HK1153362A - Filter for a smoking article - Google Patents

Description

Filter for a smoking article

Technical Field

The present invention relates to multi-section filters for smoking products, such as cigarettes.

Background

Cigarettes typically comprise a tobacco rod and a filter. The filter is located at the mouth end of the cigarette, between the smoker and the tobacco rod. The filter improves the draw of tobacco smoke (mainstream smoke) through it. Filters are understood to be used to reduce or modify various smoke constituents, including particulate matter and/or gas phase substances.

Multi-section filters are becoming more and more popular. For example, in one arrangement, the filter comprises a segment of activated carbon having good filtration properties. The filter may comprise a further segment between the activated carbon and the mouth end of the cigarette. This helps to ensure that the activated carbon does not enter the user's mouth.

There are a number of known methods for altering the characteristics of filters. One approach is to include ventilation holes on the outside of the filter. This allows air to be drawn into the filter and thus dilutes the cigarette smoke inhaled by the user. Another known method is to provide grooves in the filter, often along the outside of the filter. These grooves can be used to control the flow properties through the filter. Examples of grooves and/or vents may be found in: WO 03/051144; GB 2150809; GB 2150412; GB 2118819; GB 2089641; GB 2088692; GB 2088193; GB 2088191; GB 1585862; GB 1308661; EP 047969; US 4527573; US 4527572; US 4256122; US 4135523; US 3768489 and US 3752165.

It is still desirable to provide better filtration properties to multi-section filters.

Disclosure of Invention

One embodiment of the present invention provides a multi-section filter for a smoking article. The filter comprises at least first and second filter segments. The first filter segment is located at the mouth end of the filter. The second filter section includes a set of ventilation holes and a set of grooves or channels. The grooves extend from the respective ventilation holes along the second filter section towards, but not into, the first filter section.

Such filters allow for the separation of an external air inlet from atmosphere into the filter (also referred to herein as the actual air entry point) occurring at the beginning of the groove from an internal air inlet (also referred to herein as the vent location or region) into the filter body where mainstream smoke is connected, occurring at the end of the groove. This gives more flexibility in filter design. For example, the external air inlet is relatively remote from the mouth end, thereby reducing the likelihood of the external air inlet becoming blocked by a smoker, while still allowing air to mix with smoke relatively close to the mouth end of the filter. The region of filter material between the actual air entry point and the location of the ventilation holes is subject to slower smoke flow for any given puff than if dilution air were entering the filter body at the location of the ventilation holes. The reduction in velocity results in a higher degree of filtration of the smoke. This also makes the filter particularly suitable for having a multi-segment construction, and in particular a construction in which the filter segments contain adsorbent material such as carbon to enhance filtration of certain toxic substances. To facilitate construction of the filter, the grooves may be confined within a single segment of the filter.

In a particular embodiment, the grooves extend along the outside of the filter body parallel to the major axis of the filter. The groove is substantially impermeable along its length. The grooves extend substantially the length of the second filter section. The filter is arranged such that air flows through the ventilation holes, travels along the groove towards the first filter section and exits the groove into the body portion of the filter adjacent the first filter section. In this particular embodiment there are three filter segments arranged end to end and the second (fluted) filter segment constitutes the middle section of the filter. The second filter segment has an impermeable inner tipping paper and is joined to another filter segment with a permeable outer tipping paper. The groove is located between the inner and outer tipping papers, and the body of the second filter segment is therefore isolated from the groove by an impermeable barrier layer. The filter is then attached to the tobacco rod with an outer permeable tipping paper layer through which the ventilation holes are formed. Thus, the grooves are substantially impermeable to air and smoke entering or exiting the filter body. The only air inlet into the recess is through the ventilation holes in the outer tipping paper and then through the permeable outer tipping paper into the recess. The dilution air travels along the grooves to enter the filter body at or towards the junction of the first and second filter sections.

In certain embodiments, all fresh air entering through the vent is directed along the groove. In other embodiments, the grooves extend from part of the ventilation holes in the ventilation zone, but other ventilation holes are introduced into the body portion of the filter segment, whereby part of the fresh air enters the filter body directly at the location of the ventilation zone. These additional ventilation holes in the ventilation zone may be introduced into the body portion of the filter segment between the grooves. Additional ventilation holes may be introduced into the body portion near the end of the groove furthest from the first filter section (mouth end) and/or additional ventilation holes may be introduced into the body portion near the end of the groove closest to the first filter section.

In a further embodiment, the tipping paper is processed from a naturally permeable material, and fresh air can thus enter the grooves over the entire length of the second filter segment. Additional vent holes may also be added to further enhance the overall level of venting.

These different configurations provide considerable flexibility in the design and operation of the filter. For example, part of the air may be made to enter the body of the filter section with the grooves to mix with the main smoke stream there, while more air (from the grooves) may be made to mix with the smoke as it enters the first filter section.

In one embodiment, the ventilation holes are at least about 11mm from the mouth end of the first filter section. For example, the ventilation holes may be about 12 to about 25mm from the mouth end of the first filter section.

In one embodiment, an isolation layer is located at the end of each groove furthest from the first filter section. The barrier layer ensures that this end of the recess is accessible only through the vent hole. The barrier may be provided by hot melt fusion of the filter material, by glue applied to the end of each groove, or by an annular element located at the end of the second filter segment furthest from the first filter segment, or by any other suitable mechanism. In a further embodiment, the barrier is provided in that the grooves in the second section extend along only a portion of the filter section so that the open ends of the grooves abut the end of the first filter section.

The invention also provides a smoking article incorporating a tobacco rod and such a multi-section filter.

The invention further provides a smoking article comprising a tobacco rod and a multi-section filter having at least first and second filter sections, wherein the first filter section is located at the mouth end of the filter and wherein the second filter section comprises a set of ventilation holes and a set of grooves extending from respective ventilation holes along the second filter section towards but not into the first filter section.

Another embodiment of the invention provides a method of making a smoking article comprising: combining a second fluted filter section and a mouth end filter section by overlapping the fluted filter section with a permeable tipping paper and then overlapping the combined fluted filter section and mouth end filter section with a tipping paper containing ventilation holes, wherein the positions of some or all of the ventilation holes correspond to the positions of the flutes. More segments may be added to the tobacco end of the second segment during assembly. The grooves may be plugged at the end opposite the mouth end during the combining operation. In certain embodiments, such plugging is achieved by the addition of an adhesive. Alternatively, the blocking is achieved by hot melting of the filter material or by adding an annular material to the end of the fluted filter segment.

The vent holes can be easily added using standard on-machine laser machining techniques such as in-line or off-line perforation.

In a particular embodiment, the fluted filter segment is made by forming a filter rod or by forming and wrapping a tipping paper and the formed tipping paper around the filter rod.

Another method of making a smoking product involves combining an entirely fluted second filter segment with a mouth end segment in a porous plug wrap, and plugging the flutes in the second segment at the tobacco end by adding material during the combination, for example adhesive at multiple points or in pieces around the filter. More segments may be added to the tobacco end of the second segment during assembly.

Another method of making a smoking article includes combining a second filter segment, which is entirely fluted, within the first and third filter segments and inserting an annular shaped material between the second and third filter segments such that the ends of the flutes are blocked by the annular shaped material.

Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

figure 1 shows a longitudinal cross-section of a cigarette comprising a multi-section filter according to one embodiment of the present invention;

FIG. 2 is a schematic view of the cigarette filter of FIG. 1;

FIG. 3 is an axial cross-sectional view of the cigarette filter of FIG. 1;

figures 4a and 4b are schematic views of filters according to two further embodiments of the invention, with additional ventilation holes; and

figures 5a to 5b constitute a schematic representation of the assembly of fluted filter segments according to one embodiment of the present invention.

Detailed Description

The cigarette 1 shown in figure 1 comprises a tobacco rod 3 and a multi-section filter 5 which can be secured together by tipping paper 15 as is well known in the art. The multi-section filter 5 is formed of three filter sections 5A, 5B, 5C arranged end-to-end. In particular, the filter 5 comprises a fluted middle filter section 5A, a mouth end filter section 5B and a filter section 5C adjacent to the tobacco rod 3. The fluted filter segment 5A is disposed (relative to the main axis of the cylinder of the filter) intermediate the other two filter segments 5B, 5C. The grooves 7 are located on the outside of the filter and extend substantially in the axial direction. The filter segment 5A is provided with a plurality of grooves 7 distributed around the circumference of the filter segment 5A. The grooves extend substantially along the intermediate filter segment 5A from the segment 5C of the tobacco end to the segment 5B of the mouth end. However, the grooves do not extend into the filter segment 5C of the tobacco end or into the mouth end filter segment 5B.

The grooves 7 are isolated from the filter segment 5C of the tobacco end by an impermeable barrier layer 9. Similarly, the grooves are isolated from the body 11 of the central filter segment 5A by the impermeable layer 6. However, the grooves are open at the end opposite the barrier layer 9 to allow air or other gas/vapour to flow along the grooves 7 to be delivered into the mouth end of the filter segment 5B.

In one embodiment, the impermeable layer 6 comprises a non-porous tipping paper surrounding the body (periphery) of filter material 11 within the filter segment 5A. The filter material 11 may comprise any suitable filter material or structure, such as acetate tow, paper, and the like. The filter material may be provided with one or more additives such as activated carbon or the like. The non-porous tipping paper 6 may be embossed to define grooves 7 (with the embossing extending parallel to the cylindrical axis of the filter). The filter material 11 in the non-porous tipping paper can generally deform to occupy the entire space within the non-porous tipping paper.

The filter segments are assembled with a porous outer tipping paper 13. The outer tipping paper is then placed over raised or raised embossments of the inner tipping paper, with grooves formed between the outer and lower (reduced radius) portions of the inner tipping paper 6.

In use, the smoker draws on the mouth end filter segment 5B. This causes the smoke to travel from the burning end 2 of the tobacco rod through the filter rod to the smoker (as indicated by the arrows). The smoke travels through the remaining (uncombusted) tobacco rod 3 before entering the filter 5. The smoke passes first through the filter segment 5C at the tobacco end and then through the body 11 of the intermediate filter segment (as smoke cannot enter the grooves 7). The smoke then exits the filter 5 through the mouth end filter segment 5B.

When the smoker draws on the mouth end filter segment 5B, air is also drawn into the recess 7 through the ventilation holes 17 and through the tipping paper 13, as indicated by arrow a. Typically, the flow resistance through the ventilation holes 17 and along the grooves 7 is low, for example, compared to the flow resistance through the filter body portion 11.

After air enters the flutes 7 as indicated by arrow a, the air is constrained to travel along the flutes as indicated by arrow B, since the flute walls formed by the imperforate inner tipping paper 6 and tipping paper 15 plus barrier layer 9 are generally impermeable. Thus, the incoming air eventually exits the grooves 7 into the mouth end filter segment 5B where it mixes with and dilutes the mainstream smoke from the combustion zone.

Fig. 2 is a further schematic illustration of the embodiment of fig. 1. Thus, figure 2 is a perspective view showing the distribution of grooves 7 around the periphery of the filter. In addition, figure 2 also shows in detail the ventilation holes 17 at the end of the groove 7 remote from the filter tip. In one embodiment, the vents 17 are formed by laser perforation, but any other suitable mechanism may be used. The vents may be provided directly on the grooves (as shown schematically in figure 2) or in any one or more of the fillets which may or may not conform to the grooves.

Figure 3 is a cross-sectional view through the filter 5 at the location of the ventilation holes 17 of the outer tipping paper 15. According to the embodiment shown in fig. 3, the ventilation holes in the outer tipping paper do not all coincide with the recesses. Although the gap between the inner and outer tipping papers 6, 13 and similarly the gap between the outer tipping paper 13 and tipping paper 15 is shown in figure 3 for clarity, it will be appreciated that in practice there is no significant gap other than the flutes themselves.

It should be understood that the number and distribution of the grooves 7 shown in fig. 2, 3 and 4 are by way of example only. Other embodiments may have a different number and/or distribution of grooves.

The grooves 7 provided in the filter plug 5 allow for isolation between: (a) the vent location for air entry, which is now located at the end of the middle filter segment 5A remote from the mouth; and (B) the fresh air connects the position of the main smoke stream which is currently located at the junction between the middle filter segment 5A and the mouth end filter segment 5B. The ability to isolate these two positions provides greater flexibility in the design and control of the filter 5.

For example, locating the ventilation holes at the distal end of the intermediate filter segment 5A, remote from the mouth end, reduces the risk of the ventilation holes being accidentally blocked by the mouth (e.g. lips) during smoking. In a particular embodiment, the ventilation holes are located at least about 11mm from the mouth end of the filter, for example between about 12mm and about 25mm from the mouth end.

On the other hand, the flow of smoke re-entering the filter when the fresh air is relatively close to the mouth causes the smoke to travel relatively slowly through the middle section body 11, which correspondingly increases the filtration efficiency of the filter section body 11. In particular, as the smoke constituents stay longer near the filter material 11 of the middle section, there is a greater probability that they will be absorbed by the material. Thus, the filter material may comprise an adsorbent material such as activated carbon or other suitable adsorbent.

Fig. 4a and 4b show two alternative embodiments. In both embodiments, additional ventilation holes are provided for the middle (fluted) filter section 5A. In the embodiment of figure 4a, an additional vent 17A is provided at the distal end of the middle filter segment 5A, away from the mouth; i.e. at the same end as the vent hole 17 enters the recess. However, the outer peripheries of these holes 17A are positioned so that they are not located above the grooves. Thus, air flowing through the ventilation holes 17A enters directly into the body of filter material 11 for the filter segment 5A. Therefore, air flowing through the ventilation holes 17A does not bypass the filter material 11 of the intermediate filter segment 5A compared to air entering through the ventilation holes 17 which is directed by the grooves directly to the mouth end filter segment 5B.

The arrangement in figures 4a and 4b thus provides two effective positions for fresh air entry and thus allows enhanced control of smoke and filter properties. For example, the additional ventilation provides better ability to dilute mainstream smoke, including carbon monoxide and tar. The additional ventilation also increases the flow rate through the filter body 11, which can reduce the filtration efficiency of materials such as tar. In the embodiment of fig. 4B, an additional vent 17B is provided at the mouth end of the fluted section 5A. Air flowing through the ventilation holes 17B thus enters the main portion of the filter 5 at a location slightly upstream of the air entering through the ventilation holes 17 (and travelling along the grooves 7). The overall result of the arrangement in figures 4a and 4b is to provide better ventilation and thus enhanced smoke dilution compared to the arrangement in figure 2.

It should be understood that the embodiments in fig. 4a and 4B may be combined in a single embodiment having both additional vents 17A and additional vents 17B. That is, there are additional ventilation holes at both ends of the fluted filter section 5A. It will also be appreciated that ventilation, whether into the recess 17 or additional ventilation through the holes 17A or 17B, may be provided over a wide range or area across part or all of the filter segment 5A.

It will also be appreciated that the number of filter sections may be different from the three filter sections shown in figures 1, 2 and 4. For example, some multi-section filters may have only 2 filter segments, while other multi-section filters may have 4, 5, or more filter segments. Typically, the fluted filter section is separated from the mouth end of the filter by at least one further filter section (to help avoid blockage by the lips). Moreover, although the grooves in fig. 1-4 are shown as extending the entire length of the grooved filter segment 5A, in other embodiments the grooves may extend only a portion of the length of the grooved filter segment. In this case, the grooves may begin at the tobacco end exiting the segment and/or terminate at the mouth end of the segment. Rather, the grooves may in some cases extend (partially or fully) across a plurality of filter segments.

Figure 5 illustrates a method of processing a filter according to one embodiment of the present invention. In this example, the impermeable sheet 6 of tipping paper material is embossed or embossed to form the recesses 7. The fluted material is wrapped around a cylinder of filter material 11 (figure 5 a). The groove shown in fig. 5 has a U-shaped profile, but may have any other suitable profile such as a V-shape or square corners at the top and bottom. Although the grooves (in figure 5a) are shown as being located on the inner surface of the tipping paper material 6, thus forming channels within the body of the filter material itself, it will be appreciated that these channels may also be formed externally of the body of filter material. In addition, the number and spacing of the grooves may also vary in different embodiments. For example, there may be a continuous (non-spaced) V-shaped groove to give the inner tipping paper an effectively zig-zag configuration.

In the process of figure 5, the outer layer of tipping paper material 13 is now wrapped around the outside of the fluted filter rod (figure 5 b). The grooves 7 in the inner tipping paper material thus become a closed channel between the inner tipping paper 6 and the outer tipping paper 13. If desired, an outer tipping paper 13 may be used to bind the filter segment 11 to one or more other filter segments.

Additional ventilation holes 17 may be formed in the outer tipping paper 13 using a laser 51. Although the outer tipping paper 13 is shown as being separate from the inner tipping paper 6 for clarity, they may equally in practice be in contact as shown in figure 5b except where a groove is provided. The vent 17 coincides with the recess 7 and thus provides an inlet aperture for air to flow into the recess. Additional vents may be provided that are not connected to the recess (as shown in figures 4a and 4b above). Such ventilation holes may be formed through the outer tipping paper and also through the inner tipping paper and outer tipping paper.

Another layer of sheet material 15, commonly referred to as tipping paper, may then be added to the ventilated wrapper and cover the fluted filter section 5A (figure 5 d). Tipping paper may be used to attach the combined filter segment to the tobacco rod and thereby secure the various parts of the completed cigarette 1 together. Tipping paper may be permeable (pre-perforated) or impermeable. The impermeable tipping paper may be treated with air by means of an on-machine laser processing technique.

In another embodiment, in-line continuous grooving is applied to the filter rod, for example by wrapping an impermeable inner tipping paper around the entire length of the rod, which is then grooved through a former. The filter rod can then be segmented for combination with other segments of a multi-segment filter. Alternatively, discontinuous grooves may be applied to the filter rod, for example by pressing discontinuous grooves into the wrapped rod using a heated former.

Where a continuous grooving process is used, the grooves are brought into proximity with the elements on the tobacco side of the grooved segment by any suitable method. For example, an outer ring (washer) made of plastic may be inserted between the two elements (as shown in fig. 1). Another possible method for this sealing is to apply glue at the end of the groove furthest from the mouth end.

When using a discontinuous grooving process, the filter segments are combined in such a way that the grooves do not reach the tobacco-side end of the filter segment.

The grooves or channels may be formed by any known method. For example, in certain embodiments, the grooves may be formed directly into the filter material, such as by thermoforming of acetate filters. In other embodiments, the impermeable inner tipping paper may be formed or embossed prior to wrapping around the plug of filter material.

In certain embodiments, continuous fluting is applied by any suitable means to the filter rod lengths that are subsequently segmented. In other embodiments, fluting is applied to pre-formed filter segments.

In certain embodiments, a permeable tipping paper layer may be used to further encapsulate the fluted filter segment. Such permeable tipping paper may also be used to combine two or more filter segments.

The barrier layer 9 may be formed by any suitable material and/or mechanism. For example, one option is to incorporate adhesive dots or strips or other impermeable material into each recess 7. Another option is to provide an annular impermeable material, such as plastic, which surrounds almost the entire circumference of the filter 5 and isolates (and blocks) the grooves 7 from the filter segment 5C of the tobacco end. Another possibility is to provide the separating layer 9 by hot melting of the filter material 11.

Another layer of perforated or unperforated sheet material 15, commonly known as tipping paper, is then added to the combined filter and covers the outer tipping paper. Tipping paper may be used to attach the combined filter to the tobacco rod. Tipping paper may be bonded to the filter and tobacco rod by any suitable means, but may leave a significant portion unbonded on the grooved section 5A.

In some embodiments, the perforation of the tipping paper may be provided by a laser or by other suitable means. The tipping paper may be perforated before or after being wrapped around the filter.

The tipping paper is bonded to the three filter segments using a bonding technique across the gap so that a large glue-free area is located between the ventilation holes and the tipping paper covering the grooves. It will be appreciated that joining the three layers (inner, outer and tipping paper) together with adhesive where the vents are present will result in a blockage of the airflow and so the region remains substantially unbonded.

Various modifications to the above-described embodiments will be apparent to those skilled in the art. Therefore, the scope of the invention is to be determined by the appended claims and their equivalents.

Claims (33)

1. A multi-section filter for a smoking product comprising at least first and second filter sections, wherein the first filter section is located at the mouth end of the filter and wherein the second filter section comprises a set of ventilation holes and a set of grooves extending from respective ventilation holes along the second filter section towards, but not into, the first filter section.

2. A multi-section filter according to claim 1, wherein the grooves extend along the outside of the filter body substantially parallel to the major axis of the filter.

3. A multi-section filter according to claim 1 or 2, wherein the grooves are substantially impermeable along their length.

4. A multi-section filter according to any one of the preceding claims, wherein the body of the second filter section is separated from the grooves in the section by an impermeable barrier.

5. A multi-section filter according to any one of the preceding claims, wherein at least one filter section comprises adsorbent material.

6. A multi-section filter according to any one of the preceding claims, wherein air enters the recess through the ventilation holes through the permeable membrane.

7. A multi-section filter according to any one of the preceding claims, wherein the filter is arranged such that air flowing through the ventilation holes travels along the grooves towards the first filter section and exits the grooves into the body portion of the filter adjacent the first filter section.

8. A multi-section filter according to any one of the preceding claims, wherein all air entering through the ventilation holes is directed along the grooves.

9. A multi-section filter according to any one of claims 1 to 7, wherein the grooves extend from part of the ventilation holes, and wherein part of the ventilation holes are introduced into the body portion of the filter section.

10. A multi-section filter according to claim 9, wherein the ventilation holes introduced into the body portion are located near the end of the grooves furthest from the first filter section.

11. A multi-section filter according to claim 9, wherein the ventilation holes introduced into the body portion are located near the end of the grooves nearest the first filter section.

12. A multi-section filter according to any one of the preceding claims, wherein the ventilation holes are more than 11mm from the mouth end of the first filter section.

13. A multi-section filter according to claim 12, wherein the ventilation holes are located about 12 to 25mm from the mouth end of the first filter section.

14. A multi-section filter according to any one of the preceding claims, wherein the grooves extend substantially the length of the second filter section.

15. A multi-section filter according to any one of the preceding claims, further comprising a barrier at the end of each recess furthest from the first filter section so that this end of the recess is accessible only through the ventilation holes.

16. A multi-section filter according to claim 15, wherein the barrier is provided by hot melt fusion of the filter material.

17. A multi-section filter according to claim 15, wherein the barrier is provided by glue applied to the end of each groove.

18. A multi-section filter according to claim 15, wherein the barrier is provided by an annular element located at the end of the second filter section furthest from the first filter section.

19. A multi-section filter according to any preceding claim, comprising three filter sections arranged end to end, wherein the second filter section forms the mid-section of the filter.

20. A multi-section filter according to any one of the preceding claims, wherein the second filter section has an inner tipping paper and an outer tipping paper, and wherein the inner tipping paper is impermeable and the outer tipping paper is permeable.

21. A smoking article comprising a tobacco rod and a multi-section filter according to any one of the preceding claims.

22. A smoking article comprising a tobacco rod and a multi-section filter having at least first and second filter sections, wherein the first filter section is located at the mouth end of the filter and wherein the second filter section comprises a set of ventilation holes and a set of grooves extending from respective ventilation holes along the second filter section towards but not into the first filter section.

23. A method of making a smoking article comprising: combining the fluted filter section and the mouth end filter section by overlapping the fluted filter section with a permeable tipping paper and then overlapping the combined fluted filter section and mouth end filter section with a tipping paper containing ventilation holes, wherein the positions of some or all of the ventilation holes correspond to the positions of the flutes.

24. A method according to claim 23, wherein the fluted filter section is made by shaping a filter rod.

25. A method according to claim 23, wherein the fluted filter segment is made by forming a tipping paper and wrapping the formed tipping paper around a filter rod.

26. A method as claimed in any one of claims 23 to 25, wherein the vent holes are formed using on-line or off-line perforation.

27. A method according to any one of claims 23 to 25, wherein the groove is blocked at an end opposite the mouth end during the combining operation.

28. The method of claim 27, wherein plugging is achieved by adding a binder.

29. A method as claimed in claim 27, wherein the blocking is achieved by hot melting of the filter material.

30. The method of claim 27, wherein the blocking is accomplished by adding an annular material to the end of the fluted filter section.

31. A multi-section filter substantially as hereinbefore described and with reference to the accompanying drawings.

32. A method of making a multi-section filter as hereinbefore described and with reference to the accompanying drawings.

33. A method of making a multi-section filter smoking article substantially as hereinbefore described and with reference to the accompanying drawings.