Coaxial cigarette having cross stream barrier

The invention relates to a coaxial cigarette including a rod comprising a rod core, a rod core wrapping, a rod jacket and a rod jacket wrapping; and a filter comprising a filter core, a filter core wrapping, a filter jacket and a filter jacket wrapping, a smoke flow stopper being provided between the rod core and the filter jacket and/or the rod jacket and the filter core in the zone joining the rod core wrapping and filter core wrapping, the invention also relating to a method of producing such a cigarette.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a coaxial cigarette including a rod comprising a 
rod core, a rod core wrapping, a rod jacket and a rod jacket wrapping; and 
a filter comprising a filter core, a filter core wrapping, a filter jacket 
and a filter jacket wrapping, wherein a cross stream barrier (smoke flow 
stopper) is provided between said rod core and said filter jacket and/or 
said rod jacket and said filter core in the zone joins said rod core 
wrapping and said filter core wrapping. 
2. Description of the Related Art 
Coaxial cigarettes are designed and produced to enable the smoking and 
puffing performance to be influenced to a greater extent by the design 
configuration of the cigarette. One option with coaxial cigarettes is 
separate treatment of the flows from the rod jacket and the rod core of 
the coaxial rod through the filter jacket and filter core of the coaxial 
filter. 
In the production of coaxial filter cigarettes, the same as in the 
production of usual filter cigarettes, the filter is placed up against the 
rod where it is secured in place by means of a tipping paper placed 
thereon. This automatically results in coaxial cigarettes having gaps 
between the end of the rod core wrapping on the filter side and the end of 
the filter core wrapping on the rod side. Considered microscopically, i.e. 
when taking into account the flow paths of smoke particles approximately 
0.1 mm in size these gaps are to be viewed as being decidedly substantial. 
This means that when a separate treatment of the smoke streams from the 
corresponding rod segments is intended, i.e. when the smoke from the rod 
jacket is to pass exclusively through the filter core and the smoke from 
the rod core is to pass exclusively through the filter jacket, then 
suitable measures need to be taken in accordance with prior art to prevent 
mis-directed flow through the gaps. As a result of this, coaxial 
cigarettes known hitherto are subject to heavy restrictions since the flow 
resistances of the jackets and cores of rod and filter need to be 
precisely matched. This results in significant restrictions as regards the 
packing densities achievable in the rod, the usable grade or of other 
blend components, the coaxial filter employed as well as the achievable 
condensate target values. 
SUMMARY OF THE INVENTION 
It is the object of the present invention to provide a coaxial cigarette 
which overcomes the disadvantages of prior art as cited above. More 
particularly, the intention is to eliminate cross-flow of the smoke 
between rod core and filter jacket or between rod jacket and filter core 
without having to put up with the restrictions in configuring the 
cigarette. 
This object is achieved in accordance with the invention by providing a 
smoke flow stopper between the rod core and the filter jacket and/or the 
rod jacket and the filter core in the zone joining rod core wrapping and 
filter core wrapping. 
A smoke flow stopper in accordance with the invention prevents a 
mis-directed flow from the rod core into the filter jacket or from the rod 
jacket into the filter core, thus constructively engineering the location 
where cross-flows may occur, namely at the gap separating the end of the 
rod core wrapping on the filter side from the end of the filter core 
wrapping on the rod side. This gap is closed so that it is no longer 
necessary to influence flow control by employing specific tobacco or 
tobacco replacement materials and filter materials in special 
configurations of the puff resistances. Materials may now be used over a 
broader bandwidth as well as desired condensate target values achieved. 
When the filter core wrapping and the rod core wrapping feature 
substantially the same diameter it is possible in one advantageous 
embodiment of the smoke flow stopper to gaplessly join the two wrappings 
at their point of contact. 
In a first group of embodiments of the coaxial cigarette in accordance with 
the invention the rod core wrapping and the filter core wrapping are 
configured integrally, the filter to advantage being configured at least 
in part as a tobacco filter, whereby the filter jacket and/or the filter 
core are engineered in a tobacco material having a tobacco packing density 
modified relative to the associated rod portion. In this arrangement the 
complete cigarette is produced, for example, as a coaxial rod of tobacco. 
In the filter zone either the packing density of a rod segment or of an 
associated tobacco filter segment is increased so that the filtration 
coefficient of at least one of the filter segments differs from the 
filtration coefficient of the associated tobacco rod segment. Producing 
such a cigarette is simple in fast on-line operation. 
In a second option the inner rod is formed by a train of filter cigarettes 
in the diameter of the coaxial cigarette core. The filter cigarettes are 
joined analogously to filter and rod bonding into an endless rod and the 
rod and filter jacket consisting of tobacco. 
Producing this cigarette too, is possible with existing cigarette 
production technology in fast on-line operation. 
One possibility of producing a gapless joint for substantially the same 
diameter of the core segments in a further embodiment of the invention 
consists of joining the rod core and filter core to each other in the 
joining zone by means of a wrapping, preferably of tipping paper. The 
wrapping covers the gap, i.e. the junction between the two core wrappings 
sealing it off against mis-directed flows. 
To enable a wrapping to be applied to the juncture cross-section of the 
core wrappings, they need to be stripped of part of the jacket in 
production. After rod core and filter core have been joined together and 
wrapped a longitudinal gap materializes in the jacket which can be left 
empty, i.e. merely needing to be closed by the tipping paper. 
Advantageously, however, the rod jacket and the filter jacket may also be 
filled with a tobacco or filter material in the region of the wrapping, 
this making for a further possibility of engineering smoke flow 
performance. 
A further group of embodiments of the coaxial cigarettes in accordance with 
the invention is not aimed at gaplessly closing the junction between rod 
core wrapping and filter core wrapping. It instead makes use of the flow 
paths of the smoke flow or its predetermined direction and attaining the 
smoke stopper by the rod core and the filter core being provided differing 
in diameter and the wrapping of the filter core protruding by a defined 
distance into the rod core or rod jacket. The difference in diameter 
between the outer diameter of the filter core wrapping and the inner 
diameter of the rod core wrapping must be so small that the flow 
resistance materializing between the wrappings is so high that no smoke is 
able to flow between the wrappings, as a result of which a smoke flow 
stopper likewise materializes. Should the filter core have a smaller 
diameter than the rod core, the protruding portion of the filter core 
wrapping locates within the rod core when filter and rod are joined 
together. The two core wrappings form in the overlapping region a recess. 
In the aforementioned example it can then be prevented that smoke gains 
access from one radial segment into the other. 
As regards separate treatment of the smoke flow the aforementioned 
embodiment thus acts in one direction in each case, blocking any 
cross-flow from the rod core into the filter jacket or from the rod jacket 
into the filter core. 
The invention relates further to a method of producing a coaxial cigarette 
with said rod jacket and filter jacket being left empty in said region of 
said wrapping or filled with a tobacco or filter material. Configuring the 
smoke flow stopper preferably as an engineered smoke flow stopper has the 
advantages as already described for the coaxial cigarette in accordance 
with the invention. 
In one preferred embodiment of the method in accordance with the invention 
the rod core wrapping and the filter core wrapping are configured 
integrally, the filter being configured at least in part as the tobacco 
filter and the filter jacket and/or the filter core being configured of a 
tobacco material having a tobacco packing density modified relative to the 
associated rod portion. As already described above such a tobacco 
filtering principle is of advantage as regards on-line production. 
A further aspect of the method in accordance with the invention is 
characterized by the rod core and the filter core being gaplessly joined 
to each other in the juncture zone by means of a wrapping, preferably a 
tipping paper. As likewise discussed as regards the corresponding 
cigarette in accordance with the invention the rod jacket and the filter 
jacket may be left empty in the region of the wrapping or filled with a 
tobacco or filter material, for example with granulate or non-woven fabric 
filter. 
An alternative embodiment of the method in accordance with the invention 
consists of producing the rod core and the filter core slightly differing 
in diameter and configuring the wrapping of the filter core to protrude so 
that it juts into the rod core or rod jacket when rod and filter are 
joined.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1 there is illustrated what is probably the simplest 
configuration of a cigarette in accordance with the invention having a 
cross-flow stopper, namely comprising a tobacco filter. The cigarette 
consists of a rod 10 and a filter 20. The rod is composed of a rod core 
11, a rod core wrapping 12, a rod jacket 13 and a rod jacket wrapping 14. 
The filter consists correspondingly of a filter core 21, a filter core 
wrapping 22, a filter jacket 23 and a filter jacket wrapping 24. The cores 
11, 21 and jackets 13, 23 are each the same in diameter, i.e. coaxial. 
It is to be noted that the above assignment of reference numerals applies 
likewise to the FIGS. 2 and 3. 
The coaxial cigarette having the tobacco filter 20 as shown in FIG. 1 is 
produced in all as a coaxial rod of tobacco. The broken line 25 denotes in 
this case not a parting line indicating for instance an applied filter, 
but where in this cigarette having the tobacco filter 20 tobaccos exist on 
both sides having differing properties. These differing tobacco properties 
on both sides of the broken line 25 are the reason for the differing 
properties of the rod 10 and filter 20. 
The coaxial cigarette as shown in FIG. 1 is provided with the filter jacket 
wrapping 24. The wrapping 24 may contain a ventilation zone. The portion 
of the coaxial cigarette below the filter jacket wrapping 24 acts as a 
filter 20. The filter coefficient of at least one of the two filter 
segments (filter core 21 or filter jacket 23) differs from the filter 
coefficient of the associated tobacco rod segment (rod core 11 or rod 
jacket 13). This is achieved by the use of corresponding seepage disks in 
production, i.e. analogously to the so-called "end reinforcement" 
procedure. Depending on the desired function either the packing density of 
one of the rod segments 11, 13 or that of the associated filter segments 
21, 23 is "reinforced". By setting the packing density in the 
corresponding component parts of the coaxial cigarette a precisely defined 
filter effect may be achieved. Since it is produced in all as a coaxial 
rod of tobacco the filter cigarette comprises no gaps in the border-line 
zone between the rod core wrapping 12 and the filter core wrapping 22 due 
to the wrappings 12, 22 being configured integrally for both of these 
segments 11, 21, as a result of which the smoke from the corresponding rod 
segment may be treated separately in the corresponding filter segment, 
i.e. smoke from the rod core I1 gains access only to the filter core 21 
and smoke from the rod jacket 13 gains access only to the filter jacket 
23. 
The coaxial cigarette as shown in FIG. 1 may be additionally provided in 
the region of the filter 20 with tipping paper. 
Referring now to FIG. 2 there is illustrated a method of producing a 
coaxial cigarette comprising a separately produced coaxial rod 10 and a 
coaxial filter 20 likewise produced separately. 
Illustrated are the steps I to IV in production. In step I the assembly 
still consists of a coaxial tobacco rod 10 and a coaxial filter 20. The 
rod core 11 has substantially the same diameter as the filter core 21. 
In joining the rod 10 and filter 20 the wrapping 30 of the portion joining 
the rod core wrapping 12 and the filter core wrapping 22 is applied, it 
acting as a smoke stopper. 
For this purpose a portion of the rod jacket 13 on the filter side is 
removed with the wrapping 14 in step II. In the same way an outer ring is 
removed from the filter 20 on the rod side by cutting off the filter 
jacket 23 together with the filter jacket wrapping 24 so that at the 
juncture only the cores 11, 21 together with their wrappings 12, 22 remain 
in each case. A ring approximately 2 to 4 mm long is removed in each case. 
In step III the cores 11, 21 are butt-jointed and wrapped with a tipping 
paper 30. The tipping paper 30 is bonded, rendering it impervious to 
smoke. 
Thus, the smoke flow stopper in accordance with the invention is already 
achieved in step III, preventing a cross-flow of smoke on both sides at 
the junction between the rod core and filter core. 
After having produced this smoke flow stopper with the tipping paper 30 
which may have an axial length of 3.8 to 7.8 mm, the cigarette is then 
"completed" in step IV, for which several possibilities exist: 
In one approach, the gap 31 over the tipping paper may be simply left 
empty, resulting in a gap width of 4 to 5 mm. For such a cigarette a 
relatively stiff tipping paper 32 is used as the outer wrapping to ensure 
an adequate dimensional stability of the cigarette. 
In another approach, the gap 31 over the inner tipping paper 30 is filled 
with tobacco which is then covered by an outer tipping paper 32, the width 
of the gap 21 in this case being 4 to 8 mm. 
In yet a further embodiment the gap over the juncture of the two cores II, 
21 may be filled with granulate. The granulate may have an inactive or 
selective filtering action, as is the case, for example, in one of the 
known chamber filter materials. The outer circumference of the cigarette 
is wrapped with the tipping paper 32, the width of the gap 31 in this case 
being 4 to 8 mm. 
Still another conceivable approach in closing the aforementioned gap 31 
consists of wrapping it with non-woven fabric filter strips until the 
outer diameter of the cigarette is achieved, after which in turn a tipping 
paper 32 is applied around the outer sleeve, the gap width in this 
"filling method" too being in the range 4 to 8 mm. 
In all of the above variants the width of the tipping paper 32 applied 
surrounding the cigarette, i.e. the filter and the gap 31 on the outside 
needs to be at least 3 mm longer than the filter length plus the width of 
the rod jacket removed at the filter side. 
The material with which the gap 31 in the remaining jacket region at the 
rod and filter is filled may be bonded to the wrapping 30. 
Referring now to FIG. 3 there is illustrated an alternative possibility of 
producing a coaxial cigarette in accordance with the invention on the 
basis of the steps I to III in the method. Illustrated in this case is a 
coaxial cigarette having a rod 10 and a filter 20 in which the wrappings 
12, 22 of the rod and filter core overlap. 
Step I shows a coaxial rod 10 and a coaxial filter 20, each of which is 
prepared separately. The diameter of the rod core 11 is slightly larger 
than the diameter of the filter core 21. 
To produce the cross-flow stopper. as discussed in step II, a rod end ring 
segment of the filter jacket is removed, for example cut off, this 
resulting in the filter core 21 having a projection 40 at the side of the 
rod 10. 
As evident from step III for completing the cigarette the filter 20 is 
placed up against the rod 10 so that the projection 40 enters the rod core 
portion 11. The wrapping 12 of the rod core and the projection 40 thereby 
overlap over a specific length. 
It will be appreciated that the method of producing the cigarette as shown 
in FIG. 3 is but one of the many possible variants of the method with 
which coaxial cigarettes having a cross-flow stopper may be produced. 
The zone free of material at the end the filter core on the rod side may be 
produced in several ways, namely, for example, by stuffing the filter 
material or by cutting out/milling the filter material. The projection 40 
may be configured in both the filter maker and during attachment to the 
filter. 
The projection 40 may be produced by the methods as described above at both 
the rod and tip side of the filter 20. The zone free of material over the 
filter core 21 should have a width of 2 to 5 mm. 
The diameter of the rod core 11 must be larger than the diameter of the 
filter core 21 (FIG. 3) i.e. merely sufficient so that the filter core is 
just able to be plugged into the tobacco core. 
In the embodiment variants in which the projection 40 is configured at the 
rod side, the projection 40 is plugged into the tobacco rod, in joining 
rod 10 and filter 20, so that the filter core wrapping 22 slips under the 
wrapping 12 of the rod core 11 and closes off the filter jacket 23 at the 
rod side by the rod jacket 13 at the filter side. The filter core wrapping 
or the outer portion of the projection 40 may be bonded to the material of 
the filter jacket. 
If the projection 40 is produced at the tip side of the filter 20 the 
projection 40 is plugged into the filter 20 in joining rod 10 and filter 
20, until it concisely closes off the tip end. In this case too, the 
filter core wrapping 22 slips under the wrapping 12 of the rod core 11. In 
these variants the material of the filter jacket 23 is no longer bonded to 
the wrapping 22 of the filter jacket 21, the core 21 instead being joined 
to the jacket 23 simply by a pressure/friction connection. 
To facilitate plugging the filter core 21 into the tobacco rod 11 the 
filter wrapping 22 consists preferably of a film of cellulose acetate 
preferably 0.1-0.2 mm thick. 
In all variants the length of the filter tip paper needs to be at least 3 
mm longer than the filter length plus the width of the projection 40.