Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1
Method and device in the forming of a lead-in strip
in a paperboard machine
The invention concerns a method and a device in the forming of a lead-in strip
in a
paperboard machine.
In prior-art solutions, a narrow strip is cut from the edge of the web, which
strip is
blown or transferred by means of other devices into the rope track running
alongside
the web in between the two ropes provided in said track. The rope track guides
the
web further through the machine, after which, in said cutting position, the
web R
can be widened to its original web width.
In a prior-art device, in particular in connection with coating stations, it
has been a
problem that, by the effect of air flows and partly also by the effect of
spreader
rolls, the lead-in strip tends to get out of the machine and collides, e. g .
, against the
rope draw devices. Said phenomenon, of course, increases the time of threading
and
lowers the efficiency of the paper machine.
Various double cutters are known in connection with handling of a paperboard
web.
Solutions of said sort are, for example, the following:
From WO 92/06913 and from US S, 360,179 it is known to use water cutting at a
reel-up for cutting the web and for forming a new end during a change of reel.
In particular WO 92/06913 instructs that the cutting be started in the middle
of the
~ web. As further prior-art publications can be stated EPO 067, 051, WO 91
/03359 and
US 5) 234, 544.
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In the present patent application, it is suggested that a method of formation
of a lead-
in strip is used in which a double cutter is used, which comprises two cutters
either
in the same position or in different positions. At least one of the cutters,
which starts
the cutting from outside the web, is a liquid cutter. In the commonest
embodiment
of the invention, the first cutter can also be a cutter other than a liquid
cutter.
Preferably both cutters are liquid cutters, most appropriately water cutters.
In the
method in accordance with the invention, by means of the first cutter C 1,
first a
lead-in strip A is formed. After that a second cut is performed by means of
the
second cutter C2 at the side of said first cut, whereby an edge strip or edge
band B
is formed, preferably so that said second cutting f2 is started from the side
of the
paperboard web W. When the cutting is performed in said way, the tip of the
edge
band B is formed sharp and thereby, further, the lead-in strip A proper
becomes
continuous, with no step, and thereby the risk of its being broken is avoided.
Said
edge band B can be passed into the pulper at a suitable location. After this,
the lead-
in strip A proper is spread, by means of the two cutters, preferably water
cutters,
towards the middle of the machine width, after which, or before said stage,
spread
ing of the lead-in strip A to 1000...2000 mm is carried out. The spreading of
the
web to its ultimate width takes place by passing the cutters, preferably water
cutters,
out from opposite edges of the web at both sides of the machine-direction
centre line
X of the web W .
Double cutting can be applied to threading in a paper machine in locations in
which
the lead-in strip cut from the edge of the web can be shifted so that it runs
substan-
tially closer to the middle or in the middle of the machine. Such locations
are, for
example, threading from a forward dryer through a sizer / size press to an
after-
dryer and further through the after-dryer as well as threading from a cylinder
dryer
or equivalent through a coating machine.
In the concept and solution of equipment in accordance with the invention, the
cutters can be placed on the same beam and, thus, in the same position, or
fully
separate from one another. In such a case, the first cutter C l , which
performs the
first cut f 1 into the web, can be placed in the initial end of the dryer
section, and the
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second cutter C2, which performs the second cut f2 into the web, can be placed
in
the final end of the dryer section below the last drying cylinder, in which
case the
sharp tip that has been formed into the edge band B can be passed directly
from the
drying cylinder, by means of guides/doctors placed in its connection, into the
pulper
placed below the cylinder.
When a liquid cutter, preferably a water cutter, is used, the range of
pressure of the
liquid, preferably water, is 50...300 bars. It can be considered to be an
advantage of
water cutting that the web can be cut against the wire H. In such a case,
cutting of
the web is possible in a dryer section with single-wire draw in cylinder gaps,
for
example, in a position below the last cylinder.
Within the scope of the invention, an embodiment is possible in which the
paperboard machine comprises a number of water cutters, for example, in
different
dryer sections so that each water cutter comprises a first set of
independently
controllable cutting water-cut nozzle devices and a second set of
independently
controllable water-cut nozzle devices.
Within the scope of the invention, an embodiment is also possible in which
said first
cutting nozzle devices are placed in different positions, for example, so that
the first
cutting nozzle devices are placed in the beginning of the dryer section on the
draw
between the first V ac Roll and the drying cylinder K 1, and the second
cutting nozzle
devices are placed in the end of the dryer section below the drying cylinder
Kn on
the web/wire draw between the drying cylinder Kn and the Vac Roll Sn. If the
cutting nozzle that performs the second cutting is placed in the dryer section
in
connection with the last drying cylinder Kn below said cylinder and if the
cutting is
started by means of said second nozzle from the edge of the web, it is an
advantage
obtained from said position that the sharp-tip edge band B can be passed
directly
~ from the last drying cylinder Kn into the pulper placed below said cylinder.
In the way described above, a double cutter preferably comprises two sets of
cutter
nozzles. They are fitted so that their movements are synchronized with each
other in
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such a way that, when the so-called sharp-tip edge strip is being cut by means
of one
set of nozzles, the other set of nozzles is displaced at the same time in the
cross
direction towards the middle of the web, and the lead-in strip A proper is
made
wider. By means of the method and the solution of equipment in accordance with
the
invention, when the second cutter nozzle is brought from outside the web and
when
the supply of the cutting liquid is started from the area outside the web, a
sharp tip
is formed for the edge strip and, thus, the lead-in strip A proper is given a
continu-
ous shape with no steps. Said sharp tip can be controlled well, and it can be
passed
readily into the pulper after the cylinder. In such a case, since no notches
and no so-
called tail are present on the lead-in strip A proper, thereby the risk of
breaking off
arising from said points of discontinuity has been avoided. When liquid
cutting in
accordance with the invention is used, cutting against the wire is permitted.
This is
a significant advantage, because the cutter equipment can be placed in an
optimal
position on the wire and web draw. Thus, besides against the wire, the cutting
can
also take place against the wire and a cylinder.
In the commonest embodiment of the method in accordance with the invention,
both
the first cutter C 1 and the second cutter C2 can be placed either in
connection with
one another in the same position in the dryer section, or said cutters C 1 and
C2 can
be placed in different positions, in which case, in relation to the running
direction of
the web, the first cutter performs the first cutting in an earlier position,
as viewed
in the running direction of the wire. The second cutter CZ carries out the
forming of
the sharp-tip edge band B and, thus, of the lead-in strip A proper with no
points of
discontinuity in a position placed later, as viewed in the running direction
of the web
and the wire, for example between the last suction roll and the last drying
cylinder.
In such a case, the sharp-tip edge band B rises without separate auxiliary
conveyor
means along with the wire over the drying cylinder and is transferred into the
pulper
placed underneath after the drying cylinder, and in connection with said
cutting the
lead-in strip A is formed so that its edge becomes continuous. The lead-in
strip A
does not include notches, tails or any other detrimental points of
discontinuity.
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The method and the device in accordance with the invention are characterized
in
what is stated in the patent .claims.
The invention will be described in the following with reference to some
preferred
5 embodiments of the invention illustrated in the figures in the accompanying
draw-
ings, the invention being, however, not supposed to be confined to said
embodiments
alone.
Figures 1 A. . .1 D illustrate the forming of a lead-in strip carried out by
means of
double water cutting step by step.
Figure lE illustrates a prior-art method.
Figure 1 F illustrates the method in accordance with the present invention.
Figures 2A...2D illustrate alternative positions of the double cutter in
accordance
with the invention both in a single-wire group of drying cylinders and in a
twin-wire
group of drying cylinders.
Figure 3 shows a double cutter in which the cutting nozzles are placed at
opposite
sides of a beam frame on guides of their own.
Figure 4A shows a second embodiment of a double cutter, in which both of the
cutting nozzles are placed on the same guides on sledges of their own.
Figure 4B is an illustration of principle of the solution as shown in Fig. 4A.
Figure 4C is an axonometric view illustrating the device as shown in Fig. 4A.
Figs. lA...lD illustrate the different steps of cutting the lead-in strip. In
the com-
monest embodiment of the invention, a double cutter 10 is spoken of, which com-
prises the cutters C 1 and C2 in general, of which at least the second cutter
C2, which
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is brought from outside the web, is a liquid cutter and most appropriately a
water
cutter. Said second cutter C2 already starts the cutting outside the web. The
cutter
C2 is preferably a cutter nozzle, through which a liquid jet U2, preferably a
water '
jet, is applied with pressure to the face of the web W to be cut. The cutter C
1 is
S preferably also a liquid cutter and most appropriately a water cutter. In
such a case,
the cutter C 1 is a nozzle, through which a liquid jet U 1, preferably a water
jet, is
applied with pressure to the face of the web W to be cut.
Fig. lA shows the first step in the formation of the lead-in strip. The first
cutter jet
C 1 performs the first cut f 1. The high-pressure liquid jet U 1 is applied to
the face of
the web W. The lead-in strip A is blown to the rope draw.
Fig. 1B shows the forming of the second cut f2. In accordance with the
invention,
the cutting jet, preferably a water jet U2, of the second cutter nozzle C2 is
brought
from the side from outside the web W, in which connection a sharp tip 100 is
formed for the edge band B. In the embodiment shown in Fig. 1B, both the web
A'
adjacent to the lead-in strip A and the edge band B are passed directly from
the roll
tl into the pulper. To the edge band B, a sharp tip 100 is formed, and in such
a
case, in the lead-in strip A proper, there are no points of discontinuity
which might
constitute a risk of breaking of said strip.
In Fig. 1C, the lead-in strip is shifted to the middle of the web by
displacing the two
cutter nozzles C1,C2 to the middle of the web width.
Fig. 1D shows a stage in which the spreading of the lead-in strip A to full
web
width is carried out.
Fig. lE shows an old, prior-art method, in which the cut f2 starts from the
vicinity
of the edge and the edge band B is cut off mechanically at the point G. In the
band
A, a notch and a tail remain, which constitute a potential risk of a break.
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Fig. 1F illustrates a method solution in accordance with the invention, in
which the
cut f2 is started from outside the edge and the band A will have no notch or
tail
" which might constitute a risk of a break. On the band B that is passed into
the
pulper, a sharp tip 100 is formed, and in such a case no detrimental points of
discontinuity are formed in the lead-in strip A.
Fig. 2A shows alternative positions Bl,B2,B3 of the double cutters 10a1 in
accord-
ance with the invention in a dryer section with single-wire draw in a
paperboard
machine. The dryer section comprises drying cylinders K1,K2... and suction
cylinders S 1, S2. . . placed below them. The drying cylinders K 1,K2. . . are
preferably
steam-heated cylinders, and the suction cylinders Sl,S2..., preferably so-
called Vac
Rolls, are cylinder constructions which comprise grooves on their face and
holes
opening into said grooves through the roll mantle from the interior of the
cylinder.
A vacuum is applied to the interior of the cylinders, and the web is kept in
contact
with the wire H face by means of the vacuum. The wire H and the web W run as
meandering in loop shape from a drying cylinder onto a suction cylinder and
from
a suction cylinder onto a drying cylinder and further in the group of drying
cylin-
ders.
In the embodiment shown in Fig. 2A, the double cutter 10a1, which comprises
two
cutter nozzles C 1 and C2, is placed in alternative positions B 1, B2 and B3 .
The
position B 1 is placed in connection with the last drying cylinder K3 of the
last dryer
group Rn on the web/wire draw between the drying cylinder K3 and the suction
cylinder Sg . The position B2 is in a corresponding position in the middle
area of the
dryer group, and the position B3 is placed in the initial end of the dryer
group.
Fig. 2B shows the position B4, in which the liquid cutter 10a2 that comprises
two
cutter nozzles C 1 and C2 is placed in the initial end of the dryer section on
the
web/wire draw between the first drying cylinder K 1 and the first suction
cylinder S I
in the dryer group Rn.
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Fig. 2C shows the position BS of the double cutter 10a3 in accordance with the
invention in a twin-wire dryer group on the web draw between the last drying
cylinder KS and the lower drying cylinder K4.
Fig. 2D shows an embodiment of the invention in a group of drying cylinders,
in
which the first cutter C 1, preferably a cutter nozzle, of the double cutter
10a4 is
placed in the position B6 in the beginning of the dryer group, and in which
the
second cutter C2, preferably a cutter nozzle, of said double cutter 10a4 is
placed in
the position B~ in the end of the dryer group below the last drying cylinder
K3 of the
group. The run of the lead-in strip A and of the edge band B can be supported
by
blowing of air (ip) in the embodiments shown in this and in the preceding
figures.
Fig. 3 shows a double cutter 10, which comprises a carrier and support beam 11
passing across the web and guides 12a 1, I2a2 placed at both sides of said
beam, on
which guides the sledges that comprise the cutter nozzles are placed. The
sledge
13a1 is placed on the guide 12a1, and the other sledge 13a2 is placed on the
guide
12a2. The sledges 13a1 and 13a2 are displaced by means of a belt device, chain
device or equivalent 14a1,14a2, which are engaged with the sledges 13a1 and
13a2.
Motors are fitted to operate said belt or chain devices.
Since, as is shown in the figure, the equipment comprises an arm 15 passed
from the
second sledge 13a2 to the other side of the support beam 11 and since the
second
cutter nozzle C2 is fitted at the end of said arm 11, the cutter nozzles C1
and C2 are
placed at the same side of the beam 11.
Thus, as is shown in the figure, the guides 12a1,12a2 are placed at opposite
sides of
the support beam 11 extending across the machine width. In this way a
sufficient
space is provided for the guide constructions and for the chain drives of the
related
sledges l3ai and 13a2. The figure does not show the drive gear connected with
the
chains, such as a motor. The chain drive can be such that, by means of the
motor,
through its output shaft, a drive pulley is rotated, which is placed at the
end of the
output shaft of the motor and which operates the closed cogged chain. The end
of
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the cogged chain is connected with a reversing pulley, which is mounted on the
beam 11. Each chain thus operated is connected with a sledge, in which
connection
the cutter nozzle C1,C2 connected with the sledge can be controlled in the
desired
way.
Fig. 4A shows an embodiment of a double cutter 10 in which both of the cutter
nozzles C 1 and C2 are placed on the same guide on sledges 13a 1,13a2 of their
own.
The chain devices 14a1 and 14a2 are coupled with their sledges 13a1 and 13a2
independently . The cutter nozzle C 1 is placed on the sledge 12a 1 and the
cutter
nozzle C2 on the sledge 13x2. Through the cutter nozzles C 1, C2 a pressurized
water
jet is applied to the face of the web W. The pressure range is 50...300 bars.
Fig. 4B shows one mode of controlling a sledge 13a1 fitted on a guide 12a1 by
means of a chain device 14a 1, which sledge includes one of the cutter
nozzles, the
cutter nozzle C 1. On its output shaft 21 the motor 20 comprises a drive
pulley 22,
around which a belt, chain 23 or equivalent is passed. The belt, chain 23 or
equival-
ent is an endless drive loop, which is passed, at the opposite end, around a
drive
pulley 24 fitted revolving on the beam 11. Said drive belt 23 or equivalent is
further
coupled with a sledge 13a 1. The sledge 13a 1 is guided along the guide 12a 1.
Fig. 4C is a schematic illustration of sledges 13a1 and 13a2 mounted on the
guides
12a3. The control of the sledges is carried out in a way similar to that
described in
relation to Fig. 4B. Thus, the chain devices 14a1 and 14a2 may have drive
motors
20 and 200 of their own.
In the embodiment of Fig. 4C, the nozzles C1 and C2 are placed on the sledges
13a1
and 13x2, which are mounted on the same guide 12a3. However, the cuts fl and
f2
performed by said nozzles can overlap and even cross each other. This has been
achieved so that on their sledges l3af and 13a2 the nozzles C1 and C2 have
been
bent/inclined towards each other.
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In the embodiment with two guides in Fig. 3, a crosswise arrangement of the
cuts
f 1 and f2 has been permitted by the fact that the sledges 13a 1 and 13 a2 are
placed on
different guides l2al and 12a2.
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