Paper embossing method, embossing rollers therefor, and embossed paper obtained

Description

Field of the invention

[0001] The present invention relates to the field of the paper converting machines and, more precisely, it relates to a paper embossing method of a single or multiple web of paper, non woven fabric and similar material, such as for example, but not exclusively, for the production of rolls of all purpose paper, toilet paper, industrial rolls and the like.

[0002] Furthermore, the invention relates to a particular shape of embossing rollers, i.e. rollers used in embossing machines that carry out this method.

[0003] Finally, the invention relates to the embossed paper thus obtained.

Description of the prior art

[0004] Embossing machines are known comprising embossing rollers each of which has a plurality of rows of protrusions and recesses. On each embossing roller with a calendering function a pressure roller engages normally yielding and coated with rubberised material, suitable for pushing the web of paper against said protrusions and recesses. This way surface of paper is given a not smooth profile, with a succession of protrusions and recesses that substantially copy the surface of the embossing roller. The smooth paper is thus converted into embossed paper, which can maintain its shape up to the final utilisation

[0005] An embossing machine see e.gEP-A-738588 can comprise, in particular, two embossing rollers combined with two pressure rollers. Between each couple of embossing roller / pressure roller a corresponding web of paper passes through that matches the other web of paper at the contact line between the two embossing rollers. Previously, one of the two webs of paper has been advantageously moistened with glue so that the two webs stick to each other.

[0006] Normally, the protrusions and recesses of the embossing rollers are arranged according to rows which are parallel or slightly oblique with respect to the generating lines of the cylindrical surfaces of the rollers same. This allows to obtain different embossing patterns affecting the shape, the distances and the mutual position of the protrusions and of the recesses. US-A-4,671, 987 discloses an embossing pattern of individual pixel-shaped protrusions and recesses arranged according to wavy lines.

[0007] The succession as such of protrusions and recesses, however, does not provide to the paper an appropriate longitudinal or transversal elasticity, but it only increases the surface of contact and improves its strength and absorbing properties.

[0008] It is object of the present invention to provide a paper embossing method which, besides delivering to the paper appropriate strength and absorbing properties, gives the paper improved longitudinal and transversal elasticity.

[0009] It is another object of the present invention to provide an embossing roller that carries out this method.

[0010] It is a further object of the present invention to provide an embossed paper web that has a high longitudinal and transversal elasticity.

Summary of the invention

[0011] These and other objects are achieved by a method according to claim 1. Said method comprises the steps of:

• conveying the web through an embossing roller and a pressure roller;
• embossing by means of the embossing roller a succession of a plurality of protrusions arranged like a wave alternated to a plurality of recesses arranged like a wave.

[0012] Preferably, the protrusions and the recesses are arranged according to respective waves that extend parallel to the axis of the embossing roller.

[0013] In a preferred embodiment, the steps are provided of:

• conveying a first web of paper through a first embossing roller and a first pressure roller, on the first web being thus embossed a succession of a plurality of protrusions arranged like a wave alternated to a plurality of recesses arranged like a wave;
• conveying a second web of paper through a second embossing roller and a second pressure roller, on the second web a succession being embossed of a plurality of protrusions arranged like a wave alternated to a plurality of recesses arranged like a wave;
• conveying contemporaneously the first and the second web of paper between the first and second embossing roller, creating a doubled web of paper.

[0014] Preferably, the protrusions and recesses are arranged according to respective sinusoidal parallel waves.

[0015] Always preferably, the first and/or second web of paper are moistened with water or glue before passing through said first and second embossing roller.

[0016] According to another aspect the invention, concerns an embossing roller according to claim 5. Said roller comprises on its surface a succession of a plurality of protrusions arranged like a wave and a plurality of recesses arranged like a wave.

[0017] In a preferred embodiment the protrusions and recesses are respectively grooves and crests arranged like a continuos wave on the cylindrical surface of the roller. The grooves have tapered walls and have on their bottom a plurality of circular shallow recesses. The crests have tapered shape and have on the tip a plurality of substantially circular buttons. The shape of the buttons and of the recesses can be varied without departing from the scope of the invention. The successive waves of protrusions and recesses are preferably sinusoidal and parallel to one another. In particular, but not exclusively, they are parallel to the generating lines of the cylindrical roller.

[0018] According to a further aspect the invention concerns a web of embossed paper according to claim 8. The web has a succession of a plurality of protrusions arranged like a wave and a plurality of recesses arranged like a wave. Such protrusions and recesses have preferably sinusoidal shape and have respectively a crest with slightly raised circular buttons and a bottom with circular shallow recesses.

Brief description of the drawings

[0019] Further characteristics and advantages of the embossing method, of the embossing roller and of the embossed web according to the present invention will be made clearer with the following description of an embodiment thereof, exemplifying but not limitative, with reference to the attached drawings wherein:

• figure 1 shows a diagrammatical sectional transversal view of the embossing steps in a double web embossing machine;
• figure 2 is a cross sectional partial view of the matching step between the embossing rollers ;
• figure 3 shows a diagrammatical sectional transversal view of the embossing steps in an single web embossing machine;
• figure 4 shows a partially enlarged top plan view of an embossing roller according to the invention;
• figure 4a shows a partial cross sectional view of the embossing roller of figure 4, taken according to arrows IV-IV;
• figure 5 shows a perspective view of a portion of embossing roller, not necessarily a scale drawing, with partial view of the succession of protrusions and recesses arranged like a wave;
• figure 6 shows an enlarged impression on a plane of the protrusions of a portion of embossed paper according to the invention;
• figure 7 shows a top plan view of a portion of paper embossed with the method according to the invention;
• figures 8A and 8B show a cross sectional view of a portion of embossed paper according to the invention, in figure 8B the stretched paper being indicated with a dotted line.

Description of the preferred embodiments

[0020] With reference to figure 1, an embossing machine that carries out the method according to the present invention comprises a first and a second embossing roller, indicated with numerals 1 and 2, with axes parallel and touching each other (figure 2). In combination with embossing rollers 1 and 2, pressure rollers 3 and 4 are respectively provided having for example rubberised surface and suitable for pressing webs of paper 5 and 6, coming from separate directions, against embossing rollers 1 and 2.

[0021] The two webs 5 and 6, actually, are deformed by the calendering action of pressure rollers 3 and 4 against rollers 1 and 2, and are then coupled at 7, after that web 5 touched a gluing roller 8, creating thus a doubled embossed web 9. Deviating rollers 10 are provided upstream and downstream of point 7 for assuring to webs 5 and 6 and to doubled web 9 a correct trajectory and stretch.

[0022] With reference to figure 2, the region of contact between rollers 1 and 2 couples webs 5 and 6 through matching protrusions and recesses 1a and 1b of first embossing roller 1 with recesses and protrusions 2b and 2a of second embossing roller 2, respectively. According to the thickness of the final embossed paper it is possible an actual meshing of the protrusions and recesses (figure 2). Alternatively, it is possible a tip-to-tip coupling (not shown) of protrusions 1a and 2a against each other.

[0023] In other words, in case of embossing a doubled web, the paper can be embossed according to different techniques, for example tip-to-tip embossing type or different type. In the first case the embossing is carried out so that the depressions on both webs match to one another, whereas in the other case the depressions on both webs are opposed to one another.

[0024] As shown in figure 3, it is also possible to emboss a web 5, single or multiple, by means of its passage through a simple duo embossing roller 1 / pressure roller 3, without a further embossing step.

[0025] According to the present invention, as shown in figures 4, 4A and 5, protrusions and recesses 1a and 1b (or 2a, 2b) of embossing roller 1 (or 2) are shown as a succession of crests and grooves arranged like a wave. In particular, the wave has substantially sinusoidal shape.

[0026] As shown in said figure, from crests 1a of embossing roller 1 circular buttons 11 protrude that are arranged like a wave. Similarly, in grooves 1b circular shallow recesses 12 are made that are also arranged like a wave. Instead of a circular shape other geometric shapes can be provided for by the designers.

[0027] Buttons 11 and circular recesses 12 allow a correct embossing, giving to paper 5 a larger surface and then improving its absorbing function. In a possible embodiment, for example, the pitch between two successive wave crests is 4 mm, the distance between two buttons or circular recesses of a same wave is 2 mm and every button or circular recess has diameter 1 mm.

[0028] This allows to obtain an embossed paper whose impression seen from below is shown in figure 6. Every circle 15 is embossed by buttons 11. The profile of the protrusions and of the recesses, as well as the embossing caused by to the circular recesses 12, is not shown. Owing to the symmetry of embossing roller 1, figure 6 represents also the circular recesses 12 of the embossed paper seen from the above.

[0029] In figure 7, instead of the impression of the paper, a top plan view of the embossed paper is shown. Both the impressions 15 of buttons 11 and the impressions 16 of recesses 12 are shown. Furthermore lines 18 of the edges made on paper 5 by crests 1a and by the grooves 1b are shown.

[0030] The profile of the paper, instead, is shown in figure 8A. More precisely, the impressions 15 of buttons 11 and the impressions 16 of recesses 12 are also shown. The wave-like shape increases the elasticity of the paper both transversally and longitudinally. This is clear, in particular, in figure 8B, where the paper of figure 7 is shown also in a position stretched elastically.

[0031] Obviously, other shapes arranged like a wave are possible besides that shown in the above figures.

[0032] The foregoing description of a specific embodiment will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt for various applications such an embodiment without further research and without parting from the invention, and it is therefore to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiment. The means and the materials to realise the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Claims

1. Paper embossing method of a single or multiple web of paper, non woven fabric and similar material, such as for example, but not exclusively, for the production of rolls of all purpose paper, toilet paper, industrial rolls and the like, comprising the step of conveying said web (5, 6) through an embossing roller(1, 2) and a pressure roller(3,4); characterised in that said embossing roller (1,2) and said pressure roller (3, 4) emboss a succession of a plurality of protrusions (1a, 2a) in the shape of crests arranged like continuous waves, alternated to a plurality of recesses (1b, 2b) in the shape of grooves, arranged like continuous waves.

2. Method according to claim 1, wherein the further steps are provided of:

- conveying a first web (5) of paper through a first embossing roller(1) and a first pressure roller(3), on said first web (5) a succession being thus embossed of a plurality of protrusions (1 a) in the shape of crests arranged like continuous waves alternated to a plurality of recesses (1b) in the shape of grooves arranged like continuous waves;

- conveying a second web (6) of paper through a second embossing roller (2) and a second pressure roller(4), on said second web (6) a succession being embossed of a plurality of protrusions (2a) in the shape of crests arranged like continuous waves alternated to a plurality of recesses (2b) in the shape of grooves arranged like continuous waves;

- conveying contemporaneously said first and said second web (5, 6) of paper between said first and said second embossing rollers(1, 2), creating a doubled web (9) of paper.

3. Method according to claim 1 or 2, wherein said crests (1a, 2a) and grooves (1b, 2b) are arranged according to respective waves that extend parallel to the axis of said embossing roller(1,2), said waves being preferably sinusoidal parallel waves.

4. Method according to claim 2, wherein said or each web (5, 6) of paper is moistened with water or glue before passing through said first and second embossing roller (1, 2).

5. Embossing roller (1, 2), , including on its surface a succession of a plurality of protrusions (1a, 2a) and recesses (1, 2b), characterised in that said protrusions and recesses are in the shape of crests and grooves, respectively, arranged like respective continuous waves on the cylindrical surface of the roller.

6. Embossing roller(1, 2) according to claim 5, wherein said grooves (1b, 2b) have tapered walls and have on their bottom a plurality of shallow recesses (12) and said crests (1a, 2a) have tapered shape and have on the tip a plurality of radially protruding buttons (11).

7. Embossing roller(1, 2) according to claim 6 wherein said waves formed by said succession of crests (1a, 2a) and grooves (1, 2b) are preferably sinusoidal and parallel to the generating lines of the cylindrical roller.

8. Embossed paper comprising on its surface a succession of a plurality of protrusions (1a, 2a) and recesses (1b, 2b), characterised in that said protrusions are in the shape of crests and grooves, respectively, arranged like respective continuous waves.

9. Embossed paper according to claim 8, wherein such crests (1 a, 2a) and grooves (1b, 2b) have preferably sinusoidal shape and are provided with slightly raised buttons (15) and with shallow recesses (16), respectively.

Ansprüche

1. Papierprägeverfahren für eine einlagige oder mehrlagige Bahn aus Papier, Vlies oder ähnlichem Material, wie zum Beispiel, aber nicht darauf beschränkt, zur Herstellung von Allzweckpapier, Toilettenpapier, Industrierollen und dergleichen, umfassend den Schritt der Förderung der Bahn (5, 6) durch eine Prägewalze (1, 2) und eine Druckwalze (3, 4), dadurch gekennzeichnet, dass die Prägewalze (1, 2) und die Druckwalze (3, 4) eine Folge einer Vielzahl von Erhebungen (1a, 1b) in der Form von Kämmen, die wie durchgehenden Wellen angeordnet sind, abwechselnd mit einer Vielzahl von Vertiefungen (1b, 2b) in Form von Nuten prägen, die wie durchgehende Wellen angeordnet sind.

2. Verfahren nach Anspruch 1, wobei die weiteren Schritte vorgesehen sind:

- Fördern einer ersten Bahn (5) aus Papier durch eine erste Prägewalze (1) und eine erste Druckwalze (3), wobei auf der ersten Bahn (5) eine Folge einer Vielzahl von Erhebungen (1 a) in der Form von Kämmen, die wie durchgehenden Wellen angeordnet sind, abwechselnd mit einer Vielzahl von Vertiefungen (1b) in Form von Nuten geprägt werden, die wie durchgehende Wellen angeordnet sind;

- Fördern einer zweiten Bahn (6) aus Papier durch eine zweite Prägewalze (2) und eine zweite Druckwalze (4), wobei auf der zweiten Bahn (6) eine Folge einer Vielzahl von Erhebungen (2a) in der Form von Kämmen, die wie durchgehenden Wellen angeordnet sind, abwechselnd mit einer Vielzahl von Vertiefungen (2b) in Form von Nuten geprägt werden, die wie durchgehende Wellen angeordnet sind;

- gleichzeitiges Fördern der ersten und der zweiten Bahn (5, 6) aus Papier zwischen den ersten und zweiten Prägewalzen zur Herstellung einer gedoppelten Bahn (9) aus Papier.

3. Verfahren nach Anspruch 1 oder 2, wobei die Kämme (1a, 2a) und Nuten (1b, 2b) jeweils nach Wellen angeordnet sind, die sich parallel zur Achse der Prägewalze (1, 2) erstrecken, und die Wellen vorzugsweise sinusförmige parallele Wellen sind.

4. Verfahren nach Anspruch 2, wobei die oder jede Bahn (5, 6) aus Papier mit Wasser oder Leim befeuchtet wird, bevor sie durch die erste und zweite Prägewalze (1, 2) läuft.

5. Prägewalze (1, 2) mit einer Folge von Erhebungen (1a, 2a) und Vertiefungen (1b, 2b) auf ihrer Oberfläche, dadurch gekennzeichnet, dass die Erhebungen und Vertiefungen die Form von Kämmen und Nuten aufweisen, die jeweils gleich durchgehenden Wellen auf der zylindrischen Oberfläche der Walze angeordnet sind.

6. Prägewalze (1, 2) nach Anspruch 5, wobei die Nuten (1b, 2b) geneigte Wände und auf ihrem Grund eine Vielzahl flacher Vertiefungen (12) aufweisen und die Kämme (1a, 2a) eine sich verjüngende Form und auf der Spitze eine Vielzahl von radial vortretenden Knöpfen (11) besitzen.

7. Prägewalze (1, 2) nach Anspruch 6, wobei die durch die Folge von Kämmen (1 a, 2a) und Vertiefungen (1 b, 2b) gebildeten Wellen vorzugsweise sinusförmig und parallel zu den Erzeugenden der zylindrischen Walze sind.

8. Geprägtes Papier, umfassend eine Folge einer Vielzahl von Erhebungen (1a, 2a) und Vertiefungen (1b, 2b) auf seiner Oberfläche, dadurch gekennzeichnet, dass die Erhebungen und Vertiefungen die Form von Kämmen und Nuten aufweisen, die jeweils wie durchgehende Wellen angeordnet sind.

9. Geprägtes Papier nach Anspruch 8, wobei solche Kämme (1a, 2a) und Nuten (1b, 2b) vorzugsweise sinusförmige Form aufweisen und jeweils mit leicht überstehenden Knöpfen (15) und mit flachen Vertiefungen (16) versehen sind.

Revendications

1. Procédé de gaufrage de papier d'une feuille continue unique ou multiple de papier, de tissu non tissé et de matériau similaire, tel que, par exemple, mais non exclusivement, pour la fabrication de rouleaux de papier à usage général, de papier toilette, de rouleaux industriels et analogues, comprenant l'étape consistant à transporter ladite feuille continue (5, 6) à travers un rouleau de gaufrage (1, 2) et un rouleau de pression (3, 4) ; caractérisé en ce que ledit rouleau de gaufrage (1, 2) et ledit rouleau de pression (3, 4) réalisent un gaufrage pour créer une succession d'une pluralité de protubérances (1a, 2a) sous forme de crêtes agencées comme des ondulations continues, en alternance avec une pluralité d'évidements (1b, 2b) sous forme de rainures, agencées comme des ondulations continues.

2. Procédé selon la revendication 1, dans lequel les étapes supplémentaires sont prévues consistant à :

- transporter une première feuille continue (5) de papier à travers un premier rouleau de gaufrage (1) et un premier rouleau de pression (3), sur ladite première feuille continue (5) une succession étant ainsi gaufrée d'une pluralité de protubérances (1a) sous forme de crêtes agencées comme des ondulations continues en alternance avec une pluralité d'évidements (1b) sous forme de rainures agencées comme des ondulations continues ;

- transporter une seconde feuille continue (6) de papier à travers un second rouleau de gaufrage (2) et un second rouleau de pression (4), sur ladite seconde feuille continue (6) une succession étant gaufrée d'une pluralité de protubérances (2a) sous forme de crêtes agencées comme des ondulations continues en alternance avec une pluralité d'évidements (2b) sous forme de rainures agencées comme des ondulations continues ;

- transporter simultanément lesdites première et seconde feuilles continues (5, 6) de papier entre lesdits premier et second rouleaux de gaufrage (1, 2), créant une feuille continue doublée (9) de papier.

3. Procédé selon la revendication 1 ou 2, dans lequel lesdites crêtes (1a, 2a) et rainures (1b, 2b) sont agencées selon des ondulations respectives qui s'étendent parallèlement à l'axe dudit rouleau de gaufrage (1, 2), lesdites ondulations étant de préférence des ondulations parallèles sinusoïdales.

4. Procédé selon la revendication 2, dans lequel ladite ou chaque feuille continue (5, 6) de papier est humidifiée avec de l'eau ou de la colle avant de passer à travers lesdits premier et second rouleaux de gaufrage (1, 2).

5. Rouleau de gaufrage (1, 2), comprenant, sur sa surface, une succession d'une pluralité de protubérances (1a, 2a) et d'évidements (1b, 2b), caractérisé en ce que lesdites protubérances et lesdits évidements sont sous forme de crêtes et de rainures, respectivement, agencées comme des ondulations respectives continues sur la surface cylindrique du rouleau.

6. Rouleau de gaufrage (1, 2) selon la revendication 5, dans lequel lesdites rainures (1b, 2b) possèdent des parois effilées et possèdent, sur leur fond, une pluralité d'évidements creux (12) et lesdites crêtes (1a, 2a) possèdent une forme effilée et possèdent, sur le sommet, une pluralité de boutons faisant saillie de façon radiale (11).

7. Rouleau de gaufrage (1, 2) selon la revendication 6, dans lequel lesdites ondulations formées par ladite succession de crêtes (1a, 2a) et de rainures (1, 2b) sont de préférence sinusoïdales et parallèles aux lignes génératrices du rouleau cylindrique.

8. Papier gaufré comprenant, sur sa surface, une succession d'une pluralité de protubérances (1a, 2a) et d'évidements (1b, 2b), caractérisé en ce que lesdites protubérances sont sous forme de crêtes et de rainures, respectivement, agencées comme des ondulations continues respectives.

9. Papier gaufré selon la revendication 8, dans lequel de telles crêtes (1a, 2a) et rainures (1b, 2b) possèdent de préférence une forme sinusoïdale et sont pourvues de boutons légèrement relevés (15) et d'évidements creux (16), respectivement.

Drawing