Note: Descriptions are shown in the official language in which they were submitted.
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Filter tow strip, filter rod machine, method for producing
filter tow strips and method for producing filter rods
The present invention relates to a filter tow strip with the
features of the preamble of claim 1, a filter rod machine, a
method for producing a filter tow strip and a method for
producing filter rods.
A filter tow strip of the type mentioned at the outset is
known, for example, from EP 0 629 722 Al, which goes back to
the Applicant.
To produce cigarettes, filters are used, which are
manufactured from a band or a continuous strand of crimped
cellulose acetate fibres, the so-called filter tow. During
the production of filter tow, spun filaments of cellulose
acetate are crimped in a stuffer box, the impressed crimping
structure being fixed while passing through a dryer. Once the
filter tow has been brought to a constant final moisture, it
is loosely inserted in regular patterns in a plurality of
metre-high cans. The loose tow layer is then compressed in
bale presses to form a filter tow bale and finally packaged,
the bale then being provided for further processing into
filters.
A detailed description of the production process of filter tow
is published in the essay CA Filter Tow fur Cigarette Filter
(CA filter tow for cigarette filters), Paul Rustemeyer,
Macromolecular Syaposia 208 (2004), 267 - 291.
Filter tow is processed into filter rods on a filter rod
machine, on which the filter tow is bulked up as much as
possible in a preparation part in order to develop its maximum
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illina force and is then gathered tocether to the format of
the future cigarette filter and covered with paper. To bulk
Up the filter tow, the latter 's drawn apart by means of
compressed air-operated expander nozzles and drawn by a system
of drawing rollers with thread or screw surfaces. Thereafter,
the expanded filter tow is fed to a triacetin spray box, in
that the acetate surface has solvent applied to it and is made
tacky. In the formatting part of the filter rod machine, the
filter tow band is gathered together and compressed to the
cross section of the future filter rod. In this case, the
filaments stick together and form a three-dimensional spatial
network structure with the filter hardness desired for further
processing and for the consumer.
To increase productivity, it is known, for example, from DE 43
20 317, which also goes back to the Applicant, to produce
filter rods on double filter rod machines, in which two filter
tow strands are processed in parallel and synchronously. In
order to achieve the same properties in the two strands, EP 0
629 722 Al mentioned at the outset describes the use of a
multiple width Filter tow strip which has a desired tearing
line. The filter tow strip can be separated along the desired
tearing line into individual strips each with the same overall
titre. Eecause of the defined separating capacity of the
total or double strip into two individual strips, the double
width filter tow strip is also called twin tow. To separate
the multiple width filter tow strip, it is disclosed in EP 0
629 722 Al that the strip is loaded with an extension force in
the longitudinal direction, which leads to the fact that the
scrip is sseparated into two or more parts.
for problem-free production and quality of the filter rods
which remains the same, it is important for the separation of
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-he multiple width filter tow strip to take place as uniformly
as possible and for the partial so_Vands to run into the double
rod machine as uniformly as possible.
The invention is based on the object of disclosing a filter
tow strip, in particular twin tow made of cross-linked and
crimped filaments, which allows problem-free processing as far
as possible on a filter rod machine, in particular on a double
filter rod machine, in which the separation of the filter tow
strip is to take place as uniformly as possible for continuous
production. The invention is further based on the object of
disclosing a filter rod machine, in particular a double filter
rod machine, with which the filter tow strip can be separated
without resistance as far as possible, and a method for
producing a filter tow strip, in particular a twin tow, and a
method for producing filter rods.
According to the invention, this object is achieved with
regard to the filter tow strip, by the subject of claim 1,
with regard to the filter rod machine, by the subject of claim
7 and with regard to the method, by the subject of claim 13
and the subject of claim 19.
The invention has the advantage that the separating of the
filter tow strip according to the invention is achieved
substantially without problems even in rapidly running
processes. Tension fluctuations and therefore quality
fluctuations of the filter rods are effectively avoided by the
uniform binding force of the filter tow halves along the twin
tow. In contrast to E? 0 629 722 Al, which only discloses the
longitudinal tearing force of the filter tow strip, the filter
tow strip according to the invention is defined by the maximum
cross-separating force, which does not exceed 20 old,
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specifically on a length of about 20 cm. This has the
advantage that the separating properties of the strip can be
adjusted much more precisely than in the strip according to EP
0 629 722 Al, so the separating behaviour of the strip is
improved.
The division of the filter tow strip into two individual
filter tow strips before the spreader nozzle or before the
spreader nozzles of the filter rod machine according to the
invention, makes it possible to change without problems -
depending on the filter tow material available - between a
twin tow bale, i.e. a bale with filter tow according to the
invention and, if necessary, two bales with standard filter
tow.
Preferred embodiments of the invention are disclosed in the
sub-claims.
The invention will be described more closely below with
further details with the aid of embodiments with reference to
the accompanying schematic drawings, in which:
a f
Fig. 1 shows a schematic cross section through a
filter tow strip according to an embodiment of the invention,
which is clamped in clamping jaws to measure the cross-
separating force;
Fig. 2a - 2f show sectional views of filter tow strips
according to various embodiments of the invention, in which
the connecting region between the partial strips is
differently arranged; and
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Fig. 3a, b, c :how schematic views of a detail of a double
fi!Eer cod machine according to embodiments of the invention
in the region of the separating mechanism.
An example according to the invention of a filter tow strip 10
is shown in Fig. 1, the filter tow strip 10 shown being a
double width filter tow strip, i.e. a so-called twin tow made
of cross-linked and crimped filaments. The filter tow strip
comprises two partial strips 12a, 12b, which are connected
b_v a region of reduced cross-linking density 11. The
filaments 13, which connect the two partial strips 12a, 12b in
the region of reduced cross-linking density 11, are
interlooked and/or interlocked in such a wav that the
connecting filaments 13 form intersections 14.
The invention is not restricted here to filter tow strips 10
with two partial strips, but in general comprises multiple
width filter tow strips with a plurality of partial strips,
for example three or four partial strips, which are
correspondingly connected to one another.
0 d
The filter tow strip 10 according to Fig. 1 is clamped between
two clamping jaws A of a measuring mechanism, which are moved
so far apart that the two partial strips 12a, 12b of the
filter tow strip or of the twin tow and the connecting region
11 located in between with a reduced cross-linking density can
be seen. Instead of the clamping jaws A, clam cleats can be
used, in particular for measuring in the case of partial
strips arranged one above the other.
The connecting region 11 is configured in such a way that the
maximum cross-se ratin fG-rce ch is e
era g , =~hi r GL.ired to separate
-tile partial str' ps, does net exceed 20 cN on a length of about
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20 cm. In this case, the maximum cross-separating force
corresponds to the force perpendicular to the longitudinal
extent of the filter tow strip 10, which occurs at a
continuous extension, i.e. with a continuous moving apart of
the clamping jaws A, shortly before the cross-separating force
reduces again and the partial strips are completely separated.
The maximum cross-separating force may be less than 20 cN, for
example 15 cN, 10 cN, 7 cN, 5 cN, 4 cN, 3 cN, 2 cN or 1 cN.
In this case, the maximum cross-separating force may be in a
range of 0.5 cN to less than 20 cN, it being possible to
combine the lower limit of 0.5 cN with the aforementioned
upper limits. Further possible lower limits are 1 cN, 1.5 cN,
2 cN, 2.5 cN.
As an alternative or in addition to the maximum cross-
separating force, the separating behaviour of the filter tow
strip 10 may be determined by the number of binding filaments
13 in the connecting region 11 between the two partial strips
12a, 12b. The detecting of the connecting filaments 13 takes
place at the maximum of the cross-separating force, i.e.
shortly before the complete separating of the two partial
strips 12a, 12b, as shown in Fig. 1. During the separating of
the two partial strips 12a, 12b, or of the halves, the binding
filaments 13 are partly torn and/or unlocked, the still
intersecting or connected filaments being detected shortly
before the complete separation, i.e. at the cross-separating
force maximum, to determine the separating behaviour.
To determine the number of binding filaments 13, the connected
or intersecting filaments of the respective partial strips
12a, 12b are in each case regarded as one filament. This
means, that the number of binding filaments 13 substantially
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corresponds to the number of intersections 14. In the
embodiment according to Fia. 1, the connection designated I at
the right-hand end of the clamping jaws A comprises two
interlooped filaments 13, which are regarded as one filament
to determine the number of binding filaments 13 and have one
intersection 14. The same applies to the connection II, in
which two filaments 13 are locked, and form an intersection
14. At the connection III, four filaments 13 are connected to
one another and form two intersections 14. The connection III
therefore comprises two binding filaments 13. This means that
when loading with the maximum cross-separating force, at most
200 intersections are provided on a length of 20 cm. The
lower limit of the number of intersections on a length of 20
cm may be 1 intersection. 2, 3, 4, 5, 6, 7, 8, 9, 10
intersections are also possible as the lower limit.
Depending on the production method, the filaments 13 may
either only be looped, i.e. the individual filaments 13 form
stitches or loops, which engage in one another and form a
connection. The filaments 13 may also only be locked, at
least one filament 13 of a connecting filament pair forming a
free end and engaging in a stitch or loop or in a further
filament hook. Furthermore, a combination of looped and
locked filaments 13 is also possible. In this case, the
connecting filaments 13 form intersections 14, i.e. opposing
filaments of the two partial strips 12a, 12b meet and
intersect.
With regard to the maximum cross-separating force, it is
sufficient if 95 6 of the samples, on which the maximum cross-
separating force of the filter tow strip is measured, have an
uoper limit of 20 cN on a length -of about 20 cm for the
maximum cross-separating force. This means that the invention
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also comprises filter tow strips, in which the maximum cross-
separating force exceeds the upper limit of 20 cN in sections,
as long as the continuous operation of the filter _rod machine,
which processes the filter tow strip, is not thereby
significantly impaired. The tolerance mentioned above of 95
%, still better of 99 %, has proven to be adequate in this
case. It has furthermore proven to be advantageous if the
twin tow has a connecting region, which is such that 95 % of
the samples of a twin tow connect less than 50 cross-locking
or cross-looping filaments on a clamping length of 20 cm of
the two tow halves or partial strips. Furthermore, 99 % of
the samples of a twin tow may have less than 100 cross-locking
or cross-looting filaments on a 20 cm clamping length of the
partial strips 12a, 12b.
It is obvious that the reference length of 20 cm of the filter
tow strip portion can be selected to be different, for example
longer, to measure the maximum cross-separating force. The
maximum cross-separating force with a longer reference section
increases accordingly.
in contrast to a filter tow strip, which is optimised with
regard to a longitudinal extension or longitudinal extension
force, the filter tow strip according to the embodiment of the
invention is optimised in the connecting region, i.e. in the
region of the small or low cross-linking density 11 with
regard to the cross-separating force. As a result, an
improved and reliable separation of the partial strips 12a,
12b is achieved as the optimised parameter, namely the cross-
separating force, is correlated with the separating direction,
which runs transverse to the longitudinal direction of the
L tow strip 10
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To measure the parameters relevant to quality of the twin tow,
a force extension measuring apparatus is used with clamping
mechanisms, which have a pair of clamping jaws with a clamping
length of 20 cm. To measure the cross-separating force, a 20
cm long piece of filter tow is clamped in the longitudinal
direction by the edges of the filter tow in the pair of
clamping jaws. The clamping jaws A in the force extension
measuring apparatus are slowly moved apart, so the twin tow is
firstly extended. The force required for this is measured.
The intersecting crimped filaments of the fibre strand form a
nonwoven structure. In the connecting region between the
partial strips, i.e. in the region with the low cross-linking
density, the separating seam between the two twin tow halves
opens. The opened region is characterised by the number of
cross-locked or cross-looped filaments, which, for example,
form a cross pattern. The clamping jaws are moved further
apart, the cross-separating force passing through a maximum at
that point at which the filaments, which hold together the two
tow halves, are maximally drawn. The number of cross-locked
or cross-looped filaments is then detected.
If the clamping jaws are moved further apart, the locking or
looping points between the binding filaments of the two tow
halves of the twin tow tear apart and the cross-separating
force reduces.
Various embodiments are shown in Figs 2a to 2f, in which the
partial strips 12a, l2b of the filter tow strip 10 are
arranged differently. According to rig. 2a, the partial
strips 12a, 12b are arranged side by side, the connecting
region 11 and the partial strips 12a, 12b being arranged in a
plane. The arrangement according to Fig. 2a may, for example,
be produced in that the two partial strips 12a, 12b are
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crimped together, the cross-linking density being adjusted in
the connecting region 11 in such a way that a maximum cross-
separating force of 10 cN is produced.
According to Figs 2b to 2f, the two partial strips 12a, 12b
are arranged overlapping, i.e. at least partially or
completely overlapping. The connection of the two partial
strips may be produced by mechanical needling or by needling
by means of an air jet or water jet. In the embodiment
according to Fig. 2b, the partial strips are arranged
overlapping one another in the edge region. According to Fig.
2c, the partial strips 12a, 12b are arranged overlapping one
another completely, the connecting filaments 13 being
configured as a common centre track. In the embodiment
according to Fig. 2d, the connecting filaments 13 or the
connecting region 11 are formed as an edge track. It is also
possible, as shown in Fig. 2e, to provide the connecting
filaments 13 over the entire width of the overlapping partial
strips 12a, 12b. A further possibility of connecting the two
partial strips 12a, 12b consists in arranging the connecting
filaments 13 in the longitudinal direction of the partial
strips randomly distributed, as shown in Fig. 2f.
Three embodiments of double filter rod machines are shown in
-Figs 3a - 3c, which in each case have two spreader nozzles
20a, 20b. The further machine parts, which are generally
present, for example the drafting mechanism, the spray
mechanism and the formatting part are not shown. As can be
seen in Fig. 3a, a separating mechanism 21 in the form of a
separating wedge 23 is arranged upstream of the two spreader
nozzles 20a, 20b, the separating mechanism 21 being arranged
between the two spreader nozzles 20a, 20b. In this case, the
separating edge of the separating wedge 23 points counter to
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the conveying direction of the filter tow strip 10, so the
filter tow strip 10 is separated by the separating edge. For
better guidance, two guide rings 22a, 22b are arranged
downstream of the separating wedge 23 and a guiding ring 24 is
arranged upstream thereof. In the embodiment according to
Fig. 3a, the guide rings 22a, 22b may be attached such that
they exert a normal force component on the partial strips 12a,
12b.
The two spreader nozzles 20a, 20b can also be used as a
separating mechanism 21, in that the two spreader nozzles 20a,
20b are arranged in such a way that their entry openings are
not in a line so a normal force component is exerted on the
partial strips 12a, 12b (Fig. 3b). In this embodiment,
because of the obliquely arranged spreader nozzles 20a, 20b,
the separating point of the filter tow strip 10 is arranged
upstream of the spreader nozzles 20a, 20b. To reinforce the
separating effect, the separating wedge 23 according to Fig.
3a may be provided at or in the region of the separating point
of the obliquely arranged spreader nozzles 20a, 20b according
to Fig. 3b, as shown in Fig. 3c.
force measuring apparatus for measuring the tension of the
separated partial strips 12a, 12b may be arranged directly
downstream in situ (not shown) of the separating mechanism 21.
Furthermore, a control mechanism may be provided, which works
in such a way that the conveying speed of the individual
partial strips 12a, 12b is controlled with the aid of the
tension in the partial strips 12a, 12b.
in the method for producing filter tow strips, the cross-
linking density in the connecting region between the two
partial strips 12a, 12b is adjusted in such a way that a
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maximum cross-separating force of the partial strips of 20 cN
on a length of about 20 cm is produced or this force is not
exceeded. This may be achieved, for example, in that the
oartial strips are arranged next to one another side by side
and are crimped together, the cross-linking density being
controlled by the spacing of the partial strips from one
another during crimping. The cross-linking density can also
be controlled by mechanical needling or by needling by means
of an air jet or a water jet if the partial strips 12a, 12b
are arranged partly or completely overlapping one another.
The filter tow strip 10 may already be separated before the
bale packaging into partial strips 12a, 12b, the separated
partial strips 12a, 12b being placed in different cans or in a
divided can with a plurality of depositing regions or in a
single can. It is also possible to place the undivided filter
tow strip in a can and to package it to form a bale. In the
latter case, the separation of the filter tow strip into the
partial strips 12a, 12b takes place during the production of
the filter rods, the maximum cross-separating force with which
the filter tow strip 10 is divided not exceeding 20 cN on a
a q
length of 20 cm. To separate the filter tow strip 10, a
double filter rod machine is preferably used, which has a
separating mechanism before the spreader nozzles, as shown in
Figs 3a, 3b, 3c.
In a filter tow (twin tow) produced according to the
invention, a separating force was measured at the desired
tearing line, i.e. in the region of the reduced cross-linking
density, of 7 to 12 cif, and of 2.5 to 4 eN in another example.
These values relate to the lower and upper limit of the spread
of the measurement. Tn further examples, a maximum cross-
separating force of 1 cN to 10 cN and of 0.5 cN to 5 cN was
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measured. At the maximum cross-separating force of 1 cN to 10
cN, the number of connecting filaments or the number of
intersections was 2 to 20. At the maximum cross-separating
force of 0.5 cN to 5 cN, the number of connecting filaments or
the number of intersections was 1 to 10. The values mentioned
above for the number of connecting filaments are the median
(at most half the observations in a random sample have a value
of <m and at most half have a value of >m).
Further examples produced the following values for the mean
maximum cross-separating force / median of the number of
connecting filaments: 8 cN / 80, 7 cN / 251. 2 cN / 4 and 4 cN
8.
The cross-separating force and the number of connecting
filaments can be adjusted, for example, as described above by
a variation in the spacing of the partial strips in the
crimping machine.
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List of reference numerals
filter tow strip
1l region with a reduced cross-linking density
12a, 12b partial strips
13 filaments
14 intersections
20a, 2Gb spreader nozzle
21 separating mechanism
22a, 22b guide rings
23 separating wedge
24 guiding ring
clamping jaws
