Note: Descriptions are shown in the official language in which they were submitted.
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Vertical Former
The invention relates to a vertical former of a paper
machine, in particular for making wood-free printing paper
and liner board or test liner, comprising a twin-wire, the
two wires of which are moved together with the suspension
through an essentially vertical formation section, the
formation section consisting of at least two formation
zones in which a forming member is respectively arranged
which in the moving direction of the twin-wire are arranged
on alternative sides of the same consecutively in the
moving direction and act upon the one or the other wire.
Such a vertical former is known from US-A-9,790,909. In
this, after a forming roll curved suction boxes are
arranged lying consecutively on alternative sides in the
¦ moving direction, the one suction box lying against the one
! side of the twin-wire and the other suction box displaced
in the moving direction on the other side in order to
achieve a symmetrical de-watering and thus a symmetrical
sheet structure. ~owever, the de-watering occurs offset
timewise so that both lateral regions without a forming
member effect a different formation structure.
Additionally, the wires are not guided over longer
stretches which leads to a wave formation of the wires over
the web width and to streaked paper.
The patent FI843,081 discloses a vertical former in which a
suction former is arranged directly over a vacuum shoe with
a certain radius and opposite pressing rails. A further
suction box is arranged behind the first mentioned box in
the moving direction. Thus, an unequilateral distribution
of the de-watering quantities ensues and an asymmetrical
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web structure results. On account of the radius of the
vacuum shoe and the engagement of the rigid rails in direct
succession a very strong initial de-watering results which
leads to crushing in the web.
It is an object of the invention to provide a vertical
former of the type initially mentioned in which an improved
formation can be achieved in connection with an improved
web strength and in particular an even web structure
without streak formation .
This object is solved in accordance with the invention in
that with regard to the one for~ing members, other forming
members are arranged on the respective opposite side of the
twin-wire equally on alternative sides and consecutively in
the moving direction which guide and support the wires.
Usefully, an open former roll is connected at the inlet
side of the formation route. However, an open former roll
can also be connected at the outlet side of the formation
route. These former rolls are preferably suction rolls.
.
It is also possible to provide a vacuumed, slotted suction
device ahead of the first forming member.
On account of the inventive solution, an improved formation
can be achieved in connection with an improved web
structure and in connection with a smoother web structure
and smoothness at the surface. The formation according to
the invention is also particularly well suited for web
weights > 80 g/m2. Additionally, the device according to
the invention can be used in connection with a multi-
- layered head box with well-directed collection of the
screened water. Finally, an improved retention of the
fibers during the de-watering process is possible.
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Usefully, the one and the other forming members are
arranged on different sides of the twin-wire respectively
opposing one another.
With regard to a further improvement, the one forming
members can be suction boxes with a formation shoe (mesh)
and the other forming elements pressing rails.
Usefully, the suction boxes can have one, two or more
suction zones. ~n an advantageous embodiment (Fig. 5) the
water dams up in the suction box sections and the vacuum
acts above the water surface. In this case, the vacuum can
be of different magnitude in the different suction zones.
If one views the course of vacuum within a section of the
suction box along a stretch perpendicular to the de-
watering rails, the vacuum is then the greatest at the top
on account of the dammed up water and reduces from the top
to the bottom as seen against the moving direction of the
twin-wire. This effect is very advantageous, as the de-
watering effect can thus be dosed in such a manner that
initially, where the suspension is still de-watered less,
the applied vacuum is smaller. On account of this, the
formation is advantageously influenced. A continuous
development of the vacuum can also be achieved for the
finite division of the suction box.
Usefully, the rearward formation zones in the moving
direction of the twin-wire can be longer than the forward
formation zones. This leads to a particularly gentle
formation, in particular then if the formation shoe of the
most forward suction box in the moving direction of the
twin-wire is usefully not curved, i.e. essentially
straight. Thus, the web is treated gently in the first
phase of the formation and the de-watering.
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A further optimization possibility results if the forming
rails can be pressed elastically against the twin-wire.
On account of the arrangement on alternative sides of
different forming members in several stages, it is possible
to avoid asymmetrical blank sides, which has a positive
influence on an even and gently acting formation.
Further advantageous embodiments can be taken from the
dependent claims.
The invention is described in the following in more detail
with respect to purely schematically depicted embodiments
in the drawings, in which:
Fig. 1 shows a schematic complete side view of a
vertical former with an essentially straight
formation route,
Fig. 2 shows the formation section alone,
Fig. ~ equally shows the formation section alone, but
with a curved formation route,
Fig. 4 equally shows the formation section alone with
an oppositely curved formation route in
comparison to Fig. 3, the formation route being
straight in the first formation zone thereof,
Fig. 5 schematically shows a two-staged suction box,
Fig. 6 schematically shows a three-staged suction box
with a different water removal, and
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Fig~ 7 schematically shows a vacuumed, slotted suction
device.
The vertical former as schematically depicted in Fig. 1
comprises two wires Sl and S2 which converge as a twin-wire
in the region of a nozzle 10 feeding the suspension. This
twin-wire passes through a formation route or a formation
section 12. At the outlet side of this formation route,
the twin-wire DS is guided about a forming roll 14.
Following this forming roll 14, the wire Sl is led about a
deflection roll 16 or at the inlet about a closed breast
roll 14'. This forming roll 1~ is an open forming roll.
After the forming roll 14, the wire S2 is respectively led
about deflection rolls 16' and 16", the wires Sl and S2
converging as the twin-wire DS between the pressed roll 14'
and the deflection roll 16". The nozzle 10 is directed in-
to the converging gap in order to lead the watery
suspension into the roll gap where a first de-watering
occurs.
The formation route 12 or the formation section 12 is
divided into two zones, namely a first forming zone Zl and
a second forming zone Z2, the travel of the twin-wire DS
ensuing essentially vertically with a maximum inclination
of 30 to the vertical. Preferably, the first formation
zone Zl is shorter than the second formation zone Z2.
Naturally, several successive zones can also be provided~
It is important that in each zone a respective forming
member is arranged opposite another on the opposite ends of
the twin-wire DS, namely pressing rails 18 in the first
formation zone Zl on the right hand side which can
preferabIy be pressed elastically and possibly elastically
adjustable against the twin-wire or the wire S2 in the
region of the twin-wire DS in order to lead off the water
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removed via a removing box 18~. On the opposing side, a
suction box 19 with a formation shoe 19' is located lying
against the wire Sl, the formation shoe consisting of a
mesh-like structure comprising rails continuous across the
width and slots, as is known in principle.
In the second formation zone Z2 on the same side, like the
suction box 19, pressing rails 20 are located comprising a
water removal box 20'. On the opposing side, a suction box
21 comprising a formation shoe 21' lies against the wire
S2. This means that a forming member is arranged in each
formation stage Zl and Z2 on both sides of the twin-wire
DS, the opposing forming members being different forming
members in the form of pressing rails on the one hand and
suction boxes on the other hand which, however, are
arranged on alternative sides in the moving direction of
the twin-wire DS. In Fig. 1, the formation shoes 19', 21'
are straight. The formation route 12 also proceeds in a
straight manner between the forming rolls 14' and 14.
In Fig. 2, the forming route or the formation section 12 is
drawn in detail. A difference comprises in that the nozzle
10 guides the suspension from bottom left to top right at
an angle into the gap between the rolls 19 and 16", which
results in the initial de-watering process being influenced
in an amended form. The suction box 19 is sinsle-staged
here comprising a deflection member 19" and the suction box
21 is two-staged comprising a deflection member 21"~ A
clearer depiction of this two-staged suction box 21
comprising the water collector 22 can be seen more clearly
in Fig. 5 of the appended drawings.
In Figs. 3 and 4, one twin-wire progression in the
formation section 12 is shown respectively curved to the
left or to the right, although the formation shoe 19' in
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the first formation stage Zl is preferably straight in
order to be able to conduct a more gentle de-watering in
the first stage. However, it is also possible to embody
the formation shoe 21~ in the second zone Z2 to be equally
straight, both formation stages Zl and Z2 thus being
arranged slightly inclined at an angle to one another. In
both cases the nozzle 10 is directed in such a manner that
it directs the suspension from bottom right to top left in-
to the gap where the wires Sl and S2 converge into the
twin-wire DS. In this case the wire S2 is led about the
open forming roll 14`.
In Fig. 6 a three-staged suction box 26 is shown, namely
with a formation shoe 26' which is straight in this case.
The twin-wire progression is shown by means of an arrow
27. It can be seen from the water levels in the de-
watering water discharge 28 that a higher vacuum exists in
the uppermost section 29 than in the section 30 lying
therebeneath and the section 31 lying even further below
this. This means that the suction pressure in the suction
box sections increases from the bottom to the top in
accordance with the direction of movement 27, this also
having a positive influence on the gentle de-watering with
regard to an improved formation under the consideration of
the desired web strength and in particular an even web
structure.
It should be noted that in accordance with the depiction in
Fig. 2, 3 and 4, troughs 13 are provided for collecting the
water withdrawn by the forming breast roller 14~
Fig. 7 shows an embodiment of a vacuumed, slotted suction
device arranged ahead of an arrangement of pressing rails
34 which are movable essentially vertical to the wire S in
accordance with the arrow 36 in order to change the
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pressing force of the rails. The slotted suction device 32
consists of an inlet part 40 equally movable essentially
vertically to the wire S in accordance with the arrow 38,
the inlet part forming a gap 44 preferably converging to-
wards the wire S in the direction of the arrow 42. In this
region, a very advantageous pre-dewatering results through
the slot 46 under the influence of a vacuum effective in
the space 48. Preferably, the slot 46 extends essentially
horizontally in a first section after the gap 44 and then
essentially vertically and subsequently arrives in a
collecting container 50. A collecting container 52 serves
to take up via a collecting plate 60 the water withdrawn in
the region of the pressing rails 34.
In Fig. 4, a suction box 62 for subdividing is provided
after the open forming roll 14 under the wire S2.
