Flap cutting device for converters

Abstract

The present invention relates to a flap cutting device (28) for cutting out flaps from blanks (2) conveyed in a conveying direction (T) through a converting machine (1). The flap cutting device comprises a central rotation axis (32) located at the center of gravity of the flap cutting device. Only three extensions extend from the central rotation axis in the form of a first tool holding extension (34a), a second tool holding extension (34b), and a third extension (36) with a counterweight (37). Each of the first and second tool holding extensions is connectable to a first and second cutting tool (38a, 38b).

Description

[Technical Field]

[0001] The present invention relates to a flap cutting device for a converting machine configured to produce packaging elements, such as folding boxes, from paper and cardboard. [Background technology]

[0002] Converting machines such as flexo folder-gluers produce folding boxes and other similar folded packaging elements. These converting machines include multiple workstations that print and convert sheet substrates into printed cut-to-shaped blanks, which are then converted into packaging elements such as folding boxes. Flexo folder-gluers include a slotter module with a disc-shaped cutting and creasing tool that cuts and creases the sheet substrate.

[0003] There are several types of folding boxes, many of which require blanks with glue flaps. An example of such a box is the American-style box. The glue flaps are cut out by a side-mounted flap cutting device with two cutting blades.

[0004] EP 2750874 discloses an example of a side-mounted flap cutting device with four legs, where a first and second blade are attached to two of the legs, and the remaining two legs act as counterweights.

[0005] Depending on the desired length of the gluing flap, the flap cutting device can be configured to rotate at different speeds during one revolution. The different speeds are achieved by momentary acceleration and deceleration. However, the acceleration and deceleration are limited by the size of the flap cutting tool. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] European Patent No. 2750874 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the prior art, it is an object of the present invention to provide a flap cutting apparatus that is capable of cutting a wide range of flap sizes while ensuring high production rates through the conversion machine. [Means for solving the problem]

[0008] This object is solved by a flap cutting device according to claim 1.

[0009] According to a first aspect of the present invention, there is provided a flap cutting device for cutting out flaps from blanks conveyed in a conveying direction through a converting machine. The flap cutting device comprises a central rotation axis located at a center of gravity of the flap cutting device. The flap cutting device comprises only three extensions in the form of a first tool holding extension, a second tool holding extension, and a third extension comprising a counterweight. Each of the first and second tool holding extensions is connectable to a first and second cutting tool, respectively.

[0010] Three extensions extend from the central axis of rotation.

[0011] Preferably, the first and second tool holding extensions are of equal radial length and the third extension is shorter than the first and second tool holding extensions.

[0012] In one embodiment, the angle between the first tool holding extension and the second tool holding extension may be between 80° and 90°, preferably about 87°.

[0013] Preferably, the first and second cutting tools comprise elongated first and second cutting edges, respectively, extending transversely to the conveying direction.

[0014] In one embodiment, the first cutting edge is disposed in a first direction and the second cutting edge is disposed in a second direction, the first and second directions extending at opposite angles to the conveying direction.

[0015] In one embodiment, the first and second cutting edges are arranged in the same direction relative to the conveying direction.

[0016] In one embodiment, the cutting edge extends perpendicular to the conveying direction.

[0017] In one embodiment, the flap cutting device is made from aluminum or titanium. The counterweight may be integrally cast with the third extension and the first and second tool holding extensions.

[0018] According to a second aspect of the present invention, there is provided a double slotter module using the above-mentioned flap cutting device, the double slotter module comprising a first slotter assembly and a second slotter assembly, the first slotter assembly comprising a first flap cutting device, the second slotter assembly comprising a second flap cutting device, the first and second flap cutting devices having only three extensions in the form of a first tool holding extension, a second tool holding extension, and a third extension comprising a counterweight, the first and second tool holding extensions being coupleable to first and second cutting tools, respectively.

[0019] In one embodiment, the first and second tool holding extensions of the first flap cutting device comprise cutting tools with cutting edges positioned in a first direction relative to the conveying direction, and the first and second tool holding extensions of the second flap cutting device comprise cutting tools with cutting edges positioned in a second direction relative to the conveying direction, the first and second directions being opposite to the conveying direction of the blank.

[0020] The cutting edge can be arranged obliquely with respect to the conveying direction.

[0021] The present invention will now be described with reference to the accompanying drawings, in which like features are designated with the same reference numerals. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram of a converter in a flexo folder-gluer configuration. [Figure 2a] FIG. 2 is a schematic top view of a blank produced by the converter of FIG. 1. [Figure 2b] 2 is a schematic top view of another type of blank produced by the converter of FIG. 1. FIG. [Figure 3a] FIG. 1 is a schematic perspective view of a folding box. [Figure 3b] FIG. 1 is a schematic perspective view of an assembled folding box. [Figure 4] FIG. 1 is a schematic side view of a slotter assembly according to the prior art. [Figure 5] FIG. 1 is a schematic side view of a double slotter assembly according to the prior art. [Figure 6] 1 is a schematic cross-sectional view of a flap cutting assembly according to one embodiment of the present invention; [Figure 7] 1 is a schematic cross-sectional view of a flap cutting device according to an embodiment of the present invention; [Figure 8] FIG. 1 is a schematic diagram of an exemplary double slotter configuration for producing side-by-side blanks. [Figure 9] FIG. 1 is a schematic diagram of an exemplary double slotter configuration for producing a single blank. DETAILED DESCRIPTION OF THE INVENTION

[0023] With particular reference to Figures 2a and 2b, there is shown an example of a blank 2 made from cardboard that can be used to manufacture a folding box 2' as shown in Figure 3a.

[0024] When producing a folding box 2', the sheet substrate passes through several workstations of the converting machine 1 which can convert the sheet substrate into a blank 2 by printing, cutting, gluing and folding.

[0025] Before gluing and folding, the blank 2 may generally have a rectangular flat shape with two parallel sides 4 of greater length. The folded box 2' may be assembled in a final stage to form a three-dimensional box 2'' as shown in Figure 3b. A number of crease lines 11a, 11b are required to enable the blank 2 to be folded into the three-dimensional box 2''.

[0026] Relative to the conveying direction T, the blank 2 has two side edges 5 in the form of a left edge 5a and a right edge 5b. In the example shown, the left edge 5a has cutouts 7a, 7b in order to define a flap 6 in the middle of the left edge 5a.

[0027] 1 shows a schematic representation of a converting machine 1 in the form of a flexo folder-gluer. The converting machine 1 may comprise, successively in a conveying direction T, a loader 10 for automatically loading sheet substrates, a feeder 12, optionally a plurality of flexo printing units 14, a converting unit 16 comprising a slotter module having at least one slotter assembly 17, at least one cutting unit 18, and a folding-gluing unit 20. The converting machine 1 may also comprise further optional modules such as a counting-discharge unit, a bundler, and a palletizer (not shown).

[0028] As shown in Figure 4, the slotter assembly 17 includes a pre-creasing section 22, a first slot forming section 24, a creasing section 26, a flap cutting device 28, and a second slot forming section 30. The slotter assembly 17 includes a rotary tool including a creasing tool configured to perform the creasing and a cutting tool configured to sever the blank 2. The cutting tool and the creasing tool are mounted on a transverse shaft that is rotationally driven by a shaft motor. The tangential rotation speed of the tool preferably corresponds to the conveying speed V of the blank 2.

[0029] The pre-creasing section 22 includes a first pair of shafts arranged one above the other, which pre-crease the blank 2 and prepare it for subsequent priority fold creasing.

[0030] The first slot-forming section 24 is located downstream of the pre-creasing section 22 and is configured to make the first and second edge cuts 8a, 8b (see FIG. 2a) and cut the rearwardly located slit 13b in the blank 2. The first slot-forming section 24 includes a second pair of shafts, one above the other. The upper shaft of the first slot-forming section 24 includes a disk with a cutting blade, and the lower shaft includes a lower corresponding blade.

[0031] The creasing section 26 is located downstream of the first slot-forming section 24. The creasing section 26 includes a third pair of shafts, one above the other. The lower shaft of the creasing section can include a lower creasing tool, and the upper shaft can include an upper creasing tool that mates with the lower creasing tool. However, the tools can be reversed. The creasing tool of the slotter assembly 17 forms the longitudinal crease line 11 a. It should be noted that the transverse crease line 11 b can be formed upstream or downstream of the slotter assembly 17, or can be initially provided in the sheet substrate.

[0032] Thus, the creasing section 26 performs the second and final creasing operations, including the formation of priority folds, to ensure permanent and accurate marking of the longitudinal fold lines 11a.

[0033] Downstream of the creasing section 26 is mounted a second slot-forming section 30 comprising a fourth pair of shafts, one above the other. The upper shaft of the second slot-forming section comprises a disk containing a cutting blade, and the lower shaft comprises a lower corresponding blade. The second slot-forming section cuts a slit 13a located at the front of the blank 2.

[0034] The slotter assembly further includes a flap cutting device 28. The flap cutting device 28 may be disposed in the creasing section 26. The flap cutting device 28 is disposed at a position lateral to the converting machine 1, at an edge of the blank conveying path P of the converting machine 1.

[0035] The flap cutting device 28 comprises a first cutting tool 38a and a second cutting tool 38b configured to make front and rear cuts 7a, 7b perpendicular or oblique to the side edge 5a of the blank 2. The first and second cutting tools 38a, 38b are cutting blades with elongated cutting edges 39a, 39b. The front and rear cuts 7a, 7b are therefore made perpendicular or oblique to the conveying direction T.

[0036] The flap 6 is cut out from the remainder of the side edge 5a of the blank 2 by making a first longitudinal cut 8a and a second longitudinal cut 8b in the first slot-forming section 17 using first and second peripherally mounted slotter discs. The first and second longitudinal cuts 8a, 8b define the length Lf of the flap 6 in the conveying direction T. Thus, the longer the first and second longitudinal cuts 8a, 8b, the shorter the "uncut length" left in the flap 6.

[0037] As shown in Figure 2b, some types of blank 2 include multiple juxtaposed blanks 2a, 2b joined by lines of weakness 15. The lines of weakness 15 can then be broken by a breaker device in the converter 1 (as described in EP 3445549). Each of the juxtaposed blanks 2a, 2b includes transverse and longitudinal fold lines 11a, 11b similar to the blank 2 shown in Figure 2a.

[0038] For these types of juxtaposed blanks 2, the cutting and creasing operations can be shared between a first slotter assembly 17a and a second slotter assembly 17b, as shown in Figure 5. Such a slotter module can be called a "double slotter." A double slotter module can ensure high production rates because the cutting operations are partially shared between the cooperating cutting tools.

[0039] Each slotter assembly 17a, 17b may include a separate creasing unit 26 with a flap cutting device 28. Thus, a double slotter allows multiple juxtaposed blanks 2a, 2b to be cut from the same sheet substrate. Such a double slotter configuration is further described in EP 3934903.

[0040] The length Lf of the flap 6 in the conveying direction T can be changed by momentarily changing the rotational speed of the flap cutting device 28 when the cutting tools 38a, 38b of the flap cutting device 28 are not in contact with the blank 2. In addition, the angular positions of the cutting blades on the first and second slot-forming sections 24a, 24b are adjusted to form cuts 8a, 8b of different lengths.

[0041] The front and rear cuts 7a, 7b of the flaps are made by a flap cutting device 28 having a tangential speed that corresponds to the conveying speed V of the blank 2. Thus, at the time of the front and rear cuts 7a, 7b of the flaps 6, when the cutting tools 38a, 38b cut into the blank 2, the tangential speed of the flap cutting device 28 is equal to the conveying speed V of the blank 2.

[0042] The front cut 7a can be made first, followed by the rear cut 7b. The rotational speed of the flap cutting device 28 can be different from the conveying speed V between the front cut 7a and the rear cut 7b. The rotational speed of the flap cutting device 28 can be momentarily increased between the front cut 7a and the rear cut 7b to produce a shorter flap 6. Conversely, momentarily decreasing the rotational speed between the front cut 7a and the rear cut 7b will lengthen the flap 6. Thus, momentarily slowing down the flap cutting device 28 will lengthen the flap 6, and momentarily accelerating it will shorten the flap 6.

[0043] The diameter of the flap cutting device 28 may need to be adapted to the diameter of other rotary processing tools of the converting machine 1. Typically, a larger flap cutting device 28 is required as the diameter of the printing cylinder changes.

[0044] A larger flap cutting device 28 has a larger diameter and a larger distance between the cutting tools 38a, 38b. The weight and inertia of a large flap cutting device 28 have a limiting effect on the acceleration and deceleration that can be achieved. Therefore, it can be difficult to obtain a specific flap length Lf at high conveying speeds.

[0045] 6, the flap cutting assembly 40 of the present invention includes the flap cutting device 28, a counter cylinder 42, and a chassis 44. The flap cutting device 28 and the counter cylinder 42 are rotatably mounted on the chassis 44. The counter cylinder 42 may include an elastic layer 46 that contacts the cutting edges 39a, 39b of the first and second cutting tools 38a, 38b.

[0046] 7, a flap cutting device 28 according to an embodiment of the present invention includes a central rotation axis 32 located at the center of gravity of the flap cutting device 28. A first tool holding extension 34a and a second tool holding extension 34b extend radially from the central rotation axis 32.

[0047] The first and second tool holding extensions 34a, 34b have a first cutting tool 38a and a second cutting tool 38b coupled to their respective distal ends. A third extension 36 extending from the central rotation axis 32 includes a counterweight 37. Thus, the flap cutting device 28 includes only three extensions 34a, 34b, 36. The first and second tool holding extensions 34a, 34b have equal radial lengths.

[0048] The third extension 36 may also be referred to as a "counterweight extension" 36. The counterweight 37 may be fixedly attached to the flap cutting device 28. For example, the counterweight 37 may be integrally cast with the first, second, and third extensions 34a, 34b, 36. Alternatively, the counterweight 37 may be removably attached to the third extension 36. In that way, the weight of the counterweight 37 may be adapted to the weight of the first and second cutting edges 38a, 38b.

[0049] The radial extent of the counterweight extension 36 may be less than the radial extent of the first and second tool retaining extensions 34a, 34b, which allows the counterweight 37 to rotate without contacting the blank 2.

[0050] The first and second tool holding extensions 34a, 34b are disposed with an angle α therebetween. The angle α between the central axis of the first tool holding extension 34a and the central axis of the second tool holding extension 34b can be between 80° and 90°, preferably 87°. The counterweight extension 36 is disposed at an angle β from the first tool holding extension 34a. Because the flap cutting device 28 is symmetrical, the counterweight extension 36 is disposed at an angle β from either the central axis of the first tool holding extension 34a or the central axis of the second tool holding extension 34b. The angle β is between 140° and 135°, preferably 136.5°.

[0051] Therefore, the angle β=(360°-α) / 2.

[0052] The weight of the counterweight 37 is selected so that the flap cutting device 28 is balanced and in equilibrium throughout a 360° rotation of the flap cutting device 28 .

[0053] Each of the first and second tool holding extensions 34a, 34b may include a fastener 35 to allow for interchangeability of the first and second cutting tools 38a, 38b.

[0054] The cutting tools 38a, 38b can be arranged so that the cutting edges 39a, 39b extend in two opposite diagonal directions D1, D2 relative to the conveying direction T. This configuration is advantageous for slotter modules that include only one slotter assembly 17. This enables the flap cutting device 28 to make two diagonal cuts 7a, 7b in opposite directions to provide symmetrical flaps 6.

[0055] Alternatively, in the case of rectangular flaps 6, the cutting tools 38a, 38b extend in a direction perpendicular to the conveying direction T. These two configurations make it possible to cut out the flaps 6 with one single flap cutting device 28.

[0056] However, in the case of a double slotter module as shown in FIG. 5, the double slotter module can also be configured to process a single blank 2 using cooperating first and second flap cutting devices 28a, 28b. As best seen in FIG. 9, the first flap cutting device 28a can be positioned a distance Df upstream of the second flap cutting device 28b in the conveying direction T. In this embodiment, it is advantageous to provide the first flap cutting device 28a with a cutting edge 39a extending obliquely in the first direction D1. The second flap cutting device 28b is configured similarly to the first flap cutting device 28a, but with a cutting edge 39a extending in a second direction D2 opposite the first direction.

[0057] This is further shown in Figure 9, where a first flap cutting device 28a makes a forward cut 7a and a second flap cutting device 28b makes a rearward cut 7b of the flap 6. The first and second cuts 7a, 7b are in opposite directions D1, D2 relative to each other.

[0058] When processing a composite blank 2 having at least two juxtaposed blanks 2a, 2b, as shown in Figure 8, the first flap cutting device 28a can include a tool fastener 35 configured to position both the first cutting edge 39a and the second cutting edge 39b in a first direction D1. Similarly, the second flap cutting device 28b can include a tool fastener 35 configured to position both the first cutting edge 39a and the second cutting edge 39b in a second direction D2. The first direction D1 and the second direction D2 are opposite to each other.

[0059] The first flap cutting device 28a makes a front cut 7a on each of the juxtaposed first and second blanks 2a, 2b, and the second flap cutting device 28b makes a back cut 7b on each of the juxtaposed first and second blanks 2a, 2b. In other words, individual flaps 6 are cut out by the two cooperating flap cutting devices 28a, 28b. The advantages of using the first and second flap cutting devices 28a, 28b are that there is no limit to the sheet thickness and that waste material can be removed. For a single blank 2, there is no limit to the length of the flap 6.

[0060] 8 and 9, the first and second flap cutting devices 28a, 28b may have first and second tool extensions and first and second counterweight extensions (as shown in FIG. 4), however, the cutting blades of the first flap cutting device 28a and the second flap cutting device 28b are disposed in opposite directions D1, D2.

[0061] However, in the configurations of Figures 8 and 9, it is advantageous to use first and second flap cutting tools 28a, 28b as shown in Figure 7, where the first flap cutting device 28a has first and second cutting edges 39a, 39b extending in a first direction D1 and the second flap cutting device 28b has first and second cutting edges 39a, 39b extending in a second direction D2.

Claims

1. 1. A flap cutting device (28) for cutting out flaps from blanks (2) conveyed in a conveying direction (T) through a converting machine (1), said flap cutting device comprising a central axis of rotation (32) arranged at the centre of gravity of said flap cutting device, said flap cutting device comprising only three extensions in the form of a first tool holding extension (34a), a second tool holding extension (34b) and a third extension (36) provided with a counterweight (37), each of said first and second tool holding extensions being connectable to a first and second cutting tool (38a, 38b), respectively.

2. 2. The flap severing apparatus of claim 1, wherein the first and second tool holding extensions have equal radial lengths, and the third extension is shorter than the first and second tool holding extensions.

3. 3. A flap cutting device according to claim 1 or 2, wherein the angle (α) between the first and second tool holding extensions is between 80° and 90°, preferably about 87°.

4. 4. The flap cutting device according to claim 1, wherein the first and second cutting tools comprise elongated first and second cutting edges (39a, 39b), respectively, extending transversely to the conveying direction (T).

5. 5. The flap cutting device according to claim 4, wherein the first cutting edge (39a) is arranged in a first direction (D1) and the second cutting edge (39b) is arranged in a second direction (D2), the first and second directions extending at opposite angles to the conveying direction (T).

6. 5. The flap cutting device according to claim 4, wherein the first and second cutting edges (39a, 39b) are arranged in the same direction (D1, D2) relative to the conveying direction (T).

7. 5. The flap cutting device according to claim 4, wherein the cutting edges (39a, 39b) extend perpendicular to the conveying direction (T).

8. 8. The flap cutting device according to any one of claims 1 to 7, wherein the flap cutting device is made from aluminum or titanium.

9. 9. A flap cutting apparatus according to any preceding claim, wherein the counterweight is integrally cast with the third extension and the first and second tool retaining extensions.

10. 10. A double slotter module using a flap cutting device according to any one of claims 1 to 9, the double slotter module comprising a first slotter assembly (17a) and a second slotter assembly (17b), the first slotter assembly (17a) comprising a first flap cutting device (28a), the second slotter assembly (17b) comprising a second flap cutting device (28b), the first and second flap cutting devices (28a, 28b) having only three extensions in the form of a first tool holding extension (34a), a second tool holding extension (34b), and a third extension (36) comprising a counterweight (37), the first and second tool holding extensions being connectable to first and second cutting tools (38a, 38b), respectively.

11. 11. The double slotter module of claim 10, wherein the first tool holding extension and the second tool holding extension of the first flap cutting device (28a) are provided with cutting tools having cutting edges positioned in a first direction (D1) relative to the conveying direction (T), and the first and second tool holding extensions of the second flap cutting device (28b) are provided with cutting tools having cutting edges (39a, 39b) positioned in a second direction (D2) relative to the conveying direction (T), the first direction and the second direction being opposite to the conveying direction (T) of the blank (2).

12. 12. The double slotter module according to claim 11, wherein the cutting edges (39a, 39b) are arranged obliquely with respect to the conveying direction (T).

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