METHOD AND APPARATUS FOR EMBOSSING PAPER WEBS

Abstract: A method for producing embossed paper webs, particularly for manufacturing products of the tissue type, such as toilet tissue, which includes a step of first embossing and characterized in that it includes a second embossing, after the first one, which is deeper than the thickness of the web plus a certain value.

Description: METHOD AND APPARATUS FOR EMBOSSING PAPER WEBS Technical field The present invention relates to a method and an apparatus for embossing paper webs, particularly for forming products such as tissues, for example toilet tissue. Background Art Paper embossing systems, for example for producing composite two-ply rolls of kitchen paper, generally include a roll unwinding device which is suitable to feed two plies of paper to an embossing unit which can be provided with a system for pasting the two plies. The embossing unit may include two embossing rollers, each provided with a plurality of protrusions which are arranged in parallel rows and each cooperating with a respective presser roller to emboss each sheet. One of the two embossing rollers can be coated with paste so as to paste the two sheets. The protrusions of the embossing rollers are formed by mechanical machining or by chemical processes for removing material, so that the sheets have a uniform stippling constituted by parallel rows of points directed inward, i.e., on the facing sides of the sheets. At the output of the embossing unit, if pasting is not provided, there is generally provided a knurling unit which is suitable to knurl the roll in order to join the two plies. One problem that is currently strongly felt is to provide complex designs by embossing. The methods proposed up to now, and capable of producing complex designs, are not only extremely onerous but also scarcely versatile. To provide even minimal changes to the design it is in fact necessary to replace the embossing rollers with new rollers which include the new design. Disclosure of the Invention The aim of the present invention is to provide a method and an apparatus which can overcome the drawbacks of the prior art. Another object of the present invention is to provide a system which is capable of producing ornamental patterns or designs, with a second embossing, without altering the first foundation embossing. Another object of the present invention is to provide a method which is capable of producing ornamental patterns or designs of varying complexity according to requirements and in a highly versatile way, i.e., so that it is possible to change the design rapidly and cheaply. Another object of the present invention is to provide an embossing method which can produce even complex ornamental patterns on the finished product. Another object of the present invention is to provide a method and an apparatus which provides more flexible management, in terms of production, than prior art systems for producing complex designs. This aim, these objects and others which will become better apparent hereinafter are achieved by a method for embossing paper webs, particularly for manufacturing products of the tissue type, such as toilet tissue, comprising a step of first embossing and characterized in that it comprises a second embossing, after the first one, which is deeper than the thickness of the sheets plus a certain value. Brief description of the drawings Further characteristics and advantages of the present invention will become better apparent from the following detailed description of a preferred but not exclusive embodiment thereof illustrated only by way of non-limitative example in the accompanying drawings, wherein: Figure 1 is a schematic side elevation view of an embossing apparatus of the point-to-point type; Figure 2 is a schematic side elevation view of an embossing apparatus of the DERL or DESL type. Ways of carrying out the invention With reference to Figure 1, a machine for performing so-called point-to- point embossing is shown; the machine is generally designated by the reference numeral 1 and includes a feeder (not shown) which is suitable to feed a first embossing unit 5 with two plies of paper 7 and 9. The first embossing unit includes a first embossing roller 11, with a corresponding rubber roller 13, and a second embossing roller 15, with a corresponding rubber roller 17. Optionally, there is a pasting device 19 which is suitable to spread paste onto the roller 15 in order to paste the two plies 7 and 9 together. The output of the first embossing unit is a web of embossed paper 21 which, according to the invention, is passed through a second embossing unit 10 which is constituted, in the illustrated example, by an embossing roller 31 which cooperates with a contrast roller 23. The roller 31 is made of steel, is machined in relief and is suitable to work in contrast with the roller 23, which is made of rubber. As an alternative, the contrast roller 23 also can be made of steel and be provided with recesses for receiving the points of the roller 31. The recesses of the contrast roller are advantageously shallower than the height of the points of the roller 31. The embossing roller 31 may have a jacket which is suitable to support a plate on which the design is formed by virtue of various methods which are known in the field. In this case, the contrast roller is made of rubber. The embossing performed by the second embossing unit is at least equal in depth to the thickness of the two sheets plus a certain value, which corresponds to the intended depth of the second ornamental pattern. More particularly, the value is equal to the depth of the penetration of the points of the embossing roller into the rubber roller. By way of example, the value of the depth of the second embossing could be approximately 1 mm, to which a processing margin must be added. The second embossing unit may have a second embossing roller (not shown) which acts on the same contrast roller 23, alternatively to the roller 31. In this manner, by using alternatively one embossing roller or the other, each having a different design, it is possible to vary the embossed design in a few minutes simply by pressing one or the other of the rollers against the contrast roller 23. The system according to the invention has some important advantages: it is in fact possible to change the design on the paper in a very short time. The optional use of two embossing rollers in the second embossing unit allows to vary the ornamental pattern almost instantaneously, simply by actuating one roller instead of the other. The web 21 is thus subjected to a second embossing which is superimposed on the first embossing performed by the first embossing unit. The web 25, which includes the second embossing and therefore the final design, leaves the second embossing unit and is sent to the subsequent processing stations, for example to a roll-forming machine, not shown, in a per se known manner. The invention can also be applied to machines of a different type; for example, Figure 2 illustrates an embossing machine, generally designated by the reference numeral 101, for performing embossing of the DERL/DESL type, which includes a feeder (not shown) which is suitable to feed a first embossing unit 105 with two plies of paper 107, 109. The first embossing unit includes a first embossing roller 111, with the corresponding rubber roller 113, and a second embossing roller 115, with the corresponding rubber roller 117. Optionally, there is a pasting device 119 for pasting the two plies 7 and 9. A web of embossed paper 121 exits from the first embossing unit and, according to the invention, is passed through the second embossing unit 10, constituted by the embossing roller 31 which cooperates with the contrast roller 23, as described above. The machine according to the invention allows to produce complex designs and ornamental patterns. While the first embossing unit can provide a conventional geometric pattern, the second embossing unit can in fact be used to superimpose a particular design. In practice it has been observed that the invention achieves the intended aim and objects; it is in fact extremely simple to provide even complex ornamental patterns by superimposing two separate embossings without however altering the foundation embossing. The machine according to the invention is extremely flexible; it is in fact possible to vary the design on the paper simply by replacing the second embossing roller. The second embossing unit can be easily excluded if one wishes to emboss the paper in a conventional manner with a simple design due to production requirements. The invention is particularly advantageous for products constituted by two or more plies. The second embossing can also be utilized to mutually paste the plies, if paste has been spread onto one of the two plies in the first embossing step. The method and the apparatus according to the invention are susceptible of numerous modifications and variations, within the scope of the appended claims. All the details may be replaced with technically equivalent elements. The materials used, as well as the dimensions, may of course be any according to requirements and to the state of the art. The present application is based upon Italian patent application No. MI99A001668, filed on 27 July 1999, the disclosure of which is hereby expressly incorporated by reference thereto.

Claims: CLAIMS 1. A method for embossing paper webs, particularly for manufacturing products of the tissue type, such as toilet tissue, comprising a step of first embossing and characterized in that it comprises a second embossing, after said first one, which is deeper than the thickness of said web plus a certain value. 2. An apparatus for embossing paper webs, particularly for producing products of the tissue type, such as toilet tissue, comprising a first embossing unit which is constituted by at least one embossing roller suitable to provide a first embossing on said paper web, characterized in that it comprises a second embossing unit which is located downstream of said first embossing unit and is suitable to provide, on said paper, a second embossing which is deeper than the thickness of said web plus a certain value. 3. The apparatus according to claim 2, characterized in that said second embossing unit comprises a steel roller which is machined in relief and is suitable to work in contrast with a contrast roller made of rubber. 4. The apparatus according to claim 2, characterized in that said second embossing unit comprises a male roller made of steel which is machined in relief and is suitable to work in contrast with a female contrast roller made of steel. 5. The apparatus according to one or more of the preceding claims, characterized in that said second embossing unit comprises a second embossing roller which is suitable to operate alternatively to the other embossing roller on the same contrast roller in order to vary the design of the second embossing.

Inventors: TRONCHETTI SAURO, TRONCHETTI, SAURO
Applicants: IND CARTARIE TRONCHETTI SPA, TRONCHETTI SAURO, INDUSTRIE CARTARIE TRONCHETTI S.P.A, TRONCHETTI, SAURO
Application year: 2000
Main classification: B31F1
IPC codes: B31F1