Patent Description:
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 <NUM>-<NUM>%. 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. <CIT>, 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 <CIT>, 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 microembossed 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.

<CIT> shows an embossing and lamination assembly of the generic kind comprising two pairs of steel/rubber rolls, between which respectively a first paper ply and a second paper ply are returned, wherein an upper steel embossing roll is coupled with an upper embossing rubber counter-roll and a lower steel embossing roll is coupled with a lower rubber embossing counter-roll, and also comprising a glue delivery assembly, in contact on a side of said upper steel embossing roll, and a coupling roll, in contact with the opposite side of said upper steel embossing roll.

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.

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:.

With reference to the figures, an embossing and lamination assembly is shown indicated overall by reference <NUM>, depicted and described according to the exemplifying and not limiting embodiment that processes two plies 11A, 11B of paper for forming multi-ply laminated tissue paper <NUM>.

The embossing and lamination assembly <NUM> comprises two pairs of steel/rubber rolls, respectively comprising an upper steel embossing roll <NUM> and an upper embossing rubber counter-roll <NUM>, a lower steel embossing roll <NUM> and a lower rubber embossing counter-roll <NUM>, between which the first paper ply 11A and the second paper ply 11B are respectively returned, with the aid of relative motorized and/or non-motorized return rolls <NUM>.

The upper steel embossing roll <NUM> 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<NUM> greater than <NUM> (up to <NUM>) and with peak dimensions less than <NUM>.

"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<NUM> less than <NUM> (up to <NUM>) and with peak dimensions greater than <NUM> (up to <NUM>).

"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 11A between the upper pair of rolls, consisting of the steel embossing roll <NUM> and the embossing rubber counter-roll <NUM>, the projections of the upper steel roll <NUM> impress onto the first paper ply 11A relative protuberances, having the same height or different heights.

In the embossing and lamination assembly <NUM> the upper steel embossing roll <NUM> is on one side in abutment with a glue delivery assembly <NUM> and on the opposite side in abutment with the coupling roll <NUM>, known as the marriage roll. In particular, the upper steel embossing roll <NUM> is in abutment with a glue delivery applicator <NUM>, known as the cliché roll, which distributes onto the embossed paper ply the glue that was transferred thereto by the screen roll <NUM>, in turn also coupled with a tank of glue <NUM>. In particular, the cliché roll <NUM> distributes the glue onto the protuberances impressed by embossing on the first paper ply 11A.

The marriage roll <NUM>, adjacent to the upper embossing roll <NUM> exerts coupling pressure for performing the definitive coupling between the first ply 11A and said second ply 11B at the glue deposits, thus forming multi-ply laminated tissue paper <NUM>.

In the case in which the upper steel roll <NUM> is double height, following the passage of the first paper ply 11A between the pair of steel/rubber rolls, the projections with the greatest height of the upper steel roll <NUM> impress onto the first paper ply 11A protuberances defining a decorative pattern having a first height and the projections with a lower height impress onto the same paper ply 11A 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 <NUM> onto the protuberances with the greatest height of the first embossed paper ply 11A. On the opposite side the marriage roll <NUM> presses the two paper plies 11A and 11B against each other to ensure the gluing thereof to form the multi-ply laminated tissue paper <NUM>.

The lower steel embossing roll <NUM> is generally provided with projections all of the same height. Following the passage of the second paper ply 11B between the lower pair comprised of the steel embossing roll <NUM> and the rubber embossing counter-roll <NUM>, the projections of the lower embossing roll <NUM> impress onto the second paper ply 11B protuberances of a constant height defining a dotted background pattern, known as micro-embossing.

The embossing and lamination assembly <NUM> according to the invention comprises heating means <NUM> for heating the surface of the upper steel roll <NUM> and/or the surface of the lower steel roll <NUM>, associated with the upper steel roll <NUM> and/or the lower steel roll <NUM>.

The heating means <NUM> for heating the steel rolls <NUM>, <NUM> are associated with the upper steel roll <NUM> and/or the lower steel roll <NUM> for heating the upper steel roll <NUM> and/or the lower steel roll <NUM> and bringing the surface of the steel roll <NUM>, <NUM> wrapped by the paper plies 11A and 11B to a temperature comprised between about <NUM> and <NUM>.

The heating means <NUM> 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 <NUM> 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 <NUM> only associated with the lower steel roll <NUM>. This solution is advantageously simpler in terms of construction, as the lower steel roll <NUM> is only coupled to the relative lower rubber roller <NUM> and is therefore simpler to equip with the heating means <NUM> 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 <NUM> or possibly that the heating means <NUM> are only associated with the upper steel roll <NUM>.

In the embossing and lamination assembly <NUM> according to the invention, the upper <NUM> and/or lower <NUM> rubber rolls are mounted on a movable arm <NUM>, <NUM> when the relative steel roll <NUM>, <NUM> coupled thereto is equipped with heating means <NUM>. 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> shows by way of example a solution comprising further return rolls <NUM>' arranged both around the upper rubber roll <NUM>, which is coupled to the upper embossing roll <NUM>, and around the lower rubber roll <NUM>, which is coupled to the lower embossing roll <NUM>, to guarantee the tangential passage of paper between the two coupled rolls without wrapping the respective rubber roll <NUM>, <NUM>. In this way, the rubber roll <NUM>, <NUM> can be easily distanced from the steel roll <NUM>, <NUM> coupled thereto also when the paper plies 11A, 11B are in the machine.

Furthermore, according to a preferred embodiment, shown schematically in the section of <FIG> at least one of the two pairs comprised of an upper steel embossing roll <NUM> and an upper rubber embossing counter-roll <NUM> and/or lower steel embossing roll <NUM> and lower rubber embossing counter-roll <NUM> comprises on the side surface thereof a plurality of specular reliefs <NUM> and incisions <NUM>.

The plurality of specular reliefs <NUM> and incisions <NUM> are coupled during the embossing of the ply 11A, 11B with mutual inter-penetration according to a male/female coupling.

The steel rolls preferably have the reliefs <NUM>; the rubber rolls the specular hollows <NUM>.

The rubber embossing roll <NUM>, <NUM> 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 <NUM>, preferably with helical teeth with recovery of clearance, which take the rotation motion from the steel roll <NUM>, <NUM> (<FIG>).

Each of the pairs of steel/rubber embossing rolls provided with specular reliefs <NUM> and incisions <NUM> must maintain the gears <NUM> in a meshed configuration, but not engaged when the rubber roll <NUM>, <NUM> is open and therefore not in contact with the steel roll <NUM>, <NUM> for example in the event of machine stop.

In work conditions, i.e. with the rubber embossing roll <NUM>, <NUM> closed, the pair of steel/rubber rolls <NUM>/<NUM>, <NUM>/<NUM>, provided with specular reliefs <NUM> and protuberances <NUM>, 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 <NUM> comprising at least two paper plies 11A, 11B envisages applying heat to at least one of the upper 11A and/or lower 11B paper plies, while it is rolled onto the upper <NUM> and/or lower <NUM> steel rolls, respectively.

According to the invention, the heating of the paper ply 11A, 11B is performed at the same time as the embossing.

The embossing and laminating method for multi-ply laminated tissue paper <NUM> comprising multiple paper plies 11A, 11B according to the invention comprises the steps of.

wherein at least one from among the steps of embossing a first paper ply 11A and/or embossing a second paper ply 11B is performed on the relative first paper ply 11A and/or on the second paper ply 11B heated by direct contact with the hot surface of the upper <NUM> and/or lower <NUM> 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 11A and/or embossing the second paper ply 11B is performed by making the paper ply 11A, 11B assume the shape of both the rolls between which it passes, i.e. the shape of the plurality of specular and inter-penetrating incisions <NUM> and reliefs <NUM> 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 <NUM>, 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 <NUM> 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.

Claim 1:
Embossing and lamination assembly comprising two pairs of steel/rubber rolls, between which respectively a first paper ply (11A) and a second paper ply (11B) are returned, wherein an upper steel embossing roll (<NUM>) is coupled with an upper embossing rubber counter-roll (<NUM>) and a lower steel embossing roll (<NUM>) is coupled with a lower rubber embossing counter-roll (<NUM>), and also comprising a glue delivery assembly (<NUM>), in contact on a side of said upper steel embossing roll (<NUM>), and a coupling roll (<NUM>), in contact with the opposite side of said upper steel embossing roll (<NUM>), characterized in that said upper steel embossing roll (<NUM>) and/or said lower steel embossing roll (<NUM>) are equipped with heating means (<NUM>) for heating the surface of the upper steel roll (<NUM>) and/or the lower steel roll (<NUM>), the upper (<NUM>) and/or lower (<NUM>) rubber embossing rolls are mounted on a movable arm (<NUM>, <NUM>) and return rolls (<NUM>') are arranged around the upper rubber roll (<NUM>) and/or around the lower rubber roll (<NUM>) to guarantee a tangential passage of paper between the two coupled steel/rubber embossing rolls (<NUM>, <NUM>; <NUM>, <NUM>) without wrapping the respective rubber embossing roll (<NUM>, <NUM>).