ITFI20080229A1 - "EMBOSSER-LAMINATOR UNIT AND EMBOSSING METHOD" - Google Patents

Description

"Embosser-laminator group and embossing method"

DESCRIPTION

Technical field

The present invention relates to machines and methods for the transformation of web-like materials, in particular for the transformation or processing of paper, such as so-called "tissue" paper for the production of toilet paper, kitchen paper, napkins or other articles in absorbent paper.

State of the art

In order to impart particular aesthetic and functional characteristics to a web or web of paper, and also for the purpose of joining together several plies to form a multi-ply web-like material, it is known to carry out embossing operations of the webs of cellulosic fibers. Embossing is used in particular for the processing of so-called tissue paper, that is paper normally used for the production of absorbent articles, such as toilet paper, kitchen paper or the like, napkins and the like.

Embossing consists in passing one or more plies between an embossing roller equipped with protuberances and a pressure roller. The latter can be an engraved roller with an embossing design complementary to that of the protuberances of the embossing roller, so that the embossing roller and the pressure roller mesh with each other. More frequently, the pressure roller is a roller coated with a yielding material, for example rubber, in which case the embossing is obtained by making the embossing protuberances of the embossing roller penetrate into the elastically yielding layer that covers the pressure roller. The paper web or the paper webs which pass through the groove between the embossing roller and the pressure roller undergo a permanent deformation which entails the generation of an embossing pattern in relief on the web, corresponding to the pattern defined by the protuberances of the embossing roller. On the web, protrusions and cavities are formed corresponding to the cavities and protrusions of the embossing roller.

When two plies or groups of plies are embossed separately, each between an embossing roller and a pressure roller, they must be mutually joined to form the final multi-ply web material. The joint is normally obtained by gluing. In this case we speak of embossing-laminating units, that is capable of performing embossing on one or more plies and subsequently joining the processed plies together.

In some known embossing-laminating devices or groups, embossing and lamination are performed according to a so-called point-to-point technique, on the basis of which the two plies embossed separately between two embossing rollers and two respective pressure rollers are laminated and joined by gluing, after having applied an adhesive on at least one of the plies, making the plies pass through a groove defined by the first and second embossing roller, in which groove at least some of the protuberances of the first roller are located in correspondence with protuberances of the second roller. The protuberances in correspondence with each other exert a lamination pressure between the two plies in the areas where the glue has been applied, so that the joint is obtained by gluing.

In other embodiments, the lamination between two plies embossed separately by two embossing rollers and two respective pressure rollers are joined by gluing by means of a so-called laminating roller which cooperates with one of the embossing rollers. In this case, an embossing generally of the so-called nested type is obtained, that is, in which the embossing protrusions of one web are inserted into the cavities between the embossing protrusions of the other. The laminating roll is usually a smooth surface roll made of relatively hard material, such as a high hardness rubber, or a metal roll. An adhesive applicator is also associated with the embossing roller with which the pressure roller or laminator cooperates. The laminating roller squeezes the two plies against the embossing protuberances of the embossing roller with which it is associated. The effect obtained is a substantial crushing of the multi-layer ribbon-like product, with partial damage to the embossing patterns obtained in the previous embossing step between each embossing roller and the respective pressure roller.

In US patent 4,483,728 an embossing-laminating unit is described comprising a first embossing roller cooperating with a first pressure roller, a second embossing roller cooperating with a second pressure roller, the two embossing rollers being equipped with embossing protuberances for embossing two separately tissue paper veils. The embossing-laminating unit described in this prior document also has an adhesive applicator associated with the second embossing roller, which applies glue to the protrusions generated on the second web by the protrusions of the second embossing roller. A laminating roller is also combined with the same embossing roller to which the glue applicator is associated, which, contrary to what normally happens, is equipped with protrusions. The laminating roller defines with the second embossing roller a laminating groove, through which the two embossed plies pass. In this lamination groove the two plies previously equipped with respective embossing motifs are squeezed by the protuberances by the laminating roller. In this way, lamination is limited to the surface of the protuberances of the laminating roller, rather than being extended to the entire surface of the protuberances of the second embossing roller, as occurs in traditional embossing-laminating units. In any case, also in this known device the two previously embossed plies are at least partially squeezed in the areas on which the protuberances of the laminating roller act.

Summary of the invention

According to one aspect, the invention provides a laminator-embosser unit that allows to obtain a better processing of the web material, keeping the embossing unchanged, or substantially reducing the alteration of the embossing generated before lamination.

According to a different aspect, the invention provides an embossing and lamination method that allows to reduce the damage caused by the laminating roller to the embossing imparted to the two plies, or groups of plies, before lamination.

Basically in one embodiment the invention provides an embossing-laminating unit, comprising: a first embossing roller equipped with a series of first embossing protuberances; a first pressure roller, cooperating with said first embossing roller to emboss a first web of web material; a second embossing roller, equipped with a series of second protuberances; a second pressure roller, cooperating with said second embossing roller to emboss a second web of web material; an adhesive applicator, cooperating with said first embossing roller; a laminating roller, cooperating with said second embossing roller. The laminating roller is provided with protuberances in phase with at least some of the first protuberances of the first embossing roller to generate a laminating effect in correspondence with areas of the first web embossed by the first embossing roller. In this way a lamination between plies of the web material is obtained without crushing or in any case with a lower crushing effect of the embossing pattern of the plies.

In some advantageous embodiments the first and the second embossing roller are phased in nested arrangement, with the protrusions of the first embossing roller in phase with cavities between protuberances of the second embossing roller. Preferably, the protuberances of the laminating roller have a greater height than the protuberances of the second embossing roller and preferably also of the protuberances of the first embossing roller.

According to a different aspect, the invention provides a method for embossing and <coupling webs of web material, comprising the steps of:>

- embossing a first web between a first pressure roller and a first embossing roller equipped with first protuberances;>

- embossing a second web between a second pressure roller and a second roller <embosser equipped with second protuberances;>

- applying an adhesive on at least some of the embossing projections generated <by the first embossing roller;>

- laminating said first and said second web between said second embossing roller and a laminating roller equipped with lamination protuberances in phase with at least some of the first protuberances of the first embossing roller.

Each web can be constituted by a single layer or by a plurality of layers, for example based on cellulose fiber.

Brief description of the drawings

The invention will be better understood by following the description and the accompanying drawings, which show practical non-limiting embodiments of the invention. More specifically, in the drawings they show:

Fig.1 is a diagram of an embossing-laminating unit according to the invention;

Figs.1A, 1B, 1C enlargements of details of Fig.1;

Fig.2 is an enlargement of the rolling groove;

Fig.2A an enlargement of Fig.2;

Fig.3 is an enlargement of a schematic section of a multi-layer web-like material obtained with an embossing-laminating unit and with a method according to the invention;

Fig.4 is a section similar to those of Fig.3 in a variant embodiment.

Detailed description of forms of implementation of the invention.

Fig.1 schematically shows a possible embodiment of an embossing-laminator unit according to the invention. In this embodiment, the embossing-laminating unit, indicated as a whole with 1, comprises a first embossing roller 3 equipped (Fig.1A) with first embossing protuberances 3P. The protuberances 3P can define an embossing pattern or design of various types, intended for example to impart particular technical-functional characteristics and / or a particular exteriorly pleasing appearance to the product. The first embossing roller 3 cooperates with a first pressure roller 5. In some embodiments, the pressure roller 3 is coated with a layer 5A of elastically yielding material, for example rubber.

An adhesive applicator 7 of a per se known type and not described in greater detail here cooperates with the first embossing roller 3. The glue applicator 7 applies an glue on all or some of the protrusions generated on a first web V1, of paper or other web material, embossed between the pressure roller 5 and the embossing roller 3. The glue can be applied on all the protrusions, or, by using an adhesive applicator 7 of a particular shape, only on some of the protrusions formed on the web material. This can be achieved, for example, by means of a cliché adhesive dispenser, that is, a drawing.

The embossing-laminating unit 1 also comprises a second embossing roller 9, whose axis of rotation 9A is substantially parallel to the axis of rotation 3A of the first embossing roller 3. The second embossing roller 9 has, on its surface, protuberances of embossing indicated with 9P (see detail of Fig.1B). The second embossing roller 9 cooperates with a second pressure roller 11. In some embodiments, the second pressure roller 11 can be coated with a layer 11A of an elastically yielding material such as rubber, similarly to what is described with reference to the first pressure roller 5. A second web V2 is fed into the groove formed by the second embossing roller 9 and the second pressure roller 11, which is embossed between the second embossing roller 9 and the second pressure roller 11, in a similar way to what happens in the first web V1 in the embossing groove between the first pressure roller 5 and the first embossing roller 3.

In some embodiments, the embossing rollers 3 and 9 are arranged with their axes 3A and 9A at a distance such that they do not touch each other in the groove 13 formed between the rollers themselves. In this groove the first embossed web V1 is detached from the first embossing roller 3 and placed on the second embossing roller 9 as schematically represented in Fig.2. The embossing protuberances 3P and 9P are preferably arranged in such a way that the protrusions S1 formed by embossing on the web V1 go to insert into cavities formed between protrusions S2 generated on the second web V2, as visible in particular in the enlargement of Fig.2A.

On the protrusions S1, or on some of them, an adhesive C has been applied by the adhesive applicator 7. To obtain the gluing and therefore the junction between the plies V1 and V2 it is necessary to exert a lamination pressure between the two plies in correspondence of these bonded areas.

Characteristically, according to the invention, this lamination is obtained by providing a laminating roller 15, cooperating with the second embossing roller 9 and equipped with protuberances 15P, as shown in particular in the enlargement of Fig.1C. The protrusions 15P are made in such a way that, with appropriate synchronism between the rotation of the embossing roller 3 and of the laminating roller 15, they are inserted between adjacent protuberances 9P (Fig.2A) of the second embossing roller 9, in correspondence with the protrusions S1 of the veil V1 accompanied by glue C.

Basically, in this way, the lamination pressure between the two plies V1 and V2 is concentrated in the grooves between protuberances 9P of the second embossing roller, where the areas of the first ply V1 on which the adhesive C has been applied are found.

Contrary to what happens in traditional embossers-laminators, equipped with a laminating roller, in this case the pressure is not exerted on the protuberances 9P of the embossing roller to which the laminating roller is associated, but rather in correspondence with the cavities of this roller, or at least in some of said cavities, corresponding to the projections S1 of the web V1 which have received the glue. In essence, therefore, the laminating roller 15 has protuberances 15P in phase with protuberances 3P of the first embossing roller 3.

Furthermore, contrary to what happens in traditional devices, the laminating roller 15 and the glue applicator 7 are associated with two different embossing rollers: in the illustrated example, the glue applicator 7 is associated with the first embossing roller 3, while the roller laminator 15 is associated with the second embossing roller 9. An inverse arrangement is also possible. Vice versa, in traditional devices the laminating roller acts against the embossing roller to which the glue applicator is associated, this precisely due to the fact that the traditional laminating unit acts on the protuberances of the embossing roller to which it is associated, and in correspondence with which the adhesive was applied.

With the arrangement according to the invention, a lamination of the two plies V1 and V2 is obtained with the application of pressure which does not damage the embossing, while normally the pressure of the laminating roller is exerted on the protuberances 9P of the embossing roller 9 with consequent at least partial crushing of the design previously generated embossing.

In some embodiments, the height H (Fig.2A) of the protrusions 15B of the laminating roller 15 is greater than the height h of the protrusions 9B of the second embossing roller 9, which further reduces the risk of damage due to crushing of the embossing pattern generated by the embossing rollers 3, 9 and by the corresponding pressure rollers 5, 11.

Fig.3 schematically represents a cross section of web material obtained with the device and method described up to now. In this embodiment, the projections S1 generated on the web V1 are larger and more sparse than the projections S2 generated on the web V2, although this is not strictly necessary. In this case it has been assumed that the projections S1 impart a decorative design to the product, while the projections S2 constitute a dense and small-sized background embossing. In other embodiments, substantially equivalent dimensions and / or densities of the projections S1, S2 on the two plies, or an inverse arrangement to that illustrated can be provided.

In the configuration described so far, the two embossing rollers 3 and 9 are phased, i.e. synchronized with a nested arrangement: the protuberances 3P are arranged, with respect to the protuberances 9P, so that the protrusions S1 formed on the web V1 enter the cavities between S2 protrusions of the veil V2. However, this is only a possible embodiment of the method and device according to the invention.

Fig.4 schematically shows a web material N made with a different arrangement and phasing of the protrusions S1 of the web V1 and S2 of the web V2 in an intermediate processing step. In Fig. 4 it is observed how some of the protrusions S1, S2, here indicated with S1 (X) and S2 (X), are in a tip-toe position, that is, one in correspondence with the other. These protrusions correspond to protuberances of the embossing rollers arranged in a tip-toe position in the embossing groove 13. Other protrusions, indicated by S1 (Y) and S2 (Y), are arranged in a nested position. C indicates the glue applied by the glue applicator 7 on the protrusions S1, S1 (X), S1 (Y) of the web V1.

The section shown in Fig. 4 shows the web material in an intermediate stage of processing, before it reaches the lamination groove between the embossing roller 9 and the laminating roller 15. For the sake of clarity of drawing in Fig. 4 the rolls are not shown, but it must be understood that the web V2 is in contact with the embossing roller 9 and therefore inside the protrusions S2 there are the protuberances 9P of the embossing roller 9 and the whole web V2 is in contact with and engaged with the surface of the embossing roller 9. The web V1 has been detached from the embossing roller 3 and is placed on the web V2 to then pass into the lamination groove between the rollers 15 and 9.

In this groove, in correspondence with the arrows 15X, the protrusions 15P of the laminating roller 15 will be inserted to exert the rolling pressure by gluing the protrusions S1 (Y) inside the cavities between protrusions S2 (Y) of the web V2. What you get is a mixed product, embossed partially in tip-toe and partially nested. Also in this case, by using a laminating roller 15 according to the invention, a reduction or elimination of the phenomenon of the crushing of the embossing pattern previously imparted to the webs V1 and V2 by the embossing rollers 3 and 9 and the respective pressure rollers 5 and 11.

It is understood that the drawing shows only an exemplification given only as a practical demonstration of the invention, since it can be found to vary in forms and arrangements without however departing from the scope of the concept that informs the invention itself. The possible presence of reference numbers in the attached claims is intended to facilitate the reading of the claims with reference to the description and drawing, and does not limit the scope of protection represented by the claims.

Claims (6)

"Embosser-laminator group and embossing method" CLAIMS 1. An embossing-laminating unit, comprising - a first embossing roller equipped with a series of first embossing protuberances; - a first pressure roller, cooperating with said first embossing roller to emboss a first web of web material; - a second embossing roller, equipped with a series of second embossing protuberances; - a second pressure roller, cooperating with said second embossing roller to emboss a second web of web material; - an adhesive applicator, cooperating with said first embossing roller; - a laminating roller, cooperating with said second embossing roller; wherein said laminating roller is provided with protuberances in phase with some at least of the first protuberances of the first embossing roller to generate a lamination effect in correspondence with areas of the first web embossed by the first embossing roller. 2. Embossing-laminating unit as per claim 1, in which said first and said second embossing roll are phased in a nested arrangement, with the protuberances of the first embossing roller in phase with cavities between protuberances of the second embossing roller. 3. Embossing-laminating unit as per claim 1 or 2, in which the protuberances of the laminating roller have a greater height than the protuberances of the second embossing roller. 4. Embossing-laminating unit as per claim 1, 2 or 3, in which said first protuberances define a decorative motif and said second protuberances define a background motif. 5. A method for embossing and coupling plies of web material, comprising the steps of: - embossing a first web between a first pressure roller and a first embossing roller equipped with first protuberances; - embossing a second web between a second pressure roller and a second embossing roller equipped with second protuberances; - applying an adhesive on at least some of the embossing projections generated by the first embossing roller; - laminating said first and said second web between said second embossing roller and a laminating roller equipped with lamination protuberances in phase with at least some of the first protuberances of the first embossing roller. 6. Method according to claim 5, wherein said first and second protuberances are timed so that the first protuberances correspond to cavities between the second protuberances.