EP0030203B1 - Device for the localized distribution of electrifiable material and printing apparatus equipped with this device - Google Patents

Description

The present invention relates to a device for the localized distribution of electrifiable materials and to a printing installation equipped with at least one of these devices making it possible to continuously overprint patterns of non-fixed electrifiable materials.

Devices for distributing electrifiable materials on any support previously covered with an adhesive layer intended to receive said materials are well known. These devices essentially consist of a vibrating screen, the lower grid of which, connected to a high-voltage generator, creates an electrostatic field thanks to which the electrizable materials, whether cut fibers or flocs, or any other particulate matter are directed perpendicular to the support to be decorated and are installed on the areas of said surface previously covered with adhesive.

Some of these devices (FR-A-2110 493 and US-A-2793050) are provided with fixed partitions making it possible to divide them into different compartments containing, for example, in the case of flocking, cut fibers of different colors, which allows obtain flocked effects of different colors in a single operation.

It is always necessary, in order to obtain a perfect relief effect, to rid the support of excess electrifiable materials which have not settled in the area or areas of the support covered with adhesive. In installations using current devices, this cleaning operation involves, in particular due to the relatively large quantities of materials not retained by the adhesive layer, energetic mechanical means of suction and threshing. An electrostatic cleaning system can also be used. In fact, when the electrifiable material, which has become polarized when passing through the screen grid, comes into contact with the plate connected to ground, it changes polarity. Instead of being pushed back by the screen of the screen, it is on the contrary attracted and goes back theoretically in the screen. In practice, electrostatic deflocation often proves to be insufficient. Part of the electrifiable material adheres to the support and cleaning must be completed with a vacuum cleaner. These cleaning operations must therefore, in order not to harm the good appearance of the coated support, be carried out once the electrifiable materials implanted on the adhesive are firmly fixed to the latter.

The current processes for applying electrifiable materials require the following steps: electrostatic application of said materials to the support coated with adhesive, fixing, most often by thermal means, of said materials on the support and cleaning by suction-threshing or electrostatic process. or by the two processes combined, electrifiable materials which are not fixed.

The current process of applying electrifiable materials has the disadvantage of dispersion: Indeed, electrifiable materials, generally distributed by a screen with a rectangular grid, due to the electrostatic phenomenon, a back and forth movement between the grid polarized and the article to be decorated which is fixed on a metallic plate connected to ground. In the center of the grid, the electrifiable materials have a vertical back and forth movement. On the edges of the grid, they tend to go outwards under the influence of the lines of force of the magnetic field. Arrived outside, these electrifiable materials are attracted by any surrounding metallic mass, resulting in a disturbing dispersion for screen printing operations which are carried out nearby. It is therefore up to now impossible, except to develop a complex and bulky installation to carry out on a single installation the application of electrifiable materials on a support and the colored printing of the parts of the support thus coated. You must first apply the materials, fix the pattern obtained, then, after cleaning the support, transport everything on a printing machine.

The purpose of the present invention is to remedy this drawback, and to enable the continuous application, and on the same installation, of the application of electrifiable materials and the overprinting of the relief pattern thus obtained, without it it is necessary to proceed to the step of intermediate fixing of the electrifiable materials. The present invention makes it possible to almost completely avoid the dispersion of electrifiable materials and allows the incorporation of a flocking cell in a mechanical screen printing system without disturbing its functions and avoiding clogging of the printing frames by electrifiable materials. in dispersion.

The invention firstly relates to a device for localized distribution of electrifiable materials which can in particular be used in an installation for printing relief patterns, of the type constituted by a vibrating screen, provided with partitions, the lower grid of which is connected to a high-voltage generator and the originality of which consists of the said partitions being constituted by a series of independent removable cylindrical elements, made of non-conductive material, of parallel axes, of the same diameter or of different diameters, arranged perpendicular to the grid of the sieve, and the maintenance of which in desired position is ensured by simple contact of said cylindrical elements along their generatrices, the outer row of said elements also being in contact along the generatrices of the elements with the internal walls of the sieve.

Two devices are also associated with this device. additional removable covers which can be used successively to ensure the correct operation of the device.

The first of these covers, connected to a supply hopper for electrifiable materials, is designed to leave part of the cylindrical elements uncovered on a surface essentially corresponding to that of the pattern which it is desired to apply, the other cylindrical elements being covered , while the second cover, complementary to the first and connected to a suction device, is provided to cover at least the part of the cylindrical elements previously discovered.

There is thus a very flexible application device making it possible to modulate at will the quantity of electrifiable materials which it is desired to apply to a support.

Indeed, at first, the introduction of electrifiable materials will be limited to only cylindrical elements corresponding to the surface that one wishes to coat. This operation is carried out before the start of the application process of electrifiable materials and will only need to be renewed when the reservoir constituted by the tubes filled with electrifiable materials has emptied in the succession of application operations.

In a second step, the reservoir constituted by the tubes filled with electrifiable materials will be protected against the action of the suction device by the second cover, leaving only the cylindrical elements hidden by the first cover exposed. A judicious choice of cylindrical elements of different diameters is sufficient to adapt them to the opening made in the first cover, this opening corresponding substantially to the pattern that it is desired to obtain.

The advantages of this device are numerous. First of all, it enables significant savings to be made in electrifiable materials compared to existing devices; when the device is powered up, almost all of the electrifiable materials will settle on the part of the support previously covered, according to the chosen pattern, with a layer of adhesive.

The simple replacement of this first cover by the second additional cover, connected to the suction device, will then ensure the elimination of the small amount of electrifiable material which would not be implanted on the adhesive, the part of the support already coated with said materials being preserved from the mechanical suction action by the second cover.

In addition, the suction, carried out simultaneously with the electrostatic application of the electrifiable materials makes it possible to avoid the dispersion effect described above.

It is therefore no longer essential to carry out the fixing operation before the cleaning operation and this important fact makes it possible, according to another object of the invention, to incorporate at least one of these devices on an installation of printing, comprising several stations for placing the articles to be printed instead of, for example, at least one of the stations for placing the article. It is thus possible to continuously carry out the application of the electrifiable materials and their overprinting and then to carry out the simultaneous fixing of the electrifiable materials and of the overprinted pattern.

According to a particular embodiment of the invention and in order to improve the speed of operations, a localized distribution device is provided side by side provided with the second cover covering the surface corresponding to the pattern and connected to a first suction device, and a second similar device, but without distribution, and connected to a second suction device covering the surface corresponding to the pattern.

The pigging station immediately preceding the application device is of particular importance since it is it which conditions the supply of adhesive essential for fixing the electrifiable materials applied according to the distribution device located above.

It is indeed necessary to provide the support to be coated with a layer of adhesive which, while being well anchored in said support, has a uniformity and a thickness sufficient to ensure the implantation and then the fixing of these electrifiable materials.

In this pigging station which has two doctor blades, working in opposite directions at an angle of approximately 70 ° relative to the scraping plane, one of these doctor blades made of a material with a hardness of approximately 70 ° Shore, having a rounded lower end and the other doctor blade, made of a material with a hardness of about 60 ° Shore, having a lower bevel cut.

Thanks to the scraper head according to the invention, the adhesive is first applied in depth using the scraper with a rounded end and then the uniform coating is ensured using the other scraper at the end. bevel cut.

• Figure 1 est une vue en perspective très schématique partiellement arrachée du dispositif de distribution localisée selon l'invention,
• Figure 2 est une vue en perspective du dispositif de la figure 1, revêtu du premier cache,
• Figure 3 est une vue similaire à figure 2, dans laquelle le premier cache et été remplacé par le deuxième cache complémentaire,
• Figure 4 est une vue en coupe verticale partielle de la tête de raclage selon l'invention en position d'imprégnation,
• Figure 5 est une vue similaire à figure 4, la tête de raclage étant en position de nappage,
• Figure 6 est un plan très schématique de la disposition relative des différents postes de travail de l'installation d'impression selon l'invention.

The present invention will be better understood moreover and its advantages will emerge clearly from the description which follows with reference to the appended schematic drawing in which:

• FIG. 1 is a very diagrammatic perspective view partially cut away of the localized distribution device according to the invention,
• FIG. 2 is a perspective view of the device of FIG. 1, coated with the first cover,
• FIG. 3 is a view similar to FIG. 2, in which the first cover has been replaced by the second complementary cover,
• FIG. 4 is a view in partial vertical section of the scraper head according to the invention in the impregnation position,
• FIG. 5 is a view similar to FIG. 4, the scraper head being in the layering position,
• Figure 6 is a very schematic plan of the relative arrangement of the different stations work of the printing installation according to the invention.

In FIGS. 1 to 3, 2 represents the vibrating screen, 3 the grid, 4 the cylindrical elements, 5 the first cover connected to the feed hopper 6, and 7 the second cover connected to the suction hood 8.

The device according to the invention consists of a vibrating screen 2, the lower grid 3 of which is connected to a high-voltage generator (not shown). Inside the screen 2 and resting on the grid 3, are arranged the cylindrical elements 4, removable, independent, with parallel axes. These cylindrical elements are made of a non-conductive material such as, for example, polyvinyl chloride. The elements 4 shown in the figures all have the same diameter, but they can of course have diameters different from each other. Maintaining them in the desired position is ensured by contact with neighboring elements along their generatrices. The elements 4 forming the outer row of the assembly are also in contact with the inner walls of the screen 2 according to their generatrices.

Figure 2 shows the device of Figure 1 when it is used for loading electrifiable materials.

As can be seen in the figure, on the upper part of the screen 2, opposite the grid 3, a cover 5 is placed, connected to the feed hopper 6.

The opening of the hopper 6 adapts to a cutout 9 made in the cover 5. This cutout carried out essentially along the outline of the pattern which it is desired to cover with electrifiable materials leaves uncovered a corresponding number of cylindrical elements 4 and mask all others; the diameters of the various cylindrical elements left uncovered are chosen such that the cutout 9 of the cover 5 leaves uncovered only entire sections of cylindrical elements. During the introduction of the electrifiable materials into the hopper 6, only the cylindrical elements 4 left uncovered will therefore be supplied and which essentially correspond to the pattern which it is desired to reproduce.

The step of simultaneous application and cleaning is shown in Figure 3; the cover 5 has been replaced by a cover 7 which is complementary thereto, that is to say which corresponds at least to the cutout 9 of said cover 5; the cover 7 is then placed on the part of the cylindrical elements left uncovered, during the preceding steps, and the assembly is connected to the suction hood 8.

The support 10 was previously, as it is known per se, coated with an adhesive layer according to the same pattern and placed in a conventional manner, and not shown under the localized distribution device, in relation to the cutout 9 of the cover 5.

The grid 3 of the screen 2 is then tensioned in a conventional manner and the electrifiable materials contained in the cylindrical elements corresponding to the cutout 9 of the cover 5 are projected onto the part of the support 10, coated with adhesive according to the design of the motif.

It is clear from the above that almost all of the electrifiable materials supplied in said cylindrical elements will be installed in the glued part of said support 10, which corresponds both to a significant saving in electrifiable materials and to a substantial dimension of the pollution of the environment.

Under the action of the suction device 8, the part of the support in which the electrifiable materials have been implanted will be protected by the cover 7 against the suction action which will therefore only be exerted on the parts of the support that are not protected and will remove loose electrifiable material.

It is therefore easily understood that it is possible to carry out on the pattern thus obtained on which practically all of the electrifiable materials have been implanted in the part of the support coated with adhesive and will therefore be held there sufficiently to be able to withstand the action of 'a pressure, a colored overprint.

It is of course essential to provide the support to be coated with an adhesive layer which, while being well anchored in the support, has a uniformity and a sufficient thickness to ensure the implantation and then the fixing of the electrifiable materials.

Figures 4 and 5 show the scraper head according to the invention to achieve this goal.

In these figures, 11 generally designates the scraper head which comprises the two doctor blades 12 and 13.

The scraper head 11 of the rocking type, is integral with the movable shaft 14, connected to conventional means (not shown) allowing its transverse movement in the scraper plane 15, back and forth, and the reversal of the position of the doctor blades relative to said doctor blade 15 at the end of the stroke.

The scraping head 11 in the shape of an inverted U comprises, on one of the branches of the U a first doctor blade 12 with rounded lower end, made of rubber or any other suitable material with a hardness of about 70 ° Shore and, on the other branch of the U, a second doctor blade 13, the lower end of which is cut in a bevel, also made of rubber or any other suitable material but with a hardness of about 60 ° Shore.

The upper part of the doctor blades 12 and 13 is held, in a manner known per se between the jaws 16 and 17 which ensure perfect solidarity of the assembly.

During a first passage of the scraper head 11, as shown in FIG. 4, the doctor 12 works, in the direction of the arrow F, achieving through its rounded end a deep impregnation of the support; the doctor blade 12 works at an angle of about 70 ° relative to the doctor blade 15.

At the end of the race, the scraper head 11 having tilted, it is the scraper 13 which works, in the direction of the arrow F ′, achieving, thanks to its lower bevelled end, a good distribution and a good coating of the adhesive; the doctor 13 also works at an angle of about 70 ° relative to the doctor plane 15.

The scraping speed varies between 0.15 and 0.60 m / second.

Depending on the nature of the support to be coated, and the rheological properties of the adhesive to be applied, two or four successive passages of the doctor blades are carried out.

Once the adhesive layer on a determined frame, the raising of this frame (not shown) to make room for the next frame is advantageously done by pivoting along a horizontal axis, which allows to ensure the gradual detachment of the surface covered with adhesive.

The scraping station is mechanically and electrically synchronized with the other stations of a rotary vane printing machine or of an endless belt machine, by insertion in place of another station of the machine.

The device for localized distribution of electrifiable materials described above, used in conjunction with the scraper head, therefore makes it possible, and this constitutes another object of the invention, to carry out on the same installation, and continuously, the application , in an embossed pattern, of electrifiable materials and their overprinting without the need for an intermediate fixing step.

To do this, it suffices to replace at least one of the stations of a screen printing machine with a device according to the invention.

It is thus that on a conventional screen printing machine, such as that shown diagrammatically in FIG. 6, comprising six stations for placing the articles to be printed designated by A1, A2, A3, A4, A5 and A6, and six heads designated by B 1, B2, B3, B4, B5 and B6, only the first three posts A1, A2, and A3 are used for the placement of the articles, the three posts A4, A5 and A6, preceding the heads of printing, being equipped as follows: the first station A4 is constituted by the scraping head 11 making it possible to apply the adhesive on the support according to the pattern which it is desired to obtain, the following station A5 is constituted by a device for localized distribution according to the invention, previously filled with electrifiable materials according to the pattern to be produced using the first cover, then provided with the second cover and connected to a suction device, and the next station A6 of the same device but without distribution of materials electrifiable and connected to the hot te suction, the print heads B1, B2, B3, B4, B5 and B6 then allowing to directly overprint the desired design to the relief pattern.

The overprinted assembly then passes through a conventional fixing device, by thermal means for example, in which the attachment of the electrifiable materials to the adhesive and that of the overprinted drawing will be carried out simultaneously.

As is obvious, and as is clear from the foregoing, the present invention is not limited to the sole embodiments described above by way of nonlimiting examples, on the contrary, it embraces all of them. of realization comprising equivalent means, whatever in particular the structure of the printing installation and the number of printing heads; it also applies to the case where the adhesive is replaced by a printing color.

Claims (5)

1. A device for the localized distribution of materials that can be electrically charged, which can particularly be used in a plant for the printing of decorative designs in relief, of the type consisting of a vibrating screen (2) provided with compartments and the lower grating (3) of which is connected to a high voltage generator, characterized in that the said compartments are formed by a series of cylindrical units (4) of nonconducting material, independently movable with parallel axes, all of the same diameter or of different diameters, arranged perpendicularly to the grating of the screen, and which are maintained in the desired positions by simple contact of the said cylindrical units along their generating lines, the outside rows of the said units also being in contact, along the generating lines of the units, with the inside of the walls of the screen, and that two complementary fixed masks (5) and (7) are associated with this device and used alternatively to ensure its correct operation, the first mask (5), connected to a hopper (6) for the feeding of materials that can be electrically charged, leaving uncovered an integral number of cylindrical units essentially corresponding to the surface of the decorative design that it is desired to apply, and the second mask (7), connected to a suction hood (8), covering at least those cylindrical units that were left uncovered during the preceding stage.

2. An equipment for the printing of decorative designs in relief using materials that can be electrically charged, comprising several loading stations for the articles to be printed, at least one printing head and a fixing device, characterized in that the three loading stations A4, A5, A6 preceding the printing heads are constituted by a scraping station for the adhesive according to the decorative design, by a device for localized distribution according to Claim 1, previously loaded with materials that can be electrically charged according to the design with the help of the first mask, then fitted with the second mask connected to a suction hood, followed by a similar device but without any distribution of materials that can be electrically charged, connected to a suction hood, and that a fixing device is provided at the exit from the equipment.

3. A printing equipment according to Claim 2 in which the scraping station is characterized by the fact that the scraper head (11) comprises two scrapers (12) and (13) working in opposite directions at an angle of about 70° relatively to the scraping plane, one of these scrapers (12), produced from a material having a hardness of about 70° Shore, exhibiting a rounded-off lower extremity, and the other scraper (13), produced from a material having a hardness of about 60° Shore, exhibiting a bevelled edge lower extremity.

4. A printing equipment according to Claim 3, characterized in that the speed of scraping of the scraping station is between 0.15 and 0.60 metres/second.

5. A printing equipment according to Claims 3 and 4, characterized in that as soon as the operation of scraping ends, raising of the frame of the scraping station takes place by pivoting about a horizontal axis.

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