WO2014037221A1 - Sheet transfer cylinder and assembly consisting of a juxtaposition of such cylinders - Google Patents

Description

 SHEET TRANSFER CYLINDER AND ASSEMBLY

 CONSTITUTES A JUXTAPOSITION OF SUCH CYLINDERS

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: EP1 12432, 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, ^that is rated ^"ring" to designate his body driven in rotation on itself, this opening at its surface, a peripheral annular channel in which is positioned at least one magnet to orient said particles in ^ink.

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

In practice, the area provided ^with openings is made ^of a plate or cover plate, independent and perforated, which is attached and placed on ^the whole of ^the ring (cylinder) and whose curvature is adapted 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 protective 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, this for 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.

 The present invention aims to solve these problems.

 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.

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

 said channel of a ring extends in the median position with, on either side of it, strips of identical or substantially identical width, each strip having at least one zone provided with orifices for pressing said particles 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.

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: - Figure 1 is a simplified perspective view with partial cutaway, ^of a constituent ring of the cylinder according to ^the invention;

 - Figure 2 is a partial perspective view of the ring of Figure 1, according to a particular embodiment;

- Figure 3 shows, from the front, the juxtaposition of two rings according to ^the invention, with the interposition between them ^of a spacer;

 - Figure 4 is a view similar to the previous, showing this time the juxtaposition of five rings;

- Figure 5 is a front view ^of a printed sheet ^by means ^of a transfer assembly cylinder according to the present invention.

In a simple sake of simplicity, ^the longitudinal shaft of rotation of ^the ring or cylinder 1 on which it rests, ^has not been shown in Figs.

The ^axis XX ^{'is the} longitudinal axis of the cylinder, and therefore of ^the ring which constitutes it, around which it moves.

More particularly and with reference to Figure 1 attached, ^the ring made of metal, for example stainless steel or aluminum, comprises a first cylindrical sleeve 10 whose internal diameter is provided for that ^it is fitted and fixed on ^{the shaft} drive in rotation supra.

In this sleeve is provided a series ^of oblong openings 100, evenly distributed and which are explained below the function.

The sleeve 10 ^extends a distance and is coaxial to an annular wall 1 1 larger diameter.

The sleeve and the annular wall are part of the same part and are secured ^one to ^the other by two diverging walls 12 directed radially. These walls define a groove 13 directed parallel to ^the axis XX ^'. Its bottom is referenced 130 and its side walls 131 and 132. From base 130, s ^pupil radially pliers 134 of known type, designed 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 1 1 in which the openings 100 open. This wall 1 1 is provided with perforations 1 10, distributed in at least one zone. These perforations n ^'are shown only partially in Figure 1, for purposes of simplification.

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

The cylindrical bottom wall 30 of the channel ^extends substantially midway between the sleeve 10 and wall 1 1. Its side walls are referenced 31 and 32.

As shown more particularly in Figures 2 and 3, the channel 3 receives, according to specific and carefully selected locations, magnets hereinafter referred -after magnetized blocks 4. It is ^a question of a known type of blocks whose upper surface has the same curvature as that of the cylinder.

The above locations of course reflect the distribution of regions of the printed sheet with ^ink containing magnetic particles.

In ^the example shown in Figure 2, the channel 3 receives, above the hollow between two adjacent magnetized blocks, a spacer 5 for recovery. It is ^a question ^of a small curved plate, engaging the walls 31 and 32. Any means of mutual fixing, e.g. slide, can 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 merely optional ^and may consider leaving uncovered spaces between two magnetized blocks.

To Figures 3 and 4 were respectively represented 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. Thus, ^if it is necessary to ^print on the sheet, five columns ^of security elements, then five rings are needed.

Thus, in FIG 5, a sheet F is to enable ^the obtaining of fifty identical documents, e.g., bank B tickets, each ticket having an S B star-shaped pattern printed with an ink containing orientable particles under the effect of a magnetic field.

In this configuration, ^the set of transfer cylinders consists of five rings separated by spacers 6 as shown in Figure 4. Each ring contains ten blocks magnets 4 and thus in one revolution, ^the transfer assembly is capable of orient 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 accompanying figures n ^'have not been shown the means by which to generate a vacuum ^{within the} space E and, consequently, a flow ^of suction from ^the outside ^inwards, in Through openings 1 10. For example, a compressor is used.

In that the areas provided with said orifices are ^of a single piece with the rest of ^the ring allows to ^obtain an optimal pressing of the printed sheet to be treated. There ^{'over air} leakage compared to previously known material. The power equipment ^suction can be reduced.

Moreover, ^a manufacturing ^to another, provided that ^the location of the areas printed with magnetic ink changes, ^access to magnet blocks is easy and ease movement. 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

1. Cylinder (1) for transferring sheets, these sheets having previously received an impression produced by screen printing, using an ink containing particles that can be oriented under the effect of a magnetic field, this cylinder having the form of 'a ring,  - which presents, opening on its surface, an annular channel (3) device in which is positioned at least one magnet (4) 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 (110) for pressing said sheets against this surface,  characterized in that said at least one area provided with perforations (110) is in one piece with the remainder of the ring.  2. Cylinder according to claim 1, characterized in that said channel (3) extends in the middle position with, on either side thereof strips of the same or substantially identical width, each strip having at least an area provided with perforations (110) for pressing said particles of ink through the sheet on which it is printed against this area and exposing them as close as possible to the magnetic field of said at least one magnet (4).  3. Cylinder according to claim 1 or 2, characterized in that said channel (3) is devoid of any means of recovery.  4. Cylinder according to claim 1 or 2, characterized in that it comprises, between two adjacent magnets (4), a spacer (5) which is flush with said surface.  5. Cylinder according to the preceding claim, characterized in that said spacer (5) is a non-stick material such as polytetrafluoroethylene. 6. Assembly consisting of a juxtaposition of cylinders (1) according to one of the preceding claims, characterized in that between two adjacent cylinders (1) extends a spacer (6), substantially same diameter as said cylinders (1), a non-stick material such as polytetrafluoroethylene.  7. The assembly of claim 6, characterized in that it preferably comprises three to seven cylinders (1) and more particularly five.