State of the art In the paper processing industry to produce products in tissue paper, embossing or embossing-laminating units are known, which have the function of embossing one or more plies of tissue paper and joining together, by glu- ing, two or more plies to form a multi-layer product.

Embossing of tissue paper is performed to give characteristics of soft- ness, high thickness and high absorption capacity to the end product, as well as to provide the product with particular aesthetic characteristics.

In practice, embossing consists in permanent deformation of the ply of paper, with at least partial breakage of the fibers of which it is formed. This is obtained by feeding the ply between an embossing cylinder provided with protuberances, normally produced in a hard material such as steel or the like, and a pressure roller, usually a roller coated with an elastically yielding mate- rial, such as rubber or the like.

A glue is applied to the protuberances of an embossed ply, to join the embossed ply to a second ply, which may in turn be embossed or smooth.

Joining takes place by feeding the two plies through a lamination nip which may be defined by various members, one of which is typically the embossing cylinder. According to the cases, more than two plies may be embossed and/or laminated together. The devices or units that perform embossing and lamination are commonly named embossing-laminating devices or units.

In some embossing-laminating units, two plies are embossed sepa- rately between respective pairs formed of an embossing cylinder and a pres- sure roller. Subsequently, after glue has been applied to the protuberances produced by embossing on at least one of the two plies, the plies are joined together by feeding them through a lamination nip formed by the two em- bossing cylinders. Units of this type, commonly named point-to-point em-

bossers, are described in US-A-3,414, 459, US-A-4,978, 565, US-A-5,173, 351, US-A-5,096, 527, US-A-3,961, 119, WO-A-9720687, WO-A-9720688, WO-A- 9720689.

In embossing-laminating units of this type the plies are joined tip-to-tip, that is with the protuberances (or at least some of them) produced on one ply adhering to the protuberances (or at least some of them) produced on the other.

In other embossing-laminating units, joining of the plies is not performed between two embossing cylinders, but between an embossing cylinder and a lamination roller. In this way"nested"embossing is obtained. Examples of embossing units of this type are described in GB-A-1,225, 440, US-A- 3,694, 300.

WO-A-9944814 and WO-A-0078533 describe embossing-laminating units with a different structure. Here a first ply, which may be pre-embossed, is embossed a second time between an embossing cylinder and a pressure roller. A glue dispenser is associated with the embossing cylinder to apply glue to the protuberances of the ply produced by the protuberances of the embossing roller. Downstream of the glue dispenser the embossed ply is laminated, between a laminating roller and the embossing cylinder, with a second ply, which may in turn be pre-embossed.

As in the case of embossing-laminating units of the"nested"type, here too the use of a laminating roller for the joining of the plies takes place.

Objects and summary of the invention The object of the present invention is to produce an embossing- laminating unit which allows improved lamination between the plies and therefore improved quality of end product. In particular, the object of the pre- sent invention is to produce a device that allows more efficient use of the glue. More specifically, the invention proposes the improvement of a device, i. e. an embossing-laminating unit, wherein the plies are laminated together by pressing them against an embossing cylinder by means of a laminating member.

Essentially, the invention provides an embossing-laminating unit to pro- duce a multi-layer embossed web material, in particular a tissue paper mate- rial, comprising: an embossing cylinder with a plurality of protuberances de-

fining an embossing pattern; a pressure roller provided with a yielding sur- face, cooperating with said embossing cylinder and defining therewith an em- bossing nip ; a glue applicator; a laminating device cooperating with said first embossing cylinder to laminate and join together at least a first ply of web material and a second ply of web material, between which said glue applica- tor has applied a glue. Characteristically, according to the invention the lami- nating device comprises a continuous flexible member driven about a plurality of guide rollers, at least one of which is motorized. At least an actuator is also provided to press the flexible member against the embossing cylinder. The flexible. member is constituted, for example, by a belt. According to an advan- tageous embodiment of the invention, the guide rollers about which the flexi- ble member is driven comprise a tubular core made of carbon or another ma- terial with analogous characteristics of rigidity and lightness. Advantageously, a coating, made of rubber or the like, with a high coefficient of friction, may be provided on the carbon core, to grip the belt. A particularly light lamination device is thereby obtained.

According to an advantageous embodiment of the invention, for exam- ple when the working width of the embossing-laminating unit is relatively high, the guide rollers may be made to rest, in an intermediate area of their axial extension, on a supporting element which limits the bending strain. The sup- port may be constituted by a bushing mounted idle on a beam located in a central position between the guide rollers. In this way a compact system may be obtained, producing guide rollers even with small diameters, as any ex- cessive tendency to bend is counteracted by the central support. When the guide rollers are coated in material with a high coefficient of friction, this coat- ing may be interrupted at the level of the intermediate support, to prevent ex- cessive wear on the coating. For example, the guide rollers may have a cen- tral ring made of steel or another hard material, which rests and rolls on the bushing forming the intermediate support.

According to an advantageous embodiment, the guide rollers of the flexible member may be supported by a pair of movable side plates on side panels of the embossing-laminating unit. Advantageously, in this case at least one of said side panels may have an opening, the shape and dimensions of which are suitable to allow disassembly and replacement of the flexible

member. This facilitates replacement of the flexible member each time this is necessary, for example due to wear.

Further advantageous characteristics of the embossing unit according to the invention are indicated in the appended dependent claims and shall be described hereunder with reference to an embodiment of the invention.

According to a different aspect, the invention relates to a method to produce a multi-layer embossed web material constituted by at least two plies of tissue paper, comprising the phases of: embossing at least a first ply of web material between a pressure roller provided with a yielding surface and an embossing cylinder provided with protuberances defining an embossing pattern; laminating said first ply and at least a second ply of web material in a lamination area between said embossing cylinder and a laminating member, a glue being applied between said first and said second ply of web material, to join said plies to each other. Characteristically, according to the invention, the laminating member comprises a flexible member driven about a plurality of guide rollers.

The web material may advantageously have a weight per unit of surface area ranging from 25 to 80 g/m2. Each of said two plies of which it is com- posed, which may in turn be constituted by several layers, may have a weight per unit of surface area ranging from 10 to 30 g/m2.

The use of a continuous flexible member, such as a belt, as laminating member to press two or more plies of tissue paper against an embossing cyl- inder or roller to obtain reciprocal adhesion of the two or more plies allows considerable advantages to be obtained with respect to devices wherein lamination is obtained by means of a roller or a cylinder.

In fact, reciprocal adhesion of the plies of tissue paper is the result of a combination of factors, the main ones being the quantity of glue, the lamina- tion pressure and the lamination time. In traditional devices a considerable quantity of glue and a high pressure are applied for a tendentially infinitesimal time. This is due to the fact that lamination is obtained by means of a laminat- ing roller which ideally has rectilinear and instantaneous contact with the em- bossing cylinder, with the plies of paper which are laminated at the level of this line of contact between the embossing cylinder and the lamination roller.

The high pressure and the considerable quantity of glue compensate-

in obtaining the desired bonding-for the short contact time.

This causes two substantial drawbacks. On the one hand, the need to utilize noteworthy quantities of glue. On the other, consequent seepage of the glue through the cellulose fibers forming the plies of tissue paper (considera- bly thin and light) with consequent deposit of glue on the rollers and cylinders of the device. This makes frequent cleaning of the cylinders and rollers nec- essary.

According to the invention, the plies of tissue paper are laminated by means of a flexible member, which defines a relatively wide pressure and lamination surface, and in any case much wider than the ideal line of contact between the embossing cylinder and the laminating roller of traditional de- vices. The pressure time is 10-20 times (or more) greater than the contact time obtained with a laminating roller. This makes it possible to reduce the quantity of glue and also the contact pressure.

Reduction in the amount of glue employed provides an immediate first positive effect, consisting in the saving of material. Secondly, benefits may be obtained in terms of final characteristics of the product, which is softer, owing to the decreased quantity of glue.

The decreased quantity of glue employed on the one hand and the lower pressure on the other also reduce or almost totally eliminate the phe- nomenon of seepage of glue through the plies of tissue paper, thereby drasti- cally reducing soiling of the rollers and cylinders of the device. Therefore, un- expected and particularly important results and advantages are obtained in the tissue paper processing sector.

Brief description of the drawings The invention shall now be better understood following the description and accompanying drawing, which shows a non-limiting practical embodiment of the invention. More specifically, in the drawing: Figure 1 shows a side view of the unit according to the invention; Figures 2 and 2A show a side view according to ! t-t) in Figure 4 of the laminating unit, in two different layouts; Figure 3 shows a section according to ttt-ttt of Figure 4; Figure 4 shows a section according to IV-IV of Figures 2 and 3; and Figure 5 shows a section analogous to the section in Figure 3 in a dif-

ferent embodiment.

Detailed description of an embodiment of the invention The unit shown in the appended drawing has a structure similar to those described in WO-A-9944814 or in WO-A-0078533, although it must be understood that analogous concepts may be applied to embossing-gluing units of different types, in which a laminating member must be provided to join together two or more plies, all or only some of which are embossed.

In the example shown the embossing-laminating unit comprises an em- bossing cylinder 1, which cooperates with a pressure roller 3, coated in rub- ber or another elastically yielding material. The surface of the embossing cyl- inder 1, produced in a hard material such as steel or the like, is provided with protuberances 1 P which-cooperating with the yielding coating of the pres- sure roller 3-deform and emboss a first ply of web material V1 which is made to pass through the nip between the pressure roller 3 and the emboss- ing roller 1. The ply V1 may be formed of a single layer or of several super- imposed layers which may have been joined previously by gluing or ply- bonding. Moreover, the ply V1 may be smooth or may have been previously embossed, for example with micro-embossing.

A glue dispenser, indicated schematically and as a whole with 5, coop- erates with the embossing cylinder 1, to apply a glue to the projecting surface of the protuberances produced on the ply V1 by the protuberances 1 P of the embossing cylinder 1, when the ply V1 is still engaged with said cylinder.

A laminating device, indicated as a whole with 7 and described here- under in greater detail with reference to Figures 2 to 4, is disposed about the embossing cylinder 1. The laminating device 7 comprises a lamination belt 9 driven between three rollers 11,13, 15. The plyV1, embossed and provided with glue, and a second ply V2 (in turn formed of one or more layers), which rests on the ply V1 and which may have been embossed previously by a separate embossing unit, or may be smooth, are fed to the lamination area defined between the surface of the embossing cylinder 1 and the lamination belt 9. The two plies V1 and V2 are glued together upon delivery from the lamination nip, thanks to the relatively low pressure exerted for a relatively long time by the belt 9 and by the protuberances 1 P of the embossing cylin- der on the two plies V1 and V2. The glue has seeped through the fibers of

the two plies in contact with each other to provide adequate and efficient re- ciprocal adhesion. If one or other or both of the plies V1, V2 are composed of several layers, the glue can seep between the fibers and also glue the layers forming said plies to one another.

The surface of the belt 9 which acts against the embossing cylinder 1 is constantly or intermittently cleaned by a brush 10 positioned at the outlet of the lamination area. This allows any deposits of fibers or glue to be removed from the surface of the belt and maintains it in efficient working conditions at all times, in the event that seepage of glue should soil the belt.

The three rollers 11,13, 15 are supported by two side plates 17, 19, which can be seen in particular in the section of Figure 4. The roller 15 is mo- torized by means of a motor 21.

As can be seen again in Figure 4, the rollers 11,13, 15 are hollow tubu- tar elements, produced in carbon fiber. The carbon fiber sleeve, indicated with 11 C, 13C, 15C is coated with a layer 11 R, 13R, 15R made of rubber or another material with a high coefficient of friction, to grip the belt 9. In an in- termediate annular area of its extension, the coating 11R, 13R, 15R of each roller 11,13, 15 is interrupted and a respective collar or ring 11B, 13B, 15B, made of steel or another hard material, is inserted between the two portions of coating. These rings rest on a bushing 23 supported idle on a cylindrical beam 25 rigidly constrained to the two side plates 17,19 and disposed in a central position with respect to the rollers 11,13, 15.

Each of the two side plates 17,19 which support the rollers 11,13, 15 is provided with two pairs of guide wheels, indicated respectively with 27, 29 and 31,33. The two pairs of wheels 27,29 of the two side plates 17,19 roll on guides 41,43, supported by two fixed side panels 45,47 of the emboss- ing-laminating unit. The guide 41 is fixed on the side panel 45, while the guide 43 is easily releasable from the side panel 47 to move from a working position, indicated in Figure 2, to a withdrawn position, indicated in Figure 2A, for the purposes that will be explained hereunder. The guide 43 is moved by removing the screw 43A from the fixed side panel 47 and loosening the lower screw 43B, about which the guide, thereby released, can rotate.

Analogously, the two pairs of wheels 31,33 roll on a first guide 51 fixed to the side panel 45 and on a second guide 53 fitted in an easily releasable

way to the side panel 47. Figure 2 shows the working position-of the guide 53, while Figure 2A shows the withdrawn position of said guide.

When the laminating device 7 is at work, it is pressed against the cylin- drical surface of the embossing cylinder 1 by means of a pair of piston- cylinder actuators 55, one for each side panel of the machine. Under the thrust of the actuators 55 the laminating device 7, being free to slide with its wheels 27,29, 31,33 along the guides 41,43, 51,53, presses constantly against the embossing cylinder 1 to perform lamination of the plies V1 and V2.

When replacement of the belt is necessary, the unit formed by the side plates 17,19 with the respective guide wheels, the beam 25, the rollers 11, 13,15 and the belt 9 is lowered (in the manner described hereunder) to bring the three rollers 11,13, 15 with the belt 9 to the level of an opening 61 pro- vided in the fixed side plate 47 of the embossing-laminating unit. The lower- ing movement is guided by the wheels 27,29, 31,33 along the guides 41,43, 51,53. Figure 2A shows the position of maximum lowering of the side plates 17,19 with the relative members supported by them.

The opening 61 has an approximately triangular form with rounded cor- ners and its dimension corresponds to the overall sectional dimension of the three rollers 11,13, 15. It is normally partly obstructed by the guides 43,53 when they are in the working position, as indicated in Figure 2.

When the unit formed by the side plates 17,19 with the respective members supported by these has reached the lower position represented in Figure 2A, the side plate 19 is clamped on the fixed side panel 45. For this purpose three threaded holes 63 (Figure 3) are provided in the side plate 19 so that when the side plate reaches the lowered position, they are aligned with three corresponding through holes 65 in the fixed side panel 45, to insert three lock screws. In this way it is possible to clamp the side plates 17,19, the rollers 11,13, 15 and the beam 25 in a cantilever fashion on the side panel 45 so that the guides 43,53 integral with the side panel 47 can be re- leased without the unit oscillating. In fact, when these guides are released and taken to the position indicated in Figure 2A, the unit formed by the side plates 17,19, the rollers 11,13, 15 and the beam 25 is supported in a canti- lever fashion by only the side panel 45.

The side panel 45 has, analogously to the side panel 47, an opening 67, which however has a smaller extension to the opening 61. The object of the opening 67 is also to make the overall dimension of the motor 21 project to allow translatory movement thereof when the side plates 17,19 are moved downward.

The translatory movement of the side plates 17,19 and of the members supported by them along the guides 41,43, 51,53 may be partially controlled by retraction of the actuators 55. Nonetheless, it is preferable for this down- ward sliding and subsequent lifting to be obtained by hooking the unit consti- tuted by the side plates 17,19 and by the members supported by them to an overhead crane or another suitable device, by means of rings 69. When the unit has been hooked to the overhead crane the rods of the actuators 55 may be released and made to retract. The actuators may be made to rotate analogously to the guides to be withdrawn from the belt area. Lowering of the side plates and of the rollers 11,13, 15 is controlled by the winch of the over- head crane.

To release and remove the belt 9 when the side plates 17,19 and the rollers 11,13, 15 are in the lowered position in Figure 2A, an operation is first performed to slacken the belt 9, normally tensioned about the rollers 11, 13, 15. This operation consists in moving the axis of the roller 15 and its supports 71 with respect to the other rollers 11,13 from the position in Figure 2 to the position in Figure 2A. In fact, as can be seen by comparing Figures 2 and 2A, the path of the belt 9 in Figure 2 is greater than in Figure 2A. This means that in the layout in Figure 2A the belt is slack.

Movement of the supports 71 of the roller 15 is guided along respective curved slots 72 and 74 produced in the sides 17 and 19 respectively. When the supports 71 are in the working position of the lamination device 7 (posi- tion in Figure 2), the supports 71 are clamped against one end of the slots 72,74 and held in position by means of screws 76,78. To translate the sup- ports 71 from the position in Figure 2 to the position in Figure 2A, the screws 76,78 are unscrewed and with a pair of threaded bars 73 the supports are pushed (from left to right in the drawing) against the opposite end of the slots 72,74, that is in the position in Figure 2A. Here the screws 76,78 are re- tightened to clamp the supports 71 in this new position.

When the roller 15 has been taken and blocked in the position in Figure 2A the belt 9 is slack and may be removed from the rollers 11,13, 15. This removal is made possible by the fact that the rollers 11,13, 15 and the side plate 17 are now supported in a cantilever fashion on the fixed side panel 45.

Moreover, as can be seen in Figures 2 and 2A, the side plate 17 is shaped so that it does not form an obstruction that impedes removal of the belt, with the exception of a portion 17A, supporting the axles of the wheels 29 and 33.

This portion is disassembled by loosening the respective screws 18, which fix it to the remaining part of the side plate 17. The belt 9 is then free to be re- moved from the rollers. The supports of the rollers 11,13, 15 are positioned so that the rollers project from the profile of the side plate to allow removal of the belt 9.

The operations described above may also be performed in a different order. For example, it is possible to first slacken the belt 9 by translating the axis of the roller 15 and then lower the unit supported by the side plates 17, 19.

After removing the belt 9 to be replaced, the new belt may be fitted. Af- ter having reassembled the portion 17A of the side plate 17 the new belt 9 is tensioned with a reverse translatory movement of the axis of the roller 15 along the slots 72,74, after having removed the screws 76,78. The bars 73 are used in position 73A to push the supports 71 to the position of maximum tension of the belt and the screws 76,78 are then re-tightened to clamp the supports 71 in the position in Figure 2. The original position of the guides 43, 53 is then restored, the side plate 19 is released from the fixed side panel 45 and, finally, by means of the overhead crane hooked to the rings 69, the unit formed by the side plates 17 with the respective rollers 11,13, 15 is lifted and the rods of the actuators 55 are reconnected to the side plates 17,19 to push the laminator device 7 against the embossing cylinder 1.

Figure 5 shows a different embodiment of the device according to the invention. The same numbers are used to indicate the same or equivalent parts to those in the previous figures. In substance, the device of Figure 5 dif- fers from the previous one owing to the presence of a pressure member 101 acting on the belt 9 to press it against the surface of the embossing cylinder 1. The pressure member 101 is disposed between the guide rollers 11 and

13 and has a member with a shoe pressing element 103, with an essentially cylindrical surface, the curvature radius whereof is approximately equal to or slightly greater than the curvature radius of the embossing cylinder 1. The curvature radius of the pressing element 103 may be variable so that a vari- able pressing profile may be obtained along the circumferential extension of the cylinder, for example a gradually increasing and subsequently gradually decreasing pressure.

The extension of the shoe pressing element 103 is more or less equal to, or slightly less than, the axial length of the cylinder 1 and the width of the belt 9. It presses the belt against the surface of the cylinder 1 so as to in- crease the pressing stress without excessively increasing belt tension. The extension of the concave cylindrical surface of the shoe pressing element 103 may be more or less extended according to the circumferential direction of the cylinder 1.

The element 103 may be produced in material with an extremely low coefficient of friction, on which the belt 9 may slide directly. In an alternative embodiment (not shown) the concave surface of the shoe pressing element 103 may be provided with idle rollers, supported on axles parallel to the axis of the cylinder 1.

The shoe pressing element 103 is clamped, by means of screws 105, between two plates 107. The assembly thereby formed slides transversely with respect to a supporting beam 109, clamped on the support formed by the beam 25. At the level of the bushing 23 the beam 109 has a reduced sec- tion, so as not to interfere with the bushing.

Disposed between the beam 109 and the shoe pressing element 103 is an air chamber (or a plurality of air chambers) 111 which are filled with pres- surized air to push the shoe pressing element 103 against the belt 9. The as- sembly formed by the pressing element 103 and the plates 107 is guided by pins 113 inserted into elongated slots or notches 115 produced in the plates 107 and screwed to the beam 109. This arrangement makes it possible to ob- tain a guided movement of the shoe pressing element 103 with respect to the beam 109.

It is understood that the drawing purely shows a non-limiting practical embodiment of the invention, which may vary in forms and layouts without

however departing from the scope of the concept on which the invention is based, as defined in the appended claims. Any reference numbers in the claims have the sole purpose of facilitating reading in the light of the descrip- tion hereinbefore and of the accompanying drawings and do not limit the scope of protection.