Method for forming embossing rollers, particularly for paper webs

Abstract: A method for forming rollers (1), particularly rollers for embossing paper webs, includes a first step of forming a series of protrusions (3) and a second step of forming a pattern or design entailing the at least partial removal of a certain number of the protrusions (3).

Description: The present invention relates to a method for forming embossing rollers, particularly rollers for embossing paper webs for tissue products, such as for example kitchen paper, toilet paper, et cetera. Paper embossing machines, for example for producing composite two-ply kitchen paper rolls, include two embossing rollers: each roller has a series of protrusions arranged in parallel rows and cooperates with a respective presser roller to emboss each sheet. The embossing rollers are placed close together, so as to join the two embossed sheets, preferably by making the points coincide. One of the two embossing rollers is coated with glue to paste the two sheets together. The protrusions of the embossing rollers are provided by machining, or by means of chemical etching, so that the sheets have a uniform stippling that is constituted by parallel rows of points directed inward, that is to say, on the mutually facing sides of the sheets. An advantageous condition for making the two sheets remain stably associated, however, is to have the largest possible number of protrusions of one sheet match those of the other sheet, in order to ensure a wide pasting surface. As an alternative, in the so-called "staggered" system, the protrusions of one sheet must coincide with the spaces between the protrusions of the other sheet. GB-A-2166690 discloses an embossing process producing embossed paper sheets, such as towels, comprising embossments having a major and minor axis wherein the major axis of substantially all of the embossments is aligned in the cross machine direction. WO-A-93/25383 discloses a modular pattern roll, for embossing paper, made by assembling separate components rather than being one piece and chemically etched. This construction has advantages but is however complex and expensive. The preamble of claim 8 is based on this prior art. An aim of the present invention is to provide embossing rollers and a method for producing such rollers, particularly rollers for embossing paper webs, which are capable to form complex ornamental patterns on the finished product. An object of the invention is to provide a method that is considerably cheaper, from the production point of view, than conventional systems. A further object is to provide a method that is capable of producing ornamental patterns or designs with various degrees of complexity, according to the requirements, but always with extreme precision and reproducibility, even mirror-symmetrical reproducibility, on multiple rollers. This aim, these objects, and others which will become apparent hereinafter are achieved by a method for producing embossing rollers, particularly for embossing paper webs, comprising a first step of forming a series of protrusions and a second step of forming a pattern or design which includes the at least partial removal of a certain number of the protrusions. Said objects are also achieved by the roller according to claim 8. Further characteristics and advantages will become apparent from the description of a preferred but not exclusive embodiment of the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein: Fig. 1 is a schematic perspective view of an embossing roller according to the invention; and Fig. 2 is an enlarged partial view of a portion of the surface of the roller according to the invention. The embossing roller according to the invention, generally designated by the reference numeral 1, is suitable to be used in a substantially conventional machine for producing embossed paper, of the type that includes two embossing rollers mounted with parallel axes, so that the embossing surface of the two rollers is in contact at the points of the facing protrusions of each roller. In a per se known manner, each embossing roller cooperates with a respective presser roller, made of rubber or other flexible material, to provide embossing on the respective paper web. Two paper webs are in fact fed respectively in the first pair and in the second pair of embossing and presser rollers in order to be embossed. Once embossed, the two webs are joined at the line of contact between the two embossing rollers so as to obtain a two-ply paper web. According to the invention, the embossing roller is produced with a first step of forming a uniform series of protrusions 3, for example by machining. It is possible to perform optional finishing operations, or one may move on directly to a second step of forming an ornamental pattern or design 5 that includes the at least partial removal of a certain number of protrusions. The protrusions may be advantageously removed by means of a numeric-control machine, for example a milling machine. This allows to reproduce each ornamental pattern or design perfectly, and even in a symmetrical manner, on the second roller. It is in fact very important to match the highest possible number of facing points of the protrusions of the two rollers, in order to ensure good gluing of the two plies. Indeed, by providing the design in a symmetrically identical manner on the two embossing rollers, all the points of one roller coincide with all the points of the other roller, ensuring the maximum number of gluing points between the two plies. It has been observed in practice that the invention achieves the intended aim and objects, a method having been provided for forming embossing rollers with very complex ornamental patterns. The method according to the invention is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. All the details may be replaced with technically equivalent elements. For example, the described steps can also be performed in reverse order. The materials employed, as well as the dimensions, may of course be any according to the requirements and the state of the art.

Claims: Method for producing embossing rollers (1), particularly for embossing paper webs, characterized in that it comprises a first step of forming a series of protrusions (3) and a second step of forming a pattern or design (5) which comprises the at least partial removal of a certain number of said protrusions (3). Method according to claim 1, characterized in that said first step of forming said series of protrusions comprises a machining operation. Method according to claim 1 or 2, characterized in that said first step of forming said series of protrusions comprises a chemical process. Method according to one or more of the preceding claims, characterized in that said first step of forming said series of protrusions is followed by a finishing operation. Method according to one or more of the preceding claims, characterized in that said second step of forming a pattern or design, which comprises the at least partial removal of a certain number of said protrusions, is performed by a numeric-control machine. Method according to one or more of the preceding claims, characterized in that said second step of forming a pattern or design which comprises the at least partial removal of a certain number of said protrusions is performed by a knurling machine. Method according to one or more of the preceding claims, characterized in that said numeric-control machine is a milling machine. Roller for embossing paper webs, comprising a series of protrusions (3) distributed over the surface of the cylinder, characterized in that patterns have been formed by an at least partial removal of some of said protrusions. Machine for embossing paper webs, comprising embossing rollers according to claim 8. Machine according to claim 9, comprising two mutually opposite rollers, one of said rollers comprising patterns that are symmetrically identical to the designs of the other roller.

Inventors: TRONCHETTI SAURO, TRONCHETTI, SAURO
Applicants: IND CARTARIE TRONCHETTI SPA, INDUSTRIE CARTARIE TRONCHETTI SPA
Application year: 1997
Main classification: B31F1
IPC codes: D21F1, B31F1, F16C13, B23P13, D06C23