Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to paper machines and
in particular to a paper machine capable of embossing a
predetermined pattern in a web.
With previously known paper machines, tissue paper
is commonly manufactured in such a way that the web is formed
on a relatively short wire section similar to a normal planar
wire situated at a location where a headbox supplied the pulp
stock onto a breast roll which is in many cases of an
open construction or provided with an internal vacuum.
From the breast roll the web travels, while carried by the
wire, past conventional dewatering elements such as table
rolls, deflectors, foil strips, suction boxes and a suction
roll, each of the latter components serving to remove water
from the web. ~t the end of the wire section the partly
dried web is transferred to a so-called pick-up felt, with
the web being carried by this felt to be further dried in
the press and drying sections of the machine. In some
designs this planar wire section has been totally omitted,
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and in this case the web formation is carried out entirely on a
wire-coated suction breast roll fLom which the web is transferred
directly to the pick-up felt.
The prior art also includes several twin-wire formers
intended for manufacturing tissue paper. Most of the know twin-
wire formers are so-called full throat forme-rs, but constructions
of this type generally have the drawback that as a result of the
use of such a throat former there is a poor "formation" of the
web which is produced. Various problems affecting the running
of the machine are furthermore introduced, as a result of the
high rate of dewatering at the initial draining step.
In most widely used paper manufacturing methods, the
wet paper web is pressed on a Yankee cylinder which carries out
the drying operation, in such a way that the uniformity of the
paper structure in the direction of the thickness dimension there-
of is maintained as exact as possible. It is well known that
with increasing machine speeds the drying capacity of the Yankee
cylinder creates an obstacle to a further increase of the
production rate. In order that the drying capacity of the
Yankee cylinder shou]d be capable of being fully utilized in a
creped paper machine, it is common to subject the wet paper web
to very powerful pressure with the aid of one or two Yankee
cylinder presses prior to starting of the evaporation drying
proper. In this way it is possible to achieve a web which is
uniform over its entire breadth, but the softness and absorptivity
characteristics of the end product are substantially impaired.
It is a general object of the invention to achieve im-
provements in tissue paper machines, in particular in connection
with their total concept.
More specifically, it is an object of the invention to
provide a tissue paper machine wherein it is possible to preserve
in the web the qualities of softness, bulk, and absorptibity
which are required of tisslle paper.
It is furthermore an object of the present invention
to provide a machine which is capable of improving the fiber
retention and to achieve the highest possible strength in the
finished paper without causing the above qualities to suffer~
According to the present invention, there is provided
a tissue paper machine in which the twin-wire former section
comprises a headbox, a carrying fabric, a covering fabric,
within the loop of the carrying fabric a forming roll, this
froming roll having a smooth surface and the dewatering of the
web on this forming roll being mainly by centrifugal force
effect while the web is impacted between the fabrics, and the
tissue paper machine having as its dryer a Yankee cylinder
with which together a press suction roll defines a press nip,
characterized in that through the press nip is arranged to pass
apattern embossing fabric embossing its pattern on the web in
the nip and which is such that it also serves as a member trans-
porting the web forwardly, the web being transferred onto the
pattern embossing fabric by the aid of a pick-up means.
According to one aspect of the invention, in a paper
machine, there are provided twin-wire former means for forming
a web, headbox means cooperating with said twin-wire former
means for supplying pulp stock thereto to be formed thereby
into said web, press-nip means including a press suction roll,
situated beyond said former means for providing at least one
press nip through which the web travels, and fabric means ex-
tending between said twin-wire former means and said press-nip
means and including a former portion which participates in the
formation of the web at said twin-wire former means and a trans-
fer portion for transferring the formed web to said press-nip
means while travelling with the web through said press nip, at
least said transfer portion of said fabric means having a mesh
- for embossing a predetermined pattern in the web as it travels
through said press nip, so that
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sa.id transfer portion of said fabric means operates on the one
hand to transport the web to said press-nip means and on the
other hand to emboss a pattern in the web.
The invention is illustrated by way of example in the
accompanying drawings which form part of this application and
in which:
FIG. 1 is a schematic elevation of one possible embodi-
ment of a machine of the invention;
FIG. 2 is a schematic elevation of another embodiment
of a machine according to the invention; and
FIG. 3 is a fragmentary sectional elevation illustrating
the structure of paper manufactured with the machine of the
invention.
FIGS. 1 and 2 respectively illustrate paper machines
each of which has a twin-wire former means to which pulp stock
is supplied by way of a hydraulic headbox means lOa, in the case
of FIG. 1, and lOb in the case of FIG. 2, the twin-wire former
means of both embodiments including a smooth-surfaced forming
roll 13. In addition to the smooth-surfaced forming roll 13,
the twin-wire forming means of FIGS. 1 and 2 each includes a
pair of wires one of which is the outer wire 12, this wire 12 co-
operating with the wire lla in FIG. 1 and with the wire llb in
FIG. 2. The wire 12 is guided in both embodiments by way of
guide rolls 14 while in both embodiments the other wire of the
twin-wire former is guided by guide rolls 15. In both embodiments
there is a schematic illustration of the web W which is formed.
In order to achieve in the twin-wire former means of
FIG. 1 a draining region which is longer and more favorable than
those previously known, the twin-wire former means of FIG. 1 in-
cludes at the wire 12 an initial single-wire portion 20 situated
at a draining region, this portion 20 oE the wire 12 oE FIG. 1
extending from the breast roll 14a up to the point where the
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wires 12 and ]la of FrG. 1 start to travel along a common path
around the forming roll 13. This initial par~ 20 of the wire 12
of FIG. 1 where the web is carried only by one wire travels along
a forming board 21 situated within the loop of the wire 12,
this forming board 21 promoting the dewatering action in a well
known manner by foil action and/or suction. FIG. 1 schematically
shows connected to the headbox means lOa a suitable means 22
which serves to adjust the size and direction of the lip slice
of the headbox means lOa, for purposes which are well known.
At the sector ~ of the forming roll 13 where the web is compress-
ed between the pair of fabrics lla and 12, dewatering is carried
out primarily by the draining pressure produced by centrifugal
force (by kinetic energy). The guide rolls for the wire 12 in
FIG. 1 include the roll 14b which is arranged to be adjustable
in its location, as indicated by the double-headed arrow, so
that the vacuum at the upper tangetial point where the wire 12
departs from the forming roll 13 can be adjusted. This vacuum
adjustment is utilized to influence the detachmen-t of the web
of the web W from the wire 12, so that the web W will positively
continue to travel with the fabric lla of the twin-wire former
means. Such reliableweb transfer is only achieved by producing
a high enough dry matter content after the web-forming process,
and this result is achieved by way of the illustrated combina-
tion ~of the forming board 20 and the relatively small diameter
of the former roll 13.
In the embodiment of FIG. 2, the hydraulic headbox means
lOb has been arranged so that its lip slice is above the smooth-
surface forming roll 13, and as is illustrated in FIG. 2, the
rolls 14 which guide the wire 12 include the roll 14c which can
be adjusted as indicated by the double-headed arrow.
In both embodiments drying of the fabric takes place by
way of a Yankee cylinder 50 with which a hood 51 cooperates in a
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known way. This Yankee cylinder 50 ~orms part of a press-nip
means which includes the press suction roll 40 which defines the
single press nip Nl with the Yankee cylinder 50. In both embodi-
ments of the invention a fabric means extends between the twin-
wire former means and the prcss nip means wherc the nip Nl is
situated. This fabric means includes in both embodiments a
former portion which forms part of the twin-wire former means
and a transfer portion which transfers the web to the press nip
means to travel with the web through the nip Nl. In the case
of FIG. 2, the former portion and transfer portion form parts
of a single fabric, this being the fabric llb. However, in the
case of FIG. 1, this fabric means includes separate endless
fabrics lla and 32.
It will be seen that in the embodiment of FIG. 2 the
fabric means extending between the twin-wire former means and
the press-nip means is in the form of a single endless fabric
llb which at its left, as viewed in FIG. 2, has a portion forming
part of the twin-wire former means and participating in the
formation of the web and at its right has the transfer portion
which transfers the web fromthe twin-wire former means to the
press-nip means to travel through the nip Nl. The fabric means
llb of FIG. 2 has a mesh which will provide embossing of a
predetermined pattern in the web as the fabric means llb together
with the web travel through the nip Nl. Thus the fabric with
the mesh which provides the predetermined embossing pattern
also is utilized in the twin-wire former means in the embodiment
of FIG. 2. The former portion and transfer portion of the
fabric means llb of FIG. 2 are located one next to the other at
a jonction where the pick-up means 30b is situated, this pick-
up means 30b being in the form of a rotary suction pick~up roll.'rhus the pick-up means 30b assures that the web will be picked
up fro-m the wire 12 and delivered reliably to the transfer portion
of the fabric means llb at the l.ocation where this transfer
portion continues to travel forwardly to the right, as viewed
in FIG. 2, beyond the pick-up means 30b.
In the embodiment of FIG. 1, however, the fabric means
which extends between the twin-wire former means and the press
nip Nl formed by the press-nip means includes separate former
and transfer portions, the former portion of this fabric means
being formed by the endless fabric lla while the transfer portion
of the fabric means of FIG. 1 is formed by the separate endless
wire 32 which has a mesh which will provide embossing of a pre-
determined pattern in the web as the wire 32 travels together
with the web through the nip Nl. In FIG. 1 also the former
portion and transfer portion of the fabric means are situated
one next to the other at a junction where the pick-up means 30a
of FIG. 1 is situated, this pick-up means 30a of FIG. 1 being
in the form of a pick-up roll which assures that the web W will be
picked up from the former wire lla, which forms the former portion
of the fabric means, and delivered to the transfer portion
thereof whi.ch is formed by the embossing wire 32.
As is i.ndicated in FIG. 1, the web W which is transported
away from the forming roll 13 by way of the wire lla is detached
from the latter as a result of the effect of suction acting at
the suction zone 30 ~ of the suction roll 30a, with the web being
delivered to the underside of the pattern-embossing wire 32 or in
the alternative to an equivalent special felt provided for this
purpose. The web W continues to travel, while carried by the
fabric 32, to the first and only press nip Nl. In the case of
FIG. 2, the web W travelling downwardly beyond the forming roll
13 where it is sandwiched between the wires llb and 12, is
guided by way of the suction zone 30 ~ of the suction roll 3nb,
so as to be delivered to the underside of the pattern-embossing
wire llb, with the web W being transported to the press nip ~1
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shown in FIG. 2 at the underside of the wire llb.
As is indicated in FIGS. 1 and 2, the first and only
-actual press nip of the illustrated tissue paper machines,
namely the nip N1, is defined by a press suction roll 40 having
the suction zone 40 d~and the Yankee cylinder 50 which -Eorms part
of the drying section of the tissue paper machine. As was
indicated above, the Yankee cylinder 50 cooperates with a hood
51 in a known way.
As is indicated in FIGS. 1 and 2, an endless felt 42
laps the press suction roll 40, this felt 42 being guided by the
guide rolls 43. Thus between the transfer portion of the fabric
means, which provides the web with a predetermines pattern em-
bossed therein, and the press suction roll 40 there is the felt
42 which is acted upon by a reconditioning means which is not
illustrated. An important feature of the invention resides in
the fact that the pattern-embossing wire 32 or llb, which in and
of itself may be known, serves at the same time as a conveyor for
transporting the web in the closed conduction, which is to say
without any open draw, all the way up to and through the first
press nip N1 where the web W is embossed with the pattern of the
wire 32 or llb, for achieving in this way the eEfects desired by
the present invention.
With respect to the felt 42, instead of providing an
arrangement as shown in FIG. 1 where this felt laps only the
suction roll 40, the arrangement can be such that the felt 42
also laps the pick-up roll 30a. Moreover, in some cases the felt
42 may be entirely omitted, and in this event the suction roll
40 has an outer surface which is recessed to a large extent so
as to be open to a large extent, having the highest possible
fraction of its surface occupied by holes. For example in such
a case 72% of the outer surface of the rol] 40 may be occupied
by holes. In this latter event, the pressure which is applied
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131.~1Lf;~rj~:
at the nip Nl must be relatively light, at a maximum on the order
of 20kN/m line pressure. However, iE the felt 42 is used and
the suction roll 40 or another equiva]ent roll has a very open
surface, then large quantities of air will pass through the
web W, while the vacuum level remains minimal. The use of low
line pressures contributes to the preservation of the absorp-
tivity and porosity in the web W. On the other hand, a certain
minimum line pressure must be utilized at the nip Nl so that
the web W will reliably adhere to the surface of the Yankee
cylinder 50.
With the embodiment of FIG. 1, as well as with the em-
bodiment of FIG. 2, the pick-up means, formed by the rolls 30a
and 15 of FIG~ 1 and by the rolls 30b and 14d of FIG. 2 serves,
in addition to its inherent pick-up action, also as a dewatering
means. With this latter function in mind, the pick-up suction
rolls 30a, 30b have a;so surfaces which are relatively open,
which is to say surfaces formed with a relatively large number
of recesses. For example the outer surfaces of the pick-up
- rolls 30a, 30b may have openings or holes passing therethrough
which occupy approximately 72% of the entire outer roll shell
surface~ In this way as the web travels past the pick-up roll
it is traversed by large quantities of air, while the vacuum
levels remain relatively moderate. As a result it is possib]e
in th~e embodiment of FIG. 1, for example, to provide for the
web W a dry matter content immediately subsequent to the rolls
30a, 15 which is on the order of 25% and immediately subsequent
to the nip Nl a dry matter content on the order of 42-45%.
An important new feature of the present invention resides
in the manner in which the course of the pattern-embossing wire
32 or llb has been arranged. With the present invention the
pattern-embossing wire is understood to be fairly losse woven
wire having a mesh whose density is less than about 20 wi{es per
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cm. As is known, normal wires have a mesh density determined by
on the order of 28-31 wires per cm.
Also in accordance with the invention it is possible
to utilize as the fabric means which provides the embossed
pattern a pattern-embossing wire which has a "base" of a higher
density, for example a density equivalent to a normal wire,
while upon this latter "base" wire there is a pattern-embossing
fabric which has a lesser density, providing a relief pattern,
with this lesser density being on the order referred to above,
so that it is this mesh of lesser density which has its pattern
impressed on tlle web W.
When operating the tissue paper machine of the invention,
an attempt is made to avoid excessive pressing of the web, and
dewatering is carried out primarily by way suction and adhesion.
FIG. 1 illustrates a heating means 60, in a schematic
manner, this heating means 60 serving to heat the web W residing
on the wire lla, so as to promote in this way the dewatering at
the pick-up roll 30a and possibly also at the suctionroll 40.
The operation of the heating means 60 is based on steam supply
and/or infrared heating, for example.
Moreover, just before the web W reaches the press suction
roll 40, the water in the web is influenced by a means 61. This
water-influencing means 61 can take the form either of a de-
watering means and/or a heating means equivalent to the heating
means 60. The means 61 when influencing the water by dewatering
action may for example, be in the form of a planar perfusion
dryer. The purpose of the means 60 and 61 is to control the dry-
matter conten-t of the web W at the pattern-embossing stage so
that this dry-matter content will be appropriate for different
~issue paper brands.
FIG. 3 shows a cross section of a web lOn manufactured
with the machine of the invention, this web 100 being characte-
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rized by the pattern 101 which is impressed by the pattern-
embossing wire 32 or llb on one side only of the web 100. When
the tissue paper machine of the invention is utilized, the
paper web 100 which is produced thereby has a structure which is
characterized by absorptive, high-bulk areas 103 and areas 102
of greater density which impart mechanical strength to the web
100, these latter areas 102 of greater density being indicated
in FIG. 3 by heavier cross hatching than the other areas. The
areas 102 will be situated at the web 100 at those locations
where there wire 32 or llb has impressed the pattern 101.
As was indicated above, the inner felt 42 may be omitted,
and this is particularly the case when producing thin paper, for
example paper of less than 30 g/m base weight. As has been in-
dicated above, it is then necessary to utilize for the press roll
40 a roll which has an outer shell which is open to a very large
extent.
The tissue paper machine of the invention is characte-
rized, when relatively open suction rolls are utilized, as
described above, by economy of dewatering and furthemore by
simplicity of its construction.
Of course, the invention is not to be narrowly confimed
to the details presented above by way of example only, inasmuch
as these details may vary within the inventive concept defined
- by the claims which follow below.
