Patent Publication Number: US-11654650-B2

Title: Embossing and lamination assembly and relative embossing and lamination method

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an embossing and lamination assembly and a relative embossing and lamination method. 
     Description of the Related Art 
     The coupling of various plies, generally two or three plies, of so-called tissue paper is known, for making rolls of multi-ply laminated tissue paper, both for toilet paper and kitchen paper, through a so-called embossing and lamination process, in which protuberances are obtained on each of the paper plies, with one or more heights, and gluing material is applied in proximity to at least part of such embossings for the coupling of the two plies. 
     The transformation of individual plies of paper through hot embossing subject to a paper wetting process is also known for so-called tissue paper. 
     In this case, during the embossing, the paper undergoes plastic deformation thanks to the added water in addition to the humidity already generally contained in the plies of smooth paper coming from paper mills, such humidity being estimated at around 2-5%. This allows the original characteristics of the paper itself to be better preserved. The effect on the consistency of the paper that acquires improved characteristics in terms of volume, resistance, softness, absorbency and stability is particularly advantageous. 
     It is currently known, for example from patent no. EP1731296B1, that rolls of “tissue” type paper are made through a method of micro-embossing of paper plies that have been previously wet or onto which a lotion with a wetting effect has been previously applied. 
     The term micro-embossing means that the paper plies are embossed through a roll, or micro-embossing roll, and the related counter-roll, which has reliefs substantially equally distributed on its side surface, where the reliefs have heights generally less than half a millimetre. Micro-embossing is therefore distinguished from traditional embossing in the general sense, which involves the provision, through embossing profiles, of embossings with greater heights and generally having patterns that also have an aesthetic effect. 
     Patent application WO2018/229676A1, by the same Applicant, proposed to integrate, directly in a line for transforming tissue paper, such as so-called “converting” lines, a wetting unit and a hot paper micro-embossing device, wherein the paper is dried at the same time as the micro-embossing, for each of the plies treated. The individual paper plies, hot micro-embossed after wetting, are then fed to a traditional embossing and lamination device, comprising two pairs of rubber/steel rolls and a glue dispenser. 
     With respect to the hot micro-embossing, after wetting of individual plies, wound into spools, the integration of this process into a converting line has made it possible to prevent the need for the supply of a dedicated machine or of spools of already pretreated tissue paper. 
     However, this solution requires, with respect to a traditional converting line, the addition of a wetting station and a hot micro-embossing group with the consequent increase in the dimensions of the line and the cost of supply and maintenance of the additional devices. 
     BRIEF SUMMARY OF THE INVENTION 
     The aim of the present invention is that of realizing an embossing and lamination assembly and a related embossing and lamination method that enables tissue paper to be realized with high characteristics in particular in terms of volume, reducing the number of necessary stations and process steps. 
     Another aim of the present invention is that of realizing an embossing and lamination assembly and relative embossing and lamination method that is flexible to the different possible requirements of embossing one or both of the plies according to different types of embossing, such as micro-embossing, macro-embossing or double height embossing. 
     Another aim of the present invention is that of realizing an embossing and lamination assembly and relative embossing and lamination method that is particularly simple and functional, with contained costs. 
     These aims according to the present invention are reached by realizing an embossing and lamination assembly and relative embossing and lamination method as set out in the independent claims. 
     Further features are comprised in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The characteristics and advantages of an embossing and lamination assembly and relative embossing and lamination method according to the present invention shall become clearer from the following exemplifying and not limiting description, with reference to the attached schematic drawings in which: 
         FIG.  1    is a schematic view of an embossing and lamination assembly according to the present invention; 
         FIG.  2    schematically shows in section the coupling between the plurality of specular and mutual inter-penetrating reliefs and incisions in a pair of steel/rubber rolls; 
         FIG.  3    shows a pair of gears that drag the rubber roller in rotation taking the motion from the steel roll. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the figures, an embossing and lamination assembly is shown indicated overall by reference  10 , depicted and described according to the exemplifying and not limiting embodiment that processes two plies  11 A,  11 B of paper for forming multi-ply laminated tissue paper  11 . 
     The embossing and lamination assembly  10  comprises two pairs of steel/rubber rolls, respectively comprising an upper steel embossing roll  21  and an upper embossing rubber counter-roll  22 , a lower steel embossing roll  31  and a lower rubber embossing counter-roll  32 , between which the first paper ply  11 A and the second paper ply  11 B are respectively returned, with the aid of relative motorized and/or non-motorized return rolls  12 . 
     The upper steel embossing roll  21  can be alternatively provided with projections defining micro-embossings, macro-embossings or embossings of double height or varied height, i.e. arranged according to two or more different heights. 
     “Projections defining micro-embossings” means projections of equal height possibly defining a decorative pattern, e.g. obtained with a steel embossing roll with a density of peaks per cm 2  greater than 40 (up to 100) and with peak dimensions less than 0.7 mm. 
     “Projections defining macro-embossings” means projections of equal height possibly defining a decorative pattern, e.g. obtained with a steel embossing roll with a density of peaks per cm 2  less than 40 (up to 15) and with peak dimensions greater than 0.7 mm (up to 1 mm). 
     “Projections defining double height embossings” generally means projections of different heights, wherein the glue is dispensed onto the projections with the greatest height and the projections with the lowest height generally define a microembossed pattern. 
     Following the passage of the first paper ply  11 A between the upper pair of rolls, consisting of the steel embossing roll  21  and the embossing rubber counter-roll  22 , the projections of the upper steel roll  21  impress onto the first paper ply  11 A relative protuberances, having the same height or different heights. 
     In the embossing and lamination assembly  10  the upper steel embossing roll  21  is on one side in abutment with a glue delivery assembly  40  and on the opposite side in abutment with the coupling roll  13 , known as the marriage roll. In particular, the upper steel embossing roll  21  is in abutment with a glue delivery applicator  41 , known as the cliché roll, which distributes onto the embossed paper ply the glue that was transferred thereto by the screen roll  42 , in turn also coupled with a tank of glue  43 . In particular, the cliché roll  41  distributes the glue onto the protuberances impressed by embossing on the first paper ply  11 A. 
     The marriage roll  13 , adjacent to the upper embossing roll  21  exerts coupling pressure for performing the definitive coupling between the first ply  11 A and said second ply  11 B at the glue deposits, thus forming multi-ply laminated tissue paper  11 . 
     In the case in which the upper steel roll  21  is double height, following the passage of the first paper ply  11 A between the pair of steel/rubber rolls, the projections with the greatest height of the upper steel roll  21  impress onto the first paper ply  11 A protuberances defining a decorative pattern having a first height and the projections with a lower height impress onto the same paper ply  11 A protuberances with a lower height defining a dotted background pattern, known as micro-embossing. In this particular case, the glue is applied by the cliché roll  41  onto the protuberances with the greatest height of the first embossed paper ply  11 A. On the opposite side the marriage roll  13  presses the two paper plies  11 A and  11 B against each other to ensure the gluing thereof to form the multi-ply laminated tissue paper  11 . 
     The lower steel embossing roll  31  is generally provided with projections all of the same height. Following the passage of the second paper ply  11 B between the lower pair comprised of the steel embossing roll  31  and the rubber embossing counter-roll  32 , the projections of the lower embossing roll  31  impress onto the second paper ply  11 B protuberances of a constant height defining a dotted background pattern, known as micro-embossing. 
     The embossing and lamination assembly  10  according to the invention comprises heating means  50  for heating the surface of the upper steel roll  21  and/or the surface of the lower steel roll  31 , associated with the upper steel roll  21  and/or the lower steel roll  31 . 
     The heating means  50  for heating the steel rolls  21 ,  31  are directly associated with the upper steel roll  21  and/or the lower steel roll  31  for heating the upper steel roll  21  and/or the lower steel roll  31  and bringing the surface of the steel roll  21 ,  31  wrapped by the paper plies  11 A and  11 B to a temperature comprised between about 100° C. and 200° C. 
     The heating means  50  may be selected from the known ones, either housed within the steel roll for heating by conduction from the inside the side surface of the steel roll, or housed outside the roll and facing the side surface of the steel roll for heating by radiation and/or convection. 
     For example, the heating means  50  may comprise an electrical resistor appropriately buried in the steel roll, or an oil, water or steam heating circuit, also in part obtained inside the steel roll itself. 
     According to a preferred embodiment of the invention, it is sufficient to place the heating means  50  only associated with the lower steel roll  31 . This solution is advantageously simpler in terms of construction, as the lower steel roll  31  is only coupled to the relative lower rubber roller  32  and is therefore simpler to equip with the heating means  50  both in terms of dimensions and in terms of thermal interaction with other components of the machine. 
     Further solutions of the present invention envisage that both steel rolls are equipped with heating means  50  or possibly that the heating means  50  are only associated with the upper steel roll  21 . 
     In the embossing and lamination assembly  10  according to the invention, the upper  22  and/or lower  32  rubber rolls are preferably mounted on a movable arm  24 ,  34  when the relative steel roll  21 ,  31  coupled thereto is equipped with heating means  50 . In fact, in the event of machine stop, it is advantageous to proceed to distance the rubber roll from the heated steel roll, so as not to ruin the rubber surface thereof due to the high temperature. 
       FIG.  1    shows by way of example a solution comprising further return rolls  12 ′ arranged both around the upper rubber roll  22 , which is coupled to the upper embossing roll  21 , and around the lower rubber roll  32 , which is coupled to the lower embossing roll  31 , to guarantee the tangential passage of paper between the two coupled rolls without wrapping the respective rubber roll  22 ,  32 . In this way, the rubber roll  22 ,  32  can be easily distanced from the steel roll  21 ,  31  coupled thereto also when the paper plies  11 A,  11 B are in the machine. 
     Furthermore, according to a preferred embodiment, shown schematically in the section of  FIG.  2    at least one of the two pairs comprised of an upper steel embossing roll  21  and an upper rubber embossing counter-roll  22  and/or lower steel embossing roll  31  and lower rubber embossing counter-roll  32  comprises on the side surface thereof a plurality of specular reliefs  51  and incisions  52 . 
     The plurality of specular reliefs  51  and incisions  52  are coupled during the embossing of the ply  11 A,  11 B with mutual inter-penetration according to a male/female coupling. 
     The steel rolls preferably have the reliefs  51 ; the rubber rolls the specular hollows  52 . 
     The rubber embossing roll  22 ,  32  according to this embodiment, is not idle, i.e. drawn by the steel roll against which it presses, rather motorized by means of a pair of gears  60 , preferably with helical teeth with recovery of clearance, which take the rotation motion from the steel roll  21 ,  31  ( FIG.  3   ). 
     Each of the pairs of steel/rubber embossing rolls provided with specular reliefs  51  and incisions  52  must maintain the gears  60  in a meshed configuration, but not engaged when the rubber roll  22 ,  32  is open and therefore not in contact with the steel roll  21 ,  31  for example in the event of machine stop. 
     In work conditions, i.e. with the rubber embossing roll  22 ,  32  closed, the pair of steel/rubber rolls  21 / 22 ,  31 / 32 , provided with specular reliefs  51  and protuberances  52 , can advantageously operate with an adjustable distance between them, which will provide higher or lower pressure as a function of the desired result on the paper. 
     The reduction of embossing pressure between the steel/rubber rolls notably reduces the harmful effects caused by traditional embossing. 
     The Applicant has surprisingly noted that the embossing performed with complementary incisions and reliefs associated with a heated steel roll is more defined on the paper with a greater thickness achievable on the ply. The embossing is maintained at high speeds, instead of dropping as the speed increases like for traditional embossing. 
     Less power is used for the rolling of the rolls thanks to the “zero pressure” between the steel roll and the rubber roll, as the rubber roll is adjacent to the steel roll but generally not pressed thereon. 
     According to the invention, a relative embossing and lamination method of multi-ply tissue paper  11  comprising at least two paper plies  11 A,  11 B envisages applying heat to at least one of the upper  11 A and/or lower  11 B paper plies, while it is rolled onto the upper  21  and/or lower  31  steel rolls, respectively. 
     According to the invention, the heating of the paper ply  11 A,  11 B is performed at the same time as the embossing. 
     The embossing and laminating method for multi-ply laminated tissue paper  11  comprising multiple paper plies  11 A,  11 B according to the invention comprises the steps of 
     conveying a first paper ply  11 A between an upper steel embossing roll  21  and an upper rubber embossing counter-roll  22  to emboss first protuberances on the first paper ply  11 A; 
     conveying a second ply paper  11 B between a lower steel embossing roll  31  and a lower rubber embossing counter-roll  32  to emboss second protuberances on the second paper ply  11 B; 
     applying glue by a glue delivery assembly  40  on the protuberances realized by embossing on the first paper ply  11 A; 
     pressing the two paper plies  11 A,  11 B one against the other by the coupling roll  13  acting against the upper steel embossing roll  21 , 
     wherein at least one from among the steps of embossing a first paper ply  11 A and/or embossing a second paper ply  11 B is performed on the relative first paper ply  11 A and/or on the second paper ply  11 B heated by direct contact with the hot surface of the upper  21  and/or lower  31  steel embossing roll. 
     According to the embodiment comprising at least one pair of steel/rubber embossing rolls with inter-penetrating incisions and reliefs, the step of embossing the first paper ply  11 A and/or embossing the second paper ply  11 B is performed by making the paper ply  11 A,  11 B assume the shape of both the rolls between which it passes, i.e. the shape of the plurality of specular and inter-penetrating incisions  51  and reliefs  52  envisaged on the surfaces thereof. 
     The Applicant has surprisingly discovered that already the effects of the hot embossing only, even when unaccompanied by prior wetting, enable more effective embossing to be achieved. 
     The main effects of the hot embossing according to the invention are obtained in terms of the volume of the coupled paper  11 , known as bulk, which allows larger final diameters of the wound paper roll to be obtained, and surprisingly such as to make the inevitable reduction of the tensile strength of the paper  11  acceptable compared with the results of hot embossing subject to wetting. 
     The embossing and lamination assembly and relative embossing and lamination method according to the present invention have the advantage of obtaining a significant increase in the volume of the roll wound simply with the minimum addition of components with respect to traditional embossing and laminating assemblies. 
     This advantageously allows existing assemblies to be provided with heated steel rollers and the embossing and lamination assembly to be replaced with one according to the invention in existing lines with equivalent dimensions. 
     The embossing and lamination assembly and relative embossing and lamination method thus conceived are subject to numerous modifications and variants, all falling within the scope of the invention; furthermore, all of the details can be replaced by technically equivalent elements. In practice, the materials used, as well as the dimensions thereof, can be of any type according to the technical requirements.