FILTER TOW STRIP, FILTER ROD MACHINE, METHOD FOR PRODUCING FILTER TOW STRIPS AND METHOD FOR PRODUCING FILTER RODS

Abstract

The invention relates to a filter tow strip, especially twin tow from cross-linked and crimped filaments which form at least two partial strips (12a, 12b) that are interlinked by a section of reduced cross-linking density (11), the linking filaments (13) being interlooped and/or interlocked in such a manner that the linking filaments form intersections (14). The filter two strip is characterized in that the maximum cross-cutting force of the partial strips (12a, 12b) does not exceed 20 cN on a length of approximately 20 cm of the filter tow strip (10) and/or the number of the Baking filaments (13) does not exceed 200 cross-locking and/or cross-looping filaments on a length of approximately 20 cm of the filter tow strip (10) when impinged with the maximum cross-cutting force.

Description

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 A1, 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 für Cigarette Filter (CA filter tow for cigarette filters), Paul Rustemeyer, Macromolecular Symposia 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 filling force and is then gathered together to the format of the future cigarette filter and covered with paper. To bulk up the filter tow, the latter is 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 A1 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. Because 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 A1 that the strip is loaded with an extension force in the longitudinal direction, which leads to the fact that the strip is separated 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 the multiple width filter tow strip to take place as uniformly as possible and for the partial strands 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 EP 0 629 722 A1, 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 cN, 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 A1, 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 a 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:

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;

FIGS. 2 a-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

FIG. 3 a, b, c show schematic views of a detail of a double filter rod 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 10 comprises two partial strips 12a, 12b, which are connected by 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 interlooped and/or interlocked in such a way 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.

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-separating force, which is required to separate the partial strips, does not exceed 20 cN on a length of about 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 corresponds to the number of intersections 14. In the embodiment according to FIG. 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% of the samples, on which the maximum cross-separating force of the filter tow strip is measured, have an upper limit of 20 cN on a length of about 20 cm for the maximum cross-separating force. This means that the invention 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-looping 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 filter tow strip 10.

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, 12b of the filter tow strip 10 are arranged differently. According to FIG. 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 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 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.

A 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 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 partial 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 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 cN, and of 2.5 to 4 cN in another example. These values relate to the lower and upper limit of the spread of the measurement. In further examples, a maximum cross-separating force of 1 cN to 10 cN and of 0.5 cN to 5 cN was 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/25, 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.

LIST OF REFERENCE NUMERALS

• 10 filter tow strip
• 11 region with a reduced cross-linking density
• 12 a, 12 b partial strips
• 13 filaments
• 14 intersections
• 20 a, 20 b spreader nozzle
• 21 separating mechanism
• 22 a, 22 b guide rings
• 23 separating wedge
• 24 guiding ring
• A clamping jaws

Claims

1. A filter tow strip, comprising: a twin tow made of cross-linked and crimped filaments which form at least two partial strips, and which are connected by a region of reduced cross-linking density,wherein the connecting filaments are interlooped and/or interlocked in such a way that they form respective intersections,wherein the maximum cross-separating force of the partial strips does not exceed 20 cN on a length of about 20 cm of the filter tow strip and/or the number of connecting filaments does not exceed 200 cross-locking and/or cross-looping filaments on a length of about 20 cm of the filter tow strip when the filter tow strip is loaded with the maximum cross-separating force.

2. A filter tow strip according to claim 1, wherein the maximum cross-separating force is ≦15 cN.

3. A filter tow strip according to claim 1, wherein the number of cross-locking and/or cross-looping filaments in the region of the reduced cross-linking density is ≦150.

4. A filter tow strip according to claim 1, wherein the partial strips are arranged side by side.

5. A filter tow strip according to claim 1, wherein the partial strips are arranged overlapping one another in the edge region.

6. A filter tow strip according to claim 1, wherein the partial strips are arranged one above the other and the connecting filaments are located in the region of the overlap of the partial strips.

7. A filter rod machine, comprising at least one spreader nozzle, a drafting mechanism, a spray mechanism, a formatting part, and at least one separating mechanism for separating partial strips of the filter tow strip before the spreader nozzle.

8. A machine according to claim 7, wherein separating mechanism comprises at least two guide rings attached so as to exert a normal force component on the partial strips.

9. A machine according to claim 7, wherein the separating mechanism comprises at least one separating wedge arranged in the conveying direction of the filter tow strip.

10. A machine according to claim 7, wherein the separating mechanism comprises two spreader nozzles having entry openings out of line with one another and arranged so as to exert a normal force component on the partial strips.

11. A machine according to claim 7, further comprising a force measuring apparatus for measuring the tension of the separated partial strips, the force measuring apparatus being directly arranged downstream in situ of the separating mechanism.

12. A machine according to claim 7, further comprising a control mechanism operative to control a conveying speed of individual partial strips with the aid of a tension in the partial strips.

13. A method for producing filter tow strips, comprising the steps of: providing at least two partial strips made of cross-linked and crimped filaments;connecting the at least two partial strips by a region of reduced cross-linking density,wherein the filaments in the region of reduced cross-linking density are interlooped and/or interlocked and form intersections such that a maximum cross-separating force of the partial strips does not exceed 20 cN on a length of about 20 cm of the filter tow strip and/or the number of connecting filaments does not exceed 200 cross-locking and/or cross-looping filaments on a length of about 20 cm of the filter tow strip when the filter tow strip is loaded with the maximum cross-separating force.

14. A method according to claim 13, comprising the additional steps of arranging the partial strips side by side and crimping them together.

15. A method according to claim 13, comprising the steps of: guiding the partial strips over one another in a partially overlapping manner, andtreating the partial strips so as to produce binding filaments,wherein the treating step is performed mechanically, by needling, with an air jet or with a water jet.

16. A method according to claim 13, comprising the steps of: guiding the partial strips over one another in a completely overlapping manner, andtreating the partial strips so as to produce binding filaments,wherein the treating step is performed mechanically, by needling, with an air jet, or with a water jet.

17. A method according to claim 13, comprising the additional steps of separating the filter tow strip into the partial strips and placing the separated partial strips in at least one can.

18. A method according to claim 13 comprising placing the undivided filter tow strip in a can.

19. A method for producing filter rods from filter tow strips made of cross-linked and crimped filaments, comprising the steps of: conveying a filter tow strip through a preparation part and a formatting part, andconnecting at least two partial strips of the filter tow strip connected to one another by a region of reduced cross-linking density,wherein the filaments in the region of the reduced cross-linking density are interlooped and/or interlocked in such a way that the filaments form intersections, the partial strips being separated before the formatting part with a maximum cross-separating force, which does not exceed 20 cN on a length of the filter tow strip of about 20 cm.

20. A machine according to claim 7, wherein the filter rod machine is configured as a double filter rod machine.

21. A method according to claim 17, wherein the placing step places the separated partial strips into a divided can having a plurality of depositing regions therein.