Search

EP-4499398-B1 - EMBOSSING-LAMINATING DEVICE AND METHOD

EP4499398B1EP 4499398 B1EP4499398 B1EP 4499398B1EP-4499398-B1

Inventors

  • PETRONE, ANDREA
  • GALOPPINI, Matteo

Dates

Publication Date
20260506
Application Date
20230329

Claims (8)

  1. An embossing-laminating device (1) comprising: a first embossing roller (4) provided with first embossing protuberances (4P) forming a first embossing pattern; a first pressure roller (6) forming, with the first embossing roller (4), a first embossing nip (8); a second embossing roller (5) provided with second embossing protuberances (5P) forming a second embossing pattern; a second pressure roller (7) forming, with the second embossing roller (5), a second embossing nip (9); a heating device (40) adapted to heat the first embossing roller (4) to make the first embossing roller (4) achieve, in use, a first temperature; characterized in that : the first tremperature is higher than a second temperature of the second embossing roller (5); and wherein the first embossing pattern and the second embossing pattern are so configured as to be in phase with each other when the first embossing roller (4) is at the first temperature and the second embossing roller (5) is at the second temperature.
  2. The embossing-laminating device (1) of claim 1, wherein, in use, the first temperature is between 50°C and 200°C higher than the second temperature.
  3. The embossing-laminating device (1) of claim 1 or 2, wherein, when the first embossing roller (4) and the second embossing roller (5) are at the same temperature, the first embossing pattern and the second embossing pattern are in phase with each other at a first axial end of the first embossing roller (4) and of the second embossing roller (5) and have a phase shift increasing from the first axial end towards the second axial end of the first embossing roller (4) and of the second embossing roller (5); wherein the first embossing roller (4) is supported, at the first axial end, by a first bearing (42) and, at the second axial end, by a second bearing (44); and wherein the first bearing (42) is fixed with respect to a bearing structure (2), and the second bearing (44) is movable with respect to the bearing structure (2), to follow an axial elongation of the first embossing roller (4) caused by a thermal expansion of the first embossing roller (4), when the first embossing roller (4) is heated.
  4. The embossing-laminating device (1) of claim 1 or 2, wherein, when the first embossing roller (4) and the second embossing roller (5) are at the same temperature, the first embossing pattern and the second embossing pattern are in phase with each other in a central position between a first axial end of the first embossing roller (4) and of the second embossing roller (5) and a second axial end of the first embossing roller (4) and of the second embossing roller (5) and have a phase shift increasing from the central position towards the first axial end and the second axial end of the first embossing roller (4) and of the second embossing roller (5); wherein the first embossing roller (4) is supported, at the first axial end, by a first bearing (42) and, at the second axial end, by a second bearing (44); and wherein the first bearing (42) and the second bearing (44) are movable with respect to a bearing structure (2) to follow a symmetrical thermal expansion of the first embossing roller (4), with symmetrical displacements of the first axial end and of the second axial end, when the first embossing roller (4) is heated.
  5. A method for producing an embossed web material (N) comprising at least a first ply (V1), embossed with a first embossing pattern, and a second ply (V2), embossed with a second embossing pattern, bonded together; the method comprising the following steps: feeding the first ply (V1) through a first embossing nip (8) formed between a first embossing roller (4), provided with first embossing protuberances (4P) that form a first embossing pattern, and a first pressure roller (6), and embossing the first ply (V1) in the first embossing nip (8); wherein the first embossing roller (4) is kept at a first temperature; feeding a second ply (V2) through a second embossing nip (9) formed between a second embossing roller (5), provided with second embossing protuberances (5P) that form a second embossing pattern, and a second pressure roller (7); wherein the second embossing roller (7) is at a second temperature; bonding together the first ply (V1), provided with a first embossed pattern generated by the first embossing protuberances (4P), and the second embossed ply (V2), provided with a second embossed pattern generated by the second embossing protuberances (5P), with the first embossed pattern in phase with the second embossed pattern; characterized in that the first temperature is higher than the second temperature; and wherein the first embossing pattern and the second embossing pattern are so configured to be in phase with each other when the first embossing roller (4) is at the first temperature and the second embossing roller (5) is at the second temperature, and out of phase with each other when the first embossing roller (4) and the second embossing roller are at the same temperature (5).
  6. The method of claim 5, wherein the first temperature is between 50°C and 200°C higher than the second temperature.
  7. The method of claim 5 or 6, wherein, when the first embossing roller (4) and the second embossing roller (5) are at the same temperature, the first embossing pattern and the second embossing pattern are in phase with each other at a first axial end of the first embossing roller (4) and of the second embossing roller (5) and have a phase shift increasing from the first axial end towards the second axial end of the first embossing roller (4) and of the second embossing roller (5); wherein the first embossing roller (4) is supported, at the first axial end, by a first bearing (42) and, at the second axial end, by a second bearing (44); and wherein the first bearing (42) is fixed with respect to a bearing structure (2), and the second bearing (44) is movable with respect to the bearing structure (2), to follow an axial elongation of the first embossing roller (4) caused by a thermal expansion of the first embossing roller (4), when the first embossing roller (4) is heated.
  8. The method of claim 5 or 6, wherein, when the first embossing roller (4) and the second embossing roller (5) are at the same temperature, the first embossing pattern and the second embossing pattern are in phase with each other in a central position between a first axial end of the first embossing roller (4) and of the second embossing roller (5) and a second axial end of the first embossing roller (4) and of the second embossing roller (5) and have a phase shift increasing from the central position towards the first axial end and the second axial end of the first embossing roller (4) and of the second embossing roller (5); wherein the first embossing roller (4) is supported, at the first axial end, by a first bearing (42) and, at the second axial end, by a second bearing (44); and wherein the first bearing (42) and the second bearing (44) are movable with respect to a bearing structure (2) to follow a symmetrical thermal expansion of the first embossing roller (4), with symmetrical displacements of the first axial end and of the second axial end, when the first embossing roller (4) is heated.

Description

TECHNICAL FIELD The present invention relates to the field of paper converting machines, particularly tissue paper converting machines, or machines for converting other products in ply or web form, for example non-woven fabric or the like. Embodiments disclosed herein relate to novel engraving patterns of the embossing rollers for embossing devices, especially for embossing-laminating devices, used for embossing plies of cellulose material, synthetic material, or thermoplastic material, or combinations thereof, to form an embossed multi-ply web material. BACKGROUND ART In tissue paper producing and converting industry, to produce products like rolls of toilet paper, kitchen towels, napkins, handkerchiefs, interfolded wipes and towels and the like, it is well known to unwind a plurality of plies of cellulose fibers from one or more master rolls, and to convert the cellulose plies into a semi-finished or finished product comprising one or more plies bonded together, for example by gluing or mechanical ply-bonding. Typically, before bonding the plies together, one or both plies are embossed, i.e. subjected to an operation of permanent deformation, by making the ply pass through an embossing nip between an embossing roller, having a plurality of embossing protuberances, and a pressure roller. The pressure roller can be smooth and provided with an elastically yielding coating layer, made for example of natural or synthetic rubber. In other cases, the pressure roller is engraved with an engraving pattern which is complementary to the pattern of the embossing protuberances. The heat embossing technique, i.e. embossing by heating the embossing roller and the ply of web material driven around it, has been well known for a long time. Examples of heat embossing systems are disclosed in US2013/220151, JP2007136861, US6913673. Heat embossing devices and methods, using a heating system that is innovative and more efficient than the prior art systems, are disclosed in WO2021/205255. US6245414 discloses an embossing-laminating device with a thermostatic control system for controlling the temperatures of the embossing rollers. In embossing and embossing-laminating devices with two embossing rollers, several drawbacks may arise when heat embossing operations are carried out, due to the differential thermal expansions of the embossing rollers. There is therefore the need for embossing and embossing-laminating devices that completely or partially overcome these drawbacks. SUMMARY OF THE INVENTION According to an aspect, an embossing-laminating device is disclosed herein, comprising a first embossing roller provided with first embossing protuberances forming a first embossing pattern, and a first pressure roller forming, with the first embossing roller, a first embossing nip. The embossing-laminating device further comprises a second embossing roller provided with second embossing protuberances forming a second embossing pattern, and a second pressure roller forming, with the second embossing roller, a second embossing nip. A heating device is also provided, adapted to heat the first embossing roller to make the first embossing roller achieve, in use, a first temperature higher than a second temperature of the second embossing roller. The first embossing pattern and the second embossing pattern are so configured as to be in phase with each other when the first embossing roller is at the first temperature and the second embossing roller is at the second temperature. According to a further aspect, a method is disclosed for producing an embossed web material comprising at least a first ply, embossed with a first embossing pattern, and a second ply, embossed with a second embossing pattern, bonded together; the method comprising the following steps: feeding the first ply through a first embossing nip formed between a first embossing roller, provided with first embossing protuberances that form a first embossing pattern, and a first pressure roller, and embossing the first ply in the first embossing nip; wherein the first embossing roller is kept at a first temperature;feeding a second ply through a second embossing nip formed between a second embossing roller, provided with second embossing protuberances that form a second embossing pattern, and a second pressure roller; wherein the second embossing roller is at a second temperature, lower than the first temperature;bonding together the first ply, provided with a first embossed pattern generated by the first embossing protuberances, and the second embossed ply, provided with a second embossed pattern generated by the second embossing protuberances, with the first embossed pattern in phase with the second embossed pattern. The first embossing pattern and the second embossing pattern are so configured to be in phase with each other when the first embossing roller is at the first temperature and the second embossing roller is at the second temperature, and out of phase with each other