Embossing unit for tissue paper and the like

Abstract

The embosser is provided with at least one embossing unit with a first endless flexible member having an inner surface inside a first closed path of the first endless flexible member and an outer surface outside the first closed path. The outer surface of the first endless flexible member comprises a plurality of embossing protuberances. The embossing unit further comprises a second endless flexible member with an inner surface inside a second closed path of the second endless flexible member and an outer surface outside the second closed path. The first closed path and the second closed path have a common portion, along which the first endless flexible member and the second endless flexible member advance with the outer surface of the first endless flexible member pressed against the outer surface of the second endless flexible member and form an embossing nip.

Description

EMBOSSING UNIT FOR TISSUE PAPER AND THE LIKEDESCRIPTIONTECHNICAL FIELD

[0001] The present invention relates to improvements to embossers, including so- called embossers-laminators, for processing plies of tissue paper or the like.PRIOR ART

[0002] What is known as tissue paper is used for the production of various items for household and domestic, professional, and even industrial use. In particular, tissue paper is used to produce toilet paper, paper towels and other products in rolls or sheets.

[0003] In multiple applications, the tissue paper is subjected to a mechanical embossing process. The embossing process essentially consists of passing a single ply or multiple plies of tissue paper through a nip defined between an embossing roller and a pressure roller. The embossing roller is equipped with protuberances that cooperate with the surface of the pressure roller. In some embodiments, the embossing roller and the pressure roller are both made of hard material, such as steel, and one has protuberances and the other cavities that mesh with each other.

[0004] In other, more common embodiments, the embossing roller has protuberances that penetrate inside an elastically yielding coating layer with which the pressure roller is provided, deforming it with respect to the substantially smooth cylindrical shape that this layer takes when the pressure roller is at rest and not in contact with the embossing roller. The two rollers are pressed against each other so that the protuberances penetrate the lateral surface of the pressure roller due to the compressive deformation of the yielding coating of the pressure roller itself. The cellulosic material, forming the web material, which passes through the nip formed between the two rollers is permanently deformed with the formation of embossing protrusions having a pattern corresponding to that of the embossing protuberances of the embossing roller.

[0005] In some applications, embossing or embossing-laminating units are used, in which two or more paths are provided for as many cellulosic plies, typically tissue paper. These plies are embossed separately, each between an embossing roller and acorresponding pressure roller. A functional liquid, for example a glue, is then applied to the embossed protuberances of one of the two plies and the two plies are bonded together by lamination.

[0006] As a function of the mutual arrangement of the embossed protuberances on the two plies and the manner in which the plies are laminated together, various embossing and lamination techniques can be distinguished.

[0007] In a technique called tip-to-tip, two embossing rollers processing two separate plies of tissue paper are placed so as to form a lamination nip therebetween, at which at least some of the protuberances of one embossing roller press against the protuberances of the other embossing roller and the two plies are laminated between the two embossing rollers.

[0008] In other cases, the two plies are bonded together by inserting the embossed protuberances on one of the plies inside the cavities between embossed protuberances of the other ply. This is referred to as nested embossing. Some embossing-laminating units of this type are called DESL (Double Embossing Synchronized Lamination), as the plies are in phase, i.e., synchronized, with each other to obtain the mutual nesting of the embossing protuberances. In this technique a ply, which is embossed between a first embossing roller and a first pressure roller and downstream of the embossing nip between the first embossing roller and the first pressure roller, the functional fluid is applied to the first ply. The first ply remains engaged with the first embossing roller and advances adherent thereto until it passes through a lamination nip, defined between the first embossing roller and a laminator roller, also called marrying roller. The second ply is embossed between a second embossing roller and a second pressure roller. After embossing, the second ply is moved away from the second embossing roller and placed on the first ply, which in turn rests on the first embossing roller. The two plies advance together through the lamination nip.

[0009] In some cases, the embossing patterns of the two plies are not synchronized with each other and the plies are coupled and laminated randomly. This case is referred to as DERL (Double Embossing Random Lamination).

[0010] In all cases, embossing involves a strong mechanical stress on the cellulosic plies and localised breakage of the cellulosic fibres forming the ply of paper.

[0011] To obtain embossing, which in practice consists of a permanent deformation of the plies, high pressures must be exerted between the embossing roller and the pressure roller. This is even more true the higher the production speed of the processing line, since the time during which the ply of paper is pressed between the embossing roller and the pressure roller is short. Similar problems arise in the lamination nip, whether it is formed by the embossing rollers (tip-to-tip embossing) or whether the lamination nip is formed between an embossing roller and a laminator roller.

[0012] All this entails the risk of damaging the cellulosic material, with consequent reduction in the tensile strength of the ply caused by localized breakage of the cellulosic fibres.

[0013] Embossing is used both for aesthetic reasons, with the aim of decorating the paper ply, and above all for technical -functional purposes, for example to create areas of mutual gluing between multiple plies forming a multi -ply web material. The glue, or other functional liquid, is applied to the outer surfaces of the embossing protrusions so as to obtain an application of the glue on limited areas. Embossing is also used to modify, alter or improve peculiar characteristics of tissue paper, such as thickness, softness, and absorbency.

[0014] Due to the high stress to which the cellulosic fibres forming the ply are subjected in the areas where the cellulosic ply is deformed by embossing, the shapes of the embossing protuberances, their dimensions and their arrangement cannot be chosen at will, but rather it is necessary to consider certain restrictive criteria which impose limits on the choice of the embossing pattern. When creating a new embossing pattern, it is therefore always necessary to find a compromise between the technical- functional needs that the pattern must meet and the need not to subject the paper to excessive stress, since otherwise localized breakages or excessive weakening of the cellulosic material could occur.

[0015] It would therefore be desirable to create an embossing unit, or an embossinglaminating unit, in which embossing can be obtained with a less strong, or in any case more gradual stress on the cellulosic plies.SUMMARY

[0016] According to embodiments disclosed herein, an embosser is provided for embossing a web material, which embosser comprises at least one advancement path for a ply of web material. An embossing unit is arranged along the ply advancement path, which comprises a first endless flexible member with an inner surface inside a first closed path of the first endless flexible member and an outer surface outside the first closed path. The outer surface of the first endless flexible member comprises a plurality of embossing protuberances. The embosser further comprises a second endless flexible member with an inner surface inside a second closed path of the second endless flexible member and an outer surface outside the second closed path. The first closed path and the second closed path have a common portion, along which the first endless flexible member and the second endless flexible member advance with the outer surface of the first endless flexible member pressed against the outer surface of the second endless flexible member. The advancement path extends along the common portion, between the outer surface of the first endless flexible member and the outer surface of the second endless flexible member. Furthermore, pressure members press the first endless flexible member and the second endless flexible member against each other along the common portion.

[0017] Thereby, a more efficient embossing is obtained which overcomes in whole or in part the drawbacks of the embossers of the current art.

[0018] Further advantageous features and embodiments of the embosser according to the present invention are described below and defined in the attached figures.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The invention will be better understood by following the description and the attached drawings, which illustrate exemplary and non-limiting embodiments of the invention. More in particular, the drawings show in:Fig. 1 a lateral view of an embosser in an embodiment;Fig. 1 A an enlargement of a portion of one of the endless flexible members of the embosser of Fig. 1;Fig. 2 and 3 details of the pressure system with which the endless flexible members are pressed against each other, between which the embossing of thecellulosic ply is performed;Fig. 4 a lateral view of an embosser in a different embodiment;Fig. 4A an enlargement of a detail of the first endless flexible member of the embosser of Fig. 4;Fig. 5 a lateral view of an embosser in a further embodiment;Fig. 6 a lateral view of an embosser in a further embodiment;Fig. 7 a lateral view of an embosser in a further embodiment; andFig. 8 a lateral view of an embosser in a further embodiment.DETAILED DESCRIPTION

[0020] Figs. 1, 2 and 3 show an embodiment of a simple embosser, in which one or more plies of web material, for example cellulosic plies, typically tissue paper plies, are embossed separately and combined together but not bonded by lamination. Each ply may in turn consist of one or more cellulosic layers. The embosser of Fig. 1 comprises three units, or embossing units, but this configuration is exemplary. In other embodiments, a different number of embossing units may be provided, for example one, two or more than three embossing units.

[0021] In Fig. 1 the embosser 1 comprises a first path Pl for a first ply VI of web material, for example a cellulosic ply in tissue paper. Along the first path there is at least one guide roller 3 to guide the ply VI towards a first embossing unit 5.

[0022] The first embossing unit 5 comprises a first endless flexible member 7 having two opposite surfaces 7A and 7B. The first surface 7A is inside a first closed path of the first endless flexible member 7 and will therefore be indicated as inner surface 7A. The surface 7B is a surface outside the first closed path and will therefore be called outer surface 7B. The outer surface 7B comprises a plurality of embossing protuberances 9, as schematically indicated in the enlargement of Fig. 1A. The first endless flexible member 7 is guided around a first guide roller 11 and a second guide roller 13.

[0023] The first embossing unit 5 further comprises a second endless flexible member 15, with an inner surface 15A inside a second closed path of the second endless flexible member 15 and an outer surface 15B outside the second closed path. The two surfaces 15 A, 15B will also be indicated as inner surface and outer surface, respectively. The second endless flexible member 15 is guided around a third guide roller 17and a fourth guide roller 19.

[0024] The first closed path and the second closed path formed by the first endless flexible member 7 and the second endless flexible member 15 have a common portion, which extends between the pairs of guide rollers 11, 17 and 13, 19. Along the common portion of the closed paths of the first endless flexible member 7 and the second endless flexible member 15, the first endless flexible member 7 and the second endless flexible member 15 advance with the outer surface 7B of the first endless flexible member 7 pressed against the outer surface 15B of the second endless flexible member 15. The first advancement path Pl of the first ply VI extends along the common portion of the two closed paths, between the outer surface 7B of the first endless flexible member 7 and the outer surface 15B of the second endless flexible member 15. In the common portion of the two closed paths, the outer surfaces 7B and 15B of the endless flexible members 7 and 15 are pressed against each other in the manner described in detail below.

[0025] In some embodiments the embosser 1 comprises a second path P2 for a second ply V2 of web material, for example a cellulosic ply in tissue paper. Along the second path there is at least one guide roller 23 to guide the second ply V2 towards a second embossing unit 25.

[0026] In the illustrated embodiment, the embosser 1 further comprises a third path P3 for a third ply V3 of web material, similar to the plies V 1 and V2, along which path P3 there is a guide roller 33 for guiding the third ply V3 towards a third embossing unit 45.

[0027] The embossing units 25 and 45 are substantially the same as the first embossing unit 5 and have the same components.

[0028] The second embossing unit 25 comprises a first endless flexible member 27 having two opposite surfaces 27A and 27B. The first surface 27A is inside a first closed path of the first endless flexible member 27 and will therefore be indicated as inner surface 27A. The surface 27B is a surface outside the first closed path and will therefore be called outer surface 27B. The outer surface 27B comprises a plurality of embossing protuberances similar to the embossing protuberances 9 schematically illustrated in the enlargement of Fig. 1 A. The first endless flexible member 27 of the secondembossing unit 25 is guided around a first guide roller 31 and a second guide roller 33.

[0029] The second embossing unit 25 further comprises a second endless flexible member 35, with an inner surface 35 A inside a second closed path of the second endless flexible member 35 and an outer surface 35B outside the second closed path. The two surfaces 35 A, 35B are also indicated as inner surface and outer surface, respectively. The second endless flexible member 35 of the second embossing unit 25 is guided around a third guide roller 37 and a fourth guide roller 39.

[0030] The first closed path and the second closed path formed by the first endless flexible member 27 and the second endless flexible member 35 of the second embossing unit 25 have a common portion, which extends between the pairs of guide rollers 31, 37 and 33, 39. Along the common portion of the closed paths of the first endless flexible member 27 and the second endless flexible member 35, the first endless flexible member 27 and the second endless flexible member 35 advance with the outer surface 27B of the first endless flexible member 27 pressed against the outer surface 35B of the second endless flexible member 35. The second advancement path P2 of the second ply V2 extends along the common portion of the two closed paths, between the outer surface 27B of the first endless flexible member 27 and the outer surface 35B of the second endless flexible member 35 of the second embossing unit 25. In the common portion of the two closed paths, the outer surfaces 27B and 35B of the endless flexible members 27 and 35 are pressed against each other in the manner described in detail below.

[0031] The second endless flexible member 35 of the second embossing unit 25 may comprise an elastically deformable coating on the outer surface 35A. The elastic deformability of the coating is such that the pressure exerted, by means of first pressure members, to be described, acting on the endless flexible members 27 and 35, causes a deformation of the elastically deformable coating and a penetration of the embossing protuberances of the first endless flexible member 27 into the coating of the second endless flexible member 35. Thereby, the ply V2 that passes between the two endless flexible members 27 and 35 is permanently deformed, i.e., embossed due to the penetration of the embossing protuberances of the first endless flexible member 27 into the elastically yielding coating of the second endless flexible member 35.

[0032] In other embodiments, the outer surface 35B of the second endless flexible member 35 may comprise, instead of a predominantly smooth, elastically yielding coating, a plurality of embossing protuberances, shaped such that the embossing protuberances on the outer surface 27B of the first endless flexible member 27 are inserted into recesses between the embossing protuberances on the outer surface 35B of the second endless flexible member 35 along the common portion of the first closed path and the second closed path.

[0033] Thanks to the fact that the mutual pressure area between the first endless flexible member 27 and the second endless flexible member 35 is relatively longer than a normal embossing nip between the embossing roller and the pressure roller of a traditional embosser, the time during which the ply V2 undergoes the embossing deformation is longer than in a traditional embosser. This facilitates embossing and allows to obtain a precise and clear embossing even at high production speeds, i.e., with high advancement speeds of the ply V2 and the endless flexible members 27 and 35, also reducing shredding of the ply V2, i.e., the localized breakage of the fibres forming the ply. The endless flexible members 27 and 35, during use, advance at a speed substantially equal to each other and equal to the advancement speed of the ply V2. The same advantages are obtained in the embossing of the ply VI in the first embossing unit 5.

[0034] The third embossing unit 45, provided to emboss a third ply V3 advancing along a third advancement path P3, is configured like the first embossing unit 5 and the second embossing unit 25 and is not described in detail.

[0035] To obtain a better embossing, it is possible to moisten the material forming the ply VI and / or V2 and / or V3. It is also possible, alternatively or in combination, to heat one, the other or both of the endless flexible members in particular along the common path portion, where they are pressed against each other and generate the embossing on the ply VI, V2 and V3.

[0036] The endless flexible members 7, 15; 27, 35 and the equivalent flexible members of the third embossing unit 45 are pressed against each other by an arrangement of pressure plates, anvil plates and actuators, which may be the same for each embossing unit 5, 25, 45. The arrangement of the pressure members of only the first embossing unit 5 will be described below, with specific reference to Figs. 2 and 3.

[0037] In the illustrated embodiment, the pressure members for pressing the endless flexible members 7 and 15 together comprise a first pressure plate 51, located inside one of the closed paths formed by the endless flexible members 7 and 15. In the illustrated embodiment, the pressure plate 51 is located inside the closed path formed by the first endless flexible member 7. A first anvil plate 53 is located inside the other of said first closed path and second closed path, in the illustrated example inside the closed path formed by the second endless flexible member 15.

[0038] The first pressure plate 51 and the first anvil plate 53 are positioned opposite each other along the common portion of the first closed path and the second closed path. Furthermore, actuators configured to push the first pressure plate 51 against the first anvil plate 53 are provided.

[0039] In the embodiment illustrated in Figs. 1, 2 and 3, the actuators comprise first actuators 55 and second actuators 57, offset along the common portion of the first closed path and the second closed path defined by the first endless flexible member 7 and the second endless flexible member 15. The actuators may be configured to push the first pressure plate 51 against the first anvil plate 53 with different thrusts between the first actuators and the second actuators, to generate a variable pressure profile along the common portion of the first closed path and the second closed path and more precisely greater in the upstream area and less in the downstream area, or vice versa. The terms “upstream” and “downstream” refer to the advancement direction of the endless flexible members 7, 15 in the area where the mutual pressure is exerted between the endless flexible members 7, 15. Therefore, the actuators 55 are located upstream of the actuators 57.

[0040] Furthermore, thrust sensors, for example load cells, are provided, configured to detect the thrust exerted by the first pressure plate 51 against the first anvil plate 53. For example, the thrust sensors may comprise at least a first thrust sensor 59, in the vicinity of an upstream edge of the first pressure plate 51 and the first anvil plate 53, and a second thrust sensor 61 in the vicinity of a downstream edge of the first pressure plate 51 and the first anvil plate 53. The two sensors, or sensor units, are configured to detect differential thrusts of the first pressure plate 51 against the first anvil plate 53 along the common portion of the first closed path and the second closed path.

[0041] Figs. 2 and 3 show schematic sections according to II-II and III-III of Fig. 1 and illustrate in an exemplary manner a possible configuration of the actuators that push the first pressure plate 51 against the first anvil plate 53, which may be supported in a stationary manner on a load-bearing structure 60 (Fig. 1), which may have two sidewalls 60A and 60B (sidewall 60B not visible in the drawing) opposite each other and between which the endless flexible members of the three embossing units 5, 25, 35 are arranged.

[0042] In the illustrated embodiment, the guide rollers 17, 19 are supported in a fixed position on the sidewalls 60A, 60B. In contrast, each of the guide rollers 11 and 13 is movably supported with respect to the fixed structure 60. More specifically, each end of the roller 11 and each end of the roller 13 is supported by a respective slide, slidable along a corresponding guide integral with the fixed structure 60 by means of respective sliding blocks. With reference to the diagram in Figs. 2 and 3, each slide is indicated with 71, the guide with 73 and the sliding blocks with 75. The arrangement is substantially the same (or symmetrical) for each of the two opposite ends of the two guide rollers 11 and 13 and therefore the same reference numbers will be used for the same components of the support and pressure means of the two guide rollers. Each slide 71 is operated by a respective actuator, in the illustrated example a cylinder-piston actuator. The actuators are each indicated with 55 (for the upstream actuators) and 57 for the downstream actuators. Each actuator is constrained in 55A, 57A to the fixed structure 60 (60A, 60B) and in 55B, 57B to the respective slide 71.

[0043] In practice, therefore, the slides 71 which support the first guide roller 11 are pushed by the actuators 55 and the slides 71 which support the second guide roller 13 are pushed by the actuators 57. The two pairs of actuators 55, 57 may be controlled independently of the other, in the sense that different thrusts may be applied to the two slides 71 of the rollers 11 and 13.

[0044] The pressure plate 51 may be constrained to the four slides 71. The connecting joints of the plate 51 to each slide 71 are indicated with 77. The joints 77 allow the pressure plate 51 to be positioned slightly inclined, so that it is possible to press the pressure plate 51 against the anvil plate 53 (and therefore the endless flexible members 7, 15 therebetween) with different forces upstream and downstream according to the advancement path of the ply VI. Thereby, it is possible to easily impart a pressureprofile that varies from the starting point to the end point of the cooperation area between pressure plate 51 and anvil plate 53.

[0045] As mentioned above, the configuration of the embossing units 25 and 45 may be the same as the configuration of the embossing unit 5 also with regard to the mutual thrust members between the endless flexible members and therefore the embossing units 25, 45 will not be further described.

[0046] The embosser 1 of Figures 1 to 3 may have a variable number of embossing units 5, 25, 35. The product obtained is a web material that may comprise one or more embossed plies VI, V2, V3, placed side by side but not glued or bonded. Alternatively, devices for bonding the plies, for example by mechanical pegging, may be provided downstream of the embosser 1.

[0047] In other embodiments, the guide rollers 11, 13, 31, 33 may be mounted on the fixed structure 60 and therefore arranged with fixed axes, rather than carried by the slides 71. The actuators may be connected directly to the pressure plate 51, which is pushed by the actuators 55, 57 against the anvil plate 53.

[0048] In other embodiments, the embossing unit of the present invention may comprise lamination systems, which serve to bond plies embossed in separate embossing units together, by means of the use of a functional fluid, for example water or glue. These embossers, which comprise means for bonding the embossed plies by lamination, are commonly called embossers-laminators.

[0049] In the present context, the term “embosser” generically indicates either an embosser of the type described above and illustrated in Figs. 1, 2, and 3, in which bonding by lamination of the embossed plies is not provided, or an embosser-laminator, as described below with reference to Fig. 4 and following. In the present context, therefore, the term “embosser” is understood in a broad sense, while the term “embosser-laminator” is used to indicate an embosser that also has a lamination function.

[0050] An embodiment of an embosser-laminator is illustrated in Fig. 4. The embosser, or embosser-laminator is indicated overall with 101. The embosser-laminator 101 comprises a first path Pl for a first ply VI of web material and a second path P2for a second ply V2 of web material, for example tissue paper. Furthermore, the embosser-laminator 101 comprises a first embossing unit 103, for embossing the first ply VI and a second embossing unit 105 for embossing the second ply V2. The two plies VI, V2, separately embossed in the two embossing units 103, 105, are bonded together by lamination in the manner described below, after having applied a functional liquid, for example a glue, to the ply VI, and more precisely to at least some embossed protuberances of said ply, by means of a functional liquid applicator 107.

[0051] The first embossing unit 103, located along the first path Pl of the first ply VI, comprises a first endless flexible member 109, with an inner surface inside a first closed path along which the first endless flexible member 109 moves, and an outer surface outside the first closed path. The inner surface is indicated with 109A and the outer surface is indicated with 109B. The outer surface 109B comprises a plurality of embossing protuberances 111, schematically shown in the enlargement of Fig. 4A, which illustrates a cross-sectional portion of the endless flexible member 109.

[0052] In the embodiment illustrated in Fig. 4, the first endless flexible member 109 is guided around three guide rollers, indicated with 113, 115 and 117, respectively. In the example illustrated, the guide roller 115 has a diameter larger than the rollers 113 and 117 for reasons that will become clearer below.

[0053] The first embossing unit 103 further comprises a second endless flexible member 121, which moves along its own closed path. The second endless flexible member 121 has an inner surface 121 A inside the second closed path and an outer surface 121B outside the second closed path. The second endless flexible member 121 is guided around a first guide roller 123 and a second guide roller 125. Between the two guide rollers 123 and 125, a common portion of the closed paths of the first endless flexible member 109 and the second endless flexible member 121 is defined. Along this common path portion, the first endless flexible member 109 and the second endless flexible member 121 advance with the outer surface 109B of the first endless flexible member 109 pressed against the outer surface 121B of the second endless flexible member 121. The first advancement path Pl of the ply VI extends along the common portion of the two closed paths, between the outer surface 109B of the first endless flexible member 109 and the outer surface 121B of the second endless flexible member

[0054] Pressure members, generally indicated with 127 and described below, press the first endless flexible member 109 and the second endless flexible member 121 against each other along the common portion of the two closed paths.

[0055] The pressure members 127 may be made substantially as described with reference to Figs. 1, 2 and 3. In the embodiment illustrated in Fig. 4, the pressure members comprise a first pressure plate 131, along which the second endless flexible member 121 slides and which is positioned inside the closed path formed by the second endless flexible member 121, along the straight portion of the path common to the two closed paths. The first pressure plate 131 cooperates with an anvil plate 133 which is located, in this embodiment example, inside the closed path defined by the first endless flexible member 109. Actuators 135, 137 are combined with slides 139, 141 which slide under the thrust of the actuators along guides 143, 147, to which the slides are engaged with sliding blocks 145, 149. Similarly to what is described above with reference to Figures 1, 2, 3, the arrangement of slides, sliding blocks, guides and actuators is double, one for each sidewall of the embosser.

[0056] In practice, the guide rollers 123 and 125 are supported by two opposite slides 139, and respectively by two opposite slides 141, whose respective guides 143, 147 are fixed to two sidewalls 158 of the embosser. The arrangement is the same as that described with reference to the embossing unit 5 of Fig. 1 and therefore its operation will not be described again. The first pressure plate 131 is supported by suitable joints or junctions on the four slides 139, 141 and is then pushed against the anvil plate 133 so as to press the first endless flexible member 109 and the second endless flexible member 121 against each other.

[0057] As mentioned, in the embodiment of Fig. 4, the embosser 101 comprises a second advancement path P2 for a second ply of web material V2. The first advancement path Pl and the second advancement path P2 converge in a lamination area. In the illustrated embodiment, the lamination area is defined between the first embossing unit 103 and the second embossing unit 105, located along the second advancement path P2.

[0058] The second embossing unit 105 comprises a third endless flexible member 159 having an inner surface 159A inside a third closed path of the third endless flexiblemember 159, and an outer surface 159B outside the third closed path. The outer surface of the third endless flexible member 159 comprises a plurality of embossing protuberances similar to the embossing protuberances 9 and 111 described above. The third endless flexible member 159 is guided around guide rollers 160, 162, 164.

[0059] The second embossing unit 105 further comprises a fourth endless flexible member 161 with an inner surface 161 A inside a fourth closed path of the fourth endless flexible member and an outer surface 16 IB outside the fourth closed path. The fourth endless flexible member 161 is guided around guide rollers 166, 168. The third closed path and the fourth closed path have a common portion, along which the third endless flexible member 159 and the fourth endless flexible member 161 advance with the outer surface 159B of the third endless flexible member 159 pressed against the outer surface 161B of the fourth endless flexible member 161. The second advancement path P2 extends along the common portion, between the outer surface 159B of the third endless flexible member 159 and the outer surface 16 IB of the fourth endless flexible member 161. The common portion of the third endless flexible member 159 and the fourth endless flexible member 161 is defined between the guide rollers 160, 166 and the guide rollers 162, 168, which in this embodiment example are opposite each other.

[0060] Second pressure members 171 press the third endless flexible member 159 and the fourth endless flexible member 161 against each other along the common portion of the two closed paths along which the third endless flexible member 159 and the fourth endless flexible member 161 extend.

[0061] In some embodiments, the fourth endless flexible member 161 comprises an elastically deformable coating on the outer surface, the elastic deformability of the coating being such that the pressure exerted by the second pressure members 171 causes an elastic deformation of the elastically deformable coating and a penetration of the protuberances of the third endless flexible member 159 into the coating of the fourth endless flexible member 161.

[0062] In other embodiments, not shown, the outer surface 16 IB of the fourth endless flexible member 161 comprises a plurality of embossing protuberances, the embossingprotuberances on the outer surface of the third endless flexible member 159 being inserted into recesses between the embossing protuberances on the outer surface of the fourth endless flexible member 161 along the common portion of the third closed path and the fourth closed path along which the third endless flexible member 159 and the fourth endless flexible member 161 move.

[0063] In some embodiments, the second pressure members 171 comprise, similarly to the first pressure members 127, a second pressure plate 181, along which the fourth endless flexible member 161 slides and which is positioned inside the closed path formed by the fourth endless flexible member 161, along the common straight portion of the two closed paths formed by the third endless flexible member 159 and the fourth endless flexible member 161. The second pressure plate 181 cooperates with a second anvil plate 183 which is located, in this embodiment example, inside the closed path defined by the third flexible member.

[0064] Actuators 185, 187 are combined with slides 189, 191 sliding under the thrust of the actuators 185, 187 along guides 193, 195, to which the slides are engaged with sliding blocks 197, 199. As described with reference to the first embossing unit 103, in practice, the guide roller 166 is supported by two opposite slides 189 on the two opposite sidewalls 158 of the embosser, and the guide roller 168 is supported by two opposite slides 191 on the two sidewalls 158 of the embosser. The arrangement of the pressure members between pressure plate 181 and anvil plate 183 is substantially the same as that described with reference to the embossing unit 5 of Fig. 1 and therefore its operation will not be described again. The pressure plate 181 is supported on the slides 189, 191 by means of joints or junctions so as to cooperate with the anvil plate 183, pressing the third endless flexible member 159 and the fourth endless flexible member 161 against each other.

[0065] In some embodiments, the third closed path of the third endless flexible member 159 and the first closed path of the first endless flexible member 109 have a common portion, along which the third endless flexible member 159 and the first endless flexible member 109 advance with the protuberances of the outer surface 159B of the third endless flexible member 159 pressed against the protuberances of the outer surface 109B of the first endless flexible member 109, with the plies VI and V2 interposed between the embossing protuberances. The common portion of the third closedpath and the first closed path is defined between the guide rollers 160, 164 of the third endless flexible member 159 and between the guide rollers 115, 117 of the first endless flexible member 109.

[0066] The first advancement path Pl of the first ply V 1 and the second advancement path P2 of the second ply V2 extend along the common portion, between the outer surface 159B of the third endless flexible member 159 and the outer surface 109B of the first endless flexible member 109.

[0067] Third pressure members 221, also referred to as lamination pressure members, press the third endless flexible member 159 and the first endless flexible member 109 against each other along the common portion of the first closed path and the third closed path.

[0068] In some embodiments, the third pressure members 221, or lamination pressure members, comprise, similarly to the first pressure members 127, a third pressure plate 231, along which the third endless flexible member 159 slides and which is positioned inside the closed path formed by the third endless flexible member 159, along the common straight portion of the two closed paths formed by the third endless flexible member 159 and the first endless flexible member 109. The third pressure plate 231 cooperates with a third anvil plate 233 which is located, in this embodiment example, inside the closed path defined by the first endless flexible member 109.

[0069] Actuators 235, 237 are combined with slides 239, 241 sliding under the thrust of the actuators 235, 237 along guides 243, 245, to which the slides are engaged with sliding blocks 249, 251. As described with reference to the first embossing unit 103, in practice, the guide roller 160 is supported by two opposite slides 239 on the two opposite sidewalls 158 of the embosser, and the guide roller 164 is supported by two opposite slides 241 on the two sidewalls 158 of the embosser. The arrangement of the pressure members between pressure plate 231 and anvil plate 233 is substantially the same as that described with reference to the embossing unit 5 of Fig. 1 and therefore its operation will not be described again. The pressure plate 231 is supported on the slides 239, 241 by means of joints or junctions so as to cooperate with the anvil plate 233, pressing the third endless flexible member 159 and the first endless flexible member 109 against each other.

[0070] Along the common portion between the first closed path, along which the first endless flexible member 109 moves, and the third closed path, along which the third endless flexible member 159 moves, at least some of the embossing protuberances 111 of the first endless flexible member 109 are positioned, in a tip-to-tip arrangement, opposite embossing protuberances of the third endless flexible member 159. Thereby, thanks to the pressure exerted by the third pressure members 221 described above, the two plies VI, V2 are laminated to each other between the endless flexible members 109 and 159, after a functional fluid, for example glue, has been applied to at least some of the embossed protuberances generated on the ply VI by the first endless flexible member 109 by means of the applicator 107. The pressure exerted between pressure plate 231 and anvil plate 233 promotes bonding of the plies VI, V2 by lamination.

[0071] The plies VI, V2 bonded together form a multi -play web material N which exits the embosser 101, along a dispensing path. The dispensing path may comprise a series of rollers 261, 262, 263, which may keep the web material N under slight tension (in the machine direction, i.e., in the advancement direction) and / or which may exert a transverse stretching function, to avoid the formation of creases.

[0072] In summary, the embosser 101 is a tip-to-tip embosser-laminator, in which both the embossing and the lamination between the embossed plies VI, V2 occur due to the cooperation of endless flexible members, rather than rollers. This allows to increase the action time on the cellulosic plies VI, V2 of the mechanical members and therefore to obtain an effective embossing and lamination, even with high advancement speeds (and therefore high productivity of the embosser), and / or with lower pressures than those required in traditional embossers that use rollers.

[0073] While the embodiment of Fig. 4 illustrates an embodiment in which the pressure between each pressure plate and the respective anvil plate is obtained by means of actuators that move slides, on which the pressure plates and guide rollers of the endless flexible members are constrained, in other embodiments (similarly to what is also mentioned with reference to Fig. 1), the actuators may be connected directly to the pressure plates, while the rollers are supported with a substantially fixed axis on the sidewalls of the embosser, or embosser-laminator. In this case, the thrust is applied only to the pressure plate, which is pressed by the actuators against the anvil plate, while the rollers remain fixed. In any case, it is possible to provide, in all embodiments,a relative movement of the guide rollers, which allows the respective endless flexible member to be kept under tension. These embodiments of the thrust members also apply to the embodiments described below with reference to the remaining figures.

[0074] In some embodiments, one or more of the endless flexible members described above may be directly or indirectly heated. For example, in some embodiments one or more of the endless flexible members may be made at least partly of a material adapted to generate induction heating, for example by means of eddy currents induced by a magnetic field while the endless flexible member is in motion. In some embodiments, it may also be foreseen that one or both of the plies VI, V2 are moistened upstream of the embossing area, to perform hot embossing with a higher moisture content of the material, typically cellulosic material, which is part of the ply VI, V2.

[0075] In the illustrated embodiment, each pressure plate 131, 181 and 231 is operated by four separate actuators. It is thereby possible to modulate the pressure exerted in each nip formed between the endless flexible members that define portions of the common path. In particular, it is possible to modulate the pressure so that it is variable in the machine direction, i.e., in the advancement direction of the respective ply from the entrance to the exit of the common portion of the closed paths along which the pressure members are located. This allows, for example, to gradually increase or gradually decrease the pressure on the ply VI, V2 or V1+V2, as a function of the characteristics to be obtained on the finished product and / or as a function of the best working conditions for the plies VI, V2.

[0076] In some embodiments, one, two or all three pressure members 127, 171 and 221 may be associated with force or pressure sensors or transducers, which allow the pressure profile to be controlled and modulated along the path in which the plies VI, V2 are embossed and / or laminated. For this purpose, as already described with reference to Figs. 2 and 3, each anvil plate may be associated with load cells, generically indicated with 200 for each anvil plate. The load cells, or other suitable sensors or transducers, may be interfaced with a central control unit, by means of which it is possible, for example, to modulate the pressure exerted on the plies along the extended nip defined between endless flexible members pressed against each other, as described above.

[0077] A further embodiment of an embosser, or embosser-laminator, according to the present disclosure is illustrated in Fig. 5 and indicated overall with 301. Equal numbers in Figs. 4 and 5 indicate equal or equivalent parts of the embossers 101 and 301.

[0078] Specifically, the embosser-laminator 301 comprises a first path Pl for a first ply VI of web material and a second path P2 for a second ply V2 of web material, for example tissue paper. Furthermore, the embosser-laminator 301 comprises a first embossing unit 103, for embossing the first ply VI and a second embossing unit 105 for embossing the second ply V2. The two plies VI, V2, separately embossed in the two embossing units 103, 105, are bonded together by lamination in the manner described below, after having applied a functional liquid, for example a glue, to the ply VI, and more precisely to at least some embossed protuberances of said ply, by means of a functional liquid applicator 107.

[0079] The first embossing unit 103, located along the first path Pl of the first ply VI, comprises a first endless flexible member 109, with an inner surface inside a first closed path along which the first endless flexible member 109 moves, and an outer surface outside the first closed path. The inner surface is indicated with 109A and the outer surface is indicated with 109B. The outer surface 109B comprises a plurality of embossing protuberances 111, similar to those shown schematically in the enlargement of Fig. 4 A.

[0080] In the embodiment illustrated in Fig. 5, the first endless flexible member 109 is guided around three guide rollers, indicated with 113, 115 and 117, respectively. In the example shown, the guide roller 115 has a larger diameter with respect to the rollers 113 and 117. As in the example of Fig. 4, also in Fig. 5 the larger diameter of the guide roller 115 with respect to the guide rollers 113 and 117 allows for the arrangement of a functional liquid applicator, for example a glue, around the guide roller 115, as described below.

[0081] The first embossing unit 103 further comprises a second endless flexible member 121, which moves along its own closed path. The second endless flexible member 121 has an inner surface 121 A inside the second closed path and an outer surface 121B outside the second closed path. The second endless flexible member 121is guided around a first guide roller 123 and a second guide roller 125. Between the two guide rollers 123 and 125, a common portion of the closed paths of the first endless flexible member 109 and the second endless flexible member 121 is defined. Along this common path portion, the first endless flexible member 109 and the second endless flexible member 121 advance with the outer surface 109B of the first endless flexible member 109 pressed against the outer surface 121B of the second endless flexible member 121. The first advancement path Pl of the ply VI extends along the common portion of the two closed paths, between the outer surface 109B of the first endless flexible member 109 and the outer surface 121B of the second endless flexible member 121.

[0082] Pressure members, generally indicated with 127, press the first endless flexible member 109 and the second endless flexible member 121 against each other along the common portion of the two closed paths.

[0083] The pressure members 127 may be made substantially as described with reference to Figs. 1 to 4 and will not be described again here.

[0084] The embossing unit 301 comprises a second advancement path P2 for a second ply of web material V2. The first advancement path Pl and the second advancement path P2 converge in a lamination area described later.

[0085] The second embossing unit 105 is located along the second path P2 of the second ply V2. The second embossing unit 105 comprises a third endless flexible member 159 having an inner surface 159A inside a third closed path of the third endless flexible member 159, and an outer surface 159B outside the third closed path. The outer surface of the third endless flexible member 159 comprises a plurality of embossing protuberances similar to the embossing protuberances 9 and 111 described above. The third endless flexible member 159 is guided around guide rollers 160, 162.

[0086] The second embossing unit 105 further comprises a fourth endless flexible member 161 with an inner surface 161 A inside a fourth closed path of the fourth endless flexible member and an outer surface 16 IB outside the fourth closed path. The fourth endless flexible member 161 is guided around guide rollers 166, 168. The third closed path and the fourth closed path have a common portion, along which the third endless flexible member 159 and the fourth endless flexible member 161 advance withthe outer surface 159B of the third endless flexible member 159 pressed against the outer surface 161B of the fourth endless flexible member 161. The second advancement path P2 extends along the common portion, between the outer surface 159B of the third endless flexible member 159 and the outer surface 16 IB of the fourth endless flexible member 161. The common portion of the third endless flexible member 159 and the fourth endless flexible member 161 is defined between the guide rollers 160, 166 and the guide rollers 162, 168, which in this embodiment example are opposite each other.

[0087] Second pressure members 171 press the third endless flexible member 159 and the fourth endless flexible member 161 against each other along the common portion of the two closed paths along which the third endless flexible member 159 and the fourth endless flexible member 161 extend.

[0088] In some embodiments, the fourth endless flexible member 161 comprises an elastically deformable coating on the outer surface, the elastic deformability of the coating being such that the pressure exerted by the second pressure members 171 causes an elastic deformation of the elastically deformable coating and a penetration of the protuberances of the third endless flexible member 159 into the coating of the fourth endless flexible member 161.

[0089] In other embodiments, not shown, the outer surface 16 IB of the fourth endless flexible member 161 comprises a plurality of embossing protuberances, the embossing protuberances on the outer surface of the third endless flexible member 159 being inserted into recesses between the embossing protuberances on the outer surface of the fourth endless flexible member 161 along the common portion of the third closed path and the fourth closed path along which the third endless flexible member 159 and the fourth endless flexible member 161 move.

[0090] In some embodiments, the second pressure members 171 are made as already described with reference to Fig. 4 in relation to the equivalent pressure members 171 illustrated therein.

[0091] Differently from the embodiment of Fig. 4, the embosser, or embosser-laminator 301, of Fig. 5 comprises a lamination area that is not defined between the first endless flexible member 109 and the third endless flexible member 159. In fact, tolaminate the plies VI and V2 together after they have been separately embossed in the extended embossing nips, formed by the pairs of flexible members 109, 121 and 159, 161, a fifth endless flexible member indicated by 303 is provided and guided around two guide rollers 307, 309. The fifth flexible member 303 constitutes an endless flexible lamination member and defines a fifth closed path that has a common portion with the path of the first endless flexible member 109. More specifically, in the embodiment illustrated in Fig. 5, the common portion of the paths defined between the first endless flexible member 109 and the fifth endless flexible member 303 is delimited between the guide rollers 115, 117 of the first endless flexible member 109 and the guide rollers 307, 309 of the fifth endless flexible member.

[0092] The paths Pl and P2 of the plies VI and V2 converge in the extended nip defined between the rollers 115, 307 and 117, 309, where the plies VI and V2 are laminated between the first endless flexible member 109 and the fifth endless flexible member 303. The latter may have a smooth or protuberant outer surface 303B in phase with the protuberances of the first endless flexible member 109. Along the extended nip defined by the common path portion between the endless flexible members 109, 303, pressure members are arranged, indicated with 221 and also defined as lamination pressure members, and which may be configured like the pressure members 221 illustrated in Fig. 4 and described above. These pressure members 221 will therefore not be described again.

[0093] The embosser, or embosser-laminator 301 of Fig. 5 may operate as a DESL or DERL embosser and therefore produce a web material N with plies VI and V2 in nested or random positions. The lamination of the plies VI, V2 occurs in the extended nip formed between the first endless flexible member 109 and the fifth endless flexible member 305

[0094] The embodiments of Figures 4 and 5 comprise an extended nip for embossing both plies VI, V2 and for laminating the embossed plies. In other embodiments it may be provided that only one of the two embossing nips is extended, i.e., formed by a pair of endless flexible members pressed against each other.

[0095] For example, Fig. 6 shows an embodiment of an embosser-laminator 401 for producing a multi-ply embossed web material N using DERL or DESL techniques,similar to the embosser-laminator 301 of Fig. 5. The embosser-laminator 401 differs from the embosser-laminator 301 mainly in that the second embossing unit, indicated here with 405, comprises an embossing roller 407 cooperating with a pressure roller 409, to form an embossing nip 411, in which the second ply V2 passes, which is then embossed between the embossing roller 407, which is provided with embossing protuberances similar to the protuberances 111 of Fig. 4A, and the pressure roller 409 coated with an elastically yielding material, or provided with embossing protuberances which nest between the embossing protuberances of the roller 407.

[0096] The remaining parts of the embosser-laminator 401 are indicated with the same reference numbers as in Figs. 4 and 5 and are equal or equivalent to those described with reference to the previous figures. In particular, the embosser 401 comprises a first embossing unit, still indicated with 103 and configured like the embossing unit 103 of Figs. 4 and 5, and an endless flexible lamination member 303, similar to the endless flexible lamination member 303 of Fig. 5.

[0097] A further embodiment of a DESL or DERL type embosser-laminator is illustrated in Fig. 7, where equal numbers indicate parts equal or equivalent to those indicated with the same reference number in the previous figures described above.

[0098] The embosser-laminator of Fig. 7, generally indicated with 501, differs from the embosser-laminators 101, 301 and 401 mainly due to the different conformation of the second embossing unit, indicated here with 505. The second embossing unit 505 comprises an embossing roller 506 equipped with embossing protuberances, similar to the embossing protuberances 111 illustrated in Fig. 1 A, with which an endless flexible pressure member, indicated with 508, cooperates, guided around guide rollers 507, 509 and 511. The endless flexible pressure member 508 may be coated with elastically yielding material, such that the embossing protuberances of the embossing roller 506 penetrate the coating of the endless flexible pressure member 508 permanently deforming the ply V2 as it passes through the extended nip formed between the embossing roller 506 and the endless flexible member 508.

[0099] The remaining parts of the embosser 501 are the same as those of the embosser 301 illustrated in Fig. 5 and will not be described again.

[0100] With reference to all the embodiments illustrated, each endless flexible member provided with engraved embossing protuberances may be made in various ways. For example, the inner surface may be provided with teeth or a smooth surface adapted to take the motion of a motorized guide roller, while the outer surface is provided with embossing protuberances. These protuberances (e.g., embossing protuberances 9 of Fig. 1 A, embossing protuberances 111 of Fig. 4A) may be formed by applied elements, consisting for example of one or more blocks, or better, plastic or metal sheets (for example a metal strip of small thickness, comprised between 1 mm and 5 mm on which the embossing protuberances are present in relief). The plastic or metal blocks may be produced by means of additive manufacturing (3D printing) or other methods.

[0101] Other possible materials for making the embossing protuberances may comprise ebonite, hard rubbers and the like.

[0102] Instead of making the embossing protuberances on elements subsequently reported on the outer surface of the respective endless flexible member, it is possible to directly engrave the material from which the outermost layer of the endless flexible member is made. In this case, the latter will be produced with an adequate initial thickness (or a coating made with suitable material). The engraving of the outer surface of the endless flexible member may be carried out by means of laser, mechanical swarf removal, chemical engraving, or other suitable methods.

[0103] In some embodiments, the engraved coating material from which the endless flexible member may be made, or at least the topmost layer thereof, may be plastic, e.g., PVC. In general, possible materials for the side on which the embossing protuberances are engraved may comprise: metal alloys such as aluminium, steel, reinforced fibres, polymers, thermoplastic polymers, engineering plastics, hardening resins, fibreglass, carbon, aramid fibres, epoxy or polyester resin matrices, thermoplastic elastomers, polyurethane (PU).

[0104] The following Table 1 provides a list of possible engineering plastics that may be used to make endless flexible members provided with embossing protuberances. It is understood that in the same embosser, different materials may be used for the various endless flexible members.Table 1

[0105] The types of protuberances, for example the embossing protuberances 9 of Fig. 1 A and the embossing protuberances 111 of Fig. 4A, may be of any type known in the art, for example they may be of truncated pyramidal, truncated conical, open linear, closed linear shape. Such protuberances may have a single height, i.e., all the protuberances of an endless flexible member may be of equal height. In other embodiments, the protuberances of a single endless flexible member may be double height (or multiple height) with respect to the base of the outer surface of the respective endless flexible member, i.e., they may have two (or more) different heights. It is thereby possible to reproduce all types of embossing and products made with traditional embossers, obtaining products with improved technical characteristics as described in the introductory part.

[0106] For the endless flexible members comprising an elastically yielding outer surface, which form pressure members cooperating with the embossing protuberances of the opposite endless flexible embossing members, a basic structure made of the same materials described above may be used, except that on the face facing outwards of the closed path of each endless flexible pressure member, a coating of natural or synthetic rubber is provided, sufficiently yielding to obtain the elastic deformation and therefore the embossing of the plies. The materials that may be used for these coatings are substantially the same as those used in traditional embossers for coating the pressure rollers.

[0107] In some embodiments, the elastically yielding coating of the endless flexible pressure members intended to cooperate with the endless flexible members to perform the embossing (in particular the endless flexible members 15, 35, 121, 161, may have a Shore A hardness comprised for example between 6 Shore A and 100 Shore A.

[0108] In some embodiments, the endless flexible lamination members (endless flexible members 303) may be made of rubber of higher hardness, for example they may even reach the Shore D hardness scale. In other embodiments, the endless flexible lamination members 303 may have a smooth metal coating on the surface outside the closed path.

[0109] As mentioned, the embossing may be carried out hot. In this case it may be provided that on the outer side of the closed path defined by each endless flexible member that requires heating, it is made of conductive material, and typically for example ferromagnetic or paramagnetic. This allows induction heating, for example with temperatures up to 200° C or higher, for example between 80° C and 200° C. Alternatively, a material suitable for induction heating may be incorporated into the material forming the endless flexible member to be heated, for example a thin sheet or foil of a few tenths of a mm or less than a tenth of a mm of aluminium or iron or other magnetic or paramagnetic material.

[0110] In the case of induction heating, one or more inductors may be positioned in a portion of the closed path of the endless flexible members 7, 25, 109, 159, other than the common portions that they form respectively with the flexible members 15, 35, 121, 161, i.e., in sections that do not include the extended embossing nip, formed by the pairs of flexible members 7 and 15, 25 and 35, 109 and 121 and 159 and 161 pressed against each other.

[0111] The movement of the individual endless flexible members described with reference to all the embodiments may be imparted by a motor for a respective roller of each unit of guide or guide rollers of each endless flexible member. In other embodiments, a common motor may be provided which is adapted to operate two or more endless flexible members, through suitable transmission members, such as belts or gears, for example.

[0112] In Fig. 6 the embosser-laminator comprises a first embossing unit 101 103 which configures an extended embossing nip, while the second embossing unit 105 is configured with an embossing and pressure roller system. In other embodiments, the arrangement may be reversed, as shown in Fig. 8.

[0113] Fig. 8 illustrates an embodiment in which the embosser, here indicated with700, comprises an embossing unit 105 made as in Fig. 5, while the embossing unit 103 is made differently. The details of the embossing unit 105 are not described again and are indicated with the same reference numbers as in Fig. 5. The embossing unit 700 comprises an embossing roller 701 cooperating with a pressure roller 703, rather than endless flexible members. Between the embossing roller 701 (equipped with embossing protuberances 70 IP) and the pressure roller 703 (equipped with an elastically yielding coating 703R) an embossing nip 702 is defined, through which the first ply VI passes. The embossed ply VI receives a glue or other functional fluid from the applicator, still indicated by 107, and is laminated with the second ply V2 (embossed in the second embossing unit 105) by means of a laminating roller 705, which presses against the surface of the embossing roller 701 and which may have a smooth, rigid or elastically yielding surface.

[0114] In the various embodiments illustrated, further paths may also be provided for further plies which may not be embossed. For example, a third path may be provided for a third ply, smooth or embossed, to be inserted between the first ply and the second ply and subsequently laminated together with the first ply and the second ply.

[0115] The embossing protuberances, made on endless flexible members and / or on embossing rollers, may have a density comprised between 0.1 protuberances / cm2and 200 protuberances / cm2, and a height comprised between 0.5 mm and 2 mm, for example.

Claims

CLAIMS1. An embosser for embossing a web material, wherein the embosser comprises: at least a first advancement path for a first ply of web material; along the first path, a first embossing unit, comprising:• a first endless flexible member with an inner surface inside a first closed path of the first endless flexible member and an outer surface outside the first closed path; wherein the outer surface of the first endless flexible member comprises a plurality of embossing protuberances;• a second endless flexible member with an inner surface inside a second closed path of the second endless flexible member and an outer surface outside the second closed path; wherein the first closed path and the second closed path have a common portion, along which the first endless flexible member and the second endless flexible member advance with the outer surface of the first endless flexible member pressed against the outer surface of the second endless flexible member; wherein the first advancement path extends along the common portion, between the outer surface of the first endless flexible member and the outer surface of the second endless flexible member; and wherein first pressure members press the first endless flexible member and the second endless flexible member against each other along the common portion.

2. The embosser of claim 1, wherein the second endless flexible member comprises an elastically deformable coating on the outer surface, the elastic deformability of the coating being such that the pressure exerted by the first pressure members causes a deformation of the elastically deformable coating and a penetration of the protuberances of the first endless flexible member into the coating of the second endless flexible member.

3. The embosser of claim 1, wherein the outer surface of the second endless flexible member comprises a plurality of embossing protuberances, the embossing protuberances on the outer surface of the first endless flexible member being inserted in recesses between the embossing protuberances on the outer surface of thesecond endless flexible member along the common portion of the first closed path and the second closed path.

4. The embosser of any one of the preceding claims, wherein the first pressure members comprise: a first pressure plate located inside one of said first closed path and second closed path; a first anvil plate located inside the other of said first closed path and second closed path; wherein the first pressure plate and the first anvil plate are positioned opposite each other along the common portion of the first closed path and the second closed path; and actuators configured to push the first pressure plate against the first anvil plate.

5. The embosser of claim 4, wherein the actuators comprise first actuators and second actuators, offset along the common portion of the first closed path and the second closed path, and configured to urge the first pressure plate against the first anvil plate with preferably different thrusts between the first actuators and the second actuators, to generate a variable pressure profile along the common portion of the first closed path and the second closed path.

6. The embosser of claim 4 or 5, comprising thrust sensors, configured to detect the thrust exerted by the first pressure plate against the first anvil plate.

7. The embosser of claim 6, wherein the thrust sensors comprise at least a first thrust sensor in the vicinity of an upstream edge of the first pressure plate and a second thrust sensor in the vicinity of a downstream edge of the first pressure plate, to detect differential thrusts of the first pressure plate against the first anvil plate along the common portion of the first closed path and the second closed path.

8. The embosser of any one of claims 4 to 7, wherein: at least one of said first endless flexible member and second endless flexible member is guided around a first guide roller and a second guide roller, between which the common portion of the first closed path and the second closed path is defined; the first guide roller is supported by a first pair of slides guided on respectivefirst guides, and the second guide roller is supported by a second pair of slides guided on respective second guides; the first pressure members comprise: first actuators associated with the first guide roller, and mechanically connected to the first pair of slides; and second actuators associated with the second guide roller, and mechanically connected to the second pair of slides; and the first pressure plate is constrained to the first pair of slides and the second pair of slides.

9. The embosser of claim 8, wherein the first pressure plate is constrained to the first pair of slides and the second pair of slides by means of connections that allow angular displacement between the slides and the first pressure plate.

10. The embosser of any one of the preceding claims, comprising a second advancement path for a second ply of web material; wherein the first advancement path and the second advancement path converge in a lamination area.

11. The embosser of claim 10, wherein a second embossing unit is arranged along the second advancement path.

12. The embosser of claim 11, wherein the second embossing unit comprises:• a third endless flexible member with an inner surface inside a third closed path of the third endless flexible member and an outer surface outside the third closed path; wherein the outer surface of the third endless flexible member comprises a plurality of embossing protuberances;• a fourth endless flexible member with an inner surface inside a fourth closed path of the fourth endless flexible member and an outer surface outside the fourth closed path; wherein the third closed path and the fourth closed path have a common portion, along which the third endless flexible member and the fourth endless flexible member advance with the outer surface of the third endless flexible member pressed against the outer surface of the fourth endless flexible member; wherein the second advancement path extends along the common portion, between the outer surface of the third endlessflexible member and the outer surface of the fourth endless flexible member; and wherein second pressure members press the third endless flexible member and the fourth endless flexible member against each other along the common portion.

13. The embosser of claim 12, wherein the fourth endless flexible member comprises an elastically deformable coating on the outer surface, the elastic deformability of the coating being such that the pressure exerted by the second pressure members causes a deformation of the elastically deformable coating and a penetration of the protuberances of the third endless flexible member into the coating of the fourth endless flexible member.

14. The embosser of claim 12, wherein the outer surface of the fourth endless flexible member comprises a plurality of embossing protuberances, the embossing protuberances on the outer surface of the third endless flexible member being inserted into recesses between the embossing protuberances on the outer surface of the fourth endless flexible member along the common portion of the third closed path and the fourth closed path.

15. The embosser of claim 12, wherein the third closed path and the first closed path have a common portion, along which the third endless flexible member and the first endless flexible member advance with the protuberances of the outer surface of the third endless flexible member pressed against the protuberances of the outer surface of the first endless flexible member; wherein the first advancement path and the second advancement path extend along the common portion, between the outer surface of the third endless flexible member and the outer surface of the first endless flexible member; and wherein third pressure members press the third endless flexible member and the first endless flexible member against each other along the common portion of the first closed path and the third closed path.

16. The embosser of claim 11, wherein the second embossing unit comprises an embossing roller comprising a plurality of embossing protuberances, and a pressure roller; wherein the embossing roller and the pressure roller form an embossing nip, through which the second advancement path extends.

17. The embosser of claim 11, wherein the second embossing unit comprises an embossing roller comprising a plurality of embossing protuberances on a lateral surface, and an endless flexible pressure member pressed against the lateral surface of the embossing roller; wherein the embossing roller and the endless flexible pressure member form an embossing nip, through which the second advancement path extends.

18. The embosser of any one of claims 10 to 14, 16 and 17, further comprising an endless flexible lamination member, having an inner surface inside and an outer surface outside a closed path of the endless flexible lamination member; wherein the first closed path of the first endless flexible member and the closed path of the endless flexible lamination member comprise a common portion, along which the first endless flexible member and the endless flexible lamination member advance with the outer surface of the first endless flexible member pressed against the outer surface of the endless flexible lamination member; wherein the first advancement path and the second advancement path extend along the common portion, between the outer surface of the first endless flexible member and the outer surface of the flexible lamination member; and wherein lamination pressure members press the first endless flexible member and the endless flexible lamination member against each other along the common portion.

19. The embosser of any one of the preceding claims, comprising a functional liquid applicator, configured to apply a functional liquid to a ply of web material that advances along the first advancement path, adhering to the first endless flexible member.

Images