HK1175670A - Filter for a smoking article - Google Patents

Description

Filter for a smoking article

Technical Field

The present invention relates to a filter for a smoking article, and more particularly to a filter having a window portion therein and a method of producing the filter.

Background

Typically, a smoking article, such as a cigarette, comprises a tobacco rod in the form of a tobacco column or a tobacco-based smokable material wrapped in a wrapper, the tobacco rod or the tobacco-based smokable material being provided with a filter at one end thereof. In its basic form, the filter is a cylindrical plug formed of a filter material, such as cellulose acetate tow, which may be wrapped in a layer of plugwrap which helps maintain the cylindrical shape and configuration of the filter. The filter is bonded to the tobacco rod using tipping paper, which is an outer paper layer wrapped around the filter and overlapping the bond between the filter and the tobacco rod. The tipping paper is glued in place with glue. Known filters optionally include features that alter the smoke flow and filter function, such as recesses and gaps, and additives such as particulate carbon.

Another known filter for a smoking article comprises a transparent plugwrap and tipping paper which does not cover the entire filter, such that a portion of the plugwrap of the filter remains exposed and, because the plugwrap is transparent, a window portion is formed through which the filter material can be seen.

In addition to such "window" type filters, "multi-segment" type filters are also known which comprise a plurality of individual filter plug segments, typically each wrapped in a plugwrap ("inner" plugwrap), and the segments are held within another "outer" plugwrap, wherein the filter segments may be immediately adjacent to and in contact with each other or may be spaced from each other by a gap and thus form a cavity within the filter. In the latter form, the cavities between filter plug segments in the filter may be empty (i.e. air gaps) or may be filled with a filler material such as a particulate smoke modifying material-for example particulate carbon or particulate flavourant material. It is possible that such a window filter could also be a multi-segment filter such that the cavity, material within the cavity or one or more filter plug segments are visible through a window formed by the transparent outer plugwrap.

A conventional method of constructing known filters, particularly multi-segment filters as described above, involves applying lines of adhesive to the inner surface of the outer plugwrap immediately prior to the or each filter plug/segment being provided thereto and subsequently placing the outer plugwrap around the filter plug/segment and sealing with adhesive at the lap seam. The initial line of adhesive on the inside of the outer plugwrap is a continuous line of adhesive and is known as a "fixing line" and prevents the filter plug/segment from moving relative to the plugwrap or slipping out of the plugwrap during subsequent smoking article manufacturing steps.

In conventional smoking articles where the plugwrap is made of an opaque material, such as paper, applying a continuous fixing thread to the inside of the plugwrap is not an issue because it is not visible from the outside of the filter. However, in the manufacture of window filters where the outer plugwrap is transparent, the securing thread can be seen in the window portion of the filter, on the inside of the outer plugwrap. Multi-segment filters that form a cavity (which may be either empty or filled with other material) between two of the filter segments are particularly problematic because the line of adhesive securement in the space can be specifically seen as a line of adhesive residue and detracts from the appearance of the window filter of the smoking article.

Disclosure of Invention

It is therefore an object of the present invention to provide a method of manufacturing a filter for a smoking article which substantially compensates or overcomes the above problems, a filter which is substantially free of the above problems and a smoking article incorporating such a filter.

Accordingly, the present invention provides a filter for a smoking article comprising one or more segments of filter media and a substantially transparent wrapper, the one or more filter segments and the wrapper defining a cavity in which a fixing adhesive is disposed to fix the one or more filter segments to the wrapper, the fixing adhesive being disposed only between the wrapper and portions of the one or more filter segments other than those corresponding to the recesses or cavities.

The securing adhesive may be an activatable adhesive and may be a heat activated adhesive.

The filter may comprise two or more filter segments spaced apart from one another to define at least one cavity within the filter. The fixing adhesive may be provided only between the wrapper and the filter segment. The cavity may be an empty space filled with air or may contain another smoke modifying material, such as a granular adsorbent material.

The wrapper may be transparent or may be tinted and may include a logo or design printed thereon.

The invention also provides a smoking article comprising a rod of smokable material, such as tobacco or a tobacco substitute, a filter attached to one end of the rod of smokable material, and a window formed in the filter, the filter comprising one or more segments of filter media and a substantially transparent wrapper, at least a portion of the substantially transparent wrapper forming at least a portion of the window, wherein a fixing adhesive is provided to fix the one or more filter segments to the wrapper, the fixing adhesive being provided only between the one or more filter segments and portions of the wrapper other than those forming at least a portion of the window.

The filter may comprise a filter as described above, and the smoking article may further comprise tipping paper attaching the filter to the rod of smokable material, and the tipping paper may extend only part of the length of the filter such that a portion of the filter remains exposed so as to define the window, thereby enabling the cavity or recess of the interior of the filter to be seen through the transparent wrapper.

The tipping wrapper may comprise a first tipping wrapper and the smoking article may further comprise a second tipping wrapper circumscribing the mouth end of the wrapper and axially spaced from the first tipping wrapper so as to define the window between the first and second tipping wrappers. The window between the first and second tipping wrappers may be aligned with a cavity or recess in the filter.

The present invention also provides a method of making a filter for a smoking article, the method comprising positioning one or more segments of filter media onto a substantially transparent wrapper in axial alignment, providing a securing adhesive to secure the one or more segments to the wrapper and wrapping the wrapper around the one or more filter segments to define a recess or cavity, wherein the step of providing a securing adhesive comprises providing a securing adhesive only between the wrapper and portions of the one or more filter segments other than those corresponding to the recess or cavity.

The step of positioning one or more filter media segments comprises positioning a plurality of filter media segments in axial alignment on a substantially transparent wrapper and spaced apart from one another to define a gap therebetween, and wherein wrapping the wrapper comprises wrapping the wrapper around a filter segment to define a cavity between the filter segments.

The fixing adhesive may be applied to the wrapper at a particular location where the filter segment is to be located on the wrapper.

The method may further comprise conveying the wrapper as a continuous strip through a securing adhesive applicator and intermittently applying the securing adhesive to the wrapper strip at discrete locations as the wrapper strip passes through the securing adhesive applicator.

The method may still further comprise providing filter segments to the wrapper strip at a location downstream of the securing adhesive applicator corresponding to the speed of transport of the wrapper strip and the location of the securing adhesive on the wrapper strip such that the filter segments are disposed entirely over the discontinuous portion of the securing adhesive.

The filter segments may be provided on a wrapper and the fixing adhesive may be applied directly to each filter segment.

The method may comprise conveying the wrapper as a continuous strip, providing filter segments onto the wrapper strip at discrete locations and applying the fixing adhesive from the applicator corresponding to the speed of conveyance of the wrapper strip and the location of a particular filter segment on the wrapper strip such that the fixing adhesive is applied only to the filter segment.

The fixing adhesive may be applied to each filter segment before it is applied to the wrapper.

The securing adhesive may be an activatable adhesive and the method may further comprise transporting the wrapper as a continuous strip, disposing filter segments having activatable securing adhesive thereon at discrete locations on the wrapper strip and activating the adhesive on the filter segments using adhesive activation means.

The securing adhesive may be a heat activated adhesive and the adhesive activation device may be a heating device.

The method may further comprise wrapping the wrapper around a series of filter segments to form a continuous rod of filters and subsequently cutting the continuous rod at regular intervals.

The present invention also provides a method of manufacturing a filter segment for a filter of a smoking article, the method comprising forming a continuous rod of filter material, conveying a continuous strip of inner plugwrap through an adhesive applicator nozzle and applying adhesive to one side of the inner plugwrap, wrapping the continuous rod of filter material with the inner plugwrap having adhesive on the outside to form a continuous rod of wrapped filter material, and cutting the continuous rod of wrapped filter material into individual filter segments.

The method may further comprise applying adhesive to both sides of the inner plugwrap.

The invention also provides a method of manufacturing a filter for a smoking article, the method comprising manufacturing a filter segment as described above and subsequently using the filter segment to manufacture a filter as described above.

Drawings

In order that the invention may be more fully understood, embodiments thereof will now be described, by way of illustrative example only, with reference to the accompanying drawings, in which:

figure 1 is an exploded perspective view of a smoking article with a conventional multi-segment filter;

figure 2 is an exploded perspective view of a smoking article with an alternative type of conventional multi-segment filter;

FIG. 3 is a schematic illustration of a conventional manufacturing process for producing the filter shown in FIG. 2;

figure 4 is a perspective view of the smoking article of figure 2;

figure 5 is an exploded perspective view of a smoking article having a multi-segment filter of the present invention;

figure 6 is a schematic view of a manufacturing process of the invention for producing a filter shown by the smoking article of figure 5;

figure 7 is an exploded perspective view of a smoking article having an alternative multi-segment filter of the present invention;

figure 8 is a schematic view of an alternative manufacturing process of the invention for producing a filter shown by the smoking article of figure 7;

figure 9 is an exploded perspective view of a smoking article having another alternative multi-segment filter of the present invention;

figure 10 is a schematic view of a manufacturing process of the present invention for producing a filter plug segment, shown by the smoking article of figure 9;

figure 11 is a schematic view of another alternative manufacturing process of the invention for producing a filter shown by the smoking article of figure 9.

Detailed Description

Referring now to figure 1, a conventional smoking article 1 having a multi-segment filter is shown to comprise a tobacco rod 2 and a filter 3. The tobacco rod 2 is of conventional form and comprises a tobacco rod or tobacco-based smokable material wrapped in a wrapper. The filter 3 comprises three axially aligned cylindrical filter segments/plugs 4a, 4b, 4c of filter media, for example cellulose acetate, wrapped by an outer plugwrap 5. (although not specifically shown, each cylindrical filter segment 4a-4c may also be wrapped in its own single inner wrapper to retain the filter segment in a cylindrical shape). The filter 3 is bonded to the tobacco rod 2 by tipping paper 6, the tipping paper 6 wrapping around the filter 3 and covering the bond between the filter 3 and the tobacco rod 2.

The outer plugwrap 5 includes a "fixing thread" 7, which "fixing thread" 7 is a line of adhesive on the inside of the outer plugwrap 5, the filter segments 4a, 4b, 4c being provided on the "fixing thread" 7 and the "fixing thread" 7 fixing the filter segments 4a, 4b, 4c to the outer plugwrap 5 during subsequent stages of filter construction and smoking article manufacture, for example to prevent movement of the filter segments 4a, 4b, 4c on the outer plugwrap 5 as the outer plugwrap 5 wraps around the filter segments 4a, 4b, 4c and to prevent the filter segments 4a, 4b, 4c from slipping out of the tube of the outer plugwrap 5 when the formed filter 3 is joined to the tobacco rod 2 by tipping paper 6.

In the conventional smoking article shown in figure 1, both the outer plug wrap 5 and the tipping paper 6 are made of an opaque material, such as paper, and thus the fixing thread 7 cannot be seen on the outside of the finished smoking article.

Referring now to figures 2 and 4, there is shown another known type of smoking article 11, the smoking article 11 having a multi-segment filter and comprising a tobacco rod 12 and a filter 13. The filter 13 is of a type known as a "window" filter and comprises two axially aligned cylindrical filter segments/plugs 14a, 14b of filter media, for example cellulose acetate, surrounded by an outer plug wrap 15. (although not specifically shown, each cylindrical filter segment 14a, 14b may also be wrapped in its own single inner wrapper to retain the filter segment in a cylindrical shape). The two filter segments 14a, 14b are spaced apart from each other in the filter 13, so that a cavity 14c is defined between the two filter segments 14a, 14b within the filter 13. The filter 13 is bonded to the tobacco rod 12 by first tipping paper 16a, the first tipping paper 16a being wrapped around the filter 13 and covering the bond between the filter 13 and the tobacco rod 12. The second tipping wrapper 16b encircles the distal mouth-engaging end of the wrapped filter 13 and is spaced from the first tipping wrapper 16a so as to define a gap 16c therebetween. The outer plugwrap 15 is made of transparent material and so the interior of the cavity 14c in the filter 13 can be seen through a "window" formed by the transparent outer plugwrap 15 and the gap 16c between the first and second tipping papers 16a, 16 b.

Just as the first-described outer plugwrap 5 of the conventional smoking article 1, the outer plugwrap 15 includes an adhesive "fixing line" 17 on the inside thereof, on which adhesive "fixing line" 17 the filter segments 14a, 14b are disposed so as to fix them to the outer plugwrap 15. The conventional process of applying a fixing thread 17 to the outer plug wrap 15 is shown schematically in figure 3. The outer plugwrap 15 is delivered as a continuous ribbon in the direction of arrow "a" from a roll or other such supply (not shown) through a securing adhesive applicator nozzle 20 which applies a continuous line of securing adhesive 17 to the outer plugwrap 15. Downstream of the applicator nozzle 20, individual dual length filter segments 22 are placed onto the outer plugwrap 15 and spaces 23 are left between each dual length filter segment 22. The outer plugwrap 15 is then placed around the dual length filter segment 22 and secured in place by lap seams using suitable means (not shown) to form a continuous filter rod 24. Finally, a cutter 25 cuts the continuous filter rod 24 at a point intermediate each dual length filter segment 22 to form individual filters 13 each having a pair of filter segments 14a, 14b spaced from each other to define a cavity 14c therebetween and secured within the tube of transparent outer plugwrap 15 by adhesive securing threads 17.

Although in the process described above and shown in figure 3 the cutter 25 cuts the continuous filter rod 24 at a mid-point of each dual length filter segment 22 to form a single filter 13, in an alternative manufacturing process the cutter 25 may cut the continuous filter rod 24 at a mid-point of every four or every six dual length filter segments 22 (for example) to form four or six filter-bonded intermediate filter rods. These "four together" or "six together" (for example) filter rods are selected and formed according to the particular machine used in the subsequent smoking article manufacturing process, which may require such four together or six together format intermediate filter rods to be fed and subsequently processed and divided to form individual smoking articles with individual filters 13 attached thereto.

It will be appreciated that because the applicator nozzle 20 applies a continuous line of adhesive securing 17 to the outer plugwrap 15, the securing adhesive 17 is provided not only at the location between each filter segment 14a, 14b and the outer plugwrap 15 where it is required to hold the filter segment 14a, 14b in place, but also on the outer plugwrap 15 in the cavity 14c between the filter segments 14a, 14 b. This means that the glue residue line 21 (see figures 3 and 4) can be seen through the window of the window filter 13, which spoils the appearance of the final smoking article 11 containing the filter.

Referring now to figure 5, there is shown a smoking article 101 comprising a multi-segment filter 103 of the present invention bonded to a conventional tobacco rod 102. The filter 103 is a "window" type filter and comprises two axially aligned cylindrical filter segments/plugs 104a, 104b of filter media, for example cellulose acetate, wrapped by an outer plug wrap 105. (although not specifically shown, each cylindrical filter segment 104a, 104b may also be wrapped in its own single inner plugwrap to retain the filter segment in a cylindrical shape). The two filter segments 104a, 104b are spaced apart from each other in the filter 103, thereby defining a cavity 104c between the two filter segments 104a, 104b within the filter 103. Just as with the conventional smoking article 11 of figure 2, the filter 13 is bonded to the tobacco rod 102 by a first tipping wrapper 106a, the first tipping wrapper 106a being wrapped around the filter 103 and covering the bond between the filter 103 and the tobacco rod 102, and a second tipping wrapper 106b being wrapped around the distal mouth-engaging end of the filter 103 and spaced from the first tipping wrapper 106a so as to define a gap 106c therebetween. The outer plugwrap 105 is made of transparent material and so the interior space of the cavity 104c in the filter 103 can be seen through the "window" formed by the transparent outer plugwrap 105 and the gap 106c between the first and second tipping papers 106a, 106 b.

As can be seen in fig. 5, the outer plugwrap 105 does not include a continuous line of adhesive securement as the conventional filter shown in fig. 1 and 2, but rather includes a discontinuous line of adhesive securement 107, the discontinuous line of adhesive securement 107 including two discontinuous portions of adhesive 107a, 107b longitudinally aligned and spaced from one another and corresponding to the location at which the two filter segments 104a, 104b are disposed on the outer plugwrap 105. There is no adhesive in the space between the two non-continuous adhesive portions 107a, 107 b. It will therefore be appreciated that there is no glue residue in the cavity 104c seen through the window of the window filter 103 thus formed, and therefore the filter 103 of the present invention is not affected by the drawbacks of the conventional window filter 13 described above.

Figure 6 schematically illustrates the manufacturing process of the present invention for applying discrete fixing lines 107 to the outer plugwrap 105. As with the conventional manufacturing process described above and shown in fig. 3, the outer plugwrap 105 is delivered as a continuous strip in the direction of arrow "a" from a roll or other such supply (not shown) through a securing adhesive applicator nozzle 120, the applicator nozzle 120 applying securing adhesive 107 to the outer plugwrap 105. However, the applicator nozzle 120 does not apply a continuous line of adhesive, but is activated to dispense adhesive intermittently as the outer plugwrap 105 is conveyed through the applicator nozzle 120, thereby forming an interrupted, discontinuous line of adhesive fixation 107 of a plurality of discontinuous adhesive portions 107 a/107 b on the outer plugwrap 105. Downstream of the applicator nozzle 120, a single dual length filter segment 122 is provided onto the outer plug wrap 105, leaving a gap 123 between the dual length filter segments 122.

The filter segment positions are synchronized with the transport speed of the outer plugwrap 105 and are aligned with the positions of the non-continuous stationary adhesive portions 107 a/107 b on said outer plugwrap 105 such that each double length filter segment 122 is disposed directly on a respective non-continuous adhesive portion 107 a/107 b and such that the gaps 123 between said double length filter segments 122 correspond with the spaces between the non-continuous adhesive portions 107 a/107 b on the outer plugwrap 105 where no adhesive is deposited. In addition, the applicator nozzle 120 is actuated to deposit the non-continuous fixed adhesive portions 107 a/107 b on the outer plugwrap 105 over a length equal to or slightly less than the length of the dual length filter segment 122. This ensures that filter segments 122 can be positioned on non-continuous adhesive portions 107 a/107 b such that no adhesive extends beyond the longitudinal ends of the dual length filter segments 122 in the gaps 123 between filter segments 122.

Downstream of the point at which the dual length filter segment 122 is disposed onto the outer plugwrap 105, the outer plugwrap 105 is placed around the dual length filter segment 122 and secured in place along the lap seam in a suitable manner (not shown) to form a continuous filter rod 124. Finally, a cutter 125 cuts the continuous filter rod 124 at a point intermediate each dual length filter segment 122 to form individual filters 103, each filter 103 having a pair of filter segments 104a, 104b spaced from each other by a cavity 104c and secured within the tube of transparent outer plugwrap 105 by respective non-continuous securing adhesive portions 107 a/107 b.

Although in the process described above and illustrated in fig. 6, the cutter 125 cuts the continuous filter rod 124 at a mid-point of each dual length filter segment 122 to form a single filter 103, in an alternative manufacturing process of the invention, the cutter 125 may cut the continuous filter rod 124 at a mid-point of every four or every six dual length filter segments 122 (for example) to form four or six intermediate filter rods together. These "four together" or "six together" (for example) filter rods are selected and formed according to the particular machine used in the subsequent smoking article manufacturing process, which may require such four together or six together format intermediate filter rods to be fed and subsequently processed and divided to form individual smoking articles having individual filters 103 attached thereto.

It will be appreciated that the filter manufacturing process of the invention described above ensures that there is no anchoring adhesive 107 on the outer plugwrap 105 in the cavity 104c between the two filter segments 104a, 104b and so that glue residues are not visible through the windows of the formed window filter 103. Therefore, the filter 103 of the present invention is not affected by the disadvantages of the conventional window filter 13 described above.

Referring now to figure 7, there is shown a smoking article 201 incorporating an alternative multi-segment filter 203 of the present invention. The filter 203 is a "window" type filter and, like the filter 103 shown in fig. 5, comprises two axially aligned cylindrical filter segments/plugs 204a, 204b of filter media, e.g. cellulose acetate, spaced apart from one another to define a gap 204c therebetween within the filter 203 and wrapped by an outer plug wrap 205. (although not specifically shown, each cylindrical filter segment 204a, 204b may also be wrapped in its own single inner wrapper to retain the filter segment in a cylindrical shape). The filter 203 is bonded to the tobacco rod 202 by a first tipping wrapper 206a, the first tipping wrapper 206a being wrapped around the filter 203 and covering the bond between the filter 203 and the tobacco rod 202, and a second tipping wrapper 206b being wrapped around the distal mouth-engaging end of the filter 203 and spaced from the first tipping wrapper 206a so as to define a gap 206c therebetween. The outer plugwrap 205 is made of transparent material and so the interior of the cavity 204c in the filter 203 can be seen through a "window" formed by the transparent outer plugwrap 205 and the gap 206c between the first and second tipping papers 206a, 206 b.

As can be seen in fig. 7, the filter 203 of the alternative embodiment of the present invention differs from the filter shown in fig. 5 in that the outer plug wrap 205 does not include any continuous or discontinuous lines of adhesive securement formed thereon. Instead, the adhesive fixation line 207 is disposed directly on the filter plug segments 204a, 204b along the longitudinal direction of the filter plug segments 204a, 204 b. It will therefore be appreciated that because there is no fixing adhesive on the outer plugwrap 205, no glue residue is visible through the window of the window filter 203 thus formed, and therefore the filter 203 is not affected by the disadvantages of the conventional window filter 13 described above.

Fig. 8 schematically illustrates a manufacturing process of the present invention for applying a securing adhesive 207 to filter segments 204a, 204 b. As with the conventional manufacturing process described above and shown in fig. 3, the outer plugwrap 205 is delivered as a continuous band from a drum or other such supply source (not shown) in the direction of arrow "a". A single dual length filter segment 222 is placed onto the outer plugwrap 205 leaving a gap 223 between the dual length filter segments 222. A securing adhesive applicator nozzle 220 is provided downstream of the point at which the dual length filter plug segment 222 is placed onto the outer plugwrap 205, thereby applying the securing adhesive thread 207 directly onto the dual length filter plug segment 222. The applicator nozzle 220 is activated to dispense adhesive intermittently as the outer plugwrap 205 is conveyed through the applicator nozzle 220, thereby depositing securing adhesive 207 on the dual length filter plug segment 222 as the outer plugwrap 205 is conveyed through the applicator nozzle 220.

The applicator nozzle 220 is synchronized with the speed of conveyance of the outer plugwrap 205 and is aligned with the position of the dual length filter plug segments 222 on the plugwrap such that each line of securing adhesive 207 is deposited directly and only on each dual length filter plug segment 222 and such that no adhesive is deposited on the outer plugwrap 205 in the gap 223 between said dual length filter plug segments 222.

Downstream of the point at which the applicator 220 deposits securing adhesive onto each dual length filter segment 222, the outer plugwrap 205 is placed around the dual length filter segment 222 and secured in place (not shown) in a suitable manner along the lap seam to form a continuous filter rod 224. Finally, a cutter 225 cuts the continuous filter rod 224 at a point intermediate each dual length filter segment 222 to form a single filter 203, each filter 203 having a pair of filter segments 204a, 204b spaced from each other by a cavity 204c and secured within the tube of transparent outer plugwrap 205 by respective non-continuous securing adhesive portions 207.

Although in the alternative process of the invention described above and shown in figure 8 the cutter 225 cuts the continuous filter rod 224 at a mid-point of each dual length filter segment 222 to form a single filter 203, in the alternative manufacturing process of the invention the cutter 225 cuts the continuous filter rod 224 at a mid-point of every fourth or every sixth dual length filter segment 222 (for example) to form four or six filter-together intermediate filter rods. These "four together" or "six together" (for example) filter rods are selected and formed according to the particular machine used in the subsequent smoking article manufacturing process, which may need to be fed with such four together or six together format intermediate filter rods and then processed and further divided to form individual smoking articles with individual filters 203 attached thereto.

It will be appreciated that the alternative filter manufacturing process of the invention described above ensures that there is no anchoring adhesive 207 on the outer plugwrap 205 in the cavity 204c between the two filter segments 204a, 204b and therefore that glue residues cannot be seen through the windows of the formed window filter 203. Therefore, the alternative filter 203 of the present invention is not affected by the disadvantages of the conventional window filter 13 described above.

Referring now to figure 9, there is shown a smoking article 301 incorporating another alternative multi-segment filter 303 of the present invention. Filter 303 is a "window" type filter and, as with filters 103, 203 shown in fig. 5 and 7, respectively, comprises two axially aligned cylindrical filter segments/plugs 304a, 304b of filter media, e.g., cellulose acetate, spaced apart from one another to define a gap 304c therebetween within filter 303 and wrapped by outer plugwrap 305. The filter 303 is bonded to the tobacco rod 302 by a first tipping wrapper 306a, the first tipping wrapper 306a being wrapped around the filter 303 and covering the bond between the filter 303 and the tobacco rod 302, and a second tipping wrapper 306b being wrapped around the distal mouth-engaging end of the filter 303 and spaced from the first tipping wrapper 306a so as to define a gap 306c therebetween. The outer plugwrap 305 is made of a transparent material and so the interior space of the gap 304c in the filter 303 can be seen through a "window" formed by the transparent outer plugwrap 305 and the gap 306c between the first and second tipping papers 306a, 306 b.

As can be seen in fig. 9, another alternative embodiment of the filter 303 of the present invention differs from that shown in fig. 5 and 7 in that neither the outer plugwrap 305 nor the filter segments 304a, 304b include any continuous or discontinuous longitudinally lines of adhesive securement formed thereon. Instead, the securing adhesive 307 is disposed on the entire outer surface of the filter plug segments 304a, 304 b. It will therefore be appreciated that because there is no fixing adhesive on the outer plugwrap 305, glue residues cannot be seen through the window of the window filter 303 thus formed, and therefore the filter 303 does not have the disadvantages of the conventional window filter 13 described above.

Each filter segment 304a, 304b comprises a cylindrical plug of filter material 326, such as cellulose acetate tow, wrapped by an inner plugwrap 327 for receiving loose filter material in cylindrical form and retaining the filter material 326 in the shape of a cylindrical plug. Fig. 10 schematically illustrates a manufacturing method of the present invention for producing filter segments 304a, 304b, with a securing adhesive on the outer surface of the filter segments 304a, 304 b. A continuous rod of filter material 328 is carried in the direction of arrow "B" from a source of filter material and a rod forming device. The material of the inner plugwrap 327 is carried as a continuous ribbon from a drum or other such supply (not shown) towards a continuous rod of filter material 328 in the direction of arrow "C". Upstream of the location where the inner plugwrap material 327 meets the continuous rod of filter material 328, the material of the inner plugwrap 327 passes through a standing adhesive spray nozzle 329 which applies the standing adhesive 307 to one side of the inner plugwrap 327 (which will be the outside of the finished filter segment 304a, 304 b). Such a securing adhesive 307 is an activatable adhesive that dries without remaining tacky on the inner plugwrap 327 and may then be activated, for example by heating, to activate adhesive properties when desired.

Downstream of the spray nozzle 329, the inner plugwrap 327 meets a continuous rod of filter material 328 with the non-adhesive side of the inner plugwrap 327 in contact with the continuous rod of filter material 328, and the inner plugwrap 327 is then wrapped around the continuous rod of filter material 328 and sealed in an appropriate manner (not shown) along the lap seam, thereby producing a continuously wrapped filter rod 330. Finally, a cutter 331 cuts the continuous rod 330 into individual dual length filter segments 322, each dual length filter segment 322 having the dried activatable securing adhesive 307 applied to their outer surfaces.

Fig. 11 schematically illustrates another alternative manufacturing process for producing the filter segments 304a, 304b of fig. 9. As with the conventional manufacturing process described above and shown in fig. 3, the outer plugwrap 305 is delivered as a continuous band in the direction of arrow "a" from a drum or other such supply source (not shown). Separate dual length filter segments 322 produced as described above and shown in figure 10 are provided to the outer plugwrap 305 leaving a gap 323 between the dual length filter segments 322. A securing adhesive activation device 320 is provided downstream of the point at which the dual length filter plug segment 322 is provided to the outer plug wrap 305, thereby activating the dry securing adhesive 307 on the dual length filter segment 322. Various types of activatable adhesives 307 and adhesive activation devices 320 may be employed within the scope of the present invention. For example, the adhesive 307 may be heat activated and the activation device 320 may be a heater capable of activating the adhesive 307 using a heating element or infrared radiation to heat the dual length filter segment 322.

Downstream of the adhesive activation device 320, the outer plugwrap 305 is placed around the dual length filter segment 322 with their activated adhesive 307 and secured in place (not shown) in a suitable manner along the lap seam to form a continuous filter rod 324. Finally, a cutter 325 cuts the continuous filter rod 324 at a mid-point of each dual length filter segment 322 to form individual filters 303, each filter 303 having a pair of filter segments 304a, 304b spaced from each other by a cavity 304c and secured within the tube of transparent outer plugwrap 305 by securing adhesive 307 on the outer surface of each filter segment 304a, 304 b.

Although in another alternative process of the invention described above and shown in fig. 8, the cutter 325 cuts the continuous filter rod 324 at a mid-point of each dual length filter segment 322 to form a single filter 303, in an alternative manufacturing process of the invention, the cutter 325 may cut the continuous filter rod 324 at a mid-point of every four or every six dual length filter segments 322 (for example) to form four or six filter-together intermediate filter rods. These "four together" or "six together" (for example) filter rods are selected and formed according to the particular machine used in the subsequent smoking article manufacturing process, which may need to be fed with such four together or six together format intermediate filter rods and then processed and further divided to form individual smoking articles with individual filters 303 attached thereto.

It will be appreciated that the alternative filter manufacturing process of the invention described above ensures that there is no anchoring adhesive 307 on the outer plugwrap 305 in the cavity 304c between the two filter segments 304a, 304b and therefore that glue residues are not visible through the window of the formed window filter 303. Thus, another alternative filter 303 of the present invention does not suffer from the drawbacks of the conventional window filter 13 described above.

It will be appreciated by those skilled in the art that various modifications to the above-described embodiments of the invention are possible and are intended to be included within the scope of the appended claims. For example, in making the dual length filter segment 322 described above with reference to fig. 10, the activatable adhesive may not necessarily be sprayed onto the entire outer surface of the inner plugwrap 327, but may be sprayed as a tape or other pattern covering a portion of the surface of the inner plugwrap 327. The securing adhesive 307 may also be applied to the inner plugwrap 327 by alternative means, such as one or more rollers or one or more brushes. Additionally, adhesive may be applied to both sides of the inner plugwrap 327 to help the inner plugwrap 327 adhere to a continuous rod of filter material 328 when wrapped around.

The outer plugwrap 105, 205, 305 of the invention is described as being made of a transparent material so that the cavity within the filter 103, 203, 303 can be seen through the outer plugwrap. The term "transparent" as used herein shall refer to any material that is completely or partially transparent. That is, for example, a clear, colored, or otherwise "translucent" material is considered "transparent" regardless of color. "transparent" materials for the outer plugwrap 105, 205, 305 include, but are not limited to, polypropylene, polyvinyl chloride (PVC), cellulose acetate film, polyethylene terephthalate (PET), polyethylene oxide (PEOX), polyethylene, cellophane, Natureflex^TMOr polylactic acid (PLA). In addition to being completely transparent and clear or colored transparent ("translucent"), the outer plugwrap further includes a pattern, indicia, logo or other design or logo printed thereon.

In the various embodiments of the filter 103, 203, 303 of the present invention shown and described, the cavities 104c, 204c, 304c between the respective filter segments 104a, 104 b/204 a, 204 b/304 a, 304b are empty-i.e., air-filled spaces. However, it is contemplated within the scope of the invention that these cavities may alternatively be filled with a smoke modifying material, for example an adsorbent material such as activated charcoal/activated carbon or other known suitable materials. These embodiments will provide a different but still attractive aesthetic effect, while the filler material has the additional advantage of absorbing some other smoke components not captured by the filter segment. The particular filler material may be selected according to the smoke constituents to be absorbed, or a general adsorbent capable of absorbing many different types of smoke constituents may be selected. Alternatively, a mixture of different adsorbents may be used. As a further alternative, the cavity may be filled with a flavorant-containing material.

All the embodiments of the filter 103, 203, 303 of the invention described above show a filter comprising two filter plug sections 104a, 104 b/204 a, 204 b/304 a, 304b spaced apart from each other so as to define a single cavity 104c, 204c, 304c within said filter 103, 203, 303, said cavity 104c, 204c, 304c being either empty or filled with a filler material. However, the invention will also include filters which may comprise one filter segment or more than two filter segments spaced from each other. With a single filter segment, the filter may for example be arranged to have a window portion surrounding one or more recesses within the filter segment itself, a window portion aligned with the filter plug itself and/or a window portion surrounding a recess at the mouth end or tobacco end of the filter. The present invention may thus avoid adhesive lines in one or more of these window portions. In the case of a filter having two or more filter segments spaced apart from one another, these filter segments may, for example, form one or more cavities within the filter, which cavities may all be empty or one or more of which may have filler material. The material in each cavity may be the same or different. In these embodiments, additional outer tipping paper may be provided in alignment with any intermediate filter segments.

The various embodiments of the filters 103, 203, 303 described and illustrated and claimed within the scope of the present invention may be adapted to be manufactured in conjunction with various sized forms of smoking articles-such as those commonly referred to as "slim," "ultra-slim," "over-length," and suitable sizes of conventional smoking articles.

Only another alternative filter 303 of the present invention is shown and described as having filter segments 304a, 304b, said filter segments 304a, 304b comprising a cylinder of filter material 326 surrounded by a single inner plugwrap 327 in addition to being contained within the transparent outer plugwrap 305. However, the filter segments 104a, 104 b/204 a, 204b of the filters 103, 203 of the first and second embodiments of the invention described may comprise an inner plugwrap surrounding the filter plug in addition to the respective transparent outer plugwrap 105, 205.

All embodiments of smoking articles incorporating the filters of the invention described above comprise an outer plugwrap surrounding the filter segment and a separate tipping wrapper joining the filter to the tobacco rod. However, the scope of the invention will include alternative embodiments in which no tipping paper is provided to join the filter to the tobacco rod, but rather a transparent outer plugwrap is provided to wrap the filter segment and the end of the tobacco rod. The outer plugwrap may include non-continuous opaque portions that may be printed or painted onto the outer plugwrap material.

All embodiments of the filter of the present invention illustrated and described include a window filter having a plurality of filter segments. However, it is contemplated within the scope of the invention that the filter may comprise a single filter media segment that may include one or more indentations or depressions that form a cavity in the filter once a wrapper, such as an outer plugwrap, is wrapped. Alternatively, the single filter segment may not extend to the distal end of the filter and may thus define a recess in the filter end, possibly at the mouth end or tobacco end of the filter. Such a recess may also be formed by spacing one of the filter segments of the filter from the distal end of the filter.

Although various embodiments of the smoking article filter and method of manufacture of the present invention have been described above, the scope of the invention is not limited to these examples and any combination of the above non-mutually exclusive features will fall within the scope of the invention, which is defined by the appended claims.

Claims (26)

1. A filter for a smoking article comprising one or more segments of filter media and a substantially transparent wrapper, the one or more segments and the wrapper defining a recess or cavity, wherein a fixing adhesive is provided to fix the one or more segments to the wrapper, the fixing adhesive being provided only between the wrapper and portions of the one or more segments other than those corresponding to the recess or cavity.

2. The filter of claim 1, wherein the securing adhesive is a heat activated adhesive.

3. A filter according to claim 1 or 2, comprising two or more filter segments spaced from one another so as to define at least one cavity within the filter, wherein the fixing adhesive is provided only between the wrapper and a filter segment.

4. A filter according to any preceding claim, wherein the cavity contains a further smoke modifying material.

5. The filter of claim 4, wherein the smoke-modifying material comprises a granular adsorbent material.

6. A filter according to any preceding claim, wherein the wrapper is clear transparent.

7. A filter according to any one of claims 1 to 6, wherein the wrapper is dyed.

8. A filter according to any preceding claim, wherein the wrapper comprises a logo or pattern printed thereon.

9. A smoking article comprising a rod of smokable material, a filter attached to one end of the rod of smokable material, and a window formed in the filter, the filter comprising one or more segments of filter media and a substantially transparent wrapper, at least a portion of the substantially transparent wrapper forming at least a portion of the window, wherein a fixing adhesive is provided to fix the one or more filter segments to the wrapper, the fixing adhesive being provided only between the one or more filter segments and portions of the wrapper other than those forming at least a portion of the window.

10. A smoking article according to claim 9, wherein the filter comprises a filter according to any one of claims 1 to 8, the smoking article further comprising tipping paper attaching the filter to the rod of smokable material, the tipping paper extending only part of the length of the filter such that a portion of the filter remains exposed so as to define the window such that a cavity or recess in the interior of the filter can be seen through the transparent wrapper.

11. A smoking article according to claim 10, wherein the tipping wrapper comprises a first tipping wrapper and the smoking article further comprises a second tipping wrapper wrapped around the mouth end of the filter and axially spaced from the first tipping wrapper so as to define the window between the first and second tipping wrappers.

12. A smoking article according to claim 11, wherein the window between the first and second tipping wrappers is aligned with a cavity or recess in the filter.

13. A method of manufacturing a filter for a smoking article, the method comprising:

positioning one or more segments of filter media in axial alignment onto a substantially transparent wrapper;

providing a securing adhesive to secure said one or more filter segments to said wrapper; and

wrapping the wrapper around the one or more filter segments so as to define a recess or cavity;

wherein the step of providing said fixing adhesive comprises providing said fixing adhesive only between said wrapper and portions of said one or more filter segments other than those corresponding to said recesses or cavities.

14. A method according to claim 13, wherein the step of positioning the one or more filter media segments comprises positioning a plurality of filter media segments in axial alignment on the substantially transparent wrapper and spaced apart from one another to define one or more gaps therebetween, and wherein wrapping the wrapper comprises wrapping the wrapper around the filter segments to define cavities between the filter segments.

15. A method according to claim 14, wherein the fixing adhesive is applied to the wrapper at a particular location where the filter segment is to be located on the wrapper.

16. A method according to claim 15, comprising conveying the wrapper as a continuous strip through a securing adhesive applicator and intermittently applying securing adhesive to the wrapper strip at discrete locations as the wrapper strip passes through the securing adhesive applicator.

17. A method as claimed in claim 16, further comprising disposing the filter segment onto the wrapping paper strip at a location downstream of the securing adhesive applicator corresponding to the speed of transport of the wrapping paper strip and the location of the securing adhesive on the wrapping paper strip such that the filter segment is disposed entirely over the discontinuous portion of the securing adhesive.

18. A method according to claim 14, wherein the filter segments are provided on the wrapper and the fixing adhesive is applied directly to each filter segment.

19. A method according to claim 18, comprising conveying the wrapper as a continuous strip, providing the filter segments onto the wrapper strip at discrete locations and applying the fixing adhesive from an applicator corresponding to the speed of conveyance of the wrapping paper strip and the location of a particular filter segment on the wrapping paper strip, such that the fixing adhesive is applied only to the filter segments.

20. A method according to claim 14, wherein the fixing adhesive is applied to each filter segment before it is applied to the wrapper.

21. A method according to claim 20, wherein the securing adhesive is an activatable adhesive, the method further comprising transporting the wrapper as a continuous strip, disposing filter segments having activatable securing adhesive thereon onto the wrapper strip at discrete locations, and activating adhesive on the filter segments using adhesive activation means.

22. The method of claim 21, wherein the securing adhesive is a heat activated adhesive and the adhesive activation device is a heating device.

23. A method as claimed in any one of claims 14 to 22, further comprising wrapping the strip of wrapping paper around a series of filter segments to form a continuous rod of filters and subsequently cutting the continuous rod at regular intervals.

24. A method of manufacturing a filter segment of a filter for a smoking article, the method comprising:

forming a continuous rod of filter material;

conveying a continuous strip of inner plugwrap through an adhesive applicator nozzle and applying adhesive to one side of the inner plugwrap;

wrapping a continuous rod of filter material with said inner plugwrap having adhesive on the outside to form a wrapped continuous rod of filter material; and

cutting said continuous rod of wrapped filter material into individual filter segments.

25. A method according to claim 24, wherein adhesive is applied to both sides of the inner plugwrap.

26. A method of manufacturing a filter for a smoking article, the method comprising:

a filter segment is manufactured as claimed in claim 24 or 25 and subsequently a filter is manufactured using the filter segment as claimed in any one of claims 20 to 22.