Measuring tool and method for providing compensating sheet

Abstract

A measuring tool (28) for a pressing station (16) of a paperboard processing machine (10), in particular a die-cutting machine and / or an indenting machine, the measuring tool (28) being configured to be inserted between an upper platen (24) and a lower platen (26) of the pressing station, the measuring tool (28) comprising at least one sensor (30) consisting of one or several distance sensors (32), the sensor (32) is configured to measure a vertical distance to a support surface (38) at a plurality of measurement points when the measurement tool (28) is inserted into the pressurization station (16) and the pressurization station is closed. Furthermore, a method for providing a compensation sheet (50) for a compression station (16) of a paperboard processing machine (10) is provided.

Description

Technical Field

[0001] The invention relates to a measuring tool for a press station of a cardboard processing machine, in particular a die-cutter and / or creasing machine, and a method for providing a compensating sheet for a press station of a cardboard processing machine. Background Art

[0002] In cardboard processing machines, in particular die-cutters and creasing machines, the cardboard arranged in the feed station is gripped and conveyed through a pressing station, a waste discharge station and a blanking station.

[0003] In the press station, the cardboard can be cut and creasing lines can be produced. Crimping is the compression of the cardboard, where it is configured to be folded to produce a box. To produce the cut or creasing lines, the press station has a lower platen and an upper platen arranged above the lower platen, where the platens are movable toward each other. Each platen can be attached to a tool plate carrying a cutter and / or creasing ruler. Furthermore, there can be a tool plate carrying a creasing counterpart corresponding to the cutter and / or creasing ruler.

[0004] To perform the cutting or creasing, the press station cycles between an open position (where the press plates are spaced apart) and a closed position (where the knife or creasing blade applies pressure to the cardboard). After each cycle, the cardboard is replaced with a new one when the press station opens. The press station is configured to apply a predetermined pressure to the cardboard in the closed position.

[0005] To produce a precise cut line, the pressure applied to the cardboard must be uniform. In particular, the distance between the board and the cutter must be very precise, for example within a few tens of microns.

[0006] The pressure applied is specific to the different cardboard materials and the shape to be cut.

[0007] When cutting or creasing cardboard, high pressure may act on the plate in the press station, causing the plate to deform slightly, which has a negative impact on the cut quality. In addition, manufacturing tolerances of the plate or other machine tolerances may also impair the cut quality.

[0008] Currently, when setting up a cardboard processing machine, a test cut is performed using the desired tool layout. The results are checked by an operator, who manually adds patches to areas where the test cut was not performed correctly. These patches locally increase the thickness of the configuration and thus compensate for board deformation. However, this process is time-consuming, generates waste, and requires experienced operators.

[0009] In a more recent alternative, JP2020110837A describes a method for adjusting the height of a distance block of a die, particularly a deep-drawing die. This method uses height adjustment based on the output of a sensor that detects the contact state between the distance block and the upper die. Specifically, a control unit can determine the height correction to apply based on the stress value of the sensor. Summary of the Invention

[0010] It is therefore an object of the present invention to compensate for inaccuracies in a pressing station in a cardboard processing machine in a simple and highly precise manner.

[0011] This object is achieved by a measuring tool for a press station of a cardboard processing machine, the measuring tool being configured to be inserted between an upper platen and a lower platen of the press station, the measuring tool comprising at least one sensor, but preferably a set of a plurality of distance sensors. The sensors are configured to measure the vertical distance to the support surface at a plurality of measuring points when the measuring tool is inserted into the press station and the press station is closed.

[0012] The measuring tool may include a plurality of sensor carriers. The distance sensors are respectively attached to the sensor carriers.

[0013] As an alternative, a plurality of distance sensors may be arranged according to a two-dimensional pattern, wherein the distance sensors are held fixed on the measuring tool.

[0014] For example, the support surface is the surface to which a tool plate is typically attached when processing cardboard sheets in a press station. For example, the support surface is provided at the upper or lower press plate of the press station or at an additional plate in the configuration of the press station.

[0015] By measuring the vertical distance to the support surface, manufacturing inaccuracies or deformations of components of the pressing station, in particular of the upper and lower plates, can be detected.

[0016] The measuring tool allows such inaccuracies to be detected individually for different configurations simply by inserting the measuring tool into the pressurizing station.

[0017] Measuring the distance at multiple measuring points has the advantage that a valid and accurate measurement value can be obtained at each measuring point, even in positions where the upper and lower pressing plates are not pressed. Therefore, the quality of the compensation can also be improved.

[0018] If desired, the vertical distance measurements can be mathematically converted into a pressure distribution.

[0019] During measurement, the pressing station is operated so that the measuring tool is clamped between the upper and lower platens.

[0020] The measurement can be performed without using pressure, or it can be performed under pressure. When measuring under pressure, a set of elastic elements are added to the measuring tool. These elements can be attached to the track described below in this disclosure, or can be independent elements distributed on the surface of the measuring tool, between the distance sensors. When the measuring tool is clamped between the upper and lower platens, the elastic elements apply a constant pressure between them.

[0021] For example, the measuring tool has a plate-like shape.

[0022] Based on the vertical distance from the support surface at the measuring point, a corresponding compensation sheet is calculated and applied to the upper or lower platen. When the press station is operated regularly to process cardboard blanks, the compensation sheet compensates for detected inaccuracies. Consequently, the use of the compensation sheet significantly improves the accuracy of the pressure distribution in the press station. This allows the cardboard to be cut to specification without further adjustments.

[0023] According to one aspect, multiple distance sensors can be arranged in a two-dimensional pattern. Each sensor measures the distance at a single location in the pressurizing station. The distance sensors are fixed to the measuring tool. This aspect has the advantage of being a simple and robust measuring tool. However, it has the disadvantage of requiring a large number of sensors and connections.

[0024] According to various aspects, a measurement tool can include multiple longitudinal tracks, with at least one distance sensor guided for linear displacement along each track. This allows for a cost-effective design of the measurement tool. More specifically, by providing a linearly displaceable sensor, multiple measurement points can be covered by a single sensor, resulting in a significantly reduced number of sensors used in the measurement tool compared to measurement tools that utilize only fixed sensors. One sensor can be used for each longitudinal track, or a single sensor can be sequentially inserted into each track.

[0025] According to a different aspect, the measuring tool may include at least one track, and the at least one distance sensor may be guided displaceably along the track. For example, the track may have a shape (eg, a spiral shape) that covers the surface of the platen.

[0026] For example, the measuring tool includes a plurality of elastic elements arranged to be displaced laterally relative to the distance sensor, wherein the elastic elements are configured to exert a vertical force on the sensor carrier when the measuring tool is clamped between the upper and lower platens of the press station. By exerting the vertical force on the sensor carrier, the elements of the measuring tool abut against each other, which improves the accuracy of the measurement. Preferably, the vertical force sets the press station into a state representative of its operation, i.e., the same state as when the press station is used to cut cardboard sheets.

[0027] For example, the elastic element is a foam element or a spring.

[0028] The elastic element can act directly or indirectly on the sensor carrier.

[0029] According to one embodiment, the elastic element is attached to the longitudinal rail. This means that the elastic element acts indirectly on the sensor carrier. By attaching the elastic element to the longitudinal rail, when the pressurizing station is closed, the longitudinal rail abuts the sensor carrier, and vice versa.

[0030] For example, the distance sensor is a capacitive sensor, an inductive sensor, an optical time-of-flight sensor (in particular a laser sensor), an optical triangulation sensor or a mechanical sensor. All of these sensors are suitable for measuring vertical distances with sufficient accuracy.

[0031] For example, a mechanical sensor is a sensor that deforms when a measuring tool is inserted into a press station and the press station is operated. After the press station is operated, the deformation of the mechanical sensor is measured, thereby allowing the vertical distance to the support surface to be determined. For example, the mechanical sensor includes a plurality of deformable hardware parts that are placed at the measurement point. After the press station is operated, the deformable parts are removed from the press station and their height is measured. The deformable parts can be made of lead.

[0032] This object is further achieved by a method for providing a compensating sheet for a press station of a cardboard processing machine, particularly a die-cutter and / or creasing machine. The method comprises inserting a measuring tool according to the present invention into the press station and operating the press station so that the measuring tool is clamped between the upper and lower platens of the press station. While the measuring tool is clamped between the upper and lower platens, the measuring tool is used to measure the distance to a support surface at a plurality of measuring points. Based on the perpendicular distances to the support surface at the measuring points, at least one compensating sheet with a varying thickness is calculated to compensate for deformation of the upper and lower platens during the press process.

[0033] The method of the present invention makes it possible to detect with high accuracy any inaccuracies in the components of the press station that could affect the vertical distance to the support surface and thus negatively impact the cutting quality in the press station. Consequently, the compensation sheet calculated based on the measured vertical distance can adequately compensate for inaccuracies in the press process, thereby achieving a uniform pressure distribution in the press station. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further features and advantages of the present invention can be seen from the following description and the accompanying drawings.

[0035] - Figure 1 A cardboard processing machine with a pressing station is shown;

[0036] - Figure 2 A schematic diagram showing a pressurizing station with a measuring tool of the present invention; and

[0037] - Figure 3 A schematic cross-sectional view of a measuring tool is shown.

[0038] - Figure 4 A schematic cross-sectional view showing an alternative measuring tool.

[0039] - Figure 5 An example of a compensation sheet is shown. DETAILED DESCRIPTION

[0040] Figure 1 A cardboard processing machine 10 is shown, in particular a die-cutter and / or creasing machine.

[0041] The cardboard processing machine 10 comprises a feed station 12 in which cardboard blanks 14 to be processed are deposited.

[0042] Furthermore, the cardboard processing machine 10 comprises a pressing station 16 in which the cardboard blanks 14 are cut or creased.

[0043] Before the cardboard blanks 14 are removed from the cardboard processing machine 10 , they can be stacked in a stacking station 18 .

[0044] The cardboard blank 14 may be moved in the machine direction using a gripper bar 20 attached to a drive chain 22 .

[0045] The pressurizing station 16 is described in more detail below.

[0046] In particular, the pressing station 16 comprises an upper pressing plate 24 and a lower pressing plate 26. The upper pressing plate 24 is arranged above the lower pressing plate 26.

[0047] The platens 24 , 26 are movable toward each other to cut or score the paperboard blank 14 disposed between the platens 24 , 26 .

[0048] In the present exemplary embodiment, the upper platen 24 is fixed and the lower platen 26 is movable. The mechanism of the pressing station 16 is therefore less complex.

[0049] In order to cut the cardboard blank 14 , a tool plate (not shown) carrying a knife may be attached to the upper or lower platen 24 , 26 .

[0050] Due to the high pressure acting on the upper and lower platens 24, 26 during the cutting process, the platens 24, 26 may deform slightly when the press station 16 is actuated.

[0051] The deformation is partly due to the size of the upper platen 24 and the lower platen 26, which is 2 Up to 2m2 For example, the outer dimensions of the upper pressing plate 24 and the lower pressing plate 26 are 760 mm x 1060 mm.

[0052] Additionally, due to manufacturing tolerances, there may be inaccuracies, such as with respect to the flatness or orientation of the upper and lower platens 24 , 26 .

[0053] In order to compensate for these inaccuracies, deformations and manufacturing tolerances must be detected in a sufficiently accurate manner.

[0054] For this purpose, a measuring tool 28 according to the invention is provided, such as Figure 2 As shown in .

[0055] The measuring tool 28 is configured to be inserted between the upper platen 24 and the lower platen 26 of the press station 16, as shown in FIG. Figure 2 As shown in .

[0056] The measuring tool 28 includes a sensor group 30 having a plurality of distance sensors 32 and a plurality of sensor carriers 34. The distance sensors 32 are attached to the sensor carriers 34, respectively.

[0057] The sensor carrier 34 is attached to the frame 36 of the measuring tool 28 (see Figure 3 ).

[0058] In the illustrated embodiment, the sensor carrier 34 is linearly movable within the frame 36 , as will be described in greater detail below.

[0059] However, the sensor carrier 34 may also be fixedly attached to the frame 36 .

[0060] The sensor 32 is configured to measure the perpendicular distance to the support surface 38 at a plurality of measurement points when the measurement tool 28 is inserted into the press station 16 .

[0061] The sensor carrier 34 can have one sensor 32 or two sensors 32 arranged end to end. The latter is more accurate because it can compensate for the inaccuracies of the guide rail 40.

[0062] The support surface 38 is provided at the plate 39 in the arrangement of the pressing station. However, the support surface 38 can also be provided directly at the upper pressing plate 24 or the lower pressing plate 26.

[0063] For example, the sensor 32 is a capacitive sensor, an inductive sensor, an optical time-of-flight sensor, an optical triangulation sensor or a mechanical sensor. Preferably, the sensor is a contactless sensor, which enables it to be displaced along the platen surface.

[0064] Compared to sensors that measure other physical parameters (such as strain) and infer distance measurements, using a sensor 32 that directly measures distance is advantageous. By using a distance sensor, we do not need to use a model (such as converting strain to distance), thereby avoiding additional sources of error and obtaining more accurate results.

[0065] In an embodiment, the measuring tool 28 comprises a plurality of longitudinal rails 40, and at least one distance sensor 32 is guided linearly displaceably along each rail 40. In more detail, each sensor carrier 34 is guided between two rails 40, respectively.

[0066] The longitudinal rails 40 also serve as a suspension device for the sensor carrier 34 , ie the sensor carrier 34 is attached to the measuring tool 28 by means of the longitudinal rails 40 .

[0067] By virtue of the sensor carrier 34 being displaceable along the rails 40, the number of sensors 32 of the sensor array 30 can be significantly reduced compared to a sensor array 30 having a fixed sensor carrier 32. Ideally, we would use one sensor 32 per rail 40, but we could also use a single sensor 32 and insert it sequentially into each rail 40.

[0068] In particular, in a measuring tool 28 covering a plate 24, 26 having a size of 760 mm x 1060 mm, for example, a sensor array 30 with a movable sensor carrier 34 includes twenty sensors 32, whereas a sensor array with a fixed sensor carrier 34 would require approximately four hundred sensors. Therefore, by providing a displaceable sensor carrier 34, the measuring tool 28 is particularly cost-effective.

[0069] An alternative to implementing longitudinal rails uses rails 41 that cover the entire surface of the platen and Figure 4 The sensor is attached to the side of the track and can be moved along the entire track, covering the measurement of the complete platen in one repetition.

[0070] Another advantage of using a displaceable sensor carrier 34 is that the measuring points can be very close to each other, or even a continuous line can be measured.

[0071] A linear actuator (not shown in the figures) may be provided for displacing the sensor carrier 34 .

[0072] Figure 3 A section through the measuring tool 28 is shown, illustrating the possible range of motion of the sensor 32 .

[0073] The measuring tool 28 further comprises a plurality of elastic elements 42 which are arranged to be displaced laterally relative to the distance sensor 32 .

[0074] The elastic element 42 is attached to the longitudinal rail 40 , in particular to a bottom side 44 of the longitudinal rail 40 .

[0075] For example, the elastic element 42 is a foam strip extending along the longitudinal rail 40 .

[0076] The elastic member 42 is configured to apply a vertical force to the sensor carrier 34 when the measurement tool 28 is clamped between the upper platen 24 and the lower platen 26 of the press station 16. In particular, the height of the elastic member 42 is such that the elastic member 42 is compressed when the measurement tool 28 is inserted into the press station 16. More specifically, the elastic member 42 protrudes beyond the sensor 32.

[0077] In an embodiment, when the elastic elements 42 are compressed, they exert a perpendicular force on the longitudinal rails 40 , which in turn exert a perpendicular force on the sensor carrier 34 , causing the longitudinal rails 40 and the sensor carrier 34 to bear against each other.

[0078] The resilient element 42 may be made very similar to the resilient element used to hold the cardboard next to the cutting knife during normal pressing operation.

[0079] The sensor carrier 34 may rest against a support plate 46 of the pressurizing station 16 .

[0080] Optionally, the configuration of the pressurizing station 16 includes additional plates that are located between Figure 2 It is schematically shown in FIG, but will not be described further for the sake of simplicity.

[0081] Based on the measurements of the measuring tool 28 , a compensation sheet 50 with a varying thickness may be provided, which may be added to the configuration of the press station 16 when the press station 16 is operating normally.

[0082] The method for providing a compensating sheet 50 for a press station of a cardboard processing machine comprises inserting a measuring tool 28 as described above into the press station, such as Figure 2 As shown in .

[0083] When the measuring tool 28 is inserted into the press station 16 , the press station 16 operates such that the measuring tool 28 is clamped between the upper and lower press plates 24 , 26 of the press station 16 .

[0084] When the measuring tool 28 is clamped in the press station 16 , the distance to the support surface 38 is measured at a plurality of measurement points using the measuring tool 28 while the measuring tool 28 is clamped between the upper platen 24 and the lower platen 26 .

[0085] In particular, the sensor carrier 34 with the distance sensor 32 is displaced along the longitudinal rail 40 and measures the distance to the measuring point.

[0086] Then, based on the vertical distance to the support surface 38 at the measuring point, at least one compensation sheet 50 with a varying thickness is calculated for compensating for the deformation of the upper and lower pressing plates 24 and 26 during the pressing process.

[0087] In order to compensate for deformation and manufacturing inaccuracies of the upper and lower platens 24 and 26 , a compensation sheet 50 is added to the configuration at the pressing station 16 .

[0088] The compensating sheet 50 can be made of metal and thus have high stability. It can also be made of glass fiber with resin, carbon fiber with resin, paper printed with polymer ink or plastic.

[0089] The compensating sheet 50 can be produced by additive manufacturing techniques or subtractive manufacturing (engraving, etching, milling, etc.). For example, the compensating sheet 50 can be produced by 3D printing, chemical engraving, or laser engraving. Thus, the compensating sheet 50 can be produced with particularly high thickness accuracy.

[0090] The compensation sheet 50 is individual for the different pressing stations 16 and for each configuration of the pressing stations 16 .

Claims

1. A measuring tool (28) for a press station (16) of a cardboard processing machine (10), in particular a die-cutter and / or creasing machine, the measuring tool (28) being configured to be inserted between an upper press plate (24) and a lower press plate (26) of the press station, the measuring tool (28) comprising at least one sensor (30) consisting of one or several distance sensors (32), the sensors (32) being configured to measure the vertical distance to a support surface (38) at a plurality of measuring points when the measuring tool (28) is inserted into the press station (16) and the press station is closed.

2. The measuring tool (28) according to claim 1, comprising a plurality of sensor carriers (34), the distance sensors (32) being respectively attached to a sensor carrier (34).

3. The measuring tool (28) according to claim 1, wherein the plurality of distance sensors (32) are arranged according to a two-dimensional array, and wherein the distance sensors (32) are held fixed on the measuring tool (28).

4. The measuring tool (28) according to claim 1 or 2, wherein the measuring tool (28) comprises a track (40, 41) and at least one distance sensor (32) is displaceable along the track (40, 41).

5. The measuring tool (28) of claim 4, wherein the measuring tool (28) comprises a plurality of longitudinal rails (40), wherein the distance sensor (32) is linearly displaceable along each rail (40).

6. A measuring tool (28) according to any one of claims 1, 2, 4 or 5, wherein the measuring tool (28) includes a plurality of elastic elements (42), which are arranged to be laterally displaced relative to the distance sensor (32), and wherein the elastic elements (42) are configured to apply a vertical force to the sensor carrier (34) when the measuring tool (28) is clamped between the upper pressure plate (24) and the lower pressure plate (26) of the press station (16).

7. The measuring tool (28) according to claim 4 or 5 and claim 6, wherein the elastic element (42) is attached to the rail (40).

8. The measuring tool (28) according to any one of the preceding claims, wherein the distance sensor (32) is a capacitive sensor, an inductive sensor, an optical time-of-flight sensor, an optical triangulation sensor or a mechanical sensor.

9. A method for providing a compensating sheet (50) for a press station (16) of a cardboard processing machine (10), in particular a die-cutting and / or creasing machine, comprising the following method steps: - inserting a measuring tool (28) according to any one of claims 1 to 7 into the pressing station (16), - operating the pressing station (16) so that the measuring tool (28) is clamped between the upper pressing plate (24) and the lower pressing plate (26) of the pressing station (16), - measuring the distance to the support surface (38) at a plurality of measuring points by means of the measuring tool (28) while the measuring tool (28) is clamped between the upper platen (24) and the lower platen (26), and - Based on the vertical distance to the support surface (38) at the measuring point, calculating at least one compensation sheet (50) with a varying thickness for compensating for deformation of the upper pressing plate (24) and the lower pressing plate (26) during pressing.

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