Patent Description:
In the packaging industry, cardboard boxes are often made from cardboard sheets. The cardboard sheets can be processed in an assembly such as a folder-gluer arrangement in which they are printed (when necessary), cut and creased, and then folded and glued so as to form flat-folded boxes, also oftentimes referred to as "folding boxes".

Corrugated cardboard is a material typically comprising a fluted corrugated sheet, and two linerboards applied on each side of the fluted corrugated sheet. Corrugated cardboard combines light weight with high strength and is especially suitable as packaging material.

In order to fold the cardboard sheet, crease lines in perpendicular directions need to be created. Some of the crease lines will then coincide with the direction of the fluting, while others will be in a transverse direction. The crease lines can be made in a platen press machine, where a die is provided with a protruding edge that is pressed against the cardboard sheet to create the crease lines. It is also possible to form crease lines by using a rotating creasing disc provided with a protruding annular creasing ridge. The creasing disc is typically incorporated into a folder-gluer machine. The folder-gluer machine can also be referred to as a converting machine or converting inline machine. The converting machine converts or changes a web or sheets of material into an intermediate form or finished flat-folded boxes.

The precision of the folding process is dependent on the quality of the crease lines applied on the cardboard, i.e. on the correct position, the regularity of the shape and the depression depth of the crease. The sharper the creasing ridge becomes, the better the quality of the crease applied on the cardboard. However, sharp creasing ridges can tear the cardboard.

When the creasing ridge is applied in the direction transverse to the longitudinal direction of the flutes, the compression force from the creasing tool tends to be distributed over a plurality of points where the top paper liner and the inner fluted corrugated sheet are connected. However, if the crease line is to be formed in a direction coinciding with the longitudinal direction of the flutes, there is a large variation of the bending resistance of the cardboard. Consequently, the top linerboard may rupture if pressure is applied where the top paper liner and the inner fluted corrugated sheet are disconnected.

Documents <CIT> and <CIT> disclose creasing tools for producing a crease-line in a fibrous substrate. The creasing tools have a central portion and a fishbone-shaped peripheral portion.

In view of the above-mentioned problems, it is an object of the present invention to provide a creasing tool and a method of forming well-defined and precise crease lines while reducing the risk of tearing the paper liner.

The object of the present invention is solved by a creasing tool according to claim <NUM> and a method according to claim <NUM>.

According to a first aspect of the present invention, it relates to a creasing tool configured to create a crease line in a fibrous substrate, the creasing tool comprises a contact portion having a base surface and a relief portion, the relief portion is provided as a protruding pattern extending from the base surface and is configured to press against said fibrous substrate,.

The fibrous substrate is also referred to as corrugated cardboard substrate in the context of this invention. For a creasing tool in the form of a creasing disc, the longitudinal direction is in the direction of rotation of the creasing disc. The longitudinal direction is thus extending around the circumference of the creasing tool.

The invention is based on a realization that the deformation from the creasing tool needs to be gradually distributed over the fibrous substrate to touch both the weak areas where the paper liner and the corrugated layer are disconnected and the stronger areas where those two elements are connected. This will create a more distributed pressure onto the fibrous substrate, regardless of where the crease-line forming portion on the creasing tool contacts the fibrous substrate. The peripheral deformation portion is thus configured to apply a gradually increased contact pressure on the fibrous substrate in a direction towards the crease-line forming portion.

The plurality of discrete segments extending in a transverse direction apply pressure on the fluting of the fibrous substrate not only along the direction in which the fluting extends. With other words, the discrete segments work on the fluting to make a gradual transition into the main crease line. This helps preventing the tearing of the sheet around the main crease line.

In an embodiment, the crease line-forming portion and the peripheral deformation portion are connected. This means that the relief portion is continuous from the crease-line forming portion to the peripheral deformation portion.

Continuous in the context of the present invention means that the crease-line forming portion is in the shape of a line or a surface area with a continuous protruding relief pattern projecting from the base surface.

The relief portion can be centrally arranged on the contact portion. In an embodiment, the peripheral deformation portion is arranged laterally of the crease-line forming portion on at least one side thereof.

Preferably, the peripheral deformation portion is arranged on both sides of the crease-line forming portion. In this way, the peripheral deformation portion can extend over a larger distance on the fibrous substrate and reduces the risk for rupture on both sides of the crease-line forming portion.

The crease-line forming portion can be a continuous line. The line can be straight. Alternatively, the line can be provided with a zigzag shape.

In an embodiment, the crease-line forming portion is protruding further from the base surface than the peripheral deformation portion. The difference in height enables the formation of a well-defined crease line. In an embodiment, there is a discontinuity in the junction between the crease-line forming portion and the peripheral deformation portion, whereby the transition between the crease-line forming portion and the peripheral portion is discontinuous. In other words, there is not a constant gradual slope in the transition.

The peripheral deformation portion is preferably downwardly sloped at an angle in a direction from the crease-line forming portion and towards an edge of the creasing tool. The angle is defined in relation to the rotation axis of the tool.

This gradually increases the compression depth towards the central portion of the creasing tool when the creasing tool is in contact with the fibrous substrate. The peripheral deformation portion can be downwardly sloped in at an angle ranging from <NUM>° to <NUM>°, preferably of from <NUM>° to <NUM>°. The inclined outer surface of the creasing tool allows for a smoother contact angle between the creasing tool and the inner linerboard, thereby giving the possibility trough the mechanical calibration to manage the total width of the crease mark and thereby increase the folding angle without stress or rupture. For most cardboard substrates, angles larger than <NUM>° will typically not allow to take the full advantages of the transverse segment design. Moreover, it can concentrate the mechanical pressure on a small surface which could create an increased tearing phenomenon on the inner liner.

In an embodiment, the transverse surface areas in the peripheral deformation portion are linearly shaped and have a proximal portion located in the crease-line forming portion and a distal end shaped as a free end.

In an embodiment, the creasing tool further comprises a midrib and wherein the midrib is protruding further from the base surface than the proximal portion of the transverse surface areas. The difference in height will enable the formation of a well-defined crease line. Hence, there is a discontinuity in the junction between the crease-line forming portion and the peripheral deformation portion, whereby the transition between the crease-line forming portion and the peripheral deformation portion is discontinuous (i.e. does not show a constant gradual slope in the transition).

The transverse surface areas may have a larger cross-sectional area in their proximal portion than in their distal portion. This may achieve a less sharp crease line and can be especially used when a larger folding zone is desired. This type of transverse surface areas may be advantageous for creasing discs used as pre-creasers. The pre-creasing disc and a downstream located main creasing disc provide for a two-step crease-line forming process. This allows for a gradual and smooth crease-line forming process.

The transverse surface areas are in the context of the present invention defined as linear elements, which are curved, and may have a uniform or varying thickness.

The crease-line forming portion can be located centrally on the contact portion and the transverse surface areas on the first side and second side of the crease-line forming portion can be mirrored around a central axis defined by the crease-line forming portion and preferably offset in relation to each other. As example, the transverse surface areas on the first side can be offset in relation to the transverse surface areas on the second side. Hence, the transverse surface areas are placed so that they alternate. Hence, the pattern of the creasing tool can resemble to a herringbone. Such an arrangement provides distributed mechanical pressure applied by the creasing tool on the linerboard. This distributes the deformation footprint from the peripheral portion such that there is constantly a transverse segment contacting the fibrous substrate.

In one embodiment, the transverse surface areas can be straight. This has a technical effect that the transverse surface areas can extend over a greater length than if they were curved. In an embodiment, the transverse surface areas can have a consistent cross-sectional area along their length.

In another embodiment, the transverse surface areas are shaped as linear elements and wherein the linear elements are converging at the central crease-line forming portion, whereby the proximal portions of the linear elements form the crease-line forming portion. This arc-shape enables the transverse surface areas to form a substantially straight central creasing line on the fibrous substrate. This also enables a gradual transition as a curved edge is found to be smoother in deforming the flutes.

The present creasing tool can be used in a slotter assembly of a converting machine, which is configured for creating flat-folded cardboard boxes.

In an embodiment, the present creasing tool is provided in a platen press. The creasing tool can be a die, configured to be moved up and down and press against the fibrous substrate in the vertical direction. Alternatively, the creasing tool can be provided as a creasing disc.

The discrete segments are extending at an angle in relation to a central axis defined by the central crease-line forming portion.

The creasing tool can be generally ring-shaped. This allows for easily mounting the creasing tool e.g. on a cylinder or a shaft of a creasing device. In this way, the crease lines can be applied on the cardboard by rotating the creasing tool and thereby bringing the creasing tool into contact with the cardboard. In an embodiment, the creasing tool can be provided in two half-ring-shaped parts, such that it can be mounted around a shaft without disconnecting the ends of the shaft. The two parts can be attached together by fasteners (such as bolts or screws) and may optionally be provided with attachment brackets, which cooperate with the fasteners and creasing tool parts in order to form a rigid disc assembly.

According to a second aspect, the present invention relates to a converting machine such as a folder-gluer machine, comprising a creasing tool configured as a creasing disc as per the first aspect of the present invention, wherein the creasing disc is mounted in the converting machine such that the transverse surface areas are extending in a transverse direction at an angle in relation to the central axis and in the direction of rotation of the disc, said angle being less than <NUM> degrees such that the distal ends of the transverse surface areas are brought into contact with the fibrous substrate before the proximal portions of the discrete segments.

According to a third aspect, the invention relates to a method of creating a crease-line in a fibrous substrate with a creasing tool according to the first aspect of the present invention, the method comprises the steps of:.

In an embodiment, the transverse length of the transverse surface areas is equal or larger than the flute distance. Hence, each discrete transverse surface areas in the peripheral portion applies a compression force on at least two flutes, during formation of the crease, such that the risk of tearing or otherwise damaging the linerboard is reduced.

The creasing tool can comprise a variable number of transverse surface areas, this number being led by the number of transverse surface areas simultaneously in contact with the cardboard, less than per linear centimeter, preferably less than per linear centimeter. A lower number of transverse surface areas might not provide a sufficiently sharp folding line, while a higher number of transverse surface areas would create a too smooth outer surface on the creasing tool and the creasing ring may not create a sufficient difference of pressure compared to the peripheral portion which does not sufficiently define the folding line.

Preferably, at every position along the crease-line forming portion of the creasing tool, at least a part of a transverse surface areas is present on the outer surface of the creasing tool.

Further advantages and features will become apparent from the following description of exemplary embodiments of the present invention and from the appended figures, in which like features are denoted with the same reference numbers and in which:.

<FIG> shows an example of an intermediate blank <NUM> made from corrugated cardboard and which is used for manufacturing a folding box <NUM>', such as the one shown in <FIG>.

When a folding box <NUM>' is manufactured, a fibrous substrate <NUM> in the form of a cardboard web or sheet goes through a plurality of workstations in a converting machine <NUM> that print, cut to shape, prepare the fibrous substrate <NUM> for folding, glue and fold the fibrous substrate <NUM>. The intermediate blank <NUM> in <FIG> has been creased, cut to shape and prepared for folding. As illustrated, the intermediate blank <NUM> may present generally a rectangular flat shape with two parallel edges of larger length. In order to create a folding box <NUM>', the intermediate blank <NUM> needs to be further folded and glued in separate processing modules of the converting machine <NUM>. The folding box <NUM>' can in a final step be assembled to form a three-dimensional box <NUM>" as the one illustrated in <FIG>.

As shown in <FIG>, the intermediate blank <NUM> comprises a front edge <NUM> which should be placed forward and perpendicular to a processing/driving direction FD the converting machine <NUM>. As schematically illustrated in <FIG>, the front edge <NUM> is typically entered into folding-gluing modules <NUM> of the converting machine <NUM> which will subsequently fold and glue the blank <NUM>. The converting machine <NUM> comprises several units aligned along the longitudinal axis and the driving direction FD of the sheets.

In order to enable the blank <NUM> to be folded into a three-dimensional box, a plurality of crease lines <NUM>, <NUM> are needed. Different format and models of folding boxes <NUM>' have different number and positions of the crease lines <NUM>, <NUM>. The illustrated intermediate blank <NUM> and the configuration of the cuts and crease lines are just an example of numerous different intermediate blanks <NUM> which can be used for producing a folding box <NUM>' suitable for forming a three-dimensional folded box.

As illustrated in <FIG>, the crease lines <NUM>, <NUM> of the exemplary illustrated intermediate blank <NUM> are distinguished into two groups, where a first group <NUM> is configured as parallel crease lines 11a, 11b, 11c, 11d which are coinciding with the driving direction FD of the folder-gluer machine <NUM>. A second group of crease lines <NUM> are perpendicular crease lines 12a, 12b, and are thus perpendicular to the first group of parallel crease lines 11a, 11b, 11c, 11d.

Two lateral edges of smaller length define a left edge <NUM> and a right edge <NUM> are provided. The left edge <NUM> presents cutouts along its two end portions so as to define a flap <NUM> in the middle of the left edge <NUM>. Front 12a and rear crease lines 12b of the second group of crease lines <NUM> are respectively parallel to the front and rear edges <NUM> and <NUM> define a central portion 1a of the blank <NUM> which is intended to constitute the peripheral face of the folding box <NUM>' when assembled to form a three-dimensional box. The central portion 1a is placed between a rear portion 1b, which is intended to constitute the bottom face, and a front portion 1c which is intended to constitute the upper face of the folding box <NUM>" when assembled to form a three-dimensional box <NUM>".

The first group of parallel crease lines <NUM> are typically parallel to the left and right edges <NUM> and <NUM>, as well as to flutes <NUM> of the corrugated layer of the cardboard. This group of parallel crease lines <NUM> may extend along the whole width of the central portion 1a. One of the crease lines 11a is adjacent to the flap <NUM>, as the other of the crease lines 11c, called central crease, is aligned with the longitudinal axis A. In line with crease lines <NUM> and central crease 11a, the rear and front portions 1b and 1c can in some embodiments be cut so as to create slits <NUM> extending on the whole width of the rear and front portions 1b and 1c.

The slits <NUM> define respectively two pairs of panels in each of the rear and front portions 1b and 1c, respectively a first pair of large rear panels 6b and 6b', a second pair of large front panels 6c and 6c', a first pair of small rear panels 7b and 7b' and a second pair of small front panels 7c and 7c'. The large rear and front panels 6b, 6c and 6b', 6c' are located respectively on each side of a large central panel 6a and 6a'. In a similar manner small rear and front panels 7b, 7c and 7b', 7c' are located respectively on each side of a small central panel 7a and 7a'.

Crease lines <NUM>, <NUM> and their slits <NUM> enable to fold the blank <NUM> into a folding box <NUM>' with a rectangular shape, each crease line <NUM>, <NUM> defining a folding line (see <FIG>). During the folding process, glue is typically deposited onto the flap <NUM> and the large left central panel 6a is thus joined to the small right central panel 7a'.

Many different configurations of a converting machine <NUM> are possible. The schematically illustrated and exemplary converting machine <NUM> in <FIG> comprises successively from upstream to downstream in the driving direction FD a loader <NUM> for automatically loading the fibrous substrate <NUM> in the form of sheets, a feeder <NUM>, optionally a plurality of flexography printing units 22a to 22d, a converting unit with at least one slotter assembly <NUM> and at least one cutting unit <NUM>, a waste-stripping and an optional vibrating unit <NUM>, and a folding-gluing unit <NUM>. The converting machine <NUM> may also further comprise optional modules <NUM> such as a counting-ejecting unit, a bundler and a palletizer (represented partially with dotted lines in <FIG>).

As illustrated in <FIG>, the slotter assembly <NUM> processes printed fibrous substrates <NUM> exiting from the last printing unit 22d and transforms them into intermediate blanks <NUM> (see <FIG>). The slotter <NUM> assembly is equipped with various rotary tools that comprise cutting tools or knives that form the edge cuts (1b, 1a and 1c as seen in <FIG>), the slits <NUM>, and the cuts delimiting transversally the flap <NUM>, and creasing devices or creasers that form the longitudinal crease lines <NUM>. It will be noted that the transverse crease lines <NUM> are produced upstream or downstream of the slotter <NUM> (depending the type and configuration of the converting machine) or are initially provided in the fibrous substrate <NUM>.

The rotary tools are mounted on transverse bearing shafts driven in rotation by shaft motors. The speed of rotation of the tools preferably corresponds to the operating speed, i.e. the drive speed and running speed T of the fibrous substrate <NUM>.

In the illustrated embodiment, the slotter <NUM> comprises, from upstream to downstream, a precreasing section <NUM>, with a first pair of shafts positioned one above the other. The precreasing section <NUM> prepares the cardboard for the subsequent formation of the priority folding line. The precreaser is thus configured to create a precreasing area on the fibrous substrate <NUM>, which is a partially deformed area on the fibrous substrate <NUM>. The lower shaft is provided with a lower precreaser <NUM> and the upper shaft carries an upper precreaser <NUM>, which is the counterpart of the lower precreaser <NUM>. The precreasing section <NUM> carries out a first initial creasing operation, as the longitudinal crease lines <NUM> are being creased in two successive operations.

A first slotting section <NUM>, with a second pair of shafts positioned one above the other, is mounted downstream of the precreasing section <NUM>. The upper shaft of the first slotting section <NUM> is provided with a disk equipped with knives <NUM> and the lower shaft is provided with a lower counter blade <NUM>. The first slotting section <NUM> cuts the slits <NUM> placed at the rear of the blank <NUM>.

A creasing section <NUM>, with a third pair of shafts positioned one above the other, is mounted downstream of the first slotting section <NUM>. The lower shaft of the creasing section <NUM> is provided with a lower creaser <NUM> and the upper shaft is provided with an upper creaser <NUM>, which is the counterpart of the lower creaser <NUM>. The creasing section <NUM> carries out the second and final creasing operation, including the formation of the priority crease line and thus ensures the permanent and precise marking of the longitudinal crease lines <NUM>.

A second slotting section <NUM>, with a fourth pair of shafts positioned one above the other, is mounted downstream of the creasing section <NUM>. The upper shaft of the second slotting section <NUM> is provided with a disc equipped with knives <NUM> and the lower shaft is provided with a lower counter blade <NUM>. The second slotting section <NUM> cuts the slits <NUM> positioned at the front of the blank <NUM>.

In order to cut out the glue flap <NUM> and make the rear cut and the front cut of the flap <NUM>, the processing unit <NUM> may comprise a device <NUM> for processing the fibrous substrates <NUM>. The device <NUM> is placed in the creasing section. Given the proximal position of the flap <NUM> on the blank <NUM>, the device <NUM> is preferably mounted on the operator-side end of the upper shaft in the creasing section <NUM>.

The lower and upper pre-creasers <NUM> and <NUM> as well as the lower and upper creasers <NUM> and <NUM> are creasing devices with creasing tools <NUM>. Accordingly, the creasing tools <NUM> are mounted in the creasing section <NUM> on the shafts, which function as a support for the respective creasing tool <NUM>. It is also possible to arrange the precreaser <NUM> and the creaser <NUM> either above or below the fibrous substrate <NUM>.

In <FIG> a creasing tool <NUM> as known in the state of the art is schematically illustrated. The creasing tool <NUM> can be used in the precreasing section <NUM> and the creasing section <NUM> (see <FIG>). The creasing tool <NUM> is ring-shaped and can be mounted on a shaft of a converting machine <NUM>, as long as the inner diameter of the creasing tool <NUM> is chosen according to the respective shaft dimensions. The ring-shaped creasing tool <NUM> can be provided in two half-ring-shaped parts such that it can be mounted around the shaft and form a complete ring when mounted.

The creasing tool <NUM> comprises a relief portion <NUM> with a crease-line forming portion <NUM> in the shape of a creasing ridge or midrib <NUM> on an outer surface of the creasing tool <NUM>. By pressing the relief portion <NUM> against the fibrous substrate <NUM>, crease lines <NUM>, <NUM> can be formed by deforming the linerboard and the flutes <NUM> of the fibrous substrate <NUM>.

Now referring to <FIG>, in which embodiments of a creasing tool <NUM> according to the present invention are illustrated. As can be seen in the embodiment illustrated in <FIG>, the disc-shaped creasing tool <NUM> has a contact portion <NUM> with a total width W. The creasing tool <NUM> can be provided in two parts 53a, 53b, such that it can be mounted around a shaft without disconnecting the ends of the shaft. The two parts 53a, 53b can be assembled in a joint <NUM> such that a disc is formed.

The contact portion <NUM> comprises a relief portion <NUM> which is provided with a protruding crease-line forming pattern.

Laterally of the relief portion <NUM>, the creasing tool <NUM> may comprise an outer portion configured as a base portion <NUM>. The base portion <NUM> can be provided with a smooth surface (i.e. not provided with a creasing pattern). Optionally, the base portion <NUM> can be curved. The relief portion <NUM> is in contact with the fibrous substrate <NUM> during the creasing operation, while the base portion <NUM> is positioned at a distance from the fibrous substrate <NUM>.

As best seen in <FIG>, the relief portion <NUM> comprises a crease-line forming portion <NUM> and a peripheral deformation portion <NUM>. The peripheral deformation portion <NUM> is arranged laterally of the crease-line forming portion <NUM>.

The crease-line forming portion <NUM> is a raised line extending around the circumference of the creasing tool <NUM>. When the creasing tool <NUM> is pressed against the fibrous substrate <NUM>, the crease-line forming portion <NUM> will create a central portion of the crease line. The central portion of the crease line defines the priority folding line, which is the precise location for the fold. The peripheral deformation portion <NUM> distributes the compression force from the creasing tool <NUM> over the fibrous substrate <NUM> in a gradual manner in a direction towards the crease-line forming portion <NUM>. Hence, the compression on the fibrous substrate <NUM> is increased from the peripheral deformation <NUM> portion and thus concentrated towards the crease-line forming portion <NUM> of the creasing tool <NUM>.

The peripheral deformation portion <NUM> is a discrete protruding pattern extending from the base surface <NUM>. For instance, the peripheral deformation portion <NUM> can be designed to protrude between <NUM>,<NUM> and <NUM>,<NUM> from the base surface <NUM>. The peripheral deformation portion <NUM> is provided with a plurality of transverse surface areas <NUM>. The transverse surface areas <NUM> have a perpendicular length of d<NUM> (see <FIG>) in relation to the longitudinal direction L of the central crease-line forming portion <NUM>. The transverse surface areas <NUM> extend in a transverse direction in relation to a longitudinal direction L of the central crease-line forming portion <NUM> and in relation to a central axis M of the creasing tool <NUM>. These transverse surface areas <NUM> can be linearly shaped. The transverse surface areas <NUM> can be shaped as chevrons <NUM>, or as fishbones when seen together with the crease-line forming portion <NUM>.

As best seen in <FIG>, the transverse surface areas <NUM> have a proximal portion <NUM> arranged at the crease-line forming portion <NUM> and a distal end (i.e. free end) <NUM> arranged at an outer edge of the relief portion <NUM>. The distal end <NUM> is thus arranged further away from the crease-line forming portion <NUM> than the proximal portion <NUM>. Hence, the transverse surface areas <NUM> extend along an extension direction E from the crease-line forming portion <NUM> towards an edge <NUM> of the creasing tool <NUM>.

As the crease-line forming portion <NUM> is continuous and the peripheral deformation portion <NUM> is discrete, the deformation is concentrated to the crease-line forming portion <NUM>. Consequently, the crease-line forming portion <NUM> is configured to create a sharp and precise crease line.

The present creasing tool <NUM> can be used in both a precreasing section <NUM> and a main creasing section <NUM>.

The crease lines <NUM>, <NUM> formed on the fibrous substrate <NUM> comprise a main crease line portion which is the center part of the crease lines <NUM>, <NUM> and is provided by the crease-line forming portion <NUM>. If the crease lines <NUM>, <NUM> are provided by a main creasing tool <NUM>, the main crease-line portion corresponds to the priority folding line. In another example, if the crease lines <NUM>, <NUM> are provided by a precreaser, the main crease-line portion forms a main portion of a precreasing area. The crease lines <NUM>, <NUM> are also provided with a peripheral crease-line portion, provided by the peripheral deformation portion <NUM>.

In the embodiment illustrated in <FIG>, the proximal portions <NUM> of the transverse surface areas <NUM> on a first side of the crease-line forming portion <NUM> are touching the transverse surface areas <NUM> on a second and opposite side of the crease-line forming portion <NUM>.

Now referring to <FIG>, which further illustrates the geometry in cross-section through the creasing tool <NUM> of <FIG>. The relief portion <NUM> of the creasing tool <NUM> can be downwardly sloped from the crease-line forming portion <NUM> in a direction towards the edge <NUM> of the creasing tool <NUM> by the angle α. The peripheral deformation portion <NUM> can thus be downwardly sloped at the angle α in a direction from the crease-line forming portion <NUM> and in relation to the rotary axis Xr of the creasing tool <NUM>. This gradually increases the compression depth from the creasing tool <NUM> on the fibrous substrate <NUM> in a direction towards the central crease-line forming portion <NUM>. During the rotation of the creasing tool <NUM>, the compression depth into the fibrous substrate <NUM> caused from each transverse surface area <NUM> is gradually increased as the height of the transverse surface area <NUM> increases in the direction of rotation R.

The angle α is advantageously ranging from <NUM>° to <NUM>°, preferably from <NUM>° to <NUM>°. The angle α is determined relative to the position of the central crease-line forming portion <NUM>. This range has been found to increase the folding angle without stress and limit the double-fold (i.e. squared fold) phenomenon. This inclination can be constant along the extension E of the transverse surface areas <NUM>.

The direction of rotation R of the creasing tool <NUM> (see <FIG>) can be selected such that the distal ends <NUM> of the transverse surface areas <NUM> are pointing forward in the direction of rotation R and are therefore brought into contact with the fibrous substrate <NUM> before the proximal portion <NUM> of the transverse surface areas <NUM>. This has an effect of creating an immediate contact with several flutes in the fibrous substrate <NUM> before the central crease-line forming portion <NUM> applies the center part of the folding line to the fibrous substrate.

As illustrated in <FIG>, the proximal portions <NUM> can be arranged such that a proximal portion <NUM> is in contact with the transverse surface area <NUM> on the opposite side of the center axis M. Alternatively, in the embodiment illustrated in <FIG>, the proximal portions <NUM> can be arranged to connect to the transverse surface area on the opposite side of the central axis M in such a way that the proximal portions <NUM> are penetrating into the opposite transverse surface areas <NUM>. Commonly for both alternatives, the transverse surface areas <NUM> on one side of the central axis M preferably contact or penetrate the opposing transverse surface areas <NUM> on the other side of the central axis in the middle along its extension E.

As illustrated in <FIG>, a corrugated fibrous substrate <NUM> may have the composition of a top paper liner <NUM>, a bottom paper liner <NUM> and a corrugated fluted layer <NUM> arranged therebetween. As previously mentioned, rupture of the fibrous substrate <NUM> often occurs when a crease-line forming portion <NUM> is contacting the corrugated fibrous substrate <NUM> in positions where the top paper liner <NUM> and the corrugated fluted layer <NUM> are disconnected. This situation is illustrated in <FIG>. The paper liner <NUM> of corrugated fibrous cardboard substrate <NUM> is within the context of this invention also referred to as "layer".

As best seen in <FIG>, a transverse length d<NUM> (see <FIG>) of the transverse surface areas <NUM> is therefore advantageously selected based on the geometry of the corrugated fibrous cardboard substrate <NUM> and in particular the distances p1 between the flutes. Hence, the transverse length d<NUM> of the transverse surface areas <NUM> is selected to be equal or larger than the <NUM>% of the peak-to-peak distance p1 between the flutes in the corrugated fibrous substrate <NUM>. Alternatively, a distance of <NUM>% of the peak-to-peak distance p1 can be selected. This ensures that the transverse surface areas <NUM> are in contact with a flute even if the creasing tool <NUM> is not positioned centrally in-between the flutes. For corrugated fibrous cardboard substrates with a plurality of corrugated fluted layers 83a, 83b and as illustrated in <FIG>, the transverse length d<NUM> of the transverse surface areas <NUM> can be similarly selected to be equal or larger than <NUM>% or correspond to <NUM>% of the largest peak-to-peak distance p1 of the corrugated layers 83a, 84b. Alternatively, the transverse length d<NUM> can be selected from the peak-to-peak distance p1 of the upper corrugated layer.

As illustrated in <FIG>, the transverse surface areas <NUM> can be provided with a curved shape, such that their proximal portions <NUM> converge to form a continuous central crease-line forming portion <NUM>. The transverse surface areas <NUM> are curved from their proximal portion <NUM> to their distal ends <NUM>. The curved shape can be provided by a single radius or a combination of several different radiuses along the extension E of the transverse surface areas <NUM>. In the case where there are several different radiuses, the transverse surface areas <NUM> may have different sections, each having a different radius, The curved shape allows the transverse surface areas <NUM> to form both a continuous crease-line forming portion <NUM> and a peripheral deformation portion <NUM>.

The transverse surface areas <NUM> are thus configured to gradually increase and direct the deformation on the fibrous substrate <NUM> converge into the central main crease-line portion. Hence, the proximal portions <NUM> of the transverse surface areas <NUM> form the crease-line forming portion <NUM>. The outer periphery of the curved transverse surface areas <NUM> is concave in relation to the outer edges <NUM> of the creasing tool <NUM>. Consequently, the convex side of the transverse surface areas <NUM> is located closer to the central axis M than the concave side.

The extension direction E of subsequent transverse surface areas <NUM> on opposite sides of the annular ridge <NUM> is mirrored and preferably offset at a distance d<NUM> along a central axis M defined by the central crease-line forming portion <NUM>. This results in an alternating pattern of transverse surface areas <NUM>.

The discrete segments or transverse surface areas <NUM> are extending in a transverse direction at an angle β in relation to the central axis M and in the direction of rotation of the disc R. The angle β is less than <NUM> degrees such that the distal ends <NUM> of the discrete segments or transverse surface areas <NUM> are brought into contact with the fibrous substrate <NUM> before the proximal portions <NUM> of the discrete transverse surface areas <NUM>.

For curved transverse surface areas <NUM>, there is thus a gradually reduced angle β of the extension E from the distal end <NUM> and to the proximal portion <NUM> in relation to the crease-line forming portion <NUM>. This provides a gradual transition between the crease-line forming portion <NUM> and the peripheral deformation portion <NUM>.

The transverse surface areas <NUM> on the first side of the crease-line forming portion <NUM> and the transverse surface areas of the second side of the crease-line forming portion <NUM> cooperate such that even if the transverse surface areas <NUM> are arranged in a discrete manner, there is a continuous transverse component in the peripheral deformation portion <NUM> that is applying a pressure on the flutes <NUM> in the fibrous substrate <NUM>. This ensures a continuous compression force onto the fibrous substrate <NUM> in the transverse direction and a dense arrangement of the transverse surface areas <NUM> on the outer surface of the creasing tool <NUM>.

As best seen in <FIG>, the transverse surface areas <NUM> may be placed equidistant on the outer surface of the creasing tool <NUM>, wherein the distal ends <NUM> the transverse surface areas <NUM> are spaced apart at a distance d<NUM>. If the transverse surface areas <NUM> are all of the same size, the distance d<NUM> between the proximal portions <NUM> is the same (i.e. constant) around the outer circumference of the creasing tool <NUM>.

In the third embodiment illustrated in <FIG>, the creasing tool <NUM> is arranged in a similar way as in the first embodiment, but additionally comprises a continuous annular ridge <NUM> in the crease-line forming portion <NUM>. The annular ridge <NUM> has a linear and straight shape extending along the central axis M. The annular ridge <NUM> thus extends around the outer circumference of the creasing disc <NUM>.

The annular ridge <NUM> is arranged parallel to the edge <NUM> of the creasing tool <NUM>. The annular ridge <NUM> is placed at a distance d<NUM>, from the edge <NUM> which is preferably selected to correspond to about <NUM>% of the total width W of the creasing tool <NUM>, such that the midrib <NUM> is positioned in the center of the creasing tool <NUM>.

Accordingly, the transverse surface areas <NUM> whose extension direction E extend from the annular ridge <NUM> towards the edge <NUM> of the creasing tool <NUM> are in contact with the annular creasing ridge <NUM>. The annular ridge <NUM> may preferably protrude further from the base surface <NUM> than the proximal portions <NUM> of the transverse surface areas <NUM>.

The annular creasing ridge <NUM> provides a sharper protrusion from the outer surface of the creasing tool <NUM> compared to the creasing tool of the first embodiment, therefore further increasing the sharpness of crease lines <NUM>, <NUM> formed by the creasing tool <NUM>. However, the transverse surface areas <NUM> still provide a gradually increasing deformation on the fibrous substrate <NUM> surface to prevent the fibrous substrate <NUM> from being teared.

In <FIG> a fourth embodiment of the creasing tool <NUM> is shown. In the fourth embodiment, the creasing tool <NUM> is arranged similarly to the first embodiment, but the crease-line forming portion <NUM> and the peripheral deformation portion <NUM> are formed from a single continuous segment. The transverse surface areas <NUM> in the peripheral deformation portion <NUM> are provided with a proximal portion <NUM> that is wider than the distal portion <NUM>.

This has the effect that the deformation is distributed over a larger area at the central crease-line forming portion <NUM> than at the distal portions <NUM>. In this way, a wider (i.e. less sharp) crease-line can be achieved than with the creasing tool <NUM> of the previously described embodiments.

Additionally, only the distal ends <NUM> of the transverse surface areas <NUM> are separated from each other, while the proximal portions <NUM> are broadened in such a way that they merge to form a coalesced midrib <NUM>. Hence, the proximal portions <NUM> of preceding and subsequent transverse surface areas <NUM> merge. Additionally, the proximal portions <NUM> of the opposite transverse surface areas <NUM> merge over the central axis M.

This type of creasing tool <NUM> can advantageously be used for performing pre-creasing operations as it prepares a fold in the fibrous substrate <NUM> for a subsequent and sharper ridge of a creasing tool <NUM>.

In this embodiment, the slope angle α describes the inclination of the peripheral deformation portion <NUM> from a coalesced midrib <NUM> to the distal end portions <NUM>. and in relation to the rotation axis Xr.

In <FIG> a fifth embodiment of the creasing tool <NUM> is shown. In the fifth embodiment, the creasing tool <NUM> is arranged similar to the fourth embodiment illustrated in <FIG>, but further comprises an additional annular creasing ridge <NUM>, protruding further away from the base surface <NUM> than the proximal portions <NUM> of the transverse surface areas <NUM>. The annular creasing ridge <NUM> extends along the crease-line forming portion <NUM>.

Like in the fourth embodiment, the proximal portions <NUM> of the transverse surface areas <NUM> are broadened in a direction towards the crease-line forming portion <NUM>.

The annular creasing ridge <NUM> provides a sharper protrusion from the outer surface of the creasing tool <NUM> compared to the creasing tool <NUM> of the third embodiment, and therefore further increasing the preciseness of the crease lines formed by the creasing tool <NUM>. However, the transverse surface areas <NUM> still provide a sufficiently distributed surface to prevent the cardboard from being teared apart.

Several tests were completed for the creasing tool <NUM> of the present invention. These tests showed a significant reduced rupture phenomenon of a corrugated fibrous corrugated substrate <NUM> when using a creasing tool <NUM> according to the present invention. The result is illustrated in <FIG>, and in which <FIG> shows a fibrous substrate <NUM> contacted by a prior art creasing tool (as illustrated in <FIG>). <FIG> shows a fibrous substrate <NUM> contacted by a creasing tool <NUM> of the present invention of the type illustrated in <FIG>. Hence, the present creasing tool <NUM> is able to demonstrate a reduced tearing effect on the fibrous substrate <NUM>.

The invention can be further applied to other tools suitable for creating crease lines. For instance, as illustrated in <FIG>, the creasing tool <NUM> can be a die <NUM> for platen press. The die <NUM> can be provided with crease-forming edges (also referred to as rules) with a pattern corresponding to the relief portion <NUM>, as illustrated in the embodiments of <FIG>.

The die <NUM> comprises a die board <NUM> provided with a pattern of cutting edges <NUM> and creasing edges <NUM>. The cutting edges <NUM> are located in the periphery of the die board <NUM> and will define the outer contour of the intermediate blank <NUM>.

Claim 1:
A creasing tool (<NUM>) configured to create a crease line (<NUM>, <NUM>) in a fibrous substrate (<NUM>), the creasing tool comprises a contact portion (<NUM>) having a base surface (<NUM>) and a relief portion (<NUM>), the relief portion is provided as a protruding pattern extending from the base surface (<NUM>) and is configured to be pressed against said fibrous substrate,
wherein the relief portion (<NUM>) comprises a crease-line forming portion (<NUM>) and a peripheral deformation portion (<NUM>), and
characterized in that the peripheral deformation portion comprises a plurality of discrete segments in the shape of curved transverse surface areas (<NUM>) extending in a direction (E) transverse to a longitudinal direction (L) of the crease-line forming portion (<NUM>), and such that an outer periphery of the curved transverse surface areas (<NUM>) is concave in relation to the outer edges (<NUM>) of the creasing tool.