Method for producing a set of cooperating embossing rollers

Abstract

In the method for producing a set of cooperating embossing rollers, a modelling device is used for parameterizing the embossing rollers, the device comprising a test bench having a pair of rollers which are put under hydraulic pressure that can be measured and set, in order to determine from the measurement data the parameters for producing the embossing rollers. The use of a modelling device for obtaining the parameters for producing a set of embossing rollers makes it possible to use a very large variety of embossing patterns and foils with diverse properties as a basis and, by conducting tests on this very test bench, be able to efficiently narrow down and predetermine the properties of a final embossing device, preferably operated without hydraulics.

Claims

1. A method for determining a parameter for a set of cooperating embossing rollers for manufacturing, the method comprising the steps of: pressurizing a pair of rollers of a modelling device under a measurable and an adjustable pressure for deforming at least one roller of the pair of rollers, the at least one of roller of the pair of rollers having a structure on a surface of a shell thereof; measuring a deflection of the at least one roller of the pair of rollers during the step of pressurizing; and determining a parameter related to the structure on the surface of the shell based on the measured deflection, the parameter allowing a geometry of the set of cooperating embossing rollers for manufacturing to be predicted.

2. The method according to claim 1, wherein the step of pressurizing comprises applying a hydraulic pressure with a hydraulic fluid to the pair of rollers via a hydraulic pressure system.

3. The method according to claim 2, wherein the step of measuring the deflection comprises measuring a pressure of the hydraulic fluid to determine the deflection.

4. The method according to claim 1, wherein in the step of determining, the parameter is determined to describe a geometry of a surface of a back-up roller in the set of cooperating embossing rollers.

5. The method according to claim 4, wherein in the step of determining, the geometry of the surface of the back-up roller includes a crown that is selected to be slightly larger than the deflection of the at least one roller caused by the step of pressurizing.

6. The method according to claim 1, wherein the at least one roller of the modelling device includes the shell and an axle, the modelling device further including a housing to which the axle is attached to, and wherein in the step of pressurizing, an external pressure is applied on the axle of the at least one roller of the pair of rollers.

7. The method according to claim 6, further comprising a step of: measuring a course of a deflection of an axle of the at least one roller deformed in the step of pressurizing.

8. The method according to claim 1, wherein the at least one roller of the modelling device includes the shell and an axle, and wherein the step of pressurizing further includes applying a pressure between the shell and the axle with a hydraulic fluid at a pressure pocket that is arranged in a middle of the axle.

9. The method according to claim 8, wherein during the step of applying the pressure at the pressure pocket, the step of measuring is performed to measure the deflection of the shell along a rotational axis of the at least one roller.

10. The method according to claim 1, wherein the at least one roller of the modelling device includes the shell and an axle, and wherein the step of pressurizing further includes applying a pressure between the shell and the axle with a hydraulic fluid at a plurality of bearing pockets that are arranged circumferentially around the axle.

11. The method according to claim 1, wherein in the step of measuring, a maximal deflection of the at least one roller at a given pressure is determined.

Description

(1) In the following, the invention is explained in more detail with the help of drawings of exemplary embodiments.

(2) FIG. 1 shows in longitudinal section a roller of a modelling device,

(3) FIG. 2 shows a section according to the line II/II in FIG. 1,

(4) FIG. 3 shows a section according to the line in FIG. 1,

(5) FIG. 4A shows the roller according to FIG. 1 in a perspective view,

(6) FIG. 4B shows the roller according to FIG. 1 in a second perspective view,

(7) FIG. 4C shows the roller according to FIG. 1 in a third perspective view,

(8) FIG. 5 shows a part of one of the rollers from FIG. 1 prior to being subjected to pressure, e.g. hydraulic pressure,

(9) FIG. 6 shows both rollers of the modelling device under hydraulic pressure,

(10) FIG. 7 shows an embossing roller pair produced with data of the modelling device,

(11) FIG. 8 shows the entire deflection of an axle of a roller of the modelling device under hydraulic pressure,

(12) FIG. 9 shows the deflection of the axle according to FIG. 8 in the middle part,

(13) FIG. 10 shows the tension of the axle of FIG. 8 under load,

(14) FIG. 11 shows the deformation of the roller on the side located opposite the embossing edge and

(15) FIG. 12 shows the deformation of the axle on the embossing edge.

(16) In order to be able to produce the definitive set of for example crowned embossing rollers, their parameters, especially the crowning, are determined according to the invention by means of a modelling device, of a test stand. Here, the effect of the deflection of the for example crowned embossing roller is offset by the geometry of the counter-roller in such a manner that the thicker, for example crowned, counter-roller is given a deformed surface predetermined by the modelling device, which determines the deflection of the embossing roller.

(17) In order to predetermine the final geometry of the (counter) roller (the crowning) as described above, a test embossing stand is introduced here. This device to be produced in a few pieces at the roller manufacturer is technically significantly more complex than a combination of a crowned and of a non-crowned roller, hence not intended for the production, but offers the possibility for example of testing different embossing pressures under homogeneous embossing pressure distributions during the embossing by tuning the hydraulic pressure.

(18) FIG. 1 shows a longitudinal section through a hydrostatically mounted roller 1 of a modelling device, wherein this roller 1 comprises a shell 2 and an axle 3. In order to keep the deformation of the axle under pressure as low as possible, the same is produced from hard metal. The axle is held on two bearing regions 4 and 5 in the shell, while the hydrostatic roller is only partly shown. The axle in this case has to be embodied from hard metal since an axle made of steel would be excessively deflected under the force that occurs.

(19) The surface of the shell 2 is provided with logos 27 (see FIGS. 6 and 7), which can be equal to those that are applied to the embossing roller employed in the final product, or sample logos, which can be exemplary for a series of logos.

(20) The purpose of this roller arrangement is to put the roller axle under a certain hydraulic pressure in order to be able to measure the deflection of the same. Here it must be noted that a roller alone cannot be put under hydraulic pressure without causing deformations and damages and that the entire measurement system can only be operated in the configuration of FIG. 6. Here, the deflection of the axle can be derived from the physical parameters of the hard metal and the applied hydrostatic pressure.

(21) In order to generate hydrostatic pressure, four segments 6, 7, 8 and 9 are arranged in the two bearing regions 4 and 5 each on a bearing part of the axle, wherein each segment comprises an intermediate web 10, as a result of which four bearing pockets 11, 12, 13 and 14 are created between the axle segments and the shell. The hydraulic pressure medium, for example oil, enters a continuous pipe 16 from an inlet 15 and is distributed in the bearing region via four channels 17 between the segments and enters the bearing pockets. The return 18 on both sides is likewise drawn in.

(22) FIG. 1 furthermore shows that the two bearing regions 4 and 5 are embodied mirror-inverted. From FIG. 2 it is evident that upon hydraulic pressure built-up a symmetrical pressure loading takes place, so that the axle and the shell are held coaxially. Upon deflection from the centre position, a resetting force is created.

(23) If now a strong force is exerted from the outside via the axle, e.g. via its suspension, i.e. a pressure force in the direction of a counter-roller, the bearings can pass on this force in the bearing regions only to a limited extent since these have a symmetrical arrangement. The maximum pressure force of the rollers that can be achieved would be limited and not homogeneous in the region between the bearings, the actual embossing region.

(24) For this reason, a further sectorial pressure pocket 19 that is not symmetrically arranged to the cross section of the axle is provided. Said pressure pocket 19 is likewise subjected to hydrostatic pressure by the oil pipe 16 via the feed line 20. The pressure pocket allows directing the pressure forces exerted onto the axle from the outside via the shell to the counter-roller 21 and thus to the embossing edge PK between the rollers.

(25) This means that in the static operating state of the machine, of the stand, the external force and the force passed on to the pressure pocket are just equal. Since the axle mechanically passes on this force a deflection of the axle occurs. The pressure force applied to the two ends of the axle from the outside, e.g. via hydrostatic cylinder is thus passed on into the bearings and the pressure pocket via the axle.

(26) FIGS. 4A, B, C show three different perspective views of the axle 3, wherein the view in each case is directed at the pressure pocket. In these views the position of the elements drawn in FIGS. 1, 2 and 3 is evident.

(27) In FIG. 5, one of the rollers 1 of the modelling device is drawn in, as it presents itself prior to the pressure loading with hydraulic pressure. An external force that is symmetrically arranged on both axle ends acts on the axle from the outside. This force constitutes the external pressure force that is to be employed during the respective embossing. Of the second roller 21, merely the shell 22 is shown and of shell 2 of the first roller, the embossing edge EE, which always comes to lie opposite the counter-roller 21.

(28) In FIG. 6, both rollers of the modelling device are shown as they are being deformed under pressure loading with the hydraulic pressure of the stand. The two rollers are constructed mirror-symmetrically to the embossing edge EE and because of this a mirror-symmetrical force distribution is created. Drawn in are the forces which are created upon external pressure loading with hydraulic pressure, which act on one of the rollers, in this case roller 1. These are marked with F.sub.EX1 and F.sub.EX2 and correspond to the external force/the external pressure on the embossing rollers.

(29) This external pressure is absorbed by the mounting and creates a counter-pressure F.sub.Halt1 and F.sub.Halt2. The two external forces can be absorbed at the end of the axles and then supported by the housing at one of the two rollers, at the other axle by for example hydraulic cylinders.

(30) In order to mount the axles in the shell and in order to offset and measure the external pressure on the rollers, a hydraulic pressure system is required which in this case operates with hydraulic oil. This hydraulic oil is directed via the feed line 15 to the bearing pockets and the pressure pocket. The use of hydraulic cylinders for generating the external pressure force offers the advantage that calculating the actually acting forces via the known piston area of the hydraulic cylinders of the stand and a pressure measurement can be easily realised.

(31) On the embossing edge EE between the two rollers in the location of the two pressure pockets, mirror-inverted forces F.sub.H1, F.sub.H2 occur. For this reason, the embossing edge remains absolutely straight with external pressure. The mirror-inverted forces on the rollers via the pressure pockets correspond to the embossing pressure and are absorbed by the deflection of the axles. From this arises the objective of these measurements and calculations, the determination of the necessary forces on the embossing edge in order to achieve a good embossing quality, i.e. a qualitatively adequate reproduction of the structures the embossing roller possesses on the embossed material to a dimension and extent that the visual effects on the embossing roller are largely reproduced by the embossed material.

(32) Thus, a simple calculation of the force profile is possible and there, where the hydrostatic pressure pocket is below, a homogenous force profile is created along a straight edge. Then, the actual force distribution and thus the necessary embossing force can be inferred from the given hydraulic pressure.

(33) By configuring the modelling device, i.e. of the test stand, i.e. in that the embossing edge is always exactly flat, the calculation of the force ratios can be simplified. From the resulting measurement data, such as offsetting of the deflection of the axles and of the direct measurement of the hydrostatic pressure of the hydraulic medium employed, this deflection can be converted to a purely mechanical axle without hydrostatic system and because of this the configuration or geometrical shape, especially the crowning of the counter-roller. This simple access to the necessary embossing force via the test stand makes possible predicting the geometry (e.g. crowning) of commercially employable embossing devices.

(34) In FIG. 7, an embossing roller pair 24 is illustrated in perspective view and purely schematically, with the thinner embossing roller 25 and the backup-roller 26 with larger diameter. On the backup-roller, the logos L are symbolically drawn in (as shown with reference numeral 27), which can have very small structures.

(35) The data of the hydrostatic roller system are calculated and entered as a function of the surface structure of the embossing roller to produce and of the foil to be embossed. Foil runs are the conducted at different external pressures until the desired embossing quality has materialised and the resulting hydrostatic measure is measured. From this hydraulic pressure value, the values for the geometrical shape of the counter-roller can be calculated by means of suitable computational programs. In the present example, the effect of the deflection of the embossing roller is offset by means of a crowning of the counter-roller.

(36) Here it is assumed that through the acting external pressure, i.e. the embossing force, the normally more solid counter-roller is only imperceptibly deformed. In addition, the crowning is calculated in such a manner that the deflection of the embossing roller is predetermined by the crowning, i.e. that the crowning has a tendency to be slightly larger than the deflection of the embossing roller by the embossing pressure alone. Because of the fact that the crowning of the counter-roller determines the deflection of the embossing roller it can be achieved that the gap between the two rollers during the embossing remains constant with a great accuracy.

(37) Instead of four bearing pockets, another number of bearing pockets can also be provided, but the hydraulic pressure on the axle must be symmetrical. In addition to this, more than one pressure pocket can also be provided.

(38) FIGS. 8-12 constitute measurement results which were obtained in tests on an axle in a hydrostatic two-modelling device, with accessibility through direct measurement, partly through numerical simulation. During these tests, both rollers are clamped in a mounting of a housing which is not shown and the hydrostatic pressure is applied to an axle, the shown one, wherein all figures relate to a hydrostatic pressure corresponding to a force of 15,000 Newton (N) and the axle has a length of 225 mm and a circumference of 150 mm.

(39) In FIG. 8, the full deflection of the axle is calculated, wherein according to the diagram a total of approximately 24 ?m deflection resulted. These data apply with full hydraulic pressure of the machine of the stand. The dotted region in the middle of the axle corresponds to the increased pressure H and thus deflection. The two outer regions T of the axle shown patterned are neither under pressure nor do they show any deflection, since they are held there.

(40) The diagram of FIG. 9 shows a calculation of the deflection of the hard metal axle in the middle of the axle, i.e. above the pressure pocket 19, where a deflection of approximately 8 ?m is obtained. A pressure of approximately 100 bar was applied onto the pressure pocket in order to offset the deflection. The dotted region in the middle of the axle symbolises the increased deflection in this region. When using a steel axle, the deflection would be approximately three times as great. The position of the axle is turned in FIG. 9 by 90? relative to the position of FIG. 8.

(41) In FIG. 10, the tension of the axle in the position of FIG. 8 is shown and from this it shows that the tension on the side that is opposite to the pressure pocket is greatest and in the middle region between pressure pocket and the opposite side the tension is very small, as is depicted in the drawing by different patterns.

(42) In FIG. 11, the deformation of the axle on the side that is opposite to the pressure pocket is indicated, wherein the pressure pocket side corresponds to the embossing edge, which upon rotation of the roller in each case is created in the place located opposite the counter-roller and where the foil is passed through. From the pattern H a relatively large deformation is visible which however does not reach the limit loading of the shell anywhere, so that material failure cannot occur. In the present case, the formation reaches approximately 14 ?m.

(43) In FIG. 12, the deformation of the roller on the embossing edge is shown, wherein the same hydraulic pressure as in FIG. 11 was used and from which it results that on the embossing edge as a consequence of the pressure pocket and the fact that this embossing edge is opposed by a second roller with identical data, no deflection takes place.

(44) From the preceding figures and the description it is evident that with the described modelling device with two hydrostatically mounted rollers with hard metal axles and pressure pockets it is possible by adjusting the hydraulic pressure, which acts both on the bearing pockets and the pressure pockets, to calculate the respective deflection of the axle. The optimal contact pressure is adjusted through tests with a pattern corresponding to the embossing roller and the foil used and the hydraulic counter-pressure in the bearing pockets and the pressure pocket measured. From these data of the stand, the parameters for the geometry of the embossing and counter-roller of the commercial embossing head later on can be calculated. The evaluation of the quality of the embossing is effected visually by comparing the desired visual effect on the embossing roller and of the result on the aesthetically attractive embossing copy on the foil.

(45) Starting out from the described modelling device it is also conceivable instead of a hydraulic system with oil or compressed air to use another modelling device with pressure pickups or other similar measurement systems and to calculate the loading of the axles and their deflection with the help of other parameters.

(46) Furthermore, another deformation of the embossing rollers and thus of the geometry of the surface of the counter-roller can result. The objective of the entire calculation remains being able to calculate the geometry of the counter-roller corresponding to the embossing roller in the final purely mechanical embossing housing in such a manner that during the embossing of a certain foil and a certain embossing structure even embossing over the entire width of the foil is created even when using very small embossing elements and high embossing pressures.

(47) The use of the test stand described above remains intended to offer the manufacturer of the rollers a device which offers a homogenous force distribution on the embossing edge independently of the applied embossing pressure (e.g. via oil). Accordingly, by comparing the embossing result (on the foil to the embossing structure on the embossing roller the optimal force can be determined which is necessary (since depending on the design the force distribution is always homogeneous this presents itself comparatively simply). Once the necessary embossing pressure has been determined, crowned rollers that are optimised for the embossing effect to be achieved can be produced which then exert the embossing pressure that is needed during the operation in an embossing unit without hydraulics (purely mechanically). The characteristics of the components of this embossing unit, especially the roller geometries are known thanks to the results from the embossing on the test stand and a commercialisable one can be produced with significant cost savings (fewer tests).

LIST OF NUMBERS

(48) 1 Hydrostatic roller 2 Shell 3 Axle 4, 5 Bearing regions 6-9 Segment 10 Intermediate webs 11-14 Bearing pockets 15 Inlet oil line 16 Continuous pipe=oil line 17 Channels between the segments 18 Return 19 Pressure pocket 20 Inflow to 19 21 Second roller 22 Shell 23 Axle 24 Embossing roller pair 25 Embossing roller 26 Backup-roller 27 Logos (DT Pressure on the pressure pocket) F.sub.ex1, F.sub.ex2 External pressure F.sub.Halt1, F.sub.Halt2 Counter-pressure of the mounting F.sub.H1, F.sub.H2 Total pressure on the other roller EE Embossing edge