Note: Descriptions are shown in the official language in which they were submitted.
BACK~ROUND OF THE INVENTION
The present invention broadly relates to the paper-
making art and, more specifically, concerns a new and improved
construction of a double sieve or filter papermaking machine,
also referred to in the art as a twin-wire papermaking machine.
Generally speaking, the double sieve or twin-wire
papermaking machine is of the type comprising a dewatering
cylinder wherein along a portion of its circumference there is
wrapped thereabout a first inner wire or sieve band or belt
which, at least at the region of the dewatering cylinder, is
surrounded by a second wire or sieve band or belt. The second
wire or sieve band forms below the dewatering cylinder for-
wardly of such cylinder, viewed with respect to the direction
of movement of -the wires or sieve bands, a dewaterlng pa-th to
which there is infed the stoak suspension by a headboX. The
stock suspension serves for the fabrication o~ paper.
Such type of papermaking machine is generally known
to the art specifically from Figure 3 of United States Patent
No. 3,201,305.
~ith the prior art papermaking machine the dewatering
cylinder possesses a completely open surface through which there
can penetrate without hindrance the sieved or filtered water
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which is expressed out of the formed paper web into the in-
terior of the dewatering cylinder. However, it is unavoidable
that such penetrated water can impair the web formation at
other locations of the dewatering cylinder. On the other hand,
there is provided forwardly of the dewatering c~linder a de-
watering path which should be freely movable and at which
there should be augmented the dewatering action by a fluttering
of the wire of sieve band at such location. Because of difficul-
ties which have arisen with this prior art proposal of papermak-
ing machine, such seemingly advantageous type of papermakingmachine has not found any widespread use or acceptance in actual
practice.
SUMMARY OF THE INVENTION
Therefore, with the foregotny in mind it is a primary
object of the present invention to provide a new and imp~oved
construction of a double sieve or twin~wire paperrna]cing rnachine
with is not assoc:lated with the a~orementioned drawbacks and
limitations of the prior ar-t proposals.
Another and more specific object of the present
invention aims at providing a simple construction of papermaking
machine working in accordance with the aforementioned prior
art principle and which, however, is suitable for use in practical
applications, and which in particular possesses an increased
dewatering capacity, with lower energy xequirements, than
similar heretofore known papermaking machines~
Now in order to implement these and still further
.
objects of the inven-ti.on, which will become more readily
apparent as the description proceeds, the papermakiny machine
of the present development is manifested by the features that
the dewatering cylinder is constituted by a cylinder having
an open surface which is pervio~s to water. Below the sur-
face of the cylinder there is arranged in spaced relationship
therefrom a closed cylinder wall in a manner such that ~ -
between the pervious or foraminous surface and the cylinder
wall there is formed a receiving chamber for the sieved or
filtered water, and the dewatering path is equipped with at
least one dewatering device.
In this connection attention is directcd to Figure 1
of United States Patent ~o. 3,565,'~57 which dlsc:loses a double
sieve or twin-wire papermaking machine wherein a dewatering
cylinder is wrapped by two wires or ~elts in a similar fashion.
With this prior art machine the dewatering cylinder however is
constituted by a cylinder having a solid closed surface, so
that by virtue of thi.s design there only can be approximately
realized one-half of the dewatering capacity owing to the one-
sided dewatering action. Additionally, there is absent any
dewatering path forwardly of the cylinder, so that the dewatering
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capacity of the papermaking machine is still ~ur~her reduced.
Finally, in Figure 5 of United States Patent No.
4,209,360 there is disclosed to the art a double sieve or
twin-wire papermaking machine which utilizes a dewatering
cylinder having an open, outer surface which is formed by
a wire or sieve which is shrunk-fitted thereon. The wire
is supported upon circumferential grooves which form a re-
ceiving chamber for the expressed sieved or filtered water.
With this state-of-the-art papermaking machine there is
missing the pre-dewatering path, and also -the mannex of
guiding the wire differs in a most disadvantageous fashion
from the technique employed with the inventive papermaking
machine of this development.
Preferably, the dewa-tering cylinder can have arranyed
thereafter a wlre or sieve separation ro:L:L, at the swrfac~ o
which there is accomplished the separat:Lon of the outer sieve
band or wire from the inner sieve band or wire. This sieve or
wire separation roll is located internally of the inner wire
or sieve band. Through the use of this wire o$ sieve separation
roll there is obtained, in contrast to the papermaking machine
of the aforementioned United States Patent No. 3,201,305, an
additional path which can be equipped with dewatering devices,
such as for instance suction boxes. By virtue of the arrangement
of the wire separation roll within the inner sieve band or
wire there is obtained a low or compact structural height of
the PaPermakiny machine which, for reasons of cost for the
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s~
machine and the building and for the structural alteration
of longitudinal sieve or wire papermaking machines is favor-
able.
Finally, within the inner wire or sieve band there
can be arranged after the wire or sieve separation roll a
suction roll~ The inner wire or sieve band is provided with
additional dewatering devices between the wire or sieve separa-
tion roll and the suction roll. By virtue of these measures
the dewatering capacity of the papermaking machine can be
further augmented with modest energy requirements.
BRIEF DESCRIPTION OF THE DR~INGS
The invention will be better understood and objects
other than those set forth above, will become apparent when
consideration is given to the ~ollow:lng detailed descrlption
thereoE. Such description makes re:Ee:rence to the annexed
drawings wherein:
Figure 1 schematically illustrates an exemplary
embodiment of twin-wire or double sieve papermaking machine
according to the invention;
Figure 2 is a fragmentary sectional view of the
dewatering cylinder used in the arrangement of Figure 1 and
shown on an enlarged scalej and
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Fi.gure 3 ls, a parti.al front view o~ the sur~ace of
the dewatering cvlinder shown in the arrangement of Fiyure 2,
looking essentially in the direction of the arrow A thereof.
DETAILE~ DESCRIPTION OF THE PREFERRED EMBODIMENTS
Describing now the drawings, it is to be understood
that only enough of the construction of the twin-wire or
double sieve papermaking machine has been shown in the drawings,
while simplifying the illustration, as will enable those
skilled in the art to readily understand the underlying principles
and concep-ts of the present development. Turning attention now
to Figure 1 there is illustrated therein an exemplary embodiment
of papermaking machine which will be seen to contain a dewater-
ing cylinder 1 about which there is wrapped or trained along
a circumferential or peripheralangle ~ an inner wire or sieve
2. The inner wire or sieve 2 is guided over yuide rolls 3, a
wire or sieve separation roll ~ and a suctionroll 5. Between the
~ suction roll 5 and the guide roll 3 which is arranged after the
3", '` Y~ 99
suctionJs, viewed with respect to the direction of movement B
of the wire or sieve 2, there is arranged in known manner a
take-off or removal roll 6 containing a felt band 7 or equivalent
structure.
Additionally, the papermaking machine shown in Figure 1
is equipped with a second wire or sieve 101 the so-called outer
wire or sieve. This second wire 1.0, viewed with respect to its
v ~
direction of movernent B, forms a dewatering path or rwn E or~
wardly of the dewatering cylinder l. Following the location of
the dewatering path E this second wire or sieve 10 wraps in
conjunction with the inner wire ~r sieve 2 about the dewatering
cylinder l along a circumferential or peripheral angle a.
This second or outer wire or sieve 10 together wi-th the inner
wire sieve 2 extends conjointly up to the region of the wire
or sieve separation roll 4 where there is accomplished the
separation of both wires or sieves 2 and lO from one ano-ther.
For this purpose the outer wire or sieve 10 is guided over
guide rolls 11.
A conventionally constructed headbox 12 serves to
infeed the stock suspension needed for the paper fabrication
to the dewatering path E. This dewatering path or run ~., in
turn, is equipped wi-th a dewatering device 13 which contains
dewatering ledges or strips 1~, typically :Eor instance Eoils
or the like, or else can be constructed as a suction box. ~l.so,
suction boxes 15 and 16 o.r equivalent expedients can be arranged
between the dewatering cylinder 1 and the wire or sieve separa-
tion roll 4 as well as between the wire separation roll ~ andthe suction roll 5.
Additionally, and as will be seen by reverting -to
Figure l the twin-wire papermaking machine is also equipped
with catch or receiving contairers or vats 17 and 18 for
receiving the sieved or filtered water which has been expressed
out of the formed paper web through both of the wires 2 and 10
at the region of the dewatering cylinder 1.
This dewatering cylinder l, as best seen by referr-
ing to Figure 2, is provided with a closed f solid cylinder
wall 20 upon which there are arranged and secured in any
suitable fashion, according to one embodiment o~ the in-
vention, ribs 21 in the circumferential direction. Extend-
ing tranversally to the circumferential ribs 21 there are
arranged in axial direction transvers-ribs 22 upon which
there can be shrunk-fitted a wire or sieve 23 or the like.
To simplify the illustration such has only been shown in
Figure 2. This wire or sieve 23 forms the open surface 0
which is pervious for water and upon which there are supported
both of the wires or sieves 2 and 10.
Howevex, it should be clearly understood that it
is possible to dispense w:Lth the wse o~ the wire or sieve 23
and that also the dewatering cylinder l can be constructed in
a different similar Eashion. What is only of importance is
that between an outer cylinder surface 0, which is pervious
to the water, and the inner solid cylinder wall 20 there is
formed a receiving or collecting chamber 24 for the sieved
or filtered water.
During opera-tion, the papermaki~g machine of the
invention dewaters the fiber stock suspension which is infed
by the headbox 12 initially at the wire or sieve 10 at the
region of the dewatering path E by means of the dewatering
device 13. Thereafter, there ~s accomplished the dewatering
between both of the wires or sieves 2 and 10, and specifically,
essentially towards the ou-tside and also towards the inside,
and the inwardly expressed water arrives at the receiving
chamber 23 of the dewatering cylinder 1 and following raising
of both wires or sieves 2 and 10 from the dewatering cylinder
1 such removed water is deposi.ted into the catch or collecting
container 18. After such double-sided dewatering there is
accomplished a dewatering towards the other side, and specific-
ally, initially by the dewatering device 15 and following the
separation of -the wires or sieves 2 and 10 from one another
by the action of the wire separation roll 4 by means of the
dewatering devices 16.
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