EP2892723B1 - Sheet transfer cylinder and assembly consisting of a juxtaposition of such cylinders - Google Patents

Description

The present invention relates to a sheet transfer cylinder distinguished by the fact that it accommodates magnets flush with its surface, these sheets having previously received at least one printing by screen printing, using an ink containing particles (pigments) orientable under the effect of a magnetic field.

It also relates to an assembly consisting of a juxtaposition of at least two cylinders as designated above.

Throughout the present application, including the claims, the term "sheet" means not only a sheet itself, but also a fraction thereof, for example a long strip.

Inks for fiduciary printing containing magnetic pigments are available on the market. These pigments, commonly known under the abbreviation OVMP (for "Optically Variable Magnetic Pigment"), themselves derived from the so-called "OVI®" pigments (for "Optically Variable Ink"), have at least one color change property and are capable of being oriented on demand, under the influence of a magnetic field, especially when they are in a wet ink.

The following documents describe such products, their derivatives and / or their applications: EP1412432 , EP1854852 and EP1493590 .

In addition, KBA NotaSys has developed a screen printing machine called "NotaScreen", in which the "magnetic" ink is applied to the support consisting of a sheet, with the aid of a first cylinder. printing equipped with a sieve. The printed medium is then pressed (the printing is not yet dry) on a cylinder containing a multitude of magnets organized in a matrix, in a distribution corresponding to the impressions on the sheets.

The passage of freshly printed sheets of ink not yet dry through the magnetic fields created by the magnets has the effect of orienting the magnetic pigments contained therein. Finally, in a portion farther from the machine, the ink is dried, which permanently freezes the magnetic pigments in a given orientation.

It is these specific orientations that give the security element thus manufactured, called SPARK®, these particular optical properties. In addition to the color change obtained by tilting the support, effects of movement, depth, volume are generated. These effects are, in particular, obtained by developing different permanent magnets not only by size and contours, but also by engraving them to vary their thickness locally. This makes it possible to modulate the magnetic fields and the visual effects that result from them, on the ink.

During the phase of orientation of the pigments, it is important that the substrate and the cylinder are static with respect to each other and pressed against each other.

Such a technique is described in particular in the patent EP-B-1 648 702 .

In particular, the structure of the sheet transfer cylinder is described.

This cylinder, which is called "ring" to designate its body rotated on itself, has, opening on its surface, a peripheral annular channel in which is positioned at least one magnet to guide said particles contained in ink.

It comprises suction means opening to said surface, outside the channel, in the form of at least one zone provided with orifices for pressing said sheets against this surface.

In practice, this zone provided with orifices consists of a plate or protective plate, independent and perforated, which is reported and placed on the whole ring (cylinder) and whose curve is adapted to result.

The suction of the sheets (this makes it possible to press the sheet on the magnets) is improved by interposing a seal between the ring and the protection plate.

In the aforementioned document, it is stated that the plate covers the magnets. In practice, the plate has "windows", that is to say cutouts, through which the magnets are flush, for a better efficiency of the latter.

Such equipment generally gives satisfaction, but is however perfectible.

Thus, when it is desired to arrange the magnets in a new arrangement with respect to what was previously practiced, it is necessary to have a new sheet having windows properly distributed.

It is also necessary to perform many perforations in this sheet of thin thickness without deforming, which is long and tedious and has a significant cost.

We also note the need to enhance the magnets to compensate for any differences in thickness of the plate. More generally, there is some difficulty in tensioning the plate on the cylinder.

The latitude of adjustment of the position of the magnets (in lateral direction and in the development of the cylinder) through the windows of the plate is reduced and it is necessary to remove the ring of the machine for a possible modification of positioning of the magnets.

There are also problems of sealing between the seal of the ring and the plate. Specifically, there is air leakage, so it is necessary to provide a more powerful compressor.

The suction of the leaves is not optimum, which results from a bad plating of the latter against the ring. This phenomenon is accentuated in "tail of leaf", ie where the plating of the plate is the most critical. Document EP-A-1,961,559 discloses a sheet transfer cylinder according to the preamble of claim 1.

The present invention aims to solve these problems.

• qui présente, débouchant à sa surface, un canal annulaire périphérique dans lequel est positionné au moins un aimant pour orienter lesdites particules contenues dans l'encre ;
• et qui comporte des moyens d'aspiration débouchant à ladite surface, en dehors du canal, sous la forme d'au moins une zone pourvue de perforations pour plaquer lesdites feuilles contre cette surface,

caractérisé par le fait que ladite au moins une zone pourvue de perforations est d'une seule pièce avec le reste de l'anneau.Thus, according to a first aspect, the present invention relates to a sheet transfer cylinder, these sheets having previously received at least one printing carried out by screen printing, using an ink containing orientable particles under the effect of a magnetic field, this cylinder having the shape of a ring,

• which has, opening on its surface, a peripheral annular channel in which is positioned at least one magnet for orienting said particles contained in the ink;
• and which comprises suction means opening to said surface, outside the channel, in the form of at least one zone provided with perforations for pressing said sheets against this surface,

characterized in that said at least one area provided with perforations is in one piece with the rest of the ring.

Because the area provided with orifices is in one piece with the remainder of the ring, there is no longer any problem of sealing as has been explained above.

The suction of the sheets towards the cylinder is clearly more efficient. As a result, even with respect to the annular channel in which the magnets are housed, the sheets do not form a hollow, but rather keep the curve of the surface of the cylinder.

• ledit canal d'un anneau s'étend en position médiane avec, de part et d'autre de celui-ci, des bandeaux de largeur identique ou sensiblement identique, chaque bandeau présentant au moins une zone pourvue d'orifices pour plaquer lesdites particules de l'encre au travers de la feuille sur laquelle elle est imprimée, contre cette zone, et les exposer au plus près du champ magnétique dudit au moins un aimant ;
• ledit canal est dépourvu d'un quelconque moyen de recouvrement ;
• il comporte, entre deux aimants voisins, une entretoise qui affleure à ladite surface ;
• ladite entretoise en un matériau antiadhésif tel que par exemple du polytétrafluoroéthylène.

According to other nonlimiting and advantageous features of this cylinder, taken alone or in combination:

• said channel of a ring extends in the middle position with, on either side thereof, strips of identical or substantially identical width, each strip having at least one zone provided with orifices for pressing said particles of the ink through the sheet on which it is printed, against this area, and exposing them closer to the magnetic field of said at least one magnet;
• said channel is devoid of any means of recovery;
• it comprises, between two neighboring magnets, a spacer which is flush with said surface;
• said spacer in a non-stick material such as for example polytetrafluoroethylene.

Another aspect of the invention relates to an assembly consisting of a juxtaposition of at least two cylinders as designated above. This assembly is particularly remarkable in that between two adjacent cylinders extends a spacer, substantially of the same diameter as said cylinders, a non-stick material such as for example polytetrafluoroethylene.

Preferably, the assembly comprises from three to seven cylinders and more particularly five.

• la figure 1 est une vue simplifiée en perspective avec arrachement partiel, d'un anneau constitutif du cylindre selon l'invention ;
• la figure 2 est une vue partielle en perspective de l'anneau de la figure 1, selon un mode de réalisation particulier ;
• la figure 3 montre, de face, la juxtaposition de deux anneaux selon l'invention, avec interposition, entre eux, d'une entretoise ;
• la figure 4 est une vue analogue à la précédente, montrant cette fois-ci la juxtaposition de cinq anneaux ;
• la figure 5 est une vue de face d'une feuille imprimée à l'aide d'un ensemble de cylindres de transfert conforme à la présente invention.

Other features and advantages of the invention will appear on reading the detailed description which follows. It will be made with reference to the accompanying drawings in which:

• the figure 1 is a simplified perspective view partially broken away, of a constituent ring of the cylinder according to the invention;
• the figure 2 is a partial perspective view of the ring of the figure 1 according to a particular embodiment;
• the figure 3 shows, from the front, the juxtaposition of two rings according to the invention, with the interposition between them of a spacer;
• the figure 4 is a view similar to the previous one, this time showing the juxtaposition of five rings;
• the figure 5 is a front view of a printed sheet using a set of transfer cylinders according to the present invention.

For the sake of simplicity, the longitudinal shaft of rotation of the ring or cylinder 1 on which the latter is wedged, has not been shown in the figures.

The X-X 'axis represents the longitudinal axis of the cylinder, and therefore of the ring which constitutes it, around which it moves.

More particularly and referring to the figure 1 appended, the ring, made of metal, for example stainless steel or aluminum, comprises a first cylindrical sleeve 10 whose inner diameter is provided so that it is fitted and wedged on the aforementioned rotating drive shaft.

In this sleeve is provided a series of oblong openings 100, distributed regularly and whose function will be explained later.

The sleeve 10 extends at a distance and is coaxial with an annular wall 11 of larger diameter.

The sleeve and the annular wall are part of the same part and are secured to one another by two diverging walls 12 directed radially. These walls delimit a groove 13 directed parallel to the axis X-X '. Its bottom is referenced 130 and its side walls 131 and 132. From the bottom 130, radially rises a pair of clamps 134 of known type, intended to immobilize a previously printed sheet, relative to the cylinder.

There is therefore a large gap E between the sleeve 10 and the annular wall 11 in which the openings 100 open.

This wall 11 is provided with perforations 110 distributed in at least one zone. These perforations have only been partially represented in figure 1 , for the sake of simplification.

The cylinder 1 comprises, opening on its surface an annular channel 3. Preferably, this channel extends in the middle position. It delimits within the wall 11 two bands of the same width.

The cylindrical bottom wall 30 of the channel extends substantially midway between the sleeve 10 and wall 11. Its side walls are referenced 31 and 32.

As shown more particularly by the figures 2 and 3 , the channel 3 receives, according to determined and judiciously chosen locations, magnets designated hereinafter magnetic blocks 4. These are blocks of known type whose upper surface has the same curvature as that of the cylinder.

The aforesaid locations result of course from the distribution of the regions of the printed sheet with ink having magnetic particles.

In the example shown in figure 2 , the channel 3 receives, above the hollow separating two adjacent magnet blocks, a spacer 5 covering. It is a small curved plate, engaging with the walls 31 and 32. Any means of mutual attachment, for example slider, may be considered.

Each spacer may advantageously be made of a non-stick material such as polytetrafluoroethylene. However, it could be another material with a smooth surface and / or a sliding effect. However, the one just mentioned has the advantage of being widespread, inexpensive and easy to machine.

However, the presence of these spacers is simply optional and it is possible to consider leaving the spaces between two magnetized blocks uncovered.

To the figures 3 and 4 were represented respectively two and five rings according to the invention. They are two by two separated by an annular spacer 6 which has the same external shape as that of the cylinders. The number of rings used depends on the size of the treated sheet and more particularly the number of columns presenting the printed security elements. So, if it is necessary to print on the sheet, five columns of security elements, then five rings are needed.

So on the figure 5 a sheet F is intended to make it possible to obtain fifty identical documents, for example banknotes B, each of the banknotes B having a star-shaped pattern S printed with an ink containing particles that can be rotated under the effect of a magnetic field.

In this configuration, the set of transfer cylinders consists of five rings separated by spacers 6 as indicated in FIG. figure 4 . Each ring contains ten magnet blocks 4 and thus, in one revolution, the transfer assembly is capable of orienting the ink pigments of the star-shaped pattern on the fifty identical documents, and this simultaneously. The spacers 6 provide continuity of material and support between two cylinders. They are preferably made of the same material as the spacers 5.

In the appended figures, the means which make it possible to generate a vacuum inside the space E and, consequently, a suction flow, from the outside towards the inside, to the through holes 110. For example, a compressor is used.

The fact that the zones provided with these orifices are in one piece with the rest of the ring makes it possible to obtain optimum plating of the printed sheet to be treated. There is no more air leakage compared to previously known material. The power of the suction equipment can be reduced accordingly.

Moreover, from one manufacture to another and as far as the location of the areas printed with a magnetic ink changes, access to the magnetic blocks is easy and their movement facilitated. A great flexibility of operation is thus obtained and one can thus avoid the manufacture of the sheet of protection and suction described in the prior art and which is unique and dedicated to a given printing configuration.

With the transfer cylinder described in the present invention a multitude of printing configurations can be envisaged without having to originate anything other than the magnet blocks.

Even when no spacer 5 is present between two magnetized blocks, the plating of the sheet on the cylinder is still correct.

Claims (7)

1. A cylinder (1) for transferring sheets, these sheets having previously received an impression obtained by screen printing, using an ink containing particles that can be oriented under the influence of a magnetic field, this cylinder having the shape of a ring,

   - which has, leading to its surface, an annular peripheral channel (3) in which is positioned at least one magnet (4) to orient said particles contained in the ink;

   - and which includes aspiration means leading to said surface, outside the channel, in the form of at least one area provided with perforations (110) to press said sheets against this surface,

   characterized by the fact that said at least one area provided with perforations (110) is integral with the rest of the ring.
2. The cylinder according to claim 1, characterized by the fact that said channel (3) extends in a median position with, on either side of it, bands of identical or substantially identical width, each band having at least one area provided with perforations (110) to press said particles of ink through the sheet on which they are printed against this area and expose them as closely as possible to the magnetic field of said at least one magnet (4).
3. The cylinder according to claim 1 or 2, characterized by the fact that said channel (3) does not have any covering means.
4. The cylinder according to claim 1 or 2, characterized by the fact that it includes, between two adjoining magnets (4), a spacer (5) which flush with said surface.
5. The cylinder according to the preceding claim, characterized by the fact that said spacer (5) is made of a non-adhesive material such as polytetrafluoroethylene.
6. An assembly consisting of a juxtaposition of cylinders (1) according to one of the preceding claims, characterized by the fact that a spacer (6) extends between two adjoining cylinders (1), of substantially the same diameter as said cylinders (1), made of a non-adhesive material such as polytetrafluoroethylene.
7. The assembly according to claim 6, characterized by the fact that it preferably includes from three to seven cylinders (1), and more particularly five.

Images