulate materials to surfaces using fluidised-bed techniques
    • B05C19/025—Combined with electrostatic means

Definitions

  • the subject of the present invention is a process for electrostatic powdering intended to coat an object with powdery or granular particles, of the type consisting in directing these particles by means of an electrostatic field, towards a receiving element constituted by the object to be coated.
  • This invention extends to a device for implementing this method.
  • the coating of objects by electrostatic powdering is a process which has experienced a great boom in recent years, especially in industrial painting. This development is due to the advantages of this process, in particular as regards the improvement in the finish provided and the reduction in cost prices achieved compared with known coating processes.
  • the technique consists in placing a homogeneous layer of pulverulent material on an insulating support placed opposite the object to be coated, in fluidizing the particles either mechanically or electrically, in particular by means of a pulsating field, so as to obtain a uniform swirling and intense, and to create an electrostatic field between the support and the object so that the particles follow the lines of force of this field and come to deposit on the receiving object.
  • Such techniques in particular described in patents FR 2,146,886, FR 2,263,825 and DE 2,036,279, are very reliable when the receiving object is strictly made up of flat surfaces.
  • the present invention aims to overcome this drawback and aims to provide an improved electrostatic powdering process for coating uniformly objects of any shape with non-planar surfaces.
  • the invention relates to an electrostatic powdering process intended to coat with powdery or granular particles an object having portions of flat surfaces and portions of non-planar surfaces, said process consisting in placing a layer of particles on an insulating support. placed next to the object, to fluidize this layer of particles and to create an electrostatic field between the support and the object.
  • this process is characterized in that: the particles are subjected to the action of an electrostatic field generating lines of force driving said particles adapted to direct them towards the flat surfaces of the object, - And the trajectory of the particles is modified by means of at least one jet of fluid oriented so as to direct said particles towards the non-planar surfaces of the object.
  • the invention therefore consists in combining the action of an electrostatic field whose lines of force direct the particles towards the planar surfaces of the object, with a jet of fluid making it possible to deflect these particles from their trajectory and thus to direct them towards the non-planar surface portions of the object
  • This combination therefore makes it possible to uniformly sweep the surface to be treated and to deposit a uniform layer of coating on this surface.
  • the direction of the fluid jet relative to the surface to be covered can also be modified within a wide inclination range according to the shape and the dimensions of this surface, thus allowing the treatment of objects of very different shapes.
  • the particles are first subjected to the action of the electrostatic field, for a period of time suitable for uniformly coating the flat surfaces of the object, - secondly, the jet of fluid, while maintaining the electrostatic field in action, so as to deflect the particles towards the non-planar surfaces and uniformly coat the latter, - And the action of the electrostatic field and the jet of fluid is interrupted.
  • the particles are preferably subjected to the action of the electrostatic field for a period of time substantially comprised between 5 and 10 seconds, then to the combined action of the field and the jet of fluid for a period of time comprised substantially between 1 and 5 seconds.
  • the fluid used is preferably compressed air at a pressure substantially between 4 and 7 bars, which is delivered with a flow rate substantially between 0.1 and 0, 6 m3 / min, and at a distance substantially between 10 and 20 centimeters from the object.
  • the invention extends to an electrostatic powdering device for application to an object comprising portions of flat surfaces and portions of non-planar surfaces, of a coating of powdery or granular particles, of the type comprising an insulating support for particles, means adapted to fluidize the particles arranged on the support, and means generating an electrostatic field adapted to accelerate the fluidized particles and transport them to the object according to predetermined trajectories.
  • This device is characterized in that it comprises means for supplying a fluid provided with at least one fluid outlet disposed between the object and the support, near said support, and adapted to deliver said fluid according to a direction where it changes the trajectories of the particles.
  • the device shown in Figures 1 to 3 is an electrostatic powdering device suitable for covering objects with powdery particles.
  • This device is more particularly intended for an application of powder paint on one side of a "pedestal table".
  • Bo pedestal table we mean an object whose surface to be treated is a circular planar surface provided on its periphery with a concave groove delimited, on the one hand, by this planar surface and, on the other hand, by a cylindrical return perpendicular to said surface).
  • This device comprises, firstly, two cylindrical boxes made of a plastic material such as PVC, nested one inside the other: an internal box 2 of diameter corresponding to that of the mold of the mold, and an external box 1, intended to isolate the inner box 2 and of dimensions adapted to provide an interstitial space between the peripheral and bottom walls of said boxes. Shims 3 are also arranged in this interstitial space in order to ensure the positioning and the maintenance of the inner box 2 in the outer box 1.
  • the device also comprises two networks of electrodes disposed respectively inside the interior box 2 and in the interstitial space separating the bottom walls of the interior 2 and exterior 1 boxes.
  • the first network placed in the bottom of the inner box 2, consists of an assembly of compression springs 4 wound in the form of a spiral so that the distance between two turns is of the order of 3, 2 inches.
  • These springs 4 are carried by wires 5, arranged radially in the bottom of the inner box 2 and the ends of which are fixed to a metal ring 6 resting on the bottom wall of this box. These wires 5 and this ring 6 are furthermore arranged so as to maintain the springs 4 at approximately 1 cm above this bottom wall.
  • the second network of electrodes is made up of ten copper blades 7 30 millimeters wide welded to each other so as to form an orthogonal mesh. These blades 7 are covered with an aluminum foil intended to obtain a good distribution of the electrostatic charges and are fixed under the bottom wall of the inner box 2.
  • one of the ends of the spiral of springs 4 and one of the copper blades 7 are connected to a voltage source (not shown) so as to form an electrostatic vibrator of the type known per se, described in particular in French patents n ° 2.263.825 and 2.146.886.
  • the device also includes a compressed air supply system.
  • This system consists, first of all, of a cylindrical stitching angle fitting 8 disposed on the bottom wall of the inner box 2, in the center of the latter. On the inlet of this angle-fitting 8 is connected a pipe 9 for supplying compressed air with an internal diameter of 4 mm.
  • This pipe 9 is introduced into the inner box 2 through two openings arranged opposite in the peripheral walls of this inner box and the outer box 1, and is arranged so as to extend radially on the bottom wall of said inner box. Its external end is connected upstream to a tapping pipe (not shown) of compressed air delivered by a supply network.
  • This tapping pipe has an internal diameter of 10 millimeters greater than that of pipe 9, with a view to overcoming any fluctuations in the flow of compressed air.
  • the compressed air supply system finally comprises a plastic tip 10 mounted on the vertical outlet branch of the angle fitting 9.
  • This tip 10, of the same internal diameter as that of the angle fitting 9, has besides a length adapted so that the compressed air outlet is at a distance of between 0.5 cm and 10 cm from the bottom wall of the inner box 2.
  • the device finally comprises a mask arranged on the double box and intended to prevent the deposition of pulverulent material over a height of 20 centimeters from the surface of the return of the pedestal table.
  • this mask consists of a crown 11 of the same diameter as that of the matrix 13 of the mold, adapted to come to press internally against the return of this matrix.
  • This crown 11 made of plastic material reinforced with 30% glass fibers, is screwed onto a plywood support 12, itself secured to the outer box 1.
  • the distance between the surface to be treated and the network of springs 4 is of the order of 235 mm.
  • Such a device is adapted to be associated, in a conventional manner, with a support assembly managed by a programmable auto mat and adapted to automatically adjust this device in the mold.
  • the sequences for moving such a support are as follows: - horizontal linear movement in advance from a parking position to a position where the device is directly above the mold, - linear upward movement to the position where the mask is inserted in the mold, - linear downward movement of mask disengagement, - horizontal linear movement back to the parking position.
  • the programmable controller is also conventionally adapted to manage the operation of the electrostatic vibrator and the compressed air supply system, according to the process described below.
  • the bottom wall of the inner box 2 is uniformly covered with powder over a thickness suitable for this powder to be flush with the bottom of the springs 4 as much as possible. Furthermore, the matrix 13 of the mold is connected to the ground.
  • the powder transfer process takes place in two stages.
  • the powder is subjected to the electrostatic powdering system.
  • the powder layer resting on the bottom wall of the inner box 2 is fluidized by applying an alternating voltage between the two networks of electrodes 4 and 7 which then form an electrostatic vibrator. This vibrator continuously reverses the polarity of the powder which is thus charged.
  • the bottom of the inner box 2 is also subject to reverse polarity.
  • the network of electrodes 4 is placed under adjustable high voltage, of a value of 48 KV and between this network and the matrix 13 of the mold, grounded, forms an electrostatic field.
  • the charged particles follow the lines of force of this electrostatic field and are deposited on the flat surfaces of the matrix 13.
  • the groove of this matrix 13 receives very little powder during this operation.
  • the second step therefore consists in transferring the powder still charged, the electrodes being kept under tension, on the non-planar surfaces of the matrix 13, that is to say in the groove of the latter.
  • This result is obtained by actuating the compressed air supply system adapted to deliver compressed air at a pressure of 4.5 bars.
  • This jet of compressed air has the effect of overcoming the lines of force of the electrostatic field and deflecting the powder towards the throat of the matrix.
  • the air jet is also activated 8 seconds after the electrode arrays are energized, and for a period of 2 seconds. The actuation of the electrostatic powder system and the air supply system is then interrupted.
  • Such a process makes it possible to obtain a perfect distribution of the powder on the different surfaces of the matrix, the thickness of powder deposited being uniform and 0.25 mm ⁇ 0.1 mm.

Landscapes

  • Application Of Or Painting With Fluid Materials (AREA)
  • Electrostatic Spraying Apparatus (AREA)
  • Paints Or Removers (AREA)
  • Glanulating (AREA)

Abstract

The invention relates to the powder coating of an object having plane surface portions and non-plane surface portions. The method consists in disposing a layer of particles over an insulating support (2) placed opposite the object, in fluidising this layer of particles and in creating an electrostatic field between the support (2) and the object. It is characterised in that the particles are subjected to the action of an electrostatic field generating lines of force for entraining the said particles, which are adapted in order to direct them towards the plane surfaces of the object, and in that the trajectory of the particles is modified by means of at least one fluid jet oriented so as to direct the said particles towards the non-plane surfaces of the object. <IMAGE>

Description

La présente invention a pour objet un procédé de poudrage électrostatique destiné à revêtir un objet de particules pulvérulentes ou granuleuses, du type consistant à diriger ces particules au moyen d'un champ électrostatique, vers un élément récepteur constitué par l'objet à revêtir. Cette invention s'étend à un dispositif pour la mise en oeuvre de ce procédé.The subject of the present invention is a process for electrostatic powdering intended to coat an object with powdery or granular particles, of the type consisting in directing these particles by means of an electrostatic field, towards a receiving element constituted by the object to be coated. This invention extends to a device for implementing this method.

Le revêtement d'objets par poudrage électrostatique est un procédé qui a connu un grand essor ces dernières années, notamment dans la peinture industrielle. Cet essor est dû aux avantages de ce procédé notamment quant à l'amélioration de la finition apportée et la diminution des prix de revient réalisée par rapport aux procédés de revêtement connus.The coating of objects by electrostatic powdering is a process which has experienced a great boom in recent years, especially in industrial painting. This development is due to the advantages of this process, in particular as regards the improvement in the finish provided and the reduction in cost prices achieved compared with known coating processes.

La technique consiste à disposer une couche homogène de matériau pulvérulent sur un support isolant placé en regard de l'objet à revêtir, à fluidiser les particules soit mécaniquement soit électriquement, notamment au moyen d'un champ pulsatoire, de façon à obtenir un tourbillonnement uniforme et intense, et à créer un champ électrostatique entre le support et l'objet de façon que les particules suivent les lignes de force de ce champ et viennent se déposer sur l'objet récepteur. De telles techniques, notamment décrites dans les brevets FR 2.146.886, FR 2.263.825 et DE 2.036.279, sont très fiables lorsque l'objet récepteur est strictement constitué de surfaces planes. Par contre, lorsque cet objet présente des portions de surfaces accidentées (concaves, convexes...), il s'est avéré qu'il était très difficile, voire impossible, d'obtenir un dépôt de particules d'épaisseur uniforme sur la totalité de la surface, ce qui représente une limite importante à l'emploi de telles techniques.The technique consists in placing a homogeneous layer of pulverulent material on an insulating support placed opposite the object to be coated, in fluidizing the particles either mechanically or electrically, in particular by means of a pulsating field, so as to obtain a uniform swirling and intense, and to create an electrostatic field between the support and the object so that the particles follow the lines of force of this field and come to deposit on the receiving object. Such techniques, in particular described in patents FR 2,146,886, FR 2,263,825 and DE 2,036,279, are very reliable when the receiving object is strictly made up of flat surfaces. On the other hand, when this object has portions of uneven surfaces (concave, convex, etc.), it turned out that it was very difficult, if not impossible, to obtain a deposit of particles of uniform thickness over the whole. of the surface, which represents an important limit to the use of such techniques.

La présente invention vise à pallier cet inconvénient et a pour objectif de fournir un procédé de poudrage électrostatique perfectionné permettant de revêtir de façon uniforme des objets de forme quelconque présentant des surfaces non planes.The present invention aims to overcome this drawback and aims to provide an improved electrostatic powdering process for coating uniformly objects of any shape with non-planar surfaces.

A cet effet, l'invention concerne un procédé de poudrage électrostatique destiné à revêtir de particules pulvérulentes ou granuleuses un objet présentant des portions de surfaces planes et des portions de surfaces non planes, ledit procédé consistant à disposer une couche de particules sur un support isolant placé en regard de l'objet, à fluidiser cette couche de particules et à créer un champ électrostatique entre le support et l'objet.To this end, the invention relates to an electrostatic powdering process intended to coat with powdery or granular particles an object having portions of flat surfaces and portions of non-planar surfaces, said process consisting in placing a layer of particles on an insulating support. placed next to the object, to fluidize this layer of particles and to create an electrostatic field between the support and the object.

Selon l'invention, ce procédé se caractérise en ce que :
- l'on soumet les particules à l'action d'un champ électrostatique engendrant des lignes de force d'entraînement desdites particules adaptées pour les diriger vers les surfaces planes de l'objet,
- et l'on modifie la trajectoire des particules au moyen d'au moins un jet de fluide orienté de façon à diriger lesdites particules vers les surfaces non planes de l'objet.According to the invention, this process is characterized in that:
the particles are subjected to the action of an electrostatic field generating lines of force driving said particles adapted to direct them towards the flat surfaces of the object,
- And the trajectory of the particles is modified by means of at least one jet of fluid oriented so as to direct said particles towards the non-planar surfaces of the object.

L'invention consiste donc à combiner l'action d'un champ électrostatique dont les lignes de force dirigent les particules vers les surfaces planes de l'objet, avec un jet de fluide permettant de dévier ces particules de leur trajectoire et ainsi de les diriger vers les portions de surfaces non planes de l'objet. Cette combinaison permet donc de balayer uniformément la surface à traiter et de déposer une couche uniforme de revêtement sur cette surface. La direction du jet de fluide par rapport à la surface à recouvrir peut en outre être modifiée dans une large plage d'inclinaison selon la forme et les dimensions de cette surface, autorisant ainsi le traitement d'objets de formes très diverses.The invention therefore consists in combining the action of an electrostatic field whose lines of force direct the particles towards the planar surfaces of the object, with a jet of fluid making it possible to deflect these particles from their trajectory and thus to direct them towards the non-planar surface portions of the object This combination therefore makes it possible to uniformly sweep the surface to be treated and to deposit a uniform layer of coating on this surface. The direction of the fluid jet relative to the surface to be covered can also be modified within a wide inclination range according to the shape and the dimensions of this surface, thus allowing the treatment of objects of very different shapes.

Selon un mode de mise en oeuvre préférentiel :
- l'on soumet, dans un premier temps, les particules à l'action du champ électrostatique, pendant un laps de temps adapté pour revêtir uniformément les surfaces planes de l'objet,
- l'on délivre, dans un deuxième temps, le jet de fluide, tout en maintenant en action le champ électrostatique, de façon à dévier les particules vers les surfaces non planes et revêtir uniformément ces dernières,
- et l'on interrompt l'action du champ électrostatique et du jet de fluide.According to a preferred mode of implementation:
- the particles are first subjected to the action of the electrostatic field, for a period of time suitable for uniformly coating the flat surfaces of the object,
- secondly, the jet of fluid, while maintaining the electrostatic field in action, so as to deflect the particles towards the non-planar surfaces and uniformly coat the latter,
- And the action of the electrostatic field and the jet of fluid is interrupted.

En outre, on soumet préférentiellement les particules à l'action du champ électrostatique pendant un laps de temps sensiblement compris entre 5 et 10 secondes, puis à l'action combinée du champ et du jet de fluide pendant un laps de temps compris sensiblement entre 1 et 5 secondes.In addition, the particles are preferably subjected to the action of the electrostatic field for a period of time substantially comprised between 5 and 10 seconds, then to the combined action of the field and the jet of fluid for a period of time comprised substantially between 1 and 5 seconds.

Par ailleurs, selon une autre caractéristique de l'invention, le fluide utilisé est préférentiellement de l'air comprimé à une pression sensiblement comprise entre 4 et 7 bars, que l'on délivre avec un débit sensiblement compris entre 0,1 et 0,6 m³/mn, et à une distance sensiblement comprise entre 10 et 20 centimètres de l'objet.Furthermore, according to another characteristic of the invention, the fluid used is preferably compressed air at a pressure substantially between 4 and 7 bars, which is delivered with a flow rate substantially between 0.1 and 0, 6 m³ / min, and at a distance substantially between 10 and 20 centimeters from the object.

L'invention s'étend à un dispositif de poudrage électrostatique pour l'application sur un objet comportant des portions de surfaces planes et des portions de surfaces non planes, d'un revêtement de particules pulvérulentes ou granuleuses, du type comprenant un support isolant des particules, des moyens adaptés pour fluidiser les particules disposées sur le support, et des moyens générateurs d'un champ électrostatique adaptés pour accélérer les particules fluidisées et les transporter vers l'objet selon des trajectoires prédéterminées.The invention extends to an electrostatic powdering device for application to an object comprising portions of flat surfaces and portions of non-planar surfaces, of a coating of powdery or granular particles, of the type comprising an insulating support for particles, means adapted to fluidize the particles arranged on the support, and means generating an electrostatic field adapted to accelerate the fluidized particles and transport them to the object according to predetermined trajectories.

Ce dispositif se caractérise en ce qu'il comprend des moyens d'amenée d'un fluide dotés d'au moins une sortie de fluide disposée entre l'objet et le support, à proximité dudit support, et adaptés pour délivrer ledit fluide selon une direction où il modifie les trajectoires des particules.This device is characterized in that it comprises means for supplying a fluid provided with at least one fluid outlet disposed between the object and the support, near said support, and adapted to deliver said fluid according to a direction where it changes the trajectories of the particles.

D'autres caractéristiques, buts et avantages de l'invention ressortiront de la description détaillée qui suit en référence aux dessins annexés qui en représentent à titre d'exemple non limitatif un mode de réalisation préférentiel. Sur ces dessins qui font partie intégrante de la présente description :

  • - la figure 1 est une coupe transversale par un plan vertical A d'un dispositif conforme à l'invention,
  • - la figure 2 en est une coupe longitudinale par un plan horizontal B,
  • - la figure 3 en est une coupe longitudinale par un plan horizontal C,
  • - la figure 4 est une vue de détail, à échelle agrandie, illustrant la mise en place de ce dispositif à l'intérieur d'une matrice de moule.
Other characteristics, objects and advantages of the invention will emerge from the detailed description which follows, with reference to the appended drawings which represent, by way of non-limiting example, a preferred embodiment. On these drawings which form an integral part of this description:
  • - Figure 1 is a cross section through a vertical plane A of a device according to the invention,
  • FIG. 2 is a longitudinal section through a horizontal plane B,
  • FIG. 3 is a longitudinal section through a horizontal plane C,
  • - Figure 4 is a detail view, on an enlarged scale, illustrating the installation of this device inside a mold matrix.

Le dispositif représenté aux figures 1 à 3 est un dispositif de poudrage électrostatique adapté pour recouvrir des objets de particules pulvérulentes. Ce dispositif est plus particulièrement destiné à une application de peinture en poudre sur une face d'un "guéridon". (Par guéridon, on entend définir un objet dont la surface à traiter est une surface plane circulaire dotée sur sa périphérie d'une gorge de forme concave délimitée, d'une part, par cette surface plane et, d'autre part, par un retour cylindrique perpendiculaire à ladite surface).The device shown in Figures 1 to 3 is an electrostatic powdering device suitable for covering objects with powdery particles. This device is more particularly intended for an application of powder paint on one side of a "pedestal table". (By pedestal table, we mean an object whose surface to be treated is a circular planar surface provided on its periphery with a concave groove delimited, on the one hand, by this planar surface and, on the other hand, by a cylindrical return perpendicular to said surface).

Ce dispositif comporte, en premier lieu, deux boîtes cylindriques en un matériau plastique tel que du PVC, emboîtées l'une dans l'autre : une boîte intérieure 2 de diamètre correspondant à celui de la matrice du moule, et une boîte extérieure 1, destinée à isoler la boîte intérieure 2 et de dimensions adaptées pour ménager un espace interstitiel entre les parois périphériques et de fond desdites boîtes. Des cales 3 sont en outre disposées dans cet espace interstitiel afin d'assurer le positionnement et le maintien de la boîte intérieure 2 dans la boîte extérieure 1.This device comprises, firstly, two cylindrical boxes made of a plastic material such as PVC, nested one inside the other: an internal box 2 of diameter corresponding to that of the mold of the mold, and an external box 1, intended to isolate the inner box 2 and of dimensions adapted to provide an interstitial space between the peripheral and bottom walls of said boxes. Shims 3 are also arranged in this interstitial space in order to ensure the positioning and the maintenance of the inner box 2 in the outer box 1.

Le dispositif comporte en outre deux réseaux d'électrodes disposés respectivement à l'intérieur de la boîte intérieure 2 et dans l'espace interstitiel séparant les parois de fond des boîtes intérieure 2 et extérieure 1.The device also comprises two networks of electrodes disposed respectively inside the interior box 2 and in the interstitial space separating the bottom walls of the interior 2 and exterior 1 boxes.

Le premier réseau, disposé dans le fond de la boîte intérieure 2, est constitué d'un assemblage de ressorts de compression 4 enroulés sous la forme d'une spirale de façon que l'entraxe entre deux spires soit de l'ordre de 3,5 centimètres.The first network, placed in the bottom of the inner box 2, consists of an assembly of compression springs 4 wound in the form of a spiral so that the distance between two turns is of the order of 3, 2 inches.

Ces ressorts 4 sont portés par des fils 5, disposés radialement dans le fond de la boîte intérieure 2 et dont les extrémités sont fixées sur un anneau métallique 6 reposant sur la paroi de fond de cette boîte. Ces fils 5 et cet anneau 6 sont en outre agencés de façon à maintenir les ressorts 4 à environ 1 centimètre au-dessus de cette paroi de fond.These springs 4 are carried by wires 5, arranged radially in the bottom of the inner box 2 and the ends of which are fixed to a metal ring 6 resting on the bottom wall of this box. These wires 5 and this ring 6 are furthermore arranged so as to maintain the springs 4 at approximately 1 cm above this bottom wall.

Le deuxième réseau d'électrodes est constitué de dix lames de cuivre 7 de 30 millimètres de large soudées les unes aux autres de façon à former un maillage orthogonal. Ces lames 7 sont recouvertes d'une feuille d'aluminium destinée à obtenir une bonne répartition des charges électrostatiques et sont fixées sous la paroi de fond de la boîte intérieure 2.The second network of electrodes is made up of ten copper blades 7 30 millimeters wide welded to each other so as to form an orthogonal mesh. These blades 7 are covered with an aluminum foil intended to obtain a good distribution of the electrostatic charges and are fixed under the bottom wall of the inner box 2.

De façon classique, une des extrémités de la spirale de ressorts 4 et une des lames de cuivre 7 sont reliées à une source de tension (non représentée) de façon à former un vibreur électrostatique de type connu en soi décrit notamment dans les brevets français n° 2.263.825 et 2.146.886.Conventionally, one of the ends of the spiral of springs 4 and one of the copper blades 7 are connected to a voltage source (not shown) so as to form an electrostatic vibrator of the type known per se, described in particular in French patents n ° 2.263.825 and 2.146.886.

Le dispositif comprend par ailleurs un système d'amenée d'air comprimée. Ce système se compose, en premier lieu, d'un raccord-équerre de piquage cylindrique 8 disposé sur la paroi de fond de la boîte intérieure 2, au centre de cette dernière. Sur l'entrée de ce raccord-équerre 8 est raccordé un tuyau 9 d'amenée d'air comprimé d'un diamètre interne de 4 mm.The device also includes a compressed air supply system. This system consists, first of all, of a cylindrical stitching angle fitting 8 disposed on the bottom wall of the inner box 2, in the center of the latter. On the inlet of this angle-fitting 8 is connected a pipe 9 for supplying compressed air with an internal diameter of 4 mm.

Ce tuyau 9 est introduit dans la boîte intérieure 2 au travers de deux orifices ménagés en regard dans les parois périphériques de cette boîte intérieure et de la boîte extérieure 1, et est disposé de façon à s'étendre radialement sur la paroi de fond de ladite boîte intérieure. Son extrémité externe est raccordée en amont à un tuyau de piquage (non représenté) d'air comprimé délivré par un réseau d'alimentation. Ce tuyau de piquage présente un diamètre interne de 10 millimètres supérieur à celui du tuyau 9, en vue de pallier les éventuelles fluctuations de débit d'air comprimé.This pipe 9 is introduced into the inner box 2 through two openings arranged opposite in the peripheral walls of this inner box and the outer box 1, and is arranged so as to extend radially on the bottom wall of said inner box. Its external end is connected upstream to a tapping pipe (not shown) of compressed air delivered by a supply network. This tapping pipe has an internal diameter of 10 millimeters greater than that of pipe 9, with a view to overcoming any fluctuations in the flow of compressed air.

Le système d'amenée d'air comprimée comprend enfin un embout plastique 10 monté sur la branche de sortie verticale du raccord-équerre 9. Cet embout 10, de même diamètre interne que celui du raccord-équerre 9, présente en outre une longueur adaptée pour que la sortie d'air comprimé se trouve à une distance comprise entre 0,5 cm et 10 cm de la paroi de fond de la boîte intérieure 2.The compressed air supply system finally comprises a plastic tip 10 mounted on the vertical outlet branch of the angle fitting 9. This tip 10, of the same internal diameter as that of the angle fitting 9, has besides a length adapted so that the compressed air outlet is at a distance of between 0.5 cm and 10 cm from the bottom wall of the inner box 2.

Le dispositif comprend enfin un masque agencé sur la double boîte et destiné à éviter le dépôt de matière pulvérulente sur une hauteur de 20 centimètres de la surface du retour du guéridon.The device finally comprises a mask arranged on the double box and intended to prevent the deposition of pulverulent material over a height of 20 centimeters from the surface of the return of the pedestal table.

Tel que représenté à la figure 4, ce masque est constitué d'une couronne 11 de même diamètre que celui de la matrice 13 du moule, adapté pour venir se plaquer intérieurement contre le retour de cette matrice. Cette couronne 11, en matière plastique renforcée à 30 % de fibres de verre est vissée sur un support 12 en contreplaqué, lui-­même solidarisé à la boîte extérieure 1. Dans la position où ce masque est inséré à l'intérieur de la matrice 13 du moule, la distance entre la surface à traiter et le réseau de ressorts 4 est de l'ordre de 235 mm.As shown in Figure 4, this mask consists of a crown 11 of the same diameter as that of the matrix 13 of the mold, adapted to come to press internally against the return of this matrix. This crown 11, made of plastic material reinforced with 30% glass fibers, is screwed onto a plywood support 12, itself secured to the outer box 1. In the position where this mask is inserted inside the matrix 13 of the mold, the distance between the surface to be treated and the network of springs 4 is of the order of 235 mm.

Un tel dispositif est adapté pour être associé, de façon classique, à un ensemble support géré par un auto ma te programmable et adapté pour ajuster automatiquement ce dispositif dans le moule. Les séquences de déplacement d'un tel support sont les suivantes :
- déplacement linéaire horizontal d'avance d'une position parking vers une position où le dispositif se trouve à l'aplomb du moule,
- déplacement linéaire ascendant jusqu'à la position où le masque se trouve inséré dans le moule,
- déplacement linéaire descendant de désengagement du masque,
- déplacement linéaire horizontal de recul vers la position parking.Such a device is adapted to be associated, in a conventional manner, with a support assembly managed by a programmable auto mat and adapted to automatically adjust this device in the mold. The sequences for moving such a support are as follows:
- horizontal linear movement in advance from a parking position to a position where the device is directly above the mold,
- linear upward movement to the position where the mask is inserted in the mold,
- linear downward movement of mask disengagement,
- horizontal linear movement back to the parking position.

L'automate programmable est en outre adapté conventionnellement pour gérer le fonctionnement du vibreur électrostatique et du système d'amenée d'air comprimé, selon le processus décrit ci-après.The programmable controller is also conventionally adapted to manage the operation of the electrostatic vibrator and the compressed air supply system, according to the process described below.

Lors de ce processus, la paroi de fond de la boîte intérieure 2 se trouve uniformément recouverte de poudre sur une épaisseur adaptée pour que cette poudre affleure au maximum le bas des ressorts 4. En outre, la matrice 13 du moule se trouve reliée à la terre.During this process, the bottom wall of the inner box 2 is uniformly covered with powder over a thickness suitable for this powder to be flush with the bottom of the springs 4 as much as possible. Furthermore, the matrix 13 of the mold is connected to the ground.

Le processus de transfert de la poudre se fait en deux étapes.The powder transfer process takes place in two stages.

Dans un premier temps, et de façon connue en soi, la poudre est soumise au système de poudrage électrostatique. La couche de poudre reposant sur la paroi de fond de la boîte intérieure 2 est fluidisée en appliquant une tension alternative entre les deux réseaux d'électrodes 4 et 7 qui forment alors un vibreur électrostatique. Ce vibreur inverse continuellement la polarité de la poudre qui se trouve ainsi chargée. De même, le fond de la boîte intérieure 2 est également soumis à l'inversion de polarité.Initially, and in a manner known per se, the powder is subjected to the electrostatic powdering system. The powder layer resting on the bottom wall of the inner box 2 is fluidized by applying an alternating voltage between the two networks of electrodes 4 and 7 which then form an electrostatic vibrator. This vibrator continuously reverses the polarity of the powder which is thus charged. Likewise, the bottom of the inner box 2 is also subject to reverse polarity.

Ces deux actions, notamment grâce à la disposition en spirale du réseau de ressorts 4, provoquent un tourbillonnement uniforme et intense de la poudre.These two actions, in particular thanks to the spiral arrangement of the network of springs 4, cause a uniform and intense swirling of the powder.

En outre, le réseau d'électrodes 4 est mis sous haute tension réglable, d'une valeur de 48 KV et entre ce réseau et la matrice 13 du moule, mise à la masse, se forme un champ électrostatique. Les particules chargées suivent les lignes de force de ce champ électrostatique et viennent se déposer sur les surfaces planes de la matrice 13. Par contre, la gorge de cette matrice 13 ne reçoit que très peu de poudre pendant cette opération.In addition, the network of electrodes 4 is placed under adjustable high voltage, of a value of 48 KV and between this network and the matrix 13 of the mold, grounded, forms an electrostatic field. The charged particles follow the lines of force of this electrostatic field and are deposited on the flat surfaces of the matrix 13. On the other hand, the groove of this matrix 13 receives very little powder during this operation.

La deuxième étape consiste donc à transférer la poudre toujours chargée, les électrodes étant maintenues sous tension, sur les surfaces non planes de la matrice 13, c'est-à-dire dans la gorge de celle-ci. Ce résultat est obtenu en actionnant le système d'amenée d'air comprimé adapté pour délivrer de l'air comprimé sous une pression de 4,5 bars. Ce jet d'air comprimé a pour effet de vaincre les lignes de force du champ électrostatique et de dévier la poudre vers la gorge de la matrice.The second step therefore consists in transferring the powder still charged, the electrodes being kept under tension, on the non-planar surfaces of the matrix 13, that is to say in the groove of the latter. This result is obtained by actuating the compressed air supply system adapted to deliver compressed air at a pressure of 4.5 bars. This jet of compressed air has the effect of overcoming the lines of force of the electrostatic field and deflecting the powder towards the throat of the matrix.

Le jet d'air est en outre mis en action 8 secondes après la mise sous tension des réseaux d'électrodes, et pendant une durée de 2 secondes. L'actionnement du système de poudrage électrostatique et du système d'amenée d'air est ensuite interrompu.The air jet is also activated 8 seconds after the electrode arrays are energized, and for a period of 2 seconds. The actuation of the electrostatic powder system and the air supply system is then interrupted.

Un tel processus permet d'obtenir une répartition parfaite de la poudre sur les différentes surfaces de la matrice, l'épaisseur de poudre déposée étant uniforme et de 0,25 mm ± 0,1 mm.Such a process makes it possible to obtain a perfect distribution of the powder on the different surfaces of the matrix, the thickness of powder deposited being uniform and 0.25 mm ± 0.1 mm.

Claims (12)

1/ - Procédé de poudrage électrostatique destiné à revêtir de particules pulvérulentes ou granuleuses un objet (13) présentant des portions de surfaces planes et des portions de surfaces non planes, ledit procédé consistant à disposer une couche de particules sur un support isolant (2) placé en regard de l'objet, à fluidiser cette couche de particules et à créer un champ électrostatique entre le support (2) et l'objet (13), et étant caractérisé en ce que :
- l'on soumet les particules à l'action d'un champ électrostatique engendrant des lignes de force d'entraînement desdites particules adaptées pour les diriger vers les surfaces planes de l'objet (13),
- et l'on modifie la trajectoire des particules au moyen d'au moins un jet de fluide orienté de façon à diriger lesdites particules vers les surfaces non planes de l'objet (13).1 / - Method of electrostatic powdering intended to coat with pulverulent or granular particles an object (13) having portions of flat surfaces and portions of non-planar surfaces, said method consisting in placing a layer of particles on an insulating support (2) placed opposite the object, to fluidize this layer of particles and to create an electrostatic field between the support (2) and the object (13), and being characterized in that:
the particles are subjected to the action of an electrostatic field generating lines of force driving said particles adapted to direct them towards the flat surfaces of the object (13),
- And the trajectory of the particles is modified by means of at least one jet of fluid oriented so as to direct said particles towards the non-planar surfaces of the object (13). 2/ - Procédé selon la revendication 1, caractérisé en ce que :
- l'on soumet, dans un premier temps, les particules à l'action du champ électrostatique, pendant un laps de temps adapté pour revêtir uniformément les surfaces planes de l'objet (13),
- l'on délivre, dans un deuxième temps, le jet de fluide, tout en maintenant en action le champ électrostatique, de façon à dévier les particules vers les surfaces non planes et revêtir uniformément ces dernières,
- et l'on interrompt l'action du champ électrostatique et du jet de fluide.2 / - Method according to claim 1, characterized in that:
- the particles are first subjected to the action of the electrostatic field, for a period of time suitable for uniformly coating the flat surfaces of the object (13),
- in a second step, the jet of fluid is delivered, while maintaining the electrostatic field in action, so as to deflect the particles towards the non-planar surfaces and uniformly coat the latter,
- And the action of the electrostatic field and the jet of fluid is interrupted. 3/ - Procédé selon la revendication 2, caractérisé en ce que l'on soumet les particules à l'action du champ électrostatique pendant un laps de temps sensiblement compris entre 5 et 10 secondes, puis à l'action combinée du champ et du jet de fluide pendant un laps de temps compris sensiblement entre 1 et 5 secondes.3 / - Method according to claim 2, characterized in that the particles are subjected to the action of the electrostatic field for a period of time substantially between 5 and 10 seconds, then to the combined action of the field and the jet of fluid for a period of time substantially between 1 and 5 seconds. 4/ - Procédé selon l'une des revendications 1, 2 ou 3, caractérisé en ce que l'on modifie la trajectoire des particules au moyen d'un jet d'air comprimé.4 / - Method according to one of claims 1, 2 or 3, characterized in that one modifies the trajectory of the particles by means of a jet of compressed air. 5/ - Procédé selon la revendication 4, caractérisé en ce que l'on utilise de l'air comprimé à une pression sensiblement comprise entre 4 et 7 bars, que l'on délivre avec un débit sensiblement compris entre 0,1 et 0,6 m³/mn, et à une distance sensiblement comprise entre 10 et 20 centimètres de l'objet (13).5 / - Method according to claim 4, characterized in that compressed air is used at a pressure substantially between 4 and 7 bars, which is delivered with a flow rate substantially between 0.1 and 0.6 m³ / min, and at a distance substantially between 10 and 20 centimeters from the object (13). 6/ - Procédé selon l'une des revendications précédentes, caractérisé en ce que l'on oriente le jet de fluide orthogonalement à la surface plane de l'objet (13).6 / - Method according to one of the preceding claims, characterized in that one directs the fluid jet orthogonally to the planar surface of the object (13). 7/ - Dispositif de poudrage électrostatique de mise en oeuvre d'un procédé conforme à l'une des revendications 1 à 6 pour l'application sur un objet (13) comportant des portions de surfaces planes et des portions de surfaces non planes, d'un revêtement de particules pulvérulentes ou granuleuses, du type comprenant un support isolant (2) des particules, des moyens adaptés pour fluidiser les particules disposées sur le support, et des moyens (4, 7) générateurs d'un champ électroatatique adaptés pour accélérer les particules fluidisées et les transporter vers l'objet selon des trajectoires prédéterminées, ledit dispositif étant caractérisé en ce qu'il comprend des moyens (8, 9, 10) d'amenée d'un fluide dotés d'au moins une sortie de fluide (10) disposée entre l'objet (13) et le aupport (2), à proximité dudit support, et adaptés pour délivrer ledit fluide selon une direction où il modifie les trajectoires des particules.7 / - Electrostatic powdering device for implementing a method according to one of claims 1 to 6 for application to an object (13) comprising portions of planar surfaces and portions of non-planar surfaces, d '' a coating of powdery or granular particles, of the type comprising an insulating support (2) for the particles, means suitable for fluidizing the particles disposed on the support, and means (4, 7) generating an electro-static field suitable for accelerating the fluidized particles and transport them to the object according to predetermined paths, said device being characterized in that it comprises means (8, 9, 10) for supplying a fluid provided with at least one fluid outlet (10) disposed between the object (13) and the aupport (2), near said support, and adapted to deliver said fluid in a direction where it modifies the trajectories of the particles. 8/ - Dispositif selon la revendication 7, caractérisé en ce que chaque sortie de fluide (10) est disposée à une distance sensiblement comprise entre 10 et 20 centimètres de l'objet (13), et une distance sensiblement comprise entre 1 et 10 centimètres du support (2).8 / - Device according to claim 7, characterized in that each fluid outlet (10) is arranged at a distance substantially between 10 and 20 centimeters from the object (13), and a distance substantially between 1 and 10 centimeters of the support (2). 9/ - Dispositif selon l'une des revendications 7 ou 8, caractérisé en ce que les moyens d'amenée de fluide sont constitués de moyens d'amenée d'air comprimé (8, 9, 10).9 / - Device according to one of claims 7 or 8, characterized in that the fluid supply means consist of compressed air supply means (8, 9, 10). 10/ - Dispositif selon l'une des revendications 7, 8 ou 9, dans lequel les moyens générateurs du champ électrostatique comprennent une électrode reliée à la terre constituée par l'objet (13), une électrode (4) et une contre-électrode (7) disposées respectivement de part et d'autre du support isolant (2) par rapport à l'objet (13) et une source de tension reliée auxdites électrode (4) et contre-­électrode (7), ledit dispositif étant caractérisé en ce que l'électrode (4) disposée entre le support (2) et l'objet (13) est constituée d'un assemblage de ressorts enroulés en spirale.10 / - Device according to one of claims 7, 8 or 9, wherein the means for generating the electrostatic field comprise an electrode connected to the ground constituted by the object (13), an electrode (4) and a counter electrode (7) respectively disposed on either side of the insulating support (2) relative to the object (13) and a voltage source connected to said electrode (4) and counter electrode (7), said device being characterized in that the electrode (4) disposed between the support (2) and the object (13) consists of an assembly of springs wound in a spiral. 11/ - Dispositif selon l'une des revendications 7 à 10 pour l'application d'un revêtement sur une surface circulaire dotée de portions de surfaces non planes sur sa périphérie, caractérisé en ce que les moyens d'amenée de fluide (8, 9, 10) comprennent une sortie de fluide (10) disposée à l'aplomb du centre de cette surface et agencée pour délivrer le fluide selon une direction orthogonale à ladite surface.11 / - Device according to one of claims 7 to 10 for the application of a coating on a circular surface provided with portions of non-planar surfaces on its periphery, characterized in that the means for supplying fluid (8, 9, 10) comprise a fluid outlet (10) disposed perpendicular to the center of this surface and arranged to deliver the fluid in a direction orthogonal to said surface. 12/ - Dispositif selon la revendication 11, caractérisé en ce qu'il comprend :
- une boîte (2), dite intérieure, de forme cylindrique de diamètre conjugué de celui de la surface circulaire de l'objet (13), ladite boîte étant réalisée en un matériau isolant et comportant une paroi de fond pour le support de la couche de particules,
- une boîte (1), dite extérieure, d'isolation de la boîte intérieure (2), de diamètre supérieur à celui de ladite boîte intérieure adapté pour loger cette dernière en ménageant un espace interstitiel entre lesdites boîtes,
- une contre-électrode (7) constituée d'une pluralité de lames agencées selon un maillage orthogonal dans l'espace interstitiel ménagé entre les parois de fond des boîtes intérieure (2) et extérieure (1).12 / - Device according to claim 11, characterized in that it comprises:
- a box (2), said to be internal, of cylindrical shape with a diameter conjugate to that of the circular surface of the object (13), said box being made of an insulating material and comprising a bottom wall for supporting the layer of particles,
a box (1), called an outer box, for insulating the inner box (2), of diameter greater than that of said inner box adapted to accommodate the latter by providing an interstitial space between said boxes,
- a counter electrode (7) consisting of a plurality of blades arranged in an orthogonal mesh in the interstitial space formed between the bottom walls of the inner (2) and outer (1) boxes.
EP90201486A 1989-06-16 1990-06-09 Method for electrostatic powder coating for coating an object with powdery or granular particles and device for implementing this method Expired - Lifetime EP0403002B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT90201486T ATE99996T1 (en) 1989-06-16 1990-06-09 PROCESS FOR THE ELECTROSTATIC POWDER COATING OF AN OBJECT WITH POWDERY OR GRANULAR PARTICLES AND DEVICE FOR CARRYING OUT THE PROCESS.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8908160A FR2648369B1 (en) 1989-06-16 1989-06-16 ELECTROSTATIC POWDERING PROCESS FOR COATING AN OBJECT OF POWDERY OR GRANULAR PARTICLES, AND DEVICE FOR CARRYING OUT SAID METHOD
FR8908160 1989-06-16

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EP0403002A1 true EP0403002A1 (en) 1990-12-19
EP0403002B1 EP0403002B1 (en) 1994-01-12

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AT (1) ATE99996T1 (en)
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1282520B (en) * 1962-08-04 1968-11-07 Eric Alton Dr Ing Device for the electrostatic coating of metallic work pieces, in particular work pieces made of wire, with powdery plastics
DE1427641A1 (en) * 1962-11-30 1968-11-14 Siemens Elektrogeraete Gmbh Method and device for coating workpiece surfaces in a fluidized bed sintering bath
DE2036279A1 (en) * 1970-07-22 1972-01-27 Stutz, Erwin, 7075 Mutlangen Method and device for repelling particles from a support
DE2145039A1 (en) * 1971-09-09 1973-03-22 Ahlmann Aco Severin Enamel powder application - by fluid bed deflection

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1282520B (en) * 1962-08-04 1968-11-07 Eric Alton Dr Ing Device for the electrostatic coating of metallic work pieces, in particular work pieces made of wire, with powdery plastics
DE1427641A1 (en) * 1962-11-30 1968-11-14 Siemens Elektrogeraete Gmbh Method and device for coating workpiece surfaces in a fluidized bed sintering bath
DE2036279A1 (en) * 1970-07-22 1972-01-27 Stutz, Erwin, 7075 Mutlangen Method and device for repelling particles from a support
DE2145039A1 (en) * 1971-09-09 1973-03-22 Ahlmann Aco Severin Enamel powder application - by fluid bed deflection

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FR2648369A1 (en) 1990-12-21
DE69005911D1 (en) 1994-02-24
FR2648369B1 (en) 1993-06-11
ATE99996T1 (en) 1994-01-15
EP0403002B1 (en) 1994-01-12

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