|
(11) | EP 1 533 112 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
|||||||||||||||||||||||
| (54) | Apparatus for manufacturing multiple-ply paper products by knurling |
| (57) An apparatus for manufacturing multiple-ply paper products by knurling, having a
knurling wheel unit constituted by one or more knurling wheels (4), each of which
cooperates with a contrast roller (5) in order to decorate by knurling at least one
paper ply and in order to decorate and join at least two paper plies. Each knurling
wheel is provided with relief patterns (7) arranged so that despite appearing to be
separate they allow the knurling wheel to have a continuity of contact with the paper
and the contrast roller. |
[0001] The present invention relates to an apparatus for manufacturing multiple-ply paper products by knurling.
[0002] The invention relates in particular to so-called "tissue" products, such as toilet paper, paper handkerchiefs, rolls of absorbent paper, et cetera, constituted by at least two plies.
[0003] As is known, joining the plies of tissue paper by means of paste causes a reduction in the softness of the finished product.
[0004] In order to obviate that drawback, many tissue products in which softness is required are not pasted but are instead knurled.
[0005] Unfortunately, the knurling systems known in the art have a drawback in that the part of ply that is deformed by the knurling tools has the appearance of a line that is generally not arranged symmetrically with respect to the product.
[0006] This has always been considered as an aesthetic drawback, because it gives the product a "defective" appearance.
[0007] The aim of the present invention is to provide an apparatus for manufacturing multiple-ply paper products by knurling that overcomes the drawbacks of the cited prior art.
[0008] A particular object of the invention is to provide an apparatus that is capable of maintaining high softness characteristics of the product without using paste and at the same time of solving the aesthetic problem of conventional knurling.
[0009] A further object of the invention is to provide an apparatus that allows to produce the knurling wheels by laser engraving and etching and therefore with reduced costs.
[0010] This aim and these and other objects that will become better apparent hereinafter are achieved by an apparatus for manufacturing multiple-ply paper products as claimed in the accompanying claims.
[0011] Further characteristics and advantages of the present invention will become better apparent from the following detailed description of preferred but not exclusive embodiments thereof, illustrated by way of non-limiting example in the accompanying drawings, wherein:
Figure 1 is a partial front view of the apparatus according to the invention;
Figure 2 is a front view of the apparatus according to the invention;
Figure 3 is a partial side view of the arrangement of the contrast roller and of the knurling wheels;
Figure 4 is a view, similar to Figure 2, of an apparatus according to a further aspect of the invention, provided with two knurling wheel holders;
Figure 5 is a partial side view of the arrangement of the contrast roller and of the knurling wheels of the apparatus of Figure 4;
Figure 6 is a partial perspective view, illustrating in detail the knurling wheel holders for individual knurling wheels;
Figure 7 is a view, similar to Figure 2, of an apparatus according to a further aspect of the invention, provided with intermediate supports;
Figure 8 is a partial perspective view of the arrangement of the contrast roller and of the knurling wheels of the apparatus of Figure 7;
Figure 9 is a flat projection view of an example of a design, illustrating an example of embodiment of decorative patterns;
Figure 10 is a flat projection view of an example of a design;
Figure 11 is a flat projection view of the protrusions suitable to form the design of Figure 10;
Figure 12 is a flat projection view of a further example of design;
Figure 13 is a flat projection view of the protrusions suitable to form the design of Figure 12;
Figure 14 is a flat projection view of a further example of design;
Figure 15 is a flat projection view of the protrusions suitable to form the design of Figure 14;
Figure 16 is a flat projection view of a further example of design;
Figure 17 is a flat projection view of the protrusions suitable to form the design of Figure 16;
Figure 18 is a flat projection view of a further example of design;
Figure 19 is a flat projection view of the protrusions suitable to form the design of Figure 18.
[0012] With reference to the cited figures, an apparatus according to the invention, generally designated by the reference numeral 1, comprises a knurling wheel holder 2 which is substantially constituted by a shaft 3 that supports a plurality of knurling wheels 4, which act in contrast with a contrast roller 5 in order to join two plies of paper into a single ribbon 6.
[0013] According to the present invention, the knurling wheels 4 have dimensions that are six to thirtysix times larger than those of conventional knurling wheels. By way of example, while conventional knurling wheels have a width comprised between 5 and 30 mm, the knurling wheel according to the present invention is 181 mm wide.
[0014] The knurling wheel according to the invention has an operating principle that is similar to that of a conventional knurling wheel but, by having a larger surface available, it allows to create decorations in relief which are then transferred to the paper.
[0015] It is evident from the drawings that the decorative patterns, which in the illustrated example are wavy, are arranged so that, despite appearing to be separate, they allow the knurling wheel to have a continuous contact with the paper and the contrast roller, preventing vibrations that would be harmful for the paper and the knurling wheel.
[0016] The spacing A between each pattern allows to decorate with continuity in a transverse direction despite using a plurality of knurling rollers 4 rather than a single roller. All this is clearly beneficial to the dimensions of the knurling wheels, which in the specific case have a diameter of 150 mm and despite the intense pressures involved do not flex, because their transverse dimension is 181 mm, and therefore is short with respect to the diameter.
[0017] The distance between the knurling wheels, designated by the reference letter B in Figure 1, is such as to keep the patterns 7 with a minimal variation from knurling wheel to knurling wheel, which is reflected on the paper 6 as a design continuity effect.
[0018] According to the invention, the knurling wheel is provided by using a material that is suitable to undergo laser engraving and etching and therefore has a low cost.
[0019] With an appropriate arrangement of the decorative patterns 7, one always has a decoration of the roll that is capable of hiding the asymmetries. Continuity of contact between the contrast roller and the knurling wheel is maintained also by virtue of the width of the knurling wheel.
[0020] Figure 9 illustrates a particular embodiment of the decorative patterns, designated by the reference numeral 17, which are characterized by the insertion, between one design and the next, of a series of protrusions 18 that allow contact between the knurling wheel and the contrast roller but do not change the final effect of the decoration, because they blend with the embossing of the paper.
[0021] By using a system with a contrarotating cylindrical brush, effective cleaning of the knurling wheels is ensured.
[0022] Moreover, the apparatus according to the invention allows to provide a decoration on an existing embossed base by using a knurling wheel in which the protrusions are higher than the protrusions of the base.
[0023] Figures 4 and 5 illustrate an embodiment of the apparatus, designated by the reference numeral 101, according to another aspect of the invention.
[0024] Due to the intense forces generated by the thrust of the knurling wheels 4 against the contrast roller 5, the contrast roller 5 may flex during rotation, reducing the cohesion of the paper plies.
[0025] In order to obviate this drawback, it is possible to increase the diameter of the contrast roller 5 in order to increase its flexural strength, but this leads to high costs.
[0026] In order to avoid generating these costs and avoid further increases in the complexity of the machine, the knurling wheels 4 can be made to operate in mutually opposite directions on the same contrast roller 5, so as to cancel out the bending. With such arrangement one is free to vary the distance B at will.
[0027] In the illustrated example, by way of indication, the distance between the knurling wheels 4 on the same shaft is approximately 210 mm.
[0028] The knurling wheels 4 can be supported by a single supporting shaft, as described above, or individually by a holder for each knurling wheel, as shown schematically in Figure 6, which illustrates individual knurling wheels 4, each of which is supported by a holder 44 applied to a supporting beam 14.
[0029] An inflatable pad 8 is preferably interposed between the knurling wheels 4 and the supporting beam 14.
[0030] Figures 7 and 8 illustrate a further embodiment of the single-shaft knurling wheel holder system, in which the knurling wheels 4 are associated with the shaft 3, which is pushed at its two ends by power arms 10.
[0031] The power arms 10 act on a beam 11, which includes a series of intermediate supports 9 for the shaft 3, which avoid the flexing of the shaft.
[0032] In practice it has been found that the invention achieves the intended aim and objects, providing an apparatus that is capable of maintaining high characteristics of softness of the product without using adhesive and at the same time of solving the aesthetic problem of conventional knurling.
[0033] The apparatus according to the invention joins two or more plies of tissue paper and simultaneously decorates them by means of the impression left by the knurling tool.
[0034] The apparatus allows the plies to pass between the contrast roller and a series of knurling wheels, which are appropriately decorated in relief and are suitable, by means of the pressure applied to the contrast roller, to join the plies that are interposed between the contrast roller and the knurling wheel unit.
[0035] The apparatus according to the invention allows to join the paper plies and at the same time decorate them by using the technique of permanent deformation of the paper, which by virtue of the deformation also assumes a different coloring and impression and allows to recognize the decorative pattern.
[0036] Another characteristic of the invention consists in the particular arrangement of the decorative pattern along the circumference and in the transverse direction of the decorated wheel.
1. An apparatus for manufacturing multiple-ply paper products by knurling, characterized in that it comprises at least one knurling wheel unit constituted by one or more knurling
wheels, each of which cooperates with at least one contrast roller in order to decorate
by knurling at least one paper ply and in order to decorate and join at least two
paper plies, each of the knurling wheels being provided with relief patterns arranged
so that despite appearing to be separate they allow the knurling wheel to have a continuity
of contact with the paper and the contrast roller.
2. The apparatus according to claim 1, characterized in that each knurling wheel is relatively long in an axial direction and has a large number
of relief patterns.
3. The apparatus according to one or more of the preceding claims, characterized in that said patterns are spaced with respect to each other by a distance that is comparable
to the distance between the knurling wheels, so as to maintain the patterns with a
minimal variation among the knurling wheels, which produces an effect of design continuity
on the knurled paper.
4. The apparatus according to one or more of the preceding claims, characterized in that said spacing between the patterns allows to decorate with continuity in a transverse
direction by using a plurality of knurling wheels.
5. The apparatus according to one or more of the preceding claims, characterized in that the axial dimension of each knurling wheel is comparable with its diameter.
6. The apparatus according to one or more of the preceding claims, characterized in that said springs are made of a material that is suitable to undergo laser engraving and
etching.
7. The apparatus according to one or more of the preceding claims, characterized in that it comprises a system with a contrarotating cylindrical brush for cleaning the knurling
wheels.
8. The apparatus according to one or more of the preceding claims, characterized in that it provides a decoration on an existing embossed base by using a knurling wheel provided
with protrusions that are higher than the protrusions of the base.
9. The apparatus according to one or more of the preceding claims, characterized in that it comprises two knurling wheel holders, which are mutually opposite with respect
to the contrast roller.
10. The apparatus according to one or more of the preceding claims, characterized in that said knurling wheels are supported by a single supporting shaft.
11. The apparatus according to one or more of the preceding claims, characterized in that said knurling wheels are supported individually by a knurling wheel holder applied
to a supporting beam.
12. The apparatus according to one or more of the preceding claims, characterized in that an inflatable pad is interposed between said knurling wheels and said supporting
beam.
13. The apparatus according to one or more of the preceding claims, characterized in that said single shaft that supports said knurling wheels is pushed at its two ends by
power arms.
14. The apparatus according to one or more of the preceding claims, characterized in that said power arms act on a beam, which comprises a series of intermediate supports
for said single shaft that prevent the flexing of said shaft.
15. The apparatus according to one or more of the preceding claims, characterized in that said patterns of said decoration are arranged so that despite appearing to be separate
they allow the knurling wheel to have continuity of contact with the paper and the
contrast roller, avoiding vibration that can damage the paper and said knurling wheel.
16. The apparatus according to one or more of the preceding claims, characterized in that protrusions are interposed between said decorative patterns and allow contact between
the knurling wheel and the contrast roller but do not vary the final effect of the
decoration because they are blended with the embossing of the paper.