Stock material or miscellaneous articles – Structurally defined web or sheet – Including variation in thickness
Reexamination Certificate
1998-10-28
2001-06-12
Loney, Donald J. (Department: 1772)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including variation in thickness
C428S154000, C156S209000, C156S219000, C156S290000, C156S553000, C425S385000
Reexamination Certificate
active
06245414
ABSTRACT:
DESCRIPTION
1. Technical Field
The invention relates to an embossing machine of the tip-to-tip type comprising two embossing cylinders, each provided with corresponding sets of protuberances, and two pressure rollers, each interacting with a corresponding one of the said two embossing cylinders, to emboss two layers of material in strip form separately and then join the said layers together, using adhesive or some other substance, to form a multiple-layer material in strip form.
The invention also relates to a laminated embossed product, for example a strip of paper wound into a roll, a serviette or a paper tissue or some other item, comprising at least two separately embossed layers, each of the two layers having the same embossed pattern, consisting of a plurality of protuberances disposed in a repeated geometrical pattern in two directions of alignment forming between them an angle other than zero.
The invention further relates to a method of embossing a strip material, comprising the stages of embossing a first layer of indefinite length by forming a first set of protuberances thereon; embossing a second layer of indefinite length, separately from the first, by forming a second set of protuberances thereon; and joining the said two layers to form the said strip material.
2. Prior Art
The embossing machine and the method to which the present invention relates are commonly used for the processing of paper layers for the purpose of forming a semi-finished product intended for the production of rolls of toilet paper, rolls of kitchen towels, tissues, paper serviettes, and the like.
A device and a method of the conventional type are described, for example, in EP-B-0,370,972.
These devices are commonly provided with two symmetrical embossing cylinders such that, in the area of closest approach of the two cylinders, where they are virtually in contact with each other, and where the two layers are joined, there is an exact correspondence between the protuberances of one cylinder and the protuberances of the other cylinder. This produces a strip product in which the protuberances produced on one layer coincide with those of the other layer and adhere to them, the protuberances being pressed against each other after an adhesive has been applied to the protuberances of one of the layers.
In the patent EP-B-0,370,972, the protuberances on the two cylinders are aligned in spirals inclined with respect to the axes of the corresponding cylinders, in order to achieve certain advantageous results. According to the more conventional method, however, the protuberances of the two cylinders are aligned along lines parallel to the axes of the corresponding cylinders, as described in U.S. Pat. No. 3,414,459. In this particular case, the two embossing cylinders are not only symmetrical with respect to each other, but are identical. In both cases, a perfect phase matching is required between the two cylinders, and this requires adjustment time and specialist personnel.
In machining the embossing cylinders, there will inevitably be small errors which normally fall within the acceptable tolerances, since an imperfect match between the protuberances of the two cylinders does not entail a lack of contact, owing to the relatively large dimensions (with respect to the machining tolerance) of the points. However, when a very dense embossed pattern is desired, with protuberances of small dimensions, the machining tolerance of the embossing cylinders is of the same order of magnitude as the dimensions of the points. Consequently, it has been found that, with cylinders provided with very small and very closely-packed protuberances, the two embossed layers are not glued together, owing to the lack of pressure between the points which do not coincide over wide bands. This gives rise to serious problems since, when the strip material is wound into logs and the logs are cut into rolls, or when the material is cut longitudinally to produce serviettes or tissues, part of the final product has to be discarded because its component layers are completely detached from each other.
To overcome these problems, it has been proposed (EP-A-0,426,548) that two layers should be embossed with different patterns, in other words patterns in which in at least one direction of alignment the protuberances of one layer have a different pitch from that of the protuberances disposed in the same direction on the other layer. In this way a strip is obtained in which the layers are glued to each other in restricted areas and not over the whole area of the strip. Gluing is achieved by the lamination of the two layers between embossing cylinders which have protuberances which coincide only in certain areas. The areas of gluing between the layers are, however, sufficiently close that in the final product the two layers have at least one area of reciprocal adhesion.
The problem with this solution consists in the need to produce different embossing cylinders. This requires different tools for the two cylinders, with a doubling of costs.
DISCLOSURE OF THE INVENTION
One object of the present invention is to produce an embossing and laminating machine which overcomes the aforesaid problems of the prior art, and which requires no phase matching between the embossing cylinders.
This and further objects and advantages will be evident from the following text to those skilled in the art.
The invention is based on the recognition of the fact that it is possible to have partial correspondence between the protuberances of one cylinder and the protuberances of the other cylinder by using the same pitch in the alignment of the protuberances on the two cylinders and appropriately varying the inclination of the directions of alignment of the protuberances on the two cylinders.
For example, according to a first embodiment of the invention, two identical directions of alignment of the protuberances on the two cylinders are made to be inclined in the same direction with respect to the axes of the corresponding cylinders, in other words with respect to the corresponding generatrices.
In other words, the protuberances are aligned in two right-hand spirals or in two left-hand spirals on the two cylinders. Additionally, the protuberances are disposed in such a way that there are no alignments parallel to the axes of the corresponding embossing cylinders, contrary to what is the case in U.S. Pat. No. 3,414,459.
Whereas in the conventional art the embossing cylinders are made symmetrical (EP-A-0,370,972) or symmetrical and identical and with alignments parallel to the axes of the cylinders (U.S. Pat. No. 3,414,459) in order to have the protuberances of one cylinder exactly match the protuberances of the other in the contact area, in other words in the area in which the embossed layers are laminated and joined, according to the present invention the cylinders are not symmetrical, in order to avoid having the protuberances in the contact area matching exactly, although the pitch between the protuberances remains the same. This enables the embossing cylinders to be made with the same tool.
According to a different embodiment of the invention, the two homologous directions of alignment of the protuberances of the two cylinders are inclined in opposite directions, but form different angles with the axes of the corresponding cylinders.
In this way, in both cases, the result is an embossed sheet product comprising at least two separately embossed layers, each of which has the same embossed pattern, consisting of a plurality of protuberances disposed in a repeated geometrical pattern in two directions of alignment forming an angle other than zero between them, in which the directions of alignment of the protuberances of the first layer are inclined with respect to the corresponding directions of alignment of the protuberances of the second layer. The protuberances of the first and of the second layer are therefore in contact with each other in restricted areas of the surface development of the final embossed material.
When the two cylinders are made identical to each oth
Fabio Perini S.p.A.
Leydig , Voit & Mayer, Ltd.
Loney Donald J.
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