FORMAT-VARIABLE PUNCHING DEVICE AND METHOD THEREFOR

Description

[0001] The invention relates to a device for the format-variable punching of a plurality of sheets to be punched, each sheet having a length Lb, comprising a feeding device for sheets to be punched, a punching unit having a punching length Ls comprising a punching tool having an effective punching tool length Lw, the device comprising an acceleration device for generating a gap having a length LL between the fed sheets.

[0002] Furthermore, the invention relates to a method for the format-variable punching or embossing of sheets having a sheet length Lb, wherein the sheet is processed with a punching device having an effective punching length Ls, wherein each sheet fed to the punching device is accelerated by means of an acceleration device to produce a gap having a gap length LL.

[0003] Punching machines or punching devices are known from the prior art in which shapes such as folding boxes are punched out of printed webs or sheets and the future bending edges, tear perforations or similar are embossed.

[0004] In the following invention, therefore, no distinction is made between punching, in which the substrate of the sheet or web is severed, and embossing, in which the substrate of the sheet or web is not severed but deformed, since the only difference, irrelevant to the present invention, is the height of the patterns on the punching or embossing die and how deeply they penetrate into the substrate. Therefore, only the term "punching" is used below, although the term "embossing" is included.

[0005] US 2020 / 0298436 A1 discloses a punching device in which a web to be punched is cross-cut and separated into individual sheets, and wherein the separated sheets are fed to a punching device at a distance from one another in the transport direction.

[0006] With such punching machines or punching devices, a distinction is made between flatbed punches with a flat punching die and rotary punches with a rotating cylinder. A flatbed punch has a maximum working width and a maximum punching length Ls, which essentially corresponds to the maximum length of the punching table in the feed direction. The punching length Ls thus limits the maximum sheet length that can be punched.

[0007] Rotary die-cutting units have a rotating die-cutting cylinder which is in operative connection with the sheet or web to be die-cut, and further comprises an impression cylinder on which the sheet or web to be die-cut and, in some cases, also the die-cutting tool are supported.

[0008] The cylinder circumference of the punching cylinder therefore determines the punching length Ls.

[0009] The punching tool is formed on the outer surface of the punching cylinder. This can be done either by using a hardened cylinder with a punching length precisely tailored to the product to be punched, or by incorporating a corresponding pattern into its surface.

[0010] Manufacturing such a punching cylinder with a fixed punching length is extremely costly and time-consuming. However, if the length of the product to be punched changes, the cylinder circumference must be precisely adjusted to the new product length, requiring a new punching cylinder with a correspondingly adjusted circumference and a newly incorporated punching tool.

[0011] Another alternative is the use of so-called magnetic cylinders, i.e. punching cylinders with incorporated magnets, so that a ferromagnetic sheet with an incorporated or applied punching tool can be used as the punching tool.

[0012] Although the production of such punching sheets as a punching tool is significantly cheaper than the production of hardened punching cylinders with an incorporated pattern to be punched, the problem here is that due to the punching length Ls specified on the basis of the cylinder diameter, when the product length changes, a new magnetic cylinder with a correspondingly suitable circumference and thus with a correspondingly adapted punching cylinder is required. This makes the availability, i.e. the purchase, storage and maintenance of a large number of different magnetic cylinders necessary for different product lengths to be punched, which is very cost-intensive.

[0013] Flatbed die cutters essentially have the same requirements, albeit with flat die cutters.

[0014] It is therefore the object of the present invention to provide a device and a method with which sheets of different lengths can be processed without changing the cylinder using a punching length Ls, such as a punching cylinder with a defined effective diameter and consequently with a defined punching length Ls.

[0015] This object is achieved by a device for format-variable punching according to claim 1 or a method for format-variable punching according to claim 12.

[0016] The device according to the invention is characterized in that the punching length Ls is greater than the sheet length Lb.

[0017] The method according to the invention is characterized in that the effective punching length Ls is greater than the arc length Lb.

[0018] Such a device and method have the advantage that a single cutting bed or cutting cylinder with a specific cutting length Ls can be used for different cutting pattern lengths and thus for a variety of product lengths. The sheet length Lb can be stepped down to the cutting length Ls without changing the cutting cylinder, which minimizes the cost of purchasing, stocking, and maintaining the corresponding cutting cylinders or cutting beds. Furthermore, changing the product length does not necessarily require replacing the cutting cylinder or cutting bed, which significantly reduces setup times.

[0019] According to one embodiment, the acceleration device for generating a gap between each of the fed sheets is designed in such a way that a gap with a gap length LL equal to the punching length Ls less the sheet length Lb is obtained.

[0020] This design has the advantage that the punching cylinder can rotate at a continuous speed and / or other devices for decelerating or accelerating the punching unit or the sheets to be punched can be avoided.

[0021] Preferred developments of the invention emerge from the subclaims and the following description.

[0022] Various embodiments of the invention are explained in more detail with reference to the drawings, without being limited thereto. Fig. 1a punching unit known from the prior art to show the relevant punching length Fig. 2a side view of the punching unit known from the prior art Fig. 1 illustrated punching unit Fig. 3 a punching device according to the invention for punching variable sheet lengths using the example of a first sheet length Fig. 4 a punching device according to the invention for punching variable sheet lengths using the example of a second sheet length

[0023] Fig. 1 shows a basic structure of a punching machine 10 as is known from the prior art.

[0024] The punching unit 10 comprises a punching cylinder 11 with an effective punching cylinder diameter ds. This punching cylinder 11 carries a punching tool 16 on at least part of its outer surface, which is either machined into the outer surface of the hardened punching cylinder 11 as a pattern, or the punching tool 16 is a punching die made from a ferromagnetic sheet, to which the pattern is applied. In the latter case, the punching cylinder 11 is a magnetic cylinder.

[0025] The punching tool 16 mounted on the punching cylinder 11 is in operative connection with the web-like or sheet-like substrate passing through the punching cylinder 11 and the impression cylinder 13 during punching. In some punching units 10, an additional drive or support roller 14 is used. Drive means for the rotational drive of the individual cylinders are provided in Fig. 1 not shown due to lack of relevance.

[0026] As in both Fig. 1 as well as in Fig. 2 As can be seen from Figure 1, which is a schematic side view of the exemplary punching unit 10 shown in Figure 1, the punching cylinder 11 has an effective punching cylinder diameter ds. This can be smaller, larger, or equal to the diameter of the impression cylinder 13.

[0027] The punching length Ls is therefore determined by the punching cylinder diameter ds using the formula Ls = ds x π. After each revolution of the punching cylinder 11, the pattern of the punching tool 16 is repeated, so that the punching cylinder diameter ds, in punching units 10 known from the prior art, can be precisely adapted to the product length or the sheet length Lb or to the printing length of a web-fed printing unit. Of course, it is also possible for the punching length Ls to be an integer multiple of the sheet length Lb or an integer multiple of the printing length of a web-fed printing unit, but a change in the sheet length Lb, i.e. the length of the pattern to be punched, always requires an adjustment of the punching cylinder diameter ds.

[0028] Fig. 3 shows an exemplary device 1 for printing a web with a repeating print image, for separating the web into individual sheets 3 and for punching these sheets 3.

[0029] The printing of the web 2 is only one possibility for producing printed sheets 3 by cross-cutting the web 2 and the resulting separation of the web 2 into sheets 3. It is pointed out that already separated sheets 3 can be printed and fed to the device 1 according to the invention. The device 1 according to the invention can also be operated offline and thus parallel or independently of the printing operation. Also, the invention is Fig. 1 The rotary punching unit shown can be used with a flatbed punch, as this is also determined by a defined punching length Ls.

[0030] The invention is explained below using a rotary punching machine, although this is also possible with a flatbed punch.

[0031] The substrate web 2, which runs from left to right in the direction of travel LR through the device 1 (hereinafter referred to as web 2), first passes through a printing device 20. Here, the printing cylinder 21, which is supported on an impression cylinder 22, prints a print image with a length Lb1, which normally corresponds to the sheet length Lb1 to avoid unprinted waste. It goes without saying that a plurality of identical or different copies can be printed consecutively on a sheet length Lb1, viewed in the direction of travel LR.

[0032] The sheet length Lb1 corresponds to the circumference of the printing cylinder 21 and is calculated using the formula Lb1 = dd1 x π. The print images with the length Lb1 are printed one after the other on the web 2. In packaging printing presses, the printing cylinder diameter dd can normally be changed by replacing the printing cylinder 21 or by replacing a sleeve (not shown), although not during production. For multi-color printing, a plurality of printing devices 20 of the same or different printing processes can also be arranged one after the other in the running direction LR.

[0033] The type of printing device 20 and the printing method are irrelevant for the present invention. The printing device 20 can be configured, for example, as an offset printing unit and / or a gravure printing unit and / or a flexographic printing unit and / or a digital printing unit, such as an inkjet printing unit.

[0034] The printed web 2 passes directly or indirectly after the printing unit through a cutting device 30, with which the web 2 is divided into individual sheets 3 with the sheet length Lb1. It goes without saying that the section length corresponds to the sheet length Lb1 in order to prevent the cut from passing through the printed image over time.

[0035] The Fig. 3 The cutting device 30 illustrated by way of example comprises a pair of cutting cylinders 31 through which the web 2 passes and is cut transversely into sheets 3. However, the functioning of the cutting device 30 is not relevant to the present invention. It is also possible for the present invention to feed a pre-printed web 2 into a cutting device 30 located upstream of the punching unit 10 and to perform the cutting of the web 2 independently of the printing process.

[0036] The cutting device 30 used here is preferably designed to produce different and / or variable sheet lengths Lb. A different sheet length Lb means that the cutting device 30 can be converted and / or adjusted after a production run to separate the web 2 into a different sheet length Lb, for example by relocating knives on the circumference. Producing a variable sheet length Lb means that the cutting device 30 could also change the sheet length Lb during production, for example by a non-continuous peripheral speed of the cutting knife cylinders. Such a configuration is particularly important when the web 2 is printed using a completely format-variable printing device 20, such as a digital printing device.

[0037] Due to the Fig. 3 The printing device 20 shown as an example with a sheet length Lb1 that is constant during production separates the Fig. 3 The cutting device 30 shown cuts the web 2 into sheets 3 with a sheet length Lb1 during production.

[0038] As from Fig. 3 As can be seen, the punching cylinder diameter ds is larger than the printing cylinder diameter dd1, which means that the punching length Ls = ds x π is larger than the sheet length Lb1 = dd1 x π.

[0039] The punching cylinder 11 thus carries a punching tool 16 with an extended length Lw1 on its circumference, wherein the punching tool length Lw1 essentially corresponds to the arc length Lb1. The punching tool 16, with its effective punching tool length Lw1, at least partially covers the circumference of the punching cylinder 11.

[0040] In order to avoid having to adjust the punching length Ls and thus the punching cylinder diameter ds to the sheet length Lb during each production change, the subsequently fed sheets 3 pass through an acceleration device 40, which comprises, for example, one or more pull rollers 41 or pull roller pairs 41. This acceleration device 40 comprises, for example, an acceleration roller 42 or an acceleration cam or a belt acceleration (not shown) for accelerating each sheet 3. The acceleration device 40 accelerates the exemplary Fig. 3 sheets 3 arriving one after the other essentially without a gap, in order to create a gap 4 with a gap length LL1 between the subsequent sheets 3. The acceleration device 40 can accelerate the sheets 3 in a single step to achieve the gap length LL, but it is also possible to achieve this in several individual acceleration stages carried out one after the other. From the perspective of the function of the acceleration device 40, it can therefore also comprise several acceleration devices arranged one after the other.

[0041] In order to avoid additional interventions on each sheet 3 or on the punching unit 10, each sheet 3 is accelerated by the acceleration device 40 in such a way that the gap 4 between each of the fed sheets 3 is designed in such a way that a gap 4 with a gap length LL is obtained, which is calculated according to the formula LL = Ls - Lb, i.e. the gap length LL is preferably the difference between the punching length Ls and the sheet length Lb.

[0042] The thus accelerated sheets 3 are then fed to the punching unit 10 in precise register, so that the leading edge of each sheet 3 essentially meets, if desired, the leading edge of the punching tool 16. If the length of the pattern to be punched or embossed is shorter than the sheet length Lb, the leading edge of the punching tool 16 can also meet at any other desired location within each sheet 3. However, due to the gap 4 created between the sheets 3 by the acceleration device 40, register-accurate punching or embossing is also possible without adjusting the punching length Ls and thus without adjusting the punching cylinder diameter ds.

[0043] Although in Fig. 1 not shown, the method for generating a gap 4 between the fed sheets 3 with a defined gap length LL is also possible for flatbed punches with a defined punching length Ls.

[0044] Although Fig. 1 shows an embodiment in which the device 1 comprises a printing device 20 and a cutting device 30, the device 1 is also possible in such a way that it only comprises at least one acceleration device 40, to which the sheets 3 are fed accordingly, and a punching unit 10. Optionally, both the cutting device 30 for feeding a web 2 and / or a printing device 20 for printing either sequentially fed sheets 3 or a fed web 2 can be supplemented.

[0045] Fig. 4 shows the Fig. 3 known exemplary device 1, although the printing cylinder 21 has a printing cylinder diameter dd2 which is larger than the printing cylinder diameter dd1 of Fig. 3 is.

[0046] Due to the larger printing cylinder diameter dd2, a larger sheet length Lb2 results, which is printed with the longer print image.

[0047] Since the printing cylinder diameter dd2 is still smaller than the punching cylinder diameter ds, it is necessary to accelerate the sheets 3 in such a way that a gap 4 with the gap length LL2 is created between the sheets 3 in order to ensure register-accurate punching or embossing. The gap length LL2 is calculated according to the formula LL2 = Ls - Lb2 and is smaller than the gap length ds in Fig. 3 shown gap length LL1. In the Fig. 4 In the example shown, the punching tool length Lw2 of the punching tool 16 essentially corresponds to the arc length Lb2.

[0048] As through the Fig. 3 and 4Also illustrated, with the present invention it is possible to use a punching unit 10 with a constant punching length Ls, such as a constant punching cylinder diameter ds in the case of a rotary punching unit 10, despite a changing sheet length Lb.

[0049] In addition to creating a gap 4 between the incoming sheets 3, it is possible to vary the peripheral speed of the punching cylinder 11 during one revolution, so that in the area in which the punching tool 16 is engaged, the peripheral speed of the punching cylinder 11 corresponds to the speed of the sheets 3 to be punched, and that in the area in which the punching tool 16 is not engaged, the peripheral speed of the punching cylinder 11 is increased, so that in this way a reduction of the gap length LL and consequently a reduction of the acceleration of the sheets 3 in the acceleration device 40 is possible. List of reference symbols

[0050] 1Device 2Printing material web / web 3Sheet / printed product 4Gap 10 Punching unit 11 Punching cylinder 12 Support ring 13 Impression cylinder 14 Drive roller / support roller 15 Support ring 16 Punching tool 20Printing device 21Printing cylinder 22Impression cylinder 30Cutting device 31Cutting cylinder pair 40Acceleration device 41Pair of pull rollers / pull roller 42Pair of acceleration rollers / acceleration roller 16 dsDiameter of punching cylinder ddDiameter of printing cylinder LbArc length LsPunching length LwPunching tool length LLGap length LRTravel direction

Claims

1. Device for the variable-format punching of a plurality of sheets (3) to be punched, each sheet (3) having a sheet length Lb, comprising a feeding device for sheets to be punched, a punching unit (10) with a punching length Ls comprising a punching tool (16) with an effective punching tool length Lw, the punching length Ls being the cylinder circumference of a die-cutting cylinder (11) or the maximum length of a punching table in the throughfeed direction, wherein the device comprises an acceleration device (40) for generating a gap (4) with a gap length LL between the fed sheets (3), characterized in that the punching length Ls is greater than the sheet length Lb.

2. Device according to claim 1, characterized in that the acceleration device (40) for generating a gap (4) between each of the fed sheets (3) is designed in such a way that a gap (4) with a gap length LL = Ls - Lb results.

3. Device according to one of claims 1 to 2, characterized in that the device (1) comprises a cutting device (30) for separating a fed web (2) into sheets with a sheet length Lb.

4. Device according to claim 3, characterized in that the cutting device (30) is designed to produce different and / or variable sheet lengths Lb.

5. Device according to one of claims 1 to 4, characterized in that the device (1) comprises a printing device (20).

6. Device according to claim 5, characterized in that the printing device (20) comprises an offset printing unit and / or a gravure printing unit and / or a flexographic printing unit and / or a digital printing unit such as an inkjet printing unit.

7. Device according to one of claims 1 to 6, characterized in that the punching unit (10) is designed as a rotary die-cutting unit comprising a die-cutting cylinder (11) with an effective diameter ds and an effective punching length Ls = ds x π.

8. Device according to claim 7, characterized in that the effective punching tool length Lw of the punching tool (16) at least partially covers the circumference of the die-cutting cylinder (11).

9. Device according to one of claims 7 or 8, characterized in that the punching tool (16) is designed as a punching plate and the die-cutting cylinder (11) is designed as a magnetic cylinder.

10. Device according to one of claims 7 or 8, characterized in that the punching tool (16) is designed as a pattern engraved in a region of a lateral surface of the die-cutting cylinder (11).

11. Device according to one of claims 1 to 6, characterized in that the punching unit (10) is designed as a flatbed punch with an effective punching length Ls.

12. Method for the format-variable punching or embossing of sheets (3) with a sheet length Lb, the sheet (3) being processed with a punching unit (10) with an effective punching length Ls, the punching length Ls being the cylinder circumference of a die-cutting cylinder (11) or the maximum length of a punching table in the throughfeed direction, wherein each sheet (3) fed to the punching unit (10) is accelerated by means of an acceleration device (40) to produce a gap (4) with a gap length LL, characterized in that the effective punching length Ls is greater than the sheet length Lb.

13. Method according to claim 12, characterized in that each sheet (3) is accelerated in such a way that a gap (4) with a gap length LL = Ls - Lb is produced between two subsequent sheets (3).

14. Method according to one of claims 12 or 13, characterized in that the fed sheets (3) are produced by separating a web (2) by means of a cutting device (30).

15. Method according to one of claims 12 to 14, characterized in that the web (2) is printed by means of a printing device (20) before being separated into sheets (3).