Patent ID: 12194517

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In a first step towards addressing the object of the invention, the invention departs from prior art reference WO2015/028939 A1 that enables to obtain an embossed product with a better reflectivity of the metallized surfaces, as well as for the embossing rollers, a precise generation of pyramid shapes in the micrometer range. By using exaggerated relief heights as well as the usage of pedestal effects, increased brilliance in logo designs is achieved. However, it is noted that there was no means to create shading or half-toning using the teachings of WO2015/028939 A1.

A recent successful development of a new basic embossing structure forms the basis for the significant increase in the brilliance resulting from embossed structures. The new basic embossing structure provides a solution for fine embossing that allows producing checkered-style and larger uniformly embossed areas in a step length of about 50 to 250 μm. The new basic embossing structure further provides a configuration that also reduces uncontrollable contraction in the axial direction while foils are being embossed. In addition, the new basic embossing structure provides a solution that allows producing the fine embossing over areas in a homogeneous manner on the foil.

The new basic embossing structure may be understood from the following description of an embossing method that allows embossing a material from both sides. The embossing method comprises at least feeding the foil material into a roll nip between a pair of a first roll and a second roll, providing the first roll and the second roll each with a plurality of positive projections and a plurality of negative projections of identically shaped polyhedral structures, the positive projections are elevated above a mean cylindrical surface of their roll, and the negative projections are recesses reaching below the mean cylindrical surface of their roll, a first subset of the plurality of positive projections being disposed with a first periodicity on a first grid in axial direction and a second periodicity on the first grid in circumferential direction on the first roll, and a second subset of the plurality of negative projections being disposed with the first periodicity in axial direction and the second periodicity in circumferential direction on the first grid intertwined with the positive projections, in axial and circumferential directions respectively, and a third subset of the plurality of positive projections and a fourth subset of the plurality of negative projections being disposed on a second grid complementary to the first grid, on the second roll, each of the positive projections and the negative projections on the first roll during operation of the rolls and in the roll nip, except for projections located on edges of the first grid, being surrounded on all sides by positive projections and negative projections on the second roll, the positive projections of the first roll together with alternating corresponding negative projections on the second roll forming during the operation of the rolls and in the roll nip, a first straight line (y-y) substantially parallel to the axial direction, and the negative projections of the first roll together with alternating corresponding positive projections on the second roll forming during the operation of the rolls and in the roll nip, a second straight line (x-x) substantially parallel to the axial direction. The embossing method further comprises disposing in the first grid the positive projections and the negative projections such that in the axial direction on the first roll each positive projection shares a lateral base border with at least one negative projection adjacent to the positive projection, where the first straight line (y-y) and the second straight line (x-x) are coincident in a single third line (z-z), and during the operation of the rolls and in the roll nip, all lateral oblique surfaces of the positive and negative projections of the first roll are just above the surface in full faced view with the corresponding lateral oblique surfaces of the respective negative and positive projections of the second roll, thereby enabling a homogeneous distribution of pressure to the material.

InFIG.4, showing an example embodiment of the new basic embossing structure, the embossing pattern corresponds to a structured surface of one of the rolls, whereby the positive projections P are elevated above a mean cylindrical surface of one of the rolls (not referenced inFIG.4), and the negative projections N are recesses reaching below the mean cylindrical surface. The positive projection P and the negative projections N are identically shaped polyhedral structures, whereby the positive projections P are symmetrically shaped relative to the negative projections N when considered from the mean surface. Another one of the rolls (not shown inFIG.4) comprises on its cylindrical surface a matching embossing pattern which is positioned such that at a time of operation for embossing, both embossing patterns interact like congruent structures to emboss the product or material on both sides, such that each of the projections on each roll becomes surrounded on all sides by projections on the other roll.

FIG.5shows a layout plan of projections corresponding to embossing structures fromFIG.4, in fact only a part of the embossing pattern fromFIG.4, comprising positive projections P and negative projections N. A double arrow shows an order of magnitude for the structures in the embossing pattern, which lies around 100 μm in any lateral direction. The exact dimensions are irrelevant for the present explanation; it is only intended to indicate an order of magnitude for the size of the projections in the invention.

The use of the embossing pattern ofFIG.4and a corresponding inverse embossing pattern on respective rolls of a pair of embossing rolls, to emboss a foil or inner-liner confers a 100% embossing coverage of the embossed surface.

Returning toFIG.5, which for the sake of discussion represents the embossing pattern located on the first roll of a pair of rolls, it is to be imagined that a corresponding embossing pattern is located on the second roll of the pair of rolls (not represented inFIG.5). As is apparent fromFIG.5, the positive projections P and the negative projections N are disposed in a grid such that in the axial direction, each positive projection P shares a lateral base border—inFIG.5these are represented as the lines delimitating the projections and separating one projection from the adjacent neighboring projection—with a least one negative projection N adjacent to the positive projection P.

Using the embossing pattern with the new basic embossing structure, it is possible to obtain a homogeneous distribution of pressure to the material, i.e., a regular and homogenous balance between the pressure on the lateral oblique surfaces of the positive projections P and negative projections N, mitigated perhaps only by variations of the material thickness that occur over a certain range of tolerances. Furthermore, axial contraction of the embossed foil is reduced and a smoother surface is obtained compared to the older embossing technologies of the Applicant.

The embossing using the new basic embossing structure may also be called the polyhedron embossing technique.

A comparison of the spatial density of the embossed metallized areas between those achieved by using the approaches in EP0925911 and those achieved using the polyhedron embossing technique provides detailed information on the significant increase in the brilliance resulting from embossed structures.

It can be ascertained easily that the polyhedron embossing technique provides a doubling of the embossed, metallically reflecting surface in practice compared to prior art, such as, e.g., EP1324877 B1, since embossed structures obtained with positive projections and negative projections can be controlled. While with prior-art embossing systems like the ones shown for example inFIG.2aandFIGS.3a-3b, only the pressing edges of the embossing structures and not the entire pyramid surface press the film between the embossing rollers (see reference208inFIG.2a), it may be quite easily understood that when using a patrix-matrix type embossing and obtaining for example the embossed foil material as shown inFIG.6, there is in each embossing condition the full side surfaces of the pyramids or embossing surfaces that are enforcing pressure onto the material to be embossed (embossing not shown inFIG.6), as the two complementary structures are pinching the foil material perfectly.

Hence, in a further step towards addressing the object of the invention, which starts from the new basic surface embossing structures with pyramids or any other polyhedron shape of different heights, one comes closer to the goal of the invention. As described herein above for the new basic embossing structure, a polyhedron-like denture is used here. This means that opposing individual embossing teeth, i.e., a positive projection on one roller and a corresponding negative projection of the counter roller, of the roller pair are exactly complementary.

The individual embossing teeth in any surface of at least a determined perimeter of a roller. Taking for example a plurality of positive projections as an embodiment of the embossing teeth, theses may be arranged according to a 2-dimensional grid comprising a tessellation of grid surfaces.

FIGS.7a-7ccontain examples of 2-dimensional grids, in this case so-called regular grids.

FIG.7ashows a Cartesian grid700that comprises a tessellation of squares701. In this example, in a surface delimited by a determined perimeter enclosing 30 squares, i.e., 6 squares wide in direction of a row702, and 5 squares wide in a direction of a column703, each square comprises for example a positive projection704as represented using diagonal crosses inFIG.7a. Each square701or individual grid surface comprises at most a single positive projection.

FIG.7bshows a rectilinear grid710that comprises a tessellation of parallelepipeds711. In this example, in a surface delimited by a further determined perimeter enclosing72parallelepipeds, each parallelepiped comprises for example a positive projection714as represented using diagonal crosses inFIG.7b. Again, each individual grid surface comprises at most a single positive projection.

FIG.7cshows a further rectilinear grid720that comprises a tessellation of rectangles721of variable sizes, depending of the respective position of the rectangle721in a row722and column723. The rectangles shown inFIG.7cmay all or partly be comprised in a further surface having a determined perimeter (perimeter not shown inFIG.7c) and each comprise a positive projection (also not represented inFIG.7c).

FIG.8a-8bcontain further examples of 2-dimensional regular grids.

FIG.8ashows a curvilinear grid that comprises a tessellation of individual grid surfaces801of variable sizes, each individual grid surface being delimited by two straight lines that extend from a center802, and two curved lines that originate respectively from concentric oval shapes. In this example, a surface delimited by determined perimeter comprising an oval shape803and oval shape804comprises a plurality of individual grid surfaces801, each comprising for example a positive projection805as represented using diagonal crosses inFIG.8a. Each individual grid surface801comprises at most a single positive projection805. From viewingFIG.8ait is apparent that a size of the individual grid surface801may vary from one to another, which makes it possible to have positive projections of sizes corresponding the respective surface of the individual grid surfaces801. However, it is also possible to have identical positive projections as long as this fits in the smallest of the individual grid surfaces801.

FIG.8bshows a curvilinear grid810comprising curved lines that delimit individual grid surfaces813in rows811and column812. In this example a surface delimited by a determined perimeter that surrounds a number of individual grid surfaces813in 5 rows811of 8 columns812, comprises in each individual grid surface813a positive projection814as represented using diagonal crosses inFIG.8b. Each individual grid surface813comprises at most a single individual positive projection814.

FIGS.9a-9bcontains further examples of grids, in this case unstructured grids. In general, an unstructured grid is a tessellation of a surface by simple shapes, such as triangles, in an irregular pattern.

FIG.9ashows an unstructured grid900represented in dashed lines901, which form triangles902. Each triangle902has at least one side in common with an adjacent triangle902, in some cases two sides, or even three sides. Corners of the triangles902are indicated by circles903. In this example, the completely represented part of grid900comprises at each corner903a positive projection such as a first positive projection defined by three surfaces904or a second, adjacent positive projection defined by three surfaces905. WhileFIG.9ashows a top view of the grid900, the positive projections are understood to raise from a surface of an embossing roller, each positive projection having a pyramidal type of shape with a summit located over one of the corners903. The positive projections have lower corners such as the first lower corner906and the second lower corner907, which may be in common from one positive projection to another. From viewing the unstructured grid900it is apparent that each positive projection may have an individual pyramidal shape that varies from one to another.

FIG.9bshows a further unstructured grid910represented by straight lines911, that define triangles912having corners913represented in circles. Each triangle912has at least one side in common with an adjacent triangle912, in some cases two sides, or even three sides. In the present example, the completely represented part of grid910comprises at each corner913a positive projection914having a circular outer perimeter915at the surface of the roller (surface of the roller not shown inFIG.9b) centered on a corner913. A diameter of the outer perimeter915of the positive projection914may be adjusted to be tangent to a further outer perimeter916of a neighboring positive projection917. From viewing the unstructured grid910it is apparent that each positive projection may have an individual outer perimeter at the surface of the roller that varies from one the other.

The individual embossing teeth may have respectively an individual polyhedric shape with one or more flat top surfaces, possibly of the same type for at least a part of the first roller surface, e.g., for at least a surface having a determined perimeter and which is covered by the individual embossing teeth. The individual polyhedric shape is intended to emboss individual light-reflecting areas in the foil material in order that the reflectivity of such light-reflecting area is adjusted to correspond to a predetermined reflectivity value. In an example embodiment, the individual embossing teeth are arranged on the first roller according to a 2-dimensional grid, and the individual polyhedric shape of each tooth must be formed in line with a table of reflectivity values for the 2-dimensional grid that describes which value of reflectivity of the embossed foil material the embossing of each tooth must produce. Such a 2-dimensional grid may for example comprise 5 rows of 5 individual embossing teeth, that is 25 embossing teeth, and the table of reflectivity values may for example be given as percentages as follows:

ColRow12345120404040402204040404032040404040440606040405601001006040

In the above table, it is, for example, indicated that for row 1, column 1, the shape of the embossing tooth should be made to emboss individual light-reflecting areas that in total have a reflectivity of 20%. Another example for row 4, column 5 indicates that the shape of the embossing tooth should be made to emboss individual light-reflecting areas that have a total reflectivity of 40%. The reflectivity may be achieved by adjusting for each of the plurality of light-reflecting areas to provide, an orientation and shape of the corresponding positive projection (embossing tooth) in the 2-dimensional grid that is intended to emboss the light-reflecting areas. This adjustment may involve choosing a specific polyhedric shape, adjusting its height, its size, its tilting angle, and then modulating the achieved reflectivity by applying operations such as for example an offset operation, a gain factor operation or a cut-off operation. A few examples of this non-limitative list of operations will be described herein below in connection withFIG.10. With this knowledge, it becomes a relatively simple matter to empirically determine for a specific foil material to emboss, by a simple series of test embossing followed by reflectivity measurements, a magnitude of the operation to apply to a positive projection in order to achieve a specific value of reflectivity. For example: an unchanged positive projection may lead to an embossed light-reflecting area that has a reflectivity of 100%, while applying an offset operation of 40% may for example lead to a reflectivity of 40% and an offset operation of 60% may lead to a reflectivity of 20%. This is an example only and in no way implies that there necessarily is a linear relationship between percentage of reflectivity and value of offset operation.

This example with arbitrary numbers will be better understood after the explanations below in relation forFIG.10.

Referring now toFIG.10, this contains a table useful to explain manners in which positive projections may be designed according to the invention. We will use essentially the same nomenclature as in the description ofFIG.3bto refer geometric dimensions of a positive projection in term of individual height h, possible truncation or modified height H and pitch s.

The table inFIG.10is organized in three columns entitled Offset, Gain and Intersection to designate three types of operations that may be applied to design a positive projection. The rows of the table below the titles contain example representations of the operations being applied to a determined base shape1000of a positive projection represented generally in dashed lines above the surface1001of an embossing roller (roller not shown inFIG.10) to obtain a designed positive projection1002represented in a sectional view by a shape with textured surface. In cell a) of the table, the designed positive projection1002is of course on the side above the surface1001, but for reasons of better understanding, its sides are extended below the surface1001with dashed lines1003to show the outline of the initial determined base shape1000. Arrows such as arrows1004in cell a) are used to indicate how the determined base shape1000evolves to become the designed positive projection1002, as appropriate. In cell b) of the table, the individual height h of the determined base shape1000is indicated for a better understanding.

More specifically, referring to cell a), this shows an operation of shaping an upper part of the determined base shape1000to obtain the designed positive projection1002, the resulting shape of the upper part, i.e., the designed positive projection1002having a modified height H reduced by an individual offset Ioff as compared to the individual height h, whereby
H=h−Ioff.

The designed positive projection1002is intended to be positioned at the surface of the first roller, which is represented as a reference at the surface1001in cell a).

In cell b), in addition to applying a second individual vertical offset Ioff2(Ioff2not represented in cell b)), in a direction perpendicular to the surface1001(which is the same as in cell a)) to modify an overall height of the determined base shape1000to become H1, a further transformation leading to a lateral offset or shift of all points of the determined base shape in a direction parallel to the surface1001is applied to obtain a designed positive projection1010. It is noted that in the example of cell b), for sake of a better understanding, the base points1011and1012, which are virtual points, and indicated at the end of virtual prolongations1013of sides of the designed positive projection1010are also subjected to the vertical and lateral shift.

In cell c), a determined base shape1021represented again in sectional view has a similar shape as the determined base shape1000, but a designed positive projection1020has a more complex top side structure comprising two summits1022and1023and more than 2 sides, at various angles of inclinations, in contrast to the determined positive projection1002from cell a) which corresponds to a sectional view of a regular pyramid. However, similarly to the operation applied in cell a), here in cell c), an upper part of the determined base shape1021is shaped to obtain a designed positive projection1020that has for one summit1023a modified height H2according to a third individual offset Ioff3, but for other points of a shape contour of the designed positive projection, other individual offsets are applied, for example to obtain the modified height H3of summit1022. In overall this is represented by variable lengths of the one-pointed arrows in cell c). The shape contour of the positive projection is shown in 2 dimensions as cell c) represents a cross section, but if the whole surface of the designed positive projection1020is taken under consideration, this may be obtained by applying to a 3-dimensional shape of the determined base shape1021, described by a 3-dimensional shape-contour function, a 3-dimensional offset, which results in the different heights of the designed positive projection. The designed positive projection1020is intended to be positioned at the surface of the first roller.

In cell d), an operation of applying an individual gain or multiplication factor to the determined base shape1000is executed to obtain a designed positive projection1030, the operation being configured such to maintain a base surface and base perimeter of the determined base shape—represented by the section delimited by points1031and1032in the sectional view of cell d)—intended to be positioned at the surface of the first roller—represented here by the surface1001. This results in an overall deformation of the determined base shape1000in height direction in proportion to an individual gain factor Igain. For the height H of the designed positive projection, we have the relation:
H=Igain×h.

In cell e), in addition to an operation of applying a gain factor to obtain the overall height of the designed positive projection, a lateral deformation is also operated on all points of the determined base shape to obtain the designed positive projection1040, except on the points1031and1032that delimit the base surface at the surface of the roller of the determined base shape of the designed positive projection1040.

In general, it may be noted that the determined base shape has a 3-dimensional shape described by a 3-dimensional shape-contour function, which is not further analytically detailed here. The operation of applying an individual gain factor may be described as follows: an individual 3-dimensional gain-factor function is applied to the determined base shape to obtain the designed positive projection, that is used to emboss the light-reflective area intended to have a desired reflectivity, the individual 3-dimensional gain-factor function being configured to be applied to the 3-dimensional shape-contour function thereby such that the designed positive projection has the same base perimeter as the determined base shape, the designed positive projection has no part that overlaps beyond the base perimeter, and any point in the contour of the designed positive projection is free from overlap with another point of the contour maintaining a base surface of the determined base shape intended to be positioned at the surface of the first roller and, resulting in an overall deformation of the determined base shape in proportion to the individual 3-dimensional gain factor.

In cell f), a determined base shape1051is represented again in sectional view using dotted lines, and the designed positive projection1050has a more complex top side structure with at least two summits1052and1053and a plurality of sides at various angles of inclinations. This more complex top structure, which is just a part of an overall 3-dimensional top side of the desired positive projection, results from an individual 3-dimensional gain-factor function being applied to the 3-dimensional shape-contour function of the determined base shape1051. The desired positive projection1050is intended to be positioned at the surface of the first roller.

In cell g), the determined base shape1000is represented partly in dashed lines for its top side, and partly in a texture shape that corresponds to a designed positive projection1060. The non-textured part of the determined base shape corresponds to the result of an operation comprising cutting-off the top of the determined base shape1000according to an individual shape1061along an individual intersection1062with the determined base shape1000. The individual shape1061is represented above the designed positive projection1060for a better understanding. In a further preferred embodiment the individual shape not only affects the shape of designed positive projection1060, but may extend to further positive projections intended to be positioned on either sides of the designed positive projection on the surface of the roller represented here by surface1001, and hence affect the shapes of the further projections accordingly. It is understood that the individual shape is of virtual nature, and that the cutting-off of the determined base shape is operated according to a virtual representation of the individual shape, as may easily be done by a person skilled in the art for the shaping as such only. In the example of cell g), the designed positive projection1060corresponds to a pyramid that is cut-off parallel to the surface1001. The designed positive projection1060is intended to be positioned at the surface of the first roller.

In cell h), a similar operation of cutting off as in cell c) is executed, whereby the individual intersection results in a slanted top side1071of a designed positive projection1070.

In cell i), a similar operation of cutting off as in cells g) and h) is executed, whereby the individual intersection results in a more complex top side1081of a designed positive projection1080.

The adjusting of a determined base shape to a desired positive projection may be modeled more generally with the help of transformation matrices. For further details, see also [David Salomon: “The Computer Graphics Manual”, Springer, 2011 Edition, ISBN-13: 978-0857298850].

An offset in 3-dimensional space as applied to the determined base shape in order to move this base shape to the origin of the coordinate system X(fx,fy,fz) according to the translation transformation T as follows:
X(fx,fy,fz)=T(fx,fy,fz)

which, when expressed with the transformation matrix is:

[x′y′z′1]=[100f⁢x010f⁢y001f⁢z0001][χyz1]

Subsequently, a shear function in the xy plane and a scaling function in z-axis followed by the inverse offset operation to the original starting point and with the transformation matrix as previously demonstrated allow to obtain all desired positive projections from determined base shapes, according to the parameters of the matrices, and is expressed by the formula as follows:
X(fx,fy,fz,a,b,sx,sy)=T(fx.fy,fz)·SH(a,b)·S(sz)·T(−fx,−fy,−fz)

and using matrices:

[x′y′z′1]=[100f⁢x010f⁢y001f⁢z0001][10a001b000100001][1000010000s⁢z00001][100-f⁢x010-f⁢y001-f⁢z0001][xyz1]

Referring now toFIG.11, this contains a schematic geometric construct useful to illustrate the above operation in a graphical manner, by the operation as applied to point P of a determined base shape to obtain point P′—the summit of the desired positive projection—by the 3-dimensional vector1101. The base perimeter in this example is a rectangle defined by points1102,1103,1104and1105. More specifically, the operation that may be explained here is the application of above matrices. In this figure, the operation is explained using a Cartesian referential (x, y, z) in which point P is projected in the xy plane, then the x-coordinate is varied according to the value a, then the y-coordinate is varied according to the value b, to eventually be displaced in z-direction according to the factor sz.

In a preferred example embodiment, on both rolls, a step spacing individual embossing teeth may remain the same along a given first direction, i.e., it also may remain the same along another given second direction but possibly with another value than that used to the first direction. Hence, in case the first direction and the second direction are axial and radial directions respectively, a value of axial steps may differ from a value of radial steps.

Resulting embossed foil materials comprise embossed tooth-shapes all over the surface. At the time of filing of the present patent application, the usual step lengths s (seeFIG.2) are comprised in a range between 50 μm and 300 μm.

The principle described in EP1324877 B1 allowed the tobacco industry in year 2000 (prior art) to manufacture from 200 to about 500 sections/min for cigarette packaging in online operation, while over 1000 sections/min are possible at the time of filing the present patent application.

FIG.12a,FIG.13aandFIG.14ashow several variants of surfaces with positive projections, of a respective first embossing roller (embossing roller not shown in any of the referenced figures) according to the invention (complementary counter-roller not shown either). It is understood that for the embossing of material according to the invention, the counter roller comprises negative projections complementary to the positive projections, in a manner that the positive projections seamlessly and gaplessly join with those corresponding negative projections at the intended embossing of the foil material, hence enabling a homogeneously jointed embossed shape in the material.

FIG.12ashows an example comprising positive projections embodied as pyramidal teeth1201, each pyramidal tooth having a substantially square base, but in the overall, the pyramidal teeth being designed to comprise truncations, e.g., truncations1202,1203,1204and1205that may vary from one tooth to another one, in terms of a combination of an angle of inclination and of a height, resulting in surfaces of sizes that may vary from one tooth1201to another tooth1201. In other words, the truncations define respective top sides of the pyramids, and each pyramid extends from a base surface of the roller on which they are made (roller not shown inFIG.12a) to its top side in a direction away from a rotation axis of the roller (rotation axis also not shown inFIG.12a). The truncations may be obtained using operations described for cells g) and h) in the table ofFIG.10, i.e., they are the result of an operation comprising cutting off the tops of the determined base shapes as appropriate—the determined base shape here would be a non-truncated pyramid—with an individual shape along an individual intersection with the determined base shapes, the individual shape “covering” at least all truncated pyramids. As already explained, the individual shape is of virtual nature and the intersection is determined accordingly.

For example,FIG.12ashows that truncation1203is at a different angle than truncation1202, and that the overall height of the pyramid with truncation1202is smaller than the overall height of the pyramid with truncation1203.

The pyramids, which effectively are positive projections from the roller surface, are arranged in a plurality of rows and columns, more specifically in the present example, in a plurality of alignments on axially oriented lines, for example a first axial line1206and a second axial line1207shown in dashed lines. The pyramids are spaced in the rows according to a value of a first step function, which in the present example describes a regular spacing among each other according to an axial step AS1. Adjacent axially oriented alignments of pyramids, such as the first axial line1206and the second axial line1207are separated in distance according to a value of a second step function, which in the present example is a radial step RS1.

The axial step AS1and the radial step RS1may be equal, but in preferred embodiments, depending on the overall requirements, they may also differ from each other according to the first step function and the second step function respectively. These functions may be of any type, for example linear (as in the present example), non-linear, etc.

The variations of the truncations of the pyramids, when considered over all the pyramids, define the individual shape that is cut-off in the pyramids according to a corresponding individual intersection, over the corresponding surface of the roller that comprises the pyramids. In the example ofFIG.12athis appears to correspond to a curved plane that is at its nearest to the roller in the lower corner ofFIG.12aand rises away from the roller as we depart from the lower corner to either the left, right and upper corner of the set of pyramids illustrated inFIG.12a.

FIG.13ashows an example comprising hexagonal pyramidal teeth1301, each hexagonal pyramidal tooth having a substantially hexagonal base, and in the overall, the hexagonal pyramidal teeth being designed to comprise heights that may vary from one tooth to another one. More specifically for the shown example, the height of a tooth1302is smaller toward the inside of the overall surface, as for a peripheral tooth1303. In other words, the heights define respective top sides of the hexagonal pyramids, and each hexagonal pyramid extends from a base surface of the roller on which they are made (roller not shown inFIG.13a) to its top side in a direction away from a rotation axis of the roller (rotation axis also not shown inFIG.13a).

For example,FIG.13ashows a first individual widening of an angle Phi (Phi not shown inFIG.13a) on the top of the hexagonal pyramid1302, Phi being shown inFIG.13cand which is different from a second individual widening of angle on the top of the hexagonal pyramid1303, which leads to different heights among pyramids1302and1303. More precisely, a wider angle implies a lesser height.

In other words, the height variations of the hexagonal pyramids may be obtained by executing the operation of applying an individual gain factor as explained in relation to cell d) in the table ofFIG.10, to the determined base shape—here the determined base shape is a hexagonal pyramid with full height—to obtain a designed positive projection, the operation being configured such to maintain a base surface of the determined base shape intended to be positioned at the surface of the motor roller. This results in an overall deformation of the determined base shape in height direction in proportion to an individual gain factor Igain.

The hexagonal pyramids, which effectively are positive projections from the roller surface, are arranged in a plurality of alignments on axially oriented lines, for example a third axial line1304and a fourth axial line1305shown in dashed lines, the pyramids being regularly spaced among each other according to an axial step AS2. Adjacent axially oriented alignments of hexagonal pyramids, such as the third axial line1304and the fourth axial line1305are separated in distance by a radial step RS2.

FIG.14ashows an example comprising conical structured teeth, each conical structured tooth having a substantially circular base, and in the overall, the conical structured teeth having heights and diameters of their base that may vary from one tooth to another one. More specifically, a center of each circular base is positioned on a regular grid, and the diameter of the base varies as a function of the height of the conical structured tooth. In this example, the conical structured teeth are obtained by executing an operation described for cell a) in the table ofFIG.10. More specifically, the upper part of the determined base shape—here the determined base shape is a full conical tooth—is shaped to obtain the designed positive projection, the resulting shape of the upper part, i.e., the designed positive projection having a height reduced by an individual offset Ioff as compared to the individual height h of a determined base shape.

FIG.15ashows an example similar to the example ofFIG.12a, but applying the principle to positive projections P and negative projections N on a same roller instead of positive projections only as shown inFIG.12a.

InFIG.15a, in each of the plurality of alignments along axially oriented lines, of positive projections P, between two consecutive positive projections P, a second negative projection N is provided on the roller, such that a plurality of second negative projections N becomes arranged in the same alignment as the positive projections P, the second negative projections being regularly spaced among each other according to the axial step, and whereby adjacent axially oriented alignments of second negative projections are separated by the radial step. Each second negative projection N extends from a base surface of the motor roller, which in substance is at the level of the square drawn around all the projections inFIG.15a, to a bottom side of the second negative projection N in a direction towards the rotation axis of the motor roller (not shown inFIG.15a). Further, from one alignment to an adjacent alignment, providing next to a positive projection from the one alignment, in the adjacent alignment a further second negative projection distant from the positive projection in radial direction. Hence, effectively, each positive projection is surrounded normally by four negative projections. Two consecutive second negative projections N on a same radial axis are separated by the radial step. In the example ofFIG.15a, since the positive projections are separated by the axial step, then compared to the illustration ofFIG.12a, the length of a base side of the pyramids is in substance half of that of the pyramids inFIG.12a. Not shown inFIG.15ais the fact that the counter roller is also provided with a plurality of second positive projections complementary to the second negative projections N of the motor roller, and the plurality of second negative projections N seamlessly and gaplessly join with those corresponding second positive projections at the intended embossing of the foil material.

The principle illustrated inFIGS.12a-15ais applied in the present invention, according to which, and in contrast to EP1324877, each of the surface elements may be adapted more or less individually leading to a resulting relief-like embossed-film reflection when light is reflected from the embossed film. Overall, the designer now has multiple options at its disposition, compared to EP1324877, where only the pyramid height was utilized for the design. The multiple options are described herein above.

Referring now toFIG.16, this illustrates examples of embossing roller surfaces in which a roller is provided with a relief topography, and positive projections are arranged in a 2-dimensional grid projected thereon.

More specifically,FIG.16ashows a roller surface1610of a first roller (first roller not represented inFIG.16a) represented as a straight line with a relief topography1611provided thereon, which in this example appears as an elevation above the roller surface similar to a hill. It is understood that for the purpose of embossing, the counter roller (second roller) is provided with a complementary relief topography complementary to the relief topography. A 2-dimensional grid is projected on a surface of the relief topography1611. A plurality of positive projections embodied as conical structured teeth—similar to the ones represented inFIG.14a—wherein each conical structured tooth has a substantially circular base, and in the overall, the conical structured teeth have heights and diameters of their base that may vary from one tooth to another one. More specifically, a center of each circular base is positioned on a regular 2-dimensional grid, and the diameter of the base varies as a function of the height of the conical structured tooth (measured from the surface of the relief topography1611). In this example, the conical structured teeth are obtained by executing an operation described for cell a) in the table ofFIG.10. More specifically, the upper part of the determined base shape—here the determined base shape is a full conical tooth—is shaped to obtain the designed positive projection, the resulting shape of the upper part, i.e., the designed positive projection having a height reduced by an individual offset Ioff as compared to the individual height h of a determined base shape.

Referring now toFIG.17, this illustrates further examples of embossing roller surfaces in which a roller is provided with a relief topography, and positive projections are arranged in a 2-dimensional grid projected thereon.

FIG.17aalso shows an example a roller surface1710of a first roller (first roller not represented inFIG.16a) represented as a straight line with a relief topography1711provided thereon, which is this example appears as an elevation above the roller surface similar to a hill. A 2-dimensional grid is projected on a surface of the relief topography1711. A plurality of positive projections embodied as conical structured teeth—similar to the ones represented inFIG.14a—is arranged according to the 2-dimensional grid similar as inFIG.16a, with the difference that the conical structured teeth are oriented perpendicularly to the roller surface1710—this is illustrated inFIG.17cby the lines oriented in the axis of the conical structured teeth and perpendicular to the line1712, which rather than being parallel to the roller surface, is parallel to the rotation axis of the roller, while inFIG.16c, the lines oriented in the axis of the conical structures are shown to be perpendicular to the surface of the roller surface schematically represented by the line1612.

Continuing the explanation ofFIGS.12-17,FIG.12a-ctoFIG.17a-cshow complete examples of embossing surfaces according to the invention withforFIGS.12a,13a,14a,15a,16aand17aa quasi-three-dimensional view—already explained herein above—,forFIGS.12b,13b,14b,15b,16band17ba cross-sectional view of respective rollers during an embossing process (without material being embossed) indicating respectively a median height1200,1300,1400,1500,1600and1700of respective structures on one of the rollers—the cross-sections do not necessarily reflect an arrangement illustrated in the corresponding respectiveFIGS.12a,13a,14a,15a,16aand17a—, andforFIGS.12c,13c,14c,15c,16cand17cresulting embossed foil materials—the embossed foil materials do not necessarily result from an arrangement illustrated in the corresponding respectiveFIGS.12a,13a,14a,15a,16aand17a, or from the embossing roller pairs illustrated inFIGS.12b,13b,14b,15b,16band17b.

Drawn circles inFIGS.12c-17cmark particularly interesting embossing points K1and K2. More precisely, K1shows, e.g., how large-area brilliant stripes of embossed foil material are shaped. K2shows embossed results of particularly shaded or matted halftone dots in the embossed foil material. While not shown inFIG.12atoFIG.17c, the reflections of light from the embossed foil material may be perceived by the human eye over a wide angle, independently of any side effects related to embossing conditions and hence fulfilling the object of the invention.

FIG.18depicts an interaction between two complementary patrix/matrix embossing rollers1800and1801, with an endless web material1802(shown as a limited piece inFIG.18) such as inner-liner foils, polymeric foils, metallic foils or foils used in product packaging applications. The magnified part1803shows an example of embossing structures according to the present invention.

FIG.19shows a detailed magnification1900of an embossing1901of a packaging foil—in this example a picture of a face—according to the invention. The detailed magnification clearly shows a modulation of the reflective area, which has been obtained at the time of embossing by embossing structures that have different surfaces corresponding to the intended reflective surfaces in the packaging foil, as illustrated by the amount of surface represented in white in the figure, and hence the halftone value of the underlying graphics template.

The applications as shown inFIG.20toFIG.25are simple examples of the above-mentioned embossing technology.

FIG.20shows an application example according to the invention, namely a seal pack with decoration for, e.g., smoking articles.

FIG.21shows a further application example according to the invention, namely a blister pack with decoration on a cover foil for, e.g., smoking articles or medication.

FIG.22shows a further application example according to the invention, namely a soft-wrap for sweet goods.

FIG.23shows a further application example according to the invention, namely a Tetra Brik (registered trademark) with decoration.

FIG.24shows a further application example according to the invention, namely a decoration of cover foil for beverage capsules.

FIG.25shows a further application example according to the invention, namely a wrapping-decoration of chewing gum.

The invention may find use in decorative embossing of luxury objects, e.g., watches or jewelry, but also in the area of pharmaceuticals, food industry, sweets, snacks, etc.

Since the height of the embossing structures may be kept to a minimum while still getting very strong and weakly viewing-angle dependent shading or dithering effects, the novel embossing method may be applied to implementations where the surface of the embossed material has to be kept nearly flat.

While the invention was described to be used with rollers, and more particularly a pair of rollers, the discussed structures may well be applied to planar embossing tools for planar embossing between a pair of planar embossing tools. This is particularly of interest in case the material to emboss becomes too rigid, and rotary embossing no more provides sufficient force to deform the material during the short time-window of the material passing between the rolls. The person skilled in the art may conclude that the technology of the invention (method and device) may be adapted to the use of embossing material that is more rigid. This could be on conveyor belts that bring the material to the embossing tool, an embossing hammer that is applied during an appropriate interval to the material.

In addition, the rotational manner of embossing according to the invention may also be used when the material is presented by other means to the embossing rollers, e.g., when the material to emboss is planar, un-deformed and stamp embossed.

FIG.26illustrates a further example embodiment of an apparatus for embossing foil material on both sides according to the invention (foil material not represented inFIG.26), in the form of a quick-change device2600. The quick-change device2600includes a housing2601with two mountings2602and2603for receiving a roller carrier2604and2605each. Roller carrier2604serves for fastening the first die roller2606which is driven via the drive (not represented inFIG.26) and roller carrier2605serves for fastening the second die roller2607. The roller2604may be pushed into the mounting2602and roller carrier2605into the mounting2603. The housing2601is closed off with a termination plate2608.

In the present example, the second die roller is driven by the driven first die roller2606in each case via toothed wheels2609and2610, which are located at an end of the rollers. In order to ensure the demanded high precision of synchronization, the toothed wheels are produced very finely. Other synchronization means are also possible, e.g., electric motors.

When pushed into the mountings, a roller axle (not shown in theFIG.26) of the first die roller2606is rotatably held in a needle bearing2612in the roller carrier2604and on the other side in ball bearing (also not shown in theFIG.26). The two ends—only one end2615is shown inFIG.26—of the roller carrier2604are held in corresponding opening2616and2617in the housing, or termination plate. For the exact and unambiguous introduction and positioning of the roller carrier into the housing, the housing bottom comprises a T-shaped slot2618, which corresponds to a T-shaped key2619on the roller carrier bottom. The roller axle2620of the second die roller2607is mounted on one side, in the drawing on the left, in a wall2621of the roller carrier2605and on the other side in a second wall2622of the roller carrier. The edges2623of lid2624of the roller carrier are embodied as keys which can be pushed into the corresponding T-slot2625in the housing2601. Here, the one sidewall2621fits into a corresponding opening2626in the housing wall.

In the present description, it is referred often to the first roller and the second roller when describing the pair of rollers that are used to produce the embossed foil material. In the actual embossing system, either one of the first roller and the second roller may be the roller that is driven, this having no impact on the invention.