Stamping tool

Abstract

In a die-cutting tool for cutting plastic-based film elements (12), comprising a die-cutting unit (13) having several knife carriers (21) to which at least one die-cutting knife (25a, 25b) having a cutting wedge (31) tapering to a cutting edge (32) is attached, and comprising a die (14) assigned to the die-cutting unit (13) and opposite it for receiving the film element (12) to be processed, wherein the die-cutting unit (13) is mounted to be relatively movable relative to the die (14) during a die-cutting stroke occurring in a stroke direction (15) between a starting position (16) and a processing position (17), wherein the cutting wedges (31) of the die-cutting knives (25a, 25b) plunge into the film element (12) to be processed in the processing position (17) and, depending on their penetration depth, cut along an edge length of the cutting edge. (32) create a cutting line (43) or a break line (44) in the foil system (12),the cutting edges (32) of the punching knives (25a, 25b) are contoured such that they each have an edge section (37; 37a, 37b) which is inclined with respect to a reference line (38) perpendicular to the stroke direction (15).

Description

[0001] The invention relates to a punching tool for cutting PET-based film elements, comprising a punching unit having a plurality of blade carriers, to each of which at least one punching blade is fastened, each having a cutting wedge tapering to a cutting edge, and comprising a die assigned to and opposite the punching unit for receiving the film element to be processed, wherein the punching unit is mounted so as to be relatively movable relative to the die during a punching stroke in a stroke direction between a starting position and a processing position, wherein the cutting wedges of the punching blades, in the processing position, plunge into the film element to be processed and, depending on their immersion depth, create a cutting line or a perforation line in the film system along a processing length, wherein the cutting edges of the punching blades are contoured such that they each have an edge section,which is inclined with respect to a reference line perpendicular to the stroke direction.

[0002] Punching tools have been around for a long time. Their purpose is to cut large-area plastic film elements, which can be, for example, a two-dimensional film or a three-dimensional film element. Such three-dimensional film elements can be, for example, yogurt cups, which need to be processed in a specific way after production, for example, singulated or cut out in groups of four, six, or eight. Important components of such punching tools are punching knives, which, depending on the depth of penetration into the film element, create either a cutting line or a breaking line. If a cutting line is created, the film element is cut completely. If a breaking line is created, the film element to be processed is weakened along this line.

[0003] Conventional punching tools, especially their punching blades, are designed to process polystyrene-based film elements. For environmental reasons, such polystyrene-based film elements are increasingly being replaced by other plastic-based film elements, such as PET-based, PLA-based, or PP-based film elements. However, PET-based film elements, in particular, are tougher than polystyrene-based film elements, so the punching blades are subjected to greater stress.

[0004] EP 2 594 496 A1 discloses a cutting device, a packaging device with a cutting device, and a method for cutting a film. The cutting device comprises a knife having a blade, the blade comprising a plurality of first and a plurality of second teeth, the first teeth being longer than the second teeth, such that, in use, the first teeth contact a surface to be cut before the second teeth. A punch cut is created using the cutting device and the correspondingly contoured knife.

[0005] The object of the invention is to provide a punching tool of the type mentioned at the outset in which the load during the processing of plastic-based film elements, in particular for the punching blades, is reduced compared to conventional punching tools.

[0006] This object is achieved by a punching tool having the features of independent claim 1. Further developments of the invention are presented in the subclaims.

[0007] The punching tool according to the invention is characterized in that the cutting wedges are each formed by a wedge inner surface and a wedge outer surface and the die has a knife cavity which has a die edge associated with the wedge inner surface, wherein the wedge inner surface moves along the die edge at a certain distance transverse to the stroke direction during the punching stroke.

[0008] The design of the cutting edges of the punching knives ensures that the cutting line or break line is gradually formed as the cutting wedges penetrate the film system. The cutting line or break line is thus formed in a "pulling cut" manner. This means that when a cutting line is formed, the entire edge length is not cut simultaneously, which significantly reduces the stress on the punching knives. When forming the break lines, perforations are also not formed simultaneously across the entire edge length, but gradually.

[0009] The cutting wedges of the punching knives are each formed by an inner wedge surface and an outer wedge surface, and the die has a die cavity that has a die edge associated with the inner wedge surface. During the punching stroke, the inner wedge surface moves along the die edge at a specific distance transverse to the stroke direction. When the cutting wedges penetrate the film element to be processed, the cutting wedges are pressed towards the die edge. However, because the cutting edges of the punching knives are designed to have an edge section that is inclined with respect to a reference line perpendicular to the stroke direction, this pressure towards the die edge is reduced, which reduces the load on the punching knives and thus increases the quality of the cut or break lines produced when cutting into the plastic material.

[0010] In a further development of the invention, the cutting edge has two edge sections arranged at an angle to each other, which together form a wedge shape. This wedge shape can be created, for example, in the manner of a diamond grind of the punching blade.

[0011] An alternative geometry for the cutting edges of the punching knives is multiple edge sections that together form a wave-shaped contour. This wave shape can be created, for example, in the manner of a bread knife grind on the punching knife.

[0012] Alternatively, it is possible for the cutting edge to have several edge sections that together form a zigzag or sawtooth-like contour.

[0013] Particularly preferably, the punching unit comprises a plurality of, for example, star-shaped contour punches for punching out a surface section of the foil element, the underside of which is positioned closer to the die in the starting position than the cutting edges of the punching blades. The contour punches can precede the punching blades during the punching stroke and, for example, punch out a star-shaped contour before the punching blades come into contact with the foil element.

[0014] In a further development of the invention, it is possible for the punching knives to be detachably fastened to a knife seat of the associated knife carrier by means of fastening means, wherein the fastening means comprise a tuning element, in particular a disc-shaped element, inserted between the knife seat and the wedge inner surface for adjusting the distance between the die edge and the wedge inner surface. Once the distance between the wedge inner surface of the punching knife and the die edge has been adjusted via the tuning element, no readjustment or correction of the distance is required when changing the punching knives, for example due to wear, since even a newly clamped punching knife always maintains the distance between its wedge inner surface and the die edge specified by the tuning element.

[0015] Particularly preferably, the punching unit has a height adjustment device for adjusting the height of the punching blades between a cutting height position, in which the punching blades create a cutting line during the punching stroke, and a perforation height position, which is further away from the die than the cutting height position in the starting position and in which the punching blades create a breaking line in the form of a perforation line during the punching stroke. Particularly preferably, the height adjustment device is assigned a control device for individually controlling the punching blades in order to move them optionally to the cutting height position or the perforation height position. This allows an individual punching pattern to be created, whereby a wide variety of finishing options for the film elements to be processed can be carried out using the same punching tool.The height adjustment device can, for example, comprise a type of switching system that can be controlled by the control device, allowing the height of the punching knives to be changed. The switching system can, for example, be operated fluidically, in particular pneumatically, or electrically.

[0016] Particularly preferably, the height adjustment device comprises height adjustment units for individually adjusting the height of the punching knives relative to the die. The height adjustment units enable fine adjustment of the height of the punching knives. While the height adjustment device ensures that the punching knives are adjusted between the cutting height and the perforation height, the height adjustment unit advantageously allows for continuous adjustment of the height of the punching knives over a specific adjustment range.

[0017] In a particularly preferred manner, the height adjustment units each have a base body connected to a base plate of the punching unit, on which the knife carrier with the punching knife is movably mounted in the height direction via an adjustment drive.

[0018] Particularly preferably, the adjustment drive is designed as a spindle drive, which allows for precise height adjustment. However, other types of adjustment drives can also be used.

[0019] In a further development of the invention, the punching unit has a hold-down device with at least one hold-down device which fixes the film element to be processed in the processing position on the die.

[0020] In a particularly preferred manner, the punching unit has at least one stop element, to which at least one counter-stop element is assigned on the die such that during the punching stroke, the stop element strikes the counter-stop element to limit the stroke of the punching unit.

[0021] In a further development of the invention, the die has at least one contour cavity which interacts with the associated contour punch during the punching stroke and into which the contour punch can be moved, wherein the contour cavity borders on adjacent knife cavities for the punching knives.

[0022] Particularly preferably, the contour cavities are each surrounded by support sections that support the film element to be processed. These support sections can ensure that the film element to be processed is sufficiently supported and does not sag, which would negatively impact the cutting or perforation quality.

[0023] Preferred embodiments of the invention are illustrated in the drawing and explained in more detail below. The drawing shows: Figure 1 is a perspective view of a preferred embodiment of the punching tool according to the invention, Figure 2 is a longitudinal section through a part of the punching unit of Figure 1 , Figure 3 an enlarged view of detail X from Figure 2, Figure 4 is a perspective view of a first embodiment of a punching knife according to the first embodiment of the punching tool according to the invention, Figure 5 is a perspective view of the first embodiment with a film element to be processed, Figure 6 is a perspective view of a second embodiment of a punching knife according to a second embodiment of the punching tool according to the invention, Figure 7 is a perspective view of a punching knife module with knife carrier and punching knife as well as adjustment drive and Figure 8 is a plan view of an exemplary PET-based film element processed according to the punching tool according to the invention.

[0024] The Figures 1 to 5 , 7 and 8show a first exemplary embodiment of the punching tool 11 according to the invention for cutting plastic-based film elements 12. The punching tool 11 according to the invention is described below using a three-dimensional PET-based film element 12 as an example, which can be, for example, a yogurt cup. Of course, it is also possible to use the punching tool 11 according to the invention to cut or process completely different plastic-based film elements 12, for example, two-dimensional plastic films. For example, the punching tool 11 according to the invention can be used to process two- or three-dimensional PE, PP, PLA, or PVC-based film elements.

[0025] The aim of the punching process of the plastic, especially PET-based, film elements 12 is to assemble the film elements 12 from a virtually endless raw strand into individual groups or individual elements. An example of this is Figure 8 a group of four yogurt cups is shown.

[0026] As particularly in Figure 1 shown, the punching tool 11 has a punching unit 13, which represents the movable part of the punching tool 11. A die 14 for receiving the foil element 12 to be processed is arranged opposite the punching unit 13, wherein the punching unit 13 is movable relative to the die 14 during a punching stroke in a stroke direction 15 between a starting position 16 ( Figure 1 ) and a processing position 17 (Figures 2 and 3) is mounted relatively movably.

[0027] As in Figure 1 As shown, the punching unit 13 has a base plate 18, which is shown as an example in a rectangular shape. Several functional components of the punching unit 13 are attached to the base plate 18. The functional components include several punching knife modules 19, one of which is shown as an example in Figure 7The punching knife module 19 has an exemplary cube-shaped base body 20 on which a knife carrier 21 is movably mounted. As shown in particular in Figure 3 As shown, the knife carrier 21 has a guide section 22 mounted on the base body 20 and a bearing section 23 forming the free end of the knife carrier 21, on which a flat and planar knife seat 24 for an associated punching knife 25a is formed. As can be seen from the overview of the Figures 3 and 7 As shown, the punching knife 25a is detachably fastened to the associated knife seat 24 by means of fastening means. Examples of fastening means shown are fastening screws 26a, 26b, which penetrate associated through holes 27a, 27b in the punching knife and the associated recesses (not shown) are countersunk in the bearing section of the knife carrier 21.

[0028] An important aspect is that between the seat surface 28 of the knife seat 24 and the punching knife 25a there is a tuning element in the form of a relatively thin tuning disc 29 ( Figure 3 ). The adjusting disc 29 also has through holes through which the fastening screws 26a, 26b pass. Thus, screwing the punching blade 25a, 25b tightly onto the seat surface 28 simultaneously clamps the adjusting disc 29 between the seat surface 28 and the punching blade 25a.

[0029] As particularly in Figure 3 As shown, the punching knife 25a, 25b has a knife base 30 on which, as shown particularly in the Figures 4 to 6 shown, the through holes 27a, 27b are located, which penetrate the knife base 30 transversely to the stroke direction 15.

[0030] The punching knife also has a cutting wedge 31 which tapers in the stroke direction to a cutting edge 32.

[0031] As particularly in Figure 3As shown, the cutting wedge 31 is formed by a wedge inner surface 33 and a wedge outer surface 34, wherein the wedge outer surface 34 in the example is inclined to the stroke direction 15, while the wedge inner surface 33 runs substantially parallel to the stroke direction.

[0032] As further stated in Figure 3 As shown, the die 14 has a knife cavity 35 which has a die edge 36 associated with the wedge inner surface 33, wherein the wedge inner surface 33 moves along the die edge 36 during the punching stroke at a specific distance which is determined by the thickness of the adjusting disk 29 transversely to the stroke direction.

[0033] As particularly according to the first embodiment in the Figures 4 and 5 As shown, the cutting edge 32 of the punching knife 25a is contoured such that it has an edge portion 37a, 37b which is inclined with respect to a reference line 38 perpendicular to the stroke direction 15.

[0034] As particularly in the Figures 4 and 5 As shown, the cutting edge 32 according to the first embodiment has two edge sections 37a, 37b arranged at an angle to one another, which together form a wedge shape. This creates a wedge tip 40 or cutting tip approximately centrally with respect to the edge length 39, which first strikes the foil element 12 to be processed during the punching stroke.

[0035] The characteristic contour of the cutting edge 32 according to the first embodiment is expediently produced in the manner of a diamond cut. As shown in particular in Figure 4 As shown in Figure 5, in this case, not only is the cutting edge 32 ground with the two edge sections 37a, 37b, but the grinding also extends into the wedge outer surface 34. For example, two flank surfaces 41a, 41b, also tapering towards each other in a wedge shape, are formed here.

[0036] As further stated in Figure 4As shown, the knife cavity 35 is adapted to the contour of the cutting edge 32. In this case, the knife cavity 35 has two cavity sections 42a, 42b arranged at an angle to each other ( Fig.4 ).

[0037] The Figure 6 shows a second embodiment of the punching tool 11 according to the invention. The second embodiment differs from the previously described first embodiment in the different design of the punching blade 25b, which in this case has a differently contoured cutting edge 32. In this case, the cutting edge 32 has several edge sections 37 that together form a wave-shaped contour. This can be achieved, for example, in the manner of a "bread knife grind."

[0038] As particularly in Figure 3As shown, the cutting wedges 31 of the punching knives 37a, 37b, in the processing position, plunge into the film element 12 to be processed and, depending on their immersion depth, produce a cutting line 43 or a breaking line 44 in the film system 12 along an edge length of the cutting edge 32. A height adjustment device (not shown) belonging to the punching unit 13 is used to adjust the immersion depth of the punching knives 25a, 25b. The height adjustment device allows the punching knives 25a, 25b to be adjusted between a cutting height position 45, in which the punching knives 25a, 25b create a cutting line 43 during the punching stroke, and a perforation height position 46, which is further away from the die 14 than the cutting height position 45 in the starting position 16 and in which the punching knives 25a, 25b create a breaking line during the punching stroke. Punching knives 25b with a wave-shaped contour are also suitable for forming breaking lines 44.

[0039] The height adjustment device is a control device (not shown) that allows individual control of the punching knife modules 19, allowing them to be moved either to the cutting height position 45 or the perforation height position 46. This allows for a completely different grouping of punching knives that generate cutting lines 43 and punching knives that generate perforation lines 44, in order to produce completely different finishes for the film element to be processed. The height adjustment unit can, for example, have a switching system, via which a fluidic, for example pneumatic, height adjustment of the punching knife modules 19 can be achieved.

[0040] As particularly in Figure 7 As shown, the height adjustment device comprises height adjustment units, of which Figure 7One is shown as an example. The height adjustment units 47 include the base body 20 of the punching knife module 19, already described above, on which the knife carrier 21 is movably mounted in the stroke direction 15 via an adjustment drive 48, which also belongs to the height adjustment unit 47. In the example shown, the adjustment drive 48 is designed as a spindle drive.

[0041] The punching unit 13 also includes other functional units. The punching unit 13 has a hold-down device 49 with at least one hold-down clamp that fixes the foil element to be processed in the processing position 17 on the die 14.

[0042] Furthermore, the punching unit 13 comprises several, in the example case, star-shaped contour punches 50 for punching out a surface section 60 ( Fig.8 ) of the film element 12 to be processed. As particularly in Figure 1As shown, a contour punch 50 is arranged between adjacent punching blades 27a, 27b. The undersides 51 of the contour punches are positioned closer to the die 14 in the starting position 16 than the cutting edges 32 of the punching blades 25a, 25b. Thus, the contour punches 50 precede the punching blades during the punching stroke and penetrate into the plastic material of the film element 12 before the punching blades 25a, 25b. As can be seen particularly in the Figures 1 to 3 As shown, the die 14 has a plurality of contour cavities 52 which interact with the associated contour punches 50 during the punching stroke and into which the contour punches 50 can be inserted, wherein the contour cavities each adjoin adjacent knife cavities 35 for the punching knives 25a, 25b. As shown in particular in Figure 4 As shown, the contour cavities 52 are each surrounded by support sections 53 that support the film element 12 to be processed. A step 54 is formed between the support sections 53 and the knife cavities.

[0043] A further functional unit of the punching unit 13 is a stop element 55 arranged on the base plate 18, which interacts with a counter-stop element 56 arranged on the die 14 in such a way that the stop element 55 located on the movable punching unit 13 strikes the counter-stop element 56 to limit the punching stroke. As shown in particular in Fig. 1 shown are several pairs of stop elements 55 and counter-stop elements 56 distributed over the surface of base plate 18 on the one hand and die 14.

[0044] A key aspect is that, before the punching tool is used for the first time, the distance between the wedge inner surface 33 and the die edge 36 of each individual punching blade 25a, 25b can be precisely adjusted using appropriately selected shims 29. This distance does not need to be readjusted during operation of the punching tool 11. The punching blades 25a, 25b can be replaced, for example, in the event of wear, but the shims remain in place, ensuring that the correct distance between the wedge inner surface 33 and the die edge 36 is always set even with newly installed punching blades.

[0045] During operation, the packaging to be processed for the plastic-based film element 12 is first determined. An example of this is a group of four, such as four-cup yogurt cups, which are still connected by break lines 44 and can then be separated from each other by tearing.

[0046] Depending on the assembly task, groups of punching knives are then moved to the cutting height position 45, so that a cutting line 43 is created during the punching stroke, and other groups are moved to the perforation height position 46, so that break lines 44 are created during the punching stroke. During the punching stroke, the punching unit 13, with the punching knives 25a, 25b correctly positioned at the height, moves downwards towards the die 14, on which the film element 12 to be processed was previously placed.

[0047] Because the edge sections 42a, 42b of the cutting edges 32 of the punching blades 25, 25b are aligned obliquely to a reference line 38 oriented perpendicular to the stroke direction, cutting is not performed simultaneously across the entire edge length, but rather gradually. For example, in the first embodiment, the wedge tip 40 first cuts into the material of the film element 12. The cutting line 43 is therefore created in the manner of a pulling cut, which significantly reduces the forces acting on the punching blades 25a, 25b.

[0048] During the punching cut, the punching knives 25a, 25b move into the associated knife cavity 35 in the die 14. Following the punching knives, the punching knives 25b, located at the perforation height 46, move into the foil element 12 to be processed, but do not penetrate as deeply, creating the previously described break line 44.

[0049] In front of the punching blades 25a, 25b, the contour punches 50 have already moved into the film element 12 to be processed and have punched out a star-shaped surface section 60, for example. Because the cutting line 43 is formed over the entire cutting edge 32 of the punching blade, the transition between the punched surface section 60 and the cutting line 43 is free of any disruptive transitions, such as barb-like material residues. This is also supported by the fact that the film element 12 to be processed is supported in the area of ​​the contour cavities 52 by the adjacent support sections 53.

Claims

1. Punching tool for cutting plastic-based film elements (12), having a punching unit (13), which has a plurality of knife carriers (21), to each of which at least one punching knife (25a, 25b), which has a cutting wedge (31) tapering to a cutting edge (32), is fastened, and having a die (14), which is assigned to the punching unit (13) and is located opposite the latter, for receiving the film element (12) to be processed, the punching unit (13) being mounted such that it is relatively movable with respect to the die (14) during a punching stroke taking place in a stroke direction (15) between an initial position (16) and a processing position (17), the cutting wedges (31) of the punching knives (25a, 25b), in the processing position (17), dipping into the film element (12) to be processed and, as a function of their dipping depth, producing a cutting line (43) or a breaking line (44) in the film system (12) along an edge length of the cutting edge (32), the cutting edges (32) of the punching knives (25a, 25b) being contoured in such a way that they each have an edge section (37; 37a, 37b) which is inclined with respect to a reference line (38) at right angles to the stroke direction (15), the cutting wedges (31) each being formed by an inner wedge surface (33) and an outer wedge surface (34), and the die having a knife cavity (35) having a die edge (36) associated with the inner wedge surface (33), wherein the inner wedge surface (33) moves along the die edge (36) during the punching stroke at a certain distance defined by the thickness of a tuning disk (29) transverse to the stroke direction.

2. Punching tool according to Claim 1, characterized in that the cutting edge (32) has two edge sections (37a, 37b) which are arranged at an angle to one another and together form a wedge shape.

3. Punching tool according to Claim 1, characterized in that the cutting edge (32) has a plurality of edge portions (37) which together form an undulating contour.

4. Punching tool according to Claim 1, characterized in that the cutting edge (32) has a plurality of edge sections which together form a zigzag contour.

5. Punching tool according to one of the preceding claims, characterized in that the punching unit (13) has a plurality of, for example, star-shaped contour punches (50) for punching out a surface portion of the film element (12), the underside (51) of which, in the initial position (16), is positioned closer to the die (14) than the cutting edges (32) of the punching knives (25a, 25b).

6. Punching tool according to one of the preceding claims, characterized in that the punching knives (25a, 25b) are each releasably fastened to a knife seat (24) of the associated knife carrier (31) by means of fastening means, the fastening means having an in particular disk-shaped tuning element arranged between the knife seat (24) and the wedge inner surface (33) for adjusting the distance between the die edge (36) and the wedge inner surface (33).

7. Punching tool according to one of the preceding claims, characterized in that the punching unit (13) has a height adjustment device for adjusting the height of the punching knives (25a, 25b) between a cutting height position (45), in which the punching knives (25a, 25b) produce a cutting line (43) during the punching stroke, and a perforation height position (46), which is further away from the die (14) than the cutting height position (45) in the initial position (16) and in which the punching knives (25a, 25b) produce a breaking line (44) during the punching stroke.

8. Punching device according to Claim 7, characterized in that the height adjustment device is assigned a control device for individually actuating the punching knives (25a, 25b) in order to move them optionally into the cutting height position (45) or the perforation height position (46).

9. Punching tool according to Claim 7 or 8, characterized in that the height adjustment device has height adjustment units (47) for individually adjusting the height position of the punching knives (25a, 25b) with respect to the die (14), the height adjustment units (47) preferably each having a base body (20) which is connected to a base plate (18) of the punching unit (13) and on which the knife carrier (21) is mounted such that it can move with the punching knife in the stroke direction (15) via an adjusting drive (48).

10. Punching tool according to Claim 9, characterized in that the adjusting drive is designed as a spindle drive.

11. Punching tool according to one of the preceding claims, characterized in that the punching unit (13) has a hold-down device (49) having at least one hold-down means which fixes the film element (12) to be processed in the processing position (17) on the die (14).

12. Punching tool according to one of the preceding claims, characterized in that the punching unit (13) has at least one stop element (55), to which at least one counter-stop element (56) on the die (14) is assigned in such a way that, during the punching stroke for limiting the stroke path of the punching unit (13), the stop element (55) strikes the counter-stop element (56).

13. Punching tool according to one of Claims 5 to 13, characterized in that the die (14) has at least one contour cavity (52) which interacts with the associated contour punch (50) during the punching stroke and into which the contour punch (50) can be inserted, the contour cavity (52) adjoining adjacent knife cavities (35) for the punching knives (25a, 25b).

14. Punching tool according to Claim 13, characterized in that the contour cavities (52) are each bordered by support sections (53) supporting the film element (12) to be processed.

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