Patent Description:
The present invention relates to a method and apparatus for the relief embossing of packaging films such as those used in the tobacco and food industry, for chocolate, butter or similar foods. The so-called inner liners originally consisted of integral aluminum foils, which were passed between two rolls for embossing (see, for example, <CIT>).

In parallel with the development of embossing technology and the improved quality and lifetime of the embossing rollers, a change from integral aluminum foils to paper films that were thinner and metal-film coated was implemented for environmental reasons.

At the same time, there was an increased demand around the year <NUM> for attractive technical means to achieve intensified advertising on inner liners.

A known embossing-roller system, such as a pin-up/pin-up system <NUM> in <FIG> - patented by the same inventor in <CIT> - comprises two embossing rolls <NUM> and <NUM> that are mutually movably arranged such that a self-stabilizing effect occurs when the embossing rolls <NUM> and <NUM> intermesh. In a preferred embodiment of the roller system, the rollers have a relative axial clearance of at least one-half to three-quarter tooth pitch (not shown in <FIG>). With these and other measures, otherwise non-compensable unbalance and natural manufacturing tolerances of the roll production by means of milling can be compensated.

From the top view shown <FIG>, which is taken from publication <CIT>, it may be seen between four teeth <NUM>-<NUM> of a roller (roller not shown in <FIG>) one tooth <NUM> from a counter roller (counter roller not shown in <FIG>) positioned in midst of teeth <NUM> and <NUM>. The one tooth <NUM> is shown in transparency using dotted lines. This situation occurs when the roller and the counter roller are rolling against each other for embossing, and is known also under the name pin-up/pin-up embossing method. For a better reading of <FIG>, only one tooth <NUM> of the counter roller is shown, but further teeth of the counter roller are also positioned in a similar manner. <FIG> illustrates a stable running condition of the roller and the counter roller, whereby circles, e.g., circles <NUM>, <NUM>, <NUM> represent teeth from the roller, and triangles illustrate teeth from the counter roller, such as, e.g., tooth <NUM>. A stable running condition means that there is virtually no slip between the roller and the counter roller. Another way of expressing the stable running condition is to say that this is a condition in which pyramids self-adjust and fall in place perfectly. In <FIG> this means that the tooth <NUM> of the counter roll is positioned substantially centrally between teeth of the roller, i.e., between teeth <NUM>, <NUM> and <NUM> for example. It becomes readily apparent to those skilled in the art that in the case of a relatively large play in an axial direction <NUM>, the teeth from the counter roller, e.g., tooth <NUM>, may slip between teeth from the roller, e.g., tooth <NUM> from the counter roller is positioned in the middle of teeth <NUM> and <NUM> from the roller, as illustrated in <FIG>, hence resulting in an unstable running condition. As shown in <FIG>, marked edges <NUM> would then exert a pressure on a foil material to be embossed. Another way to express the unstable running condition is to say that the two rollers are not perfectly falling in place and the foil material during embossing may be pinched by the sidewalls of the pyramids. A slip in the axial direction <NUM> as shown in the <FIG> may be caused by a mechanical clearance <NUM> - as shown in <FIG> - of at least one-half to three-quarter tooth pitch <NUM>. An embossing of foil material with characters made of sets of teeth enables an optical read-out of the embossed characters with a stable contrast of the embossed characters (foil material, sets of teeth for characters, and embossed characters not shown in <FIG>). This may only be achieved if a high and constant pressure is exerted on the rolls and applied during the embossing process, resulting in a position of the teeth as shown in <FIG> (pressure and embossing process not illustrated in <FIG>). In this context, the term stable contrast means that a contrast level is not sensitive or only very weakly sensitive to processing conditions.

Following the prior art taught in <CIT>, the same inventor patented in <CIT> a device for producing embossing effects, which allows embossing on packaging films of signs with location and/or light-source-dependent optical and aesthetic effects in reflected light, as well as security features that are comparatively difficult to copy. These embossing effects enable the designer to add optionally shades that are highly dependent on the viewing angle. However, the original aim of the approach taught by <CIT> was to produce a variable embossing effect that exhibits the same intensity ratios in the reflected light for the viewer independent of the viewing location and without constant adjustment of a roller pressure when embossing. This goal could not be achieved with the approach described in <CIT>.

<FIG> show an operating principle of <CIT>. <FIG> shows embossing rollers <NUM> and <NUM> positioned on opposite sides of a foil material <NUM> to be embossed. The roller <NUM> carries in its configuration of the teeth a design of a character to be embossed, while roller <NUM> is entirely covered by a regular pattern of pyramidal teeth. The embossing roller <NUM> and <NUM> are intended to be positioned such that the illustrated teeth intermingle perfectly, and the embossing rollers rotate around their respective illustrated rotation axis according to the circular arrows. <FIG> is based on <CIT> and shows the embossed material foil <NUM> that results from embossing with rollers <NUM> and <NUM> (see <FIG>), and more specifically at the location indicated by the circle <NUM> in <FIG>. Essentially, a size of a reflecting surface F shown in <FIG> is responsible for the desired effects on reflected light <NUM> from a light beam <NUM>, in accordance with the description in the preceding paragraph. A pitch s, a total tooth height h - also named individual height - as well as possible height H of a tooth <NUM> during machining (machining not illustrated in <FIG>), different from the individual height, show the limits for the achievable truncated pyramidal shapes of the teeth and their possible truncation heights H. In addition, a flatness and an area size of the reflective surface F, i.e., the quality of the manufactured surface may only be controlled to a limited extent in the traditional machining environment.

If for example at least one side of foil material <NUM> is integral aluminum with specific material properties, then with an irradiation intensity of I°=<NUM> of the impinging visible light <NUM>, this aluminum foil surface exhibits a direct reflectance of approximately I'= <NUM> per unit area. On the other hand, a metallized film obtained by vapor deposition of aluminum generally has a direct reflectance of only I"= <NUM> per unit area. Practically, by skillful choice of truncation heights H of embossed truncated pyramidal shapes, four different discernible contrast levels may be achieved which is sufficient for security applications but is insufficient for aesthetic purposes.

The low level of light exploitation resulting from the use of the basic pin-up/pin-up embossing technique is an obstacle to the development of modern, brilliant embossing effects at high production speeds.

<CIT> represents a prior art that has been in use since about <NUM>, and which essentially changed only through the mastery of short pulse laser engraving. The further development of fine-embossing technology proved promising. The laser-based engraving technique has enabled for the first time pin-up/pin-down engraving of embossing rollers, e.g., in <CIT>. <CIT> pointed the way to a high precision, easily reproducible production of complementary embossing rollers, which until at the time of filing of the international application was only possible with great effort. Reliefs were built using exaggerated elevation and pedestals in order to create optically pleasing brilliance in logos. However, this technique did not allow creating half-toning directly but only using some crude approximation.

In order to account for the expected further development of the aesthetic aspects of embossing as well as the tendency of a very-low degree of metallization, the object of the present invention is to create brilliant, high-quality, and operationally easy-to-control on-line-embossing results in foil material such as traditional packaging materials and films such as metallic foils, metallized papers, polymer films or laminates. The strong dependency on the embossing pressure and the viewing angle in <CIT> must be greatly improved, if possible eliminated altogether.

In a first aspect, the invention provides a method of embossing individually light-reflecting areas on a foil material, the method comprising feeding a foil material into a roller nip between a pair of rollers, wherein the pair of rollers comprises a first roller and a second roller, providing each of the first roller and second roller at their respective surfaces at least in a determined perimeter, respectively with a plurality of polyhedron-shaped positive projections and a plurality of negative projections complementary to the positive projections, wherein the determined perimeter comprises at least one positive projection, whereby the plurality of positive projections are arranged according to a <NUM>-dimensional grid, and whereby each one of the plurality of positive projections extends over an individual height from a base side of the positive projection at the surface of the first roller to a top side of the positive projection in a direction away from a rotation axis of the first roller, and each negative projection extends from the surface of the second roller to a bottom side of the negative projection in a direction towards the rotation axis of the second roller. The plurality of polyhedron-shaped 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 polyhedron-like shape in the foil. The method further comprises, for the purpose of.

a step of adjusting for each of the plurality of light-reflecting areas to be provided, an orientation and shape of the corresponding positive projection in the <NUM>-dimensional grid, that is intended to emboss the light-reflecting area.

In a preferred embodiment, the step of adjusting comprises at least designing each one of the plurality of the positive projections of the <NUM>-dimensional grid, by departing from a determined base shape which has a base surface delimited by a base perimeter intended to be positioned on the surface of the first roller and a <NUM>-dimensional shape described by a <NUM>-dimensional shape-contour function, by applying either one operation of the following list:.

In a further preferred embodiment, the step of adjusting comprises at least designing each one of the plurality of the positive projections of the <NUM>-dimensional grid, by departing from a determined base shape which has a base surface delimited by a base perimeter intended to be positioned on the surface of the first roller and a <NUM>-dimensional shape described by a <NUM>-dimensional shape-contour function, by applying either one operation of the following list:.

In a further preferred embodiment, the <NUM>-dimensional grid comprises a tessellation of grid surfaces, each grid surface comprising a grid surface perimeter with a plurality of corners, wherein single ones of the plurality of positive projections are positioned at corresponding corners, each corner comprising at most a single positive projection.

In a further preferred embodiment, the <NUM>-dimensional grid comprises a tessellation of grid surfaces, each grid surface comprising a grid surface perimeter with a plurality of corners, wherein single ones of the plurality of positive projections are positioned in corresponding individual grid surfaces, each individual grid surface comprising at most a single positive projection.

In a further preferred embodiment, the <NUM>-dimensional grid is an unstructured grid.

In a further preferred embodiment, the <NUM>-dimensional grid is a regular grid.

In a further preferred embodiment, the <NUM>-dimensional grid is one of the list comprising: a Cartesian grid, a rectilinear grid, a curvilinear grid.

In a further preferred embodiment, the <NUM>-dimensional grid comprises a plurality of rows and columns, the tessellation of grid surfaces is organized in the plurality of rows and columns, and further single ones of the plurality of positive projections are positioned in corresponding individual grid surfaces in rows. The positive projections are spaced among each other according to a value of a first step function that describes a distance between grid surfaces in a direction of the row. Adjacent rows of positive projections are separated by a value of a second step function that describes a distance between grid surfaces in a direction of the column.

In a further preferred embodiment, wherein in each of the rows of positive projections, between two consecutive positive projections, a second negative projection is provided on the first roller, such that a plurality of second negative projections becomes arranged in the same row as the positive projections, the second negative projections of the row being regularly spaced among each other according to the value of the first step function, and whereby adjacent rows of second negative projections are separated by the value of the second step function. Each second negative projection extends from the surface of the first roller to a bottom side of the second negative projection in a direction towards the rotation axis of the first roller. The method further comprises, from one row to an adjacent row, providing next to a positive projection from the one row in the adjacent alignment a further second negative projection distant from the positive projection in column direction, whereby two consecutive second negative projections in a same column are separated by the value of the second function. The method further comprises providing on the second roller a plurality of second positive projections complementary to the second negative projections, and the plurality of second negative projections seamlessly and gaplessly join with those corresponding second positive projections at the intended embossing of the foil material.

In a further preferred embodiment, the method further comprises providing the first roller at least on the surface in the determined perimeter, with a relief topography comprising at least one of an elevation or a depression of the surface, providing on the second roller a complementary relief topography complementary to the relief topography, whereby the <NUM>-dimensional grid is projected onto the relief topography.

In a further preferred embodiment, the step of providing each of the first roller and second roller at their respective surface with respectively positive and negative projections applies to surfaces of a plurality of determined perimeters, and the <NUM>-dimensional grid is different for each of at least two surfaces of distinct determined perimeters, each of the <NUM>-dimensional grids being associated to its own table of reflectivity values.

In a further preferred embodiment, the individual height (h) is less or equal to <NUM>.

In a further preferred embodiment, the foil material is anyone of the list comprising packaging material and films such as metallic foils, metallized papers, polymer films, laminates and the like.

In a further preferred embodiment, the foil material is for anyone application of the list comprising a seal pack with decoration for, e.g., smoking articles, a blister pack with decoration on a cover foil for, e.g., smoking articles or medication, a soft-wrap for sweet goods, a Tetra Brik (registered trademark) with decoration, a decoration of cover foil for beverage capsules, a wrapping-decoration of chewing gum.

In a further preferred embodiment, the method further comprises operating the pair of rollers in a quick-change device, the quick-change device including a housing with a first and a second mounting for receiving respectively a first roller carrier and a second roller carrier, the first roller carrier configured for fastening the first or the second roller which is driven via a drive and the second roller carrier configured for fastening respectively the second or the first roller, the quick-change device further configured to enable a pushing of the first roller carrier into the first mounting and the second roller carrier into the second mounting.

In a second aspect, the invention provides an embossing device configured for embossing of individually light-reflecting areas on a foil material, the device comprising a pair of roller configured to form a roller nip for admission of the foil material, wherein the pair of rollers comprises a first roller and a second roller,.

each of the first roller and second roller comprising at their respective surfaces at least in a determined perimeter, respectively a plurality of polyhedron-shaped positive projections and a plurality of negative projections complementary to the positive projections, wherein the determined perimeter comprises at least one positive projection. The plurality of positive projections are arranged according to a <NUM>-dimensional grid. Each one of the plurality of positive projections extends over an individual height from a base side of the positive projection at the surface of the first roller to a top side of the positive projection in a direction away from a rotation axis of the first roller, and each negative projection extends from the surface of the second roller to a bottom side of the negative projection in a direction towards the rotation axis of the second roller. The plurality of polyhedron-shaped positive projections are shaped to seamlessly and gaplessly join with those corresponding negative projections at the intended embossing of the foil material, hence enabling a homogeneously jointed embossed polyhedron-like shape in the foil. The device further comprises, for the purpose of.

for each of the plurality of light-reflecting areas to be provided, a corresponding positive projection that is adjusted in an orientation and shape, in the <NUM>-dimensional grid, that is intended to emboss the light-reflecting area.

In a preferred embodiment, each one of the plurality of the positive projections of the <NUM>-dimensional grid, is described by departing from a determined base shape which has a base surface delimited by a base perimeter intended to be positioned on the surface of the first roller and a <NUM>-dimensional shape described by a <NUM>-dimensional shape-contour function, by applying either one operation of the following list:.

In a further preferred embodiment, each one of the plurality of the positive projections of the <NUM>-dimensional grid, is described by departing from a determined base shape which has a base surface delimited by a base perimeter intended to be positioned on the surface of the first roller and a <NUM>-dimensional shape described by a <NUM>-dimensional shape-contour function, by applying either one operation of the following list:.

In a further preferred embodiment, the <NUM>-dimensional grid comprises a tessellation of grid surfaces, each grid surface comprising a grid surface perimeter with a plurality of corners, and wherein single ones of the plurality of positive projections are positioned at corresponding corners, each corner comprising at most a single positive projection.

In a further preferred embodiment, the <NUM>-dimensional grid comprises a plurality of rows and columns, the tessellation of grid surfaces is organized in the plurality of rows and columns, further wherein single ones of the plurality of positive projections are positioned in corresponding individual grid surfaces in rows,.

the positive projections being spaced among each other according to a value of a first step function that describes a distance between grid surfaces in a direction of the row, whereby adjacent rows of positive projections are separated by a value of a second step function that describes a distance between grid surfaces in a direction of the column.

In a further preferred embodiment, in each of the rows of positive projections, between two consecutive positive projections, a second negative projection is provided on the first roller, such that a plurality of second negative projections becomes arranged in the same row as the positive projections, the second negative projections of the row being regularly spaced among each other according to the value of the first step function, and whereby adjacent rows of second negative projections are separated by the value of the second step function. Each second negative projection extends from the surface of the first roller to a bottom side of the second negative projection in a direction towards the rotation axis of the first roller. The device further comprises, from one row to an adjacent row, providing next to a positive projection from the one row in the adjacent alignment a further second negative projection distant from the positive projection in column direction, whereby two consecutive second negative projections in a same column are separated by the value of the second function. The device further comprises on the second roller a plurality of second positive projections complementary to the second negative projections, and the plurality of second negative projections seamlessly and gaplessly join with those corresponding second positive projections at the intended embossing of the foil material.

In a further preferred embodiment, the device further comprises on the first roller at least on the surface in the determined perimeter, a relief topography comprising at least one of an elevation or a depression of the surface, on the second roller a complementary relief topography complementary to the relief topography. The <NUM>-dimensional grid is projected onto the relief topography.

In a further preferred embodiment, on each of the first roller and second roller there is comprised at their respective surface respectively positive and negative projections in surfaces of a plurality of determined perimeters, and the <NUM>-dimensional grid is different for each of at least two surfaces of distinct determined perimeters, each of the <NUM>-dimensional grids being associated to its own table of reflectivity values.

In a further preferred embodiment, the device further comprises a quick-change device configured to operate the pair of rollers, the quick-change device including a housing with a first and a second mounting for receiving respectively a first roller carrier and a second roller carrier, the first roller carrier configured for fastening the first or the second roller which is driven via a drive and the second roller carrier configured for fastening respectively the second or the first roller, the quick-change device further configured to enable a pushing of the first roller carrier into the first mounting and the second roller carrier into the second mounting.

The invention will be better understood through the detailed description of preferred embodiments of the invention, and in view of the figures, wherein.

In a first step towards addressing the object of the invention, the invention departs from prior art reference <CIT> 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 <CIT>.

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 <NUM> to <NUM>. 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.

In <FIG>, 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 in <FIG>), 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 in <FIG>) 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> shows a layout plan of projections corresponding to embossing structures from <FIG>, in fact only a part of the embossing pattern from <FIG>, 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 <NUM> 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 of <FIG> and a corresponding inverse embossing pattern on respective rolls of a pair of embossing rolls, to emboss a foil or inner-liner confers a <NUM>% embossing coverage of the embossed surface.

Returning to <FIG>, 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 in <FIG>). As is apparent from <FIG>, 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 - in <FIG> these 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 <CIT> 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., <CIT>, 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 in <FIG> and <FIG>, only the pressing edges of the embossing structures and not the entire pyramid surface press the film between the embossing rollers (see reference <NUM> in <FIG>), it may be quite easily understood that when using a patrix-matrix type embossing and obtaining for example the embossed foil material as shown in <FIG>, 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 in <FIG>), 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 <NUM>-dimensional grid comprising a tessellation of grid surfaces.

<FIG> contain examples of <NUM>-dimensional grids, in this case so-called regular grids.

<FIG> shows a Cartesian grid <NUM> that comprises a tessellation of squares <NUM>. In this example, in a surface delimited by a determined perimeter enclosing <NUM> squares, i.e., <NUM> squares wide in direction of a row <NUM>, and <NUM> squares wide in a direction of a column <NUM>, each square comprises for example a positive projection <NUM> as represented using diagonal crosses in <FIG>. Each square <NUM> or individual grid surface comprises at most a single positive projection.

<FIG> shows a rectilinear grid <NUM> that comprises a tessellation of parallelepipeds <NUM>. In this example, in a surface delimited by a further determined perimeter enclosing <NUM> parallelepipeds, each parallelepiped comprises for example a positive projection <NUM> as represented using diagonal crosses in <FIG>. Again, each individual grid surface comprises at most a single positive projection.

<FIG> shows a further rectilinear grid <NUM> that comprises a tessellation of rectangles <NUM> of variable sizes, depending of the respective position of the rectangle <NUM> in a row <NUM> and column <NUM>. The rectangles shown in <FIG> may all or partly be comprised in a further surface having a determined perimeter (perimeter not shown in <FIG>) and each comprise a positive projection (also not represented in <FIG>).

<FIG> contain further examples of <NUM>-dimensional regular grids.

<FIG> shows a curvilinear grid that comprises a tessellation of individual grid surfaces <NUM> of variable sizes, each individual grid surface being delimited by two straight lines that extend from a center <NUM>, and two curved lines that originate respectively from concentric oval shapes. In this example, a surface delimited by determined perimeter comprising an oval shape <NUM> and oval shape <NUM> comprises a plurality of individual grid surfaces <NUM>, each comprising for example a positive projection <NUM> as represented using diagonal crosses in <FIG>. Each individual grid surface <NUM> comprises at most a single positive projection <NUM>. From viewing <FIG> it is apparent that a size of the individual grid surface <NUM> may vary from one to another, which makes it possible to have positive projections of sizes corresponding the respective surface of the individual grid surfaces <NUM>. However, it is also possible to have identical positive projections as long as this fits in the smallest of the individual grid surfaces <NUM>.

<FIG> shows a curvilinear grid <NUM> comprising curved lines that delimit individual grid surfaces <NUM> in rows <NUM> and column <NUM>. In this example a surface delimited by a determined perimeter that surrounds a number of individual grid surfaces <NUM> in <NUM> rows <NUM> of <NUM> columns <NUM>, comprises in each individual grid surface <NUM> a positive projection <NUM> as represented using diagonal crosses in <FIG>. Each individual grid surface <NUM> comprises at most a single individual positive projection <NUM>.

<FIG> contains 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> shows an unstructured grid <NUM> represented in dashed lines <NUM>, which form triangles <NUM>. Each triangle <NUM> has at least one side in common with an adjacent triangle <NUM>, in some cases two sides, or even three sides. Corners of the triangles <NUM> are indicated by circles <NUM>. In this example, the completely represented part of grid <NUM> comprises at each corner <NUM> a positive projection such as a first positive projection defined by three surfaces <NUM> or a second, adjacent positive projection defined by three surfaces <NUM>. While <FIG> shows a top view of the grid <NUM>, 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 corners <NUM>. The positive projections have lower corners such as the first lower corner <NUM> and the second lower corner <NUM>, which may be in common from one positive projection to another. From viewing the unstructured grid <NUM> it is apparent that each positive projection may have an individual pyramidal shape that varies from one to another.

<FIG> shows a further unstructured grid <NUM> represented by straight lines <NUM>, that define triangles <NUM> having corners <NUM> represented in circles. Each triangle <NUM> has at least one side in common with an adjacent triangle <NUM>, in some cases two sides, or even three sides. In the present example, the completely represented part of grid <NUM> comprises at each corner <NUM> a positive projection <NUM> having a circular outer perimeter <NUM> at the surface of the roller (surface of the roller not shown in <FIG>) centered on a corner <NUM>. A diameter of the outer perimeter <NUM> of the positive projection <NUM> may be adjusted to be tangent to a further outer perimeter <NUM> of a neighboring positive projection <NUM>. From viewing the unstructured grid <NUM> it 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 <NUM>-dimensional grid, and the individual polyhedric shape of each tooth must be formed in line with a table of reflectivity values for the <NUM>-dimensional grid that describes which value of reflectivity of the embossed foil material the embossing of each tooth must produce. Such a <NUM>-dimensional grid may for example comprise <NUM> rows of <NUM> individual embossing teeth, that is <NUM> embossing teeth, and the table of reflectivity values may for example be given as percentages as follows:.

In the above table, it is, for example, indicated that for row <NUM>, column <NUM>, the shape of the embossing tooth should be made to emboss individual light-reflecting areas that in total have a reflectivity of <NUM>%. Another example for row <NUM>, column <NUM> indicates that the shape of the embossing tooth should be made to emboss individual light-reflecting areas that have a total reflectivity of <NUM>%. 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 <NUM>-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 with <FIG>. 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 <NUM>%, while applying an offset operation of <NUM>% may for example lead to a reflectivity of <NUM>% and an offset operation of <NUM>% may lead to a reflectivity of <NUM>%. 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 for <FIG>.

Referring now to <FIG>, 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 of <FIG> to refer geometric dimensions of a positive projection in term of individual height h, possible truncation or modified height H and pitch s.

The table in <FIG> is 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 shape <NUM> of a positive projection represented generally in dashed lines above the surface <NUM> of an embossing roller (roller not shown in <FIG>) to obtain a designed positive projection <NUM> represented in a sectional view by a shape with textured surface. In cell a) of the table, the designed positive projection <NUM> is of course on the side above the surface <NUM>, but for reasons of better understanding, its sides are extended below the surface <NUM> with dashed lines <NUM> to show the outline of the initial determined base shape <NUM>. Arrows such as arrows <NUM> in cell a) are used to indicate how the determined base shape <NUM> evolves to become the designed positive projection <NUM>, as appropriate. In cell b) of the table, the individual height h of the determined base shape <NUM> is indicated for a better understanding.

More specifically, referring to cell a), this shows an operation of shaping an upper part of the determined base shape <NUM> to obtain the designed positive projection <NUM>, the resulting shape of the upper part, i.e., the designed positive projection <NUM> having a modified height H reduced by an individual offset loff as compared to the individual height h, whereby
<MAT>.

The designed positive projection <NUM> is intended to be positioned at the surface of the first roller, which is represented as a reference at the surface <NUM> in cell a).

In cell b), in addition to applying a second individual vertical offset loff2 (loff2 not represented in cell b)), in a direction perpendicular to the surface <NUM> (which is the same as in cell a)) to modify an overall height of the determined base shape <NUM> to 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 surface <NUM> is applied to obtain a designed positive projection <NUM>. It is noted that in the example of cell b), for sake of a better understanding, the base points <NUM> and <NUM>, which are virtual points, and indicated at the end of virtual prolongations <NUM> of sides of the designed positive projection <NUM> are also subjected to the vertical and lateral shift.

In cell c), a determined base shape <NUM> represented again in sectional view has a similar shape as the determined base shape <NUM>, but a designed positive projection <NUM> has a more complex top side structure comprising two summits <NUM> and <NUM> and more than <NUM> sides, at various angles of inclinations, in contrast to the determined positive projection <NUM> from 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 shape <NUM> is shaped to obtain a designed positive projection <NUM> that has for one summit <NUM> a modified height H2 according to a third individual offset loff3, 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 H3 of summit <NUM>. 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 <NUM> dimensions as cell c) represents a cross section, but if the whole surface of the designed positive projection <NUM> is taken under consideration, this may be obtained by applying to a <NUM>-dimensional shape of the determined base shape <NUM>, described by a <NUM>-dimensional shape-contour function, a <NUM>-dimensional offset, which results in the different heights of the designed positive projection. The designed positive projection <NUM> is 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 shape <NUM> is executed to obtain a designed positive projection <NUM>, the operation being configured such to maintain a base surface and base perimeter of the determined base shape - represented by the section delimited by points <NUM> and <NUM> in the sectional view of cell d) - intended to be positioned at the surface of the first roller - represented here by the surface <NUM>. This results in an overall deformation of the determined base shape <NUM> in height direction in proportion to an individual gain factor Igain. For the height H of the designed positive projection, we have the relation:
<MAT>.

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 projection <NUM>, except on the points <NUM> and <NUM> that delimit the base surface at the surface of the roller of the determined base shape of the designed positive projection <NUM>.

In general, it may be noted that the determined base shape has a <NUM>-dimensional shape described by a <NUM>-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 <NUM>-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 <NUM>-dimensional gain-factor function being configured to be applied to the <NUM>-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 <NUM>-dimensional gain factor.

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

In cell g), the determined base shape <NUM> is represented partly in dashed lines for its top side, and partly in a texture shape that corresponds to a designed positive projection <NUM>. 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 shape <NUM> according to an individual shape <NUM> along an individual intersection <NUM> with the determined base shape <NUM>. The individual shape <NUM> is represented above the designed positive projection <NUM> for a better understanding. In a further preferred embodiment the individual shape not only affects the shape of designed positive projection <NUM>, 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 surface <NUM>, 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 projection <NUM> corresponds to a pyramid that is cut-off parallel to the surface <NUM>. The designed positive projection <NUM> is 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 side <NUM> of a designed positive projection <NUM>.

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 side <NUM> of a designed positive projection <NUM>.

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 [<NPL>].

An offset in <NUM>-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:
<MAT>
which, when expressed with the transformation matrix is:
<MAT>.

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:
<MAT>
and using matrices:
<MAT>.

Referring now to <FIG>, 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 <NUM>-dimensional vector <NUM>. The base perimeter in this example is a rectangle defined by points <NUM>, <NUM>, <NUM> and <NUM>. 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 (see <FIG>) are comprised in a range between <NUM> and <NUM>.

The principle described in <CIT> allowed the tobacco industry in year <NUM> (prior art) to manufacture from <NUM> to about <NUM> sections/min for cigarette packaging in online operation, while over <NUM> sections/min are possible at the time of filing the present patent application.

<FIG>, <FIG> and <FIG> show 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> shows an example comprising positive projections embodied as pyramidal teeth <NUM>, each pyramidal tooth having a substantially square base, but in the overall, the pyramidal teeth being designed to comprise truncations, e.g., truncations <NUM>, <NUM>, <NUM> and <NUM> that 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 tooth <NUM> to another tooth <NUM>. 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 in <FIG>) to its top side in a direction away from a rotation axis of the roller (rotation axis also not shown in <FIG>). The truncations may be obtained using operations described for cells g) and h) in the table of <FIG>, 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> shows that truncation <NUM> is at a different angle than truncation <NUM>, and that the overall height of the pyramid with truncation <NUM> is smaller than the overall height of the pyramid with truncation <NUM>.

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 line <NUM> and a second axial line <NUM> shown 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 line <NUM> and the second axial line <NUM> are 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 AS1 and the radial step RS1 may 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 of <FIG> this appears to correspond to a curved plane that is at its nearest to the roller in the lower corner of <FIG> and 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 in <FIG>.

<FIG> shows an example comprising hexagonal pyramidal teeth <NUM>, 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 tooth <NUM> is smaller toward the inside of the overall surface, as for a peripheral tooth <NUM>. 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 in <FIG>) to its top side in a direction away from a rotation axis of the roller (rotation axis also not shown in <FIG>).

For example, <FIG> shows a first individual widening of an angle Phi (Phi not shown in <FIG>) on the top of the hexagonal pyramid <NUM>, Phi being shown in <FIG> and which is different from a second individual widening of angle on the top of the hexagonal pyramid <NUM>, which leads to different heights among pyramids <NUM> and <NUM>. 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 of <FIG>, 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 line <NUM> and a fourth axial line <NUM> shown 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 line <NUM> and the fourth axial line <NUM> are separated in distance by a radial step RS2.

<FIG> shows 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 of <FIG>. 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> shows an example similar to the example of <FIG>, but applying the principle to positive projections P and negative projections N on a same roller instead of positive projections only as shown in <FIG>.

In <FIG>, 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 in <FIG>, to a bottom side of the second negative projection N in a direction towards the rotation axis of the motor roller (not shown in <FIG>). 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 of <FIG>, since the positive projections are separated by the axial step, then compared to the illustration of <FIG>, the length of a base side of the pyramids is in substance half of that of the pyramids in <FIG>. Not shown in <FIG> is 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 in <FIG> is applied in the present invention, according to which, and in contrast to <CIT>, 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 <CIT>, where only the pyramid height was utilized for the design. The multiple options are described herein above.

Referring now to <FIG>, this illustrates examples of embossing roller surfaces in which a roller is provided with a relief topography, and positive projections are arranged in a <NUM>-dimensional grid projected thereon.

More specifically, <FIG> shows a roller surface <NUM> of a first roller (first roller not represented in <FIG>) represented as a straight line with a relief topography <NUM> provided 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 <NUM>-dimensional grid is projected on a surface of the relief topography <NUM>. A plurality of positive projections embodied as conical structured teeth - similar to the ones represented in <FIG> - 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 <NUM>-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 topography <NUM>). In this example, the conical structured teeth are obtained by executing an operation described for cell a) in the table of <FIG>. 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 to <FIG>, 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 <NUM>-dimensional grid projected thereon.

<FIG> also shows an example a roller surface <NUM> of a first roller (first roller not represented in <FIG>) represented as a straight line with a relief topography <NUM> provided thereon, which is this example appears as an elevation above the roller surface similar to a hill. A <NUM>-dimensional grid is projected on a surface of the relief topography <NUM>. A plurality of positive projections embodied as conical structured teeth - similar to the ones represented in <FIG> - is arranged according to the <NUM>-dimensional grid similar as in <FIG>, with the difference that the conical structured teeth are oriented perpendicularly to the roller surface <NUM> - this is illustrated in <FIG> by the lines oriented in the axis of the conical structured teeth and perpendicular to the line <NUM>, which rather than being parallel to the roller surface, is parallel to the rotation axis of the roller, while in <FIG>, 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 line <NUM>.

Continuing the explanation of <FIG> show complete examples of embossing surfaces according to the invention with.

Drawn circles in <FIG> mark particularly interesting embossing points K1 and K2. More precisely, K1 shows, e.g., how large-area brilliant stripes of embossed foil material are shaped. K2 shows embossed results of particularly shaded or matted halftone dots in the embossed foil material. While not shown in <FIG>, 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> depicts an interaction between two complementary patrix/matrix embossing rollers <NUM> and <NUM>, with an endless web material <NUM> (shown as a limited piece in <FIG>) such as inner-liner foils, polymeric foils, metallic foils or foils used in product packaging applications. The magnified part <NUM> shows an example of embossing structures according to the present invention.

<FIG> shows a detailed magnification <NUM> of an embossing <NUM> of 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 in <FIG> are simple examples of the above-mentioned embossing technology.

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

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

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

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

<FIG> shows 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> illustrates a further example embodiment of an apparatus for embossing foil material on both sides according to the invention (foil material not represented in <FIG>), in the form of a quick-change device <NUM>. The quick-change device <NUM> includes a housing <NUM> with two mountings <NUM> and <NUM> for receiving a roller carrier <NUM> and <NUM> each. Roller carrier <NUM> serves for fastening the first die roller <NUM> which is driven via the drive (not represented in <FIG>) and roller carrier <NUM> serves for fastening the second die roller <NUM>. The roller <NUM> may be pushed into the mounting <NUM> and roller carrier <NUM> into the mounting <NUM>. The housing <NUM> is closed off with a termination plate <NUM>.

In the present example, the second die roller is driven by the driven first die roller <NUM> in each case via toothed wheels <NUM> and <NUM>, 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 the <FIG>) of the first die roller <NUM> is rotatably held in a needle bearing <NUM> in the roller carrier <NUM> and on the other side in ball bearing (also not shown in the <FIG>). The two ends-only one end <NUM> is shown in <FIG>-of the roller carrier <NUM> are held in corresponding opening <NUM> and <NUM> in 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 slot <NUM>, which corresponds to a T-shaped key <NUM> on the roller carrier bottom. The roller axle <NUM> of the second die roller <NUM> is mounted on one side, in the drawing on the left, in a wall <NUM> of the roller carrier <NUM> and on the other side in a second wall <NUM> of the roller carrier. The edges <NUM> of lid <NUM> of the roller carrier are embodied as keys which can be pushed into the corresponding T-slot <NUM> in the housing <NUM>. Here, the one sidewall <NUM> fits into a corresponding opening <NUM> in the housing wall.

Claim 1:
A method of embossing individually light-reflecting areas on a foil material, the method comprising
feeding a foil material into a roller nip between a pair of rollers, wherein the pair of rollers comprises a first roller and a second roller,
providing each of the first roller and second roller at their respective surfaces at least in a determined perimeter, respectively with a plurality of polyhedron-shaped positive projections and a plurality of negative projections complementary to the positive projections, wherein the determined perimeter comprises at least one positive projection,
whereby the plurality of positive projections are arranged according to a <NUM>-dimensional grid,
whereby each one of the plurality of positive projections extends over an individual height from a base side of the positive projection at the surface of the first roller to a top side of the positive projection in a direction away from a rotation axis of the first roller, and each negative projection extends from the surface of the second roller to a bottom side of the negative projection in a direction towards the rotation axis of the second roller;
the method being characterized in that
the plurality of polyhedron-shaped 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 polyhedron-like shape in the foil material,
and in that it comprises, for the purpose of
- providing a plurality of light-reflecting areas on the foil material, that are intended to reflect light in line with a table of reflectivity values for the <NUM>-dimensional grid, according to an orientation and shape of each of the plurality of light-reflecting areas, and
- enabling a perception by the human eye of a user, of the intended reflected light on a determined wide viewing angle covered by reflected light from any of the light-reflecting areas,
a step of adjusting for each of the plurality of light-reflecting areas to be provided, an orientation and shape of the corresponding positive projection in the <NUM>-dimensional grid, that is intended to emboss the light-reflecting area.