Multilayer embossed papers, and device and method for producing same

The multi-layer paper composed of at least three embossed plies of paper (1,2,3) having regularly distributed projections characterized in that it includes two so-called external plies (1,3) of which the respective projections (10,30) are in tip-to-tip positions and a third embossed so-called middle ply (2) of which the projections (20) nest between projections of one of the two external plies (1 or 3).

The objects of the present invention are novel multi-layer papers, a 
device/apparatus and a method for their manufacture. 
FIELD OF INVENTION 
In particular, the invention concerns household and domestic papers, 
especially embossed paper based on cotton wadding or creped tissue paper. 
In this field, there is much interest in high absorption paper also having 
great softness and good mechanical strength. 
BACKGROUND OF THE INVENTION 
Already for many years multi-layer papers have been used in this field. As 
a rule, two or three previously embossed layers are made to slightly bond 
to one another with adhesive deposited upon the ends of the projections 
made during embossing. 
Presently, two different procedures for embossing, assembly and bonding are 
used which result in two different structures. A first structure involves 
two identical embossings on two separate paper plies in order to provide 
projections on the plies and forming a laminate from these two plies. The 
projections of the two plies point toward the laminate inside and are 
bonded to each other at their ends. This procedure implements what is 
appropriately called a "tip to tip" assembly. Such a procedure, as well as 
the laminates made by it, are described in U.S. Pat. No. 3,414,459. This 
procedure in essence allows for making two-layer papers having the 
structure of FIG. 6 of U.S. Pat. No. 3,414,459. A variation also described 
in that patent and shown in FIG. 7 consists in sandwiching an unembossed 
ply between the two embossed ones before bonding the tips. 
Another procedure, described in particular in U.S. Pat. No. 3,867,225, also 
provides a laminate of two embossed plies which are also arranged in such 
a manner that the projections point inward the laminate whereby the 
projection ends of one of the two plies are coated with adhesive and the 
bonding is carried out in a position such that the projections of one ply 
nest between two projections of the other ply. This is the so-called 
"nested" structure. 
In general and as regards household uses, assemblies of embossed plies of 
paper are sought which essentially combine softness, pleasant touch, good 
absorption and good mechanical strength. 
OBJECTS AND BRIEF DESCRIPTION OF THE INVENTION 
Applicant has done research in this field and now has discovered a novel 
structure composed of at least three plies of embossed paper. The 
structure has improved softness because more air is trapped between the 
paper layers while at the same time mechanical strength is increased. 
Accordingly, the present invention proposes a novel structure of 
multi-layer embossed paper evincing properties heretofore never combined. 
The invention also relates to a method and apparatus for making these 
multi-layer papers. 
In one of its essential features, the invention concerns a multi-layer 
paper composed of at least three embossed plies of paper having regularly 
distributed projections and including two so-called external plies of 
which the respective projections are placed tip to tip and an embossed 
third, so-called middle, ply of which the projections nest between the 
projections of one of the two external plies. 
Such a structure simultaneously offers the advantages of the above noted 
"tip to tip" and "nested" structures without incurring the drawbacks of 
either one and, in particular, the structure of the invention improves the 
mechanical strength over that of a simple "tip-to-tip" structure and also 
improves the softness of a simple "nested" structure. 
Accordingly, the multi-layer papers of the invention offer simultaneously 
good structural stability, good crush resistance whereby they are kindred 
to nested products, and increased thickness whereby touch and softness are 
improved. 
As regards the multi-layer papers of the invention, the two external plies 
generally have identical embossings, i.e., they have the same repeat 
patterns and the same magnitudes. These two plies are arranged 
symmetrically so that the ends of their projections are mutually opposite. 
The projections of the middle ply are nested between the projections of one 
of the external plies and advantageously have a height at most equal to 
the heights of the projections of the external ply between which they 
nest. This feature offers the advantage of precluding all asperities 
inside the compound paper which would degrade the touch and softness of 
the paper. 
However, the height of the projections of the middle ply advantageously 
should be at least 50% of the height of the projections of the external 
ply between which they are nesting. Such a proportion allows for good 
mechanical properties. 
Advantageously, and as is the case for the multi-layer papers made of 
several embossed plies of paper, the cohesion between the various plies of 
embossed paper of the invention should be implemented by adhesion. This 
bonding is implemented at the ends of the external ply projections which 
are in mutual tip to tip positions. Accordingly, each of the tips of one 
of the external plies will bond to the middle ply between two consecutive 
projections of the middle ply while being opposite a symmetrical 
projection of the other external ply. 
In a variation of the invention, and in order to further improve if called 
for, the strength of the multi-layer paper assembly, at least one of the 
two external plies can be replaced by a double-layered paper which is 
embossed in the same manner. 
In the invention, the external plies of the multi-layer paper 
advantageously are composed of creped paper of cellulose-wadding, i.e., 
tissue paper type. This tissue paper advantageously evinces a specific 
weight between 10 and 30 g/m.sup.2. 
Advantageously the middle ply is composed of a tissue paper sheet evincing 
a specific weight between 10 and 30 g/m.sup.2. 
As regards household paper, it is conventional to use tissue papers that 
have been processed to improve their wet strength. Such tissue papers can 
be used in making the three plies constituting the multi-layer paper of 
the invention. 
However, in an advantageous variation of the invention, the middle ply is a 
paper which has not been treated to improve its wet strength. 
By using such a grade of paper for the middle ply, it is possible to 
adhesively coat only the tips of the projections of a single one of the 
two external plies because the middle ply in such a case offers good 
permeability to the adhesive. 
Again, and achieving the same advantageous effect when making the middle 
ply, any ply of paper evincing good permeability to adhesive can be used. 
Another feature of the invention relates to manufacturing the above 
described multi-layer papers. 
Such a manufacturing method involves: 
embossing a first paper ply with projections on one side of the ply, 
separately embossing a second ply by making projections on it with the same 
repeat pattern as in the embossings of the first ply, 
separately embossing a third ply also having the same embossing repeat 
pattern, and 
combining the three above embossed plies so that the first two plies are 
arranged tip to tip and the third ply is sandwiched between the two first 
plies while nesting relative to one of them. 
To improve cohesion between the different plies of paper constituting the 
multi-layer paper of the invention, the various plies advantageously are 
adhesively bonded to each other. This bonding is carried out at the 
projections of the external plies and, for that purpose, adhesive is 
deposited onto the ends of the sets of projections of the two external 
plies and thereby each of the external plies is reliably bonded to the 
middle ply. 
However, and to the extent that the middle ply is sufficiently permeable to 
the adhesive, it can suffice to deposit adhesive solely on the projection 
ends of one of the two external plies. 
Another feature of the invention concerns apparatus with which to 
manufacture the above described multi-layer papers. 
Such apparatus comprises three embossing units of which at least two are 
displaceable. Each of these units comprise two cylinders, one cylinder 
being made of an engraved and undeforming material, the other cylinder 
being made of an elastic material. The three engraved cylinders comprise 
identically spaced engravings. 
Where called for the invention also can comprise an adhesive-deposition 
unit.

DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS 
FIG. 1 shows the structure of a sheet of a multi-layer paper of the 
invention. This sheet is composed of three plies 1, 2, 3. The plies 1 and 
3 constitute the external plies of the paper of the invention. They are 
fitted with symmetrical embossings arranged in such a manner that their 
respective projections 10 and 30 are arrayed tip to tip. In the structure 
shown in FIG. 1, the height h1 of the projections of ply 1 is identical 
with the height h3 of the projections of the external ply 3. 
The middle ply 2 is affixed to external plies 1 and 3 in such a manner that 
the projections 20 nest between two consecutive projections of ply 1. 
The height h2 of the projections of ply 2 in the case shown in FIG. 1 is 
slightly less than the height h1 of the projections of ply 1. This feature 
offers the advantage of precluding any asperities on the paper surface 
while still providing excellent mechanical strength. 
Bonding is implemented at the ends 11 of projections 10 of ply 1 and at the 
ends 31 of projections 30 of ply 3. The ends of these projections bond 
together while being between two consecutive projections 20 of ply 2. 
FIG. 2 shows apparatus for manufacturing a multi-layer paper made of three 
layers of embossed paper. 
This apparatus is composed of three embossing units, respectively (A1,C1), 
(A2,C2), and (A3,C3), each including a cylinder A1, A2, A3 made of an 
engraved, undeforming material, such as steel, and a cylinder C1, C2, C3 
made of an elastic material, such as rubber. In the apparatus of FIG. 2, 
two units E1 and E2 for depositing adhesive on the projection ends that 
were made by embossing plies 1 and 3, respectively, on the engraved 
cylinders A1 and A3 are shown. 
As discussed above, depending on the nature of the middle ply, a single 
adhesive-depositing unit E1 or E2 can suffice provided that this middle 
ply is sufficiently permeable to the adhesive. 
The embossing unit (A1,C1) is stationary whereas the other two embossing 
units are displaceable and are mounted in such a manner that the 
projection ends of cylinder A3 will coincide in operation with those of 
cylinder A1, whereas the projection ends made by cylinder A2 will nest 
between the projection ends of the engraving of cylinder A1. 
When operating, the various cylinders rotate in the directions of the 
arrows shown on these cylinders in FIG. 2. 
Ply 1, received from a take-off reel not shown, is embossed while passing 
between cylinders A1 and C1 of the first embossing unit. 
Ply 2, received from a take-off reel not shown, is embossed while passing 
between cylinders A2 and C2 of the second embossing unit. Ply 3 also is 
embossed while passing between cylinders A3 and C3 constituting the third 
embossing unit. 
The above described relative positions of cylinders A1, A2 and A3 are such 
that plies 1 and 3 are in a tip to tip position whereas ply 2 will nest in 
and mesh with the other two plies. 
The two adhesive depositing units E1 and E2 allow for depositing of 
adhesive to the ends of the projections made in plies 1 and 3 and ensures 
bonding of these plies when they pass between the coincident projections 
from cylinders A1 and A3.