Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHOD FOR ~ORMING ROLLERS, PARTICULARLY EMBOSSING ROLLERS
FOR PAPER WEBS
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a method for forming
rollers, particularly rollers for embossing paper webs for
tissue products, such as for example kitchen paper, toilet
paper, et cetera.
2. Description of the Prior Art
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.
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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
expenslve.
An aim of the present invention is to provide a method for
producing 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.
SUMMARY OF THE INVENTION
This aim, these objects, and others which will become
apparent hereinafter are achieved by a method for producing
rollers, particularly rollers for embossing paper webs,
comprising a first step of forming a series of protrusions
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and a second step of forming a pattern or design which
includes the at least partial removal of a certain number of
the protrusions.
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:
DESCRIPTION OF THE DRAWINGS
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.
DESCRIPTION OF A PREFERRED
EMBODIMENT OF 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
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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 comple~ ornamental
patterns.
The method according to the invention is susceptible of
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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.
