Indentation tool, converting machine, and method for producing indentation lines in a fibrous substrate

Abstract

An indentation tool (53) configured to produce indentation lines (11, 12) in a fibrous substrate (35), the indentation tool comprising a contact portion (50) having a base portion (57) and a relief portion (54), the relief portion being provided as a protruding pattern extending from the base portion (57) and configured to bear against the fibrous substrate, wherein the relief portion (54) comprises an indentation line forming portion (56) and a peripheral deformation portion (59), and wherein the peripheral deformation portion comprises a plurality of discrete portions in the form of curved transverse surface regions (58) extending in a direction E transverse to the longitudinal direction L of the indentation line forming portion (56) and such that the outer periphery of the curved transverse surface regions (58) is concave relative to the outer edge (60) of the indentation tool (53).

Description

Technical Field

[0001] The present invention relates to an indentation tool, which is particularly suitable for the production of cardboard boxes. Background Art

[0002] In the packaging industry, cardboard boxes are usually made from cardboard sheets. The cardboard sheets can be processed in components such as folder-gluers, where they are printed (if necessary), cut, and indented, and then folded and glued to form flat-fold boxes, often also referred to as "folding boxes".

[0003] Corrugated cardboard is a material that generally includes a corrugated medium and two linerboards applied on each side of the corrugated medium. Corrugated cardboard combines light weight and high strength and is particularly suitable as a packaging material.

[0004] To fold the cardboard sheet, it is necessary to form indentation lines in the vertical direction. Then some of the indentation lines will be aligned with the direction of the corrugations, while other indentation lines will be in the transverse direction. The indentation lines can be made in a flat-bed printing press, where the die in the flat-bed printing press is provided with a protruding edge that is pressed against the cardboard sheet to produce the indentation line. The indentation line can also be formed by using a rotating indentation disk provided with a protruding annular indentation ridge. The indentation disk is usually integrated into the folder-gluer. The folder-gluer can also be referred to as a converter or an in-line converter. The converter converts or changes the web material or sheet material into an intermediate form or a finished flat-fold box.

[0005] The accuracy of the folding process depends on the quality of the indentation lines applied to the cardboard, i.e., the regularity of the position, shape, and the depth of the indentation. The sharper the indentation ridge becomes, the better the quality of the indentation applied to the cardboard. However, a sharp crease ridge can tear the cardboard.

[0006] When the indentation ridge is applied in a direction transverse to the longitudinal direction of the corrugations, the compressive force from the indentation tool tends to be distributed over a plurality of points where the top paper liner and the inner corrugated medium are joined. However, if the indentation line is to be formed in a direction aligned with the longitudinal direction of the corrugations, there is a significant variation in the bending resistance of the cardboard. Therefore, if pressure is applied at the point where the top paper liner and the inner corrugated medium are disconnected, the top paper liner may rupture. Summary of the Invention

[0007] In view of the above problems, an object of the present invention is to provide an indentation tool and a method for forming well-defined and precise indentation lines while reducing the risk of tearing the paper liner.

[0008] The object of the present invention is solved by the indentation tool according to the present invention and the method according to the present invention.

[0009] According to a first aspect of the present invention, the present invention relates to an indentation tool configured to produce an indentation line in a fibrous substrate. The indentation tool includes a contact portion having a base portion and a relief portion. The relief portion is provided as a protruding pattern extending from the base portion and is configured to press against the fibrous substrate.

[0010] Wherein, the relief portion includes an indentation line forming portion and a peripheral deformation portion, and

[0011] Wherein, the peripheral deformation portion includes a plurality of discrete portions, and the plurality of discrete portions are in the shape of a curved lateral surface region extending in a direction transverse to the longitudinal direction of the indentation line forming portion.

[0012] In the context of the present invention, the fibrous substrate is also referred to as a corrugated board substrate. For an indentation tool in the form of an indentation disc, the longitudinal direction is in the rotational direction of the indentation disc. Thus, the longitudinal direction extends around the circumference of the indentation tool.

[0013] The present invention is based on the recognition that the deformation from the indentation tool needs to be gradually distributed over the fibrous substrate to contact the weak areas where the linerboard and the corrugated layer are disconnected and the stronger areas where the linerboard and the corrugated layer are connected. This will generate a more dispersed pressure on the fibrous substrate, regardless of the position where the indentation line forming portion on the indentation tool contacts the fibrous substrate. Therefore, the peripheral deformation portion is configured to apply a gradually increasing contact pressure to the fibrous substrate in a direction towards the indentation line forming portion.

[0014] The plurality of discrete portions extending in the transverse direction not only apply pressure to the corrugations of the fibrous substrate along the direction in which the corrugations extend. In other words, the discrete portions act on the corrugations to gradually transition into the main indentation line. This helps to prevent the sheet from tearing around the main indentation line.

[0015] In one embodiment, the indentation line forming portion and the peripheral deformation portion are connected. This means that the relief portion is continuous from the indentation line forming portion to the peripheral deformation portion.

[0016] In the context of the present invention, continuous means that the indentation line forming portion is in the shape of a line or a surface region having a continuous protruding relief pattern protruding from the base portion.

[0017] The relief portion may be centrally arranged on the contact portion. In one embodiment, the peripheral deformation portion is laterally arranged on at least one side of the indentation line forming portion.

[0018] Preferably, the peripheral deformation portion is provided on both sides of the indentation line forming portion. In this way, the peripheral deformation portion can extend a greater distance on the fibrous substrate and reduce the risk of rupture on both sides of the indentation line forming portion.

[0019] The indentation line forming portion may be a continuous line. The line may be straight. Alternatively, the line may be arranged in a sawtooth shape.

[0020] In one embodiment, the indentation line forming portion protrudes further from the base portion than the peripheral deformation portion. The height difference enables a well-defined indentation line to be formed. In one embodiment, there is a discontinuity at the connection between the indentation line forming portion and the peripheral deformation portion, whereby the transition between the indentation line forming portion and the peripheral portion is discontinuous. In other words, there is no constant gradual slope in the transition.

[0021] The peripheral deformation portion is preferably inclined downwardly at an angle in a direction from the creasing line forming portion towards the edge of the creasing tool. The angle is defined relative to the rotation axis of the tool.

[0022] When the creasing tool comes into contact with the fiber substrate, this gradually increases the compression depth towards the central portion of the creasing tool. The peripheral deformed portion may be inclined downward at an angle ranging from 0° to 36°, preferably from 2° to 10°. The inclined outer surface of the creasing tool allows a smoother contact angle between the creasing tool and the inner linerboard, making it possible for mechanical calibration to manage the total width of the creasing mark, thereby increasing the folding angle without stress or cracking. For most paperboard substrates, angles greater than 36° generally do not allow full use of the lateral portion design. In addition, it can concentrate the mechanical pressure on a small surface, which may produce increased tearing phenomena on the inner linerboard.

[0023] In one embodiment, the lateral surface area in the peripheral deformation portion is linear in shape and has a proximal portion located in the scoring line forming portion and a distal portion in the shape of a free end.

[0024] In one embodiment, the creasing tool further comprises an intermediate rib, wherein the intermediate rib protrudes further from the base portion than the proximal portion of the lateral surface area. The height difference will enable a well-defined creasing line to be formed. Thus, there is a discontinuity at the connection between the creasing line forming portion and the peripheral deformation portion, whereby the transition between the creasing line forming portion and the peripheral deformation portion is discontinuous (i.e., does not show a constant gradual slope in the transition).

[0025] The lateral surface area may have a larger cross-sectional area in its proximal portion than in its distal portion. This may allow for a less sharp creasing line, which may be used in particular when a larger folding area is required. This type of lateral surface area is advantageous for a creasing disc used as a pre-creasing machine. The pre-creasing disc and the downstream positioned main creasing disc provide a two-step creasing line forming process. This allows for a gradual and smooth creasing line forming process.

[0026] The lateral surface area is defined in the context of the present invention as a linear element, which may be straight or curved and may have a uniform or varying thickness.

[0027] The creasing line forming portion may be centrally located on the contact portion, and the transverse surface areas on the first and second sides of the creasing line forming portion may be mirrored around a central axis defined by the creasing line forming portion and preferably offset relative to each other. For example, the transverse surface areas on the first side may be offset relative to the transverse surface areas on the second side. Thus, the transverse surface areas are placed so that they alternate. Thus, the pattern of the creasing tool may resemble a herringbone. This arrangement provides a distributed mechanical pressure applied by the creasing tool on the linerboard. This distributes the deformation footprint from the peripheral portion so that there is always a transverse portion in contact with the fibrous substrate.

[0028] In one embodiment, the transverse surface regions may be straight. This has the technical effect that the transverse surface regions may extend over a longer length than if they were curved. In one embodiment, the transverse surface regions may have a consistent cross-sectional area along their length.

[0029] In another embodiment, the transverse surface region is formed as a linear element, wherein the linear elements converge to a central scoring line forming portion, whereby the proximal portion of the linear element forms the scoring line forming portion. This arcuate shape enables the transverse surface region to form a substantially straight central scoring line on the fibrous substrate. This also enables a gradual transition, as it has been found that curved edges are smoother when deforming the fluting.

[0030] The creasing tool of the present invention may be used in a notching assembly of a converting machine configured for producing lay-flat carton boxes.

[0031] In one embodiment, the creasing tool of the present invention is arranged in a flat-bed printing press. The creasing tool may be a mold configured to be moved up and down and pressed against the fiber substrate in a vertical direction. Alternatively, the creasing tool may be arranged as a creasing disc.

[0032] The discrete portions extend at an angle relative to a central axis defined by the central scoring line forming portion.

[0033] The creasing tool may be generally annular. This allows for easy mounting of the creasing tool, for example on a roller or shaft of a creasing device. In this way, the creasing line may be applied to the paperboard by rotating the creasing tool so that the creasing tool contacts the paperboard. In one embodiment, the creasing tool may be provided in two semi-annular parts so that it may be mounted around the shaft without disconnecting the ends of the shaft. The two parts may be attached together by fasteners, such as bolts or screws, and may optionally be provided with an attachment bracket cooperating with the fasteners and the creasing tool parts to form a rigid disc assembly.

[0034] According to a second aspect, the present invention relates to a conversion machine, such as a folder-gluer, comprising a creasing tool configured as a creasing disk according to the first aspect of the invention, wherein the creasing disk is mounted in the conversion machine such that a lateral surface area extends in a lateral direction at an angle relative to a central axis and in a rotational direction of the disk, the angle being less than 90 degrees, such that a distal portion of the lateral surface area contacts the fiber substrate before a proximal portion of the discrete portion.

[0035] According to a third aspect, the present invention relates to a method for producing an indentation line in a fibrous substrate using an indentation tool according to the first aspect of the present invention, the method comprising the following steps:

[0036] - Select a fiber substrate having at least one corrugated layer,

[0037] - measure the distance between the corrugations in at least one corrugated layer,

[0038] - Select a creasing tool with a transverse surface area equal to or greater than 50% of the fluting distance, and

[0039] - Press the tool against the fiber substrate to obtain the impression line.

[0040] In one embodiment, the transverse length of the transverse surface area is equal to or greater than the flute distance. Thus, during the formation of the indentation, each discrete transverse surface area in the peripheral portion exerts a compressive force on at least two flutes, so that the risk of tearing or otherwise damaging the linerboard is reduced.

[0041] The creasing tool may include a variable number of transverse surface areas, which is determined by the number of transverse surface areas that are in contact with the paperboard simultaneously, less than per centimeter of the liner, preferably less than per centimeter of the liner. A lower number of transverse surface areas may not provide a sufficiently sharp fold line, while a higher number of transverse surface areas will produce an overly smooth outer surface on the creasing tool, and the creasing ring may not be able to generate enough pressure difference compared to the peripheral portion, which may not adequately define the fold line.

[0042] Preferably, at each location along the scoring line forming portion of the scoring tool, at least a portion of the lateral surface area is present on the outer surface of the scoring tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Further advantages and features will become apparent from the following description of exemplary embodiments of the invention and from the accompanying drawings, in which like features are indicated by like reference numerals and in which:

[0044] Figure 1 A plan view of a flat cardboard blank is shown;

[0045] Figure 2a shows a schematic perspective view of a flat-fold glued box obtained from the Figure 1 blank shown;

[0046] Figure 2b shows a schematic perspective view of an assembled box obtained from the Figure 2a flat-fold box shown;

[0047] Figure 3 shows a schematic view of a converting machine;

[0048] Figure 4 shows a Figure 3 cross-sectional view of the slitting unit of the converting machine;

[0049] Figure 5a shows a standard scoring tool known in the art;

[0050] Figure 5b shows a Figure 5a partial view of the scoring tool;

[0051] Figure 5c shows a cross-section of the scoring tool through Figure 5a ;

[0052] Figure 6 shows a schematic cross-sectional view of the scoring tool in contact with a corrugated board substrate;

[0053] Figure 7 shows a schematic cross-sectional view of a board substrate including a double-wall corrugated board substrate;

[0054] Figure 8a shows a first embodiment of a scoring tool according to the present invention;

[0055] Figure 8b is a Figure 8a partial view of the scoring tool;

[0056] Figure 8c shows a cross-section of the scoring tool through Figure 8a ;

[0057] Figure 8d and Figure 8e show another embodiment of a scoring tool, which is similar to the embodiment shown in FIGS. 8a to Figure 8c ;

[0058] Figure 9a shows a third embodiment of a scoring tool according to the present invention;

[0059] Figure 9b shows a Figure 9a partial view of the scoring tool;

[0060] Figure 9c shows a cross-section of an indentation tool passing through Figure 9a ;

[0061] Figure 10a shows a fourth embodiment of an indentation tool according to the present invention;

[0062] Figure 10b shows Figure 10a a partial view of an indentation tool;

[0063] Figure 10c shows a cross-section of an indentation tool passing through Figure 10a ;

[0064] Figure 11a shows a fifth embodiment of an indentation tool according to the present invention;

[0065] Figure 11b shows Figure 11a a partial view of an indentation tool; and

[0066] Figure 11c shows a cross-section of an indentation tool passing through Figure 10a ;

[0067] Figure 12a shows an indentation line obtained using an indentation tool of the prior art as shown in Figure 5a ;

[0068] Figure 12b shows an indentation line obtained using an indentation tool according to the present invention; and

[0069] Figure 13 is another exemplary embodiment of the present invention, which shows an indentation tool in the form of a flat-bed printing press die. DETAILED DESCRIPTION

[0070] Figure 1 shows an embodiment of an intermediate blank 1 made of corrugated cardboard, which is used to manufacture a folding carton 1', such as Figure 2a the folding carton 1' shown.

[0071] When manufacturing the folding carton 1', a fibrous substrate 35 in the form of a cardboard roll or sheet passes through a plurality of workstations in a converting machine 19, and these workstations print, cut and form, prepare the fibrous substrate 35 for folding, glue and fold the fibrous substrate 35. Figure 1The intermediate blank 1 therein has been indented, cut and formed and is ready for folding. As shown, the intermediate blank 1 generally presents a rectangular flat shape with two parallel edges of relatively large length. To form the folding box 1', the intermediate blank 1 needs to be further folded and glued in a separate processing module of the converting machine 19. The folding box 1' can be assembled in a final step to form a three-dimensional box 1'' as shown in Figure 2b shown.

[0072] As Figure 1 shown, the intermediate blank 1 includes a front edge 2 which should be placed forward and perpendicular to the processing / driving direction FD of the converting machine 19. As schematically shown in Figure 3 , the front edge 2 generally enters into the folding and gluing module 26 of the converting machine 19 which will then fold and glue the blank 1. The converting machine 19 includes a plurality of units aligned along the longitudinal axis of the sheet and the driving direction FD.

[0073] To enable the blank 1 to be folded into a three-dimensional box, a plurality of score lines 11, 12 are required. Different formats and models of the folding box 1' have different numbers and positions of the score lines 11, 12. The shown intermediate blank 1, the configuration of the cutouts and the score lines are merely an 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.

[0074] As Figure 1 shown, the score lines 11, 12 of the exemplary illustrated intermediate blank 1 are divided into two groups, where the first group 11 is configured as parallel score lines 11a, 11b, 11c, 11d which are aligned with the driving direction FD of the folding and gluing machine 19. The second group of score lines 12 are perpendicular score lines 12a, 12b and are thus perpendicular to the first group of parallel score lines 11a, 11b, 11c, 11d.

[0075] Two lateral edges of relatively small length defining a left edge 4 and a right edge 5 are provided. The left edge 4 presents openings along its two ends to define a flap 14 in the middle of the left edge 4. The front score line 12a and the rear score line 12b of the second group of score lines 12 are respectively parallel to the front edge 2 and the rear edge 3, and the front edge 2 and the rear edge 3 define a central portion 1a of the blank 1 which is intended to constitute the outer peripheral surface of the folding box 1' when assembled to form a three-dimensional box. The central portion 1a is placed between a rear portion 1b and a front portion 1c which are intended to constitute the bottom surface and the upper surface of the folding box 1'' respectively when assembled to form a three-dimensional box 1''.

[0076] The first set of parallel score lines 11 is generally parallel to the left edge 4 and the right edge 5 and the corrugations 10 of the corrugated layer of the cardboard. This set of parallel score lines 11 may extend along the entire width of the central portion 1a. One of the score lines 11a is adjacent to the flap 14, and another score line 11c (referred to as the central score) is aligned with the longitudinal axis A. According to the score lines 11 and the central score 11a, in some embodiments, the rear portion 1b and the front portion 1c may be cut to create slits 13 that extend across the entire width of the rear portion 1b and the front portion 1c.

[0077] The slits 13 define two pairs of plates in each of the rear portion 1b and the front portion 1c, respectively defining a first pair of large rear plates 6b and 6b', a second pair of large front plates 6c and 6c', a first pair of small rear plates 7b and 7b', and a second pair of small front plates 7c and 7c'. The large rear and front plates 6b, 6c and 6b', 6c' are located on each side of the large central plates 6a and 6a', respectively. In a similar manner, the small rear and front plates 7b, 7c and 7b', 7c' are located on each side of the small central plates 7a and 7a', respectively.

[0078] The score lines 11, 12 and their slits 13 are capable of folding the blank 1 into a folding carton 1' having a rectangular shape, each score line 11, 12 defining a fold line (see Figure 1 ). During the folding process, glue is typically placed on the flap 14, and the large left central plate 6a is thus connected to the small right central plate 7a'.

[0079] The converting machine 19 may have many different configurations. Figure 3 The converting machine 19 schematically shown and exemplary includes, in the driving direction FD from upstream to downstream in sequence, a loader 20 (for automatically loading the fibrous substrate 35 in the form of a sheet), a feeder 21, optionally a plurality of flexible printing units 22a to 22d, a converting unit having at least one slotting assembly 23 and at least one cutting unit 24, a waste stripping and optionally vibrating unit 25, and a folding and gluing unit 26. The converting machine 19 may further include an optional module 27, such as a counting and ejecting unit, a bundler and a palletizer (partially shown in dashed lines in Figure 3 ).

[0080] As Figure 4 shown, the slotting assembly 23 processes the printed fibrous substrates 35 discharged from the last printing unit 22d and converts them into intermediate blanks 1 (see Figure 1 ). The slotting assembly 23 is equipped with various rotary tools, which include forming edge cuts (as Figure 1The cutting tool or cutter that forms the slits 13 and the incisions that laterally delimit the fins 14, as shown in 1b, 1a, and 1c), and the indentation device or indentation machine that forms the longitudinal indentation line 11. It should be noted that the lateral indentation line 12 is produced upstream or downstream of the slitting assembly 23 (depending on the type and configuration of the converting machine), or is initially provided in the fibrous substrate 35.

[0081] The rotary tool is mounted on a transverse support shaft driven in rotation by a shaft motor. The rotational speed of the tool preferably corresponds to the running speed, i.e., the driving speed and running speed T of the fibrous substrate 35.

[0082] In the illustrated embodiment, the slitting assembly 23 includes, from upstream to downstream, a pre-indentation section 36 having a first pair of shafts positioned one above the other. The pre-indentation section 36 prepares the cardboard for subsequent formation of the priority crease lines. The pre-indentation device is thus configured to produce a pre-indentation area on the fibrous substrate 35, which is a partially deformed area on the fibrous substrate 35. The lower shaft is provided with a lower pre-indentation device 37, and the upper shaft carries an upper pre-indentation device 38, which is a corresponding part of the lower pre-indentation device 37. When the longitudinal indentation line 11 is indented in two consecutive operations, the pre-indentation section 36 performs the first initial indentation operation.

[0083] Downstream of the pre-indentation section 36, a first slitting section 39 is installed, which has a second pair of shafts positioned one above the other. The upper shaft of the first slitting section 39 is provided with a disc on which a cutter 41 is mounted, and the lower shaft is provided with a relative lower blade 42. The first slitting section 39 cuts the slit 13 placed at the rear of the blank 1.

[0084] Downstream of the first slitting section 39, an indentation section 43 is installed, which has a third pair of shafts positioned one above the other. The lower shaft of the indentation section 43 is provided with a lower indentation device 44, and the upper shaft is provided with an upper indentation device 46, which is a corresponding part of the lower indentation device 44. The indentation section 43 performs the second indentation operation and the final indentation operation, including the formation of the priority crease lines, thereby ensuring the permanent and precise marking of the longitudinal indentation line 11.

[0085] Downstream of the indentation section 43, a second slitting section 47 is installed, which has a fourth pair of shafts positioned one above the other. The upper shaft of the second slitting section 47 is provided with a disc fitted with a cutter 48, and the lower shaft is provided with a relative lower blade 49. The second slitting section 47 cuts the slit 13 located at the front of the blank 1.

[0086] In order to cut out the glued flap 14 and make the rear cut and the front cut of the flap 14, the processing unit 43 may include a device 51 for processing the fiber substrate 35. The device 51 is placed in the impression section. Considering the proximal position of the flap 14 on the blank 1, the device 51 is preferably installed at the end of the operator side of the upper shaft in the impression section 43.

[0087] The lower pre-scorer 37 and the upper pre-creaser 38 and the lower creasing device 44 and the upper creasing device 46 are creasing devices having a creasing tool 53. Therefore, the creasing tool 53 is mounted on a shaft in the creasing portion 43, and the shaft serves as a support for the corresponding creasing tool 53. The pre-scorer 37 and the creasing device 44 may also be arranged above or below the fiber base material 35.

[0088] exist Figures 5a to 5c In FIG. 5 , a creasing tool 53 known in the art is schematically shown. The creasing tool 53 can be used for the pre-cracking portion 36 and the creasing portion 43 (see FIG. Figure 4 ). The indentation tool 53 is annular and can be mounted on the shaft of the converter 19, as long as the inner diameter of the indentation tool 53 is selected according to the corresponding shaft size. The annular indentation tool 53 can be arranged in two semi-annular parts so that it can be mounted around the shaft and forms a complete ring when mounted.

[0089] The creasing tool 53 includes an embossed portion 54 having an indentation line forming portion 56 in the shape of an indentation ridge or a middle rib on the outer surface of the indentation tool 53. By pressing the embossed portion 54 against the fiber substrate 35, the indentation lines 11, 12 can be formed by deforming the linerboard and the fluting 10 of the fiber substrate 35.

[0090] Reference now Figures 8a to 11c , which shows an embodiment of a creasing tool 53 according to the present invention. Figure 8a In the embodiment shown, it can be seen that the disc-shaped creasing tool 53 has a contact portion 50 with an overall width W. The creasing tool 53 can be provided in two parts 53a, 53b so that it can be mounted around a shaft without disconnecting the ends of the shaft. The two parts 53a, 53b can be assembled at a connection 55 to form a disc.

[0091] The contact portion 50 includes an embossed portion 54 provided with a pattern of protruding indentation lines.

[0092] On the side of the relief portion 54, the creasing tool 53 may include an outer portion configured as a base portion 57. The base portion 57 may be provided with a smooth surface (i.e., not provided with a creasing pattern). Alternatively, the base portion 57 may be curved. During the creasing operation, the relief portion 54 is in contact with the fiber substrate 35, while the base portion 57 is positioned at a distance from the fiber substrate 35.

[0093] As Figure 8c Best shown, the embossed portion 54 includes an indentation line forming portion 56 and a peripheral deformation portion 59. The peripheral deformation portion 59 is disposed on the side of the indentation line forming portion 56.

[0094] The indentation line forming portion 56 is a raised line extending around the circumference of the indentation tool 53. When the indentation tool 53 presses against the fibrous substrate 35, the indentation line forming portion 56 will produce the central portion of the indentation line. The central portion of the indentation line defines a preferred folding line, which is the exact position of folding. The peripheral deformation portion 59 distributes the compressive force from the indentation tool 53 on the fibrous substrate 35 in a progressive manner in the direction towards the indentation line forming portion 56. Thus, the compression on the fibrous substrate 35 increases from the peripheral deformation portion 59 and thus concentrates towards the indentation line forming portion 56 of the indentation tool 53.

[0095] The peripheral deformation portion 59 is a discrete protruding pattern extending from the base portion 57. For example, the peripheral deformation portion 59 can be designed to protrude from the base portion 57 by 0.5 to 1.6 mm. The peripheral deformation portion 59 is provided with a plurality of transverse surface regions 58. The transverse surface regions 58 have a vertical length d2 with respect to the longitudinal direction L of the central indentation line forming portion 56 (see Figure 8b ). The transverse surface regions 58 extend in the longitudinal direction L with respect to the central indentation line forming portion 56 and in the transverse direction with respect to the central axis M of the indentation tool 53. These transverse surface regions 58 can be in a linear shape. In some embodiments, the transverse surface regions 58 can be straight or curved. When viewed together with the indentation line forming portion 56, the transverse surface regions 58 are in a herringbone shape 58, or fishbone.

[0096] As Figure 8b Best shown, the transverse surface region 58 has a proximal portion 61 disposed at the indentation line forming portion 56 and a distal portion (i.e., free end) 63 disposed at the outer edge of the embossed portion 54. The distal portion 63 is thus disposed further away from the indentation line forming portion 56 than the proximal portion 61. Thus, the transverse surface region 58 extends along the extension direction E from the indentation line forming portion 56 towards the edge 60 of the indentation tool 53.

[0097] Since the indentation line forming portion 56 is continuous and the peripheral deformation portion 59 is discontinuous, the deformation is concentrated on the indentation line forming portion 56. Thus, the indentation line forming portion 56 is configured to produce a sharp and precise indentation line.

[0098] The indentation tool 53 of the present invention can be used for the pre-indentation portion 36 and the main indentation portion 43.

[0099] The indentation lines 11, 12 formed on the fiber substrate 35 include a main indentation line portion, which is the central portion of the indentation lines 11, 12 and is provided by the indentation line forming portion 56. If the indentation lines 11, 12 are provided by the main indentation tool 53, the main indentation line portion corresponds to the preferred folding line. In another example, if the indentation lines 11, 12 are provided by a pre-indentator, the main indentation line portion forms the main part of the pre-indentation area. The indentation lines 11, 12 are also provided with a peripheral indentation line portion provided by the peripheral deformation portion 58.

[0100] In Figures 8a to 8c the illustrated embodiment, the proximal portion 61 of the lateral surface area 58 on the first side of the indentation line forming portion 56 contacts the lateral surface area 58 on the opposite second side of the indentation line forming portion 56.

[0101] Now referring to Figure 8c , Figure 8c is further shown the geometry in a cross-section of the indentation tool 53 through Figure 8a . The relief portion 54 of the indentation tool 53 can slope downward at an angle α from the indentation line forming portion 56 in a direction towards the edge 60 of the indentation tool 53. Thus, the peripheral deformation portion 59 can slope downward at an angle α from the indentation line forming portion 56 relative to the rotation axis Xr of the indentation tool 53. This gradually increases the compression depth generated by the indentation tool 53 on the fiber substrate 35 in a direction towards the central indentation line forming portion 56. During the rotation of the indentation tool 53, as the height of the lateral surface area 58 increases in the rotation direction R, the compression depth caused by each lateral surface area 58 entering the fiber substrate 35 gradually increases.

[0102] 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 indentation line forming portion 56. It has been found that this range increases the folding angle without stress and limits the double folding (i.e., square folding) phenomenon. This inclination can be constant along the extension direction E of the lateral surface area 58.

[0103] The rotation direction R of the indentation tool 53 (see Figure 8a ) can be selected such that the distal portion 63 of the lateral surface area 58 points forward in the rotation direction R and thus contacts the fiber substrate 35 before the proximal portion 61 of the lateral surface area 58. This has the effect that the central indentation line forming portion 56 applies the central portion of the folding line to the fiber substrate before making immediate contact with multiple corrugations in the fiber substrate 35.

[0104] As Figure 8a and Figure 8bAs shown, the proximal portion 61 can be arranged such that the proximal portion 61 contacts the lateral surface area 58 on the opposite side of the central axis M. Alternatively, in Figure 8d and Figure 8e the illustrated embodiment, the proximal portion 61 can be arranged to connect to the lateral surface area on the opposite side of the central axis M in such a way that the proximal portion 61 penetrates into the opposite lateral surface area 58. Generally for both alternatives, the lateral surface area 58 on one side of the central axis M preferably contacts or penetrates the opposite lateral surface area 58 on the other side of the central axis in the middle along its extending direction E.

[0105] As Figure 6 shown, the corrugated fiber substrate 35 can be composed of a top liner paper 81, a bottom liner paper 82, and a corrugated fluting layer 83 arranged therebetween. As previously described, rupture of the fiber substrate 35 generally occurs when the indentation line forming portion 56 contacts the corrugated fiber substrate 35 at the position where the top liner paper 81 and the corrugated fluting layer 83 are disconnected. This is shown in Figure 6 . The liner paper 81 of the corrugated fiberboard substrate 35 is also referred to as a "layer" in the context of the present invention.

[0106] As Figure 8b best shown, thus advantageously, the lateral length d2 of the lateral surface area 58 is selected based on the geometry of the corrugated fiberboard substrate 35 and particularly based on the distance p1 between the flutes (see Figure 8b ). Thus, the lateral length d2 of the lateral surface area 58 is selected to be equal to or greater than 50% of the peak-to-peak distance p1 between the flutes in the corrugated fiber substrate 35. Alternatively, a distance equal to 100% of the peak-to-peak distance p1 can be selected. This ensures that the lateral surface area 58 contacts the flutes even if the indentation tool 53 is not centered between the flutes. For a corrugated fiberboard substrate having a plurality of corrugated fluting layers 83a, 83b, as Figure 7 shown, the lateral length d2 of the lateral surface area 58 can be similarly selected to be equal to or greater than 50% of the maximum peak-to-peak distance p1 of the fluting layers 83a, 84b or corresponding to 100% of the maximum peak-to-peak distance p1 of the fluting layers 83a, 84b. Alternatively, the lateral length d2 can be selected from the peak-to-peak distance p1 of the upper fluting layer.

[0107] The extending direction E of the lateral surface area 58 can be straight, particularly in combination with an annular and continuous annular ridge 66. However, as Figures 8a to 8eAs shown, the lateral surface regions 58 may be provided with a curved shape such that their proximal portions 61 converge to form a continuous central indentation line forming portion 56. The lateral surface regions 58 curve from their proximal portions 61 to their distal portions 63. The curved shape may be provided by a single radius or a combination of multiple different radii along the extension direction E of the lateral surface regions 58. In the case of multiple different radii, the lateral surface regions 58 may have different portions, each portion having a different radius, and the curved shape allows the lateral surface regions 58 to form a continuous indentation line forming portion 56 and a peripheral deformation portion 59.

[0108] The lateral surface regions 58 are thus configured to gradually increase and direct the deformation on the fibrous substrate 35 to converge into the central main indentation line portion. Thus, the proximal portions 61 of the lateral surface regions 58 form the indentation line forming portion 56. The outer periphery of the curved lateral surface regions 58 is concave with respect to the outer edge 60 of the indentation tool 53. Thus, the convex side of the lateral surface regions 58 is positioned closer to the central axis M than the concave side.

[0109] On the opposite side of the annular ridge 66, the extension direction E of the subsequent lateral surface regions 58 is mirrored and preferably offset at a distance d3 along the central axis M defined by the central indentation line forming portion 56. This results in an alternating pattern of the lateral surface regions 58.

[0110] The discrete portions or lateral surface regions 58 extend in a lateral direction at an angle β with respect to the central axis M and in the rotational direction R of the disc. The angle β is less than 90 degrees such that the distal portions 63 of the discrete portions or lateral surface regions 58 contact the fibrous substrate 1 before the proximal portions 61 of the discrete lateral surface regions 58.

[0111] For the curved lateral surface regions 58, the angle β with respect to the extension direction E of the indentation line forming portion 56 thus gradually decreases from the distal portion 63 to the proximal portion 61. This provides a gradual transition between the indentation line forming portion 56 and the peripheral deformation portion 59.

[0112] The lateral surface regions 58 on the first side of the indentation line forming portion 56 and the lateral surface regions on the second side of the indentation line forming portion 56 cooperate such that even if the lateral surface regions 58 are arranged in a discrete manner, there is a continuous lateral member in the peripheral deformation portion 59 that applies pressure on the corrugations 10 in the fibrous substrate 35. This ensures a continuous compressive force on the fibrous substrate 35 in the lateral direction and a dense arrangement of the lateral surface regions 58 on the outer surface of the indentation tool 53.

[0113] As Figure 8bAs best shown, the lateral surface regions 58 can be equidistantly placed on the outer surface of the indentation tool 53, wherein the distal portions 63 of the lateral surface regions 58 are spaced apart by a distance d4. If the lateral surface regions 58 all have the same size, the distance d4 between the proximal portions 61 is the same (i.e., constant) around the outer circumference of the indentation tool 53.

[0114] In Figures 9a to 9c the third embodiment shown, the indentation tool 53 is arranged in a manner similar to the first embodiment, but additionally includes a continuous annular ridge 66 in the indentation line forming portion 56. The annular ridge 66 has a linear and straight shape extending along the central axis M. The annular ridge 66 thus extends around the outer circumference of the indentation disk 53.

[0115] The annular ridge 66 is arranged parallel to the edge 60 of the indentation tool 53. The annular ridge 66 is placed at a distance d1 from the edge 60, which distance d1 is preferably chosen to correspond to approximately 50% of the total width W of the indentation tool 53, such that the intermediate rib is positioned at the center of the indentation tool 53.

[0116] Thus, the lateral surface regions 58, whose extension direction E extends from the annular ridge 66 towards the edge 60 of the indentation tool 53, contact the annular ridge 66. The annular ridge 66 can preferably protrude further from the base portion 57 than the proximal portions 61 of the lateral surface regions 58.

[0117] Compared with the indentation tool of the first embodiment, the annular ridge 66 provides a sharper protrusion from the outer surface of the indentation tool 53, thus further increasing the sharpness of the indentation lines 11, 12 formed by the indentation tool 53. However, the lateral surface regions 58 still provide a gradually increasing deformation on the surface of the fibrous substrate 35 to prevent the fibrous substrate 1 from being torn.

[0118] In Figures 10a to 10c shown is a fourth embodiment of the indentation tool 53. In the fourth embodiment, the indentation tool 53 is arranged similarly to the first embodiment, but the indentation line forming portion 56 and the peripheral deformation portion 59 are formed by a single continuous portion. The proximal portions 61 of the lateral surface regions 58 in the peripheral deformation portion 59 are provided wider than the distal portions 63.

[0119] This has the effect that the deformation is distributed over a larger area at the central indentation line forming portion 56 than at the distal portions 63. In this way, a wider (i.e., less sharp) indentation line can be achieved than with the indentation tool 53 of the embodiments described above.

[0120] In addition, only the distal portions 63 of the lateral surface regions 58 are separated from each other, while the proximal portions 61 are widened in such a way that they merge to form a merged intermediate rib. Thus, the proximal portions 61 of the anterior and posterior lateral surface regions 58 merge. Additionally, the proximal portions 61 of the opposing lateral surface regions 58 merge on the central axis M.

[0121] Such an indenting tool 53 can be advantageously used to perform a pre - indenting operation, since it prepares a fold in the fibrous substrate 35 for a subsequent and sharper ridge of the indenting tool 53.

[0122] In this embodiment, the tilt angle α describes the tilt of the peripheral deformation portion 59 from the merged intermediate rib to the distal portion 63 and relative to the rotational axis Xr.

[0123] In Figures 11a to 11c a fifth embodiment of the indenting tool 53 is shown. In the fifth embodiment, the indenting tool 53 is arranged similarly to the fourth embodiment shown in Figures 10a to 10c but further includes an additional annular ridge 66 which projects further from the base portion 57 than the proximal portion 61 of the lateral surface region 58. The annular ridge 66 extends along the indentation - line forming portion 56.

[0124] Similar to in the fourth embodiment, the proximal portion 61 of the lateral surface region 58 is widened in the direction towards the indentation - line forming portion 56.

[0125] Compared to the indenting tool 53 of the third embodiment, the annular ridge 66 provides a sharper protrusion from the outer surface of the indenting tool 53 and thus further increases the precision of the indentation line formed by the indenting tool 53. However, the lateral surface region 58 still provides a sufficiently distributed surface to prevent the cardboard from being torn.

[0126] Several tests were performed on the indenting tool 53 of the present invention. When using the indenting tool 53 according to the present invention, these tests showed a significantly reduced rupture phenomenon of the corrugated fibrous - based substrate 35. The results are shown in Figure 12a and Figure 12b where Figure 12a shows the fibrous substrate 35 contacted by an indenting tool of the prior art (as shown in Figure 5a ). Figure 12b shows the fibrous substrate 35 contacted by the indenting tool 53 of the present invention of the type shown in Figure 8b . Thus, the indenting tool 53 of the present invention is capable of exhibiting a reduced tearing effect on the fibrous substrate 35.

[0127] The present invention can be further applied to other tools suitable for producing indentation lines. For example, as shown in Figure 13 , the indenting tool 53 can be a die 53 of a flat - bed printing press. As shown inFigures 8a to 11c As shown in the embodiment of, the die 53 may be provided with an indentation-forming edge (also referred to as a rule) having a pattern corresponding to the relief portion 54.

[0128] The die 53 includes a die plate 90, and the die plate 90 is provided with a pattern of cutting edges 94 and indentation edges 96. The cutting edges 94 are located in the peripheral portion of the die plate 90 and will define the outer contour of the intermediate blank 1.

[0129] Thus, in Figure 13 the embodiment of, the indentation tool further includes a cutting edge. This enables the indentation tool 53 to perform an additional cutting operation when it is pressed against the fibrous substrate 35. In the previous embodiment, the cutting was achieved by a separate unit (such as Figure 3 the grooving machine 24 shown in).

Claims

1. An indentation tool (53) configured to produce indentation lines (11, 12) in a fibrous substrate (35), the indentation tool (53) comprising a contact portion (50) having a base portion (57) and a relief portion (54), the relief portion (54) being provided as a protruding pattern extending from the base portion (57) and configured to bear against the fibrous substrate (35). Among them, The relief portion (54) includes an indentation line forming portion (56) and a peripheral deformation portion (59), and wherein the peripheral deformation portion (59) includes a plurality of discrete portions in the form of curved lateral surface regions (58) extending in a direction E along a longitudinal direction L transverse to the indentation line forming portion (56), and the outer periphery of the curved lateral surface region (58) is concave with respect to the outer edge (60) of the indentation tool (53).

2. The indentation tool (53) according to claim 1, wherein the peripheral deformation portion (59) is configured to apply a gradually increasing contact pressure on the fibrous substrate (35) in a direction towards the indentation line forming portion (56).

3. The indentation tool (53) according to claim 1, wherein the indentation line forming portion (56) and the peripheral deformation portion (59) are connected.

4. The indentation tool (53) according to claim 1, wherein the relief portion (54) is centrally arranged on the contact portion (50).

5. The indentation tool (53) according to claim 1, wherein the peripheral deformation portion (59) is laterally arranged on at least one side of the indentation line forming portion (56).

6. The indentation tool (53) according to claim 1, wherein the peripheral deformation portion (59) is laterally arranged on both sides of the indentation line forming portion (56).

7. The indentation tool (53) according to claim 1, wherein the indentation line forming portion (56) is a continuous line.

8. The indentation tool (53) according to claim 1, wherein the indentation line forming portion (56) protrudes further from the base portion (57) than the peripheral deformation portion (59).

9. The indentation tool (53) according to claim 1, wherein the peripheral deformation portion (59) slopes downward at an angle α in a direction from the indentation line forming portion (56) and towards the outer edge (60) of the indentation tool (53).

10. The indentation tool (53) according to claim 10, wherein the lateral surface region (58) is linear in shape and has a proximal portion (61) located at the indentation line forming portion (56) and a distal portion (63) shaped as a free end.

11. The indentation tool (53) according to claim 10, wherein the indentation tool (53) further includes an annular ridge (66), and the annular ridge (66) protrudes further from the base portion (57) than the proximal portion (61) of the lateral surface region (58).

12. The indentation tool (53) according to claim 1, wherein the lateral surface area (58) has a larger cross-sectional area in its proximal part (61) than in its distal part (63).

13. The indentation tool (53) according to claim 1, wherein the indentation line forming part (56) is centered on the contact part (50), and wherein the lateral surface areas (58) on the first and second sides of the indentation line forming part (56) are mirror images about a central axis M defined by the central indentation line forming part.

14. The indentation tool (53) according to claim 13, wherein the lateral surface area (58) on the first side is offset relative to the lateral surface area (58) on the second side.

15. The indentation tool (53) according to claim 10 or 11, wherein the discrete part is shaped as a linear element, and wherein the linear element is curved and convergent at the central indentation line forming part, whereby the proximal part of the linear element forms the central indentation line forming part.

16. The indentation tool (53) according to claim 1, wherein the indentation tool (53) is provided as an indentation disk, and wherein the discrete part extends at an angle β relative to a central axis M defined by the central indentation line forming part.

17. A converting machine comprising the indentation tool (53) according to claim 16, wherein the indentation disk is mounted in the converting machine such that the lateral surface area (58) extends in a lateral direction at an angle β relative to the central axis M and in the rotational direction R of the indentation disk, the angle β being less than 90 degrees such that the distal part of the lateral surface area (58) contacts the blank before the proximal part of the discrete part.

18. A method of producing indentation lines (11, 12) in a fibrous substrate (35) using the indentation tool (53) according to claim 1, the method comprising the steps of: - selecting a fibrous substrate (35) having at least one corrugated layer (83), - measuring a corrugation distance p1 between corrugations (10) in the at least one corrugated layer, - selecting the indentation tool (53) having a lateral length d2 of the lateral surface area (58) equal to or greater than 50% of the corrugation distance p1, and - pressing the indentation tool (53) against the fibrous substrate (35) to obtain the indentation lines.

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