Crease tool and method for generating creases

Abstract

A creasing tool (53) configured to create creases (11, 12) in a fibrous substrate (35), the creasing tool comprising a contact portion (50) having a base surface (57) and a relief portion (54), the relief portion being provided as a protruding pattern extending from the base surface (57) and configured to be pressed against the fibrous substrate, the relief portion (54) comprising a crease-forming portion (56) and a peripheral deformation portion (59), the peripheral deformation portion comprising a plurality of discrete segments in the shape of curved cross-sectional areas (58) extending in a transverse direction (E) to a longitudinal direction (L) of the crease-forming portion (56).

Description

[Technical field]

[0001] The present invention relates to a creasing tool that is particularly suited for producing corrugated boxes. [Background technology]

[0002] In the packaging industry, corrugated boxes are often manufactured from corrugated sheets which are printed (if necessary), cut and scored, and then folded and glued together to form a flat-folded box, often also called a "folding box", in an assembly such as a folder-gluer arrangement.

[0003] Corrugated cardboard is a material that typically comprises a fluted corrugated sheet and two layers of linerboard attached to each side of the fluted corrugated sheet. Corrugated cardboard combines light weight with high strength and is particularly suitable as a packaging material.

[0004] To fold the corrugated board sheets, it is necessary to generate creases in the perpendicular direction. Some of the creases will then coincide with the direction of the flutes, while others will be in the transverse direction. The creases can be made in a platen printing machine, where the die is provided with a protruding edge that is pressed against the corrugated board sheet to generate the creases. It is also possible to form the creases by using a rotating creasing disk provided with a protruding annular creasing ridge. The creasing disk is typically incorporated in a folder-gluer machine. A folder-gluer machine can also be called a converting machine or a converting in-line machine. A converting machine converts or transforms a web or sheet of material into an intermediate form or into a finished flat-folded box.

[0005] The accuracy of the folding process depends on the quality of the crease lines imposed on the board, i.e. the correct position of the crease, the regularity of its shape and the depth of the depression. The sharper the crease ridge, the better the quality of the crease imposed on the board. However, a sharp crease ridge may tear the board.

[0006] When crease ridges are applied transverse to the length of the grooves, the compressive force from the creasing tool tends to be distributed over the points where the top liner and inner fluted corrugated sheet are connected. However, if the creases are to be formed in a direction that is consistent with the length of the grooves, there is a large variation in the bending resistance of the board. As a result, the top linerboard may break when pressure is applied where the top liner and inner fluted corrugated sheet are cut. Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above mentioned problems, it is an object of the present invention to provide a creasing tool and method that produces well-defined and accurate creases while reducing the risk of tearing the paper liner. [Means for solving the problem]

[0008] The object of the present invention is solved by a creasing tool according to claim 1 and a method according to claim 16.

[0009] According to a first aspect of the invention it relates to a creasing tool configured to generate a crease in a fibrous substrate, the creasing tool comprising a contact portion having a base surface and a relief portion, the relief portion being provided as a protruding pattern extending from the base surface and configured to press against the fibrous substrate, the relief portion comprising a crease line forming portion and a peripheral deformation portion, the peripheral deformation portion comprising a plurality of discrete segments in the shape of a curved cross-sectional area extending in a direction transverse to the longitudinal direction of the crease line forming portion.

[0010] The fibrous substrate is also called a corrugated cardboard substrate in the context of the present invention. With respect to a creasing tool in the form of a creasing disk, the longitudinal direction is the direction of rotation of the creasing disk. The longitudinal direction thus extends around the circumference of the creasing tool.

[0011] The present invention is based on the realization that the deformation from the creasing tool needs to be gradually distributed across the fibrous substrate so as to touch both the weaker areas where the paper liner and the corrugated layer are cut and the stronger areas where these two elements are connected. This will generate a more distributed pressure onto the fibrous substrate regardless of where the creasing portion on the creasing tool contacts the fibrous substrate. The peripheral deformation portion is thus configured to apply a gradually increasing contact pressure onto the fibrous substrate in the direction towards the creasing portion.

[0012] The multiple transversely extending discrete segments apply pressure on the grooves of the fibrous substrate not only along the direction of extension of the grooves, in other words, the discrete segments act on the grooves to gradually transition into the major fold lines, which helps prevent tearing of the sheet around the major fold lines.

[0013] In an embodiment, the creasing portion and the peripheral deformation portion are connected, which means that the relief portion is continuous from the creasing portion to the peripheral deformation portion.

[0014] Continuous in the context of the present invention means that the crease forming portions are in the form of lines or surface areas having a continuous protruding relief pattern that protrudes from the base surface.

[0015] The relief portion may be centrally located on the contact portion. In an embodiment, the peripheral deformation portion is located laterally of the crease forming portion on at least one side thereof.

[0016] Preferably, the peripheral deformations are arranged on either side of the fold line forming portion, in this way the peripheral deformations can extend over a greater distance on the fibrous substrate and reduce the risk of breakage on either side of the fold line forming portion.

[0017] The crease forming portion may be a continuous line. The line may be a straight line. Alternatively, the line may be provided with a zigzag shape.

[0018] In an embodiment, the crease forming portion protrudes further from the base surface than the peripheral deformation portion. This height difference allows for the formation of a well-defined crease. In an embodiment, there is a discontinuity at the junction between the crease forming portion and the peripheral deformation portion, whereby the transition between the crease forming portion and the peripheral portion is discontinuous. In other words, there is no constant gradual slope in the transition.

[0019] The peripheral deformation portion preferably slopes downwardly at an angle in a direction from the crease forming portion towards the edge of the creasing tool, the angle being defined relative to the axis of rotation of the tool.

[0020] This gradually increases the compression depth towards the central part of the creasing tool when it is in contact with the fibrous substrate. The peripheral deformation part can be inclined downwards at an angle ranging from 0° to 36°, preferably 2° to 10°. The inclined outer surface of the creasing tool allows a smoother contact angle between the creasing tool and the inner linerboard, thereby giving the possibility to control the overall width of the crease mark through mechanical calibration, thereby increasing the fold angle without stress or fracture. For most corrugated substrates, angles larger than 36° typically will not allow to fully take advantage of the transverse segment design. Furthermore, it may concentrate the mechanical pressure on a small surface, which is believed to result in increased tearing phenomena on the inner liner.

[0021] In an embodiment, the cross-sectional area within the peripheral deformation portion is straight in shape and has a proximal portion located at the crease forming portion and a distal end shaped as a free end.

[0022] In an embodiment, the creasing tool further comprises a central rib, which protrudes further from the base surface than the proximal portion of the cross-sectional area. This height difference will allow for the formation of a well-defined crease line. Thus, there is a discontinuity at the junction between the creasing portion and the peripheral deformation portion, whereby the transition between the creasing portion and the peripheral deformation portion is discontinuous (i.e. does not show a constant gradual slope at the transition).

[0023] The cross-sectional areas may have a larger cross-sectional area at their proximal portions than at their distal portions. This can be used especially when less sharp creases can be achieved and larger folding zones are desired. This type of cross-sectional area may be advantageous for a creasing disk used as a pre-crease. The pre-crease disk and the main creasing disk positioned downstream provide a two-stage creasing process. This allows for a gradual and smooth creasing process.

[0024] A cross-sectional area is defined in the context of the present invention as a linear element, which can be either straight or curved, and can have a uniform or variable thickness.

[0025] The creasing portion can be centrally located on the contact portion, and the cross-sectional areas of the first and second sides of the creasing portion can be mirrored around a central axis defined by the creasing portion, preferably offset relative to each other. As an example, the cross-sectional area of ​​the first side can be offset relative to the cross-sectional area of ​​the second side. Thus, the cross-sectional areas are placed such that they alternate. Thus, the pattern of the creasing tool can resemble a herringbone. Such an arrangement provides a distributed mechanical pressure applied by the creasing tool on the linerboard. This distributes the deformation footprint from the surrounding portion so that there is always a transverse segment in contact with the fibrous substrate.

[0026] In one embodiment, the cross-sectional areas may be straight. This has the technical effect that the cross-sectional areas may extend over a greater length than if they were curved. In an embodiment, the cross-sectional areas may have a consistent cross-sectional area along their length.

[0027] In another embodiment, the cross-sectional area is shaped as a linear element, which converges at a central crease forming portion, whereby a proximal portion of the linear element forms the crease forming portion. This arc shape allows the cross-sectional area to form a substantially straight central crease on the fibrous substrate. This also allows for a gradual transition as the curved edges are found to be smooth when deforming the groove.

[0028] The creasing tool of the present invention may be used in a groover assembly of a converting machine configured to produce flat-fold corrugated containers.

[0029] In an embodiment, the creasing tool of the present invention is provided in a platen press. The creasing tool may be a die configured to be moved up and down to press vertically against the fibrous substrate. Alternatively, the creasing tool may be provided as a creasing disk.

[0030] The discrete segments extend at an angle relative to a central axis defined by the central crease forming portion.

[0031] The creasing tool may be approximately ring-shaped. This allows the creasing tool to be easily mounted, for example, on the cylinder or shaft of a creasing device. In this way, creases can be applied to the cardboard by rotating the creasing tool and thereby bringing it into contact with the cardboard. In an embodiment, the creasing tool may be provided in two half-ring shaped parts so that it can be mounted around a shaft without cutting off the ends of the shaft. The two parts may be attached to each other by fasteners (such as bolts or screws) and, optionally, a mounting bracket may be provided which cooperates with the fasteners and the creasing tool parts to form a rigid disk assembly.

[0032] 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 according to the first aspect of the invention, the creasing disc being mounted in the converting machine such that a cross-sectional area extends in a transverse direction inclined to a central axis and in the direction of rotation of the disc, the inclination angle being less than 90 degrees such that a distal end of the cross-sectional area is in contact with the fibrous substrate before the proximal portion of the discrete segments.

[0033] According to a third aspect, the present invention relates to a method for producing a crease in a fibrous substrate using a creasing tool according to the first aspect of the invention, the method comprising the steps of: - selecting a fibrous substrate having at least one corrugated layer, - measuring the distance between grooves in at least one corrugated layer; - selecting a creasing tool having a cross-sectional area transverse length equal to or greater than 50% of the groove distance; and - pressing the tool against the fibrous substrate so as to obtain a crease, Equipped with.

[0034] In an embodiment, the cross-sectional length of the cross-sectional areas is equal to or greater than the groove distance, such that each discrete cross-sectional area within the perimeter portion applies a compressive force onto at least two grooves during crease formation such that the risk of tearing or otherwise damaging the linerboard is reduced.

[0035] The creasing tool may have a variable number of cross-sectional areas, the number being dictated by the number of cross-sectional areas that simultaneously contact the cardboard less than per linear centimeter, preferably less than per linear centimeter. A small number of cross-sectional areas may not result in a sharp enough fold line, whereas a large number of cross-sectional areas may result in a too smooth outer surface on the creasing tool, and the creasing ring may not create a sufficient pressure difference compared to the surrounding area that does not define the fold line well.

[0036] Preferably, at any location along the creasing portion of the creasing tool, at least a portion of the cross-sectional area lies on an outer surface of the creasing tool.

[0037] Further advantages and features will become apparent from the following description of illustrative embodiments of the invention and from the accompanying drawings in which like features are designated with like reference numerals and in which: [Brief description of the drawings]

[0038] [Figure 1] FIG. 1 is a plan view of a flat corrugated blank. [Figure 2a] FIG. 2 is a schematic perspective view of a flat-folded and glued box obtained from the blank shown in FIG. 1. [Figure 2b] FIG. 2b is a schematic perspective view of an assembled box obtainable from the flat-folded box shown in FIG. 2a. [Diagram 3] FIG. 1 is a schematic diagram of a transformation machine. [Figure 4] FIG. 4 is a cross-sectional view of a slotting unit of the conversion machine of FIG. 3. [Figure 5a] FIG. 1 illustrates a standard creasing tool as known in the prior art. [Figure 5b] FIG. 5b is a detailed view of the creasing tool of FIG. 5a. [Figure 5c] FIG. 5b shows a cross section through the creasing tool of FIG. 5a. [Figure 6] 1 is a schematic cross-sectional view of a creasing tool in contact with a corrugated board substrate. [Figure 7] FIG. 1 is a schematic cross-sectional view of a corrugated board substrate comprising a two-ply corrugated board substrate. [Figure 8a] FIG. 1 shows a first embodiment of a creasing tool according to the invention. [Figure 8b] FIG. 8b shows a detail of the creasing tool of FIG. 8a. [Figure 8c] FIG. 8b shows a cross section through the creasing tool of FIG. 8a. [Figure 8d] FIG. 8c shows another embodiment of a creasing tool similar to the embodiment shown in FIGS. 8a to 8c. [Figure 8e] FIG. 8c shows another embodiment of a creasing tool similar to the embodiment shown in FIGS. 8a to 8c. [Figure 9a] FIG. 3 shows a third embodiment of a creasing tool according to the invention. [Figure 9b] FIG. 9b is a detailed view of the creasing tool of FIG. 9a. [Figure 9c] FIG. 9b shows a cross section through the creasing tool of FIG. 9a. [Figure 10a] FIG. 4 shows a fourth embodiment of a creasing tool according to the invention. [Figure 10b] FIG. 10b is a detailed view of the creasing tool of FIG. 10a. [Figure 10c] FIG. 10b shows a cross section through the creasing tool of FIG. 10a. [Figure 11a] FIG. 5 shows a fifth embodiment of a creasing tool according to the invention. [Figure 11b] FIG. 11b is a detailed view of the creasing tool of FIG. [Figure 11c] FIG. 10b shows a cross section through the creasing tool of FIG. 10a. [Figure 12a]FIG. 5b illustrates creases achieved using a prior art creasing tool as shown in FIG. 5a. [Figure 12b] FIG. 13 illustrates creases achieved using a creasing tool according to the present invention. [Figure 13] FIG. 13 illustrates yet another exemplary embodiment of the present invention showing a creasing tool in the form of a platen press die. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] FIG. 1 shows an example of an intermediate blank 1 made from corrugated cardboard and used to manufacture a folding box 1' as shown in FIG. 2a.

[0040] When producing the folding box 1', the fibrous substrate 35 in the form of a corrugated web or sheet passes through multiple workstations in the converting machine 19, which print, cut and shape, prepare the fibrous substrate 35 for folding, glue and fold the fibrous substrate 35. The intermediate blank 1 in FIG. 1 has been scored, cut and shaped, and prepared for folding. As shown, the intermediate blank 1 may have a substantially rectangular flat shape with two parallel edges of greater length. To produce the folding box 1', the intermediate blank 1 needs to be further folded and glued in separate processing modules of the converting machine 19. In a final step, the folding box 1' may be assembled to form a three-dimensional box 1'' as shown in FIG. 2b.

[0041] As shown in Figure 1, the intermediate blank 1 comprises a leading edge 2 that must be positioned forward and perpendicular to the processing / driving direction FD. As shown diagrammatically in Figure 3, the leading edge 2 is typically fed into a folding-gluing module 26 of a converting machine 19, which then folds and glues the blank 1. The converting machine 19 comprises a number of units aligned along the longitudinal axis of the sheet and the driving direction FD.

[0042] A number of crease lines 11, 12 are required to enable the blank 1 to be folded into a three-dimensional box. Different types and models of folding boxes 1' have different numbers and positions of crease lines 11, 12. The illustrated intermediate blank 1 and cut and crease line configurations are only one example of many different intermediate blanks 1 that can be used to manufacture a folding box 1' suitable for forming a three-dimensional folding box.

[0043] As shown in Figure 1, the fold lines 11, 12 of the illustrated intermediate blank 1 are differentiated into two groups, the first group 11 being configured as parallel fold lines 11a, 11b, 11c, 11d coinciding with the drive direction FD of the folder-gluer machine 19. The fold lines 12 of the second group are vertical fold lines 12a, 12b and are therefore perpendicular to the parallel fold lines 11a, 11b, 11c, 11d of the first group.

[0044] Two side edges of shorter length are provided so as to define a left edge 4 and a right edge 5. The left edge 4 presents a notch along its two end portions so as to define a flap 14 in the centre of the left edge 4. The front 12a and rear 12b fold lines of the second group of fold lines 12 are parallel to the front edge 2 and the rear edge 3, respectively, and define a central portion 1a of the blank 1 intended to comprise the peripheral surface of the folded box 1' when assembled to form the three-dimensional box. The central portion 1a is located between the rear portion 1b intended to comprise the bottom surface when assembled to form the three-dimensional box 1'', and the front portion 1c intended to comprise the top surface of the folded box 1'.

[0045] A first group of parallel crease lines 11 are typically parallel to the left and right edges 4, 5, as well as the grooves 10 of the corrugated layers of the cardboard. This group of parallel crease lines 11 may extend along the entire width of the central portion 1a. One of the crease lines 11 is adjacent to the flap 14, while the other, called the central crease 11c, is aligned with the longitudinal axis A. Coincident with the crease lines 11 and the central crease 11a, the rear portion 1b and the front portion 1c may be cut to generate a slit 13 that, in some embodiments, extends the entire width of the rear portion 1b and the front portion 1c.

[0046] The slits 13 define 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 positioned on either side of the large central panels 6a and 6a', respectively. Similarly, the small rear and front panels 7b, 7c and 7b', 7c' are positioned on either side of the small central panels 7a, 7a', respectively.

[0047] The crease lines 11, 12 and their slits 13 allow the blank 1 to be folded into a rectangular shaped folding box 1', each crease line 11, 12 defining a fold line (see FIG. 1). During the folding process, adhesive is typically deposited on the flaps 14, which join the large left central panel 6a, i.e., to the small right central panel 7a'.

[0048] Many different configurations of the converting machine 19 are possible. The exemplary converting machine 19, shown diagrammatically in Fig. 3, comprises a loader 20 for automatically loading the fibrous substrate 35 in the form of sheets continuously from upstream to downstream in the drive direction FD, a feeder 21, an optional plurality of flexographic printing units 22a to 22d, at least one groover assembly 23 and at least one cutting unit 24, a waste strip and optional vibration unit 25, a folding-gluing unit 26. The converting machine 19 may also further comprise optional modules 27, such as a counting-discharging unit, a bundler, a palletizer (partially shown in dotted lines in Fig. 3).

[0049] As shown in Figure 4, the groover assembly 23 processes and transforms the printed fibrous substrate 35 exiting the final printing unit 22d into an intermediate blank 1 (see Figure 1). The groover 23 assembly comprises various rotary tools, including cutting tools or knives that make the edge cuts (1b, 1a, 1c seen in Figure 1), the slits 13 and the cuts that transversely separate the flaps 14, and creasing devices or creasers that make the longitudinal creases 11. It should be noted that the transverse creases 12 are either generated upstream or downstream of the groover 23 (depending on the type and configuration of the converting machine) or are initially provided in the fibrous substrate 35.

[0050] The rotary tool is mounted on a transverse bearing shaft which is rotationally driven by a shaft motor. The rotational speed of the tool preferably corresponds to the working speed, i.e. the drive and running speed T of the fibrous substrate 35.

[0051] In the illustrated embodiment, the groover 23 comprises a pre-creasing section 36 in which a first pair of shafts are positioned above one another from upstream to downstream. The pre-creasing section 36 prepares the board for the subsequent formation of the priority fold line. The pre-creasing section is thus configured to form a pre-creasing area, which is a partially deformed area, on the fibrous substrate 35. The lower shaft is provided with a lower pre-creaser 37, while the upper shaft is equipped with an upper pre-creaser 38, which is its counterpart. The pre-creasing section 36 provides a first initial creasing operation, since the longitudinal crease line 11 is creased in two successive operations.

[0052] A first groove section 39 with a second pair of shafts positioned above one another is mounted downstream of the pre-creasing section 36. The upper shaft of the first groove section 39 is provided with a disk with a knife 41 and the lower shaft is provided with a lower counter blade 42. The first groove section 39 cuts the slit 13 located at the rear of the blank 1.

[0053] A third pair of shafts positioned one above the other, the creasing section 43, is mounted downstream of the first groove section 39. The lower shaft of the creasing section 43 is provided with a lower creasing device 44 and the upper shaft is provided with its counterpart, an upper creasing device 46. The creasing section 43 provides a second and final creasing operation that provides for the formation of the priority crease line, thus ensuring a permanent and accurate marking of the longitudinal crease line 11.

[0054] A second groove section 47 with a fourth pair of shafts positioned above one another is mounted downstream of the creasing section 43. The upper shaft of the second groove section 47 is provided with a disk with a knife 48 and the lower shaft is provided with a lower counter blade 49. The second groove section 47 cuts the slit 13 located in the front part of the blank 1.

[0055] To cut out the adhesive flaps 14 and to perform the rear cut and the front cut of the flaps 14, the processing unit 43 can comprise a device 51 for processing the fibrous substrate 35. This device 51 is located in the creasing section. Considering the close position of the flaps 14 on the blank 1, the device 51 is preferably mounted on the operator end of the upper shaft in the creasing section 43.

[0056] The lower precreaser 37 and the upper precreaser 38 as well as the lower creaser 44 and the upper creaser 46 are creasing devices having a creasing tool 53. The creasing tool 53 is thus mounted on a shaft which serves as a support for the respective creasing tool 53 in the creasing section 43. It is also possible to arrange the precreaser 37 and the creasing tool 44 above or below the fibrous substrate 35.

[0057] In figures 5a to 5c a creasing tool 53 known in the prior art is shown diagrammatically. The creasing tool 53 can be used in the pre-creasing section 36 and in the creasing section 43 (see figure 4). The creasing tool 53 is ring-shaped and can be mounted on the shaft of the converting machine 19 as long as the inner diameter of the creasing tool 53 is selected according to the respective shaft dimensions. The ring-shaped creasing tool 53 can be provided in two half-ring-shaped parts so that they can be mounted around the shaft and can constitute a complete ring when mounted.

[0058] The creasing tool 53 includes a relief portion 54 with a crease-forming portion 56 in the form of a creasing ridge or central rib on the outer surface of the creasing tool 53. The relief portion 54 can be pressed against the fibrous substrate 35 to form the creases 11, 12 by deforming the linerboard and grooves 10 of the fibrous substrate 35.

[0059] 8a to 11c, there is shown an embodiment of a creasing tool 53 according to the present invention. As can be seen in the embodiment shown in Fig. 8a, the disc-shaped creasing tool 53 has a contact portion 50 with an overall width W, and the creasing tool 53 may be provided in two parts 53a, 53b such that it can be fitted around a shaft without cutting the end of the shaft. The two parts 53a, 53b may be assembled at a joint 55 such that a disc is formed.

[0060] The contact portion 50 includes a relief portion 54 having a protruding crease pattern thereon.

[0061] Laterally of the relief portion 54, the creasing tool 53 may comprise an outer portion configured as a base portion 57. The base portion 57 may comprise a smooth surface (i.e., no creasing pattern is provided). Optionally, the base portion 57 may be curved. The relief portion 54 contacts the fibrous substrate 35 during the creasing operation, while the base portion 57 is positioned at a distance from the fibrous substrate 35.

[0062] 8c, the relief portion 54 comprises a crease forming portion 56 and a peripheral deformation portion 59. The peripheral deformation portion 59 is positioned laterally of the crease forming portion 56.

[0063] The crease forming portion 56 is a raised line extending around the circumference of the creasing tool 53. With the creasing tool 53 pressed against the fibrous substrate 35, the crease forming portion 56 will crease the center of the crease. The center of the crease defines the preferred fold line, which is the exact location for the crease. The peripheral deformation portion 59 distributes the compressive force from the creasing tool 53 gradually throughout the entire fibrous substrate 35 in a direction toward the crease forming portion 56. Thus, the compressive force acting on the fibrous substrate 35 increases from the peripheral deformation portion 59 and is consequently concentrated toward the crease forming portion 56 of the creasing tool 53.

[0064] The peripheral deformation portion 59 is a discrete protruding pattern extending from the base surface 57. For example, the peripheral deformation portion 59 can be designed to protrude from the base surface 57 by 0.5 mm to 1.6 mm. The peripheral deformation portion 59 is provided with a plurality of cross-sectional areas 58. The cross-sectional areas 58 have a perpendicular length of d2 relative to the longitudinal direction L of the central crease line forming portion 56 (see FIG. 8b). The cross-sectional areas 58 extend transversely relative to the longitudinal direction L of the central crease line forming portion 56 and to the central axis M of the creasing tool 53. These cross-sectional areas 58 can be rectilinear in shape. In some embodiments, the cross-sectional areas 58 can be linear or curved. The cross-sectional areas 58 can be shaped as chevrons 58 or alternatively as fishbones when viewed together with the crease line forming portions 56.

[0065] 8b, the cross-sectional area 58 has a proximal portion 61 located at the crease forming portion 56, and a distal (i.e., free) end 63 disposed at the outer edge of the relief portion 54. The distal end 63 is thus located further away from the crease forming portion 56 than the proximal portion 61. The cross-sectional area 58 thus extends along an extension direction E from the crease forming portion 56 towards an edge 60 of the creasing tool 53.

[0066] Because the crease forming portion 56 is continuous and the peripheral deformation portion 59 is discontinuous, deformation is concentrated at the crease forming portion 56. As a result, the crease forming portion 56 is configured to produce sharp and precise creases.

[0067] The creasing tool 53 of the present invention may be used in both the pre-creasing section 36 and the main creasing section 43 .

[0068] The creases 11,12 formed in the fibrous substrate 35 comprise a main crease portion at the center of the crease 11,12, provided by a crease forming portion 56. If the creases 11,12 are provided by a main creasing tool 53, the main crease portion corresponds to the preferential fold line. In another example, if the creases 11,12 are provided by a pre-creasing tool, the main crease portion forms a major portion of the pre-creased area. The creases 11,12 are also provided with a peripheral deformation portion 58 provided by a peripheral crease portion.

[0069] In the embodiment shown in FIGS. 8 a - 8 c , a proximal portion 61 of a first side cross-sectional area 58 of the crease forming portion 56 abuts a second, opposing cross-sectional area 58 of the crease forming portion 56 .

[0070] 8c, the cross-sectional shape of the creasing tool 53 of FIG. 8a is further shown. The relief portion 54 of the creasing tool 53 can be inclined downwards by an angle α in a direction from the crease line forming portion 56 towards the edge 60 of the creasing tool 53. The peripheral deformation portion 59 can be inclined downwards by an angle α, i.e. towards the direction from the crease line forming portion 56 and towards the rotation axis Xr of the creasing tool 53, whereby the compression depth from the creasing tool 53 on the fibrous substrate 35 in the direction towards the central crease line forming portion 56 gradually increases. During the rotation of the creasing tool 53, the compression depth into the fibrous substrate 35 resulting from each cross-sectional area 58 gradually increases as the height of the cross-sectional area 58 increases in the rotation direction R.

[0071] The angle α is advantageously in the range of 0° to 36°, preferably in the range of 2° to 10°. The angle α is determined relative to the position of the central crease line forming portion 56. This range is known to increase the folding angle without stress and to limit the double-fold (i.e. four-fold) phenomenon. This inclination can be constant along the extension E of the cross-sectional area 58.

[0072] The direction of rotation R of the creasing tool 53 (see FIG. 8A ) can be selected such that the distal end 63 of the cross-sectional area 58 faces forward in the direction of rotation R and thus contacts the fibrous substrate 35 before the proximal portion 61 of the cross-sectional area 58. This has the effect of creating immediate contact with some of the grooves of the fibrous substrate 35 before the central crease-forming portion 56 applies the center of the crease to the fibrous substrate.

[0073] As shown in Figures 8a and 8b, the proximal portion 61 can be positioned such that the proximal portion 61 contacts the cross-sectional area 58 on the opposite side of the central axis M. Alternatively, in the embodiment shown in Figures 8d and 8e, the proximal portion 61 can be positioned to connect to a cross-sectional area on the opposite side of the central axis M such that the proximal portion 61 penetrates into the opposite cross-sectional area 58. Common to both alternative embodiments, the cross-sectional area 58 on one side of the central axis M preferably contacts or penetrates the opposing cross-sectional area 58 on the opposite side of the central axis halfway along its extension E.

[0074] As shown in Figure 6, the corrugated fibrous substrate 35 may have a configuration of an upper paper liner 81, a lower paper liner 82, and a corrugated grooved layer 83 positioned therebetween. As mentioned above, breakage of the fibrous substrate 35 often occurs when the crease forming portion 56 contacts the corrugated fibrous substrate 35 at a location where the upper paper liner 81 and the corrugated grooved layer 83 have separated. This situation is illustrated in Figure 6. The paper liner 81 of the corrugated fibrous corrugated substrate 35 is also referred to as a "layer" within the context of this invention.

[0075] As can be best seen in FIG. 8b, the transverse length d2 of the cross-sectional area 58 (see FIG. 8b) is therefore advantageously selected based on the shape of the corrugated fibrous corrugated board substrate 35, in particular the groove distance p1. The transverse length d2 of the cross-sectional area 58 is therefore selected to be equal to or greater than 50% of the peak-to-peak distance p1 of the grooves in the corrugated fibrous board substrate 35. Alternatively, a distance of 100% of the peak-to-peak distance p1 can be selected, thereby ensuring that the cross-sectional area 58 is in contact with the grooves even if the creasing tool 53 is not positioned in the center of the grooves. In the case of a corrugated fibrous corrugated board substrate having a plurality of corrugated grooved layers 83a, 83b, as shown in FIG. 7, the transverse length d2 of the cross-sectional area 58 can likewise be selected to be equal to or greater than 50% of the maximum peak-to-peak distance p1 of the corrugated layers 83a, 84b or to correspond to 100% of the maximum peak-to-peak distance p1 of the corrugated layers 83a, 84b. Alternatively, the transverse length d2 can be selected from the peak-to-peak distance p1 of the upper corrugated layer.

[0076] The extension direction E of the cross-sectional area 58 can be straight, in particular in combination with an annular continuous annular ridge 66. However, as shown in Figs. 8a to 8e, the cross-sectional areas 58 can be provided with a curved shape such that their proximal portions 61 converge to form a continuous central crease-formed portion 56. The cross-sectional areas 58 are curved from their proximal portions 61 to their distal ends 63. The curved shape can be provided by a single radius or a combination of several different radii along the extension line E of the cross-sectional area 58. In the case of several different radii, the cross-sectional area 58 can have different sections, each having a different radius. This curved shape allows the cross-sectional area 58 to form both a continuous crease-formed portion 56 and a peripheral deformation portion 59.

[0077] The transverse cross-sectional region 58 is configured, i.e., to gradually increase and guide the deformation on the fibrous substrate 35 towards the central main crease line portion. Thus, the proximal portion 61 of the transverse cross-sectional region 58 forms the crease forming portion 56. The outer periphery of the curved transverse cross-sectional region 58 is concave relative to the outer edge 60 of the creasing tool 57. As a result, the convex side of the transverse cross-sectional region 58 is positioned closer to the central axis M than the concave side.

[0078] The extension direction E of the subsequent cross-sectional areas 58 on the opposite side of the annular ridge 66 is mirrored along the central axis M defined by the central crease line forming portion 56 and is preferably offset by a distance d3. This results in an alternating pattern of cross-sectional areas 58.

[0079] The discrete segments or cross-sectional areas 58 extend transversely at an angle β relative to the central axis M in the direction of rotation of the disk R, the angle β being less than 90 degrees such that the distal ends 63 of the discrete segments or cross-sectional areas 58 contact the fibrous substrate 1 before the proximal portions 61 of the discrete cross-sectional areas 58.

[0080] With respect to the curved cross-sectional area 58, the angle β of the extension E from the distal end 63 to the proximal portion 61 relative to the crease forming portion 56 is therefore gradually reduced, thereby resulting in a gradual transition between the crease forming portion 56 and the circumferential deformation portion 59.

[0081] The cross-sectional areas 58 on the first side of the crease forming portion 56 and the cross-sectional areas on the second side of the crease forming portion 56 cooperate such that even though the cross-sectional areas 58 are discretely positioned, there is a continuous transverse component in the peripheral deformation portion 59 which applies pressure to the grooves 10 in the fibrous substrate 35. This ensures a continuous compressive force on the fibrous substrate 35 in the transverse direction and ensures a dense arrangement of the cross-sectional areas 58 on the outer surface of the creasing tool 53.

[0082] As can be best seen in Figure 8b, the cross-sectional areas 58 can be disposed equidistantly on the outer surface of the creasing tool 53, with the distal ends 63 of the cross-sectional areas 58 spaced apart by a distance d4. If the cross-sectional areas 58 were all the same size, then the distance d4 between the proximal portions 61 would be the same (i.e., constant) around the circumference of the creasing tool 53.

[0083] In the third embodiment shown in Figures 9a to 9c, the creasing tool 53 is positioned similarly to the first embodiment, but further comprises a continuous annular ridge 66 at the crease forming portion 56. The annular ridge 66 has a linear, straight shape extending along the central axis M. The annular ridge 66 thus extends around the outer periphery of the creasing disc 53.

[0084] The annular ridge 66 is positioned parallel to the edge 60 of the creasing tool 53. The annular ridge 66 is preferably positioned at a distance d1 from the edge 60, preferably selected to correspond to about 50% of the overall width W of the creasing tool 53, such that the central rib 56 is positioned at the center of the creasing tool 53.

[0085] Thus, the cross-sectional area 58 whose extension direction E extends from the annular ridge 66 towards the edge 60 of the creasing tool 53 contacts the annular creasing ridge 66. The annular ridge 66 may preferably protrude further from the base surface 57 than the proximal portion 61 of the cross-sectional area 58.

[0086] The annular creasing ridge 66 provides a sharper protrusion from the outer surface of the creasing tool 53 compared to the creasing tool of the first embodiment, thus further increasing the sharpness of the crease lines 11, 12 formed by the creasing tool 53. However, the cross-sectional area 58 still provides an increasing deformation to the face of the fibrous substrate 35 to prevent the fibrous substrate 1 from tearing.

[0087] 10a to 10c, a fourth embodiment of the creasing tool 53 is shown. In the fourth embodiment, the creasing tool 53 is positioned similarly to the first embodiment, but the crease forming portion 56 and the peripheral deformation portion 59 are formed from a single continuous segment. The cross-sectional area 58 at the peripheral deformation portion 59 is provided with a proximal portion 61 which is wider than a distal portion 63.

[0088] This has the effect that the deformation is distributed over a wider area in the central crease forming portion 56 than in the distal portion 61. In this way, wider (i.e. less sharp) creases can be produced than using the creasing tool 53 of the embodiment described above.

[0089] Further, only the distal ends 63 of the cross-sectional sections 58 are separated from one another, while the proximal portions 61 are spread apart to fuse together to form the fused central rib 56. Thus, the proximal portions 61 of the preceding and succeeding cross-sectional sections 58 are fused together. Further, the proximal portions 61 of the opposing cross-sectional sections 58 are fused together across the central axis M.

[0090] This type of creasing tool 53 can be advantageously used to perform a pre-creasing operation in preparing the folds of the fibrous substrate 35 for the subsequent sharp ridges of the creasing tool 53 .

[0091] In this embodiment, the inclination angle α describes the inclination of the circumferential deformation portion 59 from the fused central rib 56 to the distal end portion 61 relative to the axis of rotation Xr.

[0092] 11a to 11c, a fifth embodiment of the creasing tool 53 is shown. In the fifth embodiment, the creasing tool 53 is positioned similarly to the fourth embodiment shown in Figures 10a to 10c, but further comprises an additional annular creasing ridge 66 that projects further away from the base surface 57 than the proximal portion 61 of the cross-sectional area 58. The annular creasing ridge 66 extends along the crease-forming portion 56.

[0093] As in the fourth embodiment, the proximal portion 61 of the cross-sectional area 58 widens in the direction towards the fold line forming portion 56 .

[0094] The annular creasing ridge 66 provides a sharper protrusion from the outer surface of the creasing tool 53 compared to the creasing tool 53 of the third embodiment, thus further increasing the accuracy of the crease lines formed by the creasing tool 53. However, the cross-sectional area 58 still provides a sufficient distribution surface area to prevent the cardboard from tearing.

[0095] Several tests have been completed with the creasing tool 53 of the present invention. These tests show a significant reduction in the breakage phenomenon of the fibrous corrugated substrate 35 when using the creasing tool 53 according to the present invention. The results are shown in Figures 12a and 12b, where Figure 12a shows a fibrous substrate 35 contacted by a prior art creasing tool (shown in Figure 5a), and Figure 12b shows a fibrous substrate 35 contacted by a creasing tool 53 of the present invention of the type shown in Figure 8b. Thus, the creasing tool 53 of the present invention can demonstrate a tear reducing effect on the fibrous substrate 35.

[0096] The invention can also be applied to other tools suitable for generating crease lines. For example, as shown in Fig. 13, the creasing tool 53 can be a die 53 for a platen printing press. The die 53 can be provided with a crease-forming edge (also called a rule) having a pattern corresponding to the relief portion 54, as shown in the embodiment of Figs. 8A to 11C.

[0097] The die 53 comprises a die board 90 provided with a pattern of cutting edges 94 and creasing edges 96. The cutting edges 94 are positioned around the periphery of the die board 90 and will define the outer contour of the intermediate blank 1.

[0098] Thus, in the embodiment of Figure 13, the creasing tool further comprises a cutting edge. This enables the creasing tool 53 to perform an additional cutting action as it is pressed against the fibrous substrate 35. In the previous embodiments, the cutting is achieved by a separate unit such as the groover 24 shown in Figure 3.

Claims

1. A creasing tool (53) configured to generate creases (11, 12) in a fibrous substrate (35), comprising: a contact portion (50) having a base surface (57) and relief portions (54) provided as a protruding pattern extending from the base surface (57) and configured to be pressed against the fibrous substrate; The relief portion (54) comprises a crease forming portion (56) and a peripheral deformation portion (59); the peripheral deformation portion comprises a plurality of discrete segments in the form of curved cross-sectional areas (58) extending in a direction (E) transverse to the longitudinal direction (L) of the crease forming portion (56), the outer periphery of the curved cross-sectional areas (58) being concave with respect to the outer edge (60) of a creasing tool (57); A creasing tool (53).

2. 2. The creasing tool of claim 1, wherein the peripheral deformation portion (59) is configured to apply a gradually increasing contact pressure on the fibrous substrate in a direction towards the crease line forming portion (56).

3. 3. The creasing tool according to any one of claims 1 to 2, characterized in that the crease line forming portion (56) and the circumferential deformation portion (59) are connected.

4. 4. The creasing tool according to any one of claims 1 to 3, characterized in that the relief portion (54) is centrally located on the contact portion (50).

5. 5. The creasing tool according to any one of claims 1 to 4, characterized in that the crease line forming portion (56) is a continuous line.

6. 6. A creasing tool according to any one of claims 1 to 5, characterized in that the crease line forming portion (56) protrudes further from the base surface (57) than the peripheral deformation portion (59).

7. 7. The creasing tool according to claim 1, wherein the peripheral deformation portion (59) is inclined downwards at an angle (α) in a direction away from the crease line forming portion (56) and towards an edge (60) of the creasing tool.

8. 8. The creasing tool according to any one of claims 1 to 7, characterized in that the curved cross-sectional area (58) has a proximal portion (61) located at the crease forming portion (56) and a distal end (63) shaped as a free end.

9. The crease forming portion (56) comprises an annular ridge (66); the annular ridge has a linear, straight shape extending around the circumference of the creasing tool and projects away from the base surface beyond the proximal portion (61) of the curved cross-sectional area (58); 9. The creasing tool of claim 8.

10. 10. The creasing tool according to any one of claims 1 to 9, characterized in that the curved cross-sectional area (58) has a proximal portion (61) positioned at the crease forming portion (56) and a distal end (63) shaped as a free end, and has a larger cross-sectional area at their proximal portion (61) than at their distal portion (63).

11. the crease forming portion is centrally located at the contact portion; the curved cross-sectional areas of the first and second sides of the crease forming portion are mirrored about a central axis (M) defined by the crease forming portion (56); the curved cross-sectional area of ​​the first side is offset relative to the curved cross-sectional area of ​​the second side; 11. A creasing tool according to any one of the preceding claims.

12. The linear elements converge at the crease line forming portion (56), whereby the proximal portion of the linear elements forms the crease line forming portion.

10. A creasing tool according to claim 8 or claim 9.

13. The creasing tool is provided as a creasing disc, the discrete segments extend at an angle (β) relative to a central axis (M) defined by the crease forming portion (56); 13. A creasing tool according to any one of the preceding claims.

14. A conversion machine, The creasing tool according to claim 13, the creasing disk is mounted on the converting machine such that the curved cross-sectional area extends at an angle (β) to the central axis (M) and transversely to the direction of rotation (R) of the disk, the angle being less than 90 degrees such that a distal end of the discrete segment, which is shaped as a free end of the curved cross-sectional area before a proximal portion of the discrete segment, which is located in the crease line forming portion (56), is in contact with the blank. A transformation machine characterized by:

15. A method for producing creases (11, 12) in a fibrous substrate (35) using a creasing tool (53) according to claim 1, comprising the steps of: selecting a fibrous substrate (35) having at least one corrugated layer (83); measuring the distance (p1) between the grooves (10) in said at least one corrugated layer; The cross-sectional length (d) of the curved cross-sectional area (58) is equal to or greater than 50% of the distance (p1) between the grooves (10). 2 ) selecting a creasing tool (53); pressing the creasing tool (53) against the fibrous substrate to obtain a crease line; 23. A method comprising:

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