Foil web installation for a flat bed embossing machine

A foil web installation for a flat bed embossing machine with foil webs (6), which are conducted across an embossing table (3) from unwinding rolls (7) comprises a braking—and guiding wall (10) ahead of the embossing table and foil feeding devices (9) for several foil webs after the embossing table. Between the unwinding rolls (7) and the embossing table (3) at least one flat braking—and guiding wall (10) acts as a foil tensioning device. This latter element comprises a fixed supporting layer (11) as supporting surface with suction openings (14), a cloth-like contacting layer permeable to air (12) lying on top of it and a flat vacuum chamber (17) with an adjustable vacuum source (13) assigned to it, wherein foil webs (6) are pressed against the braking—and guiding wall (10) and braked as a result of this. This makes possible a foil web installation simple to adjust, easy on the foil web for achieving high embossing performances with the best quality as well as short retooling times.

The invention is related to a foil web installation for a flat bed embossing machine with foil webs, which are conducted from unwinding rolls across an embossing table. With flat bed embossing machines or foil stamping machines of this kind, particularly high embossing performances in best quality and also particularly demanding embossing tasks, such as, e.g., relief embossing, are capable of being carried out. These flat bed embossing machines on the other hand, however, also make particularly high demands of the guiding and of the precise advancing of the thin and very sensitive embossing foil webs, with layer thicknesses of, e.g., solely 12-20 um (0.02 mm).

To achieve this, several foil webs of different kinds (with different web widths, advance lengths and with differing separation forces of the foil webs depending on the embossing task) simultaneously have to be guided and conveyed impeccably smoothly. The foil guiding has to take place without any draft, formation of creases, folds and displacements in an impeccably smooth and precisely positioned manner. And the rapid, intermittent advance in a short time across the whole embossing table has to be carried out with optimum care, in order to be able to obtain a high performance and high qualities. A flat bed embossing machine and foil web guiding installation of this type is known, e,g., from EP 0 858 888 or U.S. Pat. No. 5,979,308. The foil web guiding installation comprises a tensioning roller ahead of the embossing table, on which of necessity two deflection rollers are required on the embossing layer side of the foil webs, which are capable of impairing the sensitive embossing layer. Furthermore, here the tensile stresses for several foil webs are only able to be individually adjusted to a limited extent and with a relatively great effort being required. In addition, the required setting-up—and retooling times for several foil webs are still relatively long.

It is therefore the objective of the invention presented here to create a more simple foil web guiding installation with improved care for flat bed embossing machines, which also makes possible an optimum adjustment of the individual tensile stresses of several foil webs, which simplifies the setting-up and retooling of several foil webs and which also does not require any contact of the sensitive embossing layer side (image side) of the foil web with guiding elements.

This objective is achieved according to the invention by a foil web guiding installation for a flat bed embossing machine with at least one flat braking—and guiding wall as foil tensioning device ahead of the embossing table.

The dependent claims relate to advantageous further developments of the invention with further improvements of the foil web guiding installation and therefore also of the machine performance as well as to the shortening of the setting-up—and retooling times.

FIG. 1illustrates a foil web installation2according to the invention for a flat bed embossing machine1with a flat bed press4, wherein foil webs6are conducted from unwinding rolls7to an embossing table3for the embossing of flat material5. The flat material5may consist of paper sheets or paper webs from rolls. The flat material is moved in the longitudinal direction X of the machine. In addition, it is also possible to pull foil webs on to the embossing table3in transverse direction Y (FIG. 8). The foil web installation2comprises a foil tensioning installation ahead of the embossing table and foil feeding devices9.1,9.2for several foil webs6.1,6.2after the embossing table3. Between the unwinding rolls7and the embossing table3at least one flat braking—and guiding wall10is provided as foil tensioning installation, over which the foil webs6are conducted. These braking—and guiding walls10comprise a fixed supporting layer11, which forms a supporting and guiding layer, with suction openings14and a cloth-like contacting layer12permeable to air fixed to the supporting layer11lying on it as well as an adjustable vacuum source13assigned to it, wherein in a flat vacuum chamber17a vacuum dp is produced. In this manner, the foil webs are lightly pressed on to the contacting layer12and with this guided and braked in an adjustable manner. The flat braking—and guiding walls10can also slightly be curved and with this additionally provide for a deflection of the foil webs6. (InFIG. 1, e.g., the braking—and guiding wall10.1might comprise a slight deflection in direction of the embossing location3.) The construction and the functioning of the braking—and guiding walls10are further explained in the descriptions of theFIGS. 2-4.

In preference a braking—and guiding walls10.1is located directly ahead of the embossing table3, by means of which for every foil web6.1,6.2individually an optimum tensile stress is capable of being adjusted for the embossing process, so that in particular also all foil webs6following the embossing operation are able to be impeccably separated from the embossed flat material5and taken away. The tensions for the separation are dependent on the type and the dimensions of the foil webs and on the embossing process (differing embossing surfaces and types of embossing, e.g., relief embossing).

Thanks to the space-saving, flat design of the braking—and guiding walls according to the invention, it is possible to attach additional unwinding rolls7.3for additional foil webs6.3here directly ahead of this braking—and guiding wall10.1or also for simple, smaller embossing tasks (which do not require a foil store), which here are capable of being set-up particularly rapidly and in a simple manner. A foil roll change is also possible rapidly, in that the new foil web is simply stuck to the old one on the braking—and guiding wall10.1.

On the long path of the foil web installation2from the unwinding rolls7to the embossing table3it is also possible to provide more than one braking—and guiding wall10. In the example ofFIG. 1, an additional braking—and guiding wall10.2is provided shortly after a foil store20. The foil stores are here designed as vacuum loop stores, in particular as horizontal vacuum double loop stores20and arranged in the foil web feeding installation, i.e., ahead of the embossing table3. By the vacuum loop stores20a first tensile stress Z1is produced in the foil webs6.

For the braking—and guiding wall10.2here it is possible to utilise a suction fan21of the vacuum loop stores20as vacuum source13. The vacuum dp2in a vacuum chamber17is able to be additionally adapted by means of a variable throttling point19. The mostly relatively moderate additional tensile stress Z2, which is produced by this braking—and guiding wall10.2, is adjusted in such a manner, that an impeccably stretched foil web feed up to the next braking—and guiding wall10.1. is obtained. The additional tensile stresses Z3(refer toFIG. 4) on the braking—and guiding wall10.1can individually be adjusted for every foil web6.1,6.2,6.3in such a manner, that an optimum positioning at the embossing location3and an impeccable separation of the foil webs6from the embossed flat material5following the embossing is achieved.

In the example ofFIG. 1, the foil web installation comprises a foil removal device29after the foil feeding devices9.1,9.2for the lateral taking away of the embossed foil webs6.1,6.2. With this, once more a lot of building space is freed, which is able to be made use of for additional unwinding rolls.

The adjustment of the braking forces and of the tensile stresses in the foil webs at the vacuum loop store (Z1) as well as at the braking—and guiding walls (Z2, Z3) can be adapted to one another in such a manner, that the separation of the foil webs from the embossed flat material5following the embossing operation and the guiding of the foil webs takes place impeccably over the whole length and in an optimised manner.

At the embossing table3in the foil webs here a total tensile stress of Z=Z1+Z2+Z3is produced. Through the compulsory, accurately positioned and very rapid foil advance by means of the foil feeding devices9.1,9.2a tensile stress Z4is produced, which has to correspond at least to the total tensile stress Z. The strain on the embossed foil webs at the foil feeding devices9with deflection rollers, which compulsorily also have to make contact with the image layer side6aof the foil webs, is significantly higher than at the flat braking—and guiding walls10, on which no guiding elements and no contact are required on the image layer side6a. In the example ofFIG. 1the image layer side6ais not made contact with over the whole route from the unwinding rolls7up to the embossing table3.

The vacuum dp required at the large surface area braking—and guiding walls10is correspondingly relatively low and amounts to, e.g., 500-2000 Pa and the necessary total tensile stress Z produced in the very thin foil webs6amounts to, e.g., if at all possible less than 5 N/cm foil web width.

For the better foil web guiding in case of particularly demanding embossing tasks (e.g., for relief embossing) with correspondingly higher tensile stress Z, the positioned foil webs6on the embossing table3are capable of being partially relieved prior to the embossing by briefly running the foil feeding devices9backwards, thereupon they are embossed and subsequently once again pulled away with the full tensile stress Z and in doing so separated from the embossed flat material5. For this purpose, the foil feeding devices9are able to run backwards, e.g., by 2-5 mm and with this reduce the tensile stress Z during the embossing operation.

TheFIGS. 2aand2billustrate the construction and the mode of operation of the braking—and guiding wall10.FIG. 2ashows in cross section a braking—and guiding wall10with a fixed supporting layer11(which forms a supporting—and guiding surface) with suction openings14and a flat vacuum chamber17, in which a vacuum dp is produced by means of an adjustable vacuum source13. On the supporting layer11a cloth-like contacting layer12permeable to air is attached and fixed, e.g., clamped all around. The supporting layer is permeable to air above all also in tangential direction18, so that the vacuum dp under a foil web6running over it is equalised, resp., is uniformly distributed over the surface. The foil webs therefore are uniformly pressed on to the large surface area contacting layer12with a relatively low contact pressure, braked as a result of this and uniformly and constantly conducted in the foil feed direction, resp., direction of movement v of the foil webs. The contacting layer12consists of a soft material not subject to electro-static charging, so that no electrostatic friction forces are capable of being generated between the foil web and the contacting layer. The contacting layer12, for example, may consist of natural fibres such as cotton (with a minimal electric conductivity) and may be developed as a fleece or as a textile object, such as a fabric, a knitted fabric or else as a felt and with spaces, in order for a required tangential permeability to air (18) to be produced. With this contacting layer12it is possible to obtain an essentially constant friction coefficient, wherein static friction and sliding friction hardly differ.

The layer thicknesses of this contacting layer12may amount to, e.g., 0.3-1 mm; depending on the type and the geometry of the supporting surfaces and of the contacting layer, their thickness may also amount to more, e.g., up to 3 mm. This contacting layer is able to be attached to the supporting layer11easily replaceably and it is therefore also very simple to change for the purpose of adaptation to the type of the foil webs.

FIG. 2bin horizontal projection illustrates an example of an in preference metallic supporting layer11with suction openings14, which amount to an open surface proportion of preferably 30-60% of the total surface area of the braking—and guiding wall10and which comprise an average diameter of, e.g., 1-5 mm.FIG. 2bshows an advantageous execution of the supporting layer11as a slotted wall with slits, which extend parallel to the advance direction v of the foil webs6and which make possible a particularly good guiding of it. The width of the slits as well as the spacing between the slits, e.g., may amount to 1-3 mm and the length of the slits, e.g., to 10-30 mm. Other forms of the suction openings14are also possible, e.g., a perforated plate with a small hole diameter, so that the foil webs6essentially run over it flatly.

FIG. 3illustrates an example of a braking—and guiding wall10in a section in longitudinal direction of movement v of the foil with a length L, which amounts to at least 20 cm, in preference, however, to more, e.g., to 30-50 cm.FIG. 3also illustrates the very flat construction of the braking—and guiding wall10along the foil web6, as a result of which in comparison with tensioning—and guiding installations known up until now significantly less space is required, which, e.g., creates space for additional unwinding rolls (7.3inFIG. 1).

FIG. 4illustrates an example of a braking—and guiding wall10with three foil webs6.1,6.2,6.3running over it and with coverings15.1,15.2impermeable for air under a part of the foil webs, so that solely the not covered part L1, L2, L3of the length L is under suction and corresponding proportional braking forces, resp., tensile stresses Z3.1, Z3.2, Z3.3are produced in the foil webs. In this example, with the covering15.1less, with15.2more and underneath the foil web6.3nothing at all is covered. The desired optimum braking force, resp., tensile stress Z1here therefore is capable of being adjusted individually for every foil web—and this practically between 0 and 100% and in a very simple manner.

Between the foil webs6.1,6.2,6.3it is also possible to affix impermeable for air coverings16, in order to avoid a pressure drop, resp., a loss of pressure here and in order to adjust an optimally uniform distribution of the vacuum dp on the braking—and guiding wall10.

The impermeable for air coverings15and16are very easy to cut to size out of sheets of paper and affixed to the front edge10aof the braking—and guiding wall.

The braking—and guiding walls, i.e., the supporting layers11with the contacting layers12in preference are designed to be easily interchangeable, or capable of being slid-in. In this manner they are easily removed, the coverings15,16thereupon newly adjusted and the layers11and12inserted once more, without it being necessary to move the foil webs or to have to set-up new ones. This is possible, because on the braking—and guiding walls10there are no deflection rollers present on the image layer side6aof the foil webs and because these are indeed unnecessary.

TheFIGS. 5 and 6illustrate examples of slide-in cartridges22for vacuum loop stores20, which are illustrated inFIG. 1.FIG. 5shows a perspective view andFIG. 6in horizontal projection an arrangement with partition walls and end walls of a slide-in cartridge22. A foil web installation2with braking—and guiding walls10and combined with vacuum loop stores20makes a particularly good foil web installation and foil web conveyance. In order to further improve the foil web installation with optimum tensile stresses and in order to very significantly reduce the setting-up—and retooling times, it is possible to utilise removable slide-in cartridges22in the vacuum loop stores20. On frame stanchions25here adjustable partition walls23are fixed in such a manner, that the desired foil webs are separated. The partition walls23are closed off at the bottom by end walls24, with which separated chambers26not under suction next to the foil webs6.1.,6.2are formed in the foil loop store20. With this, on the one hand a pressure loss between the foil webs is avoided and on the other hand a uniform, optimally adjustable suction force Z1in the vacuum loop store is applied to the foil webs. With these slide-in cartridges22it is possible to carry out the optimum adjustment and retooling of the partition walls very rapidly, without it being necessary to remove the foil webs6themselves (solely the foil loops are pulled out of the vacuum loop store). The foil webs do not have to be set-up again.

The braking—and guiding walls10according to the invention in flat bed embossing machines and the slide-in cartridges22in the vacuum loop stores20make significantly reduced setting-up—and retooling times, an improved foil web guiding, higher embossing performances and an extended range of embossing tasks possible. With ventilated deflection bars it is even possible to achieve further improvements.

TheFIGS. 7a,7billustrate a deflection element27for the deflection of the foil webs6in the form of a stationary, ventilated deflection bar30, which produces an air cushion underneath the foil webs6, so that these are deflected with minimum friction. With lateral guiding elements32the foil web on the air cushion is capable of being very accurately guided and stabilised. This in comparison with deflection elements27known up until now, e.g., in the form of roller axes, results in minimum friction forces and a better guidance of the foil web. Advantageously ventilated deflection bars30of this kind, as illustrated inFIG. 1, are able to be located, e.g., ahead of a rear braking—and guiding wall10.1, ahead of and after the embossing location3, at the entrance of the vacuum loop stores20and also at the foil advance in transverse direction Y (refer toFIG. 8) at the embossing station3. In principle it is possible to design all deflection elements as ventilated deflection bars. The lateral guiding elements32e.g., can be manufactured as slip-on elements (clips) made of Delrin and simply be slipped-on to the stationary deflection bar30and also be displaced and adjusted. The ventilated deflection bars30may consist of a tube ventilated with a slight overpressure with a micro-porous layer31, which produces a finely distributed air cushion underneath the foil web6. This air cushion only has to be produced in the deflection range34.

The foil web installation according to the invention with braking—and guiding walls10and with ventilated deflection bars, or air cushion axes30also makes it possible to deflect the foil web installation by means of ventilated 90°-deflection bars33from the machine running direction X to the transverse direction Y or vice versa, from the transverse direction Y to the longitudinal direction X, as is illustrated inFIGS. 8 and 9. Foil advances with unwinding rolls each respectively in longitudinal direction X and in transverse direction Y are known and are described, e.g., in EP 0 858 888 or U.S. Pat. No. 5,979,308.

FIG. 8illustrates an example with a foil advance by in transverse direction Y with a braking—and guiding wall10yin transverse direction Y and with ventilated deflection bars30with lateral guiding elements32ahead of and after the embossing location3. This is particularly advantageous here, because the foil web6yafter the embossing operation has to be removed in transverse direction and because it should not be displaced in doing so. The unwinding roll7and the vacuum loop stores20here form a foil advance in longitudinal direction X. By means of a ventilated 90°-deflection bar33, it is possible, however, to deflect (individual) foil webs6in transverse direction Y (as foil web6y) (while other foil webs6simultaneously are conducted on in longitudinal direction to the embossing location3). With this, here no additional unwinding rolls7and no vacuum loop stores20are necessary in transverse direction. The 90°-deflection bars33are arranged at an angle of 45° to the X- and Y-direction.

As is illustrated inFIG. 9, it is on the other hand also possible to deflect foil web advances in transverse direction Y with unwinding rolls7yand loop stores20yin transverse direction by means of a ventilated 90°-deflection bar33into the longitudinal direction X. With this, it is also possible to position a separate unwinding station with unwinding rolls7yand loop stores20yand braking—and guiding walls10yin transverse direction next to the machine, which unwinding station is not bounded by the chain run of the machine. The example ofFIG. 9furthermore illustrates a splicing device35, which is located between the unwinding rolls7and the vacuum loop store10(FIG. 1). With a splicing station of this kind, a new foil web is capable of being attached to a foil web running out, resp., connected to it, e.g., by gluing, welding or connection with self-adhesive tape.

Within the framework of this description, the following terms are utilised: