The present invention relates to apparatus for synchronising a printed image on an embossed web, and to a method of synchronisation useful in the production of packaging materials.

In the production of packaging, aluminium or other metal foils are frequently used because of their moisture barrier and suitability for use in connection with food and like products. In some circumstances the foil is embossed in order to improve its mechanical properties and appearance. As well as embossment, the foil may be laminated with other materials which improve its strength, particularly its tear resistance as well as the aesthetic appearance thereof. This may be enhanced by the embossment of a single or multiple formation on the foil, perhaps in the form of an advertising logo or other image, as well as a more diffuse pattern of embossment over the remaining area of the foil. In the production of cigarette packets or cartons, including the so-called"flip-top"type or hinge-lid pack, a foil element, separate from the main foil wrapping, is positioned over the product in the region of the opening so that, when the flip-top or hinged lid is first opened, the product is covered entirely by the inner lining. The removable foil element can then be pulled away to expose the product for subsequent extraction from the packet. This disposable foil element is usually simply discarded after this point as having no further use. However, it would be possible to use it for various purposes, including promotional exercises, if it were possible to place information on it. This would enable its use, for example, as a

voucher or token which is relatively incorruptible in the sense that, in order to gain access to it, the user must first remove an outer sealed layer of plastics or cellophane before being able to open the top of the carton to gain access to the foil element. This element is known in the art as a"pull-front"and the present invention is concerned, although not exclusively, with means by which such pull-front can be provided with a printed image registered precisely in relation to the cut edges of the pull-front so that, upon opening the packet, the printed image is always in exactly the same position.

However, because the foil is embossed while still in web form, that is before the individual foil elements which form the pull-fronts are separated from the web, synchronisation of the cutter which separates the individual elements from the web with the printed image on the web presents particular problems.

One problem which must be addressed is the fact that there is a very large installed base of cigarette packet manufacturing equipment so that any modification to the apparatus must be capable of being applied to existing machinery as well as being introduced into new machinery, otherwise the take-up of such improvements is likely to be low. Known package-forming machines, however, are highly developed ; in particular the drive-train rollers are synchronised with one another mechanically so that the foil is handled as it passes from a source-roll to its final destination without the introduction of excess stress which could cause tearing or rupture, and without the formation of excess slack which could form loops or wrinkles in the finished product.

Any apparatus for ensuring registration of printed images with the cut edges of the

foil must, therefore, be capable of being fitted to such existing machinery without interfering with its operation. This can be achieved, in certain circumstances, by de- coupling the drive-rollers from the existing mechanical synchronisation system, but the manner in which this is done cannot be applied in the same way to all machines due to the variations in their structure.

The applicant's co-pending international applicationNo. PCT/GB01/00637 describes one way in which the relative longitudinal position of a web passing through a machine having a plurality of pairs of rollers driven in synchronism with one another can be achieved. This involves apparatus having at least one pair of control rollers between which the web passes on its way through the machine, means that driving the control rollers independently of the said synchronised rollers, means for detecting a registration mark on the web and for comparing it with data concerning the phase of the synchronised rollers, and means for varying the speed of the control rollers when at least one pair of synchronised rollers reaches a predetermined phase range. This predetermined phase range identifies the angular position of the rollers when respective flats formed on the curved surface are facing one another with the web between them so that the web is, effectively, de-coupled from engagement with the control rollers. Especially if these control rollers are embossment rollers this allows the continuous formation of embossed film with strips which are not embossed, but which can be positioned in the finished product where the embossment is not essentially required, for example at the cut edges. Indeed, the provision of an unembossed region where the web is to be cut may constitute an advantage for the cutting operation.

According to one aspect of the present invention, therefore, there is provided apparatus for synchronising a printed image on an embossed web with a cutter for separating the printed and embossed web into separate elements whereby to ensure a consistent relative positioning of the printed image with respect to the cut edges of the elements, in which the embossing of the web is effected by embossing rollers which constitute the primary driving force for transport of the web past the cutter, and the operation of the cutter is controlled by means which determine its operation independently of the position of the printed image on the web, in which synchronisation of the image with the cutter is effected by means of a servo-control mechanism driving the embossing roller and subject to input signals from the means driving the cutter and from means for detecting registration indicia on the web identifying the position of the printed image.

In this way it is not necessary to provide the embossing rolls with flats to allow relative movement between the web and the embossing rollers to take place.

Embodiments of the present invention can be important, therefore, with continuous embossing surfaces which, in use of the apparatus, are continuously engaged with the web. By varying the speed of these rollers in relation to other parts of the equipment, however, the web can be advanced or retarded so that the images formed thereon can be positioned accurately in relation to a cutter, the operation of which is determined separately, for example by a synchronisation mechanism which synchronises the cutter with other parts of the apparatus.

The apparatus of the invention may be provided with a web transport which includes rollers or drums downstream from the cutter which are engageable with the web in such a way as to allow the possibility of slippage between them.

These rollers or drums of the web transport downstream from the cutter preferably have perforated surfaces and are connected or connectable to a vacuum source whereby, in use, to engage the web to the drum or roller by suction.

Likewise it is preferred that the means for detecting registration indicia on the web is an optical sensor such as a photocell.

Web tension adjustment means is preferably located in the path of the web upstream of the embossing roller for compensating tension variations resulting from operation of the servo-control of the embossing rollers themselves.

There may be provided a further pair of driven rollers downstream from the embossing rollers along the path of the web, the movement of the said further pair of driven rollers being synchronised with the motion of the embossing rollers. This synchronisation of the said further pair of driven rollers with the embossing rollers may be achieved by a servo-drive mechanism having an input fed with signals representing the angular position of the embossing rollers.

In alternative embodiments the embossing rollers themselves may be provided with flats on the curved surface thereof which are in register with one another when facing

the web passing between the rollers, whereby to allow further adjustment of the relative position of the web and the surface of the embossing rollers to take place by varying the angular position of the embossing roller whilst the web is effectively disengaged therefrom when the flats are facing one another. This, although superficially similar to the arrangement in the applicant's earlier application, is different in that, rather than adjusting the longitudinal position of the web whilst the rollers maintain a constant speed of rotation, the web speed is not varied and the speed of rotation of the rollers is accelerated or decelerated. This, then, allows an embossed image on the web to be synchronised with the cutter so that, as well as the printed image, the embossed image can be in a predetermined position in the final cut elements. The variation of the relative angular position of the embossing rollers with respect to the web when the flats are facing one another, does not affect the adjustment of the web position achieved by varying the angular position of the embossing rollers when engaged with the web.

Preferably the embossing rollers are driven by a servo-drive mechanism as a slave to the servo-drive mechanism driving a said further pair of rollers.

The cutter may be borne on a roller or may be a reciprocating cutter knife. In the former case, it is preferred that the roller exerts no drive function and the embossing rollers and/or the said further pair of rollers are driven as slave to the cutter roller drive mechanisms.

There may further be provided switching means for switching the servo demand

signal for the embossing rollers selectively between the servo controlling the cutter roller and the servo controlling the said further rollers whereby selectively to synchronise the embossment with the cutting position or with the printed image.

The present invention also comprehends a method of producing printed, embossed foil elements from a continuous web thereof, comprising the steps of : conveying a continuous web of printed foil from a source to an embossing station, embossing the foil at the embossing station, conveying the embossed foil to a cutter station at which the continuous web is separated into discrete lengths by a cutter, and synchronising the operation of the embossing station and the cutter station, in which the embossing station includes rollers driven by a servo-motor piloted by a signal from a sensor detecting registration marks on the web identifying the position of the printed images and a signal from a sensor responsive to the instantaneous position of the cutter.

Various embodiments of the present invention will now be more particularly described, by way of example, in which: Fig. 1 is a schematic side view of a first embodiment of the invention; Fig. 2 is a schematic side view of an alternative embodiment of the invention; and Fig. 3 is a schematic view of the servo arrangement of a further alternative embodiment of the invention.

Referring first to Fig. 1, the apparatus shown comprises a feed-roll 11 of foil 12 which is driven to rotate by an electric motor 13. In alternative embodiments, not shown,

the drive for the roll 11 may be part of a packaging machine synchronised with other rollers which will be identified herein below, or the roll 11 may be freely rotatable and turned by the tension of the web drawn from it, in which case the motor 13 would be replaced by a afriction or magnetic brake possibly controllable in synchronisation with parts of the system so as to avoid the formation of slack loops of excess tension.

Roller 14 guides the foil 12 from the feed-roll 11 into a loop defined by a resiliently mounted roller 16 and a tensioner roller 17. The loop 15 may be of variable size depending on whether the drive unwinding the reel 11 runs faster or slower than the take-up of the foil 12.

The foil 12 passes between two embossing rollers 18,19 which constitute the foil take-up drive. Each roller has a textured cylindrical surface for applying to the foil an embossed texture which provides an aesthetically pleasing attractive finish and also a degree of resilience to the foil which improves its handling properties for wrapping the products and protecting them within the carton. The rollers 18,19 are driven by servo-motor 20 which receives a piloting signal at an input 21 generated as will be described hereinbelow. From the embossing rollers the foil passes between two guide plates 22,23, under a photocell 24 to a cutter roller 25. The cutter roller 25 is relieved in such a way that only the blades 26,27 thereof engage the foil 12 so that the entirety of the drive to the foil 12 is applied by the embossing rollers 18,19 and subsequent drums 28,29 downstream of the cutter roller 25. These drums have perforated surfaces, only the surface 30 of the drum 28 of which is visible in Figure 1, and hollow interiors in communication with a vacuum source so that the foil elements 31 cut from the foil 12 are held against the surfaces 30 by suction. This allows a degree

of slippage between the drum 28 and the foil 12 so that the foil is maintained under a light tension if the drum 28 is driven at a speed slightly greater than that of the embossing rollers 18,19.

The foil 12 is preliminarily printed with images (not shown) the position of which is marked by registration marks 32 on the foil itself. As these registration marks 32 pass the photocell 24 it generates a signal on an output line 33 to a comparator 34 which also receives an input on line 36 from an encoder 37 detecting the motion of the cutter roller 25. The output from the comparator 34 is fed to line 21 which is the input to the servo-motor 20.

The drive to the cutter roller 25 is taken from the packaging machine of which the present apparatus forms part. This is synchronised with the movement of the supply reel 11 driven by the motor 13 or by the packaging machine common drive. These two rolls are, therefore, maintained, in synchronisation with one another. However, the printed image may not, of course, remain entirely in register with the motion of these rollers for which purpose the embossing rollers 18,19 can be driven slightly faster or slower to advance or retard the web 12 in relation to the cutter roller 25. A comparison between the phase of the cutter roller 25 and the instantaneous position of the web 12 is achieved at the comparator 34 to derive the piloting signal applied to the input 21 driving the servo-motor 20 which drives the two embossing rollers 18, 19. The slippage between the web 12 and the roller 28 allows for the variation in speed of the web 12 downstream of the embossing rollers 18,19 and the resiliently mounted loop roll 16 compensates for variations in the tension between the feed roll

11 and the embossing rollers 18,19.

In another embodiment (not shown) the motor 13 is driven by a demand signal derived from an encoder incorporated in the motor 20, but at a predetermined ratio which can be modified by feedback from the tensioning system, for which purpose a transducer (not shown) may be fitted to the floating roller 16.

In the alternative embodiment illustrated in Fig. 2 the same reference numerals are used to identify the same or corresponding components as in the embodiment of Fig.

1. This embodiment differs from that of Figure 1 by the presence of two additional drive rolls 49,38 between the embossing rollers 18,19 and the cutter roller 25 which, in this embodiment, has a counter roller 39. This may be necessary, for example, if the path length between the embossing roller 18,19 and the cutter roller 25 is too great such that the guide plates 22,23 may introduce too much frictional resistance to maintain the web 12 on a smooth path, or if it is necessary to change the direction of travel of the web 12 between its exit from the embossing rollers 18,19 and arrival at the cutter roller 25, as illustrated in Figure 2.

In this embodiment, the encoder 37 feeds its signal to a first comparator 40 the output from which controls the servo-motor 20 which drives the embossing roller 18 as in the embodiment of Fig. 1, but in this case the comparator 40 produces another output 41 to a comparator 42 the output from which drives a servo-motor 43 which drives the rollers 49,38. These rollers are thus slave to the embossing rollers 18,19 to maintain synchronism therewith.

In Figure 3 a further alternative embodiment is illustrated in which, again, the same reference numerals are used to identify the same or corresponding components. This embodiment is one which allows flats on the embossing rollers 18,19 so that these can be provided also with an embossed logo which can then be separately synchronised with the cutter 25. In this embodiment the encoder 37 is connected to a servo system 44 which also receives an input from the optical sensor 24 and produces an output signal which drives the motor 43 for the control rollers 49,38 (not shown in Fig. 3). This motor 43 or the rollers 49,38 have an output encoder 45 providing an output signal on a line 46 representing the actual position the rollers 49, 38 and this is fed to a second servo system 47 as a demand signal for the drive motor 20 which drives the embossing rollers 18,19 (not shown in Fig. 3). The motor 20 has an output encoder 48 providing a feedback loop to the servo system 47 so that the embossing rollers 18,19 are held in an angular relationship as a slave following the drive rollers 49,38.